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The present work shows results on elemental distribution analyses in Cu(In,Ga)Se2 thin films for solar cells performed by use of wavelength-dispersive and energy-dispersive X-ray spectrometry (EDX) in a scanning electron microscope, EDX in a transmission electron microscope, X-ray photoelectron, angle-dependent soft X-ray emission, secondary ion-mass (SIMS), time-of-flight SIMS, sputtered neutral mass, glow-discharge optical emission and glow-discharge mass, Auger electron, and Rutherford backscattering spectrometry, by use of scanning Auger electron microscopy, Raman depth profiling, and Raman mapping, as well as by use of elastic recoil detection analysis, grazing-incidence X-ray and electron backscatter diffraction, and grazing-incidence X-ray fluorescence analysis. The Cu(In,Ga)Se2 thin films used for the present comparison were produced during the same identical deposition run and exhibit thicknesses of about 2 µm. The analysis techniques were compared with respect to their spatial and depth resolutions, measuring speeds, availabilities, and detection limits.
Glass-ceramics containing Ca2KNa(PO4)2 as the main crystalline phase have a solubility which is 8 times higher than that of alpha-tricalcium phosphate ceramics. When using these compositions in drug delivery systems, especially in bone, it is necessary to create a material with a high open porosity. A Ca2KNa(PO4)2-based glass-ceramic was prepared from a borosilicate glass melt. The processed material includes minor amounts of boron which are low enough for medical application. Tissue response was studied using an animal model. Particles were implanted in rabbit femurs. Bone and soft tissue development occurred at the particle interfaces. In general, most particles were enclosed in the network of trabecular bone. The advantages of using a biomaterial with high porosity (pore size of 1-3 micron), together with rapid biodegradation, bioactivity and biocompatibility, despite traces of boron, were shown. 4 refs.
Results are reported from a pilot study under the Consultative Committee for Amount of Substance (CCQM) to compare measurements of and resolve any relevant measurement issues in, the amount of thermal SiO2 oxide on (100) and (111) orientation Si wafer substrates in the thickness range 1.5 - 8 nm. As a result of the invitation to participate in this activity, 45 sets of measurements have been made in different laboratories using 10 analytical methods: medium-energy ion scattering spectrometry (MEIS), nuclear reaction analysis (NRA), RBS, elastic backscattering spectrometry (EBS), XPS, SIMS, ellipsometry, grazing-incidence x-ray reflectrometry (GIXRR), neutron reflectometry and transmission electron microscopy (TEM). The measurements are made on separate sets of 10 carefully prepared samples, all of which have been characterised by a combination of ellipsometry and XPS using carefully established reference conditions and reference parameters.
The results have been assessed against the National Physical Laboratory (NPL) data and all show excellent linearity. The remaining data sets correlate with the NPL data with average root-mean-square scatters of 0.15 nm, half being better than 0.1 nm and a few at or better than 0.05 nm. Each set of data allows a relative scaling constant and a zero thickness offset to be determined. Each method has an inherent zero thickness offset between 0 nm and 1 nm and it is these offsets, measured here for the first time, that have caused many problems in the past. There are three basic classes of offset: water and carbonadeous contamination equivalent to ~1 nm as seen by ellipsometry; adsorbed oxygen mainly from water at an equivalent thickness of 0.5 nm as seen by MEIS, NRA, RBS and possibly GIXRR; and no offset as seen by XPS using the Si 2p peaks. Each technique has a different uncertainty for the scaling constant and consistent results have been achieved. X-Ray photoelectron spectroscopy has large uncertainties for the scaling constant but a high precision and, critically, if used correctly, has zero offset. Thus, a combination of XPS and the other methods allows the XPS scaling constant to be determined with low uncertainty, traceable via the other methods. XPS laboratories returning results early were invited to test a new reference procedure. All showed very significant improvements. The reference attenuation lengths thus need scaling by 0.986 ± 0.009 (at an expansion factor of 2) deduced from the data for the other methods. Several other methods have small offsets and, to the extent that these can be shown to be constant or measurable, then these methods will also show low uncertainty. Recommendations are provided for parameters for XPS, MEIS, RBS and NRA to improve their accuracy.
In vivo test of a high porous rapidly resorbable dicalcium potassium sodium phosphate glass-ceramics
(2002)
The formation and properties of laser-induced periodic surface structures (LIPSS) were investigated on carbon fibers under irradiation of fs-laser pulses characterized by a pulse duration τ = 300 fs and a laser wavelength λ = 1025 nm. The LIPSS were fabricated in an air environment at normal incidence with different values of the laser peak fluence and number of pulses per spot. The morphology of the generated structures was characterized by using scanning electron microscopy, atomic force microscopy and Fast-Fourier transform analyses. Moreover, the material structure and the surface chemistry of the carbon fibers before and after laser irradiation was analyzed by micro Raman spectroscopy and X-ray photoelectron spectroscopy. Large areas in the cm2 range of carbon fiber arrangements were successfully processed with homogenously distributed high- and low-spatial frequency LIPSS. Beyond those distinct nanostructures, hybrid structures were realized for the very first time by a superposition of both types of LIPSS in a two-step process. The findings facilitate the fabrication of tailored LIPSS-based surface structures on carbon fibers that could be of particular interest for e.g. fiber reinforced polymers and concretes.
A glass of the composition 37BaO·16CaO·47SiO2 wt% produced on an industrial scale is crystallized at 970 °C for times ranging from 15 min to 2 h. The crystallization at the immediate surface as well as the crystal growth into the bulk are analyzed using scanning electron microscopy (SEM) including energy dispersive X-ray spectroscopy (EDXS) and electron backscatter diffraction (EBSD) as well as X-ray diffraction in the Θ–2Θ setup (XRD). The immediate surface shows the oriented nucleation of walstromite as well as the formation of wollastonite and an unknown phase of the composition BaCaSi3O8. All three phases also grow into the bulk where walstromite ultimately dominates the kinetic selection and grows throughout the bulk due to a lack of bulk nucleation. Walstromite shows systematic orientation changes as well as twinning during growth. A critical analysis of the XRD-patterns acquired from various crystallized samples indicates that their evaluation is problematic and that phases detected by XRD in this system should be verified by another method such as EDXS.
Das Wissen über die Materialeigenschaften und die Versagensmechanismen bei Lehmbaustoffen ist begrenzt und lückenhaft. Im Rahmen des EU-Projekts NIKER (www.niker.eu) wurden deshalb die mechanischen Eigenschaften von Bauteilen aus Lehm unter statischer Druck- und Schubbeanspruchung bestimmt. Ziel der Untersuchungen war es, grundlegende Daten zum Verformungs- und Versagensverhalten von Lehmbauteilen zu erhalten und dieses mit einem numerischen Modell zu beschreiben. Die Versuchsergebnisse belegten das spröde Verhalten von Lehmsteinmauerwerk bei uniaxialer Druckbelastung und zeigten, dass das Versagen von Lehmsteinmauerwerk infolge Schubbelastung nach Erstrissbildung in Mörtelfugen und Lehmsteinen durch Gleiten der Lehmsteine entlang der Mörtelfugen erfolgt. Die numerische Makromodellierung erbrachte zwar befriedigende Resultate hinsichtlich des Spannungs-Dehnungs-Verhaltens, jedoch konnte bei der simulierten Rissbildung keine Übereinstimmung mit den in den Versuchen beobachteten Rissbildern erzielt werden. Bei Lehmsteinmauerwerk ist also eine wesentlich aufwendigere Mikromodellierung notwendig, um das Versagensverhalten korrekt beschreiben zu können.--------------------------------------------------------------------------------------------------------------
Knowledge of the material properties and failure mechanisms of earthen materials is limited and scattered. Within the framework of the NIKER project (www.niker.eu) funded by EC, the mechanical properties of earthen material elements were therefore determined under static compression and shear loads. The aim was to obtain fundamental data on deformation behaviour and failure mechanisms of earthen material structural elements and to describe them by means of a numerical model. The test results confirmed the brittle behaviour of earth block masonry under monoaxial compressive load and showed that the failure of earth block masonry under shear load occurs by sliding of the earth blocks along the mortar joints after initial cracking in mortar joints and earth block. Numerical macro modelling showed satisfying results with regard to stress-strain behaviour, but the simulated crack pattern was not consistent with experimental observations. In the case of earth block masonry, it is thus necessary to use micro modelling approaches in order to correctly predict the failure process at local level.
A combined theoretical and experimental investigation was carried out with the objective of evaluating theoretical predictions relating to a two-dimensional airfoil subjected to high amplitude harmonic oscillation of the free stream at constant angle of attack. Current theoretical approaches were reviewed and extended for the purposes of quantifying the bound, unsteady vortex sheet strength along the airfoil chord. This resulted in a closed form solution that is valid for arbitrary reduced frequencies and amplitudes. In the experiments, the bound, unsteady vortex strength of a symmetric 18 % thick airfoil at low angles of attack was measured in a dedicated unsteady wind tunnel at maximum reduced frequencies of 0.1 and at velocity oscillations less than or equal to 50 %. With the boundary layer tripped near the leading edge and mid-chord, the phase and amplitude variations of the lift coefficient corresponded reasonably well with the theory. Near the maximum lift coefficient overshoot, the data exhibited an additional high-frequency oscillation. Comparisons of the measured and predicted vortex sheet indicated the existence of a recirculation bubble upstream of the trailing edge which sheds into the wake and modifies the Kutta condition.
Without boundary layer tripping, a mid-chord bubble is present that strengthens during flow deceleration and its shedding produces a dramatically different effect.
Instead of a lift coefficient overshoot, as per the theory, the data exhibit a significant undershoot. This undershoot is also accompanied by high-frequency oscillations that are characterized by the bubble shedding. In summary, the location of bubble and ist subsequent shedding play decisive roles in the resulting temporal aerodynamic loads.
Der Beitrag gibt einen Überblick über die Eigenschaften industriell hergestellter Bauprodukte aus Lehm für den Mauerwerksbau. Die Qualität der industriellen Fertigung dieser Produktgruppe hat inzwischen einen Stand erreicht, der vergleichbar mit dem anderer Bauprodukte ist. Lehm-Putzmörtel gibt es als Universalputze für ein- oder mehrlagige Anwendung oder in Form von Unter-, Ober- oder Feinputzen. Lehmsteine werden in verschiedenen Größen und mit Lochung angeboten. Die mechanischen Eigenschaften verschiedener Lehmsteinsorten sind geprägt durch Druckfestigkeiten bis 11 N/mm2, mit üblichen Werten bei 2 bis 5 N/mm2. Ein kritischer Punkt ist die Abhängigkeit der Festigkeitseigenschaften der Lehmsteine von der Materialfeuchte. Die vorliegenden Untersuchungen haben jedoch gezeigt, dass in einem Luftfeuchtebereich von 40 bis 70 % RLF die Druckfestigkeit von Lehmsteinen verhältnismäßig konstant ist. Mauerwerk, errichtet mit Lehmsteinen und Lehm-Mauermörtel, zeigt ähnliche Druckfestigkeiten und E-Module wie Mauerwerk, das mit Porenbetonsteinen errichtet wurde. Infolge einer geringeren Haftscherfestigkeit zwischen Lehmmörtel und Lehmstein ist die Schubfestigkeit von Lehmsteinmauerwerk vergleichsweise niedrig.-------------------------------------------------------------------------------------------------------------------------------------
Properties of industrially produced earthen building products for masonry and behaviour of earth block masonry. The contribution gives an overview of the properties of industrially produced earthen building products for masonry. In the meantime the quality of the industrial production of this group of building materials reached a level similar to that of other products for construction. Earth plasters exist as plasters for universal, one or multi layer applications or as lower, upper or finish plasters. Earth blocks are provided in different sizes and with different perforations. The mechanical properties of different earth block types are signified by compressive strength of up to 11 N/mm2 but are typically in a range between 2 and 5 N/mm2. A critical point is the correlation of the strength of earthen materials with their moisture content. Results from earth blocks showed that in a relative humidity window between 40 and 70 % rh the compressive strength of earth blocks is fairly constant. Masonry made from earth block and earth mortar exhibited compressive strength and elastic modules similar to masonry made with aerated autoclaved concrete blocks. The shear strength of earth block masonry, however, is fairly low, due to the weak bond between earth block and earth mortar.