Coiled carbon fibers from PAN precursors

Acrylic (PAN) fibers with a novel coiled morphology as precursors for semiconducting carbon IR detection elements were prepared using a “hybrid” spinning technique combining principles from standard wet and dry spinning methods. Fiber structure and morphology were found to depend on furnace temperature and coagulation conditions. The highest-density fibers were formed at a furnace temperature of 180°C and a coagulation bath composition of H 2O:DMF = 3:1 at 19°C. Fibers with diameters of 100–200 μm were obtained, which when fired had resistivities in the range ≈ 3–70 Ω cm, and thermistor constants of B ≈ 1300–2500 K. Their application as IR detection elements is reported.