Shaoming Yang

Morphology and growth models of circular and flat carbon coils obtained by the catalytic pyrolysis of acetylene

Carbon micro-coils, which is a kind of novel carbon material with a 3D double-helix/spiral structure similar to DNA, were obtained by the Ni-catalyzed pyrolysis of acetylene at 750 °C. The morphology and microstructure of these carbon coils were examined in detail. The growth mechanisms of the flat coils with slender-shaped cross-sections as well as circular coils with circular-shaped cross-sections are discussed. It is considered that the circular coils are predominantly formed during the initial growth stage and then change to flat coils with increasing reaction time because of the change in the catalyst shape from a cubic-form to a slender-form. A change in the catalyst form may be effected by the electromagnetic (EM) field (force) emitted from the outer electric heater.

Tactile microsensor elements prepared from arrayed superelastic carbon microcoils

Superelastic carbon microcoils (SCMCs) with high elasticity and coiling chirality were prepared by the Ni-catalyzed pyrolysis of acetylene, and novel tactile microsensor elements using the SCMCs as the sensor material were prepared. The sensor elements with a very small size of 80×80×80μm3 showed a very high sensitivity of 0.3mgf (1Pa). It was found that the SCMC arraying in the matrix and the placement method on the electrodes dramatically affected the sensing properties.

Coiling-chirality changes in carbon microcoils obtained by catalyzed pyrolysis of acetylene and its mechanism

As can be seen in the double helix of DNA, the single helix of proteins, etc., the three-dimensional (3D) helical/spiral structure is a fundamental structure of living things, and affords them critical functionalities. Helically coiled carbon fibers, which usually take the peculiar form of either a microcoil or a helix or twisted form, referred to as “carbon microcoils hereafter,” are of great interest due to their novel functionality and various potential applications. They can potentially be used in electromagnetic absorbers and/or filters, 3D composites, smart tunable electrical devices, microsensors, chiral catalysts, etc.

Observation and analysis of percolation behavior in carbon microcoils/silicone-rubber composite sheets

The electrical properties of carbon microcoils (CMCs)/ silicone-rubber composites were studied on the changes in the values of the electrical parameters (impedance, phase angle, resistance, and capacitance) as a function of the CMC content in the matrix, using an impedance analyzer in the frequency range from 40to200kHz. Percolation paths were observed at a 3wt% CMC content in the matrix. The properties of the composites were separated at the percolation threshold. The capacitance with a small value was dominant at CMC content less than 3wt%, and the resistance was dominant at CMC content higher than 3wt%.

Conformation and growth mechanism of the carbon nanocoils with twisting form in comparison with that of carbon microcoils

Abstract Carbon nanocoils with twisting form were grown by the Ni/Al2O3-catalyzed pyrolysis of acetylene. The conformation and the tip morphologies of the carbon nanocoils were examined in detail. The growth schematics of the carbon nanocoils relating to the catalyst rotating were proposed, comparing with that of the carbon microcoils. The driving force of the coiling of the straight fibers to form carbon nanocoils was considered to be the strong catalytic anisotropy of the carbon deposition between different crystal faces, and causing the different rotation way from that of carbon microcoils.

Preparation of helical TiO2/CMC microtubes and pure helical TiO2 microtubes

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.

Biomimetic Tactile Sensors with Fingerprint-Type Surface Made of Carbon Microcoils/Polysilicone

Carbon microcoils (CMCs) were embedded into an elastic polysilicone matrix to prepare CMC tactile sensor elements with fingerprint-type surface morphologies, and compared with the smooth surface form. It was found that the CMC sensor elements with a fingerprint-type surface showed a higher tactile sensitivity than that of the smooth surface. Furthermore, when a dynamic load was applied in the vertical direction to the epidermal ridges in the fingerprints, the fingerprint-type sensor element showed a 2 times higher sensitivity than that from the horizontal direction.

The Design and Performance of Tactile/Proximity Sensors Made of Carbon Microcoils

By mimicking Meissner’s corpuscles, carbon microcoils (CMCs) were embedded into an elastic resin to produce biomimetic proximity/tactile sensors. The CMC sensors were found to have a high elasticity, high sensitivity, high discrimination ability, and a high performance, as well as being easily made in a micron size. These sensors have potential applications in robotic surgery, medical treatment, and diagnosis, etc.

Novel Tactile Sensors Manufactured by Carbon Microcoils

The carbon microcoils (CMC) with a high elasticity and coiling-chirality was prepared by the Ni catalyzed pyrolysis of acetylene containing a small amount of H2S. The morphology and their mechanical and electrical properties, especially tactile sensing properties, were examined. It was found that superelastic CMC, which could be extended and contracted to more than 15 times of the original coil length, could be obtained by controlling the reaction conditions. The extension of CMC was very high sensitive for applied load, and could be detected very low applied load of milligram orders. The electrical resistivity (R) of the CMC increased with the extension and decreased with the contraction. Inductance (L) and capacitance (C) of CMC/polysilicone composites extensively changed with the extension and contraction of the composite under various touching modes, such as pressing, picking, stretching, etc. It was supposed that these tactile sensing properties were affected by novel LCR composite hybrid resonance.

Preparation and properties of TiC micro-coils and micro-tubes by the vapour phase titanizing of carbon micro-coils

TiC micro-coils and micro-tubes were prepared by the vapour phase titanizing of the regular carbon micro-coils, and the preparation conditions and some properties were examined. The carbon coils were titanized from the surface of the fiber to the core with full preservation of the coiling morphology to form TiC micro-coils or micro-tubes. The bulk electrical resistivity was 0.1–0.01 Ω·cm depending on the titanized rate and the bulk density. The specific surface area of the source carbon coils (about 100 m2/g) was significantly decreased with increasing reaction temperature and reaction time. The tensile strength of a TiC micro-tube was 660 MPa. The attenuation ratio against an electromagnetic wave of the TiC micro-tubes (30 wt % in epoxy resin) was about 90% (dB = −10) for 800–900 MHz.