JP3594476B2 - Method for producing porous quartz glass body - Google Patents
Method for producing porous quartz glass body Download PDFInfo
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- JP3594476B2 JP3594476B2 JP3542698A JP3542698A JP3594476B2 JP 3594476 B2 JP3594476 B2 JP 3594476B2 JP 3542698 A JP3542698 A JP 3542698A JP 3542698 A JP3542698 A JP 3542698A JP 3594476 B2 JP3594476 B2 JP 3594476B2
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- quartz glass
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B19/00—Other methods of shaping glass
- C03B19/08—Other methods of shaping glass by foaming
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- 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
- 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
- C03C11/00—Multi-cellular glass ; Porous or hollow glass or glass particles
-
- 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
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/06—Glass compositions containing silica with more than 90% silica by weight, e.g. quartz
-
- 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
- C03C2201/00—Glass compositions
- C03C2201/80—Glass compositions containing bubbles or microbubbles, e.g. opaque quartz glass
-
- 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
- C03C2203/00—Production processes
- C03C2203/20—Wet processes, e.g. sol-gel process
- C03C2203/26—Wet processes, e.g. sol-gel process using alkoxides
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- Organic Chemistry (AREA)
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- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Physics & Mathematics (AREA)
- Plasma & Fusion (AREA)
- Glass Melting And Manufacturing (AREA)
- Glass Compositions (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、多孔質石英ガラス体の製造方法に関し、特に半導体工業などで高純度石英を処理する装置等の断熱材などとして利用するに適した、多孔質石英ガラス体を工業的に製造する方法に関する。
【０００２】
【従来の技術】
従来、熱処理炉の断熱材として、アルミナ・シリカ系やジルコニア系などの種々の材質で構成されたものが用いられている。しかし、このような断熱材を半導体工業用高純度石英ガラスの製造装置、特に熱処理炉などに使用すると、断熱材に含まれる金属不純物が高温で揮発して、被処理物である石英ガラスの表面を汚染することがあり、品質低下の原因の一つとなっていた。
そして、このような断熱材からの金属不純物の揮発は、高温処理を反復するに従って徐々に低下するため、被処理物表面の汚染が許容レベルまで低下するに至るには、長時間の高温運転、いわゆる「枯らし」を行うことが必要とされていた。
【０００３】
一方、石英ガラスは耐熱性が高いために、上記のような高純度石英ガラスの熱処理炉などに断熱材として利用することが提案されている。
特に、高純度石英ガラスの熱処理炉などに断熱材として、熱線の透過を遮断するために、内部に微小な気泡を包含させて赤外線を乱反射させることにより、断熱性を高めた不透明石英ガラスが知られている。
この不透明石英ガラスを得る方法として、珪酸質原料粉に窒化珪素微粉末を添加して溶融する方法（特開平４−６５３２８号）や、その泡の径分布を２０〜１８０μｍとした不透明石英ガラス（特開平５−２５４８８２号）、更に、ＯＨ基を含有する粉末状シリカ又は多孔質状シリカ体をアンモニア雰囲気中で６００〜１３００℃の範囲の温度でアンモニア処理し、得られたアンモニア処理粉体を所定形状の型の中で加圧した後に、１４００〜１９００℃の温度で溶融発泡させるシリカ発泡体の製造方法（特開平５−１７１８０号）などが知られている。
【０００４】
【発明が解決しようとする課題】
ところで、かかる多孔質石英ガラスを得るための発泡剤は、金属不純物の含有量の少ないことが望まれるが、純度の高い窒化珪素は極めて高価となり、経済的でないという課題があった。
また、アンモニアを発泡剤として使用すれば、アンモニアをＯＨ基と反応させるための特殊な装置が必要となるほか、発泡剤に含まれる金属不純物の点での問題は軽減するものの、工程が複雑となることに伴う不純物の混入を防止する対策を強化する必要があり、これもまた経済的でないという課題があった。
【０００５】
本発明は、上記課題を解決するためになされたものであり、高純度の石英ガラスを製造する熱処理装置の断熱材等に、使用することができる多孔質石英ガラス体を、工業的に製造することができる改良された製造方法を提供することを目的とするものである。
【０００６】
【課題を解決するための手段】
上記課題を解決するためになされた本発明にかかる多孔質石英ガラス体の製造方法は、シリコンアルコキシドの加水分解により得た水分含有乾燥シリカゲル粉末を、酸素水素炎中で加熱溶融して独立気泡体を形成することを特徴とする。
ここで、前記シリコンアルコキシドが、テトラメトキシシラン又はテトラエトキシシランから選択された少なくも１種であることんが望ましい。
また、前記乾燥シリカゲル粉末が、５〜２０重量％の水分を含有していることが望ましい。
【０００７】
【発明の実施の形態】
本発明の多孔質石英ガラス体の製造方法において、原料として用いられるシリコンアルコキシドは、各種のアルコキシル基を有するアルコキシシランやアルコキシシロキサンなどであってよく、例えばテトラエトキシシラン、テトラメトキシシランなどが好ましいが、テトラメトキシシランが特に好ましく用いられる。
かかるシリコンアルコキシドは、酸性或いは塩基性の触媒の存在下で水と反応させて加水分解し、シリカゾルを経て固化させるか、又はゾル化と平行して加温するなどの方法で固化させて湿潤ゲルとするが、かかる未乾燥シリカゲルは、原料に由来する水やアルコールなどを多量に含んでいる。
【０００８】
このような未乾燥シリカゲル中の水やアルコールは、シリカゲルを乾燥しても完全に脱離することはなく、また加水分解やゲル化の条件並びに乾燥条件によって、アルコキシル基やシラノール基の残留量も変化する。
従って、本発明において用いられる乾燥シリカゲルとしては、乾燥による脱水が十分でなく、水分含有量が５〜２０重量％の範囲にあるものであることが好ましい。これは、水分含有量が５重量％未満である場合には、石英ガラス体の熱伝導率が高く、充分な断熱効果を得ることができず、また水分含有量が２０重量％を越えるある場合には、石英ガラス体の変形が著しく、気泡径が中心部ほど大きくなり、均一な気泡を得ることができないためである。
かかる水分を含有する乾燥シリカゲルは、水とその他の揮発成分とが共に発泡剤として作用して気泡を生成するので、目的とする多孔質石英ガラス体に含まれる気泡の径や数に応じて、適当な水分含有量を有する乾燥シリカゲルを選択して使用することが望ましい。
【０００９】
また、シリコンアルコキシドの加水分解により得た水分含有乾燥シリカゲル粉末５０重量％以上と、シリカ粉末５０重量％以下の混合物を、酸素水素炎中で加熱溶融して独立気泡体を形成しても良い。
前記乾燥シリカゲルに併用できる原料であるシリカ粉末は、できるだけ純度の高い石英原料、例えばゾルゲル法によって製造されたシリカや、クリストバライト、水晶などの粉末が好ましい。かかるシリカ粉末の配合量は、乾燥シリカゲルの水分含有量に応じて、多孔質石英ガラス体の見掛け密度が所望の範囲に入るように、調整することが望ましい。
【００１０】
このような乾燥シリカゲルだけの粉末、又は乾燥シリカゲルとシリカ粉末との混合物は、粉末状のまま酸素水素炎中に供給され、急速に加熱溶融されることにより独立気泡体に転化する。
即ち、シリカゲル粒子は溶融が始まると共に水分やアルコール等の脱離分解が起こり、粒子の内部に気泡が生成して相互に融着し、また混在するシリカ粉末とも融着して、堆積しつつ独立気泡体が順次成長し、多孔質石英ガラス体が得られる。
なお、前記乾燥シリカゲル粉末として、ナトリウム、カリウム、リチウム、銅、カルシウム、鉄、アルミニウム、及び硼素のいずれの含有量も０．１ｐｐｍ 未満であるものを使用することが望ましい。これは、特に半導体工業で使用される高純度石英もしくは半導体ウエハを熱処理する装置に用いられる断熱材として、有効利用できるための範囲である。
【００１１】
【実施例】
以下、実施例に基づいて、本発明の多孔質石英ガラス体の製造方法を具体的に説明するが、本発明はかかる実施例の記載により何ら制限を受けるものではない。
【００１２】
（第１実施例）
精製したテトラメトキシシランとメタノールとをモル比が１：３の割合で混合したのち、これに比抵抗率が１３×１０６ Ω・ｃｍの純水を、テトラメトキシシランに対するモル比が１：１０の割合となるように加え、均一な溶液を得た。この混合溶液を密閉容器に入れて３５℃の温度に保って加水分解と重合反応をさせ、その後３５時間かけて７５℃まで昇温し、完全にゲル化させた。その後容器を開放して１００℃で乾燥し、乾燥シリカゲルとしたのち粉砕して粒径１００〜２９２μｍの粉体とし、更にこれを水分含有量を約１０重量％となるまで乾燥した。
【００１３】
上記の乾燥シリカゲル粉末を酸素水素炎中に連続的に供給して加熱溶融し、外径が約１５０ｍｍ長さ約１００ｍｍの不透明な石英ガラス体Ａを得た。この石英ガラス体Ａ中に含まれる気泡は殆ど全てが独立気泡であり、径が５０〜２２０μｍの範囲で均一に分布しているものであった。
【００１４】
（第２実施例）
第１実施例と同様の操作により、水分含有量を約５重量％になるまで乾燥した乾燥シリカゲル粉末を調製した。そして、この乾燥シリカゲル粉末を用いて第１実施例と同様に酸素水素炎で加熱溶融し、外径が約１５０ｍｍ長さ約１００ｍｍの不透明な石英ガラス体Ｂを得た。この石英ガラス体Ｂ中に含まれる気泡は殆ど全てが独立気泡であり、径が３０〜１９０μｍの範囲で均一に分布しているものであった。
【００１５】
（第３実施例）
第１実施例と同様の操作により、水分含有量を約２０重量％になるまで乾燥した乾燥シリカゲル粉末を調製した。そして、この乾燥シリカゲル粉末を用いて第１実施例と同様に酸素水素炎で加熱溶融し、外径が約１５０ｍｍ長さ約１００ｍｍの不透明な石英ガラス体Ｃを得た。この石英ガラス体Ｃ中に含まれる気泡は殆ど全てが独立気泡であり、径が１００〜５００μｍの範囲で均一に分布しているものであった。
【００１６】
（第１比較例）
第１実施例と同様の操作により、水分含有量を約１重量％になるまで乾燥した乾燥シリカゲル粉末を調製した。そして、この乾燥シリカゲル粉末を用いて第１実施例と同様に酸素水素炎で加熱溶融し、外径が約１５０ｍｍ長さ約１００ｍｍの半透明な石英ガラス体Ｄを得た。
この石英ガラス体Ｄ中に含まれる気泡は殆ど全てが独立気泡であったが、径が５〜５５μｍの範囲で均一に分布しているものであった。
【００１７】
（第２比較例）
第２実施例と同様の操作により、水分含有量を約２５重量％になるまで乾燥した乾燥シリカゲル粉末を調製した。そして、この乾燥シリカゲル粉末を用いて第１実施例と同様に酸素水素炎で加熱溶融し、外径が約１５０ｍｍ長さ約１００ｍｍの半透明な石英ガラス体Ｅを得た。
この石英ガラス体Ｅ中に含まれる気泡は殆ど全てが独立気泡であったが、その気泡径は中心部ほど大きなり、均一な気泡径を有するものではなかった。また石英ガラス体の変形が著しく実用に適するものではなかった。
【００１８】
これらの実施例及び比較例で得られた多孔質石英ガラス体Ａ〜Ｅについて、原子吸光分析法によって不純物含有量を分析したところ、ナトリウム、カリウム、リチウム、銅、カルシウム、鉄、アルミニウム、及び硼素のいずれもが、０．１ｐｐｍ 以下であった。
また、ＪＩＳのＲ１６１１（ファインセラミックスのレーザーフラッシュ法による熱拡散率・比熱容量・熱伝導率試験方法）に記載された方法に準じて、これらの多孔質石英ガラス体Ａ〜Ｏの熱伝導率（Ｗ／ｍ・Ｋ）を測定した結果を、別途に観察・測定した気泡径分布と併せて、以下の表１に示す。なお、比較例２については、前記したように実用に適さないものであるため、熱伝導率の測定及び気泡径分布の測定は行わなかった。
【００１９】
【表１】
以上のことから明らかなように、本発明の多孔質石英ガラス体の製造方法によって製造される石英ガラス体は、断熱性に優れしかも被処理物に対する汚染を極めて少なくすることができるため、高純度石英ガラスの熱処理炉の内壁材に適している。
【００２１】
【発明の効果】
本発明の多孔質石英ガラス体の製造方法は、シリコンアルコキシドの加水分解により得た水分含有乾燥シリカゲル粉末を、酸素水素炎中で加熱溶融して独立気泡体を形成するようになしているため、極めて不純物の含有量が少なく、且つ実質的に独立気泡のみからなる多孔質石英ガラス体が、簡素な工程で効率よく製造できる。
そして本発明の多孔質石英ガラス体は、高純度であって雰囲気に露出している表面積が小さいから、熱処理用炉の内壁面などに断熱材等として使用すると、被処理物に対する汚染を極めて少なくすることができる効果がある。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a porous quartz glass body, and particularly to a method for industrially producing a porous quartz glass body suitable for use as a heat insulating material or the like in an apparatus for processing high-purity quartz in the semiconductor industry or the like. About.
[0002]
[Prior art]
Conventionally, as a heat insulating material of a heat treatment furnace, a material made of various materials such as an alumina-silica-based material and a zirconia-based material has been used. However, when such a heat insulating material is used in a high-purity quartz glass manufacturing apparatus for the semiconductor industry, particularly in a heat treatment furnace, metal impurities contained in the heat insulating material volatilize at a high temperature, and the surface of the quartz glass to be processed is heated. In some cases, which is one of the causes of quality deterioration.
And since the volatilization of metal impurities from such a heat insulating material gradually decreases as the high-temperature treatment is repeated, long-time high-temperature operation, It was necessary to carry out so-called "killing".
[0003]
On the other hand, since quartz glass has high heat resistance, it has been proposed to use it as a heat insulating material in a heat treatment furnace for high-purity quartz glass as described above.
In particular, opaque quartz glass is known as a heat insulating material for heat treatment furnaces for high-purity quartz glass, which has high heat insulation properties by containing minute bubbles inside and irregularly reflecting infrared rays to block the transmission of heat rays. Have been.
As a method of obtaining this opaque quartz glass, a method of adding a fine powder of silicon nitride to a siliceous raw material powder and melting the same (Japanese Patent Laid-Open No. 4-65328) or an opaque quartz glass having a bubble diameter distribution of 20 to 180 μm ( JP-A-5-254882), and further, an ammonia-treated powdery silica or a porous silica body containing an OH group is subjected to ammonia treatment in an ammonia atmosphere at a temperature in the range of 600 to 1300 ° C. A method for producing a silica foam which is melted and foamed at a temperature of 1400 to 1900 ° C. after being pressed in a mold having a predetermined shape (Japanese Patent Laid-Open No. 5-17180) is known.
[0004]
[Problems to be solved by the invention]
By the way, it is desired that the foaming agent for obtaining such porous quartz glass has a low content of metal impurities, but high purity silicon nitride is extremely expensive and is not economical.
In addition, if ammonia is used as a foaming agent, a special device for reacting ammonia with OH groups is required, and the problem of metal impurities contained in the foaming agent is reduced, but the process is complicated. It is necessary to strengthen measures to prevent the contamination of impurities due to this, and there is a problem that this is also not economical.
[0005]
The present invention has been made in order to solve the above-mentioned problems, and industrially manufactures a porous quartz glass body that can be used as a heat insulating material of a heat treatment apparatus for producing high-purity quartz glass. It is an object of the present invention to provide an improved manufacturing method.
[0006]
[Means for Solving the Problems]
The method for producing a porous quartz glass body according to the present invention made in order to solve the above-mentioned problem is characterized in that a water-containing dried silica gel powder obtained by hydrolysis of silicon alkoxide is heated and melted in an oxygen-hydrogen flame to form a closed cell. Is formed.
Here, it is preferable that the silicon alkoxide is at least one selected from tetramethoxysilane and tetraethoxysilane.
Further, it is desirable that the dried silica gel powder contains 5 to 20% by weight of water.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
In the method for producing a porous quartz glass body of the present invention, the silicon alkoxide used as a raw material may be an alkoxysilane or an alkoxysiloxane having various alkoxyl groups, such as tetraethoxysilane or tetramethoxysilane. And tetramethoxysilane are particularly preferably used.
Such silicon alkoxide is hydrolyzed by reacting with water in the presence of an acidic or basic catalyst and solidified via a silica sol, or solidified by a method such as heating in parallel with solification to form a wet gel. However, such undried silica gel contains a large amount of water, alcohol, and the like derived from raw materials.
[0008]
Water and alcohol in such undried silica gel are not completely eliminated even when the silica gel is dried, and the residual amount of alkoxyl groups and silanol groups may be reduced depending on the conditions of hydrolysis and gelation and drying conditions. Change.
Therefore, it is preferable that the dried silica gel used in the present invention is not sufficiently dehydrated by drying, and has a water content of 5 to 20% by weight. This is because when the water content is less than 5% by weight, the thermal conductivity of the quartz glass body is high and a sufficient heat insulating effect cannot be obtained, and when the water content exceeds 20% by weight. The reason for this is that the quartz glass body is significantly deformed, the bubble diameter becomes larger toward the center, and uniform bubbles cannot be obtained.
Dry silica gel containing such water, as water and other volatile components together act as a foaming agent to generate bubbles, depending on the diameter and number of bubbles contained in the target porous quartz glass body, It is desirable to select and use a dried silica gel having an appropriate water content.
[0009]
Further, a mixture of 50% by weight or more of the water-containing dry silica gel powder obtained by hydrolysis of silicon alkoxide and 50% by weight or less of the silica powder may be heated and melted in an oxygen-hydrogen flame to form closed cells.
The silica powder, which is a raw material that can be used in combination with the dried silica gel, is preferably a quartz raw material having a purity as high as possible, for example, a powder of silica produced by a sol-gel method, cristobalite, quartz, or the like. It is desirable to adjust the blending amount of the silica powder according to the moisture content of the dried silica gel so that the apparent density of the porous quartz glass body falls within a desired range.
[0010]
Such a powder of only dried silica gel or a mixture of dried silica gel and silica powder is supplied into an oxyhydrogen flame as a powder and rapidly heated and melted to be converted into closed cells.
In other words, silica gel particles start melting and desorb and decompose water and alcohol, etc., generate bubbles inside the particles and fuse with each other, and also fuse with the mixed silica powder, depositing and becoming independent. Bubbles grow sequentially, and a porous quartz glass body is obtained.
It is desirable that the dried silica gel powder contains less than 0.1 ppm of any of sodium, potassium, lithium, copper, calcium, iron, aluminum, and boron. This is a range that can be effectively used as a heat insulating material used in an apparatus for heat-treating high-purity quartz or a semiconductor wafer used in the semiconductor industry.
[0011]
【Example】
Hereinafter, the method for producing the porous quartz glass body of the present invention will be specifically described based on examples, but the present invention is not limited at all by the description of the examples.
[0012]
(First embodiment)
After mixing purified tetramethoxysilane and methanol at a molar ratio of 1: 3, pure water having a specific resistance of 13 × 10 6 Ω · cm was mixed with the purified water at a molar ratio of 1:10 to tetramethoxysilane. To obtain a uniform solution. The mixed solution was placed in a closed vessel and maintained at a temperature of 35 ° C. to cause hydrolysis and polymerization reaction. Thereafter, the temperature was raised to 75 ° C. over 35 hours to completely gel. Thereafter, the container was opened and dried at 100 ° C. to obtain dried silica gel, followed by pulverization to obtain a powder having a particle size of 100 to 292 μm, which was further dried until the water content became about 10% by weight.
[0013]
The dried silica gel powder was continuously supplied into an oxygen-hydrogen flame and heated and melted to obtain an opaque quartz glass body A having an outer diameter of about 150 mm and a length of about 100 mm. Almost all the bubbles contained in the quartz glass body A were closed cells, and were uniformly distributed in the diameter range of 50 to 220 μm.
[0014]
(Second embodiment)
By the same operation as in the first example, a dried silica gel powder was dried to a water content of about 5% by weight. Then, the dried silica gel powder was heated and melted in an oxygen-hydrogen flame in the same manner as in the first embodiment to obtain an opaque quartz glass body B having an outer diameter of about 150 mm and a length of about 100 mm. Almost all the bubbles contained in the quartz glass body B were closed cells, and were uniformly distributed in the diameter range of 30 to 190 μm.
[0015]
(Third embodiment)
By the same operation as in the first example, a dried silica gel powder dried to a water content of about 20% by weight was prepared. Then, the dried silica gel powder was heated and melted in an oxygen-hydrogen flame in the same manner as in the first embodiment to obtain an opaque quartz glass body C having an outer diameter of about 150 mm and a length of about 100 mm. Almost all the bubbles contained in the quartz glass body C were closed cells, and were uniformly distributed in the diameter range of 100 to 500 μm.
[0016]
(First comparative example)
By the same operation as in the first example, a dried silica gel powder dried to a water content of about 1% by weight was prepared. Then, this dried silica gel powder was heated and melted in an oxygen-hydrogen flame in the same manner as in the first embodiment, to obtain a translucent quartz glass body D having an outer diameter of about 150 mm and a length of about 100 mm.
Almost all the bubbles contained in the quartz glass body D were closed cells, but were uniformly distributed in the diameter range of 5 to 55 μm.
[0017]
(Second comparative example)
By the same operation as in the second example, a dried silica gel powder dried to a water content of about 25% by weight was prepared. Then, the dried silica gel powder was heated and melted in an oxygen-hydrogen flame in the same manner as in the first embodiment to obtain a translucent quartz glass body E having an outer diameter of about 150 mm and a length of about 100 mm.
Almost all of the bubbles contained in the quartz glass body E were closed cells, but the bubble diameter was as large as the central portion and did not have a uniform bubble diameter. In addition, the quartz glass body was significantly deformed and was not suitable for practical use.
[0018]
The porous quartz glass bodies A to E obtained in these Examples and Comparative Examples were analyzed for impurity content by atomic absorption spectrometry, and found to be sodium, potassium, lithium, copper, calcium, iron, aluminum, and boron. Were 0.1 ppm or less.
In addition, according to the method described in JIS R1611 (Test method for thermal diffusivity, specific heat capacity, and thermal conductivity of fine ceramics by laser flash method), the thermal conductivity of these porous quartz glass bodies A to O ( (W / m · K) are shown in Table 1 below together with the bubble diameter distribution separately observed and measured. In addition, about Comparative Example 2, since it was not suitable for practical use as mentioned above, the measurement of the thermal conductivity and the measurement of the bubble diameter distribution were not performed.
[0019]
[Table 1]
As is clear from the above, the quartz glass body produced by the method for producing a porous quartz glass body of the present invention has excellent heat insulating properties and can extremely reduce contamination to the object to be treated, so that it has high purity. Suitable for inner wall material of quartz glass heat treatment furnace.
[0021]
【The invention's effect】
The method for producing a porous quartz glass body of the present invention is such that the dried silica gel powder containing water obtained by hydrolysis of silicon alkoxide is heated and melted in an oxygen-hydrogen flame to form closed cells, A porous quartz glass body having an extremely small content of impurities and substantially consisting only of closed cells can be efficiently produced by simple steps.
Since the porous quartz glass body of the present invention is high-purity and has a small surface area exposed to the atmosphere, when it is used as a heat insulating material or the like on the inner wall surface of the furnace for heat treatment, contamination of the object to be treated is extremely small. There is an effect that can be done.
Claims (2)
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3542698A JP3594476B2 (en) | 1998-02-02 | 1998-02-02 | Method for producing porous quartz glass body |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3542698A JP3594476B2 (en) | 1998-02-02 | 1998-02-02 | Method for producing porous quartz glass body |
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| Publication Number | Publication Date |
|---|---|
| JPH11217224A JPH11217224A (en) | 1999-08-10 |
| JP3594476B2 true JP3594476B2 (en) | 2004-12-02 |
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