A simple and effective attachment to prevent dome diffraction reaching 2D or 1D detectors in x-ray diffractometers

An attachment has been developed for x-ray diffractometer systems equipped with a domed stage when using a 2D or 1D detector. It consists of a single screen in front of the detector positioned such that it blocks diffraction from the dome. This results in measured data free of disturbing spurious peaks and background, thereby greatly facilitating further data analysis. Its working principle is universally applicable and allows for all specimen orientation movements needed for x-ray diffraction measurements, including texture, stress, and mapping.Team Amarante Bottge

Composition of mortar as a function of distance to the brick-mortar interface: A study on the formation of cured mortar structure in masonry using NMR, PFM and XRD

The formation of cured mortar structure in masonry was studied using multiple experimental techniques. Starting with fresh mortar, nuclear magnetic resonance (NMR) was used to measure the water extraction during brick laying. After curing, the composition of cured mortar was investigated with polarizing and fluorescent microscopy (PFM) and X-Ray diffraction (XRD). Two typical mortars were investigated: a cement-lime mortar and a cement mortar with air entraining agent. The measurements indicate that the mortar composition (i.e. the contents of sand, cured binder and voids) and the contents of chemical substances of the cured binder (i.e. the contents of calcite and portlandite) change with distance to the brick-mortar interface. For the cement mortar with air entraining agent, the observations are explained by the enrichment of binder towards the brick-mortar interface, resulting from the local compaction and compression of the fresh mortar. In the cement-lime mortar such an enrichment of binder hardly occurs and the observations are explained by the intense carbonation that takes place. As a result, the chemical composition of the binders is very much different in both mortars. In the cement mortar with air entraining agent, near the brick-mortar interface the enrichment of cement and the low water content (resulting from the low water retentivity of this mortar), lower the water-to-cement ratio and as a consequence the cement is not fully hydrated. In the cement-lime mortar, because the Ca(OH)2 content and the water content is higher, near the brickmortar interface, a carbonated zone is formed which is hardly permeable for CO2 (and probably water). The latter does not occur in the cement mortar, it remains permeable. The analysis of the experimental results have lead to the formulation of a conceptual model for the formation of cured mortar structure in masonry. Such a model may be helpful in analysing and predicting the durability of mortars.Applied Science

The role of the substrate on the mechanical and thermal stability of Pd thin films during hydrogen (de)sorption

In this work, we studied the mechanical and thermal stability of ~100 nm Pd thin films magnetron sputter deposited on a bare oxidized Si(100) wafer, a sputtered Titanium (Ti) intermediate layer, and a spin-coated Polyimide (PI) intermediate layer. The dependence of the film stability on the film morphology and the film-substrate interaction was investigated. It was shown that a columnar morphology with elongated voids at part of the grain boundaries is resistant to embrittlement induced by the hydride formation (α↔β phase transitions). For compact film morphology, depending on the rigidity of the intermediate layer and the adherence to the substrate, complete transformation (Pd-PI-SiO2/Si) or partly suppression (Pd-Ti-SiO2/Si) of the α to β-phase was observed. In the case of Pd without intermediate layer (Pd-SiO2/Si), buckling delamination occurred. The damage and deformation mechanisms could be understood by the analysis of the stresses and dislocation (defects) behavior near grain boundaries and the film-substrate interface. From diffraction line-broadening combined with microscopy analysis, we showed that in Pd thin films, stresses relax at critical stress values via different relaxation pathways depending on film-microstructure and film-substrate interaction. On the basis of the in-situ hydriding experiments, it was concluded that a Pd film on a flexible PI intermediate layer exhibits free-standing film-like behavior besides being strongly clamped on a stiff SiO2/Si substrate.Team Amarante BottgerQN/Afdelingsburea

Rapidly solidified (melt-spun) aluminium alloys: Morphology, texture and excess vacancies

AbstractChemical EngineeringApplied Science

Dislocations, texture and stress development in hydrogen-cycled Pd thin films: An in-situ X-ray diffraction study

For Pd thin films, microstructural changes involved during hydrogen cycling provide the information needed to predict and optimize the film's mechanical strength. In this paper, a systematic study of the morphology, microstructure, texture, and stress has been performed on Pd thin films during hydrogen loading and deloading cycles at room temperature. Pd thin films of similar morphology were prepared by magnetron sputtering on substrates of different compliances, i.e., Si-oxide, Titanium (Ti) and Polyimide (PI). The evolution of the morphology, grain-orientation distribution (texture), state of stress, and dislocation densities are analyzed for each of the film substrate types for 20 hydrogen loading/deloading cycles. The lattice expansion and contraction caused by the transition from Pd to Pd-hydride and back result in a strong stress increase. This stress increase stabilizes after a few cycles by grain boundary motion that leads to a gradual enhancement of the (111) texture and changes in the dislocation density for Pd films that are strongly clamped on to an oxidized Si(100) wafer substrate with an intermediate layer (Ti or PI). For Pd on PI, the stress is also partly released by a crack-based (crack widening/growth/propagation) pathway. Pd films on Ti and PI do not buckle or blister after 20 hydrogen cycles. By providing a sufficiently compliant substrate the traditional problems of buckle-delamination of a film on a stiff substrate are mitigated.Team Amarante Bottge

Smoothing of X-ray diffraction data and K (alpha)2 elimination using penalized likelihood and the composite link model

X-ray diffraction scans consist of series of counts; these numbers obey Poisson distributions with varying expected values. These scans are often smoothed and the K2 component is removed. This article proposes a framework in which both issues are treated. Penalized likelihood estimation is used to smooth the data. The penalty combines the Poisson log-likelihood and a measure for roughness based on ideas from generalized linear models. To remove the K doublet the model is extended using the composite link model. As a result the data are decomposed into two smooth components: a K1 and a K2 part. For both smoothing and K2 removal, the weight of the applied penalty is optimized automatically. The proposed methods are applied to experimental data and compared with the Savitzky–Golay algorithm for smoothing and the Rachinger method for K2 stripping. The new method shows better results with less local distortion. Freely available software in MATLAB and R has been developed.Materials Science and EngineeringMechanical, Maritime and Materials Engineerin

Texture-related roughness of (Nb,Ti)N sputter-deposited films

We study the properties of (Nb,Ti)N films deposited by reactive magnetron sputtering in an atmosphere of argon and nitrogen at ambient substrate temperature, focusing, in particular, on the technological factors determining film texture and roughness. We find that increasing the adatom, energy, while keeping the film chemical composition constant, results in a change of texture from [111] to [100]. Similar changes in film texture are observed as the nitrogen injection decreases for a constant sputtering pressure, indicating that adatom energy is not the only one, determining factor. Analyzing the experimental data, it is concluded that nitrogen concentration, has a very strong influence on the process of the texture formation, since an increase in nitrogen injection results in an increase in adatom energy, while the film. growth is driven toward [111] texturing. Film toughness is strongly related with texture in both experiments, i.e., decreases with an increase in the ratio of [200] and [111] XRD line intensities, indicating that film roughness is determined by crystal habit