We report the sintering behavior of nanocrystalline zinc oxide under external AC electric field between 0 and 160 V/cm. In situ acquisition of density by means of laser dilatometry, evaluation of specimen temperature, real‐time measurement of electric field and current help analyze this peculiar behavior. Field strength and blocking electrodes significantly affect densification and microstructure, which was evaluated in the vicinity of the flash event and for the fully sintered material. High current densities flow through the sample at high electric fields, entailing a sudden increment of the temperature estimated to several hundreds of K and an exaggerated grain growth. In contrast, low current density flows through the sample at lower electric fields, which guarantees normal grain growth and highest final density. Macroscopic photoluminescence measurements give insights into the development of the defect structure. Electric fields are expected to enhance defect mobility, explaining the high densification rates observed during the sintering process.

Abstract.Here we report on the high-temperature piezoresistivity of carbon-containing silicon oxycarbide nanocomposites (C / SiOC). Samples containing 13.5 vol% segregated carbon have been prepared from a polysilsesquioxane via thermal cross-linking, pyrolysis and subsequent hot-pressing. Their electrical resistance was assessed as a function of the mechanical load (1-10 MPa) and temperature (1000-1200 • C). The piezoresistive behavior of the C / SiOC nanocomposites relies on the presence of dispersed nanocrystalline graphite with a lateral size ≤ 2 nm and non-crystalline carbon domains, as revealed by Raman spectroscopy. In comparison to highly ordered carbon (graphene, HOPG), C / SiOC exhibits strongly enhanced k factor values, even upon operation at temperatures beyond 1000 • C. The measured k values of about 80 ± 20 at the highest temperature reading (T = 1200 • C) reveal that C / SiOC is a primary candidate for high-temperature piezoresistive sensors with high sensitivity.

A tubular cell design for redox flow batteries is introduced utilizing chemically, mechanically, and thermally stable ceramic membranes. The basic viability of this new cell design is demonstrated via static and pumped charge and discharge experiments with a laboratory prototype. Electrochemical impedance spectroscopy measurements are presented for the investigation of the internal Ohmic resistance. The technological benefits of a tubular cell design as well as its limitations are discussed.

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