Abstract: Aluminum dross residue is a by-product produced at secondary re-melt plants where aluminum scraps are recycled. In this study, aluminum dross residue was utilized as a major component in the fabrication of unglazed ceramics for wall tile applications. The use of this by-product can reduce the landfill and environmental problems. The amount of aluminum dross residue used in the ceramic compositions varied in the range 50-90 wt.%. Other components utilized in the ceramic compositions included recycled glass alumino-silicate based clays. Firing was carried out between 1140 and 1200°C with 4h holding time which resulted in strong ceramic samples. Alpha-alumina, α-Al2O3 was the main crystalline phase found in all sintered ceramic samples. The appearance of mullite phase, Al6Si2O13 was evident in all fired samples. Overall, the synthesized ceramics had excellent densification characteristics when the amount of aluminum dross residue was less than 70 wt% in the ceramic composition.
Abstract: This article gives a brief description of metal oxides, acceptable for using in advanced conductometric gas sensors, as well as a consideration of approaches, that can be used to select metal oxides for the manufacture of devices intended to sensor market.
Abstract: In this research, we investigated the influence of indium and antimony additions on the microstructure, mechanical and thermal properties of Sn-3.0Ag-0.5Cu lead free solder alloys. The results revealed that the addition of 0.5 wt.%InSb into SAC305 solder alloys resulted to a reduced melting temperature by 3.8 °C and IMCs phases formed new Ag3(Sn,In) and SnSb in the Sn-rich matrix with a decreased grain size of 28%. These phases improved the mechanical properties of solder alloys. In addition, the mechanical properties of SAC305 solder alloys increased by adding 0.5 wt.%InSb, resulting in an increase of ultimate tensile strength of 24%, but the percent elongation decreased to 45.8%. Furthermore, the Vickers microhardness slightly increased of the SAC305 solder alloys.
Abstract: The tensile and creep properties of near-α Ti alloys with added Al, Ga, Sn, Zr, Mo, Nb, Ta, W, Si, and Ge were analyzed by using a regression analysis technique. The tensile test was performed at room temperature for 27 alloys. The creep test was carried out under a constant stress of 137 MPa at 650 °C for 30 alloys and 310 MPa at 600 °C for 21 alloys. The squared multiple correlation coefficients for the tensile elongation and minimum creep strain rate were 0.97 and 0.84, respectively. In addition, the effect of α stabilizing elements on the tensile and creep properties of those alloys was examined. The tensile elongation and minimum creep strain rate decreased between Al equivalences of 8 and 10. However, those values can be scattered depending on the composition and microstructure even with an almost constant value regarding the Al equivalence. The effect of adding Ga on the tensile elongation and minimum creep strain rate was also examined by using regression equations.
Abstract: We report on preparation of Mg2(Si,Ge,Sn)-based thermoelectric materials by a direct induction melting method in Al2O3 crucible. A 40 g ingot of Mg2Si0.8Sn0.1Ge0.1 was prepared after addition to the batch 10 wt% of Mg excess. Evolution of crystal structure of the induction melted sample upon annealing and spark plasma sintering (SPS) was tracked by room-temperature X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. An evidence for the formation of Mg2(Si,Ge,Sn) solid solution was obtained from the crystal lattice parameter of this phase which was found to be larger than that of undoped Mg2Si. XRD and SEM indicated that alongside with the main phase of the Mg2(Si,Ge,Sn) solid solution, an impurity phase of Mg2Sn exists in the sample. Amount of the Mg2Sn impurity phase is significantly reduced in spark plasma sintered sample.
Abstract: Co-Cr-Mo alloys are currently applied as major materials for orthopedic implant because of their excellent wear resistance. The main strengthening mechanism of this alloy is the transformation of γ-phase Co-Cr-Mo alloys to the ε-phase. In this study, the evolution of the microstructure of a Co-28Cr-6Mo-0.08C-0.2N alloy has been investigated during isothermal aging. Solution treatment at 1275°C for 15 hours was carried out for as-cast alloy, followed by aging treatments at 700°C and 800°C for up to 15 hours. Microstructure evaluation, XRD analysis and micro-hardness test were carried out for both as-cast and aged alloys. From XRD analysis showed that the transformation of γ-phase to ε-phase occurred during the isothermal aging. The amount of ε-phase increased with increasing aging temperature and time, while the hardness of the alloy increased with increasing the amount of ε-phase. This led to the increasing of the hardness of alloy at higher aging temperature and time. In addition, the very fine precipitation in the cobalt matrix was observed in the aged-specimens. Aging at 800°C caused the progressive formation of very fine precipitates along intra-granular striation and the matrix. It is suggested that the precipitation was took place in the grain on the dislocations and the stacking faults.
Abstract: During surgical procedures on bone, a common method of producing haemostasis at bleeding cancellous bone is the occlusion of blood vessels. This is often achieved with bone wax, which is not bioresorbable, unlike the zein-based biomaterial investigated in the present research. Zein is a prolamin derived from corn, and has been gaining importance as a bio-medical material. Taking advantage of its solubility in ethanol-water solvents but insolubility in water, a zein-based viscoelastic solid can be produced which effectively occludes the flow of fluids through a porous surface modelling cancellous bone. Zein powder was dissolved into a 70% ethanol-in-water solution, and the ethanol was later leached out through exposure to an alcohol-free media. The insoluble zein ‘resin’ produced could occlude water flow through a porous surface. Experiments were conducted to determine the optimum composition of the precursor zein solution, varying the proportion of zein dissolved in the ethanol-water solvent. A 0.7 w/v composition was selected as the preferred ratio. A cell viability test using the resazurin assay showed that unleached ethanol in the zein-based biomaterial does not pose a threat, as the metabolic activity of osteoblasts on zein resin outperformed that on bone wax after 24 hours of incubation. Subsequent characterisation of the zein resin was performed with a rheometer: results showed that the 0.7 w/v composition had a higher storage modulus and loss modulus for the range of frequencies tested.
Abstract: Chitosan, β-glycerophosphate, and glycerol are all biocompatible materials for biomedical application. This work successfully developed a thermosensitive hydrogel composed of CS, β-GP and glycerol. The CS/β-GP/glycerol hydrogel can be made as a transparent solution at room temperature and becomes an opaque and turbid hydrogel after heating. The transmission of visible light at different temperature can be measured by a visible micro spectrophotometer combined with a precise temperature control of the demountable liquid cell. A tunable transmission of visible light hydrogel was developed. Moreover, the composition of such hydrogel is safely used and it is potential for biomedical applications.
Abstract: Malocclusion is one of the common problems encountered in the teeth and mouth of Indonesian people. This country is also confronted with problems that the bracket have to been imported from abroad. The purpose of this study is to produce national orthodontic bracket by metal injection molding (MIM) process in Indonesia, particularly by using vacuum sintering for 17-4 PH stainless steel because it is a material commonly used for orthodontic bracket. Sintering conducted at four different temperatures, at 1320 °C, 1340 °C, 1360 °C, and 1380 °C. The results showed that there are inclusions in sintering products. The relative density increases with increasing temperature sintering because the area of porosity are reduced. In addition, the results of sintering at 1360 °C has optimal hardness, which is amounted to 395 HV and higher than commercial bracket.
Abstract: Generally, metal injection molding (MIM) method utilizes SS 17-4 PH as material for application of orthodontic bracket. One of the process of MIM is thermal debinding, which binder is eliminated by thermal energy. In this study, thermal debinding process is conducted with variation of temperature, i.e. 480, 510, and 540°C, holding time, i.e. 0.5, 1 and 2 hours, heating rate, i.e. 0.5, 1, 1.5, and 2°C/min.The effect of temperature shows that the increased temperature will result in the mass reduction percentage due to formation of oxide on the sample, which will be proven through TGA testing. The highest mass reduction was 6.4137 wt% which was obtained at 480°C. For the variation of holding time, the longer the holding time will result in increased mass reduction and the highest mas reduction was 6.255 wt% which was obtained during 2 hours of holding time. For the heating rate, the slower the heating rate will result in increased mass reduction and decreased the presence of crack formation. The best variable was obtained at heating rate of 0.5°C/min, which resulted mass reduction of 6.2488 wt% and less crack formation.