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Dense K0.5Na0.5NbO3 lead‐free ceramics were successfully fabricated by combining cold sintering process (CSP) with annealing in air atmosphere or low pO2 atmosphere. Acetic acid was used as transition liquid. By optimizing the liquid content and pressure during CSP, the CSP samples with relative densities 74.2% were obtained with adding 15 wt% acetic acid under 800 MPa. The CSP samples were then annealed in air atmosphere between 1000 and 1100°C. The ceramics annealed at 1050°C exhibit excellent electrical properties with piezoelectric constant d33 = 125 pC/N, dielectric constant εr = 509, dielectric loss tan δ = 0.04, and remanent polarization Pr = 38.17 μC/cm2. Additionally, the mixture of K0.5Na0.5NbO3 and base metal Ni powders was also cold‐sintered and then annealed in the low pO2 atmospheres in order to detect whether Ni was oxidized or not. The optimized low pO2 atmospheres to protect the Ni from oxidation are pO2 = 10−10 atm followed by reoxidizing in pO2 = 10−6 atm. The K0.5Na0.5NbO3 fabricated by CSP with annealing in the optimized low pO2 atmospheres exhibits comparable electrical properties of the ceramics annealed in air atmosphere, providing an optional approach for using base metals as electrodes. [ABSTRACT FROM AUTHOR]

The isothermal phase transformation behavior of thermally grown oxide scale of FeO on high-purity Fe was investigated under conditions of low oxygen potential. The phase transformation comprised three reactions, namely Fe3O4 precipitation, magnetite seam formation, and the eutectoid decomposition. The nucleation rate of Fe3O4 precipitation decreased with decreasing oxygen potential, whereas the incubation period for the eutectoid decomposition became longer. In contrast, magnetite seam formation was independent of the oxygen potential. The overall phase transformation was found to reach completion faster in an atmosphere with a lower oxygen potential. The effect of the oxygen potential on the phase transformation of FeO scale was rationalized by the different degree of supersaturation for Fe3O4 precipitation, which plays a crucial role in the eutectoid reaction. [ABSTRACT FROM AUTHOR]

Exacerbating deoxygenation is extensively affecting marine organisms, with no exception for phytoplankton. To probe these effects, we comparably explored the growth, cell compositions, photosynthesis, and transcriptome of a diatom Thalassiosira pseudonana under a matrix of pO2 levels and Light:Dark cycles at an optimal growth light. The growth rate (μ) of T. pseudonana under a 8:16 L:D cycle was enhanced by 34% by low pO2 but reduced by 22% by hypoxia. Under a 16:8 L:D cycle, however, the μ decreased with decreasing pO2 level. The cellular Chl a content decreased with decreasing pO2 under a 8:16 L:D cycle, whereas the protein content decreased under a 16:8 L:D cycle. The prolonged photoperiod reduced the Chl a but enhanced the protein contents. The lowered pO2 reduced the maximal PSII photochemical quantum yield (FV/FM), photosynthetic oxygen evolution rate (Pn), and respiration rate (Rd) under the 8:16 or 16:8 L:D cycles. Cellular malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were higher under low pO2 than ambient pO2 or hypoxia. Moreover, the prolonged photoperiod reduced the FV/FM and Pn among all three pO2 levels but enhanced the Rd, MDA, and SOD activity. Transcriptome data showed that most of 26 differentially expressed genes (DEGs) that mainly relate to photosynthesis, respiration, and metabolism were down-regulated by hypoxia, with varying expression degrees between the 8:16 and 16:8 L:D cycles. In addition, our results demonstrated that the positive or negative effect of lowering pO2 upon the growth of diatoms depends on the pO2 level and is mediated by the photoperiod.

Exacerbating deoxygenation is extensively affecting marine organisms, with no exception for phytoplankton. To probe these effects, we comparably explored the growth, cell compositions, photosynthesis, and transcriptome of a diatom Thalassiosira pseudonana under a matrix of p O 2 levels and Light:Dark cycles at an optimal growth light. The growth rate (μ) of T. pseudonana under a 8:16 L:D cycle was enhanced by 34% by low p O 2 but reduced by 22% by hypoxia. Under a 16:8 L:D cycle, however, the μ decreased with decreasing p O 2 level. The cellular Chl a content decreased with decreasing p O 2 under a 8:16 L:D cycle, whereas the protein content decreased under a 16:8 L:D cycle. The prolonged photoperiod reduced the Chl a but enhanced the protein contents. The lowered p O 2 reduced the maximal PSII photochemical quantum yield (F V /F M ), photosynthetic oxygen evolution rate (Pn), and respiration rate (Rd) under the 8:16 or 16:8 L:D cycles. Cellular malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were higher under low p O 2 than ambient p O 2 or hypoxia. Moreover, the prolonged photoperiod reduced the F V /F M and Pn among all three p O 2 levels but enhanced the Rd, MDA, and SOD activity. Transcriptome data showed that most of 26 differentially expressed genes (DEGs) that mainly relate to photosynthesis, respiration, and metabolism were down-regulated by hypoxia, with varying expression degrees between the 8:16 and 16:8 L:D cycles. In addition, our results demonstrated that the positive or negative effect of lowering p O 2 upon the growth of diatoms depends on the p O 2 level and is mediated by the photoperiod.