Plasma-enhanced chemical vapor deposition of vanadium pentoxide thin films from a vanadyl(IV) β-diketonate compound has been performed in a low-pressure reactor under different operating conditions. The effect of various parameters, such as the flow rates of the carrier and reactive gas and the substrate temperatures, on films composition, microstructure, and morphology was investigated in detail. Controlled variations of the synthesis conditions allowed a fine modulation of the sample properties, as shown by XRD and AFM analyses. In particular, at 200 °C and moderate oxygen flow, nanophasic V 2 O 5 with a strong (001) preferential orientation could be easily obtained. The composition and purity of the films are studied by XPS and SIMS analyses, with special regard to filmsubstrate interdiffusion phenomena. Optical properties of the films are also investigated.
The microstructural stability at temperatures above 700 ЊC of weld metal of type 29Cr-8Ni-2Mo-0.39N and weld metal of type 25Cr-10Ni-4Mo-0.28N has been compared. Multipass welding was employed using the gas tungsten arc welding technique with a shielding gas of Ar ϩ 2 pct N 2 . The quantitative assessment of the intermetallic phase was performed using automatic image analysis in the light optical microscope (LOM). Detailed microanalysis was also performed using scanning and transmission electron microscopy. A computer program developed by the authors was used to calculate a continuous cooling-temperature (CCT) diagram on the basis of the experimentally determined time-temperature-transformation (TTT) diagram. Thermodynamic calculations for estimating phase stabilities and for interpreting experimental observations were performed. It was found that weld metal of type 29Cr-8Ni-2Mo-0.39N was microstructurally more stable than weld metal of type 25Cr-10Ni-4Mo-0.28N. A lower molybdenum concentration and a higher nitrogen concentration in the former alloy could explain the higher stability with respect to the intermetallic phase. The higher nitrogen concentration also provides a rationale for the higher stability against the formation of secondary austenite in weld metal of type 29Cr-8Ni-2Mo-0.39N. This effect, which is associated with a lower thermodynamic driving force for precipitation of secondary austenite during multipass welding, can be explained by nitrogen-enhanced primary austenite formation.
Vanadium pentoxide thin films are grown on glass and borosilicate substrates by PACVD using a vanadyl (IV) beta-diketonate as precursor. The depositions are can-led out in an RF-plasma reactor with Ar-O2 mixtures and soft process conditions, obtaining high-purity nanocrysralline layers with a strong preferential orientation. The microstructural and morphological characteristics of the films, analyzed respectively by XRD and AFM, show that the sample features can be accurately tailored by an adequate choice of the synthesis conditions. The composition and purity of the films are studied by XPS and SIMS analyses. Impedance Spectroscopy is used to study the conductivity of the layers and the dependence of electrical properties on microstructure
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