Preparation Of Silica Aerogel Composite Material And Research On Its Sensing Performance

Aerogel is a material with ultra-microporous.Because of the characteristics of the three-dimensional microporous network structure,it has many excellent properties,such as low dielectric constant,thermal conductivity,and low acoustic impedance.It has important applications in many fields,such as heat insulation,energy storage,and adsorption catalysis.However,there are still two problems that need to be solved urgently:one is that the application of functional silica is simple,and the other is that silica aerogel has poor mechanical properties due to its brittleness.The research purpose of this subject is to enrich the applicability of silica aerogels and improve their functionality;in addition,the mechanical properties of silica aerogels are improved by specific methods.(1)A solid fluorescent material is prepared,and the solid fluorescent material is composited with a fluorescent probe and a silica aerogel for the detection of formaldehyde.First,a new type of carbazole fluorescent probe was designed and synthesized,and the probe molecule was effectively grafted onto silica aerogel.The structure of the silica aerogel and its composite materials was determined by measuring the molecular structure of the probe by hydrogen NMR spectroscopy,Fourier transform infrared spectroscopy and photoelectron spectroscopy.Fluorescence spectrophotometer and ultraviolet-visible light spectroscopy were used to determine the optical properties of the probe molecules.Finally,a scanning electron microscope was used to determine the microscopic morphology of the silica aerogel and its composite materials.The results show that the prepared silica aerogel loaded with fluorescent probes has an average pore diameter of 16 nm,a specific surface area of 779.96 m²·g^-1,and a porosity>95.6%,which has good gas absorption properties.According to the UV absorption test,the grafting rate of the probe molecule was determined to be about 122 mg?cm^-3.The composite material can not only avoid the fluorescence quenching caused by the aggregation of probe molecules,but also the fluorescent aerogel sensor can detect formaldehyde solution and gas selectively and sensitively under optical conditions,and the minimum concentration of formaldehyde detected in the liquid is determined to be 10^-5mol·L^-1,the detection limit for formaldehyde gas is 110 ppm.The composite fluorescent aerogel is expected to be used in the actual operation of formaldehyde detection.(2)A conductive material is prepared,which is a composite of carbon fiber powder and flexible silica aerogel for pressure sensing.First,methyltrimethoxysilane(MTMS)and dimethyldimethoxysilane(DMDMS)are used as co-precursors,and then a flexible aerogel is synthesized by a one-pot method.When the co-precursor is hydrolyzed,modified carbon fiber powder(200 mesh)is added so that the carbon fiber powder can be compounded with flexible silica aerogel.Fourier transform infrared spectroscopy and scanning electron microscopy were used to determine the chemical structure and microscopic morphology of the flexible aerogel and its carbon fiber composite materials.The thermal stability,electrical conductivity and compression cycle performance of the flexible aerogel and its carbon fiber composite materials were tested by thermogravimetric analysis,electrochemistry and compressor.The results show that when the volume ratio of MTMS/DMDMS is 3:2,the thermal stability is the best.The conductive aerogel can not only achieve 50%deformation,but also can be cycled many times.Moreover,the rapid change of resistance can be monitored through electrochemical testing,so as to realize pressure sensing.