Systems and methods for sintering microspheres

Abstract

A method including providing a mixture including a plurality of microspheres; providing a mold, wherein the mold defines a desired shape; positioning the mixture within the mold; heating the mold to a softening temperature, wherein the softening temperature is a temperature that is sufficient to soften the plurality of microspheres without melting the plurality of microspheres; maintaining the mold at the softening temperature for a sufficient time for the plurality of microspheres to sinter to one another, thereby producing a sintered microsphere structure, wherein the sintered microsphere structure includes the plurality of microspheres, and wherein the sintered microsphere structure has the desired shape.

Description

SYSTEMS AND METHODS FOR SINTERING MICROSPHERESCross-Reference

[0001] This is an international (PCT) patent application relating to and claiming the benefit of commonly-owned U.S. Provisional Patent Application No. 63 / 511 ,871 , filed on July 4, 2023 and entitled “SYSTEMS AND METHODS FOR SINTERING MICROSPHERES,” the contents of which are incorporated herein by reference in their entirety.Field of the Invention

[0002] The exemplary embodiments relate generally to methods and systems for joining microspheres to one another. More particularly, the exemplary embodiments relate to methods and systems for joining microspheres to one another without the use of a binder.Background

[0003] Microspheres, such as those made of glass, plastic, and perlite have been used as lightweight fillers for various composite materials and can be added to base components, such as cements, plastics, and other common materials up to a certain critical amount. Materials composed of a majority of microspheres have also been created using various binders. However, binders have drawbacks such as cost, poor fire performance, and susceptibility to mold.Summary

[0004] In some embodiments, a method includes providing a mixture including a plurality of microspheres; providing a mold, wherein the mold defines a desired shape; positioning the mixture within the mold; heating the mold to a softening temperature, whereinthe softening temperature is a temperature that is sufficient to soften the plurality of microspheres without melting the plurality of microspheres; maintaining the mold at the softening temperature for a sufficient time for the plurality of microspheres to sinter to one another, thereby producing a sintered microsphere structure, wherein the sintered microsphere structure includes the plurality of microspheres, and wherein the sintered microsphere structure has the desired shape.

[0005] In some embodiments, the microspheres include expanded perlite. In some embodiments, the softening temperature is in a range of from 800 degrees Celsius to 1,600 degrees Celsius. In some embodiments, the softening temperature is in a range of from 850 degrees Celsius to 950 degrees Celsius.

[0006] In some embodiments, the microspheres include glass. In some embodiments, the softening temperate is in a range of from 500 degrees Celsius to 850 degrees Celsius.

[0007] In some embodiments, the microspheres include ceramic. In some embodiments, the softening temperature is in a range of from 900 degrees Celsius to 1,800 degrees Celsius.

[0008] In some embodiments, the mold includes a material having sufficient release properties to allow the sintered microsphere structure to be removed from the mold without breaking.

[0009] In some embodiments, the heating the mold to the softening temperature includes operating a sintering furnace to heat the mold to the softening temperature. In some embodiments, the mold is a part of the sintering furnace. In some embodiments, the mold is separate from the sintering furnace. In some embodiments, the method also includes preheating the sintering furnace; and placing the mold and the mixture within the furnace afterthe step of preheating the sintering furnace to thereby perform the step of heating the mold to the softening temperature. In some embodiments, the method also includes placing the mold and the mixture within the sintering furnace; and heating the sintering furnace while the mold and the plurality of microspheres are within the sintering furnace to thereby perform the step of heating the mold to the desired temperature.

[0010] In some embodiments, the method also includes applying a pressure to the mold during the step of maintaining the mold at the softening temperature. In some embodiments, the pressure is in a range of from 1 pound per square inch to a crush strength of the plurality of microspheres. In some embodiments, n the pressure is selected to control a porosity of the sintered microsphere structure.

[0011] In some embodiments, the mixture includes a plurality of solid particles.

[0012] In some embodiments, the mixture includes a further plurality of microspheres, and the further plurality of microspheres has a higher density than the plurality of microspheres.

[0013] In some embodiments, the sintered microsphere structure is a first layer, and the method also includes: positioning a further plurality of microspheres on the first layer; heating the further plurality of microspheres to a further softening temperature, wherein the further softening temperature is a temperature that is sufficient to soften the further plurality of microspheres without melting the further plurality of microspheres; and maintaining the further plurality of microspheres at the further softening temperature for a further sufficient time for the further plurality of microspheres to sinter to one another and to the first layer, thereby producing a second layer.Brief Description of the Drawings

[0014] Figure 1 shows a porous structure formed by sintering microspheres under the application of heat and low pressure or no pressure.

[0015] Figure 2 shows a generally non-porous structure formed by sintering microspheres under the application of heat and pressure.

[0016] Figure 3 shows a first layer formed by sintering microspheres under the application of heat with loose microspheres positioned on the first layer.

[0017] Figure 4 shows a sintered microsphere structure formed by sintering the loose microspheres and the first layer shown in Figure 3 together.

[0018] Figure 5 shows a top view of expanded perlite microspheres within a mold during an example sintering process.

[0019] Figure 6 shows a perspective view of the expanded perlite microspheres within the mold shown in Figure 5.

[0020] Figure 7 shows the expanded perlite microspheres within the mold as shown in Figures 5 and 6, positioned within a furnace during a heating process to sinter the expanded perlite microspheres.

[0021] Figure 8 shows the mold as shown in Figures 5 and 6 following removal from the mold as shown in Figure 7, showing the result of sintering to form a composite structure.

[0022] Figure 9 shows the mold and the composite structure as shown in Figure 6 during a cooling process.Detailed Description

[0023] Among those benefits and improvements that have been disclosed, other obj ects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying figures. Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely illustrative of the invention that may be embodied in various forms. In addition, each of the examples given in connection with the various embodiments of the invention which are intended to be illustrative, and not restrictive.

[0024] Throughout the specification and claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise. The phrases "in one embodiment," “in an embodiment,” and "in some embodiments" as used herein do not necessarily refer to the same embodiment(s), though it may. Furthermore, the phrases "in another embodiment" and "in some other embodiments" as used herein do not necessarily refer to a different embodiment, although it may. Thus, as described below, various embodiments of the invention may be readily combined, without departing from the scope or spirit of the invention.

[0025] As used herein, the term "based on" is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In addition, throughout the specification, the meaning of "a," "an," and "the" include plural references. The meaning of "in" includes "in" and "on." Ranges discussed herein are inclusive (e.g., a range of “between 0 and 2” includes the values 0 and 2 as well as all values therebetween).

[0026] As used herein, the term “microsphere” refers to a generally spherical particulate having a hollow void, a closed surface, and a size in a range of from 1 micron to 5 millimeters. As used herein, a microsphere may be single-celled or may include multiple cellswithin a single particle. Exemplary embodiments will be described herein with specific reference to expanded perlite microspheres, but the principles embodied by the exemplary embodiments are also applicable to microspheres of other materials.

[0027] The exemplary embodiments relate to systems and methods for sintering microspheres together to form a connected structure composed of the microspheres. In some embodiments, a method includes providing a plurality of microspheres. In some embodiments, the microspheres are formed from expanded perlite. In some embodiments, the microspheres are formed from glass. In some embodiments, the microspheres are formed from a ceramic. In some embodiments, the microspheres are provided in a sufficient quantity to produce a desired finished structure.

[0028] In some embodiments, the method includes providing the microspheres as feedstock to a sintering furnace. In some embodiments, additional materials are provided to the sintering furnace together with the microspheres. In some embodiments, the additional materials include solid particles and / or reinforcing fibers, such as glass fibers or mineral fibers.

[0029] In some embodiments, the sintering furnace includes a mold defines a desired shape for thereby forming the microspheres into a sintered product having the desired shape. In some embodiments, the mold is a separate element, and the microspheres are positioned in the mold prior to positioning the mold within the furnace (e.g., the furnace is preheated prior to placing the mold and the microspheres into the furnace), or after positioning the mold within the furnace. In some embodiments, the mold has sufficient release properties (e.g., flexibility, resistance to adhesion, etc.) to allow for release of a sintered composite formed from microspheres (e.g., having the crush strength of microspheres, such as a crush strength on the order of less than 2,000 psi for expanded perlite microspheres) without breakage after sintering. In some embodiments, the sintering furnace includes a heating element (e.g., a gas or electricheating element) operable to heat the microspheres to a desired softening temperature. In some embodiments, the softening temperature is a temperature that is sufficient to soften, but not melt, the microspheres (e.g., for expanded perlite microspheres, a temperature in range of from 850 to 1,600 degrees Celsius depending on the specific perlite ore; for glass microspheres, a temperature in a range of from 500 to 850 degrees Celsius depending on the specific type of glass; for ceramic microspheres, a temperature in a range of from 900 to 1 ,800 degrees Celsius). In some embodiments, the sintering furnace includes a pressure-controlled interior region that is operable to provide a suitable pressure to facilitate sintering of the microspheres (e.g., in a range of from 1 psi to 60,000 psi depending on the type of microspheres) In some embodiments, the sintering furnace is operable to provide no additional pressure (e.g., sintering occurs at atmospheric pressure).

[0030] In some embodiments, the method includes configuring the sintering furnace to operate at a suitable temperature. In some embodiments, the temperature is a temperature that causes the microspheres to soften and transition into a plastic state without entering a liquid state, in order that the microspheres are able to bond to adjacent microspheres while retaining their general shape. In some embodiments in which the microspheres are expanded perlite microspheres, the temperature depends on the specific perlite ore being used. In some embodiments in which the microspheres are expanded perlite microspheres, the temperature is in a range of 850 to 950 degrees Celsius. In some embodiments in which the microspheres are expanded perlite microspheres, the temperature is in a range of 800 to 1,600 degrees Celsius.

[0031] In some embodiments, the method includes configuring the sintering furnace to apply a suitable pressure (e.g., an additional applied pressure above atmospheric pressure). In some embodiments, the pressure depends on the specific material of the microspheres. In some embodiments, increasing pressure has the effect of lowering the temperature that is requiredfor the microspheres to bond to one another. In some embodiments, a minimum sintering pressure in the range of 1 to 20 pounds per square inch (“PSI”) has the effect of accelerating the process of bonding microspheres to one another. In some embodiments, a maximum sintering pressure (e.g., to prevent the microspheres from crushing) is less than the crush strength of the microspheres, which is less than 5,000 PSI for perlite microspheres, less than 10,000 PSI for glass microspheres, and less than 60,000 PSI for ceramic microspheres. In some embodiments, the pressure is configured to provide a desired porosity between the microspheres (e.g., in a range of between 0% and 50%) and to maintain hollow chambers within the microspheres. In some embodiments, the pressure is configured to vary the ratio of the bond area. In some embodiments, the pressure is configured to apply the microspheres as a base or core for other face materials such as a paper, a foil, a veneer, a laminate, a polymer, etc.

[0032] In some embodiments, a method includes operating the sintering furnace for a sufficient time to sinter the microspheres (e.g., cause the microspheres to bond and adhere to one another) to thereby form a composite structure. In some embodiments, the sufficient time depends on other parameters of the process as described above (e.g., material and size of the microspheres, additional materials included with the microspheres, temperature, pressure, etc.). In some embodiments, the sufficient time is in a range of from one second to 120 minutes. In some embodiments, the sufficient time depends on the desired thickness of the composite structure. For example, a composite structure that is relatively thin, such as 1 / 8 inch in thickness, may require a relatively short heating time, such as on the order of a few seconds, for the entire structure to heat sufficiently to sinter the microspheres together, while a composite structure that is relatively thick, such as several inches thick, may require a relatively long heating time, such as on the order of tens of minutes, for the entire structure to heat sufficiently to sinter the microspheres together.

[0033] In some embodiments, the method includes removing the composite structure from the sintering furnace. Figure 1 shows a porous structure formed by sintering microspheres (e.g., perlite microspheres) under the application of low pressure or no pressure. Figure 2 shows a generally non-porous structure formed by sintering microspheres (e.g., perlite microspheres) under the application of pressure. The specific shapes of the structures shown in Figures 1 and 2 are only exemplary, and the process as described herein is equally applicable to sinter microspheres to produce a composite structure of any number of other shapes. In some embodiments, the composite structure formed through the sintering process as described herein is a final product with little or no further machining required before use. In some embodiments, the sintering process described above does not involve use of a binder. In some embodiments, the composite structure formed through the sintering process as described above does not include a binder.

[0034] Exemplary embodiments are described herein with reference to a “sintering furnace”. However, the exemplary methods are not limited to being performed through the use of apparatuses that are specifically manufactured for the purpose of being used as sintering furnaces. In other embodiments, any other type of oven or heating device may be used for the application of heat to accomplish sintering in the manner described herein. In various embodiments, this may involve application of heat by convection, by radiation, or by direct heating sources such as lasers.

[0035] In some embodiments, a composite structure formed from microspheres in accordance with the exemplary embodiments described herein may have their mechanical properties controlled by varying the parameters of the sintering process (e.g., by varying the properties of the microspheres that are used, such as the particle size, distribution, and / or crush strength; by varying the temperature; and / or by varying the pressure). In some embodiments,such properties may be controlled in order to make such composite structures suitable for use as building materials. For example, such properties may include, but are not limited to, screw reception, nail pull strength, resiliency, and flexibility.

[0036] In some embodiments, the crush strength of a certain ratio of microspheres used in the formation of a composite may be controlled, e.g., reduced. In some embodiments, such microspheres having a lower crush strength fracture first when an external flexural force is applied to a composite structure (e.g., a wallboard) formed by sintering a mixture of microspheres having varying properties. In some embodiments, such a composite structure (e.g., a wallboard) will experience microfractures evenly across the composite structure, rather than experiencing larger continuous fractures, thereby causing the composite structure to be both durable and semi-flexible. In some embodiments, the properties of the microfractures (e.g., size, location, conditions under which the microfractures form) are further controlled by the addition of reinforcing fibers, such as glass fibers or mineral fibers, to the composite structure by inclusion with the microspheres prior to sintering.

[0037] In some embodiments, the mixture of materials used in a sintering process as described above (e.g., in addition to the types of microspheres described above) includes solid particles and / or higher-density microspheres. In some embodiments, inclusion of such materials with microspheres alters (e.g., increases) the overall density of the composite structure, thereby improving sound attenuation.

[0038] In some embodiments, the mixture of materials used in a sintering process as described above (e.g., in addition to the types of microspheres described above) includes lower- density microspheres. In some embodiments, composite structures made in such a manner are suitable for use in ultra-lightweight products that do not require high strength, or are reinforcedadditional materials such as glass or mineral fibers and / or facing materials such as paper, wood veneer, foil, polymers, and resins.

[0039] In some embodiments, the size of the microspheres used in a sintering process as described above is altered to thereby control properties of a composite structure formed by sintering as described herein. In some embodiments, such properties include, but are not limited to, weight, strength, sound attenuation, visual effect, workability, machinability, and handling.

[0040] In some embodiments, a sintering process includes forming a sintered microsphere structure by sintering multiple layers together to build up a total thickness of the sintered microsphere structure. For example, if the desired total thickness of the sintered microsphere structure is 1 / 2 inch, a process may include sintering a first layer that is 1 / 8 inch thick, then sintering subsequent layers that are each 1 / 8 inch thick onto the previously sintered structure until the desired total thickness is reached. Figures 3 and 4 show a structure during an exemplary sintering process involving building up multiple sintered layers to form a sintered microsphere structure. In Figure 3, a first layer (shown in a darker gray) has already been sintered to form a first layer of a sintered microsphere structure having a first thickness, and a second layer of loose microspheres (shown in a lighter gray) has been positioned on the first layer to be sintered to the first layer. In some embodiments, when a subsequent layer is to be sintered to an existing sintered microsphere structure, heat is applied from the direction of the loose microspheres toward the already sintered material (e.g., in the direction as denoted by arrows in Figure 3) in order that the loose microspheres receive more energy than the already sintered material. Figure 4 shows a sintered microsphere structure produced by sintering a subsequent layer onto an existing first sintered layer. As discussed above, heat may be applied by convection, by radiation, or by a direct heating source such as a laser. For example, in someembodiments, a heating source such as a laser may be used to apply heat only at certain locations within a subsequent layer (e.g., the layer shown in lighter gray in Figure 3) to increase the overall thickness only in some locations. In some embodiments in which each layer has a relatively low thickness, such as less than an inch, the time to sinter each layer may be relatively low, such as less than one minute.

[0041] In some embodiments, a product incorporating a sintered microsphere structure as described above is suitable for use in building materials. In some embodiments, a building material incorporating a sintered microsphere structure as described above provides advantageous properties such as light weight, sound attenuation, high strength, high strength in comparison to weight, superior moisture resistance, and / or superior fire resistance.

[0042] In some embodiments, a product incorporating a sintered microsphere structure as described above is suitable for use in structural panels. In some embodiments, a structural panel incorporating a sintered microsphere structure as described above is suitable for use in an application where light weight is advantageous, such as in marine, aerospace, and automotive applications.

[0043] In some embodiments, a product incorporating a sintered microsphere structure as described above is suitable for use as an insulation product. In some embodiments, an insulation product incorporating a sintered microsphere structure as described above provides a high degree of thermal insulation and is suitable for use in insulation of piping, construction, cryogenic applications, etc.

[0044] In some embodiments, a product incorporating a sintered microsphere structure as described above is suitable for use in furniture. In some embodiments, a furniture product incorporating a sintered microsphere structure as described above provides advantageous properties such as workability, high strength and light weight.Example

[0045] An example of sintering microspheres was performed as described below. A rectangular metal mold was created with a base plate and four sides of 1 / 2 inch square bar. The mold was lined with fine quartz sand as a release agent (i.e., to facilitate release of the sintered microsphere composite from the mold). The mold was then filled with spherical expanded perlite microspheres. Figures 5 and 6 show a top view and a perspective view, respectively, of the expanded perlite microspheres within the mold. Following filling, the mold was screeded at the top (i.e., to the side of the microspheres opposite the base plate).

[0046] The mold containing the expanded perlite microspheres was then placed in a furnace that was programmed to heat to 2,000 degrees Fahrenheit (i.e., about 1,093 degrees Celsius) over a 30-minute period. Figure 7 shows the mold within the furnace halfway (e.g., about 15 minutes) through the sintering process.

[0047] Following the heating period, the mold was removed from the furnace. Figure 8 shows the mold immediately following removal from the furnace. After removal from the furnace, the example composite structure formed by sintering expanded perlite microspheres was allowed to cool. Figure 9 shows the example composite structure within the mold during the cooling process. Following complete cooling, the example composite structure released from the mold. The composite released from the mold without significant difficulty, and formed a single rigid structure comprised of expanded perlite microspheres (e.g., similar to that shown in Figure 1) following removal from the mold.

[0048] Many modifications may become apparent to those of ordinary skill in the art, including that various embodiments of the inventive methodologies, the inventive systems, and the inventive devices described herein can be utilized in any combination with each other.Further still, the various steps may be carried out in any desired order (and any desired steps may be added and / or any undesired steps in a particular embodiment may be eliminated).

[0049] While a number of embodiments of the present invention have been described, it is understood that these embodiments are illustrative only, and not restrictive, and that many modifications may become apparent to those of ordinary skill in the art. For example, any dimensions discussed herein are provided as examples only, and are intended to be illustrative and not restrictive.

Claims

ClaimsWhat is claimed is:

1. A method, comprising: providing a mixture comprising a plurality of microspheres; providing a mold, wherein the mold defines a desired shape; positioning the mixture within the mold; heating the mold to a softening temperature, wherein the softening temperature is a temperature that is sufficient to soften the plurality of microspheres without melting the plurality of microspheres; maintaining the mold at the softening temperature for a sufficient time for the plurality of microspheres to sinter to one another, thereby producing a sintered microsphere structure, wherein the sintered microsphere structure comprises the plurality of microspheres, and wherein the sintered microsphere structure has the desired shape.

2. The method of claim 1, wherein the microspheres comprise expanded perlite.

3. The method of claim 2, wherein the softening temperature is in a range of from 800 degrees Celsius to 1,600 degrees Celsius.

4. The method of claim 3, wherein the softening temperature is in a range of from 850 degrees Celsius to 950 degrees Celsius.

5. The method of claim 1, wherein the microspheres comprise glass.

6. The method of claim 5, wherein the softening temperature is in a range of from 500 degrees Celsius to 850 degrees Celsius.

7. The method of claim 1, wherein the microspheres comprise ceramic.

8. The method of claim 7, wherein the softening temperature is in a range of from 900 degrees Celsius to 1,800 degrees Celsius.

9. The method of claim 1, wherein the mold comprises a material having sufficient release properties to allow the sintered microsphere structure to be removed from the mold without breaking.

10. The method of claim 1, wherein the heating the mold to the softening temperature comprises operating a sintering furnace to heat the mold to the softening temperature.

11. The method of claim 10, wherein the mold is a part of the sintering furnace.

12. The method of claim 10, wherein the mold is separate from the sintering furnace.

13. The method of claim 12, further comprising: preheating the sintering furnace; andplacing the mold and the mixture within the furnace after the step of preheating the sintering furnace to thereby perform the step of heating the mold to the softening temperature.

14. The method of claim 12, further comprising: placing the mold and the mixture within the sintering furnace; and heating the sintering furnace while the mold and the plurality of microspheres are within the sintering furnace to thereby perform the step of heating the mold to the desired temperature.

15. The method of claim 1, further comprising applying a pressure to the mold during the step of maintaining the mold at the softening temperature.

16. The method of claim 15, wherein the pressure is in a range of from 1 pound per square inch to a crush strength of the plurality of microspheres.

17. The method of claim 15, wherein the pressure is selected to control a porosity of the sintered microsphere structure.

18. The method of claim 1, wherein the mixture comprises a plurality of solid particles.

19. The method of claim 1, wherein the mixture comprises a further plurality of microspheres, and wherein the further plurality of microspheres has a higher density than the plurality of microspheres.

0. The method of claim 1, wherein the sintered microsphere structure is a first layer, and wherein the method further comprises: positioning a further plurality of microspheres on the first layer; heating the further plurality of microspheres to a further softening temperature, wherein the further softening temperature is a temperature that is sufficient to soften the further plurality of microspheres without melting the further plurality of microspheres; and maintaining the further plurality of microspheres at the further softening temperature for a further sufficient time for the further plurality of microspheres to sinter to one another and to the first layer, thereby producing a second layer.

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