Nano Silicon Carbide Powder: The Material of the Future

RHI Magnesita

Silicon carbide powder has been produced and utilised broadly since the late 19th century, mainly as abrasives. However, recent technologies have enabled researchers and material producers to go smaller than the familiar micron powder and produce nano silicon carbide powder. Stepping into the nanoscale has given rise to an interesting combination of material properties that bring superior performance over traditional silicon carbide powder, particularly in demanding modern applications, such as the semiconductor industry. Here, we will explore what nano silicon carbide powder is, what applications it can potentially be used in, and how RHI Magnesita, a supplier of refractory materials, has managed to produce it in unprecedentedly high volume.

Silicon carbide (SiC) is a high-grade refractory material characterised by its extremely high hardness and strength. In fact, with a Mohs hardness of 9, silicon carbide is one of the hardest available materials alongside boron carbide and diamond at 9.5 and 10, respectively. Together with a unique combination of ceramic and semiconductor properties, these characteristics have enabled its use in a wide spectrum of applications ranging from abrasives to electronics, structural materials, and semiconductors.

SiC has high chemical stability and inertness with excellent corrosion resistance, even against strong acids like hydrofluoric acid, sulphuric acid, and hydrochloric acid. It also possesses high thermal conductivity with low thermal expansion coefficient leading to high thermal shock resistance.

Silicon carbide performance is driven by its structure. Basically, finer microstructure leads to unique properties. Researchers have been observing significant improvements in properties in nano silicon carbide powder over micron powder, highlighting that production and processing methods are crucial to enabling new and high-end applications.

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Figure 1. Silicon carbide can be used as a base material for electronic devices, including transistors and diodes.

What distinguishes nano silicon carbide powder?

Silicon carbide, typically, is a semiconductor material with a wide band gap, high saturation velocity, low density, and extremely high mechanical strength. Such properties have enabled it to be a potential alternative to silicon in demanding electronics applications.

Researchers over recent years have been keen on studying various nanostructures of silicon carbide, including nano powders. This combination of silicon carbide’s distinctive properties with the quantum-size effects at the nanoscale has enabled SiC nanoparticles to be a material of interest in nanotechnology applications.

Nano silicon carbide powder is characterised by the following features:

  • High purity
  • Narrow particle size distribution range (< 100 nm)
  • Relatively large specific surface area
  • Stability against high temperatures
  • High abrasion resistance
  • High chemical inertness and corrosion resistance

 

Semiconductor properties, in particular the electrical and optical properties, can be modified by controlling existing defects in the material’s structure. These come in the form of vacancies, interstitials, or clusters, which arise mainly during the growth processes. In fact, it has been shown that carbon interstitials possess high mobility, which favours the formation of carbon clusters within the material. Thorough research has been done on the presence of such defects in bulk silicon carbide. However, rare are the studies covering vacancies and interstitials in SiC nanostructures.

RHI Magnesita, leading manufacturers of refractory materials, has developed a new production method to manufacture in high volume nano silicon carbide powder with particular agglomerates of carbon. Their SiC particles have a primary particle size ranging between 50 and 60 nm with a nearly spherical shape. The scanning-electron-microscope (SEM) analysis also showed excess carbon found in clusters reaching as large as ~ 80 μm and a crystalline structure visible through the sharp-edged particles. Figure 2 shows the relative SEM images.

SEM 01 -nSiCSEM 02 -nSiC

Figure 2. SEM images showing the spherical shape of SiC particles (RHI Magnesita)

 

In addition to that, the results of the energy dispersive x-ray (EDX) measurements show extremely high purity (> 99%) of SiC. They also, interestingly, show differences in the spot-to-spot analysis, which indicates the presence of unreacted carbon besides the pure silicon carbide. Table 1 below summarises those results. Notice the significant increase in the C values from spot 1 to spot 2.

Table 1. Summary of the EDX-analysis for SiC (credit: RHI Magnesita)

 

Spot 1

Spot 2

Element

wt%

at%

wt%

at%

C

30.7

51.67

69.97

84.91

Al

0.93

0.7

0.44

0.24

Si

65.81

47.37

28.47

14.77

 

Potential applications of nano silicon carbide powder

Silicon carbide belongs to the refractory ceramics class of ultra-high-temperature ceramics (UHTC). As it offers stability at high temperatures, it is well-suited for applications with demanding conditions. Add to that the advantages brought about by nanoscale quantum effects, and you have a nano SiC powder with huge potential.

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Figure 3. Silicon carbide (SiC) single reflector, a vital component for creating a large-scale telescope, developed by the Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) of the Chinese Acad.

 

From electronics to metallurgy and structural ceramics, the range of uses of nano silicon carbide powder is unmistakeably broad. Nano SiC powder’s high strength-to-weight ratio, low thermal expansion, high thermal conductivity, high hardness, and resistance to high temperature, abrasion, and corrosion are distinct features enabling its use in the following applications:

  • Structural material for sandblast injectors, rocket injectors, bearings, extrusion dies, pump components, and furnace components (rollers, linings, accessories)
  • Abrasives for polishing and cutting
  • Structural substrate for lightweight aerospace mirrors thanks to its high resistance to mechanical fatigue, moisture, and radiation-caused deterioration
  • Base material for electronic devices, including transistors, diodes, and suppressors
  • Structural material for spray nozzles, sealing valves, and heating elements
  • Protection of rubber material (such as rubber tyres) from wear and high-temperature degradation
  • Filler material in polymer materials, such as PEEK, for enhancing wear resistance
  • Specialty coating for surfaces that require high corrosion, abrasion, and wear resistance properties.

 

This list is merely a small portion of where this nano powder can be used. If you have further ideas, questions, or potential uses, contact RHI Magnesita directly through the “Contact Supplier” button.

 

RHI Magnesita is a worldwide leader in refractories with highly innovative and reliable materials produced through an extremely robust supply chain, thanks to their exquisite vertical integration. Their new nano silicon carbide powder is one of many high-quality materials they have been developing and exploring.

Today, they have partnered with Matmatch to bring their materials one step closer to engineers and product developers searching for such unique materials.

Article by RHI Magnesita GmbH

RHI Magnesita is the global leader in refractories. We have the largest number of locations around the world and the most innovative, reliable products and services. We also provide the most robust supply and quality security, thanks to our exceptional vertical integration – from mining to production to full-service solutions.