Exemplary Material Research Articles

Elucidating Lithium Alloying-Induced Degradation Evolution in High-Capacity Electrodes.

Alloy electrode materials offer high capacity in lithium-ion batteries; however, they exhibit rapid degradation resulting in particle disintegration and electrochemical performance decay. In this study, the evolution of lithium alloying-induced degradation due to electrochemomechanical interactions is examined based on a multipronged electrochemical and microstructural analysis. Copper-tin (Cu6Sn5) is chosen as an exemplary alloy electrode material. Electrodes with compositional variations were fabricated, and electrochemical performance was examined under varying conditions including voltage window, C-rate, and short- and long-term cycling. Morphology and composition analyses of pristine and cycled electrodes were conducted using micrography and spectroscopy techniques. Alloying-induced electrode microstructural evolution was probed using X-ray microtomography. The rapid capacity fading was found to be caused by mechanical degradation of the electrode. Driving the electrode to a lower potential ( E ≈ 0.2 V vs Li/Li+) induced Li-Sn alloy formation and provided the characteristic large capacity; however, this led to a large volume expansion and active particle cracking and disintegration. Copper expulsion was found to be a consequence of the alloy formation; however, it was not the primary contributor to the dramatic electrochemical performance decay.

Assessment of the predictive capabilities of commercial simulation software packages for the analysis of the C redistribution during Q&P processing

The C enrichment of austenite is of great importance to different kinds of transformation-induced plasticity-aided steels. Particularly, quenching and partitioning – a two-step heat treatment process, which involves the partial transformation to martensite and the subsequent C partitioning to austenite and its concomitant stabilization – has received considerable attention in recent years. The present work assesses the applicability of commercial software packages (DICTRA and MatCalc) to predict the interplay of C enrichment of austenite and concomitant C depletion of martensite. Results are additionally compared to calculations based on the “constrained carbon equilibrium” (CCE) and, moreover, to experiments conducted for two exemplary material conditions. DICTRA simulations extend the CCE calculation in terms of time dependence and allow to account for the possible displacement of the phase boundary, but lack the implications of the martensitic structure. Predictions based on MatCalc more accurately reflect experimental observations. Data gained allows for the evaluation of the predictive capabilities of commercial simulation packages corresponding to a prerequisite for the industrial implementation of novel heat treatment strategies and the required process control.

An investigation of optical constants, solid state parameters and NLO properties of glycine sodium iodide (GSI): a new auspicious semi organic NLO crystal for optoelectronics applications

Optically very nice quality single crystals of a new semi organic NLO material, glycine sodium iodide (abbreviated as GSI) C2H5NO2·NaI had been grown by exploiting slow evaporation technique. The yielded crystals had been of average dimensions 22 × 4 × 5 mm3. FTIR spectroscopy showed the vibration frequencies of numerous functional groups in the cultivated crystal. Single and powder X-ray diffraction studies were executed to determine the crystal structure and lattice parameters of the synthesized compound. Optical constants such as band gap, refractive index, reflectance, extinction coefficient and electric susceptibility have been deliberated for the cultivated material from the UV–Vis–NIR spectrum. The optical band gap of the harvested crystal is perceived to be 5.09 eV. The chemical composition of GSI is analyzed by employing EDX analysis. The dielectric constant and dielectric loss of the synthesized material have been measured in different frequency range from 100 Hz to 5 MHz at three different temperatures (40, 50 and 60 °C). Moreover, solid state electronic properties, such as plasma energy, Penn gap energy, Fermi energy and electronic polarizability of the cultivated crystal have been calculated. Surface morphology of the harvested material is studied with the aid of scanning electron microscope. From the second harmonic generation analysis, it is evident that GSI has the efficiency 1.53 times that of potassium dihydrogen phosphate and hence it is an exemplary material for optoelectronics applications.

The Dual‐Play of 3D Conductive Scaffold Embedded with Co, N Codoped Hollow Polyhedra toward High‐Performance Li–S Full Cell

AbstractLithium–sulfur (Li–S) batteries are one of the most promising battery technologies to support the fast‐expanding electrical vehicle and large‐scale energy storage market. However, several intrinsic and intractable obstacles are still impeding the practical implementation of Li–S batteries, which calls for advances in both sulfur and lithium electrodes. Herein, a 3D conductive scaffold is developed with hollow carbon polyhedra embedded on tubular carbon fabric (HPTCF) as self‐standing matrix for both improved sulfur and lithium electrodes. Attributed to the high conductivity, abundant active interfaces, and favorable surface functionalization of HPTCF, reliable sulfur and lithium electrochemistry are simultaneously achieved. The results show an outstanding cyclability with a minimum capacity decay of 0.018% per cycle over 600 cycles in half cell, while the combined cathodic and anodic improvements further contribute to an excellent Li–S full cell performance with high capacity retention of 3.1 mAh cm−2 at 200th cycle and superb rate performance of 2.5 mAh cm−2 at 4 C rate under a reasonably high sulfur loading of 4 mg cm−2. This work offers exemplary material engineering that concurrently and effectively tackles the problems in sulfur and lithium electrodes. This approach has great potential to promote the practical application of Li–S batteries.

Concept of Computer-Aided Assessment of the Technical Condition of Operated Gas Turbine Vanes

Abstract The article presents a multi-stage algorithm for automatic (without any human, user – diagnostician intervention) detection of vanes-blades (technical objects) and their surfaces on a digital image, combined with color analysis, aimed at determining the technical condition of the tested turbine elements. The images recorded with the use of a camera, containing previously dismantled from the turbine operated stator vanes, were used as the exemplary analysis material. The paper presents the algorithm for the detection of the vanes’ airfoil surfaces with the impact of the applied techniques and methods of image processing and analysis on the final result (software localization of the vane’s trailing and leading edge), Then, the obtained image data, including the structural changes of both the vane’s coating and material (metallographic testing) were correlated with the surface colour scheme (colour segmentation based on the YCbrCr colour space model). Thanks to this approach, areas on the surface of the blade were distinguished, characteristic for proper, overheated and transient condition.

Responding to English Grammatical Challenges: The Design and Development of Exemplary Material for Form One Learners in Tanzania

This article proposes strategies for designing and evaluating curriculum materials for enhancing English language grammatical competence among Form One learners in Tanzanian secondary schools. Using quasi-experimental and phenomenological designs, the authors developed an exemplary Learner Centered Instructional Grammar Material (LCIGM) focusing on Form One learners. Materials design approach and Constructivism Theory of learning guided the exercise. The data for the study were collected through documentary review, interviews, questionnaires and teaching and learning observations of 40 Form One learners chosen from three randomly selected secondary schools in the Dodoma Region of Tanzania. Both pre-test and post-tests were done to understand the suitability of the newly developed material to meet the purpose of enhancing grammatical competence among Form One learners. The findings and observations revealed that both teachers and learners benefited from the designed activity-based material which, in turn, enhanced learners’ grammatical performance, both in spoken and written form. The authors concluded by urging the stakeholders to design the material that are activity based to improve the learners’ grammatical competence.

Hyperelastic constitutive modeling with exponential decay and application to a viscoelastic adhesive

Hyperelastic materials models are well established to describe the non-linear stress-strain relations of elastomers. In this paper, a polyurethane adhesive is considered as an exemplary material and subjected to tensile, compressive and shear tests. Conventional hyperelastic models are unable to capture the mechanical behavior satisfyingly: If the model agrees with the test results at large strains, it underestimates the stiffness at low strains significantly. We propose a model extension to describe a kind of exponential decay of stiffness which bears some similarity with a specific model developed by Yeoh. The new hyperelastic model is coupled with linear viscoelasticity to account for the strain rate dependence observed for the tested material.The model parameters are identified using a tensile test at a single strain rate only and a creep test. Furthermore, the compressibility is determined by comparison of the stiffness in two butt joint tests with different aspect rations of the adhesive layer. Using this parameter set the new model provides a very good prediction of tensile, compressive and shear tests at different strain rates.

Influence of the size and boundary conditions on the predicted effective strengths of particulate reinforced metal matrix composites (PRMMCs)

Understanding how the load bearing capacity of particulate reinforced metal matrix composite (PRMMC) is related to the underlying microstructure is essential for developing new PRMMC materials. In a recent study, we presented a numerical technique which combines the homogenization technique, direct method, and statistical analyses. By using this approach, ultimate strength and endurance limit of the PRMMCs can be predicted from the composite microstructure in the mesoscale. Because PRMMCs are typical random heterogeneous materials, the size of RVE models, as well as boundary conditions, have been acknowledged to have nontrivial influence over the predicted effective behavior. In this paper, the objective is to understand how the strength predicted from the direct method is influenced by the RVE size and boundary condition. Because in our previous study it has already been shown that homogenization results are insensitive to boundary conditions applied on the RVE, the focus of the present paper is laid on the influence of the embedded cell model. In order to capture the influence of RVE size and embedded cell configuration, an exemplary PRMMC material, WC-20 Wt% Co, was selected. A great number of representative volume elements (RVE) models were built as artificial microstructures of this material. By analyzing the effective behaviors, especially the strength, predicted from these samples from a statistical point of view, the influence of the boundary condition and the size effect were revealed. On that basis, this study proposes a feasible solution to these issues.

Improved HPLC-method for estimation and correction of amino acid losses during hydrolysis of unknown samples

Amino acid analysis, commonly done by acid hydrolysis of proteins and HPLC analysis, faces one major problem: incomplete hydrolysis of stable amino acids and degradation of unstable amino acids are causing amino acid losses. As a result, amino acid recovery of unknown samples cannot be estimated. Some methods have been reported for correction of these factors in the past. This paper shows an improved and integrated method to overcome this problem by using stillage as an exemplary unknown sample material. Amino acid recovery from an unknown sample can be estimated by standard addition of a known protein. If the sample does not cause matrix effects during amino acid hydrolysis, recoveries of the standard protein are transferable to the sample. If the sample does cause matrix effects correction of amino acid losses can instead be done by determination of hydrolysis kinetics. Therefore, first order kinetics were used for amino acids that undergo degradation during hydrolysis. For all stable amino acids higher order kinetics were used, a novel approach to determine hydrolysis kinetics. The presented method can be a helpful tool for scientists who want to optimize amino acid analysis of a particular biomass substrate.

Research Update: Van-der-Waals epitaxy of layered chalcogenide Sb2Te3 thin films grown by pulsed laser deposition

An attempt to deposit a high quality epitaxial thin film of a two-dimensionally bonded (layered) chalcogenide material with van-der-Waals (vdW) epitaxy is of strong interest for non-volatile memory application. In this paper, the epitaxial growth of an exemplary layered chalcogenide material, i.e., stoichiometric Sb2Te3 thin films, is reported. The films were produced on unreconstructed highly lattice-mismatched Si(111) substrates by pulsed laser deposition (PLD). The films were grown by vdW epitaxy in a two-dimensional mode. X-ray diffraction measurements and transmission electron microscopy revealed that the films possess a trigonal Sb2Te3 structure. The single atomic Sb/Te termination layer on the Si surface was formed initializing the thin film growth. This work demonstrates a straightforward method to deposit vdW-epitaxial layered chalcogenides and, at the same time, opens up the feasibility to fabricate chalcogenide vdW heterostructures by PLD.

Ist die Unterscheidung von Sprache und Zunge im Deutschen berechtigt? Einige Gedanken zu kulturgeprägten lexikalischen Unterschieden in der Interpretation der außersprachlichen Wirklichkeit

Im Vordergrund folgender Erörterungen steht die Frage, wie sich Sprachen in semantischer Hinsicht auf kulturabhängige Art und Weise unterscheiden und ob das Deutsche Recht hat, wenn es Sprache und Zunge unterscheidet. Deswegen wird beispielhaft aufgezeigt, dass in der einen Sprache Bedeutungsabgrenzungen vorkommen, die es in einer anderen nicht gibt. Dann wird zur Sprache gebracht, in welchen Kontexten die Wörter Sprache und Zunge gebraucht werden können. Auf dieser Grundlage wird dargestellt, dass in jeder Sprache und in jeder Kultur eine ganz bestimmte Einteilung und Verfügbarmachung der Wirklichkeit zum Ausdruck kommt. Jede Kultur entwickelt sich in die Richtung, die ihr von ihren jeweiligen Umweltbedingungen vorgegeben wird. Is the distinction between Sprache and Zunge in German justified? Some information about the cultural and lexical differences in the image of extra-lingual realityThe present paper discusses the issue of culture-specific semantic differences between languages, as well as the question whether the German language has the right to differentiate between Sprache and Zunge. Using exemplary material, it is shown that semantic boundaries of one language are absent from another. Next the contexts in which the words Sprache and Zunge are used are discussed. On this basis it is explained that each language and each culture offers a specific way of classifying reality and making it available. Each culture develops in the direction which is dictated by specific environmental conditions.

Nihilizm jako literackie pogranicze oraz pole napięć aksjologicznych i estetycznych na przykładzie twórczości Jarosława Marka Rymkiewicza. Próba rozpoznania

The subject is an attempt to describe the evolution of the term „nihilism” in philosophy (hermeneutics) at the turn of centuries and the description of how this evolution influenced the ways of analyzing literary phenomena. The author wants to present judgements which revalue the approach to this way of thinking deeply rooted in culture. Nihilism in presented approaches appears to be a world view and esthetic phenomenon opening new field of interpretation of poetic and prose texts. The exemplary literary material displaying the possibilities of different interpretations of an artistic text, both an essay and a poem is the output of Jarosław Marek Rymkiewicz.

The Role of Ferric Oxide Nanoparticles in Improving Lubricity and Tribo-Electrochemical Performance During Chemical–Mechanical Polishing

The role of ferric oxide nanoparticles on the lubricating characteristics of passivating films formed on stainless steel (SS) was discussed in this study. The tribo-electrochemical behavior of mirror-like polished AISI 304 SS, used as an exemplary material, was evaluated in various electrolytes by means of a simulated chemical–mechanical polishing process in laboratory scale. It was clearly demonstrated that a suitable combination of abrasives (ferric oxide nanoparticles) and an oxidizer (nitric acid) can act as an effective lubricant that lowers the friction and wear of the AISI 304 SS surfaces. The excellent lubricating and anti-corrosion properties shown by a slurry containing a high content of ferric oxide nanoparticles at high nitric acid concentrations were attributed to the formation of a stable and robust passive film that was composed of chromium oxide and a mixture of iron oxides. The lack of ferric oxide nanoparticles in two solutions containing nitric acid of different concentrations led to pitting corrosion and abrasive wear. When low concentrations of both ferric oxide nanoparticles and nitric acid were used, wear-accelerated corrosion became the dominant mechanism that was caused by the presence of third-body wear particles in the contact zone.

Optical fingerprint of dark 2p-states in transition metal dichalcogenides

Atomically thin transition metal dichalcogenides exhibit a remarkably strong Coulomb interaction. This results in a fascinating many-particle physics including a variety of bright and dark excitonic states that determine optical and electronic properties of these materials. So far, the impact of dark states has remained literally in the dark to a large extent, since a measurement of these optically forbidden states is very challenging. Here we demonstrate a strategy to measure a direct fingerprint of dark states even in standard linear absorption spectroscopy. We present a microscopic study on bright and dark higher excitonic states in the presence of disorder for the exemplary material of tungsten disulfide (WS2). We show that the geometric phase cancels the degeneration of 2s and 2p states and that a significant disorder-induced coupling of these bright and dark states offers a strategy to circumvent optical selection rules. As a proof, we show a clear fingerprint of dark 2p states in the absorption spectrum of WS2. The predicted softening of optical selection rules through exciton-disorder coupling is of general nature and therefore applicable to related two-dimensional semiconductors.

On the calculation of Topological Derivatives considering an exemplary nonlinear material model

AbstractIn this contribution, a new approach for dealing with material nonlinearities in structural optimization is presented. The method combines the advantage of the calculation of the Topological Derivatives in elasticity problems with the use of meta‐modelling for capturing complex correlations. For an exemplary nonlinear material model, the calculation of the Topological Derivative and the resulting difference to the linear elastic material model is shown. An academic example shows the difference between the linear and the nonlinear material model. © 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Direct fabrication of high-performance high speed steel products enhanced by LaB6

A direct fabrication technology (DFT) without smelting has been developed for fabricating sophisticated high speed steel products with low pollution, near-net shaping and short process. The steel consisting of (wt.%): 6.4W, 5.0Mo, 4.2Cr, 3.1V, 8.5Co and 1.28C, was fabricated as exemplary material. The activated and reactive sintering of green compacts under vacuum with low activation energy, redox reaction enhanced diffusion and the construction of concentration gradient of alloying elements around pores, promotes the nearly full densification (>99.40%). Also, the DFT steels show high purity and superior mechanical properties. Minor strengthening agent LaB6 (0.1wt.%), which is easily to be accurately introduced in DFT, obviously increases the hot hardness, temper resistance, bend strength and toughness of DFT M3:2. The strengthening effect of boron atoms and La-rich complexes are proposed to directly result in the high hot hardness and temper resistance of LaB6 containing steel.

Ultrathin MgO diffusion barriers for ferromagnetic electrodes on GaAs(001)

Ultrathin MgO(100) films serving as a diffusion barrier between ferromagnetic electrodes and GaAs(001) semiconductor templates have been investigated. Using Fe as an exemplary ferromagnetic material, heterostructures of Fe/MgO/GaAs(001) were prepared at 200 °C with the MgO thickness ranging from 1.5 to 3 nm. Structural characterization reveals very good crystalline ordering in all layers of the heterostructure. Auger electron spectroscopy depth-profiling and cross-sectional high-resolution transmission electron microscopy evidence diffusion of Fe into MgO and—for too thin MgO barriers—further into GaAs(001). Our results recommend a MgO barrier thickness larger than or equal to 2.6 nm for its application as a reliable diffusion barrier on GaAs(001) in spintronics devices.

”En sværm af skyer, som skal tænkes” – en diskussion af kultur, kunst og æstetik

<p>These days there are many different understandings and definitions of the term aesthetics. Sometimes it is regarded as identical to the pleasing or the sensual, other times it has a more workaday meaning, being associated with e.g. a well-stocked lunch table. The common denominator, however, is that aesthetics is understood as something that can be recorded in the real world, having been assigned an independent existence. <br />The concept has thus undergone ‘ontological dumping’, by which we understand that an analytical concept has become a “thing in the world”, i.e. an epistemological state has been transformed into an ontological state. The problem with this is that what can potentially be used to understand has instead turned into something to be understood. In the endeavour not to downgrade the epistemological dimension in favour of the experiential dimension, we attempt in this article to re-establish aesthetics as an analytical concept: Something to be seen with – instead of something that is seen. In addition, we put it into perspective alongside culture and art, which we feel has undergone the same ontological dumping. The article concludes with some reflections on the implications this may have for educational practice. As its theoretical springboard, the article takes the philosopher Jean-François Lyotard, drawing its exemplary material from the Norwegian author Karl Ove Knausgård.</p>

Enhanced photoelectrochemical water oxidation via atomic layer deposition of TiO2 on fluorine-doped tin oxide nanoparticle films.

TiO2 is an exemplary semiconductor anode material for photoelectrochemical (PEC) water-splitting electrodes due to its functionality, long-term stability in corrosive environments, nontoxicity, and low cost. In this study, TiO2 photoanodes with enhanced photocurrent density were synthesized by atomic layer deposition (ALD) of TiO2 onto a porous, transparent, and conductive fluorine-doped tin oxide nanoparticle (nanoFTO) scaffold fabricated by solution processing. The simplicity and disordered nature of the nanoFTO nanostructure combined with the ultrathin conformal ALD TiO2 coatings offers advantages including decoupling charge carrier diffusion length from optical penetration depth, increased photon absorption probability through scattering, complimentary photon absorption, and favorable interfaces for charge separation and transfer across the various junctions. We examine the effects of porosity of the nanoFTO scaffold and thickness of the TiO2 coating on PEC performance and achieve an optimal photocurrent of 0.7 mA cm(-2) at 0 V vs. Ag/AgCl under 100 mW cm(-2) AM 1.5 G irradiation in a 1 M KOH aqueous electrolyte. Furthermore, the fundamental mechanisms behind the improvements are characterized via cyclic voltammetry, incident photon-to-current efficiency, transient photocurrent spectroscopy, and electrochemical impedance spectroscopy and are contrasted with those of single crystal rutile TiO2 nanowires. The strategies employed in this work highlight the opportunities inherent to these types of heteronanostructures, where the lessons may be applied to improve the PEC conversion efficiencies of other promising semiconductors, such as hematite (α-Fe2O3) and other materials more sensitive to visible light.

CHARAKTERYSTYKA REGIONALNA PIENIN NA POTRZEBY TERENOWEJ EDUKACJI PRZYRODNICZEJ

The paper comprises geographic characteristics of Pieniny region which is introductory material for field classes at university level. First, localization of the region was depicted and its division into microregions. Next, particular components of natural environment i.e. geological structure, land relief, climatic conditions, water relations, soils, vegetation and fauna were characterized. In the next part, human activity was discussed, against the background of natural environment, which results in development of cultural landscapes. The presented description of Pieniny, in the paper, may be exemplary and auxiliary material for the construction of characteristics of other regions.