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Barium titanate (BTO) is a ferroelectric perovskite used in electronics and energy storage systems because of its high dielectric constant. Decreasing the BTO particle size was shown to increase the dielectric constant of the perovskite, which is an intriguing but contested result. We investigated this result by fabricating silicone-matrix nanocomposite specimens containing BTO particles of decreasing diameter. Furthermore, density functional theory modeling was used to understand the interactions at the BTO particle surface. Combining results from experiments and modeling indicated that polymer type, particle surface interactions, and particle surface structure can influence the dielectric properties of polymer-matrix nanocomposites containing BTO.

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Increasing the strength-to-weight ratio of injection moldable polymers can benefit a broad range of applications, such as automobiles, aircraft, and consumer electronic devices. This paper demonstrates that incorporating miniscule quantities (0.1 wt %) of gas-phase-synthesized graphene into acrylonitrile–butadiene–styrene (ABS) can significantly increase the strength of injection-molded specimens by over 20%. The results transform our current understanding of the structure–property relationships of graphene-filled polymer-matrix nanocomposites because highly crumpled graphene sheets with nonfunctionalized surfaces and nanometer-scale lateral dimensions are shown to be more effective at strengthening ABS than flat graphene flakes with functionalized surfaces and micrometer-scale lateral dimensions. 

The ability of lotus leaves to repel water is desired in numerous applications, such as self-cleaning surfaces, biomedical devices, and naval vessels. Creating materials that mimic the hierarchical structure and surface chemistry of lotus leaves requires multistep processes that are impractical for the mass production of nonwettable products. Superhydrophobic surfaces have been created using graphene. However, graphene sheets obtained through graphite exfoliation or deposition on substrates are not superhydrophobic and require additional processes to achieve lotus-like water repellency. In this work, we show that graphene produced in the gas phase is inherently superhydrophobic. Gas-phase-synthesized graphene (GSG) and lotus leaves have fundamentally different structures, yet water droplets on both materials exhibit comparable contact angles, roll-off angles, and bouncing characteristics. Furthermore, hydrophilic surfaces become superhydrophobic when covered with GSG. The substrate-free synthesis of GSG is straightforward and sustainable, which could enable the manufacturing of a diverse range of water-repellent technologies. 

Abstract Barium titanate (BTO) is a ferroelectric material used in capacitors because of its high bulk dielectric constant. However, the impact of the size of BTO on its dielectric constant is not yet fully understood and is highly contested. Here, we present an investigation into the dielectric constant of BTO nanoparticles with diameters ranging between 50 and 500 nm. BTO nanoparticles were incorporated into acrylonitrile butadiene styrene and injection molded into parallel plate capacitors, which were used to determine nanocomposite dielectric constants. The dielectric constants of BTO nanoparticles were obtained by combining experimental measurements with computational results from COMSOL simulations of ABS-matrix nanocomposites containing BTO. The dielectric constant of BTO was observed to be relatively constant at nanoparticle diameters as small as 200 nm but sharply declined at smaller nanoparticle sizes. These results will be useful in the development of improved energy storage and power conditioning systems utilizing BTO nanoparticles. Graphical abstract