Strong,tough,and thermally conductive nacre-inspired boron nitride nanosheet/epoxy layered nanocomposites

Thermally conductive polymer nanocomposites integrated with lightweight,excellent flexural strength,and high fracture toughness(KIc)would be of great use in many fields.However,achieving all of these properties simultaneously remains a great challenge.Inspired by natural nacre,here we demonstrate a lightweight,strong,tough,and thermally conductive boron nitride nanosheet/epoxy layered(BNNEL)nanocomposite.Because of the layered structure and enhancing the interfacial interactions through hydrogen bonding and Si–O–B covalent bonding,the resulting nacre-inspired BNNEL nanocomposites show high fracture toughness of~4.22 MPa·m^(1/2),which is 7 folds as high as pure epoxy.Moreover,the BNNEL nanocomposites demonstrate sufficient flexural strength(~168.90 MPa,comparable to epoxy resin),while also being lightweight(~1.23 g/cm^(3)).Additionally,the BNNEL nanocomposites display a thermal conductivity(κ)of~0.47 W/(m·K)at low boron nitride nanosheet loading of 2.08 vol.%,which is 2.7 times higher than that of pure epoxy resin.The developed nacre-inspired strategy of layered structure design and interfacial enhancement provides an avenue for fabricating high mechanical properties and thermally conductive polymer nanocomposites.

Recent advances in nacre-inspired anisotropic thermally conductive polymeric nanocomposites

The rapid development of miniaturized,highly integrated,and multifunctional modern electronic devices has generated a growing demand for anisotropic heat dissipation in polymer nanocomposites for thermal management applications.These anisotropic thermally conductive multifunctional polymer nanocomposites use bio-inspired structural design based on natural nacre,which is the gold standard for biomimetics.However,to date,a comprehensive review and critique on the highly-anisotropic thermal conduction of nacre-mimetic nanocomposites is nonexistent.As such,this extensive review of the nacre-inspired highly anisotropic thermal management nanocomposites summarizes the current design strategies,and explains the thermal conduction mechanisms,and factors affecting anisotropic thermal conductivity.Furthermore,the practical applications of the asprepared nacre-inspired highly anisotropic nanocomposites are highlighted.Finally,the key challenges and potential solution strategies associated with these nacre-inspired highly anisotropic nanocomposites are discussed and outlooks for future research opportunities are also proposed.

Nacre-inspired Green Artificial Bionanocomposite Films from the Layer-by-Layer Assembly of Montmorillonite and Chitosan

The simple LBL technique was introduced to fabricate green nacre-like chatosan/montmorillonite （CHI/MMT） films. The results of SEM and XRD analysis demonstrate that the produced CHI/MMT composites films stacked densely together to bring out well-defined nacre-like brick-mortar structure. The nanoindentation technique is used to characterize the mechanical properties of the layered nanocomposite films, which show enhanced mechanical modulus （up to -6.64 GPa） compared with the pure chitosan.

Nacre-inspired Polyglutamic Acid/Layered Double Hydroxide Bionanocomposite Film with High Mechanical,Translucence and UV-blocking Properties

Due to the various needs in the current applications, multifunctional composite materials with high strength and high toughness were highly desired now. Many scholars dedicated their time to find a simple, green and fast method for the preparation of multi-functional materials. In this study, inspired by the hierarchical ＂brick-and-mortar＂ structure and excellent mechanical performance of nacre, a fast green vacuum-filtration method was used to fabricate strong and multifunctional polyglutamic acid/layered double hydroxide （PGA/LDH） films mimicking nacre. The experimental results confirm that the artificial nacre has hierarchical ＂brick-and-mortar＂ structure. It exhibits excellent strength （93.5 MPa） and flexibility （easily bendable fold）, combining with outstanding properties of UV-blocking and translucence properties. This work provides a way of fabricating multifunctional organic-inorganic hybrid films, which has potential applications in the areas of optical, transportation and construction fields.

A Thermochromic, Viscoelastic Nacre-like Nanocomposite for the Smart Thermal Management of Planar Electronics

Cutting-edge heat spreaders for soft and planar electronics require not only high thermal conductivity and a certain degree of flexibility but also remarkable self-adhesion without thermal interface materials, elasticity, arbitrary elongation along with soft devices, and smart properties involving thermal self-healing, thermochromism and so on. Nacre-like composites with excellent in-plane heat dissipation are ideal as heat spreaders for thin and planar electronics. However, the intrinsically poor viscoelasticity, i.e., adhesion and elasticity, prevents them from simultaneous self-adhesion and arbitrary elongation along with current flexible devices as well as incurring high interfacial thermal impedance. In this paper, we propose a soft thermochromic composite(STC) membrane with a layered structure, considerable stretchability, high in-plane thermal conductivity(~30 Wm^(-1) K^(-1)), low thermal contact resistance(~12 mm^2 KW^(-1), 4–5 times lower than that of silver paste), strong yet sustainable adhesion forces(~4607 Jm^(-2), 2220 Jm^(-2) greater than that of epoxy paste) and self-healing efficiency. As a self-adhesive heat spreader, it implements efficient cooling of various soft electronics with a temperature drop of 20℃ than the polyimide case. In addition to its self-healing function, the chameleon-like behavior of STC facilitates temperature monitoring by the naked eye, hence enabling smart thermal management.