Local structure of calcium silicate melts from classical molecular dynamics simulation and a newly constructed thermodynamic model

The distributions of local structural units of calcium silicate melts were quantified by means of classical molecular dynamics simulation and a newly constructed structural thermodynamic model. The distribution of five kinds of Si-O tetrahedra Q_i from these two methods was compared with each other and also with the experimental Raman spectra, an excellent agreement was achieved. These not only displayed the panorama distribution of microstructural units in the whole composition range, but also proved that the thermodynamic model is suitable for the utilization as the subsequent application model of spectral experiments for the thermodynamic calculation. Meanwhile, the five refined regions mastered by different disproportionating reactions were obtained. Finally, the distributions of two kinds of connections between Q_i were obtained, denoted as Q_i-Ca-Q_j and Q_i-[O_b]-Q_j, from the thermodynamic model, and a theoretical verification was given that the dominant connections for any composition are equivalent connections.     

Raman spectroscopy of flowing poly(ethylene terephthalate) melts

Studies have been made of the Raman spectrum of a poly(ethylene terephthalate) melt being extruded through a glass die. The effects observed in the spectrum are interpreted in terms of changes in molecular shape which vary with shear rate and melt temperature.     

HIGH SHEAR VISCOMETRY—AN OVERVIEW

An overview is presented of high shear viscometry, namely the viscous behavior of viscoelastic fluids in the second Newtonian region. Important theories are discussed and the contributions of Edward Merrill in the area are presented.     

Micro-inhomogeneous structure of liquid Al-Fe alloys

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RHEOLOGICAL BEHAVIOR OF POLYMER MELTS (I) UNIFIED MOLECULAR THEORY OF NON-LINEAR ISCOELASTICITY WITH CONSTRAINTS OF GAUSSIAN CHAIN ENTANGLEMENT FOR POLYMER MELTS

An approach with statistical mechanics and a unified molecular theory of non-linearviscoelasticity with constraints of Gaussian chain entanglement for polymer melts were proposed.Amultimode model structure for a single polymer chain with tail segments and N reversibleentanglement sites on the test polymer chain was developed.The probability distribution function ofthe end-to-end vector for a single polymer chain at entangled state and the viscoelastic free energyof deformation for polymer melts were calculated.Four types of stress-strain relationship and mem-ory function were derived from this theory.The above theoretical relationships were verified by experi-mental data of PS(polystyrene)and LDPE(low density polyethylene)melts.     

Crystal growth nucleation and Fermi energy equalization of intrinsic spherical nuclei in glass-forming melts

Abstract

The energy saving resulting from the equalization of Fermi energies of a crystal and its melt is added to the Gibbs free-energy change ΔG_2ls associated with a crystal formation in glass-forming melts. This negative contribution being a fraction ε _ls(T) of the fusion heat is created by the electrostatic potential energy ?U₀ resulting from the electron transfer from the crystal to the melt and is maximum at the melting temperature T_m in agreement with a thermodynamics constraint. The homogeneous nucleation critical temperature T₂, the nucleation critical barrier ΔG_2ls?/k_BT and the critical radius R?_2ls are determined as functions of ε_ls(T). In bulk metallic glass forming melts, ε_ls(T) and T₂ only depend on the free-volume disappearance temperature T_0l, and ε_ls(T_m) is larger than 1 (T_0l>T_m/3); in conventional undercooled melts ε_ls(T_m) is smaller than 1 (T_0l>T_m/3). Unmelted intrinsic crystals act as growth nuclei reducing ΔG_2ls?/k_BT and the nucleation time. The temperature-time transformation diagrams of Mg₆₅Y₁₀Cu₂₅, Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5, Pd₄₃Cu₂₇ Ni₁₀P₂₀, Fe₈₃B₁₇ and Ni melts are predicted using classic nucleation models including time lags in transient nucleation, by varying the intrinsic nucleus contribution to the reduction of ΔG_2ls?/k_BT. The energy-saving coefficient ε _nm(T) of an unmelted crystal of radius R_nm is reduced when R_nm ?R?_2ls; ε_nm is quantified and corresponds to the first energy level of one s-electron moving in vacuum in the same spherical attractive potential ?U₀ despite the fact that the charge screening is built by many-body effects.     

非铁合金方法冶炼不锈钢母液

采用转炉或高炉方法冶炼含铬铁水可以降低不锈钢生产的成本。总结了国内开展的铁浴熔融还原和高炉过程生产不锈钢母液工业试验的结果,着重分析了高炉冶炼含铬铁水的热力学优势和操作顺行的条件,并讨论了铬矿石在高炉内的反应机理。对工业试验中焦比和铁水磷含量高的情况提出了改进的措施。     

A Chemical Approach of the Molecular Entity Vacancy Model to the CaO‐Al2O3‐SiO2 Ternary Silicate Melt

A chemical approach of the molecular entity vacancy model (MEVM) to the CaO‐Al₂O₃‐SiO₂ ternary silicate melts has been suggested. The activities of all components in the melts were simultaneously predicted by using only the binary parameters of its sub‐binary melts which were determined by fitting the activities of their two components. The results indicated that the predicted values of activity of SiO₂ were in good agreement with the experimental data at both temperatures 1823 K and 1873 K, and those of CaO and Al₂O₃ were in reasonable agreement with the experimental data at 1823 K and were smaller than the graphical integration data of the Gibbs‐Duhem equation at 1873 K. The approach may be extended to some solution systems with the chemical interaction.     

TiCxO1-x 在450℃LiCl-KCl体系中的阳极电化学行为研究

采用化学、电化学—气相质谱分析联用等方法详细研究了TiCxO1-x固溶体在450℃LiCl-KCl熔盐体系中的阳极溶解行为和机理。研究结果表明,TiCxO1-x固溶体在450℃时具有优异的导电性能,与在750℃NaCl-KCl体系中相同,TiCxO1-x固溶体在LiCl-KCl体系450℃下可发生电化学溶解,Ti以低价钛离子的形式溶入熔盐中,同时C和O以CO的气体形式放出。