Advanced Materials Research Vols. 415-417

Abstract: Utilizing X-ray magnetic circular dichroism spectra the thickness effect on spin moment is examined in amorphous Co_0.9Fe_0.1 films fabricated by RF magnetron sputtering. As film thickness increases from 5nm to 50nm, the variations of spin moments for Fe is a gradual decrease from 1.87μB to 1.70μB, while for Co it increases from 1.41μB to 1.69μB monotonously. Based on magnetic dead layer (MDL) model, the above changes are well explained, and the thickness of MDL, 0.83 nm, is estimated as well. That is not changed with increasing CoFe layer thickness.

Abstract: Neodymium salt was used as additives for the first time in preparing anodic aluminum oxide (AAO) films to improve its performance. AAO films were prepared by anodization method from a 15 vol. % sulphuric acid solution containing neodymium salt; the effects of concentration of neodymium on microhardness and thickness of AAO film were researched, respectively. The effect of heat treatment temperature on structure of AAO film was researched. AAO films were characterized by XRD, EDAX and SEM techniques. The microhardness and thickness of AAO film were 377.2HV and 85μm respectively, which were higher 12.60% and 21.43% than those of the film prepared in electrolyte of nothing addition neodymium salt, respectively. The surface of AAO film was smoother and the aperture of AAO film was more uniform than those of films prepared in electrolyte of nothing addition neodymium salt. The apertures of AAO film were in 25～30nm. There was not neodymium in AAO film. AAO films were amorphous when heat treatment temperatures of AAO film were below 800°C, heat treatment temperature of AAO film were 850°C and 1000°C respectively, AAO films were γ-Al₂O₃ and α-Al₂O₃ film respectively.

Abstract: A new method to prepare NiTi thin film with two separate targets is presented. In this technology, two pure Ni target and pure Ti target are fixed and the substrate is rotating. The final thin film structure is analyzed by Scanning Electron Microscope. Results show that there is no layer structure in the film; the sputtering power and the substrate temperature have great influence to the morphology of the film; all the grain pattern are column under different technological parameters.

Abstract: The 2μm thick TiN coatings were deposited by arc ion plating on YW2 cemented carbide substrate, and the system of TiN/YW2 was treated with cryogenic treatment at -196°C for 30 hours. The change of the Rockwell indentation's morphology of the system (the form and density of cracks, the spalling state of the coating)before and after the treatment were investigated by means of the Rockwell hardness tester. With metallurgical microscope and SEM, the change of the microstructure of the substrate and its influence on the fracture toughness of the system were investigated. The results show that after the treatment, the density of the radiated cracks in the substrate were obviously reduced, but the main cracks hadn’t any change, the spalling of the TiN coating along the indentation was lightened. After the cryogenic treatment the dispersed granular γ phase obviously decreased or even disappeared, the pores became smaller and the microstructure of YW2 became more compact，and the microcracks were merged during the cryogenic treatment. These are beneficial to improve the fracture toughness of YW2 substrate and the coating/substrate system.

Abstract: In this paper, the corrosion properties of AISI 301 stainless steel (SS) coated with 1-micron thick titanium nitride (TiN) hard coatings is investigated. TiN was deposited by pulsed magnetron sputtering resulting in different microstructure ranging from agglomerated crystallites to homogeneous film. Microstructure of the coatings was characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). Resistance to general and localized corrosion was evaluated by potentiodynamic polarization in NaCl 1% solution. It has been shown that the existence of columnar structure in the TiN film reduces significantly the resistance to localized corrosion due to infiltration of liquid through paths at the grain boundaries. Furthermore, by comparing the polarization curves of TiN coatings deposited on SS and glass, it was shown that the electrochemical response of TiN-coated SS at low potentials is the result of electrochemical activity at the coating/electrolyte interface whereas at high potentials the increase in the current is the result of pits generated at the substrate/electrolyte interface at defects/pores within the coating.

Abstract: The optical and electrical properties of Tin oxide (SnO₂) tranparent conducting film are related to its structural properties. The films were grown by chemical vapor deposition on four different substrates at atmospheric pressure and temperatures of 420°C to investigate the effects of substrate material and surface roughness on their structure. A homemade vertical reactor was used for deposition from SnCl₄ + 2H₂O precursors. The structure were analyzed by X-ray diffraction (XRD), scanning electron microscopy( SEM). The results indicated that substrate material influenced the crystal size, compactedness and predominant planes of SnO₂ films while surface roughness influenced crystallization and compactedness of the films.

Abstract: Indium tin oxide (ITO) films are widely applied as the transparent electrode in the photoelectric device because of its high conductivity and high transmittance in the visible wavelength. But the resistivity and position of transmittance peak of ITO films were influenced by the thickness of ITO films, so it is important significant to study the deposition rate of ITO films deposited using RF magnetron sputtering. In this paper, ITO films were prepared by RF magnetron sputtering method on K9 glass substrate, the influence of RF power, sputtering pressure, oxygen ratio, and substrate temperature on the deposition rate of ITO films was mainly studied, meanwhile, the influence of annealing temperature on the film thickness and the process stability depositing ITO using RF magnetron sputtering was studied, and the influence mechanism of technique parameters was analyzed.

Abstract: Impedance spectroscopy technique was employed to characterize the Li_xZn_1-xO₂ (x=0.001~0.008) polycrystalline thin film. IS is shown to be an efficient method capable of detecting the contributions of the resistances of grains and grain boundaries resistance to the complex impedance of a compound, accurately estimating its electrical conductivity as well as its corresponding activation energies and conclude on its structural properties. This is demonstrated for the case of lithium segregation in the grain/grain boundary of Li_xZn_1-xO₂., we found that the activation energy decrease associated with grain-boundary conductivity reflects the onset of the segregation of excessive Li in the grain boundaries when the Li-content exceeds 0.5 mol%. For Li-content below 0.5mol% is the detection of a transition from p-type conductivity. It might be due to that the Li⁺ doped mainly in grains and no precipitation observed on the grain boundaries. So we could be process stable p type thin film for Li content below 0.5mol%.

Abstract: Abstract. A FePt codeposition film was prepared via electrochemical codeposition process, where FeSO₄•7H₂O and H₂PtCl₆•6H₂O were used as Fe source and Pt source，respectively. The composition and morphology of the FePt film were determined by the applied pulse potentials. Vibrating Sample Magnetometer (VSM) study show that the FePt film with Fe/Pt=1:1 was of soft magnetic properties, and its structure transformed from face-centered-cubic (fcc) to face-centred-tetragonal (fct) structure partly after it was annealed at 550°C for 30min in hydrogen (H₂).

Abstract: In recent years, advances in coating deposition technologies have led to the development of nano-structured coating materials with unique properties. Among the many systems, Cr-Al-Si-N coatings have a variety of interesting properties such as the superhardness (~40 GPa), thermal stability with high-temperature oxidation resistance. These coatings were characterized as nanocomposites consisting of nanocrystalline CrN or CrAlN embedded in amorphous Si₃N₄ matrix. Nevertheless extensive discussion has been focused on the mechanical and thermal properties of Cr-Al-Si-N coating, the corrosion resistance at higher temperature is not reported yet. Therefore, the main target of this study is to evaluate the corrosion resistance of the CrN/AlSiN multilayer coating which was synthesized by cathodic arc deposition with Cr and Al₈₈Si₁₂ dual cathodes. The as-deposited coating was following conducted with heat treatment in nitrogen atmosphere at the temperature of 400 oC, 600 oC and 800 oC for 1 hour, respectively. Microstructure of the heated films is analyzed by X-ray photoelectron spectroscope, X-ray diffractometer and scanning electron microscopy. The corrosion resistance of the heated CrN/AlSiN coatings was studied by dipping in the aluminum alloy melt for 3 hours. The results turned out that the better corrosion resistance of CrN/AlSiN multilayer coated stainless steel was obtained by post deposition annealing treatment in nitrogen at 400 oC and 600 oC if compared to that of the other samples.