Papers by Keyword: Decomposition

Abstract: The influence of annealing at 1200 °C for 2, 4 and 8 h on the carbide microstructure of AISI M2 type high-speed steel obtained by both the foundry and conventional metallurgy technologies has been studied. The primary focus was on the kinetics of eutectic carbide decomposition and dissolution in both the cast and wrought M2 high-speed steels under the effect of high temperature.

Abstract: Porous NiTi alloys were successfully synthesized by two different processes, including self-propagating high-temperature synthesis (SHS), and a combined process of decomposition – sintering. A systematic comparison of micro-structures and mechanical properties of these alloys was investigated. The results showed that the SHS process was better than decomposition – sintering process. By controlling the processing parameters of SHS, the received porous NiTi alloys showed that the porosity and pore were larger, and ratio of opened-pore reached up to 80%. The porous NiTi alloys fabricated by SHS process also exhibited good properties, such as a high compressive strength (up to 250MPa), and elastic modulus in range of 6.1 – 7.0GPa. The porous NiTi alloys synthesized by decomposition – sintering process have lower porosity (26-43%), lower compressive strength (< 110MPa), lower elastic modulus (< 1.2GPa) but the strain could be reached to 10%.

Abstract: In this paper, the groundwater sediment/titanium dioxide (Gs/TiO₂) were prepared via a conventional calcination process using groundwater sediment from natural resource at Pasao, Uttaradit province, Thailand and commercial TiO₂ as starting materials. The as–prepared were characterized by X–ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR). The photocatalytic activity toward the decomposition of agricultural residues (diazinon) at 247 nm was demonstrated under visible light irradiation for 120 min. The maximum experimental decomposition efficiency was 73.6% with the rate constant of 0.0102 min^–1 for prepared Gs/TiO₂ photocatalyst.

Abstract: Since asbestos has been classified as a hazardous chemical, it is desirable to propose a practical and safe procedure for the disposal of asbestos-cement products, or even better to re-use them. In this work, the temperature conditions of degradation of samples of various types of asbestos and products containing asbestos were examined. Samples were burnt at different temperatures and monitored by XRD, DTA, light and electron microscopy. By evaluation of changes at different burning temperatures, the previous findings on the decomposition of asbestos minerals have been confirmed. It has been found that the burning of asbestos cement materials alone or with the addition of limestone at the temperature above 1100 °C leads to the decomposition of hazardous asbestos and, with or without the addition of a setting regulator, hydraulic binder is formed with technological parameters suitable for the building industry.

Abstract: The decomposition of ethanethiol by a corona radical injection system, using water vapor and O₃ as radical source, was investigated. It is found that only 83.6% of ethanethiol can be decomposed in dry air flow with relative humidity of 13.4%. A proper quantity of water vapor injection can improve the decomposition efficiency, but which is not always increased. The maximum decomposition efficiency of 99.1% can be obtained in wet air flow with relative humidity of 74.7%. 97.6% of ethanethiol can be decomposed when the relative humidity of gas flow is 51.6%, but it is found that only 76.3% of element sulfur is converted to SO₂, based on sulfur balance. However, the conversion efficiency of sulfur to SO₂ increases obviously with the increasing of O₃ injection. The decomposition efficiency of ethanethiol and conversion efficiency of sulfur to SO₂ can reach 99.8% and 95.3% respectively, when O₃ is injected into the reactor by high voltage electrode tubes with concentration of 1 g/m3 and flow rate of 300 L/h. The decomposition products are SO₂, CO₂ and H₂O, while no organic product is found, based on which the decomposition mechanism is discussed. The weakest chemical bond C-S in ethanethiol molecule is firstly decomposed to ·SH and ·C₂H₅ radicals. ·SH can be oxidized to elemental sulfur and SO₂, and ·C₂H₅ is oxidized to CO₂ and H₂O.

Abstract: This paper describes an overall, simulation-based optimization approach to control plant operations for manufacturing calcium silicate masonry units (CS), which is directed towards and thus immediately applicable to practical processes. Starting from an investigation and classification of the CS production in order to differentiate the properties of each sub-process, specific target criteria are derived. To enable the influencing of these targets, relevant parameters including their mutual interdependencies are identified. On this basis, the criticality of each process step is assessed in order to determine improvement potentials and to investigate possible adjustments to the parameters.The elementary production types indicate a mix of the discontinuous and continuous processing in CS plants. Particularly, this work shows that through interrupting the continuous material flow, the hardening process is the main criteria for a plant’s success in meeting its targets, especially concerning energy efficiency. To achieve a feasible approach, the work develops a solving method geared to an optimized hardening process.Therefore, a formulation of a measureable target system is established, which is the prerequisite for modeling the whole optimization problem. An expedient decomposition of this optimization model to smaller sub-problems provides an efficient solving of these complex job-scheduling problems, in order to direct the method towards an operative use. The paper concludes with the determination of potential solving procedures for the overall problem and appropriate algorithms for solving the sub-problems.

Abstract: The dynamical analysis of a linkage mechanism is described in the paper. The contour graph method was utilized. The method allows for assigning a contour graph to a particular mechanism. In next step analysis is performed in algorithmic manner distinguishing the contours and generating kinematical and dynamical equations based upon theses contours. Decomposition of the system is utilized, therefore more simple subsystems are analyzed. Aggregated solution is compatible with all other classical methods however the approach is algorithmic and effective.

Abstract: The aim of the paper is focused on the analysis of the stress measurement in the railway substructure in the turnout with the movable frog prototype designed for a high speed. The evaluations were compared the measurement and the results obtained with theoretical presumptions. The Discrete Wavelet Transformation for the decomposition of the stress measurement and its evaluation is described. Two sections in the turnout with the movable frog were used for the measurement and signal analysis.

Abstract: The thermal property of new composition of eutectic molten salt was investigated to obtain low melting point and better stability at temperature of 500°C as heat transfer fluid in solar thermal energy system. The NaCl used was purified from seawater. The eutectic molten salts were prepared in ten different weight ratios and experiments were carried out using nitrogen as inert gas with heating of 10°C/min to the temperature from 25°C to 500°C. Experimental results indicated that all mixtures exhibited low melting point (<163°C) and high stability. The thermal degradation of LiNO₃, NaNO₃, KNO₃ and NaCl exhibit in the DTG profiles respectively. From the present study it can be concluded that major weight loss of the system is due to the dissociation of lithium nitrate to lithium oxides.

Abstract: In this study, non-isothermal kinetic methods for the decomposition of the adsorbed CO₂ on pure sodium hydrogen carbonate (NaHCO₃) were investigated by a thermogravimetric analysis (TG) and differential thermogravimetry (DTG). Four different heating rates were measured to calculate the order of reaction (n), the pre-exponential factor (A) and activation energy (E_a) using three different models: Kissinger-Akahira-Sunose Method (KAS), Flynn-Wall-Ozawa (FWO) and analytical method. The results showed that KAS and FWO methods gave similar values due to the approximation of employed equation whereas the analytical method gave different values. The obtained parameters from those three methods then were used to calculate the chemical reaction conversion versus temperature and their R². The results showed that analytical method provided the most accurate results comparing with KAS and FWO methods.