The plastic behaviour of Co 3 (Al,W) polycrystals with the L1 2 structure has been investigated in compression from 77 to 1273 K. The yield stress exhibits a rapid decrease at low temperatures (up to room temperature) followed by a plateau (up to 950 K), then it increases anomalously with temperature in a narrow temperature range between 950 and 1100 K, followed again by a rapid decrease at high temperatures. Slip is observed to occur exclusively on {111} planes at all temperatures investigated. The rapid decrease in yield stress observed at low temperatures is ascribed to a thermal component of solid-solution hardening that occurs during the motion of APB-coupled dislocations whose core adopts a planar, glissile structure. The anomalous increase in yield stress is consistent with the thermally activated cross-slip of APB-coupled dislocations from (111) to (010), as for many other L1 2 compounds. Similarities and differences in the deformation behaviour and operating mechanisms among Co 3 (Al,W) and other L1 2 compounds, such as Ni 3 Al and Co 3 Ti, are discussed.

How does the chemical reaction of a single polymer chain progress? This question is not proven, as long as it is studied the data of the ensemble average from the large number of molecules. In this study, we succeeded for the first time in the direct measurement of when, where, and how the chemical reaction of a polymer chain proceeds on a nanometer scale. That is, single-molecule imaging of the photodegradation reaction of a chiral helical p-conjugated polymer following laser irradiation of 405 nm was conducted. Analysis of the chemical kinetics showed that the photodegradation of the single polymer chain proceeded stepwise as a quantum phenomenon. When the motility of the chain-end increased, reactivity of the photodegradation increased. It was also discovered that the photodegradation of the polymer chain proceeded continuously in one direction, like the ''domino effect.'' Our method allowed dynamic imaging of single polymer chains at a solid/ liquid interface, and hence can be applied to the study of many types of polymers. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: [4103][4104][4105][4106][4107] 2010

The physical and mechanical properties of Co3(Al,W) with the L12 structure have been investigated both in single and polycrystalline forms. The values of all the three independent single-crystal elastic constants and polycrystalline elastic constants of Co3(Al,W) experimentally determined by resonance ultrasound spectroscopy at liquid helium temperature are 15~25% larger than those of Ni3(Al,Ta) but are considerably smaller than those previously calculated. When judged from the values of Poisson’s ratio, Cauchy pressure and Gh (shear modulus)/Bh (bulk modulus), the ductility of Co3(Al,W) is expected to be sufficiently high. Indeed, the value of tensile elongation obtained in air is as large as 28 %, which is far larger than that obtained in Ni3Al polycrystals under similar conditions.

In this work, a molecule "walking" along a single chain of a synthetic helical polymer, which is used as a rail on a substrate in an organic solvent at room temperature, is observed. The walking comprises the unidirectional processive movement of a short-chain molecule along a chiral helical chain in 3 nm steps, driven by Brownian motion and a tapping effect of the atomic force microscopy tip based on a flash ratchet mechanism. Furthermore, the rail consists of a long-chain substituted phenylacetylene polymer with pendant cholesteryl groups, along which the shortchain molecule can walk as a result of van der Waals interactions. The macromolecular motion is videoed using a fast-scanning atomic force microscope, and additionally, this phenomenon is also simulated by all-atom molecular dynamics calculations. On the basis of these results, we propose the principle of a polymer molecular motor. This is the first report of a synthetic walking machine of a chiral helical polymer driven by thermal fluctuation as an artificial life function.

In this work, the synthesis of supported Pd aggregates by plasma sputter deposition is studied. A helicoidal metal wire is negatively biased with respect to the plasma potential, which results in sputtering of the metal by the argon ions present in the plasma. The wire bias voltage is one of the most important experimental parameters because it determines the ion flux bombarding the metal surface as well as the energy of these ions. Thus, it plays a major role in the sputtering process. In order to study this aspect, deposits have been synthesized at 10 −3 mbar argon pressure and 2 min deposition time, at various wire bias voltages from −100 to 0 V. The amount of Pd deposited is measured by x-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS) analyses and is found to increase linearly with the wire bias voltage (in absolute value) from 0.2 to 1.4 equivalent monolayers. In this study, it appears that XPS analysis is not suitable for quantification in the particular case of small dispersed aggregates, certainly because of a geometrical effect (apparent roughness) in recorded XPS line intensities. Nevertheless, from the XPS Pd peak shift with decreasing coverages, morphological information can be obtained. In this manner, the presence of small aggregates on the substrate surface has been detected. The morphology is more precisely studied by grazing incidence small angle x-ray scattering (GISAXS) and transmission electron microscopy (TEM) analyses. In the present metal coverage range, the deposits are composed of small (≈2 nm) spaced-out spherical aggregates, well dispersed on the surface.