It′s important that HTS tapes have lower thermal conductivity and higher transversal resistivity in order to reduce the heat leaks conducted along the tapes and AC losses in the high temperature superconducting syste...It′s important that HTS tapes have lower thermal conductivity and higher transversal resistivity in order to reduce the heat leaks conducted along the tapes and AC losses in the high temperature superconducting system conduction cooled by GM coolers. This paper presents an experimental investigation into the effects of pure Ag and AgAu alloys sheath materials on the properties of Bi(2223) multifilamentary tapes and the optimisation of conduction cooled hybrid current leads made from copper and Bi(2223)/Ag or Bi(2223)/AgAu tapes. The thermal conductivity of the tapes were measured by cryogenic steady heat flux method and the resistance was measured by using standard DC four probe method at low temperature. The results showed that the reduction of thermal conductivity by the addition of Au into the sheath material of Bi(2223) tapes was 65 0 0, 75 0 0 and 85 0 0 lower than that of pure Ag sheathed Bi(2223) tapes and the increase of resistivity was 4.9 , 10 and 19.4 times higher than that of pure Ag for the addition of 2.2 0 0, 5.7 0 0 and 10.7 0 0Au(atom ratio) respectively. And the study also attempts to optimise thermodynamically the conduction cooled hybrid current lead by using a developed model, which took the irreversibility of commercial GM coolers, the contact resistance and thermal conductance into account. Predictions from the model showed that AgAu alloys were suitable candidate materials to replace Ag as sheath material of Bi(2223) tapes applied in HTS current leads. In addition, Bi(2223)/AgAu was a suitable material to be applied as the HTS section of hybrid current leads in conduction cooled superconducting electric systems.展开更多
通过流延成型技术,以片状K0.5Na0.5NbO3(简称为KNN)粉体为模板,结合掺杂改性后的基料粉体(K0.45Na0.55)0.98Li0.02(Nb0.77Ta0.18Sb0.05)O3-0.005Ba ZrO3(简称为KNNLST-BZ)流延制备出KNN基无铅压电陶瓷,研究了不同的工艺参数(烧结温度、...通过流延成型技术,以片状K0.5Na0.5NbO3(简称为KNN)粉体为模板,结合掺杂改性后的基料粉体(K0.45Na0.55)0.98Li0.02(Nb0.77Ta0.18Sb0.05)O3-0.005Ba ZrO3(简称为KNNLST-BZ)流延制备出KNN基无铅压电陶瓷,研究了不同的工艺参数(烧结温度、烧结次数)对于KNNLST-BZ织构化陶瓷的电学性能、显微结构的影响。结果表明:模板含量为20wt%的KNNLST-BZ织构化陶瓷在1145℃下保温2 h呈现出优异的性能:压电常数d33=204 p C/N,横向机电耦合系数k31=23%,剩余极化强度Pr=26μC/cm2,矫顽场Ec=1.2 k V/mm。同时该织构化陶瓷在1145℃下烧结2次能得到更优的电学性能:d33=248 p C/N,k31=32.54%,Pr=38μC/cm2,Ec=1.2 k V/mm,介电损耗tanδ=6.38%,机械品质因数Qm=16.76,介电常数εT33/ε0=913.7,横向伸缩振动频率常数N1=2244。展开更多
采用流延法成功制备了无铅弛豫铁电0.65(0.65Na 0.5 Bi 0.5 TiO 3-0.35BiMg 0.5 Ti 0.5 O 3)-0.35SrTiO 3陶瓷.研究了陶瓷的微观形貌、相结构、介电性能和储能行为.并在连续升温环境下,探讨了陶瓷的储能密度和储能效率的稳定性.结果表明...采用流延法成功制备了无铅弛豫铁电0.65(0.65Na 0.5 Bi 0.5 TiO 3-0.35BiMg 0.5 Ti 0.5 O 3)-0.35SrTiO 3陶瓷.研究了陶瓷的微观形貌、相结构、介电性能和储能行为.并在连续升温环境下,探讨了陶瓷的储能密度和储能效率的稳定性.结果表明:该陶瓷为纯钙钛矿赝立方结构且结晶性良好,晶粒分布均匀,并且该陶瓷表现出良好的储能性能及温度稳定性.陶瓷在275 kV/cm电场下获得了最大的储能密度3.55 J/cm 3,相应的储能效率为72.8%.在30~140℃间,储能密度最大变化率为6.4%.此研究表明0.65(0.65Na 0.5 Bi 0.5 TiO 3-0.35BiMg 0.5 Ti 0.5 O 3)-0.35SrTiO 3陶瓷在储能方向具有很大的潜力,且将推动无铅介电储能材料在实际中的应用.展开更多
文摘It′s important that HTS tapes have lower thermal conductivity and higher transversal resistivity in order to reduce the heat leaks conducted along the tapes and AC losses in the high temperature superconducting system conduction cooled by GM coolers. This paper presents an experimental investigation into the effects of pure Ag and AgAu alloys sheath materials on the properties of Bi(2223) multifilamentary tapes and the optimisation of conduction cooled hybrid current leads made from copper and Bi(2223)/Ag or Bi(2223)/AgAu tapes. The thermal conductivity of the tapes were measured by cryogenic steady heat flux method and the resistance was measured by using standard DC four probe method at low temperature. The results showed that the reduction of thermal conductivity by the addition of Au into the sheath material of Bi(2223) tapes was 65 0 0, 75 0 0 and 85 0 0 lower than that of pure Ag sheathed Bi(2223) tapes and the increase of resistivity was 4.9 , 10 and 19.4 times higher than that of pure Ag for the addition of 2.2 0 0, 5.7 0 0 and 10.7 0 0Au(atom ratio) respectively. And the study also attempts to optimise thermodynamically the conduction cooled hybrid current lead by using a developed model, which took the irreversibility of commercial GM coolers, the contact resistance and thermal conductance into account. Predictions from the model showed that AgAu alloys were suitable candidate materials to replace Ag as sheath material of Bi(2223) tapes applied in HTS current leads. In addition, Bi(2223)/AgAu was a suitable material to be applied as the HTS section of hybrid current leads in conduction cooled superconducting electric systems.
文摘通过流延成型技术,以片状K0.5Na0.5NbO3(简称为KNN)粉体为模板,结合掺杂改性后的基料粉体(K0.45Na0.55)0.98Li0.02(Nb0.77Ta0.18Sb0.05)O3-0.005Ba ZrO3(简称为KNNLST-BZ)流延制备出KNN基无铅压电陶瓷,研究了不同的工艺参数(烧结温度、烧结次数)对于KNNLST-BZ织构化陶瓷的电学性能、显微结构的影响。结果表明:模板含量为20wt%的KNNLST-BZ织构化陶瓷在1145℃下保温2 h呈现出优异的性能:压电常数d33=204 p C/N,横向机电耦合系数k31=23%,剩余极化强度Pr=26μC/cm2,矫顽场Ec=1.2 k V/mm。同时该织构化陶瓷在1145℃下烧结2次能得到更优的电学性能:d33=248 p C/N,k31=32.54%,Pr=38μC/cm2,Ec=1.2 k V/mm,介电损耗tanδ=6.38%,机械品质因数Qm=16.76,介电常数εT33/ε0=913.7,横向伸缩振动频率常数N1=2244。
文摘采用流延法成功制备了无铅弛豫铁电0.65(0.65Na 0.5 Bi 0.5 TiO 3-0.35BiMg 0.5 Ti 0.5 O 3)-0.35SrTiO 3陶瓷.研究了陶瓷的微观形貌、相结构、介电性能和储能行为.并在连续升温环境下,探讨了陶瓷的储能密度和储能效率的稳定性.结果表明:该陶瓷为纯钙钛矿赝立方结构且结晶性良好,晶粒分布均匀,并且该陶瓷表现出良好的储能性能及温度稳定性.陶瓷在275 kV/cm电场下获得了最大的储能密度3.55 J/cm 3,相应的储能效率为72.8%.在30~140℃间,储能密度最大变化率为6.4%.此研究表明0.65(0.65Na 0.5 Bi 0.5 TiO 3-0.35BiMg 0.5 Ti 0.5 O 3)-0.35SrTiO 3陶瓷在储能方向具有很大的潜力,且将推动无铅介电储能材料在实际中的应用.
