Study on Micro - Nano Sized Al2O3 Particles on Mechanical, Wear and Fracture Behavior of Al7075 Metal Matrix Composites

Having Low density and being Light weight with better mechanical properties, aluminum is the most significant material and is universally used in highly critical applications like navy, aerospace and particularly automotive activities. This research work is aimed to investigate the effect of micro and nano boron Al2O3 (Alumina Oxide) to aluminium (Al) on the mechanical and wear properties of the Al composites. The micro - nano composites with 1, 2, 3 and 4 % of Al2O3 particulates in Al are fabricated using stircasting processes. It was found that an increase of Al2O3 both as micro and nano particulates content resulted in an improved hardness, enhanced tensile strength and high wear resistance. However, nano Al2O3 reinforced MMCs have better hardness, improved tensile strength and higher wear resistance as compared with micro sized Al2O3 reinforced MMCs. Grain refinement of composite and nano composite materials as compared with pure Al were observed from the microscopic images. Analysis of wornout surface and tensile fracture surface were studied by SEM analysis to examine the nature of wear and tensile fracture mode of composite samples.

Immobilization of Potassium-Based Heterogeneous Catalyst over Alumina Beads and Powder Support in the Transesterification of Waste Cooking Oil

In this work, the beads and powder potassium hydroxide (KOH) and potassium carbonate (K2CO3) supported on alumina oxide (Al2O3) were successfully prepared via incipient wetness impregnation technique. Herein, the perforated hydrophilic materials (PHM) made from low-density polyethylene (LDPE) was used as the catalyst reactor bed. The prepared catalysts were investigated using TGA, XRD, BET, SEM-EDX, TPD, FTIR while spent catalysts were analyzed using XRF and ICP-AES to study its deactivation mechanism. The catalytic performance of beads and powder KOH/Al2O3 and K2CO3/Al2O3 catalysts were evaluated via transesterification of waste cooking oil (WCO) to biodiesel. It was found that the optimum conditions for transesterification reaction were 1:12 of oil-to-methanol molar ratio and 5 wt.% of catalyst at 65 °C. As a result, the mesoporous size of beads KOH/Al2O3 and K2CO3/Al2O3 catalysts yielded 86.8% and 77.3% at 2 h’ reaction time of fatty acids methyl ester (FAME), respectively. It was revealed that the utilization of PHM for beads K2CO3/Al2O3 increase the reusability of the catalyst up to 7 cycles. Furthermore, the FAME produced was confirmed by the gas chromatography-mass spectroscopic technique. From this finding, beads KOH/Al2O3 and K2CO3/Al2O3 catalysts showed a promising performance to convert WCO to FAME or known as biodiesel.

Forced laser nanostructuring of the surface of alumina-oxide ceramics

The possibility of creating quasiperiodic nanostructures on the surface of articles made of ceramic materials based on -Al2O3 under the action of a laser beam moved by a two-coordinate linear stepping motor (LSM) is shown. It is shown that the cause of the arising non-uniformity of heat release and convective instability of the molten layer are electromagnetic surface waves at the "conductor-insulator" interface, while the "conductor" is the melt layer. The discreteness of the laser beam movement due to LSD makes it possible to create a regular wave-like relief on the melt surface, which plays the role of an input diffraction structure for gen-erating a surface wave of TM polarization.

Influência de diferentes métodos para a realização de preparos cavitários - alta rotação, laser de Er:YAG e abrasão a ar - sobre a resistência de união de um sistema adesivo à dentina

The aim of this study was evaluated, in vitro, the tensile bond strength to dentin of the Single Bond (3M) adhesive system applied over dentin surfaces treated with hith-speed handpiece, Er.YAG laser or air abrasion. Thity four enclosed molars extracted due to therapeutic indication had been used. The teeth was sectioned on the mesial-distal sense. The dental portions was included in a selfcured acrilic resin and so fourty five samples was randomly divided in three groups. The first group was treated with a diamond bur plus high-speed handpiece (Kavo) for five seconds under water cooling. On the laser group was used the Er:YAG KavoKey laser (Kavo) with enerv of 450 mJ/pulse and 2 Hz under water cooling. In the air abrasion group was used a Mach 5 (Kreativ) device with 27 mm alumina oxide particles powder. After the treatments was applicd the Single Bond (3M) and Z 100 resin composite. The tensile test was realized in a universal testing machine EMIC DL-2000 at cross-head speed of mm / minute. The average results was: high-speed handpiece (17,52 MPa), Er:YAG laser ( 16,65 MPa) and air abrasion ( 15,83). The results was submitted to statistical treatment by ANOVA and Tukey's test (p ) that showed the diffemcc between the tested groups was not significant.