Neutron Diffraction Measurements of a Thermally Fatigued Single Crystal Superalloy

The thermally fatigued single crystal superalloy DZ125L is investigated by neutron diffraction measurements. The measurements, made using the φ angle oscillating method, provide more detailed and reliable data than those with the φ angle fixed. Diffraction studies show that the influence of thermal fatigue on the lattice parameters of the alloy is very limited. The stress analysis reveals that triaxial elastic hydrostatic stress plays a major role during thermal fatigue. The magnitude of the macrostress increases with the fatigue cycles, with the stress of the γ, phase increasing more significantly than that of the γ＇ phase, and becoming fragile after many cycles. The changes in the microstrain are dependent on the reflection planes. The microstrains at the center of the sample are released by the thermal fatigue in comparison with those at the outlying locations, which has been attributed to the advance of the dislocation slips.     

A New Approach of Quantum Mechanics for Neutron Single-Slit Diffraction

Phenomena of electron, neutron, atomic and molecular diffraction have been studied in many experiments, and these experiments are explained by many theoretical works. We study neutron single-slit diffraction with a quantum mechanical approach. It is found that the obvious diffraction patterns can be obtained when the single- slit width a is in the range of 3λ - 60λ. We also lind a new quantum effect of the thickness of single-slit which can make a large impact on the diffraction pattern. The new quantum effect predicted in our work can be tested by the neutron single-slit diffraction experiment.     

变栅距光栅的衍射实验仿真

依据多缝夫琅禾费衍射的基本原理,对一种平面变栅距光栅的光强分布作出了理论分析,导出了光强分布公式。用Matlab软件对变栅距光栅的衍射进行了模拟仿真研究,通过改变栅距变化系数和起始栅距的值,得出了在不同条件下的衍射谱线特征。该计算结果和研究方法在实际的变栅距光栅应用中具有参考价值,为变栅距光栅参数的设计和优化提供了理论依据。     

一光学极值问题

当前高考改革的大趋势已见端倪,其中考查学生的综合应用能力成为重中之重.许多综合题一改往日纯粹用于应试的面目,而更多的代之以丰富的物理情景为载体,来考查学生建构物理模型,分析、解决问题的能力.笔者以从日常生活常见现象中抽象出来的一几何光学极值问题为背景,更加形象地对物理教学作一点探索.     

Investigation of Plastically Deformed TRIP-Composites by Neutron Diffraction and Small-Angle Neutron Scattering Methods

The main parameters of the microstructure of TRIP (TRansformation Induced Plasticity) composites with an austenitic matrix and a ZrO₂ zirconium-dioxide reinforcing phase subjected to plastic deformation of different degrees (compressive uniaxial load) are studied by neutron diffraction and small-angle neutron scattering. A series of composite material samples with different contents of the ZrO₂ ceramic phase (0, 10, 20, 30, and 100 wt %) are prepared by the powder metallurgy method using hot pressing. In the region of plastic deformation at load values above 650 MPa, two phases are observed in the austenitic matrix: cubic α'-martensite and hexagonal ε-martensite. Data on the lattice strains of the observed phases, dislocation density in the austenitic matrix, and characteristic sizes of the martensitic-phase particles are obtained.     

利用金属筛网拓展光栅衍射实验

为拓展大学物理实验中光栅衍射实验的内容,使其更贴近生活,实验现象形式多样,利用生产生活中常用的金属筛网作为二维光栅设计实验内容。通过筛网的衍射,可直观地观察到二维光栅的衍射现象,并分析了不同衍射图像产生的原因。通过两种不同的方案测量衍射角,从而计算出筛网的关键参数-网孔尺寸。     

Neutron Diffraction Study of the p - T Phase Diagram for Erbium

Electrical resistivity measurements performed on a single crystal of erbium as a function of temperature and hydrostatic pressure have provided a preliminary p - T phase diagram. The results have been interpreted in terms of a model for the magnetic structures of Er deduced from neutron diffraction studies at ambient pressure. This model predicted the existence of a magnetic structure with a wave vector of Q =2/7 c * at 4.2 K, when the applied pressure is larger than 3 kbar. This paper reports a neutron diffraction study of erbium made in the temperature range of 4 to 100 K, at pressures between 0.5 and 6 kbar. We have observed the predicted suppression of the low temperature conical ferromagnetic phase and the emergence of a new phase with Q =8/33 c *. The neutron diffraction measurements has enabled us to identify the various phases that develop from the cycloidal phases previously observed at atmospheric pressure.     

干涉场的衍射实验

光是一种振动的传播.光振动可以相互叠加、形成合振动.光的干涉与衍射效应应该是光振动的叠加效应,这可以通过干涉场的衍射实验来检验.     

微波布拉格衍射实验中测量衍射极大值的新方法

介绍一种在微波布拉格衍射实验中测量模拟晶体衍射极大值的新方法.此方法是采用微波分光仪自动测试系统进行测量,并且利用绘图软件处理数据,可以同时测量简单立方模拟晶体多个晶面的衍射极大值.     

Nonstationary Diffraction of Ultracold Neutrons from a Moving Grating and Efficiency of Energy Transfer to a Neutron

Journal of Experimental and Theoretical Physics - The discrete spectrum of ultracold neutrons (UCNs) diffracting from a moving grating has been measured using a time-of-flight Fourier spectrometer....     

点光源的Fresnel圆孔衍射的实验研究

通过实验观察到衍射图样的中心可亮可暗,用Huggens—Fresnel原理加以分析、解释,通过分析总结出圆孔衍射图样的中心光强的变化规律,根据实验结果提出了对教材的修改建议．     

Neutron Diffraction of Large-Volume Samples at High Pressure Using Compact Opposed-Anvil Cells

Neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China's Mianyang research reactor. We achieve a high-pressure condition of in situ neutron diffraction by means of a newly designed large-volume opposed-anvil cell. This pressure calibration is based on resistance measurements of bismuth and the neutron diffraction of iron. Pressure calibration experiments are performed at room temperature for a new cell using the tungsten carbide anvils with a tapered angle of 30°, Φ4.5 mm culet diameter and the metal-nonmetal composite gasket with a thickness of 2 mm. Transitions in Bi(Ⅰ–Ⅱ 2.55 GPa, Ⅱ–V 7.7 GPa) are observed at 100 and 300 kN, respectively, by resistance measurements.The pressure measurement results of neutron diffraction are consistent with resistance measurements of bismuth.As a result, pressures up to about 7.7 GPa can routinely and stably be achieved using this apparatus, with the sample volume of 9 mm~3.     

Mössbauer and Neutron Diffraction Studies on Co–Al Ferrite

Hyperfine Interactions - Al substituted CoAl x Fe1?x O4 (x=0.1, 0.2, 0.3, and 0.5) have been studied with X-ray and neutron diffraction, Mössbauer spectroscopy and magnetization...     

中子检测爆炸物的原理实验研究

传统的X射线无损检测应用广泛, 但X射线对低原子序素构成为主的爆炸物不能进行有效的甄别; 中子穿透能力较强, 能和原子核相互作用产生特征γ射线, 因此中子无损检测方法能有效弥补X射线无损检测方法的不足。 介绍了几种常用的中子无损检测方法, 并采用脉冲快热中子法（为PFTNA）的方法对模拟爆炸物进行了测量。 实验结果表明, 利用密封中子发生器和采用PFTNA方法进行爆炸物检测是可行的。 Traditional X ray scatheless detecting method is used widely, but it is not useful to discriminate explosive consisting of low Z atomic elements. The penetrability of neutron is much better, and it can interact on atomic nucleus to emit characteristic γ ray. So neutron scatheless detecting methods can the used to detect the low Z atomic elements. In this paper, several neutron scatheless detecting methods are introduced briefly, and the principium experiment using Pulse Fast Thermal Neutron Analysis(PETNA) to detect a kind of explosive simulacrum is carried out. The experiment results show that PFTNA based on the sealed neutron generator is feasible to detect explosive.     

从双缝实验看干涉和衍射的本质

以双缝为例,从装置图、实验照片和光强度分布入手,讨论了双缝干涉与双缝衍射的区别和联系,从而较深入地探讨了光波干涉与衍射的本质.     

Neutron Spin Rotation at Laue Diffraction in a Weakly Deformed Transparent Crystal with No Center of Symmetry

Journal of Experimental and Theoretical Physics - The effect of neutron spin rotation at Laue diffraction in a weakly deformed neutron-transparent noncentrosymmetric crystal has been described...     

激光单缝衍射测量实验的两点改进

分析了目前激光单缝衍射光强分布测量中存在的问题,给出了两点改进的测量方法:一点测量技术上的改进和一点实验仪器上的改进更新。用改进后的实验仪器较好地测量得到各级明条纹的光强分布。实验测量结果与夫琅和费衍射理论模拟结果吻合较好。     

Compressive Behavior of TATB Grains inside TATB-Based PBX Revealed by In-Situ Neutron Diffraction

We investigate the(002)lattiee strain evolution of triaminotrinitrobenzene(TATB) grains inside one TATB-based plastic bonded explosive(PBX) through the in-situ neutron diffraction. By comparing the untreated specimen with the thermal-treated one, it is found that the volume-average response of measured TATB grains remains nearly elastic during quasi-static uniaxial compression. The observed changes in TATB(002) lattice strains correlate tightly with the evolution of damage. A damage parameter defined by the macroscopically determined residual strain is further used to describe the damage degree of PBX, which suggests that the compressive behavior of TATB-based PBX is significantly influenced by the damage evolution.     

夫琅禾费单缝衍射实验的仿真研究

根据夫琅禾费单缝衍射理论,应用MATLAB软件编程,对衍射过程进行仿真,作出单缝衍射光强分布图形,通过改变光的波长、入射方向、缝宽和焦距,观察到单缝衍射光强分布的变化规律.