Papers by Keyword: DTA

Abstract: Phase constitution and phase transition temperature are important factors to influence deformation parameters, recrystallization behavior and density of precipitates of wrought Mg-Zn-Ce alloys. In this work the microstructures and phase constitution of as-cast Mg-6Zn-xCe (x = 0.6, 1, 2) alloys were characterized by XRD, SEM, TEM and DTA. The results show that the major compounds in Mg-6Zn-0.6Ce are blocky Mg₄Zn₇ phase, laminar Mg₇Zn₃ phase and cellular T phase. All compounds are almost blocky and cellular T phase in Mg-6Zn-1Ce alloy, and all T phase transformed to block in Mg-6Zn-2Ce alloy. The onset temperatures of phase transformation of T phase are increased with increasing Ce contents due to the decrease of solid solubility of Zn in T phase. The corresponding endothermic peaks of T phase in Mg-6Zn-0.6Ce, Mg-6Zn-1Ce and Mg-6Zn-2Ce are 358 °C, 494 °C and 514 °C, respectively. The increase of content of Ce result in the decrease of the concentrations of Zn in matrix, which leads to the decrease of β₁′ precipitate density and the increase of onset temperatures of melting of matrix.

Abstract: Normal-weight mortars with quartz sand filler and lightweight mortars with expanded perlite filler were prepared from a lime-metakaolin-gypsum binder. Mortar test samples were cured in a humid atmosphere and also in the laboratory ambient conditions. Development of hardening processes was studied by X-ray diffraction, thermal analysis and SEM-EDS observation. Compressive strength, drying shrinkage, bulk density and thermal conductivity of the mortars were determined. The presence of gypsum binder in the mixtures enabled formation of ettringite that caused expansion and reduced drying shrinkage of mortars with 20% content of gypsum binder.

Abstract: On the basis of the experimental data, a method and mechanism for modifying magnesia binders with iron ore concentrate has been proposed. It consists in form of a material reinforced fine-crystalline structure with elongated magnesium oxychloride crystals, which improves its physical and mechanical characteristics. The components of iron ore concentrate and magnesia binder, having improved sorption properties, significantly accelerates the formation of such a structure.

Abstract: A glass system was prepared according to the formula 60mol%B₂O₃ – x mol %barite – (40-x) mol %Li₂O, where x=0, 5, 7.5, 10, 15 and 20 mol%. The amorphous nature of the prepared glasses was confirmed through X-ray diffraction. The prepared glasses were also characterized by FTIR spectroscopy, UV-vis absorption spectroscopy and the differential thermal analysis (DTA). The density is found to increase and this is because of the higher molecular of the added barite. The molar volume also increases with increasing barite content that indicates the structural changes occurred in borate network that were also confirmed using FTIR. Increasing the concentration of barite shifts the UV cutoff edge toward higher wavelengths from about 300 nm at 0 mol% barite to about 400 nm at 15 mol% of barite. Glass transition temperature (Tg) is found to increase with the increasing barite content. When analyzed by photoluminescence, the samples exhibit luminescence emission centered at around 400, 415, 480, 430, 485, 520, 545, and 570 nm when excited at 300 nm wavelength. The emission peaks at 420 nm, and 440 nm were assigned to F center emission. Between 440 nm and 520 nm it is rather the effect of the presence of the impurities.

Abstract: Some years ago a new process was developed for the elaboration of alloys in order to overcome drawbacks observed in samples produced by conventional casting. In the present work are shown the results obtained by high energy mechanical milling for Cu-Al-Ni. the mechanical alloying powder Cu₈₄Al₁₂Ni₄ (W%) was fabricated in high energy planetary ball milling at a speed of 250 r/min for various milling times (10 20 30 40 50 60 hours) the weight ratio of the balls of powder was 15 to 1. this mechanical alloying process is significantly modifying the characteristic of the powder, the recovered grains are ultimately compacted. The means used to study the different evolution are SEM Scaning Electron Microscopy, Differential thermal analysis DTA, X-ray Diffraction analysis and DRX in situ.

Abstract: The influence of the europium concentration on the physical and thermal properties of manganese nanoparticles (Mn₃O₄ NPs) ) embedded borotellurite glass are studied. Glasses with composition (59-x)TeO₂-30B₂O₃-10MgO-xEu₂O₃-1Mn₃O₄ (where x = 0.5, 1.0 and 1.5 mol%) are prepared by melt-quenching method and characterized using XRD and Differential Thermal Analysis (DTA). The XRD pattern confirms the amorphous nature of all samples.The physical properties such as density (ρ) and molar volume (V_m) are calculated. The thermal properties of borotellurite glasses show that the glass with 1.0 mol % of Eu₂O₃ possess the highest stability.

Abstract: The diagrams of continuous cooling transformation (CCT) of β-phase decomposition for hot-rolled VT8M titanium alloy were obtained using the differential thermal analysis, scanning electron microscopy, and X-Ray diffraction (XRD) analysis for heating temperatures from 880 to 960 °C. The decomposition process was found to occur with several distinguishable stages. The transformation begins from high-temperature stage of the growing of primary alpha precipitates. At lower temperatures, it is followed by the medium-temperature stage accompanied by precipitation of grain-boundary alpha and the formation of coarse secondary alpha-lamellae. The low-temperature stage has been established to be characterized by the formation of dispersed alpha-platelets within beta-grains.

Abstract: This article presents an investigation on phase equilibria of barium hexaferrite and neighboring phases near its melting point and on the characteristics of the compounds in the vicinity of BaFe₁₂O₁₉ phase. Fe₃O₄, BaFe₂²⁺Fe₁₆³⁺O₂₇ (W type), BaFe²⁺Fe₁₄³⁺O₂₃ (X type), BaFe₁₂O₁₉ (M type), Ba₂Fe₂2+Fe₁₂3+O₂₂ (Y type), Ba₃Fe₂²⁺Fe₂₄³⁺O₄₁ (Z type) and BaFe₂O₄ (S type) were detected in the molten and solidified stoichiometric BaFe₁₂O₁₉. Literature data are summarized and compared with results of the present work.

Abstract: In this study, the main thermal, structural and mechanical properties of optical glass materials were investigated by conventional glass melting method. The thermal properties of optical glass materials are important in that they constitute the first steps towards the investigation of other physical and chemical properties. According to the thermal properties of the material, the glass transition temperature, T_g, increases for different glass compositions. The XRD, XRF, FT-IR and hardness properties of the obtained optical glass materials were determined experimentally in terms of their structural and mechanical properties for their suitability for potential applications. XRD spectra obtained without heat treatment of glass materials show that the material structure is amorphous. In the same way, Vicker’s hardness values of the glassware increase relative to the different glass compositions, resulting in a result that the material is influenced by the bonds between the constituents of the chemical components.

Abstract: In this paper the systematized literature data about the PbO-Fe₂O₃ system and new experimental results are presented. Based on the analysis of EDX, DTA and PXRD data on a series of compositions from 5 to 85 mol % PbO, the phase diagram of the PbO-Fe₂O₃ system was updated. Using the obtained data and the data of other authors thermodynamic functions were optimized and the thermodynamic modeling of the phase equilibria in the system was performed, results of which are presented in the form of the PbO-Fe₂O₃ phase diagram.