Papers by Author: Bao Cai Xu

Abstract: Barium ferrites hollow microspheres were prepared by self-propagating high-temperature synthesis self-reactive flame spraying method. The droplets enter in the cooling medium and solidified rapidly so that the gas can not escape to remain holes inside the products. The powder samples were used for characterization. The microstructure and crystal structure were studied by SEM, EDS and XRD. The results show that the obtained particles are hollow microspheres. They are spherical or ellipsoidal shapes from nanometer dimension to several micrometers. The phase structure of composite powders is the mixtures of barium ferrite and Fe₂O₃.

Abstract: This paper aims to study preparation and mechanism of hollow ceramic microspheres. With Al+Cr₂O₃+SiO₂+sucrose+epoxy resin as reactive system, Al2O3-based hollow ceramic microspheres are synthesized and reaction mechanism of hollow ceramic microspheres is established. Results show that the quenching products consist of hollow spherical or irregularly spherical particles and irregularly powders. Spherical or irregularly spherical particles are hollow structure and constitutive of Al₂O₃-SiC diphase and a few Cr₃Si、Cr₇C₃. The preparation of hollow ceramic microspheres includes igniting by heating, forming ceramic thawy droplets and fast cooling. The great deal of air produced by burning epoxy resin and sucrose is the key reason why hollow ceramic microspheres are formed.

Abstract: The self-propagating high-temperature spraying synthesis (SHSS) route is evaluated for the synthesis of ferrite powders that are subsequently processed towards the manufacturing of high initial magnetic permeability. The powder samples are used for characterization by SEM, EDS and XRD. The results show that the obtained particles are hollow microspheres from nanometer dimension to several micrometers. The phase structure of hollow microspheres is the mixtures of ferrite and Fe2O3. Permittivity and permeability measurements are made on particles dispersed in a paraffin wax matrix. The microsphere is a ferromagnetic matter with both high magnetic loss and high dielectric loss.

Abstract: The hollow ceramic microspheres were prepared by Self-reactive flame spraying method. The structural characteristics and morphology properties of the composite powders were obtained by XRD and SEM. The results show that the obtained particles are hollow ceramic microspheres. The average particle size is about 30μm. An analytical method for the determination of electromagnetic parameters (ε, μ) of materials under test is presented by the analysis of normalized general matrix of equivalent network of coaxial line filled with samples. The analysis of vector network analyzer show that reflectance of hollow composite microspheres could well absorb microwaves in 2-18 GHz. The reflection loss is less than -l0dB in the range of 12.4 to15.2GHz while the minimum reflection loss is -18.5dB at 13.6GHz.

Abstract: Aiming at repairing aluminum alloy wear-out parts, the multiple compound metallic-membrane plating is researched with anodic oxidation, chemical plating Ni-P and later heat processing, blacken processing. Experiments show that this plating has many advances such as lower porosity, stronger binding force, higher hardness, better corrosion and abrasion resistant, another, this method of repairing only needs simple condition and is easy to be operated, this technology of repairing provides a new method for repairing of aluminum alloy wear-out parts.

Abstract: This article presents the results for the prestress of ceramics lateral confined by aluminum alloy. Prestressed ceramics composite is produced by casting molten aluminum alloy around a hot ceramic tile and then cooling it down with blowing air. Different technical parameters of the casting are investigated. Al2O3/ZrO2(4Y) composite ceramics alumina tiles prepared by combustion synthesis under high gravity are used in this study to investigate the effect of confinement and prestress. The samples of ceramics are lateral confined by aluminum alloy, which lead to monaxial compressive stress in the tile and tensile stress in the metal. Thin and thick target configurations are used to understand the effect on pre-stressing performance, which simply and approximately allows high monaxial compressive pre-stresses. The residual stress in the metal should be lower than the yield strength of the metal, and this requirement can be approximately realized by Vickers indentation crack length.

Abstract: The Al2O3/YSZ eutectic composite ceramics-lined pipes have been prepared by combustion synthesis. By adding ZrO2 (4Y) to the thermit, the influences of centrifugal force and eutectic composition on the microstructure, mechanical properties, strengthening and toughening of ceramics lining are researched. The growth of melt is based on eutectic transformation under high degree of under-cooling at centrifugal force above 200G. The linings are comprised of rod-shaped Al2O3 matrix eutectic grains. The diameters of tetragonal lattice ZrO2 fiber in rod-shaped grains are on nano-micron scale. Causing the strengthening and toughening of ceramics to be promoted, and the Al2O3/YSZ eutectic composite ceramics-lined pipes have high comprehensive mechanical properties.

Abstract: A new method, named the thermal explosive deforming synthesis (TEDS), for producing SnO2 nano-fibers is reported. The optimal condition for forming SnO2 nano-fibers is also discussed. The resulting SnO2 fibers have diameters in the range of 20 ~ 100 nm and are expected as the matrix materials for gas sensor, humidity sensor and piezoresistive pick-up.