杂质P对α-Fe中刃型位错上扭折电子结构的影响

利用离散变分方法和DMol方法,研究了P对bcc Fe中［100］(010)刃型位错上扭折电子结构的影响,计算了杂质偏聚能、原子间相互作用能、电荷密度及态密度.计算结果表明：微量P引入体系后,电荷发生了重新分布,P原子得到电子,其周围Fe原子失去电子,由于P原子的3p轨道与近邻Fe原子的3d4s4p轨道之间杂化,使P原子与近邻Fe原子间有较强的相互作用,不利于扭折的迁移,使位错运动受阻,有利于材料强度的提高.同时,杂质P原子与基体原子间的成键主要是d,p轨道起作用,使得它们之间的成键有较强的方向性,有可能 关键词： 电子结构 刃型位错 扭折 杂质元素     

镍基单晶高温合金γ/γ′（001）相界面上原子构型的分子动力学研究

用分子动力学方法研究了镍基单晶高温合金γ/γ′（001）相界面上三种各具特征的原子堆垛结构. 能量学计算发现，存在最优构型，动力学模拟显示不同构型的界面弛豫后，在相界面上都“成对”出现刃型错配位错. 相关计算表明体系能量、界面形成能及弛豫能都依赖于界面原子堆垛特征，而几何特征则具共性，即不同原子构型的界面具有同一的应力释放模式.     

塞曼石墨炉原子吸收法测定水产品中的铬

研究了石墨炉原子吸收法测定的方法 ,对多种方法比较研究得出 ,样品经过干法灰化 ,以硝酸溶解未消解完全的样品 ,用硝酸镁作基体改进剂 ,利用塞曼扣背景技术 ,热解平台石墨管进行测定 ,线性范围为2 .5— 5 0 μg·L-1,回收率为 90 %— 10 3% ,相对标准偏差为 6 .8%。     

界面反射光的偏振态分析

首先利用菲涅尔反射公式,给出界面反射光s分量和p分量的光强反射率公式.然后分析并推导出自然光和部分偏振光分别入射介质界面时,反射形成的部分偏振光偏振度的一般表达式.对反射光偏振度的模拟分析表明,当自然光入射时,随入射角增加反射光的偏振度先增大后减小.当部分偏振光入射时,若Is>Ip,随入射角增加反射光的偏振度也是先增加...     

纳米结构SmCo/FeCo多层薄膜的磁性

研究了用磁控溅射方法制备的纳米结构Sm₂₂Co₇₈单层膜、Sm₂₂Co₇₈/Fe₆₅Co₃₅双层膜及Sm₂₂Co₇₈/Fe₆₅Co₃₅/Sm₂₂Co₇₈三层膜的磁性,特别是双层膜及三层膜系统中的Fe₆₅Co₃₅软磁层厚度d对薄膜剩磁比(M_r/M_s)和矫顽力(H_c)的影响.所有样品的磁滞回线测量表明,该系列薄膜的易磁化轴在膜面内.磁滞回线的单一硬磁相特征,说明SmCo硬磁层与FeCo软磁层之间的交换相互作用使两相很好地复合在一起.在双层膜和三层膜中,M_r/M_s随软磁层厚度d的增加单调上升,而矫顽力随d的变化出现一峰值.通过研究ΔM随磁场H的变化,发现随着软、硬磁相界面数的增加,ΔM曲线的正峰数量逐渐减少;负峰数量逐渐增强,负峰的半高宽逐渐减少. 关键词：     

Site preferences of alloying transition metal elements in Ni-based superalloy: A first-principles study

Atomistic characterization of chemical element distribution is crucial to understanding the role of alloying elements for strengthening mechanism of superalloy. In the present work, the site preferences of two alloying elements X -Y in γ-Ni of Ni-based superalloy are systematically studied using first-principles calculations with and without spin-polarization. The doping elements X and Y are chosen from the 27 kinds of 3 d, 4 d, 5 d group transition metals(Sc, Ti, V, Cr, Mn, Fe, Co,Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au) and Al. We find that the spin-polarized calculations for Re-Re, Re-Ru, Re-Cr, Ru-Cr show a strong chemical binding affinity between the solute elements and are more consistent with the experimental results. The binding energies of pairs between the 28 elements have an obvious periodicity and are closely related the electronic configuration of the elements. When the d-electrons of the element are close to the half full-shell state, two alloying elements possess attractive binding energies, reflecting the effect of the Hund's rule. The combinations of early transition metals(Sc, Ti, V, Y, Zr, Nb, Hf, Ta) have a repulsive interaction in γ-Ni. These results offer insights into the role of alloying elements for strengthening mechanism of superalloy.     

Morphologies of epitaxial islands on a lattice-misfitted substrate

Under certain growth conditions for systems with a film/substrate lattice misfit, the deposited material is known to aggregate into island-like shapes. We have obtained an analytical expression of the total free energy, which consists of strain energy, surface energy and interfacial energy of a coherent island/substrate system, and the change of equilibrium aspect ratio versus the volume of the island and the misfit of lattices in the system, which provides a broad perspective on island behaviour. These then were used to study the equilibrium shapes of the system. The results show that in order to minimize the total free energy, a coherent island will have a particular height-to-width aspect ratio, called equilibrium aspect ratio, that is a function of the island volume and misfit. The aspect ratio is increased with increasing island volume at a fixed misfit, and with increasing misfit strain between the island and substrate at a fixed island volume. Moreover, the effect of misfit dislocation on the equilibrium shape of the island is also examined. The results obtained are in good agreement with experiment of observations and thus can serve as a basis for interpreting the experiments.     

The ternary Ni–Al–Co embedded-atom-method potential for γ/γ Ni-based single-crystal superalloys: Construction and application

An Ni–Al–Co system embedded-atom-method potential is constructed for the γ(Ni)/γ(Ni3Al) superalloy based on experiments and first-principles calculations. The stacking fault energies(SFEs) of the Ni(Co, Al) random solid solutions are calculated as a function of the concentrations of Co and Al. The calculated SFEs decrease with increasing concentrations of Co and Al, which is consistent with the experimental results. The embedding energy term in the present potential has an important influence on the SFEs of the random solid solutions. The cross-slip processes of a screw dislocation in homogenous Ni(Co) solid solutions are simulated using the present potential and the nudged elastic band method. The cross-slip activation energies increase with increasing Co concentration, which implies that the creep resistance of γ(Ni)may be improved by the addition of Co.     

bcc Fe中刃型位错的结构及能量学研究

基于位错理论，利用分子动力学方法建立了〈100〉{010}，〈100〉{011}，1/2〈111〉{011}和1/2〈111〉{112}刃型位错的芯结构，并计算了这四种刃型位错的形成能、位错芯能量和芯半径.计算结果表明：〈100〉{010}和〈100〉{011}刃型位错的形成能比1/2〈111〉{011}和1/2〈111〉{112}刃型位错的要高，这表明〈100〉刃型位错比1/2〈111〉刃型位错更难形成.而〈100〉{010}和〈100〉{011}刃型位错的芯半径比1/2〈111〉{011}和1/2〈111〉{112}刃型位错的小，这说明在1/2〈111〉刃型位错中位于奇异区的原子数多于〈100〉刃型位错，而这些原子要比完整晶体中的原子具有更大的活性.可见，1/2〈111〉刃型位错比〈100〉刃型位错更易运动，且〈100〉刃型位错在bcc Fe中难以形成. 关键词： bcc Fe 刃型位错 分子动力学模拟     

铂原子高激发态能级自然辐射寿命测量研究

运用时间分辨激光诱导荧光技术和激光诱导等离子体方法测量了铂原子的15条奇宇称高激发态能级的自然辐射寿命．测量结果处于6.1到116 ns之间,且误差低于10%．经比较,与前人结果在误差范围内符合很好．据文献调研所知,结果中有5条高度接近60000 cm−1的高激发态能级的寿命值是未见报道的．