Miteva Svetla, Stoimenova Maria
Institute of Physical Chemistry, Bulgarian Academy of Sciences, "Acad. G. Bonchev" Street, Bl. 11, Sofia 1113, Bulgaria.
J Colloid Interface Sci. 2004 May 15;273(2):490-6. doi: 10.1016/j.jcis.2004.02.030.
This paper presents a detailed analysis of the electro-optic behavior of suspensions of noninteracting monodisperse beta-FeOOH particles. The electro-optic parameters are determined for aqueous suspensions of the oxide particles and the influences of surface charge and Debye layer thickness are verified. Since the conventional method of frequency analysis is inconsistent in the low-frequency range, new electro-optic parameters are introduced to define the frequency variation of the effects. Electric polarizability is determined with precision to a constant, and its relative variations are followed. As reported for other oxides, electric polarizability correlates with charge variations in the diffuse part of the particle surface electric layer, and its relaxation frequency increases with surface charge density, indicating a Maxwell-Wagner type of surface polarization. The alternating component of the responses yields particle relaxation frequency and the phase shift of the responses at this frequency. For all studied samples the phase shift at particle relaxation frequency is 45 degrees. The relative changes in the steady component of the responses in the low-frequency range are followed by field intensity curves at characteristic frequencies of the samples. Electrophoretic rotation is the process consistent with our data for the low-frequency effect. The results show that it is enhanced by the combined actions of low or slowly relaxing polarizability and significant electrophoretic mobility.
本文详细分析了非相互作用单分散β-FeOOH颗粒悬浮液的电光行为。测定了氧化物颗粒水悬浮液的电光参数，并验证了表面电荷和德拜层厚度的影响。由于传统的频率分析方法在低频范围内不一致，因此引入了新的电光参数来定义效应的频率变化。精确测定了恒定的电极化率，并跟踪其相对变化。正如其他氧化物所报道的那样，电极化率与颗粒表面电层扩散部分的电荷变化相关，其弛豫频率随表面电荷密度增加，表明是麦克斯韦-瓦格纳型表面极化。响应的交流分量产生颗粒弛豫频率和该频率下响应的相移。对于所有研究的样品，颗粒弛豫频率下的相移为45度。在低频范围内，响应稳定分量的相对变化由样品特征频率处的场强曲线跟踪。电泳旋转是与我们关于低频效应的数据一致的过程。结果表明，低极化率或缓慢弛豫极化率与显著的电泳迁移率的联合作用增强了这种效应。
