质子辐照对永磁合金微观结构演化的研究

钐钴和钕铁硼稀土永磁合金已经广泛应用于粒子加速器的波荡器和其他器件中,作为加速器的重要组成部分,永磁合金在辐照环境中长期服役会出现磁性能损失的现象,这会影响束流的品质.为了探讨产生这个现象的微观机理,采用透射电镜对质子辐照前后的钐钴和钕铁硼稀土永磁合金进行了微观结构演化的表征和分析,统计了由辐照析出的纳米晶体积密度和粒径分布,并讨论了微观结构演化对宏观磁性能损失的影响.结果表明,随着质子辐照损伤程度的增加,永磁合金的微观结构从单晶结构转变为纳米晶多晶结构,且纳米晶和基体的晶体结构相同.钕铁硼的纳米晶体积密度先增大后减小,粒径分布先增大后不变;钐钴的纳米晶体积密度逐渐减小,粒径逐渐增大.在2 dpa的质子辐照损伤程度下,钕铁硼稀土永磁合金比钐钴永磁合金的非晶化趋势更明显.     

烧结Sm2Co17型永磁材料的力学性能及断裂行为的各向异性

对从同一磁体上切取的取向方向不同的三组烧结Sm2Co17试样的抗弯强度进行测定,对其抗弯断口进行宏观观察和扫描电镜观察.对烧结Sm2Co17型永磁材料的力学性能和断裂行为的各向异性进行了研究.研究结果表明:烧结Sm2Co17型永磁材料的抗弯强度和断裂行为具有明显的各向异性,烧结Sm2Co17型永磁材料断裂的微观机制为解理断裂,材料易于沿密排面(0001)面或沿与密排面的夹角大约为60°的晶面解理断裂 关键词： Sm2Co17型永磁 抗弯强度 解理断裂 各向异性     

Sm_2Co_（17） magnet blocks for the in-vacuum undulators （IVU20） at the SSRF

The design and development status of Sm₂Co₁₇ magnet blocks for two in-vacuum undulators (IVU20) at the SSRF with the same hybrid design has been described. By the technological improvement of some processes and comparison with the experimental Sm₂Co₁₇ magnet blocks for the IVU25A, magnetic properties such as the intrinsic coercive force H_ci and the average magnetic moment M are increased, the bend point magnetic field H_k value and pass rate are significantly increased, and the magnetic field uniformity of the magnet blocks are significantly improved. The basic developmental method of high uniformity Sm₂Co₁₇ magnet blocks for IVU20 is presented. The magnetic field qualities of the magnet blocks, including the magnetic property, the magnetic moment distribution, the magnetization deviation angle and the magnetic field uniformity, basically satisfy the specifications of the two IVU20 in-vacuum undulators.     

非晶合金的离子辐照效应

非晶合金作为一种快速凝固形成的新型合金材料,引起了材料研究者的极大兴趣.微观结构上长程无序、短程有序的特征使其具有独特的物理、化学和力学性能,在许多领域展现出良好的应用前景,尤其是有望成为核反应堆、航空航天等强辐照环境下的备选结构材料.本文深入探讨非晶合金的辐照效应,主要讨论离子辐照对非晶合金微观结构、宏观力学性能以及其他物理化学性能的影响,可为进一步理解非晶合金的微观结构和宏观力学性能之间的关系提供有效的实验和理论基础,也可为非晶合金在强辐照环境下的服役性能预测提供实验依据,对推进非晶合金这一先进材料的工程化应用具有重要的理论与实际意义.     

Relation between oxidation microstructure and the maximum energy product loss of a Sm2Co17 magnet oxidized at 500 ℃

The oxidation microstructure and maximum energy product (BH)_max loss of a Sm(Co_0.76, Fe_0.1, Cu_0.1, Zr_0.04)₇ magnet oxidized at 500 ℃ were systematically investigated. Three different oxidation regions were formed in the oxidized magnet: a continuous external oxide scale, an internal reaction layer, and a diffusion zone. Both room-temperature and high-temperature (BH)_max losses exhibited the same parabolic increase with oxidation time. An oxygen diffusion model was proposed to simulate the dependence of (BH)_max loss on oxidation time. It is found that the external oxide scale has little effect on the (BH)_max loss, and both the internal reaction layer and diffusion zone result in the (BH)_max loss. Moreover, the diffusion zone leads to more (BH)_max loss than the internal reaction layer. The values of the oxidation rate constant k for internal reaction layer and oxygen diffusion coefficient D for diffusion zone were obtained, which are about 1.91 × 10^-10 cm²/s and 6.54 × 10^-11 cm²/s, respectively.     

Ni离子辐照国产ZIRLO合金的辐照性能研究

国产ZIRLO合金是CAP1400重要的燃料包壳管候选材料之一,因此需要在使用前对该材料进行辐照性能考验。研究了国产ZIRLO合金的辐照性能随辐照温度和损伤剂量的变化。辐照实验在中国原子能科学研究院HI-13串列加速器上,采用80 MeV的Ni离子进行,辐照产生的损伤采用透射电子显微镜、能量色散谱和纳米压痕法等方法表征。国产ZIRLO合金在300℃经10 dpa损伤剂量辐照后观察到均匀分布的析出颗粒,同样剂量在700℃辐照析出颗粒数目减少,析出相的主要成分为Nb。辐照后出现硬化现象,辐照损伤剂量越大,硬化程度越高;随着辐照温度升高,辐照硬化呈减小趋势。The domestic ZIRLO is a promising candidate of cladding materials for CAP1400. It is necessary to test its radiation properties before its use. In this paper, the radiation properties of the domestic ZIRLO have been studied as functions of irradiation temperature and dose respectively. The experiment was performed at the HI-13 tandem accelerator of China Institute of Atomic Energy by using 80 MeV Ni ions at different temperature and different dose. The transmission electron microscopy, electron dispersive spectroscopy and nano-indentation were used to characterize the radiation damage. The experimental results show that the precipitates are uniformly distributed at 10 dpa and 300℃, while at 700℃ the number of precipitates is reduced. Among all the precipitates, Nbisthe dominant element. Hardening phenomenon was also observed after irradiation, the higher the radiation dose, the higher the degree of hardening, and it illustrates a decreasing tendency with the increasing of the irradiation temperature.     

SPRR-300研究堆随堆辐照石墨的中子辐照效应北大核心CSCD

随SPRR-300研究堆约30 a的长时间运行,位于活性区附近的石墨箱体经历了长期的中子辐照。在长期服役的石墨箱体上取样,研究了其热学、力学以及微观结构变化,并与商用IG110,NG-CT-10石墨进行了对比。研究结果表明,经长时间低剂量率的中子辐照后,SPRR-300堆内随堆辐照石墨的晶格中出现了明显的辐照损伤缺陷,这些缺陷主要为位错环、层错、孔洞和微裂纹等,并出现了一定程度的非晶化。这些辐照损伤缺陷直接或间接地引起了石墨热学、力学性能的变化,主要表现为热膨胀系数、热扩散系数、抗压强度和抗弯强度的下降以及弯曲弹性模量的上升。     

Ho2(Co,Si)17化合物的结构与磁晶各向异性

用三弧Czochralski法和真空电弧熔炼法制备了Ho2Co17-xSix化合物.通过X射线衍射和磁性测量手段研究了化合物的结构与内禀磁性.重点讨论了磁晶各向异性和自旋重取向转变.实验结果表明,Ho2Co17为Th2Ni17型六角结构,在05≤x≤3的化合物均为Th2Zn17型菱方结构,能够获得单相2∶17型化合物的最大Si含量是x=3.在x≤2的浓度范围,化合物的易磁化方向垂直于c轴.随Si含量增加,化合物的居里温度和Co原子平均磁矩单调减少.根据Ho2Co17-xSix化合物的居里温度和自旋重取向温 关键词：     

(Nd_(1-x)Er_x)_2Co_(15.5)V_(1.5)的结构转变与磁性

利用电弧熔炼制备了 (Nd1 xErx) 2 Co1 5 5V1 5(x=0— 1 0 )化合物样品 .通过x射线衍射分析和磁性测量研究了Er替代Nd2 Co1 5 5V1 5中的Nd时对化合物结构和磁性的影响 .研究结果表明 ,低Er含量 (x <0 4 ) ,化合物为Th2 Zn1 7型结构 ;高Er含量时 (x >0 5 ) ,化合物转变为Th2 Ni1 7结构 ;Er含量为x =0 4和 0 5时 ,两种结构共存 .两种结构的晶胞参数a ,c和晶胞体积V随着Er含量的增加都呈现递减的趋势 .随着Er含量的增加 ,(Nd1 xErx) 2 Co1 5 5V1 5化合物的居里温度和饱和磁化强度都单调下降 .(Nd1 xErx) 2 Co1 5 5V1 5化合物的室温各向异性由低Er含量时的易锥型转变为高Er含量时的易轴型 .x =0— 0 5的化合物在温度升高时发生自旋重取向转变 ,自旋重取向温度Tsr随Er含量的增加而减小     

Sm3（F3,Co,Mn）29 compounds：promising materials for permanent magnets

The outstanding hard-magnetic properties are reported of Sm_3Fe_{28.1-x}Co_xMo_{0.9} compounds with x=12, 14, 16. In this alloy system, only a small amount of Mo is needed to stabilize the 3:29 structure so that the magnetic properties are not seriously affected by the presence of this nonmagnetic element. Substitution of Co for Fe leads to a significant increase of the magnetic anisotropy, and for x≥14 the easy magnetization direction changes from easy plane to the easy axis. In this alloy system, the compound Sm_3Fe_{12.1}Co_{16}Mo_{0.9} is a very promising candidate for permanent magnet applications. Its room temperature saturation magnetization (μ_0M_s=1.5 T) and anisotropy field (B_{an}=6.5 T) are comparable to the values for Nd_2Fe_{14}B (μ_0M_s=1.6 T and B_{an}=7 T). However, the Curie temperature of Sm_3Fe_{12.1}Co_{16}Mo_{0.9} is 1020 K, which is appreciably higher than that for Nd_2Fe_{14}B (T_C=588 K).     

上海光源真空波荡器Sm2Co17永磁铁的实验研究

对国产Sm2Co17永磁铁(XG30/20)研制工艺进行了改进,对三种成型-烧结设计所得到的永磁铁样品(65 mm27 mm7.2 mm)进行了测试与分析,结果表明,磁性能有所改善,磁矩一致性和稳定性良好,获得了国产真空波荡器Sm2Co17永磁铁的优化成型-烧结设计和磁场分布规律数据,对永磁铁实验研究结果原理进行了解释。     

上海光源真空波荡器Sm2Co17永磁铁的实验研究

对国产Sm2Co17永磁铁(XG30/20)研制工艺进行了改进,对三种成型-烧结设计所得到的永磁铁样品(65 mm27 mm7.2 mm)进行了测试与分析,结果表明,磁性能有所改善,磁矩一致性和稳定性良好,获得了国产真空波荡器Sm2Co17永磁铁的优化成型-烧结设计和磁场分布规律数据,对永磁铁实验研究结果原理进行了解释。     

High-temperature oxidation resistance and magnetic properties of Si-doped Sm2Co17-type magnets at 500 °C

The high-temperature oxidation resistance and magnetic properties of Si-doped Sm₂Co₁₇-type magnets at 500 °C were systematically investigated. The Sm(Co_0.76, Fe_0.1, Cu_0.1, Zr_0.04)₇Si_x (x=0–0.6) magnets were prepared by the conventional powder metallurgical technique. It is found that the addition of silicon in the Sm₂Co₁₇-type magnet can remarkably improve its oxidation resistance. Moreover, a small amount of silicon addition can also increase its high-temperature intrinsic coercivity. A maximum intrinsic coercivity of 6.7 kOe at 500 °C was obtained for the Sm₂Co₁₇-type magnet with Si content x=0.4, whose high-temperature maximum energy product loss was about 2.5 times smaller than pure Sm₂Co₁₇-type magnet after oxidation at 500 °C for 100 h, indicating the enhanced oxidation resistance. Its corresponding Curie temperature and saturation magnetization are about 723.9 °C and 7.4 kG, respectively.     

Annealing dependence of magnetic properties in nanostructured Sm0.5Y0.5Co5

Nanocrystalline Sm_0.5Y_0.5Co₅ powders with high coercivity H_C and enhanced remanence M_r were prepared by mechanical milling and subsequent annealing. Annealing temperatures T ranging from 973 to 1173 K, and times t ranging from 1 to 5 min were used. X-ray diffraction (XRD) and DC-magnetization measurements were carried out to study the microstructure and magnetic properties of these samples. XRD patterns demonstrate that the average grain size D of the nanocrystalline powders depends on the annealing temperature T and time t: D ranges from 11 nm (for T=973 K and t=1 min) to 93 nm (for T=1173 K and t=5 min). Magnetic measurements performed at room temperature indicate high coercivity values (H_C>955 kA/m), and enhanced remanence (M_r/M_max>0.5) for all samples. A strong annealing-induced grain size dependence of these magnetic properties was found.     

Magnetic properties of Lu2Co17−xSix single crystals

The Co-sublattice anisotropy in Lu₂Co₁₇ consists of four competitive contributions from Co atoms at crystallographically different sites in the Th₂Ni₁₇-type of crystal structure, which result in the appearance of a spontaneous spin-reorientation transition (SRT) from the easy plane to the easy axis at elevated temperatures. In order to investigate this SRT in detail and to study the influence of Si substitution for Co on the magnetic anisotropy, magnetization measurements were performed on single crystals of Lu₂Co_17−xSi_x (x=0−3.4) grown by the Czochralski method. The SRT in Lu₂Co₁₇ was found to consist of two second-order spin reorientations, “easy-plane”–“easy-cone” at T_SR1≈680 K and “easy-cone”–“easy-axis” at T_SR2≈730 K. Upon Si substitution for Co, both SRTs shift toward the lower temperatures in Lu₂Co₁₆Si (T_SR1≈75 K and T_SR2≈130 K) with the further onset of the uniaxial type of magnetic anisotropy in the whole range of magnetic ordering for Lu₂Co_17−xSi_x compounds with x>1 due to a weakening of the easy-plane contribution from the Co atoms at the 6g and 12k sites to the total anisotropy.     

Effect of microstructure on the thermoelectric properties of CSD-grown Bi2Sr2Co2Oy thin films

Three Bi2Sr2Co2Oy thin films with different microstructures have been prepared by chemical solution deposition on LaAlO 3(001) through varying the annealing temperature.With the decrease in the annealing temperature,both the size and c-axis alignment degree of grains in the film decrease as well,leading to an increase in the film resistivity.In addition,the decrease in the annealing temperature also results in a slight increase in the Seebeck coefficient due to the enhanced energy filtering effect of the small-grain film.The nanostructured Bi2Sr2Co2Oy film with an average grain size of about 100 nm shows a power factor comparable to that of films with larger grains.Since the thermal conductivity of the nanostructured films can be depressed due to the enhanced phonon scattering by grain boundary,a higher figure of merit is expected in Bi2Sr2Co2Oy thin film with grains in nanometer size.     

Structural and magnetic properties of Dy2Co17—xMnx compounds

Using x-ray diffraction and magnetic measurements, we have studied the structural and magnetic properties of Dy₂Co_17-xMn_x (x=0∽5) compounds with a rhombohedral Th₂Zn₁₇-type structure. With an increasing Mn concentration x, the unit-cell volume V was found to increase linearly. The Curie temperature T_c decreases linearly, and the saturation magnetization M_s at 5K first increases slightly for x<1, then decreases rapidly for x>1 with a further increase of Mn concentration x. In compounds for x=1～3, a spin reorientation was found. A magnetic diagram of the compounds is given.