共查询到20条相似文献,搜索用时 109 毫秒
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同样由熔体凝固、溶液沉淀或者气相沉积出来,为什么有的材料呈晶相,有的呈非晶相? 晶体生长是由自组装形成的还是由外界条件决定的?是哪项因素决定了晶体生长时原子的有序排列?本文根据实际现象,用晶体生长的热力学理论分析了逆向离子解离对晶体成核及生长的作用机理,并对固态材料的形成与晶体成核生长之间的关系也作了进一步的阐述和分析,由此得出结论认为,由化学键结合的材料在晶体生长时必须伴随着逆向离子解离平衡,正是固态材料形成过程中的逆向离子解离过程,如同时伴随着电离的溶解、熔化及升华过程,决定了晶体生长时原子的有序排列. 相似文献
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“如何突破大尺寸晶体材料的制备理论和技术”是中国科协发布的2021年度的十大前沿科学问题之一,揭示晶体生长机制和突破生长关键技术是大尺寸功能晶体发展的两个趋势。在原子分子尺度上,晶体生长可以是有势垒的热激活过程,也可以是无势垒的超快结晶过程,这与具体的体系以及晶面有关。从界面属性角度来看,光滑界面是以台阶拓展的方式生长;粗糙界面没有明显的固-液分层,通过局部原子固化进行生长。本文从晶体生长理论模型、生长技术及其应用实例,以及分子动力学方法在晶体生长中的应用等方面探讨了近些年大尺寸晶体快速生长理论和技术的研究进展。目前有多种方法制备大尺寸晶体,但普遍存在制备的晶体质量差和性能不稳定等问题。需要突破对晶体生长微观机制上的认识,建立机制与温度、流速等外界因素的内在联系。而利用机器学习力场以及分子动力学模拟方法,建立固-液界面,模拟晶体生长,将是探究晶体生长微观机制的一种有效方式。 相似文献
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Myron Pankevich Ju. Linhart 《人工晶体学报》2006,35(5):963-975
本文通过分析光学材料中光谱与温度之间的关系证实了晶体生长过程中的相变团簇模型,认为晶体内部热辐射流是引起固-液界边界层温度场发生传导的可能原因.引入了前结晶的概念,并结合实际中的不同晶体生长方法讨论了包裹体及气泡的抑止机理,通过计算得到了生长理想晶体的最大生长速率并且解释了由于界面层的摆动使得晶体生长过程中产生的微气泡没有被移动的界面层所捕获. 相似文献
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采用DTA对不同铟含量(x)的AgGa1-xInxSe2多晶熔化和结晶温度进行了测试.结果表明:随着x值的增加其过冷度增大.采用改进的垂直布里奇曼法和实时补温技术,对AgGa1-xInxSe2晶体生长过程中的结晶特性和生长温度场关系进行了研究,并对其结晶形态进行了观测.发现:随着晶体生长过程的进行,熔体结晶温度呈下降趋势,固-液界面发生移动;生长晶体表面存在外形规则、形状相同的半球状小孔,有取向一致的台阶反光面,小孔底部为{112}面.研究结果为大尺寸、高质量的AgGa1-xInxSe2单晶体生长奠定了基础,生长出了尺寸达20 mm×60 mm的完整AgGa1-xInxSe2单晶体. 相似文献
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为选择合理的晶体生长速度,在用改进Bridgman法生长直径为φ19mm的HgCdTe(x=0.21)晶体过程中,对正在生长的单晶体及熔体进行淬火,以观察其固液界面形态.初步的实验结果表明:在2mm/d及9mm/d的两种生长速度条件下,石英安瓶中的固液界面形态均为凹形抛物面,但其凹陷深度分别为10mm和14mm.较低的晶体生长速度条件下,凹陷深度较小,固液界面形态较平.由实验和讨论得知,宜选择较低的晶体生长速度用改进Bridgman法生长HgCdTe晶体. 相似文献
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Alexander Hübner Daniel Strobusch Hans-Wolfram Lerner Michael Bolte 《Journal of chemical crystallography》2008,38(12):953-957
Abstract The crystal structure of the title compound, C30H42O12Zn3, originally determined from untwinned crystals (Bennett et al. Acta Cryst B 24:904, 1968) has been redetermined from twinned
crystals. The effect of the twinning is that additional reflections appear in the diffraction pattern leading to a unit cell
with a too long c-axis in which the structure cannot be solved. Thus, for a successful structure solution the correct unit cell has to be found
and for refinement the twinning has to be taken into account. The central Zn atom is located on a twofold rotation axis. It
is hexacoordinated in a distorted octahedral mode, whereas the coordination geometry of the two terminal Zn atoms is distorted
trigonal bipyramidal.
Index Abstract The crystal structure of the title compound, Zinc(II) acetylacetonate trimer, has been redetermined from twinned crystals.
For a successful structure solution the correct unit cell had to be found and for refinement the twinning had to be taken
into account. The central Zn atom is located on a twofold rotation axis. It is hexacoordinated in a distorted octahedral mode,
whereas the coordination geometry of the two terminal Zn atoms is distorted trigonal bipyramidal.
An erratum to this article can be found at 相似文献
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The present study investigates the effects of magnetic field orientation, magnetic field strength and growth rate on the dopant segregation in semiconductor crystals, and presents results of dopant composition in the crystal and in the melt at several different times during growth for several combinations of process parameters. The crystal's lateral segregation depends on the magnetic field's orientation and strength while the axial segregation depends on the magnetic field's strength and the growth rate. If either convective or diffusive transport truly dominates, then the crystal's dopant distribution is laterally uniform. The axial distribution in the crystal approaches the well-mixed limit if the melt motion is strong and the growth rate is slow, and the distribution approaches the diffusion-controlled limit if the melt motion is slow and the growth rate is fast. The deviations of the dopant distribution in the crystal from lateral uniformity and from the classical limits are quantified for several combinations of process parameters. 相似文献
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V. N. Kanishchev 《Crystallography Reports》2004,49(6):1053-1055
The variational method is applied to the study of crystal growth from melt under the condition that the boundary between the liquid and solid phases has a cellular structure. The surface energy of the interface is taken into account. 相似文献
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《Progress in Crystal Growth and Characterization of Materials》2016,62(2):203-211
Crystal growth occurs at the interface of a crystal and its growth medium. Due to the abrupt termination at the surface, at the interface the properties of the crystal will typically deviate from the bulk and this can affect the growth behaviour. Also the properties of the growth medium at the interface will typically differ from the bulk. In growth from solution, for example, the liquid will show ordering induced by the crystal surface or have a different composition. Here techniques to study such growth interfaces will be discussed together with examples of the effect that the properties of the interface can have on the growth. 相似文献
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以2,6-双(2-吡嗪基)吡啶-4-对苯甲酸和MnCl2为原料,在水热条件下合成了二维锰(Ⅱ)配位聚合物[Mn2(bppc)4(H2O)]n·2nH2O,并用元素分析、红外光谱、X射线单晶衍射对此配位聚合物进行了表征,测定结果表明,晶体属于单斜晶系,P2(1)/c空间群,晶胞参数为:a=10.3918(9) nm, b=24.519(2) nm ,c=7.0140(6) nm,α=90°,β=105.0890(10)°,γ=90°.此配位聚合物中MnII之间通过配体中吡嗪环上的氮和羧基氧的桥连形成一维链状结构,一维链再通过羧基基团上的氧的进一步桥连形成二维结构.另外,热重分析表明,此配位聚合物具有较好的热力学稳定性. 相似文献
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