Advances in Science and Technology Vol. 105

Abstract: Ethanol sensor has been widely used in our daily life and industrial production, such as drunk driving test, food fermentation monitoring, and industrial gas leakage monitoring. With the advent of the Internet of Things (IoT) era, ethanol sensors will develop towards miniaturization and low-power consumption in the near future. However, traditional ethanol sensors with large volumes and high-power consumption are difficult to meet these requirements. Therefore, it is urgent to study ethanol gas sensors based on new materials and new structures. Here, we demonstrated a flexible ethanol sensor based on an ion gel-coated graphene field-effect transistor (IGFET). The device has a small graphene channel size with a width of 300 μm and a length of 200 μm. The device showed a low operating voltage of less than |±1| V. When the device was put into an ethanol gas condition, the Dirac point voltage of the IGFET showed a negative shift, which means an n-type doping effect to the graphene channel. Furthermore, the sensor showed a normalized current change of-11% against an ethanol gas concentration of 78.51 g/L at a constant drain-source voltage of 0.1 V. In addition, the device exhibited a fast response time of ~10 s and a recovery time of ~18 s. Moreover, the detectable range of the device was found to as wide as 19.76-785.1 g/L. Based on the above results, the flexible IGFET-based ethanol sensor with small size and low-power consumption has great potential to be used in the industrial production of the IoT era.

Abstract: Metal matrix composites attain a significant position in Industrial, defense, structural and automobile applications. To amplify that strategy there is a need to find out the conditional behavior of the composites and enhancing the properties will be mandatory. The present work mainly investigates on the effect of processing parameters like densification rates, sintering temperature, reinforcement content on the microstructure, mechanical properties of the Al7175/B4C composite material fabricated by mechanical milling and powder metallurgy techniques. Results show there is a grain size reduction and refinement in the composite material through ball milling operations and along with that increasing B4C content in the composite powders make milling conditions very effective. Increasing the sintering temperature results in a consistent grain growth along with that porosity level decreases up to a limit and then attain a steady state, the strength of the composites increases with compaction pressures but reinforcements content effects the strength of the material by losing its ductility making it brittle.

Abstract: Microstructure characterization and defects formation of a joint fabricated by friction stir welding on two plates of Al 6061 were studied. In this study, plates were in the height of 2mm and input parameters were pin profile (square and cylindrical shape), rotating speed (800 and 1600 rpm) and traverse speed (40, 80 and 120 mm/min). Also, some experiments were conducted and the effects of input variables on the microstructure of the samples are studied by using an optical microscope. Based on the results, a sound defect-free weld could be achieved by optimizing the ratio of traverse speed to rotational one, due to the influence of this ratio on the amount of heat generated during the FSW process. It has been also concluded that higher ratios of traverse speed to rotating speed can result in poor welds.

Abstract: This paper presents the current major research developments and growths in the area of microwave hybrid heating-based joining of similar and dissimilar materials. The study discusses on the different types of specimen materials, susceptor materials, fillers and microwave power level used by researchers for joining process. Comparative studies of joints using different parametric conditions are also mentioned. Physical characterization of joint has been investigated with optical microscope, scanning electron microscope, energy dispersive spectroscopy, electron probe micro analysis, X-ray diffraction and mechanically with hardness test, tensile test, 3-point bend test, impact test. Various methods for design of experiment and optimization are also used to obtain better results. Current study will facilitate the proper choice of input parameters for easy and good joints formation through the microwave hybrid heating method.

Abstract: Some hydrophilic drugs (e.g. anti-tumor drug of doxorubicin (DOX) and anti-osteoporosis drug of alendronate sodium (ALN)) have great toxic and adverse effects on the human body. In this paper, two kinds of drug-loaded composite gel systems were prepared via mild and efficient chemical reaction synthesis, hyaluronic acid-linked ALN (HA-ALN) hydrogel and polyethylene glycol-linked DOX (Tetra-PEG-DOX) hydrogel. By characterizing their chemical structures, morphological networks, and ultraviolet absorption behaviors, two different types of drug-loaded composite gels can be constructed well. It is expected to achieve effective drug loading and controlled release. The two drug-loaded gels are applied in the fields of antitumor and anti-osteoporosis and exert their application value in the field of biomedicine.

Abstract: The aim of this work is to investigate the optimum heat treatment for Al-5.7Si-2Cu-0.3Mg aluminium alloys and study its effect on microstructure, phase transformations, and hardness. The test specimens were taken from the as-received alloy. Solution treatment was performed at 485°C and 500°C under various solution treatment times for 4, 8, 10, and 12h, and the samples were then hot water quenched at 60°C, followed by aged hardening at 150°C, 170°C and 190°C for 2,6,10, and 14h, and subsequently air-cooled. The hardness of the Al-5.7%Si-2Cu%-0.3%Mg alloys were determined using a Rockwell hardness tester. Scanning electron microscopy (SEM) and optical microscopy (OM) were used to determine the microstructure of the samples, while X-ray diffraction (XRD) was used to identify the phase compositions. The resulting microstructures and hardness values were compared to the corresponding as-cast samples. It can be seen that the solution treatment at 485°C for 12 h and aging at 190°C for 10 h are the optimum T6 heat treatment conditions that would result in hardening precipitates over the as-cast alloy. OM and SEM morphologies show significant microstructure evaluation of improved distribution of the Si particles. After T6 treatment, the morphology of Si particles in the as-cast Al-5.7Si-2Cu-0.3Mg alloy changes from long and coarse plate-like grains to fine spherical shaped grain. The XRD plots confirmed the relatively high concentration of Al, Si, and Al₂Cu in the heat treated Al-5.7%Si-2Cu%-0.3%Mg alloy relative to that of the as-cast alloy. The hardness of the T6 alloy also increased.

Abstract: Carburizing is a heat treatment process, which used widely for surface hardening. In this process, the parts are placed in a concentrated atmosphere of Carbon atoms. The carbon atoms diffuse in the samples from the surface. In the present article, the effects of carburizing temperature on fatigue life will be studied. The St37 steel material is selected for study due to its wide range of usage in industry and little attention on the carburizing of this material. The samples are prepared by implementing the carburizing process at different temperatures (300, 400, 500, and 600 °C). The holding time is 1 hour for all samples. The two-point bending fatigue tests had been carried out on constant loading stresses. The results of the fatigue life test show that the fatigue life enhances the carburizing process. The fatigue life improved from about 45000 cycles to about 65000 cycles (about 44% increase) by increasing the temperature from 300°C to 600°C. Holding at higher temperatures leads to an increase in fatigue life smoothly due to the increase in the diffusivity coefficient. Also, the fracture surface demonstrates that the crack initiation starts from outer surfaces very slowly and failure happens as a brittle fracture in the samples.

Abstract: The utilization of nanoparticle filled composite materials in many different engineering fields has undergone a tremendous increase. Accordingly, the need for accurate machining of composites has increased enormously. In the present study, an attempt has been made to assess the factors influencing surface roughness on the machining of nanocomposites and base composites. The Taguchi L16 experimental design concept has been used for experimentation. The drilling experiments were conducted considering spindle speed, drill tool diameter, and feed rate as machining parameters. The empirical model was developed based on the input parameters. Analysis of Variance (ANOVA) established the relation between predicted and experimental values. The regression model was found to be within the level of confidence with greater accuracy indicated by R² value. The addition of Nanoclay and Graphene as fillers in the matrix improved the surface roughness of the hole. Feed rate and spindle speed were found to be the significant factors of machining and Graphene reinforced composites had better surface finish.

Abstract: X-ray fluorescence (XRF) spectrometry has certain difficulties of detecting trace amount material components accurately when measuring material samples composed of variable elements, mainly due to low Signal to Noise Ratio (SNR) issues of the characteristic spectroscopic peaks from the measurement. In this paper, a novel method called background noise reduction using Iterative Discrete Wavelet Transform (IDWT) methodology for trace element material analysis by advanced X-ray fluorescence spectrometer is proposed to improve SNR, thereby decreasing the Limit of Detection (LOD) for elemental qualitative analysis, and then achieve a more accurate quantitative analysis of trace elemental concentration. This paper utilized handheld X-ray fluorescence spectrometer to obtain the content of Sulphur in petroleum and 4 major pollution elements in soil. A total of 81 standard samples were collected and measured. The hardware parameters of the instrument were adjusted to optimize the SNR before background noise reduction. Experimental results illustrate that X-ray tube parameters have great influences on the calibration regression. Different X-ray tube voltages were tested and the optimal results were achieved at 5kV. Furthermore, IDWT algorithm was implemented and the optimal results were achieved by wavelet base “db5” and “sym4” with 7 level decomposition. The calibration regression curves were established for the Sulphur in petroleum. The regression R² values after IDWT were increased effectively when compared with original data without IDWT. Finally, the experimental results demonstrate a very good linearity between the weight contents of the target material and the XRF spectral characteristic peak intensity, and also it is found the LOD for Sulphur in petroleum can be reduced when combing with the IDWT.