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431.
Li-Li Zhou Rang-Su Liu Ze-An TianHai-Rong Liu Zhao-Yang HouPing Peng Xuan-Min ZhuQuan-Hui Liu 《Physica B: Condensed Matter》2012,407(2):240-245
The kinetic details of crystallization in supercooled liquid Pb during the isothermal relaxation process have been investigated by molecular dynamics simulations, and the microstructure evolution analyzed by the cluster-type index method (CTIM) and the tracing method. It has been found that, the dynamic features are consistently correlated with the microstructure evolution and the crystallization characteristics in the mean square displacement (MSD) and the non-Gaussian parameter (NGP): the β relaxation regime corresponds to the minor structural rearrangement because of the “cage effect”, and the atoms attempt to escape from the “cages”; the α relaxation regime is related to a more diffusive movement of atoms, and the appearance of the second plateau in MSD and the non-zero plateau in NGP corresponds to the completion of crystallization. In addition, three distinct stages of nucleation, growth of nuclei and coarsening of crystallites in the crystallization process have been clearly revealed. 相似文献
432.
Sanghwa Lee Taegeon Oh Boa Shin Chinkyo Kim Dong Ryeol Lee Hyun-Hwi Lee 《Journal of Crystal Growth》2010,312(14):2038-2043
GaN nanorods were grown on Si(1 1 1) substrates by using hydride vapor phase epitaxy, and the crystallographic characteristics associated with their preferred growth directions were investigated by utilizing synchrotron X-ray reciprocal space mapping in a grazing incidence geometry and scanning electron microscopy. Crystallographic analysis reveals that the nanorods containing both wurtzite and zinc blende phase tend to have narrower distribution of the preferred growth directions than those containing only wurtzite phase. This tendency is partly attributed to the subtle interplay between polytypism and the preferred growth directions of GaN nanorods. 相似文献
433.
V.P. Solntsev A.V. Davydov V.K. Malinovsky N.V. Surovtsev 《Journal of Crystal Growth》2010,312(20):2962-2966
Melting and crystallization scenarios of barium tetraborate BaB4O7 (BaO·2B2O3) are studied in situ by Raman spectroscopy. It is shown that the scenario depends on the temperature–time history of melt. Crystallization conditions of the beta modification of barium tetraborate (β-BaB4O7) from a stoichiometric glass structure BaO·2B2O3 were investigated. 相似文献
434.
近年来, 单原子催化剂因其最大化的金属原子利用效率和高催化性能, 已成为能量存储和转化领域中的研究热点. 单原子催化剂的高活性主要来源于其低配位结构、 量子尺寸效应和原子与载体之间的强相互作用. 因此, 如何根据构-效关系开发通用且简单的制备高效单原子催化剂的方法具有重要的意义. 从实际应用的角度而言, 湿化学法因具有工艺简单和易于大规模生产的特性, 被认为是一种实现工业化制备单原子催化剂的方法, 现已开发了一系列制备负载型单原子催化剂的策略. 本文从独特的抑制反应物前驱体物质形核的角度出发, 总结了冷冻合成方法对形核的抑制机制, 进一步针对不同方面的应用, 探讨了单原子材料的催化机理, 并对其未来的发展进行了展望. 相似文献
435.
Dr. Biao Jin Ying Chen Jinhui Tao Dr. Kacper J. Lachowski Mark E. Bowden Zihao Zhang Dr. Lilo D. Pozzo Nancy M. Washton Karl T. Mueller James J. De Yoreo 《Angewandte Chemie (International ed. in English)》2023,62(28):e202303770
Hierarchical nucleation pathways are ubiquitous in the synthesis of minerals and materials. In the case of zeolites and metal–organic frameworks, pre-organized multi-ion “secondary building units” (SBUs) have been proposed as fundamental building blocks. However, detailing the progress of multi-step reaction mechanisms from monomeric species to stable crystals and defining the structures of the SBUs remains an unmet challenge. Combining in situ nuclear magnetic resonance, small-angle X-ray scattering, and atomic force microscopy, we show that crystallization of the framework silicate, cyclosilicate hydrate, occurs through an assembly of cubic octameric Q38 polyanions formed through cross-linking and polymerization of smaller silicate monomers and other oligomers. These Q38 are stabilized by hydrogen bonds with surrounding H2O and tetramethylammonium ions (TMA+). When Q38 levels reach a threshold of ≈32 % of the total silicate species, nucleation occurs. Further growth proceeds through the incorporation of [(TMA)x(Q38)⋅n H2O](x−8) clathrate complexes into step edges on the crystals. 相似文献
436.
Marcel J. Rost Leon Jacobse Marc T. M. Koper 《Angewandte Chemie (International ed. in English)》2023,62(27):e202216376
Many chemical surface systems develop ordered nano-islands during repeated reaction and restoration. Platinum is used in electrochemical energy applications, like fuel cells and electrolysers, although it is scarce, expensive, and degrades. During oxidation-reduction cycles, simulating device operation, nucleation and growth of nano-islands occurs that eventually enhances the dissolution. Preventing nucleation would be the most effective solution. However, little is known about the atomic details of the nucleation; a process almost impossible to observe. Here, we analyze the nuclei-distance distribution mapping out the underlying atomic mechanism: a rarely observed, non-random nucleation takes place. Special, preferential nucleation sites that a priori do not exist, develop initially via a precursor and eventually form a semi-ordered Pt-oxide structure. This precursor mechanism seems to be general, possibly explaining also the nano-island formation on other surfaces/reactions. 相似文献
437.
Lingjuan Hu Qin Li Yunjun Luo Bixin Jin Shumeng Chi Xiaoyu Li 《Angewandte Chemie (International ed. in English)》2023,62(42):e202310022
The fabrication of uniform cylindrical nanoobjects from soft materials has attracted tremendous research attention from both fundamental research and practical application points of view but has also posed outstanding challenges in terms of their preparation. Herein, we report a one-step method to assemble cylindrical micelles (CMs) with highly controllable lengths from a single liquid crystalline block copolymer by an in situ nucleation-growth strategy. By adjusting the assembly conditions, the lengths of the CMs are controlled from hundreds of nanometers to micrometers. Several influencing factors are systematically investigated to comprehensively understand the process. Particularly, the solvent quality is found determinative in either enhancing or suppressing the nucleation process to produce shorter and longer CMs, respectively. Taking advantage of this strategy, the lengths of CMs can be nicely controlled over a wide concentration range of four orders of magnitude. Lastly, CMs are produced on decent scales and applied as additives to dramatically toughen glassy plastic matrix, revealing an unprecedented length-dependent toughening effect. 相似文献