High density (∼96%) garnet-type Al-contained Li 6.75 La 3 Zr 1.75 Ta 0.25 O 12 (LLZTO-Al) solid electrolytes are prepared by conventional solid-state reaction and the following flowing oxygen sintering process . An overall ionic conductivity as high as 7.4 × 10 −4 S cm −1 at 25 °C is achievable, remarkably higher than that obtained by sintering in other atmospheres. The dependence of density and conductivity of solid electrolytes on sintering under different oxygen partial pressures is discussed. Atmosphere sintering is proved to be an effective method to improve the relative density of lithium oxide ceramics .
Yan Nie,Wei Xiao,Chang Miao,Mingbiao Xu,Changjun Wang
To understand the effects of the calcining pressure gradient on the structure, morphology, and electrochemical properties of LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA), Ni 0.8 Co 0.15 Al 0.05 (OH) 2 precursors prepared using a coprecipitation method are calcined under gradually increasing oxygen pressures to fabricate different cathode materials. The results of characterization using X-ray diffraction and scanning electron microscopy suggest that the material (NCA-0.6) possesses the best comprehensive properties when the calcining oxygen pressure is 0.6 MPa, at which the values of I(003)/I(104) and D 50 are appropriately 1.727 and 11.06 μm, respectively. A cell assembled with NCA-0.6 delivers a discharge specific capacity of 143.3 mAh g −1 with a capacity retention ratio of 80.3% after 100 cycles at 1.0 C . Moreover, it presents a lower resistance of 327.5 Ω and redox peak difference of 0.11 V compared to the values of 1953.2 Ω and 0.26 V for NCA-0.1. These results suggest that appropriately enhancing the calcining oxygen pressure is an effective way to improve the cycle stability of NCA materials without any modified method.
Bamboo is a fast-growing, high-biomass, and mechanically strong renewable resource. It shows great potential in cellulose-based materials and bio-based products. However, its complex tissue structure and unique lignin distribution limit the efficiency and applicability of conventional delignification processes. In this study, a synergistic lignin removal strategy combining high-proportion chlorine dioxide (ClO 2 ) pretreatment with oxygen delignification was developed. Two process sequences, O-D PI and D PI -O, were systematically compared in terms of reaction mechanisms during bamboo fiber lignin removal. Results showed that, in the D PI -O process, ClO 2 preferentially oxidized lignin to form quinone-type intermediates. These intermediates were then effectively degraded in the subsequent oxygen delignification stage. This led to a significantly higher lignin removal rate (84.90 %) and a notable reduction in kappa number (2.49) and AOX generation (0.267 kg/t pulp). Multidimensional characterization using 2D HSQC NMR and 31 P NMR confirmed more complete cleavage of S/G units and β-O-4 linkages in the D PI -O system. The carboxyl group content of residual lignin increased significantly to 1.194 mmol/g, revealing the critical role of quinone intermediates in deep oxidative degradation. Kinetic studies further showed that the lignin removal rate was highly sensitive to alkali concentration (a 1 = 0.6012), especially under low oxygen pressure. In low-alkali environments, oxygen pressure became more influential (b 1 = 0.1382). This study elucidates the reaction pathway and key controlling parameters of oxygen-assisted, high-proportion ClO 2 delignification. It provides both theoretical and practical support for efficient lignin degradation and high-purity cellulose fiber production.
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