Preparation Of Glass-ceramics Research Articles

Preparation of glass-ceramics with diopside as the main crystalline phase from low and medium titanium-bearing blast furnace slag

Because of the low content of TiO2, the utilization of low and medium Ti-bearing blast furnace slag is a difficult problem. In this study, glass-ceramics with diopside as the main crystalline phase was made by using TiO2 in the blast furnace slag as the nucleating agent and adding additional elements of TiO2, Fe2O3 and Cr2O3. The effects of these three nucleating agents on the phase composition and structural properties of the prepared glass-ceramics were evaluated by DSC, XRD, and SEM to determine their optimal dosage. Research results show that the suitable mass percentages of the TiO2, Fe2O3 and Cr2O3 crystal nucleation agents of the glass-ceramics are 7.69%, 0.96%, and 2.88%, respectively. The prepared glass-ceramics have excellent physical and chemical properties, e.g., a bending strength of 114.74MPa, a bulk density of 2.77g/cm3, a water absorption rate of 0, and a mass-loss rate of only 0.085%.

Preparation of Glass Ceramics by Reactive Crystallization with Waste Glass and Spinel

Magnesium silicate glass ceramics were prepared by reactive crystallization with mixed powder of waste glass and spinel. The effects of spinel content and sintering temperature and holding time on the crystal phase and morphology of magnesium silicate glass ceramics were investigated. The reactive crystallizing behavior between waste glass powder and spinel was studied using energy dispersive spectrdmeter during the holding process. The result show that the optimum preparation conditions were as follows: the addition of 30 wt% spinel used as crystallization promoting agent, sintering temperature of 900 oC and holding time of 2 h. The magnesium silicate and alumina crystals were formed via an interaction between glass powder and spinel instead of direct precipitation from the parent glass. With increasing of the holding time, the Al and Mg element contents of the glass were increased, on the contrary, that Si element content was decreased in the glass phase. It shows that the Si element is diffused from glass into spinel phase and subsequently magnesium silicate crystals are formed.

Ferroelectric glass-ceramics

Abstract

Glass-ceramics one-step crystallization accomplished by building Ca2+ and Mg2+ fast diffusion layer around diopside crystal

CaOMgOSiO2 (CMS) glass-ceramics preparation normally needs two-step heat treatment (nucleation and crystal growth). In this work, CMS glass-ceramics are successfully produced by one-step heat treatment by building Ca2+ and Mg2+ fast diffusion layer between the residual glass and diopside crystal. High-temperature X-ray diffraction (HTXRD) shows that diopside crystals formed during the crystallization of CMS glass. At the glass layer between diopside crystal and residual glass, an enrichment of Na+ is observed by energy dispersive spectroscopy line scanning (EDSLS), which increases the SiONa bonds that promote Ca2+ and Mg2+ ions diffusion. This layer eventually promotes further growth or ripening of the diopside crystals. Thus, nucleation and crystal growth of the CMS glass proceed continuously at the crystallization peak temperature (Tnc), detected by differential scanning calorimetry. Thereby, one-step crystallization of the CMS glass-ceramics becomes possible and practical.

Preparation of Glass-Ceramics by Reactive Crystallization with Waste Glass and Mullite

Diopside glass-ceramics were prepared by reactive crystallization with mixed powder of waste glass and mullite. The effects of mullite content and sintering temperature and holding time on the crystal phase and morphology of diopside glass-ceramics were investigated. The reactive crystallizing behavior between waste glass powder and mullite was studied using energy dispersive spectrdmeter during the sintering and holding process. The result show that the optimum preparation conditions were as follows: the addition of 30 wt% mullite used as crystallization promoting agent, sintering temperature of 900 °C and holding time of 2h. The main difference between reactive crystallization method and the traditional method of preparing diopside glass-ceramics was the reactive crystallization mechanism. The diopside and corundum crystals were formed via an interaction between glass powder and mullite instead of direct precipitation from the parent glass during the calcining and holding process. With the increasing of sintering temperature and holding time, the Ca and Mg element concents of the glass were increased, on the contrary, that Si element concent was decreased in the mullite. It shows that the Si element diffused from mullite to glass and precipitated diopside crystals.

One-step Crystallization Kinetic Parameters of the Glass-ceramics Prepared from Stainless Steel Slag and Pickling Sludge

AbstractOne-step crystallization is one of the most energy conserving methods for glass-ceramics preparation. However, only a few kinetics studies focused on the glass-ceramics prepared by the one-step crystallization. The one-step crystallization kinetic parameters were studied using differential scanning calorimetry. The activation energy (Ea) and the Avrami parameter (n) were calculated as 152. 79 kJ · mol−1 and 4. 39, respectively. These parameters indicate that continuous nucleation and three-dimensional crystal growth are the dominating mechanisms in the one-step crystallization process of the parent glass. The properties of the obtained glass-ceramics can be compared to the glass-ceramics prepared by the two-stage heat treatment and sintering method. This crystallization kinetics research can be used to evaluate the one-step crystallization potential of a parent glass.

Preparation of glass-ceramics using high contents of red mud and fly ash

The preparation of glass-ceramics with high contents of red mud ash using TiO2 and titanium slag as nucleation agents, respectively, is proposed. The effects of different formulations on physicochemical properties, microstructure and phase composition of glass-ceramics were investigated, followed by the analysis of the crystallisation behaviours. The results showed that the primary crystalline phase was Ca2(Al(AlSi)O7) in both cases, while the secondary crystalline phase was (CaFeO6Si2) and Ca(Al2Si2O8), respectively. Also, the crystallinity increased with increasing content of nucleation agent, and condensations were observed once the nucleation agent content exceeded a critical value. With the contents of TiO2 and titanium slag to be 1 and 6·6%, respectively, the overall content of industrial solid wastes achieved 93·9 and 95·3%, respectively. The performance of as-prepared glass-ceramics can satisfy the requirements of JC/T 872–2000 standard. Therefore, this study is of great significance for the recycling of industrial solid wastes.

Effect of MgO/Al<sub>2</sub>O<sub>3</sub> Ratio on Properties and Crystallization of Glass-Ceramics

Reduction electric furnace slag, quartz sand and soapstone were used as the raw materials for preparation of glass-ceramics according to their compositions and characteristics. Differential thermal analysis, X-ray diffraction, scanning electron microscopy were used to investigate the crystallization mechanism, microstructure and main mechanical properties of slag glass-ceramics with different mass ratios of MgO/Al2O3. The exothermic peaks of the DTA curves shift to higher temperature with the decrease of MgO/Al2O3 ratio. And along with the decreasing of the MgO/Al2O3, the crystallization of the glass-ceramics also decreased. The bending strength can reach 153.09MPa when the MgO/Al2O3 ratio is 3.03.

Effects of the replacing content of ZnBr2 on the properties of ZnO–B2O3–SiO2:Mn2+ glass-ceramics

ZnBr2-doped ZnO–B2O3–SiO2:Mn2+ (ZBSM) optical-storage glass-ceramics were successfully prepared by a sol–gel method. The crystalline phase and microstructure of ZBSM were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy. The addition of ZnBr2 influenced the crystallization of the ZBSM glass-ceramics. Moreover, the effects of ZnBr2 additive on the preparation of glass-ceramics were analyzed by differential scanning calorimetry. The optical storage properties of the samples were investigated by photoluminescence spectroscopy, long-lasting phosphor (LLP) decay curves, and thermoluminescence (TL) spectroscopy. The LLP decay curves show that the lower phonon energy of Br− ions generates more stable metastable energy. The TL spectra and Gaussian fitting indicate that the sample with 20mol% ZnBr2 content exhibited the best performance.

Novel preparation of glass ceramics from amorphized tungsten tailings

Glass ceramics were successfully prepared from amorphized tungsten tailings after magnetic separation. Samples were characterized by DSC, XRD, SEM, and FTIR. The results demonstrated the main crystalline phases of the as-prepared glass ceramics were gehlenite (Ca2Al2SiO7) and hedenbergite (CaFeSi2O6), and the amount and size of the crystalline phases increased with increase of crystallization temperature. The morphology of crystalline grains varied from tiny granular to plate-like crystals. The crystalline phases would melt again, and hedenbergite would partially transform into gehlenite at a crystallization temperature of 1100°C. Based on the kinetics analysis for crystallite growth, the activation energy (Eα) and Avrami constant (n) were calculated as 381.16kJ/mol and 2.04, respectively, indicating that the crystallization mechanism followed two-dimensional growth. The glass ceramics from tungsten tailings at 1050°C showed proper crystal structure and high performance, which could be considered for potential applications in building materials.

Effect of CaO/SiO2 ratio on the preparation and crystallization of glass-ceramics from copper slag

Glass-ceramics were synthesized successfully from iron-rich copper slag and the iron was recovered in the same process so that iron-rich copper slag was recycled efficiently. The influence of CaO/SiO2 ratio on the preparation of glass-ceramics was emphasized using differential scanning calorimetry (DSC), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results show that the residual iron concentration of the quenched glass is less than 1.43mass% and Fe concentration in recovery of copper slag is more than 96.6mass%, highlighting that the iron is extracted effectively from copper slag. Crystallization kinetics result shows an increase in the activation energies of crystallization with an increase in CaO/SiO2 ratio up to 0.38 and subsequently a decrease with further increase in CaO/SiO2 ratio up to 0.42. Anorthite with lamellar shape and diopside with irregular column shape are developed as the major phases in all the glass-ceramics samples with different CaO/SiO2 ratios. The increase in CaO/SiO2 ratio hinders the crystal growth of lamellar anorthite but benefits the formation of diopside crystals. For CaO/SiO2=0.42, the optimal comprehensive properties of the glass-ceramics are achieved: low porosity of 0.11%, low bibulous rate of 0.04%, high density of 2.75g/cm and high hardness of 85.75HBa.

Preparation of Glass-Ceramics Using Industrial Solid Wastes in China

The industrial solid wastes mainly include mining tailings and industrial slags. Their typical applications in glass-ceramics are reviewed. The compositional design of the glass-ceramics based on the compositional features of wastes and the routes to increase the percentage of wastes in the glass batches are emphasized. To increase the addition of industrial solid wastes in the glass preparation is one of the key factors influencing the utilization of the wastes. One way to achieve this is to apply different wastes with compositional complementarity in glass batches. A few successful examples are summarized in this paper to provide good references for the further related research.

Mutual Influence of Special Components in Baotou Steel Blast Furnace Slag on the Crystallization Behavior of Glass

In the process of glass-ceramics prepared with Baotou steel blast furnace slag, quartz sand, and other raw materials by melting method, the mutual influence of the special components such as CaF2, REXOY, TiO2, K2O, and Na2O in the blast furnace slag on the crystallization behavior of parent glass was investigated using differential thermal analysis (DTA) and X-ray diffraction (XRD). The results show that the special components in slag can reduce the crystallization temperature and promote crystallization of glass phase, which belongs to surface crystallization of glass, and they cannot play the role of the nucleating agent; the major crystal phase composed of diopside, diopside containing aluminum and anorthite, is slightly different from the expected main crystal phase of diopside. Therefore, the nucleating agents of proper species and quantity must be added into the raw materials in order to obtain glass-ceramics. The results have important theoretical guidance meaning for realizing industrial production of Baotou steel blast furnace slag glass-ceramics preparation.

Crystallization Behavior during Preparation of Glass-Ceramics from BF Slag of Baotou Iron and Steel Company

In this paper, the crystallization behavior including crystallization temperature, nucleation temperature, microstructure of glass-ceramics and crystal phase composition during preparation of glass-ceramics by melting method from blast furnace(BF) slag of Baotou iron and steel company, quartz sand and other materials was investigated using differential thermal analysis, X-ray diffraction and scanning electron microscopy. The results show that the crystallization peak temperatures of the parent glasses are 962~966°C when the ratio of blast furnace slag changes from 20% to 50%, and uniform, compact grains in the prepared glass-ceramics are obtained, whose diameters are about 0.2-0.5μm. In addition, the major crystalline phases are identified as diopside(Ca(Mg,Al)(Si,Al)2O6）and diopside containing aluminum(Ca(Mg0.5Al0.5)(Al0.5Si1.5O6), and the mechanical properties of glass-ceramics are good, among which the flexural strength is more than 110Mpa. The results have theoretical guidance meaning and practical reference value for realizing industrial production of preparation of glass-ceramics from BF slag of Baotou iron and steel company.

Preparation of Glass-Ceramics Using Molybdenum Tailings

In order to utilization the molybdenum tailings which be deposited in large quantities. Test used it to prepare glass-ceramics as main raw material, TiO2 as nucleation agents and CaO-Al2O3-SiO2 system and wollastonite as the principal crystalline phase. Heat treatment system of glass-ceramics was based on the differential thermal analysis. The crystalline phase, microstructure and characteristics of glass-ceramics were analysis by XRD, SEM and physical, chemical properties test. The result shows that the performance of glass-ceramics was superior to the other types of building decoration stone.

Preparation of glass ceramics containing ruby crystals

We have developed the red-colored glass ceramics containing ruby crystals by heat-treatment of a Cr3+-doped SiO2-Al2O3-Y2O3 glass at 1550 °C. The shape of precipitated crystals in the glass matrix was rod type whose average width and length were around 10μm and 200μm, respectively. From an X-ray diffraction measurement and an electron probe X-ray microanalysis, the rod crystals were found to be α-Al2O3. Intense emission bands of Cr3+ at 694 nm, called the R-lines, were observed in the glass ceramics. In addition, the intense R-lines were observed only in the α-Al2O3 rod crystals by a photoluminescence mapping image.

Bioactivity of thermal plasma synthesized bovine hydroxyapatite/glass ceramic composites

Bone injuries and failures often require the inception of implant biomaterials. Research in this area is receiving increasing attention worldwide. A variety of artificial bone materials, such as metals, polymeric materials, composites and ceramics, are being explored to replace diseased bones. Calcium phosphate ceramics are currently used as biomaterials for many applications in both dentistry and orthopedics. Bioactive silicate-based glasses show a higher bioactive behaviour than calcium phosphate materials. It is very interesting to study the mixtures of HA and silicate-based glasses. In the present study; natural bovine hydroxyapatite / SiO2-CaO-MgO glass composites were produced using the Transferred arc plasma (TAP) melting method. TAP melting route is a brisk process of preparation of glass-ceramics in which the raw materials are melted in the plasma and crystallization of the melt occurs while cooling down at a much faster rate in relatively short processing times compared to the conventional methods of manufacture of glass ceramics/composites. It is well known that; one essential step to the understanding of the biological events occurring at the bone tissue/material interface is the biological investigation by in vitro tests. Cell lines are commonly used for biocompatibility tests, and are very efficient because of their reproducibility and culture facility. In this study, we report the results of a study on the response of primary cultures of human fibroblast cells to TAP melted bioactive glass ceramics.

Crystallization of KNbO3 in a B2O3 glass network

The ferroelectric material potassium niobate (KNbO 3 ) has a large number of exceptional electronic and optical properties with important technological applications. Due to the high preparation difficulties and costs of the single crystals, a considerable interest in the preparation of glass-ceramics with the KNbO 3 crystal phase exists. In this work we present the preparation of a glass, with the composition 40B 2 O 3 –40K 2 O–20Nb 2 O 5 (% mole), through the melt-quenching method and glass-ceramics obtained by controlled heat-treatments. The samples structure was analyzed using X-ray power diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy. KNbO 3 crystals were detected in the glass sample treated at 500 °C. For treatments at temperatures above 500 °C, other niobium-based crystal phases are present. The behavior of the heat-treatment temperature parameter, in the glass and glass ceramic structure, is discussed.

NaNbO 3 crystals dispersed in a B 2O 3 glass matrix – Structural characteristics versus electrical and dielectrical properties

Sodium niobate (NaNbO 3) is a crystal with a perovskite structure that exhibits, at room temperature, an antiferroelectric behaviour. It is a very interesting material due to the several phase transitions that it presents as a function of the temperature (ferroelectric–antiferroelectric–paraelectric). Thus, the preparation of glass-ceramics containing NaNbO 3 crystals is scientifically and technologically important. Besides, there is actually few works available about the preparation of NaNbO 3 crystals embedded in a glass matrix. The present work reports the preparation process and the study of glass and glass-ceramics in the B 2O 3–NaNbO 3 system. The glass with the molar composition 60B 2O 3–30Na 2O–10Nb 2O 5 (mol%) was prepared by the melt-quenching method. Sodium niobate (NaNbO 3) crystallites were precipitated through a controlled heat-treatment (HT) process. NaNbO 3 crystallites were detected by X-ray diffraction (XRD) in the samples treated above 500 °C. The treatments above 600 °C favour also the formation of Na 2B 4O 7 and Nb 2O 5 crystalline phases. Scanning electron microscopy (SEM) reveals that the crystallization occurs in volume and that the number of particles increases with the rise in HT temperature. The number of network modifier ions (Na + and Nb 5+) in the glass network is the main factor in the dc and ac conductivity behaviours. The dielectric constant ( ɛ′) value increases with the increase of the volume ratio between the particles and the glass matrix. The sample heat-treated at 550 °C shows two thermally stimulated depolarization current (TSDC) peaks. The high temperature peak can be related to the presence of NaNbO 3 particles.

Structural and spectroscopic study of oxyfluoride glasses and glass-ceramics using europiumion as a structural probe

Transparent oxyfluoride glasses andβ-PbF2 nanocrystals containing glass-ceramics were prepared with varyingEu3+ content (0.3, 0.4, 0.5 and 0.6%). The effect ofEu3+ content on the preparation of glass-ceramics was investigated. From differential scanning calorimetry,the Tx–Tg (Tx—temperature of the onset of crystallization;Tg—glasstransition temperature) parameter for glasses has shown slight variation, and an exothermic peak nearTg called the ceramizationtemperature (Tc) has been observed. Heat treatments were performed at thistemperature to obtain transparent glass-ceramics containingβ-PbF2 nanocrystals, identified by x-ray diffraction. Heat treatments for different periods of time wereperformed and were observed to be very important in the control of the crystal size and of thecrystallization rate. Based upon the absorption spectra, the scattering level due to the presence ofβ-PbF2 nanocrystals in the glass-ceramics was observed to be similar to that for the mother glasses.Detailed analysis of emission spectra and decay time measurements led to the identification ofEu3+ ionsas the β-PbF2 crystalline phase. Excitation spectra at 70 K show the interaction ofEu3+ ions with the fluorogermanate network.