OBJECTIVES: The aim of the present study was to test cutting efficiency of different materials against conventional alumina in an air abrasion system.
MATERIALS AND METHODS: The powder samples were divided into three groups: Group 1 - alumina (control), Group 2 - 45S5 bioactive glass, and Group 3 - hydroxyapatite. 30 microscope glass slides of 0.5 mm thickness were used as an alternative of human enamel and were also divided randomly into these three groups. The time taken by the abrasive particles to cut a hole through the microscope glass slide was recorded with a stop watch. In addition, morphology of the particles was observed through scanning electron microscopy (SEM). A t-test was used to compare the times taken to cut a hole through the microscope glass slides, and the level of significance was set at P < 0.05.
RESULTS: The mean time taken to cut a hole through the microscope glass slide was 2.96 s and 23.01s for Groups 1 and 2, respectively, whereas powder of Group 3 did not cut after 120 s. The differences between cutting times of Groups 1 and 2 were statistically significant (P < 0.05). The SEM micrographs revealed coarse angular shape for particles of Groups 1 and 2 but Group 3 particles were with round ends and presence of smaller particles was also observed in Groups 2 and 3.
CONCLUSION: The alumina particles demonstrated excellent cutting efficiency followed by 45S5 particles. The use of bioactive glass particles should be encouraged for cutting purposes whenever a shortage of time for practitioners is not a concern.
A systematic study to assess the concentration of radionuclides in primary coolant and associated water samples from the operation of a TRIGA Mark II reactor has been carried out. The samples were transferred into appropriate counting container and were counted by efficiency-calibrated gamma spectrometer systems for several hours to obtain statistically adequate data for qualitative and quantitative evaluation of the radioactive materials presence. The primary coolant was found to contain various gamma emitting radionuclides including 24Na, 41Ar, 42K, 51Cr, , 54Mn, 56Mn, 60Co, 99mTc, 122Sb, 124Sb and 187W. Most of the detected radionuclides were inferred to be originated from activation products of (n,) nuclear reactions of elements of reactor components such as stainless steel and aluminium alloy used in the reactor system. The study confirms the integrity of the reactor system with no apparent release of any fission products radionuclide into the coolant water system.
Compartmented Fluidized Bed Gasifier (CFBG), consisting of two compartments - the combustorand gasifier, uses air blown instead of pure oxygen for syngas production in bubbling fluidization mode, eliminating the need of air separation unit, and reducing the capital cost, thus distinguishes it from other traditional ones. Fluidization quality is a determining factor in the CFBG to guarantee its well-lifted behaviour. Previous study, without solid circulation at ambient conditions, brought to the fore the necessity of considering the effect of the minimum allowable effective diameter. The study was then performed in the CFBG cold physical model of 0.66m overall diameter (effective diameter for combustor and gasifier is 0.413m and 0.257m) to investigate the fluidization quality and compare it with the results obtained from the previous cold model of about 1.36 times smaller, but with the same compartmented ratio of 65:35. Different inert particles (river sand, quartz sand and alumina) were used, over a range of aspect ratios, for the aforementioned objective. The results showed that the fluidization quality in the gasifier has not been achieved and the degradation of fluidization quality in the combustor is still observed, notwithstanding the fact that the condition of the minimum allowable effective diameter has been met. The reduction of distributor free area, to increase the distributor pressure drop, showed a marginal effect on the quality. The effect of the minimum allowable effective diameter on fluidization quality in CFBG as well as the interplay of geometric and operational parameters require further studies be carried out. The fluidization quality of the binary mixture is also currently under investigation.
The adsorption equilibrium time and effects of pH and concentration of ¹⁴C-labeled chlorpyrifos
O,O-diethyl O-(3, 5, 6 trichloro-2-pyridyl)-phosphorothiote in soil were investigated. Two types of Malaysian soil under oil palm were used in this study; namely clay loam and clay soil obtained from the Sungai Sedu and Kuala Lumpur International Airport (KLIA) Estates, respectively. Equilibrium studies of chlorpyrifos between the agricultural soil and the pesticide solution were conducted. Adsorption equilibrium time was achieved within 6 and 24 hours for clay loam and clay soil, respectively. It was found that chlorpyrifos adsorbed by the soil samples was characterized by an initial rapid adsorption after which adsorption remained approximately constant. The percentage of ¹⁴C-labeled chlorpyrifos adsorption on soil was found to be higher in clay loam than in clay soils. Results of the study demonstrated that pH affected the adsorption of chlorpyrifos on both clay loam and clay soils. The adsorption of chlorpyrifos on both types of soil was higher at low pH with the adsorption reduced as the pH increased. Results also suggest that chlorpyrifos sorption by soil is concentration dependent.
Aluminium titanate (AT) (Al2TiO5) is a promising engineering material because of its low thermal expansion coefficient, excellent thermal shock resistance, good refractoriness and non-wetting with most metals. Functionally graded material (FGM) is generally a particulate composite with continuously varying volume fractions. FGMs are alternative materials for dental implants, building materials and ballistic protection. It has been of great interest to future engines, internal combustion engines, metal cutting and other high temperature engineering application. There has been a demand for an adequate disc brake that requires less maintenance in the automotive manufacturing industry. FGM, the next evolution of layered structure, consists of graded compositions that are dispersed across the ceramic which produces a gradual improvement in the properties across the ceramic at a steady pace.
The long term objective of this research is to look into the possibility of replacing soil strength parameters such as cohesion and angle of friction with electrical resistivity value for the purpose of computing among others, factor of safety in slopes or bearing capacity of soil. This paper however is limited to the investigation of correlation between electrical resistivity with some selected soil parameters. Electrical resistivity tests, using a basic multi meter, steel moulds and other related equipment, were conducted in the laboratory on soil samples with variations in soil type, compaction energy and moisture content. The samples consisted of predominantly clay, silt and sandy size particles and were compacted in a 100 x 100 mm square mould, while the corresponding electrical resistivity tests were carried out using the disc electrode method in accordance to BS 1377. The values of the electrical parameters such as voltage, current and resistance, with the corresponding value of soil parameters such as cohesion, angle of friction and moisture content, were measured and recorded. The results of the tests produced some initial crude relationships between electrical resistivity and the selected soil parameters. The strongest correlation between electrical resistivity and angle of internal friction, φ, was obtained from the clay size samples with R2 of 0.824, while the maximum correlation between electrical resistivity and moisture content again was obtained through the clay samples with R2 of 0.818. From the other results and graphs analyzed, some consistencies and specific trends of behaviour observed gave some early indications that a more detail and precise correlation between electrical resistivity and soil strength parameters could be very well possible in future.
Silicon, as the most important electronic material, has a lot of applications in the electronic industry and this includes the use of silicon in solar cells. One of the solar grade silicon production processes is the use of acid leaching for the removal of metallic impurities from silicon. The main advantage of this process for silicon purification is that it is based on a low temperature process. The purification of metallurgical grade silicon by acid leaching was studied as a function of time, temperature and etching. Based upon experimental results and under optimum conditions, it was possible to remove 41%, 71% and 25% of iron, calcium and aluminum respectively, with the use of aqua regia.
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.
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.
The purpose of this study was to determine the adsorption coefficient (Koc) of chlorpyrifos in clay soil by measuring the Freundlich adsorption coefficient (Kads(f)) and desorption coefficient (1/n value) of chlorpyrifos. It was found that the Freundlich adsorption coefficient (Kads(f)) and the linear regression (r 2 ) of the Freundlich adsorption isotherm for chlorpyrifos in the clay soil were 52.6 L/kg and 0.5344, respectively. Adsoprtion equilibrium time was achieved within 24 hours for clay soil. This adsoprtion equilibrium time was used to determine the effect of concentration on adsorption. The adsorption coefficient (Koc) of clay soil was found to be 2783 L/kg with an initial concentration solution of 1 µg/g, soil-solution ratio (1:5) at 30 o C when the equilibrium between the soil matrix and solution was 24 hours. The Kdes decreased over four repetitions of the desorption process. The chlorpyrifos residues may be strongly adsorbed onto the surface of clay.
Electrocoagulation has proven to be an effective method in the treatment of wastewater. This study evaluated the decolourisation of Palm Oil Mill Effluent (POME) using electrocoagulation (EC) batch reactor by utilising aluminium as sacrificial electrode. POME sample source from a final discharged pond at a palm oil mill was characterised for its colour, chemical oxygen demand (COD), pH, conductivity and turbidity; were found to be 2707 PtCo, 3909 mg/L, 7.63, 12.82 mS/cm and 755 NTU respectively. The respective effects of operating parameters such as pH (3 to 11), applied voltage (5 V to 20 V), plate gap (7.5 to 11.5 cm) and operating time (1 to 8 hours) were investigated. The decolourisation of POME was observed to increase with increasing voltage and operating time. Highest removal efficiency was observed at pH 5, 20 V applied voltage, 9.5 cm plate gap and at 8-hour operating time with colour removal efficiency of 89, 79, 78 and 64% respectively. From the findings, it can be concluded that electrocoagulation process using aluminium electrodes is a reliable technique for the removal of colour from POME.
The mismatch in coefficient of thermal expansion (CTE) between the veneered
porcelain and the ceramic core has been primarily identified as the cause of core/veneer chipping
in all-ceramic restorations. This study aimed to evaluate the effect of sodalite infiltration on the
CTE behaviour and bond strength of different all-ceramic prostheses. Materials and Methods: The
experimental groups were synthesised sodalite-infiltrated alumina (IA-SOD) and synthesised
sodalite-infiltrated zirconia-toughened alumina (ZTA) (IZ-SOD), while the control groups were glassinfiltrated alumina (IA-glass) and glass-infiltrated ZTA (IZ-glass). (Copied from article).
This study utilized the incorporation of nanoparticle filler into an epoxy system to study the effect of different nanosized
montmorillonite (MMT) fillers on the thermal stability and mechanical properties of epoxy. The sample was prepared
using diglycidyl ether of bisphenol A (DGEBA) with different surface treatments of montmorillonite filler by mechanical
stirring. The results of thermal stability and mechanical properties of epoxy/clay system obtained from thermal gravimetric
analyzer (TGA), universal testing machine (UTM) and scanning electron microscopy (SEM) were discussed. With the same
amount of filler introduced into the system, different thermal stability of epoxy composite can be observed. Bentonite,
which contained other contaminant components, can downgrade the enhanced properties of the filler.
Co-synthesis of In2O3 and ZnO nanowires (NWs) were grown on silicon and alumina substrates using vapour transport deposition method. Their morphological structures showed that the NWs were rather aligned on silicon substrate and randomly oriented on alumina substrate. The formation of NWs on silicon substrate was found to be dominated by the growth of ZnO NWs while that on alumina substrate was dominated by the growth of In2O3 NWs. The In2O3 and ZnO NWs were highly crystalline and have wurtzite structure.
A steady laminar mixed convection boundary layer flow about an isothermal solid sphere embedded in a porous medium filled with a nanofluid has been studied for both cases of assisting and opposing flows. The transformed boundary layer equations were solved numerically using an implicit finite-difference scheme. Three different types of nanoparticles, namely Cu, Al2O3 and TiO2 in water-based fluid were considered. Numerical solutions were obtained for the skin friction coefficient, the velocity and temperature profiles. The features of the flow and heat transfer characteristics for various values of the nanoparticle volume fraction and the mixed convection parameters were analyzed and discussed.
Aluminum foams were fabricated by sintering dissolution process (SDP) using sodium chloride (NaCl) as space holder. The compositions of space holder, used in this study were 40 and 60 wt. % with different dissolution times; 1, 2 and 3 h. The effect of different dissolution times on compressive behavior and energy absorption of foams were evaluated. The result showed that by increasing space holder and dissolution times, energy absorption capability increases. For aluminum foam contains 60 wt. % NaCl, longer dissolution times resulted in thinner cell wall and cell structure become more unstable which lead to lower plateau region.
Effects of aluminium hydroxide (ATH) addition on the properties of palm-based polyurethane composites were investigated. The hybrid composites were prepared by mixing 10 wt% of oil palm empty fruit bunch fiber (EFB) with ATH at varying amount of 2, 4 and 6 wt% of the overall mass of the resin. The compression stress and modulus gave the highest values of 575 and 2301 kPa, respectively at 2 wt% loading of ATH. The compression stress and modulus decreased drastically at 4 wt% (431 kPa and 1659 kPa, respectively) and further decreased at 6 wt% ATH (339 and 1468 kPa, respectively). However, the burning rate is inversely proportional to the loading percentage where the highest burning rate was observed at 2 wt% ATH. Sound absorption analysis indicated a large absorption coefficient at high frequency (4000 Hz) for all samples. The highest absorption coefficient was obtained from PU-EFB/ATH with 4 wt% ATH.
Hybrid composites of polypropylene (PP)/nanoclay (NC)/glass fiber (GF) were prepared byextrusion and injection molding. Molded specimens were analyzed by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), tensile and flexural tests. TEM results revealed NC particle intercalation. TGA results showed that the incorporation of clay into the GF composite improves the thermal stability of the material. The initial thermal decomposition temperatures also shifted to higher values. Incorporation of GF into PP lowers the tensile strength of the binary composite, indicating poor fiber-matrix interfacial adhesion. However, introducing NC increased the strength of the ternary composites. Tensile modulus was enhanced with the incorporation of GF and further increased with an introduction of NC. Flexural strength and flexural modulus are both enhanced with an increase in GF and NC loading.
This study analyzes the heat transfer of a thin film flow on an unsteady stretching sheet in nanofluids. Three different types of nanoparticles are considered; copper Cu, alumina Al2O3 and titania TiO2 with water as the base fluid. The governing equations are simplified using similarity transformations. The resulting coupled nonlinear differential equations are solved by the Homotopy Analysis Method (HAM). The analytical series solutions are presented and the numerical results obtained are tabulated. In particular, it shows that the heat transfer rate decreases when nanoparticles volume fraction increases.
Termites are found in various habitats, particularly diverse communities occurring in tropical forest and peatlands.
Termites are beneficial insects, which function as soil engineers, improving the soil quality. However, in peatlands
converted to commercial oil palm plantations, they are considered as pests. There is lack of studies on termite communities
in converted peatlands in Peninsular Malaysia. Thus, this study investigated termite species associated with oil palm
stands in three soil types (clay, shallow peat and deep peat) in Endau Rompin Plantation. The stand scouting method
was used to record the numbers and types of termites associated with palm trees in the individual stands on different
soil types. A total of 29 termite species associated with the palm stands were identified morphologically. All the species
belonged to the families Rhinotermitidae and Termitidae. Twenty-three of the 29 species were found in the shallow peat,
16 in clay soil and 15 in deep peat. The community structure was synthesized by two-way cluster analysis with Sorensen
(Bray Curtis) distance measure. Five termite groups associated with two soil types (clay soil and shallow/deep peat)
were generated. Moisture levels and organic content were likely to determine the presence of soil feeders identified in
the presence study. This study provides information on the status of termite species in oil palm plantation areas. Such
information may be useful in future planning strategies by the plantation management.