炭化ケイ素

外観

灰色粉末

性質

シリコンカーバイドは水に不溶です。液体にはならず、2,545°Cで昇華し、2,800°C以上で熱分解します。モース硬さは9.5であり、ダイヤモンドや炭化ホウ素に次いで硬いです。屈折率は2.65と大きいため、大きな結晶は鏡のように輝きます。

純粋なシリコンカーバイドは無色透明です。工業製品は緑色や黒色を呈し、製造の環境を清浄にすると色は薄くなります。シリコンカーバイドの着色は、アルミニウムや窒素のような元素が、結晶格子に入り込むためです。結晶の電気抵抗は薄い色ほど高くなり、発熱体の原料では緑色が用いられています。

シリコン原子は炭素原子よりも大きいです。そのためC＜SiC＜Siの順で原子間距離が広がり、熱伝導率は小さくなり、柔らかくなります。

定義

本品は、β型炭化ケイ素の微粉末である。

歴史

1891年にアメリカのエドワード・グッドリッチ・アチソン  (英: Edward Goodrich Acheson) が、コークスと粘土の混合物を炭素弧光灯で熱して製造しました。これをきっかけにカーボランダム社 (英: Carborundum Abrasives Co.) が設立され、工業的に製造されるようになったため、カーボランダム (英: Carborundum) と呼ばれる場合もあります。

1905年にアリゾナ州の隕石中で、フェルディナン・フレデリック・アンリ・モアッサン (英: Ferdinand Frédéric Henri Moissan) がシリコンカーバイドを発見しました。鉱物学上、モアッサン石 (英: Moissanite) とも呼ばれます。

解説

純粋なものは無色の結晶。通常は褐色ないし黒色。きわめて硬く（硬度９以上），酸に侵されず，高温でも他と反応しにくい。ケイ砂とコークスとを約2000℃で反応させてつくる。炭化ケイ素は，ダイヤモンドに次ぐ硬さと高融点をもち，薬品に侵されにくく，熱，電気はややよく伝える。これらの特性のため，砥石材料，研磨材，化学工業用ライナ (被覆材) ，耐熱ライナ，電気炉の抵抗発熱体などにつくられる。原料は粉状なので，砥石では熱硬化性樹脂などで成形し，高温用には焼結成形する。

用途

ガラス研磨剤、研磨布、砥石、耐火レンガ

用途

おもに研削材で、トイシ、研摩布、ラップにも用い、特殊耐火物、化学反応容器や抵抗体、非直線性抵抗体として避雷器などに用いられ、高温でも使用できる整流器やトランジスターとしての用途も研究されている。

構造

シリコンカーバイドのCとSiは、周期表上で同じ14族に属しています。共有結合性ですが、電気陰性度が異なるためイオン性も有します。したがって、安定に1対1の定比化合物として存在します。モル質量は40.097g/molで、密度は3.22g/cm³です。

一方の原子の周囲に他方の原子が四面体型に配置され、層構造の繰り返しパターンによって、200種類以上が存在します。基本的には、六方晶系のα型と立方晶系のβ型に分けられます。

電気炉で2,100°C以上にコークスとけい石を熱すると、α型のシリコンカーバイドの粉末を生成可能です。アルゴン気流中でカーボンブラックとケイ素を1,800°Cに加熱するとβ型が生じます。

化粧品の成分用途

着色剤

使用上の注意

アルゴン封入

説明

Silicon carbide is a hard covalently bonded material predominantly produced by the carbothermal reduction of silica. Silicon carbide is made by heating silica sand and petroleum coke packed around electrodes in an electric resistance furnace to above 2200°C. Depending on the exact reaction conditions the resulting silicon carbide is either a fine powder or a bonded mass that requires crushing and milling to produce a usable feedstock. This material is very resistant to abrasion and to corrosion with a molten slag. It also has excellent resistance to thermal spalling. However as it is a carbide, it will oxidise readily, silicon carbide has a fairly high conductivity.
Several hundred structures of silicon carbide (polytypes) have been identified which have different stacking arrangements for the silicon and carbon atoms. The simplest structure is a diamond structure which is designated /3-SiC. Other structures are either hexagonal or rhombic and are referred to as a-SiC.

化学的特性

Silicon carbide is a yellow to green to bluishblack, iridescent crystalline substance. Colorless when pure.

物理的性質

Green to bluish black, iridescent crystals. Soluble in fused alkali hydroxides. Abrasives best suited for grinding low-tensilestrength materials such as cast iron, brass, bronze, marble, concrete, stone and glass, optical structural, and wear-resistant components. Corroded by molten metals such as Na, Mg, Al, Zn, Fe, Sn, Rb, and Bi. Resistant to oxidation in air up to 1650°C. Maximum operating temperature of 2000°C in reducing or inert atmosphere.

物理的性質

Semiconductor (Eg=3.03 eV) soluble in fused alkali hydroxides

物理的性質

the properties of silicon carbide are that it is a refractory material (high melting point), it has excellent thermal conductivity and low thermal expansion, consequently it displays good thermal shock resistance. In addition, the high hardness, corrosion resistance and stiffness lead to a wide range of applications where wear and corrosion resistance are primary performance requirements. Silicon carbide possesses interesting electrical properties due to its semiconductor characteristics, the resistance of different compositions varying by as much as seven orders of magnitude.

特性

Silicon carbide is a premium-priced unit which is employed in lining work for its uniformity, abrasion resistance and dimensional stability. It is resistant to most organics, inorganic acids, alkalis and salts in a variety of concentrations except to hydrofluoric acid and acid fluorides. The permeable units have the lowest resistance.

使用

Silicon carbide is widely used as an abrasive in grinding and cutting glasses; in polishing glass and sharpening stones. It is used in the manufacture of porcelain, refractory brick, furnace linings, and emery paper. The compound also is used in semiconductor technology.

定義

Bluish-black, iridescent crystals. Insoluble in water and alcohol; soluble in fused alkalies and molten iron. Excellent thermal conductivity, electrically conductive, resists oxida- tion at high temperatures. Noncombustible, a nui- sance particulate.

調製方法

SiC was synthesized at the end of the 18th century with the name carborundum, and it was used as abrasive. In 1920 in Russia, O.V. Losev discovered two types of SiC from electro-luminescence and named them Type I and Type II. The electro-luminescence of Type I is greenish blue colored and that of Type II changes from orange to violet via yellow and green as the voltage increases from 6 to 28 V. The pure crystal is nominally obtained as 6H (a-II) SiC and the crystals with impurity are obtained as 15R and 4H. a-SiC (6H, 15R) is mainly synthesized using the sublimation method by heating the mixture of coke and silica sands at 2000℃ in the electrical furnace. SiC is segregated by cooling after melting Si in the carbon crucible.

調製方法

Silicon carbide, also known by the trade name Carborundum, has been manufactured and used as an abrasive material for more than a century. It combines desirable properties of hardness and thermal resistance. It is produced by heating high-grade silica sand with finely ground carbon at 2400°C in an electric furnace. In its powdered or granular form, it has been used as the abrasive material in “paper and wheels.” It is used as an abrasive in sandblasting and engraving. It has been incorporated into ceramics and glass and especially into refractory ceramic materials.

製造方法

Silicon carbide is prepared by fusing a mixture of silica (sand) and carbon (coke) with some salt and saw dust in an electric arc furnace at 3000°C.
SiO2(Sand)+3C(Coke)--(3000℃)--Sic+2CO
Salt and saw dust is added to infuse air into the product so that it can be broken into pieces easily. The product obtained is first washed with strong acid followed by strong base to remove basic and acidic impurities respectively. Finally, it is washed with water.

反応性

SiC is formed by the reaction with C at high temperature. It is not etched by acid other than the mixture of hydrofluoric acid and nitric acid. It reacts with caustic solution generating H2 to produce alkali silicate. Good alloys can be formed at the composition ratio of 0%–100% with Ge. (Refer to Ge.)

一般的な説明

Yellow to green to bluish-black, iridescent crystals. Sublimes with decomposition at 2700°C. Density 3.21 g cm-3. Insoluble in water. Soluble in molten alkalis (NaOH, KOH) and molten iron.

反応プロフィール

Silicon carbide is non-combustible. Generally unreactive. Soluble in molten alkalis (NaOH, KOH) and in molten iron.

危険性

Upper respiratory tract irritant. Probable carcinogen.

健康ハザード

Silicon carbide, in certain forms, may be a cause of pneumoconiosis in exposed workers. Silicon carbide has generally been considered to be an inert dust with little adverse effect on the lungs.

関連する反応

シリコンカーバイドは化学的に不活性です。水、酸、アルカリに溶けず、王水や熱濃硝酸とも反応せず、N₂、H₂、COなどとも反応しません。大気中で800°C以上で酸化しますが、表面にSiO₂が生じ、保護被膜として酸化を遅くします。Cl₂と800°C以上で反応し、CとSiCl₄が生成します。

使用用途

シリコンカーバイドの特徴として、高硬度、耐摩耗性、高熱伝導性、耐食性などが挙げられます。、シャフトなどの摺動部品だけでなく、分級機などの部品に加えて、高温試験機、金属溶融用のるつぼのような耐熱部品に利用可能です。

また、近年は電源の変換効率が従来の半導体より高いパワー半導体 (SiCパワー半導体) の材料として注目されています。SiCパワー半導体は、HEV (ハイブリッド車) にも使用されています。

工業用途

Silicon carbide is one of the very few totally man-made minerals used in refractory work. These are:
Oxide-bonded-(S102, A1201, Si02 or silicate glass), silicon oxynitride (Si2 ON2), silicon nitride (S13N4)
The first three of these four bonding systems result in a permeable product, and when failure occurs in such masonry systems due to chemical degradation, it is usually due to attack on the bond. Thus, permeable units (where the corrodent penetrates the mass) are far more rapidly damaged.
Self-bonded”—(silicon carbide to silicon carbide) impermeable ones, where the attack is limited to the surface.
The self-bonded product can be manufactured by either of two methods: reaction bonded or sintered. Both will produce an impermeable unit, and they have roughly comparable chemical resistances, but they do not have identical physical properties.

安全性プロファイル

Suspected carcinogen with experimental neoplastigenic data. A nuisance dust.

職業ばく露

A potential danger to those involved in the manufacture of silicon carbide abrasives, refractories, and semiconductors. Silicon carbide fibers are also produced in fibrous form as reinforcing fibers for composite materials.

不和合性

Dust may form explosive mixture with air. Sublimes with decomposition @ 2700C.

廃棄物の処理

Landfill

参考文献

1.https://en.wikipedia.org/wiki/Silicon_carbide#Uses
2.http://www.softschools.com/formulas/chemistry/silicon_carbide_uses_properties_structure_formula/282/
3.https://www.britannica.com/science/silicon-carbide
4.http://accuratus.com/silicar.html
5.https://www.intechopen.com/books/mostdownloaded/silicon-carbide-materials-processing-and-applications-in-electronic-devices
6.https://www.azom.com/article.aspx?ArticleID=3271
7.https://www.chemicalbook.com/productchemicalpropertiescb2431905.htm