Journal of Materials Research
Based on the best bulk metallic glass (BMG) forming alloy in the Mg-Cu-Y ternary system, we introduced Ag (or Ni) to partially substitute for Cu to improve the glass-forming ability (GFA). The objective of this paper is twofold. First, we illustrate in detail a recently developed search strategy, which was proposed but only briefly outlined in our previous publication [H. Ma, L.L. Shi, J. Xu, Y. Li, and E. Ma: Discovering inch-diameter metallic glasses in three-dimensional composition space. Appl. Phys. Lett. 87, 181915 (2005)]. The protocol to navigate in three-dimensional composition space to land large BMGs is spelled out step-by-step using the pseudo-ternary Mg-(Cu,Ag)-Y as the model system. Second, our ability to locate the best BMG former in the composition tetrahedron allows us to systematically examine, and conclude on, the effects of a given alloying element. The large improvement in glass-forming ability in the Mg-(Cu,Ag)-Y system relative to the based ternary will be contrasted with the reduced glass-forming ability in the Mg-(Cu,Ni)-Y pseudo ternary system. It is demonstrated that the improvement of glass-forming ability requires judicious choice of substitutional alloying elements and concentrations, rather than simple additions of multiple elements assuming the "confusion principle."
关键词:
bulk metallic-glass;shaped copper mold;amorphous-alloys;thermal-stability;ternary-system;casting method;p system;diameter;zr;mm
Journal of Physical Chemistry C
We report the electrical, thermal, magnetic, and thermoelectric properties of Y-doped Ca(3)Co(4)O(9) from 300 down to 5 K. The results indicate that with Y doping, the increase of resistivity originates from the decreases of carrier concentration and mobility, while the increase of Seebeck coefficient is caused by the reduction of carrier concentration together with the enhanced electronic correlation. Point-defect scattering, is the dominant thermal transport mechanism in this system. Due to the considerable difference in mass between Y(3+) and Ca(2+), thermal conductivity is observably suppressed by doping. The substitution of Y also disturbs the interlayer ferrimagnetic coupling. The ground state of this System converts front ferrimagnetism to paramagnetism gradually. The alteration of transport properties of Ca(3-x)Y(x)Co(4)O(9) reveals two Crossovers: the transition from Fermi-liquid-like metal to thermally activated semiconductor occuring at x approximate to 0.25, and the transition from thermally activated semiconductor to two-dimensional variable range hopping semiconductor occurring at x approximate to 0.5. The optimal thermoelectric response In Ca(3-x)Y(x)Co(4)O(9) is found to exist only at the critical state after which the doping-induced metal-insulator transition takes place. Oil the basis of these experimental results, a possible phase diagram for Ca(3-x)Y(x)Co(4)O(9) is proposed.
关键词:
temperature thermoelectric properties;giant magnetoresistance;solid-solutions;conductivity;electron;system;ca3co4o9+delta;thermopower;crystals;behavior
Applied Physics Letters
The effect of nonmagnetic Y partial substitution at the Dy site in Dy(1-x)Y(x)MnO(3) up to x=0.2 on magnetism, specific heat, and ferroelectricity is investigated, which resulted in a preliminary multiferroic phase diagram. It is revealed that the Y partial substitution suppresses the Dy-spin ordering point (T(Dy)) and ferroelectric ordering point (T(FE)) but enhances the Mn-spin ordering point (T(N)). The interaction between the spins of Dy and Mn is remarkably affected by Y substitution. The measured electrical polarization depends on the Y substitution in a complex way because the ferroelectricity is sensitive to the interaction between the spins of Dy and Mn. (c) 2011 American Institute of Physics. [doi: 10.1063/1.3536506]
关键词:
ferroelectricity;polarization
Transactions of Nonferrous Metals Society of China
The influence of Zr and Y on the cast microstructure of a nickel-based superalloy was investigated by optical microscopy (OM), scanning electron microscopy(SEM), electron probe micro-analysis (EPMA) and X-ray diffraction (XRD). The gamma+gamma' eutectic volume in the superalloy rises notably with the increase of Zr or Y content. Meanwhile, the morphologies of primary MC carbides change from needle and platelet-like to blocky shape with increasing Zr and Y doped. The XRD results show that the primary MC carbide lattice constant increases with Zr and Y additions, and EPMA investigation shows that the platelet-like MC carbides contain primarily Nb and C, while those carbides in blocky shape have 39.2% Zr and 39.6% Nb in average,. These influences on the cast microstructure can be attributed to the atomic size effects of Zr and Y.
关键词:
yttrium;zirconium;carbides;nickel based superalloys;microstructure;solidification;carbide morphology;mechanical-properties;boron;ni3al;yttrium;sulfur
材料科学技术（英文）
The corrosion of an Fe-based alloy containing 15 wt pet Y in H-2-H2S mixtures under 10(-3) Pa S-2 was studied at 600 similar to 800 degrees C in an attempt to find materials with improved sulphidation resistance with respect to pure Fe. The presence of Y has been shown to be beneficial, but not sufficient to the level expected. In fact, the alloy is able to form at all tested temperatures an external FeS layer, beneath which a zone containing a mixture of the two sulphides is also present. Thus, Fe can still diffuse through this region to form the outer FeS layer with non-negligible rate. The corrosion rate of Fe is considerably reduced by the Y addition, but the alloy corrodes still much more rapidly than Y. The sulphidation kinetics is generally rather irregular for both the pure metals, while the corrosion rate of the alloy decreases with time and tends to become parabolic after an initial period of 12 similar to 17 h. The sulphidation behaviour of the alloys is discussed by taking into account the presence of an intermetallic compound Fe17Y2 and the limited solubility of Y in Fe.
关键词:
high-temperature sulfidation;most-reactive component;ni-nb alloys;h2-h2s mixtures;behavior;600-degrees-c-800-degrees-c;oxidation
白咏梅
,
刘芳凌
,
邱鹏
,
韩绍昌
功能材料
以酚醛树脂为碳源,利用固相反应合成了Li0.99Y0.01FePO4/C复合材料.采用X射线衍射分析(XRD)、扫描电镜(SEM)、高分辨透射电镜(HRTEM)以及恒电流充放电等方法对该材料的晶体结构、表面形貌、界面结构及电化学性能进行表征.结果表明,所合成的Li0.99Y0.01FePO4/C材料为单一的橄榄石晶体结构,包覆碳后的复合材料颗粒形成了良好的导电网络,电化学性能得到很大改善.在0.1C的电流密度下进行充放电时,首次放电容量为143.43mAh/g,充放电效率为90.54%,在1.0C的电流密度下进行充放电时的首次放电容量仍有101.17mAh/g.
关键词:
锂离子电池
,
正极材料
,
复合材料
,
Li0.99Y0.01FePO4/C
Applied Physics Letters
The structure, Curie temperature, and magnetostriction of R(1-x)Pr(x)Fe(1.85) and R(0.7)Pr(0.3)Fe(y) (R = Dy0.7Tb0.3, x less than or equal to 0.5, 1.55 less than or equal to y less than or equal to 1.85) alloys were investigated. The matrix of R(1-x)Pr(x)Fe(1.85) alloys is the MgCu2-type cubic (Dy,Tb,Pr) Fe-2 and the second phase was found to be (Dy,Tb,Pr) Fe-3 when x less than or equal to 0.3. When x>0.4, (Dy,Tb,Pr) Fe-3 is the main phase with the PuNi3-type structure and (Dy,Tb,Pr) Fe-2 becomes the minority phase. In the range of 0.3<x less than or equal to 0.4, both MgCu2- and PuNi3-type structures coexist. The R(0.7)Pr(0.3)Fe(y) alloys contain a small amount of (Dy,To,Pr) Fe-3 phase when y>1.55, which increased with increasing y. When y = 1.55, the alloy is essentially single phase with the MgCu2-type cubic structure. The lattice parameter of (Dy,Tb,Pr) Fe-2 compound for R(1-x)Pr(x)Fe(1.85) alloys increases slowly with increasing x when x less than or equal to 0.3, and sharply increases when x>0.3. The Curie temperature of the alloys decreases steadily with increasing Pr content. The magnetostrictions of R(1-x)Pr(x)Fe(1.85) and R(0.7)Pr(0.3)Fe(y) alloys decrease with increasing Pr content and Fe content, respectively. The largest magnetostriction at room temperature was found in the alloy R(0.7)Pr(0.3)Fe(1.55) (1480 x 10(-6) at H = 796 kA/m). (C) 1996 American Institute of Physics.
关键词:
沈保根
,
孔麟书
,
曹蕾
,
王芳卫
,
詹文山
,
郭慧群
,
赵见高
金属学报
用快淬方法制备了单相(Er_(1-x)Sm_x)_2Fe_(17)C_y(x=0.2,<3.0;x=0.5,y<2.0)化合物,研究了它们的形成、结构、稳定性及内禀磁性结果表明,它们在高温是稳定的,随碳含量的增加,晶体结构由六角的Th_2Ni_(17)型向菱方的Th_2Zn_(17)型转变间隙碳原子的引入导致了单胞体积的膨胀、室温饱和磁化强度和Curie温度的增加当y>1.0时,(Er_(1-x)Sm_x)_2Fe_(17)C_y样品在室温均显示出单轴各向异性
关键词:
(Er(1-x)Sm_x)_2Fe_(17)C_y间隙碳化物
,
interstitial carbides
,
magnetic properties
