Increasing CaO Content Research Articles

Investigating the mechanical properties and corrosion resistance of extruded Mg-1Zn-xCaO (x=0, 0.5, 1.0 wt%) materials

The effect of nano-CaO content on the microstructure, mechanical properties, and in vitro degradation performance of extruded Mg-1Zn alloys was investigated to enhance the strength and corrosion resistance of biodegradable materials for medical implants. The results showed that the addition of CaO nanoparticles effectively refined the size of dynamic recrystallization grains in the extruded composites. During the extrusion process, Ca2Mg6Zn3 and Mg2Ca phases precipitated in the Mg-1Zn-0.5CaO and Mg-1Zn-1CaO composites, respectively. As the CaO content increased, the basal texture strength was elevated from 3.97 for the Mg-1Zn alloy to 12.05 for the Mg-1Zn-1CaO composite. Benefiting from the combined mechanisms of grain refinement, dislocation strengthening, and precipitation strengthening, the yield strength of the materials was fortified with an increase in CaO content. During the short immersion time, the matrix of the extruded Mg-1Zn-0.5CaO composite was preferentially corroded, resulting in the formation of a dense corrosion product layer that impeded the transport of ions in the electrolyte solution, thereby exhibiting the lowest annual corrosion rate. With an increase in the immersion time, galvanic corrosion destroyed the protective film, leading to a slightly higher corrosion rate in the extruded Mg-1Zn-0.5CaO composite compared to the Mg-1Zn alloy. The substantial nano-Mg2Ca phase particles were preferentially degraded, causing severe pitting corrosion in the extruded Mg-1Zn-1CaO composite, which exhibited the highest degradation rate. The extruded Mg-1Zn-0.5CaO composite exhibited superior overall properties; its yield strength, elongation, and annual corrosion rate after immersion (21 d) were 334.9 MPa, 8.9 %, and 1.06 mm/y, respectively.

Optimizing damage resistance and structural evolution in CaO-modified Li2O-Al2O3-B2O3-TiO2-P2O5 glass-ceramics

Aluminoborate glass, recognized for its remarkable crack resistance, presents significant potential as a cover material for portable electronic devices. Nevertheless, its relatively low hardness has been a limiting factor. This study synthesized a series of 11 Li2O-30 Al2O3-(55-x) B2O3-2 TiO2-2 P2O5-xCaO (wt%), with x varying from 0 to 10, employing the melt-cast method. The resultant glass-ceramics were produced via heat treatment at 590 °C for 2 h, followed by a systematic examination of their structural and mechanical properties. The investigation demonstrated that an increase in CaO content diminishes crystallization and induces a morphological transition in the crystalline phases from granular and short rod-like structures to lath-like formations, which subsequently impacts the coordination environment of Al and B atoms. With a CaO content of 2 %, the GC2 sample precipitated Li(Al7B4O17) and Li2AlB5O10 phases, achieving a compressive strength (CR) value of 15.0 N, a hardness of 7.51 GPa, and a fracture toughness of 1.50 MPa m0.5. This glass-ceramic exhibited optimal scratch resistance and visible light transmittance exceeding 85 %, underscoring its considerable promise for application as smartphone cover glass due to its impressive overall damage resistance.

Thermodynamic modelling on the reaction between steel and slag

An integrated thermodynamic model was developed to determine the equilibrium between the slag and the steel at high temperatures, employing the Unified Interaction Parameter Formalism (UIPF) and the Associate Model (AM) for a twelve-element molten steel system (Fe–Al–C–Ca–Cr–Mg–Mn–N–O–S–Si–Ti). A model for slag activity was based on the Ion and Molecular Coexistence Theory (IMCT) and applied to a refining slag system (CaO–MgO–FeO–MnO–CaF2–SiO2–Al2O3–Fe2O3). Comparative analyses were conducted using FactSage software and experimental data, validating the accuracy of the established model. The impact of slag modifiers, specifically aluminum granules, on slag oxidability, and the role of CaO/Al2O3 ratio in slag desulfurization were investigated. The effect of slag modifier on the oxidability and the influence of CaO/Al2O3 on the desulfurization of the slag were determined using the current model. Aluminum in the slag modifier reacted with MnO and FeO in the slag, thereby reducing the oxidability of the slag. With a 30 wt% slag modifier, the MnO content in the slag (initially 15 wt%) stabilized and showed minimal change, dropping below 1 wt%. An increase in CaO content above 80 wt% in the slag led to a reduction of equilibrium sulfur in the steel to below 10 ppm. Little amount of calcium transferred from the slag into the steel with the increase in CaO content, but the [Ca] content remained below 0.5 ppm even though the content of CaO in the slag was greater than 80 wt%. The developed model offered a versatile tool for designing slag compositions tailored to various purposes.

Indirect Enhancement of ALD Thin-Film Properties Induced by the ECAP Modification of an As-Extruded Mg-Ca Alloy.

The purpose of this study is to investigate the indirect effects on the properties of ZrO2 films deposited by atomic layer deposition (ALD) when an Mg-Ca alloy is modified through equal-channel angular pressing (ECAP) following extrusion. The study aims to understand how the increase in CaO content in the native oxide layer of the Mg-Ca alloy influences the crystallinity and defect density of the ZrO2 film. Consequently, the corrosion protection performance of the ZrO2 film is enhanced by 1.2 to 1.5 times. A reduction in the anti-scratch property of the ZrO2 film was also observed, with a critical load reduction of 34 μN. This research provides a detailed analysis of the modifications induced by ECAP on the as-extruded Mg-Ca alloy and its subsequent impact on the properties of the ZrO2 film.

Effect of desalination of Sargassum algae on its potential use as a stabilizer in sustainable earth-based bricks

Since 2011, Caribbean beaches have been flooded by massive quantities of pelagic Sargassum, causing environmental, health and financial problems. The use of Sargassum ash as a stabilizer in the manufacture of bricks can help mitigate the economic impact of Sargassum grounding by adding value. This study assesses the effect of the Pelagic Sargassum algae desalination process on the properties of the biomass as well as the potential application of their ash as a stabilizer in soil-based bricks. Fresh Sargassum algae was subjected to two cycles of immersion in water, then calcined under different conditions (temperature and time) and characterized. The desalinated Sargassum ash (SA) was used to partially replace cement in the stabilization of earth bricks. Characterization of raw and desalted Sargassum shows a reduction in ash content from 28.44 to 17.25 % after desalination. Furthermore, the thermo gravimetric analysis show a slight reduction in the initial degradation temperature between 204 and 602 °C, which is associated with a reduction in the amount of residual char from 35 % to 27 %. The results of the XRF analysis of the SA showed a very low alumiosilica content (SiO3 + Al2O3 < 4 %), but a significant increase in CaO content after desalination from 21.96 to 50.17 %. The XRD results of the SA are consistent with the XRF analysis which reveals that the desalination process significantly increased the CaCO3 content from 19 to 67 %, while KCl decreased significantly from 26 to 8 %. Furthermore, the characterization of the composites reveal that partial substitution of 10 wt% cement by SA calcined at 700 °C for 2 h has no significant effect on water absorption, density, compressive strength and chemical composition of earth bricks. This material could help reduce pollution linked to the decomposition of sargassum on Caribbean coasts and beaches, as well as greenhouse gas emissions linked to cement production.

Unveiling the structure of calcium borate glass by neutron diffraction, MAS-NMR, Raman and first-principles calculations

Calcium borate glass is a challenging system, due to the rich variety of borate units and alterable boron coordination number, and hence they are also of particular interest for academic study. In this study, neutron diffraction, solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) and Raman spectroscopy were combined with first-principles calculations, experience potential structure refinement (EPSR) simulations to investigate the structure of xCaO·(1-x)11B2O3 glass. Property data such as density and glass transition temperature were also measured to study the impact of structural changes on the properties of glasses. The structure of calcium borate glass was analyzed using various methods including structural unit, atomic pair bond length, coordination number, ring structure, chain structure and cavity distribution. Most notably, the atomic labeling method plays a key role in the structural analysis process. Through this method some new conclusions were obtained. For example, the increase of CaO content mainly leads to the conversion of BO to NBO in the glass structure, and has little effect on the content of BO3 and BØ4-. This result further leads to an increase in Ca-NBO interactions. Interestingly, the bond length distribution of Ca-NBO and B-NBO is shorter than that of Ca-BO and B-BO, so the glass structure becomes denser. The structural reason why the density of calcium borate glass is less than the crystal density was also revealed. This study contributes to unveiling the structure of calcium borate glass and exploring the correlation between the structure and properties of calcium borate glass, which provides a valuable reference for developing more valuable amorphous materials.

Sol-gel derived B2O3-CaO borate bioactive glasses with hemostatic, antibacterial and pro-angiogenic activities.

Sol-gel borate bioactive glasses (BGs) are promising ion-releasing biomaterials for wound healing applications. Here, we report the synthesis of a series of binary B2O3-CaO borate BGs (CaO ranging from 50 to 90 mol%) using a sol-gel-based method. The influence of CaO content in B2O3-CaO borate BG on morphology, structure and ion release behavior was investigated in detail. Reduced dissolution (ion release) and crystallization could be observed in borate BGs when CaO content increased, while the morphology was not significantly altered by increasing CaO content. Our results evidenced that the ion release behavior of borate BGs could be tailored by tuning the B2O3/CaO molar ratio. We also evaluated the in vitro cytotoxicity, hemostatic, antibacterial and angiogenic activities of borate BGs. Cytocompatibility was validated for all borate BGs. However, borate BGs exhibited composition-dependent hemostatic, antibacterial and angiogenic activities. Generally, higher contents of Ca in borate BGs facilitated hemostatic activity, while higher contents of B2O3 were beneficial for pro-angiogenic activity. The synthesized sol-gel-derived borate BGs are promising materials for developing advanced wound healing dressings, given their fast ion release behavior and favorable hemostatic, antibacterial and angiogenic activities.

Slag chemistry, element distribution behaviors, and metallurgical balance of e-waste smelting process

The co-smelting of electronic waste (e-waste) in copper/lead pyrometallurgical processes is widely recognized as the preferred solution for sustainable development. However, aluminum and halogen elements in e-waste causes new challenges. To address this, the slag chemistry of high Al2O3-containing slag was studied, and the distribution behaviors of Au, Ag, Sn, and other elements in the copper alloy/slag/gas system were investigated in the presence of halogen elements (F/Cl/Br) using the equilibration method. The industrial practice of electronic waste smelting was modeled using METSIM, and the material and energy balances of one industrial process were obtained. Under the conditions of electronic waste smelting, the solubility of Al2O3 in the FexO–SiO2–Al2O3–CaO slag system decreased with increasing CaO content. When the CaO content was 20 wt%, and the Fe/SiO2 mass ratio was 0.62–0.95, the solubility of Al2O3 in the slag reached 20 wt%. When 1%–10% CaF2 was added, 93% of Au entered the metal phase. When the same amount of CaCl2 or CaBr2 was added, up to 32% Au entered the gas phase. When CaF2 was added to the system, 22%–49% of Ag entered the gas phase. However, when CaCl2 or CaBr2 was added, 3%–34% of Ag entered the gas phase. The proportion of tin in the gas and slag phases increased with increasing temperature or the addition of halides. The METSIM simulation results showed that under optimized conditions, the crude copper contained more than 90 wt% copper, the discharged slag contained approximately 0.5 wt% copper, and the recovery rates of copper, gold, and silver were ≥98%. The heat generated from raw materials and fuel accounted for the largest part of the heat income, representing 65.32% of the total.

Impact of CaO addition on physico-chemical properties, crystallization, chemical durability and in vitro behavior of Na2O-ZnO-TiO2-P2O5 glasses

This work investigates the effect of CaO addition on physico-chemical properties, crystallization, chemical durability and bioactivity of phosphate-based glasses. To this end, five glass compositions in the system (40-x)Na2O-xCaO-10ZnO-20TiO2-30P2O5 with x = 0, 5, 10, 15 and 20 mol % have been elaborated by the conventional melt-quenching technique. Replacing Na2O with CaO oxide in the studied glasses increased remarkably the glass transition temperature Tg and density (ρ), while VM decreased with increasing CaO content indicating the high strength in the glass network. The existence of PO3 and PO4 units with P-O-P and P-O-Ti linkages in the glassy network was revealed by Infrared spectroscopy. The chemical durability was improved with increasing calcium content, indicating that replacing Na-O bonds with more covalent and stronger Ca-O bonds strengthen and crosslink the glassy network. The in vitro bioactivity of the two glass samples (x = 0 and 15 mol %) was studied using SBF solution. XRD, Infrared, ICP, and pH measurements proved the formation of a hydroxyapatite layer on the glass surface after interaction with the SBF medium, which is a crucial property of a potential bioactive glass. The correlation between XRD, Infrared, and ICP techniques indicated that glass containing calcium is more bioactive than free-calcium glass.

Study on the influence of different contents of impure CaO on the process of electromelting magnesia

PurposeThe aim of this study is to report the effect of different content of calcium oxide on the process of electromelting magnesia.Design/methodology/approachThe process of molten magnesia was analyzed by finite element simulation and proved by scanning electron microscope.FindingsThe results show that with the increase of CaO content, the maximum temperature appreciation increases from 3,616°C To 3,729°C, showing an approximate nonlinear evolution. Low thermal conductivity and low specific heat of CaO result in higher temperature. With the increase of CaO content and temperature, the maximum flow velocity of MgO slag increases from 0.043 to 1.34 mm/s. Under different initial CaO contents, the distribution trend of CaO volume fraction is basically the same, and the CaO volume fraction is evenly distributed between 50 and 225 mm in the furnace.Originality/valueThe influence of different contents of impurity calcium oxide on the process of electromelting magnesia was analyzed and a theoretical system was established.

Phase Formation and Stabilization Behavior of Ca-PSZ by Post-Heat Treatment II: CaOx-ZrO2(1 − x) (x = 5–10 mol%)

The effects of CaO content and post-heat treatment were investigated on the phase stability and mechanical and thermal properties of Ca-PSZ. ZrO2 specimens with 5–10 mol% CaO were sintered, and post-heat treatment was performed at 1200 °C for 100 h. Subsequently, to test and analyze the crystal structure and the microstructure, the mechanical and thermal properties of the specimens were evaluated. All specimens were partially stabilized by 5–10 mol% CaO (5CSZ–10CSZ) in a mixed monoclinic and tetragonal phase; however, peaks of the secondary phase of CaZrO3 were observed in 10CSZ. The ratio of the monoclinic phase decreased from 62.50% (5CSZ) to 21.02% (10CSZ) as the CaO content increased. Additionally, the monoclinic phase ratio decreased from 59.38% (5CSZ) to 19.57% (9CSZ) after the post-heat treatment; an increase to 24.84% was observed for 10CSZ. An increase in Vickers hardness from 676.02 to 1256.25 HV and flexural strength from 437.7 to 842.7 MPa was observed with increasing CaO content. The post-heat treatment resulted in further increases in these values as the CaO content increased from 5CSZ to 9CSZ; however, the Vickers hardness and flexural strength of 10CSZ decreased by approximately 8% and 9%, respectively. The thermal expansion coefficient exhibited the same tendency as the mechanical properties. This coefficient increased from 8.229 × 10−6 to 9.448 × 10−6 K−1 with increasing CaO content and was enhanced after the post-heat treatment in 5CSZ to 9CSZ; however, the thermal expansion coefficient of 10CSZ decreased by approximately 4% after the post-heat treatment. The mechanically and thermally stable tetragonal phase increased, and the monoclinic phase decreased as the doped Ca replaced the Zr sites, as was confirmed by the X-ray diffraction (XRD) analysis. The post-heat treatment and the increased Ca addition further facilitated the replacement of Zr sites by Ca. However, at high Ca concentrations of 10CSZ, an equilibrium phase of CaZrO3 was formed as a secondary phase at the post-heat treatment temperature, resulting in low performance.

Preparation and properties of CaO-added Mn-Zn ferrite ceramic

In the present work, spinel ferrite Mn0.76Zn0.24Fe2O4 were fabricated at the presence of the 0, 0.15, 0.30, 0.45 wt% CaO addition. The synthesis of Mn-Zn ferrites was accomplished using solid-state reaction of oxidative powders. The samples were created by sintering the powdered synthetic spinel. The findings show that any Fe2O3 that persisted after calcination at 1100 °C vanished after further sintering at 1250 °C, and all of the spinel structure-related diffractions in the X-ray diffraction (XRD) patterns were found. The scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) analyses indicated the well-dispersed metallic cations in the spinel structure and solution of Ca ions. Theoretical density of sintered sample was improved by CaO addition, and a maximum value 96.2 % of theoretical density was obtained with addition of 0.30 wt% CaO. Increasing CaO content from 0 to 0.30 wt% causes increasing the saturation magnetization (Ms) from 34.6 to 42.4 emu/g in terms of the substitution of Ca2+ cations in the tetrahedral sites. Further increasing of CaO to 0.45 wt% causes decreasing Ms to 33.4 emu/g as a result of octahedral occupation of Ca2+ cations.

Solid Precipitation Behaviors in Coal Slag from Different Primary Phases and Their Effects on Slag Viscosity from Thermochemistry and Experimental

Undesired solid precipitation in coal slag at high temperatures can cause serious blockages, or even the shutdown of coal gasifiers, due to a rapid increase in slag viscosity. In this study, the solid precipitation behaviors of coal slag from different primary phases and under different atmospheres were both experimentally and theoretically investigated. Our results demonstrated that the viscosity of the coal slag in the primary phase of mullite was strongly influenced by the atmosphere at a typical tapping temperature of 1300 °C because of the high content of network formers. The viscosity of the partially crystallized slag was significantly affected by solid precipitation behavior. Iron was converted to magnetite and hematite in air and was reduced to metallic iron under a reducing atmosphere. Increasing CaO content improved both the iron reduction reaction and the slag crystallization behavior. Anorthite precipitation was largely inhibited under a mild reducing atmosphere, leading to a large difference in the viscosity of coal slag under different atmospheres. In contrast, the viscosity of the coal slag in the primary phase of mullite was slightly influenced by the atmosphere due to the weak crystallization tendency of mullite, as well as its high slag viscosity.

Influences of Friedel's Salt Produced by CaO-Activated Titanium-Extracted Tailing Slag on Chloride Binding.

Titanium-extracted tailing slag (TETS) has high activity, but the content of chloride ions is high. To effectively bind the chloride ions, CaO was used to activate the TETS, and the solidified cementitious material of CaO-activated TETS was prepared. The effects of CaO content and curing age on the strength of solidified samples, chloride binding capacity, and chloride binding mechanism were studied. By means of XRD, FTIR, SEM, and EDS, the hydration reaction products, microstructure, morphology, and micro-components of the solidified sample were characterized. The results show that the chloride ions can be effectively bound by using CaO to activate TETS with higher mechanical strength. When the CaO content is 10 wt%, the strength of the 28-day-cured body can reach more than 20 MPa, the chloride ion binding amount is 38.93 mg/g, and the chloride binding rate is as high as 68%. The new product phases of the solidified sample are mainly Friedel's salt (FS) and calcite, in which the amount of FS production and the degree of crystal development are affected by the CaO content and curing age. The chloride binding ions in the solidified sample are mainly the chemical binding by FS. The FS diffraction peak strength increases with the increase of CaO content and curing age, but the calcite diffraction peak strength is less affected by them. FS mainly accumulates and grows in the pores of the solidified sample. It can optimize the pore structure of the solidified sample and improve the strength of the solidified sample while binding chloride ions. The results can provide useful information for the resource utilization of chlorine-containing TETS, the improvement of durability of Marine concrete, and the application of sea sand in concrete.

Prediction Model for SiO2 Activity in the CaO-Al2O3-SiO2-MgO Quaternary Slag System

Activity models based on the ion and molecule coexistence theory have been widely used in the refining of metallurgical slags, with the SiO2 content of slag playing a crucial role in improving the mechanical properties of refining slag-based cementitious materials. In order to improve the reactivity of SiO2 in slag, this study established a SiO2 activity prediction model for the CaO-Al2O3-SiO2-MgO quaternary slag system based on the ion and molecule coexistence theory, validating the prediction results using reference values from the literature. Following this, the effects of w(SiO2), w(CaO), w(CaO)/w(Al2O3), and R(w(CaO)/w(SiO2)) on SiO2 activity were explored (where w and R represent content and alkalinity, respectively). The results show that the model could accurately predict the SiO2 activity of refining slag at 1873k. When the SiO2 content was increased from 10% to 30%, with 60% w(CaO) and a w(MgO)/w(Al2O3) ratio of 0.25, the SiO2 activity exhibited a trend of initially increasing and then decreasing, with a maximum activity value of 0.1359 reached at 17.5% w(SiO2). When slag contained 15% w(SiO2) and a w(MgO)/w(Al2O3) ratio of 0.25, the SiO2 activity decreased with increasing CaO content, reaching a maximum activity value of 0.1268 when 55% w(CaO) was present. Therefore, by controlling the ratio of w(CaO)/w(Al2O3) and w(CaO)/w(SiO2) in the slag to maintain a ratio of 3, the activity of SiO2 can be effectively increased.

A Statistical Method for Component Analysis and Identification of Differentiated Glass Products

As the most widely used product in human daily life, glass was used as important material evidence for trade in ancient times. With the continuous development of my country's archaeological undertakings, the analysis and identification of the components of ancient glass products have become a research topic of practical significance. In order to predict the chemical composition content before weathering, we first analyze the relationship between surface weathering and the three variables of glass type, texture, and color from two aspects: correlation and difference. According to the discrete distribution state after quantification of qualitative data does not meet the normal distribution, Spearman correlation analysis and chi-square test model are used to draw the conclusion: relatively speaking, the degree of correlation between glass surface weathering and glass type is relatively high; glass type is closely related to the other three There are significant differences among the variables, decoration, and color. From the analysis of the influence of chemical composition, combined with relevant chemical data and verification, we can draw the following conclusions. In a certain range, the increase of CaO content is beneficial to increase the stability of the glass. From the point of view of numerical fitting solutions, we consider that the ridge regression model prediction model has higher sensitivity than other models such as Lasso regression due to the large difference in component values. Therefore, in this paper, we use the ridge regression model to fit the functional relationship between weathering and different categories of attributes and then use the prediction model obtained by ridge regression to solve the content before weathering.

Effect of multi-phase slag on dephosphorization in BOF steelmaking

In basic oxygen furnace double slag process, the slag shows a coexisting state of both liquid and solid. In order to study the effect of multi-phase slag on dephosphorization, heat experiments were conducted in this study, and the multi-phase slag was analyzed with the method of SEM-EDS. The results show that the mass fraction and size of solid solution increase with increasing basicity and decreasing FetO concentration. The distribution of P2O5 (LP2O5) between the solid solution and liquid phase increases with the T.Fe content in the liquid phase. While the increase of CaO content in liquid phase shows the opposite effect. A higher CaO content in liquid phase brought a decrease in γP2O5. The increase of T.Fe content in liquid slag has no notable effect on γP2O5 of dephosphorization slag, but increases γP2O5 of decarburization slag. The partition ratio of phosphorus between slag and steel (LP) increases with the increase of basicity, for conditions of FetO content in dephosphorization slag less than 25%. In the case of basicity of 3.0, LP reaches a maximum at FetO = 15%. When the basicity is 3.5 and 4.0, LP value is the largest at FetO of 15% or 20%.

Distribution behavior and deportation of arsenic in copper top-blown smelting process

In recent years, the impurity content in copper concentrate increases gradually with the consumption of high-grade copper ore. When the arsenic content in the raw materials increases, large amounts of arsenic enter the sulfuric acid system, resulting in large amounts of waste acid that put great pressure on production and environmental protection. Using the distribution characteristics of arsenic in each phase, the possibility of enriching arsenic in the form of stable arsenates in the slag was investigated to enrich arsenic in the form of stable arsenates in the slag. It is shown that increasing CaO content in slag at relatively low temperatures, controlling the slag type and changing the slag composition effectively improved the ability of the slag to absorb arsenic. Based on a theoretical analysis used to optimize the process parameters and determine a reasonable slag type, an oxygen-enriched top-blown smelting experiment was conducted with mixed copper concentrates. The mechanism of arsenic fixation in smelting slag at a smelting temperature of 1180 °C (1453 K) was investigated, and the results showed that the As content in slag was increased by 20∼50% and decreased by 10∼30% and 10∼20% in the dust and matte, respectively. Thus, arsenic is fixed in silicate in the form of stable arsenate, which can be an effective and safe treatment solution for copper smelting processes.

Influence of CaO and Fe2O on the surface tension and structure of SiO2-Al2O3-CaO-Fe2O3-MgO synthetic slags

The surface tension of coal slags influences the adhesion between the slag and furnace walls in slagging gasifiers, which further influences the efficiency, maintenance cost and reliability of the gasifier. The influence of CaO and Fe2O3 on the surface tension and structure of synthetic slags were investigated. The results indicate that the surface tension linearly increases with the increase of CaO content in the synthetic slag. When Fe2O3 exceeds 3.8 mole%, the surface tension of synthetic slag increases slowly with the increase of Fe2O3, which is related to Fe2O3 acting as an intermediate oxide. The degree of polymerization and the electrostatic potential of ions are related to a variation in surface tension, and the number of unsatisfied bonds increases because the Si-O-Si network structure was depolymerized. Here, NBO/T cannot reflect the degree of depolymerization of slag due to the variation in intermediate Fe2O3 contents.

Long-Term Leaching Effects on CaO-Modified Iron Silicate Slag

Granulated iron silicate slag, a by-product of pyrometallurgical copper extraction, has excellent properties for construction applications. Slag modification with CaO enhances the application properties regarding pozzolanic reactivity, potentially extending slag use in the future. The slags’ short-term leaching behavior has already been investigated with promising results, while the long-term leaching effects are less studied. Therefore, this study aims to determine the long-term leaching effects on CaO-modified iron silicate slags. The CaO-modifications were conducted during full-scale slag treatment operation. The slags were characterized and leached, and the remaining slags were investigated regarding the formation of secondary phases. The long-term leaching of main and trace elements was determined over 30 days using a dynamic leaching method corresponding to an extended time period. The leaching tests showed increased leaching of the main slag elements (Si, Ca). Zn and Cu showed peak leaching after four days of leaching, and the leaching of As and Sb decreased with the increasing CaO content in the samples. After dynamic leaching, secondary phases formed on the Cu-containing inclusions on the sample surfaces. Independent of the CaO content, the leaching of Cu was increased when subjected to external acidic and oxidating conditions using static pH titration at pH 5 in dilute nitric acid.