Covalently Functionalized Leakage‐Free Healable Phase‐Change Interface Materials with Extraordinary High‐Thermal Conductivity and Low‐Thermal Resistance

Abstract

Phase-change materials (PCMs) have received considerable attention to take advantage of both pad-type and grease-type thermal interface materials (TIMs). However, the critical drawbacks of leaking, non-recyclability, and low thermal conductivity (𝜿) hinder industrial applications of PCM TIMs. Here, leakage-free healable PCM TIMs with extraordinarily high 𝜿 and low total thermal resistance (R t ) are reported. The matrix material (OP) is synthesized by covalently functionalizing octadecanol PCM with polyethylene-co-methyl acrylate-co-glycidyl methacrylate polymer through the nucleophilic epoxy ring opening reaction. The OP changes from semicrystalline to amorphous above the phase-transition temperature, preventing leaking. The hydrogen-bondforming functional groups in OP enable nearly perfect healing efficiencies in tensile strength (99.7%), 𝜿 (97.0%), and R t (97.4%). Elaborately designed thermally conductive fillers, silver flakes and multiwalled carbon nanotubes decorated with silver nanoparticles (nAgMWNTs), are additionally introduced in the OP matrix (OP-Ag-nAgMWNT). The nAgMWNTs bridge silver-flake islands, resulting in extraordinarily high 𝜿 (43.4 W m −1 K −1 ) and low R t (30.5 mm 2 K W −1 ) compared with PCM TIMs in the literature. Excellent heat dissipation and recycling demonstration of the OP-Ag-nAgMWNT is also carried out using a computer graphic processing unit. The OP-Ag-nAgMWNT is a promising future TIM for thermal management of mechanical and electrical devices.

Significantly Enhanced Conformal Contact by the Functional Layers on a Copper Film for Thermal Interface Materials

“…Figure 1a shows the R t measurement setup constructed according to the ASTM-D5470 standard. [11,24,25] A copper metering bar is heated using three cartridge heaters, and the temperature distribution is measured using three T-type thermocouples (TC 1 -TC 3 ) inserted at equal intervals (20 mm). The average of the heat-transfer rate (Q av ) through the metering bar is calculated through the 1D Fourier's law of conduction.…”

“…The pressure and BLT are also monitored during the measurements using pressure and thickness sensors, respectively. [11,25] The specimen is preheated above the phase change temperature of PEG (60 °C for 30 min), followed by cooling down to 40 °C for the R t measurement. The preheating softens PEG for conformal mating, decreasing R c , as will be discussed later.…”

“…where Q av is the average heat-transfer rate obtained from the Cu metering bar; t Cu is the distance between the thermocouples (TC 4 and TC 5 ) and specimen (1 mm); and κ Cu and A Cu are the thermal conductivity and area (10 Â 10 mm 2 ) of the Cu plate, respectively. [11,24,25] The R t is sum of R c and R s .…”

“…[55] A detailed description about the R t measurement setup, constructed according to the ASTM-D5470 standard, was provided elsewhere. [11,24,25] Three cartridge heaters connected to a DC power supply (G-TEK, GP-1001) were used to generate heat flux, and T-type thermocouples (Omega Engineering, SCP-SS-020-G-2) were used for temperature measurements. The elastic modulus of specimen (E s ) was measured at room temperature using a nanoindentation system (Micro Materials Ltd., NanoTest Vantage).…”

Flexible Fluorinated Graphene/Poly(vinyl Alcohol) Films toward High Thermal Management Capability

“…The higher the operating power density of electronic devices, the more severe the heat generation, which seriously affects their efficiency and useful life. − This development also foreshadows the importance and rise of the field of heat dissipation. Researchers have long investigated the development and application of highly thermally conductive materials. − Metals such as silver, copper, and aluminum are widely used in thermal management because of their high thermal conductivity; however, their high density limits their application in portable devices. The emergence of two-dimensional materials with high thermal conductivity, such as graphene and boron nitride, has sparked a wave of research. − Of these, graphene has been widely studied because it has the highest known theoretical thermal conductivity (∼5300 W m –1 k –1 ) and is flexible and light, among other desirable properties. − …”