Functionally-oriented composite layered materials with martensitic transformations

The studies carried out show that the task of ensuring the reliability and expanding the functionality of products operating under multifactorial effects (temperature, force, deformation) can be successfully solved by functionally oriented surface composite materials with thermoelastic martensitic transformations (TMT). The authors proposed the technology of layer-by-layer synthesis of functionally-oriented composite layered materials with TMT in argon environment, implemented on patented equipment in a single technological cycle. This technology determines not only the novelty, but also the economic feasibility of technical solutions. We also suggested step-by-step methods of thermal and thermomechanical treatment of composite layered materials with TMT, which contribute to the structure stabilization while decreasing residual stress. On the basis of complex X-ray diffraction and electron microscopic studies, we determined the structural parameters of High Velocity Oxy-Fuel (HVOF) materials obtained by HVOF with subsequent thermal and thermomechanical treatment and ceramic materials ZrO2-Y2O3-CeO2-Al2O3 stabilized with Al2O3 with subsequent heat treatment. We investigated the microhardness of surface high-entropy and ceramic materials. Tests for "friction-wear" and mechanical high-cycle fatigue of steels with a composite surface laminate showed decrease in the wear rate and increase in the cyclic durability.

Electrochemical detection of adrenaline and hydrogen peroxide on carbon nanotube electrodes

Adrenaline and hydrogen peroxide have neuromodulatory functions in the brain and peroxide is also formed during reaction of adrenaline. Considerable interest exists in developing electrochemical sensors that can detect their levels in vivo due to their important biochemical roles. Challenges associated with electrochemical detection of hydrogen peroxide and adrenaline are that the oxidation of these molecules usually requires highly oxidising potentials (beyond 1.4 V vs Ag/AgCl) where electrode damage and biofouling are likely and the signals of adrenaline, hydrogen peroxide and adenosine overlap on most electrode materials. To address these issues we fabricated pyrolysed carbon electrodes coated with oxidised carbon nanotubes (CNTs). Using these electrodes for fast-scan cyclic voltammetric (FSCV) measurements showed that the electrode offers reduced overpotentials compared with graphite and improved resistance to biofouling. Adrenaline oxidises on this electrode at 0.75(±0.1) V and reduces back at −0.2(±0.1) V while hydrogen peroxide oxidation is detected at 0.85(±0.1) V on this electrode. The electrodes are highly sensitive with a sensitivity of 16 nA µM−1 for Adrenaline and 11 nA µM−1 for hydrogen peroxide on an 80 µm2 electrode. They are also suitable to distinguish between adrenaline, hydrogen peroxide and adenosine thus these probes can be used for multimodal detection of analytes.

Corrosion and Wear Properties of h-BN Modified TC4 Titanium Alloy Micro-Arc Oxide Coatings

In this study, ceramic coatings were prepared on the surface of TC4 titanium alloy by micro-arc oxidation (MAO). The morphology, element distribution and phase composition of MAO coatings were analyzed by SEM, EDS, XRD and other analytical methods. The effect of hexagonal boron nitride(h-BN) doping on wear resistance and corrosion resistance of micro-arc oxidation layer was studied. The results show that the coating is mainly composed of rutile TiO2, anatase TiO2 and a small amount of h-BN. Furthermore, the composite coating containing h-BN was less porous than particle-free coating. The test results show that h-BN doping slightly affects the hardness of the MAO coating, and it is helpful in improving the thickness, corrosion resistance and wear resistance of the coatings. When the amount of h-BN is 3 g/L, the corrosion current density of the coating is the smallest; When the addition of h-BN is 1.5 g/L, the friction coefficient of the coating is the smallest. The wear mechanism was adhesive wear, accompanied by slight abrasive wear.

Defects and passivation in perovskite solar cells

This organic-inorganic hybrid perovskite materials have attracted great attention by virtue of their high absorption coefficient, low cost and simple film deposition technique. Based on these advantages, perovskite solar cells have reached an impressive power conversion efficiency over 25%. However, the low-temperature process inevitably leads to a large number of defects in the perovskite film. These defects would exacerbate the carrier recombination, induce crystal degradation, phase transformation and seriously affect the performance of devices. Studying the defects in perovskite film is of great significance for the development of high-performance perovskite solar cells. Herein, the authors summarise the causes, distribution and features of defects, as well as their effects on the performance of perovskite solar cells. Furthermore, some defect-passivation strategies on perovskite film or the device, including grain boundary passivation, surface passivation, capping layer modification and charge transport layer passivation, are discussed, respectively. Lastly, some remaining challenges in the commercialisation of perovskite solar cells are proposed.

Progress in fabrication and applications of micro/nanostructured superhydrophobic surfaces

Natural biological surfaces such as lotus leaves and water striders have micro- and nanostructures and low-surface-energy materials, possessing excellent superhydrophobicity. It has become an important research topic to construct bionic superhydrophobic surfaces and explore their functional applications. This paper reviews the research progress on the fabrication and applications of superhydrophobic surfaces with micro/nanostructures. The techniques used for fabricating superhydrophobic surfaces, including the template method, nano-imprinting technique, laser-treatment, plasma treatment, electrospinning technique, solution-chemical etching method, electrochemical technique, phase separation method and sol–gel process, were introduced. Also, the diverse functional applications of superhydrophobic surfaces such as self-cleaning, anti-icing, oil–water separation, anti-corrosion and drag reduction were summarised. It is believed that green fabrication will become the future development direction of superhydrophobic surfaces. Further exploration for the superhydrophobic surfaces with mechanical stability and durability will be expected to expand the application prospect and commercial value of superhydrophobic surfaces.