Silicon nanowires were synthesized on Si substrates (111) via thermal evaporation using AuPd thin layer catalyst. Pre cleaned of Si wafer was used as a substrate to assemble the nanostructure products. In this work, the effect of growth temperature that ranging from 800 to 1000°C on the formation of silicon nanowires studied extensively. X-ray diffraction and field emission scanning electron microscope were employed to characterize the structures and morphology of nanowires. Vertical aligned silicon nanowires have been successfully grown on Si substrates at 900 and 1000°C. At 1100°C, the high aspect ratio of silicon nanowires can be produced but the formation density is low. The presence of AuPd catalyst on the tip of nanowires, it is expected that VLS is the most suitable to explain the growth mechanism of obtained SiNWs. The crystalline structure of SiNWs was proved by XRD data.
Concentrations of Natural Occurring Radioactive Material (NORM) and terrestrial gamma radiation have been shown to be associated with certain lithology and soil types. An attempt was made to statistically predict and validate environmental gamma radiation dose rates based on limited number of actual field measurements using sodium iodide (NaI(Tl)) detector. Statistical analysis including the correlations between the actual and predicted dose were made based on 32 different lithology and soil type combinations. Results of field measurements, have shown that more than 50% of the predicted data were not significantly different from the actual measured data. The interpolation method in GIS was used to produce an isodose map based on the prediction equation. A correlation of multiple regression on the predicted versus lithology and soils dose rates gave relationships of DP = 0.35 DL + 0.82 DS – 0.02, r2 = 0.736. A predicted isodose map was subsequently plotted base on 4 dose rates classes, ranging from 0.1 – 0.3 μSvhr-1.
A month hourly measurement of radon concentration was taken in the bedroom of a two story link house in Kuala Lumpur. The house is a typical urban house in Malaysia, constructed with bricks, concrete and cement plaster. These materials are natural sources of radon in the house. The hourly radon concentration was found to vary from 0 pCiL-1 to 3 pCiL-1. It was found to peak during early morning and to minimize in the evening. The daily average radon concentration varied from 0.2 pCiL-1 to 1.0 pCiL-1.
Herein, we report on the optimum condition for TiO2, titania nanotubes formation and the effect of annealing on the formation of anatase and rutile titania. Anodic oxidation was carried out in two electrodes bath consisting of 5wt% NH4F ions. The anode was a 0.1mm thick Ti foil and the cathode was Pt electrode. Anodisation was conducted at 20V. The anodised foils were subjected to morphological and structural characterizations. As-anodised foil was found to be amorphous or weakly crystalline. When the oxide was heat treated, x-ray diffraction analysis revealed the presence of (101) anatase at annealing temperature from 400-500°C. This indicates that the transformation occurs at this range of temperatures. Raman spectroscopy analysis showed the diminishing of anatase peaks for samples annealed at 500°C. At above 600°C, x-ray diffraction pattern shows a peak belonging to the rutile peak. Transformation from anatase to rutile is thought to occur at about 500°C with a more complete transformation at higher temperature. Annealing at higher than 600°C induces thickening of the nanotubes wall and at above 700°C, the nanotubes structure has completely disappeared.
This research was conducted to study the effect of reinforcement particles on iron-cobalt (FeCo) composites. The composition of silicon carbide (SiC) was varied from 0 to 20 wt%. The composite was fabricated via powder metallurgy (PM) method, which consists of mixing, compaction and sintering processes. The powder was mixed for 2 hours to obtain uniformity between SiC and Fe-Co matrix and compacted to a cylindrical shape at 250 MPa. Samples were sintered for 2 hours at 900 o C with 10 o C/minute heating rate in argon atmosphere. The influences of reinforcement particle on the sintered samples were characterized in terms of microstructure and hardness testing. The Fe-Co/20wt%SiC composites show highest hardness value.
For more than two decades, biodosimetry has been used in biomonitoring of occupational and envir onmental exposure to ionising radiation. Chromosome aberration analysis is a method used to dete ct unstable aberrations in the lymphocytes of irradiated personnel. The Malaysian National Biodosi metry Laboratory is a referance centre for activity relating to biodosimetry in the country. This pap er aims at presenting dicentric assay technique for the assessment of whole body dose to low LET ra diation at the Malaysian National Biodosimetry Laboratory.
The experiment aims to investigate the effect of high energy milling to the crystallite size of α-alumina. The starting material used is α-alumina powder with starting crystal size of 86nm. This powder was milled at different time ranges from 0 to 60 minutes and milling speed ranges from 400 rpm to 1100 rpm using a wet milling technique in corundum abrasive materials. The wet milling technique involved the use of water with the alumina to water ratio of 1:6.1. Samples prepared were then examined using the X-Ray Diffraction (XRD) to calculate the crystallite size and scanning electron microscope (SEM) was also used to determine changes in the morphology. Results from these analysis showed that the crystallite size will get smaller when milling speed and time of more than 600rpm and 30 minutes respectively were used. Optimum conditions to achieve the smallest crystal size of 79.7nm are 1000 rpm and 60 minutes.
A co-deposition of nickel-phosphorus-alumina (NiPA) composite coatings were obtained from an ordinary sulphate-based plating bath consisting of 5 g/l alumina (Al2O3) particles. The particles were dispersed by using mechanical agitation at 125 rpm. The presence of Ni3P and Al2O3 phases in the coatings was confirmed by XRD analysis. SEM/EDX results indicated that a smooth Ni3P coating was obtained and Al2O3 particles were embedded into the coating. Microscopic observation showed that the bonding between the Ni3P metal matrix and the Al2O3 ceramic particles was compact.
A process to produce calcium phosphate biomaterial was done using an organic based diethylhexyl phosphoric acid (DEHPA) as its starting material. The gel obtained from this reaction was used to study calcium phosphate transformation using in-situ XRD with temperature ranges from room temperature to 1300 o C. The results obtained from this analysis show the following phase transformation sequence gel > β-Ca2P2O7 > β-TCP + HA > α-TCP + HA. β-Ca2P2O7 was formed at 400 o C and the sample when heated up to 1000 o C, peaks of β- TCP and HA appeared showing the transformation of the β-Ca2P2O7 phase. When the sample was heated up further to 1200 o C, β-TCP transformed into α-TCP.
This study was designed to investigate the crystallite sizes of Porites species. A set of 9 Porites skeletons i.e. Porites australiensis, Porites cylindrica, Porites lutea, Porites lichen, Porites digitata, Porites nigrescens, Porites rus, Porites annae and Porites sp. were studied by using XRay Diffraction method. The values of FWHM and theta (θ) are used in Scherrer equation to determine the crystallite sizes of all Porites samples. It was found that the crystallite sizes were in the range of 1007.78 Ǻ – 1706.04 Ǻ.
A study to determine the influence of soil water status on the physiology of rice plant Oryza sativa var. MR220 after panicle initiation stage was carried out at Ladang Merdeka Mulong Lating in the Kemubu Agricultural Development Authority (KADA) area, Kelantan. Five water management treatments imposed on direct seeded rice were; T1. Continuous flooding, T2. Early flooding up to panicle initiation stage followed by saturated (F55-saturated), T3. Early flooding for the first month followed by saturated (F-30 saturated), T4. Continuous saturated, and T5. Continuous field capacity condition throughout the growth stage. The treatments were arranged in Randomized Complete Block Design (RCBD) with four replicates. In-situ stomatal conductance measurement was carried out at 68 DAS (days after seeding) and the elemental analysis of soil and plant samples was carried out using the Instrumental Neutron Activation Analysis (INAA). Results from this study showed significant differences between treatments for soil moisture content and plant moisture content, but no significance different in leaf stomatal conductance. Rice plant moisture, soil moisture and leaf stomatal conductance showed no interaction. Early flooding up to panicle initiation stage followed by saturated (T2: F55-saturated) resulted in higher plant moisture content. Soil plant transfer coefficient was highest in continuous saturated (T4) for nitrogen, early flooding for the first month followed by saturated (T3: F-30 saturated) for potassium, continuous field capacity condition throughout the growth stage (T5) for magnesium, and continuous flooding (T1) for sodium.
At present, research in composite materials is being directed at using natural fibres instead of synthetic fibres. Kenaf which is extensively grown in the Far East including Malaysia, has been identified as a bast (stem) fibre with significant market potential. In this work, long and random kenaf fibres (non-woven mat form) were used in the as-received condition and alkalized with a 0.06M NaOH solution. They were combined with polypropylene thin sheets, sandwiched between layers of kenaf fibres and hot-pressed to form natural fibre composites. The mechanical properties of the composites were investigated to observe the effect of fibre alignment, fibre treatment and pre-irradiation method used. A general trend was observed whereby alkalized and long fibre composites gave higher flexural modulus and flexural strength compared with random mat and untreated fibres. The long fibre composites also gave a higher work of fracture. However, the correlation between fibre surface treatment and the work of fracture was less clear. Pre-irradiation on the polypropylene pellets and fibres before the composite is manufactured showed significant improvement on the flexural modulus and flexural strength. The bond performance test performed on the treated composites demonstrated good bonding and interfacial adhesion between the fibre and matrix. However, the method of moulding used need to be improved to optimize the performance of the composites.
A study to measure the concentrations of long-lived radionuclides of the uranium and thorium series in naturally occurring radioactive materials (NORM) wastes was carried out using gamma spectrometry and neutron activation analysis methods. It was found that radionuclides in the NORM wastes of the oil/gas production and ores/minerals processing industries were not in equilibrium. The 226 Ra/ 238 U and 228 Ra/ 232 Th ratios were between 0.001 and 2220 indicating that the concentrations of daughters radionuclides ( 226 Ra, 228 Ra) were very low or very high compared to the parent radionuclides ( 238 U, 232 Th) in the NORM wastes.
A Monte Carlo simulation of the Malaysian nuclear reactor has been performed using MCNP Version 5 code. The purpose of the work is the determination of the multiplication factor (k eff ) for TRIGA Mark II research reactor in Malaysia based on Monte Carlo method. This work has been performed to calculate the value of k eff for two cases, which are the control rod either fully withdrawn or fully inserted to construct a complete model of the TRIGA Mark II PUSPATI Reactor (RTP). The RTP core was modeled as close as possible to the real core and the results of k eff from MCNP5 were obtained. When the control-fuel rods were fully inserted, the k eff value indicates the RTP reactor was in the subcritical condition with a value of 0.98370 ± 0.00054. When the control-fuel rods were fully withdrawn the value of k eff value indicates the RTP reactor is in the supercritical condition, that is 1.10773 ± 0.00083.
The measurements of absorbed dose rate in air around amang plant buildings were carried out using a scintillation detector. It was found that the mean radiation levels at seven amang plants were in the range of 1.6 – 5.5 µGy h -1. The individual maximum value measured was 56 µGy h -1. The annual dose to a worker transporting the minerals to the plant was estimated to be 1.5 mSv y -1.
Production of carbon dioxide from degraded woods especially Karas or Aquilariella Malaccensis using integrated pyrolysis-combustion is important for radiocarbon dating application. The effects of pyrolysis temperatures (300-400 0 C), retention times (20-35 minutes) and flow rates of argon (400- 1000 ml/min) on the production of carbon dioxide were studied. The experiments were arranged according to a 2 3 response surface central composite statistical design (CSD). This response surface methodology (RSM) was used to assess factor interactions and empirical models regarding carbon dioxide yield. The optimized yield of carbon dioxide was 82.57% for Karas and the optimum reaction conditions are 300 0 C of pyrolysis temperature, 20 minutes retention time and 982ml/min flow rates of argon. Scanning electron microscope (SEM) and X-ray Diffraction (XRD) were conducted to assess the morphological characteristics of the woods and to look at the potential crystalline structure produced after the process took place, respectively.
Effects of organoclay concentration on the properties of radiation crosslinked natural rubber (NR)/ ethylene vinyl acetate (EVA)/clay nanocomposites were investigated. The NR/EVA blend with a ratio of 40/60 was melt blended with different concentration of either dodecyl ammonium montmorillonite (DDA-MMT) or dimethyl dihydrogenated tallow quarternary ammonium montmorillonite (C20A). Composite of NR/EVA blend with unmodified clay (Na-MMT) was also prepared for comparison purposes. The composites were irradiated with electron beam (EB) at an optimum irradiation dose. The formation of radiation-induced crosslinking depends on the type and concentration of the organoclay used in the preparation of nanocomposites as measured by gel content. Changes in the interlayer distance of the silicate layers with the increase of organoclay concentration were shown by the XRD results. Variation in the tensile properties of the nanocomposites with the increase of organoclay concentration depends on the formation of crosslinking as well as reinforcement effect of the organoclay. Improvement in thermal stability of the NR/EVA blend was also observed with the presence of organoclay.
Clay has been regarded as very important natural industrial materials. All these industries exploit the properties that clay can be molded into any shape and fired to dry without losing its form. A study was carried out on clay samples from eight sites in the north-eastern part of Peninsular Malaysia. The study was accomplished by using X-ray diffraction (XRD) technique. The x-ray diffraction spectra obtained enable the determination of the lattice spacing associated with the types of clay and nonclay minerals present in the samples. Results of the study shows that the major components of clay minerals present in all samples studied are kaolinite and illite. The presence of kaolinite is confirmed by firing test in which the kaolinite diffraction peaks disappeared upon heating the samples at 600 o C. The presence of non-clay minerals such as quartz, mica, feldspar and chlorite are also observed.
The linear and the mass attenuation coefficients of Rhizophora spp. wood in the photon energy range of 11.22 - 28.43 keV were determined. This was done by studying the attenuation of x-ray fluorescent (XRF) photons from selenium, molybdenum, silver and tin targets. Both the Kα and Kβ peaks were utilised. The results were compared with theoretical values for average breast tissues for youngage, middle-age and old-age groups calculated by using a XCOM computer programme. The mass attenuation coefficient of Rhizophora spp. was found to be close to that of the calculated young-age breast in this photon energy range.
Thirteen solid waste samples labeled as scales were collected from a storage area of a crude oil production industry and were analysed for radionuclides concentrations. The radium-226 and radium- 228 concentrations were found to be unexpectedly low, i.e. less than 20 Bqkg. However, six samples were found to contain 7 to 2240 Bq/kg 60 Co. Thus, besides naturally occurring radionuclides, there is a possibility to find artificial radionuclides in solid wastes from crude oil production industry.