A series of Cu-23Zn-10Al (at pet) alloy specimens subjected to different heat-treatment processes have been studied by means of Doppler broadening technique of positron annihilation combined with mechanical test. Resu...A series of Cu-23Zn-10Al (at pet) alloy specimens subjected to different heat-treatment processes have been studied by means of Doppler broadening technique of positron annihilation combined with mechanical test. Results show that the mechanism of quenched-in vacancies, instead of the other suggested ones, plays a dominant role in thermoelastic martensite stabilization of Cu-based shape memory alloy. Knowing the character of the movement of quenched-in vacancies and eliminating them as rapidly as possible are the basis for further optimizing heat-treatment process to obtain desired shape memory performance.展开更多
For Ti-Ni alloy, it is exceedingly difficult; to prepare an element that has a desired and defined hysteresis temperature for its preparing process is not perfect at present. Because the mechanism of transformation in...For Ti-Ni alloy, it is exceedingly difficult; to prepare an element that has a desired and defined hysteresis temperature for its preparing process is not perfect at present. Because the mechanism of transformation in Ti-Ni has not been fully clarified, it is far more exceedingly difficult to explain the hysteresis temperature only by using the traditional metal physics techniques. But position annihilation seems to be a suitable method for it. The positron annihilation measurements show that the hysteresis temperature may be controlled mainly by the relative fraction of the defects contained in a two-way shape memory element.展开更多
The bridged tri imidazoliums 3·3X --5·3X - (X -=PF - 6, Br -, I -) and bis imidazoliums 6·2PF - 6 were synthesized by N quaternization of imidazole derivative 1 in acetonitrile under ref...The bridged tri imidazoliums 3·3X --5·3X - (X -=PF - 6, Br -, I -) and bis imidazoliums 6·2PF - 6 were synthesized by N quaternization of imidazole derivative 1 in acetonitrile under reflux. UV spectroscopic titration experiments showed that the halide salts and hexafluorophosphate salts of these imidazoliums exhibited good recognition toward anions in water and in acetonitrile, respectively.展开更多
文摘A series of Cu-23Zn-10Al (at pet) alloy specimens subjected to different heat-treatment processes have been studied by means of Doppler broadening technique of positron annihilation combined with mechanical test. Results show that the mechanism of quenched-in vacancies, instead of the other suggested ones, plays a dominant role in thermoelastic martensite stabilization of Cu-based shape memory alloy. Knowing the character of the movement of quenched-in vacancies and eliminating them as rapidly as possible are the basis for further optimizing heat-treatment process to obtain desired shape memory performance.
文摘For Ti-Ni alloy, it is exceedingly difficult; to prepare an element that has a desired and defined hysteresis temperature for its preparing process is not perfect at present. Because the mechanism of transformation in Ti-Ni has not been fully clarified, it is far more exceedingly difficult to explain the hysteresis temperature only by using the traditional metal physics techniques. But position annihilation seems to be a suitable method for it. The positron annihilation measurements show that the hysteresis temperature may be controlled mainly by the relative fraction of the defects contained in a two-way shape memory element.
文摘The bridged tri imidazoliums 3·3X --5·3X - (X -=PF - 6, Br -, I -) and bis imidazoliums 6·2PF - 6 were synthesized by N quaternization of imidazole derivative 1 in acetonitrile under reflux. UV spectroscopic titration experiments showed that the halide salts and hexafluorophosphate salts of these imidazoliums exhibited good recognition toward anions in water and in acetonitrile, respectively.
