Cation and anion disorder in HgBa2Can−1CunO2n+2+δ

Cu and C substitution for Hg in Hg-based cuprate superconductors is discussed. The large Hg Debye-Waller factor usually obtained from refinements based on diffraction data should be interpreted as an indication of carbon substitution for the Hg cations. This assumption is corroborated by HREM, powder x-ray anomalous dispersion, and powder neutron diffraction investigations.     

镍纳米管阵列的电沉积合成及其磁学性能表征

以氧化铝膜为模板、金属汞为电阴极,采用简单的直流电沉积方法制备出高度有序的镍纳米管阵列。利用扫描电子显微镜、透射电子显微镜、选区电子衍射、能谱仪、X射线粉末衍射和样品振动磁强计对样品进行形貌表征、成分及磁性能分析。结果表明,阵列中的镍纳米管彼此平行,尺寸均匀,纳米管外径为260～360nm;镍纳米管阵列表现出良好的磁各向异性,其易磁化方向垂直于镍纳米管阵列。以金属汞为电阴极是易形成纳米管的关键条件。     

Structural Anomalies of 1223 Hg(Tl)–Ba–Ca–Cu–O Superconductors in the Temperature Range 100–300 K

The crystal structure of Hg-based 1223 phases, Hg_1–x Tl _x Ba₂Ca₂Cu₃O₈₊, with different oxygen content and Hg/Tl substitution having critical temperature from 114 to 133 K has been investigated by the X-ray powder diffraction technique over the temperature range from room temperature to 100 K. Rietveld analysis results indicate the presence of two different structure anomalies at temperatures 138 and 165K, respectively. The changes in lattice parameters, fractional coordinates, and individual atom thermal parameters near the observed anomalies are discussed.     

Malayaite ceramic pigments: A combined optical spectroscopy and neutron/X-ray diffraction study

Ceramic pigments based on the Cr-doped malayaite structure were synthesized by solid state reaction and characterized by optical spectroscopy and combined X-ray and neutron powder diffraction in order to elucidate the still unclear chromium substitution mechanisms. The results show that coloration is actually due to simultaneous occurrence of Cr⁴⁺ and Cr³⁺ ions in the crystal lattice. Spectroscopy data confirm that Cr⁴⁺ is replacing Sn⁴⁺ in the octahedral site and, in minor amount, Si⁴⁺ in the tetrahedral site. In addition, neutron powder diffraction data suggest that Cr³⁺ substitution for octahedral Sn⁴⁺ is charge balanced by the formation of oxygen vacancies with no preference over the different oxygen sites. Upon incorporation of Cr ion, the SnO₆ octahedra exhibit an off-centre displacement of central cation which in turn induces a rearrangement of both the octahedral and tetrahedral coordination shells.     

Ge取代P型高锰硅合金的晶粒细化及其热电性能

采取悬浮熔炼法制备Ge取代的高锰硅试样Mn(Si1-xGex1).733(x取0.004,0.006,0.008,0.010,0.012),采用甩带法得到快凝高锰硅合金粉末,XRD分析表明快速凝固能够减少MnSi金属相的含量,Ge对Si位的取代产生晶格畸变,使得衍射峰向低角区偏移;将悬浮熔炼和快速凝固所得试样进行放电等离子烧结,测试并比较其热电性能。结果显示,快速凝固有效地降低了材料的热导率,Ge取代则使得有效载流子浓度增加,提高了电导率,从而提高材料的热电性能。实验范围内,当Ge取代量x=0.010时,ZT值最高,悬浮熔炼试样在850K时ZT值为0.53,快速凝固试样在750K时ZT值达到0.55。     

Three-dimensional distribution of polymorphs and magnesium in a calcified underwater attachment system by diffraction tomography

Biological materials display complicated three-dimensional hierarchical structures. Determining these structures is essential in understanding the link between material design and properties. Herein, we show how diffraction tomography can be used to determine the relative placement of the calcium carbonate polymorphs calcite and aragonite in the highly mineralized holdfast system of the bivalve Anomia simplex. In addition to high fidelity and non-destructive mapping of polymorphs, we use detailed analysis of X-ray diffraction peak positions in reconstructed powder diffraction data to determine the local degree of Mg substitution in the calcite phase. These data show how diffraction tomography can provide detailed multi-length scale information on complex materials in general and of biomineralized tissues in particular.     

碲铟汞晶体制备及其热稳定性研究

以高纯Hg、In、Te单质为原料,通过元素直接化合反应合成了碲铟汞(MIT)多晶料,并利用合成的高纯多晶料,在特殊设计的坩埚中,采用垂直Bridgman法通过自发成核方式成功地生长了尺寸为Φ15mm×175mm的MIT单晶体.利用X射线粉末衍射技术对MIT晶体结构及物相进行的分析表明,所获得的晶体是单相的MIT晶体,为缺陷闪锌矿结构,空间群为F43m.采用高分辨X射线衍射仪测量了所生长MIT晶体的摇摆曲线,结果表明所得晶体完整性较好,为高质量的单晶体.对所生长的MIT晶体进行了热分析,发现在MIT晶体中有Hg溢出现象.     

Synthesis and characterization of iron-substituted hydroxyapatite via a simple ion-exchange procedure

Hydroxyapatite (HA), the main inorganic component of natural bones, is widely studied as a biomaterial due to its excellent biocompatibility and osteoinductivity. The crystal structure of HA lends itself to a wide variety of substitutions and ion doping, which allows for tailoring of material properties. In this study, iron-doped HA was synthesized via a simple ion-exchange procedure and characterized thoroughly for crystal structure and phase purity using X-ray diffraction, energy-dispersive X-ray spectroscopy, inductively coupled plasma atomic emission spectroscopy, and Fourier transform infrared spectroscopy. Magnetic properties were studied using vibrating sample magnetometer and superconducting quantum interference device analysis. Ion-exchange was attempted using both ferric and ferrous chloride iron solutions, but a substitution was only achieved using ferric chloride solution. The results showed that after iron substitution the powder retained characteristic apatite crystal structure and functional groups, but the iron-doped samples displayed paramagnetic properties, as opposed to the diamagnetism of pure HA. The effect of soaking time on iron content was also examined, and collectively X-ray diffraction and inductively coupled plasma atomic emission spectroscopy results suggested that an increase in soaking time led to an increase in iron content in the sample powder. Iron-substituted HA nanoparticles, a biomaterial with magnetic properties, could be a promising biomaterial to be used in a variety of biomedical fields, including magnetic imaging, drug delivery, or hyperthermia-based cancer treatments.     

Dissolution Properties of Piroxicam Powders and Capsules as a Function of Particle Size and the Agglomeration of Powders

The poor dissolution characteristics of relatively insoluble drugs have long been a problem to the pharmaceutical industry. An example is piroxicam, a highly potent anti-inflammatory agent. In many countries, a large number of generic piroxicam products are available to the prescriber. The aim of this study was to investigate the cause of the dissolution problems experienced by manufacturers of generic piroxicam capsules. Two raw material batches and the dissolution properties of several piroxicam capsules were studied. Differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD) results showed that the two raw material samples were identical with respect to polymorphic modification. The particles of powder 1 were smaller than those of powder 2, but the dissolution of powder 1 was much slower than that of powder 2. The dissolution results for the capsules showed a marked difference among different brands, with capsule C not meeting the USP tolerance. Adding surfactant to the dissolution medium increased the dissolution of both powder 1 and capsule C. Failure of powder 1 or capsule C to meet USP dissolution criteria could result in differences in product efficacy, as well as in potential side effects. Such observations should be taken into account along with other relevant considerations when decisions regarding the generic substitution of oral piroxicam products are made.     

Dissolution properties of piroxicam powders and capsules as a function of particle size and the agglomeration of powders

The poor dissolution characteristics of relatively insoluble drugs have long been a problem to the pharmaceutical industry. An example is piroxicam, a highly potent anti-inflammatory agent. In many countries, a large number of generic piroxicam products are available to the prescriber. The aim of this study was to investigate the cause of the dissolution problems experienced by manufacturers of generic piroxicam capsules. Two raw material batches and the dissolution properties of several piroxicam capsules were studied. Differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD) results showed that the two raw material samples were identical with respect to polymorphic modification. The particles of powder 1 were smaller than those of powder 2, but the dissolution of powder 1 was much slower than that of powder 2. The dissolution results for the capsules showed a marked difference among different brands, with capsule C not meeting the USP tolerance. Adding surfactant to the dissolution medium increased the dissolution of both powder 1 and capsule C. Failure of powder 1 or capsule C to meet USP dissolution criteria could result in differences in product efficacy, as well as in potential side effects. Such observations should be taken into account along with other relevant considerations when decisions regarding the generic substitution of oral piroxicam products are made.