Facile synthesis of nanosized sodium magnesium hydride, NaMgH₃

The ternary magnesium hydride NaMgH3 has been synthesised via reactive milling techniques. The method employed neither a reactive H2 atmosphere nor high pressure sintering or other post-treatment processes. The formation of the ternary hydride was studied as a function of milling time and ball:powder ratio. High purity NaMgH3 powder (orthorhombic space group Pnma, a=5.437(2) Å, b=7.705(5) Å, c=5.477(2) Å; Z=4) was prepared in 5 h at high ball:powder ratios and characterised by powder X-ray diffraction (PXD), Raman spectroscopy and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX). The products formed sub-micron scale (typically 200–400 nm in size) crystallites that were approximately isotropic in shape. The dehydrogenation behaviour of the ternary hydride was investigated by temperature programmed desorption (TPD). The nanostructured hydride releases hydrogen in two steps with an onset temperature for the first step of 513 K

Porous single-phase NiTi processed under Ca reducing vapor for use as a bone graft substitute

Porous nickel–titanium alloys (NiTi, nitinol®) have recently attracted attention in clinical surgery because they are a very interesting alternative to the more brittle and less machinable conventional porous Ca-based ceramics. The main remaining limitations come from the chemical homogeneity of the as-processed porous nickel–titanium alloys, which always contain undesired secondary Ti- and Ni-rich phases. These are known to weaken the NiTi products, to favor their cavitation corrosion and to decrease their biocompatibility. Elemental nickel must also be avoided because it could give rise to several adverse tissue reactions. Therefore, the synthesis of porous single-phase NiTi alloys by using a basic single-step sintering procedure is an important step towards the processing of safe implant materials. The sintering process used in this work is based on a vapor phase calciothermic reduction operating during the NiTi compound formation. The as-processed porous nickel–titanium microstructure is single-phase and shows a uniformly open pore distribution with porosity of about 53% and pore diameters in the range 20–100 μm. Furthermore, due to the process, fine CaO layers grow on the NiTi outer and inner surfaces, acting as possible promoting agents for the ingrowth of bone cells at the implantation site

The temperature dependence of the Raman T2g lattice mode in K2S crystals

The first-order Raman spectrum of K[2]S was measured over the temperature range from 10 to 742 K. The temperature dependence of the linewidth can be explained using results from the anharmonic lattice dynamics approach. Both the cubic and the quartic anharmonic interactions are of importance for this system. At 293 K, the Raman line is at ω[T2g]=128 cm[−1] with a full width at half maximum Γ[T2g]=2.9 cm[−1]

Alternative powder metallurgical processing of Ti-rich NiTi shape-memory alloys

Ti-rich NiTi shape-memory alloys have been fabricated from elemental powders using an alternative powder metallurgical method based on the use of a reducing metal vapor during sintering. The produced alloys show high chemical homogeneity, low porosity and large shape-memory effects with recovery strains up to 3.9% for an applied stress of 80 MPa