Abstract: In this study, a symmetric electrochemical capacitor has been fabricated by adopting the lithiated compound (LiFePO4)-activated carbon (AC) composite as the core electrode materials. The electrochemical performances of the prepared supercapacitor were studied using cyclic voltammetry (CV) in 1.0 M Na2SO3 solution. Experimental results reveal that the maximum specific capacitance of 112.41 F/g is obtained in 40 wt % LiFePO4 loading on AC electrode in comparison to that of pure AC electrode (76.24 F/g) in 1 M Na2SO3. The enhanced capacitive performance of the 40 wt % LiFeO4 –AC composite electrode is believed attributed to the contribution of synergistic effect of electric double layer capacitance (EDLC) on the surface of AC as well as pseudocapacitance via intercalation/extraction of Na+, SO32-and Li+ ions in LiFePO4 lattices. The composite electrodes can sustain a stable capacitive performance at least 1000 cycles with only ~5 % specific capacitance loss after 1000 cycles. Based on the findings above, 40 wt % LiFeO4 –AC composite electrodes which utilise low cost materials and environmental friendly electrolyte is worth being investigated in more details.
Abstract: Asbestos in various building materials were measured by spectral sensor to examine the shift in reflectance wavelength according to asbestos concentration in different materials. Asbestos glove, asbestos soil, asbestos fiber insulation board, slate and bamlite panel were tested under several experimental conditions to alter reflectance intensity at each wavelength to find the optimum condition to detect asbestos selectively from other particulate matters. Chrysotile was found to have specific wavelength range regardless of concentration and type of materials as detected under blue color filter and dyed with refractive index liquid.
Abstract: This paper investigates the effects of polysaccharide additive agent on the morphological and thermal properties of thermosetting polymer. The weight percentage (wt%) of Diglycidyl Ether of Bisphenol A (DGEBA) epoxy resin to Hexamethylenediamine (HMDA) hardener were kept constant while a varying wt% of chitosan, ranging from 0 to 10 wt% was introduced. The chitosan filled epoxy hardener mixture was allowed to cure at 40°C for a period of 12 hours. Dynamic Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) were conducted on the specimens to analyse the effects of chitosan loading on thermal stability and transition temperature while Atomic Force Microscopy (AFM) was used to investigate the changes to its morphological property. At chitosan loading of 2.5 wt% and below, good dispersion of the additive was observed. Apparent agglomeration and phase separation were formed when chitosan content increases above 7.5 wt%. The formation of bulky chitosan agglomeration was found capable of enhancing the thermal stability of the thermoset polymer. The diamine acted as the co-reactants with DGEBA as well as spacer which decrease the effect of material brittleness due to addition of chitosan.
Abstract: Microwave heating technology promising shorter processing times and less energy consumption beneficial for economic perspective with improved properties and better microstructural control. This study focussed on microwave sintered bioceramics material of 60YSZ-Al2O3/10HAP mixture fabricated by powder metallurgy route. The study was conducted based on three different sintering temperatures, starting with 900 °C, 1000°C ended with 1100°C. Mechanical properties of materials such as porosity, density, hardness and compressive strength were then determined for each composites. Results showed that lowest porosity was obtained at 1000°C which promoting to higher density, hardness and compressive strength. However, the increasing sintering temperature up to 1100 °C was initiated the decomposition of HAP and constitutes the formation of CaZrO3 determined by X-ray Diffraction (XRD) analysis. Microstructure characterization by Scanning Electron Microscope (SEM) observed the growth of large particles and pores result in excessive grain coarsening. Better sinterability was achieved through an adequate sintering temperature of 1000°C with no reaction reported between HA and ZrO2 during the sintering process facilitate by microwave hybrid heating. The pores was found to be interconnected for each composites via microwave heating expected to be useful for biomedical application which was favorable to osteo-integration.
Abstract: Water retted kenaf fibre reinforced epoxy laminates with five distinct fibre orientations, unidirectional, [+30/0/-30], [+45/0/-45], [+60/0/-60] and [90/] s were produced through resin infusion technique. The fibre weight fraction in each laminate was controlled and the effects of varying orientation in the resulting composite lamina were characterized through tensile and impact properties of the specimens. Superior tensile strength and modulus were observed for the unidirectional lamina while the orthogonal lamina [90/] s depicted the greatest resistance to impact. Specimen with higher proportion of fibres aligned parallel to the loading direction show greater enhancement in tensile strength while impact property of the lamina was found to be greater with increases in fibre orientation perpendicular to the direction of impact load.
Abstract: The purpose of this research is to develop the models to predict the average surface roughness and the surface roughness during the in-process grinding by monitoring the cutting force ratio. The proposed models are developed based on the experimentally obtained results by employing the exponential function with four factors, which are the spindle speed, the feed rate, the depth of cut, and the cutting force ratio. The experimentally obtained results showed that the dimensionless cutting force ratio is usable to predict the surface roughness during the grinding process, which can be calculated and obtained by taking the ratio of the corresponding time records of the cutting force Fy in the spindle speed direction to that of the cutting force Fz in the radial wheel direction. The multiple regression analysis is utilized to calculate the regression coefficients with the use of the least square method at 95% confident level. The experimentally obtained models have been verified by the new cutting tests. It is proved that the developed surface roughness models can be used to predict the in-process surface roughness with the high accuracy of 93.9% for the average surface roughness and 92.8% for the surface roughness.
Abstract: This study focused on the ultrasonic nanomachining by atomic force microscopy (AFM) to understand the phenomena of the ultrasonic nanomachining. The workpiece is an Au/Ti thin film and coated on the quartz crystal resonator (QCR). The ultrasound vibration of workpiece is carried out by used the Quartz crystal microbalance (QCM). And a normal force measurement model was built by force curve measurements in ultrasound vibration environment. The influence of different experimental parameters can be studied such as normal force and repeat number on the cutting depth and chip stacking. After the experiments, it can be found that the ultrasonic nanomachining by AFM is possessed great influence on the cutting depth.
Abstract: Graphene oxide (GO) thin films were fabricated into thin film sensor for the selective VOCs detection. Different concentrations of GO aqueous solutions (6.2g/L and 5.0 g/L) were tested and thermally treated to obtain the appropriate sensing layer in terms of specific surface area and functional group. For the selectivity, it was assumed that different numbers and types of attached functional group of GO could induce the difference in gas adsorption, which may consequently derive to the selective VOCs detection. FE-SEM, XRD, and FTIR were utilized to characterize crystalline phase and functional group change by heat treatment condition and resistance measurements were followed. We suggest that thermally treated GO thin film sensor can be the alternative approach to achieve the improved selectivity in multiple gas detection by controlling the degree of gas adsorption.
Abstract: To improve the pouring process efficiently, mold flow analysis and experimental design are adopted to provide feedbacks from defect prediction and thermodynamics evolutions by considering thermal radiation effect between shell molds and the molten metal. Processing parameter, gate and runner layout were regulated to prevent the formation of casting defects, so as to promote pouring yields and reduce the costs and product development cycle effectively.