Papers by Author: Mao Sheng Cao

Abstract: One-dimensional orthorhombic NaNbO₃ long rods were successfully prepared by combining a traditional hydrothermal method with the post-heat treatment. In the hydrothermal reaction process, sandia octahedral molecular sieves (SOMS) were synthesized at 160°C using Nb₂O₅ and NaOH as the initial reactants. Then, the effects of different post-heat treatment conditions on the morphology and crystallinity of product were investigated. Results showed that post-heat temperature could promote the crystal of the product to form orthorhombic NaNbO₃, and the axis of the long rod ran along the [001] direction of NaNbO₃ orthorhombic unit cell. Our study may provide a new approach for the preparation and investigation of one-dimensional alkali niobate photocatalytic materials and template grain for textured alkali niobium.

Abstract: The in-situ synthesized TiB reinforced titanium matrix composites have been prepared by spark plasma sintering technique at 950–1250°C, using mixtures of 10wt% TiB2 and 90wt% Ti powders. The effects of the sintering temperature on the mechanical properties (Vickers microhardness, yield strength and Young`s modulus) of the composites were investigated. SEM was used to analyze the reaction process and the microstructure of the compacts synthesized at different sintering temperatures. The results indicated that the in situ synthesized TiB grow rapidly with increasing sintering temperature. The composite sintered at 1250°C have the highest relative density of 99.2%. However, the composite sintered at 950°C exhibits the best Vickers microhardness of 4.64GPa and yield strength of 989MPa, respectively.

Abstract: The present work focused on the study of preparing processes and the ferroelectric properties of a crack-free and PZT nanoparticle modified PZT thick film by alternately spinning technique. With the increase of the annealing temperature, Pr increased and Ec changed inconspicuously. When the thickness of PZT thick film increased, Ec decreased but Pr increased. For the 4μm-thick film, Ec and Pr were 23 kV/cm and 60 μC/cm2，respectively. The results also confirmed that the alternately spinning technique not only improved the film thickness, but also solved the membrane surface roughness problem of the thick film prepared by PZT 0-3 composite sol method.

Abstract: A sol-gel technology to fabricate PZT thick film for cantilever beam was investigated. In this process, PZT nano-powder is dispersed into a PZT sol solution, which is identical with the powder in composition, and then the PZT suspension and clean PZT sol solution were deposited alternately on an Au/Cr/SiO2/Si substrate using spin-coating route. Above process was repeated in order to deposit the desired thickness. The results showed that the perovskite PZT thick film with thickness of about 4 μm was obtained after annealing at 650 °C for 2 h and it has the saturation polarization of 54 μC/cm2, the remnant polarization of 30 μC/cm2 and the coercive field of 50 kV/cm.

Abstract: SiO2/ SiO2 nanocomposites dipped with silicon resin was ablated and the physical state and phase transformation were characterized. Trace impurity in raw material and compound obtained by chemical reaction were analyzed. Moreover, the high-temperature dielectric properties were investigated. On the basis of above, it is found that the impurity carbon and silicon carbide are the key factors influencing dielectric properties.

Abstract: The effect of strain rate on the dynamic compressive of carbon/epoxy composite materials was investigated via the split Hopkinson pressure bar (SHPB) technique. The specimens were tested in the thickness, as well as in the in-plane direction at different high strain rates. The macro- and micro-fracture morphology of the damaged laminated specimens was obtained utilizing the scanning electron microscope (SEM). The experimental results showed that the compressive properties could be significantly affected by the strain rates. The compressive strength and the ultimate strain in the in-plane direction were obviously lower than that in the thickness direction. As the strain rate increased, the laminate had not enough time to respond, the splitting failure of 0° ply of laminates loaded in-plane along 0° was firstly found, then interfacial crack and delamination were induced, the specimens were crushed to fragments at the highest strain rate. No obvious damage of laminates loaded through the thickness could be observed at strain rate below 2000 s-1. The main way of the dynamic compressive failures through the thickness was shear failure due to the brittle fracture of the fiber at 2260 s-1.