Theoretical investigation of the crystallographic structure,anisotropic elastic response,and electronic properties of the major borides in Ni-based superalloys

ABSTRACT

In Ni-based superalloys, it is usually found that borides can strengthen the grain boundaries, thereby resulting in an increase in mechanical strength and high-temperature creep properties. Due to their importance and prevalence in Ni-based superalloys, this study employs first-principles methods to investigate the crystallographic structure, anisotropic elastic response, and electronic properties of the major borides, such as M₂B, M₅B₃ and M₃B₂ (M: Cr, Mo, W), respectively, which is necessary for the assessment of complex mechanical responses of Ni-based superalloys. The results demonstrate that the studied borides are all thermodynamically and mechanically stable. Among the M _x B _y binary borides analysed, Cr _x B _y exhibits the largest shear modulus, Young’s modulus, and Vicker hardness values, and these properties increase with the increase of B contents. The studied borides display nearly isotropic elastic properties except for W₅B₃ and W₃B₂. The electronic structure analysis of M _x B _y shows that the strong hybridisation between M-d and B-p orbitals leads to these borides exhibiting higher theoretical hardness, and the overlapping peaks of M-d and B-p orbitals move to a lower energy area with the increase of B contents, which leads to the increase of shear and Young’s moduli of M _x B _y . Furthermore, for M₃B₂ borides, the Cr-B bonds and Cr–Cr bonds are much stronger than the W-B & Mo-B bonds, and W-W & Mo-Mo bonds, respectively, which leads to Cr _x B _y yielding the largest values of elastic moduli.     

An improved evaluation of the neutron background in the PandaX-Ⅱ experiment

In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively.     

Polarization in D-shaped fiber modulated by magneto-optical dichroism of magnetic fluid

The polarization of a D-shaped fiber is modulated after immersing it in magnetic fluid(MF)and applying a magnetic field.Theoretical analysis predicts that magneto-optical dichroism of MF plays a key role in light polarization modulation.During light polarization modulation,the evanescent wave polarized parallel to the magnetic field has greater loss than its orthogonal component.Light polarization of a D-shaped fiber with a wide polished surface can be modulated easily.High concentration MF and a large magnetic field all have great ability to modulate light polarization.     

Accurate correction of arbitrary spin fermion quantum tunneling from non-stationary Kerr-de Sitter black hole based on corrected Lorentz dispersion relation

According to a corrected dispersion relation proposed in the study on the string theory and quantum gravity theory, the Rarita-Schwinger equation was precisely modified, which resulted in the Rarita-Schwinger-Hamilton-Jacobi equation. Using this equation, the characteristics of arbitrary spin fermion quantum tunneling radiation from non-stationary Kerr-de Sitter black holes were determined. A number of accurately corrected physical quantities, such as surface gravity, chemical potential, tunneling probability, and Hawking temperature, which describe the properties of black holes, were derived. This research has enriched the research methods and enabled increased precision in black hole physics research.     

担载型Fe2O3／ACDM催化剂用于甲醇转化反应的研究

担载型Ｆｅ＿２Ｏ＿３／ＡＣＤＭ催化剂用于甲醇转化反应的研究夏清华，陈国权，王清遐，王公慰（中国科学院大连化学物理研究所大连１１６０１２）关键词ＺＳＭ－５沸石，铁浸渍改性，甲醇转化，低碳烯烃，酸性在煤基甲醇制低碳烯烃的ＭＴＯ过程的研究中，通常是对ＺＳＭ...     

2-〔2′-(6-溴-苯并噻唑)-偶氮〕-1,8-二羟基萘-3,6-二磺酸的合成及其与钛的显色反应

本文合成了一种新的革并座隆类显色试剂—2－［2′－（6－溴－苯并噻唑）－偶氮］－1，8－二羟基萘－3，6－二磺酸（简称Br－BTCA），并研究了其与钛的显色反应。在CTMAB存在下，钛与试剂形成稳定的络合物，其ε616=1．15×105L·mol－1·cm-1，组成为Ti（Ⅳ）：R：=1：2：钛浓度在0～0．5mg／L范围内符合比尔定律，该方法灵敏度高，选择性好，并用于铝合金及硅铁试样中微量钛的测定     

流变学法研究交联聚合物凝胶的抗剪切性能

流变学法研究交联聚合物凝胶的抗剪切性能;交联聚合物;凝胶;屈服应力;流变学方法     

配位作用毛细管电泳方法研究

研究了一种以过渡金属离子为添加剂,基于配位相互作用的毛细管电泳技术。选择7种芳香胺类化合物作为分析对象,考察了金属离子种类和浓度、运行介质酸度、电压对配位毛细管电泳的影响。通过对邻苯二胺变质样品的鉴别以及实际合成药磺胺类药物的分离,考察了这种毛细管电泳分离技术的分离能力,效果令人满意。应用于颠茄磺苄啶片中磺胺甲噁唑(SMZ)的定量测定时,SMZ的检出限为0.12 mmol/L;线性范围为0.25~10 mmol/L(r2=0.9917);平均加样回收率为97.8%,表明所建立的配位作用毛细管电泳(C ICE)方法,具有稳定、可靠的定性和定量分析能力。     

农作物秸秆解聚研究

农作物秸秆是重要的生物质资源。本文从我国建立资源节约和环境友好社会目标的角度,论述了农作物秸秆高效利用的重要性和研究农作物秸秆解聚对开发农作物秸秆高效利用的新工艺的重要意义。介绍了农作物秸秆解聚的典型工艺及解聚产物组成分析和利用研究的进展,预测了农作物秸秆解聚研究的发展方向。     

Sr2YRuO6有序双钙钛矿结构及其Mott绝缘体的研究

运用第一性原理方法对双钙钛矿Sr2YRuO6各种可能的无序结构和有序结构的能量进行计算,计算结果显示有序结构双钙钛矿具有最低能量,说明该结构最稳定,这一结果也与实验中样品的多晶样品X射线衍射图(XRD)中出现超晶格有序峰相符合。通过计算给出该材料的能带,显示该材料是Mott绝缘体,这一结论也与实验结果相一致。