Multi-contact hybrid thermal conductive filler Al2O3@AgNPs optimized three-dimensional thermal network for flexible thermal interface materials

In this work, a multi-contact Al₂O₃@AgNPs hybrid thermal conductive filler was synthesized by in-situ growth method to fill high thermal conductivity polydimethylsiloxane (PDMS)-based composites to prepare TIMs. And the thermal conductivity, electrical conductivity, and mechanical properties of the composite materials were studied. During the synthesis process of the multi-contact hybrid filler, different concentrations of silver ions were reduced to generate silver nanoparticles and attached to the surface of Al₂O₃. Al₂O₃@AgNPs/PDMS thermally conductive composites were prepared by changing the filler addition. Using SEM, XPS, and XRD is used to characterize the morphology and chemical composition of Al₂O₃@AgNPs hybrid filler. The thermal conductivity of PDMS-based composites with different AgNPs content under 70 wt% filler loading was studied. The results show that the thermal conductivity of PDMS-based composites filled with 7owt%Al₂O₃@3AgNPs/PDMS multi-contact hybrid filler is 0.67 W/m·K, which is 3.72 times that of pure PDMS, and is higher than that of unmodified Al₂O₃ with the same addition amount. /PDMS composite material has a high thermal conductivity of 24%. This work provides a new idea for the design and manufacture of high thermal conductivity hybrid fillers for TIMs.     

Polymer composites with enhanced thermal conductivity via oriented boron nitride and alumina hybrid fillers assisted by 3-D printing

Herein, oriented boron nitride (BN)/alumina (Al₂O₃)/polydimethylsiloxane (PDMS) composites were obtained by filler orientation due to the shear-inducing effect via 3-D printing. The oriented BN platelets acted as a rapid highway for heat transfer in the matrix and resulted in a significant increase in the thermal conductivity along the orientation direction. Extra addition of spherical Al₂O₃ enhanced the fillers networks and resulted in the dramatic growth of slurry viscosity. This, together with filler orientation induced the synergism and provided large increases in the thermal conductivity. A high orientation degree of 90.65% and in-plane thermal conductivity of 3.64 W/(m∙K) were realized in the composites with oriented 35 wt% BN and 30 wt% Al₂O₃ hybrid fillers. We attributed the influence of filler orientation and hybrid fillers on the thermal conductivity to the decrease of thermal interface resistance of composites and proposed possible theoretical models for the thermal conductivity enhancement mechanisms.     

A Concurrent Enhancement of Both In-Plane and Through-Plane Thermal Conductivity of Injection Molded Polycarbonate/Boron Nitride/Alumina Composites by Constructing a Dense Filler Packing Structure

In this work, a facile strategy is proposed to concurrently enhance both in-plane and through-plane thermal conductivity of injection molded polycarbonate (PC)-based composites by constructing a dense filler packing structure with planar boron nitride (BN) and spherical alumina (Al₂O₃) particles. The state of orientation of BN platelets is altered with the presence of Al₂O₃, which is favorable for improving both in-plane and through-plane thermal conductivity of subsequent moldings. Rheological analysis showed that the formation of intact thermal conductive pathways is crucial to the overall enhancement of thermal conductivity. Both in-plane and through-plane thermal conductivity of PC/BN(20 wt%)/Al₂O₃(40 wt%) composites reached as high as 1.52 and 1.09 W mK⁻¹, which are 485% and 474% higher than that of pure PC counterparts, respectively. Furthermore, the prepared samples demonstrated excellent electrical insulation and dielectric properties which show potential application in electronic and automotive industries.     

Preparation of a novel bi-layer modified alumina-based hybrid material and its effect on the thermal conductivity enhancement of polymer composites

In this work, a new kind of double layers modified alumina-based hybrid (silver@copper@alumina (Ag@Cu@Al₂O₃) hybrid) was successfully synthesized through the two-step layer-by-layer process. First, copper (Cu) nanoparticles were assembled onto alumina (Al₂O₃) particles by reduction of Cu²⁺. Second, Ag@Cu@Al₂O₃ hybrids were assembled via Ag deposition on the surface of Cu@Al₂O₃ particles. The obtained Ag@Cu@Al₂O₃ hybrids served as thermally conductive fillers to greatly boost the thermal conductivity of poly (dimethylsiloxane) (PDMS). The thermal conductivity reached 1.465 W m^?1 K^?1 at 85 wt% filler loading. The thermal conductivity of PDMS matrix was increased more than 7 times by the addition of Ag@Cu@Al₂O₃ hybrid, which was much higher than single layer modified alumina-based hybrids (Ag@Al₂O₃ and Cu@Al₂O₃ hybrids) and virgin Al₂O₃ particle. The effect of double layers modified filler, single layer modified filler and virgin filler on the thermal conductivity of PDMS matrix was discussed in detail and the mechanism of these fillers for improving thermal conductivity was studied through Foygel's thermal conduction model. Otherwise, electric, mechanical and thermal properties of Ag@Cu@Al₂O₃/PDMS composites were also further tested and analyzed.     

Effect of different size complex fillers on thermal conductivity of PA6 thermal composites

ABSTRACT

Nylon 6 (PA6) thermal conductive composites were prepared by melt blending with different sizes of spherical Al₂O₃ and AlN and the filling amount was 60 wt%. This paper explored the effects of different particle sizes and filler kinds on the thermal conductivity and mechanical properties of the composites. The results showed that the composites filled with AlN and spherical Al₂O₃ had higher thermal conductivity than the composites filled with single filler under the same filling amount. When the mass ratio of 48 μm spherical Al₂O₃ and 14 μm AlN was 1:2, the thermal conductivity and thermal diffusivity was 2.44 W/(m·K) and 0.72 mm²/s, respectively. In addition,the tensile strength was 57.50 MPa and the impact strength was 6.13 KJ/m². By comparing actual thermal conductivity value with the theoretical value calculated by Agari model, we found that actual value of alumina filling was close to the theoretical value.     

Process induced alignment of carbon nanotube decreases longitudinal thermal conductivity of Al2O3 based porous composites

Alumina (Al₂O₃) based porous composites, reinforced with zirconia (ZrO₂), 3 and 8 mol% Y₂O₃ stabilized ZrO₂ (YSZ) and 4 wt% carbon nanotube (CNT) are processed via spark plasma sintering. The normalized linear shrinkage during sintering process of Al₂O₃-based composite shows minimum value (19.2–20.4%) for CNT reinforced composites at the temperature between 1650 °C and 575 °C. Further, the combined effect of porosity, phase-content and its crystallite size in sintered Al₂O₃-based porous composite have elicited lowest thermal conductivity of 1.2 Wm⁻¹K⁻¹ (Al₂O₃-8YSZ composite) at 900 °C. Despite high thermal conductivity of CNT (∼3000 Wm⁻¹K⁻¹), only a marginal thermal conductivity increase (∼1.4 times) to 7.3–13.4 Wm⁻¹K⁻¹ was observed for CNT reinforced composite along the longitudinal direction at 25 °C. The conventional models overestimated the thermal conductivity of CNT reinforced composites by up to ∼6.7 times, which include the crystallite size, porosity, and interfacial thermal resistance of Al₂O₃, YSZ and, CNT. But, incorporation of a new process induced CNT-alignment factor, the estimated thermal conductivity (of <6.6 Wm⁻¹K⁻¹) closely matched with the experimental values. Moreover, the high thermal conductivity (<76.1 Wm⁻¹K⁻¹) of the CNT reinforced porous composites along transverse direction confirms the process induced alignment of CNT in the spark plasma sintered composites.     

Synthesis of a novel biphenyl epoxy resin and its hybrid composite with high thermal conductivity

A novel biphenyl epoxy monomer of p-methyl phenylhydroquinone epoxy resin (p-MEP) was synthesized and characterized. We researched its potential in the area of thermal conduction application and prepared a series of hybrid composites based on it with different mass ratios of sphere Al₂O₃ filler. From the good mobility and low viscosity of p-MEP, it allowed mixing with more Al₂O₃ fillers. The hybrid epoxy resins owned the advantages of traditional epoxy resins as well as quite considerable thermal conductivity. Therefore, the hybrid composite at the maximum mass fraction of 70% possess the highest thermal conductivity of 5.6 W mK⁻¹, which is 5.6 times higher than that of pristine p-MEP (0.1 W mK⁻¹). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47078.     

Al2O3/h-BN/epoxy based electronic packaging material with high thermal conductivity and flame retardancy

The long-term and stable operation of integrated circuits and microelectronics requires packaging epoxy resin (EP) exhibit high thermal conductivity for efficient heat dissipation, and excellent flame retardancy in case of thermal runaway. We achieved such EP composite via filling poly-dopamine (PDA) modified nanoscale Al₂O₃ spheres and microscale h-BN sheets. The PDA modification increases the compatibility between fillers and EP and largely reduces the viscosity, improving the dispersion of fillers in EP thus the thermal conductivity of EP composites. In addition, NH₃, H₂O, and N₂ generated during the combustion of phenolic hydroxyls and aminos in PDA combined with the physical barrier effect of Al₂O₃ and h-BN can improve the flame retardancy of EP composites. As a consequence, the EP composite filled with PDA modified Al₂O₃ (26.67 wt%) and h-BN (13.33 wt%) (i.e., PDA-BNAO/EP) shows a thermal conductivity of 1.192 W/mK (654.9% of EP), a peak heat release rate of 194.9 W/g (33.8% of EP), and total heat release of 15.2 kJ/g (54.5% of EP), respectively. What's more, the viscosity of PDA-BNAO/EP is 20,443 mPa s, which is only 20% of BNAO/EP (whose viscosity is 102,281 mPa s). More importantly, the PDA-BNAO/EP has good dynamic mechanical properties with the storage modulus of 14.69 Gpa, glass transition temperature of 91.9°C and good electrical insulation, which is desired for packaging of microelectronics. PDA-BNAO/EP composite should be a promising candidate for widespread packaging materials of microelectronics.     

Highly electrically and thermally conductive silicon carbide-graphene composites with yttria and scandia additives

Dense silicon carbide/graphene nanoplatelets (GNPs) and silicon carbide/graphene oxide (GO) composites with 1 vol.% equimolar Y₂O₃–Sc₂O₃ sintering additives were sintered at 2000 °C in nitrogen atmosphere by rapid hot-pressing technique. The sintered composites were further annealed in gas pressure sintering (GPS) furnace at 1800 °C for 6 h in overpressure of nitrogen (3 MPa). The effects of types and amount of graphene, orientation of graphene sheets, as well as the influence of annealing on microstructure and functional properties of prepared composites were investigated. SiC-graphene composite materials exhibit anisotropic electrical as well as thermal conductivity due to the alignment of graphene platelets as a consequence of applied high uniaxial pressure (50 MPa) during sintering. The electrical conductivity of annealed sample with 10 wt.% of GNPs oriented parallel to the measuring direction increased significantly up to 118 S·cm⁻¹. Similarly, the thermal conductivity of composites was very sensitive to the orientation of GNPs. In direction perpendicular to the GNPs the thermal conductivity decreased with increasing amount of graphene from 180 W·m⁻¹ K⁻¹ to 70 W·m⁻¹ K⁻¹, mainly due to the scattering of phonons on the graphene – SiC interface. In parallel direction to GNPs the thermal conductivity varied from 130 W·m⁻¹ K⁻¹ up to 238 W·m⁻¹ K⁻¹ for composites with 1 wt.% of GO and 5 wt.% of GNPs after annealing. In this case both the microstructure and composition of SiC matrix and the good thermal conductivity of GNPs improved the thermal conductivity of composites.     

Synergistic thermal conductivity enhancement of PC/ABS composites containing alumina/magnesia/graphene nanoplatelets

Graphene nanoplatelets (GNPs) have attracted considerable attention in the field of thermal management materials due to their unique structure and exceptional thermal conductive properties. In this work, we demonstrate a significant synergistic effect of GNPs, alumina (Al₂O₃), and magnesia (MgO) in improving the thermal conductivity of polycarbonate/acrylonitrile‐butadiene‐styrene polymer alloy (PC/ABS) composites. The thermal conductivity of the composites prepared through partial replacement of Al₂O₃ and MgO with GNPs could increase dramatically compared with that without GNPs. The maximum thermal conductivity of the composite is 3.11 W mK⁻¹ at total mass fraction of 70% with 0.5 wt% GNPs loading. It increases 60% compared with that without GNPs (1.95 W mK⁻¹). The synergistic effect results from the compact packing structure formed by Al₂O₃/MgO and the bridging of GNPs with Al₂O₃/MgO, thus promoting the formation of effective thermal conduction pathways within PC/ABS matrix. More importantly, together with the intrinsically high thermal conductivity of GNPs, boosted and effective pathways for phonon transport can be created, thus decrease the thermal resistance at the interface between fillers and PC/ABS matrix and increase the thermal conductivity of composites. POLYM. COMPOS., 38:2221–2227, 2017. © 2015 Society of Plastics Engineers     

High lumen density of Al2O3-LuAG: Ce composite ceramic for high-brightness display

Thermally robust and highly efficient green-emitting luminescent ceramics are gradually attracting great attention as promising phosphors using in high-brightness laser phosphor display to reduce serious speckle noise as well as high cost. However, lumen density is still seriously restricting their potential applications especially under high-power density laser due to insufficient absorption of blue laser and significant thermal quenching. Here, we report an Al₂O₃-LuAG: Ce composite ceramic phosphor (CCP) for high-brightness laser phosphor display. Owing to good optical properties and high thermal conductivity of Al₂O₃, the Al₂O₃-LuAG: Ce CCP shows high photoluminescence quantum yield (79.6%), low thermal quenching (only 3.2% loss in luminescence at 200°C), and high thermal conductivity (18.9 W·m⁻¹·K⁻¹). Moreover, the Al₂O₃, as scattering centers, enhances the Rayleigh–Mie scattering of the blue laser, and hence the absorption of the Al₂O₃-LuAG: Ce CCP exhibits a remarkable improvement (~2.3 times) at 450 nm. Finally, with optimized thickness (0.3 mm) of Al₂O₃-LuAG: Ce CCP, an excellent luminous efficiency (216 lm·W⁻¹) and outstanding lumen density (6129 lm·mm⁻²) of the green-emitting light source was obtained by driving under a high-power density (28.33 W·mm⁻²) blue laser. All of those validate the suitability of the Al₂O₃-LuAG: Ce CCP for high-brightness display.     

Simultaneously enhanced mechanical properties and thermal properties of ultrahigh‐molecular‐weight polyethylene with polydopamine‐coated α‐alumina platelets

Polydopamine (PDA) was employed to modify micrometric Al₂O₃ platelets to improve the interfacial compatibility between α‐Al₂O₃ powder and ultrahigh‐molecular‐weight polyethylene (UHMWPE). The structure of PDA‐coated Al₂O₃ and UHMWPE composites was investigated via Fourier transform infrared spectroscopy, scanning electron microscopy and X‐ray photoelectron spectroscopy. The thermal stability and mechanical performance of the samples were also evaluated. It is clear that UHMWPE/PDA‐Al₂O₃ composites exhibit better mechanical properties, higher thermal stability and higher thermal conductivity than UHMWPE/Al₂O₃ composites, owing to the good dispersion of Al₂O₃ powder in the UHMWPE matrix and the strong interfacial force between the macromolecules and the inorganic filler caused by the presence of PDA. The tensile strength and the tensile elongation at break of UHMWPE/PDA‐Al₂O₃ composite with 1 wt% PDA‐Al₂O₃ are 62.508 MPa and 462%, which are 1.96 and 1.98 times higher than those of pure UHMWPE, respectively. The thermal conductivity of UHMWPE/PDA‐Al₂O₃ composite increases from 0.38 to 0.52 W m^?1 K^?1 with an increase in the dosage of PDA‐Al₂O₃ to 20 wt%. The results show that the prepared PDA‐coated Al₂O₃ powder can simultaneously enhance the mechanical properties and thermal conductivity of UHMWPE. © 2018 Society of Chemical Industry     

Mechanical and thermal properties of spark plasma sintered Al2O3-graphene-SiC hybrid composites

Monolithic Al₂O₃ and Al₂O₃-graphene-SiC hybrid composites were prepared by spark plasma sintering (SPS) under vacuum atmosphere. The results show that the hybrid composites were almost completely dense (>97%). SiC content has a significant effect on the microstructure of the composites. With the increase of SiC content, the average grain size of alumina decreased gradually. The addition of SiC to alumina changed fracture mode from inter-granular fracture to mixed fracture mode of inter-granular fracture and trans-granular fracture. The Al₂O₃-0.4 wt%graphene-5 wt% SiC hybrid composite has the highest bending strength and hardness, which were 57% and 19.22% higher than those of the monolithic alumina, respectively. The room temperature (RT) thermal conductivity of the monolithic Al₂O₃ (25.5 W/m·K) was the highest. The thermal conductivity and thermal diffusivity coefficient of the composites decreased with the increase in temperature, while the specific heat of monolithic alumina and composites increased with the increase in temperature and additives. These properties were related to the microstructure of materials and the possible transport mechanisms were discussed.     

Thermal Stability and Ionic Conductivity of Calcia‐Stabilized Zirconia with Alumina Addition

The thermal expansion and ionic conduction of 15 mol% CaO‐stabilized zirconia (CSZ) with added Al₂O₃ were investigated. Specimens with 0.5 and 1 mol% Al₂O₃ maintained the cubic phase, and the thermal diffusivity increased from 0.499 to 0.661 mm²/s with a 1 mol% addition. The addition of 5 mol% caused a decrease in the thermal diffusivity (0.609 mm²/s) with the formation of the monoclinic phase. The thermal expansion coefficient of the CSZ decreased, and the thermal diffusivity increased with the addition of Al₂O₃. The ionic conductivity was increased up to the addition of 1 mol% due to scavenging of siliceous by Al₂O₃, while the 5 mol% addition showed a decrease in conductivity with the formation of the intergranular phase.     

Simultaneously enhanced thermal conductivity and dielectric properties of borosilicate glass-based LTCC with AlN and h-BN additions

Microwave devices with reduced dielectric loss and electronic components with increased integration density necessitate the higher performance of electronic packaging materials. The h-BN/AlN/CaCO₃-MgO-B₂O₃-SiO₂-Li₂CO₃ glass composites were prepared via tape-casting and then sintered by pressureless and hot-pressing, respectively. The thermal conductivity of pressureless sintered composite was increased to 6.55 W/(m·K) by incorporating 3 wt% h-BN, and the thermal expansion of 4.47 ppm/K was achieved along with low dielectric constant of 5.76 and dielectric loss of 7.02 × 10⁻⁴ at 24 GHz. In contrast, the hot-pressing sintered composite containing 4 wt% h-BN exhibited higher thermal conductivity of 10.3 W/(m·K) and lower dielectric loss of 4.77 × 10⁻⁴. The microstructure characterization indicated the construction of heat conduction networks, and XRD analysis illustrated the formation of crystallization in the glass. Such low-temperature co-fired ceramic (LTCC) with high thermal conductivity and low dielectric loss would be a promising candidate for electronic packaging and 5G communication applications.     

Heat transport enhancement of thermal energy storage material using graphene/ceramic composites

Graphene/ceramic composites are proposed by directly depositing graphene on the insulating Al₂O₃ particles by chemical vapor deposition without any metal catalysts. Carbothermic reduction occurring at the Al₂O₃ surface is vital during the initial stage of graphene nucleation and the graphene sheet can connect with neighboring sheets to completely cover Al₂O₃ particles. The quality and layer number of graphene on Al₂O₃ can be finely tailored by changing the growth temperature and gas ratio. Graphene coated Al₂O₃ (G-Al₂O₃) composites are used as effective fillers of stearic acid (SA) to increase the thermal transport property. By the optimization of the layer number of graphene, size of Al₂O₃ particles and ratio of G-Al₂O₃/SA in a quantitative, their thermal conductivities significantly increase up to 11 folds from 0.15 to 1.65 W m⁻¹ K⁻¹. The great improvement is attributed to the high thermal transfer performance of graphene and excellent wettability between graphene and SA. When the G-Al₂O₃/SA composites with the graphene coated porous Al₂O₃ foam, the thermal conductivity further reaches to 2.39 W m⁻¹ K⁻¹, and the corresponding latent heat is 38 J g⁻¹. It demonstrates the potential applications of graphene in thermal transport and thermal energy storage devices.     

Properties of thermally conductive silicone rubbers filled with admicellar polymerized polypyrrole-coated Al2O3 particles

Polypyrrole (PPy) nanolayers were introduced on the surface of alumina (Al₂O₃) particles via admicellar polymerization. The properties of silicone rubbers (SRs) filled with PPy-coated Al₂O₃ and pristine Al₂O₃ as thermally conductive fillers were studied and compared. The results demonstrate that the addition of PPy-coated Al₂O₃ leads to a better interfacial compatibility but lower cross-linking density of the composites than pristine Al₂O₃. The improvement in the compatibility and the decrease in the cross-linking density are paradoxes in affecting mechanical properties. The improvement in the compatibility shows a slight predominance on the strength at low-filler contents. Lower cross-linking density of modified-Al₂O₃/SR composites led to a better processing performance and a higher maximum filler loading amount than the pristine Al₂O₃/SR composites, which is beneficial to increasing the thermal conductivity and maintaining a relatively good strength. The PPy-coated Al₂O₃/SR composite with 83 wt% filler content has a thermal conductivity of 1.98 W/(m K) and a tensile strength of 2.9 MPa, and the elongation at break was 63%. Functionalized fillers by admicellar polymerization used in the fabrication of filler/SR composites not only improve the interfacial compatibility but also optimize and expand the functions of the composites, which has great significance for the production and application of thermally conductive SR in some branches of industry (automotive, electrical engineering, etc.) in the future.     

Effect of Al2O3@CaCO3 spherical particles on microstructures,phase compositions and performances of lightweight MA spinel-corundum refractories

The lightweight spinel-corundum refractory was prepared using the Kirkendall effect when spherical particles Al₂O₃@CaCO₃ were introduced into the ingredient. The mechanism of pore formation through in-situ pore formation combined with the Kirkendall effect to reduce the bulk density of the refractory to the lightweight has been investigated in detail. The properties of the lightweight spinel-corundum refractory have also been studied. The results showed that the calcium at the center of the spherical particle spreads outwards and reacts with Al₂O₃ in the shell to form calcium hexaluminate (CA₆). After which a portion of CA₆ reacts with spinel in the matrix to manufacture a solid solution phase (CM₂A₈). At the same time, the hollow structure forms at the center of the spherical particle due to the buildup of the Kirkendall pore. With the additional amount of the Al₂O₃@CaCO₃ spherical particles reaches 30%, the samples fired in 1650 °C for 3 h can gain high compressive strength (119.8 MPa), high refractoriness under load (>1700 °C), low bulk density (2.76 g cm⁻³) and low thermal conductivity (1.36 W·(m·K) ⁻¹).     

Preparation and thermophysical properties of LaMgAl11O19–Yb3Al5O12 ceramic composites

LaMgAl₁₁O₁₉–Yb₃Al₅O₁₂ ceramic composites were prepared by pressureless sintering process at 1700 °C for 10 h in air. The microstructure and thermophysical properties of the composites were characterized by X-ray diffraction, scanning electron microscopy, high-temperature dilatometer and laser flash diffusivity measurements. LaMgAl₁₁O₁₉–Yb₃Al₅O₁₂ ceramic composites are composed of magnetoplumbite and garnet structures. LaMgAl₁₁O₁₉–Yb₃Al₅O₁₂ ceramic composites exhibit typical linear increase in thermal expansion with the increase of temperature. The measured thermal diffusivity gradually decreases with increasing temperature. Thermal conductivity of LaMgAl₁₁O₁₉–Yb₃Al₅O₁₂ ceramic composites is in the range of 2.6–3.9 W·m⁻¹·K⁻¹ from room temperature to 1200 °C.     

Effect of nanoparticles on the performance of thermally conductive epoxy adhesives

Microsized or nanosized α‐alumina (Al₂O₃) and boron nitride (BN) were effectively treated by silanes or diisocyanate, and then filled into the epoxy to prepare thermally conductive adhesives. The effects of surface modification and particle size on the performance of thermally conductive epoxy adhesives were investigated. It was revealed that epoxy adhesives filled with nanosized particles performed higher thermal conductivity, electrical insulation, and mechanical strength than those filled with microsized ones. It was also indicated that surface modification of the particles was beneficial for improving thermal conductivity of the epoxy composites, which was due to the decrease of thermal contact resistance of the filler‐matrix through the improvement of the interface between filler and matrix by surface treatment. A synergic effect was found when epoxy adhesives were filled with combination of Al₂O₃ nanoparticles and microsized BN platelets, that is, the thermal conductivity was higher than that of any sole particles filled epoxy composites at a constant loading content. The heat conductive mechanism was proposed that conductive networks easily formed among nano‐Al₂O₃ particles and micro‐BN platelets and the thermal resistance decreased due to the contact between the nano‐Al₂O₃ and BN, which resulted in improving the thermal conductivity. POLYM. ENG. SCI., 50:1809–1819, 2010. © 2010 Society of Plastics Engineers