Papers by Author: Tian Wen Guo

Abstract: The effects of different surface treatments on tribological and electrochemical properties of cast pure titanium were investigated. In this study two different surface treatments were performed which were TiN film deposition by arc ion plating, duplex treatment of plasma nitriding and TiN film deposition. Both surface treatment improved tribological and corrosion behavior of cast titanium. The duplex treated specimens exhibited higher surface hardness, better wear and corrosion resistance compared with TiN film deposited ones. All these results indicate that plasma nitriding and TiN film deposition duplex treatment can improve surface characteristics of cast titanium significantly.

Abstract: Two different surface engineering technologies, plasma nitriding and titanium nitride (TiN) film deposition by closed-field unbalanced magnetron sputtering (CFUBMS), were used to improve the tribological properties of pure titanium. Surface characteristics were evaluated by microhardness tester, scanning electron microscopy(SEM), X-ray diffraction (XRD) and pin-on-disc tribotester. The influence of the two surface treatments on wear resistance of titanium was investigated. After plasma nitriding or TiN film deposition by CFUBMS, the microhardness of the surface increased approximately 3 to 5 times when compared with that of untreated pure titanium and the wear resistance was improved significantly. The wear resistance of TiN film deposited titanium specimens was higher than that of plasma nitrided ones.

Abstract: The commercially pure(CP) titanium specimens were modified with Direct current(DC) plasma nitriding and arc ion plating of TiN film. The duplex treated titanium samples were characterized by scanning electron microscopy(SEM), microhardness tester and ball-on-disc tribotester. The results showed that the duplex treated CP titanium appeared uniform and bright golden, microhardness and wear resistance improved substantially and were superior to that of only TiN coated ones. All these results indicate plasma nitriding and TiN film deposition duplex treatment can improve surface characteristics of CP titanium significantly. The method can be applied to the titanium denture to improve the tribological properties and color.

Abstract: In the acidic oral environments containing fluoride ions, hydrofluoric acid (HF) would form and affect the color of Titanium porcelain crown, but there is a lack of information on how color is affected by this oral fluid. The purpose of this study was to investigate the effects of various artificial saliva simulating oral environments in the presence of fluoride ions with different pH value on the color of self-made dental opaque, body porcelain, belonging to the Na2O-K2O–MgO–CaO–Al2O3–SiO2 glass system. Disc-shaped specimens, 5 mm diameter and a 2-mm thickness, were made by firing. Specimens were immersed in artificial saliva in the presence of fluoride ions with different pH value for 7, 14, 21 days, and then the color of the specimens was compared with the color of the initial specimen. The interactions were present in L*a*b* values between pH value and the day of immersion. The changes in L*a*b* color data as the day of immersion and pH value increased were revealed, which can resulted in perceptual color changes in L*a*b* color parameters.

Abstract: Low-fusing dental porcelain was fused on titanium surface. The adhesion between the titanium and porcelain was evaluated by three-point flexure test. It was shown that the failure of the titaniumporcelain predominantly occurred at the alloy-oxide interface. Rutile phase was present on the interface debonding from porcelain. The influence of corrosion on bonding strength was also investigated. The results suggested that, after being immersed in artificial saliva with pH of 2.7, 5.4 and 7.0, no decreasing of the bonding strength of Ti-porcelain occurred.

Abstract: The aim of this investigation is to study the effect of SnO coatings on the bond strength between titanium and porcelain. The coatings were produced by sol-gel method and heat-treatment at 300°C. Once the coatings have been formed on the titanium substrates, self-made porcelain was fused. The specimens with pre-oxidation before porcelain fused were set as control group. It was shown SnO gel formed completely at 300°C and was composed by SnO and SnO2 in the form of a uniform film. The bond strength between titanium and porcelain of the specimens with SnO coatings was greater than those in control group statistically, which might prove that the coatings reduced the oxidation of titanium surface in the porcelain fusing progress. EDS result showed almost all fractures between titanium and porcelain occurred at the oxide layer. Si and Sn might attend the reaction at interface. It was concluded that the SnO coatings produced in this study can improved the titanium-porcelain bond strength.