Das R K, Das M
Department of Physics, Saroj Mohan Institute of Technology, Guptipara, Hooghly 712512, West Bengal, India.
Department of Nanoscience and Technology, JIS College of Engineering, Kalyani, Nadia 741235, West Bengal, India.
Ultrason Sonochem. 2015 Sep;26:210-217. doi: 10.1016/j.ultsonch.2014.11.018. Epub 2014 Dec 2.
The effects of both acid (acetic acid) and base (ammonia) catalysts in varying on the sol-gel synthesis of SiO2 nanoparticles using tetra ethyl ortho silicate (TEOS) as a precursor was determined by ultrasonic method. The ultrasonic velocity was received by pulsar receiver. The ultrasonic velocity in the sol and the parameter ΔT (time difference between the original pulse and first back wall echo of the sol) was varied with time of gelation. The graphs of ln[ln1/ΔT] vs ln(t), indicate two region - nonlinear region and a linear region. The time corresponds to the point at which the non-linear region change to linear region is considered as gel time for the respective solutions. Gelation time is found to be dependent on the concentration and types of catalyst and is found from the graphs based on Avrami equation. The rate of condensation is found to be faster for base catalyst. The gelation process was also characterized by viscosity measurement. Normal sol-gel process was also carried out along with the ultrasonic one to compare the effectiveness of ultrasonic. The silica gel was calcined and the powdered sample was characterized with scanning electron microscopy, energy dispersive spectra, X-ray diffractogram, and FTIR spectroscopy.
采用超声波法测定了酸（乙酸）和碱（氨）催化剂对以正硅酸乙酯（TEOS）为前驱体溶胶 - 凝胶法合成SiO₂纳米颗粒的影响。超声波速度由脉冲星接收器接收。溶胶中的超声波速度和参数ΔT（溶胶原始脉冲与第一个后壁回波之间的时间差）随凝胶化时间而变化。ln[ln1/ΔT]对ln(t)的曲线表明有两个区域——非线性区域和线性区域。对应于非线性区域转变为线性区域的时间点被视为相应溶液的凝胶时间。发现凝胶化时间取决于催化剂的浓度和类型，并基于阿弗拉米方程从图表中得出。发现碱催化剂的缩合速率更快。凝胶化过程还通过粘度测量进行表征。同时进行了常规溶胶 - 凝胶过程和超声过程以比较超声的效果。对硅胶进行煅烧，并用扫描电子显微镜、能量色散光谱、X射线衍射图和傅里叶变换红外光谱对粉末样品进行表征。
