Applied Mechanics and Materials Vols. 465-466

Abstract: Currently higher requirements in thermal performance is needed for the quality of building materials especially fired clay bricks. Thermal conductivity is an important criterion as it will influences the heat losses from building. The objective of this study is to validate the estimation value of thermal conductivity by using theoretical value with the experimental work conducted in the laboratory. The experiment data was collected in order to compare with a theoretical model that obtained the thermal conductivity value based on it relationship with dry density of fired clay bricks. Different percentages of CBs (0%, 2.5% and 5.0%) were incorporated into fired clay bricks. Different heating rates were applied during firing stage, which are 1°C/min, 3°C/min and 5°C/min respectively. All samples were fired up to 1050°C. The experimental work for thermal conductivity was carried out using the Hot Guarded Plate Method. Meanwhile, the theoretical result was obtained from the previous study using model developed. Throughout statistical analysis, some trend of thermal conductivity and dry density were revealed. The analysis results show that as the dry density decreased, thermal conductivity also decreased.

Abstract: Nowadays, ceramic foam was widely used in bio-medical as well as engineering field such as thermal insulation and adsorption of environmental pollutants. Ceramic foam made of a porous structure that provides the physical and mechanical properties of both, low specific weight and high thermal fluidity. In this study, the selected starting ceramics powder are titanium dioxide (TiO₂), aluminum oxide (Al₂O₃) and Silver Nitrate (AgNO₃). In general, TiO₂ is very light weight compared to other substance. It is brightness and very high refractive index. On the other hand, Al₂O₃ is responsible for the resistance of metallic aluminum to weathering while AgNO₃ is plays important role as antiseptics. These unique properties of these ceramics has encouraged more study to be implemented on it. Preferred method for the ceramic foam fabrication is via slurry method. In which consists steps of mixing, dipping, pressing, drying and sintering. Three different temperatures of 1200°C, 1250°C and 1300°C, with compositions of 22.5wt% of TiO₂ + 7.5wt% Al₂O₃ + 1.25 wt% AgNO₃ with 2.5wt% of Carbolic methylcelulose (CMC) and 7.5wt% Polyethylene glycol (PEG) are apply in this study. Analysis of the phases, morphology, porosity, density and sringkage were carried out on all samples. From this study, foams of 47.8% to 62.6% porosity using TiO₂ + Al₂O₃ + AgNO₃ were successfully produced. The highest porosity value of 62.61% was fabricated at 1200°C and the highest density value of 2.06% at 1300°C. Thus, it is concluded that the optimal fabrication slurry method parameters of sintering temperature of 1300°C and the compositions of 22.5wt% of TiO₂ + 7.5wt% Al₂O₃ + 1.25wt% AgNO₃ with 2.5 wt% of CMC and 7.5wt% PEG has absorbability of heavy metal and bacteria in pre-treatment process can be develope.

Abstract: This work studies the effect of a post-weld heat treatment (PWHT) on the mechanical and microstructure properties of an AA6061 sample welded using Tungsten Inert Gas (TIG) method. TIG method is comparatively flexible and has good economy. The welded samples were divided into as-welded and PWHTs samples. The PWHTs samples were solution heat treatment, water quenching and artificial aging. Both welded samples were cut according to the ASTM E8M-04 standard to obtain the tensile strength and the elongation of the joints. The failure pattern of the tensile tested specimens was analysed using scanning electron microscopy (SEM). A Vickers microhardness testing machine was used to measure the hardness across the joints. From the results, the PWHTs were able to enhance the mechanical properties and microstructure characteristics of the AA6061 joints welded by the TIG method.

Abstract: Tronohs raw sand was converted into fine silica particles via a series of milling process. Addition of these fine particles into iron composite was found to modify its mechanical properties. The composite was prepared using powder metallurgy technique with varying percentage of silica particles; 5, 10, 15, 20 and 25wt%. The composites were sintered at three different temperatures; 1000° C, 1100° C and 1200° C to find the most suitable sintering temperature. Changes in density and hardness were observed. The results showed that composite consist of 20wt% silica particles and sintered at 1100° C exhibits best improvement.

Abstract: Nickel (Ni)/ Copper (Cu) multilayer were deposited on Cu substrate by electroplating process using dual bath technique. Individual sample of multilayer with sublayer thicknesses of 1 μm, 5 μm, 10 μm and 50 μm have been produced. The structure of the multilayer was characterized by X-Ray Diffraction and Scanning Electron Microscopy whereas one of the mechanical properties of the samples was investigated by means of Vickers Hardness. The results showed that the surface hardness of the coated Cu substrate increases if compared to that of pure Cu substrate. Additionally, these values increased when sublayer thickness of samples were decreased.

Abstract: The effects of chemically treated natural fibres (rice straw and kenaf) embedded as filler into polypropylene matrix were investigated for its sound absorption properties to regulate the industrial noise. In this respect, untreated natural fiber as well as treated natural fiber reinforced with polypropylene composites were fabricated and compared. The composites were prepared by compression moulding technique. Its sound absorbing characteristic was investigated with the Impedance tube, according to a transfer function method. A two microphone setup was fabricated according to American society for testing materials ASTM E1050-10 and it is used to measure sound absorption coefficients of composites in the frequency range of 300 Hz to 2000 Hz. The sound absorption coefficients of the composites increased with the frequency. However, at 1000 Hz, the sound absorption coefficient decreased for all treated samples and then increased again which is due to specific character of natural fibers. This point of inflexion was due to the specific characteristic of natural fiber reflecting sound at around 1000 Hz, but absorbing sound in the middle and high frequencies. The results indicates that the process of chemical treatment enhanced the sound absorption coefficients by 12.5% for rice straw reinforced Polypropylene and 15.78% for kenaf fiber reinforced Polypropylene composites respectively.

Abstract: This research investigates the sound absorption coefficients of betel nut fibers (Areca Fibers) reinforced with thermoplastic (Polypropylene) and thermoset (Unsaturated polyester) matrix composites with different fiber loadings and frequencies. In this research we used 5%, 10%, 15%, and 20% of betel nut fibers in the polymer matrix and the test frequencies are from 400 Hz to 1800 Hz. There are two standardized methods used for measuring the normal incidence sound absorption coefficient of composites namely, standing wave method (ISO 10534-1) and two fixed microphone method (ISO 10534-2). From this research, betel nut fibers reinforced with polymer matrix composites have good sound absorption coefficients at high frequency although the overall sound absorption coefficient is quiet low. The Increase in fiber loading increases the sound absorption coefficients of composites. The types of polymer did not have significant influences on sound absorption coefficients. Both methods of measurement show the same results where the two fixed microphone method is much quicker than standing wave method.

Abstract: Water pollution by heavy metal is great concern due to its toxicity to nature and environment. Extensive studies were carried out to remove heavy metal through physical, chemical and biological approaches. One of the biological approaches is biosorption. This study was conducted under several conditions namely pH, biosorbent dosage, initial wastewater concentration and contact time. Final concentrations of metals were tested using Atomic Absorption Spectrometry (AAS). The results revealed that optimum removal for Lead and Zinc was 77.3% and 90.30%. Optimum pH, for Lead was 6.0 whereas Zinc was 7.0 respectively. Both metals have showed the same optimum biosorbent dosage of 0.02g and 30 minutes of contact times. Meanwhile, the optimum initial metal concentration for Lead and Zinc were 5 ppm and 1ppm. It is proven that watermelon rind is able to treat wastewater with the present of Lead and Zinc.

Abstract: This paper presents a research on 3D part fabrication from composition of photo initiator (Phenylbis (2,4,6-trimethylbenzoyl)), photo absorber (Sudan I) and 1, 6-Hexanediol polymer effect based on curing parameters. A DLP projector was used as energy light source which initiated the photo reactive polymer at three different light source distances with three different exposed time to evaluate photoreactive polymer solidification phenomena. The experiment results obtained shows that Sudan I composition, light intensity value and exposure time of the varied photo absorber give significant effect to layer thicknes, surface roughness and hardness value. These works also prove that photo absorber composition solution gave a different mechanical properties effect for 3D microstructure fabrication.

Abstract: Atomic layer deposition (ALD) is a precision growth technique that is able to deposit either amorphous or epitaxial layer on a wide range of substrates. Multilayer thin films have been widely studied because their properties are different from those of bulk materials constituents owing to the two-dimensional films and high density of interfaces. Multilayer nanostructured thin films were fabricated on silicon and glass substrates by ALD. The optical and electrical of multilayer ZnO/TiO₂/ZnO films were investigated. The microstructure compositions and surface morphology of these multilayer films were analyzed by X-ray diffraction (XRD), Atomic force microscope (AFM) and Scanning electron microscope (SEM). The optical properties were characterized using photoluminescence (PL) and UV-VIS spectroscopy. XRD patterns confirmed that ZnO with wutrtize crystal structure and TiO₂ with anatase structure were presented. The degree of crystallinity of multilayer thin films has been improved through the deposition of ZnO. The intensity of UV luminescence of the multilayer has increased as compared to the single layer TiO₂ and bilayer ZnO/TiO₂. The multilayer ZnO/TiO₂/ZnO has high transmittance (above 80%) in visible region. All the result suggested that the use of multilayer thin films effectively enhanced the quality of films crystallinity and optical properties as compared to single layer ZnO and bilayer ZnO/TiO₂.