Glass-ceramic Foams Research Articles

Microstructure and physico-mechanical properties of Al2O3-doped sustainable glass-ceramic foams

Glass-ceramics foams (GCs foams) were manufactured with the aid of the replica method and from cheap and sustainable raw materials (waste glass bottle, bentonite, and alumina). In order to evaluate the Al2O3 effect on the microstructure and physico-chemical properties of the GCs foams, the precursor aqueous solutions were prepared with different contents of the waste glass bottles (30 wt% and 35 wt%), alumina (0 wt%, 2 wt%, 5 wt%, and 8 wt%), and sintered at temperatures 750 °C and 800 °C. The amorphous/crystalline nature of the GCs foams was investigated by XRD, and the calcium sodium silicate (Na2Ca3Si6O16), cristobalite, and corundum were the main crystalline phases identified. In general, the addition of alumina increased porosity and water absorption with a consequent reduction in flexural strength. The manufactured glass-ceramic foams showed average pore sizes in the range of 240–360 μm, porosity between 52% and 85%, and flexural strength between 0.2 MPa and 3.7 MPa.

Effect of Na2CO3 content on thermal properties of foam-glass ceramics prepared from smelting slag

A new type of foam-glass ceramics was synthesized, by the method of powder sintering (one-step), with smelting slag and porcelain powder as the main raw material. Besides, the influence of sodium carbonate content on the changing trend of glass structure at high temperature and crystal structure of foam-glass ceramics were explored by modern analytical techniques such as DSC, XRD, Tom-ac, and the influence of Na2CO3 content on the viscosity of glass liquid during sintering was studied by VFT inverse proportional formula. When Na2CO3 content was between 0% and 5%, as Na2CO3 content increased, the volume density of the porous glass-ceramic continued to decrease, its porosity continuously increased. The sample prepared by the experiment is composed of wollastonite CaSiO3 and salite CaMgSi2O6. The sample's compressive strength in amounts up to 13.06 MPa and the density is 0.731 g/cm3. The results show that the addition of Na2CO3 has a great effect on the softening point, sintering temperature interval, and volume expansion rate of the mixtures, but has little effect on the crystal phase of the samples.

Reuse of Eggshell Waste and Recycled Glass in the Fabrication Porous Glass–Ceramics

This study was conducted to fabricate and characterize of glass–ceramic foam derived from soda-lime silica (SLS) glass waste and eggshell (ES) waste as a foaming agent by using empirical formula [ES] × [SLS]100−x where x = 1 wt%, 3 wt%, 6 wt%, 9 wt%. The samples undergo a heat-treatment process at temperature 800 °C with a heating rate of 10 °C/min. The properties of the samples were measured by average density measurement and linear expansion. The structural properties were studied by XRD, FESEM and FTIR concerning the different composition of the foaming agent while the mechanical properties were determined by compressive strength using UTM. The lowest density and compressive strength were achieved by 0.326 g/cm3 and 0.04 MPa, respectively with the highest linear expansion at 77.33% by the addition of 3 wt% of ES. Moreover, the cristobalite phase (SiO2) were identified after the heat treatment process. The production of foam glass–ceramics using SLS glass and ES can be applied to prepare different type of porosity that gives benefit to the environment and energy usage.

Synthesis and characterization of low-cost glass-ceramic foams for insulating applications using glass and pumice wastes

At present, there is an increasing need to integrate ceramic materials with insulating properties for housing construction (for energy saving), mainly in areas where extreme temperature occurs. The objective of this work was to synthesize low-cost glass-ceramic foams, using recycled glass and waste materials near to Chihuahua city, Mexico, such as pumice and limestone mineral residues; the last one was used as a foaming material. The precursors were grounded, pressed forming pellets by cold pressing, and subsequently sintered using different conditions of temperature and time. The thermal conductivity, compressive strength, bulk density, actual density and percent expansion of prepared samples were evaluated and discussed in this work. Based on the experimentation, we found that optimum sintering time for this material is 20 minutes. Following this cheap and convenient procedure, a sample obtained at 800°C showed the best properties with a density of 0.44 g/cm3 and a thermal conductivity coefficient of 0.096 W/m K. These values indicated that is feasible to synthesize these foams construction industry applications working as appropriate thermal insulators.

Effect of sintering temperature on the crystal growth, microstructure and mechanical strength of foam glass-ceramic from waste materials

This study was conducted to synthesize foam glass-ceramic using SLS glass as a precursor; eggshell (ES) as a foaming agent and investigated the effect of sintering temperature on the crystal growth, microstructure and mechanical properties of the final product. The samples undergo the sintering process at different temperatures such as 700, 800 and 900°C for 60min with the heating rate of 10°C/min. The structural properties were studied by XRD, FTIR and FESEM measurement. The cristobalite (SiO2) and wollastonite (CaSiO3) phases were identified after the sintering process and their microstructure was recorded by the FESEM micrograph. The physical properties of the samples were measured by average density measurement, linear expansion and compressive strength. The lowest density measurement using the Archimedes principle was achieved by 0.421g/cm3 with the highest volumetric expansion at 92% after the sample sintered at 800°C. Good correlations between porosity, mechanical strength and crystal phase were observed. The invention of foam glass-ceramics from waste materials can be applied as a potential building insulation material that gives benefit to the environment and energy usage.

Sustainable glass-ceramic foams manufactured from waste glass bottles and bentonite

Glass-ceramic foams were manufactured with waste glass bottle (85.7 wt%, 87.5 wt%, and 88.9 wt%) and bentonite. The raw materials were characterized by Energy-dispersive X-ray spectroscopy (EDX) and thermal gravimetric analysis (TGA). The thermal treatment to obtain the glass-ceramic foams were conducted to eliminate the polyurethane without damaging their structure. The glass-ceramic foams sintering was performed at 750 °C, 800 °C, and 850 °C. The macro and microanalysis (optical microscopy) showed a significant porosity reduction, in the samples with higher waste glass contents. Pore closure also was found in samples sintered at 850 °C. In both cases, the pore closure resulted from melting of the glass-ceramic foam. The X-ray diffraction results show that the calcium sodium silicate (Na2Ca3Si6O16) was the main crystalline phase. The physico-mechanical properties (linear shrinkage-LS, loss of mass on fire-LMF, water absorption-WA, apparent porosity-AP, bulk density-BD, and flexural strength-σf) were evaluated for glass-ceramics foams containing 85.7 wt% and 87.5 wt% of waste glass, sintered at 750 °C and 800 °C. The glass-ceramic foams sintered at 750 °C showed an average pore size of 275 μm and 330 μm, porosity of 65.1% and 39.8% and flexural strength of 0.32 MPa and 1.42 MPa for samples containing 85.7 wt% and 87.5 wt% waste glass, respectively. Already sintered foams at 800 °C, the average pore size was 283 μm and 239 μm, the porosity of 37.7% and 18.8% and the flexural strength of 1.90 MPa and 3.77 MPa for samples containing 85.7 wt% and 87.5 wt% waste glass, respectively. In general, the LMF, PA and WA values decrease with the increasing temperature, while the BD, LS, and σf values increase with temperature.

Use of Granulated Foam Glass Ceramics to Protect Heaving Soil from Seasonal Freezing

The effectiveness of applying granular foam glass ceramics to protect a roadbase from seasonal freezing is demonstrated. Observational results of the base temperature regime are presented along with a comparative assessment of risk zones characterizing the depth of freezing and possibility of intense frost heaving.

Glass-Ceramic Foams and Reticulated Scaffolds by Sinter-Crystallization of a Hardystonite Glass

Glass-Ceramic Foams and Reticulated Scaffolds by Sinter-Crystallization of a Hardystonite Glass

Preparation, characterization and discussion of glass ceramic foam material: Analysis of glass phase, fractal dimension and self-foaming mechanism

Resource utilization of waste has always been the focus attention due to the increased environmental problems. In this work, glass ceramic foam was prepared using coal gangue, fly ash and silica sand as raw materials without addition agent. The pore morphology, microstructure and some physical properties of the samples with different silica sand contents were investigated. In addition, the fractal dimension was introduced to quantitatively describe the variation in pore morphology. The results illustrated that the addition of silica sand in the samples is beneficial to form a unique close-pore construction which endows the prepared material with good performance for using as a lightweight wall material in the construction field. Discussion indicated that the introduction of silica sand was found to promote the formation of glass phase, which possibly was the Si–Al–O glass system. The variation of fractal dimension inferred that the co-existence of large and small pores formed in samples with high content silica sand may be originated from the interaction of the two glass phases. The analysis of self-foaming mechanism revealed that only the gases released after glass phase formation were effective to build pore structure. This study provides a highly efficient and clean utilization route for recycling solid waste by preparing lightweight glass ceramic foam.

Effect of sintering temperatures and foaming agent content to the physical and structural properties of wollastonite based foam glass-ceramics

This study aims to fabricate low-cost foam glass-ceramic using soda-lime-silica (SLS) glass waste and clamshells (CS) as foaming agent in content between 1 and 12 wt.% by conventional powder processing method. The samples were undergoing sintering process between 700 and 1000?C with holding time of 30 minutes and characterized according to the physical and structural properties. Samples containing 3 wt.% CS treated at 800?C show the greatest size of porosity. As the sintering temperature increased, the samples tend to become less dense. However, for the samples sintered at 900 and 1000?C, the trend of the density changes because of the excess CO2 gases generated during the heat treatment process promotes an increase in internal pressure, which results in the rupture of the pore walls. For linear expansion, for samples with a sintering temperature of 800?C and higher, the increment of the temperature will lead to the decrement of linear expansion (%). As the sintering temperature increases from 700 to 800?C, the water absorption (%) increases. However, the percentage of water absorption decreases with the further increment of sintering temperature. The XRD characterization showed the formation of wollastonite phase (CaSiO3) and further revealed the formation of greater peaks of CaSiO3 at the higher sintering temperatures. The results of compressive mechanical strength between 0.15 and 1.50 MPa indicate that the obtained glass-ceramic foams have potential for building material applications.

Novel eco-friendly fabrication of foam glass-ceramics via waste glass and fly ash from fused brown corundum

Novel eco-friendly fabrication of foam glass-ceramics via waste glass and fly ash from fused brown corundum

Sintered glass-ceramics and foams by metallurgical slag with addition of CaF2

The possibilities for the production of self-glazed sintered glass-ceramics or/and glass-ceramic foams using metallurgical slag are discussed. The effect of CaF2 addition on the glass melting, the densification and the foaming is also studied.The sintering and the bloating trends are evaluated by hot stage microscopy and the phase formation is estimated by X-ray diffraction spectroscopy. The structure of the obtained samples is studied with scanning electron microscopy and with computed tomography.The results demonstrate a good sinter ability of the used glass powders in the interval 800–950 °C and a subsequent intensive bloating behaviour of the sintered samples in the range 1050–1150 °C.The addition of a certain amount of CaF2 in the glass batches leads to a noticeable decrease of both the melting and the sintering temperatures as well as to some increase of the crystallinity. As a result, self-glazed glass-ceramics with high percentage of CaF2 and with an improved micro-hardness and crystallinity can be obtained using finer glass powders, moderate heating rates and holding temperatures of 950–1000 °C.At the same time, glass-ceramic foams with closed porosity of about 80 vol % can be synthesized using glass powders with a modest addition of CaF2 by applying higher heating rates and holding temperatures of 1100–1150 °C.

Glass-ceramic foams and reticulated scaffolds by sinter-crystallization of a hardystonite glass

In the present investigation, we focused on a glass-based route to hardystonite ceramics, which represent one of the most promising classes of biomaterials, in the form of highly porous scaffolds. A glass corresponding to the stoichiometry of a hardystonite solid solution (Ca2Zn0.85Mg0.15Si2O7) was first synthesized and reduced in the form of fine powders (<40 μm). Highly crystallized samples were obtained by sinter-crystallization, in air, at 1000–1200 °C, starting from highly porous green bodies (porosity >70 vol%), obtained by direct foaming or stereolithography of specifically formulated suspensions. More precisely, foams were obtained by intensive mechanical stirring (with the help of a surfactant) of suspensions undergoing gelation, in weakly alkaline aqueous solutions. Reticulated structures with complex non-stochastic geometry, on the other hand, were obtained by digital light processing of glass powders suspended in a photosensitive organic binder. The intensive crystallization caused an excellent retention of the shapes generated at room temperature. The uniform microstructures, all comprising quite dense struts, favored the mechanical properties (with crushing strength well exceeding 2 MPa, with open porosity above 65 vol%).

Waste-derived glass-ceramics fired in nitrogen: Stabilization and functionalization

In a circular economy perspective, waste-derived materials are attractive once the adopted manufacturing technology combines low costs, absolute stabilization of pollutants and interesting functionalities of the product. This paper deals with the enhancement of chemical stability and functionalities of highly porous glass-ceramic foams, from vitreous residues the plasma processing of municipal solid waste (‘Plasmastone’), by firing in nitrogen, at 800–1000 °C. Before firing, the processing relied on alkali activation of glass suspensions, followed by intensive mechanical stirring. Previous experiments had demonstrated that the stabilization of pollutants could be achieved only by mixing Plasmastone with 30 wt% recycled boro-alumino-silicate glass, in samples fired in air. The change in the atmosphere had a significant impact on the Fe2+/Fe3+ balance, leading to a different phase assemblage, in turn causing the stabilization of pollutants even operating with more common recycled soda-lime glass. The new phase assemblage also promoted functionalities such as electrical conductivity, relative permittivity and electromagnetic shielding effectiveness.

Elastic Mechanical Properties of 45S5-Based Bioactive Glass-Ceramic Scaffolds.

Porosity is recognized to play a key role in dictating the functional properties of bioactive scaffolds, especially the mechanical performance of the material. The mechanical suitability of brittle ceramic and glass scaffolds for bone tissue engineering applications is usually evaluated on the basis of the compressive strength alone, which is relatively easy to assess. This work aims to investigate the porosity dependence of the elastic properties of silicate scaffolds based on the 45S5 composition. Highly porous glass–ceramic foams were fabricated by the sponge replica method and their elastic modulus, shear modulus, and Poisson’s ratio were experimentally determined by the impulse excitation technique; furthermore, the failure strength was quantified by compressive tests. As the total fractional porosity increased from 0.52 to 0.86, the elastic and shear moduli decreased from 16.5 to 1.2 GPa and from 6.5 to 0.43 GPa, respectively; the compressive strength was also found to decrease from 3.4 to 0.58 MPa, whereas the Poisson’s ratio increased from 0.2692 to 0.3953. The porosity dependences of elastic modulus, shear modulus and compressive strength obeys power-law models, whereas the relationship between Poisson’s ratio and porosity can be described by a linear approximation. These relations can be useful to optimize the design and fabrication of porous biomaterials as well as to predict the mechanical properties of the scaffolds.

Integrated utilization of municipal solid waste incineration fly ash and bottom ash for preparation of foam glass–ceramics

For the purpose of solid waste co-disposal and heavy metal stabilization, foam glass–ceramics were produced by using municipal solid waste incineration (MWSI) bottom ash and fly ash as main raw materials, calcium carbonate (CaCO3) as foamer and sodium phosphate (Na3PO4) as foam stabilizer. The influences of the raw material composition, foaming temperature and foaming time on the properties were investigated. Porosity, bulk density, mechanical property and leaching of heavy metals were analyzed accordingly. The product, foamed at 1150 °C for 30 min with 14% fly ash and 74% bottom ash, exhibits excellent comprehensive properties, such as high porosity (76.03%), low bulk density (0.67 g·cm−3) and high compressive strength (10.56 MPa). Moreover, the amount of leaching heavy metals, including Cr, Pb, Cu, Cd and Ni, in foam glass–ceramics is significantly lower than that of the US EPA hazardous waste thresholds. This study not only realizes the integrated utilization of bottom ash and fly ash, but also addresses a new strategy for obtaining foam glass–ceramics.

ФИЗИКО-МЕХАНИЧЕСКИЕ И ТЕПЛОФИЗИЧЕСКИЕ СВОЙСТВА ПЕНОСТЕКЛОКЕРАМИКИ НА ОСНОВЕ КРЕМНЕЗЕМСОДЕРЖАЩЕЙ ПОРОДЫ

Obtaining the foam-glass ceramic building materials bypassing the process of high-temperature glass melting and the use of local rocks as raw materials, which can significantly reduce the cost of the final product, is an urgent task of modern building materials science. The aim of this work is to study the physical, mechanical and thermal properties of foam- glass ceramic building materials obtained by one heating of the mixture consisting of silica-containing rock (tripoli) and soda ash. The developed heat-insulating building materials have an average density of 200 to 600 kg/m3, compressive strength of 1.2 to 9.8 MPa, thermal conductivity of 0.053 to 0.065 W/m °C. Studies establishes a rational ratio of components in the composition of foam glass ceramics based on silica rock. In the production of foam materials, the heating rate of the charge should vary from 3 to 4.5 ° C / min, and the maximum heating temperature from 800 to 850 ° C. The developed material will expand the range of thermal insulation building materials and can be used in the construction of industrial and civil facilities, nuclear power plants, in the gas and oil industry.

Low temperature upcycling of vitreous byproduct of the MSW plasma processing into multifunctional porous glass-ceramics

ABSTRACTMixtures of glass residues, deriving from the plasma processing of municipal solid waste (‘Plasmastone’), and recycled glasses have been already converted into highly porous glass-ceramics by application of an inorganic gel casting technique (foaming, by intensive mechanical stirring, of alkali activated slurries) followed by sintering at 1000°C. The full potential of recycled glass, however, has not been disclosed yet. The present investigation, in fact, demonstrates that boro-alumino-silicate glass, from discarded pharmaceutical vials, may allow for sintering of cellular glass-ceramics at particularly low temperature, i.e. at 800°C. The full stabilisation of heavy metals from Plasmastone (already assessed for treatments at 1000°C) is not compromised, whereas the low processing temperatures favour the separation of magnetite, in turn imparting new functionalities (e.g. electromagnetic shielding) to waste-derived glass-ceramic foams.

The utilization of electrical insulators waste and red mud for fabrication of partially vitrified ceramic materials with high porosity and high strength

Preparation of glass ceramic foam materials from solid waste is a practicable technique that could alleviate the environmental challenges caused by solid waste and obtain products with high added value. We prepared glass ceramic foams with high porosity and high strength using electrical insulators waste and red mud as raw materials. The effect of different electrical insulators waste/red mud ratios on the pore structure, physical properties, mechanical strength, and chemical stability of the glass ceramic foams was investigated. In addition, a leaching test of heavy metal ions and multiple recycling of the prepared glass ceramic foams were analyzed. The results showed that with increasing electrical insulators waste content, the different chemical components of the waste promoted the formation of a liquid phase, the composition of which transformed from a Ca-Al-Si-O to an Al-Si-O glass system, and therefore, caused a variation in the pore structure of the glass ceramic foams. Meanwhile, the bulk density, porosity, compressive strength and acid corrosion resistance of the prepared glass ceramic foams displayed a satisfactory trend. The leaching toxicity results of the prepared glass ceramic foams revealed that the heavy metal ions were solidified by the formed glass phase during sintering. When the electrical insulators waste/red mud ratio was 8/2, the glass ceramic foams exhibited optimal comprehensive properties in the prepared samples, with a bulk density of 0.66 g/cm3, porosity of 73.6% and compressive strength of 11.3 MPa.

Structure Formation in the SiO2–Na2O–H2O System during the Fabrication of Foam Glass Ceramics by Extrusion

This paper presents a method for the fabrication of a foam glass ceramic, an inorganic heat-insulating material, by extruding a mixture of opal–cristobalite rock and a sodium hydroxide solution through calibrated holes. The method ensures excellent mixture homogenization and allows mixing of components and granulation of the mixture to be combined in a single step. As a result of active reactions of amorphous phases in the opal–cristobalite rock with sodium hydroxide in the SiO2–Na2O–H2O system, the average density of the material decreases by a factor of 1.5. This ensures an economic benefit: a proportional reduction in the percentage of sodium hydroxide, an expensive component. Using electron microscopy, we have assessed the effect of temperature on structure formation in the material. The pore formation process begins at 200°C and is accompanied, up to 500°C, by the formation of a loose structure in the form of an inhomogeneous network. In the range 400–500°C, the material undergoes a transition. Above 600°C, a cellular structure begins to form. As a result, the materials synthesized at 850°C have an average density from 0.38 to 0.57 g/cm3 and compressive strength from 3.1 to 5.9 MPa.