The influence of graphene oxides (GOs) on the cure behavior and thermal stability of a tetrafunctional tetraglycidyl-4,4’-diaminodiphenylmethane cured with 4,4’-diaminodiphenylsulfone was investigated by using dynamic differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The dynamic DSC results showed that the initial reaction temperature and exothermal peak temperature decreased with the increase of GO contents. Furthermore, the addition of GO increased the enthalpy of epoxy cure reaction. Results from activation energy method showed that activation energies of GO/epoxy nanocomposites greatly decreased with the GO content in the latter stage, indicating that GOs significantly hindered the occurrence of vitrification. The oxygen functionalities, such as hydroxyl and carboxyl groups, on the surface of GOs acted as catalysts and facilitated the curing reaction and the catalytic effect increased with the GO contents. TGA results revealed that the addition of GOs decreased the thermal stability of epoxy

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Nanosized La0.7Sr0.3MnO3/Pr0.5Sr0.5MnO3 (LSMO1−xPSMOx) ceramic composites are prepared using solid-sate sintering. Their microstructural, electro- and magnetotransport properties are characterized by means of various techniques. It is found that the antiferromagnetic/ferromagnetic coupling between PSMO/LSMO at low temperature and the weak ferromagnetic order of PSMO at high temperature results in enhanced low-field magnetoresistance (LFMR) of the composites. With increasing temperature up to 250 K the observed LFMR decays more slowly than that for pure LSMO and this behavior may be explained by the spin coupling near boundaries between LSMO and PSMO grains.

Investigation of BiFeO 3 is being conducted intensively. However, preparing perfect samples with high resistance is still a prerequisite for the clarification of the properties of BiFeO 3 . Here we report electrical and magnetic properties and phase transitions of BiFeO 3 ceramic synthesized by a rapid sintering processing. The dependence of the sintering products on the sintering temperatures revealed that single-phased BiFeO 3 ceramic was synthesized at 880 • C using this rapid sintering technique. The as-prepared BiFeO 3 sample shows a high resistivity of 6.7 × 10 10 cm at an external electric field of 100 kVcm −1 . Vibrating sample magnetometer (VSM) measurement verified that the high resistance BiFeO 3 ceramic presented an antiferromagnetic characterization.