| Silica aerogel is a kind of solid nano material with air in the microstructure.Silica aerogel has high porosity,specific surface area,low thermal conductivity,low phonon rate,low refraction rate,ect,which makes it different from conventional solid materials.However,silica aerogel is brittle due to the low elastic modulus,which limits its wide application.Moreover,the traditional supercritical drying of silica aerogel is not only costly and dangerous,but also difficult to achieve mass production.The optimum process of silica aerogel by using ambient pressure drying was investigated in the thesis.The silica aerogel was in-situ loaded on the basalt needle-punched felt,and the modification with graphene oxide?GO?and titanium oxide?TiO2?was studied.By acid-base two step and sol-gel methods,tetraethoxysilane?TEOS?as a precursor was used to make a silica gel.After gelling,aging and solvent exchange,the gel was hydrophobically modified with trimethylchlorosilane?TMCS?.Subsequently,the gel was dried in ambient pressure condition.The chemical structure,morphology and thermal stability of silica aerogel were characterized.The influence of different factors on the properties of silica aerogel was investigated and the optimum technological condition was determined.The result shows that the silica aerogel can be quickly prepared at the optimum ratio of n?TEOS?:n?EtOH?:n?H2O?:n?NH4·H2O?:n?HCl?=1:4:7:1.25×10-3:8.75×10-3.The silica aerogel with the density of 0.116g/cm3,the porosity of 94.73%and the thermal conductivity of 0.0245 W/?m·K?is obtained.The silica aerogel/basalt needle-punched felts?SBF?were prepared by the in-situ growing of silica on basalt needle-punched felt.The effects of the ratio of alcohol to silicon and the ratio of water to silicon on the properties of SBF,such as contact angle,thermal stability,thermal conductivity,mechanical properties,acoustic absorption coefficient,etc,were studied.The results show that the SBF with high porosity,low density,good thermal stability and sound insulation can be quickly prepared at the optimum ratio of n?TEOS?:n?ethanol?:n?H2O?=1:8:7.The loading of hydrophobic silica aerogels improves the mechanical properties?maximum 2.46MPa?and hydrophobicity?contact angle of 136°?,and decreases its thermal conductivity(the lowest is 0.045W/?m K?of SBF.When the ratio of alcohol to silicon increases,the thermal conductivity,mechanical property and hydrophobicity of SBF decrease.With the increasing of the ratio of water to silicon,the thermal conductivity and mechanical properties of SBF decrease,whereas the hydrophobicity slightly increases.The graphene oxide?GO?/SiO2 aerogel/basalt fiber felts?GO/SBF?were prepared by doping GO into SiO2 aerogel/basalt fiber felts?SBF?.The influence of GO doping content on the thermal conductivity,hydrophobicity,adsorption,mechanical properties and acoustic absorption coefficient of the GO/SBF was studied.Compared with SBF,the GO/SBF has a superior thermal conductivity.The GO/SBF changes from hydrophobic to hydrophilic at the2%GO doping content,which is attributed to the good thermal conductivity and strong hydrophilicity of functional groups of GO.In addition,the amount of GO has a certain influence on the mechanical properties of SBF.With the increase of GO content,the mechanical properties increase first and then decrease.With doping 1%GO,the tensile stress of the GO/SBF increases 97%and reaches the maximum value of 2.66MPa.It is mainly attributed to the good mechanical properties of GO.With the increase of GO content,the mechanical properties of the GO/SBF begin to decrease because of stress concentration of uneven dispersion of GO.The adsorption property of the GO/SBF improves owing to the addition of GO.For GO/SBF with 6%GO doping,the maximum adsorption capacity to methylene blue attains 4.88mg/g.Besides,the adsorption kinetics of the GO/SBF can be better described by the pseudo-second order mechanism.Compared with SBF,the GO/SBF shows a superior acoustic absorption performance at 1800-4000Hz owing to the doping of GO and the optimum content of GO is 6%.The TiO2/SBF and TiO2/GO/SBF were prepared with doping TiO2 into SBF and GO/SBF,respectively.The effect of TiO2 doping on the hydrophobicity,thermal conductivity,adsorption properties and mechanical properties of TiO2/SBF and TiO2/GO/SBF was studied.The result shows that the prepared TiO2/SBF and TiO2/GO/SBF possess excellent hydrophobicity and good thermal stability,and are suitable for use in high temperature environment.The TiO2/SBF has an increase in thermal conductivity compared with SBF.The mechanical stress of the TiO2/SBF with 3%TiO2 doping increases 25.2%.Compared with single doped SBF?TiO2/SBF or GO/SBF?,the thermal conductivity of the TiO2/GO/SBF decreases,whereas the mechanical properties increases at a small proportion of Ti O2.The adsorption of the Ti O2/GO/SBF on methylene blue improves after co-doping.The adsorption capacity of the TiO2/GO/SBF with 2%TiO2/4%GO is 4.85 mg/g and the removal rate is 97.56mg/g.Moreover,the pseudo-second order adsorption model is applicable to the adsorption kinetics by the TiO2/GO/SBF.The TiO2/SBF and TiO2/GO/SBF have good sound absorption properties.The acoustic absorption coefficients of the TiO2/SBF and TiO2/GO/SBF reduce in1800-4000Hz and increase in 4000-6300Hz of the addition of TiO2,respectively,indicating that TiO2 can improve the sound acoustic coefficient of the TiO2/SBF and TiO2/GO/SBF in the high frequency region. |
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