共查询到17条相似文献,搜索用时 203 毫秒
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纳米 KTi6O13w合成中的形态演化和生长机理 总被引:1,自引:0,他引:1
以纳米TiO2为原料,通过煅烧反应制备了纳米K2Ti6O13晶须,对晶须合成中温度和时间诱导的相变、形态演化和生长机理等进行了原位研究.结果表明;纳米TiO2作原料可显著降低晶须合成温度,适宜的煅烧温度为900-1100℃.形态演化观察和高温XRD分析表明;K2Ti6O13晶须的相变及生长对温度极为敏感,形态演化是基于初期爆发式的相变和随后串并联式的长大.K2Ti6O13晶须的生长遵守本研究提出的串并联机制,晶须轴向的生长台阶是串并联生长的直接结果. 相似文献
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316不锈钢应力腐蚀断裂扫描电镜研究 总被引:2,自引:1,他引:1
应用扫描电镜和X射线能量色散谱仪对316不锈钢应力腐蚀断口形貌、腐蚀产物及裂纹扩展的晶体学特征进行研究。结果表明,断裂为穿晶断裂,断口形貌为台阶条纹和河流花样,并有腐蚀产物和腐蚀坑等。通过对腐蚀坑形貌的研究,提出了腐蚀坑形态与晶面之间的关系,证明了316不锈钢在氯离子环境下的应力腐蚀开裂主要沿{100}、{111}、{110}晶面扩展的机制。 相似文献
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用原位自生法制备了Ti-40Al-2B(wt%)复合材料,并用XRD、SEM对复合材料的相组成和微观组织,特别是TiB2的形貌进行了研究。结果表明:该合金由TiAl和TiB2两相组成。其中TiB2颗粒以初生的块状和共晶的片状或细棒状形式共存。初生TiB2呈六面棱柱体,端面有清晰的生长台阶,其显露晶面分别为(0001)和{101 - 0}。结合晶体生长理论分析认为:TiB2的生长单元为一个硼原子和六个钛原子组成的三棱柱,硼原子位于三棱柱的中心,生长方式以台阶式生长为主。其中{112 - 1}面生长速率最快,{101 - 0}面生长速率最慢,导致TiB2形成以{101 - 0}面为棱柱面的六面棱柱结构。 相似文献
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Aluminium nitride (AlN) with various morphologies was fabricated through a sublimation-recrystallization method. The influences of type of reactor and temperature gradient were explored, as well as the orientations and growth mechanism of the obtained AlN whiskers. In the early stage of preparation, a vapour-liquid-solid (VLS) mechanism dominated, producing AlN pillars, whiskers and noncrystalline fibres. In the later stage, as the catalyst liquid was removed by volatilization, the pillars and noncrystalline fibres stopped growing, but the growth of AlN whiskers continued through a vapour-solid (VS) mechanism. By Laue method and rotating-crystal method of x-ray diffraction, together with electron diffraction, most of the AlN whiskers were discovered to grow on planes
, or
, where l=0, 1, 2, 3, along crystal axes
, or
, where w=0, 1, 2, 3. Oblique grown whiskers also appeared, with a growth direction at an angle of about 54° to the growth plane,
. 相似文献
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ShanrongZHAO JiyangWANG DaliangSUN JingLI XiaoboHU 《材料科学技术学报》2003,19(2):120-122
The {0001} face develops on the habit of self-frequency doubling laser crystal Yb: YAl3(BO3)4 (YbYAB) only under high growth rate condition, and its morphology is rough. To study the growth mechanism of {0001} face, we have observed the growth morphology on {0001} polishing section by atomic force microscopy (AFM). A series of AFM images captured in different growth durations on the {0001} polishing section reflect the crystal growth process. It is shown that the growth morphology on the {0001} polishing section was rough with many hillocks at the first growth stage, and it can become smooth finally, although the growth morphology on the {0001} face develoFed naturally on YbYAB crystal habit is always rough. On the smooth {0001} surface formed at the last growth stage, there aresome triangular pits. This fact is different from that of hillocks in most crystal growth morphologies. AFM can easilydistinguish the pits or hillocks on the surface, but differential interfere contrast microscopy (DIC) can not do. Theorientation of the triangular pits is just the opposite to the triangular {0001} faces. The chemical etching patternis also composed of this kind of triangular pits. These growth morphology and etching pattern of the {0001} facesshow 3m symmetry, but the point group of YbYAB crystal is 32. The symmetric contradiction between morphologyand point group does not exist for quartz, although whichsurface morphology we can distinguish the right form ormorphology we can not do. The reason for the symmetricand its point group is not known yet.has the same point group as YbYAB. From quartz {0001}left form of the crystal, but from YbYAB {0001} surfacecontradiction between YbYAB {0001} surface morphology and its point group is not known yet. 相似文献
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The atomic structure of [0001] Σ 7 tilt grain boundaries with {
}‖ {
}, {
}‖ {
}, and {
}‖ {
} boundary planes in ZnO was investigated through high-resolution transmission electron microscopy observation of fiber-textured thin films and atomistic calculations. These boundaries were found to comprise three kinds of common structural units that are characterized by fourfold- to eightfold-coordinated channels along the [0001] direction in contrast to sixfold-coordinated channels in wurtzite structure. The boundary structural units are very similar to the multiple core structures of edge dislocations with Burgers vectors of 1/3 <
> . Transformation between two of the three configurations can easily occur through an atom flipping corresponding to dislocation glide. Depending on the orientation of boundary planes with respect to the Burgers vectors, the dislocation-like units exhibit straight or zigzag arrangements with periodicities corresponding to the Σ 7 misorientation. 相似文献
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Potassium Dihydrogen Phosphate (KDP) crystal doped with L-arginine (L-arg) amino acid with 1.4 wt% concentration in the solution was grown onto a point seed by the method of temperature reduction. For the first time an attempt was made to grow large-size (7 × 6 × 8 cm3) optically transparent crystals, which allowed to analyze the effect of L-arg additive on the physical properties of the different growth sectors ({100} and {101}) of KDP. The incorporation of L-arg into both growth sectors of the crystal was confirmed by the methods of optical and IR spectroscopy and found to be caused by the ability of the amino acid to form hydrogen bonds with the face {100} and electrostatically interact with the positively charged face {101} of KDP crystal. A slight variation in the unit cell parameters was reported, the elementary cell volume of KDP:L-arg crystal increased in comparison with the one of pure KDP by 2·10−2 and 2.07·10−2 Å3 in the sectors {100} and {101}, respectively. It was found that the doping of L-arg enhanced the SHG efficiency of KDP and depended on the crystal growth sectors. The SHG efficiency of KDP:L-arg was by a factor 2.53 and 3.95 higher in comparison with those of pure KDP for {101} and {100} growth sector, respectively. The doping was found to lead to softening of both faces by ∼3–10% and ∼14–17% in the sectors {101} and {100}, respectively. Investigation of the influence of L-arg molecules on the bulk laser damage threshold of the crystals showed that the bulk laser damage threshold of the samples of KDP:L-arg crystal was higher than the one of the pure crystal in the sector {101} and lower in the sector {100}. The correlation between microhardness and laser damage threshold were discussed. The study is helpful for further searching, designing and simulation of hybrid NLO materials. 相似文献
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硫化物晶体的生长习性 总被引:5,自引:0,他引:5
在自然界中硫化物晶体的种类较多,其结构较复杂,其中硫离子以S2-和对硫S2-2形式存在.一部分晶体的生长习性得不到满意的解释.本文采用配位多面体生长习性法则合理地解释了MoS2、ZnS、CuFeS2和PbS晶体的生长习性.发现MOS2晶体的生长习性为六方平板状{0001},其各晶面的生长速度为:V<0001><V<1010>;CuFeS2和ZnS晶体的生长习性为四面体,其各晶面的生长速度为:V<111>>V<001>>V<111>;PbS晶体的生长习性为八面体{111},立方体只是它的一种习性变化. 相似文献