Advanced Materials Research Vol. 858

Abstract: The main objective of this study was to investigate the effect of the pre-vulcanization temperature on mechanical and rheological properties of starch filled natural rubber (NR) latex films. The 10 phr filler loading of starch was added into the latex prior to the pre-vulcanization process at 60°C to 140°C. The dipped films were cured in the oven at 100°C for 20 minutes and cooled at room temperature for 24 hours before stripping. The rheological properties of NR latex compounds were studied based on the viscosity measurement. The tensile and tear tests of starch filled NR latex films were also carried out. The results indicated that the rheological properties of the latex compounds showed shear thickening behavior where viscosity was increased with the increase in shear rate and pre-vulcanization temperature proportionally. The pre-vulcanization temperature at 80°C showed the optimum mechanical properties of starch filled NR latex films.

Abstract: Incorporated with pore sizes of 2-50 nm, CHA was found to be a promising drug delivery agent for disease treatment and could be a carrier for different types of proteins. A desired drug delivery system should consist of an ordered pore network, optimum pore size, and volume, as well as a high surface area, to allow a high drug adsorption rate, controllable drug loading, and release. However, until now, most results are still not up to expectation; since the BET surface area and pore volume obtained has been rather low, compared to the existing mesoporous silica. The objective of this work was to investigate the effect of surfactant washing on the pore characteristics and the importance of this step in the synthesis process of mesoporous carbonated hydroxyapatite (CHA). In this study, mesostructured CHA particles were prepared, via a self-assembly mechanism, between CHA and non-ionic surfactant (P123), using the co-precipitation synthesis method. The synthesized mesoporous CHA samples were washed five times using different types of solvents for surfactant removal. A sphere-like particle shape of CHA was observed under SEM for all samples; regardless of the type of solvent used. The formation of CHA was confirmed by FTIR analysis, where the carbonate ion peaks were observed in the spectrums. It was found that the mesoporous CHA with a high surface area was synthesized when high polarity solvents were used during surfactant washing. These results imply that high surface area mesoporous CHA can be obtained through surfactant washing, without applying calcination for surfactant removal, which may change the structure of the CHA during heat treatment.

Abstract: Wollastonite filled natural rubber (NR) compounds were prepared using a laboratory two-roll mill. The filler was loaded into NR at different loading, i.e., 0, 10, 20, 30 and 40 part per hundred of rubber (phr). The effect of wollastonite on curing characteristic, tensile and morphology properties has been studied. Results indicated that the cure time (t₉₀), scorch time (t₂), tensile strength and elongation at break of the NR compounds decrease with increasing wollastonite loading but the maximum torque, tensile modulus M100 (stress at 100% elongation), M300 (stress at 100% elongation) increase with increasing wollastonite loading. The fracture surface morphology of the NR compounds was investigated with a scanning electron microscope (SEM). More filler detachment from NR surface was observed with increasing wollastonite loading.

Abstract: A study on the crystallization behavior of a soda-lime-silica glass composition incorporating rice straw ash was carried out. Melting was carried out at 1500^°C in an alumina crucible for 5 hours. The glass produced was examined by differential scanning calorimetry to determine the glass transition and crystallization temperatures for use as heat-treatment temperatures to transform the glass into glass-ceramics. A similar composition made up using industrial chemicals was also melted for comparative purposes. Both glasses were heat-treated at 750°C and 920°C for 3 different soaking durations. Both glasses exhibited crystallization from the outer surface which increased in thickness as the soaking time was increased. Scanning electron microscopy was used to study the thickness and identity of the crystalline phases formed. Density and hardness measurements showed that the rice straw glass ceramics exhibited higher values than the glass-ceramics using industrial chemicals. The morphologies of the fracture surfaces of both glass-ceramic compositions were also evaluated by scanning electron microscopy.

Abstract: Since the introduction of the so-called Green Tyre concept, in the early 90ies, the use of silica as reinforcing fillers has spread and grown worldwide. The general advantages of silica as reinforcing filler over carbon black filler are better rolling resistance by achieving at least equal wet traction while tread wear should not be adversely affected.In general, high filler loading attributes poor dispersion and lack of adhesion to the rubber matrix which in turn affect the processability and physical properties of the rubber compounds. In this work, the objective of the study was to investigate the influence of viscosity on silica dispersion and in relation to mechanical and performance properties of Epoxidised Natural Rubber (ENR) compound. The viscosity of the compound was measured via viscometer. The filler flocculation and dispersion was monitored by following the changes in torque and storage modulus at low strain using rheometer MDR 2000 and DisperGrader. The filler network on the other hand was characterised by Rubber Processing Analyzer (RPA) and bound rubber measurements. The physical tests were also done according to the ASTM methods such as tensile strength and abrasion. Results showed that low viscosity of rubber will facilitate further the dispersion of the filler in the system although other physical properties will be affected.

Abstract: Statistical design analysis (factorial design) was utilized to verify the significance and the interaction between the studied factors include temperature, reduction time and catalyst amount. Carbothermal reduction of iron ore sample was carried out at temperature between 1000°C to 1200°C. The effects of operating parameters studied were extent of reduction (X), carbon consumed (C_consumed ) and nitridation (X_N). Temperature was the most influential parameter that showed strong interaction with the operating parameters, meanwhile, reduction time and catalyst have showed the contrary results and had a very low percentage of contribution. The results of the experimental design showed that the extent of reduction reached up to 93% at 1200°C using 10 wt. % catalysts after 180 minutes reduction. The use of 0-10 wt % catalyst at 1200°C for 180 min reduction significantly affect the X but did not for C_consumed and X_N.Keywords: Carbothermal Reduction, Factorial Design, Malaysian Ilmenite, Nitridation.

Abstract: Electric arc furnace (EAF) steel slag solubility was studied using experimental design and statistical analysis. The solutions between pH 4 and 10, were mixed with the EAF steel slag for 0.5 hours at 350 rpm. The effects of the operating parameters, individually and their interaction, on the dissolution of slag elements were assess using full factorial design in the statistical design of experiment. The various parameters studied were pH (4-10), size (+0.2-1.2 mm), speed (0-700 rpm) and temperature (26-50°C). The results of the experimental design indicated that the main significant parameter within the ranges studied for Cr (VI) dissolution in solution was higher speed, lower size for Ca dissolution while for Si, was the positive interaction of speed and size. Maximum Cr (VI) of 0.0104 mg/L was obtained in solution at pH 10, slag size of 0.2 mm, temperature of 50°C and rotational speed of 700 rpm. Also, complimenting the solubility studies was slag characterization using XRF, XRD and SEM/EDX analysis. From these results, it can be concluded that the operating parameters considered individually and their interaction have effect on the solubility of EAF steel slag.

Abstract: The Pulai fluviatile gold placer deposit stretches along 17 km of the upper reaches of Sungai Galas, Gua Musang, Kelantan. Malaysia Mining Corporation (MMC) had proved-up sizeable reserves following drilling and bulk testing during 1979-1983. The valley alluvium ranges up to 1200 m wide and averages 6.2 m in thickness. The basal gold-bearing Kaksa comprises bimodal channel lag pebble-gravels with the gold especially concentrated immediately above the bedrock and in potholes. The detrital gold is medium to very coarse sand size, moderately sorted, and occurs as fine grains, scaly flakes and platy nuggets. Concentration of gold was especially favoured in two depositional environments. In the slope interruption zones at the confluence of the Galas and Tuang streams, coarse platy gold was deposited while the finer gold was able to be entrapped further downstream above irregular limestone bedrock surfaces. The gold is of relatively high fineness (950-982), and is probably related genetically to acid intrusions. Important primary sources lie near the Kelantan-Pahang border, 35 km SE of Pulai village, while small granite stocks occurring 3 km west of Pulai are an additional likely source [1].

Abstract: The low grade gold ore obtained from a local gold mine in Malaysia was characterized using X-ray fluorescence analysis and scanning electron microscope/ energy dispersive X-ray analysis for the deportment of gold. Acid digestion was carried out to determine iron, aluminium, sulphur and arsenic using ICP-OES. Chemical assaying methods viz aqua regia leaching and lead fire assay followed by acid digestion were conducted to determine the head grade of the gold ore. Assessment of gold using fire assay was found reliable to reduce the interferences from the gangue minerals. Despite the lower limit of detection of ICP-OES, there was no appreciable amount of gold detected in the samples leached using aqua regia because of the interference from the gangue minerals and also due to the interlocking of gold with aluminosilicates phase which require high pressure and temperature leaching using hydrofluoric acid to liberate the gold. ICP-OES analysis is reliable depending on the degree of liberation of gold during acid digestion. The head grade for this type of low grade gold ore was found to be in the range of 0.31 g/t to 0.55 g/t where the gold was highly associated with aluminosilicate minerals.

Abstract: Silica sand from Kandal province, Cambodia and Tapah Perak, Malaysia was grounded into an average micron size of 128.12 and 132.68µm. Both sands were characterized by X-ray fluorescence (XRF), X-ray Diffraction, particle Size Analysis, Differential Thermal Analysis and Thermogravimetric Analysis (DTA/TGA). Malaysian silica sand was designated SDMTP and Cambodian Silica sand as SDCK. From theanalysis, XRF showed that the major impurities in SDMTP were Al₂O₃, K₂O and TiO₂. On the other hand, SDCK had impurities of Al₂O₃,K₂O and Na₂O. DTA results from SDMTP and SDCK showedthere is an endothermic peak occurring at 572°C which can be attributed to β-quartz transformation into α-quartz. TGA for SDMTP showed that maximum weight lost was at 441°C with a weight percent (wt%) change of 0.48%. The TGA for SDCK showed a wt% change of 1.298% at temperature of 1000°C. From XRD analysis, the main phase of SDCK and SDMTP were quartz. The impurities of both sands play an important role in determining the optical and mechanical properties of the soda lime silicate (SLS) glass formed. Particle size of silica sand affects the mechanical properties such as compression, hardness, and transmittance of SLS glass. The smaller particle size would be ideal choice for glassmaking. Melting temperature, soaking time, and melt accelerant can also affect the mechanical properties of SLS glass. The best result obtained for Vickers hardness in this study was the SLS glass sample designated as Run No 12 with a value of 525.02 kg.mm^-2. It had a particle size range from 500-600µm, a furnace soaking time of 4 hours at a melting temperature of 1500°C with 1.0 wt% of Sodium Chloride (NaCl) as meltingaccelerant. On the other hand, the highest compressive strength of 356.22 MPa was found in sample designated as Run No 1. It had a particle size range from 75-1800µm, a soaking time of 5 hours at a melting temperature of 1550°C with 0.5 wt% of NaCl. Lastly,the highest UV-VIS transmittance at 520 nm was obtained from sample designated as Run No 5 within the value of 84.26 %Transmittance (T). It had a particle size range of 75-1800µm, soaking time of 3 hours at a melting temperature of 1550°C with 1.5 wt% of NaCl. .