Search

Undoped, Cu and/or Y doped ZrO2 nanopowders were synthesized with Zr, Y, and Cu nitrates using a co-precipitation approach. Their structural and optical properties were examined regarding dopant content (0.1–8.0 mol.% of CuO and 3–15 mol.% of Y2O3) and calcination conditions (400 °C– 1000 °Cand, 1,2 or 5 h) through Raman scattering, XRD, TEM, EDS, AES, EPR,UV–vis and FTIR diffused reflectance methods. The results showed that both Cu and Y dopants promoted the appearance of additional oxygen vacancies in ZrO2 host, while the formation of tetragonal and cubic ZrO2 phases was primarily influenced by the Y content, regardless of Cu loading. The bandgap of most of the powders was observed within the 5.45–5.65 eV spectral range, while for those with high Y content it exceeded 5.8 eV. The (Cu,Y)-ZrO2 powders with 0.2 mol.% CuO and 3 mol.% Y2O3 calcined at 600 °Cfor 2 h demonstrated nanoscaled tetragonal grains (8–12 nm) and a significant surface area covered with dispersed CuxOspecies. For higher calcination temperatures, the formation of CuZr 2+ EPR centers, accompanied by tetragonal-to-monoclinic phase transformation, was found. For fitting of experimental FTIR reflection spectra, theoretical models with one, five, and seven oscillators were constructed for cubic, tetragonal, and monoclinic ZrO2 phases, respectively. Comparing experimental and theoretical spectra, the parameters of various phonons were determined. It was found that the distinct position of the high-frequency FTIR reflection minimum is a unique feature for each crystalline phase. It was centered at 700–720 cm−1, 790–800 cm−1, and 820–840 cm−1 for cubic, tetragonal, and monoclinic phases, respectively, showing minimal dependence on phonon damping coefficients. Based on the complementary nature of results obtained from structural and optical methods, an approach for monitoring powder properties and predicting catalytic activity can be proposed for ZrO2–based nanopowders.

Zirconia (ZrO₂), the main corrosion product of the zircaloy cladding material of nuclear fuel rods, might potentially act as the first barrier for radionuclides. Thus, the interactions of radionuclides, such as the long-lived actinide neptunium, with zirconia have to be considered in the safety assessment process of a repository for radioactive waste. The sorption of Np(V) onto zirconia (ZrO₂) was investigated in the absence of carbonate at the macroscopic and molecular scale. For the macroscopic description, pH-dependent batch sorption experiments under varying ionic strength (0.1 and 0.01 mol∙L⁻¹ NaCl), Np(V) concentration (1∙10⁻⁶ or 6∙10⁻⁶ mol∙L⁻¹) and solid-to-liquid ratio (m/V = 0.5 or 4 g∙L⁻¹ ZrO₂) were conducted. Np(V) sorption isotherms at pH 4.5 and 6.0 were additionally obtained at 0.01 mol∙L⁻¹ NaCl. The Np(V) uptake on zirconia strongly depends on pH, with sorption starting from acidic pH and maximum sorption was reached at pH 6 and above. Increasing the m/V ratio caused a significant shift of the sorption edge towards lower pH values. This indicates the presence of different kinds of sorption sites, which was supported by the results of the Np(V) sorption isotherms, where the shape of the isotherm suggested the presence of strong and weak sorption sites. The Np(V) uptake was independent of ionic strength, suggesting the presence of inner-sphere Np(V) surface complexes on zirconia. This was also supported by zeta potential measurements where a shift of the isoelectric point of the pristine zirconia towards higher pH values in the presence of Np(V) was observed. Molecular level investigations by means of spectroscopic techniques, namely in situ attenuated total reflection Fourier transform Infrared Spectroscopy (ATR FT-IR) and extended X-ray absorption fine structure spectroscopy (EXAFS), confirmed the predominant presence of Np(V) inner-sphere complexes on the zirconia surface. EXAFS experiments conducted in the weak sorption site regime revealed the form

Gliomas present one of the most prevalent malignant tumors related to the central nervous system. Surgical extraction is still a preferred route for glioma treatment. Nonetheless, neurosurgeons still have a considerable challenge to detect actual margins of the targeted glioma intraoperatively and correctly because of its great natural infiltration. Here we evaluated the possibility of using surface-enhanced Raman spectroscopy to analyze freshly resected brain tissues. The developed method is based on the application of Au@ZrO2 nanosensor. The plasmonic properties of the sensor were first tested on the analysis of Rhodamine 6G, where concentrations down to 10-7 mol/L can be successfully detected. We also compared the performance of the nanosensor with silver plasmonic nanoparticles, where similar results were obtained regarding the reduction of the fluorescence background and enhancement of the intensity of the measured analytical signal. However, application of silver nanospheres led to increased variations in spectral data due to its probable aggregation. Applied ZrO2@Au nanosensor thus dramatically lowers the fluorescence present in the Raman data, and considerably improves the quality of the measured signal. The developed method allows for rapid discrimination between the glioma's periphery and central parts, which could serve as a steppingstone toward highly precise neurosurgery.

© 2005 IOP Publishing Ltd. This work has been partially financed by the Spanish Ministerio de Educación y Ciencia and the DGICyT under contracts MAT2003-04278, MAT2004-05348 and CAM2004-0440, and by the Ramón y Cajal program. J.I. B. acknowledges financial support from the I3P program of the CSIC., The occurence of spin-polarization at ZrO_(2), Al_(2)O_(3) and MgO surfaces is proved by means of abinitio calculations within the density functional theory. Large spin moments, as high as 1.56 µB, develop at O-ended polar terminations, transforming the non-magnetic insulator into a half-metal. The magnetic moments mainly reside in the surface oxygen atoms and their origin is related to the existence of 2p holes of well-defined spin polarization at the valence band of the ionic oxide. The direct relation between magnetization and local loss of donor charge makes possible to extend the magnetization mechanism beyond surface properties., Spanish Ministerio de Educación y Ciencia, DGICyT, Ramón y Cajal program, I3P program of the CSIC, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

The interactions of long-lived radionuclides, such as uranium and the transuranium element neptunium, with corroded phases in the near-field of a repository are crucial processes that have to be taken into account in the safety assessment of a repository. Neptunium(V) and uranium(VI) were chosen as representatives of pentavalent and hexavalent actinides, respectively. Zirconia (ZrO₂) is the main corrosion product of the zircaloy cladding material of spent nuclear fuel rods and constitutes as one of the first barriers encountered by mobilized radionuclides. A comprehensive, multi-method approach was pursued to obtain a detailed understanding of the Np(V)/U(VI) interactions at the zirconia-water interface. pH-dependent batch sorption studies and isotherm experiments as well as spectroscopic techniques (EXAFS, IR) were employed to gain information on the macroscopic and the molecular scale, respectively. The derived information about Np(V)/U(VI) binding sites as well as number and structure of the formed surface species were then used to constrain the parametrization of a thermodynamic surface complexation model. The results of this work will contribute to more reliable predictions about the environmental fate of Np(V)/U(VI) surrounding the near-field of a repository.

Down-conversion photoluminescent ZrO2: Ln3+ (Ln = Eu, Sm, Er, Tb, Ho, Tm, Pr, Gd, Dy) films were prepared by the plasma electrolytic oxidation (PEO) method from a pure zirconium foil, by adding Ln2 O3 particles to a basic electrolyte. Photoluminescence (PL) emission spectra of ZrO2: Ln3+ films are characterized by a broad band of ZrO2 host with a maximum positioned at about 490 nm and sharp emission bands ascribed to 4f–4f transitions of Ln3+ ions. The most intense 4f–4f transitions of Ln3+ are 5 D 0  →  7 F2 at 613 nm for Eu3+,4 G5/2  → 6 H7/2 at 617 nm for Sm3+,4 S3/2  → 4 I15/2 at 548 nm for Er3+,5 D4  → 7 F5 at 543 nm for Tb3+,5 F4  → 5 I8 at 540 nm for Ho3+,1 D2  → 3 F4 at 456 nm for Tm3+,3 P0  → 3 H6 at 608 nm for Pr3+,6 P7/2  → 8 S7/2at 313 nm for Gd3+, and4 F9/2 → 6 H13/2at 578 nm for Dy3+. Ln3+ ions in ZrO2 host can be directly excited into 4f levels. For Eu3+ more efficient excitation is through charge transfer band caused by electron transfer between the completely filled 2p orbital of O2− ions and the partially filled 4f orbital of Eu3+, while for Tb3+ through the inter-configurational 4f8  → 4f7 5d1 transition.

This study reports the successful synthesis and comprehensive characterization of ZrO2:Dy3+ phosphors with the incorporation of K+ ions. The introduction of Dy3+ and K+ in the ZrO2 lattice as lanthanide activators demonstrates its potential as an efficient host material. The structural integrity of ZrO2 remains unaltered following the doping process. Fourier-transform infrared spectroscopy (FTIR) analysis confirms the presence of Zr-O and O-H stretching, along with H2O bending modes in the phosphor sample. The wide luminescence band seen at 460 nm is attributed to luminescence defects in the ZrO2 induced by oxygen, and the presence of water molecules. Photoluminescence (PL) spectra analysis reveals pronounced emission peaks at 491 and 578 nm, corresponding to 4 F9/2 → 6 H15/2 and 4 F9/2 → 6 H13/2 transitions, respectively, upon excitation at 349 nm. Optimizing the Dy3+ doping concentration to 0.4 wt% and achieving a critical distance of 31.82 Å resulted in efficient energy transfer. Notably, co-doping K+ as a charge compensator significantly enhances the luminescence intensity. Moreover, at lower temperatures, direct excitation of Dy3+ ions through our pump wavelength, coupled with exciton-mediated energy transfer, leads to a remarkable increase in PL intensity. Tailoring the doping concentrations effectively shifts the emission spectrum of the phosphor mixture, aligning with the standard white light illumination coordinates (0.333, 0.333). This property positions the material as a promising candidate for applications in white light-emitting diodes (WLEDs) and various high-quality lighting applications. The enhanced photoluminescence and temperature dependence observed in ZrO2:Dy3+ phosphors upon the incorporation of K+ ions pave the way for their potential utilization in advanced luminescent devices.

Zirconia (ZrO2) membranes experienced rapid progress in applications demanding high-stability membranes own to their higher chemical resistance and hydrophilicity compared to silica and alumina. Moreover, ZrO2 membranes have increased fouling resistance, high permeability, and a long lifetime making them broadly applied in drinking water production, wastewater treatment, petrochemical, food, and beverages industries. However, fabricating ZrO2 membranes for Nanofiltration and Gas Separation is still challenging. This paper reviews the progress in fabricating ZrO2 membranes, focusing on strategies for achieving smaller pores without losing their high permeability and selectivity. The current state of the art in commercial ZrO2 membranes and the recent innovations in academia are critically reviewed. A comprehensive revision of sol-gel technique's critical synthesis and process parameters is presented along with the most recent molecular layer deposition method. This work aims to provide a guide for both starting and established researchers, thus filling a gap in the present literature.

Mixed zinc-zirconium oxides, ZnZrOx, are highly selective and stable catalysts for CO2 hydrogenation to methanol, a pivotal energy vector. However, their activity remains moderate, and descriptors to design improved systems are lacking. This work applies flame spray pyrolysis (FSP), a one-step and scalable method, to synthesize a series of ZnZrOx catalysts, and systematically compares them to coprecipitated (CP) analogs to establish deeper synthesis-structure-performance relationships. FSP systems (up to 5 mol%) generally display a threefold higher methanol productivity compared to their CP counterparts. In-depth characterization and theoretical simulations show that, unlike CP, FSP maximizes the surface area and formation of atomically dispersed Zn2+ sites incorporated in lattice positions within the ZrO2 surface, which is key to improving performance. Analysis by in situ electron paramagnetic resonance (EPR) spectroscopy reveals that the specific architecture of the flame-made catalyst markedly fosters the generation of oxygen vacancies. Together with surrounding Zn and Zr-O atoms, the oxygen vacancies create active ensembles that favor methanol formation through the formate path while suppressing undesired CO production, as confirmed by kinetic modeling. This study elucidates the nature of active sites and their working mechanism, pushing forward ZnZrOx-catalyzed methanol synthesis by providing a new benchmark for this cost-effective and earth-abundant catalyst family.

This paper describes fabrication of aluminium-zinc (Al-Zn) alloy (AZ91E) metal matrix composites augmented with Fly Ash (FA) and zirconium dioxide (ZrO2) particulate utilising the vortex method and a stir casting process. The researchers introduced composites with ZrO2and fly ash at varied weight % ranging from 0 to 10 with 53 µm particle sizes. The inclusion of ZrO2 particle reinforcement increased the hardness significantly, whereas the ultimate yield and tensile strengths increased somewhat. As the weight % of ZrO2 particles was increased, the permeability and density of Al-Zn alloy based composites increasing. Additionally, the compressive and tensile crack properties of the composites produced were investigated. Microstructural analyses confirmed the presence of evenly dispersed FA and ZrO2 particles throughout the matrix, but an EBSD study revealed that this led to diminished reduction. The inclusion of FA particles enhanced the material’s tensile properties and hardness including ultimate yield and tensile strengths. The strengthening mechanisms underlying the enhanced properties were discussed.

The interactions of long-lived actinides, such as the transuranium element neptunium, with corrosion products in the near-field of a repository are important processes that have to be considered when assessing the safety of a nuclear waste repository. As a main corrosion product of the zircaloy cladding material of spent nuclear fuel rods, zirconia (ZrO₂) constitutes a first possible barrier against the release of radionuclides. To gain a detailed understanding of the surface processes in the Np(V)−zirconia system, a comprehensive, multi-method approach was applied. The Np(V)−ZrO₂ system has been studied on the macroscopic level by conducting pH-dependent batch sorption experiments under varying conditions (ionic strength, Np(V) concentration, and solid-to-liquid ratio (m/V)). In addition, a Np(V) sorption isotherm at pH 6 was collected. The results revealed that Np(V) sorption onto ZrO₂ was affected by pH, Np(V) concentration, and solid-to-liquid ratio. Uptake of Np(V) increased with pH, starting around pH 3 with maximum sorption reached from pH 6. The shift of the sorption edge towards lower pH with increase of the m/V ratio points to the presence of different kinds of sorption sites. This is supported by the Np(V) sorption isotherm results, where the shape suggests strong and weak binding sites. Furthermore, Np(V) uptake was found to be independent of ionic strength and zeta potential measurements revealed a shift towards higher pH values of the isoelectric point of the neat ZrO₂ in the presence of Np(V). Hence, the formation of Np(V) inner-sphere surface complexes is indicated. Molecular information about the surface species were obtained by Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS) and in situ Infrared (IR) Spectroscopy, revealing the predominant formation of inner-sphere Np(V) surface complexes. A short Np−Zr distance derived from EXAFS suggests the presence of Np(V) bidentate inner-sphere complexes on the ZrO₂ surface. These information ob

The interactions of long-lived radionuclides, such as uranium and the transuranium element neptunium, with corroded phases in the near-field of a repository are crucial processes that have to be taken into account in the safety assessment of a repository. Neptunium(V) and uranium(VI) were chosen as representatives of pentavalent and hexavalent actinides, respectively. Zirconia (ZrO₂) is the main corrosion product of the zircaloy cladding material of spent nuclear fuel rods and constitutes as one of the first barriers encountered by mobilized radionuclides. A comprehensive, multi-method approach was pursued to obtain a detailed understanding of the Np(V)/U(VI) interactions at the zirconia-water interface. pH-dependent batch sorption studies and isotherm experiments as well as spectroscopic techniques (EXAFS, IR) were employed to gain information on the macroscopic and the molecular scale, respectively. The derived information about Np(V)/U(VI) binding sites as well as number and structure of the formed surface species were then used to constrain the parametrization of a thermodynamic surface complexation model. The results of this work will contribute to more reliable predictions about the environmental fate of Np(V)/U(VI) surrounding the near-field of a repository.

When assessing the safety of a nuclear waste repository, the interactions of dissolved long-lived radionuclides, such as the actinide neptunium, with corrosion products in the near-field of the repository are crucial processes that have to be taken into account. Zirconia (ZrO₂), the main corrosion product of the zircaloy cladding material of nuclear fuel rods, constitutes a first barrier against the release of radionuclides into the environment. A multimethod approach was pursued to gain a thorough understanding of the Np(V) sorption processes on the water−zirconia interface. For the macroscopic description of the Np(V)−ZrO₂ system, pH-dependent batch sorption experiments (varying ionic strength, Np(V) concentration, and the solid-to-liquid ratio) as well as a sorption isotherm experiment at pH 6 were conducted. The uptake of Np(V) was pH-dependent, with an increased sorption starting from pH 3 and being at a maximum at pH 6 and above. The Np(V) sorption was independent of ionic strength, hinting to the presence of Np(V) inner-sphere complexes on the zirconia surface. This was supported by zeta potential measurements in the presence of neptunium, where a shift to higher pH values of the isoelectric point of the neat ZrO₂ was observed. The Np(V) sorption edge was shifted towards lower pH values with increasing solid-to-liquid ratio, indicating the presence of different kinds of sorption sites, which was also deduced from the shape of the sorption isotherm. Molecular information of the surface species were obtained by Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS) and in situ Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) revealing the predominant formation of inner-sphere Np(V) surface complexes. A short Np−Zr distance derived from EXAFS spectra suggested the presence of Np(V) bidentate complexes at the zirconia surface. Reliable information about the number and denticity of surface species obtained by macroscopic and mo

The interactions of long-lived actinides, such as the transuranium element neptunium, with corrosion products in the near-field of a repository are important processes that have to be considered when assessing the safety of a nuclear waste repository. As a main corrosion product of the zircaloy cladding material of spent nuclear fuel rods, zirconia (ZrO₂) constitutes a first possible barrier against the release of radionuclides. To gain a detailed understanding of the surface processes in the Np(V)−zirconia system, a comprehensive, multi-method approach was applied. The Np(V)−ZrO₂ system has been studied on the macroscopic level by conducting pH-dependent batch sorption experiments under varying conditions (ionic strength, Np(V) concentration, and solid-to-liquid ratio (m/V)). In addition, a Np(V) sorption isotherm at pH 6 was collected. The results revealed that Np(V) sorption onto ZrO₂ was affected by pH, Np(V) concentration, and solid-to-liquid ratio. Uptake of Np(V) increased with pH, starting around pH 3 with maximum sorption reached from pH 6. The shift of the sorption edge towards lower pH with increase of the m/V ratio points to the presence of different kinds of sorption sites. This is supported by the Np(V) sorption isotherm results, where the shape suggests strong and weak binding sites. Furthermore, Np(V) uptake was found to be independent of ionic strength and zeta potential measurements revealed a shift towards higher pH values of the isoelectric point of the neat ZrO₂ in the presence of Np(V). Hence, the formation of Np(V) inner-sphere surface complexes is indicated. Molecular information about the surface species were obtained by Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS) and in situ Infrared (IR) Spectroscopy, revealing the predominant formation of inner-sphere Np(V) surface complexes. A short Np−Zr distance derived from EXAFS suggests the presence of Np(V) bidentate inner-sphere complexes on the ZrO₂ surface. These information ob

This paper describes fabrication of aluminium-zinc (Al-Zn) alloy (AZ91E) metal matrix composites augmented with Fly Ash (FA) and zirconium dioxide (ZrO2) particulate utilising the vortex method and a stir casting process. The researchers introduced composites with ZrO2and fly ash at varied weight % ranging from 0 to 10 with 53 µm particle sizes. The inclusion of ZrO2 particle reinforcement increased the hardness significantly, whereas the ultimate yield and tensile strengths increased somewhat. As the weight % of ZrO2 particles was increased, the permeability and density of Al-Zn alloy based composites increasing. Additionally, the compressive and tensile crack properties of the composites produced were investigated. Microstructural analyses confirmed the presence of evenly dispersed FA and ZrO2 particles throughout the matrix, but an EBSD study revealed that this led to diminished reduction. The inclusion of FA particles enhanced the material’s tensile properties and hardness including ultimate yield and tensile strengths. The strengthening mechanisms underlying the enhanced properties were discussed.

In this paper, the synthesis of Zirconium oxide (ZrO2) nanoparticles was carried out by the conventional precipitation method. Ultraviolet, visible spectroscopy (UV-Vis) and dynamic light scattering analysis (DLS) were performed to find the particles' bandgap and size. Fourier transform infrared spectroscopy (FT-IR) observed the characteristic bands of Zirconium oxide nanoparticles. Dynamic light scattering analysis showed that the size of the particle was found to be 119 nm.

Zirconia-based ceramics are becoming a popular biomaterial in dental implantology due to their natural silver-white color, excellent mechanical properties, and good biocompatibility. However, zirconia-based ceramics are biologically inert, which limits their ability to integrate with the surrounding human tissues. To solve this problem, the bioactive elements of calcium (Ca) and phosphorus (P) were doped in high-strength ZrO2-SiO2 nanocrystalline glass-ceramics (NCGCs) to overcome the biological inertness of ZrO2-based ceramics. XRD results showed that tetragonal zirconia (t-ZrO2) and monoclinic zirconia (m-ZrO2) were the only two crystalline phases after spark plasma sintering. Ca and P dopants acted as destabilizer of t-ZrO2, enhancing its transformability to m-ZrO2 during sintering. The amount of t-ZrO2 exerted significant effects on the average flexural strength of the NCGCs. The NCGC with 45 mol% ZrO2 were composed of 64.5 vol% t-ZrO2 and 35.5 vol% m-ZrO2 after sintering at 1230 degrees C. And, the average flexural strength and Vickers hardness of the NCGC was 615 MPa and 1049 HV, respectively. In comparison, the NCGC with 65 mol% ZrO2 were composed of 12.6 vol% t-ZrO2 and 87.4 vol% m-ZrO2 after sintering at 1150 degrees C. The average flexural strength and Vickers hardness of the NCGC was 293 MPa and 839 HV, respectively. Interestingly, the NCGCs exhibited a plastic deformation behavior during flexural strength test, which was different from traditional brittle ceramics. The ion release results demonstrated that Ca2+ and Si4+ ions kept on releasing from the surface of the material. The formation of hydroxyapatite in the in-vitro apatite formation test indicated that the NCGCs had good biological activity. The doped ZrO2-based NCGCs combined moderate strength and good bioactivity. Hence, the NCGCs show promising potential to be used in sub-gingival regions, such as dental abutments.

Systematic studies on polycrystalline Hf1–xZrxO2 films with varying Zr contents show that HfO2 films are paraelectric (monoclinic). If the Zr content is increased, films become ferroelectric (orthorhombic) and then antiferroelectric (tetragonal). HfO2 shows very good insulating properties and it is used in metal-oxide-semiconductor field-effect devices, while ZrO2 shows good piezoelectric properties, but it is antiferroelectric. In between, Hf0.5Zr0.5O2 shows good ferroelectric properties at the expense of poorer insulating and piezoelectric properties than HfO2 and ZrO2, respectively. Here, we explore the ferroelectric, insulating, and piezoelectric properties of a series of epitaxial films of Hf1–xZrxO2 with different compositions. We show that epitaxial growth permits the stabilization of the ferroelectric phase in a whole range of Zr content (from x = 0 to x = 1). In epitaxial ZrO2 films, ferroelectricity coexists with better piezoelectric and insulating properties than Hf0.5Zr0.5O2, and in HfO2 epitaxial films, ferroelectricity coexists with better insulating properties than Hf0.5Zr0.5O2. For the case of ZrO2 films, large electroresistance is also observed. In both cases, the ferroelectric endurance is poorer than that for Hf0.5Zr0.5O2.

Microstructures of ZnO and ZrO and the corresponding composites have been grown by the Vapor-Solid method. A detailed characterization of their structural, compositional and optical properties has been performed. X-ray diffraction (XRD) and Raman spectroscopy measurements, let us identify two main phases, wurtzite ZnO and monoclinic ZrO, reinforcing the hypothesis of ZnO/ZrO composite formation. Scanning Electron Microscopy observations reveal the presence of different morphologies depending on the synthesis conditions. Chemical composition was analyzed by energy dispersive X-ray (EDX) spectroscopy. Luminescence properties were studied by photoluminescence and cathodoluminescence. Our results indicate that doping is occurring in both phases: ZnO is doped with Zr and ZrO is doped with Zn. However important differences between Zr rich and Zn rich structures are encountered. While the Zn rich structures are single phase with the characteristic wurtzite crystal structure of ZnO, the Zr rich structures are multiphase with both monoclinic and wurtzite crystal structures present, then leading to formation of the composites with interesting luminescence properties, with intense emissions in the near UV and the visble range, even at room temperature.

Alkyl and alkoxy phenols are desirable products from the catalytic depolymerisation of lignin. In this work, ex-situ catalytic pyrolysis of Etek lignin in presence of Na, Ce, NiCe, MgCe, Fe and FePd on ZrO2 was studied. The largest combined yield of monomeric phenolics and alkylphenols was produced by Na/ZrO2 catalysts. A parametric study of the most promising Na/ZrO2 then resulted in using a catalyst:lignin ratio of 3:1 at 500 degrees C as the best option, enhancing at 17.5 wt% the recovery of total phenolics including 6 wt% alkyl phenols, which is equivalent to 27.8 wt% and 9.5 wt% of the starting lignin in Etek lignin waste. The study of the catalyst basicity indicates that the mild basicity of Na/ZrO2 was mostly responsible for the enhanced mono phenols recovery. Due to formation of thermally stable Na2CO3 during pyrolysis, successful Na/ZrO2 regeneration requires temperature of 900 degrees C or higher.

Pure and a series of Fe3+ doped zirconia nanopowders were synthesized combining colloidal chemistry and solvothermal method from organometallic precursors in order to correlate doping and properties of zirconia matrix. After annealing of washed nanopowders at 600 °C, detailed characterization was performed using X-ray diffraction, UV/Vis absorption and luminescence, infrared and electron paramagnetic spectroscopy, transmission electron microscopy and BET measurements. Zirconia samples had mixed monoclinic and tetragonal crystalline phase; increasing Fe3+ ions concentration was followed by increasing of tetragonal phase share. In the sample with highest Fe3+ concentration, hematite can be detected. Also, UV/Vis spectrophotometry showed that Fe3+ doping lowers effective band gap of zirconia matrix from 4.5 eV (bulk value) to 2.1 eV for doped/nanocomposite samples. EPR measurements proved presence of dopant and showed that isolated Fe3+ ions in zirconia matrix exist in both crystalline phases; monoclinic and tetragonal (g ~ 4.8 and g ~ 4.27–4.2, respectively) surroundings. Zirconia samples were also successfully used as photocatalysts for photocatalytic degradation of 2, 4, 6, trichlorophenol.

Pure and a series of Fe3+ doped zirconia nanopowders were synthesized combining colloidal chemistry and solvothermal method from organometallic precursors in order to correlate doping and properties of zirconia matrix. After annealing of washed nanopowders at 600 °C, detailed characterization was performed using X-ray diffraction, UV/Vis absorption and luminescence, infrared and electron paramagnetic spectroscopy, transmission electron microscopy and BET measurements. Zirconia samples had mixed monoclinic and tetragonal crystalline phase; increasing Fe3+ ions concentration was followed by increasing of tetragonal phase share. In the sample with highest Fe3+ concentration, hematite can be detected. Also, UV/Vis spectrophotometry showed that Fe3+ doping lowers effective band gap of zirconia matrix from 4.5 eV (bulk value) to 2.1 eV for doped/nanocomposite samples. EPR measurements proved presence of dopant and showed that isolated Fe3+ ions in zirconia matrix exist in both crystalline phases; monoclinic and tetragonal (g ~ 4.8 and g ~ 4.27–4.2, respectively) surroundings. Zirconia samples were also successfully used as photocatalysts for photocatalytic degradation of 2, 4, 6, trichlorophenol.

Pure and a series of Fe3+ doped zirconia nanopowders were synthesized combining colloidal chemistry and solvothermal method from organometallic precursors in order to correlate doping and properties of zirconia matrix. After annealing of washed nanopowders at 600 °C, detailed characterization was performed using X-ray diffraction, UV/Vis absorption and luminescence, infrared and electron paramagnetic spectroscopy, transmission electron microscopy and BET measurements. Zirconia samples had mixed monoclinic and tetragonal crystalline phase; increasing Fe3+ ions concentration was followed by increasing of tetragonal phase share. In the sample with highest Fe3+ concentration, hematite can be detected. Also, UV/Vis spectrophotometry showed that Fe3+ doping lowers effective band gap of zirconia matrix from 4.5 eV (bulk value) to 2.1 eV for doped/nanocomposite samples. EPR measurements proved presence of dopant and showed that isolated Fe3+ ions in zirconia matrix exist in both crystalline phases; monoclinic and tetragonal (g 4.8 and g 4.27–4.2, respectively) surroundings. Zirconia samples were also successfully used as photocatalysts for photocatalytic degradation of 2, 4, 6, trichlorophenol. © 2019 Elsevier Ltd and Techna Group S.r.l.

Pure and a series of Fe3+ doped zirconia nanopowders were synthesized combining colloidal chemistry and solvothermal method from organometallic precursors in order to correlate doping and properties of zirconia matrix. After annealing of washed nanopowders at 600 °C, detailed characterization was performed using X-ray diffraction, UV/Vis absorption and luminescence, infrared and electron paramagnetic spectroscopy, transmission electron microscopy and BET measurements. Zirconia samples had mixed monoclinic and tetragonal crystalline phase; increasing Fe3+ ions concentration was followed by increasing of tetragonal phase share. In the sample with highest Fe3+ concentration, hematite can be detected. Also, UV/Vis spectrophotometry showed that Fe3+ doping lowers effective band gap of zirconia matrix from 4.5 eV (bulk value) to 2.1 eV for doped/nanocomposite samples. EPR measurements proved presence of dopant and showed that isolated Fe3+ ions in zirconia matrix exist in both crystalline phases; monoclinic and tetragonal (g 4.8 and g 4.27–4.2, respectively) surroundings. Zirconia samples were also successfully used as photocatalysts for photocatalytic degradation of 2, 4, 6, trichlorophenol. © 2019 Elsevier Ltd and Techna Group S.r.l.

Pure and a series of Fe3+ doped zirconia nanopowders were synthesized combining colloidal chemistry and solvothermal method from organometallic precursors in order to correlate doping and properties of zirconia matrix. After annealing of washed nanopowders at 600 °C, detailed characterization was performed using X-ray diffraction, UV/Vis absorption and luminescence, infrared and electron paramagnetic spectroscopy, transmission electron microscopy and BET measurements. Zirconia samples had mixed monoclinic and tetragonal crystalline phase; increasing Fe3+ ions concentration was followed by increasing of tetragonal phase share. In the sample with highest Fe3+ concentration, hematite can be detected. Also, UV/Vis spectrophotometry showed that Fe3+ doping lowers effective band gap of zirconia matrix from 4.5 eV (bulk value) to 2.1 eV for doped/nanocomposite samples. EPR measurements proved presence of dopant and showed that isolated Fe3+ ions in zirconia matrix exist in both crystalline phases; monoclinic and tetragonal (g ~ 4.8 and g ~ 4.27–4.2, respectively) surroundings. Zirconia samples were also successfully used as photocatalysts for photocatalytic degradation of 2, 4, 6, trichlorophenol.

Pure and a series of Fe3+ doped zirconia nanopowders were synthesized combining colloidal chemistry and solvothermal method from organometallic precursors in order to correlate doping and properties of zirconia matrix. After annealing of washed nanopowders at 600 °C, detailed characterization was performed using X-ray diffraction, UV/Vis absorption and luminescence, infrared and electron paramagnetic spectroscopy, transmission electron microscopy and BET measurements. Zirconia samples had mixed monoclinic and tetragonal crystalline phase; increasing Fe3+ ions concentration was followed by increasing of tetragonal phase share. In the sample with highest Fe3+ concentration, hematite can be detected. Also, UV/Vis spectrophotometry showed that Fe3+ doping lowers effective band gap of zirconia matrix from 4.5 eV (bulk value) to 2.1 eV for doped/nanocomposite samples. EPR measurements proved presence of dopant and showed that isolated Fe3+ ions in zirconia matrix exist in both crystalline phases; monoclinic and tetragonal (g ~ 4.8 and g ~ 4.27–4.2, respectively) surroundings. Zirconia samples were also successfully used as photocatalysts for photocatalytic degradation of 2, 4, 6, trichlorophenol.

A series of gold catalysts supported on pure CeO, ZrO, and two different Ce-Zr mixed oxides have been prepared and tested in the 5-hydroxymethyl-2-furfural oxidation reaction. All catalysts show high catalytic activity (100% conversion) and important selectivity (27–41%) to the desired product i.e., 2,5-furandicarboxylic acid at low base concentration. Products selectivity changes with the support nature as expected, however, the observed trend cannot be related neither to gold particle size, nor to catalyst reducibility and oxygen mobility. An important relation between the FDCA selectivity and the support textural properties is observed, conducing to the general requirement for optimal pore size for this reaction.

The aim of this study is to prepare CuO-CeO2 composite by means of mechanical milling and to investigate its characteristics as a catalyst. The structural and morphological features of milled samples are observed by X-ray diffractometry and scanning electron microscopy. The redox property and total OSC (oxygen storage capacity) of the milled sample were measured by using GC-TCD and TG-DTA, which are important parameters to indicate the effectiveness of catalysts. Interestingly, reduction of CuO is repeatedly observed when milling of CuO-CeO2 powder mixture is processed in air. The redox property of milled CuO-CeO2 sample is investigated by H2-TPR, where three reduction peaks are observed for 0 h milling and only one broad peak for various other milling times. The total OSC of mechanically driven CuO-CeO2 catalyst is much higher than that of the CeO2-ZrO2 traditional catalyst system at low temperatures.

In this paper, we report an atomic layer deposited (ALD) zirconium oxide-based micro humidity sensor. The sensor comprises of a pair of interdigital platinum electrodes on a silicon substrate and a humidity sensing film (ZrO2) coated on the electrodes. The atomic layer deposition technique is utilized to conformally coat 42 nm thick zirconium oxide on 410 nm thick electrodes to increase the surface area of the sensing film. The sensor is tested under various humidity levels. It is evident from experimental results that the impedance of the sensor decreases with increase in relative humidity. Furthermore, the sensor is highly sensitive to humidity at the low frequency of the applied signal. At 20 Hz frequency when relative humidity is varied from 0.1% to 92%, the impedance of the sensor decreased from 143.46 M to 62.04 k with a net change in impedance of about 2,312 times, which is much higher than most of the reported zirconium oxide based humidity sensors. © 2019 IEEE.

In this paper, we report an atomic layer deposited (ALD) zirconium oxide-based micro humidity sensor. The sensor comprises of a pair of interdigital platinum electrodes on a silicon substrate and a humidity sensing film (ZrO2) coated on the electrodes. The atomic layer deposition technique is utilized to conformally coat 42 nm thick zirconium oxide on 410 nm thick electrodes to increase the surface area of the sensing film. The sensor is tested under various humidity levels. It is evident from experimental results that the impedance of the sensor decreases with increase in relative humidity. Furthermore, the sensor is highly sensitive to humidity at the low frequency of the applied signal. At 20 Hz frequency when relative humidity is varied from 0.1% to 92%, the impedance of the sensor decreased from 143.46 M to 62.04 k with a net change in impedance of about 2,312 times, which is much higher than most of the reported zirconium oxide based humidity sensors. © 2019 IEEE.

In this paper, we report an atomic layer deposited (ALD) zirconium oxide-based micro humidity sensor. The sensor comprises of a pair of interdigital platinum electrodes on a silicon substrate and a humidity sensing film (ZrO2) coated on the electrodes. The atomic layer deposition technique is utilized to conformally coat 42 nm thick zirconium oxide on 410 nm thick electrodes to increase the surface area of the sensing film. The sensor is tested under various humidity levels. It is evident from experimental results that the impedance of the sensor decreases with increase in relative humidity. Furthermore, the sensor is highly sensitive to humidity at the low frequency of the applied signal. At 20 Hz frequency when relative humidity is varied from 0.1% to 92%, the impedance of the sensor decreased from 143.46 M to 62.04 k with a net change in impedance of about 2,312 times, which is much higher than most of the reported zirconium oxide based humidity sensors. © 2019 IEEE.

Pt-20Rh dispersion strengthened by ZrO2 particles in different volume fractions has been produced by consolidation of milled powder which has been internally oxidized. The microstructure has been characterized by scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy; tensile properties have been determined at RT and 1000 °C. The Pt-20Rh matrix is subdivided on the submicrometer scale by low angle dislocation boundaries and high angle boundaries. ZrO2 particles with sizes in the range 5–35 nm are uniformly distributed and with increasing volume fraction the flow stress increases and at 0.9% it is doubled both at RT and at 1000 °C. Based on the superposition of particle and matrix strengthening, the flow stress has been calculated and good accord has been found with experiment both at RT and 1000 °C.

[EN] The incorporation of Al2O3-NbC-nanopowder reinforcement in a 3Y-TZP matrix, and its influence on the mechanical properties of 3YTZP/Al2O3-NbC nanocomposites, obtained by conventional and spark plasma sintering (SPS), was investigated. Nanometric powders of Al2O3-NbC were prepared by reactive high-energy milling, deagglomeration, and leaching with acid, and added to the 3Y-TZP matrix, at a proportion of 5 vol%. The final powders were dried under airflow, compacted, and sintered in the temperature range of 1300-1500 degrees C. The effects of the sintering technique and final temperature, on the microstructure and mechanical properties, such as hardness, toughness, and Young's modulus, were analysed. Fracture toughness of the material reinforced with Al2O3-NbC nanopowders, which is one of its most important properties, differed significantly from that of the 3Y-TZP monolith (5.2 MPa m(1/2)). The nanocomposites, sintered conventionally at 1450 degrees C, showed higher fracture toughness (8.7 MPa m(1/2)). Microstructure observations indicated that NbC nanoparticles were dispersed homogeneously within the 3Y-TZP matrix, and limited its grain growth. However, partial oxidation of the NbC on the nanocomposite surface, at the conventional sintering temperature of 1500 degrees C, caused a reduction in the fracture toughness.

[EN] The incorporation of Al2O3-NbC-nanopowder reinforcement in a 3Y-TZP matrix, and its influence on the mechanical properties of 3YTZP/Al2O3-NbC nanocomposites, obtained by conventional and spark plasma sintering (SPS), was investigated. Nanometric powders of Al2O3-NbC were prepared by reactive high-energy milling, deagglomeration, and leaching with acid, and added to the 3Y-TZP matrix, at a proportion of 5 vol%. The final powders were dried under airflow, compacted, and sintered in the temperature range of 1300-1500 degrees C. The effects of the sintering technique and final temperature, on the microstructure and mechanical properties, such as hardness, toughness, and Young's modulus, were analysed. Fracture toughness of the material reinforced with Al2O3-NbC nanopowders, which is one of its most important properties, differed significantly from that of the 3Y-TZP monolith (5.2 MPa m(1/2)). The nanocomposites, sintered conventionally at 1450 degrees C, showed higher fracture toughness (8.7 MPa m(1/2)). Microstructure observations indicated that NbC nanoparticles were dispersed homogeneously within the 3Y-TZP matrix, and limited its grain growth. However, partial oxidation of the NbC on the nanocomposite surface, at the conventional sintering temperature of 1500 degrees C, caused a reduction in the fracture toughness.

[EN] Thermal barrier coatings have been extensively studied in the last years in order to increase the operational temperature of the current gas turbines as well as to improve the coating lifetime. Many coating characteristics must be met to achieve these requirements (low thermal conductivity, high thermal fatigue resistance...); therefore, complex systems have been engineered for these purposes. One of the possibilities to optimise the different properties deals with the design of multilayer or functionally-graded coatings where various types of microstructures with different characteristics are combined. One of the most important cause of gas turbines degradation relates to the attack of different type of particles which are suspended in the atmosphere (sand, fly ash...). These solid particles are molten at the operational temperatures and then, the molten salts chemically react with the coating. For this reason, the present research was focused on this type of attack. In the present work, the molten salt attack of various YSZ coatings with multilayer and functionally-graded design was addressed. Two different type of microstructures were specifically combined for this design: the APS coating microstructure obtained from conventional (microstructured) powder and a bimodal structure with nanozones obtained from nanostructured feedstock. Besides, different salts were used to simulate different attack environments (desert sand and volcanic fly ash). Findings show that nanozones act as barrier against the penetration of molten salts toward deeper layer. However, a layer formed by nanozones can detach when the salt attack is too aggressive. Hence, functionally-graded coatings, where two types of microstructures are combined through the whole coating, become ideal to diminish the molten salt attack.

For the first time, ZrO2 dielectric deposition on pristine monolayer MoS2 by atomic layer deposition (ALD) is demonstrated and ZrO2/MoS2 top-gate MOSFETs have been fabricated. ALD ZrO2 overcoat, like other high-k oxides such as HfO2 and Al2O3, was shown to enhance the MoS2 channel mobility. As a result, an on/off current ratio of over 10(7), a subthreshold slope of 276 mV dec(-1), and a field-effect electron mobility of 12.1 cm(2) V-1 s(-1) have been achieved. The maximum drain current of the MOSFET with a top-gate length of 4 mu m and a source/drain spacing of 9 mu m is measured to be 1.4 mu A mu m(-1) at V-DS = 5 V. The gate leakage current is below 10(-2) A cm(-2) under a gate bias of 10 V. A high dielectric breakdown field of 4.9 MV cm(-1) is obtained. Gate hysteresis and frequency-dependent capacitance-voltage measurements were also performed to characterize the ZrO2/MoS2 interface quality, which yielded an interface state density of similar to 3 x 10(12) cm(-2) eV(-1).

[EN] Thermal barrier coatings have been extensively studied in the last years in order to increase the operational temperature of the current gas turbines as well as to improve the coating lifetime. Many coating characteristics must be met to achieve these requirements (low thermal conductivity, high thermal fatigue resistance...); therefore, complex systems have been engineered for these purposes. One of the possibilities to optimise the different properties deals with the design of multilayer or functionally-graded coatings where various types of microstructures with different characteristics are combined. One of the most important cause of gas turbines degradation relates to the attack of different type of particles which are suspended in the atmosphere (sand, fly ash...). These solid particles are molten at the operational temperatures and then, the molten salts chemically react with the coating. For this reason, the present research was focused on this type of attack. In the present work, the molten salt attack of various YSZ coatings with multilayer and functionally-graded design was addressed. Two different type of microstructures were specifically combined for this design: the APS coating microstructure obtained from conventional (microstructured) powder and a bimodal structure with nanozones obtained from nanostructured feedstock. Besides, different salts were used to simulate different attack environments (desert sand and volcanic fly ash). Findings show that nanozones act as barrier against the penetration of molten salts toward deeper layer. However, a layer formed by nanozones can detach when the salt attack is too aggressive. Hence, functionally-graded coatings, where two types of microstructures are combined through the whole coating, become ideal to diminish the molten salt attack.