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Aluminium doped zinc oxide is considered an interesting, earth abundant alternative to the transparent conductor indium tin oxide. In this respect, we synthesized Al-ZnO (AZO) thin films by a chemical solution deposition approach. Using water-based inks, the AZO thin films were printed in one single step on glass substrates in non-vacuum conditions. The drying process and the humidity of the atmosphere proved to be crucial during the thermal processing of the wet deposited thin films. To improve the understanding of the phenomena involved, the influence of these processing parameters on the final properties of the AZO thin films are investigated by FTIR, XRD, SEM, 1H and 27Al NMR and resistivity measurements. Optimal conditions were obtained by drying the wet thin film at 120 °C, followed by heating in a tube furnace until 500 °C under a 200 ppm O2/N2 atmosphere with a humidity controlled by bubbling the gas flow through 2 glass bottles containing water at 20 °C. AZO thin films with an resistivity of 2.54 × 10−2 Ω cm were obtained.

Titania has already proven its added value for air and water treatment. The higher the surface-to-volume area, the better the performance of the TiO 2 photocatalyst. These nanoparticles are typically applied in a slurry form. The use of titania nanoparticles in suspension has, however, multiple disadvantages such as a high turbidity and complex recovery of the photocatalyst after use. Therefore, immobilization of titania nanoparticles on a porous support such as a nanofibrous membrane, can be highly valuable for water treatment. These TiO 2 functionalized nanofibrous membranes may be used not only in a membrane separation reactor, but also in a contact reactor. In this study, TiO 2 nanoparticles were immobilized on both polymer (polyamide 6) and ceramic (silica) nanofibrous membranes. Polymer nanofibers are chosen as they are the state-of-the-art material, silica nanofibers on the contrary are less studied but show additional advantages due their excellent chemical and thermal stability and can thus offer a clear benefit for a wider range of applications. Two immobilization techniques were used, namely inline functionalization and dip-coating. Inline functionalization showed to be the preferred method for polyamide 6 nanofibrous membranes, dip-coating for silica nanofibrous membranes. Complete degradation of isoproturon, an actual concern in water treatment, is shown. Even the widely available commercial TiO 2 nanoparticles allowed for a complete isoproturon removal as the result of a correct immobilization process on nanofibrous materials. This clearly opens up the high value of TiO 2 functionalized nanofibrous membranes for organic (micro)pollutants removal.

In today’s cement and concrete research, mineralogical quantification of (un)hydrated cement samples by X-ray Diffraction/Rietveld analysis becomes more and more important. As the results from XRD/Rietveld analysis are becoming increasingly more accurate, it became a widely used tool to study the hydration of cementitious materials besides other techniques e.g. isothermal calorimetry or thermogravimetric analysis. To quantify amorphous or non-identified phases, an internal standard might be added to estimate these so-called ‘other’ phases. Compared to unhydrated samples which are almost completely crystalline, it has a higher significance in hydrated samples, as certain cement hydrates, such as C-S-H, hydrogarnet, hydrotalcite, AFm, etc., are often poorly crystalline. Within the development of Completely Recyclable Concrete (CRC – a concrete designed for reincarnation within the cement production following the Cradle-to-Cradle Principle) the hydration of the regenerated cement was assessed by XRD/Rietveld analysis. Within this study it was found that the particle size distributions of the sample and the internal standard should not be underestimated within the quantification of the ‘other’ phases.

Although concrete is a durable material, it has a big impact on the environment due to its high production volumes. This impact is mostly related to the consumption of virgin raw materials, the production of waste and the emission of carbon dioxide. To optimize the recycling opportunities of concrete, Completely Recyclable Concrete is designed as a raw material for clinker production, without the need for ingredient adjustments. However, CRC concrete constructions may be exposed to environments rich in chlorides, sulphates and other ions, affecting the clinkering process of CRC rubble. Therefore, it is important to know the effect of these ions on the mineralogy of CRC clinker. In this study the effect of sulphate additions to CRC raw meals on the final clinker mineralogy was studied by XRD/Rietveld analysis. It was found that an increasing sulphate content stimulates the formation of CaO containing sulphates such as calcium langbeinite and anhydrite. Additionally SO3 was found to stabilize belite at the expense of alite.

This paper presents a study of the hydration reactions of a cement regenerated from Completely Recyclable Concrete by thermogravimetric analysis and X-ray powder diffraction/Rietveld analysis. The experimental results for the hydration reactions of the clinker phases in the regenerated cement were compared to a hydration model for OPC. A good agreement between the experimental and modeling results was observed. Therefore in terms of both reaction kinetics and hydration product assemblages the hydration of cement regenerated from CRC is concluded to be very similar to the hydration of OPC.

In this Article, epitaxial thin films of SrTiO3 were prepared on single crystalline (100) LaAlO3 by an aqueous chemical solution deposition method. By using different chelating agents to stabilize the metal ions in water, the impact of the precursor chemistry on the microstructural and crystalline properties of the films was studied. Thorough investigation of the precursor by means of infrared and Raman spectroscopy as well as thermogravimetric analysis revealed that stable precursors can be obtained in which strontium ions can be either free in the solution or stabilized by one of the chelating agents. This stabilization of strontium ions appeared to be essential in order to obtain single phase SrTiO3 films. Precursors in which Sr(2+) remained as free ions showed SrO microcrystal segregation. Precursors in which both metal ions were stabilized gave rise to strongly textured, dense, and terraced SrTiO3 films, allowing subsequent deposition of YBa2Cu3O7-δ with superior superconducting performances.

This paper aims to investigate the use of cellular concrete as an alternative raw material (ARM) for Portland clinker kilns. The possibility to generate a raw material with a stable compositional variation was investigated as well as simulations were carried out to maximise their use in clinker kilns. Based on these simulations, experimental clinkers were produced with dosages that were esteemed as realistic. Because of the presence of important levels of quartz sand in the cellular concrete materials, the energy necessary to grind the alternative raw material in comparison with comparable classic raw materials was investigated as well as the influence of the final particle size distribution of the Cold Clinker Meal (CCM) on the mineralogical composition of the final clinkers. It will be demonstrated that cellular concrete materials can be used as ARM for clinker production although there are some important restrictions that will limit the practical implementation. This investigation will also provide some interesting knowledge on the use of other recycled concrete materials as alternative raw material for Portland clinker production.

In this paper, the formation of ZrO2 and yttria-stabilised-zirconia (YSZ) aqueous colloidal systems via microwave assisted hydrothermal synthesis is studied. Microwave synthesis allows a fast screening of the influence of different parameters such as time and temperature. The temperature varied from 140 degrees C up to 180 degrees C and the used reaction time varied from 5 min up to 1 h. The synthesised zirconia nanoparticles have a particle size of 50 nm confirmed by TEM. A H-1 NMR (nuclear magnetic resonance) study helped to understand the stabilization mechanism of the synthesised particles. By the addition of ytrrium ions into the zirconia colloidal solution, YSZ could be formed via an additional thermal treatment. Hereby, the samples are heated up to 400 degrees C for 1 h. YSZ colloidal solutions are synthesised by making use of complexing agents such as nitrilotriacetic acid, ethylenediaminetetraacetic acid and citric acid to control the hydrolysis and condensation of both ions to avoid non-stoichiometric phases. The ratio of Zr/Y in the particles is quantified by XRF. The amorphous structure of those particles necessitates an additional thermal treatment up to 600 degrees C during 1 h in order to obtain crystalline YSZ.

This paper aims to examine the use of fines and sludge generated out of the production of porphyry and dolomitic limestone as an alternative raw material for Portland clinker kilns with enumeration of possible limitations. The possibility to generate a raw material with a stable compositional variation was investigated and simulations were carried out to maximise their use in clinker kilns. Furthermore, experimental clinkers were produced with dosages that were esteemed as realistic by the numerical simulations. The final clinkers were fully analysed and evaluated on possible mineralogical influences.

The concrete industry is known for its big impact on the environment, therefore the concept of Completely Recyclable Concrete (CRC) has been developed. After the demolition of a CRC construction, the concrete rubble is recycled as raw material for cement production, without need for ingredient adjustments. In this paper the design method and regeneration process are presented. It was proven by microscopic and XRD analysis that the recycled clinker contains the traditional clinker minerals. Isothermal calorimetry showed that after 7 days the regenerated clinkers reach a hydration heat which varies between 73% and 94% of the heat produced by a commercial OPC.

In this article, Al-doped ZnO thin films deposited by a one single-layer approach are studied. An aqueous precursor solution was prepared for the deposition of Al-doped ZnO thin film via ink-jet printing. The physical properties of the ink were studied in detail by rheology measurement and drop visualization. The wetting of the ink with the substrate was studied by the use of wetting envelopes. A single layer of the ink was deposited on the substrate and fully processed. The thin films were studied by X-ray diffraction, scanning electron microscopy, resistivity measurements, and optical transmission measurements. The optimal dopant concentration was set at 3 at.%, which resulted in thin films with a resistivity of 2.54 cΩ cm and an optical transmission larger than 90% over the visible range of the electromagnetic spectrum.

Colorimetric sensors for monitoring and visual reporting of acidic environments both in water and air are highly valuable in various fields, such as safety and technical textiles. Until now sol-gel-based colorimetric sensors are usually nonflexible bulk glass or thin-film sensors. Large-area, flexible sensors usable in strong acidic environments are not available. Therefore, in this study organically modified silicon oxide nanofibrous membranes are produced by combining electrospinning and sol-gel technology. Two pH-indicator dyes are immobilized in the nanofibrous membranes: methyl yellow via doping, methyl red via both doping, and covalent bonding. This resulted in sensor materials with a fast response time and high sensitivity for pH-change in water. The covalent bond between dye and the sol-gel network showed to be essential to obtain a reusable pH-sensor in aqueous environment. Also a high sensitivity is obtained for sensing of HCl and NH3 vapors, including a memory function allowing visual read-out up to 20 min after exposure. These fast and reversible, large-area flexible nanofibrous colorimetric sensors are highly interesting for use in multiple applications such as protective clothing and equipment. Moreover, the sensitivity to biogenic amines is demonstrated, offering potential for control and monitoring of food quality.

The critical parameters determining the electrospinning of silica nanofibers starting from tetraethoxysilane sols are reported. By controlling the reaction conditions, the rheological properties of the sol allowed for electrospinning without needing the addition of an organic polymer. This allows the polymer removal step, which is deleterious to the fibers and an economic and ecological inconvenience, to be skipped. The effects on the electrospinning process of the viscosity of the sol, the concentration of ethanol, the degree of crosslinking and the size of the colloidal species were studied in depth with ATR-FTIR, Si-29 NMR, H-1 NMR and DLS. Moreover, to separate the contributions of the different parameters three different set-ups for sol preparation were used. An optimum amount of 9 mol L-1 ethanol for electrospinning was determined. In addition, the optimum degree of crosslinking and size of colloidal particles, approximately 3.5-7 nm, were obtained for stable electrospinning and for producing uniform, beadless nanofibers that were stable in time. The optimum viscosity range is in between 100 and 200 mPa s, which is in line with previous work. Using these optimum conditions, continuous electrospinning was carried out for 3 h, resulting in large flexible silica nanofibrous membranes.

A high-throughput preparation, processing and analysis of titania coatings prepared by chemical solution deposition from water-based precursors at low temperature (≈250 °C) on two different types of steel substrates (Aluzinc® and bright annealed) is presented. The use of the high-throughput equipment allows fast preparation of multiple samples saving time, energy and material; and helps to test the scalability of the process. The process itself includes the use of IR curing for aqueous ceramic precursors and possibilities of using UV irradiation before the final sintering step. The IR curing method permits a much faster curing step compared to normal high temperature treatments in traditional convection devices (i.e., tube furnaces). The formulations, also prepared by high-throughput equipment, are found to be stable in the operational pH range of the substrates (6.5–8.5). Titanium alkoxides itself lack stability in pure water-based environments, but the presence of the different organic complexing agents prevents it from hydrolysis and precipitation reactions. The wetting interaction between the substrates and the various formulations is studied by the determination of the surface free energy of the substrates and the polar and dispersive components of the surface tension of the solutions. The mild temperature program used for preparation of the coatings however does not lead to the formation of pure crystalline material, necessary for the desired photocatalytic and super-hydrophilic behavior of these coatings. Nevertheless, some activity can be reported for these amorphous coatings by monitoring the discoloration of methylene blue in water under UV irradiation.

Thermal transformations occurring during firing of recyclable concrete and hydrated Portland cement paste were monitored quantitatively by in situ and ex situ X-ray diffraction, thermal analysis, and clinker microscopy. Reactions below 1150°C were dominated by either the decarbonation of calcium carbonates of the limestone aggregate fraction in the recyclable concrete or the low temperature decomposition of cement hydrates of the cement paste. Continued heating of the cement paste showed a rapid and extensive reaction of the free lime to form intermediate calcium silicate and aluminate phases such as belite, gehlenite, mayenite, and ye'elimite. The combination of free lime was less rapid in the dominantly limestone-rich recyclable concrete. Similarly, subsequent melt and clinker phase formation (1250°C and higher) occurred more rapidly in the hydrated cement paste, indicating a positive contribution of cement hydrates to raw meal burnability. Reactions below typical cement clinkering temperatures were enhanced (1) by the intimate mixing of lime, silicate, and aluminate components in the hydrated cement and (2) by the elevated sulfate content that acted as flux and belite mineralizer. Lime formed in the thermal decomposition of portlandite (±450°C) was partially carbonated to calcite at temperatures below the onset of calcite decarbonation (±650°C).

In this work, aqueous chemical solution deposition route suited for inkjet printing is used for the synthesis of photocatalytically active TiO 2 coatings. Environmentally friendly precursor solutions with electromagnetic ink-jet printing, allows cheap and simple processing of TiO 2 films on glass. The hydrolysis reaction of water sensitive titanium alkoxide (Ti-alkoxide) precursor is controlled by adding complexing agents as citric acid and triethanolamine prior to water addition, and aqueous stable solutions are achieved. The pH of the solutions is brought to neutral to guarantee flexible processing, avoid damage to substrates and equipment. Solution parameters are adapted to obtain optimal gelation conditions and good jettability. The influence of processing parameters on the phase formation and surface morphology is studied by thermogravimetric analysis and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The photocatalytic activity of the films is evaluated by the degradation of methyl orange.

In this work, the reaction mechanism used in the preparation of fluorine-free superconducting YBa(2)Cu(3)O(7-delta) (YBCO) was investigated. To determine which precursor interactions are dominant, a comprehensive thermal analysis (thermogravimetric analysis-differential thermal analysis) study was performed. The results suggest that a three step reaction mechanism, with a predominant role for BaCO(3), is responsible for the conversion of the initial state to the superconducting phase. In the presence of CuO, the decarboxylation of BaCO(3) is kinetically favored with the formation of BaCuO(2) as a result. BaCuO(2) reacts with the remaining CuO to form a liquid which ultimately reacts with Y(2)O(3) in a last step to form YBCO. High temperature X-ray diffraction experiments confirm that these results are applicable for thin film synthesis prepared from an aqueous fluorine-free sol-gel precursor.

Stable TiO2 sols were prepared using two non-aqueous sol–gel processes with titanium n-butoxide and titanium isopropoxide, respectively. Crystallization and phase transitions of powders and thin films were studied by ex situ and in situ X-ray diffraction. For both methods, TiO2 began to crystallize around 320 °C in air. Using helium instead of air during heat treatment slowed down the crystallization and substoichiometric powders were formed. TiO2 thin films were obtained by spin coating. The morphology of the films was evaluated using scanning electron microscopy. The films were homogeneous and transparent in the visible range. The effect of the heating atmosphere and the type of substrate was investigated.

Remarkable color changes can be seen when ammonium metatungstate - citric acid gels are submitted to sunlight. The colors strongly depend of the pH values of the precursor solution. Luminescence measurements reveal that gels at pH 7 exhibit a strong blue emission resulting from the presences of WO 2 4 tetrahedra while a slight green emission is due to WO 6 6 octahedra. The shift in equilibrium from octahedral to tetrahedral coordination upon increase in pH is confirmed by detailed EXAFS analysis.

Powder XRD-analysis and thermo-mechanical analysis on sintered TiO 2 –WO 3 –ZrO 2 mixtures revealed the formation of Zr 1− x Ti x W 2 O 8 solid solutions. A noticeable decrease in unit cell parameter ‘ a ’ and in the order–disorder transition temperature could be seen in the case of Zr 1− x Ti x W 2 O 8 solid solutions. Studies performed on other ZrW 2 O 8 solid solutions have attributed an increase in phase transition temperature to a decrease in free lattice volume, whereas a decrease in phase transition temperature was suggested to be due to the presence of a more disordered state. Our studies indicate that the phase transition temperature in our materials is strongly influenced by the bond dissociation energy of the substituting ion–oxygen bond. A decrease in bond strength may compensate for the effect of a decrease in lattice free volume, lowering the phase transition temperature as the degree of substitution by Ti 4+ increases. This hypothesis is proved by differential scanning calorimetry.

This paper describes the synthesis of ZrW2O8 by the use of an aqueous citrate-gel method in order to prepare a fine, pure and homogeneous oxide mixture suitable for ceramic processing. The thermal expansion coefficient thus obtained for α-ZrW2O8 is −10.6 × 10−6 °C−1 (50–125 °C) whereas for the β-ZrW2O8 a value of −3.2 × 10−6 °C−1 (200–300 °C) is obtained. The advantages of the use of a sol–gel method is expressed in the very homogeneous end-products. The paper describes crystallographic data, morphological structure and the thermal expansion properties of the ZrW2O8 material. Moreover, photoluminescence and photochromic properties specific to the precursor gel are described and analyzed. These effects support our views that the precursors show homogeneity up to nanometer level.

This study aims to examine the use of concrete sludge from water treatment installations of ready-mixed concrete plants as an alternative raw material for portland clinker kilns, and to enumerate possible limitations. By its extensive and representative collection of concrete sludge samples data, it may also be used for other investigations. The chemical variations of this sludge were evaluated by gathering 87 sludge samples over a period of two years. Furthermore, a treatment phase was proposed. Numerical simulations were conducted based on the chemistry of a representative concrete sludge sample, before and after a specific treatment phase, together with classic raw materials of three reference clinker factories to investigate the influence of the sludge on the clinker meal composition. Based on these simulations, experimental clinkers were produced, which were fully analyzed and evaluated for possible mineralogical influences. Based on the findings of this investigation, it was concluded that s...

In this paper, we report on the synthesis of BaZrO3 nanostructures by novel bottom-up synthesis methods. Nanocrystals with diameters ranging from 5 to 10 nm are prepared from aqueous or multiple phase precursor solutions. In order to transform the precursor solutions into nanocrystal containing suspensions, both conventional and microwave-assisted solvothermal treatments are used. An additional heat treatment was necessary to obtain crystalline particles starting from the aqueous precursor, while crystalline particles are directly obtained after solvothermal treatment of the multiple phase precursor. The crystallinity and size of the obtained nanoparticles are investigated by means of dynamic light scattering, X-ray diffraction and transmission electron microscopy. We found that the nature of the bases used in the multiple phase precursor have an effect on the particle morphology. In general, the microwave-assisted solvothermal synthesis renders the best prospects towards small particle sizes between 3 and 5 nm in diameter with a narrow size distribution. In addition, the process exhibits higher energy efficiency, resulting in lower reaction times (5 min-2 h) in comparison with the conventional solvothermal treatment (4-24 h).

Chemical solution deposition techniques are a very competitive low cost method to achieve coated conductors. Recently, fluorine-free CSD methods have made a great progress for the preparation of YBCO thin films and became a sustainable alternative for the well-known trifluoroacetate CSD approach. By elucidating the reaction mechanism behind this new approach, finally giving an answer to the question why it is possible to fabricate YBCO films without TFA, different processing routes were discovered giving rise to high superconducting YBCO films (>1MA.cm-2). Each route has it's own benefits. One specific route offers the opportunity to tune the crystallographic orientation. By changing one process parameter, a shift from complete c-axis to complete a-axis orientation is observed. This can be very useful for e.g. Josephson Junctions.We particularly investigated the fundamental reaction mechanism of each reaction route, with the focus on the corresponding barium compound. Although good superconducting properties are obtained, still one major drawback limits industrial implementation: thickness. It is observed that a critical thickness of ∼500 nm eliminates the superconducting properties. Therefore, this paper gives a summary of all progress made regarding to fluorine-free water-based CSD YBCO thin films with emphasis on the possibility to control the crystallization rate.

Silica nanofibres have, due to their excellent properties, promising characteristics for multiple applications such as filtration, composites, catalysis, etc. Silica nanofibres can be obtained by combining electrospinning and the sol–gel process. To produce silica nanofibres most of the time organic solutions are applied containing a carrying polymer, which is afterwards removed by a thermal treatment to form pure ceramic nanofibres. Although electrospinning of the pure silica precursors without carrying polymer is preferred, the parameters influencing the stability of the electrospinning process are however largely unknown. In addition, this knowledge is essential for potential upscaling of the process. In this study, the optimum viscosity to electrospin in a stable manner is determined and the way to obtain this viscosity is evaluated. Sols with a viscosity between 120 and 200 mPa.s could be electrospun in a stable way, resulting in uniform and beadless nanofibres. Furthermore, this viscosity region corresponded with nanofibres having the lowest mean nanofibre diameters. Electrospinning with diluted sols was possible as well, but electrospinning of the fresh sols was more stable. These results illustrate the importance of the viscosity and degree of crosslinking of the sol for the stable electrospinning of silica nanofibres and demonstrate that upscaling of the electrospinning process of silica nanofibres is feasible.

Zirconia and Yttrium stabilized zirconia are well-known ceramic materials. Scaling down the dimension of these ceramics can result in a faster sintering process at lower temperatures. Microwave synthesis of nano-structured particles is a very attractive synthesis route because of the short synthesis time and low reaction temperature. This allows a fast screening of the influence of different parameters such as time, temperature and pressure on the final size and crystal phase of the particles. In this study Zr and Zr/Y aqueous precursors are mixed with a variety of complexing agents or surfactants in different ratios. The reason is twofold: (1) we aim for a stable precursor solution which is established by lowering the free ion concentration and (2) we want to see the influence of the complexing agents on the growth of the particles and the formation of crystalline phases. Particle sizes of these particle vary from 40 -200 nm. The crystallinity is confirmed by X-ray diffraction. The stabilization of these particles and possible exchange of the ligands is examined with NMR measurements (1D - proton combined with 2D NOESY) and is compared with TGA-DTA analysis of the isolated particles.

This paper aims to examine the use of fibrecement waste as an alternative raw material for Portland clinker kilns with enumeration of possible limitations. Numerical simulations were carried out to maximise the use of fibrecement waste in clinker kilns taking into account the compositional variation of the waste, its behaviour within a clinker kiln, the impact on the energy consumption and finally the influence on the carbon footprint calculated from the decarbonation. Furthermore, experimental clinkers were produced corresponding with waste dosages that were esteemed as realistic by the numerical simulations. These clinkers were fully analysed and evaluated according to the above described evaluation concept. © 2012 Elsevier Ltd.

Lanthanumcerium oxide (LCO) films were deposited on Ni-5%W substrates by chemical solution deposition (CSD) from water-based precursors. LCO films containing different ratios of lanthanum and cerium ions (from CeO2 to La2Ce2O7) were prepared. The composition of the layers was optimized towards the formation of LCO buffer layers, lattice-matched with the superconducting YBa2Cu3Oy layer, useful for the development of coated conductors. Single, crack-free LCO layers with a thickness of up to 140 nm could be obtained in a single deposition step. The crystallinity and microstructure of these lattice-matched LCO layers were studied by X-ray diffraction techniques, RHEED and SEM. We find that only layers with thickness below 100 nm show a crystalline top surface although both thick and thin layers show good biaxial texture in XRD. On the most promising layers, AFM and (S)TEM were performed to further evaluate their morphology. The overall surface roughness varies between 3.9 and 7.5 nm, while the layers appear much more dense than the frequently used La2Zr2O7 (LZO) systems, showing much smaller nanovoids (12 nm) than the latter system. Their effective buffer layer action was studied using XPS. The thin LCO layers supported the growth of superconducting YBCO deposited using PLD methods.

In this work, water-based precursor solutions suitable for dip-coating of thick La{sub 2}Zr{sub 2}O{sub 7} (LZO) buffer layers for coated conductors on Ni-5%W substrates were developed. The solutions were prepared based on chelate chemistry using water as the main solvent. The effect of polymer addition on the maximum crack-free thickness of the deposited films was investigated. This novel solution preparation method revealed the possibility to grow single, crack-free layers with thicknesses ranging 100-280 nm with good crystallinity and an in-plane grain misalignment with average FWHM of 6.55{sup o}. TEM studies illustrated the presence of nanovoids, typical for CSD-LZO films annealed under Ar-5%H{sub 2} gas flow. The appropriate buffer layer action of the film in preventing the Ni diffusion was studied using XPS. It was found that the Ni diffusion was restricted to the first 30 nm of a 140 nm thick film. The surface texture of the film was improved using a seed layer. - Graphical abstract: Thick LZO buffer layers from water-based precursor solutions were synthesized and their crystallinity, microstructure and buffer layer action were studied. The buffer layer action of the LZO layer was substantial to restrict the Ni penetration within 30 nm of a 140 nm thickmore » film. Highlights: > LZO buffer layers with high thicknesses for use in coated conductors were prepared. > Prepared from water-based solutions. > Polymeric PVP increases the crack-free critical thickness of thick films. > Thick films showed good barrier action against Ni penetration. > Seed layers promote epitaxial growth of thick layers.« less

The negative-thermal-expansion material ZrW(2)O(8) is known to undergo an order-disorder phase transition which affects its expansion behavior. In this study, Ti(4+) and Sn(4+) are examined as possible substituting ions for the Zr(4+) position in ZrW(2)O(8). This substitution leads to a decrease in cell parameters, as the ionic radii of the substituents are smaller than the Zr(4+) ionic radius. A remarkable decrease in transition temperature is noticed. DSC is used to quantify the enthalpy and entropy changes during the phase transition in order to reveal the mechanisms behind this decrease. It is shown that the strength of the M-O bond plays an important role, as it is a partner in the rigid unit mode motion and the order-disorder transition mechanism.

The thermal expansion of a ceramic material in general leads to a positive thermal expansion coefficient (α). In the last decennium, several families of materials which exhibit negative thermal expansion, arising from a specific geometrical effect in their so-called open framework structures, have been discovered. Usually, this negative thermal expansion coefficient is small, anisotropic and the phenomena occur in a very small temperature interval. ZrW2O8 is an exception because of its large and isotropic negative thermal expansion coefficient (NTE) in a temperature range from 0.5K to 1050K. A cubic symmetry is found over the entire stability range with a phase transition from α-ZrW2O8 to β-ZrW2O8 near 430K. This phase transition is noticed by a change in α. The aqueous citrate-gel method is a suitable synthesis route for negative thermal expansion ceramics and will give a fine, pure and homogenous oxide mixture, well suitable for the preparation of ZrW2O8. The expansion coefficient of α–ZrW2O8 is -11 μm/m K whereas for the β- ZrW2O8 a value of -3 is obtained.

In this paper, the formation of YBiO3 starting from a new water-based precursor was studied in both bulk and thin films under different processing conditions. The decomposition of this precursor was studied with thermogravimetric and differential thermal analysis and the reaction products were identified with X-ray diffraction. Our results show that starting from our water-based solutions, polycrystalline YBO powders can be obtained in air and argon atmospheres. Once the partial oxygen pressure was reduced using an Ar–5% H2 mixture, reduction of Bi3+ was observed, restricting YBO formation. When thin film synthesis on single crystal LaAlO3 is performed, clear differences in processing conditions were observed regarding powder synthesis. The addition of water vapour to the argon gas is necessary in order to suppress Bi2O3 sublimation. Using the appropriate synthesis conditions, well-textured, homogeneous, dense and smooth (Ra = 2.6–1.8 nm) films of 140 nm and 40 nm thickness are obtained at sinter-temperatures as low as 750 °C. YBa2Cu3O7−x deposited by Pulsed Laser Deposition on the 40 nm thick YBiO3 films yielded a Jc (77 K) of 3.6 MA cm−2 in self-field, indicating the potential of this material as an alternative for CeO2 in the CeO2/La2Zr2O7/Ni–5%W and CeO2/YSZ/Stainless Steel coated conductor architectures.

In this work, we investigate the chemistry for an aqueous acetate-triethanolamine-ammonia based YBa(2)Cu(3)O(7-δ) (YBCO) precursor system. These precursor solutions are suited for the chemical solution deposition of superconducting YBCO layers on top of single crystal SrTiO(3) or buffered NiW tapes. The development of this kind of precursor inks often involves trial-and-error experimenting and thus is very time-consuming. To reduce labwork to the minimum, the theoretical prediction of pH stability limits and the complexation behaviour of the different metal ions and complexants in the inks are very important. For this purpose, we simulated, based on literature values, the complexation behaviour of Cu(2+) in the aqueous precursor solutions as a function of pH. To validate the used model, we performed potentiometric pH titrations for solutions with similar composition and checked the correctness of fit between experiment and model. The generated complexometric results are coupled with X-band EPR spectra to further confirm the results. EPR spectra for fully prepared precursor solutions as well as for Cu(2+) reference solutions containing only one type of ligand (acetate, triethanolamine or ammonia) were investigated as a function of pH. We find that, in line with speciation simulation, only acetates are actively complexing the Cu(2+) ions at pH values below 7, while when reaching higher pH levels mainly triethanolamine complexes are formed. Over the entire pH range, no trace of free Cu(2+)or Cu(OH)(2), possibly creating precipitation during gelation and thus complicating further processing, could be found.

Low-power and compact phase shifters are crucial for large photonic circuits, both to cope with variability and to create programmable waveguide circuits scaling to thousands of tuning elements. This work demonstrates a liquid crystal phase shifter where there is a lateral silicon electrode "rail" on one side of the waveguide core. Using this architecture, a strong quasi-static electric field E actuation can be applied over the gap, which is filled with liquid crystal cladding material, with modest voltages. Because the mode is largely confined in the waveguide, optical losses are limited, compared to earlier experiments with slot waveguides. The liquid crystal is deposited locally on three different device variations using inkjet printing. The local deposition avoids unwanted interference of the liquid crystal with other optical components such as grating couplers. Measurements show similar trends as simulations of the liquid crystal orientations. For one device with a length of 50 µm, a phase shift of almost 0.9π is shown at 10 VRMS. We also discuss the challenges with this first demonstration of this phase shifter geometry using a silicon side-rail as an electrode.

Nanofibrous materials produced via electrospinning are characterized by a high porosity, large specific surface area, and high pore interconnectivity and, therefore, show potential for, e.g., separation and filtration. The development of more inert nanofibers with higher thermal and chemical resistance extends the application field. Silica nanofibrous membranes produced by direct electrospinning of a sol–gel solution without a sacrificing carrier meet these challenging demands. A combination of hydrolysis and condensation reactions of the tetraethoxysilane (TEOS) precursor, results in dense silica nanofibers with superior mechanical properties, without a rough and uneven surface, allowing the use in advanced engineering applications.

We report a low-voltage optical phase shifter using liquid crystal actuation integrated in IMEC's iSIPPSOG platform fabricated using inkjet printing as a deposition mechanism. A π phase shift is obtained at 3Vrms, almost 3π is obtained at 9Vrms. (Abstract)