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We report a carbon nanotube array-encapsulatedphase change compositein which the nanotube distribution (or areal density) could be tailoredby uniaxial compression. The n-eicosane (C20) wasinfiltrated into the porous array to make a highly conductive nanocompositewhile maintaining the nanotube dispersion and connection among thematrix with controlled nanotube areal density determined by the compressivestrains along the lateral direction. The resulting electrically conductivecomposites can store heat at driven voltages as low as 1 V at fastspeed with high electro-to-heat conversion efficiencies. Increasingthe nanotube density is shown to significantly improve the polymercrystallinity and reduce the voltage for inducing the phase changeprocess. Our results indicate that well-organized nanostructures suchas the nanotube array are promising candidates to build high-performancephase change composites with simplified manufacturing process andmodulated structure and properties. [ABSTRACT FROM AUTHOR]

High-performance solid electrolytes are critical for realizing all-solid-state batteries with enhanced safety and cycling efficiency. However, currently available candidates (sulfides and the NASICON-type ceramics) still suffer from drawbacks such as inflammability, high-cost and unfavorable machinability. Here we present the structural manipulation approaches to improve the sodium ionic conductivity in a series of affordable Na-rich antiperovskites. Experimentally, the whole solid solutions of Na 3 O X ( X = Cl, Br, I) are synthesized via a facile and timesaving route from the cheapest raw materials (Na, NaOH and Na X ). The materials are nonflammable, suitable for thermoplastic processing due to low melting temperatures (<300 °C) without decomposing. Notably, owing to the flexibility of perovskite-type structure, it's feasible to control the local structure features by means of size-mismatch substitution and unequivalent-doping for a favorable sodium ionic diffusion pathway. Enhancement of sodium ionic conductivity by 2 magnitudes is demonstrated by these chemical tuning methods. The optimized sodium ionic conductivity in Na 2.9 Sr 0.05 OBr 0.6 I 0.4 bulk samples reaches 1.9 × 10 −3 S/cm at 200 °C and even higher at elevated temperature. We believe further chemical tuning efforts on Na-rich antiperovskites will promote their performance greatly for practical all-solid state battery applications. [ABSTRACT FROM AUTHOR]

Phase transition is a natural phenomenon happened around our daily life, represented by the process from ice to water. While melting and solidifying at a certain temperature, a high heat of fusion is accompanied, classified as the latent heat. Phase change material (PCM) has been widely applied to store and release large amount of energy attributed to the distinctive thermal behavior. Here, with the help of nanoporous materials, we introduce a general strategy to achieve the binary eicosane/PEG4000 stuffed reduced graphene oxide aerogels, which has two ends with different melting points. It's successfully demonstrated this binary PCM composites exhibits thermal rectification characteristic. Partial phase transitions within porous networks instantaneously result in one end of the thermal conductivity saltation at a critical temperature, and therefore switch on or off the thermal rectification with the coefficient up to 1.23. This value can be further raised by adjusting the loading content of PCM. The uniqueness of this device lies in its performance as a normal thermal conductor at low temperature, only exhibiting rectification phenomenon when temperature is higher than a critical value. The stated technology has broad applications for thermal energy control in macroscopic scale such as energy-efficiency building or nanodevice thermal management. [ABSTRACT FROM AUTHOR]