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Abstract: The thermodynamics of nanocrystalline TiO2 ceramics during the whole sintering process were analyzed using differential scanning calorimetry (DSC) for different heating rates (10, 20 and 30°C/min). The raw TiO2 powder was also studied comparably. The DSC and specific heat capacity (C p ) were also studied. The results show that there is no obvious endothermic or exothermic peak at the stage where the maximum densification rate occurred for TiO2 ceramics. The ordering process induced by the microstructural densification counteracts the disordering process induced by increasing the sintering temperature. The sintering process is a result of combination of the ordering process and the disordering one. The activation energy of nanometer TiO2 ceramics determined by Kissinger method is 103.8kJ/mol. [Copyright &y& Elsevier]

Abstract: The Master Sintering Curve (MSC) of rutile TiO2 was constructed using constant heating rate dilatometry data based on the combined-stages sintering model. The present research was carried out to predict and control densification evolution of TiO2 ceramics during pressureless sintering. Densification of TiO2 was continuously recorded at heating rate of 2°C/min and 5°C/min using high temperature dilatometer. The results demonstrate that the MSC, in which the sintered density is a unique function of the integral of a temperature function over time, is insensitive to the heating path. The MSC theory can be applied to predict the shrinkage and final density and to design a reproducible process to fabricate ceramics with required density. [Copyright &y& Elsevier]

Based on the renormalized t - J model and self-consistent mean field theory, the doping and energy dependence of optical conductivity and effective electron number in cuprate superconductors are discussed. As the result of the presence of the pseudogap in normal state, the optical conductivity exhibits two main components from underdoping to overdoping, a narrow band peaked around zero energy and a broadband centered in the mid-infrared region which deviates the Drude formula. With increasing the doping concentration, the spectral weight of the optical conductivity suppressed strongly in underdoped region increases quickly, and the peak position of the mid-infrared band moves towards to the lower energy region, then incorporates into the narrow band centered in zero energy in the heavily overdoped region. By virtue of the integral, the effective electron number is obtained, and it increases monotonically from zero energy to mid-infrared characteristic energy with increasing energy, then shows a plateau feature when the energy is larger. In particular, the mid-infrared characteristic energy scales with the pseudogap, reflecting the presence of the mid-infrared band is the result of the pseudogap effect. [ABSTRACT FROM AUTHOR]