A novel process termed low-temperature combustion-synthesis (LCS) ofBa(NO_3)_2-TiO_2-C_6H_8O_7.centre dot H_2O system was investigated at the initial temperature of 600deg C and ultrafine BaTiO_3 powders with a partic...A novel process termed low-temperature combustion-synthesis (LCS) ofBa(NO_3)_2-TiO_2-C_6H_8O_7.centre dot H_2O system was investigated at the initial temperature of 600deg C and ultrafine BaTiO_3 powders with a particle size of 200-350 nm were prepared. It was foundthat the molar ratio of NO_3^- / citric acid and the homogeneity of combustion have remarkableeffect on the characteristics of the powder. The reaction mechanism of LCS BaTiO_3 powders wasproposed on the basis of thermodynamic analysis.展开更多
The effects of Cu and Ni (x=0, 10, 20 and 40 wt pet) and compaction pressures (12, 24, 84 and 108 MPa) on combustion wave velocity and wave front shape for Ti-2B-Cu/Ni and 3Ti-2BN-Cu/Ni bilayered cermets were investig...The effects of Cu and Ni (x=0, 10, 20 and 40 wt pet) and compaction pressures (12, 24, 84 and 108 MPa) on combustion wave velocity and wave front shape for Ti-2B-Cu/Ni and 3Ti-2BN-Cu/Ni bilayered cermets were investigated by a video camera. Since the boiling point of Cu is lower, the wave velocities of specimens are slower. Due to the higher specific heat of Ni than that of Cu, the wave velocities of specimens was slowed down a lot with increasing the Ni diluent. The wave velocity differences of the specimens containing Ni are more than that of the bilayered specimens containing Cu. Wave velocities of the specimens containing Ni increased more than that of the specimens containing Cu when higher pressure was employed for green mixture. The more the wave velocity difference of the bilayer, the more curved the specimen.展开更多
Autoigniting synthesis of gel from Ba(NO_3)_2, TiO(NO_3)_2 and C_6H_8O_7centre dot H_2O aqueous solution was investigated at an initial temperature of 600 deg C andtetragonal BaTiO_3 nanopowder with particle size of 8...Autoigniting synthesis of gel from Ba(NO_3)_2, TiO(NO_3)_2 and C_6H_8O_7centre dot H_2O aqueous solution was investigated at an initial temperature of 600 deg C andtetragonal BaTiO_3 nanopowder with particle size of 80nm was prepared. It is indicated that thespecific surface area of the combustion product before and after calcinations is 14.74 m^2/g and12.49 m^2/g, respectively. The combustion wave is composed of solid phase reaction zone and gaseousphase flame reaction zone. The combustion flame temperature is 1 123 K derived from thermocouplemeasurement. The characteristics and densification behavior of the sol-gel autoigniting synthesizedBaTiO_3 nanopowder were investigated.展开更多
In order to find more suitable materials as barriers and to improve the thermoelectric properties, p-type (Bi1-xSbx) 2Te3 (x = 0.85, 0.9) two segments compositionally graded thermoelectric materials (CGTM) with differ...In order to find more suitable materials as barriers and to improve the thermoelectric properties, p-type (Bi1-xSbx) 2Te3 (x = 0.85, 0.9) two segments compositionally graded thermoelectric materials (CGTM) with different barriers were fabricated by conventional hot pressure method. Metals Fe, Co, Cu and Al were used as barriers between two segments. The effects of different barriers on thermoelectric properties of CGTM were investigated. The results show that metal Fe is more stable and suitable as the barrier.展开更多
文摘A novel process termed low-temperature combustion-synthesis (LCS) ofBa(NO_3)_2-TiO_2-C_6H_8O_7.centre dot H_2O system was investigated at the initial temperature of 600deg C and ultrafine BaTiO_3 powders with a particle size of 200-350 nm were prepared. It was foundthat the molar ratio of NO_3^- / citric acid and the homogeneity of combustion have remarkableeffect on the characteristics of the powder. The reaction mechanism of LCS BaTiO_3 powders wasproposed on the basis of thermodynamic analysis.
基金This work was supported by the National Natural Science Foundation of China,Grant No.59672032 and 59811120918(Chinese Russian joint research program 98-001).
文摘The effects of Cu and Ni (x=0, 10, 20 and 40 wt pet) and compaction pressures (12, 24, 84 and 108 MPa) on combustion wave velocity and wave front shape for Ti-2B-Cu/Ni and 3Ti-2BN-Cu/Ni bilayered cermets were investigated by a video camera. Since the boiling point of Cu is lower, the wave velocities of specimens are slower. Due to the higher specific heat of Ni than that of Cu, the wave velocities of specimens was slowed down a lot with increasing the Ni diluent. The wave velocity differences of the specimens containing Ni are more than that of the bilayered specimens containing Cu. Wave velocities of the specimens containing Ni increased more than that of the specimens containing Cu when higher pressure was employed for green mixture. The more the wave velocity difference of the bilayer, the more curved the specimen.
文摘Autoigniting synthesis of gel from Ba(NO_3)_2, TiO(NO_3)_2 and C_6H_8O_7centre dot H_2O aqueous solution was investigated at an initial temperature of 600 deg C andtetragonal BaTiO_3 nanopowder with particle size of 80nm was prepared. It is indicated that thespecific surface area of the combustion product before and after calcinations is 14.74 m^2/g and12.49 m^2/g, respectively. The combustion wave is composed of solid phase reaction zone and gaseousphase flame reaction zone. The combustion flame temperature is 1 123 K derived from thermocouplemeasurement. The characteristics and densification behavior of the sol-gel autoigniting synthesizedBaTiO_3 nanopowder were investigated.
基金[This work is financially supported by National Natural Science Foundation of China (No. 59772012 and 50042014).]
文摘In order to find more suitable materials as barriers and to improve the thermoelectric properties, p-type (Bi1-xSbx) 2Te3 (x = 0.85, 0.9) two segments compositionally graded thermoelectric materials (CGTM) with different barriers were fabricated by conventional hot pressure method. Metals Fe, Co, Cu and Al were used as barriers between two segments. The effects of different barriers on thermoelectric properties of CGTM were investigated. The results show that metal Fe is more stable and suitable as the barrier.
