This article reports the different steps of the design, development and validation of a process for continuous production of carbon nanotubes （CNTs） via catalytic chemical vapor deposition from the laboratory scale ...This article reports the different steps of the design, development and validation of a process for continuous production of carbon nanotubes （CNTs） via catalytic chemical vapor deposition from the laboratory scale to the industrial production. This process is based on a continuous inclined mobile-bed rotating reactor and very active catalysts using methane or ethylene as carbon source. The importance of modeling taking into account the hydrodynamic, physicochemical and physical phenomena that occur during CNT production in the process analysis is emphasized. The impact of this invention on the environment and human health is taken into consideration too.展开更多
The present work aims at utilizing compressed natural gas （CNG） as carbon source for the synthesis of carbon nanotubes （CNTs） over CoO-MoO/Al2O3 catalyst via catalytic chemical vapor deposition （CCVD） method. Th...The present work aims at utilizing compressed natural gas （CNG） as carbon source for the synthesis of carbon nanotubes （CNTs） over CoO-MoO/Al2O3 catalyst via catalytic chemical vapor deposition （CCVD） method. The as-produced carbonaceous product was characterized by thermal gravimetric analyzer （TGA）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and Raman spectroscopy. The experimental finding shows that CNTs were successfully produced from CNG while carbon nanofibers （CNFs） were formed as the side products. In addition, the catalytic activity and lifetime were found sustained and prolonged, as compared with using high purity methane as carbon source. The present study suggests an alternative route which can effectively produce CNTs and CNFs using low cost CNG.展开更多
Nitrogen-doped carbon nanotubes（NCNTs） were synthesized by chemical vapor deposition using cobaltbased oxides as catalyst and ethylenediamine（EDA） as carbon/nitrogen precursor. The influence of growth time,EDA con...Nitrogen-doped carbon nanotubes（NCNTs） were synthesized by chemical vapor deposition using cobaltbased oxides as catalyst and ethylenediamine（EDA） as carbon/nitrogen precursor. The influence of growth time,EDA concentration and growth temperature on the morphology,yield,composition,graphitization and oxidation resistance of the NCNTs was systematically investigated by using Raman spectroscopy,temperature-programmed oxidation and other techniques. The NCNT growth from ethylenediamine with a high N/C ratio involves several processes including mainly（1） catalytic growth of NCNTs,（2） homogeneous gas-phase decomposition of EDA,（3） non-catalytic deposition of pyrolytic carbon/nitrogen species and（4）surface etching of amorphous carbon or carbon at defect sites through gasification. At a later growth stage the etching process appears to be dominating,leading to the thinning of nanotubes and the decrease of yield.Moreover,the surface etching through carbon gasification strongly influences the structure and degree of graphitization of NCNTs.展开更多
Doped micro-crystalline silicon films are deposited at temperatures as low as 400 ℃ by the catalytic chemical vapor deposition method using a silane and hydrogen gas mixture. Electrical properties such as the carrier...Doped micro-crystalline silicon films are deposited at temperatures as low as 400 ℃ by the catalytic chemical vapor deposition method using a silane and hydrogen gas mixture. Electrical properties such as the carrier concentration and the Hall mobility are investigated for various measuring temperatures. It is found that the grains of micro-crystalline silicon are preferentially oriented along the (220) direction , and that the Hall mobility is larger than 8 cm 2·V -1 ·s -1 , the carrier concentration is about 1×10 17 cm -1 ～1×10 19 cm -3 at room temperature.展开更多
X-Ray Absorption Spectroscopy (XAS) on the carbon K edge of carbon nanostructures (nanotubes, nanofibers, nanowalls) is reported here. They are grown on plain SiO2 (8 nm thick)/Si(100) substrates by a Plasma and Hot F...X-Ray Absorption Spectroscopy (XAS) on the carbon K edge of carbon nanostructures (nanotubes, nanofibers, nanowalls) is reported here. They are grown on plain SiO2 (8 nm thick)/Si(100) substrates by a Plasma and Hot Filaments-enhanced Catalytic Chemical Vapor Deposition (PE HF CCVD) process. The morphology and the nature of these carbon nanostructures are characterized by SEM, TEM and Raman spectroscopy. According to conditions of catalyst preparation and DC HF CCVD process, carbon nanotubes (CNTs), carbon nanofibers (CNFs), carbon nanowalls (CNWs), carbon nanoparticles (CNPs) with different orientation of the graphene plans or shells can be prepared. From the angular dependence of the incident light and geometrical morphology of the nanostructures, wide variations of the C K-edge intensity of the transitions to the empty π* and σ* states occur. A full lineshape analysis of the XAS spectra has been carried out using a home-made software, allowing estimating the relative proportion of π* and σ* transitions. A geometrical model of the angular dependence with the incidence angle of the light and the morphology of the carbon nanostructures is derived. With normalization to the HOPG (Highly Oriented Pyrolytic Graphite graphite) reference case, a degree of alignment can be extracted which is representative of the localized orientation of the graphitic carbon π bonds, accounting not only for the overall orientation, but also for local defects like impurities incorporation, structural defects ... This degree of alignment shows good agreement with SEM observations. Thus CNTs films display degrees of alignment around 50%, depending on the occurrence of defects in the course of the growth, whereas no special alignment can be detected with CNFs and CNPs, and a weak one (about 20%) is detected on CNWs.展开更多
Carbon nanotubes(CNTs)have attracted intensive interests of researchers for a long time due to their fascinating physical and chemical properties promising for various potential applications,including advanced ceramic...Carbon nanotubes(CNTs)have attracted intensive interests of researchers for a long time due to their fascinating physical and chemical properties promising for various potential applications,including advanced ceramics,nanoelectronic devices,nanoscale sensors,solar cells,battery electrode,field emitters,etc..This review summarized the synthetic methods of CNTs,with an emphasis on the chemical vapor deposition(CVD)method,especially catalytic CVD.Although there still are some challenges in the way,with the development of the technology,a hope for widespread applications always exists.展开更多
文摘This article reports the different steps of the design, development and validation of a process for continuous production of carbon nanotubes （CNTs） via catalytic chemical vapor deposition from the laboratory scale to the industrial production. This process is based on a continuous inclined mobile-bed rotating reactor and very active catalysts using methane or ethylene as carbon source. The importance of modeling taking into account the hydrodynamic, physicochemical and physical phenomena that occur during CNT production in the process analysis is emphasized. The impact of this invention on the environment and human health is taken into consideration too.
基金supported by the Universiti Sains Malaysia under the Research University Grant Scheme(Project A/C No.814004)USM-RU-PRGS(Project A/C No.8032038)the Malaysian Technology Development Corporation (MTDC) under the Commercialization of Research & Development Fund(CRDF)(MBF065-USM/05)
文摘The present work aims at utilizing compressed natural gas （CNG） as carbon source for the synthesis of carbon nanotubes （CNTs） over CoO-MoO/Al2O3 catalyst via catalytic chemical vapor deposition （CCVD） method. The as-produced carbonaceous product was characterized by thermal gravimetric analyzer （TGA）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and Raman spectroscopy. The experimental finding shows that CNTs were successfully produced from CNG while carbon nanofibers （CNFs） were formed as the side products. In addition, the catalytic activity and lifetime were found sustained and prolonged, as compared with using high purity methane as carbon source. The present study suggests an alternative route which can effectively produce CNTs and CNFs using low cost CNG.
基金supported by the German Federal Ministry of Education and Research(BMBF) through the Project "Carbo Elch"(Grant 03X0207C) within the scope of the Inno.CNT Alliancethe IMPRS-Sur Mat of the Max-Planck Society
文摘Nitrogen-doped carbon nanotubes（NCNTs） were synthesized by chemical vapor deposition using cobaltbased oxides as catalyst and ethylenediamine（EDA） as carbon/nitrogen precursor. The influence of growth time,EDA concentration and growth temperature on the morphology,yield,composition,graphitization and oxidation resistance of the NCNTs was systematically investigated by using Raman spectroscopy,temperature-programmed oxidation and other techniques. The NCNT growth from ethylenediamine with a high N/C ratio involves several processes including mainly（1） catalytic growth of NCNTs,（2） homogeneous gas-phase decomposition of EDA,（3） non-catalytic deposition of pyrolytic carbon/nitrogen species and（4）surface etching of amorphous carbon or carbon at defect sites through gasification. At a later growth stage the etching process appears to be dominating,leading to the thinning of nanotubes and the decrease of yield.Moreover,the surface etching through carbon gasification strongly influences the structure and degree of graphitization of NCNTs.
基金The National Science Foundation of China under Grant
文摘Doped micro-crystalline silicon films are deposited at temperatures as low as 400 ℃ by the catalytic chemical vapor deposition method using a silane and hydrogen gas mixture. Electrical properties such as the carrier concentration and the Hall mobility are investigated for various measuring temperatures. It is found that the grains of micro-crystalline silicon are preferentially oriented along the (220) direction , and that the Hall mobility is larger than 8 cm 2·V -1 ·s -1 , the carrier concentration is about 1×10 17 cm -1 ～1×10 19 cm -3 at room temperature.
文摘X-Ray Absorption Spectroscopy (XAS) on the carbon K edge of carbon nanostructures (nanotubes, nanofibers, nanowalls) is reported here. They are grown on plain SiO2 (8 nm thick)/Si(100) substrates by a Plasma and Hot Filaments-enhanced Catalytic Chemical Vapor Deposition (PE HF CCVD) process. The morphology and the nature of these carbon nanostructures are characterized by SEM, TEM and Raman spectroscopy. According to conditions of catalyst preparation and DC HF CCVD process, carbon nanotubes (CNTs), carbon nanofibers (CNFs), carbon nanowalls (CNWs), carbon nanoparticles (CNPs) with different orientation of the graphene plans or shells can be prepared. From the angular dependence of the incident light and geometrical morphology of the nanostructures, wide variations of the C K-edge intensity of the transitions to the empty π* and σ* states occur. A full lineshape analysis of the XAS spectra has been carried out using a home-made software, allowing estimating the relative proportion of π* and σ* transitions. A geometrical model of the angular dependence with the incidence angle of the light and the morphology of the carbon nanostructures is derived. With normalization to the HOPG (Highly Oriented Pyrolytic Graphite graphite) reference case, a degree of alignment can be extracted which is representative of the localized orientation of the graphitic carbon π bonds, accounting not only for the overall orientation, but also for local defects like impurities incorporation, structural defects ... This degree of alignment shows good agreement with SEM observations. Thus CNTs films display degrees of alignment around 50%, depending on the occurrence of defects in the course of the growth, whereas no special alignment can be detected with CNFs and CNPs, and a weak one (about 20%) is detected on CNWs.
基金This research was supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MEST)by a grant from the 2012 Fundamental R&D Program of Hanseo University,Korea.
文摘Carbon nanotubes(CNTs)have attracted intensive interests of researchers for a long time due to their fascinating physical and chemical properties promising for various potential applications,including advanced ceramics,nanoelectronic devices,nanoscale sensors,solar cells,battery electrode,field emitters,etc..This review summarized the synthetic methods of CNTs,with an emphasis on the chemical vapor deposition(CVD)method,especially catalytic CVD.Although there still are some challenges in the way,with the development of the technology,a hope for widespread applications always exists.
