Investigation of the sodium storage mechanism of iron fluoride hydrate cathodes using X-ray absorption spectroscopy and mossbauer spectroscopy

Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_(3)·0.5H_(2)O)electrode for sodium-ion batteries(SIBs).The electrode material is prepared by employing an ionic liquid 1-butyl-3-methylimidazolium-tetrafluoroborate,which serves as a reaction medium and precursor for F^(-)ions.The crystal structure of FeF_(3)·0.5H_(2)O is observed as pyrochlore type with large open 3-D tunnels and a unit cell volume of 1129A^(3).The morphology of FeF_(3)·0.5H_(2)O is spherical shape with a mesoporous structure.The microstructure analysis reveals primary particle size of around 10 nm.The FeF_(3)·0.5H_(2)O cathode exhibits stable discharge capacities of 158,210,and 284 mA h g^(-1) in three different potential ranges of 1.5-4.5,1.2-4.5,and 1.0-4.5 V,respectively at 0.05 C rate.The specific capacities remained stable in over 50 cycles in all three potential ranges,while the rate capability was best in the potential range of 1.5-4.5 V.The electrochemical sodium storage mechanism is studied using X-ray absorption spectroscopy,indicating higher conversion at a more discharged state.Ex-situ M?ssbauer spectroscopy strengthens the results for reversible reduction/oxidation of Fe.These results will be favorable to establish high-performance cathode materials with selective voltage window for SIBs.

电子辐照对4H-SiC MOS材料缺陷的影响

4H-SiC金属氧化物半导体(MOS)基器件在电子辐照环境下应用时可能产生新的材料缺陷,导致其电学性能发生退化。本文选取结构最简单的MOS基器件(4H-SiC MOS电容器)为对象,研究了一系列电子辐照剂量下材料缺陷的演变情况。在10 MeV电子束下对MOS样品进行30、50、100、500、1 000 kGy剂量的辐照,对辐照前、后样品进行深能级瞬态谱测试(DLTS)和电容-电压(C-V)曲线表征。DLTS实验结果表明,低剂量电子辐照前、后4H-SiC/SiO_(2)界面及近界面处的缺陷没有发生明显变化,而高剂量辐照导致双碳间隙原子缺陷的构型发生了改变,演变后的构型能级位置更深,化学结构更加稳定。C-V曲线测试结果发现,不同电子辐照剂量导致MOS电容器平带电压发生不同程度的负向漂移,这很可能是SiO_(2)氧化层中氧空位数量和4H-SiC/SiO_(2)界面及近界面处缺陷数量共同影响的结果。本文研究结果对研发和优化抗电子辐照的4H-SiC MOS制备工艺具有一定的参考价值。

Mössbauer Spectroscopic Characterization of Fe Occupation of Columns in the Nb28O70 Structure

In search of an experimental route to produce linear arrays of spins without the use of nanotechnological tools, we have doped Nb28O70 with small amounts of transition metal oxides (TM;in this case Fe2O3) or rare-earth oxides3, and investigated the location of the alien metal (Fe in this case) in the structure. Previous AC magnetic susceptibility measurements at low temperatures have been consistent with the formation of arrays of TM magnetic moments along the widely spaced columns parallel to the crystallographic b-axis in the Nb28O70 structure. To obtain further details about the TM distribution, the previous investigation has been extended now to include a room-temperature Mössbauer spectroscopic analysis of the Fe-doped material. The data are consistent with the presence of low-spin Fe3+ ions in both octahedral and tetrahedral coordinations of oxygens, and confirm (as suggested in the previous work) that Fe also interchanges positions with Nb ions located at tetrahedrally coordinated sites in the columns of the structure.

Mössbauer Spectroscopic Characterization of Fe Occupation of Columns in the Nb28O70 Structure

In search of an experimental route to produce linear arrays of spins without the use of nanotechnological tools, we have doped Nb28O70 with small amounts of transition metal oxides (TM;in this case Fe2O3) or rare-earth oxides3, and investigated the location of the alien metal (Fe in this case) in the structure. Previous AC magnetic susceptibility measurements at low temperatures have been consistent with the formation of arrays of TM magnetic moments along the widely spaced columns parallel to the crystallographic b-axis in the Nb28O70 structure. To obtain further details about the TM distribution, the previous investigation has been extended now to include a room-temperature Mössbauer spectroscopic analysis of the Fe-doped material. The data are consistent with the presence of low-spin Fe3+ ions in both octahedral and tetrahedral coordinations of oxygens, and confirm (as suggested in the previous work) that Fe also interchanges positions with Nb ions located at tetrahedrally coordinated sites in the columns of the structure.

EMISSION MSSBAUER SPECTROSCOPY OF NiTi SHAPEMEMORY ALLOY

The emission Mssbauer Spectroscopy in cotnbination with transmission electron microscope was used to study NiTi shape memory alloy. The damage and the precipitated phase in NiTi alloy have heen discussed.

双钙钛矿型Sr_2Fe_xMo_(2-x)O_6系列氧化物的Mssbauer谱研究

通过M ssbauer谱对Sr2 FexMo2 -xO6 系列氧化物进行研究 ,结果表明该系列氧化物在室温下仍然存在磁有序 ,而且样品中Fe的化合价随着Fe含量x的增加而升高 ,当x =1 0时Fe的化合价处于 + 2与 + 3之间 ,从而验证了能带计算的结果 .

The metallogenic environment of the Dounan manganese deposit,Southeast Yunnan, China: evidence from geochemistry and Mössbauer spectroscopic

The Dounan manganese deposit is a typical large-scale marine sedimentary manganese deposit of the Middle Triassic in China. The metallogenic environment and change process directly dictate the migration, enrichment, and precipitation of Mn. To better understand its metallogenetic environment, a detailed study was undertaken involving field observation, mineralogical and geochemical and M?ssbauer spectroscopic analyses. The major findings are as follows:(1) Lithofacies paleogeography, sedimentary structural characteristics, and geochemical indexes indicate that the deposits were formed in an epicontinental marine sedimentary basin environment of normal salinity;(2) there were three ore phases including Mn oxides, Mn carbonates, and mixed Mn ores. The ore minerals found were braunite, manganite, Ca-rhodochrosite, manganocalcite, and kutnahorite. Petrographic and mineralogical information indicates that the metallogenic environment was a weakly alkaline and weakly oxidized to weakly reduced environment, and the mineralization occurred near the redox interface;(3) the V/(V + Ni)ratios, δCe and Fe^(2+)/Fe^(3+) found in profiles of Baigu and Gake ore sections show that the redox conditions of the ore-forming environment were continuously changing; and(4) three Fe species, α-Fe_2O_3, para-Fe^(3+), and para-Fe^(2+),were found in hematite and clay mineral samples using M?ssbauer spectrum analysis. The presence and distribution of these Fe species indicate that the deposit was formed in a typical sedimentary environment during the mineralization process. In summary, our study showed that redox was a key factor controlling the mineralization of the Dounan manganese deposit. Our results have led us to the conclusion that transgression and regression caused fluctuations in sea level, which in turn caused the change of the redox environment. M?ssbauer spectroscopy is an effective tool for studying the redox conditions of the paleoenvironment in which sedimentary manganese deposits were formed.

In Situ IR Spectroscopic Study on the Hydrogenation of 1,3-Butadiene on Fresh Mo_2C/γ-Al_2O_3 Catalyst

The surface species formed from the adsorption of 1,3-butadiene and 1,3-butadiene hydrogenation over the fresh Mo2C/γ-Al2O3 catalyst was studied by in situ IR spectroscopy. It is found that 1,3-butadiene adsorption on the Mo2C/γ-Al2O3 catalyst mainly forms π-adsorbed butadiene(πs and πd) and σ-bonded surface species. These species are adsorbed mainly on the surface Moδ+(0<δ<2) sites as evidenced by co-adsorption of 1,3-butadiene and CO on the fresh Mo2C/γ-Al2O3 catalyst. The IR spectrometric analysis show that hydrogenation of 1,3-butadiene over fresh Mo2C/γ-Al2O3 catalyst produces mainly butane coupled with a small portion of butene. The selectivity of butene during the hydrogenation of 1,3-butadiene over fresh Mo2C/γ-Al2O3 catalyst might be explained by the adsorption mode of adsorbed 1,3-butadiene. Additionally, the active sites of the fresh Mo2C/γ-Al2O3 catalyst may be covered by coke during the hydrogenation reaction of 1,3-butadiene. The treatment with hydrogen at 673 K cannot remove the coke deposits from the surface of the Mo2C/γ-Al2O3 catalyst.

Studies on the Hydrogenation of Acetonitrile over Fresh Mo_2C/γ-Al_2O_3 Catalyst by In-situ IR Spectroscopy

The adsorption of acetonitrile, the co-adsorption of acetonitrile with CO, and hydrogenation of acetonitrile on fresh Mo2C/γ-Al2O3 catalyst were studied by in situ IR spectroscopy. It was found out that CH3CN exhibited strong interaction with the fresh Mo2C/γ-Al2O3 catalyst and was adsorbed mainly on Moδ+ sites of fresh Mo2C/γ-Al2O3 catalyst. Moreover, CH3CN could affect the shifting of IR spectra for CO adsorption towards a lower wave number. The IR spectroscopic study on acetonitrile hydrogenation showed that CH3CN could be easily hydrogenated in the presence of H2 on the Mo2C/γ-Al2O3 catalyst. Furthermore, it was observed that CH3 CN could be selectively hydrogenated to imines on fresh Mo2C/γ-Al2O3 catalyst. Additionally, the active sites of fresh Mo2C/γ-Al2O3 catalyst might be covered with coke during the hydrogenation reaction of acetonitrile. The treatment of catalyst with hydrogen at 673 K could not completely remove coke deposits on the surface of the Mo2C/γ-Al2O3 catalyst.

Theoretical Review of Mossbauer Effect,Hyperfine Interactions Parameters and the Valence Fluctuations in Eu Systems

In this paper, an overview of the theory of M&#246;ssbauer effect is covered, and the main hyperfine interactions parameters which affect the shape of the resultant M&#246;ssbauer spectrum are explained and illustrated as well. In principle, M&#246;ssbauer effect applies to any and all nuclides, but in practice, certain ideal properties are desirable;that is, the conditions for recoil-free emission and absorption of gamma rays must be optimized. Therefore, briefly discussed in this review, one of the most commonly used for practical and fundamental studies the 151Eu M&#246;ssbauer isotope. Also, the intermediate valence phenomena and their theoretical treatments are briefly discussed.

PS－FeCl_3催化剂结构及活性的MOSSBAUER谱的研究

不同交联度的ＰＳ－ＦｅＣｌ＿３配位化合物的Ｍｓｓｂａｕｅｒ谱吸收峰皆由三组双峰组成，除强度不同外，其余参数均相同，可指派其结构为及此类配位结构在反应体系中分别瞬间转化为及是其具有催化活性的关键．

地外样品的核分析技术研究进展

地外样品是目前能获取到的来自其他天体的最直接地质证据。研究地外样品的目的在于揭示太阳系及其所含天体的宏观与微观演化过程,并为行星与星际环境和星际移民与外星生命的可能性提供新的见解。地外样品成分的原位或地面实验室精细分析研究对于人类认识天体演化以及我国后续月球探测与资源就地开发利用具有重要的意义。鉴于地外样品的特殊和珍贵,通常优先选用非破坏分析方法对其开展研究。而核分析技术是在实验核物理和核化学基础上发展起来的一门新型学科,是利用粒子与物质的相互作用、辐射效应、核谱学和核效应等基本原理和实验的方法,比如中子活化分析、离子束分析以及X射线荧光光谱分析等,利用其非破坏性、灵敏度高、准确度好和多元素同时分析等优点,非常适合开展地外珍贵样品的分析研究。未来十年是我国深空探测的关键时期,其主要目标是加深对宇宙的认知、拓展人类的活动空间、探寻地外生命信息,并进一步揭示宇宙奥秘与生命起源、了解保护地球以及激发科学探索精神。核分析技术作为对样品无损分析的科学手段,其生命力在于与物理、化学、材料、医学、地质、环境等学科领域的高度融合。随着我国深空探测的发展需求,核分析技术将会在我国月球、小行星、火星等深空探测以及采集的珍贵样品分析中发挥重要的作用。

RFe_(10.5)Mo_(1.5)C_x化合物的穆斯堡尔谱研究

利用熔炼法制备了低碳含量的 1∶ 12型 RFe10 .5Mo1.5Cx(R=Y,Nd)化合物 .X射线衍射结果表明化合物在碳加入后 ,单胞体积膨胀 .77K下测量了化合物的 57Fe穆斯堡尔谱 ,发现 C原子加入后 ,化合物中各铁晶位的超精细场均有所增加 ;化合物的平均同质异能移及平均超精细场增加 .同时 ,轻稀土 Nd的 1∶ 12型化合物同 Y的化合物相比 。

激光诱导击穿光谱技术定量分析钢铁合金中痕量Mo元素实验研究

探索在内标物谱线选择受限情况下利用激光诱导击穿光谱(LIBS)技术进行定量分析的可行方案,并应用到复杂钢铁合金中痕量金属元素钼(Mo)的检测分析中。实验中烧蚀激光波长为532 nm,LIBS信号的采集通过光栅单色仪、CCD、Boxcar和PMT来完成。对Mo的550.649,553.305和557.045 nm三条原子谱线峰高值随Mo元素含量的改变进行分析,利用双盲法检测分析一待测样品中所含Mo元素质量分数。待测样品中Mo元素质量分数标定值为2.111%,其中利用MoⅠ550.649 nm谱线进行分析得待测样品中Mo元素质量分数为2.229%,与标定值相对误差5.57%为最小;利用MoⅠ553.305 nm谱线分析结果次之;由于MoⅠ557.045 nm谱线发射强度较低且受到合金中FeⅠ556.9618 nm和FeⅠ557.2841 nm等元素谱线干扰,所得Mo元素质量分数为2.346%,与标定值相对误差11.15%为最大。利用三条谱线的峰高值之和进行分析得Mo元素质量分数为2.271%,与标定值相对误差为7.58%,结果优于三条谱线分别定标结果的平均值。可见,采用上述三条Mo原子谱线峰高值之和进行定量分析或对三条谱线定标分析的结果取平均值,可在一定程度上解决用单一谱线定标时由于选择受干扰谱线而引起的分析误差较大的问题。本文还讨论了实验中保持样品有效烧蚀效率稳定性的方法。结果表明,在内标选择受限情况下,保证实验条件一致性,选择合理的分析谱线以及方案也可以得到较高定量分析精度。

Ni/Mo/N催化剂合成及其在噻吩存在体系下苯加氢反应中的应用(英文)

Ni/Mo/N间隙型催化剂具有高的加氢活性及良好耐硫性, 可应用于煤液化油加氢精制高性能喷气燃料. N原子由于只占据晶格间隙位置, 在进入Ni/Mo过程中会因不占据晶格中的特定晶位, 容易从金属晶格溢出导致无法形成稳定的Ni/Mo/N间隙型催化剂. 为此, 本文利用前驱体晶型控制的方式来实现Ni/Mo/N催化剂合成. 采用络合物分解一步法, 考察了不同结晶过程和老化时间对合成的Ni/Mo/N催化剂用于苯加氢反应活性影响, 并采用X射线衍射、X射线光电子能谱和透射电镜-能量色散X射线光谱对催化剂结构组成进行表征. XRD分析结果显示, 钼酸铵[(NH4)6Mo7O24·4H2O]、乙酸镍[Ni(CH3COO)2·4H2O]和六亚甲基四胺(HMT)添加顺序、结晶过程和老化时间直接影响催化剂组成, 并决定Ni/Mo/N晶相的形成. 结晶过程慢速搅拌速度和短老化时间有利于合成含Ni2Mo3N, Mo2C和Ni晶相的高活性Ni/Mo/N间隙型催化剂, 使苯加氢制环己烷模型反应苯的最大转化率达93%, 环己烷选择性为100%. 含0.01 wt%噻吩的存在使苯转化率由72%降至50%, XPS分析结果表明, 催化剂表面形成的MoS2是催化剂活性降低的重要因素.

Mssbauer谱学及其在熔渣铁离子行为研究中的应用

综述了M¨ossbauer谱学原理、基本参数和测定方法 ;分析了熔渣中铁离子行为 ,并从化学和谱学角度阐述了Fe2 +、Fe3 +tet 和Fe3+oct 离子的M¨ossbauer谱特征 ;讨论了铁离子行为与熔渣碱度、渣中全铁量及Na2 O、Al2 O3 含量的关系 ;

用FT-IR技术研究Mo/HZSM-5分子筛的骨架结构

在两种不同硅铝比的ＨＺＳＭ５分子筛上担载不同量的钼物种后，对甲烷无氧脱氢芳构化反应呈现出不同的催化活性．使用ＦＴＩＲ技术测定了催化剂样品的骨架结构，结果表明，在两种分子筛载体上，钼物种的存在状态及其与载体间的相互作用各不相同；分子筛载体的酸性环境决定了浸渍时钼物种的可能存在状态．

现场表面拉曼光谱研究Fe-Mo合金诱导共沉积

现场表面拉曼光谱结果显示，在0．2mol·L-1Na2MoO4,pH＝4．0的溶液中，电位正于0．5V（vsSCE）时只观察到多钼酸盐的拉曼峰（940、880和450cm-1）．负于-0．5V时，出现中心位于730cm-1的宽峰．同时电极表面有蓝色膜生成．表明混合氧化态（MO（Ⅳ），MO（Ⅴ））氧化膜的形成．730cm-1的峰在-1．9V时仍然存在，说明氧化膜没有被进一步还原．在钼酸钠溶液中同时含有0．1mol·L-1FeSO4和0．2mol·L-1柠檬酸时，中间态氧化膜的拉曼峰的中心移到740cm-1．且峰强度随着电位从-1．3V负移到-1．9V而逐渐减弱并最终消失．电极表面沉积层呈银白色，说明由于Fe2+的存在，钼的中间态氧化膜的结构发生了变化，能够被进一步还原形成Fe－Mo合金，表现出诱导共沉积的特征．

氮在含氧Mo(100)面上的吸附与反应

用ＨＲＥＥＬＳ，ＡＥＳ，ＬＥＥＤ 和ＴＤＳ考察了氮在含氧Ｍｏ（１００） 上的吸附和热脱附．１２０ Ｋ 下氮在含氧Ｍｏ（１００）上吸附时存在着Ｎ—Ｎ 伸缩振动频率２ １５０ 和１ ６００ ｃｍ －１ ， 分别对应于线式（γ态） 和侧位（α态） 两种分子吸附态．升温引起γ态氮的脱附和α态氮的解离． 其中γ态氮的脱附峰温位于１５５ Ｋ， 遵循一级脱附动力学； 由α态解离生成的Ｎ 原子占据Ｍｏ（１００） 的四重空位（ 即β态） ， 并在高于１１５０ Ｋ 的温度重新化合形成氮而脱附．１２０ Ｋ时，氮的吸附是无序的； 吸附了氮的表面经１ １００ Ｋ退火后生成了有序的ｃ（２×２）Ｎ表面结构．

EDXRF法测定W-Mo-Ni-Fe合金组分

介绍了用能量色散X射线荧光光谱法（EDXRF）同时测定W—Mo—Ni—Fe合金组分的分析方法。当W、Mo、Ni和Fe的质量分数依次为70％～90％、7％～21％、2％～6％和1％～3％时，其测量结果的相对标准偏差依次不大于0．5％、1．5％、3％和4％。该方法快速、简便。