P2O5—Li2O—BaO系统玻璃结构的X射线衍射研究

用径向分布函数(RDF)法研究了在P_2O_5-Li_2O二元系统玻璃中引入Ba~(2+)离子取代Li~+离子对玻璃结构的影响。RDF曲线可以提供关于Ba~(2+)离子分布的重要信息。同时,也可以判断含钡锂磷酸盐玻璃的主要结构是以〔PO_4〕四面体为单元的链状网络结构。RDF曲线上的1.54-1.56A的峰,归属为〔PO_4〕四面体中P-O最近邻距离(统计平均值)的贡献;而4.00-4.15A和7.15-7.45A的特征峰,归属为Ba-Ba近邻距离的贡献。玻璃中Ba~+离子的存在,使连结非桥氧的方向键有所加强,将影响磷酸盐链之间离子键的强度,从而导致玻璃的一些物理性质变化。     

超硬材料C_3N_4的X射线衍射图谱模拟

运用材料模拟软件Materials Studio计算模拟了α-C3N4及β- C3N4的晶体结构及X射线衍射图谱,并将实验所得的XRD数据与模拟结果进行了对比分析.通过数值模拟,可以为实验结果提供标准的参考数据,并检验实验结果.     

多晶X—射线衍射在催化研究中的应用

通过研究工作中的一些实例,介绍了ＸＲＤ在催化研究中的应用,它涉及物相分析、晶粒大小和晶格常数的测定等。用这些方法,研究了催化剂的活性组分、制备条件和制备过程的相变。     

拉伸CPE结晶度的X射线衍射测定

为了校正用赤道线的衍射数据代替倒易空间内的衍射数据计算拉伸CPE结晶度所造成的偏差,本文在高聚物两相模型的基础上,根据概率论原理,假设拉伸后的CPE的非晶散射强度符合均匀分布,结晶衍射强度在赤道线附近符合正态分布,以分布曲线在赤道线上的概率的倒数为校正因子K,对拉伸CPE赤道线X射线衍射谱的强度进行了校正。结果表明;和其他方法相比,此法具有较好的全反射空间统计性,是测定拉伸高聚物结晶度的实用方法。     

X射线衍射技术在聚酯研究中的应用

X射线衍射技术在研究材料晶体结构方面作用显著,是聚酯产品研究过程中晶型结构研究的重要工具,能够直观反映晶体结构的变化.聚酯产品的结晶性能与其加工性能直接相关,利用X射线衍射仪测定聚酯产品的结晶度具有明确意义且应用广泛.     

碳纤维的X—射线衍射和喇曼散射的研究

本文利用X射线衍射和喇曼散射研究了三种国产碳纤维高温热处理后结构变化的规律。结果表明，随热处理温度升高，碳纤维的微晶变大，择优取向程度增加，并逐步向多晶石墨转化，MPPCF和BDF石墨化程度高，属于易石墨化碳纤维，PANGF石墨化程度低，属于难石墨化碳纤维。     

X射线衍射法测定PBAT聚酯的结晶度

X射线衍射技术在研究材料晶体结构方面作用显著,是聚酯产品晶型结构研究的重要工具,能够直观反映晶体结构的变化。聚酯产品的结晶性能与其加工性能直接相关,利用X射线衍射仪测定PBAT聚酯切片的结晶度,同时考察不同加工条件下PBAT聚酯注塑片的结晶度变化,随着熔体温度的升高,PBAT聚酯注塑片的结晶度逐渐下降。     

MgF2氧化现象的X射线衍射研究

采用X射线衍射方法，研究高稳定化学结构的MgF2在30％Ag（质量分数，下同）掺杂下，在低真空中（≥30Pa）高温（≥600℃）烧结后，氧化成为MgO的过程。在烧结温度为600℃，恒温时间为2h时，XRD出现d为24326,2.1065,1.4896A的MgO衍射峰。随着烧结温度升高，MgF2的衍射峰逐渐减弱减少，MgO的衍射峰则逐渐增强增多。到1250℃时，MgF2的衍射峰全部消失。然而，将MGf2-30%Ag样品在高真空中（＜10^-3Pa)1000℃烧结，恒温2h，未观察到MgF2有氧化现象。如果将纯MgF2样品在开口高温炉中（即大气中）1000℃烧结，仅发现3个较弱的MgO衍射峰（相应的d值为2.1008,1.4882,1.0525A),MgF2衍射峰全部出现。讨论了MgF2的氧化机理，指出Ag在MgF2的氧化过程中起了中间媒介作用。     

X-RAY DIFFRACTION STUDY OF SODA-BORIC OXIDE GLASS *

X-ray diffraction patterns have been made of three samples of soda-boric oxide glass of the following molal compositions: 0.114 Na₂O, 0.225 Na₂O, and 0.333 Na₂O. The patterns were made in an evacuated camera, using MoK α radiation monochromatic by reflection from rock salt. Radial distribution curves for the three compositions were obtained by Fourier analysis. The first peak of the distribution curves is due to the boron-oxygen separation. The distances are 1.37, 1.42, and 1.48A. From the peak areas, the number of oxygens about a boron is found to be 3.2, 3.7, and 3.9. The continuous change, both in interatomic distance and number of surrounding oxygens, indicates that the borons are partly in triangular and partly in tetrahedral coordination, the fraction in the latter increasing with increase of soda. Six oxygens about each sodium at 2.4A and from five to six oxygens about each oxygen at 2.4A are consistent with the distribution curves. The results can be interpreted in terms of a random network picture of vitreous soda-boric oxide, in which the borons are bonded either to three or four oxygens and the sodium atoms are randomly distributed in holes in the boron-oxygen network. Maxima and minima in the physical properties of glasses containing boric oxide and soda are explained in terms of the ability of the boron atom to change to tetrahedral coordination when some oxide such as Na₂O is present to supply the necessary extra oxygen.     

X-RAY STUDY OF LIME-PHOSPHATE AND LIME-BORATE GLASS*

X-ray diffraction patterns have been made of two lime-phosphate glasses with compositions of 23% and 28% of CaO by weight, and of one lime-borate glass with 25% of CaO. Fourier analyses of these patterns were carried out, and the radial distribution curves were plotted. In the lime-phosphate glasses, each phosphorus is tetrahedrally bonded to 4 oxygens at a distance of 1.57 A, and each oxygen is bonded to either 1 or 2 phosphorus atoms. The calcium ions, Ca⁺⁺, are situated in the holes in the phosphorus-oxygen network and have about 7 oxygen neighbors. In the lime-borate glass, some of the borons are triangularly bonded to 3 oxygens, and the others are tetrahedrally bonded to 4 oxygens.     

THE STRUCTURE OF SILICA GLASS BY X-RAY DIFFRACTION STUDIES *

Three definite conclusions can be drawn from the X-ray diffraction studies of vitreous silica. (1) The tetrahedral scheme of coordination, in which each silicon is tetrahedral surrounded by four oxygens and each oxygen shared between two silicons, is given directly by the Fourier analysis. (2) The liquid-like continuity in the structure of glassy silica with no indication of discrete particles is given by the absence of small-angle scattering. (3) If the diffraction pattern is explained by assuming small cristo-balite crystals in the glass, calculations are made from the peak breadth that the particles can not be greater than about 8A. The random-network theory of the structure of glass is in agreement with these experimental facts.     

X-RAY STUDY OF SODA-LIME-SILICA GLASS*

X-ray diffraction patterns of three compositions of soda-lime-silica glass were made, and radial distribution curves for the three glasses were obtained from Fourier analyses of the patterns. The results indicate that the silicon atoms are tetrahedrally bonded to 4 oxygens. Each oxygen is bonded to either 1 or 2 silicons. If each sodium is assumed to be surrounded by 6 oxygens, each calcium must be surrounded by about 7 oxygens. The structure is similar to that of soda-silica glass except that some of the sodiums are replaced by calciums. A qualitative correlation of the structure with density and coefficient of expansion is made.     

X-RAY STUDY OF POTASH-SILICA GLASS*

X-ray diffraction studies have been made of two samples of potash-silica glass whose composition is 20.9% and 29.1% of K₂O by weight. A Fourier analysis of the intensity curves indicates a structure similar to that found in soda-silica glass. Each silicon is tetrahedrally bonded to 4 oxygen ions, with each oxygen bonded either to 1 or 2 silicons. The K⁺ potassium ions are situated in holes in the silicon-oxygen network with an average of about 10 oxygen neighbors.     

钾基蒙脱石的分子力学和分子动力学模拟

利用分子力学(molecular mechanics,MM)和分子动力学(molecular dynamics,MD)模拟了K-蒙脱石层间阳离子和水的结构及动力学特征,并将模拟的X射线衍射结果与实验值进行比较.结果显示:在K-蒙脱石的最优构型中,层间距随着水含量的增加而增大;X射线衍射的模拟结果和实验结果一致;K+的位置和蒙脱石层间电荷位置有关,K+在1,2层水合物中依附于黏十的表面附近,而在3层水合物中K+则脱离表面开始向层中其它方向扩散.水分子在黏土层间分散于各个方向,而且存在水质子和K+竞争电荷位置的现象.水和K+在钾基蒙脱石中的活动性低于其在水中和溶液中的活动性.径向分布函数分析结果表明K+组织水分子的能力有限,说明K+对蒙脱石的水化膨胀起抑制作用.     

煤及半焦X射线衍射原子分布函数解析程序

应用FORTRAN5．1编制了煤及半焦X射线衍射原子分布函数解析程序,可以解析长程无序而短程有序的结构,得到原子间距、配位数、有序度等结构信息．该程序实现了数据处理与图形显示一体化．简述了该程序的基本结构、功能和特点,并进行了例证分析．     

CaO-Al2O3-SiO2系玻璃陶瓷的析晶动力学研究

采用差热分析方法(DTA)对CaO-Al2O3一SiO2体系玻璃陶瓷的析晶动力学参数进行了测定,研究了该系统微晶玻璃的析晶动力学.结果表明:随着CaO/SiO2比的增大,该系统玻璃的析晶活化能E变小,析晶动力学反应速率k(T)增大,玻璃稳定性变小.所有玻璃样品的析晶指数(n)约为1,为表面析晶机制.