Showing papers in "Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science in 1980"

Densities, electrical conductivities and viscosities of CuSO4/H2SO4 solutions in the range of modern electrorefining and electrowinning electrolytes

Abstract: Densities, electrical conductivities and viscosities of CuSO4-H2SO4-H2O solutions are reported for electrorefining electrolytes over the ranges: Temperature 50 to 70°C Copper concentration 40 to 55 g · dm-3 H2SO4 concentration 160 to 220 g · dm-3 and for electrowinning electrolytes over the ranges: Temperature 20 to 70°C Copper concentration 10 to 60 g · dm-3 H2SO4 concentration 10 to 170 g · dm-3 Empirical and semiempirical equations describing the measured properties are presented.

The modeling of pool profiles, temperature profiles and velocity fields in ESR systems

Abstract: Through the simultaneous statement of Maxwell’s equations, the turbulent Navier-Stokes equations and the differential thermal energy balance equations a mathematical model has been developed to represent the pool profiles, the velocity fields and the temperature profiles in an ESR system. The major advance over earlier modeling efforts is the fact that the model is capable of predicting the pool profiles from first principles. The theoretically predicted pool profiles and temperature fields were found to be in reasonable agreement with experimental measurements reported by Mellberg for a laboratory scale system. The model is used to investigate the interdependence of key process parameters, with the power input, fill ratio, amount of slag used and the position of the electrode as the independent variables and the casting rate, pool depth, velocity and temperature fields as the dependent variables.

On the kinetics of the chlorination of titanium dioxide in the presence of solid carbon

Abstract: The influence of solid carbon on the chlorination of TiO2 with Cl2 and CO-CO2-Cl2 gas mixtures was investigated gravimetrically using rutile and graphite tablets. In the experiments, the temperature, composition and total pressure of the gas phase as well as the TiO2-C separation were varied. The chlorination rate of TiO2 was found to be 40 to 50 times faster with TiO2-C contact than in the absence of carbon. The acceleration of the chlorination rate is due to the kinetic influence of solid carbon and takes place even when TiO2 and C are separated by the gas phase. In the latter case the C influence decreases with increasing TiO2-C separation. In the case of flowing Cl2-Ar mixtures at 105 Pa total pressure this influence exists within a critical TiO2-C separation,L, which is approximately 40 μm at 1273 K and PCl2 = 2.7 × 104 Pa.L increases linearly with increasing temperature and decreases approximately linearly with increasing total gas pressure in the case of a closed reaction vessel. The ratio of the reacted amounts of TiO2 and C is also dependent on the TiO2-C separation. From the experimental results a kinetic reaction model is proposed to provide a quantitative description of the influence of solid carbon. The dependence of the chlorination rate,i, of TiO2 on the TiO2-C separation,l, is given byi ∼ (l + Β) −2 whereΒ is a constant.

Electrochemical investigtion of solubility and chemical diffusion of lithium in aluminum

Abstract: The solubility of lithium in aluminum and the chemical diffusion coefficient in this solid solution have been investigated as a function of temperature between 400 and 600°C using the electrochemical cell: (-)A1, “LiAl”/LiCl-KCl(eut.)/Al(Li)(+) The solubility limit of lithium in aluminum was found to decrease from 13.8 at. pct at 595°C to 8.0 at. pct at 395°C, in good agreement with data previously reported by other investigators using different techniques. The chemical diffusion coefficient has been measured by two different electrochemical transient techniques. The data can be represented by the relation: $$\tilde D = 0.155\exp (--\Delta H/RT)cm^2 /s$$ (1) where ΔH is 119.2 kJ/mol. This electrochemical technique has also been used to obtain values of the composition dependence of the Gibbs free energy of mixing and the enhancement factor d lnaLi/dlnXLi which relates the chemical diffusion coefficient and the self diffusion coefficients within the Li-Al solid solution.

The rate of absorption of nitrogen into liquid iron containing oxygen and sulfur

Abstract: The rate of nitrogen absorption into and desorption from liquid iron containing sulfur and/or oxygen was measured by employing a constant-volume technique with a highly sensitive pressure transducer. Critical evaluation of the results demonstrated conclusively that the chemical rate at high oxygen or sulfur contents is second order with respect to nitrogen content in the metal and probably controlled by the dissociation of the nitrogen molecule on the surface. The effect of sulfur on the rate is complex because of the influence of 1) liquid-phase mass transfer at low sulfur contents, 2) the chemical rate on vacant iron sites at intermediate sulfur contents, and 3) the rate on the adsorbed sulfur layer or the limiting rate at high sulfur contents. However, at intermediate concentrations the limiting case for the adsorption isotherm for sulfur is adhered to and the rate is inversely proportional to the sulfur concentration. For Fe-O melts the rate is inversely proportional to the oxygen content except at low oxygen levels where mass transfer affects the rate. The rate for Fe-S-O melts can be calculated reasonably well from the results for the Fe-S and Fe-0 alloys, assuming that oxygen does not effect the adsorption of sulfur andvice versa and that there is nearly complete coverage of the surface with oxygen and sulfur atoms.

A thermodynamic analysis of the copper-sulfur system

Abstract: An associated solution model is applied to describe the thermodynamic behavior of Cu-S liquid. This model assumes the existence of ‘Cu2S’ species in addition to Cu and S in the liquid. With two solution parameters for each of the binaries Cu-‘Cu2S’ and ‘Cu2S’-S, this model accounts for the compositional dependence of the thermodynamic properties of Cu-S liquid from pure Cu to pure S over a wide range of temperature. The binary Cu-S does not contribute significantly to the excess Gibbs energy of the liquid due to the rather small dissociation constant of ‘Cu2S’ to Cu and S. Using this model for the liquid phase, a statistical thermodynamic model for the digenite phase, and appropriate thermodynamic equations for the other phases, the Cu-S phase diagram is calculated. The calculated diagram is in excellent agreement with the experimental data, accounting for the range of homogeneity of digenite at all temperatures.

Heat flow in atomized metal droplets

Abstract: The solidification of spherical droplets with a discrete melting temperature is analyzed using an enthalpy model. Equations describing the cooling of the initially superheated liquid droplet and a numerical heat flow model for its subsequent solidification are presented. Important parameters like times for initiation and completion of solidification, cooling rates and interface velocities in aluminum, iron, and nickel are related to the process variables governing the rate of heat extraction from the droplets. The analysis is performed for the range of Biot numbers of practical interest where Newtonian cooling models are not considered applicable, 0.01 ≤ Bi ≤ 1.o, and the results are presented in the form of normalized or dimensionless quantities. It is shown that the average cooling rate in the liquid prior to solidification can be computed with the Newtonian cooling expressions. However, significant temperature gradients are noted at the droplet surface even for Biot numbers as low as 0.01. Reducing the droplet diameter reduces the time necessary for the initiation and completion of solidification, increases the interface velocities at equivalent fractions solidified and decreases theG L /R ratio. Although smaller droplet diameters promote higher cooling rates in the liquid at the beginning and in the solid at the end of solidification, the effect at the intermediate stages is more complex and depends on the initial superheat, the Biot number and the thermophysical properties of the material.

Thermodynamic properties of Na2O-SiO2-CaO melts at 1000 to 1100 °C

Abstract: The thermodynamic properties of Na2O-SiO2 and Na2O-SiO2-CaO melts have been measured using the galvanic cell\(\begin{array}{*{20}c} {O_2 (g), (Na_2 O), Pt} \\ {Na_2 O - WO_3 liq} \\ \end{array} \left| \begin{gathered} Na^ + \hfill \\ \beta - alumina \hfill \\ \end{gathered} \right| \begin{array}{*{20}c} {Pt,(Na_2 O), O_2 (g)} \\ {Na_2 O - SiO_2 - CaO liq} \\ \end{array} \) Activities of Na2O were calculated from the reversible emf of the cell. This is possible because the activity of Na2O in the Na2O-WO3 liquid is known from previous work. Data for the binary Na2O-SiO2 system were obtained between 1000 and 1100 °C and for compositions ranging from 25 wt pct to 40 wt pct Na2O. At 1050 °C, Log\(a_{Na_2 O} \) varied from approximately 10.2 at 25 wt pct Na2O to approximately −8.3 at 40 wt pct Na2O, the dependence with respect to composition being nearly linear. The Gibbs-Duhem equation was used to calculate the activities of SiO2(s), and the integral mixing properties,GM, HM, andSM, were derived. At the di-silicate composition,GM = −83 kJ/mol,HM = −41 kJ mol andSM = 33 J/mol K at 1000 °C. (Standard states are pure, liquid Na2O and pure, solid tridymite.) The activity data are interpreted in terms of the polymeric nature of silicate melts. Activities of Na2O in the Na2O-CaO-SiO2 system were measured for the 25, 30 and 35 wt pct Na2O binary compositions with up to 10 wt pct CaO added. The addition of CaO caused an increase in the activity of Na2O at constant\(N_{Na_2 O} /N_{SiO_2 } \). The experimental data agree well with the behavior predicted by Richardson’s ternary mixing model.

A kinetic study of nonoxidative dissolution of galena in aqueous acid solution

Abstract: This paper presents the results obtained through a kinetic study of the nonoxidative dissolution of natural galena in hydrochloric acid and perchloric acid solutions with and without the addition of sodium chloride. Under the experimental conditions employed in this study, the dissolution rates were controlled by a chemical reaction on the surface of the galena sample. The galena dissolution rate is of the first order with respect to hydrochloric ion activity in hydrochloric acid and perchloric acid solutions. The addition of sodium chloride to the acid solutions greatly enhanced the dissolution rate. The effect of sodium chloride has two possible interpretations: First, it may be the result of an increase in hydrogen ion activity. Second, the enhancement of the dissolution rate observable at high sodium chloride concentration may be due to the specific adsorption of chloride ions or the surface complexing of chloride ions on the galena surface.

Acid dissolution of cupric oxide

Abstract: The rates of dissolution of synthetic cupric oxide in solutions containing perchloric, sulfuric, nitric or hydrochloric acid were studied using sintered disks. In each case, the dissolution rate increased with elapsed retention time until an essentially constant value was reached. This phenomenon can be attributed to an increase in the disk’s effective surface area. The dissolution rate is of the first order with respect to aH + for perchloric, nitric, and hydrochloric acids, while it is of a half order for sulfuric acid. High activation energies, ranging from 12.4 to 20.5 kcal/mol, and the independence of agitation speed on cupric oxide dissolution reaction rate suggest that chemical reactions are the major determinants of dissolution rates. The addition of electrolytes having anions common with the acids resulted in an acceleration of the dissolution rate due to increases in aH + values. However, the addition of electrolytes of noncommon anions revealed a quite different effect on dissolution rate. This suggests that the adsorption and/ or complexing of anions on the cupric oxide surface may have had a significant role in the determination of the dissolution rates. The type of acid used determined the identity of the adsorbed anion.

Aspects of the interf Ci l chemistry of nickel extraction with LIX63-HDNNS mixtures

Abstract: The extraction of nickel from acidic aqueous solutions with LDC63(HOx:)-dinonylnaphtha-lenesulfonic acid (HDNNS) mixtures has been studied using purified reagents. Interfacial tension data and infrared spectra are provided which indicate the presence of an oximesulfonate interaction. Extraction of nickel is significant only if HDNNS micelles and HO* molecules are present together in the organic phase. The stoichiometry of the extracted nickel complex appears to be Ni: oxime = 1:3. An extraction mechanism is proposed involving HDNNS micellar enhancement of the oxime-nickel chelation reaction.

Chemistry, microstructure, and reduction characteristics of dolomite-fluxed magnetite pellets

Abstract: The addition of dolomite to iron ore pellets improves high temperature reduction properties, primarily by increasing their softening point and reducibility. This study was made to ascertain the compositional ranges within which dolomite fluxed magnetite pellets show such an improvement over good acid pellets. A variety of compositions with MgO levels from 1 to 2 wt pct and CaO/SiO2 ratios of 0.6 to 1.8 were prepared using Hibbing magnetic concentrate. These compositions were balled and then pot-grate fired to various temperatures. Petrographic examination and electron microprobe analyses were used to characterize the phase assemblages. Reduction characteristics were also evaluated. As evidenced by the following petrographically observed relationships, the CaO/SiO2 ratio (c/S) was found to be the controlling factor for pellet microstructure: a) The low c/S ( 1.3) pellets were mostly calcium ferrite-bonded. Intermediate c/S compositions contain more magnesioferrite than do either low or high basicity compositions. Pellets must be fired to a high enough temperature to generate sufficient liquid for ion transport but not so high as to cause pellets to stick together. Well-fired pellets with a c/S of 1.3 or less performed adequately in low temperature degradation tests. Pellets with a c/S of 0.8 or greater displayed satisfactory swelling behavior. Therefore, we determined that pellets within a c/S range of 0.8 to 1.3 are technically acceptable. Pellets containing 1.5 wt pct MgO had the best reduction characteristics, but all fluxed compositions reduced faster and more completely than did acid pellets. Increasing MgO content up to 2.0 pct increased the softening temperature by 165‡C over acid pellets. On the basis of pellet test results and taking into consideration the auxiliary influence of economic and operating considerations, we determined the optimum composition of dolomite fluxed Hibbing pellets to be 1.5 pct MgO and a C/S of 0.8.

Rapid melting and solidification of surface due to stationary heat flux

Abstract: A general two-dimensional computer heat flow model is developed in an oblate spheroidal coordinate system for rapid melting and subsequent solidification of the surface of a semiinfinite solid subjected to a high intensity heat flux over a circular region on its bounding surface. Generalized numerical solutions are presented for an aluminum substrate subjected to both uniform and Gaussian heat flux distributions. Temperature distributions, melt depth and geometry, and melting and solidification interface velocities are calculated as a function of applied heat flux, radius of the circular region, and time. It is shown that the important melting and solidification parameters are a function of the product of the absorbed heat flux, q, and the radius of the circular region, a. General trends established show that melt depth perpendicular to the surface is inversely proportional to the absorbed heat flux for a given temperature at the center of the circular region. Dimensionless temperature distributions and the ratio of liquid-solid interface velocity to absorbed heat flux,R/q, as a function of dimensionless melt depth remain the same if the productqa is kept constant, whileq anda are varied. For a given total power absorbed melting and solidification parameters are compared for uniform and Gaussian heat flux distributions. For a given temperature at the center of the circular region both melt depth and width are smaller for the Gaussian distribution while temperature gradients and interface velocities are larger.

Activities of oxygen in liquid thallium and indium from electrochemical measurements

Abstract: Modified coulometric titrations on the galvanic cell;O in liquid Tl or In/ZrO2(+CaO)/Air, Pt, were performed at 973, 1073, and 1173 K to determine the oxygen activities in liquid thallium and liquid indium. The standard Gibbs energies of solution of oxygen in liquid thallium and liquid indium for l/2 O2 →O (1 at. pct) were determined respectively to be δG‡(in Tl) = -22000 + 0.74T (±300) cal/g-atom = -92000 + 3.10T (±1300) J/g-atom, δG‡(in In) = -42450+ 3.30T (±350) cal/g-atom = -177600 + 13.8T (±1500) J/g-atom, where the reference state for dissolved oxygen was an infinitely dilute solution. It was reconfirmed that the apparent initial oxygen concentration observed in the range of very low oxygen concentration in liquid metal was attributed to the oxygen released from the solid electrolyte.

Mathematical description of the thermodynamic properties of the systems Fe-0 and Fe-O-SiO 2

Abstract: The thermodynamic properties of the liquid slag and iron phases in the system Fe-O-SiO2 and the solid and liquid phases in the system Fe-O have been correlated by mathematical relations that describe the solution phases in terms of hypothetical solution species in equilibrium with each other, and behaving in a nonideal manner, described by a form of the Margules equations. Parameters that describe the properties of the species, and their nonideal behavior, are determined empirically from existing thermochemical measurements. The correlations are, for the most part, as accurate as the data on which they are based. The method supplies a much needed practical description of slag chemistry that can be extended to complex slags of four or more components.

Thermodynamic properties of molten sulfides: Part II. The system Co-S

Abstract: The equilibrium partial pressure of sulfur vapor over Co-S melts has been determined by equilibrating the melts with H2S-H2 gas mixtures at temperatures ranging from 1378 to 1617 °C and for melt compositions ranging from approximately cobalt saturation up to about 31 wt pct sulfur. As in a previous publication from these laboratories, an optical interferometer was employed to monitor the system’s approach to equilibrium and to analyze the composition of the equilibrium gas phase. A correlation based on the experimental data and that of other investigators is described. The correlation is based on the assumption of species in solution, and reproduces well all thermodynamic properties of Co-S melts.

Thermodyn mics of oxygen in liquid tellurium from electrochemical me surements

Abstract: The activity coefficient of oxygen in liquid tellurium at 753 nd 823 K w s measured by the coulometric titration method employing solid electrolyte. The oxygen was found to obey Henry’s law, and the standard Gibbs energy of solution of oxygen in liquid tellurium for l/2O2 O (1 t. pct) was determined to be: 1 % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyiLdqKaam% 4ramaaCaaaleqabaGaam4taaaakiaacIcaieaacaWFPbGaa8NBaiac% Sd4FubGaiWoG-vgacaWFGaGaa8hiaiaa-LcacaWFGaGaa8xpaiaa-b% caruauHXwy0LMBVbctP52B0LhCLbacfaGaa4hfGiaa+jdacaGFXaGa% a4hlaiaa+HdacaGF0aGaa4hmaiaa+bcacaGFRaGaa4hiaiaa+fdaca% GFWaGaa4Nlaiaa+ndaiuGacaqFubGaa4hiaiaa+HcacaGFJbGaa4xy% aiaa+XgacaGFVaGaa43zaerbmv3yPrwyGmvyUnhiv5wAJ9gzLbacga% GaaW3eGiaa+fgacaGF0bGaa43Baiaa+1gacaGFPaaaaa!6730! $$\Delta G^O (inTe ) = ---21,840 + 10.3T (cal/g--atom)$$ 2 % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaacbaGaa8xpai% aa-bcaruat1nwAKfgid9MBZ9gBLbacfaGaa4hfGiaa-LdacaWFXaGa% a8hlaiaa-ndacaWF4aGaa8hmaiaa-bcacaWFRaGaa8hiaiaa-rdaca% WFZaGaa8Nlaiaa-fdacaWFubGaa8hiaiaa-HcacaWFkbGaa83laiaa% -DgacaWFtaIaa8xyaiaa-rhacaWFVbGaa8xBaiaa-Lcaaaa!4FF5! $$ = ---91,380 + 43.1T (J/g--atom)$$ . The standard Gibbs energy of formation of TeO2 was also determined by using similar electrochemical cell; the result is: 3 % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyiLdqKaam% 4ramaaCaaaleqabaGaam4taaaakiaacIcaieaacaWFubGaa8xzaiaa% -9eadaWgaaWcbaGaaGOmaaqabaGccaGGPaGaeyypa0JaeyOeI0IaaG% 4naiaaiMdacaGGSaGaaGyoaiaaikdacaaIWaGaey4kaSIaaGinaiaa% iAdacaGGUaGaaGynaiaadsfacaGGOaGaa83yaiaa-fgacaWFSbGaai% 4laiaa-1gacaWFVbGaa8hBaiaacMcaaaa!509E! $$\Delta G^O (TeO_2 ) = - 79,920 + 46.5T(cal/mol)$$ 4 % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaeyypa0Jaey% OeI0IaaG4maiaaiodacaaI0aGaaiilaiaaisdacaaIWaGaaGimaiab% gUcaRiaaigdacaaI5aGaaGinaiaac6cacaaI2aGaamivaiaacIcaie% aacaWFkbGaai4laiaa-1gacaWFVbGaa8hBaiaacMcaaaa!480E! $$ = - 334,400 + 194.6T(J/mol)$$ The solubility of oxygen in liquid tellurium was calculated from the combination of these two results to be: 5 % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4qamaaBa% aaleaatCvAUfKttLearyqr1ngBPrgaiuGacqWFtbWuaeqaaOGaeyyp% a0JaciyzaiaacIhacaGGWbGaaiikaiaaiAdacaGGUaGaaGynaiaaik% dacqGHsislcaaI5aGaaGymaiaaigdacaaI5aGaai4laiaadsfacaGG% PaacbaGaiWoG+HcacGa7a6xyaiacSdOF0bGaiWoG+5cacGa7a6hCai% acSdOFJbGaiWoG+rhacaGFGaGaa4xkaaaa!5C0A! $$C_S = \exp (6.52 - 9119/T)(at.pct )$$ By comparison of the present results for tellurium with the published values for the other elements, thermodyn mic behavior of oxygen dissolved in liquid elements was discussed and compared with sulfur dissolved in liquid elements.

The rate and activation enthalpy of decomposition of CaCO3

Abstract: The heat balance during steady state decomposition of CaCO3 single crystals in vacuum is analyzed. It is shown that, contrary to the contention of others, the rate of decomposition of CaCO3 can be measured under conditions which make the slowest chemical step of the process, rather than heat transfer or gas phase diffusion, rate limiting. From new experimental measurements and measurements of previous investigators the apparent enthalpy of activation for CaCO3 decomposition (when the CO2 background pressure is negligible) is found to be 50 ± 3 kcal (calculated in terms of pressures equivalent to the CO2 decomposition flux densities), compared to 40.5 kcal for the equilibrium decomposition reaction. The rates of decomposition of single crystals which are measured in different studies differ by as much as a factor of 4, but average only about 10-5 times the flux densities that are theoretically achievable for the reaction.

The cracking of zinc spangles on hot-dipped galvanized steel

Abstract: The cracking of zinc spangles on hot dipped galvanized sheet steel was studied under controlled conditions. It was confirmed that there are two major modes of failure—boundary cracking and intragranular basal cleavage. There are four types of surface topographiesviz “mirror-like”, “feathery”, “dimpled” and “ridged”. Of these only the last type, “ridged”, was found to have its basal planes lying at an angle to the plane of the sheet. These spangles also tended to fracture most readily when strained. Hence a relationship between surface topography, crystallographic orientation and fracture behavior has been established. The implications of these findings for paint adherence is discussed.

Production of aluminum and aluminum coatings by thermal decomposition of aluminum alkyls

Abstract: The kinetics of the thermal decomposition of aluminum alkyls, in the presence of a carrier gas, to produce aluminum have been studied for tri-n-propyl aluminum, tri-n-butyl aluminum, and tri-i-butyl aluminum in the temperature range 540 to 740 K. The reactions were found to be first order with respect to alkyl; activation energies for reaction and diffusivities were obtained from the experimental data by fitting an equation for a heterogeneous reaction. The deposited aluminum was found to have a carbon content which increased with temperature. Gaseous products of reaction were observed to contain hydrocarbons other than the principal olefin, although these other hydrocarbons were present in only small amounts in the case of tri-i-butyl aluminum.

Computation of temperatures in thin tantalum sheet welding

Abstract: A two-dimensional mathematical model was developed to calculate the temperature distribution during welding of thin tantalum sheets. The solution of the unsteady heat flow equation was obtained employing a computer program based on the finite difference method. The model does not require any assumptions regarding the shape of the welding pool. Arc parameters, radiative and convective heat losses and the dependence of the relevant physical properties on temperature are taken into account. The shape of the welding pool and isotherms are calculated and compared to experimental results.

Thermodynamic properties of liquid copper-lead alloys

Abstract: Activities of lead in liquid copper-lead alloys were measured in the temperature range 1000 to 1200 °C at intervals of 50 °C by the dew-point technique. Various partial and integral molar properties of the liquid alloys were evaluated from the data, and the boundaries of liquid immiscibility in the Cu-Pb phase diagram were calculated. The activity coefficients of lead and copper in dilute solutions are represented by: In γo Pb = (346/T@#@) + 0.181, and In γo cu = (3852/T) − 0.945. The temperature dependence of Gibbs energy self-interaction coefficients for lead and copper are given by: ePb Pb = − (7828/T) − 3.506, and eCu Cu = − (8804/T) + 3.140. Various coefficients have the following values at 1200 °C: γo Pb = 12.58,ePb Pb = − 8.85.ηPb Pb = − 52,197 J/gfw, σPb Pb = 38.15 J/gfw-K, γo Cu = 5.31, eCu Cu = −2.92,ηCu Cu = − 63,970 J/gfw, and σCu Cu = 19.19 J/gfw-K.

The Influence of calcia and magnesia in wustite on the kinetics of metallization and iron whisker formation

Abstract: Calcium oxide andJor magnesium oxide are introduced in different ways to high purity wustite powders, followed by metallization in mixtures of CO, CO2, and N2 at 750, 900, and 1100 °C. A new technique is developed to study the nucleation and growth of iron where wustite plates are coated with thin films of CaO of MgO prior to metallization. Calcia, in solid solution with wustite, influences the kinetics of metallization and the morphology of iron. It is reasonably confirmed that nucleation and outward growth of iron, to form iron whiskers, occur at sites higher in CaO concentration on the wustite surface. MgO, on the other hand, has almost no noticeable effect on the iron whisker formation.

The high temperature heat content and heat capacity of liquid cerium-copper alloys by levitation calorimetry

Abstract: The electromagnetic method of heating was used to determine the heat contents of liquid-cerium-copper alloys over the complete range of alloy composition. The temperatures of the levitated samples were determined pyrometrically utilizing the normal spectral emissivity data measured in an earlier work. The heat capacity was derived from analytic expression for heat contents. The composition dependence of the heat capacity goes through a maximum at 67 at. pct Cu. This behavior is ascribed to the effect of a Ce-Cu2-type atomic clustering in the liquid phase.

A solid electrolyte oxygen sensor for steelmaking slags of the basic oxygen converter

Abstract: Oxygen pressure in the slag phase is an important parameter in steelmaking processes. Consequently, an in situ solid electrolyte oxygen sensor for the steelmaking slags was developed in the present work. EMF measurements, optical examination, and EPMA analysis of cross sections of the electrolyte tubes used in laboratory experiments indicated that magnesia-stabilized zirconia was suitable for this purpose. The oxygen sensor was also tested on slags of a 100,000 kg LD converter at the end of the normal blowing operation. The stable oxygen pressure in the slag was successfully obtained by the simultaneous measurements of EMF and temperature. By using the oxygen sensor, a simple empirical relation was obtained between the oxygen pressure and ratio of ferric to the total iron ion content in the slag. Also, the oxygen pressure in the LD converter slag was found an order of magnitude higher than that in the metal at the end of the normal blowing operation.

Early stages of reduction of nickel oxide single crystals: An investigation by transmission electron microscope

Abstract: Because of the practical importance of the reaction, a great deal of work has been done on the reduction of metallic oxides to metals. In this laboratory all stages of the reduction of nickel oxide to nickel are being studied using a transmission electron microscope. Small, pre-thinned single crystals of nickel oxide have been reduced outside the microscope in a hydrogen atmosphere and the reduction temperatures and times were varied. The resulting foils were then examined in a Phillips 301 100 kV electron microscope and the relationships between the nickel metal particles and the nickel oxide single crystal matrix were established. During the early stages of the reduction both epitaxial and non-epitaxial nuclei were observed, the latter becoming predominant as reduction time progressed. The nuclei were frequently separated from the nickel oxide matrix by a fissure and as they impinged and coalesced, a large scale structure resulted with internal porosity as often seen by optical microscopy.

Activity of arsenic in copper

Abstract: Values have been reported in the literature for the Henrian activity coefficient for arsenic in molten copper ranging from 1.45 × 10-4 to 5 × 10-7 at temperatures between 1273 and 1573 K. In this study, that data was reexamined and was found to be in closer agreement than originally reported. The Henrian activity coefficient was found to range from 2.2 × 10-3 at 1273 K to 5.6 × 10-3 at 1373 K. The experimental data indicate that at 0.21 < NAs < 0.30 the activity coefficient γAs can be determined from the following equations: log γAs = -5.58 NCu2+ 1.65(T = 1273 K) log γas = -6.22 NCu/2+ 2.25(T = 1373 K) This study also examined the extent of the disassociation of tetratomic arsenic vapor as As, As2 and As3. The results of the analysis indicate that As2 is the predominant species when arsenic vapor, equilibrated with metallic arsenic at temperatures below 873 K, is heated to temperatures above 1273 K.

Inclusion precipitation diagram for the Fe-O-Ca-AI system

Abstract: The inclusion precipitation diagram for the Fe-O-Ca-Al system at 1823 K was developed in terms of Henrian activities from thermodynamic data. In the diagram, stability surfaces separate the O-Ca-Al saturated and unsaturated volumes and the location of a point represents the chemistry of the steel. By allowing the chemistry of the steel to change by the formation of reaction products, the sequence of precipitation of the inclusion phases can be predicted. From the inclusion precipitation diagram, projections of interphase boundaries on the Ca-Al, Ca-O and Al-O planes and the stability lines for constant aluminum contents, it was concluded that 1) the Ca:Al ratio in liquid iron determines the identity of the inclusion phases, 2) the calcium and aluminum contents can vary over a narrow range for each calcium aluminate phase, 3) in steels containing aluminum with an activity >0.01, calcium has little effect as a deoxidizer, and 4) close control of the calcium and aluminum contents is required to obtain a specific calcium aluminate inclusion phase. Activity coefficients are hypothesized that relate the ratios of the calcium and aluminum contents of liquid steel, the identity of the precipitating inclusion phases and the calculated activity ratioshCa/hAl.

Computer analysis of phase diagrams and thermodynamic properties of cryolite based systems: I. The AIF 3 -LiF-NaF system

Abstract: Calculations of the phase diagram of the AlF3-LiF-NaF system up to 35 mol pct A1F3 and of the binary subsystems are presented. For the binary LiF-NaF, AlF3-NaF, AlF3-LiF, and the quasibinary Li3AlF6-Na3AlF6 systems, thermodynamic properties of the unary and binary phases are used to numerically generate the corresponding phase diagram. The calculated and measured values are in good agreement. The broad data base thus constructed is used with equations from the conformai ionic solution theory to derivea priori phase equilibria of the AlF3-LiF-NaF system. Ternary liquidus temperatures are calculated covering compo-sitions outside the range of measurements.

Hot workability of nickel-containing alloys after reheating using sulfur-containing fuel

Abstract: The effects of fuel sulfur on the hot workability of several nickel-containing alloys have been explored in static exposures and in hot rolling trials following reheating in S-bearing. combustion atmospheres. Using thermochemical calculations, it is shown that the locus of oxidation and sulfidation potentials of such gases over practical air-fuel ratios can be made to coincide for a variety of hydrocarbon fuels, and propane doped with H2S has been used as a fuel to simulate environments resulting from firing distillate and residual oils. Nickel-base alloys containing chromium are not affected by the presence of sulfur species, and workability is independent of reheating conditions at fuel sulfur levels of up to 2 wt pct. Stainless steels may form solid subscale sulfides under air deficient heating, but there is no effect under lean firing conditions; billet workability is not influenced by sulfur. Nickel and nickel-copper alloys form liquid sulfides during air deficient heating, and very poor workability results. Sulfur is also picked up from the gas, and other properties may be affected. The thermochemical predictions for the occurrence of these liquid sulfides agree well with observations. An attempt has been made to identify safe reheating conditions (temperature and air-fuel ratio) for sensitive alloys on the basis of equilibrium combustion gas computations.