Preparation of high surface area ZrO2 and ZrO2-Y2O3 from the alkoxide

In order to obtain a catalyst support with a high surface area, ZrO₂ and ZrO₂-Y₂O₃ were prepared by the hydrolytic decomposition of the corresponding isopropoxide dissolved in benzene. The hydrolysis was carried out at 80°C using an excess amount of distilled water in flowing dry nitrogen. The precipitates thus obtained were dried at 100°C followed by calcination at 500°C in air or nitrogen for 1 h. The specific surface areas for both of the ZrO₂ and ZrO₂-Y₂O₃ increased with increasing amount of water added for hydrolysis, and the surface areas for ZrO₂-Y₂O₃ increased with increasing yttrium content. A ZrO₂ having a surface area of 130 m²/g was produced, and a stabilized tetragonal ZrO₂ with 15 mol% Y³⁺ having a surface area of 200 m²/g was produced. Furthermore, despite the difference in the ZrO₂ and ZrO₂-Y₂O₃ crystal structures, the lattice-strain of ZrO₂ has been unequivocally related to the surface area.     

Reactivity of nanoparticles; interaction between zinc and copper oxide nanoparticles and iron ions in an alkaline medium

The reactivity of zinc and copper oxide nanoparticles was investigated upon their interaction with iron oxides. It was ascertained that, depending on the reaction conditions, nanoparticles of zinc and copper ferrites (ZnFe₂O₄ and CuFe₂O₄) or core/shell nanoparticles (Fe₃O₄/ZnO) are produced. Size, composition, and structure of the resulting nanoparticles were determined by transmission electron microscopy and X-ray diffraction analysis. The average size of zinc and copper ferrite nanoparticles was ascertained to be 9–10 and 2–3 nm, respectively. For core/shell Fe₃O₄/ZnO nanoparticles, the average size is 20 nm. It was experimentally proved that the photoluminescence radiative characteristics of ZnO nanoparticles are retained in core/shell Fe₃O₄/ZnO nanoparticles.     

Characterization and application of Fe3O4/SiO2 nanocomposites

A sol-gel procedure was used to cover Fe₃O₄ nanoparticles with SiO₂ shell, forming a core/shell structure. The core/shell nanocomposites were synthesized by a two-step process. First, Fe₃O₄ nanoparticles were obtained through co-precipitation and dispersed in aqueous solution through electrostatic interactions in the presence of tetramethylammonium hydroxide (TMAOH). In the second step, Fe₃O₄ was capped with SiO₂ generated from the hydrolyzation of tetraethyl orthosilicate (TEOS). The structure and properties of the formed Fe₃O₄/SiO₂ nanocomposites were characterized and the results indicate that the Fe₃O₄/SiO₂ nanocomposites are superparamagnetic and are about 30 nm in size. Bioconjugation to IgG was also studied. Finally, the mechanism of depositing SiO₂ on magnetic nanoparticles was discussed.     

Effective synthesis of novel O-acetylated compounds over ZrO2-Al2O3 solid acid

The solid acids such as ZrO₂, Al₂O₃ and ZrO₂-Al₂O₃ containing different ZrO₂ loadings (10–80 mol%) were prepared by solution combustion method (SCM) and characterized for their total surface acidity by NH₃-TPD/n-butylamine back titration method and crystallinity by powder X-ray diffraction (PXRD) technique. These solid acids were evaluated for their catalytic activity in the synthesis of novel O-acetylated products from substituted phenols, pyridine alcohols and aryl alcohols with acetic anhydride (AA) as an acetylating agent. The reaction conditions were optimized by varying the catalyst, molar ratio of the reactants, reaction temperature and amount of the catalyst. All the solid acids used in this study exhibited good catalytic activity in the reaction. In particular, ZrO₂-Al₂O₃ containing 80 mol% of ZrO₂ was found to be highly active in the acetylation reaction with high yield of acetylated products. Triangular correlation between the surface acidity, crystallinity and catalytic activity of solid acids was observed. These solid acids were found to be reactivable and reusable.     

Au@Y2O3:Eu3+ rare earth oxide hollow sub-microspheres with encapsulated gold nanoparticles and their optical properties

A facile method to synthesize novel Au@Y₂O₃:Eu³⁺ hollow sub-microspheres encapsulated with moveable gold nanoparticle core and Y₂O₃:Eu³⁺ as shell via two-step coating processes and a succeeding calcination process has been developed. Silica coating on citrate-stabilized gold nanoparticles with a size of 25 nm can be obtained through a slightly modified Stöber process. Gold particles coated with double shell silica and Eu doped Y(OH)₃ can be obtained by coating on the Au@SiO₂ spheres through simply adding Y(NO₃)₃, Eu(NO₃)₃ and an appropriate quantity of NH₃·H₂O. Au@Y₂O₃:Eu³⁺ hollow sub-microspheres with moveable individual Au nanoparticle as core can be obtained after calcination of Au@Y₂O₃:Eu³⁺ particles at 600 °C for 2 h. These new core–shell structures with encapsulated gold nanoparticles have combined optical properties of both the Au nanoparticles and the Y₂O₃:Eu³⁺ phosphor materials which might have potential applications.     

Electrophoretic deposition of Al2O3/ZrO2 layer with controllable thickness in ethanol medium

ZrO₂ toughened Al₂O₃ (Al₂O₃/ZrO₂) ceramic layers with required thickness were prepared by electrophoretic deposition (EPD) method using ethanol suspensions with stabilizing agent of polyethyleneimine (PEI) under constant-voltage mode in this paper. The deposition of Al₂O₃/ZrO₂ ceramic powders occurred on the titanium alloy cathode. A stable suspension with 1wt% PEI in ethanol at pH 5 was prepared in terms of the zeta potential and sedimentation of the suspension. The effects of the suspension concentration, applied voltage, deposition time and processing method of titanium alloy cathode on the coating thickness and morphology were investigated. The deposition layers on titanium alloys with smooth surfaces and thickness of 0.35?C1.2 mm could be obtained by adjusting the aforementioned parameters. In addition, after being sintered at 1500°C for 3 h in air atmosphere, ZrO₂ toughened Al₂O₃ ceramic layers became smooth and dense.     

Nanostructured ZrO2-Coated TiO2 Electrodes for Dye-Sensitised Solar Cells

Thin films of ZrO₂ were deposited on nanostructured anatase TiO₂ electrodes via sol-gel route and utilised in the assembly of a dye-sensitised solar cells (DSSCs) forming nanostructured core-shell networks. The ZrO₂-coated TiO₂ electrodes were characterised by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and constructing a DSSC. The characterisation concluded that core-shell morphologies were produced with varying ZrO₂ shell thickness without altering the anatase TiO₂ core. When a DSSC was constructed from the ZrO₂:TiO₂ core-shell electrode, the efficiency increased to 2.27% from 0.42% for the uncoated TiO₂ electrode. As the ZrO₂ shell thickness increased, the cell efficiency was reduced.     

Magnetic poly(glycidyl methacrylate) particles prepared in the presence of surface‐modified γ‐Fe2O3

Maghemite (γ‐Fe₂O₃) colloid has been synthesized by coprecipitation of ferrous and ferric salts in alkaline medium and oxidation. The obtained nanoparticles were complexed with a phosphate macromonomer—penta(propylene glycol) methacrylate phosphate (PPGMAP). Complexes with the weight ratio PPGMAP/γ‐Fe₂O₃ 0.01–10 were investigated using a range of characterization methods. The amount of PPGMAP attached to the particles was about 22 wt %. The size and size distribution of the γ‐Fe₂O₃ core particles in the dry state was measured by TEM. To complete the TEM images, the hydrodynamic size of the nanoparticles including polymer shell and the maghemite core was determined by DLS measurements in toluene. Magnetic poly(glycidyl methacrylate) (PGMA) nanospheres were obtained by Kraton G 1650‐stabilized and 2,2′‐azobisisobutyronitrile‐initiated polymerization of glycidyl methacrylate (GMA) in toluene or toluene/cyclohexane mixture in the presence of PPGMAP‐coated γ‐Fe₂O₃ colloid. The effect of Kraton G 1650 concentration on the morphology, PGMA nanosphere size and polydispersity was investigated. The particles were characterized also by both thermogravimetric analysis and magnetic measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4982–4994, 2009     

Synthesis of solid solutions of double-layered Ruddlesden-Popper phases in the Gd2O3-SrO-Fe2O3-Al2O3 system

The continuous Gd₂Sr(Al_{1 ? x} Fe _x )₂O₇ solid solution series was synthesized by a solid-state route over the entire concentration range (0 < x < 1). The processing stages of Gd₂Sr(Al_{1 ? x} Fe _x )₂O₇ series were investigated, and phase interaction schemes reflecting the multistaged formation of double-layered Ruddlesden-Popper solid solution are constructed. The closeness of the reactive mixture composition to the composition of individual compounds Gd₂SrAl₂O₇ or Gd₂SrFe₂O₇ is of importance for the realization of a particular way of Gd₂Sr(Al_{1 ? x} Fe _x )₂O₇ solid solutions formation.     

Substrate temperature influenced ZrO2 films for MOS devices

The effect of substrate temperature on the direct current magnetron-sputtered zirconium oxide (ZrO₂) dielectric films was investigated. Stoichiometric of the ZrO₂ thin films was obtained at an oxygen partial pressure of 4.0 × 10⁻² Pa. X-ray diffraction studies revealed that the crystallite size in the layer was increased from 4.8 to 16.1 nm with increase of substrate temperature from 303 to 673 K. Metal-oxide-semiconductor devices were fabricated on ZrO₂/Si stacks with Al gate electrode. The dielectric properties of ZrO₂ layer and interface quality at ZrO₂/Si were significantly influenced by the substrate temperature. The dielectric constant increased from 15 to 25, and the leakage current density decreased from 0.12 × 10⁻⁷ to 0.64 × 10⁻⁹ A cm⁻² with the increase of substrate temperature from 303 to 673 K.     

PVP-Assisted ZrO2 coating on LiMn2O4 spinel cathode nanoparticles prepared by MnO2 nanowire templates

LiMn₂O₄ spinel nanorods prepared from nanowire MnO₂ templates were capped with polyvinyl pyrrolidone (PVP) and coated with ZrC₂O₄ precursors in aqueous solution. Upon annealing at 600 °C in air, an amorphous ZrO₂ nanoscale coating layer was obtained on the spinel nanoparticles with a particle size of <100 nm that formed from the splitting of the original spinel nanorods. The electrochemical cycling results clearly showed that nanoscale ZrO₂ coating significantly improved the rate capability and cycle life at 65 °C in spite of very high surface area of the spinel nanoparticles.     

ZrO2- and Li2ZrO3-stabilized spinel and layered electrodes for lithium batteries

Strategies for countering the solubility of LiMn₂O₄ (spinel) electrodes at 50 °C and for suppressing the reactivity of layered LiMO₂ (M=Co, Ni, Mn, Li) electrodes at high potentials are discussed. Surface treatment of LiMn₂O₄ with colloidal zirconia (ZrO₂) dramatically improves the cycling stability of the spinel electrode at 50 °C in Li/LiMn₂O₄ cells. ZrO₂-coated LiMn_0.5Ni_0.5O₂ electrodes provide a superior capacity and cycling stability to uncoated electrodes when charged to a high potential (4.6 V vs Li⁰). The use of Li₂ZrO₃, which is structurally more compatible with spinel and layered electrodes than ZrO₂ and which can act as a Li⁺-ion conductor, has been evaluated in composite 0.03Li₂ZrO₃ · 0.97LiMn_0.5Ni_0.5O₂ electrodes; glassy Li_xZrO_2 + x/2 (0<x⩽2) products can be produced from colloidal ZrO₂ for surface coatings.     

Hydrothermal synthesis and characterization of nanocrystalline ZrO2 and surface modification with 2-acetoacetoxyethyl methacrylate

For the utilization as inorganic/organic hybrid nanomaterials for optical purposes, nanocrytalline tetragonal ZrO₂ was synthesized by hydrothermal method using zirconium(IV)-n-propoxide as precursor material. Surface of the ZrO₂ particles was then modified with 2-acetoacetoxyethyl methacrylate used as a copolymer for coatings. X-ray diffraction analysis revealed that both ZrO₂ and modified ZrO₂ are in tetragonal crystalline phase. As proved by transmission electron microscope and particle size analysis, average particle sizes of ZrO₂ and modified ZrO₂ were found as 6.22 and 14.7 nm, respectively. ZrO₂ powder was easily dispersed either in water or n-hexane. Ultraviolet diffuse reflectance spectrophotometer analysis for ZrO₂ and surface modified ZrO₂ showed that maximum absorption peaks are at 215 and 225 nm, respectively.     

A template-free solvothermal synthesis and photoluminescence properties of multicolor Gd2O2S:xTb3+, yEu3+ hollow spheres

The multicolor Gd₂O₂S:xTb³⁺, yEu³⁺ hollow spheres were successfully synthesized via a template-free solvothermal route without the use of surfactant from commercially available Ln (NO₃)₃·6H₂O (Ln = Gd, Tb and Eu), absolute ethanol, ethanediamine and sublimed sulfur as the starting materials. The phase, structure, particle morphology and photoluminescence (PL) properties of the as-obtained products were investigated by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) and photoluminescence spectra. The influence of synthetic time on phase, structure and morphology was systematically investigated and discussed. The possible formation mechanism depending on synthetic time t for the Gd₂O₂S phase has been presented. These results demonstrate that the Gd₂O₂S hollow spheres could be obtained under optimal condition, namely solvothermal temperature T = 220 °C and synthetic time t = 16 h. The as-obtained Gd₂O₂S sample possesses hollow sphere structure, which has a typical size of about 2.5 μm in diameter and about 0.5 μm in shell thickness. PL spectroscopy reveals that the strongest emission peak for the Gd₂O₂S:xTb³⁺ and the Gd₂O₂S:yEu³⁺ samples is located at 545 nm and 628 nm, corresponding to ⁵D₄→⁷F₅ transitions of Tb³⁺ ions and ⁵D₀→⁷F₂ transitions of Eu³⁺ ions, respectively. The quenching concentration of Tb³⁺ ions and Eu³⁺ ions is 7%. In the case of Tb³⁺ and Eu³⁺ co-doped samples, when the concentration of Tb³⁺ or Eu³⁺ ions is 7%, the optimum concentration of Eu³⁺ or Tb³⁺ ions is determined to be 1%. Under 254 nm ultraviolet (UV) light excitation, the Gd₂O₂S:7%Tb³⁺, the Gd₂O₂S:7%Tb³⁺,1%Eu³⁺ and the Gd₂O₂S:7%Eu³⁺ samples give green, yellow and red light emissions, respectively. And the corresponding CIE coordinates vary from (0.3513, 0.5615), (0.4120, 0.4588) to (0.5868, 0.3023), which is also well consistent with their luminous photographs.     

Synthesis and optical properties of Gd2O3:Pr3+ phosphor particles

Spherical-shaped Gd₂O₃:Pr³⁺ phosphor particles were prepared with different concentrations of Pr³⁺ using the urea homogeneous precipitation method. The resulting Gd₂O₃:Pr³⁺ phosphor particles were characterized by X-ray diffraction, field emission scanning electron microscope, and photoluminescence spectroscopy. The effects of the Pr³⁺ doping concentration on the luminescent properties of Gd₂O₃:Pr³⁺ phosphors were investigated. Photoluminescence measurements revealed the Gd₂O₃:1?% Pr³⁺ phosphor particles to have the strongest emission. The luminescence properties of Gd₂O₃:Pr³⁺ particles are strongly affected by the phosphor crystallinity and X-ray diffraction measurements confirmed that the crystallinity of Gd₂O₃ cubic structure could be enhanced by increasing the firing temperature. The luminescent Gd₂O₃:Pr³⁺ phosphor particles have potential applications in areas, such as optical display systems, lamps and etc.     

Sol-Gel Synthesis and Characterization of SiO2—P2O5—ZrO2

Zirconia phosphosilicates were prepared by the sol-gel method using tetraethylorthosilicate, triethyl phosphate, and zirconium n-propoxide. Monolithic, transparent gels were formed with 10 mole% ZrO₂, and 10, 20 or 30 mole% P₂O₅. The influence of the mole% P₂O₅, treatment temperature and water content, on thermal behavior, water adsorption, and proton conductivity were studied. A heat treatment at 200°C was effective in removal of residual organics, creating a porous material capable of good water retention upon rehydration.     

Influence of ZrO2 on Carbon Monoxide Oxidation Over Pd/Al2O3

The influence of ZrO₂ on the properties of Al₂O₃ and performances of Pd/Al₂O₃ catalyst in CO oxidation have been investigated. TPD results show that the activity enhanced is due to the increase of the adsorptive capacity of CO and the activation of C=O bond after the introduction of ZrO₂.     

Gd2O3:Eu@mSiO2核壳双功能纳米棒的制备及性质

通过水热法和正硅酸乙酯水解法制备了一种新颖的Gd2O3:Eu@mSiO2核壳双功能(荧光和介孔)纳米棒。用扫描电镜(SEM)、透射电镜(TEM)、X射线粉末衍射(XRD)、红外光谱(FTIR)等多种测试手段对样品的形貌、物相结构进行分析表征。结果表明,该核壳结构纳米材料以Gd2O3:Eu纳米棒(长~400 nm,直径~100 nm)为核,介孔SiO2为壳,尺寸均匀,分散性良好。荧光光谱表明,在紫外光激发下,核壳纳米棒发射强烈的橙红色荧光。同时该核壳纳米棒能成功标记NCI-H460肺癌细胞。以布洛芬(IBU)为药物模型研究核壳纳米棒的药物负载和释放行为,结果表明,Gd2O3:Eu@mSiO2核壳纳米棒对IBU的负载量可达10.25%,而且其具有明显的缓释效果。IBU负载的样品(IBU-Gd2O3:Eu3+@mSiO2)在紫外光照射下仍呈现Eu3+的橙红色发光,且Eu3+在载药系统中的发光强度随IBU释放量的变化而变化,因此通过发光强度的变化可以跟踪和监测药物及其释放情况。     

Oxidation of carbon monoxide in the presence of hydrogen on the CuO, CoO, and Fe2O3 oxides supported on ZrO2

The catalytic activity of the CuO/ZrO₂, CoO/ZrO₂, Fe₂O₃/ZrO₂, and CuO/(CoO, Fe₂O₃)/ZrO₂ systems in the reaction of selective CO oxidation in the presence of hydrogen was studied at 20–450°C over the oxide concentration range of 2.5–10 wt % on the surface of ZrO₂. The conversion of CO on the CoO/ZrO₂ systems was almost independent of the concentration of CoO: 88 or 90% for 2.5 or 10% CoO, respectively. TPR data allowed us to relate the catalytic activity of CoO/ZrO₂ to Co-O-Zr clusters, the amount of which was almost constant over the test range of CoO concentrations. The conversion of CO on 2.5% CuO/ZrO₂ was 32% (190°C) or 62–66% on 5–10% CuO/ZrO₂ (170°C). According to TPR data, clusters like Cu-O-Zr occurred on the surface of ZrO₂, and the amount of these clusters reached a maximum upon supporting 5% CuO. The catalytic properties of 5% CuO/5% CoO/ZrO₂ and 5% CoO/5% CuO/ZrO₂ samples were identical to those of 5% CuO/ZrO₂ samples. It is likely that the formation of active reaction sites upon consecutively supporting the oxides occurred on the same surface sites of ZrO₂. In this case, Co and Cu oxides competed for cluster formation, and the copper cation can displace the cobalt cation from the formed clusters. The Fe₂O₃ samples were inactive; a maximum conversion of 34% (290°C) was observed on 10% Fe₂O₃/ZrO₂. The catalytic properties of CuO/Fe₂O₃/ZrO₂ were also identical to those of CuO/ZrO₂, and they depended on the presence of Cu-O-Zr clusters on the surface.     

New strategies for trace analyses of ZrO2, SiC and Al2O3 ceramic powders

The progress possible in the analysis of refractory powders such as ZrO₂, SiC and Al₂O₃ by the use of new sample preparation, processing and introduction techniques elaborated for AAS, ICP-OES and ICP-MS with low and high mass resolution is demonstrated. For optimized sample preparation techniques based on dissolution of ZrO₂, e.g. fusion with (NH₄)₂SO₄, it is shown to what extent impurities present in (NH₄)₂SO₄ determine the detection limit. Hydraulic high pressure nebulization with and without matrix removal by complexing the impurities with dithiocarbamates (Cu, Co, Cr and Ni) or oxine (Fe, Mn and Mo) and fixing them on a C₁₈ solid phase for subsequent solid phase extraction coupled with flame atomic absorption was used to determine Fe, Cu, Cr, Mn, Ni, Co and Mo impurities in (NH₄)₂SO₄ in the 10–100 ng/g range. Further a method to synthesize (NH₄)₂SO₄ with higher purity than some commercially available high-purity (NH₄)₂SO₄ with respect to Fe, Cu, Cr and Mn using high-purity NH₃ and chlorosulphonic acid is shown. Reliable determinations of Fe and Al at the 100 μg/g level in ZrO₂ with ICP-OES with matrix removal as well as with ICP-MS without matrix removal are reported. For the direct analysis of Al₂O₃ powders, slurry nebulization ICP-MS sample introduction is shown to improve detection limits and to reduce sample preparation, if the leachable and non-leachable fractions are analyzed separately. For powders such as SiC, the matrix or solvents can cause spectral interferences. Matrix removal is shown to be useful to improve detection limits for the interfered elements. High resolution ICP-MS can be used to control the completeness of matrix removal techniques and to overcome limitations due to spectral interferences even in case of complex materials.