Arc Discharge Preparation and Structural Characterization of sp-based One-dimensional Carbon Nanomaterials

Author:Zhang Yi Fan

Supervisor:zhao xin luo

Database:Doctor

Degree Year:2019

Download:11

Pages:120

Size:6634K

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Carbyne as one-dimensional carbon nanomaterial made of pure sp hybridization structure is becoming a new hotspot in nanoscience and nanotechnology,because they are theoretically predicted to own superior and unique properties such as the highest Young’s modulus in the world(twice of graphene and carbon nanotube)and tunable direct band gap under tension.Although carbyne has not been prepared experimentally,the breakthroughs in relative area present that sp-based carbon nanomaterials own special physical and chemical property and potential prospects of future applications.The representative examples are:carbon nanowire,which is a long linear carbon chain encapsulated inside carbon nanotube;white carbon consisting of short carbon chains;two dimensional graphyne film made of sp-sp~2hybrid structure,et al.The dissertation is focusing on sp-based one-dimensional carbon nanomaterials.The main goals are to expand the narrow scope of suitable condtions for the preparation of carbon nanowire by arc discharge method;to improve the growth yield and purity of carbon nanowire;and to reseach on the possibility to prepare sp-based carbon nanomaterials in gas phase.There are three parts in the dissertation.The first part contains Chapter 1,which introduces the catagories of sp-based carbon nanomaterials,the history and the new progress.The second part contains Chapter 2 and 3.We present a new strategy to adjust the properties of arc plasma by controlling the arc environment,which benefits the preparation of carbon nanowire.Relative characterizations of the samples are shown.Detailed mechanism is discussed through finite element simulation.The third part contains Chapter 4,which shows the possibility to prepare polyyne-like structure in gas phase by arc discharge method in the conditions deviated from the suitable parameters to produce sp~2-based carbon nanomaterials.The main achievements are as follows:1.We presented a strategy to ajust the properties of arc plasma aiming to expand the scope of suitable conditions for the preparation of carbon nanowire and improve the growth yield.2.We succeeded in preparing carbon nanowire in large yield and high purity by gas environment cooling enhanced hydrogen arc discharge method.The scope of suitable current parameter was expanded to 50-80 A in-20-20°C cooling.In the case of liquid nitrogen cooling,the optimal pressure moved to 100 Torr and the optimal current moved to 90 A.3.We succeeded in preparing carbon nanowire in large yield and high purity by magnetic field enhanced hydrogen arc discharge method.The scope of current parameter could be expanded to 30 A.The optimal current was found to be 40 A.4.The distribution of the band gap of carbon nanowire samples prepared by the two enhanced methods was found to change largely compared to the conventional samples.It provides the potential to a selective growth of carbon nanowire in different band strutures.5.The close relationship between the yield of carbon nanowire and the quality of multi-walled carbon nanotube was determined by Raman spectra and SEM observation.Both of the two enhanced methods are able to improve the purity of multi-walled carbon nanotube,resulting in improving the yield of carbon nanowire.6.The influences of the two enhanced methods to the arc plasma were discussed by finite element simulation.Both of the two enhanced methods could increase the temperature of arc plasma,which benefits the growth of multi-walled carbon nanotube and carbon nanowire.7.We summarized the experiences on the preparation of carbyne from history and speculate it might be possible to prepare sp-based carbon nanomaterials in low current and low pressure condition.We obtained polyyne-like structure in the current of 10-20 A and hydrogen pressure of 10-50 Torr.