Synthesis and morphological control of rare earth oxide nanoparticles by solvothermal reaction

Eu doped Y₂O₃ and some kinds of other rare earth oxides nanoparticles such as Er₂O₃, Nd₂O₃, Ho₂O₃, Lu₂O₃, and Dy₂O₃ were prepared by a simple co-precipitation-solvothermal treatment-calcination process, where the co-precipitated amorphous hydroxide precursors obtained by adding rare earth nitrate solutions in ammonia solutions were heated in solvents such as water, alcohols and glycols, followed by calcination in air. The morphology of rare earth oxide particles strongly depended on the solvothermal reaction medium but not related to the kind of rare earth oxide. The powders prepared in water and ethanol possessed nanowire structure, where the aspect ratio of powder treated in water was higher than that in ethanol. The powders prepared by co-precipition-solvothermal treatment-calcination process using ethylene glycol consisted of near-spherical nanoparticles whereas that prepared by conventional co-precipitation-calcination method consisted of hardly agglomerated submicron particles. The nanoparticles of Eu³⁺ doped Y₂O₃ prepared by co-precipition-solvothermal treatment-calcination process showed similar intensity of photoluminescence with the submicron particles by co-precipition-calcination process.     

Dispersion stability of nano-Sb2O3 particles modified with polyethylene glycol

The surface of nano-Sb₂O₃ particles was modified with polyethylene glycol (PEG) using the mechanochemical method, and the dispersion mechanism of modified nano-Sb₂O₃ particles was also discussed. The modified nano-Sb₂O₃ particles were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermal analysis (TGA) and UV absorbance. The results showed that the surface of nano-Sb₂O₃ particles was successfully coated by PEG molecules through the effect of hydrogen bonding, and the dispersion of nano-Sb₂O₃ particles in ethyl alcohol (C₂H₅OH) was significantly improved. Due to the different adsorption conformations of PEG molecules, the dispersion stability of nano-Sb₂O₃ particles was gradually improved with the increase of PEG average molecular weight and concentration. However, the superfluous PEG molecules would weaken the dispersion stability of nano-Sb₂O₃ particles.     

Yb3+ concentration dependence of upconversion luminescence in Y2Sn2O7:Yb3+/Er3+ nanophosphors

Pyrochlore Y₂Sn₂O₇ nanophosphors codoped with Er³⁺ (fixed 2 at.%) and Yb³⁺ ions (2–16 at.%) were synthesized via hydrothermal process followed by heat treatment. We investigate the infrared-to-visible upconversion (UC) luminescence properties of Er–Yb codoped Y₂Sn₂O₇. Upon 980 nm excitation at room temperature, green (at ~522 and 544 nm) and red (at ~661 nm) UC emissions were observed, which are ascribed to the (²H_11/2, ⁴S_3/2) → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions, respectively. It has been found that the Yb³⁺-doping concentrations have greatly influenced on the UC luminescence intensity and the emission ratio of the red and green in Y₂Sn₂O₇:Yb³⁺/Er³⁺ nanophosphors. The tunable emission is due to the energy back transfer from Er³⁺ to Yb³⁺ and the cross relaxation between the two neighboring Er³⁺ ions. It is expected that the achieved single and intense red emission band may have potential application for in vivo bioimaging.     

Synthesis and characterization of pyrochlore-type yttrium titanate nanoparticles by modified sol–gel method

Pyrochlore-type yttrium titanate (Y₂Ti₂O₇) nanoparticles were successfully synthesized by a simple soft-chemistry technique viz. citric acid sol–gel method (CAM). The preparation process was monitored by X-ray diffraction, thermogravimetric–differential thermal analysis and Fourier transform–infrared experiments and the microstructures and average size of as-prepared products were characterized by transmission electron microscopy and high resolution transmission electron microscopy images. It was found that compared with traditional solid state reaction (SSR), Y₂Ti₂O₇ nanopowders were synthesized at a relatively low temperature (750°C) for shortened reaction time. Detailed analysis showed that the as-prepared Y₂Ti₂O₇ with good dispersibility and narrow size distribution were quasi-spherical; the average size was about 20–30 nm, also, the obtained products had higher BET surface area (50 m²/g). These properties are very helpful for a photocatalyst to achieve excellent activity and may result in better behaviour in hydrogen storage.     

Improvement in fatigue strength while keeping low Young's modulus of a β-type titanium alloy through yttrium oxide dispersion

Improvement in fatigue strength in spite of maintaining low Young's modulus was achieved in Ti-29Nb-13Ta-4.6Zr (TNTZ) by hard-particles dispersion. A certain amount of Y₂O₃ additions was added into TNTZ. TNTZ with 0.05-1.00mass%Y consists of a β-phase with a small amount of Y₂O₃. Young's moduli of TNTZ with 0.05-1.00mass%Y are maintained low, and are almost similar to that of TNTZ without Y₂O₃. The tensile strength of TNTZ with 0.05-1.00mass%Y is slightly improved and the elongation does not deteriorate by Y₂O₃ additions. However, the 0.2% proof stress decreases with the increase in Y concentration. Although tensile properties are not changed drastically, the fatigue strength is significantly improved by Y₂O₃ additions. The dispersion of Y₂O₃ particle increases the resistance to fatigue initiation. However, Y₂O₃ with too large diameter at the surface of the specimen works harmfully as the fatigue initiation site. The Y₂O₃ diameter and volume fraction increase with the increase in Y concentration. As a result, the fatigue limit of the alloys with 0.05-1.00mass%Y firstly increases and then decreases with the increase in Y concentration. TNTZ with 0.1mass% Y exhibits the best combination of higher fatigue strength and low Young's modulus.     

Magnetic and luminescent properties of Fe3O4@Y2O3:Eu3+ nanocomposites

The multifunctional Fe₃O₄@Y₂O₃:Eu³⁺ nanocomposites were prepared by a facile solvothermal method with Fe₃O₄ nanoparticles as the core and europium-doped yttrium oxide (Y₂O₃:Eu³⁺) as the shell. It is shown that Fe₃O₄@Y₂O₃:Eu³⁺ nanocomposites have a strong photoluminescence and special saturation magnetization Ms of 6.1 emu/g at room temperature. The effects of the magnetic field on the luminescence intensities of the nanocomposites are being discussed. The multifunctional nanocomposites with magnetic resonance response and fluorescence probe properties may be useful in biomedical applications, such as cell separation and bioimaging.     

Preparation of Y2O3 stabilised ZrO2 ceramic nanopowders by surface doping

Abstract

Weakly agglomerated nanocrystalline Y₂O₃–ZrO₂ powder was prepared by dispersion Y₂O₃ on the surface of ZrO₂ nanopowder (7·3 nm) that was derived from gas phase synthesis. The utmost dispersion capacity of Y₂O₃ on the surface of ZrO₂ was determined to be 0·16 gY₂O₃ /gZrO₂ (or 8·7 mol.-%Y₂O₃–ZrO₂ ) which suggests that 3 mol.-%Y₂O₃ would be homogeneously dispersed on ZrO₂ and no phase segregation would occur during surface doping. The results show that the tetragonal phase content in surface doped ZrO₂ increased with grain growth or heating temperatures, unlike the undoped and the bulk doped ZrO₂ . The stabilisation of the tetragonal phase resulted from the incorporation of Y ³⁺ cations from the surface into the grains of ZrO₂ . This conclusion is supported by the X-ray photoelectron spectroscopy and X-ray diffraction evidence. Surface doped powders have a strong tendency to improve the anticoarsening ability and suppress grain growth, especially at higher doping levels and at lower heating temperatures.     

Y2O3/(Cu–Me) systems (Me=Al, Ti): interface reactions and wetting

Wetting behavior and interface interaction between Y₂O₃ and Cu–alloys were investigated at 1,423 K. Pure copper does not wet yttria substrate but the wettability is significantly improved by additions of Al and Ti. Different interface structures were observed in the Y₂O₃/(Cu–Al) and Y₂O₃/(Cu–Ti) systems. Relatively deep crater was detected at the interface in the first system, while Cu alloying by Ti led to formation of a flat interface with a thin reaction layer. The results of the wetting experiments and the interface features were well accounted of by thermodynamic analysis of the Y₂O₃/(Cu–Me) systems.     

Study on microstructure and properties of Ni-based alloy/Y2O3-deposited metals by laser cladding

Laser cladding of Ni-based alloy/Y₂O₃ (Yttrium Oxide) powder on 6061 aluminum alloy was carried out using 3 kW CW Nd:YAG laser to strengthen and improve hardness and corrosion resistance of substrate. Metal matrix composite composed of aluminum substrate, Ni-based alloy, refining and dispersion strengthening Y₂O₃, and particle hardening W, Cr was obtained. The microstructure and morphology, phase identification, element diffusion, and composition analysis of the Ni-based alloy/Y₂O₃-deposited metal and deposited metals/6061 aluminum substrate interface were examined using scanning electron microscopy (SEM), Electron Probe Micro-analyzer (EPMA) with energy-dispersive spectrometer (EDS) analysis. The micro-hardness distribution and corrosion-resistance property were investigated also. The results showed: (1) with the addition of Y₂O₃, more fine microstructures consisted of isometric crystal, white acicular crystal, and fringe crystal, primary phases were mainly Ni₃Al, NiAl, NiAl₃, W, α-Al, and Cr _x C. (2) Micro-hardness of deposited metals was 780–1100 HV_0.2 and distributed smoothly near interface. The corrosion rate of aluminum substrate was nearly twice that of deposited metals with addition of Y₂O₃.     

Effect of surface modification of Fe3O4 nanoparticles on thermal and mechanical properties of magnetic polyurethane elastomer nanocomposites

Magnetic polyurethane elastomer nanocomposites were prepared by incorporating pure and thiodiglycolic acid (TDGA) surface-modified Fe₃O₄ nanoparticles into polyurethane matrix using in situ polymerization method. Surface modification of Fe₃O₄ nanoparticles was carried out to enhance the dispersion of the nanoparticles in polyurethane matrix. Pure and TDGA surface-modified Fe₃O₄ nanoparticles were synthesized by coprecipitation method and characterized by Fourier Transform Infrared Spectroscopy, X-ray diffraction, and Vibrating Sample Magnetometer. The morphology and dispersion of the nanoparticles in the magnetic polyurethane elastomer nanocomposites were studied by Scanning Electron Microscope. It was observed that surface modification of Fe₃O₄ nanoparticles with TDGA enhanced the dispersion of the nanoparticles in polyurethane matrices. Furthermore, effect of surface modification of Fe₃O₄ nanoparticles on thermal and mechanical properties of magnetic polyurethane elastomer nanocomposite was investigated by thermogravimetric analysis, dynamic mechanical thermal analysis, and an Instron type Tensile Tester. It was concluded that surface modification of Fe₃O₄ nanoparticles allowed preparation of the magnetic nanocomposites with better mechanical properties. Moreover, study of fibroblast cells interaction with magnetic nanocomposites showed that the products can be a good candidate for biomedical application due to their in vitro biocompatibility and non-toxicity.     

Upconversion and infrared luminescences in Er/Yb codoped Y2O3 and (Y0.9La0.1)2O3 transparent ceramics

Er³⁺ and Yb³⁺ codoped Y₂O₃ and (Y_0.9La_0.1)₂O₃ transparent ceramics were fabricated by the conventional ceramics processing with nanopowders. Compared to Er/Yb:Y₂O₃, Er/Yb:(Y_0.9La_0.1)₂O₃ ceramics had higher transmittance. Intense upconversion (UC) and infrared emission (1543 nm) were observed under excitation of 980 nm. According to three intensity parameters Ω₂, Ω₄, and Ω₆ fitted by the Judd-Ofelt theory, the spectroscopic quality parameters (X), radiative lifetimes (τ_rad), and emission cross-sections (α_em) were determined. Er/Yb:(Y_0.9La_0.1)₂O₃ ceramics owned broader peaks and longer lifetime (12.3 ms) at 1548 nm due to the glass-like structure of (Y_0.9La_0.1)₂O₃ ceramics. The results showed Y₂O₃ and Y_1.8La_0.2O₃ transparent ceramics are promising gain media for developing the solid-state 1.5 μm optical amplifiers and tunable UC lasers.     

Ionic liquid mediated green synthesis of Ag-Au/Y2O3 nanoparticles using leaves extracts of Justicia adhatoda: Structural characterization and its biological applications

In the present work, a facile synthesis was applied for the silver-gold decorated yttrium oxide nanoparticles with the use of Justicia adhatoda (leaves extract) and [BMIM] PF₆ (Ionic liquid) as a capping/stabilizing agent. The XRD analysis showed that Ag-Au/Y₂O₃ nanoparticles have a face-center cubic structure and crystallite size of 30 nm. The Y-O stretching bands were observed in the FT-IR spectrum at 464 to 495 cm^?1. The band gap of the silver-gold decorated Y₂O₃ nanoparticles was estimated as 5.75 eV from the UV-DRS spectrum. In the SEM and TEM images, the morphology of silver-gold/Y₂O₃ nanoparticles shows a nanoflake-like structure. The presence of silver, gold, yttrium and oxygen of elements has been confirmed by the EDX spectrum. The antibacterial activity of the nanoparticles was evaluated for the Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) bacteria. The anticancer activity was also studied by the human cervical cancer cell line. The silver-gold decorated yttrium oxide nanoparticles revealed an exceptional microbicidal and antitumor activity when compared with yttrium oxide, silver decorated yttrium oxide and gold decorated yttrium oxide.     

A biocompatible approach to surface modification: Biodegradable polymer functionalized super-paramagnetic iron oxide nanoparticles

In the study, Fe₃O₄ nanoparticles with a size range of 10–20 nm were firstly prepared by the modified controlled chemical coprecipitation method from the solution of ferrous/ferric mixed salt-solution in alkaline medium. Then, the super-paramagnetic iron oxide nanoparticles were covalently modified by biodegradable polymers such as polyethylene glycol (PEG) and poly(ethylene glycol)-co-poly(d,l-lactide) (PELA). The size and its distribution of the nanoparticles were determined by dynamic light scattering measurements (DLS). The magnetic nanoparticles was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), Fourier transform infrared spectroscopy (FT-IR) and UV–visible spectrophotometry (UV). Magnetic properties were measured using a vibrating sample magnetometer. And the 5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT) assay was performed to evaluate the biocompatibility of the magnetic nanoparticles. The results showed that the Fe₃O₄ nanoparticles functionalized by PEG and PELA possessed a mean size of 43.2 and 79.3 nm, respectively, and exhibited an excellent biocompatibility.     

Saturation magnetic properties of Y3?xRexFe5O12(Re: Gd, Dy, Nd, Sm and La) nanoparticles grown by a sol–gel method

Re³⁺-substituted garnet nanoparticles Y_3−x Re _x Fe₅O₁₂ (Re = Gd, Dy, Nd, Sm and La) were fabricated by a sol–gel method .The XRD patterns of all samples have only peaks of the garnet structure and the sizes of nanoparticles rang from 34 to 69 nm. Results of VSM show that the saturation magnetization of Y_3−x Gd _x Fe₅O₁₂, Y_3−x Dy _x Fe₅O₁₂ and Y_3−x Sm _x Fe₅O₁₂ nanoparticles decrease evidently as the Re³⁺ concentration (x) is increased. The saturation magnetization of Y_3−x Nd _x Fe₅O₁₂ and Y_3−x La _x Fe₅O₁₂ increases firstly and then decreases as the Re³⁺ concentration (x) is increased. In the meanwhile, it is observed that may be due to the enhancement of the surface spin effects, the saturation magnetization rises as the nanoparticle size is increased.     

Covalent functionalization of metal oxide and carbon nanostructures with polyoctasilsesquioxane (POSS) and their incorporation in polymer composites

Polyoctasilsesquioxane (POSS) has been employed to covalently functionalize nanostructures of TiO₂, ZnO and Fe₂O₃ as well as carbon nanotubes, nanodiamond and graphene to enable their dispersion in polar solvents. Covalent functionalization of these nanostructures with POSS has been established by electron microscopy, EDAX analysis and infrared spectroscopy. On heating the POSS-functionalized nanostructures, silica-coated nanostructures are obtained. POSS-functionalized nanoparticles of TiO₂, Fe₂O₃ and graphite were utilized to prepare polymer-nanostructure composites based on PVA and nylon-6,6.     

Luminescence and crystallinity of flame-made Y2O3:Eu3+ nanoparticles

Cubic and/or monoclinic Y₂O₃:Eu³⁺ nanoparticles (10–50 nm) were made continuously without post-processing by single-step, flame spray pyrolysis (FSP). These particles were characterized by X-ray diffraction, nitrogen adsorption and transmission electron microscopy. Photoluminescence (PL) emission and time-resolved PL intensity decay were measured from these powders. The influence of particle size on PL was examined by annealing (at 700–1300°C for 10 h) as-prepared, initially monoclinic Y₂O₃:Eu³⁺ nanoparticles resulting in larger 0.025–1 μm, cubic Y₂O₃:Eu³⁺. The influence of europium (Eu³⁺) content (1–10 wt%) on sintering dynamics as well as optical properties of the resulting powders was investigated. Longer high-temperature particle residence time during FSP resulted in cubic nanoparticles with lower maximum PL intensity than measured by commercial micron-sized bulk Y₂O₃:Eu³⁺ phosphor powder. After annealing as-prepared 5 wt% Eu-doped Y₂O₃ particles at 900, 1100 and 1300°C for 10 h, the PL intensity increased as particle size increased and finally (at 1300°C) showed similar PL intensity as that of commercially available, bulk Y₂O₃:Eu³⁺ (5 μm particle size). Eu doping stabilized the monoclinic Y₂O₃ and shifted the monoclinic to cubic transition towards higher temperatures.     

Spectroscopic characterisation of local structure in Y<Subscript>2</Subscript>O<Subscript>3</Subscript>–B<Subscript>2</Subscript>O<Subscript>3</Subscript>–Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> glasses doped with gadolinium

Gadolinium doped bismuth borate glasses containing up to 30 mol% Y₂O₃ were prepared by fast melt quenching method. The effect of yttrium on the local order in 3B₂O₃ · Bi₂O₃ and B₂O₃ · Bi₂O₃ glass matrices, particularly on the bismuth sites, was investigated by infrared (IR) spectroscopy and electron paramagnetic resonance (EPR) of Gd³⁺ ions. The IR results show that the local structure is more ordered in the glass system with higher bismuth content and the progressive addition of yttrium increases the local disorder in both bismuth–borate glass matrices. The EPR results indicate that Gd³⁺ ions occupy both bismuth and yttrium sites and reflect the same structural disorder like that suggested by IR results.     

Synthesis of nanocrystalline rare earth oxides by glycothermal method

The reaction of yttrium acetate hydrate in 1,2-propanediol at 300 °C yielded a product containing acetate groups and glycol moieties. From this product, Y₂O₃ was directly crystallized at 400 °C without the formation of a carbonate oxide phase. The thus-obtained Y₂O₃ samples had a small crystallite size (2.2 nm) and significantly large surface area (280 m²/g). Other nanocrystalline rare earth (Gd-Yb) oxides were also obtained by this method.     

Destabilization of cubic-stabilized zirconia electrolyte induced by boron oxide under reducing atmosphere

The stability of yttria-stabilized zirconia (YSZ) and scandia-stabilized zirconia (ScSZ) electrolytes against boron oxide was examined. Boron oxide was painted on the polished surface of YSZ and ScSZ and annealed at 1273 K for 100 h under wet hydrogen flowing condition. The X-ray diffractometry, scanning electron microscopy/energy dispersive X-ray analysis, and Raman studies revealed that formation of Y₂O₃ and Sc₂O₃ occurred on YSZ and ScSZ surfaces contacting the boron oxide, but rare earth borates were not observed. The surface of electrolytes around precipitated particles became rough and phase transformation was confirmed from the cubic to the tetragonal or the monoclinic phases due to stabilizer removal from cubic zirconia. It has been also verified that small amounts of zirconium and yttrium were transported from the electrolyte to the gas phase via boron component. This destabilization effect induced by boron oxide was more serious for ScSZ than for YSZ. A destabilization mechanism under wet hydrogen atmosphere is proposed based on pseudo ternary phase diagrams for the YO_1.5–BO_1.5–ZrO₂ system and the ScO_1.5–BO_1.5–ZrO₂ system and thermodynamic considerations.     

Relation between microstructure and Charpy impact properties of an elemental and pre-alloyed 14Cr ODS ferritic steel powder after hot isostatic pressing

This article describes the microstructure and Charpy impact properties of an Fe–14Cr–2W–0.3Ti–0.3Y₂O₃ oxide dispersion strengthened (ODS)-reduced activation ferritic (RAF) steel, manufactured either from elemental powders or from an Fe–14Cr–2W–0.3Ti pre-alloyed powder. ODS RAF steels have been produced by mechanical alloying of powders with 0.3 wt% Y₂O₃ nanoparticles in either a planetary ball mill or an attritor ball mill, for 45 and 20 h, respectively, followed by hot isostatic pressing (HIPping) at 1,150 °C under a pressure of 200 MPa for 4 h and heat treatment at 850 °C for 1 h. It was found that the elemental ODS steel powder contains smaller particles with a higher specific surface area and a two times higher oxygen amount than the pre-alloyed ODS steel powder. After HIPping both materials exhibit a density higher than 99%. However, the pre-alloyed ODS steel exhibits a slightly better density than the elemental ODS steel, due to the reduced oxygen content in the former material. Charpy impact experiment revealed that the pre-alloyed ODS steel has a much larger ductile-to-brittle transition temperature (DBTT) (about 140 °C) than the elemental ODS steel (about 25 °C). However, no significant difference in the upper shelf energy (about 3.0 J) was measured. TEM and SEM–EBSD analyses revealed that the microstructure of the elemental ODS steel is composed of smaller grains with a larger fraction of high-angle grains (>15°) and a lower dislocation density than the pre-alloyed ODS steel, which explains the lower DBTT value obtained for the elemental ODS steel.