For the first time, a molecular dynamics simulation study has been performed for a liquid metal system consisting of 50000 atoms to deeply investigate the transitions of microstructure configurations during the rapid ...For the first time, a molecular dynamics simulation study has been performed for a liquid metal system consisting of 50000 atoms to deeply investigate the transitions of microstructure configurations during the rapid cooling processes. Especially, the cluster-type index method has been adopted to analyze the transforming and evolving processes of clusters and cluster configurations from liquid metal atoms. It has been found that the bigger cluster configurations in the system are formed by means of connecting some small clusters (they are combined by several smaller clusters), and not taken on the multi-shells configuration accumulated with an atom as the center and the surrounding atoms arranged according to some fixed pattern. With the decrease in temperature, the probability of repetitive appearance for clusters increases largely, which reveals that clusters are indeed possessing a certain relative stability and continuity ( namely hereditary effect). These results will give us an important enlightenment to understand not only the forming mechanisms and microscopic processes of the short-order sections and disorder sparse seiions in amorphous structures but also the freezing processes of liquid metals.展开更多
基金This work was supported by the National Natural Science Foundation of China (Grant No. 59871016) .
文摘For the first time, a molecular dynamics simulation study has been performed for a liquid metal system consisting of 50000 atoms to deeply investigate the transitions of microstructure configurations during the rapid cooling processes. Especially, the cluster-type index method has been adopted to analyze the transforming and evolving processes of clusters and cluster configurations from liquid metal atoms. It has been found that the bigger cluster configurations in the system are formed by means of connecting some small clusters (they are combined by several smaller clusters), and not taken on the multi-shells configuration accumulated with an atom as the center and the surrounding atoms arranged according to some fixed pattern. With the decrease in temperature, the probability of repetitive appearance for clusters increases largely, which reveals that clusters are indeed possessing a certain relative stability and continuity ( namely hereditary effect). These results will give us an important enlightenment to understand not only the forming mechanisms and microscopic processes of the short-order sections and disorder sparse seiions in amorphous structures but also the freezing processes of liquid metals.
文摘采用固相反应法制备了Ca Cu_(3)Ti_(4)O_(12)(CCTO)及Y^(3+)掺杂的Ca_(0.97)Y_(0.03)Cu_(3)Ti_(4)O_(12) (CYCTO)陶瓷,研究了陶瓷烧成过程中采用随炉冷却和在空气中快速冷却的工艺对陶瓷样品物相结构、微观形貌和介电性能的影响。结果表明,当采用随炉冷却工艺时,Y^(3+)掺杂的CYCTO陶瓷的介电常数(ε′)相对于未掺杂的CCTO陶瓷有所提高,同时介电损耗(tanδ)也得到同步降低。而当采用在空气中快速冷却的工艺时,CYCTO陶瓷的ε′和tanδ得到进一步优化。阻抗分析表明,在空气中快速冷却的CYCTO陶瓷的晶粒导电性和晶界的绝缘性得到同步提高,从而增强了CYCTO陶瓷的介电响应而提高了ε′;而晶界绝缘性地提高导致了tanδ的进一步降低。快速冷却的CYCTO陶瓷在1 k Hz时,其ε′高达4.06×10~4,tanδ降低到0.036,其介电性能比随炉冷却的CCTO陶瓷(ε′=1.68×10~4,tanδ=0.16)得到显著提升。
