摘要:

Quantitative liquid‐structure analysis using energy‐scanning diffraction rather than the traditional angle‐scanning diffraction is introduced. In the experimental method, white radiation and a solid‐state detector are employed. This new method is inherently faster and less beset with problems of experimental instability than are angular‐scanning methods. However, many differences in analysis are introduced. In particular, measurement of the primary beam spectrum, the nature of the absorption and dispersion corrections, details of the polarization correction, the ranges of the atomic scattering factor and of the incoherent scattering term, and the mating of different scattering regimes all require special consideration. Application of the new instrumental method and the reconstructed analytical procedure to liquid mercury at room temperature has produced a result in agreement with other recen

ISSN:1600-5767    

DOI:10.1107/S0021889875010898

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

A lattice‐imaging technique is applied in a study of the intimate structure of non‐graphitizing PVDC C atoms heat treated in the range 803 K to 2973 K. Fine detail in the resulting electron micrographs indicates that the bulk material consists of a high proportion of intertwined crystallites comprising turbostratically packed aggregates of graphitic basal planes. Schematic models are presented incorporating the electron‐microscope observations of this particular geometrical arrangement of ribbon‐shaped layer planes which is thought to be responsible for the inhibition of recrystallization,i.e.graphitization at elevated temperatures. Evidence is presented which indicates that the structural transformation in PVDC differs from that of other non‐graphitizing C atoms recently investigated. There is discussion of the structural factors which give rise t

ISSN:1600-5767    

DOI:10.1107/S0021889875010904

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

A new small‐angle X‐ray scattering facility which utilizes a 6 kW rotating anode, pin‐hole collimation, and a position‐sensitive proportional counter has been developed. As presently constructed, the minimum scattering vector κ (= 4π sin θ/2) which can be reached with CuKα radiation is 5 × 10−3 Å−1. Under these conditions the flux incident on the specimen has been found to be 6 × 105photons s−1. The system has several advantages compared with traditional long‐slit geometries; namely, (i) it can quantitatively measure anisotropic scattering distributions, (ii) it avoids large mathematical corrections of the data for slit‐smearing effects, and (iii) it minimizes double Bragg scattering in crystalline materials and multiple diffuse scattering in amorphous or liquid materials. To illustrate the performance of this instrument, the scattering curves obtained from four widely different samples are shown. These are: polyethylene, a neutron‐irradiated aluminium single‐crystal containing voids, a dilute suspension of Ludox spheres, and duck tendon collagen. Quantitative comparisons of the performance with a Kratky camera and with the neutron small‐angle scatt

ISSN:1600-5767    

DOI:10.1107/S0021889875010916

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

Values of fault probabilities, lattice parameter and residual stress in deformed specimens are sometimes obtained from positions of several peaks in a standard diffraction pattern. In the light of recent results on the effects of macro‐ and micro‐stresses on peak positions, it is shown that this procedure is often inadequate and an alternative method is sugges

ISSN:1600-5767    

DOI:10.1107/S0021889875010928

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

With almost perfect silicon crystals and cleaved lithium fluoride crystals as extreme examples, the feasibility of using synchrotron radiation for X‐ray diffraction topography has been investigated. In both spatial resolution and strain resolution the synchrotron source diffraction topographs are competitive with topographs obtained using conventional X‐ray sources but exposure times are reduced from several hours per cm2to one second per cm2using standard recording techniques with Ilford nuclear emulsions. Contrary to (the author's) expectations, the instrumentation required is far simpler for synchrotron radiation than for conventional sour

ISSN:1600-5767    

DOI:10.1107/S002188987501093X

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

The paper presents the analysis of formation of the image of non‐perfect crystals in the Schulz method. Methods are suggested to determine the angles between blocks by using either `singular' points or the displacement of characteristic lines. Accuracy of these methods is discusse

ISSN:1600-5767    

DOI:10.1107/S0021889875010941

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

A procedure for the determination of lattice constants, accurate to from 1 to 4 parts per million, from measurements of multiple diffraction peak locations is described. Experimental techniques and systematic errors are discussed. Large numbers of multiple diffraction peaks become available for measurement in the course of 360° of rotation about one axis. The method can be used with wide ranges of crystal sizes, shapes and degrees of perfection

ISSN:1600-5767    

DOI:10.1107/S0021889875010953

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

The lattice constants of a diamond platelet and of large single, undoped, crystals of silicon and germanium have been determined from measurements of multiple diffraction patterns by the method described in Part I [Post (1975).J. Appl. Cryst.8, 452–456]. The mean values, based on measurements of eight to twelve reflections, and their standard deviations are: diamonda= 3.566986 Å,Aa/a= 2.6 × 10−6; silicona= 5.430941 Å,Aa/a= 2 × 10−6; germaniuma= 5.657820 Å,

ISSN:1600-5767    

DOI:10.1107/S0021889875010965

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

X‐ray line profiles of annealed tungsten powder of 99.9% purity were measured with a high resolution of the order of 0.01° (2θ). A primary beam of MoKα1radiation which had a divergence of less than 0.01° in the plane of the diffractometer was used. After elimination of all instrumental effects, the mosaic particle‐size broadening and the strain broadening were obtained. With the approximation of spherical particles a generalized Maxwellian mass distribution with a mean particle radius of 2500 Å and a poly dispersity of 25% was found. A strain of 3.6 × 10−4in the mosaic particles was observed. The results are compared with various theories of X‐ray scattering from dislocation arrangements. Two interpretations of the strains are discussed. The strains originate either from dislocations in the walls of the mosaics or from dislocations inside the mosaics. In the latter case less than two dislocations are present in the mosaic particles. The strain broadening function was found to be Gaussian for strains less than 2 × 10−4and to be above the Gaussian function

ISSN:1600-5767    

DOI:10.1107/S0021889875010977

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY

摘要:

A simple device is described which allows copper crystals to be bent elastically and plastically with cylindrical curvature down to a radius of 1 m, without destroying the homogeneity of the mosaic structure. This is proved by measurements with a γ‐diffractometer. The focusing behaviour of a bent monochromator, designed for the modified Laue technique, is as expected and the crystal reflects nearly homogeneous neutrons in the wavelength band 1.3 ± 0.05 Å with a reflectivit

ISSN:1600-5767    

DOI:10.1107/S0021889875010989

出版商:International Union of Crystallography    

年代:1975

数据来源: WILEY