Advanced Materials Research Vol. 1024

Abstract: Equal channel angular pressing (ECAP) could be used to achieve ultra fine grains in bulk aluminum alloy through severe plastic deformation. Typically a feed material of as-cast aluminum alloys is used with a typical hypoeutectic solidification structure, consisting of primary aluminum dendrites and interdendritic network of lamellar eutectic silicon. On the other hand, semi-solid metal casting provides non-dendritic and globular microstructure which is one of a considerable factor in obtaining homogenous microstructure after ECAP. This work is an attempt to produce aluminum alloy with globular microstructure using cooling slope semi-solid casting process which is believed suitable as a feedstock for ECAP. The aim of this work described in this paper was to understand of microstructural evolution of aluminum structure during cooling slope casting process. Two experiments were carried out. A sample was casted via a cooling slope into a vertical cold mild steel mould at pouring temperature of 640°C. Cooling slope length of 250 mm, slope temperature of room temperature and tilt angle of 60^o was applied. Another sample was casted directly into a vertical cold mild steel mould at pouring temperature of 640°C. The primary α-Al phases in the sample that casted without cooling slope was mostly in dendritic throughout the section of sample whilst the primary α-Al phases transformed completely into non-dendritic in the sample that was casted via the cooling slope. Therefore, the transformation is believed resulted from the effect of cooling slope

Abstract: Grain refining has been studied in the semi-solid-metal (SSM) casting by addition of master alloy Al-5Ti-1B using inclined slope. A356 aluminium alloy was melted at 850 °C and poured at 660 °C on the inclined slope into the steel mould. Grain refiner was added in various percentages of 0.2%, 0.5% and 1.0% in A356 aluminium alloy melt. Microstructure and microhardness were characterized using optical microscope and Vicker’s microhardness tester. The addition of master alloy Al-5Ti-1B not only refined but also increased the globularity of the primary α-Al particles. The higher hardness was achieved with 1% addition of master alloy Al-5Ti-1B.

Abstract: Recently, pure PZT have been used as a piezofan in electronic application. Properties that piezoelectric fan should have are high mechanical piezoelectric coupling factor, high dielectric constant, easily polarized and high piezoelectric charge constant. Soft PZT is a suitable candidate to fulfill this requirement. The samples will be prepared via high planetary mill; due to this process can skip calcinations process, which can reduce a lot of cost. This process also can avoid PbO loss during sintering process. The microstructure and electrical properties of PZT ceramic were found to be more sensitive to the sintering condition. Preliminary works have been done in order to find a suitable sintering duration in order to produce a good PZT formation. SEM analysis indicated that shorter sintering time promotes fine structure and densification. This have been proves where relative density of the obtained sintered PZT ceramics was measured to be approximately 99 % of the theoretical density.

Abstract: Laminated natural rubber latex with cleaning agent and waste latex compound was prepared by arranging half-cured latex sheets with various thicknesses of core layer then moulding using hot press according to the Rheometer graph. Laminated layers consist of outer layer (natural rubber latex films with cleaning agent) and core layer (waste natural rubber latex film). The core layer and outer layer are prepared through casting method with different thickness. For core layer, three different thickness of film is cast and for outer layer the thickness is control. The aim of this paper is to study the effect of different thickness of core layer and the different molding temperature on tensile and swelling properties of laminated films. The tensile test was carried out to acquire good interfacial adhesion between the laminates films. The fractured surface morphologies were carried out using digital microscope (Dino-Lite) to understand the interfacial interaction between core and outer layer of the films. The use of NRL lamination films with NRL waste will contribute to novel materials for as mould cleaning product with green and easier cleaning compare to conventional cleaning process.

Abstract: Sidoarjo mudflow occurred in 2006 has been causing major environmental problems in a wide area surrounding the region. The utilization of the sludge from this mudflow as useful materials is a potential solution to this problem. In this study, we proposed a hydrothermal treatment method to convert the silica-rich sludge into zeolites useful as adsorbent for inorganic pollutants such as heavy metals. Prior to the hydrothermal treatment, the sludge was contacted with NaOH solution in a teflon vessel. During the hydrothermal treatment, the mixture was subjected to increasing temperature for a certain period of time. After hydrothermal treatment, the solid phase was filtered, washed thoroughly until neutral pH and dried. In this study, we evaluated the effect of NaOH concentration and hydrothermal treatment temperature on the type of zeolite formed. The surface morphology and composition of prepared zeolite was characterized by SEM-EDS while the type of zeolite was determined by XRD analysis. Preliminary study of the adsorption ability of the zeolites towards metal ions was carried out by CEC measurement using sodium acetate method.

Abstract: This study evaluates the performance of nonwoven kenaf mat reinforced epoxy that was fabricated by vacuum resin transfer molding method. Kenaf mats were formed by carding and needle punching technique at 50 cm² sticthing density and 1.5 cm penetration depth. The specimens were prepared from different volume fraction of kenaf mat and epoxy resin, which consist of 18% kenaf mat/ 82% epoxy resin and 27% kenaf / 73% epoxy resin. Tensile and compression properties were studied at 0^o, 45^o and 90^o needle punching direction. The tensile properties increased with the increase of composites volume fraction and were decreased with the increase of needle punching direction degree. On the other hand, the compression properties of composites were reduced with the increase of volume fraction and needle punching direction degree. The composites properties were affected by the orientation and interlocking of fiber caused by needle penetration in direction of depth and movement direction.

Abstract: This work describes the formation of silver-coated gold nanoparticles (Ag-AuNPs) using the seeding-growth method. 15 nm AuNPs seeds were synthesized using the citrate reduction method. In the growth stage, the adding sequence of seeds, ascorbic acid (AA), gold chloride (HAuCl₄) and silver nitrate (AgNO₃) was explored. The effect AgNO₃ volume (20 mM) was varied at 0.10, 0.25, 0.50, 1.00, 1.25 and 1.50 ml. Morphology of Ag-AuNPs was observed using a Transmission Electron Microscope (TEM) while UV-Vis Spectrophotometer was used to study the concentration and absorption spectra of colloidal Ag-AuNPs. Zeta-sizer analysis was used to study the particle size distribution of Ag-AuNPs in colloidal form. In the growth stage, the optimum adding sequence was found by adding AA as a reducing agent into AuNPs seeds followed by the addition of HAuCl₄ and AgNO₃. This reshuffle sequence is chosen due to the presence of two absorbance peaks at 398 nm and 501 nm compared to others. From TEM images, increasing concentration of silver ions affected the optical properties, end size of Ag-AuNPs as well as raises the concentration of the colloids suspension. The biological properties of samples Ag-AuNPs (0.1 ml to 0.5 ml AgNO₃) were studied by performing the conjugation process between samples and antibody; goat anti-human IgA (GaHIgA). An additional washing process was required to perform conjugation for Ag-AuNPs in order to remove by-product or unreacted chemical produced during synthesis process. The Ag-AuNPs was successfully conjugated with GaHIgA and required a minimum concentration of antibody (9µg/ml) after washing process. In addition, the washed Ag-AuNPs also improved its binding capability with GaHIgA by giving higher intense signal when tested with lined Human IgA on the lateral flow immunoassay (LFI) compared to un-washed Ag-AuNPs.

Abstract: In this study, the influence of hydrogen peroxide (H₂O₂) concentration to the iron oxide nanoparticles (IONPs) properties prepared using the precipitation method was investigated. The H₂O₂ concentration was varied from 0.85 M to 5.1 M. The concentration of H₂O₂ influenced the crystallinity and the growth rate of the IONPs precipitates. Increasing the concentration of H₂O₂ increased the crystallinity and expedited the growth rate of IONPs. The optimum concentration of H₂O₂ was 1.7 M. From the transmission electron microscopy (TEM) images, the size of IONPs obtained was ~14 nm and the X-ray diffraction (XRD) spectra showed the presence of spinel cubic lattice of maghemite (γ-Fe₂O₃). The magnetic measurement of IONPs using vibrating sample magnetometer (VSM) was showed that the IONPs exhibited superparamagnetic properties. Furthermore, the electrostatic repulsion using percloric acid (HClO₄) and steric stabilization using silane polyethelene glycol (SiPEG) were created surround IONPs in order to obtain a stable colloidal IONPs for the conjugation process. The stable IONPs were then conjugated to the antibody and tested in the lateral flow immunoassay as the labelling agent.

Abstract: The aim of the study was to investigate the influence of ZrO₂ on the crystallization and properties of leucite phase from K₂O -Al₂O₃- SiO₂ glass-forming melts. A starting glass composition of weight %; 60.7-63.2% SiO₂, 16.6% Al₂O₃, 11.6% K₂O, 5.10% Na₂O, 2.5-5.0% ZrO₂, 0.5% TiO₂ and 0.5% LiO₂ was melted in an electric furnace, followed by quenched in cool water to produce glass frit. Malaysian silica sand from Terengganu was used as the SiO₂ source. The glass powders were ball milled and compressed to form 13mm diameter discs using cool isostatic pressing. The discs were sintered at 650°C, 700°C, 750^°C, 800^°C and 850^°C for 1 hour and characterised using X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). The results indicate that the amount of ZrO₂ additive is one of the key factors controlling of leucite crystallization. The properties of sintered disc specimens were studied using three point bending, diametral and Vickers microhardness test. The results showed that the mechanical properties of leucite glass-ceramics increased as the amount of ZrO₂ was increased.

Abstract: The goal of our study is to develop genetically engineered polypeptides that self-assemble into nanoparticulates, which can present functional moieties on their exterior and sequester drugs and/or imaging agents within their interior. These particulates are intended to improve the detection and treatment of malignancy.