共查询到19条相似文献,搜索用时 125 毫秒
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本文研究了常压下液态Bi在落管所提供的高清洁、无容器环境中自由下落和在氦气保护下经循环过热处理后的过冷行为。通过控制液滴的尺寸和冷却速率得到了较大的过冷度。过冷样品具有与常压稳定相Bi-Ⅰ(三角点阵)完全不同的单斜点阵。其点阵参数为a=0.696 8 nm,b=0.628 6 nm,c=0.339 7 nm, β=110.33°;单胞体积为0.148 8 nm3,它与Brugger等人在2.6 GPa下得到的Bi-Ⅱ高压相(单斜点阵)的单胞体积相比,后者有一个9.34%的体积压缩,这与Bridgman的结果符合得很好。 相似文献
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采用水热合成法,合成了一种新型的Cd(II)配合物Cd1O8C9H8.为单斜晶系,c1 2/c1(12)空间群,a=1.97328(9)nm,b=0.91088(4)nm,c=1.33636(6)nm,α=90°,β=117.884(1)°,γ=90°,V=2123.12(17)(0.1nm)^3,Z=8。 相似文献
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一维链状配合物[BrBzPy][Ni(dmit)2]的合成和红外光谱研究 总被引:1,自引:0,他引:1
合成了一种新的化合物[BrBzPy][Ni(dmit)2](1),并进行了红外光谱表征.晶体的结构结果表明它的空间点群为P21/c,a=0.627 5(1)nm,b=1.743 8(3)nm,c=2.283 9(3)nm,α=90°,β=9.187(1)nm,γ=90°,V=2.497(7)nm3,Z=4,Mr=700.57,Dc=1.863 g·cm-3.晶体中[Ni(dmit)2]-非常接近平面,共轭性相当显著,且成为一维链状结构. 相似文献
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用X射线衍射仪测量了La0.25Ca0.75MnO3多晶粉末在300K和70K时的晶体结构衍射谱,并用Rietveld全谱拟合法对这些数据进行了拟合.结果表明,在室温时,La0.25Ca0.75MnO3由于MnO6八面体的Jahn-Teller晶格畸变,其晶体结构已发生了扭曲,晶格常数分别为a=0.53559nm,b=0.75537nm,c=0.53587nm.温度降至70K时,X射线衍射谱上出现了比室温更多的衍射峰,有些峰发生了“双峰”劈裂,但仍然具有与室温相同的晶体对称性(空间群为Prima).70K时的晶格常数分别为a=0.53673nm,b=O.74785nm,c=O.53718nm,与300K时的晶格常数比较,a和c分别增大了O.21%和O.24%,而b减小了1.O%,这一晶体结构的巨大变化源于在电荷有序态下形成了静态的合作Jahn-Teller效应. 相似文献
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Abstract A metastable hexagonal close-packed (hcp) phase obtained by rapid quenching from the melt has been compressed to 5.7 GPa and annealed up to 1023 K. The axial ratios (c/a) of the hcp structure at the initial state, the stable state annealed under high pressure (5.7 GPa, 673 K) and the quenched state from high pressure and high temperature condition are 1.630, 1.635 and 1.628, respectively. The volume reduction of the hcp structure by application of high pressure gives rise to increase the c/a ratio, which corresponds to an apparent reduction in the number of valence electrons per atom (e/a) in the Hume-Rothery alloys. 相似文献
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L. Si J. Ding Y. Li B. Yao H. Tan 《Applied Physics A: Materials Science & Processing》2002,75(4):535-539
The structure and magnetic properties of amorphous melt-spun and subsequently crystallized GdNiAl ribbons were investigated.
An amorphous phase was formed after the quenching process by melt spinning with a copper wheel having a surface speed of 30 m/s.
A hexagonal phase with lattice parameters a=7.023 ? and c=3.916 ? was formed in the GdNiAl ribbon after annealing above its
crystallization temperature. Magnetic entropy change was calculated directly from isothermal magnetic measurements. The results
show that both the amorphous and annealed samples have a high magnetocaloric effect, indicating that these alloys can be considered
as candidates for magnetic refrigeration applications.
Received: 14 August 2001 / Accepted: 18 September 2001 / Published online: 23 January 2002 相似文献
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本文研究了低压低质量流速条件下垂直圆管管内顶部骤冷过程中骤冷温度的分布特性。采用瞬态热块实验技术和非稳态两维数值分析技术,得到了实验段内壁温度随时问的分布规律:以此为基础,采用双切线交点模型,确定骤冷前沿点的位置,温度和时间,以相应的骤冷温度理论关系式为基础,同时考虑管道内流动参数对骤冷温度的影响,建立了本文的骤冷温度半经验关系式模型和半经验关系式。 相似文献