The sol-gel route via sodium silicate precursor is known as a practical synthesis method to prepare silica gels in a cost effective way. In the current research, rheological properties of the synthesized silica gels were investigated at different pH values. The gelation time (t_gel) was determined from the rheological measurements at different frequencies of 0.1, 0.3 and 0.5 Hz. The results were analyzed using rheological equations of state and the concept of the gelation point was discussed. The results revealed that t_gel increases by increasing the pH value. Moreover, it was proved that the fractal value (d_f) is dependent on the pH value. The relaxation exponent (Δ) value was measured as 0 < Δ < 1/2, which shows that the gel system follows the non-stoichiometrically balanced reactions. Finally, it was shown that the gelation process is divided into three stages, namely, induction, gelation and over curing. The results revealed that by increasing the pH value, stage I is extended while stage II is diminished.

通过硅酸钠前体的溶胶-凝胶途径是一种以成本有效的方式制备硅胶的实用合成方法。在当前的研究中，研究了在不同pH值下合成硅胶的流变特性。由流变学测量在0.1、0.3和0.5Hz的不同频率下确定胶凝时间（t _gel）。使用状态流变方程分析了结果，并讨论了胶凝点的概念。结果表明，t_凝胶通过增加pH值而增加。此外，证明了分形值（d _f）取决于pH值。测量松弛指数（Δ）值为0 <Δ<1/2，这表明凝胶体系遵循非化学计量平衡的反应。最后，表明了胶凝过程分为三个阶段，即诱导，胶凝和过度固化。结果表明，通过增加pH值，阶段I延长而阶段II减少。