Mo–Si–B alloys for ultra-high-temperature space and ground applications: liquid-assisted fabrication under various temperature and time conditions

Journal of Materials Science - Boron-doped molybdenum silicides have been already recognized as attractive candidates for space and ground ultra-high-temperature applications far beyond limits of...     

The stiffness of laser stake welded T-joints in web-core sandwich structures

The purpose of this paper is to describe experiments carried out on laser stake welded T-joints of web-core steel sandwich structures. A special test setup was developed to measure the shear-induced rotation at the T-joint. The ratio of the shear force to rotation angle gave the joint stiffness. This stiffness was measured for specimens with two different face-plate thicknesses. The influence of weld thickness, root gap and occurrence of contact were further investigated with finite element simulations. Finally, the shear stiffness of the sandwich structure transverse to the web plate direction was determined using the experimentally obtained average joint stiffness value. The validation of the shear stiffness was carried out by considering a beam in four-point bending. The agreement between calculated deflection and stress and experimental results was found to be good.     

Integrating Ecological,Social and Cultural Dimensions in the Implementation of the Landscape Convention

Implementation of the European Landscape Convention requires new tools that link ecological, social and cultural dimensions in practical planning. Here, we propose connectivity as a conceptual tool to include different dimensions into landscape and spatial planning. We present a short review of the connectivity concept in relation to ecological, social and cultural dimensions and illustrate it by examples from a real landscape planning case.     

Origin of Violet‐Blue Emission in Ti‐Doped Gahnite

ZnAl₂O₄ doped with Ti⁴⁺ (2%) was synthesized by the hydrothermal method at 220°C at pressure of 25 bars. An average grain size of the as‐prepared sample was 3 nm, the samples with biggest grain size were obtained after annealing at 300°C, 500°C, 600°C, 700°C, and 900°C, diameter of the latter was about 33 nm. IR spectroscopy indicated that ZnAl₂O₄ was partially inverted. The degree of the inversion decreases with increase in the annealing temperature but increases with increasing Ti⁴⁺ content. Absorption and emission spectra as well as emission decay profiles were recorded at 300 and 77 K. The observed spectra are due to charge‐transfer O^2??Ti⁴⁺ transitions. Color of the emission depends on the nanocrystal size and with increase in its diameter changes from violet to blue, accordingly the absorption bands exhibit redshift. The calculations based on Density Functional Theory confirmed the experimental results. 3d electrons of titanium ions form the bottom of the ZnAl₂O₄:Ti⁴⁺ conduction band, oxygen, aluminum or zinc vacancies create additional levels in the gahnite energy band gap. It was also found that in ZnAl₂O₄ aluminum or zinc vacancy induces magnetism with relatively high magnetic moment close to 1 μ_B per vacancy.     

On the usefulness of guidelines and instructions for environmental assessment – a qualitative study of the helpfulness perceived by Polish practitioners

Guidelines and instructions for Environmental Impact Assessment and Strategic Environmental Assessment (together referred to as EA here) are developed to improve the quality of legal requirements’ implementation and to support EA procedure accomplishment. However, to date, it has not been checked whether they are useful for practitioners. Therefore, the aim of the study underlying this paper was to verify, based on the experience of Polish EA experts, whether guidelines and instructions are useful in their everyday work. A qualitative study comprising of a questionnaire survey and interviews tested whether (1) EA practitioners know and use the Polish and EU guidelines, (2) how EA practitioners evaluate the validity and usefulness of such instructions, and (3) in which areas there is a lack of instructions and guidelines. The results show a low level of knowledge of national and EU handbooks. Those guidelines focusing on legal procedures, road investments and designing animal passageways are considered to be the most useful. Moreover, practitioners indicate that EU guidelines should be translated into Polish. Most important for practitioners is the linking of guidelines with the EA procedure, so that they can become a platform for dialogue of all stakeholders.     

The influence of volume fraction of amorphous phase on corrosion resistance of Mg67Zn 29Ca 4 alloy

The aim of this study was to investigate the structure and corrosion resistance of amorphous, amorphous‐crystalline, and crystalline Mg₆₇Zn₂₉Ca₄ alloy for biodegradable applications. This paper presents a preparation method and results of the structural characterization and corrosion resistance analysis of the material. Samples were prepared in the form of 3 mm diameter rods. The structure of the alloy was examined with the use of X‐ray diffractometry and scanning electron microscopy. The thermal properties of the samples were examined with differential scanning calorimetry (DSC). Results of DSC analysis were used to determine heat treatment temperatures, allowing to obtain different fractures of crystalline phase in the material. Corrosion resistance of heat‐treated samples was investigated by immersion tests and electrochemical measurements performed in the simulated body fluid. The X‐ray diffraction results confirmed that the prepared Mg₆₇Zn₂₉Ca₄ alloy's structure is fully amorphous. After heat treatment, samples with different fractions of amorphous phase in the structure were obtained. Immersion tests of the samples showed that the structure significantly influenced corrosion resistance in examined materials. It should be pointed out, that certain amounts of crystalline phase in amorphous matrix can greatly improve the corrosion resistance of Mg₆₇Zn₂₉Ca₄ alloy.     

The Effect of Implanted Al and/or Y on the Scale Formation on Low-Al Fe20Cr2Al Alloy

The very early stages of the oxidation of an Fe20Cr2Al alloy, unmodified and ion-implanted by aluminium, yttrium and a combination of both elements, Al and Y, were studied at 1100 °C in oxygen using two-stage-oxidation exposures with ¹⁸O₂ as a tracer and subsequent characterisation of the scales using SIMS analyses of distribution of oxygen isotopes and oxide-related negative ion clusters, SEM observations of the surface morphology and photoluminescence spectroscopy analysis of the phase composition. The scales formed in all cases, except for the Al-implanted alloy, exhibited layered structures, with the outer part comprising Fe- and Cr-rich oxide, and the inner part being Al₂O₃, which grew due to a mixed outward–inward mechanism . The alumina sub-layers contained the transient oxides and α-Al₂O₃. Implanted Al significantly affected the mechanism of the scale growth, providing that the scale consisted essentially of α-Al₂O₃, and grew via a mixed inward-outward mechanism typical for scales on alumina formers.     

The use of the internet by older adults in Poland

Universal Access in the Information Society - It is generally accepted that it is young people who are particularly interested in information and communication technologies (ICT). Older adults...     

Evaluation of Damage Degree of Inconel 718 Alloy with the Use of Non-Destructive Methods

The article presents results of the investigation of the quantitative evaluation of the degree of damage, described by the measure of accumulated plastic strain obtained in a static tensile test, using selected non-destructive techniques. Inconel 718 alloy was tested. The tests were conducted using a new type of specimens of variable cross-sectional area of measuring part. This provided a continuous distribution of plastic strain in the gage part of the specimen. The permanent deformation that varies along the sample axis enables an analysis of damage induced by a plastic deformation. The proposed method enables replacing the series of specimens by one sample. Degradation of the alloy corresponds with the changes of the electromagnetic properties of the material—the phase angle of the complex impedance of the eddy current, as well as with acoustics properties of material—acoustic birefringence of ultrasonic waves. It allows to determine the degree of damage of the material using noninvasive, non-destructive methods. Using the damage parameter proposed by Johnson it is possible to obtain the correlation between the non-destructive results and a damage degree of the material. The presented testing method delivers information about changes in the material structure caused by permanent deformation.