Authors:C. U. Aniz, P. P. Robinson, K. K. Abdul Rashid, and T. D. Radhakrishnan Nair
The kinetics of the reduction of nickel, cobalt and copper ferrites was studied by the temperature programmed reduction method at different heating rates in hydrogen atmosphere. The activation energy values of the reduction processes were calculated using the non-isothermal isoconversional method according to the Kissinger-Akahira-Sunose equation and the dependence of apparent activation energy on the degree of conversion was determined. The carbon monoxide oxidation activities of all the three samples were determined at various temperatures up to 140 °C. An interesting correlation between the apparent activation energies for the reduction process was observed. The decreasing trend of activation energy on the ‘extent of conversion’ in all cases showed that the reduction is a multi-step process involving a reversible process followed by an irreversible step.
Authors:I. Hanafi, A. Khamlichi, F. Mata Cabrera, E. Almansa, and A. Jabbouri
Non-reinforced and reinforced Poly-Ether-Ether-Ketone (PEEK) plastics have excellent mechanical and thermal properties. Machining is an efficient process that can be used to manufacture specific mechanical parts made from PEEK composites. Researchers have focused on improving the performance of machining operations with the aim of minimizing costs and improving quality of manufactured products, in order to get the best surface roughness and the minimum cutting force. The parameters evaluated are the cutting speed, the depth of cut and the feed rate. In this paper, the effect of the mentioned parameters on surface roughness and cutting force, in dry turning of reinforced PEEK with 30% of carbon fibers (PEEK CF30) using TiN coated cutting tools, is analyzed through using robust design techniques such as Taguchi's design method, signal-to-noise (S/N) ratio and statistical analysis tools such as Pareto-ANOVA. The obtained results have shown that Taguchi method and Pareto ANOVA are suitable for optimizing the cutting parameters with the minimum possible number of experiments, and the optimized process parameters were determined for surface roughness and cutting force criteria.
Six coloured and six non-coloured waxy rice varieties were analyzed by determining amylose, fat, and protein content, pasting, and thermal properties. Significant differences in protein content as well as pasting properties between coloured and non-coloured waxy rice were identified. It was demonstrated that protein may have a main influence on pasting and thermal properties of waxy rice. In addition, the optimal linear relationship between protein and pasting or thermal properties was found by combining RVA and DSC data using Principal component analysis (PCA). Typical indicators, which can classify coloured and non-coloured waxy rice, could be identified by Hierarchical cluster analysis (HCA). In pasting properties, trough and consistency viscosity were typical indicators; in thermal properties, enthalpy and stop temperature were typical indicators.