...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Nucleation mechanisms: A crystal-chemical investigation of phases forming in highly supercooled aluminosilicate liquids
【24h】

Nucleation mechanisms: A crystal-chemical investigation of phases forming in highly supercooled aluminosilicate liquids

机译：成核机理：高度过冷硅铝酸盐液体中相形成的结晶化学研究

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Crystal nucleation and growth have been investigated approximately 100 K above the glass transition for 12 liquids in the system CaO-Al2O3-SiO2.Nucleation takes place heterogeneously at the gas-liquid interface, yielding various crystal structures, namely, those of yoshiokaite, gehlenite, larnite, anorthite and wollastonite. Characterization by Raman spectroscopy, transmission electron microscopy and electron microprobe indicate that these phases are highly disordered, poorly crystallized and generally nonstoichiometric. Even for incongruent crystallization, crystals have the same Si/Al ratio as their parent melts but variable CaO contents. These features may be rationalized in terms of the contrasting mobility of network-forming cations, which practically vanishes at the glass transition, and that of calcium which remains significant. The fact that the mobility of network-modifying cations controls the structure and composition of nucleating phases implies that liquid viscosity (controlled by the mobility of network formers, i.e. the frequency of Si-O and Al-0 bond breaking) is not an appropriate scaling parameter for crystal nucleation. In turn, this may provide an explanation for the discrepancies, reaching many orders of magnitude, between experimentally determined nucleation rates and those predicted from classical and non-classical nucleation theories. An additional factor contributing to such discrepancies is that thermodynamic data obtained on stoichiometric phases stable at liquidus temperatures are not appropriate for estimating the thermodynamic barrier to nucleation of the metastable crystals that actually form at large degrees of supercooling. (c) 2005 Elsevier B.V. All rights reserved.
机译：对于CaO-Al2O3-SiO2系统中的12种液体，已经在玻璃化转变温度以上约100 K处研究了晶体成核和生长。成核发生在气液界面的异质状态，产生了各种晶体结构，即吉冈石，钠钙石，芒硝，钙长石和硅灰石。通过拉曼光谱，透射电子显微镜和电子探针的表征表明，这些相高度无序，结晶性差并且通常是非化学计量的。即使结晶不一致，晶体的Si / Al比也与其母体熔体相同，但CaO含量可变。这些特征可以根据形成网络的阳离子的对比迁移率来合理化，该迁移率实际上在玻璃化转变时消失，而钙的迁移率仍然很重要。网络修饰阳离子的迁移率控制着成核相的结构和组成这一事实表明，液体粘度（由网络形成剂的迁移率控制，即Si-O和Al-0键断裂的频率控制）不是适当的缩放比例晶体成核的参数。反过来，这可以为实验确定的成核速率与根据经典和非经典成核理论预测的成核速率之间达到许多数量级的差异提供解释。导致这种差异的另一个因素是，在液相线温度下稳定的化学计量相上获得的热力学数据不适用于估算实际上在很大程度过冷时形成的亚稳晶体成核的热力学势垒。 （c）2005 Elsevier B.V.保留所有权利。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号