Exploring battery material failure mechanisms through synchrotron X-ray characterization techniques

Rechargeable battery cycling performance and related safety have been persistent concerns.It is crucial to decipher the capacity fading induced by electrode material failure via a range of techniques.Among these,synchrotron-based X-ray techniques with high flux and brightness play a key role in understanding degradation mechanisms.In this comprehensive review,we summarize recent advancements in degra-dation modes and mechanisms that were revealed by synchrotron X-ray methodologies.Subsequently,an overview of X-ray absorption spectroscopy and X-ray scattering techniques is introduced for charac-terizing failure phenomena at local coordination atomic environment and long-range order crystal struc-ture scale,respectively.At last,we envision the future of exploring material failure mechanism.

Understanding Pseudocapacitance Mechanisms by Synchrotron X-ray Analytical Techniques

Pseudocapacitive materials that store charges via reversible surface or near-surface faradaic reactions are capable of overcoming the capacity limitations of electrical double-layer capacitors.Revealing the structure–activity relationship between the microstructural features of pseudocapacitive materials and their electrochemical performance on the atomic scale is the key to build high-performance capacitor-type devices containing ideal pseudocapacitance effect.Currently,the high brightness(flux),and spectral and coherent nature of synchrotron X-ray analytical techniques make it a powerful tool for probing the structure–property relationship of pseudocapacitive materials.Herein,we report a comprehensive and systematic review of four typical characterization techniques(synchrotron X-ray diffraction,pair distribution function[PDF]analysis,soft X-ray absorption spectroscopy,and hard X-ray absorption spectroscopy)for the study of pseudocapacitance mechanisms.In addition,we offered significant insights for understanding and identifying pseudocapacitance mechanisms(surface redox pseudocapacitance,intercalation pseudocapacitance,and the extrinsic pseudocapacitance phenomenon in battery materials)by combining in situ hard XAS and electrochemical analyses.Finally,a perspective for further depth of understanding into the pseudocapacitance mechanism using synchrotron X-ray analytical techniques is proposed.

Ultrasmall CoS nanoparticles embedded in heteroatom-doped carbon for sodium-ion batteries and mechanism explorations via synchrotron X-ray techniques

Transition metal sulfides have been regarded as promising anode materials for sodium-ion batteries(SIB).However,they face the challenges of poor electronic conductivity and large volume change,which result in capacity fade and low rate capability.In this work,a composite containing ultrasmall CoS(~7 nm)nanoparticles embedded in heteroatom(N,S,and O)-doped carbon was synthesized by an efficient one-step sulfidation process using a Co(Salen)precursor.The ultrasmall CoS nanoparticles are beneficial for mechanical stability and shortening Na-ions diffusion pathways.Furthermore,the N,S,and O-doped defect-rich carbon provides a robust and highly conductive framework enriched with active sites for sodium storage as well as mitigates volume expansion and polysulfide shuttle.As anode for SIB,CoS@HDC exhibits a high initial capacity of 906 mA h g^(-1)at 100 mA g^(-1)and a stable long-term cycling life with over 1000 cycles at 500 mA g^(-1),showing a reversible capacity of 330 mA h g^(-1).Meanwhile,the CoS@HDC anode is proven to maintain its structural integrity and compositional reversibility during cycling.Furthermore,Na-ion full batteries based on the CoS@HDC anode and Na_(3)V_(2)(PO_(4))_(3)cathode demonstrate a stable cycling behavior with a reversible specific capacity of~200 m A h g^(-1)at least for 100 cycles.Moreover,advanced synchrotron operando X-ray diffraction,ex-situ X-ray absorption spectroscopy,and comprehensive electrochemical tests reveal the structural transformation and the Co coordination chemistry evolution of the CoS@HDC during cycling,providing fundamental insights into the sodium storage mechanism.

RECOVERY EXPERIMENTAL TECHNIQUES OF TENSILE IMPACT

Based on loading-unloading test, tensile impact recovery experimental techniques have been developed to obtain the isothermal stress-strain curves of materials under high strain rates. The thermal softening effect can be decoupled by comparing the isothermal stress-strain curves with the adiabatic stress-strain curves at the same strain rate. In the present paper, recovery experiments of brass have been carried out on a self-designed rotating disk tensile impact apparatus. According to the parabolic strain hardening power-law thermo-viscoplastic constitutive model, strain hardening parameter, strain rates strengthening parameter and thermal softening synthetical parameter have been decoupled from experimental results. Furthermore, from these parameters, one can determine the theoretical isothermal curves and adiabatic curves at high strain rates well-coinciding the experimental results respectively. It indicates that the recovery experimental techniques of tensile impact are effective and reliable and are important means for the study of thermo-mechanical coupling. The experimental results also reveals that brass is a typical thermo-viscoplastic material.

The application of synchrotron X-ray techniques to the study ofrechargeable batteries

The increased use of rechargeable batteries in portable electronic devices and the continuous develop-ment of novel applications （e.g. transportation and large scale energy storage）, have raised a strong de-mand for high performance batteries with increased energy density, cycle and calendar life, safety andlower costs. This triggers significant efforts to reveal the fundamental mechanism determining batteryperformance with the use of advanced analytical techniques. However, the inherently complex character-istics of battery systems make the mechanism analysis sophisticated and difficult. Synchrotron radiationis an advanced collimated light source with high intensity and tunable energies. It has particular ad-vantages in electronic structure and geometric structure （both the short-range and long-range structure）analysis of materials on different length and time scales. In the past decades, synchrotron X-ray tech-niques have been widely used to understand the fundamental mechanism and guide the technologicaloptimization of batteries. In particular, in situ and operando techniques with high spatial and temporalresolution, enable the nondestructive, real time dynamic investigation of the electrochemical reaction,and lead to significant deep insights into the battery operation mechanism. This review gives a brief introduction of the application of synchrotron X-ray techniques to the inves-tigation of battery systems. The five widely implicated techniques, including X-ray diffraction （XRD）, PairDistribution Function （PDF）, Hard and Soft X-ray absorption spectroscopy （XAS） and X-ray photoelectronspectroscopy （XPS） will be reviewed, with the emphasis on their in situ studies of battery systems during cycling.

Dynamic phase transition behavior of a LiMn_(0.5)Fe_(0.5)PO_(4) olivine cathode material for lithium-ion batteries revealed through in-situ X-ray techniques

LiMn_(0.5)Fe_(0.5)PO_(4) has attracted great interest due to its good electrochemical performance and higher operating voltages.This has led to a greater than 30 percent higher energy density than for commercial Li Fe PO4 olivine cathodes.Understanding the phase transition behaviors and kinetics of this material will help researchers to design and develop next generation cathodes for Li-ion batteries.In this study,we investigated non-equilibrium phase transition behaviors in a LiMn_(0.5)Fe_(0.5)PO_(4) cathode material during charge–discharge processes by varying current rates(C-rates)using synchrotron in-situ X-ray techniques.These methods included wide angle X-ray scattering(in-situ WAXS)and X-ray absorption spectroscopy(in-situ XAS).The WAXS spectra indicate that the phase transition of LiMn_(0.5)Fe_(0.5)PO_(4) material at slow C-rates is induced by a two-phase reaction.In contrast,at a high C-rate(5 C),the formation of an intermediate phase upon discharge is clearly observed.Concurrently,the oxidation numbers of the redox reactions of Fe^(2+)/Fe^(3+)and Mn^(2+)/Mn^(3+)were evaluated using in-situ XAS.This combination of synchrotron in-situ X-ray techniques gives clear insights into the non-equilibrium phase transition behavior of a LiMn_(0.5)Fe_(0.5)PO_(4) cathode material.This new understanding will be useful for further developments of this highly promising cathode material for practical commercialization.

A review of rockburst:Experiments,theories,and simulations

Rockburst is becoming a huge challenge for the utilization of deep underground space.Extensive efforts have been devoted to investigating the rockburst behavior and mechanism experimentally,theoretically,and numerically.The aim of this review is to discuss the novel development and the state-of-the-art in experimental techniques,theories,and numerical approaches proposed for rockburst.The definition and classification of rockburst are first summarized with an in-depth comparison among them.Then,the available laboratory experimental technologies for rockburst are reviewed in terms of indirect and direct approaches,with the highlight of monitoring technologies and data analysis methods.Some key rockburst influencing factors(i.e.size and shape,rock types,stress state,water content,and temperature)are analyzed and discussed based on collected data.After that,rockburst theories and mechanisms are discussed and evaluated,as well as the microscopic observation.The simulation approaches of rockburst are also summarized with the highlight of optional novel numerical methods.The accuracy,stability,and reliability of different experimental,theoretical and numerical approaches are also compared and assessed in each part.Finally,a summary and some aspects of prospective research are presented.

Experimental Study of Overtopping on Sea Dikes and Coastal Flooding Under the Coupled Processes of Tides and Waves

Storm surges are cataclysmic natural disasters that occur along the coasts and are usually accompanied by large waves.The effects of coupled storm surges and waves can pose a significant threat to coastal security.Previous labo-ratory studies on the effects of storm surges and waves on coastal structures have typically utilized steady water levels and constant wave elements.An indoor simulation of the coupled processes of tides and waves is developed by adding a tide generation system to an existing laboratory wave basin to model continuous dynamic tide levels so that tide generation and wave-making occur synchronously in the pool.Specific experimental methods are given,which are applied to further study waves overtopping on artificial sea dikes and coastal flooding evolution under the coupled actions of tides and waves.The results of the overtopping discharge obtained by the test with a dynamic water level are compared with those obtained from steady water level tests and the existing empirical formula.In addition,the impacts of ecological coastal shelterbelts and structures on coastal flood processes and distributions are also investi-gated.The proposed simulation methods provide a new approach for studying the effects of storm surges and waves on coastal areas.The study also aims to provide a reference for coastal protective engineering.

Experimental investigation on the phase equilibria of the Mg-Sn-Ag system in the Mg-rich corner

Phase equilibria of the Mg-Sn-Ag system in Mg-rich corner at 320 and 400℃ were experimentally investigated with nine ternary alloys subjected to electron probe microanalysis and X-ray diffraction techniques.No ternary compounds were observed at both isothermal sections.Two three-phase triangles,i.e.hcp(Mg)+Mg_(2)Sn+Mg_(3)Ag and Mg_(2)Sn+Mg_(3)Ag+MgAg(bcc_B2),were both observed at 320 and 400℃.A new three-phase region of Ag3Sn+Mg2Sn+MgAg(bcc_B2)was additionally observed at 320℃,which implied that the binary phase Ag3Sn has a considerable solubility of Mg in the ternary system at the temperature.And the maximal solubility of Mg in Ag3Sn was measured to be 27.2 at.%.This result is not consistent with the thermodynamic calculated isothermal section at 350℃ from Wang et al.[11]and put forward a new requirement or refinement for the optimization of the Mg-Sn-Ag ternary system.At 400℃,the maximal solubility of Sn in the Mg3Ag phase was determined to be about 3.0 at.%Sn,and the solubility of Ag in Mg2Sn was negligible.The temperature of ternary eutectic reaction at Mg-rich corner(L↔hcp(Mg)+Mg_(54)Ag_(17)+Mg_(2)Sn)was measured by differential scanning calorimetry.The partial isothermal sections in Mg-rich corner of the ternary system at 320 and 400℃ were then constructed based on the above experimental data.

An experimental proposal for low order laboratory animals’ extension of metabolic life

Essential bibliography, with therein references included, is presented owing to the contribution of the author groups to Mitochondrial Filamentation, which is a new emerging field of physiological energy metabolism. These studies provide the first seed concept for trials to extend the metabolic life, for a few days, in low order laboratory mammals killed by electrocution, as a first type of accidental death. It is proposed, essentially, to cool out the corpses very soon after death at 12oC-14oC and take advantage of the effect super magnetism to counteract the force of gravity to install a net recurrent cycle of oxygen consumption and oxygen production by filamented mitochondria in all the organism tissues. Once the cause of death had been corrected adequately, it is possible to try the reanimation to experience the full life of the corpse with highly sophisticated methodology.

CFD-Based Performance Analysis and Experimental Investigation of Design Factors of Vertical Axis Wind Turbines under Low Wind Speed Conditions in Thailand

This paper presents effects of design factors on mechanical performance of Vertical Axis Wind Turbines (VAWTs), and an experimental investigation of optimal VAWT performance under low wind speed conditions in Thailand. Design factors include types of wind turbines, number of blades, types of materials, height-to-radius ratios, and design modifications. Potential VAWT models with different design factors are numerically analyzed within a virtual wind tunnel at various wind speeds by utilizing XflowTM?Computational Fluid Dynamics (CFD) software. The performance curves of each VAWT are obtained as plots of power coefficients against tip speed ratios. It is found that the type of wind turbine, number of blades, and height-to-radius ratio have significant effects on mechanical performance whereas types of materials result in shifts of operating speeds of VAWTs. Accordingly, an optimal VAWT prototype is developed to operate under actual low speed wind conditions. The performance curve from experimental results agrees with the CFD results. The proposed methodology can be used in the computer design of VAWTs to improve mechanical performance before physical fabrication.

The Effect of a Liquid Cover on the Thermal Performance of a Salinity Gradient Solar Pond:An Experimental Study

SalinityGradient Solar Ponds(SGSPs)offer the potential to capture and store solar energy for use in a range of domestic and industrial activities in regions with high solar insolation.However,the evaporation of water from these ponds is a significant problem that must be overcome for them to be deployed successfully.Thus,two ponds were constructed in the city of Nasiriya,Iraq.The two ponds were cylindrical with a diameter of 1.4 m and a total depth of 1.4 m.The water body in the two ponds was constructed with layer depths of 0.5,0.75 and 0.1 m for the lower convective zone(LCZ),non-convective zone(NCZ)and the upper convective zone(UCZ)respectively.One of the two ponds was covered with a thin liquid paraffin layer(0.5 cm)to eliminate evaporation from the surface of the UCZ.The behavior of the standard SGSP and that of the covered pond with evaporation suppressed can be straightforwardly compared.The experimental units were run for six months from 1st of February to 31st of July 2019.It was shown in the first instance that by covering the pond with a thin layer of paraffin,that evaporation could be suppressed.The results showed that for the conventional SGSP,the temperature of the LCZ reached a maximum of ca.76℃ while in the covered pond the temperature of the LCZ was consistently lower than that in the uncovered pond by approximately 5-6℃.The results also indicated that the temperature of the UCZ in the covered pond was higher than that in the uncovered pond by about 10℃ in the second half of the study period.However,it was noted that on rainy days the paraffin layer was swept away from the surface;and this could hinder the implementation of thin liquid cover in the large SGSP.

Technique and experiment of active direct gas pressure measurement in coal roadway

An active measurement method and its principle was introduced consideringthe low success rate,special difficulty,and long measurement time of the direct gas pressuremeasurement currently used in coal roadways.The technology of drilling,boreholesealing depth,borehole sealing length,sealing control of the measuring process,compensatorycomputation of gas loss quantity and other key techniques were discussed.Finally,based on the latest instrument the authors developed,a series of experiments of directgas pressure measurement in the coal roadways of the Jincheng and Tongchuanmine district,were carried out.The experimental results show that active gas pressuremeasurement technique has advantages as follows:(1) the application scope of direct gaspressure measurement technique is wide and it does not have the restriction of coalhardness,coal seam fissure and other conditions;(2) the measured results are credible,which can be tested by the same gas pressure value acquired from a different borehole inthe same place;(3) the measurement process is convenient and quick,it takes about 2 to3 days to acquire the gas pressure value in a coal seam.

钻柱动力学研究进展及发展趋势

钻柱动力学是安全、高效钻井的基础,许多研究人员对此进行了深入研究,成果累累。然而,钻柱具有超大长细比,工作环境恶劣,非线性特征显著,使得钻柱的安全性面临严峻挑战,这在超万米特深井中尤为突出。因此,把握钻柱动力学研究历程,提炼钻柱动力学核心关键问题十分必要。本文在简要回顾3种基本钻柱振动形式的研究进展基础上,重点阐述了这3种基本振动的耦合振动的研究进展,详细讨论了粘滑和涡动这2种复杂振动的危害、形成机制、研究方法、测量技术和控制方法,并对近十年来备受关注的高频扭转振动(HFTO)的研究进展进行了归纳。现有研究成果表明,涡动是井下钻柱最易出现的一种复杂振动形式,包括向前、向后规则涡动和不规则涡动形式,且大都体现为不规则涡动。其中,反向涡动对钻柱的危害很大,不但会加剧钻具的疲劳破坏,而且会降低钻头的机械钻速。粘滑振动是另一种危害极大的复杂振动形式,其形成机制在于钻头与岩石之间的相互作用,并可用速度弱化效应进行很好描述;粘滑振动与涡动密切相关,粘滑振动中的滑脱阶段的最大转速可能达到地面转速的3倍以上,并伴随着剧烈的涡动。而振动频率远高于涡动和粘滑振动的高频扭转振动的危害不容忽视,但相关机理远未探明,迫切需要攻关研究。

工程领域裂纹检测实验方法的进展

裂纹故障是影响生产生活和设备安全运行的一大因素,裂纹检测实验对于检测技术应用和裂纹故障信息获取具有重要意义,但领域内缺乏对检测实验的系统性归纳与剖析。该文对当前代表性的裂纹检测实验方法进行了分类比较,针对裂纹信息介绍了定位、形貌和深度的检测实验,从先进传感器、数据处理与机器学习应用等3个方面探究了裂纹检测实验方法进展。最后根据国内外裂纹检测实验的研究现状,提出了在裂纹扩展方向检测、误报漏报及实验与实际工况贴近程度方面所面临的挑战,并从实时动态、远程无线和多故障耦合检测等方面进行了展望,为今后裂纹检测实验方法的研究与发展提供了参考。

CBL教学在临床免疫学检验技术实验教学中的应用初探

目的:探讨以案例为基础的教学法(CBL)在临床免疫学检验技术实验教学中的应用及教学效果。方法:随机选取医学检验技术专业2020级本科大三两个班学生为研究对象,试验组50人,对照组52人。其中对照组采用传统教学,试验组采用CBL教学。对比两组观察指标:实验报告成绩、实验考核成绩及学生满意度等指标。结果:试验组学生实验报告成绩、实验考核成绩及对教学的满意度评价均高于对照组(P<0.05)。结论:在临床免疫学检验技术实验教学中应用CBL教学法,可以明显提高学生的学习兴趣,并显著提升实验成绩以及对教学的满意度,值得推广。

沥青温拌技术分类及温拌效果的试验评价方法

沥青温拌技术日益广泛应用于路面工程,为了定量评价温拌沥青混合料在拌和生产过程中的温拌效果,提供试验评价方法,本研究自主开发了一种沥青混合料变速拌和试验装置,采用70^(#)基质和SBS改性两种沥青、自主研发的一种表面活性剂型沥青温拌剂(取名为Alube)和一种有机降黏型沥青温拌剂(取名为ACMP),以市场成熟产品Evotherm为参照,分别制备了温拌沥青及其AC-13C型混合料,测试了不同沥青和温拌沥青的三大指标、布氏黏度和动态剪切流变指标,分析了沥青的黏温曲线特性,通过混合料的变温击实试验和变速拌和试验,研究了沥青混合料的压实特性和拌和流动特性,提出了沥青混合料的拌和流动模型。研究结果表明,有机降黏型温拌剂减小了沥青的黏度,增大了沥青的流动性,改变了沥青的技术性能,如针入度、延度、相位角等增大,软化点、布氏黏度等减小,而表面活性剂型温拌剂不改变沥青的基本技术性能;黏温曲线法仅可表征有机降黏型温拌沥青的温度变化,等黏温度降低约9℃,变温击实法和变速拌和法则可以同时表征两大类温拌剂的温拌效果;沥青混合料的拌和流动性服从宾汉黏塑性模型,从流变理论上解答了混合料的拌和流动性及和易性,推荐采用变速拌和试验来评价温拌沥青混合料的温拌效果;综合考察现有沥青温拌技术可知,在常用温拌剂掺量下,温拌沥青的生产拌和温度可比热拌沥青混合料低20~30℃,符合常规认识。

赛教融合视域下高职化工专业课程改革与实践研究

目前高职化工专业课程教学改革势在必行,而职业技能大赛作为职业教育的风向标,必对化工专业建设、课程改革、实践教学资源建设及教学团队建设产生很好的导向和促进作用。结合化学实验技术赛项,主要从课程改革实施路径、课程改革成效等方面探索“赛教融合”视域下的化工专业高素质技术技能人才培养路径,以达到提高课堂教学质量和服务社会的目标。

互联网+时代新医科临床血液学检验技术虚拟仿真案例式实验教学案例库的构建与实践研究

案例教学法是高校教学改革的重要手段,互联网+时代新医科临床血液学检验技术虚拟仿真案例式实验教学案例库资源匮乏,因此构建案例库迫在眉睫。案例库建设能满足多元化教学及教学改革的需求,对优化课程体系、改革教学模式、创建一流本科课程及培养能适应现代医学发展的复合型、创新型、应用型医学检验技术专业人才具有重要意义。

对比冷冻消融与微波消融治疗兔VX2椎旁肿瘤的有效性及安全性

目的对比冷冻消融(CA)与微波消融(MWA)治疗兔VX2椎旁肿瘤的有效性及安全性。方法选取48只新西兰大白兔建立VX2椎旁肿瘤模型并随机分为CA组(n=24)及MWA组(n=24),比较组间完全消融率、生存率、布里斯托尔兔疼痛量表(BRPS)评分及并发症发生率。结果CA组完全消融率及治疗后21天生存率分别为91.67%(22/24)及33.33%(8/24),均高于MWA组[66.67%(16/24)及16.67%(4/24)](P均<0.05)。CA组治疗后4 h、1天、4天、7天及14天BRPS评分均低于MWA组(P均<0.001);2组上述时间点BRPS评分均低于治疗前(P均<0.05)。CA组并发症发生率(3/24,12.50%)低于MWA组(8/24,33.33%)(P<0.05)。结论CA治疗兔VX2椎旁肿瘤的安全性及有效性均优于MWA。