Magnetic composites systems

Generally, the literature shows that, for magnetic composite systems, relative permittivity decreases as frequency increases, this behavior being attributed to the interfacial polarization predicted by Maxwell-Wagner model, derived for the permittivity of a homogeneous two-phase system. In addition, a decrease in electrical resistivity for these magnetic composites was recorded with an increase in frequency... 

Figure 1 Time-dependent composition data is shown for the hydrogenation of aqueous 3-buten-2-ol for both (a) ultrasound irradiated and (b) magnetically stirred systems. The symbols correspond to experimental measurements (3-buten-2-ol 3BEN20L-solid circles 3-buten-2-one 3BEN20NE-open hourglass 2-butanone 2BONE-open triangles 2-butanol 2BOL-crossed squares). The lines in the ultrasound experiment simply connect the data points, whereas for the stirred experiment the lines correspond to a modeled fit (see text).

For composite systems, like an electron in an atom or a nucleon in a nucleus, the (magnetic) spin quantum number m may have two values, +1/2 or —1/2, because the spin vector has two possible orientations (up or down) with regard to the orbital angular momentum. 

The main interest in developing composite systems with interpenetrating, graded and layered microstmctures as well as hybrid composites is the improvement of thermomechanical properties. However the composites are usually designed for specific applications where functional properties are also required, i.e. electric, magnetic, dielectric, etc., or a combination of them. 

As a result, two composite systems derived from partially aliphatic polyimides— 5-(2,5-dioxotetra-hydrofurfuryl)-3-methyl-3-cyclohexene-l,2-dicarboxylic acid anhydride reacting with 4,4 -oxydianiline (DOCDA-ODA) and with iron oxide as Fe304—were prepared at different temperatures, 250 and 300°C (Nica et al. 2015). Correlations among the structural, morphological, thermal, and magnetic properties were established for possible application as humidity sensor devices. In addition, the influence of humidity on the electrical properties of poly(DOCDA-ODA)/iron oxide composite were discussed, which led to an analysis of the humidity sensitivity of pure polyimide and of a poly(DOCDA-ODA)/Fe304 with different filler contents of iron oxides at various values of relative humidity (RH). 

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