To improve the electrochemical and kinetic performances of the Mg2Ni-type hydrogen storage alloys, Mg was partially substituted by La, and the rapid solidification technology was used for the preparation of Mg20−xLaxNi10 (x = 0, 2, 4, 6) alloys. The microstructures of the as-cast Mg20−xLaxNi10 (x = 0, 2, 4, 6) and as-spun Mg20−xLaxNi10 (x = 2) alloys were systematically studied through x-ray diffraction and high-resolution transmission electronic microscopy. Electrochemical hydrogen storage properties were measured by the automatic galvanostatic system. Electrochemical impedance spectrum, linear polarization, and step-potential discharge curves were plotted using electrochemical workstation. The results showed that substitution of La for Mg was helpful for forming multiphase structures, increasing the discharge capacity of the as-cast Mg20−xLaxNi10 (x = 0, 2, 4, 6) alloys. The increasing quenching rate facilitated the formation of amorphous and nanocrystalline structures of Mg18La2Ni10 (La2) alloy, effectively improving the electrochemical and kinetic properties of Mg18La2Ni10 (La2) alloys.

SnZn(OH)6 (ZHS) with different morphologies were synthesized by a facile self-templated method at room temperature. It was found that the morphology of ZHS could be controlled by varying the concentration of OH−. The crystalline structure and morphology of the particles were characterized by x-ray diffraction, UV-vis diffuse reflectance spectroscopy, scanning electron microscopy images, and N2 adsorption. The results indicated that the particles had almost uniform monoclinic geometry and uniform size. The photocatalytic activity of ZHS with different morphologies was tested through degradation of Rhodamine B (RhB). Therein, the hollow ZHS showed the highest light catalytic performance due to its large BET surface area, wide band gap, and high crystallinity.

Carbon nanocoils (CNCs) with different diameters have been synthesized on different substrates by thermal chemical vapor deposition using Fe films as catalysts prepared by ion sputtering. It is found that CNCs with diameters greater than 100 nm are obtained as the main products in large quantities on Fe film coated indium tin oxide substrates. However, on Fe film coated SiO2 substrates, multiwall CNCs (MWCNCs) along with carbon nanotubes (CNTs) are grown, and the yield of MWCNCs is decreased rapidly with a lower Fe film thickness. The as-grown MWCNCs with observed coil diameters less than 100 nm and filament diameters less than 30 nm are much thinner than the conventional CNCs. Plate-like catalyst particles with sizes much larger than the filament diameter of the MWCNCs are observed at the roots of these MWCNCs, indicating a base growth mechanism. Furthermore, it is also observed that large particles with irregular shapes lead to the growth of helical MWCNCs, while large particles with steady circular shapes tend to grow as straight CNTs. Based on the experimental results, a growth model for MWCNCs is proposed.

The synthesis, structure, and electrical performances of titanium dioxide (TiO2 and also doped TiO2) thin films, a capacitor dielectric for dynamic random access memory (DRAM) and a resistance switching material in resistance switching RAM (ReRAM), are reviewed. The three-dimensionality of these structures and the extremely small feature sizes (<20 nm) of these memory devices require the synthesis method of TiO2-based layers to exhibit high degree of conformality. Atomic layer deposition is, therefore, the method of choice in respect of film growth for these applications. The unique arrangement of the TiO6-octahedra in the rutile structure, which results in the value for dielectric constant of the dielectric layer, εr (>100), makes the material especially attractive as the capacitor dielectric layer in DRAM. Removing some of the oxygen ions from the rutile structure and arranging the resulting oxygen vacancies on a specific crystallographic plane results in the so called Magnéli phase materials, which show distinctive conducting semiconductor or metallic characteristics. External electrical stimuli can cause the repeated formation and rupture of conducting channels that consist of these Magnéli phase materials in the insulating TiO2 matrix, and this aspect makes the material a very feasible choice for applications in ReRAM. This article reviews the material properties, fabrication process, integration issues, and prospect of TiO2 films for these applications.

Li-stabilized Na-β″/β-Al2O3(Na1.61Li0.29Al10.70O17) nanorods were prepared by a soft chemistry process using a 1-alkyl-3-methylimidazolium bromide ([CXmim]Br, X = 4, 12, 16) ionic liquid as a template. Pure Na-β″/β-Al2O3 rods were obtained by heating at 1100 °C with [C16mim]Br as the template, resulting in nanorods of approximately 50 nm in diameter and 200–300 nm in length. It is demonstrated that alkyl chain length is the main factor determining the aspect ratio of the nanorods. The specific surface area of the powder is 81.3 m2/g, which is more than one order of magnitude higher than that of the powder prepared by a conventional solid state reaction process. The formation mechanism of the nanorods is proposed.

Pure platinum was probed with a nanoindenter fitted with a Berkovich tip to various depths. The indent pattern was made on the as-polished specimen prior to heat treating, after heat treating at 500 °C for 30 min, and again after further heat treating at 1000 °C for 30 min. The variability in the measured hardness decreased as the indentation depth increased from 50 to 300 nm. When the sampled was annealed, the hardness variation was also greater. Increasing hardness variation with decreasing dislocation density and sampling volume indicates that dislocation density plays a critical role in the observed variation, beyond solely instrumentation uncertainty, and supports a defect-based explanation for the stochastic behavior. It appears that the stochastic behavior occurs when multiple dislocations are present in the sampled volume rather than sampling only a single dislocation.

Ceramic parts possessing an ordered porosity were produced for the first time by powder-based three-dimensional printing of a preceramic polymer followed by pyrolysis in an inert atmosphere. The main parameters involved in the process were investigated, and the precision of the printed and ceramized parts was assessed by means of scanning electron microscopy and micro computed tomography. The influence of two different printing solvents was investigated and the use of a mixture of 1-hexanol and hexylacetate in particular allowed the production of parts with a relative density of 80% both in the polymeric and in the ceramic state. The mixing of a cross-linking catalyst directly with the printing liquid greatly simplified the process, minimizing the necessity of preprocessing the starting powder. Three-dimensional printing of a preceramic polymer not containing any inert or active fillers was proved to be a feasible, convenient and precise process for the production of porous ceramic possessing a complex, ordered structure, such as stretch-dominated lattices.

This work attempts to optimize past research results on lead zirconate titanate (PZT) using the fabrication processes at the U.S. Army Research Laboratory so as to achieve a high degree of {001} texture and improved piezoelectric properties. A comparative study was performed between Ti/Pt and TiO2/Pt bottom electrodes. The results indicate that the use of a highly oriented {100} rutile phase TiO2 led to highly textured {111} Pt which in turn improved both the PTO and PZT orientations. PZT (52/48) and (45/55) thin films with and without PTO seed layers were deposited and examined via x-ray diffraction (XRD) methods as a function of annealing temperature. The seed layer provides significant improvement in the {100} orientation generally, and in the {001} subset of planes specifically, while suppressing the {111} orientation of the PZT. Improvements in the Lotgering factor (f) were observed from an existing Ti/Pt/PZT process (f = 0.66) to samples using the PTO seed layer deposited onto the improved Pt electrodes, TiO2/Pt/PTO/PZT (f = 0.96).

Using metal-oxide-semiconductor devices, we show that the density of interface states at the SiO2/4H–SiC interface can be reduced by applying a N2 heat treatment to a silicon carbide (SiC) surface prior to the deposition of a gate dielectric. Remarkably, this technique yields an interface that is at least as good as the one formed by thermal oxidation in terms of electrically active defects. This improvement can be traced to nitrogen insertion at the semiconductor surface, which provides a seed layer for subsequent deposition. The nature of N incorporation and its impact on electrical properties were studied using x-ray photoelectron spectroscopy, secondary ion mass spectroscopy, and capacitance-voltage measurements. These results offer a new perspective in the quest to maximize minority carrier mobility and minimize energy loss in 4H–SiC switches.

Polyaniline/nano titanium dioxide/graphene nanoplatelet (PANI/TiO2/G) composite was synthesized by mechanochemical route. The structure and morphology of the composite were characterized by Fourier transform infrared spectra, ultraviolet-visible absorption spectra, x-ray diffraction and transmission electron microscopy. The electrochemical performances of the composite were investigated by galvanostatic charge-discharge, cyclic voltammetry, cycling stability and electrochemical impedance spectroscopy. The structure and properties of PANI/TiO2/G composite were compared with that of polyaniline/ graphene nanoplatelet (PANI/G) composite prepared under the same polymerization conditions. After comparative analysis with PANI/G, the effects of the nano titanium dioxide (TiO2) on the structural and physicochemical properties of the PANI/G have been discussed in depth. The comparison suggested that the PANI/TiO2/G composite has higher oxidation degree and lower crystallinity than PANI/G due to the addition of nano-TiO2. Morphology studies showed that PANI and nano-TiO2 particles were both observed on the bent and flat surfaces of graphene nanoplatelet in the PANI/TiO2/G composite. The electrochemical tests showed that the PANI/TiO2/G composite displayed a higher electrochemical activity with specific capacitance of 516 F/g (3 mA/cm2) and better cycle stability than PANI/G.

We present results of a molecular dynamics study using adaptive intermolecular reactive empirical bond order interatomic potential to analyze thermal transport in three-dimensional pillared single-walled carbon nanotube (SWCNT)–graphene superstructures comprised of unit cells with graphene floors and SWCNT pillars. The results indicate that in-plane as well as out-of-plane thermal conductivity in these superstructures can be tuned by varying the interpillar distance and/or the pillar height. The simulations also provide information on thermal interfacial resistance at the graphene–SWCNT junctions in both the in-plane and out-of-plane directions. Among the superstructures analyzed, the highest effective (based on the unit cell cross-sectional area) in-plane thermal conductivity was 40 W/(m K) with an out-of-plane thermal conductivity of 1.0 W/(m K) for unit cells with an interpillar distance Dx = 3.3 nm and pillar height Dz = 1.2 nm, while the highest out-of-plane thermal conductivity was 6.8 W/(m K) with an in-plane thermal conductivity of 6.4 W/(m K) with Dx = 2.1 nm and Dz= 4.2 nm.

Antiperovskite manganese nitrides Mn3MN (M = Zn, Ni, Cu…) have been extensively studied in the past decade due to their many interesting properties, such as negative thermal expansion. To get a better understanding of the origin of these phenomena, the information from the microscopic scale is necessary, so we performed systematic transmission electron microscopic study of Mn3Zn0.8Ni0.2N and found that the sample particle is wrapped in a thin MnO layer. The same result was also found in Mn3Zn0.5Ni0.5N and Mn3ZnN, indicating that it is a common phenomenon in this kind of compound. The presence of the MnO surface layer was also confirmed by the macroscopic XPS measurements. Our study suggests that M is easier to be lost than Mn in manganese nitrides Mn3MN (M = Zn, Ni, Cu…), and this character is much more obvious on the surface, i.e., this kind of compound has a strong surface activity. Figure 6 could best represent this manuscript.

Ni–base alloy coatings were fabricated on 45 steel by laser cladding using a CW-CO2 laser system. The microstructure of the coatings was analyzed using optical microscope (OM), scanning electronic microscope (SEM), and x-ray diffractometer (XRD). The phase fractions, phase compositions, and solidification process in the coatings were calculated using Thermo-Calc software and compared with experimental results. The results show that a dense crack- and porous-free coating with good metallurgical bond is obtained under optimal process parameters. The coatings can be divided into three regions: clad zone (CZ), bonding zone, and heat-affected zone of the substrate. The CZ consists of γ-Ni, M7C3, CrB, and Ni3B phases. Based on the calculated results, the solidification process and reaction scheme in the coatings were discussed. The calculated results obtained from Thermo-Calc software agree with the experimental data well. It is beneficial to the coating design for a desirable microstructure and mechanical properties.

Aluminum alloy castings find extensive applications in automobile and other engineering industries. Production of defect-free castings requires a good understanding of the volume deficit characteristic. The volume deficit of a casting depends on the casting material and casting conditions. Patterson and Engler have classified the volume deficit into four types namely, macrocavities, internal porosity, surface sinking, and volumetric contraction. The influence of process parameters on the characteristics determines the casting quality. The process parameters considered in this study are bottom chill, casting shape, and pouring temperature. Two basic shapes rectangle and cylinder are considered. The volume deficit decreases with an increase in the silicon content. The AA 356.0 alloy shows more amount of volume deficit than AA 413.0 alloy. X-ray computer tomography (XCT) helps to reveal the size, shape, and location of defects in castings. Quantification of internal closed porosity of AA 413.0 casting is done using XCT and successfully validated through destructive testing of castings.

The probability for amorphous silicon (a-Si) to phase transform under indentation testing is statistically determined as a function of annealing temperature from the probability of a pop-out event occurring on the unloading curve. Raman microspectroscopy is used to confirm that the presence of a pop-out event during indentation is a clear signature that a-Si undergoes phase transformation. The probability for such a phase transformation increases with annealing temperature and reaches 100% at a temperature of 340 °C, a temperature well before the temperature where the average bond-angle distortion is fully minimized. This suggests that multiple processes are occurring during full relaxation.

Activated carbon adsorbents with superhigh specific surface areas (SHACs), which are used as adsorbents, were prepared by chemical activation of petroleum coke with potassium hydroxide. We investigated the influence of specific surface area on hydrogen desorption capacity using SHACs with the same pore size distribution, whereas the effect of pore size distribution on hydrogen desorption capacity was studied using SHACs with same specific surface area. Results revealed that hydrogen desorption capacity (N) increased with higher specific surface area (S) of SHAC adsorbents, according to the linear relation: N = k·S + b (k > 0). At 273 K and 9.0 MPa, hydrogen desorption capacity of 20.96 mmol/g (4.02 wt%) was observed on a SHAC adsorbent with a specific surface area of 3348 m2/g. There was a linear relationship between hydrogen desorption capacity and mesopore percentage in SHAC adsorbents, described as: N = k2·Xmic + b (k2 > 0). Hydrogen desorption per unit mesopore surface amounted to 0.72 mmol/m2.

Hyperbranched polyurethane/Fe3O4 nanoparticles decorated multiwalled carbon nanotube (Fe3O4-MWCNT) nanocomposites were prepared by the in situ polymerization technique. The presence of Fe3O4 nanoparticles on the surface of the MWCNTs was confirmed by x-ray diffraction and transmission electron microscopic studies. The saturation magnetization value of Fe3O4-MWCNT was 0.23 emu/g. The glycidyl ether of bisphenol-A epoxy cured thermosetting nanocomposites exhibited enhanced tensile strength (6.4–38.5 MPa), scratch hardness (3.0–8.5 kg), and thermal stability (241–292 °C) with the increase of loading of Fe3O4-MWCNT (0–2 wt%). The nanocomposites possess good shape fixity over the repeated cycles of test. The nanocomposites also showed good shape recovery under the application of microwave irradiation. The shape recovery speed was found to be increased with the increase of the content of Fe3O4-MWCNT. Thus, the studied thermosetting nanocomposites have potential to be used as noncontact shape memory materials.

Copper oxide (CuO) nanosheets synthesized in polyvinylpyrrolidone (PVP) were characterized with respect to antimicrobial activity by quick precipitation method. Different sizes and shapes of CuO nanosheets were obtained by simple variations of PVP concentrations. The x-ray diffraction results revealed the formation of pure-phase CuO with monoclinic structure. Transmission electron microscopy analysis showed that the average ratio of length to width of these nanosheets increased with increasing PVP concentrations. Due to the quantum size effect, CuO nanosheets exhibit a blue shift in the ultraviolet-visible spectra. Field emission scanning electron microscopy results showed that as the concentration of PVP increased, well-defined morphologies were formed on the surface of the products. Energy dispersive analysis of x-ray clearly confirmed the presence of Cu and O with an atomic ratio of 1:1. Fourier transform infrared spectroscopy results showed that C=O in PVP coordinated with CuO and formed a protective layer. The mechanism of the reaction was also discussed. CuO nanosheets in suspension showed activity against a range of bacterial pathogens and fungi with minimum bactericidal concentrations (MBCs) ranging from 100 to 5000 µg/mL. The extent of the inhibition zones and the MBCs was found to be size-dependent.

Novel europium- and gadolinium-doped bismuth phosphate (Eu/BiPO4 and Gd/BiPO4) microcrystals have been synthesized by a hydrothermal route. The morphologies and optical properties of the as-prepared samples were characterized carefully. Their photocatalytic activities were determined by oxidative decomposition of methylene blue (MB) in aqueous solution. The results revealed that europium and gadolinium doping greatly improves the photocatalytic efficiency of BiPO4 microcrystals. Among these as-prepared europium and gadolinium dopant samples, 1% Eu/BiPO4 and 5% Gd/BiPO4 displayed the highest photocatalytic activity, and the degradation rates are 2 and 2.7 times greater than pure BiPO4, respectively. The photodegradation reactions of MB by Eu- and Gd-BiPO4 followed first-order kinetics. The different photocatalytic mechanisms of Eu/BiPO4 and Gd/BiPO4 photocatalysts are discussed.