Specific Features of Structural Changes in Lanthanum–Nickel–Aluminum Alloys in the Process of Heating in Hydrogen

We study interactions in LaNi_{5 – x} Al _x –H₂ (x = 0, 0.2, 0.4, 0.6, and 0.8) systems by the methods of differential thermal and X-ray phase diffraction analyses within the temperature range from the room temperature to 920°C in hydrogen whose initial pressure can be as high as 5.7 MPa. In LaNi_{5 – x} Al _x –H₂ systems with x = 0, 0.2, and 0.4, the processes of formation and decomposition of the intermetallic hydride run without changes in its symmetry. The process of heating of LaNi_{5 – x} Al _x (x = 0, 0.2, and 0.4) alloys in hydrogen results in their homogenization. Thus, the process of heating of the LaNi_4.4Al_0.6 alloy in hydrogen to 700°C for an initial pressure of about 5.7 MPa results in a partial decomposition (disproportionation) of the original phase accompanied by the formation of lanthanum hydride and Ni₃Al. As a result of heating to 575°C in hydrogen ( 5.0 MPa), the LaNi_4.2Al_0.8 compound disproportionates into Ni₃Al and an unknown phase. After heating to 840°C followed by holding for 1.5 h, we detect the original phase, lanthanum hydride, Ni₃Al, and an unknown phase. At the same time, as a result of heating to 910°C followed by holding for 2 h, we observe the formation of a hydride of the original phase with doubled spacing c, lanthanum hydride, and Ni₃Al.     

Quo vadis,lition?

Projections of lithium metal requirements to satisfy the needs of the automotive and storage batteries have imposed an enormous demand on the lithium industry. These mathematical projections have been based on various demand assumptions and have raised questions on the ability of the industry to supply such a demand. A review of supply and demand projections suggests that the gap may not be as wide as led to believe.Confidence in the future supply of sufficient lithium is further strengthened by the discovery of lithium brines of the Salar de Atacama, where the Foote Mineral Company has been evaluating the feasibility of developing an additional source of lithium chemicals. The geology, geochemistry and reserves of the salar suggest a vast supply for the future.     

Interaction of intermetallic compounds of rare-earth metals, nickel, and aluminum with hydrogen

AtT=293 K andp _H2≤10 MPa. we synthesized hydridesR _3Ni8Al-H_7.2–15.2 (R=Nd. Sm. Gd. Tb. Dy, Ho, Er, Tm, and Lu). The X-ray analysis revealed an isotropic deformation of the original crystal lattice due to hydrogen penetration. For the hydrides obtained, the lattice constanta exceeds that of the original intermetallide by 3.9–6.0% and the constantc and the cell volumeV are increased by 6.0–12.6% and 15.6–26.4%, respectively. The volume expansion per absorbed hydrogen atom is (2.4–3.6)·10⁻³ nm⁻³. By construction of the isotherms of hydrogen desorption for the systemsR _3Ni>8Al-H, we established the existence of the α-solid hydrogen solution and the region of its coexistence with β-hydride, the region of coexistence of β- and γ-hydrides, and the β- and γ-hydride phases. Heats of the phase transitions were determined as follows: ΔH=31.4±0.8 kJ/(mole H₂) in the system Gd₃Ni₈Al-H for the transition γ→β, ΔH=39.8±1.1 kJ/(mole H₂) in the system Tb₃Ni₈Al−H for the transition β→α. and ΔH=37.1±5.1 kJ/(mole H₂) in the system Tm₃Ni₈Al−H for the transition γ→β. Among the products of hydrogenation, intermetallic compounds Lu₃Ni8Al and Tm₃Ni₈Al. we revealed the β′- and γ-phases. We also found that, atp _H2≤10 MPa andT=400–430 K, the phases of Sm₃Ni₈Al and Gd₃Ni₈Al decay into two hydridesRH_2–3 andR(Ni.Al)₅H _x . Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 36, No. 1, pp. 76–82, January–February, 2000.     

Flexible hydrogen gas sensor based on a capacitor-like Pt/TiO2/Pt structure on polyimide foil

Metal oxide semiconductor gas sensors of hydrogen with a typical capacitor-like Pt/TiO₂/Pt electrode arrangement exhibit excellent sensitivity to hydrogen even at room temperature. At the same time, very similar Pt/TiO₂/Pt cells can also be used as memristive elements exhibiting resistive switching between two resistive states, which has been recently exploited to create a gas sensor with built-in memory. Merging of these two functionalities within a single device also opens new possibilities for smart gas sensor arrays. However, so far such sensors have been prepared only on rigid substrates. In this work, a flexible hydrogen gas sensor with such capacitor-like Pt/TiO₂/Pt electrode arrangement fabricated on polyimide foil is presented and characterized in terms of hydrogen gas sensing properties and bending endurance. The sensor exhibits high response (R_air/R_H2) of more than 10⁵ to 10 000 ppm H₂ at 150 °C with minor decline at elevated humidity and is capable of room temperature operation. The lowest detected concentration was 3 ppm at 150 °C and 300 ppm at room temperature in dry conditions. Bending the sensor 10⁵ times over diameter of 10 mm led to slight improvement of the sensing performance.     

Synthesis and properties of novel fluorinated poly(arylene ether)s

Dibromomethylene‐containing monomer with a tetrafluorobenzene central unit was synthesized using 2,3,5,6‐tetrafluoro‐1,4‐bis(4‐methylphenoxy)benzene as a starting material. This approach enabled preparation of several fluorinated poly(arylene ether)s containing isomeric fragments, with or without allyl or acetyl side groups, which were prepared by interaction of the synthesized tetrafluorobenzene‐based monomer with various types of hydroxyl‐substituted diphenyl ethers. The structure of the synthesized compounds was determined using Fourier transform infrared, ¹H NMR and ¹⁹ F NMR spectroscopy techniques. Most of the resulting polyethers were soluble in chlorinated, ether‐type or polar amide solvents. The molecular weight, mechanical and thermal properties of the synthesized fluorinated poly(arylene ether)s were studied depending on the inherent isomery of macromolecular chains and the nature of functional groups. Some ways of functionalization of the prepared fluorinated polyethers with epoxy and triethoxysilyl groups were proposed. © 2015 Society of Chemical Industry     

On determination of sign of the piezo-optic coefficients using torsion method

We have shown that a high-accuracy torsion method recently developed by the authors for measuring piezo-optic coefficients allows determining not only the absolute value of the coefficients but also their sign. The techniques and experimental procedures used for determination of the sign are described in detail and proven based on studies of α-BaB2O4 and LiNbO3 crystals. The piezo-optic coefficients are determined for both crystals, and a combination of the corresponding photoelastic coefficients is determined for the case of α-BaB2O4 crystals.