| Recently, alumina membranes have been extensively investigated because of theirhigh thermal and chemical stability, long lifetime, so alumina membranes have greatapplication fieldsand market prospects. Recent years, alumina membranes with thermal stability in the higher temperature aredemanded for the development of gas separated, petrochemical industry andhigh-temperature catalysis. Therefore, thermal stability has attracted more and moreattention for alumina membranes. The alumina membranes were synthesized by a sol-gel process, which doped Y,Nd,PVA,Ce. The thesis has studied that the dopants impact on the thermal stability of thealumina membranes. Because silicon dioxide membrane is still stable amorphous state in thermodynamicsat 900℃, and itself inherent chemical property, therefore silicon dioxide membrane hasmore superiority and research value in some fields such as: adsorption and catalysis as thecarrier of the catalyst. While preparation of silicon dioxide membrane by sol-gel, differentpreparation conditions will make the difference of microstructure performance. Theresearches show that: choose C2H5OH/TEOS=0.8-1.2, H2O/TEOS=6. 8-10, HNO3/TEOS=0.12, RefluxH2 /TEOS=30, which can get the silicon dioxide membrane with relatively Obetter microstructure. While alumina inorganic membranes are prepared by Sol-Gel, the results indicate thatgenerally choose to use nitric acid as the peptizing agent, nitric acid consumption in0.25~0.30, adds water for 100, hydrolysis temperature for 80℃, reflow time for10h, whichcan get the alumina membrane with relatively better microstructure. When researchesabout doped alumina membranes, XRD shows that the phase constitution of pure aluminamembrane and the alumina membranes which doped PVA,Y,Nd,Ce is the same whenfritting temperature under 1000℃,theirs phase constitutions are ?-AlOOH (400℃),?-Al2O3 (400~1000℃), respectively. When fritting temperature at 1150℃, the phaseconstitutions of pure alumina membrane and the alumina membranes which doped PVA orCe is a-Al2O3,however the alumina membrane doped Y or Nd are ?-Al2O3 and a- Al2O3.DTA and TG show that the volatilizing of moisture in the sol before 500℃, there is noobvious hot change among 500-1000℃. Above 1150℃, the strong crystallization Iphenomenon takes place in the alumina membrane which pure alumina membrane and thealumina membranes which doped PVA or Ce. it does not take place in the aluminamembrane which doped Y or Nd. IR shows that: the alumina membrane is formed by Al-Onetwork. Studies about microstructure have shown that doped PVA, Y, Nd can improveperformance of alumina membrane , but doped PVA or Ce can not improve performanceof alumina membrane when are used in the high temperature. The composite membrane has different absorbing and catalysis of surface, besidesgenerality separability, therefore the composite membrane has better properties and widerapplication. The thesis have studied that surface performance of composite system was improvedby utilizing catalysis characteristic of Al2O3 and surface modify of SiO2. Al2O3-SiO2, andthe composite membrane is prepared by Sol-Gel. The results show that the compositemembrane with different ratio of Al2O3 to SiO2 is composed of amorphous matter oramorphous matter and ?-Al2O3. When rising of fritting temperature, the phase constitutionof the composite membrane with mullite composition is ?-AlOOH and ?-Al2O3 at 400℃,?-Al2O3 at 550℃ to 1150℃, ?-Al2O3 and a-Al2O3 at 1220℃, mullite and a-Al2O3 at1300℃. The composite membrane has high thermal stability. The composite membrane isform by Si-O and Al-O network, when the temperature of fritting is lower than 1100℃,the chemical reaction has not taken place between SiO2 and Al2O3. Performance ofcomposite membrane is better than pure alumina membrane and pure silicon membrane.
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