This study presents a high-performance ZnO piezoelectric transducer integrated with the flexible stainless steel substrate. The ZnO piezoelectric film of 1.08nm was deposited on the flexible stainless steel substrate using a RF magnetron sputtering system. The cantilever length of 1cm and the vibration area of 1cm2 were designed for low-frequency environment according to the Cantilever Vibration Theory. The effects of various sputtering parameters such as substrate temperature, RF power and sputtering pressure were investigated to improve the piezoelectric characteristics of ZnO thin films. It was also discussed the unit thickness of open voltage values, and then the optimal sputtering parameters were determined. The physical characteristics of ZnO thin films were obtained by the analyses of the scanning electron microscopy (SEM) and X-ray diffraction (XRD) to discuss the surfaces, cross section and crystallization of ZnO thin films. The voltage analysis were measured the open and load voltage by the measurement system. The optimal deposition parameters for ZnO thin films are substrate temperature of 300¢J, RF power of 75W, sputtering pressure of 9 mTorr and oxygen concentration of 60%, which were determined by physical characteristics and voltage analysis. The study employs a precise mass loading of 0.57g on the cantilever to increase the vibration amplitude. The vibration source from 1~150Hz was provided to the piezoelectric transducer, and then the experimental results were showed resonance frequency of 75Hz by oscilloscope. When the optimal thickness of ZnO films is 1.08£gm and vibration amplitude is 1.19mm, the open circuit voltage of the power generator is 5.25V.After rectifying and flitting with a capacitor of 33nF,the maximum power of 1.0£gW/cm2 was achieved with the load resistance of 5M£[.

This investigation examines a novel means of integrating high-performance AlN piezoelectric thin films with a flexible stainless steel substrate (SUS 304) to fabricate a double-sided piezoelectric transducer. Various sputtering parameters, such as sputtering pressure, substrate temperature, nitrogen concentration, and RF power, were investigated to improve the piezoelectric characteristics of AlN thin films. Scanning electron microscopy and X-ray diffraction of AlN piezoelectric film reveal a rigid surface structure and highly c-axis-preferring orientation. The maximum output power per unit thickness was discussed, and the optimal sputtering parameters were determined. The double-sided piezoelectric transducer is constructed by depositing AlN piezoelectric thin films on both the front and the back sides of SUS 304 substrate. The titanium (Ti) and platinum(Pt) layers were deposited using a dual-gun DC sputtering system between the AlN piezoelectric thin film and the SUS 304 substrate. The optimal deposition parameters for AlN thin films are sputtering pressure of 5 mTorr, substrate temperature of 300 ¢J, nitrogen concentration of 40 %, and RF power of 250 W. The maximum open circuit voltage of the transducer under the vibrational frequency of 80 Hz, vibration amplitude of 4mm, and mass loading of 0.5g, is approximately 20 V, or 5.3 V/£gm. After full-wave rectification and filtering through a 33 nF capacitor, a specific output power of 1.462 £gW/cm2 is obtained from the transducer with a load resistance of 7 M£[.

In case of metalworking operations, the purpose of lubrication is served by a complex mixture of two or more phases, these mixtures are known as metalworking fluids (MWFs). For many decades oil-in-water emulsions have been used as metalworking fluids. The particular advantage of using oil-in-water emulsion in metalworking operations is that it combines the cooling property of water and the lubrication property of the oil. To explain the lubrication mechanism for oil-in-water emulsions as metalworking fluids a variety of models and theories has been proposed. To understand the lubrication mechanism, the role of each ingredient in the tribological process needs to be studied. In the present study a model for lubrication which determines force and proximity regimes of droplets based on the droplet size distribution is proposed. Dynamic light scattering (DLS) is used to characterize the emulsions. The small droplets are found to be the ones which enhance lubricity. DLVO (Derjaguin-Landau-Verwey-Overbeek) theory is used to validate the results. The concentration and type of surfactant is found to be the performance controlling parameter. A further analysis of the three interfacial energetics; oil/water, oil/substrate, water/substrate, is studied in the presence and absence of surfactants with the help of a Goniometer, Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM). Such energetics reflects the rate at which the excess surfactant molecules accumulate at the water/oil interface and desorb into the phases. The tribological response is recorded using AFM and the nanotribometer (NTR). Frictional response of the chemisorbed self-assembled monolayer of surfactant (sodium oleate) on the steel substrate reflects that a tribofilm helps in lubricating the contact under boundary lubrication by creating a low shear strength material. Water being the continuous phase in oil/water emulsion a thin water layer adjacent to steel substrate is always present. This thin layer on the solid substrate acts as a barrier to the lubricating oil droplets to reach the metal surface. The focus of the present work is also to investigate conditions which permit the disjoining of the water film to allow the oil to lubricate the metal substrate. AFM is used to study the interaction force between an oil droplet and the steel substrate through water. An oil encapsulated SiO2 colloidal probe used to simulate the oil droplet. The charge regulatory status of the substrates and interfaces are found to be critical in mapping the force characteristics when DLVO interaction is considered. The condition for activation of non-DLVO (hydration, hydrophobic, capillary) forces are also identified and found to be dependent on the physical states of surfaces. Disjoining of the thin film can be controlled by selecting surfactants based on interfacial energetics and attractive force characteristic can be achieved to facilitate lubrication.