bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Cell Layout and Device Structure on On-Voltage Reduction of 6.5-kV n-Channel SiC IGBTs
Authors: Watanabe Naoki , Yoshimoto Hiroyuki , Shima Akio
Published: June 2018

A box cell layout and a hole-barrier structure were used to realize low-on-voltage n-channel 4H-SiC IGBTs with 6.5-kV blocking capability. Box cell layout can increase the channel width, leading to reduction of the channel resistance and an enhancement of electron injection from an emitter. Hole-barrier structure, which is a potential barrier for holes to prevent them from flowing out of the emitter, can enhance conductivity modulation. An on-voltage of 3.98 V at a collector current of 100 A/cm2 was achieved from a fabricated SiC IGBTin this study. Since the on-voltage of a SiC IGBT with a conventional structure was 4.81 V at the same collector current, the effect of our new structure was successfully shown to reduce the on-voltage of SiC IGBTs. An estimation of each voltage component involved in the on-voltage was also carried out by utilizing a device simulation, and the estimation shows that a SiC IGBT incorporating a box layout and hole-barrier structure will thus have quite a low drift-layer voltage and an on-voltage close to the limit determined by the bipolar built-in voltage.
Simulation-Based Sensitivity Analysis of Conduction and Switching Losses for Silicon Carbide Power MOSFETs
Authors: Müting Johanna , Grossner Ulrike
Published: June 2018

The behavior of silicon carbide power MOSFETs is analyzed using TCAD device simulations with respect to conduction and switching losses. Device designs with varying breakdown voltages are simulated. The contributions to the on-state resistance are shown at room and elevated temperature. Whereas channel and substrate resistance dominate at low breakdown voltages, drift and JFET resistance dominate at high breakdown voltages. With increasing temperature, the channel resistance decreases and thus the drift resistance is the main contributor already at medium breakdown voltages. Manufacturing processes of a device can have a high influence on its losses. Variations in interface mobility, drift doping, and p-body doping can lead to a significant change of on-resistance, internal capacitances, and reverse recovery charge. For higher voltage classes the drift layer properties should be of major interest as it influences on-resistance and reverse recovery charge.
Influence of the Magnesium Treatment in a Georg Fischer Converter
Authors: Lueben Mathias
Published: June 2018

With up-to-date thermal analysis equipment, it is possible to control and regulate the melting and treatment process of ductile iron, more or less at every step of the process. Changes in the composition can be handled by controlling and then regulating each single step. The complete process, starting with the melting in a cupola furnace, followed by the holding process in an induction channel furnace and finally the magnesium treatment in a converter has been analysed. A correlation to control and regulate the eutectic undercooling of the melt has been developed.
Maximization and Control of Nodular Iron Melt’s Self-Feeding Characteristics to Minimize Shrinkage
Authors: Anjos Vítor , Silva Ribeiro Carlos A.
Published: June 2018

This paper describes one possible method to anticipate and control the development of solidification shrinkage, during solidification of nodular cast iron melts, based upon industrial trials made using special designed test castings and closed volume thermal analysis cartridges.The methodology considers both the solidification morphology and solidification shrinkage critical size, which is always a difficult component of analysis, along with a developed contraction defect index, that allows the application to several types of molten metal and inoculation practices.The use of thermal analysis allows the recognition of unique melt characteristics, in real time, that are not accessed by more traditional measurement equipment. This allows the definition of thermal analysis patterns that characterize the best melt quality for self-feeding. This is a practical to use and powerful tool for modern foundries, taking advantage of new metric, data collection and data analysis. We aim to contribute to scientific knowledge and simultaneously to provide information that can be useful for foundries to improve their process efficiency.
Density Variations during Solidification of Grey Cast Iron
Authors: Hellström Kristina , Svidró Péter , Diaconu Lucian Vasile , Diószegi Attila
Published: June 2018

As part of moving towards a sustainable production of diesel engines for heavy vehicle applications, the ability to predict casting defects has become ever so important. In order to model the solidification process for cast components correctly, it is of essence to know how the material will actually behave. To produce sound castings, often of complex geometry, the industry relies on various simulation software for the prediction and avoidance of defects. Thermophysical properties, such as density, play an important part in these simulations.Previous measurements of how the volume of liquid grey iron changes with temperature has been made with a conventional dilatometer. Measurements have also been made in the austenitic range, then on iron-carbon-silicon alloys with a carbon content lower than 1.5 wt%. Based on these measurements the density variations during solidification were calculated. The scope for this paper is to model the volume changes during solidification with the control volume finite difference method, using data from the density measurements.
ADI 1050-6 Mechanical Behavior at Different Strain Rates and Temperatures
Authors: Ruggiero Andrew , Iannitti Gianluca , Masaggia Stefano , Vettore Federico
Published: June 2018

An experimental characterization of the austempered ductile iron ISO 17804/JS/1050-6/S was performed carrying out tensile tests under different strain rates, temperatures and stress triaxiality levels. Then, composing a yield function surface, a hardening relation, and a damage criterion, a constitutive model was developed to describe the salient features of the observed macroscopic response. In particular, the Mohr-Coulomb yield function was selected to account for the pressure effect observed on the yield surface. A new hardening relation was proposed in order to account for both strain rate and temperature effects. The Bonora’s damage model, developed in the framework of the continuum damage mechanics, was adopted to capture the failure condition under different stress triaxiality levels. The damage model was appropriately modified to account for the effect of strain rate and temperature on the failure strain.
Austempering Experiments of Production Grade Silicon Solution Strengthened Ductile Iron
Authors: Soivio Kaisu
Published: June 2018

Austempered ductile iron provides a feasible way to produce high strength components. However, in heat treatments resulting in highest strengths some of the ductility is lost due to formation of bainitic carbides. The role of silicon in inhibiting the formation of iron carbides in as-cast ductile irons as well as its solution strengthening effect is well known and acknowledged in industry. The effect of silicon on austemperability, resulting microstructures, and mechanical properties of austempered ductile irons with silicon contents with 3.4-3.8 w-% was researched. Quenching and austempering heat treatments were carried out for production grade silicon solution strengthened ductile irons EN GJS 500-14. Results indicate, that it is possible to manufacture a fully ausferritic structure into a silicon solution strengthened matrix and indeed good ductility can be achieved in combination with ultimate tensile strength of 1600 MPa. Segregation of silicon reduces the solubility of carbon into the matrix especially close to the graphite nodules which reduce the stability of carbon stabilized austenite and leads into compromised machinability.
Effect of Boron and Cross-Section Thickness on Microstructure and Mechanical Properties of Ductile Iron
Authors: Kasvayee Keivan Amiri , Ciavatta Matteo , Ghassemali Ehsan , Svensson Ingvar L. , Jarfors Anders E.W.
Published: June 2018

Eeffect of Boron addition on the microstructure and mechanical properties of ductile iron, GJS-500-7 grade was studied. Three cast batches with the Boron content of 10, 49 and 131ppm were cast in a casting geometry containing plates with thicknesses of 7, 15, 30, 50 and 75mm. Microstructure analysis, tensile test, and hardness test were performed on the samples which were machined from the casting plates. Addition of 49 ppm Boron decreased pearlite fraction by an average of 34±6% in all the cast plates. However, minor changes were observed in the pearlite fraction by increasing Boron from 49 to 131 ppm. Variation in the plate thickness did not affect the pearlite fraction. The 0.2% offset yield and ultimate tensile strength was decreased by an average of 11±1% and 18±2%, respectively. Addition of 49 ppm Boron decreased Brinell hardness by 16±1%, while 11±2% reduction was obtained by addition of 131ppm Boron.
The Role of Compounds in Graphite Formation in Cast Iron - A Review
Authors: Riposan Iulian , Chisamera Mihai , Stan Stelian
Published: June 2018

The paper reviews original data obtained by the authors, from recent separate publications, specifically concerning graphite formation in the solidification pattern of industrial cast irons, focussing on grey iron versus ductile iron. Additional unpublished data and selected data from literature are represented in the paper. Complex compounds act as nucleation sites in commercial cast irons, generally in a three-stage graphite formation, but with different sequences: (1) first micro-compound formation is oxide/silicate in grey iron and sulphide in ductile iron; (2) the second compound nucleates on the first one, as complex manganese sulphide in grey iron and complex silicates in ductile iron; (3) graphite nucleation on the sides of stage 2 compounds, which have low crystallographic misfit with graphite. Resulphurization (Mn/S control), preconditioning with strong oxide forming elements (Al, Zr), more potent inoculants and inoculation enhancement with S, O and oxy-sulphide forming elements were found to be beneficial treatments especially in critical solidification conditions
Mechanical Properties and Impact Toughness of Nickel and Aluminum Alloyed High Silicon Ductile Iron
Authors: Weiß Philipp , Riebisch Moritz , Bührig-Polaczek Andreas
Published: June 2018

High silicon grades of ductile cast iron are known to be highly advantageous in regard to technically relevant properties and economic efficiency. In particular, the outstanding mechanical properties lead to an increasing demand since 2011, the year of incorporation to the EN 1563 standard. However, low impact resistance and spontaneous failure are concerns that limit the application, especially at lower temperatures. Silicon serves as a solid solution strengthener. By the addition of cobalt, aluminum and nickel as additional solid solution strengthener, an improvement in mechanical properties compared to only silicon could be obtained. Previous studies showed that the addition of 1.5 wt.% Ni to an EN-GJS-500-14 grade with 3.8 wt.% Si resulted in a tensile strength of 650 MPa at 15 % elongation. In the present study, silicon was substituted stepwise by nickel and aluminum, simultaneously aiming at the retention of the mechanical properties of the EN-GJS-500-14 grade. By decreasing the silicon content to 3.3 wt.% Si at 1.1 wt.% Ni and 0.2 wt.% Al, EN-500-14 was obtained. Even though, the presence of pearlite in the matrix was observed, this substitution of silicon led to an increase in Charpy-V-notch toughness by 4 Joule at room temperature. For further alloy design of high silicon ductile cast iron for simultaneously substituting silicon and improving the mechanical properties and notch toughness, the restrictions for pearlite formation must be complied.
Scratch Behaviour of Silicon Solid Solution Strengthened Ferritic Compacted Graphite Iron (CGI)
Authors: Ghasemi Rohollah , Jarfors Anders E.W.
Published: June 2018

The present study focuses on scratch behaviour of a conventional pearlitic and a number of solid solution strengthened ferritic Compacted Graphite Iron (CGI) alloys. This was done by employing a single-pass microscratch test using a sphero-conical diamond indenter under different constant normal loads conditions. Matrix solution hardening was made by alloying with different content of Si alloy; (3.66, 4.09 and 4.59 wt%. Si) which are named as low-Si, medium-Si and high-Si ferritic CGI alloys, respectively. A good correlation between the tensile and scratch test results was observed explaining the influence of CGI’s matrix characteristics on scratch behaviour both for pearlitic and fully ferritic solution strengthened ones. Both the scratch depth and scratch width showed strong tendency to increase with increasing the normal load, however the pearlitic one showed more profound deformation compared to the solution strengthened CGI alloys. Among the investigated alloys, the maximum and minimum scratch resistance was observed for high-Si ferritic CGI and pearlitic alloys, respectively. It was confirmed by the scratched surfaces analysed using Scanning Electron Microscopy (SEM) as well. In addition, the indenter’s depth of penetration value (scratch depth) was found as a suitable measure to ascertain the scratch resistance of CGI alloys.Keywords: Silicon solution strengthening, CGI, Abrasion, Scratch testing, Scratch resistance
Modelling Approach and Challenges in Simulating Dross Formation in Ductile Iron Castings
Authors: Hojjat Majidi Seyyed , Beckermann Christoph , Fainberg Jakob , Schäfer Wilfried , Bodenburg Mathias
Published: June 2018

Dross is one of the most challenging quality issues in high integrity ductile iron castings. The formation of dross is linked to the applied metallurgy, metal treatment, process control and gating/rigging design. One of the primary concerns in this regard is entrainment of air into the melt during filling of the casting. Today, avoiding and controlling dross relies on the practical experience and process know-how of foundry experts. A quantitative understanding of the formation mechanisms or the prediction of final amounts and locations of dross in castings is not available. In this paper a computational model is developed for predicting the formation, motion and final location of dross inclusions during pouring of ductile iron castings. The focus is on the important mechanism of dross generation due to air entrainment during filling of the mold. The model predicts the local air entrainment rate as a function of the turbulent kinetic energy of the liquid metal and the normal velocity gradient of the metal at the liquid metal-air interface. The dross inclusions resulting from the exposure to the entrained air are transported with the melt flow under the combined influences of drag and buoyancy, and captured by the solidifying casting structure. The model is implemented in a commercial casting simulation software code. Ductile iron casting experiments are conducted to validate the model using castings having a variety of gating systems, section thicknesses, and surface orientations. Dross is measured by serial sectioning of the solidified castings. Good agreement between measured and predicted dross amounts and locations is obtained. The results reveal how gating system design affects dross formation. Clean ductile iron castings can be obtained by minimizing air entrainment during pouring. The present model allows foundries to evaluate different gating designs and pouring parameters before the first casting is poured. The paper also discusses open issues and practical challenges in quantifying the amounts of dross as a function of the entire processing route of a casting.
"Cast Iron - A Predictable Material” 25 Years of Modeling the Manufacture, Structures and Properties of Cast Iron
Authors: Sturm Jörg C. , Schäfer Wilfried
Published: June 2018

During the last 25 years, casting process simulation has developed from predicting hot spots and solidification paths to an integral assessment and optimization tool for foundries for the entire manufacturing route of castings. Modeling cast irons has always been a special challenge due to the strong interdependency between the alloy composition, applied metallurgy and metal treatment with the solidification, phases and structures which form and the resulting properties of the material.
Recent Advances in Cast Iron Structure and Properties Ultrasonic Testing and Flaw Detection
Authors: Voronkova Liubov V.
Published: June 2018

The advantage of ultrasonic testing of iron castings prior to destructive control consists of an impressive reduction in time and costs, as well as the ability to assess the quality of the metal anywhere on the castings. According to the acoustic characteristics of cast iron it is possible to determine the form of graphite in it and its strength. The presence of chill in the metallic base and the thickness of the chilled layer is also determined by ultrasonic method. The use of electronic signal processing allows to distinguish it from high structural noise, which makes possible the testing of cast iron for a thickness of several meters. The use of transducers with phased array is the basis of the flaw detection of containers for nuclear waste from cast iron with globular graphite with a thickness of 500 mm.
Effect of Trace Elements on the Liquid Structure of Sn-Cu Alloys Investigated by High Energy X-Ray Diffraction
Authors: Qu Dong Dong , McDonald Stuart D. , Yasuda Hideyuki , Ohara Koji , Kohara Shinji , Nogita Kazuhiro
Published: June 2018

Liquid metal structure of Sn-Cu alloys studied by synchrotron high energy X-ray diffraction have been performed to investigate the effect of the trace elements Ni and Al. It has been demonstrated that trace Ni and Al additions are able to alter the liquid Sn-4wt%Cu structure. The refinement of the primary Cu6Sn5phase after trace Al additions is proposed to be caused by the consumption of Cu atoms involved in a AlCu chemical ordering and an associated change in the undercooling for Cu6Sn5nucleation.
Palladium(II) Picoline Thiourea Complex as Homogenous Catalyst in Heck Cross-Coupling Reaction in the Formation of C=C Bond
Authors: Khairul Wan M. , Mei Meei , Rahamathullah Rafizah , Soh Siti Kamilah Che , Shamsuddin Mustaffa
Published: June 2018

Palladium (II) complex containing picoline thiourea (Pd-PTu) was prepared by reacting bis (benzonitrile) palladium (II) chloride (Pd-PhCN) withN’-2-(5-picolyl)-N-4-bromobenzoylthiourea (PTu). All synthesized compounds have been characterized via several selected typical spectroscopic and analytical techniques namely elemental analysis, Infrared (IR) spectroscopy, Ultraviolet-visible (UV-Vis) spectroscopy, Nuclear Magnetic Resonance (1H and13C NMR) and gas chromatography-flame ionization detector (GC-FID). For Pd-PTu, IR spectrum showed significant shift in the ν (C=N) on the pyridine ring and ν (C=S) stretching vibration at around 30cm-1compared to the free ligand. The finding indicated that the expected coordination of ligand to the palladium metal centre took place via N and S atoms. The catalytic reaction was monitored using GC-FID with conversion of 83.81 %, proved that Pd-PTu can be used as an ideal homogenous catalyst in any Heck cross-coupling reactions in the near future.
Synthesis and Characterization of Ag/TiO2 Thin Film via Sol-Gel Method
Authors: Halin Dewi Suriyani Che , Mahmed Norsuria , Mohd Salleh Mohd Arif Anuar , Mohd Sakeri A.N. , Abdul Razak Kamrosni
Published: June 2018

Ag/TiO2thin films were prepared via sol-gel spin coating method. Structural, surface morphology and optical properties were investigated with the addition of two different amount of silver (Ag). X-ray diffraction pattern shows the sample with pure TiO2, the only phase presence was brookite TiO2. When the Ag content added into the solution, the phase existed for the samples with TiO2doped 0.5g Ag and TiO2doped 1.0g Ag were anatase TiO2with no peak corresponds to Ag phase. The surface morphology of film was characterized by scanning electron microscopy (SEM). The films were annealed at 450 °C and it shows non-uniform films. The films have a large flaky and cracks film which was attributed to surface tension between the film and the air during the drying process. When the solution of sol was added with Ag content, it shows the porous structure with flaky-crack films. With the increasing of the Ag content from 0.5g to 1.0g, the structure is more porous and it is good for the photocatalytic activity. The UV-Vis spectra shows that the film exhibits a low absorbance which was due to the substrate is inhomogeneously covered by the flaky-crack films.
Effect of Surface Potential Distribution on Corrosion Behavior of SnAgCu Solder/Cu Substrate Interface
Authors: Mokhtari Omid , Nishikawa Hiroshi
Published: June 2018

While various mechanical properties of SnAgCu (SAC) solder has been reported in the literature the corrosion resistance of solder materials has not been widely reported. This study shows regions adjacent to the Cu6Sn5 intermetallic compounds (IMCs) as the corroded region. To investigate the possible formation of a galvanic cell at the interface of SAC solder and the Cu substrate the surface potential distribution at this interface has been evaluated. Results exhibited a comparatively large surface potential difference between SAC solder and the Cu6Sn5 IMC indicating SAC solder and Cu6Sn5 IMC as the anode and cathode in this system, respectively.
Effect of Trace Phosphorus on the Dross Formation in Tin-Copper-Nickel Wave Solder
Authors: Xuan Quy Tran , Mohd Salleh Mohd Arif Anuar , McDonald Stuart D. , Nogita Kazuhiro
Published: June 2018

Additions of trace elements such as Phosphorus (P) and Germanium (Ge) are common practice to improve the oxidation resistance in Tin-Copper (Sn-Cu) wave solder systems, however, little insights are available regarding their combined role. In this article, the effect of trace P (<100ppm), in the presence of Ge (<100ppm), on the phase composition and microstructure of Sn-Cu-Ni wave solder dross is studied using various techniques including Synchrotron XRPD, SEM, FIB and TEM. We find that P additions, in the presence of Ge, result in the formations of SnO, SnO2 and Ni2SnP intermetallic in the dross whereas only SnO is present in the P-free equivalent. The crystal structure of Ni2SnP is identified as orthorhombic with the space group Pnma. Based on the findings, it is evident that P not only influences the oxidation state of tin oxides but also reduces the concentration of effective Ni in the alloys via the formation of Ni2SnP intermetallic.
STEM Analysis of Atom Location in (Cu, Au, Ni)6Sn5 Intermetallic Compounds
Authors: Yang Wen Hui , Yamamoto Tomokazu , Nogita Kazuhiro , Matsumura Syo
Published: June 2018

Cu6Sn5 is an important intermetallic compound in soldering and electronic packaging. It is formed at the interface between molten solder and substrate during the soldering process, and the evolution of microstructure and properties also occurs in service. Previous studies revealed that Au and Ni are stabilization alloying elements for hexagonal η-Cu6Sn5 intermetallic. For better understanding of stabilization mechanisms at atomic resolution level, in this work, we made an attempt atomic structure analysis on a stoichiometric (Cu, Au, Ni)6Sn5 intermetallic prepared by direct alloying. High-angle annular dark-field (HAADF) imaging and atomic-resolution chemical mapping were taken by the aberration-corrected (Cs-corrected) scanning transmission electron microscopy (STEM). It is found that Au and Ni doped Cu6Sn5 has hexagonal structure. The atom sites of Cu1 and Sn can be distinguished in atomic-resolution images after being observed from orientation [2110], which is also confirmed by atomic-resolution chemical mapping analysis. Importantly, atomic-resolution about distribution of alloying Au atom was directly observed, and Au atoms occupy the Cu1 sites in η-Cu6Sn5.
Thermochemical Basis of the Preparation of Well-Defined Transition Metal Carbide, Nitride and Carbonitride Reference Materials for Electron-Probe Microanalysis (EPMA)
Authors: Lengauer Walter , Bohn Marcel
Published: June 2018

A common and straightforward method for the standardisation in electron-probe microanalysis (EPMA) is the use of homogeneous reference materials prepared by various techniques such as by melting, sintering, high-temperature annealing and hot-pressing. The reference materials have to be analysed by independent methods accurately in order to define their “true” composition. For some compounds the preparation techniques are difficult because of their specific thermo-chemical properties (e.g. low diffusivities, high equilibrium nitrogen pressure, incongruent melting). In addition, many compounds show large homogeneity ranges with an a priori existing uncertainty in composition, contrary to what is generally preferred: to use compounds with a narrow homogeneity range (“line compounds”). For the latter, diffusional preparation techniques can be applied to yield diffusion layers instead of massive samples for standardisation. However, also single-phase samples with narrow homogeneity ranges can be prepared by diffusion, depending on the phase equilibria in the corresponding system. The presentation summarises efforts that have been made in order to prepare various reference materials for carbon and nitrogen standardisation of EPMA by various techniques. The boundary conditions such as phase stabilities, phase compositions and diffusion kinetics, which are important for their preparation to obtain well-defined reference samples are discussed. These samples were applied to various WDS/EPMA-based studies of phase diagrams and diffusion kinetics by means of Cameca SX 50 and SX 100 microprobes.
Effect of Ti(C0.7N0.3) Content on the Microstructure and Mechanical Properties of Ni Bonded NbC-Ti(C0.7N0.3) Based Cermets
Authors: Huang S.G. , Vleugels J. , Mohrbacher H. , Woydt M.
Published: June 2018

NbC-xTi (C0.7N0.3)-10Ni-7.5VC (vol%) based cermets with 0, 5, 10, 15 or 25 vol% Ti (C0.7N0.3) were prepared by conventional pressureles liquid phase sintering at 1420°C in vacuum. Detailed microstructural investigation was performed by SEM, EPMA and XRD analysis. Sintering results indicated that the partial replacement of NbC by Ti (C0.7N0.3) had a significant effect on the carbide grain growth, microstructure, hardness as well as fracture toughness of the fully densified NbC-based cermets. The Ti (C0.7N0.3)-free NbC cermet was composed of homogeneous cubic (Nb,V)C solid solution grains, whereas core-rim structured NbC grains were observed in cermets with Ti (C0.7N0.3) addition. All sintered cermets with  15 vol% Ti (C0.7N0.3) were composed of a fcc solid solution Ni binder and a cubic core-rim solid solution (Nb,V,Ti)C phase with a Nb-rich core and a Ti-rich rim. 3.8 vol% of residual pristine Ti (C0.7N0.3) was present in the cermets with 25 vol% Ti (C0.7N0.3) addition. The 15 vol% Ti (C0.7N0.3) starting powder based cermet exhibited the finest average NbC grain size of 1.48 μm, with a core-rim structure and an interesting combination of hardness (1486 kg/mm2) and fracture toughness (8.7 MPa.m1/2).
The Influence of Severe Plastic Deformation Process on Structure and Properties of AZ 31 Alloy after Selected Heat Treatment
Authors: Rusz Stanislav , Hilšer Ondřej , Tylšar Stanislav , Čížek Lubomír , Tański Tomasz , Maziarz Wojciech
Published: June 2018

The technology of structure refinement in materials with the aim of achieving substantial mechanical properties and maintaining the required plasticity level is becoming increasingly useful in industrial practice. Magnesium alloys are very progressive materials for utilization in practice thanks to their high strength-to-weight ratios (tensile strength/density). The presented paper analyses the effect of the input heat treatment of the AZ31 alloy on the change of structure and strength properties through the process of severe plastic deformation (SPD), which finds an increasing utilization, especially in the automotive and aviation industry. For the study of the influence of the SPD process (ECAP method) on the properties of the AZ31 alloy, two types of thermal treatment of the initial state of the structure were selected. The analysis of the structure of the AZ31 alloy was performed in the initial state without heat treatment and subsequently after heat treatment. In the next part, the influence of the number of passes on the strengthening curves was evaluated. Mechanical properties of the AZ31 alloy after ECAP were evaluated by hardness measurement and completed by structure analysis.
Effect of ECAP Strain on the Precipitation Kinetics of the AlMg3 Aluminium Alloy
Authors: Snopiński Przemysław , Tański Tomasz
Published: June 2018

Variation of hardness and microstructure evolution in a solution treated AlMg3 aluminium processed by equal channel angular pressing and subjected to subsequent artificial ageing are investigated. The microstructure features of the UFG aluminium alloy are studied by light, electron microscopy and using X-ray diffraction analysis. Microstructural observations showed significant grain refinement. After four ECAP passes microstructure consist of elongated grains with average widths of shear bands of ∼100 nm. A significant increase in the microhardness was observed in the ECAPed samples due to the grain refinement and strain hardening. Prior ECAP solution treatment and a short time artificial ageing can additionally increase the strength of AlMg3 aluminium alloy.
Structure and Mechanical Properties of Composite Layers Prepared by Laser Alloying of Aluminium Alloy
Authors: Pakieła Wojciech , Tański Tomasz , Labisz Krzysztof , Pakieła Katarzyna , Brytan Zbigniew
Published: June 2018

Increasingly high expectations for modern engineering, make the constantly being sought-after new processes giving traditional materials new, better features. Nowadays, next to the classic heat treatments, advanced technologies are being used increasingly, leading to much better results than ever before. The most commonly used technologies that allow for obtaining new, enhanced properties of various metal alloys in the area of surface engineering include, among others laser surface treatment. The main objective of this paper was to analyze the influence of laser surface treatment on structural change and mechanical properties improvement of Al-Mg alloy by VC alloying. The remelted layer on the aluminium alloy surface was obtained using high power fiber laser "Ytterbium Laser System YLS-4000". The surface sample was remelted using a rectangular laser beam (2 x 4mm) with a power of 3 kW (1.53e+4w/cm2). Scanning speed of the laser beam was 0.8 cm/s (0.48 m/min). The remelting area has been protected by the use of technical argon blowing. During the process, sintered particles of vanadium carbide with an average size of about 50-100 μm was introduced into the liquid metal. Ceramic powder in the remelting volume was fed with a pressure feeder (constant rate of 5 g/min). As a substrate, the ENAC AlMg3 alloy has been used. During the laser treatment, a composite layer with much better mechanical properties was obtained comparing the base material. The average hardness of the layer was about 19 HV0.1higher than that of the base material. Chemical analysis, carried out with the EDS (energy dispersive spectroscopy) detector and transmission microscope revealed many undissolved powder particles used in the alloying process as well as those of Al8V5precipitated in the Al-Mg matrix.
Shaping Mortar Parameters in Terms of their Tendency to Form Shrinkage Cracks
Authors: Brachaczek Wacław
Published: June 2018

The most common reason for the appearance of cracks or delamination of plaster is their too high strength - higher than the strength of the substrate, their low flexibility and high shrinkage during curing. The article presents a study on influences of natural and synthetic polymers with different chemical composition of the physical properties of category CS II mortars. Polymer additives in the form of dry powders were selected for testing. Studies were carried out in two versions: with constant consistence and with a constant w/c ratio maintained. It has been found that modifying mortars with synthetic polymers improves their flexibility and flexural tensile strength. The shrinkage is dependent on the ability of the synthetic polymer to liquefy fresh mortar where the tests were conducted maintaining constant consistence. Similar relationships were determined for cellulose ethers. Also in this case, the increase in the contents of the cellulose ethers increases their tensile strength and decreases the shrinkage. It was found that the impact of cellulose ethers on the shrinkage depends on their surface activity.
Modification of Technological Properties of Laboratory Premixes
Authors: Hájková Iveta , Novosad Petr
Published: June 2018

Sulfur binders belong to the group of airbrushes. They can therefore only harden and harden in the air. The main raw material, gypsum, can be mined in several places in the world. Even in the Czech Republic there is a deposit of natural gypsum in Kobeřice u Opavy. [5] In spite of this fact, we use mostly industrially produced gypsies, because the natural gypsum deposit has only very limited capacity. The Energogypsum, produced in the Czech Republic by ČEZ Energetické Produkty s.r.o., is the waste product of flue gas desulphurization using the wet limestone scrubbing method. Like the chemosynthesis, it is characterized by its high purity (the content of pure CaSO4 2 H2O is at least 90%). The one in the Czech Republic is manufactured by Precheza, a.s. in Přerov. The use of sulphate binders is varied. A better form in the form of alpha plaster is used to produce self-leveling floors and dentistry. Less-quality beta gypsum has a larger application. From it we can produce both gypsum and monolithic partitions. We can also use it for the production of plasterboard and gypsum fiber boards and, last but not least, as internal plasters for its good fire performance. [1]
Plasters are being prepared today in two different ways. Firstly, they are still prepared in the original outpatient way directly on the building from individual raw materials, but they are also industrially produced in the form of dry mortar mixtures, which are mixed on the building only with water. The second way is more progressive with the fact that nowadays it is even more widespread. For many builders, however, it remains financially scarce. That is why we have recently begun to find a compromise solution that will satisfy both the technical and the economic ones. This is the development of the so-called binder premixes, ie the industrially produced mixed binder, which is mixed only with sand and water on the site. The situation on our market shows that the recently developed special premix for lime-cement plaster and mortar mixtures is very positive for the building public and therefore the effort is to generalize this mixed mortar in the production raw material base and, in addition, to develop its analogue based on sulphate binder. [2]
Effect of the Milling Agents on Pozzolanic Activity of Glass
Authors: Dvořák Karel , Ravaszová Simona , Gazdič Dominik
Published: June 2018

Currently the replacement of primary raw materials in cement production is relevant topic. One of the potentially usable materials can be recycled glass. But its disadvantage is tendency to agglomeration. This experiment describes the effects of the milling agents on the milling process of the glass powder. At first step seven different milling agents were compared among others and next the dependence between pozzolanic activity and specific surface are were monitored for two of them. The utilization of milling agents increased glass specific surface area significantly. Nevertheless, pozzolanic activity of the glass can be reduced when using milling agents because they may also act to a certain extent repellently to the reaction solution.
Study of the Hydration Process of Synthetic Preparation of Ettringite by Direct Addition of Aluminum Sulfate and Calcium Hydroxide
Authors: Fridrichová Marcela , Gazdič Dominik , Mokrá Jana , Dvořák Karel
Published: June 2018

The stability of ettringite as high-watery mineral is highly dependent on the ambient temperature. Under standard laboratory conditions, onset of decomposition of this phase occurs at temperature of 80°C already and the theoretical temperature of the complete decomposition of ettringite is 180°C. Ettringite decomposition can occur at significantly different temperatures under humidity conditions other than the laboratory ones. Within the work verification of the possibility of synthetic preparation of ettringite by direct addition of aluminum sulfate, Al2(SO4)3·18H2O, and calcium hydroxide, Ca (OH)2, as an alternative method to the yeelimite hydration procedure was carried out. The stability of the resulting systems was examined in two different environments, namely in a laboratory environment and the environment of saturated water vapour. The phase composition of the samples was determined by X-ray diffraction (XRD) analysis, thermal analysis and scanning electron microscopy (SEM).
Classification of Theories about Rock Pressure
Authors: Khomenko Oleh , Kononenko Maksym , Bilegsaikhan Janchiv
Published: June 2018

The first classificationsw of physical properties of rocks and hypotheses of rock pressure in the world practice are analysed. The analysis of internationally widely known theories about rock pressure and physical processes around mine workings is executed. Classification of theories about rock pressure on classification feature “condition of investigated massif” is constructed. The energy theory that describing capsulation by the massif of underground mine working is offered.
Influence of Particle Size and Calcination Temperature on the Abrasiveness of Garnet for Water Jet Cutting of Tough Materials
Authors: Rabah Mahmoud A.
Published: June 2018

This study shows the influence of calcinations temperature and particle size of natural garnet mineral on its hardness and abrasiveness (H/A) for use in water jet cutting of tough materials. A standard commercial sample of the mineral was characterized in terms of the hardness and abrasiveness properties. The sample was sized to 4 fractions having the size of <60 um, > 60 < 100 um, > 100 < 200 um and > 200 < 250 um designated the symbols, FF, MF, MC and C respectively. Each fraction was separately heated in controlled conditions at temperatures up to 1000°C at a heating rate of 10°C/min in an electrically heated tube furnace. Soaking time at the maximum temperature was 60 minutes. Hardness and abrasiveness properties of the heat treated samples were tested to cut marble having a thickness of 30 mm. Results revealed that H/A of the garnet mineral increased by heating at temperatures up to 750°C and exhibited gradual decrease with higher temperatures up to 1000°C. Results were explained in the light of a structural irreversible metamorphism (SM) of the garnet crystals; almandine Fe2+ 3Al2Si3O12and propel Mg3Al2Si3O12. Metamorphism involved reorientation of the crystals followed by coherence to form dense grouping. At higher temperature, irreversible thermal expansion of the structure sets in. Characterization of the mineral was carried out with the help of XRD, SEM and FT-IR measurements.
Changes in Density of Carbon Atomic Packing in Natural Formations
Authors: Lukinov Vyacheslav , Prykhodchenko Vasyl , Prykhodchenko Oleksii , Tykhonenko Valeriia
Published: June 2018

Generalized data of paleotemperature conditions, elemental compositions, technological properties, density, and methane content of coals at different stages of methane generation in terms of catagenetic changes of coalbed organic substance have been studied. Theoretical calculations of changes in averages values of density of carbon atomic packing in natural formations ranging from lignite to anthracite, graphite, and diamond have been represented. Mechanism of the formation of reverse methane content of anthracites at the expense of carbon restructuring of coal, increase in density of carbon atomic packing, and involvement of occluded methane and radicals of СН3 group in the process of anthracite polymerization has been substantiated.
Complex Processing of Brown Coal in Ukraine: History, Experience, Practice, Prospects
Authors: Belov Oleksandr , Shustov Oleksandr , Adamchuk Andrii , Hladun Olena
Published: June 2018

Experience, current situation and the prospects for operation of mining and processing enterprises for production of montan wax from brown coal are analyzed. Classification of the main technologies for the use of solid fossil fuel mineral has been performed. The features the technological process for production of montan wax, taking into account the experience of leading enterprises in Germany and Ukraine, are considered. Prospective directions for renewing the production of montan wax on the basis of brown coal reserves of Dneprovskiy brown coal basin are indicated. The evaluation of the attractiveness of production montan wax with the application of cash flow projection methods was carried out. Recommendations on the integrated development of brown coal deposits and processing of brown coal in order to attract foreign investment and support the competitiveness of the country's market have been developed.
Atti Sociali
Authors: Italiana Società Entomologica
Published: June 2018

Prof. Salvatore Carfi (1939-2014) Convocazione di assemblea generale ordinariaIndice dei nuovi taxa e dei nuovi atti nomenclatoriali Indice del Vol. 146
Contribution to the knowledge of Ichneumonidae from Sicily. III. Pimplinae and Poemeniinae (Hymenoptera)
Authors: Zwakhals Kees , Turrisi Giuseppe Fabrizio
Published: June 2018

Faunistic data on Hymenoptera pimplinae and poemeniinae (Ichneumonidae) from Sicily are provided. Thirty-two pimplinae species are recorded, 24 of which are new for Sicily and 1, Perithous speculator Haupt, 1954, is new also to Italy; the only recorded poemeniinae, Poemenia notata Holmgren, 1859, is new to Italy. The number of the two treated subfamilies known for Sicily is increased up to 39.
Grammognatha euphratica euphratica (Dejean, 1822) nell’isola di S. Antioco (Sardegna), nuova vistosa specie che si aggiunge alla fauna d’Italia (Coleoptera: Cicindelidae)
Authors: Cassola Fabio , Richoux Philippe , Bonneau Patrick
Published: June 2018

Una nuova, vistosa specie di Coleotteri, il Cicindelide Megacefalino Grammognatha euphratica euphratica (Dejean, 1822), rinvenuta nell’Isola di S. Antioco in Sardegna (Sulcis) da uno degli autori, si è recentemente e inaspettatamente aggiunta alla fauna d’Italia ed è segnalata per la prima volta nella presente nota.
Segnalazioni Faunistiche Italiane
Authors: V.V. A.A.
Published: June 2018

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A new species of glyptomeroid Lathrobium from Campania, Italy (Coleoptera, Staphylinidae)
Authors: Bordoni Arnaldo
Published: June 2018

Lathrobium petruzzielloi sp. n. from Grotta degli Angeli (Picentini Mounts, Cervialto Mount, Acerno, Campania, Italy), the most southern species in the Italian peninsula of this group, is described and compared with L. angelae Bordoni and Magrini, 1996 from Grotta dei diavoli (Matese Monts, Letino, Caserta, Campania, Italy). A map of the distribution of the glyptomeroid Lathrobium Gravehorst, 1802 in the Italian Apennines is presented. The following synonymy is validated: Lathrobium Gravenhorst, 1802 Glyptomerus H. Müller, 1856.
Examining the Relationship Between Social Support Satisfaction and Perceived Stress and Depression in Athletic Training Students
Authors: Crutcher Bryan , Moran Ryan N. , Covassin Tracey
Published: June 2018

Context:

Although social support has been reported to be a factor that increases retention of athletic trainers in their profession, there is a lack of literature examining the specific relationship of social support satisfaction and its predictive influence on stress and depression among athletic training students.

Objective:

To determine which sources of social support were perceived to be the most salient and ascertain whether social support satisfaction can predict stress and depression among athletic training students.

Design:

Cross-sectional study.

Setting:

Nine Commission on Accreditation of Athletic Training Education–accredited professional athletic training programs.

Patients or Other Participants:

A total of 204 athletic training students from Commission on Accreditation of Athletic Training Education–accredited athletic training programs were included in this study.

Main Outcome Measure(s):

Participants completed the Perceived Stress Scale, Center for Epidemiologic Studies Depression Scale, and the Social Support Questionnaire.

Results:

Social Support Satisfaction significantly predicted overall perceived stress (P = .010) and depression (P < .001). Satisfaction of support from family (P = .043) and other athletic trainers (P = .011) were significant predictors of perceived stress, whereas satisfaction of support from family (P = .003), other athletic trainers (P = .002), and athletes (P = .038) significantly predicted depression.

Conclusions:

The current study suggests that having an increased satisfaction of social support may reduce stress perceptions and depression in athletic training students.
Formal Mentoring in Athletic Training Higher Education: Perspectives from Participants of the National Athletic Trainers' Association Foundation Mentor Program
Authors: Mazerolle Stephanie M. , Nottingham Sara L. , Barrett Jessica L.
Published: June 2018

Context:

Formal mentoring programs can help to socialize new faculty members in higher education and orient them to faculty life. Organizations may implement formal mentoring programs to create connections between professionals, and formal mentoring is occurring in athletic training.

Objective:

To explore the experiences of athletic training faculty as they participate in a formal mentoring program.

Design:

Qualitative phenomenology.

Setting:

Higher education institutions.

Patients or Other Participants:

Ten members of the 2015 National Athletic Trainers' Association (NATA) Foundation Mentor Program, 6 mentees and 4 mentors. Mentees: 2 male and 4 female with an average of 3 years (±4; range, 1–12) in their current position. Mentors: 2 male and 2 female with an average of 10 years (±3; range, 6–12) of experience in their current positions.

Main Outcome Measure(s):

Participants completed 1 telephone interview prior to starting the NATA Mentor Program and completed 1 telephone interview upon completion of the mentor program. Participants also completed 3 online structured journals at 3-month increments while participating in the program. Two investigators independently analyzed data with a phenomenological approach, and a third investigator reviewed findings as a peer reviewer. Trustworthiness was addressed with member checking, piloting, and peer review of the interview guides, and multiple analyst triangulation.

Results:

Mentors completed the program as a way to stimulate collaboration and give back to the athletic training profession. Mentees sought out the program as a means to gain support in their research endeavors and to stimulate networking opportunities.

Conclusions:

The NATA Foundation Mentor Program offers a mutually beneficial experience for mentors and mentees, and participants were satisfied with their experiences. Mentee participants recognized the program gave them a chance to gain an external perspective and advance their research agendas, while mentors learned from their mentees and were able to use the program as a means to gain professional service.