Study On Fast Synthesis And Regulation Of Carbon Nanomaterials Using Inverse Diffusion Biofuel Flames

Carbon nanomaterials have attracted significant attention from researchers due to their excellent physical and chemical properties,which can be applied in mechanical,thermal,electrical,optical and biomedical fields.How to achieve the stable,controllable,large-scale,low-cost and fast synthesis of carbon nanomaterials is a major problem and challenge for us.Some scholars have proposed a new and potential synthesis method,call as flame synthesis.Various experiments have shown that flames can be used for the synthesis of carbon nanotubes and carbon films.However,the research about flame synthesis is still in primary stage.Therefore,studying the effects of different experimental conditions on the growth of carbon nanomaterials is conducive to understand the synthesis of carbon nanomaterials in flames better,and provide some experimental references and theoretical direction for finding the best synthesis conditions.In this paper,renewable biofuels are used as carbon sources,and inexpensive and easily available metal materials are used as synthetic substrates.The fast synthesis and regulation of carbon nanotubes and amorphous carbon films in open atmosphere are studied,and the growth characteristics of carbon nanomaterials are analyzed by optical microscopy,scanning electron microscopy(SEM),transmission electron microscopy(TEM),Raman spectroscopy(Raman),X-ray diffraction(XRD)and atomic force microscopy(AFM).Firstly,the growth of carbon nanotubes on brass mesh and nickel mesh are explored by using the inverse diffusion flame of renewable biofuel such as ethanol and n-butanol.The effects of fuel type,substrate material,flame temperature and synthesis time on the synthesis of carbon nanotubes are considered.The results show that the brass mesh can be utilized in the synthesis of carbon nanotubes with the inverse diffusion flame of ethanol and n-butanol,but the nickel mesh does not have the catalytic properties of the carbon nanotubes synthesis.As the synthesis time increases,the density and tube length of the carbon nanotubes generate on the brass mesh increase.The flame temperatures of 1023K and 1273K are suitable for the synthesis of carbon nanotubes.In the ethanol flame,the carbon nanotubes synthesized in1023K have higher degree of crystallinity,lower disorder and fewer defects than 1273K,while the results in n-butanol are reversed.Secondly,the synthesis of amorphous carbon film on copper foil by using the biofuel ethanol inverse diffusion flame is investigated.The influences of experimental parameters such as fuel flow rate,substrate height and synthesis time on the growth of amorphous carbon film are discussed.The results show that the amorphous carbon film with a certain level of flexibility and transparency emerged at only 10 seconds.As the fuel flow rate increases and the substrate moves upwards in the flame,the area of the amorphous carbon film increases,and the amount of impurities decreases.When the copper foil is placed on top of the flame,the amorphous carbon film grows best.During the synthesis time of 10 seconds,the local growth of amorphous carbon film has occurred.The content of sp~2 bonds in the carbon film is higher,the structure is loose,and the surface is uneven.When the synthesis time is 30 seconds,the content of sp~3 bonds in the amorphous carbon film increases,the degree of disorder increases,and the roughness of the film surface is the smallest.With the synthesis time continues to increase,the growth of the carbon film slows down.When the synthesis time reaches 10 minutes,obvious carbon-containing impurities appear on the amorphous carbon film surface,which increases the surface roughness of the film.Finally,the synthesis of amorphous carbon film is regulated by adding hydrogen to change the ethanol inverse diffusion.The effects of the presence of hydrogen and its flow rate on the growth of amorphous carbon film on copper foil are investigated.The results show that under different hydrogen flow rates,as the substrate height increases,the synthetic area of amorphous carbon film increases,and the content of impurities decreases gradually.If the copper foil is inserted in the outer flame region of the flame,the amorphous carbon film grows unevenly due to excessive disturbance.When the copper foil is placed on top of the flame inner flame,the amorphous carbon film grows best.When hydrogen is added,the complete continuous amorphous carbon film can form in a short time of 30 seconds.The presence of hydrogen accelerates the local growth of carbon film,the degree of order about amorphous carbon film increased.If hydrogen is excessive,the etching effect of hydrogen on the amorphous carbon film enhanced at a high temperature,resulting in the increase of the carbon film surface roughness.