Reparation Of Heteroatomic Modified Carbon-based Materials By RF Plasma

Carbon is the only element with zero-dimensional to three-dimensional allotropes in the periodic table.Carbon nanomaterials have a wide application in electrochemical devices,field emitters,new energy materials,sensors,multiphase catalysis,biology and medicine due to their unique physical,chemical and mechanical properties.Due to the large specific surface area of multi-wall carbon materials,it can be expected to be widely used in fuel cells,the field-emission display,battery capacitors,gas sensors,and so on.So far,plasma technology has been widely and successfully applied to the graphene and carbon nanomaterial growth.The morphology and structure of carbon materials depend upon the preparation conditions including the plasma source,precursor,pressure,temperature,etc.Heteroatomic modification by plasma technology can effectively modulate the structure and properties of carbon-based nanomaterials,thereby improving its application value on various occasions.In this doctoral dissertation,nitrogen-modified vertical graphene nanosheets(N/VGs),silver-modified vertical graphene nanosheets(Ag/VGs),and silicon-modified graphene nanosheets(SiC/GNS)were prepared by the RF plasma system.The transformation from N/VGs to N-DLC was realized by adjusting the plasma parameters.The one-step synthesis of organosilicon modified graphene nanomaterials was realized by changing the plasma precursor.1.Ag-decorated vertical-oriented graphene nanosheets(Ag/VGs)were synthesized via helicon wave plasma chemical vapor deposition(HWP-CVD)and radio frequency plasma magnetron sputtering(RF-PMS).The VGs were directly grown on the silicon substrate by HWP-CVD system.Then the silver nanoparticles were modified on the prepared VGs using the RF-PMS system under different sputtering times and RF powers.Due to the uniqueness of VGs,Ag nanoparticles are highly dispersed on the wall surface of VGs.The oxygen evolution reaction(OER)performances of Ag/VGs profited from uniquely ordered and interconnected high walls of the VGs,which were conducive to high Ag particle dispersion and facile mass/charge transport.In addition,the double layer capacitance of Ag/VGs under different Ag loads(Cdl,up to 1.04 mF/cm2)were studied.The Ag/VGs is expected to be a substitute for platinum-decorated carbon materials.2.This section reports the successful control of 2D nitrogen-doped verticallyoriented graphene nanosheets(2D N/VGs)via HWP-CVD employing argon(Ar),methane(CH4),and nitrogen(N2)by varying the N2 flow rate(RN2)during growth.With the increase in RN2,the walls of N/VGs were densely packed and almost vertically aligned with the decrease in growth height rate.More excited N atoms could be embedded into the C vacancy to replace the missing C atom and restore the hexagonal network,which can lead to an increase in the nitrogen content.The peak intensity ratio of the D and G bands(ID/IG)decreased significantly from 2.72 to 2.14,indicating that the incorporation of nitrogen into the VGs led to a decrease in surface defects,and the defects gradually reduced with increasing nitrogen content.The effective average distance between defects increases with the nitrogen content,and the tunneling phenomenon is apparent as the resistance increases.The electrical behavior indicates that the materials are suitable for transducers based on the carbon nanomaterial.3.By adjusting plasma parameters,the nitrogen-doped diamond-like(N-DLC)films were successfully prepared on silicon substrates in Ar/CH4/N2 gas mixtures at different DC negative bias voltages(-VDC).The effects of-VDC on the surface morphology,structure and properties of N-DLC films were investigated.As-VDC increases,the N content and sp3/sp2 ratio of the film increases.The Young’s modulus increases with the increase of-VDC.The test of electrochemical performance shows that the electrode reaction on the N-DLC electrode is reversible,which is an ideal diffusion control process.Therefore,in this study,the N-DLC films prepared by HWPCVD technique exhibit excellent electrochemical reversibility.The optimized N-DLC film deposited by HWP could be used in various microelectrode fields.4.An approach for the rapid,one-step,preparation of a variety of wide-bandgap SiC/graphene nanosheet(SiC/GNSs)composites using a high-density helicon wave plasma(HWP)source was investigated.The nucleation mechanism and growth model were discussed.The PL peak of SiC/GNSs(2.95 eV)was blue-shifted,which indicated that SiC/GNSs have the potential for use of light-emitting materials with excellent thermal and oxidation stabilities.The large surface area and sharp edges of VGs were proved useful for a number of different promising applications such as electron field emitters and electrodes for fuel cell,gas storage,membrane filter,electron emitters,etc.