Advanced Materials Research Vols. 47-50

Abstract: A molecular dynamic (MD) method is used to simulate Al atom depositing on Cu substrate by controlling the incident energy and the deposition rate for dual-target magnetron sputtering. At the interface, functional graded material (FGM) will be created to reduce the residual stress after the deposition process. The results indicate that the surface roughness of the deposited film will be reduced with the assistance of FGM, and more layers of FGM will reduce more the root-mean-square (RMS) value and the residual stress to obtain excellent quality of the deposited film.

Abstract: The effect of low-level oxidation (weight loss less than 6wt.%) on mechanical property of two-dimension (2D) carbon/carbon (C/C) composites was investigated in present work. C/C samples were oxidized in a mixture gas, composed of 10vol%O2 and 90vol%N2, at temperatures of 850°C and 1300°C, respectively. The strength of C/C composites before and after oxidation was measured by three point flexural tests. At different temperature, similar influences of low-level oxidation on mechanical property of C/C samples were observed. As a result, failure of the as-received composites was accompanied by brittle, catastrophic reduction in force. As oxidation progressed, the fracture model of oxidized samples changed from brittle model to pseudoplastic failure model. Especially, the changes of flexural strength with the weight loss increasing could be divided into two stages: (i) at low weight loss, the strength increased with weight loss and is slightly higher than that of the unoxidized composites; (ii) at high weight loss, the strength decreased gradually with the weight loss.

Abstract: Adhesion, or the binding of different materials at an interface, is of general interest to many branches of technology, e.g., micro-electronics, tribology, manufacturing, construction, etc. In addition, varieties of plasma treatments for the adhesion control of polymers are still extensively studied by a lot of researchers. However, there is a lack of research that decreases the adhesion force by using plasma treatment devices. Thus, this paper study to decrease the adhesion force between a medical rubber, chloride-isobutene-isoprene rubber (CIIR), and stainless-steel SUS440C by using oxygen plasma treatment. The different adhesion forces were measure after plasma treatment with various methods. The elastic modulus was increased by oxygen plasma treated to the CIIR specimen. The results show that the elastic modulus was increased 15% to 28% as the plasma treated to the CIIR specimen. Experiment results showed that the adhesion force decreased by about 95-99.8% by using oxygen plasma treatments between CIIR and SUS440C. The different adhesion forces were explained based on the morphology and Attenuated Total Reflectance (ATR) FTIR.

Abstract: The shape memory alloy strips of Ti50Ni15Cu35 and Ti50Ni10Cu40 had been fabricated by arc melt overflow. Their microstructures and shape memory characteristics were investigated by means of X-ray diffraction, optical microscopy and differential scanning calorimetries. The microstructure of as-cast strips exhibited columnar grains normal to the strip surface. X-ray diffraction analysis showed that one-step martensitic transformation of B2-B19 occurred in the alloy strips. According to the DSC analysis, it was known that the martensitic transformation temperature (Ms) of B2→B19 was 71.2°C in Ti50Ni15Cu35 and 64.5°C in Ti50Ni10Cu40 alloy strip, respectively. During thermal cyclic deformation with the applied stress of 60 MPa, transformation hysteresis and elongation associated with the B2-B19 transformation were observed to be 4.9°C and 1.4% in Ti50Ni15Cu35 alloy strip. However, Ti50Ni10Cu40 alloy strip was so brittle that its mechanical properties could not be measured.

Abstract: The osseointegration capability of titanium dental implants is related to their chemical composition and surface roughness. In this study, the combination of grit-blasting and micro-arc oxidation had been used for producing the improved implant surfaces. The ceramic particles were projected to titanium dental implants through a nozzle at high velocity by means of compressed air to get high surface roughness. Then the surface of titanium implants was modified by micro-arc oxidation treatment. The current density, frequency and duty were 50-300 mA/cm2, 100 Hz, and 50%, respectively. A porous TiO2 layer was formed on the surface after the oxidation treatment. The surface structure of oxidized implants exhibited nanometer-sized pores with an average diameter of 0.2 µm. The TiO2 passive layer of the implant surface can attribute to the excellent biocompatibility. The high roughness (Ra=0.182 µm) formed by grit-blasting maximizes the interlocking between mineralized bone and the surface of the implant. Surface roughness in the manometer range formed by micro-arc oxidation treatment would play an important role in the adsorption of proteins, adhesion of osteoblastic cell and thus the rate of osseointegration.

Abstract: The use of TiO2 as photocatalyst to degrade the organic compounds is an effective method of oxidation process and has been widely studied in environmental engineering. However, TiO2 absorbed the UV light which is only small part of sunlight reaching earth surface to activate photocatalytic procedure is a major disadvantage. Therefore, studies on the development of new TiO2 that its photocatalytic activity can be activated by visible light which is the major part of sunlight will be valuable for field application. In this study, we evaluate the photocatalytic degrading efficiency of porphyrins/TiO2 complexes on the organic pollutants under irradiation with visible light (λ= 419 nm). The results showed that the photodecomposition efficiency of methylene blue were up to 95% and 90% respectively after using NiTPP/TiO2 and ZnTPP/TiO2 irradiated with visible light for 6 h. These evidences reveal that the system of porphyrin/TiO2 complexes has significantly high efficiency of photocatalytic degradation under visible light irradiation.

Abstract: In this paper, carbon nanotubes were used as the reinforcements in the polymer composites for the application of electromagnetic interference, due to their outstanding mechanical and electrical properties. The multi-walled carbon nanotubes (MWNTs) synthesized by the chemical vapor deposition method were used to reinforce the epoxy resin by both mixing and spreading processes. The effects of the weight percentage and the reinforced form of MWNTs on electromagnetic interference shielding effectiveness, including the absorbance and the reflectance, were investigated. From experimental results, the electromagnetic shielding effectiveness of the nanocomposite specimens is improved with increasing content of MWNTs. The nanocomposites fabricated by the spreading process have better shielding effectiveness than those made by the mixing process. The nanocomposites, made by the spreading process with 2 wt% MWNTs, had up to 22.69 dB of electromagnetic shielding effectiveness. The reflectance percentage of electromagnetic shielding increases for higher content of MWNTs. The layerwise form of MWNTs in the nanocomposites, resulting from the spreading process and having a better electromagnetic shielding effectiveness, can be observed from the morphologies of the tensile failure surfaces of the nanocomposite specimens by filed emission scanning electron microscopy.

Abstract: A new solid-electrolyte impedance-metric NOx sensor device composed of a lithium ionic solid electrolyte: Li1.5Al0.5Ti1.5(PO4)3 (LATP) as a transducer and ceramic oxides (perovskite-type oxides, TiO2, SnO2, etc) as a receptor, respectively, have been systematically investigated for the detection of NOx (NO and NO2 ) in the range 10 – 200 ppm at 400 - 500°C. Responses of the sensors were able to divide component between resistance and capacitance, and it was found that the device was applicable to the selective detection of NO or NO2 concentration in each ingredient. Especially, those using TiO2, SnO2 (n-type semiconductor) and perovskite-type oxides (LaCoO3, LaNiO3 and LaCrO3) based receptors gave good responses to NO and NO2. It was also found that the responses were different between n-type or p-type semiconductors, in which we tried to elucidate the sensing mechanism

Abstract: Smart materials, which present significant multiphysical couplings, are now widely used for the conception of smart structures whose mathematical modelings are here presented in the case of thin plates or slender rods made of piezoelectric or electromagneto-elastic materials.

Abstract: Natural fiber reinforced polymer composites became more attractive due to their light weight, high specific strength, biodegradability. However, some limitations e.g. low modulus, poor moisture resistance were reported. The mechanical properties of natural fiber reinforced composites can be improved by hybridization with synthetic fibers such as glass fiber. In this research, mechanical properties of short sisal-PP composites and short sisal/glass fiber hybrid composites were studied. Polypropylene grafted with maleic anhydride (PP-g-MA) was used as a compatibilizer to enhance the compatibility between the fibers and polypropylene. Effect of weight ratio of sisal and glass fiber at 30 % by weight on the mechanical properties of the composites was investigated. Morphology of fracture surface of each composite was also observed.