Key Engineering Materials Vol. 908

Abstract: Sn-based lead-free solder alloys have been explored extensively as an alternative to the conventional Sn–Pb solder alloys. While the miniaturization of electronic devices and the growth of appliance area, the corrosion resistance of solder alloys play a crucial element in the reliability of electronic devices in a prolonged period of service. This paper determines the corrosion effect of Sn-Bi solder lead-free solder, particularly immersed in alkaline solution which is potassium hydroxide. Morphological and elemental analyses reveal the formation of oxides on the surface after immersion after using a scanning electron microscope, dispersive energy X-ray and X-ray diffraction. The result of morphology reveals that the Sn matrix in plateau indicated dark contrast while Bi-rich in the lamellar eutectic structure indicated in light contrast appearance. In addition, phase and elemental analyses revealed the formation of mixed corrosion products of SnO, SnO₂ and Bi₂O₃ on the surface after testing. It is hoped that this finding will provide some helpful evidence in clarifying the corrosion progress of lead-free solder alloys. Furthermore, the remaining corrosion potential and current of Sn-Bi in 6 M potassium hydroxide solutions in this research are proposed.

Abstract: In this study, the crack propagation of the automotive engineering component is investigated through experimental and simulation work on crankshaft of automotive component car named connecting rod. The experimental work is conducted at STRIDE, Kajang Malaysia, with the load of 106.707 kN by tensile testing using Instron machine. The Finite Element analysis of crack model of connecting rod is successfully developed. The stress intensity factor is successfully determined via experimental and simulation. Both experiment and simulation work are successfully validated and shows strong in agreement in term of location of crack, its propagation and its stress intensity factor.

Abstract: This paper demonstrates a simple technique to detect vibration-induced fatigue cracks using a hybrid method by vibration and acoustic emission techniques. A thin aluminum plate of 6082-T6 was excited using a vibration shaker to achieve a bending mode where the maximum stress exhibited at the plate mid-span. To simulate crack formation, a sharp notch was created. This systematic setup allows mode I crack propagation through plate thickness. The development of cracks over time changed the natural frequency of the plate which leads to the reduction of vibration amplitudes. This experimental technique facilitates the identification of acoustic emission waves during the onset of damage in the presence of noise due to dynamic motion. The effect of crack development on Lamb waves was investigated. The acoustic emission signals were cross-correlated with a Gaussian window of a central frequency of 250kHz. The results show a reduction in the fundamental wave A₀, whilst an increase in S₀ wave amplitudes at some stages during crack extension. The current experimental work can be an alternative technique for vibration-induced fatigue test evaluation.

Abstract: The objective of this study to investigate microwave-assisted digestion as a rapid sample preparation method for the determination of REEs in Malaysian monazite using Inductively Coupled plasma-mass spectrometry (ICP-MS). Finely powdered monazite (D90 < 75μm) was the raw material for the digestion and fusion procedures. In the Li-borate fusion method, the digestion was achieved by lithium tetraborate: metaborate flux (Li₂B4O₇: LiBO₂) flux fusion followed by acid attack, using nitric acid (HNO₃). The second method, the microwave-assisted digestion method, involved digestion of the monazite in a mixture of H₂SO₄, HNO₃, and HF, followed by neutralization of the insoluble fluorides and complexation of residual HF. The concentrations of REEs, measured by both the methods, were in agreement with each other, except for the values of P and Si, which were slightly apart. Both the sample dissolution methods offer feasible means of quantifying REEs in the monazite sample, but only a combined microwave digestion-fusion technique yields complete quantitative data for monazite-type samples.

Abstract: Metallurgical coke is the main source of fuel and reducing agent for iron and steel industry. Empty fruit bunch (EFB) biomass which is abundantly available in Malaysia could be utilized as a source of energy as well as reducing agent in iron making process. This research presents carbon infiltration within low-grade iron ore via chemical vapor infiltration (CVI) method from EFB pyrolysis vapor. Low-grade iron ore was first heated to remove the combined water (CW) that consequently created pore network within the iron ore. These pores would act as sites for carbon infiltration in the iron ore. The EFB treatment on iron ore has been carried out at different temperatures and the effect of pyrolysis temperature on the carbon infiltration has been investigated. The Brunauer−Emmet−Teller (BET) and Barrett−Joyner−Halenda (BJH) methods have been performed to analyze pore surface and pore volumes of the iron ore. Pore surface and pore volume decreased as the temperature increased indicated that more carbon has been deposited. Using X-ray diffraction (XRD) analysis, it was shown that the low-grade iron ore has been transformed into iron (Fe). The infiltrated carbon from the EFB pyrolysis vapor in the pore surface iron ore is proven to be able to be utilized as source of energy and reducing agent to partially replace metallurgical coke in the blast furnace in order to reduce emission of harmful gas.

Abstract: Amang is known as a waste product after extraction of tin oxide (cassiterite, SnO₂) from its ore. Not long ago, in Malaysia, these tin ore tailings were left in abundance after long years of mining activities. Little had it been realized then, of the importance and future economics of the heavy minerals present in these tailing ‘deposits’ may offer. It is known that the heavy minerals from amang contained rare earth elements that are beneficial in various applications in different types of industries, such as monazite ([Ce, La, Nd, Gd, Th] PO₄), zircon (ZrSiO₄), ilmenite (FeOTiO₂), xenotime (YPO₄) and struverite (NbTaTiO₂). This paper looks briefly in Malaysia’s REE story and the contents of amang, that makes the story. Amang samples from Kinta Valley were chosen to be characterized, being reminiscent of the country’s REE exploits. Mineral characterization were achieved via various equipment and techniques; this includes utilizing Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray spectroscopy (EDX), X-ray Fluorescence (XRF) and X-ray diffraction (XRD) techniques, to determine (amongst others) surface morphology and morphological element/mineral identification, chemical element identification and mineral phases present, respectively. Mineralogical studies were also done by scrutinizing polished sections, interpreted under the reflected-light microscope and SEM/EDX, providing more insight into the mineral distribution in the amang and the possibility of liberation. All analyses were done at different size fractions for good comparison with possible indication of ample physical processing, before any proposed chemical processing can take place. Results showed that the chemical and phase constituents in amang were conclusively identified, with the complex distribution of mineral phases reaching 80% liberation at sizes below 125 μm.

Abstract: Malaysia has many potential mineral resources including some rare earth elements (REE) minerals such as monazite. REE play critical roles in the applications of advanced materials. Alkaline fusion was introduce to monazite to break the bonding between Light Rare Earth Elements (LREE) and phosphate. In this study, critical parameter such as fusion temperature (100 °C to 250 °C) and duration (1 to 4 hours) were studied. The results shows that it is possible to recover nearly 100% of Neodymium after 2 hours fusion at 150 °C. In the other hand, more than 99% of Cerium and Lanthanum were recovered after 3 hours fusion at similar temperature. By recover most of the element, expectantly high yield of single LREE can be achieved in the forthcoming.

Abstract: Extraction of thorium oxide (ThO₂) from monazite mineral specifically from Perak, Malaysia become a bright opportunity for the new income generation in Malaysia eventhough it is involved complex processing routes and require variety of chemicals. Monazite that is known as monazite-(Ce)-PO₄ minerals, not just contain thorium, but it also consist rare earth elements (REE) such as cerium (Ce), neodymium (Nd), lanthanum (La) and gadolinium (Gd) and also associated with thorium (Th) and uranium (U) at about 7 wt% and 0.2 wt% respectively. One of the challenges in this R&D work is to determine the presence of thorium, uranium and REE at each processing step due to its similarities of chemical composition and physical properties. Therefore, the aim of this paper is to use several x-ray characterization techniques to identify elemental composition obtained at each processing route to show the evidence of the presence of ThO₂ extracted from Malaysia monazite. This paper focused on the use of wavelength dispersive x-ray fluorescence (WDXRF), field emission scanning electron microscope (FESEM) with energy dispersive x-ray (EDX) and x-ray diffraction (XRD) spectrometer to show evidence of ThO₂ formation. Result shows that the final product contain of 85 wt% of ThO₂ and it is thorianite with nanorod morphology. Thus, conforming that the feasibility of the current processing route to produce ThO₂ from Malaysia monazite.

Abstract: Rapid growths in the electronic industries provide opportunities for the industries to expand the using of silicon wafer in modern and advanced technologies especially Micro Electromechanical Systems (MEMS). Laser cutting is one of the most significant and important application for fabrication MEMS components. The objective of this study is to investigate the cutting capability of industrial laser, CO₂ laser, in silicon wafer processing. Experiment was conducted in two conditions which is with assisted of pyrex glass and without assist of pyrex glass. In this work, silicon wafer with thickness 525 μm were cut into several rectangular sample shapes. The surface roughness produce at the cutting edge on each sample were investigated and analyzed. Analysis of Variance (ANOVA) was used to analyze the result and generated an appropriate model for the laser cutting processing. The laser parameters involved were laser power, cutting speed, and pulse frequency. Experimental results evident that, the laser cutting process with assist of glass give a better surface roughness on silicon cutting edge compared to without assist of glass.

Abstract: A study on the dimensional tolerance for CO₂ laser wood cutting is focused on the Meranti (Shorea) wood with the thickness of 19 mm. The results on kerf width for two surfaces which are top surface (K_t) and bottom surface (K_b) are investigated. It is interested to find out the optimum cutting parameters to achieve the smallest variance on top and bottom kerf to improve dimensional quality. Laser power, cutting speed, and gas pressure had been selected as investigate parameters and the cut kerf had been analysed. The investigations revealed that laser power and cutting speed are the significant parameters not only in producing a good surface finish, but also in yielding much narrower kerf with to ensure there will be no dimensional errors of the shore wood products. Besides quality, the laser processing approach has overcome most of the challenges faced by conventional production method.