Surfactant-decorated graphite nanoplatelets(GNPs) reinforced aluminum nanocomposites: sintering effects on hardness and wear

The exceptional properties of graphene make it ideal as a reinforcement to enhance the properties of aluminum matrices and this critically depends on uniform dispersion. In this study, the dispersion issue was addressed by sonication and non-covalent surface functionalization of graphite nanoplatelets（GNPs） using two types of surfactant： anionic（sodium dodecyl benzene sulfate（SDBS）） and non-ionic polymeric（ethyl cellulose（EC））. After colloidal mixing with Al powder, consolidation was performed at two sintering temperatures（550 and 620°C）. The structure, density, mechanical and wear properties of the nanocomposite samples were investigated and compared with a pure Al and a pure GNPs/Al nanocomposite sample. Noticeably, EC-based 0.5 wt% GNPs/Al samples showed the highest increment of 31% increase in hardness with reduced wear rate of 98.25% at 620°C, while a 22% increase in hardness with reduced wear rate of 96.98% at 550°C was observed, as compared to pure Al. Microstructural analysis and the overall results validate the use of EC-based GNPs/Al nanocomposites as they performed better than pure Al and pure GNPs/Al nanocomposite at both sintering temperatures.

First-Principles Calculations of the Structural, Mechanical and Thermodynamics Properties of Cubic Zirconia

The structural, mechanical and thermodynamics properties of cubic zirconium oxide (cZrO2) were investigated in this study using ab initio or first-principles calculations. Density functional theory was used to optimize the crystal structure of cZrO2 and thereafter, simulations were conducted to predict the lattice parameters and elastic constants. The Zr-O bond distance was calculated as 2.1763 &#197 with unit cell density of 6.4179 g/cm3. The data obtained were used to determine Young’s modulus, bulk modulus, Poisson’s ratio and hardness of cZrO2 as 545.12 GPa, 136.464 GPa, 0.1898 and 12.663(Hv) respectively. The result indicates that cZrO2 is mechanically stable with thermodynamics properties of a refractory material having potential for structural and catalytic applications in various forms as a nanomaterial.

Effect of Conduction Pre-heating in Au-Al Thermosonic Wire Bonding

This paper presents the recent study by investigating the vital responses of wire bonding with the application of conduction pre-heating. It is observed through literature reviews that, the effect of pre-heating has not been completely explored to enable the successful application of pre-heating during wire bonding. The aim of wire bonding is to form quality and reliable solid-state bonds to interconnect metals such as gold wires to metalized pads deposited on silicon integrated circuits. Typically, there are 3 main wire bonding techniques applied in the industry;Thermo-compression, Ultrasonic and Thermosonic. This experiment utilizes the most common and widely used platform which is thermosonic bonding. This technique is explored with the application of conduction pre-heating along with heat on the bonding site, ultrasonic energy and force on an Au-Al system. Sixteen groups of bonding conditions which include eight hundred data points of shear strength at various temperature settings were compared to establish the relationship between bonding strength and the application of conduction pre-heating. The results of this study will clearly indicate the effects of applied conduction pre-heating towards bonding strength which may further produce a robust wire bonding system.

The Development and Characterization of Zirconia-Silica Sand Nanoparticles Composites

The present study aims to develop zirconia-Silica sand nanoparticles composites through powder processing route and to study the physical properties, mechanical properties and microstructure of the composites. Zirconia based silica sand nanoparticles composite with 5, 10, 15 and 20 wt.% were developed through powder processing technique and sintered at 1500 ℃ for two hours. A decreasing trend of green density however an improvement in sintered density was observed. Also the addition of silica sand nanoparticles with 20 wt.% increased the hardness up to 12.45 GPa and microstructures indicated the diffusion mechanism of silica sand nanoparticles into pore sites of the composites.

Thermal expansion behavior,phase transitions and some physico-mechanical characteristics of fired doped rice husk silica refractory

This paper presents the findings on thermal expansion behavior of slaked lime doped rice husk silica(RHS)refractory monitored between 25℃and 1500℃.It also reports the phase transition analysis within the temperature range of 850-1450℃.A sudden expansion of 0.7%noticed at 220℃is due to the transformation ofα-cristobalite toβ-cristobalite.The highest expansion(0.85%)reached within the temperature range of 650-850℃,remains almost constant for the investigated temperature range,and is not high enough to cause macro cracks in the refractory.The phase transition order is similar to those reported for quartzite refractory after 600℃,though the crystallization temperature is lowered due to the presence of the dopant.Modulus of rupture,apparent porosity,bulk density,refractoriness and reheat change are reported and their results meet with the standards qualifying them for use in coke ovens.