Silicate Formation Research Articles

THERMODYNAMIC MODELING OF OXIDE MELTS OF CaO - Al2O3 - SiO2 SYSTEMS

Oxide melts of the CaO – Al2O3 – SiO2 system are the basis of metallurgical slags. Therefore, the thermodynamic properties of this system have been repeatedly studied experimentally, and attempts have been made to describe them theoretically. Thermodynamic modeling of the state diagrams of the CaO – Al2O3, CaO – SiO2, Al2O3 – SiO2 binary systems, as well as the CaO – Al2O3 – SiO2 ternary system was performed. In the course of the work, expressions for the thermodynamic description of the activities of the components of the oxide melt of this system are derived. For the calculation, a generalized theory of regular ionic solutions was used. The energy parameters of the theory are determined, depending on the temperature and composition of the solution, using experimental data on the heat and melting point of oxides of calcium, aluminum and silicon. According to the results of the simulation, the coordinates of the points of nonvariant transformations in the phase diagrams of the binary and ternary systems under study are determined. The obtained results on thermodynamic modeling of the coordinates of the liquidus lines of the phase diagrams of the CaO – Al2O3, CaO – SiO2, Al2O3 – SiO2 binary systems were compared with the literature data for the studied systems. The calculated diagrams are in good agreement with the experimental ones, which indicates the applicability of the chosen system for the description of such oxide melts. The modeling technique used in this work allowed to estimate the Gibbs energies of formation of silicates and calcium aluminum silicates to be 3Al2O3∙2SiO2, 3CaO∙SiO2, 2CaO∙SiO2, 3CaO∙2SiO2, CaO∙SiO2, CaO∙Al2O3∙2SiO2, 2CaO∙Al2O3∙SiO2 on the base of obtained aquations for of activities of the components and calculated parameters of the theory. The calculated diagrams will allow to determine the nature of the interaction between the components of the system, the conditions of formation, the composition and properties of the compounds formed, without isolating them from the system.

Physical and chemical processes of volcanic rock hardening with alkaline silicates

The thermodynamic probability of reactions in volcanic rock compositions — an alkaline silicate binder, which is used to produce artificial stone (concrete) products with high physical and mechanical properties and with wide range of colors for interior and exterior wall tiling and external masonry, manufacturing of decorative architectural details, etc. are considered. Silicate and aluminosilicate rocks of volcanic origin (perlite, pumice, tuff, etc.) of various deposits of Armenia are dispersed volcanic glasses with feldspar inclusions and are characterized by a large variety of colors: white, beige, yellow, orange, violet-pink, pinkish, red, brown, black, greenish, bluish-white, etc. Dolomite hardener is introduced into the composition for manufacturing of waterproof concrete on a base of a chemical binder at low temperatures.The possibility of reactions in a mixture of volcanic rock – alkaline silicate – dolomite – water was assessed by thermodynamic method. The calculation of Gibbs energy of the interaction reactions in the indicated system witnessed the possibility of realization of hydration, hydrolysis, silicate formation reactions even at a temperature of 298K.The formation of hydrated silicates and calcium and sodium aluminosilicates, guarantees the binding properties of the composition under normal conditions. With an increase of the temperature to 375, 475, 574K, the probability of reactions increases.

Oxidation behavior and mechanism of MoSi2-Y2O3 composite coating fabricated by supersonic atmospheric plasma spraying

MoSi2-based coatings with different Y2O3 additive contents were fabricated using supersonic atmospheric plasma spraying, its microstructural features and oxidation behavior as well as protective mechanism at 1500 °C were diligently studied. Experimental results revealed that the sprayed MoSi2-Y2O3 (MY) composite coatings exhibited the dense microstructure and adhered well to SiC transition layer without obvious defects at their interfaces. Moreover, the composite coating with 20 wt% Y2O3 possessed the best oxidation resistance with a lowest mass loss percentage at 1500 °C among all sprayed MY coatings. The incorporation of rare earth Y2O3 accelerated the formation of multiple yttrium silicates containing Y2SiO5, Y2Si2O7 and Y4Si3O12 with high melting point and matching thermophysical property to SiO2, which could occupy the open spaces and enhance the viscosity of glassy SiO2-rich Si-O-Y compound scale. The increased viscosity of Si-O-Y multicomponent scale could delay the permeation of reactive oxygen species inwardly, enhancing the oxidation resistance of sprayed composite coating effectively.

Interaction of FeII and Si under anoxic and reducing conditions: Structural characteristics of ferrous silicate co-precipitates

The interaction of FeII and Si is at the heart of many critical geochemical processes in diverse natural and engineered environments. The resulting FeII-silicate phases play important roles in regulating the concentrations and bioavailability of FeII and Si, as well as serve as sinks for trace and hazardous elements. Therefore, a detailed understanding of their structural characteristics and the underlying formation mechanisms may provide insights useful to predicting their reactivity and stability under different conditions. In this work, co-precipitates with different Si/FeII ratios (0.5, 1.0 and 2.0) were synthesized under anoxic and reducing conditions at different solution pH (7, 9 and 11). Thermodynamic calculations from solution chemistry data were carried out and co-precipitates were studied using X-ray diffraction (XRD), infrared (IR) spectroscopy and Fe K-edge extended X-ray absorption fine structure spectroscopy (EXAFS). Thermodynamic calculations predict the formation of phyllosilicate phases such as greenalite in all the samples. Solid characterization data, however, reveal significant structural variabilities and phase heterogeneity. Incipient phyllosilicate structures tend to be more pronounced in samples from pH 9 and 11, while at neutral pH conditions, polymeric silicate phases like amorphous SiO2 become predominant. These variabilities are possibly linked to heterogeneous formation processes arising from relative solubility differences between SiO2 and Fe(OH)2. High pH (>8) conditions favor the polymerization of Fe(OH)2 layers which likely serve as templates for layered silicate formation, while neutral pH conditions favor the precipitation of polymeric silicate phases like amorphous SiO2 to which aqueous Fe species may adsorb. In samples from Si/FeII = 0.5, relatively well developed Fe(OH)2 layers were identified from the EXAFS data. Increasing Si/FeII ratios lead to amorphous SiO2 precipitation and inhibition of Fe(OH)2 polymerization, resulting in smaller phyllosilicate domains embedded in a polymeric SiO2 matrix. The results of this work may be useful in interpreting structural variabilities of FeII-Si phases observed both in nature and in engineered environments. Such variabilities may influence subsequent phase recrystallization processes as well as reactivity towards environmentally relevant elements such as radionuclides.

Interior plastering of Ottoman bath buildings

Ottoman baths were peculiar buildings with their function in community life, architectural characteristics and material use. Their interior spaces were exposed to high humidity and temperatures that made the building structure vulnerable to physical, chemical, physicochemical and biological degradations. Plasters used on the interior wall surfaces were the most important agents to protect the structure from deterioration and provide durability. This study aims to exhibit the plaster characteristics of Çinili Bath in İstanbul which was an outstanding example of Ottoman baths and built by Great Architect Sinan. Basic physical properties, raw material compositions, mineralogical, microstructural and hydraulic properties of original brick-lime plasters called as horasan (khorasan) plasters used on the walls were determined by XRF, XRD, SEM-EDS and TGA. Multilayered plaster application together with the use of glazed tiles were observed on the wall surfaces of all interior spaces. The plasters were produced from pure lime and pozzolanic crushed brick or tile aggregates and hydraulic because of the pozzolanic properties of aggregates. They are stiff, compact and durable in hot and humid conditions of bath buildings due to their self-healing properties and the formation of calcium silicate hydrates and calcium aluminate hydrates at the lime-brick interfaces and in the pores of the pozzolanic brick aggregates by the reaction of lime. Characteristics of brick aggregates were compared with the construction bricks used in the building. Their chemical and mineralogical compositions revealed that the aggregates had not been produced from construction bricks. All the results indicated that brick-lime plasters were the most suitable materials for bath buildings to protect the structure from the effect of water.

Influence of Lysinibacillus sphaericus on compressive strength and water sorptivity in microbial cement mortar

Cement structures are subject to degradation either by aggressive media or development of micro/macro cracks which create external substance ingress pathways. Microbiocementation can be employed as a self-intelligent solution to this deterioration process. This paper presents study results on the effects of Lysinibacillus sphaericus microbiocementation on Ordinary Portland cement (OPC), normal consistency, setting time, soundness, compressive strength and water sorptivity. Microbial solutions with a concentration of 1.0 × 107 cells/ml were mixed with OPC to make prisms at a water/cement ratio of 0.5. Mortar prisms of 160 mm × 40 mm x 40mm were used in this study. A maximum compressive strength gain of 17% and 19.8% was observed on the microbial prism at the 28th and 56th day of curing respectively. A minimum of 0.0190 and a maximum of 0.0355 water sorptivity coefficient was observed on the OPC microbial prism and OPC control prism, after 28th day of curing respectively. Scanning electron microscope images taken after the 28th day of curing showed formation of vast calcium silicate hydrates and more calcite deposits on microbial mortars. Statistical findings of this study indicate that Lysinibacillus sphaericus significantly retarded both the setting time and normal consistency, but has no influence on the mortar soundness.

Analysis of Kushan Coins (1st–3rd Centuries C.E.) by Multi-Spectroscopic Techniques

Seven Indian copper coins of the Kushan Period (1st–3rd centuries C.E.) were studied by multi-analytical techniques like WD-XRF, XRD, and FESEM-EDX to understand coin composition and the metallurgical process of fabrication. Analytical results reveal a compositional gradient in the distribution of elements between the external surface and the inner core of the coins, and the coins show isolated patches of surface mineralization leading to the formation of copper oxides, magnesium silicate, and silica. The analysis also showed the probable use of sulfide ore of copper for smelting and poor workmanship for this hoard. The impurities like sulfur, iron, silica, etc. could not be removed due to low firing temperature and improper poling during smelting. Striations have formed in the coin interior, with grain boundaries showing micro-cracks due to stress like punching or hammering with the die. The coins under study are a single-phase copper with associated impurities of Si, Al, P, and Mg in all coins and black spots of copper sulfide in coin inner core.

Sintering and sliding wear studies of B4C-SiC composites

Dense boron carbide (B4C) – silicon carbide (SiC) composites were obtained by spark plasma sintering technique at 1800°C with 3 wt% and 6 wt% aluminium oxide (Al2O3) additives. Addition of sintering additives results in formation of aluminium silicate (Al2SiO5) liquid phase which accelerates sintering kinetics and helps in obtaining high density ~ 99%. Microstructures reveal uniformly distributed SiC particles in B4C matrix. Increase in alumina from 3 wt% to 6 wt% results in decrease in hardness from 35.1 ± 0.8 to 33.7 ± 0.9 GPa, and increase in fracture toughness from 5.9 ± 0.4 to 6.5 ± 0.4 MPam0.5. Using a ball-on-disk tribo tester under dry unlubricated conditions at 5, 10 or 15 N load, influence of alumina content on friction and wear properties of B4C-SiC composites was investigated against SiC counterbody with a linear speed of 0.08 m/s for 60 min. The coefficient of friction (COF) increased from 0.25 to 0.65 with load, and the influence of alumina on frictional behaviour appeared to be negligible. With increase in load, wear volume of the composites increased from 7.5 × 10−2 mm3 to 16.1 × 10−2 mm3 for B4C-10 wt% SiC - 3 wt% Al2O3 and from 4.7 × 10−2 mm3 to 14.8 × 10−2 mm3 for B4C-10 wt% SiC - 6 wt% Al2O3 composites. Microcracking, abrasion and pull-outs contributed as major wear mechanisms of composites in selected wear conditions. The relation between wear behaviour and mechanical properties of sintered composites is discussed.

Effects of biomass blending, ashing temperature and potassium addition on ash sintering behaviour during co-firing of pine sawdust with a Chinese anthracite

When biomass and coal are co-combusted, the ash sintering behaviour cannot be directly predicted on the basis of the properties of individual fuel ash. Knowledge of the ash sintering behaviour can help understanding the subsequent ash fouling and slagging. Herein, the ash sintering characteristics during co-combustion of Jincheng coal (JC) and pine sawdust (PS), together with the effects of biomass blending ratio, ashing temperature and K2CO3 catalyst addition were investigated in depth. The results indicated that for a given JC/PS blend, the ash slagging degree expressed by different decision indices was different, but the tendency was consistent. No obvious fusion phenomenon was observed among the individual particles from the blends without K2CO3 addition. Both types of the particles from individual fuel could be separately identified with obvious difference from their respective particles. When K2CO3 was added to the blends, the ash surface structure varied from unmelted to slightly adhesion. The formation of potassium silicates made great contributions to slagging. The molten and solidified zone on the agglomerate surface featured high contents of K, Si, O and Al, and the coating on the melting surface was composed of the mixture of K-bearing aluminosilicates, potassium chloride and smaller amounts of Ca-bearing aluminosilicates.

Silicate Formation in a Ternary Alkali Metal Carbonate Melt

Studies have shown that doping carbonates with silica destabilizes the liquid phase by reducing the temperature window over which the mixture resides in a molten state. This work demonstrates that liquid-phase disruption is caused by silicate formation in the melt due to reactions between carbonate and silica. These results were verified using differential thermal analysis (DTA), X-ray diffraction, and thermogravimetric analysis, all of which pointed to the same conclusion. The exact amount of silica produced was measured using DTA, which precisely matched the theoretical yield. These results are particularly relevant to the direct carbon fuel cell (DCFC) when carbonate is used as an electrolyte and coal char is used as a fuel, given that silica is an abundant mineral in high-rank coals. In this situation, liquid-phase disruption would destabilize the carbonate electrolyte, thus having a deleterious impact on the DCFC.

Sintering Optimisation and Recovery of Aluminum and Sodium from Greek Bauxite Residue

Bauxite residue is treated for the recovery of aluminum and sodium by sintering with the addition of soda, metallurgical coke and other reagents such as CaO, MgO and BaO. A thorough thermodynamic analysis using Factsage 7.0™ software was completed together with XRD mineralogy of sinters with different fluxes and reagents additions. Through both thermodynamic interpretation and mineralogical confirmations, it was observed that the type of desilication product in bauxite residue influences the total aluminum recovery through the sintering process and formation of sodium aluminum silicate exists in equilibrium with sodium aluminate, unless silica is consumed by additives (such as CaO, MgO, BaO etc.) forming other more thermodynamically favorable species and liberating alumina. Addition of barium oxide improves the aluminum and sodium recovery to 75% and 94% respectively. Complex sinter product formation that are triggered due to high calcium content in the Greek bauxite residue reduces aluminum recovery efficiency. Optimised and feasible recovery of aluminum and sodium for Greek bauxite residue was proved to be 70% and 85% respectively, when sintered with 50% excess stoichiometric soda. It was observed that stoichiometric carbon addition in inert atmosphere only assisted recovery up to 75% of aluminum and 83% of sodium, though there are benefits gained from pre-reducing iron from hematite for downstream recovery.

Experimental comparative study on ash fusion characteristics of Ningdong coal under oxidizing and reducing atmosphere by means of SiO2-Al2O3-(CaO + MgO + Na2O + K2O) pseudo-ternary diagrams

Concern about the serious slagging during combustion and the troublesome liquid slag tapping during gasification has motivated the study on ash fusion characteristics of Ningdong coal under oxidizing and reducing atmosphere by SiO2-Al2O3-(CaO + MgO + Na2O + K2O) pseudo-ternary diagrams of ash fusion temperatures (AFTs). The AFTs contours in the pseudo-ternary diagrams presented inverted V-shape distributions. Al2O3 showed positive effect on the AFTs; with unchanged Al2O3 content (less than 0.5), the AFTs went down first and then up with increasing SiO2 content; whereas with consistent AAEM (CaO + MgO + Na2O + K2O), the AFTs decreased with increasing SiO2 content. By doping SiO2 and Al2O3 or the mixtures into the coal, the AFTs increased significantly due to the formation of high-melting quartz, corundum, silicates, and aluminosilicates, which impeded melt-induced slagging under both oxidizing and reducing atmosphere. On the contrary, when doping AAEM, the AFTs plunged because of the formation of low-melting akermanite, which favored liquid slag tapping during gasification. The pseudo-ternary diagrams indicated that the AFTs under reducing atmosphere were higher than that under oxidizing atmosphere, with an exception of around the limited region of SiO2:Al2O3:AAEM = 0.25:0.45:0.3. Ningdong coal located in the singularity region, where the existing forms of Fe as low-melting FeS and FeO under reducing atmosphere and high-melting Fe2O3 under oxidizing atmosphere resulted in slightly higher AFTs under oxidizing atmosphere. Besides, the atmosphere difference had more influence on IDT, ST, and HT, and less influence on FT. This research provides valuable practical guidance for the selection and dosage of additives during the combustion and gasification of Ningdong coal.

Cesium retention and release from sulfur polymer concrete matrix under normal and accidental conditions

This paper proposes an efficient two-stage process for stabilization and solidification of the Cs-137 isotope in a sulfur polymer concrete (SPC) matrix. Lignite slag (SL) and fly ash (FA) were applied as active fillers for cesium immobilization. To study the release of Cs-137 isotope and determine the tracer activity in the leachates, we applied a slightly modified ANSI/ANS 16.1 protocol and the gamma spectrometry technique. The measured effective diffusion coefficients for the Cs-137 isotope were between 0.84·10−9 and 3.10·10−9 cm2·s−1. Normalized leaching rates were within the range of 1.74·10−5 – 3.85·10−5 g·cm−2·d−1, fulfilling acceptance criteria for radioactive wasteforms. As well as standard leaching under static conditions, we also studied dynamic leaching of SPC samples at increased temperatures and leaching in an aggressive environment. The Cs-137 effective diffusion coefficients were found to increase by 3 – 4 orders of magnitude (10−6 – 10−5 cm2·s−1), while the normalized leaching rate reached values of up to 2.36·10−3 g·cm−2·d−1 after 28 days of leaching. The proposed cesium immobilization mechanism is based on the formation of cesium silicate and aluminosilicate phases, together with effective matrix sealing during the SPC manufacturing process.

Effect of Fe2O3 on the size and components of spinel crystals in the CaO−SiO2−MgO−Al2O3−Cr2O3 system

The stability of chromium in stainless steel slag can be enhanced by increasing the spinel crystal size. The effect of Fe2O3 on the size of spinel crystals in the CaO−SiO2−MgO−Al2O3−Cr2O3 system was investigated using lab experiments carried out in a carbon tube furnace. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM−EDS) and X-ray diffraction (XRD) were used to analyze the microstructure, components, and the mineral phases of synthetic slags. FactSage 7.1 was used to calculate the crystallization process of the molten slag. The results showed that the addition of Fe2O3 promoted the precipitation of spinel crystals and inhibited the formation of dicalcium silicate. The size of spinel crystals increased from 2.74 to 8.10 µm and the contents of chromium and iron in the spinel varied as the Fe2O3 addition was increased from 0 to 20wt%. Fe2O3 thermodynamically provided the spinel-forming components to enhance the formation of FeCr2O4, MgFe2O4, and Fe3O4. The addition of Fe2O3 increased the fraction of liquid phase in a certain temperature range and promoted diffusion by decreasing the slag's viscosity. Therefore, Fe2O3 is beneficial to the growth of spinel crystals in stainless steel slag.

Formation of Magnesium Silicide in bulk diffusion couples

Formation of Magnesium Silicide in binary Mg/Si diffusion couples and in reactions of Mg with Silicon Dioxide was investigated. The position of the Kirkendall marker plane inside the reaction zone of the bulk diffusion couples revealed that at 500 °C, Mg is virtually the only mobile species in the Mg2Si intermetallic compound. Such diffusion behaviour was rationalized using crystallographic information about anti-fluorite structure of the Mg2Si phase. Using general relations between integrated diffusion coefficient for a stoichiometric compound, tracer diffusivities of the components and data on thermodynamic stability of the phases involved in the interaction, the tracer diffusion coefficient DMg⁎ in the Mg2Si was derived.During diffusion-controlled interaction of Mg with Silicon Oxide, the Mg2Si intermetallic is formed within the transition zone microstructure as a continuous phase with the periodically arranged bands of MgO-particles embedded in the matrix phase. In the case of bulk Mg/quartz-SiO2 couples annealed at 500 °C, MgSiO3 and Mg2SiO4 silicates are also found in the reaction zone next to the SiO2-substrate. This can be explained with the help of the equilibrium Mg–Si–O phase diagram. However, no formation of Magnesium Silicates was observed in diffusion-controlled reactions between Mg and fused (amorphous) Silica.At the early stages of the interaction in bulk Mg/SiO2 couples, the situation was found to be different. No quasi-binary compounds MgSiO3 and Mg2SiO4 were detected in the diffusion zone after reaction of Mg with monocrystalline SiO2 as well as fused Silica at 550 °C. In both cases, the layer adjoining the SiO2-substrate is Magnesium Oxide.The formation of periodic layered morphology is considered to be a manifestation of the Kirkendall effect accompanying reactive phase formation in the solid state. The suggested mechanism is operative when the components have distinctly different mobilities in adjacent reaction product layers.

Episodic fluid flow in an active fault

Abstract We present a reconstruction of episodic fluid flow over the past ∼250 k.y. along the Malpais normal fault, which hosts the Beowawe hydrothermal system (Nevada, USA), using a novel combination of the apatite (U-Th)/He (AHe) thermochronometer and a model of the thermal effects of fluid flow. Samples show partial resetting of the AHe thermochronometer in a 40-m-wide zone around the fault. Numerical models using current fluid temperatures and discharge rates indicate that fluid flow events lasting 2 k.y. or more lead to fully reset samples. Episodic fluid pulses lasting 1 k.y. result in partially reset samples, with 30–40 individual fluid pulses required to match the data. Episodic fluid flow is also supported by an overturned geothermal gradient in a borehole that crosses the fault, and by breaks in stable isotope trends in hydrothermal sinter deposits that coincide with two independently dated earthquakes in the past 20 k.y. This suggests a system where fluid flow is triggered by repeated seismic activity, and that seals itself over ∼1 k.y. due to the formation of clays and silicates in the fault damage zone. Hydrothermal activity is younger than the 6–10 Ma age of the fault, which means that deep (∼5 km) fluid flow was initiated only after a large part of the 230 m of fault offset had taken place.

Low CO2 emission cements of waste glass activated by CaO and NaOH

Abstract The recycling of Silica soda lime waste glass (WG) as a precursor of low emissions alkaline cements activated with CaO and NaOH was investigated in pastes and mortars. The experimental factors were the WG surface area, curing temperature, Na2O %wt. and %CaO wt. %, each with 3 levels using an experimental design based on orthogonal arrays. The use of CaO favored the reactivity of the WG in combination with Na2O; the CaO reduced the demand for Na2O to create an alkaline environment that promoted the dissolution of WG and provided Ca2+ for the formation of cementitious hydrated calcium silicates. The mortars showed hydraulic behavior and increasing strengths greater than 15 and 29 MPa after 28 and 180 days, respectively. The formation of the calcium silicate hydrates intermixed with silica gel was evidenced by energy dispersive spectroscopy, with reaction products of Ca/Si ratios of 0.35–0.75 for pastes, while 29Si Nuclear magnetic resonance indicated the formation of chain structures with a predominance of Q2 signals. Waste glass is an abundant promising precursor for new green cements, which creates a sustainable and simpler route to revalorize large volumes of this urban and industrial waste.

Sustainable solidification of ferrochrome slag through geopolymerisation: a look at the effect of curing time, type of activator and liquid solid ratio

Ferrochrome (FeCr) slag was used as a precursor for the synthesis of a geopolymer. The effect of KOH concentration, liquid solid ratio (L/S), content of potassium metalisicate (KS) or potassium aluminate (KA), curing time on the unconfined compressive strength (UCS) and metal leachability of the synthesised geopolymer was investigated. A 10 M KOH and an L/S of 0.26 yielded a geopolymer with a UCS 13.0 MPa after 28 d of ambient temperature curing. A 0.125 wt KS:KOH addition yielded a geopolymer with a UCS of 14.7 MPa whilst a 1.25 wt KA:KOH addition yielded a geopolymer with a UCS of 24.5 MPa. The increase in strength was due to the formation of Calcium Silicate (Aluminate) hydrate. The aluminate activated FeCr slag geopolymer was the most competent of all geopolymers synthesised as it resulted in over 97% immobilisation of Fe, Zn, Mn, Ni and Cr. The 360-d static leachability tests for the aluminate activated geopolymer yielded a metal release rate lower than 90 mg mm− 2 of the geopolymer. The aluminate activated geopolymer also was resistant to changes in wet and dry cycles as it had a UCS reduction of 42% after 10 cycles whereas the pure FeCr slag geopolymer and the silicate activated geopolymer had a UCS reduction of 91 and 72% respectively after 10 cycles. The aluminate activated geopolymer met the minimum requirements for use as a paving brick for low traffic pavements. The study provides opportunities for sustainable use of FeCr slag with minimal environmental impact.

Research Methods of Making Glass and its Physico-Chemical Properties

This article discusses the modern methods of physico-chemical properties of glass manufacturing, through the use of a wide spectrum of glass-forming. Description of the implementation of the staged methods of chemical-technological processes of silicate formation, implying the lowest energy consumption, in connection with the transition to the processing of secondary raw materials.

Microstructure and Minerals Evolution of Iron Ore Sinter: Influence of SiO2 and Al2O3

SiO2 and Al2O3 are two important minerals that can affect the mechanical and metallurgical properties of sinter. This investigation systematically studied the influences of these minerals and revealed their functional mechanisms on sinter quality. Results showed that with an increasing Al2O3 content in sinter, the sintering indexes presented an improvement before the content exceeded 1.80%, while the quality decreased obviously after the content exceeded 1.80%. With an increasing SiO2 content, the sinter quality presented a decreasing tendency, especially when the content exceeded 4.80%. Consequently, the optimal content of Al2O3 was ≤1.80% and that of SiO2 was ≤4.80%. The evolution of the microstructure and minerals in sinter showed that enhancing the Al2O3 content increased the proportion of SFCA generated, which improved the sinter’s mechanical strength, while excessive Al2O3 led to the formation of sheet-like SFCA with weak mechanical strength. Increasing the content of SiO2 strained the formation of SFCA and promoted the formation of calcium silicate, the mechanical strength of which is lower than that of SFCA. The research findings will be useful in guiding practical sintering processes.