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Mechanical and electrical properties of porous composites consisting of spring-shape carbon microcoils (CMCs) and silicone-rubber were investigated. The CMC/rubber porous composites having 71–81% porosity had compressive elastic moduli of 0.04–0.1 MPa which were 2–4% of a composite having the same ingredients without pores. The porous structure gave the composites not only the flexibility but a unique piezoresistivity in a wide compressive strain range. Resistivities of the porous composites increased over 104 times with a compressive strain up to 80%, while those of other porous composites including fibrous or particulate carbon fillers decreased only several tens of percent. CMC/rubber porous composites having such a unique piezoresistivity enabled us to develop a new tactile sensor system.

Magnetic nanoparticles consisted of nickel zinc ferrite (NZF) were chemically synthesized by co-precipitation and simultaneously coated onto carbon microcoils (CMC), and their structure and magnetic properties were investigated. The samples were prepared at various mass ratios of CMC : NZF ranging from 1 : 5 to 5 : 1. According to X-ray diffraction (XRD) measurements, all the samples synthesized in this study exhibit peaks associated with the spinel ferrite structure of NZF nanoparticles along with a fairly broad peak due to the amorphous structure of CMC. The sample synthesized at CMC: NZF = 1 : 1 gives the highest crystallinity and the largest magnetization at 300 K for NZF according to XRD and magnetization measurement using a superconducting quantum interference device magnetometer. Microstructural analysis of the CMC-NZF assemblies using scanning electron microscopy shows that the use of oleic acid and oleylamine improves the coverage of NZF on CMC and that the assembly made at CMC: NZF = 2 : 1 yields the highest coverage of NZF nanoparticles onto the CMC surface.

Helical TiO2/CMC (carbon microcoils) microtubes and helical TiO2 microtubes were obtained by making TiO2 layer coatings on the surface of CMC templates using a sol-gel and chemical vapor deposition (CVD) processes. The preparation conditions, morphologies and some properties were examined. Uniform TiO2 (anatase) layers were obtained on the CMC templates by a CVD process using vapor phase hydrolysis of titanium tetra-isopropoxide at 300°C followed by heat treatment in N2 or by calcination in air at 500–;650°C. The helical TiO2/CMC microtubes showed good photocatalytic activity. It was considered that the helical structure activated and enhanced the photocatalytic activity of TiO2, probably caused by the generation of inductive microelectric current induced by the irradiation of UV light, resulting in the generation of micromagnetic fields around the tubes.

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