J.J. Murray

Equilibrium vapour concentrations of some polycyclic aromatic hydrocarbons, As4O6 and SeO2 and the collection efficiencies of these air pollutants

Abstract The saturated or equilibrium vapour concentrations of the following inorganic substances and polycyclic aromatic hydrocarbons are reported: SeO 2 , As 4 O 6 , pyrene, B(a)A, B(a)P, B(e)P, B(k)F, B(ghi)P and coronene. The significance of these results with respect to the efficacy of collection of these pollutants on particulate filters and the validity of the previous measurements of collection efficiency are considered in detail. The conclusion is that significant losses may be expected for some of these compounds (As 4 O 6 , SeO 2 , pyrene and B(a)A), that the efficacy of collection is subject to considerable question for some others [B(a)P, B(e)P and B(k)F] although losses may be minimized by adsorption effects, and that for others still [B(ghi)P, coronene] losses should be insignificant.

Lithium-ion cell based on orthorhombic LiMnO2

Abstract This paper will demonstrate that cathodes based on the high temperature form of orthorhombic LiMnO 2 , with the structure described by Hoppe, Brachtel and Jansen, have good capacity and cycle life. X-ray diffraction studies have revealed that cathodes prepared from orthorhombic LiMnO 2 undergo a structural change on being charged beyond a certain potential in which the original structure is converted to spinel Li 1− x Mn 2 O 4 . Orthorhombic LiMnO 2 has been found to have long-term stability in ambient conditions and is easily prepared in a one-step reaction.

Hydrides and deuterides of CaNi5

Abstract CaNi5 is unique among the known AB5 hydrogen storage compounds in that three distinct hydride phases can be formed at room temperature and modest H2 pressures. These hydrides have average compositions of approximately CaNi5H, CaNi5H5 and CaNi5H6, designated herein as β, γ and δ hydride respectively. Deuteride phases of identical composition can be formed but the isotopic pressure effects are different for each of the three phases. Thermodynamics of the β and γ hydrides are presented along with comments on the tendency for CaNi5 to disproportionate when hydrided.

Calibration and testing of a Tian-Calvet heat-flow calorimeter Enthalpies of fusion and heat capacities for ice and tetrahydrofuran hydrate in the range 85 to 270 K☆

Abstract An automated Tian-Calvet heat-flow calorimeter operating under digital control is described. It was calibrated in the range 85 to 290 K using synthetic sapphire. Procedures for measuring heat capacity and enthalpy of fusion are described. The accuracy of the heat-capacity measurements is 1.5 per cent between 85 and 100 K and 1 per cent above 100 K. Enthalpies of fusion are accurate to 1 per cent. Enthalpies of fusion and heat capacities between 85 and 270 K are reported for ice and tetrahydrofuran hydrate and compared with literature values.

Vapour pressures of arsenic over InAs(c) and GaAs(c). The enthalpies of formation of InAs(c) and GaAs(c)

Abstract The equilibrium vapour pressures of arsenic over InAs(c) and GaAs(c) have been studied using the Knudsen-cell mass-spectrometric technique. Appropriate corrections were made for the solubility of arsenic in the liquid metals Ga and In which were produced in the decomposition. The following enthalpies of decomposition were derived: 2 GaAs(c)=2Ga(c)+As 2 (g); δH°(298.15 K)=(89.7±1.2) kcal th mol −1 ; 2 InAs(c)=2In(c)+As 2 (g); δH°(298.15 K)=(77.7±1.2) kcal th mol −1 ; The errors assigned are estimates of total error. Enthalpies of formation of GaAs(c) and InAs(c) were also derived. From measurements of the partial pressures of both As2 and As4 over InAs(c), the enthalpy of dissociation of As4 was also determined. As 1 (g)=2As 2 (g); δH°(298.15 K)=(54.4±1.5) kcal th mol −1 . This is in excellent agreement with the result obtained previously when MoAs2(c) and Mo2As3(c) were used as sources.

The thermodynamics of the LaNi5-H2 system by differential heat flow calorimetry I: Techniques; the α + β two-phase region

Abstract The use of a heat flow calorimeter with the differential twin cell configuration to study intermetallic compound-hydrogen reactions is described. The techniques of calibration and operation of both the gas titration system and the calorimeter, which are required to obtain high precision enthalpies, are described and discussed. Enthalpies for the reaction in the two-phase region of the LaNi5-H2 system are independent of the overall composition but exhibit a small hysteresis with ΔHabs = −32.30 ± 0.07 kJ (mol H2)−1ΔHdes = 31.83 ± 0.09 kJ (mol H2)−1 where ΔHabs is the enthalpy of absorption, ΔHdes is the enthalpy of desorption and the errors are the standard deviations. The value of ΔHdes is the best value for the enthalpy of reaction between equilibrium phases with a total probable error of ±0.5 kJ (mol H2)−1.

The rare-earth arsenides: Non-stoichiometry in the rocksalt phases

Abstract The rare-earth arsenides with the rocksalt structure are non-stoichiometric compounds. Both anion and cation lattice sites are incompletely occupied. A range of arsenic solubility is observed in all cases, and in samarium arsenide at 700 °C, it extends from Sm 0.98 As 0.81 to Sm 0.98 As 0.98 . Over part of the solubility range at the arsenic-rich end, variations in arsenic content can occur with no detectable change in lattice parameter. Further decrease in arsenic content can occur at 700 °C in all but Y, Ho, Er and Yb arsenides, and is accompanied by a reduction in the lattice parameter. A range of metal solubility exists at high temperatures for all phases and results in considerable reduction of lattice parameter at the lower metal concentrations. There is no evidence for vacancy ordering.

The thermodynamics of the LaNi5-H2 system by differential heat flow calorimetry II: The α and β single-phase regions

Abstract Simultaneous pressure-composition isotherms and partial relative molar enthalpies of hydrogen for the single-phase portions of the system LaNi5Hx with 0 ⩽ x ⩽ 6.4 were obtained. In absorption the system exhibits chemisorption for 0 ⩽ x ⩽ 0.05 with ¦Δ H ∞ o ¦ = 80 kJ ( mol H 2 ) −1 , followed by trapping for 0.05 ⩽ x ⩽ 0.23 with ¦ Δ H o ¦ = 59 kJ ( mol H 2 ) −1 at x = 0.05 and then contains an α solid solution to the phase limit at x = 0.42. In desorption this phase limit is at x = 0.34. Both the α−(α + β) and the (α + β)−β phase boundaries exhibit discontinuous changes in Δ H with single-phase ¦ΔH¦ values of 26.5 kJ (mol H2)−1 and 38.5 kJ (mol H2)−1 respectively. The partil relative enthalpy for the β single phase for x > 6.05 decreases slowly with increasingx.

Rechargeable cathodes based on Li2CrxMn2−xO4

Abstract Phases in the solid-state solution series Li 2 Cr x Mn 2− x O 4 were prepared as single-phase compounds over the range 0 x 3+ , with a smaller ionic radius, is substituted for Mn 3+ . The X-ray powder diffraction patterns of phases in the range 1.5≤ x 2 , while the diffraction patterns of Li 2 Cr x Mn 2− x O 4 phases over the range 0 x ≤1.25 resemble that of λ-Li 2 Mn 2 O 4 . Selected phases of Li 2 Cr x Mn 2− x O 4 were formed into cathodes and evaluated in lithium-ion cells with petroleum coke-based anodes.

Electrochemistry and structure of Li2-xCryMn2-yO4 phases

The synthesis of phases in the solid state solution series Li 2 Cr y Mn 2-y O 4 where 0 < y < 2 and their use as cathodes in lithium ion cells was reported previously [I.J. Davidson, R.S. McMillan, J.J. Murray, J. Power Sources, 54 (1995) 205-208]. This paper reports the results of electrochemical evaluations with metallic lithium anodes and on Rietveld refinements of X-ray and neutron powder diffraction data for these phases. Although these materials are prepared at moderately high temperatures, the refinements show that they have a structure similar to the monoclinic layered form of LiMnO 2 prepared by soft chemistry at low temperatures by Armstrong and Bruce [A.R. Armstrong, P.G. Bruce, Nature, 381 (1996) 499-500] and by Delmas and Capitaine [C. Delmas, F. Capitaine, Extended Abstracts of the Eighth International Meeting on Lithium Batteries (1996) 470-471]. The degree of monoclinic distortion in the initial materials has an effect on the structural changes that occur on charging. The phases with a small monoclinic distortion change to an undistorted hexagonal structure on their first charge while those with a large monoclinic distortion change to a spinel-like structure on cycling.