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Enhancement of wettability in AZ91/B_(4)C system by a mechanical purification of liquid alloy

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Journal of Magnesium and Alloys 2022年第11期10卷 3133-3142页

作者： Artur Kudyba Wojciech Polkowski Grzegorz Bruzda Adelajda Polkowska Donatella Giuranno Łukasiewicz Research Network-Krakow Institute of Technology Zakopian´ska 73 Str.30-418 KrakówPoland National Research Council of Italy Institute of Condensed Matter Chemistry and Technologies for EnergyVia De Marini 616149GenovaItaly

Mg-based alloys are potential candidate materials for a fabrication of lightweight boron carbide based composites through a reactive melt infiltration approach. In this paper, the effect of a mechanical purification of molten AZ91 alloy’s surface on its wettability with polycrystalline B_(4)C is experimentally evaluated for the first time. For this purpose, sessile drop experiments were performed under the same operating conditions(700℃/5 min;Ar atmosphere), by using both the classical contact heating(CH) and the improved capillary purification(CP) procedure. It was found that the evolution of contact angle values was strongly influenced by the applied procedure. In particular, by using the classical CH procedure, the presence of a native oxide layer on the metal surface hinders the observations of melting process, resulting in a misleading conclusion that the system is non-wettable. Contrarily, during the wetting test performed by applying the CP procedure, the surface oxide layer was mechanically removed by squeezing the molten AZ91 alloy through a capillary. Accordingly, the oxide-free AZ91 drop with a regular and spherical shape was successfully obtained and dispensed on the B_(4)C substrate. A reliable contact angle value of θ =83° was measured at the AZ91/B_(4)C triple line at 700 ℃, which in turn proves that B_(4)C is wetted by the liquid AZ91 alloy. In contradiction to the literature, these good wetting conditions were assisted by a non-reactive wetting mechanism occurring at the AZ91/B_(4)C interface. To succeed in the fabrication of AZ91/B_(4)C composites by liquid metal infiltration, such experimental observations make it reasonable to expect a spontaneous infiltration process exclusively driven by capillarity, which in turn increases the efficiency of the process by the absence of reaction products that could be a potentially detrimental factor.

关键词： AZ91 magnesium alloy Magnesium matrix composites sessile drop Capillary purification procedure Wettability Contact angle MMCs B_(4)C

A Study of the Velocity Field during Evaporation of sessile Water and Water/Ethanol drops

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Journal of Bionic Engineering 2010年第4期7卷 321-328页

作者： John R.E.Christy Khellil Sefiane Euan Munro School of Engineering University of Edinburgh

Many studies have investigated evaporation of sessile drops in an attempt to understand the effect of wetting on theevaporation process.Recently interest has also increased in the deposition of particles from such drops,with evaporative massflux being deemed to be responsible for ring-like deposits,and counteraction of the mass flux by Marangoni convection explainingmore uniform deposition patterns.Understanding of such deposition processes is important in biological applications,such as the Litos test-system endorsed by the Russian Ministry of Health for diagnosis of urolithiasis and the evaporation ofcolloidal drops for depositing and organizing proteins and DNA.In most cases where deposition from evaporating drops hasbeen studied,velocity information is inferred from the final deposition pattern or from mathematical modeling based on simplifiedmodels of the physics of the evaporation process.In this study we have directly measured the flow velocities in the baseof sessile drops,using micro particle image velocimetry,viewing the drop from below,through the cover slide.For water drops,a radial pattern of flow was observed with a maximum velocity close to but not at the pinned outer edge.For ‘azeotropic’ethanol/water mixtures,the velocity field is more chaotic to begin with,passing through a phase involving three or four recirculationcells and finally having the same radial pattern as for water drops.

关键词： evaporation sessile drop velocimetry particle deposition μPIV

Improved methodological concepts for processing liquid Mg at high temperature

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Journal of Magnesium and Alloys 2021年第1期9卷 183-191页

作者： Artur Kudyba Natalia Sobczak Wojciech Polkowski Grzegorz Bruzda Adelajda Polkowska Donatella Giuranno Lukasiewicz Research Network-Krakow Institute of Technology Zakopianska 73 Str.30-418 KrakowPoland Institute of Metallurgy and Materials Science Polish Academy of Science25 Reymonta St.30-059 KrakówPoland National Research Council of Italy Institute of Condensed Matter Chemistry and Technologies for EnergyVia De Marini 616149GenovaItaly

In this paper,new improvements of methodological concepts upon examining wettability of high vapor pressure liquid metal systems(e.g.Mg-based alloys)in contact with refractory materials,are presented and discussed.In this regard,high-temperature experiments on molten magnesium(Mg)in contact with graphite as a refractory substrate,were performed by utilizing a newly developed testing device and by applying a suitable experimental procedure.The wetting experiments were carried out by the sessile drop method and under identical testing conditions(700℃/10 min under a protective gas atmosphere).Two different procedures were applied:the classical contact heating(CH)or a newly introduced capillary purification(CP)one.The contact angle behaviors observed under the same conditions were strongly influenced by the applied procedure.Specifically,in the case of using the CH procedure,a presence of native surface oxide layer on the metal surface hinders the observations of melting process,making not possible to experimentally determine the wetting kinetics curveθ=f(t).Contrarily,during the wetting test performed on the Mg/graphite couple by applying the CP procedure,the native surface oxide layer was mechanically removed during the squeezing of the molten Mg through the hole of a capillary.Indeed,an oxide-free squeezed Mg-drop with regular and spherical shape was successfully obtained and dispensed on the graphite substrate.Consequently,the reliable contact angle value aroundθ=150°for the Mg/graphite system,was measured within the wetting test.

关键词： Mg-alloys Magnesium matrix composites sessile drop Capillary purification procedure Wettability Contact angle

Application of Annexation Principle in Investigation of Thermodynamic Property of Ternary Metallic Melt Fe-Cr-Ni

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Journal of Iron and Steel Research(International) 2002年第1期9卷 1-5页

作者： ZHANG Jian University of Science and Technology Beijing

The interfacial tension at the Na 2O Li 2O SiO 2 B 2O 3 slag steel boundary has been determined in the temperature range of 1 803-1 873?K by sessile drop method with the transmission X ray technique. It was found that the variation of interfacial tension with temperature in the system of molten steel/Na 2O Li 2O SiO 2 B 2O 3 slag in the temperature range of 1 803 1 873?K is pretty little. The interfacial tension remarkably decreases with increasing the oxygen and/or sulfur content in molten steel. It suggesed that the oxygen and sulfur dissolved in molten steel act as a surface active solute at the slag steel interface. Consequently, the interfacial tension depends, in most part, on the oxygen content in molten steel, but the composition of the slag has a minor effect on the interfacial tension. In order to clear the effect of slag composition on the interfacial tension, the experimental results are discussed. The interfacial tension is observed to increase with increasing Na 2O and Li 2O contents, and decrease with increasing silica content in slag. The influence of B 2O 3 on the interfacial tension is pretty little.

关键词： interfacial tension slag molten steel sessile drop