RESUMO Neste trabalho, foram produzidas espumas vitrocristalinas a partir de vidros de garrafas descartadas e casca de arroz (3 a 25% em massa), como agente porogênico. Diferentes composições foram preparadas de maneira a se obter materiais com porosidade controlada para aplicações, nas quais o isolamento térmico e a não-inflamabilidade são os principais requisitos técnicos. Os pós de cada matéria-prima (resíduos) foram homogeneizados e as misturas foram então prensadas uniaxialmente (20 MPa). Os compactos obtidos foram queimados em diferentes temperaturas (700 – 950 °C) e tempos de patamares (30 – 120 min). As matérias-primas e as espumas vitrocristalinas produzidas foram caracterizadas de acordo com suas propriedades químicas, físicas e estruturais. Os resultados mostraram que é possível produzir espumas vitrocristalinas a partir de composições otimizadas com 85% de vidros de garrafas e 15% de casca de arroz, queimadas a 900 °C por diferentes tempos. Tais espumas vitrocristalinas apresentaram porosidade variando entre 80 e 84% enquanto a condutividade térmica e a resistência mecânica à compressão variaram entre 0,068 e 0,082 W/m.K e entre 1,1 e 1,8 MPa, respectivamente.

ABSTRACT Vitrocrystalline foams from discarded glass bottles and rice husk (3 to 25 wt%) as pore forming agent were produced in this work. Different compositions were prepared in order to obtain materials with controlled porosity in applications where thermal insulation and non-flammability are major requirements. Well-homogenized powders of the formulated compositions were uniaxially pressed (20 MPa) and the obtained compacts fired at different temperatures (700 - 950°C) and holding times (30 - 120 min). Raw materials and the obtained vitrocrystalline foams were characterized according to their chemical, physical and structural properties. The results showed that it is possible to produce vitrocrystalline foams from optimized compositions containing 85% glass bottle and 15% rice husk, fired at 900°C for different holding times. These vitrocrystalline foams presented porosity varied from 80 to 84% while the thermal conductivity and compressive strength varied between 0.068 and 0.082 W/m.K and from 1.1 to 1.8 MPa, respectively.

RESUMO A cinética de crescimento da camada superficial cristalizada em um vidro de composição do sistema LZSA, 11,7Li2O·12,6ZrO2·68,6SiO2·7,1Al2O3 (% massa), foi estudada. Para a produção do vidro, utilizou-se matérias-primas comerciais (Li2CO3, ZrSiO4, SiO2, Al2O3), as quais foram homogeneizadas e fundidas a 1550 °C por 120 min e então vazadas em molde metálico. Amostras do vidro obtido foram seccionadas e submetidas a tratamentos térmicos em diferentes temperaturas (825–925 °C) e tempos (30–150 min) para formação e crescimento da camada cristalina. Seções transversais das amostras tratadas termicamente foram lixadas e polidas, tal que imagens das camadas cristalizadas pudessem ser visualizadas e medidas por microscopia. Os resultados mostraram que é possível obter vidros do sistema LZSA com camadas cristalizadas contendo principalmente espodumênio-β e silicatos de zircônio e lítio, de espessuras entre 13 e 665 µm, as quais crescem com velocidades entre 0,4 e 4,8 µm/min no intervalo de temperatura estudado.

ABSTRACT Growth kinetics of crystallized surface layer in a LZSA glass composition, 11.7Li2O·12.6ZrO2·68.6SiO2·7.1Al2O3 (wt%), was studied. For the production of the LZSA glass, it was used commercial raw materials (Li2CO3, ZrSiO4, SiO2, Al2O3) which were mixed and melted at 1550 °C for 120 min and then poured into a metallic mold. Samples of the obtained glass were cut and subjected to heat-treatments at different temperatures (825 - 925 °C) and times (30 - 150 min) for formation and growth of crystalline layer. Cross-sections of the heat-treated samples were ground and polished such that images of the formed crystallized layers could be visualized and measured by microscopy. Results showed that it is possible to obtain LZSA glasses with crystallized layers formed by β-spodumene, zircon and lithium silicate, which present thicknesses between 13 and 665 µm and grow at rates varying from 0.4 to 4.8 µm/min in the studied temperature range.

In this work, nanometric Al2O3 (1-5 vol.%) particles (13 nm, 100 m2/g) were added to a 19.58Li2O•11.10ZrO2•69.32SiO2 (mol%) (3.5 µm, 2.5 m2/g) parent glass-ceramic matrix to prepare composites with the purpose of studying the influence of Al2O3 on their structure, microstructure, mechanical, thermal and electrical properties when sintered by fast firing. The parent glass-ceramic was prepared by melting and fast cooling (in water) to obtain a glass frit. The resulting glass frit was milled according to a two-step procedure consisting on a dry milling stage followed by a long wet milling step down. Each composition was wet homogenized and then dried at 110 ºC for 48 h for disaggregation. The obtained powders were uniaxially pressed (100 MPa) and compacts sintered by fast firing (175 ºC/min) between 800 and 900 ºC for 30 min. The composites, with relative densities ranging from 89% to 93%, showed zircon and β-spodumene as main crystalline phases. The hardness and Young's modulus varied from 4.5 to 6.5 GPa, and from 65 to 102 GPa, respectively. The formation of β-spodumene in the obtained composites leads to reduce the CTEs, whose values ranged from 13 to 7 x 10-6 ºC-1.

In this work, discarded soda-lime glasses (from glass bottles) and recycled polystyrene (PS) spheres (d50 < 300 µm) were successfully converted into vitrocrystalline foams for thermal insulation applications. Physical and chemical properties of the selected and prepared raw materials (wastes) were characterized. Batches containing well mixed glass powder (d50 < 5 µm), PS spheres (10 - 80 vol.%) and PVA (8 vol.% ) were obtained and uniaxially pressed at 20 MPa. The obtained powder compacts were dried in air for 24 h and then fired at different temperatures (850 to 900 °C, 10 °C/min) for 30 min. Vitrocrystalline foams with interconned cells sizes between 86 and 815 µm, homogeneously distributed in a crack free matrix, were characterized from the point of view of their typical physical, chemical, morphological and mechanical properties. The results showed that it is possible to obtain vitrocrystalline foams with porosities up to 89% and compressive strength varying from 4 to 25 MPa.

This paper presents an evaluation study of wastes from pulp and paper as well as construction and demolition industries for application in cement-based materials. The alternative raw materials were used as a source of calcium carbonate (CaCO3) and as pozzolanic material (water-reactive SiO2) in partial replacement of Portland cement. In addition to the hydraulic binder, coating mortars were composed by combining the pulp and paper fluidized bed sand residue with construction and demolition wastes, both added as small aggregates. Rheological and mechanical characterization showed that the waste additions changed the behavior of the cement materials, increasing both the viscosity of the pastes (at constant shear stress or rate). The formation of agglomerates in the cement hydration process made the mortars with additions of residues (lime and ash sludge) have an increase in the mechanical strength of the hardened bodies when compared to the mortar (M0W) prepared only with the residues (fluidized bed sand and C & D) as aggregates.

In this work, ceramic shell (mullite source), an industrial solid waste from the lost-wax casting process, after crushing and milling steps, was used and evaluated as an alternative raw material source for the production of cellular ceramics for high temperature applications (> 1400 °C). The obtained ceramic shell powder, with particle size distribution (d50 < 2 µm) suitable for the production of ceramic foams, was characterized from the point of view of their physical, chemical, morphological and crystallographic properties. Samples were prepared and obtained by direct foaming and gelcasting routes, dried at room temperature and then fired in two steps (650 °C/2 h and 1550 °C/2 h), and cooled in the furnace to room temperature. The effects of solids loading (35 and 42 vol. %) and stirring velocity (500 and 2000 rpm) on the cellular structure (pore size distribution and porosity) and mechanical properties of the produced ceramic shell foam samples were evaluated. The results showed that it is possible to obtain ceramic foams based on mullite-zirconite, with pore sizes between 100 and 900 µm, porosities up to 77% and compressive strength varying from 3 to 20 MPa.

Abstract In this work, compositions containing transparent glass bottles and banana leaves (desiccated and crushed), with different mass fractions (30-50%), were prepared for obtaining cellular materials for thermal insulation purposes. The formulated and prepared compositions were uniaxially pressed (10 MPa) and the compact powders fired between 700 and 850°C for 30 min in order to investigate the effect of the banana leaves on the formation of pores and on the thermal and mechanical properties of the processed glass foams. The results indicated that the obtained glass foams with porosities between 58.5 and 87.5%, compressive strength ranging between 1.17 and 3.50 MPa and thermal conductivity ranging between 0.06 and 0.15 W/mK, are potential candidates to work as thermal insulators with appropriate properties for a specific application.

RESUMO Resíduos de vidro podem ser reutilizados para o desenvolvimento de materiais alternativos. Uma opção viável são os materiais celulares para isolamentos térmicos já que, apresentando poros isolados, possuem baixa condutividade térmica, baixa densidade aparente e temperaturas de serviço mais altas que a dos materiais isolantes poliméricos. Neste trabalho, foi preparada uma suspensão aquosa com resíduos de vidro previamente moídos, Ágar-ágar (gelificante) e Emustab(r) (emulsificante), a qual foi adicionada diferentes frações de óleo de soja (50, 70 e 90% em massa). Subsequentemente, foi realizada a emulsificação do óleo vegetal no líquido da suspensão por meio de agitação em misturador mecânico de alto cisalhamento. Corpos de prova cilíndricos foram produzidos via colagem por gelificação e queimados a 700 °C/30 min. Os resultados mostraram que os vidros celulares obtidos apresentaram porosidade entre 74 e 93% com poros bem definidos e distribuídos e baixas condutividades térmicas (0,05 a 0,09 W/m.K). Tais resultados indicam que os materiais obtidos são potenciais candidatos para atuarem como isolantes térmicos, como por exemplo, painéis para revestimentos utilizados na construção civil.

ABSTRACT Glass wastes can be reused for the development of alternative materials. A viable option are the cellular materials for thermal insulation since with isolated pores they show low thermal conductivity, low density and service temperatures higher than those of the polymeric insulating materials. In this work an aqueous suspension was prepared with previously milled glass wastes, agar (gelling) and Emustab(r) (emulsifier), in which different soy oil fractions (50, 70 and 90 wt% ) were added. Subsequently, the emulsification of the vegetable oil was carried out in the liquid suspension by stirring in a mechanical mixer at high shear. Cylindrical samples were produced by gelation slip casting and fired at 700 °C/30 min. The results showed that the obtained cellular glasses had porosity between 74 and 93% with well-defined and distributed pores and low thermal conductivity (0.05 to 0.09 W/mK). These results indicate that the obtained materials are potential candidates to act as thermal insulators, such as panels for coatings used in construction.

The aim of this study was to obtain and evaluate the electrical, thermal and mechanical properties of iron oxide-filled castor oil polyurethane (PU/Fe2O3). The iron oxide used in this study was a residue derived from the steel pickling process of a Brazilian steel rolling industry. Polymeric composites with different iron oxide volume fractions (2.5, 5.0, 7.5, 10.0 and 12.5%) were prepared through the casting process followed by compression molding at room temperature. The composites were analyzed by FTIR, XRD and densities, tensile strength, Young's modulus, electrical and thermal conductivities measurements. By increasing the iron oxide content, the apparent density, tensile strength, Young's modulus and electrical conductivity values of the composites were also increased. The iron oxide additions did not change significantly the value of thermal conductivity (from 0.191 W.mK-1 for PU up to 0.340 W.mK-1 for PU enriched with 12.5% v/v of iron oxide). Thus, even at the higher iron oxide concentration, the compounds as well as the pure polyurethane can be classified as thermal insulators.

Ceramic foams were produced from a sludge generated in the aluminum anodizing process by using an industrial polyurethane foam (replication method) with open cell sizes of 10 ± 5 ppi (porosity = 97%) which were impregnated with suspensions containing 50-61 wt.% alumina, 1 wt.% citric acid, 6 wt.% bentonite and fired at 1600 ºC for 2 h. The aluminum anodizing sludge shows a high alumina content (87.5 wt.%) and a low particle size (~1.7 mm) after calcination and milling. The obtained filters show porosity of approximately 70%, filtration capability (mass water flow) of 1.7 kg/s and mechanical strength under compression of 2.40 MPa.

Ion exchange method was employed by means of surface modification of the glass powders of LZSA (Li2O-ZrO2-SiO2-Al2O3) system submitted to a 70wt% NaNO3/30wt% NaSO4 bath salt followed by a heat treatment. Chemical analysis by X-ray fluorescence was used to evaluate the efficiency of ion exchange, while optical dilatometry was employed to evaluate sintering of compacts. Evaluation of the structure of sintered bodies was made by scanning electron microscopy. Substitution of Li+ ions by Na+ ions on the surface of powders during heat treatments of 450 and 600 ºC for 2-10 h promoted an increase in densification of the sintered bodies.

This article reports research results related to bioactivity and cytotoxicity tests using neutral red uptake method for glass powders and bulk glass ceramics belonging to the SNCP (SiO2-Na2O-CaO-P2O5) system. The obtained materials showed bioactivity when immersed in SBF promoting the surface deposition of HAp. When analyzed as powders, cytotoxicity was evidenced in the processed materials but not when bulk samples were tested.

Glass-ceramics foams prepared from glasses of the SiO2-Na2O-CaO-P2O5 by replication process were obtained and characterized in terms of their chemical and physical properties by X-ray fluorescence, X-ray diffraction, laser diffraction, thermal analysis, density, mechanical strength, microstructural and cytotoxic analysis. The results showed that it is possible to produce glass-ceramic foams by the replication method with optimized properties but cytotoxic analysis indicates that the glass-ceramic foams are not bioactive materials. Mechanical strength values varying from 0.5 to 1.0 MPa and from 0.8 to 2.3 MPa were reached for mean particle sizes of 10 and 6 µm, respectively.

A comparison between silica by acid leaching of rice husk (RH) and silica obtained from thermal treatment of rice husk ash (RHA) is presented. The best leaching results were obtained using 10% hydrochloric acid followed by washing with water. The alternative method, calcination of RHA at 700 ºC for 6 h followed by grinding for 80 min, was more effective. Silica obtained from RH was about 97% amorphous, had a 17.37 µm mean particle size, and a specific surface area of 296 m²/g. On the other hand, for silica obtained from RHA the values were about 95% amorphous material 0.68 µm, and 81 m²/g.