Zhidong ZHANG+
,
Changheng WU
,
Zhenchen ZHONG
,
Xiaokai SUN
,
Y.C. Chuang
,
Institute of Metal Research
,
Academia Sinica
,
Shenyang
,
110015
,
China
材料科学技术（英）
In present investigation exchange interactions of Pr_(n+1)Co_(3n+5)B_(2n)-type compounds have been evalu- ated in the light of molecular-field theory. The exchange interactions and ferromagnetism in these compounds are discussed in terms of lattice parameters and interatomic distance between Co atom.
关键词:
Pr-Co-B alloy
,
null
,
null
Physics Letters A
The magnetic properties of the mixed ferro-ferrimagnetic compounds with (A(a)B(b)C(c))(y)D, in which A, B, C and D are four different magnetic ions and form four different sublattices, are studied by using the Ising model. And the Ising model was dealt with standard mean-field approximation. The regions of concentration in which two compensation points or one compensation point exit are given in c-a, b-c and a-b planes. The phase diagrams of the transition temperature T-c and compensation temperature T-comp are obtained. The temperature dependences of the magnetization are also investigated. Some of the result can be used to explain the experimental work of the molecule-based ferro-ferrimagnet ((NiaMnbFecII)-Mn-II-Fe-II)(1.5) [Cr-III (CN)6] - zH(2)O. (C) 2003 Elsevier B.V. All rights reserved.
关键词:
mixed ferro-ferrimagnet;Ising model;four sublattices;phase diagram;transition temperature;compensation temperature;magnetic-properties;prussian blue;alloy
Corrosion Science
The oxidation of pure Co and two Co-Y alloys containing 2 at.% and 5 at.% Y has been studied at 600-800 degrees C in air. The oxidation of pure cobalt at all temperatures followed the parabolic rate law. The oxidation of the two alloys approximately followed the parabolic rate law at 800 degrees C, but was closer to cubic behavior at 600 and 700 degrees C except Co-5Y at 600 degrees C, which deviated from the cubic and parabolic rate law. The corrosion of both alloys at the three temperatures produced an external scale containing Co oxides (Co3O4, CoO) and Y2O3 and an internal oxidation region where Co17Y2 was converted into Co and Y2O3. The distribution of Y2O3 closely followed that of the intermetallic compound (Co17Y2) in the original alloy. The corrosion mechanism of the alloys is examined. (C) 1999 Elsevier Science Ltd. All rights reserved.
关键词:
Co;Y;oxidation;high-temperature oxidation;possible scaling modes;internal oxidation;oxidant pressures;h-2-h2s mixtures;sulfidation;oxygen
Oxidation of Metals
The oxidation of Fe- Y alloys containing 2 and 5 at.% Y and pure iron has been studied at 600-800 degrees C in air. The oxidation of pure iron follows the parabolic rate law at all temperatures. The oxidation of Fe-Y alloys at 600 degrees C approximately follows the parabolic rate law, but not at 700 and 800 degrees C, where the oxidation goes through several stages with quite different rates. The oxide scales on Fe-2Y and Fe-5 Y at 700 and 800 degrees C are composed of external pure Fe oxides containing Fe2O3, Fe3O4, and FeO, with FeO being the main oxide and an inner mixture of FeO and YFeO3. The scales on Fe-2Y and Fe-5Y at 600 degrees C consist of Fe2O3, Fe3O4, and Y2O3, with a minor amount of FeO. Significant internal oxidation in both Fe-Y alloys occurred at all temperatures. The Y-containing oxides follow the distribution of the original intermetallic compound phase in the alloys. The effects of Y on the oxidation of pure Fe are discussed.
关键词:
pure Fe;Fe-Y alloys;oxidation;high-temperature oxidation;possible scaling modes;2-phase;binary-alloys;low-oxygen pressures;oxidant pressures
李鹏
,
胡耀波
,
熊惟皓
,
林真
硬质合金
doi:10.3969/j.issn.1003-7292.2000.02.001
研究了稀土元素Y对Ti(C,N)基金属陶瓷微观组织和性能的影响.Y在Ti(C,N)基金属陶瓷中可以起到净化粘结相/硬质相界面的作用,并使其包覆层的厚度略有增加,从而使硬质相颗粒得到细化.当Y含量为0.8wt%时细化效果最明显,此时Ti(C,N)基金属陶瓷的抗弯强度和硬度值最大.
关键词:
稀土元素
,
Y
,
金属陶瓷
,
组织与性能
Journal of Applied Physics
The magnetic properties of R2Co14B1-xCx (x=0, 0.5 and R=Y, Sm) compounds have been studied by measuring the temperature dependence of the easy- and hard-magnetization curves on magnetically aligned samples between 1.5 and 300 K for Y2Co14(B,C) and at 4.2 K for Sm2Co14(B,C). The magnetic anisotropy of Y2Co14B increases due to the substitution of C for B, whereas the saturation magnetization decreases. Between 1.5 and 300 K, the anisotropy field of Y2Co14B0.5C0.5 increases about 2 T and the Co moment decreases about 0.05mu(B). The anisotropy field Of Sm2Co14B also increases upon C substitution and the saturation magnetization decreases slightly. The ac susceptibilities of both SM2Co14B and Sm2Co14B0.5C0.5 exhibit anomalies that may arise from a spin reorientation within the basal plane.
关键词:
nd2fe14b;exchange;nd2co14b;r2fe14b;field
Corrosion Science
The corrosion of pure yttrium and of a cobalt alloy containing approximately 15 wt% yttrium was studied at 600-800 degrees C in H-2-CO2 mixtures providing an equilibrium oxygen pressure of 10(-24) atm at 600 degrees C and 10(-20) atm at 700 and 800 degrees C. The corrosion of yttrium under these low oxygen pressures resulted in the growth of Y2O3 scales which was rather protective at 800 degrees C, presenting two approximately parabolic stages with a smaller rate Constant at longer times, but non-protective and faster at lower temperature. The oxidation of Co-15Y was rather irregular under all conditions, but generally slow: in particular, at 800 degrees C the rate decreased almost to zero after about 17 h oxidation. The oxidation of this alloy produced a thin external layer of pure cobalt metal overlying a region of internal oxidation, where the Y-rich phase was transformed into a mixture of cobalt metal and yttrium oxide. The microstructure of the internal oxidation region followed closely that of the original alloy, while no yttrium depletion was observed beneath the front of internal oxidation. These results are examined by taking into account the low solubility of Y in Co and the existence of an intermetallic compound in the alloy. (C) 1997 Elsevier Science Ltd.
关键词:
cobalt;yttrium;alloys;internal oxidation;2-phase binary-alloys;high-temperature oxidation;most-reactive;component;possible scaling modes;low oxidant pressures;internal;oxidation;a/o al;corrosion;1173-k
Oxidation of Metals
The corrosion of pure yttrium and of two Fe-base alloys containing approximately 15 and 30 wt.% Y was studied at 600-800 degrees C in H-2-CO2 mixtures providing an equilibrium oxygen pressure of 10(-24) atm 600 degrees C and 10(-20) atm at 700 and 800 degrees C. The corrosion of yttrium under these low oxygen pressures resulted in the growth of Y2O3 scales and presented two approximately parabolic stages at 800 degrees C, while at 600-700 degrees C it was faster and nonprotective. The corrosion of the two alloys followed approximately the parabolic rare law, except for Fe-15Y at 600 degrees C which oxidized nearly linearly. At 600 and 700 degrees C, when the gas-phase oxygen pressure was in the field of stability of iron oxide, the alloys formed also a thin external Fe3O4 layer, while at 800 degrees C, when the oxygen pressure was below the stability of FeO, a thin outermost layer of pure iron was observed to form. Under all conditions a region of internal oxidation formed in the alloy, in which the yttrium-rich phases were transformed into a mixture of iron metal and oxides, which included double Fe-Y oxides as well as Y2O3. The microstructure of the internal-oxidation region followed closely that of the original alloys, which moreover did not undergo any yttrium depletion. These results are examined by taking into account the low solubility of yttrium ib iron and the presence of intermetallic compounds in the alloys.
关键词:
iron;yttrium;alloys;internal oxidation;2-phase binary-alloys;high-temperature oxidation;most-reactive;component;possible scaling modes;low oxidant pressures;internal;oxidation;al alloys;a/o al;corrosion;1173-k
Journal of Applied Physics
Y2Fe14B0.5C0.5 has the same tetragonal structure as Y2Fe14B with space group P4(2)/mnm. Magnetic properties of the Y2Fe14B0.5C0.5 compound have been studied using an extraction magnetometer with a maximum field of 6 T, in the temperature range from 1.5 to 300 K. By means of fitting the hard magnetization curves, the magnetocrystalline anisotropy constants K1, K2, and K3 were determined. It was found that although the magnetocrystalline anisotropy field (mu-0H-a) increases abnormally with increasing temperature as in the case of Y2Fe14B, the dependence of anisotropy constants on temperature is quite different from that of Y2Fe14B. K1 and K3 decrease slightly with increasing temperature. K2 increases abnormally with increasing temperature, which contributes to the abnormal dependence of anisotropy field on temperature. In addition, the substitution of carbon for boron leads to a reduction of 3d-3d interaction and spontaneous magnetization. In contrast, uniaxial anisotropy is increased by the addition of carbon below room temperature.
关键词:
alloys
