Magnetic composites thermal properties

The theory of the electronic properties of the simple metals that has been built from simple free-electron theory is extraordinary. It extends to thermal properties such as the specific heat, magnetic properties such as the magnetic susceptibility, and transport properties such as thermal, electrical, thermoelectric, and galvano-magnetic effects. This theory is discussed in standard solid state physios texts (see, for example, Harrison, 1970) and will not be discussed here. As a universal theory for all metals, it is not sensitive to the electronic structure it depends only upon the composition of the metals through simple parameters such as those of Table... 

Closed-form expressions from composite theory are also useful in correlating and predicting the transport properties (dielectric constant, electrical conductivity, magnetic susceptibility, thermal conductivity, gas diffusivity and gas permeability) of multiphase materials. The models lor these properties often utilize mathematical treatments [54,55] which are similar to those used for the thermoelastic properties, once the appropriate mathematical analogies [56,57] are made. Such analogies and the resulting composite models have been pursued quite extensively for both particulate-reinforced and fiber-reinforced composites where the filler phase consists of discrete entities dispersed within a continuous polymeric matrix. 

In the nanotechnology field, carbon-based materials and associated composites have received special attention both for fundamental and applicative research. In the first kind, carbon compounds may be included, often taking the form of a hollow spheres, ellipsoids, or mbes. Spherical and ellipsoidal carbon nanomaterials are referred to as fullerenes, while cylindrical ones are called nanombes and nanofibers. In the second class, one includes composite materials that combine carbon nanoparticles with other nanoparticles, or nanoparticles with large bulk-type materials. The unique properties of these various types of nanomaterials provide novel electrical, catalytic, magnetic, mechanical, thermal, and other features that are desirable for applications in commercial, medical, military, and enviromnental sectors. This is the case for conducting polymers (CPs) and carbon nanombes (CNTs) [1-5]. 

Zhitomirsky et al. [8] have shown that electrodeposited hybrid composites of iron oxides can be studied with magnetic and thermal (TGA) methods. The nanocomposites produced here are superparamag-netic. Such properties are dependent on the nanosizes of these systems. 

In our minds, the suitability of C/C composites as armaments for magnets in fusion technology should be proved. First steps in this direction were done by investigating the thermal properties of carbon-fibre-reinforced carbon composites at low temperatures. Because of the chemical and physical properties of carbon, along with the various parameters that influence the properties of this composite material, it seems possible to tailor a material to the special requirements of that application. 

---