Applied Mechanics and Materials Vol. 761

Abstract: This paper presents the mechanical properties of oil palm empty fruit bunch (OPEFB) fiber/epoxy resin reinforced cast LM6 (aluminum based) alloy composites. The metal matrix composite was fabricated by incorporating OPEFB/epoxy resin using mono filaments concept in the as cast LM6 alloys. Three different diameters (10, 12 and 14 mm) of the maximum force of metal matrix composite materials along with controlled sample (cast LM6 alloy + OPEFB/epoxy resin) were determined from three point bend testing. Test results showed that maximum force of mixture between OPEFB fibers composite and cast LM6 alloy for metal matrix composite are higher than that of cast LM6 alloy. Thus the utilization of OPEFB/epoxy composite as mono filaments in metal matrix composite can be significant in improving the strength of the cast LM6 alloy. Beside that increasing the diameter size of OPEFB/epoxy composite will reduce the weight of metal matrix composite (cast LM6 + OPEFB/epoxy composite).

Abstract: The aim of this study is to determine the effect of different types of pore-forming agent and sintering temperature on the pore size of ceramics. The porous ceramic material was developed by mixing of alumina, zeolite and calcium oxide (CaO) as the main materials and ethylene glycol as the binder. Meanwhile, two types of pore-forming agent were used, i.e., yeast and a mixture of aluminium powder and expandable polymeric spheres (EPS). The content of pore-forming agent was at 10 wt% of the mixture and the samples were shaped by using plaster of paris mould. After being dried, the samples were sintered at temperature range of 1000 up to 1500 °C for two hours. Microstructural analysis and pores size measurement were performed to determine the effect of pore-forming agent and sintering temperature on the ceramic. The result showed that yeast yielded larger pore sizes in the porous ceramic upon being sintered at 1400 °C for two hours, which were up to 402 μm. Therefore, yeast has the potential to be utilized as pore-forming agent in development of filter and wall insulation material.

Abstract: Graphene nanoplatelets (GNPs) surface modification was performed by using a simplified dual-action of ultrasonication and high speed mechanical shearing. This approach induced a non-covalent polymeric wrapping interaction between GNPs surfaces with IGEPAL-C0890 (ethoxylated nonyl phenol with 40 moles ethylene oxide). Various characterization tools like FTIR, Raman spectroscopy, FESEM and TEM were utilized to confirm the success of the surface treatment. The efficacy and suitability of non-covalent treated GNPs-C0890 as nanofiller reinforcement and inorganic compatibilizer in NR/EPDM rubber blends were evaluated. Effects of GNPs-C0890 loading variation to the mechanical tensile properties and fracture morphologies of NR/EPDM nanocomposites rubber blend were studied. It is interesting to note that the GNPs-C0890 was not able to reinforce NR/EPDM blend at a higher loading addition (≥ 3.00 wt.%) due to the agglomeration and crosslinking retardation phenomena by phase separation. However, at a lower loading (≤ 1.00 wt.%), the blend strengthening effects promise the improvement at about 64.55% of tensile strength and 14.20% of elongation percentage as compared than unfilled NR/EPDM blend. Obvious fractured morphological changes due to the absence and presence of GNPs provide hints on the role of GNPs treatment in effecting the NR/EPDM rubber blend mechanical properties.

Abstract: Graphene nanoplatelets (GNPs), a newly discovered nanomaterial, promise a great potential in many technological applications. However, the direct usage of GNPs was limited due to several surface property factors that require innovative modifications and treatments. In this study, the GNPs surface treatment is carried out by using a covalent and non-covalent approach. The success of the treatment was determined and evaluated through the Raman and FTIR spectroscopy analysis, FESEM, TEM and XRD morphological observation. A strong vibration of Raman peak at 2081.11 cm^-1 represent a possible covalent bonding of C=C due to the ATPS-silane treatment, while the characteristic peak at 1013.82 cm^-1 indicates the aromatic ring nature of polyimide that non-covalently associated with C-H and C-C, as well as C-O-C linkage from the polyether. From the IR spectroscopy, the covalent treatment on GNPs was occurred through the dehydration mechanism while hydrogen bonding in the multiple structures of –OH that associated to the carboxylic acids was obviously involved for non-covalent treatment of GNPs. TEM observation of GNPs-PEI (polyetherimide) revealed a unique phenomenon of a polymeric adsorption as represented by a nanosize gray dot morphology in between of the GNPs platelets. In overall, the facile procedure of the surface treatment that was applied in this study is reliable to yield a different type of GNPs characteristic of covalent and non-covalent surface active, which may open up broad possibilities for various cutting edges applications.

Abstract: This paper reported the doping effect on BIT by two different rare-earth compounds i.e. Nd and Sm, each at different mole content (0.25, 0.5, 0.75 and 1.0 mol). The so-called single-step combustion synthesis was used to produce the as-combusted powders, whereby the intermediate calcination step was then eliminated. This method was able to sinter the samples at temperature as low as 1000°C for 3 h. The entire ceramics were characterized for phase detection and stability, microstructure and dielectric properties. It was found that the single phase BIT was successfully formed with Nd and Sm doping. However, little content of pyrochlore phase was detected in the sample with Sm doping particularly at high mole content. (0.5 to 1.0 mol). Besides, a remarkable decrease in the grain size with better microstructure was observed particularly at high mole content (1.0). The improvement in microstructure led to the increase in dielectric constant with low dielectric loss.

Abstract: The antibacterial activity of functionalized zeolite NaY (CBV100) with different concentrations of 3-aminopropyltriethoxysilane (APTES) (0.01, 0.05, 0.20 and 0.40 M) was studied against Staphylococcus aureus ATCC 6538 (Gram positive) and Escherichia coli ATCC 11229 (Gram negative) through disc diffusion technique (DDT). The characterization of functionalized zeolite NaY with fourier transform infrared (FTIR) spectroscopy indicated the attachment of APTES on zeolite NaY. Through DDT, the inhibition zone of functionalized zeolite NaY increased proportionally to the amount of the amine-functional group attached onto zeolite NaY. Functionalized zeolite NaY showed higher antibacterial activity against Gram-positive compared to Gram-negative bacteria. It can be concluded from this study that amine-functionalized zeolite NaY shows evidence of antibacterial activities.

Abstract: Zinc and copper addition into electroless Ni-P alloy matrix produces quaternary Ni alloy that exhibits lower corrosion resistance behavior compared to Ni-P and Ni-Cu-P alloy in 3.5 wt% NaCl solution. The corrosion behavior of the alloy is previously studied using the anodic polarization curve measurement. The results show that the corrosion potential of different alloy composition is almost similar to each other for electroless Ni-Zn-Cu-P alloy. However, the surface resistance of the alloy needs to be confirmed by using electrochemical impedance spectroscopy. The alloy was first deposited on an iron substrate using electroless Ni alloy deposition method approximately similar thickness at different plating bath pH of 8.50 and 9.50. The Ni alloy coated substrate was used as working electrode immersed into a solution of 3.5 wt% NaCl. The electrochemical cell consists of Pt and Ag/AgCl/KCl (saturated) as counter and reference electrode respectively. Electrochemical impedance measurement was done at open circuit potential. The measurement started from 100 kHz to 10 mHz with 10 mV of sinusoidal perturbation applied to the cell. Other types of alloy including Ni-P, Ni-Cu-P and Ni-Zn-P, were compared with Ni-Zn-Cu-P alloy. From the results, the Ni-Zn-Cu-P exhibits the lowest corrosion behavior compared to other Ni alloy due to low charge transfer resistance (R_ct) observed small inductive loop at low frequency region of the Nyquist plot. Furthermore, the Nyquist plot for Ni-Zn-Cu-P for pH 8.50 and 9.50 showed comparable result; hence, the effect of pH has less effect on corrosion resistance of the electroless Ni-Zn-Cu-P alloy.

Abstract: Polymeric poly (vinyliden fluoride) (PVDF) is nontoxic. It possesses a better mechanical flexibility and requires a lower synthesis temperature, as compared to the piezoceramic counterparts. In order to achieve a competitive advantage against the current piezoelectric sensor, graphite could replace a more expensive silver-palladium as the electrodes for the piezoelectric PVDF. This paper reports the preliminary results on the synthesis of steel-supported graphite-PVDF/PVDF/graphite-PVDF composite films using the two-step process, consisted of the electrophoretic deposition (EPD) and heat treatment. The composite films were characterized by means of the optical microscopy, scanning electron microscopy, X-ray diffraction and differential scanning calorimetry. The heat treated graphite-PVDF electrode deposited by EPD provides adequate mechanical strength for the subsequent depositions of pure PVDF layer and the second layer of graphite-PVDF composite electrode. However, the final heat treatment stage did not eliminate the fine and large cracks of the composite film, which might be attributed to high residue stresses and weak bonding between graphite and PVDF particles in the post-heat treated composite films. Nevertheless, the increase in final heat treatment temperature of the composite film at Stage 3 improved the graphite and PVDF grain alignment, as well as its crystallinity.

Abstract: TiN/AlTiN multilayer coatings were deposited on tungsten carbide cutting tool by applying a direct current on a pulsed bias arc ion plating system. The effect of pulsed bias layer thickness on sample properties was investigated. The amount of grain size decreased with increasing layer thickness. The crystal structure of the coatings was determined using a D8 Advance Bruker X-ray diffractometer with CuKa (λ = 1.5405 Å) radiation. TiN/AlTiN multilayer coatings were crystallized with orientations in the (111), (200), (222), and (311) crystallographic planes, and the microstructure was enhanced with preferred orientation in the (111) plane. Compared with the substrate, all the specimens coated with TiN/AlTiN multilayer coatings exhibited better X-ray diffraction properties.

Abstract: Cobalt (Co) catalyst thin film is an active metal catalyst that can be very helpful to grow carbon nanotubes (CNTs). The catalyst thin films were prepared on silicon wafers by spin coating the solution of cobalt acetate tetrahydrate and ethanol. The effects of different spin speed parameter during the spin coating process were investigated. The findings showed that the optimum thickness of the Co catalyst thin films, i.e., 12.1 nm, was obtained at the highest spin speed of 8000 rpm. The uniformity of the thin films was also found to increase with increasing spin speed. The study also demonstrated that single-walled carbon nanotubes could be grown from Co catalyst particles after the catalytic chemical vapor deposition of ethanol. The particle and thickness analysis, as performed by means of FESEM while the existence of CNTs, was performed by Raman spectroscopy.