Materials Science Forum Vols. 505-507

Abstract: The multi-walled carbon nanotubes (MWNTs) were added into the phenolic resin to fabricate MWNTs/phenolic nanocomposites. The pressure and temperature were applied to cure MWNTs/phenolic compound by hot press method, then followed by a post curing process. The results showed that post-curing of the nanocomposites specimen is necessary for better mechanical properties. The temperature used for post curing should be higher than the curing temperature. The higher curing pressure improved the Young’s modulus of the nanocomposites. The tensile failure morphologies of MWNTs/phenolic nanocomposites were examined using field emission scanning electron microscope (FESEM) to evaluate the effects of manufacturing processes on the mechanical properties of MWNTs/phenolic nanocomposites.

Abstract: This paper presents the fabrication and preliminary experimental studies of flow performance on a valveless micro impedance pump actuated by the shear mode PZT actuator, a novel method of pumping fluid on the microscale. The micro impedance pump was constructed of three nickel electroforming components, two glass tubes, a PZT actuator and a glass substrate. The three electroforming components include a bottom structure plate, a channel plate and a top structure plate. The AZ-type positive photoresist was used as the electroforming mould, which was patterned by UV lithography. The top and bottom structure plates were aligned and assembled with the channel plate by epoxy adhesive such that a micro channel with a compressible section coupled at both ends to rigid sections of different impedance was formed. A pressure head can be built up to drive flow through the accumulative effects of wave propagation and reflection originating from the periodic PZT excitation, located asymmetrically along the length of the compressible section of the channel. Experimental results showed that the flow was reversible and pressure heads had a highly non-linear dependence on the frequency and amplitude of the excitation. Maximum flow rates of 13 μl min-1 have been achieved with the channel size of 15μm high and 4 mm wide.

Abstract: The nanoimprinting process between a nickel mold and a gold thin film consisting of 9500 – 11000 atoms was studied using molecular dynamics computational simulation. The nickel mold and the gold thin film were both formed in face central cubical (FCC) single crystal, and the simulation condition was in an isothermal state of 300K. The Morse potential was utilized in order to determine interatomic forces and potentials. During the nanoimprinting process, jump-to-contact, thin-film recovery, slip-line like, dead-metal zone and dislocation phenomena were observed. After finishing nanoimprinting processes, the interactive force curves between the mold pattern and thin film, and those inside the thin film were measured. By varying the pattern width of the mold and incorporating the measured force curves inside the thin film, the length effect on metallic pattern formation can be determined. In addition, through analytical investigation, it can be observed that the thin-film thickness, the pattern width of the mold, and the applied force should be matched up very well in order to obtain good formation of metallic pattern.

Abstract: This paper presents a novel and high-precision technology for extracting the Young’s modulus of thin films through the capacitance-voltage (C-V) measurement of microstructures. An algorithm considering the electric-mechanical coupling effect and the distributed character of microstructures is developed for extracting the Young’s modulus through the C-V measurement of microstructures. The average error percentage of the extracted Young’s modulus of single-crystalline silicon is below 1% and the high precision and repeatability of the present methodology are verified. Since the driving and response signals are both electric, they could be accomplished using existing semiconductor testing equipments through probing on the bonding pads of devices. Because hardware replacement could be avoided, this methodology shows substantial advantage over other property-extraction methods for large-scale implementation in semiconductor or MEMS fabs.

Abstract: Molecular dynamics (MD) simulation and the experiment of adhesion force measurement were introduced to study the nanostructure formation process in the atomic force microscopy. The atomic level process of the nanostructure formation and the thermo-mechanical effect caused by the factors of the contact area, the adhesion force, and the temperature were clearly shown and discussed. The size of the forming nanostructures was found to be positively related to the contact area and temperature, but the adhesion force would decrease as the temperature increase. In the case of higher temperature with smaller adhesion force, however, the larger-size nanostructure could still be made.

Abstract: The compensation of thermal deformation is the most significant for the accuracy of a machine tool. This study proposes an approach based on genetic algorithms (GA) to build the dynamic model of the prediction for thermal deformation of a machine tool. GA is used to optimize the prediction accuracy by using appropriate number and locations of temperature sensors, the model order and the time delay between temperatures and thermal deformation. The compared results show that the proposed approach can improve the accuracy of prediction results and better than other methods.