Controlled Growth And Electrochromic Properties Of Nickel Oxide-based Nanocomposites

Since the 21st century,with the development of science and technology,there were immense amounts of energy has been used,so the energy crisis and environmental pollution problems have become more and more serious.The research and development of energy-saving materials is an important topic in the field of material science development.Electrochromic materials refer to reversible color changes under external electric field,which can realize reversible modulation of absorption and transmission of light of different wavelengths.Because of the electrochromic performance,it has great application prospects in smart windows,anti-glare mirrors,display screens and other fields.It is an important field in the development of energy-saving materials.As a transition metal oxide,nickel oxide is widely used in the fields of electronics,catalysts and batteries.Nickel oxide is also a typical anodic electrochromic material,which has the advantages of low cost,simple preparation method and high optical contrast.However,the current application of nickel oxide materials has the disadvantages of poor cycle stability and long response time,and the color change of nickel oxide materials is not aesthetic.Therefore,how to improve the electrochromic performance of nickel oxide is a subject to be studied by scientific researchers.In this paper,a series of methods are used to improve the electrochromic properties of nickel oxide.In the third chapter,nickel oxide nanosheet thin films and hierarchical structural nickel oxide thin film were prepared by metal-organic framework method.The results show that the nickel oxide films with hierarchical structure have high optical contrast,fast response speed and good cyclic stability,while the dense structural nanosheet thin film have poor electrochromic performance compared with the hierarchical structural nickel oxide film.The performance analysis shows that the nickel oxide films with graded structure have higher optical contrast(44.2%)and faster electrochromic response(t_b=4s,t_c=3.3s),while the contrast of the dense nickel oxide films is 31.13%,the coloring time is 13.7s and the fading time is 4.5s.In the fourth chapter,nickel oxide nanotubes with hierarchical structure were prepared by chemical bath deposition combined with zinc oxide nanorod template.By analyzing the electrochromic properties of the samples,it was found that the nickel oxide nanotube arrays with hierarchical structure had higher contrast,faster response speed,higher color efficiency and better cyclic stability than the nickel oxide nanotube arrays.The response speed of nanotube arrays film is(t_c=5.4s,t_b=5.2s),and that of nanosheet films is(t_c=8s,t_b=10s).The color efficiency of nanotube films and nanosheet films are 51 cm~2/C and 22 cm~2/C,respectively.In the fifth chapter,nickel oxide nanowires and nano-sheet films were prepared by hydrothermal method,and the two kinds of film materials were compounded with polyaniline by electrodeposition.Through the analysis of the electrochromic properties of the materials,Ni O nanowires have faster response speed,while Ni O nanosheets have larger optical contrast.The electrochromic properties of two kinds of composite materials and PANI films show that the contrast of the two composite films is greater than that of pure polyaniline,and the Ni O nanowires/polyaniline materials have greater contrast and faster response speed.This composite structure material not only embodies the high contrast of nickel oxide material,but also the advantages of polyaniline material,such as fast response speed and rich color.The optical contrast of nickel oxide nanowires/polyaniline composite films is 45%,the colored time is 1.2 s,the bleached time is 1.2 s,and the dyeing efficiency is 134.2 cm~2/C.