Alves Rosa M A, Sanhueza C S S, Santilli C V, Pulcinelli S H, Briois V
Instituto de Quimica/UNESP, P.O. Box 355, CEP 14801-970 Araraquara, SP, Brazil.
J Phys Chem B. 2008 Jul 31;112(30):9006-12. doi: 10.1021/jp803039p. Epub 2008 Jul 2.
A thermostimulated sol-gel transition in a system prepared by mixing a ZrOCl(2) acidified solution to a hot H(2)SO(4) aqueous solution was studied by dynamic rheological measurements and quasi-elastic light scattering. The effect of temperature and of molar ratio R(S) = [Zr]/[SO(4)] on the gelation kinetics was analyzed using the mass fractal aggregate growth model. This study shows that the linear growth of aggregates occurs at the early period of transformation, while bidimensional growth occurs at the advanced stage. The bidimensional growth can be shifted toward monodimensional growth by decreasing the aggregation rate by controlling the temperature and/or molar ratio R(S). EXAFS and Raman results gave evidence that the linear chain growth is supported by covalent sulfate bonding between primary building blocks. At the advanced stage of aggregation, the assembly of linear chains through hydrogen bonding gave rise to the growth of bidimensional particles.
通过动态流变测量和准弹性光散射研究了将ZrOCl₂酸化溶液与热的H₂SO₄水溶液混合制备的体系中的热刺激溶胶-凝胶转变。使用质量分形聚集体生长模型分析了温度和摩尔比R(S)=[Zr]/[SO₄]对凝胶化动力学的影响。该研究表明，聚集体的线性生长发生在转变初期，而二维生长发生在后期。通过控制温度和/或摩尔比R(S)降低聚集速率，可使二维生长向一维生长转变。扩展X射线吸收精细结构（EXAFS）和拉曼结果表明，线性链生长由初级结构单元之间的共价硫酸键支持。在聚集后期，通过氢键作用的线性链组装导致二维颗粒的生长。
