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This article presents a study of the surface tension and phosphorus surface segregation in Fe-P alloys. The surface tension was measured by the sessile drop technique. The result of the dynamic surface tension for the low phosphorus content alloys shows that the alloy surface vaporization has a clear effect on the surface tension and causes a positive surface tension temperature coefficient. However, from this article, it is evident that phosphorus in liquid iron acts as a surface active element similar to arsenic. The surface segregation was determined using Auger electron spectroscopy. The result on the surface analysis of as-solidified sample indicates that the adsorption of impurity elements, such as oxygen, carbon, and nitrogen, can conceal phosphorus segregation on the free surface. Phosphorus segregation was also examined in the samples as-cleaned by Ar+ and then treated 30 minutes at 650°C. Phosphorus was found to segregate extensively on the surface of the alloys. On the basis of the analysis of the published data, the surface active intensity sequence of some nonmetallic elements was arrayed, and the surface active intensity of fluorine and boron in liquid iron was estimated.  相似文献   

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Summary A study was made of the effect of composition on the surface tension of nickel-silicon alloys with up to 50 at.% Si. An inflection was observed on the isotherm at 28 at.% Si. The unusual shape of the surface tension versus composition curve is ascribed to a microheterogeneous structure of the melt and the presence in the latter of short-range order.  相似文献   

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Surface tensions of iron-nickel alloys were measured as a function of oxygen potential at 1550 °C using the sessile drop technique. The surface tension of pure liquid nickel and iron-nickel alloys was measured at a total pressure of 1 atmosphere under varying CO2/CO ratios. An increase in the oxygen potential in the gas phase was found to correspond to a decrease in surface tension of pure nickel and iron-nickel alloys, indicating that oxygen is surface active in both liquid nickel and iron-nickel alloys. At low oxygen potentials, nickel additions to liquid iron were found to cause small decreases in alloy surface tensions; however, at higher oxygen potentials, the surface tension of the alloy exhibited a minimum value as nickel was added to iron. The adsorption coefficients of oxygen in liquid iron-nickel alloys and pure liquid nickel were determined from the surface-tension data using Belton’s analysis, and were found to be similar to those calculated from kinetic studies. Wettability of iron-nickel alloys on an alumina substrate was studied through contact-angle measurements. At a constant alloy nickel content, the contact angle between the alloy and alumina decreased with increased oxygen potential in the gas phase.  相似文献   

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Surface tension measurements on liquid metals in microgravity   总被引:2,自引:0,他引:2  
The results of surface tension measurements on liquid metals and alloys, performed in microgravity, are presented. Using electromagnetic levitation and the oscillating drop technique, the surface tension of gold, gold-copper, and zirconium-nickel was measured. We find excellent agreement with available results obtained on earth by the same technique, but only if the latter are corrected to account for gravity effects. This not only shows the necessity for the correction of surface tension data derived from earthbound oscillating drop experiments but also proves its correctness.  相似文献   

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The surface tension of liquid Fe-Cr-O alloys has been determined by using the sessile drop method at 1823 K. It was found that the surface tension of liquid Fe-Cr-O alloy markedly decreases with oxygen content at constant chromium content, and the surface tension at a given oxygen content remains almost constant, regardless of the chromium content. When the surface tension of liquid Fe-Cr-O alloys is plotted as a function of oxygen activity, with an increase in the chromium content, the surface tension shows a much steeper decrease with respect to oxygen activity. The surface tension of liquid Fe-Cr-O alloys at 1823 K is given as follows: σ=1842-279 ln (1+K O a O). Here, assuming a Langmuir-type adsorption isotherm, the adsorption coefficient of oxygen, K O(Fe-Cr), as a function of chromium content, was shown to be K O=140+4.2 × [wt pct Cr]+1.14 × [wt pct Cr]2.  相似文献   

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The influence of oxygen on the surface tension of liquid copper has been determined by the sessile drop technique. The surface tension of pure liquid copper at 1108 °C is found to be equal to 1.320 ± 0.015 N/m. The effect of oxygen is investigated for partial pressures of oxygen ranging from 10?13 to 5 X 10?6 atm. The surface activity of oxygen is deduced to equal 3200 ± 600 N/m and the saturation adsorption to equal 5.72 X 10"6 mole/m2, which corresponds to a saturation area of 29 ±5Å2 per adsorbed oxygen atom. The adsorption of oxygen on liquid copper is consistent with the formation at the metal surface of a two-dimensional compound of stoichiometry Cu3O. It is also concluded that equivalent attractive forces operate between neighboring adsorbed atoms.  相似文献   

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A summary concerning the measurement of liquid density relying on the Archimedes principle has been presented, based on which a new effective method with a specially designed bob for determining liquid density has been suggested. The application of this method to ethyl alcohol solution and liquid glycerol, as well as a theoretical error analysis, shows that this new method is significant, because not only can it simplify the procedure of measurement but it can also offer more precise results. Besides, this method can further provide surface tension or contact angle simultaneously. It is expected that this new method will find its application in hightemperature melts. leave from Thermodynamics and Phase Diagram Lab, University of Science and Technology Beijing  相似文献   

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The density and surface tension of five liquid Na-ln alloys, containing between 0.5 and 7 at. pct In, have been measured in the temperature range 170° to 400°C using a maximum bubble pressure technique which incorporates an automatic pressure measuring and recording device. The results are compared with corresponding data reported previously for Na-Cd alloys. The gram-atomic volumes of the Na-ln alloys, calculated from the densities, indicate a substantial contraction on alloying which is, on average, about double that for the Na-Cd alloys and qualitatively consistent with thermodynamic data for the two systems. The surface tension of liquid sodium is increased slightly on adding indium, indicating a lower indium concentration in the surface than in the bulk, in contrast to the marked surface active behavior of cadmium. The surface excess concentrations of indium and cadmium are calculated using Gibbs’ adsorption equation. The surface excess entropy, estimated from the temperature dependence of the surface tension, is compared and briefly discussed for the two systems.  相似文献   

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Abstract

The oscillating drop technique was used to measure the surface tension of liquid iron-oxygen alloys in the temperature range 1560–1645°C. No noticeable temperature dependence of the surface tension was observed. The surface activity of oxygen in iron was determined to be 2.1 × 106 dynes/cm. This value is twice as large as the accepted value in the literature. According to the monolayer approximation, the liquid iron surface becomes saturated with oxygen when each adsorbed oxygen atom occupies an area of 11.4 Å2. Data-analysis suggests that saturation of the surface of liquid iron with oxygen results from the formation of a two-dimensional ionic compound. This compound seems to correspond to Fe2O or FeVO, where V stands for a vacancy.

Résumé

La technique de la goutte oscillante a ét é employ ée pour mesurer la tension superficielle des alliages liquides fer-oxyg ène entre 1560°C et 1645°C. Aucune variation de la tension superficielle avec la temperature n'a été observée. L'activité suferficielle de l'oxygéne dans le fer a été établie comme étant 2.1 × 106 dynes/cm. Cette valeur est deux fois celle admise dans la littéature. Selon l'approximation d'une monocouche, la surface du fer liquide sera saturée d'oxygé ne quand chaque at orne d'oxygene absorbe occupe une superficie de 11.4 A2. L'analyse des données indique que la saturation de la surface du fer liquide par l'oxygéne résulte de la formation d'un composé ionique bi-dimensionnel. Il semble que ce compose corresponde à Fe2O ou FeVO, ou V est une lacune dans le réseau.  相似文献   

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The surface tensions of liquid Fe, Co, Ni, Cu, Ag, Zn, Pb, Cd, and Sn have been measured by the sessile droplet method and/or the levitated droplet method over wide ranges of temperature. The values of surface tension obtained by the levitated droplet method have always been found to be higher than those measured by the sessile droplet method, a result which is attributed to decreased droplet contamination with the containerless levitation method. Negative temperature coefficients of surface tension have been obtained for all of the metals investigated in this work. Based on a literature survey of the available experimental data, it is shown that the values of both surface tension and the temperature coefficient are influenced in a systematic manner by the presence of surface active impurities. On this basis, positive values of the temperature coefficient of surface tension for liquid Zn and Cd found in the literature may be explained in terms of impurity effects which tend to be particularly pronounced in volatile metals. Formerly Research Associate in the Department of Metallurgy and Materials Science, University of Toronto  相似文献   

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Thermodynamic equations have been derived to evaluate the surface tension of liquid metal‐oxygen systems. On the basis of these equations, the effect of the oxygen on the surface tension of liquid metals has been evaluated by using the fundamental information on the oxygen solubility in the metals, the surface tension and the molar volume of pure liquid metals and oxides. The calculated results from these equations agree with the literature values of the surface tension of liquid Fe‐O, Co‐O, Ni‐O, Cu‐O and Si‐O systems.  相似文献   

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Buckwheat flour, mainly used for pancakes, may induce asthma following inhalation and anaphylactic reactions following ingestion. These allergic reactions are mediated by specific IgE and may be confirmed by skin test and radio-allergo-sorbent test. The occupational asthma of a patient working in pancake restaurant was confirmed by specific challenge test with a computerised device to generate particles. A very small amount of buckwheat flour (10 micrograms) induced an immediate fall of the FEV1 to 56% of the initial value. No bronchial reaction was observed with lactose nor with wheat flour. Specific bronchial challenge identifies the allergen responsible for asthma, measures the level of sensitization and thus can prevent the occupational exposure.  相似文献   

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