Ankoma Anderson

Polymer/Boron Nitride Nanocomposite Materials for Superior Thermal Transport Performance

Boron nitride nanosheets were dispersed in polymers to give composite films with excellent thermal transport performances approaching the record values found in polymer/graphene nanocomposites. Similarly high performance at lower BN loadings was achieved by aligning the nanosheets in poly(vinyl alcohol) matrix by simple mechanical stretching (see picture).

Boron Nitride Nanomaterials for Thermal Management Applications

Hexagonal boron nitride nanosheets (BNNs) are analogous to their two-dimensional carbon counterparts in many materials properties, in particular, ultrahigh thermal conductivity, but also offer some unique attributes, including being electrically insulating, high thermal stability, chemical and oxidation resistance, low color, and high mechanical strength. Significant recent advances in the production of BNNs, understanding of their properties, and the development of polymeric nanocomposites with BNNs for thermally conductive yet electrically insulating materials and systems are highlighted herein. Major opportunities and challenges for further studies in this rapidly advancing field are also discussed.

Flexible Graphene–Graphene Composites of Superior Thermal and Electrical Transport Properties

Graphene is known for high thermal and electrical conductivities. In the preparation of neat carbon materials based on graphene, a common approach has been the use of well-exfoliated graphene oxides (GOs) as the precursor, followed by conversion to reduced GOs (rGOs). However, rGOs are more suitable for the targeted high electrical conductivity achievable through percolation but considerably less effective in terms of efficient thermal transport dictated by phonon progression. In this work, neat carbon films were fabricated directly from few-layer graphene sheets, avoiding rGOs completely. These essentially graphene-graphene composites were of a metal-like appearance and mechanically flexible, exhibiting superior thermal and electrical transport properties. The observed thermal and electrical conductivities are higher than 220 W/m · K and 85000 S/m, respectively. Some issues in the further development of these mechanically flexible graphene-graphene nanocomposite materials are discussed and so are the associated opportunities.

Light-weight nanocomposite materials with enhanced thermal transport properties

Abstract Polymeric nanocomposite materials that are highly thermally conductive are important to a variety of applications, with examples ranging from flexible radiators in space to high-performance aircrafts and vehicles and to cutting-edge electronics. Among widely used nanoscale fillers in the development of these materials are carbon nanotubes and graphene sheets. As concluded in previous reviews, the performance of carbon nanotubes for imparting high thermal conductivity into polymeric matrices was generally poor. Here recent results associated with the effort on significant performance improvements are reviewed as an update. By contrast, graphene sheets have emerged as effective nanoscale fillers for polymeric nanocomposites of excellent thermal transport performance, reaching levels that are competitive to those achieved by metals. The significant recent results on thermally conductive polymeric nanocomposites with graphene sheets are highlighted, and their potential applications and issues on their further performance improvements are discussed.

Chapter 6:Metallic Single-walled Carbon Nanotubes for Electrically Conductive Materials and Devices

Carbon nanotubes are often described in the literature as being extremely electrically conductive.1–5 For single-walled carbon nanotubes (SWNTs), however, the widely prescribed high electrical conductivity is associated only with the metallic ones. The currently available production methods for SWNT...

Towards nanostructured boron nitride films

Boron nitride film could be developed for unique thermal management needs that require electrical insulation and also for applications that benefit from the other advantageous properties of boron nitride. In this work the two related major issues on the neat boron nitride films were identified, including the quality of the precursor boron nitride nanosheets (BNNs) and the dispersion of the BNNs relevant to the film fabrication. These issues were explored by examining various solvent systems and experimental conditions for the exfoliation of commercially acquired hexagonal boron nitride into BNNs and their ability to form relatively stable dispersions. The more stable dispersions were used for the fabrication of neat films of BNNs, and the results suggested that the films were too brittle to serve the film functions as those performed by their carbon-based counterparts. As an alternative approach, a small amount of graphene oxides (GOs) was used as binder for BNNs-GOs composite films of significantly improved mechanical characteristics. Thermal and electrical conductivities in these films were evaluated, so was the tuning of the conductivity ratios via thermal annealing of the as-fabricated films. The challenges and opportunities with the development of BNNs-derived neat boron nitride films are discussed, and their potential technological applications are highlighted.