Ball-Milling Exfoliation of Hexagonal Boron Nitride in Viscous Hydroxyethyl Cellulose for Producing Nanosheet Films as Thermal Interface Materials

Abstract

Boron nitride nanosheets (BNNS) exfoliated by physical or chemical methods frequently exhibit poor dispersity in common solvents due to incomplete exfoliation and a low degree of functionalization, which has severely impacted BNNS application performances as polymer and lubricant additives. In this work, we mechanically exfoliated the bulk boron nitride into nanosheets through a ball-milling method by adopting the viscous hydroxyethyl cellulose (HEC) solution as a medium. Because of the abundant hydroxyls and strong hydrogen bonding interactions with BNNS, the HEC can not only serve as an intercalator and a protective agent of the BNNS during ball milling but can also benefit the stable dispersion of the fabricated HEC/BNNS mixture in water. The HEC/BNNS aqueous dispersion obtained by directly pouring deionized water into the ball-milled product is easy to form a two-dimensional film via the solution-casting method. Because of the good exfoliation and dispersion of the BNNS in the HEC matrix, the HEC/BNNS films have high mechanical strength and thermal conductivity and have the potential to be used as thermal interface materials.

In Situ Loading of Polypyrrole onto Aramid Nanofiber and Carbon Nanotube Aerogel Fibers as Physiology and Motion Sensors

“…The highest temperature of the ANF/CNT/PPy aerogel fiber increased as the heating voltage increased from 10 V to 30 V (Figure d). As shown in the thermal diffusion image (Figure e), the aerogel fibers heated to their maximum temperature in 30 s and cooled to below 30 °C in 15 s …”

“…54 The highest temperature of the ANF/CNT/PPy aerogel fiber increased as the heating voltage increased from 10 V to 30 V (Figure 6d). As shown in the thermal diffusion image (Figure 6e), the aerogel fibers heated to their maximum temperature in 30 s and cooled to below 30 °C in 15 s. 55 The ANF/CNT/PPy aerogel fiber has a porous internal structure and is separated from the conductive fiber. This structure induces a resistance response to both pressure and conductive ions (Figure 6f).…”

Formation Mechanisms of Hexagonal Boron Nitride Nanosheets in Solvothermal Exfoliation

“…For example, ball milling the mixture of h -BN and urea at 700 rpm for 20 h can give −NH 2 -modified BNNSs, which could form colloidal solutions, ultralight aerogels, and freestanding membranes . Glycine, hydroxyethyl cellulose, sugar, H 3 BO 3 , 2-furoic acid, NaOH, etc. have been reported as assistant reagents in ball milling exfoliation.…”

“…To functionalize and stabilize the BNNSs, h-BN has been ultrasonically treated in pure methanesulfonic acid, 38 chlorosulfonic acid, 39 and ionic liquid, 40 or in common solvents with the assistance of extracts of plant materials, 41 hyperbranched polyethylene, 42 and polyethyleneimine. 43 In the proposed exfoliation routes, high-energy ball milling, [27][28][29]31 intense ultrasonication, 41 and vigorous chemical oxidation 26 would cut h-BN into small nanosheets, produce large amounts of pores and defects, and graft numerous functional groups (−NH 2 or −OH) on the BNNSs, 44 while the mild treatments face the issues of incomplete exfoliation and low yield. Recently, solvothermal methods have been explored to exfoliate h-BN with the assistance of lithium chloride (LiCl) and cetyltrimethylammonium bromide (CTAB), 45,46 which display relatively high efficiency and can even massively produce monolayer BNNSs.…”

Significantly Enhancing Mechanical and Thermal Properties of Cellulose-Based Composites by Adding Small Amounts of Lysozyme-Modified Graphene Nanoplatelets via Forming Strong Double-Cross-Linked Interface Interactions

“…The tensile strength of the composites exceeded 50 MPa, and the in-plane TC was 8.55 W•m −1 •K −1 , when the content of GNP and MXene was 10 and 40 wt %, respectively. Huang et al 25 obtained nanofilm composites by blending the ball-milled BNNS and hydroxyethyl cellulose, and when the BNNS content reached 20 wt %, the composite achieved a tensile strength of 34.0 MPa and an in-plane TC of 0.234 W•m −1 •K −1 . However, in most situations, the interfacial force between cellulose and filler is not strong enough, resulting in a poor interconnection between cellulose and filler, thus reducing the composite's mechanical and thermal properties.…”