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With the rapid development of the electronics industry, there is a growing demand for packaging materials that possess both high thermal conductivity (TC) and low electrical conductivity (EC). However, traditional insulating fillers such as boron nitride, aluminum nitride, and alumina (Al2O3) have relatively low intrinsic TC. When graphene, which exhibits both superhigh TC and EC, is used as a filler to fill epoxy resin, the TC of blends can be much higher than that of blends containing more traditional fillers. However, the high EC of graphene limits its application in cases where electrical insulation is required. To address this challenge, a method for coating graphene sheets with an in situ grown Al2O3 layer has been proposed for the fabrication of epoxy-based composites with both high TC and low EC. In the presence of a cationic surfactant, a dense Al2O3 layer with a network structure can be formed on the surface of graphene sheets. When the total content of Al2O3 and graphene mixed filler reached 30 wt%, the TC of the epoxy composite reached 0.97 W m−1 K−1, while the EC remained above 1011 Ω·cm. Finite element simulations accurately predicted TC and EC values in accordance with experimental results. This material, with its combination of high TC and good insulation properties, exhibits excellent potential for microelectronic packaging applications. [ABSTRACT FROM AUTHOR]

Copper and copper alloys own high thermal conductivity, electrical conductivity, good plasticity, and corrosion resistance, which are widely used in electric power, aerospace, and marine engineering. Due to low absorption rate of infrared and near infrared light, high thermal conductivity and high activity with oxygen, laser cladding of copper, and copper alloys are difficult to be conducted in air since the problems associated to cracks and voids are always hardly to be eliminated. In this paper, C-Al2O3-Cu composite powder mixed with Ni and Fe was developed to solve these problems. Use of carbon was to depress the oxidation and improve the laser absorption, while alumina was used to improve the laser absorption and mechanical strength. To improve the bonding strength between cladding layer and substrate, Ni and Fe were used. Experimental results showed that no obvious aggregation was observed and the powder showed good fluidity. The tensile strength of the cladding layer is 406.7 ± 0.1MPa which is about 1.7 times higher than that of pure copper substrate, and the tensile fracture of the cladding layer revealed microporous aggregation fracture due to the existence of Al2O3 in the cladding layer. [ABSTRACT FROM AUTHOR]

• Ultrahigh through-plane thermal conductivity achieved by continuous carbon fibers. • Thermal-induced and slant slicing-induced flexibility. • Leakage proof capacity from polymer skeleton and carbon fiber arrays. • Novel thermal management capacity from high through-plane thermal conductivity and heat absorbed during phase change. With the rapid development of micro-nano electronics, thermally conductive materials with remarkable through-plane thermal conductivity (κ ⊥) and great flexibility are greatly urgent to effective thermal management. The fillers with high thermal conductivity (TC) are commonly assembled to achieve this target. However, the imperfect contact between the joint fillers will lead to high thermal resistance (R), hindering thermal transport. Herein, we fabricated thermal interface materials (TIMs) with ultra-high κ ⊥ (up to 168.4 W m−1 K−1) and adjustable flexibility by the combination of highly thermally conductive carbon fiber bundles (CF) and polymer encapsulated phase change materials (PCMs). The alignment of consecutive CF guarantees the continuity of thermal paths, greatly facilitating thermal transport. While the slantly slicing technique and softening effect of PCMs beyond phase transition temperature lead to an attenuated compression stress (1.6 MPa@10% strain with a CF loading of 50 wt%). What's more, the latent heat absorbed by PCMs is also conducive to thermal management. Thus, during a CPU temperature-control experiment, the application of as-prepared TIMs manifests a temperature decline of 33.9 °C of CPU. This work opens a new perspective to fabricating TIMs with ultrahigh κ ⊥ and low compression stress (σ) by the combination of thermally induced flexible matrix and the slantly slicing technique of aligned CFs. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) are potential candidates in passive thermal regulation and energy storage fields due to their high latent heat capacity around phase transition temperature. However, the leakage problem and low thermal conductivity are two obstructive factors for the extended application of PCMs. Herein, a series of paraffin@silicon dioxide microcapsules (Pa@SiO 2)/graphene sheets (GS)/silicone rubber (SR) phase change composites (PCCs) were prepared. It is found that the inorganic SiO 2 shell is conducive to enhancing the thermal conductivity of PCCs and the double encapsulation by the SiO 2 shell and SR skeleton can restrict the leakage of liquid Pa during phase transition. With a Pa@SiO 2 content of 70 wt%, the PCCs have a high latent heat of 126.1 J/g and enhanced thermal conductivity of 0.37 W m−1 K−1, which is 131.25% higher compared to that of pure SR. In addition, the introduction of graphene sheets further boosts the thermal conductivity of PCCs to 2.69 W m−1 K−1. The obtained PCCs lead to a surprising temperature decline of nearly 35 °C of a commercial lithium-ion battery during a high discharge rate (7.4 C). This work provides an efficient route to fabricate microcapsules-based PCCs for passive thermal regulation. [Display omitted] [ABSTRACT FROM AUTHOR]

Thermal interface materials (TIMs) with high through-plane thermal conductivity (TC), softness, and electrical insulation are highly desired for modern electronics. However, it is challenging to simultaneously achieve these properties. Boron nitride (BN)-based polymer composites are promising candidates for advanced TIMs owing to the high TC and great electrical insulation of BN. However, previous works perform either low TC (< 8 W m−1 K−1) or high stiffness. The ultimate properties of BN-based TIMs remain largely unclear and unrealized. Here, we fabricate BN film-filled silicone rubber composites by a facile stacking-cutting method, which maintains the high degree of orientation the BN film, so that a record-high though-plane TC of 19.1 W m−1 K−1 and a low compressive modulus of 5.42 MPa are achieved. The low BN content (37 vol%) ensures the softness and resilience of the as-prepared TIMs. This work presents a highly efficient strategy to enhance the performance of BN based TIMs, promoting their large-scale manufacturing and practical applications. • Thermal interface materials based on boron nitride film (BNF) were fabricated by a facile stacking-cutting method. • The composites exhibit a high degree of orientation and densely overlapped structures. • The composites show a record-high though-plane TC of 19.1 W m−1 K−1 at 37 vol% BN content and a low compressive modulus of 5.42 MPa. [ABSTRACT FROM AUTHOR]

High thermally conductive materials with good electrical insulating and mechanical properties are indispensable for electronics. Aiming for all-polymer composites with light weight, electrical insulation and high thermal conductivity (TC), ultrahigh molecular weight polyethylene (UHMWPE) fibers/epoxy composites with two kinds of fiber orientation structures (0°/90°, ±45°) were fabricated by hot-pressing. It is found that the in-plane TC of ±45° composite is approximately 1.3–1.4 times that of 0/90° one, and the corresponding mechanism is verified by finite element simulation and model calculation. Thermally conductive pathways formed by UHMWPE fibers endow 0/90° and ±45° composites with the in-plane TC of 9.94 and 13.61 Wm−1K−1, respectively. Through depositing polydopamine (PDA) and grafting polyether amine (PEA) onto the surface of fibers, the poor fiber/epoxy interface was improved, resulting in 40.7% and 52.3% improvement in interlaminar shear strength (ILSS) and shear modulus, respectively. Simultaneously, a higher in-plane TC as high as 15.76 Wm−1K−1 is achieved. The heat dissipation evaluation indicates that the composite can reduce the temperature of the resistance wire by 14 °C. This work reveals the great potential of UHMWPE fibers in heat dissipation and provides a strong candidate for electrical insulating support materials with high TC for heat management of electronics. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • h-BN assembles into spherical aggregated BN (A-BN) assisted by the vortex flow. • The mechanism and operating conditions of A-BN formation are systematically studied. • A through-plane TC of 6.56 W/(mK) is achieved due to the formation of A-BN. • A-BN/AlN/SR composite demonstrates excellent heat dissipation performance as TIMs. Thermal interface materials (TIMs) with high thermal conductivity and good insulation properties are in high demand for thermal management systems. Platelet-like materials such as BN and graphene usually orient horizontally in polymer composites, causing minor Through-plane thermal conductivity (TC) enhancement. Herein, aggregated BN (A-BN)/AlN/silicone rubber (SR) composites with enhanced through-plane TC are fabricated assisted by vortex flow during the planetary centrifugation process. It is found that BN platelets assembled into A-BN with spherical AlN as cores based on concentric vortex. Due to the formation of spherical A-BN, through-plane TC of as-prepared composites with 40 wt% BN and 45 wt% AlN is as high as 6.56 W/(m·K) while it is only 4.62 W/(m·K) for composites without A-BN. Such high TC should mainly be attributed to the large-sized spherical BN interconnected structure which constructs an efficient thermally conductive path in the through-plane direction. The heat dissipation evaluation test also demonstrates the excellent performance of the A-BN/AlN/SR composite. This work provides a facile strategy to produce large-sized BN agglomerates and gives insights into the vortex flow during the planetary centrifugation process. [ABSTRACT FROM AUTHOR]