The aging of the global population has resulted in a significant increase in the incidence of bone and joint defects. Hydroxyapatite (HAP) exhibits remarkable biocompatibility and other advantageous properties. Consequently, it is extensively employed as a surface coating for titanium and various other substrates, including stainless steel and ceramics, to address joint defects. This application of HAP in the context of orthopedic repair is of significant importance in the field of biomedical engineering. Currently, the preparation of industrial-grade HAP mainly relies on chemically pure reagents, leading to the excessive consumption of natural mineral resources and making it difficult to reduce the production cost. Steel converter slag, as the main solid waste of steel converter steelmaking, has a Ca content of 40%- 60% which exists mostly in the water-soluble phase, making it an ideal source of Ca for HAP preparation. This study was carried out for the selective extraction of Ca from steel slag, the synthesis of steel slag-derived nano-HAP microsphere powders, and the preparation of related coatings. The results demonstrate that the selective leaching of Ca can be achieved by employing a 0.5 mol/L acetic acid solution, controlling the liquid-to-solid ratio at 5:1, and conducting the leaching process at 45 degrees C for 30 min. Moreover, well-dispersed spherical nano HAP particles were prepared via the template-assisted hydrothermal synthesis method. Among the tested spraying distances, 70 mm gave the best bonding strength, but coating uniformity was not yet satisfactory. A novel process of HAP coating material preparation from steel slag was proposed in this work.

ABSTRACT The CaO–SiO 2 –La 2 O 3 system serves as a foundational La‐containing system for materials science, mineral processing, and metallurgical engineering. The phase diagram is indispensable for the thermodynamic database of multicomponent RE‐containing slag systems. In this paper, we employed high‐temperature equilibrium experiments and quenching methods, followed by EPMA and WDS to determine the morphology, composition, and type of equilibrium phases in the CaO–SiO 2 –La 2 O 3 system, respectively. Combining current work and literature data, the isothermal sections at 1600°C (including 3 three‐phase fields, 4 two‐phase fields, and a liquid phase field) and at 1500°C (including 3 three‐phase fields, 4 two‐phase fields, and a liquid phase field) were clarified. The liquidus projection of the CaO–SiO 2 –La 2 O 3 system with primary phase fields and Alkemade lines was obtained. Subsequently, the types and possible temperature ranges of the univariant lines and invariant points were discussed.

Precipitation behavior of Ti-containing inclusions play an important role in the wear resistance and mechanical strength of high-titanium wear-resistant steel. In this study, the evolution of inclusions during the solidification of high-titanium wear-resistant steel with La treatment was systematically investigated through high-temperature simulation experiments combined with thermodynamic calculations. The results show that under the La→ Ti addition condition, the precipitation sequence of inclusions in the steel during solidification was: oxide→ Ti(C,N)→ (Mo,Ti)C→ Ti4C2S2. With increasing La content, the oxide inclusions formed in the steel were Al2O3, LaAlO3 and La2O2S, respectively. When La treatment was conducted after Ti alloying, the overall precipitation sequence remained basically unchanged; however, Ti4C2S2 inclusions did not form, and (Mo,Ti)C inclusions, exhibiting the highest number density, were significant refined to an mean size of 2.76 m, compared to 5.84 μm in Al-deoxidation steel, 5.61 μm in 0.0032% La-treated steel and 4.08 μm in 0.03% La-treated steel under La→Ti condition. This refinement may attribute two main factors: thermodynamically, La delays the precipitation of TiC and reacts with sulfur to promote the formation of La2O2S, thereby suppressing the formation of Ti4C2S2; and according to edge-to-edge matching model, La₂O₂S can act as an effective heterogeneous nucleation site for TiC with a preliminarily predicted orientation relationship: . From the perspective of inclusion engineering, La treatment applying to the Ti-alloyed molten steel refines the Ti-containing inclusions during the solidification, thereby potentially improving the properties of the high titanium wear resistant steel

Phase diagram data for the basic CaO-SiO 2 -CeO 2 ceramic system can provide theoretical basis and data support for the discovery of potential Ce-based material species, material composition design, material preparation conditions, and the establishment of rare earth-related thermodynamic databases. In this study, we employ hightemperature equilibrium experiments and quenching method conducted at 1600/1500/1400 degrees C in air atmosphere followed by EPMA, WDS and XRD to determine the morphology, composition and type of equilibrium phases in the CaO-SiO 2 -CeO 2 ceramic system, respectively. Based on the experimental results, three isothermal sections were clarified. In addition, CaO center dot 3SiO 2 center dot 2Ce 2 O 3 and Ce 2 O 3 center dot 2SiO 2 can exist stably in a high-temperature air atmosphere; no tetravalent cerium-containing compounds were observed in this system.

To efficiently recover crucial elements from the Bayan Obo polymetallic associated ore, this study employed hydrogen reduction to selectively reduce iron minerals and transform the mineral phases and valence states of niobium and titanium. After iron was recovered by magnetic separation, oxalic acid was used as a leaching agent to extract niobium and titanium. Thermodynamic analysis reveals that, within the temperature range of 500 degrees C to 1200 degrees C, the reduction of iron oxides occurs prior to that of niobium and titanium oxides, and stronger reducing conditions enable complete conversion of iron oxides to metallic iron. Under pure hydrogen conditions, niobium and titanium are reduced to a lower valence state. Hydrogen reduction roasting experiments demonstrated that this process disrupted the original mineral phases, transforming the dominant minerals from aegirine, hematite, and magnesio-riebeckite to fayalite and metallic iron, and forming new Nb-bearing and Ti-bearing mineral phases. Compared to direct oxalic acid leaching without hydrogen reduction, the leaching efficiencies of niobium and titanium were significantly enhanced following hydrogen reduction, while iron leaching was effectively inhibited. Following the recovery of iron through hydrogen reduction and magnetic separation, the leaching efficiencies of niobium and titanium reached 83.2% and 99.3%, respectively, under optimal conditions: a temperature of 95 degrees C, an oxalic acid concentration of 2 mol/L, a liquid-to-solid ratio of 20:1 mL/g, and a leaching time of 7 h. In contrast, the leaching efficiency of iron was only 5.94%.

The wettability between inclusions and molten steel are critical factors influencing the formation of large inclusion clusters. In this study, Ti-based oxide inclusions in steel were analyzed through thermodynamic calculations, and steels equilibrated with these inclusions were prepared. Subsequently, various Ti-based oxide inclusions substrate were prepared using a three-step route consisting of pressing, vacuum sealing, and high-temperature sintering. Their interfacial behaviors with molten steel were investigated by a sessile drop method combined with vacuum sealing. The results indicate that Ti2O3 inclusion formed in Ti-deoxidized steel, whereas pseudobrookite-type Al-Ti-O inclusions with an Al/Ti ratio of about 1:2, corresponding to Al2O3·4/3Ti3O5 formed in Al-Ti complex deoxidized steel. Both the Ti2O3 and Al2O3·4/3Ti3O5 substrates exhibited non-wetting behavior with molten steels, yielding average contact angles of 131.4° and 108.32°. In contrast, the TiO2 substrate was wetted by the Ti-deoxidized molten steel with a contact angle of 85.57° and showed clear evidence of erosion. No intermediate reaction layers were observed at any of the substrate-steel interfaces. Furthermore, an evaluation of agglomeration behavior based on the measured interfacial properties demonstrates that the pseudobrookite phase possesses a smaller contact angle than both Ti2O3 and Al2O3, which results in a weaker agglomeration tendency. Therefore, controlling the steel composition to favor the formation of the pseudobrookite phase can effectively suppress the clustering of large inclusions and thereby alleviate nozzle clogging during the continuous casting process.

The flow of molten steel at the solidification front in a continuous casting mold has a significant impact on slab quality. However, due to the high temperature and opacity of the mold, direct velocity measurements are extremely challenging. The functional relationship between flow speed at the solidification front and the temperature of the outer surface of the solidified shell is derived heat conduction equations. Subsequently, a coupled flow-heat transfer-solidification model for the mold is developed to numerically determine the flow speed and temperature distribution. Based on thermocouple installation positions and the impingement point location of the molten steel jet on the narrow face of the mold, 33 sampling points are selected along both the narrow/wide face centerline and corresponding heights at the solidification front. Finally, the flow speed at the solidification front is fitted as a function of the outer surface temperature of solidified shell and the distance from the meniscus, with detailed analysis of its distribution characteristics.

Rare earth silicate materials have been widely applied in various fields due to their excellent comprehensive properties. With the aim of developing novel rare-earth silicate materials and evaluating their performance under various preparation and service conditions, this work adopted the high-temperature equilibrium and quenching method to investigate the phase equilibria of the MgO-SiO2-La2O3 and MgO-SiO2-Ce2O3 systems at 1600 °C. Combined with scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron probe microanalysis (EPMA), the corresponding isothermal sections were constructed. The solid solubility limit of MgO in rare earth silicates was clarified, and the distribution characteristics of phase fields were also revealed.

To address the problem of excessive sulfur in high-sulfur magnetite concentrates when used directly, this study systematically investigated the desulfurization behavior and mechanism during oxidative roasting. Green pellets were prepared by mixing high-sulfur iron concentrate fines with 1% bentonite, followed by roasting experiments in air at 800–1200 °C. Thermogravimetric analysis (TG), real-time flue gas analysis (DOAS), X-ray diffraction (XRD), and scanning electron microscopy–energy dispersive spectroscopy (SEM–EDS) were employed to characterize the process and products. The results show that sulfur release is mainly concentrated in two stages: intensive oxidative decomposition of FeS/FeS2 in the range of 480–580 °C and release of reacted sulfur originally encapsulated within the pellets in the range of 940–1080 °C. It was found that alkali metal oxides CaO and MgO in the feed can fix sulfur at a high temperature. They react with released SO2 and iron oxides to form Ca/Mg sulfate–iron oxide composite phases, such as (Ca0.75Mg0.25)SO4·0.38Fe2O3 and (Ca0.91Mg0.09)SO4·3.66Fe2O3·1.47MgO, which slow the SO2 emission rate. A desulfurization ratio above 99% can be achieved when roasting at 1100 °C and above. This study clarifies the sulfur migration mechanism during the roasting of high-sulfur iron concentrate pellets, providing a theoretical basis for optimizing the roasting process to achieve efficient desulfurization and recovery of iron resources.

The CaO-SiO2-La2O3 system serves as a foundational La-containing system for materials science, mineral processing, and metallurgical engineering. The phase diagram is indispensable for the thermodynamic database of multicomponent RE-containing slag systems. In this paper, we employed high-temperature equilibrium experiments and quenching methods, followed by EPMA and WDS to determine the morphology, composition, and type of equilibrium phases in the CaO-SiO2-La2O3 system, respectively. Combining current work and literature data, the isothermal sections at 1600 degrees C (including 3 three-phase fields, 4 two-phase fields, and a liquid phase field) and at 1500 degrees C (including 3 three-phase fields, 4 two-phase fields, and a liquid phase field) were clarified. The liquidus projection of the CaO-SiO2-La2O3 system with primary phase fields and Alkemade lines was obtained. Subsequently, the types and possible temperature ranges of the univariant lines and invariant points were discussed.

The Al2O3-SiO2-CeOx system is one of the basic rare-earth (RE)-containing ceramic systems. The phase diagram of this system is useful for the research and development of related processes (e.g., metallurgical, material, mining and other technological); moreover, it is also indispensable for the thermodynamic database of multi-component RE-containing ceramic systems. In this study, we employed high-temperature equilibrium experiments and quenching methods followed by EPMA (electron probe microanalysis), WDS (wavelength dispersive spectroscopy) and XRD (X-ray diffraction) to determine the morphologies, composition and type of equilibrium phases in the Al2O3-SiO2-Ce2O3 system (reducing atmosphere) and Al2O3-SiO2-CeO2 system (air atmosphere) at 1500 degrees C. Based on the experimental results, the isothermal sections of the Al2O3-SiO2-Ce2O3 system (including seven three-phase fields, seven two-phase fields and a liquid phase field) and Al2O3-SiO2-CeO2 system (including five three-phase fields, five two-phase fields and a liquid phase field) at 1500 degrees C are clarified.

The moderate slag foaming is required for the intelligent control of metallurgy, the separation of slag and metal, and the removal of impurity elements. The investigation elucidated the effects of temperature and iron oxide content on the foaming behavior of slag through high-temperature experiment via the slag microstructure. As the temperature elevated from 1400 OC to 1600 OC, the acceleration of gas released by slag/metal reaction increased the foaming rate and maximum foaming height of the slag, and slag depolymerization of silicon-oxygen structural units caused a rapid collapse of the foamed slag with non bridging oxygen number rising from 3.01 to 3.97. Raising the iron oxide addition from 10% to 30% depolymerized the silicon-oxygen groups, thereby leading to an increase in the mole fraction of low-polymerization-degree silicon-oxygen structures from 86% to 98%. Accordingly, the foaming rate and the maximum foaming height of the slag exhibited an increasing trend with rising of the reaction rate of slag/metal with reactant iron oxide being added. The increase in the relative area of ferric-oxygen tetrahedron in the ferric-oxygen groups from 93% to 98% improved the stability of the foamed slag to a certain extent. The research results provide an important reference for the regulation of foaming behavior.

For continuous casting of strong reducing steels, the low-reactive aluminate-based mold flux consisting of CaO-SiO2-Al2O3-CaF2-Li2O-B2O3-Na2O with low SiO2 content was designed. The correlation between the melt structure under high temperature and the crystallization phases during the cooling process and the change of viscosity was analyzed. The following conclusions were obtained. The polymerization degree of the mold flux consistently decreased as the w(CaO)/w(Al2O3) ratio increased from 0.93 to 1.65. Due to melt structure depolymerization, the viscosity at 1300 degrees C dropped from 0.132 Pa & centerdot;s to 0.054 Pa & centerdot;s. As the w(CaO)/w(Al2O3) ratio increases near the breaking temperature, the crystalline phases in the mold flux transition from LiAlO2 to Ca2Al2SiO7, and finally to a combination of Ca12Al14O32F2 and LiAlO2. The rapid viscosity increase at the breaking temperature was primarily due to the precipitation of these phases. Furthermore, influenced by the changes in crystallization tendency and crystalline phase precipitation, the breaking temperature first decreased and then increased. Increasing the Li2O mass fraction from 5% to 9% led to a decrease in the polymerization degree of the mold flux. Due to the depolymerizing impact of Li2O on the slag network, the mold flux viscosity at 1300 degrees C decreased from 0.102 Pa & centerdot;s to 0.047 Pa & centerdot;s. The breaking temperature of the mold flux rose notably with a higher Li2O mass fraction. At the breaking temperature, the crystalline phases in the mold flux transition from Ca2Al2SiO7 to a combination of LiAlO2 and Ca12Al14O32F2. The precipitation of these phases at the breaking temperature directly caused a rapid increase in viscosity. The results systematically reveal the coupling mechanism between melt structure, crystalline phase evolution, and viscosity variation of low-SiO2 aluminate-based mold flux, which provides an important theoretical basis for composition design and performance regulation of mold fluxes for high-aluminum steel continuous casting.

Industrial solid waste is an abundant but underexploited feedstock for advanced materials production. Herein, we develop a scalable strategy for the high-value utilization of flue gas desulfurization gypsum from Baotou Iron and Steel Group. We converted it into high-aspect-ratio (∼160) calcium sulfate whiskers (CSWs) via a hydrothermal route and modified their interfacial compatibility using stearic acid with an optimal concentration of 4 wt%, under which the modified CSWs exhibit an activation index of 0.618 and a water contact angle of 108°. When they are added to ultra-high-molecular-weight polyethylene (UHMWPE) as a reinforcement phase, the stiffness and toughness of the composite are enhanced, showing a maximum elongation at break of 331.16%, unchanged yield strength, improved flexural performance, and notched impact strength exceeding 70 kJ·m -2 . These results demonstrate the technical feasibility of transforming flue gas desulfurization gypsum into calcium sulfate whiskers for polymer reinforcement, offering an environmental and economical pathway for industrial solid waste valorization and advanced composite fabrication.

Rare-earth aluminates/silicates are currently widely employed in ceramic matrix composites, environmental barrier coatings, luminescent materials, refractory materials, and other fields. The phase diagram of the representative RE-containing ceramic system Al2O3-SiO2-CeOx provides a basis for the preparation of relevant RE materials, supports the identification of potential RE-containing compounds, and offers data support for the thermodynamic databases of multicomponent RE-containing ceramic systems.In this study, we employed high-temperature equilibrium experiments and quenching methods followed by EPMA, WDS and XRD to determine the morphologies, composition and type of equilibrium phases in the Al2O3-SiO2-Ce2O3 system (reducing atmosphere) and the Al2O3-SiO2-CeO2 system (air atmosphere) at 1600 °C. Within the composition range of the present study, a total of 19 phase fields in the isothermal sections of the two systems were determined by phase equilibrium experiments.

Elucidating the agglomeration behavior of inclusions is critical for optimizing the quality of high-manganese and high-aluminum steels. This study predicted the precipitation behavior of inclusions using thermodynamic modeling. Six experimental groups with different Mn and Al contents were designed to obtain specific inclusions, and their agglomeration was observed in situ via confocal laser scanning microscopy (CLSM). Capillary forces were quantified using a theoretical model. The results showed the agglomeration tendency order: AlN (in Fe-30Mn-6Al melt) > AlN (in Fe-30Mn-3Al melt) > AlN (in Fe-10Mn-3Al melt) > Al2O3 (in Fe-10Mn-0.2Al melt) > Al2O3 (in Fe-30Mn-0.2Al melt) > Al2O3 (in Fe-30Mn-0.5Al melt). With increasing Al content, the capillary force of Al2O3 inclusions first increased from 5.75 & times; 10(-19) N to 6.22 & times; 10(-19) N and then decreased to 1.34 & times; 10(-19) N. A similar trend occurred with rising Mn content: from 5.75 & times; 10(-19) N to 6.52 & times; 10(-19) N, then to 6.01 & times; 10(-19) N. In contrast, the capillary force of AlN inclusions continuously increased from 4.1 & times; 10(-19) N to 8.29 & times; 10(-19) N with higher Mn and Al contents. A critical relationship between Mn and Al contents, which determines the transition in dominant capillary force, was established: y((Mn,mass%)) _ - 31.38x((Al,mass%)) + 97.27. This study provides theoretical guidance for regulating inclusion size distributions in high-manganese and high-aluminum steels.

[Objective]The hydrothermal method has attracted attention in recent years as an effective method for producing inorganic single crystals.The liquid-solid ratio emerges as a key parameter influencing the growth of gypsum crystals at hydrothermal conditions,with direct implications for product quality,energy consumption,and production efficiency.[Method]Herein,sintered flue gas desulphurization gypsum is adopted as raw materials to explore the effect of liquid-solid ratio on the preparation of columnar gypsum crystals at hydrothermal conditions.[Result]The raw materials consist of calcium sulfate dihydrate with various morphologies and diameters,including prismatic,lamellar,and column,as well as agglomerated silicate phases.However,after hydrothermal treatment,these desulfurization gypsum particles with different sizes can grow into columnar single crystal hemihydrate gypsum with controllable morphology.With increase in liquid-solid ratio,the compactness of crystal surface increases,pore defects disappear,and the length-diameter ratio is shortened gradually.[Conclusion]In order to produce densely compact,short columnar hemihydrate gypsum with an aspect ratio of approximately 2∶1,the optimal liquid-solid ratio is 10∶1.These findings offer substantial insights into regulating the structure and morphology of desulfurization gypsum.

To address toughness and fatigue-life limitations of high-strength wheel steel, the effects of Ce additions (0.0030, 0.0160, and 0.0340 wt.%) on dynamic continuous cooling transformation (DCCT), hot-rolled microstructure, and mechanical properties were examined. The transformation response depended on the solid-solution Ce content. The 0.0030 wt.% Ce steel, with insufficient solid-solution Ce, showed only a slight DCCT shift. At 0.0160 and 0.0340 wt.% Ce, solid-solution Ce reached ~0.0050 and ~0.0072 wt.%, respectively; the DCCT curves shifted progressively lower-right, reflecting delayed ferrite/pearlite transformation, prolonged bainite incubation, and expansion of the bainite transformation region toward lower cooling rates. Under identical rolling-coiling conditions, all steels exhibited a ferrite-pearlite-granular bainite microstructure; increasing solid-solution Ce increased the granular bainite fraction and reduced the pearlite fraction. Compared with the Ce-free steel, the 0.0160 wt.% Ce steel reduced the effective grain size from 7.61 to 4.96 μm and increased the high-angle grain boundary fraction from 53.22% to 69.84%. TEM revealed refined bainitic-ferrite (BF) laths, fewer coarse blocky martensite/austenite (M/A) islands, a higher fraction and number density of fine M/A islands, and film-like retained austenite at M/A-BF interfaces. Ce addition maintained a favorable strength-ductility balance and increased room-temperature impact energy from 85.8 to 108.6 J. Fatigue life was non-monotonic: the 0.0160 wt.% Ce steel showed the greatest improvement, whereas the 0.0340 wt.% Ce steel improved but did not surpass it. Overall, Ce altered the continuous cooling transformation path through solid-solution Ce and promoted microstructural refinement; its addition should therefore be appropriately controlled.

Understanding the phase equilibria of the CaO-Al2O3-La2O3-MgO system provides a crucial theoretical foundation for designing optimized refining slags used in rare earth steel production and for the modification of undesirable high-melting-point rare earth inclusions. An additional objective of this work was to explore the existence of any refractory quaternary compound in this system that could be suitable for development as an advanced thermal barrier coating (TBC) material. Experimental investigation of the phase relations for a selected composition region within the quaternary system was conducted at 1773 K via the equilibration and rapid quenching technique. The equilibrium phases present were characterized and their compositions measured using scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and x-ray diffraction (XRD). Based on these results, the 1773 K isothermal tetrahedral phase diagram was developed, along with a series of corresponding pseudo-ternary sections at fixed w(MgO) levels. The established phase diagram features three four-phase fields (i.e. Liquid + 2CaO·3Al2O3·La2O3 + Al2O3·La2O3 + MgO, Liquid + 2CaO·3Al2O3·La2O3 + MgO·Al2O3 + MgO, Liquid + 2CaO·3Al2O3·La2O3 + CaO·2Al2O3 + MgO·Al2O3), 7 three-phase fields (i.e. Liquid + Al2O3·La2O3 + MgO, Liquid + 2CaO·3Al2O3·La2O3 + Al2O3·La2O3, Liquid + 2CaO·3Al2O3·La2O3 + MgO, Liquid + MgO·Al2O3 + MgO, Liquid + 2CaO·3Al2O3·La2O3 + MgO·Al2O3, Liquid + 2CaO·3Al2O3·La2O3 + CaO·Al2O3, Liquid + CaO·2Al2O3 + MgO·Al2O3), and four two-phase fields (i.e. Liquid + MgO, Liquid + 2CaO·3Al2O3·La2O3, Liquid + MgO·Al2O3, Liquid + CaO·Al2O3).

Al2O3-SiO2-La2O3 system is a typical basic RE-containing ceramic system. The phase diagram of this system is useful for the research and development of RE in ceramic materials; besides, it is also indispensable for the thermodynamic database of multicomponent RE-containing ceramic systems. In this paper, we employed hightemperature equilibrium experiments and quenching methods followed by scanning electron microscope (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD) to determine the morphology, composition and type of equilibrium phases in the Al2O3-SiO2-La2O3 system, respectively. Based on the experimental results, three isothermal sections at 1873 K, 1773 K and 1673 K were clarified; the solid solubility of the compound phase at the experimental temperature were clarified.