An improved process is provided for the formation of metal ion containing carbon fibers which particularly are suited for utilization in electron shielding applications. An acrylic fibrous material is formed having substantially uniformly dispersed therein a halide of a transition metal. The metal halide (e.g. a chloride) present within the fibrous material is (1) converted to an oxide, (2) the fibrous material containing the metal oxide is heated in an oxygen-containing atmosphere until thermally stabilized, and (3) the thermally stabilized fibrous material is carbonized or carbonized and graphitized at a more highly elevated temperature in an appropriate atmosphere. The resulting product comprises ions of a transition metal substantially uniformly dispersed in an amorphous carbon or graphitic carbon matrix. The halide of a transition metal may be incorporated into the acrylic precursor by co-spinning and/or padding prior to thermal stabilization. The conversion of the halide of a transition metal to an oxide prior to thermal stabilization may be conducted by contact with a base or with an oxidizing agent as described.