No abstract

A systematic investigation of the dependence of the Verwey phase transition in magnetite on the metal-to-oxygen ratio, by thermomagnetic analysis of the initial permeability, reveals that the transition temperature is a maximum for pure stoichiometric Fe3O4 and is strongly depressed by departures from ideal stoichiometry. Homogeneous single crystalline samples were prepared by subsolidus controlled oxygen fugacity annealing at 1400 °C. Heat capacity measurements by relaxation calorimetry techniques indicate a drastic reduction in the entropy, as well as temperature, of the transition with departures from ideal stoichiometry. For high levels of cation deficiency, a second, instead of a first-order, transition is observed.

No abstract

No abstract

No abstract

No abstract

We describe a simple analog electronic circuit to measure the voltages of a thermocouple and solid electrolyte sensor and calculate and diplay the temperature and log fO2. This circuit monitors conditions in a simple annealing system where the oxygen atmosphere is controlled by continuous flow of a gas buffer.

Articles you may be interested inEffects of charged Higgs bosons in the ντ N deep inelastic scattering within the 2HDM(II) and the UHE ντ detection AIP Conf. Proc. 917, 408 (2007); 10.1063/1.2751985Enthalpy relaxation of homogeneous polystyrene/poly(2-chloro styrene) blends measured by differential scanning calorimetry AIP Conf.A general analysis of approximate nonlinear lumping in chemical kinetics. II. Constrained lumping A general analysis of approximate nonlinear lumping in chemical kinetics. I. Unconstrained lumpingIn thermal relaxation calorimetry, the heat capacity can be calculated from the time constant 1'1 = C p / K b of the exponential decay ofthe cooling curve. If the thermal bond between the sample and sample holder is poor, the cooling curve is described by T -To = A] exp(t / 1'1) + A2 exp(t ir z ). Analysis shows that the heat capacity of the sample plus addenda is C p = Kb(AITI + A z 1'z)/(A 1 + Azl· For most cases, a good approximation is given by Cp = Kb (A 11'/..::1 T), which does not require the measurement of A z or 1'z. An expression is presented for calculating the conductance of the thermal bond of the sample to the substrate.