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As new technological tasks arise, electroless coatings on the basis of cobalt have come into use in microelectronics and micromechanics in order to form a protective layer against copper migration in integral schemes. Copper possesses a low specific resistance, however it also has some disadvantages, such as a low corrosion resistance and a high diffusion coefficient into So and SiO2 as well as into other substances. These problems can be diminished by using a thin barrier layer protecting from copper diffusion. The barrier properties of CoP and CoB layers which can be further improved by addition of tungsten would be suited for this purpose. At present, investigations of this kind are being carried out in many countries. Recently much attention is given to the search of new substances, which could be used in direct borohydride fuel cells as catalysts for the borohydride oxidation reaction. The aim of our work was to investigate the peculiarities of electroless cobalt coatings deposition in glycine solutions using sodium hypophosphite and morpholine borane as reducing agents, as well as to determine the composition of the coatings obtained and the possibilities of their employment for the formation of barrier layers on copper and application for fuel cells production. It has been determined that using hypophosphite as a reducing agent the rate of CoP and CoWP coatings deposition and the quantity of P in them increases with increase in solution pH. After appropriate... [to full text] / Iškilus naujiems technologiniams uždaviniams, chemines dangas kobalto pagrindu, pradėta naudoti mikroelektronikoje ir mikromechanikoje siekiant sudaryti apsauginį sluoksnį vario migracijai integralinėse schemose. Varis turi mažą specifinę varžą, tačiau turi ir keletą trūkumų, tokių kaip blogas korozinis atsparumas ir aukštas difuzijos koeficientas į Si ir SiO2, bei kitas medžiagas. Šios problemos gali būti sumažintos naudojant ploną barjerinį sluoksnį, apsaugantį nuo vario difuzijos. Tam tiktų CoP bei CoB sluoksnių barjerinės savybės, kurias galima pagerinti įvedant volframą. Šiuo metu tokie tyrimai vyksta daugelyje šalių. Taip pat pastaruoju metu skiriamas didelis dėmesys naujų medžiagų paieškai, kurios būtų taikomos tiesioginiuose borohidrido kuro elementuose katalizatoriais borhidrido oksidacijos reakcijai. Mūsų darbo tikslas ištirti kobalto dangų cheminio nusodinimo glicininiuose tirpaluose ypatumus, reduktoriais naudojant natrio hipofosfitą ir morfolino boraną, bei nustatyti gaunamų dangų sudėtį ir jų panaudojimo galimybes barjerinių sluoksnių formavimui ant vario bei taikymui kuro elementų gamybai. Nustatyta, kad naudojant reduktoriumi hipofosfitą didinant tirpalų pH, CoP ir CoWP dangų nusėdimo greitis ir P kiekis jose didėja. Parinkus tinkamas sąlygas buvo gautos kokybiškos kobalto dangos, į kurias patenka nuo 2,9 iki 6,3 at.% P ir nuo 3 iki 5 at.% W. Nustatyta, kad dikarboninės rūgštys gerina tirpalų buferines savybes, pagreitina kobalto dangų nusėdimą ir didina... [toliau žr. visą tekstą]

Different types of biomass samples including fungi and algae were treated for their gold and cobalt uptake capacity. The performance of activated carbon and ion-exchange resins were compared with the metal uptake capacity of the biosorbents. Sargassum natans, a brown seaweed, exhibited a high gold uptake capacity outperforming the ion-exchange resin and equalling activated carbon. Algal biomass of Ascophyllum nodosum proved to be a very potent biosorbent for cobalt. While the temperature, agitation and biomass particle size did not affect the metal uptake process, the effect of pH was significant for both gold and cobalt uptakes. The optimum pH for gold uptake was 2.5 and for cobalt, was 4-5. The kinetics of cobalt biosorption was relatively rapid (5 min) at the initial concentration of the metal in solution, 100 mg/L. The biosorptive uptake of gold required 2 h to reach equilibrium when the initial concentration of gold was 100 mg/L. None of the tested cations, such as K$ sp+$, Ca$ sp{2+}$, Fe$ sp{2+}$, Cr$ sp{3+}$, UO$ sbsp{2}{2+}$, Ni$ sp{2+}$, Zn$ sp{2+}$, Ag$ sp+$, affected the gold uptake capacity of S. natans biomass under the optimum conditions. Anions, such as NO$ sbsp{3}{-}$, SO$ sbsp{4}{2-}$, CO$ sbsp{3}{2-}$, PO$ sbsp{4}{3-}$, and Pb$ sp{2+}$ suppressed the gold uptake somewhat. Under the optimum process conditions cations, except K$ sp+$ and Fe$ sp{2+}$, and anions, NO$ sbsp{3}{-}$ in particular, exhibited a pronounced negative effect on the cobalt uptake by A. nodosum biomass. / Sequestered gold was eluted with a mixture of thiourea and ferric ammonium sulphate solution. Approximately 98% of sequestered gold was eluted with 17 h in a batch contacting system at the optimum solids (biomass)-to-liquid ratio of 5 and pH of 5. At increased temperatures, the gold elution rate increased only slightly. Efficient desorption of cobalt was achieved using CaCl$ sb2$/HCL solution at pH 3. Cobalt elution time was quite short. Temperature affected neither desorption rate nor the equilibrium. The optimum solid-to-liquid ratio was 12 for desorption of cobalt from A. nodosum biomass. / The gold taken up by the biosorbent was deposited in its elemental form. / Available mathematical models, including the REDEQL2 chemical equilibrium model, were tested for theoretical predictions of co-ion competition in attempt to better understand the biosorption mechanism. (Abstract shortened with permission of author.)

The aim of this study was to investigate the removal of cobalt from zinc sulfate solution by cementation with the help of conventional and new type of additives that were 4% Sn-zinc alloy powder and 10% Sn-zinc alloy powder, respectively. Synthetic leach solutions containing 150 g/l Zn and 75 mg/l Co were prepared and used in all of the experiments. The parameters researched with the conventional method were the amount of arsenic trioxide and the effect of copper sulfate on cementation of cobalt. While using the alloys, the parameters studied were the amounts of arsenic trioxide, copper sulfate and tin containing zinc alloy powder additions, cementation duration and temperature. The difference in the optimization of alloy additions was in the amount of addition of arsenic trioxide. The amount of 4%Sn-zinc alloy powder was tried to be optimized with the addition of arsenic trioxide whereas the optimization was tried to be done without any arsenic addition while using 10%Sn-zinc alloy. The XRD and SEM studies of the cementates were also performed. The obtained results indicated that tin containing alloys were much better than pure zinc. With the additions of 4 g/l 4%Sn-Zn alloy dust, 1.2 g/l CuSO4.5H2O, 0.12 g/l As2O3 and in 2 hours of cementation duration at 85-90oC, the maximum amount of cobalt cementation efficiency was achieved. The experiments indicated that cobalt in the solution could be reduced to about 2 mg/l by using 10%Sn-zinc alloy powder with an initial Sn/Co weight ratio of 13.25:1 without the addition of arsenic trioxide at 85oC in 2 hours of cementation duration.

Thesis (Ph.D.)--Tufts University, 1996. / Adviser: Terry E. Haas. Submitted to the Dept. of Chemistry. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Zugl.: Berlin, Freie Univ., Diss., 2006

Darmstadt, Techn. Universiẗat, Diss., 2007.

Thesis (M.S.)--University of Nevada, Reno, 2007. / "August, 2007." Includes bibliographical references (leaves 62-63). Online version available on the World Wide Web.

Thesis (MSc.(Chemistry))--University of Pretoria, 2007. / Summary in English. Includes bibliographical references.

Zugl.: Konstanz, Univ., Diss., 2008