An electrodeposition method for growing epitaxial Co(OH)2 films on single crystalline gold (111), (100), and (110) substrates is described. The films were grown by electrochemical reduction of [Co(en)3]3+ in an alkaline electrolyte. The Co(OH)2 grew with a [0001] out-of-plane orientation on all the gold crystal orientations. The in-plane orientation follows the symmetry of the gold (111), (100), and (110) substrates. The Co(OH)2 can be converted to CoOOH by electrochemical oxidation in 1 M KOH at 95 °C, and after conversion remains epitaxial with a [0001] out-of-plane orientation. The CoOOH film can be further converted to epitaxial Co3O4 with a [111] out-of-plane orientation by decomposition of the CoOOH film in air at 300 °C. This synthesis method allows for a simple fabrication of epitaxial catalysts and could be useful to probe the catalytic activity of specific crystal planes.

The effects of annealing temperatures on the structure and photocurrent response of nanoporous iron oxide film prepared by anodization of iron foil in an ethylene glycol, NH4F, and H2O electrolyte were studied. The as-anodized anodic film was found to be rather amorphous and crystallized to predominantly α-Fe2O3 upon annealing in nitrogen. Nitrogen was used as to reduce the thickening of the barrier layer which affects the photocurrent response of the oxide. However, annealing must be done above 300 °C to produce crystalline oxide but must be kept lower than 500 °C since high temperature promotes grain growth, destroying the nanoporous structure and also thickens the barrier layer, which significantly reduce the photocurrent of the film. Sample annealed at 450 °C in nitrogen has the highest photocurrent of 1.04 mA/cm2 (0.5 V versus Ag/AgCl in 1 M NaOH) compared to 0.13 mA/cm2 at 0.5 V for air-annealed sample.

This paper presents an atomistic scale model on sintering of nickel particles in direct metal laser sintering process. Both sintering phenomena and mechanical strength of sintered particles are simulated using molecular dynamics method. A two-particle atomistic model is developed to investigate the diffusion of atoms during nickel sintering. The diffusion of particle surface is higher than the particle core, with calculated activation energy of nickel particle diffusion 6.10 kJ/mol in the particle core, and 6.24 kJ/mol on the particle surface, which are reasonably in agreement with the experimental data of 7.89 kJ/mol. The sintered model shows a 5-fold twinning structure at 1200 K, and two parallel twin boundaries at 1300 K. The mechanical properties of nickel nanoparticles sintered at various heating rates are investigated using uniaxial tensile test simulations. The results show that higher heating rate during sintering increases the mechanical strength of the sintered material. Deformation mechanism of sintered structures is illustrated from the correlation between stress and dislocation evolution.

Although there are numerous reports on the synthesis of spherical materials, the development of new approaches remains important for theory construction to realize tailor-made synthesis of spherical materials. Herein, we report the synthesis of polydispersed spherical particles of H2Ti2O5 intercalated with a polyethyleneamine, such as an ethylenediamine, on the basis of a solvothermal treatment using concentrated polyethyleneamine aqueous solutions. The diameter of the micrometer-sized spheres enlarged with increasing amine concentration in the reaction solution. It was speculated that high ionic strength caused the self-assembly of polyethyleneamine-intercalated H2Ti2O5, resulting in the formation of spherical agglomerates. The spheres had a specific a surface area of 200 m2 g−1 and approximately 5 nm pores, and these values were controlled by amine concentration and treatment time. Conversion to single phase anatase and rutile without changes in spherical morphology was achieved by heat treatment. The present approach may assist with the design morphology of agglomerates.

This paper critically evaluates methods used to synthesize boride compounds with emphasis on diborides of the early transition metals. The earliest reports of the synthesis of boride ceramics used impure elemental powders to produce multiphase reaction products; phase-pure borides were only synthesized after processes were established to purify elemental boron. Carbothermal reduction of the corresponding transition metal oxides emerged as a viable production route and continues to be the primary method for the synthesis of commercial transition metal diboride powders. Even though reaction-based processes and chemical synthesis methods are mainly used for research studies, they are powerful tools for producing diborides because they provide the ability to tailor purity and particle size. The choice of synthesis method requires balancing factors that include cost, purity, and particle size with the performance needed in expected applications.

C3N4/Bi2WO6 heterojunction photocatalysts were successfully synthesized using consecutive hydrothermal and calcination processes. These photocatalysts were characterized using x-ray diffraction, scanning electron microscopy, transmission electron microscopy, ultraviolet-visible diffuse reflectance spectroscopy, x-ray photoelectron spectroscopy, and photoluminescence measurements. The results of these measurements indicated that the Bi2WO6 nanoparticles were approximately 30–50 nm and uniformly distributed on the surface of C3N4 lamellar structures. The 20% C3N4/Bi2WO6 displayed enhanced visible-light absorption from 432 nm to 468 nm. Photocatalytic tests also revealed that the 20% C3N4/Bi2WO6 photocatalyst exhibited significantly enhanced photocatalytic activity compared to that of pure C3N4 and Bi2WO6 under irradiation by visible light (λ > 420 nm). Furthermore, the excellent photocatalytic efficiency of the 20% C3N4/Bi2WO6 photocatalyst was determined to be related to the formation of C3N4/Bi2WO6 heterojunctions, and their presence was found to be generally beneficial for the separation of photogenerated electron–hole pairs.

This study reports new facile approach for gram-scale synthesis of graphene-like nanosheets fine powder, using glucose as precursor. Reduced graphene oxide (RGO) has been prepared in gram-scale via hydrothermal treatment of glucose. Upon increasing the vapor/liquid ratio for aqueous glucose solution within the autoclave system to 3/2, RGO-rich graphitic powder, containing small graphene oxide and amorphous carbon contents and having spherical morphology, is obtained. Then, introducing ammonia into the reaction medium resulted in the formation of pure RGO with reduced O-content and flat nanosheet-like morphology (Amm–RGO3/2). Interestingly, few-layer graphene-like nanosheets with slight oxygen and amorphous carbon contents and few structural defects are produced when annealing Amm–RGO3/2 at 600 °C under inert atmosphere. In summary, hydrothermal treatment of aqueous solution containing just glucose and ammonia followed by moderate-temperature thermal annealing, lead to few-layer graphene-like nanosheets with good structural characteristics. This new simple and efficient approach can be of great potential in the mass production of graphene-like nanosheets.

Selective area growth of thin films reduces the number of steps in microfabrication processing and enables novel device structures. Here, we report, for the first time, selective area epitaxy of an oxide material on a GaN surface. Chlorination of the GaN surface via wet chemical processing is found effective to disrupt Mg adsorption and selectively prevent molecular beam epitaxy growth of MgO. MgO films grown on neighboring, nonchlorinated surfaces are epitaxial with a (111) MgO||(0001) GaN crystallographic relationship. Better than 3 μm lateral resolution for the selective area growth of MgO on GaN is demonstrated.

We investigated FeCoNiCrAl0.8 high entropy alloy and amorphous alloy powders synthesized simply via high energy ball milling for 10 and 20 h. The electromagnetic wave absorption properties of FeCoNiCrAl0.8 high entropy alloy and amorphous alloy powders were investigated. The structure and morphology of FeCoNiCrAl0.8 were analyzed by scanning electron microscopy with energy-dispersive spectrometry and x-ray diffraction, which demonstrated that FeCoNiCrAl0.8 powders were in irregular shape and monodisperse with an average size of 5–15 µm. The minimum reflection loss of FeCoNiCrAl0.8 high entropy alloy powders was −41.8 dB at 11.9 GHz with a thickness of 2.3 mm and effective bandwidth (RL ≤ −10 dB) was up to 4.7 GHz (8.7–13.4 GHz), while the minimum reflection loss of FeCoNiCrAl0.8 amorphous alloy powders was observed to be −35.5 dB at 14.6 GHz with a thickness of 1.7 mm and effective bandwidth varied from 12.7 to 16.3 GHz (3.6 GHz). Electromagnetic wave absorption properties of FeCoNiCrAl0.8 high entropy alloy powders is better than that of amorphous alloy powders, which demonstrated that phase structures of FeCoNiCrAl0.8 alloy powders affect electromagnetic wave absorption properties.

The deformation mechanisms responsible for the strength and ductility of nanostructured Cu and Cu–Al alloys processed by high pressure torsion have been analyzed in frames of a model of elastic–plastic medium and using the available experimental data. The income of the Peierls strength, as well as solid solution hardening, dislocation hardening, twinning hardening, taking into account possible annihilation processes has been estimated. It was shown that in the Cu–5 at.% Al alloy annihilation processes contribute to the maintenance of deformation. The material is hardened by the accumulation of dislocations at the twin boundaries, postponing the moment of reaching the ultimate strength. In the Cu–16 at.% Al alloy processes of the annihilation are limited. As a result, the possibility of further deformation is limited and the degree of homogeneous deformation decreases in comparison with the case of the Cu–5 at.% Al alloy. Significantly increased concentration of deformation vacancies contributes to the destruction of the former alloy as well.

The mechanical behavior of superconductor lamellar-like BaFe2As2 single crystals was investigated at nanoscale by instrumented indentation. The unique responses of the ab- and a(b)c-crystallographic planes were discussed based on their influence in hardness (H) and elastic modulus (E). The results allowed two main conclusions. (i) The choice of testing parameters strongly affected the scaling of mechanical properties on the lamellar surfaces. Lamellar cracking was the leading mechanism of deformation, featuring a brittle-like behavior and affecting considerably H and E. However, the plastic deformation history allowed different elastic–plastic responses on the ab-plane owing to the compaction of the material. Threshold loads for cracking depended on both loading rate and penetration velocity, pointing out to time-dependent plastic deformation mechanisms. (ii) Proper estimates were achieved for H in multiple loading tests [3.4 GPa for ab- and ∼1 GPa for a(b)c-planes], and for E under loads less than 3 mN (∼55 GPa for both planes).

Experimental studies have shown capacity loss and impedance rise on the surfaces of cathode particles during (dis)charging in lithium-ion batteries. However, there are surprisingly few studies focusing on the cathode–electrolyte interface. The current study uses multiphysics finite element models to understand fluid–structure interactions in a half-cell battery system. Effects of C-rate, particle sizes, lithiation, and phase transformation of the cathode at the interface are investigated. Results demonstrate that doubling the particle size results in larger available lithium intercalation areas, giving rise to increased tension 1.40 times and compression 1.82 times at the interface. Moreover, higher C-rate with high lithium-ion concentration gradient results in higher mechanical stresses at the interface. These coupling factors are strongly related to the experimentally observed battery degradation. Our simulations demonstrate that both electrode and electrolyte have pronounced effects when investigating mechanical stresses at the electrode–electrolyte interface.

Dynamic loading of the hat-shaped specimen of 2195-T6 aluminum lithium alloy was carried out with a split Hopkinson pressure bar at ambient temperature. The formation and evolution mechanisms of adiabatic shear band (ASB) in this alloy were investigated and then microstructure was further observed. The microstructure within ASB in 2195 aluminum alloy was characterized by means of optical microscopy and transmission electron microscopy. The width of ASB was about 20–30 um. Nano-grains (50–100 nm) were observed in the middle of shear zone. Experimental results show that the diffusive transformation took place within ASB during high strain rate deformation, namely the precipitates dissolving in the matrix in the process (within about 71 µs). Based on thermodynamics and kinetics analyses, dissolution of precipitates was firstly investigated during adiabatic shearing deformation, and a dissolution model was suggested in the present work. The diffusive transformation and the microstructure evolution within ASB in 2195 alloy were explained.

The mesoporous network within photocatalytically and photoelectrochemically active LaTiO2N (LTON) single crystals was investigated by electron microscopy techniques including electron diffraction and scanning transmission electron microscopy imaging. The perovskite-related oxynitride particles were obtained by thermal ammonolysis from monocrystalline micrometer-sized La2Ti2O7 (LTO) particles grown by flux-assisted solid state synthesis. Special attention was paid to the crystal transformation from the monoclinic layered LTO to the orthorhombic perovskite-related LTON within the monocrystalline particles. A detailed analysis of pore directions and pore sizes with respect to the LTON particle shape was performed. The pore formation mechanism taking place during thermal ammonolysis was discussed. Based on the mechanistic understanding of the transformation from the oxide to the oxynitride, a further extension of the mesoporous network toward higher surface areas was proposed for improved photoelectrochemical activity of oxynitride particles, while high crystallinity and particle sizes in the micrometer range continue to enable efficient charge transport.

In this paper, we determine the electronic transport properties of Au–C20–Au molecular system under finite bias voltage using the non-equilibrium Green function and the density functional theory, along its localized pseudo atomic orbitals. Our aim is to peruse the various nanometer-scale transport properties and eventually predict the overall quantum transport behavior of this organic mesoscopic system. We investigate the density of states, transmission spectrum, molecular orbitals, current–voltage characteristics, rectification ratio, and differential conductance characteristics at discrete bias voltages to get the insight about various transport phenomena. The observed results elucidate that the quantum tunneling causes the electron transport in this molecular bridge and becomes prominent due to strong mechanical interactive coupling between the molecule and the electrodes having low HOMO–LUMO (highest occupied molecular orbital–lowest unoccupied molecular orbital) gap of 0.55 eV. We conclude that Au–C20–Au device exhibited metallic nature forming the current coulomb staircase with transition points at ±1 V and the quantum conductance of order 2G0 at low bias voltages.

Pt based alloys are one of the most important intermetallic materials with widespread applications. In this article, we have investigated the structural stability, elastic modulus, and electronic structure of Pt3M alloys by applying first-principles density functional theory, where M atom covers alkali metals, alkali earth metals, main group metals, and transition metals. The calculated elastic constants and elastic modulus demonstrated that all Pt3M alloys studied in this article are mechanically stable, possess good stability against shear and behavior in a ductile manner. The equilibrium lattice constant and the binding energy are also calculated to reveal the law with the change of elements. In addition, the LDOS and deformation charge density is presented to reveal the structural stability and the extent of charge transfer between Pt and M atoms. These results help us to better understand the physical properties of Pt3M alloys and also indicate that Pt3M alloys provide an extensive selection of intermetallic materials.

Poly(lactic acid) (PLA)/graphene oxide (GO) nanocomposites were prepared by solution mixing. Differential scanning calorimetry results indicated that GO was an effective nucleating agent. The size of spherulites decreased, the density of spherulites increased with increasing GO and the crystallinity of PLA increased from 4.34 to 49.01%. For isothermal crystallization, the crystallization rates of PLA/GO nanocomposites were significantly higher than that of neat PLA, in which t 0.5 reduced from 9.0 to 2.8. Spindle-like nanopores (about 100–200 nm) that arranged like spherulites were prepared by low temperature foaming. It was found that the crystallization rate increase and spherulite morphology change were insignificant when the content of GO exceeded 0.5 wt%, because the excessive GO increased the number of nucleation sites while restricting the PLA crystal growth. Thus, the arrangement of nanopores did not mimick the spherulites because of imperfect crystal morphology.

A series of Ni0.5Zn0.5Fe2O4 (NZO)/polyvinylidene fluoride (PVDF) composites were prepared and studied for their potential application as magneto-dielectric antenna substrate materials. The NZO ferrite powders were synthesized by the solid-state reaction method and then annealed at different temperatures of 700, 900 and 1100 °C. The influence of the annealing treatment on the grain size, crystallinity and magneto-dielectric properties were discussed. The magnetic and dielectric properties of the composites were measured in 1 MHz–1 GHz and 100 Hz–1 GHz, respectively. With the annealing temperature increase from 700 to 1100 °C, the initial permeability of the composites increases from 3.89 to 7.93, while the static permittivity changed regularly with the growing grain size. Almost equal values of μ′ and ε′ are obtained in the composite sample with the 1100 °C annealed NZO powders. Considering the relatively low magnetic and dielectric loss tangent, this material is the promising candidate for the design of miniaturized antennas.

The structure changes and lithium intercalation properties in the surface region of Li4Ti5O12 were investigated using epitaxial Li4Ti5O12(111) film model electrodes. The discharge–charge measurements, which were conducted with 1 mol/dm3 LiPF6-containing propylene carbonate, revealed that a 23.8 nm-thick film exhibited a small capacity of 115 mA h/g compared to the theoretical value of 175 mA h/g. In situ neutron reflectometry and ex situ x-ray diffractometry and reflectometry indicated that an irreversible phase change had occurred in the 10-nm surface region of Li4Ti5O12 during the initial reaction processes. The level of deterioration of the surface structure was significantly reduced by decreasing the LiPF6 concentration; in addition, side reactions of the cell components with the electrolyte species, and their products, may be associated with the deterioration of the Li4Ti5O12 surface. The surface reactions have a significant impact on the capacity of lithium intercalation in nano-sized Li4Ti5O12.

A series of Ag2S/Ag2WO4 composite microrods with different Ag2S contents (10–50 wt%) were synthesized via a facile successive precipitation route. The texture and optical properties of the pure Ag2S, Ag2WO4, and Ag2S/Ag2WO4 composites were intensively characterized by some physicochemical characterizations like N2 physical adsorption, x-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, Ultraviolet–visible spectroscopy, x‐ray photoelectron spectroscopy, photoluminescence spectroscopy, and photocurrent measurements. Under visible light irradiation, different organic dyes, e.g., methylene blue and methyl orange dye were applied to evaluate the photocatalytic performances by their photocatalytic degradation reactions. The Ag2S/Ag2WO4 composite microrods exhibited superior photocatalytic activity and stability. The high crystallinity of Ag2WO4 and improved texture properties of Ag2S/Ag2WO4 resulted in their enhanced photocatalytic property. More importantly, the Ag2S/Ag2WO4 heterojunctions with matching electronic band structures obviously enhanced the separation of photo‐generated electrons and holes, further promoting the photocatalytic reaction.