Transparent Silicone Calcium Fluoride Nanocomposite with Improved Thermal Conductivity

Abstract

Heat dissipation is an important issue in many electronic devices and therefore materials showing high thermal conductivity are required for their construction and packaging. The intrinsically low thermal conductivity of polymeric materials can be improved when employing (nano-) composites; however, the required high filler content then renders these materials opaque. This paper reports on a composite material that combines high transparency and improved thermal conductivity by using calcium fluoride (CaF 2 ) particles in a silicone elastomer. The refractive index of the silicone matrix is matched to the filler material, light scattering is prevented, and transparent composites with enhanced thermal conductivity at modest filler content (starting at 0.2 volume fraction) are obtained.

Single-Step Fabrication of Polymer Nanocomposite Films

“…The ability to rapidly prepare homogeneous and highly loaded nanocomposites is quite helpful for realizing electrically conductive films [ 6 ], cantilevers [ 19 ], gas barriers [ 20 ], dielectric elastomers [ 21 ] and shape memory polymers [ 3 ] because agglomerating nanoparticles, formation of voids and/or difficulties during fabrication have limited the filler content [ 22 ]. Small nanoparticles (<20 nm) are especially difficult to incorporate homogeneously above 7 vol % into a polymer due to their high specific surface area [ 4 ].…”

Nanoparticle Filler Content and Shape in Polymer Nanocomposites

“…These benefits are quite attractive in consideration of large scale fabrication and customized 3D-printed devices. Nevertheless, strong particle agglomeration (especially at the nanoscale) and high viscosity of the blend remain prominent hurdles that can lead to long processing (Chen Z. et al, 2015), inhomogeneities (Niu Y. et al, 2015), clogging of dispensing equipment (Lei Q. et al, 2016) and limitations of feasible nanocomposite dimensions (Suter M. et al, 2011a) and filler content (Schneider R. et al, 2015). Altering the nanoparticle surface chemistry (Bruno T.J. andSvoronos P.D., 2005, Iijima M. andKamiya H., 2009) can mitigate these effects but requires additional, possibly tedious and lengthy processing (Wang D. et al, 2014).…”

“…8c): Coincidence? It could suggest an ideal range up to which the greatest gain is obtained before being counterbalanced by deteriorating effects such as the difficulty to compound, filler agglomeration and nanocomposite embrittlement (Schneider R. et al, 2015).…”

“…A critical evaluation needs to be made to verify if anticipated specifications coincide with realistic ones. For this, filler composition (Yi P. et al, 2014), size (Schneider R. et al, 2015), shape (Bhanushali S. et al, 2017), surface chemistry (Niu Y. et al, 2015) and quantity (White S.I. et al, 2010) as well as choice of host polymer (Zhi C. et al, 2009) and manufacturing route (Slobodian P. et al, 2007) need to be considered.…”

Fluorescent Enhancement of CaF2: Nd3+ Nanoparticles through a Concentration‐Gradient Core/Shell Hybrid Structure

“…Meanwhile, CaF 2 host materials have an important application in dental medicine, [4] multifunctional nanoprobes in vitro and in vivo, [5] transparent laser ceramics, [6] enhance thermal conductivity of a composite, [7] et al What's more, like other lanthanide-based host materials such as LnF 3 or ALnF 4 (where A = Li, Na, K), CaF 2 is a potential host for phosphors with excellent up/down-conversion luminescent properties. [8] Firstly, the edge of the fundamental absorption band in CaF 2 lies in the vacuum UV at ∼ 12 eV.…”