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The waste vitrification of abandoned open sky vermiculite deposits has been considered by combining with a natural phosphate mineral residue. Several batches haven been designed from the composition system: Li 2 O-MgO-Al 2 O 3 -P 2 O 5 -SiO 2 including some Fe 2 O 3 and Fluoride. The resulting glasses are transparent and smooth green coloured, giving rise after TTT treatments to several opal, opaque glass-ceramics with iridescent surface. Full characterization has been carried out by XRD and electron microscopy with EDS, as well as by XPS spectroscopies, concluding that the main crystalline phases formed were α-cordierite and β-spodumene. The surface of these glass-ceramics from vermiculite-amblygonite is enriched in Fe 2 O 3 . Compared to the parent glasses, the final glass-ceramics exhibited and improvement in fracture toughness. [ABSTRACT FROM AUTHOR]

In order to encapsulate nuclear wastes (NW) enriched in Uranium, they have been designed and obtained vitrified matrices of iron aluminum phosphates including substitution of U by Bi. These glasses have been designed and obtained formulating all from the starting binary composition: 60P 2 O 5 ·40Fe 2 O 3 where the Fe/P ratio was 0.67. The thermal behavior has been investigated by DTA/TG analysis and thermal expansion, as well as identification of some phases by TEM/EDS. The vitrified structures are difficult to crystallize as is the case of the (Fe + U) contents in the range of 0.50 per P atom. Glasses with Bi-oxide are less resistant to crystallization than those containing U. The glasses here investigated depict a reasonable water chemical stability due to the high percentage of P O Fe O bonds and the presence of U (4+ to 6+). Lately, it has been also investigated the calcination of simulated miniplates of Si 2 U 3 /Al having additions of these glasses and U 3 O 8 to dilute this Uranium enriched in MTR combustible (Material Testing Reactor). [ABSTRACT FROM AUTHOR]

Abstract: Porcelain stoneware tile is a non-equilibrium porcelain material produced by a fast firing process of kaolinitic clay, quartz and feldspar mixtures. This building material, generally used in pavements and also as wall covering and ventilated façades, is endowed with high technological properties such as low water absorption, high bending strength and abrasion resistance, and excellent chemical and frost resistance. These properties cause that porcelain stoneware tile was actually the material with the highest increase in production and sales over all other ceramic building material. Nevertheless, there is a scarcity of high quality research focused on the effect of mullite growth on technological properties of porcelain stoneware tile and on the effect of different fluxing agents on both mullite growth and evolution of physical and technological properties during firing. In this paper, the behaviour of a potassic porcelain stoneware body during the firing process is investigated. A porcelain stoneware composition was prepared by mixing 50% kaolinitic clay, 40% feldspar and 10% quartz. The samples were sintered following a fast firing process. The sintering behaviour of the fired samples was evaluated by linear shrinkage, water absorption and porosity measurements. Both green powder and fired samples were characterized by means of differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), dilatometry and bending strength measurements. [Copyright &y& Elsevier]

It has been determined the thermal behaviour at high temperatures of an iron aluminum arsenate mineral first described in the location of La Serena Valley, Extremadura, Spain, which expands until 1173 K contracting later and softening at 1653 K and full melting at 1773 K. The DTA/TG experiment only detects some rearrangement with an endothermic at 1173 K due to the mica mixing. The mineral is a scorodite variety mixed with micaceous clay which has been found as aggregates of pyramidal crystals associated with quartz, wolframite, molibdenite, cassiterite and other secondary minerals in the pegmatite of the San Nicolas mine. The chemical composition, the physico- chemical characteristics such as density and hardness, as well as the thermal behaviour has allowed to conclude that this mineral can be an Al-enriched scorodite (mansfieldite): (Fe, Al) AsO4·2H2O mixed with illite from the scorodite-mansfieldite series. [ABSTRACT FROM AUTHOR]

The effect of iron oxide content on the crystallisation of a zirconium-based glass-ceramic glaze was investigated using a glass-ceramic “white of zirconium” frit and a granite waste glass. Measurements by X-ray diffraction (XRD) combined with scanning electron microscopy (SEM) and EDX microanalysis showed that Fe2O3 gives rise to the crystallisation of an iron-zinc ferrite, which is acting as nucleating agent of feather-like crystals of pyroxene while granite frit enhances the partial dissolution of zircon into the glassy phase, which is sharply increased for granite frit additions greater than 50%. [Copyright &y& Elsevier]

The effect of iron oxide content on the crystallisation of a diopside glass–ceramic glaze was investigated using a glass–ceramic frit in the K2O–ZnO–MgO–CaO–Al2O3–SiO2 system and a granite waste glass. Measurements by X-ray diffraction (XRD) combined with scanning electron microscopy (SEM) and EDX microanalysis showed that the distribution of Fe3+ ions among different crystalline phases such as franklinite (ZnFe2O4) and hematite Fe2O3 depends on the iron content in the original diopside mixture. Thus, the original glaze crystallises to franklinite or hematatite when iron content is greater than 2 and 15%, respectively. [Copyright &y& Elsevier]

• The thermal plasma treatment for the hospital incineration fly ash utilization. • Chemical stabilization studies by leachability tests in raw materials and ceramics. • The physical features comparison of vitrificates in the hardness tests. The thermal plasma treatment is an effective method which can be used to convert hazardous waste into less toxic or inert glassy products. The aim of this paper is to show the experimental use of a thermal plasma treatment process to transform the hospital incineration fly ash into glassy products (vitrificates) that can be stored on the land without harmful environmental effects or sintered for producing with some additives coloured tiles useful as construction materials. The aims were achieved by: (i) optimization of temperature and energy used adjusting the process to minimum cost and (ii) stabilization of vitrificates with different compositions of waste mixtures. The chemical stabilization of final products was examined by heavy metals leachability tests. Hardness measurements were done to verify the physical stabilization of vitrificates. Also, it has been tested if the reinforcement and coloration of raw material by various pigments as well as the chemical compounds affect the stability of the final products. It was seen that chemical composition of raw materials influenced the chemical and physical properties of the vitrificates and decided about their internal structures. [ABSTRACT FROM AUTHOR]

The effect of chromium oxide additions (0.05–1.00 mol% interval) on the crystallization of an original 26Li 2 O·74SiO 2 glass (mol%) formulated in the liquid metastable immiscibility dome of the binary system has been investigated by XRD and TEM-replica electron microscopy. Results were discussed by considering the phases that can be formed in the Li 2 O-Cr 2 O 3 -SiO 2 partial equilibrium ternary diagram. From these glasses, lithium disilicate is the main crystalline phase after thermal treatments at 550–650 °C. Maximum crystallization is obtained with the lowest content addition of Cr 2 O 3 (0.05 mol%). Glass-in-glass phase separation was observed in these glasses coexisting with the crystallization areas. [ABSTRACT FROM AUTHOR]

The arc plasma vitrification of hospital wastes containing metals and inorganic oxides yields to a leach resistant glassy or vitreous slag, which can be environmentally safe for landfill disposal or could be transformed in glass-ceramic tiles with physical and mechanical properties similar to those showed by marketable products for building applications. Standard methods have been used for testing the leachability of elements from this new type of tiles. The water resistance was evaluated by the DIN 38414 S4 standard and the chemical durability of glass and glass ceramics by the weight losses per surface unit, employing NaOH and HCl (5%) aqueous solutions, at boiling temperature. Results show that although glass-ceramic tiles are most water leachable than original plasma vitreous glass, the concentration of toxic minor elements in their leaching solutions are lower than those allowed by the Normative. [ABSTRACT FROM AUTHOR]

Abstract: Integrated gasification in combined cycle (IGCC) is an electrical power generation system which is characterized to be a clean coal technology different than conventional process in combustible treatment. IGCC process gives rise to inorganic solid wastes in the form of vitreous slag and fly ashes with singular thermal properties. The gasification of the fuel takes place at high temperature and pressure in reducing atmosphere. Under that conditions, gases such as H2, N2 or CO, which are the main components of the gas mixture in the gasifier, show a high solubility in the melt and during the cooling remain enclosed in the vitreous slag. When these wastes are afterward thermal treated in oxidizing conditions, two phenomena occur. The development of a crystalline phase by devitrification of the glassy matrix and the releasing of the enclosed gas, which starts at temperatures nearly to the softening point. At higher temperatures the bubbles with increasing kinetic energy tend to ascent with difficult through the viscous liquid phase and promotes an expansive reaction, giving rise to a foam glass-ceramic product. This paper has been focused on the study of thermal expansion in slag and fly ash samples from the ELCOGAS IGCC power plant located in Puertollano (Spain). [Copyright &y& Elsevier]

Mullite precursors were prepared using kaolin waste, sericite clay containing kaolinite and industrial kaolin with addition of alumina in a wet medium to synthesize mullite (72 wt% Al 2 O 3 and 28 wt% SiO 2 ). Uniaxial pressed bars of the powdered mullite precursors were fired in the range 1400–1600 °C with soaking times 30–120 min. The resultant materials were studied by XRD and SEM-EDX. Bulk densities, apparent porosities and flexural strengths in four points were determined in the fired bars at 1500, 1550 and 1600 °C. It was concluded that the thermal behaviour of these mullite precursors was influenced by the presence of impurities in the raw materials. These impurities originate a liquid phase forming a glassy phase which produces a progressive and enhanced densification of the mullite materials by reaction sintering at 1500–1600 °C. The technical properties were also influenced by the relative proportion of vitreous phase. The microstructure of characteristic mullite crystals was revealed by SEM. It was emphasized the use of kaolin waste by-products of mining and sericite clays as valuable raw materials for mullite preparation. [ABSTRACT FROM AUTHOR]

Abstract: This study reports the feasibility of reusing glass fibre waste resulting from the thermolysis of polyester fibreglass (PFG) to produce a glass–ceramic material. PFG was treated at 550°C for 3h in a 9.6dm3 thermolytic reactor. This process yielded a solid residue (≈68wt%), an oil (≈24wt%) and a gas (≈8wt%). The oil was mainly composed of aromatic (≈84%) and oxygenated compounds (≈16%) and had a fairly high gross calorific value (≈34MJkg−1). The major PFG degradation products were styrene, toluene, ethylbenzene, α-methyl styrene, 3-butynyl benzene, benzoic acid and 1,2-benzenedicarboxylic acid anhydride. The gas contained basically CO2 and CO; the hydrocarbon content was below 10vol%. The higher gross calorific value of the gas was low (26MJNm−3). The solid residue (97wt% fibreglass, 3wt% char) was converted into a glass–ceramic material. For this, a mixture consisting of 95wt% of this solid residue and 5% Na2O was melted at 1450°C to obtain a glass frit. A powder glass sample (<63μm) was then sintered and crystallized at 1013°C, leading to the formation of a glass–ceramic material composed of wollastonite and plagioclase s.s. with possible building applications. [Copyright &y& Elsevier]

Abstract: It is presented the Nd doping of the glassy ZnO–CdO–TeO2 ternary system. The Nd-doped oxide glasses were prepared by conventional melt-quenching method using three different compositions from this system. X-rays diffraction (XRD) diagrams in these materials reveal that they are basically vitreous structure. Infrared (IR) spectra of the glasses showed the characteristic bands at 665, 670, and 675cm−1, which correspond to the trigonal structure of TeO3. The presence of Nd3+ was detected in the visible and infrared region of the spectra by optical absorption (OA) measurements of the band gap and by photoluminescence (PL) experiments. Glasses showed light emission due to the transition: 4F3/2 → 4I9/2. Differential thermal analysis (DTA) of these glasses have shown that T g temperatures are in the 465–485°C and T c in the 800–1000°C ranges. [Copyright &y& Elsevier]

Abstract: Six new glasses having 45–65wt.% P2O5, 18–42% Fe2O3, 6.2–18.7%UO2.67 and about 6% (Na2O+Al2O3 +MgO) were finally obtained after melting the batches in Al2O3/MgO crucibles. The higher Tg–TSOFT values were obtained for glasses AR6 (main components: 57.3%P2O5. 18.4%Fe2O3. 18.9%UO2.67) and AR7 (mc: 65%P2O5, 19%Fe2O3, 9.5%UO2.67) and were the most stable glasses against crystallization. The lowest thermal expansion α was measured for AR1 (mc: 54%P2O5, 27%Fe2O3, 13.5%UO2.67). AR7 was the least chemically durable composition, whereas the most durable glasses were those containing the highest percentages of UO2.67 (AR6, AR1 and AR5). The least stable glasses against crystallization were AR4 (mc: 45.8% P2O5, 42.2%Fe2O3, 6.4%UO2.67), AR5 (mc: 46.2%P2O5. 35.4%Fe2O3. 13.0%UO2.67) and AR2 (mc: 54.2% P2O5, 33.1%Fe2O3, 6.4%UO2.67); their DTA crystallization (Tc) peaks were met at 560°C (AR4), 600°C (AR5) and 620°C (AR2). For these glasses Tc increased with UO2.67 increasing. The highest internal crystallizations were met for AR2 and AR5. Dendritic crystal growth mode was detected for slowly heat treated (up to 650°C) AR5 glass. The dendrite arms were clearly seen by SEM and the EBSD (electron back scattered diffraction) patterns (fitted to phase FePO4) remained unaltered upon moving slightly the detection position throughout those arms. [ABSTRACT FROM AUTHOR]

Abstract: The effect of the heating temperature on the properties of sintered ceramic bodies from three different contaminated marine sediments was investigated. The sintering behaviour was evaluated by means of the variation of shrinkage degree, bulk density, water absorption, open and closed porosity, while the phases transformation were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results have shown that the sintering process follows a viscous liquid phase mechanism due to the formation of a glassy phase. The optimum sintering temperature is 1125°C for Astilleros and Cuchia sediments and 1150°C for Raos sample. Above this temperature, a significant overfiring with an increase of closed porosity was observed. Water absorption values and mechanical properties as bending and compressive strengths of sintered bodies show that the investigated marine sediments are suitable to be used as secondary raw materials in ceramic tiles and bricks production. [Copyright &y& Elsevier]

The subject of this study is the application to the construction of soft mud bricks (also known as pressed bricks), both green and heat-treated bodies, built from raw materials from Santa Cruz de Mudela, Ciudad Real, and IGCC slag from the power central of Puertollano (Ciudad Real, Spain). For this purpose, industrial level tests have been performed: the production of these kind of bricks from mixes of waste from ores of construction clays and to significant fraction of different ratios and clay granulometries mixed with IGCC slag. The results of this experimentation suggests that not only can IGCC slag be applied to a ceramic process, but also its use gives several advantages, as water and energy savings, as well as improvements on the final properties of products. [Copyright &y& Elsevier]