Materials Literature
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A new and general way to prepare porous metals with highly ordered 3D arrays of void spaces is reported here. The technique involves filling the spaces between colloidal crystals in a 3D array with a metal ion solution, and removing the solvent to produce a salt skeleton. The skeleton then undergoes chemical transform…
Polyelectrolytes are macromolecules which carry a large quantity of ionizable groups along their chains. By dissolving them in suitable solvents, for example water, these groups dissociate in highly charged macroions and an equivalent quantity of low-molecular counter ions. Through the connection between polymer and e…
The application of the viscous analogy, known as the Hele-Show model, for seepage investigation is demonstrated in the paper. The changes in the viscous properties of the model fluid (glycerine) resulting from the changes of the atmospheric conditions - temperature and humidity, have been taken under consideration as…
Based on a recently introduced generalized mixing rule, which contains the results of the reptation and double reptation model as special cases, it is possible to determine the molecular weight distribution (MWD) from rheological data. By evaluating data from bimodal PS-mixtures Maier et al. (1998) have shown how the…
Cu-Ni castings and wrought pipes nominally contain 1% Fe to 2% Fe, which is added to improve the Cu-Ni alloy’s erosion-corrosion resistance. After fabrication, Cu-Ni products are solution heat-treated to dissolve the iron uniformly and form a single-phase alloy. During welding, however, iron can precipitate from solid…
Abstract Development of preferred orientations of illite-smectite (I-S) has been studied using X-ray diffraction (XRD) texture goniometry to produce pole figures for clay minerals of a suite of 16 mudstone samples from a core from the Gulf Coast. Samples represent a compaction-loading environment in which the smectite…
We present a theoretical study of ultrafast phase transitions induced by femtosecond laser pulses of arbitrary form. Molecular-dynamics simulations on time dependent potential-energy surfaces derived from a microscopic Hamiltonian are performed. Applying this method to diamond, we show that a nonequilibrium transition…
We show that metal particles encapsulated by thin silica shells can catalyze redox reactions on their surface. The surface charge of both silica-coated and uncoated colloidal silver particles has been varied by chemical electron injection, using controlled amounts of borohydride ions. The charging and discharging proc…
We present a novel picture of a non-isothermal solidification process starting from a molecular level, where the microscopic origin of the basic mechanisms and of the instabilities characterizing the approach to equilibrium is rendered more apparent than in existing approaches based on coarse-grained free-energy funct…
A general formulation of scalar hysteresis is proposed. This formulation is based on two steps. First, a generating function g(x) is associated with an individual system, and a hysteresis evolution operator is defined by an appropriate envelope construction applied to g(x), inspired by the overdamped dynamics of syste…
The solid nematic equivalent of the Fredericks transition is found to depend on a critical field rather than a critical voltage as in the classical case. This arises because director anchoring is principally to the solid rubbery matrix of the nematic gel rather than to the sample surfaces. Moreover, above the threshol…
A Fibonacci-like terrace structure along a fivefold axis of $i\ensuremath{-}{\mathrm{Al}}_{68}{\mathrm{Pd}}_{23}{\mathrm{Mn}}_{9}$ monograins has been observed by Schaub et al. with scanning tunneling microscopy. In the planes of the terraces they see patterns of dark pentagonal holes. These holes are well oriented bo…
Abstract The crystal structure of single crystals of kaolinite from Keokuk, Iowa, was refined using data measured at the microfocus X-ray beamline at the ESRF, Grenoble, France (λ = 0.6883, T = room temperature). The volume of the crystals was 8 and 0.8 μm 3 , respectively. Unit-cell parameters are: a = 5.154(9) Å, b…
High yields of nanocrystals at ambient temperaturehave been attained for several inorganic salts such as ZnS and CuO. The authors report one-step, solid-state reactions between easily obtained starting materials such as CuCl2·2H2O and NaOH to give nanoparticles with narrow size distribution. The process is carried out…