锂离子电池正极材料原位漫反射光谱电化学研究

发展原位电化学光谱方法对深入研究电化学反应机理,并最终提高电池性能有着重要价值。建立在这一认识之上,能够应用于电池体系的原位光谱电化学表征技术被认为是表征电池电极材料性能的有效方法。但是受限于电池严格密封的不透明外壳和当前商用电池体系严格隔绝水氧的客观要求,开发更贴近真实电池工作条件的原位光谱电化学表征技术仍有较大需求。基于此,本文设计了一种基于传统纽扣电池架构的原位电化学池,该装置通过特殊设计实现了在尽可能模拟电池工作环境的前提下拥有透明的上盖,从而使发生电化学反应的同时进行光学检测成为可能。利用这一电化学池,本文以锂离子电池中常用的正极材料LiFePO_(4)(LFP)、NCM811和LiCoO_(2)(LCO)为例,对其电化学反应过程中的漫反射光谱进行了采集和分析。相关数据定量地揭示了不同种类电极材料在一般反射光路架构下对不同波长可见光的响应关系,并能够直接用于对单色光检测场景下的波长优化提供指导和依据。更进一步,本文还对不同材料在充放电过程中的光谱特征进行了定量分析,揭示了其光谱特征同材料内在能级状态间的相关性。综上,本文提出了一种基于漫反射光谱的原位光谱电化学表征方法,作为对光谱电化学应用于电池体系的有效补充,本方法能够为评估电极材料性能提供一种全新且简单直接的途径,并最终助力电池性能的提升。

Fluidized roasting reduction kinetics of low-grade pyrolusite coupling with pretreatment of stone coal

Based on the fluidized roasting reduction technology of low-grade pyrolusite coupling with pretreatment of stone coal, the manganese reduction efficiency was investigated and technical conditions were optimized. It is found that the optimum manganese reduction efficiency can be up to 98.97% under the conditions that the mass ratio of stone coal to pyrolusite is 3：1, the roasting temperature of stone coal is 1000℃, the roasting temperature of pyrolusite is 800℃, and the roasting time is 2 h. Other low-grade pyrolusite ores in China from Guangxi, Hunan, and Guizhou Provinces were tested and all these minerals responded well, giving -99% manganese reduction efficiency. Meanwhile, the reduction kinetic model has been established. It is confirmed that the reduction process is controlled by the interface chemical reaction. The apparent activation energy is 36.397 kJ/mol.

Preparation of sodium manganate from low-grade pyrolusite by alkaline predesilication-fluidized roasting technique

Low concentration alkaline leaching was used for predesilication treatment of low-grade pyrolusite. The effects of initial NaOH concentration, liquid-to-solid ratio, leaching temperature, leaching time and stirring speed on silica leaching rate were investigated and the kinetics of alkaline leaching process was studied. The results show that silica leaching rate reached 91.2% under the conditions of initial NaOH concentration of 20%, liquid-to-solid ratio of 4：1, leaching temperature of 180 ℃, leaching time of 4 h and stirring speed of 300 r/min. Shrinking-core model showed that the leaching process was controlled by the chemical surface reaction with activation energy Ea of 53.31 k J/mol. The fluidized roasting conditions for preparation of sodium manganate were optimized by the orthogonal experiments using the desiliconized residue. The conversion rate of sodium manganate was obtained to be 89.7% under the conditions of silica leaching rate of 91.2%, NaOH/MnO2 mass ratio of 3：1, roasting temperature of 500 ℃ and roasting time of 4 h, and it increased with the increase of silicon leaching rate.

铝锂合金板材的各向异性及其在旋压壳体力学性能分布中的遗传效应

研究厚度为20 mm的2A55铝锂合金板T6态时效(165℃,24 h)后的力学性能及晶粒组织。以20 mm厚度板材为原料,旋压制备直径为1 m的2A55铝锂合金旋压壳体,研究旋压壳体相同T6态时效后的时效析出相、晶粒组织及沿壳体轴向和周向的力学性能分布。结果表明,旋压壳体T6态时效后的析出相包括大量T1相(Al_(2)CuLi)、部分δ’相(Al_(3)Li)和θ’相(Al_(2)Cu)。T1相分布不均匀,亚晶界分布密集,但沿大角度晶界形成沿晶无沉淀带。板材同一方向力学性能基本一致,但不同方向存在各向异性,沿轧制方向强度最高而沿45°方向强度最低。旋压过程导致壳体不同位置周向和轴向与原始轧制方向的夹角变化,晶粒长宽比和织构不同。相应地,旋压壳体沿相同周向或轴向的力学性能分布存在很大差异。原始板材的各向异性在旋压壳体晶粒组织及力学性能分布方面存在遗传效应。

铝锂合金晶粒组织与拉伸性能的关系

从新的视角对部分铝锂合金晶粒组织(织构和晶粒形状)与屈服强度和伸长率的相关性进行研究。研究材料包括2195、2A96、2A55及2050铝锂合金2 mm厚度薄板和5 mm与10 mm厚度板材以及厚度为80~85 mm具有不同厚度层的2297-T87和2050-T83铝锂合金厚板。较高取向因子平均值(M)一般对应较高的屈服强度,但存在一些例外。由于拉伸屈服时不同晶粒内启动滑移系数量不同,而且部分晶粒只发生转动,因此,M值计算时应在剔除无滑移系激活的晶粒并考虑最易激活滑移系的基础上进行修正及归一化处理。同时,晶粒形状对铝锂合金屈服强度有重要影响;尽管几乎发生完全再结晶,但晶粒长厚比增加时,晶粒转动困难,塑性屈服需启动更多滑移系,从而有利于提高铝锂合金屈服强度。另外,上述铝锂合金的伸长率与总等效滑移系数量及晶粒形状直接相关,增加总等效滑移系数量或降低晶粒长厚比低均有利于伸长率的提高。

静调引风机变转速运行叶片开裂机理研究及解决方案

针对汽轮机驱动的静叶调节轴流引风机叶轮叶片开裂故障问题,对引风机叶轮本体进行了有限元静力学和模态数值计算及现场测试,结合理论计算结果和现场实测结果,对叶片产生裂纹的机理进行分析。有限元静力学计算结果表明,叶片开裂位置的叶片应力为312MPa,安全系数达2.24,满足设计裕量要求。分析结果表明,叶片在风机变速运行过程中存在共振现象是其断裂的主因。叶片发生共振时,受力强度激增,从而对引风机叶片寿命产生负面影响,发生疲劳断裂。最后,建议通过采用风机分档运行的办法来处理叶片开裂问题。

Electrochemical Cascade Annulation for the Synthesis of 3-Sulfanylquinoline Derivatives under Mild Conditions

An efficient electrochemical approach has been developed for the construction of 3-sulfanylquinoline derivatives by treating phenylethynylbenzoxazinanones with disulfides in an undivided cell.The protocol provided a convenient route to functionalized quinolines with good functional group tolerance.Moreover,it does not require any metal catalysts or additives,furnishing a series of biologicalquinolines inmoderatetogoodyields.

Simultaneous extraction of gold and zinc from refractory carbonaceous gold ore by chlorination roasting process

A novel process based on chlorination roasting was proposed to simultaneously recover gold and zinc from refractory carbonaceous gold ore by using NaCl as chlorination agent.The effects of roasting temperature,roasting time and NaCl content on the volatilization rates of gold and zinc were investigated.The reaction mechanism and the phase transition process were also analyzed by means of SEM,EDS and XRD.The results demonstrated that under the optimal conditions of NaCl content of 10%,roasting temperature of 800℃,roasting time of 4 h and gas flow rate of 1 L/min,the rates of gold and zinc were 92%and 92.56%,respectively.During low-temperature chlorination roasting stage,a certain content of sulfur was beneficial to the chlorination reactions of gold and zinc;and during high-temperature chlorination roasting stage,the crystal structure of vanadium-bearing mica was destroyed,and the vanadium-containing oxides were beneficial to the chlorinating volatilization of gold and zinc.Eventually,the chlorinated volatiles of gold and zinc could be recovered by alkaline solution.

Extraction of valuable metals from Ti-bearing blast furnace slag using ammonium sulfate pressurized pyrolysis−acid leaching processes

A novel method of extracting valuable metals from Ti-bearing blast furnace slag(TBBF slag)via pressure pyrolysis of recyclable ammonium sulfate(AS)−acid leaching process was proposed.The results show that when pressurized roasting at an AS-to-slag mass ratio 3:1 and 370℃for 90 min,the extraction rates of titanium,aluminum and magnesium reached 94.5%,91.9%and 97.4%,respectively.The acid leaching solution was subjected to re-crystallization in a boiling state to obtain a titanium product having a TiO2 content of 94.1%.The above crystallization mother liquor was adjusted to pH=6 and pH≥12.2,respectively,and then qualified Al2O3 and MgO products were obtained.The analysis through XRD and SEM−EDS proves that the main phases in roasted samples were NH4AlSO4,CaSO4 and TiOSO4.The thermodynamic analysis presents that the main minerals of perovskite,spinel and diopside in raw ore could spontaneously react with the intermediate produced by AS under optimal conditions.

Reductive leaching of manganese from low-grade pyrolusite ore in sulfuric acid using pyrolysis-pretreated sawdust as a reductant

Manganese （Mn） leaching and recovery from low-grade pyrolusite ore were studied using sulfiaric acid （H2SO4） as a leachant and pyrolysis-pretreated sawdust as a reductant. The effects of the dosage of pyrolysis-pretreated sawdust to pyrolusite ore, the concentration of sulfuric acid, the liquid/solid ratio, the leaching temperature, and the leaching time on manganese and iron leaching efficiencies were inves- tigated. Analysis of manganese and iron leaching efficiencies revealed that a high manganese leaching efficiency was achieved with low iron extraction. The optimal leaching efficiency was determined to be 20wt% pyrolysis-pretreated sawdust and 3.0 mol/L H2SO4 using a liq- uid/solid ratio of 6.0 mL/g for 90min at 90℃. Other low-grade pyrolusite ores were tested, and the results showed that they responded well with manganese leaching efficiencies greater than 98%.

Reductive leaching of low-grade manganese ore with pre-processed cornstalk

Cornstalk is usually directly used as a reductant in reduetive leaching manganese. However, low utilization of cornstalk makes low manganese dissolution ratio, In the research, pretreatment for cornstalk was proposed to improve manganese dissolution ratio. Cornstalk was preprocessed by a heated sulfuric acid solution （1.2 M of sulfuric acid concentration） for 10 min at 80℃. Thereafter, both the pretreated solution and the residue were used as a reductant for manganese leaching. This method not only exhibited superior activity for hydrolyzing cornstalk but also enhanced manganese dissolution. These effects were attributed to an increase in the amount of reductive sugars resulting from lignin hydrolysis. Through acid pretreatment for cornstalk, the manganese dissolution ratio was improved from 50.14% to 83.46%. The present work demonstrates for the first time the effective acid pretreatment of cornstalk to provide a cost-effective reductant for manganese leaching.

“Steric Armor”Strategy of Blue Fluorescent Emitters against Photooxidation-Induced Degradation

Stability against oxygen is an important factor affecting the performance of organic semiconductor devices.Improving photooxidation stability can prolong the service life of the device and maintain the mechanical and photoelectric properties of the device.Generally,various encapsulation methods from molecular structure to macroscopic device level are used to improve photooxidation stability.Here,we adopted a crystallization strategy to allow 14H-spiro[dibenzo[c,h]acridine-7,9′-fluorene](SFDBA)to pack tightly to resist fluorescence decay caused by oxidation.In this case,the inert group of SFDBA acts as a“steric armor”,protecting the photosensitive group from being attacked by oxygen.Therefore,compared with the fluorescence quenching of SFDBA powder under 2 h of sunlight,SFDBA crystal can maintain its fluorescence emission for more than 8 h under the same conditions.Furthermore,the photoluminescence quantum yields(PLQYs)of the crystalline film is 327%higher than that of the amorphous film.It shows that the crystallization strategy is an effective method to resist oxidation.

Corrected stress field intensity approach based on averaging superior limit of intrinsic damage dissipation work

Corrected stress field intensity obtained by averaging the superior limit of intrinsic damage dissipation work in critical domain, which considers thoroughly thermodynamic consistency within irreversible thermodynamic framework, was proposed for predictions of high-cycle fatigue endurance limits. Simultaneously, the effects of mean stress, additional hardening behavior related to non-proportional loading paths and stress gradients on multiaxial high-cycle fatigue are taken into account in the proposed approach. The approach is an extension of the general stress field intensity. For a better comparison, existing multiaxial high-cycle fatigue criteria were employed to predict the endurance limits of different metallic materials subjected to different multiaxial loading paths, and it is shown that present proposal performs better from statistical value of error indexes, which make the proposed approach of corrected stress field intensity and its associated concepts provide a new conception to predict endurance limits of multiaxial high-cycle fatigue with high accuracy.

Dynamics of rolling mill drive system considering arc tooth gear dynamic characteristics

The arc tooth gear spindle (ATGS) is the key structure of the drive system of hot finishing rolling mills. To investigate the dynamic characteristics of ATGS of the drive system of hot finishing rolling mills, a dynamic mechanical model of ATGS was established. The influences of dynamic displacement and dynamic torque on dynamic load (meshing force, additional torque and friction torque) were studied during the non-steady-state operation of ATGS. On this basis, a dynamic model of rolling mill drive system was established considering the arc tooth gear dynamic characteristics. The dynamic response of the drive system was simulated and analyzed. The results showed that the nonlinear characteristics of ATGS were obvious;the meshing force (PX and PZ) could restrain the increase in dynamic displacement, which reflected the positive stiffness of ATGS;there was a coupling among the vertical, horizontal and torsional directions in the drive system model considering the dynamic characteristics of the arc tooth gear;the vibration intensity of ATGS in the horizontal direction is greater than that in the vertical direction when the self-excited torsional vibration happens;the greater the axial inclination angle was, the more complex the vibration mode was, and the lower the stability of the drive system was.