Electrokinetics methods have attracted increasing interest to characterize hydrogeological processes in geological media, especially in complex hydrosystems such as fractured formations. In this work, we conceptualize fractured media as a bunch of parallel capillary fractures following the fractal size distribution. This conceptualization permits to obtain analytical models for both the electrical conductivity and the electrokinetic coupling in water saturated fractured media. We explore two different approaches to express the electrokinetic coupling. First, we express the streaming potential coupling coefficient as a function of the zeta potential and then we obtain the effective charge density in terms of macroscopic hydraulic and electrokinetic parameters of porous media. We show that when the surface electrical conductivity is negligible, the proposed models reduces to the previously proposed one based on a bundle of cylindrical capillaries. This model opens up a wide range of applications to monitor the water flow in fractured media.

SrFe12O19/La1−xCaxMnO3 (SFO/LCMO) composites with x = 0.1 and 0.5 were synthesized via a two stage combined citrate precursor sol-gel and hydrothermal method. The structure and composition of the samples were refined from the X-ray diffraction patterns. The morphologies of the composites were investigated using transmission and scanning electron microscopies, which revealed micron-sized hexagonal platelets of SFO with LCMO particles with average diameters of 110–130 nm formed at the surface. An investigation of the temperature and field dependence of the magnetization found that the SFO phase with a ferrimagnetic characteristic up to 720 K dominates the magnetic properties of the composite samples. The SFO/LCMO composite samples showed a reduction in saturation magnetization and coercivity when compared with pure SFO. However, low temperature hysteresis loops recorded after cooling in applied fields up to 5 T revealed the absence of exchange bias in the SFO/LCMO composite, ruling out the possibility of significant interfacial magnetic coupling between SFO and LCMO.

A composite system composed of SrFe 12 O 19 (SFO) and La 0.5 Ca 0.5 MnO 3 (LCMO) was prepared by a two-stage sol-gel/hydrothermal synthesis technique. Starting conditions were varied to obtain products with 1:1 and 1:2 molar ratios of SFO:LCMO. The morphology and composition of the composites were characterized by SEM and room-temperature Mӧssbauer spectroscopy, revealing the growth of nanocrystalline La 0.5 Ca 0.5 MnO 3 particles (d ≤ 150 nm) on the surface of SrFe 12 O 19 platelets. Mӧssbauer spectra not only confirm the presence of well-formed M-type hexagonal ferrite in the composite materials, but also demonstrate the formation of a new, intermediate phase La 0.5 Ca 0.5 Mn(Fe)O 3 at the interface between SFO and LCMO. The signature of the intermediate Fecontaining phase increases with the starting molar content of La 0.5 Ca 0.5 MnO 3 , as a greater fraction of the SrFe 12 O 19 surface is covered by La 0.5 Ca 0.5 MnO 3 , increasing the total interfacial area. The trends in coercivity in the series of samples between 10 K and 300 K are reported and discussed in terms of sample morphology.