为了提高凝胶的防灭火性能及热稳定性，用光电分析法研究了新型无氨复合凝胶的胶凝特性。采用光电法测出无氨复合凝胶的成胶时间，分析温度对复合凝胶成胶时间影响，并在同环境下对比了普通凝胶和复合凝胶的热稳定性。结果表明，复合凝胶的成胶时间随环境温度的升高而缩短，且环境温度对成胶时间的影响程度与复合胶凝剂的质量分数有关，影响程度为：6%的胶凝剂＞8%的胶凝剂＞10%的胶凝剂。Na₂SiO₃·nH₂O溶液中添加含有多种Lewis酸的复合胶凝剂后，中和了硅酸胶团的电荷，破坏硅酸胶团的融合膜，促使胶粒发生沉聚而转变为有弹性的凝胶，并且复合胶凝剂的粒度为破碎多面体，进而增加了比表面积，增加了吸水量，提高了热稳定性。

In order to improve fire extinguishing properties and thermal stability of gel, the gelation characteristics of ammonia-free compound gel were investigated by photoelectric analysis. The gelling time of ammonia-free compound gel was measured by photoelectric method and the effect of temperature on gelling time of compound gel was analyzed and the thermal stability of plain gel and compound gel were compared with each other in different environments. The results show that the gelling time of compound gel shortens rapidly with temperature increasing and the influence of environmental temperature on the gelling time has a relationship with the mass fraction of compound gel, the degree of influence is that 6% gelatinizing agent＞8% gelatinizing agent＞10% gelatinizing agent. Adding gelling agent composed of varied complex Lewis acid to Na₂SiO₃·nH₂O solution could counteract the charge of the micelle silicate, damage the fusion membrane of the micelle silicate, and promote colloidal particle coagulation in order to convert into full of flexibility. Because the composite gelling agent is crushing polyhedron, the increases of specific surface area and water absorption improve the thermal stability of the gel.