ASSESSMENT AND OPTIMIZATION OF THE PHASE DIAGRAMS AND THERMODYNAMIC DATA OF SOME BINARY SYSTEMS CONTAINING PRASEODYMIUM CHLORIDES

In this paper a critical assessment and optimization of the phase diagrams and thermodynamic properties of the PrCl_3-MCl(M=Li,Na)and PrCl_3-MCl_2(M=Mg,Ca,Sr,Ba) binary systems have been per- formed.The assessed and optimized binary phase diagrams and thermodynamic data with self consistency are a better basis for constructing multicomponent phase diagrams.

FactSage Thermodynamic Database for Steelmaking Refractory Research

Thermodynamic databases are very useful to analyze the complex chemical reactions happening in high temperature material processes. An accurate thermodynamic database based on physically sound thermodynamic models can provide thermodynamic calculations of useful phase diagrams and comprehensive chemical reactions related to refractory corrosion in steelmaking processes. In this study,the FactS age thermodynamic database,one of the most comprehensive thermodynamic databases for oxide systems among other commercial software,is reviewed in particular for the steelmaking refractory research,and several applications to refractory corrosion are presented.

Thermodynamic Analysis of Chemical Vapor Deposition of BCl_3-NH_3-SiCl_4-H_2-Ar System

The thermodynamic phase stability area diagrams of BCl3-NH3-Si Cl4-H2-Ar system were plotted via Factsage software to predict the kinetic experimental results. The effects of parameters(i e, partial pressure of reactants, deposition temperature and total pressure) on the distribution regions of solid phase products were analyzed based on the diagrams. The results show that:(a) Solid phase products are mainly affected by deposition temperature. The area of BN+Si3N4 phase increases with the temperature rising from 650 to 900 ℃, and decreases with the temperature rising from 900 to 1 200 ℃;(b) When temperature and total pressure are constants, BN+Si3N4 phase exists at a high partial pressure of NH3;(c) The effect of total system pressure is correlated to deposition temperature. The temperature ranging from 700 to 900 ℃ under low total pressure is the optimum condition for the deposition.(d) Appropriate kinetic parameters can be determined based on the results of thermodynamic calculation. Si–B–N coating is obtained via low pressure chemical vapor deposition. The analysis by X-ray photoelectron spectroscopy indicates that B–N and Si–N are the main chemical bonds of the coating.

Thermodynamic Assessments of Ternary Ga-As-P,Ga-P-Sb,In-As-P and In-P-Sb Systems

The experimental phase diagram data of the Ga-As-P,Ga-P-Sb,In-As-P and In-P-Sb ternary systems were critically assessed. A set of self-consistent thermodynamic model parameters were obtained and used to describe the phase equilibria of these systems. In most cases, the calculated values agree very well with the experimental data.

INFLUENCE OF ALCOHOL-BASED NONSOLVENTS ON THE FORMATION AND MORPHOLOGY OF PVDF MEMBRANES IN PHASE INVERSION PROCESS

Through the preparation of PVDF membranes using various nonsolvent coagulation baths following the phase inversion process, the influence of alcohol-based nonsolvents on the formation and structure of PVDF membranes were investigated. The light scattering and light transmission measurements were used to characterize the equilibrium phase diagram and the gelation speed, respectively. The locations of the crystallization-induced gelation boundaries for various systems and precipitation processes were explained from the corresponding thermodynamic and kinetic parameters. It was found that the better affinity between alcohol-based nonsolvents and DMAc solvent caused the gelation boundaries further away from the PVDF-DMAc axis with the coagulation bath varying from water, methanol, ethanol to iso-propanol. Due to the lower exchange rate of DMAc and alcohols, the delayed demixing took place for the membrane-forming using alcohols as baths, and the delayed time became longer when the coagulation bath was changed from methanol, ethanol to iso-propanol. The characterization results of membranes indicate that the influence of nonsolvents on the phase diagram and the precipitation process are in agreement with those on the membrane morphology. The better thermodynamic stability and a low exchange diffusion rate of PVDF/DMAc/alcohols favor the liquid-solid phase separation in gelation process, and therefore yield the membranes with a porous upper surface, a particular bottom surface and symmetrical structure.

Order of sphalerite and galena precipitation: A case study from lead-zinc deposits in southwest China

Most of the lead and zinc deposits in Southwest China, are characterized by mineral zoning, which is especially true for the Huize and Zhaotong deposits. The mineral assemblage zoning is consistent for both horizontal and vertical zoning, from the base(center) of the ore body to the top(outermost), the mineral zones are as follows. I-1: coarse-grained pyrite and a little puce sphalerite;I-2: brown sphalerite, galena, and ferro-dolomite;I-3: galena, sandy beige and pale yellow sphalerite, and calcite;and I-4: fine-grained pyrite, dolomite, and calcite. Among them, sphalerite is the landmark mineral of different zoning. From I-1 to I-3, the color of sphalerite changes from dark to light, its crystalline size changes from coarse to fine, and its structure changes from disseminated to veinlet. This mineral zoning is seen not only on a microscopic scale, but is also clear on a mesoscopic and macroscopic scale. It is caused by the order of the sphalerite and galena precipitation. We studied the metallic minerals and fluid inclusions using a thermodynamic phase diagram method, such as lgfO2–lgfS2, pH–lgfO2, pH–lg[Pb^2+] and pH–lg[HS^-], discussed the constraints on the order of the sphalerite and galena precipitation in the migration and precipitation process of lead and zinc under different pH values, oxygen fugacity, sulfur fugacity, and ionic activity. We also explain the formation mechanism and propose that the main controlling factor of the order of the sphalerite and galena precipitation is sulfur fugacity.

Thermodynamic and Phase Diagram Modeling of CsF-MF4（M=U, Th） Systems

Phase diagrams for the CsF-UF4 and CsF-ThF4 systems were modeled in the present work through computational thennodynamics. The associate solution model with various complex species（CsMFs, Cs2MF6 and Cs3MF7; M=Th, U） was used to thermodynamically describe the binary molten salts. A total of ten intermediate phases were treated as stoichiometric compounds with their Gibbs energies modeled according to the Neumann-Kopp rule. All these model parameters were optimized by the least squares procedure until good coincidence was achieved between the calculated results and most of the experimental data. The derived thermodynamic parameters will be merged into the multicomponent CsF-LiF-BeF2-ThF4-UF4 database for analyzing physicochemical behavior of CsF in the fuel salt of the molten salt breeder reactor.

Experimental study and thermodynamic calculation of Lu2O3-SiO2 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.

二维有序碳氮材料选择性生长的衬底调控机制

Two-dimensional(2D)ordered carbon–nitrogen binary compounds(C_(x)N_(y))show great potential in many fields owing to their diverse structures and outstanding properties.However,the scalable and selective synthesis of 2D C_(x)N_(y)compounds remain a challenge due to the variable C/N stoichiometry induced coexistence of graphitic,pyridinic,and pyrrolic N species and the competitive growth of graphene.Here,this work systematically explored the mechanism of selective growth of a series of 2D ordered C_(x)N_(y)compounds,namely,the g-C_(3)N_(4),C_(2)N,C_(3)N,and C_(5)N,on various epitaxial substrates via first-principles calculations.By establishing the thermodynamic phase diagram,it is revealed that the individualized surface interaction and symmetry match between 2D C_(x)N_(y)compounds and substrates together enable the selective epitaxial growth of single crystal 2D C_(x)N_(y)compounds within distinct chemical potential windows of feedstock.The kinetics behaviors of the diffusion and attachment of the decomposed feedstock C/N atoms to the growing C_(x)N_(y)clusters further confirmed the feasibility of the substrate mediated selective growth of 2D C_(x)N_(y)compounds.Moreover,the optimal experimental conditions,including the temperature and partial pressure of feedstock,are suggested for the selective growth of targeted 2D C_(x)N_(y)compound on individual epitaxial substrates by carefully considering the chemical potential of carbon/nitrogen as the functional of experimental parameters based on the standard thermochemical tables.This work provides an insightful understanding on the mechanism of selective epitaxial growth of 2D ordered C_(x)N_(y)compounds for guiding the future experimental design.

Manipulating single oxygen at Cu_(2)O-island surfaces through thermomechanical coupling

Single oxygen diffusion event,the most favorable rate-limiting process of epitaxial Cu_(2)O oxide-island layerby-layer growth kinetics,may lead to oxygen defects due to thermomechanical coupling.However,the formation rules of oxygen defects remain unclear,preventing the realization of controllable oxygen defects on oxide-island surfaces.Here,we utilize the first-principles method to investigate the formation rules of intrinsic oxygen defects in the surface layers of prototypical metal-oxide(Cu_(2)O)surfaces under thermomechanical coupling effects.We establish the thermodynamic phase diagram for oxygen-defect-modulated Cu_(2)O surfaces,enabling the prediction of the growth of oxide islands during Cu oxidation,which aligns closely with in-situ environmental transmission electron microscopy(ETEM)experiment observations.By exploring the strain-modulated phase diagrams,we propose a potential strategy for controlling the type and concentration of oxygen defects on oxide-island surfaces.Our findings provide an effective approach to theoretically understanding the oxidation process of metal surfaces,thus enabling the computational design of high-performance corrosion-resistant surfaces.