Slag Glass-ceramics Research Articles

Influence of high field strength ions on the crystallization characteristics and properties of slag glass-ceramics

Blast furnace slag glass–ceramics were prepared by melting using rare-earth-containing blast furnace slag (REBFS) as the main raw material and Fe2O3 and Cr2O3 as composite nucleating agents. By adding different TiO2 contents, the study comprehensively revealed the effects of high field strength ions on the glass network structure, crystalline properties, elemental distribution and physicochemical properties. Raman spectroscopy and differential scanning calorimetry revealed that TiO2 acted primarily as a network modifier in the glass network. The appropriate TiO2 content disrupted the glass network, decreasing the crystallization activation energy (EC) of the glass–ceramic. However, excess TiO2 repaired the network structure, thereby increasing the EC. The combined effect of the Cr and Ti substantially improved the crystallization characteristics of the glass-ceramics. Cr2O3 induced the formation of spinel, which promoted the crystallization of the main crystalline augite phase. The self-aggregation of the high field strength Ti4+ ion induced the formation of a titanium- and cerium-containing titanite phase, which also contributed to grain refinement. This titanite phase effectively increased the Vickers hardness and acid and alkali resistances of the glass-ceramics to 9.16 GPa and over 98.5 %, respectively. The excellent physicochemical properties render REBFS glass–ceramics as being promising materials for various construction applications. This research provides theoretical support for comprehensively utilizing blast furnace slag and provides theoretical guidance for preparing slag glass–ceramics possessing desirable physicochemical properties.

Effect of manganese on the structure of CMAS slag glass–ceramics

With the acceleration of industrialization, environmental issues have received great attention from governments and societies around the world. Utilizing solid wastes containing valuable heavy metals and exploring their role and application in materials is one of the focal issues of environmental protection in recent years. In this paper, in order to explore the effect of Mn content on the crystallization of CaO-MgO-Al2O3-SiO2 glass–ceramics, glass–ceramics with different content of MnO2 were prepared by sintering method and the effect of MnO2 doping on the crystalline properties, glass stability and heavy metal fixation properties of the stainless steel slag glass–ceramics was investigated by differential scanning calorimetry (DSC), Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscope (SEM). The analysis using crystallization kinetics showed that surface crystallization dominated the whole crystallization process in the range of 0% to 10% MnO2 content. The peak glass crystallization and depolymerisation temperatures of the glass–ceramics increased gradually with increasing MnO2 content, and the main crystallization mode of the samples was one-dimensional crystallization. The main crystalline phase of the resulting glass–ceramics was transformed from diopside to spinel, with a crystallization temperature of 860℃. Heavy metals solidified in the spinel phase. This study shows that heavy metals can be effectively immobilized in glass–ceramics. In summary, the use of solid waste to prepare final products with good environmental performance provides a feasible way to utilize solid waste resources.

Molecular Dynamics Simulation and Viscosity Analysis of Red Mud-Steel Slag Glass-Ceramics.

The preparation of glass-ceramics with red mud and steel slag can not only solve the pollution problem caused by industrial waste slag but also produce economic benefits. It is difficult to analyze the high-temperature melt with the existing test methods, so the simulation experiment with molecular dynamics calculation becomes an important research method. The effects of steel slag content on the microstructure of red mud glass-ceramics were studied by molecular dynamics method. The results show that the binding ability of Si-O, Al-O, and Fe-O decreases with the increase in steel slag content. The number of Si-O-Si bridge oxygen increased gradually, while the number of Al-O-Al, Al-O-Fe, and Fe-O-Fe bridge oxygen decreased significantly. The number of tetrahedrons [SiO4] increased, the number of tetrahedrons [FeO4] and [AlO4] decreased, and the total number of three tetrahedrons decreased. The mean square displacement value of Si4+ and O2- increases first and then decreases, resulting in the viscosity of the system decreasing first and then increasing. The molecular dynamics method is used to analyze the structure of red mud-steel slag glass-ceramics on the microscopic scale, which can better understand the role of steel slag and has guiding significance for the experiment of this kind of glass-ceramics.

Effect of TiO2 on the occurrence and distribution of chromium in stainless‐steel slag glass ceramics

AbstractStainless steel slag waste can be used to prepare value‐added glass ceramics, which can fix potentially toxic Cr from the slag within the crystalline phase. The occurrence and distribution of Cr during the preparation of glass ceramics has a great influence on the final Cr fixation effect. In this study, the effects of the TiO2 content on the occurrence and distribution of Cr during the nucleation and crystallization steps and on the final properties of the glass ceramics were systematically studied. In the nucleation stage, with increasing TiO2 content, the Cr distributed in the spinel containing chromium nuclei first increases and then decreases. In the crystallization stage, Diopside crystal phase nucleates and grows with spinel containing chromium nanocrystals as heterogeneous nuclei. X‐ray photoelectron spectroscopy analysis showed that the chromium distributed in the diopside crystals first increased and then slightly decreased as the TiO2 content increased. The optimal TiO2 content is 3.4 wt.%, which resulted in 97 wt.% of the total Cr being fixed in the diopside crystalline phase (with a very low Cr leaching concentration of 0.009 mg/L), and a high compressive strength of the final glass ceramic of 267.4 MPa, and a Vickers hardness of 1211.8 HV. The research results provide theoretical and technical support for strengthening Cr fixation to enable harmless and high‐value utilization of stainless steel slag for fabricating glass ceramics.

Effect of Al2O3 on migration and distribution of chromium and chromium fixation effect in stainless-steel slag glass-ceramics

Stainless-steel slag was used to prepare glass-ceramics, which could solidify chromium (Cr) in the slag. The migration and distribution state of chromium in the slag during the preparation of the glass-ceramics have a great influence on the chromium fixation ability of the glass-ceramics. In this paper, the effects of Al2O3 content in the glass-ceramics on the migration and distribution of chromium during the nucleation and crystallization steps, and on the chromium fixation effect of the glass-ceramics were systematically studied. The results show that in the nucleation stage, with the increase of Al2O3 content, the number of chromium spinel (Cr-spinel) nanocrystals formed in the glass first increases and then decreases, and Cr in the glass phase gradually migrates to Cr-spinel nanocrystals. TEM and XPS analyses show that during crystallization, part of Cr in Cr-spinel diffuses into diopside lattice, and the other part of Cr still exists in Cr-spinel wrapped by diopside. Cr in the glass phase also diffuses and migrates into the diopside lattice with the formation of diopside crystals. The optimal Al2O3 content is 11.8wt.%, which results in 97.94wt.% of the total Cr being fixed in the diopside crystalline phase. The ability of chromium fixation is very high giving a very low Cr leaching concentration of 0.004mg/l. The research results provide theoretical and technical support for increased chromium fixation and realizing harmless and high-value utilization of stainless-steel slag.

The excellent properties and solidifying effect of Cr providing by micro-crystal grain in slag glass-ceramics

The excellent properties and solidifying effect of Cr providing by micro-crystal grain in slag glass-ceramics

Structure and Crystallization of High-Calcium, CMAS Glass Ceramics Synthesized with a High Content of Slag.

In this work, more than 70 wt % of ferromanganese slag (containing 40 wt % CaO) was used to synthesize high-calcium, CaO-MgO-Al2O3-SiO2 (CMAS) glass ceramics. The effect of SiO2/CaO on the structure, crystallization behavior and microstructure of high-calcium, CMAS, slag glass ceramics was studied by IR, NMR, DSC, XRD and SEM. The results showed that in the high-calcium, CMAS glass ceramics, the main existing forms of silicon–oxygen tetrahedra (Qn) were Q0 and Q1. With the increase in the SiO2/CaO, Qn changed from Q0 and Q1 (main units) to Q1 (main units) and Q2, and then to Q1 and Q2 (main units). The polymerization degree of Qn changed from low to high, making the glass more stable, which led to the increase in crystallization temperature and the decrease in crystallization kinetic constant (k) and frequency factor (υ). At the same time, the change in the Qn structure resulted in a gradual change to the main crystal, from akermanite to diopside–wollastonite.

Effect of Ce2o3 Migration on the Crystallization Properties of Slag Glass-Ceramics in Microwave Electric Field

Effect of Ce2o3 Migration on the Crystallization Properties of Slag Glass-Ceramics in Microwave Electric Field

Effect of Ce2o3 Migration on the Crystallization Properties of Slag Glass-Ceramics in Microwave Electric Field

Effect of Ce2o3 Migration on the Crystallization Properties of Slag Glass-Ceramics in Microwave Electric Field

DETERMINATION OF THE COMPRESSION STRENGTH RP OF MULTILAYER PLATES MADE OF SLAGOSITALS

The methodology of creating multifunctional acoustic automated devices has been further developed, it is based on the construction of simple algorithms for transforming and processing signals of measuring instruments. A differential acoustic method for controlling the physical and mechanical parameters of multilayer plates made of slag glass-ceramics has been investigated. A structural diagram of an automated device for measuring acoustic control of the ultimate compressive strength Rр of a controlled slag glass-ceramics plate is proposed. The option of automation of the measurement process considered in the article makes it possible to carry out measuring control of the strength characteristics for a relatively short period of time and by averaging the results of measurements of the physical and mechanical parameters of slag glass-ceramic plates, leads to a decrease in the values of random measurement errors and thereby contributes to an increase in the accuracy of measurements of physical and mechanical parameters of slag glass-ceramics products. The values of the relative increments of the attenuation coefficient ∆ƞ23/ƞ4were obtained, while the ranges of the values of the attenuation coefficient of a transmission of various waveforms of the piezoelectric transducer correspond to the ranges of the compressive strength Rр of the test sample. At the same time, the control of the strength of the material Rр at multiple frequencies is due to the fact that even a slight change in the geometric parameters of the slag glass-ceramics slab leads to a change in the generalized parameters of the universal transformation functions of the measuring differential acoustic devices, which are associated with the physical and mechanical characteristics of the controlled material of the sample The proposed two-parameter differential acoustic control method allows to keep in mind the linkage between temperature and mechanical parameters: the unequal distribution of the temperature along the length of the sample and the uneven distribution deformation of temperature with the localization of this plastic component in the middle part of the slag glass-ceramics plate, which is most significantly affected by temperature and, as a consequence, is subject to gradual destruction.

Crystallization and thermal stability effects on tailings glass-ceramics by various heat treating processes

Increasing environmental concerns raise attention on the recycling of mining wastes and smelting of byproducts. As one of the candidate materials, slag glass-ceramics give full play to effective use of tailings resources with excellent performance. In the present research, Bayan Obo tailings are used to produce slag glass-ceramics. However, the effect of the preparation process on the stable behavior and crystallization mechanism of glass-ceramics is still being explored. In this study, different heat treatment processes are used to prepare slag glass-ceramics and its effects on the stability and performance are evaluated through different glass crystallization characteristics. X-ray diffraction (XRD), differential scanning calorimetry (DSC), high-resolution scanning electron microscopy (SEM), Spectral analysis techniques (FT-IR and Raman spectroscopy), and high-temperature thermal imaging system (Tomac) are performed to study and characterize the stable behavior and mechanism of glass-ceramics. Results show that glass-ceramics with heat treatment at 1000 °C exhibit competitive mechanical properties. High crystallization temperature promotes the crystallization of the glass and enhances the growth of crystal grains to optimize the stability and physical properties of the glass-ceramics. In this research, a new process parameter model is provided for process optimization in the industrial production process of glass-ceramics.

Non-equilibrium cooling regulating vitrification and crystallization of Canasite-A glass-ceramics from high sodium solar silicon waste slag

This work provides an effective method for realizing both resource utilization and high-value utilization of bulk industrial solid waste. The influence of non-equilibrium cooling rates on the internal energy and amorphous structure of the precursor glass is studied to clarify the nucleation process of various crystals. A new method is proposed to control the glass formation and crystal growth process by using the cooling rate of the high-temperature melt. Research results show that the crystallization enthalpy (ΔHc) of the precursor glass decreases with decreasing cooling rates, and the NBO/T gradually decreases. When the non-equilibrium cooling rate is (k) > 10 °C/min, ΔHc is ≥ 157.05 kJ/mol and NBO/T increases to 1.09. Additionally, the glass network structure is unstable and mainly consists of Q4 structural units, which promote canasite-A crystal nucleation. The Cxonotlite:Ccanasite-A ratio increases from 1:1 to 1:5, and the crystallinity increases by 25.49%. The flexural strength of the silicon slag glass-ceramics also increases by 59.19%.

Effect of Sintering Time on Crystal and Structure of Chlorine-containing Low-titanium Slag Glass-ceramics

Glass-ceramics with akermanite, diopside, spinel and perovskite crystalline phases were prepared by using the direct sintering method and using chlorine-containing low-titanium slag as a raw material. The changes in crystalline phase composition, relative content and microstructure of glass-ceramics sintered at different times were studied. The results suggested crystalline phases remained steady while the relative content of each phase changed significantly. The relative content of akermanite decreased firstly and then increased while those of diopside changed oppositely. The relative content of spinel rose from 6.6% to 9.3% and perovskite stabilized at 10.0-11.1%. In addition, the pore size of glass-ceramics declined firstly and then increased. The optimal microstrure of glass-ceramics were obtained when crystallized at 890 °C for 60 min and sintered at 1185 °C for 60 min. In general, glass-ceramics with compact microstructures could be obtained at appropriate sintering times.

Relationship between thermophysical properties and structure of CMAS glass melts based on chromium slag

In an attempt to determine the relationship among the network structure, viscosity, electrical conductivity, surface tension, and density of chromium-containing glass melts, the variation in glass melt thermophysical properties of the CaO–MgO–Al2O3–SiO2 quaternary system were investigated by comprehensive physical property analysis and Raman spectroscopy. The results demonstrated that the network structural units Qn (n = 0, 1, 2, 3) coexisted in the glass melts and their mutual transformation caused changes in the depolymerization degree, leading to a range of viscous activation energies, conductive activation energies, surface tension, and melt densities. Additionally, the logarithm of viscosity varied linearly with the logarithm of electrical conductivity (slope: 0.67–1.54). Meanwhile, the surface tension and melt density decreased with temperature. Consideration of these interrelations is indispensable during the development of chromium-containing slag glass ceramics, particularly for pilot and industrial applications.

Effects of fluoride content on structure and properties of steel slag glass-ceramics

The hot steel slag were utilized for preparing the glass-ceramics by melting method with different fluoride contents. The crystallization behaviors of the glass-ceramic were characterized by Differential Scanning Calorimeter (DSC), X-ray Diffraction (XRD), Fourier Transform Infrared Spectrometer (FTIR), Raman, and the Field Emission Scanning Electron Microscope (FESEM).The results established that the transition from Nepheline to Cuspidine, and then to Kalsilite, and finally became Combeite in glass-ceramics occurred with the decrease of fluoride content. Besides, a comprehensive analysis of FTIR and Raman revealed that the addition of fluoride contributed to the formation of the Si–O bridge oxygen in the glass structure, which improved the degree of polymerization of the glass structure and further affected the crystal phase of the glass-ceramics. In addition, when Nepheline and Cuspidine constituted as the major crystalline phases for the prepared glass-ceramics, a higher flexural strength and a smaller volume shrinkage were achieved. SEM depicted that the above mentioned results were ascribed to from the changes in the crystal type and the degree of crystallization, in which the size of the crystal phase had a greater influence on the performance of the glass-ceramic. It was worth noting that the highest flexural strength was 177.76 MPa with the lowest volume shrinkage of 0.06%.

Mössbauer and photocatalytic studies of CaFe2O4 nanoparticle-containing aluminosilicate prepared from domestic waste simulated slag

The relationship between local structure and visible-light activated photocatalytic effect of simulated domestic waste slag glass–ceramics (R-NaWSFe) was investigated. The largest pseudo-first-order rate constant of 9.75 × 10−3 min−1 was estimated for methylene blue decomposition test under the visible-light irradiation using R-NaWSFe with additional 30 mass% of Fe2O3 heat-treated at 900 °C for 100 min. The reason for the high photoactivity of this sample was mainly due to nanoparticles of CaFe2O4 and α-Fe2O3 confirmed by the Mossbauer spectrum measured at 77 K. It is concluded that the nanoparticles of magnetic components in silica are essential for exhibiting visible-light activated catalytic effect.

Effect of SiO2/MgO ratio on the crystallization behavior, structure, and properties of wollastonite-augite glass-ceramics derived from stainless steel slag

Wollastonite-augite glass-ceramics of the CaO–SiO2–Al2O3–MgO system were prepared from stainless steel slag as the main raw material. The effects of SiO2/MgO mass ratio on the crystallization behavior, crystalline phases, structure, and properties of the as-prepared stainless steel slag glass-ceramics were investigated by differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and physicochemical property measurements. The results showed that with decreasing SiO2/MgO ratio, the crystallization activation energies of the samples decreased from 436.48 kJ/mol to 383.84 kJ/mol, and their crystallization indexes increased from 1.67 to 3.21; in addition, the augite crystals were gradually refined and their content increased. On the other hand, the amount of elongated wollastonite crystals decreased and the crystals gradually dispersed in the augite crystals. Furthermore, among all the prepared glass-ceramics, the one with a density of 3.08 g/cm3 exhibited the best mechanical properties with a bending strength of 176.21 MPa and microhardness of 8.81 GPa.

Effects of SiO2/CaO ratio on viscosity, structure, and mechanical properties of blast furnace slag glass ceramics

In an attempt to improve the effective utilization of solid waste generated in the steel industry and reduce the production cost of glass ceramics, glass ceramics were prepared from blast furnace slag as the main raw material. The effects of SiO2/CaO molar ratio on the viscosity, structure, and properties of the as-prepared CaO–MgO–Al2O3–SiO2 (CMAS) blast furnace slag glass ceramics were investigated by viscometry, X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and physicochemical property measurements. The results showed that with decreasing SiO2/CaO ratio, the viscosity and degree of polymerization of molten glass significantly decreased, and the main crystalline phase transformed from single diopside to a combination of augite and gehlenite phases, which affected the physicochemical properties of the glass ceramics. The glass ceramic sample with a density of 2.78 g/cm3 exhibited the best comprehensive performance: bending strength of 182.86 MPa, microhardness of 7.34 GPa, acid resistance of 95.21%, and alkali resistance of 98.43%. The various characterization results proved that the prepared glass ceramics could be potentially used for several industrial applications.

The Formation of a Comfortable Habitat and the Economic Feasibility of Using Alternative Thermal Insulation Technologies

The pace of construction and renovation of buildings is increasing every year. This encourages the search and introduction of new materials and technologies to improve the comfort of housing. An important problem is also the need to ensure the energy efficiency of buildings. A peculiarity of the Russian natural conditions is a significant daily and annual difference in atmospheric temperatures. The use of various thermal insulation materials in the construction process will significantly reduce the cost of maintaining buildings and provide comfortable conditions for people, regardless of natural events. In addition, the use of certain facade treatments solves the aesthetic problem and can protect against precipitation and industrial emissions. Therefore, the purpose of this study is to find additional possibilities for thermal insulation of buildings using non-traditional technologies and materials. Modern approaches to the aesthetics of buildings involve the use of expensive mineral thermal insulation materials. Reducing the cost of their manufacture is possible through the use of industrial waste. Wastes from non-ferrous metallurgy are suitable for the production of slag wool or for the production of slag glass-ceramics. A wide range of possibilities allows the use of various wastes in the manufacture of bricks to increase porosity, strength and frost resistance. The use of a number of additives also provides an increase in economic efficiency and environmental friendliness of production. The use of special coatings for gypsum finishing materials could increase their strength and water resistance. The quality of facade paints is significantly increased when using aluminum silicate liquid sodium glass. Fine-dispersed waste of metallurgical enterprises will allow to lower the cost of production of liquid glass and aluminosilicate glue. The use, obtained from waste, astringent, provides for the production of heat-insulating materials the production of bright colors without the use of pigments. High strength and water resistance of materials can ensure the use of magnesian waste. Keywords: thermal insulation, energy efficiency, industrial waste, building materials, finishing materials, paints.

Effect of CaF2 on viscosity, structure and properties of CaO-Al2O3-MgO-SiO2 slag glass ceramics

Bayan Obo tailings (BOTs), fly ash (FAS), and stainless-steel slag (SSS) are industrial wastes that require reasonable, clean, and effective utilization for environment protection. The paper focuses on the structure and properties of glass-ceramics that were prepared by melting BOT, FAS, and SSS raw materials. The effect of CaF2 on the viscosity, structure, and performance of CaO-Al2O3-MgO-SiO2 (CAMS) slag glass-ceramics is determined by viscometer, differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and physicochemical properties measurements. The results show that moderate amounts of CaF2 facilitates depolymerization of the silicate networks, which leads to a decrease in the melting temperature, viscosity and viscous activation energy of glass. However, the content of more than 3% CaF2 results in a dramatic decreases in the chemical stability of the glass-ceramics because of the transformations of the main crystalline phase from diopside to anorthite, which is accompanied by fluorite precipitation.