Preparation And Performance Study Of TiO₂/cellulose Aerogel Composite Multifunctional Thermal Insulation Material

Cellulose aerogel,due to strong heat insulation,easy degradation and good biocompatibility,exhibits a wide range of potential applications in metallurgical insulation,building energy conservation and otherr fields.Studies have shown that by combining cellulose aerogel and the functional material nano-TiO2,excellent flame mechanical properties,pliotocatalysis and retardancy can be obtained.However,the controllable preparation and intrinsic mechanism of nano-TiO2/cellulose aerogel are unclear,which limits its further development and application in the insulation and energy saving field.In this work,the nanowire,nanosheet and nanoparticle anatase nano-TiO2/cellulose aerogel composites were designed and synthesized based on first principles and thermodynamics theory,and doe composite material's properties were analyzed in detail by various testing methods.The mechanics and thermal insulation properties of the composite materials were tested through various test methods,the photocatalytic and flame-retardant mechaaisms of dye materials were discussed,and the following conclusions were obtained:(1)A sol-get process was carried out with different concentrations of nanocellulose hydrogels,determining optimal parameters of cellulose aerogel using a supercritical CO2 drying temperature of 4O?,with pressure at 12 MPa,for 120 minutes.Analysis of the structure and chaxacteristics of different concentrations of cellulose aerogel were obtained,with an increase of nano-cellulose concentration,airgeI pore size distribution tends to be more uniform,with improved porosity,surface area,density and mechanical properties.In addition,with an increase in thermal insulation,performance is further enhanced.When a concentration of cellulose airgeI of 3.5%,cellulose aerogels shrinkage and weight loss ratio no longer changed in the process;having a porous three-dimensional network structure,an average pore size of 19 nm,the maximum adsorption capacity is 432.43 cm3/g,and the specific surface area is 316.10 m2/g,the compressive strength and compressive modulus are 0.52 MPa and 2.02 MPa;at 25?,the thermal conductivity is 0.0333 W/(m·K).(2)Nano-TiO2 modification can effectively increase the specific surface area of cellulose acrogel,increase its total pore volume and average pore size,and improve the mechanical properties and thermal insulation properties of cellulose aerogel.Among the three different morphologies of nanowires,nanosheets and nanoparticles,TiO2 nanopartic.les/cellulose aerogel can obtain the largest specific surface area.The average pore size is 26 nm,the maximum adsorption capacity is 466.41 cm3/g,and the specific surface area is 427.62 m2/g;its transverse compressive strength and compressive modulus are 1.18 MPa and 4,55 MOa;at 25?,the thermal conductivity is 0.0243 W/(m·K).(3)Nano-TiO2/cellulose aerogel has good photocatalytic sterilization function and formaldehyde degradation function.For Escherichia coli,Staphylococcus aureus,Yeast and Candida albicans,TiO2 nanoparticle/cellulose aerogel has the best bactericidal performance against these four bacteria.After photocatalysis for 30 min,the bactericidal rate of TiO2 nanoparticle/cellulose aerogel against Escherichia coli and Staphylococcus aureus reached 100%;after photocatalysis for 100 min,the bactericidal rate of TiO2 nanoparticle/cellulose aerogel to Yeast and Candida albicans reached 100%,Among the three different morphologies of nanowires,nanosheets and nanoparticles,the TiO2 nanoparticle/cellulose aerogel has the best formaldehyde degradation performance.After 120 minutes of experimental photocatalysis,the degradation rate of formaldehyde by TiO2 nanoparticle/cellulose aerogel can reach 83%.The photocatal.ytic mechanism is further revealed by the energy band theory.(4)Among the three different morphologies of nanowires,nanosheets and nanoparticles,TiO2 nanoparticle/cellulose aerogel has the best thermal stability and its decomposition temperature is 332.2 ?.The nano TiO2/cellulose aerogels with different morphologies were evaluated for fire rating.The TiO2 nanoparticle/cellulose aerogels have the highest combustion performance level,reaching V-0 and LOI>32%,Compared with unmodified cellulose aerogel,the parameters such as heat release peak and total heat release of TiO2 nanoparticle/cellulosc acrogel decreased significantly.The thermodynamic process of thermal degradation of TiO2/cellulose aerogels with different morphologies was studied by using Kissinger and Ozawa-Flynn-Wall methods,The flame retardant mechanism of nano-TiO2/cellulose aerogels was revealed and the best doping concentration of the TiO2 nanoparticles was 10 wt.%.