Preparation Of Tungsten Bronze By One-step Ball Milling And Its Application In Heat-insulating Glass

Tungsten bronze（M_xWO₃,M=Cs,NH₄,K,Na,Li,H,Rb,etc.）materials are a class of non-stoichiometric compounds with abundant crystal structures,tunneling structures and special valence conditions.The large number of free carriers contained in the tunneling structure of tungsten bronze will oscillate at particular wavelength to generate local surface plasmon resonance（LSPR）effect,and the interconversion of W⁵⁺-W⁶⁺will generate small polariton effect.The synergistic action of the above two effects makes tungsten bronze materials exhibit great near-infrared（NIR）absorption properties,which promotes the widely use of tungsten bronze materials in the fields of photochromism,NIR shielding,photocatalysis and gas sensing fields.Among various tungsten bronze materials,hexagonal Cs_0.32WO₃material,which has the advantages of wider NIR absorption range,better NIR shielding capacity and cheaper price,has received much more attentions.Up to now,researchers have explored various methods to prepare Cs_0.32WO₃.Benefiting from the controllable particle size and morphology,hydrothermal method has become one of the most common methods to prepare Cs_0.32WO₃nanoparticles.However,its practical production application has been greatly hindered because of low yield,long reaction period,high reaction temperature and high waste liquid discharge.In contrast,the ball milling method is a solid-solid reaction with the advantages of low pollution,low cost and simple operation,which mainly relies on the strong mechanical force to the raw materials.Therefore,the ball milling method has become a more suitable preparation method for large-scale production of Cs_0.32WO₃.However,there are only few related studies on the mechanism of ball milling reaction and property regulation have been reported.Based on the above discussions,Cs_0.32WO₃was prepared by a one-step ball milling method,and the preparation mechanism and properties of the Cs_0.32WO₃products have been optimized systematically.Furthermore,the small polarizer effect and LSPR effect have been modulated to further optimize the optical performances of the Cs_0.32WO₃products.The specific research contents of this paper include the following three parts.1.Feasibility study on the preparation of Cs_0.32WO₃by one-step ball milling method.In this chapter,glucose,oxalic acid,ascorbic acid and cellulose were used as reducing agents to study the feasibility of preparing Cs_0.32WO₃powder by one-step ball milling method.Meanwhile,the optical properties of Cs_0.32WO₃products prepared with different reducing agents were characterized and the reducing agent with the best reducing performance has been screened out.Compared with oxalic acid,glucose and ascorbic acid,the cellulose showed better reduction effect during ball milling process,and the prepared Cs_0.32WO₃exhibited the best optical properties.2.Research on the reaction mechanism and performance optimization of Cs_0.32WO₃preparation by one-step ball milling.On the basis of the previous work,this chapter studied the preparation and reaction mechanism of Cs_0.32WO₃by one-step ball milling method with cellulose as reducing agent,and the NIR shielding properties of the products was optimized by controlling various ball milling parameters.In the series of Cs_0.32WO₃samples,the product obtained by ball milling time for 15 h exhibited high visible light transmittance（72.6%）and extremely low NIR light transmittance（5.3%）.Compared with blank glass,the Cs_0.32WO₃glass can effectively reduced the indoor temperature by 11.1℃,which proved that the Cs_0.32WO₃obtained by ball milling reaction for 15 h had great NIR shielding performance and heat insulation capacity.3.Optimization of NIR shielding performance of Cs_0.32WO₃by one-step ball milling method.In order to further enhance the NIR shielding performance of the Cs_0.32WO₃products,a one-step ball milling method with Na BH₄as the reducing agent was used to synergistically modulate the LSPR effect and small polariton effect of the Cs_0.32WO₃.Meanwhile,the modulation mechanism was investigated to characterize the NIR shielding performance of the Cs_0.32WO₃products.It was found that the Cs_0.32WO₃prepared by ball milling time of 9 h had the highest visible light transmittance of 80.1%and the lowest NIR light transmittance of7.9%,and the coated glass could effectively reduce the room temperature by 13.1℃compared to the blank glass.Compared with Cs_0.32WO₃synthesized with cellulose,the Cs_0.32WO₃product prepared with Na BH₄had a wider absorption range in the whole NIR region,and it showed better shielding effect on the shortwave NIR region with higher energy and exhibited excellent practical application potential.In this paper,Cs_0.32WO₃nanoparticles were prepared by a one-step ball milling method with organic weak reducing substance as reducing agent,and the reaction mechanism has been investigated systematically.Besides that,a ball milling method with Na BH₄as the reducing agent was used to simultaneously modulate the LSPR effect and the small polariton effect of Cs_0.32WO₃,which has greatly improved the NIR shielding performance and optical characteristics.In general,the investigations of the reaction mechanism and optical performance optimization in this paper have certain reference significance for the preparation of other nanomaterials by the one-step ball milling method.