Preparation Of Glass-ceramics Research Articles

Preparation of Glass-Ceramics via Cosintering and Solidification of Hazardous Waste Incineration Residue and Chromium-Containing Sludge.

Residues from the incineration of hazardous wastes are classified as hazardous byproducts because they contain heavy metals. Chromium-containing sludge (CCS) is industrial sludge produced during the electroplating process and includes heavy metals, such as Cr, Pb, and Cu. These heavy metals can infiltrate natural ecosystems and cause significant environmental damage. To limit the toxicity of leached products, hazardous waste incineration residues (HWIRs) can be repurposed as raw materials for producing glass-ceramics. In this study, we designed an orthogonal experiment to optimize the heat treatment process, yielding glass-ceramics with excellent properties and realizing heavy metal solidification. The toxic characteristic leaching procedure was used to determine the leaching toxicity of the cosintered solidified heavy metals, revealing that their solidification efficiencies exceed 90%. Moreover, X-ray diffraction analysis indicates that certain heavy metals participate in the formation of heavy-metal-containing crystal lattices (FeCr2O4 and PbFe12O19), thereby reducing their leaching concentration. These results show that cosintering HWIR and CCS is an effective approach for heavy metal solidification and provides valuable insights into its utilization for producing building materials.

Crystallization of glasses – When to use the Johnson-Mehl-Avrami kinetics?

Applicability of the Johnson-Mehl-Avrami (JMA) model was tested based on the universal criterion of the kinetic peak asymmetry. Theoretical simulations were used to prepare variety of kinetic peaks with different asymmetries, which were described by the JMA model and the masterplot function z(α). Based on the correlation between the simulated crystallization peaks and the JMA description, the following intervals of the degrees of conversion corresponding to the z(α) function maxima can be attributed to the respective values of the correlation coefficients: αmax,z = 0.620 – 0.665 corresponds to the better correlation with the JMA model than r2 = 0.999; αmax,z = 0.585 – 0.705 indicates the correlation better than r2 = 0.995. These intervals are significantly more lenient than those proposed in the original derivation of the masterplot approach. Even at r2 = 0.995 the fit by the JMA model provides very accurate kinetic predictions utilizable for preparation of glass-ceramics.

Technological aspects of borate glass–ceramics preparation doped with transition metals for optoelectronic applications

Chromium-doped borate glass-ceramics are prepared at different temperatures via bulk crystallization of the borate glass matrix. The temperature influence on the spectral and operational characteristics of the material is observed. Rod-shaped LiAl7B4O17 crystals nucleate in a glassy matrix during two stage heat treatment. Borate glass-ceramics possess luminescence in the 650–800 nm region when excited with “green” light. An increase in the annealing temperature of glass-ceramics lead to several changes: (1) the luminescence quantum yield increase from 13% to 50%, (2) color coordinates of glass-ceramics luminescence shift towards to the red spectral region, (3) hardness and resistance to acid solutions of glass-ceramics increase. XRD experiments are carried out within the direct heating of a glass sample. The results show that the maximum size of nanocrystals was reached at a temperature of 600 °C, which coincided with the maximum of the exothermic region on the DSC curve. Thus, the spectral and operational properties of borate glass-ceramics exceed those of the initial borate glass, which makes borate glass-ceramics doped with chromium ions promising material for creating red and near infra-red emitters .

Preparation of glass-ceramics from chromite-containing tailings solidified with Red Mud

In order to solve the problem of chrome slag returning to yellow and Red Mud accumulating in large amounts, this study proposes to use Red Mud and chromite ore process residue instead of clay to make glass-ceramics, and seal chromium, so as to achieve the purpose of waste control by waste and high-valued of final product. The Red Mud (RM), Chromite ore process residue (COPR) and silicon dioxide were homogenized in ethanol and fired at 1200 ℃ for 2 h. The results of XRD and SEM-EDS show that part of chromium enters the lattice, and the rest is wrapped in silicate glass. The leaching toxicity test data of solidified samples showed that the leaching concentrations of hexavalent chromium and total chromium were below the detection limit. In the process of sintering, solidification and preparation of glass-ceramics, Red Mud is not only used as one of the raw materials of glass-ceramics, but also plays the role of fluxing agent and nucleating agent, which greatly reduces comprehensive energy consumption and the production cost of glass-ceramics. This study provides a new way to solve the environmental problems caused by RM and COPR.

Study on glass-ceramics made from MSWI fly ash, pickling sludge and waste glass by one-step process

Municipal solid waste incinerated (MSWI) fly ash and pickling sludge contain heavy metals such as Cr, Pb, Ni, etc., which are harmful to the environment but also suitable to be the nucleating agents in glass-ceramics preparation. In this paper, MSWI fly ash, pickling sludge, and waste glass were melted at 1400 °C for 3 h, and the obtained parent glass was nucleated and crystallized at 800 °C for 0.5 h. Glass-ceramics was successfully prepared by the one-step process. The effects of the content of pickling sludge on crystalline properties of parent glass and the physicochemical properties of glass-ceramics have been systematically discussed. The gap between nucleation temperature (Tn) and crystallization temperature (Tc) can be narrowed with higher content of pickling sludge, which caused fracture of the glass network (Si-O) and generation of the nonbridging oxygen (NBO), promoting the formation of diopside phase. As a result, nucleation and crystallization can be finished at the same temperature, called one-step process. The sample PS22 with 22 wt% pickling sludge added performed the best crystallization ability for having the narrowest gap (ΔT = 177 °C) between Tc and glass transition temperature (Tg) and the highest ratio of NBO to total oxygen (T) (NBO/T = 1.72). The Vickers’ hardness and bending resistance of the products are 13.11 GPa and 135.84 MPa, respectively. The glass-ceramics are composed of homogeneously distributed diopside, donathite-spinel and glass phase. The toxic heavy metals are effectively stabilized by glass-ceramics. This study provides insights into more efficient and cleaner utilization of MSWI fly ash, pickling sludge and waste glass as glass-ceramic materials.

Transformation of unstable heavy metals in solid waste into stable state by the preparation of glass-ceramics

In this study, glass-ceramics were prepared from stainless steel slag and iron tailing. Consequently, unstable heavy metals were converted to stable. With the adding of stainless steel slag, crystallization temperature and the mechanical properties of the resultant glass-ceramics increased first and then decreased, and it was found that secondary phase (Spinel) differed from major phase (Augite). The results of toxicities leaching test and Tessier five step sequential extraction showed that Cr content in the exchangeable state, carbonate bind state, ferromanganese oxide state and organically bind state of the basic glass were 0.04%, 0.08%, 7.82% and 1.13%, respectively. However, in the glass-ceramics, they exhibited the low content of 0, 0.04%, 2.02% and 0.40%. The residual content of Cr reached to 90.93% in the glass, whereas 97.55% in the glass-ceramics, being higher than that in the glass. The results indicated that Cr enters the silicate lattice, so as to realize the curing of chromium.

Glass-Ceramics Processed by Spark Plasma Sintering (SPS) for Optical Applications

This paper presents a review on the preparation of glass-ceramics (GCs) and, in particular, transparent GCs by the advanced processing technique of spark plasma sintering (SPS). SPS is an important approach to obtain from simple to complex nanostructured transparent GCs, full densification in a short time, and highly homogeneous materials for optical applications. The influence of the different processing parameters, such as temperature, pressure, sintering dwell time on the shrinkage rate, and final densification and transparency, are discussed and how this affects the glass material properties. Normally, transparent glass-ceramics are obtained by conventional melt-quenching, followed by thermal treatment. Additionally, the GC scan is produced by sintering and crystallization from glass powders. Hot pressing techniques (HP) in which the source of heating is high-frequency induction can be also applied to enhance this process. In the case of transparent ceramics and glass-ceramics, spark plasma sintering is a promising processing tool. It is possible to enhance the material properties in terms of its compactness, porosities, crystallization, keeping the size of the crystals in the nanometric scale. Moreover, the introduction of a high concentration of active gain media into the host matrix provides functional glass-ceramics systems with enhanced luminescence intensity through reducing non-radiative transitions like multi phonon relaxation (MPR) and cross relaxations (CR), thus providing longer lifetimes. More effort is needed to better understand the sintering mechanisms by SPS in transparent GC systems and optimize their final optical performance.

Effect of La2O3 on crystallization of Glass-ceramics

The existing form and crystallization behavior of La3+ in the preparation of glass ceramics were studied. Research shows that the addition of La2O3 can effectively promote the base glass nucleation and crystallization at a relatively low temperature. The addition of La2O3 had no effect on the type of the main crystalline phase of the glass-ceramics. The main crystalline phase was wollastonite, which mainly reacted with F in the raw material, and existed in the residual glass phase in the form of LaF3. The addition of La2O3 enhanced the crystallization tendency of the base glass, and the crystallization mechanism converted the surface crystallization into two-dimensional growth; the crystal shape changed from plate-like to crisscross rod-like structure, which enhanced the compactness of glass-ceramics. When 1 wt% La2O3 was added, the transformation and the crystallization temperature reached the lowest, the crystallization activation energy was the smallest, and the crystallization effect was the best.

Structure, viscosity, and crystallization of glass melt from molten blast furnace slag

AbstractMolten blast furnace slag (BF slag) was modified using liquid‐liquid mixing method for glass ceramics preparation, and the structure and viscosity of glass melt after modification were investigated. The BF slag proportion increased from 52.72 wt. % to 67.05 wt. %, and CaO/(SiO2 + Al2O3) also varied from 0.33 to 0.47. The structure of BF slag melt after modification was investigated using 29Si and 27Al MAS NMR spectra. With increasing CaO/(SiO2 + Al2O3), the amount of Q1 remarkably increased while that of Q2 decreased significantly. Specifically, when CaO/(SiO2 + Al2O3) was more than 0.38, Q3 disappeared in glass melt. The viscosity of glass melt with CaO/(SiO2 + Al2O3) of 0.47 exhibited a steep change at 1169°C, which was mainly caused by the sufficient crystallization of gehlenite confirmed by DTA cooling analysis, XRD, and FE‐SEM‐EDS analysis.

Review of Resource Utilization Technology of Steel Slag and Carbon Capture Utilization

Steel slag is a kind of alkaline solid waste produced in the process of steel production. In China, the annual steel slag production is very large but the utilization rate is only 20%. Therefore, technologies disposing steel slag effectively need to be developed. In traditional resource utilization technology, steel slag is used in sintering flux, road construction, cement and concrete production, preparation of glass ceramics and agriculture. In these fields, we mainly give full play to steel slag’s mechanical properties. Although these traditional technologies are simple and easy to use, the main reason for their limited application is the low value of resource-based products and the lack of market competitiveness. Therefore, some new exploration has been made on the resource utilization of steel slag, including dephosphorization of sewage, heavy metal adsorption, hazardous gas removal, fixed CO2 by mineral carbonation. Compared with the traditional resource utilization technologies, these new technologies mainly utilize the physical and chemical properties of steel slag, such as alkalinity and pore characteristics. However, these new technologies also have some limitations, so it is necessary to develop a resource-based technology with strong pertinency, large consumption and high added value of products to treat steel slag. Carbon dioxide is the most important greenhouse gas leading to global climate change. At present, China’s carbon dioxide emissions are high, so it is urgent to develop effective carbon dioxide emission reduction technology. In recent years, carbon capture, utilization and storage (CCUS) technology has received extensive attention. This paper summarizes the carbon capture utilization and sequestration technology, and discusses its problems at present.

Investigation on the Iron Oxide Behaviors in the SiO2-based Slag

Various waste blast furnace slag not only occupies a large amount of land, but also seriously pollutes environment. Preparation of glass-ceramics using the waste blast furnace slag receives more and more attention. In this work, effect of iron oxide behaviour on the crystallization and physical and chemical properties in the SiO2-based slag was studied. Results show that the presence of small amount of iron oxide in slag can promote the crystallization of CaO-MgO-Al2O3-SiO2 quaternary basic glass. With the increase of Fe2O3, the crystalline phase content increases, and the glass phase content decreases. Meanwhile, the density of glass-ceramics increases, but the water absorption decreases. Alkali corrosion resistance of glass-ceramics increases with the increase of iron oxide content in range of 0.5 wt. % - 3 wt. %.

Preparation of iron tailings glass-ceramics by sol-gel method

For the preparation of glass-ceramics by iron tailings, the sintering and melting methods have been used in the past, but the two methods are short of high energy consumption. In this test, the sol-gel method has been adopted. Because the sol-gel method requires high purity to prepare raw materials, and there are many impurities in iron tailings, which is inconsistent with the preparation requirements of sol-gel method. Therefore, in this experiment, useful elements in iron tailings were extracted. Iron tailings were obtained by thermal-alkali reaction, and Fe was obtained by acid reaction, so as to prepare Ca-Mg-Al-Si system glass-ceramics. After the preparation of sol-gel, the basic glass was obtained, and after nucleation and crystallization, the microcrystalline glass whose main phase was diopside was obtained.

Preparation of Glass-ceramics Using Chromium-containing Stainless Steel Slag: Crystal Structure and Solidification of Heavy Metal Chromium

It is a useful way to stabilize the elements of heavy metal in the glass-ceramics with the form of ions due to the environmental pollution of heavy metal, such as Cr. The glass-ceramics of excellent combination properties were prepared, and the effect of stabilizing Cr-containing stainless steel slag with different concentrations of nitric acid leaching test were investigated. It was found that the major crystalline phase was diopside or anorthite with or without the amount stainless steel slag. Moreover, the continuous refinement of grains exhibited with the increase of amount of stainless steel slag. The results indicated that the excellent physical and mechanical properties, including density (2.9 g/cm3), hardness (729.27HV0.3), bending strength (222.9 MPa), and the solid solution of Cr in excess of 0.00057% for the glass-ceramics were related to the change of microstructure and phase structure. There showed the potential for reusing and detoxifying stainless steel slag.

Enhanced antimicrobial properties of bioactive glass using strontium and silver oxide nanocomposites

ABSTRACTBioactive glass has a wide range of biomedical applications. It has attracted immense interest due to its unique ability to bond with a bone through ion exchange in simulated body fluid (SBF) when implanted inside the body. This study concerns sol-gel synthesis of a new bioactive glass composition: 55SiO2-40CaO-(5-x) SrO-xAg2O doped with different mol% of silver as an antibacterial agent, i.e. 0%, 2% and 4% AgSr(0), AgSr(2) & AgSr(3), respectively. This method is a widely used in the preparation of glass ceramics because of its low-temperature. The effect of introducing strontium in addition to silver as an antimicrobial agent into the bioglass matrix was studied. Structural studies were conducted using various techniques including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM) and High-resolution transmission electron microscopy (HR-TEM). Bioactivity was investigated by in-vitro synthesis involving immersion of the samples in SBF for different time intervals. The XRD, FTIR and FE-SEM results confirmed the formation of a hydroxylapatite layer on the surface of the finally prepared bioglass materials. An antimicrobial study revealed that the prepared bioactive glass showed a significant effect on two bacteria E. coli and S. aureus.

Preparation of Glass-ceramics from Phosphogypsum

CaO-Al2O3-SiO2 glass-ceramics was prepared from phosphogypsum and studied by differential thermal analysis (DTA) and X-ray diffraction (XRD). CaSO4 in phosphogypsum decomposed into CaS and then it reacted with CaSO4 forming CaO and SO2 when the most energy-efficient reaction by Factsage calculated. SiO2, AlPO4, CaSiO3 (wollastonite-1A) and CaSiO3 (calcium silicate) were identified as the main phases in the glass-ceramics prepared from phosphogypsum.

Influence of the phosphate glass melt on the corrosion of functional particles occurring during the preparation of glass-ceramics

We report our findings on the impact of the glass composition on the corrosion of microparticles occurring during the preparation of glass-ceramics using the direct doping method. Microparticles (MPs) with the composition Sr4Al14O25:Eu2+,Dy3+ with blue-green persistent luminescence were chosen as the changes in their spectroscopic properties can be related to the MPs’ corrosion. The MPs were added in phosphate-based glasses with different compositions. When using the same doping parameters, the glass system with the composition 90NaPO3-10Na2O (mol%) was found to be the least corrosive on the MPs whereas the glass system with the composition 90NaPO3-10NaF (mol%) is the most corrosive on the MPs probably due to their different viscosity at 575 °C, the temperature at which the MPs are added in the glass melts.

Glass-ceramics from a zinc-electroplating solid waste: Devitrification promoted further crystallization of parent glass upon heat treatment

A solid waste from a zinc electroplating production line was successfully used as a main raw material for synthesizing glass-ceramics with a fine microstructure. X-ray fluorescence spectroscopy analysis on dried solid waste shows that the waste mainly contains iron and zinc oxides. X-ray diffraction (XRD) analysis identifies Fe3O4 and ZnO phases in calcined waste samples. Based on the above results, silica sand, lime stone and potassium feldspar were proportionally added to make parent glasses by melting the batches at 1450 °C for 2 h. The as-synthesized products show typical DSC and thermal expansion curves with obvious glass transition phenomenon. However, XRD patterns reveal that they had devitrified to form ZnFe2O4 phase during the shaping and cooling of the melts. The devitrification became weaker when more potassium feldspar was added. It is interesting to find that the pre-crystallization of ZnFe2O4 in the devitrified sample was beneficial to its further crystallization during the following heat-treatment. The result implies that the devitrification of parent glasses is not necessarily a detriment to the preparation of glass-ceramics via controlled crystallization process.

Preparation of glass-ceramics with low density and high strength using blast furnace slag, glass fiber and water glass

To reduce the production costs of glass-ceramics and broaden the application field of solid waste in steel industry, low-density and high-strength glass-ceramics were produced by using blast furnace slag as the basic material, choosing glass fiber and water glass as the strengthening agents. The effects of glass fiber and water glass on the phase composition, microstructure, apparent density, water absorption and compressive strength of glass–ceramics were investigated. The results show that the rod structure of glass fiber can be retained in the sintered samples and high content of diopside and augite significantly improve the compressive strength of glass-ceramics. Tiny spherical crystalline phases can be obtained for the glass-ceramics soaked in the moderate concentration of water glass. The BGW-2 samples fabricated with 70% blast furnace slag, 30% glass fiber and 4% water glass, exhibit excellent comprehensive properties. The bulk density, water absorption and compressive strength of BGW-2 are 1.76g/cm3, 2.26% and 68MPa, respectively. Consequently, using blast furnace slag to prepare glass-ceramics can be another applicable way to utilize blast furnace slag efficiently.

The evidence of phase separation droplets in the crystallization process of a Li2O-Al2O3-SiO2 glass with TiO2 as nucleating agent – An X-ray diffraction and (S)TEM-study supported by EDX-analysis

Lithiumalumosilicate glasses are of great importance for industrial applications, because they enable the preparation of glass ceramics with coefficients of thermal expansion close to zero. While detailed studies of the effect of ZrO2 on nucleation and crystal growth have already been performed in recent years, the effect of TiO2 was up to now not reported in detail. It is shown for the first time, that liquid/liquid phase separation is the initial step of nucleation in lithiumalumosilicate glasses containing TiO2. During temperature treatment above the glass transition temperature, at 740°C for 0.25–24h, in the formed droplets, TiO2 nanocrystals precipitate. The formed phases were investigated by XRD- and TEM and STEM-EDX to illustrate the phase developments as well as the resulting microstructures and the local enrichments of the respective components as a function of time.Longer crystallization times resulted in the formation of crystalline lithiumalumosilicate (LAS) with a high-quartz structure. These crystals are notably larger than the TiO2 crystals and are growing with increasing treatment time and temperature. The evidence of anatase formation was obtained from high resolution TEM from the lattice spacings because it cannot be distinguished from the high quartz structure using XRD.

Research on a novel modifying furnace for converting hot slag directly into glass-ceramics

Utilization of hot slag and its waste heat (1450–1650 °C) constitute a great challenge for iron and steel industry. In recent years, a method different from the traditional one, has been developed to integrate utilization of waste heat and mass of hot slag, which has as an objective to prepare value-added materials and to establish a much cleaner production. During the process, composition and structure of hot slag are modified to meet the need of target materials, while its waste energy is utilized to lower heat consumption during the melting and reactions of raw materials. To carry out such modification process, a novel modifying furnace, which was composed of an upper part, cyclone furnace (CFu) and the bottom part, modifying chamber (MCh), was designed and constructed during this research. Experiments to investigate the effect of different process parameters on temperature distribution in the furnace and preparation of glass-ceramics from the modified hot slag were conducted. Cooled modifiers mainly composed of fly ash were initially heated in CFu and then placed into the molten bath in MCh to mix with hot steelmaking slag. During the modification process, the maximum temperature reached 1500 °C in the mid-bottom part of CFu. An increase of a secondary air stream could decrease the CFu temperature but had no significant impact on the MCh temperature. Input of a primary oxygen-rich air stream could guarantee higher temperature in both the CFu at 1400–1600 °C and the MCh at 1400–1450 °C. The optimum parameter of velocities was (100–120) × 2 m3/h for primary air stream, (10–16) × 2 m3/h for oxygen gas stream and 315–568 m3/h for secondary air stream. To achieve efficient flow ability and take advantage of more hot slag, the steel slag was modified to include a higher basicity (CaO/SiO2) of 0.6–0.7 compared to the traditional product (commonly below 0.5). Glass-ceramics, derived from the water quenched modified slag after heat treatment, was finally prepared with excellent performances.