Papers by Author: Azmi Rahmat

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Authors: M.A. Sri Asliza, K. Mohd Zaheruddin, Azmi Rahmat, Shamsul Baharin Jamaludin, Rafezi Ahmad Khairel
Abstract: Ni deposited Hydroxyapatite powder was prepared by electroless deposition technique without sensitization and activation treatments. The composition and phase of deposition were studied. The surface morphologies and composition of initial pure HA powder, as received Ni deposited HA powder and compacted Ni deposited HA powder after sintering were characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) respectively. The phases in the powder before and after sintering were investigated by x-ray diffraction (XRD). From the experiment, with the increase of reduction agent, the plating time becomes shorter and optimal concentration of reduction agent and powder ratio is 3:1. The result shows that Ni succesfully deposited on HA powder and confirmed by EDX result. The Ni grain size distribution of 75nm to 250nm can be clearly observed on the HA surface from the micrograph after sintering. Decomposition of hydroxyapatite into α-TCP (α tricalcium phosphate) and TTCP (tetracalcium phosphate) did not occur in nickel deposited HA before and after sintering. On the other hand, a sharp Ni peak were detected
Authors: Farah Farhana Zainal, Kamarudin Hussin, Azmi Rahmat, Mohd Mustafa Al Bakri Abdullah, Andrei Victor Sandu
Abstract: This paper presents an experimental study on corrosion of carbon steel as reinforcement bar in artificial solution of geopolymer paste by Open Circuit Potential (OCP). The OCP measurements have been used in reinforcement bar concrete studies for many years to determine the corrosion behavior of materials. OCP is the potential of the working electrode relative to the reference electrode when no current or potential is being applied to cell. The OCP of reinforcement bar was recorded with time and this experiment has been done for 30 days. A copper/copper sulfate (Cu/CuSO4) reference electrode with a potential V-SHE of +0.318 V (at 25oC) was used in this study. The pH of geopolymer concrete was observed to be in the range of 11.5 to 12.5 depending on the formulations. Thus, in this study the artificial solutions of geopolymer paste that were used are pH 11, pH 12 and pH 13. It has been found that the potential values of three solutions were fluctuated from the beginning until day 30. The highest potential value was indicated by pH 13 whereas the maximum value is 0.542 V and minimum value is 0.205 V while pH 11 shows the lowest potential value with the maximum value 0.356 V and the minimum value-0.047 V. However, all the redox potential values for pH 11, pH 12 and pH 13 were located at passivity region, Fe2O3. The Fe2O3 is the stable phase in which this oxide acts as a protective film or passive layer in this region. It would be expected to provide some protection against corrosion. Keywords: corrosion, artificial solution, geopolymer paste, reinforcement bar, open circuit potential, passivity
Authors: Mohd Darus Daud, Aimi Noorliyana Hashim, Azmi Rahmat, Mohd Mustafa Al Bakri Abdullah, Ahmad Hadzrul Iqwan Jalauddin
Abstract: An innovative and novel technology method of processing called Turbo-Mixing Reactive Precipitation (TMRP) design proposed as an alternative to this current processing or conventional productions of fine precipitated calcium carbonate (nanoPCC) in turbo-mixing conditions. In this paper, the effect of the stirring rate onto morphology, particle sizes and reaction time of the precipitated CaCO3 particles was discussed. CaCO3 nanoparticles with an average particle size of approximately 15.75 nm were successfully obtained by stirring rotation speed at 900 rpm. The structural analysis was conducted using a Scanning Electron Microscope (SEM) and a Field Emission Scanning Electron Microscope (FESEM). The results showed that the increasing of the multiple’s impeller stirring rotation speed is in favor of the formation of the spherical vaterite.
Authors: Sri Asliza Md Amin, Kasmuin Mohd Zaheruddin, Azmi Rahmat, Shamsul Baharin Jamaludin, R.A. Khairel
Abstract: Ni deposited on HA powder was prepared by electroless plating process without sensitization and activation treatment. The deposited powder obtained was characterized by energy dispersive spectroscopy (EDX) and x-ray diffraction (XRD). The microstructure and hardness of the sintered powder were examined by scanning electron microscopy (SEM) and Vickers hardness respectively. From the result, the nickel existence in the deposition was confirmed by the EDX analysis. The diffraction peaks at 44.5 and 64.7o (2θ) of planes (111) and (211) respectively were belong to nickel. Nickel are homogeneously dispersed in HA matrix with grain size between 0.25-2μm after sintered at 1250°C. The improvement of 93% and 180% in average hardness and flexural strength respectively were achieved with nickel presence in HA compared to pure HA.
Authors: Farah Farhana Zainal, Muhammad Faiz Fazill, Kamarudin Hussin, Azmi Rahmat, Mohd Mustafa Al Bakri Abdullah, Warid Wazien
Abstract: This paper presents the results of a study on the effect of geopolymer coating on mild steel. Geopolymer is synthesis of a fly ash and alkaline activators which are sodium hydroxide solution (NaOH) and sodium silicate solution (Na2SiO3). Fly ash is one of residue produced during the combustion of coal in coal power plant. In this study, fly ash class F based geopolymer was used as a source material. The alkaline activators then were mixed with fly ash to produce the geopolymer paste which acts as a coating material. The mixture was placed in molds and reinforcement bar were embedded in geopolymer paste. After that, the corrosion behavior of reinforcement bars for all samples were observed by using Open Circuit Potential (OCP) testing. Referring the pourbaix diagram regarding OCP testing, samples are in passivity region. Besides that, mild steel also were coated with geopolymer paste for adhesion test. Elcometer 108 was used for adhesion strength test. Morphology analysis also been used to determine the microstructure of fly ash and geopolymer paste. Phase analysis was used for the analysis phase between fly ash, geopolymer paste and mild steel coated with geopolymer paste. From OCP test, pourbaix diagram shows that samples is placed in the passivity region, iron (III) oxide (Fe2O3) which is in stable phase and iron (II, III) oxide same results as in phase analysis. The minimum potential value for OCP is 0.015 V and the maximum potential value is 0.133 V. For adhesion strength, day 14 got the highest results compared day 7 and day 3 which the results are 2.0 Mpa, 1.9 Mpa and 1.5 Mpa respectively. It is because from day 3 until day 14, the structure of geopolymer paste becomes more compact, denser and better crystallization as shown in morphological analysis.
Authors: Shaiful Rizam Shamsudin, Mohd Harun, Mohd Noor Mazlee, Azmi Rahmat, Rohaya Abdul Malek
Abstract: A failure analysis of a broken multi strand wire rope from an offshore platform crane was performed. The wire rope was operated for less than 5 years. The wire consists of seven strands, one central strand and six strands around it. The diameter of the small wires was about 0.78-0.94 mm and the larger wires was a round of 1.52 - 1.78 mm. The large size wires were found fractured by cyclic torsional stresses as characterized by the presence of fatigue cracking originating from the outer surface of the wire. Meanwhile the smaller wires were fractured in a ductile manner under excessive load after the larger wire broken out due to the fatigue mechanism.
Authors: Yuriz Yasmin, Mohd Noor Mazlee, W.H. Chan, J.B. Shamsul, Azmi Rahmat
Abstract: Greenhouse effects were generated from anthropogenic emissions of carbon dioxide (CO2) into the atmosphere. High concentration of CO2 has recognised as major causes of global warming. In order to keep CO2 at a manageable level, adsorptions of these gases from the flue gases is necessary. Developing a low cost porous solid adsorbent as adsorption media become a great attention due to environmental and economic concerns. This paper has reviewed the cost effective materials with a suitable methods to fabricate the porous solid adsorbent. This paper also has discussed the adsorption mechanisms of CO2 on the selective cost effective materials.
Authors: Ali Basheer Azeez, Kahtan S. Mohammed, Mohd Mustafa Al Bakri Abdullah, Andrei Victor Sandhu, Azmi Rahmat, Hussin Kamarudin, Liyana Jamaludin
Abstract: Lead metal proved to be toxic. Its lethal effect became eminent. Many developed countries have banned lead usage in various applications. Seeking alternative material to replace lead is a crucial goal. As density concerns, tungsten-brass composite is a good candidate for lead replacement. In this study the radiation shielding effects of tungsten-brass composites were evaluated. To attain this goal, four tungsten-brass sets were prepared. The tungsten (W) wt. % in these specimens was ranged from 50 to 80, the balance is brass. The specimens were sintered at 10500C in alumina tube furnace under protective environment. To evaluate the radiation shielding performance of these specimens, two gamma ray sources, 137Cs and 60Co were utilized. The photon energy levels for these sources were of o.662MeV and 1.25MeV respectively. The measurements were performed using gamma spectrometer contains NaI (Tl) detector. The anti-radiation performance of the tungsten-brass was correlated to that of lead under similar conditions. Vickers micro hardness, relative sintered density, micro structural characterisation and linear attenuation coefficient (μ) were carried out. Samples with the highest Weight percentage of W has the highest hardness value while the one with the lowest Weight percentage of W. The linear attenuation coefficients of the specimens were significantly improved by increasing the W wt. % of the specimen. The linear attenuation coefficients of the tested specimens ranged from 0.85±0.010cm-1 to 1.12±0.049cm-1for 60Co and0.73±0.012 cm-1 to 0.97±0.027 cm-1 for 137Cs. This result indicates that W-brass composites are suitable material for lead replacement as a shielding barrier.Keywords: Attenuation coefficient, radiation shielding, lead, tungsten-brass composites, NaI (Tl).
Authors: Farah Farhana Zainal, Kamarudin Hussin, Azmi Rahmat, Mohd Mustafa Al Bakri Abdullah, Shaiful Rizam, Mohammad Tamizi Selimin, Andrei Victor Sandu
Abstract: This paper presents an experimental study of the electrical resistivity of geopolymer paste by using a non-destructive test employing Wenner four probe method. Geopolymer is produced from a combination mixture of aluminosilicate materials which is rich in Si and Al such as fly ash with an alkaline activator. Geopolymer paste in this study was made from a mixture of class F fly ash, sodium hydroxide (NaOH) solution and sodium silicate (Na2SiO3) solution. An alkaline activator was prepared 24 hrs prior to use with the ratio mixture of Na2SiO3/NaOH being 2.5. Then, the prepared alkaline activator was mixed with the fly ash for about 30 minutes. After that, the mixture was placed in a 100 mm x 103 mm x 495 mm mould. After 24 hrs, the sample was taken out from the mould and cured at 60°C in the oven for 24 hrs. The sample was then tested after 7, 14 and 28 days. The current applied in this study was from 0.01 mA to 1.00 mA and the electrode spacing used were 0.02 m, 0.04 m, 0.06 m, 0.08 m and 0.10 m. The results showed that the geopolymer paste after 28 days with the current of 0.01 mA and 0.10 m electrode spacing showed the highest resistivity with 61575 Ω.m while the geopolymer paste after 7 days with 0.95 mA and 0.02 m electrode spacing showed the lowest resistivity with 537 Ω.m. Hence, the corrosion rate of geopolymer paste in this study was negligible and if occur, was very low.
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