Advanced Materials Research Vols. 26-28

Abstract: (Ti, Al) N coating had been deposited by Arc Ion Plating, in an atmosphere of nitrogen. The structure of the coatings was examined as a function of deposition conditions by X-ray diffraction, and the crystallographic orientation was determined by use of a texture coefficient. The coatings on ground titanium substrates developed a strong (111) orientation from the earliest stages of growth, although the degree of orientation was dependent on deposition conditions. TiAlN coatings, however, showed relatively multiple orientations mainly of (111) and (200). Furthermore, TiAlN films demonstrated superior corrosion resistance in a molten aluminum alloy at 680°C. This paper described in detail the corrosion and mass loss phenomena related to this steel-cast metal interaction.

Abstract: Low-temperature plasma-enhanced chemical vapor deposition of amorphous carbon (a-C:H) films was investigated for surface passivation of carbon-doped silicon oxide (SiOCH) films. The a-C:H films were deposited using CH4 and Ar gases at 40–65°C. FT-IR results showed that the deposited films are a-C:H which incorporates hydrocarbon groups. In current−voltage measurements, the a-C:H showed a low leakage current of ~10–10 A/cm2 in air, indicating that the a-C:H films have a potential as a surface passivation layer to prevent moisture absorption in air. The insulating properties of room-temperature deposited SiOCH covered by the a-C:H strongly depended on radio frequency (RF) power in the SiOCH deposition. In the SiOCH film deposited at high RF power of 200 W, the resistivity in air was improved by the a-C:H passivation.

Abstract: With Ti(OBu)4 as precursor, and HAC as complexing agent, pure and Fe-doped TiO2 gelatins were prepared by sol-gel method. During the process of gel formation, metal ions were dispersed into the porous TiO2 matrix. Then, powders of pure nano-TiO2 and Fe-doped nano-TiO2 were prepared by drying, grinding and calcining at different temperatures. The grain size and phase structure of pure and Fe-doped TiO2 after calcined at different temperatures, were studied by X-ray diffraction (XRD) and Beckman Coulter Sorption Analysis. The results showed that, the Fe3+-TiO2 had better photocatalytic activity in degradation rate of methyl orange under sunlight. The degradation rate was up to 93% as the system was placed under sunlight for 5 h. The optimum calcination temperature for the best catalytic activity was determined to be 500°C, and the mechanism was discussed.

Abstract: p doped nano-crystal l ine si l icon (nc-Si) were deposi ted by hot wire chemical vapour deposi t ion (HWCVD) using SiH4 , H2 and B2H6 precursors. nc-Si was characterized by XRD, Raman and residual st ress. Residual stress of nc-Si were measure by Sin2ψ vs d method. As deposi ted fi lms show tensi le st ress and decreases from 2500 MPa to 250 MPa wi th increase of B2H6 f low rate f rom 0.01 to 5 %. Crystal l ine f ract ion of p doped nc-Si decreases f rom 35 to 57% as wi th increase of B2H6 concent rat ion

Abstract: We report the growth of silicon carbide (SiC) nanowires on silicon substrates by metal organic chemical vapor deposition (MOCVD) using dimethylvinyllsilane [CH2CHSi(CH3)Cl2] as a source gas and metal catalysts of Ni and Fe. Various growth conditions such as the growth temperature and the pressure of the source gas are examined to achieve high yield growth of SiC nanowires and to control their shape. No SiC nanowires were formed when using Fe. In contrast, by using Ni catalyst, numerous SiC nanowires of about 30 nm thick can be grown at the pressure of the source gas of 30 Pa at 800 °C. Their microstructure is revealed by scanning electron microscopy (SEM) and transmission electron microscope (TEM).

Abstract: The gate, source, and drain electrodes of organic thin-film transistor(OTFT) to use as a switching device for a flexible display was fabricated in microcontact printing process with hard poly(dimethylsiloxane)(h-PDMS) stamp. The OTFT with thin-film dielectric layer of parylene-C(4300Å, 5000Å, 6500Å, 7500Å, and 9000Å) were formed using special coating system, and organic semiconductor layer was ink-jet printing process at room temperature. The microcontact printing process using self-assembled monolayer(SAM) and h-PDMS stamp made it possible to fabricate OTFT with channel length down to 600nm, fabricated thin film electrode of Au/Cr (100nm/5nm), and reduced the fabrication process by 20steps compared with photolithography process. Since the fabrication process was done in room temperature, there was no appeared such as pattern shrinkage, pattern transformation and bending problem.

Abstract: Y3Al5O12 (YAG) is one of the important and extensively used solid state laser host materials. YAG nanocrystals were synthesized by low temperature glycol method. This is a modified sol–gel method performed at low temperature that consists of a mixture of salts, mostly nitrates in an aqueous media. Single phase nanocrystalline YAG was obtained at 850 °C, which is lower temperature compared to the other methods such as wet-chemical method. This is however, little higher than the material made by alkoxide sol–gel process. The structural characterization is done by powder XRD, SEM and TEM techniques. The crystallite sizes range from 20-50 nm for the materials prepared at 850- 950 °C.

Abstract: Nano-particles of metal oxides Mn3O4, Cu2O, Fe3O4, the mixture of Zn(OH)2 and ZnO have been successfully prepared via a novel solid-liquid mechanochemical reaction technology. The metal powders are ground in water solutions using planetary ball mill. The solid-liquid reactions can occur on the surface of the powders and the reacted layer can be continuously peeled off during milling. The mean sizes of the as-prepared particles are approximately 20~100nm.The formation of nano-particles is attributed to the reactions between particles and solution as well as the repeated and quick peeling of the formed oxides on the surface of metal particles. Furthermore, the reaction rate and phase types of the products can be controlled by adjusting the pH value of the solution.

Abstract: A crystallization process in an amorphous state under isothermal condition is examined for binary alloys ZrNi and ZrNi2 by differential thermal analysis (DTA). Time dependence of DTA curves is measured at several constant temperatures just below crystallization temperature. The fraction of crystallized volume in amorphous state and its time evolution during isothermal annealing are measured. These data are analyzed by the Johnson-Mehl–Avrami formula. The Avrami exponent is 2.4±0.1 for ZrNi and 3~4 depending on the set temperature for ZrNi2. The activation energy for crystallization of amorphous ZrNi and ZrNi2 was estimated by plots of lnt1/2 vs. 1/T.