Dense glass-ceramic articles obtained by additive manufacturing of a glass frit

Abstract

Dense glass-ceramic articles obtained by additive manufacturing of a glass frit are provided. A method of forming a glass frit for additive manufacturing includes: providing a mixture having at least one silicon (Si) compound, at least one calcium (Ca) compound, and at least one zirconium (Zr) compound; melting the mixture at a temperature of at least 1400 °C; cooling the mixture to room temperature to obtain a glass frit, the glass frit comprising: at least 50 wt% SiO2, at least 30 wt% CaO, and at least 10 wt% ZrO2.

Description

Technical Field

[0001] This specification relates to additive manufacturing processes and articles produced by additive manufacturing processes. More specifically, this specification relates to the additive manufacturing of glass-ceramic objects from glass particles. Most specifically, this specification relates to the manufacture of dense, low-porosity glass-ceramic objects using additive manufacturing processes. Background Technology

[0002] Additive manufacturing uses solid freeform (SFF) technology to build or print physically three-dimensional (3D) objects based on computer-aided design (CAD) models. Additive manufacturing is attractive because it can produce objects with complex geometries with minimal setup time and without complex tooling. Additive manufacturing is effective with solid, liquid, and powder starting materials. Therefore, theoretically, if an object can be formed from materials that can be provided in solid, liquid, or powder form, then that object can be produced via additive manufacturing.

[0003] 3D glass-ceramic objects are currently manufactured through processes such as molding and pressing. These processes require specialized tools, such as molds, which makes it difficult to produce objects quickly. The more complex the geometry of an object, the longer and more expensive it is to produce it using traditional methods such as molding and pressing. Therefore, additive manufacturing is an attractive option for producing complex glass-ceramic objects in a shorter time.

[0004] Stereolithography (SLA), selective laser melting or sintering (SLM / SLS), and 3D printing (3DP) TM This is an example of SFF (Surface Finishing) technology used to construct 3D glass-ceramic objects. However, additive manufacturing processes using these technologies currently only provide glass-ceramic objects with high porosity. There is a current need for additive manufacturing processes capable of producing dense, low-porosity glass-ceramic objects. Summary of the Invention

[0005] A printing material and method for producing dense glass-ceramic articles by additive manufacturing are described. The printing material comprises a glass frit, which is densified to a degree very close to the theoretical density before significant crystallization occurs. Densification without interference from crystalline phases enables even greater densification. Further heating and sintering of the printing material induces crystallization to form glass-ceramic articles with low residual porosity and a density close to the theoretical density. The printing material and method enable the production of glass-ceramic articles with low residual porosity at moderate process temperatures.

[0006] This disclosure extends to:

[0007] A method for manufacturing glass-ceramic articles, the method comprising:

[0008] A 3D structure is constructed from a printing material comprising a glass frit and a binder composition, the binder composition comprising a curable resin, the construction comprising:

[0009] (i) Applying a layer of the printing material onto a substrate;

[0010] (ii) Printing the printing material layer to form a cross-section of the 3D structure, the printing including curing a selected portion of the printing material layer to form a printed area, the cross-section also including an unprinted area, the unprinted area comprising an uncured portion of the printing material layer; and

[0011] (iii) Repeatedly applying and printing the printing material layer to form multiple cross-sections of the 3D structure, each of the multiple cross-sections including a printed area and an unprinted area, each of the multiple cross-sections in

[0012] Formed on a previously formed section among the plurality of sections;

[0013] Clean the 3D structure to remove most of the uncured resin;

[0014] The 3D structure is debonded, which allows the cured resin and remaining uncured resin to be removed from the printed and unprinted areas of the 3D structure to leave holes in the remaining printed 3D structure.

[0015] The porous 3D structure is sintered to form a sintered 3D structure; and

[0016] A glass-ceramic article is formed from the sintered 3D structure, the glass-ceramic article having a theoretical density, the glass-ceramic article comprising glass and a crystalline phase, the glass-ceramic article comprising at least 1% by weight of the crystalline phase and having a density of at least 90% of the theoretical density.

[0017] This disclosure extends to:

[0018] A printing material for additive manufacturing, comprising:

[0019] Glass material having a crystallization temperature and a sintering temperature, wherein the crystallization temperature exceeds the sintering temperature, and the difference between the crystallization temperature and the sintering temperature is less than 300°C; and

[0020] An adhesive composition comprising a curable resin.

[0021] This disclosure extends to:

[0022] A printing material for additive manufacturing, comprising:

[0023] Glass material having a glass transition temperature and a crystallization temperature, wherein the crystallization temperature exceeds the glass transition temperature, and the difference between the crystallization temperature and the glass transition temperature is greater than 75°C; and

[0024] An adhesive composition comprising a curable resin.

[0025] In some embodiments, a method of forming a glass frit for additive manufacturing includes: providing a mixture comprising at least one silicon (Si) compound, at least one calcium (Ca) compound, and at least one zirconium (Zr) compound; melting the mixture at a temperature of at least 1400°C; and cooling the mixture to room temperature to obtain a glass frit comprising at least 50 wt% SiO2, at least 30 wt% CaO, and at least 10 wt% ZrO2. In one aspect, which can be combined with any other aspect or embodiment, the glass frit has a particle size distribution of less than 200 μm. In one aspect, which can be combined with any other aspect or embodiment, the glass frit has a particle size distribution of less than 50 μm.

[0026] In some embodiments, the glass frit used for additive manufacturing comprises at least 50 wt% SiO2, at least 30 wt% CaO, and at least 10 wt% ZrO2. In one aspect that can be combined with any other aspect or embodiment, the glass frit has a particle size distribution of less than 200 μm. In one aspect that can be combined with any other aspect or embodiment, the glass frit has a particle size distribution of less than 50 μm. In one aspect that can be combined with any other aspect or embodiment, the glass frit described herein comprises 50-70 wt% SiO2, 30-50 wt% CaO, and 10-20 wt% ZrO2.

[0027] In some embodiments, an additive manufacturing method includes: constructing a 3D structure from a printing material comprising a glass frit and a binder composition, the construction comprising: (a) applying a layer of the printing material to a substrate; (b) printing the printing material layer to form a cross section of the 3D structure, the printing comprising curing selected portions of the printing material layer to form a printed region, the cross section further comprising an unprinted region comprising an uncured portion of the printing material layer; and (c) repeatedly applying and printing the printing material layer to form a plurality of cross sections of the 3D structure, each of the plurality of cross sections comprising a printed region and an unprinted region, each of the plurality of cross sections being formed on a previously formed cross section of the plurality of cross sections; cleaning the 3D structure to remove most of the uncured resin; debonding the 3D structure to form a porous 3D structure; sintering the porous 3D structure to form a sintered 3D structure; and forming a glass-ceramic article from the sintered 3D structure.

[0028] In one aspect that can be combined with any other aspect or embodiment, the adhesive composition comprises a curable resin. In one aspect that can be combined with any other aspect or embodiment, the debonding step comprises: removing cured and remaining uncured resin from the printed and unprinted areas of the 3D structure to form pores in the remaining printed 3D structure. In one aspect that can be combined with any other aspect or embodiment, the glass-ceramic article: has a theoretical density, comprises a glassy phase and a crystalline phase, and comprises at least 1% by weight of the crystalline phase and has a density of at least 90% of the theoretical density. In one aspect that can be combined with any other aspect or embodiment, the crystalline phase comprises a wollastonite main crystalline phase. In one aspect that can be combined with any other aspect or embodiment, the glass-ceramic further comprises a Zr-containing crystalline phase. In one aspect that can be combined with any other aspect or embodiment, the Zr-containing crystalline phase comprises ZrO2 and / or Ca2Si4ZrO. 12 .

[0029] Other features and advantages are set forth in the following detailed description, some of which will be readily understood by those skilled in the art, or will be recognized by practicing the embodiments described in the written description and its claims and the accompanying drawings.

[0030] It should be understood that the general description above and the specific embodiments below are merely exemplary and are intended to provide a general overview or framework for understanding the nature and features of the claims.

[0031] The accompanying drawings, which are incorporated in and constitute a part of this specification, provide further understanding. The drawings are illustrative of selected aspects of this specification and, together with the description, explain the principles and operation of the methods, products, and components contained herein. The features shown in the drawings are illustrative of selected embodiments of this specification and are not necessarily depicted to scale. Attached Figure Description

[0032] Although the specification concludes with claims that specifically point out and expressly claim protection for the subject matter of this written specification, it is believed that this specification can be better understood from the following written description when taken in conjunction with the accompanying drawings, wherein:

[0033] Figure 1 The flowchart illustrates an additive manufacturing process for manufacturing glass-ceramic products, according to some embodiments.

[0034] Figure 2A-2C According to some implementation methods, a method for constructing 3D structures using printing materials is illustrated.

[0035] Figures 3A-3DAccording to some implementation methods, a method for constructing 3D structures using printing materials is illustrated.

[0036] Figures 4A-4D According to some implementation methods, a method for constructing 3D structures using printing materials is illustrated.

[0037] Figures 5A-5C According to some implementation methods, a method for constructing 3D structures using printing materials is illustrated.

[0038] Figure 6 According to some implementation methods, the particle size distribution of the glass frit is described.

[0039] Figure 7 According to some embodiments, a thermodynamic analysis (TMA) diagram of the glass charge is shown.

[0040] Figure 8 According to some embodiments, a differential scanning calorimetry (DSC) chart of the glass frit is shown.

[0041] Figure 9 According to some embodiments, TMA and DSC plots of the E31 glass composition at a heating rate of 10°C / min are shown.

[0042] Figure 10 According to some embodiments, the microstructures of E31 and E33 after ceramization at 950°C for 2 hours and at 1000°C for 2 hours are shown (both with a heating rate of 10°C / min; white bars represent 100 μm).

[0043] Figure 11 According to some embodiments, the results of the ring-on-ring (ROR) test for E31, E33 and Comparative Example E3 are shown.

[0044] The embodiments illustrated in the accompanying drawings are exemplary in nature and are not intended to limit the scope of the specific embodiments or the claims. Wherever possible, the same reference numerals are used in the drawings to denote the same or similar features. Detailed Implementation

[0045] This disclosure is provided as a teaching that enables implementation, and it will be more readily understood with reference to the following description, drawings, embodiments, and claims. Therefore, those skilled in the art will recognize and understand that various changes can be made to various aspects of the embodiments described herein while still obtaining beneficial effects. It will also be apparent that some desired benefits of this embodiment can be obtained by selecting some features without utilizing others. Therefore, those skilled in the art will recognize that many changes and modifications are possible, and in some cases even desirable, and are part of this disclosure. Therefore, it should be understood that this disclosure is not limited to the specific compositions, articles, apparatus, and methods disclosed, unless otherwise stated. It should also be understood that the terminology used herein is for the purpose of describing particular aspects only and is not restrictive.

[0046] The illustrative embodiments described herein will now be described in detail.

[0047] This disclosure provides an additive manufacturing method for producing glass-ceramic articles. The glass-ceramic articles have low porosity and a density very close to the theoretical density of glass-ceramic articles. The glass-ceramic articles are produced by an additive manufacturing method using a printing material. The printing material comprises a glass frit and a binder composition. The glass frit consists of glass particles. The binder composition comprises a resin. The resin comprises one or more compounds that can be cured to form oligomers or polymers, which act as a matrix to bind the glass particles of the glass frit. The resin is thermosetting or photosetting. The binder composition optionally includes a thermal initiator or a photoinitiator for promoting resin curing. The binder composition optionally includes one or more additives.

[0048] In additive manufacturing, a layer of printing material is applied to a surface and cured in selected areas. These selected areas are indicated by the design (shape, size, etc.) of the intended article of the additive manufacturing method. The selectively cured layer of printing material corresponds to a cross-section of the article. The portion of the cured layer of printing material is referred to herein as the printed area. In the printed area, the cured resin provides a rigid matrix that binds the glass frit in a relatively fixed state. In the unprinted area, the resin is in a less rigid, uncured state, and the glass frit is in a more mobile state. After selective curing of the printed material layer, a second layer of printing material is applied and selectively cured to provide a second cross-section of the article. The cured area of ​​the second cross-section is selected according to the design of the article. This process is repeated layer by layer to provide a three-dimensional (3D) glass structure comprising printed and unprinted areas. The 3D glass structure is subjected to a debonding process, in which the unprinted areas are removed, leaving pores surrounded by the printed areas. After debonding, the porous 3D glass structure is heated to sinter and to induce nucleation and growth of one or more crystalline phases in the sintered glass structure, thereby forming the desired glass-ceramic article.

[0049] Figure 1 An embodiment of an additive manufacturing process for producing glass-ceramic articles from glass frit is illustrated. In step 2, the glass frit is prepared. The preparation of the glass frit includes obtaining a glass frit having the composition required for the glass-ceramic article. The glass frit is formed by melting, soot deposition, vapor deposition, spray deposition, sol-gel, or other methods known in the art. In the case of melting, the glass is milled after cooling. In one embodiment, the preparation of the glass frit includes controlling the particle size distribution. The particle size distribution can be controlled, for example, by grinding, milling, inter-grinding, screening, and / or filtering the glass frit. The particle size distribution of the powder will be affected by the minimum feature size of the required pattern or shape in the printed 3D glass-ceramic article. In one embodiment, the maximum particle size of the glass frit is smaller than the minimum feature size to be printed with the design of the glass-ceramic article. The average particle size (by volume) should generally be in the submicron to micron range; for example, in the range of 1 μm–500 μm, or in the range of 1 μm–100 μm, or in the range of 1 μm–25 μm, or in the range of 5 μm–400 μm, or in the range of 5 μm–100 μm, or in the range of 5 μm–25 μm, or in the range of 10 μm–300 μm, or in the range of 10 μm–100 μm, or in the range of 10 μm–25 μm, or in the range of 25 μm–250 μm, or in the range of 5 μm–75 μm, or in the range of 10 μm–60 μm, or greater than 10 μm, or greater than 25 μm, or greater than 50 μm, or greater than 100 μm. If the average particle size distribution is small (e.g., below 10 μm), it is more difficult to obtain crack-free materials after sintering and crystallization.

[0050] As described above, the product of the printing process is a 3D glass structure with printed and unprinted areas. The unprinted areas are removed during a debinding process to form a porous 3D glass structure made of glass frit. In a heat treatment following printing and debinding, the porous glass structure is sintered and transformed into a glass-ceramic product. During sintering, the pores of the glass structure close, and the glass structure becomes denser. Transforming the sintered glass structure into a glass-ceramic product involves the nucleation and growth of one or more crystalline phases. The composition of the glass frit is selected such that the densification of the glass structure during sintering is substantially completed before crystallization begins.

[0051] To obtain dense glass-ceramic objects, it is preferable to increase the density of the glass structure as much as possible before crystallization begins. While not wishing to be confined to theory, it is believed that the presence of a crystalline phase inhibits densification and pore closure during sintering. The viscous nature of glass enables pore closure and densification during sintering. The crystalline phase is essentially non-viscous and represents a physical barrier against densification. Therefore, the composition of the glass stock is selected to preferentially induce significant densification during heat treatment before the formation of the crystalline phase. Since the reduction in pore volume achieved during sintering is not significantly affected by the subsequent nucleation and growth of the crystalline phase, the additive manufacturing method of this disclosure is capable of producing dense glass-ceramic articles.

[0052] The densification achieved in the additive manufacturing process of this disclosure can be described by the density of the glass-ceramic article relative to its theoretical density. The theoretical density of the glass-ceramic article is the density of the article when its pores are completely closed and it is fully densified. The description of theoretical density is similar for glass and other types of materials. As sintering progresses and the pore volume decreases, the density of the glass structure increases. The further the densification progresses during sintering, the higher the density of the resulting glass-ceramic article after crystallization. Due to time constraints in actual processes, the glass structure may not be fully densified at the start of crystallization, and the density of the glass-ceramic article may be lower than the theoretical density. However, compared to prior art processes where crystallization occurs when the glass structure has a high degree of porosity, the additive manufacturing process of this disclosure achieves greater densification of the glass structure and a higher density (lower porosity) in the resulting glass-ceramic article.

[0053] The density of the glass-ceramic articles formed by the methods described herein is at least 90% of the theoretical density, or at least 93% of the theoretical density, or at least 96% of the theoretical density, or at least 99% of the theoretical density.

[0054] Back Figure 1After the glass frit is prepared at two locations, it is optionally dried and cleaned at four locations. In one embodiment, drying includes vacuum drying. Drying may include, for example, heating the glass frit to a temperature well below its melting or sintering temperature, and removing any vapors generated during heating using a vacuum system.

[0055] At point 6, printing materials are manufactured from glass frit. The printing materials are in the form of paste, liquid, slurry, dispersion, or suspension. The printing materials are manufactured by combining glass frit with a binder composition. The binder composition comprises a curable resin. The curable resin comprises one or more monomers or oligomers, each having one or more curable functional groups. A monomer, oligomer, or polymer having one curable functional group is called monofunctional, a monomer, oligomer, or polymer having two curable functional groups is called difunctional, and a monomer, oligomer, or polymer having three or more curable functional groups is called polyfunctional. In one embodiment, the curable resin is thermocurable. In another embodiment, the curable resin is photocurable. In one embodiment, the photocurable resin is cured with ultraviolet (UV) light. In one embodiment, the curable resin comprises a monomer, oligomer, or polymer having one or more olefinic unsaturated groups per molecule. The olefinic unsaturated groups are curable functional groups. The olefinic unsaturated groups include acrylate groups or methacrylate groups. In another embodiment, the curable resin comprises a monomer, oligomer, or polymer having epoxy group functionality. In one embodiment, the resin comprises an oligomer selected from epoxy resin oligomers, unsaturated polyester resin oligomers, and acrylic resin oligomers. In another embodiment, the resin comprises polyamide, polyimide, polyketide, polyolefin, cellulose, or derivatives thereof (e.g., ethyl cellulose).

[0056] The binder composition preferably includes an initiator for initiating a reaction in the curable resin. The curable resin reacts to form oligomers or polymers, which bind the glass frit during printing. The initiator is a thermal initiator or a photoinitiator. The photoinitiator can be radical or cationic. Examples of photoinitiators include ketone photoinitiators, phosphine oxide photoinitiators, 1-hydroxycyclohexylphenyl ketone [e.g., IRGACURE 184 from BASF]; bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide (e.g., commercial blends of IRGACURE 1800, 1850 and 1700 from BASF); 2,2-dimethoxy-2-phenylacetophenone (e.g., IRGACURE 651 from BASF); bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (IRGACURE 819); (2,4,6-trimethylbenzoyl)diphenylphosphine oxide [LUCIRIN TPO from BASF (Munich, Germany)]; and ethoxy(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (LUCIRIN TPO-L from BASF). Examples of free radical photoinitiators are trichloroacetophenone, benzophenone, and azobenzoyl dimethyl ketal. Examples of cationic photoinitiators are ferrocene salts, triarylsulfonium salts, and diaryliodomonium salts. In one embodiment, if the photoinitiator is free radical, the curable resin comprises epoxy-functionalized or unsaturated polyester or acrylic compounds. In another embodiment, if the photoinitiator is cationic, the curable resin is an unsaturated polyester or acrylic compound.

[0057] The binder composition optionally includes one or more additives. These additives can be selected to achieve one or more of the following: controlling the viscosity of the printing material, stabilizing the printing material, and preventing glass frit agglomeration. Viscosity control additives include reactive diluents, which are typically low molecular weight monofunctional curable monomers. Stabilizers for the printing material include UV blockers. In one embodiment, the binder composition includes natural or synthetic wax additives for promoting the formation of a paste-like form of the printing material. Examples of waxes include paraffin wax, beeswax, carnauba wax, and polyethylene wax. Additives may also include organic solvents, dispersants, surfactants, etc., especially in embodiments where the printing material is in the form of a paste, liquid, or suspension.

[0058] A representative commercially available adhesive composition is PR48 (purchased from Colorado Photopolymer Solutions, Boulder, Colorado). PR48 comprises a curable oligomer [39.8 wt% Allnex Ebecryl 8210, 39.8 wt% Sartomer SR494], a reactive diluent (19.9 wt% Rahn Genomer 1122), a UV blocker (0.16 wt% Mayzo OB+), and a photoinitiator (0.4 wt% Esstech TPO+).

[0059] In one embodiment, the method includes removing air bubbles (8) trapped within the printing material under vacuum. The vacuum pressure used to remove air bubbles from the printing material is a design variable depending on the composition of the printing material. In one embodiment, the vacuum pressure is in the range of 1 mbar to 10 mbar. In another embodiment, processing the printing material under vacuum includes vacuum degassing of the printing material. The mixing of the glass frit and binder composition for forming the printing material, as well as the removal of trapped air bubbles within the printing material, can be performed in a mixing system capable of achieving a vacuum and repressurization sequence. The mixing of the glass frit and binder composition for forming the printing material, and the vacuum processing of the printing material for removing trapped air bubbles, can be performed simultaneously, or the vacuum processing of the printing material can be performed after initial mixing.

[0060] In some embodiments, the glass flotation and binder composition are heated during mixing. The heating temperature is, for example, as high as about 100°C. This heating reduces the viscosity of the binder composition to promote uniform mixing of the glass flotation and the binder composition. This heating is optional and may not be necessary if the binder composition is fluid at room temperature. Any vapors generated during heating can be removed by vacuum degassing or other suitable methods.

[0061] The weight ratio of glass frit, curable resin, initiator, and one or more additives in the printing material is selected such that sufficient binder (cured resin) can contact between the glass frit particles, and sufficient open pores allow for complete removal of the binder during thermal cycling before final sintering of the glass frit particles. The glass frit constitutes more than 30% by weight, or more than 40% by weight, or more than 50% by weight, or more than 60% by weight, or more than 70% by weight, or is in the range of 30% to 80% by weight, or in the range of 40% to 75% by weight, or in the range of 50% to 70% by weight. The balance of the printing material is the binder composition. The curable resin constitutes more than 50% to 95% by weight, or in the range of 55% to 90% by weight, or in the range of 60% to 85% by weight, or in the range of 65% to 80% by weight. The initiator is present in the binder composition at a concentration ranging from 0.1 wt% to 5.0 wt%, or from 0.2 wt% to 4.0 wt%, or from 0.3 wt% to 3.0 wt%. The additive is present in the binder composition at a concentration ranging from 1.0 wt% to 40 wt%, or from 2.0 wt% to 30 wt%, or from 3.0 wt% to 25 wt%, or from 5.0 wt% to 20 wt%.

[0062] At point 10, the printing material is optionally shaped to be suitable for dispensing and forming layers of printing material during the printing of the 3D structure. When the printing material is in paste form, for example, it can be shaped into rods or granules to facilitate dispensing and application to the surface. Shaping can be performed under vacuum to avoid trapping new air bubbles in the printing material.

[0063] Continuing with the method described above, at point 12, a 3D structure is constructed using printing material. The 3D structure is based on a design for a glass-ceramic article to be produced using this method. The 3D structure is constructed using Solid Freeform Manufacturing (SFF) technology. Before constructing the 3D structure, a model of the 3D article is built using CAD software (such as PRO-ENGINEER or I-DEAS). CAD software typically outputs a .stl file, which is a file containing a subdivision model of the 3D article. The subdivision model is an array of triangles representing the surfaces of the CAD model. The .stl file contains the coordinates of the vertices of these triangles and an index indicating the normal of each triangle. The subdivision model is sliced ​​into layers (sections) using slicing software (e.g., MAESTRO from 3D Systems). The slicing software outputs a build file containing information about each slice or layer of the subdivision model. This information about each slice or layer contains the necessary geometric data for constructing the cross-sections of the article. The build file is then sent to the SFF system to construct the 3D structure, which is ultimately further processed to form the desired article. Newer generations of CAD software may be able to output build files directly from CAD models, eliminating the need for separate slicing software, or may be able to "print" build data directly to a suitable SFF system.

[0064] In one implementation, using Figure 1The improved stereolithography technique described at points 14, 16, 18, 20, and 22 is used to construct 3D structures. Using this technique, a 3D structure is constructed layer by layer on a construction platform or substrate. At point 14, a first layer of printing material is applied, deposited, or otherwise formed on the construction platform or substrate. The thickness of this layer of printing material is typically in the submicron to micron range, for example, from a few nanometers to up to 200 μm. At point 16, the first layer of printing material is printed. During this printing process, the layer of printing material is selectively cured to form printed areas. Curing is induced by applying a heat source or light source to selected spatial portions of the layer of printing material, effectively thermosetting or photocuring the curable resin contained in the layer of printing material. Curing of the curable resin induces a reaction, such as polymerization or oligomerization, which increases the rigidity of the curable resin in the printed areas. In one embodiment, curing solidifies the curable resin. The uncured resin in the unprinted areas is fluid. This results in a stark contrast in resin rigidity between the printed and unprinted areas. The pattern of the printed areas in the printing material layer corresponds to the cross-section of the 3D structure. Using information about the corresponding layers of the 3D structure contained in the build file, the selected area to be printed for the printing material layer is determined to define the cross-section. At point 18, a decision is made as to whether the 3D structure is complete or requires additional printing material layers to form additional cross-sections of the 3D structure. If the 3D structure is incomplete, the method moves to point 20 and applies a new printing material layer on top of the previously printed layer. At point 22, a new layer is printed according to the information contained in the build file to form the next cross-section of the 3D structure. Steps 18, 20, and 22 are repeated until a complete 3D structure is printed.

[0065] At step 23, the printed part is cleaned and the support structure is removed. Once the 3D structure is complete, contact with the adhesive composition is severed. Optionally, any excess uncured resin on the surface of the 3D structure is then removed. Removal of uncured resin occurs during the cleaning step, in which the 3D structure is washed for several minutes with a solvent (e.g., an alcohol, such as isopropanol) to dissolve or drain excess uncured resin. The washing process may also remove a portion of the uncured resin from unprinted areas of the 3D structure, after which the support structure can be removed.

[0066] The method continues for 24 seconds to debond the 3D structure. During debonding, cured and uncured resins are removed from both the printed and unprinted areas of the 3D structure to leave pores in the remaining printed 3D structure. Debonding involves heating the 3D structure in air at a controlled rate to a temperature insufficient for sintering the 3D structure. Debonding allows any remaining resin in the 3D structure to burn, decompose, and / or volatilize. The glass portion of the 3D structure is retained. A typical heating scheme for debonding is heating at a rate of ~5°C / min to up to 90°C and at a rate of ~2°C / min to an upper limit temperature of about 100°C or higher, which is below the temperature required to induce sintering of the glass composition of the 3D structure. The 3D structure can be held at the upper limit temperature for a specified dwell time (typically several minutes to several hours) and then cooled to room temperature at a rate of ~5°C / min. The porous 3D structure can be air-cleaned after debonding to remove any remaining debris or loose material from the structure.

[0067] Following debonding, the porous 3D structure is sintered at point 26. Sintering is a heat treatment process that closes the pores and densifies the porous 3D structure to form a sintered 3D structure. Sintering occurs at a higher temperature than debonding. In one embodiment, debonding and sintering are completed in a continuous thermal cycle. Debonding and / or sintering can be performed under vacuum, which may include selective vacuum degassing to avoid or remove bubbles trapped in the porous 3D structure during pore collapse during the formation of the sintered 3D structure, thereby ensuring more complete densification. Typical vacuum pressures are in the range of 1 mbar to 10 mbar. Sintering is optionally performed in a helium atmosphere, wherein helium removes gases trapped as bubbles in the porous 3D structure. Sintering is also optionally performed in a chlorine atmosphere, wherein chlorine removes residual hydroxides in the porous 3D structure.

[0068] Both debinding and sintering are heat treatment processes carried out in a suitable furnace. In one embodiment, the rate of temperature change and residence time during debinding and sintering are defined based on differential thermal analysis, a technique indicating the heat of reaction and weight changes during thermal cycling. Generally, debinding should be performed with a very slow rate of temperature change, for example, 1°C / min to 2°C / min, to heat the 3D structure as uniformly as possible, so that all surfaces of the 3D structure have sufficient heating time to ensure complete removal of the binder. Preferably, the rate of temperature change and residence time are controlled to ensure that the binder inside the 3D structure evaporates before the glass frit particles in the 3D structure begin to sinter.

[0069] The sintered 3D structure undergoes further heat treatment at 28 points to induce crystallization and transform it into a glass-ceramic product. Crystallization involves the nucleation and growth of crystalline phases. The proportion of crystalline phases depends on the degree of crystallization and is controlled by the time and temperature of the crystallization process.

[0070] The sintering and crystallization times and temperatures depend on the composition of the glass frit. As mentioned above, to obtain high-density glass-ceramic articles, densification is preferably completed as early as possible before significant crystallization occurs. In a preferred embodiment, densification occurs substantially during sintering, and crystallization occurs substantially after densification is complete. In one embodiment, heat treatment cycles are controlled (e.g., by adjusting the time and / or temperature after sintering) to induce crystallization after sintering without cooling the sintered 3D structure. In another embodiment, the sintered 3D structure is cooled (e.g., cooled to room temperature) and reheated to induce crystallization.

[0071] In one embodiment, the sintered 3D structure comprises at least 90% by weight of glass having a glass frit composition, and the density is at least 90% of the theoretical density of the glass frit composition. In another embodiment, the sintered 3D structure comprises at least 95% by weight of glass having a glass frit composition, and the density is at least 90% of the theoretical density of the glass frit composition. In yet another embodiment, the sintered 3D structure comprises at least 98% by weight of glass having a glass frit composition, and the density is at least 90% of the theoretical density of the glass frit composition.

[0072] In one embodiment, the sintered 3D structure comprises at least 90% by weight of glass having a glass frit composition and a density at least 95% of the theoretical density of the glass frit composition. In another embodiment, the sintered 3D structure comprises at least 95% by weight of glass having a glass frit composition and a density at least 95% of the theoretical density of the glass frit composition. In yet another embodiment, the sintered 3D structure comprises at least 98% by weight of glass having a glass frit composition and a density at least 95% of the theoretical density of the glass frit composition.

[0073] In one embodiment, the sintered 3D structure comprises at least 90% by weight of glass having a glass frit composition and a density at least 98% of the theoretical density of the glass frit composition. In another embodiment, the sintered 3D structure comprises at least 95% by weight of glass having a glass frit composition and a density at least 98% of the theoretical density of the glass frit composition. In yet another embodiment, the sintered 3D structure comprises at least 98% by weight of glass having a glass frit composition and a density at least 98% of the theoretical density of the glass frit composition.

[0074] In one embodiment, the sintered 3D structure comprises a glass having the composition of a glass frit and a crystalline phase, wherein the crystalline phase content of the sintered 3D structure is less than 1% by weight, and the density of the sintered 3D structure is at least 90% of the theoretical density of the glass frit composition. In another embodiment, the sintered 3D structure comprises a glass having the composition of a glass frit and a crystalline phase, wherein the crystalline phase content of the sintered 3D structure is less than 1% by weight, and the density of the sintered 3D structure is at least 95% of the theoretical density of the glass frit composition. In yet another embodiment, the sintered 3D structure comprises a glass having the composition of a glass frit and a crystalline phase, wherein the crystalline phase content of the sintered 3D structure is less than 1% by weight, and the density of the sintered 3D structure is at least 98% of the theoretical density of the glass frit composition.

[0075] In one embodiment, the sintered 3D structure comprises a glass having the composition of a glass frit and a crystalline phase, wherein the crystalline phase content of the sintered 3D structure is less than 0.5% by weight, and the density of the sintered 3D structure is at least 90% of the theoretical density of the glass frit composition. In another embodiment, the sintered 3D structure comprises a glass having the composition of a glass frit and a crystalline phase, wherein the crystalline phase content of the sintered 3D structure is less than 0.5% by weight, and the density of the sintered 3D structure is at least 95% of the theoretical density of the glass frit composition. In yet another embodiment, the sintered 3D structure comprises a glass having the composition of a glass frit and a crystalline phase, wherein the crystalline phase content of the sintered 3D structure is less than 0.5% by weight, and the density of the sintered 3D structure is at least 98% of the theoretical density of the glass frit composition.

[0076] The sintered 3D structure undergoes further heat treatment to induce crystallization, thereby forming a glass-ceramic product. Crystallization results in the formation of one or more crystalline phases, each corresponding to a unique crystalline composition or a polymorph with a unique crystalline composition. The crystalline composition may be the same as or different from that of the glass frit.

[0077] Figure 2A-2C Examples of performing Figure 1 One method is described in steps 14-22. In this method, printing material is provided as a paste. Figure 2AA laser beam 40 from a laser source 44 is shown, which is focused onto a layer (printing material layer) 48 of printing material on a build platform 52 using, for example, a scanning mirror 60. (Although only one mirror 60 is shown for illustrative purposes, two mirrors, one for the X-axis and the other for the Y-axis, could also be used to guide the laser beam 40.) The laser beam 40 may first pass through a beam shaper 56 and then be focused onto the printing material layer by the scanning mirror 60. The laser beam 40 has a wavelength that is selected to induce photocuring of the printing material layer 48. Depending on the composition of the printing material layer 48, the wavelength of the laser beam 40 is ultraviolet, visible, or infrared. The laser source 44 preferably operates at a wavelength that is not absorbed by the glass frit in the printing material layer. In one embodiment, the laser source 44 operates at a wavelength in the range of 350 nm to 430 nm. The laser beam 40 scans the surface of the printing material layer 48 according to information about the printing material layer 48 contained in the build file. The build file can be provided to the controller 62, which can operate the scanning mirror 60 to position the laser beam 40 at a desired location on the printing material layer 48. In the area of ​​the printing material layer 48 exposed to the laser beam 40, radiation activates the photoinitiator in the printing material layer 48, which triggers a chemical reaction that polymerizes and hardens the curable resin in the printing material layer to form the printed area.

[0078] After the first cross-section of the 3D structure is formed in the first printing material layer 48, a second printing material layer 64 is applied, deposited, or otherwise formed on the first printing material layer 48, such as... Figure 3B As shown. A scraper 70 can be used to apply or spread the printing material layer 64. (As illustrated...) Figure 3C As shown, the printing process is repeated for the next cross-section of the 3D part. During the printing process, the curable resin in the second printing material layer 64 is cured and also bonds to the cured resin in the underlying first printing material layer 48. The process of laying new printing material layers one by one and forming the cross-section of the 3D structure in the new layers is repeated until the 3D structure is completed. Figure 3B As shown, the printing material layer can be spread or deposited in the vacuum chamber 68 to keep the printing material layer substantially free of trapped air bubbles. Although the printing material layer can be kept substantially free of trapped air bubbles as described above, the printing material layer can be spread or deposited without using a vacuum.

[0079] Figure 3A This illustrates another method for constructing 3D structures using stereolithography. In this method, the printing material is provided as a slurry or liquid suspension. Figure 3AA cylinder 100 containing printing material 102 is shown. A build platform 104 is placed within the cylinder 100 and below the surface 105 of the printing material to form a printing material layer 108A on the build platform 104. The printing material layer 108A can be uniformly spread on the build platform 104 using a doctor blade 106. The spreading of the printing material layer can be performed in a vacuum chamber 109 to keep the printing material layer 108A substantially free of trapped air bubbles. Air bubbles can be removed during the spreading of the printing material layer using vacuum degassing. In alternative embodiments, it may not be necessary to spread the printing material layer under vacuum, or vacuum degassing may not be necessary, and the action of the doctor blade 106 can be expected to avoid trapped air bubbles in the printing material layer 108A.

[0080] like Figure 3B As shown, after the printing material layer 108A is laid out, the XY scanning laser 110 prints the first cross-section of the 3D structure on the printing material layer 108A. The "printing" consists of scanning the layer 108A with a laser beam 112 according to the information about the printing material layer 108A contained in the build file. This is consistent with the previous... Figure 2A-2C As in the example, in the region of the printing material layer 108A exposed to the laser beam 112, radiation activates the photoinitiator in the printing material, which triggers a chemical reaction that polymerizes and hardens the curable resin in the printing material layer, thereby forming a printing region 109 in the printing material layer 108A corresponding to the first cross-section of the 3D structure.

[0081] After the first cross-section of the 3D structure is formed in the printing material layer 108A, the build platform 104 (and the printing area 109 formed thereon) is lowered in the cylinder 100, as follows. Figure 3C As shown, a new print material layer 108B is formed on the first print material layer 108A. Any suitable actuator 113 can be used to lower the build platform 104. The new print material layer 108B is then uniformly spread on the underlying print material layer 108A using the scraper 106 again. In one embodiment, the lowering of the build platform 104 and the spreading of the new print material layer 108B are performed under vacuum to avoid trapping air bubbles in the new print material layer 108B. Figure 3D As shown, the next cross-section of the 3D structure is printed on a new printing material layer 108B. The cured resin in the new printing material layer 108B will bond to the structure 109 in the underlying printing material layer 108A. The process of spreading new printing material layers while avoiding trapping air bubbles in the layers, and printing new cross-sections of the 3D part in the new printing layers, is repeated until all cross-sections of the 3D structure have been printed.

[0082] Figure 4A Examples of performing Figure 1Another method for steps 14-22. In this method, the printing material is provided as a slurry or liquid suspension. Figure 4A A certain amount of printing material 102A is shown poured into cylinder 120. Actuator 126 is used to position build platform 124 at a distance from the bottom of cylinder 120. The gap 125 between the bottom of cylinder 120 and the bottom of build platform 124 determines the thickness of the first layer 122A of printing material. The pouring of printing material 102A into cylinder 120 and the positioning of build platform 124 within cylinder 120 to form the first layer 122A of printing material can be performed in a vacuum environment 123, thereby avoiding the trapping of air bubbles in the first layer 122A of printing material. If necessary, vacuum degassing can be used to further ensure that the printing material layer 122A is substantially free of trapped air bubbles.

[0083] like Figure 4B As shown, below cylinder 120 is a UV digital light processing (DLP) projector 128, which exposes the printing material layer 122A using a continuous layer mask (2D image). The UV DLP projector 128 is used to print the cross-section of a 3D structure in the printing material layer 122A. (It should be noted that a UV laser can be used instead of UV DLP to print the cross-section of a 3D structure in the printing material layer 122A.) Figure 4B In the setup shown, the cylinder 120, at least at its bottom portion, needs to be made of a suitable material to allow the light beam from the UV DLP projector 128 to pass through and reach the printing material layer 122A. In one embodiment, the UV DLP projector 128 operates in the range of 350 nm to 430 nm. The printed regions 129, constructed in the printing material layer 122A by selective exposure to radiation, will adhere to the build platform 124. This can be achieved by providing a suitable bottom surface of the build platform 124 for the adhesion of the printed regions 129.

[0084] After printing the cross-section of the 3D structure in the first printing material layer 122A, the building platform 124 and the printing area 129 will be raised to a height equal to the height of the next printing material layer 122B, such as... Figure 4C As shown. The printing material 102A in cylinder 120 will flow to fill the voids created by raising the build platform 124 and the printing area 129, thereby forming the next printing material layer 122C. The raising of the build platform 124 can be performed in a vacuum environment 123 to avoid introducing or trapping air bubbles in the next printing material layer 122B due to the movement of the printing material 102A within cylinder 120. If necessary, vacuum degassing can be used to further ensure that the next printing material layer 122B is substantially free of trapped air bubbles. Figure 4DNext, using a DLP projector 128, the next section of the 3D structure is printed in a new printing material layer 122B. This process is repeated. Figure 4C and 4D This continues until all cross-sections of the 3D part have been printed sequentially in the printing material layer.

[0085] For all the methods described above and their variations, steps involving the movement of the printing material can be performed in a vacuum environment (e.g., when spreading a new layer of printing material on a previous layer or build platform). This may involve vacuum degassing, as needed, to avoid trapping air bubbles in the printing material layer. When in a vacuum environment, a vacuum degassing procedure can be employed. This also avoids trapping air bubbles in the printing material layer without using a vacuum. For example, the possibility of using a doctor blade to smooth and remove air bubbles from the printing material layer has been described above. Furthermore, any means of printing a 2D image on the printing material layer, including those described above, can be used with any of the methods described above.

[0086] Figures 5A-5C Examples Figure 1 A variation of the method. Instead of forming a printing material in the form of a liquid, slurry, dispersion, paste, or suspension by combining glass frit and binder composition and applying the printing material to a build platform, glass frit is applied as a layer to the build platform, and the binder composition is applied as a liquid, slurry, dispersion, paste, or suspension to selected portions of the glass frit layer. Unselected portions remain free of the binder composition. When exposed to a source for thermosetting or photosetting, printing occurs only in portions of the glass frit layer wetted by the binder composition. This process is repeated layer by layer to build the 3D structure. Upon completion, the 3D structure is debonded, sintered, and crystallized as described above.

[0087] like Figure 5AAs shown, glass frit 200 is applied to support 204 to form a glass frit layer 202A. The glass frit layer 202A forms a powder bed into which droplets of binder composition 206 are deposited. Preferably, the glass frit 200 is spread into layer 202A under vacuum, which may optionally include vacuum degassing to prevent the incorporation of air bubbles or gas pockets. This can be achieved by encapsulating the glass frit spreading tool 208, the glass frit 200, and support 204 in a vacuum environment 210 during glass frit spreading. To form a 3D structured cross-sectional layer, droplets of binder composition 206 are delivered to selected areas of glass frit layer 202A via printhead (or nozzle) 212. In one embodiment, the delivery of droplets of binder composition in a vacuum environment prevents air bubbles from being trapped in glass frit layer 202A. The print head 212 moves relative to the glass frit layer 202A to deliver droplets to a selected area of ​​the glass frit layer 202A, determined by information about that layer contained in the 3D structure's build file. This can be seen as described above regarding... Figure 1 The method described above is used to create the build file.

[0088] like Figure 5B As shown, the glass frit layer 202A can be irradiated with a suitable source (e.g., a UV laser 214) or heated to cure the curable resin of the binder composition deposited on the glass frit layer 202A. Curing cures the cross-sectional layers of the 3D structure in the glass frit layer 202A. Then, as... Figure 5C As shown, a new glass frit layer 202B is spread on a previous glass frit layer 202A (optionally performed under vacuum). Droplets of binder composition 206 are selectively delivered to the new glass frit layer 202B, followed by curing of the binder composition deposited in the new glass frit layer 202B. The following process is repeated: spreading a new glass frit layer, delivering droplets of binder composition to the new layer according to information about the layer contained in the construction file, and curing the deposited binder composition until all cross-sectional layers of the 3D structure are constructed. As described above, the process also includes debonding the 3D structure, sintering the 3D structure, and forming a glass-ceramic article by inducing crystallization in the sintered 3D structure.

[0089] Comparative Example E3

[0090] The following examples illustrate glass materials having the compositions listed in Table 1.

[0091]

[0092]

[0093] Table 1

[0094] The raw materials were mixed and introduced into a furnace preheated to 1400°C. After the starting material was introduced, the furnace temperature was increased from 1400°C to 1600°C over a two-hour period. The mixture was held at 1600°C for 5 hours and then reduced to 1500°C. The molten mixture was then poured into water to allow the glass to cool and form. The glass was dried, ball-milled for 8 hours, and passed through a 50 μm sieve. The portion passing through the sieve was collected and used as the glass feedstock for forming glass-ceramic products.

[0095] Figure 6 The particle size distribution of the glass frit is shown [measured using a Microtrac S3500 laser diffractometer]. Particle size distribution is a measure of the volume fraction of particles as a function of particle size. The average particle size of the glass frit is 19 μm.

[0096] Figure 7 The thermodynamic analysis (TMA) plot of the glass frit is shown. The TMA results were measured using a Q400TMA thermodynamic analyzer. Samples with a diameter of 4-7 mm and a thickness of at least 10 mm were mounted in the analyzer's sample chamber and heated in air at a rate of 10 °C / min. The TMA plot includes two traces. Trace 80 shows the fractional change in the size of the glass frit sample as a function of temperature (expressed as a percentage). Trace 82 shows the derivative of trace 80 (expressed in % / °C). Trace 80 shows significant shrinkage of the glass frit at temperatures between ~850 °C and ~925 °C. This shrinkage is a result of glass frit sintering. Shrinkage is a result of pore closure and densification of the glass frit.

[0097] Figure 8 Differential scanning calorimetry (DSC) plots of the glass frit are shown. DSC measurements were performed using a NETZSCH 4040Cell DSC instrument. The sample was heated at a rate of 10 °C / min. Exothermic and endothermic transitions in the glass were monitored. Trace 84 shows the DSC signal as a function of temperature, and trace 86 shows the baseline of the calculated region below the peaks of the DSC trace. Trace 84 shows feature 88 marking the onset of the glass transition region (~760 °C), and peaks 90 (~960 °C), 92 (~1060 °C), and 94 (~1240 °C) associated with crystalline phase formation. The DSC plot indicates that crystallization initiation occurs at ~925 °C.

[0098] Prepare glass granules with a diameter of ~30mm and a thickness of several millimeters, and subject them to the following heat treatment process:

[0099] temperature Rate (°C / minute) Time (minutes) RT to 350℃ 2 165 350℃ to 585℃ 0.8 294 585℃ to 700℃ 5 23 700℃ to 950℃ 0.8 313 950℃ 0 240 total 1035

[0100] Table 2

[0101] Where "RT" refers to room temperature, temperature refers to the lowest and highest temperatures in the temperature interval, rate refers to the heating rate within the temperature interval, and time refers to the heating time within the temperature interval.

[0102] At the end of the heat treatment, the granules were analyzed. X-ray diffraction (XRD) was used to confirm crystallization and identify the present crystalline phases. Based on XRD analysis, the heat treatment transformed the glass frit granules into a glass-ceramic material. The estimated crystallization fraction of the glass-ceramic material was above 70% by weight. Multiple crystalline phases were detected and had the following proportions:

[0103]

[0104] Table 3

[0105] Here, % by weight refers to the weight percentage of a specific crystalline phase relative to the total crystalline phase content of the glass-ceramic material. The density of the glass-ceramic material was measured to be 2.684 g / cm³. 3 .

[0106] To determine the effect of the binder on the sintering and crystallization processes, the following further experiments were conducted:

[0107] The glass frit and binder (Castable resin v2, purchased from Formlabs) were mixed in the following proportions (volume %): glass frit (50%) + binder (29%) + IBOA (isoborneol acrylate) (21%). The mixture was poured into a cylindrical mold made of the binder (dimensions: 40 mm in diameter, height: a few millimeters). The mixture was cured in the mold under UV light to form granules, and the granules were subjected to the following thermal cycles for debinding, sintering, and crystallization:

[0108] 25-100℃ (100℃ / h),

[0109] 100-600℃ (100℃ / h),

[0110] 600–800℃ (300℃ / h),

[0111] 800–900℃ (50℃ / h),

[0112] 900-950℃ (300℃ / h),

[0113] Keep at 950℃ for 2 hours.

[0114] Cool at furnace rate.

[0115] After thermal cycling, a 20% linear shrinkage was observed (particle diameter 32 mm). Density was measured using a helium hydrometer. The measured density was 2.668 g / cm³. 3Without a binder, applying the same thermal cycle to the glass frit yielded a density of 2.692 g / cm³. 3 The results show that the binder does not significantly affect sintering and crystallization.

[0116] Example 1

[0117] In some implementations, dense glass-ceramic objects can be produced using calcium zirconium silicate glass frit via additive manufacturing (i.e., 3D printing). As mentioned above, stereolithography (SLA) can be a very promising method for inorganic materials such as glass, ceramics, or glass-ceramics.

[0118] As described above, the glass-ceramic manufacturing process is described using stereolithography (SLA). The finished product is dense and possesses interesting properties, such as excellent mechanical strength, low CTE, and / or excellent chemical durability. Glass precursors for the glass ceramic are added to a binder composition containing a resin. After 3D printing of the article via SLA, heat treatment is performed to sequentially achieve debonding, sintering of the glass particles, and final crystallization to form the final glass-ceramic material, which exhibits non-porous properties and extremely low residual porosity. The resulting glass-ceramic has potential applications in a variety of fields, such as consumer products and technology artifacts.

[0119] In the examples disclosed herein, novel glass-ceramics are proposed, which feature wollastonite as the main crystalline phase (compared to cordierite as the main crystalline phase in other examples) and exhibit increased chemical durability (in acids and alkalis) and mechanical strength for use in 3D printing processes. The chemical and mechanical properties of the glass-ceramic material depend on the glass frit composition and heat treatment, resulting in unique crystalline phases and microstructures depending on the process used.

[0120] Conventional techniques often describe the binder compositions used in 3D printing as comprising a resin combination of (1) ceramic and / or glass-ceramic particles or (2) a mixture of glass and crystalline powder. After heat treatment, these 3D printed articles are transformed into ceramic materials. These conventional techniques yield materials with high porosity after heat treatment, which is the opposite of the desired non-porous and extremely low residual porosity characteristics.

[0121] Therefore, as described in this embodiment, the novel glass-ceramic with wollastonite as the main crystalline phase exhibits increased chemical durability (in acids and alkalis) and mechanical strength for use in 3D printing processes. In other words, by using a glass comprising SiO2-CaO-ZrO2 as the glass stock in additive manufacturing processes (e.g., stereolithography), and after complete sintering and crystallization, a glass-ceramic with high mechanical properties and excellent chemical durability (in acids and alkalis) can be formed.

[0122] experiment

[0123] Glass Formation

[0124] The following examples illustrate glass frits with sintering and crystallization characteristics for use in obtaining dense glass-ceramic articles via additive manufacturing processes. Glass frits having the compositions listed in Table 4 were prepared:

[0125] Composition <![CDATA[SiO2 (wt%)]]> CaO (wt%) <![CDATA[ZrO2 (wt%)]]> E31 52 32 16 E32 56 34 10 E33 51 37 12

[0126] Table 4

[0127] The raw materials were mixed and introduced into a furnace preheated to 1400°C. After the introduction of the starting material, the furnace temperature was increased from 1400°C to 1670°C over a period of 5 hours. The mixture was then held at 1670°C for 5 hours. In other words, 1 kg of raw material was glass-melted in a platinum crucible in a furnace heated by SiMo electrodes at 1670°C for 5 hours. After melting, the molten mixture could be (A) poured directly into water, or (B) rolled into a low thickness, in either case allowing the mixture to cool and solidify. Subsequently, the glass was optionally dried and pulverized by ball milling or vibratory grinding for 8 hours. Finally, the pulverized glass was passed through a 50 μm sieve, and the portion passing through the sieve (i.e., with a particle size distribution less than 50 μm) was collected and used as glass feedstock for forming glass-ceramic products. Figure 6 The particle size distribution is illustrated. Small glass blocks were also produced, and at the glass transition temperature (T0). g Anneal for 1 hour, then slowly cool to room temperature. Table 5 below indicates the Tg.

[0128] Glass material characterization

[0129] To determine the sintering / crystallization regime and to preliminarily estimate the sintering capability of the glass, differential scanning calorimetry (DSC) and thermal analysis (TMA) were performed. DSC was performed using a NETZSCH 4040 Cell DSC. The sample (sieved powder) was analyzed by heating from room temperature to 1300°C at a heating rate of 10 K / min in air. TMA was performed using a TMA Q400 TAINSTRUMENT system. The sample (sieved powder) was analyzed by heating from room temperature to 1000°C in air at a heating rate of 10 K / min.

[0130] Subsequently, sintered granules are manufactured and subjected to a predetermined ceramization cycle, by first pressing the glass frit into granules at low pressure using a laboratory press, and then heat-treating them in a furnace using the desired thermal cycle. The granule diameter ranges from 20 mm to 40 mm, and the thickness is less than 10 mm. Exemplary thermal cycles used include heating from room temperature to a holding temperature at a rate of 10 °C / min, holding at the holding temperature for approximately 2 hours, and then cooling at the furnace rate. Several holding temperatures between 900 °C and 1000 °C were tested. Shrinkage occurring during ceramization was measured to estimate the material's ability to be fully sintered. Holding temperatures below 950 °C resulted in high porosity. Sintering occurred during the temperature rise to the holding temperature, while crystallization occurred at the holding temperature. After sintering / ceramization was completed, the final glass-ceramic material was achieved.

[0131] The crystalline particles were then analyzed by X-ray powder diffraction (XRD) to determine the phase composition, and the crystalline particles were observed by scanning electron microscopy (SEM) to assess the presence of residual porosity and potential cracks. XRD was performed using a Philips X'Pert Pro diffractometer with θ / 2θ geometry. Experimental conditions included: a 3kW copper tube (λ = 1.540593) configured with Kα1, power 45kV / 40mA, 2θ range: 5–140°, divergence source: 1 / 4°, step size = 0.008°; scan speed = 40s, mask = 20mm, rotation: 3.75rpm, detector: X-Celerator. SEM analysis was then performed as follows: the sample was fractured and the crack surface was studied using a desktop SEM, Phenom Pure PW-100-015.

[0132] The fracture modulus and chemical durability of the crystalline granules were measured. Ring-on-ring (ROR) tests were performed on a Zwick dynamometer (5 kN) to estimate biaxial flexural strength according to ASTM C1499. Several samples (32 mm diameter, 2.1 mm thickness) fractured. The results are reported as the strength distribution. Strength values ​​at a failure probability of 63.2% and the Weibull slope (shape parameter) are also reported. Acid and alkali chemical durability tests were performed according to DIN 12116 and ISO 695 standards, respectively. Two polished samples, 32 mm in diameter and 3 mm thick, were used for each test. For the acid test (DIN 12116), the sample was immersed in a boiling hydrochloric acid solution of 6 mol / L for 6 hours, and half the mass loss per surface unit was calculated. The resistance grade was determined based on the obtained values. For the alkali test (ISO 695), the sample is immersed in a boiling solution of 0.5 mol / L sodium carbonate and 1 mol / L sodium hydroxide for 3 hours, and the weight loss per unit surface area is calculated. The resistance grade is determined based on the obtained values.

[0133] result

[0134] sintering

[0135] Figure 9 The TMA and DSC plots of the E31 glass composition at a heating rate of 10 °C / min are shown. Furthermore, Table 5 below shows the shrinkage measured on the pellets after different heat treatments, along with the TMA and DSC results.

[0136]

[0137] Table 5

[0138] DSC and TMA experiments showed excellent sintering behavior for E31 and E33. In other words, after heat treatment, the shrinkage rates of E31 and E33 are relatively high (e.g., close to 20%) compared to the shrinkage rate of E32 (e.g., about 5-6%), resulting in final glass-ceramic materials exhibiting non-porous and extremely low residual porosity properties. The shrinkage rate can depend on various factors, such as glass composition or glass grain size. Additionally, the difference between the crystallization temperature (Tc) and the glass transition temperature (Tg) is greater than 190°C. A large difference between Tc and Tg (e.g., in the range of 120°C to 200°C, or preferably 140°C to 200°C) means that sintering can occur before crystallization begins, and crystallization can hinder the sintering process. At least according to Figure 9 Based on the results in Table 5, for E31 and E33, an advantageous sintering / crystallization regime is to hold at 1000°C for 2 hours. Figure 10 The microstructures of E31 and E33 after ceramization at 1000 °C for 2 hours are shown (both heated at a rate of 10 °C / min; white bars represent 100 μm). SEM observations show low residual porosity (i.e., a finite number of residual pores) under both ceramization conditions, as the microstructure images are similar. Ceramization at lower temperatures (e.g., <925 °C, e.g., around 910 °C) results in higher porosity. For E32, the shrinkage during sintering, as measured by TMA, is extremely low (<6%) compared to E31 and E33, which may be related to the increased SiO2 level in the glass (see Table 4).

[0139] X-ray powder diffraction (XRD)

[0140] Table 6 reports the results of XRD analysis performed after ceramization.

[0141]

[0142]

[0143] Table 6

[0144] After ceramization at 950℃ for 2 hours, the main phase of each of E31-E33 was wollastonite. Significant amounts of Ca2Si4ZrO were formed in the glass containing a high level of ZrO2. 12 (E31). In E32 and E33, ZrO2 was observed only as a secondary phase. After ceramization at 1000 °C for 2 hours, both E31 and E33 showed a higher crystallinity than after ceramization at 950 °C for 2 hours, especially for E31, Ca2Si4ZrO2. 12 It no longer exists. Significant amounts of ZrO2 are present in each of E31 and E33.

[0145] Mechanical testing

[0146] Figure 11 Table 7 shows the results of the ring-on-ring (ROR) test (e.g., strength distribution) for E31, E33, and Comparative Example E3. Compared to Comparative Example E3, both E31 and E33 showed higher strength at a failure probability of 63.2% (138 MPa and 111 MPa, respectively, compared to 76 MPa for Comparative Example E3). This is likely due to the well-sintered samples and the presence of a large amount of ZrO2 crystals. The higher Weibull modulus indicates better mechanical strength, as measured by the ROR test.

[0147]

[0148] Table 7

[0149] Chemical durability

[0150] Table 8 shows the chemical durability results for E31, E33 and Comparative Example E3.

[0151]

[0152]

[0153] Table 8

[0154] In both E31 and E33, the mass loss after exposure to acid or alkali was less than that observed in Comparative Example E3 under the same tests. In the ISO 695 alkali test, all three materials were classified as exhibiting low etching, while in the DIN 12116 acid test, all three materials were classified as Grade 4. However, in alkaline environments, E31 was almost 5 times more durable, while Comparative Examples E3 and E33 were more than 2 times more durable. Furthermore, in acidic environments, E31 was nearly 6.5 times more durable, while Comparative Examples E3 and E33 were almost 9 times more durable. These durability results may be related to the higher levels of ZrO2 and the relatively higher SiO2 content in the E31 and E33 compositions.

[0155] Therefore, as presented in Examples 1, E31, and E33, the mixture contains wollastonite and zirconium-rich phases (ZrO2 or Ca2Si4ZrO). 12 As a crystalline phase, glass-ceramics exhibit superior properties compared to those with related materials due to their improved density and significantly better chemical durability and mechanical resistance. These results have been demonstrated in binder-free sintered pellets. These materials are compatible with the SLA process, and the final parts produced by this additive manufacturing method will include similar density, mechanical strength, and chemical durability as the sintered pellets.

[0156] Unless otherwise stated, none of the methods described herein are intended to be construed as requiring their steps to be performed in a specific order. Therefore, when a method claim does not actually state that its steps follow a certain order, or when it does not in any other way specify in the claims or description that the steps are limited to a specific order, it is not intended to imply any particular order.

[0157] It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the illustrated embodiments. Because those skilled in the art can make various improvements, combinations, sub-combinations, and variations to the disclosed embodiments in conjunction with the spirit and essence of the illustrated embodiments, this specification should be considered to include the entire contents of the appended claims and their equivalents.

Claims

1. An additive manufacturing method, the method comprising: A 3D structure is constructed from a printing material comprising a glass frit and a binder composition, wherein the glass frit comprises at least 50 wt% SiO2, at least 30 wt% CaO, and at least 10 wt% ZrO2, and the construction comprises: (a) Applying a layer of the printing material onto a substrate; (b) Printing the printing material layer to form a cross-section of the 3D structure, the printing including curing a selected portion of the printing material layer to form a printed area, the cross-section also including an unprinted area, the unprinted area comprising an uncured portion of the printing material layer; and (c) Repeatedly apply and print the printing material layer to form multiple cross sections of the 3D structure, each of the multiple cross sections including a printed area and an unprinted area, each of the multiple cross sections being formed on a previously formed cross section of the multiple cross sections; Clean the 3D structure to remove most of the uncured resin; The 3D structure is debonded to form a porous 3D structure; The porous 3D structure is sintered to form a glass-ceramic product.

2. The additive manufacturing method as described in claim 1, wherein, The adhesive composition includes a curable resin.

3. The additive manufacturing method as described in claim 1, wherein, The steps for detaching the adhesive include: Remove cured resin and remaining uncured resin from the printed and unprinted areas of the 3D structure to form holes in the remaining printed 3D structure.

4. The additive manufacturing method according to any one of claims 1-3, wherein, The glass-ceramic product: It has theoretical density. Including glassy phase and crystalline phase, and It includes at least 1% by weight of a crystalline phase and has a density of at least 90% of the theoretical density.

5. The additive manufacturing method as described in claim 4, wherein, The crystalline phases include the wollastonite main crystalline phase.

6. The additive manufacturing method as described in claim 5, wherein, The glass-ceramic also includes a Zr-containing crystalline phase.

7. The additive manufacturing method as described in claim 6, wherein, The Zr-containing crystalline phase includes ZrO2 and / or Ca2Si4ZrO 12 .

8. The additive manufacturing method as described in claim 1, wherein, The particle size distribution of the glass frit is less than 200 µm.

9. The additive manufacturing method as described in claim 1 or claim 8, wherein, The particle size distribution of the glass frit is less than 50 µm.

10. The additive manufacturing method as claimed in claim 1, wherein, The glass material includes: 50-70% by weight SiO2, 30-50% by weight of CaO, and 10-20% by weight ZrO2, The total content of all components is 100 by weight.

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