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With the increasing demand for thermal management materials in the highly integrated electronics area, building efficient heat-transfer networks to obtain advanced thermally conductive composites is of great significance. In the present work, highly thermally conductive poly­(vinyl alcohol) (PVA)/boron nitride nanoplatelets@silver nanowires (BNNS@AgNW) composites were fabricated via the combination of the electrospinning and the spraying technique, followed by a hot-pressing method. BNNS are oriented along the in-plane direction, while AgNWs with a high aspect ratio can help to construct a thermal conductive network effectively by bridging BNNS in the composites. The PVA/BNNS@AgNW composites showed high in-plane thermal conductivity (TC) of 10.9 W/(m·K) at 33 wt % total fillers addition. Meanwhile, the composite shows excellent thermal dispassion capability when it is taken as a thermal interface material of a working light-emitting diode (LED) chip, which is certified by capturing the surface temperature of the LED chip. In addition, the out-of-plane electrical conductivity of the composites is below 10–12 S/cm. The composites with outstanding thermal conductive and electrical insulating properties hold promise for application in electrical packaging and thermal management.

Organo-layered double hydroxide/polypropylene (LDH/PP) nanocomposites were successfully synthesized via a solution blending method. As an attempt to improve the compatibility with hydrophobic PP, the LDH surface was modified by the incorporation of various anionic surfactants via electrostatic interaction with LDH cationic layers. Surfactants were selected by considering the aliphatic carbon chain length (laurate, palmitate, stearate and dodecyl sulfate) and anionic functional groups (-COO À , -OPO 3 2À , and -OSO 3 À ) with the purpose of optimizing the homogeneous dispersion in the PP matrix. In PP nanocomposites containing LDH modified with alkyl carboxylate, the (00l) X-ray diffraction (XRD) peaks originating from organo-LDH were not observed, indicating that organo-LDH layers were fully exfoliated and homogeneously dispersed within the PP matrix, which were also confirmed by cross-sectional TEM analysis. However, PP nanocomposites containing LDH modified with dodecyl sulfate and lauryl phosphate showed broad (00l) XRD peaks, indicating that organo-LDH was partially exfoliated.According to the thermogravimetric analysis, the thermal stability (T 0.5 ) of organo-LDH/PP nanocomposites was significantly improved by 37-60 K, depending on the type and loading content of organo-LDH compared to that of pristine PP. PP nanocomposites containing well-dispersed organo-LDH showed substantial enhancement of the elastic modulus with little decrease of tensile strength.These results are due to the increased interface volume fraction provided by the exfoliated LDH nanosheets.

A novel conductive composite consisting of polyimine vitrimer matrix and multiwalled carbon nanotube (MWCNT) filler that allows bending, stretching, rehealing, and closed-loop recycling was developed. Such composites can be easily prepared by simply heating a mixed solution of the polyimine precursors and less than 10 wt % of MWCNTs. The resulting composites combine both advantages of the polyimine vitrimer (i.e., dynamic covalent bond exchange) and carbon nanotubes (i.e., electron conducting), and the as-fabricated thin films exhibit malleability, rehealability, recyclability and good electron conductivity. Impressively, the electrical conductivity of the composite could remain almost the same after bending, reshaping, rehealing, and reuse, thus making it an excellent candidate for flexible electronics. Moreover, such composites can also be fully recycled at the end of their service life, which would greatly reduce the electronic waste, manufacturing cost, and environmental impact.

Carbon nanotubes, with their unusual blend of mechanical, thermal, and electrical properties, have been the focus of intense research in a wide variety of disciplines.[1] Carbon nanotubes can be formed by rolling up graphene sheets into a seamless cylindrical shape. Nanotubes can be classified into two major types: single-wall carbon nanotubes (SWNTs) and multiwalled carbon nanotubes (MWNTs). MWNTs comprise concentric SWNTs held together by weak van der Waals' forces. The Young's modulus and strength of individual SWNTs have been found to be ∼ 1 TPa and ∼ 50 GPa, respectively, [2,3] which is significantly better than current state-ofthe-art engineering materials such as carbon-fiber composites. This has generated great interest in the use of nanotubes as reinforcement fibers in composite materials. [4][5][6] While most of the work to date has focused on quantifying the tensile strength and Young's modulus of nanocomposites, the buckling stability of nanocomposite structures is yet to be investigated in detail. In this paper, we perform carefully designed compression tests to quantify the buckling behavior of nanocomposite systems.Buckling is a structural instability failure mode and a major concern for structural design. Buckling is related to both the geometry and the material properties of the structure. For a slender column under compression, buckling usually occurs well before the allowable normal stress of the material is reached. For a column under an axial compressive load, the smallest critical load which defines the onset of structural instability is given by Euler's equation [7] where P buckling is the critical buckling load, E is the elastic modulus of the column, L e is the effective length of the column, and I is the moment of inertia of the cross section. The effective length L e depends on the column boundary conditions. For fixed boundary conditions, the effective length is half of the gage length of the column. The specimens used in this study have a slenderness ratio L e /q ≈ 52.3 (where q is the column radius), greater than the critical slenderness ratio SR c ≈ 32.9, which means that the column can be considered to be long and Euler's equation can be utilized. The slenderness ratio and the critical slenderness ratio are computed usingwhere L gage is the gage length, I is the least moment of inertia of the cross section, A is the area of the cross section, and r pl is the proportional limit of the material. For the polycarbonate specimens used in this study, the proportional limit r pl obtained from the stress-strain curve is approximately 20 MPa (∼ 1/3 of the yield strength of the material). From the classical Euler equation, it is clear that addition of nanotube reinforcement fibers into the matrix material will increase the elastic modulus of the sample, causing a corresponding increase in the critical buckling load. Therefore, the buckling stability enhancement is expected to be proportional to the stiffening (i.e., the elastic modulus enhancement) of the composite structure. To investigate ...