Papers by Author: Zainal Arifin Ahmad

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Authors: Chea Chandara, Khairun Azizi Mohd Azizli, Zainal Arifin Ahmad, Syed Fuad Saiyid Hashim, Etsuo Sakai
Abstract: The purpose of this paper is to investigate the mineralogical components of palm oil fuel ash (POFA) with or without unburned carbon by using semi-quantitative X-ray diffraction (XRD). Original POFA taken from palm oil mill was ground in ball mill, producing ground POFA (GPOFA). Unburned carbon was removed by heating the GPOFA at 500 °C for 1 h, producing treated POFA (TPOFA). Neither glassy phase crystallization nor agglomeration of GPOFA particles occurred during the heat treatment. The content of crystalline phase and glassy phase in GPOFA or TPOFA was determined using semi-quantitative XRD analysis internal standard method. The results showed that GPOFA and TPOFA contained 67.22% and 73.89% of glassy phase, respectively, which could be used as pozzolanic materials. The presence of P2O5, K2O and Na2O in POFA was the reason of reducing the melting point of POFA in boiler.
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Authors: Johar Banjuraizah, Mohamad Hasmaliza, Zainal Arifin Ahmad
Abstract: α Cordierite is very important phase in MgO-Al2O3-SiO2 system because of their very outstanding thermal, chemical and electrical properties. In this presents study non-stoichiometry cordierite (MgO:Al2O3:SiO2 = 3:1.5:5) using 2 different initial raw materials ( (i)mixture of pure oxide, and ii) mainly mixture of minerals) were fabricated and compared in terms of phase transformation and physical properties. Cordierite was prepared by glass method at low melting temperature (1350oC). Low melting temperature has resulted in partly crystalline glass which has possesses higher hardness, required longer milling time and result in contamination from grinding media. However, α-cordierite has successfully crystallized and fully densified at 850oC/2h. Activation energy for densification was investigated from thermal expansion coefficient (TCE) results. Other properties that were discussed included thermal properties using DTA/TGA.
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Authors: Mohd Nazri Idris, Zainal Arifin Ahmad, Mohd Azmier Ahmad
Abstract: In the present work, activated carbon was prepared from rubber seed coat by physicochemical activation for the removal of Remazol Brilliant Blue R (RBBR) dye from aqueous solution. The effects of dye initial concentration, contact time, solution temperature and pH on RBBR adsorption onto rubber seed coat based activated carbon (RSCAC) were investigated. The adsorption uptake was found to increase with increase in initial dye concentration and contact time. Change in temperature and pH also played an important role to RBBR adsorption capability. Study showed that rubber seed coat is suitable to be used as activated carbon precursor.
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Authors: Shamsuddin Saidatulakmar, Shamsul Baharin Jamaludin, Zuhailawati Hussain, Zainal Arifin Ahmad
Abstract: Fe-Cr matrix composite reinforced with alumina with mean powder sizes of 13, 23, 24 and 64 μm was successfully obtained through powder metallurgy method. The powder mixture were blended at a rotating speed of 250 rpm for thirty minutes and uni-axially pressed at a pressure of 750 MPa. Samples identified as J13, J23, J24 and J64 according to alumina particles size were sintered in a vacuum furnace under 10-2 Torr at a temperature of 1100°C for two hours with 10°C/minutes heating rate. The peaks of XRD patterns have been identified as belonging to the phases of Fe, Cr and alumina. The EDX analysis confirms the existence of Fe, Cr, Al and O. Reinforcing the Fe-Cr matrix with alumina particles bigger than 13 µm deteriorated the microstructure and mechanical properties of the composites. The wear coefficient for sample reinforced with 13 µm alumina particles is 2.46 × 10-11 with compressive strength of 278 MPa. Meanwhile for sample reinforced with 64 µm alumina particles its wear coefficient is 5.09 × 10-11 and compressive strength is 81 MPa. It is found that reinforcing smaller alumina particles sizes to Fe-Cr matrix resulted in better wear and strength properties of the composites.
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Authors: Aishah Syed Salim Sharifah, Julie Juliewatty Mohamed, Zainal Arifin Ahmad
Abstract: ZrxNi1-xO was prepared by conventional solid state reaction. The properties of undoped and ZrO2 doped NiO ceramics have been studied. The raw mixture of ZrO2 and NiO were ball milled for 24 hours. The samples were calcined at 1000°C for 2 hours, pressed into pellet shape at 200 MPa and sintered at 1300°C for 10 hours. The sintered samples were subjected to XRD, Scanning Electron Microscopy (SEM) and Impedance Analyzer for phase identification, microstructural observation and dielectric analysis. The grains size decrease with the increment of dopant amount. Enhanced dielectric constant was observed in the ZrO2 doped NiO with x= 0.02 for the frequency range from 1MHz to 1GHz. The dielectric constant of sintered ZrxNi1-xO decreased with an increasing frequency. The result indicates that Zr ions have effectively changed the dielectric properties of NiO.Keywords: NiO, Zr-doped, XRD, SEM, Dielectric.
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Authors: Ahmed Omran Alhareb, Zainal Arifin Ahmad
Abstract: The investigation of ceramic filler on the properties of denture base materials made from PMMA filled with Al2O3/ZrO2 was carried out. The amount of Al2O3/ZrO2 filler was fixed at 5 wt%. However, the ratios of Al2O3 to ZrO2 added were varied from 0 to 100. Samples were prepared for fracture toughness and flexural test. The findings were analyzed using scanning electron microscopy (SEM). The findings were recorded that the Al2O3/ZrO2 ratios show higher fracture toughness and flexural properties than PMMA matrix. SEM micrographs indicate that distribution of Al2O3 and ZrO2 in the PMMA matrix is fairly homogeneous. The mixing method was good between reinforcement particles and PMMA matrix. Therefore, addition of six ratios of Al2O3/ZrO2 with PMMA and this mixture is able to improve the mechanical properties of this denture base material.
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Authors: Ahmad Zahirani Ahmad Azhar, Mohamad Hasmaliza, Manimaran Ratnam, Zainal Arifin Ahmad
Abstract: The mechanical properties and microstructure of zirconia-toughened-alumina ceramic composite doped with nanoparticle of MgO is investigated. The nanoMgO weight percent was varied from 0.3 wt % to 1.3 wt %. Each batch of composition was mixed using ultrasonic cleaner and mechanical stirrer, uniaxially pressed and sintered at 1600 °C for 4 h in pressureless conditions. Analysis of bulk density, Vickers hardness and microstructural observation has been carried out. Results of Vickers hardness increased linearly with addition of more nanoMgO until a certain composition. Maximum Vickers hardness obtained was 1740HV with 1.1 wt % MgO. Furthermore, microstructural observations show that the Al2O3 grain size depends on the particle size of MgO, and is directly related to its hardness property.
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Authors: Sharifah Aishah Syed Salim, Julie Juliewatty Mohamed, Zainal Arifin Ahmad, Zainal Arifin Ahmad
Abstract: Numerous methods have been used to produce high purity TiC. There is no previous study has been reported on the formation using single elemental powders of Titanium (Ti) and Carbon (C) with addition Nickel (Ni) by tungsten inert gas (TIG) weld method. In this work, TiC was synthesized via TIG method by arc melting elemental powder mixture of Ti and C at ~5 second (s) and 80 ampere (A). The effect Ni contents on TiC formation was investigated. The mixed raw material was ball milled for 24 hours followed by synthesis via TIG method. The arced samples were characterized by X-ray diffraction (XRD) and Scanning electron microscope (SEM). It was revealed, that small amount of Ni additive to the metal powder allows the production of dense and tough TiC.
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Authors: Ahmad Zahirani Ahmad Azhar, Foo Tai Kong, Mohamad Hasmaliza, Manimaran Ratnam, Zainal Arifin Ahmad
Abstract: Vickers hardness of zirconia toughened alumina added MgO with different composition and particle size has been studied. Five different size of magnesium oxide particle at different composition (0.5 wt % to 0.9 wt %) were used in this experiment. Each batch of composition was mixed, uniaxially pressed into 13 mm pellets and sintered at 1600oC for 4 hours in pressureless conditions. Analysis of Vickers hardness, microstructural observation and EDX analysis has been carried out. Microstructural observation showed that the addition of magnesium oxide greatly affected zirconia toughened alumina microstructure. Smaller Al2O3 grain size is observed with the presence of MgO thus improving its mechanical properties such as hardness and density. Results of Vickers hardness increased linearly with addition of more MgO until a certain composition. Each particle size of MgO addition show different composition is needed to reach the optimum Vickers hardness, depending on the particle size. The increase of hardness of the cutting insert is mainly contributed by small sized Al2O3 grains due to the microstructure pinning effect introduced by MgO. Maximum Vickers hardness achieved in this experiment is 1710 Hv, obtained at 0.7 wt% MgO with 0.15 µm particle size.
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Authors: Firdaus Omar Mohd, Md Akil Hazizan, Zainal Arifin Ahmad
Abstract: Filler-related characteristic such as particle size, shape and geometry are essential factors that need to be considered during the evaluation of the material’s performance especially in the area of particle filled composites. However, there is limited number of works are reported on this particular issue under high strain rate condition. Based on this concern, the paper presents an experimental results on the effect of particle sizes towards rate sensitivity and dynamic compressive properties of polypropylene/silica nanocomposites across strain rate from 10-2 to 10-3 s-1. The composite specimens were tested using universal testing machine for static loading and a compression split Hopkinson pressure bar apparatus for dynamic loading. Results show that, the stiffness and strength properties of polypropylene/silica nanocomposites were affected by the size of silica particles. However, the magnitudes of changed are somehow different between micro and nanosizes. On the other hand, particle size also plays a major contribution towards sensitivity of the polypropylene/silica nanocomposites where the smaller the reinforcement sizes, the less sensitive would be the composites. Overall, it is convenience to say that the particle size gives significant contribution towards rate sensitivity and dynamic mechanical properties of polypropylene/silica nanocomposites.
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