STM/AFM studies of the evolution of morphology of electroplated Ni/W alloys

The surface morphology evolution of Ni/W alloys was studied, as a function of the alloy composition. Using the modified plating baths developed in our laboratory recently, electroplated Ni/W alloys with different W content, in the range of 7–67 atom percent (a/o), can be obtained. This was found to lead to different structures, ranging from polycrystalline fcc-Ni type structure to amorphous, followed by orthorhombic with increasing W content in the alloy. Powder XRD was studied to determine the crystal structures. Ex situ STM, AFM and SEM were used to study in detail the surface morphologies of the different alloys, and their evolution with increasing W content.

The important findings are that a mixture of two crystalline forms can give rise to an amorphous structure. Hillocks that are usually a characteristic of epitaxial growth can also exist in the amorphous alloys. Oriented scratches caused by stress can also be formed.

Up to 20 a/o of W is deposited in the alloys in crystalline form, with the fcc-Ni type structure. Between 20 and about 40 a/o an amorphous structure is observed, and above that an orthorhombic crystal structure is seen, which is characteristic of the NiW binary alloy. Careful choice of the composition of the plating bath allowed us to deposit an alloy containing 67 a/o W, which corresponds to the composition NiW₂.     

The effect of size and location of adsorbed intermediates in the double layer on the tafel slope the reduction of hydroxylamine on the dropping mercury electrode

The reduction of hydroxylamine on the dropping mercury electrode was studied. Kinetic parameters were determined from measurements at the foot of the polarographic wave. Tafel plots were extended to higher current densities with the use of the Koutecký correction.This molecule was chosen as an example of a relatively small species for which the effect of competition with water is small and the importance of the location of the adsorbed intermediate in the double layer can be demonstrated. The experimentally observed value of b = 96 ± 3 mV (combined with reaction orders of unity both with respect to hydroxylamine and hydrogen ions) was found to be consistent with the notion of an adsorbed intermediate whose reduction is brought about by a potential difference φ_M - φ_x, where φ_x has an intermediate value between φ_M and φ_s. These results were compared with earlier results found in a study of the reduction of nitroalkanes under similar conditions.The advantages of making measurements on the DME at the foot of the polarographic wave are emphasized.     

Are quantum processes cosmologically induced?

Why, among ～10 ¹⁶ possibilities, does a wave function of a fast ion, spread over several centimeters, collapse in a crystal within a region measuring a few angstroms across? The most direct answer to this question would be the existence in this region of a cosmic particle, called a dybbuk, which induces the collapse. If dybbuks exist, deviations from conventional theory might be expected to occur for experiments involving ultrasmall space-time intervals less than the characteristic space-time interval of a dybbuk. It is shown that a dybbuk theory having the above characteristics can be constructed and can be tested experimentally by the decay of a0 ^? (J ^P) meson into two vector mesons.     

News and Views: Challenges of Relativistic Astrophysics

I discuss some of the most outstanding challenges in relativistic astrophysics in the subjects of compact objects (black holes and neutron stars), dark sector (dark matter and dark energy), plasma astrophysics (origin of jets, cosmic rays, and magnetic fields), and the primordial universe (physics at the beginning of the Universe). In these four subjects, I discuss 12 of the most important challenges. These challenges give us insight into new physics that can only be studied in the large scale universe. The near-future possibilities, in observations and theory, for addressing these challenges are also discussed.     

The equitable location problem on the plane

This paper considers the problem of locating M facilities on the unit square so as to minimize the maximal demand faced by each facility subject to closest assignments and coverage constraints. Focusing on uniform demand over the unit square, we develop upper and lower bounds on feasibility of the problem for a given number of facilities and coverage radius. Based on these bounds and numerical experiments we suggest a heuristic to solve the problem. Our computational results show that the heuristic is very efficient, as the average gap between its solutions and the lower bound is 4.34%.     

Measurements of electrical conductivity in solid bromine and iodine

Measurements of the electrical conductivity were performed with bromine and iodine in the liquid and the solid states, both containing low concentrations of the corresponding halide ions. In bromine the specific conductivity increases dramatically upon solidification and in iodine it changes only slightly. In both systems the conductivity in the solid is rather high, with remarkably low temperature coefficients, pointing to an unusual mechanism of conduction (of the Grotthuss type) requiring very little movement of the heavy nuclei while the charge is transferred. In mixtures of bromine with a small amount of nitrobenzene (NB) an equivalent conductivity as high as 12 cm² mol^?1 Ω^?1 was observed at ?25°C. In iodine the specific conductivity reached a value of about 0.01 Ω^?1 cm^?1 at 100°C. The energy of activation for conduction in bromine down to ?40°C was found to be about 23 kJ mol^?1, increasing sharply below this temperature. In iodine, values of about 21–27 kJ mol^?1 were observed over the whole temperature range measured.     

457—The mechanism of low frequency a.c. electrochemical disinfection

The mechanism of low frequency a.c. electrochemical disinfection was studied. A random oriented graphite fiber-epoxy matrix composite material was employed to fabricate the electrodes. This material was found to have very good electrochemical stability when cycled anodically and cathodically in solutions containing NaCl or NaBr.The lethal species was identified as HClO and HBrO in solutions containing Cl^? and Br^?, respectively, although the free halogen molecule may contribute to the observed disinfection activity under certain experimental conditions.The efficiency of disinfection increases with increasing concentration of Cl^? (or Br^?) and with decreasing pH. Deaerating the solution decreases the efficiency of disinfection significantly. NaBr was found to be effective at much lower concentrations than NaCl at all pH values but the effect is enhanced at pH > 7 due to ionization of HClO.The unique advantage of the method described in this paper is that a high transient concentration (in time and space) of the lethal species is generated, enough to destroy the most resistant microorganisms, while the average concentration of active halogen in the effluent liquid remains well below the objectionable level.