Controllable Preparation And Pferformance Of Infrared Transmittance Materials

Far-infrared materials have attracted a lot of attention with thedevelopment of infrared technology and nano materials. Transition metalchalcogenides （e.g., ZnS and ZnSe） are widely used as infrared transmittancematerials because of their excellent optical performances. As one of mature farinfrared materials, ZnS and ZnSe are used as infrared window and fairingmaterials with the form of polycrystalline made by the hot pressing technology.Properties of hot pressing polycrystalline materials are determined by those ofraw material powder. Therefore, it is an important and necessary issue todevelop novel synthesis routes to prepare raw materials,which meet therequirement of the industrial applications.An effective and simple method have been developed to preparenanomaterials with narrow size distribution, which involves separatenucleation and aging steps （SNAS method）. This method has been successfully employed to produce inorganic nanomaterials in the laboratoryand the industry.In this thesis, ZnS nanoparticles, Cu²⁺doped-ZnS （ZnS:Cu） nanoparticlesand hexagonal ZnSe nanoflakes were prepared by the SNAS method. Besides,cubical ZnSe nanoclusters were synthesized by chemical precipitation. Theseinvestigated materials were systematically characterized in the aspects ofstructure, composition, properties and infrared performances using varioustechniques such as XRD, SEM and IR.The cubic ZnS samples, prepared with the S^2-ions concentration of1.1Mand aged for8h, have small particle size of ca.3nm, narrow size distributionand high infrared transmittance. However, crystal structure of the obtainednanoparticles is unstable under the high temperature condition. Hence, dopingCu²⁺ions modification was employed to solve this problem. All obtainedZnS:Cu nanoparticles are cubic phase and Cu²⁺ions effectively adjust particlesize, inhibit phase transformation and improve infrared transmittanceproperties. When0.5%Cu²⁺was doped, the infrared transmittance reachesbeyond90%in3¹4μm.The cubical ZnSe nanoclusters, synthesized with the Zn（NO₃）₂to SeO₂ration of1.0and the reaction solution pH of11.0, have high purity andexcellent infrared transparency of85%in2.5²5μm. Besides, the precursorsof hexagonal ZnSe nanoflakes prepared by the SNAS method are ZnSe N₂H₄,which were annealed in nitrogen at high temperature for1h to obtain ZnSe nanoflakes. The flakelike nanoparticles of ZnSe precursors are prepared onlywith excessive Zn2+cations. Moreover, there is an optimal addition amount ofsurfactant diethanolamine, which alters the surface flatness of ZnSe precursornanoflakes. The infrared transmittance of ZnSe annealed at700℃for itsprecursors is above92%in2.5²5μm, higher than the commercially requiredvalue of69%for an optical window.