In order to clarify the influence of methane concentration and deposition time on self-organized nano-multilayers,three serial copper-carbon films have been prepared at various methane concentrations with different de...In order to clarify the influence of methane concentration and deposition time on self-organized nano-multilayers,three serial copper-carbon films have been prepared at various methane concentrations with different deposition times using a facile magnetron sputtering deposition system. The ratios of methane concentration(CH4/Ar+CH4) used in the experiments are 20%, 40%, and 60%, and the deposition times are 5 minutes, 20 minutes, and 40 minutes, respectively.Despite the difference in the growth conditions, self-organizing multilayered copper-carbon films are prepared at different deposition times by changing methane concentration. The film composition and microstructure are investigated by x-ray photoelectron spectroscopy(XPS), x-ray diffraction(XRD), field emission scanning electron microscopy(FESEM), and high-resolution transmission electron microscopy(HRTEM). By comparing the composition and microstructure of three serial films, the optimal growth conditions and compositions for self-organizing nano-multilayers in copper-carbon film are acquired. The results demonstrate that the self-organized nano-multilayered structure prefers to form in two conditions during the deposition process. One is that the methane should be curbed at low concentration for long deposition time,and the other condition is that the methane should be controlled at high concentration for short deposition time. In particular, nano-multilayered structure is self-organized in the copper-carbon film with copper concentration of 10-25 at.%.Furthermore, an interesting microstructure transition phenomenon is observed in copper-carbon films, that is, the nanomultilayered structure is gradually replaced by a nano-composite structure with deposition time and finally covered by amorphous carbon.展开更多
Amorphous carbon films with high sp2 concentrations are deposited by unbalanced magnetron sputtering with a narrow range of substrate bias voltage. Field emission scanning electron microscopes （FESEMs）, high resolut...Amorphous carbon films with high sp2 concentrations are deposited by unbalanced magnetron sputtering with a narrow range of substrate bias voltage. Field emission scanning electron microscopes （FESEMs）, high resolution transmission electron microscopes （HRTEMs）, atomic force microscopes （AFMs）, the Raman spectrometers, nano- indentation, and tribometers are subsequently used to characterize the microstructures and the properties of the resulting films. It is found that the present films are dominated by the sp2 sites. However, the films demonstrate a moderate hardness together with a low internal stress. The high hardness of the deposited film originates from the crosslinking of the sp2 clusters by the sp3 sites. The presence of the graphite-like clusters in the film structure may be responsible for the low internal stress. What is more important is that the resulting films show excellent tribological properties with high load capacity and excellent wear resistance in humid atmospheres. The relationship between the microstructure determined by the deposition condition and the film characteristic is discussed in detail.展开更多
In this work, a series of CrA1YN films doped with 1 at.% yttrium were deposited by unbalanced reactive magnetron sputtering under different bias voltages, The effects of bias voltage on microstrncture and properties o...In this work, a series of CrA1YN films doped with 1 at.% yttrium were deposited by unbalanced reactive magnetron sputtering under different bias voltages, The effects of bias voltage on microstrncture and properties of the CrA1YN films were subsequently investigated. It is found that all the as-deposited films have similar chemical composition and crystalline structure. However, the bias voltage has significant impact on the mechanical properties and oxidation resistance of the resulting films. Namely, the film deposited at 100 V has the highest hardness and best oxidation resistance, which are mainly attributed to its denser structure and higher A1 content than others. In addition, the film obtained at 100 V exhibits superior oxidation resistance even at 1000℃, and good friction and wear properties at 600 and 800 ℃, and the latter two are mainly ascribed to the formation of compact transfer layer on the worn surfaces. However, this film experienced obvious wear loss at low testing temperatures （i.e., 200 and 400 ℃） due to the serious abrasive wear.展开更多
Current-carrying sliding is widely applied in aerospace equipment,but it is limited by the poor lubricity of the present materials and the unclear tribological mechanism.This study demonstrated the potential of MoS_(2...Current-carrying sliding is widely applied in aerospace equipment,but it is limited by the poor lubricity of the present materials and the unclear tribological mechanism.This study demonstrated the potential of MoS_(2)-based materials with excellent lubricity as space sliding electrical contact materials by doping Ti to improve its conductivity.The tribological behavior of MoS_(2)-Ti films under current-carrying sliding in vacuum was studied by establishing a simulation evaluating device.Moreover,the noncurrent-carrying sliding and static current-carrying experiments in vacuum were carried out for comparison to understand the tribological mechanism.In addition to mechanical wear,the current-induced arc erosion and thermal effect take important roles in accelerating the wear.Arc erosion is caused by the accumulation of electric charge,which is related to the conductivity of the film.While the current-thermal effect softens the film,causing strong adhesive wear,and good conductivity and the large contact area are beneficial for minimizing the thermal effect.So the moderate hardness and good conductivity of MoS_(2)-Ti film contribute to its excellent current-carrying tribological behavior in vacuum,showing a significant advantage compared with the traditional ones.展开更多
Molecular dynamical simulation is carried out to investigate the effects of the incident energy on a-C：H film growth from C and tt atomic flux. Our simulations show that the film growth at low incident energy （1 eV...Molecular dynamical simulation is carried out to investigate the effects of the incident energy on a-C：H film growth from C and tt atomic flux. Our simulations show that the film growth at low incident energy （1 eV） is dominated by the adsorption of H and C atoms. At moderate incident energy （10 and 20eV）, the abstraction reaction of incident H atoms with H atoms adsorbed at the surface becomes important. At high incident energy （30 and 40eV）, the a-C：H film growth is a two-step process： one is the adsorption and the shallow implantation of C atoms, and the other is the deep implantation of H atoms.展开更多
The thermal stability of hydrogenated carbon films with H fraction from zero to 51.5% is studied by carrying out a molecular dynamical simulation on the annealing process in vacuum. Our simulations show that both grap...The thermal stability of hydrogenated carbon films with H fraction from zero to 51.5% is studied by carrying out a molecular dynamical simulation on the annealing process in vacuum. Our simulations show that both graphitization temperature and dehydrogenization temperature decrease with H fraction in the films, which is in good agreement with the available experimental data. The dehydrogenization temperature is found to be much higher than the graphitization temperature. It is indicated that graphitization is the dominant process causing the degeneration of hydrogenated carbon films.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51472250,U1637204,and 51775537)
文摘In order to clarify the influence of methane concentration and deposition time on self-organized nano-multilayers,three serial copper-carbon films have been prepared at various methane concentrations with different deposition times using a facile magnetron sputtering deposition system. The ratios of methane concentration(CH4/Ar+CH4) used in the experiments are 20%, 40%, and 60%, and the deposition times are 5 minutes, 20 minutes, and 40 minutes, respectively.Despite the difference in the growth conditions, self-organizing multilayered copper-carbon films are prepared at different deposition times by changing methane concentration. The film composition and microstructure are investigated by x-ray photoelectron spectroscopy(XPS), x-ray diffraction(XRD), field emission scanning electron microscopy(FESEM), and high-resolution transmission electron microscopy(HRTEM). By comparing the composition and microstructure of three serial films, the optimal growth conditions and compositions for self-organizing nano-multilayers in copper-carbon film are acquired. The results demonstrate that the self-organized nano-multilayered structure prefers to form in two conditions during the deposition process. One is that the methane should be curbed at low concentration for long deposition time,and the other condition is that the methane should be controlled at high concentration for short deposition time. In particular, nano-multilayered structure is self-organized in the copper-carbon film with copper concentration of 10-25 at.%.Furthermore, an interesting microstructure transition phenomenon is observed in copper-carbon films, that is, the nanomultilayered structure is gradually replaced by a nano-composite structure with deposition time and finally covered by amorphous carbon.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.50705093 and 50575217)the Innovative Group Foundation of the National Natural Science Foundation of China(Grant No.50421502)the National Basic ResearchProgram of China(Grant No.2007CB607601)
文摘Amorphous carbon films with high sp2 concentrations are deposited by unbalanced magnetron sputtering with a narrow range of substrate bias voltage. Field emission scanning electron microscopes （FESEMs）, high resolution transmission electron microscopes （HRTEMs）, atomic force microscopes （AFMs）, the Raman spectrometers, nano- indentation, and tribometers are subsequently used to characterize the microstructures and the properties of the resulting films. It is found that the present films are dominated by the sp2 sites. However, the films demonstrate a moderate hardness together with a low internal stress. The high hardness of the deposited film originates from the crosslinking of the sp2 clusters by the sp3 sites. The presence of the graphite-like clusters in the film structure may be responsible for the low internal stress. What is more important is that the resulting films show excellent tribological properties with high load capacity and excellent wear resistance in humid atmospheres. The relationship between the microstructure determined by the deposition condition and the film characteristic is discussed in detail.
基金supported by the National Basic Research Program of China(Grant No.2013CB632302)the National Natural Science Foundation of China(Grant No.51175491)
文摘In this work, a series of CrA1YN films doped with 1 at.% yttrium were deposited by unbalanced reactive magnetron sputtering under different bias voltages, The effects of bias voltage on microstrncture and properties of the CrA1YN films were subsequently investigated. It is found that all the as-deposited films have similar chemical composition and crystalline structure. However, the bias voltage has significant impact on the mechanical properties and oxidation resistance of the resulting films. Namely, the film deposited at 100 V has the highest hardness and best oxidation resistance, which are mainly attributed to its denser structure and higher A1 content than others. In addition, the film obtained at 100 V exhibits superior oxidation resistance even at 1000℃, and good friction and wear properties at 600 and 800 ℃, and the latter two are mainly ascribed to the formation of compact transfer layer on the worn surfaces. However, this film experienced obvious wear loss at low testing temperatures （i.e., 200 and 400 ℃） due to the serious abrasive wear.
基金supported by the National Natural Science Foundation of China(Grant No.51775537)Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.Y202084)。
文摘Current-carrying sliding is widely applied in aerospace equipment,but it is limited by the poor lubricity of the present materials and the unclear tribological mechanism.This study demonstrated the potential of MoS_(2)-based materials with excellent lubricity as space sliding electrical contact materials by doping Ti to improve its conductivity.The tribological behavior of MoS_(2)-Ti films under current-carrying sliding in vacuum was studied by establishing a simulation evaluating device.Moreover,the noncurrent-carrying sliding and static current-carrying experiments in vacuum were carried out for comparison to understand the tribological mechanism.In addition to mechanical wear,the current-induced arc erosion and thermal effect take important roles in accelerating the wear.Arc erosion is caused by the accumulation of electric charge,which is related to the conductivity of the film.While the current-thermal effect softens the film,causing strong adhesive wear,and good conductivity and the large contact area are beneficial for minimizing the thermal effect.So the moderate hardness and good conductivity of MoS_(2)-Ti film contribute to its excellent current-carrying tribological behavior in vacuum,showing a significant advantage compared with the traditional ones.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50705093 and 50575217, the Science Fund for Creative Research Groups of the National Natural Science Foundation of China under Grant No 50421502, and the National Basic Research Program of China under Grant No 2007CB607601.
文摘Molecular dynamical simulation is carried out to investigate the effects of the incident energy on a-C：H film growth from C and tt atomic flux. Our simulations show that the film growth at low incident energy （1 eV） is dominated by the adsorption of H and C atoms. At moderate incident energy （10 and 20eV）, the abstraction reaction of incident H atoms with H atoms adsorbed at the surface becomes important. At high incident energy （30 and 40eV）, the a-C：H film growth is a two-step process： one is the adsorption and the shallow implantation of C atoms, and the other is the deep implantation of H atoms.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50705093 and 50575217, the Science Fund for Creative Research Groups of the National Natural Science Foundation of China under Grant No 50421502, and the National Basic Research Program of China under Grant No 2007 CB607601.
文摘The thermal stability of hydrogenated carbon films with H fraction from zero to 51.5% is studied by carrying out a molecular dynamical simulation on the annealing process in vacuum. Our simulations show that both graphitization temperature and dehydrogenization temperature decrease with H fraction in the films, which is in good agreement with the available experimental data. The dehydrogenization temperature is found to be much higher than the graphitization temperature. It is indicated that graphitization is the dominant process causing the degeneration of hydrogenated carbon films.
