Papers by Keyword: Recovery

Abstract: The influence of the recovery characteristics on the switching behavior of SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) with different switching speeds was investigated. A comparative analysis of the devices with different recovery characteristics revealed an increase in the turn-on loss (E_on) owing to the higher output capacitance charge (Q_oss) and reverse recovery charge (Q_rr) in the recovery arm. On the other hand, a higher Q_oss in the recovery arm resulted in a lower turn-off loss (E_off). In addition, an increase in Q_oss and Q_rr further influenced E_on and E_off at a higher switching speed. Furthermore, a higher Q_rr observed at a higher switching speed indicated a more significant impact of Q_rr on E_on at a high switching speed than that of Q_oss. The findings clarified in this study highlight the necessity of focusing the recovery characteristics to ensure a desirable switching loss of SiC MOSFETs.

Abstract: The viscoelastic and creep and recovery behaviors of a carbonyl iron (CI)-water-based magnetorheological fluid (MRF) were studied under dynamic and constant loading conditions. The feature of MR fluid is to change from liquid to semi-solid state just in a few milliseconds after applying a magnetic field. ThereforeMR fluid is a kind of smart material whose rheological properties change with step-change in a magnetic field. We prepared MR fluids comprising CI 65 wt%, water 35 wt %, bentonite 3 wt %, and oleic acid 1 wt %. Because bentonite with nanosized fills the voids between the CI particles, it was used with oleic acid to enhance the MR response of the CI/water suspension. The strain amplitude tests reveal that MR fluid behaves as a viscoelastic material in the LVE range and a transition of fluid occurred from linear viscoelastic to non-linear viscoelastic behavior at the critical strain of 0.1%. Its storage moduli confirmed a steady plateau region for the entire angular frequency range, suggesting the well-known solid-like behavior of the MR suspension. The creep and recovery result signified that as the magnetic field increased, the instantaneous creep strain contributions decreased dramatically.

Abstract: The article presents the results of studies on recovery of lithium from reservoir brines using both commercial and synthesized aluminum hydroxide and hydrated manganese oxide as sorbents. The research results showed that, when using commercial aluminum hydroxide and synthesized hydrated manganese oxide as sorbents, lithium recovery from brine was 21.8 and 20.1%, respectively. Studies were conducted on lithium chemisorption on freshly precipitated aluminum hydroxide, which was obtained by adding aluminum chloride solution and tri-calcium hydro-aluminate to the brine. Chemisorption of lithium was carried out under the following conditions: T = 50 °C; AlCl₃ solution concentration - 120 g/dm³; molar ratio Li/Al = 7; pH equal = 8.0-8.8; holding time with stirring 1 h. The degree of lithium extraction from brine was 71%; lithium capacity of freshly precipitated Al (OH)₃ was 5.9 mg/g. During calcareous leaching of lithium-aluminum precipitate, lithium was extracted into a solution by 74.7%.

Abstract: Extensive processes and costly precursors for the fabrication of existing sorbents for oil spills urges to look for more renewable sorbent sources. In this work, hollow, tubular, cellulosic fibers (kapok, Ceiba pentandra) were successfully converted to carbon sponges by pyrolysis at increasing temperature and time. Fourier Transform Infrared (FTIR) spectroscopy confirmed the complete carbonization of the kapok fibers at 800 °C. Scanning Electron Microscope (SEM) images revealed that the carbonized kapok fibers maintained their original tubular structures, suggesting high surface area. Water contact angle measurement showed improved hydrophobicity, with a maximum value of about 135°. The carbonized fibers were able to hold selected organic and oil solvents ranging from 16-20 times the weight of the fibers. The fiber pyrolyzed at 400 °C for 0.5 h showed the highest sorption capacity at 45.56 g/g for palm oil, almost matching that of raw kapok.

Abstract: Stress corrosion cracking (SCC) is one of serious aging degradation problems for the Alloy 600 components of pressurized water reactors (PWRs). In order to prevent SCC, various methods such as water jet peening (WJP), laser peening (LP), surface polishing have been used to introduce compressive stresses at the surfaces of the PWR components. However, it has been reported that such compressive residual stress introduced by these methods might be relaxed during the practical operation, because of high temperature environment. In this study, the hardness reduction behavior of the Alloy 600 processed by LP, Buff and WJP in the thermal aging process has been investigated to estimate the stability of the residual stress improving effect by each method, based on the fact that there is a correlation between the compressive residual stress relaxation and the decrease of hardness. The behavior of the residual stress relaxation in the processed materials in the high temperature environment has been discussed with kinetic analysis.

Abstract: We investigate the effect of the cold reduction rate on ferrite recrystallization behavior during the annealing of low-carbon steel with different initial microstructures. Three types of hot-rolled sheet specimens are prepared: specimens P, B, and M, which consist of ferrite and pearlite, bainite, and martensite, respectively. To evaluate the effect of the cold reduction rate on ferrite recrystallization behavior, hot-rolled sheet specimens are cold-rolled at cold reduction rates of 40% and 67%. The cold-rolled sheet specimens are heated to the target temperature, and then water-quenched to room temperature. Irrespective of the initial microstructures, the ferrite recrystallization is accelerated by increasing the cold reduction rate. In addition, the dislocation densities of specimens P and B increase at the larger cold reduction rate, which accelerates ferrite recrystallization in these specimens. In the case of specimen M, the dislocation arrangement parameter remarkably decreases at the larger cold reduction rate, whereas the dislocation density hardly changes. Thus, we conclude that the accelerated ferrite recrystallization at the larger cold reduction rate for specimen M can be mainly attributed to an increase in the amount of interactions between dislocations in the specimen.

Abstract: Using the electrical-field (E-field) stress at the positive and negative directions to generate the degradation and form the recovery effect is a useful metrology to evaluate the integrity of gate dielectric. This consequence deeply influences the drive current of 2D MOSFET or 3D FinFET species. According to the experimental results with the short and long-term stresses, we found the electrical performance of Hf-based tested devices represented the better recovery than that of SiON-based ones. And the recovery effect is more regular, not only in V_T shift, but in gate leakage due to the high-k dielectric probably providing the polar effect and more trap assistants.

Abstract: The paper presents the materials on researching the use of current conductor copper waste for getting new functional materials. The changes of maximum deformation ratio, density, microstructure and hardness of powder copper preforms at different temperatures and deformation rates have been studied. The result is that the value of the maximum deformation ratio depends on kinetics of dynamic weakening processes. The change of the microstructure depending on the temperature and deformation ratio has been scrutinized. It has been established that the most fine-grained structure was got at the temperatures of dynamical recovery and recrystallization. The temperature intervals of stamping for manufacturing products by pressing are recommended. On the basis of experimental researches a resource-saving manufacturing method of producing axisymmetric details of high density from powder copper material with the use of maximum deformation ratios has been elaborated.

Abstract: In countries like Australia and South Africa, even less than 2% grade THM samples are being mined and processed for recovery of heavy minerals. In this paper, an attempt has been made to recover heavies from lean deposits of Brahmagiri coast of India. The Brahamagiri coast contains substantial amount of heavy minerals. Still at some locations of this coast, the heavy mineral deposit is very low. The present paper deals with the recovery of values from these lean deposits. Initially, a composite sample was prepared from samples containing less than 3 % heavy minerals. The composite sample is subjected to spiral concentrator in stages to recover total heavy minerals. The results of the investigation reveal that 12 stages of spiral concentrator are essential to recover a concentrate of 90.3% grade, 1.95% yield and 99 % recovery from a composite sample containing 2.9 % heavy minerals.

Abstract: The article reviews the need to involve poor raw materials in processing, presents the results of the information search on the processing of technogenic wastes from beneficiation. It is shown which factors influence the choice of a specific flowsheet. The review of processing technologies for poor refractory raw materials was performed. The basic trends in processing of technogenic wastes from polymetallic ores beneficiation were established. It is noted that it is more advantageous to use combined hydrometallurgical methods for processing of technogenic wastes from beneficiation.