We found that very thin carbon nanotube films, once fed by sound frequency electric currents, could emit loud sounds. This phenomenon could be attributed to a thermoacoustic effect. The ultra small heat capacity per unit area of carbon nanotube thin films leads to a wide frequency response range and a high sound pressure level. On the basis of this finding, we made practical carbon nanotube thin film loudspeakers, which possess the merits of nanometer thickness and are transparent, flexible, stretchable, and magnet-free. Such a single-element thin film loudspeaker can be tailored into any shape and size, freestanding or on any insulating surfaces, which could open up new applications of and approaches to manufacturing loudspeakers and other acoustic devices.

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Intumescent flame-retardant poly(lactic acid)/starch (PLA/starch) biocomposites were prepared by means of melt blending. Microencapsulated ammonium polyphosphate (MCAPP) was added to the PLA/starch biocomposites not only to improve its flame retardancy but also to restrain the reaction between ammonium polyphosphate and starch during processing. The flame-retardant properties of PLA/starch biocomposites were evaluated by limiting oxygen index, UL-94 test, and microscale combustion calorimetry (MCC) test. The results of MCC showed that the peak of heat release rate and total heat release of PLA/starch biocomposites decreased dramatically compared with those of pure PLA. The thermal degradation and gas products of PLA/starch/MCAPP systems were monitored by thermogravimetric analysis and thermogravimetric analysis−infrared spectrometry. Scanning electron microscopy and X-ray photoelectron spectroscopy were utilized to explore the surface morphology and chemical components of the char residues.

Hierarchical mesoporous silica@Co–Al layered double hydroxide (m-SiO2@Co–Al LDH) spheres were prepared through a layer-by-layer assembly process, in order to integrate their excellent physical and chemical functionalities. TEM results depicted that, due to the electrostatic potential difference between m-SiO2 and Co–Al LDH, the synthetic m-SiO2@Co–Al LDH hybrids exhibited that m-SiO2 spheres were packaged by the Co–Al LDH nanosheets. Subsequently, the m-SiO2@Co–Al LDH spheres were incorporated into epoxy resin (EP) to prepare specimens for investigation of their flame-retardant performance. Cone results indicated that m-SiO2@Co–Al LDH incorporated obviously improved fire retardant of EP. A plausible mechanism of fire retardant was hypothesized based on the analyses of thermal conductivity, char residues, and pyrolysis fragments. Labyrinth effect of m-SiO2 and formation of graphitized carbon char catalyzed by Co–Al LDH play pivotal roles in the flame retardance enhancement.