Materials Science Forum Vol. 1000

Abstract: Peatland fire became a serious problem in Indonesia until nowadays. The most problem of peat fire was caused by converting peatland become plantation area, wherein need canal blocking to adjust water ground as crop planting requirement in peatland. The structure design of this canal blocking should be strong enough to block excessive water level degradation so that can sustain the peatland environment. The current design of canal blocking was used wood as building structure, which has nor water-resistant, therefore, it can be rotten and easy to collapse. Indonesian Rubber Research Institute (IRRI) has already developed novel technology of canal blocking, namely natural rubber composite based water level canal blocking to overcome this problem. This novel technology was used natural rubber composite as material structure, therefore it has higher water-resistant, longer service life, and higher acid resistance than traditional canal blocking. In addition, novel canal blocking has equipped with water level system, which could control the groundwater level were suitable enough for crop planting requirement in peatland. Indeed, novel canal blocking could sustain peatland environment through peatland fire risk reduction, carbon dioxide (CO₂) emission reduction and increase peatland plantation production. This technology has already installed in South Sumatera. Present work would be detailed review structure strength novel canal blocking, environment and economic impact on its application. The application result had determined successful to reduce CO₂ emissions up to 3,723.38 ton CO₂ /ha during 7 months installation. Furthermore, the production of the intercropping system (palm oil and corn) in peatland within novel canal blocking was increasing the profit wherein the B/C of novel canal blocking application was 1.77, while traditional design canal blocking application was 1.55.

Abstract: This study was conducted to investigate the effect of Al2O3 on characteristics of A356 reinforced composites. The addition of Al2O3 as reinforced varied from 2 vf-% to 15 vf-% through Stir Casting methods to obtain the optimum addition Al2O3 as reinforced in mechanical properties of composite A356 as matrix and Al2O3 as reinforcement. Magnesium with of 10 wt-% was added to improve wettability between Al2O3 particles and Al A356. Addition of Magnesium is expected to form the spinel phase MgAl2O4 in interface area between Al2O3 and Al A356.The optimum tensile strength was found at 2 vf- Al2O3 with value 131.55 Mpa. However, the value is still lower than the tensile strength of Al A356 As cast. It is caused due to the porosity and the agglomeration of Al2O3 were found in the microstructure of the composite Al A356/Al2O3. The Hardness increased from material monolithic Al A356 as cast, reached 37.43 HRB.

Abstract: There are more than 1000 species of cellulose plants available in fiber form. A number of them are by-products from the major food crops contain lignocellulosic sources and being investigated as composite reinforcement materials. Sugarcane bagasse and rice husk are potential reinforcement materials and they were used to reinforce polylactic acid (PLA) matrix to make green composites. In this research work, sugarcane bagasse was given two different kinds of treatment; some were alkali treated using 8 wt.% NaOH at room temperature for an hour and some other were steam treated at 0.75 MPa for 30 minutes. The fiber content of the composites changed with weight percentage ratios of sugarcane bagasse/rice husk/PLA was 25/0/75, 25/5/70 and 25/10/65. Flexural strength was tested in accordance with ASTM D790-17 and structural evaluation was evaluated using scanning electron microscope (SEM) on the fracture section of the flexural test samples. Composites produced using steam treated sugarcane bagasse and rice husk have lower area density (1277-1385 g/m²) compared to the ones formed using NaOH treated bagasse and rice husk (1162-1500 g/m²). Both values of area density are below the density of neat PP and wood flour reinforced PP/PE composites used as reference materials. The flexural test shows the NaOH treatment on the bagasse fibers improve the flexural strength of the composites but the rice husk content introduced to the structure reduces the strength of the composites. SEM evaluation shows fiber fracture and few pull-out.

Abstract: Magnetite nanoparticles have been successfully prepared by hydrothermal method from FeCl₃ as starting material. The properties and morphology of the products with different synthesis time and FeCl₃ concentration were investigated. Firstly, the FeCl₃ with concentration of 0.05 – 0.15 M and 0.10 M sodium citrate as well as 0.15 M were mixed with distilled water containing 0.1 g polyethylene glycol. Subsequenly, the solution was transferred into a Teflon-lined autoclave and it heated into an oven at 210°C for 12 hours. The black precipitate that formed was separated by a bar magnet, then washed with water and ethanol, and dried at 60°C overnight. The magnetite formation begun at 3.5 hours synthesis time with crystal diameter in range of 9.4-30 nm. The crystallinity and crystal size of magnetite increased with reaction time and concentration of FeCl₃. The magnetite nanoparticles had a mesoporous structure and bigger pores at higher concentration. The saturation magnetization (Ms) of magnetite was in the range of 59 – 81 Emu/g with coercivity value was near to zero showing that magnetite nanoparticle had superparamagnetic properties.

Abstract: The purpose of this study was to investigate the influence of oleic acid as an additive in palm and coconut oils on tribological properties. Palm and coconut oils are vegetable oils that are consisted of free fatty acid, which one of the materials used as a source of environmental lubricant. Fatty acids in vegetable oil consist of saturated fatty acids and unsaturated fatty acids. Palm and coconut oils are rich in palmitic acid, which is categorized as saturated fatty acids. Whereas oleic acid is unsaturated fatty acids, and it has good lubricity as a lubricant. The effect of variation of oleic acid (10wt%, 20wt%, and 30wt%) in palm and coconut oils was investigated on tribological properties. The tribological properties were investigated by using a pin on disc apparatus and a ball bearing test rig. The results show that the effect of 10%wt oleic acids in coconut oil significantly increased its tribological properties with Δ scar width around 96 μm and 154 μm for the inner race and outer race, respectively.

Abstract: Compressive strength of cement mortar is an important parameter in the quality control of Portland cement. The limitation of Ottawa sand imports has prompted a study on the potential and utilization of local silica sand available in several regions in Indonesia. The purpose of this study was to investigate the potential and possibility of utilizing local silica sand from several regions in Indonesia including Bangka, Belitung, Sidrap (South Sulawesi Province) as a substitute for standard Ottawa sand in cement mortar testing. Evaluation of local silica sands consisted of SEM analysis, characterization of silica sands and testing of cement mortar compressive strength. Silica sands from Bangka, Belitung and Tuban had silica content of more than 90%, while that from Sidrap was more or less 90%. Based on the SEM analysis, characteristic of silica sands, and compressive strength of cement mortar, local silica sand from Sidrap (South Sulawesi Province) has a good potential to be used as a substitute for standard Ottawa sand in testing of cement mortar.

Abstract: Zirconia (ZrO₂) powders doped with cobalt were prepared by sol-gel method using inorganic salt of zirconium (IV) chloride (ZrCl₄) as precursor. The amount of cobalt was varied in the range of 4–16% weight percent to study the effect to structural properties. X-ray diffraction (XRD) analysis suggested the resulting phases were zirconium oxide (Baddeleyite) with monoclinic crystal system along with cobalt oxide as secondary phase. The increasing cobalt content caused the XRD peaks to shift into lower angle due to substitution of Zr atom to smaller Co atom in crystal lattice. Scanning electron microscope (SEM) images showed the samples with higher Co content had smoother surface. Generally, the microstructures of Co doped zirconia powders consisted of large agglomerates with small particles on the surface.

Abstract: Gallium-based liquid metals have been used widely in many industries because of their unique properties such as high electrical conductivity, the superconductive character at low temperature, and high thermal conductivity. For heat management application, Gallium based metal can be used directly in the liquid form, or in solid particle form. The solid form, however, has extensive application because it can be used as a microparticle additive to create a microfluid. In this research, the ultrasonic oscillator was used to synthesize sub-micron Gallium based particles. Ethanol and Polyethylene Glycol was used and compared as a medium during ultrasonication. Up to 15 %wt of the solid particle was successfully synthesized from one gram of liquid metal source using this simple method.

Abstract: Tungsten Carbide (WC) hard coating is widely used to coat the surface of the steel tools which provide tribological properties. In this paper, 0.25 wt% & 0.35 wt% of Carbon Nanotubes (CNT) were mixed with tungsten carbide (WC) powders as the feedstock powders. Method of solution dispersion in ethanol media using an ultrasonic device was used for coating the surface of WC powders with CNT powder. The mixed powders were then used as the feedstock powder to coat onto the surface of tool steel using the flame spraying process. The coated surface microstructures were observed under a scanning electron microscope (SEM), x-ray diffraction (XRD), and the energy dispersive spectroscopy (EDS) was used for the phase characterization and identification. The wear rate of coated steels was determined using the Ogoshi machine, and the Vickers hardness method used to measure their microhardness. The effects of CNT on the microstructure of the coated material and the surface mechanical properties were investigated. The results showed that the mixture powder preparation using an ultrasonic method in SDS solution and the ball-milling process was suitable to disperse the CNT on the surface of WC feed powders due to produce an adequate relationship between CNT' and WC powders increasing the surface mechanical properties of coatings. The wear resistance of the coated material produce using the mixture of WC powder with 0.35 wt% CNT increased around 50% higher than the WC coated steel without CNT addition. Also, the hardness of coating reinforced CNT increased significantly compared with the hardness of WC coated and the steel substrates. Microhardness value from the base metal to the WC-CNT coated steel increased from 550 HV to 1717 HV and also the wear rate from the base metal to the WC-CNT coated steel decreased from 0.86 mm³/min to 0.017 mm³/min. These results indicate that CNT is an excellent alternative to improve the surface mechanical properties of WC coatings.

Abstract: The chrome alloy has better affinity with nitrogen atom in nitriding process than any other alloy elements in steel. The higher content of chrome element binds larger number of nitrogen atoms. However, the higher concentration of nitrogen atom on the surface of the steel does not often make thicker case depth. This study clarified the phenomenon. The nitriding process was performed in two stages, namely the boost stage in the fluidized bed with the composition of 80 % NH₃ and 20 % of N₂ in 4 hours at 550 °C. Subsequently, the diffusion process was carried out in fluidized bed with the gas composition of 100 % N₂ HP (high purity) in 2 hours. The chemical composition was measured by spectrometry and EDAX. The case depth was identified by micro-Vickers, and metallography was observed by SEM. The concentration of nitrogen atom on the surface of AISI 316 L is twice higher than that on the AISI 4140. The result shows that 0.1 to 1 wt % of nitrogen atom creates diffusion layer, 1 to 5 wt % of nitrogen atom produces nitride layer of γꞌ and ε, and nitrogen atom above 5 wt % forms white layer. The layer strongly depends on the percentage of nitrogen atom concentration. The nitrogen atom concentration is determined by the concentration of chromium element within the steel (AISI 316 L). Meanwhile, the depth of nitrogen atom diffusion is highly determined by the alloy element of Fe (AISI 4140).