Papers by Author: Mohd Hamdi Bin Abd Shukor

Abstract: Microwave hybrid heating (MHH) technique was used to investigate the formation of intermetallic compound layer at Cu-7.0Ni-9.3Sn-6.3P/Cu interface. Two different susceptor materials; graphite and silicon carbide were used to provide initial heating of the filler alloy before it starts couple with the microwaves and melted on the Cu surface. The interface of IMC layer was characterized using Scanning Electron Microscope (SEM), energy dispersive X-ray spectrometry (EDS) and microhardness. Metallurgical study showed the formation of the IMC layer with multiphase at the joint interface for microwave heating of both susceptor materials. The thickness of IMC layer heating in silicon carbide susceptor was three times thinner than heating in graphite susceptor; 16.5 μm and 50.5 μm, respectively. The findings showed that microwave hybrid heating can be used to join Cu-7.0Ni-9.3Sn-6.3P/Cu and controlled the thickness of IMC layer.

Abstract: Hydroxapatite (HA) is a stable phase with low dissolution rate in body fluid. Meanwhile, β-tricalcium phosphate (β-TCP) is rather soluble but the dissolution rate is too fast for bone bonding. Therefore a mixture of both is desirable to control the bioresorbability. In this work, calcium phosphate powder has been synthesized via sol gel and wet precipitation method to compare phase behaviour of these powders upon calcination. XRD result clearly revealed that both as-synthesized powders were pure HA with good purity. The decomposition of HA to TCP took place in the range of 700-800 °C and 800-900 °C for sol gel and wet chemical precipitation powder, respectively. The weight loss detected at 700-850°C in TGA analysis confirmed the presence of this biphasic mixtures_. From FTIR analysis, profound change in OH^- band intensity was attributed to the increased in HA crystallinity with calcination temperature.

Abstract: One of the main concerns of the automotive industry is reduction in structural weight of automobiles. Reduction of weight on vehicles has been proven to lower the usage of fuel, and therefore save a lot of energy in order to move from one place to another. At the same time, reduction of weight often means reduction in material usage, often regarded to be threatening structural strength of parts, components or vehicles body in white (BIW). Truss Core Panel, which has been developed from the study of origami engineering, specifically plane-tilings and space fillings, is a suitable candidate because it can be produced from thin sheet metals and can be joined using spot welding. In this paper, method for evaluating truss core panels for crashworthiness has been established based previous research on crashworthiness evaluation on thin shells. The effect of different configuration of spot welding has been investigated. The number of spot weld (n) along central member and side members of truss core panel has been varied and modeled from n = 2, 4, 6 ... to n = 30, and compared to a truss core panel model that is fully welded along central member and side members. The results also show that it is possible to attain similar mean crush force to fully welded structure with smaller number of spot welds.

Abstract: Mechanochemical synthesis of two or more different precursors is a simple method to prepare metallic alloys, polymer and ceramic composite materials. This mechanical reaction based synthesis also has been employed to produce hydroxyapatite (HA) powder for bone implant application. In this present study, we employed mechanochemical method to synthesize hydroxyapatite nanopowder from dry mixture of calcium hydroxide (Ca (OH)₂) and di-ammonium hydrogen phosphate [(NH₄)₂HPO₄] powders. The effect of mechanochemical process on powder properties was investigated. Three rotation speeds of 170 rpm (M1), 270 rpm (M2) and 370 rpm (M3) were chose with 15 hours milling time respectively. The milling time at 370 rpm (M3) was extended to 30 hours (T1) and 60 hours (T2). Characterization of nanopowders were accomplished by Fourier transform infrared (FTIR), X-ray diffraction (XRD), nanosizer analysis, field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). Rotation speed and milling time affected the obtained powders with nanocrystallite HA structure. The narrow peaks appeared with the incremental of crystallite size (9 – 21 nm) and crystallinity (21-59%) when the rotation speed was increased to 370 rpm (M3). However, particle size distribution (322-192 nm) was decreased with the rotation speed. Morphological evaluation indicated that the average particle size of resultant powder which consists of agglomerate crystals and irregular shapes reached about 17 - 36 nm. The as synthesized nanopowder showed that 370 rpm at 15 hours of milling is the suitable parameter to be applied for hydroxyapatite nanopowder synthesis in mechanochemical method.

Abstract: In this work, nanosized hydroxyapatite (HA) powder was synthesized via mechanochemical method by a dry mixture of calcium hydroxide Ca(OH)2 and di-ammonium hydrogen phosphate (NH4)2HPO4 powders. The effect of mechanochemical process on powder properties was investigated. Three rotation speeds of 170 rpm, 270 rpm and 370 rpm were chose with 15 hours milling time respectively. Characterization of nanopowders was accomplished by Fourier transform infra red (FTIR), X-ray diffraction (XRD) and nanosizer analysis. The green compacted powders with 200 MPa isostatically pressed were prepared and sintered in atmosphere condition at various temperatures ranging from 1150oC - 1350oC. The results showed that the rotation speed affected the obtained powders where the crystallite size was found increased with rotation speed (9 – 21 nm). In contrast, the particle size distribution decreased with rotation speed (322-192 nm). The sintering process has influenced the stability of powder by yielding TCP phase at a lower sintering temperature, 1150oC. However, powder synthesized at 370 rpm has showed a significant hardness, 5.3 GPa after compacted and sintered at 1250oC with the relative density of 95%. This phenomenon is believed to be related with the nanosize powder synthesized at high speed which has contributes the high strength of the sintered bodies.

Abstract: Glass is one of the most difficult materials to be machined due to its brittle nature and unique structure such that the fracture is often occurred during machining and the surface finish produced is often poor. CNC milling machine is possible to be used with several parameters making the machining process on the glass special compared to other machining process. However, the application of grinding process on the CNC milling machine would be an ideal solution in generating special products with good surface roughness. This paper studies how to optimize the different machining parameters in glass grinding operation on CNC machine seeking for best surface roughness. These parameters include the spindle speed, feed rate, depth of cut, lubrication mode, tool type, tool diameter and tool wear. To optimize these machining parameters in which the most significant parameters affecting the surface roughness can be identified, Taguchi optimization method is used with the orthogonal array of L8(26). However, to obtain the most optimum parameters for best surface roughness, the signal to noise (S/N) response analysis and Pareto analysis of variance (ANOVA) methods are implemented. Finally, the confirmation test is carried out to investigate the improvement of the optimization. The results showed an improvement of 8.91 % in the measured surface roughness.