bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subsolidus phase equilibria in the CeO2−x–SiO2–ZrO2 system: An experimental study
Authors: Zec Slavica , Bošković Snežvana , Popovic Nada , Bogdanov Žvarko 
Published: December 2013

Abstract
The phase equilibria in the CeO2–x–SiO2–ZrO2 system were studied in the subsolidus region in argon atmosphere, under isothermal heating and hot pressing, at 1400°C, different ceria, silica, and zirconia mixtures. X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) were performed to identify phases and to establish phase equilibria. Based on the results of many preliminarily investigated ternary compositions, possible tie lines are predicted. Compositions from the proposed tie lines were successively fired and ground until the changes of the phase compositions were not detected or were low enough to be neglected. Phases identified in these compositions confirmed the existence of five tie lines: Ce2Si2O7–ZrSiO4, Ce2Si2O7–ZrO2, Ce4.67(SiO4)3O–ZrO2, Ce4.67(SiO4)3O–Ce2Zr2O7 and Ce2SiO5–Ce2Zr2O7, which divide the CeO2–x–SiO2–ZrO2 composition triangle into six compatibility triangles. The formation of ternary compounds or ternary solid solutions in the CeO2–x–SiO2–ZrO2 system was not observed. The monoclinic high temperature polymorph of Ce2Si2O7 was detected. The cubic pyrochlore phases had different lattice parameters, caused by incomplete reduction of the tetravalent cerium ions also observed in the non-stoichiometric cerium oxide.
Thermal evolution of free volumes and of crystallization in amorphous Si–B–C–N ceramics
Authors: Reichle Klaus J. , Reimann Klaus , Sprengel Wolfgang , Rempel Andrej A. , Müller Anita , Schaefer Hans-Eckhardt 
Published: December 2013

Abstract
We report on the crystallization behavior of initially amorphous precursor-derived Si3B1C4.3N2 ceramics, making use of macroscopic and atomic scale investigation techniques. As derived from our kinetic studies upon heating, the following temperature sequence of solid state processes is observed with approximately the same kinetic time constants: after an initial densification in the amorphous state (1673K), crystallization occurs (1873K) with subsequent strain relaxation and disappearance of nanovoids (2073K). This behavior indicates an increasing activation enthalpy of the atomic mechanisms giving rise to these processes when the annealing temperature is increased. The nanovoids may be located in the turbostratic BNCx layers as derived from positron annihilation studies. For grain growth at high temperatures an activation energy of HG=3.9eV is derived.
Nanopowder dispersion and spray-drying process: the case of Cr2O3
Authors: Cellard Audrey , Zenati Rachid , Garnier Vincent , Fantozzi Gilbert , Baret Guy 
Published: December 2013

Abstract
The work reported in this paper was performed in order to develop and to optimize the dispersion of Cr2O3 nanopowders by a ball-milling method and to produce spherical micrometer-sized granules by spray-drying. The targeted application for such granules is the development of wear resistant nanostructured Cr2O3 coatings by plasma spraying. Cr2O3 nanopowders were dispersed in deionized water. The suitable dispersant (DarvanC) was determined by zeta potential measurements and the dispersant quantity was optimized by rheological tests. The influence of milling time, diameter of milling balls and weight ratio of milling balls to powder was studied by granulometric measurements. A well-dispersed and stable suspension was then obtained and spray-dried. Dense and spherical micrometer-sized granules, with a monodispersed distribution centered about 50μm, have been achieved and Cr2O3 plasma-sprayed coatings have been realized.
The role of chemisorbed anions in the aqueous processing of AlN powder
Authors: Krnel Kristoffer , Kosmačv Tomažv 
Published: December 2013

Abstract
In the production of ceramics containing AlN it is necessary to prevent the AlN powder from reacting with water. To do that, non-aqueous powder processing is required or water-resistant AlN powders must be used. Alternatively, as in the Hydrolysis Assisted Solidification process, which exploits the hydrolysis of AlN for the solidification of the ceramic suspensions, the hydrolysis has to be prevented at room temperature but initiated at elevated temperatures. In this study the role of the chemisorbed anions in the hydrolysis of the AlN was investigated in order to make the control of the hydrolysis reactions possible. The method for preparing water-resistant, hydrophilic AlN powder using the dispersion of the powder in a solution of aluminium dihydrogen phosphate is also presented. The mechanism leading to the formation of the protective surface layer is proposed and explained. The method was also successfully tested on nanosized AlN powder. This powder was processed in water and sintered to high density.
Development of high-temperature thermoelectric materials based on SrTiO3-layered perovskites
Authors: Wunderlich Wilfried , Koumoto Kunihito 
Published: December 2013

Abstract
For improving the performance of ceramic thermoelectric materials an increase in the effective mass is required because it is the main factor determining the Seebeck coefficient, in the case of a semiconductor with sufficiently high carrier concentration. The Ruddlesden–Popper phase Sr3Ti2O7, with its conducting perovskites layer in between the phonon absorbing SrO layers, is an example for advanced material design by nano-block integration. Using ab-initio simulations, the electronic bandstructure was calculated, and from the curvature of the bands the effective mass was deduced. While Sr3Ti2O7 has a smaller effective mass than the Nb-doped SrTiO3, the layered perovskites with substitution of Ta instead of Ti possess very large effective masses (m*/m0=9 in average) and a large thermopower is expected. In the experiments, however, the sufficient charge carrier concentration could not yet be reached.
The influence of the preparation method on the microstructure and properties of Al2O3/TiN nanocomposites
Authors: Gao Lian , Jin Xihai , Li Jingguo , Sun Jing 
Published: December 2013

Abstract
Al2O3/TiN nanocomposites were fabricated by hot pressing of powders prepared through ball milling (BM) and in-situ nitridation (PN) methods, respectively. And the mechanical and electrical properties as well as microstructure of the nanocomposites were studied. It was found that TiN showed a strong reinforcing effect in both materials. Due to the difference in the powder preparation method, the Al2O3/TiN nanocomposite from PN powder showed a finer TiN particle size and a more uniform microstructure than the nanocomposite from BM powder. As a result, the former material showed a superior electrical conducting behavior and better mechanical properties.
Quasi-equilibrium sintering of particle clusters containing Bernal holes
Authors: Wakai Fumihiro , Shinoda Yutaka , Akatsu Takashi 
Published: December 2013

Abstract
The transformation of spherical particle assemblies into dense materials by sintering is an idealized micromechanical model for studying the densification. The equilibrium configurations of particle clusters containing canonical Bernal holes, which are typical structural units in random packing of spheres, were calculated by using the Surface Evolver program. The quasi-equilibrium sintering of particle clusters, in which pores shrink keeping their equilibrium shapes, were analyzed as a response to the sintering stress and the macroscopic viscosity. Both sintering stress and macroscopic viscosity were determined as a function of the pore volume, the dihedral angle, and the pore coordination number. The densification curves in sintering simulation agreed with the predicted shrinkage rate.
Microstructure and mechanical behavior of Pt-modified NiAl diffusion coatings
Authors: Riethmueller J. , Dehm G. , Affeldt E. E. , Arzt E. 
Published: December 2013

Abstract
The performance of thermal barrier coatings (TBCs) in jet engines is strongly influenced by thermal and mechanical properties of the bond coat. In this investigation two different types of Pt-modified diffusion coatings developed for application as oxidation protection or as a bond coat in TBC systems were studied with respect to their microstructure and mechanical properties. The microstructural analyses based on different microscopy techniques and X-ray diffraction measurements revealed distinct differences between the two coatings: the coating aluminized by a gas phase process consisted solely of a (NiPt)Al phase, while the coating fabricated by pack-cementation consisted mainly of the two phases (NiPt)Al and Al2Pt, leading to a higher strength in comparison with the single-phase coating. In contrast, the ductility determined with 3-point bend tests between room temperature and 700°C was clearly better for the single-phase coating. Additionally, the substrate curvature of coated sheets was measured to gain some information about coating stresses.
Thermodynamic assessment of the Ce–O system in solid state from 60 to 67mol.% O
Authors: Seifert Hans Jürgen , Nerikar Pankaj , Lukas Hans Leo 
Published: December 2013

Abstract
A thermodynamic dataset was developed for the central part of the Ce–O system covering the range between CeO and CeO up to about 2000K. All literature data for the thermodynamic functions, the phase diagram and crystallography were critically assessed. The modeling of the phases takes into account their crystal chemistry including order–disorder behavior. From the dataset, diagrams were calculated for the (1) heat capacities of CeO and CeO, (2) enthalpy increment of CeO, (3) chemical potentials of oxygen in CeO, (4) partial enthalpies of oxygen in CeO, (5) the partial phase diagram of Ce–O and (6) chemical potentials of oxygen in the two-phase areas. These diagrams reproduce fairly well the experimental data from literature.
Phase transformations of iron nitrides at low temperatures (<700 K) – application of mechanical mixtures of powders of nitrides and iron
Authors: Leineweber Andreas , Aufrecht Jochen , Mittemeijer Eric Jan 
Published: December 2013

Abstract
Annealing at low temperatures (T<670K) of mixtures of iron nitride powders and iron powder is shown to induce phase transformations through nitrogen transfer between different powder particles. This nitrogen transfer occurs via loose mechanical contact points between different powder particles; nitrogen transport via the gas phase can be excluded. Unique scientific possibilities offered by this type of phase transformation studies are discussed.
Reconstruction and structural transition at metal/diamond interfaces
Authors: Zhang Wenqing 
Published: December 2013

Abstract
Based on density-functional calculations, interfacial reconstruction and structural transition at diamond(111)/M/copper (M = Ag, Cu, Ni, Co) interfaces are studied by analyzing the atomistic structures of the interfaces. Tuning the strength of chemical bonds across the interfacial plane (out-of-plane), we show that interfacial reconstruction happens as a result of competition between the out-of-plane chemical bonds and the in-plane bonds within the diamond substrate. A relatively weak out-of-plane bond may easily lead to reconstruction of interfacial structures. A structural transition from one-dangling-bond- to three-dangling-bond-terminated interface is also observed as the out-of-plane bond is sufficiently strong, which leads to a dramatic enhancement of the adhesion of the interface.
Aqueous solution deposition of indium hydroxide and indium oxide columnar type thin films
Authors: Qiu Yu , Gerstel Peter , Jiang Linqin , Lipowsky Peter , Bauermann Luciana Pitta , Bill Joachim 
Published: December 2013

Abstract
Crystalline In(OH)3 and UV-emitting In2O3 thin films with a unique columnar morphology have been successfully prepared for the first time via a simple aqueous solution deposition method. In the present study, sulfonate-terminated self-assembled monolayers on single-crystal Si wafers were used as substrates for the film deposition. Uniform In(OH)3 thin films formed on self-assembled monolayers in aqueous solutions of InCl3.4H2O at 60°C. These films, containing columnar In(OH)3 crystals, showed preferential growth orientation along the [100] direction. The current understanding of the film formation mechanism was discussed. After annealing in air at 400°C, these films were converted to nanocrystalline In2O3 films without modification of the morphology. Photoluminescence emission from In2O3 films was reported at approximately 3.4eV, which was ascribed to the near-band-edge emission.
On the mechanisms governing the texture and microstructure evolution during static recrystallization and grain growth of low alloyed zirconium sheets (Zr702)
Authors: Dewobroto N. , Bozzolo N. , Barberis P. , Wagner F. 
Published: December 2013

Abstract
Low alloyed zirconium sheets (Zr702) have been cold-rolled up to 80% thickness reduction and submitted to various isothermal treatments. The aim was to identify the mechanisms which produce microstructure and texture changes during recrystallization and grain growth. XRD and texture analysis, FEG–SEM with EBSD as well as TEM were used to analyze the various specimens. Three types of substructures were observed in the initial deformed material. Accordingly, the nucleation starts in the most deformed areas and continues in the somewhat less deformed areas, which corresponds to a non oriented nucleation and results in a set of new grains, the size of which is very rapidly stabilized. In the last stage of recrystallization, the grains which have resisted the recrystallization disappear progressively by several mechanisms including in situ recrystallization. Therefore, the texture at the end of the recrystallization resembles the one of the deformed state. Normal grain growth leads to a moderate grain size increase due to the precipitates which slow down the grain boundary motion. This is also the stage where the texture changes due to the size advantage, after recrystallization, of grains in some specific orientations.
Sintering of Si3N4 with Li-exchanged zeolite additive
Authors: Matovic B. , Rixecker G. , Boskovic S. , Aldinger F. 
Published: December 2013

Abstract
This paper deals with the densification and phase transformation of Si3N4 with additives of Li-exchanged zeolite during pressureless sintering at significantly reduced temperatures. Dilatometric shrinkage data show that the first liquid forms as low as 1080°C. Upon sintering at 1500°C the bulk density increases to more than 95% of the theoretical density without phase transformation from -S3N4 to -Si3N4, i.e. the phase transformation lags behind the densification process. Above 1500°C the secondary phase is completely converted into a glass and the -to- transformation takes place. Under these conditions the grain growth is anisotropic, leading to a microstructure which has potential for enhanced fracture toughness. The results show that a very effective low-temperature sintering additive for silicon nitride can be obtained from Li-exchanged zeolite.
Laser Interference Metallurgy – using interference as a tool for micro/nano structuring
Authors: Mücklich Frank , Lasagni Andrés , Daniel Claus 
Published: December 2013

Abstract
Interfering laser beams of a high-power pulsed laser provide the opportunity of applying a direct lateral interaction with the surface microstructure of metals in micro/nano-scale based on photo-thermal nature mechanisms. This “Laser interference metallurgy” allows the creation of periodic patterns of features with a well defined long-range order on metallic surfaces at the scale of typical microstructures (from the sub micrometer level up to micrometers). This technique is an approach to initiate metallurgical processes such as melting, recrystallization, recovery, and defect and phase formation in the lateral scale of the microstructure itself and with an additional long range order given by the interference periodicity. In this work, the laser interference theory is described and used to calculate multi-beam interference patterns. A method to calculate the numbers of laser beams as well as the geometrical arrangement of the beams to obtain a desired periodical pattern prior to experiments is presented. The formation of long-range-ordered intermetallic compounds as well as macroscopic and microscopic variations of mechanical properties on structured metallic thin films are presented as examples.
On dynamic and static strain ageing in Cu-2at.% Mn polycrystals
Authors: Dierke H. , Klose F. B. , Nortmann A. , Neuhäuser H. 
Published: December 2013

Abstract
Measurements of the yield points ΔσA on reloading after ageing at various stress levels (obtained by partial unloading of the tensile specimen) have been performed with Cu-2at.% Mn polycrystals at 313K (strain rate 310−5s−1). At these temperatures solute atoms are supposed to increase the effective obstacle strength (intersections of mobile with forest dislocations) by pipe diffusion from the forest to the mobile dislocations during the waiting time for thermal activation. The stress dependence ΔσA ∝ (σ*)1/3, (with the effective stress σ*) expected according to Friedel's equation is observed. This supports the intersection strengthening model and, hence, the pipe diffusion mechanism for static and dynamic strain ageing in the temperature and strain rate regime of this study.
Microcracks in superalloys: From local in-situ measurements to lifetime prediction
Authors: Marx Michael , Vehoff Horst 
Published: December 2013

AbstractThe establishedK-concept with the Paris law as the central equation often used for life-time prediction and dimensioning does not fit with the micromechanical crack tip opening displacement (CTOD) concept. While theK-concept is based on continuum mechanics, the CTOD is influenced by the local microstructure. Consequently, the CTOD-concept is checked in situ in the scanning electron microscope and is found to be the appropriate micromechanical description of the crack propagation mechanism. However, it is shown that during low cycle fatigue of turbine materials, even under extreme conditions short cracks behave less harmfully than expected. Additionally a new technique of artificial crack initiation by operating with a focused ion beam is used to investigate special crack problems such as the interaction of cracks with microstructural barriers in detail, which was not previously possible in this systematic way.
Residual stress development due to thermal cycling of the particle-reinforced alloy EN AW-6061– experiment and simulation
Authors: Heimann Sebastian , Pohl Michael , Klaska Arne M. , Beck Tilmann 
Published: December 2013

Abstract
The development of residual stresses and strains in the matrix material of the extruded aluminium alloy EN AW-6061-T6 both with no reinforcement and also reinforced with 15vol.% and 22vol.% α-alumina particles was investigated in thermal cycling tests and additionally by finite-element-simulation for the non-reinforced material. For this purpose cylindrical specimens were heated by a 3kW diode laser and cooled by a water quench. Residual stresses in the surface area of the laser beam and temperature distribution inside the specimen were measured. The results were used to validate the finite-element model for calculating stress and strain distributions inside the specimens.
Investigation and modelling of theplasticity-induced martensite formation in metastable austenites
Authors: Smaga Marek , Walther Frank , Eifler Dietmar 
Published: December 2013

Abstract
Mechanical stress–strain hysteresis, temperature and magnetic measurements were performed for the detailed characterisation of the cyclic deformation behaviour of metastable austenitic steels with particular attention to plasticity-induced martensite formation. Specimens of AISI 304, AISI 321 and AISI 348 stainless steels were investigated under plastic strain control at ambient temperature. On the basis of comprehensive experimental data, a model was developed for the description of the plasticity-induced martensite formation in metastable austenites under cyclic loading. The process of martensite formation was described as a function of the cumulative plastic strain and the cumulative strain energy density.
Strengthening of silicon nitride ceramics by shot peening
Authors: Pfeiffer Wulf , Gumbsch Peter 
Published: December 2013

Abstract
Shot peening is a common procedure for improving the static and cyclic strength of metal components by a combination of work hardening and the introduction of compressive stresses into the surface region. Recent investigations showed that high compressive stresses of more than 1 GPa can also be introduced in brittle ceramics such as alumina and silicon nitride under specific shot peening conditions. These stresses dramatically increase the near-surface strength. This paper compiles the current state of the art of shot peening for silicon nitride ceramics. Detailed information about the influence of shot peening on the residual stress state, dislocation density and damage are given. The effect of the residual stresses on the static and cyclic nearsurface strength is quantified.
Assessment of creep behaviour of the die-cast cylinder-head alloy AlSi6Cu4-T6
Authors: Dehler Anja , Knirsch Stefan , Srivastava Vivek , Saage Holger , Heilmaier Martin 
Published: December 2013

Abstract
Mechanical properties of a T6-AlSi6Cu4 cylinder-head alloy are investigated at 4 stress levels up to 545 K through tensile and compressive test to assess creep damage. The effect of over-ageing for 200 h at comparable temperatures was studied through RT hardness tests. Creep behaviour was characterised by a minimum creep rate and an extended steady state was not observed. No threshold stresses were apparent from minimum creep rate vs. stress plots at any of the temperatures studied here. Apparent stress exponents were both temperature and stress dependent and the apparent creep activation energy was 2–3 times the lattice selfdiffusion activation energy for aluminium. The Norton plot was best described by an exponential relation. The total strain to failure exhibited a maximum for a particular applied stress and decreases for both higher and lower applied stress. Creep life is well described by the Monkman– Grant relation at the highest temperature, but exhibits deviations from the idealised behaviour at the lower test temperatures.
New aspects of bending rotation fatigue in ultra-fine-grained pseudo-elastic NiTi wires
Authors: Wagner Martin Franz-Xaver , Eggeler Gunther 
Published: December 2013

Abstract
Bending rotation fatigue experiments are a standard evaluation procedure for pseudo-elastic NiTi wires used in the medical device industry. However, the non-linear mechanical behavior and the possible occurrence of localized deformation during bending complicate the physical interpretation of fatigue life data. In the present study, some related experimental and theoretical aspects are addressed: Optical measurements are used to characterize the local deformation of the wire specimens in a typical experimental setup, and a simple mechanical model of stresses and strains associated with bending rotation is employed to rationalize the impact of several experimental parameters on fatigue life data. Dissipated energies per cycle and unit length are calculated. How dissipation leads to an increase of both specimen temperature and maximum stresses and, therefore, considerably decreases fatigue lives is demonstrated.