Advanced Materials Research Vol. 576

Abstract: This paper examines the friction behaviour of AlCrN and TiN PVD coatings in atmospheric air and vacuum using a ball-on-disc and a reciprocating tribotesters. Comparative study on the coating sliding in air and in high vacuum environment provides important insight on the effect of oxidation on the friction behaviour of the coatings. Other important factors such as load, sliding velocity, temperature effects on the frictional behaviour of these coatings were also investigated. In the ball-on-disc tests carried out in vacuum, (i) TiN gave lower coefficient of friction (COF) than AlCrN, indicating that TiN was more lubricous, (ii) higher speed resulted in lower COF, and (iii) the COF of both coatings were lower than that produced in air. In ambient air, (i) AlCrN gave lower COF than TiN with high wear debris retention on the sliding interface due to the effect of oxidation, and (ii) higher speed resulted in lower COF, similar to that observed in vacuum. In the reciprocating tests, at low load, increasing the temperature from room temperature to 150 °C resulted in a reduction in the COF. However, at high load, the temperature virtually did not affect the COF. Higher nominal load resulted in lower COF while higher speed resulted in higher COF.

Abstract: Cobalt-Iron (CoFe) nanocrystalline coatings are successfully prepared in 30, 60 and 90 minutes time depositions using electrodeposition method. The effect of time deposition towards crystallographic structure, elemental composition, surface morphology, microhardness and corrosion behaviour of CoFe coatings were investigated. The CoFe nanocrystalline coatings were deposited on stainless steel substrate at pH 3 environment. The grain sizes of the coatings are in the range of 57.88 to 70.18 nm. The CoFe nanocrystalline coating prepared at 90 minutes deposition achieves the highest microhardness of 290 HV. This coating also exhibits the lowest corrosion rate with 1.086 mpy. It is found that the increment of time deposition improves the microhardness and corrosion behavior of CoFe nanocrystalline coatings.

Abstract: The electrophoretic deposition (EPD) technique was applied in order to produce titanium dioxide (TiO2) coating on stainless steel. Voltages of 2V, 4V, 6V and 8V and two types of TiO2 suspensions; (i) acidic (pH 4) and (ii) alkaline (pH 8) were used. Depositions were carried out for duration of 10 minutes. The TiO2 coatings phases, morphologies, thicknesses and weight were analysed. It was found that thickness and weight of coatings produced using both acidic and alkaline TiO2 suspensions increased proportionally. However, from the uniform and dense morphology of coatings, acidic TiO2 suspension was observed to yield better TiO2 depositions through the EPD technique.

Abstract: Zinc Oxide (ZnO) nanostructured was successfully synthesis by electrochemical deposition method. In this paper present the ZnO nanorods growth in a zinc nitrate/hexamethylenetetramine solution at 90°C with different potential applied. The effect of the growth process was investigated by the cyclic voltametric curve and the current-time curve. The structural of ZnO nanorods evidence that it has single crystalline, a wurtzite crystal structure with markedly preferential orientation along (001) direction was measured x-ray diffraction. The observation of ZnO nanorods was measured on field emission scanning electron microscopy that diameter of ZnO rods were below than 100 nm sizes. Uv-Vis spectrophotometer used to determine the transparency of ZnO nanorods through the UV light. The ZnO nanorods show the average transmittance (<90%) for all potential applied. The piezoelectric property of ZnO nanorods were measuring connected with two electrodes to the metal contact on the film that was driven by an ultrasonic wave. The piezoelectric output current was gained and characteristics curve have been illustrated for different voltage with constant driving frequency of ultrasonic wave at 40 kHz.

Abstract: The effect of RF power on the formation and morphology evolution of ZnO nanostructured thin films deposited by magnetron sputtering are presented. This project focused on electrical, optical and structural properties of ZnO thin films. The effect of variation of RF power at 50 watt-250 watt at 200 °C on glass substrate of the ZnO thin films was investigated. The thin films were examined for electrical properties and optical properties using two point probe current-voltage (I-V) measurement (Keithley 2400) and UV-Vis-NIR spectrophotometer (JASCO 670) respectively. The structural properties were characterized using field emission scanning electron microscope (FESEM) (JEOL JSM 7600F) and atomic force microscope (AFM) (Park System XE-100). The IV measurement indicated that at RF power 200 watt the conductivity of ZnO thin film show the highest. All films show high UV absorption properties using UV-VIS spectrophotometer (JASCO 670). The root means square (rms) roughness for ZnO thin film were about 4 nm measured using AFM. The image form FESEM observed that transformation of structure size started to change as the RF power increase.

Abstract: This paper reports on the dielectric properties of multilayer PVDF-TrFE/PMMA:TiO2 thin film. Two samples were fabricated on ITO substrates; one with PVDF-TrFE only and another PMMA:TiO2 on PVDF-TrFE on (PVDF-TrFE/PMMA:TiO2). Both samples were produced by spin coating method. Dielectric properties were characterized using impedance spectroscopic. Dielectric constant, k, capacitance and dielectric loss, tan δ values of PMMA:TiO2/PVDF-TrFE were measured in the frequency range 0 – 50 kHz. The result for dielectric loss did not show any significant different between the samples with and without nanocomposite PVDF-TrFE layer. However, the dielectric constant are affected when depositing a nanocomposite PVDF-TrFE layer on PMMA:TiO2. The dielectric constant is decreased by 0.3 from 7.9 to 7.6.

Abstract: In this study nanocrystalline anatase TiO2 thin films were prepared by electrophoretic deposition of titania sol at various applied voltages. The well-known sol-gel method was used to prepare the titania sol. The influence of applied voltage on the structure, morphology and optical properties of thin films has been characterized by X-ray diffraction, field emission scanning electron microscopy and UV-Vis spectroscopy. The results show that the thickness of the films formed on the substrate increases with increasing the applied voltage. However, with increasing the thickness of the films, the cracks increased and the transparency reduced in the visible region.

Abstract: An endeavor has been made to study and compare the friction coefficient of different polymer and composite materials. Experiments were carried out when stainless steel 304 (SS 304) pin slides on different types of composite and polymer materials such as cloth reinforced ebonite (commercially known as gear fiber), glass fiber reinforced plastic (glass fiber), nylon and polytetrafluoroethylene (PTFE). Experiments were conducted at normal load 5, 7.5, 10 N, sliding velocity 0.5, 0.75, 1 m/s and relative humidity 70%. Variations of friction coefficient with the duration of rubbing at different normal loads and sliding velocities were investigated. Results show that friction coefficient varies with duration of rubbing, normal load and sliding velocity. In general, friction coefficient increases with the increase in normal load and sliding velocity for all the tested materials except nylon. At identical operating conditions, the magnitudes of friction coefficient are different for different polymer and composite materials.

Abstract: A hot filament thermal chemical vapor deposition (CVD) reactor was used to deposit solid thin films on stainless steel 316 (SS 316) substrates at different flow rates of natural gas. The variation of thin film deposition rate with the variation of gas flow rate has been investigated experimentally. During experiment, the effect of gap between activation heater and substrate on the deposition rate has also been observed. Results show that deposition rate on SS 316 increases with the increase in gas flow rate. It is also observed that deposition rate increases with the decrease in gap between activation heater and substrate within the observed range. In addition, friction coefficient and wear rate of SS 316 sliding against SS 304 under different normal loads are also investigated before and after deposition. The experimental results reveal that improved friction coefficient and wear rate are obtained after deposition as compared to that of before deposition.

Abstract: ZnO thin films were deposited on Teflon substrates by RF magnetron sputtering at different substrate temperature and different RF power. In this work, we investigated the dependence of the deposition rate and also the ZnO physical and electrical properties on the substrate temperature and RF power. It is observed that the deposition rate increased as the temperature and RF power increased. FE-SEM images confirmed that microstructure of the thin films consists of nanoparticles. XRD data confirmed that the ZnO thin films at various RF power and substrate temperature have (002) structure.