Preparation And Properties Of Metal Oxide Nanowires

This thesis systemically investigates the preparation of In₂O₃,SnO₂,Bi₂O₃ nanowires and Sn-doped In₂O₃ nanowires by thermal evaporation method using self-assembled device and studies the effects of the heating temperature and time for the preparation of these nanowires.The morphology,phase,microstructure and composition of these nanowires were characterized by SEM,XRD,TEM and EDS.On the basis,their growth mechanisms were discussed,and their gas sensing properties were tested.The main achievements are as follows:?1?The key factor in preparing metal oxide nanowires successfully is heating temperature which affects directly the evaporation rate and the vapor pressure of the evaporation source in the lumen of quartz tube.The length and quantity of nanowires are affected by the heating time:the length and quantity of nanowires increase with the increasing of heating time.The type of the growth substrate has no significant effect on the growth of nanowires.?2?The optimal process of In₂O₃ nanowires preparation is that the In block was heated at 700? for 8h.The single crystal nanowire matches body-centered cubic,and crystallizes well.The oriented growth of In₂O₃ nanowires is preferentially along the[100]direction.The diameter of them is about 80nm,the length reaches micron level.The optimal process of SnO₂ nanowires is that the Sn block was heated at 750? for 4h.The single crystal nanowire matches with tetragonal rutile SnO₂,and crystallizes well.The oriented growth of SnO₂ nanowires is preferentially along the[101]direction.The diameter of them is within 100nm,the length reaches micron level.The optimal process for Bi₂O₃ nanowires is that the Bi and Sn block was heated at 750? for 4h.The single crystal nanowire matches with Monoclinic Bi₂O₃,and crystallizes well.The oriented growth of Bi₂O₃ nanowires is preferentially perpendicular to the?120?plane.The VLS and VS growth mechnasims occur simultaneously during the preparations of In₂O₃,SnO₂,Bi₂O₃ nanowires.?3?The In₂O₃ nanowires nanowires show certain sensitivity for C₂H₅OH,C₃H₆O except CH3OH.The Bi₂O₃ nanowires show certain sensitivity for C₂H₅OH,C2H5OH and C3H6O.The SnO₂ nanowires show excellent sensitivity and fast response/recovery characteristics for low concentration of C₂H₅OH,C2H5OH and C3H6O.The response of each sensor increases with the increase of gas concentration.?4?Sn-doped In₂O₃ nanowires were also successfully prepared by using the self-assembled system at 750? for 4h.The composition of Sn-doped In₂O₃ nanowires changed with the ratio of the evaporation source In and Sn.Sn-doped In₂O₃ nanowires have the same crystal structure with In₂O₃ nanowires.The oriented growth of Sn-doped In₂O₃ nanowire is preferentially along the[100]direction.The diameter of them is within 100nm,the length reaches micron level.The VLS growth of Sn-doped In₂O₃ nanowire was confirmed.