Ballistic thermal phonons traversing nanocrystalline domains in oriented polyethylene.

ABSTRACT: Thermally conductive polymer crystals are of both fundamental and practical interest for their high thermal conductivity that exceeds that of many metals. In particular, polyethylene fibers and oriented films with uniaxial thermal conductivity exceeding 50 [Formula: see text] have been reported recently, stimulating interest into the underlying microscopic thermal transport processes. While ab initio calculations have provided insight into microscopic phonon properties for perfect crystals, such properties of actual samples have remained experimentally inaccessible. Here, we report the direct observation of thermal phonons with mean free paths up to 200 nm in semicrystalline polyethylene films using transient grating spectroscopy. Many of the mean free paths substantially exceed the crysta

SUBMITTER: Robbins AB 

PROVIDER: S-EPMC6717268 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature