Magnetohydrodynamic phenomena in the CT-6B Tokamak based on Mirnov oscillations have been investigated by applying the limiter biasing potentials and changing the vacuum chamber gas pressure and plasma displacement.Th...Magnetohydrodynamic phenomena in the CT-6B Tokamak based on Mirnov oscillations have been investigated by applying the limiter biasing potentials and changing the vacuum chamber gas pressure and plasma displacement.The results show that setting up a radial electric field at the plasma edge could drive electromagnetic instabilities in the tokamak plasma.Magnetic oscillation frequency upon application of a positive bias decreases about 10-15%and then after a delay time,τ_(d)=2.5-3 ms increases about 20-25%with respect to their value without biasing.In the negative bias regime the oscillation frequency increases about 10%in 1 ms after the application of the bias pulse.The poloidal rotation velocity changes during two steps are related to its link with the radial electric field and the time scale of the density gradient.The frequency of oscillations increases with the increasing chamber gas pressure and decreases with the increasing the outward plasma displacement.展开更多
The effect of time of applied bias on the edge turbulent transport is analyzed by the multi-fractal detrend fluctu- ation analysis （MF-DFA） method in the IR-Tl tokamak. The generalized Hurst exponents and the multif...The effect of time of applied bias on the edge turbulent transport is analyzed by the multi-fractal detrend fluctu- ation analysis （MF-DFA） method in the IR-Tl tokamak. The generalized Hurst exponents and the multifractal spectrum are computed by this method. The MF-DFA method is applied to the fluctuation of gradient of float- ing potential time series collected by a multipurpose probe. Tile monofractality or multifractality of the time series can be detected by generalized exponent. The multifractal spectrum describes the singularity content of the process. The results show that with applying bias to the plasma at different times （t = 15 ms, 18ms and 22ms）, the degree of multifractality changes. It reaches the minimum when the bias is applied at t = 18 ms. The multifractality source of data is investigated by the surrogate method （phase randomization techniques）. The surrogate method can destroy the different types of correlations in all the sizes of fluctuations. The results show that the long-range correlation contributes more to multifractality than the fat tail distribution.展开更多
In this study, commercial biaxially oriented polypropylene （BOPP）, polyvinyl chlo- ride （PVC） and poly （methyl methacrylate） （PMMA） films were treated with nitrogen plasma over different exposure times in a Py...In this study, commercial biaxially oriented polypropylene （BOPP）, polyvinyl chlo- ride （PVC） and poly （methyl methacrylate） （PMMA） films were treated with nitrogen plasma over different exposure times in a Pyrex tube surrounded by a DC variable magnetic field. The chemi- cal changes that appeared on the surface of the samples were investigated using Fourier transform infrared （FT4R） spectroscopy and attenuated total reflectance Fourier transform infrared （ATR- FTIR） spectroscopy after treatment for 2 min, 4 min and 6 rain in a nitrogen plasma chamber. Effects of the plasma treatment on the surface topographies and contact angles of the untreated and plasma treated films were also analyzed by atomic force microscopy （AFM） and a contact angle measuring system. The results show that the plasma treated films become more hydrophilic with an enhanced wettability due to the formation of some new polar groups on the surface of the treated films. Moreover, at higher exposure times, the total surface energy in all treated films increased while a reduction in contact angle occurred. The behavior of surface roughness in each sample was completely different at higher exposure times.展开更多
In this research the effects of mordant and plasma sputtering treatments on the crystallinity and morphological properties of wool fabrics were investigated. The felting behavior of the treated samples was also studie...In this research the effects of mordant and plasma sputtering treatments on the crystallinity and morphological properties of wool fabrics were investigated. The felting behavior of the treated samples was also studied. We used madder as a natural dye and copper sulfate as a metal mordant. We also used copper as the electrode material in a DC magnetron plasma sputtering device. The anti-felting properties of the wool samples before and after dying was studied, and it was shown that the shrink resistance and anti-felting behavior of the wool had been significantly improved by the plasma sputtering treatment. In addition, the percentage of crystallinity and the size of the crystals were investigated using an X-ray diffractometer, and a scanning electron microscope was used for morphological analysis. The amount of copper particles on the surface of the mordanted and sputtered fabrics was studied using the energy dispersive X- ray （EDX） method, and the hydrophobic properties of the samples were examined using the water drop test. The results show that with plasma sputtering treatment, the hydrophobic properties of the surface of wool become super hydrophobic.展开更多
Tin oxide （SnO2） is one of the most promising transparent conducting oxide materials, which is widely used in thin film gas sensors. We investigate the dependence of the deposition time on structural, morphologicaJ ...Tin oxide （SnO2） is one of the most promising transparent conducting oxide materials, which is widely used in thin film gas sensors. We investigate the dependence of the deposition time on structural, morphologicaJ and hydrogen gas sensing properties of SnO2 thin films synthesized by dc magnetron sputtering. The deposited samples are characterized by XRD, SEM, AFM, surface area measurements and surface profiler. Also the H2 gas sensing properties of SnO2 deposited samples are performed against a wide range of operating temperature. The XRD analysis demonstrates that the degree of crystallinity of the deposited SnO2 films strongly depends on the deposition time. SEM and AFM analyses reveal that the size of nanoparticles or agglomerates, and both average and rms surface roughness is enhanced with the increasing deposition time. Also gas sensors based on these SnO2 nanolayers show an acceptable response to hydrogen at various operating temperatures.展开更多
Microbial contamination induces surface deformations and strength degradation of cotton fabrics by invading deeply into the fibers. In this study, the sterilization effects of low pressure plasmas on bacteria-inoculat...Microbial contamination induces surface deformations and strength degradation of cotton fabrics by invading deeply into the fibers. In this study, the sterilization effects of low pressure plasmas on bacteria-inoculated cotton fabrics were investigated. Oxygen plasma treatment completely sterilized the cotton fabrics inoculated with various concentrations of staphylococcus aureus. Also, the influence of plasma treatment on physical properties of fabrics was examined. It was found that the plasma treatment did not affect ultimate tensile strength and surface morphology of the fabrics because it took advantage of relatively low plasma temperature.展开更多
We investigate the effects of etching gases on the synthesis of nano crystalline diamonds grown on silicon substrate at the substrate temperature of 550℃ and the reaction pressure of 4 kPa by hot filament chemical va...We investigate the effects of etching gases on the synthesis of nano crystalline diamonds grown on silicon substrate at the substrate temperature of 550℃ and the reaction pressure of 4 kPa by hot filament chemical vapor deposition method, in which CH4 and H2 act as a source and diluting gases, respectively. N2, H2, and NH3 were used as the etching gases, respectively. Results show that the optimum conditions can be obtained only for the case of H2 gas. The crystal morphology and crystallinity of the samples have been examined by scanning electron microscopy and X-ray diffraction, respectively.展开更多
In the present investigation, Ni_（50）Ti_（25）Al_（25）（at.%） mechanically alloyed powder is deposited on carbon steel substrate.Before the coating process, the substrate is heated to temperature ranging from room...In the present investigation, Ni_（50）Ti_（25）Al_（25）（at.%） mechanically alloyed powder is deposited on carbon steel substrate.Before the coating process, the substrate is heated to temperature ranging from room temperature to 400℃. The microstructure, porosity, microhardness, adhesion strength, and corrosion behavior of the coating are investigated at different substrate temperatures. Results show that coating porosity is lower on high temperature surface. Microhardness and adhesion strength of the deposition layer on the substrate without preheating have lower values than with preheating. The polarization test result shows that corrosion performance of the coating is dependent on micro cracks and porosities and the increasing of substrate temperature can improve the quality of coating and corrosion performance.展开更多
Plasma-surface interaction experiments on TiN coated stainless steel 316L （S.S.316L） using a plasma focus （PF） device have been performed in an attempt to investigate whether we can use the hardness property of Ti...Plasma-surface interaction experiments on TiN coated stainless steel 316L （S.S.316L） using a plasma focus （PF） device have been performed in an attempt to investigate whether we can use the hardness property of TiN against erosion to increase the lifetime of the mirrors used in plasma diagnostics equipment. Firstly, two similar S.S.316L samples were chosen for this purpose. One of the samples was coated with TiN by using a PF device, while the other was kept intact as a reference for investigating the effect of TiN coating. Then, in order to study the coating effects, these samples were exposed to 200 shots of hydrogen plasma with a total duration of 7 s in a tokamak. Before and after exposure, samples were analyzed by using atomic force microscopy （AFM）, scanning electron microscopy （SEM）, X-ray diffraction （XRD） and a spectrophotometer. It was found that the uncoated sample was severely damaged, its reflection dropped significantly, and it developed some cracks and lines, while no significant change was observed on the surface characteristic of the coated sample. Moreover the weight loss of the uncoated sample was higher in comparison to the coated one. Therefore the results of this experiment showed that the coating of S.S.316L by TiN using a PF device is a useful method to strengthen it against plasma erosion and with further optimization it could possibly be used in preparing plasma diagnostics mirrors.展开更多
The titanium oxide （TiO2） nanotubes have attracted attention for their use in dye-sensitized solar cells as photoanode. In this study semiconducting cadmium sulfide （CdS） nanoparticles arc grown on top opened TiO2...The titanium oxide （TiO2） nanotubes have attracted attention for their use in dye-sensitized solar cells as photoanode. In this study semiconducting cadmium sulfide （CdS） nanoparticles arc grown on top opened TiO2 nanotubes arrays by radio-frequency magnetron sputtering. X-ray diffraction, scanning electron mieroscopy, transmission electron microscopy and diffuse reflection spectra are used to study structural, morphological and optical properties of the CdS/TiO2 bilayer.展开更多
Titanium dioxide （TiO2） nanosheet, nanorod and nanotubes are synthesized using chemical vapor deposition （CVD） and anodizing processes. TiO2 nanosheets are grown on Ti foil which is coated with Au catalyst in CVD,...Titanium dioxide （TiO2） nanosheet, nanorod and nanotubes are synthesized using chemical vapor deposition （CVD） and anodizing processes. TiO2 nanosheets are grown on Ti foil which is coated with Au catalyst in CVD, TiO2 nanorods are synthesized on treated Ti foil with HCl by CVD, and TiO2 nanotubes are prepared by the three-step anodization method. Scanning electron microscopy shows the final TiO2 structures prepared using three processes with three different morphologies of nanosheet, nanorod and nanotube. X-ray diffraction verifies the presence of TiO2. TiO2 sheets and rods are crystalized in rutile phase, and TiO2 tubes after annealing turn into the anatase crystal phase. The optical investigations carried out by diffuse reflection spectroscopy reveal that the morphology of TiO2 nanostructures influencing their optical response and band gap energy of TiO2 is changed for different TiO2 nanostructures.展开更多
ZnS/graphene nanocomposites with different graphene concentrations （5, 10 and 15 wt.%） were synthesized using L-cysteine as surfactant and graphene oxide （GO） powders as graphene source. Excellent performance for ...ZnS/graphene nanocomposites with different graphene concentrations （5, 10 and 15 wt.%） were synthesized using L-cysteine as surfactant and graphene oxide （GO） powders as graphene source. Excellent performance for nanocomposites to remove methylene blue （MB） dye and hexavalent chromium （Cr（VI）） under visible-light illumina- tion was revealed. TEM images showed that ZnS NPs were decorated on GO sheets and the GO caused a significant decrease in the ZnS diameter size. XRD patterns, XPS and FTIR spectroscopy results indicated that GO sheets changed into reduced graphene oxide （rGO） during the synthesis process. Photocurrent measurements under a visible- light source indicated a good chemical reaction between ZnS NPs and rGO sheets.展开更多
In this work, the effect of a low-temperature plasma on the zeta potential of cotton fabric was studied. The silver particle absorption on cotton fabric when modified by a low-temperature plasma was also investigated....In this work, the effect of a low-temperature plasma on the zeta potential of cotton fabric was studied. The silver particle absorption on cotton fabric when modified by a low-temperature plasma was also investigated. The modification consisted of plasma pre functionalization followed by a one-step wet treatment with silver nitrate solution. The process was performed in a low-temperature plasma medium, using a magnetron sputtering device. Oxygen and nitrogen were used as working gases in the system, and the results were compared. After preparing the samples, the zeta potentials of the untreated and plasma-treated cotton under a constant pH value solution were estimated and compared. Also, Fourier transform infrared spec troscopy （FTIR） was used to examine the functional groups of the corresponding samples. The amounts of silver absorption on plasma treated and untreated cotton were examined using the energy dispersive X-ray （EDX） method. The results show that the amount of zeta potential for the nitrogen plasma treated sample is less and the absorption of silver particles by cotton can be increased strongly with nitrogen plasma treatment.展开更多
In this study, commercial poly vinyl chloride （PVC） films were treated by oxygen and argon plasmas in a cylindrical glass tube which was surrounded by a DC variable magnetic field, with different sample positions in...In this study, commercial poly vinyl chloride （PVC） films were treated by oxygen and argon plasmas in a cylindrical glass tube which was surrounded by a DC variable magnetic field, with different sample positions in the plasma reactor and also different exposure durations. Effects of the plasma treatment on the hydrophilic properties of the films were studied by mea- suring the water drop contact angle on the surface of the samples. The surface topography of the untreated and plasma treated films was analyzed and compared by atomic force microscopy （AFM）. The optical characteristic changes in treated samples were investigated using reflective spectrophotometry. Also, the chemical changes which appeared on the surface of the samples were investigated using Fourier transform infrared spectroscopy （FTIR）. The results show that the plasma treated PVC becomes more hydrophilic with an enhanced wettability. A sharp de- crease in the water contact angle may also be a consequence of the surface texturization. The aging effect on wettability of the samples was also investigated. The results show that the effect of oxygen plasma on the surface properties of the samples is more pronounced compared with that of argon plasma.展开更多
The effect of the positive bias on Reynolds stress （RS） and its effect on the radial turbulent transport at the edge plasma （r/a =0.9） and scrape-off layer （SOL） region of plasma in tokamak are investigated. The...The effect of the positive bias on Reynolds stress （RS） and its effect on the radial turbulent transport at the edge plasma （r/a =0.9） and scrape-off layer （SOL） region of plasma in tokamak are investigated. The radial and poloidal electric fields （Sr, Ep） and ion saturation current （Is） are measured by multi-purpose probe （MPP）. This probe is fabricated and constructed for the first time in the IR-T1 tokamak. The most advantage of this probe is that the variations of Er and Ep can be measured in different radii at the single shot. Thus the information of different radii can be compared with high precision. The bias voltage is fixed at Vbias = 200 V and it has been applied with the limiter bias that is fixed in r/a = 0.9. Moreover, the phase difference between radial and poloidal electric fields, and temporal evolution of the RS .spectrum detected by MPP are calculated. RS magnitude on the edge （r/a = 0.9） is more than its value in the SOL （r/a = 1.02）. With the applied bias 200 V, ItS and the magnitude of the phase difference between Er and Ep are increased, while the radial turbulent transport is decreased simultaneously. Thus it can be concluded that RS affects radial turbulence. Temporal evolution of the RS spectrum shows that the frequency of RS is increased and reaches its highest value at r/a=0.9 in the presence of bias.展开更多
The investigation of runaway electrons is expanded by different methods. The aim of this study is to show sawtooth oscillations of hard x-ray emission and with the help of sawtooth oscillations to obtain radial diffus...The investigation of runaway electrons is expanded by different methods. The aim of this study is to show sawtooth oscillations of hard x-ray emission and with the help of sawtooth oscillations to obtain radial diffusion coefficient and magnetic fluctuations. In the same way, the hard x-ray spectral evaluation is compared in several time intervals and it is shown that during discharge, the energy of the runaway electrons is less than 200？keV. Also, for typical plasmas, population of runaway electrons is measured at seven time intervals of 5ms and temporal evaluation of runaway electron mean energy. The sawtooth-like shape is observed in the hard x-ray range （10–1000？keV）. By the sawtooth oscillation method, the RE diffusion coefficient in radial transport in the IR-T1 plasma is Dr～0.5Dr～0.5m^2s^-1. The magnetic field fluctuation due to magnetic diffusion DmDm is given as br/Bt～10^-4.展开更多
Tungsten nitride(W_(x)N)thin films with good crystalline structure,high quality and relatively low resistivity were deposited by hot filament chemical vapor deposition(HFCVD)technique at different mixtures of N2 and A...Tungsten nitride(W_(x)N)thin films with good crystalline structure,high quality and relatively low resistivity were deposited by hot filament chemical vapor deposition(HFCVD)technique at different mixtures of N2 and Ar gases.Experimental data demonstrate that different N_(2) contents in gas mixture strongly affect microstructure,phase formation,texture morphology and resistivity of the W_(x)N films.According to X-ray diffraction(XRD)patterns,the growth of tungsten nitride films promotes δ-WN phase for lower N_(2) contents in gas mixture.At higher N_(2) contents,a phase transition is observed in the tungsten nitride films.Both hexagonal δ-WN and cubic β-W_(2)N phases coexist,and WN phase approximately disappears with N_(2) contents in the gas mixture increasing.Scanning electron microscope(SEM)images for deposited films at lower N_(2) contents in gas mixture indicate a definite dense columnar nanostructure.The electrical resistivity results exhibit a significant drop for the W_(x)N thin films with N_(2) contents in the mixed gas increasing.The changes in N_(2) content in gas mixture are found to be responsible for variation in the film resistivity values.Thus,the deposited tungsten nitride thin film at higher N_(2) contents in gas mixture has noncolumnar microstructure and lower resistivity,which may be used as a superior diffusion barrier.展开更多
Effects of both electron beam irradiation on the properties of polypropylene （PP） films and the irradiation on the different layers of a multilayer PP film are studied. A Fourier transform infrared spectroscope was ...Effects of both electron beam irradiation on the properties of polypropylene （PP） films and the irradiation on the different layers of a multilayer PP film are studied. A Fourier transform infrared spectroscope was used to investigate the chemical structure of the films. The results showed that the chemical properties of the first layer were improved, that is, more functional groups responsible for dye ability and hydrophilicity of the film were produced on its surface, while noticeable improvement was not detected on the surface of other layers. This was also confirmed by testing the dye ability of the layers. However, the results obtained by atomic force microscopy showed that the electron irradiation caused some topographical changes, not only on the surface of the first layer but also on the others.展开更多
Since runaway electrons and magnetohydrodynamics activity can contribute to serious damage and energy losses in tokamaks, the effect of an external electric field on runaway electrons and hard x-ray spectra is investi...Since runaway electrons and magnetohydrodynamics activity can contribute to serious damage and energy losses in tokamaks, the effect of an external electric field on runaway electrons and hard x-ray spectra is investigated. Parameters such as the plasma current, the hard x-ray photons count and the mean energy of runaway electrons are measured. Positive and negative voltages of 300 V are applied at lOms after the plasma initiation （while the plasma is forming）, at 15ms （while the plasma is stable） and at 20ms （while the plasma is fading away） to attain the most effective time of applying the external electric field. The number of hard x-ray photons has the most changes in the range of O-200 keV when the external electric fields are applied. Also in the duration of 20-30ms of plasma the greatest number of hard x-ray spectra is detected. When the external electric fields are applied, the mean energy of runaway electrons reduces significantly, especially at 15 ms （while the plasma is stab/e）.展开更多
The radial dependence of edge plasma turbulence is investigated in the IR-T1 tokamak.The radial profile of the fluctuation level and spectra are measured using an array of Langmuir probes(rake probe)in the r/a=0.75-1....The radial dependence of edge plasma turbulence is investigated in the IR-T1 tokamak.The radial profile of the fluctuation level and spectra are measured using an array of Langmuir probes(rake probe)in the r/a=0.75-1.2 region.In all radial positions the edge plasma is turbulently unstable,with a broad band fluctuation spectrum in the frequency range f=10-1000 kHz.The relative fluctuation level,as monitored by the ion saturation current J_(+),is always highest near the wall and decreases monotonically toward the plasma center,while the shape of the fluctuation power spectra is almost unchanged.The result of this experiment shows that in contrast to the more inner regions,the plasma near the wall does not simply have a small density fluctuation about a mean,but rather a shredded structure in which one can imagine that discrete shreds of plasma interact with one another rather than with the average background.展开更多
基金Supported by the AAAPT Research and Training Centrethe Institute of Physics,Chinese Academy of Sciencesthe Third World Academy of Sciences,ICTP,Trieste。
文摘Magnetohydrodynamic phenomena in the CT-6B Tokamak based on Mirnov oscillations have been investigated by applying the limiter biasing potentials and changing the vacuum chamber gas pressure and plasma displacement.The results show that setting up a radial electric field at the plasma edge could drive electromagnetic instabilities in the tokamak plasma.Magnetic oscillation frequency upon application of a positive bias decreases about 10-15%and then after a delay time,τ_(d)=2.5-3 ms increases about 20-25%with respect to their value without biasing.In the negative bias regime the oscillation frequency increases about 10%in 1 ms after the application of the bias pulse.The poloidal rotation velocity changes during two steps are related to its link with the radial electric field and the time scale of the density gradient.The frequency of oscillations increases with the increasing chamber gas pressure and decreases with the increasing the outward plasma displacement.
文摘The effect of time of applied bias on the edge turbulent transport is analyzed by the multi-fractal detrend fluctu- ation analysis （MF-DFA） method in the IR-Tl tokamak. The generalized Hurst exponents and the multifractal spectrum are computed by this method. The MF-DFA method is applied to the fluctuation of gradient of float- ing potential time series collected by a multipurpose probe. Tile monofractality or multifractality of the time series can be detected by generalized exponent. The multifractal spectrum describes the singularity content of the process. The results show that with applying bias to the plasma at different times （t = 15 ms, 18ms and 22ms）, the degree of multifractality changes. It reaches the minimum when the bias is applied at t = 18 ms. The multifractality source of data is investigated by the surrogate method （phase randomization techniques）. The surrogate method can destroy the different types of correlations in all the sizes of fluctuations. The results show that the long-range correlation contributes more to multifractality than the fat tail distribution.
文摘In this study, commercial biaxially oriented polypropylene （BOPP）, polyvinyl chlo- ride （PVC） and poly （methyl methacrylate） （PMMA） films were treated with nitrogen plasma over different exposure times in a Pyrex tube surrounded by a DC variable magnetic field. The chemi- cal changes that appeared on the surface of the samples were investigated using Fourier transform infrared （FT4R） spectroscopy and attenuated total reflectance Fourier transform infrared （ATR- FTIR） spectroscopy after treatment for 2 min, 4 min and 6 rain in a nitrogen plasma chamber. Effects of the plasma treatment on the surface topographies and contact angles of the untreated and plasma treated films were also analyzed by atomic force microscopy （AFM） and a contact angle measuring system. The results show that the plasma treated films become more hydrophilic with an enhanced wettability due to the formation of some new polar groups on the surface of the treated films. Moreover, at higher exposure times, the total surface energy in all treated films increased while a reduction in contact angle occurred. The behavior of surface roughness in each sample was completely different at higher exposure times.
文摘In this research the effects of mordant and plasma sputtering treatments on the crystallinity and morphological properties of wool fabrics were investigated. The felting behavior of the treated samples was also studied. We used madder as a natural dye and copper sulfate as a metal mordant. We also used copper as the electrode material in a DC magnetron plasma sputtering device. The anti-felting properties of the wool samples before and after dying was studied, and it was shown that the shrink resistance and anti-felting behavior of the wool had been significantly improved by the plasma sputtering treatment. In addition, the percentage of crystallinity and the size of the crystals were investigated using an X-ray diffractometer, and a scanning electron microscope was used for morphological analysis. The amount of copper particles on the surface of the mordanted and sputtered fabrics was studied using the energy dispersive X- ray （EDX） method, and the hydrophobic properties of the samples were examined using the water drop test. The results show that with plasma sputtering treatment, the hydrophobic properties of the surface of wool become super hydrophobic.
基金Supported by the Bandar Abbas Branch of the Islamic Azad University
文摘Tin oxide （SnO2） is one of the most promising transparent conducting oxide materials, which is widely used in thin film gas sensors. We investigate the dependence of the deposition time on structural, morphologicaJ and hydrogen gas sensing properties of SnO2 thin films synthesized by dc magnetron sputtering. The deposited samples are characterized by XRD, SEM, AFM, surface area measurements and surface profiler. Also the H2 gas sensing properties of SnO2 deposited samples are performed against a wide range of operating temperature. The XRD analysis demonstrates that the degree of crystallinity of the deposited SnO2 films strongly depends on the deposition time. SEM and AFM analyses reveal that the size of nanoparticles or agglomerates, and both average and rms surface roughness is enhanced with the increasing deposition time. Also gas sensors based on these SnO2 nanolayers show an acceptable response to hydrogen at various operating temperatures.
基金Iran National Science Foundation(INSF) for providing grant of members
文摘Microbial contamination induces surface deformations and strength degradation of cotton fabrics by invading deeply into the fibers. In this study, the sterilization effects of low pressure plasmas on bacteria-inoculated cotton fabrics were investigated. Oxygen plasma treatment completely sterilized the cotton fabrics inoculated with various concentrations of staphylococcus aureus. Also, the influence of plasma treatment on physical properties of fabrics was examined. It was found that the plasma treatment did not affect ultimate tensile strength and surface morphology of the fabrics because it took advantage of relatively low plasma temperature.
文摘We investigate the effects of etching gases on the synthesis of nano crystalline diamonds grown on silicon substrate at the substrate temperature of 550℃ and the reaction pressure of 4 kPa by hot filament chemical vapor deposition method, in which CH4 and H2 act as a source and diluting gases, respectively. N2, H2, and NH3 were used as the etching gases, respectively. Results show that the optimum conditions can be obtained only for the case of H2 gas. The crystal morphology and crystallinity of the samples have been examined by scanning electron microscopy and X-ray diffraction, respectively.
文摘In the present investigation, Ni_（50）Ti_（25）Al_（25）（at.%） mechanically alloyed powder is deposited on carbon steel substrate.Before the coating process, the substrate is heated to temperature ranging from room temperature to 400℃. The microstructure, porosity, microhardness, adhesion strength, and corrosion behavior of the coating are investigated at different substrate temperatures. Results show that coating porosity is lower on high temperature surface. Microhardness and adhesion strength of the deposition layer on the substrate without preheating have lower values than with preheating. The polarization test result shows that corrosion performance of the coating is dependent on micro cracks and porosities and the increasing of substrate temperature can improve the quality of coating and corrosion performance.
文摘Plasma-surface interaction experiments on TiN coated stainless steel 316L （S.S.316L） using a plasma focus （PF） device have been performed in an attempt to investigate whether we can use the hardness property of TiN against erosion to increase the lifetime of the mirrors used in plasma diagnostics equipment. Firstly, two similar S.S.316L samples were chosen for this purpose. One of the samples was coated with TiN by using a PF device, while the other was kept intact as a reference for investigating the effect of TiN coating. Then, in order to study the coating effects, these samples were exposed to 200 shots of hydrogen plasma with a total duration of 7 s in a tokamak. Before and after exposure, samples were analyzed by using atomic force microscopy （AFM）, scanning electron microscopy （SEM）, X-ray diffraction （XRD） and a spectrophotometer. It was found that the uncoated sample was severely damaged, its reflection dropped significantly, and it developed some cracks and lines, while no significant change was observed on the surface characteristic of the coated sample. Moreover the weight loss of the uncoated sample was higher in comparison to the coated one. Therefore the results of this experiment showed that the coating of S.S.316L by TiN using a PF device is a useful method to strengthen it against plasma erosion and with further optimization it could possibly be used in preparing plasma diagnostics mirrors.
文摘The titanium oxide （TiO2） nanotubes have attracted attention for their use in dye-sensitized solar cells as photoanode. In this study semiconducting cadmium sulfide （CdS） nanoparticles arc grown on top opened TiO2 nanotubes arrays by radio-frequency magnetron sputtering. X-ray diffraction, scanning electron mieroscopy, transmission electron microscopy and diffuse reflection spectra are used to study structural, morphological and optical properties of the CdS/TiO2 bilayer.
文摘Titanium dioxide （TiO2） nanosheet, nanorod and nanotubes are synthesized using chemical vapor deposition （CVD） and anodizing processes. TiO2 nanosheets are grown on Ti foil which is coated with Au catalyst in CVD, TiO2 nanorods are synthesized on treated Ti foil with HCl by CVD, and TiO2 nanotubes are prepared by the three-step anodization method. Scanning electron microscopy shows the final TiO2 structures prepared using three processes with three different morphologies of nanosheet, nanorod and nanotube. X-ray diffraction verifies the presence of TiO2. TiO2 sheets and rods are crystalized in rutile phase, and TiO2 tubes after annealing turn into the anatase crystal phase. The optical investigations carried out by diffuse reflection spectroscopy reveal that the morphology of TiO2 nanostructures influencing their optical response and band gap energy of TiO2 is changed for different TiO2 nanostructures.
文摘ZnS/graphene nanocomposites with different graphene concentrations （5, 10 and 15 wt.%） were synthesized using L-cysteine as surfactant and graphene oxide （GO） powders as graphene source. Excellent performance for nanocomposites to remove methylene blue （MB） dye and hexavalent chromium （Cr（VI）） under visible-light illumina- tion was revealed. TEM images showed that ZnS NPs were decorated on GO sheets and the GO caused a significant decrease in the ZnS diameter size. XRD patterns, XPS and FTIR spectroscopy results indicated that GO sheets changed into reduced graphene oxide （rGO） during the synthesis process. Photocurrent measurements under a visible- light source indicated a good chemical reaction between ZnS NPs and rGO sheets.
文摘In this work, the effect of a low-temperature plasma on the zeta potential of cotton fabric was studied. The silver particle absorption on cotton fabric when modified by a low-temperature plasma was also investigated. The modification consisted of plasma pre functionalization followed by a one-step wet treatment with silver nitrate solution. The process was performed in a low-temperature plasma medium, using a magnetron sputtering device. Oxygen and nitrogen were used as working gases in the system, and the results were compared. After preparing the samples, the zeta potentials of the untreated and plasma-treated cotton under a constant pH value solution were estimated and compared. Also, Fourier transform infrared spec troscopy （FTIR） was used to examine the functional groups of the corresponding samples. The amounts of silver absorption on plasma treated and untreated cotton were examined using the energy dispersive X-ray （EDX） method. The results show that the amount of zeta potential for the nitrogen plasma treated sample is less and the absorption of silver particles by cotton can be increased strongly with nitrogen plasma treatment.
文摘In this study, commercial poly vinyl chloride （PVC） films were treated by oxygen and argon plasmas in a cylindrical glass tube which was surrounded by a DC variable magnetic field, with different sample positions in the plasma reactor and also different exposure durations. Effects of the plasma treatment on the hydrophilic properties of the films were studied by mea- suring the water drop contact angle on the surface of the samples. The surface topography of the untreated and plasma treated films was analyzed and compared by atomic force microscopy （AFM）. The optical characteristic changes in treated samples were investigated using reflective spectrophotometry. Also, the chemical changes which appeared on the surface of the samples were investigated using Fourier transform infrared spectroscopy （FTIR）. The results show that the plasma treated PVC becomes more hydrophilic with an enhanced wettability. A sharp de- crease in the water contact angle may also be a consequence of the surface texturization. The aging effect on wettability of the samples was also investigated. The results show that the effect of oxygen plasma on the surface properties of the samples is more pronounced compared with that of argon plasma.
文摘The effect of the positive bias on Reynolds stress （RS） and its effect on the radial turbulent transport at the edge plasma （r/a =0.9） and scrape-off layer （SOL） region of plasma in tokamak are investigated. The radial and poloidal electric fields （Sr, Ep） and ion saturation current （Is） are measured by multi-purpose probe （MPP）. This probe is fabricated and constructed for the first time in the IR-T1 tokamak. The most advantage of this probe is that the variations of Er and Ep can be measured in different radii at the single shot. Thus the information of different radii can be compared with high precision. The bias voltage is fixed at Vbias = 200 V and it has been applied with the limiter bias that is fixed in r/a = 0.9. Moreover, the phase difference between radial and poloidal electric fields, and temporal evolution of the RS .spectrum detected by MPP are calculated. RS magnitude on the edge （r/a = 0.9） is more than its value in the SOL （r/a = 1.02）. With the applied bias 200 V, ItS and the magnitude of the phase difference between Er and Ep are increased, while the radial turbulent transport is decreased simultaneously. Thus it can be concluded that RS affects radial turbulence. Temporal evolution of the RS spectrum shows that the frequency of RS is increased and reaches its highest value at r/a=0.9 in the presence of bias.
文摘The investigation of runaway electrons is expanded by different methods. The aim of this study is to show sawtooth oscillations of hard x-ray emission and with the help of sawtooth oscillations to obtain radial diffusion coefficient and magnetic fluctuations. In the same way, the hard x-ray spectral evaluation is compared in several time intervals and it is shown that during discharge, the energy of the runaway electrons is less than 200？keV. Also, for typical plasmas, population of runaway electrons is measured at seven time intervals of 5ms and temporal evaluation of runaway electron mean energy. The sawtooth-like shape is observed in the hard x-ray range （10–1000？keV）. By the sawtooth oscillation method, the RE diffusion coefficient in radial transport in the IR-T1 plasma is Dr～0.5Dr～0.5m^2s^-1. The magnetic field fluctuation due to magnetic diffusion DmDm is given as br/Bt～10^-4.
文摘Tungsten nitride(W_(x)N)thin films with good crystalline structure,high quality and relatively low resistivity were deposited by hot filament chemical vapor deposition(HFCVD)technique at different mixtures of N2 and Ar gases.Experimental data demonstrate that different N_(2) contents in gas mixture strongly affect microstructure,phase formation,texture morphology and resistivity of the W_(x)N films.According to X-ray diffraction(XRD)patterns,the growth of tungsten nitride films promotes δ-WN phase for lower N_(2) contents in gas mixture.At higher N_(2) contents,a phase transition is observed in the tungsten nitride films.Both hexagonal δ-WN and cubic β-W_(2)N phases coexist,and WN phase approximately disappears with N_(2) contents in the gas mixture increasing.Scanning electron microscope(SEM)images for deposited films at lower N_(2) contents in gas mixture indicate a definite dense columnar nanostructure.The electrical resistivity results exhibit a significant drop for the W_(x)N thin films with N_(2) contents in the mixed gas increasing.The changes in N_(2) content in gas mixture are found to be responsible for variation in the film resistivity values.Thus,the deposited tungsten nitride thin film at higher N_(2) contents in gas mixture has noncolumnar microstructure and lower resistivity,which may be used as a superior diffusion barrier.
文摘Effects of both electron beam irradiation on the properties of polypropylene （PP） films and the irradiation on the different layers of a multilayer PP film are studied. A Fourier transform infrared spectroscope was used to investigate the chemical structure of the films. The results showed that the chemical properties of the first layer were improved, that is, more functional groups responsible for dye ability and hydrophilicity of the film were produced on its surface, while noticeable improvement was not detected on the surface of other layers. This was also confirmed by testing the dye ability of the layers. However, the results obtained by atomic force microscopy showed that the electron irradiation caused some topographical changes, not only on the surface of the first layer but also on the others.
文摘Since runaway electrons and magnetohydrodynamics activity can contribute to serious damage and energy losses in tokamaks, the effect of an external electric field on runaway electrons and hard x-ray spectra is investigated. Parameters such as the plasma current, the hard x-ray photons count and the mean energy of runaway electrons are measured. Positive and negative voltages of 300 V are applied at lOms after the plasma initiation （while the plasma is forming）, at 15ms （while the plasma is stable） and at 20ms （while the plasma is fading away） to attain the most effective time of applying the external electric field. The number of hard x-ray photons has the most changes in the range of O-200 keV when the external electric fields are applied. Also in the duration of 20-30ms of plasma the greatest number of hard x-ray spectra is detected. When the external electric fields are applied, the mean energy of runaway electrons reduces significantly, especially at 15 ms （while the plasma is stab/e）.
文摘The radial dependence of edge plasma turbulence is investigated in the IR-T1 tokamak.The radial profile of the fluctuation level and spectra are measured using an array of Langmuir probes(rake probe)in the r/a=0.75-1.2 region.In all radial positions the edge plasma is turbulently unstable,with a broad band fluctuation spectrum in the frequency range f=10-1000 kHz.The relative fluctuation level,as monitored by the ion saturation current J_(+),is always highest near the wall and decreases monotonically toward the plasma center,while the shape of the fluctuation power spectra is almost unchanged.The result of this experiment shows that in contrast to the more inner regions,the plasma near the wall does not simply have a small density fluctuation about a mean,but rather a shredded structure in which one can imagine that discrete shreds of plasma interact with one another rather than with the average background.
