Grain growth kinetics and magnetic properties of a V-doped ZnO dilute magnetic oxide

Zn_0.95V_0.05O ceramics, elaborated from milled ZnO and V₂O₅ nanopowders, were sintered at 900, 1000 and 1100 °C for 1, 2, 4, 6, 10 and 14 h. The growth kinetics was studied identifying the grain growth exponent, the activation energy and the pre-exponential factor. The high V₂O₅ concentration allowed a rapid grain growth at 900 °C only at the very first stages (t < 1 h). Meanwhile, at temperatures of 1000 and 1100 °C, the grain growth was extremely fast with a growth exponent of 0.72. The magnetic properties of the samples indicate that ferromagnetism exist in all samples in different magnitudes depending on the sintering conditions. In particular, the maximum magnetization was obtained on the sample sintered at 1100 °C for 14 h, despite the reduction of V concentration. Additionally, secondary paramagnetic phases were detected in the samples sintered at lower temperatures and shorter sintering times.     

基于CO2循环的低碳高效白云石煅烧新工艺

白云石是一种广泛应用的冶金、建材和化工原料。针对白云石煅烧过程中CO₂排放严重等问题,构建了基于CO₂循环载热与资源化回收的白云石低碳煅烧竖窑新工艺。通过白云石（CaCO₃·MgCO₃）煅烧过程的Gibbs自由能变计算,发现提高煅烧温度（50~100 K）可有效克服CO₂对反应的抑制作用;通过纯CO₂环境中CaCO₃分解过程的热重实验分析,验证了CO₂循环煅烧白云石煅烧的可行性;通过化学反应动力学计算,解析了全CO₂组分环境下CO₂压力对CaCO₃·MgCO₃高温分解过程的影响,并发现提高CO₂压力可促进气固传热,从而提升分解速率和改善矿料分解均匀性;对CO₂循环煅烧工艺系统能-质平衡计算表明：该工艺理论能耗仅为140 kg/(t 煅白),且煅烧过程的CO₂排放降低70%以上,环境效益显著。     

Effects of preform pore structure on infiltration kinetics and microstructure evolution of RMI-derived Cf/ZrC-ZrB2-SiC composite

Reactive melt infiltration (RMI) is often used to fabricate highly dense ceramic matrix composite by infiltration of alloy melt into porous preform. Here, C_f/B₄C-C preforms with various pore structures were prepared, and the effects of pore structure on the ZrSi₂ melt infiltration and the as-received C_f/ZrC-ZrB₂-SiC composites were investigated. Compared with the preform prepared by slurry impregnation (SI), the preform prepared by sol impregnation shows more uniform pore size distribution, which leads to more homogeneous melt infiltration, as well as more uniform formation of ZrC-ZrB₂-SiC and better mechanical properties in the composites. The calculation results of infiltration kinetics indicate that the pore radius decreases quickly during the melt infiltration. As the time needed for pore closure in sol-preform is longer than that in SI-preform, it makes the infiltration kinetics more favorable in the former preform. This study can provide guidance for the pore structure regulation in the fabrication of RMI-composites.     

季戊四醇锌与月桂酸锌并用对天然橡胶硫化特性的影响

采用季戊四醇锌与月桂酸锌并用作为硫化活性剂,考察其对天然橡胶硫化特性及物理机械性能的影响。结果表明,季戊四醇锌具有较高的硫化活性,可使胶料的硫化速率加快,硫化活化能下降,硫化活性高于月桂酸锌,但抗硫化返原性能较差,胶料的物理机械性能较低,耐磨性较差。将季戊四醇锌与月桂酸锌并用可产生硫化协同效应,明显提高胶料的表观交联密度,改善抗硫化返原性能,同时还能降低门尼黏度、提高填料分散性并降低生热和滚动阻力。加入6.70份季戊四醇锌并用5.56份月桂酸锌的天然橡胶硫化胶,其综合性能优于添加5.00份氧化锌的硫化胶,并且含锌质量分数减少48%。     

富镍锂离子电池三元材料NCM的研究进展

锂离子电池作为新能源电池符合时代要求,具有良好的应用前景。电池容量、倍率性能与循环性能是电池性能的重要评价指标,在选取高能量密度电极材料的同时要充分考虑电池结构稳定性及其安全性能,三元材料基于这种思路进行设计。目前,针对电池中锂离子导通率与结构不可逆坍塌问题,通过包覆涂层、离子掺杂等手段改善锂离子电池性能已经常态化,实际需求要求有更有效的改性方法。因此,本文综述了富镍锂离子电池三元材料LiNi_0.4Co_0.2Mn_0.4O₂（NCM424）、LiNi_0.5Co_0.2Mn_0.3O₂(NCM523)、LiNi_0.6Co_0.2Mn_0.2O₂(NCM622)和LiNi_0.8Co_0.1Mn_0.1O₂(NCM811)的研究现状与发展导向,认为简单的单一材料改性已遇到瓶颈,改性方法复合、设计材料多元结构是提升电池性能的一大发展方向;从改性材料的合成和运行路径入手,研究分子水平上的作用机制,建立统一理论模型,通过计算模拟手段设计电极结构,实现锂离子电池突破性的发展。     

温度对生物净化滤柱中氨氮、铁、锰去除效果的影响

温度是生物净化滤柱运行的一个重要参数,采用生物净化滤柱处理模拟含氨氮、铁、锰地下水,考察水温从约25℃降到约6℃过程中氨氮、铁、锰的去除效果。结果表明,出水氨氮、总铁、锰的浓度分别低于0.15mg/L、0.1mg/L、0.05mg/L,均低于国家标准。出水总铁、锰均未受到水温下降的影响,但是出水氨氮浓度逐渐从约0.02mg/L升高到约0.12mg/L。进一步分析发现,铁主要在滤层的0~0.4m段去除,去除效果没有受到水温变化的影响。氨氮、锰主要在滤层的0~0.8m段去除,其沿程浓度均随水温降低而明显升高。氨氮、锰的生物去除符合一级动力学反应,水温为24.6℃、15.3℃、6.7℃时,两者的动力学常数k分别为0.154min^-1、0.186min^-1,0.143min^-1、0.175min^-1,0.103min^-1、0.163min^-1;半反应时间t_1/2分别为4.51min、3.72min,4.83min、3.96min,6.72min、4.24min。随着试验水温的降低,氨氮、锰的去除效果明显受到影响。     

锂辉石-氧化钙烧结法提锂的物相重构与动力学

对锂辉石-氧化钙烧结过程进行热力学分析,绘制了各反应Gibbs自由能与温度的关系图。结果表明,Al₂O₃会优先和Na₂O、Li₂O、K₂O反应,然后与CaO反应生成CaO·Al₂O₃,而且烧结温度需高于1060℃以保证LiAlSi₂O₆能够完成晶形转变。并探讨了锂辉石-氧化钙烧结法提锂的反应机理。考察了不同烧结条件对锂浸出率的影响并对熟料进行X射线衍射（XRD）分析表征。实验结果表明,在配料比为1∶1.25、烧结温度1150℃、烧结时间60min时,锂的浸出率达到92.14%,熟料中的主要物相为Ca₂SiO₄与LiAlO₂。利用XRD和扫描电镜-能谱联用仪（SEM-EDS）对熟料与浸出渣的物相、显微形貌及元素分布情况进行了分析表征。为了确定烧结反应的控制性步骤,在最优烧结条件的基础上对烧结过程进行动力学分析,结果表明,锂辉石-氧化钙烧结体系属于球形颗粒三维界面化学反应控制,烧结过程的动力学拟合方程为\mathrm{1}-{(\mathrm{1}-x)}^{\mathrm{1}/\mathrm{3}}=\mathrm{0.00677}t。     

Unraveling the film-formation kinetics of interfacial polymerization via low coherence interferometry

Interfacial polymerization (IP) is one of the most important methods for fabricating thin film composite (TFC) membranes. Understanding the film-formation mechanisms is of great value for developing membranes with enhanced performance. This work proposed a novel method to in situ characterize the film-formation kinetics via low coherence interferometry (LCI). The polyamide film formed at the liquid–substrate interface was scanned in real time; the polymerization induced significant variations in the optical properties around the reaction zone. After mitigating the effects of the perturbed interface, the surface-averaged intensity profiles provide a solid basis for analyzing the film-formation kinetics at various depths. In particular, the effects of the monomer concentrations were investigated to reveal the asymmetric growth and development of irregular substructures. All the characterization results confirm that the LCI-based characterization is a powerful tool for studying the structural evolution of the IP layer and thereby providing deeper insights for optimizing TFC membranes.     

A UV-LEDs based photomicroreactor for mechanistic insights and kinetic studies in the norbornadiene photoisomerization

In this work, we report a simple and inexpensive UV-LEDs based photomicroreactor assembly constructed by commercially available components. The photoisomerization of norbornadiene to quadricyclane was selected to validate this novel photomicroreactor design. Mass transport limitation was eliminated and indicated by dimensionless numbers Fo and Da _II, and photons loss was evaluated considering the absorption and reflection of the microreactor walls. The solvents, photosensitizers, and light sources selections were optimized for achieving better photochemical performance and mechanistic insights. The detailed comparison between the high-pressure mercury arc lamp and the UV-LEDs strip revealed great potential of UV-LEDs as appealing light source for photochemical transformations. Moreover, the reaction mechanism was thoroughly discussed and illustrated by the Jablonski diagram indicating electronic states transitions. According to possible intermediate steps, a kinetic model was proposed with the reaction rate constant being correlated with the photon flux, which is valuable for process optimization and further understanding reaction mechanisms.     

Quantitative estimation of crystallization kinetics in GeGaS and Au-doped GeGaS glass-ceramics

Ge_26.7Ga₈S_65.3 (GGS) and 0.1% Au-doped Ge_26.7Ga₈S_65.3 (GGS-Au) glasses were prepared and annealed at a temperature that is 20 K higher than their respective glass transition temperature in order to create chalcogenide glass-ceramics. X-ray diffraction results showed that, thermal annealing can induce large amount of the crystal growth in the pure glass but this can be significantly suppressed by Au doping in the glass, which is in agreement with the previous results. We further employed various calorimetric methods, together with Mauro-Yue-Ellison-Gupta-Allan viscosity model, to investigate their crystallization kinetics. The crystal growth rate at annealing temperature of 723 K was quantitatively deduced to be 2.5 × 10⁻⁸ μm/s in Au-doped GGS, which is about 20 times slower than that in the pure GGS with a growth rate of 4.7 × 10⁻⁷ μm/s.