[en] By irradiating a solution in electroless Ni deposition using synchrotron X-rays, Ni composite was found to nucleate homogeneously and eventually precipitate in the form of nanoparticles. The size of the nanoparticles precipitated is rather uniform (100-300 nm depending on the applied temperature). By the addition of an organic acid, well-dispersed nanoparticles could be effectively deposited on glass substrate. The hydrated electrons (e_aq^-), products of radiolysis of water molecules by synchrotron X-rays, may be responsible for the effective reduction of the metal ions, resulting in homogeneous nucleation and nanoparticle formation. Our results suggest that synchrotron X-ray can be used to induce solution precipitation of nanoparticles and therefore lead to a new method of producing nanostructured particles and coating

[en] Phase contrast radiology using unmonochromatic synchrotron X-ray successfully imaged the grain boundaries of Al and AlZn alloy without contrast agent. Combining the high penetration of X-ray and the possibility of 3D reconstruction by tomorgraphy or stereography method, this approach can be very used for nondestructive characterization of polycrystalline materials. By examine the images with 3D perspective, we were able locate the observed void-like defects which lies exclusively on the grain boundary and identify their origin from last stage of the rolling process. We studied the Ga Liquid metal diffusion in the AlZn alloy, under different temperature and stress conditions. High resolution images, ∼2 μm, of Ga liquid metal diffusion in AlZn were obtained in real time and diffusion paths alone grain boundaries and surfaces were clearly identified. Embrittled AlZn responses to the tensile stress and fractures in a drastic different manner than the pure AlZn. These results, although very much expected from the known weakening effect of the liquid metal embrittlement demonstrated, however, that this particular radiology method is fully capable of dynamic study in the micrometer scale

[en] We used phase contrast radiography to study the electro-deposition of Zn in real time and with high lateral resolution. Using unmonochromatic synchrotron X-rays and an optics-less imaging setup, we were able to obtain real-time radiographs of the electro-deposition in situ with μm resolution. A detailed analysis of the microstructure evolution relates the different growth parameters - such as the electric current density, the voltage bias, the pH value and the ion concentration - to very different growth morphology, ranging from film, porous, whisker and dendrite deposition. This link is both global and local. Local variations of the metal ion concentration in the electrolyte were also successfully imaged and the density profile is used to compare with the standard theory to explain the phenomenon of metal ion depletion near the electrode. The potential application of this technique to study growth with micropatterned electrodes and pulsed electric current is evaluated

[en] We compared the photoemission edge line shape of Bi₄Ca₃Sr₃Cu₄O/sub 16+//sub x/ with those of the Au and Al Fermi edges. Specifically, we searched for the intensity decrease in the neighborhood of the Fermi level, predicted in the case of photoemission from a resonating-valence-bond (RVB) state. We found no positive evidence for this decrease and we estimated that, if the RVB state exists, then the upper limit for the maximum spinon energy is 65 meV. Our data analysis also indicates that the mere observation of an apparent spectral edge is not sufficient per se to rule out a RVB state

[en] Since its invention in 1930, Zernike phase contrast has been a pillar in optical microscopy and more recently in x-ray microscopy, in particular for low-absorption-contrast biological specimens. We experimentally demonstrate that hard-x-ray Zernike microscopy now reaches a lateral resolution below 30 nm while strongly enhancing the contrast, thus opening many new research opportunities in biomedicine and materials science.

[en] We investigated the structural behavior of the Ni/Au contact on GaN(0001) and found the catalytic role of Au during annealing, using in situ x-ray scattering. The oxidation kinetics of Ni during annealing in air was greatly affected by the presence of Au. The accelerated GaN decomposition and Ni nitride formation during annealing in N₂ also provide evidence of the catalytic role of Au. The results suggest that oxidized Ni/Au ohmic contact exhibit better thermal stability than that of the N₂ annealed Ni/Au contacts. [copyright] 2001 American Institute of Physics

[en] Broadband synchrotron X-rays with limited coherence can be used for high resolution phase contrast radiology. Our experimental results confirm the prediction that the extreme spatial coherence of third-generation synchrotron sources although helpful but not strictly necessary for refraction-based or diffraction-based edge enhancement. Source with rather limited lateral coherence can produce Fresnel diffraction fringes. The direct observation of the same fringes using broadband synchrotron lights demonstrates that high time coherence is also not required. Broadband light produces a high photon flux and high average photon energy, that was exploited for real-time radiology (5 ms frame) studies with high lateral resolution (1 μm) and excellent contrast, without using a sophisticated detecting system. These results enhance the potential impact of phase contrast on medical X-ray applications, materials science and other domains

[en] We first present real-time microradiology of disintegration of self-fluxing iron ore sinters in low temperature reduction using highly collimated synchrotron source. The experiments were performed on the 5C1 beamline at PLS (Pohang Light Source, Pohang, Korea), operating at 2.5 GeV. We used unmonochromatized ('white') light with no optical elements except beryllium windows. The images of the crack superimpose, on the two-dimensional projection of a three-dimensional phenomenon, suggest that cracks are always initiated from pores in the sinters and propagate along neighboring pores. Interestingly, cracking occurs mostly on macropores (>800 μm), preferentially initiated from stress concentrated sites on pore surfaces. This dynamic study of the disintegration of sinters clearly shows that the crack initiation temperature is as low as 450 deg. C

[en] We present the first electron-energy-loss data taken on cleaved single-crystal YBa₂Cu₃O/sub 7-//sub x/. The data confirm in part the results obtained from sintered materials, e.g., on the bulk-plasmon energy. However, the high surface quality and the corresponding better resolution revealed fine structure that requires substantial changes in the interpretation of the spectra

[en] Highly collimated synchrotron sources are the essential ingredient of novel radiology and micro-radiology techniques for materials science, medicine and biology--with contrast based on the refractive index rather than on absorption. We were able to implement a real-time version of such techniques. Successful test studies included thin-foil breaking and electrodeposition processes in the areas concerning materials properties. Meanwhile, extensive effort was dedicated to obtain high-quality X-ray images of live specimens on a microscopic scale and in real time. These tests achieved a lateral resolution better than 2 μm and a time per image of 10 ms, with clear potential for further improvements. The images revealed in great detail moving parts of different specimens, opening the way to a wide variety of applications in the life sciences, medicine and materials science