Papers by Keyword: Recovery

Abstract: In this work, we report the impact of combined surge current stress and bipolar gate switching stress (GSS) on the threshold voltage (V_th) shift of planar SiC MOSFETs. The V_th shift exhibits a strong dependence on the sequence of these two applied stresses. It is found that both the surge current stress and GSS can separately result in a positive shift in V_th, and the V_th shift is cumulatively aggravated in the combined stresses only if the bipolar GSS is applied first. This is attributed to the generation of new defects during the bipolar gate switching, which act as trap centers for subsequent surge stress. This finding reveals the cumulative damage characteristics of SiC MOSFETs under complex operating conditions.

Abstract: In the present work artificial neural networks (ANN) models have been implemented and trained as surrogate models to replicate two physics-based microstructure models for Al-alloys, i.e. the ALFLOW model, which predicts the sub-structure evolution and associated flow stress during plastic deformation and the softening model ALSOFT, which predicts the softening behavior after hot/cold deformation, in view of the combined effect of recovery and recrystallization. Input for both ANN models was limited to variables such as strain, strain rate, time, temperature and solute concentration, and the flow stress as the output. Accuracy and efficiency were tested for different ANN architectures. It is demonstrated that fully connected feed-forward neural network architectures with ∼3 hidden layers are suitable as surrogate models for both ALFLOW and ALSOFT, with a potential speed-up of ∼100x for ALFLOW and ∼10x for ALSOFT.

Abstract: Scale deposits in geothermal power plants are well-known potential sources of minerals. Extensive research in mineral recovery is crucial due to the considerable variability in scale composition and geochemistry based on location. Geothermal scales from Batangas, Philippines, were used to synthesize size-modified amorphous silica (SiO₂) via sol-gel method. Initial analyses employing x-ray fluorescence spectroscopy (XRF), total dissolved solids (TDS), electrical conductivity (EC), and pH measurements confirmed that the scale is rich in silica and salts at neutral pH. Then, the effect of varying scale concentration, precipitation pH, and aging time on the particle size distribution of recovered amorphous silica were investigated. Dynamic light scattering (DLS) for particle size analysis (PSA) revealed that the sample with 2.5% (w/v) scale precursor in NaOH and precipitated until pH 10 had the lowest average cumulant diameter (1.66 μm). Moreover, the synergy of precipitation pH and aging time was found to significantly affect the polydispersity index and cumulative diameter of precipitated SiO₂ based on 2³ factorial ANOVA at 0.05 significance level. X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) confirmed that the precipitates were amorphous SiO₂ with spherical morphology. This study proves the viability of utilizing geothermal scales from Batangas, Philippines for the synthesis of amorphous SiO₂ with controlled particle size, which is a potential filler for composite materials.

Abstract: The technology repair and restoration dies for hot punching is considered. During the overhaul the hammer die, a layer of metal is removed from the side the mirror to the entire depth the cavity of the stream, then the figure the new stream is marked, and then the stream is milled as in a new punch. Sometimes such methods restoring punches as electric arc surfacing welding or deformation with a special punch in the form of a stream are used. When installing inserts in a punch, it is necessary to compensate for the removed metal layer with special linings. Welding electrodes must be selected depending on the requirements for the base metal and service properties the deposited layer – hardness, heat resistance, allowable specific pressures, machinability, heat treatment acceptance, etc.

Abstract: Sidoarjo mud contains potentially valuable minerals, the largest content of which is silica. Silica decomposition from Sidoarjo mud can be done by using alkaline fusion method. The purpose of this study is the recovery of silica from the Sidoarjo mud against variations in Na₂CO₃ alkaline fusion time. Stages Sidoarjo mud mass ratio Na₂CO₃ 1:3 is inserted into the furnace at a temperature of 700°C with a long alkaline fusion time of 1:1.5;2;2.5; and 3 hours. Based on the calculation results, the best % recovery occurred for 3 hours, which was 48.3%. It can be concluded that the alkaline fusion time can affect the silica decomposition of the Sidoarjo mud

Abstract: The use of technology in Indonesia has resulted in an increasing demand for electronic and electrical goods, including printed circuit board (PCB) waste. Currently, PCB waste amounts to 20-50 million tons and continues to grow annually. Given that the composition of PCB waste consists of approximately 40% metals such as Ag, Cu, Fe, Au, Sn, and Mn, recycling PCB FR-2 waste can significantly increase its added value. One effective method is employing a concentration technique to recover these metals. This study aims to investigate the impact of particle size and centrifugal force variations on the content and recovery of Cu and Ag metals in PCB FR-2 waste using a Knelson concentrator. The concentration process involved three size variations: -63+100, -100+150, and-150#, along with three centrifugal force values: 60, 90, and 120 G Force. The results indicate that the size variation-100+150# and a centrifugal force value of 90 G Force exhibited effectiveness in recovering Cu and Ag metals, with a minimal mass loss of 3.9%. The Cu and Ag levels reached 67.49% and 0.18%, respectively, with recovery rates of 53.22% and 39.96%.

Abstract: Heating and cooling activities of buildings consume a considerable amount of energy used in building envelopes and are responsible for almost 16 % of CO2 emissions in the air. This problem has been confronted with a recent worldwide trend by introducing eco-friendly buildings with net zero emissions. Currently used thermal insulators in building envelopes are usually made from synthetic polymers which are difficult to recycle or dispose of. This paper presents a novel bio-composite mats using Egyptian pulled wool fiber waste and flax fibers waste as an alternative to commercial polystyrene foam. High loft nonwoven mats with different blends of wool and flax are fabricated and characterized to utilize a composite structure with satisfactory thermal and physical properties. Thermal conductivity test, ignition test, and compression and recovery test are applied to the developed specimens. The results proved the competitiveness and suitability of the proposed composites to be used as building interior insulators when compared to polystyrene and other similar composite materials from literature.

Abstract: Modifying asphalt mixtures with recycled components is common practice due to their environmental and economic merits. However, due to the oxidized air-blown asphalt binders in recycled asphalt shingles (RAS) and aged binders in reclaimed asphalt pavement (RAP), adopting RAP and/or RAS as recycled components in asphalt mixtures influences the performance of the overall asphalt binder in these mixtures. The percentages of recycled components and performance grade (PG) of virgin asphalt binders (VABs) in the asphalt mixtures govern the performance of the overall asphalt binder. Therefore, the main idea of this study was to investigate the effect of the percentages of RAP/RAS and PGs of the VABs on the load- and non-load-associated cracking resistance of the extracted asphalt binders (EABs) from field cores. Rheological tests were performed on the EABs to assess the load-associated cracking (fatigue cracking) and non-load-associated cracking (low-temperature and block cracking) resistance. The VAB's PGs, mixtures' ages, and the percentages of RAP/RAS affected the EABs' cracking resistance. When compared to EABs from mixtures with lower amounts of RAP, employing RAS in the asphaltic mixtures improved EABs' resistance to fatigue and block cracking. However, using RAS deteriorated EABs' resistance to low-temperature cracking. Increasing the RAP's percentage in the asphaltic mixtures decreased the cracking resistance of the EABs. Strong relationships were established between EABs' load- and non-load-associated cracking resistance.

Abstract: The cobalt content in LIB (Lithium-ion Battery) can be recycled using green technology through a bioleaching process with the help of microorganisms to have high efficiency, low cost, easy method, and environmentally friendly. The bacterial strain of A. ferrooxidans in the bioleaching process isolated from acid mine water was capable to extracting cobalt in LIB to obtain pure metal ions. The aim of this research is to isolate bacteria A. ferrooxidans from acid mine water in order to extract the element cobalt from a LIB. This study has recovery with culture time of 0-14 days, aerobic systems, inoculum concentrations of 5%, 10%, and 20%. The optimization of bacterial growth was done by aerating the culture. The recovered cobalt were analyzed from the filtrate after the bioleaching process using ICP analysis. LIB and sediment of the bioleaching process were analyzed by XRD, SEM and EDX. The conclusion of this study showed that the recovery of cobalt metal (Co) using the bacterial strain of A. ferrooxidans was obtained at 73.95% for 14 days with the addition of a battery cathode of 1 gram/100 ml at the optimum conditions obtained when the addition of 20% inoculum, pH: 2-4, temperature: 30°C, and the aeration system uses an aerator. Bacterial strains isolated from acid mine drainage have the potential as oxidizing agents for lithium and cobalt metals in bioleaching processes.

Abstract: This work describes the advances in manufacturing for the recovery of hydraulic turbines. One of the key components in the operation of hydraulic turbines is the blades; as they are part of the impeller, they are in constant motion and directly receive all the loads produced by the impact of the water and the abrasive effects caused by sediment. The interaction between abrasion, cavitation, and corrosion accelerates the wear of these components, so it is necessary to apply coatings to prolong their useful life. When these elements lose their hydrodynamic profile, they must be submitted to a recovery process; typically, welding is used. However, due to the advancement of additive manufacturing (AM) and the development of new materials, AM appears as a disruptive technology capable of recovering the dynamic profile and improving surface properties such as hardness and wear resistance. The results show the effectiveness of the wire and arc additive manufacturing technology for the recovery of hydraulic turbines, increasing surface hardness from 285 to 325 HB.