Applied Mechanics and Materials Vols. 465-466

Abstract: Titanium (Ti) alloy foam was prepared by using potassium bromide (KBr) as space holder with percentage between 20 to 40 wt.%. In this work, the potential of KBr as a new space holder was determined. The Ti alloy powder and space holder were first manually mixed before being compacted using hydraulic hand press. The green compacts were then sintered at temperature of 1160°C, 1200°C and 1240°C in a tube furnace. The microstructure of the Ti alloy foams were observed by Scanning Electron Microscope (SEM). It was revealed that the porosity content in the Ti foam was in the range of 16% to 31% and density in the range of 1.5 g/cm³ to 2.6 g/cm³. Moreover, the pore size of the titanium alloy foam is in the range of 187μm to 303μm. Although the sintering temperatures were found incapable of promoting overall densification to the Ti alloy foam, 1200°C was denoted to be the maximal temperature for promoting maximal porosity to the Ti alloy foam. Nonetheless, KBr was proven to be suitable as space holder for Ti foam preparation as referred to its stability and insolubility in the Ti alloy.

Abstract: Bamboo-shaped Carbon Nanostructures (BSCNs) and carbon nanofilaments (CNFs) have been successfully grown on carbon fibre coated with iron catalyst by chemical vapour deposition of ethene (C₂H₄). The reaction was carried out at 800°C with varied hydrogen and ethene ratios of 20/80, 50/50 and 80/20. TEM analysis showed the bamboo-shaped carbon nanostructures were best grown at 50/50 of hydrogen and ethene ratio, whilst disorder carbon nanofibres were grown when the ratio increased to 80/20, and less or no carbon nanofibres were observed at hydrogen and ethane ratio of 20/80 due to inactive of catalyst particle. The outer diameter of BSCNs consisting of hollow compartment was in the range of 40 ~ 48 nm and encapsulated catalyst particle were not observed at the tip or in the middle, indicating a bottom-growth. The formation of compartment was dependent on diffusion of carbon atom in the catalyst and the possible growth mechanism is explained.

Abstract: Plastic waste is a current major environmental concerns leading to long-term hazards. Recycling concept is the best practice to minimise the amount of plastic waste in the environment. This initiative promotes development of sustainable technology. Recently, plastics are gaining more recognition in construction field and are being applied widely due to its improved performance, versatility, durability and lightweight. In this study, the use of recycled polypropylene (rPP) and recycled high density polyethylene (rHDPE) as an alternative material for construction are investigated. The thermal degradation and mechanical properties were studied using thermogravimetric analysis (TGA) and tensile testing method respectively. TGA analysis conducted on recycled and virgin PP and HDPE showed that they have a stable composition. Moreover, TGA was also done to compare recycled and virgin material to assess the degradation process with respect to the total weight loss of samples. The results obtained indicate that the composition of rPP gives higher tensile strength. 100% rPP/rHDPE blend gave the best performance in mechanical properties and have a lower degradation temperature which are requirements for the sintering process necessary in this research study, to produce new lightweight product.

Abstract: In Malaysia, coal has been used as a raw material to generate electricity since 1988. In the past, most of the wastage of coal burning especially the bottom ash was not managed properly as it was dumped in the waste pond and accumulated drastically. This research has been conducted to explore the physical characteristic and geotechnical properties of fly ash-bottom ash (FA-BA) mixtures that consist of 30% FA, 50% FA, 70% FA and 90% FA by weight. The physical characteristics, that include the specific gravity, particle size distribution and compaction, were tested for each mixture without any curing. However, the geotechnical properties of the mixtures that include the permeability and shear strength had been studied at various curing periods (0, 14 and 28 days) to review the effect of time on the geotechnical properties of the mixtures. The results show that mixtures with higher FA composition have lower value of specific gravity, well-graded, and need less moisture to be compacted efficiently compared to those mixtures with lower FA composition. The results also show that mixtures with higher FA composition have less drainage characteristics but can be improved by prolonging the curing period. The maximum shear strength was obtained at mixture with 50%FA and the value increased with curing periods. The friction angle obtained ranged from 27⁰ to 37⁰. It is also found that the mixtures with lower FA composition are more compressible compared to the mixtures with higher FA composition. The results obtained could be used by others to determine the suitability of different FA-BA mixtures for various usage in Geotechnical Engineering work such as for soil improvement work in weak soils or as backfill materials in embankment construction.

Abstract: This paper presents a review on the preparation, processing, properties and the recent applications of polypropylene-nanoclay nanocomposites. The material has attracted many researchers to explore more about the processing techniques, optimizations, and mainly the potential applications reflecting the advantages of these promising materials. The review consists of preparation of nanocomposites master batch, properties such as mechanical and thermal properties the effects of compatibilizers and clay content, as well as the recent application of these composites. The findings of this review might lead to more curiosity and investigating regarding to the above matters.

Abstract: The correlation between calcination temperature and properties (physical and electrochemical) of composite cathodes comprising lanthanum strontium cobaltite ferrite (LSCF) with samarium-doped ceria carbonate (SDCC) has been investigated. LSCF-SDC carbonate (LSCF-SDCC) composite cathode powders prepared via ball-milling were calcined at various temperatures in the range of 700850 °C. X-ray diffraction (XRD) results confirmed that the applied calcination temperatures do not affect the chemical compatibility and the LSCF perovskite cubic structure of the composite powders. FTIR spectra verified the presence of carbonates in the composite powders after calcination. The increment of the calcination temperature reduced the surface area of the particle from 10.9 m²/g to 6.5 m²/g. The electrochemical results revealed that the resistance of LSCF-SDC carbonate composite cathodes is dominated by the oxygen surface exchange reaction at the electrode surface. 750 °C was identified as the most appropriate calcination temperature for the LSCF-SDC carbonate powder when the cathode electrode showed the lowest resistance with conductivity value of 0.95 x 10^-3 Scm^-1. The findings are of potential relevance to utilizing the LSCF-SDC carbonate cathodes for low temperature solid oxide fuel cells (LT-SOFC).

Abstract: The effect of Cr addition on the fluidity of aluminum (LM6) alloy has been investigated by spiral fluidity test. Presence of 0.1 wt.% Cr decreased fluidity of melt due to formation of sludge. In fact Cr changes the morphology of the intermetallic phase from β-intermetallics less harmful polyhedral morphology (α-intermetallics). The β-phases have largest surface to volume ratio, hence they have the largest interfacial region with the melt and are the most detrimental intermetallic to drop off the fluidity. In Cr-containing alloys the effect of α-phase is less detrimental than β-phase to the fluidity. On the other hand sludge formation and consuming Si and shifts the local chemical composition of the melt to the aluminum side of the phase diagram which has lower fluidity than eutectic and hypereutectic compositions.

Abstract: This article investigates the effects of addition of alloying element on the impact toughness of as-cast aluminum (LM6) alloy. Presence of 0.1 wt.% Cr increases the toughness up to 38%. In fact the sharp tips Fe intermetallics which have needle shape act as stress raisers with a general reduction of the ductility and ultimate tensile strength. On the other hand by increasing the Cr content in the base alloy the size distribution of the compounds becomes more spread. Therefore addition of Cr improves toughness impact by two mechanisms. First eliminating harmful β-intermetallics and second providing microstructure with more spread particles.

Abstract: To produce a good quality of dry fabric for reinforced material in a natural-based polymer composite, yarn linear density should be in consideration. A woven kenaf dry fabric with three different linear densities of 276tex, 413.4tex and 759tex were produced. The fabrics with different linear densities were been optimize with the assistance of WiseTex software. The optimized dry fabrics were infused with unsaturated polyester to produce composite panel using vacuum infusion process. The composites properties were tested on the tensile strength, flexural strength and the impact strength. The result shows that the mechanical properties of the composite increased when the yarn linear densities increased.

Abstract: Natural fibre composite materials have been highlighted in recent years as they have the potential to mitigate the pollution and global warming. Kenaf is a high yield and fast growing plant. Kenaf does not require a lot of energy in production. Furthermore, the kenaf plant can absorb carbon dioxide when breathing. The objective of this paper is to relate the effect of different environment to the mechanical properties of kenaf and kenaf hybrid (fiberglass) polyester composites for 60 days period. Kenaf composite (containing 20 wt% of Kenaf fibres) and kenaf hybrid (containing 20 wt% kenaf fibre and 16 wt% fiberglass) were produced in cold press hand lay-up technique and then cured for 24 hours. The specimens were cut as required in EN ISO 527. The specimens were immersed in 3 different water sources, which were rain water, salt water and tap water. Tensile and hardness test were conducted to study the mechanical properties at 10, 20, 30, 40, 50 and 60 days. Both kenaf polyester and kenaf hybrid polyester show reduction on mechanical properties after immersion in the solutions. Kenaf polyester and kenaf hybrid polyester followed fickian behaviour after 40 days water immersion.