升华再结晶法制备AIN晶须及其生长特性

以AIN粉体为原料，加入适量的CaO-B2O3矿化剂，采用升华再结晶法制备AIN晶须．初步探讨了反应器及其合成温度对产物种类的影响，研究了晶须的结构特征及其生长机理．结果表明，初期的合成产物包括AIN晶柱、晶须和非晶AIN纤维，以VLS机制生长：后期产物为AIN晶须，表现为VS生长机制：XRD及TEM分析表明，晶须大多呈现沿｛2110｝、｛101l｝和｛0001｝，l＝0、1、2、3的晶面生长．多数晶须宏观生长轴向平行于这些晶面的法线，而部分晶须由于发生斜生长，导致宏观生长轴向与这些晶面的法线斜交．     

AlN晶须的形貌及取向

利用VLS法制备了AlN晶须,观察了诸如生长“小山”、堆垛等各种晶须形态．对AlN晶须的取向进行了研究,发现了一些不同于密排面的生长面,诸如{101n}（n＝1,2,3）．对AlN晶须的生长机制进行了初步探索,验证了螺旋位猪生长机制,并提出了斜生长机制,从而解释了VLS法制备的AlN晶须无[0001]取向的问题     

升华再结晶法制备AIN晶须及其生长特性

以ＡｌＮ粉体为原料，加入适量的ＣａＯ－Ｂ２Ｏ３矿化剂，采用升华再结晶法制备ＡｌＮ晶须，初步探讨了反应器及其合成温度对产物的种类的影响，研究了晶须的结构特征及其生长机理，结果表明，初期的合成产物包括ＡＬＮ晶柱、晶须和非晶ＡｌＮ纤维，以ＶＬＳ机制生长；后期产物为ＡｌＮ晶须，表现为ＶＳ生长机制：ＸＲＤ及ＴＥＭ分析表明，晶须大多呈现沿（２１１０）、（１０１ｌ）和（０００１），ｌ＝０、１、２、３的晶面生长，     

高温熔剂法制备氧化镁晶须的研究

采用MgCl₂·6H₂O为原料、KCl为助熔剂, 分段灼烧制备出直径1～50μm、长50～2000μm的MgO晶须. 通过对水氯镁石热解的理论分析、以及对灼烧各阶段产物的化学分析, 确定生成晶须的中间产物为无水氯化镁, 然后直接从无水氯化镁制备出MgO晶须. 并探讨了MgCl₂、HCl和H₂O浓度的变化对晶须形貌的影响. 提出了MgO晶须生长的机制: 即MgO分子在容器壁上非均相成核, 晶须生长的初期是以VLS机制进行, 在合成的后期, VLS机制变成VS机制.     

不同形貌TaCx晶须的制备及生长机理

通过不同的原料体系在合适的工艺条件下成功制备出碳化钽晶须（TaCx）。由Ta2O5-NaCl-C-Ni和Ta2O5-NaF-C-C12H22O11（蔗糖）体委制备的晶须呈平直的纤维形态，其生长机理为气-液-固（VLS）机制。由Ta2O5-KCl-C-Ni体系制备的晶须一部分通过VLS机理生长，而另一部分则通过LS机理生长，前者呈四方柱状，后者呈具有锥状柱体和之字形端部的特殊形貌。所有的原料体系均是在相近的工艺条件下进行，即反应温度1150-1350℃，氮气气氛保护。本工作对晶须的化学成分、形貌、晶体结构和生长机理进行了较详细的研究。     

TiO2和O-Al2O3晶体的生长习性

通过水热法制备粉体的实验观察到金红石、锐钛矿和α-Al2O3晶体的生长习性．采用配位多面体生长习性法则合理地解释了Ti O2和α-Al2O3的生长习性．其主要结果为α-Al2O3晶体的生长习性为平板{0001}，其各晶面的生长速度为：V｛0001 }＜V｛1123}；锐钛矿的生长习性为四面体，其各晶面的生长速度为V<010>=V<001>>V<010>>V<111>．而PBC理论很难合理地解释α-Al2 O3晶体的生长习性．     

草酸盐法制备硼酸镁晶须及其生长机理

以MgCl2·6H2O、H3BO3和H2C2O4·2H2O为原料,利用草酸盐法制备出长度为4.0～8.0μm,直径为0.6～1.5μm,长径比约为10,形貌良好的硼酸镁晶须。采用XRD、SEM及TG-DTA等分析手段,研究了烧结温度、烧结时间、n(B)/n(Mg)、n(H2C2O4)/n(Mg)对硼酸镁晶须的生长过程和质量的影响,探讨了其最佳制备条件。结果显示,硼酸镁晶须的最佳制备条件为:烧结温度为800℃,烧结时间为4.0h,n(B)/n(Mg)=1.2,n(H2C2O4)/n(Mg)=1.2。根据XRD和TG-DTA分析,MgC2O4前驱体对硼酸镁晶须的形成和生长有较大的促进作用,分解产物不引入其它杂质,使得制备的晶须纯度较高。晶须的生长机理为S-L-S机理。     

碳热还原法合成AlN晶须及其生长机理

以Ａｌ２Ｏ３和石墨为原料，采用碳热还原法制备ＡｌＮ晶须，研究了矿化主 种类及温度等工艺对ＡｌＮ晶须合成的影响。结果表明，以ＣａＦ２和Ｂ２Ｏ３为矿化剂的ＡｌＮ晶须是以ＶＬＳ机制生长的，     

高纯AlN晶须的制备

以A1,A1N粉为原料,采用合适的矿化剂,通过控制反应器内的温度和气相过饱和度,可以获得不同尺度的A1N晶须或枝晶,合成出的A1N晶须纯度高,晶体结构完整,晶须直径可控（1－20μm),长度为cm级,高温合成的A1N枝晶,直径为1mm,长度约0.5cm,为六棱椎形针状晶体,在｛21^-1^-1｝,｛101^-1｝面存在明显的择优取向,生长机理为气－固（VS）机理。     

水热法制备硫酸钙晶须及其结晶形态的研究

以天然生石膏为原料，氯化镁为晶型助长剂，研究了用水热合成法制备硫酸钙晶须的工艺影响因素．详细考察了料浆浓度、反应温度、反应时间、晶型助长剂种类及用量等对硫酸钙晶须形态的影响，用扫描电镜（SEM）及X射线衍射分析了硫酸钙晶须的形貌和相组成，并对晶须生长机理做了分析讨论．     

Structure characteristics of AlN whiskers fabricated by the carbo-thermal reduction method

With Al2O3 and graphite as raw materials, CaF2 and B2O3 as additives, AlN whiskers were fabricated by a carbo-thermal reduction method. The fabrication mechanism and growth characteristics of AlN whiskers were investigated. At the beginning of the high-temperature fabrication, AlN whiskers grew by the vapour/liquid/solid (VLS) mechanism, and defects existed on the surfaces of the whiskers. In later stages, the VLS mechanism possibly changed to a vapour/solid (VS) mechanism, and the defects disappeared. The orientation of most AlN whiskers was normal to (n=0, 1, 2, 3), and normal to (n=0, 1, 2). The growth processes of both two-dimensional nucleation and screw dislocations existed at the same time. © 1998 Kluwer Academic Publishers     

Al2O3/Ti-Al复合材料中Al2O3晶须的原位合成

利用氧对金属Ti、Al粉的部分氧化,原位合成了含有氧化铝晶须的Al2O3/Ti-Al复合材料,通过XRD和SEM等测试手段,发现Al2O3晶须呈网状交叉分布于基体内部的孔隙中.分析了晶须的生成机理,认为氧化铝晶须是通过VLS机理生成,复合材料的原始组成和温度对晶须的显微型貌有直接的影响:随原始组成中铝含量的增加,产物中晶须的数量总体上是在递增的,且发达程度逐渐提高;热处理温度对晶须直径有直接影响,温度升高可以增加晶须直径.     

含氢硅油制备SiC晶须的研究

以高含氢硅油为原料,在石墨基体上生长出SiC晶须。主要研究石墨基体的表面状态和加热温度对SiC晶须生长的影响,探究SiC晶须形成过程。影响SiC晶须形核和生长的主要因素为热处理温度,随着热处理温度的升高,SiC晶须的结晶产量也相应增高。石墨基体的表面状态对SiC晶须的形成也有一定的影响,随着石墨基体缺陷提供形核点的增多,SiC晶须的结晶产量提高,并且出现相互搭接的现象。SiC晶须的形成过程分为形核和生长两个部分,低温形核,高温生长,遵循VLS(气-液-固)生长机理。     

AN EXAMINATION OF THE GROWTH MODELS FOR TiC WHISKERS MADE BY CVD

Whiskers of refractory compounds such as carbides, nitrides and oxides have been grown by many researchers by chemical vapor deposition. The growth of whiskers from the vapor phase has been suggested to occur by the vapor-solid (VS) and/or the vapor-liquid-solid (VLS) mechanisms. In the growth of TiC whiskers with nickel as the catalyst, the VLS mechanism is widely accepted as the primary initial growth mechanism in which a ternary eutectic of Ni, Ti and C is considered to provide the growth path for the whiskers. In this paper, we examine the published literature on the growth of TiC whiskers by several researchers and show that this view of the ternary eutectic may not explain the whisker growth at temperatures below the eutectic point of the Ti-Ni-C system. This paper attempts to formalize a VLS mechanism model based on a binary eutectic for the observed formation of whiskers at lower temperatures,     

Formation of MgO whiskers on the surface of bulk MgB<Subscript>2</Subscript> superconductors during in situ sintering

Magnesium oxide (MgO) whiskers (with diameters of about 60–80 nm) formed on the surface of bulk polycrystalline MgB₂ superconductor at a relative low temperature (720 °C) during in situ sintering process. The reaction between Mg and B powders begins at a temperature below melting point of Mg and maintains till about 750 °C. The residual Mg powders evaporate and react with trace oxygen to form MgO vapor as the temperature exceeds the melting temperature of Mg and a low supersaturation is required for the growth of MgO whiskers. The preformed MgB₂ and MgO crystals act as substrates and the melted Mg powders on the surface of them serve as catalysts during the growth process of MgO whiskers. The growth process of MgO whiskers is dominated by a self-catalytic vapor–liquid–solid (VLS) mechanism.     

The morphology and growth mechanism of TiC whisker prepared by chemical vapour deposition

TiC whiskers with good quality and high yield are prepared by a modified chemical vapour deposition (CVD). The whisker morphology and factors affecting its formation have been investigated. Various whisker morphologies such as Wool-, Hassock-, Cluster-, bar-, Hedgehog-, and bamboo-like, are observed under different conditions. The morphologies of TiC whiskers are markedly affected by the gas flow rate and the C/Ti ratio, which is supposed to be related to concentration variation and the formation of Ni-Ti eutectic liquid phase. The growth characteristics of TiC whiskers are also affected by the stability of deposition parameters. It is found that in the course of whisker growth on nickel substrate, the well known VLS mechanism is not necessarily dominant. It is effective in the initial stage, but then might change to the VS mechanism with the dissipation of liquid droplets at the whisker tips. The deposition temperature plays an important role in changing from the VLS to the VS mechanism.