Crystal structure and hyperfine interactions of delafossite (CuFeO2) synthesized hydrothermally

The powder specimen of CuFeO2 delafossite was synthesized by a hydrothermal method at 453 K. X-ray diffraction studies confirmed that the obtained pure delafossite phase was a mixture of the 3R and 2H polytypes, predominantly the former. Mössbauer spectral analysis revealed the paramagnetic state of the copper ferrite at room temperature. Below 12 K the spectra had complicated shapes of Zeeman sextets. Changes in the character of the hyperfine interactions did not correspond to the data reported for the single-crystal CuFeO2. Magnetization measurements revealed that magnetic transition occurred at Néel temperature (T N) = 12.5 K.

Deconvolution–convolution treatment on powder diffraction data collected with CuKα X-ray and NiKβ filter

A method to remove small CuKβ peaks and step structures caused by NiK-edge absorption as well as CuKα2 sub-peaks from powder diffraction intensity data measured with Cu-target X-ray source and Ni-foil filter is proposed. The method is based on deconvolution–convolution treatment applying scale transform of abscissa, Fourier transform, and a realistic spectroscopic model for the source X-ray. The validity of the method has been tested by analysis of the powder diffraction data of a standard LaB6 powder (NIST SRM660a) sample, collected with the combination of CuKα X-ray source, Ni-foil Kβ filter, flat powder specimen and one-dimensional Si strip detector. The diffraction intensity data treated with the method have certainly shown background intensity profile without CuKβ peaks and NiK-edge step structures.

Study on Temperature Field of Low Heat Accumulation Asphalt Concrete Pavement

Experimental results showed that low heat accumulation asphalt mixture had a marked effect on the reduction of surface temperatures. However changes in temperature over the test methods were not thoroughly studied. In the process of test, LJ infrared powder is used to prepare for making the content of 6% asphalt mixture specimen. Several temperature data of infrared powder specimen were compared with the data of ordinary specimen. Each number was compared and analyzed. At last, concrete temperature variation discipline of the temperature field was found.

Fundamentals of Spark-Plasma Sintering: Applications to Net-Shaping of High Strength Temperature Resistant Components

Spark-plasma sintering (SPS) is an emerging powder consolidating technique which provides significant advantages to the processing of high temperature materials with poor deformability into configurations previously unattainable. Net-shaping capabilities of spark-plasma sintering are analyzed both theoretically and experimentally. Modeling and experimentation are conducted for cylindrical, prismatic, and complex powder specimen shapes. The impact of the “shape factor” on the non-uniformity of temperature, relative density, and grain size spatial distributions is analyzed. The modeling results are compared to the experimentally obtained data on the spark plasma sintering of high strength temperature resistant powder-based materials. The conducted research indicates the promising capabilities and addresses the challenges of spark-plasma sintering of complex-shape parts.

Preferred orientation in Debye–Scherrer geometry: interpretation of the March coefficient

The March function is a widely used preferred-orientation correction function that, in flat-plate geometry, often closely approximates the pole-density profile of axially symmetric textures. It is shown that in Debye–Scherrer geometry, the assumption that the pole-density profile of a powder specimen can be described by a March function with coefficientR, leads to an intensity correction factor that can be approximated quite well by another March function, with coefficientR−1/2. This result validates the use of the March function correction in Debye–Scherrer geometry, facilitates the comparison of results obtained in the different geometries and should prove useful in some studies of axially symmetric textures and in residual-stress analysis.

Experimental comparison between the conversion electron yield and X-ray fluorescence in catalyst analysis

To evaluate the application of the conversion-electron-yield (CEY) method in catalyst analysis, the intensities of the CEY and X-ray fluorescence (XRF) as a function of glancing angle were measured simultaneously. The probing depth of the CEY method is shallower than that of the XRF method. The CEY method also shows potential application for the analysis of even a powder specimen of a low-concentration zeolite catalyst.

An Analysis of the Effect of Different Instrumental Conditions on the Shapes of X-ray Powder Line Profiles

In this investigation we have examined how the full width at half maximum intensity (FWHM) and asymmetry of x-ray powder diffraction line profiles are influenced by the instrumental conditions adopted. Experimental x-ray data has been collected for a matrix of instrumental conditions by systematically varying the divergence slit angle (and the corresponding anti-scatter slit) over the range 0.25° to 1.25°, by using either a 0.05mm or 0.2mm receiving slit, or by removing the diffracted beam Soller slit. The line profile Standard Reference Material, SRM, 660 (LaB6) was used as the powder specimen in that it imparts minimal specimen induced broadening to the diffraction profiles. X-ray data were collected on a conventional, divergent beam, x-ray diffractometer using CuKα radiation. The FWHM of the CuKα1 component can be as low as 0.035°2θ for high resolution conditions, but is normally ∼0.1°2θ at 2θ ≈ 30° for the instrumental conditions adopted in routine diffractometry. Below 2θ = 50°, the divergence slit has a significant effect on the FWHM and is the major cause of the increase in FWHM with decreasing 2θ. Results are presented of the 2θ dependence of FWHM values for each of the instrumental conditions recorded. A general relationship for the 2θ dependence of the FWHM and the asymmetry has been investigated to supersede the inappropriate Cagliotti expression frequently used in x-ray Rietvcld refinement.

Quantitative phase analysis of α-Fe impurity in Ce2Fe17 matrix from neutron powder diffraction data

The multicomponent Rietveld profile refinement technique for powder neutron diffraction patterns has been applied to arrive at a quantitative phase analysis of crystalline Ce2Fe17 and α-Fe impurity in a powder specimen of Ce2Fe17.

On The Harris Texture Index

The texture index introduced by Harris (1952) is reconsidered from the point of view of the orientation distribution of crystallites in a flat powder specimen. It is shown that the texture index can be used as an approximate measure of texture degree or as a texture correction factor in cases of a weak texture. Its failure in both these aspects for the strong textures is caused by an incorrect averaging of pole densities contained in the original definition of this quantity.

Basic Aspects of X-Ray Absorption In Quantitative Diffraction Analysis of Powder Mixtures

The mathematical relationships are developed which are pertinent to the quantitative analysis of powder mixtures for the case of diffraction from the surface of a flat powder specimen. These formulas relate the diffracted intensity to the absorptive properties of the sample. Three important cases are treated: (1) Mixture of n components; absorbing powder of the unknown equal to that of the matrix; concentration proportional to intensity. Direct analysis is permitted. (2) Binary mixture; absorbing powder of the unknown not equal to that of the diluent; concentration not proportional to intensity. Direct analysis is possible by means of calibration curves prepared from synthetic mixtures. (3) Mixture of n components; absorbing power of the unknown not equal to that of the matrix; general case. Analysis is accomplished by the addition of an internal standard. Concentration is proportional to the ratio of the intensity of a selected reflection from the unknown to the intensity of a reflection from the internal standard.