To achieve the first demonstration of non-polar a-plane gallium nitride (GaN) epitaxy on (0 1 0) gallium oxide substrates by metal organic chemical vapor deposition (MOCVD), a low temperature AlGaN nucleation layer was engineered. Specific low temperature AlGaN growth parameters were necessary because the gallium oxide substrate begins to decompose at ∼600 °C in the ambient of H2. To achieve a smooth GaN epitaxial surface, low V/III molar ratio, and low pressure were required. To characterize the GaN film, AFM along with an orientation-dependent crystal tilt mosaic study by X-ray diffraction was performed. We effectively reduced threading dislocation density by applying in situ SiN interlayers grown by MOCVD. The oxygen contamination in the GaN film was found to originate from the substrate decomposition during GaN growth and can be reduced more than 10 times by using GaN buffer layer grown under N2 ambient.

Two-step crystallization process based on a low-Pb-content seed layer is proposed to form PZT films by the chemical solution deposition. The first crystallization step was performed after the deposition from precursor solutions with 0 and 5 wt% Pb excess, which provides a low nucleation rate and the strong perovskite (111) orientation. The bulk film was obtained from solutions with a 30 wt% Pb excess, which ensures a high growth rate and eliminates formation of pyrochlore residuals. Some films with a fixed Pb excess were prepared for comparison. It is shown that the low-Pb-content seed layer can sufficiently enhance the texture of perovskite (111) grains thus providing the highest polarization magnitudes as compared to films prepared with the fixed Pb content. The lead content and the crystallization of the seed layer are found to affect the grain-boundary conduction, which, in turn, influences the polarization dependence of transient currents.

Personal, multifunctional, and smart electronic devices/systems are indispensable components of the internet of things for modern information collection and exchange, which play a key role in facilitating the development of human civilization. Traditional technique for powering these sensor nodes mainly relies on batteries, which may not be favorable owing to the limited battery lifetime, large sensor population, wide distribution, as well as the potential of environmental detriment. Extricated from external power sources, triboelectric nanogenerators (TENGs) based active sensors have been extensively spread into a variety of fields for self-powered high-performance sensing, featured as being lightweight, extremely cost-effective, and environmentally friendly. In this article, current progress of TENGs as smart sensors for self-powered touch detection, vibration and acoustic sensing, biomedical applications, as well as human-machine interfacing, has been comprehensively reviewed, from aspects of materials usage, device fabrication to practical applications. The latest representative achievements regarding the TENG based self-powered sensing systems were also systematically presented. In the end, some perspectives and challenges for the TENG based self-powered smart sensors were also summarized.

Polystyrene spheres were found to be an effective assisted material in the growth of indium-tin-oxide (ITO) nanowire networks, bearing low temperature, high purity, and good control of size. The temperature and time of growth were studied to achieve ITO nanowire networks with high transmission and low resistivity. When prepared by PS spheres of 670 nm dia. for 15 min at 300 °C, the transmittance is above 90% after the wave length of 400 nm, and the sheet resistance is ∼200 Ω/□. Polystyrene-assisted ITO nanowires showed the high degree of crystallinity with lattice fringes, and well coincided cubic phase of In2O3. The density of ITO nanowire networks were controlled by polystyrene spheres and the residual polystyrene was removed by thermal annealing. ITO nanowire networks open new opportunities for optoelectronic devices needing special morphology for the improvement of light extraction efficiency, and as a new type of conductive film, which have an even broad application arena.

Copper(I) oxide (Cu2O) is a very favorable p-type semiconductor. It is an appealing candidate for photoelectrochemical water splitting. Here we report the fabrication and performance of gold (Au) underlayer–Cu2O composite photocathode for photoelectrochemical water splitting. The composite photocathode was fabricated by the electrodeposition technique. The different morphologies of the Au underlayer were achieved via variation in the process parameters including applied potential, electrolyte pH, and the presence of L-cysteine in the electrolyte. The Cu2O overlayer was also deposited using electrodeposition. Additionally, the influence of morphology variation, of the Au underlayer, on the performance of the composite photocathode was evaluated. It was observed that the performance of the composite photocathode increased by 81% when compared to a control sample of Cu2O. The composite photocathodes were characterized by scanning electron microscopy, X-ray diffraction, and electrochemical impedance spectroscopy.

A novel hybrid processing has been developed to achieve dense and crack-free mullite films with large critical thicknesses. The amorphous solid nanoparticles obtained from the mullite sol–gel precursor were mixed with the same liquid precursor to form stable suspensions, which were subsequently used to form mullite coatings with the dip-coating method, followed by drying and firing. The hybrid precursor suspensions resulted in highly close-packed nanoparticles, which reduced shrinkage during sintering. Selecting the solvent with a low evaporation rate and high surface tension can effectively eliminate the surface instability caused by the lateral flow during solvent evaporation. The mullite film density was significantly improved at low sintering temperatures, because of the high packing density and viscous flow at above the glass transition temperature of the amorphous gel nanoparticles before crystallization. Dense and crack-free mullite films with 500–600 nm thickness can be obtained from the novel hybrid approach.

The NiAl matrix composite coatings containing silver and molybdenum were prepared by atmospheric plasma spraying and their tribological properties were investigated in details from 25 to 900 °C. The X-ray diffraction (XRD), micro-Raman, scanning election microscopy (SEM) and transmission election microscopy (TEM) were used to analyze the composition and microstructure of composite coatings. The X-ray diffraction (XRD) results shown that molybdenum and silver were exist in single-phase, but not alloyed in composite coatings. The addition of silver could effectively improve the tribological properties of composite coatings at the wide range of temperature. The silver, nickel and molybdenum could occur the tribo-chemical reaction and form silver molybdates and nickel molybdates lubricating films inside the wear track of composite coatings at high temperature. The friction process promoted the formation of the silver molybdates. The silver molybdates, nickel molybdates and NiO were the main components in composite coatings at high temperature, which could effectively improve tribological properties of composite coatings.

Surface texture was prepared on the ASTM1045 steel substrate before spraying. Three texturing patterns (groove pattern, square pattern, and hexagon pattern) were acquired by laser processing to investigate the influence of texturing patterns on the adhesion strength of sprayed coatings. The Ni60 coatings were prepared on the textured surface by atmosphere plasma spraying technology. Scanning electron microscopy and laser 3D microscope were used to characterize the morphology of texturing. The adhesion strength between coating and substrate was examined by the tensile test. Image pro plus software was used to calculate the contact area ratio of the textured substrate. The results show that the texturing processed substrates by laser radiation present plain area between two dimples and the protrusion around texturing, and the contact area between coating and substrate is increased. The adhesion strength of coatings with a groove pattern, a square pattern, and a hexagon pattern is 58, 33, and 47 MPa, respectively. The adhesion strength of sprayed coatings varies with the change of the texturing pattern, and it does not only depend on the contact area ratio but also on the texturing density and the texturing microstructure.

A TiAlN coating was deposited on a YT14 cemented carbide cutting tool using a cathodic arc ion plating, the surface-interface morphologies, chemical elements, phases, and microhardness of the obtained TiAlN coating were analyzed with a field emission scanning electronic microscope, energy dispersive spectrometer, X-ray diffraction, and microhardness tester, respectively, and the coating surface roughness and grain scale were characterized with a atomic force microscope. The bonding strength of the coating was measured with a scratch tester, and the friction–wear properties were investigated with a reciprocation type fiction–wear tester. The results show that the bonding strength of the coating is 54.9 N, and the coating microhardness reaches 2724 HV. The average coefficient of friction of the coating is 0.59, the wear mechanism is abrasive wear and slight brittle fracture.

We report a novel approach to the instantaneous photoinitiated synthesis of mixed anatase-rutile nanocrystalline TiO2 thin films with a three-dimensional nanostructure through pulsed white light irradiation of photosensitive Ti-organic precursor films. Pulsed photoinitiated pyrolysis accompanied by instantaneous self-assembly and crystallization occurred to form graphitic oxides-coated TiO2 nanograins. Subsequent pulsed light irradiation working as in situ pulsed photothermal treatment improved the crystalline quality of TiO2 film despite its low attenuation of light. The non-radiative recombination of photogenerated electrons and holes in TiO2 nanograins, coupled with inefficient heat dissipation due to low thermal conductivity, produces enough heat to provide the thermodynamic driving force for improving the crystalline quality. The graphitic oxides were reduced by pulsed photothermal treatment and can be completely removed by oxygen plasma cleaning. This photoinitiated nanofabrication technology opens a promising way for the low-cost and high-throughput manufacturing of nanostructured metal oxides as well as TiO2 nanocrystalline thin films.

Atom probe tomography and transmission electron microscopy are used to analyze magnetron-sputtered MoS2 films containing Ti and Au/Sb2O3 as a model system for tribological coatings. Transmission electron microscopy characterization showed that the Ti–MoS2 film is dense and featureless whereas Sb2O3/Au–MoS2 film is less dense and have columnar morphology. Three-dimensional atom probe reconstructions revealed that the Ti–MoS2 films have a homogeneous composition and contain about 15 at.% Ti, which is uniformly distributed throughout the MoS2 matrix without any evidence of Ti precipitation. Sb2O3/Au–MoS2 films also showed homogeneous distribution of Sb2O3 throughout the MoS2 matrix and the presence of Au-rich precipitates. The complementary techniques of atom probe tomography and transmission electron microscopy indicate that Ti and Sb2O3 incorporation in the deposition of MoS2 produces amorphous microstructures, whereas the addition of Au forms nano-sized and well-dispersed precipitates.

Effects of Mo addition on the microstructure, mechanical properties, and abrasive wear properties of an oriented bulk Fe2B crystal have been investigated systematically in the present paper. Five groups of pure Fe2B samples with different Mo contents have been examined by optical microscope, X-ray diffraction, scanning electron microscope integrated with energy disperse spectroscopy, microhardness tester, and three-point bending testing of fracture toughness. The results indicate that Mo tends to segregate on the grain boundaries after doping; with increasing Mo addition, interplanar spacing of the (002) crystal plane of Fe2B decreases firstly and then increases slightly while that of (200) increases gradually; microhardness on the transversal section changes little while that on the longitudinal section increases firstly and then decreases [possessing the opposite trend to interplanar spacing of (002)]; fracture toughness and wear resistance of both transversal and longitudinal samples can be improved to some extent with Mo addition less than 2.0 wt%. In conclusion, appropriate Mo addition plays a positive role in the improvement of mechanical properties of oriented bulk Fe2B.

Composite copper oxide–copper bromide films were electrodeposited on gas diffusion layer (GDL) supports under controlled potential from aqueous copper salt solutions in the presence of a complexing/surfactant agent such as lactate. The solution pH was adjusted to target simultaneous deposition of cubic nanostructures composed of copper, oxygen, and bromine elements. The film composition and morphology were carefully tuned for enhanced electrochemical conversion of CO2 to hydrocarbons. Hydrocarbon products, predominantly ethylene and minor amounts of methane, ethane, and propylene were observed along with inevitable H2 co-generation. Importantly, CO gas was not detected during CO2 electrolyses. Low temperatures (3–5 °C) enhanced the conversion of CO intermediate to C2H4. The durability and electroactivity of these composite films were maintained for extended periods (up to 10 h) of CO2 electrolysis by periodic in situ application of anodic pulses to regenerate the cathode surface.

Comparative studies between doped conducting polymers and electrochemical deposited organometallic compounds reveals the interplay between crystalline-amorphous phases with significant contributions to the internal quantum efficiency in the OLED devices. The coexistence of the amorphous and crystalline phase in the electrodeposited film is revealed by the minor micro-crystal products which are present in the amorphous phase in thin films, while the many micro-crystals are randomly distributed in the thick films. Concerning the doped conducting polymers, the level of doping induces crystalline effects as a result of the π–π stacking between molecules, due to the Forester energy transfer processes in which the transfer rate is increased with decreasing of the distances between neighboring molecules. The crystallization processes change the emission properties of the active layers both for the luminance level and all over color, ranging from yellow to red in the case of IrQ(ppy)2 compounds.

Thermal stability up to 400 °C of nanocrystalline (NC) Ni electrodeposits (EDs) with a mean grain size of 28 nm and dispersions of a small amount of CeO2 nanoparticles has been investigated by comparing with two CeO2-free NC Ni counterparts, one with a slightly smaller mean grain size of 18 nm and the other with a slightly larger mean grain size of 34 nm. The results show that the co-deposition of CeO2 particles has dual effects on the thermal stability of the NC Ni EDs, i.e., it promotes the grain growth at the beginning but retards subsequently. It is proposed that the CeO2 co-deposition leads to a decrease in sulfur level and an increase in the plane defects as a result of introduction of incoherent Ni/CeO2 interfaces, which play dominant roles in the grain growth at low temperatures; while the drag effect of CeO2 dispersions becomes dominant at higher temperatures.

Four 9Cr2WVTa deposited metals with different titanium contents were studied to reveal the role of minor elements titanium, which guide for the design of welding consumables for reduced activation ferritic/martensitic steel and meet for the requirements of accelerator driven systems-lead fusion reactors. The microstructural evolution of 9Cr2WVTa deposited metals was analyzed and discussed. Results show that the surface layer of 9Cr2WVTa deposited metal exhibits the columnar structure and the δ-ferrite is seen as a film distributed along the martensite lath. The microstructures are uniform in the middle of the deposited metal and exhibit the equiaxed structure. The fine stripe δ-ferrite decorates along the prior austenite grain boundaries and therefore, refines the grain size. The primary blocky Ti-enriched particles are the main factor affecting the mechanical properties for the 9Cr2WVTa deposited metal. The 9Cr2WVTa deposited metals obtain good mechanical properties when the titanium content does not exceed 0.08 wt%.

Mechanical stability of Ag and Cu printed and evaporated metallization lines on polymer substrates is investigated by means of monotonic tensile and cyclic bending tests. It is shown that lines which demonstrate good performance during monotonic tests fail at lower strains during a cyclic bending tests. Evaporated lines with the grain size of several hundreds of nanometers have good ductility and consequently good stability during monotonic loading but at the same time they fail at low strains during cyclic bending. Printed lines with nanocrystalline microstructure, in contrast, demonstrate more intensive cracking during monotonic loading but higher failure strains during cyclic bending. Apart from the grain size effect, the effect of film thickness on the saturation crack density after cyclic bending is also demonstrated. Thinner films have higher crack density in accordance with the shear lag model.

It is important to fabricate iron-based nitride/conductive material composite to obtain good catalytic performance. In this work, Fe2N nanoparticles with diameter of approximately 30 nm have been successfully dispersed on the surface of nitrogen-doped graphite oxide (NrGO) by a facile sol–gel method and further ammonia atmosphere treatment. XPS, XRD, Raman, and TEM proved that Fe2N nanoparticles are well monodispersed, and nitrogen atoms are doped in NrGO. The composite possessed two merits, that is, the more catalytic active site in Fe2N nanoparticles due to the well monodispersion, and fast electron transfer due to the nitrogen dope in rGO. With the proper ratio, the composite exhibited brilliant catalytic activity and durability in acidic media. It possesses overpotential of 94 mV to approach 10 mA/cm2, a small Tefel slope of 49 mV/dec, and maintains the good electrocatalytic activity for 10 h. Cyclic voltammetry and electrochemical impedance spectroscopy indicated that the electrocatalyst possessed high catalytic active area and fast electron transfer. Our work may provide a new avenue for the preparation of low-cost iron-based nitride/NrGO composite for highly efficient electrochemical hydrogen evolution.

The development of highly efficient and stable inexpensive catalysts for the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 in an aqueous solution by utilizing metal-organic frameworks (MOFs) as precursor and template remains a hot topic. Herein, a simple self-template strategy was developed to synthesize a porous nitrogen-doped carbon frameworks embedded with zinc and cobalt nanoparticles (Zn0.3Co2.7@NC) catalyst by thermal annealing of the bimetallic zinc-cobalt zeolitic imidazolate framework (Zn0.3Co2.7-ZIF) as an effective precursor and template. The resulting Zn0.3Co2.7@NC catalysts show an excellent catalytic activity for the reduction of 4-NP and the reduction reaction was completed only in 5 min with nearly 100% conversion. The apparent rate constant for the reaction of 4-NP reduction was estimated to be 0.683 min−1. Moreover, the catalyst was extended to reduce other nitro compounds and exhibited excellent catalytic activity. When compared to other related catalysts in the literature, the catalytic activity of catalyst is superior. Therefore, the resulting Zn0.3Co2.7@NC is expected to get more extensive application in the field of catalysis.

Conventional metallic antibacterial materials release metal ions and reactive oxygen species (ROS) for killing bacteria. Herein, we found that nanoporous gold (NPG) exhibits antibacterial activity (AA) at an intermediate relative humidity (RH) of 60% against Escherichia coli and Staphylococcus epidermidis in contrast to the inert behavior of bulk gold. The dependence of AA on RH, morphological observations of bacteria on NPG, and transcriptomic analyses of NPG-treated Escherichia coli were investigated. These observations collectively suggest that biological processes in cell walls containing peptidoglycan and cell membranes are significantly disrupted by direct contact with NPG. Metal ions and ROS were not detected, and therefore are not responsible for the present antibacterial properties of NPG. The catalytic nature of NPG may be responsible for its AA, probably because of lattice distortion at the surface of nanosized ligaments with large curvature.