Gd99.75Fe0.25合金的大磁热效应及应用特性研究

采用X射线衍射、物理性能测试系统、显微硬度计及电化学工作站研究了经氩弧熔炼、1123 K均匀化热处理168 h的 Gd99.75Fe0.25合金的磁热效应及应用特性。结果表明：Gd99.75Fe0.25合金仍保持纯Gd的六方晶体结构;Gd99.75Fe0.25合金的居里温度为294 K,且在居里点附近发生铁磁到顺磁的二级相变,2和5 T外场下的最大磁熵变分别为4.99和9.37 J·kg-1·K-1,均大于纯Gd;Gd99.75Fe0.25合金的显微硬度（HV0.2）590 MPa,与纯Gd相当,但少量Fe的掺杂提高了Gd的耐蚀性。含少量Fe的Gd99.75Fe0.25合金具有大的磁热效应及良好的应用特性,是一种有很大应用潜力的室温磁致冷材料。     

固溶处理中Mg-9Gd-2Er-0.4Zr合金的组织演变(英文)

利用OM、SEM和TEM研究了固溶处理过程中Mg-9Gd-2Er-0.4Zr铸造镁合金的微观组织演变,其固溶处理温度和时间范围分别为460～520℃和3～12h。结果表明,随着固溶时间的延长和(或)温度的升高,合金的晶粒尺寸和第二相形态均有显著变化。当固溶温度和时间分别为460℃和3h时,Mg5(GdEr)相的体积分数降低并转变为破碎的岛状。当固溶温度和时间分别为460℃和6h时,Mg5(GdEr)相已经完全溶解,但是析出了少量的立方状富RE相。随着固溶温度的升高,Mg5(GdEr)相的形貌演变与固溶温度460℃和时间6h时的相似。在固溶处理过程中合金的组织演变为:Mg5(GdEr)共晶相→Gd/Er原子向基体扩散→类球形Mg5(GdEr)相→立方状富RE相→晶界迁移。     

Gd对ZL205A合金显微组织和力学性能的影响

研究了不同质量分数Gd对ZL205A合金铸态及T6态显微组织和力学性能的影响.采用光学显微镜、荧光光谱仪和电子探针对制备的试样微观组织和元素分布进行分析,并利用电子拉伸试验机对铸锭的力学性能进行测试.结果表明:微量稀土元素Gd能细化ZL205A合金的晶粒,并与合金中的其他元素形成新相,能提高合金铸态和T6后的力学性能;当Gd加入量为0.06％时,综合力学性能最优,铸态时抗拉强度为192MPa,伸长率为11.1％;T6态时抗拉强度达到421.1MPa,伸长率为10.2％.但当Gd添加量过多时,合金的组织与性能均产生恶化.     

热处理对γ-TiAl合金中Gd化合物的影响研究

针对含0.15%（原子分数）稀土元素Gd的变形γ-TiAl合金,研究1 300℃/0.5h/空冷热处理前后稀土化合物种类、形态和分布变化。变形γ-TiAl合金中存在两种稀土化合物,分别是富Al元素的Al-Gd化合物和富O元素的O-Gd化合物。在热处理过程中Al元素向Al-Gd化合物边缘扩散,基体的Ti、O元素向Al-Gd化合物扩散,因此部分Al-Gd化合物转变为由Al-Gd包围O-Gd的包裹状化合物。热处理后,Al-Gd化合物球化、尺寸减小、数量减少,体积分数由2.78%减少至1.13%,O-Gd化合物数量增加但形貌基本不变。     

Photoluminescent properties of Eu3＋ and Tb3＋ codoped Gd2O3 nanowires and bulk materials

In this paper, the Gd2O3：Eu3＋,Tb3＋phosphors with different doping concentrations of Eu3＋and Tb3＋ions were prepared by a hydrothermal method for nanocrystals and the solid-phase method for microcrystals. The interaction of the doped ions with different concentrations and the luminescent properties of the nanocrystals and microcrystals were studied systematically. Their structure and morphology of Gd2O3：Eu3＋,Tb3＋phosphors were analyzed by means of X-ray powder diffraction （XRD）, transmission electron mi-croscopy （TEM） and scanning electron microscopy （SEM）. The photoluminescence （PL） properties of Gd2O3：Eu3＋,Tb3＋phosphors were also systematically investigated. The results indicated that when the concentration of doped Eu3＋was fixed at 1 mol.%, the emis-sion intensity of Eu3＋ions was degenerating with Tb3＋content increasing, while when the Tb3＋content was fixed at 1 mol.%, the emission intensity of Tb3＋ions reached a maximum when the concentration of Eu3＋was 2 mol.%, implying that the energy transfer from Eu3＋to Tb3＋took place. In addition, Tb3＋could inspire blue-green light and the Eu3＋could inspire red light. Therefore co-doping systems by controlling the doping concentration and the hosts are the potential white emission materials.     

Preparation of Gd-Co alloy in dimethylsulfoxide by electrodeposition method

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Tb~(3+)掺杂Gd_2Sn_2O_7纳米荧光材料的制备与光学性能

采用共沉淀-水热法合成Tb3+掺杂Gd2Sn2O7纳米荧光材料,并采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、傅里叶变换红外光谱(FT-IR)、拉曼光谱(Raman)和荧光光谱对合成产物的晶体结构、颗粒尺寸、形貌和光学性能进行研究。研究结果表明水热合成产物为单一相立方烧绿石结构Gd2Sn2O7:Tb3+晶体,产物由尺寸约为50~70 nm的一次纳米颗粒团聚而成的不规则球。激发光谱和发射光谱测试结果表明,Gd2Sn2O7:Tb3+样品可以被379 nm的紫外光有效地激发而发射出纯度高的Tb3+离子特征的绿光,在高浓度Tb3+掺杂时可观察到Tb3+发光浓度猝灭现象。在样品的激发光谱中观察到不同激发带的猝灭浓度并不相同,并对其原因进行了分析。     

磁控溅射工艺参数对Cu,Al薄膜与Gd基底附着性的影响

为了探讨Gd表面溅射保护膜的附着性能,利用直流磁控溅射技术在Gd基体上分别镀Cu和Al膜.用扫描电镜(SEM)和能谱仪对薄膜进行表征,用引拉法测定了薄膜的附着强度.结果表明:A1膜表面质量好,Al/Gd界面结合好,附着强度高,在优化工艺参数条件下薄膜附着强度可达到27.60 MPa;Cu膜表面质量较差,Cu/Gd界面结合差,附着强度低,在优化工艺参数条件下薄膜附着强度最高仅为3.02 MPa.     

Sn合金化对Gd5Si2Ge2磁致冷材料结构和性能的影响

以商业纯Gd为原料,采用非自耗电弧炉氩气保护下熔炼了Gd5Si2Ge2-xSnx(x=0.2,0.5,1)和Gd5Si2-yGe2Sny(y=0.1,0.2,0.5)系列合金,研究Sn合金化对Gd5Si2Ge2晶体结构和磁热性能的影响.粉末XRD结果表明Sn代Ge样品具有正交Gd5Si4型结构;Sn少量代Si(y=0.1,0.2)的样品具有单斜Gd5Si2Ge2型结构;Gd5Si1.5Ge2Sn0.5则为单斜和正交的混合结构.用超导量子磁强计(SQUID)测定了样品的M-T和不同温度的M-H曲线,结果表明Gd5Si2Ge2-xSnx(x=0.2,0.5,1)不具有巨磁热效应;Gd5Si1 9Ge2Sn01合金的最大磁熵变达15.3 J/kg·K(0 T～5 T),具有巨磁热效应.     

Thermodynamic assessment of BaO–Ln2O3 (Ln = La,Pr, Eu,Gd, Er) systems

Heat capacities and enthalpies of formation of BaGd₂O₄ were determined by high-temperature differential scanning calorimetry and high-temperature oxide melt solution calorimetry, respectively. Thermodynamic stability of BaLn₂O₄ compounds increases with decreasing Ln³⁺ ionic radius. Previously reported data on BaNd₂O₄ and BaSm₂O₄ corroborate this trend. Missing data for compounds in BaO–Ln₂O₃ (Ln = La, Pr, Eu, Er) systems were estimated from established relations, thermodynamic assessment was performed, and binary phase diagrams were calculated.