Anne Zulfia

The production of Al-Mg alloy/SiC metal matrix composites by pressureless infiltration

Metal matrix composites have been produced by pressureless infiltration of Al-Mg alloys into SiC preforms at 900°C under N2 for different infiltration times. The wettability of the ceramic reinforcement by the Al-Mg alloy is crucial in determining whether an MMC can be produced by pressureless infiltration. Sessile drop results show that Al alloys with Mg contents greater than 8 wt% had a contact angle lower than 90°C after 5 minutes contact time. This was in agreement with the pressureless infiltration results as MMCs have been produced after 30 minutes with these alloys. Sessile drop experiments also show that SiC is similarly wetted by Al-Mg alloys under both N2 and Ar. It is concluded that the infiltration process does not involve the intermediate nitride phase suggested by other authors.

Role of Mg and Mg+Si as external dopants in production of pure Al–SiC metal matrix composites by pressureless infiltration

Abstract Metal matrix composites have been produced by pressureless infiltration of pure Al into Mg doped SiC preforms after 1 h at 900°C. Aluminium has been found to infiltrate preforms containing between 2 and 14 wt-%Mg, however Al did not infiltrate a preform containing 1 wt-%Mg. Preforms doped with 1 wt-%Mg and Si did result in infiltration. Increasing the Mg content or increasing the Si content in the preform resulted in more extensive infiltration. The effect of Mg and Mg mixed with Si on pressureless infiltration of pure Al, microstructure of MMC as well as mechanical properties are discussed. Although the dopant was uniformly distributed throughout the preform microstructural analysis and hardness measurements indicate that the resultant composite may not be uniform due to infiltration inwards from the edge to the centre of preform.

Effect of hot isostatic pressing on cast A357 aluminium alloy with and without SiC particle reinforcement

The effect of Hot Isostatic Pressing (HIPping) treatments on porosity in the aluminium casting alloy A357 and stir-cast A357/15 vol % SiC particulate Metal Matrix Composite has been investigated. Densitometry and image analysis have been used to determine the apparent percentage porosity. Four HIPping temperature profiles have been investigated (103 MPa pressure) and mechanical testing has been carried out by single notch four point bending. The bend strength was increased after HIPping relative to as-received. The optimum HIPping cycle involved HIPping for a short time in the semi-solid region followed by a sustain below the solidus.

Hot isostatic processing of metal matrix composites

Abstract The effect of four different Hot Isostatic Pressing (HIPping) treatments on porosity in the aluminium casting alloy A357 and stir-cast A357/15 vol% SiC particulate MMC has been investigated and the optimum treatment identified. The bend strength increased after HIPping relative to as-received. Such ceramic particle reinforced MMCs, however, do not have adequate toughness for many commercial applications. Metal reinforced MMCs made by combining an Al alloy matrix with stainless steel wire can provide a compromise between weight saving and toughness. The production, involving HIPping, of such a composite is discussed.

Analysis of Coconut Carbon Fibers for Gas Diffusion Layer Material

The main compound of natural fibers is a hydrocarbon. The heating of hydrocarbon in inert gas produces charcoal or carbon. Carbon materials are widely used for several purposes depending on the physical and electric properties, for example for hydrogen storage, conductive or reinforced plastics, catalyst supports, batteries and fuel cells. The main raw material of Gas diffusion Layer (GDL) of the Proton Exchange Membrane Fuel Cell (PEMFC) is a carbon. The properties of GDL are porous and electron-conductive material, because of the function of GDL is to distribute the gas as fuel and electricity conductors. This study aims to analyze the carbon fibers made from coconut fibers for the application of GDL materials. The carbon fiber was made using pyrolysis process in the inert gas (nitrogen) at a certain temperature according to the analysis of Differential Thermal Analysis (DTA) 3000C, 4000C, 5000C, 6000C, and 9000C. The crystalstructure, carbon content, powder density and morphology of carbon fibers were observed using X-Ray Diffraction (XRD), fixed carbon according to ASTM D 1762-64, Archimedes method (BS 19202 Part 1A), and Scanning Electron Microscope (SEM), respectively. The results showed that the structure of carbon was amorphous, and content of 51% ̶ 71%, powder density of 0.42g/cm3 ̶ 0.71g/cm3. The morphology having many parallel hollows like a tube that are close to each other with diameters of 2m ̶ 10m, and in the wall of tube there are some porous with sizes around 1m. According to this analysis, the coconut carbon fiber enables to be applied as candidate for a basic material of GDL.

Study of the Electical Conductivity of Oil Palm Fiber Carbon

The physical properties of carbon from natural fibers are strongly influenced by the conditions of carbonization process. Temperature carbonization process of natural fibers affects the structure and electrical properties of carbon. This research studied the influence of carbonization process to the electrical conductivity and the microstructure of carbon from oil palm fibers. Oil palm fiber carbonization process has been carried out at the temperature of 500°C and 900°C for 1 hour in the atmosphere of inert gas (nitrogen) and at a temperature of 1300°C performed using a Spark Plasma Sintering (SPS). Structure of oil palm fiber carbon analyzed using XRD and SEM, electrical conductivity measurements carried out using LCR meter. XRD data analysis showed that the carbon structure is amorphous, and carbonization process up to 1300°C cause increase of the degree of crystallinity, that are 36.92%, 39.07% and 42.48% for 500°C, 900°C and 1300°C respectively. Increase of carbonization temperature also causes the electrical conductivity of carbon that are (3.3 x10-6) S/m – (4.8 x10-6) S/m for carbon 500°C, 1.29 S/m – 1.3 S/m for carbon 900°C, and (1.4 x10) S/m – (1.7 x10) S/m for carbon 1300°C.

Characterization of Al-Si-Mg/Al2O3 Nanocomposite Produced by Stir Casting Method

Al-Si-Mg reinforced with Al2O3 nano particles have been made by stir casting method. The vortex produced by stirrer is to distribute the Al2O3 nano particles in the molten aluminium. The volume fraction of Al2O3 nano particles was varied from 0.5, 1, 2, 3, to 5 Vf%, while the addition of magnesium was 3 Vf% as wetting agent to improve the wettability between Al2O3 nano particle and Al-Si-Mg matrix. The effect of Al2O3 on characteristic of Al-Si-Mg composites was studied. It is found that the presence of Al2O3nano particle led to significant improve in mechanical properties, especially at addition of 0.5 Vf% Al2O3. The ultimate tensile strength reached to 154 MPa with 10.24 % elongation, while the hardness reached to 37.7 HRB followed by decrement in wear rate. The porosity level tend to increase with increasing of Al2O3 and caused decrement in mechanical properties.

Effect of Artificial Aging (T6) on Microstructure of Al-AC8H/Al2O3 MMC Produced by Stir Casting Route

The purpose of this research is to systematically study the influence of artificial aging (T6) on evaluation of microstructure changed and hardness of Al-Al2O3 composite produced by stir casting route. The Al2O3 particle reinforced previously was coated by electroless coating method to improve wetting system between Al-AC8H and Al2O3 when aluminium composites fabricated by stir casting route. The volume fraction of Al2O3 which added into Al melts was various from 2% to 22.5%. The stirring process was carried out at 500-700 rpm to achieve vortex in alumnium melt using graphite impeller for 15 minutes. The prepared aluminium composites then heat treated by T6 treatment with different aging time. Microstructure and hardness after T6 treatment were investigated. It was observed that microstructure changed after T6 while hardness increase after T6 due to the Mg2Si precipitation hardening was present in Al matrix as well as Si eutectic accumulated on the surface of Al2O3. It was found that the optimum hardness occurred after aging for 3 hours.

Use of carbon pyrolyzed from rice husk in LiFePO4/V/C composite and its performance for lithium ion battery cathode

The characteristics of activated carbon pyrolyzed from rice husk used in the synthesis of LiFePO4/V/C for the development of lithium ion battery cathode has been examined. The synthesis was begun by synthesizing LiFePO4 (LFP) via hydrothermal route using the precursors in stoichiometric amounts of LiOH, NH4H2PO4, and FeSO4.7H2O. The assynthesized LFP was then added with variation of vanadium concentrations and a fix concentration of the carbon pyrolyzed from rice husk to form a composite of LiFePO4/V/C. The composites were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM), and electrochemical impedance spectroscopy (EIS). The XRD results showed that the LiFePO4/V/C has been successfully formed whereas SEM results showed a difference in morphology of vanadium and activated carbon addition. The EIS results showed that the conductivity of LiFePO4/C-0 wt.% V is 1.0196×10-2 S/cm, LiFePO4/C-3 wt.% V is 1.0302×10-2 S/cm, LiFePO4/C-5 wt.% V is 6.1282×10-3 S/cm, and LiFePO4/C-7 wt.% V is 8.3843×10-3 S/cm. The best performance for lithium ion battery cathode was given by LiFePO4/V/C at 3 wt.% vanadium. This result indicated that rice husk can be used as a cheap resource for activated carbon in the development of lithium ion battery cathode.

Effect of the Cerium Oxide (CeO2) on the Structural and Electrochemical Properties of the LaNi5Ce Metal Hydride Anode

One of negative electrode, AB5-type alloy electrodes, have been extensively studied and applied in rechargeable Ni-MH batteries due to their excellent electrochemical characteristics. Some researchers have found that addition of rare earth oxides (La, Ce, Pr, Er, Tm, Yb) to AB5-type alloy (MH) electrode improves battery performance significantly. Cerium Oxide (CeO2) is a light rare earth oxide is widely obtained from the processing of tailings in mining activities. During this time, there is still little data for research applications of cerium oxide for electrode materials. In this paper, the effects of adding CeO2 on the performance metal hydride electrode were investigated. In order to study the effects of CeO2 on the performance of anode material, 1%, 2%, and 3% of weight ratio CeO2 was mixed to LaNi5 as an negative electrode. The powder mixtures were mechanically milled at a speed of rpm 240 for 2 hours using ball mill. The powder mixtures were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). Electrochemical characteristics were measured using electrochemical impedance spectroscopy (EIS). The powder mixing showed the presence of Ce atom substitution into LaNi5 structures that affect the electrochemical properties of the material. The addition of cerium oxide at LaNi5 increase of the value of impedance. However, the addition of the value of impedance at 1% CeO2 is not significant when compared with the addition of 2% and 3% CeO2 that actually make the electrochemical properties of LaNi5 worst. Although the addition of 1% CeO2 also slightly increases the impedance value of LaNi5, but the addition of 1% CeO2 showed increase the corrosion resistance than without the addition of CeO2 and the addition of 2% and 3% CeO2.