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Abstract: The pressure-induced phase transformations in LiNH2 have been studied by using ab initio total-energy calculations and evolutionary structure prediction simulations. Two stable high-pressure polymorphs of LiNH2 are found: β-LiNH2 (orthorhombic, NaNH2-type, Fddd) and γ-LiNH2 (orthorhombic, P21212). The β→γ structural transition occurs at 10.7GPa, which is in good agreement with experimental observation. Further analysis of the structural properties, charge density distribution, and calculated phonon density of states indicates that the possibility of the N–H⋯N hydrogen bond occurring in the high-pressure γ-LiNH2 is extremely high. The existence of hydrogen bond weakens the N–H polar covalent bonds within NH2 groups, which can facilitate the hydrogen desorption. [Copyright &y& Elsevier]

Vanadium-based materials are considered ideal for hydrogen separation membranes owing to their higher hydrogen permeability and mechanical strength and lower cost compared with other widely used materials such as Pd alloys. However, pure V exhibits severe hydrogen embrittlement, which is often solved by alloying. In the present study, we used first-principles method to systematically calculate the hydrogen solubility, diffusivity, and other mechanical properties of different V-based binary alloys, namely, V–Co, V–Mo, V–Pd, V–Ru, and V–W. The alloys were found to possess stable crystal structures, and on exposure to hydrogen, the H atoms preferentially occupied the tetrahedral interstitial sites (TISs) in both the pure V and alloy within the material matrix, preferentially diffusing between TISs. The hydrogen diffusion coefficients of the different alloys decreased in the order V–Pd > V–Co > V–Ru > V–Mo > V–W. The alloys and their hydrides also exhibited good mechanical properties, with their resistances to hydrogen embrittlement decreasing in the order V–Co > V–Ru > V–Pd > V–Mo > V–W. This revealed that the resistance to hydrogen embrittlement of the alloy increased with decreasing atomic size of the alloying element. The findings of this study promise to facilitate the development of novel V-alloy membranes for hydrogen separation and purification. Image 1 • Hydrogen prefers tetrahedral interstitial sites in V-based alloys. • Hydrogen embrittlement and diffusion depend on doping element for V-based alloys. • Effects of alloying elements explained by elastic and electronic effects. • Pd-doped sample has higher D H values and better mechanical properties. [ABSTRACT FROM AUTHOR]

Herein a novel carbon nitride (CN) homojunction between Co2+, cyanate group spatially co-doped and undoped domain is first designed via the ZIF-67 self-templated doping and polymeric condensation of CN, for efficient photocatalytic H 2 evolution (PHE). The microstructure characterizations on the ZIF-67 amount-dependent crystallinity and modifications confirm the successful construction of CN homojunction between Co2+-concentrated domain and undoped domain (CoCN). As a result, the optimized CoCN shows an improved PHE rate (2512 μmol·g−1·h−1) 2.93 times that of pristine CN, with further 1.7 times increase after 5 rounds of cycling (4305 μmol·g−1·h−1). Steady-transient photoluminescence and photo-electrochemical investigations demonstrate that ZIF-67 self-templated doping enhances visible light absorption and the separation/transfer of photogenerated carriers. Further energy-band analysis suggests that the coupling of the doped and undoped domains facilitates the built-in electric field and band bending, leading to Self-S-Scheme mechanism of photocatalysis. This work provides a new method for the design of CN-based junctions via ZIF-67 templated doping boosting photocatalytic activity. [Display omitted] • g-C 3 N 4 homojunction between Co2+, cyanate doped and non-doped domains is designed via ZIF-67 self-templated doping. • The optimized CoCN shows improved PHE rate (2512 μmol·g-1·h-1), 2.93 times higher than that of pristine CN. • The 40 CoCN exhibits superior stability and improved PHE rate with cycling (to 4305 μmol·g−1·h−1 after 5th cycling). • The Self-S-Scheme mechanism was proposed to explain the superior PHE performance. [ABSTRACT FROM AUTHOR]

In this study, it is reported for the first time that porous Sm-doped CaFe 0.5 Mn 0.5 O 3-δ (CFMO) has good microwave absorption properties. In this paper, Sm x Ca 1−x Fe 0.5 Mn 0.5 O 3-δ (x = 0,0.05, 0.1, 0.15, 0.2) (Sm-CFMO) sample powders were prepared by the sol-gel method after calcination at 750 °C. Sm-CFMO was characterized using XRD, SEM, TEM, XPS and VSM, and mixed with paraffin wax for VNA testing. The addition of Sm elements increased the porous structure of CFMO, increased interfacial polarization and defect polarization, and increased oxygen vacancy content, resulting in enhanced charge polarization and dipole polarization, while greatly optimizing the impedance matching of CFMO, and the compounding with paraffin wax also increased the composite with paraffin also increases the interfacial polarization capacity of the material, thus improving the microwave absorption performance of the sample. Moreover, as a new type of absorbing material, this material has great potential for development in the field of absorbing materials and provides a new direction for the development of absorbing materials in the future. • A new oxide wave absorbing material. • Sm doping modulates the holes and oxygen vacancies thus changing the microwave absorption properties. • There is still much room for development in the field of wave absorbing materials. [ABSTRACT FROM AUTHOR]

Perovskite LaCoO 3 has unique mixed ionic electronic and structural defects, which has high research value in microwave absorption field. LaCoO 3 precursor was prepared by sol-gel method, and LaCo 1− x Fe x O 3 (Fe-LCO, x = 0, 0.05, 0.1 and 0.15) with rhombic symmetric structure was successfully synthesized at 600 °C. By refinement of X-ray diffraction (XRD) (Rietveld analysis), it was found that Fe doping makes LaCoO 3 lattice constant and cell volume increase. As a dielectric loss microwave absorbing material, the electromagnetic attenuation of LaCoO 3 is mainly due to the conduction loss, while the interface and dipole polarization are secondary reasons. It finds that Fe doping can improve the wave absorption performance of LaCoO 3. The best absorbing performance was obtained when Fe content is x = 0.1, with the maximum reflection loss of − 38.99 dB at 10.8 GHz and the effective absorption bandwidth (RL<−10 dB) is 4.48 GHz, while the corresponding thickness was only 3 mm. In summary, LaCoO 3 has broad application prospects in X and Ku bands. • The study focus on rare earth perovskite can expand and popularized of their application in the field of absorption. • LaCo 1- x Fe x O 3 composites have tunable Impedance matching performance and high-performance microwave absorption by ions doping. • The influence of dielectric loss and magnetic loss on material is analyzed in detail. • Composites can still maintain the effective bandwidth at 4–5 GHz when the reflection loss reached − 30 dB and above. • This work develops the application potential of LaCoO 3 in the field of absorption other than photocatalytic field. [ABSTRACT FROM AUTHOR]

The glass transition kinetics of melt-spun La 65 Al 20 Co 15 amorphous alloy ribbons has been investigated using differential scanning calorimetry (DSC) technique with continuous heating of the sample at different heating rates. The dependence of the glass transition temperature ( T g ) on the heating rate ( β ) has been determined by Lasocka’s relationship. The activation energy ( E ) of the glass transition has been obtained by employing Moynihan and Kissinger methods, respectively. It is found that the glass transition process cannot be described in terms of single activation energy. The variation of E with the extent of conversion ( α ) is further analyzed by using two iso-conversional methods. It is observed that the E of glass transition demonstrates a significant increase with the extent of conversion from amorphous to supercooled liquid phase of La 65 Al 20 Co 15 metallic glass. [ABSTRACT FROM AUTHOR]

The phase equilibrium relationships of the Ho-Fe-B system at 800 °C were investigated using diffusion couples and aided by the application of equilibrium alloys. This is critical for the design of high performance multiphase rare earth permanent magnetic materials. The experimental data were obtained from diffusion couples using scanning electron microscopy (SEM) and electron probe microanalysis (EPMA),and the isothermal section of the Ho-Fe-B system at 800 °C was established. The X-ray diffraction was used to analyze eight essential equilibrium alloys at 800 °C to further determine the reliability of the diffusion couple determination phase diagram. Experimental results clearly show the applicability of the diffusion couples' approach in determining such complex phase diagrams as Ho-Fe-B. The isothermal section at 800 °C was constructed from the results obtained from diffusion couples which contains 17 three-phase equilibrium regions and three stable ternary compounds Ho 2 Fe 14 , Ho 5 Fe 17 B 17 and HoFeB 3. • The phase equilibrium relationship of Ho-Fe-B ternary system is determined by diffusion couple method. • Intermetallic compounds: Ho 2 Fe 14 B, Ho 5 Fe 17 B 17 and HoFeB 3. • High performance multi-phase rare earth permanent magnetic materials. [ABSTRACT FROM AUTHOR]