Silicon Carbide (SiC) ideal material for Armor, military systems and telescopes for space situational awareness

Rajesh Uppal June 5, 2020 Geopolitics, Material Comments Off on Silicon Carbide (SiC) ideal material for Armor, military systems and telescopes for space situational awareness 1,704 Views

Silicon carbide, also known as carborundum, is a unique compound of carbon and silicon and is one of the hardest available materials. Characteristics such as relatively low thermal expansion, high force-to-weight radius, high thermal conductivity, hardness, resistance to abrasion and corrosion, and most importantly, the maintenance of elastic resistance at temperatures up to 1650 ° C, have led to a wide range of uses.

Silicon carbide has been the most widely used material for the use of structural ceramics. SiC is the ideal material for high-defense body armor, chosen for its excellent protection performance, advanced properties, and good adaptability to any threat level encountered.

SiC can be doped with nitrogen or phosphorus to form an n-type semiconductor and doping it with beryllium, boron, aluminum, or gallium to form a p-type semiconductor. SiC is Wide-bandgap power semiconductor which withstands high voltages, works even at high temperatures, is chemically robust and is able to work at high switching frequencies, which enables even better energy efficiency.

SiC’s material characteristics make it highly advantageous for high power applications where high current, high temperatures, and high thermal conductivity are required. SiC has demonstrated greater than twice the power density of Si power devices and at greater efficiency, researchers point out. These properties make them prime candidates for next-generation high-power switching devices for military and commercial, applications.

The ability of SiC-based systems to operate in harsh environments or at high temperatures (up to 600 ºC) also opens the door for new systems impacting applications such as space exploration vehicles and landers, nuclear power reactors, and petroleum and geological exploration instrumentation. Ultimately, any system that would see improvement from highdensity or high-efficiency power electronics would benefit from SiC.

Silicon carbide properties

It is a simple compound with the carbon atom attached to silicon through a triple bond, leaving both atoms with a positive and negative charge. However, the bonding between them has a predominantly covalent character, rather than ionic. Solid silicon carbide exists in many different crystalline forms, with the hexagonal crystal structure being the most commonly found one.

SiC is a ceramic material with an outstanding hardness, only surpassed by diamond, cubic boron nitride and boron carbide. Pure SiC is obtained as colorless crystals, with a density of 3.21 g/mL and an extremely high melting point of 2,730 °C.

The material is highly wear resistant and chemically inert to all alkalies and acids. It is also highly heat resistant. These properties makes Silicon Carbide an outstanding abrasive and ceramic material to be used under extreme operating conditions. It is also characterized by its high thermal conductivity, high-temperature strength, low thermal expansion, resistance to chemical reaction, and ability to function as a semiconductor.

SiC has one-tenth the switching losses of silicon, 10 times the blocking voltage, four times the thermal conductivity, and 10 times the switching speeds. SiC technology also provides a junction temperature threshold in excess of 600 °C. All of these physical advantages that SiC has over current silicon technology will greatly enable increased power density, which is the chief limiting factor of today’s power electronic systems.

It will also significantly enhance energy efficiency, and shrink the size of power electronics systems by an order of magnitude. All of these factors will also result in cost savings. Whereas the IC drove the computer revolution that shrank mainframes to the size of wall cabinets to fit on a desktop, so too will SiC technology be the prime mover behind shrinking wall-sized power electronics systems to the size of a suitcase.

Silicon carbide applications

As a very hard substance, silicon carbide is widely used as an abrasive. It is used to make various materials such as sandpapers, grinding wheels, cutting tools, hard ceramics, automobile parts, refractory linings, high temperature bricks, heating elements, wear-resistant parts for pumps and rocket engines, and even jewelry.

They are used more for operation with wear at low temperature than for high temperature behavior. SiC applications are such as sandblasting injectors, automotive water pump seals, bearings, pump components, and extrusion dies that use high hardness, abrasion resistance, and corrosion resistance of carbide of silicon. High-temperature structural uses extend from the rocket injector grooves to the furnace rollers and the combination of high thermal conductivity, hardness and high temperature stability makes the components of the exchanger tubes of silicon carbide heat.

Many manufacturers are charging forward in using SiC in applications such as electric vehicles, solar energy systems, and data centers.

Goldman Sachs even predicts that utilizing silicon carbide in electric vehicles can reduce EV manufacturing cost and cost of ownership by nearly $2,000 per vehicle. SiC also optimizes EV fast-charging processes, which typically operate in the kV range, where it can reduce overall system loss by almost 30%, increase power density by 30%, and reduce the component count by 30%. This efficiency will allow fast charging stations to be smaller, faster, and more cost effective.

It is also an important material in the electronics industry and used for making light-emitting diodes (LEDs) and semiconductor devices. In recent years, SiC has become a key player in the semiconductor industry, powering MOSFETs, Schottky diodes, and power modules for use in high-power, high-efficiency applications.

In the solar industry, SiC-enabled inverter optimization also plays a large role in efficiency and cost savings. Utilizing silicon carbide in solar inverters increases the system’s switching frequency by two to three times that of standard silicon. This switching frequency increase allows for a reduction in the circuit’s magnetics, resulting in considerable space and cost savings. As a result, silicon carbide-based inverter designs can be nearly half the size and weight than that of a silicon-based inverter. Another factor that encourages solar manufacturers and engineers to use SiC over other materials, such as gallium nitride, is its robust durability and reliability. Silicon carbide’s reliability enables solar systems to achieve the stable longevity they need to operate continuously for over a decade.

China produces largest aspheric mirror with potential military, space applications

China has developed a high accuracy four-meter-aperture optical mirror, an important tool for deep space and astronomical observation. The silicon carbide aspheric optical mirror measures 1.6 tonnes. The silicon carbide used in production provides more stability to the surface of the mirror, allowing for greater accuracy at 20 nanometers. (Xinhua/Xu Chang)

The wide-diameter aspheric mirror is a key component of systems used for Earth observations from space, deep space exploration and astronomical observation, the report said. The report added that the mirror will be used in the country’s large ground-based facility. Song Zhongping, a military expert and TV commentator, told the Global Times on Wednesday that such a photoelectric facility can be used to observe low earth orbit satellites of other countries and to support measurement work in rocket and missile launches.

SiC can also be used in other important fields, Song said, such as space telescopes. “The use of SiC could also support China’s launch of space telescopes after 2025,” Song said. China’s first Hard X-ray Modulation Telescope HXMT was launched in 2017. An even more capable telescope called enhanced X-ray Timing and Polarimetry mission (eXTP), the consortium of which includes Chinese research institutes and international partners, is scheduled for launch in 2025.

UChicago team discovers Silicon Carbide as important material for Quantum revolution

Scientists with the University of Chicago’s Pritzker School of Molecular Engineering announced a significant breakthrough: Quantum states can be integrated and controlled in commonly used electronic devices made from silicon carbide.

In two papers published in Science and Science Advances, Awschalom’s group demonstrated they could electrically control quantum states embedded in silicon carbide. The breakthrough could offer a means to more easily design and build quantum electronics—in contrast to using exotic materials scientists usually need to use for quantum experiments, such as superconducting metals, levitated atoms or diamonds.

These quantum states in silicon carbide have the added benefit of emitting single particles of light with a wavelength near the telecommunications band. “This makes them well suited to long-distance transmission through the same fiber-optic network that already transports 90% of all international data worldwide,” said Awschalom, senior scientist at Argonne National Laboratory and director of the Chicago Quantum Exchange.

“The ability to create and control high-performance quantum bits in commercial electronics was a surprise,” said lead investigator David Awschalom, the Liew Family Professor in Molecular Engineering at UChicago and a pioneer in quantum technology. “These discoveries have changed the way we think about developing quantum technologies—perhaps we can find a way to use today’s electronics to build quantum devices.”

“This work brings us one step closer to the realization of systems capable of storing and distributing quantum information across the world’s fiber-optic networks,” Awschalom said. “Such quantum networks would bring about a novel class of technologies allowing for the creation of unhackable communication channels, the teleportation of single electron states and the realization of a quantum internet.”

Military Applications

Ceramic materials, such as silicon carbide (SiC), are considered to be ideal for stopping rifle bullets due to their impressive strength and hardiness. SiC can be combined with backing materials and inserted into protective vests to provide vital body protection against any high-velocity projectiles.

A typical rifle bullet includes a case, powder charge, and projectile. Projectiles that can pierce armor have a jacket, which is a sheath of a metallic alloy that surrounds a denser, stronger core generally made of steel or other very hard or dense materials. Once the gun is fired, this causes the powder charge to ignite and energy enters the projectile of the bullet.

The kinetic energy in a 7.62 mm AK-47 round is approximately 2,000 joules; Clearly, armor materials must be extremely hardy in order to disperse the energy of a projectile and protect the body from consequent damage. When a projectile collides with a ceramic armor plate, the projectile’s jacket is removed. This exposes the projectile core, which wears away upon impact with the much harder ceramic. The SiC armor system and supportive backing absorbs the energy from the projectile and spreads this across the area of the vest. Any energy that is transmitted to the user is reduced to a level that is survivable; ultimately, the wearer is protected from deadly penetration and trauma during a ballistic event.

Manufacturing technology

Silicon carbide occurs naturally as the rare mineral moissanite. The simplest silicon carbide manufacturing method involves melting silica sand and carbon, such as coal, at high temperatures―up to 2500 degrees Celsius.

Silicon carbide is prepared industrially by the Acheson method, in which pure silica sand (SiO2) and finely ground coke (carbon) are mixed together and heated to very high temperatures in the range of 1700 – 2500°C in an electric furnace. In an Acheson furnace, a mixture of carbon material (usually petroleum coke) and a silica or quartz sand is reacted chemically at high temperatures resulting in the formation of α-SiC. The energy for the reaction is provided by the resistive heating of a graphite core done by connecting this core to two electrodes at both ends of the furnace.

Silicon carbide dust and fibers produced during its processing are the main hazards of this material. The SiC dust can irritate the eyes, skin, and upper respiratory system and lead to lung fibrosis and lung cancer.

German Researchers discover accurate method for finding defects in the latest generation of silicon carbide transistors.

Researchers at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have developed a simple yet accurate method for finding defects in the latest generation of silicon carbide transistors. This will speed up the process of developing more energy-efficient transistors in future.

Power electronic switches made of silicon carbide, known as field-effect transistors or MOSFETs for short, work on the basis of the interface between the SiC and a very thin layer of silicon oxide which is deposited or grown on it. It is this interface, however, which poses a significant challenge for researchers: during fabrication, undesired defects are created at the interface which trap charge carriers and reduce the electrical current in the device.

Research into these defects is therefore of paramount importance if we are to make full use of the potential offered by the material. This is the reason why researchers at the Chair of Applied Physics at FAU decided to focus on finding new, improved methods for investigating interface defects – and they were successful. They noticed that the interface defects always follow the same pattern.

“We translated this pattern into a mathematical formula,” explains doctoral candidate Martin Hauck. “Using the formula gives us a clever way of taking interface defects into account in our calculations. This doesn’t only give us very precise values for typical device parameters like electron mobility or threshold voltage, it also lets us determine the distribution and density of interface defects almost on the side.”

In experiments conducted using transistors specially designed for the purpose by the researchers’ industrial partners Infineon Technologies Austria AG and its subsidiary Kompetenzzentrum für Automobil- & Industrie-Elektronik GmbH, the extremely simple method also proved to be highly accurate. Taking a close look at the inner core of the field-effect transistors allows now for improved and shorter innovation cycles. Using this method, processes aimed at reducing defects can be evaluated accurately, quickly and simply, and work at developing new, more energy-saving power electronics can be accelerated accordingly.