Rare-earth element geochemistry reveals the provenance of sediments on the southwestern margin of the Challenger Deep

The hadal zone represents one of the last great frontiers in modern marine science,and deciphering the provenance of sediment that is supplied to these trench settings remains a largely unanswered question.Here,we examine the mineralogical and geochemical composition of a sediment core(core CD-1)that was recovered from the southwestern margin of the Challenger Deep within the Mariana Trench.Major element abundances and rare-earth element patterns from these sediments require inputs from both terrigenous dust and locally sourced volcanic debris.We exploit a two-endmember mixing model to demonstrate that locally sourced volcanic material dominates the sediment supply to the Challenger Deep(averaging^72%).The remainder,however,is supplied by aeolian dust(averaging^28%),which is consistent with adjacent studies that utilized Sr-Nd isotopic data.Building on a growing database,we strengthen our understanding of Asian aeolian dust input into the northwestern Pacific,which ultimately improves our appreciation of sedimentation in,and around,the hadal zone.

Geochemical characteristics and their significances of rare-earth elements in deep-water well core at the Lingnan Low Uplift Area of the Qiongdongnan Basin

A geochemical analysis of rare-earth elements （REEs） in 97 samples collected from the core of deep-water Well LS-A located at the Lingnan Low Uplift Area of the Qiongdongnan Basin is conducted, with the pur-pose of revealing the changes of sedimentary source and environment in the study region since Oligocene and evaluating the response of geochemical characteristics of REEs to the tectonic evolution. In the core samples, both∑REE and∑LREE （LREE is short for light-group REEs） fluctuate in a relatively wide range, while∑HREE （HREE is short for heavy-group REEs） maintains a relatively stable level. With the stratigraphic chronology becoming newer, both∑REE and∑LREE show a gradually rising trend overall. The∑REE of the core is relatively high from the bottom of Yacheng Formation （at a well depth of 4 207 m） to the top of Ledong Formation, and the REEs show partitioning characteristics of the enrichment of LREE, the stable content of HREE, and the negative anomaly of Eu to varying degrees. Overall the geochemical characteristics of REEs are relatively approximate to those of China＇s neritic sediments and loess, with significant ＂continental ori-entation＂. The∑REE of the core is relatively low in the lower part of Yacheng Formation （at a well depth of 4 207-4 330 m）, as shown by the REEs partitioning characteristics of the depletion of LREE, the relative enrich-ment of HREE, and the positive anomaly of Eu; the geochemical characteristics of REEs are approximate to those of oceanic crust and basalt overall, indicating that the provenance is primarily composed of volcanic eruption matters. As shown by the analyses based on sequence stratigraphy and mineralogy, the provenance in study region in the early Oligocene mainly resulted from the volcanic materials of the peripheral uplift ar-eas; the continental margin materials from the north contributed only insignificantly; the provenance devel-oped to a certain extent in the late Oligocene. Since the Miocene, the provenance has ceaselessly expanded from proximal to distal realm, embodying a characteristic of multi-source sedimentation. In the core strata with 31.5, 28.4, 25.5, 23, and 16 Ma from today, the geochemical parameters of REEs and Th/Sc ratio have significant saltation, embodying the tectonic movement events in the evolution of the Qiongdongnan Basin. In the tectonic evolution history of the South China Sea, the South China Sea Movement （34-25 Ma BP, early expansion of the South China Sea）, Baiyun Movement （23 Ma BP）, late expansion movement （23.5-16.5 Ma BP）, expansion-settlement transition, and other important events are all clearly recorded by the geochemi-cal characteristics of REEs in the core.

Rare-earth and trace elements and hydrogen and oxygen isotopic compositions of Cretaceous kaolinitic sediments from the Lower Benue Trough, Nigeria: provenance and paleoclimatic significance

This study evaluated the Cretaceous(Campanian–Maastrichtian) kaolinitic sediments of the Ajali/Mamu and Enugu/Nkporo Formations from the Lower Benue Trough of Nigeria. A combined method of inductively coupled plasma–mass spectrometry and isotope ratio mass spectrometry was used to investigate trace and rareearth element geochemistry and hydrogen and oxygen isotopic compositions. These data were then used to infer the sediments' provenance and paleoclimatic conditions during their deposition. The sediments contained low concentrations of most trace elements, with the exceptions of Zr(651–1352 ppm), Ba(56–157 ppm), V(38–90 ppm),and Sr(15.1–59.6 ppm). Average values of Co and Ni were1.5 and 0.7 ppm, respectively. Trace and rare earth element values were lower than corresponding values for upper continental crust and Post-Archean Australian Shale, with the exception of Zr. The samples showed only slight light rare-earth enrichment and nearly flat heavy rare-earth depletion patterns, with negative Eu and Tm anomalies,typical of felsic sources. Geochemical parameters such as La/Sc, Th/Sc, and Th/Co ratios support that the kaolinitic sediments were derived from a felsic rock source, likely deposited in an oxic environment.^(18 )O values ranged from+ 15.4 to + 21.2% for the investigated samples, consistent with a residual material derived from chemicalweathering of felsic rock and redeposited in a sedimentary basin(typical values of + 19 to + 21.2%). While in the basin, the sediments experienced extended interactions with meteoric water enriched in d D and d16 O. However,the variation in d D and d16 O values for the investigated samples is attributed to the high temperature of formation(54–91 °C). The d D and d^(18 )O values suggest that the sediments, although obtained from different localities within the Lower Benue Trough, formed under similar hot,tropical climatic conditions.

Mechanism of interaction relation between the rare-earth element Ce and impurity elements Pb and Bi in Ag-based filler metal

The mechanism of interaction relation between the rare-earth element Ce and elements Pb and Bi in Ag-based filler metal has been studied. The results show that the compounds CePb and CeBi with high melting point can be easily produced between these three elements in the filler metal, which greatly limited the formation of the isolated phase Pb or Bi and also eliminated the bad effect of impurity elements Pb and Bi on the spreading property of Ag-based filler metal. The metallurgical and quantum-mechanical bond formation analysis show that a strong chemical affinity was existed between the rare-earth element Ce and impurity elements Pb and Bi, which was proved by the XRD analysis results.

Effects of rare-earth elements on the glass-forming ability and mechanical properties of Cu_(46)Zr_(47-x)Al_7M_x(M = Ce,Pr,Tb,and Gd) bulk metallic glasses

Cu46Zr47-xA17Mx （M = Ce, Pr, Tb, and Gd） bulk metallic glassy （BMG） alloys were prepared by copper-mold vacuum suction casting. The effects of rare-earth elements on the glass-forming ability （GFA）, thermal stability, and mechanical properties of Cu46Zr47-xA17Mx were investigated. The GFA of Cu46Zr47-xA17Mx （M = Ce, Pr） alloys is dependent on the content of Ce and Pr, and the optimal content is 4 at.%. Cu46Zr47-xA17Thx（X = 2, 4, and 5） amorphous alloys with a diameter of 5 mm can be prepared. The GFA of Cu46Zr47-xA17Gdx（x = 2, 4, and 5） increases with increasing Gd. Tx and Tp of all decrease. Tg is dependent on the rare-earth element and its content. ATx for most of these alloys decreases except the Cu46Zra2Al7Gd5 alloy. The activation energies △Eg, △Ex, and △Ep for the Cu46Zr42A17Gd5 BMG alloy with Kissinger equations are 340.7, 211.3, and 211.3 kJ/mol, respectively. These values with Ozawa equations are 334.8, 210.3, and 210.3 kJ/mol, respec- tively. The Cu46Zr45Al7Tb2 alloy presents the highest microhardness, Hv 590, while the Cu46Zr43A17Pr4 alloy presents the least, Hv 479. The compressive strength （at.f.） of the Cu46Zra3A17Gd4 BMG alloy is higher than that of the Cu46Zr43Al7Tb4 BMG alloy.

INFLUENCE OF RARE-EARTH ELEMENTS ON THERMAL STABILITY OF PdSi_(16.5)GLASS

The influence of rare-earth elements,La,Ce,Pr,Nd,Sm,Eu,Gd,Dy,Ho,Er and Yb on the thermal stability of PdSi_(16.5) glass was studied systematically by means of DSC.All rare-earth elements,especially heavy ones,increase obviously the thermal stability parameters,including T_θ(T_g ,T_x ,T_g),T_(rg) and ΔE etc.The crystallization temperatures T_(p1) and T_(p2) increase linearly with the lanthanide constriction increasing,but Eu shows an anomalous influence:Pd-Si-Eu metallic glass possesses the highest thermal stability and the lowest concentration limit of glass forming among Pd-Si-R glasses.

Study Segregation of Alloying Elements in Continuous Casting Slab with Valence Electron Structure

By calculating the electron structures of the phases that phosphor, sulfur and alloying elements dissolving inγ-Fe, the reason why alloying elements can bring centerline segregation in continuous casting slab (CCS) with nA, the number of electrons on the strongest covalent bonds, and the structure formation factor S were investigated, and an electron structural criterion to control and to eliminate the centerline segregation was advanced. Basing on this, the electron structures of a part of rare earth phosphides and sulfides are calculated, the physical mechanism that rare earth elements can control the segregation of phosphor and sulfur is analyzed, and the criterion is well verified.

Influence of Rare-Earth Elements on ElectricalProperties of Pd

The influence of RE (RE = La, Ce. Pr. Nd, Sm, Eu, Gd. Tb. Dy, Er, Yb) additives with dilute concentrations on the electrical properties of Pd has been studied. All RE elements increase the specific resistivity (ρ) and decrease the resistance temperature coefficient (α) of Pd. and (ρ.α) Pd-RE ls equal to (ρ· α)Pd.The RE elements before Gd reduce the thermo-emf of Pd on Cu. other heavy RE enhance the thermo-emf.The experimental data of normalized Pd-0.1 at.-%RE alloys indicate that the effect of light RE additives on the specific resistivity of Pd is larger than that of heavy RE and Ce. Eu and Yb show anomalous strong effect. The valence and atomic size are main factors influencing the electrical properties.

稀土元素Dy在MIM隧道结发光中的作用研究

制备了掺稀土元素Ｄｙ的ＭＩＭ隧道发光结，得到结的发射光谱、伏安特性及对各层膜的成份分析，结果显示Ｄｙ元素的加入提高了ＭＩＭ结的发光强度．讨论了Ｄｙ元素在提高ＭＩＭ隧道结的发光效率中所起的作用．

MIDyM隧道发光二极管的研究

稀土元素Dy引入以玻璃为基底的隧道发光二极管（简称为MIDyMTD）后，其发光强度得到了明显提高，Ⅰ－Ⅴ特性的负阻现象变弱，并出现了较弱的量子共振隧穿现象。量子共振隧穿导致了起发光中介作用的SPP慢模式的增强，最终导致了MIDyMTD发光的增强。另外，以铌酸锂单晶片为基底的MIDYMTD出现了较大的负阻（峰：谷—7：1），并且发射光谱的短波方向出现了戏剧性的增加。

Dy纳米粉含量对烧结Nd-Fe-B磁体的影响

为了改善烧结Nd-Fe-B磁体的磁性能和力学性能,采用二元合金法添加Dy纳米粉制备了高性能Nd-Fe-B磁体.利用扫描电子显微镜、X射线衍射仪、粒度分布仪、磁滞回线测试仪与维氏硬度仪对烧结Nd-Fe-B磁体的形貌、微观结构、化学成分、磁性能和力学性能进行了分析.结果表明,随着Dy元素质量分数的增加,磁体矫顽力大幅提高,剩磁和最大磁能积略有下降.相比未添加Dy元素的磁体,当Dy元素质量分数为0.8%时,磁体矫顽力提高了5.4%,剩磁和最大磁能积分别下降了1.3%和1.5%,维氏硬度提高了7.1%,此时磁体的综合磁性能最优.

掺稀土Dy的双势垒薄膜结构隧道发光结的研究

将少量稀土元素 Ｄｙ掺入隧道结制备成 Ｃｕ－Ｄｙ－Ａ１２Ｏ３－ＭｇＦ２－Ａｕ结构双势垒发光结。结果表明，稀土元素 Ｄｙ的引入，改善了结的粗糙度，使结由界面等离极化激元（ｓｕｒｆａｃｅ ｐｌａｓｍｏｎ ｐｏｌａｒｉｔｏｎ，ＳＰＰ）耦合发光的阈值电压有所降低，结的发光强度得到提高，改善了结的发光性能，与不掺Ｄｙ的结相比，其发光光谱在４６０．８ ｎｍ处发生了分裂，这与Ｄｙ掺入后栅区形成的附加能级有关。

基于ANSYS/LS-DYNA的高铁轴承动态仿真

基于Solidworks建立某型号高铁轴承的实体模型,在ANSYS/LS-DYNA的平台上使高铁轴承承受径向、轴向载荷的联合作用,分析其在匀速直线和以最小转弯半径行驶情况下的动态特性。结果表明,轴承外圈在运动过程中承受更大的载荷,滚子运动接近于纯滚动。

自我决定理论视域下高校课程思政优化路径探究

在自我决定理论视域下推进课程思政建设,是破解课程思政建设中为“思政”而“思政”、学生主体性缺失等困境,提升思政铸魂育人实效的有效路径。“大思政”格局背景下,需要深入挖掘高校课程思政育人元素,充分发挥课堂教学主渠道作用,以学生个体特征及学习需求为基础,为学生创设利于生成学习动机的学习环境,促使学生由被动接收知识转变为主动接受价值引领,在内化思政元素的过程中提高思政育人实效。

双三角点阵夹芯结构低速冲击下的动态响应与失效机制

采用非线性有限元仿真方法研究双三角点阵夹芯结构抗冲击性能,使用直径为16 mm的半球形冲击器以不同的冲击能量分别对夹芯板的节点和基底位置进行冲击,研究了点阵夹芯板的失效机理和动态响应,以及各个变量对夹芯板的抗冲击性能的影响规律。结果表明:双三角点阵夹芯结构的主要失效形式为面板的基体拉伸破裂;芯子的失效形式受自身结构和受力方式影响,主要为脆性坍塌断裂和塑性变形。载荷-时间曲线表明,冲头能量与冲击位置对夹芯板的损伤失效行为有着显著的影响。相同冲击能量下,与基底冲击相比,夹芯板在节点冲击时的损伤程度及载荷峰值都更优,抗冲击性能更加优异;高冲击能量下,节点冲击的吸能效果更优,但二者载荷变化趋势却越来越相似。

荧光磁性纳米微球Dy：Fe3O4／PHEMA-Tb的制备与表征

采用改进化学共沉淀法制备了镝掺杂铁氧体磁流体,然后以甲基丙烯酸-2-羟基乙酯为单体,N,N′-亚甲基双丙烯酰胺为交联剂,采用光化学方法在Dy∶Fe3O4磁流体中制备了磁性聚甲基丙烯酸-2-羟基乙酯(PHEMA)微球,进而合成了含有稀土元素Tb的荧光磁性高分子微球。用振动样品磁强计(VSM)、光子相关光谱(PCS)、傅里叶变换红外光谱仪(FT-IR)、热重-差热分析(TG-DTA)、扫描电镜(SEM)和全功能荧光光谱(FLS)等技术对微球的性能进行了表征,并与文献[5]中Fe3O4/PHEMA-Tb进行了对比分析。结果表明,荧光磁性高分子微球粒径为22.8 nm,比饱和磁化强度为68.1emu/g,变异系数为3.7%,具有超顺磁性和荧光性,分散性好,呈圆球形。

碱土金属离子(Mg^(2+),Ca^(2+),Ba^(2+))掺杂对长余辉荧光粉SrAl_2O_4:Eu^(2+),Dy^(3+)发光性能的影响

采用高温固相法制备了碱土金属离子(Mg2+,Ca2+,Ba2+)掺杂的SrAl2O4∶Eu2+,Dy3+长余辉荧光粉。XRD谱分析表明,随着基质中掺入的碱土金属离子(Mg2+,Ca2+,Ba2+)浓度增加,基质晶格常数也随之发生变化。Mg2+,Ca2+和Ba2+3种碱土离子在SrAl2O4中的固溶范围分别为40%,15%和30%。光谱分析则表明在固溶范围内随着掺杂Mg2+,Ca2+和Ba2+浓度的增大,样品的发射峰值会在480~530 nm范围出现规律性移动。适当浓度的Mg2+,Ba2+掺杂会不同程度地提高样品的发光强度,而Ca2+的掺杂则会降低发光强度。但是碱土金属离子(Mg2+,Ca2+,Ba2+)的掺杂并不能延长SrAl2O4∶Eu2+,Dy3+荧光粉的余辉时间。

Recent developments and applications on high-performance cast magnesium rare-earth alloys

During the past decades,with the increasing demands in lightweight structural materials,Mg alloys with low density and high performance have been extensively investigated and partly applied in some industries.Especially when rare earth(RE)elements are added as major alloying elements to Mg alloys,the alloy strength and creep resistance are greatly improved,which have promoted several series of Mg-RE alloys.This paper reviews the progress and developments of high-performance Mg-RE alloys in recent years with emphasis on cast alloys.The main contents include the alloy design,melt purification,grain refinement,castability,novel liquid casting and semisolid forming approaches,and the industrial applications or trials made of Mg-RE alloys.The review will provide insights for future developments of new alloys,techniques and applications of Mg alloys.

Corrosion rate determination of rare-earth Mg alloys in a Na_(2)SO_(4)solution by electrochemical measurements and inductive coupled plasma-optical emission spectroscopy

The corrosion resistance of three Mg alloys containing rare-earth elements(WE43,EV31 and ZE41)was studied and compared to that of two Mg-Al alloys(AZ31 and AZ91)and of pure Mg(99.95 wt.%).Current-voltage curves and electrochemical impedance measurements were performed with rotating disk electrodes in an aerated 0.1 M Na_(2)SO_(4)solution.For all the alloys,it was confirmed that the intermetallic particles acted as local cathodes and that more protective films were formed on the alloys surface by comparison with the pure Mg.Corrosion rates were determined from inductive coupled plasma-optical emission spectroscopy measurements and from the electrochemical measurements.Higher corrosion rates were observed for the rare-earth Mg alloys compared to the AZ series alloys.These data allowed the corrosion mechanisms to be discussed.

Research of Optical Performance On Rare-Earth Optical Fiber

The rare-earth optical fiber is made of organic material and inorganic rare earth material.It can be used to absorb and transfer solar energy.When sunlight irradiates, it may absorb and transfer solar energy automatically; while at night or without sunlight it may give out light and play role of decoration.By utilizing high transmissivity of organic material and heat-resisting performance of inorganic material, we know the reorganization of material performance under the melting condition, and make empty core bear the high temperature of 150 ~200 ℃.When the light spreads in light guide, some light energy travels along the direction of light guide, and is introduced in the room directly.Another part of light energy is absorbed and stored by light guide, and can release light again after 8 ~ 12 h.