Materials Science Forum Vol. 819

Abstract: The effect of fly ash-based geopolymer in epoxy-layered silicates nanocomposites was studied through flexural properties and morphological characterization. In this study, a series of nanocomposites with fly ash-based geopolymer containing 1-7% wt were prepared. It was found that the addition of fly ash with lower content in the beginning showed lower flexural strength than nanocomposites without fly ash. However, flexural properties suddenly increased at 3% wt of fly ash geopolymer content in comparison to origin. This indicates the blending of fly ash geopolymer in nanocomposites systems have the ability for further studied.

Abstract: This paper describes the experimental investigation of the tensile and flexural strength of untreated Napier grass fibre reinforced polyester composites. Napier grass fibres were extracted trough conventional water retting process and used as reinforcing materials in the polyester composite laminates. Tensile tests were then conducted for the composite specimens from the laminates at 25% fibre loading using the electronic extensometer setup to obtain the tensile properties. The results show significant differences in tensile strength between random short fibres laminates and random long fibrelaminates with the long fibres yield over 30 % higher in strength.Both the short and long fibre composites exhibits similar strength with short fibres having slightly higher flexural strength to long fibres The laminate also shows higher maximum strength compared to other commonly available natural fibre composites with almost 75 % improved in the maximum strength compared to the short kenaf fibre reinforced composites.

Abstract: The use of Magnesium alloys as bioresorsable metallic implant is interesting to study due to the properties of magnesium ions which can be found naturally in bone tissue as well as are essential to human metabolism. However, its fast degradation rate and excess of these ions in the body may cause undesirable health effects. Therefore, surface treatment such as coating can offer an alternative solution to slow down the fast degradation rate of magnesium alloy. Thus, in this study, attempt has been made to coat the AZ91 magnesium alloy substrate with TiN, AlN and TiAlBN coatings using single hot press target with r.f. magnetron sputtering technique. During deposition, target power, working pressure and bias voltage were optimized for each coating deposition. Coating microstructure and its crystal phases are analysed using SEM and glancing angle X-ray diffraction analysis (GAXRD). Corrosion properties were evaluated using potentiodynamic polarization using Hank’s Solution as a medium to simulate body fluid. Result showed that TiAlBN coating is acting most successfully as a protection layer by slowing down the penetration of corrosion towards AZ91 Mg alloy substrate. SEM micrographs show a minimum damage to the substrate’s surface seen after subjected to corrosion test. In conclusion, TiAlBN coating is able to protect AZ91 Mg alloy substrate surface from corrosion and able to slow down their degradation rate. The better performance of TiAlBN coating create interest to further works on exploring the potential of this hard coated on AZ91 Mg alloy for biomaterial application.

Abstract: Magnesium (Mg) has a great potential to be used in various field of work since it is lightweight and has low density properties. However, its application is limited due to its poor properties for Mg has a relatively low strength. Improvement is made by mixing Mg with calcium (Ca) as composite element for it is lightweight and non-toxic. In this research, Mg is prepared with different weight percentage (0, 0.5, 1, 1.5, 2 wt. %) of Ca with pure Mg as reference prepared by powder metallurgy (PM) method to study the mechanical properties. Morphological analysis carried out by optical microscope shows increase grain refinement with the increase of calcium content in Mg-Ca composites. The phase transition upon addition of Ca is determined using XRD method detects formation of Mg₂Ca. Range from 1.78 g/cm³ to 1.83 g/cm³, the density of each sample composite increase. While porosity profiles show inverse characteristics upon addition of Ca. Microhardness strengths also intensifies up to 193.20 MPa as more Ca content added in.

Abstract: This paper presents the corrosion behavior of the composite Mg-10wt.% bio-glass (45S5) with different concentration of Zn. Bio-glass (BG) was added to the composite in order to improve bioactivity behavior of magnesium. The composite was fabricated by mixing, compacting followed by sintering. Composites was compacted at 550 MPa and sintered at 450°C under an argon atmosphere. Corrosion behavior was investigated by the immersion test. Sintered samples were immersed in 0.9 % NaCI solution and monitored by hydrogen evolution and XRD analysis. The results showed that hydrogen evolution rate decreased with addition of Zn content. The microstructure and phase analysis were observed by optical microscope, scanning electron microscope and x-ray diffraction.

Abstract: The objective of this work is to fabricate composite Mg-Zn filled with 45S5 bio-glass (5, 10, and 15 wt. %) via powder metallurgy. The microstructure of the sintered composite was investigated using optical microscope and scanning electron microscope. The densities of the composites were also evaluated. The densities of the compacts are increasing with increasing bio-glass content. Compression test was done by the Instron machine. The result showed that bio-glass was dispersed in the Mg-Zn matrix. Compressive strength was decreased as the amount of bio-glass increased. However, the results are still comparable to natural bone, which is important to reduce the stress shielding effect.

Abstract: Magnesium and bioglass are a good combination to create biocompatible and bioactive materials. Magnesium-bioglass composites can be manufactured by casting or sintering. This work was aimed to manufacture the composite Mg-3wt.%Zn filled with 5, 10, 15, 20, 25 and 30wt.% bioglass (45S5) by powder metallurgy. Two sintering temperatures of 450 °C and 550 °C were used to sinter the samples. The sintered samples were characterized using optical micrograph and X-Ray diffraction (XRD). Optical micrograph shows that increasing of bioglass content lead to smaller grain size. XRD analysis shows no new crystalline compound detected on XRD pattern for Mg-3wt%Zn sintered at 450 °C ad 550 °C.

Abstract: Magnesium and its alloys have great potential as biodegradable metallic implant materials with good mechanical properties. However, the poor corrosion rate and the production of hydrogen during degradation hindered its application. Binary alloy, Mg-3Ca and ternary alloy, Mg-3Ca-3Zn alloy were studied to investigate their bio-corrosion properties. Microstructure evolution and surfaces of corroded alloys were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The bio-corrosion behavior of the Mg alloys was investigated using immersion and electrochemical tests in Kokubo solution. Microstructural analysis showed that binary Mg-3Ca alloy consisted of α-Mg and Mg₂Ca phases and ternary Mg-3Ca-3Zn alloy consisted of α-Mg, Ca₂Mg₆Zn₃ and Mg₂Ca phases. These phases had significant effect on the corrosion resistant of the alloy. Electrochemical test showed an improvement in ternary alloys where the corrosion current density reduced from 0.497 mA/cm² in Mg-3Ca to 0.312 mA/cm² in Mg-3Ca-3Zn alloy. Ternary Mg-3Ca-3Zn showed significant lower corrosion rate (1.1 mg/cm²/day) compared to binary Mg-3Ca (5.8 mg/cm²/day) alloy after 14 days immersion test.

Abstract: Recently, many researchers focused on biocompability, corrosion resistance and properties behavior of implant materials in order to length the endoprostheses life. One of the rapid development areas of research is in the biomaterials field. Historically the uses of biomaterials has been to replace diseased or damaged tissues. This present paper reviews the research works carried out in the field of composite metal alloys reinforced with additive and to analyze the influence of modifying additive on mechanical properties of composite materials on the cobalt (Co), titanium (Ti) and magnesium (Mg) based alloy. The desirable mechanical properties of the matrix component compensate for the poor mechanical behavior of the biomaterials, while in turn the desirable bioactive properties of the additives improve those of metal alloys. The following additives were reviewed for research: poly methyl methacrylate (PMMA), fluoroapatite (FA) and bioglass. Results show that these composites can be the alternative materials for biomedical applications.

Abstract: In this study, hydroxyapatite powder was sprayed onto pure magnesium plate using a simple modified cold spray process. The effects of process parameters (i.e.standoff distance, surface roughness, substrate, substrate heating temperature and number of spray) were studied using 2^k-1 factorial design.Analysis of variant (ANOVA) were used to determine the significant of process parameters on the coating. Thickness of coating, nanohardness and elastic modulus were chosen as the responses for assessing the most significant parameters that affected the hydroxyapatite coated onto pure magnesium plate. HAP particles have found to be bonded well in sample of run 11 while sample of run 4 show poor bonding between HAP particles and magnesium substrate. The effect of individual variables on the response was briefly discussed.