Yin-Yu Chang - Academia.edu (original) (raw)

Papers by Yin-Yu Chang

Research paper thumbnail of Frictional Forces of Conventional and Improved Superelastic NiTi-Alloy Orthodontic Archwires in Stainless Steel and Plastic Brackets

This study evaluated the static and kinetic frictional forces produced between different combinat... more This study evaluated the static and kinetic frictional forces produced between different combination of orthodontic archwires and brackets. Three types of archwires were examined: (1) stainless steel, (2) conventional NiTi alloy, and (3) improved superelastic NiTi alloy. Two types of brackets were tested: (1) stainless steel and (2) plastic. Both static and kinetic frictional forces were measured on a customdesigned apparatus under elastic ligature in the dry state. Each archwire-bracket combination was subjected to 20 independent evaluations. All data were statistically analyzed using two-way analysis of variance and Duncan’s test. The experimental results indicated that the static frictional force was significantly higher than the kinetic frictional force in all archwire-bracket combinations. The frictional force was lower for the stainless steel bracket than for the plastic bracket with stainless steel wire and the improved superelastic NiTi-alloy wire. The frictional force was lower for the improved superelastic NiTi-alloy wire than for NiTi wire with the stainless steel bracket, but higher for NiTi wire with the plastic bracket. The frictional force was lowest for stainless steel wire for both two types of bracket. This study demonstrates that the frictional forces of brackets are influenced by different combinations of bracket and archwire, and that the improved superelastic NiTi-alloy wire does not exhibit “low friction” (as claimed by the manufacturers) in all cases.

Research paper thumbnail of Antibacterial TaN-Ag coatings on titanium dental implants

Surface & Coatings Technology, 2010

a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Sputtering Antibacterial Bi... more a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Sputtering Antibacterial Biocompatibility TaN Silver Coating

Research paper thumbnail of Characterization of nanocrystalline AlTiN coatings synthesized by a cathodic-arc deposition process

Surface & Coatings Technology, 2007

Graded and multilayered Al x Ti 1−x N nanocrystalline coatings were synthesized by using cathodic... more Graded and multilayered Al x Ti 1−x N nanocrystalline coatings were synthesized by using cathodic-arc evaporation (CAE) process. Ti 33 Al 67 and Ti 50 Al 50 alloy cathodes were used for the deposition of Al x Ti 1−x N nanocrystalline coatings with different Al/(Ti+Al) ratios. Optical emission spectra of the plasma species including atomic and ionized Ti, atomic Al, excited and ionized nitrogen (N 2 and N 2 + ) revealed that the excitation, ionization and charge transfer reactions of the Al-Ti-N plasma occurred during the Al x Ti 1−x N coating process. A preferred (111) orientation was shown in the Al 0.67 Ti 0.33 N with high Al/(Ti+Al) atomic content ratio (0.63) and small grain size (29 nm). The graded Al 0.67 Ti 0.33 N/TiN possessed the highest hardness of Hv 25 g 3850 ± 180. However, the multilayered Al 0.67 Ti 0.33 N/TiN coating supported a longer tool life with lower residual stress. It has been found that the wear performance and mechanical properties of the films were correlated with the Al/(Ti+Al) content ratio and multilayered structure.

Research paper thumbnail of Microstructural and mechanical properties of graded and multilayered Al xTi 1-xN/CrN coatings synthesized by a cathodic-arc deposition process

Surface & Coatings Technology, 2009

In this study, nanocomposite foams reinforced with different weight percentages of silicon dioxid... more In this study, nanocomposite foams reinforced with different weight percentages of silicon dioxide nanoparticles (0.25, 0.5, 0.75 and 1.0 wt%) were fabricated using the ultrasonic and stir casting techniques. For this purpose heat treated TiH 2 was used as foaming agent. Microstructural studies were done by optical microscope and scanning electron microscope. Hardness evaluation of precursor nanocomposites showed that the hardness was significantly increased by the addition of SiO 2 nanoparticles and Al-0.75 wt% SiO 2 nanocomposite makes the highest hardness. Evaluation of compressive behavior of Al-SiO 2 nanocomposite foams showed that the plateau stress increases more than 3 times as the foam relative density increases from 0.09 to 0.16. Energy absorption of Al-SiO 2 nanocomposite foams has been found to be dependent on both relative density and structural properties.

Research paper thumbnail of Catalysis effect of metal doping on wear properties of diamond-like carbon films deposited by a cathodic-arc activated deposition process

Thin Solid Films, 2002

Diamond-like carbon (DLC) films containing various metal dopings were synthesized by using a cath... more Diamond-like carbon (DLC) films containing various metal dopings were synthesized by using a cathodic-arc activated deposition process. Metal plasma with intensive ion energies catalyzes the decomposition of hydrocarbon gases (C H ), and 2 2 induces the formation of hydrogenated DLC films with a mixture of sp and sp carbon bonds. The composite film structure 2 3 consists of a metal-doped DLC film on top of a graded metal nitride interlayer, which provides enhanced mechanical and tribological properties. The catalysis effect of three common transition metal plasmas, including Cr, Ti, and Zr was investigated. This experiment depicts the advantage of the catalysis effect of Cr plasma in synthesizing DLC films with a higher sp carbon 3 bond ratio comparing with that of Ti and Zr plasma. The wear properties were correlated with the metal doping. The optimized Cr-C:H films with Cr and CrN interlayers give satisfactory wear performance in a ball-on-disk test with a lower wear rate of 2=10 m yNm and a lower friction coefficient of 0.1 sliding against WC counterparts. Wear life of Cr plasma activated DLC y17 3

Research paper thumbnail of High temperature oxidation resistance of multilayered Al xTi 1 − x N/CrN coatings

Thin Solid Films, 2011

Al x Ti 1 − x N and CrN have been widely used as a protective coating material in many types of t... more Al x Ti 1 − x N and CrN have been widely used as a protective coating material in many types of tools and mechanical components because of high wear performance and high temperature resistance. In this study, the high temperature oxidation behavior of Al 0.63 Ti 0.37 N and multilayered Al 0.63 Ti 0.37 N/CrN coatings was studied. These coatings were synthesized by a cathodic-arc deposition system with plasma enhanced duct equipment. The nanolayer thickness and alloy content of the deposited multilayered coating were correlated with the emission rate of alloy cathode materials. The multilayered Al 0.63 Ti 0.37 N/CrN coating revealed a laminate structure with stacking of Al 0.63 Ti 0.37 N and CrN layers, and the periodic thickness (Λ) was 16 nm. For the high temperature oxidation test, the coated samples were annealed in the temperature range of 700-1000°C in air for 2 h. The multilayered Al 0.63 Ti 0.37 N/CrN possessed much thinner oxide layer thickness than Al 0.63 Ti 0.37 N. Even after oxidation at 1000°C, the multilayered Al 0.63 Ti 0.37 N/CrN still retained their crystalline structure. An interface effect served as a barrier, and retarded the diffusion of oxygen into the multilayered Al 0.63 Ti 0.37 N/ CrN. Thus, the multilayered Al 0.63 Ti 0.37 N/CrN showed a high temperature oxidation resistance superior to the Al 0.63 Ti 0.37 N.

Research paper thumbnail of Tribological analysis of nano-composite diamond-like carbon films deposited by unbalanced magnetron sputtering

Surface & Coatings Technology, 2004

Ti-containing nano-composite diamond-like carbon (DLC) coatings have been developed with improved... more Ti-containing nano-composite diamond-like carbon (DLC) coatings have been developed with improved tribological characteristics. These coatings were synthesized by sputtering of pyrolitic graphite and titanium targets using unbalanced magnetrons with pulsed plasma technology. Compared with the Ti-containing nano-composite DLC film, a graded Ti-C:HyTiCNyTiN film was also deposited by sputtering of titanium targets in reactive gases (nitrogen and C H ) using the same deposition system. The Tiy 2 2 C multi-layered DLC coating deposited at a substrate rotation speed of 5 rev.ymin depicted an amorphous structure with 2-nm periodic thicknesses, and gave satisfactory friction performance in the pin-on-disk tests with a wear rate of 1-3=10 m yNm y17 3 and a friction coefficient of 0.09-0.1 against 100Cr6 steel and WC. The steady-state friction coefficient of nano-composite DLC films is lower than that of graded Ti-C:H DLC films (0.15-0.17). When sliding against soft copper ball, the friction coefficients of the DLC films were higher and increased with the sliding process from an initial friction coefficient of 0.15 with a promising wear behavior. Wear debris were primarily composed of copper mixed with surface impurities. SEM, EDX and XPS analyses depicted that the initial Ti contained C-O transfer films possess good adhesion between the sliding counterparts (100Cr6 and WC) and the coatings during the initial sliding stage. Micro-Raman spectra acquired from the nano-composite DLC coatings demonstrated a tendency of graphite formation of the transfer film. The readily transferred oxide-free graphite-like sp films form 2 a lubricious layer, which possess low shear strengths under applied loads. The XPS analysis of DLC C1s core level also suggests that transfer film is sp dominated.

Research paper thumbnail of Mechanical and tribological properties of multilayered TiSiN/CrN coatings synthesized by a cathodic arc deposition process

Surface & Coatings Technology, 2008

The monolayered TiSiN and multilayered TiSiN/CrN were synthesized by cathodic arc evaporation. Th... more The monolayered TiSiN and multilayered TiSiN/CrN were synthesized by cathodic arc evaporation. The Ti/Si (80/20 at.%) and chromium targets were used as the cathodic materials. With the different I [TiSi] /I [Cr] cathode current ratios of 1.8, 1.0, and 0.55, the multilayered TiSiN/CrN coatings possessed different multilayer periods (Λ) of 8.3 nm, 6.2 nm, and 4.2 nm. From XRD and TEM analyses, both the monolayered TiSiN and multilayered TiSiN/CrN revealed a typical columnar structure and B1-NaCl crystalline, no peaks of crystalline Si 3 N 4 were detected. Among the multilayered TiSiN/CrN coatings, the multilayered coating with Λ = 8.3 nm possessed higher hardness of 37 ± 2 GPa, higher elastic modulus of 396 ± 20 GPa and the lower residual stress of −1.60 GPa than the monolayered (Ti 0.39 Si 0.07 )N 0.54 coating(− 7.25 GPa). Due to the higher Cr/(Ti + Cr + Si) atomic ratio, the multilayered TiSiN/CrN with Λ = 5.5 nm possessed the lowest friction coefficient. But the lowest of wear rate was obtained by the multilayered TiSiN/CrN with Λ = 8.3 nm, because of higher H 3 /E ⁎ 2 ratio of 0.323 GPa. The monolayered TiSiN possessed the highest wear rate of 2.87 μm 2 /min. Therefore, the mechanical and tribological property can be improved by the design of multilayered coating.

Research paper thumbnail of Plasma properties of CrO x films synthesized by a cathodic arc evaporation process

Thin Solid Films, 2008

The plasma in a cathodic arc evaporation process used for the deposition of Cr 1−x O x films was ... more The plasma in a cathodic arc evaporation process used for the deposition of Cr 1−x O x films was studied by an optical emission spectroscopy (OES). With the introduction of Ar and oxygen into the chamber at deposition pressures from 0.7 Pa to 2.7 Pa, high density of evaporated chromium catalyzes the decomposition of oxygen reactive gas, and induces the formation of Cr 1−x O x films. Optical emission spectra including atomic and ionized Cr, excited and ionized oxygen revealed that excitation, ionization and charge transfer reactions of the Cr-O plasma occurred during the Cr 1−x O x deposition process. A simplified empirical model which incorporates the relevant atomic processes in the gas phase with the chemical composition and deposition rate of the deposited Cr 1−x O x coating was developed. Rhombohedral Cr 2 O 3 and tetragonal CrO 2 were observed in the Cr 1−x O x coatings deposited at higher pressure than 1.3 Pa. The Cr 1−x O x coating depicted a dense and compact microstructure with well-attached interface.

Research paper thumbnail of Effect of nickel incorporation on structural, nanomechanical and biocompatible properties of amorphous hydrogenated carbon thin films prepared by low energy biased target ion beam deposition

Thin Solid Films, 2010

Keywords: Amorphous hydrogenated carbon Low energy biased target ion beam deposition XPS Nanomech... more Keywords: Amorphous hydrogenated carbon Low energy biased target ion beam deposition XPS Nanomechanical properties Osteoblasts cells Nickel incorporated amorphous hydrogenated carbon (Ni/a:C-H) thin films were deposited onto the Si substrates via biased target ion beam sputtering of nickel combined with reactive ion beam deposition of a:C-H using CH 4 /Ar gas mixture. The effects of Ni doping and target bias voltage on the microstructure and mechanical properties of the as-deposited films were investigated by means of X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, transmission electron microscopy and nanoindentation. It was found that the Ni content in the films gets increased with increasing target bias voltage, and most of the Ni atoms react with C atoms to form NiC x phases in the Ni/a:C-H films. Moreover, the nickel carbide nanoparticles attain crystallinity even at low deposition temperature and get embedded in the cross-linked carbon matrix. It was found that the presence of Ni 3 C nanoparticles tends to increase the content of sp 2 carbon, thus decreasing the hardness of Ni/a:C-H films as compared with that of a:C-H films. Additionally it was found that the nickel incorporated films do not show any adverse effect on the osteoblast cellular adhesion. Overall, these carbidic nanocrystals initiate direct graphitization and intend to change diamond-like to graphite-like carbon structure in Ni/a:C-H films with promising biocompatibility.

Research paper thumbnail of Corrosion behavior of electroless nickel-coated AISI 304 stainless steel enhanced by titanium ion implantation

Surface & Coatings Technology, 2005

Metal plasma ion implantation has been successfully developed to improve the wear, corrosion, and... more Metal plasma ion implantation has been successfully developed to improve the wear, corrosion, and physical properties of various engineering materials. In this study, Ti ions were implanted into electroless nickel coating at 100 keV and 5Â10 16 -3Â10 17 ions/cm 2 using a metal plasma ion implantation apparatus. Within the implanted region, the hardness of the electroless nickel coating is increased from 14 to 18-22 GPa by Ti ion implantation at doses of 1Â10 17 -3Â10 17 ions/cm 2 . The electrochemical behavior of the Ti-implanted electroless nickel in a 3.5 wt.% NaCl solution was investigated by the potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS). The corrosion resistance of Ti-implanted electroless nickel was improved by the formation of chemically inert titanium oxides and Ti-Ni alloys in the ion-implanted layer, which leads to the increase of polarization resistances in the EIS analysis. At the dose of 3Â10 17 ions/cm 2 , the Ti-implanted electroless nickel possesses the best corrosion resistance due to the highest polarization resistance (3.05Â10 5 V/cm 2 ) and the lowest capacitance (1.5Â10 À5 F/cm 2 ). Results of this study demonstrate the potential of metal plasma ion implantation in improving the corrosion resistance of the electroless nickel with enhanced mechanical properties. D

Research paper thumbnail of Structural and mechanical properties of nanolayered TiAlN/CrN coatings synthesized by a cathodic arc deposition process

Surface & Coatings Technology, 2005

Monolayered AlTiN and Multilayered AlTiN/CrN coatings were synthesized by a cathodic-arc depositi... more Monolayered AlTiN and Multilayered AlTiN/CrN coatings were synthesized by a cathodic-arc deposition process, using TiAl (with 50/50 and 33/67 at.%) and Cr elemental cathodes. The atomic ratio of Al/(Ti + Al) in the AlTiN coatings was reduced to 0.44 and 0.61, respectively, compared with the corresponding Ti 50 Al 50 and Ti 33 Al 67 cathode materials. The multilayered AlTiN/CrN films showed smaller crystallite size, larger lattice strain, higher hardness, higher residual stress, and better adhesion strength as well than the monolayered AlTi films. The multilayered Al 0.35 Ti 0.22 N 0.43 /CrN coating exhibited the highest hardness of about 38 GPa and the highest H 3 /E* 2 ratio value of 0.188 GPa, indicating the best resistance to plastic deformation, among all the coatings studied.

Research paper thumbnail of Deposition of diamond-like carbon films containing metal elements on biomedical Ti alloys

Surface & Coatings Technology, 2005

Three kinds of diamond-like carbon (DLC) films, which contain different metals (Ti, Cr, Zr) and d... more Three kinds of diamond-like carbon (DLC) films, which contain different metals (Ti, Cr, Zr) and different interface designs, were deposited on biomedical titanium alloy (Ti -6Al -4V, ASTM F136) by using a cathodic arc evaporation system. Preliminary results showed that the DLC films are hydrogenated, amorphous and dense in structure. Scratch tests and Rockwell indentation tests reveal that the graded structures can improve the adhesion of DLC films. The Raman analyses showed that the Cr-containing DLC films possess lower I D /I G ratio, lower G-peak positions, and higher coating hardness. The pin-on-disk wear test in different environments (air and simulated body fluid) revealed that all the DLC films improve the wear performance of the substrates, and the wear coefficient is lower in simulated body fluid than that in air. In addition, the Cr-containing DLC films exhibited the lowest friction coefficient of 0.06 in simulated body fluid and 0.16 in air with the counterface of UHMWPE. Because of their dense structure, good adhesion and superior corrosion resistance in SBF, the Cr-C:H/ CrN films exhibited significantly low friction in SBF. The ICP-MS analysis revealed the release of Cr ion is 2.22 -10.03 ppm from the Crcontained DLC films, which is less than that from Co -Cr -Mo alloy (106.17 ppm), showing that the Cr-containing DLC films meet the requirement of biomedical applications. The potentiodynamic test revealed that the corrosion resistance of the ASTM F136 titanium alloys is increased substantially by the metal-containing DLC coating. D

Research paper thumbnail of High temperature oxidation resistance of CrAlSiN coatings synthesized by a cathodic arc deposition process

Journal of Alloys and Compounds, 2008

The high-temperature oxidation behavior of the CrN and Cr–Al–Si–N coatings was studied. These coa... more The high-temperature oxidation behavior of the CrN and Cr–Al–Si–N coatings was studied. These coatings were deposited on silicon substrates by using a cathodic-arc deposition system with lateral rotating arc cathodes. Chromium and Al88Si12 cathodes were used for ...

Research paper thumbnail of Characterization of TiCr(C,N)/amorphous carbon coatings synthesized by a cathodic arc deposition process

Thin Solid Films, 2007

Ternary TiCrN and nanocomposite TiCr(C,N)/amorphous carbon (a-C) coatings with different carbon c... more Ternary TiCrN and nanocomposite TiCr(C,N)/amorphous carbon (a-C) coatings with different carbon contents (0-26.6 at.%) were synthesized by cathodic arc evaporation with plasma enhanced duct equipment. The structural, chemical, and mechanical properties of the deposited films were studied by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and nanoindentation measurement. The atomic content ratios of carbon/(Ti + Cr) and carbon/nitrogen increased with increasing C 2 H 2 flow rate. A nanocomposite structure of coexisting metastable hard TiCr(C, N) crystallites and amorphous carbon phases was found in the TiCr(C,N)/a-C coatings, those possessed smaller crystallite sizes than the ternary TiCrN film. XPS analyses revealed the concentration of a-C increased with increasing carbon content from 8.9 at.% to 26.6 at.%. Exceeding the metastable solubility range of carbon within the TiCrN lattice, the carbon formed a-C phase in the deposited coatings. The nanocomposite TiCr(C, N)/a-C coatings exhibited higher hardness value of 29-31 GPa than the deposited TiCrN coating (26 ± 1 GPa). It has been found that the structural and mechanical properties of the films were correlated with the carbon content in the TiCr(C,N)/a-C coatings.

Research paper thumbnail of Influence of cobalt ion implantation on optical properties of titanium dioxide thin films

Thin Solid Films, 2010

Nano-crystalline TiO2 thin films were synthesized by using sol–gel and spin-coating techniques on... more Nano-crystalline TiO2 thin films were synthesized by using sol–gel and spin-coating techniques on glass substrates for photo-catalytic applications. Prior to deposition, a TiO2 colloidal suspension was synthesized by microwave-induced thermal hydrolysis of the titanium tetrachloride aqueous solution. In this study, the deposited TiO2 coating with a grain size of 13±2nm was uniform without aggregation. Co ion implantation into the as-calcined

Research paper thumbnail of Tribological enhancement of CrN coatings by niobium and carbon ion implantation

Surface & Coatings Technology, 2004

Metal plasma ion implantation has being successfully developed for improving wear, corrosion and ... more Metal plasma ion implantation has being successfully developed for improving wear, corrosion and physical properties of engineering materials. In this study, Nb and C ions were co-implanted into CrN films using a metal-plasma ion implantation apparatus. The accelerating voltage of metal ions were set at 50 kV with implantation doses of 5=10 ionsycm for Nb and 16 2

Research paper thumbnail of Mechanical properties of nano-structured Ti-Si-N films synthesized by cathodic arc evaporation

Journal of Alloys and Compounds, 2007

Ti 1−x Si x N coatings were synthesized by cathodic arc evaporation with plasma-enhancing filter ... more Ti 1−x Si x N coatings were synthesized by cathodic arc evaporation with plasma-enhancing filter duct, using Ti 80 Si 20 alloy target as cathodes. Optical emission study revealed that excitation, ionization and charge transfer reactions of the Ti-Si-N plasma occurred during the Ti 1−x Si x N deposition process. The chemical content of Si varied from 3.3 to 6.0 at% in Ti 1−x Si x N depending on the nitrogen partial pressure of the reaction chamber. All the Ti 1−x Si x N coatings displayed a NaCl structure and a preferred (2 0 0) orientation parallel to the substrate surface. Among the studied Ti 1−x Si x N coatings, the Ti 1−x Si x N with 6 at.% Si possessed the highest hardness of 45 GPa and H 3 /E* 2 ratio of 0.527 GPa, indicating the best resistance to plastic deformation. We found that the structure and mechanical properties of the Ti 1−x Si x N films were correlated with the nitrogen pressure and silicon content of the coatings.

Research paper thumbnail of Tribological enhancement of CrN coatings by niobium and carbon ion implantation

Surface & Coatings Technology, 2003

Metal plasma ion implantation has being successfully developed for improving wear, corrosion and ... more Metal plasma ion implantation has being successfully developed for improving wear, corrosion and physical properties of engineering materials. In this study, Nb and C ions were co-implanted into CrN films using a metal-plasma ion implantation apparatus. The accelerating voltage of metal ions were set at 50 kV with implantation doses of 5=10 ionsycm for Nb and 16 2

Research paper thumbnail of Structural and electrical properties of Cr doped aC:H films synthesized by a cathodic-arc activated deposition process

Surface & Coatings Technology, 2006

Nitrogen-doped Cr -C:H/N films were synthesized by using a cathodic-arc activated deposition proc... more Nitrogen-doped Cr -C:H/N films were synthesized by using a cathodic-arc activated deposition process. Chromium plasma with intensive ion energies catalyzes the decomposition of hydrocarbon gas (C 2 H 2 ), and results in the deposition of amorphous carbon films. Nitrogen was introduced to form nitrogen-containing Cr -C:H/N films, which contained a mixture of sp 2 and sp 3 carbon bonds. The deposited carbon films consist of nanocomposite Cr -C:H/N films on top of a graded chromium nitride interlayer. It has been found that the structural and electrical properties of the films were correlated as a function of nitrogen doping. The nature of the heterojunction is confirmed by the spreading resistance characteristics of the Cr -C:H/N film/Si junction showing a behavior dependant on the nitrogen doping induced structure changes. With increasing nitrogen concentration, the increasing k states of sp 2 hybridization results in a more pronounced enhancement of conductivity. D

Research paper thumbnail of Frictional Forces of Conventional and Improved Superelastic NiTi-Alloy Orthodontic Archwires in Stainless Steel and Plastic Brackets

This study evaluated the static and kinetic frictional forces produced between different combinat... more This study evaluated the static and kinetic frictional forces produced between different combination of orthodontic archwires and brackets. Three types of archwires were examined: (1) stainless steel, (2) conventional NiTi alloy, and (3) improved superelastic NiTi alloy. Two types of brackets were tested: (1) stainless steel and (2) plastic. Both static and kinetic frictional forces were measured on a customdesigned apparatus under elastic ligature in the dry state. Each archwire-bracket combination was subjected to 20 independent evaluations. All data were statistically analyzed using two-way analysis of variance and Duncan’s test. The experimental results indicated that the static frictional force was significantly higher than the kinetic frictional force in all archwire-bracket combinations. The frictional force was lower for the stainless steel bracket than for the plastic bracket with stainless steel wire and the improved superelastic NiTi-alloy wire. The frictional force was lower for the improved superelastic NiTi-alloy wire than for NiTi wire with the stainless steel bracket, but higher for NiTi wire with the plastic bracket. The frictional force was lowest for stainless steel wire for both two types of bracket. This study demonstrates that the frictional forces of brackets are influenced by different combinations of bracket and archwire, and that the improved superelastic NiTi-alloy wire does not exhibit “low friction” (as claimed by the manufacturers) in all cases.

Research paper thumbnail of Antibacterial TaN-Ag coatings on titanium dental implants

Surface & Coatings Technology, 2010

a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Sputtering Antibacterial Bi... more a b s t r a c t a r t i c l e i n f o Available online xxxx Keywords: Sputtering Antibacterial Biocompatibility TaN Silver Coating

Research paper thumbnail of Characterization of nanocrystalline AlTiN coatings synthesized by a cathodic-arc deposition process

Surface & Coatings Technology, 2007

Graded and multilayered Al x Ti 1−x N nanocrystalline coatings were synthesized by using cathodic... more Graded and multilayered Al x Ti 1−x N nanocrystalline coatings were synthesized by using cathodic-arc evaporation (CAE) process. Ti 33 Al 67 and Ti 50 Al 50 alloy cathodes were used for the deposition of Al x Ti 1−x N nanocrystalline coatings with different Al/(Ti+Al) ratios. Optical emission spectra of the plasma species including atomic and ionized Ti, atomic Al, excited and ionized nitrogen (N 2 and N 2 + ) revealed that the excitation, ionization and charge transfer reactions of the Al-Ti-N plasma occurred during the Al x Ti 1−x N coating process. A preferred (111) orientation was shown in the Al 0.67 Ti 0.33 N with high Al/(Ti+Al) atomic content ratio (0.63) and small grain size (29 nm). The graded Al 0.67 Ti 0.33 N/TiN possessed the highest hardness of Hv 25 g 3850 ± 180. However, the multilayered Al 0.67 Ti 0.33 N/TiN coating supported a longer tool life with lower residual stress. It has been found that the wear performance and mechanical properties of the films were correlated with the Al/(Ti+Al) content ratio and multilayered structure.

Research paper thumbnail of Microstructural and mechanical properties of graded and multilayered Al xTi 1-xN/CrN coatings synthesized by a cathodic-arc deposition process

Surface & Coatings Technology, 2009

In this study, nanocomposite foams reinforced with different weight percentages of silicon dioxid... more In this study, nanocomposite foams reinforced with different weight percentages of silicon dioxide nanoparticles (0.25, 0.5, 0.75 and 1.0 wt%) were fabricated using the ultrasonic and stir casting techniques. For this purpose heat treated TiH 2 was used as foaming agent. Microstructural studies were done by optical microscope and scanning electron microscope. Hardness evaluation of precursor nanocomposites showed that the hardness was significantly increased by the addition of SiO 2 nanoparticles and Al-0.75 wt% SiO 2 nanocomposite makes the highest hardness. Evaluation of compressive behavior of Al-SiO 2 nanocomposite foams showed that the plateau stress increases more than 3 times as the foam relative density increases from 0.09 to 0.16. Energy absorption of Al-SiO 2 nanocomposite foams has been found to be dependent on both relative density and structural properties.

Research paper thumbnail of Catalysis effect of metal doping on wear properties of diamond-like carbon films deposited by a cathodic-arc activated deposition process

Thin Solid Films, 2002

Diamond-like carbon (DLC) films containing various metal dopings were synthesized by using a cath... more Diamond-like carbon (DLC) films containing various metal dopings were synthesized by using a cathodic-arc activated deposition process. Metal plasma with intensive ion energies catalyzes the decomposition of hydrocarbon gases (C H ), and 2 2 induces the formation of hydrogenated DLC films with a mixture of sp and sp carbon bonds. The composite film structure 2 3 consists of a metal-doped DLC film on top of a graded metal nitride interlayer, which provides enhanced mechanical and tribological properties. The catalysis effect of three common transition metal plasmas, including Cr, Ti, and Zr was investigated. This experiment depicts the advantage of the catalysis effect of Cr plasma in synthesizing DLC films with a higher sp carbon 3 bond ratio comparing with that of Ti and Zr plasma. The wear properties were correlated with the metal doping. The optimized Cr-C:H films with Cr and CrN interlayers give satisfactory wear performance in a ball-on-disk test with a lower wear rate of 2=10 m yNm and a lower friction coefficient of 0.1 sliding against WC counterparts. Wear life of Cr plasma activated DLC y17 3

Research paper thumbnail of High temperature oxidation resistance of multilayered Al xTi 1 − x N/CrN coatings

Thin Solid Films, 2011

Al x Ti 1 − x N and CrN have been widely used as a protective coating material in many types of t... more Al x Ti 1 − x N and CrN have been widely used as a protective coating material in many types of tools and mechanical components because of high wear performance and high temperature resistance. In this study, the high temperature oxidation behavior of Al 0.63 Ti 0.37 N and multilayered Al 0.63 Ti 0.37 N/CrN coatings was studied. These coatings were synthesized by a cathodic-arc deposition system with plasma enhanced duct equipment. The nanolayer thickness and alloy content of the deposited multilayered coating were correlated with the emission rate of alloy cathode materials. The multilayered Al 0.63 Ti 0.37 N/CrN coating revealed a laminate structure with stacking of Al 0.63 Ti 0.37 N and CrN layers, and the periodic thickness (Λ) was 16 nm. For the high temperature oxidation test, the coated samples were annealed in the temperature range of 700-1000°C in air for 2 h. The multilayered Al 0.63 Ti 0.37 N/CrN possessed much thinner oxide layer thickness than Al 0.63 Ti 0.37 N. Even after oxidation at 1000°C, the multilayered Al 0.63 Ti 0.37 N/CrN still retained their crystalline structure. An interface effect served as a barrier, and retarded the diffusion of oxygen into the multilayered Al 0.63 Ti 0.37 N/ CrN. Thus, the multilayered Al 0.63 Ti 0.37 N/CrN showed a high temperature oxidation resistance superior to the Al 0.63 Ti 0.37 N.

Research paper thumbnail of Tribological analysis of nano-composite diamond-like carbon films deposited by unbalanced magnetron sputtering

Surface & Coatings Technology, 2004

Ti-containing nano-composite diamond-like carbon (DLC) coatings have been developed with improved... more Ti-containing nano-composite diamond-like carbon (DLC) coatings have been developed with improved tribological characteristics. These coatings were synthesized by sputtering of pyrolitic graphite and titanium targets using unbalanced magnetrons with pulsed plasma technology. Compared with the Ti-containing nano-composite DLC film, a graded Ti-C:HyTiCNyTiN film was also deposited by sputtering of titanium targets in reactive gases (nitrogen and C H ) using the same deposition system. The Tiy 2 2 C multi-layered DLC coating deposited at a substrate rotation speed of 5 rev.ymin depicted an amorphous structure with 2-nm periodic thicknesses, and gave satisfactory friction performance in the pin-on-disk tests with a wear rate of 1-3=10 m yNm y17 3 and a friction coefficient of 0.09-0.1 against 100Cr6 steel and WC. The steady-state friction coefficient of nano-composite DLC films is lower than that of graded Ti-C:H DLC films (0.15-0.17). When sliding against soft copper ball, the friction coefficients of the DLC films were higher and increased with the sliding process from an initial friction coefficient of 0.15 with a promising wear behavior. Wear debris were primarily composed of copper mixed with surface impurities. SEM, EDX and XPS analyses depicted that the initial Ti contained C-O transfer films possess good adhesion between the sliding counterparts (100Cr6 and WC) and the coatings during the initial sliding stage. Micro-Raman spectra acquired from the nano-composite DLC coatings demonstrated a tendency of graphite formation of the transfer film. The readily transferred oxide-free graphite-like sp films form 2 a lubricious layer, which possess low shear strengths under applied loads. The XPS analysis of DLC C1s core level also suggests that transfer film is sp dominated.

Research paper thumbnail of Mechanical and tribological properties of multilayered TiSiN/CrN coatings synthesized by a cathodic arc deposition process

Surface & Coatings Technology, 2008

The monolayered TiSiN and multilayered TiSiN/CrN were synthesized by cathodic arc evaporation. Th... more The monolayered TiSiN and multilayered TiSiN/CrN were synthesized by cathodic arc evaporation. The Ti/Si (80/20 at.%) and chromium targets were used as the cathodic materials. With the different I [TiSi] /I [Cr] cathode current ratios of 1.8, 1.0, and 0.55, the multilayered TiSiN/CrN coatings possessed different multilayer periods (Λ) of 8.3 nm, 6.2 nm, and 4.2 nm. From XRD and TEM analyses, both the monolayered TiSiN and multilayered TiSiN/CrN revealed a typical columnar structure and B1-NaCl crystalline, no peaks of crystalline Si 3 N 4 were detected. Among the multilayered TiSiN/CrN coatings, the multilayered coating with Λ = 8.3 nm possessed higher hardness of 37 ± 2 GPa, higher elastic modulus of 396 ± 20 GPa and the lower residual stress of −1.60 GPa than the monolayered (Ti 0.39 Si 0.07 )N 0.54 coating(− 7.25 GPa). Due to the higher Cr/(Ti + Cr + Si) atomic ratio, the multilayered TiSiN/CrN with Λ = 5.5 nm possessed the lowest friction coefficient. But the lowest of wear rate was obtained by the multilayered TiSiN/CrN with Λ = 8.3 nm, because of higher H 3 /E ⁎ 2 ratio of 0.323 GPa. The monolayered TiSiN possessed the highest wear rate of 2.87 μm 2 /min. Therefore, the mechanical and tribological property can be improved by the design of multilayered coating.

Research paper thumbnail of Plasma properties of CrO x films synthesized by a cathodic arc evaporation process

Thin Solid Films, 2008

The plasma in a cathodic arc evaporation process used for the deposition of Cr 1−x O x films was ... more The plasma in a cathodic arc evaporation process used for the deposition of Cr 1−x O x films was studied by an optical emission spectroscopy (OES). With the introduction of Ar and oxygen into the chamber at deposition pressures from 0.7 Pa to 2.7 Pa, high density of evaporated chromium catalyzes the decomposition of oxygen reactive gas, and induces the formation of Cr 1−x O x films. Optical emission spectra including atomic and ionized Cr, excited and ionized oxygen revealed that excitation, ionization and charge transfer reactions of the Cr-O plasma occurred during the Cr 1−x O x deposition process. A simplified empirical model which incorporates the relevant atomic processes in the gas phase with the chemical composition and deposition rate of the deposited Cr 1−x O x coating was developed. Rhombohedral Cr 2 O 3 and tetragonal CrO 2 were observed in the Cr 1−x O x coatings deposited at higher pressure than 1.3 Pa. The Cr 1−x O x coating depicted a dense and compact microstructure with well-attached interface.

Research paper thumbnail of Effect of nickel incorporation on structural, nanomechanical and biocompatible properties of amorphous hydrogenated carbon thin films prepared by low energy biased target ion beam deposition

Thin Solid Films, 2010

Keywords: Amorphous hydrogenated carbon Low energy biased target ion beam deposition XPS Nanomech... more Keywords: Amorphous hydrogenated carbon Low energy biased target ion beam deposition XPS Nanomechanical properties Osteoblasts cells Nickel incorporated amorphous hydrogenated carbon (Ni/a:C-H) thin films were deposited onto the Si substrates via biased target ion beam sputtering of nickel combined with reactive ion beam deposition of a:C-H using CH 4 /Ar gas mixture. The effects of Ni doping and target bias voltage on the microstructure and mechanical properties of the as-deposited films were investigated by means of X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, transmission electron microscopy and nanoindentation. It was found that the Ni content in the films gets increased with increasing target bias voltage, and most of the Ni atoms react with C atoms to form NiC x phases in the Ni/a:C-H films. Moreover, the nickel carbide nanoparticles attain crystallinity even at low deposition temperature and get embedded in the cross-linked carbon matrix. It was found that the presence of Ni 3 C nanoparticles tends to increase the content of sp 2 carbon, thus decreasing the hardness of Ni/a:C-H films as compared with that of a:C-H films. Additionally it was found that the nickel incorporated films do not show any adverse effect on the osteoblast cellular adhesion. Overall, these carbidic nanocrystals initiate direct graphitization and intend to change diamond-like to graphite-like carbon structure in Ni/a:C-H films with promising biocompatibility.

Research paper thumbnail of Corrosion behavior of electroless nickel-coated AISI 304 stainless steel enhanced by titanium ion implantation

Surface & Coatings Technology, 2005

Metal plasma ion implantation has been successfully developed to improve the wear, corrosion, and... more Metal plasma ion implantation has been successfully developed to improve the wear, corrosion, and physical properties of various engineering materials. In this study, Ti ions were implanted into electroless nickel coating at 100 keV and 5Â10 16 -3Â10 17 ions/cm 2 using a metal plasma ion implantation apparatus. Within the implanted region, the hardness of the electroless nickel coating is increased from 14 to 18-22 GPa by Ti ion implantation at doses of 1Â10 17 -3Â10 17 ions/cm 2 . The electrochemical behavior of the Ti-implanted electroless nickel in a 3.5 wt.% NaCl solution was investigated by the potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS). The corrosion resistance of Ti-implanted electroless nickel was improved by the formation of chemically inert titanium oxides and Ti-Ni alloys in the ion-implanted layer, which leads to the increase of polarization resistances in the EIS analysis. At the dose of 3Â10 17 ions/cm 2 , the Ti-implanted electroless nickel possesses the best corrosion resistance due to the highest polarization resistance (3.05Â10 5 V/cm 2 ) and the lowest capacitance (1.5Â10 À5 F/cm 2 ). Results of this study demonstrate the potential of metal plasma ion implantation in improving the corrosion resistance of the electroless nickel with enhanced mechanical properties. D

Research paper thumbnail of Structural and mechanical properties of nanolayered TiAlN/CrN coatings synthesized by a cathodic arc deposition process

Surface & Coatings Technology, 2005

Monolayered AlTiN and Multilayered AlTiN/CrN coatings were synthesized by a cathodic-arc depositi... more Monolayered AlTiN and Multilayered AlTiN/CrN coatings were synthesized by a cathodic-arc deposition process, using TiAl (with 50/50 and 33/67 at.%) and Cr elemental cathodes. The atomic ratio of Al/(Ti + Al) in the AlTiN coatings was reduced to 0.44 and 0.61, respectively, compared with the corresponding Ti 50 Al 50 and Ti 33 Al 67 cathode materials. The multilayered AlTiN/CrN films showed smaller crystallite size, larger lattice strain, higher hardness, higher residual stress, and better adhesion strength as well than the monolayered AlTi films. The multilayered Al 0.35 Ti 0.22 N 0.43 /CrN coating exhibited the highest hardness of about 38 GPa and the highest H 3 /E* 2 ratio value of 0.188 GPa, indicating the best resistance to plastic deformation, among all the coatings studied.

Research paper thumbnail of Deposition of diamond-like carbon films containing metal elements on biomedical Ti alloys

Surface & Coatings Technology, 2005

Three kinds of diamond-like carbon (DLC) films, which contain different metals (Ti, Cr, Zr) and d... more Three kinds of diamond-like carbon (DLC) films, which contain different metals (Ti, Cr, Zr) and different interface designs, were deposited on biomedical titanium alloy (Ti -6Al -4V, ASTM F136) by using a cathodic arc evaporation system. Preliminary results showed that the DLC films are hydrogenated, amorphous and dense in structure. Scratch tests and Rockwell indentation tests reveal that the graded structures can improve the adhesion of DLC films. The Raman analyses showed that the Cr-containing DLC films possess lower I D /I G ratio, lower G-peak positions, and higher coating hardness. The pin-on-disk wear test in different environments (air and simulated body fluid) revealed that all the DLC films improve the wear performance of the substrates, and the wear coefficient is lower in simulated body fluid than that in air. In addition, the Cr-containing DLC films exhibited the lowest friction coefficient of 0.06 in simulated body fluid and 0.16 in air with the counterface of UHMWPE. Because of their dense structure, good adhesion and superior corrosion resistance in SBF, the Cr-C:H/ CrN films exhibited significantly low friction in SBF. The ICP-MS analysis revealed the release of Cr ion is 2.22 -10.03 ppm from the Crcontained DLC films, which is less than that from Co -Cr -Mo alloy (106.17 ppm), showing that the Cr-containing DLC films meet the requirement of biomedical applications. The potentiodynamic test revealed that the corrosion resistance of the ASTM F136 titanium alloys is increased substantially by the metal-containing DLC coating. D

Research paper thumbnail of High temperature oxidation resistance of CrAlSiN coatings synthesized by a cathodic arc deposition process

Journal of Alloys and Compounds, 2008

The high-temperature oxidation behavior of the CrN and Cr–Al–Si–N coatings was studied. These coa... more The high-temperature oxidation behavior of the CrN and Cr–Al–Si–N coatings was studied. These coatings were deposited on silicon substrates by using a cathodic-arc deposition system with lateral rotating arc cathodes. Chromium and Al88Si12 cathodes were used for ...

Research paper thumbnail of Characterization of TiCr(C,N)/amorphous carbon coatings synthesized by a cathodic arc deposition process

Thin Solid Films, 2007

Ternary TiCrN and nanocomposite TiCr(C,N)/amorphous carbon (a-C) coatings with different carbon c... more Ternary TiCrN and nanocomposite TiCr(C,N)/amorphous carbon (a-C) coatings with different carbon contents (0-26.6 at.%) were synthesized by cathodic arc evaporation with plasma enhanced duct equipment. The structural, chemical, and mechanical properties of the deposited films were studied by X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and nanoindentation measurement. The atomic content ratios of carbon/(Ti + Cr) and carbon/nitrogen increased with increasing C 2 H 2 flow rate. A nanocomposite structure of coexisting metastable hard TiCr(C, N) crystallites and amorphous carbon phases was found in the TiCr(C,N)/a-C coatings, those possessed smaller crystallite sizes than the ternary TiCrN film. XPS analyses revealed the concentration of a-C increased with increasing carbon content from 8.9 at.% to 26.6 at.%. Exceeding the metastable solubility range of carbon within the TiCrN lattice, the carbon formed a-C phase in the deposited coatings. The nanocomposite TiCr(C, N)/a-C coatings exhibited higher hardness value of 29-31 GPa than the deposited TiCrN coating (26 ± 1 GPa). It has been found that the structural and mechanical properties of the films were correlated with the carbon content in the TiCr(C,N)/a-C coatings.

Research paper thumbnail of Influence of cobalt ion implantation on optical properties of titanium dioxide thin films

Thin Solid Films, 2010

Nano-crystalline TiO2 thin films were synthesized by using sol–gel and spin-coating techniques on... more Nano-crystalline TiO2 thin films were synthesized by using sol–gel and spin-coating techniques on glass substrates for photo-catalytic applications. Prior to deposition, a TiO2 colloidal suspension was synthesized by microwave-induced thermal hydrolysis of the titanium tetrachloride aqueous solution. In this study, the deposited TiO2 coating with a grain size of 13±2nm was uniform without aggregation. Co ion implantation into the as-calcined

Research paper thumbnail of Tribological enhancement of CrN coatings by niobium and carbon ion implantation

Surface & Coatings Technology, 2004

Metal plasma ion implantation has being successfully developed for improving wear, corrosion and ... more Metal plasma ion implantation has being successfully developed for improving wear, corrosion and physical properties of engineering materials. In this study, Nb and C ions were co-implanted into CrN films using a metal-plasma ion implantation apparatus. The accelerating voltage of metal ions were set at 50 kV with implantation doses of 5=10 ionsycm for Nb and 16 2

Research paper thumbnail of Mechanical properties of nano-structured Ti-Si-N films synthesized by cathodic arc evaporation

Journal of Alloys and Compounds, 2007

Ti 1−x Si x N coatings were synthesized by cathodic arc evaporation with plasma-enhancing filter ... more Ti 1−x Si x N coatings were synthesized by cathodic arc evaporation with plasma-enhancing filter duct, using Ti 80 Si 20 alloy target as cathodes. Optical emission study revealed that excitation, ionization and charge transfer reactions of the Ti-Si-N plasma occurred during the Ti 1−x Si x N deposition process. The chemical content of Si varied from 3.3 to 6.0 at% in Ti 1−x Si x N depending on the nitrogen partial pressure of the reaction chamber. All the Ti 1−x Si x N coatings displayed a NaCl structure and a preferred (2 0 0) orientation parallel to the substrate surface. Among the studied Ti 1−x Si x N coatings, the Ti 1−x Si x N with 6 at.% Si possessed the highest hardness of 45 GPa and H 3 /E* 2 ratio of 0.527 GPa, indicating the best resistance to plastic deformation. We found that the structure and mechanical properties of the Ti 1−x Si x N films were correlated with the nitrogen pressure and silicon content of the coatings.

Research paper thumbnail of Tribological enhancement of CrN coatings by niobium and carbon ion implantation

Surface & Coatings Technology, 2003

Metal plasma ion implantation has being successfully developed for improving wear, corrosion and ... more Metal plasma ion implantation has being successfully developed for improving wear, corrosion and physical properties of engineering materials. In this study, Nb and C ions were co-implanted into CrN films using a metal-plasma ion implantation apparatus. The accelerating voltage of metal ions were set at 50 kV with implantation doses of 5=10 ionsycm for Nb and 16 2

Research paper thumbnail of Structural and electrical properties of Cr doped aC:H films synthesized by a cathodic-arc activated deposition process

Surface & Coatings Technology, 2006

Nitrogen-doped Cr -C:H/N films were synthesized by using a cathodic-arc activated deposition proc... more Nitrogen-doped Cr -C:H/N films were synthesized by using a cathodic-arc activated deposition process. Chromium plasma with intensive ion energies catalyzes the decomposition of hydrocarbon gas (C 2 H 2 ), and results in the deposition of amorphous carbon films. Nitrogen was introduced to form nitrogen-containing Cr -C:H/N films, which contained a mixture of sp 2 and sp 3 carbon bonds. The deposited carbon films consist of nanocomposite Cr -C:H/N films on top of a graded chromium nitride interlayer. It has been found that the structural and electrical properties of the films were correlated as a function of nitrogen doping. The nature of the heterojunction is confirmed by the spreading resistance characteristics of the Cr -C:H/N film/Si junction showing a behavior dependant on the nitrogen doping induced structure changes. With increasing nitrogen concentration, the increasing k states of sp 2 hybridization results in a more pronounced enhancement of conductivity. D