A multiscale experimental analysis of mechanical properties and deformation behavior of sintered copper–silicon carbide composites enhanced by high‑pressure torsion

Experiments were conducted to investigate, within the framework of a multiscale approach, the mechanical enhancement, deformation and damage behavior of copper–silicon carbide composites (Cu–SiC) fabricated by spark plasma sintering (SPS) and the combination of SPS with high-pressure torsion (HPT). The mechanical properties of the metal–matrix composites were determined at three different length scales corresponding to the macroscopic, micro- and nanoscale. Small punch testing was employed to evaluate the strength of composites at the macroscopic scale. Detailed analysis of microstructure evolution related to SPS and HPT, sample deformation and failure of fractured specimens was conducted using scanning and transmission electron microscopy. A microstructural study revealed changes in the damage behavior for samples processed by HPT and an explanation for this behavior was provided by mechanical testing performed at the micro- and nanoscale. The strength of copper samples and the metal–ceramic interface was determined by microtensile testing and the hardness of each composite component, corresponding to the metal matrix, metal–ceramic interface, and ceramic reinforcement, was measured using nano-indentation. The results confirm the advantageous effect of large plastic deformation on the mechanical properties of Cu–SiC composites and demonstrate the impact on these separate components on the deformation and damage type

Europe's cross-border trade, human security and financial connections: A climate risk perspective

As the impacts of climate change begin to take hold, increased attention is being paid to the consequences that might occur remotely from the location of the initial climatic impact, where impacts and responses are transmitted across one or more borders. As an economy that is highly connected to other regions and countries of the world, the European Union (EU) is potentially exposed to such cross-border impacts. Here, we undertake a macro-scale, risk-focused literature and data review to explore the potential impact transmission pathways between the EU and other world regions and countries. We do so across three distinct domains of interest - trade, human security and finance - which are part of complex socio-economic, political and cultural systems and may contribute to mediate or exacerbate risk exposure. Across these domains, we seek to understand the extent to which there has been prior consideration of aspects of climate-related risk exposure relevant to developing an understanding of cross-border impacts. We also pro-vide quantitative evidence of the extent and strength of connectivity between the EU and other world regions. Our analysis reveals that - within this nascent area of research - there is uncer-tainty about the dynamics of cross-border impact that will affect whether the EU is in a relatively secure or vulnerable position in comparison with other regions. However, we reveal that risk is likely to be focused in particular ‘hotspots’; defined geographies, for example, that produce materials for EU consumption (e.g. Latin American soybean), hold financial investments (e.g. North America), or are the foci for EU external action (e.g. the Middle East and North Africa region). Importantly, these domains will also interact, and - via the application of a conceptual example of soybean production in Argentina based on a historical drought event - we illustrate that impact and response pathways linked to EU risk exposure may be complex, further heightening the challenge of developing effective policy responses within an uncertain climatic and socioeconomic future

Analysis of the impact of selected hydrometeorological conditions on the accuracy of oil spill simulations on the PISCES II simulator

Computer simulations used for predicting the behavior of oil spills at sea allow optimizing the deployment of oil spill response personnel and resources, and using the backtracking method to identify the polluter in cases where spills are sighted some time after they occurred. Predicting the direction and speed of oil slick spreading is of fundamental importance. An attempt was made to verify the influence of selected simulation parameters, related to hydrometeorological conditions, on the behavior of the resulting oil pollution. Different responses were obtained under the same simulated weather conditions, depending on the type of spilled oil. The experiment was conducted on a PISCES II oil spill simulator

New method for measurement of viscosity of ultrathin polymeric films

W artykule przedstawiono nową, metodę pomiaru lepkości ultracienkich warstw polimerów. Polega ona na zanurzeniu w warstwie drgającej sondy pomiarowej. Na podstawie zmian częstotliwości rezonansowej oraz fazy jej drgań można wyznaczyć wartość lepkości w funkcji głębokości zanurzenia. Grubość najcieńszej przebadanej warstwy wynosiła 30 nm, a dokładność pomiaru lepkości około 10%. Otrzymane wyniki są zgodne z przewidywaniami oraz z wynikami otrzymywanymi innymi metodami. Nowa metoda pomiarowa może być przydatna w rozwoju nowych technologii takich jak proces nanoimprint lithography.A new method of measurement viscosity of thin polymeric films is presented. The probe, which is placed on the end of the arm of the mini tuning fork (Fig. 2) is made to oscillate and than is put into the PMMA (poly(methyl methacrylate)) films. Because of the rheological properties of measured samples, the amplitude and resonant frequency are changed. Simple mathematical model of probe, which is immersed partially into a liquid and oscillates, was elaborated. Thirteen samples were examined which differed from each other by the thickness of the film and the molecular weight. The thickness of the films is from 30 nm up to 1080 nm (Tab. 1). All measured properties are depended on temperature, thickness of the film, the depth of indentation of the probe and the molecular weight of PMMA. The viscosity is lower in higher temperatures (Fig. 5) but higher with bigger molecular weight (Fig. 6). They are also lower for thicker films. The results gained from this experiment may be useful in development of nanoimprint lithography and many other branches of nanotechnology. What is more, the method gives a possibility of fast and precise measure-ment of rheological properties of many different thin films in function of temperature

Model of navigational safety of vessels in Polish EEZ

The paper presents the assumptions of a simulation model for assessing the navigational safety of fishing vessels. The model consist of submodels of merchant and fishing vessels traffic, submodel of external condition and submodel of accident consequences. Paper present also a results of simulation experiment which was carried out for Polish EEZ. Model takes into account all Polish fishing vessels operating in the Polish EEZ with length more than 15 meters and the merchant vessels traffic in South Baltic Sea area. As a results positions of simulated collisions of fishing and merchant vessels, positions and sizes of simulated bunker spills and the positions of losses of fishing equipment were achieved.W artykule przedstawiono założenia złożonego modelu symulacyjnego dla szacowania bezpieczeństwa nawigacyjnego statków rybackich. Model składa się z modeli ruchu statków handlowych i statków rybackich, modelu warunków środowiskowych oraz modelu skutków zdarzenia. Ponadto w artykule przedstawiono rezultaty eksperymentu symulacyjnego przeprowadzonego dla polskiej wyłącznej strefy ekonomicznej. Model uwzględnia wszystkie polskie statki rybackie operujące w polskiej wyłącznej strefie ekonomicznej o długości większej niż piętnaście metrów oraz ruch statków handlowych na południowej części Morza Bałtyckiego. W rezultacie otrzymano pozycje prawdopodobnych kolizji statków transportowych oraz rybackich, pozycje i rozmiary prawdopodobnych rozlewów olejowych oraz pozycje utraty narzędzi połowowych

Model Of Navigational Safety Of Fishing Vessels In Polish EEZ

The paper presents the assumptions of a simulation model for assessing the navigational safety of fishing vessels. The model consist of submodels of merchant and fishing vessels traffic, submodel of external condition and submodel of accident consequences. Paper present also a results of simulation experiment which was carried out for Polish EEZ. Model takes into account all Polish fishing vessels operating in the Polish EEZ with length more than 15 meters and the merchant vessels traffic in South Baltic Sea area. As a results positions of simulated collisions of fishing and merchant vessels, positions and sizes of simulated bunker spills and the positions of losses of fishing equipment were achieved.W artykule przedstawiono założenia złożonego modelu symulacyjnego dla szacowania bezpieczeństwa nawigacyjnego statków rybackich. Model składa się z modeli ruchu statków handlowych i statków rybackich, modelu warunków środowiskowych oraz modelu skutków zdarzenia. Ponadto w artykule przedstawiono rezultaty eksperymentu symulacyjnego przeprowadzonego dla polskiej wyłącznej strefy ekonomicznej. Model uwzględnia wszystkie polskie statki rybackie operujące w polskiej wyłącznej strefie ekonomicznej o długości większej niż piętnaście metrów oraz ruch statków handlowych na południowej części Morza Bałtyckiego. W rezultacie otrzymano pozycje prawdopodobnych kolizji statków transportowych oraz rybackich, pozycje i rozmiary prawdopodobnych rozlewów olejowych oraz pozycje utraty narzędzi połowowych

Optical Properties of Semiladder Polymer Foils

Optical transmission of amorphous polyimidazopyrrolone foils (pyrrons) were investigated in the spectral range 200-3300nm. The investigated materials exhibit a high transmission level (up to 85%) in a wide range from about 500 to 2750nm. The short wavelength edge of transmission depends on the pyrron chemical structure being different for ether-, amide- and ester bridges. When analysing the experimental data, we applied the approach used for amorphous materials in order to determine the electronic structure parameters which may be related to the influence of polyimidazopyrrolone bridge structure and structural disorder on the optical properties and probable electronic transitions

Investigations of Interface Properties in Copper-Silicon Carbide Composites

This paper analyses the technological aspects of the interface formation in the copper-silicon carbide composite and its effect on the material’s microstructure and properties. Cu-SiC composites with two different volume content of ceramic reinforcement were fabricated by hot pressing (HP) and spark plasma sintering (SPS) technique. In order to protect SiC surface from its decomposition, the powder was coated with a thin tungsten layer using plasma vapour deposition (PVD) method. Microstructural analyses provided by scanning electron microscopy revealed the significant differences at metal-ceramic interface. Adhesion force and fracture strength of the interface between SiC particles and copper matrix were measured. Thermal conductivity of composites was determined using laser flash method. The obtained results are discussed with reference to changes in the area of metal-ceramic boundary

The effect of ceramic type reinforcement on structure and properties of Cu-Al2O3 composites

The purpose of this paper is to elaborate on mechanical alloying conditions for a composite powder consisting of copper and brittle aluminium oxides. Detailed analysis of the Cu-Al2O3 powder mixture structure obtained in the mechanical alloying process allows for the study of the homogenization phenomena and for obtaining grains (in composite form) with a high degree of uniformity. The Cu-5vol.%Al2O3 composites were obtained by means of the spark plasma sintering technique. The results presented herein were studied and discussed in terms of the impact of using a different form of aluminium oxide powder and a different shape of copper powder on composite properties. Research methodology included microstructure analysis as well as its relation to the strength of Cu-Al2O3 interfaces. It transpires from the results presented below that the application of electrocorundum as a reinforcement phase in composites decreases porosity in the ceramic phase, thus improving thermal properties and interfacial strength