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Ceramic strontium ferrites belonging to the M-type hexagonal ferrites have been prepared by the ceramic technique. They were then characterized using x-ray diffraction method and incorporated into natural rubber (NR) matrix according to a specific recipe to ORDER REPRINTS produce rubber ferrite composites (RFC). RFC are magnetic polymer composites, which have a variety of applications as flexible magnets, pressure/photo sensors, and microwave absorbers. The mechanical properties were studied using a universal testing machine (UTM) and the magnetic properties were studied using a vibrating sample magnetometer (VSM). The present study indicates that flexible magnets having appropriate mechanical strength and magnetic properties can be prepared by the incorporation of strontium ferrite in elastomer matrixes. The magnetic measurements indicated that composites having appreciable coercivity (Hc) and saturation magnetization (Ms) could be synthesized by the incorporation of the ceramic ferrites in natural rubber matrix. It has also been found that the coercivity of the ceramic ferrite and the rubber ferrite composites remained almost the same.

Fine particles of barium ferrite (BaFe 12 O 19 ) were synthesized by the conventional ceramic technique. These materials were then characterized by the X-ray diffraction method and incorporated in the natural rubber matrix according to a specific receipe for various loadings of ferrite. The rubber ferrite composites (RFC) thus obtained have several applications, and have the advantage of molding into complex shapes. For applications such as microwave absorbers, these composites should have an appropriate dielectric strength with the required mechanical and magnetic properties. The N330 (HAF) carbon black has been added to these RFCs for various loadings to modify the dielectric and mechanical properties. In this article we report the effect of carbon black on the mechanical and dielectric properties of these RFCs. Both the mechanical and dielectric properties can be enhanced by the addition of an appropriate amount of carbon black.

Flexile single layer electromagnetic wave absorbers were designed by incorporating appropriate amounts of carbon black in a nitrile butadiene rubber matrix along with an optimized amount of magnetic counterpart, namely, barium hexaferrite for applications in S, C, and X-bands. Effective dielectric permittivity and magnetic permeability were measured using cavity perturbation method in the frequency range of 2–12 GHz. The microwave absorbing characteristics of the composites were studied in the S, C, and X-bands employing a model in which an electromagnetic wave is incident normally on a metal terminated single layer. Reflection loss exceeding −20 dB is obtained for all the samples in a wide frequency range of 2–12 GHz when an appropriate absorber thickness between 5 and 9 mm is chosen. The impact of carbon black is clearly observed in the optimized composites on the mechanical strength, thickness, band width of absorption, dielectric properties, and absorptivity.

Hexagonal strontium ferrite (SrFe12O19) powders were synthesized by the conventional ceramic techniques. They were then characterized by the X-ray diffraction method and incorporated in the natural rubber matrix according to a specific recipe for various loadings of ferrite to produce rubber ferrite composites (RFCs). The processability of these compounds was determined by evaluating the cure characteristics namely, scorch time, cure time, minimum and maximum torque. The evaluation of the dielectric properties of ceramic strontium ferrite (SrF), natural rubber gum vulcanizate, and RFCs were done with the help of a Hewlett Packard (HP) impedance analyzer. The magnetic properties of these composites were studied using a Vibrating Sample Magnetometer (VSM). The effect of carbon black on the processability, and the magnetic and dielectric properties were also studied by the incorporation of carbon black into these composites. It has been found that the addition of these ferrites and carbon black does not affect the processability of these composites, whereas the physical properties are found to be modified. From the magnetic and dielectric measurements it has been found that flexible magnets having appropriate dielectric strength can be prepared by the incorporation of appropriate amount of SrF and carbon black in the natural rubber matrix.

The incorporation of various types of ferrites in rubber matrixes leads to the development of rubber ferrite composites (RFC). These RFC have a large number of applications as flexible magnets, high-tech sensors, for telecommunication and radiowave absorbers. Both natural and synthetic rubber has the potential of being value added by the incorporation of ferrites. Applications like microwave absorbers warrant that these composites have an appropriate dielectric strength with the required magnetic property. This can be achieved by synthesizing composites based on natural rubber and ferrites. In this paper we report the synthesis of RFC containing barium ferrite according to a specific recipe and its evaluation of dielectric and mechanical properties.