Cycling performance of layered oxide cathode materials for sodium-ion batteries

Layered oxide is a promising cathode material for sodium-ion batteries because of its high-capacity,high operating voltage,and simple synthesis.Cycling performance is an important criterion for evaluating the application prospects of batteries.However,facing challenges,including phase transitions,ambient stability,side reactions,and irreversible anionic oxygen activity,the cycling performance of layered oxide cathode materials still cannot meet the application requirements.Therefore,this review proposes several strategies to address these challenges.First,bulk doping is introduced from three aspects:cationic single doping,anionic single doping,and multi-ion doping.Second,homogeneous surface coating and concentration gradient modification are reviewed.In addition,methods such as mixed structure design,particle engineering,high-entropy material construction,and integrated modification are proposed.Finally,a summary and outlook provide a new horizon for developing and modifying layered oxide cathode materials.

Green Tribology： Influence of New DLC Coatings-Orientants and Amorphous on Antifriction Properties of Lubricants

Tribological properties of two new DLC--monocrystalline and amorphous nanostructural coating--are studied under conditions of boundary lubrication in inactive oil, as green tribology aspect. The friction tests were carried out by using two test configurations： ＂ball-on-disc＂ and ＂ring-to-ring＂. Friction surfaces were coated by carbon of two types： monocrystalline and amorphous ones. As lubricants some model and commercial oils were used. It is found that the friction coefficient and its temperature dependence differ significantly for carbon films under study. The obtained results were attributed to different orientating effect of these coatings on structural ordering in boundary layers, which structure is considered as a mesophase of liquid crystals. The findings suggest that the carbon coatings with orientating effect on boundary layers are advantageous for improving antifriction characteristics and for governing processes of boundary lubrication.

One-step electrochemical in-situ Li doping and LiF coating enable ultra-stable cathode for sodium ion batteries

Despite of the higher energy density and inexpensive characteristics,commercialization of layered oxide cathodes for sodium ion batteries(SIBs)is limited due to the lack of structural stability at the high voltage.Herein,the one-step electrochemical in-situ Li doping and LiF coating are successfully achieved to obtain an advanced Na0.79Lix[Li_(0.13)Ni_(0.20)Mn_(0.67)]O_(2)@LiF(NaLi-LNM@LiF)cathode with superlattice structure.The results demonstrate that the Li^(+)doped into the alkali metal layer by electrochemical cycling act as"pillars"in the form of Li-Li dimers to stabilize the layered structure.The supplementation of Li to the superlattice structure inhibits the dissolution of transition metal ions and lattice mismatch.Furthermore,the in-situ LiF coating restrains side reactions,reduces surface cracks,and greatly improves the cycling stability.The electrochemical in-situ modification strategy significantly enhances the electrochemical performance of the half-cell.The NaLi-LNM@LiF exhibits high reversible specific capacity(170.6 m A h g^(-1)at 0.05 C),outstanding capacity retention(92.65%after 200 cycles at 0.5 C)and excellent rate performance(80 mA h g^(-1)at 7 C)in a wide voltage range of 1.5-4.5 V.This novel method of in-situ modification by electrochemical process will provide a guidance for the rational design of cathode materials for SIBs.

To the New Concept of Green Tribology

The aim of the present work is to confirm the fundamental possibility of creating new generation of the nanostructured composite coatings-orientants are studied under conditions of boundary lubrication in inactive oil, as green tribology aspect and to experimentally prove the efficacy of the nanostructured composite coatings-orientants for engineering applications. Tribological properties of nanostructured composite coatings-orientants are studied under conditions of boundary lubrication in inactive oil, as green tribology aspect. The friction tests were carried out by using two test configurations: “ball-on-disc” and “ring-to-ring”. As lubricants some model and commercial oils were used. It is found that the friction coefficient and its temperature dependence differ significantly for nanostructured composite coatings under study. The obtained results were attributed to different orientating effect of these coatings on structural ordering in boundary layers, which structure is considered as a mesophase of liquid crystals. The findings suggest that the nanostructured composite coatings-orientants with orientating effect on boundary layers are advantageous for improving antifriction characteristics and for governing processes of boundary lubrication. The nanostructured composite coatings-orientants can improve lubricating properties of oils (with and without additives) and may be advantageous for engineering practice as they improve antifriction characteristics of rubbing pairs and allow controlling the processes of boundary lubrication. Thus, received nanostructured composite coatings-orientants can be today the best materials of green tribology in engineering.

低浓度硫酸铜对化学镀Ni-P镀层微观结构及性能的影响

为改善镍磷(Ni-P)镀层的表面质量、提高Ni-P镀层的性能,在化学镀Ni-P镀液中加入少量的硫酸铜(CuSO_(4)·5H_(2)O)制备Ni-P镀层。利用扫描电镜、能谱仪、X射线衍射仪分析了镀层的表面形貌、成分和结构,研究了CuSO_(4)·5H_(2)O浓度对镀层的微观结构、表面粗糙度、光泽度、硬度、耐磨性和耐蚀性的影响。研究表明:当CuSO_(4)·5H_(2)O浓度为0.1 g/L时,镀层为致密的非晶态节瘤状组织,具有最佳的耐蚀性;当CuSO_(4)·5H_(2)O浓度为0.2 g/L时,镀层表面质量最好,硬度高、耐磨性优异,但镀层中出现少量微晶态Ni-Cu固溶体,耐蚀性下降;当CuSO_(4)·5H_(2)O浓度超过0.2 g/L后,镀层为混晶态菜花状组织,镀层表面的质量和耐蚀性随CuSO_(4)·5H_(2)O浓度的增加不断恶化。

碳纳米管-铜复合薄膜材料的抗辐照损伤性能研究

利用磁控溅射沉积技术获得的碳纳米管-金属复合材料是一种新型的纳米多孔材料,涂覆碳纳米管-金属复合材料的结构组件在新型核反应堆中具有广阔的应用前景。但是目前的报道中对碳纳米管-金属复合材料抗辐照损伤性能的研究还很少。因此,本工作通过磁控溅射沉积技术,制备了两种不同厚度的碳纳米管-铜复合薄膜,结合室温下的He离子辐照对石蜡基矿物油有机蒸汽的脱氢效应在复合薄膜表面包覆碳层,研究了碳层包覆前后碳纳米管-铜复合薄膜的抗辐照损伤性能。结果表明,随着辐照剂量和辐照温度升高,样品内逐渐产生孔洞等缺陷,且孔洞尺寸较小,这与碳纳米管-铜复合薄膜较高的晶界体积分数和比表面积以及降低的缺陷迁移速率有关。与平面基底上沉积的铜薄膜相比,复合薄膜在室温和高温辐照后,晶粒尺寸明显减小,这与一维碳纳米管基底可显著限制碳纳米管轴向垂直方向上的晶界迁移有关。碳层包覆后的碳纳米管-铜复合薄膜的高温结构稳定性和抗辐照损伤性能明显增强,这得益于碳包覆碳纳米管-铜复合薄膜较高的晶界体积分数和比表面积以及稳定的纳米晶粒。

质子交换膜电解池阳极钛基气体扩散层研究进展

气体扩散层在质子交换膜(PEM)水电解池中有着支撑膜组件、供给反应水、移除气体产物以及降低欧姆电阻的重要作用。PEM水电解池阳极区具有酸性、富氧且高电位的工作环境,对阳极区的气体扩散层具有严苛的要求。气体扩散层结构特性、导电性与耐腐蚀性是决定其电化学性能的关键。本文总结了可用于PEM电解池阳极气体扩散层的材料,简述了其结构特性对PEM电解池电化学性能的影响,分析了各种镀层材料在提高气体扩散层的导电性、耐腐蚀性以及电解池阳极氧析出反应(OER)性能方面的作用。最后,展望了气体扩散层在降低成本和提高电解池性能方面的研究趋势。

在役路面不同结构层沥青老化特性分析

为分析沥青路面在使用过程中的综合老化过程和机理,选取代表性在役路面的桥面铺装、普通路段行车道和匝道三种结构层并分别钻取芯样,通过凝胶渗透色谱(GPC)分析和傅立叶红外光谱(FTIR)分析研究芯样中抽提沥青的不同性能指标,分析不同结构层沥青的老化程度,明确不同路面结构层对沥青老化的影响。结果表明:沥青路面各结构层中,上面层沥青老化程度最严重,下面层沥青老化程度最弱;沥青老化主要由氧化所致,老化过程遵循沥青大分子链断裂成小分子、小分子含量增加、分子量宽度增加的规律;老化后沥青组分发生变化,进而影响路面结构的整体性能。

膜层结构对光伏镀膜玻璃的影响研究

为更好地分析和评估膜层结构对光伏镀膜玻璃的影响,对采用不同厚度、不同膜层结构的光伏镀膜玻璃的光学性能、膜层铅笔硬度、膜层微观结构进行了对比,分析了不同类型环境老化试验对光伏镀膜玻璃性能的影响,并研究了不同膜层结构对光伏镀膜玻璃性能的影响机理。研究结果表明:在光伏玻璃表面镀减反射膜能有效提升其光学性能,在380~1100 nm波段,相较于3.2 mm光伏玻璃原片,3.2 mm单层和双层镀膜玻璃的平均太阳光有效透射比增益分别为2.27%和2.50%;光伏镀膜玻璃的光学性能受膜层结构、膜层厚度及膜层孔隙率的影响,单层镀膜及双层镀膜表层膜孔隙率均约为49%,双层镀膜底层膜的孔隙率约为12%;双层镀膜玻璃的膜层铅笔硬度比单层镀膜玻璃的低,主要是因为表层膜的Si—O—Si网络结构建立在底层膜的网络结构上,表层膜与底层膜之间的结合力低于网络结构与玻璃基体之间的结合力;双层镀膜玻璃由于有1层致密底层膜,能有效阻隔水汽及污染物与玻璃基体发生反应,使其具有更好的耐环境老化性能。

COATS:Comprehensive observation on the atmospheric boundary layer three-dimensional structure during haze pollution in the North China Plain

The North China Plain(NCP)is troubled by severe haze pollution and the evolution of haze pollution is closely related to the atmospheric boundary layer(ABL).However,experimental and theoretical studies on the physical-chemical processes of the ABL in the NCP are lacking,with many scientific problems to be addressed.To solve these problems,the Comprehensive Observation on the Atmospheric boundary layer Three-dimensional Structure(COATS)during haze pollution was carried out in the NCP from 2016 to 2020.The COATS experiment adopted a"point-line-surface"spatial layout,obtaining both spatial-temporal profiles of the meteorological and environmental elements in the ABL and the turbulent transport data of fine particulate matter(PM_(2.5))in winter and summer.The research achievements are as follows.The spatial-temporal distribution characteristics of the ABL structure and PM_(2.5)concentrations in NCP were determined.The typical thermal structure of persistent heavy haze events and the pollutant removal mechanism by low-level jets were revealed.It was determined that the spatial structure of the ABL adjusted by the Taihang Mountains is responsible for the heterogeneous distribution of haze pollution in the NCP,and that mountain-induced vertical circulations can promote the formation of elevated pollution layers.The restraints of the atmospheric internal boundaries on horizontal diffusion of pollutants were emphasized.The contribution of the ABL to haze pollution in winter and summer was qualitatively compared and quantitatively estimated.The turbulent transport nature behind the relationship between the atmospheric boundary layer height(ABLH)and surface PM_(2.5)concentrations was analyzed.The concept of"aerosol accumulation layer"was defined,and the applicability of the material method in determining ABLH was clarified.A measurement system for obtaining the turbulent flux of PM_(2.5)concentrations was developed,and the turbulence characteristics of PM_(2.5)concentrations were demonstrated.The COATS experiment is of great theoretical significance for thoroughly understanding the physical mechanisms of the ABL during haze pollution and filling the knowledge gap on the impacts of the ABL three-dimensional structure on haze pollution.The results of this study are conducive to the improvement and development of ABL parameterization schemes and serve as a scientific basis for formulating regional pollution prevention and control measures.

Characterization of cake layer structure on the microfiltration membrane permeability by iron pre-coagulation

A cake layer is formed by coagulation aggregates under certain transmembrane pressure in the coagulation-microfiltration （MF） process. The characteristics of humic acid aggregates coagulated by different iron-based coagulants, such as charge, size, fractal dimension and compressibility, have an effect on the cake layer structure. At the optimum iron dose of 0.6 to 0.8 mmol/L for ferric chloride （FC） and polymer ferric sulfate （PFS） pre-coagulation, at the point of charge neutralization for near zero zeta potential, the aggregate particles produced possess the greatest size and highest fractal dimension, which contributes to the cake layer being most loose with high porosity and low compressibility. Thus the membrane filterability is better. At a low or high iron dose of FC and PFS, a high negative or positive zeta potential with high charge repulsion results in so many small aggregate particles and low fractal dimension that the cake layer is compact with low porosity and high compressibility. Therefore the membrane fouling is accelerated and MF permeability becomes worse. The variation of cake layer structure as measured by scanning electric microscopy corresponds with the fact that the smaller the coagulation flocs size and fractal dimension are, the lower the porosity and the tighter the cake layer conformation. This also explains the MF membrane flux variation visually and accurately.

Optical coatings:trends and challenges

New applications in optoelectronics, photonics, telecommunication, displays, optical data processing, biomedicine, sensors, energy control, automobile, aerospace, and architecture stimulation are important developments in physics and technology of optical coatings. This paper will focus on the latest advances in the areas of new optical film systems and devices, new optical coating materials and film fabrication techniques, process control and monitoring, and different advanced applications. Particularly, focus is on optical films that combine optical design with microstructural features tailored on the nanometer and micrometer scales. Evaluation of film stability and integrity in harsh industrial environments and their compatibility with organic polymers are important as well.

无卤阻燃高残炭环氧树脂对环氧膨胀型防火涂料的性能影响研究

通过在涂层体系中用无卤阻燃高残炭环氧树脂(EP-DOPO)替代普通环氧树脂(EP)的方法,确定了无卤阻燃高残炭环氧树脂在环氧膨胀型防火涂料中的作用,并明确最佳用量。分别添加不同比例的无卤阻燃高残炭环氧树脂,研究这种情况下环氧膨胀型防火涂料各项性能及膨胀炭层的结构。结果表明:无卤阻燃高残炭环氧树脂可明显改善环氧膨胀型防火涂料的烟密度、炭层结构,同时可以明显提高发泡炭层的柔韧性及致密性,EP-DOPO/EP为40/60时涂层综合性能达最优。

NiCoCrAlY/YSZ梯度涂层热力学性能的有限元模拟

采用代表体积单元法建立NiCoCrAlY/YSZ梯度热障涂层的有限元二维微观模型,计算不同相成分配比下梯度层的热物理性能参数,将参数结果推广到三维多层涂层实体模型,研究热循环过程中双层结构涂层和梯度结构涂层的热力学性能。结果表明:梯度层的弹性模量、泊松比、热膨胀系数、导热系数与各相成分比例近似呈线性关系,导热系数受各相分布形态的影响;当梯度层中NiCoCrAlY相成分比例在0.7以下时,导热系数较低,常温状态最高为2.91 W·m^(-1)·K^(-1)。相比于双层结构涂层,梯度结构涂层的YSZ成分比例降低20%,隔热温度降低14%,陶瓷面层在高温时产生的热失配径向拉应力降低47%,轴向拉应力降低32%,切应力降低37%,冷却后的残余应力降低50%,这归因于涂层结构的梯度化有效降低涂层与基体热膨胀系数不同而产生的热失配应力。根据涂层应力分布结果,涂层易在TC/BC界面的中心区域形成垂直裂纹,靠近外侧边缘区形成水平裂纹。

用显微镜观察氧化铁皮分层结构的方法

阐述了一种用光学显微镜观察氧化铁皮分层结构的方法。用防止铁皮掉落的制样方法加工试样,试样表面涂铸工胶,放到箱式烘干炉烘干,采用小颗粒和低转抛光,保证氧化铁皮完整。配制氧化铁皮侵蚀液,2%的盐酸酒精溶液能根据每层氧化铁皮的特性进行不同程度的腐蚀。最终目的是在显微镜下观察铁皮结构,能清晰的显示分层中每层结构的形貌及分布状态,颜色由外到内分别为浅灰、深灰、白色,用金相分析软件定量测量每层厚度,成功替代XRD方法。

聚脲/铝分层复合结构的抗爆性能研究

为研究聚脲/铝分层复合结构的抗爆性能,对在空爆载荷下的聚脲/铝结构进行了数值模拟,并与文献中的试验结果进行对比,验证数值模型的准确性。在此基础上研究了等质量条件下,复合结构层数、复合结构中金属铝的体积分数以及聚脲层位置对靶板中心点挠度的影响,分析爆炸过程中结构的能量吸收特点。结果表明:在等质量下,聚脲/铝分层复合结构存在最优的结构设计;在所讨论的结构中,除铝体积分数为90%的4层结构外,其他结构的抗爆性能均优于均质铝板,铝体积分数为10%的一层结构的抗爆炸性能最好;聚脲涂覆位置影响结构的抗爆性能,且聚脲涂覆在背爆面时抗冲击性能更优;铝板的内能吸收是复合结构能量吸收的主要部分,铝板的内能吸收比例随着铝体积分数的增加先减小后增大。研究结果可为聚脲/铝复合结构的抗爆设计提供参考。

抗剥落金属基可磨耗封严涂层结构匹配制备研究

新一代航空发动机对推重比提出更高的要求,而发动机叶尖与机匣的间隙是影响发动机效率的关键因素之一。在机匣内壁制备可磨耗封严涂层能有效减小气流泄漏、避免叶尖与机匣碰磨,从而使发动机高效、安全地运行。可磨耗封严涂层通常具有高孔隙率,然而高孔隙率易降低可磨耗面层/陶瓷隔热层界面强度,引发可磨耗涂层整体剥落。为此,开展可磨耗封严面层/陶瓷隔热层界面结构匹配设计,在保证涂层可磨耗封严功能的基础上,增强二者界面抗剥落能力。首先,通过数值分析方法发现,可磨耗层/陶瓷层界面处孔隙特征尺寸和孔隙率增加均会加剧可磨耗层沿界面剥落的风险。进一步,提出可磨耗封严涂层的结构匹配设计,即在靠近界面处增加抗剥落过渡层。最后,通过模拟和试验相结合,优化抗剥落过渡层厚度,证实过渡层可显著延长体系的服役寿命。

氧化锆间隔层的低温喷涂制备及其三层结构钙钛矿太阳能电池应用性能

氧化钛/氧化锆/碳三层结构钙钛矿太阳能电池(Perovskite solar cells,PSCs)具有原材料廉价、制备工艺易放大和稳定性好等优势,受到了广泛关注。但三层结构PSCs的低温制备研究进展缓慢,主要原因之一在于难以在低温条件下构建合适的氧化锆间隔层。本研究以尿素为孔隙率调节剂,用简单的喷涂法制备多孔氧化锆间隔层用于三层结构PSCs。通过调节喷涂次数优化氧化锆层厚度为1100 nm时,电池的性能最优,单电池功率转换效率达到14.7%,5块电池串联模块(5×0.9 cm×2.5 cm)达到10.8%。PSCs在恒温恒湿箱(25℃,湿度40%)保存200 d,功率转换效率保持稳定,没有明显下降。柔性基底上的氧化锆层经50次弯曲测试后保持完整,未见脱落。与传统的丝网印刷氧化锆间隔层制备方法相比,本研究的喷涂方法具有方法简便、操作温度低、与柔性基底兼容性好的优点。

NiCoCrAlYTa/Ag/Mo复合自润滑涂层的制备及其高低温循环摩擦学性能

为了开发适用于苛刻工况的长寿命、高可靠的自润滑涂层,选择NiCoCrAlYTa作为黏结相,Ag作为润滑相,Mo作为增强相,采用超音速火焰喷涂(high-velocity oxy-fuel spraying,HVOF)技术在Inconel718高温合金基体上制备复合涂层。考察该复合涂层在室温及800℃循环交变条件下的摩擦学行为,研究磨损表面的形貌特征、化学成分、相组成,揭示摩擦过程中元素之间的相互作用以及摩擦表面的物理化学本质,探究其在高低温交变环境下的多循环“自适应”润滑机理。结果表明:复合涂层致密均匀,力学性能良好,主要有γ-Ni,β-NiAl,γ′-Ni_(3)Al,Ag和Mo等物相;复合涂层表面生成的β-Ag_(2)MoO_(4)类层状润滑剂,可大大改善涂层在高温条件下的摩擦磨损性能;在多循环交变条件下,复合涂层后续循环摩擦因数较首次循环而言有所增大,但在室温条件下的磨损率却有所减小;这是涂层在高温条件下生成的β-Ag_(2)MoO_(4)类层状尖晶石润滑相与Al2O3、MoO3硬质相氧化物在摩擦剪切力的作用下相互影响而导致的。

敷设空腔覆盖层水下复杂目标的声散射特性研究

研究敷设空腔覆盖层水下复杂目标的声散射特性具有重要的意义。首先通过建模软件构建目标模型,然后利用分层近似法,结合多层介质的传递矩阵方法,将含有变截面空腔的吸声覆盖层分为多个可视为圆柱空腔结构的薄层,进而实现复合结构的声反射系数的求解,最后利用基于戈登(Gordon)积分的板块元方法对目标强度进行预报,并针对复杂目标提出基于光线投射的可见面元判别方法。在此基础上,以BeTSSiⅡ标准模型为例,研究敷设空腔覆盖层的水下复杂目标的声散射方位特性和频率特性。结果表明:文中提出的基于光线投射的可见面元判别方法可以快速有效地提供板块元方法所需的可见面元;板块元方法对BeTSSiⅡ标准模型的预报结果可以很好地反映其目标强度的特征及其变化规律;模型敷设空腔覆盖层可以有效降低目标强度,与敷设等厚均匀覆盖层时相比,复合结构声反射系数曲线的第一谷值频率降低,在频率较低时敷设空腔覆盖层的吸声效果更好,可以进一步减小目标强度。该研究有助于实际工程中实现对水下平台散射特性的快速预报。