| Summary: | 博士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 90 === Titanium-aluminum-carbonitride system nanostructured coatings are investigated in this study. Firstly the effects of graded interlayer and coffee-bean-like morphology on the preferred orientation of Ti-C-N coatings are discussed. TiN, TiC, and TiCxN1-x were prepared by plasma-enhanced chemical vapor deposition. The results showed that the topography of the TiCxN1-x, which resembled coffee beans, resulted from a twinning core structure that caused the dendritic grain shape and enhanced the (422) texture of TiC0.62N0.38 and TiC0.75N0.25. As graded coating was used as a transition layer, the texture of TiC was changed from (111) to (200), and TiN was changed from (200) to (111) due to the pseudomorphic forces provided by the first layer plus graded layer. The residual stress contributions to this phenomenon are also discussed.
Then the nanostructured and the corresponding mechanical behavior of Ti-Al-N coatings are investigated. The phase and microstructure of Ti1-xAlxN deposited were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Film hardness and reduced elastic modulus were measured by nanoindentation interfaced with an atomic force microscopy. High-resolution transmission electron micrograph shows that the grain size of Ti1-xAlxN decreased to less than 10 nm as aluminum contents in the film increased up to the ratio of Al/(Al+Ti)=0.63. The hardness measurement shows that the microstructure feature is the major factor to determine the film hardness.
Finally, a new metastable phase of TiAlCN is identified and a new nanocomposite, titanium aluminum carbonitride/amorphous-carbon, is invented using titanium tetrachloride, aluminum trichloride, methane and nitrogen as reactants. In this study hydrogen was used as carrier gases. A substrate temperature of 500 ℃ and an RF power of 100 W were used in all depositions. The films were characterized by X-ray powder diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and scanning electron microscopy. The results show that nanograins of titanium aluminum carbonitride with B1-NaCl structure are embedded in an amorphous carbon matrix. The coatings have a (200) preferred orientation with columnar cross-section morphology. Mechanical properties were analyzed by nanoindentation and hardness was demonstrated to increase via this microstructure design approach. The effects of microstructure on mechanical properties, especially the high plasticity property at room temperature, are also determined.
|
|---|
