Papers by Keyword: Differential Thermal Analysis (DTA)

Abstract: The ceramic glaze is a glass layer with an amorphous structure. Crystalline glazes are special glazes used to decorate ceramic products. It is based on the research results, the authors proposed a novel crystalline glaze from titanium frit (denoted by FV090/540) for pottery and ceramics with the heating temperature at 1200°C. The heating temperature for the crystallization of glaze was determined by differential thermal analysis (DTA). This study aimed to synthesis willemite crystals (Zn₂SiO₄) in pottery and ceramics. These crystals were detected and identified using X–ray diffraction (XRD), optical microscope (OM), and scanning electron microscope (SEM). The chemical composition of the samples was analyzed by X-ray fluorescence (XRF). From the results of experiments, the authors carried out decorating on industrial ceramic pottery products using this novel crystalline glaze and adjusted the required technological parameters.

Abstract: The aim of the work was to investigate the influence of extremely low and high temperature on the course of hydration of cement stone compared to the reference sample hydrated at normal conditions. The work was structured in such a way that Portland cement was first subjected to standard technological tests. Next, sets of test prisms using cement paste were prepared. This samples were immediately exposed to saturated water vapor in three temperature environments: 5 °C, 20 °C and 80 °C. The course of the hydration process during the first 28 days was monitored by the determination of the phase composition by XRD analysis and thermal analysis, and mediated by means of determination of tensile strength after bending and compressive strength. The low temperature did not have a negative effect on the final properties of the hardened cement stone. On the other hand, high temperature accelerated the initial phase of the hydration process, but negatively affected the resulting mechanical parameters

Abstract: This paper deals with the verification of the possibility of preparing synthetic ettringite in a way of direct addition of aluminum sulfate and calcium hydroxide as an alternative to the hydration of yeelimite. The stability of the resulting system was studied using the X-ray diffraction (XRD) and differential thermal analysis (DTA) in two different environments, namely in a laboratory environment and the environment of saturated water vapour. The evaluations of X-ray diffraction analysis and thermal analysis show that in the ettringite sample stored in the laboratory environment, evaporation of molecular water and subsequent transformation of ettringite into metaettringite or monosulfate can occur over time. Conversely, exposition of saturated water vapour environment can lead to saturation of the system by free calcium ions due to the slow dissociation of calcium carbonate, and thereby increase the amount of ettringite at the expense of gypsum and aluminum amorphous phase. To verify the above, it is recommended long-term monitoring of samples exposed in monitored environments.

Abstract: The phase diagram for MnBi was investigated in high fields up to 18 T at temperatures ranging from 300 to 730 K. We used the differential thermal analysis (DTA), in order to examine the equilibrium phase change of ferromagnetic MnBi by applying high magnetic fields. In particular, the first-order magnetic phase transition to the paramagnetic phase at the decomposition temperature Tt ~ 628 K for ferromagnetic MnBi was evaluated in fields up to 26 T. It was found that Tt increases with increasing magnetic fields at the rate of 2 K/T in low fields up to 18 T, and clearly deviates from the linear increase above 20 T. From a viewpoint of application, it is important that the decomposition of MnBi can be controlled by a magnetic field. As a result, Tt on the liquid phase line changes the amount of Mn content from 10 to 16.5at.% at 26 T, and the heat-treatment at 26 T improves the volume fraction of MnBi. Further, it is quite interesting to directly synthesize ferromagnetic MnBi from the liquid phase without the paramagnetic phase transformation.

Abstract: Nickel–titanium- group 5A metal (V, Nb, Ta, Zr) alloys are known as promising hydrogen-selective membrane materials. They can potentially be used in membrane reactors, which can produce high-purity H₂ and CO₂ streams from coal-derived syngas at elevated temperatures. The master alloys were prepared by arc melting using high purity metals in a Ti-gettered argon atmosphere. The alloys were melted several times in order to improve homogeneity. The ingots were induction-melted under a high-purity argon atmosphere in a quartz tube and graphite crucible injected through a nozzle onto a Cu wheel to produce rapidly solidified amorphous ribbons. Thermal stability of the Ni40Ti40Nb20 and Ni32Ti48Nb20 thin tapes has been examined using DTA analysis.

Abstract: Research focused mainly on Fe-based matrix composite (the wrapped diamond), used Fe powder to replace the expensive cobalt powder (Co-based matrix composite), and add the rare earth (RE) elements to reinforce the related physical properties of this Fe-based matrix composite for diamond tools. Conducted on the related matrix composite differential thermal analysis (DTA), in particular Fe-based matrix composite containing 35% iron powder (with RE or without RE) Were discussed for DTA and the package insert forces. DTA and the analysis is consistent with the empirical formula. By hot pressing the composite with diamond as the research object, having researched the relationship among the heat capacity (CP) at constant pressure and other related physical parameters （the package inserts force and E etc.）. Take 35%Fe-based powder composite materials for diamond tools (with RE or without RE) as the research objiect, combining analysis of the problem for the porosity, and the densification, and the package inserts force, and the DTA tests, which the addition manner of rare earth, add form , and quantity are determined, so that the changes laws of DTA curve and heat capacity (CP) of Fe-based composite containing 35% iron powder( with the RE) are similar to the that of pure Co composites. Apply these laws to improve the hot pressing technology and mechanical properties of the diamond tools (bending strength, impact toughness, hardness and porosity) and so on

Abstract: Despite the tremendous success of phase-field (PF) modelling in predicting many of the experimentally observed microstructures in solids, additional progress is required in order to apply it to predict microstructure evolution in real alloy systems. One way to achieve this is to couple thermodynamic and kinetic databases with PF model. In this work, we present phase-field simulations of spinodal decomposition in Fe-Cr alloy during thermal ageing and anisothermal heating. In the PF method, the local free energy is directly constructed using the CALPHAD method. During isothermal ageing, the morphology of decomposed phases consisted in an interconnected irregular shape for short ageing times, and a further ageing caused the change to a droplet like shape of the decomposed Cr-rich phase. The influence of heating rate on phase transformations is then simulated and compared with experimental results obtained by differential thermal analysis, carried out with heating rates in the range 0.5 °C.min^-1 to 15 °C.min^-1. The simulation results show that heating rate strongly influences the microstructure morphology.

Abstract: Alloys of (Se100-xBix)90Te10 (x =0, 0.5, 1, 1.5, 2, 2.5, 3 at.%) were prepared by using a conventional melt-quench technique. The samples under investigation were characterized using X-ray diffraction (XRD) and differential analysis (DTA) at a heating rate of 10K/min. It was found, from the XRD studies, that the alloys were amorphous in nature. The glass transition temperatures of the alloys were found to increase with increasing bismuth content. This increase in the glass transition temperature was explained on the basis of a chemically ordered network model.

Abstract: The microstructure characterization of Al73Mn23Pd4 and Al73Mn21Pd6 alloys was done after annealing at 900°C for 312 h and subsequent water quenching, as well as after thermal cycling. DTA and EDX/WDX/SEM techniques were used in the investigation. It was found out that the alloys consist of the single ternary T-phase after annealing and water quenching. The DTA experiment confirmed the stability of this phase also at lower temperatures. After DTA, the alloys exhibited double-phase microstructure consisting of the ternary T-phase and probably the icosahedral I-phase. It was proved an incongruent transformation of the ternary T-phase into the liquid and vice versa.

Abstract: In order to be considered as a material for semi-solid processing, an alloy has to possess solid spheroids within liquid matrix. Therefore, it is important to investigate the structure of the candidate alloy prior to forming process by conducting partial melting experiment. In this research, the partial melting was conducted for XW-42 steel directly from as annealed condition without any pre-treatment (Direct Partial Remelting). Liquid Fraction Profile obtained from Differential Thermal Analysis (DTA) showed that temperature of 1340°C was located in a low temperature sensitivity region, hence making it as a candidate for processing temperature. Direct Partial Remelting at this temperature for 0, 2 and 5 minutes revealed near spheroidal structure with average grain size between between 45-51 µm which can be considered suitable for semi-solid processing.