Advanced Materials Research Vols. 93-94

Abstract: The UV-visible spectra of soda-lime-silicate glass system with the base composition (65-x) SiO2: 10CaO: 25Na2O: xMnO2 % mol, (where x is 0.0, 0.02, 0.05, 0.10, 0.30 and 0.50 %mol) were studied at room temperature. The results are shown that the colors of glass samples were altered from colorless to dark purple with increasing of MnO2 concentration and were stable at room temperature. The color of glass sample with 0.3 %mol MnO2 was purple. Moreover, it has been found that the density and refractive index were contiguous. The optical absorption spectra can be confirmed the color of these glass samples. They exhibited a predominant broadband around 500 nm and it was clearly observed, its increasing since 0.1 %mol of MnO2. This band corresponds to an allowed transition from 5Eg5T2g, which attributed to Mn3+. When increasing MnO2 concentration, the absorption band due to Mn3+ ion was dominating.

Abstract: In this study Polyurethane (PU)/glass fiber (GF) foam composites have been produced. The PU matrix consisted of Polyol and Diphenylmethane Diisocyanate (MDI). A long glass fiber (GF) at different aspect ratio (L/D ratio) was used to study the effect of reinforcement content on their properties such as; mechanical properties (flexural modulus, stress and strain at break, hardness, impact strength) and thermal properties (heat distortion temperature, HDT). It is found that the mechanical properties such as the flexural properties (strength, strain, and modulus) and impact strength increase as increasing GF aspect ratio and optimum at aspect ratio = 7.05. However, GF aspect ratio has a slight effect on the composites hardness due to GF contents and PU densities of PU/GF foam composites are not different, significantly. And the heat distortion temperature slightly increases as GF aspect ratio.

Abstract: Effect of plasma treatments (power, pressure and treatment time) on hydrophobicity (contact angle and water absorption time) and sorption isotherm of methylcellulose (MC) film using sulphur hexafluoride (SF6) were investigated. MC film specimens were precondition in desiccators containing silica gel at 25 ±2°C for 48 h. MC film specimens were plasma treated by an inductivity coupled plasma discharged (ICP) at 13.56 MHz with operating powers (25-75 W) and gas pressures (20-200 mTorr). The treatment times (10-300 second). Hydrophobicity of treated methylcellulose film outstandingly increased. The best plasma treatment condition was power 50 W and 100 mTorr. The treated MC film had higher contact angle and water absorption time than untreated sample at all operated treatment times; contact angle was increased up to 56-80°. These results were corresponding to sorption isotherm. The treated film was absorbed moisture higher than untreated film.

Abstract: The compressive properties of aluminium foams have been shown to be affected by the oxide content in aluminium powders. An increase in the oxide content results in increasing compressive strength and energy absorption of the foams. Oxides were found to form a network of crumpled films which retards the drainage of aluminium melt during foaming. The presence of larger oxide network in foam structure due to higher oxide content in aluminium powders can effectively strengthen the Plateau borders and cell walls of the foams.

Abstract: Polylactic acid (PLA), one of the most promising bio-based materials currently available on the market, has gained much attention recently as an alternative to non-biodegradable synthetic polymers due to its comparable properties and biodegradability. The objectives of this work were to prepare a green composite between PLA and coconut fiber (CF) to investigate an aerobic biodegradation of the biocomposites under controlled composting condition according to the ISO 14855-2. The composites were prepared at various ratios by a twin screw extruder and compression molding, respectively. Based on this research, the maximum content of coconut fiber added was 4 wt%. The addition of coconut fiber can improve the impact strength of the PLA composites. The increasing amount of coconut fiber had no effect on the specific tensile properties. The prototype of biodegradation testing unit - Gravimetric measurement respirometric (GMR) system - was successfully set up according to the ISO 14855-2 standard. The coconut fiber/PLA composite can be degraded significantly, i.e., 60 wt% within only 26 days.

Abstract: The SnO2 nanostructures have been synthesized by carbon-assisted growth at 800 oC for 3 hours. Using high pure tin powder as the source materials. The synthesized products were investigated by stereo microscope, X-rays diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns show that the prepared products are tetragonal-structures with the lattice constant a = 0.4718 nm and c = 0.3187 nm. SEM images indicate that SnO2 nanowires are about tens of micrometers in length, 80-100 nm in width. The diameter of SnO2 nanoparticles vary from 10 nm to 100 nm. The synthesized products are high sensitivity and fast response time to ethanol gas at room temperature.

Abstract: Strontium substituted hydroxyapatite(SrHAp) were fabricated both in the form of powder as reference and thin film by using inorganic precursor reaction. The sol-gel process has been used for the deposition of SrHAp layer on stainless steal 316L substrate by spin coating technique, after that the films were annealed in air at various temperatures. The chemical composition of SrHAp is represented (SrxCa1-x)5(PO4)3OH, where x is equal to 0, 0.5 and 1.0. Investigations of the phase structure of SrHAp were carried out by using X-ray diffraction technique (XRD). The results showed that strontium is incorporated into hydroxyapatite where its substitution for calcium increases in the lattice parameters, and Sr3(PO4)2 can be detected at 900°C. The SEM micrographs showed that SrHAp films exhibited porous structure before develop to a cross-linking structure.

Abstract: In this paper, the conduction mechanism in organic bistable memory device was investigated by both experimental and theoretical method. The current voltage (J-V) characteristics showed the electrical bistable properties between an initial low-conductivity state and a high-conductivity state upon application of an external electric field at room temperature. The current transition exhibited a very narrow voltage range that causes an abrupt increase of current. The on-state and the off-state were proposed by space-charge-limited current and thermionic emission model, respectively. That supported by the experimental data to explained the charge transfer mechanism in organic memory device.

Abstract: Adsorption of soybean oil Silica particles modified by cationic polymer (Polyethyleneimine, PEI) was studied. Zeta potential result shows an increase in positive charge on the surface of modified silica particles. The effects of various parameters on oil adsorption such as PEI concentration, pH, electrolyte concentration, and temperature were investigated. It was found that PEI enhances an adsorption of soybean oil on PEI-modified silica particles. The soybean oil adsorption on the modified silica increased with respect to PEI concentrations. It was revealed that the higher pH, the more soybean oil can be adsorbed on PEI-modified silica surfaces. The electrolyte and high temperature reduces the soybean oil adsorbed on the PEI-modified silica particles.

Abstract: This study is to characterize and estimate preferential flow and solute transport in soft tissue. In soft tissues, large molecules such as proteoglycans trapped in the extracellular matrix generate high levels of osmotic pressure to counter balance external pressures. The semi-permeable matrix and fixed negative charges on these molecules serve to promote the swelling and collapse behaviour of cartilaginous tissues when there is an imbalance of molecular concentrations. At the same time, the collagen fibres were a network of stretch-resistant matrix, which prevents tissue from over-swelling and keeps tissue integrity. Therefore, a simplified mathematical model is proposed, and implemented in the finite element method. Analytic solutions for solute distribution in the extracellular matrix were derived by solving under loading conditions. The results were found that the estimate with field fluctuations led to the numerical results in most cases, and significant differences were only found under conditions of highly constrained deformation.