Abstract: Epoxy adhesive used in electronic packaging could normally be cured by ultraviolet light, heat at high temperature or dual cured by both processes. Differential scanning calorimetry (DSC) has been used to identify and analyze the occurred reaction during the curing process. The structural modification of epoxy during curing could be examined by measuring its thermal properties, and the change in molecular structure of epoxy could be observed by a relative small area of DSC peak. This provided the heat amount required for complete cure. It is found that the DSC peak area after heat cure at 90 °C increased linearly as a function of heating time while that at 120 °C decreased exponentially. For UV cure, it indicated that the curing mechanism was strongly depend on the energy from UV light. For dual cure at 90 °C, the heat curing time could be reduced from single curing process of 50 minutes to 6 minutes, while the heating time for dual cure at 120 °C could be reduced from 4 minutes to 2 minutes.
Abstract: The reduced wear rate of hip-joint bearing components is the main issues in biotribology researches for the biomedical implants. Ultra-high molecular weight polyethylene (UHMWPE) is extensively used as a bearing material because of having its great properties of friction and wear. Surface texturing can be selected as a method of enhancing tribology properties of engineering surfaces. In this present study, surface texturing examination was performed by 3D finite element method under influence of normal load. Stress distribution of UHMWPE surface under the influence of texturing with the variation in diameter cavities and separation was investigated. The result showed that the surface texturing provided the higher stress distribution of the lower separation in the cylindrical cavities.
Abstract: Maleic anhydride grafted natural rubber compatibilizer was prepared in molten state using twin screw extruder. Amount of maleic anhydride and initiator, as well as screw rotation were varied according to Box-Behnken experimental design. Titration of acid group from the anhydride function and FTIR spectra analysis were carried out as quantitative and qualitative analysis of grafted MA, respectively. The results showed that the percentages of grafted MA for all samples were ranged from 1.31 to 5.36%. The optimum conditions are predicted at 14.4 phr of MA level, 0.41 phr of BPO level, and 71 rpm screw rotation giving 5.39 ± 0.16% of grafted MA. FTIR spectra showed that the MA and carbonyl functional group were found in the compatibilizer suggested the presence of grafted MA and ring opening reaction.
Abstract: Epoxy adhesive has been widely used in microelectronic production process and the technique to determine the degree of tiny dot adhesive cure is essential to evaluate the products. In this work, micro Raman spectra were demonstrated to examine the adhesive curing at small diameter of about hundred micrometers. There are two Raman peaks that can be observed then modification during the curing process while it is bond to observe the change in the infrared absorption due to the background absorption. These two Raman peaks located at 1260 and 790 cm-1 due to C-C breathing and C-O-C epoxide ring vibrating, respectively. It is found that the relative peak heights decrease as a function of UV exposure time. The vibration of Raman peak for heat cure were investigated for comparison the bond vibration of epoxy was also study by DFT in term of vibration rotation analysis for both close and open epoxy ring models which used to describe the vibration before and after curing processes. The open epoxide ring model shows the reducing of epoxide peak. Relative Raman peak heights are proposed to be used for determining the degree of adhesive cure. With imaging ability of micro Raman system, the mapping of curing sample can be illustrated by setting the color map with the proposed relative Raman peak height.
Abstract: Structural sealants are one of the most essential construction materials due to a rising demand of buildings having glass panel faćades. Silicones are the most preferred base component due to their excellent properties appropriate for structural applications. The effect of titanium dioxide (TiO2) nanofillers on the mechanical and thermal properties of commercially available silicone-based sealants was investigated. The incorporation of 1 wt% and 2 wt% of TiO2 has caused an increase on the elongation at break SSG4000E and SilPruf SCS2000N sealants while an increase on the modulus of resilience was observed at SilPruf SCS2000N with 1wt% TiO2. The elastic modulus was highest at 5 wt% TiO2 for all sealants. Swelling behavior decreased with increasing nanofiller due to the physical crosslinking effect, thus preventing the diffusion of the solvent into the material. Thermal stability also improved with the incorporation of 2 wt% TiO2 as observed in the increase of the onset temperature of decomposition.
Abstract: Optimization of molding parameter on the flexural strength of carbon black/graphite/epoxy (CB/G/EP) nanocomposites using Taguchi method was studied. Three molding parameters was chosen in this study which are molding temperature, molding pressure and molding time. Experimental trials were carried out based orthogonal array design using those three parameters. The results were analyses using the signal to noise (S/N) and analysis ofvariance (ANOVA). Flexural strength of the CB/G/EP nanocomposites increases from 56.23 MPa to 65.11 MPa usingoptimize parameter obtained from the analysis method. These results shown that the Taguchi method is successfully to get optimum parameters of molding parameters to produce CB/G/EP nanocomposites.
Abstract: This paper presents the optical properties of erbium doped tellurite glasses with the composition of 55TeO2-2Bi2O3-35ZnO-5PbO-(3-x)Na2O-xEr2O3 where x = 0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mol% . Refractive index of the glasses was measured using Brewster’s angle method and their optical absorption spectra were measured in spectral range 200 – 1100 nm recorded at room temperature. The results show that the glass refractive index increases with the increase of Er3+ ion content in the glass and the optical band gap energy decreases with the increase of erbium content in the glass.
Abstract: Single-phase of BaCe0.57Zr0.38Yb0.05O2.975 (BCZYb) has been successfully prepared by a Pechini method using metal nitrate salts as pre-cursor. Dielectric behavior of the BCZYb sample was studied using impedance data collected from High Frequency Response Analyzer (HFRA). The frequency and temperature dependence of the dielectric constant and dielectric loss of the BCZYb solid solutions were investigated in the 1 Hz - 1 MHz frequency range. Dielectric relaxation mechanism was observed in the plots of dielectric constant and loss versus temperature. It was studied by the measurements of intermediate temperature, 500 - 800 ° C. All the responses were revealed by the analysis of impedance spectroscopy, using Z-man program. The present results are used to observe the relation between orientation polarization and dielectric relaxation of the material.
Abstract: Silicon nitride with 50 mass zirconia ceramic matrix composites were processed by mechanical milling (MM) followed by spark plasma sintering (SPS). Two different of Si3N4 particle shapes for create harmonic microstructure were investigated. The microstructure of Si3N4-ZrO2 with initial Si3N4 shape is like coin/flakes after MM for 144 ks was failed to create the harmonic microstructure after SPS. With another sphere shape of Si3N4 after MM for 144 ks, the harmonic microstructure could be formed after SPS. Thus, the initial powders shape of Si3N4 have an effect in the formation of harmonic microstructure could be fully achieved. The highest mechanical properties of Si3N4-ZrO2 are on the powders with mechanical milling time for 144 ks. The Si3N4 ceramic with homogeneous fine grains of ZrO2 dispersed on its surface was obtained, and the mechanical properties were improved. The Vickers hardness obtained on 144 ks is 1031 MPa and the bending strength is 262 MPa. The main factors explaining the improvement in the mechanical properties of Si3N4-ZrO2 are considered to be the porosity decrease caused by the particles shape and appropriate condition of powder processing i.e. MM and SPS.