Electrochemical Processing of a Heavy W–Ni–Fe Alloy by Direct and Alternating Currents in Ammonia–Alkali Solutions

The features of the hydrodynamics of the electrolyte in the interelectrode gap during electrochemical processing of a profile axisymmetric workpiece are considered. The distribution of average flow rates and flow lines is calculated for a specified electrolyte supply. The nature and rate of the electrolyte flow are established. The unevenness of the current density is determined taking into account the change in the electrical conductivity of the electrolyte from heating and gas filling of the interelectrode gap, as well as the quality of the treated surface. Keywords: electrochemical treatment, roughness, electrolyte, electrical conductivity, gas filling. [email protected]

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Alkali Attack on Cation-Exchange Membranes with Polyvinyl Chloride Backing and Binder: Comparison with Anion-Exchange Membranes

Membranes ◽

10.3390/membranes10090228 ◽

2020 ◽

Vol 10 (9) ◽

pp. 228 ◽

Cited By ~ 1

Author(s):

Shoichi Doi ◽

Nobuya Takumi ◽

Yuriko Kakihana ◽

Mitsuru Higa

Keyword(s):

Cation Exchange ◽

Anion Exchange ◽

Polyvinyl Chloride ◽

Chemical Structure ◽

Immersion Test ◽

Ion Concentration ◽

Membrane Properties ◽

Anion Exchange Membranes ◽

Alkali Solutions ◽

Exchange Membrane

Systematic alkali immersion tests of cation-exchange membranes (CEM) with polyvinyl chloride (PVC) as their backing and binder were conducted to compare that of an Anion-exchange membrane (AEM) with the same PVC materials to investigate the mechanism of dehydrochlorination. In the immersion tests, originally colorless and transparent AEM turned violet, and chemical structure analysis showed that polyene was produced by the dehydrochlorination reaction. However, the CEM did not change in color, chemical structure or membrane properties during the test with less than 1M alkali solutions. According to the Donnan equilibrium theory and the experiments using CEM and AEM, the hydroxide ion concentration in the CEM was much lower than that in the AEM under the same conditions. However, when the alkali immersion test was performed using the CEM under more severe conditions (6 M for 168 h at 40 °C), there was a slight change in the color and chemical structure of the CEM, clearly indicating that not only AEMs, but also CEMs with PVC matrixes were deteriorated by alkali, depending on the conditions.

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Mechanical Properties of Mortars Prepared by Alkali Activated Fly Ash Coming from Different Production Batches

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.244.140 ◽

2015 ◽

Vol 244 ◽

pp. 140-145 ◽

Cited By ~ 1

Author(s):

Matej Špak ◽

Pavel Raschman

Keyword(s):

Mechanical Properties ◽

Fly Ash ◽

Construction Materials ◽

Chemical Properties ◽

Raw Material ◽

Fly Ashes ◽

Coal Burning ◽

Alkali Solutions ◽

One Year ◽

Alkali Activated

Fly ash is a well utilizable secondary raw material for the production of alkali activated construction materials. It is a significant alumina-silicates source suitable for the chemical reaction resulting in hardened composites. Physical and chemical properties of fly ashes as a co-product of coal burning mainly depend on characteristics of coal, burning temperature and combustion conditions. High variability of the properties of fly ash causes an uncertainty in the properties of alkali activated mortars. Time behaviour of the composition of the fly ash produced in a heating plant located in Košice, Slovakia as well as leaching behaviour of both alumina and silica from particular batches during one-year period was documented. Leaching tests were carried out using the distilled water and alkali solutions with three different concentrations. Both compressive and tensile strengths of alkali activated mortars were measured, and the correlation between the mechanical properties of hardened mortars and the chemical composition of fly ashes as well as their leaching characteristics was investigated.

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