研究在N2O/N2/NH3氛围中对Ni催化剂进行退火处理,旨在探讨退火处理对所生成碳纳米管的表面结构及其发射特性的影响.从表面结构及表面元素分析结果发现:Ni催化剂在N2O/N2/NH3氛围中退火处理之后,Ni催化剂的颗粒大小及催化剂的化学成分发生改变,进而影响所合成的碳纳米管的表面结构及场发射特性.扫描电镜显示:经过N2O退火前处理后,催化金属薄膜在成核时较易形成均匀性的金属颗粒,且金属颗粒较小.比较经N2O/N2/NH3氛围退火处理之后所合成的碳纳米管结果,经过N2O前处理可以有效抑制非品质碳的成长,使所成长出的碳纳米管数量最多、场发射电流最大.原因主要是因为N2O对催化剂镍膜金属前处理过程中分解出的氮原子及氧原子会活化及氧化催化剂Ni金属,并使所形成的Ni金属颗粒较小且更为均匀,造成表面型态上的显著改变,有助于使合成的碳纳米管场发射电流变大.
Ni catalyst was annealed in N2O/N2/NH3 in order to study the effects of the annealing on the surface morphology and field-emission characteristics of synthesized carbon nanotubes (CNTs).The morphology and composition of the CNTs show that the grain size and composition of the Ni catalyst can be modified by N2O,N2,and NH3 pretreatments.Scanning electron microscopy images of evaporated Ni after N2O pretreatment show that the Ni particles are more uniformly distributed,and their sizes are relatively small.It is found that the CNTs grown on Ni pretreated with N2O have the highest surface density and the highest emission current.This improvement is accomplished through the more uniformly distributed and smaller Ni particles obtained by N2O pretreatment.The growth of amorphous carbon is also suppressed.The reasons for this improvement are that nitrogen and oxygen atoms dissociated from N2O in the pretreatment can oxidize the catalyst particles and inhibit their growth so that the resulting Ni metal nuclei become smaller and more uniformly distributed,which is beneficial to CNT growth.
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