非晶态贮氢材料锆镍合金的结构研究

本文报道了非晶态贮氢合金在吸氢前、后两种情况下作X射线散射分析得到的结果。根据对实验得到的径向分布函数RDF(r),简约径向分布函数G(r)的分析,表明吸氢后氢原子主要进入单一由锆原子组成的四面体间隙中,少部分进入由一个镍原子、三个锆原子组成的四面体间隙中;非晶态Ni_0.243Zr_0.757合金的平均配位数为10.6,内部原子配位情况在吸氢前后没有改变;样品在约20?范围内具有短程有序结构。 关键词：     

氢化金属玻璃Ni24.3Zr75.7H0.65的结构研究

本工作应用X射线大角散射技术测定金属玻璃氢化前后的径向分布函数,以探讨氢化对金属玻璃结构的影响,弄清氢在金属玻璃结构中的位置及其局域环境。 关键词：     

Local atomic structures in Zr-Ni metallic glasses

Local atomic structures of Zr100−xNix (x=33.3, 36, 50 at%) binary metallic glasses were investigated by means of extended X-ray absorption fine structure (EXAFS) probe. Structural parameters show that the Zr-Ni bond length, RZr-Ni, keeps a constant value of 2.62 Å, regardless of alloy compositions. This result implies that there is a strongly chemical interaction between Zr and Ni atoms, leading to significant chemical short-range orders (CSROs) in the present metallic glasses. Further analysis indicates that the SRO structures in these metallic glasses are extremely similar with those in their crystalline counterparts. It is interesting to note that the CSROs in the eutectic Zr₆₄Ni₃₆ metallic glass consist of Zr₂Ni-like and ZrNi-like CSROs.     

Vibrational and electronic properties of the amorphous systems Ni<Subscript>44</Subscript>Nb<Subscript>56</Subscript>, Ni<Subscript>62</Subscript>Nb<Subscript>38</Subscript>, and Cu<Subscript>33</Subscript>Zr<Subscript>67</Subscript> as derived from specific heat measurements

The specific heats of the amorphous systems Ni₄₄Nb₅₆, Ni₆₂Nb₃₈, and Cu₃₃Zr₆₇ were studied in the temperature range 3–273 K. The data obtained allow one to isolate the contribution due to atomic vibrations from the experimentally measured specific heat, to determine the density of electronic states at the Fermi level and the temperature dependence of the characteristic Debye parameter Θ over a broad temperature range, and to calculate a few frequency moments that characterize the vibrational spectrum. The information derived on the average characteristics of vibrational spectra is in good agreement with earlier data on inelastic neutron scattering. In transferring from Ni₄₄Nb₅₆ to Ni₆₂Nb₃₈, the density of electronic states at the Fermi level decreases and the characteristic vibrational frequencies increase. The density of electronic states at the Fermi level for Cu₃₃Zr₆₇ is close to that for Ni₆₂Nb₃₈. The characteristic frequencies of the vibrational spectrum of the Cu₃₃Zr₆₇ system are substantially lower (by 30%) than those of the Ni₄₄Nb₅₆ and Ni₆₂Nb₃₈ systems.     

用原位x射线小角散射研究块体非晶合金Zr55Cu30Al10 Ni5的结构弛豫

应用同步辐射x射线小角散射法在原位对块体非晶合金Zr₅₅Cu₃₀Al ₁₀Ni₅在等温退火过程中的微结构变化进行研究.实验表明：在等温退火过程中电子 密度涨落反映了晶化之前的结构弛豫过程；在一定的退火温度下、随退火时间的增加，拓扑短程序弛豫与化学短程序弛豫之间存在一个电子密度均匀化的过程；导致这两种弛豫过程转变的退火时间与退火温度有关，温度越高，所需的退火时间越短. 关键词： 原位x射线小角散射 块体非晶合金 等温退火 结构弛豫     

Positron studies of defect structures in metallic glasses

A variety of metallic glasses (Cu_xZr_100?x with x = 30, 40 and 50, Ni₂₄Zr₇₆ and RE₆₇ Co₃₃, RE = Nd, Sm, Gd, Dy, Er) were studied using 2γ angular correlation techniques. Significant positron trapping is observed in all the glassy alloys investigated. The defect structure changes drastically during crystallization. For the RE-Co glasses the results suggest the existence of vacancy-like defects in the amorphous alloys.     

Atomic vibration spectra of the metallic glass Ni64Zr36

This paper describes measurements of the inelastic neutron scattering spectrum of samples of the metallic glass Ni₆₄Zr₃₆ grown using an isotope of Ni. These measurements were used to reconstruct the partial densities of vibrational states of the atoms Ni and Zr. A weakening of the interatomic interactions of Ni with surrounding atoms was identified, but found to be less important than numerical calculations predicted. Fiz. Tverd. Tela (St. Petersburg) 40, 3–6 (January 1998)     

Structural relaxation of metallic glasses studied by Mössbauer spectroscopy

We present microscopic evidence of structural relaxation in the purely metallic glass Zr₆₇Ni₁₀Cu₂₃ doped with 0.5 at.% of⁵⁷Fe. The Mössbauer spectra under different heat treatments were analyzed by a six-parameter model. Two regimes of structural relaxation, irreversible and reversible relaxation, are clearly distinguished and the latter involves different atomic processes over different temperature regions.     

Compression Behaviour of Bulk Metallic Glasses and Binary Amorphous Alloy

The compression properties of Zr41Ti14Cu12.aNi10Be22.5, Zr44.4Nb7Cu13.5Ni10.8Be24.3 bulk metallic glasses and Ni77P23 binary amorphous alloy are investigated at room temperature up to 24 GPa, 39 GPa and 30.5 GPa, respectively, using in-situ high pressure energy dispersive x-ray diffraction with a synchrotron radiation source. The pressure-volume relationship of Ni77P23 amorphous alloy is consistent well with the second order BirchMurnaghan （B-M） equation within the experimental pressure range. However, under higher pressure, the experimental data of Zr-based specimens deviate from the B-M equation. Compare to the binary amorphous alloy less excess free volume existing in the bulk metallic glass and multi-component atomic configuration results in a two-stage relationship between compressibility and pressure.     

Effects of nickel on the crystallization of Zr70Cu20Ni10 amorphous alloy

Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) are employed to investigate the effects of nickel on the crystallization of the amorphous Zr₇₀Cu₂₀Ni₁₀ alloy. We have found that the crystallization process of the amorphous Zr₇₀Cu₂₀Ni₁₀ alloy is strongly influenced by the addition of nickel. Addition of 10 at% Ni to the Zr₇₀Cu₃₀ amorphous alloy makes the crystallization process proceed from a single-stage mode to a double-stage mode. The activation energy for crystallization of the amorphous Zr₇₀Cu₂₀Ni₁₀ alloy is calculated to be about 388kJ·mol^-1 on the basis of the Kissinger equation. The effects of nickel on the crystallization of the amorphous Zr₇₀Cu₂₀Ni₁₀ alloy are discussed in terms of the genetics of metals.     

Chemical short-range order in Zr2Ni amorphous alloy

Extended X-ray absorption fine structure (EXAFS) and molecular dynamic (MD) simulation were used to study the short-range order in Zr₂Ni amorphous alloy. It is found that the bond length is significantly shorter for unlike atoms but longer for like atoms in amorphous state than that in the crystalline state. Meanwhile, the coordination number of Ni atom in amorphous structure is only half of that in ideal Zr₂Ni crystalline. Based on these results, we proposed that there exists Zr₂Ni-like chemical short-range order in the Zr₂Ni amorphous alloy.     

Magnetic properties of nanocrystalline FeNiCo x ZrB alloys (x=0, 10, 20)

Magnetic properties of amorphous and nanocrystalline Fe₃₁Ni₅₀Zr₇B₁₂, Fe₃₁Ni₄₀Co₁₀Zr₇B₁₂ and Fe₃₁Ni₃₀Co₂₀Zr₇B₁₂ alloys were studied by an unconventional “rf-Mössbauer” technique. Introduction of Co atoms into FeNiZrB alloy leads to a large increase of anisotropy field that suppresses the rf collapse effect. The rf induced crystallization effect observed in Co-containing alloys was attributed to the rf sidebands effect which induced in the alloys mechanical deformations via the magnetostriction. This effect is particularly strong in amorphous alloys and in nanocrystalline alloys containing significant fraction of amorphous matrix and is absent in Co-free alloy.     

Ni-Zr非晶合金晶化的透射电子显微镜研究(Ⅰ) ——Ni67Zr33晶化过程中的亚稳相

利用透射电子显微镜对Ni₆₇Zr₃₃非晶合金晶化的研究发现了两个新的亚稳相T₀与T₁0。其中T₁相为体心正交(准四方〕晶体,点阵常数a≌b=0.89nm,c=3.14nm,空间群为Iba2或Ibam。温度升高,T₁相转变为含有大量错排的A心正交Ni₁₀Zr₂相,用1/2(a+b)位移错排模型可以圆满地解释其电子衍射图中仅h+k为奇数的衍射斑沿c^*方向拉长的现象,晶化稳定相为Ni₁₀Zr,与Ni₂₁Zr₈(Ni₅Zr₂)相。 关键词：     

Anisotropy of the solid–liquid interface properties of the Ni–Zr B33 phase from molecular dynamics simulation

Solid–liquid interface (SLI) properties of the Ni–Zr B33 phase were determined from molecular dynamics simulations. In order to perform these measurements, a new semi-empirical potential for Ni–Zr alloy was developed that well reproduces the material properties required to model SLIs in the Ni_50.0Zr_50.0 alloy. In particular, the developed potential is shown to provide that the solid phase emerging from the liquid Ni_50.0Zr_50.0 alloy is B33 (apart from a small fraction of point defects), in agreement with the experimental phase diagram. The SLI properties obtained using the developed potential exhibit an extraordinary degree of anisotropy. It is observed that anisotropies in both the interfacial free energy and mobility are an order of magnitude larger than those measured to date in any other metallic compound. Moreover, the [0 1 0] interface is shown to play a significant role in the observed anisotropy. Our data suggest that the [0 1 0] interface simultaneously corresponds to the lowest mobility, the lowest free energy and the highest stiffness of all inclinations in B33 Ni–Zr. This finding can be understood by taking into account a rather complicated crystal structure in this crystallographic direction.     

Influence of deformation on the structural transformation of the Pd<Subscript>40</Subscript>Ni<Subscript>40</Subscript>P<Subscript>20</Subscript> amorphous phase

The influence of plastic deformation on the structure of the Pd₄₀Ni₄₀P₂₀ amorphous alloy has been investigated using X-ray diffraction and measurements of the velocity of sound. It has been revealed that the rolling of the sample leads to a change in the structure of the amorphous phase (distortion of the first coordination sphere) and that the structural transformations are more pronounced in the near-surface region of the sample. The rolling also results in a decrease in the transverse velocity of sound. The observed effects decrease with time. It has been demonstrated that the revealed effects are associated with the inelastic deformation of the amorphous alloy.     

Research on Zr50Al15−xNi10Cu25Yx amorphous alloys prepared by mechanical alloying with commercial pure element powders

Amorphous Zr₅₀Al_15−xNi₁₀Cu₂₅Y_x alloy powders were fabricated by mechanical alloying at low vacuum with commercial pure element powders. The effects on glass forming ability of Al partial substituted by Y in Zr₅₀Al₁₅Ni₁₀Cu₂₅ and thermal stability of Si₃N₄ powders addition were investigated. The as-milled powders were characterized by X-ray diffraction, scanning electron microscopy and differential scanning calorimeter. The results show that partial substitution of Al can improve the glass forming ability of Zr₅₀Al₁₅Ni₁₀Cu₂₅ alloy. Minor Si₃N₄ additions raise the crystallization activation energy of the amorphous phase and thus improve its thermal stability.     

超导金属玻璃Zr78Co22的结晶化动力学研究

综合利用x射线小角散射、广角衍射、场离子显微镜等测量,并结合超导临界温度和显微硬度的观测,研究了金属玻璃Zr₇₈Co₂₂的结构及其结构弛豫和结晶化过程.结果表明,淬态金属玻璃Zr₇₈Co₂₂中存在明显的相分离,其中一个相的组分似乎趋向于纯Zr,另一相的组分则与ZO₄Co接近.在结构弛豫过程中,主要是拓扑短程序发生了变化,它受成核长大机理支配.当核的数量足够多时,两相均匀一致地长大. 关键词：     

EXAFS analysis of Zr-based quasicrystals

The character of transformation of the local environment of zirconium and palladium atoms in Zr₇₀Pd₃₀ binary alloy at a transition from the amorphous state to the quasicrystalline and crystalline states and in Zr₇₀Be₃₀ and Zr₈₀Pt₂₀ binary alloys at a transition from the amorphous to the quasicrystalline state have been investigated by extended X-ray absorption fine-structure (EXAFS) spectroscopy and X-ray diffraction. The parameters of the zirconium, palladium, and platinum local environment are determined, and the general features and differences in the local atomic rearrangement during formation of icosahedral clusters around zirconium atoms in these three compounds are established.     

Mössbauer spectroscopical investigation of amorphous Fe–Y alloy ribbons prepared by melt spinning

Fe–Y amorphous alloy ribbons were prepared by the melt spinning method and characterized by X-ray diffraction, Mössbauer spectroscopy and inelastic neutron scattering. X-ray diffraction demonstrates that the Fe_0.7Y_0.3 ribbons are completely amorphous, whereas the Fe_0.3Y_0.7 ribbons contain a small fraction of crystalline Y precipitates in the amorphous Fe–Y matrix. Mössbauer spectroscopy between 4.2 to 300 K reveals the amorphous nature of the Fe–Y matrix and the Fe_0.7Y_0.3 ribbons. The preliminary neutron scattering results S(Q, ω) show excess low energy vibrational modes which gives rise to the so called “boson peak” in this amorphous material.     

Atomic dynamics of a <Emphasis Type="Italic">d</Emphasis>-AlNiFe decagonal quasicrystal

The atomic dynamics of an Al_71.3Ni₂₄Fe_4.7 decagonal quasicrystal has been investigated using the isotopic contrast method for inelastic neutron scattering. The partial vibrational spectra of the Ni, Fe, and Al atoms and the spectrum of the thermal vibrations of the alloy have been reconstructed directly from the experimental data without any model assumptions. The cutoff energies and the positions of the main features of the spectra have been determined. It has been revealed that the average binding energy of the nickel atoms in the quasicrystal under investigation is lower than that of the iron atoms and the vibrational spectrum of the aluminum atoms is noticeably harder than the spectrum of the pure metal. The results obtained for the d-AlNiFe decagonal quasicrystal have been compared with the previously published data for an i-AlCuFe icosahedral quasicrystal.