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Growth units and the crystallization habit of BaTiO3 nanocrystals have been investigated. It has been proposed that the growth units of BaTiO3 were surface hydroxylated Ti(OH)62- octahedra. The relationship between crystal morphology and the variation of the current intensity in the solution has been obtained through the measurement of the OH in the solution and the hydrothermal experiment with superimposed direct electric field. Based on the computation of the stability energy of the growth units, the relationship between the crystallized morphology of crystallites and the most favorable growth units under different conditions has been derived. It has been found that there is structure similarity between anatase (TiO2) and BaTiO3 from the crystal chemistry viewpoint, so they are soluble in each other, which can serve as a reasonable explanation for the abnormal phenomenon of the retention of cubic substable phase at room temperature. 相似文献
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Computing technology is developing very fast and has permeated among many fields of sci-ence and technology, giving rise to many interdisciplinary subjects. Crystallography, originating from the activity of mining and smelting, has now become a comprehensive subject concerning crystal growth mechanism, chemical composition, structural morphology and physical properties and its research scope is widened by introducing many new achievements from basic sciences such as physics, chemistry, and math… 相似文献
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The crystal structure of lead tungstate (PbWO4) can be regarded as ordered combination of the tungsten oxide tetrahedrons (WO4) and lead ions (Pb2 ). According to the growth unit model, the growth units of lead tungstate are the aggregations of the tungsten oxide tetrahedrons and lead cations with various geometry configurations. It is suggested that the favorable growth units of lead tungstate crystal are pyramidal, tetragonal prism and quadrangular units corresponding to geometric orientations of the simple forms of the crystal. Under low restricted growth conditions, the growth form of lead tungstate crystallites is the aggregation of the geometric configurations of these favorable growth units. The above conclusions are completely confirmed by the experiment on hydrothermal preparation of lead tungstate crystallites. 相似文献
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Theprocessofcrystalgrowthisgenerallydividedinto3stepsinsuccession,(i)thedissolutionofsolute,(ii)theformationofgrowthunits,and(iii)thetransportationandcombinationofgrowthunitsonthegrowthinterfaces.Theexistingformsofgrowthunitsareunderhotdiscussionnow,whilet… 相似文献
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Corundum(αAl2O3)isanimportanthightemperaturestructuralceramicmaterial.Inordertoimprovetheceramicpropertiesofthematerials,itisessentialforustopreparehighqualitysuperfinepowders(crystallites).Hydrothermalmethodmaybeusedtopreparemanykindsofsuperfinepowders(c… 相似文献
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本文分别以四氯化钛、硫酸钛和钛酸丁酯为前驱物,研究了水热条件下二氧化钛微晶粉体的结晶晶型、晶粒形貌和晶粒度.采用XRD和TEM等分析手段分别对产物的晶相和晶粒形貌进行表征.实验结果表明:对于200℃水热反应,以四氯化钛为前驱物,通过加入氢氧化钠调节反应介质酸碱度,当溶液pH值小于1时,有利于形成金红石型粉体;当溶液pH值大于3并小于7时,有利于形成锐钛矿型粉体;当溶液ph值大于7时,有利于形成板钛矿型粉体.以硫酸钛为前驱物,通过控制胶体制备工艺及反应温度,制备得到锐钛矿型和板钛矿型粉体.金红石型粉体呈长条柱状,锐钛矿呈菱形或双锥状,板钛矿呈板块状.经过较为系统的实验研究,获得了金红石、锐钛矿、板钛矿三种晶相的粉体,并可通过控制前驱物的种类及酸碱度和水热反应条件随意地制备出以上三种晶相中的单晶相粉体.从结晶学出发,解释了二氧化钛纳米粉体的结晶形貌,并从晶体生长过程及生长机理的角度讨论了二氧化钛同质变体的形成机理. 相似文献
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若干晶体中氧八面体结晶方位与晶体形貌 总被引:1,自引:0,他引:1
本文从结晶化学角度出发,研究了AB和A2B3和ABO3型氧化物晶体中的氧配位八面体的结晶方位与晶体结晶形貌之间的关系,提出晶体的结晶形貌是受晶体中负离子配位多面体结构和结晶方位所制约的。配位多面体顶角所对向的晶面生长速率最快,而面所对向的晶面生长速率最慢,配位体的棱所对向的晶面,生长速率居于两者之间,负离子配位多面体在晶体中的各个面族上连接和稳定性,决定了晶面的显露程度和晶体的结晶形貌。 相似文献
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