Deformation twinning is a prevalent plastic deformation mode in hexagonal close-packed (HCP) materials, such as magnesium, titanium, and zirconium, and their alloys. Experimental observations indicate that these twins occur heterogeneously across the polycrystalline microstructure during deformation. Morphological and crystallographic distribution of twins in a deformed microstructure, or the so-called twinning microstructure, significantly controls material deformation behavior, ductility, formability, and failure response. Understanding the development of the twinning microstructure at the grain scale can benefit design efforts to optimize microstructures of HCP materials for specific high-performance structural applications. This article reviews recent research efforts that aim to relate the polycrystalline microstructure with the development of its twinning microstructure through knowledge of local stress fields, specifically local stresses produced by twins and at twin/grain–boundary intersections on the formation and thickening of twins, twin transmission across grain boundaries, twin–twin junction formation, and secondary twinning.

SmTaO4 ceramics have excellent high-temperature phase stabilities and mechanical properties and show great potential for use as next-generation thermal barrier coating (TBC) materials. CeO2–SmTaO4 ceramics are prepared via high-temperature solid–state reaction. It retains a single monoclinic phase structure. Ce4+ was reduced to Ce3+ by high-temperature deoxidation, and the Ce3+ ions substitute for an equal number of Sm3+ ions. The CeO2–SmTaO4 ceramics had lower thermal conductivities [1.09–2.75 W/(m K)] than yttria-stabilized zirconia (YSZ) [2.1–2.7 W/(m K)] at 100–800 °C, which decreased dramatically with increasing temperature. SmTaO4 doped with 2% CeO2 had lower thermal conductivity [1.09 W/(m K), 800 °C] than SmTaO4 [1.42 W/(m K), 800 °C] and 2% ZrO2-doped SmTaO4 ceramics [1.22 W/(m K), 800 °C]. The low thermal conductivity is attributed to Ce3+ substitution for an equal number of Sm3+ ions, and because Ce3+ ions are the strongest phonon scattering centers, they can decrease the phonon mean free path effectively. The thermal expansion coefficient of 8% CeO2–SmTaO4 ceramics is approximately 10.3 × 10−6 K−1 at 1200 °C, which is slightly higher than that of both YSZ (10.0 × 10−6 K−1) and SmTaO4 (9.58 × 10−6 K−1). The outstanding thermophysical properties indicate that CeO2–SmTaO4 ceramics are potential TBC materials.

An atomistic kinetic Monte Carlo coupled with the embedded-atom method is used to simulate film growth and morphology evolution of a Cu–Zn–Sn precursor of Cu2ZnSnS4 solar cells by single-step electrodeposition. The deposition and diffusion events of three different metallic atoms are described by the simulation. Moreover, the multibody Cu–Zn–Sn potential is used to calculate diffusion barrier energy. The effects of process factors, including temperature and electrode potential, on the cross-section morphology and surface roughness are explored, while keeping the elemental composition ratios constant. The lowest roughness with the smoothest morphology is obtained at the optimal parameters. The distribution and transformation behaviors of cluster sizes are investigated to describe the alloy film growth process. Furthermore, the comparison between deposition events and diffusion events reveals that deposition events depend primarily on individual deposition rates of different metallic atoms, but diffusion events are mainly dependent on the interaction of metallic atoms. The film morphology evolution is visualized by three-dimensional configuration with increasing numbers of atoms, which suggests a competing mechanism between nucleation and growth of the thin film alloy.

Using the first-principles calculation combined with the structure searching method, the ternary intermetallic compound (IMC) (Ni0.66, Zn0.33)3Sn4 with $R\bar 3m$ space group is predicted. The energetic, dynamic, thermal, and mechanical stabilities of the (Ni0.66, Zn0.33)3Sn4 IMC are confirmed. The mechanical, thermodynamic, and electronic characteristics at different pressures from 0 to 20 Gpa for the (Ni0.66, Zn0.33)3Sn4 IMC are also investigated. The results show that the (Ni0.66, Zn0.33)3Sn4 IMC possesses a ductile trait within 20 Gpa and that pressurization can increase its elastic modulus, hardness, anisotropy, Debye temperature, and minimum thermal conductivity. At a given pressure, the thermal expansion coefficient α increases significantly below 200 K, and then its increase rate approaches a linear mode as the temperature increases. Compared with the case of 0 GPa, the shapes of the total density of states and partial density of states for the (Ni0.66, Zn0.33)3Sn4 IMC change slightly at pressure 20 Gpa, implying that its structure is still stable under pressure 20 GPa.

Electrochemical reduction of CO2 to formic acid is a good strategy to address both environmental and energy issues. However, some drawbacks including low activity, selectivity, and stability of electrocatalysts must be overcome. We propose a method for tailoring Bi2O2CO3-coated carbon fiber electrodes with higher selectivity and stability for electrochemical CO2 reduction to formic acid. We evaluated the effect of Bi2O2CO3 and Nafion contents on the electrocatalysts performance for CO2 reduction reaction (CO2RR). All electrodes produced only HCOO− in the liquid phase with a maximum faradaic efficiency (FE) of 69%. The electrocatalysts were stable under 24 h of continuous CO2RR operation. The FE increased with the increasing electrolyte concentration and cation radius size, which indicates that the anion stabilization in solution is critical for adequate formate generation. The CO2RR mechanism was proposed with basis on the literature. The structural carbonate of Bi2O2CO3 acts as an intermediate species in the formate production from CO2.

Co–Cr–B amorphous catalysts have been synthesized by the chemical reduction method. Catalyst powders were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Brunner-Emmet-Teller measurements (BET). Catalytic performance of the catalyst was measured by the hydrolysis rate of the sodium borohydride solution. Results showed that the particle size of the catalyst was reduced with the addition of a small amount of Cr. The specific surface area increased significantly, and the performance of the catalyst was improved. However, excess addition of Cr caused excess oxides and Cr3+, covering the surface active sites of the catalyst, which degraded the performance of the catalyst. When the ratio of Cr/Co is 0.005, the catalyst performance was optimal and showed nearly 2 times higher H2 generation rate than that of pure Co–B catalyst. In addition, the effect of catalyst content, NaBH4 concentration, reaction temperature, and NaOH concentration on the hydrogen generation of NaBH4 solution was also studied.

The advantage of alcohol–calcium method on the formation and the stability of vaterite against ethanol–water binary solvents (EWBS) method was studied through comparative experiment. The polymorphs and morphologies of CaCO3 were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results show that vaterite slowly decreases from 90.4 to 82.5% as increasing aging time from 0 to 1320 min in alcohol–calcium system, while quickly decreases from 46.5% to 0% at the same aging time in EWBS system. The similar variation as reaction temperature was found in both systems. SEM images indicate that calcite presents its typical rhombohedral morphology in both systems, while the morphologies of vaterite particles in two systems are different. In alcohol–calcium system, small vaterite nanoparticles aggregate into spherical microparticles, and these microparticles become porous, loose, and irregular, even incomplete, as increasing aging time and reaction temperature, while in EWBS system, vaterite nanoparticles aggregate into irregular microparticles. The advantage of alcohol–calcium method was discussed from the formation of the complex compound CaCl2·n(C2H5OH) in alcohol and its decomplexation in aqueous medium.

The safe and efficient capture of radioactive iodine is highly necessary, but still remains an ongoing challenge. Herein, because of its special layer structure, CuBi–CO3-layered double hydroxides (CuBi–CO3-LDHs) are used to serve as a generic platform, and 3D hierarchical flowerlike ZIF-67/CuBi–CO3-LDH composites are synthesized by a simple coprecipitation method. After immobilization, the flowerlike morphology of CuBi–CO3-LDHs can be completely preserved and proved by scanning electron microscope. Various affecting factors on adsorption performance are investigated, including adsorbent dose, initial concentration of iodine, and temperature. The experimental and modeling results manifest that iodine adsorption is accurately elucidated by pseudo-second-order model, and the equilibrium isotherm is accordant with the Freundlich model. Moreover, the regeneration experiment indicates that ZIF-67/CuBi–CO3-LDH composites possess good stability and reusability for the removal of iodine. The possible adsorption mechanisms of iodine on ZIF-67/CuBi–CO3-LDHs involve particular layer structure and the strong interaction between nitrogen of imidazole ring and iodine, which were investigated by X-ray diffraction, energy-dispersive X-ray, and X-ray photoelectron spectroscopy spectra. The good performance for the iodine adsorption indicates that ZIF-67/CuBi–CO3-LDHs may be identified as a promising adsorbent in the field of iodine capture.

A novel photocatalyst Tm3+/Yb3+–co-doped bismuth molybdate (Bi2MoO6) were synthesized via the hydrothermal method. The samples were characterized through X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectra, and photoluminescence. XPS characterization confirmed the doped rare earth elements. Analysis of the optical properties explained the up-conversion process and its effect on the photocatalytic performance. The as-synthesized samples were employed to decompose Rhodamine B to value its photocatalytic activities under visible light irradiation. The doped samples showed an enhanced photocatalytic activity compared with the bare Bi2MoO6. When the ratio of Tm3+ and Yb3+ was 0.5:5, the degradation efficiency was the highest of 96.1% within 25 min, which was higher than that (74.9%) of pure Bi2MoO6. Moreover, the photocatalytic mechanism of improving the photocatalytic properties was discussed. Besides, the sample showed a super stability in photocatalytic activity. A novel catalyst for industrial pollutant degradation was proposed.

Using evanescent wave (EW)–based optical detection methods coupled with video microscopy, we investigated in situ trajectories, diffusion, and interaction energies of ∼140 nm ceria particles near a glass surface at pH 3, 5, and 7. Trajectories of a single ceria particle in a 2D (x–y) plane were obtained by linking its time-sequenced positions. Diffusion coefficients of several single ceria particles were calculated from their respective mean-square displacement (MSD) versus time curves, and the results were interpreted based on the interaction potential energy curves obtained from Boltzmann statistics of the EW scattering intensity fluctuations of the particles. The types and characteristics of particle motions were determined by analyzing the MSD curves. Whereas both confined or subdiffusive and Brownian motions of the particles were observed at pH 7, only confined motion was seen at pH 3 and 5, and their corresponding diffusion coefficients are similar to those reported by several authors.

In this study, the surface morphology of electrospun polycaprolactone (PCL) fibers was investigated. PCL was dissolved in various solvent/nonsolvent systems (acetone/dimethylformamide (DMF), tetrahydrofuran (THF)/DMF, dichloromethane (DCM)/DMF, chloroform (CF)/DMF, acetone/dimethyl sulfoxide (DMSO), THF/DMSO, DCM/DMSO, CF/DMSO) at a fixed ratio of 80/20 v/v. PCL solutions from these solvent systems were electrospun under varying high relative humidity (60–90%), and also room humidity. Characterization of fibers was evaluated by a scanning electron microscope, an atomic force microscope, water contact angle measurements, the Brunauer–Emmett–Teller method, and a strain–stress test. Results revealed that the surface texture of individual fibers changed with the presence of different types of pores and surface roughness depending on both humidity and solvent/nonsolvent properties. Miscibility with water was another factor to be taken into account for understanding mechanisms that contributed to the formation of surface defects. Fibrous materials having such a surface architecture, especially the porous ones, are potential candidates for various applications such as tissue engineering, drug delivery, catalysis, and filtration.