Advanced Materials Research Vols. 47-50

Abstract: This paper presents the development of a variable stiffness and damping isolator using magnetorheological (MR) fluid technology. The MR fluid isolator is composed of two variable volume rubber bladder filled with MR fluid, a pipe and a MR valve connecting them. One of the bladders supports disturbance force and the MR fluid flows between two bladders because of the variation of bladder volume due to deformation. The shear stress of the MR fluid in MR valve is varied by an applied magnetic field, which thereby varies the characteristics of the isolator, such as its stiffness and damping. A mathematical model of the isolator was derived, and a prototype of the MR fluid bladder spring was fabricated and its dynamic behavior was measured in vibration force for a wide range of frequencies under various applied magnetic fields. The parameters of the model under various magnetic fields were calculated and the bladder dynamic performances were evaluated. A non-resonant control was employed to minimize the vibration amplitude of the system. Numerical simulation results indicated that the semiactive control system produced much better isolation performance than a passive system.

Abstract: Optical fibers, in particular, glass fibers, are mostly used in the field of optical communication, however in recent years new optical sensors based on the optical fibers have been reported in literature and produced commercially. Extrinsic and intrinsic character of the fibers have been implemented in development of such sensing devices. Glass Optical Fibers (GOF) because of low attenuation are more suitable for the optical communication purposes while Plastic Optical Fibers are advantageous for the linking purpose and some sensing operations. Considering this point different (POF) optical fiber sensors have been developed by author to show potential applications of POFs in sensor technology. New simple devices at the minimum cost are introduced in this study. Results for light reflection sensing, light leakage sensing, level sensing, and distance gauging are obtained. Presented systems are mostly in bulk form, however, these devices with good results show that in principle, these ideas can be implemented in design of small scale devices. It seems to be a great potential to apply these ideas in order to develop new devices suitable for compact and integrated applications. In this article some examples are given in which the reported results verify the concept and applicability of such devices for future sensing technology.

Abstract: In this paper, we described the synthesis of N,N’-di-(2-ammoniumethyl)perylene- 3,4,9,10-bis(dicarboximide) ditrifluoroacetate (1), an ionic organic compound that self-organized to give chromonic liquid crystals and anisotropic crystals. Using a polymer template with micrometer-scale features to direct the ordered arrangement of 1, patterned structure with micrometer-scale local order was fabricated. The anisotropic (direction-dependent) properties of the crystals and micropatterns of 1 were investigated.

Abstract: Biofilm formation and the adsorption of nonsulfate-reducing marine bacterium Vibrio natriegens (V. natriegen) to different metallic surfaces have been studied by atomic force microscopy (AFM). The nature of extracellular polymeric substance (EPS) has been monitored through the force-distance curve. EPS may act as adhesive binding adjacent cells and thus further enhance the aggregation of microbes during cluster formation due to its adhesiveness in nature. The AFM images supply the change of the morphology of microbial cells and colonies, the distribution of microbial colonies and the presence of EPS on the surfaces with immersion. Results show that the biofilms formed on the surfaces increase in thickness and heterogeneity with time and that 3~7 days is the proliferation period of the bacteria on metallic surfaces. The corrosion type of the metals by V. natriegens could be confirmed as typical pitting attack through scanning electron microscopy (SEM) observation.

Abstract: A novel super-hydrophobic film was prepared by myristic acid (CH3(CH2)12COOH) chemically adsorbed onto the polyethyleneimine (PEI) coated Fe3Al-type intermetallic wafer. The film character and structure were probed with contact angle measurement, scanning electron microscopy (SEM) and atomic force microscope (AFM). The results suggest that the structure of the film is similar to lotus and the seawater contact angle is larger than 150◦. Moreover, the corrosion resistances of untreated and modified samples in seawater were investigated by electrochemical impedance spectroscopy (EIS). Experimental results show that the corrosion rate of Fe3Al-type intermetallic with super-hydrophobic surface decreases dramatically because of its special microstructure.

Abstract: In terms with the natural structure and property of microbe film, microbe film was simulated by Calcium Alginate gel Acetic acid, manganese dioxide, sodium sulfide were added separately into sodium chloride solution to simulate different bacteria culture systems. The corrosion behavior of Fe3Al was characterized based on the analysis of open circle potential, polarization curves, and electrochemical impedance. The corrosion potential of simulating SRB was 0.6V negative-moved in comparison with that of the other two bacteria. The results indicate that Fe3Al electrodes were much easier eroded by SRB environment.

Abstract: Melt-laminates of wood/NR and expanded ethylene-propylene-diene-rubber (EPDM) were prepared for rubber composite roofs. The ethylene-propylene bound OBSH (EPR-b-OBSH) blowing agent was introduced as an effective blowing agent in the EPDM layer and the foam property results were compared with the pure OBSH blowing agent. It was found that the EPR-b- OBSH gave expanded EPDM layer with a larger number of more uniform cells. The optimum concentration for EPR-b-OBSH blowing agent for achieving the maximum peel strength and for lowering the thermal conductivity of the wood/NR-eEPDM laminate was 3.0phr.

Abstract: Notched tensile tests were performed to evaluate the presence of notch on the tensile strength of Ti-6Al-6V-2Sn laser welds, which were post-weld aged at different temperatures. Ti-6Al-6V-2Sn laser welds showed notch brittleness except for the welds aged at/above 704 oC. Fine acicular α uniformly distributed in β matrix in the fusion zone accounted for the high hardness (Hv 440) as compared with mill-annealed base metal. Overaging at/above 704 oC resulted in coarsening the microstructures and decreased notch brittleness. The fracture features of the weld were strongly affected by the orientation of the solidified structures with respect to the crack growth direction.

Abstract: The purpose of this paper is to apply MEMS techniques to manufacture a gas flow sensor that consists with an airflow rate and airflow direction sensing units for detection of airflow states. This study uses a silicon wafer as a substrate which is deposited silicon nitride layers. To form the airflow rate sensing unit, a micro heater and a sensing resistor are manufactured over a membrane that released by a back-etching process. The airflow direction sensing unit is made of four cantilever beams that perpendicular to each other and integrated with piezoresistive structure on each micro-cantilever, respectively. As the cantilever beams are formed after etching the silicon wafer, it bends up a little due to the released residual stress induced in the previous fabrication process. As air flows through the airflow rate sensor, the temperature of the sensing resistor decreases and the evaluation of the local temperature changes determines the airflow rate. On the proposed sensor, the airflow direction can be determined through comparing the resistance variation caused by different deformation of cantilever beams at different directions.

Abstract: Recently, the interest has increased to recycle things after use. In addition, the pressure of the environment defence organizations has increased in the same direction. Accordingly, the composite industry has begun investigating the possibility of increasing the proportion of recycled or biodegradable composites. This leaded to search about environment eco-friendly reinforcement and resins systems while providing the same performance as their man made counterparts. Natural fibers offer the possibility to play the role of the reinforcing material. In this study, we mix the 25% untreated date palm tree fibers with 75% polypropylene using double screw extruder. Comparison between plane polypropylene and 25 % raw date palm fiber was done. Tensile test and water absorption test were done upon plain polypropylene and 25% raw date palm fiber specimens. Tensile strength of reinforced polypropylene was about 20% lower than plain polypropylene. In the other hand, modulus of elasticity of composite showed an increase of about 30% compared to plane polypropylene. Water absorption was less sound in deterioration of the composite.