Nickel decorated MoO3 single crystal microflakes with multi-site functionality for enhanced hydrogen evolution reaction

Role of hybrid material with metal-oxide interface has been explored by coating 2 nm nickel on α-MoO₃ single crystals for hydrogen evolution reaction (HER). The investigated aspects reveal that α-MoO₃/Ni hybrid exhibits a remarkable performance in HER showing +6 mV onset potential and 37 mV overpotential at 10 mA/cm² current density along with Tafel slope of 47 mV/dec. The single crystalline-stepped CVD-grown MoO₃ microflakes having the advantage of higher hydrogen binding energy of Ni exhibits the enhanced catalytic performance due to strong electronic coupling at the metal-oxide interface and hydrogen spill over effect. Similar hybrid material composed of Cu-MoO₃ does show improvement but not as good as Ni-MoO₃. A decrease of ~36% is observed in the overpotential for Ni-coated MoO₃ compared to pure MoO₃ crystals indicating the positive contribution of Ni-coating. The hybrid Ni-MoO₃ shows the new route to develop alternate transition metal oxide-based hybrid catalyst towards production of hydrogen fuel.     

Dielectric behavior of polyetheretherketone (PEEK) using TSDC technique

The dielectric relaxation behavior of Polyetheretherketone (PEEK) has been investigated by using thermally stimulated discharge current (TSDC) technique. The dependence of TSDC characteristics of PEEK on poling temperature (T_P) [50–200 °C], poling field (E_P) [200–500 kV/cm], storage time (t_S) [2–120 hrs] and various thicknesses 25 μm, 50 μm and 75 μm have been investigated in the temperature range [60–230 °C]. The TSDC spectra shows a prominent maxima around glass transition temperature (T_g) i.e. at 143 °C named as α-peak and the other peak is observed around 200 °C named as β-peak. The α-dipolar relaxation is taking place because of the movement of ketone (>C = 0) dipoles linked to the main chain. The β-peak is attributed to the space charges. It is observed that the magnitude of α-peak increases with the increase in poling field. The peak current and area under the α-peaks are found to be diminished with the increase of storage time (t_s) for electrets. The amplitude of α-peak decreases with the increase in thickness. The activation energies for PEEK sample at different conditions in the present work are found to be 0.38 eV–1.70 eV. The values of activation energy (U) and pre-exponential factor (τ _o) for α- relaxation are determined using Bucci plot method and support the nature of the relaxations.     

Cryogenic Processing: A Study of Materials at Low Temperatures

Cryogenics is an exciting, important and inexpensive technique that already has led to main discoveries and holds much future assurance. Cryogenic processing is the treatment of the materials at very low temperature around 77 K. This technique has been proven to be efficient in improving the physical and mechanical properties of the materials such as metals, alloys, plastics and composites. It improves the wear, abrasion, erosion and corrosion resistivity, durability and stabilizes the strength characteristics of various materials. Cryogenic refines and stabilizes the crystal lattice structure and distribute carbon particles throughout the material resulting a stronger and hence more durable material. In present paper, we have reviewed the effect of cryogenic treatment on some metals, alloys, plastics and composites.     

Conifer-Derived Metallic Nanoparticles: Green Synthesis and Biological Applications

The use of metallic nanoparticles in engineering and biomedicine disciplines has gained considerable attention. Scientists are exploring new synthesis protocols of these substances considering their small size and lucrative antimicrobial potential. Among the most economical techniques of synthesis of metallic nanoparticles via chemical routes, which includes the use of chemicals as metal reducing agents, is considered to generate nanoparticles possessing toxicity and biological risk. This limitation of chemically synthesized nanoparticles has engendered the exploration for the ecofriendly synthesis process. Biological or green synthesis approaches have emerged as an effective solution to address the limitations of conventionally synthesized nanoparticles. Nanoparticles synthesized via biological entities obtained from plant extracts exhibit superior effect in comparison to chemical methods. Recently, conifer extracts have been found to be effective in synthesizing metallic nanoparticles through a highly regulated process. The current review highlights the importance of conifers and its extracts in synthesis of metallic nanoparticles. It also discusses the different applications of the conifer extract mediated metallic nanoparticles.     

Dynamics of Consolidation and Crack Growth in Nanocluster-Assembled Amorphous Silicon Nitride

Consolidation and fracture dynamics in nanophase amorphous Si3N4 are investigated using 106-atom molecular-dynamics simulations. At a pressure of 15 GPa and 2000 K, the nanophase system is almost fully consolidated within a fraction of a nanosecond. The consolidation process is well-described by the classical theory of sintering. Under an applied strain the consolidated system develops several cracks which propagate parallel to each other, causing failure at multiple sites. The critical strain at which the nanophase system fractures is much larger than that for crystalline Si3N4.