Method of forming a ceramic fluid module having a smooth inner surface and the module produced

Abstract

A fluidic module includes a monolithic closed-pore ceramic body having first and second regions, with the first regions disposed between the second regions. The first and second regions are configured to differ from one another with respect to a common property of the ceramic material of the ceramic body. The common property can differ by forming the first and second regions from ceramic particles that differ in particle size. The fluidic module further includes a tortuous fluidic channel extending through the ceramic body. The fluidic channel is surrounded by the first regions such that the fluidic channel is completely separated from the second regions at least within planar regions of the ceramic body. The fluidic channel has an interior surface with a surface roughness of less than or equal to 5 pm Ra. A method of forming the fluidic module is disclosed.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 275,680, filed November 4, 2021, pursuant to U.S. C. § 119, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a method for forming a ceramic fluid module, and more specifically, to a method for forming a high-density, closed-porosity monomeric silicon carbide fluid module having smooth, tortuous internal channels extending therethrough and into the fluid module itself. Background Technology

[0004] The applicant has developed a ceramic powder pressing method configured to form a fluid module with a complex internal channel structure within a high-density, closed-pore monomeric ceramic body. This ceramic fluid module enables numerous continuous-flow chemical reactions. The method typically involves binder-coated ceramic powder (e.g., ready-to-press (RTP) silicon carbide (SiC) powder) surrounding a channel mold formed of wax or a similar thermally fusible material. The RTP SiC powder is typically spray-dried, causing primary SiC particles to aggregate into larger particles. The diameter of these RTP SiC powder particles can be, for example, from 30 μm to 200 μm, and may also include other subranges depending on the powder supplier. The primary SiC particles before coating may have a particle size distribution with a D50 of approximately 0.7 μm.

[0005] During the pressing process, RTP SiC powder is pressed around a channel mold. After pressing, the mold material is removed by heating to expose one or more tortuous fluid channels extending through the pressed (green) ceramic body. The pressed ceramic body is then subjected to debinding and sintering processes to remove the binder and densify and further solidify the pressed body into a monomeric ceramic body. The surface roughness of the inner surface of the tortuous fluid channels depends on various factors. It has been found that an extremely smooth inner surface is preferred for certain chemical reactions. Therefore, a method is needed to reduce the surface roughness of the fluid channels extending through the fluid module formed from the pressed ceramic powder. It is further advantageous to provide a fluid module with smooth, tortuous internal channels formed by this method. Summary of the Invention

[0006] A first aspect of this disclosure includes a method for forming a ceramic fluid module for a flow reactor, comprising: surrounding a positive channel mold with first ceramic particles, the positive channel mold defining a channel having a tortuous shape, the first ceramic particles having a first particle size defined by a first particle size distribution (PSD) having a first average, a first median, and a first mode; positioning the first ceramic particles and the positive channel mold between second ceramic particles, the second ceramic particles having a second particle size defined by a second PSD having a second average, a second median, and a second mode, wherein at least one of the following is satisfied: (i) the first average is less than the second average, (ii) the first median is less than the second median, and (iii) the first mode is less than the second mode; pressing the first ceramic particles, the second ceramic particles, and the positive channel mold to form a pressed body; heating the pressed body to remove the positive channel mold; and sintering the pressed body to form a high-density, closed-pore ceramic body having a tortuous fluid channel extending therethrough.

[0007] The second aspect of this disclosure includes the method according to the first aspect, wherein surrounding the positive channel mold with the first ceramic particles comprises: forming a first layer having a first portion of the first ceramic particles, positioning the positive channel mold on the first layer, and forming a second layer on the first layer by covering the first portion of the first ceramic particles and the positive channel mold with a second portion of the first ceramic particles.

[0008] A third aspect of this disclosure includes a method according to the second aspect, wherein positioning the first ceramic particle and the positive channel mold between the second ceramic particle comprises: forming a base layer having a first portion of the second ceramic particle, a first layer of the first ceramic particle being formed on the base layer, and forming a covering layer on the second layer by covering the first ceramic particle and the positive channel mold therearound with the second portion of the second ceramic particle.

[0009] The fourth aspect of this disclosure includes a method according to any one of the first to third aspects, further comprising forming an intermediate layer at the junction between the first ceramic particle and the second ceramic particle, the intermediate layer including intermediate ceramic particles having an intermediate particle size defined by an intermediate PSD having an intermediate average, an intermediate median and an intermediate mode, wherein at least one of the following is satisfied: (i) the intermediate average is between the first and the second average, (ii) the intermediate median is between the first and the second median and (iii) the intermediate mode is between the first and the second mode.

[0010] The fifth aspect of this disclosure includes the method according to the fourth aspect, wherein the intermediate ceramic particles increase in size in the direction from the first ceramic particle through the intermediate layer to the second ceramic particle.

[0011] The sixth aspect of this disclosure includes a method according to any one of the first to third aspects, wherein the first ceramic particle has a thickness of from about 40% to about 60% of the total thickness of the first and second ceramic particles before pressing.

[0012] The seventh aspect of this disclosure includes a method according to the third aspect, wherein the base layer and the cover layer each have a thickness of about 15% to about 30% of the total thickness relative to the total thickness of the first and second ceramic particles before pressing, and the first layer has a thickness of about 5% to about 20% of the total thickness.

[0013] The eighth aspect of this disclosure includes a method according to the first aspect, wherein surrounding the positive channel mold with the first ceramic particles includes applying the first ceramic particles to the surface of the positive channel mold to form a surface coating thereon.

[0014] The ninth aspect of this disclosure includes the method according to the eighth aspect, wherein applying the first ceramic particles to the surface of the positive channel mold comprises one or more of washing, spraying, and flocking to form the surface coating.

[0015] The tenth aspect of this disclosure includes a method according to the eighth or ninth aspect, wherein one or more of the first ceramic particles and intermediate ceramic particles are applied separately, such that the surface coating has multiple continuous layers.

[0016] The eleventh aspect of this disclosure includes the method according to the tenth aspect, which further includes modifying the properties of the material of each successive layer to form a gradient boundary between the first ceramic particles and the second ceramic particles.

[0017] The twelfth aspect of this disclosure includes the method according to the eleventh aspect, wherein the property includes the particle size of the intermediate ceramic particles, the particle size increasing with each successive layer.

[0018] The thirteenth aspect of this disclosure includes a method according to the eleventh or twelfth aspect, wherein the properties include one or more of at least one component of ceramic slurry, ceramic powder, solvent, adhesive, and binder associated with the continuous layer.

[0019] The fourteenth aspect of this disclosure includes a method according to any one of the first to thirteenth aspects, wherein the first particle size is at least about 1 μm and the second particle size is at most about 250 μm.

[0020] The fifteenth aspect of this disclosure includes a method according to any one of the first to fourteenth aspects, which further includes processing common ceramic particles to provide the first ceramic particles.

[0021] The sixteenth aspect of this disclosure includes a method according to any one of the first to fifteenth aspects, which further includes processing common ceramic particles to provide the first ceramic particles and the second ceramic particles.

[0022] The seventeenth aspect of this disclosure includes a method according to the fifteenth or sixteenth aspect, wherein processing the common ceramic particles includes sieving the common ceramic particles with a sieve having a sieve aperture size, the sieve being configured to separate the common ceramic particles into first ceramic particles and second ceramic particles.

[0023] The eighteenth aspect of this disclosure includes the method according to the seventeenth aspect, wherein substantially all of the first ceramic particles have a first particle size smaller than the sieve aperture size and substantially all of the second ceramic particles have a second particle size greater than or equal to the sieve aperture size.

[0024] The nineteenth aspect of this disclosure includes a method according to the seventeenth or eighteenth aspect, wherein the sieve aperture size is selected to separate a sufficient amount of the first ceramic particles from the common ceramic particles.

[0025] The twentieth aspect of this disclosure includes a method according to any one of the seventeenth to nineteenth aspects, wherein the common ceramic particles have a common particle size defined by a common PSD prior to sieving, and wherein the sieve aperture size is a value within a range centered on one or more of the average, median, and mode of the common PSD.

[0026] The twentieth aspect of this disclosure includes a method according to any one of the seventeenth to nineteenth aspects, wherein the sieve aperture size is a value in the range of about 70 μm to about 210 μm.

[0027] The twenty-second aspect of this disclosure includes a method according to the fifteenth or sixteenth aspect, wherein processing the common ceramic particles includes mixing uncoated ceramic particles with the common ceramic particles to provide the first ceramic particles, the common ceramic particles having a common particle size defined by the common PSD, and the uncoated ceramic particles having an uncoated particle size configured to reduce one or more of the mean, median, and mode of the common PSD by mixing.

[0028] The twenty-third aspect of this disclosure includes the method according to the twenty-second aspect, wherein the first ceramic particles comprise: about 50 wt% to about 85 wt% of the common ceramic particles, and about 15 wt% to about 50 wt% of the uncoated ceramic particles.

[0029] The twenty-fourth aspect of this disclosure includes a method according to the twenty-second or twenty-third aspect, wherein the uncoated particle size is defined by an uncoated PSD having a median value of approximately 0.7 μm.

[0030] The method according to the 25th aspect of this disclosure includes the method according to the 15th or 16th aspect, wherein processing the common ceramic particles includes grinding the common ceramic particles to provide the first ceramic particles.

[0031] The twenty-sixth aspect of this disclosure includes the method according to the twenty-fifth aspect, wherein grinding the common ceramic particles comprises subjecting the common ceramic particles to turbulent mixing in the presence and / or absence of a ball medium.

[0032] The 27th aspect of this disclosure includes a method according to the 25th or 26th aspect, which further includes mixing uncoated ceramic particles with the common ceramic particles before and / or after grinding to provide the first ceramic particles.

[0033] The twentieth aspect of this disclosure includes a method according to any one of the first to twenty-seventh aspects, wherein one or more of the first ceramic particles and the second ceramic particles comprise α-silicon carbide.

[0034] The twentieth aspect of this disclosure includes a method according to any one of the first to twenty-eighth aspects, wherein the first PSD and the second PSD are symmetrical.

[0035] The thirtieth aspect of this disclosure includes a method according to any one of the first to twenty-eighth aspects, wherein the first PSD and the second PSD are asymmetric.

[0036] A thirty-first aspect of this disclosure includes a method according to any one of the first to twenty-eighth aspects, wherein one of the first PSD and the second PSD is symmetrical, and the other of the first PSD and the second PSD is asymmetrical.

[0037] The thirty-second aspect of this disclosure includes a method according to any one of the first to thirty-first aspects, wherein the difference between the first average and the second average, the first median and the second median and / or the first mode and the second mode is at least 10 μm.

[0038] The thirty-third aspect of this disclosure includes a method according to any one of the first to thirty-first aspects, wherein the difference between the first average and the second average, the first median and the second median and / or the first mode and the second mode is at least 25 μm.

[0039] The thirty-fourth aspect of this disclosure includes a method according to any one of the first to thirty-first aspects, wherein the difference between the first average and the second average, the first median and the second median and / or the first mode and the second mode is at least 50 μm.

[0040] The thirty-fifth aspect of this disclosure includes a method according to any one of the first to thirty-fourth aspects, wherein the positive channel mold comprises a mold material that is meltable, sublimable, or otherwise thermally removable, the mold material having a hardness configured to resist indentations from the first ceramic particles during pressing.

[0041] The thirty-sixth aspect of this disclosure includes the method according to the thirty-fifth aspect, wherein the hardness of the mold material is in the range of about 20 to about 50 Shore D hardness.

[0042] The thirty-seventh aspect of this disclosure includes the method according to the thirty-sixth aspect, wherein the hardness of the mold material is in the range of about 30 to about 40 Shore D hardness.

[0043] The thirty-eighth aspect of this disclosure includes a method according to any one of the first to thirty-seventh aspects, wherein pressing the first ceramic particle, the second ceramic particle, and the positive channel mold includes a pressing pressure in the range of about 30 to about 80 MPa.

[0044] The thirty-ninth aspect of this disclosure includes a fluid module comprising: a monomeric closed-pore ceramic body having a first region and a second region disposed between the second region, the first region and the second region differing in common properties of the ceramic material relative to the ceramic body; and a tortuous fluid channel extending through the ceramic body and surrounded by the first region such that the tortuous fluid channel is completely separated from the second region, the tortuous fluid channel having an inner surface with a surface roughness less than or equal to 5 μm Ra.

[0045] The fortieth aspect of this disclosure includes a fluid module according to the thirty-ninth aspect, wherein the surface roughness is in the range of 0.1 to 5 μm Ra.

[0046] According to the forty-first aspect of this disclosure, a fluid module according to the thirty-ninth aspect is included, wherein the surface roughness is in the range of 0.1 to 1 μm Ra.

[0047] The forty-second aspect of this disclosure includes a fluid module according to any one of aspects thirty-nine to forty-one, wherein the ceramic material of the ceramic body has a density of at least 97% of the theoretical maximum density of the ceramic material.

[0048] The forty-third aspect of this disclosure includes a fluid module according to any one of the thirty-ninth to forty-first aspects, wherein the ceramic material of the ceramic body has a density of at least 98% of the theoretical maximum density of the ceramic material.

[0049] The forty-fourth aspect of this disclosure includes a fluid module according to any one of the thirty-ninth to forty-first aspects, wherein the ceramic material of the ceramic body has a density of at least 99% of the theoretical maximum density of the ceramic material.

[0050] The forty-fifth aspect of this disclosure includes a fluid module according to any one of the thirty-ninth to forty-fourth aspects, wherein the common attribute is density, and a first density of the first region is greater than a second density of the second region.

[0051] The forty-sixth aspect of this disclosure includes a fluid module according to any one of the thirty-ninth to forty-fifth aspects, wherein the ceramic material of the ceramic body has a closed-porosity of less than 3%.

[0052] The forty-seventh aspect of this disclosure includes a fluid module according to any one of the thirty-ninth to forty-fifth aspects, wherein the ceramic material of the ceramic body has a closed-porosity of less than 1.5%.

[0053] The forty-eighth aspect of this disclosure includes a fluid module according to any one of the thirty-ninth to forty-fifth aspects, wherein the ceramic material of the ceramic body has a closed-porosity of less than 0.5%.

[0054] The forty-ninth aspect of this disclosure includes a fluid module according to any one of the thirty-ninth to forty-eighth aspects, wherein the common attribute is closed-pore porosity, and a first closed-pore porosity of the first region is less than a second closed-pore porosity of the second region.

[0055] The fiftieth aspect of this disclosure includes a fluid module according to any one of the thirty-ninth to forty-ninth aspects, wherein the common material property is average grain size, and the first average grain size of the first region is smaller than the second average grain size of the second region.

[0056] A 51st aspect of this disclosure includes a fluid module according to any one of aspects 39 to 50, wherein the second region includes at least two outer layers and the first region includes an inner layer disposed between the at least two outer layers.

[0057] The fifty-second aspect of this disclosure includes a fluid module according to the fifty-first aspect, wherein the at least two outer layers and the inner layer are planar layers disposed between the main surfaces of the fluid module.

[0058] The 53rd aspect of this disclosure includes a fluid module according to any one of the 39th to 50th aspects, wherein the first region has a substantially uniform thickness extending substantially vertically from the inner surface of the tortuous fluid channel.

[0059] The fifty-fourth aspect of this disclosure includes a fluid module according to the fifty-third aspect, wherein the thickness of the first region is in the range of about 50 μm to about 500 μm.

[0060] The 55th aspect of this disclosure includes a fluid module according to any one of the 39th to 54th aspects, wherein at least one boundary between the first region and the second region comprises the ceramic material, and wherein the value of a common property of the at least one boundary is between the value of the common property of the first region and the value of the common property of the second region.

[0061] The fifty-sixth aspect of this disclosure includes a fluid module according to the fifty-fifth aspect, wherein the at least one boundary comprises a plurality of boundaries, and the common attribute value of each boundary is between the value of the common attribute of the first region and the value of the common attribute of the second region.

[0062] The fifty-seventh aspect of this disclosure includes a fluid module according to the fifty-fifth or fifty-sixth aspect, wherein the common property of at least one boundary and / or all boundaries gradually transitions between the common property of the first region and the common property of the second region.

[0063] The fifty-eighth aspect of this disclosure includes a fluid module according to any one of the thirty-ninth to fifty-seventh aspects, wherein the inner surface of the tortuous fluid channel includes a bottom plate and a top plate separated by a height h and two opposing sidewalls connecting the bottom plate and the top plate, the sidewalls being separated by a width W measured at a location perpendicular to the height h and corresponding to half of the height h, wherein the height h of the tortuous fluid channel is in the range of 0.1 to 20 mm. Attached Figure Description

[0064] Figure 1 It is a plan view outline of the fluid channel of the type of fluid module that can be used in a flow reactor, and shows some features of the fluid channel;

[0065] Figure 2 A three-dimensional view of the exterior of the ceramic fluid module according to the implementation plan;

[0066] Figure 3 A cross-sectional view of a ceramic fluid module according to an embodiment, showing the portion through which the fluid channels extend;

[0067] Figure 4 A cross-sectional view of a ceramic fluid module having a first region and a second region respectively formed by coarse ceramic particles and fine ceramic particles, according to the implementation scheme;

[0068] Figure 5 A cross-sectional view of a ceramic fluid module having a first region and a second region respectively formed by coarse ceramic particles and fine ceramic particles, according to the implementation scheme;

[0069] Figure 6 Showing the formation Figure 4 and Figure 5 A flowchart of an implementation scheme for a ceramic fluid module method;

[0070] Figures 7A to 7G For a series of progressively cross-sectional representations, depict Figure 6 Used to form Figure 4 Various aspects of the method for ceramic fluid modules;

[0071] Figures 8A to 8E For a series of progressively cross-sectional representations, depict Figure 6 Used to form Figure 5 Various aspects of the method for ceramic fluid modules;

[0072] Figures 9A to 9C For a series of progressively cross-sectional representations, depict Figure 6 Used to form Figure 4 and Figure 5 Common aspects of the method for ceramic fluid modules;

[0073] Figure 10 A graph showing the measured channel surface roughness Ra values ​​of a sample formed from sieved SiC powder with different particle sizes and a sample formed from unmodified commercially available SiC powder according to Example 1.

[0074] Figure 11 The cross-section of the sample after debonding according to the method of Example 2 shows the fine SiC powder layer surrounding the channel and the coarse SiC powder layer positioned above and below the fine SiC powder layer.

[0075] Figure 12 To show photographs of several channel molds according to Example 3, some of the channel molds are dipped in SiC slurry;

[0076] Figure 13 To ensure a smooth surface after the sample has been pressed, debonded, and sliced ​​to expose internal features. Figure 12 A photograph of a sample with internal features formed in a dip-coating channel mold;

[0077] Figure 14 To have partially dipped in Figure 12 The surface profile of a sample containing internal channels formed by wax strips in SiC powder slurry was measured, including portions of the internal channels formed by the uncoated parts of the wax strips; and

[0078] Figure 15 for Figure 14 The surface profile of the sample was measured, including portions of the internal channels formed by the coating portion of the wax strip. Detailed Implementation

[0079] To facilitate an understanding of the principles of this disclosure, reference will now be made to the embodiments shown in the accompanying drawings and described in the following written description. It should be understood that this disclosure is not intended to limit the scope of the disclosure. It should also be understood that this disclosure includes any alternatives and modifications to the illustrated embodiments, and includes further applications of the principles disclosed herein that would commonly occur to those skilled in the art to which this disclosure pertains.

[0080] As used herein, the term "and / or," when used in a list of two or more items, means that any one of the listed items can be used alone, or any combination of two or more listed items can be used. For example, if a composition is described as containing components A, B, and / or C, then the composition may contain only A; only B; only C; a combination of A and B; a combination of A and C; a combination of B and C; or a combination of A, B, and C.

[0081] In this document, relational terms such as first and second, top and bottom are used only to distinguish one entity or action from another, and do not necessarily require or imply any actual such relationship or order between such entities or actions.

[0082] As used herein, the term “about” means that quantities, dimensions, formulations, parameters, and other quantities and characteristics are not and need not be accurate, but may be approximate and / or larger or smaller as required, reflecting tolerances, conversion factors, rounding, measurement errors, and other factors known to those skilled in the art. When the term “about” is used to describe the value or endpoint of a range, this disclosure should be understood to include the specific value or endpoint referred to. Regardless of whether the numerical values ​​or endpoints of a range in the specification are marked with “about,” the numerical values ​​or endpoints of a range are intended to include two embodiments: one modified by “about” and one not modified by “about.” It will be further understood that each endpoint of a range is significant relative to and independent of the other endpoint.

[0083] As used herein, the terms “substantially,” “basically,” and variations thereof, unless otherwise defined in relation to a particular term or phrase, are intended to indicate that the described feature is equal to or approximately equal to a value or description. For example, a “substantially planar” surface is intended to mean a planar surface or a surface that is approximately planar. Furthermore, “substantially” is intended to indicate that two values ​​are equal or approximately equal. In some embodiments, “substantially” may indicate a value within plus or minus about 10% or a corresponding ideal quantity (e.g., all, each, every), or within plus or minus about 5%, or within plus or minus about 2%.

[0084] The directional terms used in this article, such as up, down, right, left, front, back, top, bottom, above, and below, are used only for reference in the accompanying drawings and are not intended to imply absolute orientation.

[0085] Unless explicitly stated otherwise, as used herein, the terms “the,” “a,” and “an” mean “at least one” and should not be limited to “only one.” Thus, for example, unless the context clearly indicates otherwise, reference to “a component” includes embodiments having two or more such components.

[0086] As used herein, the term "ceramic particles," whether used succinctly or preceded by the terms "coated," "binder-coated," "to be pressed," "RTP," and / or any similar variations thereof, refers to ceramic particles containing a binder and / or lubricant that facilitates the pressing of the ceramic particles. The term "ceramic particles" has the above meanings unless preceded by one or more terms such as "unbinder-coated," "non-coated," "uncoated," "raw," or other terms indicating that no binder and / or lubricant has been added to the ceramic particles.

[0087] As used herein, the “particle size distribution” or “PSD” of powdered or particulate materials (such as ceramic powders and ceramic particles described herein) is a list or mathematical function of the relative quantities of particles that exist according to their size. The PSD is a useful method for describing particle size in powders. The PSD can be described by many distribution characteristics, such as the mean, median, mode, and width. The mean is a calculated value similar to the concept of the average. The mean has multiple definitions because it relates to the basis (quantity, surface area, volume) on which the distribution is calculated. Various mean calculations are defined by known standards (e.g., ISO 9276-2:2001). The median is defined as the value at which half the population is above a certain point and the other half is below it. For particle size distributions, the median is called D50. D50 is a size in micrometers that divides the distribution into half above and half below that diameter. The mode is the peak value of the frequency distribution, or the highest peak observed in the distribution. The mode represents the most frequently found particle size (or particle size range) in the distribution. Unless otherwise specified, the particle size values ​​disclosed herein refer to the diameter of the particle or equivalent sphere diameter.

[0088] A frequency distribution with only one peak is called a "unimodal" or "monomodal" distribution. A typical example of a unimodal distribution is the normal distribution, which is also symmetrical. For a symmetrical distribution, all central values ​​are identical, such that the mean = median = mode. In contrast, many unimodal (single peak) frequency distributions are asymmetrical (e.g., "left-skewed" or "right-skewed"). For asymmetrical or non-symmetrical distributions, the mean, median, and mode will be three different values. In a unimodal PSD, particles of moderate size typically have the highest frequency. There is no further dominant mode in the PSD. For production-related reasons, one or more secondary modes may exist at particle sizes unrelated to measurement. The corresponding unimodal PSD can have a sharp or broad configuration around the mode with the median particle size. In the case of a "sharp" PSD, the frequency decreases significantly from the mode. In the case of a "broad" PSD, particle sizes that are more significantly distant from the median particle size still have relevant frequencies.

[0089] As used herein, a "tortuous" passage refers to a passage without a direct line of sight and whose path has at least two distinct radii of curvature. The path of this passage is mathematically and geometrically defined as a curve formed by the continuous geometric centers of the continuous minimum area planar cross-sections of the passage (i.e., the angle of a given planar cross-section is the angle that produces the minimum area of ​​the planar cross-section at a specific location along the passage), taken from any closely spaced consecutive locations along the passage. Typical machining-based forming techniques are often insufficient to create such tortuous passages. Such passages may comprise one or more reorganizations that divide the passage into sub-passages (with corresponding sub-paths) and sub-passages (and their corresponding sub-paths).

[0090] As used herein, “morsolithic” ceramic structure does not imply zero inhomogeneity at all scales. A “morsolithic” ceramic structure or “morsolithic” ceramic fluid module, as defined herein, refers to a ceramic structure or fluid module having one or more tortuous channels extending therethrough, wherein no inhomogeneities, openings, or interconnecting pores (other than the channels) exist in the ceramic structure, said ceramic structure having a length greater than the average vertical depth d of the one or more channels from the outer surface of the structure or module 300. Figure 3 As shown. Providing this type of monolithic ceramic structure or monolithic ceramic flow module helps ensure the fluid tightness and good pressure resistance of the flow reactor fluid module or similar products.

[0091] As used herein, “monomer” has the meaning provided above. However, the applicant reserves the right to define the monomer in other ways unless expressly stated, such as in the claims, wherein the monomer may alternatively be defined as a sintered polycrystalline ceramic material body having a chain of grains that is continuous and uniformly distributed throughout the body in any direction, for example when grain growth occurs simultaneously during a single sintering cycle, but wherein the body may contain internal channels as disclosed herein, as well as interstitial pores between grains, and optionally wherein most of the interstitial pores have a maximum lateral dimension of less than 5 μm (e.g., in the range of 2 to 3 μm), and / or wherein the body has no (observable and / or detectable) separated components (e.g., halves of the body) adhering to each other at the joint, for example at the joint plane in the case of components prepared via a sandwich assembly approach. The connector can be observable and / or detectable, for example, by visual inspection, cross-sectional microscopy, scanning electron microscopy (SEM), far-infrared reflectance spectroscopy, electron backscatter diffraction (EBSD), post-etching surface profilometry, and analysis of compositional changes by Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and / or X-ray CT scanning.

[0092] Figures 1 to 3A ceramic fluid module 300 for a flow reactor (not shown) is disclosed. The fluid module 300 includes a monomeric closed-pore ceramic body 200 and a tortuous fluid channel P extending along a path through the ceramic body 200. The ceramic body 200 is formed from a ceramic material comprising any compressible powder held together by a binder, and formed by thermal processing to melt the powder particles together to form a structure. In some embodiments, the ceramic material comprises oxide ceramics, non-oxide ceramics, glass ceramics, glass powders, metal powders, and other ceramics capable of achieving a high-density, closed-pore monomeric structure. Oxide ceramics are inorganic compounds of metals (e.g., Al, Zr, Ti, Mg) or metalloids (Si) with oxygen. Oxides may be combined with nitrogen or carbon to form more complex oxynitride or carbon oxide ceramics. Non-oxide ceramics are inorganic non-metallic materials comprising carbides, nitrides, borides, silicides, and others. Some embodiments of non-oxide ceramics that can be used for the ceramic body 200 include boron carbide (B4C), boron nitride (BN), tungsten carbide (WC), titanium diboride (TiB2), zirconium diboride (ZrB2), molybdenum disilicide (MoSi2), silicon carbide (SiC), silicon nitride (Si3N4), and silane (aluminum oxysilicate). In an exemplary embodiment, the ceramic body 200 is formed of SiC.

[0093] According to the implementation scheme, the tortuous fluid channel P includes a bottom plate 212 and a top plate 214 separated by a height h, and two opposing sidewalls 216 connecting the bottom plate 212 and the top plate 214. The sidewalls are composed of a width W ( Figure 1 The width W is measured perpendicular to the height h and along the direction of the channel (corresponding to the main flow direction during use). Further, the width W is measured at a location corresponding to half the height h. According to embodiments, the height h of the tortuous fluid channel P is in the range of 0.1 to 20 mm, or 0.2 to 15 mm, or 0.3 to 12 mm. The width W of the tortuous fluid channel P can vary depending on the method and / or reaction set to occur at each location or zone along the path.

[0094] According to the embodiment, the inner surface 210 of the fluid channel P at the intersection of the sidewall 216 and the base plate 212 (at reference numeral 218) has a radius of curvature greater than or equal to 0.1 mm, or greater than or equal to 0.3 mm, or even greater than or equal to 0.6 mm, or 1 mm or 5 mm, 1 cm or 2 cm. When viewed in a cross-section perpendicular to the path orientation, the inner surface 210 of the fluid channel P may have the same and / or different geometries at different locations along the path. For example, in some embodiments, the inner surface 210 may have a cross-sectional shape of square, rectangle, circle, oval, stadium shape (i.e., a circle elongated on a mirror surface), and other shapes. The relative dimensions of the same or different geometries may also vary along the path. The transition of the dimensions and / or geometry of the inner surface along the path is gradual to avoid introducing a stepped structure within the fluid channel P. The inner surface 210 in the embodiment preferably has a circular cross-sectional shape, which achieves higher pressure resistance.

[0095] According to the implementation scheme, the single closed-pore ceramic body 200 of the fluid module 300 has first regions 222, 322 and second regions 226, 326, wherein the first regions 222, 322 are disposed between the second regions 226, 326, as shown in the following figure. Figure 4 and 5 As shown in the diagram, the ceramic body 200 has a thickness t in a direction extending between opposing first and second main surfaces 228, 229. In this embodiment, the first main surface 228 and the second main surface 229 are defined by second regions 226, 326, and the thickness extends approximately perpendicular to the first and second main surfaces 228, 229. The first regions 222, 322 and the second regions 226, 326 are configured to differ from each other in common properties relative to the ceramic material forming the ceramic body 200.

[0096] As used herein, a “common property” of ceramic materials refers to the same physical property or attribute of the ceramic materials that is simultaneously measurable and / or otherwise determined in both first regions 222, 322 and second regions 226, 326. Further illustrated by example, if the common property is density, then to some degree that is measurable and / or otherwise determined, the density of the ceramic material forming the first regions 222, 322 of the ceramic body 200 will differ from the density of the ceramic material forming the second regions 226, 326. In the embodiments, the common property is the average value of the physical property or attribute throughout the entire volume of either the first regions 222, 322 or the second regions 226, 326. As described later in this disclosure, the common property can be differentiated by forming the first and second regions from respective amounts of ceramic particles of the same type of ceramic material, but differing in particle size. For example, as described later in this disclosure, the first regions 222, 322 may be formed from fine SiC particles, while the second regions 226, 326 may be formed from coarse SiC particles.

[0097] A common property in the implementation scheme may be the density of the ceramic material in each of the first zones 222, 322 and the second zones 226, 326 after the ceramic body 200 is sintered. The first zone is formed or configured to have a first density. The second zone is formed or configured to have a second density. The first density of the first zones 222, 322 is greater than the second density of the second zones 226, 326. The first density and the second density may be the average or average density of all portions of the ceramic body 200 comprising the first zones 222, 322 and the second zones 226, 326, respectively. Without being bound by theory, it is believed that the first density will be greater than the second density because the closer packing of smaller particles will result in smaller gaps and pores between them after pressing, allowing voids to close more effectively during firing due to shorter surface diffusion distances. Exemplary standards for density measurement include, for example, ASTM C329-88 (2020) "Standard Test Method for Specific Gravity of Fired Ceramic Whiteware Materials".

[0098] A common property in the implementation scheme may be the porosity of the ceramic material in each of the first zones 222, 322 and the second zones 226, 326 after sintering of the ceramic body 200. The first zone is formed or configured to have a first porosity. The second zone is formed or configured to have a second porosity. The first porosity of the first zones 222, 322 is less than the second porosity of the second zones 226, 326. The first porosity and the second porosity may be the average or average porosity of all portions of the ceramic body 200 comprising the first zones 222, 322 and the second zones 226, 326, respectively. Without being bound by theory, it is believed that the first porosity will be less than the second porosity because for smaller particles, there will be a more efficient reduction in pore size during firing.

[0099] In the implementation scheme, the porosity of the ceramic material can be characterized by the type or property of porosity, which includes open (effective) porosity and closed (ineffective) porosity. Open porosity refers to the portion of the total volume where fluid flow can occur effectively, excluding closed or non-connected cavities, pores, or voids. Closed porosity refers to the portion of the total volume where fluid or gas is present but fluid flow cannot occur effectively, including closed cavities, pores, or voids. The sum of open and closed porosity is sometimes referred to as total porosity. The porosity of the ceramic material in the implementation scheme can also be characterized by the size of interstitial pores or voids.

[0100] In the implementation scheme, at least one of the following conditions is met: (i) the first closed-pore porosity of the first regions 222 and 322 is less than the second closed-pore porosity of the second regions 226 and 326; (ii) the first open-pore porosity of the first regions 222 and 322 is less than the second open-pore porosity of the second regions 226 and 326; and (iii) the first void size of the first regions 222 and 322 is less than the second void size of the second regions 226 and 326. Exemplary standards for porosity measurement include, for example, ASTM D4404-18 "Standard Test Method for Determination of Pore Volume and Pore Volume Distribution of Soil and Rock by Mercury Intrusion Porosimetry", ASTM D4284-12(2017)e1 "Standard Test Method for Determining Pore Volume Distribution of Catalysts and Catalyst Carriers by Mercury Intrusion Porosimetry", and ASTM C949-80(2020) "Standard Test Method for Porosity in Vitreous Whitewares by Dye Penetration".

[0101] A common attribute in the embodiments may be the particle size of the ceramic material in each of the first zones 222, 322 and the second zones 226, 326 after the ceramic body 200 has been sintered. The first zone is formed or configured to have a first particle size. The second zone is formed or configured to have a second particle size. The first particle size of the first zones 222, 322 is smaller than the second particle size of the second zones 226, 326. The first and second particle sizes may be the average or average particle size of all portions of the ceramic body 200 that respectively include the first zones 222, 322 and the second zones 226, 326. Exemplary standards for particle size measurement include, for example, ASTM C1730-17 "Standard Test Method for Particle Size Distribution of Advanced Ceramics by X-Ray Monitoring of Gravity Sedimentation".

[0102] Continue to refer to Figure 4 and 5The tortuous fluid channel P is surrounded by first regions 222 and 322, such that the tortuous fluid channel P is separated from the second regions 226 and 326. In the illustrated embodiment, the first regions 222 and 322 surround the tortuous fluid channel P such that the tortuous fluid channel P is completely separated from the second regions 226 and 326, at least in the planar region extending laterally through the ceramic body 200. Figure 4 The planar region shown corresponds to the first region 222. Figure 5 The planar region 327 shown extends laterally through the ceramic body 200 and has a height that approximately corresponds to the outermost extent of the first region 322 in the thickness t direction of the ceramic body 200. Figure 5 The dashed line extending from the square brackets in the figure, bearing reference numeral 327, is used only to delineate planar regions and does not represent additional structures within the ceramic body 200. Planar regions 222 and 327 are configured centered on the location and / or extension of the tortuous fluid channel P through the ceramic body 200. In the illustrated embodiment, planar regions 222 and 327 are centered at the midpoint between opposing main surfaces 228 and 229. Planar regions 222 and 227 in the embodiments may be spaced apart from the midpoint.

[0103] The tortuous fluid channel P has an inner surface 210. In portions of the ceramic body 200 surrounding the tortuous fluid channel P in the first regions 222, 322, for example, in planar regions, the inner surface 210 is defined by the ceramic material of the first regions 222, 322. The inner surface 210 has a surface roughness in the range of less than or equal to 5 μm Ra, or 0.1 to 5 μm Ra, or even 0.1 to 1 μm Ra, typically lower than values ​​previously achieved in SiC fluid modules. Due to the common properties of the ceramic material in the first regions 222, 322, and the common properties of the ceramic material in the second regions 226, 326, the lower surface roughness of the inner surface 210 in the portion defined by the first regions is achievable.

[0104] The surface roughness of the inner surface 210 occurs along any measured profile of the inner surface 210. For example, when viewed in a cross-section perpendicular to the path orientation, the inner surface 210 defines an internal profile that completely surrounds the path of the channel P. The surface roughness of the inner surface 210 appears at every location along the entire internal profile. Due to the monolithic structure of the ceramic body 200, the inner surface 210 does not have any joints, seams, steps, or discontinuities along its length.

[0105] According to the implementation scheme of fluid module 300, the first zones 222 and 322 and the second zones 226 and 326 can have different configurations. (Refer to...) Figure 4The second region may include at least two outer layers 226a and 226b, and the first region may include an inner layer 222 disposed between the two outer layers 226a and 226b. The at least two outer layers 226a and 226b and the inner layer 222 are configured in series in a planar layer between the main surfaces 228 and 229 of the fluid module 300. A first boundary 232a is disposed between the first outer layer 226a of the second region 226 and the inner layer of the first region 222. A second boundary 232b is disposed between the second outer layer 226b of the second region 226 and the inner layer of the first region 222. The first boundary 232a and the second boundary 232b are located between the second outer layer 226b of the second region 226 and the inner layer of the first region 222. Figure 4 The first boundary 232a and the second boundary 232b are located at the intersection of the loose pattern fill associated with the first and second outer layers 226a, 226b and the compact pattern fill associated with the inner layer 222. The first boundary 232a and the second boundary 232b are substantially free of or have no gaps between the first region 222 and the second region 226.

[0106] According to Figure 4 In one embodiment, at least one or both of the first boundary 232a and the second boundary 232b may have a thickness of zero, such that the first region 222 abruptly transitions into the second region 226. In this embodiment, common properties of the ceramic material in the first region (e.g., first density, first porosity, and / or first particle size) abruptly change to common properties of the ceramic material in the second region (e.g., second density, second porosity, and / or second particle size).

[0107] According to Figure 4 In some embodiments, at least one or both of the first boundary 232a and the second boundary 232b may have a thickness greater than zero and comprise a ceramic material. In these embodiments, the common properties of the first boundary 232a and / or the common properties of the second boundary 232b may lie between the common properties of the first region 222 and the common properties of the second region 226, such that the first region 222 gradually transitions into and / or progressively enters the second region 226.

[0108] Reference Figure 5 The second region may include a block 326 disposed between the main surfaces 228 and 229, and the first region may include one or more contour regions 322 disposed within the block 326. In this embodiment, the one or more contour regions 322 have a thickness extending vertically from the inner surface 210 of the tortuous fluid channel P. The thickness of the one or more contour regions 322 may be substantially uniform, such as... Figure 5As shown. As used herein, a substantially uniform thickness may be a thickness that deviates from the average thickness of the contour region 322 by no more than 10%, 5%, or 2% over a given length of channel P (e.g., 75%, 85%, or 100% of the channel length). In embodiments, the thickness of one or more contour regions 322 may vary along the path of the tortuous fluid channel P. The thickness of one or more contour regions 322 may range from at least about 50 μm to about 500 μm.

[0109] The boundary 332 is located between block 326 of the second region and one or more contour areas 322 of the first region. The boundary 332 is... Figure 5 The diagram shows the intersection of a loose pattern filling associated with block 326 of the second region and a compact pattern filling associated with one or more outline areas 322 of the first region. The solid line drawn at the intersection 332 is used only to clarify the intersection between the first region 322 and the second region 326. In practice, the intersection 332 may be coarse at the grain level where the ceramic materials of the first region 322 and the second region 326 come into contact with each other. The intersection 332 is substantially free of voids or has no voids between the first region 322 and the second region 326. Figure 5 The boundary 332 may have the same characteristics as the aforementioned relative to... Figure 4 The boundaries 232a and 232b have the same thickness and / or transition.

[0110] The first and second densities of regions 222 and 322 in the first region and regions 226 and 326 in the second region are respectively at least 95% of the theoretical maximum density of the ceramic material, or even at least 96%, 97%, 98%, or 99% of the theoretical maximum density. The theoretical maximum density (also called maximum theoretical density, theoretical density, crystal density, or X-ray density) of polycrystalline materials (such as SiC) is the density of a perfect single crystal of the sintered material. Therefore, the theoretical maximum density is the maximum density achievable for a given structural phase of the sintered material.

[0111] In an exemplary embodiment, the ceramic material is α-silicon carbide (α-SiC) having a hexagonal 6H structure. The theoretical maximum density of sintered SiC(6H) is 3.214 ± 0.001 g / cm³. 3 Munro, Ronald G., “Material Properties of a Sintered α-SiC”, Journal of Physical and Chemical Reference Data, 26, 1195 (1997). The ceramic material in the embodiments may comprise SiC in different crystalline forms or entirely different ceramics. The theoretical maximum density of other sintered SiC crystalline forms may differ from the theoretical maximum density of sintered SiC(6H), for example, in the range of 3.166 to 3.214 g / cm³.3 Within this range. Similarly, the theoretical maximum density of other sintered ceramics differs from the maximum density of sintered SiC(6H). As used herein, a “high-density” ceramic body is a sintered ceramic material in which the density of the ceramic body is at least 95% of the theoretical maximum density of the ceramic material.

[0112] In embodiments where the common attribute is closed porosity, the corresponding closed porosities of the first regions 222 and 322 and the second regions 226 and 326 are each less than 3%, or less than 1.5%, or even less than 0.5%. In embodiments where the common attribute is open porosity, the corresponding open porosities of the first regions 222 and 322 and the second regions 226 and 326 are each less than 1%, or even less than 0.5%, 0.4%, 0.2%, or 0.1%. As used herein, a “closed-pore” ceramic body is a ceramic body in which the ceramic material of the ceramic body exhibits a closed pore topology, such that the pores or units in the material are isolated from or only connected to adjacent pores or units and are not permeable to fluids.

[0113] According to the implementation plan, the ceramic body 200 of the fluid module 300 has an internal pressure resistance of at least 50 bar, or even at least 100 bar, or 150 bar under pressurized water testing.

[0114] Figure 6 A simplified flow diagram of method 600 for forming a ceramic fluid module for a flow reactor having one or more desirable properties disclosed herein. Method 600 refers to... Figures 7A to 7G , Figures 8A to 8E and Figures 9A to 9C They are described, showing the formation Figure 4 and 5 A cross-sectional representation of an aspect of the ceramic fluid module. Method 600 includes obtaining or forming a positive channel mold (frame 604). The positive channel mold is configured to define a channel having a tortuous shape. The positive channel mold can be obtained by molding, machining, 3D printing, or other suitable forming techniques, or combinations thereof. The positive channel mold comprises a mold material that is meltable, sublimable, or otherwise thermally removable. The mold material in the embodiments is a relatively incompressible material.

[0115] Method 600 in the implementation may include obtaining or processing ceramic powder to provide a quantity of fine ceramic particles and a quantity of coarse ceramic particles, the coarse ceramic particles being separated from the fine ceramic particles (box 608). As used herein, "fine ceramic particles" and "coarse ceramic particles" are interchangeably referred to as "first ceramic particles" and "second ceramic particles," respectively. The first ceramic particles and the second ceramic particles have a first particle size and a second particle size, respectively. In the implementation, the first particle size of the first ceramic particle is smaller than the second particle size of the second ceramic particle. The first particle size of the first ceramic particle is defined by a first PSD having a first average, a first median, and a first mode. The second particle size of the second ceramic particle is defined by a second PSD having a second average, a second median, and a second mode. In the implementation, at least one of the following is satisfied: (i) the first average is less than the second average, (ii) the first median is less than the second median, and (iii) the first mode is less than the second mode.

[0116] In embodiments of obtaining ceramic powder, the ceramic powder may be one or more commercially available real-time pressed (RTP) ceramic powders, which provide appropriate amounts of one or more of first and second ceramic particles. For example, the second ceramic particles may be provided as standard spray-dried ceramic powder, and the first ceramic particles may be provided as custom-formulated spray-dried ceramic powder with a particle diameter smaller than that of standard spray-dried ceramic powder.

[0117] In embodiments of processing ceramic powder, the unprocessed ceramic powder may comprise base or common ceramic particles having a common particle size defined by a common particle size distribution (PSD) having a common mean, a common median, and a common mode. In embodiments, the unprocessed common ceramic particles comprise one or more of first ceramic particles and second ceramic particles. In other words, one or more of the first and second ceramic particles are present in and / or derived from the common ceramic particles. In embodiments of processing ceramic powder, method 600 includes processing the common ceramic particles to provide a corresponding amount of first ceramic particles, second ceramic particles, or both first and second ceramic particles.

[0118] The processing of common ceramic particles to provide first and / or second ceramic particles may include one or more methods, which may be performed individually or in combination. In one approach, the processing of common ceramic particles includes sieving the particles with a sieve having an aperture size that allows the sieve to be configured to separate the common ceramic particles into first and second ceramic particles (frame 612). In an embodiment, at least one sieve is used to separate the common ceramic particles into two powder groups: ceramic powder containing the first ceramic particles and ceramic powder containing the second ceramic particles. The first or fine ceramic particles are those that fall through the sieve and are sometimes referred to as a "negative" or "-" product. The second or coarse ceramic particles are those that remain on the sieve and are sometimes referred to as a "positive" or "+" product.

[0119] After sieving the common ceramic particles (frame 612), substantially all of the first ceramic particles (e.g., more than 99% of the first ceramic particles) have a first particle size smaller than the sieve aperture size, and substantially all of the second ceramic particles (e.g., more than 97% of the second ceramic particles) have a second particle size greater than or equal to the sieve aperture size. It should be understood that due to the nature of the sieving process, the second ceramic particles may contain a small amount of the first ceramic particles. After sieving, the first ceramic particles may have a first PSD, which has a corresponding first average, a first median, and a first mode. After sieving, the second ceramic particles may have a second PSD, which has a corresponding second average, a second median, and a second mode. In the embodiment after sieving, at least one of the following is satisfied: (i) the first average is less than the second average, (ii) the first median is less than the second median, and (iii) the first mode is less than the second mode. In the embodiment, the first particle size may be at least about 1 μm, or at least about 10 μm, at least about 20 μm, at least about 30 μm, at least about 40 μm, at least about 45 μm, or even at least about 50 μm. The second particle size in the embodiments may be up to about 500 μm, or up to about 400 μm, up to about 350 μm, up to about 300 μm, up to about 275 μm, up to about 250 μm, or even up to about 225 μm. In other embodiments, the second particle size may be up to about 200 μm, up to about 100 μm, or even up to about 70 μm.

[0120] In an embodiment where method 600 includes sieving common ceramic particles (frame 612), the sieve aperture size is selected to separate a sufficient amount of first ceramic particles from the common ceramic particles. Although using first ceramic particles with a very fine particle size (e.g., 50 μm or less) to form the first regions 222, 322 of the ceramic body 200 will produce the smoothest inner surface 210 of the fluid channel P, as described herein, it may be necessary to process a large number of common ceramic particles to obtain a sufficient amount of first ceramic particles. Therefore, the sieve aperture size is selected to separate a sufficient amount of first ceramic particles from the common ceramic particles, even if the first particle size is not the finest possible.

[0121] In this embodiment, the sieve aperture size is selected as a value within a range centered on one or more of the average, median, and mode of the common PSD. This selection of the sieve aperture size helps ensure that a sufficient quantity of first ceramic particles can be separated from the common ceramic particles. The range in this embodiment can be centered on one or more of the average, median, and mode of the common PSD, located to its left (towards smaller sizes), or to its right (towards larger sizes). The sieve aperture size in this embodiment can be a value in the range of about 70 μm to about 210 μm, or a value in the range of about 80 μm to about 200 μm, or a value in the range of about 90 μm to about 190 μm, or a value in the range of about 100 μm to about 180 μm, or a value in the range of about 110 μm to about 170 μm, or even a value in the range of about 120 μm to about 160 μm. In this embodiment, the sieve aperture size is selected to separate approximately 33 wt% of the common ceramic particles as first ceramic particles to provide a sufficient quantity of first ceramic particles.

[0122] In another approach, the processing of the common ceramic particles includes mixing uncoated ceramic particles with the common ceramic particles to provide a first ceramic particle (box 616). In an embodiment, the common ceramic particles may also be mixed with uncoated ceramic particles to provide a second ceramic particle. The uncoated or unprocessed ceramic particles are ceramic particles that do not contain binders and / or lubricants, which may be added to facilitate the pressing of the ceramic particles. In an embodiment, the particle size of the uncoated ceramic particles is smaller than that of the common ceramic particles. The uncoated PSD of the uncoated ceramic particles has an uncoated average, an uncoated median, and an uncoated mode. In an embodiment, at least one of the following is satisfied: (i) the uncoated average is less than the common average, (ii) the uncoated median is less than the common median, and (iii) the uncoated mode is less than the common mode. In an embodiment, the uncoated ceramic particles are raw αSiC particles with an uncoated median or D50 of approximately 0.7 μm. The uncoated ceramic particles are mixed with the common ceramic particles to adjust the common PSD. Specifically, by mixing uncoated ceramic particles with common ceramic particles, the size of the uncoated particles is reduced to one or more of the common average, common median, and common mode.

[0123] Common ceramic particles and uncoated ceramic particles can be mixed in various proportions to form a series of powder compositions for first ceramic particles. The first ceramic particles in embodiments may comprise about 50 wt% to about 85 wt% of common ceramic particles and about 15 wt% to about 50 wt% of uncoated ceramic particles. Some example compositions of the first ceramic particles may comprise an 85 / 15 mixture having 85 wt% common ceramic particles and 15 wt% uncoated ceramic particles, an 80 / 20 mixture having 80 wt% common ceramic particles and 20 wt% uncoated ceramic particles, a 75 / 25 mixture having 75 wt% common ceramic particles and 25 wt% uncoated ceramic particles, and a 50 / 50 mixture having 50 wt% common ceramic particles and 50 wt% uncoated ceramic particles. If the common ceramic particles are mixed with uncoated ceramic particles to further provide second ceramic particles, the mixture will result in the first and second ceramic particles having the particle size relationship disclosed herein. In the implementation, about 60 wt% may be a limit for the proportion of uncoated ceramic particles in the composition, because the uncoated ceramic particles may not adhere sufficiently together in the gaps between the spray-dried particles.

[0124] In yet another approach, the processing of the common ceramic particles involves grinding the common ceramic particles to provide first ceramic particles (box 620). In this approach, the common ceramic particles undergo a grinding process to reduce their size. In an embodiment, the common ceramic particles may also be ground to provide second ceramic particles. Various types of grinding processes can be used individually or in combination with each other. One type of grinding involves containerized batch mixing using mixing blades within a rotating container. This type of grinding can be achieved using a Readco mixer, Readco Kurimoto LLC, model RK-Labmaster, 65 lb (York, PA, USA). Another type of grinding involves turbulent mixing with or without ball media. This type of grinding can be achieved using a CMR Turbula mixer, model T2C, Willy A. Brachofen AG Machinenfabrik (Basel / Schweiz, Germany). Yet another type of grinding involves ball milling with or without media. This type of grinding can be achieved using a Paul O. Abbé CMR ball mill, model MJRM-253643 (Wood Dale, IL, USA). In this approach, uncoated ceramic particles can be added to the common ceramic particles before and / or after grinding to further reduce one or more of the common mean, common median, and common mode. If the common ceramic particles are further ground to provide a second ceramic particle, the grinding method will result in the first and second ceramic particles having the particle size relationship disclosed herein.

[0125] The first or fine ceramic particles and the second or coarse ceramic particles may each be obtained or manufactured with specified characteristics and relationships in particle size. In embodiments, the first PSD and the second PSD may each be symmetrical or asymmetrical. Alternatively, in embodiments, one of the first PSD and the second PSD may be symmetrical and the other of the first PSD and the second PSD may be asymmetrical. In embodiments, the difference between the first mean and the second mean, the first median and the second median and / or the first mode and the second mode may be at least 10 μm, or at least 25 μm, or at least 50 μm, or at least 75 μm, or at least 100 μm, at least 125 μm, at least 150 μm, at least 200 μm, or even at least 250 μm. Regardless of the magnitude of the difference, the mean, median, and mode of each of the first PSD and the second PSD have the same relationship with each other, as previously described herein.

[0126] Once the first ceramic particles and / or the second ceramic particles (frames 608, 612, 616, 620) are obtained or formed, method 600 further includes filling a press housing (or mold) 100, which is closed by a plunger 110, forming a base layer together with the first portion 124a of the second or coarse ceramic particles, as... Figure 6 As described in box 624 and as follows Figure 7A The cross-section is shown. Method 600 determines whether the positive channel mold 130 should be passed according to the formation Figure 4 Layering of fluid modules or by forming Figure 5 The coating of the fluid module is performed by being surrounded by first ceramic particles or fine ceramic particles 120 (box 628).

[0127] If the positive channel mold 130 is formed by being surrounded by the first ceramic particles 120 through layering... Figure 4 The fluid module, method 600, includes covering a base layer comprising a first portion 120a of first ceramic particles with a first portion 124a of second ceramic particles to form a first layer (frame 632). Figure 7B Next, method 600 includes positioning the positive channel mold 130 on the first layer comprising the first portion 120a of the first ceramic particles (frame 636). Figure 7B and 7C Once the channel mold 130 is positioned on the first layer, method 600 includes covering the first portion 120a of the first ceramic particles and the channel mold 130 with the second portion 120b of the first ceramic particles to form the second layer (frame 640). Figure 7D Next, method 600 includes covering the first and second portions 120a, 120b of the first ceramic particle and the surrounding positive channel mold 130 with the second portion 124b of the second ceramic particle to form a covering layer (frame 644). Figure 7E ).

[0128] In one embodiment, surrounding the positive channel mold with first ceramic particles includes forming a first layer with a first portion 120a of the first ceramic particles, positioning the positive channel mold 130 on the first layer, and forming a second layer on the first layer by covering the first portion 120a of the first ceramic particles and the positive channel mold 130 with a second portion 120b of the first ceramic particles. In another embodiment, positioning the first ceramic particles and the positive channel mold between second ceramic particles includes forming a base layer with a first portion 124a of the second ceramic particles, positioning the first and second layers 120a, 120b of the first ceramic particles and the surrounding positive channel mold 130 on the base layer, and forming a cover layer on the second layer by covering the first ceramic particles and the surrounding positive channel mold with the second portion 124b of the second ceramic particles.

[0129] like Figure 7EAs shown, the corresponding layers of the first and second ceramic particles may have different thicknesses relative to the total thickness of the loose ceramic powder in the press housing 100 before pressing. In one embodiment, the base layer including the first portion 124a of the second ceramic particles may have a thickness of about 15% to about 30% of the total thickness of the first and second ceramic particles before pressing. In one embodiment, the first layer including the first portion 120a of the first ceramic particles may have a thickness of about 5% to about 20% of the total thickness of the first and second ceramic particles before pressing. In one embodiment, the first layer including the first portion 120a of the first ceramic particles and the second layer including the second portion 120b of the first ceramic particles may have a combined thickness of about 40% to about 60% of the total thickness of the first and second ceramic particles before pressing. In one embodiment, the cover layer including the second portion 124b of the second ceramic particles may have a thickness of about 15% to about 30% of the total thickness of the first and second ceramic particles before pressing.

[0130] In the implementation, prior to the addition of further layers and / or the positive channel mold 130, the corresponding layers of the first and second ceramic particles are made flat or otherwise leveled. Any tool can be used to level or flatten the corresponding layers. Although the cross-section in the figure shows a solid line delineating the boundary between the different layers of ceramic particles, it should be understood that when they are in contact with each other, the ceramic particles in the different layers are mixed to some extent, and the boundary actually appears blurred at the particle level. After each layer is leveled, the percentage thickness of the corresponding layers of the first and second ceramic particles relative to the total thickness of the loose ceramic powder in the press housing is determined in a direction generally parallel to the pressing force AF. Figure 7F The thickness of each layer includes the shortest distance between the bottom and top surfaces of the entire reference layer.

[0131] In one embodiment, method 600 may include forming an intermediate layer comprising intermediate ceramic particles at the interface between a first ceramic particle and a second ceramic particle (not shown). The intermediate ceramic particles may have an intermediate particle size defined by an intermediate PSD having an intermediate average, a intermediate median, and a intermediate mode. In one embodiment, at least one of the following is satisfied: (i) the intermediate average is between the first average and the second average, (ii) the intermediate median is between the first median and the second median, and (iii) the intermediate mode is between the first mode and the second mode. In one embodiment, multiple intermediate layers comprising intermediate ceramic particles may be formed at the interface between the first ceramic particle and the second ceramic particle. In one embodiment, one or more intermediate layers are formed at all interfaces between the first ceramic particle and the second ceramic particle. In one embodiment, in a direction passing through one or more intermediate layers, the intermediate particle size of the intermediate ceramic particles increases from a first particle size at the first ceramic particle to a second particle size at the second ceramic particle. The increase in the intermediate ceramic particle size may be gradual, discrete, or a combination thereof.

[0132] In the formation of having or not having one or more intermediate layers Figure 4 In an embodiment of the method for the fluid module, method 600 includes pressing first ceramic particles 120a, 120b, second ceramic particles 124a, 124b, and a positive channel mold 130 to form a pressed body (frame 646). Figure 7F To perform pressing, a piston or hammer 140 is inserted into the press housing 100, and a uniaxial force AF is applied from above to press the first and second ceramic particles and the internal positive channel mold 130 to form a pressed body. Figure 7F The force AF applied by the hammer 140 is configured to generate a pressure of approximately 30 to 40 MPa on the ceramic particle layer and the positive channel mold 130. The pressure may vary between embodiments depending on the material and size of the ceramic particles and the material of the positive channel mold. For example, the force AF may be configured to generate at least 28 MPa, at least 25 MPa, or even at least 20 MPa on the contents of the press housing 100. The force may also be configured to generate up to 42 MPa, up to 45 MPa, up to 50 MPa, up to 70 MPa, up to 80 MPa, or even up to 100 MPa on the contents of the press housing 100. During pressing, a reactive force or an equal reaction force AF (not shown) is provided at the plunger 110.

[0133] After pressing (box 646), the pressing body 150 is ejected from the press housing 100 to provide the green pressing fluid module. Figure 7GIn one embodiment, the pressed body 150 can be removed by applying a (small) force AF (not shown) to the piston 140 and by configuring the plunger 110 to move out of the press housing 100. The first ceramic particles, the second ceramic particles, and the positive channel mold 130 are compressed by approximately 30% to 60% during pressing. The positive channel mold 130 is surrounded by a first layer and a second layer of the first ceramic particles, which have been joined together during pressing to form the inner layer of the first zone 222g or the live fluid module. The base layer and the cover layer of the second ceramic particles form the outer layer of the second zone 226g or the live fluid module. The first ceramic particles, the second ceramic particles, and any intermediate ceramic particles are joined together during pressing to create a void-free interface. After pressing, one or more holes may be drilled to the main surface or sidewall / edge surface of the live fluid module to serve as a fluid interface.

[0134] If the positive channel mold 130 is to be formed by coating surrounded by the first ceramic particles 120 Figure 5 For a fluid module, method 600 includes applying first ceramic particles to the surface of a positive channel mold 130 to form a surface coating 128 thereon (box 648). The first ceramic particles can be applied to the surface of the positive channel mold via one or more methods, which can be performed individually or in combination. In one method, the first ceramic particles are applied by a washing method, which includes immersing the positive channel mold in a ceramic slurry or paste in which the first ceramic particles are dispersed. In another method, the first ceramic particles are applied via a spraying method, which includes spraying droplets containing first ceramic particles dispersed in a solvent suspension. In yet another method, the first ceramic particles are applied via a flocking method. The flocking method in the embodiments includes wetting the surface of the positive channel mold with a material used as an adhesive, and then exposing the wetted surface to a ceramic powder containing or composed of the first ceramic particles. In the embodiments, electrostatic forces can assist the flocking process. An overmolding process can also be used to apply ceramic powder with a liquid binder to the surface of the positive channel mold 130, wherein a portion of the liquid binder evaporates and / or cures to leave a layer of bonded ceramic powder.

[0135] In one embodiment, the first ceramic particles can be applied in a single application manner, such that the surface coating 128 has a single layer comprising the first ceramic particles. In another embodiment, the first ceramic particles can be applied in multiple separate application methods, such that the surface coating 128 has multiple continuous layers comprising the first ceramic particles. The single layer and / or continuous layers in the embodiments can have a total thickness of at least about 50 μm to about 500 μm. In another embodiment, the thickness of the surface coating 128 is configured to prevent second ceramic particles of a larger second particle size that separate from the surface of the positive channel mold 130 from passing through the single layer and / or continuous layers containing the first ceramic particles. In another embodiment, the total thickness of the single layer and / or continuous layers is at most about 10% to about 15% of the total thickness of all powders placed in the press housing.

[0136] Once the first ceramic particles are applied to the surface of the positive channel mold 130 to form a surface coating 128 (box 648), method 600 further includes positioning the coated positive channel mold 130 on a base layer including a first portion 124a of the second ceramic particles (box 652). Figure 8A and 8B In the implementation, the thickness of the base layer is configured to ensure proper vertical positioning of the positive channel mold 130 within the press housing 100. Next, method 600 includes covering the first portion 124a of the second ceramic particles and the positive channel mold 130, including the surface coating 128, with the second portion 124b of the second ceramic particles to form a covering layer (frame 656). Figure 8C ).

[0137] In one embodiment, the surface coating 128 including the first ceramic particles may comprise a layer of one or more intermediate ceramic particles applied between the first and second ceramic particles. The intermediate ceramic particles may have the features described above for forming... Figure 4 The features described in the aspects of the fluid module method 600, and / or the intermediate ceramic particles, may have additional or alternative features. In embodiments in which the surface coating 128 comprises layers of one or more intermediate particles, method 600 may further include modifying the material properties of each successive layer of intermediate ceramic particles to form a hierarchical or gradient interface between the first ceramic particles and the second ceramic particles.

[0138] The material properties may include the intermediate particle size of the intermediate ceramic particles, with the intermediate particle size increasing with each successive layer. For example, the intermediate particle size may increase from smaller diameter particles similar to the first particle size of the first ceramic particles near the surface of the positive channel mold 130 to larger diameter particles further away from the positive channel mold 130. The material properties may also include at least one component of a slurry or paste associated with the washing process, a solvent associated with the spraying process, an adhesive associated with the flocking process, and a binder for the intermediate ceramic particles associated with one or more successive layers.

[0139] In the implementation, prior to the addition of further layers and / or the positive channel mold 130, the corresponding layer of the second ceramic particles is made flat or otherwise smoothed. Any tool can be used to make the corresponding layer flat or smooth. Although the cross-section in the figure shows a solid line to delineate the boundary between the different layers of ceramic particles, it should be understood that when they are in contact with each other, the ceramic particles in the different layers are mixed to some extent, and in fact the boundary appears blurred at the particle level.

[0140] In the formation of having or not having one or more intermediate layers Figure 5 In an embodiment of the method for the fluid module, method 600 includes pressing second ceramic particles 124a, 124b and a positive channel mold 130 therearound, and a surface coating 128 including first ceramic particles to form a pressed body (frame 660). Figure 8D To perform pressing, a piston or hammer 140 is inserted into the press housing 100, and a uniaxial force AF is applied from above to press the second ceramic particles and the internal positive channel mold 130 to form a pressed body 151. The force AF applied by the hammer 140 is configured to generate a pressure of approximately 30 to 40 MPa on the ceramic particles and the coated positive channel mold 130. In embodiments, the pressure may vary depending on the material and particle size of the ceramic particles and the material of the positive channel mold, sometimes in the direction of higher pressure, as shown in the reference. Figure 7F As described. During compression, a reactive force or an equal reaction force AF (not shown) is provided at plunger 110.

[0141] After pressing (frame 660), the pressing body 151 is ejected from the press housing 100 to provide the raw pressing fluid module. Figure 8EIn one embodiment, the pressed body 151 can be removed by applying a (small) force AF (not shown) to the piston 140 and by configuring the plunger 110 to move out. The positive channel mold 130, the surface coating 128 comprising the first ceramic particles, and the second ceramic particles are compressed by approximately 30% to 60% during pressing. The surface coating 128 surrounding the positive channel mold 130 comprises a single layer and / or a continuous layer of the first ceramic particles, which are bonded together during pressing to form the first zone 322g or one or more contoured regions of the live fluid module. The first and second portions 124a, 124b of the second ceramic particles, corresponding to the base layer and the cover layer respectively, are bonded together during pressing to form the second zone 326g or the body of the live fluid module. The first ceramic particles, the second ceramic particles, and any intermediate ceramic particles are bonded together during pressing to create a void-free interface.

[0142] Now refer to Figures 9A to 9C Description for forming Figure 4 Ceramic fluid modules and Figure 5 Ceramic fluid module Figure 6 The common aspects of method 600. In an embodiment, the press bodies 150, 151 are now detached from the press housing 100 and can be machined at selected locations, for example by drilling, to form holes or fluid ports 160 extending from the outside of the press body 150 to the positive channel mold 130. Figure 9A In some embodiments, the hole may be additionally or alternatively formed using a mold, the mold comprising the shape of the hole or fluid port as part of the mold. In some embodiments, drilling may be delayed and used as part of a demolding step, as described below.

[0143] Next, method 600 includes removing the positive channel mold 130 by heating the press bodies 150, 151 (preferably at a relatively high rate), causing the positive channel mold 130 to melt and be removed from the press bodies 150, 151 by flowing out of them (box 664). Figure 9B In one embodiment, removing the positive channel mold 130 (box 664) can be divided into two parts, wherein first the pressed bodies 150, 151 are heated, and then, separately, the material of the positive channel mold can flow out of the pressed bodies. In one embodiment, removing the positive channel mold (664) may include heating the pressed bodies 150, 151 to melt the positive channel mold 130, and then drilling holes or fluid ports to allow the mold material to flow out while the pressed bodies are still hot, thereby completing demolding. Heating may be performed under partial vacuum if necessary. Heating may optionally include additionally applying uniaxial pressure on the main surface, or applying isostatic pressure (e.g., 20 to 80 bar) on all surfaces to prevent the expansion of the mold material from causing the green pressed body to crack during melting.

[0144] Finally, method 600 includes debonding the pressed bodies 150, 151 to remove any binder from the ceramic particles, and then firing (sintering) the pressed bodies 150, 151 to densify and further solidify the pressed bodies into a structure including first regions 222, 322 and second regions 226, 326 (frame 668, ...). Figure 4 , 5 200 monomer ceramic bodies (and 9C).

[0145] The ceramic fluid module and its forming method disclosed herein include a tortuous fluid channel having an inner surface with reduced surface roughness compared to existing ceramic fluid modules. The surface roughness of the inner surface of the fluid channel may depend on several factors related to the materials and methods used to form the ceramic fluid module.

[0146] The hardness of the mold material forming the positive channel mold can affect the surface roughness of the fluid channels in a fluid module formed by pressing ceramic powder. During the pressing process, individual particles or grains of ceramic powder are compacted around the positive channel mold. The pressure of the pressing process can cause the ceramic powder particles to impact and / or be pressed into the surface of the positive channel mold. Greater impact / indentation of the positive channel mold results in a rougher inner surface of the fluid channel, while less impact / indentation results in a smoother inner surface of the fluid channel. If the positive channel mold is made of a softer material, such as a soft wax with a Shore D hardness of 20 to 30, the ceramic particles will cause noticeable indentations on the surface of the positive channel mold. If the positive channel mold is made of a harder material, such as a hard wax with a Shore D hardness of 40 to 50, the ceramic particles cannot be pressed into the surface of the positive channel mold, resulting in a smoother inner surface of the fluid channel. However, using a harder material can still present various processing challenges. To address these processing challenges, the positive channel mold used in the methods disclosed herein is formed from a mold material whose hardness is configured to resist indentations by ceramic particles, particularly first or fine ceramic particles, during pressing. In the implementation scheme, the mold material of the positive channel mold has a hardness in the range of about 20 to about 50 Shore D hardness, or even in the range of about 30 to about 40 Shore D hardness.

[0147] The mold material can be an organic material, such as an organic thermoplastic. The mold material may contain organic or inorganic particles suspended or otherwise distributed within the material as a means of reducing expansion during heating / melting. In embodiments, the mold material is ideally a relatively incompressible material—specifically, a material with low resilience after compression relative to the resilience of pressed ceramic or SiC powder. Mold materials loaded with particles exhibit lower resilience after compression. Mold materials capable of undergoing some degree of inelastic deformation under compression (e.g., materials with a high loss modulus) also naturally tend to have low resilience. For example, polymeric substances with little or no crosslinking and / or materials with some localized hardness or brittleness that allow for localized fracture or microfracture upon compression may exhibit low resilience. Useful mold materials may include waxes with suspended particles such as carbon and / or inorganic particles, rosin-containing waxes, high-modulus brittle thermoplastics, organic solids suspended in organic fats (e.g., cocoa powder in cocoa butter), or combinations thereof. Low-melting-point metal alloys can also be used as mold materials, especially alloys that have low or no expansion when melted.

[0148] The particle size of ceramic powder can affect the surface roughness of the inner surface of fluid channels in a fluid module formed from pressed ceramic powder. For the same channel die hardness (hard or soft), larger ceramic particles typically penetrate the surface of the channel die further during pressing compared to smaller ceramic particles. In some cases, the penetration depth of ceramic particles is directly related to the diameter of the ceramic particles. Given this correlation, reducing the size of ceramic particles is one mechanism for reducing the surface roughness of the inner surface of fluid channels in a fluid module formed from pressed ceramic powder. Some examples disclosed herein have shown that using ceramic powders including fine particles can produce fluid channels with smoother inner surfaces compared to coarse particles.

[0149] Compression pressure can affect the surface roughness of the inner surface of the fluid channels in a fluid module formed from compressed ceramic powder. Minimal compression pressure can be used to obtain a leak-free, high-density ceramic material after sintering. Using higher compression pressures increases the density of the ceramic material, but it also tends to further increase the indentation of the ceramic particles into the surface of the channel mold. Therefore, the surface roughness of the inner channel sidewalls is expected to increase with higher compression pressures. Given this correlation, it is generally preferable to compress the ceramic powder with the lowest possible compression pressure to achieve the smoothest possible inner surface of the fluid channels.

[0150] Example

[0151] The following examples include the results of experiments conducted to evaluate the formation of fluid channels with smooth internal surfaces using fine ceramic powders derived from different approaches described herein. Several different approaches for manufacturing fine SiC powders were evaluated, including sieving RTP SiC powder to obtain smaller SiC particles and grinding methods to reduce the PSD of RTP SiC powder. Furthermore, a layered approach for forming ceramic modules (see reference) was evaluated. Figure 4 Description) and coating method (reference) Figure 5 The surface roughness of the inner surface of the fluid channels in the sample (described). Although the following embodiments may refer to specific mold materials for forming the channels in the test sample, such references should not be construed as limiting the scope of this disclosure to those specific mold materials. For example, it should be understood that useful mold materials may include different types of waxes (e.g., red wax, stacking wax, beeswax, bay wax, retaining wax, rosin-containing wax, and cocoa chocolate wax) or different versions / formulations of the same type of wax (e.g., stacking waxes #4, #5, #6, and #444 from Universal Photonics).

[0152] Example 1

[0153] Test samples were fabricated by embedding wax rods into fine SiC powder, followed by pressing, dewaxing, and debonding. The debonded samples were cut to expose the channel sidewalls and then fired. After firing, the surface roughness of the channels was measured. Wax rods were fabricated by casting #444 stacked wax (Universal Photonics (Central Islip, NY, USA)) into a generally rectangular cuboid shape. The wax rods were sized to fit into a pressing mold with a measured diameter of approximately 2.25”. The pressing method involved placing the wax rod on a flat layer of SiC powder, covering it with another layer of the same SiC powder, and then pressing the contents into the mold. The mold contained a hammer capable of applying a maximum pressure of 11 tons (equivalent to 37 MPa on the contents of the mold) for one minute. The test sample was ejected from the mold by pushing the hammer through it.

[0154] After pressing, the test samples containing wax rods underwent the same rapid heating, debonding, cutting, and firing to ensure that the only variable in the experiment was the mechanism for obtaining or manufacturing the ceramic powder. The samples were then held at 150°C for one hour to melt the wax. After rapid heating, the samples were debonded in a pyrolyzer at 600°C for 2 hours in a nitrogen atmosphere. After debonding, the samples were cut to expose the internal channel surfaces. The cut portions were labeled “a” and “b” to track which channel surface was on top (“a”) and which was on the bottom (“b”) during pressing.

[0155] The surface roughness of the top and bottom channel surfaces was measured using a Keyence VHS-5000 digital microscope. Surface roughness measurements were accurate to approximately 1 μm because they were based on optical techniques that observed the focusing and defocusing of images in multiple z-stack images taken at different sample distances from the microscope objective. The surface roughness profile was created on a 2D curve, but surface roughness could be measured along any user-defined path across the 2D curve. The debonded cut sections were sintered for four hours in a Centorr Vacuum Industries graphite vacuum furnace under argon at a maximum temperature of 2100 °C. The surface roughness of the top and bottom channel surfaces was measured again using the VHS-5000 digital microscope for comparison.

[0156] Smooth channel sidewalls used for sieving RTP SiC powder

[0157] Commercially available RTP SiC powder (Superior Graphite 2500NDP) was sieved to provide a uniform distribution of fine and coarse RTP SiC powder. A single sieve was used to separate the commercially available RTP SiC powder into two groups of powders: fine SiC powder that fell through the sieve openings (referred to as the “negative” product) and coarse SiC powder that remained in the sieve (referred to as the “positive” product). In these experiments, three different sieves were used to produce six different powder compositions. The three sieves used were: (1) a #80 sieve, where the particle diameter of the product from the -80 sieve was <180 μm and the particle diameter of the product from the +80 sieve was ≥180 μm; (2) a #100 sieve, where the particle diameter of the product from the -100 sieve was <150 μm and the particle diameter of the product from the +100 sieve was ≥150 μm; and (3) a #120 sieve, where the particle diameter of the product from the -120 sieve was <125 μm and the particle diameter of the product from the +120 sieve was ≥125 μm.

[0158] Three 100g batches of commercially available ceramic powder were passed through the three types of sieves described above. Each sieve was vibrated on a vibrating table (at 50% setting) for fifteen minutes to accelerate powder flow through the sieve openings. The SiC powder remaining on the sieves and the powder that passed through the sieves were collected and weighed. The weight percentages corresponding to each sieve opening were as follows: (1) #80 sieve, 60 wt% of product from -80 sieve and 40 wt% of product from +80 sieve; (2) #100 sieve, 30 wt% of product from -100 sieve and 70 wt% of product from +100 sieve; and (3) #120 sieve, 20 wt% of product from -120 sieve and 80 wt% of product from +120 sieve. As expected, the weight percentage of the negative composition decreased with the increase of the number of sieve openings (corresponding to smaller sieve openings and smaller particles passing through the sieve openings).

[0159] Using the above six sieved powder compositions and commercially available SiC powder as a control, test samples with wax rods were pressed, dewaxed, debonded, cut, and fired. The channel surface roughness Ra measurement results were recorded in... Figure 10 The diagram shown illustrates this. The text along the x-axis corresponds to the positive or negative ("minus") sieve aperture product and its size. For example, Figure 10 The text “minus 125 micrometers” refers to the surface roughness of the channel formed by the -120 sieve product containing particles with a diameter of less than 125 μm. Figure 10 The results reported indicate a strong correlation between the reduction in large particles in SiC powder and the reduction in channel surface roughness Ra. For example, using fine particles (<125 μm particle diameter) from the -120 sieve product, the channel top surface roughness decreased from approximately 2.7 μm (based on measurements of channel surface roughness formed from unmodified commercially available RTP SiC powder in Table 1) to 1.85 μm, a reduction of 34%. Similarly, using fine particles from the -120 sieve product, the channel bottom surface roughness decreased from approximately 4 to 6 μm (based on measurements of channel surface roughness formed from unmodified commercially available RTP SiC powder in Table 1) to approximately 2 μm, a reduction of 50% to 66%.

[0160] Turbulent mixing and milling of RTP SiC powder to create smooth channel sidewalls

[0161] Samples were prepared using fine SiC powder formed through a milling process to evaluate channel sidewall smoothness. Sample 1 contained fine SiC particles formed by turbulent mixing of an 85 / 15 powder mixture (85 wt% Superior Graphite 2500NDP RTP SiC powder and 15 wt% Superior Graphite 2500N SiC powder) with a mixing medium for three hours. Sample 3 contained fine SiC particles formed by ball milling Superior Graphite 2500NDP RTP SiC powder for 28 hours, followed by turbulent mixing with a medium for 2 hours. Two other samples were prepared as control samples. Samples 2A and 2B each contained Superior Graphite 2500NDP without ball milling or mixing. All four samples were pressed, dewaxed, debonded, cut, and fired. The samples were cut to expose the top and bottom channel surfaces.

[0162] Table 1 below provides measurements of channel roughness and density. Sample 1 has a high top channel surface roughness (16.6 μm) and a bottom channel surface roughness comparable to that of control sample 2A. Although the material of sample 1 may lack very fine particles, it is unclear why the top surface is so rough. Furthermore, the mixing method may have caused small particles to fuse together or fuse with larger particles. The lack of fine particles could explain why the top surface of the channel is rougher when SiC particles are deposited on it.

[0163] Table 1

[0164]

[0165] The surface roughness results for the top and bottom surfaces of Sample 3, expressed in Ra units, are both approximately 2 μm. For the top surface, the measured surface roughness is slightly improved compared to control samples 2A and 2B. Compared to control samples 2A and 2B, the bottom surface roughness of Sample 3 shows a significant improvement (reduction of 50% to 66%). Measurements of the channel surface roughness of the turbulently mixed and ball-milled samples indicate that ball-milled SiC powder is superior to the control samples, with Ra values ​​of approximately 2 μm for both the top and bottom channel surfaces. Experiments show that techniques for reducing SiC particle size can decrease channel surface roughness.

[0166] Example 2

[0167] Samples were fabricated to evaluate a layered sieving approach for SiC powder to reduce channel sidewall roughness (see reference). Figure 4 (Description). The layered sample was assembled in the following order: (1) bottom layer of coarse powder: approximately 30 g of +100 sieve SiC powder (>150 μm diameter); (2) first layer of fine powder: approximately 15 g of -100 sieve SiC powder (<150 μm); (3) wax rod formed by #444 stacked wax (Universal Photonics (Central Islip, NY, USA)); (4) second layer of fine powder: approximately 25 g of -100 sieve SiC powder (<150 μm); and (5) top layer of coarse powder: approximately 30 g of +100 sieve SiC powder (>150 μm).

[0168] The sample was then pressed (using the same pressing mold as in Example 1), dewaxed, and debonded. After debonding, the sample was sawn into five pieces to allow for the measurement of the surface roughness at the top and bottom of the channel. Figure 11A cross-section of the sample after debonding is shown. As shown, channel P is surrounded by fine SiC powder in the central layer 222, and coarse SiC powder layers 226a and 226b are arranged above and below the fine SiC powder layers, respectively. After debonding, no visible cracks are found along any boundary between the coarse and fine powder layers.

[0169] The samples were then fired. No cracks or separation of fine and coarse layers were observed after firing. The first row of Sample 2-1 in Table 2 below provides the measured values ​​of the surface roughness of the channel top and bottom. Based on the measurements of the channel surface roughness formed by unmodified commercially available RTP SiC powder in Table 1, the surface roughness of the channel top decreased from approximately 2.7 μm to 1.43 μm (a reduction of 47%), and the surface roughness of the channel bottom decreased from 4 to 6 μm to approximately 1.97 μm (a reduction of 51%–67%).

[0170] Table 2

[0171]

[0172] For comparison, the measured channel surface roughness of a single, non-layered sample made entirely of similar fine SiC powder (-100 mesh, particle diameter <150 μm) is shown in the second row of Table 2 for Sample 2-2. The measured channel top and bottom surface roughness of Sample 2-2 is very similar to the surface roughness observed using sieved SiC powder layers as confirmed by Sample 2-1.

[0173] The porosity of the outer surface of the layered sample was evaluated after firing. The outer surface of the +100 sieve, as the fired surface, passed the leakage test, with ΔP = -0.02 bar within 30 minutes (where ΔP < -0.05 bar is considered passing). The channel sidewall surface formed using fine SiC powder also showed no leakage.

[0174] Example 3

[0175] Experiments were conducted to evaluate the SiC powder coating approach for reducing channel sidewall roughness (see reference). Figure 5 (Description). In particular, the experiment explored the dip-coating of fine SiC powder onto the surface of a channel mold. An ethanol-based slurry was developed using the following formulation: 80 wt% ethanol solvent, 4 wt% polymer binder, and 16 wt% raw material SiC powder (Superior Graphite 2500N).

[0176] Several channel molds were prepared using #444 stacking wax (Universal Photonics (Central Islip, NY, USA)) for dip-coating experiments. The channel molds contained different geometries, such as mixers and sheets (…). Figure 12The channel mold is immersed in SiC powder slurry and then allowed to air dry at room temperature. At least two dip-coating cycles are used to cover the channel mold. Generally, four dip-coating cycles are used to provide a thicker coating. Figure 12 In the diagram, the number of dip-coating cycles is listed below each channel mold sample. A potential advantage of the SiC powder coating approach is that, if the coating is applied in a sufficiently thick layer, it helps stabilize thin channel molds that might otherwise break during processing and / or insertion pressing.

[0177] Using commercially available RTP SiC powder (Superior Graphite 2500NDP RTP SiC powder), a dip-coated channel mold was pressed into a disc approximately 1.5” in diameter. A first layer or base layer of SiC powder was formed on the bottom of the pressing mold. The dip-coated channel mold was then placed on top of the SiC powder base layer. A second layer of SiC powder was then applied over the dip-coated channel mold, and the disc was pressed with sufficient force to generate a pressure of at least approximately 40 MPa. After pressing, the disc sample was debonded and then cut in half to expose the top and bottom surfaces of the internal channels. Figure 13 These samples demonstrate that a smooth channel surface layer can be formed using a dip-coating method.

[0178] Additional samples were prepared by dip-coating wax rods into a SiC slurry. The wax rods were sized to fit into a pressing mold with a measured diameter of approximately 2.25”. The pressing mold was used to press these samples into discs using commercially available RTP SiC powder. The wax rods used in these samples were only partially dipped into the SiC slurry so that each sample contained both coated and uncoated areas. This partial coverage allowed for direct comparison of the dip-coated and uncoated surfaces for visual inspection and surface roughness measurement. The samples were then debonded and fired.

[0179] Figure 14 and 15 The uncoated area of ​​one of the samples is shown. Figure 14 ) and coating area ( Figure 15 The surface profile measurements are shown. Note that the two surface profile plots are not shown at the same ordinate scale, but are divided into ordinate segments every 5 μm. Comparing the two profiles, the dip-coated surface is clearly smoother than the uncoated surface. The two plots were obtained along similar lengths of the surface (approximately 3.0 mm for the uncoated surface and approximately 2.6 mm for the dip-coated surface).

[0180] Although this disclosure has been illustrated and described in detail in the accompanying drawings and description above, the drawings and description above should be considered illustrative in nature and not limiting. It should be understood that only preferred embodiments are given, and protection is intended to be sought for all changes, modifications, and further embodiments falling within the spirit of this disclosure. While the performance of the flow reactor is one embodiment that can benefit from the use of a smoother channel surface, in other embodiments, increasing surface roughness using coarse particles may be preferred. For example, rough surfaces can be used to reduce heat transfer by forming a thin fluid insulating layer near the boundary surface, and rough surfaces can also be used to locally enhance heat transfer via nucleate boiling (the purpose of which is to extract heat from the substrate in the heat exchange channel). The proposed approach allows for free adjustment of the channel surface roughness along the channel path to optimize performance.

Claims

1. A method for forming a ceramic fluid module for a flow reactor, comprising: A first ceramic particle surrounds a positive channel mold, the positive channel mold defining a channel with a tortuous shape, the first ceramic particle having a first particle size defined by a first particle size distribution PSD having a first average value, a first median value and a first mode; The first ceramic particle and the positive channel mold are positioned between the second ceramic particle, the second ceramic particle having a second particle size defined by a second PSD having a second average value, a second median value and a second mode, wherein at least one of the following is satisfied: (i) the first average value is less than the second average value, (ii) the first median value is less than the second median value, and (iii) the first mode value is less than the second mode value; The first ceramic particles, the second ceramic particles, and the positive channel mold are pressed together to form a pressed body; Heating the pressing body to remove the positive channel mold; and The pressed body is sintered to form a high-density, closed-pore ceramic body having tortuous fluid channels extending therethrough.

2. The method of claim 1, wherein surrounding the positive channel mold with the first ceramic particles comprises: A first layer is formed having a first portion of the first ceramic particles. Position the positive channel mold on the first layer, and A second layer is formed on the first layer by covering the first portion of the first ceramic particle and the positive channel mold with the second portion of the first ceramic particle.

3. The method according to claim 2, wherein positioning the first ceramic particle and the positive channel mold between the second ceramic particle comprises: A base layer having a first portion of the second ceramic particles is formed, and a first layer of the first ceramic particles is formed on the base layer. A covering layer is formed on the second layer by covering the first ceramic particle and the positive channel mold therearound with the second portion of the second ceramic particle.

4. The method of claim 1, further comprising forming an intermediate layer at the interface between the first ceramic particle and the second ceramic particle, the intermediate layer comprising intermediate ceramic particles having an intermediate particle size defined by an intermediate PSD having an intermediate average, an intermediate median, and an intermediate mode, wherein at least one of the following is satisfied: (i) the intermediate average is between the first and second averages, (ii) the intermediate median is between the first and second medians, and (iii) the intermediate mode is between the first and second modes.

5. The method of claim 4, wherein the intermediate ceramic particles increase in size in the direction from the first ceramic particle through the intermediate layer to the second ceramic particle.

6. The method of claim 1, wherein the first ceramic particle has a thickness of 40% to 60% of the total thickness of the first and second ceramic particles before pressing.

7. The method of claim 3, wherein the base layer and the cover layer each have a thickness of 15% to 30% of the total thickness relative to the total thickness of the first and second ceramic particles before pressing, and the first layer has a thickness of 5% to 20% of the total thickness.

8. The method of claim 1, wherein one or more of the following conditions are met: Surrounding the positive channel mold with the first ceramic particles includes applying the first ceramic particles to the surface of the positive channel mold to form a surface coating thereon; and Applying the first ceramic particles to the surface of the positive channel mold includes one or more of washing, spraying, and flocking, thereby forming the surface coating.

9. The method of claim 8, wherein one or more of the first ceramic particles and intermediate ceramic particles are applied separately, such that the surface coating has multiple continuous layers.

10. The method of claim 9, further comprising modifying the properties of the material of each successive layer to form a gradient interface between the first ceramic particles and the second ceramic particles, wherein the properties include one or more of the following: The particle size of the intermediate ceramic particles, the particle size increasing with each successive layer, and The continuous layer comprises at least one of one or more components of ceramic slurry, ceramic powder, solvent, binder and adhesive.

11. The method of claim 1, wherein the first particle size is at least 1 µm and the second particle size is at most 250 µm.

12. The method of claim 1, further comprising processing common ceramic particles to provide the first ceramic particle or providing the first ceramic particle and the second ceramic particle.

13. The method of claim 12, wherein one or more of the following conditions are met: Processing the shared ceramic particles includes sieving the shared ceramic particles using a sieve with mesh sizes, the sieve being configured to separate the shared ceramic particles into first ceramic particles and second ceramic particles. Essentially all of the first ceramic particles have a first particle size smaller than the sieve aperture size, and essentially all of the second ceramic particles have a second particle size greater than or equal to the sieve aperture size. The sieve aperture size is selected to separate a sufficient amount of the first ceramic particles from the common ceramic particles.

14. The method of claim 13, wherein one or more of the following conditions are met: The common ceramic particles have a common particle size defined by a common PSD before sieving, and the sieve aperture size is a value within a range centered on one or more of the average, median, and mode of the common PSD. The sieve aperture size is a value in the range of 70µm to 210µm.

15. The method of claim 12, wherein one or more of the following conditions are met: Processing the common ceramic particles includes mixing uncoated ceramic particles with the common ceramic particles to provide the first ceramic particles, the common ceramic particles having a common particle size defined by a common PSD, and the uncoated ceramic particles having an uncoated particle size configured to reduce one or more of the mean, median, and mode of the common PSD by mixing. The first ceramic particles include: The aforementioned common ceramic particles comprise 50 wt% to 85 wt%, and 15wt% to 50wt% of the uncoated ceramic particles, and The uncoated particle size is defined by an uncoated PSD having a median value of 0.7 µm.

16. The method of claim 12, wherein one or more of the following conditions are met: Processing the common ceramic particles includes grinding the common ceramic particles to provide the first ceramic particles, and Grinding the common ceramic particles includes subjecting the common ceramic particles to turbulent mixing in the presence and / or absence of a spherical medium, and The method further includes mixing uncoated ceramic particles with the common ceramic particles before and / or after grinding to provide the first ceramic particles.

17. The method according to any one of claims 1-16, wherein the first PSD and the second PSD are symmetrical or asymmetrical.

18. The method according to any one of claims 1-16, wherein one of the first PSD and the second PSD is symmetrical, and the other of the first PSD and the second PSD is asymmetrical.

19. The method of claim 1, wherein the difference between the first average and the second average, the first median and the second median and / or the first mode and the second mode is at least 10µm.

20. The method of claim 1, wherein the positive channel mold comprises a mold material that is meltable, sublimable, or otherwise thermally removable, the mold material having a hardness configured to resist indentations from the first ceramic particles during pressing.

21. The method of claim 1, wherein pressing the first ceramic particles, the second ceramic particles, and the positive channel mold comprises a pressing pressure in the range of 30 to 80 MPa.

22. A fluid module comprising: A monolithic closed-pore ceramic body, the monolithic closed-pore ceramic body having a first region and a second region, the first region being disposed between the second region, the first region and the second region differing in terms of common properties of the ceramic material of the ceramic body; and A tortuous fluid channel extends through the ceramic body and is surrounded by the first region, such that the tortuous fluid channel is completely separated from the second region, and the tortuous fluid channel has an inner surface with a surface roughness of less than or equal to 5µm Ra.

23. The fluid module of claim 22, wherein the surface roughness is in the range of 0.1 to 5 µm Ra.

24. The fluid module of claim 22, wherein the ceramic material of the ceramic body has a density of at least 97% of the theoretical maximum density of the ceramic material.

25. The fluid module of claim 22, wherein the common property is density, and a first density of the first region is greater than a second density of the second region.

26. The fluid module of claim 22, wherein the ceramic material of the ceramic body has a closed-porosity of less than 3%.

27. The fluid module of claim 22, wherein the common property is closed-pore porosity, and the first closed-pore porosity of the first region is less than the second closed-pore porosity of the second region.

28. The fluid module of claim 22, wherein the common attribute is average particle size, and the first average particle size of the first region is less than the second average particle size of the second region.

29. The fluid module of claim 22, wherein the second region comprises at least two outer layers and the first region comprises an inner layer disposed between the at least two outer layers, and wherein the at least two outer layers and the inner layer are planar layers disposed between the main surface of the fluid module.

30. The fluid module of claim 22, wherein the first region has a substantially uniform thickness extending substantially vertically from the inner surface of the tortuous fluid channel.

31. The fluid module of claim 30, wherein the thickness of the first region is in the range of 50µm to 500µm.

32. The fluid module of claim 22, wherein at least one boundary between the first region and the second region comprises the ceramic material, and wherein the value of a common property of the at least one boundary is between the value of the common property of the first region and the value of the common property of the second region.

33. The fluid module of claim 32, wherein the at least one interface comprises a plurality of interfaces, and the value of a common attribute of each interface is between the value of the common attribute of the first region and the value of the common attribute of the second region.

34. The fluid module of claim 33, wherein the common property of at least one interface and / or all interfaces gradually transitions between the common property of the first region and the common property of the second region.

35. The fluid module according to any one of claims 22-34, wherein the inner surface of the tortuous fluid channel includes a bottom plate and a top plate separated by a height h and two opposing sidewalls connecting the bottom plate and the top plate, the sidewalls being separated by a width W measured at a location perpendicular to the height h and corresponding to half of the height h, wherein the height h of the tortuous fluid channel is in the range of 0.1 to 20 mm.

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