Multiscale SiCnw and carbon fiber reinforced SiOC ceramic with enhanced mechanical and microwave absorption properties

The hierarchical SiOC/SiCnws/CF composites (A/B/C structure) were designed via precursor infiltration and pyrolysis process. The SiOC ceramics served as the wave-transparent characteristic materials to adjust the impedance matching. Herein, the in situ growth of SiCnws not only was used for the absorber but served as the reinforcement of SiOC matrix composites. In detail, the SiOC/SiCnws/CF-1200°C-2 exhibits excellent electromagnetic absorption performance with minimum reflection loss of −46 dB at 14.4 GHz with the thickness of 1.6 mm, and its effective absorption band reaches 4.3 GHz. Its compressive strength reaches 8.69 and 16.41 MPa in z and x/y directions, separately. This contribution has a guidance for the application of carbon fiber/ceramics matrix composites in harsh environment.     

Enhanced Mn2+ solidification and NH4+-N removal from electrolytic manganese metal residue via surfactants

Electrolytic manganese metal residue (EMMR) harmless treatment has always lacked a low-cost and quick processing technology. In this study, surfactants, namely tetradecyl trimethylammonium chloride (TTC), sodium dodecyl benzene sulfonate (SDBS), sodium lignin sulfonate (SLS), and octadecyl trimethylammonium chloride (OTC), were used in the solidification of Mn²⁺ and removal of NH₄⁺-N from EMMR. The Mn²⁺ and NH₄⁺-N concentrations under different reaction conditions, Mn²⁺ solidification and NH₄⁺-N removal mechanisms, and leaching behavior were studied. The results revealed that the surfactants could enhance the Mn²⁺ solidification and NH₄⁺-N removal from EMMR, and the order of enhancement was as follows: TTC > SDBS > OTC > SLS. The NH₄⁺-N and Mn²⁺ concentrations were 12.3 and 0.05 mg·L^-1 with the use of 60.0 mg·kg^-1 TTC under optimum conditions (solid–liquid ratio of 1.5:1, EMMR to BRM mass ratio of 100:8, temperature of 20 ℃, and reaction duration of 12 h), which met the integrated wastewater discharge standard (GB8978-1996). Mn²⁺ was mainly solidified as Mn(OH)₂, MnOOH and MnSiO₃, and NH₄⁺-N in EMMR was mostly removed in the form of ammonia. The results of this study could provide a new idea for cost-effective EMMR harmless treatment.     

生物质与烟煤混合燃烧特性及动力学分析研究

使用非等温热分析方法研究了生物质(麦秆)和烟煤混合燃烧的反应特性。结果表明,生物质的添加可以降低混合样品的燃烧着火温度和燃烬温度,且混合样品燃烧反应性能随着生物质混合比例的增加而提升;生物质添加质量分数为20%时,煤和生物质混合燃烧协同作用最明显。使用Coats-Redfern(CR)、Flynn-Wall-Ozawa(FWO)和Kissinger-Akahira-Sunose(KAS)动力学模型对混合样品燃烧活化能进行计算,其值在挥发分燃烧阶段随着生物质混合比例的增加而增加,在焦炭燃烧阶段呈现下降趋势;通过对FWO和KAS动力学模型有效性进行分析发现,FWO和KAS模型在描述混合样品燃烧动力学时存在一定的局限性,而采用适宜机理函数的CR模型更适用于描述混合样品的燃烧反应动力学,对燃烧机理的分析也印证了动力学的分析结果。     

碱性蛋白酶洗涤稳定性提高的研究进展

碱性蛋白酶是液体洗涤剂中使用量最大的一类酶制剂,应用于洗涤剂行业的碱性蛋白酶占碱性蛋白酶市场的60%以上。不同于粉状洗涤剂中的酶制剂被造粒所包裹,液体洗涤剂中的碱性蛋白酶直接暴露于溶液中,与洗涤剂成分如表面活性剂、洗涤助剂及漂白剂直接接触作用,使得蛋白酶洗涤稳定性下降。除此之外,蛋白酶在液体洗涤剂环境中存在普遍的自溶失活现象,对其洗涤性能造成不利影响。如何提升碱性蛋白酶的稳定性是液体洗涤剂领域中的一个热点问题。本文介绍了碱性蛋白酶的催化与失活机制,综述了几种常用于稳定碱性蛋白酶的策略,即添加稳定剂、分子改造和化学修饰,重点介绍了化学修饰中的聚乙二醇化修饰与多糖修饰,对比了两种修饰方法的过程与效果,并在最后对碱性蛋白酶稳定性提高策略进行了展望。     

电极上气泡分离行为及其强化技术研究进展

电解水作为大规模生产氢气的途径,增强电解水效率对于氢能源的生产具有十分重要的意义。而如何提高电解水工艺的电解效率是一个被广泛关注的问题。在电解过程中,电极两端产生的气体有三种去向：逸出电解槽、溶解于电解质中、附着在电极上。但在电解过程中,附着在电极上的气泡会严重影响电极与电解质之间的接触面积,直接降低了电解效率。降低气泡在电极上的停留时间能够有效增加电解质与电极的接触时间,提高产氢效率。本工作主要综述了近年来促进电解过程中极板上氢氧气泡从电极分离行为的研究,分别从极板属性、电流、溶液浓度和外加物理场这几个方面对气泡成核、生长、聚结和分离行为进行了具体的归纳总结,讨论了各种强化气泡分离方法的特点,并展望了未来的发展方向和路线,为未来的电解气泡脱离技术的研究提供参考。     

Effect of solid loading and carbon additive on microstructure and mechanical properties of 3D-printed SiC ceramic

3D-printed SiC ceramics were prepared by direct ink writing and solid-phase sintering. The effects of sintering temperature, solid loading, and carbon additive on microstructures and mechanical properties of 3D-printed SiC parts were investigated. It was found that the sintering temperature affected the evolution of the microstructure and mechanical properties of the sintered SiC parts. A high solid loading promoted the densification and mechanical properties of the sintered SiC parts. However, the solid loading exceeded 40 vol.%, which decreased the density and mechanical properties of the samples. The carbon additives could improve the densification of the SiC parts and enhance their mechanical properties. When the sucrose content increased from 0 to 8 wt.%, the open porosity of the SiC part decreased from 26.12% to 3.15%, whereas the flexural strength increased 2.19 times. Using the optimized components and process parameters, the high-performance 3D-printed SiC parts were achieved.     

Effects of Y2O3/MgO ratio on mechanical properties and thermal conductivity of silicon nitride ceramics

In this work, the effects of Y₂O₃/MgO ratio on the densification behavior, phase transformation, microstructure evolution, mechanical properties, and thermal conductivity of Si₃N₄ ceramics were investigated. Densified samples with bimodal microstructure could be obtained by adjusting the ratio of Y₂O₃/MgO. It was found that a low Y₂O₃/MgO ratio facilitated the densification of Si₃N₄ ceramics while a high Y₂O₃/MgO ratio benefited the phase transformation of Si₃N₄ ceramics. Best mechanical properties (flexural strength of 875 MPa, and fracture toughness of 8.25 MPa·m^1/2, respectively) and optimal thermal conductivity of 98.04W/(m·K) were achieved in the sample fabricated with Y₂O₃/MgO ratio of 3:4 by sintering at 1900°C for 4 h.     

Molecular level understanding of CO2 capture in ionic liquid/polyimide composite membrane

Ionic liquid(IL)/polyimide(PI)composite membranes demonstrate promise for use in CO₂separation applications.However,few studies have focused on the microscopic mechanism of CO₂in these composite systems,which is important information for designing new membranes.In this work,a series of systems of CO₂in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide composited with 4,4-(hexafluoroisopropylidene)diphthalic anhydride(6FDA)-based PI,6FDA-2,3,5,6-tetramethyl-1,4-phenylene-diamine,at different IL concentrations were investigated by all-atom molecular dynamics simulation.The formation of IL regions in PI was found,and the IL regions gradually became continuous channels with increasing IL concentrations.The analysis of the radial distribution functions and hydrogen bond numbers demonstrated that PI had a stronger interaction with cations than anions.However,the hydrogen bonds among PI chains were destroyed by the addition of IL,which was favorable for transporting CO₂.Furthermore,the self-diffusion coefficient and free energy barrier suggested that the diffusion coefficient of CO₂decreased with increasing IL concentrations up to 35 wt-%due to the decrease of the fractional free volume of the composite membrane.However,the CO₂selfdiffusion coefficients increased when the IL contents were higher than 35 wt-%,which was attributed to the formation of continuous IL domain that benefitted the transportation of CO₂.     

Rational design on photoelectrodes and devices to boost photoelectrochemical performance of solar-driven water splitting: a mini review

As an eco-friendly, efficient, and low-cost technique, photoelectrochemical water splitting has attracted growing interest in the production of clean and sustainable hydrogen by the conversion of abundant solar energy. In the photoelectrochemical system, the photoelectrode plays a vital role in absorbing the energy of sunlight to trigger the water splitting process and the overall efficiency depends largely on the integration and design of photoelectrochemical devices. In recent years, the optimization of photoelectrodes and photoelectrochemical devices to achieve highly efficient hydrogen production has been extensively investigated. In this paper, a concise review of recent advances in the modification of nanostructured photoelectrodes and the design of photoelectrochemical devices is presented. Meanwhile, the general principles of structural and morphological factors in altering the photoelectrochemical performance of photoelectrodes are discussed. Furthermore, the performance indicators and first principles to describe the behaviors of charge carriers are analyzed, which will be of profound guiding significance to increasing the overall efficiency of the photoelectrochemical water splitting system. Finally, current challenges and prospects for an in-depth understanding of reaction mechanisms using advanced characterization technologies and potential strategies for developing novel photoelectrodes and advanced photoelectrochemical water splitting devices are demonstrated.     

260 t转炉负能炼钢生产实践

结合鞍钢股份有限公司鲅鱼圈钢铁分公司260 t转炉的能耗情况,对涉及煤气回收、蒸汽回收、电耗、气体介质消耗的相关设备、工艺和管理进行了研究和优化.通过采取优化煤气回收连锁条件、优化蒸汽回收系统、优化电耗管理方式和开发高效氧枪等措施,取得了较好的效果,转炉炼钢工序能耗由-16 kgce/t降至-20 kgce/t.