Key Engineering Materials Vols. 594-595

Abstract: Stainless steels, such as 440C steel are commonly used for engineering applications. The high carbon contents of this steel have significantly been attributed to low corrosion resistance properties. Surface modification such as electrolytic double layer coating with ZrO₂/Al₂O₃ was carried out to control the performance. Samples were deposited in ZrO(NO₃)₂ and Al (NO₃)₃ aqueous solution respectively. Potentiodynamic examination (Tafel Extrapolation test) was conducted to measure the corrosion resistance of coated steel. The results showed improvements in hardness properties and corrosion rate as the Al₂O₃ concentration had been increased.

Abstract: The droplet impact behaviour provides the particle coating characterization during the coating process of controlled release fertiliser. To have a good coating uniformity around the urea granules, it is necessary to enhance the wettabitily properties between the coating material and urea surface. The biopolymer material is preferred as the coating material because this polymer may degrade and will not cause any environmental impact to the environment. Various compositions of starch/urea /borate/lignin were prepared and evaluated for the wettability properties. The wettability characteristic measured is the dynamic contact angle. The high speed Charged-Couple Device (CCD) camera was used to capture the images of this droplet impact behaviour. Temperature plays an important factor during wetting stage because the coating material must be completely dried in continuous coating process in fluidised bed. From this analysis, it indicates that a composition of starch/urea/ borate (50/15/2.5) with 10% lignin has the best wettability characteristic and thus suitable to be used as a coating material. The ideal temperature for the coating process is 60°C.

Abstract: Oxide coatings on AZ91D magnesium alloy were prepared using anodizing technique with 10mA/cm² current density for 5 minutes in electrolyte containing Mg (NO₃)₂ with NaVO₃ as an additive. The corrosion behaviors of different coatings condition were evaluated by immersion test in 5.0% NaCl electrolyte for 72 hours. The microstructures were analyzed by Optical Microscope (OM) and Scanning Electron Microscope (SEM). It was found that coatings with the addition of NaVO₃ produced homogeneous primary α-matrix and bigger β-phase (Mg₁₇Al₁₂) compared to untreated AZ91D magnesium alloy. The oxide film formed by anodizing in electrolyte with NaVO₃ enhances the corrosion resistance of the AZ91D magnesium alloy significantly.

Abstract: Geopolymerization is an alternative for ceramic industry by using clay based material such as kaolin or calcined kaolin geopolymer. Geopolymer paste is initially produced by alkaline activation of calcined kaolin with NaOH and Na₂SiO₃ solution), dried at 80oC for 4 hours, pulverized and sieved to fixed particle size powder. The parameters involved in this processing route (alkali concentration, kaolin or calcined kaolin to activator ratio, alkali activator ratio and heating conditions) are investigated. Geopolymeric powder is added with water to produce slurry to be coated on the surface of clay ceramic. It undergoes heat treatment at high temperature to produce glaze on the surface. Flexural strength and hardness analysis are studied. Result evidences the processing show of incresing strength value between 8-10% after treatment with geopolymer glaze and also the Vickers hardness values of geopolymers improved.

Abstract: In this work, electrodeposition of copper on AISI 430 steels substrate with relatively low current density followed by oxidation of Cu to form protective and conductive oxide layer is examined. Result shows that the activation by Ni strike plating on AISI 430 steels substrate prior to electroplating improves the coating ability of copper. Phase identification by XRD on the oxidized sample confirms that as coated Cu layer was transformed into CuO. The growth of CuO scales was relatively low and effectively prevents Cr outward diffusion from the ferritic steels.

Abstract: SS440C steels show potential as highest mechanical properties compared to others martensitic stainless steels. As their properties can be altered by some particular heat treatments, this steel is suitable for a extensive ranges of applications such as bearings, gage blocks, races, valve parts and many other manufacturing important components. Unfortunately, bare SS440C substrates corrode too quickly under corrosive environments. Surface modifications that are able to reduce corrosion rates to suitable levels will allow SS440C to become a reality for much more applications [1-.

Abstract: The challenging in injection molding process is to get the uniform thermal distribution on the molded parts during the cooling stage which is mainly depend on the design of the cooling channels in injection mold. Poor design of cooling channels will result a non-uniform thermal distribution which lead to a longer cycle time, differential shrinkage and warpage defects on the molded parts. In this study, the performance of conformal cooling channels compared to the straight drilled cooling channels in order to minimize the warpage on the front panel housing is evaluated. The simulation results from Autodesk Moldflow Insight (AMI) 2013 are analyzed by using Taguchi Method and Analysis of Variance (ANOVA). The analyses show that conformal cooling channels are able to improve the quality of the molded parts in term of warpage compared to the conventional straight drilled cooling channels and the results are beneficial for the molding industries which involving the precise parts.

Abstract: In this study, Poly (vinylidene fluoride-co-hexafluoropropylene)/Poly (ethyl methacrylate (PEMA) nanocomposite polymer electrolytes was prepared by solution casting technique. The effects of TiO₂ nanofiller on the structural, thermal and conductivity characteristics were examined using x-ray diffraction, scanning electron microscopy, differential scanning calorimetry and impedance spectroscopy. The crystallinity and conductivity of the salted system are found to increase with the addition of TiO₂. The system containing 5 wt % of TiO₂ exhibited the highest room temperature conductivity of 1.32 × 10^-3 S cm^-1.

Abstract: Hexanoyl chitosan-based polymer electrolytes were prepared using the solution casting technique. The effect of dimethyl carbonate (DMC) plasticizer on the structural and electrical properties of the prepared electrolyte system was investigated by X-ray diffraction and impedance spectroscopy, respectively. Upon addition of 15 wt. % of DMC, the ionic conductivity was increased to 4.09 x 10^-4 S cm^-1 from 3.06 x 10^-4 S cm^-1. The XRD results revealed the variation in conductivity from the structural aspect. For example, sample with lower crystallinity exhibits higher conductivity. The Rice and Roth model was employed to understand the variation in conductivity on the basis of number and mobility of free ions.

Abstract: Composites of polypropylene/Acylonitrile butadiene rubber/Rice husk powder/ (PP/NBRr/RHP) with and without trans-polyoctylene rubber (TOR) were prepared, and the effects of trans-polyoctylene rubber were investigated. By using rice husk powder of 150300μm, five different compositions of PP/NBRr/RHP composites (i.e.100/0, 80/20, 70/30, 60/40 and 40/60 phr) were prepared in an internal mixer at 180 °C and 50 rpm rotor speed. The results indicate that the incorporation of TOR improved the tensile properties of PP/NBRr/RHPcomposites. Scanning electron microscopy of the fractured surfaces proved that TOR promoted good adhesion between the PP-NBRr matrices and RHP.Keywords: Polypropylene; Trans-polyoctylene rubber; Rice husk powder; Acrylonitrile Butadiene rubber; composite