Search results for "differential thermal analysis"
showing 10 items of 66 documents
Corundum type indium oxide nanostructures: ambient pressure synthesis from InOOH, and optical and photocatalytic properties
2016
A simple, cost effective, surfactant free and scalable synthesis of rhombohedral In2O3 (rh-In2O3) nanostructures with controllable size and shape has been developed under ambient pressure by thermal dehydration of InOOH nanostructures. The InOOH nanostructures have been prepared by solvothermal reaction between indium nitrate hydrate with tetramethylammonium hydroxide (TMAH) in anhydrous methanol at 140 °C without any surfactant. The structure and morphology of the nanostructures have been characterized in detail by X-ray powder diffraction (XRD), Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM). The studies reveal that highly crystalline nanostructures of In…
Effect of the dopant selection (Er, Eu, Nd or Ce) and its quantity on the formation of yttrium aluminum garnet nanopowders
2008
Abstract Hydroxide precursors, synthesized using the co-precipitation method, were calcined for 1 h at the temperatures of 900, 1000 and 1100 °C, respectively, and heated directly to 1500 °C to produce various Y 3 Al 5 O 12 (YAG) nanopowders with different doping quantities of erbium, europium, neodymium and cerium. All samples were investigated using thermo-gravimetry (TG) and differential thermal analysis (DTA), field emission gun-scanning electron microscopy (FEG-SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). TG and DTA experiments were performed from room temperature up to 1500 °C; the weight loss curves combined with the presence of exo- and endo-thermal even…
Use of kinetic DTA and TG methods for compatibility tests on 2,4,6--trinitrotoluene
1986
We have investigated the suitability of thermoanalytical methods for compatibility tests on explosives and contact materials. DTA and TG curves of various materials were evaluated using two DTA and four TG methods and one DSC method. TNT was used as model substance. The contact materials were paraffin, polyethylene, an epoxy resin paint and an epoxy glue. In earlier tests the first two were found compatible and the latter two incompatible with TNT. None of the methods provides an absolute value for the activation energy. However, in compatibility tests only the relative change in the activation energy is of interest and, for this, three of the methods proved informative.
Li2OSiO2Al2O3MeIIO Glass-Ceramic Systems for Tile Glaze Applications
1991
In order to verify the possibility of using glass-ceramic materials as tile coatings, the devitrification processes of three industrial formulations belonging to the Li2O─Al2O3─SiO2 glass-ceramic system were investigated by differential thermal analysis, X-ray diffractometry, scanning electron microscopy, and IR spectroscopy. Compositional variations were made by addition of large amounts of MgO or CaO or PbO (ZnO) oxides as well as through smaller additions of other oxides. In these systems the surface crystallization contributes appreciably to the bulk crystallization mechanism. All the systems investigated show a high tendency toward crystallization even at very high heating rates, devel…
Investigation of eutectic transformation of Zn−Al alloy by DTA
1995
The paper discusses the investigation of crystallization of metals and alloys by differential thermal analysis (DTA). It was assumed that this method allows determination of the mechanism and kinetics of volumetric crystallization underiso conditions (e.g. anisothermal) on the basis of the parameters of the equation expressing an integral form of the DTA curve. From DTA, a course of eutectic transformation was determined for a technical Zn−Al alloy containing 4wt% Al. Investigations were carried out under continuous cooling at various rates and the kinetics parameters were determined with the KEKAM equation:-ln(1-x)=kln
Effects of ZrO2 precursors on the synthesis of V-ZrSiO4 solid solutions by the sol-gel method
1992
The preparation of V-ZrSiO4 solid solutions starting from different ZrO2 precursors by using sol-gel methods is reported. The starting materials were hydrolysed and the dried gels were fired at a temperature between 500 and 900 °C with soaking times of 12h. The organic character of zirconia precursors was stronger, i.e. the starting material had more carbon atoms, a higher temperature was necessary to make the first crystalline phase appear (ZrO2(tetragonal)) and the temperature range for the whole phase transformation was narrower. In all dried gel samples the presence of infrared bands which might be associated with either Si-O-Zr or Si-O-V was not observed. On the other hand, some bands …
Layered-structural monoclinic–orthorhombic perovskite La2Ti2O7 to orthorhombic LaTiO3 phase transition and their microstructure characterization
2014
The layered-structural ceramics, such as lanthanum titanate (La{sub 2}Ti{sub 2}O{sub 7}), have been known for their good temperature and low dielectric loss at microwave frequencies that make them good candidate materials for high frequency applications. However, few studies have been conducted on the synthesis optimization by sol gel reaction, in particular by acrylamide polymerization route. The interest in La{sub 2}Ti{sub 2}O{sub 7} ceramic has been greatly increased recently due to the effect of oriented grains. This anisotropy of the microstructure leads to anisotropy in dielectric, electrical and mechanical properties. In this study, grain oriented lanthanum titanate was produced by t…
Effect of additives on the crystallization of cordierite-based glass-ceramics as glazes for floor tiles
2003
Abstract The effect of several additives such as fluxes and/or nucleants on a parent glass with composition located in the primary field of cordierite within the quaternary system CaO–MgO–Al 2 O 3 –SiO 2 has been examined. Crystallization path of glasses was determined by differential thermal analysis (DTA) and X-ray powder diffraction (XRD). Pressed pellets of powdered glasses containing different additives were submitted at thermal treatments up to 1200 °C. The microstructural development at several temperatures was followed by field emission scanning electron microscopy and energy-dispersive X-ray analysis. The results shown that additions of TiO 2 as nucleant and/or B 2 O 3 as flux to a…
Low-temperature Ti-containing 3:2 and 2:1 mullite nanocrystals from single-phase gels
2007
Abstract TiO 2 -containig single-phase gels with (Al 2 O 3 + TiO 2 )/(SiO 2 ) molar ratios 3/2 and 2/1 were prepared by gelling mixtures of aluminium nitrate, tetraethylorthosilicate and titanium isopropoxide. Gels were fast heated at several temperatures up to 1100 °C. Dried and heated gels were characterized by differential thermal analysis (DTA), magic angle spinning nuclear magnetic resonance (MAS-NMR), X-ray powder diffraction (XRD), and scanning and transmission electron microscopies (SEM and TEM). Coupled DTA and XRD results of gels fast heated at 900 °C showed the crystallisation of two mullites as well as a small amount of alumina-silica spinel. 27 Al NMR spectra showed the format…
Local structure of gadolinium in oxyfluoride glass matrices containing SrF2 and BaF2 crystallites
2016
Abstract Gd3 + doped aluminosilicate oxyfluoride glasses and glass-ceramics containing SrF2 and BaF2 crystallites have been studied by differential thermal analysis (DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopy techniques. A pronounced EPR fine structure emerges after the heat treatment of the glass matrix. EPR spectra simulations indicate the formation of cubic, tetragonal and trigonal Gd3 + centres in the studied compositions.