The electrodeposition of zinc; changes in current efficiency and surface structure resulting from various addition agents

An examination of the surface structure of zinc electrodeposited from an acid-sulfate solution was made by scanning electron microscopy techniques. The current efficiencies were also determined, to a lesser extent, in order to correlate the results with the surface structures. Commercial and pure zinc oxide were used to prepare the neutral zinc sulfate solutions. The starting solutions were in a range of acid and zinc concentrations commonly used in commercial practice. Changes in morphology resulting from addition agents such as animal glue, gum arabic, and sodium silicate are compared --Abstract, page ii

The effect of impurities and additives on the electrowinning of zinc

The effect of various impurities, commonly found in zinc electro-winning solutions, on the surface morphology of deposited zinc was investigated. Individual additions of the impurities Al, Ag, Cd, Co, Cr, Cu, Ge, Mn, Ni, Sb, Sn, Ti, PbO₂ , PbSO₄, and HCl were studied. In a few cases additives of animal glue, gum arabic, and Na₂SiO₃, were used individually or in combination, to determine their effect on the surface structure of the deposited zinc. Comparisons were then made with deposits from a pure electrolyte consisting of H₂SO₄ and Zn⁺², 200 and 65 g/l, respectively. The zinc was deposited on a 99.9% pure AI sheet using Pt anodes in all but a few cases. Time, temperature, current density, and impurity concentrations were also varied for a few of the impurities. The bulk of the work was conducted at 40º C and 75 A/ft² (82 mA/cm²). Zinc was also deposited using Pb-Ag (0.75%) anodes with or without a precoated PbO₂ layer, obtained by electrolyzing in a NaF solution. Pressed PbO₂ anodes were also used to determine the stability of the anode under the electrolyzing conditions. The surface morphology was examined by a scanning electron microscope (SEM). X-ray diffraction techniques were used to determine crystal orientation. A non-dispersive X-ray spectrometer was used in an attempt to locate impurity concentrations on the zinc deposit when pitting or re-solution occurred. The impurities were categorized by the effect they had on current efficiency, morphology, and apparent mechanism of H₂ evolution from the cathode --Abstract, page ii

Spot Improvement of Rural Roads Using a Local Resource‐ Based Approach: Case Studies from Asia and Africa

Rural roads in developing countries continue to be in poor condition despite multiple interventions. To provide access to markets, hospitals and schools for rural communities, capacity building has been conducted, enabling rural communities to participate in road projects. This process has included the transfer of Do‐nou technology, which is appropriate for spot improvement using a local resource‐based approach. The goal has been to transform the road projects implemented through community initiatives, maximizing their effectiveness and practicality, and thus improving the conditions of rural roads. Case studies have been conducted in Myanmar, the Philippines and Kenya. They demonstrate that spot improvement and the use of locally available materials can provide socioeconomic benefits to communities. Designs based on this approach have been developed for the construction of base courses, retaining walls and causeways. These designs can be applied over wide areas and modified to reflect the unique conditions of each project area. The experience gained in community mobilization and stakeholder involvement, which is essential in the proposed approach, can serve as a guide when applying the approach in new areas

DEMONSTRATION OF ROAD IMPROVEMENT BY LOCAL INHABITANTS AT THE BAYTSEMAL VILLAGE IN THE SOUTH OMO ZONE IN SOUTHERN ETHIOPIA

MNGD Special issue 02: Making Networks for Glocal DevelopmentThe SATREPS-MNGD Project implemented a demonstration of participatory road improvement with local inhabitants at the Baytsemal village in the South Omo Zone in Southern Ethiopia from November 25th, 2019 to December 9th, 2019. The activity lasted for 12 days. The first five days were for the preparation, including measuring, designing, and information sessions for the local inhabitants to build consensus on work plan, whereas the remainder for the actual implementation