Low-temperature heat capacities of crystalline Ho(Gly)_3Cl_3·3H_2O from 78 to 348 K

Heat capacities of the rare-earth complex with glycine [Ho(Gly)3Cl3·3H2O] were measured with a high-precision automatic adiabatic calorimeter over the temperature range from 78 to 348 K.In the experimental temperature range,the heat capacities increased in a smooth and continuous manner and no phase transition or thermal anomaly occurred.Therefore,the sample was stable in the above temperature range.The values of experimental heat capacities were fitted to a polynomial equation with least square method and ...     

Isothermal compressibility,isochoric heat capacity,and intrinsic pressure of KCl-NdCl<Subscript>3</Subscript> melts

The temperature dependences of the isothermal compressibility, isochoric heat capacity, intrinsic pressure, expansion work, number of vibrational degrees of freedom, and parameter a of KCl-NdCl₃ melts are calculated from experimental data on the ultrasound velocity, density, and heat capacity of these melts.     

Sulfide capacities of fayalite-base slags

The sulfide capacities of fayalite-base slags were measured by a gas-slag equilibration technique under controlled oxygen and sulfur potentials similar to those encountered in the pyrometallurgical processing of nonferrous metals. The oxygen pressure range was from 10^−9.5 to 10⁻¹¹ MPa and the sulfur pressure range from 10⁻³ to 10^−4.5 MPa, over a temperature range of 1473 to 1623 K. The slags studied were FeO-SiO₂ at silica saturation and those with addition of CaO, MgO, and Al₂O₃ to determine their effect on sulfide capacities. For these slags, the sulfide capacities were found to vary from 10^−3.3 to 10⁻⁵. The sulfide capacities increased with increasing temperature from 1473 to 1623 K. A comparison of the reported plant data on sulfur content of industrial slags shows good agreement with the present experimental results. The present data will be useful in estimating metal losses in slag due to metal sulfide entrainment in nonferrous smelters.     

Thermodynamic Properties of Y5Sn3 over a Wide Range of Temperature

The heat capacity and enthalpy of Y₅Sn₃ were investigated in the temperature range 58-2294 K for the first time. Values of the standard enthalpy, entropy, and reduced Gibbs energy of the stannide were calculated from the low-temperature heat capacity data. The temperature dependencies of the thermodynamic functions for the solid state of Y₅Sn₃ in the range 298.15-2300 K were found. The temperature, enthalpy, and entropy of melting of the compound were determined.     

Water Capacity Model of Al2O3‐CaO‐MgO‐SiO2 Quaternary Slag System

The focus of the present work was to develop a water capacity model for the quaternary slag system Al₂O₃‐CaO‐MgO‐SiO₂. In the model, a silicate melt was considered to consist of two ion groupings, viz. cation grouping and oxygen ion. The water capacity of a melt is supposed to depend on the interactions between the cations in the presence of oxygen ions. These interactions were determined on the basis of the experimentally measured water solubility data. Only binary interactions were employed in the model. For the system CaO‐SiO₂, disagreement in the literature data was found. Since the interaction between Ca²⁺ and Si⁴⁺ would play an important role, experiments were carried out to determine the water capacities of some CaO‐SiO₂ slags. For this purpose a thermogravimetric method was employed. Iso‐lines of water capacities at constant MgO contents were predicted by the model and compared with the experimental data from literature. The model calculations agreed well with the experimental results.     

Thermodynamics of BPTI folding

A calorimetric study of the basic pancreatic trypsin inhibitor (BPTI) has been performed using the new generation of the adiabatic scanning microcalorimeters, operating in an extended temperature range of 5-130 degrees C. Precise measurements of the heat capacities of the native and unfolded states of BPTI show that the heat capacity change upon unfolding strongly depends on temperature; its value is maximal at about 50 degrees C and diminishes as the temperature is increased. The temperature dependencies of the enthalpy and entropy changes upon BPTI unfolding were found to be similar to those normally observed for other small globular proteins. The stability of BPTI has been correlated with its structure.     

Experimental study and thermodynamic calculation of Lu_2O_3-SiO_2 binary system

As a binary system of BaO-Lu_2O_3-SiO_2 ternary system, Lu_2O_3-SiO_2 system was optimized and calculated by CALPHAD approach based on available phase diagram and relevant thermodynamic data of RE_2O_3-SiO_2(RE=Lu,Yb,Y) binary systems as well as our experimental data of Lu_2O_3-SiO_2 system obtained by quenching experiment. The Gibbs free energy of high temperature solution was described by an ionic two-sublattice model as(Lu~(3+))P(O~(2-), SiO_2~0)Q. The calculated phase diagram below 1873 K was in good agreement with experimental data at 1573, 1773 and 1873 K. The calculated Gibbs energies of two intermediate phases Lu_2SiO_5 and Lu_2Si_2O_7, the activity of Lu_2O_3 and SiO_2 and specific heat capacities of intermediate phases agreed well with experimental results of Y_2O_3-SiO_2 system. This tentative study will offer help for the research of single-phase phosphor and related metallurgical slags, refractories, high-temperature superconductivity material systems.     

Influence of heat treatment on the efficiency of impact fragmentation of amorphous alloy Fe<Subscript>73.5</Subscript>Cu<Subscript>1</Subscript>Nb<Subscript>3</Subscript>Si<Subscript>13.5</Subscript>B<Subscript>9</Subscript> ribbons

The mechanism of impact fracture of soft magnetic amorphous alloy Fe_73.5Cu₁Nb₃Si_13.5B₉ ribbons in a disintegrator after heat treatment at a temperature from the range 300–700°C and the fractional composition of the formed powder are studied. The temperature ranges of a change in the mechanism of ribbon fracture are determined. The particle size distribution is shown to change weakly within the revealed temperature ranges.     

Viscosities of the Quaternary Al2O3‐CaO‐MgO‐SiO2 Slags

Viscosities of some quaternary slags in the Al₂O₃‐CaO‐MgO‐SiO₂ system were measured using the rotating cylinder method. Eight different slag compositions were selected. These slag compositions ranging in the high basicity region were directly related to the secondary steel making operations. The measurements were carried out in the temperature range of 1720 to 1910 K. Viscosities in this system and its sub‐systems were expressed as a function of temperature and composition based on the viscosity model developed earlier at KTH. The iso‐viscosity contours in the Al₂O₃‐CaO‐MgO‐SiO₂ system relevant to ladle slags were calculated at 1823 K and 1873 K for 5 mass% MgO and 10 mass% MgO sections. The predicted results showed good agreement with experimental values and the literature data.     

稀土脯氨酸高氯酸盐配合物[RE_2(Pro)_6(H_2O)_4](ClO_4)_6(RE=Pr,Er)的低温热容及热力学性质

合成了两种纯度分别是 99.2 4%和 98.2 0 %的单晶稀土脯氨酸高氯酸盐配合物 [Pr2 (Pro) 6 (H2 O) 4](Cl O4) 6 和 [Er2 (Pro) 6 (H2 O) 4](Cl O4) 6 ,对该配合物进行了热容、热重、差热和标准燃烧热等测定。在 78～ 370 K温度区 ,用高精密全自动绝热量热仪测定了热容值 ,计算机拟合得其热容对温度的多项式方程分别为 :Cp=140 7.0 8 75 1.6 7X 170 .17X2 89.5 9X3- 76 .11X4和 Cp=1317.99 6 33.0 5 X 16 3.82 X2 15 0 .2 3X3- 86 .2 1X4,[Er2(Pro) 6 (H2 O) 4](Cl O4) 6 的 Cp- T曲线有一熔化峰 ,计算熔点为 35 5 .5 5 K,熔化熵为 6 9.5 42 J/(K m ol) ,熔化焓为2 472 5 .81J/m ol。 TG、DTA技术研究了其热分解过程 ,初步分析了配合物的分解机理。燃烧热实验给出了它们的标准燃烧热分别为 1772 0 .41k J/mol和 1810 1.6 5 k J/m ol     

Solubilities of Chlorine in CaO-SiO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-MgO Slags: Correlation Between Sulfide and Chloride Capacities

To derive a correlation between sulfide and chloride capacities through our own systematic experimental studies by using a gas equilibrium technique involving Ar-H₂-H₂O-HCl gas mixtures, the solubilities of chlorine were determined for CaO-SiO₂-MgO-Al₂O₃ slags at temperatures between 1673 K and 1823 K (1400 °C and 1550 °C). As a formula to correlate sulfide and chloride capacities, the following equation that is the function of temperature only was obtainable;

A study of the sulfide capacities of iron-oxide containing slags

Sulfide capacities of iron-oxide containing slags in the “FeO”-Al₂O₃-SiO₂, “FeO”-CaO-SiO₂, “FeO”-MgO-SiO₂, and “FeO”-MnO-SiO₂ systems were experimentally determined using gas-slag equilibration technique. The experiments were conducted in a temperature range of 1673 to 1923 K. The experimental data were employed to optimize the model parameters of a sulfide capacity model developed earlier in the present laboratory. Based on these parameters, along with those obtained in previous works, an equation was suggested to predict the sulfide capacities of the “FeO”-Al₂O₃-CaO-MgO-MnO-SiO₂ slags. The results of model predictions show reasonable agreement with the experimental values of the six-component slags determined as a part of this work.     

Effect of Bath Temperature on Cooling Performance of Molten Eutectic NaNO3-KNO3 Quench Medium for Martempering of Steels

Martempering is an industrial heat treatment process that requires a quench bath that can operate without undergoing degradation in the temperature range of 423 K to 873 K (150 °C to 600 °C). The quench bath is expected to cool the steel part from the austenizing temperature to quench bath temperature rapidly and uniformly. Molten eutectic NaNO₃-KNO₃ mixture has been widely used in industry to martemper steel parts. In the present work, the effect of quench bath temperature on the cooling performance of a molten eutectic NaNO₃-KNO₃ mixture has been studied. An Inconel ASTM D-6200 probe was heated to 1133 K (860 °C) and subsequently quenched in the quench bath maintained at different temperatures. Spatially dependent transient heat flux at the metal–quenchant interface for each bath temperature was calculated using inverse heat conduction technique. Heat transfer occurred only in two stages, namely, nucleate boiling and convective cooling. The mean peak heat flux (q _max) decreased with increase in quench bath temperature, whereas the mean surface temperature corresponding to q _max and mean surface temperature at the start of convective cooling stage increased with increase in quench bath temperature. The variation in normalized cooling parameter t ₈₅ along the length of the probe increased with increase in quench bath temperature.

     

Thermal diffusivity measurements of some synthetic CaO-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-SiO<Subscript>2</Subscript> slags

In an attempt to systematize the knowledge of the heat conduction of liquid silicates, the effective thermal diffusivities of some synthetic slags containing CaO, Al₂O₃, and SiO₂ have been measured, using the three-layer laser-flash method on a differential scheme in the temperature range of 1625 to 1825 K. The effective thermal diffusivities measured, which are a combination of the phononic and photonic heat-transfer mechanisms, were found to increase with increasing temperature for all the presently investigated slags. The slag compositions were chosen in such a way that the changes in the effective thermal diffusivities would reflect the changes in the structure of the slags. It was observed that, at a CaO/Al₂O₃ molar ratio of 4.42, an increase of the SiO₂ content had very little effect on the effective thermal diffusivity values. On the other hand, addition of SiO₂ to a slag with the CaO/Al₂O₃ molar ratio of 2.59 resulted in a significant increase in the effective thermal diffusivity. The addition of Al₂O₃ to slags with a constant CaO/SiO₂ molar ratio resulted in a marked increase in the effective thermal diffusivity. Both these trends indicate that there might be an influence of the network formation in silicate melts on the effective thermal diffusivity.     

Raman spectra of crystalline and molten GdCl<Subscript>3</Subscript>

The Raman spectra of crystalline (over a wide temperature range) and molten GdCl₃ are mea- sured. The hexagonal structure C ² _6h (UClC26h₃ type) of crystalline GdCl₃ is found to change weakly over the entire temperature range under study. The temperature dependences of the characteristic frequencies change in the premelting range.     

Preparation and luminescence properties of Eu3+ doped oxyfluoride borosilicate glass ceramics

Oxyfluoride borosilicate glass with the molar composition of 60SiO2-15B2O3-15Na2O-8CaF2-2NaF-0.25Eu2O3 was synthesized by a traditional glass melting method. Glass ceramics containing CaF2 nanocrystals were prepared by heat treating the glass samples at a tem-perature in the range of 620-680 °C. The results of X-ray diffraction (XRD) indicated that the average crystallite size and the lattice constant of CaF2 nanocrystals increased with the heat treatment temperature increasing. The luminescence spectra showed that the emission intensity of Eu3+ doped glass ceramics was stronger than that of the glass matrix, and increased with the heat treatment temperature increasing. The left edge of excitation band shifted to shorter wavelength in the glass ceramics. The local environments of Eu3+ ions in the glass and glass ceram-ics were different.     

Solubilities of carbon dioxide in sodium silicate melts

Carbonate solubilities in Na₂O-SiO₂ melts were measured over the composition range X_{Na 2}O/ (X_{Na 2}O + X_{SiO 2}) = 0.5 to 1.0 and the temperature range 1100 to 1300 ‡C. The solubility increased with increasing X_Na2_O and decreased with increasing temperature. Carbonate capacities calculated from the experimental results compared favorably with values for sulfide and phosphate capacities obtained from the literature. In addition, an excellent correlation was obtained between carbonate capacity and the activity of sodium oxide. The carbonate capacity, which is an easier parameter to obtain, is a good measure of the basicity of sodium silicate melts. It would appear that carbonate capacity could be an excellent basicity index for iron and steelmaking slags as well as for fluxes used in other high temperature technologies. Formerly with University of Toronto. Formerly with the Department of Metallurgy, University of Tokyo.     

The Dissolution of Alumina in CaO‐SiO2‐Al2O3 Slags

The dissolution of alumina inclusions in CaO‐SiO₂‐Al₂O₃ based slags have been measured using laser scanning confocal microscopy (LSCM). Experiments were carried out over a temperature range of 1477 to 1577°C. It was found that diffusion coefficients calculated from the experimental results showed a dependence on the slag viscosity. This is considered strong evidence that the dissolution process is at least in part controlled by mass transfer in the slag phase. The diffusion coefficients for the alumina particles are estimated to be in the range 10^?11 to 10^?10 m²/s.     

Influence of heat treatment parameters on structure and mechanical properties of an HSLA‐100 steel

An HSLA‐100 steel received from the US Naval Research Laboratory has been characterised. The effects of heat treatment parameters such as austenitisation time and temperature, tempering time and temperature on mechanical properties have been studied. The microstructures resulting from different heat treatment conditions have been correlated with mechanical properties through SEM and TEM studies. Quantitative relationships have been developed between mechanical properties and the operational variables within a narrow range of variation of the variables by statistical design of experiments. A quantitative relationship has also been developed for the same for a wider experimental region through curve fitting technique. The best combination of strength and low‐temperature toughness was obtained in the region of 700 °C tempering temperature and 0.3 ‐ 0.4 h tempering time.     

Characterisation of 316L powder injection moulding feedstock for purpose of numerical simulation of PIM process

Abstract

Viscosity, specific heat and thermal conductivity of the standard feedstock of 316L stainless steel have been measured under the typical conditions of a real powder injection moulding (PIM) process. The viscosity was measured in a wide range of shear rates at four different temperatures. The experimental viscosity data were fitted into the Carreau-Yasuda model. Both specific heat and thermal conductivity were measured in the temperature range that overlaps the recommended processing range for the studied feedstock. It has been shown that at high cooling rates the transition temperature of the binder material is shifted towards lower temperatures. Tabulated values of thermal conductivity and specific heat for the studied feedstock are presented. The obtained data can be used for numerical simulation of the powder injection moulding process.