The initial field electron emission degradation behaviour of original nano-structured sp^2-bonded amorphous carbon films has been observed, which can be attributed to the increase of the work function of the film in t...The initial field electron emission degradation behaviour of original nano-structured sp^2-bonded amorphous carbon films has been observed, which can be attributed to the increase of the work function of the film in the field emission process analysed using a Fowler-Nordheim plot. The possible reason for the change of work function is suggested to be the desorption of hydrogen from the original hydrogen termination film surface due to field emission current-induced local heating. For the explanation of the emission degradation behaviour of the nano-structured sp2-bonded amorphous carbon film, a cluster model with a series of graphite （0001） basal surfaces has been presented, and the theoretical calculations have been performed to investigate work functions of graphite （0001） surfaces with different hydrogen atom and ion chemisorption sites by using first principles method based on density functional theory-local density approximation.展开更多
The bulk,pristine sp^(2) carbons,such as graphite,carbon nanotubes,and graphene,are usually assumed to be typical diamagnetic materials.However,over the past two decades,there have been many reports about the ferromag...The bulk,pristine sp^(2) carbons,such as graphite,carbon nanotubes,and graphene,are usually assumed to be typical diamagnetic materials.However,over the past two decades,there have been many reports about the ferromagnetism in these sp^(2) carbon materials,which have attracted intense interest for basic research and potential applications.In this review,we focus on the evidence and developments of the emergent ferromagnetism in sp^(2) carbon revealed by nine kinds of experimental methods:magnetic force microscopy(MFM),magnetization measurements with physical property measurement system(PPMS),X-ray magnetic circular dichroism(XMCD),scanning tunneling microscopy(STM),miniaturized magnetic particle inspection(MPI),anomalous Hall effect(AHE),mechanical deflection of carbon nanotube cantilevers,magnetoresistance,and spin-related devices(spin field effect transistor and spin memory).The advantages,conclusions,challenges,and future of these methods are discussed.The ferromagnetism in sp^(2) carbon will open a door to explore exotic physical phenomena and lay the basis for the development of integrated circuit of spintronics,which is fundamentally different from charge-based conventional electronics.展开更多
Diamond like carbon films, prepared by RF glow discharge on glass substrates, were irradiated by γ rays. The as deposited and irradiated films were characterized by Raman spectroscopy, electrical resistivity, a...Diamond like carbon films, prepared by RF glow discharge on glass substrates, were irradiated by γ rays. The as deposited and irradiated films were characterized by Raman spectroscopy, electrical resistivity, and infrared transmittance. It is shown that the irradiation of the γ rays can lead to the breaking of SP 3 C H and SP 2 C H bonds, slight increasing of SP 3 C C bonds, and induced hydrogen recombination with H 2 molecules, subsequently diffusing to the surface of the films. When the γ rays irradiation dose reached 10×10 4 Gy, the numbers of SP 3 C H bonds was decreased by about 50%, the resistivity of irradiated DLC films was increased, and the diamond like character of the films became more obvious. The structure of DLC films was modified when irradiated by γ rays. The irradiation mechanisms are briefly discussed.展开更多
sp^(2) nanocrystallited carbon films with large nanocrystallite sizes,smooth surfaces,and relative high hardness were prepared with different ion irradiation densities regulated with the substrate magnetic coil curren...sp^(2) nanocrystallited carbon films with large nanocrystallite sizes,smooth surfaces,and relative high hardness were prepared with different ion irradiation densities regulated with the substrate magnetic coil current in an electron cyclotron resonance plasma sputtering system.Their multiscale frictional behaviors were investigated with macro pin‐on‐disk tribo‐tests and micro nanoscratch tests.The results revealed that,at an ion irradiation density of 16 mA/cm^(2),sp^(2) nanocrystallited carbon film exhibits the lowest friction coefficient and good wear resistant properties at both the macroscale and microscale.The film sliding against a Si_(3)N_(4) ball under a contact pressure of 0.57 GPa exhibited a low friction coefficient of 0.09 and a long wear life at the macroscale.Furthermore,the film sliding against a diamond tip under a contact pressure of 4.9 GPa exhibited a stable low friction coefficient of 0.08 with a shallow scratch depth at the microscale.It is suggested that sp^(2) nanocrystallites affect the frictional behaviors in the cases described differently.At the macroscale,the contact interface via the small real contact area and the sp^(2) nanocrystallited transfer layer dominated the frictional behavior,while the sp^(2) nanocrystallited structure in the film with low shear strength and high plastic resistivity,as well as the smooth surface morphology,decided the steady low nanoscratch properties at the microscale.These findings expand multiscale tribological applications of sp^(2) nanocrystallited carbon films.展开更多
sp^2 carbon nanomaterials are mainly composed of sp^2-hybridized carbon atoms in the form of a hexagonal network. Due to the p bonds formed by unpaired electrons, sp^2 carbon nanomaterials possess excellent electronic...sp^2 carbon nanomaterials are mainly composed of sp^2-hybridized carbon atoms in the form of a hexagonal network. Due to the p bonds formed by unpaired electrons, sp^2 carbon nanomaterials possess excellent electronic, mechanical, and optical properties, which have attracted great attention in recent years.As the advanced sp^2 carbon nanomaterials, graphene and carbon nanotubes(CNTs) have great potential in electronics, sensors, energy storage and conversion devices, etc. The low-temperature synthesis of graphene and CNTs are indispensable to promote the practical industrial application. Furthermore, graphene and CNTs can even be expected to directly grow on the flexible plastic that cannot bear high temperature,expanding bright prospects for applications in emerging flexible nanotechnology. An in-depth understanding of the formation mechanism of sp^2 carbon nanomaterials is beneficial for reducing the growth temperature and satisfying the demands of industrial production in an economical and low-cost way. In this review, we discuss the main strategies and the related mechanisms in low-temperature synthesis of graphene and CNTs, including the selection of precursors with high reactivity, the design of catalyst, and the introduction of additional energy for the pre-decomposition of precursors. Furthermore, challenges and outlooks are highlighted for further progress in the practical industrial application.展开更多
Rice (\%Oryza sativa\% cv. Jindao 1187) was grown in open_top chambers which contained ambient and enriched CO\-2. CO\-2 elevation stimulated rice tillering during early vegetative stage. However, panicle dry weight p...Rice (\%Oryza sativa\% cv. Jindao 1187) was grown in open_top chambers which contained ambient and enriched CO\-2. CO\-2 elevation stimulated rice tillering during early vegetative stage. However, panicle dry weight per plant did not change at maturity stage. Root biomass was enhanced by high CO\-2. Root / shoot ratio was increased under high CO\-2 at maturity, indicating more carbon allocation to the below_bround part in rice under high CO\-2.展开更多
To meet the surging needs in energy efficiency and eco-friendly lubricants,a novel superlubricious technology using a vegetable oil and ceramic materials is proposed.By coupling different hydrogen-free amorphous carbo...To meet the surging needs in energy efficiency and eco-friendly lubricants,a novel superlubricious technology using a vegetable oil and ceramic materials is proposed.By coupling different hydrogen-free amorphous carbon coatings with varying fraction of sp^(2) and sp^(3) hybridized carbon in presence of a commercially available silicon nitride bulk ceramic,castor oil provides superlubricity although the liquid vegetable oil film in the contact is only a few nanometres thick at most.Besides a partial liquid film possibly separating surfaces in contact,local tribochemical reactions between asperities are essential to maintain superlubricity at low speeds.High local pressure activates chemical degradation of castor oil generating graphitic/graphenic-like species on top of asperities,thus helping both the chemical polishing of surface and its chemical passivation by H and OH species.Particularly,the formation of the formation of–(CH_(2)–CH_(2))n–noligomers have been evidenced to have a major role in the friction reduction.Computer simulation unveils that formation of chemical degradation products of castor oil on friction surfaces are favoured by the quantity of sp^(2)-hybridized carbon atoms in the amorphous carbon structure.Hence,tuning sp^(2)-carbon content in hydrogen-free amorphous carbon,in particular,on the top layers of the coating,provides an alternative way to control superlubricity achieved with castor oil and other selected green lubricants.展开更多
文摘The initial field electron emission degradation behaviour of original nano-structured sp^2-bonded amorphous carbon films has been observed, which can be attributed to the increase of the work function of the film in the field emission process analysed using a Fowler-Nordheim plot. The possible reason for the change of work function is suggested to be the desorption of hydrogen from the original hydrogen termination film surface due to field emission current-induced local heating. For the explanation of the emission degradation behaviour of the nano-structured sp2-bonded amorphous carbon film, a cluster model with a series of graphite （0001） basal surfaces has been presented, and the theoretical calculations have been performed to investigate work functions of graphite （0001） surfaces with different hydrogen atom and ion chemisorption sites by using first principles method based on density functional theory-local density approximation.
基金supported by Major Nanoprojects of Ministry of Science and Technology of China(No.2018YFA0208403)the National Natural Science Foundation of China(No.21973021)+2 种基金The GBA National Institute for Nanotechnology Innovation,Guangdong,China(No.2020B0101020003)Chinese Academy of Sciences Project for Young Scientists in Basic Research(No.YSBR-030)Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDB36000000 and NBSDC-DB-18).
文摘The bulk,pristine sp^(2) carbons,such as graphite,carbon nanotubes,and graphene,are usually assumed to be typical diamagnetic materials.However,over the past two decades,there have been many reports about the ferromagnetism in these sp^(2) carbon materials,which have attracted intense interest for basic research and potential applications.In this review,we focus on the evidence and developments of the emergent ferromagnetism in sp^(2) carbon revealed by nine kinds of experimental methods:magnetic force microscopy(MFM),magnetization measurements with physical property measurement system(PPMS),X-ray magnetic circular dichroism(XMCD),scanning tunneling microscopy(STM),miniaturized magnetic particle inspection(MPI),anomalous Hall effect(AHE),mechanical deflection of carbon nanotube cantilevers,magnetoresistance,and spin-related devices(spin field effect transistor and spin memory).The advantages,conclusions,challenges,and future of these methods are discussed.The ferromagnetism in sp^(2) carbon will open a door to explore exotic physical phenomena and lay the basis for the development of integrated circuit of spintronics,which is fundamentally different from charge-based conventional electronics.
文摘Diamond like carbon films, prepared by RF glow discharge on glass substrates, were irradiated by γ rays. The as deposited and irradiated films were characterized by Raman spectroscopy, electrical resistivity, and infrared transmittance. It is shown that the irradiation of the γ rays can lead to the breaking of SP 3 C H and SP 2 C H bonds, slight increasing of SP 3 C C bonds, and induced hydrogen recombination with H 2 molecules, subsequently diffusing to the surface of the films. When the γ rays irradiation dose reached 10×10 4 Gy, the numbers of SP 3 C H bonds was decreased by about 50%, the resistivity of irradiated DLC films was increased, and the diamond like character of the films became more obvious. The structure of DLC films was modified when irradiated by γ rays. The irradiation mechanisms are briefly discussed.
基金The research work was supported by the National Natural Science Foundation of China(No.51975382)Natural Science Foundation of Guangdong Province(No.2018A030313908)Shenzhen Fundamental Research Free‐exploring Project(JCYJ20170817100822005).
文摘sp^(2) nanocrystallited carbon films with large nanocrystallite sizes,smooth surfaces,and relative high hardness were prepared with different ion irradiation densities regulated with the substrate magnetic coil current in an electron cyclotron resonance plasma sputtering system.Their multiscale frictional behaviors were investigated with macro pin‐on‐disk tribo‐tests and micro nanoscratch tests.The results revealed that,at an ion irradiation density of 16 mA/cm^(2),sp^(2) nanocrystallited carbon film exhibits the lowest friction coefficient and good wear resistant properties at both the macroscale and microscale.The film sliding against a Si_(3)N_(4) ball under a contact pressure of 0.57 GPa exhibited a low friction coefficient of 0.09 and a long wear life at the macroscale.Furthermore,the film sliding against a diamond tip under a contact pressure of 4.9 GPa exhibited a stable low friction coefficient of 0.08 with a shallow scratch depth at the microscale.It is suggested that sp^(2) nanocrystallites affect the frictional behaviors in the cases described differently.At the macroscale,the contact interface via the small real contact area and the sp^(2) nanocrystallited transfer layer dominated the frictional behavior,while the sp^(2) nanocrystallited structure in the film with low shear strength and high plastic resistivity,as well as the smooth surface morphology,decided the steady low nanoscratch properties at the microscale.These findings expand multiscale tribological applications of sp^(2) nanocrystallited carbon films.
基金supported by the National Natural Science Foundation of China (21673161)the Sino-German Center for Research Promotion (1400)the Postdoctoral Innovation Talent Support Program of China (BX20180224)
文摘sp^2 carbon nanomaterials are mainly composed of sp^2-hybridized carbon atoms in the form of a hexagonal network. Due to the p bonds formed by unpaired electrons, sp^2 carbon nanomaterials possess excellent electronic, mechanical, and optical properties, which have attracted great attention in recent years.As the advanced sp^2 carbon nanomaterials, graphene and carbon nanotubes(CNTs) have great potential in electronics, sensors, energy storage and conversion devices, etc. The low-temperature synthesis of graphene and CNTs are indispensable to promote the practical industrial application. Furthermore, graphene and CNTs can even be expected to directly grow on the flexible plastic that cannot bear high temperature,expanding bright prospects for applications in emerging flexible nanotechnology. An in-depth understanding of the formation mechanism of sp^2 carbon nanomaterials is beneficial for reducing the growth temperature and satisfying the demands of industrial production in an economical and low-cost way. In this review, we discuss the main strategies and the related mechanisms in low-temperature synthesis of graphene and CNTs, including the selection of precursors with high reactivity, the design of catalyst, and the introduction of additional energy for the pre-decomposition of precursors. Furthermore, challenges and outlooks are highlighted for further progress in the practical industrial application.
文摘Rice (\%Oryza sativa\% cv. Jindao 1187) was grown in open_top chambers which contained ambient and enriched CO\-2. CO\-2 elevation stimulated rice tillering during early vegetative stage. However, panicle dry weight per plant did not change at maturity stage. Root biomass was enhanced by high CO\-2. Root / shoot ratio was increased under high CO\-2 at maturity, indicating more carbon allocation to the below_bround part in rice under high CO\-2.
基金This research is supported by TOTAL,Solaize Research Center and Federal Ministry of Economic Affairs and Energy Germany(BMWi)within project CHEOPS3(Funding number 03ET1286B).
文摘To meet the surging needs in energy efficiency and eco-friendly lubricants,a novel superlubricious technology using a vegetable oil and ceramic materials is proposed.By coupling different hydrogen-free amorphous carbon coatings with varying fraction of sp^(2) and sp^(3) hybridized carbon in presence of a commercially available silicon nitride bulk ceramic,castor oil provides superlubricity although the liquid vegetable oil film in the contact is only a few nanometres thick at most.Besides a partial liquid film possibly separating surfaces in contact,local tribochemical reactions between asperities are essential to maintain superlubricity at low speeds.High local pressure activates chemical degradation of castor oil generating graphitic/graphenic-like species on top of asperities,thus helping both the chemical polishing of surface and its chemical passivation by H and OH species.Particularly,the formation of the formation of–(CH_(2)–CH_(2))n–noligomers have been evidenced to have a major role in the friction reduction.Computer simulation unveils that formation of chemical degradation products of castor oil on friction surfaces are favoured by the quantity of sp^(2)-hybridized carbon atoms in the amorphous carbon structure.Hence,tuning sp^(2)-carbon content in hydrogen-free amorphous carbon,in particular,on the top layers of the coating,provides an alternative way to control superlubricity achieved with castor oil and other selected green lubricants.
