THE DIFFUSIVITY OF ZINC VAPOR IN HELIUM

The exchange kinetics of zinc vapor with polycrystalline zinc sulphide, wurtzite structure, have been studied in a static system in the temperature range 720–960 °C.Plots of log10(1−α*), i.e. exchange fraction, versus time reveal two processes. The initial process is a rapid simple exchange, for which the data fit a first-order rate law and which persists to a depth of 15–18 molecular thicknesses. At this depth the second, slower process, which appears to be diffusion-controlled, sets in. Kinetic and structural interpretations of these results along with the existing data on Zn–ZnO exchange are discussed.

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The Weldability of Primer-Coated Steel for Shipbuilding by CO2 Laser

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.321-323.1745 ◽

2006 ◽

Vol 321-323 ◽

pp. 1745-1749 ◽

Cited By ~ 1

Author(s):

Jong Do Kim ◽

Jin Seok Oh ◽

Hyun Joon Park

Keyword(s):

Welding Parameters ◽

Coated Steel ◽

Zinc Vapor ◽

Welding Technology ◽

Weld Material ◽

Welding Defects ◽

Lap Welding ◽

Welding Defect ◽

Alternative Idea

The application of laser welding technology has been considered to shipbuilding structure. However, when this technology is applied to primer-coated steel, good quality weld beads are not easily obtained. Because the primer-coated layer caused the spatter, humping bead and porosity which are main part of the welding defect attributed to the powerful vaporizing pressure of zinc. So we performed experiment with objectives of understanding spatter and porosity formation mechanism and producing sound weld beads in 6 t primer coated steels by a CO2 CW laser. The effects of welding parameters; defocused distance, welding speed, coated thickness and coated position; were investigated in the bead shape and penetration depth on bead and lap welding. Alternative idea was suggested to suspend the welding defect by giving a reasonable gap clearance for primer coated thickness. The zinc of primer has a boiling point that is lower than melting point of steel. Zinc vapor builds up at the interface between the two sheets and this tends to deteriorate the quality of the weld by ejecting weld material from lap position or leaving porosity. Significant effects of primer coated position were lap side rather than surface. Therefore introducing a small gap clearance in the lap position, the zinc vapor could escape through it and sound weld beads can be acquired. In conclusion, formation and suspension mechanism of the welding defects was suggested by controlling the factors.

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Splitting Water and Carbon Dioxide via the Heterogeneous Oxidation of Zinc Vapor: Thermodynamic Considerations

ASME 2010 4th International Conference on Energy Sustainability, Volume 2 ◽

10.1115/es2010-90014 ◽

2010 ◽

Cited By ~ 2

Author(s):

Luke J. Venstrom ◽

Jane H. Davidson

Keyword(s):

Carbon Dioxide ◽

Mass Transfer ◽

Carbon Monoxide ◽

Reaction Path ◽

Zinc Vapor ◽

Complete Conversion ◽

Heterogeneous Oxidation ◽

Carbon Dioxide Splitting ◽

Heat Recuperation ◽

Splitting Water

The heterogeneous hydrolysis/oxidation of zinc vapor is proposed as a promising reaction path for the exothermic step in two-step Zn/ZnO solar thermochemical water and carbon dioxide splitting cycles. This approach circumvents mass transfer limitations encountered in the oxidation of solid or liquid zinc, promising rapid hydrogen/carbon monoxide production rates and complete conversion of zinc. In this paper, a parametric thermodynamic analysis is presented to quantify the penalty of generating zinc vapor as well as the benefit of achieving complete conversion of zinc via the heterogeneous oxidation of zinc vapor. The penalty for generating zinc vapor is a reduction in water splitting efficiency from 36% to 27% and a reduction in carbon dioxide splitting efficiency from 39% to 31%. However, with heat recuperation this penalty can be avoided. The benefit of completely converting zinc via the heterogeneous oxidation of zinc vapor is an increase in efficiency from ∼6% to 27% and 31% for water and carbon dioxide splitting, respectively.

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