كربيد السيليكون

كربيد السيليكون
Silicon carbide
تمييز
رقم CAS	[409-21-2]
PubChem	9863
رقم RTECS	VW0450000
الخصائص
الصيغة الجزيئية	SiC
كتلة مولية	40.0962 g/mol
المظهر	transparent to black powder depending on purity
الكثافة	3.21 g/cm3 (جميع polytypes)
نقطة الانصهار	2730°C (decomposes)
قابلية الذوبان في الماء	غير قابل للذوبان
قابلية الذوبان	غير قابل للذوبان في الحامض
حركية الإلكترون	~900 cm2/(V·s) (all polytypes)
معامل الانكسار (nD)	2.55 (تحت الحمراء؛ جميع الأنواع المتعددة)
المخاطر
تبويب الاتحاد الاوروپي (DSD)	not listed
(معيـَّن النار)
	ما لم يُذكر غير ذلك، البيانات المعطاة للمواد في حالاتهم العيارية (عند 25 °س [77 °ف]، 100 kPa).
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	مراجع الجدول

كربيد السيليكون Silicon carbide (نطقب:SiliconC)، ويعهد أيضاً بإسم كربورندم carborundum، هومركب من السيليكون والكربون صيغته الكيميائية SiC. ويتواجد في الطبيعة في صيغة المعدن شديد الندرة مويسانيت moissanite. مسحوق كربيد السيليكون يـُنتـَج منذ 1893 للاستخدام كصنفرة. ويمكن لحبيبات كربيد السيليكون حتى ترتبط معاً بالتحميص ليشكلوا أنواع من السيراميك شديدة الصلابة تـُستخدم على نطاق واسع في تطبيقات تتطلب تحمل عالي، مثل مكابح السيارات والألواح السيراميكية في السترات الواقية من الرصاص. التطبيقات الإلكترونية لكربيد السيليكون مثل المصباح الثنائي الباعث للضوء والكواشف في أجهزة الراديوالمبكرة ظهرت حوالي 1907، والآن فإن كربيد السيليكون يـُستخدم على نطاق واسع في إلكترونيات أشباه الموصلات الحرارة العالية. البلورات المفردة الكبيرة من كربيد السيليكون يمكن الحصول عليهم بطريقة لـِلي؛ ويمكن بترهم إلى جواهر تـُعهد بإسم "مويسانيت إصطناعي". ويمكن انتاج كربيد سيليكون بمساحة سطحية عالية من SiO₂ المتواجد في مواد الأفران.

الاكتشاف والانتاج المبكر

إعادة انتاج تجارب هـ.ج. راوندز على المصباح الثنائي الباعث للضوء.

Early, non-systematic and often non-recognized syntheses of silicon carbide had been reported by Despretz (1849), Marsden (1880) and Colson (1882).

التواجد الطبيعي

Moissanite single crystal (~1 mm in size)

الانتاج

Synthetic SiC crystals ~3 mm in diameter

البنية والخصائص

Structure of major SiC polytypes.
(β)3C-SiC
4H-SiC
(α)6H-SiC

خصائص الأنواع المتعددة الرئيسية من كربيد السيليكون
Polytype	3C (β)	4H	6H (α)
البنية البلورية	Zinc blende (cubic)	مسدسة	مسدسة
Space group	T²_d-F43m	C⁴_6v-P6₃mc	C⁴_6v-P6₃mc
رمز پيرسون	cF8	hP8	hP12
ثوابت العقد (Å)	4.3596	3.0730; 10.053	3.0730; 15.11
الكثافة (g/cm³)	3.21	3.21	3.21
Bandgap (eV)	2.36	3.23	3.05
Bulk modulus (GPa)	250	220	220
الموصلية الحرارية (W/(cm·K))	3.6	3.7	4.9

كربيد السيليكون النقي عديم اللون. اللون البني إلى الأسود للمنتج الصناعي سببه شوائب الحديد. البريق المشابة لقوس قزح للبلورات تسببه طبقة التخميل من ثاني أكسيد السيليكون التي تتكون على السطح.

الاستخدامات

معدات الصنفرة والبتر

Cutting disks made of SiC

In the arts, silicon carbide is a popular abrasive in modern lapidary due to the durability and low cost of the material. In manufacturing, it is used for its hardness in abrasive machining processes such as grinding, honing, water-jet cutting and sandblasting. Particles of silicon carbide are laminated to paper to create sandpapers and the grip tape on skateboards.

In 1982 an exceptionally strong composite of aluminium oxide and silicon carbide whiskers was discovered. Development of this laboratory-produced composite to a commercial product took only three years. In 1985, the first commercial cutting tools made from this alumina and silicon carbide whisker-reinforced composite were introduced by the Advanced Composite Materials Corporation (ACMC) and Greenleaf Corporation.

مادة هيكلية

Silicon carbide is used for inner plates of ballistic vests

In the 1980s and 1990s, silicon carbide was studied in several research programs for high-temperature gas turbines in the الولايات المتحدة, Japan, and Europe. The components were intended to replace nickel superalloy turbine blades or nozzle vanes. However, none of these projects resulted in a production quantity, mainly because of its low impact resistance and its low fracture toughness.

Like other hard ceramics (namely alumina and boron carbide), silicon carbide is used in composite armor (e.g., Chobham armor), and in ceramic plates in bulletproof vests. Dragon Skin, which is produced by Pinnacle Armor, uses disks of silicon carbide.

بتر غيار السيارات

The Porsche Carrera GT's carbon-ceramic (silicon carbide) disc brake

Silicon-infiltrated carbon-carbon composite is used for high performance "ceramic" brake discs as it is able to withstand extreme temperatures. The silicon reacts with the graphite in the carbon-carbon composite to become carbon fiber reinforced silicon carbide (C/SiC). These discs are used on some road going sports cars, including the Porsche Carrera GT, the Bugatti Veyron, Bentleys, Ferraris, Lamborghinis, and some specific high performance Audis. Silicon carbide is also used in a sintered form for diesel particulate filters.

الأنظمة الكهربائية

الموصلية الكهربائية

كربيد السيليكون هوأشباه الموصلات، والتي يمكن إعتبارها من أنواع مركبات النيتروجين أوالفسفور ومن أنواع الألومنيوم ، والبورون ، الغاليوم أوالبريليوم Metallic conductivity has been achieved by heavy doping with boron, aluminium or nitrogen. Superconductivity has been detected in 3C-SiC:Al, 3C-SiC:B and 6H-SiC:B at the same temperature of 1.5 K. or aluminum. A crucial difference is however observed for the magnetic field behavior between aluminum and boron doping: SiC:Al is type-II, same as Si:B. On the contrary, SiC:B is type-I. In attempt to explain this difference, it was noted that Si sites are more important than carbon sites for superconductivity in SiC. Whereas boron substitutes carbon in SiC, Al substitutes Si sites. Therefore, Al and B "see" different environment that might explain different properties of SiC:Al and SiC:B.

عناصر الدوائر الكهربائية

Silicon carbide is used for ultrafast, high-voltage Schottky diodes, MOSFETs and high temperature thyristors for high-power switching. Currently, problems with the interface of SiC with silicon dioxide has hampered the development of SiC based power MOSFETs and insulated-gate bipolar transistors. Another problem is that SiC itself breaks down at high electric fields due to the formation of extended stacking faults, but this problem may have been resolved relatively recently.

الفلك

The low thermal expansion coefficient, high hardness, rigidity and thermal conductivity make silicon carbide a desirable mirror material for astronomical telescopes. The growth technology (chemical vapor deposition) has been scaled up to produce disks of polycrystalline sililcon carbide up to 3.5 m in diameter, and several telescopes are already equipped with SiC optics.

فهم اشتعال الفتائل الرفيعة

Image of the test flame and glowing SiC fibers. The flame is aboutسبعة cm tall.

Silicon carbide fibers are used to measure gas temperatures in an optical technique called thin filament pyrometry. It involves the placement of a thin filament in a hot gas stream. Radiative emissions from the filament can be correlated with filament temperature. Filaments are SiC fibers with a diameter of 15 micrometers, that isخمسة times thinner than human hair. Because the fibers are so thin, they do little to disturb the flame and their temperature remains close to that of the local gas. Temperatures of about 800 - 2500 K can be measured.

عناصر التسخين

References to silicon carbide heating elements exist from the early 20th century when they were produced by Acheson's Carborundum Co. in the U.S. and EKL in Berlin. Silicon carbide offered increased operating temperatures compared with metallic heaters, although the operating temperature was limited initially by the water-cooled terminals, which brought the electric current to the silicon carbide hot zone. The terminals were not attached to the hot zone, but were held in place by weights, or springs. Operating temperature and efficiency was later increased by the use of separate low resistance silicon carbide "cold ends", usually of a larger diameter than the hot zone, but still held in place only by mechanical pressure. The development of reaction-bonding techniques led to the introduction of jointed elements. Initially, these featured larger diameter cold ends, but by the 1940s, equal diameter elements were being produced. From the 1960s onwards, one-piece elements were produced, with cold ends created by filling the pore volume with a silicon alloy. Another one-piece technique is to cut a spiral slot in a homogeneous tube where the hot section is desired. Further developments have included the production of multi-leg elements, where two or more legs are joined to a common bridge, and the production of high density, reaction-bonded elements, which provide additional resistance to oxidation and chemical attack. Silicon carbide elements are used today in the melting of non-ferrous metals and glasses, heat treatment of metals, float glass production, production of ceramics and electronics components, etc.

عناصر الوقود النووي

Silicon carbide is often used as a layer of the tristructural-isotropic coating for the nuclear fuel elements of high temperature gas cooled reactors or very high temperature reactors such as the Pebble Bed Reactor. Silicon carbide provides the mechanical stability to the fuel and is the main diffusion barrier to the release of fission products.

المصوغات

Gem-cut synthetic silicon carbide

As a gemstone used in jewelry, silicon carbide is called "synthetic moissanite" or just "moissanite" after the mineral name. Moissanite is similar to diamond in several important respects: it is transparent and hard (9-9.5) on the Mohs scale (compared toعشرة for diamond), with a refractive index between 2.65 and 2.69 (compared to 2.42 for diamond). Moissanite is somewhat harder than common cubic zirconia. Unlike diamond, moissanite can be strongly birefringent. This quality is desirable in some optical applications, but not in gemstones. For this reason, moissanite jewels are cut along the optic axis of the crystal to minimize birefringent effects. It is lighter (density 3.21 g/cm³ vs. 3.53 g/cm³), and much more resistant to heat than diamond. This results in a stone of higher luster, sharper facets and good resilience. Loose moissanite stones may be placed directly into wax ring moulds for lost-wax casting; unlike diamond, which burns at 800 °C, moissanite remains undamaged by temperatures up to 1800 °C (cf. the 1064 °C melting point of pure gold). Moissanite has become popular as a diamond substitute, and may be misidentified as diamond, since its thermal conductivity is much closer to that of diamond than any other diamond substitutes. Many thermal diamond testing devices are fooled by moissanite, but the gem can be distinguished from diamond by its birefringence and a very slight green or yellow fluorescence under ultraviolet light. Some moissanite stones also have curved string-like inclusions, which diamond will never have.

انتاج الصلب

Piece of silicon carbide used in steel making

Silicon carbide dissolved in a basic oxygen furnace used for making steel acts as a fuel and provides energy which increases the scrap to hot metal ratio. It can also be used to raise tap temperatures and adjust the carbon content. Use of silicon carbide costs less than of ferrosilicon and carbon combination, produces cleaner steel due to low level of trace elements, it has a low gas content and it does not lower the temperature of steel.

دعم المحفزات

The natural resistance to oxidation exhibited by silicon carbide, as well as the discovery of new ways to synthesize the cubic β-SiC form, with its larger surface area, has led to significant interest in its use as a heterogeneous catalyst support. This form has already been employed as a catalyst support for the oxidation of hydrocarbons, such as n-butane, to maleic anhydride.

الطبع بالكربورندم

Silicon carbide is used in carborundum printmaking - a collagraph printmaking technique. Carborundum grit is applied in a paste to the surface of an aluminium plate. When the paste is dry, ink is applied and trapped in its granular surface, then wiped from the bare areas of the plate. The ink plate is then printed onto paper in a rolling-bed press used for intaglio printmaking. The result is a print of painted marks embossed into the paper.

انتاجه في العالم العربي

شراكة سعودية أمريكية يابانية

أعربت فيتسعة مارس 2009 جميع من شركة أحمد حمد القصيبي وإخوانه السعودية، وشركة واشنطن ميلز الأمريكية وشركة سوميتوموللمواد الصناعية اليابانية، عن توقيع مذكرة تفاهم لإنشاء مشروع مشهجر لتصنيع مادة كربيد السيليكون في المملكة العربية السعودية، بتكلفة أولية تصل إلى 250 مليون ريال سعودي. وسيتم إنشاء المصنع في مدينة الجبيل الصناعية في المملكة العربية السعودية، وفقاً للدراسة الأولية للمشروع المتسقط استكماله في مطلع 2011، بطاقة إنتاجية أولية تصل إلى 24,000 طن من مادة كربيد السيليكون فائقة الجودة سنوياً. وبهذه المناسبة صرح السيد سعود عبد العزيز القصيبي، العضوالمنتدب لشركة أحمد حمد القصيبي وإخوانه: "إن توقيع هذه المذكرة يعتبر إضافة قيّمة للاقتصاد والتنويع الصناعي السعودي، إذ حتى المشروع سيعزز من فرص نشوء صناعات جديدة ويساهم في تعزيز الصادرات، بالإضافة إلى توفيرعدد كبير من فرص العمل الجديدة للشباب السعودي". وأضاف القصيبي قائلا:" شركاؤنا في مصنع كربيد السيليكون هم من رواد هذه الصناعةالمتميزين على المستوى العالمي، الأمر الذي سيؤدي إلى تبادل نافع للخبرات بين جميع الشركاء القائمين على المشروع لتطوير هذه الصناعة داخل المملكة".

الهامش

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