Kefeng Cai

Facile Preparation and Thermoelectric Properties of Bi2Te3 Based Alloy Nanosheet/PEDOT:PSS Composite Films

Bi2Te3 based alloy nanosheet (NS)/poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) composite films were prepared separately by spin coating and drop casting techniques. The drop cast composite film containing 4.10 wt % Bi2Te3 based alloy NSs showed electrical conductivity as high as 1295.21 S/cm, which is higher than that (753.8 S/cm) of a dimethyl sulfoxide doped PEDOT:PSS film prepared under the same condition and that (850-1250 S/cm) of the Bi2Te3 based alloy bulk material. The composite film also showed a very high power factor value, ∼32.26 μWm(-1) K(-2). With the content of Bi2Te3 based alloy NSs increasing from 0 to 4.10 wt %, the electrical conductivity and Seebeck coefficient of the composite films increase simultaneously.

Ultra long SiCN nanowires and SiCN/SiO2 nanocables: synthesis, characterization, and electrical property.

SiCN nanowires are synthesized by pyrolysis of hexamethyldisilazane (HMDSN) using ferrocene as a catalyst precursor at 1200 degrees C in a flowing argon atmosphere on the surface of mullite substrate, polycrystalline alumina wafer and quartz tube. In oxygen-contained argon atmosphere, SiCN/SiO2 nanocables are synthesized. The as-synthesized products are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and high-resolution electron microscopy equipped with energy dispersive X-ray spectroscopy. The lengths of the nanowires and nanocables are in the millimeter range. The diameter of the SiCN nanowires grown on mullite substrate and alumina wafer ranges from about 10-70 nm, while that of the nanowires grown on quartz tube surface is in the range of around 7-10 nm. The diameters of the SiCN/SiO2 nanocables are relatively large. A vapor-liquid-solid growth mechanism of the nanostructures is proposed. The electrical resistivity of a single SiCN/SiO2 nanocable is reported for the first time.

FACILE PREPARATION AND CHARACTERIZATION OF GRAPHENE NANOSHEET/POLYANILINE NANOFIBER THERMOELECTRIC COMPOSITES

Graphene nanosheet (GNs)/polyaniline (PANI) nanofiber composites were prepared by oxidative polymerization of aniline in a GNs dispersed 1 mol/L HCl solution. The phase composition of the composites was analyzed by Fourier Transform Infrared Spectroscopy and X-ray Diffraction. The thermoelectric properties of the composite powders, after cold pressing into pellets, were measured at room temperature. As the content of GNs increased from 0 to 40 wt.%, the electrical conductivity and Seebeck coefficient of the composite pellets increased simultaneously; especially the electrical conductivity increased dramatically from 15.4 to 120.1 S/cm. The highest power factor (~ 394.4 × 10-8 Wm-1K-2) was obtained from the 40 wt.% GNs/PANI composite sample, which is ~200 times as high as that of HCl-doped PANI.

Multifold enhancement of the output power of flexible thermoelectric generators made from cotton fabrics coated with conducting polymer

Thermoelectric (TE) conversion of human body heat is highly desirable for powering microelectronic devices. However, most of the existing TE generators are not practical because they contain toxic substances, are difficult to process, are rigid and impermeable, or are unable to be produced on a large scale. Previously, we have demonstrated a flexible, air-permeable TE power generator fabricated from polyester fabric coated with a conducting polymer, poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate), and fine silver wires [Y. Du, et al., Sci. Rep., 2015, 5, 06411]. Here, we show a multifold enhancement of the output power of this type of flexible thermoelectric generator using poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) coated cotton fabric, and fine Constantan wires. A fabric device consisting of 5 TE units was found to generate a voltage output (V) of 18.7 mV and maximum output electrical power of 212.6 nW at a temperature difference (ΔT) of 74.3 K. The fabric generators can be rolled up and remain operational after being bent at different bending radii and in different directions. Furthermore, a TE generator has been shown to be stable even after 10 days of continuous operation at a ΔT up to ∼78 K. This fabric-based TE generator is seen to be useful for the development of self-powered, wearable electronic devices.