Nancy J. Siambun

The effectiveness of palm oil methyl ester as lubricant additive in milling and four-ball tests

This paper examines the effectiveness of palm oil methyl ester (POME) as lubricant additive using the four-ball and milling tests. In milling 55 HRC-stavax® (modified AISI 420 stainless steel) under flood lubrication, three stages of tool wear occurred: 1) initial wear by delamination, attrition and abrasion; 2) cracking at the substrate, 3) followed by formation of individual surface fracture at the cracks which would then enlarge and coalesce to form a large fracture surface. Mineral oil sprayed in mist form was more effective in reducing the coating delamination and delaying the occurrence of cracking and fracture. The effectiveness of mineral oil in suppressing these wear modes could be enhanced by the presence of POME. The mechanism by which the POME suppressed these wear modes could be explained by the results obtained in the four-ball tests which showed that the presence of POME as additive in the mineral oil reduced the friction coefficient, severity of welding and increased the critical load for welding to occur.

Dry Sliding Behaviour of AlCrN and TiN Coatings

This paper examines the friction behaviour of AlCrN and TiN PVD coatings in atmospheric air and vacuum using a ball-on-disc and a reciprocating tribotesters. Comparative study on the coating sliding in air and in high vacuum environment provides important insight on the effect of oxidation on the friction behaviour of the coatings. Other important factors such as load, sliding velocity, temperature effects on the frictional behaviour of these coatings were also investigated. In the ball-on-disc tests carried out in vacuum, (i) TiN gave lower coefficient of friction (COF) than AlCrN, indicating that TiN was more lubricous, (ii) higher speed resulted in lower COF, and (iii) the COF of both coatings were lower than that produced in air. In ambient air, (i) AlCrN gave lower COF than TiN with high wear debris retention on the sliding interface due to the effect of oxidation, and (ii) higher speed resulted in lower COF, similar to that observed in vacuum. In the reciprocating tests, at low load, increasing the temperature from room temperature to 150 °C resulted in a reduction in the COF. However, at high load, the temperature virtually did not affect the COF. Higher nominal load resulted in lower COF while higher speed resulted in higher COF.

Variation of reaction stages and mole composition effect on melamine-urea-formaldehyde (MUF) resin properties

MUF resin is widely used as an adhesive in wood industries, coating technology, paper industries and a main material in kitchenware production. In various applications, different resin properties are needed to suit its application. Important resin properties are for example higher resin solubility, low curing period with lower temperature and catalyst amount, good stability for longer shelf life, and lower free )brmaldehyde emission, as formaldehyde is very toxic, and can cause cancer. One of the factors that affecting the MUF resin properties is the mole composition. The mole composition is a ratio of/brmaldehyde to amino compound i.e. melamine or urea, in each reaction stages. Besides that addition of other chemical such as sorbitol, may be added to enhance the resin properties. In Turin (1998)and Gapud et al. (1999) researches, addition of sorbitol has improve the resin stability and solubility in water and also cured resin flexibility. Using experimental design such as Surface Response Method optimises the product formulation. This method is more satisfactory and effective than other methods such as classical one-at-a-time or mathematical methods because it can study many variables simultaneously with a low number of observations, saving time and costs. Hence in this research, statistical experimental design or mixture design is used in this work in order to optimise the MUF resin formulation.

The Effect of Cooling Rate in Molten Salt Electro-Carburisation Process

In the recent development of a new process of electro-carburisation of mild steel in 800 °C molten carbonate based salts, further investigation has been carried out to study the effects of the cooling rate after the electro-carburisation process. In the process, the mild steel to be carburised was made the cathode and an inert SnO2 as anode. Salt mixture of Na2CO3-NaCl (mole ratio 4:1) was used as the electrolyte, and the process was carried out at voltage range of 1.0 to 2.5 V for 60 minutes, and thereafter cooled at certain rate. As revealed by the optical microscopy, the microstructural changes in samples that have been electro-carburised and thereafter cooled either rapidly or naturally in air, were featured by the increase of the carbon rich in the martensite structure at the expense of the original ferrite phase near the surface of the samples. Micro-hardness profiles measured from the surface to the centre of the electro-carburised sample presented clear evidence of carbon penetration as a function of the electrolysis voltage, and significant effects of cooling rate after the electro-carburisation process.

The Effect of WS2 Powder Added Lubricant on Friction and Wear of Tetrahedral Amorphous Carbon Coating Films

The influence of nanopowder on the tribological properties of ta-C films were examined under the lubrication condition. The addition of the tungsten disulphide, WS2 nanopowder in the synthetic oil, polyalpha- olefin, PAO4 was used as the base lubricant in this experiment. The weight percentages of the additive used are 0, 3.0, 4.0, and 5.0 wt % to understand the concentration effect on the tribological behavior of ta- C films in this study. For the sliding test, the result has shown it is not much different in the friction coefficient results for all cases. Whereas, the wear rate result has shown the obvious trend of which the weight percentage of additives changes the wear resistivity. In this study, 3.0 wt % shows the lower wear rate result at 0.1494 × 10–6; 0.1819 × 10–6 mm3/mN for 4.0 and 5.0 wt % shows the highest wear rate result at 0.2393 × 10–6 mm3/mN. These results were due to the changes in surface roughness due to the different amounts of the additive that have been added.

Carbon materials derived from rice husks at low and high temperatures

Rice husk (RH) can be classified as an agriculture residue, majorly produced from by-product of rice milling industries. However, RHs are only mainly utilized for low value energy resource. A great number of researches and innovations have shown that heat treated RHs can turn into valuable carbon materials. In this study, the RHs were carbonized at 800°C and 2500°C, respectively. Their structure, morphology, elemental composition, and quality were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The carbon materials obtained from low and high temperature carbonization processes showed different characteristics. High purity and crystallinity of carbon materials were obtained from RHs carbonized at 2500°C. Furthermore, from Raman results, RHs carbonized at 2500°C exhibited low D/G ratio. This further reveals that the RHs carbonized at 2500°C possess minimal defects. The unique characteristics of RHs carbonized at high temperature indicate that they could be a promising material to be utilized in particular or various applications.

Fabrication and Characterization of Carbonized Rice Husk/Barium Titanate Nanocomposites

Carbon materials were prepared by carbonizing rice husk (RHs) at 2500°C. Few- and multi-layer graphene were obtained from this carbonization process. Barium titanate (BTO) nanoparticles were fabricated by using sol-gel method. Then, the BTO nanoparticles were grafted onto the surface of carbonized rice husk (CRH) to fabricate CRH/BTO nanocomposites. The nanocomposites were characterized using scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman measurement, and X-ray photoelectron spectroscopy (XPS). Based on the broadening of (1 1 0) peak from XRD result, the average crystalline size of BTO nanoparticles were calculated to be 16.5 nm. Coexistence of cubic and tetragonal phase of BTO nanoparticles is expected, based on the XRD and Raman results. From XPS result, carbon, barium, titanium, and oxygen peaks were also observed. The combination of CRH with BTO can integrate the properties of these two components to form nanocomposites for broad applications.

Electromagnetic wave absorption properties of rice husks carbonized at 2500 °C

The rice husk (RH) samples were prepared by pre-carbonization at 800 °C, and then further carbonization at 2500 °C (RH2500), under the presence of Argon gas. The RHs were characterized using Field Emission Scanning Electron Microscopy, Transmission Electron Microscopy, and X-ray Photoelectron Spectroscopy. The RH2500 were then incorporated into paraffin wax with different weight percentage (20, 30, 40 wt.%), and designed into toroidal shape with thickness of 1.0 mm to evaluate their complex permittivity and complex permeability using vector network analyzer. The reflection loss (R.L.) of the samples was calculated according to their measured complex permittivity and permeability. The RH 30 wt.%, with thickness of 1.0 mm showed highest electromagnetic wave absorption performance in contrast to the samples with similar thickness but different weight percentage, with minimum R.L. of ∼-14.04 dB (over 96% absorption) at 10.0 GHz. Furthermore, based on the calculation using transmission line theory, RH 30 wt.% ...

Synthesis, characterization and catalytic activity of carbon-silica hybrid catalyst from rice straw

The hybrid-carbon catalyst has been studied because of its promising potential to have high porosity and surface area to be used in biodiesel production. Silica has been used as the support to produce hybrid carbon catalyst due to its mesoporous structure and high surface area properties. The chemical synthesis of silica-carbon hybrid is expensive and involves more complicated preparation steps. The presence of natural silica in rice plants especially rice husk has received much attention in research because of the potential as a source for solid acid catalyst synthesis. But study on rice straw, which is available abundantly as agricultural waste is limited. In this study, rice straw undergone pyrolysis and functionalized using fuming sulphuric acid to anchor –SO3H groups. The presence of silica and the physiochemical properties of the catalyst produced were studied before and after sulphonation. The catalytic activity of hybrid carbon silica acid catalyst, (H-CSAC) in esterification of oleic acid with me...

Synthesis and characterization of supported sugar catalyst by dip coating method

Sugar catalyst is a novel solid acid catalyst with reactivity comparable to that of sulphuric acid in biodiesel production. However, the fine powder form of sugar catalyst with the non-porous structure might cause large pressure drop in a packed bed reactor due to low bed porosity, affecting the reaction conversion especially in gas phase reaction. Furthermore, higher pressure drop requires higher electrical energy to drive the fluid through. Increasing the particle size is anticipated to be able to overcome the pressure drop matter. Hence, a deposition of sugar catalyst on larger particle materials was studied. Three types of materials were used for this investigation namely aluminum, silica and clay. The deposition was done via dip-coating method. The materials were characterized for their total acidity, thermal stability, functional groups, surface area, and element composition. The total acidity for SCDCAl, SCDCSi, and SCDCCl were 0.9 mmol/g, 0.2 mmol/g, and 0.4 mmol/g, respectively. The ratio of char deposited on SCDCAl, SCDCSi and SCDCCl were 0.9 g of support/g of carbon, 0.040 g of support/g of carbon, and 0.014 g of support/g of carbon respectively. FTIR and EDX analyses were carried out to determine the presence of active sites of the catalysis by identifying the functional groups such as -COOH, -OH, -SO3H. The results showed that -SO3H was detected on the surface of synthesized catalysts, except for SCDCC1.The pore size of SCDCAl, SCDCSi and SCDCCl were classified as macropores because the average diameter were greater than 50nm.. The catalysts were stable up to 400°C. The results showed that the dipcoating method could deposit sugar catalyst on aluminum, silica, and clay at low total acidity concentration.