Search Results (13)

This paper investigates the application of non-calcined metal tartrate as a novel alternative pore former to prepare functional ceramic composites to fabricate solid oxide fuel cells (SOFCs). Compared to carbonaceous pore formers, non-calcined pore formers offer high compatibility with various ceramic composites, providing better control over porosity and pore size distribution, which allows for enhanced gas diffusion, reactant transport and gaseous product release within the fuel cells’ functional layers. In this work, nanocrystalline gadolinium-doped ceria (GDC) and Ni-Gd-Ce-tartrate anode powders were prepared using a single-step co-precipitation synthesis method, based on the carboxylate route, utilising ammonium tartrate as a low-cost, environmentally friendly precipitant. The non-calcined Ni-Gd-Ce-tartrate was used to fabricate dense GDC electrolyte pellets (5–20 μm thick) integrated with a thin film of Ni-GDC anode with controlled porosity at 1300 °C. The dilatometry analysis showed the shrinkage anisotropy factor for the anode substrates prepared using 20 wt. The percentages of Ni-Gd-Ce-tartrate were 30 wt.% and 40 wt.%, with values of 0.98 and 1.01, respectively, showing a significant improvement in microstructural properties and pore size compared to those fabricated using a carbonaceous pore former. The results showed that the non-calcined pore formers can also lower the sintering temperature for GDC to below 1300 °C, saving energy and reducing thermal stresses on the materials. They can also help maintain optimal material properties during sintering, minimising the risk of unwanted chemical reactions or contamination. This flexibility enables the versatile designing and manufacturing of ceramic fuel cells with tailored compositions at a lower cost for large-scale applications. Full article

This study explores cobalt–cerium (Co₉₀Ce₁₀) thin films deposited on silicon (Si) (100) and glass substrates via direct current (DC) magnetron sputtering, with thicknesses from 10 nanometer (nm) to 50 nm. Post-deposition annealing treatments, conducted from 100 °C to 300 °C, resulted in significant changes in surface roughness, surface energy, and magnetic domain size, demonstrating the potential to tune magnetic properties via thermal processing. The films exhibited hydrophilic behavior, with thinner films showing a stronger substrate effect, crucial for surface engineering in device fabrication. Increased film thickness reduced transmittance due to photon signal inhibition and light scattering, important for optimizing optical devices. Furthermore, the reduction in sheet resistance and resistivity with increasing thickness and heat treatment highlights the significance of these parameters in optimizing the electrical properties for practical applications. Full article

Thin films of transition metal oxides and oxynitrides have proven highly effective in protecting stainless steels against corrosion in both chemically aggressive environments and biological fluids. In the present work, cerium zirconium oxynitride thin films were deposited to enhance the corrosion resistance of surgical-grade stainless steel to be used in osteosynthesis processes. Two techniques were employed: co-sputtering and radiofrequency (RF) sputtering, and the morphology and corrosion efficiency of the coatings deposited by each technique were evaluated. X-ray diffraction, X-ray photoelectron spectroscopy and field emission transmission electron microscopy were used to characterize the morphological and chemical structure, respectively. Additionally, the corrosion resistance of the oxynitride-coated surgical grade stainless steel system (ZrCeO_xN_y-AISI 316L) was assessed using Hank’s solution as the corrosive electrolyte, to determine its resistance to corrosion in biological media. The results show that ZrCeO_xN_y coatings increase the corrosion resistance of surgical grade stainless steel by two orders of magnitude and that the Ce(III)/Ce(IV) equilibrium decreases the corrosion rate, thereby increasing the durability of the steel in a biological environment. The results show that Ce coatings increase the corrosion resistance of surgical grade stainless steel by two orders of magnitude and that the Ce(III)/Ce(IV) equilibrium decreases the corrosion rate, thereby increasing the durability of the steel in a biological environment. Full article

The application-attractive form of TiO₂, CeO₂ and CuO-based open-cell foam supported catalysts was designed to investigate their catalytic performance in oxidation of two model volatile organic compounds—methanol and dichloromethane. TiO₂-CeO₂, TiO₂-CuO and TiO₂-CeO₂-CuO catalysts as thin films were deposited on VUKOPOR^®A ceramic foam using a reverse micelles-controlled sol-gel method, dip-coating and calcination. Three prepared catalytic foams were investigated via light-off tests in methanol and dichloromethane oxidation in the temperature range of 45–400 °C and 100–500 °C, respectively, at GHSV of 11, 600 h⁻¹, which fits to semi-pilot/industrial conditions. TiO₂-CuO@VUKOPOR^®A foam showed the best catalytic activity and CO₂ yield in methanol oxidation due to its low weak Lewis acidity, high weak basicity and easily reducible CuO species and proved good catalytic stability within 20 h test. TiO₂-CeO₂-CuO@VUKOPOR^®A foam was the best in dichloromethane oxidation. Despite of its lower catalytic activity compared to TiO₂-CeO₂@VUKOPOR^®A foam, its highly-reducible -O-Cu-Ce-O- active surface sites led to the highest CO₂ yield and the highest weak Lewis acidity contributed to the highest HCl yield. This foam also showed the lowest amount of chlorine deposits. Full article

Fuel electrode-supported tubular protonic ceramic cells (FETPCCs) based on the BaZr_0.4Ce_0.4Y_0.15Zn_0.05O_3−δ (BZCYZ) membrane electrolyte was fabricated through a two-step method, in which the polyporous electrode-support tube was prepared with a traditional slip casting technique in a plaster mold, and the BZCYZ membrane was produced by a dip-coating process on the outside surface of the electrode-support tube. The dense thin-film electrolyte of BZCYZ with a thickness of ~25 μm was achieved by cofiring the fuel electrode support and electrolyte membrane at 1450 °C for 6 h. The electrochemical performances of the FETPCCs were tested under different solid oxide cell modes. In protonic ceramic fuel cell (PCFC) mode, the peak power densities of the cell reached 151–191 mW·cm⁻² at 550–700 °C and exhibited relatively stable performance during continuous operation over 100 h at 650 °C. It was found that the major influence on the performance of tubular PCFC was the resistance and cathode current collectors. Additionally, in protonic ceramic electrolysis cell (PCEC) mode, the current densities of 418–654 mA·cm⁻² were obtained at 600–700 °C with the applied voltage of 2.0 V when exposed to 20% CO₂–80% H₂ and 3% H₂O/air. Using distribution of relaxation time analysis, the electrolytic rate-limiting step of the PCEC model was determined as the adsorption and dissociation of the gas on the electrode surface. Full article

The current work deals with the fabrication of novel MoO₃ nanostructured films with Ce and Cu co-doping through the spray pyrolysis route on a glass substrate maintained at 460 °C for the first time. The phase of developed films was approved by an X-ray diffraction study, and the crystallite size was determined between 82 and 92 nm. The optical transmission of the developed films was noticed to be reduced with doping and found between 45 and 90% for all films, and the absorption edge shifted to a higher wavelength with doping. The optical energy gap of the fabricated films was found to be reduced from 3.85 to 3.28 eV with doping. The developed films were used to degrade the harmful Eosin-Y dye under UV light. The system with 2% Ce and 1% Cu-doped MoO₃ turned out to be the most effective catalyst for photodegradation of the dye in a period of 3H and almost degrade it. Hence, the MoO₃ films prepared with 2% Ce and 1% Cu will be highly applicable as photocatalysts for the removal of hazardous dye from wastewater. Full article

Gadolinium-doped ceria (GDC) nanopowders, prepared using the co-precipitation synthesis method, were applied as a starting material to form ceria-based thin films using the electron-beam technique. The scanning electron microscopy (SEM )analysis of the pressed ceramic pellets’ cross-sectional views showed a dense structure with no visible defects, pores, or cracks. The AC impedance spectroscopy showed an increase in the total ionic conductivity of the ceramic pellets with an increase in the concentration of Gd₂O₃ in GDC. The highest total ionic conductivity was obtained for Gd_0.1Ce_0.9O_2-δ (σ_total is 11 × 10⁻³ S∙cm⁻¹ at 600 °C), with activation energies of 0.85 and 0.67 eV in both the low- and high-temperature ranges, respectively. The results of the X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma optical emission spectrometer (ICP-OES) measurements revealed that the stoichiometry for the evaporated thin films differs, on average, by ~28% compared to the target material. The heat-treatment of the GDC thin films at 600 °C, 700 °C, 800 °C, and 900 °C for 1 h in the air had a minor effect on the surface roughness and the morphology. The results of Raman spectroscopy confirmed the improvement of the crystallinity for the corresponding thin films. The optimum heat-treating temperature for thin films does not exceed 800 °C. Full article

A new electrochemical sensor of metal cation in an aqueous solution based on homobifunctional tridentate disulfide Schiff base and named 1,1′-(-((disulfanediylbis(2,1-phenylene))bis(azaneylylidene))bis(methaneylylidene))bis(naphthalene-2-ol) (ATNA) was easily obtained quantitatively from the condensation reaction of 2-hydroxy-1-naphthaldehyde and 2-aminothiophenol, and then fully characterized by spectroscopic techniques for structure elucidation. The molecular structure of ATNA was also confirmed by a single-crystal X-ray diffraction study to reveal a new conformation in which the molecule was stabilized by the O–H…N type intramolecular hydrogen bonding interactions in both moieties. The ATNA was used as a selective electrochemical sensor for the detection of chromium ion (Cr³⁺). A thin film of ATNA was coated on to the flat surface of glassy carbon electrode (GCE) followed by 5 % ethanolic Nafion in order to make the modified GCE (ATNA/Nafion/GCE) as an efficient and sensitive electrochemical sensor. It was found to be very effective and selective against Cr³⁺ cations in the company of other intrusive heavy metal cations such as Al³⁺, Ce³⁺, Co²⁺, Cu²⁺, Ga³⁺, Hg²⁺, Mn²⁺, Pb²⁺, and Y³⁺. The detection limit at 3 S/N was found to be 0.013 nM for Cr³⁺ ions within the linear dynamic range (LDR) (0.1 nM–10.0 mM) of Cr³⁺ ions with r² = 0.9579. Moreover; this work instigates a new methodology for developing the sensitive as well as selective electrochemical toxic cationic sensors in the field of environmental and health care. Full article

Platinum-free counter electrodes (CE) were developed for use in efficient and cost-effective energy conversion devices, such as dye-sensitized solar cells (DSSCs). Electrochemical deposition of CoS₂ on fluorine-doped tin oxide (FTO) formed a hierarchical sheet-like structured CoS₂ thin film. This film was engaged as a cost-effective platinum-free and high-efficiency CE for DSSCs. High stability was achieved using a phthaloychitosan-based gel-polymer electrolyte as the redox electrolyte. The electrocatalytic performance of the sheet-like CoS₂ film was analyzed by electrochemical impedance spectroscopy and cyclic voltammetry. The film displayed improved electrocatalytic behavior that can be credited to a low charge-transfer resistance at the CE/electrolyte boundary and improved exchange between triiodide and iodide ions. The fabricated DSSCs with a phthaloychitosan-based gel-polymer electrolyte and sheet-like CoS₂ CE had a power conversion efficiency (PCE, η) of 7.29% with a fill factor (FF) of 0.64, J_sc of 17.51 mA/cm², and a V_oc of 0.65 V, which was analogous to that of Pt CE (η = 7.82%). The high PCE of the sheet-like CoS₂ CE arises from the enhanced FF and J_sc, which can be attributed to the abundant active electrocatalytic sites and enhanced interfacial charge-transfer by the well-organized surface structure. Full article

The properties of 20 wt % CeO₂ and 21 wt % Ce_0.5Zr_0.5O₂ films, deposited onto a γ-Al₂O₃ by Atomic Layer Deposition (ALD), were compared to bulk Ce_0.5Zr_0.5O₂ and γ-Al₂O₃-supported samples on which 20 wt % CeO₂ or 21 wt % CeO₂–ZrO₂ were deposited by impregnation. Following calcination to 1073 K, the ALD-prepared catalysts showed much lower XRD peak intensities, implying that these samples existed as thin films, rather than larger crystallites. Following the addition of 1 wt % Pd to each of the supports, the ALD-prepared samples exhibited much higher rates for CO oxidation due to better interfacial contact between the Pd and ceria-containing phases. The redox properties of the ALD samples and bulk Ce_0.5Zr_0.5O₂ were measured by determining the oxidation state of the ceria as a function of the H₂:H₂O ratio using flow titration and coulometric titration. The 20 wt % CeO₂ ALD film exhibited similar thermodynamics to that measured previously for a sample prepared by impregnation. However, the sample with 21 wt % Ce_0.5Zr_0.5O₂ on γ-Al₂O₃ reduced at a much higher $P_{O_2}$ and showed evidence for transition between the Ce_0.5Zr_0.5O₂ and Ce_0.5Zr_0.5O_1.75 phases. Full article

In this work, three different types of Reverse Osmosis (RO) (Thin-Film Composite (SE), Cellulose Acetate (CE), and Polyamide (AD)) were used to perform foulant analysis (autopsy) study on the deposited materials from three different simulated brackish surface feed waters. The brackish surface water qualities represented the water quality in Iraqi marshes. The main foulants from the simulated feed waters were characterized by using Scanning Electron Microscope (SEM) images and Energy-Dispersive X-ray Spectroscopy (EDXS) spectra. The effect of feed water temperatures (37 °C and 11 °C) on the formation of the fouled material deposited on the membrane surface was examined in this study. Also, pretreatment by a 0.1 micron microfiltration (MF) membrane of the simulated feed water in advance of the RO membrane on the precipitated material on the membrane surface was investigated. Finally, Fourier Transform Infrared Spectroscopy (FTIR) analysis was used to identify the functional groups of the organic matter deposited on the RO membrane surfaces. The SEM images and EDSX spectra suggested that the fouled material was mainly organic matter, and the major crystal deposited on the RO membrane was calcium carbonate (CaCO₃). The FTIR spectra of the fouled RO membranes suggested that the constituents of the fouled material included aliphatic and aromatic compounds. Full article

Achieving monolithic integration of nonreciprocal photonic devices on semiconductor substrates has been long sought by the photonics research society. One way to achieve this goal is to deposit high quality magneto-optical oxide thin films on a semiconductor substrate. In this paper, we review our recent research activity on magneto-optical oxide thin films toward the goal of monolithic integration of nonreciprocal photonic devices on silicon. We demonstrate high Faraday rotation at telecommunication wavelengths in several novel magnetooptical oxide thin films including Co substituted CeO_2−δ, Co- or Fe-substituted SrTiO_3−δ, as well as polycrystalline garnets on silicon. Figures of merit of 3~4 deg/dB and 21 deg/dB are achieved in epitaxial Sr(Ti_0.2Ga_0.4Fe_0.4)O_3−δ and polycrystalline (CeY₂)Fe₅O₁₂ films, respectively. We also demonstrate an optical isolator on silicon, based on a racetrack resonator using polycrystalline (CeY₂)Fe₅O₁₂/silicon strip-loaded waveguides. Our work demonstrates that physical vapor deposited magneto-optical oxide thin films on silicon can achieve high Faraday rotation, low optical loss and high magneto-optical figure of merit, therefore enabling novel high-performance non-reciprocal photonic devices monolithically integrated on semiconductor substrates. Full article

Thin films of tin oxide mixed cerium oxide were grown on unheated substrates by physical vapor deposition. The films were annealed in air at 500 °C for two hours, and were characterized using X-ray photoelectron spectroscopy, atomic force microscopy and optical spectrophotometry. X-ray photoelectron spectroscopy and atomic force microscopy results reveal that the films were highly porous and porosity of our films was found to be in the range of 11.6–21.7%. The films were investigated for the detection of carbon monoxide, and were found to be highly sensitive. We found that 430 °C was the optimum operating temperature for sensing CO gas at concentrations as low as 5 ppm. Our sensors exhibited fast response and recovery times of 26 s and 30 s, respectively. Full article