Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
  • B29C64/10—Processes of additive manufacturing
  • B29C64/106—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y10/00—Processes of additive manufacturing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y70/00—Materials specially adapted for additive manufacturing
  • B33Y70/10—Composites of different types of material, e.g. mixtures of ceramics and polymers or mixtures of metals and biomaterials
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/01—Other methods of shaping glass by progressive fusion or sintering of powdered glass onto a shaping substrate, i.e. accretion, e.g. plasma oxidation deposition
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/06—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B19/00—Other methods of shaping glass
  • C03B19/06—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction
  • C03B19/066—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction for the production of quartz or fused silica articles
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D1/00—Coating compositions, e.g. paints, varnishes or lacquers, based on inorganic substances
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D11/00—Inks
  • C09D11/02—Printing inks
  • C09D11/03—Printing inks characterised by features other than the chemical nature of the binder
  • C09D11/033—Printing inks characterised by features other than the chemical nature of the binder characterised by the solvent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
  • C03B2201/40—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn
  • C03B2201/42—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with transition metals other than rare earth metals, e.g. Zr, Nb, Ta or Zn doped with titanium

Definitions

• the present invention relates to glass components , and more particularly, this invention relates optical and non-optical glass components with custom-tailored composition profiles and methods for preparing same.
• silica glass of a single composition has been prepared via additive manufacturing using the selective laser melting (SLM) to melt and fuse silica particles in a silica powder bed.
• SLM selective laser melting
• glass of a single composition has been prepared via an additive manufacturing method (G3DP) that melts silica in a kiln-like high temperature reservoir and deposits a ribbon of molten glass through a nozzle.
• G3DP additive manufacturing method
• the selective melted regions may also leave trapped porosity between segments thereby resulting in resistance in merging the segments.
• these methods are not amenable to tightly controlled introduction of different compositions. It would be desirable to print and completely form the structure in the absence of high temperature.
• Various embodiments described herein use direct ink writing (DIW) additive manufacturing to introduce the composition gradient into an amorphous, low density form (LDF). Following complete formation, the LDF is heat treated to transparency as a whole structure, thus reducing edge effects.
• DIW direct ink writing
• LDF amorphous, low density form
• Current methods to form glass of gradient composition have also proven challenging.
• S-3DP slurry-based 3D printing
• composition gradients may also be limited to material that can incorporate readily into the LDF by diffusion (e.g. small molecules, ions).
• the dopants are a component of the mixture during formation of the LDF and before drying the LDF.
• Some embodiments described herein introduce a gradient via DIW additive manufacturing and use continuous in-line mixing of glass-forming species, with or without dopant, to achieve the desired composition changes.
• the LDF is fully formed before drying.
• the dopant itself can be an ion, molecule, and/or particle, and it may be premixed with the glass-forming species in a high viscosity suspension, which limits its diffusion at low temperature within the LDF.
• a method includes forming a structure by printing an ink, the ink including a glass-forming material, and heat treating the formed structure for converting the glass-forming material to glass.
• a product includes a monolithic glass structure having physical characteristics of formation by three dimensional printing of an ink comprising a glass-forming material.
• FIG. 1 is a flow chart of a method to prepare glass components with custom- tailored composition profiles, according to one embodiment.
• FIG. 2A is a schematic drawing of a method to prepare a single composition glass components, according to one embodiment.
• FIG. 2B is a schematic drawing of a method to prepare a multiple composition glass components, according to one embodiment.
• FIG. 3A is an image of an extrusion of glass-forming ink onto a substrate, according to one embodiment.
• FIG. 3B is an image of a printed low density form, according to one embodiment.
• FIG. 3C is an image of a glass form following heat treatment of a printed low density form, according to one embodiment.
• FIG. 4A is a schematic drawing of a low density form that includes a gradient in a material property of the low density form along an axial direction, according to one embodiment.
• FIG. 4B is a schematic drawing of a low density form that includes a gradient in a material property of the low density form along a radial direction, according to one embodiment.
• FIG. 5A is an image of a low density form with a gradient in the axial direction following multiple component printing, according to one embodiment.
• FIG. 5B is an image of a glass form with a gradient in the axial direction following heat treatment of a printed low density form, according to one embodiment.
• FIG. 5C is an image of a low density form with a gradient in the radial direction following multiple component printing, according to one embodiment.
• FIG. 4B is an image of a glass form with a gradient in the radial direction following heat treatment of a printed low density form, according to one embodiment.
• FIGS. 6A-6C are images of printed parts formed with a silica composition, according to one embodiment.
• FIGS. 6D-6E are images of printed parts formed with a silica-titania composition, according to one embodiment
• FIG. 7A is a plot of refractive index profile verses titania concentration of glass formed according to one embodiment.
• FIG. 7B is an image of the resultant glass structures formed with different titania concentrations, according to one embodiment.
• FIG. 8 is a plot of the thermal treatment profile of the formation of a consolidated structure according to one embodiment. Images of each step are included as insets on the profile plot.
• FIG. 9A is an image of a gradient refractive index silica-titania glass lens prepared by direct ink writing, according to one embodiment.
• FIG. 9B is a surface-corrected interferogram of the glass lens of FIG. 9A.
• FIG. 9C is an image of the 300- ⁇ focal spot from the lens of FIG. 9A.
• FIG. 1 OA is an image of a composite glass comprised of a gold-doped silica glass core, according to one embodiment.
• FIG. 10B is a plot of the absorbance as a function of wavelength of light of the composite glass of FIG. 10A.
• FIG. IOC is a plot of the absorbance at 525 nm versus position along the glass surface of the composite glass of FIG. 10A.
• a method includes forming a structure by printing an ink, the ink including a glass-forming material, and heat treating the formed structure for converting the glass-forming material to glass.
• a product in another general embodiment, includes a monolithic glass structure having physical characteristics of formation by three dimensional printing of an ink comprising a glass-forming material. [0040] A list of acronyms used in the description is provided below.
• Various embodiments described herein provide methods for fabricating active or passive optical or non-optical glass components and/or glass sensors with custom material composition profiles in 1-, 2-, or 3-dimensions.
• Various embodiments described herein enable the three dimensional (3D) printing of a variety of inorganic glasses, with or without compositional changes. Depending on glass composition and processing conditions, the glasses may appear either transparent or opaque to the human eye.
• FIG. 1 shows a method 100 for preparing optical glass components with custom-tailored composition profiles in accordance with one embodiment.
• the present method 100 may be implemented to devices such as those shown in the other FIGS, described herein.
• this method 100 and others presented herein may be used to form structures for a wide variety of devices and/or purposes which may or may not be related to the illustrative embodiments listed herein.
• the methods presented herein may be carried out in any desired environment.
• more or less operations than those shown in FIG. 1 may be included in method 100, according to various embodiments. It should also be noted that any of the aforementioned features may be used in any of the embodiments described in accordance with the various methods.
• a method 100 begins with an operation 102 that includes forming a structure by printing an ink.
• printing an ink may involve one of the following additive manufacturing techniques that may have an ink mixing capability: direct ink writing (DIW),
• DIW direct ink writing
• stereolithography in 3D systems projection microstereolithography, fused deposition modeling, electrophoretic deposition, PolyJet processing, Direct Deposition, inkjet printing, inkjet powder bed printing, aerosol jet printing, etc.
• the method 100 may be used to create filaments, films, and/or 3D monolithic or spanning free-forms.
• the ink includes a glass-forming material.
• the glass-forming material includes prepared dispersions of particles, where the particles range in size from nanometers to microns.
• particles may be mono-dispersed.
• particles may be poly-dispersed.
• particles may be agglomerated.
• the glass-forming material may be a single composition of inorganic particles, for example, but not limited to, fumed silica, colloidal silica, LUDOX colloidal silica dispersion, titania particles, zirconia particles, alumina particles, metal chalcogenide particles (e.g. CdS, CdSe, ZnS, PbS), etc.
• the glass-forming material may be a single composition of inorganic- containing particles.
• the glass-forming material may be a plurality of a mixed composition particle, for example, but not limited to, a binary silica-titania particle, silica-germanium oxide particle, and/or may be a particle with an inorganic or organic chemically modified surface (i.e. titania-modified silica particles; silica-modified titania particles; 3-aminopropyltriethoxysilane modified silica particles).
• a mixed composition particle for example, but not limited to, a binary silica-titania particle, silica-germanium oxide particle, and/or may be a particle with an inorganic or organic chemically modified surface (i.e. titania-modified silica particles; silica-modified titania particles; 3-aminopropyltriethoxysilane modified silica particles).
• the glass-forming material may be a mixture of particles of different compositions, for example but not limited to, a silica particle plus titania particle mixture that when fused together forms silica-titania glass.
• the glass-forming material may be a single composition of glass-forming material that may not be in the form of particles.
• a dopant may be directly incorporated into polymers, for example but not limited to, silica, silica-titania containing polymers, silica-germanium oxide polymers, silica-aluminum oxide polymers, silica-boron trioxide polymers, etc.
• the glass-forming material of the ink may include large molecules and/or polymers (linear or branched) prepared from smaller metal-containing organic precursors. Examples of polymers include
• large molecules include polyoxometalate clusters, oxoalkoxometalate clusters.
• Designer Si/Ti containing polymers may be synthesized via acid-catalyzed hydrolysis of organosilicates and organotitanates, e.g., tetraethylorthosilicate and titanium isopropoxide, with additional transesterification steps if necessary.
• Modifications to this process include: utilizing organometallic chemistries containing bonds other than metal-oxygen, e.g., (3- aminopropyl)triethoxysilane; doping via direct addition of salts to the polymer solution, e.g., NaF, Cu(N03)2, L-2CO3; doping via inclusion of metal species into polymer chain during acid-catalyzed hydrolysis; replacement of major (for example, silicon (Si)), and minor (for example titanium (Ti)) glass components with alternatives that are able to undergo linear polymerization, e.g., Ge, Zr, V, Fe.
• organometallic chemistries containing bonds other than metal-oxygen e.g., (3- aminopropyl)triethoxysilane
• doping via direct addition of salts to the polymer solution e.g., NaF, Cu(N03)2, L-2CO3
• the glass-forming material of the ink may include small metal-containing organic precursors and/or inorganic precursors, such as metalalkoxides, siloxanes, silicates, phosphates, chalcogenides, metal-hydroxides, metal salts, etc. Examples may include silicon alkoxides, boron alkoxides, titanium alkoxides, germanium alkoxides.
• the glass-forming material of the ink may include titanium isopropoxide, titanium diisopropoxide bis(acelylacetonate), tetraethyl orthosilicate, zinc chloride, titanium chloride.
• the glass-forming material may be suspended in a solvent.
• the solvent is preferably a polar, aprotic solvent.
• the solvent may be a pure component or mixture of the following:
• the solvent may be a polar, protic solvent, for example, alcohol and/or water.
• the solvent may be a non-polar solvent, for example, but not limited to, xylenes, alkanes.
• the ink may be a combination of the glass- forming material and at least one second component that alters a property of the heat treated glass structure.
• the second component may be a property altering dopant.
• more than one material property may be affected by the addition of a second component.
• the second component may affect the material property (e.g. characteristics) of the resulting structure in terms of one or more of the following: optical, mechanical, magnetic, thermal, electrical, chemical characteristics, etc.
• the second component may be in the form of ions.
• the second component may be molecules.
• the second component may be particles.
• the ink may contain an effective amount of one or more second components that may alter a property of the heat treated glass structure.
• the effective amount of a second component is an amount that alters a property of the heat treated glass structure may be readily determined without undue experimentation following the teachings herein and varying the concentration of the additive, as would become apparent to one skilled in the art upon reading the present description.
• the color of the resulting structure may be affected by the addition of one or more second components selected from the following group: metal nanoparticles (gold, silver) of various sizes, sulfur, metal sulfides (cadmium sulfide), metal chlorides (gold chloride), metal oxides (copper oxides, iron oxides).
• the absorptivity (linear or nonlinear) of the resulting structure may be affected by the addition of a one or more second components selected from the following group: cerium oxide, iron, copper, chromium, silver, and gold.
• the refractive index of the resulting structure may be affected by the addition of one or more second components selected from the following group: titanium, zirconium, aluminum, lead, thorium, barium.
• the dispersion of the resulting structure may be affected by the addition of one or more second components selected from the following group: barium, thorium.
• the attenuation/optical density of the resulting structure may be affected by the addition of one or more second components selected from the following group: alkaline metals and alkaline earth metals.
• the photosensitivity of the resulting structure may be affected by the addition of one or more second components selected from the following group: silver, cerium, fluorine.
• the electrical conductivity of the resulting structure may be affected by the addition of one or more second components selected from the following group: alkali metal ions, fluorine, carbon nanotubes.
• the birefringence such as having a refractive index that depends on polarization and propagation direction of light imparted by the crystalline phase formed from the second component, of the resulting structure may be affected by the addition of one or more second components selected from the following group: titanium, zirconium, zinc, niobium, strontium, lithium, in combination with silicon and oxygen.
• the thermal conductivity of the resulting structure may be affected by the addition of one or more second components selected from the following group: carbon nanotubes, metals.
• the thermal emissivity of the resulting structure may be affected by the addition of one or more second components selected from the following group: tin oxide, iron.
• the thermal expansion of the resulting structure may be affected by the addition of a one or more second components selected from the following group: boron oxide, titanium oxide.
• the glass transition temperature of the resulting structure may be affected by the addition of sodium carbonate as the second component.
• the melting point of the resulting structure may be affected by the addition of one or more second components selected from the following group: sodium, aluminum, lead.
• the gain coefficient of the resulting structure may be affected by the addition of one or more second components selected from the following group: rare earth ions (e.g. neodymium, erbium, ytterbium); transition metal ions (e.g. chromium).
• the photoemission of the resulting structure may be affected by the addition of a second component.
• the photoemission of the resulting structure may be affected by the addition of a second component.
• luminescence of the resulting structure may be affected by the addition of a second component.
• the fluorescence of the resulting structure may be affected by the addition of a second component.
• the chemical reactivity of the resulting structure may be affected by the addition of one or more second components selected from the following group: alkaline metals, alkaline earth metals, silver.
• the density of the resulting structure may be affected by the addition of one or more second components selected from the following group:
• titanium, zirconium, aluminum, lead, thorium, barium titanium, zirconium, aluminum, lead, thorium, barium.
• the concentration of the second component in the ink may change during the printing for creating a compositional gradient in the printed structure.
• the second component in the ink may create a compositional gradient in the final heat treated structure.
• the concentration of the second component in the ink may create a compositional change (e.g. gradient, pattern, etc.) that may not be symmetrical about any axis, for example but not limited to, a pattern may change radially around the structure, a pattern may be formed as a complete 3D structure, etc.).
• the ink may contain an effective amount of one or more additional additives that may perform specific functions.
• the additives may enhance dispersion, phase stability, and/or network strength; control and/or change pH; modify rheology; reduce crack formation during drying; aid in sintering; etc.
• the effective amount of an additive is an amount that imparts the desired function or result, and may be readily determined without undue experimentation following the teachings herein and varying the concentration of the additive, as would become apparent to one skilled in the art upon reading the present description.
• the ink may include one or more of the following additives to enhance dispersion: surfactants (e.g. 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEAA)), polyelectrolytes (e.g. polyacrylic acid), inorganic acids (e.g. citric acid, ascorbic acid).
• surfactants e.g. 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MEEAA)
• MEEAA 2-[2-(2-methoxyethoxy)ethoxy]acetic acid
• polyelectrolytes e.g. polyacrylic acid
• inorganic acids e.g. citric acid, ascorbic acid
• the ink may include an additive (e.g. boric anhydride (B 2 O 3 )) to enhance phase stabilization (i.e. to prevent phase/composition separation, which may or may not be a crystalline phase separation).
• an additive e.g. boric anhydride (B 2 O 3 )
• phase stabilization i.e. to prevent phase/composition separation, which may or may not be a crystalline phase separation.
• ZnO can act as a phase stabilizer for alkali silicate.
• the ink may include an additive (e.g. boric anhydrideB 2 O 3 ) to inhibit crystallization.
• an additive e.g. boric anhydrideB 2 O 3
• Other crystallization inhibitors include AI 2 O 3 and Ga 2 0 3 .
• the ink may include an additive (e.g.
• the ink may include one or more of the following additives to control pH: organic acids, inorganic acids, bases (e.g. acetic acid, HC1, KOH, NH4OH).
• the ink may include one or more of the following additives to modify rheology: polymers (e.g. cellulose, polyethylene glycols, poly vinyl alcohols); surfactants (e.g. MEEAA, sodium dodecyl sulfate, glycerol, ethylene glycol); metal alkoxides (e.g. titanium diisopropoxide bis(acetylacetonate)).
• the ink may include one or more of the following additives as a drying aid to increase resistance to cracking and/or reduce crack formation during drying: polymers (e.g. polyethylene glycol, polyacrylates), cross-linkable monomers or polymers and crosslinking reagents (e.g. polyethylene glycol diacrylate (PEGDA)).
• polymers e.g. polyethylene glycol, polyacrylates
• cross-linkable monomers or polymers e.g. polyethylene glycol diacrylate (PEGDA)
• PEGDA polyethylene glycol diacrylate
• the ink may include an additive as a sintering aid.
• Sintering aids enhance the sintering/densification process.
• a sintering aid may lower the viscosity of the material being sintered to glass.
• boric anhydride B 2 O 3
• B 2 O 3 boric anhydride
• the formulation of glass-forming ink i.e. glass-forming material
• the formulation of glass-forming ink is optimized for the following combination of factors: printability (depending on the method of 3D printing), resistance to cracking, and sintering to transparency.
• printability depending on the method of 3D printing
• resistance to cracking and sintering to transparency.
• volumetric loading of the formulation of glass- forming ink is optimized.
• the characteristics of the composition gradient of the glass-forming material may be optimized.
• a formulation of glass-forming material may include: glass-forming, inorganic species in the range of about 5 vol% to about 50 vol% of total volume; solvent in the range of about 30 vol% to about 95 vol%; a second component(s) (i.e. dopants) in the range of 0 wt% to about 20 wt%; and an additive(s) from 0 wt% to about 10 wt%.
• the concentration of the second component in the ink may change during the printing for creating a compositional gradient in the structure and thus, the final heat treated structure.
• the temperature of the ink may be less than about 200°C during the printing.
• the method 100 includes drying the formed structure for removing a sacrificial material, where the drying is done prior to heat treating the formed structure. Ideally, the fully formed structure is dried in a single process.
• method 100 includes operation 104 that involves heat treating the formed structure for converting the glass- forming material to glass.
• the method includes additional processing of the heat- treated glass structure.
• the method includes grinding the heat-treated glass structure.
• the method includes polishing the heat-treated glass structure.
• the method includes grinding and polishing the heat- treated glass structure.
• the heat-treated glass structure may be in the form of a fiber.
• the heat-treated glass structure may be in the form of a sheet.
• the heat-treated glass structure may be in the form of a three-dimensional monolith.
• the heat-treated glass structure may be in the form of a coating on a substrate such as a part, a tool, etc.
• FIGS. 2A-2B depict methods 200 and 250 for preparing an optical glass component with custom-tailored composition profiles in accordance with one embodiment.
• the present methods 200 and 250 may be implemented in conjunction with features from any other embodiment listed herein, such as those described with reference to the other FIGS.
• such methods 200 and 250 and others presented herein may be used in various applications and/or in
• FIG. 2A An exemplary embodiment of method 200 to prepare a single component silica glass is illustrated in FIG. 2A.
• the method to print the ink involves DIW printing as shown in steps 222 and 224.
• DIW is a 3D printing process based on extrusion of viscoelastic material.
• Air pressure or positive displacement pushes the ink 202 through a small nozzle 208.
• the nozzle 208 is controlled by a computer and has three degrees of freedom (x, y, and z). In other approaches the nozzle 208 may be expanded to have six axes for printing.
• the nozzle 208 may be positioned to extrude the ink in a controlled spatial pattern.
• DIW deposits filaments 212 of Theologically tuned glass-forming DIW ink 202 containing glass-forming species in a prescribed geometry to create a weakly associated, near net-shaped, porous amorphous low density form (LDF) 214.
• LDF low density form
• the extruded filament 212 into the LDF 214.
• the LDF 214 may be referred to as a green body, glass-forming species, etc.
• the glass-forming species may be introduced as either precursors and/or as colloids/particles.
• the glass-forming DIW ink 202 may be colloidal silica ink.
• the formulation of the glass-forming DIW ink is optimized for printability, drying/bakeout, and sintering.
• the formulation of the glass-forming DIW ink may be optimized for printability in terms of shear thinning, ability to flow (steady flow), ability to hold shape (shape retention), low agglomeration, long print time, stable pot life (stability), etc.
• the formulation of the glass-forming DIW ink may be optimized for drying in terms of robustness to handling, crack resistance, low/uniform shrinkage, porosity suited to organic removal, etc.
• the formulation of the glass-forming DIW ink may be optimized for sintering in terms of crack resistance, low/uniform shrinkage, able to densify/become transparent, low tendency to phase separate, etc.
• step 222 involves the glass-forming DIW ink 202 extruded through a nozzle 208 to deposit filaments 212 onto a substrate 210 in a single layer.
• Step 224 of method 200 involves building layer upon layer of glass-forming DIW ink 202 to form a LDF 214.
• FIG. 3A shows an image of the colloidal silica ink being extruded onto the substrate.
• the LDF 214 may be treated to multiple steps to consolidate and convert the LDF 214 to the heat-treated glass form 216.
• the LDF 214 may undergo additional processing to further change the composition of the part.
• additional processing may include diffusion, leaching, etching, etc.
• additional processing may include light, sound, vibration to alter the characteristics of the printed form, or a combination thereof.
• a chemical treatment before closing the porosity of the LDF by heat treatment may define the optical quality of the resulting glass form.
• the LDF may be dried, calcined (i.e. removal of residual solvents/organics at elevated temperature), etc. During drying, the liquid/solvent phase may be removed. The LDF 214 may be released from the substrate 210 on which the LDF 214 was printed.
• the drying step 226 may involve dwelling hours to weeks at temperatures below the boiling point of the solvent.
• a processing step 226 may involve a lower heating step (i.e. burnout) to remove organics as well as any residual and/or adsorbed water/solvent phase.
• the burnout step may involve dwelling 0.5 to 24 hours at 250- 600°C.
• the processing step 226 may include heating the LDF 214 under alternate gas atmospheres for chemically converting the surface (e.g.
• the processing step 226 may include heating the LDF 214 under oxidative gas atmospheres (e.g. O 2 gas). In other approaches, the processing step 226 may include heating the LDF 214 under reducing gas atmospheres (e.g. H 2 gas). In yet other approaches, the processing step 226 may include heating the LDF 214 under non-reactive gas atmospheres (e.g. Ar, He). In yet other approaches, the processing step 226 may include heating the LDF 214 under reactive gas atmospheres (e.g. N2, Cl 2 ). In yet other approaches, the processing step 226 may include heating the LDF 214 under vacuum.
• oxidative gas atmospheres e.g. O 2 gas
• the processing step 226 may include heating the LDF 214 under reducing gas atmospheres (e.g. H 2 gas).
• the processing step 226 may include heating the LDF 214 under non-reactive gas atmospheres (e.g. Ar, He).
• the processing step 226 may include heating the LDF 214 under reactive gas atmospheres (e.g.
• the processing step 226 may also include compacting the parts (i.e. reducing porosity) of the LDF 214 using uniaxial pressure or isostalic pressure thereby resulting in a compact form.
• the processing step 226 may also include compacting the parts (i.e. reducing porosity) of the LDF 214 under vacuum.
• FIG. 3B shows an image of a LDF that has been dried.
• the method involves heat treating the dried LDF 214, as shown in step 228 of FIG. 2A, to close the remaining porosity and form a consolidated, transparent glass part.
• a compact form of the LDF may be heat treated.
• the heat treating step 228 may involve sintering, in which the LDF 214 (i.e. inorganic, glass-forming species) completely densities into a solid glass consolidated form 216 at elevated temperatures.
• sintering the LDF may involve dwelling minutes to hours at 500-1600°C. The temperature for sintering depends on material composition and initial inorganic loading and porosity of the LDF.
• the sintering of the LDF may involve simultaneous use of applied pressure.
• the heat treating step 228 may occur under different atmospheric conditions. In other approaches, the heat treating step 228 may occur under vacuum.
• the heat treated glass form 216 may be a monolithic glass structure.
• FIG. 3C shows an image of a monolithic glass structure after heat treatment of the LDF shown in FIG. 3B.
• the resultant glass consolidated form 216 may retain the characteristics of the ink 202 that may have been imparted during DIW printing (steps 222 224).
• the glass consolidated form 216 may have a physical characteristic of the LDF 214 including spiral-shaped, arcuate and/or straight ridges along one surface of the glass form 216.
• the glass form 216 in the post-processing step 230, may be post-processed, for example to achieve the desired figure and/or surface finish of a final polished optic form 218 through techniques such as grinding and/or polishing.
• the polished optic 218 is a polished formation by 3D printing and heat treatment, such that the properties of the LDF 214 remain and are not removed by polishing.
• the polished optic 218 is a monolithic glass structure that has been polished.
• the glass form 216 may be treated as bolt glass, thereby allowing removal any of the evidence of the printing process by conventional techniques known in the art
• the glass form 216 retains features achievable only by the printing processes described herein, even after post-processing.
• a schematic representation of a method 250 to form a gradient and/or a spatial pattern in a glass product is illustrated in FIG. 2B.
• the method may create a compositional change (e.g. gradient, pattern, etc.) that may not be symmetrical about any axis, for example but not limited to, a pattern may change radially around the structure, a pattern may be formed as a complete 3D structure, etc.).
• the method may form a gradient index (GRIN) glass.
• GRIN gradient index
• Printing a GRIN glass involves printing a monolith with no porosity in which the characteristics of the formation of the LDF result in favorable elastic modulus/viscosity as indicated by space filling, high aspect ratio, and spanning.
• the method may involve matching the rheology of the two DIW inks desired to create the gradient.
• two, three, four, etc. inks may be combined by mixing before extrusion of the filament onto the substrate.
• the filament composition 213 may be tuned during printing by adjusting the flow rates of separate streams to introduce desired composition changes within the LDF 214 at the desired locations.
• inks 203, 204 may be introduced separately to create the LDF 215.
• characteristics of formation by 3D printing may include a gradient in a refractory index of the monolithic glass structure 400 along an axial direction of the monolithic glass structure 400.
• the axial 408 direction is perpendicular to the plane 410 of deposition.
• the glass structure is formed as a LDF (LDF 215 in FIG. 2B) in which a first glass-forming ink 203 may be extruded followed by extrusion of a second glass-forming ink 204.
• LDF LDF 215 in FIG. 2B
• the resulting glass structure 400 in FIG. 4A has a first glass 403 and a second glass 404, from the first glass-forming ink 203 and second glass- forming ink 204, respectively.
• the resulting glass structure 400 of FIG. 4A may include an interface 406 between first glass 403 formed from the glass-forming material and second glass 404 formed from a second glass-forming material having a different composition than the glass-forming material.
• first glass 403 formed from the glass-forming material
• second glass 404 formed from a second glass-forming material having a different composition than the glass-forming material.
• there may be no intermixing of the first glass 403 in the second glass 404 because there may no migration of the second glass-forming material into the first glass-forming material across the interface, or vice versa.
• the interface 406 may be oriented substantially along a plane 410 of deposition of the monolithic glass structure 400 thereby bifurcating the monolithic glass structure into two portions, the first glass 403 and the second glass 404, having different compositions directly adjacent the interface.
• FIGS. 5A-5D two different inks, silica and silica with 20 nm gold nanoparticles were used to form a compositional change leading to a change in material property in the final heat-treated structure.
• FIGS 5A-5B show the formation of an axial step in absorption in a final heat-treated structure.
• the LDF was formed with a conformational change in which the first ink silica was used to form a portion of the LDF (bottom of LDF in FIG. 5A), and then the ink was switched to the second ink, silica/gold nanoparticle ink (top of LDF in FIG. 5A).
• the LDF was then consolidated to glass by sintering in the heat treatment (step 238 of FIG. 2B).
• a resultant monolithic glass structure with a gradient in absorbance along an axial direction is shown in FIG. 5B in which the silica/gold nanoparticle portion of the glass is up in FIG. 5B.
• a physical characterization of the monolithic glass structure 217 includes a gradient comprising two or more glass-forming materials such that the interface between a first glass-forming material and a second glass-forming material that is uniform. As illustrated in FIG. 5A, there is an interface between the upper glass-forming material (silica/gold nanoparticles) and the lower material (silica).
• a smooth composition change may be created by blending inline the ink streams from the different inks 203, 204 via active mixing with a mixing paddle 206 near the tip of the nozzle 208. As illustrated in a schematic
• a monolithic glass structure 420 with physical characteristics of formation by 3D printing may include a gradient in the refractive index, or another material property such as
• the glass structure is formed as a LDF (LDF 215 in FIG. 2B) in which a radial step in refractive index in which the two inks 203, 204 in FIG. 2B were blended inline the ink streams.
• LDF LDF 215 in FIG. 2B
• the resulting glass structure 420 in FIG. 4B has a first glass 414 and a second glass 413, from the first glass-forming ink 203 and second glass-forming ink 204, respectively.
• the resulting glass structure 420 of FIG. 4B includes an interface 416 between first glass 414 formed from the glass-forming material and second glass 413 formed from a second glass-forming material having a different composition than the glass-forming material.
• first glass 414 formed from the glass-forming material
• second glass 413 formed from a second glass-forming material having a different composition than the glass-forming material.
• there may be no intermixing of the first glass 414 in the second glass 413 because there may no migration of the second glass- forming material into the first glass-forming material across the interface, or vice versa.
• the interface 416 may be oriented substantially perpendicular to a plane 410 of deposition of the monolithic glass structure 420 thereby bifurcating the monolithic glass structure 420 into two portions, the first glass 413 and the second glass 414, having different compositions directly adjacent the interface 416.
• two different inks may be used to print a conformational change in a LDF that leads to a material property of a radial step in absorbance in the final heat-treated structure.
• a first ink of silica and a second ink of silica/gold nanoparticles were used to print a radial step in absorbance in which the two inks were blended inline the ink streams.
• FIG. 5C shows the LDF form with the silica/gold nanoparticle ink in the center of the LDF and the silica ink on the outer portions of the LDF.
• a resultant monolithic glass structure with a gradient in the absorbance along a radial direction is shown in FIG. 5D.
• compositional changes may not be limited to axial and/or radial gradients (such as those that can be achieved by diffusion techniques) but rather can be made to create arbitrary profiles in the LDF.
• compositional changes in the LDF 215 may lead to varying material properties within the formed glass 217.
• material properties that may be affected by compositional changes in the LDF 215 are detailed more fully above, and may include, but may not be limited to: absorptivity, transmission, refractive index, dispersion, scatter, electrical conductivity, thermal conductivity, thermal expansion, gain coefficient, glass transition temperature (Tg) melting point, photoemission, fluorescence, chemical reactivity (e.g. etch rate), density/porosity.
• DIW printing in steps 232, 234 may involve forming the LDF 215, according to one embodiment.
• the LDF begins in the first step 232 of DIW printing as a single layer on a substrate 210.
• the LDF 215 may be formed layer by layer until the desired LDF 215 (i.e. green body) is formed.
• formation of a LDF with single composition (method 200) or a multiple composition (for example, a gradient) (method 250) may involve fused deposition modeling (FDM).
• FDM uses thermoplastic filament, that may be a composite mixture of several materials combined with a mixing paddle similar to the ink mixture of DIW (see steps 232-234 of FIG. 2B).
• the resulting filament may be extruded through a heated nozzle to form a LDF on a substrate as shown in steps 222-224 or steps 232-234 in FIGS. 2 A and 2B, respectively.
• the heated nozzle at temperatures in the range of about 150°C to 200°C, partially heats the filament for extrusion.
• a sacrificial support material may be extruded by a second nozzle to provide a support for the glass-forming material extruded by the mixing nozzle.
• the polymer of the extruded filament and/or support material may be removed after formation of the LDF.
• the LDF may be formed in a complex shape, for example, but not limited to, a conical form, a corkscrew pattern, a cylinder, etc.
• the LDF 215 may be treated to multiple steps to consolidate and convert the LDF 215 to the heat-treated glass form 217. [00136] Once formed, the LDF 215 may be dried and/or receive additional processing as described above for step 226 in method 200 in FIG. 2A.
• step 238 of method 250 includes heat treating the dried LDF 215 to close the remaining porosity and form a consolidated, transparent glass part.
• the resultant glass consolidated form 217 may retain the compositional variation that may have been imparted during DIW printing (steps 232, 234).
• the glass consolidated form 217 may have a physical characteristic of the LDF 215 including spiral-shaped, arcuate and/or straight ridges along one surface of the glass form 217.
• the glass form 217 may be further processed, for example to achieve the desired figure and/or surface finish of a final polished optic 220 through techniques such as grinding and/or polishing.
• the polished optic 220 is a polished formation by 3D printing and heat treatment, such that the properties of the LDF 215 remain and are not removed by polishing.
• the polished optic 220 is a monolithic glass structure that has been polished.
• amorphous, inorganic glass materials in addition to silica-based glasses, including phosphate-based glasses, borate glasses, germanium oxide glasses, fluoride glasses, aluminosilicate glasses, and chalcogenide glasses.
• Example 1 of Heat Treatment Printed monolithic silica or silica-titania green-bodies (25 mm diameter, 5 mm thick) are placed onto a hot-plate at 100°C. After 3 hours, the printed green bodies are released from the substrate. The green bodies are then dried in a box furnace at 100 °C for 110 hours. Next, the liquid-free green bodies are heated to 600°C at a ramp rate of 10 °C/min and left to dwell for 1 hour to burn out remaining organic components. The green bodies are then ramped at 100°C/hr to 1000°C and held for 1 hr under vacuum. Last, the part is sintered in a preheated furnace at 1500°C for 3-10 minutes. The parts are then removed and rapidly cooled to room temperature. All non-vacuum processing steps are performed in air.
• Printed monolithic silica green-bodies composed of 25-nm diameter silica or silica-titania particles (25 mm diameter, 5 mm thick) ramped in a box furnace to 75 °C at a rate of 3 °C/h. Once the oven reaches 75°C, the printed green bodies are released from the substrate. The green bodies are then dried in a drying oven at 75°C for 120 hours. Next, the liquid-free green bodies are heated to 600°C at a ramp rate of 1 °C/min and left to dwell for 1 hour to burn out remaining organic components. Last, the part is sintered in a preheated furnace at 1150°C for 1 hour. The parts are then removed and rapidly cooled to room temperature. All non-vacuum processing steps are performed in air.
• FIGS. 6A-6F are images of printed parts made with Formulation 3 of Ink (as described above).
• FIGS. 6A-6C are images of printed parts formed with a silica-only composition.
• FIG. 6A is an images of the green body formed after printing.
• FIG. 6B is an image after drying of the green body of FIG. 6A.
• FIG. 6C is an image after consolidation of the dried green body of FIG. 6B.
• FIGS. 6D-6F are images of printed parts formed with a silica-titania composition.
• FIG. 6D is an image of the green body formed after printing.
• FIG. 6E is an image after drying of the green body of FIG. 6D.
• FIG. 6F is an image after consolidation of the dried green body of FIG. 6E.
• FIG. 7A is a plot of refractive index profile (y-axis) versus titania (TiCh) concentration (wt%, x-axis) in a resultant glass. Glasses made from the inks of
• Formulation 1 (as described above) are represented on the plot as diamonds ( ⁇ , solid line) and have a variation in refractive index comparable to commercial silica (A) and silica- titanate glasses (o, ⁇ ) (dotted line).
• FIG. 7B is an image of the resultant glass structures formed from the ink formulations represented by the diamonds ( ⁇ ) of FIG. 7A at different concentrations of wt% TiO2 (2 wt%, 4 wt%, 5 wt%, 6 wt%, 8 wt%, 9 wt%, 10 wt%).
• FIG. 8 is a plot of the thermal treatment profile of the formation process of a consolidated printed parts using Formulation 1 Ink (as described above).
• the volumetric shrinkage (V ink ) of the structure at each step during the heat treatment process is shown next to the image of the structure.
• FIG. 9A is an optical image of a gradient refractive index silica-titania glass lens prepared by direct ink writing the LDF while blending two inks inline at the printhead in the required ratio to deposit a radial gradient in TiO2 concentration.
• Two inks were used from the Formulation 1 Ink (described above), Ink A contained 0% titanium alkoxide and Ink B contained enough titanium alkoxide to result in 1.6 wt%
• FIG. 9B is a surface- corrected interferogram, which shows how the refractive index changes within the bulk of the material shown in the image of FIG. 9A.
• the refractive index is highest at the center, where the Ti0 2 composition is highest, and lowest at the edges, where the TiCh concentration is lowest.
• a lineout across the center shows that the refractive index change across the center is parabolic, as shown by the inset plot of FIG. 9B ( ⁇ /( ⁇ -1) on y-axis, Distance (mm) on x-axis), which suggests the part can function as a lens.
• FIG. 9C is an image of the 300- ⁇ focal spot from the lens, which has a focal length of 62 cm.
• FIG. 10A is an optical image of a composite glass comprised of a gold-doped silica glass core with an undoped silica glass cladding, which was prepared by direct ink writing the composition change into the LDF. Two silica inks were used, with one ink containing gold nanoparticles.
• FIG. 10B is a plot of the absorbance as a function of wavelength of light, with each spectrum corresponding to the indicated positions across the glass. The peaks at 525 tun were attributed to absorbance from the gold nanoparticles.
• FIG. IOC is a plot of the absorbance at 525 nm (y-axis) versus position along the glass surface (x-axis, with the position 0 being the center of the glass). The plot of FIG. IOC represents that the absorbance at 525 nm was tuned within this glass. The spot size measured was an average over a ⁇ 1mm diameter spot.
• Various embodiments described herein may be used to make active or passive optical glass components (e.g. lenses, corrector plates, windows, screens, collectors, waveguides, mirror blanks, sensors, etc.) with specialized compositions and material properties for both commercial or government applications. These methods may be used to introduce ions, molecules, or particles in arbitrary (i.e. custom) locations within the glass components (monoliths, films, or free-forms) to achieve spatially varying material properties within the glass, including: absorptivity, transmission, refractive index, dispersion, scatter, electrical conductivity, thermal conductivity, thermal expansion, gain coefficient, glass transition temperature (Tg), melting point, photoemission, fluorescence, chemical reactivity (e.g. etch rate), or density/porosity.
• active or passive optical glass components e.g. lenses, corrector plates, windows, screens, collectors, waveguides, mirror blanks, sensors, etc.
• These methods may be used to introduce ions, molecules, or particles in arbitrary (i.
• Various embodiments described herein provide methods for preparing intricate 3D and controlled color glass art, jewelry, etc.
• the control of the dopants of silver and gold nanoparticles allows control of the reflective and transmissivity properties of the art piece.
• Further embodiments include active or passive optical glass components useful for lenses, corrector plates, windows, screens, collectors, waveguides, mirror blanks, sensors, etc., as well as non-optical glass components useful in conventional applications.

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