共查询到20条相似文献,搜索用时 31 毫秒
1.
Takamasa Ishigaki Shigeru Yamauchi Junichiro Mizusaki Kazuo Fueki Hifumi Tamura 《Journal of solid state chemistry》1984,54(1):100-107
The tracer diffusion coefficient, , of oxide ions in LaCoO3 single crystal was determined over the temperature range of 700–1000°C by a gas-solid isotopic exchange technique using 18O tracer. For the determination, two methods, the gas phase analysis and the depth profile measurement, were employed. Under an oxygen pressure of 34 Torr, the temperature dependence of in LaCoO3 was expressed by at 950°C was found to be proportional to P?0.35O2. The diffusion of oxide ions occurs through a vacancy mechanism. The activation energy for the migration of oxide ion vacancies was estimated as 18 kcal · mole?1. 相似文献
2.
R.J. Gaboriaud 《Journal of solid state chemistry》1980,35(2):252-261
Yttrium self-diffusion in monocrystalline yttrium oxide (Y2O3) is studied by means of the classical radio tracer technique. The few reliable diffusion data obtained in the temperature range 1600–1700°C lead to the following diffusion coefficient .Experimental errors on the above numerical values are large and give, for the preexponential and energy terms, respectively: .Nevertheless these results seem in good agreement with those deduced from high-temperature and low-stress creep experiments. The theoretical aspect of self-diffusion of yttrium in Y2O3 is studied in terms of point defects and lattice disorder due to the equilibrium between the oxide and its environment. This last part is confined to the restricted range of high oxygen partial pressure in which oxygen interstitials are supposed to be majority defects. Intrinsic and extrinsic diffusion behavior are both considered on the basis of a vacancy diffusion mechanism. 相似文献
3.
The kinetics, mechanism, and activation energy of the isothermal decomposition of CuCrO4 was studied using an isothermal TG method and an X-ray high-temperature diffraction technique in either air or a flowing atmosphere of N2. The enthalpy change ΔH of the decomposition reaction was determined by DSC analysis. The mechanism of the thermal decomposition of CuCrO4 is well represented by the standard Avrami-Erofeev kinetic equation . According to this mechanism, the reaction rate is controlled by the formation and growth of nuclei on the surface of the reactant. The activation energy EA of the process in air is EA = (248 ± 8) kJ mole?1, in flowing atmosphere of nitrogen EA = (229 ± 8) kJ mole?1. ΔH in air is 110 kJ mole?1, in flowing nitrogen 67 kJ mole?1. The lower values of ΔH and EA in the flowing atmosphere of nitrogen are due to the fast elimination of O2 from the reaction interface. However, the decay of the crystalline portion of CuCrO4 during its thermal decomposition, studied by the X-ray diffraction, is controlled by a different reaction mechanism (first-order kinetics). The reaction mechanism is discussed in the relation to the crystal structure of the reactants. 相似文献
4.
The standard enthalpy of formation of γ-UO3 has been critically assessed; the value ?(292.5 ± 0.2) kcalth mol?1 is suggested.The enthalpies of solution of β-UO3 and γ-UO3 in 3 M H2SO4 have been measured and used to derive: 相似文献
5.
Benzophenone (BP) in low concentrations (<0.001 mol 1?1) produces a rate enhancing effect in the H2O2-induced bulk photopolymerization of MMA. Rp is proportional to [H2O2]0.4 and [BP]0.4, and at 30° is 1.00 × 10?2 1.mol?1 sec?1. In diluted systems, different solvents produce different kinetic effects, reaction order with respect to monomer being negative for IPA and THF as solvent, positive but <1.0 for benzene and chloroform, 1.2 for acetonitrile, CCl4 and t-butanol and 1.8 for DMA. The variable solvent effect is attributed to modification of the initiation process by the various solvents to different extents. Kinetic analysis of data for bulk photopolymerization gives evidence for primary radical termination and degradative initiator transfer. 相似文献
6.
The luminescence associated with the Eu3+ ion in LiEuCl4 has been studied at cryogenic temperatures under conditions of high resolution. Emission was observed to originate from both the 5D0 and 5D1 excited states, and transitions to the , and 7F4 ground levels were observed. The fine structure observed within these emission bands was found to be consistent with the existence of an effective D4 site symmetry for the emitting Eu3+ species, even though the europium polyhedron was found to be that of a bisdisphenoid. 相似文献
7.
Joaquín García Juan Bartolomé Domingo González Rafael Navarro Willem Jacobus Crama 《The Journal of chemical thermodynamics》1983,15(12):1109-1126
We present the heat capacities measured by adiabatic calorimetry from 6 to 350 K, and by differential scanning calorimetry from 300 to 500 K, of CsCrCl3 and RbCrCl3. A first-order transition at Tc = (171.1±0.1) K was detected for CsCrCl3. The RbCrCl3 showed at Tc = (193.3±0.1) K a transition with thermal hysteresis at temperatures just below the maximum. At T1 = (440±10) K a continuous transition was also detected. Furthermore, at TN ≈ 16 K, and for both compounds, a small bump due to magnetic long-range ordering was observed. The thermodynamic functions at 298.15 K are
CsCrCl3 | 15.38 | 26.49 | 3503.2 | 14.735 |
RbCrCl3 | 15.76 | 25.99 | 3556.8 | 14.384 |