Volume 115, Issue 1

Thanks to the development of quantum mechanics-based crystal structure prediction methods in the past decade, numerous new compounds with low temperature thermodynamic stability, mainly binary intermetallic compounds, have been predicted. Differing from conventional alloy materials, the synthesis of these low temperature stable compounds may be impossible relying on traditional thermal activation methods since thermally activated atomic diffusion at low temperatures is so slow that phase formation may require cosmic-scale time. Strikingly, it has been shown that some special experimental methods can successfully synthesize low temperature stable compounds by introducing a large number of vacancies and defects into the material to enable atomic rearrangement and simultaneously increasing the phase transformation driving force to accelerate the reaction kinetics. This review summarizes the predictions of compounds that have not been experimentally reported to be stable at low temperatures and provides some experimental approaches that can be used for future synthesis. We describe the basic thermodynamics and kinetics of phase formation, show how compound formation is constrained at low temperatures, and illustrate that the formation of some compounds is nearly impossible without enhanced kinetics.

BaTi 5 O 11 nanocrystals were synthesized by a hydrothermal method, and the effect of oleic acid (OA) in the Ba–Ti precursors on morphologies of BaTi 5 O 11 nanocrystals was investigated. As the OA/(Ba 2+ + Ti 4+ ) molar ratio ranged from 0 to 8, single-phase BaTi 5 O 11 nanocrystals were synthesized at 260 °C for 20 h. When OA reagent was not added to the precursors, rice-like BaTi 5 O 11 nanocrystals were obtained. As the OA/(Ba 2+ + Ti 4+ ) molar ratio was 1, elongated lath-like BaTi 5 O 11 nanocrystals were synthesized with the width of about 130 nm, thickness of about 50 nm and length of about 400 nm. With increasing the OA/(Ba 2+ + Ti 4+ ) molar ratio from 1 to 6, the grain size of elongated lath-like BaTi 5 O 11 nanocrystals gradually decreased. As the OA content increased, the amount of adsorbed OA molecules on the surface of Ti(OH) x nucleus increased and hindered the reaction of Ba 2+ ions with Ti(OH) x nucleus, which caused the decrease of grain size of lath-like BaTi 5 O 11 nanocrystals. When the BaTi 5 O 11 nanocrystals were synthesized at OA/(Ba 2+ + Ti 4+ ) molar ratio of 1, they had the largest dielectric constant ( ε r ) of 40.9 at 5 GHz.

The present study reports an economical and environmentally friendly technique for the synthesis of zinc oxide nanoparticles. The water extract of Averrhoa bilimbi (L) fruit was used in this one-pot synthesis approach for ZnO nanoparticle reduction and stabilisation. Varied size, shape and properties of the synthesized nanomaterials were obtained by tuning the pH of the synthesis medium. X-ray diffraction techniques, diffuse reflectance spectroscopy, photoluminescence and scanning electron microscopy analysis were used for characterizing phytochemical capped ZnO nanoparticles. The morphological change with varying pH was observed from scanning electron microscopy images. Short duration of synthesis with high yield product at ambient room temperature are the salient features of this procedure. The synthesised ZnO nanoparticles showed excellent photocatalytic activity and superhydrophilicity to be used in a wide range of applications.

In this study, a nanocomposite film comprising poly(vinyl alcohol) (PVA) and rice husk-derived cellulose nanocrystals (CNC) was introduced as a novel sorbent for removing copper (II) cations. First, CNC was isolated from neat rice husk, and then these particles with many ratios compared to PVA (2, 4, 6, and 10 wt.%) were added to the PVA solution to render the nanocomposite films. The obtained films were evaluated using scanning electron microscopy, Fourier-transform infrared spectroscopy, and water uptake tests. The optimal condition for the sorbent preparation was 10 wt.% of CNCs to PVA. The maximum ion adsorption percentage of the PVA/CNC 10 % film reached 55 % after 3 h exposure to 70 ppm Cu (II) ion solution at 25 °C. This research suggested a facile and feasible fabrication method of a nanocomposite film, considered a potential sorbent for the adsorption of copper (II) ions.

Titanium and its alloys are extensively used for medical implant material due to their superior biocompatibility, corrosion resistance, and strength. However, fabrication of corrosion free titanium and its alloys is still a challenging task since it might affect the surrounding tissues. Therefore, some protection is needed to enhance the performance of the implants in the body in terms of biocompatibility and corrosion resistance. In this work, the hybrid of gelatin-based forsterite–hydroxyapatite synthesized by the sol–gel process was coated by dip-coating on titanium alloy (Ti6Al4V). The variable concentration effects of forsterite–hydroxyapatite in gelatin matrix and the coating applications on the surface morphology as well as corrosion performance of coated substrates were evaluated. The electrochemical corrosion behaviour was investigated through Tafel polarization curves. Outcomes show that the substrate prepared with 5 wt.% of forsterite–hydroxyapatite has a maximum corrosion resistance, crack-free coating, is hermetic and adherent to the substrate.

Nanostructured molybdenum (Mo)-doped Mn 3 O 4 thin films were successfully deposited on stainless steel substrates by a facile electrophoretic deposition technique. The effect of Mo doping on the structural and supercapacitive properties of Mn 3 O 4 thin films was investigated. The nanostructured morphology of spinel tetragonal Hausmannite Mn 3 O 4 thin films was elucidated with the help of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Raman studies. The presence of mesopores in the nanostructure with an average pore size of 41 nm was confirmed by Brunauer–Emmett–Teller studies. The different valence states of Mn and Mo are confirmed by X-ray photoelectron spectroscopy. The symmetrical quasi-rectangular-shaped cyclic voltammetry curves without any redox peak and nearly triangular/symmetric galvanostatic charge–discharge curves for Mn 3 O 4 thin films elucidated the pseudocapacitive behavior. Electrochemical impedance spectroscopy revealed that pure and Mo-doped Mn 3 O 4 thin films have lower resistances. Improved supercapacitive performance of 2 % Mo-doped Mn 3 O 4 thin film was confirmed by higher specific capacitance 497 F g −1 at a current density of 1.6 A g −1 . The boosted supercapacitive performance of Mo-doped Mn 3 O 4 thin films has identified the outstanding incorporation of Mo ions into the Mn 3 O 4 lattice.

The micro-arc oxidation process is used to improve the properties of 6063 aluminum alloy by forming coatings on the surface of the alloy, in order to further enhance the features of the basic micro-arc oxidation coatings, graphene was added into the silicate alkaline electrolyte. The addition of the graphene influences the surface morphologies, thickness, element distributions, phase compositions, wear resistance and corrosion resistance of the formed coatings. They were studied by means of scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, friction and wear testing and an electrochemical workstation. The results show that the microstructure and properties of the coating were modified with the increase of graphene concentration. However, when too much graphene was added, the performance of the coating became worse.

In this current research work, magnesium AZ61 (Advancing Side) and aluminum 6061-T6 (Retreating Side) alloys were joined using the zinc interlayer friction stir welding technique at the optimum process parameters. The aim of this work is to propose an effective alternative to overcome issues related to aluminum/magnesium joints. This article investigates the effects of zinc foil (0.2 mm) on the weld surface (3 mm aluminum/magnesium plates), intermetallic compound characteristics, microstructure, fracture surface and strength of joint. The emergence and nature of intermetallic compounds during aluminum/magnesium and aluminum/zinc/magnesium friction stir welded joints were studied in detail. As can be seen from the findings, using zinc in aluminum/magnesium friction stir welded joints inhibits the emergence of brittle aluminum–magnesium intermetallic compounds and promotes the formation of magnesium–zinc intermetallic compounds in the stir zone by introducing the zinc interlayer, confirmed through X-ray diffraction analysis. Furthermore, the average tensile performance (181.33 MPa) of friction stir welded aluminum/zinc/magnesium joints was enhanced up to 18.26 % compared to aluminum/magnesium friction stir welded joints (153.33 MPa). The promising results of this research establish an alternative route with a cost-effective technique to enhance the aluminum/magnesium dissimilar joint strength.