| In order to solve the global problems of the energy demand and environmentpollution from the human societal development,exploiting the new energy resource isan important hot point of global investigating field.Vanadium pentoxide (V2O5)materials with the special layer structure are not only the cathode material of Li ionrechargeable battery,but also one of the rare active materials that are hoped to use forthe active materials in the cathode of Mg rechargeable battery.Therefore,V2O5 is akind of important new energy materials and it is significant to study the preparation,structure and properties of V2O5In this thesis,α-V2O5 andβ-V2O5 films were prepared using sputtering,VOxwith various morphologies were formed by thermal evaporation chemical vapordeposition (CVD)and VOx-NTs were synthesized through hydrothermal treatment.The morphologies,structure and formation mechanism of V2O5 films andnanomaterials were studied.(1)V2O5 films were prepared by sputtering and electrochemical properties werestudied.The influence of conditions on the structure ofα-V2O5 films was investigated.α-V2O5 films with perfect layer structure were easily obtained at the high oxygenpartial pressure.As the annealing temperature is too high (over 550℃),the V=Obonds can be broken,which leaded to the oxygen vacancies and the collapse ofα-V2O5(001)planes.A proper depositing temperature is favorable for thecrystallization ofα-V2O5 films.The preparation and formation mechanism ofβ-V2O5 films were studiedsystemically,which has not been reported.β-V2O5 films were formed at 550℃(40%oxygen partial pressure).It is revealed that the depositing temperature and oxygenpartial pressure are the needed factor forβ-V2O5 films.During the sputtering process,high depositing temperature gives the V and O atoms strong energy to move and keeps from the formation ofα-V2O5 structure.The vanadium oxides with low valencestate are not formed in the high oxygen partial pressure,butβ-V2O5.In the medialdepositing temperature,films withα-andβ-V2O5 were obtained,andαphase cantransform toβphase by annealing.β-V2O5 films can be prepared on Si,quartz,glassand ITO substrates.The electrochemical properties of V2O5 films deposited on ITO substrates werestudied by cyclic voltammograms.The results revealed thatα-andβ-V2O5 filmsshowed electrochemical reversible to Li+ and Mg2+.In the inaqueous Mg(ClO4)2/PCsolution,the reversible properties of V2O5 were poor for Mg2+,might result form thestructure distortion of V2O5 caused by the insertion of Mg2+.(2)Different vanadium oxides were prepared by thermal evaporation CVD usingVO(acac)2 powder as V source and formation mechanism were investigated.In the low vacuum and at 650℃,V2O5 nanosheets were obtained by directlyheating VO(acac)2.This is a simple and effective way for preparation V2O5nanosheets.Heating VO(acac)2 at 650℃,VOx with various morphologies were formed atdifferent temperature zones.The content ratio of V5+/V4+in VOx,caused by thevarious growth temperatures,was the main factor for the different morphologies.Planting the VO(acac)2 and the substrates in the low and high temperaturezones respectively,V2O5 nanowires and V2O5 nanospheres were prepared.Themechanism was suggested for the nanomaterials formation using metal organic asprecurs during thermal evaporation CVD process.The formation of V2O5 nanowireand V2O5 nanospheres from two different mechanism:the former comes from thenucleation and growth of VO ion groups which were produced by the decompositionand oxidation of VO(acac)2 powder;the latter were formed directly through thedecomposition of VO(acac)2 powder during the transfer process.(3)VOx nanotubes (VOx-NTs)were prepared by hydrothermal treatment andelectrochemical properties were studied.VOx-NTs were prepared by hydrothermal treatment using V2O5powder,H2O2and dodecylamine/ethanol solution.The relationship between the formation of VOx-NTs and pH value was studied.It revealed that nanosheets and nanobelts withV6O13structure were found under strong acid conditions.Under alkaline conditions,VOx-NTs were formed.However,other products including sheets and belts were alsoobtained.During the hydrothermal treatment process,the pH value is important to theformation of VOx-NTs.On one hand,the creation of V2O5·nH2O sol depends on thepH value;on the other hand,it can influence the dodecylamine's proponation.Thestrong acid conditions disturbed the formation of VOx-NTs.Prolong the stirring time of V2O5·nH2O sol and dodecylamine/ethanol solution,meanwhile increasing the mol ratio of V2O5·nH2O and dodecylamine to 1:1,samplescontained a great deal of VOx-NTs were synthesized.Using V2O5 powder,deionized water and HAD/ethanol solution as source,desirable VOx-NTs were prepared.When the pH value was adjusted as high as 8 or 10,VOx-NTs with several micrometers were synthesized.The results from cyclic voltammograms showed that the Li+ can insert/deinsert inVOx-NTs better than that in the VOxsheet.
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