In this work, a facile strategy for the fabrication of PANI/multi-walled carbon nanotube (MWCNT) nanocomposites without the assistance of a dispersant is introduced. MWCNTs and polyaniline were homogeneously mixed by cryogenic grinding (CG) and then consolidated via Spark Plasma Sintering (SPS). X-ray power diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM) were employed to characterize the as-prepared composites. The XRD results showed that cryogenic grinding can refine the grain size of PANI and induce more dislocations. The FTIR spectra data showed that the peaks of the PANI/MWNT composites displayed a red shift. In the high resolution FESEM image, the layer-by-layer structure and smooth surface can be observed. The thermoelectric properties of the as-prepared nanocomposites were investigated as a function of MWCNT content. The results showed that the electrical conductivity increased remarkably with the increasing MWCNT content, and the maximum power factor was 10.73 × 10−8 W mK−2, higher than pure PANI. Additionally, as the MWNT content increased from 10% to 30%, the electrical conductivity of the PANI/MWNT composite increased from 3.51 S m−1 to 1.59 × 102 S m−1. This work demonstrates a simple and effective method for improving the dispersity of carbon nanotubes and the thermoelectric properties of conducting polymers.

As a relatively novel sintering technique, spark plasma sintering (SPS) has been used extensively over the past decade to prepare a wide variety of materials, e.g., ceramics, composites, cermets, metals and alloys. Many applications of the SPS technique are the fabrication of nanostructured materials using nanosize powdered precursors as starting materials. This article provides a review of research activities that concentrate on the development of the SPS reaction sintering (SPS-RS) to produce dense nanostructured materials, which indicate that it is possible to synthesize and compact dense bulk materials with controlled sub-micron or even nanoscale grain sizes by the use of the SPS technique.•This is a review about fabrication of nanostructured materials using SPS reaction sintering.•Nano-structured bulk materials are prepared using micron-size powders via SPS.•The challenges in SPS reaction sintering for preparing nano-structured bulk materials are given.

A novel method for rapid preparation of Bi2Te3 nano-sized powders with an average particle size of about 70 nm was developed. A starting powder mixture consisting of Bi2Te3 coarse particles of ∼5 mm was ground using cryogenic grinding in the liquid nitrogen. For comparison, the conventional high-energy ball milling was used to prepare the Bi2Te3 nano-sized powders. Sintering properties of as-prepared powders was investigated by spark plasma sintering (SPS). The effects of the preparation procedure on the crystallinity, morphology and structure were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that Bi2Te3 was not transformed into a non-equilibrium amorphous phase or decomposed during the cryogenic grinding process, and as-prepared nano-powders possessed excellent sinterability. This technique might also be applicable to other thermoelectric materials.

Graphene nanoribbons (GNR) have been fabricated by a microexplosion method without severe oxidation – filling multi-walled carbon nanotubes (MWCNT) with potassium and then reacting with water vigorously. Transmission electron microscopy and scanning transmission electron microscopy have verified the synthesis mechanism: when MWCNTs are effectively filled with potassium, the microexplosion generated by reaction between water and potassium can split the MWCNTs to form GNRs. Most of the obtained GNRs have smooth edges and the maximum wall thickness of MWCNTs that can be split by this method is around 10 nm.

A novel method for rapid preparation of Bi2Te3 nano-sized powders with an average particle size of about 70 nm was developed. A starting powder mixture consisting of Bi2Te3 coarse particles of ∼5 mm was ground using cryogenic grinding in the liquid nitrogen. For comparison, the conventional high-energy ball milling was used to prepare the Bi2Te3 nano-sized powders. Sintering properties of as-prepared powders was investigated by spark plasma sintering (SPS). The effects of the preparation procedure on the crystallinity, morphology and structure were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that Bi2Te3 was not transformed into a non-equilibrium amorphous phase or decomposed during the cryogenic grinding process, and as-prepared nano-powders possessed excellent sinterability. This technique might also be applicable to other thermoelectric materials.

In this work, a facile strategy for the fabrication of PANI/multi-walled carbon nanotube (MWCNT) nanocomposites without the assistance of a dispersant is introduced. MWCNTs and polyaniline were homogeneously mixed by cryogenic grinding (CG) and then consolidated via Spark Plasma Sintering (SPS). X-ray power diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and field-emission scanning electron microscopy (FESEM) were employed to characterize the as-prepared composites. The XRD results showed that cryogenic grinding can refine the grain size of PANI and induce more dislocations. The FTIR spectra data showed that the peaks of the PANI/MWNT composites displayed a red shift. In the high resolution FESEM image, the layer-by-layer structure and smooth surface can be observed. The thermoelectric properties of the as-prepared nanocomposites were investigated as a function of MWCNT content. The results showed that the electrical conductivity increased remarkably with the increasing MWCNT content, and the maximum power factor was 10.73 × 10−8 W mK−2, higher than pure PANI. Additionally, as the MWNT content increased from 10% to 30%, the electrical conductivity of the PANI/MWNT composite increased from 3.51 S m−1 to 1.59 × 102 S m−1. This work demonstrates a simple and effective method for improving the dispersity of carbon nanotubes and the thermoelectric properties of conducting polymers.