冷却条件对Fe-Si-B非晶态合金内场分布函数的影响

以示差热分析(DTA)和穆斯堡尔谱学(MS)研究了冷却条件对Fe-Si-B非晶态合金微观结构及热稳定性的影响。实验结果表明,在形成非晶的临界冷却条件下,冷速增大,非晶态合金的热稳定性有所改变,但并不能显著改变非晶态合金的微观结构;与微晶模型相比,硬球无规混乱密堆积(DRPH8)模型较为符合实际。     

高聚物玻璃化转变的一种微观解释——兼论高聚物非晶态的结构

高聚物非晶态的玻璃化转变的理论研究,提出了几种机理,而非晶态的结构研究,也提出了各种模型。本文试将玻璃化转变看成是非晶态的结构转变,提出一种玻璃化转变的微观解释——局部有序化假设,并用其说明非晶态的各种状态可用不同的模型来表示,最后给出了有待实验验证的几点推论。     

非晶态合金的双层单元结构模型与类金属成分范围

本文提出在液态淬火形成的非晶态合金中,其微观结构是由短程有序的双层四面体和八面体以及它们的组合单元无序堆积而成.并由这种双层单元结构模型导出非晶态合金中类金属成分范围及其上限约为30.47at%.就目前所收集的80种上述合金的实验数据来看,其成分范围的上限近于100%都在计算结果以内.这可为今后制备液态淬火非晶态合金的类金属成分范围提供一个重要的参考判据.同时,双层单元结构模型也为今后深人研究非晶态合金的结构与物理性能的关系提供一个较好的理论模型.     

非晶态Fe-Si-B系合金的临界厚度极大值与类金属成分关系的研究

本文根据作者新近提出的非晶态合金中的"双层单元结构模型",对于由液态淬火制备的非晶态Fe-Si-B系合金的临界厚度在类金属总成分约为25at%左右、B含量在14at%左右时出现极大值这一具有重要实际意义的结果,作出了相当合理的解释,并对非晶态合金的结构层次和形成机理进行了较为详细的分析和讨论.     

Ni82B18和Ni64B36非晶态合金电子性质DFT研究

根据Ni82B18和Ni64B36非晶态合金的原子簇构成、结构的短程有序、Ni和B之间是较强的化学作用和结构中存在B-B直接相连的实验事实,选择了Ni4B2,Ni4B3和Ni6B2原子簇模型,用DFT方法对其进行高水平的量子化学计算.结果表明,模型体系中B原子供给Ni原子电子,与Ni82B18和Ni64B36非晶态合金的实验结果一致,说明Ni4B2,Ni4B3和Ni6B2原子簇模型能够反映Ni82B18和Ni64B36非晶态合金的结构特点.     

Ni82B18和Ni64B36非晶态合金电子性质DFT研究

根据Ni82B18和Ni64B36非晶态合金的原子簇构成、结构的短程有序、Ni和B之间是较强的化学作用和结构中存在B-B直接相连的实验事实,选择了Ni4B2,Ni4B3和Ni6B2原子簇模型,用DFT方法对其进行高水平的量子化学计算.结果表明,模型体系中B原子供给Ni原子电子,与Ni82B18和Ni64B36非晶态合金的实验结果一致,说明Ni4B2,Ni4B3和Ni6B2原子簇模型能够反映Ni82B18和Ni64B36非晶态合金的结构特点.     

原子簇Ni4-mComB(m=0-3)的结构和性质DFT研究

根据非晶态合金的结构特点,选择系列原子簇模型Ni4-mComB(m=0-3)对Ni_Co_B非晶态合金用DFT方法进行高水平的量子化学计算,结果表明,在Ni_Co_B非晶态合金中,Co_B键强于Ni_B键,Co原子的引入及Co含量的变化对镍原子的电子结构有调变作用.     

关于Mie理论移植问题的讨论

本基于非晶态金属cluster结构模型，对Mie理论作了相应的分析，将其引进具体的非晶电输运问题，并对非晶态合金紧邻晶化前电阻率极大峰理作了较深入的讨论，取得了比较好的效果。     

原子簇Ni4-mComB(m=0-3)的结构和性质DFT研究

根据非晶态合金的结构特点,选择系列原子簇模型Ni4-mComB(m=0-3)对Ni_Co_B非晶态合金用DFT方法进行高水平的量子化学计算,结果表明,在Ni_Co_B非晶态合金中,Co_B键强于Ni_B键,Co原子的引入及Co含量的变化对镍原子的电子结构有调变作用.     

关于Mie理论移植问题的讨论

本文基于非晶态金属cluster结构模型，对Mie理论作了相应的分析，将其引进具体的非晶电输运问题，并对非晶态合金紧邻晶化前电阻率极大峰的机理作了较深入的讨论，取得了比较好的效果．     

Three-dimensional atomic-scale structure of size-selected gold nanoclusters

An unambiguous determination of the three-dimensional structure of nanoparticles is challenging. Electron tomography requires a series of images taken for many different specimen orientations. This approach is ideal for stable and stationary structures. But ultrasmall nanoparticles are intrinsically structurally unstable and may interact with the incident electron beam, constraining the electron beam density that can be used and the duration of the observation. Here we use aberration-corrected scanning transmission electron microscopy, coupled with simple imaging simulation, to determine with atomic resolution the size, three-dimensional shape, orientation and atomic arrangement of size-selected gold nanoclusters that are preformed in the gas phase and soft-landed on an amorphous carbon substrate. The structures of gold nanoclusters containing 3096 atoms can be identified with either Ino-decahedral, cuboctahedral or icosahedral geometries. Comparison with theoretical modelling of the system suggests that the structures are consistent with energetic considerations. The discovery that nanoscale gold particles function as active and selective catalysts for a variety of important chemical reactions has provoked much research interest in recent years. We believe that the detailed structure information we provide will help to unravel the role of these nanoclusters in size- and structure-specific catalytic reactions. We note that the technique will be of use in investigations of other supported ultrasmall metal cluster systems.     

纳米尺寸非晶氮化硅结构模型研究

根据晶态和非晶态氮化硅原子的相关性结构特征，构造出了正四面体Ｎ结构和平面三角形Ｓｉ结构相互嵌套的基本结构单元，模拟出了纳米量级非晶氮化硅的结构模型，其主要结构参数与实验吻合，这种模型可进一步用于非晶和纳米非晶氮化硅材料的结构和性能研究之中．     

金纳米微粒晶格畸变和结合能的尺寸形状效应

利用紧束缚分子动力学的方法,模拟了球形和立方体金纳米微粒的最近邻原子间距以及结合能. 研究表明,原子数为108, 256的立方体纳米微粒的稳定结构是非晶态,而其他尺寸的球形和立方体形微粒则是面心立方结构. 对于晶态结构,在一定的形状下,金纳米微粒的最近邻原子间距以及结合能随着微粒尺寸的减小而降低;而在微粒原子数一定时,球形金纳米微粒的最近邻原子间距以及结合能的变化量分别要小于立方体形微粒的相应变化量. 由于晶体-非晶转变对于最近邻原子间距的影响非常明显,因此最近邻原子间距可以作为晶态和非晶态纳米微粒的一个判据. 通过线性拟合模拟数据, 定量地给出了形状对于最邻近原子间距变化量的贡献为总变化量的2%,而对于结合能的贡献为总变化量的15%. 本文模拟的最近邻原子间距的数值与文献上报道的实验结果符合得很好.     

Self-supported amorphous nanoporous nickel-cobalt phosphide catalyst for hydrogen evolution reaction

Hydrogen evolution reaction(HER) through electrocatalysis using cost-efficient and long-term stable bimetallic phosphide as electrocatalyst holds a great promise for sustainable clean energy technologies. In this study, self-supported nanoporous Ni-Co-P(np-Ni-Co-P) catalyst with amorphous structure was synthesized by utilizing a facile electrochemical dealloying strategy. The results showed that due to the nanoporous structure, disorder atomic arrangement and alloying effect, the np-Ni-Co-P exhibited outstanding electrocatalytic performance for HER with low overpotential of 114 m V at a current density of 10 mA cm~2, small Tafel slope(57.3 mV dec~(-1)) and good long-term durability in 1 M KOH. The synergetic effect of Ni and Co elements improves the intrinsic activity of the active sites. This research provides a direction for the exploration of bimetallic phosphides toward HER in the water splitting process.     

Solid solution or amorphous phase formation in TiZr-based ternary to quinternary multi-principal-element films

TiZr-based multicomponent metallic films composed of 3–5 constituents with almost equal atomic concentrations were prepared by cosputtering of pure metallic targets in an Ar atmosphere.X-ray diffraction was employed to determine phase composition,crystalline structure,lattice parameters,texture and crystallite size of the deposited films.The deposited films exhibited only solid solution(fcc,bcc or hcp) or amorphous phases,no intermetallic components being detected.It was found that the hcp structure was stabilized by the presence of Hf or Y,bcc by Nb or Al and fcc by Cu.For the investigated films,the atomic size difference,mixing enthalpy,mixing entropy,Gibbs free energy of mixing and the electronegativity difference for solid solution and amorphous phases were calculated based on Miedema’s approach of the regular solution model.It was shown that the atomic size difference and the ratio between the Gibbs free energies of mixing of the solid solution and amorphous phases were the most significant parameters controlling the film crystallinity.     

Folded-chain lamellae interphase in flexible polymers

In a semicrystalline aggregate of flexible chain polymers, a large amount of the adjacent regularly-folded tiny lamellae coexists with the amorphous phase whose chains have only random spatial arrangement. This 'crystalline-noncrystalline' two-phase model has been widely accepted and used to describe the structure and properties of polymers in condensed state. The crystalline morphology of PE prepared by various methods have been     

非晶铁结构的分形特征

引用分形概念研究了非晶铁模形的结构特征,用测度关系求分维的方法考察了模型中原子的分布后发现,非晶铁的结构为统计自相似结构,其分维值介于2～3之间,同时,还发现分维值随压力而变化,分维D呈下降→增长→再下降→再增长的趋势变化,整体上呈缓慢增长之势。     

W/SiC纳米多层膜的调制结构及调制界面

采用XRD和HREM技术研究了多靶磁控溅射法制备的W／SiC纳米多层膜的微结构，结果表明，在多层膜中，SiC调制层为非晶态；W调制层在大调制周期时为纳米晶，随调制周期减小逐渐转变为非晶态，W／SiC纳米多层膜的调制结构界面平直，清晰，周期性好，而在原子尺度上，界面存在一个成分混合和结构调整的过渡区。     

玻璃转变时非晶合金微观结构演变的新进展

在玻璃转变时,金属玻璃只吸收少量热量(与结晶化相比)却引起其物理和力学性能的巨大变化.为了研究玻璃转变时的原子结构演变,采用原位同步辐射X射线的方法测定了在温度连续变化的情况下Zr-Cu-Al金属玻璃的结构函数.纵观本研究:该材料原子级的热膨胀比宏观热膨胀要小,而且在玻璃转变温度以上时明显增大;超过玻璃转变温度时,最近邻原子对中键长较长的原子对数量的变化率!N/N0(N0代表原子对的数量)明显变大.此类现象既可以用我们建立的过渡区链接团簇的非晶原子结构模型解释,又有力地支持此模型.该模型包含三个主要部分:1)原子紧密结合的团簇;2)团簇之间的自由体积;3)连接团簇的过渡区.