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• Layer-by-layer scraping can produce a powerful shearing effect for UHPE/GNPs gel. • Strong shearing induced dense stacking and ordered alignment of GNPs and PE chains. • The dense and ordered structure drastically enhanced in-plane TC up to 28.88 W/mK. • The solar-thermal conversion ability was also improved by the ordered structure. The simultaneous achievement of ordered alignment for fillers and polymer matrix is highly desired in polymer-based thermally conductive composites, but it is still extremely challenging. Herein, we put forward a layer-by-layer scraping (LbLS) method to simultaneously arrange ultra-high molecular weight polyethylene (UHPE) chains and graphene nanoplates (GNP) into a highly oriented structure. When UHPE/GNP gel suffering the strong shearing effect during LbLS process, the inner UHPE chains and GNP were dragged and orderly arranged along shearing direction, and these oriented structures were retained after rapidly drying by distillation. After layer-by-layer stacking, nacre-like UHPE/GNP films with tightly layered structure were obtained. By adjusting the scraping gap from 200 to 50 μm, the oriented structure can be effectively reinforced with the Herman orientation factors f increasing from 0.83 to 0.88 for GNP and 0.75 to 0.82 for UHPE chains. The highly ordered structure can form a tight and oriented thermal conduction network with low interfacial thermal resistance in plane. The LbLS composite film thus significantly enhanced the in-plane thermal conductivity up to 28.88 W/mK, compared with traditional solution casting film (9.63 W/mK). Moreover, the highly oriented structure can significantly increase the solar-thermal conversion performance (58.1 °C@100 mW/cm2) by improving its light absorption ability comparing to that of solution casting film. Besides, the mechanical strength and toughness that depend on the filler and chain alignment were effectively increased by the oriented structure. [ABSTRACT FROM AUTHOR]

[Display omitted] • ANF-carbonized welding is used to reduce the ITR of 3D graphene architecture. • PCM containing graphene architecture shows a TC of 4.85 W/mK at 4.26 vol% content. • Thermal conductive architecture achieves the rapid heat transfer/storage in PCM. • Graphene architecture enables PCM solar/electric-to-thermal conversion capacity. Graphene-based porous architectures are promising in addressing the poor thermal conductivity, leakage, shape stability problems of organic phase change materials (PCMs), meanwhile endowing them with excellent solar/electric-to-heat conversion ability, but they are still limited by the high interfacial thermal/electrical resistance in architectures caused by organic "binders". In this work, in view of the excellent gel ability of aramid nanofibers (ANF) and its highly ordered conjugate molecular structure, a promising graphene porous architecture assisted by ANF was constructed by unidirectional freeze casting coupled with carbonization welding technique. Due to the similar graphite lattice structure of ANF-derived carbonization and graphene, the interfacial thermal/electrical resistance in highly vertically oriented graphene architecture was greatly reduced. As a result, the PCMs composite encapsulated by the graphene architecture carbonizing at 1500 °C exhibited an outstanding thermal conductivity of as high as 4.85 W/mK at only 4.26 vol%, which enables a rapid heat transfer and storage in PCM composite. The honeycomb porous graphene architecture with high porosity can accommodate sufficient PCMs for energy storage, showing a high latent heat enthalpy of 149.7 J/g with excellent shape stability during phase change process. More importantly, the graphene architecture endows PCM composites with excellent solar/electric-to-thermal conversion capacities, which not only expands the types of energy stored by PCMs, but is also promising in the thermal management application requiring a continuous and stable temperature environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ammonium polyphosphate functionalized BNNS (BNNS@APP) was prepared by one-step wet ball milling method. • The macromolecular APP play the role of organic "binders" to construct 3D BNNS skeleton. • The 3D BNNS@APP skeleton with a highly oriented structure was obtained by unidirectional freezing. • The EP/BNNS@APP composite presented excellent thermal conductivity and flame retardancy. Three-dimensional (3D) boron nitride skeleton has a promising prospect in improving the thermal conductivity and flame retardancy of polymer composites, yet the problems of interface thermal resistance and combustion collapse in the skeleton caused by organic adhesives still need to be solved. In this work, macromolecular flame retardancy, ammonium polyphosphate (APP) with high polymerization degree, was firstly used to modify and assemble boron nitride nanosheets (BNNS) into 3D thermally conductive skeleton, in which APP with rich amino groups can result in the strong grafting modification to reduce the interfacial thermal resistance in BNNS skeleton, meanwhile, the catalytic carbonization of APP can reinforce the 3D skeleton barrier without collapse during combustion. Typically, one-step wet ball-milling with assisted APP was used to exfoliate and modify BNNS, followed by unidirectional freezing to achieve 3D BNNS@APP skeleton with highly oriented structure. As expected, the constructing 3D skeleton with low interfacial thermal resistance can effectively form a heat transfer path in polymer matrix. The obtained epoxy-based composite showed a high thermal conductivity of 3.28 W/mK at 9.28 vol% BNNS@APP. Meanwhile, the producing 3D skeleton barrier during combustion induced the significant improvement in flame retardancy, with heat release rate (HRR) and total heat release (THR) decreasing by 68.3% and 52.7%, respectively. This work provides a new adhesive choice in constructing 3D thermal conductive and flame retardant skeleton, which exhibits high potential in thermal management application. [ABSTRACT FROM AUTHOR]

Graphical abstract The multilayered ACPCs based on PP/MWCNTs composites were prepared with outstanding conductive anisotropy, excellent current-carrying capability and directional heat dissipation, demonstrating the applications for electrical and thermal management. Highlights • Multilayered composites were fabricated via a facile but environmental friendly way. • Such composites show remarkable anisotropic electrical and thermal conductivity. • Such composites exhibit strong interfacial strength and enhanced thermal stability. • Such composites can be easily processed into desired macroscopic shapes. • This approach can be easily scaled up for industrial production. Abstract Multilayered objects are some of the most common composites in nature with outstanding performance that cannot be achieved by a single component. To expand the application of multilayered composites with excellent anisotropic properties, facile and environmental friendly fabrication methods and low-cost raw materials are unambiguously required. The Chinese traditional food called "thousand-layer pie" is an example of such composites with multilayered structure, showing visual attractiveness and having delicious taste. Borrowing the idea from the method of preparing this food, anisotropic conductive polymer composites (ACPCs) with alternating microlayers of pure polypropylene (PP) and PP filled multi-walled carbon nanotubes (PPCNTs) were prepared by a combined polymer melt processing technique. The multilayered structure endowed the ACPCs with inner layer conduction but interlayer insulation. The electrical conductivity in X direction reached up to 1 S/m and exhibited a value almost 16 orders of magnitude higher than the value in Z direction, which was by far the most remarkable conductive anisotropy compared with the reported counterparts. The anisotropic functionality of the ACPCs enabled them to be used in electrical and thermal management applications, such as subminiature integrated circuits, highly reliable electrical interconnects and anisotropic thermal conduction. Considering the low-cost raw materials used and the facile preparation process, this approach can be scaled up for industrial production, promoting such ACPCs with high performance and functionality to be implemented in a variety of applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ionic liquid functionalized BNNS (BNNS@IL) was performed by one-step ball milling. • High-orientation layered EP/BNNS@IL film was fabricated via CLbL blade-casting. • Well-dispersed BNNS@IL is highly stacked in EP matrix along the in-plane direction. • The film showed excellent anisotropic thermal conductivity and flame retardancy. Increasing power density and excess heat production in integrated electronic devices create the strong demand for polymeric thermal management materials with excellent thermal stability, flame retardancy and thermal conductivity. To this end, high-performance ionic liquid-wrapped boron nitride nanosheets (BNNS@IL) were firstly simultaneously exfoliated and flame-retardant functionalized via one-step ball milling process based on the strong mechanochemical action. Epoxy (EP)-based layered films with highly in-plane oriented BNNS@IL were then fabricated by a novel, effective and solvent-free cyclic layer-by-layer (CLbL) blade-casting method. Arising from the highly flat oriented structure and rich flame-retardant functional groups of BNNS@IL, as well as the high compatibility between filler and matrix, the as-fabricated EP/BNNS@IL films exhibited high anisotropic thermal conductivity (K ∥ of 8.3 and K ⊥ of 0.8 W m−1 K−1), outstanding thermal stability and flame retardancy with a dramatic decrease in PHRR (104.2 W/g) and THR (8.1 kJ/g) corresponding to reductions of 72.9% and 75.7% compared with neat EP, respectively. Additionally, the flat oriented structure and strong interfacial interaction also endow EP/BNNS@IL films with high flexibility and excellent mechanical properties. Therefore, the high-effective CLbL casting method and the obtained high-performance EP-based film exhibit a significant potential application in high power flexible electrical devices and thermal management products. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon welding is used to reduce filler-to-filler ITR in 3D graphene skeleton. • Introducing the graphene skeleton into PCM improves its thermal conductivity. • The graphene skeleton can avoid the leakage of PCM during solid–liquid phase change. • The graphene skeleton endows PCM with solar-to-heat conversion capacity. Advanced phase change materials (PCMs) with three-dimensional (3D) thermal conductive skeletons reveal the promising prospect in the thermal management of lithium battery. However, the high filler-to-filler interfacial thermal resistance (ITR) arising from the weak interfacial contact connection in 3D skeleton is still challenging. Herein, we demonstrate a "carbon welding" strategy for reducing the filler-to-filler ITR in 3D graphene skeleton by achieving the lattice connection between contact graphene. Typically, the ordered 3D graphene skeleton was constructed by unidirectionally ice template assembling graphene nanoplates (GNP) with the assistance of poly (amic acid) (PAA). Imidization and carbonization treatments were employed to weld the adjacent GNP in 3D skeleton. The similar lattice structure of carbonized polyimide (PI) and graphene can result in the significant reduction of phonon scattering and ITR at these contact areas. After impregnation with polyvinyl alcohol (PEG), the high-performance PCMs with high-efficient phonon transmission expressway were obtained. As expected, the prepared composites reveal the high thermal conductivities with a maximum value of 7.032 W m−1 K−1 at ~11.6 vol% GNP, which is more than two-fold than that of the composite with uncarbonized skeleton. Finite element simulation and nonlinear model analyses confirm that the reduced filler-to-filler ITR in skeleton is the main reason for the improving thermal conductivity. In addition, the presence of 3D graphene skeleton can effectively avoid the leakage during solid–liquid phase change, and significantly improve the shape stability of the PCMs. At the same time, the graphene skeleton can endow the PCM with an excellent solar-to-heat conversion performance, which ensure a wide range of application in actual environment. [ABSTRACT FROM AUTHOR]

• Flexible HAMS films with alternant graphene and Ni chains were designed firstly. • High-effective electrons and phonons conductive paths were formed in HAMS films. • HAMS films reveal remarkable EMI shielding and thermal conductivity simultaneously. • Stacking hot-pressing for preparing HAMS films is easy to large-scale application. Flexible polyvinylidene fluoride (PVDF) films with various heterogeneous alternating multilayer structure (HAMS) containing high-aligned graphene nanosheets and Ni nanochains were designed for electromagnetic interference (EMI) shielding and heat dissipation applications. Because of the unique structure and highly aligned nanofillers, effective electron and phonon conductive paths were formed in HAMS films with optimal electrical and thermal conductivity of 76.8 S/m and 8.96 W/mK, respectively. Combining the high electrical conductivity and the synergetic electromagnetic loss, as well as multi-level electromagnetic multireflection, the optimal HAMS film with thickness of 0.5 mm exhibits a high EMI shielding effectiveness (SE) of 43.3 dB, showing 98.6% increment compared to homogeneous film (21.8 dB), which can further improve to 51.4 dB when increasing the thickness to 0.7 mm. Simultaneously, the highly concentrated and aligned graphene in alternating layers can contribute to the significant improvement in in-plane thermal conductivity of HAMS films with 14.3% and ~1200% increment comparing to the homogeneous film (7.84 W/mK) and pure PVDF (0.69 W/mK), respectively. Considering the outstanding performance and high-efficiency stacking hot-pressing preparation technique, HAMS films with alternating aligned graphene/Ni nanochain layers present a huge potential in practical large-scale application as advanced EMI protection and thermal management materials. [ABSTRACT FROM AUTHOR]

• Multiple synergistic effects were employed to prepare high performance PTCs. • RGO@Ni(OH) 2 with multiple flame-retardant effects was used as synergistic filler. • Synergistic dispersion and bridging connection induce the high heat conduction. • Catalytic, endothermic, barrier effects contribute to the improved fire resistance. The heat shock, thermal aging and fire hazard of induced by delayed heat diffusion in microelectronic devices require a high-efficiency thermal management system with high-performance electronic packaging materials. In this work, the significant thermal conductivity and flame retardancy of polymer-based thermally conductive composites (PTCs) are addressed by multiple synergistic effects of hexagonal born nitride (h BN) and few flame-retardant functionalized graphene. Briefly, a multifunctional hydrophilic graphene-based hybrid containing Ni(OH) 2 nanoribbons and reduced graphene oxide (RGO) was synthesized by two-step hydrothermal process. The resulted RGO@Ni(OH) 2 hybrid and h BN sheets (lateral size of 4.37 ± 1.68 μm and thickness of 80 ± 21 nm) used as synergistic and main fillers, respectively, was simultaneously added into EP matrix. As expected, the binary fillers showed multiple synergistic effects for improving the thermal conductivity and flame retardancy of composites. Typically, the good dispersion and interfacial interaction of RGO@Ni(OH) 2 hybrid in matrix can not only inhibit the stacking aggregation behavior of h BN sheets, but also bridge adjacent h BN sheets, both of which resulted in a high thermal conductivity (2.01 W/mK) of ternary composites with a synergistic increment of 39.4% comparing to EP/ h BN. On the other hand, their synergistic flame retarding effect including catalytic carbonization, endothermic action and barrier effect induced by RGO@Ni(OH) 2 , as well as "tortuous path" effect of h BN sheets, jointly led to the formation of a compact and robust char layer in condensed phase during combustion. As a result, EP/ h BN/RGO@Ni(OH) 2 exhibited a desired flame ratardancy with considerable reductions being seen in peak heat release rate, total heat release and total smoke production, i.e. , 33.5%, 33.8% and 43.0% comparing to neat EP. [ABSTRACT FROM AUTHOR]