The influences of surface molecular structure of carbon nanotubes on the stability of thermal conductivity enhancement of CNT NFs

9^th World Congress on Materials Science and Engineering

June 12-14, 2017 Rome, Italy

Haibin Cheng, Wentao Ma and Norman M Wereley

Wuhan University of Technology, China
University of Maryland, USA

Posters & Accepted Abstracts: J Material Sci Eng

Abstract :

Statement of the Problem: Pristine CNT, which have a strong tendency to entangle with each other and to rapidly aggregate due to large hydrophobic surface area. CNT in the CNT-based NFs tend to quickly stratify and precipitate to the bottom of the container. Such rapid sedimentation, which can clog any flow channels, seriously decays heat transfer effectiveness, and renders practical engineering applications infeasible. Therefore, improving the stability is the key challenge to enable successful engineering applications of the CNT-based NFs. The purpose of this study is to reveal the influences of surface molecular structure changes of CNT on the stability of suspension and thermal conductivity enhancement of CNT NFs. Methodology & Theoretical Orientation: In this study, multi-walled carbon nanotubes (CNT) was used as the objects of study, a mixed acid composed of nitric acid (HNO3) and sulfuric acid (H2SO4) was used as oxidative modification agent, and different oxidation acid treatment times were adopt to investigate the effect of structural changes of CNT on the stability of suspension and thermal conductivity enhancement of carbon nanotubes/ethylene glycol (EG) nano-fluids (CNT/EG NFs). The effects of oxidative acid treatment on the morphology and surface molecular structure of CNT were investigated by SEM, TEM, FTIR, respectively; and the influence of structure changes of CNT on the stability of suspension and thermal conductivity enhancement of CNT/EG NFs was evaluated by sedimentation observation method, centrifugation method and optical microscopy method and transient line heat source method. Findings: The stability of suspension is proportional to the abundance of functional carboxyl group �COOH on CNT. Conclusion & Significance: The formation of carboxyl group COOH plays a major role in improving the stability of suspension and thermal conductivity enhancement of CNT/EG NFs.

Biography :

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