We use new neutron scattering instrumentation to follow in a single quantitative time-resolving experiment, the three key scales of structural development which accompany the crystallisation of synthetic polymers. These length scales span 3 orders of magnitude of the scattering vector. The study of polymer crystallisation dates back to the pioneering experiments of Keller and others who discovered the chain-folded nature of the thin lamellae crystals which are normally found in synthetic polymers. The inherent connectivity of polymers makes their crystallisation a multiscale transformation. Much understanding has developed over the intervening fifty years but the process has remained something of a mystery. There are three key length scales. The chain folded lamellar thickness is ∼ 10nm, the crystal unit cell is ∼ 1nm and the detail of the chain conformation is ∼ 0.1nm. In previous work these length scales have been addressed using different instrumention or were coupled using compromised geometries. More recently researchers have attempted to exploit coupled time-resolved small-angle and wide-angle x-ray experiments. These turned out to be challenging experiments much related to the challenge of placing the scattering intensity on an absolute scale. However, they did stimulate the possibility of new phenomena in the very early stages of crystallisation. Although there is now considerable doubt on such experiments, they drew attention to the basic question as to the process of crystallisation in long chain molecules. We have used NIMROD on the second target station at ISIS to follow all three length scales in a time-resolving manner for poly(e-caprolactone). The technique can provide a single set of data from 0.01 to 100Å-1 on the same vertical scale. We present the results using a multiple scale model of the crystallisation process in polymers to analyse the results.

Dynamics of structural phase transition in polycrystalline samples (tetragonal stabilized zirconia and bismuth) under laser-shock compression has been studied using nanosecond time-resolved X-ray diffraction technique based on synchrotron radiation. Tetragonal zirconia shows the structural phase transition to the monoclinic phase within 20 ns during shock compression without any intermediate and reverts back to the tetragonal phase during pressure release. Bismuth shows more complex phase transition dynamics. The Bi-I phase, which is the stable phase at ambient pressure and temperature, transfers to Bi-V phase within 4 ns under shock compression and gradually reverts back following the path of Bi-V →Bi-III → Bi-II → Bi-I within 30 ns during pressure release.

Developments of composites materials had begun in the 1970's. They aimed in improving mechanical properties due to the presence of reinforcement particles. The addition of particles in a matrix led to different modifications: considering the nature of the phases and the microstructure, we can mention interface reactivity between matrix and particles, changes in the chemical composition of the matrix and modified kinetics of microstructure evolution in the matrix (as compared to the matrix without particles); considering the mechanical aspects, thermal stresses may be generated due to the differences in expansion coefficients between the particles and the matrix, or any changes in the matrix leading to a phase transformation. In the present work, we studied the evolution of the phases and the behavior of a steel based MMC during thermal treatments, for which a phase transformation occurred on cooling. Experiments and numerical simulation are considered.

In order to elucidate a link between density and structure of liquid Si-M (M=Fe, Ni, and Ge) alloys, synchrotron x-ray diffraction experiments have been conducted with the use of a conical nozzle levitation technique. Liquid structure factors of the Si-Fe and the Si-Ni alloys indicate a correlation of medium range ordering with the increase of the Si content. Although the total molar volume expands with the increase of the Si content in these alloys, the concentration dependence of the average interatomic distance shows a minimum around 70 at.% Si content. On the other hand, the Si-Ge alloys shows tendency of concentration dependence as ideal mixture in both total molar volume and the average interatomic distance. These results were discussed taking into account the formation of anisotropic bonds between 3d transition metal and Si atoms, which may induce a spatial expansion in the microscopic scale.

CrB2 possess the hexagonal AlB2 structure which belongs to the spacegroup of P6/mmm. The compound exhibits para- to antiferro-magnetic transition at about 88 K. By using a macroscopic measurement technique, that is, a conventional resonant ultrasound spectroscopy (RUS) with a millimeter size mono-crystal, significant elastic anomalies have been observed just above the magnetic transition temperature. On the other hand, elastic constants determined by a microscopic measurement technique, that is, an inelastic X-ray scattering method (BL35XU of SPring-8, Japan) do not show any elastic anomalies at around the transition temperature. In order to explain the discrepancy, we have introduced a kind of so called ΔE effect resulting from a multidomain structure. If crystal lattice is slightly deformed by a spontaneous magnetostriction in the antiferromagnetic state, the symmetry of crystal lattice is lowered from hexagonal to monoclinic when the symmetry of magnetic structure is taken into account. By the lowering of the symmetry, the crystal consists of six magnetic domains in the antiferro magnetic state. If magnetic domain boundaries move in response to externally applied stresses, the mechanical deformation is absorbed by nonelastic deformations induced by the movement of magnetic domain boundaries. This multidomain model well explains the experimental results obtained by both microscopic (X-ray) and macroscopic (ultrasound) measurements. The microscopic measurement technique is useful to obtain the true elastic properties of crystal lattice without effects coming from a multidomain structure.

A series of laser pump, x-ray probe experiments show that above band gap photoexcitation can generate a large out-of-plane strain in multiferroic BiFeO3 thin films. The strain decays in a time scale that is the same as the photo-induced carriers measured in an optical transient absorption spectroscopy experiment. We attribute the strain to the piezoelectric effect due to screening of the depolarization field by laser induced carriers. A strong film thickness dependence of strain and carrier relaxation is also observed, revealing the role of the carrier transport in determining the structural and carrier dynamics in complex oxide thin films.

Grazing Incidence Small-Angle X-ray Scattering (GISAXS) is a versatile technique for the analysis of nano and micro thin films surfaces. The scattering data depend strongly on the form and distribution of the scattering objects. In the present work GISAXS is used to study hafnium dioxide (HfO2) thin films deposited by magnetron sputtering using different deposition processes and post-deposition annealing conditions. Two distinct types of 15 nm thick samples were produced using different sputtering targets and different gas mixtures. The GISAXS results show that the ellipsoids that compose the thin films present a reduction in their size for both samples sets. For the sputtered Hf metal target samples, the ellipsoid diameter value shifted from 9 nm (as-deposited) to 6 nm following a 800 °C thermal treatment. For the sputtered HfO2 target samples the diameter value shifts from 19 nm (as-deposited) to 3 nm after a 800 °C anneal in oxygen. The size distribution, for both sets of samples, follows a Gaussian distribution function.

Modeling of the mechanical behavior of a two-phased material, even with a simple microstructure such as a single crystal superalloy remains a difficult task, for lack of phase specific experimental data. The combination of Three Crystal Diffractometry with high energy synchrotron radiation and in situ experiments can give access to such data in real time. A few examples are given on load transfer between phases, dislocation densities, and the stress – strain behavior of a phase.

The temperature induced structural transformations in physical mixtures of 1nm palladium and ultrafine (∼0.5nm) copper nanoparticles supported on carbon were studied using in-situ real time synchrotron based x-ray diffraction. These nanoparticles were subjected to two-step thermal annealing from 25°C to 700°C. The Pd and Cu nanoparticles were found to coalesce forming alloy nanoparticles that subsequently undergo a structural phase transformation from ordered B2 to disordered fcc. The random alloy formed at the end of the thermal treatments was found to be copper-rich.

Aqueous solutions containing Cd2+ and S2- ions have been brought together in a T-mixer, and the formation of CdS nanoparticles has been monitored by ultrafast X-ray small angle scattering down to 0.2 ms. While no particle formation is observed for a laminar flow, their growth can be followed in-situ for conditions of turbulent flow.

Deformation behaviors of two TRIP-type multiphase steels with different carbon contents were studied by in situ neutron diffraction measurement during tensile deformation at RT. The tensile test was conducted in a step-load controlling manner during the elastic region, and in a continuous manner with a constant crosshead speed by an initial strain rate of 1.8×10-5 s-1 during the plastic region. Austenite grains were observed to bear higher phase stresses than ferrite grains in both steels. Austenite peak intensities started to decrease at the onsets of plastic deformation in both steels, showing the occurrence of stress induced martensitic transformations. Martensite peaks were carefully analyzed to estimate phase strains, and as the results martensite grains were found to bear largest phase stresses during plastic deformation.

The effect of the micro-porous layer (MPL) in polymer electrolyte fuel cells (PEFCs) was studied by a combination of in situ visualization of the liquid water distribution and advanced electrochemical analysis using helox and O2 pulses. Four cells with and without MPLs on the anode and cathode side were tested. Visualization studies showed that the significant changes in performance observed when using an MPL on the cathode side cannot be related to a reduction of the water content in the cathode side diffusion layer (GDL). The helox/O2 pulse analysis indicated that two different mechanisms are responsible for the performance loss without an MPL.

The influence of oxygen content on containerless solidification of Zr80Pt20 alloy has been studied by using conical nozzle levitation (CNL) technique. The doping level of oxygen from 41 to 5450 ppm mass oxygen (PMO) affects the undercooling of the liquid Zr80Pt20 alloy. Time-resolved synchrotron x-ray diffraction revealed that the quasicrystalline (QC) phase precipitated as a primary phase during solidification of the Zr80Pt20 alloy. The amount of the QC phase depends on the oxygen content in the alloy. This indicates that the doping level of oxygen in Zr80Pt20 alloy can be related to the metastable phase formation as well as the glass-formation ability.

The hydrogen uptake and redistribution in Zircaloy-4 specimens applied to loss of coolant accident (LOCA) simulation experiments and in mechanical pre-loaded samples were investigated by means of ex-situ and in-situ neutron imaging. The results of these investigations were compared with results from mechanical tests. Hydrogen absorption may have a strong influence on the mechanical properties of zirconium alloys. A local enrichment of the absorbed hydrogen may result in brittle fracture at these positions in the tensile test. On the other hand, stress fields in the material affect the hydrogen uptake as well as its distribution in the material. In-situ investigations confirmed the existence of an initial oxide layer formed at room temperature by contact with air. This oxide layer suppresses the hydrogen uptake until dissolution in the zirconium matrix.

Simultaneous use of neutron diffraction and attenuation based transmission Bragg edge imaging for strain measurements is demonstrated in this paper using the pulse neutron source at Los Alamos National Laboratory. Cylindrical samples made from ferritic steel have been subjected to in-situ elastic loading in tension and torsion. Lattice strains were investigated for both deformation modes by time-of-flight (TOF) neutron diffraction using two detector banks at 2θ of ±90°. At the same time, the transmitted portion of the neutron beam was recorded with the goal to analyze the position and shape of the Bragg edges, using a novel time/energy resolved Microchannel Plate (MCP) detector with pixel size of 55 µm and a 28x28 mm2 field of view. Lattice strains obtained using neutron diffraction indicate that the deformation path (tension versus torsion) has important effect on their evolution and related results are summarized.

The emphasis of this paper is to explain the aspects of the experimental setup and data interpretation associated with neutron Bragg edge transmission technique for obtaining through-thickness averaged strain measurements. Implications of using transmission imaging based strain mapping for samples subjected to deformation under tensile loading (where stress at a given cross-section is constant) versus torsional loading (where stress varies linearly from center to outer radius) are discussed. In the case of samples subjected to tensile loading, analysis of the Bragg edge shifts provides the strain value in the direction of the transmitted beam. Thus, three strain components are measured simultaneously when performing Bragg edge imaging in addition to diffraction using two detector banks. For specimens subjected to pure shear by torsion, the Bragg edge transmission technique cannot readily provide quantitative strain information as the mid-point of the Bragg edge does not shift uniformly due to external loading, but results in a broadening of the Bragg edge. Such information can be used to describe the variation of strain distribution along the transmitted beam direction. Spatially resolved Bragg edge maps will be very helpful to detect d-spacing inhomogeneities within the illuminated volume, which may remain undetected when using diffraction only measurements.