真空快淬材料研究的新近进展

真空快淬材料也叫急冷材料或快速凝固材料,真空快淬技术是制备非晶态金属和纳米晶合金的重要手段.近年来,真空快淬材料发展迅速,其性能指标已经达到实用化、产业化要求,本文主要介绍了真空快淬技术在贮氢合金、Nd-Fe-B永磁材料、非晶态钛基钎焊料、Ni-Mn-Ga磁性形状记忆合金等金属功能材料制备中的应用研究进展.研究实践证明应用真空快淬技术,不仅可以研究新型非晶态和纳米晶合金,进一步发展新型合金相,而且还可以定性、定量控制晶态材料的晶粒,如非晶、纳米晶、微晶的形成及其含量比例.     

溶质钒原子与铁的[100](001)位错的相互作用

采用改进分析型EAM模型（MAEAM）研究了溶质钒与铁的[100]（001）位错的相互作用.对铁的[100]（001）位错及掺杂结构用分子动力学方法进行了弛豫.计算了钒在这些掺杂格点上的能量,以及溶质钒与铁的[100]（001）位错缺陷系统的能量,发现在位错芯区域钒的格点能高,随着钒与位错芯之间距离的增加,其格点能降低;溶质钒替代拉伸区位错芯位置的铁原子时,钒与位错的相互作用能最强,缺陷系统的能量最低、结构最稳定.     

制备工艺对无钴AB5型贮氢合金的相结构和电化学性能的影响

用真空熔炼、快淬工艺以及球磨工艺制备稀土基无钴AB5型La（NiMnAlFe）5贮氢合金，用XRD测试了合金的相结构，并测试了不同制备工艺下合金的电化学性能。研究了制备工艺对无钴合金的相结构和电化学性能的影响。结果表明，由真空熔炼和快淬工艺制备的合金为CaCu5型单相结构，球磨合金由CaCu5型相和游离Ni相组成，并出现了非晶化趋势。快淬和球磨均使合金的放电容量降低，循环稳定性提高，但球磨工艺的影响更为显著，主要原因是球磨后合金中出现非晶化趋势。     

Electronic Structure of Hydrogen Storage Compounds, LaNi5 and Its Micro-Hydrogenated Compounds

The electronic structures of LaNi5 hydrogen storage alloys and its micro-hydrogenated compounds with two hydrogen atoms in the center of two octahedral interstices and two tetrahedral interstices, were investigated by the first principles discrete variational method （DVM）. The results of density of states and the difference of charge distribution clearly show that the s electrons of H mainly interact with the s electrons of hydride-non-forming element Ni, despite there being a larger affinity of La for hydrogen than that of Ni in pure metal-hydrogen system. From the cohesive energy of systems, we also found two systems have almost same stability with occupation of H atoms.     

Effects of rapid quenching on structure and electrochemical characteristics of La0.5Ce0.2Mg0.3Co0.4Ni2.6-xMnx （x=0-0.4） electrode alloys

The La-Mg-Ni system PuNi3-type La0.5Ce0.2Mg0.3Co0.4Ni2.6-xMnx (x=0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of the rapid quenching on the structure and electrochemical characteristics of the alloys were studied. The results obtained by XRD, SEM and TEM indicate that the as-cast and quenched alloys mainly consist of two major phases, (La,Mg)Ni3 and LaNi5, as well as a residual phase LaNi. The rapid quenching does not exert an obvious influence on the phase composition of the alloys, but it leads to an increase of the LaNi5 phase and a decrease of the (La, Mg)Ni3 phase. The as-quenched alloys have a nano-crystalline structure, and the grain sizes of the alloys are in the range of 20-30 nm. The results by the electrochemical measurements indicate that both the discharge capacity and the high rate discharge(HRD) ability of the alloy first increase and then decrease with the variety of quenching rate and obtain the maximum values at the special quenching rate which is changeable with the variety of Mn content. The rapid quenching significantly improves the cycle stabilities of the alloys, but it slightly impairs the activation capabilities of the alloys.     

RE-X二元合金相图的热力学数据库

利用CALPHAD方法,采用亚正规溶体模型、亚点阵模型以及理想气体模型来描述RE-X(Ag,Bi,Cr,Mn,Mo,V,Zn)中二元系各相的Gibbs自由能,并结合相平衡及热力学性质的实验结果,对Ag-RE(RE:Sc,Y Nd,Sm,Gd,.Tb,Ho,Er)、Bi-RE(RE:Nd,Tm,Er,Ho,Pr,Gd)、...     

快淬纳米晶和非晶Mg_(20)Ni_(10-x)Co_x(x=0～4)合金的贮氢性能(英文)

为了改善Mg2Ni型合金的贮氢性能,采用Co部分替代合金中的Ni以及快淬工艺制备了纳米晶和非晶态Mg20Ni10-xCox(x=0,1,2,3,4)贮氢合金。用XRD、SEM、HRTEM分析了铸态及快淬态合金的微观结构,并测试了合金的气态吸/放氢动力学及电化学贮氢性能。结果表明,在快淬无Co合金中没有形成非晶相,但快淬含Co合金中形成一定量的非晶相。Co替代Ni及快淬处理显著地改善了合金的气态吸放氢性能。同时,Co替代Ni也显著地提高了快淬态合金的放电容量和电化学循环稳定性。     

Electrochemical Hydrogen Storage Characteristics of the as-Cast and Annealed La0.8-xPrxMg0.2Ni3.35Al0.1Si0.05 (x=0~0.4) Electrode Alloys

采用铸造及退火工艺制备了La0.8-xPrxMg0.2Ni3.35Al0.1Si0.05 (x=0, 0.1, 0.2, 0.3, 0.4)电极合金。系统研究了Pr的替代对合金的结构与电化学储氢性质的影响,结果表明除少量残余LaNi3相外,铸造及退火合金是由六方Ce2Ni7型(La, Mg)2Ni7相与六方CaCu5型LaNi5相构成的。Pr对La的置换对合金的电化学储氢性质产生明显影响,铸造及退火合金的放电容量和高倍率放电能力随Pr含量的增加先升后降。当Pr含量由0增加至0.4时,铸造及退火合金的100次充放电循环后容积保持率S100从64.96%和72.82%分别增加至77.94%和91.81%     

Enhanced Hydriding and Dehydriding Kinetics of as-Spun Nanocrystalline Mg2Ni-Type Alloy Substituting Ni with Cu

为了改善Mg2Ni型合金的吸放氢动力学性能,用Cu部分替代合金中的Ni。用快淬工艺制备了纳米晶Mg2Ni1-xCux(x=0,0.1,0.2,0.3,0.4)贮氢合金,用XRD、SEM、HRTEM分析了铸态及快淬态合金的微观结构;用自动控制的Sieverts设备测试了合金的吸放氢动力学性能。结果表明,快淬态合金具有纳米晶结构,Cu替代Ni不改变合金的主相Mg2Ni,但导致形成第二相Mg2Cu。随Cu含量的增加,合金的吸氢量先增加而后减小,但合金的放氢量随Cu含量的增加而单调增加。快淬显著提高合金的吸放氢量并改善合金的吸放氢动力学。     

Fe3O4/CNT复合材料的制备与吸波性能研究

为进一步优化材料的阻抗匹配,调节并提高材料的吸收性能,通过热溶剂法制备了不同CNT含量的Fe₃O₄/CNT材料。结果发现,当CNT添加量为50 mg(Fe₃O₄/CNT-50)时,样品在4.15 GHz,厚度为5.5 mm时的最佳损耗值可达-50.37 dB。当CNT添加量增加到70 mg(Fe₃O₄/CNT-70)时,样品的最佳损耗值降低为-29.44 dB,对应匹配厚度降低至2.5 mm,值得注意的是,此样品在匹配厚度为1.5 mm时,有效带宽进一步拓宽为3.83 GHz(13.75～17.58 GHz)。这些说明通过调节材料中介电材料(CNT)的含量,不仅可以调节材料的损耗值,还可以调节材料的微波吸收峰位和带宽,进而调整材料的整体吸波性能,得到满足特殊需求的微波吸收材料。