A_Ⅰ型多元固溶体价电子结构的计算

利用“固体与分子经验电子理论”提出:1)A(?)型多元置换、间隙式固溶体价电子结构计算的模型;z)末知键距结构的键距差(BLD)分析方法;3)BLD分析中解的不唯一性的处理。     

陶瓷材料的原子复合与固溶强化

陶瓷材料的制备技术正在朝着更加精细和更加微观可控的方向发展,继纳米复合后,原子和分子尺度的复合技术将受到关注,陶瓷材料的固溶强化将成为２１世纪提高材料性能的主要方法之一,收集了陶瓷材料的固溶强化的部分实例,归纳了陶瓷材料原子复合的基本方法,旨在提醒陶瓷学界更加重视固溶技术的作用。     

TixCrFeCoNiAl多组元固溶体合金系的力学性能及其强化机

依据等原子比和高混合熵的合金设计理念制备TixCrFleCoNiAl多组元圃溶体合金系,研究了该合金系的室温压缩力学性能和显微硬度,并对其强化机制进行了探讨.结果表明:TixCrFeCoNiAl合金系具有很高的强度和优异的综合力学性能,其中T1合金的屈服强度、断裂强度和塑性变形量分别高达2.259 Gpa、3.135 Gpa和23.22%;该合金系具有很高的显微硬度,且随着Ti含量的提高而近线性地提高,T3合金的显微硬度达到HV768;固溶强化机制、纳米相弥散强化机制和品格畸变效应使合金系具有很高的强度和显微硬度.     

TixCrFeCoNiAl多组元固溶体合金系的力学性能及其强化机制

依据等原子比和高混合熵的合金设计理念制备TixCrFeCoNiAl多组元固溶体合金系,研究了该合金系的室温压缩力学性能和显微硬度,并对其强化机制进行了探讨.结果表明：TixCrFeCoNiAl合金系具有很高的强度和优异的综合力学性能,其中Tl合金的屈服强度、断裂强度和塑性变形量分别高达2.259 GPa、3.135 GPa和23.22%;该合金系具有很高的显微硬度,且随着Ti含量的提高而近线性地提高,T3合金的显微硬度达到HV768;固溶强化机制、纳米相弥散强化机制和晶格畸变效应使合金系具有很高的强度和显微硬度.     

PtSi的价电子结构

利用固体与分子经验电子理论（ＥＥＴ）理论计算了ＰｔＳｉ的价电子结构。并利用Ｘ身线光电子谱（ＸＰＳ）分析了ＰｔＳｉ薄膜中阶电子的能谱。结果表明,Ｐｔ和Ｓｉ化合形成ＰｉＳｉ以后,Ｓｉ和Ｐｔ的杂阶均向较低杂阶方向移动,化合物中含有较高密度的晶格电子,使ＰｔＳｉ具有良好的导电性。Ｘ射线光电子谱测试结果表明,ＰｔＳｉ中价电子的能谱向高结合能方向移动,Ｐｔ的５ｄ电子是化合物中重要的成键电子。     

高熵合金固溶强化问题的研究进展

区别于传统的合金材料,高熵合金没有溶质溶剂概念的划分.多主元成分配比造成的晶格畸变、尺寸错配等使高熵合金表现出显著的固溶强化效应,因而可获得优异的力学强度.然而,经典合金固溶强化理论中关于稀释溶质的假设并不适用于高熵合金,相关强化模型无法有效预测其力学强度,这阻碍了高熵合金成分的理性设计及相关应用.近年来,基于高熵合金的成分特点,人们不断探究其固溶强化的起源,尝试建立有效的预测模型,实现合金强度的准确预测,进而指导面向性能需求的高熵合金快速设计,最终推动高熵合金的科学研究和工程应用.本文总结了高熵合金固溶强化问题的研究进展,介绍了三种典型的固溶强化模型,对比分析了各模型的建模思路、预测效果、存在问题及在高熵合金设计中的具体应用,最后对高熵合金固溶强化机制的探索、强化模型的发展及应用进行了展望.     

TiC-Mo-Fe体系价电子结构的模拟计算

以EET理论为基础,通过建立TiC-Mo-Fe体系金属陶瓷结构模型,分别计算了陶瓷相TiC、环形相(Ti1-xMox)C和金属相Fe的价电子结构,并在此基础上计算了各相间界面原子状态的变化和界面结合情况,以及环形相理论晶格常数值.结果表明:环形相的存在能使金属/陶瓷两相原子状态的突变差异形成渐变过渡;计算获得的环形相的晶格常数对Mo的掺入量不敏感,在x取不同值时仅有很小的变化,相对误差不超过1.2%,环形相与TiC间的原子状态差异非常小,二者界面结合良好;环形相与Fe界面结合明显强于TiC与Fe的界面结合,并且当x=0.5时,这种界面结合最强.     

W—Ni—Cu重合金不平衡凝固与固溶强化

利用电子探针的Ｗ－Ｎｉ－Ｃｕ重合金不平衡凝固与固溶强化进行研究，表明了Ｗ－Ｎｉ－Ｃｕ重合金的断口静貌，微观组织的结构与力学性能，密度有密切关系，阐述了合金断裂的机理，提出了改进合金性能的方法。     

Np,Pu和Am氧化物的价电子结构研究

本文应用ＥＥＴ理论和三价锕系元素的单键半径Ｒ计算公式及杂阶表，对ＮｐＨ３，ＰｕＨ３和ＡｍＨ３等氢化物进行了价电子结构分析。结果表明：每种氢化物都存在六种主要键，键距差ΔＤ〈０．０５，在允许误差范围之内，强键分别为Ｈ１－Ｐｕ，Ｈ１－Ｎｐ和Ｈ１－Ａｍ。研究结果为三价锕系元素氢化物的性能分析可提供价电子结构方面的基本数据。     

强化固溶对含Sc超高强铝合金组织性能的影响

为了提高含Sc超高强Al-Zn-Cu-Mg-Zr合金的固溶程度,减少未溶结晶相的数量,用极差分析方法对强化固溶处理制度进行了优化.采用拉伸试验、金相和透射电镜分析、扫描电镜观察和能谱分析等方法研究了强化固溶对合金力学性能和组织的影响.结果表明,与常规固溶相比,强化固溶后合金的屈服强度和抗拉强度分别提高了28MPa和18MPa,合金的断口形貌呈现晶内韧窝与沿晶破裂的混合断裂,强化固溶后合金的力学性能有所改善,残余的第二相数量明显减少,η′析出相也更细小、弥散.     

Ni2 MnGa合金的价电子结构研究

用“固体与分子经验电子理论”研究了Ni2MnGa合金的价电子结构,研究结果表明,在Ni2MnGa中,Ni的杂化状态为A'种杂化第2阶;Mn的杂化状态为B种杂化第9阶,Ga为A种第9阶杂化。Ni的原子磁矩计算值为3.8666μB十分接近。最强的共价键是Ni-Mn键,其上的共价电子对数为0．577,其次为Ni-Ga键,其价电子对数为0．542,其它键上的共价电子对数小于0．2。     

蒙脱土的价电子结构与其同晶置换

为研究蒙脱土结构与其性能的关系,根据蒙脱土的晶体结构,设定其结构单元,运用"固体与分子经验电子理论(EET)"对蒙脱土的价电子结构进行计算.研究表明:与理想蒙脱土相比,八面体中0.66个铝被镁同晶置换后蒙脱土结构单元的结合能基本不变,且与氧桥相连的四面体和八面体中主要键的共价电子分布差距变小;蒙脱土3个亚层之间的作用力比片层之间的分子间作用力大两个数量级,证明了蒙脱土的3个亚层结构稳定;在极性介质中可以改变蒙脱土片层间距,但其3个亚层不易分离.     

快凝Al-Fe-V-Si-Nd合金中纳米相穆斯堡尔谱的介电子结构分析

测量了快凝Ａｌ－Ｆｅ－Ｖ－Ｓｉ－Ｎｄ合金在６４８Ｋ热处理前后的穆斯堡尔谱。依据固体与分子经验电子理论（ＥＥＴ）,计算了快凝Ａｌ－Ｆｅ－Ｖ－Ｓｉ－Ｎｄ合金中Ａｌ８Ｆｅ４Ｎｄ相的介电子结构,并建立了Ｆｅ与近邻原子的空间键络。通过与α－Ａｌ３（Ｆｅ,Ｖ）３Ｓｉ相中Ｆｅ原子的价电子的价电子结构的比较分析,从键络的微观角度出发初步探讨了Ａｌ－Ｆｅ－Ｖ－Ｓｉ－Ｎｄ合金在相变前后穆斯堡尔谱参数变化的原因。     

A model of valence electron structure for embrittlement of TiAl

In this paper, the valence electron structure and embrittlement of TiAl are studied theoretically based on the empirical electron theory (EET). From the viewpoint of the EET, a model for the space topographic distribution of valence electron structure is proposed. This model can be used to simply explain the embrittlement of TiAl and could be extended to other intermetallic compounds.     

Microstructure and mechanical properties of Ti-based solid-solution cermets

The microstructure and mechanical properties of various (Ti_1−xW_x)C-20 wt.%Ni cermets were investigated, where x varies from 0.07 to 0.3. Homogeneous solid-solution (Ti_1−xW_x)C powders were prepared by carbothermal reduction via planetary milling of Ti, TiO₂, WO₃ and carbon powder mixtures. The cermets made of the powders showed a simple core-rim structure consisting of solid-solution carbides. The hardness of the solid-solution cermets is somewhat lower than that of conventional cermets, but they show greater toughness. The transverse rupture strength increases with increasing W content.     

About copper valence and superconductivity

We describe the copper valence in superconductors based on our arguments on La₂O₃ crystal structure. In order to explain the two oxygen sites in La₂O₃, it has been supposed that O _II ¹⁻ ions occupy the tetrahedral site while O _II ²⁻ occupy the octahedral site. Oxygen ions in tetrahedral site form a covalent bond with lanthanum, which can be written [LaO]¹⁺. Considering the chemical and crystallographic properties of Tl and Bi compounds, [TlO]¹⁺ and [BiO]¹⁺ groups appear as defined by strong covalent bonds between Bi or Tl and O. This leads to the supposition that the four oxygen ions which coordinate to copper in Tl and Bi copper oxide-based superconductors are O _II ¹⁻ ions. The bivalent character of copper is then obtained through covalent bonds. For La_2−x Sr _x O₄ compounds, copper is supposed to have valence three, but spectroscopic studies point out bivalent copper. We show that krypton shell of Sr is responsible for the lack of one unit of valence as expected from krypton compounds for example KrF₂.     

Atomic-level heterogeneity and defect dynamics in concentrated solid-solution alloys

Performance enhancement of structural materials in extreme radiation environments has been actively investigated for many decades. Traditional alloys, such as steel, brass and aluminum alloys, normally contain one or two principal element(s) with a low concentration of other elements. While these exist in either a mixture of metallic phases (multiple phases) or in a solid solution (single phase), limited or localized chemical disorder is a common characteristic of the main matrix. Fundamentally different from traditional alloys, recently developed single-phase concentrated solid-solution alloys (CSAs) contain multiple elemental species in equiatomic or high concentrations with different elements randomly arranged on a crystalline lattice. Due to the lack of ordered elemental arrangement in these CSAs, they exhibit significant chemical disorder and unique site-to-site lattice distortion. While it is well recognized in traditional alloys that minor additions lead to enhanced radiation resistance, it remains unclear in CSAs how atomic-level heterogeneity affects defect formation, damage accumulation, and microstructural evolution. These knowledge gaps have acted as roadblocks to the development of future-generation energy technology. CSAs with a simple crystal structure, but complex chemical disorder, are unique systems that allow us, through replacing principal alloying elements and modifying concentrations, to study how compositional complexity influences defect dynamics, and to bridge the knowledge gaps through understanding intricate electronic- and atomic-level interactions, mass and energy transfer processes, and radiation resistance performance. Recent advances in defect dynamics and irradiation performance of CSAs are reviewed, intrinsic chemical effects on radiation performance are discussed, and direction for future studies is suggested.     

Effect of the W addition content on valence electron structure and properties of MoSi2-based solid solution alloys

Based on the empirical electron theory (EET) of solids and molecules, the valence electron structures (VES) of MoSi₂-based solid solution alloys have been analyzed using the average atom model. The results showed that with the increase of the W addition content, the hybridization steps of Mo and Si atom of the alloys occurred in C3 and 1, respectively. The hybridization step of W was always C5. The bond energy of the main bond branch, the covalence electron number on the strongest bond and the percentage of the total covalent electron numbers accounting for the total valence electron number of (Mo_1−x, W_x)Si₂ solid solutions increased with the increase of W addition content. These suggested that the addition of W would increase the melting point, hardness and strength and decrease the fracture toughness of (Mo_1−x, W_x)Si₂ solid solutions. Based on those results, MoSi₂-based solid solution alloys were manufactured, and the results of the experiments were in accordance with those of the theory.     

金属滑移面的价电子结构特性

为在价电子结构层次分析和研究A1型与A2型结构滑移面问题,以“固体与分子经验电子理论”为指导,计算了A1型与A2型结构的低指数晶面的价电子结构,提出了表征晶体沿晶面发生滑移难易的价电子结构参数F及其计算方法．研究结果表明,在A1型结构中,{111}面的F值最小,在Az型结构中,{110}面的F值最小,并以此解释了A1型与A2型结构滑移面分别为{111}与{110}这一金属学问题,从而把滑移面的本质追溯到金属平面的价电子结构上．     

固溶处理对AM60B＋xRE及AZ9lD＋xRE镁合金性能的影响

研究了添加少量富铈混合稀土的AM60B xRE及AZ9lD xRE合金(x＝0．4、0．8、1．2、1．6和2．0％，质量分数)固溶处理后的显微组织与机械性能．结果表明，添加混合稀土能显著提高合金的抗拉强度σb和屈服强度σ0.2，固溶处理明显提高AZ9lD xRE合金的强度；AM60B xRE及AZ9lD xRE合金的铸态组织由α(Mg)固溶体、杆状Al11RE3相、颗粒状Al10Ce2Mn7相以及网状Mg17Al12相组成，经过固溶处理后，网状Mg17Al12相完全溶解，只剩下热稳定性较高的Al11RE3相和Al10Ce2Mn7相，随固溶时间的延长，其形态略有改变．AM60B xRE合金拉伸试样断口呈带局部韧窝的准解理断裂形式，而AZ9lD xRE合金则呈现沿晶断裂 解理断裂的混合断口形态．