合金Co-Zr-B纳米粉末的相组成及磁性能研究

将硼氢化钠(NaBH4)的水溶液加入到氯化钴(CoCl2·6H2O)和硫酸锆(Zr(SO4)2·4H2O)的混合水溶液中,利用BH-4把混合溶液中的CO2 和Zr4 同时还原出来,首次成功制备出非晶态Co-Zr-B三元纳米合金粉末.用电感耦合等离子体发射光谱(ICP)、X射线衍射(XRD)、选区电子衍射(SAED)、透射电子显微镜(TEM)、差示扫描量热法(DSC)以及振动样品磁强计(VSM)分析了样品的成分、结构和磁性能.发现所制备的不同成分的粉末颗粒呈球形,粒径在20～60nm之间.纳米粉末由非晶相基体和少量晶体相杂质组成,而非晶相基体又由Zr基非晶颗粒和含有Zr的Co基非晶颗粒构成.还原产物中的Co原子和Zr原子的分数之比与金属盐混合溶液中的Co2 与Zr4 离子的分数之比几乎相等.提高NaBH4溶液的加入速度,可增加产物中B元素的含量.样品的晶化温度在765.1～771.3K之间,样品的热稳定性随Zr含量的增加而增加,样品的磁性能也与样品中Co、Zr原子的含量之比有关.当原子数x(Co)/x(Zr)比值从1.94增加到5.14时,饱和磁化强度从4.76emu/g增加到8.87emu/g,矫顽力在1271.66A/m(15.98Oe)到2133.49A/m(26.81Oe)之间不规则变化.     

RE_2(CoFe)_(17-x)Ti_x型合金的结构和磁性(RE=Nd,La)

用电子探针 (EPMA)、X射线衍射仪和 2 0T脉冲强磁场测试仪研究了RE2 (CoFe) 1 7-xTix(RE =Nd ,La)的结构与磁性。结果表明 ,Nd2 Co1 7-xTix经过 10 5 0℃× 15h均匀化处理 ,在x =1时 ,Nd2 Co1 7型化合物变成Nd(CoTi) 1 2 和Nd2 (CoTi) 7型化合物 ,而呈现出单轴各向异性。此时合金的饱和磁化强度为 0 .7T ,各向异性场为 2 2 5 0 .3kA·m- 1 。对La Co Fe Ti2∶17型合金的磁特性进行了研究。随着铁含量的增加 ,合金的饱和磁化强度明显增加 ,但也明显地降低了各向异性场     

Y基非晶合金的形成及晶化动力学

利用单辊急冷法制备Y56-xZrxA124Co20(x=0,5,10)非晶合金,研究Zr含量对该非晶合金的形成能力及热稳定性的影响.研究结果表明,添加元素Zr可以提高Y56A124Co20合金的非晶形成能力和热稳定性,而且随着Zr含量增加,合金的非晶形成能力提高.通过示差扫描量热法(DSC)研究了Y56A124Co20和Y46Zr10A124Co20的晶化动力学,前者的玻璃转变激活能和晶化激活能分别为366.5 KJ/mol和259.7 KJ/mol,后者的玻璃转变激活能和晶化激活能分别为415.6 KJ/mol和319.5KJ/mol,从理论上说明添加元素Zr可以改善Y56A124Co20合金的非晶形成能力和热稳定性.     

机械合金化法制备含Nd多元铁基合金粉末微观组织结构分析

根据Inoue经验原则设计了一种添加Nd元素多元铁基合金,其成分为 Fe56-x Co7 Ni2 Zr10 Mo5 B20 Ndx （ x=0．2%、0．5%、0．8%,原子分数%）,并通过机械合金化法制备了该合金粉末。利用X射线衍射（XRD）、扫描电镜（ SEM）、差示扫描量热仪（ DSC）研究了Nd含量对多元铁基合金粉末组织结构与热稳定性能的影响。结果表明：在球磨转速300 r/min、球料比30∶1、球磨时间为40 h的条件下,所制备的含Nd多元铁基合金粉末均含有部分的非晶相;球磨后的粉末大多呈近球形,Nd含量为0.8%（原子分数）时,合金粉末颗粒尺寸最为细小且热稳定性较高。     

Zr对Y56Al24Co20非晶形成能力和热稳定性的影响

以Y56Al24Co20非晶合金为基础合金系,用廉价Zr替代部分高价Y,通过单辊急冷法成功地制备出Y56-x-ZrxAl24Co20(x=5,10,15)非晶合金;通过X射线衍射(XRD)和差示扫描量热法(DSC)研究其非晶形成能力和热稳定性.结果表明,随Zr含量增加,合金的非晶形成能力提高,但当Zr含量超过10%(摩尔分数)时,其非晶形成能力反而降低;Y46Zr10Al24Co20具有最大的非晶形成能力和良好的热稳定性.以上结果均从组元个数、原子半径、混合热和电负性的角度进行了实验论证.     

RE2(CoFe)17-xTix型合金的结构和磁性(RE=Nd,La)

用电子探针(EPMA)、 X射线衍射仪和20 T脉冲强磁场测试仪研究了RE2(CoFe)17-xTix(RE=Nd, La)的结构与磁性. 结果表明, Nd2Co17-xTix 经过1050 ℃×15 h均匀化处理, 在x=1时, Nd2Co17型化合物变成Nd(CoTi)12和Nd2(CoTi)7型化合物, 而呈现出单轴各向异性. 此时合金的饱和磁化强度为0.7 T, 各向异性场为2250.3 kA*m-1. 对La-Co-Fe-Ti 2∶17型合金的磁特性进行了研究. 随着铁含量的增加, 合金的饱和磁化强度明显增加, 但也明显地降低了各向异性场.     

新型大块非晶软磁合金的制备和应用

最近，罗马尼亚材料研究者利用吸铸法和铜模浇铸法开发了一系列具有大的过冷液相区和良好软磁性能的(Fe，Co，Ni)70M10B20(M=Zr，Nb，Ti，Ta)大块非晶合金。这些大块非晶合金的关键尺寸都大于3mm，电阻为18×10^-7～23×10^-7Ωm，矫顽力小于6A／m，磁导率为3     

Fe74Al4Sn2M2P10Si4B4系非晶合金带材的制备及其热、磁性能

利用单辊法制备了Fe74 Al4Sn2M2P10Si4B4(M为Nb、Mo、V)、Fe74 Al4SnzMo2P8Si4B4C2和Fe75Al4Sn2Mo2Nd1P8Si4B4非晶合金薄带,并测试了该非晶合金系的差示扫描量热曲线和动、静态软磁性能.结果表明,Fe74Al4Sn2NbzP10Si4B4非晶合金具有相对较宽的超冷液相区,其△Tx=51.41 K;而Fe74Al4Sn2MozP10Si4B4非晶合金具有较好的软磁性能,其最大磁导率μm=53.5×104,μe(1 kHz)=7.02×104,损耗P1.1T/50Hz=0.096 W/kg;Fe74Al4Sn2Mo2P8Si4B4C2非晶合金具有宽的超冷液相区和良好的软磁性能,其超冷液相区的宽度△Tx=48.81 K,μm=23.3×104,P1 1T/50 Hz=0.153 W/kg;Fe75Al4SnzMozNd1P8Si4B4非晶合金具有很宽的超冷液相区,其△Tx=60.06 K.     

机械球磨法制备纳米复相Nd2Fe14B/α-Fe永磁材料的微观组织及磁性能

通过在氩气保护下对成分为Nd8Fe86B6（原子数比）铸态合金机械球磨，随后进行真空晶化处理，制备了纳米复相Nd2Fe14B／α—Fe永磁合金。通过X射线衍射（XRD）、差示扫描量热法（DSC）、透射电子显微镜（TEM）以及振动样品磁强计（VSM）等分析方法研究了不同球磨时间及晶化处理温度对Nd8Fe86B6合金组织及磁性能的影响。结果表明，随着球磨时间的延长，Nd2Fe14B相及α—Fe的晶粒尺寸迅速减小，球磨25h后粉末由一些晶粒尺寸约为10nm的Nd2Fe14B／α—Fe复相组织以及非晶相组成，非晶相通过随后的晶化处理可转变成Nd2Fe14B／α—Fe复相组织。球磨及晶化处理工艺参数对Nd8Fe86B6合金磁性能有很大的影响，通过优化球磨以及晶化处理工艺，可制备出较高性能的粘结磁体。球磨25h，在700℃下晶化处理30min，获得Nd8Fe86B6磁体最佳磁性能为：Br=0．63T；Hci=449kA／m；（BH）max=62kJ／m^3。     

多元微合金化对Mg-14Li-Al合金组织及力学性能的影响

采用球磨法制备Mg-4Y-2Nd-1Gd-0.4Zr合金颗粒,将其作为多元微合金化材料,通过搅拌铸造法制备Mg-14Li-Al-xRE (Y, Nd, Gd, Zr)合金。采用金相显微镜(OM)、扫描电镜(SEM)、 X射线衍射仪(XRD)及电子万能试验机等,研究了RE (Y, Nd, Gd, Zr)添加量对Mg-14Li-Al合金的显微组织、力学性能及时效行为的影响。结果表明,与基体合金Mg-14Li-Al相比,多元微合金化后在合金中形成了大量针状、块状的Al_2Y相和少量棒状的Al_3Nd相,很少出现富Gd的第二相, AlLi软化相减少;随着RE含量的增加,晶界处的Al-RE相数量密度逐渐增加,晶粒得到显著细化,添加1.6%RE(质量分数)时铸态合金平均晶粒尺寸达到最小,细化率约76.6%,挤压变形后合金的晶粒得到进一步细化,达到10μm左右;随着RE含量的增加,力学性能明显提升,添加0.8%RE时,铸态合金的抗拉强度相对于Mg-14Li-Al基体提高了57%,继续增加RE含量,强度基本保持稳定,挤压变形后合金的强度和塑形得到进一步提高;室温条件下,多元微合金化后形成的Al-RE相对Mg-14Li-Al基体时效行为产生了明显的影响,合金在各个时期的硬度均显著上升,过时效软化程度有所降低。     

Effects of cerium substitution on phase components,microstructures and magnetic properties of Nd-Fe-Ti-B alloy

(Nd_(1-x)Ce_x)_(12)Fe_(77)Ti_5B_6(x = 0,0.2,0.3,0.4,0.6,0.8)alloys were prepared by melt-spinning and annealing techniques.The phase constitutions,microstructures and magnetic properties were investigated by powder X-ray diffraction(XRD),a differential scanning calorimeter(DSC),a vibrating sample magnetometer(VSM)and a transmission electron microscope(TEM).It is found that with the increase of Ce content,the coercivity of the(Nd_(1-x)Ce_x)_(12)Fe_(77)Ti_5B_6 alloys reaches maximum first and then decreases.The maximum coercivity reaches 18.5 kOe obtained in the sample of 20% Ce substituted which is 34%higher than the Ce-free sample.TEM results reveal that the micro structure refinement effect is responsible for the coercivity improvement.This phenomenon implies that in some cases,Ce and Ti co-doping is more beneficial to improving of the coercivity than Ti single doping in Nd-Fe-B alloys.With further Ce addition,magnetic properties deteriorate due to the formation of CeFe_2 and TbCu_7-type phases.     

Magnetic Properties of Ga Doped Nd-Fe-B Sintered Magnets

The magnetic properties of Nd_(16)Fe_(77)B_7 and Nd_(16)Fe_((61-x))Co_(16)Ga_xB_7(x=0,1,2,4,7)have been measured.Itis found that the remanent magnetization(Br),maximum energy product(BH)_(max)and the Curie temperature(T_c)decrease with the increase of Ga content.The coercive force(He)increases with the increase of Ga contentwhen x is less than 2,but decreases when x>2.At x=2,the coercive force reaches its maximum value.It is alsofound in all the samples investigated that there is a linear relationship between H_c~(1/2)and T~(2/3),which can not beexplained by Gaunt's wall barrier model.The temperature dependence of the calculated values of H_v and(4bf)has been discussed.     

High coercivity Nd-Ce-Fe-B nanostructured ribbons prepared from melt spinning technique

The Ce-substituted(Nd_(1-x)Ce_x)_(12.2) Fe_(81.6) B_(6.2)(x=0.0, 0.2, 0.4, 0.6) nanocrystalline ribbons were prepared by annealing amorphous ribbons from melt spinning. It is found that all ribbons are in a multiphase state consisting of a-Fe phase, Nd(Ce)-rich phases and RE_2 Fe_(14) B(RE = Nd, Ce) phases. However, the coercivity of all annealed ribbons can reach a considerably high value without doping any heavy rare earth or other coercivity enhanced elements. A strong intergranular exchange coupling appears in these nanocrystalline ribbons. The Nd_(12.2) Fe_(81.6) B_(6.2) ribbons with multiphase have a coercivity of about 11.3 k Oe, and the coercivity decreases slightly with increasing Ce content. A coercivity of 7.5 kOe can be obtained when60 at% of Nd is replaced by Ce(x = 0.6) due to the grain refinement and the strong intergranular exchange coupling. This provides a practical approach of fabricating high coercivity Ce-substituted Nd-Fe-B materials.     

微量元素Y、Ag对Cu基非晶合金玻璃形成能力的影响

采用单辊旋淬法制备了Cu50Zr42Al8,Cu46 Zr47-xAl7Yx(x=2,5),Cu43Zr42AlsAg7和Cu43Zr42Al8Ag5 Y2非晶合金薄带,利用X射线衍射和差示扫描量热分析研究了合金样品的玻璃形成能力和热稳定性.结果表明,在Cu50Zr42Al8中添加适量的Ag、Y后使得非晶合金的短程有序结构发生改变.合金Cu46Zr47-xAl7Yx(x=2,5)的过冷液相区宽度ΔTx分别比Cu50 Zr42 Al8增加了19K、30K,约化玻璃转变温度Trg从0.565分别增加到0.579和0.566,参数γ从0.402分别增加到0.418和0.420,说明Y的添加提高了非晶合金的热稳定性和玻璃形成能力.合金Cu43Zr42 Al8Ag7和Cu43Zr42Al8Ag5Y2与Cu50Zr42Al8相比,约化玻璃转变温度Trg及参数γ均有了明显的提高,达到了0.619、0.416和0.609、0.411,表明Ag的添加、Ag和Y的同时添加均提高了Cu - Zr -Al系非晶合金的玻璃形成能力,但Ag的效果更加显著.     

Effects of grain boundary diffusion of PrCu alloy on microstructure and coercivity of hot deformed(Nd,Ce)-Fe-B magnets

The technology of using high abundance rare earth element Ce in permanent magnets has attracted many concerns.In this work,the magnetic properties and microstructures of hot deformed(Nd_(1-x)Ce_x)_(13.8)Fe_(76.1)Co_4 Ga_(0.5)B_(5.6) magnets and a selective magnet treated with PrCu grain boundary diffusion process(GBDP) were investigated systematically.It is found that Ce is beneficial to improving the plastic deformation ability of NdFeB magnets.The strongest c-axis orientation is achieved in the HD magnets with Ce concentration of x=0.3,resulting in good comprehensive magnetic properties of B_r=13.00 kGs,H_(cj)=10.12 kOe,(BH)_(max)=38.42 MGOe.Based on that,the GBDP was implemented on the magnets with the best orientation using Pr_(68)Cu_(32) ribbons and the magnetic properties of B_r=12.87 kGs,H_(cj)=15.65 kOe,(BH)_(max)=37.48 MGOe were obtained.The results of composition distribution and Curie temperature test of the GBDPed magnets illustrate that Pr diffuses into the(Nd,Ce)_2(Fe,Co)_(14)B grains to substitute Ce,which not only improves the Curie temperature of the grains,but also enhances the magnetic performance of the magnets.Through GBDP,the thermal stability of magnets has also been improved.     

Structure and intrinsic magnetic properties of MM_2Fe_(14)B(MM=La,Ce, Pr,Nd) alloys

MM_(33)Fe_(66)B(MM=La, Ce, Pr, Nd) alloys(mass ratio) were prepared by induction melting and heat-treated at 1353 K for 24 h to produce homogeneous MM_2Fe_(14) B phase. The phase structure and element distribution of the alloys were analyzed by X-ray diffraction(XRD) and scanning electron microscope(SEM). The alloys were applied ball milling to obtain powders with good size distribution and then magnetic aligned in a static magnetic field of 2 T for 4 h, in order to achieve the intrinsic magnetic properties by vibrating sample magnetometer(VSM). XRD results showed that the alloys were composed of the single 2:14:1 main phase and RE-rich phase, which was similar to Nd_2Fe_(14)B structure. Magnetic measurements showed that the saturation magnetization(Ms) and anisotropy field(HA) of the MM_(33)Fe_(66)B alloy were 11.3 k Gs and 48.4 k Oe, respectively, demonstrating its good potential as permanent magnets. The Curie temperature of the MM_(33)Fe_(66)B alloy was determined as 502.9 K by magnetization-temperature curves. Microstructure observation showed that Nd and Pr were mainly in the 2:14:1 ferromagnetic phase, while La and Ce prefered to aggregate in the RE-rich grain boundary phase, which is beneficial to fabricating(Pr, Nd, MM)_2Fe_(14)B magnets with good magnetic properties.     

Effect of Nd3+ substitution on structural and magnetic properties of Mg–Cd ferrites synthesized by microwave sintering technique

Nd~(3+) substituted spinel ferrites with formula Mg_xCd_(1-x)Nd_(0.03)Fe_(1.97)O_4(x = 0.0.2,0.4,0.6.0.8 and 1.0)were prepared by oxalate co-precipitation method using novel microwave sintering technique. AR grade sulphates were used as starting chemicals. The samples were sintered at optimized power of 70 W for10 min in a microwave oven(800 W). The structural analysis of these samples was done by using X-ray diffraction, scanning electron microscope and Fourier transform IR techniques. The XRD analysis of the synthesized ferrite confirms the formation of cubic spinel structure of ferrite. The influence of Nd3+substitution on various structural parameters of Mg-Cd ferrites was reported. IR study indicates the spectra contain two intense absorption bands around 600 and 400 cm~(-1) in addition with four extra bands. The magnetic properties of all ferrites were studied by using a vibration sample magnetometer.The crystallite and grain size dependant magnetic properties are observed. The composition Mg_(0.6)Cd_(0.4)Nd_(0.03)Fe_(1.97)O_4 has better magnetic properties that can be used in recording media. The fast synthesis of spinel ferrites is yielded due to use of the microwave sintering technique.     

Electrochemical synthesis,structure characterization and magnetic properties of Tb_xFe_7Co_3(x=0,0.6,0.8) nanowires

Highly ordered Tb_xFe_7 Co_3(x=0,0.6,0.8) nanowires were synthesized in alumina templates by electrochemical deposition method.Here,the effects of Tb content and annealing treatment on the phase composition,morphology,crystalline structure and magnetic properties were investigated.The asdeposited Tb_0 Fe_7 Co_3 nanowires comprise Fe_7 Co_3 phase.While after adding Tb,the diffraction peaks slightly shift left,indicating the infiltration of Tb atoms into Fe_7 Co_3 phase.After annealing,Tb_0 Fe_7 Co_3 nanowires still consist of Fe_7 Co_3 phase with a slight enhancement on coercivity.While the annealed nanowires with Tb doped present a complex phase composition containing Fe3 Tb,Fe_2 Tb,Co_3 Tb,Co_(17)Tb_2,TbFeO_3 and Fe_2 O_3 phases distribute in the central portion,and Co_(0.72)Fe_(0.28) at the nanowire outer walls.The annealed Tb_xFe_7 Co_3(x=0.6,0.8) nanowires show higher magnetic performance owing to the formation of hard magnetic phases,the interfacial elastic coupling between hard and soft phases and the coherent Fe3 Tb/Co_3 Tb interface which restrain the domain wall motion.To be specific,the coercivity and remanence ratio of TbxFe_7 Co_3(x=0.6,0.8) nanowires significantly enhance with increasing Tb content.     

Influence of magnesium content on structure and electrochemical properties of La_(1-x)Mg_xNi_(1.75)Co_(2.05) hydrogen storage alloys

La_(1-x)Mg_xNi_(1.75)Co_(2.05)(x=0.07, 0.08, 0.10, 0.13, 0.15) alloys were prepared by high-frequency inductive method, and then their structure and electrochemical properties were investigated systematically. The XRD analysis revealed that the alloys consisted of LaNi_5 phase and La_4MgNi_(19)(Ce_5Co_(19) + Pr_5Co_(19)) phase, and the introduction of Mg could promote the formation of La_4MgNi_(19) phase. The observation of microstructure showed that all the alloys processed dendritic structure, which was refined with the increase of x value. The electrochemical measurements showed that all the alloys could be activated within 2 cycles, and with increasing x, the maximum discharge capacity obviously increased from 254.00 m Ah/g(x=0.07) to 351.51 mAh/g(x=0.15), but the cycling stability(S_(80)) decreased somehow from 78.4% to 73.9%. Meanwhile, the appropriate addition of Mg could improve the high-rate discharge capacity(HRD) of the alloy electrodes, which was mainly controlled by the electrochemical reaction rate on the surface of the alloys.     

Preparation and Structure of Mg2-xRExNi （RE = La, Ce, Pr, Nd, Y） Ternary Alloys

A series of Mg2-xNdxNi (x =0.05, 0.1, 0.2, 0.3) alloys and Mg1.95RE0.05Ni (RE= La, Ce, Pr, Nd, Y)ternary alloys were prepared by ball milling of mixted powder of Mg, Ni, RE and sintering under the protection of argon. XRD analysis shows that Mg2-xNdxNi (x = 0.05, 0.1 ) and Mg1.95RE0.05Ni consist of single phase with the same crystal structure as Mg2Ni. While three-phase alloys including Mg2Ni, NdNi and NdMgNi4 were formed in Mg1.8Nd0.2Ni and Mg1.7Nd0.3Ni alloys respectively. The lattice constants of Mg2Ni in those ternary alloys were calculated. The decomposition of Mg2Ni occurs in the milling process of Mg2Ni and Mg1.95RE0.05Ni alloys respectively. For the latter, another earlier reaction occurs in milling process, which means that atoms of RE are separated from crystal structure of Mg2Ni and form relevant oxides by combination with oxygen existed in argon atmosphere.