Surface Preparation of Alumina for Improved Adhesive Bond Strength in Armor Applications
Surface treatments of alumina have been investigated with the aim of increasing the strength of the bond created between the alumina and a toughened epoxy adhesive. Four surface conditions have been assessed: as-fired; grit blasted; and krypton fluoride excimer laser treated under two sets of conditions. Compared with the as-fired surface, the grit blasted surface was rougher with poorer wettability, probably due to surface contamination. It was found that the laser treatments removed some of the sintering additives and caused rounding of the alumina grains, slightly increasing the surface roughness. Further, the laser treatment led to an increased surface energy and wettability, which has been linked tentatively to an observed increase in the hydroxyl groups on the surface. The adhesive bond strength was assessed by testing joints in tension and shear. It was found that the laser treated surfaces demonstrated slight improvements in bond strength, with a cohesive failure of the adhesive in tension for surfaces subjected to one of the two laser treatments, compared with failure at the interface for the as-fired, grit blasted and other laser treated samples in tension and for all samples in shear. Thus, it has been demonstrated that modifications to the surface of alumina can result in mechanical and chemical changes which affect roughness, wettability, bond strength and the locus of failure.
Compositions Optimization of Antang Corundum for Developing Advanced Ceramic
The research aims to study and optimize the formulation of materials required for advanced ceramic production using response surface methodology (RSM). In this research effort, the five (5) process independent variables studied with their corresponding levels are: Antang corundum powder, A (92.2 – 100 %W); polyvinyl alcohol, B (0 – 5 %W); CaO, C (0 – 2.3 %W); MgO, D (0 – 0.5 %W); and the sintering temperature, E (1200 – 1500 °C). The mechanical property responses determined were density, ρ , compressive strength, C/S, flexural strength, F/S ; which are key characteristics of ceramics for armour applications. The optimized density, compressive strength and flexural strength of the sintered Antang corundum are 3.45 g/cm 3 g, 1982 MPa and 295 MPa respectively; while the respective RSM prediction values are 3.45 g/cm 3 g, 1982 MPa and 295 MPa. On comparing the determined optimum mechanical responses of the sintered Antang ceramic with the maximum RSM prediction values, there is high level of assurance in using RSM for the formulation process in ceramic armour development.
Cutaneous myiasis caused by the housefly, Musca domestica
Summary We report a case of cutaneous myiasis by the housefly. Musca domestica.