摘要:

Five powder diffractometers have been interfaced with a time‐shared computer, equipped with a comprehensive set of X‐ray powder‐pattern analysis programs, to facilitate data acquisition and analysis. The disk‐oriented line‐broadening analysis routine provides estimates of particle size and micro‐strain distributions together with estimates of average particle sizes and macro‐strains for cubic crystalline systems. All calculations are performed routinely for all samples, providing comprehensive reports at little more effort and expense than that incurred in the routine preparation ofd‐value and

ISSN:1600-5767    

DOI:10.1107/S0021889872010003

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

The scattering of amorphous solid or liquid samples with moderate absorption coefficients is advantageously measured in the symmetrical transmission arrangement. For this case, the steps of data processing, converting the raw intensity data into the reduced intensity function, are discussed. The correcting functions are expressed as explicit functions of the angle (θ or 2θ), and ofs(= sin θ/λ) as well. The advantages of the latter formulae are demonstra

ISSN:1600-5767    

DOI:10.1107/S0021889872010015

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

Single‐crystal reflexion topographs from various planes in gallium arsenide are presented and the contrast is compared, in some cases, with double‐crystal topograph equivalents. Theory is presented to explain the numerous effects observed but principally the lack of contrast when the absorption distance is small. This aspect of reflexion theory is combined with an evaluation of the effective tilt round a dislocation at various depths below the surface. Tables are also presented giving good and bad choices of reflecting planes for single‐crystal topography in gallium ars

ISSN:1600-5767    

DOI:10.1107/S0021889872010027

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

It has been found that the relation of integrated intensities of the 00lreflections of pyrolytic carbons to the uniaxial orientation is amenable to a theoretical treatment. The resulting expression is rather simple and permits the evaluation of commonly used anisotropy factors, such as 〈sin2ϕ〉 or the Bacon anisotropy factor, from measurements of integrated intensities at two different orientation angles (ϕ). The applicability of the equation has been tested with data involving 44 pyrolytic carbons covering a wide range of anisotropy. The same relation has also been found to be applicable to a nylon po

ISSN:1600-5767    

DOI:10.1107/S0021889872010039

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

An elastic deformation wave initiates loops on edges and steps of a crystallographically perfect ribbon (copper whisker). Multiple loops move and intersect on two glide‐plane families normal to the plane of the whisker and the tensions produced in this way probably move loops on two other plane families parallel to the axis of the ribbon. It is assumed that these loops meet Lomer–Cottrell dislocations, which were originally formed, normal to the ribbon surface, and Frank–Read sources are created. To increase the contrast of the Lang method topograms, the plate is kept dark in vacuum during the exp

ISSN:1600-5767    

DOI:10.1107/S0021889872010040

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

The particle size distributions calculated from diffraction profiles are often disturbed by spurious oscillations. We propose a method for suppressing or reducing the parasitic effects due to wrong correction of the peak at the origin (zero size) and incorrect background. The method uses a single correction function, of the formKsinX/X,Kbeing determined from the intercept of the variance–range function asymptote. The discussion considering a theoretical example shows that a big error may remain near the origin of the distribution (very small particle size) but that for other sizes, the results are generally better than those obtained when one fixes the distribution at its correct value at the origi

ISSN:1600-5767    

DOI:10.1107/S0021889872010052

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

A simple and automatic technique is described for the continuous recording on X‐ray photographs the behaviour of single crystals as a function of temperature, pressure, timeetc. With a careful choice of axis and oscillation ranges, a distorted, but recognixable, plot of the phase diagram is obtained in a few hour

ISSN:1600-5767    

DOI:10.1107/S0021889872010064

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

The shape of the two phase, β‐Nb + β‐Zr, monotectoid loop in the niobium–zirconium phase diagram has been re‐investigated by X‐ray analysis for alloys with controlled content of interstitial

ISSN:1600-5767    

DOI:10.1107/S0021889872010076

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

It is pointed out that, when determining the crystal structure of a precipitate in a two‐phase alloy, it is not sufficient to consider only the overall symmetry of the combined precipitate and matrix reciprocal lattices. If several precipitate variants exist in the parent crystal, and if all variants have an equal probability of being present, then the combined reciprocal lattice will always demonstrate the symmetry of the parent crystal. Recently, [Lee (1970).J. Appl. Cryst.3, 413] the symmetry of the reciprocal lattice was used to deduce that the ω‐phase precipitate formed in the b.c.c. matrix of a Ti–30 %V alloy has a b.c.c. structure. The extra information that is available for the ω‐phase can be used to demonstrate that this conclusion is incorrect, and that the ω unit cell has hexagona

ISSN:1600-5767    

DOI:10.1107/S0021889872010088

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY

摘要:

The equation of a small‐angle X‐ray scattering intensity curve, which would fulfil exactly Porod's law and which could be obtained by using cameras with a rectangular, triangular, or one of a number of trapezoidal cross‐sectional profiles of the intensity of the primary beam, has been calculated. The equation thus obtained can be used to determine the effect of finite slit height of the collimating system on the tail of the diffraction

ISSN:1600-5767    

DOI:10.1107/S002188987201009X

出版商:International Union of Crystallography    

年代:1972

数据来源: WILEY