Papers by Keyword: X-Ray Diffractometry

Abstract: The structural changes of a type of polydiacetylene single crystal obtained via the physical vapor transport technique induced by the formation of polymeric backbone chains upon ultraviolet irradiation are discussed in this paper. On the basis of the results of X-ray diffractometry, X-ray topography, and atomic force microscopy, the structural changes were confirmed to be due to the formation of backbone chains along the basal (010) plane. The high periodicity between equivalent (010) planes is maintained regardless of the formation of backbone chains. The observation of the surface morphology on the basal (010) plane revealed that many polymeric bundles were formed in both the [001] and [101] directions.

Abstract: Preparation conditions of titanium oxide (TiO₂) powders were examined by the hydrolysis of titanium potassium oxalate (K₂TiO(C₂O₄)₂), through the homogeneous precipitation method (80oC for 24 h) and hydrothermal treatment (160 or 170oC for 1 h). According to the Rietveld analysis, almost a single phase of anatase TiO₂ could be obtained by the hydrothermal treatment at 160oC for 1 h, followed by the heating at 900oC for 10 min in air. The molar ratio of anatase to rutile TiO₂ was found to be controlled by optimizing the hydrothermal conditions in the solution and the heating conditions in air for the photocatalytic activity.

Abstract: The formation of polymeric acetylacetonates of magnesium, aluminum, iron, zirconium, and vanadyl under conditions of mechanochemical activation with subsequent condensation in boiling toluene has been investigated. The obtained compounds have been studied by the methods of gel chromatography, X-ray diffractometry, and positron annihilation and IR spectroscopy. Aluminum chelates have been studied by means of NMR spectroscopy. It has been demonstrated that the mechanochemical activation with subsequent boiling in toluene results in the formation of polymeric chelates, mostly those of iron, zirconium and, to a smaller degree, chelates of aluminum, magnesium, and vanadyl. The molecular weight of soluble high-molecular fractions is in the range 3000–5000 Da. The layered polymer structure has been revealed. Cross-section areas of polymer chains and volumes of coherent scattering regions have been calculated from the diffractometry data. The morphology of polymers consisting of spherical particles of sizes in the range 100–700 nm has been investigated. Based on the data of positron annihilation spectroscopy (PAS), density, and nitrogen low-temperature adsorption, the dependence of the chelate stability on the specific polarizing potential has been determined. A fractal structure of solid-state polychelates has been revealed.

Abstract: The problems of improving operating procedures and diagnosing the bearing capacity of metal structures designed and operating in the Arctic and subarctic regions of the country with a long period of low climatic temperatures remain unresolved. The paper notes that the development of digital methods of non-destructive testing, primarily X-ray diffractometry methods, can provide technical diagnostics of structures by identifying the features of the deformation of the crystalline structure of structural materials in an elastic stress-strain state. It is shown that the application of the method of X-ray diffractometry of complex polycrystalline structural steels has sufficient resolution to detect changes in the fine structure under the elastically stressed state of the samples. The broadening of the diffraction line (B) profile characterizes the effect of the elastically stressed state of steel samples 08 ps and 09Г2С on the course of microdeformation processes in the surface layers of the metal. The effect of periodic annual temperature fluctuations on the profile characteristics of the diffraction lines of 08 ps structural steel samples was studied experimentally. It is established that low climatic temperatures contribute to the elimination of individual instrumental errors due to the design conditions of the experiment. A sharp change in the true half-width of the profile of diffraction lines (В) at stresses σ ≥ 0.5 σ_т indicates the minimum possible value of the allowable stress [σ] for structural steel 08 ps.

Abstract: Monitoring of residual stresses in components can be useful in predicting damage incidences caused by workload over lifetime of components. Non-destructive measuring and evaluation of residual stresses and chemical properties of stainless steel sample and its possibility to affect functional properties of the material by using the X-ray diffraction has some advantages. Measured sample or part does not require special preparation or destruction and so it is capable to operate after measuring. This method also determines orientation of residual stress, so it is possible to identify absolute values of shear and normal stress with high accuracy.

Abstract: Results of plasmodynamic synthesis of silicon carbide nanopowders are given in the article. Studies of the synthesis product by X-ray diffractometry and transmission electron microscopy indicated that the product consists mainly of cubic silicon carbide and also includes cubic silicon, ultradispersed graphite and carbon onion-like structures. It was shown that a phase composition change in the synthesis product is possible by changing the ratio of precursor mixture.

Abstract: The plasmodynamic synthesis was conducted in the electric hypervelocity pulse jet of carbon-silicon electric discharge plasma influenced on a copper target in an argon atmosphere. Some samples of a powder product with a high content of β-SiC were produced. The results of the experiments made at different levels of supplied energy were compared. It was shown that the sizes of crystals grew, when the energy of a plasma shot increased.

Abstract: The ZnO nanorods were fabricated on top of the seeded gold layer by the aqueous solution method with the solution of zinc nitrate and hexamethylenetetramine (HTMA) at 90°C for 24 hours. The variety of the ZnO nanorods were prepared and investigated based on the precursor concentrations, in a range of 1 to 40 mM. The physical morphologies and crystal structures were characterized by field-emission scanning electron microscopy (FE-SEM) and X-ray diffractometry (XRD), respectively. The results showed that, with the small precursor concentrations, the lateral growth of the nanorods was highly significant when compared to their axial growth. The precursor concentration of 20 mM was best optimized for the preparation of the ZnO nanorod arrays with the hexagonal structures at the highest rod diameter and length. At the higher concentrations, although the nanorod size remained nearly constant, the length was however rapidly decreased. Further analyses also proved that, with the increased precursor concentrations, the number density of the ZnO nanorods was progressively increased along with the more complete hexagonal wurtzite structures.

Abstract: In this present work, nanodiamond (ND) particles were successfully prepared from commercial micron diamond powder at room temperature by high energy ball milling process using an oscillatory mill (SPEX8000). The size reduction and structural evolutions of the milled samples were investigated as a function of the milling time by means of X-ray diffraction, and field emission scanning electron microscopy. The line broadening technique was used to determine the crystallite size and lattice strain. After 40 h of milling, obtained ND particles possessed uniform shape and 25 nm of average particle size. Also, energy dispersive X-ray results revealed the high purity of ND and demonstrated that the purification process using harsh acid mixture were effective to remove metal and non-diamond carbon impurities produced in milling stage. All results propose a scalable method to preparation ND particles as well as nanocrystalline materials.

Abstract: A new approach is explored to achieve sintered aluminium alloy from metallic powder mixtures without compression or adding Mg. In this approach, mixtures of micron-sized aluminium powder (average size of 2.5 μm) and nano-sized alloying elemental powder of Cu and Sn (less than of 70nm), at appropriate proportions to compositions of Al-6wt%Cu, Al-6wt%Cu-3wt%Sn with and without adhesive binder were prepared by magnetic stirring. Then, the powder mixture was poured into a crucible and heat treated at a temperature of 600°C for 11 hours in inert atmosphere of N2 or Ar. In this paper, we investigate the debinding behavior of loosely packed Al-based powder mixture and the microstructural development and mechanical property sintered parts using a combination of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffractrometry (XRD) and hardness test.