Engineered feedstocks for additive manufacturing of glass

Abstract

According to one aspect of the inventive concept, a composition for an additive manufacturing process includes a glass-forming material, the composition configured to form a three-dimensional structure, and the three-dimensional structure is freestanding. According to another aspect of the inventive concept, the composition for an additive manufacturing process includes a glass-forming material including blended particles including at least two types of particles having different compositions, and a solvent. According to yet another aspect of the inventive concept, the composition for an additive manufacturing process includes a glass-forming material including core-shell particles, and a solvent.

Description

Technical Field

[0001] The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the United States Department of Energy and Lawrence Livermore National Security, LLC for the operation of Lawrence Livermore National Laboratory.

[0002] Field of the Invention The present invention relates to glass compositions, and more particularly, to optical and non-optical glass components having a custom composition profile and methods for their preparation.

Background Art

[0003] Background The composition of glass determines its material properties. Therefore, there are hundreds of different types of industrial glasses to meet numerous requirements. Most glass compositions contain two or more different oxide species. During conventional glass melting manufacturing processes, various raw materials (powders or cullets) with different compositions are batch-processed together in specific ratios. These materials are first blended as powders and then melted in a crucible and thoroughly mixed in the liquid phase to produce the desired final glass composition with the desired homogeneity. The raw materials can include particles of unspecified size, shape, and various degrees of aggregation, and even individual compositions can vary. Therefore, although individual raw materials may start melting at different temperatures (for example, each melting point is specific to the individual raw materials being blended), since these materials remain confined together in the crucible, they are blended together and become homogeneous in the final melt. Thus, although raw materials with low impurity levels and high purity are important for conventional glass melting processes, the powder size, size uniformity, particle shape, chemical distribution, and other characteristics of the raw materials do not determine the optimal processing parameters or the optimal material homogeneity.

[0004] In addition, using conventional processes, the gradient of glass material composition is introduced either (1) axially by melting together multiple layers containing a homogeneous composition, or (2) radially by diffusing species (typically small, fast-diffusing ions) into or out of a rod-shaped silica sol gel or solid at high temperatures. However, gradients that simply utilize diffusion are limited to symmetrical parabolic profiles, and while they can be made up to approximately 20 mm in diameter (in the case of radially gradient refractive index lenses), the most commercially available versions have diameters smaller than 2 mm. Introducing larger, slowly diffusing species has proven to be more difficult.

[0005] Attempts have been made to produce single-composition glass using additive manufacturing (AM). Single-composition silica glass has been prepared using selective laser melting (SLM), which involves melting and dissolving silica particles in a silica powder bed. Furthermore, single-composition glass has been prepared using a galvanic deposition modeling (G3DP) method, in which silica is melted in a high-temperature vessel such as a furnace, and the molten glass ribbons are layered through a nozzle. In these methods, the filaments or selectively melted regions remain susceptible to heat-induced stress during cooling, potentially preventing them from possessing optical properties by creating undesirable refractive index gradients across the thickness of these regions. Additionally, the selectively melted regions leave trapped pores between parts, creating resistance when joining these parts. Moreover, these methods are unsuitable for introducing different compositions in a tightly controlled manner. It is desirable to print and fully form structures at lower temperatures.

[0006] Recent research shows that additive manufacturing (AM) processes for forming glass rely on feedstocks such as fine silica particles, glass rod stock, and glass powder or cullet, which are made from molten glass. While numerous industrial glasses are listed in catalogs, only a limited number of glass compositions have been demonstrated using AM technology. However, many of these glass compositions are generally opaque, due to challenging factors such as chemical composition and the spatial distribution of its composition. Furthermore, the shape and form factors of the feedstocks used to manufacture glass through AM technology are crucial to the processability of the feedstocks using AM technology. In addition, the composition, shape, and morphology of the feedstocks determine the inherent properties of the glass formed from them. These feedstock elements can influence the yield, clarity, and homogeneity of glass formed using AM technology.

[0007] The characteristics of the feedstock become even more important in processes involving multiple feedstocks with multiple compositions that are patterned and processed together. Therefore, engineering the size, structure, composition, format, and surface properties of the feedstocks is essential for successfully forming glass by additive manufacturing (AM). [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Various aspects of the concept of the invention described herein involve introducing a compositional gradient into an amorphous low-density form (LDF) using direct ink writing (DIW) additive manufacturing. Once fully formed, the LDF is heat-treated to become transparent as a complete structure, thereby reducing the edge effect.

[0009] Furthermore, current methods for forming glass with a gradient composition are known to be challenging. In slurry-based 3D printing (S-3DP) systems, dopants are added after the LDF has formed from the slurry and dried. This process addresses structural integrity within the LDF. In addition, the introduction of low-viscosity, droplet-like dopants across the dried body leaves open the possibility that the target species may diffuse radially and axially and fill the pores of the dried structure below through capillary forces, potentially reducing control over the introduced compositional gradient. The compositional gradient is also limited to materials that can be easily mixed into the LDF by diffusion (e.g., small molecules, ions). Therefore, it is desirable to develop a process in which dopants form glass with a gradient composition, which is a component of the mixture, during LDF formation and before the LDF dries. [Means for solving the problem]

[0010] overview Various aspects of the concept of the invention described herein make it possible to (1) form optical or non-optical glass with a custom composition profile that cannot be achieved with conventional glass processing techniques, (2) introduce species that cannot be easily introduced by diffusion methods, and (3) manufacture glass optical components with custom patterns of material properties far larger than those achievable by diffusion methods.

[0011] According to one aspect of the concept of the invention, a composition for an additive manufacturing process comprises a glass-forming material, which is configured to form a three-dimensional structure, and which is self-supporting.

[0012] According to another aspect of the concept of the invention, the composition for the additive manufacturing process comprises a glass-forming material containing blended particles comprising at least two types of particles with different compositions, and a solvent. In addition, the composition is configured to form a three-dimensional structure, which is self-supporting.

[0013] According to yet another aspect of the concept of the invention, the composition for the additive manufacturing process comprises a glass-forming material containing core-shell particles and a solvent.

[0014] Other aspects and advantages of the present invention will become apparent from the following detailed description illustrating the principles of the invention, in conjunction with the drawings. [Brief explanation of the drawing]

[0015] [Figure 1] This is a flowchart illustrating a method for preparing glass components having a custom composition profile, relating to a certain aspect of the concept of the invention. [Figure 2A] This is a schematic diagram of a method for preparing a single-composition glass component, relating to a certain aspect of the concept of the invention. [Figure 2B] This is a schematic diagram of a method for preparing a multi-composition glass component, relating to a certain aspect of the concept of the invention. [Figure 3A] This is a diagram illustrating an aspect of the concept of the invention, showing the process of extruding glass-forming ink onto a substrate. [Figure 3B] This is an image of a printed low-density form relating to a certain aspect of the concept of the invention. [Figure 3C] This is a diagram illustrating a glass foam image following heat treatment of printed low-density foam, relating to a certain aspect of the concept of the invention. [Figure 4A] This is a schematic diagram of a low-density foam, including a gradient in the material properties of the low-density foam along the axial direction, relating to a certain aspect of the concept of the invention. [Figure 4B] This is a schematic diagram of a low-density foam, including a gradient in the material properties of the low-density foam along the radial direction, relating to a certain aspect of the concept of the invention. [Figure 5A] This is a diagram showing an image of a low-density foam with an axial inclination following multi-component printing, relating to a certain aspect of the concept of the invention. [Figure 5B] This is a diagram of an image of a glass foam having an axial inclination following heat treatment of a printed low-density foam, relating to a certain aspect of the concept of the invention. [Figure 5C] This is a diagram illustrating an image of a low-density foam having a radial gradient following multi-component printing, relating to a certain aspect of the concept of the invention. [Figure 5D]A diagram of an image of a radially inclined glass form following heat treatment of a printed low-density form, related to an aspect of the inventive concept. [Figure 6A] A diagram of an image of a printed portion formed using a silica composition, related to an aspect of the inventive concept. [Figure 6B] A diagram of an image of a printed portion formed using a silica composition, related to an aspect of the inventive concept. [Figure 6C] A diagram of an image of a printed portion formed using a silica composition, related to an aspect of the inventive concept. [Figure 6D] A diagram of an image of a printed portion formed using a silica-titania composition, related to an aspect of the inventive concept. [Figure 6E] A diagram of an image of a printed portion formed using a silica-titania composition, related to an aspect of the inventive concept. [Figure 6F] A diagram of an image of the dried substrate after consolidation of FIG. 6E. [Figure 7A] A diagram plotting the refractive index profile against the titania concentration of glass formed according to an aspect of the inventive concept. [Figure 7B] A diagram of an image of the resulting glass structure formed at different titania concentrations, related to an aspect of the inventive concept. [Figure 8] A diagram showing a plot of the heat treatment profile of a consolidation structure formation, including images of each step as inset diagrams in the profile plot, related to an aspect of the inventive concept. [Figure 9A] A diagram of an image of an inclined refractive index silica-titania glass lens prepared by direct ink writing, related to an aspect of the inventive concept. [Figure 9B] A diagram of the surface correction interferogram of the glass lens of FIG. 9A. [Figure 9C] A diagram of an image at a focus of 300 μm from the lens of FIG. 9A. <000011​This is a diagram showing an image of a composite glass made of gold-doped silica glass, relating to a certain aspect of the concept of the invention. [Figure 10B] This figure (Figure 10A) plots the absorbance of the composite glass as a function of the wavelength of light. [Figure 10C] This figure plots the absorbance at 525 nm against a position along the glass surface of the composite glass shown in Figure 10A. [Figure 11] This is a series of schematic diagrams illustrating various aspects of the concept of the invention related to glass-forming materials. [Figure 12] This is a schematic diagram illustrating the preparation of glass-forming feed materials for inks used in printing 3D glass structures, relating to various aspects of the concept of the invention. [Figure 13A] This figure plots the average diameter of the measured particle preparations, determined by dynamic light scattering (DLS). [Figure 13B] This figure includes low-magnification (a) and high-magnification (b) portions of transmission electron microscope (TEM) images of core particles, as well as a schematic diagram of the core particles (c), relating to a certain aspect of the concept of the invention. [Figure 13C] This figure includes low-magnification (a) and high-magnification (b) portions of transmission electron microscope (TEM) images of core-shell particles, as well as a schematic diagram of the core-shell particles (c), relating to a certain aspect of the concept of the invention. [Figure 13D] This figure includes low-magnification (a) and high-magnification (b) portions of transmission electron microscope (TEM) images of core-shell particles, as well as a schematic diagram of the core-shell particles (c), relating to a certain aspect of the concept of the invention. [Figure 13E] This figure shows a low-magnification portion (a) and a high-magnification portion (b) of a transmission electron microscope (TEM) image of core-shell particles relating to a certain aspect of the concept of the invention. [Figure 14A] This diagram shows images of the supernatant and nanoparticle pellets of two mixed particle preparations relating to various aspects of the concept of the invention. [Figure 14B]This is a diagram showing images of vials containing a dried mixed particle preparation relating to various aspects of the concept of the invention. [Figure 15A] This figure shows a schematic portion (a) of a molecular precursor contained in a mixed hybrid particle preparation relating to a certain aspect of the concept of the invention, and a schematic portion (b) of a mixed hybrid particle relating to a certain aspect of the concept of the invention. [Figure 15B] This is a diagram showing an image of a vial containing a mixed hybrid particle preparation in a suspension, relating to a certain aspect of the concept of the invention. [Figure 15C] This figure shows low-magnification (a) and high-magnification (b) portions of transmission electron microscope (TEM) images of mixed hybrid particles relating to a certain aspect of the concept of the invention. [Figure 16A] This is a schematic diagram of a general process for forming an inorganic polymer suitable for printing, relating to a certain aspect of the concept of the invention. [Figure 16B] This figure shows a portion of the image of a product made from inorganic polymer feedstock relating to a certain aspect of the invention (a), a portion of the image of a glass product formed from inorganic polymer feedstock relating to a certain aspect of the invention (b), and a portion of the image of a fired product obtained from inorganic polymer feedstock relating to a certain aspect of the invention (c). [Figure 17A] This is a schematic diagram illustrating the formation of layered shell particles, relating to a certain aspect of the invention's concept. [Figure 17B] This figure shows a series of scanning electron microscope (SEM) images of the formation of layered shell particles relating to a certain aspect of the concept of the invention, where part (a) shows core particles, part (b) shows core particles having one layer of shell, and part (c) shows core particles having two or more layers of shell. [Figure 18A] This is a schematic diagram illustrating the formation of hollow layered particles, relating to a certain aspect of the concept of the invention. [Figure 18B] This figure shows a series of transmission electron microscope (TEM) images of hollow-layer particles relating to a certain aspect of the invention concept, where (a) is a low-magnification portion and (b) is a high-magnification portion. [Figure 18C]This figure plots the energy-dispersive X-ray (EDX) spectrum of a hollow shell particle relating to a certain aspect of the invention's concept. [Modes for carrying out the invention]

[0016] Detailed explanation The following description is provided for the purpose of illustrating the general principles of the present invention and is not intended to limit the concept of the invention claimed herein. Furthermore, certain features described herein can be used in combination with other features described herein in each of the various possible combinations and arrangements.

[0017] Unless otherwise defined herein, all terms should be given the broadest possible interpretation, including the meaning implied herein and the meaning understood by those skilled in the art, and / or defined in dictionaries, papers, etc.

[0018] It should also be noted that, unless otherwise specified, the singular forms "a," "an," and "the" used in this specification and the appended claims refer to multiple subjects.

[0019] The nanoscale is defined as having a diameter or length of less than 1,000 nanometers (nm).

[0020] Please note that ambient room temperature can be defined as a temperature ranging from approximately 20°C to approximately 25°C.

[0021] It should also be noted that as used herein and in the appended claims, wt% is defined as the percentage of the weight of a particular component relative to the total weight / mass of a mixture. vol% is defined as the percentage of the volume of a particular compound relative to the total volume of a mixture or compound. mol% is defined as the percentage of the number of moles of a particular component relative to the total number of moles of a mixture or compound. atom% (at%) is defined as the percentage of one type of atom relative to the total number of atoms of a compound.

[0022] Unless otherwise explicitly defined herein, each component listed in a particular method may be present in an effective amount. An effective amount of a component means that, as a result of its sufficient presence, a discernible change occurs, preferably within a desired range, in the target feature of the ink, printed structure, and / or final product in which the component is present. A person skilled in the art, having received the teachings herein, will be able to readily determine the effective amount of a particular component without relying on excessive experimentation.

[0023] This disclosure includes some description of “inks” as specific examples used in additive manufacturing processes that form the concept of the invention described herein. It should be understood that “ink” (and its singular form) can be used indistinguishably and means a composition of an object comprising multiple particles, wherein these particles are coated in a liquid phase / dispersed throughout the liquid phase and the composition of the object is “written,” extruded, printed, or otherwise deposited, thereby substantially retaining the form and shape when deposited, and possibly accompanied by some, but preferably not excessive, slack, slump, or other deformation when deposited on top of other layers of ink and / or when other layers of ink are deposited on top of this layer. Thus, it will be understood that the inks described herein exhibit suitable fluid properties that enable the formation of a monolithic structure through a series of depositions of multiple layers consisting of ink (or, in some cases, multiple inks of different compositions).

[0024] The following description discloses several preferred structures that are formed by direct ink writing (DIW), free-form extrusion manufacturing, or other equivalent techniques, and thus exhibit unique structural and compositional characteristics obtained through the precise control enabled by such techniques. Physical characteristics of structures formed by DIW may include that the lower layers of the structure are slightly flattened and slightly deformed from the time of the initial extrusion due to the weight or gravity of the upper layers of the structure. A three-dimensional structure formed by DIW may have a single continuous filament that constitutes at least two layers of this 3D structure.

[0025] The following description discloses some preferred aspects of the concept of the invention of systems and methods for preparing optical and non-optical glass components having custom composition profiles, and / or related systems.

[0026] According to a general aspect of the concept of the invention, a composition for an additive manufacturing process comprises a glass-forming material, which is configured to form a three-dimensional structure, and which is self-supporting.

[0027] According to another general aspect of the concept of the invention, the composition for the additive manufacturing process comprises a glass-forming material, which comprises a solvent and a blend of particles containing at least two types of particles with different compositions. In addition, the composition is configured to form a three-dimensional structure, which is self-supporting.

[0028] According to another general aspect of the concept of the invention, the composition for the additive manufacturing process comprises a glass-forming material comprising core-shell particles and a solvent.

[0029] The following is a list of acronyms used in this explanation. 3D 3D DIW Direct Ink Writing DLS (Dynamic Light Scattering) EDX energy-dispersive X-ray FDM (Fused Deposition Modeling) IR infrared G3DP Glass 3D Printing GRIN Refractive Index Glass LDF (Low-Density Foam) Si silicon S-3DP 3D printing using slurry SLM Selective Laser Melting TEM (Transmission Electron Microscope) Ti Titanium TIP Titanium (IV) Isopropoxide UV ultraviolet light A key difference between materials used to form glass in additive manufacturing (AM) and those used in conventional processing techniques lies in the fact that the physical and chemical properties of the raw materials used to form glass are essential for determining optimal processing parameters and optimal material homogeneity. For example, during AM processing, raw materials are not prepared all at once, but rather deposited in small areas or layers. Furthermore, mixing the materials prior to the heating stage (e.g., melting and mixing in a crucible in conventional processes) ensures a high degree of chemical homogeneity. For this reason, the spatial distribution, shape, and shape factors of the composition of the feedstock used to manufacture glass in AM are important for achieving the best processability using AM. For example, the shape and size of the particles, as well as their size distribution, determine the physical properties of the feedstock, such as how the particles clump together, flow, or diffuse. In addition, it is important to understand whether the physical properties of the feedstock are affected by whether the material is solid particles or dispersed in a solvent or resin.

[0030] The regularity of particle size and shape also affects the consistency and reliability of the AM process. In addition, void size (space between particles) controls the temperature at which materials of a fixed composition can be sintered via viscous flow. Both the chemical properties of the particle surface and particle size affect the amount of solid input achievable at a given viscosity in the resin, paste, or solvent, which also affects the degree of component shrinkage and, in some cases, the yield. Furthermore, particle size and the distribution of chemicals within the glass-forming species control the diffusion distance that must be ensured. If this distance is too large, it results in poor homogeneity and leads to phase separation and / or crystallization. These characteristics of the feedstock become even more important when patterning and processing multiple glass compositions together. Therefore, engineering the size, structure, composition, format, and surface properties of the feedstock is essential for successful glass formation by AM. Unfortunately, controlling many of these characteristics is extremely difficult when crushing or milling glass produced from molten material.

[0031] Current additive manufacturing (AM) processes for glass formation rely on supply materials such as glass powder or cullet produced from molten glass, which may contain dopants such as fine silica particles or salts or other dissolved species to alter the composition. Moreover, despite hundreds of industrial glasses being listed in catalogs, only a small number of glass compositions (mostly silica) have been demonstrated using AM technology, and attempts to produce clear glass are even rarer. Although other glass compositions have been demonstrated using sol-gel chemistry along with casting / molding processes, these formulations are not particularly engineered, nor are they designed to meet the requirements of AM processing technology, and the material is deposited layer by layer (forming the structure).

[0032] Various aspects of the invention described herein provide methods for manufacturing active or passive optical or non-optical glass components and / or glass sensors having one-dimensional, two-dimensional, or three-dimensional custom material composition profiles. These various aspects of the invention enable three-dimensional (3D) printing of various inorganic glasses, with or without compositional modifications. Depending on the glass composition and processing conditions, glass may appear transparent or opaque to the human eye. However, the term “optical glass” can be extended beyond glass useful in the visible portion of the spectrum to include UV, visible, near-infrared, mid-infrared, and far-infrared.

[0033] Figure 1 shows a method 100 for preparing an optical glass component having a custom composition profile relating to a particular aspect of the concept of the invention. Optionally, the method 100 can also be carried out on apparatus as shown in other figures described herein. However, it goes without saying that the method 100 and other methods presented herein can be used to form structures for a wide range of apparatuses and / or purposes, which may or may not relate to the specific aspects of the concept of the invention enumerated herein. Furthermore, the methods presented herein can be carried out in other desirable environments. In addition, depending on the various aspects of the concept of the invention, the method 100 may include operations that are more or less different from those shown in Figure 1. It should also be noted that any of the features described above can be used in any aspect of the concept of the invention described according to various methods.

[0034] In one aspect of the concept of the invention shown in Figure 1, Method 100 begins with Operation 102, which includes forming a structure by an additive manufacturing (AM) process. According to various aspects of the concept of the invention, additive manufacturing techniques may include processes having composition mixing capabilities. In one method, a 3D structure can be formed from a composition that is an ink by an extrusion-based AM process, such as direct ink writing (DIW), fused deposition modeling, inkjet printing, inkjet powder bed printing, or aerosol jet printing. In another method, a 3D structure can be formed from a composition that is a resin for an optical AM process, such as stereolithography or projection microstereolithography. In yet another method, a 3D structure can be formed from a composition that is a powder for a laser-assisted melting AM process, such as selective laser melting or a powder bed process. In yet another method, a 3D structure can be formed from a composition used in a deposition-mediated AM process, such as electrophoretic deposition, PolyJet processing, or direct deposition.

[0035] In one method, a newly formed or formed structure can be UV-cured by combining additive manufacturing techniques such as DIW, projection microstereolithography (PμSL), and inkjet printing, using the ink composition as described herein, with UV curing during or after printing of the ink. In another method, the glass structure described herein may be fabricated by using UV-assisted DIW.

[0036] According to various aspects of the concept of the invention, Method 100 may be used to produce filaments, films, and / or 3D monoliths, spanning free-forms, self-supporting structures, and the like.

[0037] According to one aspect of the concept of the invention, the ink comprises a glass-forming material. According to another aspect of the concept of the invention, the glass-forming material comprises a dispersion of prepared particles, the size of which ranges from nanometers to microns. In some methods, the particles may be monodisperse particles. In other methods, the particles may be polydisperse particles. In yet another method, the particles may be aggregated particles.

[0038] In another aspect of the concept of the invention, the glass-forming material may be, but is not limited to, a single composition of inorganic particles, such as fine silica particles, colloidal silica, LUDOX colloidal silica dispersions, titania particles, zirconia particles, alumina particles, or metal chalcogenide particles (e.g., CdS, CdSe, ZnS, PbS). In yet another aspect of the concept of the invention, the glass-forming material may be a single composition of inorganic-containing particles.

[0039] In a certain aspect of the concept of the invention, the glass-forming material may be a plurality of mixed composition particles, for example, but not limited to, two-component silica-titania particles, silica-germanium oxide particles, and / or particles having an inorganic or organic chemically modified surface (i.e., titania-modified silica particles, silica-modified titania particles, 3-aminopropyltriethoxysilane-modified silica particles).

[0040] In certain aspects of the concept of the invention, the glass-forming material may be a mixture of particles of different compositions, for example, a mixture of silica particles and titania particles that melt together to form silica-titania glass, but is not limited thereto.

[0041] According to certain aspects of the concept of the invention, the glass-forming material may not be in the form of particles, or it may be a single composition of the glass-forming material. In some methods, the dopant may be directly mixed with the polymer, and may be, but not limited to, silica, silica-titania-containing polymers, silica-germanium oxide polymers, silica-aluminum oxide polymers, silica-boron trioxide polymers, etc.

[0042] According to several methods, the glass-forming material of the ink may include macromolecules and / or polymers (linear or branched) prepared from small metal-containing organic precursors. Examples of polymers include poly(dimethylsiloxane), silicone, diethoxysiloxane-ethyl titanate copolymer, polyhedral oligomer-silsesquioxane polymer and copolymer. Examples of macromolecules include polyoxometalate clusters and oxoalkoxometalate clusters. Si / Ti-containing polymers manufactured to perform specific functions can be synthesized by acid-catalyzed hydrolysis of organic silicates and organotinates, for example, tetraethyl orthosilicate and titanium isopropoxide, with an additional transesterification step if necessary. Modifications to this process include the use of organometallic chemicals with non-metal-oxygen bonds, such as (3-aminopropyl)triethoxysilane; doping by direct addition of salts to polymer solutions, such as NaF, Cu(NO3)2, and Li2CO3; doping by incorporating metal species into polymer chains during acid-catalyzed hydrolysis; and substitution of major (e.g., silicon (Si)) and secondary (e.g., titanium (Ti)) glass components with linearly polymerizable alternatives, such as Ge, Zr, V, and Fe.

[0043] According to several methods, the glass-forming material of the ink may contain small metal-containing organic and / or inorganic precursors, such as metal alkoxides, siloxanes, silicates, phosphates, chalcogenides, metal hydroxides, and metal salts. Examples include silicon alkoxides, boron alkoxides, titanium alkoxides, and germanium alkoxides. In some methods, the glass-forming material of the ink may contain titanium isopropoxide, titanium diisopropoxide bis(acetylacetonate), tetraethyl orthosilicate, zinc chloride, and titanium chloride.

[0044] In certain aspects of the invention, the glass-forming material can be suspended in a solvent. In some methods, the solvent may be a suspension. In certain aspects of the invention where the glass-forming material is a polar and / or hydrophilic glass-forming material, the solvent is preferably a polar aprotic solvent. In some methods, the solvent may be pure or a mixture of propylene carbonate, dimethyl ether (e.g., tetra(ethylene glycol)dimethyl ether), and / or dimethylformamide. In other methods, the solvent may be a polar protic solvent, such as alcohol and / or water. In some methods where the glass-forming material is hydrophobic, the solvent may be a nonpolar solvent, such as xylene or alkanes, but is not limited to these.

[0045] According to a certain aspect of the invention's concept, the ink may be a combination of a glass-forming material and at least one second component that modifies the properties of the heat-treated glass structure. In some methods, the second component may be a property that modifies the dopant. In other methods, two or more material properties may be affected by the addition of the second component. In various methods, the second component may affect one or more properties among optical, mechanical, magnetic, thermal, electrical, and chemical properties, which may affect the material properties (e.g., features) of the resulting structure.

[0046] In one method, the second component can be ionic. In another method, the second component can be molecular. In yet another method, the second component can be particle.

[0047] In some aspects of the concept of the invention, the ink may contain one or more effective amounts of a second component that can alter the properties of the heat-treated glass structure. The effective amount of the second component is the amount that alters the properties of the heat-treated glass structure and can be easily determined without conducting any further experiments than necessary to change the concentration of the additive in accordance with the teachings herein, as will become apparent to those skilled in the art from reading this specification.

[0048] In a certain method, the color of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of metal nanoparticles of various sizes (gold, silver), sulfur, metal sulfurs (cadmium sulfurs), metal chlorides (gold chloride), and metal oxides (copper oxide, iron oxide).

[0049] In a certain method, the absorbance (linear or nonlinear) of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of cerium oxide, iron, copper, chromium, silver, and gold.

[0050] In a certain method, the refractive index of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of titanium, zirconium, aluminum, lead, thorium, and barium.

[0051] In a certain method, the dispersion of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of barium and thorium.

[0052] In a certain method, the resulting attenuation / optical density of the structure may be affected by the addition of one or more second components selected from the group consisting of alkali metals and alkaline earth metals.

[0053] In a certain method, the photosensitivity of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of silver, cerium, and fluorine.

[0054] In a certain method, the conductivity of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of alkali metal ions, fluorine, and carbon nanotubes.

[0055] In a certain method, the birefringence of the resulting structure, which has a refractive index dependent on the polarization and propagation direction of light imparted by the crystalline phase formed by the second component, may be influenced by the addition of one or more second components selected from the group consisting of titanium, zirconium, zinc, niobium, strontium, and lithium, in combination with silicon and oxygen.

[0056] In a certain method, the thermal conductivity of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of carbon nanotubes and metals.

[0057] In a certain method, the thermal emissivity of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of tin oxide and iron.

[0058] In a certain method, the thermal expansion coefficient of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of boron oxide and titanium oxide.

[0059] In a certain method, the glass transition temperature of the resulting structure may be affected by the addition of sodium carbonate as a second component.

[0060] In a certain method, the melting point of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of sodium, aluminum, and lead.

[0061] In a certain method, the gain coefficient of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of rare earth ions (e.g., neodymium, erbium, ytterbium) and transition metal ions (e.g., chromium).

[0062] In one method, the photoemission of the resulting structure may be affected by the addition of a second component. In another aspect of the concept of the invention, the luminescence of the resulting structure may be affected by the addition of a second component. In yet another aspect of the concept of the invention, the fluorescence emission of the resulting structure may be affected by the addition of a second component.

[0063] In a certain method, the chemical reactivity of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of alkali metals, alkaline earth metals, and silver.

[0064] In a certain method, the density of the resulting structure may be affected by the addition of one or more second components selected from the group consisting of titanium, zirconium, aluminum, lead, thorium, and barium.

[0065] In some methods, the concentration of a second component of the ink may change during printing to create a compositional gradient in the printed structure. In some methods, the second component of the ink may create a compositional gradient in the ultimately heat-treated structure.

[0066] In some methods, the concentration of the second component of the ink can create compositional changes that are not symmetrical with respect to any axis (e.g., slopes, patterns), for example, patterns may vary radially around a structure (and may form as a finished 3D structure), but are not limited to these.

[0067] In some methods, the ink may contain one or more additional additives in an effective amount that can perform a specific function. For example, additives may improve dispersion, phase stability, and / or network strength, control and / or change pH, modify rheology, reduce crack formation during drying, and promote sintering, but are not limited to these. The effective amount of an additive is the amount that produces the desired function or result, and as will be apparent to those skilled in the art who have read this specification, it can be easily determined without performing any more experiments than necessary to change the concentration of the additive according to the teachings herein.

[0068] In some methods, to enhance dispersibility, the ink may contain one or more additives, such as surfactants (e.g., 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEAA)), polyelectrolytes (e.g., polyacrylic acid), and inorganic acids (e.g., citric acid, ascorbic acid).

[0069] In some methods, the ink may contain additives (e.g., diboron trioxide (B2O3)) to increase phase stability (i.e., to prevent phase / composition separation, which may or may not be crystalline phase separation). Another example is ZnO, which can act as a phase stabilizer for alkali silicates.

[0070] In some methods, the ink may contain additives (e.g., diboron trioxide B2O3) to inhibit crystallization. Other crystallization inhibitors include Al2O3 and Ga2O3.

[0071] In some methods, the ink may contain additives (e.g., polydimethylsiloxane) to enhance the network.

[0072] In some methods, to control the pH, the ink may contain one or more additives from among organic acids, inorganic acids, and bases (e.g., acetic acid, HCl, KOH, NH4OH).

[0073] In a certain method, to modify the rheology, the ink may contain one or more additives from among polymers (e.g., cellulose, polyethylene glycol, polyvinyl alcohol), surfactants (e.g., MEEAA, sodium dodecyl sulfate, glycerol, ethylene glycol), and metal alkoxides (e.g., titanium diisopropoxide bis(acetylacetonate)).

[0074] In some methods, the ink may contain a UV-curable material to adjust its fluidity. In some methods, the UV-curable material may be contained in the solvent of the ink. In other methods, functional groups on the components of the feedstock may be affected by UV curing before, during, or after printing the 3D glass structure. In some methods, functional groups that may be affected by UV curing include acrylate, vinyl, and styrene functional groups. In some methods, the UV-curable component may be included in the feedstock design.

[0075] For example, in one method, a UV-curing material may be added to enable the ink to have an optimal viscosity prior to extrusion, and then the ink may be cured by irradiation with UV light as the nozzle is extruded.

[0076] In one method, the ink may contain one or more additives, such as polymers (e.g., polyethylene glycol, polyacrylate), crosslinkable monomers, or polymers and crosslinkable reagents (e.g., polyethylene glycol diacrylate (PEGDA)), as drying aids to enhance or suppress cracking during drying.

[0077] In some methods, inks may contain additives as sintering aids. Sintering aids improve the sintering / densification process. In the case of glass, the sintering aid may have a viscosity lower than that of the material being sintered into the glass. For example, diboron trioxide (B2O3) may be included as a sintering aid.

[0078] In various methods, the formulation of the glass-forming ink (i.e., the glass-forming material) is optimized for a combination of factors including printability (depending on the 3D printing method), resistance to cracking, and sintering until transparency. In some methods, the volume loading of the glass-forming ink formulation is optimized. In some methods, the compositional gradient characteristics of the glass-forming material can be optimized.

[0079] According to a certain aspect of the concept of the invention, the glass-forming material formulation may include a glass-forming element in the range of about 5 vol% to about 50 vol% of the total volume, a solvent in the range of about 30 vol% to about 95 vol%, a second component (i.e., a dopant) in the range of 0 wt% to about 20 wt%, and an additive in the range of 0 wt% to about 10 wt%.

[0080] Ink Mixing Example 1 5-15 vol% fumed silica (Cabosil EH-5 or Cabosil OX-50) 30-95 vol% tetraethylene glycol dimethyl ether 0-20 wt% Titanium diisopropoxide bis(acetylacetonate) 0-6 wt% ethylene glycol 0-2wt% poly(dimethylsiloxane) Ink Mixing Example 2 75-95 vol% silica-titania-containing polymer 10-25 vol% tetraethylene glycol dimethyl ether 0-10 vol% H2O for pre-hydrolysis Ink Mixing Example 3 5-20 vol% 25-nm titania-coated silica particles 25-45 vol% propylene carbonate 25-45 vol% tetraethylene glycol dimethyl ether 0-5wt% MEEAA According to a certain method, the concentration of the second component of the ink can change during printing to form a compositional gradient in the final heat-treated structure.

[0081] In one method, the ink temperature may be lower than approximately 200°C during printing. In one method, method 100 includes drying the formed structure to remove sacrificial material, which is performed before heat treatment of the formed structure. Ideally, the entire formed structure should be dried in a single process.

[0082] In one method, method 100 includes an operation 104 which involves heat-treating the formed structure in order to convert the glass-forming material into glass.

[0083] In one method, the method comprises further processing of a heat-treated glass structure. In another method, the method comprises grinding a heat-treated glass structure. In yet another method, the method comprises polishing a heat-treated glass structure.

[0084] In a certain method, a heat-treated glass structure may have a fibrous structure. In another method, the heat-treated glass structure may be in sheet form.

[0085] In one method, the heat-treated glass structure may have a three-dimensional monolithic shape. In another method, the heat-treated glass structure may be self-supporting.

[0086] In another method, the heat-treated glass structure may be in the form of a coating on a substrate, such as on a component or tool.

[0087] Figures 2A and 2B illustrate methods 200 and 250 for preparing optical glass components having a custom composition profile, relating to a certain aspect of the concept of the invention. Optionally, methods 200 and 250 can be implemented in connection with features from any other aspect of the concept of the invention listed herein, as described with reference to other drawings. However, it goes without saying that such methods 200 and 250, as well as other methods presented herein, can be used in a variety of applications and / or sorts described in detail or not described in the exemplary aspects of the concept of the invention listed herein. Furthermore, methods 200 and 250 presented herein can be used in any desired environment.

[0088] Figure 2A illustrates a specific aspect of the concept of the invention of method 200 for preparing single-component silica glass. According to one method, the method for printing ink includes DIW printing as shown in steps 222 and 224. DIW is a 3D printing process that utilizes the extrusion of viscoelastic materials. By air pressure or positive displacement, ink 202 is pushed through a small nozzle 208. In some methods, the nozzle 208 is computer-controlled and has three degrees of freedom (x, y, z). In other methods, the nozzle 208 can be expanded to have six axes for printing. The nozzle 208 can be positioned to extrude the ink in a controlled distribution pattern.

[0089] In steps 222 and 224, the DIW is used to laminate hydrodynamically tuned glass-forming DIW ink 202 containing glass-forming species into specified shape dimensions to form a weakly bonded, nearly net-like, porous amorphous low-density foam (LDF) 214. In some methods, the extruded filaments 212 are rapidly solidified into the LDF 214. In some methods, the LDF 214 may be referred to as the substrate, glass-forming species, etc. The glass-forming species can be introduced as a precursor and / or colloid / particle. In some methods, the glass-forming DIW ink 202 may be a colloidal silica ink.

[0090] According to certain methods, glass-forming DIW ink formulations can be optimized for printability, drying / burning, and sintering. Glass-forming DIW ink formulations can be optimized for printability in terms of shear viscosity reduction, flowability (stable flow), shape retention, low aggregation, long print time, and stable pot life (stability). Glass-forming DIW ink formulations can be optimized for drying in terms of handling resistance, resistance to cracking, low / uniform shrinkage, and porosity suitable for the removal of organic compounds. Glass-forming DIW ink formulations can be optimized for sintering in terms of resistance to cracking, low / uniform shrinkage, densification / transparency, and low tendency for phase separation.

[0091] The glass structure manufacturing methods 200 and 250 shown in Figures 2A and 2B, respectively, are highly scalable and compatible with additive manufacturing methods (e.g., 3D printing) such as direct ink writing (DIW) and projection microstereolithography (PμSL). In each method, the glass structure may have physical characteristics formed by additive manufacturing techniques. In each method, physical characteristics may include geometrically arranged filaments, a patterned outer surface defined by the layering of filaments, defined porosity (e.g., ordered, controlled, non-random, etc.), and pore porosity with a moderate average diameter. Thus, by using these three additive manufacturing techniques, it is possible to engineer parts and products with optimal shapes for efficient mass transport and mechanical strength.

[0092] According to one method, step 222 includes extruding the glass-forming DIW ink 202 through the nozzle 208 to deposit the filament 212 onto the substrate 210 in a single layer.

[0093] Step 224 of Method 200 includes forming a layer on top of the glass-forming DIW ink 202 to form an LDF 214. Figure 3A is an image of the colloidal silica ink extruded onto the substrate.

[0094] The LDF214 may be processed in multiple steps to convert it into a heat-treated glass foam 216.

[0095] If necessary, the LDF214 may be further treated either before or after drying to further alter the composition of that portion. In some methods, the additional treatment may include diffusion, leaching, etching, etc. In other methods, the additional treatment may include the use of light, sound, vibration, or a combination thereof to modify the characteristics of the printed form. In yet another method, the optical quality of the resulting glass form may be defined by chemical treatment prior to closing the pores of the LDF by heat treatment.

[0096] In step 226, the LDF may be dried, calcined (i.e., removed at high temperature to remove any remaining solvent / organic matter). During drying, the solvent / solvent phase may be removed. The LDF 214 may be separated from the substrate 210 on which the LDF 214 is printed. In some methods, the drying step 226 may include leaving the LDF at a temperature below the boiling point of the solvent for several hours to several weeks. In some aspects of the concept of the invention, the processing step 226 may include a low-temperature processing step (i.e., burnout) to remove any remaining and / or adsorbed water / solvent phase and organic matter. In some methods, the burnout step may include leaving the LDF at 250-600°C for 0.5-24 hours.

[0097] In some methods, processing step 226 may include heating the LDF214 under an alternative gas atmosphere to chemically convert the surface (e.g., converting free surface hydroxyls to anhydrous siloxane). In some methods, processing step 226 may include heating the LDF214 under an oxidizing gas atmosphere (e.g., O2 gas). In other methods, processing step 226 may include heating the LDF214 under a reducing gas atmosphere (e.g., H2 gas). In yet another method, processing step 226 may include heating the LDF214 under a non-reactive gas atmosphere (e.g., Ar, He). In yet another method, processing step 226 may include heating the LDF214 under a reactive gas atmosphere (e.g., N2, Cl2). In yet another method, processing step 226 may include heating the LDF214 under a vacuum.

[0098] In some methods, processing step 226 may also include compressing a portion of the LDF 214 using uniaxial pressure or equilibrium pressure (i.e., reducing pores) to obtain a compressed form. In some methods, processing step 226 may also include compressing a portion of the LDF 214 under vacuum conditions (i.e., reducing pores).

[0099] Figure 3B is an image of the dried LDF. According to one method, the procedure involves heat-treating the dried LDF 214 to close the remaining pores and form a compacted, transparent glass portion, as shown in step 228 of Figure 2A. In some methods, the compacted form of LDF can be heat-treated.

[0100] The heat treatment step 228 may include sintering, which completely densifies the LDF 214 (i.e., the inorganic glass-forming species) into a solid glass compacted foam 216 at a high temperature. In some methods, the sintering of the LDF may involve leaving it at 500–1600°C for several minutes to several hours. The sintering temperature is determined by the material composition of the LDF, the initial inorganic composition, and the porosity. In some methods, the sintering of the LDF may involve the simultaneous use of applied pressure. In some methods, the heat treatment step 228 may be carried out under different atmospheric conditions. In other methods, the heat treatment step 228 may be carried out in a vacuum.

[0101] In some methods, the heat-treated glass foam 216 can be a monolithic glass structure. Figure 3C is an image showing the monolithic glass structure after heat treatment of the LDF shown in Figure 3B. In some methods, the resulting glass compaction foam 216 can retain the characteristics of the ink 202 that would have been applied during DIW printing (steps 222, 224).

[0102] In one method, the glass compaction foam 216 may have physical features of the LDF 214 including spiral, arched, and / or linear ridges along one surface of the glass foam 216.

[0103] In one method, in post-processing step 230, the glass form 216 may be post-processed to obtain a desired pattern and / or surface finish of the optical component form 218, which is ultimately polished by techniques such as grinding and / or polishing. In one method, the polished optical component 218 is a molded product polished by 3D printing and heat treatment, in which the properties of the LDF 214 are maintained and not removed by polishing. In one method, the polished optical component 218 is a polished monolithic glass structure.

[0104] In some methods, the glass form 216 can be processed as bolt glass, thereby removing any traces of printing by conventionally known techniques. In other methods, the glass form 216 retains characteristics that can only be achieved by the printing processes described herein, even after post-processing.

[0105] Figure 2B shows a schematic diagram of a method 250 for forming inclined and / or distributed patterns in glass products according to one technique. In other techniques, the method may form compositional changes (e.g., inclined, patterns, etc.) that are asymmetric with respect to any axis, for example, the pattern may vary radially around the structure (for example, the pattern may be formed as a complete 3D structure), but is not limited to this.

[0106] In a certain method, a distributed refractive index (GRIN) glass can be formed. Printing of GRIN glass involves printing a non-porous monolith in which the characteristics of the LDF formation lead to a desirable modulus / viscosity, such as space-filling, a high aspect ratio, and spanning. In addition, this method may involve matching the rheology of two types of DIW inks required to form a gradient. In a certain aspect of the concept of the invention, for example, two, three, or four types of inks can be mixed by mixing them before extruding the filament onto the substrate.

[0107] According to one method, during DIW printing, between steps 232 and 234, the filament composition 213 can be adjusted during printing by adjusting the flow rates of separate flows to introduce a desired compositional change into the LDF 214 at the desired locations.

[0108] In some methods, LDF215 can be created by introducing different inks 203 and 204 separately. As schematically shown in the side view of Figure 4A, in one method, the monolithic glass structure 400 (LDF215 in Figure 2B) having the physical characteristics of a 3D printed object may include a gradient of the fire resistance index of the monolithic glass structure 400 along the axial direction of the monolithic glass structure 400. The axial direction 408 is perpendicular to the plane 410 of the laminate.

[0109] Referring again to Figure 2B, in step 234, the glass structure is formed as an LDF (LDF 215 in Figure 2B) in which the first glass-forming ink 203 can be extruded following the extrusion of the second glass-forming ink 204. The resulting glass structure 400 shown in Figure 4A has a first glass 403 and a second glass 404 formed from the first glass-forming ink 203 and the second glass-forming ink 204, respectively.

[0110] In some methods, processing step 236 may also include compressing a portion of the LDF 215 using uniaxial pressure or equilibrium pressure (i.e., reducing pores) to obtain a compressed form. In some methods, processing step 236 may also include compressing a portion of the LDF 215 under vacuum (i.e., reducing pores).

[0111] Furthermore, the resulting glass structure 400 in Figure 4A may include an interface 406 between a first glass 403 formed from a glass-forming material and a second glass 404 formed from a second glass-forming material having a different composition from the first glass-forming material. In some methods, the second glass-forming material cannot move across the interface to the first glass-forming material, so the first glass 403 is not mixed with the second glass 404, and vice versa.

[0112] In one method, the interface 406 can be substantially oriented along the plane 410 of the monolithic glass structure 400 so that the monolithic glass structure is divided into two parts having different compositions directly adjacent to the interface, namely, a first glass 403 and a second glass 404.

[0113] As shown in Figures 5A to 5D, the material properties of the final heat-treated structure were altered using two different inks, namely silica and silica with 20 nm gold nanoparticles. Figures 5A and 5B show the formation of an axial step in the absorbance of the final heat-treated structure. As shown in Figure 5A, a conformational change was formed in the LDF where the first ink silica was used to form a portion of the LDF (the bottom of the LDF in Figure 5A), and then the ink was switched to a second ink, namely silica / gold nanoparticle ink (the top of the LDF in Figure 5A). Subsequently, the LDF was compacted into glass by sintering during heat treatment (step 238 in Figure 2B). The resulting monolithic glass structure, which has a gradient in absorbance along the axial direction, is shown in Figure 5B, where the silica / gold nanoparticle portion of the glass is the top in Figure 5B.

[0114] In one aspect of the concept of the invention, the physical features of the monolithic glass structure 217 are a gradient containing two or more glass-forming materials such that the interface between the first glass-forming material and the second glass-forming material is uniform. As shown in Figure 5A, an interface exists between the upper glass-forming material (silica / gold nanoparticles) and the lower material (silica). Furthermore, there is no movement of the first glass-forming material (silica) to the second glass-forming material (silica / gold nanoparticles), and conversely, there is no movement from the second glass-forming material (silica / gold nanoparticles) to the first glass-forming material (silica).

[0115] Conventional methods for 3D printing optical glass have failed to realize aspects of the concept of the invention described herein. This is because conventional methods have difficulty controlling the thermal gradient during 3D printing, resulting in non-uniform interfaces between filaments, and / or lack the ability to incorporate multiple materials within the substrate or LDF.

[0116] In other methods, a smooth compositional change is formed by harmonizing and mixing the ink flows from different inks 203 and 204 through active mixing using a mixing paddle 206 near the tip of the nozzle 208. As schematically shown in the top view of Figure 4B, in one method, the monolithic glass structure 420 (LDF215 in Figure 2B) having the physical characteristics of a 3D printed object may have other material properties such as a gradient in refractive index or absorbance along the radial direction of the monolithic glass structure 420. The radial direction 412 is along the plane 410 of the laminate in any direction. Referring again to Figure 2B, the glass structure is formed as an LDF (LDF215 in Figure 2B) with a radial step in refractive index, which is an ink flow in which the two types of inks 203 and 204 in Figure 2B are harmoniously blended. The resulting glass structure 420 in Figure 4B has a first glass 414 and a second glass 413 formed from a first glass-forming material 203 and a second glass-forming material 204, respectively.

[0117] Furthermore, the resulting glass structure 420 in Figure 4B includes an interface 416 between a first glass 414 formed from a glass-forming material and a second glass 413 formed from a second glass-forming material having a different composition from the first glass-forming material. In some methods, the second glass-forming material cannot move across the interface to the first glass-forming material, so the first glass 403 is not mixed with the second glass 404, and vice versa.

[0118] In one method, the interface 416 can be oriented substantially perpendicular to the plane 410 of the monolithic glass structure 420, thereby dividing the monolithic glass structure 420 into two parts having different compositions directly adjacent to the interface 416, namely, a first glass 414 and a second glass 413.

[0119] According to a certain method, conformational changes can be printed onto LDF using two different inks, resulting in a material property of radial step in absorbance of the final heat-treated structure. As shown in Figures 5C and 5D, a radial step in absorbance, which is a flow of ink harmoniously blended from the two inks, can be printed using a first ink of silica and a second ink of silica / gold nanoparticles. Figure 5C shows an LDF form with silica / gold nanoparticle ink in the center of the LDF and silica ink in the outer part of the LDF. Figure 5D shows the resulting monolithic glass structure with a gradient in absorbance along the radial direction.

[0120] Compositional changes are not limited to axial and / or radial gradients (such as gradients obtained by diffusion techniques), but can be shaped to generate any desired profile in the LDF.

[0121] Compositional changes in LDF215 can alter the material properties within the formed glass 217. Examples of material properties that may be affected by compositional changes in LDF215 have been described in detail earlier. These examples may include, but are not limited to, absorbance, propagation coefficient, refractive index, dispersibility, scattering, conductivity, thermal conductivity, thermal expansion coefficient, gain coefficient, glass transition temperature (Tg), melting point, photoemission, fluorescence emission, chemical reactivity (e.g., etching rate), and concentration / porosity.

[0122] As shown in Figure 2B, the DIW printing in steps 232 and 234 may include the formation of an LDF 215 relating to a certain aspect of the concept of the invention. The LDF begins in the first step 232 of the DIW printing as a single layer on the substrate 210. As the DIW printing continues in step 234, the LDF 215 may be formed layer by layer until the desired LDF 215 (i.e., substrate) is formed.

[0123] In some methods, the formation of LDFs with a single composition (Method 200) or LDFs with multiple compositions (e.g., gradients) (Method 250) may involve fused deposition modeling (FDM). FDM uses thermoplastic filaments, which may be composite mixtures of multiple materials combined with a mixing paddle similar to the ink mixture of DIW (see steps 232-234 in Figure 2B). As shown in steps 222-224 or 232-234 in Figures 2A and 2B, respectively, the resulting filaments can be extruded through a heated nozzle to form an LDF on a substrate. The nozzle is heated to a temperature in the range of about 150°C to 200°C, specifically to heat the filament for extrusion. In some methods, a sacrificial support material is extruded by a second nozzle to support the glass-forming material extruded by the mixing nozzle. In some methods, the extruded filaments and / or polymers of the support material are removable after the formation of the LDF.

[0124] In various methods, LDF can be formed in complex shapes, such as cones, spirals, or cylinders, but is not limited to these.

[0125] The LDF215 may be processed in multiple steps to compact it and convert it into glass foam 217.

[0126] As described in step 226 of method 200 in Figure 2A, the formed LDF 215 can be dried and / or subjected to additional processing.

[0127] Referring again to Figure 2B, according to one embodiment, step 238 of method 250 includes heat-treating the dried LDF 215 to close any remaining pores and form a compacted, transparent glass portion. The resulting glass compacted foam 217 retains the compositional changes that would have been given during DIW printing (steps 232, 234).

[0128] In one method, the glass compaction foam 217 may have physical features of the LDF 215 including spiral, arched, and / or linear ridges along one surface of the glass foam 217.

[0129] According to one method, in post-processing step 240, for example, the glass form 217 can be further processed to achieve the desired shape and / or surface finish of the final polished optical component 220 by methods such as grinding and / or polishing. In one aspect of the concept of the invention, the polished optical component 220 is a molded product polished by 3D printing and heat treatment, and the properties of the LDF 215 are preserved and not removed by polishing. In one aspect of the concept of the invention, the polished optical component 220 is a polished monolithic glass structure.

[0130] The various methods described herein are applicable to a variety of (mainly) amorphous inorganic glass materials, in addition to silica-based glasses such as phosphate-based glasses, borate-based glasses, germanium oxide-based glasses, fluoride-based glasses, aluminosilicate-based glasses, and chalcogenide-based glasses.

[0131] Engineered feedstock One aspect of the invention's concept describes a process for producing feedstocks that can enable the production of glasses with different compositions and material properties using additive manufacturing. For example, inks may include glass-forming materials for extrusion-based AM processes, resins may include glass-forming materials for photocurable AM ​​processes, and powders may include glass-forming materials for selective laser melting AM processes. The feedstocks are engineered to not only meet the requirements of a particular AM process but also to provide desired glass compositions and properties by adjusting the size and chemical composition (as well as chemical distribution) of the feedstocks that form the glass. By reacting liquid chemical precursors or mixtures of precursors, such as metallic organic substances or silanes, together under controlled reaction conditions, particles or long chains of a predetermined size and various shape factors can be formed by performing a series of reaction steps in sol-gel chemistry.

[0132] Figure 11 is a schematic diagram of various examples of the techniques described herein for engineered feedstocks for the additive manufacturing of glass.

[0133] (a) Blended particles. A blend of different particles of a single composition (blended particles) can be used. As shown in the schematic diagram in part (a) of Figure 11, a glass-forming feedstock consisting of blended particles relating to one aspect of the concept of the invention includes particles of different compositions grown separately. For example, the particles can be grown by base-catalyzed sol-gel chemistry. In one method, the particles of different compositions may include SiO2 particles 1102 and GeO2 particles 1104. The particle size scale will determine the sufficient mixing during co-thermal processing and the mixing of these particles during preparation for the subsequent AM process. In some methods, the average diameter d1 of the particles in the blended particle feedstock may be in the range of about 30 nm to about 50 nm, and this average diameter can be larger or smaller than that.

[0134] In one method, the composition comprises a glass-forming material containing blended particles. This composition having blended particles may contain at least two types of particles with different compositions from each other, and a solvent. This composition may be configured to form a 3D structure. In one method, this composition containing blended particles may be an ink for an extrusion-based AM process. In another method, this composition containing blended particles may be a resin for a light-based AM process. In yet another method, this composition containing blended particles may be a powder for a laser-assisted melting AM process, such as selective laser melting or a powder bed process. In some methods, the formed 3D structure may be self-supporting.

[0135] In some methods, the blended particles may contain oxide species. In some methods, the blended particles may contain at least one of SiO2, GeO2, TiO2, ZrO2, etc. In some methods, the blended particles may contain SiO2 together with metal nanoparticles. In some methods, the blended particles may contain SiO2 together with at least one of metal nanoparticles of gold, silver, nickel, copper, or a combination thereof. In some methods, the blended particles may contain SiO2-PbO (silica lead oxide).

[0136] In some methods, the blended particle composition may contain three or more oxide species. For example, the blended particle composition may include SiO2-NaO-TiO2, SiO2-BaO-TiO2, SiO2-PbO-TiO2, SiO2-GeO2-PbO, SiO2-GeO2-TiO2, SiO2-NaO-Al2O3, SiO2-B2O3-Al2O3, SiO2-GeO2-ZrO2-TiO2, SiO2-ZrO2, etc. In some methods, each type of particle may have a unique oxide species in comparison to other types of particles.

[0137] (b) Core-shell particles. As shown in the schematic diagram of part (b) of Figure 11, the feedstock may include core-shell particles. Core-shell particles can be formed by first growing core particles from molecular precursors, and then by subsequent reactions growing a shell or coating on the surface of the core particles. In one method shown in part (b), an SiO2 core particle 1106 may have a TiO2 shell 1108 formed on the surface of the SiO2 core particle 1106. In one method, the shell may be an island dispersed around the particle. In another method, the shell may be a fully formed continuous layer. In some methods, the average diameter d2 of the core particle 1106 may be in the range of about 25 nm to about 200 nm, and the average diameter may be greater or smaller than that. In some methods, the average thickness th1 of the shell 1108 may be in the range of about 2 nm to about 4 nm, and may be greater or smaller than that.

[0138] In some methods, core-shell particles may contain SiO2, GeO2, TiO2, etc. In some methods, core-shell particles may contain SiO2 together with metal nanoparticles. In some methods, core-shell particles may contain SiO2 together with at least one of the following metal nanoparticles: gold, silver, nickel, copper, or a combination thereof. In some methods, core-shell particles may contain SiO2-PbO (silica lead oxide).

[0139] In some methods, the core-shell particle composition may contain three or more oxide species. For example, the core-shell particle composition may include SiO2-NaO-TiO2, SiO2-BaO-TiO2, SiO2-PbO-TiO2, SiO2-GeO2-PbO, SiO2-GeO2-TiO2, SiO2-NaO-Al2O3, SiO2-B2O3-Al2O3, SiO2-GeO2-ZrO2-TiO2, SiO2-ZrO2, and the like.

[0140] In one method, the composition comprises a glass-forming material containing core-shell particles and a solvent. In another method, the core-shell particle composition may be configured to form a 3D structure. In one method, the core-shell particle composition may be an ink for an extrusion-based AM process. In yet another method, the core-shell particle composition may be a resin for an optical AM process. In yet another method, the core-shell particle composition may be a powder for a laser-assisted melting AM process, such as selective laser melting or a powder bed process. In one method, the formed 3D structure may be self-supporting.

[0141] In one method, the composition for the AM process may include a glass-forming material, which may be configured to form a 3D structure. In one method, the formed 3D structure may be self-supporting. In one method, the composition may include a glass-forming material and a solvent.

[0142] (c) Mixed particles. As shown in part (c) of Figure 11, the feedstock may include mixed particles. In various methods, mixed particles are particles grown together from a mixture of molecular precursors using chemical reactions that are tuned to produce a mixture of different chemical species within the same particle. In one method, as shown in part (c), particle 1110 may include a mixture 1112 consisting of O, Si, and Ti (mixture 1112 is shown in a magnified view of a portion of particle 1110). In various methods, the average diameter d4 of particle 1110 may be in the range of about 100 nm to about 400 nm, and this average diameter may be larger or smaller than this.

[0143] In some methods, the glass-forming feedstock may include a mixture within the formation of small clusters of particles grown together (shown in the enlarged view of mixture 1112), which may not form particles. In some methods, the mixed feedstock may include clusters of particles, such as oxoclusters, oligomer-based clusters, small structures, or aggregates, consisting of particles containing different chemical species. In some methods, the average diameter of small clusters, aggregates, oxoclusters, etc., may be in the range of about 100 nm to about 400 nm, and may be larger or smaller than this range.

[0144] In some methods, the mixed particles may include SiO2, GeO2, TiO2, ZrO2, etc. In some methods, the mixed particles may include SiO2 together with metal nanoparticles. In some methods, the mixed particles may include SiO2 together with at least one of the metal nanoparticles of gold, silver, nickel, copper, or a combination thereof. In some methods, the mixed particles may include SiO2-PbO (silica lead oxide).

[0145] In some methods, the mixed particle compositions may contain three or more oxide species. For example, the mixed particle compositions may include SiO2-NaO-TiO2, SiO2-BaO-TiO2, SiO2-PbO-TiO2, SiO2-GeO2-PbO, SiO2-GeO2-TiO2, SiO2-NaO-Al2O3, SiO2-B2O3-Al2O3, SiO2-ZrO2-TiO2, SiO2-GeO2-ZrO2-TiO2, and the like.

[0146] In some methods, the composition for the AM process includes a glass-forming material containing mixed particles. In one method, the mixed particles can be defined as a cluster of particles containing at least two different chemical species. In another method, the composition includes a cluster of particles having at least one oxide species and at least one metal nanoparticle.

[0147] In one method, the composition containing the mixed particles may be configured to form a 3D structure. In another method, the composition containing the mixed particles may be an ink for an extrusion-based AM process. In yet another method, the composition containing the mixed particles may be a resin for a light-based AM process. In yet another method, the composition containing the mixed particles may be a powder for a laser-assisted melting AM process, such as selective laser melting or a powder bed process. In one method, the formed 3D structure may be self-supporting. In one method, the composition may contain a glass-forming material and a solvent.

[0148] (d) Inorganic polymers. As shown in part (d) of Figure 11, the feedstock may include inorganic polymers. In one method, when a polymer is grown together from a mixture of molecular precursors by acid-catalyzed sol-gel chemistry, a mixture of closely related chemical species is obtained in long molecular chains rather than in particles. As shown in part (d), the long molecular chains 1114 of the polymer may have a mixture of closely related chemical species 1116. A magnified view of mixture 1116 shows that the various chemical species may include species having Ti, Si, O, -OH, or OR groups. The listed chemical species are for illustrative purposes only and are not intended to be limiting.

[0149] In one method, the composition may include a glass-forming material having an inorganic polymer. In one method, the inorganic polymer may be a linear polymer. In another method, the inorganic polymer may be a branched polymer. In yet another method, the inorganic polymer may be a combination of a linear polymer and a branched polymer. In one method, the glass-forming material may include a low molecular weight inorganic polymer; for example, the glass-forming material may include an inorganic oligomer. In a method for obtaining an oligomer, the length of the polymer chain may include a small number of repeating units whose physical properties are determined by the length of the polymer chain. In one method, the inorganic oligomer may be a linear oligomer. In one method, the inorganic oligomer may be a branched oligomer. In yet another method, the inorganic oligomer may be a combination of a linear oligomer and a branched oligomer.

[0150] In one method, a composition containing a glass-forming material having an inorganic polymer may be configured to form a 3D structure. In another method, the composition containing the inorganic polymer may be an ink for an extrusion-based AM process. For example, the polymer-type glass-forming material may have a viscosity suitable for extrusion. In yet another method, the composition containing a glass-forming material having an inorganic polymer may be a resin for a light-based AM process. In yet another method, the composition containing a glass-forming material having an inorganic polymer may be a powder for a laser-assisted melting AM process. In various methods, the 3D structure formed from the composition containing the inorganic polymer may be self-supporting. In one method, the composition containing a glass-forming material having an inorganic polymer may contain a solvent.

[0151] (e) Layered shell particles. As shown in part (e) of Figure 11, the feed material for forming the glass may include layered shell particles, such as layered onions. In various methods, the layered shell particles have core particles and shells similar to the core-shell particles in part (b), but further include layers of different composition produced by repeated surface reactions on the core-shell particles. The thickness of each layer may be adjusted according to the desired specifications. In some methods, the thickness of each layer of shell may be in the range of about 2 nm to about 10 nm, but this thickness can be greater or less than that. In some methods, the total thickness of multiple layers of shell may be in the range of about 4 nm to about 50 nm, but this thickness can be greater or less than that.

[0152] As shown in part (e), an example of a layered shell particle 1118 may include an SiO2 core particle 1120 and several layers of different compositions, these layers including two GeO2 layers 1122, two alternating TiO2 layers 1124, and a final SiO2 shell layer 1126. In one method, the layered shell particle includes at least two shell layers on top of the core particle, and each of these at least two shell layers has a different composition. In one method, the shell layers on top of the core particle have alternating compositions, for example, composition 1-composition 2-composition 1-composition 2.

[0153] In some methods, layered shell particles may contain SiO2, GeO2, TiO2, etc. In some methods, layered shell particles may contain SiO2 together with metal nanoparticles. In some methods, layered shell particles may contain SiO2 together with at least one of the following metal nanoparticles: gold, silver, nickel, copper, or a combination thereof. In some methods, layered shell particles may contain SiO2-PbO (silica lead oxide).

[0154] In some methods, the layered shell particle composition may contain three or more oxide species. For example, the layered shell particle composition may include SiO2-NaO-TiO2, SiO2-BaO-TiO2, SiO2-PbO-TiO2, SiO2-GeO2-PbO, SiO2-GeO2-TiO2, SiO2-NaO-Al2O3, SiO2-B2O3-Al2O3, SiO2-GeO2-ZrO2, and the like.

[0155] In one method, a composition having core-shell particles may include layered shell particles, each of which has at least two shell layers on top of the core particle. In one method, the shell layers have different compositions from each other.

[0156] In one method, the composition comprises a glass-forming material having layered shell particles. In one method, the composition comprising layered shell particles may be configured to form a 3D structure. In one method, the composition comprising layered shell particles may be an ink for an extrusion-based AM process. In another method, the composition comprising the glass-forming material comprising layered shell particles may be a resin for a light-based AM process. In yet another method, the composition comprising the glass-forming material comprising layered shell particles may be a powder for a laser-assisted melting AM process. In one method, the formed 3D structure may be self-supporting. In one method, the composition comprising the glass-forming material comprising layered shell particles may contain a solvent.

[0157] (f) Hollow layered shell particles. As shown in part (f) of Figure 11, the feed material for forming the glass may include hollow layered shell particles. In one method, all or part of the original core of the layered shell particles shown in part (e) may be removed before the subsequent sol-gel chemistry layering of the species. In one method, the hollow layered shell particles can limit the central domain size of the composition, prevent phase separation, or achieve a combination of these.

[0158] As shown in part (f), in one method, the hollow layered shell particle 1132 has a hollow core region 1130 and layers in a format similar to that described for the layered particle 1118 in part (e).

[0159] In one method, the composition comprises a glass-forming material having core-shell particles, which include layered shell particles having a hollow core. In one method, the composition comprising layered shell particles having a hollow core may be configured to form a 3D structure. In one method, the composition comprising layered shell particles having a hollow core may be an ink for an extrusion-based AM process. In another method, the composition comprising a glass-forming material comprising layered shell particles having a hollow core may be a resin for an optical AM process. In yet another method, the composition comprising a glass-forming material comprising layered shell particles having a hollow core may be a powder for a laser-assisted melting AM process. In one method, the formed 3D structure may be self-supporting. In one method, the composition comprising a glass-forming material having layered shell particles having a hollow core may contain a solvent.

[0160] (g) Combined or hybrid particles. In various methods, hybrid and / or combined particles may be formed by combining the particles of the feedstock described in parts (a) to (f). For example, as shown in part (g), the combined particle 1140 may be a combination of the core-shell particle shown in part (b) and the core particle 1134, which is a mixed particle shown in part (c). As shown in the figure, the core particle 1134 may include the mixed particle 1136 shown in the enlarged view, and the core particle may have a GeO2 shell 1138. These methods are merely illustrative and not intended to be limiting.

[0161] In various methods, the composition may include a glass-forming material containing multiple combination particles and a solvent. In some methods, the composition may be configured to form a self-supporting 3D structure.

[0162] In various methods, the raw materials used to form the glass may include combined particles having at least two of the following characteristics as described herein: shells, mixed cores, layered shells, layered shell particles having hollow cores, and inorganic polymers.

[0163] Figure 12 is a schematic diagram of a process for engineering a feedstock for AM technology resulting in the formation of a glass structure, relating to one aspect of the concept of the invention. Steps 1202 and 1204 show a process 1200 for growing the feedstock SiO2-TiO2 particles, thereby forming SiO2 particles. In one method, the process for preparing the feedstock includes a Stober sol synthesis process, which will be generally understood by those skilled in the art. Step 1206a includes producing SiO2-TiO2 core-shell particles, which are the feedstock for the AM process, by adding TiO2 shells to SiO2 particles. Step 1206a produces the feedstock for SiO2-TiO2 core-shell particles for the AM process by adding TiO2 shells to SiO2 particles. Figure 1206b shows a suspension of SiO2-TiO2 core-shell particles.

[0164] Process 1220 in Figure 12 illustrates several possible steps for forming a glass structure using engineered feedstocks, following a certain aspect of the concept of the invention. The SiO2-TiO2 core-shell particles shown in step 1206 may be one of several engineered feedstocks 1212 that can be used for printing. Blended particles 1208 and / or mixed particles 1210 can be used for printing as two other engineered feedstocks 1212, though not intended to be limiting. A magnified view of 1210 shows the different chemical compositions that may be contained in the mixed particles.

[0165] In various aspects of the invention's concept, printed glass can be formed by using engineered glass-forming feedstocks in conjunction with AM technology.

[0166] In some methods, the type of engineered feedstock used may depend on the desired length scale for printing. In some methods, a blended particle feedstock may be preferable for a larger length scale of 10 μm. In other methods, a mixed particle feedstock may be preferable for a shorter length scale of 1 nm. These methods are given as examples only and are not intended to be limiting.

[0167] By adjusting the properties of the feedstock, elements essential to the processing of feedstock by AM may be optimized. In some methods, these properties include particle sphericity and cohesiveness, which can affect the fluidity of particles as a powder or suspended in a solvent or resin. In some methods, these properties include the compatibility of the feedstock material with the solvent. In some methods, these properties include the relative miscibility of the feedstock material with other feedstock materials.

[0168] Furthermore, by adjusting the feedstock, further processing of the substrate (manufactured by AM technology) formed from the feedstock for forming the glass may be optimized. In some methods, the properties of the particles in the feedstock may affect the sintering temperature during further processing for forming the glass. In some methods, the properties of the particles in the feedstock include packing density and void size, which may affect the possibility of achieving clear, crack-free glass.

[0169] In addition, the particle feedstock described herein allows for predetermined uniformity / homogeny of the feedstock material by adjusting the length scale to the desired specifications in comparison with the distribution of each of the different species, and also reduces the tendency of the species to undergo phase separation and crystallization during heat treatment.

[0170] In various methods, the preparation of ink from the raw materials used to form glass may include single-pot solvent exchange, size-selective precipitation, and ink filtration.

[0171] In some methods, the glass formed by the methods described herein may contain rare earth dopants. In some methods, the formed glass may include P2O5-based glass having dopants such as Nd, Yb, Ce, Er, Ho, Gd, Dy, Eu, Y, and combinations thereof. In some methods, the glass may include SiO2-based glass having dopants such as Nd, Yb, Ce, Er, Ho, Gd, Dy, Eu, Y, and combinations thereof.

[0172] In some methods, the glass formed by the methods described herein can have improved solubility and phase stability by including oxide species such as Al2O3 and alumina as additives.

[0173] Mixing inks for printing glass structures may include mixing calibration methods and printing compensation mechanisms that enable the printing of parts according to specifications.

[0174] In some methods, the glass structure may be printed on a substrate that prevents the glass portion from breaking. Specific examples of substrate materials include silicone rubber, silicone-treated surfaces, paper, aluminum, Teflon®, porous substrates (such as porous paper), and others.

[0175] In some methods, the printed glass portion of the substrate may be treated by chemical treatment. For example, the chemical treatment of the substrate may include NH3, CH3COOH, TEOS, triethylamine atmosphere, etc., for purposes such as promoting the formation of chemical bonds, facilitating the removal of solvents, etc.

[0176] In some methods, the printed glass portion of the substrate stage may be treated with a heat treatment atmosphere technique. For example, the heat treatment atmosphere technique may include air, vacuum, nitrogen, helium, or mixtures containing a chlorine or fluorine source (e.g., Cl2, F2, HF, fluorinated alkoxides (e.g., Si(OC2H5)3F)) and others.

[0177] In some methods, the printed glass portion in the substrate stage may be treated by microwave drying. In some methods, the printed glass portion in the substrate stage may be treated by a pressure-based method, such as a cold isostatic press, a press, a hot isostatic press, or the like.

[0178] Engineering-designed raw materials can be used to produce multi-component or single-component glasses of various compositions using a variety of additive manufacturing techniques. This will make it possible to prepare glasses for which no currently available raw materials exist by AM processes.

[0179] In various aspects of the concept of the invention, the engineered feedstock can be used to prepare glass by additive manufacturing processes, including direct ink writing, robocasting, computational axis lithography, projection microstereolithography (or other stereolithography printing techniques), inkjet printing, electrophoretic deposition, and powder bed techniques, such as selective laser melting / sintering, binder jetting, and others. In various aspects of the concept of the invention, the engineered feedstock can also be used in coating processes such as dip coating, meniscus coating, spin coating, and others.

[0180] Heat treatment example 1 A printed monolith of silica or silica-titania substrate (25 mm in diameter, 5 mm thick) is placed on a hot plate at 100°C. After 3 hours, the printed substrate is removed from the substrate. The substrate is then dried in a box furnace at 100°C for 110 hours. The liquid-free substrate is then heated to 600°C at a heating rate of 10°C / min and left for 1 hour to burn out any remaining organic components. The substrate is then heated to 1000°C at 100°C / hour and left in a vacuum for 1 hour. Finally, the portion is sintered in a furnace preheated to 1500°C for 3-10 minutes. These portions are then removed and rapidly cooled to room temperature. All non-vacuum processing steps are performed in the atmosphere.

[0181] Heat treatment example 2 A printed monolithic silica substrate, composed of silica or silica-titania particles with a diameter of 25 nm (25 mm in diameter, 5 mm thick), is heated to 75°C in a box furnace at a rate of 3°C / hour. Once the furnace reaches 75°C, the printed substrate is removed from the substrate. The substrate is then dried in a drying oven at 75°C for 120 hours. Next, the liquid-free substrate is heated to 600°C at a rate of 1°C / minute and left in that state for 1 hour to burn out any remaining organic components. Finally, this portion is sintered in a furnace preheated to 1150°C for 1 hour. These portions are then removed and rapidly cooled to room temperature. All non-vacuum processing steps are performed in the atmosphere.

[0182] experiment Figures 6A to 6F are images of the printed area created using ink formulation 3 (as described above). Figures 6A to 6C are images of the printed area formed using a silica-only composition. Figure 6A is an image of the substrate formed after printing. Figure 6B is an image of the substrate from Figure 6A after drying. Figure 6C is an image of the dried substrate from Figure 6B after compaction.

[0183] Figures 6D to 6F are images of the printed area formed using the silica-titania composition. Figure 6D is an image of the substrate formed after printing. Figure 6E is an image of the substrate from Figure 6D after drying. Figure 6F is an image of the dried substrate from Figure 6E after compaction.

[0184] Figure 7A plots the refractive index profile (y-axis) of the resulting glass against the titania (TiO2) concentration (wt%, x-axis). The glass formed with formulation 1 ink (as described above) is shown as diamond (◆, solid line) in the plot and exhibits a refractive index change comparable to that of commercially available silica (▲) and silica titanate glass (○, □) (dotted line). Figure 7B is an image of the resulting glass structures formed from the ink formulations, shown by diamond (◆) in Figure 7A, at different TiO2 concentrations wt% (2wt%, 4wt%, 5wt%, 6wt%, 8wt%, 9wt%, 10wt%).

[0185] Figure 8 plots the heat treatment profile of the formation process of a compacted printed portion using ink formulation 1 (described above). The volume shrinkage rate (V) of the structure at each step during the heat treatment process is shown. ink ) is shown next to the image of the structure.

[0186] Figure 9A is an optical image of a gradient refractive index silica-titania glass lens prepared by direct ink writing on an LDF while harmonizing and mixing two inks in the required proportions using a printhead. Two inks were used from formulation 1 (described above): ink A containing 0% titanium alkoxide, and ink B containing enough titanium alkoxide to obtain 1.6 wt% TiO2 in the final compacted glass. The glass was compacted using the heat treatment profile shown in Figure 8 and then polished using ceria pad polishing. Figure 9B is a surface-modified interferogram showing how the refractive index changes within most of the material shown in the image in Figure 9A. The refractive index is highest at the center, where the TiO2 composition is highest. The refractive index is lowest at the edges, where the TiO2 composition is lowest. The lineout crossing the center indicates that the change in refractive index across the center is parabolic, as shown by the inset plot of δη / (η0-1) on the y-axis and distance (mm) on the x-axis in Figure 9B, suggesting that the portion can function as a lens. Figure 9C is an image at a focal length of 300 μm from a lens with a focal length of 62 cm.

[0187] Figure 10A is an optical image of a composite glass composed of a gold-doped silica glass core with an undoped silica glass cladding, prepared by direct ink writing onto an LDF of compositional variation. Two types of silica ink were used, one of which contained gold nanoparticles. Figure 10B is a plot of absorbance as a function of wavelength of light, where each spectrum corresponds to a position shown across the glass. The peak at 525 nm was attributed to absorbance from the gold nanoparticles. Figure 10C is a plot of absorbance at 525 nm (y-axis) against a position along the glass surface (x-axis, position 0 is the center of the glass). The plot in Figure 10C shows that the absorbance at 525 nm was tuned within this glass. The measured spot sizes averaged up to 1 mm in diameter.

[0188] Experiments on raw materials for additive manufacturing of foamed glass. Core-shell particles SiO2 particles were prepared by the Stober process, which involved mixing tetraethyl orthosilicate (TEOS), water, and an ammonia catalyst in ethanol (EtOH) solvent. The particles were grown for approximately 5 days until they reached a stable state, and measured by dynamic light scattering (DLS). As shown in Figure 13A, the average diameter was 23.6 ± 0.7 nm. As shown in the magnified sections (a) and (b) of Figure 13B, the particle size and spherical morphology were confirmed by transmission electron microscopy (TEM).

[0189] For SiO2-TiO2 core-shell nanoparticles (Figures 13C-13E), raspberry-shaped particles were obtained by adding titanium(IV) isopropoxide (TIP) to an aged SiO2 sol and heating at 55°C to control the reaction due to the evaporation of the ammonia catalyst. As shown in Figure 13A, the diameters of the obtained nanoparticles containing 1.5 and 5 wt% TiO2, measured by DLS, were 25.4 ± 0.4 and 34.1 ± 4.8 nm, respectively.

[0190] The TEM images in section (a) and the magnified view in section (b) of Figures 13C and 13D show the nanoparticle size and raspberry-like particle morphology development of 1.5 wt% and 5.0 wt% TiO2-containing nanoparticles, respectively.

[0191] For each particle, schematic diagrams of the particle are shown in part (c) of Figure 13B for SiO2, part (c) of Figure 13C for 1.5 wt% TiO2-SiO2, and part (c) of Figure 13D for 5.0 wt% TiO2-SiO2. Each schematic diagram shows the relative extent of the TiO2 coating of 1.5 and 5 wt% TiO2-SiO2 nanoparticles.

[0192] Figure 13E shows the addition of 8 wt% TiO2, and the SiO2-TiO2 nanoparticles do not clearly form a raspberry-like morphology (partial (a) and magnified (b)). However, DLS measurements indicate that the particles were typically 38.8 ± 0.5 nm, which suggests a large TiO2 shell as shown in Figure 13A.

[0193] Mixed particles and substructures Figures 14A and 14B show samples of mixed particles formed by the method described herein. Two samples 1402 and 1404 of mixed titania and silica particles are shown in Figure 14A. After centrifugation, there were no countable particles in the supernatant of each sample, and each sample had a pellet of nanoparticles collected at the bottom of the centrifuge tube.

[0194] The collected titanium-silica mixed nanoparticles were filtered and dried to form a powder, as shown in the images of vials 1406 and 1408 in Figure 14B.

[0195] An example of hybrid mixed particles relating to a certain aspect of the invention's concept is shown in Figures 15A to 15C. Part (a) of Figure 15A shows examples of molecular precursors TEOS and TIP that can be used to form the hybrid particles depicted in part (b). The resulting hybrid particles may not be distinct particles, as shown, but may be in the form of small clusters, oxoclusters, oligomer-based particles, or other forms. The average diameter of the clusters forming the hybrid mixed particulate morphology may be in the range of 100 nm to 400 nm.

[0196] Figure 15B is an image of suspended hybrid particles with an estimated average diameter of approximately 250 nm, as measured by DLS.

[0197] Figure 15C is a TEM image of a hybrid particle, with portion (a) at low magnification and portion (b) at high magnification. The clusters shown in the image may consist of small structures with an average diameter of approximately 12 nm. Each of these structures may have a different chemical composition, as shown in the schematic diagram in Figure 15A.

[0198] Inorganic polymers Figures 16A and 16B show an example of an inorganic polymer engineered as a feedstock for AM technology to form glass structures, according to one aspect of the concept of the invention. Figure 16A shows a general process for forming an inorganic polymer suitable for printing, which involves, in sequence, (1) hydrolyzing a silicon alkoxide under acidic conditions with quasi-stoichiometric H2O for hydrolysis, (2) adding a titanium alkoxide to introduce titanium into the partially hydrolyzed silicon oxopolymer, (3) further hydrolysis to promote crosslinking and viscosity adjustment, (4) neutralizing the acidic species, (5) functionalizing the polymer strands by transesterification of the alkoxide ligand, and (6) removing the solvent and unreacted reactants by evaporation. The non-volatile alkoxide ligand prevents shrinkage and / or cracking during ambient drying, resulting in an air-unstable, oil-like ink.

[0199] The image shown in Figure 16B illustrates different products of inorganic polymer feedstock after AM treatment. Part (a) shows Cr heated at 500°C and 200°C. III The image shows a substrate using inorganic polymer feedstock. Part (b) shows Al inorganic polymer feedstock and Al / Cr III This shows glass products obtained from a process using inorganic polymer feedstock. Part (c) shows the product of the Ti inorganic polymer feedstock after firing of the substrate.

[0200] Layered shell particles Figures 17A and 17B show an example of engineered layered shell particles as a feedstock for using AM technology to form glass structures, relating to a certain aspect of the concept of the invention. Figure 17A is a schematic diagram of process 1700 for forming layered shell particles. The core particle 1702 is an SiO2 nanoparticle, and a core-shell particle 1706 is formed by adding a TiO2 layer 1704 shell. Next, by alternately adding Si layers 1708 and Ti layers 1704 to the core-shell particle, an onion structure of layered shell particles 1710 having a number of alternating layers is obtained.

[0201] Figure 17B shows a series of SEM images of the suspension of layered shell particles in a subsequent step of preparation. Part (a) is an image of the SiO2 core particle 1702 (shown in Figure 17A). Part (b) is an image of Figure 17 A The image shows a SiO2-TiO2 core-shell particle 1706 having an SiO2 core particle 1702 together with a first shell of TiO2 layer 1704, as shown in (c). Part (c) is an image of a core-shell particle 1706 having a second layer of SiO2 added on top of the TiO2 layer.

[0202] Table 1 shows the average diameter values ​​obtained by DLS for each step in the formation of the layered shell particles, as shown in the image in Figure 17B.

[0203] [Table 1]

[0204] As shown in Table 1, the average particle diameter increases with each additional layer added to the SiO2 core particle, suggesting that the particle size grows with the addition of additional layers.

[0205] Hollow layered shell particles Figures 18A to 18C show an example of hollow layered shell particles engineered as a feedstock for using AM technology to form glass structures, following a certain aspect of the concept of the invention. Figure 18A is a schematic diagram of process 1800 for forming hollow layered shell particles. As previously described for process 1700 for forming layered shell particles, process 1800 begins with an SiO2 core particle 1802 having a TiO2 shell 1804. By adding an etching solution, such as NaOH, the SiO2 core 1802 of the SiO2-TiO2 core-shell particle is dissolved, creating a hollow space 1806 in the core location of the core-shell particle. Once the core material, in this case SiO2, is dissolved, etching is stopped or suppressed, and only the hollow space 1806 remains within the layered shell. In one method, as shown in the hollow layered shell particle 1810, the TiO2 shell layer 1804 retains the hollow space 1806. This method is merely illustrative and is not intended to be limiting. Hollow layered shell particles may have multiple layers with different compositions.

[0206] Figure 18B shows a series of SEM images of hollow layered shell particles at low magnification (part (a)) and high magnification (part (b)).

[0207] Figure 18C shows the energy-dispersive X-ray (EDX) spectrum of the hollow layered shell particle, which supports the idea that the core particle material has been removed from the particle by confirming that the amount of Si in the particle is significantly less than the amounts of Ti and O.

[0208] use Various aspects of the concept of the invention described herein can be used to form active or passive optical glass components (e.g., lenses, correctors, windows, screens, concentrators, waveguides, mirror blanks, sensors, etc.) with specific compositions and material properties for both commercial and government applications. Using these methods, it is possible to introduce ions, molecules, or particles to any location (i.e., application-specific) within a glass component (monolith, film, or freeform) to realize spatially different material properties within the glass, such as absorbance, propagation rate, refractive index, dispersibility, scattering, conductivity, thermal conductivity, thermal expansion coefficient, gain coefficient, glass transition temperature (Tg), melting point, photoemission, fluorescence emission, chemical reactivity (e.g., etching rate), or concentration / porosity.

[0209] Various aspects of the invention described herein provide methods for preparing complex 3D and controlled colored glass art, gemstones, and the like. By controlling silver and gold nanoparticle dopants, it becomes possible to control the reflective and transmissive properties of the artwork.

[0210] Further aspects of the invention's concept include active or passive optical glass components useful for lenses, corrector plates, windows, screens, light concentrators, waveguides, mirror blanks, sensors, and the like, as well as non-optical glass components useful for conventional applications.

[0211] Various aspects of the invention described herein as engineered feedstocks can be used to produce multi-component or single-component glasses of diverse compositions using a variety of additive manufacturing techniques. This will enable the preparation of glasses for which no currently available feedstocks exist by AM processes. Engineered feedstocks can be used to prepare glasses by additive manufacturing processes including direct ink writing, robocasting, computational axis lithography, projection microstereolithography, inkjet printing, electrophoretic deposition, and powder bed technologies, such as selective laser melting / sintering or binder jetting. These glasses produced by AM can be used in a wide range of applications, including active and passive optical components, packaging, laboratory equipment, household goods, art and jewelry, glass seals, microfluidic and millifluidic devices, sensors, radiation shielding, and bioglass.

[0212] The concepts of the invention disclosed herein are presented as examples to illustrate their numerous features in a number of exemplary scenarios, aspects of the invention, and / or embodiments. Generally, the disclosed concepts should be considered modular and may be implemented in any combination, rearrangement, or synthesis. Furthermore, any changes, modifications, or equivalents of the currently disclosed features, functions, and concepts, which will be understood by those skilled in the art by reading this specification, should also be considered within the scope of this disclosure.

[0213] While various aspects of the concept of the invention have been described, please understand that these are merely examples and not limiting. Therefore, the breadth and scope of the concept of the present invention should not be limited by any of the above-mentioned specific examples of the concept, but should be defined solely by the following claims and their equivalents.

Claims

1. A composition for additive manufacturing processes, The aforementioned composition includes a glass-forming material, The glass-forming material comprises at least one particle selected from the group consisting of layered shell particles having an onion structure with layers of different compositions, and hollow layered shell particles having a hollow space at the core location. The aforementioned composition is configured to form a three-dimensional structure, The aforementioned three-dimensional structure is self-supporting, and is a composition.

2. The composition according to claim 1, comprising a solvent.

3. The composition according to claim 2, wherein the composition is an ink for an extrusion-based additive manufacturing process.

4. The composition according to claim 1, wherein the average diameter of the mixed particles is in the range of about 100 nanometers to about 400 nanometers.

5. The glass-forming material is SiO ２ , GeO ２ , TiO ２ , ZrO ２ , and SiO ２ The composition according to claim 1, comprising three or more oxide species selected from the group consisting of -PbO.

6. The composition according to claim 1, wherein the glass-forming material comprises an inorganic polymer.

7. The composition according to claim 1, wherein the glass-forming material comprises at least one combination of particles selected from the group consisting of layered shell particles having a mixed core, hollow layered particles having a mixed core, an inorganic polymer containing layered shell particles having a mixed core, and an inorganic polymer containing hollow layered shell particles having a mixed core.

8. The composition according to claim 1, wherein the composition is a resin for a light-based additive manufacturing process.

9. The composition according to claim 1, wherein the composition is a powder for a laser-assisted melt addition process.

10. A composition for additive manufacturing processes, The composition comprises a glass-forming material containing blended particles, the blended particles comprising at least two types of particles with different compositions. At least one type of particle included in the blended particles is selected from the group consisting of layered shell particles having an onion structure with layers of different compositions, hollow layered shell particles having a hollow space in the location of the core, core-shell particles having a mixed core, and layered shell particles having a mixed core. The composition further comprises a solvent, The aforementioned composition is configured to form a three-dimensional structure, The aforementioned three-dimensional structure is self-supporting, and is a composition.

11. The blended particles are SiO ２ , GeO ２ , TiO ２ , ZrO ２ , and at least one oxide species selected from the group consisting of SiO ２ -PbO, the composition according to claim 10.

12. The composition according to claim 10, wherein each type of particle has a unique oxide species.

13. The composition according to claim 10, further comprising an effective amount of a second component for changing the properties of a glass structure made using the composition.

14. The composition according to claim 13, wherein the aforementioned properties are selected from the group consisting of optical properties, mechanical properties, magnetic properties, thermal properties, electrical properties, and chemical properties.

15. The composition according to claim 10, wherein the composition is an ink for an extrusion-based additive manufacturing process.

16. The composition according to claim 10, wherein the composition is a resin for a light-based additive manufacturing process.

17. The composition according to claim 10, wherein the composition is a powder for a laser-assisted melt addition process.

18. A composition for an additive manufacturing process, wherein the composition is A glass-forming material containing layered shell particles, A solvent is included, The layered shell particle comprises at least two shell layers on a core particle, and the shell layers have different compositions. The composition is configured to form a self-supporting three-dimensional structure.

19. The composition according to claim 18, wherein the average diameter of the core particles of the layered shell particles is in the range of about 25 nanometers to about 200 nanometers.

20. The composition according to claim 18, wherein the total thickness of the multiple layers of shells of the layered shell particles is in the range of about 4 nanometers to about 50 nanometers.

21. The layered shell particles are SiO ２ , GeO ２ , TiO ２ , ZrO ２ , and SiO ２ The composition according to claim 18, comprising at least one oxide species selected from the group consisting of -PbO.

22. The composition according to claim 18, wherein the layered shell particles contain three or more oxide species.

23. The composition according to claim 18, wherein the layered shell particles have a hollow core.

24. The composition according to claim 18, wherein the composition is an ink for an extrusion-based additive manufacturing process.

25. The composition according to claim 18, wherein the composition is a resin for a light-based additive manufacturing process.

26. The composition according to claim 18, wherein the composition is a powder for a laser-assisted melt addition process.

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