摘要：
Thin films of barium hexaferrite were prepared on fly ash cenosphere particles by the sol-gel method using Fe(NO3)3·9H2O, Ba(NO3)2 and citric acid as raw materials. The prepared films were characterized by differential thermal and thermogravimetric analysis (DTA-TG), X-ray diffractions analysis (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry. The magnetic and structural properties of barium hexaferrite coated cenosphere particles were also studied. The experimental results show that even and continual barium hexaferrite coatings were prepared on fly ash cenospheres, and the magnetic conductivity was imparted to these non-conducting oxide ceramic particles. The low density barium hexaferrite coated cenosphere particles may be utilized for manufacturing microwave absorbing materials.
作者机构：
[匡加才; 刘冶球; 叶昌] College of Material Sci. and Eng., Changsha Univ. of Sci. and Technol., Changsha 410076, China;[陈亚平] Hunan Hydroeletric Occuptional College, Changsha 410131, China;[符寒光] Key Lab. for Advanced Manufacturing by Materials Processing Technol., Tsinghua Univ., Beijing 100084, China
通讯机构：
College of Material Sci. and Eng., Changsha Univ. of Sci. and Technol., China
摘要：
Cu matrix composites reinforced by carbon nanotubes(CNTs) were prepared. The effect of carbon nanotubes on mechanical and tribological properties of the Cu matrix composites were investigated. The chemical method for coating CNTs was reported. The morphology of the fracture surfaces and worn surface were examined by SEM.The results show that Cu/coated-CNTs composites have higher hardness, much better wear resistance and antifriction properties than those of the reference Cu alloy (Cu-10Sn) and Cu/uncoated-CNTs composite sintered under the same conditions. The optimal mechanical properties of the composites occurred at 2. 25% (mass fraction) of CNTs. The excellent wear resistance and anti-friction properties are attributed to the fiber strengthening effect of CNTs and the effect of the spherical wear debris containing carbon nanotubes on the tribo-surface.
摘要：
Cubic aluminum nitride has been obtained in carbothermal reduction reaction at 1700–1800 °C under a flowing nitrogen stream. The as-synthesized products were characterized by XRD, SAD and IR spectrum. The results indicated the product was consisted of wurtzite hexagonal AlN, cubic AlN and corundum. It is speculated that the nucleation and growth of cubic AlN result from the transition of cubic AlON, since intermediate AlON in carbothermal reduction has the same cubic symmetry as cubic AlN. Cubic AlN are unstable metastable phase and are easily transformed into stable hexagonal AlN via crystalline transition with increasing reaction temperature or reaction time. The formation mechanism of cubic AlN is also discussed.
摘要：
Mixture of green petroleum coke, B4 C and SiC together with short carbon fiber were employed as starting materials, the mixture was press formed without any binder after grinding, dense and homogeneous binderless SiC-B4 C-C（carbon/ceramic） composites were then obtained after sintering. Composites thus prepared possess excellent anti-oxidation property, that is, mass loss less than IG within the temperature range from 900 to 1 100 ℃ for 10 h. Anti-oxidation mechanism was also discussed from the viewpoint of thermodynamics, excellent anti-oxidation property of materials thus prepared can be discribed to 1） solid SiO2 formed from SiC, which restrains the filtering of oxygen and simultaneously, its volume expansion brought about by the reaction takes roles both walling up the original pores and making the material more compact; 2） liquid B2O3 from the reaction of B4C not only makes the combination with C, B4 C and SiC tighter through forming solid solution, but also effect of reaction SiC（s）＋2CO（g） =SiO2 （s）＋3C（s） is an expansive process, which improves the microstructure of the material.
