Applied Mechanics and Materials Vols. 754-755

Abstract: This work investigates the possibility of using fly ash (FA) and Vietnam residual rice husk ash (RHA) in producing unfired building bricks with applying densified mixture design algorithm (DMDA) method. In this research, little amount of cement was added into the mixtures as binder substitution. Unground rice husk ash (URHA), an agricultural by-product, was used as partial fine aggregate replacement (10% and 30%) in the mixtures. The solid bricks of 220×105×60 mm in size were prepared in this study. The hardened properties of the bricks were investigated including compressive strength, flexural strength and water absorption according to corresponding Vietnamese standards. Forming pressure of 35 MPa was applied to form the solid bricks in the mold. The test results show that all brick specimens obtained good mechanical properties, which were well conformed to Vietnamese standard. Compressive strength and flexural strength of the bricks were respectively in range of 13.81–22.06 MPa and 2.25–3.47 MPa. It was definitely proved many potential applications of FA and RHA in the production of unfired building bricks.

Abstract: Self-compacting concrete has been accepted as a quality product. A Suitable method for estimating the instantaneous deflection for SFRSCC is not available. In this study an effective moment of inertia function has been formulated with a power coefficient obtained from authors and others data. The proposed method is found to predict the instantaneous deflections satisfactorily.

Abstract: Thin film piezoelectric material plays a vital role in micro-electromechanical systems (MEMS), due to its low power requirements and the availability of high energy harvesting. Zinc oxide is selected for piezoelectric material because of its high piezoelectric coupling coefficient, easy to deposit on silicon substrate and excellent adhesion. Deposited ZnO and Al improve the electrical properties, electrical conductivity and thermal stability. The design, fabrication and experimental test of fabricated MEMS piezoelectric cantilever beams operating in d33 mode were presented in this paper. PVD (Physical Vapor Deposition) was selected as the deposition method for aluminium while spincoating was chosen to deposit ZnO thin film. The piezoelectric cantilever beam is arranged with self-developed experimental setup consisting of DC motor and oscilloscope. Based on experimental result, the longer length of piezoelectric cantilever beam produce higher output voltage at oscilloscope. The piezoelectric cantilevers generated output voltages which were from 2.2 mV to 8.8 mV at 50 Hz operation frequency. One of four samples achieved in range of desired output voltage, 1-3 mV and the rest samples produced a higher output voltage. The output voltage is adequate for a very low power wireless sensing nodes as a substitute energy source to classic batteries.

Abstract: SN100C lead-free solder coating wettability on SN100C solder has been investigated on as soldered samples and exposed intermetallic compound (IMC). In addition, the effect of oxidation on its wettability has also been investigated. Oxidation layer on the coated copper surface was developed after 120 hours of exposure on as soldered samples and exposed IMC samples. GEN3 solderability test machine in globule mode was used to determine the wettability of each sample. The influence of oxidation and the effect of exposed IMC were established. Results show that oxidation affected wettability by increasing the wetting time. On the other hand, exposed IMC had increased the wetting time and decreased the maximum force.

Abstract: The effect of dipping time to the intermetallic compound and free solder thickness of Sn-Cu-Ni (SN100C) lead-free solder has been investigated. Dipping of copper strips in molten solder was carried out using GEN3 solderability test machine with 20 s, 60 s, 120 s, 180 s, and 240 s of dipping time. Scanning Electron Microscope (SEM) was used to observe the solder coating on the copper strips. Thickness of IMC, free solder and total solder coating was calculated. The influence of dipping time was established. The results indicated that longer dipping time produced high IMC thickness while the free solder thickness reduced with the growth of IMC. Solderability test was also conducted to know the wettability of SN100C coating for the lowest dipping time which had resulted in 1.571 s of wetting time and 4.066 mN of maximum force.

Abstract: In particular, the PES substrate, the crystal structure of the amorphous as well as the surface morphology is not good. So research of thin films growth for epitaxial growth by the use of a buffer layer on the amorphous PES substrate is essential. Therefore, in this study, we deposited ZnO thin-film on PES substrate, and grown ZnO nanorods at various ZnO concentrations during 1 hour. We used SEM, XRD, and HP 4145B for observe the structural and electrical characteristics of ZnO nanorods. UV-visible spectrometer was used to get the band gap and transmittance.

Abstract: Epoxidised silsesquioxane (EPSQ) polymer was prepared by hydrosilylation process involving epoxy-disiloxane (EDS) and vinyl silsesquioxane (VSQ). They were characterised and analysed using Fourier Transformed Infrared (FTIR) and H-and Si-Nuclear Magnetic Resonance (NMR) spectroscopy. Pattern development was successfully performed affording well defined features of micron scale using suitable solvent developer. It was demonstrated that the feature definition was highly dependent on time of solvent dissolution and stirring rate. Optimization of several parameters such as resist thickness, pre-bake and post-bake time, ultra-violet (UV) intensity and exposure time are still required for the improved performance photo-resist material. However the results proved that the EPS can be potentially used as photoresist in photolithography application.

Abstract: This paper demonstrates the development of an experimental technique of in-situ observation for soldering of Sn-0.7wt%Cu lead-free solder on a Cu substrate which was achieved for the first time by synchrotron X-ray imaging. Reactions between liquid solder and Cu substrate during a soldering process were able to be recorded in real-time. Individual stages of the soldering process consisted of flux activation in removal of Cu oxide, solder melting and contact with the Cu substrate (wetting) and intermetallic compound (IMC) and void formation between the solder and Cu substrate. The technique development which includes experimental setup with calculated optimum beam energy in the range of 20 – 30 keV appears to result in a clear observation of real-time X-ray imaging of the soldering process. This technique provides a key method to understand the mechanism of formation of micro-electronic inter-connects for future electronic packaging applications.

Abstract: Composite solder has drawn attention improvement in microstructural modification and mechanical properties. This research was done to investigate the influence of activated carbon (AC) particulate on the commercial Sn-Cu-Ni solder system (SN100C) solder alloy. The SN100C+AC composite solder was fabricated via powder metallurgy (PM) technique. In this study, five different AC compositions were chosen; (0, 0.25, 0.5, 0.75 and 1.0 wt. %. This study has shown that composite solder has better properties compared to the monolithic solder alloy. A small amount of AC particulate had improved the physical properties of the composite solder. Microstructural analysis showed that the reinforcement was well distributed along the grain boundaries and no significant influence on the melting point of SN100C. Apart from that, 1.0 wt. % of AC additions results with the highest hardness value compared to the other composition.

Abstract: The effect of micron-size silicon nitride (Si₃N₄) particles additions, up to 1.0 wt. % on Sn-Cu-Ni (SN100C) solder alloy was investigated. Sn-Cu-Ni composite solder were prepared via powder metallurgy (PM) technique. Different percentages of Si₃N₄ (0, 0.25, 0.5, 0.75 and 1.0 wt. %) were added into the alloy. Result revealed that reinforcement was well distributed between the grain boundaries which could positively affect the properties of the composite solder.