Search Results (26)

The present study investigates the synthesis and characterization of a zirconium oxide (ZrO₂)-based metal composite doped with cerium (Ce) and yttrium (Y), using chromium (Cr) and nickel (Ni) as base metals. These constituents were selected for their superior mechanical properties and compatibility with the ceramic phase. High-purity powders were homogenized via high-energy ball milling, followed by cold pressing and sintering in a controlled atmosphere of hydrogen. The sintering process was conducted at temperatures ranging from 850 °C to 1350 °C to examine the evolution of microstructure, grain growth, and densification. Scanning electron microscopy (SEM) revealed a homogeneous distribution of phases, with distinct microstructural features attributed to each element at different sintering temperatures. The experimental results revealed that the composite’s density was increased by 30% and porosity was reduced by 61% at a sintering temperature of 1350 °C. The hardness and flexural strength of composite were found to be 23% and 60% higher at 1350 °C, respectively, compared to that at 850 °C, suggesting enhanced mechanical properties due to cerium and yttrium reinforcement within matrix and efficient doping and phase transformation. Overall, incorporation of cerium and yttrium significantly improved mechanical behavior and phase stability of ZrO₂–Cr–Ni composite, highlighting its potential for advanced engineering 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

Zirconium-doped ceria is a promising and extensively researched catalytic material with notable use in three-way catalytic converters, the oxidation of volatile organic compounds and solid oxide fuel cells. In this work, pure and zirconium-doped ceria nanoparticles (Ce_1−xZr_xO₂, where x = 0, 0.1, 0.2, and 0.3) were prepared by combustion synthesis using glycine as the fuel and cerium and zirconium nitrate as oxidants. The obtained powders were characterized using X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, differential thermal and thermogravimetric analysis, UV–Vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. The combustion temperature increases with the increase in zirconium content in the samples, but the XRD patterns exclusively show ceria diffraction peaks. The crystallite sizes are in the range from 25.2 to 11.7 nm, and do not vary substantially after thermal treatment, indicating the good thermal stability of the prepared nanocatalysts. XPS analysis showed that the surface amount of zirconium is lower than the nominal and that the ceria sample with 10 mol. % of zirconium has a higher amount of oxygen vacancies than the 30 mol. % Zr-doped sample. The 10 mol. % Zr-doped sample displays the best catalytic activity in the BTEX (benzene, toluene, ethylbenzene, and o-xylene) oxidation process. Full article

It is confirmed that Fluorite-structured Entropy-Stabilized Oxides (F-ESO) can be obtained with multicomponent (5) equimolar systems based on cerium, zirconium, and other rare earth elements, selected according to the predictor already proposed by the authors. Indeed, in the present study, three different samples owning a standard deviation (SD in the following) of their cationic radii greater than the threshold value (i.e., SD > 0.095 with cationic radii measured in Å) needed to ensure the formation of the single-phase fluorite structure, were prepared via co-precipitation method. After a calcination step at 1500 °C for 1 h, the entropy-driven transition from multiple phases to single-phase fluorite-like structure has been actually confirmed. Thus, with the aim of defining the temperature at which such entropy-driven transition occurred, and identifying possible relation between such temperature and the actual value of SD, the phase evolution of all the prepared samples as a function of temperature (ranging from 800 °C to 1300 °C) was analyzed by in situ High Temperature X-ray Diffraction. An apparent inverse correlation between the standard deviation and the entropy-driven transition temperature has been identified, i.e., the higher the former, the lower the latter. These results, based on the conducted basic structural analysis, provide further support to the SD-based empirical predictor developed by the authors, suggesting that high values of SD could bring additional contribution to the overall entropy of the system, other than the configurational one. Thus, this SD-driven entropy contribution directly increases with the increasing of the standard deviation of the cationic radii of a given F-ESO. Full article

Commercial cerium–zirconium oxide supports (Ce_0.5Zr_0.5O₂, Ce_0.75Zr_0.25O₂, and Ce_0.4Zr_0.5Y_0.05La_0.05O₂) were used to prepare Ru/CeZrO_x catalysts. According to the XRD and IR spectroscopy data, the supports consist of ceria-based substitutional solid solutions. The specific surface areas of supports and catalysts are similar and range from 71–89 m²/g. As shown by TEM and XRD methods, the size of support particles equals 6–11 nm. According to the TEM data, the size of ruthenium particles does not exceed 1.3 nm. The catalyst activity in the ammonia decomposition process was studied. The Ru/Ce_0.75Zr_0.25O₂ catalyst at temperature 500 °C and GHSV 120,000 h⁻¹ demonstrated the highest hydrogen productivity of 53.3 mmol H₂/(g_cat·min) and compares well with the best results reported in the literature. The kinetics of ammonia decomposition reaction were calculated using the Temkin–Pyzhov exponential expression. The developed mathematical model well described the experimental data. The studied catalysts demonstrated high activity for the ammonia decomposition reaction. Full article

Copper was incorporated into the Ce-Sn and comparative Ce-Zr oxide supports by one-pot precipitation in the presence of CTAB template and by the impregnation of templated Ce-Sn and Ce-Zr oxides. The synthesized Cu-Ce-Sn and Cu-Ce-Zr catalysts were tested in the continuous-flow preferential oxidation of CO in hydrogen excess. The one-pot synthesized tin- and zirconium-doped catalysts demonstrated better CO conversion and CO₂ selectivity than their impregnated counterparts. For the tin-modified ternary system that showed the best catalytic performance, the copper content was further optimized. The structure, reducibility, surface chemical state and textural properties of the catalysts were analyzed by SEM-EDX, XRD, H₂-TPR, Raman spectroscopy, XPS and TEM. The nonmonotonic changes in the specific surface area, Cu⁺/Cu²⁺ ratio and ratio of lattice and non-lattice oxygen with increasing the Cu content are discussed in terms of copper distribution in the catalysts. The influence of the interaction between copper oxide species and the cerium–tin/cerium–zirconium oxide support on the performance of the ternary catalysts was thoroughly analyzed and discussed. Full article

Partial oxidation of dimethyl ether (DME) to hydrogen is an efficient route for hydrogen production for application in SOFC. However, quite a large amount of CO₂ as a byproduct has been an important obstacle. In this work, cerium–zirconium solid solution (Ce_xZr_1−xO₂) was applied to determine how the oxidative properties of the catalyst affect the production of CO₂ in the partial oxidation of DME. The results show that the catalyst with more adsorbed oxygen (O_ads) rather than the lattice oxygen has stronger oxidizability and gives higher DME conversion as well as higher CO₂ yield, due to the overoxidation of CO. Full article

The activity of emission control catalysts must be improved in urban mode at low temperatures. One possible way is to tailor the metal-support interaction between platinum group metals (PGMs) and ceria to stabilize small clusters or single atoms, optimizing the utilization of costly PGMs. In this study, a small loading of Pd (<0.2 wt.%) was dispersed on Pr-rich cerium–zirconium–praseodymium mixed oxides (CZP45: Ce_0.45Zr_0.10Pr_0.45O_2−x). After the initial calcination at 800 °C, Pd was mainly in the form of dispersed isolated cations which were found to be efficient for low-temperature CO oxidation but inactive for propane combustion. Nevertheless, a pre-reduction step can trigger the formation of Pd nanoparticles and promote the propane oxidation. Pd nanoparticles, formed during the reduction step, coupled with the high oxygen mobility of CZP45, lead to outstanding catalytic activity for propane oxidation starting from 250 °C. However, the re-oxidation of Pd nanoparticles and their partial re-dispersion, promoted by the fast oxygen mobility of the mixed oxide, rapidly deactivate the catalysts in lean conditions. Full article

The aim of these studies was to perform thorough research on the influence of alkali metal ions (Li, Na, K and Cs) on the properties of nanogold catalysts supported on ceria–zirconia. The addition of alkali metal ions onto CeO₂ further affected the reducibility, which was not noted for the Zr-doped support (Ce_0.85Zr_0.15O₂). Despite the substantial impact of alkali metal ions on the reducibility of ceria, the activity in CO oxidation did not change much. In contrast, they do not have a large effect on the reducibility of Au/CZ but suppressed the activity of this system in CO oxidation. The results show that for CO oxidation, the negative effect of potassium ions is greater than that of sodium, which corresponds to the shift in the T_max of the reduction peak towards higher temperatures. The negative effect of Li⁺ and Cs⁺ spans 50% CO conversion. The negative effect was visible for CO oxidation in both the model stream and the complex stream, which also contained hydrocarbons and NO. In the case of NO oxidation to NO₂, two temperature regimes were observed for Au + 0.3 at% K/CZ, namely in the temperature range below 350 °C; the effect of potassium ions was beneficial for NO oxidation, whereas at higher temperatures, the undoped gold catalyst produced more NO₂. Full article

Zirconium-Yttrium-co-doped ceria (Ce_0.85Zr_0.13Y_0.02O_1.99) compacts consisting of fibers with diameters in the range of 8–10 µm have been successfully prepared by direct infiltration of commercial YSZ fibers with a cerium oxide matrix and subsequent sintering. The resulting chemically homogeneous fiber-compacts are sinter-resistant up to 1923 K and retain a high porosity of around 58 vol% and a permeability of 1.6–3.3 × 10⁻¹⁰ m² at a pressure gradient of 100–500 kPa. The fiber-compacts show a high potential for the application in thermochemical redox cycling due its fast redox kinetics. The first evaluation of redox kinetics shows that the relaxation time of oxidation is five times faster than that of dense samples of the same composition. The improved gas exchange due to the high porosity also allows higher reduction rates, which enable higher hydrogen yields in thermochemical water-splitting redox cycles. The presented cost-effective fiber-compact preparation method is considered very promising for manufacturing large-scale functional components for solar-thermal high-temperature reactors. Full article

This study aimed at optimizing the production of glycolic acid from glycerol catalytic oxidation over a silver catalyst supported on a mixed cerium-zirconium oxide, to progress towards the industrialization of a derived process. Optimization of the operating conditions was performed using the response surface methodology. We concluded that the production of glycolic acid depends mainly of glycerol concentration, NaOH/glycerol ratio, catalyst/glycerol ratio, and O₂/glycerol ratio. The optimal conditions we found were a temperature of 60 °C, a NaOH/glycerol molar ratio of 2, an O₂/glycerol molar ratio of 0.23, and a catalyst/glycerol mass ratio of 0.07. With these optimal conditions, it was possible to increase the glycerol concentration from 0.3 M to 2 M, obtaining an increase in the concentration of glycolic acid in the liquid fraction, from 0.27 mol/L of glycolic acid (with initial glycerol solution 0.3 M) to 0.88 mol/L (with initial solution 2 M), while keeping a 100% glycerol conversion. Full article

Doping process is widely used to improving emission performance of MgO films thicker than 10 nm via assisting the surface recharge and changing in electron structure. The present paper briefly reviews this strategy in a search for the new materials and structures being effective for secondary electron emission (SEE) and their diagnostics. Then, Metal-Organic Chemical Vapor Deposition (MOCVD) coupled with the specially selected precursor is suggested here as a new technique that transforms the refractory oxides to nanoscale, defect-disordered materials able to solid-solid interaction at 450 °C. Primary experiments have been performed for demanded mixed films based on MgO with ZrO₂ and CeO₂ additions. A dopant impact on facilitating the formation of oxygen vacancies in the host oxide and on the features of new mixed phases have been studied by new diagnostic means, based primarily on chemical method of differential dissolution. The method brought out the effective solvents that were the probes for identifying the nanoscale and amorphous phases possessing by the different defects on the surface of MgO films and determining contents of these phases. This approach allowed us to explain the origin of mixed phases and to estimate contribution of each from them in the macroscopic SEE properties. Full article

The crude glycerol is produced during the transesterification of animal fats and vegetable oils, but it is a by-product of this process. Currently, its elimination is a problem in the chemical industry. The main goal of this work was the preparation, characterization and application of mesoporous cerium-zirconium oxide as supports for copper and gold species and the comparison of selected factors on the properties of catalysts in glycerol oxidation in the liquid phase. The samples were characterized using adsorption and desorption of nitrogen, XRD, UV-vis, XPS, TEM, SEM, and STEM-EDXS. The obtained results of glycerol oxidation show that the bimetallic copper-gold catalysts are more active and selective to glyceric acid in this reaction than analogous monometallic gold catalysts. Additionally, bimetallic catalysts are also characterized by the catalytic stability, and their application leads to the increase of selectivity to glyceric acid during their reusing in glycerol oxidation in alkali media. In this work, the influence of selected factors, e.g., oxygen source and its pressure, solution pH, and base content on the catalytic activity of bimetallic catalysts is discussed. Full article

Since there is no potential, effective vaccine available, treatment is the only controlling option against hydatid cyst or cystic echinococcosis (CE). This study was designed to systematically review the in vitro, in vivo, and ex vivo effects of nanoparticles against hydatid cyst. The study was carried out based on the 06- PRISMA guideline and registered in the CAMARADES-NC3Rs Preclinical Systematic Review and Meta-analysis Facility (SyRF) database. The search was performed in five English databases, including Scopus, PubMed, Web of Science, EMBASE, and Google Scholar without time limitation for publications around the world about the protoscolicdal effects of all the organic and inorganic nanoparticles without date limitation in order to identify all the published articles (in vitro, in vivo, and ex vivo). The searched words and terms were: “nanoparticles”, “hydatid cyst”, “protoscoleces”, “cystic echinococcosis”, “metal nanoparticles”, “organic nanoparticles”, “inorganic nanoparticles, “in vitro”, ex vivo”, “in vivo”. Out of 925 papers, 29 papers including 15 in vitro (51.7%), 6 in vivo (20.7%), ex vivo 2 (6.9%), and 6 in vitro/in vivo (20.7%) up to 2020 met the inclusion criteria for discussion in this systematic review. The results demonstrated the most widely used nanoparticles in the studies were metal nanoparticles such as selenium, silver, gold, zinc, copper, iron nanoparticles (n = 8, 28.6%), and metal oxide nanoparticles such as zinc oxide, titanium dioxide, cerium oxide, zirconium dioxide, and silicon dioxide (n = 8, 28.6%), followed by polymeric nanoparticles such as chitosan and chitosan-based nanoparticles (n = 7, 25.0%). The results of this review showed the high efficacy of a wide range of organic and inorganic NPs against CE, indicating that nanoparticles could be considered as an alternative and complementary resource for CE treatment. The results demonstrated that the most widely used nanoparticles for hydatid cyst treatment were metal nanoparticles and metal oxide nanoparticles, followed by polymeric nanoparticles. We found that the most compatible drugs with nanoparticles were albendazole, followed by praziquantel and flubendazole, indicating a deeper understanding about the synergistic effects of nanoparticles and the present anti-parasitic drugs for treating hydatid cysts. The important point about using these nanoparticles is their toxicity; therefore, cytotoxicity as well as acute and chronic toxicities of these nanoparticles should be considered in particular. As a limitation, in the present study, although most of the studies have been performed in vitro, more studies are needed to confirm the effect of these nanoparticles as well as their exact mechanisms in the hydatid cyst treatment, especially in animal models and clinical settings. Full article

Pure and doped vanadia (VO₂, V_0.98Zr_0.02O₂, V_0.98Ce_0.02O₂) samples were prepared by wet chemistry synthesis from vanadyl glycolate intermediate phase and tape casted into films. Combining in-operando grazing incidence synchrotron X-ray diffraction and Raman spectroscopy, we studied the structural evolution of the films under isothermal conditions. The setup allowed assessment of the thermochromic functionality with continuous monitoring of the monoclinic to tetragonal transition in pure and doped vanadia phases, responsible for the transmission and reflection of light in the infrared part of the solar spectrum. The materials characterisation by X-ray diffraction beamline (MCX) goniometer demonstrated ideal performance, combining flexible geometry, high resolution, and the potential to accommodate the multi-channel equipment for in-operando characterisation. This method proved viable for evaluating the relevant structural and physical, and thereof functional properties of these systems. We revealed that dopants reduce the transition temperature by 5 °C on average. The synthetic route of the films was held responsible for the observed phase separation. The more favourable behaviour of cerium-doped sample was attributed to cerium alkoxide behaviour. In addition, structural, microstructural, thermal, and spectroscopic characterisation on powder samples was performed to gain more insight into the development of the phases that are responsible for thermochromic features in a broader range of doping ratios. The influence of the dopants on the extent of the thermochromic transition (transmission to reflection hysteresis) was also evaluated using (micro) structural, thermal and spectroscopic methods of powder samples. Characterisations showed that zirconium doping in 2, 4, and 6 mol% significantly influenced the phase composition and morphology of the precursor. Vanadium oxides other than VO₂ can easily crystallise; however, a thermal treatment regime that allowed crystallisation of VO₂ as a single phase was established. Full article