Ball Milling Synthesis,Characterization And Properties Of VO₂(M) And W-doped VO₂(M) Nanoparticles

Monoclinic vanadium dioxide(VO₂(M))exhibits a kind of phase transition material,which can be induced by external heat,light,electricity and force to undergo a reversible phase transition,accompanied with abrupt change in electrical and optical properties.Based on the unique phase change characteristics of VO₂(M),it can be widely used in laser protection,intelligent window,temperature control switch and other fields.Since Morin first reported the phase transformation properties of VO₂(M)in 1959,VO₂(M)has been extensively studied.A large number of methods have been explored to prepare VO₂(M).Among them,the hydrothermal method has been widely used due to its precise control of phase,high crystallinity,controllable particle size,etc.However,it has long reaction time,reaction temperature and waste fluid,which hinders its practical application.Ball-milling technique is regarded as a new and potential preparation method to prepare VO₂(M)due to its solid-solid reaction,low pollution,high yield and short processing time.However,there are few relevant researches at present.In view of this,we use ball-milling method to prepare VO₂(M),optimize preparation process and explore the preparation mechanism of VO₂(M).Furthermore,W doping is used to lower the phase transition temperature of VO₂(M).The specific research contents include:(1)VO₂(M)was prepared by ball milling,and the two-step method to prepare VO₂(M)and one-step ball milling to prepare VO₂(M)were compared.The mechanism and process were discussed.By adjusting the parameters of ball milling and annealing,VO₂(M)can be prepared with different phase,particle size,dispersity and crystallinity.However,due to the need of high temperature annealing treatment,the sample particle size is larger and the agglomeration is serious,which seriously affects the optical properties of VO₂(M).(2)The tungsten doped VO₂(M)was prepared by ball milling,and the phase transition temperature of VO₂(M)was reduced by tungsten doping on the basis of one-step ball milling to prepare VO₂(M).However,the doping efficiency of ball milling alone is low,which can not effectively reduce the phase transition temperature of VO₂(M).Therefore,the doping effect of ball milling is improved by low temperature treatment(300 ^oC).Finally,VO₂(M)composite film with excellent performance is obtained.When T_lum is 44.18%,?T_sol is 9.64%,and T_c is maintained at about 42 ^oC.However,compared with hydrothermal doping,the doping efficiency of ball milling is still low,which needs to be further improved.