SiC nanomaterials

Silicon carbide nanomaterials

Silicon carbide nanomaterials refer to materials composed of silicon carbide (SiC) that have at least one dimension at the nanoscale (typically defined as 1-100nm) in three-dimensional space. Silicon carbide nanomaterials can be classified into zero dimensional, one-dimensional, two-dimensional, and three-dimensional structures based on their structure.

Zero dimensional nanostructures are structures with all sizes at the nanoscale, mainly including solid nanocrystals, hollow nanospheres, hollow nanocages, and core-shell nanospheres.

One dimensional nanostructures refer to structures that are confined to two dimensions in three-dimensional space within the nanoscale range. These structures come in various forms, including nanowires (solid center), nanotubes (hollow center), nanoribbons or nanoribbons (narrow rectangular cross-section), and nanoprisms (prism shaped cross-section). This structure has become a focus of in-depth research due to its unique applications in mesoscopic physics and nanoscale device manufacturing. For example, charge carriers in one-dimensional nanostructures can only propagate in one direction of the structure (i.e. the longitudinal direction of nanowires or nanotubes), and can be used as interconnects and key devices in nanoelectronics.

Two dimensional nanostructures, such as nanosheets, nanosheets, nanosheets, and nanospheres, have recently received special attention at the nanoscale, with only one dimension typically perpendicular to their layer planes. This not only provides a basic understanding of their growth mechanisms, but also explores their potential applications in light emitters, sensors, solar cells, and more.

Three dimensional nanostructures are commonly referred to as complex nanostructures, which are formed by the collection of one or more basic structural units in zero, one, or two dimensions (such as nanowires or nanorods connected by single crystal junctions), with overall geometric dimensions on the nanometer or micrometer scale. This complex nanostructure with a high unit volume surface area provides many advantages, such as a long optical path for effective light absorption, fast interface charge transfer, and adjustable charge transfer capability. These advantages enable three-dimensional nanostructures to advance design in future energy conversion and storage applications. From 0D to 3D structures, various nanomaterials have been studied and gradually introduced into industry and daily life.

Synthesis methods of SiC nanomaterials

Zero dimensional materials can be synthesized using methods such as hot flux, electrochemical etching, and laser pyrolysis to obtain SiC solid nanocrystals ranging from a few nanometers to tens of nanometers, but they are usually pseudo spherical in shape, as shown in Figure 1.

Figure 1 TEM images of β - SiC nanocrystals prepared by different methods

(a) Solvothermal synthesis [34]; (B) Electrochemical etching method [35]; (c) Hot processing method [48]; (d) Laser pyrolysis method [49]

Dasog et al. synthesized spherical β - SiC nanocrystals with controllable size and clear structure through solid-state decomposition reaction between SiO2, Mg, and C powders [55], as shown in Figure 2.

Figure 2 FESEM images of spherical SiC nanocrystals with different diameters [55]

（a）51.3 ± 5.5 nm； （B）92.8 ± 6.6 nm； （c）278.3 ± 8.2 nm

Gas phase growth of silicon carbide nanowires. Gas phase synthesis is the most mature method for forming SiC nanowires. In typical processes, vapor substances used as reactants to form the final product are generated through evaporation, chemical reduction, and gaseous reactions (requiring high temperatures). Despite the additional energy consumption caused by high temperatures, SiC nanowires grown by this method typically exhibit high crystal integrity, clear nanowires/nanorods, nanoprisms, nanoneedles, nanotubes, nanoribbons, nano cables, and more, as shown in Figure 3.

Figure 3 Typical morphology of one-dimensional SiC nanostructures (a) nanowire array on carbon fibers; (b) Ultra long nanowires on Ni Si spheres; (c) Nanowires; (d) Nanoprism; (e) Nano bamboo; (f) Nanoneedles; (g) Nano bone; (h) Nanochains; (i) Nanotubes

Preparation of SiC nanowires by solution method. SiC nanowires were prepared using the solution method, which reduced the reaction temperature. This method may include crystallizing the precursor of the solution phase through spontaneous chemical reduction or other reactions at relatively mild temperatures. As representatives of solution synthesis, solvothermal synthesis and hydrothermal synthesis have been widely used to obtain SiC nanowires at low temperatures.

Two dimensional nanomaterials can be prepared through processes such as solvothermal method, pulsed laser, carbon thermal reduction, mechanical exfoliation, and microwave plasma enhanced CVD method. Ho et al. achieved a 3D SiC nanostructure with nanowire flower shape, as shown in Figure 4. SEM images showed that the flower shaped structure had a diameter of 1-2 μ m and a length of 3-5 μ m.

Figure 3 SEM image of 3D SiC nanowire flower

Properties of SiC Nanomaterials

SiC nanomaterials are advanced ceramic materials with excellent properties, including good physical, chemical, electrical, and other properties.

✔ physical property

High hardness: The microhardness of nano silicon carbide is between that of corundum and diamond, with higher mechanical strength than corundum, high wear resistance, and good self-lubricating properties.

High thermal conductivity: Nano silicon carbide has excellent thermal conductivity and is an excellent thermal conductive material.

Low thermal expansion coefficient: This enables nano silicon carbide to maintain stable size and shape in high-temperature environments.

High specific surface area: One of the characteristics of nanomaterials, which is beneficial for improving their surface activity and reactivity.

✔ Chemical properties

Chemical stability: Nano silicon carbide has stable chemical properties and can maintain its performance unchanged in various environments.

Antioxidant properties: It can resist oxidation at high temperatures and exhibits excellent high-temperature resistance.

✔ Electrical performance

High bandgap width: The high bandgap width makes it an ideal material for producing high-frequency, high-power, and low-energy electronic devices.

High electron saturation mobility: conducive to rapid electron transfer.

✔ Other characteristics

Strong radiation resistance: able to maintain stable performance in a radiation environment.

Good mechanical performance: It has excellent mechanical properties such as high elastic modulus.

Application of SiC Nanomaterials

Electronic and semiconductor devices: Due to its excellent electronic performance and high-temperature stability, nano silicon carbide is widely used in high-power electronic components, high-frequency devices, optoelectronic components, and other fields. Meanwhile, it is also one of the ideal materials for manufacturing semiconductor devices.

Optical applications: Nano silicon carbide has a wide bandgap and excellent optical properties, which can be used to manufacture high-performance lasers, LEDs, photovoltaic devices, etc.

Mechanical components: Utilizing their high hardness and wear resistance, nano silicon carbide has a wide range of applications in manufacturing mechanical components, such as high-speed cutting tools, bearings, mechanical seals, etc., which can greatly improve the wear resistance and service life of components.

Nano composite materials: Nano silicon carbide can be combined with other materials to form nano composite materials, in order to improve the mechanical properties, thermal conductivity, and corrosion resistance of the materials. This type of nanocomposite material is widely used in aerospace, automotive industry, energy sector, and other fields.

High temperature structural material: Nano silicon carbide has excellent high-temperature stability and corrosion resistance, and can be used in extreme high-temperature environments. Therefore, it is used as a high-temperature structural material in aerospace, petrochemical, metallurgical and other fields, such as manufacturing high-temperature furnaces, furnace tubes, furnace linings, etc.

Other applications: Nano silicon carbide has also been applied in fields such as hydrogen storage, photocatalysis, and sensing, demonstrating broad application prospects.

reference

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