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This work describes the study of phase development during the setting of various clinker formulations prepared with industrial wastes or by-products, namely sludges (generated in the Al-anodising and surface coating industrial processes, in potable water filtration/cleaning operations and in the cutting process of natural marble) and foundry sand. For comparison, similar formulations were also prepared with commercial high purity grade raw materials and processed in identical conditions. To circumvent the experimental restrictions imposed by the use of Vicat’s needle (i.e. large amount of material), electrical resistivity measurements were conducted by alternate current (a.c.) impedance spectroscopy to follow the hydration process and setting behaviour. During setting, the temperature evolution of the water/cement pastes was also recorded. Impedande spectroscopy (IS) studies were found to be a reliable method and, in some systems, can be a more sensitive technique to detect on-going hydration reactions.Este trabajo describe el estudio del desarrollo de fases durante el fraguado de diferentes formulaciones de clinker preparados con residuos industriales o subproductos, denominados barros (generados en los procesos de recubrimientos industriales por anodizado de Al, en procesos de filtración/depuración de agua potable y en procesos de corte de mármol) y arenas de fundición. Con el objeto de comparar, se prepararon formulaciones similares a partir de materias primas comerciales de alta pureza y procesadas en idénticas condiciones. Para sortear las restricciones experimentales de inherentes a la aguja de Vicat (esto es, grandes cantidades de material), se realizaron medidas de resistividad eléctrica en corriente alterna (a.c.) de espectroscopía de impedancia para seguir el proceso de hidratación y fraguado. Durante el fraguado, la evolución de la temperatura de las pastas de agua/cemento se registró. Los estudios de espectroscopía de impedancia mostraron ser un método fiable y en algunos casos, pueden emplearse como técnica sensible para detectar el inicio de las reacciones de hidratación.

We report the preparation of ceramic pigments using industrial wastes as primary sources. In this context, the use of Al-rich sludge generated in the wastewater treatment unit of an anodising or surface coating industrial plant, and a galvanizing sludge from the Cr/Ni plating process, will be detailed. The ceramic pigments reported here were prepared using typical solid state reactions involving the metal rich sludge. The main focus will be on the synthesis of chrome-tin orchid cassiterite (Sn,Cr)O2, chrome-tin red malayaite Ca(Cr,Sn)SiO5, victoria green garnet Ca3Cr2Si3O12, and chrome alumina pink/green corundum (Cr,Al)2O3 pigments. The pigments were fully characterised and then were tested in a standard ceramic glaze after. Typical working conditions and colour development will be reported.Se presenta la preparación de pigmentos cerámicos empleando residuos industriales como fuente de materias primas. Se detallan el uso de barros ricos en aluminio obtenidos en los tratamientos de depuración de aguas de plantas industriales de anodizado y barros de galvanizados de chapados de Cr/Ni. Los pigmentos cerámicos se prepararon empleando reacción en estados sólido a partir del barro rico en metal. Los principales pigmentos estudiados son orquídea casiterita de cromo-estaño (Sn,Cr)O2, malayita rojo de cromo-estaño Ca(Sn,Cr)SiO3, granate verde victoria Ca3Cr2Si3O12, y corindón rosa/verde de cromo alúmina (Cr,Al)2O3. Los pigmentos fueron caracterizados y ensayados después de ser vidriados en cerámicas estándares. Se presentan las condiciones de trabajo y el desarrollo de color.

Alumina based ceramic materials, containing Al-rich sludge as the major component, were processed by extrusion. The sludge derived from the wastewater treatment of aluminium anodising industrial process. Long rods were produced using a vacuum screw extruder, by a careful control of all relevant processing parameters. Then, thick discs were obtained by cutting dried selected rods, to be tested as probes for sintering-dependent electrical properties. The sintering process was followed by performing common dilatometric/thermal analyses but the evolution of electrical conductivity, estimated by impedance spectroscopy (IS), was also used for this purpose. Results show that sintering-dependent morphological evolution up to 1300ºC strongly affects the electrical behaviour of samples, and as a consequence IS seems to be a useful technique to follow the firing process.Los materiales cerámicos basados en alúmina, conteniendo barros ricos en Al como componente mayoritario fueron procesados por extrusión. Los barros empleados provienen de tratamientos de lavado de residuos de un proceso industrial de anodizado de aluminio. Se produjeron varillas empleando un extrusor de tornillo en vacío con control de todos los parámetros relevantes del proceso. A partir de varillas seleccionadas, se obtuvieron por corte en seco discos cerámicos para evaluar la dependencia de la sinterización y las propiedades eléctricas. El proceso de sinterización se siguió mediante ensayos dilatométricos y análisis térmicos, junto con la evolución de la conductividad eléctrica mediante espectroscopia de impedancia. Los resultados mostraron la evolución de la sinterización y la dependencia morfológica hasta 1300ºC, que afecta fuertemente a la respuesta eléctrica y como consecuencia la espectroscopia de impedancia parece ser una técnica útil en el seguimiento de los procesos de cocción.

Graphitic carbon nitride (g-C3N4), possessing high thermal and chemical stability, non-toxicity, facile synthesis, and low band gap energy is a promising candidate for photocatalytic applications. In this study, bulk and exfoliated g-C3N4 were synthesised from different precursors (melamine and urea). Moreover, the surface of bulk g-C3N4 and exfoliated g-C3N4 was modified with graphene (0.5 wt% and 1 wt%) aiming to obtain a prolonged carrier lifetime. The effect of g-C3N4 synthesis from various precursors and the influence of graphene content on the photocatalytic activity during the degradation of a water–methanol mixture under UVC irradiation were examined, in comparison to commercial P25. Hydrogen, methane and carbon monoxide were the decomposition products; hydrogen was the main product of decomposition, whereas CH4 and CO resulting from the reduction of CO2 were generated in a significantly smaller amount. All the produced photocatalysts, whether pure or modified with graphene, exhibited higher activity than the commercial photocatalyst P25. [ABSTRACT FROM AUTHOR]

This paper evaluates the use of lightweight aggregates (LWA), namely perlite (PER) and vermiculite (VER) in cement mortars. The workability of mortars was defined in rheometer and flow table tests. Three distinct LWA levels were added (0 - 3, 4.5 - 7, and 9- 10.5 wt%) requiring the use of distinct water/solids (W/S) ratios (0.18, 0.265 and 0.35, respectively). In order to evaluate the performance of such formulations in the hardened state, the flexural and compressive strength after 28 days curing was also measured. In general, LWA caused a high variation on the yield stress and spread on table, being the yield stress the best rheological parameter to be related with the flow table. PER exerts a strong impact on initial yield stress, while the effect of VER is stronger for longer rheology testing periods. The compressive strength ranged from 12.3 MPa (0 % LWA) to 2.77 MPa (PER) and 2.39 MPa (VER).

The application of sustainability principles in construction encourages the development of new products, with new functionalities and applications, able to improve buildings environmental performance. The use of latent heat storage materials in lime mortars aims to reduce the energy consumption of buildings. This work intends to evaluate the impact of phase change materials (PCM) incorporation in rheological and hardened state properties of aerial lime mortars. A fresh state characterization was conducted through the rheological study complemented with flow table tests of different mortar formulations. To complete the mortar characterization some hardened state properties (porosity, mechanical strength and microstructure) after 28 days, were also evaluated. It was concluded that, the PCM microcapsules incorporation does not compromise aerial lime mortars overall performance and may help to improve some characteristics like workability and mechanical strength. Therefore, it is possible to reduce the energy demand in old buildings, improving their performance and sustainability.

Copyright of Ceramica is the property of Associacao Brasileira de Ceramica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ceramica is the property of Associacao Brasileira de Ceramica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Achieving advanced multifunctional materials displaying several coexisting properties is currently one of the most exciting and innovative research topics. In this study, we report the engineering of a multifunctional material exhibiting, at the same time, tuneable photochromic behaviour and gas-sensing properties for acetone detection. The photochromic property of silver modified (1–10 mol% Ag) titanium dioxide (titania, TiO2) NPs was monitored under consecutive UVA-light exposure times, and the change in colour was thoroughly investigated with both spectroscopic and colourimetric analyses. All Ag modified samples exhibited a significant change in colour and visible spectra after only 15 seconds of exposure, and this increased with further exposure. It was shown that both the silver molar content in the Ag–TiO2 nano-heterostructure, as well as the UVA-light irradiation time, governed the tunability of the photochromic behaviour (the colour changed from pale yellow to dark blue in Ag-modified specimens, while it remained white in unmodified TiO2). The same nano-heterostructures were also tested as sensing materials for resistive metal oxide gas sensors (MOS). These Ag–TiO2 nano-heterostructures proved to be highly sensitive for the detection of acetone vapours at low concentrations (＜1 ppm), superior to the best TiO2-based sensors so far reported. This is the first thorough study to qualitatively monitor, in real-time, the growth of Ag0 NPs on a TiO2 matrix, assessing both optical spectroscopy and colourimetric CIEL*a*b* analysis (e.g. what meets the eye), and to also demonstrate the superior acetone gas-sensing properties of such nano-heterostructures. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) nanoparticles are extremely attractive materials for numerous applications, especially in the anatase form. We have made these shaped, ＜10 nm anatase nanoparticles (NPs) via the supercritical (SC) drying of a titania sol, made by a “green” aqueous sol–gel nanosynthesis route. The SC drying was carried out in alcohol at 255–260 °C, and no further heating or processing of the NPs was required. The true phase composition (crystalline and amorphous phases) and the microstructure of the NPs was thoroughly characterised by the advanced X-ray methods, such as Rietveld-reference intensity ratio (RIR) and the whole powder pattern modelling (WPPM) technique, and HR-TEM analysis. Furthermore, the NPs were also characterised by Raman, FT-IR and optical spectroscopy. These anatase NPs showed themselves to exhibit a truncated tetragonal bipyramidal shape, exposing the {101} (side) and {001} (top) faces. They had a euhedral crystal habit, with sharply defined and easily recognised faces, and were very homogeneous and monodisperse in both shape and size. The photocatalytic activity (PCA) of the samples was assessed in gas–solid phase by monitoring the degradation of nitrogen oxides (NOx), a major atmospheric pollutant. Results showed that the particular shape of these anatase NPs played a key role in their photocatalytic behaviour. In fact, these truncated tetragonal bipyramidal nanocrystals exhibited an enhanced photocatalytic activity, double that of spherical anatase NPs of a similar size reported previously by the authors. This was attributed to the exposure of mainly the {101} and, to a lesser extent, {001} crystal faces, which are more reactive under photocatalysis for redox reactions. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) nanomaterials are attracting increasing interest, mostly because of their superior photocatalytic and antibacterial properties. In this work, we report the synthesis, by a “green” aqueous sol–gel route, of TiO2 doped with Eu and Nd (1 and 5 mol%), in order to extend its photocatalytic activity to the visible range, and also take advantage of the luminescent features of the rare earth metals (REs). Gels were dried in an oven at 75 °C, and then thermally treated at 450 °C in a static air flow furnace. Semi-quantitative phase composition (QPA) and microstructure (crystalline domain shape and size distribution) of the synthetic powders were studied by means of advanced X-ray methods: Rietveld refinements, and the whole powder pattern modelling (WPPM) technique, respectively. From these X-ray techniques, it was seen that the unit cell volume of RE-modified titania underwent a huge expansion, thus suggesting the incorporation of RE into the TiO2 lattice, accompanied by a decrease in the average crystalline domain diameters of anatase, rutile and brookite. The optical properties were also investigated by diffuse reflectance spectroscopy (DRS). Photoluminescent behaviour was assessed in the visible and near infra-red (NIR) spectral ranges. Photocatalytic activity of the samples was assessed both in liquid–solid and in gas–solid phases. The influence of the lighting conditions (UV- and visible-light exposure) was also taken into account for evaluating the photocatalytic activity. Nd–TiO2 was shown to be a bifunctional material, having both photocatalytic activity and NIR photoluminescent emission induced by the same excitation source, an unprecedented result. [ABSTRACT FROM AUTHOR]

Co-processing is an industrial technique of using wastes as a substitute for raw materials and/or fuels, as a way to minimize the consumption of minerals and non-renewable fossil fuels. This paper presents a brief overview on such practices conducted by the cement industry in Latin America. The main issue addressed is co-processing as a contribution to develop a more sustainable scenario in cement production and as a valuable tool in waste management. Cement industries are particularly suitable for wastes co-processing, due to the high temperatures reached inside their kilns, which favor the degradation of toxic compounds formed upon burning of certain wastes. Developed countries, particularly in the European Union, have been replacing fossil fuels by wastes since the 1970's. In the Netherlands, the calorific substitution rate is higher than 80%, while in Austria, Germany and Norway it is over 60%. In Latin America, those values vary between 7 and 20% according to the country. This study has found that the main differences between European and Latin American regions are caused by distinct implementation degrees of waste management chain and by legal requirements and inspection practices of industrial activities. However, the Cement Sustainability Initiative (CSI) estimates that until 2030, the substitution of fossil fuels by wastes in Latin America will reach 25 to 35%. This numbers are the same reached by Denmark, France and Sweden in 2010. [ABSTRACT FROM AUTHOR]

Amongst nanomaterials, metal oxides play an increasingly dominant role, with titanium dioxide (titania, TiO2) being widely used for various applications, such as light-to-energy conversion and storage, and photocatalysis. In this work, TiO2 has been synthesised via an aqueous sol–gel method, using three different mineral acids (HNO3, HCl and HBr) to peptise the sol, and hence provide counter-ions. Dried sols were thermally treated at three different temperatures (450, 600 and 800 °C), using three different dwell times (2, 4, and 8 h). Advanced X-ray methods were used to monitor the effect that the counter-ions had on the anatase-to-rutile phase transformation (ART). Quantitative phase analysis (QPA) using the Rietveld method was applied to assess the true amount of crystalline phases in the systems, and the amount of amorphous phase. Furthermore, the average crystalline domain diameter was also investigated, using whole powder pattern modelling (WPPM). With the advanced XRPD data (actual crystalline phase weight fraction in the samples and their average domain diameter and size distribution), it was possible to carry out a semi-quantitative study of the ART transformation kinetics. At a low temperature of 75 °C, the Cl− counter-ion was the most favourable to obtain anatase as the major crystalline phase, delaying the onset of the ART. Conversely, the Br− ions, maintained more anatase at 450 °C, with a lower ART rate. In general, halides were more effective in delaying the ART than NO3− counterions. Moreover, we observed an inverse linear relationship between the lattice volume expansion of rutile and the increase of its crystalline domain size at 450 and 600 °C isotherms. As the domain sizes increased with temperature, this effect reversed and became a direct linear dependence at the 800 °C isotherm, suggesting a critical size limit ＜90 nm for this effect. [ABSTRACT FROM AUTHOR]

A novel non-aqueous sol-gel route for synthesizing pure indium oxide (In2O3) nanoparticles (NPs) using indium acetylacetonate and n-butylamine as the reactive solvent, under solvothermal conditions, is herein proposed. The samples were characterized by an advanced X-ray method, whole powder pattern modeling (WPPM) and high-resolution transmission electron microscopy (HR-TEM), showing the exclusive presence of pure In2O3. Diffuse reflectance spectroscopy (DRS) was used to determine the optical band gap (Eg) of the sample. Moreover, these investigations also revealed that the In2O3 nanoparticles are quasi-spherical in shape, with a diameter of around 7 nm as prepared and 9.5 nm after thermal treatment at 250 °C. In2O3 NPs worked as highly sensitive sensing interfaces to provide resistance changes during exposure to sevoflurane, a volatile anesthetic agent used in surgical wards. The developed sensor demonstrated a good response and fast response/recovery time towards very low concentrations of sevoflurane in air, suggesting a very attractive application as a real-time monitoring analyzer in a hospital environment. [ABSTRACT FROM AUTHOR]

The use of sunscreens as protective barriers against skin damage and cancer, by absorbing harmful UVA and UVB rays, is becoming an increasingly important issue. Such products are usually based on TiO[sub 2] or ZnO, although both Fe[sub 2]O[sub 3] and hydroxyapatite (Ca[sub 10](PO[sub 4])[sub 6](OH)[sub 2], HAp) doped with metal ions have been reported as being ultraviolet (UV) absorbing materials. HAp is the main component of bone; it is, therefore, highly biocompatible. In the present work, an iron-doped HAp-based material, containing both Fe ions substituted into the HAp structure and iron oxide in hematite (α-Fe[sub 2]O[sub 3]) form, was successfully developed from waste cod fish bones. This was achieved through a simple process of treating the bones in a Fe(II) containing solution, followed by heating at 700 °C. The material showed good absorption in the whole UV range and did not form radicals when irradiated. The sunscreen cream formulated with this material could be used as a broad sunscreen protector (λ[sub crit] > 370 nm), showing high absorption both in the UVA and UVB ranges. Because of its absorption properties it would be classified as 5 star protection according to the Boots UVA star rating system. The cream is also photostable, and does not cause irritation or erythema formation when in contact with the human skin. These results show that a food by-product such as fish bones could be converted into a valuable product, with potential applications in health care and cosmetics. This is the first time a HAp-based sunscreen cream has been developed and validated as a proof of concept. [ABSTRACT FROM AUTHOR]

Copyright of Ceramica is the property of Associacao Brasileira de Ceramica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Ceramica is the property of Associacao Brasileira de Ceramica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The article presents a study that evaluates the alkali-silica reactions (ASR) on the use of red mud in plastering mortars. It explores the method of the study in which red mud was generated in aluminum and alumina production through the Bayer process from bauxite ore. It notes the result of the study, which indicates that satisfactory mortar behavior of the ASR despite the high alkali concentration in red mud.

Abstract This paper reports the effect of silica fume (SF), nanosilica (NS) and superplasticiser (SP) addition on the rheological behaviour of Portland cement pastes with different amounts of SF (0-10%), NS (1%) and SP (0-0·4%) and water to binder (W/B) ratio of 0·4. A rheometer with concentric cylinders geometry was used and the maximum shear rate of 100 s-1 was applied. SP decreased the hysteresis area, while SF and NS increased it. Samples with NS showed high slopes in descending curves, while samples with SF and high dosages of SP showed lower values. In both cases, the Bingham model resulted in negative values for the yield stress, so that the Herschel-Bulkley model was used instead. The spread values variation on flow table did not follow a linear regression model. For this investigation, commercially available SF and NS were used. [ABSTRACT FROM AUTHOR]