Thermodynamic Software Research Articles

Study on the Mechanism and Control of Clogging Growth on the Submerged Entry Nozzle of Q355 Steel

To clarify the formation mechanism of clogging on submerged entry nozzle of Q355 steel, scanning electron microscope‐energy dispersive spectrometer (SEM‐EDS), cathodoluminescence and FactSage7.1 thermodynamic software are used to study the morphology and stratified structure of Q355 steel nozzle. The results show that, clogging on Q355 steel can be divided into decarburized layer, ≈1.5 mm, dense accumulation layer, about 2 mm, and loose accumulation layer, ≈1.5 mm. The phenomenon of CaO·2Al2O3, CaO, Ti2O3, Al2O3, and 2CaO·Ti2O3 inclusions precipitated from the molten steel and deposited in the inner wall of the nozzle during continuous casting is analyzed. The formation mechanism of the clogging is explained by drawing the clogging process diagram and thermodynamic calculation. The range of total Ca content in molten steel which should be controlled between 0.0012% and 0.0016% to reduce clogging at the nozzle is given.

Distribution characteristics of trace elements (As/Cr/Mn/Cu/Pb) in the thermal fragmentation and strengthening fragmentation processes of low-rank coal with high sulfur content

The thermal fragmentation of low-rank coal had been proven to be a new way of desulfurization for char with coarse-size. However, whether harmful trace elements (HTEs) could be effectively removed in coarse-size char by thermal fragmentation action demand for further study. Two high-sulfur low-rank coals were used to explore the distribution behavior of As, Cr, Cu, Mn, and Pb in thermal fragmentation char with different particle sizes obtained by the fixed-bed and rotary kiln pyrolysis. Combined with the occurrence forms of HTEs in raw coal and volatilization characteristics of HTEs obtained by thermodynamic simulation software, the distribution of HTEs in thermal fragmentation char was analyzed. The effectiveness of thermal fragmentation of HTEs components in fixed-bed pyrolysis was reliant on high temperatures, with poor distribution resulting in less than 20 % of As, Cu, and Pb components being allocated to pulverization char. The thermal fragmentation of Cu components in disulfide form, was severely hindered by the binding effect of metaplast. In contrast, rotary kiln pyrolysis facilitated a greater distribution proportion of HTEs components into pulverization char at lower temperatures. Under optimal conditions, the distribution of As, Pb, and Cr into pulverization char surpassed 70 %. The strengthening thermal fragmentation in the rotary kiln reduce the binding effects, effectively increasing the distribution of copper-rich components into pulverized char.

Kinetics of medium-manganese steel prepared by solid-state decarburisation

This paper analyses solid-state decarburisation kinetics with the aim to clarify the transition rule of restrictive links in the process of decarburisation, providing a theoretical basis for regulating the solid-state-decarburisation rate. Experimental calculation of the Fe–Mn–C ternary alloy phase diagram using FactSage thermodynamic software, with medium manganese cast steel as the research object, experiments conducted at [Formula: see text] and a total gas flow rate of 1500 mL·min−1.The results show that the increase in manganese content has little effect on the carbon equivalent of solid solution in the γ-phase. This is because the proportion of γ-phase in the manganese cast steel decreases as the manganese mass fraction increases, but the increase in the γ-phase-carbon mass fraction makes the change in the carbon equivalent of solid solution in the small manganese cast steel plate. At 950°C, the internal diffusion of carbon in a 1 mm manganese cast steel plate has an obvious limiting effect on the decarbonisation process. When the decarburisation temperature rises to 1090°C, the effect of carbon diffusion on the whole decarburisation process decreases. The limiting factors inhibiting the whole decarbonisation process are the surface chemical reaction, that is, the temporary surface chemical reaction, as well as the internal diffusion limit of solid carbon, which leads to cementite decomposition. In the entire process of solid decarbonisation, a higher manganese content is beneficial for improving the reaction rate because, at the temperature of this experiment, manganese carbide dissolved into solid carbon, thus reducing the restrictive effect of the cementite decomposition on the decarbonisation process.

Kinetic Analysis of Molten Oxide Reduction Using Bottom-Blown Hydrogen Injection

Hydrogen-based smelting reduction has received widespread attention as an important technology for realizing low-carbon development in hydrogen metallurgy. In this study, the thermodynamics of smelting reduction was firstly analyzed by using FactSage 8.1 thermodynamic software, on the basis of which smelting reduction experiments of iron oxides by using bottom-blown hydrogen were carried out. The experiments used oxidized pellets as experimental materials, and the effects of the reduction process were analyzed in terms of the reduction temperature, the reduction time, and the hydrogen flow rate. The experimental results show that under the experimental conditions of a temperature of 1550 °C and a hydrogen flow rate of 0.2 Nm3/h, the reduction rate of iron oxides in the process of reducing iron oxides by hydrogen is significantly faster in the first 10 min than after 10 min. The hydrogen utilization rate reached a maximum of 41.87%, then decreased continuously and finally maintained at about 20%. Using the method of model fitting, it was found that the hydrogen-based molten reduction conformed to the phase boundary reaction model (Gα=1−(1−α)1/2), the corresponding mechanism function is fα=2(1−α)1/2, where α stands for the reduction conversion, and the reaction rate constant k(T) is 2.37 × 10−4 s−1 under the experimental conditions.

Effect of al content on microstructure and corrosion resistance of Zn-Al-Mg alloy

In order to solve the solidification microstructure of Zn-1.7Al-1.1Mg alloy on the surface of steel plate during hot dip plating, the solidification path and microstructure of Zn-1.7Al-1.1Mg alloy were studied by Thermo-Calc thermodynamic software, differential thermal analysis (DSC) and scanning electron microscopy (SEM). The results show that during cooling from melting to room temperature, Zn-1.7Al-1.1Mg alloy begins to precipitate Zn-rich η phase at 386.5 °C, binary eutectic structure consisting of η phase and Mg2Zn11 at 350.0 °C, and ternary eutectic structure consisting of η phase, Al-rich metastable β phase and Mg2Zn11 at 343.4 °C,at 276.7 °C, β phase transforms into stable aluminum-rich α and η phases.

Evaluation and quantification of diffusion wear between cutting chip and workpiece using forging press

The state of the interface between the workpiece and the cutting tool affects the cutting temperature and pressure on the tool surface during the cutting process. In particular, while cutting difficult-to-cut materials such as Ni-based alloy 718, the workpiece exhibits a high affinity for cutting tool materials and could easily adhere to them. Adhesion can, at times, adversely affect productivity. The diffusion between the cutting tool and the workpiece is a factor considered to contribute to the adhesion phenomenon during cutting. Addressing this issue involves choosing tool materials and coated materials with high resistance to diffusion and optimizing cutting conditions, particularly the cutting speed, which significantly impacts cutting temperature. However, because cutting tool wear comprises various forms, clarifying the effect of diffusion on tool wear remains open. In this study, to reproduce the diffusion phenomenon between cutting tool and workpiece, two pairs of test specimens were prepared: (1) cemented carbide-AISI 1045 and (2) cemented carbide-Alloy718, which could be held at high temperature under vacuum conditions by a forging press. The degree of diffusion phenomena was evaluated at each tool-work material interface, and the quantification of diffusion amount was performed by diffused element in each work material. Additionally, the theoretical analysis of the diffusion phenomenon using the thermodynamic and phase diagram calculation software Thermo-Calc was also performed.

Effect of alloying elements on coexisting phases and microstructure of M174 heat-resistant aluminum alloy

Abstract This article mainly focuses on high-power density diesel engine piston alloys, with the main component system being M174 heat-resistant aluminum alloy. On this basis, the main heat-resistant alloying elements Cu, Ni, and Fe were optimized and designed. This article is based on Thermo-Calc thermodynamic software, and comprehensively calculates and analyzes the multi-component alloy equilibrium phase diagram and Scheil non-equilibrium solidification of Al-(4-6)Cu-(1.5-3)Ni-(0.7-1.1Fe)-12.5Si-0.85Mg (mt.%) heat-resistant aluminum alloy system. Through the orthogonal experimental method of alloy composition, the phase distribution and microstructure composition of different alloy compositions are obtained. Research has found that Fe-rich phases such as Al5FeSi and Al9FeNi, as well as Ni-rich phases such as A13CuNi, A17Cu4Ni, and Al3Ni, are the main heat-resistant phases of the alloy in the temperature range of 350°C-420°C, providing important support for the high-temperature mechanical properties and creep damage resistance of piston aluminum alloy. At the same time, this article further studies the solidification history and microstructure precipitation of alloys. Fe-rich heat-resistant phases such as Al5FeSi and Al9FeNi have a higher solidification sequence. As primary and secondary phases, it is easy to generate coarse solidified structures. The organizational content is sensitive to the alloy composition. A13CuNi and A17Cu4Ni mainly precipitate in a multi-component eutectic structure, with layered and petal-shaped morphologies. The research results of this article have important theoretical significance and application value for the optimization design of high-power density piston aluminum alloy composition and the coordinated control of multi-phase structure.

Effect of P2O5 on the viscous flow and crystallisation behaviour of slag in the double slag converter steelmaking process

In the current study, the effect of P2O5 on the viscous flow and crystallisation behaviour of slag in the double slag converter steelmaking process was investigated in laboratory. The results indicated that with the increase of P2O5 content, the softening temperature, hemispherical temperature and flowing temperature of steelmaking slag showed a decreasing trend, however, the viscosity increased. The FactSage thermodynamic software was used to predict the types and contents of crystallisation phases in the crystallisation process of steelmaking slag. It showed that with the increase of P2O5 content, the precipitation content of Ca5P2SiO12 increased, while the precipitation content of melilite decreased. The composition and microstructure of crystallisation phases were analysed using X-ray diffraction and scanning electron microscopy. The phase composition did not change with the increase of P2O5 content, but the diffraction peak intensity of each crystallisation phase was different. Besides, the precipitation of phosphorus-enriched phase was enhanced with the increase of P2O5 content.

Bridging Thermochemical Technology and Ecology: Research Progress on Utilization of Factsage Software for Environmental Applications

Factsage is a robust thermodynamic calculation software that enables simulation and computation of complex multi-component and multi-phase system reactions. It has a variety of application fields such as metallurgy, energy, and environmental domains. This article elucidates the key functionalities of Factsage’s diverse modules, including Equilib, Viscosity, EpH, Reaction, and Phase Diagram modules. Furthermore, it delineates the present usage and research progress of the software in the realms of air pollution, water pollution, and solid waste treatment. By predicting the thermodynamic properties of pollutants, their chemical reactions, and complex phase changes, Factsage provides a critical scientific foundation for environmental decision-making and optimization of waste treatment processes. It showed its greater contributions to environmental protection and sustainable development.

Thermodynamics analysis and experimental investigation of EAF slag based ceramics materials for circular economy

The disposal of electric arc furnace (EAF) slag is often problematic, with most of it ending up being landfilled rather than recycled. Incorporating EAF slag into the typical clay-feldspar-quartz system to produce useful ceramics offers a potential and environmentally safer option. Thermodynamics package FactSage 8.2 was employed to predict the equilibrium-products of sintering process of EAF slag mixtures at different temperatures ranging from 600 to 1600 °C. Subsequent ceramic products were fabricated at a temperature of 1150 °C following the thermodynamic analysis by considering the fraction of liquid formation and the viscosity of the system. These products were further subjected to X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses and compared to the thermodynamic predictions. The physical performance of the products was also examined by evaluating the shrinkage, water absorption, apparent porosity, bulk density and modulus of rupture (MOR). When EAF slag was added to the base mixture, there was a positive trend of improvement in the physical properties and specifically, MOR peak value of 37.56 MPa was obtained when 40 % EAF slag was added. However, the MOR value as well as other physical properties started to decline when the base mixture had more than 40 % EAF slag. Conclusively, incorporating 40 % EAF slag improved the final product and correlated with the thermodynamic studies, process parameters, and experimental assessments of the ceramic tiles.

Prediction on Air-Nasal Mucus Partition Coefficients of Odor Compounds.

The air-nasal mucus partition coefficient is a crucial property among all of the interaction mechanisms between odor molecules and olfactory receptors, since this property contributes to our sense of smell. Due to the complexity of the mucus composition, in vivo determination of the air-mucus partition coefficient is a technical challenge. A predictable model of the air-mucus partition coefficient can provide valuable insights into the chemical properties that govern olfactory perception and can help design desired odorants. In this study, we propose a novel model based on the deep-layer neural network (DNN) algorithm to predict the air-mucus partition coefficients for a range of odor compounds. The molecular surface charge density (σ-profile) calculated from the COnductor like Screening MOdel for Real Solvents (COSMO-RS) thermodynamic package was adapted as descriptors of structural features of odor molecules. The results revealed that the air-mucus partition coefficients are highly correlated to the σ-profile of the studied compounds. The information obtained from the study provided interpretable results, which not only help in identifying the molecular features that contribute to the air-mucus partition coefficient of odorants but also aid in the design of compounds with the desired odor properties.

Melting Behavior of a CaO–SiO2–Al2O3 Flux with Varying MnO Concentration for Use in Fusion Welding of Low‐Carbon Steel

CaF2 has been a very common constituent in the fluxes used for welding of low‐carbon steel plates, owing to its strong ability to lower the liquidus temperature as well as viscosity of the molten flux. But the adverse impact of fluoride evaporation from molten slag on the health of operating personnel and the environment has prompted a worldwide effort to replace CaF2 with more benign constituents. Three compositions with varying MnO concentration in the CaO–MnO–SiO2–Al2O3 system, identified in the current work, have shown promise in terms of ability to control oxygen transfer and modify inclusion generation in the molten metal during the welding of low carbon low alloy steels. However, the melting behavior of a flux needs to be established before recommending its use for welding. Three compositions, with varying MnO concentration, are chosen in the current work. Aided by experimental measurements using high‐temperature microscopy, DTA and simulations using the commercially available thermodynamic package FactSage (version 8.3), this work aims to understand the melting characteristics of the developed fluxes. These characteristics seem to be comparable with a commercial CaF2‐containing welding flux, used as a reference for comparison. In addition, simulations using FactSage suggest that transfer of dissolved O, Si and Mn to the weld metal, while using these fluxes, would be benefitial to performance of the welded joint.

The Effect of Composition and Temperature on the Hydrogen Reduction Behavior of Sintered Pellets of Bauxite Residue-Lime Mixtures

This study explores the isothermal hydrogen reduction of sintered pellets made of a mixture of bauxite residue and calcite with varying compositions at different reduction temperatures. Sintered pellets with varying compositions show three primary iron-containing oxide phases including brownmillerite, srebrodolskite, and fayalite; however, brownmillerite is the major phase in all the sintered pellets. The sintered pellets were reduced in a thermogravimetry furnace to establish instantaneous weight reduction with respect to time. Phases and microstructural analysis were carried out using X-ray diffraction and scanning electron microscopy, respectively. Mercury intrusion porosimeter and pycnometer were utilized to assess the porosity and density of the reduced pellets. Thermochemistry calculations were performed using the thermodynamics software FactSage 8.2. The reduction rate is most pronounced at a temperature of 1000 °C for all pellet compositions. It is intriguing to note that the rate of reduction shows minimal variance across pellets with different compositions; however, the higher calcite pellets exhibit a higher initial rate of reduction. Various kinetic models were examined to determine the activation energies for three different composition pellets, and the three-dimensional diffusion model has been well suited for this process. Close activation energies in the range of 84.6 to 94.8 kJ were obtained. A slightly higher activation energy was obtained for lower CaCO3 added pellets, and it was attributed to their reduced porosity and increased sintering, impeding the reaction kinetics. There were no significant differences in the formation of mayenite with varying the calcite amount; however, higher calcite pellets indicated more mayenite formation.Graphical

Regional potential of coastal ocean alkalinization with olivine within 100 years

The spreading of crushed olivine-rich rocks in coastal seas to accelerate weathering reactions sequesters atmospheric CO2 and reduces atmospheric CO2 concentrations. Their weathering rates depend on different factors, including temperature and the reaction surface area. Therefore, this study investigates the variations in olivine-based enhanced weathering rates across 13 regional coasts worldwide. In addition, it assesses the CO2 sequestration within 100 years and evaluates the maximum net-sequestration potential based on varying environmental conditions. Simulations were conducted using the geochemical thermodynamic equilibrium modeling software PHREEQC. A sensitivity analysis was performed, exploring various combinations of influencing parameters, including grain size, seawater temperature, and chemistry. The findings reveal significant variation in CO2 sequestration, ranging from 0.13 to 0.94 metric tons (t) of CO2 per ton of distributed olivine-rich rocks over 100 years. Warmer coastal regions exhibit higher CO2 sequestration capacities than temperate regions, with a difference of 0.4 t CO2/t olivine distributed. Sensitivity analysis shows that smaller grain sizes (10 µm) exhibit higher net CO2 sequestration rates (0.87 t/t) in olivine-based enhanced weathering across all conditions, attributed to their larger reactive surface area. However, in warmer seawater temperatures, olivine with slightly larger grain sizes (50 and 100 µm) displays still larger net CO2 sequestration rates (0.97 and 0.92 t/t), optimizing the efficiency of CO2 sequestration while reducing grinding energy requirements. While relying on a simplified sensitivity analysis that does not capture the full complexity of real-world environmental dynamics, this study contributes to understanding the variability and optimization of enhanced weathering for CO2 sequestration, supporting its potential as a sustainable CO2 removal strategy.

Clays to lightweight aggregates: Thermochemical modeling and industrial validation

The creation of thermochemical models to forecast the dependent variables governing the bloatability of lightweight aggregates (LWAs) is the goal of this work. Laser particle size analysis, XRD, XRF, IR, TGA-DTA, SEM-EDX, Laser imaging system, µ-CT, hot-stage microscope and Factsage (8.3) thermodynamic software were used for clays and LWAs characterization in the temperature range 900–1250°C. It was found that the LWAs bloating zone occurs at 1050–1250°C with a minimum bulk density (BD) of (0.74 g/cm3) at 1250°C. During the LWAs pyroplastic state, the crystallization of anorthite from the silicate melt lowers its viscosity due mainly to the alkalis’ uptake into the anorthite lattice. However, the silicate melt is still viscous enough to trigger the reduction of hematite and consequently guarantees the evolution of bloating gases. The simultaneous association of higher evolved gas with less melt content of higher viscosity would promote the LWAs bloatability. The higher the gas that accompanied with low melt of lower viscosity would loosen the LWAs their consistency and sphericity upon their sudden cooling. Based on the LWAs bulk density and lab experimental observations, the production window limits of successful LWAs are ≥40 wt% silicate melt of 103-107 Pa.s viscosity that accompanied with (0.50–4.00 wt%) gas content. This production window has been verified by Liapor industrial kiln feed. The LWAs pyroplastic and post-quenching characteristics are all statistically significant variables (<0.05) for prediction modeling. The forecasting models are statistically verified by the multi-collinearity testing that shows VIF values <10 indicating the absence of any multi-collinearity among the models’ explanatory variables.

Melting and Flow Behavior of Coal Ash at High Temperatures Based on SiO2-Al2O3-CaO/Na2O Pseudoternary Phase Diagram.

The entrained-flow gasifier has a better adaptability to various coals. The composition of coal ash is an important factor affecting the high-temperature flow characteristics of molten slag. Based on the SiO2-Al2O3-CaO/Na2O ternary phase diagram, the high-temperature molten flow characteristics of slag located in the main phase regions of feldspar, melilite, diopside, and mullite were investigated by experiments and thermodynamic software calculations. The results indicate that the melting process of ash in the three phase zones is influenced by different factors. It was discovered by infrared spectroscopy analysis that the slag was dominated by Si2O52- ion clusters in the feldspar region. The slag in the diopside region had a slightly higher proportion of simple silicate ion clusters than the slag in the feldspar region, resulting in better fluidity. This is significant for revealing the mechanism of coal ash melting and flowing and guiding industrial coal blending.

Silicon regulation of the interface microstructure and shear strength of rheological cast-rolling aluminum/steel composite plates

This study reports the preparation of medium-thickness aluminum/steel composite plates with different diffusion layers using rheological cast-rolling technology. The thermodynamic software and first-principles were employed to determine the effects of different silicon contents on the solidification process and mechanical properties of the 6061 aluminum/steel composite plates. The research revealed that the Fe2Al5 phase on the steel side possessed a tongue-like preferential growth at a silicon content of less than 1.2 wt%. A granular Al–Fe–Si phase was formed on the aluminum side of the diffusion layer when the silicon content exceeded the saturation solubility (1.8 wt%), which completely suppressed the tongue-like preferential growth of the Fe2Al5 phase. First-principles calculations revealed that the matrixes showed superior toughness in comparison to binary intermetallic compounds (IMCs), while the toughness of binary IMCs surpassed that of ternary IMCs. The mechanical properties showed that the shear strength of the sample prepared by rheological cast-rolling was higher than that of composite casting and close to that of composite rolling, reaching a maximum value of 73.4 MPa. The shear strength initially increased and then decreased with an increase in isothermal diffusion time, and the fracture location was transferred from the loose FeAl3 to the Fe2Al5 phase. An increase in silicon content resulted in a slight increase in the microhardness of the diffusion layer, a delay of the peak value of the shear strength, and a reduction in the gradient of the shear strength. A substantial decrease in peak shear strength was observed when the silicon content reached 1.8 wt%.

Waste control by waste: Extraction of valuable metals from mixed metallurgical dust by boiling furnace roasting

Electric arc furnace dust (EAFD) is a hazardous waste by-product generated during the process of electric furnace steelmaking, which is rich in valuable metal elements. In order to solve the problem of environmental pollution and resource utilization of EAFD, we propose a new process for medium-temperature suspension roasting EAFD and coke dry quenching dust to extract valuable metals. The thermodynamic properties and migration behavior of valuable elements involved in the reaction were analyzed using thermodynamic simulation software FactSage8.1 and thermogravimetric mass spectrometry. The mechanism and kinetic equation of the dezincification process were investigated using the Kissinger method and Coats-Redfern model. The impact of various parameters on the process efficacy and ash fusion characteristics of the material were investigated through boiling furnace experiments. The results demonstrate that elevating the reaction temperature and decreasing the zinc partial pressure is more favorable for reducing and separating zinc. The corresponding kinetic equations for the decomposition of ZnFe2O4 and reduction of ZnO are denoted as dα/dT = 1.69 × 1012exp (−3.37 × 104/T) and dα/dT = 6.76 × 106 exp (−2.08 × 104/T) × (1 − α) [−ln(1 − α)]3/4, respectively. The optimum reaction temperature was 1050 °C, the C/O ratio was 0.8, the reaction time was 40 min, and the ventilation rate was 3500 mL/min. Under these conditions, the material had no liquid phase agglomeration, and the removal rates of zinc and lead were 93.38 % and 98.14 %, respectively. The crude zinc dust with a zinc grade of 87.57 % and the alloy slag with an iron grade of 52.38 % was obtained. The new process utilizes the excellent heat transfer characteristics and fluidization conditions of the boiling furnace to efficiently realize the high-grade recovery of valuable metals in the EAFD, which provides new insights for the clean treatment of zinc-containing waste.

Effect of gangue on CO2 emission for different decarbonisation pathways

At present, iron and steelmaking industry worldwide is going through the transition of decarbonisation to meet its goal of reaching net zero by 2050. In addition, Australian iron and steelmaking industry is facing its own challenge of processing lower grade ores with increasing gangue content. Two major pathways are direct reduction of iron – electric arc furnace pathway (DRI-EAF) and direct reduction of iron – electric smelter-BOF (DRI-electric smelter-BOF) pathway. In the present work, a mass and energy balance model of basic oxygen furnace (BOF) and electric arc furnace (EAF) have been developed using thermodynamic software. The EAF model showed that with 100 wt-% cold DRI, the specific electric energy requirement varied between 514 and 651 kWh/tls whereas in case of hot DRI, it varied between 399 kWh/tls and 510 kWh/tls. As the gangue content increased from 10.7 wt-% to 19.1 wt-%, yield decreased from 88 wt-% to 75.5 wt-% and slag weight increased from about 200 kg/tls to 630 kg/tls. The BOF model showed that the slag produced in a BOF varied between 63 kg/tls and 73 kg/tls for lower to higher grade ores reflecting different hot metal chemistry (P, Mn) coming from different ores. The results indicated that electric smelter-BOF is more compatible to process lower grade ores than EAF where quantity of slag and loss of yield are very high with increasing gangue content. CO2 emissions from H2DRI-EAF and H2DRI-electric smelter-BOF pathway for different types of ores increased with the increasing gangue content. For H2DRI-EAF pathway, as gangue content increases from 10.7 wt-% to 19.1 wt-%, CO2 emission rises from 0.10 t/tls to 0.19 t/tls as more limestone is needed to remove the gangue which also increases the production of CO2. In case of H2DRI-electric smelter-BOF pathway, CO2 emission increases from 0.12 t/tls to 0.19 t/tls with increasing gangue content. CO2 emissions from both pathways are significantly lower than the current BF-BOF pathway.

Defect-regulated synthesis of ZrB2 powders via carbon thermal reduction and elucidation of its hot-pressing densification mechanism

Through defect modulation, ZrB2 powder was controllably synthesized using the carbon thermal reduction (CTR) method, with boron powder serving as a novel additive. Thermodynamic data for the ZrO2-B2O3-C system in the presence of boron were calculated using HSC thermodynamic software. Additionally, TG-DSC thermal analysis combined with XRD was used to investigate the reaction process. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to analyze the defect structure and grain surface characteristics of the reaction products. The results indicate that the reaction of B with ZrO2 and C exothermically alters the nucleation environment of ZrB2 grains. The helical dislocations generated act as a source of crystal growth steps, promoting the growth of smooth interfaces and leading to a transformation of the ZrB2 grain growth mechanism. Quantitative calculations of the dislocation density of ZrB2 powders, using the convolutional multiple whole profile fitting (CMWP-fit), suggest that the inclusion of boron as an additive can modulate the defect concentration of the products. ZrB2 powders with varied dislocation densities were achieved through meticulously controlled synthesis methods, followed by subsequent densification via hot pressing sintering. The results indicated that the relative density of ZrB2 ceramics increased from 83.9 % to 96.7 % as the dislocation density of the powder increased from 2.7 × 1013 m−2 to 7.6 × 1014 m−2 with the rise in boron content from 0 wt% to 3 wt%. In addition, the defects create extra sintering-driving forces that induce a shift in the densification mechanism from grain boundary diffusion to dislocation slip during hot-pressing sintering. This shift results in an increase in the apparent activation energy from 105 kJ/mol to 210 kJ/mol.