溶融シリカ 化学特性,用途語,生産方法
定義
本品は、次の化学式で表される無機酸化物である。
解説
石英ガラス，シリカガラス(silica glass)，溶融シリカ(fused silica)ともいう．シリカSiO2だけを成分とするガラス．石英，水晶，けい石あるいはけい砂を溶融した後，冷却して加工する．ケイ素のアルコキシドの加水分解によって得られるゲルを融点以下の温度で焼成する方法もある．220 nm までの紫外線を通し，熱衝撃に強く，化学的耐久性もすぐれている．密度2.20 g cm－3．軟化点1650 ℃．製品として不透明なものは無数の微泡を含み，性能はやや劣る．光ファイバー用の原料となる高純度な石英ガラスの製造は，石英を原料とせず，SiCl4の気相分解物を用いる方法で行われる．
用途
半導体封止剤用フィラー、樹脂充填剤、医薬部外品添加物(薬用石けん、化粧品等)、シリカビーズ用 (NITE総合検索 (2015))
化粧品の成分用途
不透明化剤、非活性剤系分散剤、抗ケーキング剤、吸着剤、研磨.スクラブ剤、増量剤
化学的特性
Made up of spherical submicroscopic particles under
0.1 micron in size.
天然物の起源
This material is known largely as a synthetic material, but there are instances of the material occurring in nature. Vitreous tubes called fulgurites are produced when lightning fuses quartz sand. Large deposits of fulgurite exist in the Libyan desert. Vitreous silica can also be produced by meteor impact. The impact leads to rapid adiabatic heating of the quartz above its melting point. The quartz forms a glass on cooling. Examples of this type of vitreous silica have been found near Canyon Diablo, Arizona, and in meteorite craters in Australia and Arabia.
使用
Concrete, grouts, mortars, elastomers, refrac-
tory and coating applications.
調製方法
Modern manufacturing processes of vitreous typically involve the fusion or viscous sintering of silica particles; the particles can be derived from sand crystals or are produced through a chemical process, e.g., flame hydrolysis or sol–gel. In one practice of the flame hydrolysis process, the powder is produced and fused into glass a single step, without the isolation of a porous body. Dopant and additive profiles are concentration are then controlled by the deposition conditions. When a process involving a discrete porous silica body as an intermediate is used, subsequent processing steps can be used to control dopant levels and in particular, the hydroxyl level of the final glass. The choice of fabrication method is often dictated by the end-use specifications. Flame hydrolysis or similar chemical techniques that allow for the production of very high purity glass are the methods of choice for optical applications but may be economically wasteful for less demanding applications.
Translucent Vitreous Silica. Translucent vitreous silica is produced by fusion of high purity quartz sand crystals. Sand is packed around a graphite rod through which a current is passed. The resistance heating produces a plastic mass that can be blown into molds, drawn into tubing, or shaped by rolling or pressing. Separation from the graphite rod is facilitated by gaseous products formed by interfacial reaction. Because the outside is sandy, the product is known as sand-surface ware. A matte finish is obtained by mechanical buffing. A glazed surface is produced by fusing the outside surface with an electric carbon arc or flame.
Transparent Vitreous Silica. Clear, transparent, bubble-free vitreous silica may be obtained by melting natural quartz minerals by flame or plasma vapor deposition (synthetic fused silicas), and by sol–gel processing.
用途
珪砂(けいさ)または水晶から電気溶融でつくる。前者は微細な気泡のため不透明だが、後者は透明で品質も高い。光通信や半導体プロセスなどに使う超高純度のものは四塩化ケイ素（液体）、モノシラン（気体）などから気相合成でつくられ、光吸収損失の原因となる遷移元素などの不純物含有率が最低10億分の1以下のものまである。光通信用ファイバーは気相合成法の一種の化学蒸着によってつくられる。
一般的な説明
Silicon dioxide is one of the important constituents of sedimentary rock bauxite, basalt fibers and ceramic fibers. It is added to cement for improving the hydraulic properties of cement.
危険性
Questionable carcinogen.
安全性プロファイル
An inhalation hazard. Questionable carcinogen with experimental tumorigenic data. Poison by intraperitoneal, intravenous, and intratracheal routes. See also other shca entries.
職業ばく露
Amorphous fumed silica is used as a mineral, natural or synthetic fiber. A potential danger to those involved in the production and handling of fumed silica for paint pigments or catalysts. Diatomaceous earth is used in clarifying liquids, in manufacture of fire brick and heat insulators; used as a filtering agent; as a filler in construction materials; pesticides, paints, and varnishes. A potential danger to those involved in mining of diatomaceous earth or fabrication of products there from.
純化方法
Purification of silica for high technology applications uses isopiestic vapour distillation from concentrated volatile acids and is absorbed in high purity water. The impurities remain behind. Preliminary cleaning to remove surface contaminants uses dip etching in HF or a mixture of HCl, H2O2 and deionised water [Phelan & Powell Analyst 109 1299 1984].
不和合性
Silica, amorphous is a noncombustible solid. Generally unreactive chemically. Incompatible with fluorine, oxygen difluoride, chlorine trifluoride. Soluble in molten alkalis and reacts with most metallic oxides at high temperature.
廃棄物の処理
Sanitary landfill.
溶融シリカ 上流と下流の製品情報
原材料
準備製品