Advanced Materials Research Vol. 911

Abstract: Hot swaging experiments were carried out on as-sintered Al composite preforms in order to evaluate its pore closure characteristics. The effect of tungsten carbide and iron carbide in plain aluminium has been investigated under triaxial stress state condition. Cylindrical preforms with 0.5 aspect ratio and 88% fractional theoretical density have been produced for pure Al, Al-2WC and Al-2WC-4Fe₃C through classical powder metallurgy route. Then, the as-sintered preforms are hot swaged to various height strains to further enclose the residual porosities; thereby to enhance density and mechanical properties. It is observed that induced strain substantially helped to close the porosities; however this largely depends on the reinforcing carbide particles in the Al-matrix.

Abstract: AMC (Aluminum Matrix Composite) as a main material for automotive and aircraft applications has the keyadvantage that islighter thanaluminumalloys. So, it can be ascertained that fuel comsumption forthoseapplicationswill be reduced. However, AMC materials are generally suceptible to galvanic corrosion due to galvanic reaction between aluminum matrix and reinforcement, and the formation of microstructure at matrix/reinforcement interface as well. Anodizing is the most effective surface modification method in order to protect AMCs surfaces. This process produces porous anodic coating which has the characteristics of high corrosion resistance and hardness layer. However, the presence of reinforcement particles in AMC hinders the initiation and growth of the protective oxide layer by forming cavities and micro crack. Therefore cerium sealing has been done to remedy the poor anodic film in order to further enhance the corrosion resistance in aggressive circumstances. The material studied in this research was AMC Al7xxx/SiC. Anodizing process were conducted in H₂SO₄ solution at current densities 15, 20, and 25 mA/cm² at 0°C for 30 minutes. Subsequently, continuedwithelectro lesssealinginCeCl3.6H₂O+H₂O₂ solutionat room temperature atpH9 for 30 minutes. The morphologies of anodic coating and sealing layer were examined by means of FE-SEM, the corrosion resistance of composites was estimated in a 3.5 wt.% NaCl solution by potentiodynamic polarization test. Coating process conducted by anodizing and cerium sealing in various of anodizing current densities at 0°C results in protective layers which lead to the decreasing of corrosion rate and current density up to four orders magnifications than that of bare and anodizedAl7xxx/SiCcomposite.

Abstract: Damage classification is considered as an important feature in pattern recognition, which led to providing significant information. This research work explores damage size classification for several impact events in natural fibre reinforced composites, which is based on the information provided by the ten piezoceramics (PZT) sensors. An Impact event produced strain waves which several data features were obtained through the response captured. An effective impact damage classification procedure is established using a multilayer perceptron neural network approach. The system was trained to predict the damage size based on the actual experimental data. The data features were mapped into five output class labels, presented as a target confusion matrix. The classification results revealed that the damage sizes were successfully mapped according to its respective class, with the peak to peak feature gives the highest classification rate at 98.4%.

Abstract: The classical P/M technique was used to produce composites of Al-2WC-4Fe₃C, Al-2WC-8Fe₃C and Al-2WC-12Fe₃C and it is further subjected to hot upsetting to evaluate densification and corrosion characteristics.Process parameters such as initial density, preform geometry and deformation media were kept constant to analyse this behaviour. The as-sintered compacts were subjected to swaging to different height strains, thus expected to eliminate residual porositiesout of classical P/M technique consequently improve its densification and corrosion characteristics. As the known limitation of the classical P/M process is the presence of porosity that restricts structural and corrosion related applications. It is observed from the results that strain induced improves the density substantially, which eventually promoted anti-corrosion properties. Further prediction was the addition of carbide particle in pure Al decreases the densification and increases the corrosion rate.

Abstract: Hydroxyapatite (HAp) is a kind of bioceramic based material that has been used extensively in many medical applications. Owing to nearly similar mineral contents to natural bone, the material has been accepted as an implant in order to improve the osteointegration with the bone tissue. In this work, an alternative processing route from waste materials, namely clamshell in producing HAp powder is presented. The effects of processing temperatures, ranging from 750°C to 950°C and pH values, ranging from 6.5 to 8.5 on the synthesized HAp prepared via chemical precipitation method were investigated. From the XRD, FTIR and EDX results, it was observed that the lowest pH value of 6.5 with the temperature of 850°C is the optimum parameters to synthesize HAp.

Abstract: This research aims to examine the chemical properties of waste rubber tyre granules. Rubber granules were analysed by using X-ray fluorescence to establish its chemical composition. Thermogravimetry and differential thermogravimetric analyses were performed to investigate the relationship between temperature and the minerological compositions of rubber granules to determine its suitability as an aggregate replacement in concrete mix. Fourier Transform Infra-Red (FTIR) indicated that due to the stability of the structures developed in OPC samples, the reactions between the structure bonds are less at the range of 650-1500 cm^-1. Scanning electron microscopy (SEM) was performed to examine the physical properties of rubber granule particles and to magnify the bonds between cement and rubber granules in a concrete mix. The results of the SEM analysis showed that carbon, zinc, magnesium, and calcium are the major components of waste tyre rubber granules.

Abstract: Cermet alloys are a combination of ceramic and metal. Therefore, cermets exist in high corrosion resistance in aqueous media. However, because of the nature of cermet alloys, which have a metal and ceramic composition, the corrosion rate is complex to identify. The corrosion attack could be assessed by calculating the corrosion rate or through electrochemistry evaluation. Generally, the corrosiveness of media increased as the anions contents increased. This paper presents the corrosion mechanism of cobalt tungsten-carbide (WC-Co) exposed to a high concentration of sulphate in the salinity of seawater. The solution (media) was prepared according to the same composition as seawater including pH, salinity and dissolved oxygen. The corrosion rate was then identified and the corrosion mechanism revealed. The corrosion rate was identified at 4°C, 20°C, 50°C and 80°C and compared with the corrosion rate of WC-Co in seawater. The results revealed that sulphate has an inhibiting effect that minimises the corrosion attack on WC-Co. The corrosion rate decreased as the sulphate content in seawater increased, and an increase in the temperature increased the corrosion attack on WC-Co.

Abstract: In metallurgical engineering, there are different criteria affected on coating on surface of the material such as physical, chemical, mechanical, electrical and economical properties. In this study, using the Analytic Hierarchy Process (AHP) to calculation the performance of criteria for priority by addition of different concentration alumina (Al₂O₃)nanoparticles in Electrolyte and heat treatment on substrate nickel-borne electroless method has been calculated. The alumina particles with an average grain size of 50nm in different concentrations were added to a solution electroless Ni-B plating which were coated on conventional steel sample. The AHP determined that the most favorable concentration of alumina particles is 1gr/lit .

Abstract: The heterostructures of BiPO₄/Ag₃PO₄ were synthesized using a hydrothermal method with starting materials of Bi₅O(OH)₉(NO₃)₄, AgNO₃ and Na₂HPO₄.12H₂O at pH 1 under heating of 180°C for 12 h. The products were characterized using XRD, DRS and BET specific surface area. The photocatalytic activities were determined through the phenol decomposition under UV light (λ=390 nm) and blue light (λ=445 nm) irradiation. The heterostructures of BiPO₄/Ag₃PO₄ with the body-centered cubic structure of Ag₃PO₄ and monoclinic of BiPO₄ were successfully synthesized. The photocatalytic activity of BiPO₄ under UV light irradiation could be enhanced by designing of BiPO₄/Ag₃PO₄ heterostructure with the molar ratio of 0.75/0.25.

Abstract: Stellite 6 was deposited by laser cladding on a P22 steel substrate with energy inputs of 1 kW (P22-1) and 1.8 kW (P22-1.8). The chemical compositions and microstructures of these coatings were characterized by atomic absorption spectroscopy, optical microscopy and scanning electron microscopy. The microhardness of the coatings was measured and the wear mechanism of the coatings was examined using a pin-on-plate (reciprocating) wear testing machine. The results showed less cracking and pore development for Stellite 6 coatings applied to the P22 steel substrate with the lower heat input (P22-1). Further, the Stellite coating for P22-1 was significantly harder than that obtained for P22-1.8. The wear test results showed that the weight loss for P22-1 was much lower than for P22-1.8. It is concluded that the lower hardness of the coating for P22-1.8, markedly reduced the wear resistance of the Stellite 6 coating.