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Spray pyrolysis is a promising method for producing thin, transparent films on glass substrates. ZnO thin films synthesized by this method exhibit high crystallinity, adhesion and chemical resistance. They also possess the ability to degrade water pollutants and exhibit antibacterial properties under UV light. The crystalline structure of these films has been studied using grazing X-ray diffraction (GIXRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM), while transmission electron microscopy (TEM) has been used to investigate their composition and purity. Other techniques such as X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and ultraviolet–visible spectroscopy were also employed. ICP-OES was used to evaluate photocatalyst leaching. These transparent thin films have exceptional optical properties, with a transmittance of 95%. The photocatalytic degradation of 4-Nitrophenol (4-NP) by ZnO thin films showed a degradation rate of 94% in 270 min with a kinetic constant value of 3.1 × 10−3 mM/min. The films are also highly durable and reusable, exhibiting superior performance compared to other ZnO photocatalysts. The bactericidal activity of these transparent films was also evaluated, with a value of 60.6% being obtained using Escherichia coli after irradiating the films with UV light for 3 h. [Display omitted] [ABSTRACT FROM AUTHOR]

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 work reports the influence of pore forming agents, their incorporation content and particle size distribution on the bi-layered ceramics porosity, mechanical resistance and thermal conductivity. The results demonstrate that the porosity level on the bi-layered ceramics bottom layer can be easily controlled by the porogen amount, while porogen particle size affects both the number and size distribution of the pores. Two different pore forming agents were evaluated, namely polypropylene (PP) and polymethyl methacrylate (PMMA). The nature of the pore forming agent, however, did not affect the bi-layered ceramics' properties. The incorporation of porosity into the bi-layered ceramics promotes thermal conductivity attenuation (up to 79%) in comparison with conventional porcelain stoneware ceramics, yet maintaining suitable mechanical strength. Thermal conductivity decrease is adjustable as a function of the volume and size of the generated pores, thus enabling materials to be tailored for the envisaged applications. [ABSTRACT FROM AUTHOR]

It is well known that the extrudability of a ceramic paste is strongly dependent on materials composition and formulation, basically because it controls the resulting plasticity. Accordingly, the characterisation of the plastic behaviour is essential to adjust the fluxing properties of the material. In the current work, three industrially prepared ceramic pastes (porcelain, earthenware and terracotta) were tested, using stress–deformation curves obtained by compression of cylindrical probe tests. To achieve good extrusion performance, the design and operating conditions also need to be considered in detail. The ram extrusion of adjusted pastes was followed by the Benbow–Bridgwater model. Differences in the flow behaviour were related with stress–deformation curves and with the surface quality of the extrudate (by using the static friction coefficient). [ABSTRACT FROM AUTHOR]

The addition of fine-grained polycrystalline tetragonal zirconia (3%Y2O3–TZP, or 3Y–TZP) to conventional, single-firing, ceramic glazes was studied with the aim to enhance their hardness, fracture toughness and wear resistance for floor tile applications. The stability of the added tetragonal zirconia towards solution in the glaze and/or zircon crystallization was found strongly dependent on glaze composition, firing treatment, and on the way of preparing the samples (uniaxially-pressed pellets or thin-layer coatings). 3Y–TZP remained stable in fast-fired pellets, but partial crystallization of prismatic zircon microcrystals (2–3 μm) occurred in samples prepared as thin-layer coatings. Addition of 10–30 wt.% of 3Y–TZP to a conventional single-firing glaze that was industrially enameled (thin films) onto low-porous floor tiles, promoted an important enhancement of Vickers microhardness (Hv from 6.0 to 8.4 GPa), fracture toughness (KIC from 1.35 to 2.23 MPa m1/2), and wear resistance (PEI abrasion number from 2 to 5). The achieved reinforcement was higher with 3Y–TZP than with zircon addition, and must be attributed to the stress-induced transformation-toughening mechanism promoted by the undissolved stabilized tetragonal zirconia, and also to partial zircon crystallization. The possibility of obtaining ceramic coatings mechanically reinforced with 3Y–TZP additions, while also maintaining a glossy aspect, was also confirmed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of transparent TiO 2 thin films functionalised with silver NPs for photocatalytic and antimicrobial surfaces. • The synthesis methodologies used, such as spray pyrolysis and pulsed laser ablation (PLAL), have a wide industrial application. • The addition of silver NPs on the TiO 2 surface improves the photocatalytic and antimicrobial properties. • Photocatalytic tests confirm that these thin films could be used to degrade pollutants such as Rhodamine B by UV light. Transparent TiO 2 thin films coated with Ag NPs were synthesized using two industrially applicable techniques,pulsed laser ablation (PLAL) and spray pyrolysis without using high vacuum. These transparent thin films were deposited on glass in order to generate glass materials with photocatalytic and antimicrobial properties and a minimum loss of transparency. The structural, morphological and optical properties of the thin films were examined using Grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, Scanning electron microscopy (SEM) and ultraviolet–visible spectroscopy. Transmission electron microscopy (TEM) was used to identify the NPs on the TiO 2 surface. The transmittance value for the thin films was greater than 80%.The thin films thus synthesized were then assessed to determine their photocatalytic capacity by monitoring the degradation of Rhodamine B (RhB) under UV light irradiation. Ag NPs on the TiO 2 surface ensures an improvement in the photocatalytic properties, with a 99% degradation of RhB in 210 min under UV light. In addition, these transparent thin films showed high antimicrobial activity on Gram-negative bacteria when irradiated by UV light for 4 h, killing 93% of these bacteria. [ABSTRACT FROM AUTHOR]

Waste streams generated from pulp and paper mills show high potential to be used as alternatives raw materials for production of clinker. In this context, this work aims to evaluate the use of such materials to obtain hydraulic binders, which are referred to as Ecoclinfeers and Ecocements. Lime mud, wastewater treatment process sludge and biomass ashes were characterized, and five formulations (F1-F5) were developed by applying the Bogue equations. These compositions were processed at three different clinkering temperatures (1350,1440 and 1455 "C). The formulated Ecoclinfeers and a reference hydraulic binder were characterized by X-ray diffractometry to identify the crystalline phases, which were subsequently quantified by the Rietveld method. The results showed that crystalline phase characteristics of clinkers and cements, and compression strengths of ~20 MPa after 28 days curing time were obtained, confirming the potential use of the investigated waste as alternative materials for production of clinker. [ABSTRACT FROM AUTHOR]

We report titania nanoheterostructures decorated with silver, exhibiting tuneable photochromic properties for the first time when stimulated only by visible white light (domestic indoor lamp), with no UV wavelengths. Photochromic materials show reversible color changes under light exposure. However, all inorganic photochromic nanoparticles (NPs) require UV light to operate. Conventionally, multicolor photochromism in Ag-TiO2 films involves a change in color to brownish-gray during UV-light irradiation (i.e., reduction of Ag+ to Ag0) and a (re)bleaching (i.e., (re)oxidation of Ag0 to colorless Ag+) upon visible-light exposure. In this work, on the contrary, we demonstrate visible-light-induced photochromism (ranging from yellow to violet) of 1-10 mol % Ag-modified titania NPs using both spectroscopic and colorimetric CIEL*a*b* analyses. This is not a bleaching of the UV-induced color but a change in color itself under exposure to visible light, and it is shown to be a completely different mechanism-driven by the interfacial charge transfer of an electron from the valence band of TiO2 to that of the AgxO clusters that surround the titania-to the usual UV-triggered photochromism reported in titania-based materials. The quantity of Ag or irradiation time dictated the magnitude and degree of tuneability of the color change, from pale yellow to dark blue, with a rapid change visible only after a few seconds, and the intensity and red shift of surface plasmon resonance induced under visible light also increased. This effect was reversible after annealing in the dark at 100 °C/15 min. Photocatalytic activity under visible light was also assessed against the abatement of nitrogen oxide pollutants, for interior use, therefore showing the coexistence of photochromism and photocatalysis-both triggered by the same wavelength-in the same material, making it a multifunctional material. Moreover, we also demonstrate and explain why X-ray photoelectron spectroscopy is an unreliable technique with such materials. [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]

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]

This paper presents an alternative approach to estimate the parameters of the Benbow equation, widely used to define the contribution of parallel and convergent fluxes during the extrusion of ceramic bodies. The proposed method is based on a simplification of the equation that describes the difference of the extrusion pressure through dies with distinct lengths. This simplification, combined with an analytic change of the equation, allows obtaining two parameters from the experimental results, instead of using numerical fitting of reported values on the literature. The advantages of the proposed strategies are: (i) only three of the five parameters are numerically obtained, minimizing the risks of convergence to solutions mathematically corrected but without physical significance; and (ii) the relative deviations between Benbow's model and experimental results are lower when compared with those obtained when all parameters are numerically obtained. [ABSTRACT FROM AUTHOR]

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]