Interface-Driven Strain in Heavy Ion-Irradiated Zr/Nb Nanoscale Metallic Multilayers: Validation of Distortion Modeling via Local Strain Mapping

Nanolayered metallic alloys are promising materials for nuclear applications thanks to their resistance to radiation damage. Here, we investigate the effect of ion (C, Si, and Cu) irradiation at room temperature with different fluences into sputtered Zr/Nb metallic multilayer films with periods 27 nm (thin) and 96 nm (thick). After irradiation, while a high strain in the entire thin nanoscale metallic multilayer (NMM) is observed, a quite small strain in the entire thick NMM is established. This difference is further analyzed by a semianalytical model, and the reasons behind it are revealed, which are also validated by local strain mapping. Both methods show that within a thick layer, two opposite distortions occur, making the overall strain small, whereas in a thin layer, all the atomic planes are affected by the interface and are subjected to only a single type of distortion (Nb─tension and Zr─compression). In both thin and thick NMMs, with increasing damage, the strain around the interface increases, resulting in a release of the elastic energy at the interface (decrease in the lattice mismatch), and the radiation-induced transition of the Zr/Nb interfaces from incoherent to partially coherent occurs. Density functional theory simulations decipher that the inequality of point defect diffusion flux from the inner to the interface-affected region is responsible for the presence of opposite distortions within a layer. Technologically, based on this work, we estimated that Zr/Nb55 with thicknesses around Zr = 24 nm and Nb = 31 nm is the most promising multilayer system with the high radiation damage resistance and minimum swelling for nuclear applications.

[Measurement of acetabular polyethylene wear of total hip replacement, using a universal measuring microscope. Characteristics of measurements]

PURPOSE OF THE STUDY

The aim of the study was to present our own method of measuring acetabular polyethylene wear in total hip arthroplasty, including assessment of basic measurement characteristics. It is a well known fact that, in total hip replacement, polyethylene liners wear out with use. The rate of acetabular polyethylene wear can then be related to clinical or demographic data.

MATERIAL AND METHODS

Our method, using a universal measuring microscope, is based on the ability of exact identification of central positions of the head of total hip replacement before implantation and after prosthesis removal. The difference between the original and final positions allows us to calculate both linear and volumetric wear of polyethylene. During one month, the same components were repeatedly measured by two independent investigators and a total of 10 ABG 1 acetabular components were checked. The results of measurements were evaluated by a series of statistical tests, including correlation and regression analyses and analysis of variance.

RESULTS

High correlations were found among individual measurements made by each observer (r = 0.998; r = 0.973) as well as between the mean values obtained from the two observers (r = 0.996). The reliability of measurements was proved by a high correlation of the regression curve of each measurement with the "ideal" line. With two exceptions, the differences between paired measurements were not significant.

CONCLUSIONS

Our method facilitates an in vitro measurement of polyethylene wear with considerable accuracy and high reliability.

Quality control materials for the determination of trace elements in airborne particulate matter

The development of quality control materials for the determination of selected trace elements in air pollution studies is described. Three types of test samples were prepared for proficiency testing: (1) filters loaded with PM10 fraction of urban air particulate matter (APM) using high-volume air samplers, which were subsequently divided into smaller sections, (2) a bulk sample of APM collected in an automobile tunnel in Prague, and (3) simulated air filters loaded with APM using a wet deposition process. Homogeneity of the test samples was studied using instrumental neutron activation analysis, proton induced X-ray emission and atomic absorption spectrometry, and inductively coupled plasma optical emission spectrometry and mass spectrometry. Sufficiently homogeneous samples were prepared by all three procedures. The simulated air filters appeared to be the most suitable test samples for proficiency testing.

Preparation and characterization of a set of IAEA reference air filters for quality control in air-pollution studies

Several sets of reference air filters were prepared as part of an IAEA evaluation of the performance of laboratories involved in air-pollution studies. Each set comprised three polycarbonate membrane filters, two of which were loaded with urban air particulate matter (APM) obtained in Vienna or Prague, and one unloaded filter. The filters were loaded by filtration of a suspension of the APM materials in water. The homogeneity both of bulk APM materials and of the loaded filters was evaluated and found suitable by determining several elements by instrumental neutron-activation analysis (INAA), proton-induced X-ray emission (PIXE), and micro-X-ray energy-dispersive fluorescence analysis (micro-EDXRF). After evaluation of the homogeneity, INAA, PIXE, EDXRF, atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), and ICP mass spectrometry (ICP-MS) were used to characterize the filter materials and establish "target values" and their associated standard deviations for 15 elements. Problems encountered during the preparation of these unique, simulated air filters and the criteria for setting both the target values and standard deviations are presented.

INAA and PIXE of atmospheric and combustion aerosols

Using instrumental neutron activation analyses and photon-induced x-ray emission techniques for analysis of size-fractionated atmospheric and combustion aerosols and other emission samples arising from fluidized-bed combustion of North Bohemian lignites up to 42 elements were determined in all samples types. This allowed the evaluation of element enrichment, time trends, and inter-element correlations and the performance of factor analysis of various fractions of atmospheric aerosols. The data obtained on mass and element size distributions of aerosols and emission samples obtained upon lignite combustion in an experimental scale atmospheric fluidized-bed combustor without and with added hydrated lime and limestone were used to elucidate the mechanism of abatement of toxic trace and matrix elements from flue gas.

Matrix effects in PIXE analysis of aerosols and ashes

A comparison of instrumental neutron activation analysis (INAA) and proton-induced X-ray emission (PIXE) results for size-fractionated atmospheric aerosols ("coarse" and "fine" fractions with an equivalent aerodynamic diameter of 2-10 microns and < 2 microns, respectively, or the PM10 fraction) showed that PIXE yielded significantly lower results for the PM10 and coarse fractions, especially for elements with a low Z resulting from a particle size effect. Somewhat lower PIXE results were also obtained for the fine fraction of atmospheric aerosols. A correction is also needed for irregularly shaped deposits of combustion aerosols collected by a cascade impactor in 11 size fractions ranging from 0.016 to 14.3 microns, as well as for thick samples of fly and bottom ashes. An equivalent layer thickness (ELT) model is proposed to correct the matrix effects in PIXE. The approaches for the calculation of ELT using a comparison of PIXE and INAA results or by comparing PIXE results obtained using two different incident proton beam energies (1.31 and 2.35 MeV) are described. The correction for the ash pellets and irregular deposits are also discussed.

Analysis of membrane filters and thick fly ash samples by PIXE

The possibility of the routine PIXE measurement of environmental samples has been tested at the INP in Rez. Both thin samples of aerosols collected on membrane filters Synpor and Nuclepore and thick aerosols and fly ashes samples pressed into pellets were analyzed. The Nuclepore filter was found more suitable for PIXE analysis of aerosols than the Synpor, and the thin aerosol sample analysis was found to be easier than the thick sample analysis. The grain size effect in the case of thick fly ash samples is discussed.