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- Author or Editor: S. Rajakumar x
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Abstract
Thermal decomposition behaviour of ten Indian limestones of marine origin have been studied by thermogravimetric (TG) and differential thermal analysis (DTA). DTA curves of limestone samples show asymmetric peak with index of shape about 0. 25. The size of calcite characteristic endothermic DTA peak remains unaffected due to the presence of impurities such as SiO2 and Al2O3. The presence sodium and potassium carbonate salts in the limestone have a strong effect on their decomposition. From the thermogravimetric data the activation energy, Arrhenius factor, order of reaction and entropy for activation were calculated using three different methods. TG and DTA results indicate that both temperature of decomposition and the activation energy for decomposition of limestone is reduced and that the rate of decomposition is enhanced relative to pure calcium carbonate. The formation of portlandite and wollastonite are strongly exothermic and thus helps in maintaining the required retorting temperature.
Abstract
The objective of this work is to investigate the rotary friction welding of AA1100 aluminum alloy with mild steel, and to optimize the welding parameters of these dissimilar materials, such as friction pressure/time, forging pressure/time and rotational speed. The optimization of the welding parameters was deduced by applying Response Surface Methodology (RSM). An empirical relationship was also applied to predict the welding parameters. Tensile test and micro-hardness measurements were used to determine the mechanical properties of the welded joints. Some joints were analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) in order to investigate the formation of intermetallic compound (IMC) layer at the weld interface. Experimentally, the tensile strength of the weld increases with increasing the forging pressure/time, while the low level of forging pressure/time allows the formation of an IMC layer which reduces the tensile strength of the weld.
