bluuebunny/crossref_metadata_2025 huggingface dataset:
Condensation induced water hammer – overview and own experiments
Authors: Dirndorfer S. , Doerfler M. , Kulisch H. , Malcherek A.
Published: December 2013

A condensation induced water hammer is a severe effect that has caused damages and even fatalities worldwide. This effect is not limited to the nuclear industry only. Generally it can occur in every pipe that contains water and steam (two-phase-flow). To date many experiments were executed to study this phenomenon and to validate existing water hammer codes. But theoretically versus measured results show a very high degree of deviation. Information about those experiments was obtained by literature review. This information is presented additionally to a test facility, which has been developed in order to generate water hammers. The test device is introduced in this paper and its main functions are briefly explained.

In contrast to other experiments, water hammers at the UniBw are performed under controlled conditions. Air in water is a disruptive parameter that causes vigorous deviations between the theoretical system code and the experimental measurements. As in the test device presented in this paper, deionised water without air is used, this effect is ruled out. Furthermore the inception of a water hammer is controlled by a scientist. The experimental results will characterise the dynamic response of the test device as a function of system pressure, filling degree and sub-cooling.
Qualification of the APOLLO2 lattice physics code of the NURISP platform for VVER hexagonal lattices
Authors: Hegyi G. , Keresztúri A. , Tóta A.
Published: December 2013

The experiments performed at the ZR-6 zero power critical reactor by the Temporary International Collective (TIC) and a burnup benchmark specified for depletion calculation of a VVER-440 assembly containing Gd burnable poison were used to qualify the APOLLO2.8-3.E (APOLLO2) code as a part of its ongoing validation activity. The work is part of the NURISP project, where KFKI AEKI undertook to develop and qualify some calculation schemes for hexagonal problems. Concerning the ZR-6 measurements, single cell, macro-cell and 2D calculations of selected regular and perturbed experiments are used for the validation. In the 2D cases, the radial leakage is also taken into account by the axial leakage represented by the measured axial buckling. Criticality parameter and reaction rate comparisons are presented. Although various sets of the experiments have been selected for the validation, good agreement of the measured and calculated parameters could be found by using the various options offered by APOLLO2. An additional mathematical benchmark – presented in the paper – also attests for the reliability of APOLLO2. All the test results prove the reliability of APOLLO2 for VVER core calculations.
The simplified P3 approach on a trigonal geometry of the nodal reactor code DYN3D
Authors: Duerigen S. , Fridman E.
Published: December 2013

DYN3D is a three-dimensional nodal code for steady-state and transient analyses of Light Water Reactors applicable for square and hexagonal fuel assembly geometries. Several versions of the DYN3D code are available including a multigroup diffusion and a simplified P3 (SP3) neutron transport option. The multi-group SP3 method based on a trigonal geometry was developed recently. This method is applicable to the analysis of reactor cores with hexagonal fuel assemblies and allows flexible mesh refinement. In this paper, the theoretical background for the SP3 method is briefly described. The consistency of the implementation of the trigonal SP3 methodology in DYN3D is demonstrated by means of a simplified VVER-440 core test example. The corresponding few-group homogenized cross sections and reference solutions were produced by the Monte Carlo code Serpent. The DYN3D results are in good agreement with the reference solutions.
Analysis of coolant flow in central tube of VVER-440 fuel assemblies
Authors: Zsíros G. , Tóth S. , Aszódi A.
Published: December 2013

A CFD model has been developed to investigate the coolant flow in the central tube of VVER-440 fuel assemblies. The model has been validated with measured data of Kurchatov Institute. With this model a peripheral and an inner fuel assembly of the core have been investigated and the mass flux and heatup ratios of the central tube flow have been determined. Based on this study, the outlet mass flux of the tube is 1.2 times higher than the inlet mass flux of the rod bundle and heat-up in the tube is 0.35 times lower than the heat-up in the rod bundle. The ratios are not sensitive to the operational conditions within the scope of these investigations. The results of these simulations can be used as boundary conditions for the central tube in the assembly head calculations.
Study on severe accidents and countermeasures for VVER-1000 reactors using the integral code ASTEC
Authors: Tusheva P. , Schäfer F. , Reinke N. , Altstadt E. , Kliem S.
Published: December 2013

The research field focussing on the investigations and the analyses of postulated severe accidents is an important part of the nuclear safety. To maintain the safety barriers as long as possible and to retain the radioactivity within the airtight premises of the containment, to avoid or mitigate the consequences of such events and to assess the risk, thorough studies are needed. This paper is focused on the possibilities for accident management measures in case of severe accidents. The analyses performed with the integral code ASTEC cover two accident sequences which could lead to a severe accident: a small break loss of coolant accident and a station blackout. The discussed issues concern the main phenomena during the early and late in-vessel phase of the accidents, the time to core heat-up, the hydrogen production, the mass of corium in the reactor pressure vessel lower plenum and the failure of the reactor pressure vessel. Additionally, possible operator's actions and countermeasures in the preventive or mitigative domain are addressed.
VVER-440 with inert matrix fuel – viable direction to sustainability
Authors: Dařílek P. , Strmenský C. , Zajac R. , Majerčík J.
Published: December 2013

Reutilisation of fissile nuclides after reprocessing in light water reactor VVER-440 with inert matrix fuel (IMF) is analysed. Development of transmutation combined fuel assembly, containing two pin types – with metal molybdenum + PuO2 mixture and with classical UO2 – is described. Static characteristics of five-year VVER-440 fuel cycle with IMF are given. Results of control rod ejection accident analysis are presented. Necessary improvements of transmutation combined fuel assembly with IMF for the reactor VVER-440 are mentioned.
The world we really live in – communication on radiation
Authors: Gellermann R.
Published: December 2013

In order to make the communication on radiation and radiation levels more tangible and clear to the general public, measured results from actual living environments are needed. The paper demonstrates by means of measured results of the ambient dose rates (ODL) that the ambient dose rates in the centre of German cities locally exceed levels typical for the respective geogenic environment significantly. The highest dose rates which have been measured up to now reach 680nSv/h. The role of these results from the radiation protection point of view is discussed and a level of 300nSv/h is suggested as an upper level of the normal ambient dose rate in the urban environment. Still higher dose rates have been found in areas with radioactively contaminated soil. The need for remediation of such contaminated sites is indicated.
Appraisal of long-term radiation trends in the environs of nuclear power plants – Examples from Switzerland
Authors: Bucher B. , Rybach L. , Schwarz G.
Published: December 2013

Annually since 1989, biannually since 1994 the sites of the Swiss nuclear facilities (4 power plant sites, a nuclear research institute and a waste storage facility) are surveyed flying the same survey lines by airborne gamma ray spectrometry. The equipment and the data processing software used for those surveys was built and developed at the Institute of Geophysics, ETH Zurich. For mapping the ground radiation around the nuclear facilities a pixel representation and a modified Spectrum Dose Index (SDI) method is used. In the search for long-term trends the local dose-rates are calculated first and in turn the net dose rates over the time span 1992–2010. So far no significant change in the radiation levels was detected over the last 18 years outside of the fenced sites of the nuclear facilities, except for the operation of an industrial radiation facility in 1995.
Radiation shielding is not a solution – radiation protection of air crews
Authors: Boehm Th.
Published: December 2013

In most working environments it is fairly easy to minimize radiation doses of workers as postulated by radiation protection basics: Increasing the distance to the radiation source, reducing the exposure time, and the use of protective clothing or shielding. With air crews however, being the largest group of exposed persons and receiving the highest collective doses, classical protective measures are difficult or even impossible to enforce. Without neglecting the economical situation, effective measures could nevertheless be realized. Planning flights at slightly lower altitudes and further away from the geomagnetic poles can significantly reduce the radiation exposure for both crew and passengers. Furthermore, affordable high-quality dosimeters with the size of mobile phones have reached marketability. If installed on board, they could measure and display the actually received radiation during normal operation and additionally warn the flight crew in case of an abnormally high dose rate during solar particle events. Pilots could react to such warnings according to procedures that are yet to be installed.
Radon at workplaces in Bavaria and experiences with remediation
Authors: Körner S. , Reifenhäuser C.
Published: December 2013

In Germany radon exposure at certain workplaces has been regulated by the Radiation Protection Ordinance since 2001. However in Bavaria studies have been conducted since 1996. The radon exposure of all staff concerned was estimated and thereby several companies were identified where the exposure exceeded 6 mSv per year. Since then the exposure of the staff has been continuously monitored in these companies. Remediation measures specifically adjusted to local conditions led to a reduction of the exposure in many of these companies. Therefore only in 11 of the original 81 companies exposures of more than 6 mSv/a persist until today. As the Bavarian Environment Agency (LfU) oversaw the measurements and remediation measures there exists profound knowledge within the LfU of the local conditions mainly in water supply facilities as well as of the various remediation measures and their success. Furthermore, a few investigations concerning radon are carried out at workplaces not regulated by the Radiation Protection Ordinance. As an example we present a town hall where the measured radon concentrations led to a heated public dispute. Here the LfU successfully communicated factual information and the evaluation of the radon situation with regard to international recommendations.
Heat transfer study of a submerged reactor channel under boil-off condition
Authors: Mukhopadhyay D. , Sahoo P. K. , Ghosh A. K.
Published: December 2013

Experiments have been carried out to study the heatup behavior of a single segmented reactor channel for Pressurized Heavy Water Reactor under submerged, partially submerged and exposed conditions. This situation may arise from a severe accident scenario of Pressurised Heavy Water Reactors where full or segmented reactor channels are likely to be disassembled and form a submerged debris bed. An assembly of electrical heater rod, simulating fuel bundle and channel components like Pressure Tube and Calandria Tube constitutes the segmented reactor channel. Heatup of this assembly is observed with respect to different water levels ranging from full submergence to totally exposed and power levels of 6–8 kW, typical to decay power level. It has been observed from the set of experiment that fuel bundle local dry out followed by heatup does not happen till the bundle is partially submerged. Temperature excursion of the bundle is evident when the bundle is exposed to steam-air environment.
Modelling, simulation and experiments on boiling processes in pressurized water reactors
Authors: Krepper E.
Published: December 2013

A collaborative project funded by the Federal Ministry of Education and Research (BMBF) in the framework of the R&D program “Energie 2020+” by four Universities, two Research Centres and ANSYS is coordinated by Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The project is directed towards the development and validation of CFD models of boiling processes in PWR in the range from subcooled nucleate boiling up to the critical heat flux. The work is oriented towards basic research and focused on model development, simulation and experiments on different scales. An important objective is the education and maintaining of competence in nuclear technology.
CFD-modelling of subcooled boiling
Authors: Krepper E. , Rzehak R. , Lifante C. , Frank Th.
Published: December 2013

In this paper new developments in the framework of a common project simulating subcooled boiling are described. The computational model used combines the Euler/Euler two-phase flow description with heat flux partitioning. Main achievements were a comprehensive study of the boiling process itself and a better description of the interfacial area by coupling of wall boiling with a population balance model. The model extensions are validated and the present capabilities of CFD for wall boiling are investigated.
Small scale boiling experiments using two-dimensional imaging with high-speed camera and optical coherence tomography
Authors: Schneider C. , Kirsten L. , Meissner S. , Hurtado A. , Koch E. , Hampel R.
Published: December 2013

To investigate boiling processes, a test facility has been constructed, which allows the use of optical techniques for the detection of individual vapor bubbles. Demineralized water was used as working fluid at ambient pressure whereat temperature, flow rate and heat flux density can be varied. The growth of individual vapor bubbles was recorded by high-speed camera and analyzed by digital image processing (DIP). Optical coherence tomography (OCT) enabled the visualization of steam bubbles in cross-sections perpendicular to the heated surface.
CFD-Modeling of turbulent flows in rod bundle and comparison to experiments
Authors: Lifante C. , Krull B. , Frank T. , Franz R. , Hampel U.
Published: December 2013

Turbulent single-phase simulations in a geometrical domain reproducing the new ROFEX test facility (3×3 rod bundle) were conducted. These investigations were aimed to perform an initial study for future analysis of boiling processes in the same test facility. The final goal of these experiments in ROFEX is the validation of CFD boiling models. The current CFD simulations allow an assessment of the turbulent flow conditions in this test facility.
Simulation of external reactor vessel cooling in a lumped-parameter code
Authors: Schittek U. , Koch M. K.
Published: December 2013

In the course of a severe accident in a nuclear power plant the integrity of the reactor vessel may be preserved by External Reactor Vessel Cooling (ERVC). By flooding the cavity surrounding the reactor vessel the decay heat is removed from molten core material through the vessel wall to water at the submerged vessel surface. In order to simulate the boiling process at the external vessel wall during ERVC in the framework of lumped parameter codes a model based on a boiling model used in the code ANSYS CFX 13.0 is developed.
External hazards – in focus after the Fukushima accident
Authors: Krauß M. , Berg H. P.
Published: December 2013

International experience has shown that external hazards can be safety significant contributors to the risk of industrial plants with a high potential of damage to the environment; this has become evident after the Fukushima accident. As a consequence main focus has been set on adequate design measures against external hazards and appropriate assessment methods. Possible methods to analyse existing plants systematically regarding the adequacy of their existing protection equipment against hazards can be deterministic as well as probabilistic. On international level, new recommendations regarding external hazards are recently issued. In that context, in particular earthquakes and flooding scenarios have been re-evaluated to some extent. Also in Germany, a revised guideline on probabilistic safety analyses (PSA) and corresponding technical documents are issued in 2005 addressing external hazards. As a reaction to the accidents in Japan in March 2011, the German Reactor Safety Commission has issued a catalogue of requirements for plant-specific reviews of German nuclear power plants, and the status of the plants have been evaluated with respect to these requirements. The results of these investigations have been the basis for the German report in the frame of the European stress tests; the results with respect to natural external hazards are presented.
Frequency of damage by external explosion hazards based on geographical information
Authors: Becker G. , Camarinopoulos A. , Camarinopoulos L. , Karali T. , Schubert B.
Published: December 2013

External explosions can significantly contribute to risk of damage for industrial plants. External explosions may origin from other plants in the neighbourhood, which store and operate with explosive substances, or from transport of such substances on road, rail, or water. If deflagration is involved, ignition will not necessarily occur at the place of the accident, but a cloud of a combustible gas-air mixture may develop, which will ignite at some distance depending on wind velocity. A probabilistic model has been developed to calculate frequencies of damage based on numerical integration or on Monte Carlo simulation. Geographical information systems provide map material for sites, roads, rail and rivers on a computer. Data has been collected and applied for a nuclear power plant in Germany as an example. The method, however, can be used for any type of plant subject to external explosion hazards.
Investigation of neutronic effects in structural material of a hybrid reactor by using the MCNPX Monte Carlo transport code
Authors: Günay M.
Published: December 2013

In this study, 98–90% Li2BeF4-2–10% ThF4, 98–90% Li2BeF4-2–10% UF4, 98–90% Li2BeF4-2–10% UO2 and 100% Li2BeF4 molten salt-heavy metal was used as fluid. The fluids were used in the liquid first wall, liquid second wall and shield zones of the designed hybrid reactor system. A steel wall of 4 cm thickness is used as structural material. Proton, deuterium, tritium, He-3 and He-4 gas production rates are the parameters of radiation damage. In the study, the effect of liquid second wall thicknesses (20 cm, 30 cm, 40 cm, 50 cm) on the neutron flux distribution and the parameters of radiation damage according to neutron energy spectrum in the structural material were investigated for the selected fluids. A three-dimensional analysis was done by using the most recent version of the MCNPX-2.7.0 Monte Carlo code and the nuclear data library ENDF/B-VII.
Chemistry aspects of the source term formation for a severe accident in a CANDU type reactor
Authors: Constantin A. , Constantin M.
Published: December 2013

The progression of a severe accident in a CANDU type reactor is slow because the core is surrounded by a large quantity of heavy and light water which acts as a heat sink to remove the decay heat. Therefore, the source term formation is a complex and long process involving fission products transport and releasing in the fuel matrix, thermal hydraulics of the transport fluid in the primary heat system and containment, deposition and transport of fission products, chemistry including the interaction with the dousing system, structural materials and paints, etc. The source term is strongly dependent on initial conditions and accident type. The paper presents chemistry aspects for a severe accident in a CANDU type reactor, in terms of the retention in the primary heat system. After releasing from the fuel elements, the fission products suffer a multitude of phenomena before they are partly transferred into the containment region. The most important species involved in the deposition were identified. At the same time, the influence of the break position in the transfer fractions from the primary heat system to the containment was investigated.
Calculation of age-dependent effective doses for external exposure using the MCNP code
Authors: Van Hung Tran
Published: December 2013

Age-dependent effective dose for external exposure to photons uniformly distributed in air were calculated. Firstly, organ doses were calculated with a series of age-specific MIRD-5 type phantoms using the Monte Carlo code MCNP. The calculations were performed for mono-energetic photon sources with source energies from 10 keV to 5 MeV and for phantoms of newborn, 1, 5, 10, and 15 years-old and adult. Then, the effective doses to the different age-phantoms from the mono-energetic photon sources were estimated based on the obtained organ doses. From the calculated results, it is shown that the effective doses depend on the body size; the effective doses in younger phantoms are higher than those in the older phantoms, especially below 100 keV.
T
N approximation for the critical size of one-speed neutrons in a slab with anisotropic scattering
Authors: Öztürk H.
Published: December 2013

The critical thickness for one-speed neutrons in a uniform finite slab with anisotropic scattering is investigated using Marshak boundary condition. The angular part of the neutron angular flux is expanded in terms of the Chebyshev polynomials of first kind. Numerical results for the critical thickness of the slab are calculated for various values of the collision and the anisotropy parameters and they are given in the tables together with the ones obtained by Legendre polynomials approximation and the ones available in literature for comparison. The results obtained by the present method are in good accordance with the literature values.
Experimental investigations on control of flow instability in single-phase natural circulation loop
Authors: Bodkha K. , Kumar N. , Vijayan P. K.
Published: December 2013

Natural circulation systems offer simplicity, enhanced safety and reliability and thus are advantageous over their forced circulation counterpart. However, natural circulation is susceptible to flow instabilities. These instabilities are undesirable for various reasons. Literature suggests the use of orifices at the inlet to suppress instability. However, orificing introduces pressure drop which limits the flow rate and hence the heat carrying capacity of the fluid. In the present study, investigations have been carried out with different mechanical gadgets to control the natural circulation flow instabilities. Extensive experiments have been carried out in a single-phase rectangular natural circulation loop to study the effect of these mechanical gadgets on instability. The paper brings out the results of experimental investigations carried out on the role of mechanical gadgets in controlling instability.
Analytical study on degraded core quenching
Authors: Gokhale O. S. , Puranik B. P. , Ghosh A. K.
Published: December 2013

Severe accident analysis of a reactor helps in emergency planning and evolution of Severe Accident Management Guidelines (SAMG). Actions recommended in the SAMG aim at arresting accident progression and limiting significant radioactive release. However, success of these SAMG actions needs to be assessed with respect to the evolution of accident. Analysis of consequences of injection of water into the reactor pressure vessel from bottom only as a SAMG action has been carried out for VVER-1000 (V320) reactor. The analysis shows that the success of this SAMG action depends not only on the state of core degradation at the time of injection, but also on the highest temperature reached in the reactor core at the time of injection as well as the availability of steam in the RPV.
Results of precision calculations of three-dimensional power density in VVER-1000 core with feedbacks using MCU code
Authors: Bikeev A. S. , Shkarovsky D. A.
Published: December 2013

Accounting of feedbacks on the density and temperature of the coolant, the fuel temperature, as well as on the equilibrium concentration of xenon is important for VVER reactors, since it has a significant influence on the neutron-physical characteristics of such systems. Therefore, there is a need to incorporate feedbacks into precision calculations of the power density of the VVER-1000 core. In the present work, we used a model of the core, divided into 30 layers by height. The calculations were carried out by means of Russian Monte Carlo code MCU (Monte-Carlo Universal). Individual values of densities and temperatures of the coolant, the fuel temperatures, as well as the equilibrium concentration of xenon were calculated in each layer of every fuel assembly. In addition, power density was calculated pin-by-pin in each layer. The obtained results were compared to the results obtained by means of the certified BIPR-7A code. It is shown that within a reasonable computational time using currently available hardware resources one can obtain the three-dimensional power density with an acceptable accuracy and taking into account the feedbacks on the density and temperature of the coolant, the fuel temperature, as well as the equilibrium concentration of xenon.
A comparison of the FA's models with the detailed and simplified description in the MCU code calculations
Authors: Bikeev A. S. , Marin S. V. , Sukhino-Khomenko E. A.
Published: December 2013

Full-scale three-dimensional computer model describing neutron-physical processes that occur in the VVER-1200 reactor core involves detailed FA geometry description. However, the detailed description significantly complicates input data, increases calculation time and error probability. Consequently, creation of simplified models of the design elements becomes necessary. In present work, simplified geometrical models of FA design elements are suggested. Calculations of simplified models are compared to calculations of exact models that completely correspond to the working general view drafts provided by OKB “Hydropress”. It is demonstrated that in many problems the use of simplified description of FA elements geometry is possible.
Account for uncertainties of control measurements in the assessment of design margin factors
Authors: Dementiev V. , Sidorenko V. , Shishkov L.
Published: December 2013

This paper considers two interrelated issues and – proceeding from the conditional probability concept and Bayes’ statistical theorem – suggests a universal method to process measured data with account of prior information available. To assure reliable reactor operation, at the design stage it is suggested to account for errors of subsequent control measurements while assessing the engineering margin factors for reactor parameters to be measured.
Solid-state reaction in Ni/Si multilayered films, characterized by magneto-optical and optical spectroscopies
Authors: Lee Young Pak , BaeKim Jin , Yoo Young Joon , Kudryavtsev Yuri V.
Published: December 2013

Solid-state reactions, induced by ion-beam mixing (IBM) and thermal annealing, in Ni/Si multilayered films (MLF) with an overall stoichiometry of Ni2Si, NiSi and NiSi2, and with a constant Ni sublayer thickness (nominally, 3.0 nm), were studied by optical and magneto-optical spectroscopies as well as X-ray diffraction (XRD). The layer mixing was performed with Ar+ ions of an energy of 80 keV and a dose of 1.5 × 1016 Ar+/cm2. It was shown that the IBM leads to structural changes in the Ni/Si MLF, which cannot be easily detected by XRD but are recognized by optical tools. An annealing at 1073 K of the Ni/Si MLF with an overall stoichiometry of NiSi and NiSi2 induces formation of predominantly the η-NiSi and the NiSi2 phases, respectively. IBM of all the investigated Ni/Si MLF leads to the formation of regions with a short-range order of the crystalline NiSi silicide, and of Ni2Si (and/or Ni3Si) additionally for the Ni/Si MLF with an overall stoichiometry of Ni2Si.
Effects of an electric field applied during the solution heat treatment of the Al–Mg–Si–Cu alloy AA 6111 on the subsequent natural aging kinetics and tensile properties
Authors: Jung Kang , Conrad Hans
Published: December 2013

The effects of an external dc electric field of 0–5 kV/cm, applied at 475–550°C during solution heat treatment (SHT) to AA6111, on the subsequent natural aging kinetics and volume fraction of precipitated clusters were determined employing resistivity. The field increased the as-quenched resistivity and that during natural aging, the effect being significant from 0 to ≈0.5 kV/cm and increasing only slightly, if at all, thereafter. An Avrami-type analysis of the natural aging kinetics gave n = 0.59 ± 0.2 and k = (1.2 ± 0.8) · 10−2 min−1, relatively independent of SHT temperature and field strength. The field increased the volume fraction of precipitated clusters which occurred during natural aging. This was attributed to the increase in solubility during SHT produced by the field. Tensile properties equivalent to those obtained by the SHT at 550°C without a field were obtained at 500°C with a field of only 200 V/cm, representing a reduction of 50°C in the nominal SHT temperature.
Liquid–liquid interfacial tension in the monotectic alloy (Al34.5Bi65.5)95Si5 (wt.%)
Authors: Kaban Ivan , Hoyer Walter
Published: December 2013

The liquid–liquid interfacial tension and the density difference of the coexisting phases in the immiscible alloy (Al34.5Bi65.5)95Si5 (wt.%) have been measured between 873 and 1238 K. The interfacial tension equals (73.0 3.6) mN/m at 873 K and it decreases with increasing temperature proportionally to (1–T/TC)δ. The critical-point exponent δ=1.38, and the critical temperature TC=1410 K were determined from the experimental data.
Activity measurements on the Al-rich region of the Ni–Al system – A high temperature mass spectrometric study
Authors: Narasimhan Tiruppatur Subramaniam Lakshmi , Kath Dieter , Markus Torsten , Hilpert Klaus
Published: December 2013

Systematic vaporisation studies on the Ni–Al system with 0.32 x(Ni) 0.50 were carried out in the temperature range 1077–1592K by Knudsen effusion mass spectrometry. While Al(g) was the vapour species observed over all the samples, Ni(g) was also detected over samples with the compositions x(Ni)=0.50 and 0.49. From the p(Al)–T relations, activities of Al, and subsequently activities of Ni (by Gibbs–Duhem integration) were obtained. Moreover, partial and integral molar enthalpies and Gibbs energies of formation were evaluated. The variation of activities and other thermodynamic properties with composition are discussed. The enthalpy and Gibbs energy of formation of Ni0.5Al0.5(s) at 298.15K were obtained as = −62.1 4.2kJ mol−1 and = −57.71.2kJ mol−1, respectively. This is the first time that a systematic mass spectrometric investigation has been carried out on the aluminium rich region of Ni–Al system where the vacancy concentration in the NiAl phase can be as high as 10%.
Solid-State17O NMR studies on Yttria-stabilized zirconia
Authors: Viefhaus Tillmann , Müller Klaus
Published: December 2013

Variable temperature17O NMR measurements, covering a temperature range from room temperature to 973K, were conducted on various samples from17O enriched yttria-stabilized zirconia for the first time. It is shown that spin-lattice (T1) relaxation exhibits a strong temperature dependence originating from the motional displacements of the oxygen ions, and which is almost independent of the actual sample constitution. In addition, large temperature effects are found for the17O NMR line widths (i.e. spin-spin relaxation) which – as the spin-lattice relaxation data – reflect the onset of the oxygen ion mobility. It is anticipated that the NMR line width effects are caused by motions on a length-scale which is different from that examined by spin-lattice relaxation.
Mg-rich phase equilibria of Mg–Mn–Zn alloys analyzed by computational thermochemistry
Authors: Ohno M. , Schmid-Fetzer R.
Published: December 2013

The phase equilibria of Mg-rich Mg–Mn–Zn alloys are scrutinized on the basis of computational thermochemistry. The experimentally well-established facts are very well reproduced by the present calculation. The important invariant reaction involving Mg-solid solution is calculated to be a transition type reaction L+(Mg)↔αMn+Mg51Mn20 at 340.18°C. Some aspects that were incorrectly interpreted in early experimental works are pointed out and are explained by the present calculations also involving non-equilibrium effects.
Generalized Maugis–Dugdale model of an elastic cylinder in non-slipping adhesive contact with a stretched substrate
Authors: Chen Shaohua , Gao Huajian
Published: December 2013

We have recently developed a generalized JKR model for non-slipping adhesive contact between an elastic cylinder and a stretched substrate where both tangential and normal tractions are transmitted across the contact interface. Here we extend this model to a generalized Maugis–Dugdale model by adopting a Dugdale-type adhesive interaction law to eliminate the stress singularity near the edge of the contact zone. The non-slipping Maugis–Dugdale model is expected to have a broader range of validity in comparison with the non-slipping JKR model. The solution shares a number of common features with experimentally observed behaviors of cell reorientation on a cyclically stretched substrate.
Implications of linear relationships between local and macroscopic flow stresses in the composite model
Authors: Mughrabi Hael
Published: December 2013

Earlier results obtained by X-ray diffraction studies on tensile-deformed [001]-orientated copper single crystals have recently been re-assessed with respect to the evolution of the long-range internal stresses and the local flow stresses of the dislocation cell walls and the cell interiors. It was noted that the magnitudes of the long-range internal stresses and of the local flow stresses increase in good approximation linearly with the applied macroscopic flow stress. In the present work, the results of a similar analysis of earlier published X-ray data, which were obtained on tensile-deformed [001]-orientated Cu–Mn single crystals, are reported. When the friction stress of the alloy is taken into account, similar linear relationships to the case of deformed [001]-orientated copper single crystals were obtained. The implications of these results are analyzed in the framework of the composite model of crystal plasticity. It is shown that linear relationships of the type considered imply, in terms of the composite model, that the ratio between the local dislocation densities in the dislocation cell walls and the cell interiors must remain constant during deformation. This result is discussed with respect to the experimentally obtained data on local dislocation densities.
Thin film formation by oriented attachment of polymer-capped nanocrystalline ZnO
Authors: Lipowsky Peter , Jia Shijun , Hoffmann Rudolf C. , Jin-Phillipp Neng Yun , Bill Joachim , Rühle Manfred
Published: December 2013

Chemical bath deposition has been introduced as a means to produce films of inorganic substances with low engineering expenditure and close to ambient temperature. Organic additives have been used to control the growth of zinc oxide particles in solution and prevent the formation of the typical rod-like morphology. In the present work an attempt is made to combine these two approaches in order to produce thin films of zinc oxide. In the presence of β-cyclodextrin, spherical nano-crystalline deposits were obtained from solution; polyethylene glycol induced the formation of nano-structured thin films. With polyvinylpyrrolidone as an additive, uniform films were deposited. The structure of these films was analyzed by X-ray diffraction and transmission electron microscopy, which revealed the presence of domains of locally oriented nanocrystals. A mechanism of oriented attachment is proposed to explain the formation of domained ZnO films.
High-temperature deformation behavior of nanocrystalline precursor-derived Si–B–C–N ceramics in controlled atmosphere
Authors: Kumar Ravi , Mager R. , Phillipp F. , Zimmermann A. , Rixecker G.
Published: December 2013

In precursor-derived nanocrystalline Si–B–C–N materials, grain or interphase boundaries constitute a major part of the material. They control various properties of nanostructured solids, e.g., by forming fast diffusion pathways. In such highly covalent materials, where the interfaces between the individual crystallites or domains tend to be broadened and structurally disordered, high-temperature plastic deformation (i.e., the creep behavior) can be used as a probe which is particularly sensitive to processes involving internal interfaces and glass-like features of the microstructure. The focus of the present study is an investigation of the deformation behavior of precursor-derived nanocrystalline Si–B–C–N ceramics in the phase-separated amorphous and nanocrystalline states under inert atmospheres. A concise analysis of creep mechanisms free of any oxidation effects was carried out. Isothermal compression creep experiments at 1400°C and at various loads (50MPa–150MPa) have indicated a stress exponent near to unity hinting diffusion creep, and an activation energy of 0.16 ± 0.03 MJ/mol was derived from temperature change experiments under an iso-stress condition. The mechanisms of deformation are elucidated using a free volume model.
Infrared properties of sintered α-MnSe
Authors: Nikolić Maria Vesna , Nikolić Pantelija M. , Blagojević Vladimir , Paraskevopoulos Konstantinos M. , Zorba Triantafyllia T. , Vasiljević-Radović Dana , Risticć Momčvilo M.
Published: December 2013

Far-infrared reflection spectra of sintered α-MnSe were measured at room temperature. The measured spectrum had one pronounced peak in accordance with literature data and group theory estimation and one smaller peak resulting from the applied sintering procedure. The measured reflection spectrum was analyzed using Kramers–Kronig analysis and a three-component effective medium model based on Bruggeman's theory assuming the presence of a small amount of pores, dominant crystalline grains and intergranular material. In the model the crystalline grains were modeled as a single oscillator appropriate to the single crystal and the intergranular material was also defined as a single ionic oscillator.
Evolution of C-rich SiOC ceramics
Authors: Kleebe Hans-Joachim , Gregori Giuliano , Babonneau Florence , Blum Yigal D. , MacQueen D. Brent , Masse Sylvie
Published: December 2013

Carbon-rich Si–O–C polymer-derived ceramics (PDCs) were investigated by various spectroscopic techniques, in order to characterize the evolution of their predominantly amorphous microstructure upon thermal treatment up to 1450°C. Particular attention was addressed to modifications of the excess free carbon phase present in these materials. Surprisingly, the carbon clusters exhibited high stability above the pyrolysis temperature. Despite the high volume fraction of carbon, only a very limited carbothermal reduction process was detected. This study is divided into two parts: PartI deals with characterization tools that reveal a rather low lateral resolution and are hence termed here as integral spectroscopic techniques, i.e., solid-state NMR and Raman spectroscopy. In contrast, PartII illustrates the experimental results obtained from the very same materials characterized by spectroscopic and imaging techniques with high lateral resolution, i.e., electron energy-loss spectroscopy (EELS), high-resolution transmission electron microscopy (HRTEM), and energy-filtered TEM. In addition to materials characterization, emphasize of both papers is also to compare the information gained by either integral or local spectroscopy techniques and to highlight the strengths and weaknesses of either approach.
Microstructure, hardness, and fracture toughness evolution of hot-pressed SiC/Si3N4 nano/micro composite after high-temperature treatment
Authors: Šajgalík Pavol , Hnatko Miroslav , Lojanová Štefánia , Lenčéš Zoltán , Pálková Helena , Dusza Ján
Published: December 2013

The grain boundary phases in SiC/Si3N4 nano/micro-composite changes with time of high temperature treatment at 1750°C in nitrogen atmosphere. Stable phases were obtained after 26 hours of annealing. Moreover, the average grain diameter distribution was significantly changed. The hardness and fracture toughness of the SiC/Si3N4 nano/micro-composites decreased with the duration of the high-temperature treatment. Both findings can be explained by the different secondary crystalline phases formed during the high-temperature treatment. Phases Si2N2O, Y2SiO5, and Y2Si2O7, typical for the samples treated up to 4 h, were replaced by the YNSiO2 phase in the samples treated longer than 26 h. Anisotropy of the measured mechanical properties in different sample cross-sections caused by the Si3N4 grain alignment become negligible after long term high-temperature treatment.
Microstructural characterisation of a Co–Cr–Mo laser clad applied on railway wheels
Authors: Farooq Muhammad Umar , Klement Uta , Nolze Gert
Published: December 2013

A Co–Cr–Mo laser cladding applied on railway wheels is characterised by a combination of EBSD and EDX. A complete pass of the cladding is investigated to achieve a better understanding of the microstructure evolution during laser cladding. A microstructure with columnar grains extending over the whole thickness of the cladding is observed. The grains have a <001>-fibre texture with the fibre axis parallel to the normal of the substrate surface, and a substructure consisting of cells/dendrites. During the cladding process, two different kinds of precipitates form in the cell walls, which can be identified as M6C and a non-equilibrium phase. Furthermore, stacking faults are observed to occur in the cladding grains and are discussed with respect to the laser cladding process.
Calorimetric investigation of the binary Cu–In system
Authors: Knott S. , Mikula A.
Published: December 2013

Although some investigations of the integral enthalpy of mixing of the binary Cu–In system have already been done, there is a lack of conformity of these data within the literature. Therefore the integral enthalpy of mixing was determined with a Calvet-type calorimeter. The measurements were performed at four different temperatures to determine the temperature dependence of the integral enthalpy of mixing.
Neutron diffraction analysis of martensite ageing in high-carbon FeCMnSi steel
Authors: Barbé Liesbeth , Samek Ludovic , Verbeken Kim , Conlon Kelly , De Cooman Bruno C.
Published: December 2013

A high-carbon metastable austenite phase was quenched in liquid nitrogen to obtain fresh athermal martensite. Different ageing treatments were performed in order to study the transformation of the martensite phase and the formation of carbides. Neutron diffraction experiments give detailed information on the transformations during the annealing treatment itself. The tetragonal athermal martensite transformed immediately, i.e. during the heating to the ageing temperature, to cubic martensite. Ageing at 400°C resulted in the decomposition of the austenite in ferrite and carbides and the formation of bainite. Those carbides could be determined as -carbides transforming in -carbides after extended annealing times. As was expected, ageing at 170°C resulted in the formation of a small amount of carbides while the austenite phase remained stable.
Novel combinatorial microstructures in Ti-6Al-4V alloy achieved byan electric-current-pulse treatment
Authors: Zhang Wei , Zhao Wei-song , Li Dou-xing , Sui Man-ling
Published: December 2013

An electric-current-pulse (ECP) treatment was employed to rapidly heat a dogbone-shaped Ti-6Al-4V sheet. After the treatment, the alloy was modified from a single micrometer-sized structure to a shape-associated combinatorial counterpart. Coexisting with the original equiaxed coarse-grained -Ti and the intergranular -Ti, two kinds of novel ultrafine structures, nanometer-sized lamellar twins of -Ti martensites and refined bimodal structure have been produced in the different parts of the bulk sample. Formation of the novel microstructures during the ECP treatment was systematically investigated. This work demonstrated that the ECP rapid heating treatment is a promising method to tailor the microstructures of the metallic alloys basically by designing the shape-associated distribution of the current density and offer a new possibility for improving the conventional alloys.
The Effect of Ti–B and Sr on the mechanical behaviour of the Zinc–Aluminum-based ZA-12 alloy produced by gravity casting
Authors: Kurnaz S. Can , Sevik Hüseyin , Türk Ahmet , Ozsarac Uğuur
Published: December 2013

In this study, the effect of Ti–B (0.05–0.7wt.% Ti, 0.01–0.13wt.% B) and Sr additions (0.05–0.7wt.%) on the hardness, ultimate tensile strength (UTS), strain and fatigue properties of the gravity cast Zn–Al-based ZA-12 alloy was investigated. While the Ti–B additions had no significant effect on the hardness of the alloys, the Sr additions lowered the hardness by a small amount. UTS and fatigue resistance of the ZA-12 alloy increased with 0.05wt.% Ti, but the addition of 0.05wt.% Sr to the standard alloy did not change these properties significantly. In excess of 0.05wt.% Ti and Sr, the UTS and fatigue resistance of the alloys decreased and reached a lower value than that of the standard alloy. The failure strain only increased for the ZA-12 alloy containing 0.05wt.% Ti, then decreased with further increase in Ti content. The failure strain values of the alloys decreased with addition of Sr. Metallographic examination indicated that the addition of Ti–B strongly modified the microstructure of the standard ZA-12 alloy, but Sr did not. Ti and Sr have also formed complex-shaped intermetallic compounds, which were identified as Al5Ti2Zn and Zn5Al3Sr by X-ray diffraction and EDS analyses. It can be suggested that these particles cause a decrease in UTS, fatigue resistance, and strain to failure of the ZA-12 alloy.
Determination of retained austenite in multiphase steels by magnetic force microscopy
Authors: Zens Aloisia Saiz , Appel Tamara , Broekaert Jose A. C. , Friedel Frank
Published: December 2013

The use of atomic force microscopy (AFM) in the magnetic force mode (MFM) for the determination of austenite (non-magnetic phase) in duplex and TRIP (transformation-induced plasticity) steels is described. The influence of the sample preparation for the MFM measurements is investigated, showing that a final electropolishing stage is necessary in the case of TRIP-steels.

The results of the determination of austenite in the range of 6–15% with AFM were compared with those obtained with electron backscattered diffraction (EBSD) and light optical microscopy. For TRIP-steels an identification of retained austenite with MFM was found to show a better resolution than classical light optical microscopy.
Determination of the critical tensile stress of sapphire by spherical indentation with additional lateral forces
Authors: Linss V. , Chudoba T.
Published: December 2013

The comprehensive mechanical characterisation of thin films and surfaces is very important for a suitable optimisation of protection layers and layer systems. The Young's modulus and the yield strength are widely accepted material parameters which can be determined by spherical nanoindentation in normal direction. This article reports on the determination of a further parameter, the critical tensile stress, by spherical nanoindentation with additional lateral forces. The critical tensile stress was determined for sapphire. It will be shown that the results obtained with two different nanoindentation devices equipped with spherical diamond indenters of different radii agree with less than 10% deviation.