高压对大块（PrNd）xAl0．6Nb0．5Cu0．15B1．05Fe97．7-x合金微观结构和性能的影响冰

经配料、熔炼、制粉、成型和烧结后制备了（PrNd）xAl0．6Nb0．5Cu0．15B1．05Fe97．7-x（质量百分比）合金,将该合金分别采用1．5GPa和3．0GPa的压强进行压制,研究了此高压对其显微结构和磁性能的影响．分析发现,该块状合金承受的压强越高,其外观和微观结构破坏越严重,抗弯强度也会降低,但高温抗氧化性能却有一定程度的提高．与没有经过高压处理的磁体相比,经过1．5GPa和3．0GPa高压的样品最大磁能积分别提高了7．69kJ．m^-1和0．94kJ．m^-1,剩余磁通密度分别提高了0．02T和0．01L内禀矫顽力分别提高了20．06kA．m-1和30．33kA．m^-1．结果表明,高压对块状NdFeB烧结磁体的显微结构和力学性能及磁性能均有一定的影响．     

烧结NdFeB断裂方式及其断面的微观结构

 经熔炼、制粉、成型、烧结和回火等工序制备了成分为Nd₃₃Fe_65.95B_1.05（质量分数）的烧结NdFeB磁体,将铸锭样品和烧结磁体样品折断,并采用扫描电子显微镜和金相显微镜对二者的断裂方式和断面的微观结构进行了对比分析。结果表明：烧结NdFeB铸锭的断裂方式为沿晶断裂,断面处有较多的层状富钕相,多边形的主相较为完整;烧结NdFeB磁体既有沿晶断裂也有穿晶断裂,但是以沿晶断裂为主。分析造成烧结NdFeB磁体断裂的原因为：（1）其微观结构中有大量的孔洞等缺陷,这是外部原因;（2）微观结构中占主要成分的主相的维氏硬度为6 235.94 N·mm^-2,富钕相的维氏硬度为5 947.42 N·mm^-2,二者有较大的差距,这是本征因素。针对磁体中孔洞和夹杂等缺陷存在而造成的断裂提出了相应的解决措施。     

用热压法制备NdFeB各向异性粉末及粘结磁体

将氢处理法得到的各向同性ＮｄＦｅＢ粉末采用包套热压的方法处理，可获得各向异性粉末和粘结磁体，热压工艺参数（热压温度，形变量，热压速率）及热处理工艺条件对热压磁体的组织结构及磁各向异性明显影响。热压法存在形变不均匀性，但可通过加大钢套尺寸和在钢套表面涂敷润滑剂的方法加以改善。     

爆炸压实制取W-Cu纳米复合材料的实验研究

采用机械合金化法制备了W-Cu合金粉末。将制备出的W-Cu合金粉末置于爆炸压制成型的装置中进行爆炸压实,得到了最高致密度达98%的W-Cu合金。利用X射线衍射(XRD)分析了W-Cu混合粉末的合金化过程,研究了W-Cu合金粉末的还原温度对压实坯致密度的影响。通过电子探针微量分析仪(EPMA)观察了样品内部的成分与元素分布,利用扫描电子显微镜(SEM)对样品断口形貌进行了观察,并对样品的维氏硬度和电导率进行了测量。结果表明,W-Cu合金化粉末在爆炸冲击波作用下能够结合成高致密体,复合材料具有高硬度、组织均匀、晶粒细小的特点。     

纳米Mg-Ni合金的制备技术

纳米Mg-Ni贮氢材料具有成本低，活化容易、贮氢容量大，吸放氢动力学性能优异等特点，有很大的应用前景。本文用机械合金化法进行了纳米Mg-Ni合金的制备，且对制备的粉末进行了XRD，TEM，SEM等微观结构的分析。     

不同热处理条件下Bi-2212超导线材的临界性能研究

Bi-2212高温超导材料在4.2K具有优异的磁场载流性能,并且是目前高温超导材料当中唯一可制备成各向同性圆线的材料,可以绞制成大电流的CICC电缆,也是大型超强磁场磁体的首选材料之一。高压热处理技术可以大幅提高材料超导性能。临界电流与n值是超导导线的主要性能参数。本文测量了两组分别经过常压和高压热处理的超导线在不同背景磁场中的临界电流和n值。测试所用Bi-2212导线是以Ag和Ag/Mg合金为基体,采用粉末装管法制备而成,两组导线在890℃下经不同压强热处理。从对比的数据中定性地分析热处理压强和超导线性能之间的关系。     

溶剂热法制备的纳米BaSnO3及其近红外发光

用溶剂热法制备了BaSn(OH)6前驱体,经煅烧后,得到BaSnO3纳米粉末。用XRD、TEM、纳米粒度仪、紫外-可见-近红外分光光度计、光纤光谱仪等对样品的结构、形貌和性能进行了表征。BaSnO3纳米粒子为粒径约为30～50 nm的球形颗粒,具有良好的分散性,也具有很好的近红外发光性能,其最大激发和发射波长分别位于385 nm和895 nm。与高温固相法得到的样品相比,该方法所得纳米BaSnO3样品的近红外发光强度提高近10倍,样品结晶程度的提高和缺陷的减少可能是样品近红外发光强度提高的主要原因。     

红外光谱技术在纳米NiFe2O4制备过程中的应用

采用溶胶 凝胶法制备NiFe2 O4 纳米粉末 ,并经不同温度热处理 .测定了制备过程中各阶段的红外吸收光谱和不同温度处理样品的红外漫反射光谱 .结果表明 ,红外吸收光谱较好地反映了溶胶 凝胶法制备NiFe2 O4 纳米粉末过程中结构的变化 ,为确定热处理温度提供了实验依据 ,彻底消除有机物 ,热处理需在 40 0℃以上 ;红外漫反射谱可以较好地反映粉末的尺寸效应和形态效应 ,粉末粒径越小 ,漫反射函数 (K M)值越大 ;当粒径达到一定尺寸时 ,红外漫反射的尺寸效应消失     

高压处理的α－Fe_2O_3超微粒的X射线衍射研究

采用沉淀法制备了α－Ｆｅ２Ｏ３超微粒，将超微粒粉末在不同温度下进行了高压处理，利用Ｘ射线衍射，ＴＥＭ和穆斯堡尔谱学对高压处理前后的样品进行了研究。结果表明，室温下压力对微晶的晶粒尺寸没有产生明显的影响，热压使晶粒尺寸有较大增长。压力主要对微晶的晶格畸变程度及取向产生了影响     

稀土含量对速凝工艺制备(Nd,Dy)-(Fe,Al)-B合金结构和磁性能的影响

采用双合金法制备了不同稀土含量的(Nd,Dy)-(Fe,Al)-B合金系列,研究了稀土含量的多寡对薄带和最终烧结磁体的微观结构和磁性能的影响.研究结果表明,适量的稀土含量(～3145%)不仅能改善速凝带主相(Nd,Dy)₂Fe₁₄B的单相性,还有利于富稀土(Nd,Dy)相在晶界的均匀分布.当主相薄带的稀土含量在接近2∶14∶1相稀土含量时,磁体的内禀矫顽力和磁能积显著提高.当稀土含量较少时,对速凝薄带的合适时效热处理将能有效地提高最终烧结NdFeB磁体的磁特性. 关键词： 双相烧结 速凝技术 微观结构 磁性能     

Improved magnetic properties and fracture strength of NdFeB by dehydrogenation

Effects of the dehydrogenation of the hydrogen decrepitated (HD) powders on the magnetic properties and the fracture strength of sintered NdFeB magnets were studied. It was found that the lattice parameters and the crystal phase of NdFeB changed significantly with the various hydrogen contents of the resultant HD powders due to the different degrees of dehydrogenation. The magnetic properties and fracture strength increased with decreasing hydrogen content, reaching the maximum increases of 200% for both intrinsic coercivity and bending strength, which can be ascribed to the improved microstructure of the sintered NdFeB magnets. The hydrogen remaining in the HD powders diffused out and affected drastically the grain and grain boundaries by the hydrogen out-take channel during the subsequent sintering process.     

Effects of powder flowability on the alignment degree and magnetic properties for NdFeB sintermagnets

The magnetic powders for sintered NdFeB magnets have been prepared by using the strip casting (SC), hydrogen decrepitation (HD) and jet milling (JM) techniques. The effects of powder flowability and addition of a lubricant on the alignment degree and the hard magnetic properties of sintered magnets have been studied. The results show that the main factor affecting powder flowability is the aggregation of magnetic particles for powders in a loose state, but it is the friction between the powder particles for powders that are in a compact state. The addition of a lubricant with suitable dose can slightly prevent the congregating of powders, obviously decrease the friction between the powder particles, improve the powder flowability, and increase the alignment degree, remanence and energy product density of sintered magnets. Mixing a suitable dose of lubricant and adopting rubber isostatic pressing (RIP) with a pulse magnetic field, we have succeeded in producing the sintered NdFeB magnet with high hard magnetic properties of B_r=14.57 KG, _jH_c=14.43 KOe, (BH)_max=51.3 MGOe.     

Study of high-coercivity sintered NdFeB magnets

Magnetic powders for sintered NdFeB magnets have been prepared by using an advanced processing method including strip casting, hydrogen decrepitation, jet milling and rubber isotropic press. The effects of Dy, Ga and Co addition on the microstructure and magnetic properties of sintered magnets have been investigated. By adopting a suitable component ratio and adjusting proper technological parameters, we have prepared high-coercivity sintered NdFeB magnets with hard magnetic properties of _jH_c=25.6 kOe, B_r=13.2 kG and (BH)_max=39.9 MGOe. The temperature coefficient of coercivity of the magnets (between 20 and 150 °C) is –0.53%/°C. The magnetic properties at high temperature satisfy the needs of permanent magnet motors.     

用模拟退火法进行纯永磁波荡器磁块组合优化

 纯永磁波荡器由多个磁块组成，磁块的剩磁离散性会引起波荡器磁场误差，从而影响储存环工作状态和自发辐射谱质量。在波荡器磁块安装之前，使用模拟退火法对磁块进行组合排序优化，可以使峰值场强误差降低到10 ^-4量级以下，磁场一次积分降低到10^-6 T·m量级，二次积分降低到10 ^-6 T·m ²量级，优化结果不依赖于初始状态的选择。给出优化的详细过程，提出了根据磁块剩磁快速计算波荡器峰值场强误差和积分场的方法。     

Highly anisotropic resin-bonded magnets processed with surfactant-coated SmCo5 nanocrystalline powders

Highly anisotropic SmCo₅ nanocrystalline powders with grain size in the range 5-20 nm were processed through surfactant and magnetic field-assisted milling. The SmCo₅ nanocrystalline powders so obtained by this method possess unusual characteristics such as reduction in particle size, platelet-structure and high remanence values. A possible mechanism for achieving remanence enhancement with the surfactant-coated SmCo₅ powders has been discussed. Besides, the resin-bonded magnets processed with the surfactant-coated SmCo₅ powders showed relatively higher density, induction remanence and energy product with strong anisotropic behavior than those of the magnets processed with the conventionally milled SmCo₅ powders. Maximum values of H_ci (16 kOe), B_r (4.66 kG) and (BH)_max (5.5 MG Oe) were achieved for the resin-bonded magnets processed with the surfactant-coated powders.     

利用金属掩模法制备钉扎型磁性隧道结

利用金属掩模法和Ir22Mn78合金反铁磁钉扎层，制备了四种钉扎型的Py/Al2O3/Py，Py/Al2O3/Co，Co/Al2O3/Py和Co/Al2O3/Co磁性隧道结，坡莫合金的成分为Py＝Ni79Fe21.例如：利用狭缝宽度为100?μm的金属掩模，直接制备出室温隧穿磁电阻比值为17.2%的磁性隧道结Co/Al2O3/Co，其结电阻为76Ω,结电阻和结面积的积矢为76×10_{4Ωμm2，自由层的偏转场为1114?A/m，并且在外加磁场0.1114A·m-1之间时室温磁电阻比值 关键词： 磁性隧道结 隧穿磁电阻 磁随机存储器 金属掩模}     

Hybrid techniques of pre and assisted processing modify structural,physicochemical and functional characteristics of okra pectin: Controlled-temperature ultrasonic-assisted extraction from preparative dry powders and its field monitoring

Diversiform okra dry powders were prepared and controlled-temperature ultrasonic-assisted extraction (CTUAE) was then utilized to obtain okra pectin (OP) from the preparative powders. During processing of hybrid techniques, 6 types of dry powders were prepared through different drying technologies (hot air drying, HD; freeze-drying, FD) and meshes (60, 80, 120 meshes) at first. Next, the extraction yield, physicochemical and function characteristics, and molecular structure of OP were analyzed with or without CTUAE technique. Meanwhile, the time–frequency domains of acoustic fields during extraction process of OP were monitored to analyze the effects of ultrasonic fields. Results showed that OP main chains with less cracking by FD than that by HD; the yield, GalA, esterification degree (DE), M_w and viscosity of OP increased, but its particle size decreased. Water holding capacity (WHC) and oil holding capacity (OHC) of OP by HD were more prominent. Secondly, HD OP had dendritic rigid chains, while FD OP had flexible chains with multiple branches. For HD OP, as meshes of okra dry powders decreased, GalA, viscosity and emulsification ability decreased; while gel strength and thermal stability increased. For FD OP, the reduction of meshes improved thermal stability. Above all, CTUAE technique increased the yield and GalA, and decreased DE, M_w and particle size of OP. In terms of functional characteristics, the technique also improved gel strength, resilience and viscoelasticity, enhanced emulsifying stability, WHC and thermal stability, and reduced viscosity. Finally, the correlation between functional and structural characteristics of OP was quantified, and some suggestions were made for its application in food areas.     

Abnormal variation of magnetic properties with Ce content in(PrNdCe)_2Fe_(14)B sintered magnets prepared by dual alloy method

Resource-saving(PrNdCe)_2Fe_(14)B sintered magnets with nominal composition(PrNd)_(15-x)Ce_xFe_(77)B_8(x=0–10)were prepared using a dual alloy method by mixing(PrNd)_5Ce_(10)Fe_(77)B_8 with(PrNd)_(15)Fe_(77)B_8 powders. For Ce atomic percent of 1% and 2%, coercivity decreases dramatically. With further increase of Ce atomic percent, the coercivity increases, peaks at 6.38 kOe in(PrNd)_(11)Ce_4Fe_(77)B_8, and then declines gradually. The abnormal dependence of coercivity is likely related to the inhomogeneity of rare earth chemical composition in the intergranular phase, where Pr Nd concentration is strongly dependent on the additive amount of(PrNd)_5Ce_(10)Fe_(77)B_8 powders. In addition, for Ce atomic percent of 8%,7%, and 6% the coercivity is higher than that of magnets prepared by the conventional method, which shows the advantage of the dual alloy method in preparing high abundant rare earth magnets.     

Calculations of the 3-D neutronics for CH HCSB TBM with 3×3 sub-modules

Using three dimension MCNP code and FENDL2.0 data library, neutronics calculation for a HCSB (helium cooling solid breeder) TBM (test blanket module) with 3×3 sub-modules has been performed. Local tritium breeding ratio (TBR) of 0.907, total tritium generation rate of 0.0175g·d-1, peak power density of 9.27MW·m-3 and total power deposit of 0.422MW·m-3 are obtained under neutron wall loading of 0.78MW·m-2 and duty factor of 22%.     

Nanocrystalline and nanocomposite permanent magnets by melt spinning technique

The melt-spinning technique offers an opportunity for tailoring magnetic properties by controlling the structures and microstructures in both single-phase and composite magnets. This review first broadly discusses the principle of cooling control, amorphization, crystallization, annealing, and consolidation of the melt-spun ribbons. The phase, microstructure,and magnetic properties of popular single-phase nanocrystalline magnets are reviewed, followed by the nanocomposite magnets consisting of magnetically hard and soft phases. The precipitation-hardened magnetic materials prepared by melt spinning are also discussed. Finally, the role of intergrain exchange coupling, thermal fluctuation, and reversible/irreversible magnetization processes are discussed and correlated to the magnetic phenomena in both single-phase and nanocomposite magnets.