A modified electrolyte （CH3COOH-HClO4-A-B） for electropolishing （EP） of NiTi was presented for improving the corrosion resistance and biocompatibility of the alloy. Using the proposed parameters, a homogeneous and...A modified electrolyte （CH3COOH-HClO4-A-B） for electropolishing （EP） of NiTi was presented for improving the corrosion resistance and biocompatibility of the alloy. Using the proposed parameters, a homogeneous and uniform surface was obtained. Atomic force microscopy （AFM） revealed that the surface roughness （Ra） for EP sample （23.21 nm） was close to mechanical polishing （MP） sample （19.36 nm）. Analysis by X-ray photoelectron spectroscopy （XPS） showed that Ti/Ni ratio increased from 3.1 for MP sample to 27.6 for EP sample. Measurements using potentiodynamic polarization in Hanks＇ solution showed that no pitting occurred for EP sample even though the applied potential increased up to 1500 mV （vs SCE）, while the MP sample was broken down at 650 mV. The present study indicates that electropolishing NiTi with this modified electrolyte contributes to the improved biocompatibility of NiTi.展开更多
Using the optical microscope, tensile test machine and micro hardness meter, the effect of heat input on the microstructure and mechanical properties in fusion welding joints of AZ31B wrought alloys was investigated s...Using the optical microscope, tensile test machine and micro hardness meter, the effect of heat input on the microstructure and mechanical properties in fusion welding joints of AZ31B wrought alloys was investigated systematically, the mechanism on joint properties losing was analyzed, and a valid method to improve joint properties of the magnesium alloy fusion welding was explored. The results show that the heat input has an obvious effect on the microstructure and properties. Under the condition of penetration, with the heat input decreasing, the crystal grain in the weld and heat affected zone (HAZ) becomes fine, the width of HAZ becomes obviously narrow, and the molding of the weld is improved, so the tensile strength and elongation are increased and the hardness of joints is improved. When the heat input reaches 60 J/mm, the high quality joints can be gained.展开更多
The non-chain chemical HF(DF)laser is one of the most powerful electrically-driven lasers operating in mid-infrared,in which SF6-C2H6 mixtures are often used as lasering media.Due to the electronegativity of SF6,the d...The non-chain chemical HF(DF)laser is one of the most powerful electrically-driven lasers operating in mid-infrared,in which SF6-C2H6 mixtures are often used as lasering media.Due to the electronegativity of SF6,the discharge in SF6-C2H6 presents a complicated discharge mode.To achieve reproducible pulsed laser output,pulsed discharge in SF6-C2H6 mixtures is investigated for discharge mode using plane electrodes assisted by array pre-ionization spark pins in cathode surface.Firstly,two modes can be distinguished.One mode is called the selfsustained volume discharge(SSVD),which is characterized by spatial uniformity in the discharge gap and pulse to pulse repeatability.On the contrary,another mode includes random arc passages in the discharge gap and therefore cannot conduct lasering.By varying discharge conditions(gap voltage,gas pressure,etc)two discharge modes are observed.Secondly,the holding scope of the SSVD mode is analyzed for the optimal mixture ratio of 20:1,and the boundary tend of the holding scope of SSVD indicates there exists maximum gas pressure and maximum charging voltage for SSVD.Finally,the peak current of SSVD relates positively to charging voltage,while negatively to gas pressure,from which it is drawn that synchronous electron avalanches initiated by the sliding array overlap spatially into SSVD and thus SSVD is essentially an α ionization avalanche.展开更多
The structures of diamond-like carbon （DLC） films, including a-C：H, a-C, ta-C：H and ta-C films have been investigated as a random covalent network with a dense film structure. The results show that sp2 C in a-C：H...The structures of diamond-like carbon （DLC） films, including a-C：H, a-C, ta-C：H and ta-C films have been investigated as a random covalent network with a dense film structure. The results show that sp2 C in a-C：H and a-C films tends to form olefinic and aromatic groups while sp^3 C in ta-C：H and ta-C films tends to form single or multiple sixfold groups. The hydrogen atoms in hydrogenated DLC films contribute to stabilizing the carbon skeletal networks. The film structures are well related to their properties such as optical gaps, density and hardness. The results also indicate that the high density and the extreme hardness of ta-C films are attributed to the forming of large sp^3 C bonded sixfold groups.展开更多
Plasma polymerized fluorocarbon （FC） films have been deposited on silicon substrates from dielectric barrier discharge （DBD） plasma of C4Fs at room temperature under a pressure of 25～125 Pa. The effects of the di...Plasma polymerized fluorocarbon （FC） films have been deposited on silicon substrates from dielectric barrier discharge （DBD） plasma of C4Fs at room temperature under a pressure of 25～125 Pa. The effects of the discharge pressure and frequency of power supply on the films have been systematically investigated. FC films with a less cross linked structure may be formed at a relatively high pressure. Increase in the frequency of power supply leads to a significant increase in the deposition rate. Static contact angle measurements show that deposited FC films have a stable, hydrophobic surface property. All deposited films show smooth surfaces with an atomic surface roughness. The relationship between plasma parameters and the properties of the deposited FC films are discussed.展开更多
By using an Ar+ ion laser, a tunable Rh 6G dye laser(Linewidth: 0.5 cm -1) and a Coherent 899-21 dye laser as light sources and using a monochromator and a phase-locking amplifier, the optical properties of Eu 3+∶Y_2...By using an Ar+ ion laser, a tunable Rh 6G dye laser(Linewidth: 0.5 cm -1) and a Coherent 899-21 dye laser as light sources and using a monochromator and a phase-locking amplifier, the optical properties of Eu 3+∶Y_2SiO_5 crystal were detected. Persistent spectral hole burning (PSHB) were also observed in 5D_0-7F_0 transition in the crystal at the temperature of 16 K. For 15 mW dye laser (Wavelength: 579.62 nm) burning the crystal for 0.1 s a spectral hole with about 80 MHz hole width were detected and the hole can been keep for longer than 10 h.展开更多
By using an Ar^＋ ion laser, a tunable Rh6G dye laser（linewidth： 0.5 cm^-1） pumped by the second harmonic of a YAG：Nd laser and an 899-21 dye laser as light sources and using a monochromator, a phase-locking ampli...By using an Ar^＋ ion laser, a tunable Rh6G dye laser（linewidth： 0.5 cm^-1） pumped by the second harmonic of a YAG：Nd laser and an 899-21 dye laser as light sources and using a monochromator, a phase-locking amplifier and a computer as the data detecting system, the spectra and spectral hole burning of Eu^3＋：Y2SiO5 crystal were researched in this paper.Photoluminescence excitation spectrum and site selective fluorescence spectrum were detected at room temperature and 77 K. Hole burning experiments were reached at 16 K. A spectral hole with hole width of about 80 MHz were detected and it could be kept for 10 h.展开更多
Diamond-like carbon （DLC） films have been deposited using three different techniques： （a） electron cyclotron resonance——plasma source ion implantation, （b） low-pressure dielectric barrier discharge, （c） fil...Diamond-like carbon （DLC） films have been deposited using three different techniques： （a） electron cyclotron resonance——plasma source ion implantation, （b） low-pressure dielectric barrier discharge, （c） filtered——pulsed cathodic arc discharge, The surface and mechanical properties of these films are compared using atomic force microscopebased tests. The experimental results show that hydrogenated DLC films are covered with soft surface layers enriched with hydrogen and sp^3 hybridized carbon while the soft surface layers of tetrahedral amorphous carbon （ta-C） films have graphite-like structure, The formation of soft surface layers can be associated with the surface diffusion and growth induced by the low-energy deposition process. For typical CVD methods, the atomic hydrogen in the plasmas can contribute to the formation of hydrogen and sp^3 hybridized carbon enriched surface layers, The high-energy ion implantation causes the rearrangement of atoms beneath the surface layer and leads to an increase in film density. The ta-C films can be deposited using the medium energy carbon ions in the highly-ionized plasma.展开更多
A layer of TiO_(x) was deposited on powdery γ-Al_(2)O_(3) by using Sat-target magnetron sputtering in microwave electron cyclotron resonance plasma.A vibrator was developed to coat the γ-Al_(2)O_(3) particles evenly...A layer of TiO_(x) was deposited on powdery γ-Al_(2)O_(3) by using Sat-target magnetron sputtering in microwave electron cyclotron resonance plasma.A vibrator was developed to coat the γ-Al_(2)O_(3) particles evenly by TiO_(x).The conversion efficiency of methane and both the yield and the selectivity of C_(2) hydrocarbons and C_(2)H_(2) were revealed to be superior to that by conventional chemical method.The use of vibrator is effective.展开更多
Atomic force microscopy is used to estimate and compare the surface morphology of hydrogenated and hydrogen-free diamond-like carbon （DLC） films. The films were prepared by using DC magnetron sputtering of a graphit...Atomic force microscopy is used to estimate and compare the surface morphology of hydrogenated and hydrogen-free diamond-like carbon （DLC） films. The films were prepared by using DC magnetron sputtering of a graphite target, pulsed cathodic carbon arcs, electron cyclotron resonance （ECR）, plasma source ion implantation and dielectric barrier discharge （DBD）. The difference in the surface structure is presented for each method of deposition. The influences of various discharge parameters on the film surface properties are discussed based upon the experimental results. The coalescence process via the diffusion of adsorbed carbon species is responsible for the formation of hydrogen-free DLC films with rough surfaces. The films with surface roughness at an atomic level can be deposited by energetic ion impacts in a highly ionized carbon plasma. The hydrocarbon species dangling bonds created by atomic hydrogen lead to the uniform growth of at the a-C：H film surfaces of the ECR or DBD plasmas展开更多
Deposition of CN_(x) thin films on Si(111)has been performed by laser ablation of graphite under a low-energy nitrogen ion beam bombardment.Films with a maximum N-concentration of 34%are obtained.The N species is foun...Deposition of CN_(x) thin films on Si(111)has been performed by laser ablation of graphite under a low-energy nitrogen ion beam bombardment.Films with a maximum N-concentration of 34%are obtained.The N species is found to be relatively constant along the depth of films.X-ray spectroscopy data confirm the existence of covalent C-N bonds.Nanocrystallites structure has been detected in the amorphous matrix of the films.Qualitative hardness tests indicate that the films are relatively hard and adhesive.展开更多
文摘A modified electrolyte （CH3COOH-HClO4-A-B） for electropolishing （EP） of NiTi was presented for improving the corrosion resistance and biocompatibility of the alloy. Using the proposed parameters, a homogeneous and uniform surface was obtained. Atomic force microscopy （AFM） revealed that the surface roughness （Ra） for EP sample （23.21 nm） was close to mechanical polishing （MP） sample （19.36 nm）. Analysis by X-ray photoelectron spectroscopy （XPS） showed that Ti/Ni ratio increased from 3.1 for MP sample to 27.6 for EP sample. Measurements using potentiodynamic polarization in Hanks＇ solution showed that no pitting occurred for EP sample even though the applied potential increased up to 1500 mV （vs SCE）, while the MP sample was broken down at 650 mV. The present study indicates that electropolishing NiTi with this modified electrolyte contributes to the improved biocompatibility of NiTi.
文摘Using the optical microscope, tensile test machine and micro hardness meter, the effect of heat input on the microstructure and mechanical properties in fusion welding joints of AZ31B wrought alloys was investigated systematically, the mechanism on joint properties losing was analyzed, and a valid method to improve joint properties of the magnesium alloy fusion welding was explored. The results show that the heat input has an obvious effect on the microstructure and properties. Under the condition of penetration, with the heat input decreasing, the crystal grain in the weld and heat affected zone (HAZ) becomes fine, the width of HAZ becomes obviously narrow, and the molding of the weld is improved, so the tensile strength and elongation are increased and the hardness of joints is improved. When the heat input reaches 60 J/mm, the high quality joints can be gained.
基金National Natural Science Foundation of China(No.11375041).
文摘The non-chain chemical HF(DF)laser is one of the most powerful electrically-driven lasers operating in mid-infrared,in which SF6-C2H6 mixtures are often used as lasering media.Due to the electronegativity of SF6,the discharge in SF6-C2H6 presents a complicated discharge mode.To achieve reproducible pulsed laser output,pulsed discharge in SF6-C2H6 mixtures is investigated for discharge mode using plane electrodes assisted by array pre-ionization spark pins in cathode surface.Firstly,two modes can be distinguished.One mode is called the selfsustained volume discharge(SSVD),which is characterized by spatial uniformity in the discharge gap and pulse to pulse repeatability.On the contrary,another mode includes random arc passages in the discharge gap and therefore cannot conduct lasering.By varying discharge conditions(gap voltage,gas pressure,etc)two discharge modes are observed.Secondly,the holding scope of the SSVD mode is analyzed for the optimal mixture ratio of 20:1,and the boundary tend of the holding scope of SSVD indicates there exists maximum gas pressure and maximum charging voltage for SSVD.Finally,the peak current of SSVD relates positively to charging voltage,while negatively to gas pressure,from which it is drawn that synchronous electron avalanches initiated by the sliding array overlap spatially into SSVD and thus SSVD is essentially an α ionization avalanche.
文摘The structures of diamond-like carbon （DLC） films, including a-C：H, a-C, ta-C：H and ta-C films have been investigated as a random covalent network with a dense film structure. The results show that sp2 C in a-C：H and a-C films tends to form olefinic and aromatic groups while sp^3 C in ta-C：H and ta-C films tends to form single or multiple sixfold groups. The hydrogen atoms in hydrogenated DLC films contribute to stabilizing the carbon skeletal networks. The film structures are well related to their properties such as optical gaps, density and hardness. The results also indicate that the high density and the extreme hardness of ta-C films are attributed to the forming of large sp^3 C bonded sixfold groups.
基金National Natural Science Foundation of China(No.10405005)
文摘Plasma polymerized fluorocarbon （FC） films have been deposited on silicon substrates from dielectric barrier discharge （DBD） plasma of C4Fs at room temperature under a pressure of 25～125 Pa. The effects of the discharge pressure and frequency of power supply on the films have been systematically investigated. FC films with a less cross linked structure may be formed at a relatively high pressure. Increase in the frequency of power supply leads to a significant increase in the deposition rate. Static contact angle measurements show that deposited FC films have a stable, hydrophobic surface property. All deposited films show smooth surfaces with an atomic surface roughness. The relationship between plasma parameters and the properties of the deposited FC films are discussed.
文摘By using an Ar+ ion laser, a tunable Rh 6G dye laser(Linewidth: 0.5 cm -1) and a Coherent 899-21 dye laser as light sources and using a monochromator and a phase-locking amplifier, the optical properties of Eu 3+∶Y_2SiO_5 crystal were detected. Persistent spectral hole burning (PSHB) were also observed in 5D_0-7F_0 transition in the crystal at the temperature of 16 K. For 15 mW dye laser (Wavelength: 579.62 nm) burning the crystal for 0.1 s a spectral hole with about 80 MHz hole width were detected and the hole can been keep for longer than 10 h.
文摘By using an Ar^＋ ion laser, a tunable Rh6G dye laser（linewidth： 0.5 cm^-1） pumped by the second harmonic of a YAG：Nd laser and an 899-21 dye laser as light sources and using a monochromator, a phase-locking amplifier and a computer as the data detecting system, the spectra and spectral hole burning of Eu^3＋：Y2SiO5 crystal were researched in this paper.Photoluminescence excitation spectrum and site selective fluorescence spectrum were detected at room temperature and 77 K. Hole burning experiments were reached at 16 K. A spectral hole with hole width of about 80 MHz were detected and it could be kept for 10 h.
基金Project supported by National Natural Science Foundation of China （Grant No 10405005）.
文摘Diamond-like carbon （DLC） films have been deposited using three different techniques： （a） electron cyclotron resonance——plasma source ion implantation, （b） low-pressure dielectric barrier discharge, （c） filtered——pulsed cathodic arc discharge, The surface and mechanical properties of these films are compared using atomic force microscopebased tests. The experimental results show that hydrogenated DLC films are covered with soft surface layers enriched with hydrogen and sp^3 hybridized carbon while the soft surface layers of tetrahedral amorphous carbon （ta-C） films have graphite-like structure, The formation of soft surface layers can be associated with the surface diffusion and growth induced by the low-energy deposition process. For typical CVD methods, the atomic hydrogen in the plasmas can contribute to the formation of hydrogen and sp^3 hybridized carbon enriched surface layers, The high-energy ion implantation causes the rearrangement of atoms beneath the surface layer and leads to an increase in film density. The ta-C films can be deposited using the medium energy carbon ions in the highly-ionized plasma.
基金Supported by National Natural Science Foundation of China under Grant No.69493502。
文摘A layer of TiO_(x) was deposited on powdery γ-Al_(2)O_(3) by using Sat-target magnetron sputtering in microwave electron cyclotron resonance plasma.A vibrator was developed to coat the γ-Al_(2)O_(3) particles evenly by TiO_(x).The conversion efficiency of methane and both the yield and the selectivity of C_(2) hydrocarbons and C_(2)H_(2) were revealed to be superior to that by conventional chemical method.The use of vibrator is effective.
基金supported by National Natural Science Foundation of China(No.10405005)
文摘Atomic force microscopy is used to estimate and compare the surface morphology of hydrogenated and hydrogen-free diamond-like carbon （DLC） films. The films were prepared by using DC magnetron sputtering of a graphite target, pulsed cathodic carbon arcs, electron cyclotron resonance （ECR）, plasma source ion implantation and dielectric barrier discharge （DBD）. The difference in the surface structure is presented for each method of deposition. The influences of various discharge parameters on the film surface properties are discussed based upon the experimental results. The coalescence process via the diffusion of adsorbed carbon species is responsible for the formation of hydrogen-free DLC films with rough surfaces. The films with surface roughness at an atomic level can be deposited by energetic ion impacts in a highly ionized carbon plasma. The hydrocarbon species dangling bonds created by atomic hydrogen lead to the uniform growth of at the a-C：H film surfaces of the ECR or DBD plasmas
文摘Deposition of CN_(x) thin films on Si(111)has been performed by laser ablation of graphite under a low-energy nitrogen ion beam bombardment.Films with a maximum N-concentration of 34%are obtained.The N species is found to be relatively constant along the depth of films.X-ray spectroscopy data confirm the existence of covalent C-N bonds.Nanocrystallites structure has been detected in the amorphous matrix of the films.Qualitative hardness tests indicate that the films are relatively hard and adhesive.
