YIG陶瓷对三价锕系模拟核素的固化行为研究

石榴石具有较大的锕系包容量及化学灵活性, 被认为是潜在的锕系核素固化基材。本工作以Nd³⁺模拟三价锕系核素, 通过高温固相法成功合成了Y_3-xNd_xFe₅O₁₂(0≤x≤2)系列钇铁石榴石(YIG)固化体。研究了Nd在YIG固化体中的固溶极限和Nd掺杂量对固化体的物相和微观结构的影响规律, 以及不同pH条件下Nd掺杂钇铁石榴石固化体的化学耐久性。研究结果表明, 当x≤1.7时, YIG基固化体为纯相YIG; 当x≥1.8时, YIG基固化体中YIG、NdFeO₃和Fe₂O₃三相共存。纯相YIG基固化体对Nd³⁺的固溶极限约为29.5%(质量分数)。随着Nd掺杂量增加, 固化体的密度增大, 体积减小, 孔隙率减小。浸出实验结果显示, 28 d后元素归一化浸出率(LR_i)逐渐趋于平衡, 42 d后, 其元素的LR_i为10^-6~10^-5 g·m^-2·d^-1。LR_Y小于LR_Nd, 且酸性溶液中元素归一化浸出率也略高于中性和碱性溶液。这些结果表明, YIG陶瓷是理想的三价锕系核素候选固化基材。     

Wave-vector dependence of spin-wave line-width in yttrium iron garnets

The wave-vector dependence of the spin-wave line-width in yttrium iron garnets has been studied for samples of grain diameter varying from 1·2μm to 12μm. An expression for the spin-wave line-width as a function of wave-vector and grain diameter has been obtained, which agrees satisfactorily with experiment.     

掺铋钇铁石榴石磁光陶瓷的热压烧结及其性能研究

钇铁石榴石(Y₃Fe₅O₁₂, YIG)材料因其优异的磁性能和磁光性能在微波通信、激光技术和光纤通讯等领域具有重要应用。离子掺杂是提高YIG材料磁光性能的有效途径之一, 本研究选择离子半径适配的Bi³⁺掺杂改性YIG陶瓷以提高材料的磁光性能。本工作采用固相法热压烧结制备Bi_xY_3-xFe₅O₁₂ (x=0、0.3、0.6、0.9)陶瓷, 并研究Bi³⁺掺杂对YIG陶瓷材料相结构、微观形貌、红外透过性、磁性能以及磁光性能的影响。结果表明: 陶瓷样品均呈石榴石立方相结构; 显微结构致密, Bi³⁺掺杂后晶粒尺寸不同程度增大; 样品红外透过率良好, 随Bi³⁺掺杂量增大而降低; 陶瓷样品的法拉第旋转角随Bi³⁺掺杂量增加呈线性变化, Bi³⁺掺杂量每增加1% (原子分数), 在波长1064 nm和1550 nm处变化量分别约为-49.0 (°)/cm和-30.2 (°)/cm。Bi_0.6Y_2.4Fe₅O₁₂陶瓷样品在1064 nm和1550 nm波长下法拉第旋转角分别达到-703.3 (°)/cm和-461.5 (°)/cm, 绝对值远高于未掺杂YIG陶瓷的277.6 (°)/cm和172.0 (°)/cm。由此可见, 掺杂适量Bi³⁺可以显著增强YIG陶瓷材料的磁光性能。     

聚焦离子束系统中微波离子枪的束光学特性研究

通过实验和数值模拟研究了聚焦离子束系统中微波离子枪的离子束光学特性，该离子枪由微波等离子体源和Orloff-Swason引出透镜组成。该透镜除了广泛用于场致发射离子枪外，在等离子体源情况下，也能获得很好的离子束光学性能。     

离子掺杂钇铁石榴石磁光材料研究进展

综述了钇铁石榴石型磁光材料的研究进展,以及通过离子掺杂提高单晶和薄膜材料的比法拉第旋转角、改善材料温度稳定性以及近年来受到重视并有望在磁光器件中得到广泛应用的低成本钇铁石榴石纳米晶/有机分散介质复合薄膜材料的研究进展与存在的问题,概述了目前实际使用中的磁光法拉第转子材料的应用情况,并展望了高性能磁光材料的发展。     

氧化石墨烯的离子束辐照表面改性

采用低能N+离子束对氧化石墨烯进行辐照,研究离子束辐照对石墨烯表面的改性作用,通过拉曼光谱仪(Raman)、原子力显微镜(AFM)和透射电子显微镜(TEM)表征了氧化石墨烯的辐照效果。结果表明,由于辐照产生的原子碰撞和热效应,在一定的N+辐照剂量下,氧化石墨烯表面发生原子的迁移、重排,在表面产生了纳米孔和晶化现象。Raman结果显示,相对于未辐照组,辐照后的氧化石墨烯特征峰相对强度比值ID/IG明显降低,表明离子束辐照减少了氧化石墨烯表面缺陷,具有明显的改性效果。     

离子束合成的钇硅化物结构相变研究

为了获得高品质的欧姆接触和线路连接材料，利用离子注入方法在n型单晶Si(111)基底上制备了钇硅化物，并对其在高真空下红外光辐照处理过程中的结构相变进行了研究，X射线衍射测量表明，在Y离子注入过程中已形成了部分六方相YSi2，800℃下红外光辐照处理30min后YSi2呈现出择优结晶取向，从辐照过程中原位测量样品的方块电阻变化发现，当温度升至160℃时，Y与Si反应首先形成了斜方相YSi，YSi/YSi2的相转变出现在240℃，随温度的进一步升高，Y原子完全与Si原子发生反应，形成了结晶取向良好的六方相YSi2。     

双离子束溅射法制备铁氮薄膜

使用双离子束溅射法制得了铁氮薄膜,随着基片温度的变化,薄膜的成分是ε－Fe2-3N,γ′－Fe4N或是二相的混合物,薄膜的晶粒尺寸随基片温度的升高而增大。以振动样品磁强计（VSM）测定了薄膜的磁性能。另外,研究了在基片温度为160℃时,改变主源中通入N2／Ar的比例对薄膜成分的影响。     

Engineering Chemically Active Defects in Monolayer MoS2 Transistors via Ion‐Beam Irradiation and Their Healing via Vapor Deposition of Alkanethiols

Irradiation of 2D sheets of transition metal dichalcogenides with ion beams has emerged as an effective approach to engineer chemically active defects in 2D materials. In this context, argon‐ion bombardment has been utilized to introduce sulfur vacancies in monolayer molybdenum disulfide (MoS₂). However, a detailed understanding of the effects of generated defects on the functional properties of 2D MoS₂ is still lacking. In this work, the correlation between critical electronic device parameters and the density of sulfur vacancies is systematically investigated through the fabrication and characterization of back‐gated monolayer MoS₂ field‐effect transistors (FETs) exposed to a variable fluence of low‐energy argon ions. The electrical properties of pristine and ion‐irradiated FETs can be largely improved/recovered by exposing the devices to vapors of short linear thiolated molecules. Such a solvent‐free chemical treatment—carried out strictly under inert atmosphere—rules out secondary healing effects induced by oxygen or oxygen‐containing molecules. The results provide a guideline to design monolayer MoS₂ optoelectronic devices with a controlled density of sulfur vacancies, which can be further exploited to introduce ad hoc molecular functionalities by means of thiol chemistry approaches.     

Highly Efficient Sodium Storage in Iron Oxide Nanotube Arrays Enabled by Built‐In Electric Field

High‐power sodium–ion batteries capable of charging and discharging rapidly and durably are eagerly demanded to replace current lithium–ion batteries. However, poor activity and instable cycling of common sodium anode materials represent a huge barrier for practical deployment. A smart design of ordered nanotube arrays of iron oxide (Fe₂O₃) is presented as efficient sodium anode, simply enabled by surface sulfurization. The resulted heterostructure of oxide and sulfide spontaneously develops a built‐in electric field, which reduces the activation energy and accelerates charge transport significantly. Benefiting from the synergy of ordered architecture and built‐in electric field, such arrays exhibit a large reversible capacity, a superior rate capability, and a high retention of 91% up to 200 cycles at a high rate of 5 A g^?1, outperforming most reported iron oxide electrodes. Furthermore, full cells based on the Fe₂O₃ array anode and the Na_0.67(Mn_0.67Ni_0.23Mg_0.1)O₂ cathode deliver a specific energy of 142 Wh kg^?1 at a power density of 330 W kg^?1 (based on both active electrodes), demonstrating a great potential in practical application. This material design may open a new door in engineering efficient anode based on earth‐abundant materials.     

Effect of self-generated axial magnetic field and on propagation of intense laser radiation in plasmas

The present paper deals with an analytical study of a self-generated axial magnetic field (SGAMF) through the inverse Faraday effect (IFE) and its influence on the propagation of circularly polarized light wave for relativistic intensities. As a first step, the non-linear dielectric constant incorporating a magnetic field in the relativistic factor within the framework of WKB (for Wentzel, Kramers, and Brillouin) and a paraxial ray theory is formulated. It is noticed that for intensities (>10¹⁸ W cm^?2), circularly polarized radiation can propagate in electron plasma whose density is greater than the critical density as well as a strong flow of relativistic electrons, axially co-moving with the pulse rise. The above generates a magnetic field up to 100 MG and strongly influences the light propagation. Two modes of propagation exist, namely, extraordinary and ordinary, and critical power for focusing is different for the two modes. The non-linear dielectric tensor, propagation equation, and the self-trapped radius are evaluated incorporating an induced magnetic field. The focusing conditions strongly depend on the power of the beam, strength of the magnetic field as well as on the density of the medium. Numerical calculations are made for a typical set of relativistic laser plasma interaction processes.     

Study of FePt films prepared by reactive sputtering

In the present study, ⁵⁷FePt films are prepared with reactive ion beam sputtering using mixture of argon and nitrogen gases. Energy-dispersive X-ray reflectivity is used to estimate the thickness of the as-deposited films. Structural and magnetic properties of the as-deposited and annealed films are studied using grazing incidence X-ray diffraction (GIXRD), magneto-optical Kerr effect (MOKE) and conversion electron Mossbauer spectroscopy (CEMS). Significant difference in structural and magnetic properties i.e., formation of ordered L1₀ phase and perpendicular magnetic anisotropy are observed for the films prepared with mixture of nitrogen and argon as compared to the film prepared with argon only. From the GIXRD, peaks corresponding to the ordered face-centred tetragonal FePt phase are observed for the films prepared with mixture gas. The results of CEMS clearly show the perpendicular magnetic anisotropy (PMA) for the films prepared with mixture of nitrogen and argon. The observed enhanced chemical ordering and the development of PMA in the films prepared with mixture gas is due to the role played by the defects created as a consequence of nitrogen escape in the films with high temperature annealing.     

Amorphous state ferroelectricity,magnon scattering and phase stability in microparticle materials

Microparticles and micrograin ceramics show features distinct from the usual-sized polycrystalline materials. Amorphous state material combined with microparticle size for Pb(Zr_0.51 Ti_0.49)O₃ mimics the dielectric behaviour of crystalline ferroelectricity in ABO₃ compounds. Fine-grained Y₃Fe₅O₁₂ (yig) synthesized by pressure sintering ofyig microparticles exhibit spinwave relaxation due to transit time across grain diameter. Applying microemulsion techniques for microparticle synthesis,γ-Fe₂O₃ has been synthesized. The phase stability fractionγ-Fe₂O₃/α-Fe₂O₃ is found to be a function of particle size. At very small sizesγ-Fe₂O₃ becomes amorphous, leading to interesting Mössbauer studies.     

Direct evidence for dislocation-free zone in Fe–5% Si fractured by Charpy impact test

Defect structure in the subsurface region below a fracture surface of an Fe–5% Si specimen that had been fractured by a Charpy impact test at 77 K was examined by transmission electron microscopy. The specimen was fabricated by a focused ion beam technique to enable analysis of areas that had been carefully selected on the basis of observation. Near the nucleation site of the crack, many dislocations were observed just beneath the fracture surface. Far away from the nucleation site, no dislocations at all were observed in the subsurface region of the fracture surface. Between these two extreme positions, a dislocation-free zone was observed.