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Monteiro, R. C. C., F. P. Glasser, and E. E. Lachowski. "Crystallization of CaO-Al2O3-SiO2 and CaO-MO-Al2O3-SiO2 (M=Mg, Zn) glasses." Journal of Materials Science. 24 (1989): 2839-2844. AbstractWebsite

A range of CaO-Al2O3-SiO2 glasses have been prepared by fusion of pure starting materials in platinum crucibles. Compositions containing large amounts on network formers, Al2O3 and SiO2, are difficult to crystallize. If the amount of network former is reduced, glasses will self-nucleate and crystallize more readily, but the products of crystallization tend to react with water. This conflict has been partly resolved by adding MgO and ZnO and tailoring compositions so as to produce a phase, variously designated "Q" or "pleochroite", ideally Ca20Al32-2 vMg vSivO68, with v close to 4. Pleochroite crystallizes with a typically fibrous morphology. Preliminary experiments on fragments and melt-cast glass rods indicate that these compositions can be heat treated without deformation to yield highly crystalline, transparent ceramics. © 1989 Chapman and Hall Ltd.

Lima, M. M., and R. Monteiro. "Characterisation and thermal behaviour of a borosilicate glass." Thermochimica Acta. 373 (2001): 69-74. AbstractWebsite

The changes occurring during the heating of a borosilicate glass have been investigated by differential thermal analysis, dilatometric analysis and thermomechanical analysis. The thermal properties of this glass, such as glass transition temperature, dilatometric softening temperature and linear thermal expansion coefficient, have been determined. Viscosity measurements in the temperature range 898-1048 K were performed in a thermomechanical analyser equipped with a penetration attachment for isothermal measurement, and from the temperature dependence of viscosity a value of 290 kJ mol-1 was obtained for the activation energy for viscous flow. Devitrification of the glass was observed, specifically in finely powdered glass samples, where the precipitation of cristobalite was identified by X-ray diffraction. Glass powder compacts sintered by viscous flow and cristobalite precipitation reduced strongly the shrinkage rate. © 2001 Elsevier Science B.V.

Leroy, C. a, M. C. a Ferro, R. C. C. b Monteiro, and M. H. V. a Fernandes. "Production of glass-ceramics from coal ashes." Journal of the European Ceramic Society. 21 (2001): 195-202. AbstractWebsite

Coal fly ashes produced by an extinguished power plant in the north of Portugal have been melted with addition of CaCO3 and Na2CO3 to obtain glasses. One of the formulated compositions was selected for further studies and it was possible to manufacture glass-ceramics by crystallizing the parent glass through adequate time-temperature schedules. The macroscopic appearance, microstructure, mechanical, thermal and chemical properties indicated that these materials are quite attractive for cladding applications, exhibiting in some cases better performances than the conventional ceramic tiles.

Ferro, M. C., C. Leroy, R. C. C. Monteiro, and M. H. V. Fernandes. "Fine-grained glass-ceramics obtained by crystallisation of vitrified coal ashes." Key Engineering Materials. 230-232 (2002): 408-411. AbstractWebsite

Coal fly ashes have been vitrified by melting with Na2O and CaO as fluxing additives. Adequate heat treatments on the fly ash derived glass produced attractive dark green glass-ceramics. These glass-ceramics exhibited fine-grained microstructures consisting of esseneite and nepheline crystals, with average size below 200 nm, homogeneously dispersed in a residual glassy matrix. Several properties, such as density, thermal expansion coefficient, bending strength, hardness and brittleness index were determined and the correlation microstructure-properties is discussed. The results suggest that these coal ash-based glass-ceramics have potential applications as structural materials or as cladding materials.

Lima, M. M. R. A., F. M. Braz Fernandes, and R. C. C. Monteiro. "Study of the crystallization of a borosilicate glass." Key Engineering Materials. 230-232 (2002): 157-160. AbstractWebsite

The crystallization of a commercial borosilicate glass powder has been studied in the temperature range 750-900°C. Crystal growth was investigated by high temperature XRD and cristobalite precipitation was identified. Glass devitrification exhibited a characteristic incubation period that decreased with increasing temperature: 25-30 min at 750°C, 9-12 min at 775°C, 5-10 min at 810°C, and 0-5 min at 840°C. Cristobalite is an unfavorable transformation product in terms of thermal expansion behavior. The precipitation of cristobalite in sintered glass compacts was confirmed by dilatometric analysis, where the increase in thermal expansion coefficient due to the presence of cristobalite and its transition from the tetragonal to the cubic phase were verified. Correlation between the XRD results and the dilatometric data from sintered glass compacts showed the partial dissolution of cristobalite when the glass was heated at the highest temperatures.

Lopes, A., P. Nunes, P. Vilarinho, R. Monteiro, E. Fortunato, and R. Martins. "Study of the sensing mechanism of SnO2 thin-film gas sensors using hall effect measurements." Key Engineering Materials. 230-232 (2002): 357-360. AbstractWebsite

Hall effect measurements are one of the most powerful techniques for obtaining information about the conduction mechanism in polycrystalline semiconductor materials, which is the basis for understanding semiconductor gas sensors. In order to investigate the correlation between the microscopic characteristics and the macroscopic performances exhibited by undoped tin oxide gas sensors deposited by spray pyrolysis, Hall effect measurements were performed at different temperatures, from room temperature up to 500 K, and in the presence of two different atmospheres, air and methane. From these measurements, it was possible to infer the potential barrier and its dependence with the used atmosphere. The obtained results were analysed in terms of the oxygen mechanism at grain boundaries on the basis of the grain boundary-trapping model. In the presence of methane gas, the electrical resistivity decreases due to the lowering of the inter-grain boundary barrier height.

Mei, S., J. Yang, R. Monteiro, R. Martins, and J. M. F. Ferreira. "Synthesis, characterization, and processing of cordierite-glass particles modified by coating with an alumina precursor." Journal of the American Ceramic Society. 85 (2002): 155-160. AbstractWebsite

The surfaces of cordierite and glass particles were modified by coating them with an alumina precursor using a precipitation process in the presence of urea. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy, X-ray diffraction, electrophoresis, and rheological measurements were used to characterize the coated powders. SEM and transmission electron microscopy morphologies of the coated powders revealed that amorphous and homogeneous coatings have been formed around the particles. The morphology of the coated powders showed a coiled wormlike surface. The coating Al2O3 layer dominated the surface properties of the coated glass and cordierite powders. The influence of the coating layer on the processing ability of cordierite-based glass-ceramics substrates by tape casting was studied in aqueous media. It could be concluded that the coating of the powders facilitates the processing and yields green and sintered tapes with denser, more homogeneous microstructures compared with the uncoated powders.

Monteiro, R. C. C., and M. M. R. A. Lima. "Effect of compaction on the sintering of borosilicate glass/alumina composites." Journal of the European Ceramic Society. 23 (2003): 1813-1818. AbstractWebsite

The effect of initial compaction on the sintering of borosilicate glass matrix composites reinforced with 25 vol.% alumina (Al2O3) particles has been studied using powder compacts that were uniaxially pressed at 74, 200 and 370 MPa. The sintering behaviour of the samples heated in the temperature range 850-1150 °C was investigated by density measurement, axial and radial shrinkage measurement and microstructural observation. The density of the sintered composites increased continuously with temperature for compacts pressed at 74 MPa, while for compacts pressed at 200 and 370 MPa it reached the maximum value at 1050 °C and at higher temperatures it decreased slightly due to swelling. The results showed anisotropic shrinkage behaviour for all the samples, which exhibited an axial shrinkage higher than the radial shrinkage, and the anisotropic character increased with the initial compaction pressure. © 2003 Elsevier Science Ltd. All rights reserved.

Muşat, V. a, R. b Monteiro, and R. b Martins. "Thermal decomposition of a sol-gel precursor for C-axis oriented Al-doped ZnO thin films." Revue Roumaine de Chimie. 48 (2003): 967-974. AbstractWebsite

The thermal decomposition and crystallization behaviour of a sol-gel precursor used for the preparation of c-axis oriented Al-doped ZnO thin films were investigated in the temperature range 20-600°C by TG-DTA, IR spectroscopy and XRD analysis. At low temperature, the formation of ZnO crystallites from the sol precursor, prepared by dissolving Zn(CH 3COO)2·2H2O and AlCl 3·6H2O in 2-methoxyethanol and monoethanol amine, takes place via zinc carbonate hydroxide (sclarite/hydrozincite) and occurs simultaneously with the decomposition of this intermediary compound, which occurs above 150°C. At 200°C, the crystalline structure is well defined in terms of ZnO hexagonal lattice parameters, although an important amount of residual organic compounds and water was not yet removed. Increasing the treatment temperature up to 300, 400 and 600°C leads to a gradual removal of the residual organic compounds and therefore to a small change of the ZnO crystalline structure in terms of lattice parameters and grain size.

Musat, V. a, B. b Teixeira, E. b Fortunato, R. C. C. b Monteiro, and P. c Vilarinho. "Al-doped ZnO thin films by sol-gel method." Surface and Coatings Technology. 180-181 (2004): 659-662. AbstractWebsite

Transparent and conductive high preferential c-axis oriented ZnO thin films doped with Al have been prepared by sol-gel method using zinc acetate and aluminium chloride as cations source, 2-methoxiethanol as solvent and monoethanolamine as sol stabilizer. Film deposition was performed by dip-coating technique at a withdrawal rate of 1.5 cm min-1 on Corning 1737 glass substrate. The effect of dopant concentration, heating treatment and annealing in reducing atmosphere on the microstructure as well as on the electrical and optical properties of the thin films is discussed. The optical transmittance spectra of the films showed a very good transmittance, between 85 and 95%, within the visible wavelength region. The minimum resistivity of 1.3 × 10-3 Ω cm was obtained for the film doped with 2 wt.% Al, preheated at 400 °C and post-heated at 600 °C, after annealing under a reduced atmosphere of forming gas. © 2003 Elsevier B.V. All rights reserved.

Lima, M. M. R. A., and R. C. C. Monteiro. "Crystallization of a borosilicate glass during sintering studied by dilatometry and XRD analysis." Materials Science Forum. 455-456 (2004): 212-215. AbstractWebsite

The crystallization of a borosilicate glass, when compacts of powdered glass were sintered under various conditions, was investigated by dilatometric and XRD analysis. The dilatometry results from non-isothermal sintering experiments until 800°C, performed at different heating rates (1, 2, 5, 8 and 10°C/min), revealed that the compacts started to shrink above ∼ 600°C and that the shrinkage decreased with the increase of the heating rate for temperatures up to ∼750°C. Above this temperature, and specifically when the samples were heated at heating rates < 5°C /min, the shrinkage was hindered, while samples heated at heating rates ≥ 5°C/min showed continuous shrinkage. XRD results showed that the formation of cristobalite had occurred during the sintering at the lowest heating rates and therefore, the presence of this crystalline phase was affecting the shrinkage of the compacts, inhibiting further sintering of the glass. The crystallization of the glass when sintered at a temperature in the range 700-850°C and hold at the selected temperature during various times was also analysed. XRD results showed that both cristobalite and quartz were present in glass compacts sintered under particular conditions (for example, after heating during 24h at 725°C and 765°C). Quartz dissolution took place when the glass samples were sintered at 850°C. At this temperature and whatever the sintering time, cristobalite was the only crystalline phase present in the sintered compacts.

Muşat, V. a, B. b Teixeira, E. b Fortunato, R. C. C. b Monteiro, and P. c Vilarinho. "Effect of thermal treatment on the properties of sol-gel derived Al-doped ZnO thin films." Materials Science Forum. 455-456 (2004): 16-19. AbstractWebsite

This paper presents preliminary results on Al doped ZnO thin films prepared by the solgel method. The thin films were produced by a dip-coater technique on glass substrate, using zinc acetate dihydrate, aluminium chloride hexahydrate, 2-methoxyethanol and monoethanolamine as raw materials. The ZnO thin films were analysed by XRD, Hall effect and SEM measurements. In order to determine the influence of the thermal treatments on the film properties, a set of four different heat treatments (atmosphere and temperature) were studied. All the films are polycrystalline presenting a crystallographic c-axis orientation (002) perpendicular to the substrate. The best results were obtained for films pre-heated at 400°C and post-heated for 1 hour in air at 600°C, after annealing under a reduced atmosphere of forming gas, where a resistivity of 3.9×10-3 Ωcm, a Hall mobility of 34.1 cm2/Vs, a carrier concentration of 4.7×1019 cm-3 and an optical transmittance of 90% were achieved.

Ferro, M. C. a, M. H. V. a Fernandas, C. F. M. L. b Figueiredo, M. S. J. G. b Alendouro, and R. C. C. b Monteiro. "Effect of TiO2 on the crystallization of fly-ash based glass-ceramics." Materials Science Forum. 455-456 (2004): 831-834. AbstractWebsite

A batch of coal fly-ash, soda and lime was melted, quenched to a glass and then devitrified, by one-step heating cycles, forming coarse fibrous microstructures with pores and cracks, resulting in low strength materials. The crystallization behaviour of the based glass was further studied by adding a nucleating agent, TiC2. The resulting structural and microstrutural changes were investigated by differential thermal analysis, scanning electron microscopy, x-ray diffraction, dilatometry and density measurements. The results indicated that the addition of TiO2 could provide a finer grained microstructure, suitable for the production of structural materials.

Alendouro, M. S. J. G. a, R. C. C. a Monteiro, C. F. M. L. a Figueiredo, R. M. S. a Martins, R. J. C. a Silva, M. C. b Ferro, and M. H. V. b Fernandas. "Microstructural characterization and properties of a glass and a glassceramic made from municipal incinerator bottom ash." Materials Science Forum. 455-456 (2004): 827-830. AbstractWebsite

A glass was made using bottom ash produced by a Portuguese municipal solid waste (MSW) incinerator. The bottom ash was the single batch material used in the formation of the glass, which was obtained through a conventional melt-quenching method. The glass was then converted to glass-ceramic for further recycling to construction materials. After submitting the glass samples to several heat treatments, between 820 and 1050°C and during different times, it was verified that the optimum heat treatment schedule for the ceramization of the glass was at 1000°C for 10h, as confirmed by microstructural observation and by X-ray diffraction. The major crystalline phases precipitated in the glass-ceramic were wollastonite (CaSiO3) and diopside (Ca(Mg,Al)(Si,Al)2O6). Microstructural analysis of the glass-ceramic revealed that the crystalline phases were present as dendrites and fiber-like structures that were homogeneously distributed in the material. The glassceramic showed good mechanical properties with a hardness of 5.6 MPa and a bending strength of 101 MPa. This material had a density of 2.8 gcm-3 and a thermal expansion coefficient of 9.10-6°C-1. The glass and the glass-ceramic showed an excellent chemical stability against leaching in acidic solution and in alkaline solution. In summary, both the glass and the glass-ceramic have good chemical and mechanical properties and can, therefore, be applied as construction materials.

Ferro, M. C. a, M. H. V. a Fernandes, and R. C. C. b Monteiro. "Effect of heat treatment on the microstructure of fly ash derived glass ceramics." Glass Technology. 46 (2005): 151-154. AbstractWebsite

Mixtures of fly ash, calcite and soda ash were prepared by keeping the amount of fly ash at 80 wt% and adding the other raw materials in order to obtain Na2O/CaO ratios of 1/3, one and three. On melting all mixtures led to black glassy materials. Several heat treatments were performed on these glasses at temperatures suggested by DTA. The crystalline phases precipitated during the heat treatments were identified by XRD on powdered samples and the microstructures of the obtained glass ceramics were observed by SEM. The formulations tended to precipitate pyroxene solid solutions and aluminium silicates of calcium and/or sodium, during the heat treatments. The glass ceramics mainly contained fine crystals. However some of the materials obtained from glasses with Na2O/CaO ratios of 1/3 and three had non-uniform microstructures. It is generally concluded that the microstructure of these crystallised glasses is critically dependent on both composition and heat treatment.

Muşat, V. a, C. a Gheorghieş, R. C. C. b Monteiro, E. b Fortunato, and E. c Segal. "Kinetics of oxides thin films crystallization from sol-gel precursor." Revista de Chimie. 56 (2005): 367-370. AbstractWebsite

The kinetics of crystallization of transparent and conductive high preferential c-axis oriented Aldoped ZnO thin films on Corning 1737 glass substrate from amorphous sol-gel precursor prepared using zinc acetate and aluminum chloride as cations source, 2-methoxiethanol as solvent and monoethanolamine as sol stabilizer has been investigated. The effect of preheating temperature on the values of the kinetic parameters and crystallization mechanism is discussed. Some data concerning the microstructure, the electrical and optical properties of the thin films are presented.

Monteiro, R. C. C. a, S. J. G. a Alendouro, F. M. L. a Figueiredo, M. C. b Ferro, and M. H. V. b Fernandes. "Development and properties of a glass made from MSWI bottom ash." Journal of Non-Crystalline Solids. 352 (2006): 130-135. AbstractWebsite

A uniform shiny black-coloured glass was obtained using bottom ash produced by a Portuguese municipal solid waste incinerator (MSWI). The bottom ash was the single batch material used in the formation of the glass, which was obtained by vitrification of the solid waste at 1400 °C for 2 h. Under these conditions, a homogeneous melt with an appropriate viscosity to be shaped was obtained, indicating the suitability of this waste material to be employed in the development of vitreous products. The characterization of the resulting glass was performed in order to assess its structural, physical, mechanical, thermal and chemical features. The glass had a density of 2.69 g cm -3, a hardness of 5.5 GPa, a fracture strength of 75 MPa, a thermal expansion coefficient of 9.5 × 10-6 °C-1 and it exhibited a very good chemical stability. In summary, the MSWI bottom ash glass has good mechanical and chemical properties and may, therefore, be used in several applications, particularly as a construction material. © 2005 Elsevier B.V. All rights reserved.

Monteiro, R. C. C., C. S. Mota, and M. M. R. A. Lima. "Effect of dolomite addition on the densification of fly ash based ceramics." Materials Science Forum. 514-516 (2006): 1711-1715. AbstractWebsite

Fly ash from Tapada do Outeiro, a coal power plant in the north of Portugal, has been processed by a powder technology route in order to obtain durable and mechanical resistant ceramics. Dolomite (CaC03.MgC03) was added in different proportions to the waste material, from zero up to 10 wt%, and the effect of this addition on the densification behaviour of the fired samples was investigated by measuring the apparent density, the open porosity and the linear shrinkage. The powder mixtures were uniaxially dry pressed in a steel die and fired at temperatures ranging from 950 to 1150°C XRD and SEM were used to identify the phases present in the sintered materials and the degree of densification. The results revealed that added dolomite was responsible for the appearance of anorthite, an extra phase besides mullite and quartz, for an increase in the amount of liquid phase and for the swelling of closed pores at the highest firing temperatures. Significant morphological changes and phase transformations occurred during sintering and their effects on the physical-mechanical and leaching characteristics of the sintered materials were analyzed.

Musat, V. a, B. b Teixeira, E. b Fortunato, and R. C. C. b Monteiro. "Effect of post-heat treatment on the electrical and optical properties of ZnO:Al thin films." Thin Solid Films. 502 (2006): 219-222. AbstractWebsite

This paper presents the effect of post-heating temperature and atmosphere on the electrical and optical properties of ZnO:Al thin films prepared by the sol-gel method. The electrical properties of the n-type semiconductor thin films showed that for the final films, the values of carrier concentration ranged between 2.76 and 9.96 × 1019 cm- 3, the Hall mobility values between 7 and 34.1 cm2/V s and the resistivity values between 2.9 × 10- 3 and 5.0 × 10- 2 Ω cm, depending on the processing conditions. For the thin film doped with 2 wt.% Al, preheated at 400 °C and post-heated for 1 h in air at 600 °C, a resistivity of 2.9 × 10- 3 Ω cm has been reached after annealing under a reducing atmosphere of forming gas. The optical transmittance spectra of the only post-heated films and of the post-heated and annealed films showed a good transmittance (75-90%) within the visible wavelength region and some small effects of Al-doping concentration and annealing treatment in forming gas. © 2005 Elsevier B.V. All rights reserved.

Lapa, N. a, R. a Barbosa, S. a Camacho, R. C. C. b Monteiro, M. H. V. c Fernandes, and J. S. a Oliveira. "Leaching behaviour of a glass produced from a MSWI bottom ash." Materials Science Forum. 514-516 (2006): 1736-1741. AbstractWebsite

This paper is mainly focused on the characterisation of a glass material (GM) obtained from the thermal treatment of a bottom ash (BA) produced at the Municipal Solid Waste (MSW) incineration plant of Valorsul. By melting the BA at 1400°C during 2 hours, and without using any chemical additives, a homogeneous black-coloured glass was obtained. The thermal and mechanical properties of this glass were characterised. The thermal expansion coefficient, measured by dilatometry, was 9-10 × 10-6 per °C and the modulus of rupture, determined by four-point bending test, was 75±6 MPa, which are similar values to those exhibited by commercial soda-lime-silica glasses used in structural applications. The chemical and the ecotoxicological leaching behaviour of the GM were also analysed. The GM was submitted to a leaching procedure composed of 15 sequential extraction cycles. A liquid/solid (L/S) ratio of 2 1/kg was applied in each cycle. The leachates were filtered through a membrane of PTFE (porosity: 0.45 μm). The filtered leachates were characterised for different chemical parameters and for an ecotoxicological indicator (bacterium Vibrio fischeri). The GM was also submitted to a microwave acidic digestion for the assessment of the total metal content. The crude BA was also submitted to the same experimental procedures. The GM showed levels of chemical emission and ecotoxicity for V. fischeri much lower than those determined for the crude BA. Similar characterisation studies will be pursued with the glass-ceramics produced by adequate thermal treatment of the glass, in order to investigate the effect of the crystallization on the final properties.

Drasovean, R. a, R. b Monteiro, E. b Fortunato, and V. c Musat. "Optical properties of cobalt oxide films by a dipping sol-gel process." Journal of Non-Crystalline Solids. 352 (2006): 1479-1485. AbstractWebsite

Cobalt oxide thin films were prepared by using the dipping sol-gel process. The films were deposited onto glass slides, starting from methanolic solution of cobalt acetate Co(CH3COO)2 · 4H2O. The effects of film thickness and sol concentration on structural and optical properties were studied. Structural analyses of Co3O4 films were performed by X-ray diffraction. The film thickness was varied by using different withdrawal speeds and the number of dipping-heating cycles. It was found that the grain size increases with the number of dipping N. The results point out to some compacting effect that increases with the number of dippings: the films exhibit direct and indirect optical transition, absorption coefficients are of the order of 104 cm-1, and upon annealing the absorption coefficient increases. © 2006 Elsevier B.V. All rights reserved.

Lima, M. M. R. A., and R. C. C. Monteiro. "Shrinkage behaviour of borosilicate glass-Al2O3 composites during isothermal sintering." Materials Science Forum. 514-516 (2006): 648-652. AbstractWebsite

The effect of rigid inclusions on the densification during isothermal sintering of glass matrix composites was investigated. Mixtures containing borosilicate glass powder and 0, 5, 10 and 25 vol. % alumina (Al 2O3) particles were prepared and powder compacts isostatically pressed at 200 MPa have been used. The sintering behaviour of the samples heated at 800°C during various times was investigated through density measurement, axial and radial shrinkage measurements. The microstructure was analysed by SEM and the crystalline phases present in the sintered composites were identified by XRD. The relative density of the isothermally treated borosilicate glass-Al2O3 composites decreased significantly with the increase in Al2O3 content because the presence of rigid inclusions retarded the densification of the compacts. The borosilicate glass exhibited anisotropic shrinkage behaviour, showing a radial shrinkage higher than the axial shrinkage and isotropic shrinkage was favoured by Al2O3 additions. Sintered glass showed a dense microstructure with some spherical closed pores. The microstructure of composites with 5 vol. % Al2O3 revealed that most of the pores were filled by capillary flow of the glass. The microstructure of composites with higher Al2O3 additions showed dense areas together with interconnected pores, which appeared at the sites of large glass particles in the green compacts.

Muşat, V. a, P. b Vilarinho, R. c Monteiro, E. c Fortunato, and E. d Segal. "Thermoreactivity of sol-gel precursor for ZnO-based thin films." Materials Science Forum. 514-516 (2006): 73-77. AbstractWebsite

The thermoreactivity of a zinc acetate non-alkoxide solution used for the preparation of ZnO-based thin films was investigated in the temperature range 20-600°C by TG-DTA, XRD and SEM data. We found that the formation in air of ZnO crystallites from the sol-gel precursor occurs above 150°C simultaneously with the decomposition of an intermediary compound, most probably carbonate hydroxide (sciante and/or hydrozincite). At 200°C, the crystalline structure is well defined in terms of ZnO hexagonal lattice parameters, although residual organic compounds and water were not yet fully removed and an amorphous phase coexists. A kinetic investigation on the thermal decomposition of sol-gel precursor from DTA data using Kissinger differential equation is also presented. Apparent activation energy values of about. 100 kJ mol-1 corresponding to the non-isothermal decomposition of solid precursors in the temperature range 170-250°C have been found.

Davim, E. a, M. H. V. a Fernandes, and R. C. C. b Monteiro. "Glass-ceramics produced from incinerated municipal solid waste." Glass Technology: European Journal of Glass Science and Technology Part A. 48 (2007): 164-167. AbstractWebsite

A homogeneous black coloured glass was obtained by melting the bottom ashes produced by a municipal solid waste incinerator at 1300°C for 2 h without any chemical additives. Based on thermal analysis data glass-ceramics were produced by heat treating the glass, doped with additional TiO2 as a nucleating agent, at temperatures between 870 and 1000°C. The crystalline phases precipitated during the heat treatments were identified by powder XRD and the microstructures were examined using SEM. After a heat treatment at 900°C for 2 h, the glass was converted into a fine grained glass-ceramic with uniform microstructure. The major crystalline phases precipitated in the glass-ceramics were augite (Ca(Mg,Fe)Si2O6), gehlenite (Ca2Al2SiO7) and clinopyroxene (Ca(Ti,Mg,Al)(Si,Al)2O6). Preliminary evaluation of the mechanical and chemical properties of the bottom ash glasses and glass-ceramics suggest that they have potential to compete with existing natural and commercial outdoor cladding materials.

Muşat, V. a, P. b Budrugeac, R. C. C. c Monteiro, E. c Fortunato, and E. d Segal. "Non-isothermal kinetic study on the decomposition of Zn acetate-based Sol-gel precursor: Part 1. Application of the isoconversional methods." Journal of Thermal Analysis and Calorimetry. 89 (2007): 505-509. AbstractWebsite

The isoconversional methods (Friedman (FR), Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS)) were applied for evaluating the dependencies of the activation energy (E) on the mass loss (Δm) corresponding to the non-isothermal decomposition of two Zn acetate-based gel precursors for ZnO thin films whose preparation differs by the drying temperature of the liquid sol-precursor (125°C for sample A, and 150°C for sample B). Although both investigated samples exhibit similar decomposition steps, strong differences between E vs. Δm curves as well as among the characteristic parameters of the decomposition steps, directly evaluated from TG, DTG and DTA curves, were put in evidence. © 2007 Springer Science+Business Media LLC.