1,720,976 research outputs found
Development and mechanical characterization of Al2O3 platelet-reinforced glass matrix composites obtained from glasses coming from dismantled cathode ray tubes
No full textA cold-pressing and pressure-less viscous flow sintering treatment for the manufacturing of dense alumina platelet reinforced glass matrix composites was proposed for the recycling of glasses coming from dismantled cathode ray tubes (CRTs). Mixtures of three different glasses from CRTs and Al2O3 platelets were investigated regarding the introduction in glass of rigid, non sintering, inclusions and the nature of the matrix glasses. An innovative short-time sintering procedure was found to be advantageous, leading to significant increases in bending strength, microhardness and fracture toughness, despite the relatively low Al2O3 platelet addition. Both the morphology of the residual porosity, due to the sintering process and particular chemical and physical interactions within the matrix, and the crack deflection effect, due to the specific matrix-reinforcement combination, were found to be the determinant of the observed mechanical properties. The obtained bending strength, Vickers’ microhardness and fracture energy are comparable to the values reported for glass-ceramics for technical applications in the building industry
Sintered glass-ceramics from mixtures of wastes
No full textPanel glass from dismantled cathode ray tubes, mining residues from feldspar excavation and lime from fume abatement systems of the glass industry have been employed as raw materials for several glass compositions. The prepared glasses were ground into fine powders and subjected to sintering treatments at low temperatures (880-930°C), with concurrent crystallization, thus obtaining sintered glass-ceramics. The mechanical properties (for example, bending strength exceeding 100 MPa) and the aesthetic appearance of the materials, together with the simplicity of the manufacturing method, are promising for applications in the building industry
Sintered Wollastonite-based Glass-Ceramics from Mixtures of Wastes
No full textRecycled soda-lime glass, feldspar mining residues and lime from fume abatement systems have been employed for the production of two glasses, later converted into wollastonite-based glass-ceramics. The glass-ceramics were developed by sintercrystallization, starting from fine powders (<37 μm), for short sintering times at 930°C. The properties of the glass-ceramics were due to both the enhanced nucleating activity of glass surfaces and the formation of micro-porosity. The relevant mechanical properties (bending strength and Vickers’ micro-hardness exceeding 130 MPa and 8 GPa, respectively, for samples sintered for only 30 min), make the investigated glass-ceramics suitable for construction applications
Foam glass as a way of recycling glasses from cathode ray tubes
No full textThe manufacturing of glass foams is proposed as a way of recycling glasses from cathode ray tubes (CRTs), following a simple and low cost processing route. No melting of CRT glasses is required, and the foaming occurs at relative low temperatures, thus preserving the chemical stability of glasses. The obtained foams have promising mechanical properties
Al2O3-platelet reinforced glass matrix composites from a mixture of wastes
No full textWastes consisting of mining residues from feldspar excavation, lime from fume abatement systems of the glass industry and panel glass from dismantled cathode ray tubes have been converted into an opaque fluorine-containing glass, featuring the precipitation of CaF2 crystals just upon cooling. Fine glass powders were added with Al2O3 platelets (from 5% to 15% by vol.) and viscous flow pressureless sintered at 800°C for 1h, leading to dense glass matrix composites. Due the overall mechanical properties, approaching those available for glass-ceramics, coupled with a simple and economical manufacturing procedure, the obtained products could find applications in the building industry and constitute a promising way for the absorption of the investigated wastes
Reutilization and stabilization of wastes by the production of glass foams
No full textGlass foams are known to represent highly valuable products for thermal and acoustic insulation, often produced by employing wastes. Although the usage of recycled glass is widely reported for developing the glass matrix, little research has been due to the usage of wastes for the foaming reaction. In this work the cellular structure is achieved after oxidation of SiC-based wastes coming from the polishing of glass articles. The foamed recycled soda-lime glass incorporated the residues from oxidation and provided a reasonably good chemical stability. The addition of MnO2 to the starting mixtures of wastes led to a certain improvement of the oxidation of SiC, and a complex effect on the correlation between density and mechanical strength. For selected additions, a more homogeneous foaming was found to provide a stronger cellular structure
Sintered sanidine glass-ceramics from industrial wastes
No full textGlass obtained from melting a mixture of industrial wastes (panel glass from dismantled cathode ray tubes, mining residues from feldspar excavation and lime from fume abatement systems of the glass industry) has been employed for the production of sanidine based glass-ceramics. The glass-ceramics were developed by a sintering treatment with concurrent crystallization, from fine powders (<37 μm), at a relatively low temperature (880°C). The enhanced nucleating activity of glass surfaces likely promoted the formation of sanidine, hardly found in glass-ceramics, as the main crystal phase. Due to the achieved mechanical properties (bending strength of about 120 MPa, Vickers’ microhardness exceeding 7 GPa) and aesthetic appearance, resulting from a compact and homogeneous microstructure, the obtained sanidine glass-ceramics may find applications as construction materials
Development and mechanical properties of metal-particulate glass matrix composites from recycled glasses
No full textThe great number of glasses available from recycling activity and vitrification treatment of industrial wastes leads to the need for new applications, with the development of new materials, such as low-cost composite materials from a powder technology route. In the present
work a variety of recycled glasses is investigated, in order to obtain aluminium reinforced glass matrix composites via cold-pressing and viscous flow sintering. A good compatibility between lead silicate glasses from cathode ray tubes dismantling and aluminium reinforcement is found to be effective. Composites exhibiting good mechanical properties were developed from these materials. A particular attention was
due to fracture toughness (KIC) determination. The absolute KIC of glass matrix composites value remains low, but a notable increment in relation to unreinforced matrix is observed
Vitrification of wastes and preparation of chemically stable sintered glass-ceramic products
No full textThe present work illustrates the conversion of wastes, like panel glass from dismantled cathode ray tubes, mining residues from feldspar excavation and lime from fume abatement systems of the glass industry, into two glasses which were subjected to a sinter-crystallization process. The surface mechanism of nucleation, starting from finely ground powders (<37μm) allowed a rapid crystallization at a relatively low temperature (2h at 880°C), with the preparation of glass-ceramics possessing a complex of mechanical properties (bending strength and microhardness exceeding 60 MPa and 6.3 GPa, respectively) comparable of that of commercial glass-ceramics and natural stones for building applications, coupled with a good chemical durability. This feature, together with the type of crystals developed, was reasonably correlated to the fluorine content of the parent glasses
Effect of time and furnace atmosphere on the sintering of glasses from dismantled cathode ray tubes
No full textThe dismantling of cathode ray tubes (CRTs) represents a pressing environmental problem. CRTs consist of three distinguished glass parts. The front part is a barium-strontium glass, while the parts hidden inside the TV sets consist of lead silicate glasses. The high quality standards in manufacturing new CRTs impose a very limited amount of glasses to be recycled in the production of the original components. In addition, the presence of easily reducible oxides (like PbO) in the chemical composition of CRT glasses causes the risk of dispersing poisonous substances during remelting. Sintering of powdered glass could be a profitable way to produce new dense glass based materials without remelting. CRT glasses were found to be strongly susceptible to both the duration of the firing at the sintering temperature and the furnace atmosphere (oxygen, air, nitrogen). The evolution of the relatively large amount of dissolved oxygen, typical of CRT glasses, is found to contrast densification. Very short firing times (up to 15 min) are found to limit gas evolution. In addition, oxidative atmospheres lead to high quality sintered materials, capable of optical transparency comparable to that of pristine glasses
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