X-ray Diffraction Study Of Order Research Articles

Leak testing of carbon\u2013tin nanocomposites by thermal analysis methods

Electrode materials consisted of tin nanograins encapsulated in different origin carbon buffer matrix (starch or water soluble polymer) were obtained in a simple and inexpensive process. The tin precursor was synthesized using modified reverse nanoemulsion technique (w/o) and then coated by a source of carbon. The composites precursors were pyrolysed, affording formation of C/Sn anode materials. The resulting samples were investigated by powder X-ray diffraction studies in order to verify the structure and calculate crystallites sizes. The morphology of the nanocomposites was characterized by low-temperature nitrogen adsorption method (N2-BET). Thermal analysis measurements (EGA-TG/DTG/DTA and DSC) allowed determining optimal conditions of preparation process and estimating carbon content in the obtained anode materials. Thermogravimetric studies also proved to be highly useful in establishing the leak behaviour of C/Sn nanocomposites. The electrochemical performance of the nanopowders was examined by charge–discharge tests in R2032-type coin cell. The thermal analysis results as well as low-temperature nitrogen adsorption data indicated that the origin of carbon precursor has major impact on morphology and leak behaviour of the obtained carbon buffer matrix. The electrochemical tests showed that better tightness of carbon–tin nanocomposites resulted in higher gravimetric capacity and better cell performance.

Solid state dye sensitized solar cells: Eosin-Y sensitized TiO2–ZnO/PEO–PVDF-HFP-MMT electrolytes/MWCNT–Nafion® counter electrode

The present work aims to reduce the cost of solid state dye sensitized solar cells employing inexpensive materials for various components of the device. First, TiO2 and flower shaped ZnO nanoparticles were synthesized by sol–gel processes and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–vis spectra confirm that the photon absorption is increased in the visible region with the addition of ZnO. Second, poly(ethylene oxide) and poly(vinylidenefluoride-co-hexafluoropropylene) with silane modified montmorillonite membrane was prepared (PEO/PVDF-HFP-MMT) for electrolyte applications. The membranes were subjected to XRD studies in order to understand the intercalation/exfoliation and crystallinity. The porosity measurements and SEM revealed that addition of surface modified MMT increased the porosity of PEO/PVDF-HFP. The ionic conductivity increased with the incorporation of MMT and reaches to maximum value about 1.6mS/cm for 6wt%. Finally, MWCNT/Nafion® composite prepared counter electrode applications and its catalytic activity has studied. The solid state dye sensitized solar cell has been fabricated by using optimized composition of TiO2/ZnO, PEO/PVDF-HFP/MMT, MWCNT/Nafion® and eosin-Y as a sensitizer. The photovoltaic performance exhibits an enhanced open circuit voltage (Voc) and short circuit current density (Jsc) were 0.65V and3.3mA/cm2 respectively at an incident light intensity of 100mW/cm2. The EIS spectra of the DSSCs were shown reduced charge transfer resistance for TiO2/ZnO nanocomposite electrode. The stability of device is studied using amperometric technique under several on–off cycles.

Particle size dependence of magnetization and phase transition near TN in multiferroic BiFeO3

We report results of a comprehensive study of the phase transition at TN (∼643K) as a function of particle size in multiferroic BiFeO3 system. We employed electrical, thermal, and temperature dependent x-ray diffraction studies in order to characterize the transition in a host of samples. We also carried out detailed magnetic measurements over a temperature regime of 2–300K under a magnetic field of 100–10000Oe both on bulk and nanocrystalline systems. While in the bulk system a sharp endothermic peak at TN together with a broad feature, ranging over nearly ∼100K (ΔT), could be observed in calorimetry, the nanoscale systems exhibit only the broad feature. The characteristic dielectric anomaly, expected at TN, is found to occur both at TO and TN across ΔT in the bulk sample. The Maxwell-Wagner component due to interfaces between heterogenous regions with different conductivities is also present. The magnetic properties, measured at lower temperature, corroborate our observations in calorimetry. The metastability increases in the nanoscale BiFeO3 with divergence between zero-field cooled and field cooled magnetizations below ∼100K and faster magnetic relaxation. Interestingly, in nanoscale BiFeO3 one also observes finite coercivity at lower temperature, which points out that suitable design of particle size and shape may induce ferromagnetism. The inhomogeneous distribution of Bi∕Fe ions and/or oxygen nonstoichiometry seems to be giving rise to broad features in thermal, magnetic as well as electrical responses.

High-temperature plastic behavior of reaction-bonded CuO and TiO2 co-doped alumina–zirconia

The high-temperature plastic behavior of reaction-bonded alumina doped with equimolar amounts of copper and titanium oxides has been studied by means of creep and stress relaxation tests in air. Deformation results have been correlated with microstructural observations and X-ray diffraction studies in order to deduce the mechanism responsible for the deformation. The material exhibits plasticity at temperatures as low as 900 °C in contrast with other aluminas. At temperatures near 1000 °C a linear relation between the strain rate and the stress has been detected (corresponding to mechanism with a stress exponent n equal to one) but both above and below this temperature higher values of n have been observed.

Synthesis, characterization and X-ray crystal structures of cyclam derivatives. Part IV. 1,4,8,11-Tetraazacyclotetradecane-5,12-dione and its diprotonated forms

The synthesis, spectroscopic characterization (NMR, IR, MS) and protonation constants of a dioxocyclam derivative, 1,4,8,11-tetraazacyclotetradecane-5,12-dione (1), are described. The crystal structures of the free-base macrocycle and two diprotonated forms, with bromide and perchlorate as counter ions, have been determined by X-ray diffraction studies in order to evaluate the influence of both the secondary amine's protonation state and of the intermolecular hydrogen-bonding interactions on the macrocycle conformation. The spectroscopic, potentiometric and structural data indicate that both secondary amines behave independently from each other, their protonation inducing only limited conformational changes of the macrocyclic framework. In the crystal, the diprotonated species adopt two different [3,4,3,4] diamond-lattice-type conformations as a consequence of intermolecular hydrogen bonds involving the oxo groups and the surrounding anions.

X-Ray Diffraction Study of Ordering in Two Sigma Phases

AbstractX-ray powder pattern line intensities were measured for the (Cr, Re)σ and (Re, Fe)σ phases by a step-scanning diffractometer, using CrKα radiation, scintillation counter, and a pulse height analyzer. The measured intensity ratios for all available pairs of adjacent lines were compared by means of a computer with the corresponding calculated intensity ratios based on approximately 1800 different ordering schemes for each alloy. The results showed ordering in both alloys, and indicated that the ordering was based on atomic size. These results are different from those obtained previously by Kasper and Waterstrat (no ordering), and by Ageyev et al. [In (Cr, Re)σ the Cr atoms are preferentially in large coordination number positions.]