We have investigated the hydrogen storage properties of a ball-milled mixture of 3Mg(NH 2 ) 2 and 8LiH after first synthesizing Mg(NH 2 ) 2 by ball milling MgH 2 under an atmosphere of NH 3 gas at room temperature. The thermal desorption mass spectra of the mixture without any catalysts indicated that a large amount of hydrogen (∼7 wt %) was desorbed from 140 °C, and the desorption peaked at ∼190 °C under a heating rate of 5 °C/min with almost no ammonia emission. Moreover, the reversibility of the hydrogen absorption/desorption reactions was confirmed to be complete. The above results indicate that this system is one of the promising metal-N-H systems for hydrogen storage.

The mechanism of the hydrogen desorption (HD) reaction from the 1:1 mixture of lithium amide (LiNH2) and lithium hydride (LiH) to lithium imide (Li2NH) and hydrogen (H2) has been proposed on the basis of our experimental results in this paper. The proposed model is constituted by 2 kinds of elementary reactions:  the one is that 2LiNH2 decomposes to Li2NH and ammonia (NH3), the other is that the emitted NH3 reacts with LiH and transforms into LiNH2 and H2. Since the former and the latter reactions are, respectively, endothermic and exothermic, the HD reaction corresponding to the latter reaction occurs as soon as LiNH2 has decomposed into Li2NH and NH3. Therefore, the HD reaction can be understood by the following processes:  at the first step, LiNH2 decomposes into Li2NH/2 + NH3/2, and then the emitted NH3/2 quickly reacts with LiH/2, transforming into LiNH2/2 + H2/2; at the second one, the produced LiNH2/2 decomposes to Li2NH/4 + NH3/4, and then NH3/4 + LiH/4 transform to LiNH2/4 + H2/4, and such successive steps continue until LiNH2 and LiH completely transform into Li2NH and H2, even at low temperatures, by the catalytic effect of TiCl3.

The superconductor PdTe2 was recently classified as a Type II Dirac semimetal, and advocated to be an improved platform for topological superconductivity. Here we report magnetic and transport measurements conducted to determine the nature of the superconducting phase. Surprisingly, we find that PdTe2 is a Type I superconductor with Tc = 1.64 K and a critical field µ0Hc(0) = 13.6 mT. Our crystals also exhibit the intermediate state as demonstrated by the differential paramagnetic effect. For H > Hc we observe superconductivity of the surface sheath. This calls for a close examination of superconductivity in PdTe2 in view of the presence of topological surface states.Recently the transition metal dichalcogenide PdTe 2 was reported to be a Type II Dirac semimetal [1][2][3]. Topological Dirac semimetals form a new class of topological materials, where non-trivial surface states arise due to the topology of the bulk band structure (for recent reviews see [4][5][6]). Dirac semimetals are the 3D analog of graphene and have a cone-shaped linear energy dispersion around the Dirac point with massless fermions [7].

Solid solution is a potential way to optimize thermoelectric performance for its low thermal conductivity compared to those of the constituent compounds because of the phonon scattering from disordered atoms. Tin(II) sulfide (SnS) shows analogous band structure and electrical properties with tin selenide (SnSe), which was the motivation for investigating the thermoelectric performance of SnS and SnS-SnSe solid solution system. SnS compound and SnS 1Àx Se x (0 < x < 1) solid solution were fabricated using the melting method and they exhibited anisotropic thermoelectric performance along the parallel and perpendicular to the pressing directions. For the SnS compound, the maximum zT k value is 0.19 at 823 K along the parallel to pressing direction, which is higher than that along the perpendicular to the pressing direction (zT t ¼ 0.16). The zT values of SnS 0.5 Se 0.5 and SnS 0.2 Se 0.8 were higher than those of the SnS compound and a maximum zT value of 0.82 was obtained for SnS 0.2 Se 0.8 at 823 K, which is more than four times higher than that of SnS.