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The present work reports a feasibility study of the direct mechano-chemical synthesis by controlled reactive mechanical alloying (CRMA) in a magneto-ball mill of the nanostructured magnesium tetrahydroaluminate (magnesium alanate) Mg(AlH(4))(2) complex hydride. Three stoichiometric Mg-2Al mixtures, (a) elemental Mg and Al powders, (b) elemental Al powder and commercial AZ91 alloy (Mg-Al-Zn alloy) and (c) powder of as-cast Mg-2Al alloy, have been used. No successful synthesis of Mg(AlH(4))(2) has been achieved. The only nanocrystalline hydride formed up to 270 h of CRMA is beta-MgH(2), and it does not react with Al and H(2) to form Mg(AlH(4))(2). It has been found that there is strong competition between formation of Al(Mg) solid solution and the beta-MgH(2) hydride occurring to a various extent up to approximately 10 h of CRMA in all three Mg-2Al mixtures. It is hypothesized that the presence of Al(Mg) solid solution inhibits the reaction of beta-MgH(2), Al and H(2) to form Mg(AlH(4))(2). Furthermore, despite the fact that after prolonged milling the Al(Mg) solution eventually decomposes into secondary Al(s) (derived from solid solution), the latter retains its physico-chemical characteristics of the former solid solution which still inhibits the reaction to form Mg(AlH(4))(2). Experimental evidence from DSC measurements shows increasing ranges of the melting enthalpy with increasing amounts of Al(Mg) solid solution and consequently the secondary Al(s) for all the three Mg-2Al mixtures. This strongly supports the hypothesis about the different nature of Al(Mg) and the secondary Al(s) as compared to the primary elemental Al powder.

MgB2 precursor wires were prepared using powder in tube technique by Institute of High Pressure PAS in Warsaw. All samples were annealed under isostatic pressure generated by liquid Argon in the range from 0.3 GPa to 1 GPa. In this paper, we show the effects of different processing routes, namely, cold drawing (CD), cold rolling (CR), hot isostatic pressure (HIP) and doping on critical current density (Jc), pinning force (Fp), irreversible magnetic-field (Birr), critical temperature (Tc), n value, and dominant pinning mechanism in MgB2/Fe wires with ex situ MgB2 barrier. The results show that medium pressures (∼0.35 GPa) lead to high Jc in low and medium magnetic fields (0 T – 9 T). On the other hand, higher pressures (∼1 GPa) lead to enhanced Jc in high magnetic fields (above 9 T). Transport measurements show that CD, CR, and HIP have small effects on Birr and Tc, but CD, CR, HIP, and doping enhance Jc and Fp in in situ MgB2 wires with ex situ MgB2 barrier. Transport measurements on in situ undoped MgB2 ...

Keywords: carbon nanotubes, polymer, functional composite, thermal properties of functional composite. A functional composite (FC) was obtained by mixing polymers from the group of polyacrylic acid ester derivatives and polymethylacrylate, copolymers of polyvinyl alcohol (PVA), polyurethanes, ethoxylate derivatives of silicones and chemically functionalized multiwall carbon nanotubes (FMCN). The result was a subject of temperature dependence measurement on electrical resistivity, as well as mechanical strength and flexibility. FC has presented durable, flexible properties and demonstrated a resistance in the range of 20 - 40 Ω. A silicone composite has presented a best chemical and physical properties in broad range of temperature (up to 100°C). Thermal images were studied using infrared (IR) camera and characterized by histograms. The morphology of the functional composites have been observed by SEM and discussed. The work also presents number of methods of nanostructures preparation, which are the most commonly used.

Multifilamentary MgB2 wires were annealed under the high pressure of low-friction, solid state media such as BN and graphite powders. The idea was to replace the hot isostatic pressing in argon medium, which is beneficial to wires transport properties but is difficult for application on an industrial scale. The experimental results show that annealing in BN or graphite under 200 MPa leads to enhancement of the critical current, similar to that observed earlier for high pressure argon annealing. An unwanted effect of the process is the flattening of the round wires, which after the treatment yields an elliptical cross section with b to a ratio of around 85 ± 5%. Comparison of critical currents and microstructure of samples synthesized with different parameters are presented.

This article presents measurements of the chemical composition of Al–Li samples using a reflectron mass analyzer and laser ionization of the sample. The measurements were taken of as-received samples with rough surfaces to ascertain if useful results could be obtained from samples that had not been cleaned or prepared in any way. The power density of the laser used (Nd:yttrium–aluminum–garnet λ=1.06 μm, E≅6 mJ, τ=5 ns) was I∼3×109 W/cm2. We have described the quantitative processing of our results using the measured analog particle gains of the Galileo microchannelplates. The problems associated with quantitative measurements of ion pulses using a microchannelplate detector assembly are also discussed.