Mohd Hamdi Abdul Shukor

Preparation and Characterization of Natural Hydroxyapatite: A Comparative Study of Bovine Bone Hydroxyapatite and Hydroxyapatite from Calcite

The production of natural hydroxyapatite (HAp) specifically from cortical bovine bones and natural calcite was studied in this paper. Bovine hydroxyapatite (BHA) was produced from bovine bone in bulk form by de-fatting continued with calcination at 900°C. Natural calcite hydroxyapatite (CHA) was produced by hydrothermal method. It was confirmed from XRD, FTIR, and SEM results that HA have been successfully produced from natural sources like bulk bovine bone and natural calcite. The results also show that the crystallinity of BHA is higher than CHA, matching with the hardness test results of sintered BHA and CHA.

XRD and EDXRF Analysis of Anatase Nano-TiO2 Synthesized from Mineral Precursors

This work details the characterization of anatase nanoTiO2 particles synthesized from Malaysian mineral precursors using the XRD and EDXRF. The properties that were analyzed were its crystallite sizes, relative crystallinity, phases, and chemical composition. It was determined that the crystallite size was quite small (15.6 nm), although the crystallinity of the sample is relatively low. The anatase phase seems to be dominant (100%), although in some cases when the processing parameters were changed or heat treatment were conducted, the existence of rutile is detected. The chemical composition showed that TiO2 is the majority compound in the sample (~96%), although some metallic and non-metallic impurities are present (Zr, Nb, and S). It is concluded that Malaysian mineral precursors are capable of producing relatively high quality nanoTiO2.

Fabrication of TiB2-TiC Composites Optimized by Different Amount of Carbon in the Initial Ti-B-C Powder Mixture

Composites of TiC and TiB2 (TiC-TiB2) were prepared by self-propagating high-temperature synthesis (SHS), using compacted reactant different combinations of Ti, C, and B powders. It is very difficult to densify these materials using conventional sintering techniques. It was found that the chemical reaction between the starting Titanium, boron and carbon particles could be completed at 1200°C producing a pure TiB2+TiC ceramic composite. Various carbon content causes the microstructure of the final products was different.

Wear characteristics and adhesion behavior of calcium phosphate thin-films

Wear resistance is an important mechanical property expected from coatings intended for any type of applications. Understanding of this quantity is very practical because in real situations, coatings are subjected to repeating loads experienced not in a gradual orderly fashion but abruptly and indeterminately. This study looked into the wear characteristic and adhesion behavior of calcium phosphate, a known bioceramics, and hopes to provide better understanding of these properties. Radio frequency-magnetron sputtering (RF-MS) was used to deposit thin film (CaP) on glass. The coatings were subjected to single-pass microscratch and multi-pass wear test while monitoring the depth, load and displacement in situ. The results have shown that the changes in the surface topography can give an indication of the wear resistance of CaP. Coatings with good adherence to the substrate have shown less alteration of its surface roughness, measured in terms of Ra values, even after several scratch passes. The study on the different parameters revealed that deposition time is the most influential factor in CaP wear behavior. This was attributed to its correlation with coating thickness. Analysis of variance (ANOVA) also suggested that the other sputtering parameters studied in the experiments (argon pressure and RF power) did not have very significant effect on the wear pattern of the CaP thin films.

Feasibility Study of Low Power Fiber Laser Welding AA2024 and AA7075 Alloys T-Joint

Dissimilar aluminum alloys, AA2024-0 and AA7075-T6 were laser welded on both sides in a T-joint configuration using a low power fiber laser. The effect of welding speed (9, 12, 15, 18 and 21 mm/s) on weldability was evaluated at laser power of 270W with argon gas as the shielding gas. The sample welding angle was fixed at 45° with an interval of 180 seconds between each welding pass. Macrograph observations revealed that full penetration with pore free weld of these dissimilar joint was obtained at the laser parameters of 270 W and 9 mm/s, suggesting that lower welding speed is preferred during low power laser welding.

Characterization of Titania Nanoparticles Synthesized by the Hydrothermal Method with Low Grade Mineral Precursors

The objective of this work is to utilize a low-grade synthetic rutile to produce high-grade titania nanoparticles. Due to the nature of the precursor, the hydrothermal method needs modification in order to accommodate the precursors and chemical reagents. The product will be characterized with the XRD (crystallite size and crystallinity), EDXRF (chemical composition), SEM (Morphology), N2 adsorption-desorption (Surface Area) and UV-Vis-NIR. Results revealed a crystallite size of less than 20 nm, a surface area of 186.8 m2/g, a morphology that is a combination of agglomeration and particles, and an optical band gap of 3.23 eV. It is concluded that synthetic rutile is a viable precursor to produce high quality titania nanoparticles.

Effects of Annealing on Sn Whisker Formation Under Temperature Cycling and Isothermal Storage Conditions

The global move toward reducing the usage of lead in electronics manufacturing industry is driving the industry to switch from tin-lead alloys to pure tin (Sn) for its component plating process. This transition has resulted in a reliability concern due to the formation of conductive Sn whiskers, which can grow from the component after the plating process within a few hours to months, with their length ranging from 10 micrometers up to several millimeters. The conductive Sn whiskers may cause current leakage or short circuits, leading to catastrophic failure in the field. This paper presents the results of an experimental study on Sn whisker formation based on the effects of annealing for 1 h at 150°C and environmental test conditions from the joint electron devices engineering council standards. This paper consisted of one temperature cycling test and two isothermal storage tests. The characterization results obtained confirm that temperature cycling and isothermal storage favor the formation of whiskers on Sn-plated copper lead frames. The average maximum length of the whiskers increased with the number of temperature cycles and duration of isothermal storage. It is also shown that annealing for 1 h at 150°C of the samples is effective in reducing the average maximum length of whiskers. Growth mechanisms of the Sn whiskers due to the effects of annealing and without annealing are also discussed.

Effect of Curvature and Thickness of Aluminum Shells on the Energy Absorption in Low Velocity Impact

The objective of this study is to investigate the behavior of Aluminum shells AA5083-H116 under low energy impact and the effects of curvature and thickness were assessed under different impact velocities (5.6, 7.5, 9.5, 11.5 m/s). LS-DYNA software was used to evaluate the amount of absorbed energy by the Aluminum shell during impact under different curvature parameter c. The results showed that the amount of absorbed energy incereases with increasing curvature in a linear relationship which make it possible to predict the amount of absorbed energy for this aluminum alloy under different impact energy. Aslo, the amount of absorbed energy has a direct linear relation with the rise of impact energy. The slopes of curves for absorbed energy with respect to the imapct energy are similar for all curvatures. Shell thickness has inverse effect on the amount of absorbed energy and the relation shows similar ternds with diffrent curvatures. However thick shells show significant increase in maximum force and better stability in the dynamic behavior with less fluctuations in the impact force as the cuvature increases.

Development and Characterization of Bovine Hydroxyapatite Porous Bone Graft for Biomedical Applications

The porous Hydroxyapatite (HA) ceramics have found enormous use in biomedical applications including bone tissue regeneration, cell proliferation, and drug delivery. This paper investigates the preparation and characterization of bovine Hydroxyapatite (BHA) porous bone graft by mixing sucrose powder as porogens with bovine bone powder. After uniaxially pressing at 156 MPa and pressurelessly sintering in air atmosphere at 1200°C for 2 hours the bioceramic showed an interconnecting porosity. The XRD analysis indicated that bovine hydroxyapatite (BHA) porous bone graft resulted in this research is single phase HA and is believed to be pure HA as indicated by the peak of the diffraction patterns (JCPDS 9-432). The phase analysis also shows that BHA porous bone graft is highly crystalline with domain crystallites sizes are between ~46 to ~99 nm (~4.6 to ~9.9 Å). Several trace elements in human bone such as titanium (Ti), iron (Fe), nickel (Ni), copper (Cu) and Zinc (Zn) were also detected in BHA porous bone graft as indicated by SR-XRF. This object is promising for bone regeneration because the interconnecting porosity in carbonated apatite provides a good environment for bone attachment and ingrowths

Effect of Slurry Preparation on Physical Properties of Porous Hydroxyapatite Prepared via Polymeric Sponge Method

Hydroxyapatite porous materials for cancellous bone applications were prepared via polymeric sponge method. Suspensions of the nanostructured hydroxyapatite powders were prepared via stirring of the mixture of hydroxyapatite powder, water, and dispersing agent. The stirring time was adjusted at 4 and 20 hours. After soaking cellulosic sponges into the suspension, the sponges were dried and then subjected to heat-treatment at 600°C, followed by sintering at 1250°C for 1 h. No additional phases were identified in the sintered porous hydroxyapatite. This result showed that the sintering process did not alter the hydroxyapatite phase composition. The study found that the apparent density of the porous bodies varied from 1.69 g/cm3 to 2.03 g/cm3 with 35.6 – 46.2 % porosities and 100-500 microns macropore size depending on the composition of slurry and the stirring time. Longer stirring time resulted in the breakdown of HA agglomerates and the slurry obtained tends to be more homogeneous, leading to higher density and better compressive strength of the sintered porous bodies. The measurement of compressive strength provided the values of 4.3 MPa and 10 MPa for 4 h and 20 h stirring time, which is in the range of mechanical strength of human cancellous bone.