Aligned carbon nanotubes (CNTs) were synthesized on glass by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at the low temperature of 550 ℃. The experimental results ...Aligned carbon nanotubes (CNTs) were synthesized on glass by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at the low temperature of 550 ℃. The experimental results show that both the self-bias potential and the density of the catalyst particles are responsible for the alignment of CNTs. When the catalyst particle density is high enough, strong interactions among the CNTs can inhibit CNTs from growing randomly and result in parallel alignment.展开更多
Methane was decomposed to hydrogen and carbon nanotubes (CNTs) by microwave plasma, using Fe/Si catalyst activated by biased (—150 V) hydrogen plasma for various treatment times. Upon exposure to biased hydrogen plas...Methane was decomposed to hydrogen and carbon nanotubes (CNTs) by microwave plasma, using Fe/Si catalyst activated by biased (—150 V) hydrogen plasma for various treatment times. Upon exposure to biased hydrogen plasma, the catalyst surface becomes lumpy within 1 min, coheres between 5 and 10 min and forms particles after 20 min. The methane conversion increased up to 93% over the treatment time of 5 min. The hydrogen yield showed as similar tendency as the methane conversion and kept 83% at treatment time of 5 min. The treatment time up to 1 min increased the amount of deposited carbon, and after treatment time of 5 min it dropped;then again after treatment time of 20 min, it increased to reach a maximum value of 22 gc/gcat. Deposited carbon was found to be consisted of carbon nanotubes. It grew vertically on the catalyst surface and reached a maximum length of 30.7 nm after treatment time of 10 min. Multiple types of CNTs were present, and the CNT diameters decreased with increasing plasma treatment time.展开更多
We theoretically investigate the microwave absorption properties of hydrogen plasma in iron-catalyzed high- pressure disproportionation-grown carbon nanotubes under an external static magnetic field in the frequency r...We theoretically investigate the microwave absorption properties of hydrogen plasma in iron-catalyzed high- pressure disproportionation-grown carbon nanotubes under an external static magnetic field in the frequency range 0.3 GHz to 30 GHz, using the Maxwell equations in conjunction with a general expression for the effective complex permittivity of magnetized plasma known as the Appleton Hartree formula. The effects of the external static magnetic field intensity and the incident microwave propagation direction on the microwave absorption of hydrogen plasma in CNTs are studied in detail. The numerical results indicate that the microwave absorption properties of hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes can be obviously improved when the exter- nal static magnetic field is applied to the material. It is found that the specified frequency microwave can be strongly absorbed by the hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes over a wide range of incidence angles by adjusting the external magnetic field intensity and the parameters of the hydrogen plasma.展开更多
This paper reported that the nano-catkin carbon films were prepared on Si substrates by means of electron cyclotron resonance microwave plasma chemical vapour deposition in a hydrogen and methane mixture. The surface ...This paper reported that the nano-catkin carbon films were prepared on Si substrates by means of electron cyclotron resonance microwave plasma chemical vapour deposition in a hydrogen and methane mixture. The surface morphology and the structure of the fabricated films were characterized by using scanning electron microscopes and Raman spectroscopy, respectively. The stable field emission properties with a low threshold field of 5V/μm corresponding to a current density of about 1μA/cm^2 and a current density of 3.2mA/cm^2 at an electric field of 10V/μm were obtained from the carbon film deposited at CH4 concentration of 8%. The mechanism that the threshold field decreased with the increase of the CH4 concentration and the high emission current appeared at the high CH4 concentration was explained by using the Fowler-Nordheim theory.展开更多
Nano-sheet carbon films are prepared on Si wafers by means of quartz-tube microwave plasma chemical vapour deposition (MPCVD) in a gas mixture of hydrogen and methane. The structure of the fabricated films is invest...Nano-sheet carbon films are prepared on Si wafers by means of quartz-tube microwave plasma chemical vapour deposition (MPCVD) in a gas mixture of hydrogen and methane. The structure of the fabricated films is investigated by using field emission scanning electron microscope (FESEM) and Raman spectroscopy. These nano^carbon films are possessed of good field emission (FE) characteristics with a low threshold field of 2.6 V/μm and a high current density of 12.6 mA/cm^2 at an electric field of 9 V/μm. As the FE currents tend to be saturated in a high E region, no simple Fowler-Nordheim (F-N) model is applicable. A modified F N model considering statistic effects of FE tip structures and a space-charge-limited-current (SCLC) effect is applied successfully to explaining the FE data observed at low and high electric fields, respectively.展开更多
Carbonaceous nanomaterials such as carbon nanotubes (CNTs), magnetic metal nanomaterials and semicon- ductor nanomaterials are superior candidates for microwave absorbers. Taking full advantage of the features of CN...Carbonaceous nanomaterials such as carbon nanotubes (CNTs), magnetic metal nanomaterials and semicon- ductor nanomaterials are superior candidates for microwave absorbers. Taking full advantage of the features of CNTs, nanophase cobalt and nanophase zinc oxide, whose main microwave absorption mechanisms are based on resistance loss, magnetic loss and dielectric loss, we fabricate CNT/Co and CNT/ZnO heterostructure nanocom- posites, respectively. By using the CNTs, CNT/Co nanocomposites and CNT/ZnO nanocomposites as nanofillers, composites with polyester as matrix are prepared by in situ polymerization, and their microwave absorption per- formance is studied. It is indicated that the synergetic effects of the physic properties of different components in nano-heterostructures result in greatly enhanced microwave absorption performance in a wide frequency range. The absorption peak is increased, the absorption bandwidth is broadened, and the maximum peak shifts to a lower frequency.展开更多
The determination of carbon by means of microwave plasma torch atomic emission spectrometry(MPT-AES) was studied. Aqueous samples were introduced with a pneumatic nebulization system. The detection limit for carbon wa...The determination of carbon by means of microwave plasma torch atomic emission spectrometry(MPT-AES) was studied. Aqueous samples were introduced with a pneumatic nebulization system. The detection limit for carbon was 0. 047μg/mL.The method was applied to the analysis for tap water and results were satisfactory.展开更多
The effective parameters on the diameter of carbon nanotubes (CNTs) by plasma enhanced chemical vapor deposition (PECVD) were presented.Among lots of influential parameters,the effects of the catalytic film thickness ...The effective parameters on the diameter of carbon nanotubes (CNTs) by plasma enhanced chemical vapor deposition (PECVD) were presented.Among lots of influential parameters,the effects of the catalytic film thickness and the pretreatment plasma power on the growth of CNTs were investigated.The results show that the size of catalytic islands increases by increasing the thickness of catalytic layer,but the density of CNTs decreases.The pretreatment duration time of 30 s is the optimal condition for growing CNTs with about 50 nm in diameter.By increasing the pretreatment plasma power,the diameter of CNTs decreases gradually.However,the diameter of CNTs does not change drastically from 80 to 120 W.The uniformly grown CNTs with the diameter of 50 nm are obtained at the pretreatment plasma power of 100 W.展开更多
In this work, multi-walled carbon nanotubes (MWCNTs)-epoxy composites with MWCNTs (outer diameter less 8 nm) loadings from 1 to 10 wt% were fabricated. The microstructures, dielectric constant, and microwave absorptio...In this work, multi-walled carbon nanotubes (MWCNTs)-epoxy composites with MWCNTs (outer diameter less 8 nm) loadings from 1 to 10 wt% were fabricated. The microstructures, dielectric constant, and microwave absorption properties of the MWCNTs-epoxy composite samples were investigated. The measurement results showed that the microwave absorption ratio of the MWCNTs-epoxy composite strongly depend on the MWCNT loading in the composites. The microwave absorption ratio up to 20%-26% around 18-20 GHz was reached for the samples with 8-10 wt% MWCNT loadings. The high absorption performance is mainly attributed to the microwave absorption of MWCNTs and the dielectric loss of MWCNTs-epoxy composites.展开更多
Polylactic acid (PLA) was successfully covalently grafted onto multi-walled carbon nanotubes (MWCNT) by microwave-assisted polymerization of lactide monomers. The final products MWCNT-g-PLA were characterized with Fou...Polylactic acid (PLA) was successfully covalently grafted onto multi-walled carbon nanotubes (MWCNT) by microwave-assisted polymerization of lactide monomers. The final products MWCNT-g-PLA were characterized with Fourier-transform IR (FTIR), Raman spectroscopy, thermogravimetric analyses (TGA) and transmission electron microscopy (TEM). The results indicated PLA chain was covalently attached to the MWCNT. The grafted PLA was uniformly coated on the surface of MWCNT with a layer thickness of 2 ~ 6 nm. The grafted PLA content could be controlled by microwave irradiation time and the concentrations of reactant. The product with 60.5% grafted PLA content can be synthesized in one hour.展开更多
Aligned carbon nanotubes (CNTs) were prepared on Ni-coated Ni substrate by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at temperature of 550℃.The experimental resu...Aligned carbon nanotubes (CNTs) were prepared on Ni-coated Ni substrate by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at temperature of 550℃.The experimental results show a direct correlation between the alignment of CNTs and the density of the catalyst particles at low temperature.When the particle density is high enough,among CNTs there are strong interactions that can inhibit CNTs from growing randomly.The crowding effect among dense CNTs results in the aligned growth of CNTs at low temperature.展开更多
Functionalized multi-walled carbon nanotubes( fMWNTs) were prepared with chitosan via controlled surface deposition and crosslinking process and scanning electron microscopy( SEM),Fourier translation infrared spectros...Functionalized multi-walled carbon nanotubes( fMWNTs) were prepared with chitosan via controlled surface deposition and crosslinking process and scanning electron microscopy( SEM),Fourier translation infrared spectroscopy( FT-IR) and Xray diffraction( XRD) are used to character properties. A novel high-density chitosan( HCS) was dissolved in f-MWNTs dispersed dilute acetic acid with a maximal concentration of 5. 8%. The hollow fibers can be made by extruding the solution into a dilute alkali solution through a wet-spinning process and the tensile properties of the materials were evaluated by universal tester. The surface property of fibers,pretreated by Helium( He) and the following grafted with gelatin was evaluated with X-ray photoelectron spectroscopy( XPS).As the hollow fibers were intended for neural tissue engineering,its suitability was evaluated in vitro using rat Schwann cells( RSC96) as model cells. The cells attachment,proliferation and morphology,were studied by various microscopic techniques. Based on the results,the gelatin grafted HCS / f-MWNTs hollow fibers could be used as a potential cell carrier in neural tissue engineering.展开更多
Ilmenite was reduced through microwave plasma-assisted chemical vapor deposition with continuously flowing hydrogen and methane gas. The reduction products were analyzed by XRD and SEM technology, and the component pr...Ilmenite was reduced through microwave plasma-assisted chemical vapor deposition with continuously flowing hydrogen and methane gas. The reduction products were analyzed by XRD and SEM technology, and the component products were TiO 2 -Carbon Nanotubes (CNTs) composite powders. The reduction process was in good agreement with the Jander equation. Compared with other reduction process by kinetics analysis, microwave plasma could significantly facilitate the reduction process at low temperature.展开更多
Carbon nanotubes (CNTs) were coated by tungsten using metal organic chemical vapor deposition. Magnetic stirring was employed to disperse the W-coated CNTs (W-CNTs) in a Cu matrix, and then, the mixed powders were...Carbon nanotubes (CNTs) were coated by tungsten using metal organic chemical vapor deposition. Magnetic stirring was employed to disperse the W-coated CNTs (W-CNTs) in a Cu matrix, and then, the mixed powders were consolidated by spark plasma sintering. The W-CNTs obtained a uniform dispersion within the Cu matrix when the W-CNT content was less than 5.0vo1%, but high content of W-CNTs (10vol%) resulted in the presence of clusters. The W-CNT/Cu composites containing low content of W-CNTs (〈5.0vol%) exhibited a higher thermal conductivity than the sintered pure Cu, while the CNT/Cu composites exhibited no increase in thermal conductivity after the incorporation of uncoated CNTs. The W-CNT content was found to play a crucial role in determining the thermal conductivity of the W-CNT/Cu composites. The thermal conductivity of the W-CNT/Cu composites increased first and then decreased with the W-CNT content increasing. When the W-CNT content was 2.5vo1%, the W-CNT/Cu composite obtained the maximum value of thermal conductivity. The thermal resistance of the (W-CNT)-Cu interface was predicted in terms of Maxwell-Gamett effective medium approximation, and its calculated value was about 3.0× 10-9 m2.K.W-l.展开更多
Multi-walled carbon nanotubes (MWCNTs) are grown by arc discharge method in a controlled methane environment. The arc discharge is produced between two graphite electrodes at the ambient pressures of 100 tort, 300 t...Multi-walled carbon nanotubes (MWCNTs) are grown by arc discharge method in a controlled methane environment. The arc discharge is produced between two graphite electrodes at the ambient pressures of 100 tort, 300 torr, and 500 torr. Arc plasma parameters such as temperature and density are estimated to investigate the influences of the ambient pressure and the contributions of the ambient pressure to the growth and the structure of the nanotubes. The plasma temperature and density are observed to increase with the increase in the methane ambient pressure. The samples of MWCNT synthesized at different ambient pressures are analyzed using transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. An increase in the growth of MWCNT and a decrease in the inner tube diameter are observed with the increase in the methane ambient pressure.展开更多
Multi-Walled carbon nanotubes are used as preconcentrating probes for the quantitative determination of trace cadmium, copper and lead in environmental and biological sample using graphite Furnace Atomic Absorption Sp...Multi-Walled carbon nanotubes are used as preconcentrating probes for the quantitative determination of trace cadmium, copper and lead in environmental and biological sample using graphite Furnace Atomic Absorption Spectrometry and inductively coupled Plasma Optical Emission spectrometry. The method is based on the electrostatic interactions of positively charged Cd+, Cu+ and Pb+ with the negatively charged multi-walled carbon nanotubes (MWCNTs) for the preconcentration and isolation of analytes from sample solutions. Effective preconcentration of trace cadmium, copper and lead was achieved in a pH range of 5 - 7, 5 - 7 and 4 - 7, respectively. The retained cadmium, copper and lead were efficiently eluted with 0.3 mol·L-1 HCl for graphite Furnace Atomic Absorption Spectrometry determination. The multi-walled carbon nanotubes packed micro-column exhibited fairly fast kinetics for the adsorption of cadmium, copper and lead, permitting the use of high sample flow rates up to at least 3 mL·min-1 for the flow injection on micro-column preconcentration without the loss of the retention efficiency. The detection limits (3σ) were 0.03, 0.01 and 0.5 ng·mL-1 for Cd, Cu and Pb, respectively. The relative standard deviation under optimum condition is less than 2.9% (n = 10). The developed method was successfully applied to the determination of trace Cd, Cu and Pb in a variety of environmental and biological samples.展开更多
The etching effect of ammonia (NH3) on the growth of vertically aligned nanotubes/nanofibers (CNTs) was investigated by direct-current plasma enhanced chemical vapor deposition (DC-PECVD). NH3 gas etches Ni catalyst l...The etching effect of ammonia (NH3) on the growth of vertically aligned nanotubes/nanofibers (CNTs) was investigated by direct-current plasma enhanced chemical vapor deposition (DC-PECVD). NH3 gas etches Ni catalyst layer to form nanoscale islands while NH3 plasma etches the deposited amorphous carbon. Based on the etching effect of NH3 gas on Ni catalyst, the differences of growing bundles of CNTs and single strand CNTs were discussed; specifically, the amount of optimal NH3 gas etching is different between bundles of CNTs and single strand CNTs. In contrast to the CNT carpet growth, the single strand CNT growth requires shorter etching time (5 min) than large catalytic patterns (10 min) since nano dots already form catalyst islands for CNT growth. Through removing the plasma pretreatment process, the damage from being exposed at high temperature substrate occurring during the plasma generation time is minimized. High resolution transmission electron microscopy (HTEM) shows fishbone structure of CNTs grown by PECVD.展开更多
The production of high quality single-walled carbon nanotubes(SWCNTs)on a bulk scale has been an issue of considerable interest.Recently,it has been demonstrated that high quality SWCNTs can be continuously synthesize...The production of high quality single-walled carbon nanotubes(SWCNTs)on a bulk scale has been an issue of considerable interest.Recently,it has been demonstrated that high quality SWCNTs can be continuously synthesized on large scale by using induction thermal plasma technology.In this process,the high energy density of the thermal plasma is employed to generate dense vapor-phase precursors for the synthesis of SWCNTs.With the current reactor system,a carbon soot product which contains approximately 40 wt%of SWCNTs can be continuously synthesized at the high production rate of~100 g/h.In this article,our recent research efforts to achieve major advances in this technology are presented.Firstly,the processing parameters involved are examined systematically in order to evaluate their individual inuences on the SWCNT synthesis.Based on these results,the appropriate operating conditions of the induction thermal plasma process for an effective synthesis of SWCNTs are discussed.A characterization study has also been performed on the SWCNTs produced under the optimum processing conditions.Finally,a mathematical model of the process currently under development is described.The model will help us to better understand the synthesis of SWCNTs in the induction plasma process.展开更多
文摘Aligned carbon nanotubes (CNTs) were synthesized on glass by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at the low temperature of 550 ℃. The experimental results show that both the self-bias potential and the density of the catalyst particles are responsible for the alignment of CNTs. When the catalyst particle density is high enough, strong interactions among the CNTs can inhibit CNTs from growing randomly and result in parallel alignment.
文摘Methane was decomposed to hydrogen and carbon nanotubes (CNTs) by microwave plasma, using Fe/Si catalyst activated by biased (—150 V) hydrogen plasma for various treatment times. Upon exposure to biased hydrogen plasma, the catalyst surface becomes lumpy within 1 min, coheres between 5 and 10 min and forms particles after 20 min. The methane conversion increased up to 93% over the treatment time of 5 min. The hydrogen yield showed as similar tendency as the methane conversion and kept 83% at treatment time of 5 min. The treatment time up to 1 min increased the amount of deposited carbon, and after treatment time of 5 min it dropped;then again after treatment time of 20 min, it increased to reach a maximum value of 22 gc/gcat. Deposited carbon was found to be consisted of carbon nanotubes. It grew vertically on the catalyst surface and reached a maximum length of 30.7 nm after treatment time of 10 min. Multiple types of CNTs were present, and the CNT diameters decreased with increasing plasma treatment time.
基金Project supported by the Science Research Program of Hunan Province, China (Grant No. 2010FJ4092)the National Natural Science Foundation of China (Grant No. 11075073)
文摘We theoretically investigate the microwave absorption properties of hydrogen plasma in iron-catalyzed high- pressure disproportionation-grown carbon nanotubes under an external static magnetic field in the frequency range 0.3 GHz to 30 GHz, using the Maxwell equations in conjunction with a general expression for the effective complex permittivity of magnetized plasma known as the Appleton Hartree formula. The effects of the external static magnetic field intensity and the incident microwave propagation direction on the microwave absorption of hydrogen plasma in CNTs are studied in detail. The numerical results indicate that the microwave absorption properties of hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes can be obviously improved when the exter- nal static magnetic field is applied to the material. It is found that the specified frequency microwave can be strongly absorbed by the hydrogen plasma in iron-catalyzed high-pressure disproportionation-grown carbon nanotubes over a wide range of incidence angles by adjusting the external magnetic field intensity and the parameters of the hydrogen plasma.
文摘This paper reported that the nano-catkin carbon films were prepared on Si substrates by means of electron cyclotron resonance microwave plasma chemical vapour deposition in a hydrogen and methane mixture. The surface morphology and the structure of the fabricated films were characterized by using scanning electron microscopes and Raman spectroscopy, respectively. The stable field emission properties with a low threshold field of 5V/μm corresponding to a current density of about 1μA/cm^2 and a current density of 3.2mA/cm^2 at an electric field of 10V/μm were obtained from the carbon film deposited at CH4 concentration of 8%. The mechanism that the threshold field decreased with the increase of the CH4 concentration and the high emission current appeared at the high CH4 concentration was explained by using the Fowler-Nordheim theory.
文摘Nano-sheet carbon films are prepared on Si wafers by means of quartz-tube microwave plasma chemical vapour deposition (MPCVD) in a gas mixture of hydrogen and methane. The structure of the fabricated films is investigated by using field emission scanning electron microscope (FESEM) and Raman spectroscopy. These nano^carbon films are possessed of good field emission (FE) characteristics with a low threshold field of 2.6 V/μm and a high current density of 12.6 mA/cm^2 at an electric field of 9 V/μm. As the FE currents tend to be saturated in a high E region, no simple Fowler-Nordheim (F-N) model is applicable. A modified F N model considering statistic effects of FE tip structures and a space-charge-limited-current (SCLC) effect is applied successfully to explaining the FE data observed at low and high electric fields, respectively.
基金Supported by the National Natural Science Foundation of China under Grant No 10332020
文摘Carbonaceous nanomaterials such as carbon nanotubes (CNTs), magnetic metal nanomaterials and semicon- ductor nanomaterials are superior candidates for microwave absorbers. Taking full advantage of the features of CNTs, nanophase cobalt and nanophase zinc oxide, whose main microwave absorption mechanisms are based on resistance loss, magnetic loss and dielectric loss, we fabricate CNT/Co and CNT/ZnO heterostructure nanocom- posites, respectively. By using the CNTs, CNT/Co nanocomposites and CNT/ZnO nanocomposites as nanofillers, composites with polyester as matrix are prepared by in situ polymerization, and their microwave absorption per- formance is studied. It is indicated that the synergetic effects of the physic properties of different components in nano-heterostructures result in greatly enhanced microwave absorption performance in a wide frequency range. The absorption peak is increased, the absorption bandwidth is broadened, and the maximum peak shifts to a lower frequency.
文摘The determination of carbon by means of microwave plasma torch atomic emission spectrometry(MPT-AES) was studied. Aqueous samples were introduced with a pneumatic nebulization system. The detection limit for carbon was 0. 047μg/mL.The method was applied to the analysis for tap water and results were satisfactory.
基金Project supported by a 2-Year Research Grant of Pusan National UniversityProject(2011-0006257)supported by National Core Research Center(NCRC)Program through the National Research Foundation of Korea funded by the Ministry of Education,Science and Technology
文摘The effective parameters on the diameter of carbon nanotubes (CNTs) by plasma enhanced chemical vapor deposition (PECVD) were presented.Among lots of influential parameters,the effects of the catalytic film thickness and the pretreatment plasma power on the growth of CNTs were investigated.The results show that the size of catalytic islands increases by increasing the thickness of catalytic layer,but the density of CNTs decreases.The pretreatment duration time of 30 s is the optimal condition for growing CNTs with about 50 nm in diameter.By increasing the pretreatment plasma power,the diameter of CNTs decreases gradually.However,the diameter of CNTs does not change drastically from 80 to 120 W.The uniformly grown CNTs with the diameter of 50 nm are obtained at the pretreatment plasma power of 100 W.
文摘In this work, multi-walled carbon nanotubes (MWCNTs)-epoxy composites with MWCNTs (outer diameter less 8 nm) loadings from 1 to 10 wt% were fabricated. The microstructures, dielectric constant, and microwave absorption properties of the MWCNTs-epoxy composite samples were investigated. The measurement results showed that the microwave absorption ratio of the MWCNTs-epoxy composite strongly depend on the MWCNT loading in the composites. The microwave absorption ratio up to 20%-26% around 18-20 GHz was reached for the samples with 8-10 wt% MWCNT loadings. The high absorption performance is mainly attributed to the microwave absorption of MWCNTs and the dielectric loss of MWCNTs-epoxy composites.
文摘Polylactic acid (PLA) was successfully covalently grafted onto multi-walled carbon nanotubes (MWCNT) by microwave-assisted polymerization of lactide monomers. The final products MWCNT-g-PLA were characterized with Fourier-transform IR (FTIR), Raman spectroscopy, thermogravimetric analyses (TGA) and transmission electron microscopy (TEM). The results indicated PLA chain was covalently attached to the MWCNT. The grafted PLA was uniformly coated on the surface of MWCNT with a layer thickness of 2 ~ 6 nm. The grafted PLA content could be controlled by microwave irradiation time and the concentrations of reactant. The product with 60.5% grafted PLA content can be synthesized in one hour.
文摘Aligned carbon nanotubes (CNTs) were prepared on Ni-coated Ni substrate by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at temperature of 550℃.The experimental results show a direct correlation between the alignment of CNTs and the density of the catalyst particles at low temperature.When the particle density is high enough,among CNTs there are strong interactions that can inhibit CNTs from growing randomly.The crowding effect among dense CNTs results in the aligned growth of CNTs at low temperature.
基金State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,China(No.LZ0902)Shanghai Science and Technical Committee,China(No.12DZ194030)
文摘Functionalized multi-walled carbon nanotubes( fMWNTs) were prepared with chitosan via controlled surface deposition and crosslinking process and scanning electron microscopy( SEM),Fourier translation infrared spectroscopy( FT-IR) and Xray diffraction( XRD) are used to character properties. A novel high-density chitosan( HCS) was dissolved in f-MWNTs dispersed dilute acetic acid with a maximal concentration of 5. 8%. The hollow fibers can be made by extruding the solution into a dilute alkali solution through a wet-spinning process and the tensile properties of the materials were evaluated by universal tester. The surface property of fibers,pretreated by Helium( He) and the following grafted with gelatin was evaluated with X-ray photoelectron spectroscopy( XPS).As the hollow fibers were intended for neural tissue engineering,its suitability was evaluated in vitro using rat Schwann cells( RSC96) as model cells. The cells attachment,proliferation and morphology,were studied by various microscopic techniques. Based on the results,the gelatin grafted HCS / f-MWNTs hollow fibers could be used as a potential cell carrier in neural tissue engineering.
基金supported by National Natural Science Foundation of China (No.51072140)the program for excellent youth team and the scientific research foundation of the higher education commission of Hubei Province of China (Nos.Z200715001 and T201004)the program for excellent subject leader of Wuhan (No.201150530151)
文摘Ilmenite was reduced through microwave plasma-assisted chemical vapor deposition with continuously flowing hydrogen and methane gas. The reduction products were analyzed by XRD and SEM technology, and the component products were TiO 2 -Carbon Nanotubes (CNTs) composite powders. The reduction process was in good agreement with the Jander equation. Compared with other reduction process by kinetics analysis, microwave plasma could significantly facilitate the reduction process at low temperature.
基金supported by the National High-Tech Research and Development Program of China (No.2009AA03Z116)the National Natural Science Foundation of China (No.50971020)
文摘Carbon nanotubes (CNTs) were coated by tungsten using metal organic chemical vapor deposition. Magnetic stirring was employed to disperse the W-coated CNTs (W-CNTs) in a Cu matrix, and then, the mixed powders were consolidated by spark plasma sintering. The W-CNTs obtained a uniform dispersion within the Cu matrix when the W-CNT content was less than 5.0vo1%, but high content of W-CNTs (10vol%) resulted in the presence of clusters. The W-CNT/Cu composites containing low content of W-CNTs (〈5.0vol%) exhibited a higher thermal conductivity than the sintered pure Cu, while the CNT/Cu composites exhibited no increase in thermal conductivity after the incorporation of uncoated CNTs. The W-CNT content was found to play a crucial role in determining the thermal conductivity of the W-CNT/Cu composites. The thermal conductivity of the W-CNT/Cu composites increased first and then decreased with the W-CNT content increasing. When the W-CNT content was 2.5vo1%, the W-CNT/Cu composite obtained the maximum value of thermal conductivity. The thermal resistance of the (W-CNT)-Cu interface was predicted in terms of Maxwell-Gamett effective medium approximation, and its calculated value was about 3.0× 10-9 m2.K.W-l.
文摘Multi-walled carbon nanotubes (MWCNTs) are grown by arc discharge method in a controlled methane environment. The arc discharge is produced between two graphite electrodes at the ambient pressures of 100 tort, 300 torr, and 500 torr. Arc plasma parameters such as temperature and density are estimated to investigate the influences of the ambient pressure and the contributions of the ambient pressure to the growth and the structure of the nanotubes. The plasma temperature and density are observed to increase with the increase in the methane ambient pressure. The samples of MWCNT synthesized at different ambient pressures are analyzed using transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. An increase in the growth of MWCNT and a decrease in the inner tube diameter are observed with the increase in the methane ambient pressure.
文摘Multi-Walled carbon nanotubes are used as preconcentrating probes for the quantitative determination of trace cadmium, copper and lead in environmental and biological sample using graphite Furnace Atomic Absorption Spectrometry and inductively coupled Plasma Optical Emission spectrometry. The method is based on the electrostatic interactions of positively charged Cd+, Cu+ and Pb+ with the negatively charged multi-walled carbon nanotubes (MWCNTs) for the preconcentration and isolation of analytes from sample solutions. Effective preconcentration of trace cadmium, copper and lead was achieved in a pH range of 5 - 7, 5 - 7 and 4 - 7, respectively. The retained cadmium, copper and lead were efficiently eluted with 0.3 mol·L-1 HCl for graphite Furnace Atomic Absorption Spectrometry determination. The multi-walled carbon nanotubes packed micro-column exhibited fairly fast kinetics for the adsorption of cadmium, copper and lead, permitting the use of high sample flow rates up to at least 3 mL·min-1 for the flow injection on micro-column preconcentration without the loss of the retention efficiency. The detection limits (3σ) were 0.03, 0.01 and 0.5 ng·mL-1 for Cd, Cu and Pb, respectively. The relative standard deviation under optimum condition is less than 2.9% (n = 10). The developed method was successfully applied to the determination of trace Cd, Cu and Pb in a variety of environmental and biological samples.
基金Project supported by Intelligent Microsystem Center(IMC)Project(2010-0008-276) supported by the National Core Research Center through the National Research Foundation of Korea funded by the Ministry of Education, Science and TechnologyProject(2010) supported by Pusan National University
文摘The etching effect of ammonia (NH3) on the growth of vertically aligned nanotubes/nanofibers (CNTs) was investigated by direct-current plasma enhanced chemical vapor deposition (DC-PECVD). NH3 gas etches Ni catalyst layer to form nanoscale islands while NH3 plasma etches the deposited amorphous carbon. Based on the etching effect of NH3 gas on Ni catalyst, the differences of growing bundles of CNTs and single strand CNTs were discussed; specifically, the amount of optimal NH3 gas etching is different between bundles of CNTs and single strand CNTs. In contrast to the CNT carpet growth, the single strand CNT growth requires shorter etching time (5 min) than large catalytic patterns (10 min) since nano dots already form catalyst islands for CNT growth. Through removing the plasma pretreatment process, the damage from being exposed at high temperature substrate occurring during the plasma generation time is minimized. High resolution transmission electron microscopy (HTEM) shows fishbone structure of CNTs grown by PECVD.
基金This work was supported by the Natural Science and Engineering Research Council(NSERC)of Canada.
文摘The production of high quality single-walled carbon nanotubes(SWCNTs)on a bulk scale has been an issue of considerable interest.Recently,it has been demonstrated that high quality SWCNTs can be continuously synthesized on large scale by using induction thermal plasma technology.In this process,the high energy density of the thermal plasma is employed to generate dense vapor-phase precursors for the synthesis of SWCNTs.With the current reactor system,a carbon soot product which contains approximately 40 wt%of SWCNTs can be continuously synthesized at the high production rate of~100 g/h.In this article,our recent research efforts to achieve major advances in this technology are presented.Firstly,the processing parameters involved are examined systematically in order to evaluate their individual inuences on the SWCNT synthesis.Based on these results,the appropriate operating conditions of the induction thermal plasma process for an effective synthesis of SWCNTs are discussed.A characterization study has also been performed on the SWCNTs produced under the optimum processing conditions.Finally,a mathematical model of the process currently under development is described.The model will help us to better understand the synthesis of SWCNTs in the induction plasma process.