Synthesis Of Several Silicon-nitrogen Containing Aerogels And Their Thermal Insulation And Flame Retardant Properties

As a new type of nano-materials,aerogels have the advantages of large specific surface area,high porosity,low thermal conductivity,low relative density,and environmental friendliness.Energy storage,electroc hemistry and aerospace have huge application prospects,and have aroused widespread concern in the academic circle.Therefore,aerogel is the best choice for insulation materials.however,organic aerogels are flammable,and inorganic aerogels have the disadvantages of poor mechanical properties,which limits their practical application to a large extent.how to make aerogel materials have good mechanical properties and at the same time improve their thermal insulation and flame retardant properties has become a hot spot for researchers.This paper starts with improving the thermal insulation and flame retardant performance and mechanical properties of aerogel.This paper uses natural environmental protection and low cost inorganic nanomaterials combined with different types of aerogel through reasonable experimental design,and regulate the pore performance,flame retardant chemical composition and the amount of inorganic substances added to the aerogel materials,several new aerogel organic-inorganic polymeric materials were prepared,and their mechanical properties and thermal insulation and flame retardant properties were investigated.The systematic research also provides new research ideas and basic data for the development of new aero gel materials and their practical production and application in the field of thermal insulation and flame retardancy.The main research content of t his article is divided into three parts:（1）Take methyltrimethoxysilane（MTMS）and dimethyldimethoxysilane（DMDMS）as monomers at a ratio of 3:2,using cetyltrimethylammonium bromide（CTAC）as the Surfactant,through the hydrolysis reaction,produces a silicone aerogel（SEA-1）that is flexible like"marshmallow".The synthesis process is a typical one-pot reaction,and the surface is self-assembled with MgCl₂ and NaOH（LBL）to obtain the modified aerogel（SEA-2）.The structure and morphology of SEA-1 are thermally stable.The performance,mechanical properties,hydrophobic properties and thermal insulation and flame retardant properties were characterized and compared.The thermal insulation properties of SEA-1 and SEA-2 at normal temperature and pressure were discussed and the flame retardant mechanism of SEA was analyzed.The temperature in TGA test was 500℃Previously showed excellent thermal stability,SEA-2 can maintain its original shape after hammer calorimetric combustion.During the research,it was found that SEAs had better thermal insulation performance and self-floatin gability,and further hydrophobic modification was carried out for various c haracterization of solar evaporation.It was found that 82.7%evaporation efficiency can be achieved in one sun.（2）Using natural polymer chitosan（CTS）as raw material,glutaraldehyde as cross-linking agent,and adding different proportions of inorganic claymineral halloysite（HNTs）as natural flame retardants after simple mechanical mixing,The chitosan/halloysite composite aerogel（CSA）was prepared by freeze-drying,and the samples were tested by SEM,TGA,specific surface area（BET）,Raman,thermal imaging,micro combustion calorimetry（MCC）,etc.Characterization was carried out to study its morphology structure,thermal stability,pore size distribution,thermal insulation performance,and the combustion behavior and flame retardant mechanism of CSA were analyzed at normal temperature and pressure.（3）Using cellulose fiber（CNF）as raw material,polyvinyl alcohol（PVA）as adhesive,and melamine（Melamine）as flame retardant,through simple mechanical mixing,a series of good mechanical properties are made by freeze-drying technology,Thermal insulation and flame retardant cellulose composite aerogel（CNF-PVA/ME-x,x=0³0%,ie CNF-PVA/ME-0%,CNF-PVA/ME-10%,CNF-PVA/ME-20%,CNF-PVA/ME-30%）.Through SEM,TEM,TGA,thermal imaging,thermal conductivity,torch combustion experiment,hammer calorimetry and other characterization methods,the morphology,thermal stability,thermal conductivity,flame retardancy and other properties of the cellulose composite aerogel Were studied.The results show that with the increase of melamine,the aerogel morphology appears from sheet,disorder to small pores and honeycomb.The mechanical properties gradually increase up to the maximum data;the thermal conductivity thermal conductivity test isλ=x;after the torch burning experiment,the surface of the sample can be clearly seen to form a carbon protective layer and keep the original sample Appearance;the flame retardant properties of the samples in the hammer calorimetry test increase with the increase of the added amount.