摘要
以Na_2SiO_3为前驱物,研究了碳化合成纳米SiO_2颗粒比表面积的控制机理.正交实验结果表明,影响其比表面积的次序为Na_2SiO_3浓度>PEG6000添加量>反应温度>CO_2/N_2混合气流量.当反应温度80℃、Na_2SiO_3浓度40g/L、PEG60004g/L、CO_2/N_2混合气流量1.2L/min时,所制SiO_2颗粒的比表面积为318.9m^2/g.随Na_2SiO_3浓度增大,SiO_2胶粒在pH>7的碳化液中Ostwald凝聚生长过程相对延长,颗粒的一次粒径增大,比表面积却随之减小.由于温度对SiO_2溶解度和胶粒Brownian运动的影响,降低反应温度可促进SiO_2成核、减少Si(OH)_4和≡SiOSi(OH)_3的聚合,SiO_2颗粒的比表积增大.添加剂PEG6000的空间架构效应抑制纳米SiO_2颗粒团聚,从而促进SiO_2颗粒比表面积增大;但当其浓度大于7g/L时,Na_2SiO_3分子进入缠绕着的PEG长链架构内部,所得SiO_2颗粒比表面积有所降低.
Using sodium silicate as precursor,the controlling mechanism of specific surface area（S_（BET）） of silica nanoparticles synthesized by carbonation process was investigated.The results of orthogonal experiments demonstrated that the order of factors affecting S_（BET） was：sodium silicate concentrationadded mass of PEG6000reactive temperatureflow rate of CO_2/N_2 mixed gas.Under the optimal conditions of concentration of sodium silicate at 40 g/L,added mass of PEG6000 4 g/L,reactive temperature 80℃,and flow rate of CO_2/N_2 mixed gas 1.2 L/min,silica nanoparticles synthesized exhibited a high S_（BET） of 318.9 m^2/g.With the increase of concentration of sodium silicate,the size of primary particles increased,but S_（BET） of silica particles decreased due to extension of Ostwald ripening process of SiO_2 sol in the carbonation solution where pH7.Due to the effect of temperature on the solubility and Brownian motion of SiO_2 sol,the decrease of reaction temperature could accelerate the nucleation of silica and restrain the agglomeration of Si（OH）_4 and ≡ SiOSi（OH）_3,therefore the S_（BET） increased.The increase of S_（BET） was facilitated by PEG6000 due to its steric hinderance effect.However,when PEG6000 in solution exceeded to 7 g/L,the precursor molecules entered into the PEG with tangled long chain,the S_（BET） of synthesized silica nanoparticles would be decreased.
出处
《过程工程学报》
CAS
CSCD
北大核心
2010年第4期795-801,共7页
The Chinese Journal of Process Engineering
基金
国家自然科学基金资助项目(编号:20976181)
关键词
碳化反应
SiO2纳米颗粒
比表面积
控制机理
carbonation
silica nanoparticles
specific surface area
mechanism controlling
