Silicon Carbide

Zhen An: Leading Silicon Carbide Manufacture in China

ZhenAn International Co., Limited. is located in Anyang City, China, and has more than 30 years of experience and technology accumulation in the metallurgical industry.

Currently, Zhenan operates fully automatic and intelligent production lines for metallurgical and metal materials, with a stable annual output and sales volume of 150,000 metric tons.

Our factory covers an area of approximately 30,000 square meters, supporting stable and large-scale production.

Quality Assurance
Our quality inspectors strictly control the quality of each link to ensure that each batch of products meets international standards.

Good Service
Zhenan has an excellent and professional team dedicated to providing you with high-quality metallurgical product materials and services.

Customization
According to customer requirements, we also provide customized metallurgical material products with special specifications, shapes and materials.

Fast Delivery
With huge production capacity, we ensure in time delivery and transport to the destination in the first time.

Wide Range Of Applications
ZhenAn metallurgical materials products are widely used in casting, steelmaking, electricity, non-ferrous metals, petrochemicals, glass, building materials and other fields, and are exported to more than 80 countries and regions in the world.

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Introduction of Silicon Carbide

Silicon carbide, also known as SiC, is a semiconductor base material that consists of pure silicon and pure carbon. You can dope SiC with nitrogen or phosphorus to form an n-type semiconductor or dope it with beryllium, boron, aluminum, or gallium to form a p-type semiconductor. While many varieties and purities of silicon carbide exist, semiconductor-grade quality silicon carbide has only surfaced for utilization in the last few decades.

Properties of Silicon Carbide

Robust Crystal Structure
Silicon carbide is composed of light elements, silicon (Si) and carbon (C). Its basic building block is a crystal of four carbon atoms forming a tetrahedron, covalently bonded to a single silicon atom at the centre. SiC also exhibits polymorphism as it exists in different phases and crystalline structures

High Hardness
Silicon carbide has a Mohs hardness rating of 9, making it the hardest available material next to boron carbide (9.5) and diamond (10). It is this apparent property that makes SiC an excellent material choice for mechanical seals, bearings, and cutting tools.

High-temperature Resistance
Silicon carbide’s resistance to high temperature and thermal shock is the property that allows SiC to be used in the manufacturing of fire bricks and other refractory materials. The decomposition of silicon carbide starts at 2000°C

Conductivity
If SiC is purified, its behaviour manifests that of an electrical insulator. However, by governing impurities, silicon carbides can exhibit the electrical properties of a semiconductor. For example, introducing varying amounts of aluminium by doping will yield a p-type semiconductor. Typically, an industrial-grade SiC has a purity of about 98 to 99.5%. Common impurities are aluminium, iron, oxygen, and free carbon

Chemical Stability
Silicon carbide is a stable and chemically inert substance with high corrosion resistance even when exposed or boiled in acids (hydrochloric, sulphuric, or hydrofluoric acid) or bases (concentrated sodium hydroxides). It is found to react in chlorine, but only at a temperature of 900°C and above. Silicon carbide will start an oxidation reaction in the air when the temperature is at approximately 850°C to form SiO2

The Advantages of Silicon Carbide

Higher Temperature Capability: SiC can operate at much higher temperatures than silicon, often up to 400 degrees C and potentially up to 800 degrees C, allowing for more efficient electronic devices that can handle extreme conditions without significant performance degradation. This impressive capability is due to the high thermal conductivity of SiC and the low intrinsic concentration of charge carriers. High thermal conductivity means that a SiC transistor can use a much smaller heatsink than an equivalent silicon chip or can use a comparable heat sink and tolerate much more heat. Low concentration of charge carriers at room temperature means that SiC can tolerate greater electrical load before thermally liberated electrons add to the intrinsic charge carriers, flooding the transistor, and locking it in the “on” position (conducting state).

Higher Breakdown Voltage: SiC has a breakdown voltage roughly eight times greater than that of silicon (~300 kV/cm versus 2400 kV/cm), meaning that it can withstand higher voltages before experiencing unpredictable conduction behavior and potentially catastrophic failure.

Smaller Form Factor: This advantage follows from the higher breakdown voltage and thermal conductivity of SiC relative to silicon. If a silicon and a silicon carbide transistor were each designed to withstand up to the same breakdown voltage, the traditional silicon transistor would need to be much larger than the SiC transistor. The smaller SiC transistor could have as little as 0.25-0.5% as much “on” resistance as the larger silicon transistor. This property enables the design of more efficient and compact power electronic systems with lower power losses.

Higher Switching Frequencies: The smaller form factor of SiC transistors and consequent higher switching frequency enables the design of lighter weight and less expensive inductors and capacitors for use in a power converter like those used to charge EV batteries.

How Is Silicon Carbide Made?

The simplest silicon carbide manufacturing method involves melting silica sand and carbon, such as coal, at high temperatures―up to 2500 degrees Celsius. Darker, more common versions of silicon carbide often include iron and carbon impurities, but pure SiC crystals are colorless and form when silicon carbide sublimes at 2700 degrees Celsius. Once heated, these crystals deposit onto graphite at a cooler temperature in a process known as the Lely method.

Lely method

During this process, a granite crucible heats to a very high temperature, usually by way of induction, to sublimate silicon carbide powder. A graphite rod with lower temperature suspends in the gaseous mixture, which inherently allows the pure silicon carbide to deposit and form crystals.

Chemical vapor deposition

Alternatively, manufacturers grow cubic SiC using chemical vapor deposition, which is commonly used in carbon-based synthesis processes and used in the semiconductor industry. In this method, a specialized chemical blend of gases enters a vacuum environment and combines before depositing onto a substrate.
Both methods of silicon carbide wafer production require vast amounts of energy, equipment, and knowledge to be successful.

What Are the Uses of Silicon Carbide?

Silicon Carbide Used in Military Bulletproof Armor
Silicon carbide is used to manufacture bulletproof armor. The property of this compound that makes it to be applied for such a purpose is its hardness. Bullets and other harmful objects will have to contend with the hard ceramic blocks that silicon carbide forms. Bullets can't penetrate the ceramic blocks.

Silicon Carbide Used in Semiconductors
Silicon carbide becomes a semiconductor when dopants are added to it. Dopants like boron and aluminum added to silicon carbide make it become a p-type semiconductor. On the other hand, dopants such as nitrogen and phosphorus added to silicon carbide make it become an n-type semiconductor.

Silicon Carbide Used in Abrasives
Silicon carbide is commonly used as an abrasive because of how hard it is. It is used in the manufacture of grinding wheels, cutting tools, and sandpaper. Silicon carbide abrasives are usually cheaper than other abrasives of similar quality. The abrasives are used to grind materials such as steel, aluminum, cast iron, and rubber.

Silicon Carbide Used in Electric Vehicles
Silicon carbide is a better choice over silicon for powering electric vehicles. Electric vehicles powered by silicon carbide are highly efficient and cost-effective.

Silicon Carbide Used in Jewelry
Structurally similar to diamond, yet more lustrous, cheaper, more durable, and lighter than diamond, silicon carbide is a well-deserved alternative to diamond in the jewelry industry.

Silicon Carbide Used in Fuel
In addition to its other uses, silicon carbide is used as fuel. It is used as a fuel in steel manufacture and produces purer steel than most other fuels. It is also a cheaper and more environmentally-friendly fuel.

Silicon Carbide Used in LEDs
The first set of light-emitting diodes (LEDs) to be produced made use of silicon carbide technology. It was used to manufacture blue, red, and yellow LEDs. LEDs are used in televisions, display boards, and computers.

Certifications

Common Problems of Silicon Carbide

Q: Which are the applications of SiC in electronic devices?

A: Silicon carbide is a semiconductor that is perfectly suited to power applications, thanks above all to its ability to withstand high voltages, up to ten times higher than those usable with silicon. Semiconductors based on silicon carbide offer higher thermal conductivity, higher electron mobility, and lower power losses. SiC diodes and transistors can also operate at higher frequencies and temperatures without compromising reliability. The main applications of SiC devices, such as Schottky diodes and FET/MOSFET transistors, include converters, inverters, power supplies, battery chargers and motor control systems.

Q: Why SiC overcomes Si in power applications?

A: Despite being the most widely used semiconductor in electronics, silicon is beginning to show some limitations, especially in high-power applications. A relevant factor in these applications is the bandgap, or energy gap, offered by the semiconductor. When the bandgap is high, the electronics it uses can be smaller, run faster, and more reliably. It can also operate at higher temperatures, voltages, and frequencies than other semiconductors. While silicon has a bandgap of around 1.12eV, silicon carbide has a nearly three times greater value of around 3.26eV.

Q: Which impurities are used to dope silicon carbide material?

A: In its pure form, silicon carbide behaves like an electrical insulator. With the controlled addition of impurities or dopants, SiC can behave like a semiconductor. A P-type semiconductor can be obtained by doping it with aluminum, boron, or gallium, while impurities of nitrogen and phosphorus give rise to a N-type semiconductor. Silicon carbide has the ability to conduct electricity under some conditions but not in others, based on factors such as the voltage or intensity of infrared radiation, visible light, and ultraviolet rays. Unlike other materials, silicon carbide is capable of controlling the P-type and N-type regions required for device fabrication over wide ranges. For these reasons, SiC is a material suitable for power devices and able to overcome the limitations offered by silicon.

Q: How can SiC semiconductors achieve better thermal management than silicon?

A: Another important parameter is the thermal conductivity, which is an index of how the semiconductor is able to dissipate the heat it generates. If a semiconductor is not able to dissipate heat effectively, a limitation is introduced on the maximum operating voltage and temperature that the device can withstand. This is another area where silicon carbide outperforms silicon: the thermal conductivity of silicon carbide is 1490 W/m-K, compared to the 150 W/m-K offered by silicon.

Q: What are the raw materials for silicon carbide?

A: The main raw materials are SiO2 and C which are made to react at a high temperature. Saw dust and salt (sometimes) are also added, so that saw dust burns and provides pores, facilitating the escape of evolved gases (at high temperature). Firing is done for about 40 hours and after cooling, the side walls are removed.

Q: How do you get silicon carbide?

A: Typically, Silicon Carbide is produced using the Acheson process which involves heating silica sand and carbon to high temperatures in an Acheson graphite resistance furnace. It can be formed as a fine powder or a bonded mass that must be crushed and milled before it can be used as a powder feedstock.

Q: Is silicon carbide hard to produce?

A: The simplest process to manufacture silicon carbide is to combine silica sand and carbon in an Acheson graphite electric resistance furnace at a high temperature, between 1,600 °C (2,910 °F) and 2,500 °C (4,530 °F).

Q: What are the key uses of silicon carbide?

A: Silicon carbide is a very popular abrasive in modern lapidary owing to its durability and the relatively low cost of the material. It is, therefore, crucial to the art industry. In the manufacturing industry, this compound is used for its hardness in several abrasive machining processes such as honing, grinding, water-jet cutting, and sandblasting.

Q: Is silicon carbide soluble in water?

A: Silicon carbide is insoluble in water. However, it is soluble in molten alkalis (such as NaOH and KOH) and also molten iron. Silicon carbide can be considered as an organosilicon compound.

Q: Can silicon carbide conduct electricity?

A: Yes, but under certain conditions.
Silicon carbide, in its pure form, behaves as an electrical insulator. However, with the controlled addition of impurities or doping agents, and because SiC has the necessary resistivity, it can express semi-conduction properties; in other words, as a semiconductor, it neither allows a free-flowing current nor completely repels it.

Q: Where do we get silicon carbide from?

A: Silicon carbide (SiC) or carborundum is a synthetic abrasive manufactured through the fusion of high-grade silica sand and finely ground carbon (petroleum coke) in an electric furnace at high temperature (1600–2500°C).

Q: Is silicon carbide stronger than diamond?

A: Silicon carbide is hard with a Mohs hardness of 9.5, which is second only to the world's hardest diamond. In addition, silicon carbide has excellent thermal conductivity. It is a kind of semiconductor and can resist oxidation at high temperature.

Q: What does silicon carbide react with?

A: The SiC powder can be mixed with carbon and/or silicon powder, formed into shapes, and then reacted at high temperature to form self-bonded (Si+C forms SiC to bond grains), nitride bonded (silicon reacted with N2 to form Si3N4), or silicon bonded (siliconized SiC) silicon carbide.

Q: What are the different types of SiC crystals?

A: The crystal structures of SiC are cubic, hexagonal, and rhombohedral. The notation system used for SiC indicates the number of layers in the atomic stacking sequence and a letter representing the crystal structure of the polytype (C for cubic, H for hexagonal, and R for rhombohedral).

Q: What is the difference between alpha and beta silicon carbide?

A: What distinguishes the two forms of silicon carbide is the microcrystalline structure. Whereas beta silicon carbide has a cubic microcrystalline structure, alpha crystalline carbide has a spherical microcrystalline structure.

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