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The lead-free piezoelectric material sodium bismuth titanate (NBT, Na0.5Bi0.5TiO3) has attracted considerable attention owing to its promising dielectric, piezoelectric, and electrical properties. However, the literature on the binary subsystems is contradictory and there are only limited data for the ternary system. The present work surveys all of the reports of the binary subsystems Bi2O3 – TiO2 and Na2O – TiO2 and synthesizes these data into inclusive revised versions. The compatibilities for the ternary system Na2O – Bi2O3 – TiO2 were determined experimentally, thus enabling the construction of a complete isothermal section at 800 °C. The compatibilities associated with the problematic binary subsystem Na2O – Bi2O3, which experiences extreme volatilisation, were determined through the generation of the absent standard-state thermodynamic functions for the relevant binary and ternary phases, thus providing a full suite of thermodynamic data for this system. The thermodynamic stability diagrams for Na2O, Bi2O3, and TiO2 thus were calculated. The isothermal section also addresses the contradictions in the literature concerning the formation of solid solutions of Bi12TiO20-x / Bi12-xTi1+xO20+0.5x, pyrochlore (Bi2Ti2O7 / NawBi2-xTi2-yO7-z), BTO (Bi4Ti3O12 / NaxBi4Ti3O12+0.5x), and NBT (Na0.5Bi0.5TiO3 / Bi1±xNaxTiO3.5±x). Further, it was observed that the congruent melting point of NBT, which was determined to be 1225 °C, was preceded by the onset of gradual structural destabilization at 940 °C. Also, the NBT rhombohedral → tetragonal phase transformation was observed at an onset temperature of ∼250 °C. The present work thus provides platform data for the fabrication and reactivities of materials in the ternary system Na2O – Bi2O3· TiO2 and its binary subsystems.

TiO2 coatings were fabricated by anodization of Ti6Al4V in 1 M H3PO4 or H2SO4, at room temperature at 120 V for 10 min, and followed by annealing at 300° or 500 °C for 8 h. Analyses include mineralogy (GAXRD, Raman), chemistry (XPS), morphology and microstructure (FESEM, FIB, 3D confocal microscopy), thermodynamic, optical (UV–Vis), and photocatalytic performance (MB degradation). The present work highlights factors that govern the nature of the materials and their performance. The influence of the oxidation strength of the acid is pervasive in that it impacts on the crystallinity, microstructural homogeneity, coating thickness, Ti3+ concentration, gas generation during arcing to form pores, and resultant pore size and distribution density. A key observation is that the pores form a subsurface network of variable continuity, which has a significant impact on the surface area and associated density of photocatalytically active sites, access by liquids and gases inside the coating, penetration depth of incident radiation, gas condensation, and residual liquid trapping. These data and the related thermodynamic analyses of the acids, anodization processes, and oxidation processes facilitate the generation of schematic models for the anodization mechanisms and the resultant surface, bulk, and microstructural effects that dominate the photocatalytic performance.

Oxide perovskites have emerged as an important class of materials with important applications in many technological areas, particularly thermocatalysis, electrocatalysis, photocatalysis, and energy storage. However, their implementation faces numerous challenges that are familiar to the chemist and materials scientist. The present work surveys the state-of-the-art by integrating these two viewpoints, focusing on the critical role that defect engineering plays in the design, fabrication, modification, and application of these materials. An extensive review of experimental and simulation studies of the synthesis and performance of oxide perovskites and devices containing these materials is coupled with exposition of the fundamental and applied aspects of defect equilibria. The aim of this approach is to elucidate how these issues can be integrated in order to shed light on the interpretation of the data and what trajectories are suggested by them. This critical examination has revealed a number of areas in which the review can provide a greater understanding. These include considerations of (1) the nature and formation of solid solutions, (2) site filling and stoichiometry, (3) the rationale for the design of defective oxide perovskites, and (4) the complex mechanisms of charge compensation and charge transfer. The review concludes with some proposed strategies to address the challenges in the future development of oxide perovskites and their applications.

Precise control over the morphology of nanomaterials is critical yet challenging. The present work reports an efficient approach to tailor the architecture of nanostructures. The process involves rapid disassembly/reassembly of an unstable metal-based coordination polymer (MCP) by controlling the kinetics of the reassembly process. The synthesis procedure delivers unprecedented polycrystalline nanostructures, e.g., holey 2D CeO2−x nanosheets, with precisely tailored thicknesses in the range of 10–100 nm, and hollow 3D pseudo-octahedra and spheres. The consequent high surface areas and pore volumes, short diffusion distances, and high defect densities of the holey 2D CeO2−x indicate significant densities of active sites. This holey architecture exhibits rapid CO conversion and outstanding solar light photocatalytic performance. This approach of directed assembly offers a template-free, controllable, and cost-effective approach to achieve engineered CeO2−x architectures, which are nearly impossible through existing approaches.

Methanol decomposition is a promising method for hydrogen production. However, the performance of current catalysts for this process is not sufficient for commercial applications. In this work, methanol adsorption on the CeO2 low-index surfaces is studied by density functional theory (DFT). The results show that methanol always dissociates spontaneously on the (100) surface, whereas dissociation on the (110) surface is site-selective; dissociation does not occur at all on the (111) surface, where only weak physisorption is found. The results confirm that surfaces with higher energies are more catalytically active. Analysis of the surface geometries shows that the dominant factors for the dissociation of methanol are the degree of undercoordination and the charges of the surface ions. The adsorption energy of each methanol molecule decreases with increasing coverage and there is a transition threshold between dissociative and associative adsorption. The present work indicates that a strategy to design catalysts with high activity is to maximize exposure of surfaces on which the ions have a high degree of undercoordination and a strong tendency to donate/accept electrons. The results demonstrate the importance of appropriately selecting and controlling exposed facets and particle morphology for optimizing catalyst performance.

The present work reports a new method for the green chemical synthesis of biomaterials using an integrated, room-temperature, aqueous, chemical technique involving surfactant-free precipitation of ...

Of the utmost importance of chirality in organic compounds and drugs, the present work reports structure-chirality relationship of three steroidal quinoxalines, which were synthesised by condensing diaminobenzenes with cholestenone. All the compounds were purified and characterised by varying analytical tools prior to their chiroptical analysis by circular dichroism (CD) technique. The substituent groups on quinoxalines contributed to determining the chiroptical properties of the compounds. The positive Cotton effects have been observed in the CD spectra of unsubstituted and methyl-substituted quinoxalines, which indicated their P helicity. Importantly, chloro-substituent on quinoxalines produced different CD behaviour, which can be attributed to the presence of three lone pairs of electrons on Cl atom. The present work provides guidelines for determining the chiral properties of steroidal quinoxalines, which can be useful to design and develop potential molecules of biological importance.

Hypothesis The air-solution interface of supersaturated calcium hydrogen carbonate (Ca(HCO3)2) represents the highest saturation state due to evaporation/CO2-degassing, where calcite crystals are expected to nucleate and grow along the interface. Hence, it should be possible to form a free-standing mineral-only calcium carbonate (CaCO3) microfilm at the air-solution interface of Ca(HCO3)2. The air-solution interface of phosphate buffered saline (PBS) could represent a phase boundary to introduce a hybrid microstructure of CaCO3 and carbonate-rich dicalcium hydroxide phosphate (carbonate-rich hydroxylapatite). Experiments Supersaturated Ca(HCO3)2 was prepared at high pressure and heated to form CaCO3 microfilms, which were converted to bone-like microfilms at the air-solution interface of PBS by dissolution-recrystallisation. The microfilms were characterised by scanning electron microscopy, 3D confocal microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, laser Raman microspectroscopy, and X-ray photoelectron spectroscopy. An in situ X-ray diffraction (XRD) system that simulates the aforementioned interfacial techniques was developed to elucidate the microfilms formation mechanisms. Findings The CaCO3 and bone-like microfilms were free-standing, contiguous, and crystalline. The bone-like microfilms exhibited a hybrid structure consisting of a surface layer of remnant calcite and a carbonate-rich hydroxylapatite core of plates. The present work shows that the air-solution interface can be used to introduce hybrid microstructures to mineral microfilms.

The major downsides of cement manufacturing are the high CO2 emissions and high energy usage. Geopolymers, which are fabricated by activation of blends of fly ash (FA) and ground granulated blast furnace slag (GGBFS) using an alkaline activator, offer a promising solution to this issue. However, to enhance the replacement of cement in construction applications, geopolymer compositions have to be designed such that they can be activated on site by just adding water, similar to how cements are used. Therefore, the present work uses solid sodium metasilicate (MS, Na2SiO3) as the alkaline activator in order to design an add-water-style FA/GGBFS-based geopolymer composition. These compositions were designed by optimising the binder (FA/GGBFS) ratio, Na2SiO3/binder ratio, and water/binder ratio individually to assess the effects of these parameters on the setting times and mechanical (flexural and compressive) strengths over extended curing times (three months). The major factors affecting the strength development and setting times (initial and final) were the amounts of GGBFS and Na2SiO3, with the former demonstrating the more dominant effect. The consistent strength development with curing time was attributed to calcium aluminium silicate hydrate (CASH) gel formation in the early curing times which was affected by the slag addition levels, and sodium aluminium silicate hydrate (NASH) gel formation at later curing times which was influenced by the metasilicate addition levels. The metasilicate amounts were observed to impact on CASH gel formation in early stage curing. Geopolymer compositions with FA/GGBFS ratio of 35/65 and MS/water ratios of 0.2 showed high compressive strengths of ~70 MPa at 28 days, which are superior to values seen in conventional ordinary Portland cement (OPC) mixes for the same curing times.

Removal of rare earth elements (REEs) from industrial wastewater is a continual challenge. To date, several approaches to the synthesis of nanoadsorbants for this application have been reported, although these are characterized by insufficient adsorption capacity and limitations in cycling stability. The present work reports the fabrication and performance of hierarchical hybrid transition metal oxide (TMO) nanowires deposited on carbon fibers. An ordered assembly of hybrid TMO nanowires exhibits an outstanding adsorbance of 1000 mg·g-1 of REEs with 93% recyclability. This superior performance is attributed to the unique mesoporous architecture of the nanowires, which exhibits a high surface area of 122 cm3·g-1. Further, rapid adsorption/desorption of the REEs reveals minimal morphological alteration and hence high structural stability of these hybrid TMO nanowires after multiple cycles. The ready accessibility of the adsorption sites at crystallite boundaries and the surfaces as well as rapid adsorption of the REEs on the mesoporous nanostructure facilitate considerable adsorption capacity, improved structural stability, and extended cyclability, all of which suggest the potential for this material in REE extraction.

The effects of curing temperature, blast furnace slag content, and Ms on the initial and final setting times, and compressive strengths of geopolymer paste and mortars are examined. The present work demonstrates that ambient-cured geopolymer pastes and mortars can be fabricated without requiring high alkalinity activators or thermal curing, provided that the ratios of Class F fly ash (40&ndash, 90 wt%), blast furnace slag (10&ndash, 60 wt%), and low alkalinity sodium silicate (Ms = 1.5, 1.7, 2.0) are appropriately balanced. Eighteen mix designs were assessed against the criteria for setting time and compressive strength according to ASTM C150 and AS 3972. Using these data, flexible and reproducible mix designs in terms of the fly ash/slag ratio and Ms were mapped and categorised. The optimal mix designs are 30&ndash, 40 wt% slag with silicate modulus (Ms) = 1.5&ndash, 1.7. These data were used to generate predictive models for initial and final setting times and for ultimate curing times and ultimate compressive strengths. These projected data indicate that compressive strengths &gt, 100 MPa can be achieved after ambient curing for &gt, 56 days of mixes of &ge, 40 wt% slag.

Flat TiO2 thin films were dip coated on contact lens polymer substrates (fluorinated ethylene propylene copolymer, FEP) using a hybrid sol-gel and annealed for 12 h at ≤200 °C. The grain sizes were in the range 10–20 nm but extensive shrinkage cracking was present. The crystallinities of the films annealed at ≤150 °C increased with increasing temperature gradually but only to a limited extent, although the crystallinity at 200 °C was significant. Recrystallisation resulted in decreased transparency, increased reflectivity, and a red shift to lower band gap. The methylene blue (MB) degradation was in the order 25 °C

Bismuth-based metal oxide compounds are promising candidates as novel photocatalysts for environmental remediation. However, their low quantum efficiencies and rapid electron-hole recombination times have hindered their uptake for photocatalytic applications. The present work reports an investigation of the effects of variable Bi/Ti ratio during hydrothermal synthesis on the phase assemblage, nanostructure, surface chemistry, band gap, and photocatalytic performance. Increasing Ti concentration resulted in variations in characteristics and properties according to the sequential formation of the principal phases α-Bi2O3 (BO), Bi4Ti3O12 (BTO), and (Na0.5Bi0.5)TiO3 (NBT). Samples fabricated with precursors having a Bi/Ti ratio of 12/12 exhibited the highest methylene blue (MB) photodegradation rate of 92% under UV irradiation for 2 h. This excellent photocatalytic performance is attributed to the formation of an NBT/BTO heterojunction with advantageous band alignment.

Highly-transparent V-doped TiO2 thin films were prepared by sol-gel processing, spin coated on fused silica glass substrates, and annealed in air at 450 °C for 2 h. All of the films were comprised of anatase as the sole crystalline phase. The XPS data suggested that V formed an interstitial solid solution with anatase. The formation of an unsaturated solid solution at the lowest doping level of 0.05 mol% resulted in the formation of lattice defect sites, which enhanced anatase recrystallisation, grain growth, and crystallinity. In contrast, the formation of supersaturated/oversaturated solid solutions at the higher doping levels of 0.10–1.00 mol% resulted in lattice deformation, partial amorphisation, precipitation, and liquid formation. The coexistence of multiple valence states, viz., Ti4+/3+, V4+/3+, and possibly V5+ in the doped TiO2 films was attributed to intervalence charge transfer. Dye degradation tests revealed that the 0.05 mol% V-doped films showed the best photocatalyic performance and this was attributed to the combined effects of greater anatase crystallinity and reduced band gap. In contrast, increasing V-doping levels resulted in gradual decreases in the photocatalytic performance, which are attributed principally to the decrease in areal density of the surface-active sites owing to liquid-phase densification. The greater degradation of MB solution relative to that of RhB solution is attributed principally to the cationic nature of MB, which allows greater adsorption on the photocatalyst surface in comparison to the anionic RhB.

Altres ajuts: ICN2 is supported by the CERCA Programme/Generalitat de Catalunya. Holey 2D metal oxides have shown great promise as functional materials for energy storage and catalysts. Despite impressive performance, their processing is challenged by the requirement of templates plus capping agents or high temperatures; these materials also exhibit excessive thicknesses and low yields. The present work reports a metal-based coordination polymer (MCP) strategy to synthesize polycrystalline, holey, metal oxide (MO) nanosheets with thicknesses as low as two-unit cells. The process involves rapid exfoliation of bulk-layered, MCPs (Ce-, Ti-, Zr-based) into atomically thin MCPs at room temperature, followed by transformation into holey 2D MOs upon the removal of organic linkers in aqueous solution. Further, this work represents an extra step for decorating the holey nanosheets using precursors of transition metals to engineer their band alignments, establishing a route to optimize their photocatalysis. The work introduces a simple, high-yield, room-temperature, and template-free approach to synthesize ultrathin holey nanosheets with high-level functionalities.

Since the permeation of the inflammatory cytokines into hydrogel scaffolds has been shown to cause dysfunction of encapsulated cells, appropriate design strategies to circumvent this are essential. In the present work, it was hypothesized that highly crosslinked PVA-fucoidan and PVA-carrageenan hydrogels can control permeation of the trefoil-shaped inflammatory cytokine IL-1β while allowing the permeation of the globular protein albumin. PVA, fucoidan, and carrageenans were functionalized with methacrylate groups and the functionalized polymers were co-crosslinked by UV photopolymerization. The resultant hydrogels were characterized physicochemically and the release of fucoidan and carrageenans was quantified by developing a colorimetric assay, which was validated by XPS analysis. The permeability characteristics of the hydrogels were evaluated using bovine serum albumin (BSA), IgG, and IL-1β. The results demonstrated an increase in hydrogel swelling through the incorporation of the polysaccharides with minimal overall mass loss. The release studies showed hydrogel stability, where the formulations exhibited ~43% retention of fucoidan and ~60-80% retention of carrageenans consistently up to 7 days. The permeation data revealed very low permeation of IgG and IL-1β through the hydrogels, with1% permeation after 24 h, while allowing6% permeation of BSA. These data indicate that such hydrogels can be used as the basis for cytokine-protective implantable devices for clinical applications.

TiO x C y powders with tunable composition and high specific surface areas have been synthesized by impregnation of porous carbon black with titanium isopropoxide and firing in argon at 1400 °C. The compositional ratio of the individual ions can be controlled over a broad compositional range by tuning the stoichiometric ratio of the initial reactants. The resultant powders show no detectable oxide or carbonaceous impurity phases. The powders retain artefacts of the porosity of the templating carbon and yield specific surface areas as high as 108 m 2 g −1 , which makes them useful in catalytic/electrocatalytic applications.

Photocatalytic materials are pivotal for the implementation of disruptive clean energy applications such as conversion of H$_{2}$O and CO$_{2}$ into fuels and chemicals driven by solar energy. However, efficient and cost-effective materials able to catalyze the chemical reactions of interest when exposed to visible light are scarce due to the stringent electronic conditions that they must satisfy. Chemical and nanostructuring approaches are capable of improving the catalytic performance of known photoactive compounds however the complexity of the synthesized nanomaterials and sophistication of the employed methods make systematic design of photocatalysts difficult. Here, we show by means of first-principles simulation methods that application of biaxial stress, $\eta$, on semiconductor oxide thin films can modify their optoelectronic and catalytic properties in a significant and predictable manner. In particular, we show that upon moderate tensile strains CeO$_{2}$ and TiO$_{2}$ thin films become suitable materials for photocatalytic conversion of H$_{2}$O into H$_{2}$ and CO$_{2}$ into CH$_{4}$ under sunlight. The band gap shifts induced by $\eta$ are reproduced qualitatively by a simple analytical model that depends only on structural and dielectric susceptibility changes. Thus, epitaxial strain represents a promising route for methodical screening and rational design of photocatalytic materials.

Innovative approaches to the control of immune response to tissue engineering scaffolds is of high priority. IL-10, an anti-inflammatory cytokine, has traditionally been conjugated to synthetic polymers for local immunomodulation. Marine-sulfated polysaccharides have been reported to possess anti-inflammatory properties. In the present work, it was hypothesized that photopolymerizable fucoidan and carrageenan play similar roles as the IL-10. The polysaccharides were functionalized with methacrylate groups. Their immunomodulatory properties were evaluated and compared relative to IL-10. The polysaccharides were characterized by NMR spectroscopy, revealing 12-13 % functionalization. The data revealed that fucoidan had the same activity as the IL-10 in decreasing LPS- and IFN-γ-stimulated CD86 expression. In addition, fucoidan had a protective role against LPS- and IFN-γ-induced cell growth inhibition. All polysaccharides demonstrated ∼90 % superoxide radical scavenging and they considerably decreased LPS-stimulated nitric oxide production. These results suggest that photopolymerizable fucoidan can be an alternative to IL-10 in the design of immunomodulatory biomaterials.

Background In this study, a historical case series is reported of reaction bonded silicon nitride (Si3N4) implants for anterior lumbar interbody fusion (ALIF) for a patient population of 30 and surgery levels L3/4, L4/5, and/or L5/S1. Before the study, the only work on Si3N4 as a biomedical material was associated preliminary work, which involved animal trials using a rabbit model. The objective was to undertake the first use of Si3N4 as a biomedical material for humans, as an implant for ALIF. Methods The Si3N4 implants were prepared by die-pressing silicon powder and reaction bonding in 95 N2/5 H2 at ∼1400°C for ∼50 hours. The surgeries involved a retroperitoneal approach for L3/4 and L4/5 levels and a transperitoneal approach for L5/S1 level. The patient follow-up involved assessment of radiologic fusion up to 30 years and clinical outcomes to 10 years. Results The reaction bonded Si3N4 implants were found to be biologically safe and to show high fusion rates with minimal subsidence, no abnormal reaction, and no other complications. The primary outcome measure, visual analog scale back pain, improved from a preoperative mean of 8.4 (range, 6–10) to a mean of 3.7 (range, 0–9) at 5 years and a mean of 4.9 (range, 0–9) at 10 years. The Oswestry Disability Index improved from a preoperative mean of 48 (range, 26–84) to a mean of 35 (range, 4–76) at 10 years. Conclusions This study confirms that Si3N4 is biologically safe in the long-term, with capacity for excellent radiologic osseointegration.

Polyvinyl alcohols (PVAs) are used commonly in polymer-modified mortars to manipulate their properties. The present work reports the kinetics of hydration of off-white Portland cement pastes modified by PVA (PVA/cement = 0.5 mass%) as a function of the degree of hydrolysis (DH) and the degree of polymerisation (DP). To this end, the hydrolysis of PVAs in extracted cement pore water and in cement paste was analysed using titration method, the heat flow from the hydration of unmodified and PVA-modified cement pastes were monitored over the first 24 h following mixing using isothermal calorimetry, and the Ca(OH)2 (CH) contents of these cement pastes were calculated from thermogravimetric analysis. The results show that PVAs underwent near-complete hydrolysis within the first hour following the mixing of the aqueous PVA solution with cement, i.e., the original PVA was present in the pore solution as fully hydrolysed PVA chains and released acetate groups. Addition of PVA retarded the hydration of C3S to form C–S–H and CH and also the hydration reaction of C3A and gypsum to form ettringite; however, the addition of PVA had no effect on the formation of monosulphate except for the case of samples with high DP and fully hydrolysed PVA was added which resulted in the accelerated formation of monosulphate. The DH and DP of PVA have an important effect on the hydration of Portland cement. The effects of DH resulted from the variations in the amounts of fully hydrolysed PVA and the released acetate groups.

Anodic oxidation is an electrochemical method for the production of ceramic films on a metallic substrate. It had been widely used to deposit the ceramic coatings on the metals surface. In this study, the surface morphology and crystallinity of titanium foil was modified by anodising in mixture of β-glycerophosphate disodium salt pentahydrate (β-GP) and calcium acetate monohydrate (CA). The experiments were carried out at high voltage (350 V), different anodising time (1, 3, 5 and 10 min) and current density (10 and 20 mA.cm-2) at room temperature. Anodised titanium was characterised by using glancing angle X-ray diffraction (GAXRD), field emission scanning electron microscope (FESEM) and focused ion beam (FIB) milling. The result of the experiment show that colour, porosity, crystallinity and thickness of the titanium films depended strongly on the current density. More porous surface and large amount of anatase was produced at higher current density. FIB results indicated that the thickness of oxide layer increased as increasing of current density.

Anodic oxidation is a surface modification method which combines electric field driven metal and oxygen ion diffusion for formation of oxide layer on the anode surface. Anodised titanium has been widely use in biomedical applications especially in dental implant. This study aimed to investigate the effect of electrolyte concentration on titanium. Specifically, the titanium foil was anodised in mixture of β-glycerophosphate disodium salt pentahydrate (β-GP) and calcium acetate monohydrate (CA) with different concentration (0.02 M + 0.2 M and 0.04 M + 0.4 M), anodising time (10 min), applied voltage (150, 200, 250, 300 and 350 V) and current density (10 mA.cm-2) at room temperature. Surface oxide properties of anodised titanium were characterised by using glancing angle X-ray diffraction (GAXRD), field emission scanning electron microscope (FESEM), focused ion beam (FIB) milling and digital camera. With increasing electrolyte concentration, the oxide layer became more porous. The GAXRD results also showed that rutile formed at high applied voltage (≥300 V) when the higher concentration of electrolyte was used.

Gel oxidation is an effective thermochemical method for the preparation of bioactive titanium surfaces. This study aims to investigate the effect of low concentration of NaOH on gel oxidation of titanium when subjected to various temperatures. Titanium foils were soaked in NaOH aqueous solutions with the concentration of 0.5 M or 1.0 M, followed by oxidation in the range of 400°C to 800°C. The crystallinity of the film was determined using glancing angle X-ray diffraction (GAXRD). The microstructures were examined using field emission scanning electron microscope (FESEM). Focused ion beam milling (FIB) was used for cross-sectional imaging. At low NaOH concentration, the amount of sodium titanate hydrogel, if present, was too low to detect after gelation. Subsequent oxidation at 400°C was insufficient to form sufficient anatase and/or rutile to be detectable by GAXRD. Oxidation at 600°C and 800°C resulted in the detection of rutile. The concentration of the NaOH solution was important that it affected the dissolution or retention of the anatase passive oxidation layer whereby low concentrations of the NaOH solution (0.5 M and 1.0 M) resulted in a low degree of dissolution.

The corrosion of duplex stainless steel 2205 was investigated both under service conditions and via an electrochemical study in chlorinated media. The steel sample surfaces showed pitting, crevice and selective dissolution, with the ferrite phase being more susceptible to dissolution in this media. The dissolution of MnS was identified to be a contributing factor for pitting corrosion, while electrochemical investigations revealed that the presence of hypochlorite ions caused a switching from a general corrosion phenomenon to a localized one.

Solid-state (non-activated) and mechanochemical activation (activated) synthesis methods were used to produce Sm-modified BiFeO 3 ceramics of composition Bi 0.88 Sm 0.12 FeO 3 . The first part shows that the formation of Bi 0.88 Sm 0.12 FeO 3 using the two synthesis methods followed a different reaction pathway on annealing the powders. The non-activated ceramics reacted by forming two intermediate phases, isostructural to BiFeO 3 and SmFeO 3 , and then inter-diffusing, forming the final Bi 0.88 Sm 0.12 FeO 3 solid solution. Unlike the non-activated samples, the activated ceramic powders formed Bi 0.88 Sm 0.12 FeO 3 phase on annealing the powders, without apparent intermediate phases. As revealed by transmission electron microscopy, the non-activated reaction pathway caused the Pbam phase to form as chemical inhomogeneous (Sm-rich) isolated nano-sized grain inclusions in the final ceramics. Conversely, the activated reaction pathway caused the Pbam phase to form chemically homogeneous nano-regions within the R 3 c phase grains. The results demonstrate the important role of processing in the appearance of the frequently discussed anti-polar Pbam phase in this system. In the second part, the high electric-field-induced polarization and strain behaviors of these ceramics were studied by means of polarization–electric (P–E) and strain–electric field (S–E) hysteresis loops, and the S–E loops were compared with those of unmodified BiFeO 3 . Bipolar S–E loops of Bi 0.88 Sm 0.12 FeO 3 had a distinctive butterfly shape with less frequency dependence relative to BiFeO 3 at driving-field frequencies of 0.1–100 Hz. BiFeO 3 ceramics exhibite strong driving electric-field-frequency-dependent domain switching, the origins of which were previously attributed to a domain-wall pinning mechanism and “hardening” behavior. This study shows that Sm-modification induces a “hardening–softening” transition in BiFeO 3 ceramics.

This Gel oxidation is a thermochemical method for the production of an oxide film on a metallic substrate, where the metallic substrate is subjected to gelation by immersion in NaOH solution, followed by oxidation. These films are suitable for thicknesses of a few microns owing to the risk of cracking and discontinuity of the gel during drying and firing. However, the firing can have deleterious effects on the mechanical properties of the substrate. Continuous and discontinuous gelled and TiO2 films of submicron thickness were produced on high-purity Ti foil substrates (50 μm thickness) by soaking in NaOH solutions (0.5 M, 1.0 M, 5.0 M, and 10.0 M). Gelation involved soaking at 60°C for 24 hours. After drying in air for 24 hours, the samples were heated at 300oC/hour and soaked for 1 hour in air at 400oC, 600oC, and 800°C. The compositions, microstructures, and thicknesses of the films were determined using: glancing-angle X-ray diffraction, Raman microspectroscopy, and field emission scanning electron microscopy (FESEM). Raman microspectroscopy revealed the formation of an amorphous sodium titanate gel layer following chemical treatment. As expected, the thickness of the gel layer increased with increasing NaOH concentration. However, the two highest concentrations (5.0 M and 10.0 M) resulted in cracking of the gel layer upon drying in air. TiO2 did not crystallise during heating at 400oC but rutile formed directly upon heating at 600oC and 800oC.

Conductive metal oxides represent a new category of functional material with vital importance for many modern applications. The present work introduces a new conductive metal oxide V13 O16 , which is synthesized via a simplified photoelectrochemical procedure and decorated onto the semiconducting photocatalyst BiVO4 in controlled mass percentages ranging from 25% to 37%. Owing to its excellent conductivity and good compatibility with oxide materials, the metallic V13 O16 -decorated BiVO4 hybrid catalyst shows a high photocurrent density of 2.2 ± 0.2 mA cm-2 at 1.23 V versus reversible hydrogen electrode (RHE). Both experimental characterization and density functional theory calculations indicate that the superior photocurrent derives from enhanced charge separation and transfer, resulting from ohmic contact at the interface of mixed phases and superior electrical conductivity from V13 O16 . A Co-Pi coating on BiVO4 -V13 O16 further increases the photocurrent to 5.0 ± 0.5 mA cm-2 at 1.23 V versus RHE, which is among the highest reported for BiVO4 -based photoelectrodes. Surface photovoltage and transient photocurrent measurements suggest a charge-transfer model in which photocurrents are enhanced by improved surface passivation, although the barrier at the Co-Pi/electrolyte interface limits the charge transfer.

Optimisation of particle sizes of WO3 films is important for photoelectrochemical applications. However, most of the developed size-controlled synthesis techniques involve complicated instruments or vacuum systems. The present work presents an alternative method using carboxylic acid-assisted electrodeposition where WO3 thin films were deposited from peroxotungstic acid (PTA) solution containing different carboxylic acids (formic, oxalic, citric). The effects of carboxylic acids on the electrodeposition and the resultant morphological, mineralogical, optical, and photoelectrochemical properties of the WO3 films were investigated. The analysis showed that the films consisted of equiaxed nanoparticulate monoclinic WO3. The deposition thicknesses and the average grain (individual particle and agglomerate) sizes of the films were dependent on the amount of hydronium ions and the molecular weight and associated sizes of the conjugate bases released upon the dissociation of carboxylic acids in the PTA solutions, which result in hydrogen bond formation and molecular dispersion. The photocurrent densities of the films deposited with carboxylic acids were greater than that of the film deposited from pure PTA. These differences were attributed to improvements in (1) grain size, which controls photogenerated electron-hole transport, and (2) effective grain boundary area, which controls the numbers of active reaction sites and electron-hole recombination sites.

Cellulose ethers (CEs) are employed in many polymer-modified mortars, such as cement renders, masonry mortars, tile adhesives, repair mortars, skim coats, and self-levelling mortars. The addition of CEs to mortars causes the retardation of cement hydration and modifies the microstructural characteristics and the properties of these mortars. The present work attempts to provide a comprehensive review of the current state of knowledge on the effects of CEs and critically identifies gaps in the knowledge. A fundamental scientific understanding concerning the chemistry and hydration of cement, chemical natures, and relevant properties of CEs are discussed. The behaviours and mechanisms of CE adsorption on cement are assessed. The influences of CEs on the kinetics of cement hydration, mechanisms of retardation, and microstructural evolution of the mortars also are reviewed. Finally, the impact of CEs on the properties of fresh and hardened mortars as well as the approaches used to mitigate the negative impacts of CEs are discussed.

The present work reports the synthesis of transparent (∼60–80% transmission) WO3 thin films by electrodeposition using peroxotungstic acid (PTA) solutions containing different carboxylic acids (formic, oxalic, and citric) of varying concentrations. The effects of these acids on the deposition kinetics and the morphological, mineralogical, optical, and photoelectrochemical properties of the films were investigated using scanning electron microscopy, X-ray diffraction, UV–vis spectrophotometry, and photoelectrochemical measurements. The deposited film thickness was dependent on the availability of hydronium ions (for hydrogen bonding with PTA ions) and molecular drag in the electrolytes, both of which were controlled through the use of carboxylic acids of different concentrations, degrees of dissociation, molecular weights, and associated sizes of the conjugate bases. The films consisted of agglomerates/particles (42–132 nm), the sizes of which decreased and the true porosities (

This paper investigates the effects of AlPO 4 addition on the corrosion resistance of andalusite LCC refractories. Corrosion tests using the Alcoa cup test (850 °C and 1160 °C for 150 h and 72 h, respectively) were conducted to determine the extent of penetration. The addition of AlPO 4 was shown to improve the corrosion resistance of the castables in contact with molten Al-alloy. SEM/EDS analyses of the interfacial reaction zone showed the formation of corundum in the interfacial layer, along with a significant decrease in the phosphorus content in the interface. Thermodynamic calculations revealed that reaction with the alloy leads to the formation of corundum as the reaction product along with gaseous products (phosphorus trioxide gas) and small amounts of aluminum phosphide. Corundum formation at the interface enhances the corrosion resistance of sample due to high stability of corundum against molten Al alloy, while the metal quality is enhanced due to absence of dissolved phosphorus in the metal.

TiO2 films of varying mineralogical and microstructural characteristics were fabricated on sand-blasted Ti6Al4V plates by anodisation in 2 M sulphuric acid (H2SO4) and 2 M phosphoric acid (H3PO4) at 120 V and 300 mA/cm2 for 10 min and 15 min, respectively. The film formed by anodisation in H2SO4 consisted of both anatase and rutile while the film formed by anodisation in H3PO4 consisted only of rutile. This inconsistency is attributed to the presence of anatase below the level of detection in the sample anodised in the H3PO4, which consisted of a thinner TiO2 anodised film. SEM images demonstrated that H2SO4 resulted in arcing and resultant porosity while H3PO4 did not. Profilometry revealed that the former was rougher than the latter and that the latter was nearly the same roughness as the sand-blasted plate. These observations are consistent with the conclusion that H3PO4 formed a thinner anodised film and that the greater thickness from H2SO4 resulted in asperity formation, which enhanced arcing and densification. Although the anatase-rutile mixture and the greater roughness of the sample anodised in H2SO4 could be expected to have yielded superior performance, the fact that it did not is attributed to the greater bulk density and associated lower surface area of the TiO2 matrix. Preliminary cell culture tests showed that human osteoblast-like cells (MG63) were attached effectively on smooth anodised films (on polished plates) after 4 h of incubation while cell proliferation was confluent after 2 days. The major finding of the present work is that X-radiation in clinical doses (

Sodium titanate gels have been formed on the surface of titanium metal using sodium hydroxide solution and then oxidised at 400° - 800°C. The reaction sequence for these processes with increasing temperature is Ti sodium titanate gel crystalline sodium titanate gel porous (top) and dense (bottom) anatase porous (top) and dense (bottom) rutile. These samples were subsequently soaked in simulated body fluid in order to study the precipitation of hydroxyapatite.

Thin films of WO3 were deposited on FTO-coated glass substrates by electrodeposition using aqueous solutions of peroxotungstic acid. The effects of varying the tungsten concentration of peroxotungstic acid and deposition time on the mineralogical, microstructural, morphological, optical, and photoelectrochemical properties were determined using X-ray diffraction, scanning electron microscopy, focused ion beam milling, UV–vis spectrophotometry, and linear potentiodynamic voltammetry, respectively. The films consisted of monoclinic WO3 of grain sizes in the range 77–122 nm and thicknesses in the range 258–1394 nm; the true porosities were

Iron-doped titanium dioxide thin films were coated on fluorine-doped tin oxide coated glass using the spin coating technique. The concentration of the dopant was varied up to 7 mol% iron (metal base). The films were characterised for their structural, morphological, and optical properties. Glancing angle X-ray diffraction and laser Raman microspectroscopy indicate that the films consisted solely of the anatase polymorph of titanium dioxide, without any contamination phases, such as iron oxide. Field emission scanning electron microscopy indicates that the films were microstructurally homogeneous and fully dense, with grains in the size range of ∼10–20 nm. UV-VIS spectrophotometry shows that the optical indirect band gap of the films decreased with increasing iron doping (3.36 eV for undoped and 2.95 eV for 7 mol% Fe).

Anodic oxidation is an electrochemical method for the production of an oxide film on a metallic substrate. It involves the application of an electrical bias at relatively low currents while the substrate is immersed in an acid bath. The films can be very dense and stable, with a variety of microstructural characteristics. In the present work, films of the anatase polymorph of TiO2were formed on high-purity Ti foil (50 μm thickness) using phosphoric acid (0.3 M H3PO4). The conditions of oxidation involved the application of potentials (5 to 350 V) and current densities (5 to 60 mA.cm-2) for 10 min at room temperature. The films were characterised using a digital photography, laser Raman microspectroscopy, and field emission scanning electron microscopy. The thicknesses of the oxide films on Ti were measured using a thin film analyser based on optical spectroscopy principles. The colours, thicknesses, and microstructures of the films depended strongly on the applied voltage and current density. At bias more than 15 V, single-phase anatase was observed to form on Ti at low (5 mA.cm-2) and higher (up to 60 mA.cm-2) current density.

Sodium titanate gels on the surface of titanium metal have been formed using sodium hydroxide solution and oxidised at 400°-800°C. The reaction sequence for these processes with increasing temperature is Ti → sodium titanate gel → crystalline sodium titanate gel → porous (top) and dense (bottom) anatase → porous (top) and dense (bottom) rutile. These samples subsequently were soaked in simulated body fluid in order to study the precipitation of hydroxyapatite in the absence and presence of long UV radiation, which has not been investigated before. One sample showed greatly enhanced hydroxyapatite deposition, this being the one oxidised at 400°C, consisting of small amounts of crystalline sodium titanate and anatase, and subjected to UV irradiation. More generally, enhancement of hydroxyapatite precipitation is observed in the presence of anatase and/or sodium titanate; suppression of hydroxyapatite precipitation is observed in the presence of gels and rutile. However, UV light with anatase enhanced precipitation while UV light with rutile suppressed it. This is attributed to the morphological effect of the larger grain of rutile compared to the smaller anatase.

Mn-doped TiO2 thin films were produced by spin coating on FTO glass substrates to investigate the effects of Mn concentration on the structural, morphological, and optical properties of the films. Titanium isopropoxide and manganese chloride tetrahydrate were used as titanium and manganese sources respectively, in the precursor solution with isopropanol. The solution was added drop-wise on the substrate which was spun at 2000 rpm; annealing was done in air at 500°C for 5 h. Films with very low dopant concentrations (≤ 1 wt%) were composed of anatase; those with moderate concentrations (3—5 wt%) showed the presence of anatase and rutile; while those with high Mn concentrations (≤ 7 wt% Mn) showed rutile formation. Increasing the dopant concentrations resulted in a slight increase in the surface roughness, except for the sample with 15 wt% Mn, that showed surface dimple formation. The films containing ≤ 10 wt% Mn showed similarity in grain sizes (∼ 10 nm) and thickness (∼ 300 nm). All the films showed relatively high transparencies, with the absorption edges shifting to longer wavelengths with increasing Mn levels. The optical indirect band gaps of the films decreased from 3.32 eV to 2.86 eV, and this data suggests that the formation of shallow trapping sites and reduced rate of electron-hole recombination are the result of the variable valence of Mn. [DOI: 10.1380/ejssnt.2012.103]

Thick anatase films were fabricated on graphite substrates using a method of anodic aqueous electrophoretic-deposition using oxalic acid as a dispersant. Thick films were subsequently fired in air and in nitrogen at a range of temperatures. The morphology and phase composition were assessed and the photocatalytic performance was examined by the inactivation of Escherichia coli in water. It was found that the transformation of anatase to rutile is enhanced by the presence of a graphite substrate through reduction effects. The use of a nitrogen atmosphere allows higher firing temperatures, results in less cracking of the films and yields superior bactericidal performance in comparison with firing in air. The beneficial effects of a nitrogen firing atmosphere on the photocatalytic performance of the material are likely to be a result of the diffusion of nitrogen and carbon into the TiO2 lattice and the consequent creation of new valence band states.

International audience; Thin TiO 2 films on quartz substrates were prepared by spin coating of undoped and metal-ion-doped Sol-Gel precursors. These films were characterised by Scanning Electron Microscopy, Laser Raman Microspectroscopy, X-ray Diffraction and UV-Vis Transmission. The photocatalytic performances of the films were assessed by the photo-degradation of methylene-blue in aqueous solution under UV irradiation. Films exhibited a high degree of orientation and a thermal stabilization of the anatase phase as a result of substrate effects. In the absence of dopants, the rutile phase formed as parallel bands in the anatase which broadened as the transformation progressed. TiO 2 films doped or co-doped with transition metals exhibited the formation of rutile in segregated clusters at temperatures under ~800°C as a result of increased levels of oxygen vacancies. Photocatalytic activity of the films synthesised in this work was low as likely result of poor TiO 2 surface contact with dye molecules in solution. The presence of transition metal dopants appears detrimental to photocatalytic activity while the performance of mixed phase films was not observed to differ significantly from single phase material.

Titanium dioxide films were prepared by ultrasonic spray pyrolysis on (0001) α -quartz substrates at 400 °C and/or annealed in air at 600°, 800°, or 1000 °C. The as-deposited films at 400 °C (50 nm grains) and annealed at 600 °C (100 nm grains) showed single-phase anatase of high transparency in the visible region. Films annealed at 800 °C and 1000 °C showed mixed-phase anatase (100 nm grains) plus rutile (700 nm agglomerates) and pure rutile, (700 nm grains), respectively. Raman and X-ray data indicate the presence of residual stress in the films, which may arise from contamination, silicon diffusion into the films, and/or oxygen deficiency.

Fully dense anatase and rutile (TiO2) films were coated on (0001) α-quartz wafers using ultrasonic spray pyrolysis in air at 400°C for 2 h. The TiO2 films were annealed subsequently in air for 4 h at 600, 800 and 1000°C respectively. The films were characterised using X-ray diffraction (mineralogy), ultraviolet visible spectrophotometry (optical properties) and photoluminescence (structural defects). These data are interpreted in terms of phase transformation temperature, optical mean free path, refractive index and effect of heat treatment on the concentration of oxygen vacancies and/or silicon contamination.

Aqueous solutions of tin (II) chloride dihydrate and oxalic acid dihydrate (both 0.04 M) were prepared and mixed by (1) dropwise addition and (2) instantaneous addition, with both involving addition of the latter to the former. Following filtering, washing, and drying, the precipitates were calcined and ground. The particle size and morphology of uncalcined and calcined tin oxalate were examined by electron microscopy and laser diffraction. The method of addition was important in that it influenced both the particle size and shape of tin oxalate. This resulted from the time effect of the ionic collision frequency and the proximity effect of the diffusion distance. As expected, ageing was important in that it caused grain growth and reduction of surface area of the tin oxalate. Although there appeared to be an effect of the method of addition on agglomeration of the tin oxide, this was a result of adsorption of atmospheric moisture, which depended on the relative humidity of the environment during grinding.

Aqueous solutions of tin (II) chloride dihydrate and oxalic acid dihydrate were prepared and mixed using two protocols: (1) fixed former concentration and variable latter concentrations and (2) fixed latter concentration and variable former concentrations. Following filtering, washing, and drying, the precipitates were calcined and ground. The calcined powders were characterised in terms of mineralogy and the particle size and morphology of the resultant tin oxide particles and agglomerates. The morphologies of the uncalcined tin oxalate also were examined. In nine of the ten samples, the tin oxalate precipitates consisted of prismatic elongated crystals. In the remaining sample, the low concentrations of solutions probably resulted in the crystallisation of smaller equiaxed particles. Regardless of the particle size or shape of the tin oxalate, the resultant particle size of the tin oxide was ~75 nm and the morphology was consistently spherical. The consistent particle size is attributed to the low solution concentrations used. The tin oxide particles were heavily agglomerated into plates of ~0.5 μm diameter. This morphology probably resulted from the plastic deformation during grinding of the calcined tin oxide, which was likely to have been subject to surface water adsorption on the fine particles. Under the experimental conditions investigated, there were no particle or agglomerate size dependencies on the solution concentrations and mixing method.

The present work provides a brief but wide ranging survey of the different methods that may be used to apply thick films of titanium dioxide for self-cleaning building materials. This survey is preceded by a general description of the photocatalytic applications of TiO2, a tabulated list of some relevant properties of the three naturally occurring polymorphs of TiO2 and a tabulated survey of world market shares and resources of TiO2. The survey of coating technologies consists of succinct coverage of twenty potential periodic and continuous routes for the application of liquid borne suspensions of TiO2 to building units. This coverage consists mainly of an illustration accompanied by relevant comments concerning the advantages and disadvantages of each method.