Synthesis and characterization of ZSM-8-type zeolite crystals

Procedure for hydrothermal synthesis of ZSM-8-type zeolite crystals, using TEA—OH as a template, in the system having molar composition 16.2 (Na₂O) — Al₂O₃ — 117 (SiO₂) — 4.8 (TEA)₂O — 3887 H₂O at 170 °C is described. Results of characterization of these crystals by XRD, IR, EDAX, SEM, TGA, and adsorption studies are described and discussed. X-ray diffraction studies establish that the crystals are ZSM-8-type with structure similar to that of ZSM-5-type crystals. Crystals have prismatic bipyramidal morphology with average size 18–25 microns. Degased calcined samples adsorb xylenes in the order p > m > 0. Pore length per unit cell, estimated from n-hexane adsorption studies, is 46 Å.     

Effect of structure on low temperature plasticity and magnetic properties of ageing Pb?Sb alloys below Tc

It was carried out comparative structural, magnetic and mechanical studies of single crystals of Pb—Sb alloys with 0.5–5 at.% Sb, which are II type superconductors. The structure was studied by X-ray diffractometry, small-angle X-ray scattering, microhardness and resistometry methods. It was determined the total volume fraction and the precipitate size. The second critical field H_c2 and the magnetic flux trapping measured at 4.2 K are determined by the solid matrix concentration and the precipitate volume fraction respectively. Plasticity of Pb—Sb crystals was investigated by tension tests at 4.2 K. The dependence of the change of the flow stress, Δτ_sn, at superconducting transition on ageing time and antimony concentration was obtained.     

On Some Features of X-Ray Powder Patterns of OD Structures

X-ray powder data of OD crystals may be misinterpreted, if the OD character of the substance is not taken into account. For some typical OD structures, problems in connection with their identification and the determination of lattice parameters are discussed. Some features of X-ray powder patterns, which — on principle — are relevant to all OD crystals are summarized.     

New Data on the Isomorphism in Eudialyte-Group Minerals. IV: Modular Structure of Titanosilicate with Replacement of Na by Mn in the Alluaivite Module

Crystallography Reports - A new modular eudialyte-group mineral—titanosilicate—from the Lovozero massif has been investigated using X-ray diffraction. The trigonal-cell parameters are...     

New Data on the Isomorphism in Eudialyte-Group Minerals. III: Modular Structure of K Analog of Centrosymmetric Labyrinthite

Crystallography Reports - The crystal structure of a new modular eudialyte-group mineral from the Khibiny massif—potassium-rich analog of labyrinthite—has been investigated using X-ray...     

Diophantine laws for nets of the highest symmetries

The theoretical-numerical properties of the square and the hexagonal nets are presented as well as their characteristic triads of integers—the Denis numbers—applicable to the practical X-ray diffraction analysis of single crystals.     

Growth of USb2 single crystals and their structural perfection

USb₂ single crystals were grown by three methods; I — Chemical vapour transport with iodine as transporting reagent, II — Crystallization from U Sb liquid solution, III — Crystallization from U Sb Sn liquid solution. The morphology of growth and results of X-ray topography examination of crystal surface are given.     

Methods of chemical and phase composition analysis of gallstones

This review presents the instrumental methods used for chemical and phase composition investigation of gallstones. A great body of data has been collected in the literature on the presence of elements and their concentrations, obtained by fluorescence microscopy, X-ray fluorescence spectroscopy, neutron activation analysis, proton (particle) induced X-ray emission, atomic absorption spectroscopy, high-resolution gamma-ray spectrometry, electron paramagnetic resonance. Structural methods—powder X-ray diffraction, infrared spectroscopy, Raman spectroscopy—provide information about organic and inorganic phases in gallstones. Stone morphology was studied at the macrolevel with optical microscopy. Results obtained by analytical scanning and transmission electron microscopy with X-ray energy dispersive spectrometry are discussed. The chemical composition and structure of gallstones determine the strategy of removing stone from the body and treatment of patients: surgery or dissolution in the body. Therefore one chapter of the review describes the potential of dissolution methods. Early diagnosis and appropriate treatment of the disease depend on the development of clinical methods for in vivo investigation, which gave grounds to present the main characteristics and potential of ultrasonography (ultrasound scanning), magnetic resonance imaging, and X-ray computed tomography.     

The Influence of the X-ray Wavelength on the Behaviour of Polar Kossel Reflections

The Kossel effect permits a determination of polar directions in non-centrosymmetrical structures. To identify polar reflections unambiguously, differences — as large as possible — in their fine structures are necessary. These differences considerably depend on both the diffraction geometry and the characteristic X-ray wavelength applied. The reasons of such behaviour are deliberated upon hereinafter and a good harmony achieved of theoretical predictions and experimental findings.     

X-ray diffraction topography and diffuse scattering techniques applied to study the defect structure of plastically deformed al single crystals

X-ray diffraction topography and diffuse scattering techniques were used to study the defect structure formation of plastically deformed Al single crystals. The investigated X-ray scattering has been found out materially to depend upon the character of the dislocation structure (upon the geometry of the dislocation distribution). This dependence is manifested in different distribution of the intensity and in the changed form of the isointensity curves of diffuse and regular (Laue) reflections. In spite of the fact that the distribution of the internal stresses acting in different glide systems under conditions of uniaxial stretching is of complicated character, it is possible to trace the development of the glide process in the body of a sample and to obtain satisfactory interference patterns both of regular reflexions (on topograms) and of diffuse ones (on Laue photographs) up to severe deformations of a crystal at 300, 4.2, and 1.6 K. The following diffuse effects connected with structural changes in deformed crystals have been ascertained on the X-ray photographs:

• —diffuse regions are elongated in the reciprocal lattice space along the glide directions or other crystallographic directions;
• —these diffuse regions are split into separate areas along the directions of the said elongations;
• —the diffuse regions are changed in length: the diffuse reflexes are diffused or condensed;
• —the diffuse scattering isointensity curves are “zigzag”-shaped.

     

Specific physical and chemical properties of two modifications of poly(N-vinylcaprolcatam)

Two modifications of poly(N-vinylcaprolactam)—PVCL25 and PVCL40 (drying of a PVCL solution at 25 and 40°С, respectively)—as powdered films and their solutions were systematically investigated for the first time. Powders were studied by X-ray diffraction, IR spectroscopy, scanning electron microscopy, low-temperature krypton adsorption, and differential scanning calorimetry. Solutions were studied by smallangle X-ray scattering and dynamic light scattering. It was demonstrated that powders of PVCL25 and PVCL40 differ in the characteristics of the sub- and microstructure and in the water content and the solutions differ in the particle size. The relationships between the characteristics of the systems in the solid and liquid state and between the hydrodynamic diameter of PVCL particles in solution and their coagulation time were found.     

Synthesis and Crystal Structure of NdCaGaO4

The crystal structure of the NdCaGaO₄ compound was investigated by means of X-ray structure analysis (powder diffractometer HZG-4, CuK_α): structure type LaCuO₄, space group Cmca, a = 5.3700(2) Å, b = 12.1058(3) Å, c = 5.3937(2) Å, Z = 4, R_I = 0.126. The shortest interatomic distances are: Nd(Ca)—O — 2.240(14) Å; Ga—O — 1.913(2) Å, O—O — 2.6852(2) Å, Nd(Ca)—Nd(Ca) — 3.442(3) Å, Nd(Ca)—Ga — 3.154(4) Å, Ga—Ga — 3.8056(2) Å. Atoms have the following coordination numbers: Nd(Ca) — 8; Ga — 6; O1 — 14(6); O2 — 9(5).     

Defects of different sizes in large paratellurite single crystals

Paratellurite single crystals have good acoustooptical properties that are important for various devices, such as deflectors, modulators, and tunable noncollinear filters. Paratellurite single crystals of up to 80 mm in diameter and 100 mm in height were grown using the Czochralski method from ultrapure melts. Optical anomalies in the grown crystals—gas bubbles, striations, impurity inclusions with nearby stresses, and regions with high dislocation densities—were studied with chemical, X-ray, and optical methods.     

Structural and Electrical Characterization of Ag3Ga5Te9 and Ag3In5Se9 Crystals

X-ray powder diffraction studies revealed that Ag₃Ga₅Te₉ and Ag₃In₅Se₉ crystallize in orthorhombic and tetragonal systems, respectively. The temperature dependent conductivity and Hall effect measurements have been carried out between 65—480 K. Ag₃Ga₅Te₉ exhibits p-type conduction with a room temperature conductivity of 4.3 × 10^—4 (Ω · cm)^—1 and mobility less than 1 cm²/V · s. Ag₃In₅Se₉ was identified to be n-type with room temperature conductivity 7.2 × 10^—5 (Ω · cm)^—1 and mobility 20 cm²/V · s. From temperature dependence of the conductivity three different impurity ionization energies were obtained for both compounds. The anomalous behavior observed in the temperature dependence of mobility was attributed to the different features of the microstructure.     

磷掺杂介孔碳的制备及其电化学性能

以酚醛树脂为碳前驱体,磷酸为磷源,三嵌段共聚物F127为软模板,通过溶剂挥发诱导自组装(EISA)法制备了具有介孔结构的磷掺杂介孔碳(PMCs)。通过场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)等测试方法研究所制备的PMCs的形貌与结构并利用电化学工作站测试其电化学性能。实验结果表明,磷元素在介孔碳中主要以C—P键和P—O键两种形式存在。电化学测试表明,通过调整磷掺杂量可获得最大比电容。当电流密度为0.5 A/g时,介孔碳比电容为140 F/g,而优化后的磷掺杂介孔碳比电容可达176 F/g。     

Crystal Structures of Methyl and Ethyl N-(2,3-Dimethoxybenzyl)-N-(p-toluenesulfonyl)-2-phenylglycinates

The crystal structures of methyl and ethyl N-(2,3-dimethoxybenzyl)-N-(p-toluenesulfonyl)-2-phenylglycinates 4a and 4b respectively, have been determined by X-ray diffraction analysis. The presence of different alkyl ester groups in both molecules does not affect the geometry retaining a synclinal conformation for the N atom and the O atom of the C=O group [N—C17—C18—O5 38.1(5)° for 4a and 33.3(4)° for 4b ].     

Sintering and crystallization of titanium-containing lead borate glasses

The sintering and crystallization of glass powders with chemical composition 47 PbO—38 B₂O₃—15 TiO₂ (mole %) was investigated under non-isothermal conditions by shrinkage measurements, differential thermo-analysis (DTA), X-ray diffraction (XRD), dielectric measurement and positron annihilation (Doppler broadening). The correlation between changes of macroscopic properties and positron annihilation results recommends this method for the detection of structural changes in glasses.     

Ein Beitrag zur Ausscheidungsfolge in AlZnMg-Legierungen

The decomposition behaviour of some Al Zn(6)—Mg(X) and Al Zn(4.5)—Mg(X) alloys is studied by means of X-ray small angle scattering, microhardness, and dilatometric investigations. The mean results are: a) The minimum of the microhardness occuring in the binary Al Zn alloys at about 31 Å, is not shifted essentially by addition of Mg; b) The maximum of the microhardness measured at about 49 Å in Al Zn alloys is removed to lower values of the Guinier radius by increase of the Mg content; c) Probably the formation of the partial coherent η′-phase followed from elliptical GP zones. — Conclusions of these results are given.     

Insights into Biaxial Ordering of Bent-Core Nematics: X-Ray Diffraction Evidence

Recently we have reported the first X-ray diffraction evidence of biaxial order in the fluid cybotactic nematic phase of a pair of trimethylated bent-core mesogens. This evidence is based on the splitting of the wide-angle diffuse scattering in the plane normal to the nematic director. The additional experimental data presented here provide further insights into this unprecedented behavior observed over the entire nematic phase. Although we could not determine the spatial extent of biaxial order—intracluster or intercluster—our observations reveal an enhanced biaxial orientational correlation in the transverse molecular packing, possibly reflecting stronger anisotropic interactions between nearest-neighbor mesogens.