SHS method with reductive process was used to synthesize TiB2 ceramic powder from B2O3-TiO2-Mg system. X-ray diffraction, SEM and Image analysis were used to analyse microstructure of TiB2 powder and compare with micr...SHS method with reductive process was used to synthesize TiB2 ceramic powder from B2O3-TiO2-Mg system. X-ray diffraction, SEM and Image analysis were used to analyse microstructure of TiB2 powder and compare with microstructure of TiB, fabricated by SHS elements syn-thesis from Ti+B system. The results show that TiB? powder fabricated by SHS reductive synthesis is finer (about 1. 5?m) ,uni former and free-agglomerate.展开更多
The graft copolymerization of acrylic acid (AA) with unswollen and swollen ramie fibers using chromic acid (H 2CrO 4) as the initiator has been studied in the presence of air. The effects of initiator concentration,...The graft copolymerization of acrylic acid (AA) with unswollen and swollen ramie fibers using chromic acid (H 2CrO 4) as the initiator has been studied in the presence of air. The effects of initiator concentration, monomer concentration, perchloric acid (HClO 4) concentration, time of polymerization, reaction temperature, and amount of ramie fibers on the graft percentage have been found out. The graft copolymer was characterized by IR spectra, scanning electron microscopy(SEM), differential thermal analysis (DTA), and thermogravimertric analysis (TGA).展开更多
In this paper, a mathematical strip-saturation model is proposed for a poled transversely isotropic piezoelectric plate weakened by two impermeable unequal-collinear hairline straight cracks. Remotely applied in-plane...In this paper, a mathematical strip-saturation model is proposed for a poled transversely isotropic piezoelectric plate weakened by two impermeable unequal-collinear hairline straight cracks. Remotely applied in-plane unidirectional electromechanical loads open the cracks in mode-I such that the saturation zone developed at the interior tips of cracks gets coalesced. The developed saturation zones are arrested by distributing over their rims in-plane normal cohesive electrical displacement. The problem is solved using the Stroh formalism and the complex variable technique. The expressions are derived for the stress intensity factors （SIFs）, the lengths of the saturation zones developed, the crack opening displacement （COD）, and the energy release rate. An illustrative numerical case study is presented for the poled PZT-5H ceramic to investigate the effect of prescribed electromechanical loads on parameters affecting crack arrest. Also, the effect of different lengths of cracks on the SIFs and the local energy release rate （LERR） has been studied. The results obtained are graphically presented and analyzed.展开更多
An investigation of the pressureless sintering of Si3N4 with MgO-CeO2 reveals that MgO-CeO2 is a much more effective sintering aid for silicon nitride than either MgO or CeO2. The amount of MgO-CeO2 and MgO/CeO, weigh...An investigation of the pressureless sintering of Si3N4 with MgO-CeO2 reveals that MgO-CeO2 is a much more effective sintering aid for silicon nitride than either MgO or CeO2. The amount of MgO-CeO2 and MgO/CeO, weight ratio has a strong influence on the densification be-haviour and mechanical properties of the sintered materials. The silicon nitride pressureless sintered with MgO-CeO2 re-tains a relative density of 98. 5% , a bending strength of 950 MPa. The Si-Mg-Ce-O-N system is of great value for appli-cation and theoretical study.展开更多
文摘SHS method with reductive process was used to synthesize TiB2 ceramic powder from B2O3-TiO2-Mg system. X-ray diffraction, SEM and Image analysis were used to analyse microstructure of TiB2 powder and compare with microstructure of TiB, fabricated by SHS elements syn-thesis from Ti+B system. The results show that TiB? powder fabricated by SHS reductive synthesis is finer (about 1. 5?m) ,uni former and free-agglomerate.
文摘The graft copolymerization of acrylic acid (AA) with unswollen and swollen ramie fibers using chromic acid (H 2CrO 4) as the initiator has been studied in the presence of air. The effects of initiator concentration, monomer concentration, perchloric acid (HClO 4) concentration, time of polymerization, reaction temperature, and amount of ramie fibers on the graft percentage have been found out. The graft copolymer was characterized by IR spectra, scanning electron microscopy(SEM), differential thermal analysis (DTA), and thermogravimertric analysis (TGA).
基金ministry of Human Resource Development for the financial support
文摘In this paper, a mathematical strip-saturation model is proposed for a poled transversely isotropic piezoelectric plate weakened by two impermeable unequal-collinear hairline straight cracks. Remotely applied in-plane unidirectional electromechanical loads open the cracks in mode-I such that the saturation zone developed at the interior tips of cracks gets coalesced. The developed saturation zones are arrested by distributing over their rims in-plane normal cohesive electrical displacement. The problem is solved using the Stroh formalism and the complex variable technique. The expressions are derived for the stress intensity factors （SIFs）, the lengths of the saturation zones developed, the crack opening displacement （COD）, and the energy release rate. An illustrative numerical case study is presented for the poled PZT-5H ceramic to investigate the effect of prescribed electromechanical loads on parameters affecting crack arrest. Also, the effect of different lengths of cracks on the SIFs and the local energy release rate （LERR） has been studied. The results obtained are graphically presented and analyzed.
文摘An investigation of the pressureless sintering of Si3N4 with MgO-CeO2 reveals that MgO-CeO2 is a much more effective sintering aid for silicon nitride than either MgO or CeO2. The amount of MgO-CeO2 and MgO/CeO, weight ratio has a strong influence on the densification be-haviour and mechanical properties of the sintered materials. The silicon nitride pressureless sintered with MgO-CeO2 re-tains a relative density of 98. 5% , a bending strength of 950 MPa. The Si-Mg-Ce-O-N system is of great value for appli-cation and theoretical study.
