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In this study, flotation of oxidised ores rich in copper and cobalt from Mupine deposit in the Democratic Republic of Congo had been investigated. This ore contains 4.85% copper, 0.16% cobalt. The recovery of copper and cobalt was performed using flotation to increase the concentration of copper and cobalt. Flotation of the oxidized ore was performed with fatty acid type Rinkalore. Copper and cobalt present in the ore were concentrated with optimal doses of sodium silicate, Rinkalore mixture of 500 g/t, 1500 g/t respectively and optimum tall oil and pH of 23% and 9.5 respectively. The influence of Rinkalore Bioex, Rinkalore Booster Q, pH and sodium silicate on optimum operating conditions were studied. Improved performance of operating conditions was obtained with the mixture of reagents Rinkalores 10 and Booster Q. Primary feed titrating 8.70% copper and 0.31% cobalt respectively had a recovery yield of 53% and 34% respectively, and rougher concentrate titrating 8.13% copper and 0.33 % Cobalt respectively had a recovery yield of 97% and 70% respectively.
Poly (cyclohexanedimethanol cyclohexanedicarboxlic acid) (PCC), a fairly newly synthesized polyester, has been studied. Having a good experience of increasing both thermal stability and service temperature when applied to typical polymers, poly (tetramethylene glycol) (PTMG) was selected as a softening agent that was randomly copolymerized into the PCC chains. Another widely-used polyester, poly (ethylene terephthalate) (PET) was also produced in order to investigate the effect of PTMG, which was compared with the properties of the newly developed random PCC-PTMG copolymers (PCCP). In this study, the crystalline structures, the thermal and the mechanical properties of both PCC and PET containing different ratios of the random segment of PTMG were investigated by differential scanning calorimetery (DSC) and tensile tester.
It was found that the crystallization rate of pure PCC was significantly slow, whereas for PCCP, PTMG effectively accelerated the crystallization rate with increasing PTMG, and the sample with 25 wt% of PTMG had the fastest crystallization rate in all PCCP samples. Here, the PTMG acted as an accelerator, simultaneously depressing the movement of PCC molecular chains. The elastic recovery test indicated that the ability of PTMG as a softening agent was highly demonstrated at 20 wt% of PTMG. The results of PCCP were compared with those of PET-PTMG copolymers (PETP) and it was found that there were optimum values of PTMG for the crystallization rate on both samples. Additionally, the results of the elastic recovery test indicated that the softening effects observed in PCCP were more pronounced than those observed in PETP.
InGaN films were successfully fabricated using radio frequency (RF) magnetron sputtering technique with a sputtering target of pure In and Ga metal alloys under a flow of nitrogen. Films were deposited on quartz substrates, with the ratio of In to Ga varied from 0.46 to 0.85 in the alloys. The structures and compositions have been studied using X-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDX), respectively. Multiple crystallographic phases have been observed indicating phase segregation and inhomogeneous distribution of the metal compositions in the films. The existence of wurtzite structures has been observed in all samples, with the In percentage (y) in a crystalline phase calculated from the XRD being less than the total In percentage (x) in each film as determined by the EDX spectroscopy. The (0002) orientation has been observed in all films, and the (10-11) orientation has been observed for x = 0.46 and 0.70 only. The optical transmission and absorbance of the films were studied by the spectrophotometry technique, which indicate that the dominant phases in all samples are amorphous. Consequently, the corresponding optical bandgaps have been characterized. Hall Effect measurements were made in 0.55 T magnetic field at room temperature to characterize the electrical conductivity, free carrier concentration, and mobility.
Cold spray is a relatively new coating technology in which coatings can be produced by powdered particles under large plastic deformation without significant heating. In this paper, nickel coatings were fabricated by cold spray process followed by heat treatment in inert gas. Structural transformation of both as-sprayed and annealed coatings was investigated by Electron Backscattering Diffraction (EBSD) in a FEG-SEM. The results show that after cold spraying sub-micron grains and subgrains with high crystal strain appear in the particle bond interface, but not shown in the center of particles. Microstructure was transformed to be uniform and stresses were released after annealing in 400°C for one hour. And ductility and formability were significantly improved due to recovery and recrystallization. Continuous recrystallization after large strain deformation could occur after cold spraying followed by annealing.
Zn/Al layered double hydroxide was synthesized in micro-emulsion system with the oil phase comprising of cyclohexane + TX100 (surfactant) + n-hexanol (co-surfactant). Aqueous NaOH solution was used as the precipitating agent. The XRD pattern showed Zincite as the primary and hydrotalcite as the secondary phase. The d003 diffraction peak corresponded to interlayer hydroxide ion. There was no interlayer NO3- ion. The synthesized LDH showed much higher BET surface area (116.3 m2/g) than similar LDH synthesized by conventional co-precipitation technique (4.2 m2/g). Well defined flaky nano-crystals having an average dimension of 5-20 nm were observed by HRTEM.