Silicon Carbide Nanostructures as Potential Carbide Material for Electrochemical Supercapacitors: A Review

Silicon carbide (SiC) is a very promising carbide material with various applications such as electrochemical supercapacitors, photocatalysis, microwave absorption, field-effect transistors, and sensors. Due to its enticing advantages of high thermal stability, outstanding chemical stability, high thermal conductivity, and excellent mechanical behavior, it is used as a potential candidate in various fields such as supercapacitors, water-splitting, photocatalysis, biomedical, sensors, and so on. This review mainly describes the various synthesis techniques of nanostructured SiC (0D, 1D, 2D, and 3D) and its properties. Thereafter, the ongoing research trends in electrochemical supercapacitor electrodes are fully excavated. Finally, the outlook of future research directions, key obstacles, and possible solutions are emphasized.

Effect of carbon nanotexture on the synthesis, initial growth mechanism and photoluminescence properties of SiC nanowires

Although the spontaneous vapor-solid growth of SiC nanowires is a well-established phenomenon, the exact mechanism by which nanowires grow on substrates is still poorly understood. Here, we studied the initial growth of SiC nanowires on carbon sources with different nanotextures via a catalyst-free vapor reaction between a polyacrylonitrile-based carbon fiber and a silicon powder. The results revealed that the SiC nanowires were preferentially formed on the carbon fiber with a higher degree of graphitization. Detailed analyses suggested that the growth behavior of the underlying SiC film formed on the carbon fibers, which is strongly affected by the microstructures of the carbon fibers, plays an important role in the formation of nanowires. In addition, the photoluminescence spectrum of SiC nanowires showed strong ultraviolet-visible emission peaks at an excitation wavelength of 250 nm, which may provide potential applications in the field of optoelectronic devices.

Nanoarchitectonics for Wide Bandgap Semiconductor Nanowires: Toward the Next Generation of Nanoelectromechanical Systems for Environmental Monitoring

Semiconductor nanowires are widely considered as the building blocks that revolutionized many areas of nanosciences and nanotechnologies. The unique features in nanowires, including high electron transport, excellent mechanical robustness, large surface area, and capability to engineer their intrinsic properties, enable new classes of nanoelectromechanical systems (NEMS). Wide bandgap (WBG) semiconductors in the form of nanowires are a hot spot of research owing to the tremendous possibilities in NEMS, particularly for environmental monitoring and energy harvesting. This article presents a comprehensive overview of the recent progress on the growth, properties and applications of silicon carbide (SiC), group III-nitrides, and diamond nanowires as the materials of choice for NEMS. It begins with a snapshot on material developments and fabrication technologies, covering both bottom-up and top-down approaches. A discussion on the mechanical, electrical, optical, and thermal properties is provided detailing the fundamental physics of WBG nanowires along with their potential for NEMS. A series of sensing and electronic devices particularly for environmental monitoring is reviewed, which further extend the capability in industrial applications. The article concludes with the merits and shortcomings of environmental monitoring applications based on these classes of nanowires, providing a roadmap for future development in this fast-emerging research field.

Wetting Behavior of Metal-Catalyzed Chemical Vapor Deposition-Grown One-Dimensional Cubic-SiC Nanostructures

Superhydrophobic surfaces can be fabricated by using the self-assembled nanoarchitecture of 3C-SiC one-dimensional (1D) nanostructures as they are capable of forming a dense network of micro-nano air pockets without any help from external sources. Herein, the metal-catalyzed growth of 3C-SiC nanowires/nanorods on Si substrates via vapor-liquid-solid mechanism using five different catalysts, that is, chemically synthesized Au nanoparticles and direct current-sputtered thin films of Au, Cu, Ni, and Ti, is reported. Relatively new or unexplored catalysts such as thin films of Cu and Ti, as well as drop-cast Au nanoparticles, were used. An optimized and separate growth was carried out for each catalyst in an inductively heated horizontal cold-wall atmospheric pressure chemical vapor deposition reactor. An insight into the catalytic growth mechanism of 3C-SiC 1D nanostructures has been presented. All of the bare samples exhibited superhydrophilic behavior, whereas hierarchical Au/Pd nanostructure-coated 3C-SiC nanorod samples grown using Au and Ni thin-film catalysts exhibited hydrophobic and superhydrophobic behavior, respectively. As the better results were obtained for Ni thin-film catalysts in terms of growth density and high water contact angle (WCA ≈ 160°), therefore, the growth temperature, as well as the growth time-dependent wetting behavior, was also studied. It was found that the WCA increased as the growth time and temperature increased because of the increase in the growth density, and it finally reached to an optimum value at the growth temperature of 1200 °C and the growth time of 1 h. Furthermore, their wetting behavior was studied by using a variety of high surface tension (water, milk, tea, and glycerin) and low surface tension (organic liquids such as n-hexane, ethanol, etc.) liquids. High surface tension liquids exhibited superhydrophobic behavior, whereas low surface tension liquids exhibited superhydrophilic behavior. Hence, these fabricated nanostructured surfaces can be exploited for oil-water separation, electrowetting, water harvesting, self-cleaning, lab on a chip, and micro-/nanofluidic device applications.

The controllable growth of superhydrophobic SiC nanowires by tailoring the cooling rate

In the present work, we report the controlled growth of SiC nanowires on a silicon substrate by tailoring the cooling rate of a catalyst-assisted method. The SiC nanowire film obtained at the fast cooling rate exhibited excellent superhydrophobicity with a water contact angle up to 150° without any surface functionalization.

High-temperature stable field emission of B-doped SiC nanoneedle arrays

Current emission stability is one of the key issues for field emitters for them to be practically applied as electron sources. In the present work, large-scale and well-aligned B-doped SiC nanoneedle arrays have been grown on 6H-SiC wafer substrates via pyrolysis of polymeric precursors. The measured field emission (FE) characteristics suggest that the turn-on fields of the as-synthesized SiC nanoneedle arrays are reduced from 1.92 to 0.98 V μm(-1) with temperature increasing from room temperature (RT) to 500 °C, suggesting their excellent FE performances. The slightly changed current fluctuations (only ∼1.3%) between RT and 200 °C confirm that the present SiC nanoarrays with B dopants could be highly stable field emitters to be used in service under harsh conditions of high temperatures.

Large-scale growth of well-aligned SiC tower-like nanowire arrays and their field emission properties

Fabrication of well-aligned one-dimensional (1D) nanostrucutres is critically important and highly desired since it is the key step to realize the patterned arrays to be used as the display units. In the present work, we report the large-scale and well-aligned growth of n-type SiC nanowire arrays on the 6H-SiC wafer substrates via pyrolysis of polymeric precursors assisted by Au catalysts. The obtained n-type SiC nanowires are highly qualified with sharp tips and numerous sharp corners around the wire bodies, which bring the emitters excellent field emission (FE) performance with low turn-on fields (1.50 V/μm), low threshold fields (2.65 V/μm), and good current emission stabilities (fluctuation <3.8%). The work abilities of the n-type SiC tower-like nanowire arrays under high-temperature harsh environments have been investigated, suggesting that the resultant field emitters could be well serviced up to 500 °C. The temperature-enhanced FE behaviors could be attributed to the reduction of the work function induced by the rise of temperatures and the incorporated N dopants. It is believed that the present well-aligned n-type SiC tower-like nanowire arrays could meet nearly all stringent requirements for an ideal FE emitter with excellent FE properties, making their applications very promising in displays and other electronic nanodevices.

Ultra-long SiC nanowires synthesized by a simple method

Ultra-long SiC nanowires synthesized by alumina-assisted growth of the vapor–solid (VS) mechanism.

Controlled growth of SiC flexible field emitters with clear and sharp tips

We report the controlled growth of 3C-SiC flexible field emitters with clear and sharp tips based on the VLS mechanism.

Synthesis and formation mechanism of twinned SiC nanowires made by a catalyst-free thermal chemical vapour deposition method

Twinned SiC nanowires were prepared on a silicon wafer by a simple catalyst-free thermal chemical vapour deposition (CVD) method.