Study On Synthesis Of Al₂O₃-SiO₂Light Porous Hybrid Material By Sol-Gel

With the development of science and technology, a single-component materialscan not meet the actual needs, composite materials is the development trends of modernmaterials. Through compositing of two or more materials, the use of the merits of theparties to make up for deficiencies, can prepared a composite material with excellentperformance. Organic-inorganic hybrid materials is a new field of composite materials.Adding organic functional molecules to the inorganic network, between organic andinorganic components through some chemical bonds, such as hydrogen bonding,covalent and ionic-covalent bond, etc., make the material to achieve thelevel—molecular complex. Organic-inorganic hybrid material combines the merits oforganic and inorganic, owning high thermal stability and many excellent performance inthe mechanical, thermal, optical, electromagnetic, and biology.Porous organic-inorganic hybrid materials with high porosity and permeability ismade of organic components and inorganic components. Common characteristics ofporous materials is low density, high hole rate and surface area, the role of selectivethrough of the gas. Due to the high surface area and molecular or nano-aperture, thesematerials have widely applications, which conducted a lot of research, such as adsorbent,gas storage, sensors, membranes, functional membranes, catalysts and catalyst supports.In addition, these materials can be used according to molecular size for packagingmolecules and separated molecules. Porous materials are widely used in energy,environmental protection, chemical industry, and further development, application andpromotion will bring endless economic and social benefits.In this paper, PDMS contained end of hydroxyl, TEOS and boehmite sol or ethanolsolution of aluminum as raw materials, hydrochloric acid as catalyst by sol-gelsynthesized at50℃light porous PDMS/（SiO₂+Al₂O₃） hybrid materialsand its variousproperties were tested and characterized, the following conclusions: （1） Based on SiO₂-Al₂O₃sol-gel reaction mechanism, synthesis of thePDMS/（SiO₂+Al₂O₃） light porous hybrid materials. Initially identified in theexperimental conditions, prepared light porous PDMS/（SiO₂+Al₂O₃） hybrid material ofthe optimal process parameters were: ethanol as co-solvent, HCl as catalyst, preparedSiO₂-Al₂O₃sol under acidic conditions. n （H₂O）/n （TEOS）=3, n （ethanol）/n （TEOS）=3,pH=2.0.（2） Sol aging methods on light porous PDMS/（SiO₂+Al₂O₃） hybrid materials havea great effect on strength and crack resistance. In the aging process we should not touchthe samples as much as possible so as to avoid cracking. In the early aging sampleshould be completely closed, later stage puncturing membrane, which is easy to get amore uniform and greater strength gel.（3） Al component have two ways to introduce, boehmite sol and ethanol solutionof aluminum. Using FTIR, SEM, etc. the structure of the hybrid materials is analyzedand characterized. The results show that PDMS/（SiO₂+Al₂O₃） organic-inorganic hybridmaterials adding boehmite sol or alcohol solution formed a network structure bySi-O-Si, Si-O-Al, Al-O-Al. PDMS/（SiO₂+Al₂O₃） hybrid materials added boehmite solare denser, higher shrinkage, and pore size tends to nano-pore. PDMS/（SiO₂+Al₂O₃）hybrid material adding ethanol solution of aluminum have loose and lightweight porousstructure, and strong adsorption of water.（4） In the system regardless of adding formamide or oxalic acid, hybrid materialsare able to form vesicular and fibrous structures. When aluminum addition is5%,PDMS/（SiO₂+Al₂O₃） light porous hybrid material prepared have a certain strength andporous structure. When aluminum addition is8%, PDMS/（SiO₂+Al₂O₃） light poroushybrid material prepared have a certain intensity, showing fiber network structure.（5） By XRD analysis, research shows that light porous PDMS/（SiO₂+Al₂O₃） hybridmaterials are amorphous, after heat treatment hybrid materials is still amorphous.（6） After PDMS/（SiO₂+Al₂O₃） light porous hybrid materials prepared are calcinedat about1000℃, pore structure have not changed much, still maintain high surface areaand porosity. The results show that the hybrid materials have good thermal stability.