Advanced Materials Research Vol. 545

Abstract: The preparation of nanocomposite resins by solution (toluene) mixing was conducted, aiming at disaggregating silica agglomerates down into primary nanoparticles. The obtained nanocomposite resin was spun into monofilament fibers using ThermoHaake® single screw extruder. The characterizations including morphological analyses (SEM and AFM) and crystallization profile (DSC). AFM images revealed that silica particles having nanoscale sizes were evenly distributed on the surface. The presence of silica nanoparticles resulted at higher crystallization temperature (Tc) of the nanocomposite fiber when compared to those of neat fiber. As a result, the shrinkage resistance of the nanocomposite fibers was significantly improved due to an effective reinforcement. The surface hydrophobicity of the nanocomposite fibers was found higher than neat fiber due to an increase in surface roughness arising from the presence of nanoparticles on the surface.

Abstract: The experimental work for this project involved several strands; to study the water absorption characteristic of kenaf and flax in composites, to investigate the influence of fibre types on water absorption, and finally to investigate the influence of chemical treatment on water absorption. Hydrophilic character of natural fibres is responsible for the water absorption in the composites. Water absorption of kenaf and flax reinforced polyester composites was occurred via fibres lumen. Mechanical properties are affected by water absorption. After water absorption test, the specimens present poor mechanical properties such as lower value of flexural strength and flexural modulus. The matrix structure was also affected by water absorption by processes such as chain orientation and shrinkage. It was found that the different fibre types had influenced the different percentage of water absorption in composite. It seems that the compatibilization between fibres and matrix has influenced the water absorption of fibres. Acetylation of kenaf and flax fibres has reduced the hygroscopic nature of natural fibres and increased the dimensional stability of composites. The flexural strength properties of acetylated fibres were higher than untreated fibres composites.

Abstract: The aim of this research is to prepare biodegradable plastics which are made from the natural materials. In this study, solution casting technique is used to prepare the cassava starch nanocomposite reinforced kenaf. Prior to that, kenaf fibers undergo alkali and bleaching treatments in order to prepare the cellulose. Nanocellulose which used as reinforcing nanoparticle in the composites was then prepared by acid hydrolysis of obtained cellulose with 65% sulphuric acid. The preparation of cassava starch biocomposites was done using the mixture of sorbitol/glycerol (1:1) with various cellulose loading (0%, 2%, 4%, 6%, 8% and 10%). Finer size of cellulose is examined from the transmissions electron microscopy (TEM) analysis with diameter of 12±3.04 nm and length of 70-190 nm recorded. As for field emission scanning electron microscope (FESEM) analysis, good dispersion and strong interaction between starch and cellulose had been observed for the nanocomposite films. These contribute for enhancement in the mechanical performance which demonstrated improvement of all nanocomposite films compared to the neat matrix with 6 % cellulose composition showed the highest tensile stress value of 6.3 MPa.

Abstract: The effect of the free carrier absorption loss on the split-ridge waveguide based phase modulator is analyzed at 1.3 and 1.55 µm. The electrical device performance is predicted using the 2-D semiconductor package SILVACO software under DC operation. Based on the simulation results, it is shown that there is a penalty of increased free carrier absorption as the injected electrons and holes are getting higher. Meanwhile, the loss of the device at 1.3 µm is smaller than that of 1.55 µm at an equal applied voltage.

Abstract: Micro-Electro-Mechanical-Systems (MEMS) are miniaturized devices built at micro/nano-scales. At these scales, friction force is extremely strong as it resists the smooth operation and reduces the useful operating lifetimes of MEMS actuator devices. In order to reduce friction and wear in MEMS devices, we have undertaken a bio-inspired approach by applying the underlying principle of the “Lotus Effect”. Lotus leaf surfaces have small-scale protuberances and wax covered on them, which make the surfaces water-repellent in nature. By creating textured surfaces that mimic these bio-surfaces, surface energy and contact area can be reduced. This in turn reduces friction force and eventually increases the wear durability of surfaces. In our work, we have fabricated bio-inspired surfaces that resemble the texture on lotus leaf. The method includes oxygen plasma treatment of polymeric thin/thick films and application of a nanolubricant namely, perfluoropolyether (PFPE). When this method was applied to SU8 polymer thin/thick films spin coated on silicon wafers, friction reduced considerably, and simultaneously the wear durability increased by >1000 times. The method is time and cost effective, and is commercially viable.

Abstract: Ionic Liquids (ILs) based on 1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI.NTf₂) and ILs based on choline chloride (ChCl) under acidic condition was used as catalysts for esterification reaction between alcohol with fatty acid. Combination various acid namely sulphuric acid, perchloric acid, p-toulene sulphonic and various chloride salts such as ZnCl₂, SnCl₂ and FeCl₃ with ionic liquids BM.NTf₂ and choline chloride gave acidic ILs. These acidic ILs were tested as catalysts for esterification reaction. Esterification of alcohol (methanol) with fatty acid (lauric acid) using BMI.NTf₂ ILs combination with H₂SO₄ gave high activity (100 %) and selectivity (100 %) was observed over a period of 2 hours reaction with reaction temperature 70 °C. The ester was easily separated due to ILs form as biphasic with product after reaction where is ester accumulates as the upper phase and ILs with water that produce after reaction at below phase. These ILs were characterized using FTIR and NMR. From FTIR result no significant difference between ILs with combination ILs in acidic condition. The advantages of ILs as catalyst are “clean process” and “green chemistry” due to its behaviour such as non-volatile, no loss of solvent through evaporation and reduced environmentally impact. This ILs-catalyst system can be recycle for futher reaction.

Abstract: In this work, we were study the selective synthesis of GME from oleic acid and glycerol using two types of solid heteropoly acid catalysts, namely silicotungstic acid bulk (STAB) and STA-silica sol gel (STA-SG). The performance and selectivity of STAB and STA-SG in the esterification reaction have been investigated and compared to the sulphuric acid (H₂SO₄) as conventional homogeneous catalyst. The catalysts were then characterized their physical and chemical properties using BET, XRD, TEM and XPS. XPS analyses were shown a significant formation of W-O-Si, W-O-W and Si-O-Si bonding in STA-SG compared to that in STAB. The main spectra of O1s (90.74 %, 531.5 eV) followed by other O1s peak (9.26 %, 532.8 eV) were due to the presence of W-O-W and W-O-Si bonds, respectively. The STA-SG catalyst was found to be the more environmentally benign solid acid catalyst for the esterification reaction between oleic acid and glycerol due to its lower toxicity in terms of the relatively lower pH value (pH 3.7) than the STAB (pH 2.8). In addition, the ease of separation for STA-SG catalyst was attributed to its insoluble state in the product phase. The esterification products were then analysed by FTIR and HPLC. Both the H₂SO₄ and the STAB gave high conversion of 100 % and 98 %, but at a lower selectivity of GME with 81.6% and 89.9%, respectively. On the contrary, the STA-SG enabled a conversion of 94 %, but with a significantly higher GME selectivity of 95 % rendering it the more efficient solid acid catalyst.

Abstract: The Claisen–Schmidt condensations stand out to be important reaction in carbon–carbon bond formation as well as in the preparation of fine chemicals and intermediates with the presence of base catalyst such as NaOH. However, only few studies concern the synthesis and catalytic activity of mesoporous silica containing bimetallic compound as catalyst for aldol condensation of bulky aldehydes. The advantages of mesoporous systems with respect to zeolites are the improved reactant accessibility to the active sites and enhanced catalyst stability. Mesoporous silica with exceedingly high surface area (> 800 m²/g) and very high concentration of surface silanol groups fulfill most of the criteria for catalyst support. In this contribution, we report on the incorporation of Nb and Cs, alone or together, into the mesoporous silica with cubic mesostructure and the investigation of their catalytic properties in the Claisen-Schmidt condensation of acetophenone with benzaldehyde to produce chalcone, an aromatic ketone that forms the active sites for important biological compounds with antibacterial activities.

Abstract: The Bi₂Sr₂CaCu₂O₈ (Bi-2212) high-temperature ceramic superconductor has the potential to be applied in power system applications due to its low thermal conductivity. However due to the material’s brittle nature and low strength, reinforcement of the Bi-2212 superconductor is necessary for such applications. Due to its high melting point and lower heat capacity, magnesium oxide (MgO) is an excellent candidate as the reinforcement material. In this study, 3% to 8% weight percentage of nanosize MgO powder was added to Bi-2212 superconductor. The Bi-2212/MgO compounds were palletized and heat treated, followed by partial melting and slow-cooling. X-ray diffraction (XRD) was used to study the phases present in the samples. Scanning electron microscopy (SEM) with energy dispersive X-ray (EDAX) analysis was performed to investigate the microstructure, and for identifying the elemental composition of the samples. Electrical resistance and critical current density (Jc) measurements were carried out using the standard four-probe dc method. The degree of texturing of the microstructure was determined using the texture coefficient calculations. In addition, the mechanical strength of the samples was studied by conducting compression test. The results show that the addition of small amount of MgO particles has improved the texture of the Bi-2212/MgO compound. The compound with 5% MgO addition shows significantly higher strength. Addition of higher than 8% of MgO has resulted in highly porous microstructure and subsequently decreasing the strength of the Bi-2212/MgO compound.

Abstract: This work describe the optical and electrical properties of indium tin oxide (ITO) thin films prepared by thermal evaporation method on flexible plastic substrate (polyethylene terephthalate (PET)). The optical transmission and absorption of ITO films in the visible and UV rang have been studied. The resistivity, sheet resistant, carrier concentration and mobility have been evaluated by Hall Effect measurement. The surface morphology and roughness were investigated by atomic force microscopy (AFM). The results indicate that the optical transmission greater than 85% over the visible rang and it was found to be strongly dependent on the thickness of ITO films. The Resistivity and sheet resistant with low values (10^-4 Ω-cm, 9.22 Ω/ respectively) were obtained and ties values were increased with ITO thin films thickness increasing .AFM investigation showed that the roughness surface of (8 – 30) RMS have been obtained over different thickness of ITO films. The obtained results of the deposited films by this method were analyzed. Details of sample preparation, experimental methods and results are given and discussed.