A zone melting device for the in situ observation of directional solidification using high-energy synchrotron x rays.

Directional solidification (DS) is an established manufacturing process to produce high-performance components from metallic materials with optimized properties. Materials for demanding high-temperature applications, for instance in the energy generation and aircraft engine technology, can only be successfully produced using methods such as directional solidification. It has been applied on an industrial scale for a considerable amount of time, but advancing this method beyond the current applications is still challenging and almost exclusively limited to post-process characterization of the developed microstructures. For a knowledge-based advancement and a contribution to material innovation, in situ studies of the DS process are crucial using realistic sample sizes to ensure scalability of the results to industrial sizes. Therefore, a specially designed Flexible Directional Solidification (FlexiDS) device was developed for use at the P07 High Energy Materials Science beamline at PETRA III (Deutsches Elektronen-Synchrotron, Hamburg, Germany). In general, the process conditions of the crucible-free, inductively heated FlexiDS device can be varied from 6 mm/h to 12 000 mm/h (vertical withdrawal rate) and from 0 rpm to 35 rpm (axial sample rotation). Moreover, different atmospheres such as Ar, N2, and vacuum can be used during operation. The device is designed for maximum operation temperatures of 2200 °C. This unique device allows in situ examination of the directional solidification process and subsequent solid-state reactions by x-ray diffraction in the transmission mode. Within this project, different structural intermetallic alloys with liquidus temperatures up to 2000 °C were studied in terms of liquid-solid regions, transformations, and decompositions, with varying process conditions.

Thermo-mechanical characterization of NiTi orthodontic archwires with graded actuating forces.

Functionally graded NiTi orthodontic archwire was tested to assess the evolution of the actuation force as a function of the temperature. Varying actuation forces on the same orthodontic wire allow the optimization of repositioning of the different types of teeth, according its radicular support. The wire was separated into three segments: Incisive, Premolar and Molar. The functionally graded NiTi orthodontic archwire segments have distinct structural and mechanical behavior as confirmed by differential scanning calorimetry, synchrotron-based X-ray diffraction, and thermomechanical analysis. The mechanical behavior was analyzed by three-point bending tests at four different temperatures (5, 20, 25 and 37 °C). In parallel, three-point bending tests were performed by TMA analysis in a temperature range from 5 °C (from cold water) to 40 °C (hot meal). This study showed the comparison of the different segments on the same archwire, providing a better understanding of the behavior of these functionally graded materials.

Industry-relevant magnetron sputtering and cathodic arc ultra-high vacuum deposition system for in situ x-ray diffraction studies of thin film growth using high energy synchrotron radiation.

We present an industry-relevant, large-scale, ultra-high vacuum (UHV) magnetron sputtering and cathodic arc deposition system purposefully designed for time-resolved in situ thin film deposition/annealing studies using high-energy (>50 keV), high photon flux (>10(12) ph/s) synchrotron radiation. The high photon flux, combined with a fast-acquisition-time (<1 s) two-dimensional (2D) detector, permits time-resolved in situ structural analysis of thin film formation processes. The high-energy synchrotron-radiation based x-rays result in small scattering angles (<11°), allowing large areas of reciprocal space to be imaged with a 2D detector. The system has been designed for use on the 1-tonne, ultra-high load, high-resolution hexapod at the P07 High Energy Materials Science beamline at PETRA III at the Deutsches Elektronen-Synchrotron in Hamburg, Germany. The deposition system includes standard features of a typical UHV deposition system plus a range of special features suited for synchrotron radiation studies and industry-relevant processes. We openly encourage the materials research community to contact us for collaborative opportunities using this unique and versatile scientific instrument.

Filling the gaps of dinosaur eggshell phylogeny: Late Jurassic Theropod clutch with embryos from Portugal.

The non-avian saurischians that have associated eggshells and embryos are represented only by the sauropodomorph Massospondylus and Coelurosauria (derived theropods), thus missing the basal theropod representatives. We report a dinosaur clutch containing several crushed eggs and embryonic material ascribed to the megalosaurid theropod Torvosaurus. It represents the first associated eggshells and embryos of megalosauroids, thus filling an important phylogenetic gap between two distantly related groups of saurischians. These fossils represent the only unequivocal basal theropod embryos found to date. The assemblage was found in early Tithonian fluvial overbank deposits of the Lourinhã Formation in West Portugal. The morphological, microstructural and chemical characterization results of the eggshell fragments indicate very mild diagenesis. Furthermore, these fossils allow unambiguous association of basal theropod osteology with a specific and unique new eggshell morphology.

Structure refinement of the silicon carbide polytypes 4H and 6H: unambiguous determination of the refinement parameters.

The atomic positions of the silicon carbide (SiC) polytypes 6H and 4H differ slightly from an ideal tetrahedron. These small deviations can be investigated by X-ray diffraction of so-called 'quasiforbidden' reflections, which are very sensitive with respect to the extremely small variations in the structure. Nevertheless, an unambiguous calculation of the refinement parameters from the absolute values of the structure factors of the 'quasiforbidden' reflections is not possible. In the case of SiC-4H, there are two and, in the case of SiC-6H, six different structure models, which yield the same absolute values of the structure factors. In order to distinguish between these models, additional phase information about the measured reflections is needed. To achieve this, Renninger-scan (psi-scan) profiles in the vicinity of three-beam cases are used. These experimentally measured psi-scans are compared with theoretical calculated profiles for each model. Another method to distinguish the different models is to compare the bond lengths between atoms of the two polytypes, which have equivalent vicinities. For both SiC-4H and SiC-6H, an unambiguous determination of the structure refinement parameters was possible.

First observation of inelastic X-ray scattering from condensed (4)He using high energy resolution.

Recently, the suitability of inelastic X-ray scattering for the investigation of solid and fluid (4)He has been demonstrated. For the test experiments an energy resolution of the order of 10-15 meV was used at the backscattering spectrometer INELAX at the storage ring DORIS of DESY, Hamburg. Lattice excitations were observed for momentum transfers along the c axis of h.c.p. helium crystals which were grown in situ at pressures of 54-63 MPa and at temperatures of 4.2-6.4 K. At 10 K above the melting point, energy-loss signals could also be detected from the liquid helium at equivalent momentum transfers.

Subclinical levels of lead and developmental deficit--a multivariate follow-up reassessment.

Scores on the McCarthy Scales of Children's Abilities, school reading tests, teacher ratings, and several exploratory measures were obtained for urban black school-aged children, first studied five years previously. These were related, for 63 children, to preschool blood lead, school-age blood lead, and free erythrocyte protoporphyrin levels, and, for 34 children, to dentine lead. Most outcome variables were not significantly related to the lead variables. Preliminary analyses indicated that results of several of the McCarthy Scales, including the critical General Cognitive Index and Verbal Scales, and the reading test were significantly impaired in higher lead level groupings. However, incorporating a brief measure of parent IQ into the analyses decreased variance associated with lead and led to a strong suspicion of the remaining significant results. Few investigators reporting positive effects have considered parent intelligence, which is known to be a major determinant of developmental status. For this and other admittedly difficult methodologic reasons, conclusions from prior studies are questioned.