Advanced Materials Research Vol. 871

Abstract: The interest in using fibers as reinforcement in composites has increased in recent years due to its lightweight, combustible, non-toxic, non-abrasive, low cost and biodegradable properties. In this study, two difference types of long kenaf fiber (LKF) used in fiber-reinforced composites which are untreated and treated with 1% sodium hydroxide (NaOH). The volume fraction of LKF used are 20%, 25% and 30% prepared by cold pressed hand lay-up technique were investigated. A series of tensile tests were performed to evaluate the effect of their modulus and ultimate tensile strength (UTS). The morphological and structural changes of the fibers were investigated by using scanning electron microscopy (SEM). It has found that the treated long kenaf fiber (TLKF) shows the higher value of tensile strength compared to untreated long kenaf fiber (ULKF).

Abstract: Two different clay loadings were added to OPEFB/PP/MAPP which was 7 phr and 10 phr in order to see its effect on the fracture toughness. Standard dimension of samples was prepared for 180 μm, 355 μm and 355 μm treated with 1% NaOH. The result showed that 7 phr clay contents had the highest fracture toughness of 1.16 MPa.m^1/2. Alkali treatment on OPEFB fiber gave 7% improvement of fracture toughness for samples with 7 phr PPnanoclay loading. SEM images show the improvement of bonding between the fibers and the matrix upon alkali treatment.

Abstract: The effect of oil palm empty fruit bunch (OPEFB) fiber size on the fracture toughness of OPEFB/PP/PPnanoclay composites was investigated. Four fiber sizes ranging from 180 μm, 250 μm, 300 μm, and 355 μm were used to reinforce PP/PPnanoclay composites. The ratio of PP/PPnanoclay was 7:100 by weight (7 phr). Fracture toughness of the composite was determined according to ASTM D5045 and single edge notch bending (SENB) been employed during the test. The result indicates that the fracture toughness of OPEFB/PP/PPnanoclay composites has decreased as OPEFB fiber size increased. Fracture surfaces investigated through the scanning electron microscopy (SEM) showed that the bonding between fiber and matrix for OPEFB/PP/PPnanoclay composites with smaller OPEFB fibre size has better bonding as compared to OPEFB/PP/PPnanoclay composites with larger OPEFB fiber size.

Abstract: Pulsed Laser Ablation in Liquid (PLAL) has become an increasingly important technique for metals production and metal oxides nanoparticles (NPs) and others. This technique has its many advantages compared with other conventional techniques (physical and chemical). This work was devoted for production of Zirconia (ZrO2) nanoparticles via PLAL technique from a solid zirconium target immersed in a group of wet environments in order to study the effect of different surfactants on the optical properties and structure of ZrO2 nanoparticles. The solutions which used for this purpose are sodium dodecyl sulfate (SDS). The produces NPs were characterized by mean of many tests such as UV-visible (UV-Vis.), Transmission Electron Microscope (TEM) and Z-Potential. The UVVis spectra show a blue shift in the presence of SDS solution which indicates quantum confinement property of the NPs. The TEM test shows less than 10 nm average particle sizes with spherical and irregular shapes. It was found that use surfactant solution leads to significantly higher ablation efficiency accomplished with finer spherical nanoparticles sizes. Z-Potential test shows values in the range of (-41.3) mV and (+56.1) mV which indicate for NPs stability with extremely low agglomeration solution.

Abstract: The dry sliding wear behavior of graphite (HK-6) that is used as the sealing material to cut off hot gas was evaluated as a function of applied load, sliding speed and temperature. The reciprocating wear tests were carried out at room temperature and elevated temperatures. An attempt has been made to develop a mathematical model by response surface methodology (RSM) and an analysis of variance (ANOVA) technique was applied to confirm the validity of the developed model. Also, the effect of applied load, sliding speed and temperature on wear the behavior of graphite was investigated. The wear mechanism was compared through the observation of the worn surface by SEM analysis. The specific wear rate was dependent on the interaction between temperature, applied load and sliding speed. A developed model can be used to effectively predict the specific wear rate of graphite as a sealing material within the range of variables studied.

Abstract: To find a cheap and effective hydrogen evolution reaction catalyst, a series of Ni-doped MoS₂ microspheres consisting of MoS₂ nanosheets have been prepared via hydrothermal synthesis and characterized by scanning electron microscopy (SEM), and X-ray powder diffraction (XRD). Their performance as electrochemical hydrogen evolution reaction (HER) catalyst was studied. It is found that the Ni-doped MoS₂ exhibited superior electrocatalytic activity in the HER to undoped MoS₂ catalysts. The overpotential of Ni-doped MoS₂ has decreased compared with that of undoped sample, indicating an improved activity in HER. Furthermore, the cathodic current for the Ni-doped MoS2 catalyst is about 9 times as much as that for undoped MoS2. Based on our findings, the resulting Ni-doped MoS₂ might be promising inexpensive alternative to platinum catalysts in hydrogen production.

Abstract: Square cup drawing experiments were performed on an AZ31 sheet at various temperatures (T) ranging from room temperature to 200°C with three different punch travel speeds (V) of 3, 30 and 300mm/min. From the experiment, the highest drawability was observed either at T=175°C with V= 30mm/min or at T=200°C with V= 300mm/min. The effects of temperature and forming speed on the formability were discussed by comparing the result of drawing experiment with the high temperature tensile properties of the material. The forming limits were well predicted by FE simulation using a temperature and rate dependent constitutive model.

Abstract: Cellulose membrane was produced from bacterial cellulose in the mixture liquid medium by Acetobacterxylinum. The different medium was used including 100% coconut juice (A), 100% sugar palm juice (B) (Arengapinnata), and the mixture liquid medium between 50% coconut juice and 50% sugar palm juice (C). This cellulose membrane was applied for fermented coconut oil as a microfiltration process to determine the ability of cellulose membrane. The goal of this study is to investigate characteristic of fermented coconut oil resulted and physical properties of membrane cellulose, such as the degree of crystallinity by x-ray diffraction (XRD), water content and thermal decomposition behaviour with TGA, scanning electron microscopy analysis (SEM). From different types of cellulose membrane, cellulose membrane C (50% coconut water and 50% sugar palm juice) is the best physical properties for XRD, TGA and SEM. For all cellulose membrane which applied in fermented coconut oil it was reported that it can reduce water content and free fatty acid, but not significantly for refractive index. Cellulose membrane C was also obtained as a better cellulose membrane to increase the quality of fermented coconut oil.

Abstract: A novel polishing technology for the GaAs based diode lasers wafer is presented. Designed for technological simplicity and minimum damage generated within the GaAs based diode lasers wafer. It combines GaAs based diode lasers wafer polishing with three conditions consisting of (1) removal of thermodynamically unstable species and (2) surface oxide layers must be completely removed after thermal cleaning, and (3) a smooth surface must be provide. Revolving ultrasonic atomization technology is adopted in the polishing process. At first impurity removal is achieved by organic solvents, second NH₄OH:H₂O₂:H₂O=1:1:10 solution and HCl:H₂O₂:H₂O=1:1:20 solution in succession to etch a very thin layer, the goal of the step is removing contaminants and forming a very thin oxidation layer on the GaAs based diode lasers wafer, NH₄OH:H₂O=1:5 solution is used as the removed oxide layers in the end. The effectiveness of the process is demonstrated by operation of GaAs based diode lasers wafer, characterization of the oxide composition was carried out by X-ray photoelectron spectroscopy,and surface morphology was observed by total reflection X-ray fluorescence spectroscopy and atomic force microscope. The research results show that the polished surface without contamination, and the n-side surface are very smooth.

Abstract: The unique electrical and magnetic properties Fe86Mn13C alloy (Hadfild's steel) are due to special modulated structure. The alloy is widely used in mechanical engineering. Complex studies of the structure and properties of the alloy both in bulk samples and thin-films are suggested to describe the creation of a deformation martensite structure in Fe86Mn13C alloy in the form of self-assembled clusters. It is shown that combinations of anti-ferromagnetic austenite and ferrimagnetic martensite of deformation create unique electric and magnetic properties of Fe86Mn13C alloy both in bulk and in a thin-film state. We seek to explain the reason for the change of the sign of thermoelectric effect depending on temperature. Our task is to investigate thin Fe86Mn13C films as a possible solution to the problems of spintronics.