Advanced Materials Research Vol. 974

Abstract: The mechanical properties of Al₂O₃-SiC based composites were improved by the addition of ZrO₂(3Y) particles in the range of 10 to 25 vol.%. Al₂O₃-SiC/ZrO₂(3Y) composites were manufactured by pressureless sintering at 1550, 1600, and 1650^oC. Sintered composites were characterized for density, XRD, microstructure and mechanical properties such as flexural strength, fracture toughness and hardness. The results showed that the highest flexural strength of 250 MPa was obtained with 25 vol.% ZrO₂(3Y) composite sintered at 1600^oC due to higher density and smaller Al₂O₃ grains in comparison with samples sintered at 1550^oC and 1650^oC, respectively. The maximum fracture toughness of 5.66 MPa.m^1/2 was obtained with 20 vol.% ZrO₂(3Y) sintered at 1600^oC. The highest hardness of 9.16 GPa was obtained with composite of 10 vol.% ZrO₂(3Y) sintered at 1600^oC as it contains the largest amount of hard SiC.

Abstract: This research focuses on predicting long-term behavior of unsaturated polyester resin (UP) and kenaf unsaturated polyester composite. The objectives of these tests are to establish a relationship between stress, strain and time at constant loading and temperature. The results obtained from these tests are used in predicting the life and strength of the polymer material. Based on the 1,000 hours experimental data, curve fitting and Findley Power Law models are employed to predict long-term behavior of the material. The results showed that curve fitting model accurately predicted the non-linear time dependent creep deformation of these materials with acceptable accuracy.

Abstract: In this research, the CNT coating treatment process involves the growth of CNTs onto the surface of the carbon fibre by floating catalyst techniques using CVD. The amount of ferrocene concentration has been varied throughout this study. Different morphologies of structured CNTs through TEM instruments are discussed and the analysis study of the composition of the coated carbon fibres by the growth of CNTs using EDX is also explained. In the present study, various ferrocene concentration gives a greatest influenced to the structure of CNT growth on carbon fibre surface. Lower ferrocene concentration favoured the growth of CNTs meanwhile higher catalyst amount lead to catalyst poisoning effect which resulting lower tensile strength of the hybrid CNT-carbon fibre nanocomposite structure.

Abstract: The purpose of this study is to understand the electrophoresis of Titanium dioxide (TiO₂) nanoparticles on ceramic membrane. The ceramic substrate was prepared using commercial ceramic filter. The effect of different types of solvent used for suspension was studied. Then, the solvent that give optimum formulation for deposited microstructure on ceramic electrode from the first stage experiment is used to study the effect of concentration on the deposition behavior of TiO₂ nanoparticles during EPD technique. All the TiO₂ suspension were had been characterized using Zetasizer nanoseries. The EPD was performed at 20 V DC field for 10 minutes. The deposited of TiO₂ from both stage of experiment were then analyzed using ESEM. The suspension in organic solvent was found to obtain more deposited particles on ceramic membrane compared to water-based suspension. While, the concentration with 0.5 wt % TiO₂ nanoparticles with zeta potential 53.6 mV was found to get smaller size and uniform microstructure. The adhesion of the TiO₂ deposited layer from entire of the result on the ceramic electrode was fairly good.

Abstract: Cement is an important part in oil and gas well completion. A high quality of cement is required to seal hydraulic pressure between casing and borehole formation. Cement additives were used to enhance the cement properties such as thickening time, compressive strength, porosity and permeability of the cement. Currently, the commercial additives were imported and the price is keep increasing year by year. Therefore, the researchers were continuously looking for potential additives such as nanoparticle to improve the cement properties. This paper presents the effect nanosilica on compressive strength and porosity of oil well cement type G. In this study, two type of nanosilica were used, synthesis nanosilica from rice husk ash (RHA) and commercial nanosilica. The synthesized nanosilica was characterized using fourier transform infrared spectroscopy (FTIR), X-ray flouresece (XRF) and Field Emission Scanning Electron Microscopy (FESEM). All the experiments were conducted using API standard procedures and specifications. Based on the results, compressive strength of cement slurries was improved from 2600 psi to 2800 psi for 8-hours curing, when the amount of nanosilica increased from 0 wt% to 1.5 wt%. Besides that, incorporation of nanosilica from RHA into cement formulation resulted in reduction of cement porosity up to 18 % pore volume. Overall, the results showed that the incorporation of nanosilica from RHA improved the oil well cement compressive strength and oil well cement porosity. In conclusion, green nanosilica from RHA can be a potential candidate to replace the commercial nanosilica to enhance the oil well cement properties as well as to prevent the migration of undesirable fluid which can lead to major blowout.

Abstract: Metamaterials are artificial materials that show extra ordinary electromagnetic properties which are not available in nature. It has opened a new era in the field of material science. It can be defined as an exotic electromagnetic structure that may show both negative permittivity and negative permeability simultaneously within a frequency range. Metamaterials with simultaneous negative permeability and permittivity are called Double Negative Metamaterials (DNG). In this paper, a new metamaterial unit cell structure has been proposed that exhibits resonance within frequency of C-band and shows a negative permeability and permittivity at that resonant frequency. In the proposed structure, two separate split ring resonators and a metallic bar has been used. A commercially available simulation software CST Microwave Studio has been used to get the reflection and transmission parameters for the unit cell.

Abstract: This research is to study the acoustic property of biopolymer foam and commercial consumer petroleum based epoxy foam. This is to evaluate the influence of proportion ratio of polymers matrix and filler namely as Titanium Dioxide (TiO₂) towards the sound absorption coefficient (α) at different frequencies level (Hz). Biopolymer foam was prepared based on in-house synthesized monomer from vegetable oil with commercial polymethane diphenyl diisocyanate (Modified Polymeric-MDI) with the different proportion ratio of TiO₂. The acoustic property of samples was examined by using an impedance tube test according to ASTM E-1050 of sound absorption coefficient (α). It was observed that epoxy gives higher value of α that is 0.9995 but shifted to higher absorption frequencies level as the TiO₂ loading increased. Meanwhile the lowest composition ratio of TiO₂ loading in biopolymer foam gives the best value of α at the lowest absorption frequency level as compared to epoxy composition ratios. Evidently, different percentage ratio of TiO₂ varied α value which influence the absorption frequency level (Hz). Hence, the minimal alteration on the filler loading of epoxy or biopolymer greatly influences the acoustic performance of both polymers. Meanwhile, the commercial foam of noise reduction coefficient, NRC values of commercial foam were decreasing with the increasing proportion ratio of TiO₂ while, the NRC values ​​of biopolymer foam were increased as the TiO₂ ratio was increased. This is due to the sound coefficient in polymeric foam is related to the effect of the interaction between different characteristic for both material (biopolymer foam and commercial foam) and morphology of foam.

Abstract: Alkaline phosphate-permanganate conversion coating, chrome-free conversion coating was studied for corrosion resistance of AZ91D magnesium alloy. Also, conventional acid phosphate -permanganate conversion coating was studied for comparison. Analysis and morphology observation for conversion coating layers was investigated in details by using SEM-EDS, XRD. SEM observation showed that a lot of cracks in surface and interface between conversion coating layer and AZ91D magnesium alloy substrate was observed in acid conversion coating, whereas cracks was not almost observed in alkaline conversion coating layer. SEM-EDS and XRD analysis showed that the main elements of both alkaline and acid conversion coating were Mg, O, K, P and Mn. It was found that both conversion coating layers was consisted of MgO, Mg (OH)₂ and MnO₂. Salt spray test showed that the alkaline conversion coating have a good corrosion resistance compared with acid conversion coating.

Abstract: Metallic cobalt (Co) nanoparticles with mean diameters in the range of 50-500 nm are formed by electroless deposition at room temperature in the presence of increasing concentration of NaOH. Co deposition was investigated by in situ mixed potential measurement. Increasing concentration of NaOH shifts the mixed potential negatively, leading to faster Co deposition and smaller apparent particle diameter. The decrease in mixed potential with increasing NaOH concentration is attributed to the decrease in the activity of Co²⁺ aquo ions in equilibrium with Co (OH)₂. Consenquently, the oxidation-reduction potential of Co (II)/Co redox pair is reduced. This leads to more negative mixed potential.