PR.Dhar
,
K.Bamzai and PN.Kotru (Dept. of Physics
,
University of Jammu
,
Jammu-180004
,
India)
材料科学技术（英文）
Results on fracture toughness of natural apophyllite crystals when subjected to impact are presented. The morphology of the cracks and fracture has been studied. It is found that the crack formation does not show any anisotropic property and remains the same whatever may be the orientation of the crystal. The average values of the fracture toughness KC and brittleness index, as determined from measurements of crack length, are estimated to be 0.107 gμm-3/2and 4.19μm-1/2 respectively for the a(100) plane. The yield strength forα(100), p(111) and c(001) planes of apophyllite crystals for lower loads is 2250. 2160 and 1840 MPa and for higher loads is 1510, 1600 and 1430 MPa respectively
关键词:
Zeitschrift Fur Metallkunde
The Pr-Co binary system has been systematically investigated by DTA, optical microscopy, X-ray diffraction and electron probe micro analysis (EPMA) techniques. A revised Pr-Co binary phase diagram is proposed. This binary system consists of six peritectic reactions, two congruently melting reactions and three eutectic reactions. The six peritectic reactions result in the formation of Pr4Co3, PrCo2, PrCo3, Pr2Co7, Pr5Co19 and PrCo5, respectively. The two congruent reactions involve the formation of Pr3Co and Pr2Co17. The three eutectic reactions occur at 570-degrees-C, 533-degrees-C and 1296-degrees-C. The solid solubility of Pr in cobalt is extremely small being about 0.03 at. % at 1000-degrees-C.
关键词:
prco5
Journal of Superconductivity and Novel Magnetism
Pr-Fe-B/Fe/Pr-Fe-B films with different Fe layer thicknesses were deposited by magnetron sputtering on Si (100) substrate heated at 650 degrees C. Structural and magnetic properties of the Pr-Fe-B/Fe/Pr-Fe-B films were investigated. X-ray diffraction and magnetic measurement results reveal that the Pr-Fe-B/Fe/Pr-Fe-B films are anisotropic when the thickness of Fe layer is smaller than 50 nm. The enhancement of the saturation magnetization in nanocomposite films is attributed to the exchange coupling between the soft and hard phases. The highest coercivity of about 13.9 kOe is achieved in the Mo(50 nm)/Pr-Fe-B(50 nm)/Mo(2 nm)/Fe(2 nm)/Mo(2 nm)/Pr-Fe-B(50 nm)/Mo(50 nm) film and increasing the thickness of soft-magnetic layer results in a continuous decreasing of the coercivity.
关键词:
Magnetic films and multilayers;Anisotropy;Atomic force microscopy;Nanocomposites;remanence enhancement;multilayer magnets;exchange
Journal of Alloys and Compounds
Isoplethic section in the quaternary system Fe-Co-Sm-Pr at 800 degreesC with Sm/Pr=1 and R less than or equal to 33.3 at% (R=Sm0.5Pr0.5) was determined by using optical microscopy, X-ray diffraction analysis and electron probe microanalysis. There are five intermetallic phases: (Sm,Pr)(Fe,Co)(2), (Sm,Pr)(Fe,Co)(3), (Sm,Pr)(2)(Fe,Co)(7), (Sm,Pr)(5)(Fe,Co)(19) and (Sm,Pr)(2)(Fe,Co)(17). The isoplethic section of the Fe-Co-R system consists of eight single-phase regions, eleven two-phase regions and five three phase regions. The (Sm,Pr)(2)(Fe,Co)(7) phase in R-2(Fe1-xCox)(7) alloys dissolves nearly 15 at % Fe at 800 degreesC and no (Sm,Pr)(Fe,Co)(5) phase exists. (C) 2001 Elsevier Science B.V. All rights reserved.
关键词:
transition metals;rare earth compounds;magnetically ordered materials;phase diagram;binary-system;magnetostriction
Journal of Alloys and Compounds
Phase relationships at ambient temperature in the pseudobinary system Pr5Si4-Pr5Ge4 were studied by X-ray powder diffraction (XRD). Three structurally distinct phase regions exist in this system. The Pr5Si4-based solid solution where Ge statistically substitutes for Si crystallizes in the Zr5Si4-type tetragonal structure with space group P4(1)2(1)2. The Pr5Ge4-based solid solution where Si statistically substitutes for Ge crystallizes in Sm5Ge4-type orthorhombic structure with space group Pnma. The crystal structure of a ternary intermediate phase, which exists between 1.65 less than or equal to x less than or equal to 2.6, is determined for the first time, and shown to be the Gd5Si2Ge2-type monoclinic structure with space group P112(1)/a. The Rietveld powder diffraction profile fitting technique was used for the refinement of crystal structure. The lattice parameters, atomic occupations, interatomic distances of the Pr5Si4, Pr5Ge4 and Pr5Si2Ge2 compounds were derived. (C) 2002 Elsevier Science B.V. All rights reserved.
关键词:
rare earth compounds;crystal structure;X-ray diffraction;gd-5(si2ge2);transition;gd-5(sixge1-x)(4)
Physica Status Solidi a-Applied Research
The magnetic and electronic transport properties of the compound Pr5Ge4 were investigated by means of magnetic and electrical resistivity measurements. The results indicate that for the compound Pr5Ge4 there are two magnetic transitions at T-C(I) = 25 K and T-C(II) = 41 K in a low field of 500 Oe. In analogy to Nd5Ge4 compound, the magnetic structure of Pr5Ge4 may be a canted one, which can be induced by a competition between nearest-neighbor Pr-Pr ferromagnetic (FM) and Pr-Pr antiferromagnetic (AFM) exchange interactions. The main contribution to the electrical resistivity of Pr5Ge4 is the scattering of conduction electrons on localized magnetic moments. A large magnetoresistance (Deltarho/rho) was observed (about 25% at 24 K and 15% at 40 K) in the presence of a magnetic field of 50 kOe.
关键词:
electrical-resistance;gd-5(si2ge2);transition;nd5ge4;field
Journal of Alloys and Compounds
The isothermal section at 600 degrees C in the Co-rich ternary Pr-Co-B system was determined by means of X-ray diffraction, In this range, eleven ternary borides were observed: Pr3Co13B2, PrCo4B, Pr5Co19B6 Pr3Co11B4, Pr2Co7B3, Pr2Co14B, PrCo12B6, PrCo4B4, Pr2Co5B3, PrCo2B2, Pr2Co5B2. Among the eleven ternary compounds, two had not been reported previously: hexagonal Pr3Co13B2 with a=5.0672(3) Angstrom and c=10.6850(6) Angstrom and hexagonal Pr5Co19B6 with a=5.1264(4) Angstrom and c=16.5602(6) Angstrom. The first five borides are members of the homologous series Rm+nCo5m+3nB2n formed by alternative stacking m layers of RCo5 with n layers of RCo3B2 along the c-axis. The Pr2Co5B2 compound belongs to the Rm+nCo2m+3nB2n family which is based on the MgZn2-type and the CeCo3B2-type structures. (C) 1999 Elsevier Science SA. All rights reserved.
关键词:
Pr-Co-B;phase diagram;crystal structure
杨志平
,
郭智
,
王文杰
,
朱胜超
功能材料与器件学报
doi:10.3969/j.issn.1007-4252.2003.04.023
制备了不同Pr3+摩尔浓度下的CaTiO3:Pr3+红色长余辉材料,测量了磷光体的的初始亮度、余辉曲线、激发光谱和发射光谱、热释光曲线.研究发现CaTiO3:Pr3+合适的Pr3+摩尔浓度为0.1%-0.2%,在该摩尔浓度下,材料具有较好初始亮度和余辉时间.
关键词:
长余辉
,
摩尔浓度
,
激发光谱
,
发射光谱
,
热释光
,
CaTiO3: Pr3+
CHEN Zhongmin SHI Zhengxing WANG Leyi FU Hengzhi Northwestern Polytechnical University
,
Xi'an
,
China
金属学报(英文版)
The hot deformation process of cast Pr_(19)Fe_(74.5)B_5Cu_(1.5) magnets were studied.It is found that the easy-axes are aligned parallel to the compressive strain direction in vari- ous hot deformation process.During hot deformation,the crushing of Pr_2Fe_(14)B matrix grains and the relative slip and rotation between the grains take place and the Pr-rich melt is squeezed out of the magnet,leading to a fine,dense and well-aligned microstruc- ture in the fully-deformed magnets.Magnetic properties of B_r=990 mT,_iH_c=880 kA/m and(BH)_m=191 kJ/m~3are obtained.The increase of coercivity is attributed to the fine Pr_2Fe_(14)B grains and the thin Pr-rich phase layer continuously distributed at the grain boundaries.The increasing remanence is resulted primarily from the develop- ment of the easy-axis alignment as well as from the densification of the Pr_2Fe_(14)B matrix. The easy-axis alignment is developed by the relative slip and rotation of the crushed Pr_2Fe_(14)B grains.A full and slow hot deformation is necessary for the good easy-axis alighnment and high magnetic properties.
关键词:
Pr-Fe-B magnet
,
null
,
null
,
null
