LI Ting ¹ ,DENG Xiangyun ^1,2 ,LI Jianbao ^1,3

（1. Key Laboratory of Ministry of Education for Application Technology of Chemical Materials in Hainan Superior Resources,Hainan Provincial Key Laboratory of Research on Utilization of Si-Zr-Ti Resources, Materials and Chemical Engineering Institute, Hainan University, Haikou 570228; 2. College of Physics and Electronic Information, Tianjin Normal University,Tianjin 300387; 3. Department of Materials Science and Engineering, Tsinghua University, Beijing 100084）

Abstract: Al³⁺ modified silica gel green chemical sand-fixing brick was prepared by aqueous solution of sodium silicate (Na₂O·nSiO₂) and aluminium chloride. ²⁹Si and ²⁷Al MAS NMR spectra, SEM and energy spectrum analysis (SEM -EDS) and hydraulic universal testing machine were used in combination with the experiment to study the structure and mechanical properties of Al³⁺ modified silica gel sand-fixing materials. The results show that the compressive strength of the materials was affected by the concentration of the aluminium chloride and it reaches the maximum at the aluminium chloride concentration of 2mol/L; Al-O quadridentate is more stable than Al-O sexadentate, which was proved by crystal field energy effect, Al-O bond length and bond intension. This was the main reason for mechanical properties changing. In addition, it is supposed that aluminosilicate gel containing -Si-O-Al-O-(Si-O-)₄ groups from the result of atomic ratio of Si/Al was 5:1.

Keywords: Al³⁺ modified silica gel, mechanical strength, nuclear magnetic resonance, energy spectrum analysis