Advanced Materials Research Vols. 264-265

Abstract: Wire electrical discharge machining (WEDM) is a thermal process in which the workpiece and the wire (tool) experience an intense local heating in the discharge channel. The high power density results in the erosion of a part of the material from both electrodes by local melting and vaporization. Whilst good surface finish and high material removal rate of the workpiece is a major requirement, the effect of EDM machining factors on these requirements cannot be overlooked. This study investigate the effect of two different machining methods of dry and wet WEDM process as well as the effect of on-time and voltage on the surface roughness of the workpiece. The machining factors used for this study are the pulse current, on-time and voltage. The results of the effect of the two machining methods on the responses are investigated and reported in this paper.

Abstract: In this study, we report the synthesis of carbon nanotubes by floating catalytic chemical vapor deposition, which employs ferrocene as the catalyst precursors and ethanol as carbon source. We obtained massive deposits. The deposits were characterized by scanning electron microscopy, transmission electron microscopy, and visual laser Raman spectroscopy. We discussed the effects of synthesis temperature on the synthesis of carbon nanotubes by floating catalytic chemical vapor deposition. Our results indicated that the synthesis temperature could affect not only on the graphitization degree, but also on the aligned growth of carbon nanotubes and the diameter of carbon nanotubes.

Abstract: In this paper, the effects of position of substrates in flames, preparation time and stability of flames on carbon nanofibers are investigated in ethanol catalytic combustion. For the position of substrates, our results indicate that the temperature at the lower height (h<1cm) is too low (less that 500°C) to grow carbon nanofibers; the temperature at higher height (h>2.5cm) is suitable for the growth of carbon nanofibers, but the carbon source is insufficient because of sufficient combustion of ethanol; the optimal position of substrates in flames is more than 1cm and less than 2.5cm for massive yield because the temperature of flames is suitable for the growth of carbon nanofibers and the carbon source is also sufficient. For the preparation time, our results indicate that the optimal preparation time is more than 5min and less than 30min for massive yield. If the preparation time is excessive long (more that 30min), the deposits partly become burning in flames due to excessive products on substrates. The stability of flames has effects on the morphology and graphitization of products. Our experimental results indicate that stable flames prefer to produce noncoiled carbon nanofibers with relatively good uniformity and higher graphitization because the relatively stable flames could provide a relative stable synthesis environment.

Abstract: Functionalized conjugated polymer polyanthranilic acid (PANA)/zinc oxide (ZnO) nanocomposite has been formed using co-precipitation method followed by control heating. Carboxyl functionalized polymer PANA is chemically formed in aqueous solution at acid pH and ZnO nanoparticles is formed by hydroxide precipitation at basic pH followed by control heating. A homogeneous PANA-ZnO nanocomposite is formed by co-precipitating polymer at acidic pH followed by Zn(OH)2 precipitation by increasing pH in PANA matrix and by control heating. Resulting nanocomposite is characterized under XRD, UV-vis, FT-IR, SEM and TEM techniques. Nanocomposite is heated at various temperatures (35-600oC) and characterized using XRD for observation of formation of pure ZnO phase in polymer matrix. Pronounced amorphous behavior of nanocomposite below 100oC is observed due to characteristic amorphous nature of conjugated polymer and probably complexation of Zn2+ with carboxyl functional groups (-COO-) of polymer rather than formation of pure phase of ZnO. However, above 250oC composite shows some crystalline nature. The crystallinity is explained on basis of decomposition of carboxyl functional groups of the polymer (above 250oC) therefore decomposition of polymer zinc ions complexes and formation of polymer chains with lesser number of carboxylic groups (like polyaniline) with new arrangements and formation of ZnO nanoparticles. When the sample is heated up to 600°C highly crystalline character of the composite supported almost pure ZnO phase formation with little amorphous character due to remaining polymers. Co-precipitation technique shows the formation of uniform nanocomposite and better interaction of the two components with core shell structure, which is further supported by HRTEM.

Abstract: Zinc sulfide (ZnS) thin films as the waveguide medium have been deposited onto oxidized silicon wafer substrates at cold temperature (Tcold = –50oC) and ambient temperature (Tambient = 25oC) by thermal evaporation technique. The surface morphology of ZnS films were pictured with an atomic force microscopy (AFM) and the surface roughness were calculated from the AFM images. The propagation losses of the samples were measured using a scanning detection technique attached to a prism coupler. The AFM results revealed that the surface of cold deposited ZnS film is rougher than the surface of ambient deposited ZnS film. The propagation losses of the cold deposited ZnS waveguide are consistently lower than the ambient deposited ZnS waveguide at all measured wavelengths.

Abstract: Identification of the constants of material models is always a concern. In the present work, a combined experimental, numerical and optimization technique is employed to determine the constants of Zerilli-Armstrong model. The experiments are conducted on a compressive Hopkinson bar, the simulations are performed using finite element method and optimization is carried out using genetic algorithm. In the method adopted here, there is no need for experimental stress-strain curve which is always accompanied by restricting phenomenon such as necking in tension and bulging in compression. Instead of stress-strain curve, the difference between the post-deformation profiles of specimens obtained from experiment and the numerical simulations is adopted as the objective function for optimization purposes. The results suggest that the approach introduced in this work can substitute costly instrumentations normally needed for obtaining stress-strain curves at high strain rates and elevated temperature.

Abstract: Chicken eggshell (ES) is an industrial by product containing 95% calcium carbonate and its disposal constitutes a serious environmental hazard. ES contains about 95% calcium carbonate in the form of calcite and 5% organic materials such as type X collagen, sulfated polysaccharides, and other proteins. Although there have been several attempts to use eggshell components for different applications, its chemical composition and availability makes eggshell a potential source of filler for PP composites. In this research work, different proportions of chicken eggshell as bio-filler for polypropylene (PP) composite were compared with different operating temperature by creep test, hardness test and SEM photomicrographs. The eggshell had been prepared by blending and sieving them into granule size of less than 160μm. The granules were then mixed with polypropylene into four weight ratios, 10%, 20%, 30% and 40% respectively using fine extruder, where silane was used as the coupling agent. From the result, it was learnt that, the ES filler had improved Creep Strain and Creep Modulus for the operating temperatures of 34°C and 80°C. Tensile and flexural tests were also performed to study the pattern and behaviour of the chicken egg shell particulated polypropylene. In general, the findings can be concluded that not all ratios of particulation yielded positive as expected, but there were also conditions where virgin polypropylene yields better result depending on the test type and composite matrices.

Abstract: Calcium carbonate (CaCO3) is one of the most useful and versatile materials known to man. In this research, eggshell as a natural composite bioceramics was used to modify and improve the mechanical properties of an existing polyethylene which is widely used to manufacture daily goods by small medium industries in Malaysia. Chicken eggshell containing 95% Calcium Carbonate is highly potential to be used as bio-filler to improve poly-based matrix in improving their performance behavior. PE was chosen for this project to modify its virgin mechanical properties by reinforcing eggshell/calcium carbonate and later investigate its character to improve the current product’s performance. Tensile, creep and flexural tests were carried out to characterize the developed PE-CaCO3 composites. Eggshells which were prepared into hundreds of microns and furnace dried at 90oC continuously for eight hours to improve the bonding capability. They were then particulated into polyethylene matrix accordingly as per the designed weight ratios, 10%, 20%, 30% and 40%. From the result, it was learnt that the ES filler has improved mechanical properties of virgin PE as far as 5% to 9% depending on the filler weight ratio. Therefore, ES which was a burden for disposal and being environmental threat can now be used for the betterment of PE product performance.

Abstract: Surface finish and dimensional accuracy is one of the most important requirements in machining process. Inconel 718 has been widely used in the aerospace industries. High speed machining (HSM) is capable of producing parts that require little or no grinding/lapping operations within the required machining tolerances. In this study small diameter tools are used to achieve high rpm to facilitate the application of low values of feed and depths of cut to investigate better surface finish in high speed machining of Inconel 718. This paper describes mathematically the effect of cutting parameters on Surface roughness in high speed end milling of Inconel 718. The mathematical model for the surface roughness has been developed in terms of cutting speed, feed rate, and axial depth of cut using design of experiments and the response surface methodology (RSM). Central composite design was employed in developing the surface roughness models in relation to primary cutting parameters. Machining were performed using CNC Vertical Machining Center (VMC) with a HES510 high speed machining attachment in which using a 4mm solid carbide fluted flat end mill tool. Wyko NT1100 optical profiler was used to measure the definite machined surface for obtaining the surface roughness data. The predicted results are in good agreement with the experimental one and hence the model can be efficiently used to predict the surface roughness value with in the specified cutting conditions limit.

Abstract: Hardened materials like AISI H13 steel are generally regarded as s difficult to cut materials because of their hardness due to intense of carbon content, which however allows them to be used extensively in the hot working tools, dies and moulds. The challenges in machining steels at their hardened state led the way to many research works in amelioration its machinability. In this paper, preheating technique has been used to improve the machinability of H13 hardened steel for different cutting conditions. An experimental study has been performed to assess the effect of workpiece preheating using induction heating system to enhance the machinability of AISI H13. The preheated machining of AISI H13 for two different cutting conditions with TiAlN coated carbide tool is evaluated by examining tool wear, surface roughness and vibration. The advantages of preheated machining are demonstrated by a much extended tool life and stable cut as lower vibration/chatter amplitudes. The effects of preheating temperature were also investigated on the chip morphology during the end milling of AISI H13 tool steel, which resulted in reduction of chip serration frequency. The preheating temperature was maintained below the phase change temperature of AISI H13. The experimental results show that preheated machining led to appreciable increasing tool life compared to room temperature machining. Abrasive wear, attrition wear and diffusion wear are found to be a very prominent mechanism of tool wear. It has been also observed that preheated machining of the material lead to better surface roughness values as compared to room temperature machining.