Combustion Synthesis And Property Of LaB₆ Nanopowders For Thermal Insulation Glass

Nowadays,the heat loss in glass doors and windows for buildings and automobiles is nearly 50%,and more and more insulation materials are becoming a hot research topic today.Nano-lanthanum hexaboride has a good shielding rate in the strong near-infrared light region of 760-1500 nm,and the transmittance can be as low as 10%,which can be a good heat insulation material.In order to solve these problems of high temperature and high pressure,protective atmosphere and long preparation period in the current synthesis method of nano-lanthanum hexaboride,this paper proposes to use the solution combustion method to synthesize nano-lanthanum hexaboride.One-step synthesis of lanthanum hexaboride nanopowders by selecting fuels with high reduction capacity,high heat release and low outgassing-glycine,carbazide and ethylene glycol.And take to regulate the amount of fuel,salt content,ignition method,combustion method and boron powder particle size to explore the best process of synthesizing lanthanum hexaboride nanopowder,and study of powder phase,morphology and particle size distribution under various influencing conditions using X-ray diffractometer,field emission electron microscope,particle size analysis and other characterization tools;Testing the near infrared light shielding performance and thermal insulation of powder coatings by visible-ultraviolet-near infrared spectrophotometer and thermal insulation film temperature tester.The research results show that lanthanum hexaboride powders can be synthesized in one step by combustion synthesis under three fuels with different salt contents,ignition methods,combustion methods and boron powder particle sizes;1.LaB₆ powder with an average particle size of 81.23 nm can be synthesized by solution combustion in a muffle furnace under the conditions of glycine-lanthanum nitrate system,when the fuel amountα=0.32 and salt content X=0;The increase of fuel promotes the transformation of crystalline shape to sphere-like shape and decreases the particle size,while all other conditions cause the transformation of crystalline shape to cubic shape and increase the particle size.The best shielding effect was achieved underα=0.32 with the lowest transmittance of 5.87%under different fuel amounts,and the near infrared shielding performance of the coating prepared withα=0.32 and micro-nano boron powder as boron source was found to be excellent under other conditions with the lowest near infrared transmittance of 4.89%;The powder prepared with the best shielding conditions was used for coating preparation,and the temperature difference between the glass coated with LaB₆ and the blank glass reached 20.6°C.2.Powder with an average particle size of 82.98 nm（α=0.32,X=0）can be synthesized by ignition in a muffle furnace using the solid-phase combustion method under the condition of carbonylhydrazine-lanthanum nitrate system;The increase of fuel promotes the transformation of crystal shape to sphere-like shape and the decrease of grain size,and the solid phase combustion promotes the transformation of crystal shape to sphere-like shape and the reduction of grain size to 100 nm,and the salt blocking effect can slightly reduce the powder grain size,and the other conditions have a small reduction of grain size but the crystal shape is still cubic;The best near infrared shielding effect was achieved underα=0.32 with the lowest transmittance of 5.65%,and the near infrared shielding performance of the coating prepared byα=0.32 and solid phase combustion synthesis was found to be excellent under other conditions with the lowest near infrared transmittance of 5.84%.Temperature difference between glass coated with LaB₆ and blank glass up to 22.5°C.3.LaB₆ powder with an average particle size of 94.76 nm（α=0.32,salt content X=0）can be synthesized by ignition in a muffle furnace under the conditions of ethylene glycol-lanthanum nitrate system using the solution combustion method;The increase of fuel promotes the transformation of crystalline shape to sphere-like shape and the decrease of particle size,while all other conditions promote the transformation of crystalline shape to cubic shape making the particle size larger than 100 nm;The best infrared shielding shielding effect was achieved underα=0.64 with the lowest transmittance of 5.92%,and the comparison under other conditions revealed that the infrared shielding shielding performance of the coating prepared withα=0.32 and the powder synthesized under micro-nano boron powder was excellent with the lowest infrared shielding transmittance of 7.2%;The temperature difference between the glass coated with La B6 and the blank glass was up to 20.8°C.In conclusion,this paper proposes a one-step synthesis method of lanthanum hexaboride powder,which can effectively synthesize lanthanum hexaboride nanopowders with simple operation,energy saving and high efficiency,and easy to industrialize production.And it was found that the best thermal insulation performance of lanthanum hexaboride nanocoatings could reach 22.5℃.