Zinc oxide nanoparticles, especially those with a high aspect ratio (i. e., nanorods and nanowires), are of great interest for many applications as they are piezoelectric, photocatalytic and antimicrobial. In the present study, a plasma flight-thru synthesis method was developed that allows controlling the particle size and shape of the zinc oxide nanoparticles. In a direct current thermal plasma reactor operated at atmospheric pressure, zinc powder injected into the plasma jet was molten, vaporized and oxidized, which allowed growing zinc oxide nanoparticles. The particle spectrum ranged from small nanospheres to nanorods, nanowires and multipodic nanoparticles such as tetrapods. The influence of the oxygen rate and the plasma power (correlated to the discharge current) on the particle morphology was studied, and the feasibility of the nanowire-like particles as piezoelectric sensor material was investigated. Piezoelectric test sensors, equipped with the plasma-synthesized zinc oxide nanowires, successfully responded to mechanical stimulation after poling.

The damage behavior of hard coated structures such as used for metalworking tools is influenced by residual stresses since they are superimposed with the load stresses that arise in application. Information on the depth gradient of these residual stresses in a coating's substrate is crucial to understand the evolution of damage in the substrate-coating composite. In the current work, the equi-penetration grazing incidence X-ray diffraction (EP-GIXD) method was adapted for the determination of the residual stress depth profile in the WC-Co hardmetal substrate below an AlCrN-based hard coating. The limits of this method in terms of coating thickness, up to which the EP-GIXD method is applicable to determine the residual stress state in the substrate, were investigated by recording the X-ray absorption in the hard coating in rocking curves. To this end, the diffraction intensity was recorded as a function of the path length in the coating that depends on the incident angle of the X-rays. Subsequently, the obtained residual stress profile was determined as a function of various mean penetration depths selected via the variation of the angle of incidence. The EP-GIXD method facilitates a significant reduction of experimental effort compared to e.g. synchrotron-based approaches for the future study of the residual stress state of substrates in substrate-coating composite structures.

Niobium oxide layers with a thickness in the range of 1.0-1.4 mu m were deposited on silicon single crystal wafers by magnetron sputtering using substoichiometric niobium oxide target materials. After the deposition process, the layer material was completely amorphous. The primary crystallization of the hexagonal Nb2O5 phase and the subsequent transformation to the orthorhombic phase were investigated by means of in-situ high-temperature X-ray diffraction up to a temperature of 900 degrees C under a reducing N-2/H-2 atmosphere. The precise determination of the cell parameters by Rietveld refinement enabled the determination of the anisotropic thermal expansion behavior of the crystalline Nb2O5 phase. Besides, an activation energy of the primary crystallization reaction of + 460(50) kJ/mol was quantitatively determined by isothermal in-situ experiments in the temperature range of 505-545 degrees C.

Al2O3-Al2TiO5-TiO2 composites can be obtained by the infiltration of molecular titanium precursors into presintered α-Al2O3 (corundum) cylinders. Two titanium tetraalkoxides, and two dialkoxy titanium bis(acetylacetonates) serve as precursors for TiO2 (rutile) and Al2TiO5 (tialite). The precursors were infiltrated as ethanolic solutions. After sintering at 1550, 1600, and 1650°C, the prepared ceramics’ properties were investigated by SEM, in-situ HT-XRD, and conventional XRD. Titanium tetraisopropoxide leads to the highest content of Al2TiO5 in the composite. The more reactive the precursor, considering the Al2O3/precursor interface, the lower and more anisotropic the grain growth, the more homogeneous is the TiO2 contribution and the higher is the content of Al2TiO5. Raising the sintering temperature causes an increase of the crystalline Al2TiO5 con tent as well as of the grain growth. Moreover, the reactivity of the precursor molecule influences the Ti/(Al + Ti) ratio in the obtained tialite phase.

Reconstruction of residual stress depth profiles from diffraction data depends crucially on the underlying assumptions regarding X-ray elastic constants, stress state, and generic shape of the stress depth profile. This article addresses two issues: first, how to account for X-ray elastic constants varying according to different crystallographic planes by rearranging the underlying equation system such that it becomes amenable to linear regression again; second, how to construct the residual stress depth profile via inverse Laplace transformation of a piecewise linear approximation function, thereby obtaining maximum flexibility in the description of the generic shape of the profile. The methods are discussed by means of typical examples.

Thermally induced stresses created during package manufacturing and their roles in mechanical failure are important issues for the microelectronic industry. In the present paper, a numerical analysis of the die embedding process into a printed circuit board by means of the package assembling and lamination is presented. The complex package consisting of a silicon die, an adhesive, a copper foil, an epoxy resin and prepregs (an E-glass woven structure pre-impregnated with an epoxy resin) is investigated in terms of warpage and stress development. Both are mainly introduced due to a mismatch of coefficients of thermal expansion and particularly to shrinkage of the polymer parts (adhesive, epoxy resin). Their impact on possible package failures is discussed. A two-dimensional axisymmetric numerical model is employed for investigation of the embedding process flow. Temperature dependent material properties for all materials are used in the analysis. A special focus is set on the orthotropic properties of the prepreg materials. Those are analytically homogenized based on the lamination theory of plain woven fabric composites and implemented into the numerical model. The numerical results of embedding process steps are validated experimentally by an X-ray diffraction method (Rocking-Curve-Technique) showing a good agreement of the calculated and measured curvature radius values.

Coated WC–Co hard metal milling inserts applied in milling application show thermal fatigue induced by interrupted tool-workpiece contact and wear as the two main damage mechanisms. Depending on the magnitudes of thermal and mechanical loads, either wear or thermal fatigue in form of combcracks may be dominant and determine the insert's lifetime. The present work illustrates the evolution of residual stress in an arc-evaporated Ti–Al–Ta–N coating for two different milling test setups, in one of which wear acted as the dominant damage mechanism. In the other test setup thermal fatigue fostered the formation of combcracks. Earlier work revealed a location on the tool's rake face, referred to as region of interest, with a significant buildup of tensile residual stresses in the WC phase of the substrate using synchrotron facilities. The residual stress state in the coating was determined in this region of interest by a cover method on the tools' rake faces after a defined number of cuts by X-ray diffraction using in-house facilities. In the wear dominated test setup, compressive residual stresses remained present until the end of tool life in coatings. Tensile residual stresses were found in coatings on inserts in which thermal fatigue was dominant.

In coated hard metal milling inserts the main damage mechanisms are thermal fatigue induced by interrupted tool–workpiece contact and wear. Dependent on the magnitudes of thermal and mechanical loads in two applied test setups, either wear or thermal fatigue in the form of combcracks is induced. The evolution of residual stress and damage in the used milling inserts was documented over their complete lifetime. In a region of interest on the tool rake face a significant buildup of tensile residual stress was observed via a synchrotron based technique. A special preparation technique enabled position resolved measurements in this area by in-house X-ray diffraction facilities to study the evolution of residual stress over the entire tool lifetime. The onset of cracking was observed to happen in this region of interest by means of focused ion beam milling and scanning electron microscopy. The residual stress levels observed are comparable in used inserts at early stages of application, independent of the different cutting conditions and the applied characterization technique. At the end of tool life wear damage dominated inserts showed tensile residual stress, whereas thermal fatigue as the dominant damage mechanism resulted in compressive residual stresses.

In this work a new modification of the grazing incidence X-ray diffraction method for residual stress determination is presented. This equi-penetration grazing incidence X-ray diffraction method is especially suitable for the precise determination of the residual stress depth profile in materials. It originates from a sin2ψ approach based on the determination of the lattice spacing of various selected diffraction planes. Additionally, for each measurement the condition ∂τ/∂ψ=0 is here fulfilled and one dataset corresponds strictly to a specific mean penetration depth τ independent of the tilt angle ψ. This can be achieved by the individual adjustment of the incidence angle for each measured diffraction maximum. In the actual work, the influence of different surface finishes on the stress depth profile of commercial silicon nitride ceramic samples is investigated. The ground specimen displays an almost biaxial compressive stress parallel and near to the specimen surface of 3GPa, which decreases almost up to zero in a depth of 5μm. After the polishing process, the specimens show a strongly reduced compressive stress maximum at the surface of 1GPa, which diminishes similarly with increasing depth. The orientation between the stress component and the grinding direction is of minor influence. Furthermore, the influence of a possible residual stress component perpendicular to the sample surface is discussed.

The presented X-ray diffraction techniques enable the simultaneous characterization of phase content, dislocation densities in the austenitic and the ferritic/bainitic/martensitic phases, or the tetragonal lattice distortion and the interstitial carbon content in martensite. The capability of the diffraction methods is demonstrated using the example of heat treatment of high speed steels.

Chromium nitride/titanium–titanium carbonitride multilayers composed of a 40nm Cr interface followed by a 4.4μm thick Cr2N layer, a 150nm thick Ti layer, and a 1 μm thick TiCxNy top layer were deposited on silicon wafers by magnetron sputtering. The structural changes and the phase content changes of these multilayer samples were studied by means of high-temperature in-situ X-ray diffraction experiments at temperatures up to 550°C. The lattice constants of the Cr phase as well as the Ti phase display an aberrant expansion behaviour during these experiments which is influenced by the defect structure, a nitrogen incorporation, and residual stress in the layers. The results were compared with structural data obtained by ex-situ transmission electron microscopy investigations of pristine and heated material, revealing phase separation and strong diffusion phenomena.

Ternary Ni50Co30Fe20 powders with an open dendritic structure were made by electrodeposition. The diffusion controlled deposition allows fabrication of alloy powders with a composition corresponding to that of the electrolyte. Their morphology was studied by electron microscopy methods revealing that the particles have a highly branched dendritic structure extending from the micrometer scale to the nanoscale containing a high density of defects as grain boundaries and twin boundaries. We propose that this structure forms by massive repeated nucleation far off thermodynamical equilibrium at a high current density under strong hydrogen bubble evolution. The nanodendritic structure could be of interest for practical applications due to their high density of active sites and high surface area. The powders are envisioned for electrochemical applications.

Chromium/chromium nitride multilayer coatings consisting of a stack of alternating 82nm thick chromium and 168nm thick CrNx sublayers with a total thickness of 4μm were deposited on silicon wafers by magnetron sputtering below 70°C. X-ray diffraction revealed for the as-deposited state a significant fraction of material in amorphous state. The effect of subsequent heat treatment on the formation of the crystalline phases Cr and Cr2N, on the coherent diffracting length of the occurring crystallites, as well as the correlated variations of the lattice cell parameters was studied by in-situ high temperature X-ray diffraction techniques. Ex-situ observations of the crystallographic texture showed the presence of a fibre texture parallel to the [1 0 0] direction for the Cr-phase and a fibre texture parallel to the [1 1 2] direction for the Cr2N phase.

In this paper, a method for the continuous preparation of nanoscaled Mania with controlled phase content is presented. The method bases on the MicroJetReactor technology. The synthesis process was carried out by using the hydrolysis of titanium tetraethylate (TET). Synthesis with flow rates to 14 ml/min are implemented, and temperatures are varied between 20 and 210 degrees C. Particle size distribution measurements by dynamic light scattering (DLS) show monomodal particle size distributions from 1 to 10 nm, stable for more than 24 h. There is no correlation between hydrolysis temperature and the particle size distributions.XRD (X-ray diffractometry) investigations showed, that crystal structures of anatase, brookite, rutile and an amorphous content can be detected in all samples. Quantitative analysis using the Rietveld refinement shows a significant effect of the synthesis temperature on the phase content. The relative phase content of anatase can be raised from 40 wt% up to 75 wt%, accompanied by a loss of all other phases. (C) 2011 Elsevier Ltd. All rights reserved.

The goal of this work is the evaluation of nanoscaled reinforcements; in particular nanodiamonds (NDs) and carbon nanotubes (CNTs) on properties of titanium matrix composites (TiMMCs). By using nano sized materials as reinforcement in TiMMCs, superior mechanical and physical properties can be expected. Additionally, titanium powder metallurgy (P/M) offers the possibility of changing the reinforcement content in the matrix within a very wide range. In this work, TiMMCs have been produced from titanium powder (Grade 4). The manufacturing of the composites was done by hot pressing, followed by the characterisation of the TiMMCs. The Archimedes density, hardness and oxygen content of the specimens in addition to the mechanical properties were compared and reported in this work. Moreover, XRD analysis and SEM observations revealed in situ formed titanium carbide (TiC) phase after hot pressing in TiMMCs reinforced with NDs and CNTs, at 900°C and 1100°C respectively. The strengthening effect of NDs was more significant since its distribution was more homogeneous in the matrix.

Ribbon-shaped amorphous samples with the stoichiometric composition Fe73.5Cu1Nb3Si15.5B7 prepared by the melt spinning process were annealed at temperatures ranging from 693K to 1123K for 1 h under vacuum. In the early annealing stage, the alloy undergoes a specific nucleation process where Cu clusters precipitate from an amorphous matrix. Further heating initiates the partial crystallization of alloy forming the alpha-Fe-Si nanocrystallites. Subsequent Vickers hardness tests showed high values depending on the annealing temperature. It was found that the hardening process includes two stages. This behavior correlates well with results of density dislocation calculations. A crystallite size of 10nm for the alpha-Fe-Si particles correlated very well with a maximum hardness of the material. (C) 2010 Elsevier B. V. All rights reserved.

The spark-plasma-sintering (SPS) method was used for sintering of different tungsten carbide (WC) and titanium carbonitride (TiCN) nanopowders obtained by the method of plasma synthesis. Dense, fine-grained monophase materials (WC and TiCN) were obtained at relatively low temperatures. Obtained results were compared with that for hot pressing (HP) method.

Titanium oxide layers were prepared on pure aluminium substrates by the anodic spark deposition method. The formed crystalline titania (TiO2) phases rutile and anatase and the sodium titanium oxide (Na0.23TiO2) were identified. The corresponding crystallite size values were obtained from X-ray diffraction data by means of the Rietveld method. The crystallite size of each of these phases continuously increases with rising current density. Furthermore, the two-dimensional distribution of the titania phases on the sample surface was determined by Raman spectroscopy. It was found that the rutile/anatase ratio is inhomogeneous distributed on an observed area of 400×400μm2.

The effect of poly(ethylene glycol) (PEG) with molecular mass 400 (PEG 400) on the hydrogen evolution reaction (HER) and on the Zn reaction in a Na2SO4 solution and a Zn2+-containing electrolyte was investigated by electrochemical methods. The major effect of PEG 400 on the cathode process was in the range of HER from H2O and bulk deposition of Zn. In the electrolyte for Zn-Cr alloy deposition, the polarization effect of PEG 400 is not sufficiently strong in the potential range of Cr codeposition with Zn, as a result of which the average amount of Cr incorporated in the coatings is relatively low, up to 6 mass %. Based on X-ray photoelectron spectroscopy and X-ray diffraction analysis, it is assumed that Cr is present as metallic Cr in the coatings under the surface hydroxide oxides. Major constituents of the Zn-Cr coatings are two hexagonal phases: eta-(Zn,Cr) and delta-Zn,Cr). Also considering experiments under the industrial conditions of high electrolyte flow and high current density, it is concluded that PEG 400 is not a suitable additive for the electrodeposition of Zn-Cr alloy coatings.