Advanced Materials Research Vol. 795

Abstract: The development of precipitate during ageing treatment of A319 alloy contributed significantly to the alloy strengthening mechanism. Two solution treatment temperatures which were set at 510°C and 525°C were subjected onto the different groups of A319 alloy samples and followed by artificial ageing process at 180°C. Scanning electron microscopy was employed to observe the over-aged samples from both solution treatment temperatures. The observation shows that Mg₂Si precipitates was only appeared at the higher solution treatment condition, while the Al₂Cu precipitate developed in both solution treatment temperatures.

Abstract: The present research examined the compressive and flexural strength of nanocement mortar by using micro cement, micro sand, nanosilica and nanoclay in developing a nanocement mortar which can lead to improvements in ferrocement construction. The measured results demonstrate the increase in compressive and flexural strength of mortars at early stages of hardening. In addition, the influence of heating on compressive strength of cement mortar. General expressions to predict the compressive strength, modulus of rupture for the developed nanocement mortar in the present work are proposed.

Abstract: Antibacterial materials based on calcium phosphates have wide range of biomedical applications in the prevention of microbial infections. The synthesis of inorganic mineral component of bone i.e. hydroxyapatite was done with the addition of silver (Ag) (5-15 wt %) as antibacterial agent. The wet precipitation synthesis was carried out using diammonium hydrogen phosphate and calcium nitrate as P and Ca precursors. The presence and effect of silver addition on the structure was studied using Fourier Transform-Infrared (FTIR) spectroscopy and Energy Dispersive X-ray (EDX) techniques. The antibacterial properties of all samples were evaluated using Disc Diffusion Technique (DDT) against S. aureus, B. subtilis, P. aeruginosa and E. coli. Antibacterial activities of samples were found to vary depending on the bacterial species and Ag loading percentage. The antibacterial assay suggested that the addition of Ag ions within hydroxyapatite can be effectively provided the required level of antibacterial activity against bacteria.

Abstract: This paper presents the findings on an investigation done on the use of Quarry dust, Fly ash and Billet scale in developing bricks. Bricks were made with various proportions of those materials and cement. Tests for fresh density, compressive strength, and water absorption were conducted. The compressive strength of bricks ranged from (7.2-26.3) MPa, the water absorption fell in range between (13-14.26) %. The optimum ratio of Fly ash and Billet scale is 1:1. It is shown that bricks with enhanced properties can be developed using these industrial wastes.

Abstract: Large quantities of agricultural wastes such as palm ash and rice husk are found throughout Malaysia, have a possibility to be used as a usefully renewable source for production of energy and silica (SiO₂). Extensive researches have been carried out to extract silica from agricultural wastes such as rice husk, due to silica as a useful raw material for industrial application. In the previous studies, the strong acid leaching treatment was carried out to remove metallic impurities and organics contained in rice husk. Since leaching treatment is a proper route to extract the silica, sulphuric acid (H₂SO₄), hydrochloric acid (HCl) and nitric acid (HNO₃) solutions are currently used in leaching treatment to prepare silica materials [. A strong acid leaching treatment, however, is significantly hazardous to the environment and people. In this study, the weaker acid, citric acid solutions were used to replace strong acid in leaching processes. Preliminary results showed that silica can be extracted from palm ash using citric acid leaching treatment under the optimum extracting conditions with 70°C of solution temperature, 60 minutes of reaction time and concentration of citric acid of more than 2%. The purity of silica extracted is more than 90%.

Abstract: Conductive polypyrrole (PPy) was synthesized using a chemical polymerization method in aqueous solution. A series of reactions were carried out with different reaction times of 240 mins and 20 mins. All results were compared to find the highest conductivity and yield. The formation of PPy was verified with Fourier transform infrared (FTIR) analysis which has detected the C-N and pyrrole stretching peaks at 1462 cm^-1 and 1169 cm^-1, respectively, while the x-ray diffraction (XRD) study has shown a broad halo pattern around 25 ̊ related to PPy. The PPy particles sizes of 5-20 microns were measured from the scanning electron microscope (SEM) image. It was found that in the presence of sodium dodecylbenzene sulfonate (DBSNa) as surfactant, the highest conductivity value of 3.18 S/cm and yield of 68% were achieved at 20 mins reaction time and temperature of 0 °C.

Abstract: Ball milling is a top down approach and a method to reduce size of particle while Zeolite is a valuable inorganic materials having wide variety of applications. In this paper, ball milling of commercial synthetic Zeolite powder was studied with their time varied. Wet ball milling was selected as a potential means to decrease the particle size of Zeolite over dry grinding. The parameters that included in this study were rotational speed, balls to powder ratio, water to powder ratio and milling time. These nanozeolite were characterized via Zeta-sizer nanoseries of particle sizer, FESEM, and also FTIR. Results showed that commercial synthetic Zeolite powder with particle size larger than 45 μm may be reduced into the size range between 0.2 0.3 μm by planetary ball mill.

Abstract: This paper presents a short review of research work on the development of synthesizing the colossal magnetoresistance materials through sol-gel method. Although there are a lot number of methods available, sol-gel method has been widely used and some excellent work has been reported. Two different manganite systems, which are LSMO and PSMO, that have been prepared through sol-gel method was choose for the discussion purpose. It was found that both systems were successfully prepared via the sol-gel method. Both systems showing better magnetoresistance properties compare to sample prepared through solid state reaction. X-ray diffraction technique was used to study the structural characteristic. Atomic force microscope and field emission scanning electron microscope were used in order to investigate surface morphology. Resistivity as a function of temperature was measured by a standard four-probe method.

Abstract: In this paper self-assembled silicon nanodots have been grown on silicon substrate using radio-frequency magnetron sputtering system. This system were settled at varying experimental conditions such as substrate temperature, time of deposition, RF power and fixed argon flow rate. Then the surface roughness was measured by AFM which resulted average dots size of 113 nm. However, the presence of a small amount of grain atoms formed on the surface was confirmed using SEM measurement. The crystalline Si-NDs with (100) plane contributed sharp diffraction peak located at 69.5° was confirmed using XRD measurement. These results of Si-NDs structural properties support the possible growth technique of radio-frequency magnetron sputtering.

Abstract: The gold nanoparticles film has been successfully formed on the silicon wafer by self-assembled method. The gold colliods were prepared by chemical reduction method where sodium citrate (act as the reducing, capping and stabilizing agent) were added into the boiling 50ml of 0.01% tetrachloroauria acid (HAuCl₄) solution in reflux system. Different particle size of gold colloids (AuNPs_1 and AuNPs_2) were produced by altering the amount of sodium citrate. The as-prepared gold colloids were characterized by UV - Vis spectrometry, Malvern particle size analyzer, zeta potential and XRD. Self-assembled method of Au nanoparticles were first start with the cleaning of silicon wafers using standard RCA cleaning, and followed by the piranha treatment to producing an OH-terminated surface. Then, the wafers were functionalized with organosilane molecule by immersing the silicon wafer in 10mM of surfactant in methanolic solution to produce self-assemble monolayers (SAMs) on silicon wafer surface. These layers were used to immobilize the gold nanoparticles from as-prepared gold colloid and result of the gold nanoparticles film on silicon wafer. Effect of surfactant ((3-aminopropyl) trimethoxysilane (APTMS) and (3-mercaptopropyl) trimethoxysilane (MPTMS)), effect of particle size of gold colloid (AuNPs_1 and AuNPs_2) and the effect of deposition time (0.5, 1.0, 1.5 and 2 hours) to the surface morphology such as surface coverage, inter-particle distance were studied in this work. The surface morphology of gold nanoparticles films were characterized by FESEM and AFM.