Microcrystalline quartz ceramic, preparation method and application thereof

Abstract

The application discloses microcrystalline quartz ceramic and a preparation method and application thereof, relates to the technical field of quartz ceramic, and comprises the following steps: (1) adding nanoscale amorphous silicon dioxide and a nucleating agent into water to prepare a slurry; (2) spray drying the slurry to obtain nanoscale silicon dioxide agglomerates; (3) mechanically and statically pressing the nanoscale silicon dioxide agglomerates to obtain a silicon dioxide green body; and (4) performing microcrystallization treatment on the silicon dioxide green body to obtain the microcrystalline quartz ceramic. The microcrystalline quartz ceramic prepared by the application has good high-temperature resistance, high bending strength and a transparent appearance, and can greatly expand the application range of quartz ceramic.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of quartz ceramics, in particular to a microcrystalline quartz ceramic and a preparation method and application thereof. BACKGROUND

[0002] Quartz ceramics is a kind of heat-resistant material with excellent shock resistance, extremely low expansion coefficient and thermal conductivity, which has been widely used in aerospace, glass, photovoltaic and other fields. At present, quartz ceramics generally uses fused quartz powder or quartz glass powder as raw material for processing, which can replace quartz glass. However, the temperature resistance and strength of quartz ceramics still have deficiencies, so the quartz ceramics with good temperature resistance and high strength have been a research focus at home and abroad.

[0003] The prior art mainly adopts the following two routes to improve the temperature resistance and strength of quartz ceramics:

[0004] Route 1, adding silicon nitride and other high-temperature resistant materials into quartz ceramics. Although this doping method can improve the heat resistance of quartz ceramics, the bending strength can only be increased from 20-30 MPa to 40-50 MPa.

[0005] Route 2, by doping boron oxide, lead oxide, vanadium pentoxide and other substances, the bending strength of quartz ceramics can be increased to about 50 MPa, but the temperature resistance cannot be improved. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a preparation method of microcrystalline quartz ceramic, which has good high-temperature resistance and high bending strength, and can be made into a crucible for drawing a single crystal silicon rod, and can also be used to make a diffusion pipe, a quartz boat, a single crystal silicon feeding pipe, a high-temperature window, etc.

[0007] The technical problem to be solved by the present application is solved by adopting the following technical solution:

[0008] One of the objects of the present application is to provide a preparation method of microcrystalline quartz ceramic, which comprises the following steps:

[0009] (1) adding nano-amorphous silicon dioxide and a nucleating agent into water to prepare a slurry;

[0010] (2) spray drying the slurry to obtain nano-silicon dioxide agglomerates;

[0011] (3) mechanically and statically pressing the nano-silicon dioxide agglomerates to obtain a silicon dioxide green body;

[0012] (4) performing microcrystallization treatment on the silicon dioxide green body to obtain a microcrystalline quartz ceramic.

[0013] The second object of the present application is to provide a microcrystalline quartz ceramic prepared by the aforementioned preparation method.

[0014] The third object of the present application is to provide an application of the aforementioned microcrystalline quartz ceramic in processing of a crucible for drawing a single crystal silicon rod, a diffusion tube, a quartz boat, a single crystal silicon feeding tube, and a high-temperature window.

[0015] The present application has the following beneficial effects: the microcrystalline quartz ceramic prepared by using nanometer amorphous silica and a nucleating agent as raw materials and through spray drying, mechanical static pressure and microcrystallization treatment has good high-temperature resistance, high bending strength and a transparent appearance, which can greatly expand the application range of quartz ceramic. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 XRD pattern of the microcrystalline quartz ceramic prepared for Example 1;

[0017] Figure 2 SEM pattern of the microcrystalline quartz ceramic prepared for Example 1;

[0018] Figure 3 XRD pattern of the non-microcrystallized quartz ceramic prepared for Comparative Example 5. DETAILED DESCRIPTION

[0019] In order to make the technical means, creative features, purposes and effects of the present application easy to understand, the present application is further described below in combination with specific examples and drawings.

[0020] The present application provides a preparation method of a microcrystalline quartz ceramic, which comprises the following steps:

[0021] (1) adding nanometer amorphous silica and a nucleating agent into water to prepare a slurry;

[0022] (2) spray drying the slurry to obtain nanometer silica agglomerates;

[0023] (3) mechanically static pressing the nanometer silica agglomerates to obtain a silica green body;

[0024] (4) microcrystallizing the silica green body to obtain a microcrystalline quartz ceramic.

[0025] Further, the average particle size of the nanometer amorphous silica is 5-40 nm. Amorphous silica is a non-crystalline silica, and the present application uses nanometer amorphous silica as a raw material to prepare a microcrystalline quartz ceramic.

[0026] Further, the nucleating agent includes, but is not limited to, at least one of oxides, hydroxides, chlorides, sulfates, nitrates, carbonates, phosphates, acetates of Ba, Cr, La series elements. The nucleating agent in the present application can be attached to the surface of the nanometer-sized silicon dioxide by adsorption or precipitation.

[0027] Further, the solid content of the slurry is 5-50%. If the solid content is lower than the range, the fine particles of the powder obtained by spray drying are more, and the flowability is poor; if the solid content is higher than the range, the viscosity of the slurry is large, and the nozzle is easily blocked.

[0028] Further, the inlet air temperature of the spray drying is 280-350℃, and the outlet air temperature is 80-120℃. The nanometer-sized amorphous silicon dioxide is converted into nanometer-sized silicon dioxide agglomerates by spray drying.

[0029] Further, the average particle size of the nanometer-sized silicon dioxide agglomerates is 200-500nm. If the particle size is too large, the uniformity is poor; if the particle size is too small, it is not easy to prepare. Of course, the particle size of the nanometer-sized silicon dioxide agglomerates is also affected by the particle size of the raw material nanometer-sized amorphous silicon dioxide.

[0030] Further, the pressure of the mechanical static pressure is 5-600MPa. Since the nanometer-sized silicon dioxide powder is very fluffy, if the pressure is directly applied to the powder, the powder will expand and become loose again when the pressure is removed, so it is necessary to first add water to prepare a slurry, and then prepare large particles by spray drying. The mechanical static pressure is to overcome the repulsive force between the nanometer-sized silicon dioxide particles, so that the distance between the nanometer-sized silicon dioxide particles is closer, thereby obtaining a product with fewer pores after sintering.

[0031] Further, the temperature of the microcrystallization treatment is 1100-1650℃, and the time is 2-5h; after the treatment, the temperature is lowered to the ambient temperature at a rate of 3000-8000℃ / min. By rapid cooling, the growth of the crystal nucleus is avoided.

[0032] The present application provides a microcrystalline quartz ceramic prepared by the aforementioned preparation method.

[0033] Further, the content of the nucleating agent in the microcrystalline quartz ceramic is 0.01-20ppm. Adding a small amount of nucleating agent is beneficial to control the concentration of the crystal nucleus, and too much will aggregate into large crystals, which will cause the bending strength to be poor.

[0034] Further, the crystal size in the microcrystalline quartz ceramic is less than 3μm.

[0035] The present application also provides the application of the aforementioned microcrystalline quartz ceramic in the processing of single crystal silicon rod drawing crucible, diffusion tube, quartz boat, single crystal silicon feeding tube, high temperature window.

[0036] Example 1

[0037] Amorphous silica with an average particle size of 5 nm was added to water, barium hydroxide was added in a proportion of 0.01 ppm, and a slurry with a solid content of 20% was prepared; the slurry was spray dried (inlet air temperature of 280°C and outlet air temperature of 80°C) to obtain nanosilica agglomerates with an average particle size of 200 nm; the nanosilica agglomerates were subjected to mechanical static pressing (pressure of 100 MPa and time of 0.5 h) to obtain silica green bodies; the silica green bodies were calcined at 1100°C for 5 h and then placed in liquid nitrogen at a cooling rate of 3000°C / min to reach ambient temperature to obtain microcrystalline quartz ceramics.

[0038] Example 2

[0039] Amorphous silica with an average particle size of 30 nm was added to water, barium hydroxide was added in a proportion of 20 ppm, and a slurry with a solid content of 15% was prepared; the slurry was spray dried (inlet air temperature of 350°C and outlet air temperature of 120°C) to obtain nanosilica agglomerates with an average particle size of 300 nm; the nanosilica agglomerates were subjected to mechanical static pressing (pressure of 250 MPa and time of 0.5 h) to obtain silica green bodies; the silica green bodies were calcined at 1650°C for 2 h and then placed in liquid nitrogen at a cooling rate of 8000°C / min to reach ambient temperature to obtain microcrystalline quartz ceramics.

[0040] Example 3

[0041] Amorphous silica with an average particle size of 50 nm was added to water, barium hydroxide was added in a proportion of 5 ppm, and a slurry with a solid content of 15% was prepared; the slurry was spray dried (inlet air temperature of 300°C and outlet air temperature of 100°C) to obtain nanosilica agglomerates with an average particle size of 400 nm; the nanosilica agglomerates were subjected to mechanical static pressing (pressure of 150 MPa and time of 0.5 h) to obtain silica green bodies; the silica green bodies were calcined at 1300°C for 2 h and then placed in liquid nitrogen at a cooling rate of 6000°C / min to reach ambient temperature to obtain microcrystalline quartz ceramics.

[0042] Comparative Example 1

[0043] The method of Example 3 was followed, except that amorphous silica with an average particle size of 2 μm was used as the raw material.

[0044] Amorphous silica with an average particle size of 2 μm was added to water, barium hydroxide was added in a proportion of 5 ppm, and a slurry with a solid content of 15% was prepared; the slurry was spray dried (inlet air temperature of 300°C and outlet air temperature of 100°C) to obtain silica agglomerates with an average particle size of 20 μm; the silica agglomerates were subjected to mechanical static pressure (pressure of 150 MPa and time of 0.5 h) to obtain a silica green body; the silica green body was calcined at 1300°C for 2 h, then was placed in liquid nitrogen, and was cooled to ambient temperature at a cooling rate of 6000°C / min to obtain non-microcrystallized quartz ceramic.

[0045] Example 4

[0046] The method of Example 3 was followed, except that barium hydroxide was replaced by barium chloride, and dilute sulfuric acid was added dropwise to adjust the pH value to 5.

[0047] Amorphous silica with an average particle size of 50 nm was added to water, barium chloride was added in a proportion of 5 ppm, dilute sulfuric acid was added dropwise to adjust the pH value to 5, and a slurry with a solid content of 15% was prepared; the slurry was spray dried (inlet air temperature of 300°C and outlet air temperature of 100°C) to obtain nano-silica agglomerates with an average particle size of 400 nm; the nano-silica agglomerates were subjected to mechanical static pressure (pressure of 150 MPa and time of 0.5 h) to obtain a silica green body; the silica green body was calcined at 1300°C for 2 h, then was placed in liquid nitrogen, and was cooled to ambient temperature at a cooling rate of 6000°C / min to obtain microcrystallized quartz ceramic.

[0048] Example 5

[0049] The method of Example 4 was followed, except that the addition proportion of barium chloride was adjusted to 2 ppm.

[0050] Amorphous silica with an average particle size of 50 nm was added to water, barium chloride was added in a proportion of 2 ppm, dilute sulfuric acid was added dropwise to adjust the pH value to 5, and a slurry with a solid content of 15% was prepared; the slurry was spray dried (inlet air temperature of 300°C and outlet air temperature of 100°C) to obtain nano-silica agglomerates with an average particle size of 400 nm; the nano-silica agglomerates were subjected to mechanical static pressure (pressure of 150 MPa and time of 0.5 h) to obtain a silica green body; the silica green body was calcined at 1300°C for 2 h, then was placed in liquid nitrogen, and was cooled to ambient temperature at a cooling rate of 6000°C / min to obtain microcrystallized quartz ceramic.

[0051] Example 6

[0052] The method of Example 3 was followed, except that barium hydroxide was replaced by ammonium chromate and the addition proportion of ammonium chromate was 2 ppm.

[0053] Amorphous silica with an average particle size of 50 nm was added to water, and ammonium chromate was added in a proportion of 2 ppm to prepare a slurry with a solid content of 15%; the slurry was spray dried (an inlet air temperature of 300°C and an outlet air temperature of 100°C) to obtain silica agglomerates with an average particle size of 400 nm; the silica agglomerates were subjected to mechanical static pressing (a pressure of 150 MPa and a time of 0.5 h) to obtain a silica green body; the silica green body was calcined at 1300°C for 2 h and then placed in liquid nitrogen to reduce the temperature to ambient temperature at a rate of 6000°C / min to obtain microcrystalline quartz ceramic.

[0054] Comparative Example 2

[0055] The method of Example 6 was followed, except that amorphous silica with an average particle size of 2 μm was used as the raw material.

[0056] Amorphous silica with an average particle size of 2 μm was added to water, and ammonium chromate was added in a proportion of 2 ppm to prepare a slurry with a solid content of 15%; the slurry was spray dried (an inlet air temperature of 300°C and an outlet air temperature of 100°C) to obtain silica agglomerates with an average particle size of 20 μm; the silica agglomerates were subjected to mechanical static pressing (a pressure of 150 MPa and a time of 0.5 h) to obtain a silica green body; the silica green body was calcined at 1300°C for 2 h and then placed in liquid nitrogen to reduce the temperature to ambient temperature at a rate of 6000°C / min to obtain non-microcrystallized quartz ceramic.

[0057] Example 7

[0058] The method of Example 3 was followed, except that barium hydroxide was replaced by gadolinium chloride and the gadolinium chloride was added in a proportion of 1 ppm.

[0059] Amorphous silica with an average particle size of 50 nm was added to water, and gadolinium chloride was added in a proportion of 1 ppm to prepare a slurry with a solid content of 15%; the slurry was spray dried (an inlet air temperature of 300°C and an outlet air temperature of 100°C) to obtain silica agglomerates with an average particle size of 400 nm; the silica agglomerates were subjected to mechanical static pressing (a pressure of 150 MPa and a time of 0.5 h) to obtain a silica green body; the silica green body was calcined at 1300°C for 2 h and then placed in liquid nitrogen to reduce the temperature to ambient temperature at a rate of 6000°C / min to obtain microcrystalline quartz ceramic.

[0060] Comparative Example 3

[0061] The method of Example 7 was followed, except that amorphous silica with an average particle size of 2 μm was used as the raw material.

[0062] Amorphous silica with an average particle size of 2 μm was added to water, gadolinium chloride was added in a proportion of 1 ppm, and a slurry with a solid content of 15% was prepared; the slurry was spray dried (inlet air temperature 300°C, outlet air temperature 100°C) to obtain silica agglomerates with an average particle size of 20 μm; the silica agglomerates were subjected to mechanical static pressing (pressure 150 MPa, time 0.5 h) to obtain silica green bodies; the silica green bodies were calcined at 1300°C for 2 h, then placed in liquid nitrogen, and cooled to ambient temperature at a rate of 6000°C / min to obtain opaque non-microcrystallized quartz ceramic.

[0063] Example 8

[0064] The method of Example 3 was followed, except that barium hydroxide was replaced by cerium chloride and the addition proportion of cerium chloride was 1 ppm, and the cooling method was replaced by ice-water quenching.

[0065] Amorphous silica with an average particle size of 50 nm was added to water, cerium chloride was added in a proportion of 1 ppm, and a slurry with a solid content of 15% was prepared; the slurry was spray dried (inlet air temperature 300°C, outlet air temperature 100°C) to obtain nano-silica agglomerates with an average particle size of 400 nm; the nano-silica agglomerates were subjected to mechanical static pressing (pressure 150 MPa, time 0.5 h) to obtain silica green bodies; the silica green bodies were calcined at 1300°C for 2 h, then placed in ice-water, and cooled to ambient temperature at a rate of 5000°C / min to obtain microcrystallized quartz ceramic.

[0066] Comparative Example 4

[0067] The method of Example 3 was followed, except that the calcination temperature was adjusted from 1300°C to 1000°C.

[0068] Amorphous silica with an average particle size of 50 nm was added to water, barium hydroxide was added in a proportion of 5 ppm, and a slurry with a solid content of 15% was prepared; the slurry was spray dried (inlet air temperature 300°C, outlet air temperature 100°C) to obtain nano-silica agglomerates with an average particle size of 400 nm; the nano-silica agglomerates were subjected to mechanical static pressing (pressure 150 MPa, time 0.5 h) to obtain silica green bodies; the silica green bodies were calcined at 1000°C for 2 h, then placed in liquid nitrogen, and cooled to ambient temperature at a rate of 6000°C / min to obtain non-microcrystallized quartz ceramic.

[0069] Comparative Example 5

[0070] The method of Example 3 was followed, except that no nucleating agent was added.

[0071] Amorphous silica with an average particle size of 50 nm was added to water to prepare a slurry with a solid content of 15%; the slurry was spray dried (inlet temperature of 300°C and outlet temperature of 100°C) to obtain nano-silica agglomerates with an average particle size of 400 nm; the nano-silica agglomerates were subjected to mechanical static pressure (pressure of 150 MPa and time of 0.5 h) to obtain a silica green body; the silica green body was calcined at 1300°C for 2 h and then placed in liquid nitrogen at a cooling rate of 6000°C / min to reach ambient temperature to obtain non-microcrystalline quartz ceramic.

[0072] Comparative Example 6

[0073] The method of Example 2 was followed, except that the addition ratio of barium hydroxide was adjusted to 500 ppm.

[0074] Amorphous silica with an average particle size of 30 nm was added to water, barium hydroxide was added at a ratio of 500 ppm, and a slurry with a solid content of 15% was prepared; the slurry was spray dried (inlet temperature of 300°C and outlet temperature of 100°C) to obtain nano-silica agglomerates with an average particle size of 300 nm; the nano-silica agglomerates were subjected to mechanical static pressure (pressure of 250 MPa and time of 0.5 h) to obtain a silica green body; the silica green body was calcined at 1650°C for 2 h and then placed in liquid nitrogen at a cooling rate of 8000°C / min to reach ambient temperature to obtain non-microcrystalline quartz ceramic.

[0075] Comparative Example 7

[0076] The method of Example 2 was followed, except that spray drying and mechanical static pressure were not performed, and a silica green body was obtained by slip casting.

[0077] Amorphous silica with an average particle size of 30 nm was added to water, barium hydroxide was added at a ratio of 20 ppm, and a slurry with a solid content of 15% was prepared; the slurry was slip cast to obtain a silica green body; the silica green body was calcined at 1650°C for 2 h and then placed in liquid nitrogen at a cooling rate of 8000°C / min to reach ambient temperature to obtain porous quartz ceramic.

[0078] Figure 1 XRD pattern of the microcrystalline quartz ceramic prepared in Example 1. From Figure 1 It can be seen that sharp characteristic peaks appear in the spectrum, indicating that crystalline phases have appeared and microcrystalline ceramic has been formed.

[0079] Figure 2 SEM pattern of the microcrystalline quartz ceramic prepared in Example 1. From Figure 2 It can be seen that a structure in which fine crystals are intertwined together has appeared in the microstructure of the product prepared in Example 1.

[0080] Figure 3 The XRD pattern of the non-microcrystalline quartz ceramic prepared for Comparative Example 5. From the figure, it can be seen that the spectrum is a steamed bun peak, the peak type is relatively diffuse, and no obvious crystal diffraction peak appears, indicating that the product prepared in Comparative Example 5 is amorphous. Figure 3

[0081] The quartz ceramic samples prepared in the above examples and comparative examples were respectively tested for bending strength, light transmittance, softening temperature, and thermal expansion coefficient, and the test results are shown in Table 1.

[0082] The bending strength test standard is GB / T 37781-2019;

[0083] The light transmittance test standard is GB / T 5137.2-2020;

[0084] The softening temperature test standard is GB / T 28195-2011;

[0085] The thermal expansion coefficient test standard is GB / T 16920-2015.

[0086] Table 1

[0087] Flexural strength (MPa) Transmittance (%) Softening temperature (°C) Thermal expansion coefficient Example 1 71.4 89.1 1781 2.1 x 10 -7 / °C Example 2 72.1 89.3 1790 2.1 x 10 -7 / °C Example 3 71.6 89.0 1786 2.1 x 10 -7 / °C Comparative Example 1 26.5 3.6 1729 5.4 x 10 -7 / °C Example 4 78.6 89.5 1785 2.2 x 10 -7 / °C <!-- 5 -->]]> Example 5 77.2 89.3 1783 2.2 x 10 -7 / °C Example 6 71.8 89.2 1780 2.3 x 10 -7 / °C Comparative Example 2 27.3 3.3 1726 5.4 x 10 -7 / °C Example 7 73.8 89.1 1788 2.2 x 10 -7 / °C Comparative Example 3 28.3 4.1 1724 5.4 x 10 -7 / °C Example 8 73.2 89.5 1782 2.2 x 10 -7 / °C Comparative Example 4 27.2 4.0 1721 5.4 x 10 -7 / °C Comparative Example 5 27.6 90.1 1728 5.4 x 10 -7 / °C Comparative Example 6 26.8 58.7 1780 5.4 x 10 -7 / °C Comparative Example 7 19.2 2.3 1710 5.4 x 10 -7 / °C

[0088] From Table 1, it can be seen that:

[0089] Comparative Examples 1-3 use micron-sized amorphous silica as raw material, and the quartz ceramics prepared have poor light transmittance and high-temperature resistance, and low bending strength.

[0090] Examples 4-5 attach nucleating agents to the surface of nanoscale silica by the precipitation method, which can improve the bending strength of the prepared quartz ceramics.

[0091] Comparative Example 4 has a too low calcination temperature, and the prepared quartz ceramics have poor light transmittance and high-temperature resistance, and low bending strength.

[0092] Comparative Example 5 does not add a nucleating agent, although the prepared quartz ceramics have good light transmittance, but poor high-temperature resistance and low bending strength.

[0093] Comparative Example 6 has a too large addition ratio of the nucleating agent, resulting in a decrease in the light transmittance of the prepared quartz ceramics and low bending strength.

[0094] In Comparative Example 7, the silica green body is prepared by slip casting instead of spray drying and mechanical static pressing, and the bending strength, light transmittance, and softening temperature of the prepared quartz ceramics are the lowest among all the comparative examples, which shows that the spray drying and mechanical static pressing used in the preparation of the quartz ceramics in the present application can effectively improve the light transmittance and high-temperature resistance and bending strength of the quartz ceramics.

[0095] ​The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing microcrystalline quartz ceramics, characterized in that: The following steps are involved: (1) adding nano-sized amorphous silica and a nucleating agent into water to prepare a slurry; (2) spray drying the slurry to obtain nano-silica agglomerates; (3) mechanically statically pressing the nano-silica agglomerates to obtain a silicon dioxide embryo; (4) performing microcrystallization treatment on the silicon dioxide green body to obtain microcrystalline quartz ceramics; The temperature of the microcrystallization treatment is 1100-1650°C; The content of the nucleating agent in the microcrystalline quartz ceramic is 0.01 to 20 ppm.

2. The preparation method according to claim 1, wherein: The average particle size of the nano-scale amorphous silicon dioxide is 5 to 40 nm.

3. The preparation method according to claim 1, wherein: The nucleating agent includes at least one of oxides, hydroxides, chlorides, sulfates, nitrates, carbonates, phosphates, and acetates of Ba, Cr, and La series elements.

4. The preparation method according to claim 1, wherein: The solid content of the slurry is 5-50%.

5. The preparation method according to claim 1, wherein: The air inlet temperature of the spray drying is 280-350°C, and the air outlet temperature is 80-120°C.

6. The preparation method according to claim 1, wherein: The average particle size of the nano-silicon dioxide agglomerates is 200-500 nm.

7. The preparation method according to claim 1, wherein: The mechanical static pressure is 5-600 MPa.

8. The preparation method according to claim 1, wherein: The microcrystallization treatment lasts for 2 to 5 hours. After the treatment, the temperature is lowered to ambient temperature at a rate of 3000 to 8000° C. / min.

9. Microcrystalline quartz ceramics prepared by the preparation method according to any one of claims 1 to 8.

10. The microcrystalline quartz ceramic according to claim 9, characterized in that: The crystal size of the microcrystalline quartz ceramic is less than 3 μm.

11. Use of the microcrystalline quartz ceramic according to claim 10 in crucibles for single crystal silicon rod pulling, diffusion tubes, quartz boats, single crystal silicon feeding tubes, and high-temperature window processing.

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