JPH03137029A - Production of silica glass - Google Patents
Production of silica glassInfo
- Publication number
- JPH03137029A JPH03137029A JP27628589A JP27628589A JPH03137029A JP H03137029 A JPH03137029 A JP H03137029A JP 27628589 A JP27628589 A JP 27628589A JP 27628589 A JP27628589 A JP 27628589A JP H03137029 A JPH03137029 A JP H03137029A
- Authority
- JP
- Japan
- Prior art keywords
- gel
- sol
- silica glass
- silica
- silicon alkoxide
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 28
- 238000004519 manufacturing process Methods 0.000 title claims description 13
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 12
- 239000010703 silicon Substances 0.000 claims abstract description 12
- -1 silicon alkoxide Chemical class 0.000 claims abstract description 12
- 229920001289 polyvinyl ether Polymers 0.000 claims abstract description 10
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000003980 solgel method Methods 0.000 abstract description 6
- 238000000034 method Methods 0.000 abstract description 5
- 238000001035 drying Methods 0.000 abstract description 4
- 230000003301 hydrolyzing effect Effects 0.000 abstract description 4
- 238000005245 sintering Methods 0.000 abstract description 4
- CRNJBCMSTRNIOX-UHFFFAOYSA-N methanolate silicon(4+) Chemical compound [Si+4].[O-]C.[O-]C.[O-]C.[O-]C CRNJBCMSTRNIOX-UHFFFAOYSA-N 0.000 abstract description 3
- 229920002432 poly(vinyl methyl ether) polymer Polymers 0.000 abstract description 3
- 239000000499 gel Substances 0.000 description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 12
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 9
- 235000019441 ethanol Nutrition 0.000 description 9
- 239000003960 organic solvent Substances 0.000 description 9
- 125000000217 alkyl group Chemical group 0.000 description 5
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 3
- OEYIOHPDSNJKLS-UHFFFAOYSA-N choline Chemical compound C[N+](C)(C)CCO OEYIOHPDSNJKLS-UHFFFAOYSA-N 0.000 description 3
- 229960001231 choline Drugs 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000011259 mixed solution Substances 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000002585 base Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 238000001879 gelation Methods 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 description 1
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 125000000484 butyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000003349 gelling agent Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 125000000956 methoxy group Chemical group [H]C([H])([H])O* 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 125000001436 propyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000000741 silica gel Substances 0.000 description 1
- 229910002027 silica gel Inorganic materials 0.000 description 1
- 239000005049 silicon tetrachloride Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
- C03C1/006—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels to produce glass through wet route
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Glass Melting And Manufacturing (AREA)
Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は光学用、半導体工業用、電子工業用、理化学用
等に使用されるシリカガラスの製造法に関する。DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for producing silica glass used for optics, semiconductor industry, electronic industry, physics and chemistry, etc.
（従来の技術）
シリカガラスは耐熱性、耐食性および光学的性質に優れ
ていることから、半導体の製造に欠かせない重要な材料
であり、さらには光ファイバやＩＣ製造用フォトマスク
基板、ＴＰＴ基板などに使用され、その用途はますます
拡大している。(Prior art) Silica glass has excellent heat resistance, corrosion resistance, and optical properties, so it is an important material indispensable for semiconductor manufacturing, and is also used as a photomask substrate for optical fiber and IC manufacturing, and TPT substrate. It is used for various purposes, and its applications are expanding more and more.
従来のシリカガラスの製造法には、天然石英を電気炉ま
たは酸水素炎により溶解する方法、あるいは四塩化ケイ
素を酸水素炎又はプラズマ炎中で高温酸化し溶解する方
法があるが、いずれの方法も製造工程に２０００℃ある
いはそれ以上の高温を必要とするため大量のエネルギー
を消費し、また製造時にそのような高温に耐える材料が
必要となるほか、更に高純度のものが得にくいなど経済
的、品質的にいくつかの問題点をもっている。Conventional methods for manufacturing silica glass include melting natural quartz in an electric furnace or oxyhydrogen flame, or oxidizing and melting silicon tetrachloride at high temperature in an oxyhydrogen flame or plasma flame. However, the manufacturing process requires high temperatures of 2000°C or higher, which consumes a large amount of energy.In addition, materials that can withstand such high temperatures are required during manufacturing, and it is difficult to obtain high-purity materials, making it economically difficult. , there are some quality problems.
これに対し、近年ゾル−ゲル法と呼ばれるシリカガラス
を低温で合成する方法が注目されている。On the other hand, in recent years, a method of synthesizing silica glass at low temperature called the sol-gel method has been attracting attention.
その概要を簡単に述べる。The outline will be briefly described below.
一般式Ｓｉ （ＯＲ）４ （Ｒ：アルキル基）で表わ
されるシリコンアルコキシド（本発明においては、その
重縮合物を含む）、例えば（ＲＯ）３Ｓｉ・（Ｏ８１（
ＯＲ）ｚ）ｎ−Ｏ８ｉ （ＯＲ）（ｎ＝ｏ 〜８、Ｒ
：アルキル基）に水（アルカリまたは酸でｐＨを調整し
てもよい）を加え、加水分解し、シリカヒドロシル（本
発明においてはシリカゾルという）とする。この時、シ
リコンアルコキシドと水が均一な系となる様、一般には
溶媒として適当なアルコール等の有機溶媒が添加されて
いる。このシリカゾルを静置、昇温、ゲル化剤の添加等
によってゲル化させる。その後、ゲルを蒸発乾燥するこ
とによりシリカ乾燥ゲルとする。この乾燥ゲルを適当な
雰囲気中で焼結することによりシリカガラスを得る。Silicon alkoxides (including polycondensates thereof in the present invention) represented by the general formula Si (OR)4 (R: alkyl group), for example (RO)3Si.(O81(
OR) z) n-O8i (OR) (n=o ~8, R
: alkyl group) is added with water (pH may be adjusted with an alkali or acid) and hydrolyzed to produce silica hydrosil (referred to as silica sol in the present invention). At this time, an appropriate organic solvent such as alcohol is generally added as a solvent so that the silicon alkoxide and water form a uniform system. This silica sol is gelled by standing still, increasing the temperature, adding a gelling agent, etc. Thereafter, the gel is evaporated to dryness to obtain a dry silica gel. Silica glass is obtained by sintering this dried gel in a suitable atmosphere.
（発明が解決しようとする課題）
しかし、ゾル−ゲル法によるシリカガラスの製造にはま
だ未解決の問題が残されている。特にゲルを乾燥してい
く過程でゲルにクラックや割れが発生し易く、クラック
や割れのないモノリシックな大形の乾燥ゲルを歩留り良
く製造することが困難となることである。(Problems to be Solved by the Invention) However, there are still unresolved problems in the production of silica glass by the sol-gel method. In particular, during the process of drying the gel, cracks and fractures are likely to occur in the gel, making it difficult to produce a monolithic large-sized dry gel without cracks and fractures with a good yield.
本発明はクラックや割れの発生することのないシリカガ
ラスの製造法を提供するものである。The present invention provides a method for producing silica glass that does not cause cracks or breaks.
（課題を解決するための手段）
本発明は、ゾル−ゲル法によるシリカガラスの製造法に
おいて、ゾル調製時に、ポリビニルニーチルを添加する
ことを特徴とするものである。(Means for Solving the Problems) The present invention is a method for producing silica glass by a sol-gel method, which is characterized in that polyvinyl nythyl is added at the time of sol preparation.
本発明において、シリコンアルコキシドのアルキル基に
ついて、特に制限はないが、加水分解のし易さ、ゲル化
時間の点から、メチル基、エチル基、プロピル基、又は
ブチル基を有するシリコンアルコキシドを使用すること
が好ましい。シリコンアルコキシドに水、又は水とアル
コール等の有機溶媒の混合溶液を加えて加水分解してシ
リカゾルを生成させる際、アルコール等の有機溶媒、又
はアルコール等の有機溶媒と水の混合溶液にあらかじめ
ポリビニルエーテルを加え、均一に溶解させておく。In the present invention, there are no particular restrictions on the alkyl group of silicon alkoxide, but silicon alkoxide having a methyl group, ethyl group, propyl group, or butyl group is used from the viewpoint of ease of hydrolysis and gelation time. It is preferable. When adding water or a mixed solution of water and an organic solvent such as alcohol to silicon alkoxide and hydrolyzing it to generate silica sol, polyvinyl ether is added to the organic solvent such as alcohol or the mixed solution of organic solvent such as alcohol and water in advance. Add and dissolve evenly.
ポリビニルエーテルは、水と相溶性のある有機溶媒に溶
解するものが望ましい。The polyvinyl ether is preferably one that dissolves in an organic solvent that is compatible with water.
ポリビニルエーテルの側鎖のアルキル基としてはメチル
基、エチル基等の低級アルキル基が望ましい。The alkyl group in the side chain of polyvinyl ether is preferably a lower alkyl group such as a methyl group or an ethyl group.
ポリビニルエーテルの分子量は、アルコール等の有機溶
媒、又はアルコール等の有機溶媒と水の混合溶液へのポ
リビニルエーテルの溶解性等を考慮して選定される。The molecular weight of the polyvinyl ether is selected in consideration of the solubility of the polyvinyl ether in an organic solvent such as alcohol or a mixed solution of an organic solvent such as alcohol and water.
添加するポリビニルエーテルの量は用いるシリコンアル
コキシドの種類や加水分解速度等によって適宜調整する
。The amount of polyvinyl ether to be added is appropriately adjusted depending on the type of silicon alkoxide used, the hydrolysis rate, etc.
水と共に加える触媒は、塩基、酸等特に制限しないが、
ゲル化時間及び得られる乾燥ゲルの焼結のし易すさの点
から塩基の方が好ましい。The catalyst added with water is not particularly limited, such as bases and acids, but
Bases are preferred in terms of gelation time and ease of sintering the resulting dry gel.
水と共に加えるアルコール等の有機溶媒としては、水及
びアルコキシドの両者に対する溶解性の点から、メチル
アルコール、エチルアルコール、１−プロピルアルコー
ル、２−プロピルアルコール等のアルコール類、アセト
ン、ジメチルホルムアミド等が用いられる。As the organic solvent such as alcohol added together with water, alcohols such as methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, acetone, dimethylformamide, etc. are used from the viewpoint of solubility in both water and alkoxide. It will be done.
シリコンアルコキシド、有機溶媒、水及びポリビニルエ
ーテルは生成するゾルをできる限り均一なものとするた
めにスタークなどを用いてよく混合する。また、超音波
を照射してもよい。ゾル調製時にシリカの微粒子を加え
てもよい。The silicon alkoxide, organic solvent, water and polyvinyl ether are thoroughly mixed using a Stark or the like in order to make the resulting sol as uniform as possible. Alternatively, ultrasonic waves may be irradiated. Fine particles of silica may be added during sol preparation.
シリカガラスは、上記のようにして調製したシリカゾル
をシャーレ等の容器に移し、室温〜７０℃に保って、ゲ
ル化し、次いで室温以上の温度で数週間乾燥して、乾燥
ゲルとし、更に公知の方法、例えば、空気中で１０００
〜１４００℃に昇温しで焼結することにより得られる。Silica glass is produced by transferring the silica sol prepared as described above to a container such as a petri dish, keeping it at room temperature to 70°C to gel it, and then drying it at a temperature above room temperature for several weeks to form a dry gel. method, e.g. 1000 in air
It is obtained by sintering at a temperature of ~1400°C.
（作用）
ポリビニルエーテルの添加効果の理由について、詳細は
不明であるが、ゾル中でのシリカ微粒子の生成の制御、
ゲル中でのこれらのシリカ微粒子間の結合、乾燥過程で
ゲル中に発生する応力の緩和等に寄与し、ゲルの大形化
が可能となったものと考えられる。(Function) Although the details of the reason for the effect of adding polyvinyl ether are unknown, it is possible to control the production of silica fine particles in the sol,
It is thought that the bonding between these silica particles in the gel and the relaxation of stress generated in the gel during the drying process made it possible to increase the size of the gel.
実施例 １
３モルのメチルアルコールにポリビニルメチルエーテル
（アルドリッチ社製）を７．６ｇ充分に溶解させた後、
３モルの０．０００５モルのコリンを混合した。得られ
た溶液を１モルのシリコンメトキシド（Ｓｉ （ＯＣＨ
３）４ ）にゆっくりと加え、さらに充分混合しシリカ
ゾルを得た。これをテフロンでコーティングした直径１
５０ｍｍのガラス製シャーレに入れ、アルミ箔で密封し
、室温でゲル化した。その後、蓋に孔を開け、５０℃の
恒温槽中で２週間乾燥し、その後
１２０℃の恒温槽に移して１日乾燥して、直径約１２０
ｍｍの乾燥ゲルを得た。こうして得られた乾燥ゲルのか
さ密度は約０．６ｇ／ｃｍ３であり、クラックや割れは
全くなかった。Example 1 After sufficiently dissolving 7.6 g of polyvinyl methyl ether (manufactured by Aldrich) in 3 moles of methyl alcohol,
Three moles of 0.0005 mole choline were mixed. The resulting solution was diluted with 1 mol of silicon methoxide (Si (OCH)
3) Slowly added to 4) and mixed thoroughly to obtain silica sol. This is coated with Teflon and has a diameter of 1
It was placed in a 50 mm glass Petri dish, sealed with aluminum foil, and gelatinized at room temperature. After that, a hole was made in the lid and dried in a constant temperature bath at 50℃ for two weeks, then transferred to a constant temperature bath at 120℃ and dried for one day.
A dry gel of mm was obtained. The bulk density of the dry gel thus obtained was approximately 0.6 g/cm3, and there were no cracks or breaks.
得られたゲルを空気中１２００℃まで加熱焼結したとこ
ろクラックや割れのない直径約８０ｍｍ。When the obtained gel was heated and sintered in air to 1200°C, it had a diameter of about 80 mm without any cracks or breaks.
厚さ５ｍｍの透明なシリカガラスが得られた。このシリ
カガラスは分析の結果、市販のシリカガラスと一致した
。A transparent silica glass with a thickness of 5 mm was obtained. As a result of analysis, this silica glass matched commercially available silica glass.
実施例 ２
ポリビニルエチルエーテル（アルドリッチ社製）１５．
２ｇを３モルのメチルアルコールに充分に溶解させた後
、３モルの水、０．０００５モルのコリンとを混合した
。以下実施例１と同様の操作を行って乾燥ゲルを得た。Example 2 Polyvinylethyl ether (manufactured by Aldrich) 15.
After fully dissolving 2 g in 3 moles of methyl alcohol, 3 moles of water and 0.0005 moles of choline were mixed. Thereafter, the same operation as in Example 1 was performed to obtain a dry gel.
得られた乾燥ゲルにはクラックや割れは全くなかった。The dried gel obtained had no cracks or breaks.
実施例３
ポリビニルメチルエーテル（アルドリッチ社製）１０．
８ｇを３モルのメチルアルコールに充分に溶解させた後
、３モルの水と０．０００５モルのコリンを混合した。Example 3 Polyvinyl methyl ether (manufactured by Aldrich) 10.
After fully dissolving 8 g in 3 moles of methyl alcohol, 3 moles of water and 0.0005 moles of choline were mixed.
得られた溶液を１モルのシリコンメトキシドの重縮合物
（（ＣＨ３０）ａ Ｓｉ・（０・Ｓ ｉ （ＯＣＨ
３）２）ｎ ・Ｏ８ｉ （ＯＣＨ３）３）（ｎの平
均値は３）にゆっくりと加え、さらに充分混合しシリカ
ゾルを得た。以下実施例１と同様の操作を行って乾燥ゲ
ルを得た。得られた乾燥ゲルにはクラックや割れは全く
なかった。The obtained solution was mixed with 1 mol of silicon methoxide polycondensate ((CH30)a Si・(0・S i (OCH
3) 2) n .O8i (OCH3) 3) (average value of n is 3) was slowly added to the solution and mixed thoroughly to obtain a silica sol. Thereafter, the same operation as in Example 1 was performed to obtain a dry gel. The dried gel obtained had no cracks or breaks.
（発明の効果）
本発明によれば、クラックや割れのない大形のシリカガ
ラスをゾル−ゲル法により容易に製造可能となる。その
大きさは基本的には制約がなく、形状も板状、棒状、管
状等のいずれでも製造できる。(Effects of the Invention) According to the present invention, large-sized silica glass without cracks or breaks can be easily produced by a sol-gel method. There are basically no restrictions on its size, and it can be manufactured in any shape such as plate, rod, or tube.
Claims (1)
し、これをゲル化し、乾燥して乾燥ゲルとし、次いで焼
結するシリカガラスの製造法において、シリコンアルコ
キシドを加水分解してシリカゾルとする段階で、ポリビ
ニルエーテルを添加することを特徴とするシリカガラス
の製造法。1. In the method for producing silica glass in which silicon alkoxide is hydrolyzed to form silica sol, this is gelled, dried to form a dry gel, and then sintered, polyvinyl ether is A method for producing silica glass characterized by adding.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27628589A JPH03137029A (en) | 1989-10-24 | 1989-10-24 | Production of silica glass |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP27628589A JPH03137029A (en) | 1989-10-24 | 1989-10-24 | Production of silica glass |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH03137029A true JPH03137029A (en) | 1991-06-11 |
Family
ID=17567318
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP27628589A Pending JPH03137029A (en) | 1989-10-24 | 1989-10-24 | Production of silica glass |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH03137029A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6294601B1 (en) | 1997-10-29 | 2001-09-25 | Samsung Electronics Co., Ltd. | Silica glass composition |
-
1989
- 1989-10-24 JP JP27628589A patent/JPH03137029A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6294601B1 (en) | 1997-10-29 | 2001-09-25 | Samsung Electronics Co., Ltd. | Silica glass composition |
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