材料期刊网

PRODUCTION OF ULTRA-FINEα-AL2O3 PO WDERSFROM AMMONIUM A LUMINUM CARBONATE HY DROXIDE

F. Zhang1) , X. D. Sun1) , J. You2) , Z. Zhang2) , L. X. Ding3)and Y. M. Wang3)1) School of Materials and Metallurgy , Northeastern University , Shenyang 110006 , China2) Liaoning Analyzing and Testing Research Center , Shenyang 110015 , China3) Department of Materials , School of Mechanical Engineering , Shenyang University , Shenyang 110044 , China

金属学报(英文版)

Synthesis of a m m oniu m alu min u m carbonate hydroxide ( A A C H) w as investigated usinga m m oniu m alu min u m sulfate and a m moniu m hydro carbonate as the starting m aterials . Itw as found that A A C Hcan be synthesized by adding a m m oniu m alu m inu m sulfate solution torapidly stirred a m moniu m hydro - carbonate solution at a tem perature of 30 ℃. A A C Hcantransfor m to α Al2 O3 co m pletely by calcining at 1100 ℃ for 1 hour , and the obtained po w ders , with a particle size of 100 n m , can be sintered to 98 99 % relative density at 1500 ℃for 2 hours .

关键词: a m moniu m alu m inu m carbonate hydroxide , null , null , null

SYNTHESIS OF ULTRAFINE PLZT POWDER BY A SIMPLE CO- PRECIPITATION METHOD

H. Ying1) , X. D. Sun1) , Q. B. Yang1) , J. B. Li2) , Y. M. Wang2) , Z. Zhang3) and J. You3)1) School of Materials and Metallurgy , Northeastern University , Shenyang 110006 , China2) Departm ent of Materials , School of Mechanical Engineering , Shenyang University , Shenyang110044 , China3) Liaoning Analyzing and Testing Research Center , Shenyang 110015 , China

金属学报(英文版)

Starting from cheap inorganic salts , ultrafine P L Z T po w ders were synthesized by a co pre cipitation m ethod . The results show that the precursor precipitate obtained by the co precipita tion method transfor ms co m pletely to P L Z T phase by calcining at 420 ℃ for 4 hours , about300 ℃low er than the nor m al transform ation te m perature of P L Z T obtained by m ixed oxidemethod . The effect of residual N H4 N O3 in the precursor precipitate on transfor m ation te m perature of the P L Z Tpow der w as investigated . The residual N H4 N O3 in the precursor po w der can reduce further the P L Z Ttransfor m ation tem perature to about 300 ℃, but a sm alla mount of Zr O2 and Pb Ti O3 re m ained . By a proper control of the synthesizing route , a P L Z T po w der with a pri m ary particle size of 10 n m and an agglom eration size of 0 3 μm hasbeen produced .

关键词: P L Z T , null , null

X70管线钢J1d和K1a与V型缺口Ak关系研究

朱杰武 , 柳永宁 , 许雁 , 冯耀荣

机械工程材料 doi:10.3969/j.issn.1000-3738.2005.06.007

在不同温度下测试了X70管线钢动态断裂韧度K1d、J1d和止裂韧度K1a以及夏氏V型缺口冲击韧度Ak,对三者的关系进行了分析.结果表明:温度和加载速率都对断裂韧度产生影响;加载速率变化引起的韧-脆断裂转变具有热激活特征,在热激活分析基础上,在应力强度因子速率K=15 MPa·m1/2s-1条件下,得出断裂韧度、止裂韧度和冲击韧度三者的关系:Ak=4.84×106T-2.8K1d(或K1a).可以用小试样Ak数据计算得到K1d和K1a.

关键词: 管线钢 , 断裂韧度 , 止裂韧度 , 韧-脆断裂转变

Magnetomechanical properties of epoxy-bonded Sm(1-x)Nd(x)Fe(1.55) (0 <= x <= 0.56) pseudo-1-3 magnetostrictive particulate composites

Journal of Alloys and Compounds

Pseudo-1-3 magnetostrictive particulate composites consisting of light rare earth (Sm and Nd)-based magnetostrictive Sm(1-x)Nd(x)Fe(1.55) particles with the Nd content x of 0-0.56 and randomly distributed sizes of 10-180 mu m membedded and aligned in a passive epoxy matrix are fabricated using the particulate volume fraction of 0.5. The quasistatic magnetomechanical properties of the composites are investigated and the results are compared with their monolithic alloys for various x. The composites exhibit similar qualitative trends in properties with the alloys for all x. The Sm(0.92)Nd(0.08)Fe(1.55) composite shows a large unsaturated magnetostriction lambda of -530ppm at 500 kA/m and a high piezomagnetic coefficient d(33) of -2.0 nm/A at 100 kA/m as a result of the magnetocrystalline anisotropy compensation between Sm(3+) and Nd(3+) ions in the Sm(0.92)Nd(0.08)Fe(1.55) alloy. (C) 2011 Elsevier B.V. All rights reserved.

关键词: Light rare earths;Magnetocrystalline anisotropy;Magnetomechanical;properties;Negative magnetostriction;Magnetostrictive composites;Sm(1-x)NdxFe(1.55) alloys;terfenol-d

Magnetomechanical properties of epoxy-bonded (Tb(0.3)Dy(0.7))(1-x)Pr(x)Fe(1.55) (0 <= x <= 0.4) pseudo-1-3 magnetostrictive composites

Journal of Physics D-Applied Physics

Pseudo-1-3 magnetostrictive composites consisting of stabilizer ( B, Co)-free, light rare earth (Pr)-containing magnetostrictive (Tb(0.3)Dy(0.7))(1-x) Pr(x) Fe(1.55) (0 <= x <= 0.4) particles with a size distribution of 10-300 mu m embedded and aligned in a passive epoxy matrix using 0.5 volume fraction are fabricated. The quasistatic magnetomechanical properties of the composites are investigated and compared with their monolithic (Tb(0.3)Dy(0.7))(1-x) Pr(x) Fe(1.55) alloys, as a function of the Pr content x. The composites show similar qualitative trends in properties with the alloys for all x. The (Tb(0.3)Dy(0.7))(0.75)Pr(0.25)Fe(1.55) composite and alloy exhibit the smallest coercivity H(c), the largest magnetostriction lambda and the highest piezomagnetic coefficient d(33) due to the successful compensation for magnetocrystalline anisotropy. The ( Tb0.3Dy0.7) 0.75Pr0.25Fe1.55 composite demonstrates a large saturation magnetostriction lambda(s) of 793 ppm at 700 kAm(-1) and a high d(33) of 3.2 nmA(-1) at 140 kAm(-1). These values approach 81% and 85% of its alloy values at the same field levels. The good properties make the (Tb(0.3)Dy(0.7))(0.75)Pr(0.25)Fe(1.55) composite and alloy a promising magnetostrictive material system.

关键词: terfenol-d;magnetic-properties;alloys;boron

First-principles investigations of the stability and electronic structure of ZrV2Hx (x=0.5, 1, 2, 3, 4, 6 and 7)

Acta Materialia

A calculation of the electronic structure and formation energy for ZrV2Hx (x = 0.5, 1, 2, 3, 4, 6 and 7) is performed using a plane-wave pseudo-potential method. It is found that in ZrV2Hx hydrogen forms stronger covalent bonds with vanadium than with zirconium if Zr atoms are in the neighborhood of V. A detailed analysis of how the densities of states change with the hydrogen count x in ZrV2Hx shows the changes in the bonding and anti-bonding interactions of H with V and Zr. However, the covalent anti-bonding interactions between H and V seem to be mainly responsible for the variation in the formation energy of ZrV2Hx with x. The value of projected density of states of V 3d at the Fermi level can be used as a rough comparative measure for these antibonding interactions and therefore allows us to predict the changes in stability of ZrV2Hx with x. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

关键词: electronic structure;formation energy;plane-wave pseudo potential;hydrogen storage alloy;intermetallic compounds;convergence acceleration;population analysis;laves phases;total-energy;transition;hydrides;superconductivity;magnetism

Magnetic transitions and magnetostrictive properties of Laves compounds Sm(0.88)Nd(0.12)(Fe(1-x)Co(x))(1.93)

Journal of Magnetism and Magnetic Materials

The structure, magnetic and magnetostrictive properties of Sm(0.88)Nd(0.12)(Fe(1-x)Co(x))(1.93) (0 <= x <= 1.0) alloys have been investigated. The alloys have the cubic MgCu(2) structure over the whole composition range and the lattice parameter a decreases with increasing x. For 0 <= x <= 0.2, substitution of Co for Fe slightly increases the saturation magnetization M(s) and Curie temperature T(c), while further substitution causes a decrease in both M(s) and T(c). The spin reorientation is observed, and a phase diagram for the spin configurations of the Sm(0.88)Nd(0.12)(Fe(1-x)Co(x))(1.93) system is determined. The spontaneous magnetostriction lambda(111) increases as x is increased, while a monotonic decrease of the saturation magnetostriction lambda(s) with x originates from the increase of lambda(100) with opposite sign to that of lambda(111), which may be caused by the filling of the d band due to Co substitution. (C) 2010 Elsevier B.V. All rights reserved.

关键词: Laves phase;Spin reorientation;Magnetostriction;giant magnetostriction;phase-compounds;temperature-dependence;anisotropy;substitution;alloys;fe

5d电子掺杂的SmFe_(1-x)Ir_xAsO铁基超导体的合成及物性

陈永亮 , 崔雅静 , 杨烨 , 王磊 , 李仪成 , 张勇 , 赵勇

低温物理学报

通过在SmFeAsO中Fe位上掺入5d过渡金属Ir,得到了一种新的铁基超导体SmFe_(1-x)Ir_xAsO,当x=0.05时,样品表现出超导电性,超导转变温度为8K,当x=0. 15时,超导转变温度达到最大值17. 3K X射线衍射结果表明所有样品均属四方ZrCuSiAs-type结构,SEM结果表明SmFe_(1-x)Ir_xAsO样品具有片层状形貌特征,随着Ir掺杂量的增大,晶格参数a增大而c减小,结合EDX数据,表明Ir掺人了SmFeAsO晶格当中.

关键词: 铁基超导体 , ZrCuSiAs结构

Structural, magnetic, and magnetostrictive properties of Laves (Tb(0.3)Dy(0.7))(1-x)Pr(x)Fe(1.55) (0 <= x <= 0.4) alloys

Journal of Alloys and Compounds

Stabilizer (B, Co)-free, light rare earth (Pr)-substituted Laves alloys (Tb(0.3)Dy(0.7))(1-x)Pr(x)Fe(1.55) (0 <= x <= 0.4) are synthesized, and their structural, magnetic, and magnetostrictive properties are investigated. X-ray diffraction analysis confirms the presence of single cubic Laves phase with an MgCu(2)-type structure in the (Tb(0.3)Dy(0.7))(1-x)Pr(x)Fe(1.55) alloys with 0 <= x <= 0.35. The lattice parameter a of the Laves phase increases, while the Curie temperature decreases, with increasing x from 0 to 0.35. The saturation magnetization of the alloys decreases with increasing x. The linear anisotropic magnetostriction lambda(a) (=lambda(parallel to) - lambda(perpendicular to)) shows a maximum of 1502 ppm at x = 0.25 as a result of the magnetocrystalline anisotropy compensation. (C) 2008 Elsevier B.V. All rights reserved.

关键词: Alloys and compounds;Laves phase;Light rare earths;Magnetocrystalline;anisotropy;Magnetostriction;Terfenol-D;anisotropy compensation;boron

Theoretical calculations of spin-Hamiltonian parameters for CsCdX(3):Ni(2+) (X = Cl, Br) crystals from the two-mechanism model

Spectrochimica Acta Part a-Molecular and Biomolecular Spectroscopy

The high-order perturbation formulas of spin-Hamiltonian (SH) parameters (g factors g(||),g(perpendicular to) and zero-field splitting D) for 3d(x) ions in trigonal octahedral sites of crystals are derived considering not only the crystal-field (CF) mechanism, but also the charge-transfer (CT) mechanism (which is neglected in the extensively used CF theory). From these formulas and by considering the suitable impurity-induced local lattice relaxation. the SH parameters of CsCdX(3):Ni(2+) (X = Cl, Br) crystals are calculated. The results are in reasonable agreement with the experimental values. The sign of Q(CT) (Q = Delta g(||). Delta g(perpendicular to) or D. where the g-shift Delta g(i) = g(i) - g(c). g(c) approximate to 2.0023 is the free-electron value) due to CT mechanism is the same as that of the corresponding Q(CF) due to CIF mechanism. The relative importance of CT mechanism (characterized by Q(CT)/Q(CF)) increases with the, increasing atomic number of ligand X. So. for 3d(n) ion clusters in crystals with heavy element ligand ion (e.g., Br(-)), the reasonable explanations of SH parameters should contain the contributions from both CF and CT mechanisms. (C) 2008 Elsevier B.V. All rights reserved.

关键词: Electron paramagnetic resonance (EPR);Crystal- and ligand-field theory;Charge-transfer mechanism;Ni(2+);CsCdX(3) (X = Cl;Br);atomic screening constants;excited-state;resonance-spectra;epr;parameters;scf functions;ions;spectroscopy;vanadium(ii);nickel(ii);absorption