Gallium oxide (Ga2O3) is emerging as a viable candidate for certain classes of power electronics, solar blind UV photodetectors, solar cells, and sensors with capabilities beyond existing technologies due to its large bandgap. It is usually reported that there are five different polymorphs of Ga2O3, namely, the monoclinic (β-Ga2O3), rhombohedral (α), defective spinel (γ), cubic (δ), or orthorhombic (e) structures. Of these, the β-polymorph is the stable form under normal conditions and has been the most widely studied and utilized. Since melt growth techniques can be used to grow bulk crystals of β-GaO3, the cost of producing larger area, uniform substrates is potentially lower compared to the vapor growth techniques used to manufacture bulk crystals of GaN and SiC. The performance of technologically important high voltage rectifiers and enhancement-mode Metal-Oxide Field Effect Transistors benefit from the larger critical electric field of β-Ga2O3 relative to either SiC or GaN. However, the absence of clear demonstrations of p-type doping in Ga2O3, which may be a fundamental issue resulting from the band structure, makes it very difficult to simultaneously achieve low turn-on voltages and ultra-high breakdown. The purpose of this review is to summarize recent advances in the growth, processing, and device performance of the most widely studied polymorph, β-Ga2O3. The role of defects and impurities on the transport and optical properties of bulk, epitaxial, and nanostructures material, the difficulty in p-type doping, and the development of processing techniques like etching, contact formation, dielectrics for gate formation, and passivation are discussed. Areas where continued development is needed to fully exploit the properties of Ga2O3 are identified.

A review of Ga2O3 materials, processing, and devices

This review summarises the research work carried out in the field of carbon nanotube (CNT) metal matrix composites (MMCs). Much research has been undertaken in utilising CNTs as reinforcement for composite material. However, CNT-reinforced MMCs have received the least attention. These composites are being projected for use in structural applications for their high specific strength as well as functional materials for their exciting thermal and electrical characteristics. The present review focuses on the critical issues of CNT-reinforced MMCs that include processing techniques, nanotube dispersion, interface, strengthening mechanisms and mechanical properties. Processing techniques used for synthesis of the composites have been critically reviewed with an objective to achieve homogeneous distribution of carbon nanotubes in the matrix. The mechanical property improvements achieved by addition of CNTs in various metal matrix systems are summarised. The factors determining strengthening achieved by CNT reinforcement are elucidated as are the structural and chemical stability of CNTs in different metal matrixes and the importance of the CNT/metal interface has been reviewed. The importance of CNT dispersion and its quantification is highlighted. Carbon nanotube reinforced MMCs as functional materials are summarised. Future work that needs attention is addressed.

Carbon nanotube reinforced metal matrix composites - a review

One-dimensional (1D) ZnO nanostructures have been studied intensively and extensively over the last decade not only for their remarkable chemical and physical properties, but also for their current and future diverse technological applications. This article gives a comprehensive overview of the progress that has been made within the context of 1D ZnO nanostructures synthesized via wet chemical methods. We will cover the synthetic methodologies and corresponding growth mechanisms, different structures, doping and alloying, position-controlled growth on substrates, and finally, their functional properties as catalysts, hydrophobic surfaces, sensors, and in nanoelectronic, optical, optoelectronic, and energy harvesting devices.

/pdf/one-dimensional-zno-nanostructures-solution-growth-and-30xs4d6be7.pdf

One-dimensional ZnO nanostructures: Solution growth and functional properties

https://pureadmin.qub.ac.uk/ws/files/126683921/Edited_sudagar_R1.pdf

Electroless nickel, alloy, composite and nano coatings – A critical review

Noble metal nanocrystals have been extensively utilized as promising catalysts for chemical transformations and energy conversion. One of their significant applications lies in electrode materials in fuel cells (FCs) due to their superior electrocatalytic performance towards the reactions both on anode and cathode. Nowadays, tremendous efforts have been devoted to improve the catalytic performance and minimize the usage of precious metals. Constructing multicomponent noble metal nanocrystals with complex structures provides the opportunity to reach this goal due to their highly tunable compositions and morphologies, leading to the modification of the related electrochemical properties. In this review, we first highlight the recent advances in the controllable synthesis of noble metal alloy complex nanostructures including nanoframes/nanocages, branched structures, concave/convex structures, core–shell structures and ultrathin structures. Then the effects of the well-defined nanocrystals on the modified and improved electrochemical properties are outlined. Finally, we make a conclusion with the points on the challenges and perspectives of the controllable synthesis of noble metal alloy complex nanostructures and their electrocatalytic performance.

Noble metal alloy complex nanostructures: controllable synthesis and their electrochemical property

Nanometer Diamond (ND) was synthesized by using the detonation method. It was a kind of materials with properties of diamond and nanometer particle. The Ni–P–ND composite coating was prepared from a suspension of diamond nanoparticles in electroless bath. The tribological properties, hardness and corrosion behaviours of the composite coating on medium carbon steels were investigated. The Ni–P–ND composite coating exhibits not only high wear resistance but also low friction coefficient compared with the Ni–P composite coating. The highest microhardness of the Ni–P–ND composite coating was obtained by heat treated at 673 K. The corrosion resistance of Ni–P–ND composite coating is superior to that of Ni–P coating. The mechanisms of improvement of the tribological and electrochemical properties of the electroless composite coating are also discussed.

Synthesis and properties of electroless Ni–P–Nanometer Diamond composite coatings

Preparation and properties of Ni/P/single-walled carbon nanotubes composite coatings by means of electroless plating

Undoped and N-doped β-Ga2O3 nanowires (NWs), using NH3 as the dopant source, were successfully fabricated by the CVD method on Si substrates. The microstructure, morphology, element composition and carrier concentration of the samples were characterized by XRD, SEM, TEM, and EDX. The results revealed that well-aligned undoped NWs were perpendicular to the substrates. Comparing with undoped β-Ga2O3 NWs, the morphology of N-doped β-Ga2O3 NWs showed a significant change and they were randomly oriented relative to the substrates. As the NH3 flow was increased, the microstructure of the sample presented a lot of branched-like and trumpet-shaped structures. Simultaneously, a rougher surface has been attained. PL spectrum measurements showed that N-doped β-Ga2O3 NWs had ultraviolet (UV), blue and green emission peaks because of the N-doped process. Furthermore, micro-scale undoped β-Ga2O3/N-doped β-Ga2O3 homojunction structures were fabricated. The I–V property of the fabricated N-doped β-Ga2O3 microwire and β-Ga2O3/N-doped β-Ga2O3 microwire homojunction were compared. I–V results testified that N-doped β-Ga2O3 NWs showed p-type conductivity.

Mengke Li

Papers

Synthesis and properties of electroless Ni–P–Nanometer Diamond composite coatings

Preparation and properties of Ni/P/single-walled carbon nanotubes composite coatings by means of electroless plating

Fabrication and characteristics of N-doped β-Ga2O3 nanowires

The fabrication and corrosion behavior of electroless Ni–P-carbon nanotube composite coatings

Silicon quantum-wires arrays synthesized by chemical vapor deposition and its micro-structural properties