Key Engineering Materials Vol. 920

Abstract: The main objective of this study was to evaluate the effect of soda ash (SA) and carboxy methyl cellulose (CMC) on the rheological of white bentonite collected from Boyolali, Indonesia (BWB). The first work was the determination of BWB composition with XRF and the study on the effect of SA on the swelling index. The second step was to study adding SA and CMC on viscosity at 600 and 300 rpm. Another rheological parameter (yield point to plastic viscosity ratio, μ_P/μ_V) was determined based on the viscosity data. The results showed that the BWB sample tended to be categorized as Ca-bentonite with a calcium oxide content of 0.70 wt.% and contained montmorillonite, quartz, and pyrophyllite. SA and CMC in BWB increased the interlayer space of the montmorillonite. The addition of 14 wt.% SA to the BWB sample showed the maximum swelling index of 10 mL/2 g. The optimal formula meeting API 13A specifications is BWB sample of 81.23 wt.%, soda ash 14 % (w/w), and CMC 4.77 wt.%. This product results in the viscosity at a reading of 600 rpm of 30 cP and the μ_P/μ_V ratio of 1.0. Therefore, the product is potential as a candidate material for drilling mud.

Abstract: In this study, nanosilica for Enhanced Oil Recovey (EOR) has been successfully synthesized using geothermal waste. The method used is wet grinding method with deposition time variations to determine its effect on time deposition on particle size. Characterization using X-Ray Fluoroscene (XRF), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were also carried out to determine the characteristics of the material. Wettability of nanosilica then was confirmed by contact angle test. Based on the results, it was shown that the purified silica has silica content up to 98.85% with an amorphous phase. The results of Particle Size Analyzer (PSA) show that deposition time determines nanoparticles size. The longer time deposition, the smaller particles can be produced with the best result at 4 days deposition because it can produced the smallest particle at 71.5 nm. The morphology of nanosilica is granular that has been confirmed by SEM. Contact angle test reveals that nanosilica geothermal waste has ability to change wettability. Nanosilica can decrease contact angel of crude oil from 23,3^o to 13,9^o.

Abstract: Hydrotreating process is one of the crucial processes in petroleum refinery to remove sulfur with the aid of catalyst. By the end of hydrotreating life cycle, the catalyst contaminated by silicon cannot be reused or regenerated and have to be sent to final disposal. The previous study reported that glycerol was able to selectively remove silic on from industrial spent catalysts using severe operating conditions. However, the treatment used did not consider carbon/ coke removal steps. The present work focuses on investigating the effect of decoking pretreatment on silicon removal process using glycerol, mono ethylene glycol, and a combination of glycerol + mono ethylene glycol. It was found that the decoking pretreatment will worsen solvent selectivity. In addition, XRD analysis also revealed that decoking pretreatment caused formation of MoO₃ particles agglomerate as indicated by the presence of high crystalline. Compared with glycols, glycerol showed the best selectivity and could preserve catalyst phase from transformation that was occurred during decoking.

Abstract: The conversion of silica gels into sulfated silicas (SO₄/SiO₂) have been carried out. The sulfation process of the catalysts was carried out by impregnation of sulfuric acids at concentrations of 1; 2; and 3 M and calcination temperatures of 500, 600, and 700 °C. Sulfation with 2 M H₂SO₄ and calcination temperature of 600 °C (SS2-600) produced a catalyst with the highest acidity value (5.13 mmol NH₃ g^-1). XRD analysis showed the formation of amorphous SiO₂ phase, whereas SSA analysis showed that the SS2-600 catalyst had a mesoporous structure with a surface area of 147.728 m²/g, a total pore volume of 0.25 mL/g and a pore diameter of 6.439 nm. Characterization results show that sulfated silica gels have potency as solid acid catalysts.

Abstract: CoNi and FeCoNi hydroxide with narrow voltage distance between oxygen reduction reaction and oxygen evolution reaction was synthetized by electro-deposition in low solvent concentration. 5cm² Membrane electrode assemble (MEA) electrolyzers composed with anion exchange membrane, homogenerated catalyst on both cathode and anode gas diffusion layer (GDL) was fabricated for oxygen electrochemical production from air. The current and yield of binary CoNi device reached up to 466.7mA and 4.4mmol/h (94.7% conversion rate) at 1.2V. The ternary FeCoNi device showed only 0.5% degradation from 394.0mA during 12h. The applicability of oxygen production from air by high performance electrochemical devices was demonstrated.

Abstract: The intermediate band semiconductor of AgGa_1-xCr_xS₂ is investigated by the first principles calculations and further confirmed by the experimental results. The band structures of pure and Cr-doped crystals were calculated and it is shown that the crystal with a direct energy band gap of about 0.95 eV for AgGaS₂. Because of Cr dopant, a metallic intermediate band (IB) is successfully formed in the host. From the partial density of states (PDOS) of Cr-doped AgGaS₂, the IB mainly comes from the hybridization of the Cr-3d and S-3p states. Based on the theoretical predications, the Cr-doped AgGaS₂ is synthesized by the high-temperature solid state reaction. Two extra absorption responses are detected in the absorption spectra. The optical absorption coefficients are enhanced in the visible radiation range due to the formation of metallic and isolated IB. Therefore, Cr-doped AgGaS₂ with an intermediate band is suggested as a potential material to enhance the efficiency of solar cells.

Abstract: Stochastic tow based discontinuous composites (STBDC) are fabricated from the compression molding of chips made from chopped and slit pre-impregnated uni-directional carbon fiber reinforced polymer (CFRP) tape. The discontinuous mesostructure gives the material system increased moldability versus continuous fiber composites allowing complex three-dimensional parts to be manufactured. However, the discontinuous mesostructure creates challenges for engineers designing parts as the effective properties are variable. Furthermore, the properties have been shown to be a function of the consolidation method of the chips. This study uses finite element analysis simulations of mesostructural representative volume elements to compare the elastic response and characteristics. The results are compared to the available literature regarding the elastic response STBDCs.

Abstract: Prediction of the fatigue of rubber component can be difficult owing to rubber material being mechanically nonlinear and a large variety of randomness being invloved in production. Based on the classic metal fatigue prediction theory, this work proposes a refined cumulative fatigue predictor in a tensor form for the rubber components fagtigue life prediction using a hyperelastic FE analysis. The predictor is applied to estimate the fatigue behavior of engine rubber mounts under two working conditions while the fatigue life is measured using hydraulic testing machine. The predicted fatigue life is shown to be within ±2 times of the measurement results suggesting the effectiveness of the proposed method.The applicability of the proposed approach in rubber-related industrial products evaluation is discussed.

Abstract: In the quantitative characterization of linear defect structure of Piston Alloy, non-destructive testing and micro-morphology of defect, shape and outline of prefabricated linear defect are used in this paper. Based on ANSYS finite element software, an experimental simulation of line defect was carried out by using the finite element software of micromechanics. The defects of piston alloy components are assigned with material parameters, the model grid is divided, the boundary condition is defined and the finite element simulation is carried out under ANSYS/Mechanical environment. The calculation of the micro-stress field of the interface with various defects is obtained. Under the service condition of high-power density diesel engine, the local stress concentration caused by line defect is less than the strength limit of alloy material. Therefore, in this location eddy current testing non-destructive testing control line defect size is 0.12 mm×0.2 mm×5 mm. It is suitable for Eddy current nondestructive testing of piston components and can ensure the material safety and work reliability of Piston components under service condition.

Abstract: Surface/subsurface processing damage on optical component can severely affect its surface mechanical properties and cause its resistance to external deformation to deteriorate. At the same time, the processing damage will also affect the surface quality. The surface processing defects are the main reasons leading to the decrease in the laser induced damage threshold in high-density laser system. In this paper, the damage formation mode and morphology of the traditional optical processing methods based on the mechanical removal in brittle and plastic modes are evaluated, then the traditional processing damage model is established accordingly. The polishing technology with material removal in elastic mode is proposed based on the damage generation mechanism. In the elastic mode, it is impossible to form the material removal by mechanical action due to the inability to overcome the yield limit of the material, thus it is necessary to introduce a weakening of the chemical reaction to reduce the bonding force of the surface layer of the optical element, using less force to form the material removal to ensure the disturbance of the basic material is controlled. The mechanism of material removal in elastic mode was analyzed. The polishing process was realized by elastic hydrodynamic ultra-smooth polishing and nano-particle jet polishing. The performance of the elastic polishing process was analyzed. The experimental results show that the elastic polishing processing method can effectively remove surface damage and achieve effective control of processing damage.