Reversible cationic-anionic redox in disordered rocksalt cathodes enabled by fluorination-induced integrated structure design

Cation-disordered rocksalt oxides(DRX)have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity.However,their practical implementation has been impeded by unwanted phenomena such as irrepressible transition metal migration/dissolution and O_(2)/CO_(2)evolution,which arise due to parasitic reactions and densification-degradation mechanisms during extended cycling.To address these issues,a micron-sized DRX cathode Li_(1.2)Ni_(1/3)Ti_(1/3)W_(2/15)O_(1.85)F_(0.15)(SLNTWOF)with F substitution and ultrathin LiF coating layer is developed by alcohols assisted sol-gel method.Within this fluorination-induced integrated structure design(FISD)strategy,in-situ F substitution modifies the activity/reversibility of the cationic-anionic redox reaction,while the ultrathin LiF coating and single-crystal structure synergistically mitigate the cathode/electrolyte parasitic reaction and densification-degradation mechanism.Attributed to the multiple modifications and size effect in the FISD strategy,the SLNTWOF sample exhibits reversible cationic-anionic redox chemistry with a meliorated reversible capacity of 290.3 mA h g^(-1)at 0.05C(1C=200 mA g^(-1)),improved cycling stability of 78.5%capacity retention after 50 cycles at 0.5 C,and modified rate capability of 102.8 mA h g^(-1)at 2 C.This work reveals that the synergistic effects between bulk structure modification,surface regulation,and engineering particle size can effectively modulate the distribution and evolution of cationic-anionic redox activities in DRX cathodes.

Disordered Rocksalts with Lattice Oxygen Activation as Efficient Oxygen Evolution Electrocatalysts

The lattice oxygen oxidation mechanism(LOM)provides an efficient pathway for accelerating the oxygen evolution reaction(OER)in certain electrocatalysts by activating and involving lattice oxygen in the catalytic OER process.We investigated the potential of disordered rocksalts as catalysts for accelerating the OER through the LOM process,leveraging their unique metastable Li-O-Li bond states.Theoretical calculations were employed to predict the catalytic pathways and activities of disordered rocksalts(DRX),such as Li_(1.2)Co_(0.4)Ti_(0.5)O_(2)(LCTO).The results revealed that benefiting from the unhybridized Li-O electronic orbitals and the resulting metastable states of Li-O-Li bonds in DRX,LCTO exhibited a typical LOM pathway,and the lattice oxygen was easily activated and participated in the OER.The experimental results showed that LCTO exhibited a remarkable pH-dependent OER activity through the LOM pathway,with an overpotential of 241 mV at a current density of 10 mA/cm^(2),and excellent long-term stability.This work provides a novel chemical space for designing highly active and stable OER electrocatalysts by leveraging the LOM reaction pathway.

In situ revealing the reconstruction behavior of monolayer rocksalt CoO nanosheet as water oxidation catalyst

The reconstruction during oxygen evolution reaction (OER) significantly affects the electronic and local geometry structure of metal sites in electrocatalyst.Compared with well-investigated cobalt-based materials,the reconstruction of rocksalt CoO with purely Co^(2+) in octahedral (Oh) coordination has not been revealed in detail.Herein,monolayer Co O supported on reduced graphene oxide (r GO) was synthesized via a one-pot hydrothermal strategy with calcinating in Ar atmosphere.The structure evolution of twodimension (2D) Co O/r GO during OER was revealed by in situ X-ray absorption spectroscopy (XAS).The transition from Co O toward Co3O_(4) already occurred at open circuit potential,further enhanced at 1.23 V (vs.RHE).The Co Ox(OH)ywas determined as the active phase at 1.53 V,displaying a tetrahedral Co coordination defective spinel Co_(3)O_(4) with the Co-O shell that featured the (oxy)hydroxide,not the standard Co OOH.After OER,the irreversible transition from CoO to Co_(3)O_(4) was observed.In contrast,in situ Raman spectra revealed a reversible amorphization process on Co_(3)O_(4)/r GO under operation conditions.Furthermore,this study indicated that the reconstruction behavior could be more effectively revealed by XAS using 2D materials.

Electronic and Optical Properties of Rocksalt CdO: A first-Principles Density-Functional Theory Study

The structural, electronic and optical properties of rocksalt CdO have been studied using the plane-wave-based pseudo-potential density functional theory within generalized gradient approximation. The calculated lattice parameters are in agreement with previous experimental work. The band structure, density of states, and Mulliken charge population are obtained, which indicates that rocksalt CdO having the properties of a halfmetal due to an indirect band gap of -0.51eV. The mechanical properties show that rocksalt CdO is mechanically stable, isotropic and malleable. Significantly, we propose a correct value for ε1(0) of about 4.75, which offers theoretical data for the design and application for rocksalt CdO in optoelectronic materials.

岩盐的蠕变损伤破坏分析

蠕变损伤破坏是岩盐的主要破坏形式之一 ,为此对长山岩盐和乔后岩盐进行了蠕变试验研究。通过对岩盐试件裂纹的产生、发展直至破坏过程的观察分析得出 2种岩盐在蠕变损伤过程中有较大的差别。产生差别的原因主要是 2种岩盐中NaCl的含量、晶粒大小、晶粒之间的胶结不同。造成 2种岩样在蠕变过程中表现的现象不同 ,其岩盐力学性质也有差异。其次是岩盐在晶粒结晶过程中 ,因地质、环境等因素的影响 ,使晶粒内部存在着大量的缺陷 ,晶粒之间的交界面极不规则。因此 ,位错在这些晶体内占有重要地位 ,位错就控制了该晶粒的力学性质。

盐岩中能源(石油和天然气)地下储存力学问题研究现状及其发展

盐岩作为石油和天然气等战略与商业地下储存介质在欧洲、美国和加拿大等国家获得了广泛的应用。首先将盐岩中能源储存的相关力学问题的研究,划分成4个发展阶段:(1)20世纪60年初——简单应用阶段。此阶段利用采矿工程方面的力学知识和经验,对能源地下储存的力学方面进行了简单研究和应用;(2)20世纪60年代中期到70年初——模型研究与应用阶段。此阶段利用大型盐岩试样在实验室进行模拟石油或天然气储存,研究盐岩在储存方面的力学特性;(3)20世纪70年代末到90年代中期——数值模拟计算阶段。此阶段利用有限元技术,结合盐岩的试验结果,模拟能源储存过程,进行储存力学方面模拟计算与分析研究;(4)20世纪90年代中期直到现在——损伤模型设计阶段。结合盐岩的损伤与损伤恢复特性及其试验研究,提出了盐岩的几个损伤与损伤恢复本构模型。利用这些模型,使储存库的力学特性得到了更充分的发挥;同时对每个阶段的研究情况进行了分析,重点指出了每一个阶段的主要代表人物及其主要研究成果;其次,对盐岩的本构方程进行了系统总结与评价,指出了各类本构方程的建立依据与工程应用特点,重点介绍了Norton材料模型和Hou/Lux盐岩损伤与损伤恢复本构模型,并指出了这两种计算模型的优缺点;最后提出了今后盐岩研究的主要发展趋势。

岩盐变形特性的试验研究

在实验的基础上，对岩盐的变形特性进行了研究。结果表明，岩盐是一种软岩，在单轴压缩状态下具有很强的横向变形能力，泊松比大于０－５ ，且变形破坏过程具有明显的分阶段特征；随着围压增大，弹性模量和应力峰值应变增大，最终扩容量减少；在三轴应力状态下具有更好的线性关系。

水对岩石力学特性影响的研究

岩盐水溶采矿过程中 ,水对岩盐矿体及其顶底板岩石有很大的影响。基于试验研究 ,探讨了水对岩石力学特性的影响问题。研究表明 ,水对岩石力学特性的影响主要与岩石的硬石膏含量和岩芯采取率有关。

岩盐溶腔围岩地应力场有限元分析——计算模型与分析方法

在建立岩盐溶腔围岩地应力场有限元数值分析的计算模型 (包括地质模型和力学模型 )的基础上 ,探讨了岩盐溶腔围岩地应力场有限元数值分析的方法。为研究岩盐溶腔围岩地应力场规律和岩盐溶腔稳定性打下了基础。

干燥、潮湿合成盐岩流变细观机制的对比研究

针对盐岩流变细观机制的研究,对于合理建立本构模型、实验室尺度数据外推均具有重要意义。采用盐岩合成技术进行恒定应变率条件下的干燥盐岩流变实验,并对其细观结构进行了显微镜观测,同时借助于潮湿盐岩的研究成果作为对比,结果表明在晶界水的促进作用下,盐岩流变细观机制将会发生转化:干燥盐岩应力—应变曲线较为平缓,晶内存在波状滑移线、亚晶粒等细观特征,表明位错交叉滑移或位错攀移为流变主导机制;潮湿盐岩应力—应变曲线形状较为波动并存在晶界迁移等细观结构,动态重结晶机制将对流变产生重要作用;对干燥、潮湿盐岩的实验数据拟合分析表明,流变机制由位错流变向纯压溶转化。因此在盐构造地质演化、盐岩地下储库稳定性等研究过程中,要注意温度、应变率、应力水平、含水量等因素对流变应变率控制机制的影响。

压力对岩盐相InN电子结构和光学性质的影响

用基于密度泛函理论的第一性原理结合广义梯度近似研究了高压下盐岩相InN的电子结构和光学性质．计算得到的晶格常数与实验值非常吻合，并发现Г和X的带隙随压力增加而增大，而带隙存L点却并不明显．计算出Г点的带隙的压力系数是44meV／GPa．讨论计算得到的InN的光学性质，结合能带结构和电子态密度．

金属-氧共价性增强的缺陷态高熵岩盐型氧化物用于电催化析氧

高熵材料可以在单一晶相中引入五种或五种以上元素以优化电子结构和配位环境,可作为一类新兴的电催化剂.本文制备了一种岩盐型高熵氧化物Mg_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)Zn_(0.2)O(HEO)用于催化氧析出反应(OER).由于相邻的不同金属离子晶格失配,所制备的HEO具有丰富的缺陷.此外,电负性更小的Mg和Zn元素的存在使Co/Ni‒O共价性增强.得益于此,HEO在碱性条件下展现出优异的OER本征催化活性,其转换频率(TOF)在1.65 V时分别达到CoO和NiO的15和84倍.本文探究了HEO电催化性能提升机制,论证了通过合理添加低成本和低电负性元素的高熵策略在发展高效氧电催化剂方面的潜能.采用静电纺丝和热处理的方法制备了含有五种金属元素的HEO,X射线衍射(XRD)结果表明其为岩盐型晶体结构.X射线能量色散谱(EDS)和电感耦合等离子体发射光谱(ICP-OES)分析表明五种元素接近等摩尔比,且均匀分布.通过高分辨透射电子显微镜(HRTEM)发现HEO晶格中含有大量缺陷;同步辐射扩展X射线吸收精细结构(EXAFS)谱拟合数据显示HEO中Co和Ni的配位数相比CoO和NiO均有所降低,证实了缺陷的存在.此外,O 1s的X射线光电子能谱(XPS)和电子顺磁共振谱(EPR)进一步证明HEO含有大量氧缺陷.缺陷结构有利于配位不饱和的活性位点充分暴露,促进反应中间体的吸附,从而提升电催化活性.通过X射线吸收近边结构(XANES)谱分析了HEO中Co和Ni的电子结构信息.结果表明,相比CoO和NiO,HEO中Co和Ni的氧化态更低,因为HEO中电负性更低的Mg和Zn可以向O转移更多电子,使相邻的Co和Ni贡献更少电子.更高的电荷密度说明Co/Ni‒O键的共价性增强,与傅里叶变换的EXAFS谱中Co/Ni‒O键的键长变短相吻合.此外,Co和Ni2p的XPS结果表明,HEO表面Co(Ⅱ)和Ni(Ⅱ)成分占比较CoO和NiO更高,也证明HEO中Co/Ni‒O键具有更高的共价性.在1 M KOH中,HEO展现出优越的OER电催化性能,其达到10 mA cm^(−2)电流密度时过电位为360 mV,明显小于CoO和NiO,且与大多数文献报道的高熵电催化剂相当.此外,其Tafel斜率、质量比活性、单位面积活性和TOF均显著优于CoO和NiO,而采用相同方法制备的Co_(0.5)Ni_(0.5)O则性能较差.据此可以推测HEO电催化性能提升的主要原因在于:高熵策略可以调控活性金属的电子结构,通过引入低电负性元素增强Co/Ni‒O键的共价性,提升其本征催化活性;高熵体系中不同金属元素的尺寸差异导致大量缺陷产生,调控了活性位点的配位环境,从而促进活性位点暴露,提升催化性能.

DAMAGE AND CREEP MODEL FOR ROCK SALT AS WELL AS ITS VALIDATION

The constitutive model Hou/Lux,based on continuum damage mechanics and on the material model Lubby2 is presented and the damage,the healing of damage,the tertiary creep and the creep rupture of rock salt described. An application shows how phenomena observed in laboratory tests on axially perforated cylinder sample, such as softening, dilatancy, spalling and radial deformation into the axial bore as well as spalling can be numerically simulated with the model Hou/Lux. Furthermore,it is then evaluated against the measured permeability and stress profiles of a 37-year-old drift at the Sondershausen minein,Germany. Satisfactory agreement is obtained between the calculated and measured data.

岩盐结构固体的硬度与化学键特征的关系

采用离散变分Ｘ＿ａ（ＤＶ－Ｘ＿ａ）原子簇法，研究了十四种具有岩盐结构的固体中组成原子间的化学键特征，进而使微观的定量参数与固体的硬度相关联，初步实现了在电子结构水平上定量地描述固体的硬度。由于这些微观参数来自于对原子簇的量子化学计算，而不同于过去经验公式中通过经验给出经验参数，所以该方法具有更大的准确性与合理性。

A THERMO-PLASTIC/VISCOPLASTIC DAMAGE MODEL FOR GEOMATERIALS

A thermo-plastic/viscoplastic damage coupled model was formulated to describe the time independent and time dependent behaviors of geomaterials under temperature effect. The plastic strain was divided into instantaneous plastic strain and creep plastic strain. To take temperature effect into acconnt, a temperature variable was introduced into the instantaneous and creep plastic behavior descriptions and damage characterization, and a linear thermal expansion law was used in constitutive equation formulation. According to the mechanical behavior of rock salt, a specific model was proposed based on the previous model and applied to Avery rock salt, in which the numerical results obtained from our model had a good agreement with the data from experiments.