The catalytic performance is highly related to the catalyst structure.Herein,a series of Ni nanoparticles supported on Y_(2)O_(3) with different morphologies were successfully synthesized via hydrothermal process scre...The catalytic performance is highly related to the catalyst structure.Herein,a series of Ni nanoparticles supported on Y_(2)O_(3) with different morphologies were successfully synthesized via hydrothermal process screening different pH environments.These Ni/Y_(2)O_(3)catalysts were applied to efficiently produce CO_(x)-free H2through ammonia decomposition.We identify a significant impact of Y_(2)O_(3)supports on nickel nanoclusters sizes and dispersion.The experimental results show that Ni/Y11 catalyst achieves 100% ammonia decomposition conversion under a gas hour space velocity(GHSV) of 12,000 ml·h^(-1)·gcat^(-1) and temperature of 650℃.Such a high level of activity over Ni/Y11 catalyst was attributed to a large specific surface area,appropriate alkalinity,and small Ni nanoparticles diameter with high dispersion.展开更多
Y2O3 nanomaterials have been widely used in transparent ceramics and luminescent devices. Recently there are many studies focusing on controlling the size and morphology of Y2O3 in order to obtain better materials per...Y2O3 nanomaterials have been widely used in transparent ceramics and luminescent devices. Recently there are many studies focusing on controlling the size and morphology of Y2O3 in order to obtain better materials performance. In present study, yttrium oxyhydroxide precursor was synthesized via a facile solvothermal process through the dissolution-re-crystallization mechanism of Y2O3 raw powders in the ethylenediamine solvent, then nanosized yttrium oxide crystal was prepared from the precursor through post heat treatment process. The effects of solvothermal treatment temperature, holding time, solvent kinds and post heat treatment parameters on crystalline structure, grain shape and size of nanocrystal were investigated by XRD, TEM and TGA-DTA measurements. TEM images reveal that the morphology of product after post heat treatment at 460℃for 12 h is rice-like nanocrystal. XRD shows that this product is pure cubic Y2O3 cphase. Present study reveals that high purity Y2O3 with rice-like morphology can be easily prepared with average size around 30 nm under suitable post heat treatment parameters. In addition, the effects of solvents such as water and ethanol etc. on the crystal structure and morphology were also investigated. It is suggested that dissolution-recrystallization process may be the main mechanism for the formation of nano-sized YOOH precursors under solvothermal reaction condition, and the ethylenediamine solvent is likely to play an important role in controlling the transformation process of yttria precursors to the Y2O3 nanocrystal.展开更多
Zinc phosphate coatings formed on 6061-Al alloy, after dipping in phosphating solutions containing different amounts of Y2O3（yttrium oxide）, were studied by scanning electron microscopy （SEM）, X-ray diffraction （...Zinc phosphate coatings formed on 6061-Al alloy, after dipping in phosphating solutions containing different amounts of Y2O3（yttrium oxide）, were studied by scanning electron microscopy （SEM）, X-ray diffraction （XRD） and electrochemical measurements. Significant variations in the morphology and corrosion resistance afforded by zinc phosphate coating were especially observed as Y2O3 in phosphating solution varied from 0 to 40 mg/L. The addition of Y2O3 changed the initial potential of the interface between aluminum alloy substrate and phosphating solution and increased the number of nucleation sites. The phosphate coating thereby was less porous structure and covered the surface of aluminum alloy completely within short phosphating time. Phosphate coating was mainly composed of Zn3（PO4）2·4H2O （hopeite） and AlPO4（aluminum phosphate）. Y2O3, as an additive of phosphatization, accelerated precipitation and refined the gain size of phosphate coating. The corrosion resistance of zinc phosphate coating in 3% NaCl solution was improved as shown by polarization measurement. In the present research, the optimal amount of Y2O3 was 10-20 mg/L, and the optimal phosphating time was 600 s.展开更多
A novel yttrium citrate-templated conversion method for morphology controlled synthesis of Y2O3 microspheres, microflowers and microsheets was reported for the first time. The precursors with controllable morphologies...A novel yttrium citrate-templated conversion method for morphology controlled synthesis of Y2O3 microspheres, microflowers and microsheets was reported for the first time. The precursors with controllable morphologies were synthesized with a homogenous precipitation method in aqueous solution without any surfactant. Y2O3 samples with well-preserved morphological architectures were obtained by a subse-quent thermal transformation strategy. The chemical formula of the precursor was identified and a two-stage growth mechanism was proposed. The effects of the aging time, reaction temperature, reactant concentration and molar ratio of yttrium nitrate to sodium citrate were discussed. The photoluminescence properties of the Y2O3：Eu3＋ microspheres, microflowers and microsheets prepared were also studied.展开更多
The porous cubic yttrium oxides with high specific surface area were prepared yttrium nitrate and its complex formed with methyl salicylate. The specific surface area by the explosive decomposition of and properties o...The porous cubic yttrium oxides with high specific surface area were prepared yttrium nitrate and its complex formed with methyl salicylate. The specific surface area by the explosive decomposition of and properties of powders synthesized at various temperatures were characterized using BET, X-ray diffraction （XRD）, infrared spectra （IR）, and scanning electron microscopy （SEM）. The results indicate that the highest specific surface area is found to be 65.37 m^2·g^-1 at the calcination temperature of 600 ℃, and then decreases to 20.33 m2· g^- 1 with the calcination temperature rising from 600 to 900 ℃. The powders show strong surface activity for adsorping water and carbon dioxide in air, which also decreases with the rising calcination temperature. The drop both on the surface area and surface activity of samples at higher temperatures may be due to pore-narrowing（sintering） effects.展开更多
Zirconium alloys are active in the molten state and tend to react with the mold during casting. The casting technology of zirconium is not yet well established; especially in selecting the mold materials, which are di...Zirconium alloys are active in the molten state and tend to react with the mold during casting. The casting technology of zirconium is not yet well established; especially in selecting the mold materials, which are difficult to determine. In the present work, the interfacial reactions between zirconium casting and casting mold were studied. The zirconium alloy was melted in a vacuum arc skull furnace and then cast into the graphite mold and ceramic mold, respectively. The zirconium casting samples were characterized using SEM, EDS and XRD with an emphasis on the chemical diffusion of elements. A reaction layer was observed at the casting surface. Chemical analysis shows that chemical elements C, O and Y from the mold are diffused into the molten zirconium, and new phases, such as ZrC, Zr30, YO1.335 and Y6ZrO11, are formed at the surface. In addition, an end product of zirconium valve cast in a yttria mold has a compact structure and good surface quality.展开更多
The method for preparing yttrium oxide with large specific surface area was introduced. By means of BET, SEM, TG and DTA analysis, the effects of precipitant, stirring velocity, non-RE impurity in solution, calcinatio...The method for preparing yttrium oxide with large specific surface area was introduced. By means of BET, SEM, TG and DTA analysis, the effects of precipitant, stirring velocity, non-RE impurity in solution, calcination temperature, on the surface area were studied respectively. The Y_2O_3 sample with specific surface area of more than 60 m^2·g^(-1) and L.O.I less than 1% was prepared in the suitable precipitation condition and calcinations temperature when the ammonia used as precipitant. The SEM shows that the Y_2O_3 prepared with large surface area is the aggregation of about 50 nm particles.展开更多
The novel composite lithium solid polymer electrolytes （SPEs） composed of polyethylene oxide （PEO） matrix and yttrium oxide （Y2O3） nanofillers were prepared by a solution casting method. The crystal morphology o...The novel composite lithium solid polymer electrolytes （SPEs） composed of polyethylene oxide （PEO） matrix and yttrium oxide （Y2O3） nanofillers were prepared by a solution casting method. The crystal morphology of the SPEs was characterized by polarized optical microscope （POM） and wide-angle X-ray diffraction （WAXD）. The induced nucleation and steric hindrance effects of Y2O3 nanofillers result in the increased amount as well as decreased size of PEO spherulites which are closely related to the crystallinity of the SPEs. As the Y2O3 contents increase from 0 wt% to 15 wt%, the crystallinity of the SPEs decreases proportionally. The thermal, mechanical and electrical properties of the SPEs were investigated by thermal gravimetric analysis （TGA）, dynamic mechanical analysis （DMA） and AC impedance method, respectively. The physical properties including thermal, mechanical and electrical performances, depending remarkably on the polymer-filler interactions between PEO and Y2O3 nanoparticles, are improved by different degrees with the increase of Y2O3 contents. The （PEO）21LiI/10 wt%Y2O3 composite SPE exhibits the optimal room-temperature ionic conductivity of 5.95×10-5 Scm-1, which satisfies the requirements of the conventional electrochromic devices.展开更多
Determination of trace rare earth elements(REEs)in 99. 999% purity yttrium oxide using the inductively coupled plasma mass spectrometric technique (ICPMS) has been developed. Instrumental parameters and factors affeci...Determination of trace rare earth elements(REEs)in 99. 999% purity yttrium oxide using the inductively coupled plasma mass spectrometric technique (ICPMS) has been developed. Instrumental parameters and factors affecitng analytical results have been studied and then optimized.Samples are analyzed directly following an acid digestion without separation or preconcentration and with limit of detection of 0. 003～0. 02 ng/ml, precision of ±5. 4%(cofficient of variation)and recovery of 90～115%. Correction for isobaric interferences from oxide ions and hydroxide ions is made mathematically. Special internal standard procedures are used to compensate drift in metal:metal oxide ratios and sensitivity. The analytical results of several samples are accurate as compared with inductively coupled plasma atomic emission spectrometry (ICPAES) and spark source mass spectrometry (SSMS).展开更多
Compared to traditional optical domes, domes of sapphire coated with films can effectively reduce emissivity and increase transmittance. The purpose of this work is to investigate the thermal radiation effect on sapph...Compared to traditional optical domes, domes of sapphire coated with films can effectively reduce emissivity and increase transmittance. The purpose of this work is to investigate the thermal radiation effect on sapphire optical dome coated with yttrium oxide by a radio frequency mag- netron sputtering method. The emissivity of sapphire coated with Y203 films is studied by both numerical and experi- mental methods. The results indicate that the emissivity of sapphire substrate is reduced effectively with increasing the thickness of the Y203 film. In addition, a finite element model is developed to simulate the radiation intensity of the optical dome. The thermal responses indicate that the max- imum temperature is reduced apparently compared with the uncoated sapphire as Y203 film thicknesses increase. The average irradiance distribution at different film thicknesses with time shows that the self-thermal radiation disturbance of sapphire optical dome delays 0.93 s when the thickness of Y203 film is 200μm, which can guarantee the dome works properly and effectively even in a harsh environment.展开更多
Ce3＋-doped yttrium lanthanum oxide （Y0.9La0.1）2O3 transparent ceramics is fabricated with nanopowders and sintered in H2 atmosphere. The spectral properties of Ce：（Y0.9La0.1）2O3 transparent ceramics are investig...Ce3＋-doped yttrium lanthanum oxide （Y0.9La0.1）2O3 transparent ceramics is fabricated with nanopowders and sintered in H2 atmosphere. The spectral properties of Ce：（Y0.9La0.1）2O3 transparent ceramics are investigated. There appear two characteristic absorption peaks of Ce3＋ ions at 230~nm and 400~nm, separately. It is found that Ce3＋ ions can efficiently produce emission at 384~nm from （Y0.9La0.1）2O3 transparent ceramic host, while the emission is completely quenched in Re2O3 （Re=Y, Lu, La） host materials.展开更多
Nanocrystalline indium oxide powders were prepared by microemulsion and then Y2O3 and Nd2O3 doped In2O3 were synthesized separately by impregnation and chemical co-deposition. The structure and morphology were charact...Nanocrystalline indium oxide powders were prepared by microemulsion and then Y2O3 and Nd2O3 doped In2O3 were synthesized separately by impregnation and chemical co-deposition. The structure and morphology were characterized by XRD and TEM, respectively. Gas sensing properties were tested at static state. The results show that homogeneous indium oxide nanopowder with main grain size of 20 nm can be obtained from microemulsion after sintered at 600 ℃ for 1 h. Pure indium oxide gas sensor has higher sensitivity to gasoline than that to ethanol, HCHO, C6H6, NH3, C4H10, but the selectivity is not as well as sensitivity.展开更多
Lithium nickel oxide(LiNiO_(2)) cathode materials are featured with high capacity and low cost for rechargeable lithium-ion batteries but suffer from severe interface and structure instability.Here we report that rati...Lithium nickel oxide(LiNiO_(2)) cathode materials are featured with high capacity and low cost for rechargeable lithium-ion batteries but suffer from severe interface and structure instability.Here we report that rationally designed LiNiO_(2) via concentration-gradient yttrium modification exhibits alleviative side reactions and improved electrochemical performance.The LiNiO_(2) cathode with LiYO_(2)-Y_(2) O_(3) coating layer delivers a discharge capacity of 225 mAh g^(-1) with a high initial Coulombic efficiency of 93.4%.These improvements can be attributed to the formation of in-situ modified hybrid LiYO_(2)-Y_(2 O3) coating layer,which suppresses phase transformation,electrolyte oxidation and salt dissociation due to the formation of protective cathode electrolyte interface.The results indicate promising application of concentration-gradient yttrium coating as a facile approach to stabilize nickel-rich cathode materials.展开更多
The isothermal oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples are studied at 1 000 ℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） is used to examine th...The isothermal oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples are studied at 1 000 ℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） is used to examine the Cr2O3 oxide film＇s morphology after oxidation. Acoustic emission （AE） method is used in situ for monitoring the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air-cooling stages. Theoretical model is proposed relating to the film fracture process and is used for analyzing the acoustic emission spectrum both on time domain and on AE-event number domain. It is found that yttrium implantation remarkably reduces the isothermal oxidizing rate of Co-40Cr and improves the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvement are mainly that the implanted yttrium reduced the grain size of Cr2O3 oxide, increased the high temperature plasticity of oxide film, and remarkably reduced the number and size of Cr2O3/Co-40Cr inteffacial defects.展开更多
The titanium alloys with highly chemical activity require stable crucible refractories that can withstand the erosion of alloy melts.The phase composition and microstructure are crucial factors that affect the stabili...The titanium alloys with highly chemical activity require stable crucible refractories that can withstand the erosion of alloy melts.The phase composition and microstructure are crucial factors that affect the stability of the refractory crucible.The effect of Y_(2)O_(3) on the composition and microstructure of BaZrO_(3) crucible was systematically investigated,and the improved mechanism of the stability of BaZrO_(3)/Y_(2)O_(3) crucible was clarified in comparison with the BaZrO_(3) crucible.The results showed that the erosion layer thickness of the BaZrO_(3)/Y_(2)O_(3) crucible was only 63μm,which was far less than that in the BaZrO_(3) crucible(485μm),and the erosion layer in the BaZrO_(3)/Y_(2)O_(3) crucible also exhibited a higher density than that in the BaZrO_(3) crucible.During the sintering,Y_(2)O_(3) could improve the densification of the BaZrO_(3) crucible due to the solid solution effect between Y_(2)O_(3) and ZrO_(2),which also caused the evaporation of BaO,resulting in the generation of a Y_(2)O_(3)(ZrO_(2))film on the surface of the crucible.Furthermore,the Y_(2)O_(3)(ZrO_(2))had higher thermodynamic stability than Y_(2)O_(3),confirming that the BaZrO_(3)/Y_(2)O_(3) crucible with high density exhibited a superior erosion resistance to titanium alloys.This dual-phase structure provides a strategy to design a long-life and stable refractory for melting titanium alloys.展开更多
A porous yttrium oxide crucible with both thermal shock resistance and erosion resistance was developed by structural optimization.The structure-optimized yttrium oxide crucible was proved to be suitable for melting h...A porous yttrium oxide crucible with both thermal shock resistance and erosion resistance was developed by structural optimization.The structure-optimized yttrium oxide crucible was proved to be suitable for melting highly reactive titanium alloys.Low-cost(TiB+Y2O_(3))-reinforced titanium matrix composites were prepared by vacuum induction melting using the prepared crucible.The thermal deformation behavior and microstructure evolution of(TiB+Y2O_(3))-reinforced tita-nium matrix composites were investigated at deformation temperatures of 900-1100℃with strain rates of 0.001-1 s-1.The results showed that the prepared yttrium oxide crucible had both thermal shock and erosion resistance,the low-cost titanium matrix composites could be prepared by the developed yttrium oxide crucibles which were homogeneous in composition and highly sensitive to strain rate and deformation temperature,and the peak and theological stresses decreased with increasing deformation temperature or decreasing strain rate.In addition,the average thermal deformation activation energy of the composites was calculated to be 574.6 kJ/mol by establishing the Arrhenius constitutive equation in consideration of the strain variables,and the fitting goodness between the predicted stress value and the measured value was 97.624%.The calculated analysis of the hot processing map showed that the best stable thermal deformation zone was located in the deformation temperature range of 1000-1100℃and strain rate range of 0.001-0.01 s^(-1),where the peak dissipation coefficient wasη=71%.In this zone,the deformation of the reinforcement and matrix was harmonious,the reinforcement was less likely to fracture,dynamic recrystallization occurred more fully and the alloy exhibited near steady rheological characteristics.展开更多
Y2O3-doped ZnO-based varistor ceramics were prepared using high-energy ball milling （HEBM） and low-temperature sin- tering technique, with voltage-gradient of 1934-2197 V/mm, non-linear coefficients of 20.8-21.8, le...Y2O3-doped ZnO-based varistor ceramics were prepared using high-energy ball milling （HEBM） and low-temperature sin- tering technique, with voltage-gradient of 1934-2197 V/mm, non-linear coefficients of 20.8-21.8, leakage currents of 0.59-1.04 μA, and densities of 5.46-5.57 g/cm3. With increasing Y2O3 content, the voltage-gradient increases because of the decrease of ZnO grain size; the non-linear coefficient and the leakage current improve but the density decreases because of more porosity; the donor con- centration and density of interface states decrease, whereas the barrier height and width increase because of the acceptor effect of Y2O3 in varistor ceramics.展开更多
Y 2O 3/TiO 2 samples were prepared by sol-gel process and characterized by means of X-ray diffraction (XRD), laser Raman spectra (LRS), UV-visible diffuse reflectance spectra (DRS), specific surface area (BET), and...Y 2O 3/TiO 2 samples were prepared by sol-gel process and characterized by means of X-ray diffraction (XRD), laser Raman spectra (LRS), UV-visible diffuse reflectance spectra (DRS), specific surface area (BET), and transmission electron microscopy (TEM). The results show that the relative intensity of 101 peak of anatase and 002 peak of rutile, the mean crystal diameter and mean particle diameter of Y 2O 3/TiO 2 samples decrease while specific surface area increases owing to doping Y 2O 3. Y 2O 3/TiO 2 samples have a larger specific surface area and higher thermal stability. Owing to quantum size effect, the reflectance of Y 2O 3/TiO 2 samples is larger than that of pure TiO 2 in the range of 380～460 nm and the position of Raman peaks varies slightly. Being a model reaction, the photo-catalytic degradation of methylene blue (MB) with positive charge and methyl orange (MO) with negative charge was investigated in TiO 2 and Y 2O 3/TiO 2 nanopowder suspension irradiated by high-pressure mercury lamp. As a result, the addition of Y 2O 3 to TiO 2 is detrimental to photo-activity of TiO 2 for MB photo-degradation and photo-catalytic behavior is enhanced due to 5%, 10% Y 2O 3 deposited on TiO 2 for the photo-degradation of MO. And the relationship between photo-physical properties and photo-activity was discussed.展开更多
Nanostructured Y203 was successfully prepared via a two-step and template-free method. Firstly, yttrium hydroxide precursor was galvanostatically grown on the steel substrate from chloride bath by direct and pulse cur...Nanostructured Y203 was successfully prepared via a two-step and template-free method. Firstly, yttrium hydroxide precursor was galvanostatically grown on the steel substrate from chloride bath by direct and pulse current deposition modes. Direct cunent deposition was carried out at the constant current density of 0.1 A/dm2 for 600 s. The pulse current was also performed at a typical on-time and off-time （ton=l S and Germ s） with an average current density of 0.05 A/dm2 （la=0.05 A/din2） for 600 s. The obtained hydroxide films were then scraped from the substrates and thermally converted into final oxide product via heat-treatment. Thermal behaviors and phase transformations during the heat treatment of the hydroxide powder samples were investigated by differential scanning calorimetry （DSC） and thermogravimetric analysis （TGA）. The final oxide products were characterized by means of X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR） and scanning electron microscopy （SEM）. The results showed that the well-crystallized Y203 with brainand sphere-like morphology were achievable via pulse and direct deposition modes, respectively. It was concluded that pulse current cathodic electrodeposition offered a facile route for preparation ofnanostructured Y203.展开更多
The pH value and viscosity of Y2O3-SiO2 （Y-Si） slurry made by Y2O3 powders and silica sol for the face coat of Ti-6Al-4V investment casting were measured. The thermal behavior of the shell made by the Y-Si face coat...The pH value and viscosity of Y2O3-SiO2 （Y-Si） slurry made by Y2O3 powders and silica sol for the face coat of Ti-6Al-4V investment casting were measured. The thermal behavior of the shell made by the Y-Si face coat system was investigated by differential scanning calorimeter （DSC）, thermal gravimetric （TG） analysis combined with mass spectrometry （MS）, and the phase transformations were determined by X-ray diffraction （XRD）. Hot strength, residual strength, linear expansion coefficient, and wearing resistance performance of the shell were also tested. The microstructure and elements distri- bution of the interaction layer were studied by scanning electron microscope （SEM） and energy-dispersive spectrometer （EDS）, respectively. The microhardness tester was applied for the microhardness. The results showed that the slurry was stable for at least 60 h. A very small amount of YZrO3 was formed below 1050℃ and Y2SiO5 was formed around 1450℃. The shell made by Y-Si system had good mechanical property which could reduce cracks during the procedure of dewaxing and inclusions during pouring. Some Al volatilized from the melt, permeated the surface of the face coat shell, and formed the black reaction layer, which blocked the permeation of O so that O penetration was limited to 5μm. The depth of Si penetration was about 60 μm. The hard layer was also around 60 μm.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos.21868016, 21763018,22005296 and 21875096)the Key Laboratory for Environment and Energy Catalysis of Jiangxi Province (No. 20181BCD40004)+1 种基金the Natural Science Foundation of Jiangxi Province (No.20181BAB203016)the Graduate Students Innovation Special Foundation of Jiangxi Province (No.YC2021-B014)。
文摘The catalytic performance is highly related to the catalyst structure.Herein,a series of Ni nanoparticles supported on Y_(2)O_(3) with different morphologies were successfully synthesized via hydrothermal process screening different pH environments.These Ni/Y_(2)O_(3)catalysts were applied to efficiently produce CO_(x)-free H2through ammonia decomposition.We identify a significant impact of Y_(2)O_(3)supports on nickel nanoclusters sizes and dispersion.The experimental results show that Ni/Y11 catalyst achieves 100% ammonia decomposition conversion under a gas hour space velocity(GHSV) of 12,000 ml·h^(-1)·gcat^(-1) and temperature of 650℃.Such a high level of activity over Ni/Y11 catalyst was attributed to a large specific surface area,appropriate alkalinity,and small Ni nanoparticles diameter with high dispersion.
基金Project supported by SRF for ROCS, SEM (2003-14) and Science and Technology Department of Zhejiang Province (2003C11027)
文摘Y2O3 nanomaterials have been widely used in transparent ceramics and luminescent devices. Recently there are many studies focusing on controlling the size and morphology of Y2O3 in order to obtain better materials performance. In present study, yttrium oxyhydroxide precursor was synthesized via a facile solvothermal process through the dissolution-re-crystallization mechanism of Y2O3 raw powders in the ethylenediamine solvent, then nanosized yttrium oxide crystal was prepared from the precursor through post heat treatment process. The effects of solvothermal treatment temperature, holding time, solvent kinds and post heat treatment parameters on crystalline structure, grain shape and size of nanocrystal were investigated by XRD, TEM and TGA-DTA measurements. TEM images reveal that the morphology of product after post heat treatment at 460℃for 12 h is rice-like nanocrystal. XRD shows that this product is pure cubic Y2O3 cphase. Present study reveals that high purity Y2O3 with rice-like morphology can be easily prepared with average size around 30 nm under suitable post heat treatment parameters. In addition, the effects of solvents such as water and ethanol etc. on the crystal structure and morphology were also investigated. It is suggested that dissolution-recrystallization process may be the main mechanism for the formation of nano-sized YOOH precursors under solvothermal reaction condition, and the ethylenediamine solvent is likely to play an important role in controlling the transformation process of yttria precursors to the Y2O3 nanocrystal.
基金supported by the Natural Science Foundation of Henan Province (200510476009)
文摘Zinc phosphate coatings formed on 6061-Al alloy, after dipping in phosphating solutions containing different amounts of Y2O3（yttrium oxide）, were studied by scanning electron microscopy （SEM）, X-ray diffraction （XRD） and electrochemical measurements. Significant variations in the morphology and corrosion resistance afforded by zinc phosphate coating were especially observed as Y2O3 in phosphating solution varied from 0 to 40 mg/L. The addition of Y2O3 changed the initial potential of the interface between aluminum alloy substrate and phosphating solution and increased the number of nucleation sites. The phosphate coating thereby was less porous structure and covered the surface of aluminum alloy completely within short phosphating time. Phosphate coating was mainly composed of Zn3（PO4）2·4H2O （hopeite） and AlPO4（aluminum phosphate）. Y2O3, as an additive of phosphatization, accelerated precipitation and refined the gain size of phosphate coating. The corrosion resistance of zinc phosphate coating in 3% NaCl solution was improved as shown by polarization measurement. In the present research, the optimal amount of Y2O3 was 10-20 mg/L, and the optimal phosphating time was 600 s.
基金Project supported by the National Natural Science Foundation of China (50990304)State "973" Project (2007CB936704)
文摘A novel yttrium citrate-templated conversion method for morphology controlled synthesis of Y2O3 microspheres, microflowers and microsheets was reported for the first time. The precursors with controllable morphologies were synthesized with a homogenous precipitation method in aqueous solution without any surfactant. Y2O3 samples with well-preserved morphological architectures were obtained by a subse-quent thermal transformation strategy. The chemical formula of the precursor was identified and a two-stage growth mechanism was proposed. The effects of the aging time, reaction temperature, reactant concentration and molar ratio of yttrium nitrate to sodium citrate were discussed. The photoluminescence properties of the Y2O3：Eu3＋ microspheres, microflowers and microsheets prepared were also studied.
文摘The porous cubic yttrium oxides with high specific surface area were prepared yttrium nitrate and its complex formed with methyl salicylate. The specific surface area by the explosive decomposition of and properties of powders synthesized at various temperatures were characterized using BET, X-ray diffraction （XRD）, infrared spectra （IR）, and scanning electron microscopy （SEM）. The results indicate that the highest specific surface area is found to be 65.37 m^2·g^-1 at the calcination temperature of 600 ℃, and then decreases to 20.33 m2· g^- 1 with the calcination temperature rising from 600 to 900 ℃. The powders show strong surface activity for adsorping water and carbon dioxide in air, which also decreases with the rising calcination temperature. The drop both on the surface area and surface activity of samples at higher temperatures may be due to pore-narrowing（sintering） effects.
基金supported by the National Natural Science Foundation of China(No.51075285) the Provincial Natural Science Foundation of Liaoning in China(No.20102222)
文摘Zirconium alloys are active in the molten state and tend to react with the mold during casting. The casting technology of zirconium is not yet well established; especially in selecting the mold materials, which are difficult to determine. In the present work, the interfacial reactions between zirconium casting and casting mold were studied. The zirconium alloy was melted in a vacuum arc skull furnace and then cast into the graphite mold and ceramic mold, respectively. The zirconium casting samples were characterized using SEM, EDS and XRD with an emphasis on the chemical diffusion of elements. A reaction layer was observed at the casting surface. Chemical analysis shows that chemical elements C, O and Y from the mold are diffused into the molten zirconium, and new phases, such as ZrC, Zr30, YO1.335 and Y6ZrO11, are formed at the surface. In addition, an end product of zirconium valve cast in a yttria mold has a compact structure and good surface quality.
文摘The method for preparing yttrium oxide with large specific surface area was introduced. By means of BET, SEM, TG and DTA analysis, the effects of precipitant, stirring velocity, non-RE impurity in solution, calcination temperature, on the surface area were studied respectively. The Y_2O_3 sample with specific surface area of more than 60 m^2·g^(-1) and L.O.I less than 1% was prepared in the suitable precipitation condition and calcinations temperature when the ammonia used as precipitant. The SEM shows that the Y_2O_3 prepared with large surface area is the aggregation of about 50 nm particles.
基金Funded by the National Natural Science Foundation of China (No. 51003082)the Key Project of Science and Technology Research of Ministry of Education (No. 208089)+2 种基金the Educational Commission of Hubei Province (No.Q20101606)the Young Outstanding Talent Foundation of Hubei Province (No.2008CDB261)the Natural Science Foundation of Hubei Province (No. 2007ABA075)
文摘The novel composite lithium solid polymer electrolytes （SPEs） composed of polyethylene oxide （PEO） matrix and yttrium oxide （Y2O3） nanofillers were prepared by a solution casting method. The crystal morphology of the SPEs was characterized by polarized optical microscope （POM） and wide-angle X-ray diffraction （WAXD）. The induced nucleation and steric hindrance effects of Y2O3 nanofillers result in the increased amount as well as decreased size of PEO spherulites which are closely related to the crystallinity of the SPEs. As the Y2O3 contents increase from 0 wt% to 15 wt%, the crystallinity of the SPEs decreases proportionally. The thermal, mechanical and electrical properties of the SPEs were investigated by thermal gravimetric analysis （TGA）, dynamic mechanical analysis （DMA） and AC impedance method, respectively. The physical properties including thermal, mechanical and electrical performances, depending remarkably on the polymer-filler interactions between PEO and Y2O3 nanoparticles, are improved by different degrees with the increase of Y2O3 contents. The （PEO）21LiI/10 wt%Y2O3 composite SPE exhibits the optimal room-temperature ionic conductivity of 5.95×10-5 Scm-1, which satisfies the requirements of the conventional electrochromic devices.
文摘Determination of trace rare earth elements(REEs)in 99. 999% purity yttrium oxide using the inductively coupled plasma mass spectrometric technique (ICPMS) has been developed. Instrumental parameters and factors affecitng analytical results have been studied and then optimized.Samples are analyzed directly following an acid digestion without separation or preconcentration and with limit of detection of 0. 003～0. 02 ng/ml, precision of ±5. 4%(cofficient of variation)and recovery of 90～115%. Correction for isobaric interferences from oxide ions and hydroxide ions is made mathematically. Special internal standard procedures are used to compensate drift in metal:metal oxide ratios and sensitivity. The analytical results of several samples are accurate as compared with inductively coupled plasma atomic emission spectrometry (ICPAES) and spark source mass spectrometry (SSMS).
文摘Compared to traditional optical domes, domes of sapphire coated with films can effectively reduce emissivity and increase transmittance. The purpose of this work is to investigate the thermal radiation effect on sapphire optical dome coated with yttrium oxide by a radio frequency mag- netron sputtering method. The emissivity of sapphire coated with Y203 films is studied by both numerical and experi- mental methods. The results indicate that the emissivity of sapphire substrate is reduced effectively with increasing the thickness of the Y203 film. In addition, a finite element model is developed to simulate the radiation intensity of the optical dome. The thermal responses indicate that the max- imum temperature is reduced apparently compared with the uncoated sapphire as Y203 film thicknesses increase. The average irradiance distribution at different film thicknesses with time shows that the self-thermal radiation disturbance of sapphire optical dome delays 0.93 s when the thickness of Y203 film is 200μm, which can guarantee the dome works properly and effectively even in a harsh environment.
基金supported by the National Natural Science Foundation of China (Grant No. 60578041)the Shanghai Leading Academic Disciplines (Grant No. S30107)
文摘Ce3＋-doped yttrium lanthanum oxide （Y0.9La0.1）2O3 transparent ceramics is fabricated with nanopowders and sintered in H2 atmosphere. The spectral properties of Ce：（Y0.9La0.1）2O3 transparent ceramics are investigated. There appear two characteristic absorption peaks of Ce3＋ ions at 230~nm and 400~nm, separately. It is found that Ce3＋ ions can efficiently produce emission at 384~nm from （Y0.9La0.1）2O3 transparent ceramic host, while the emission is completely quenched in Re2O3 （Re=Y, Lu, La） host materials.
文摘Nanocrystalline indium oxide powders were prepared by microemulsion and then Y2O3 and Nd2O3 doped In2O3 were synthesized separately by impregnation and chemical co-deposition. The structure and morphology were characterized by XRD and TEM, respectively. Gas sensing properties were tested at static state. The results show that homogeneous indium oxide nanopowder with main grain size of 20 nm can be obtained from microemulsion after sintered at 600 ℃ for 1 h. Pure indium oxide gas sensor has higher sensitivity to gasoline than that to ethanol, HCHO, C6H6, NH3, C4H10, but the selectivity is not as well as sensitivity.
基金supported by the National Key R&D Program of China (2016YFA0202503)the SINOPEC Project (129015-1)+2 种基金the National Natural Science Foundation of China (21835004 and21925503)the 111 Project from the Ministry of Education of China(B12015)the Fundamental Research Funds for the Central Universities。
文摘Lithium nickel oxide(LiNiO_(2)) cathode materials are featured with high capacity and low cost for rechargeable lithium-ion batteries but suffer from severe interface and structure instability.Here we report that rationally designed LiNiO_(2) via concentration-gradient yttrium modification exhibits alleviative side reactions and improved electrochemical performance.The LiNiO_(2) cathode with LiYO_(2)-Y_(2) O_(3) coating layer delivers a discharge capacity of 225 mAh g^(-1) with a high initial Coulombic efficiency of 93.4%.These improvements can be attributed to the formation of in-situ modified hybrid LiYO_(2)-Y_(2 O3) coating layer,which suppresses phase transformation,electrolyte oxidation and salt dissociation due to the formation of protective cathode electrolyte interface.The results indicate promising application of concentration-gradient yttrium coating as a facile approach to stabilize nickel-rich cathode materials.
基金National Natural Science Foundation of China(No.29231011)Natural Science Foundation of Jiangsu Province,China(No.07KJD430246)
文摘The isothermal oxidizing kinetics of Co-40Cr alloy and its yttrium ion-implanted samples are studied at 1 000 ℃ in air by thermal-gravity analysis （TGA）. Scanning electronic microscopy （SEM） is used to examine the Cr2O3 oxide film＇s morphology after oxidation. Acoustic emission （AE） method is used in situ for monitoring the cracking and spalling of oxide films formed on both samples during oxidizing and subsequent air-cooling stages. Theoretical model is proposed relating to the film fracture process and is used for analyzing the acoustic emission spectrum both on time domain and on AE-event number domain. It is found that yttrium implantation remarkably reduces the isothermal oxidizing rate of Co-40Cr and improves the anti-cracking and anti-spalling properties of Cr2O3 oxide film. The reasons for the improvement are mainly that the implanted yttrium reduced the grain size of Cr2O3 oxide, increased the high temperature plasticity of oxide film, and remarkably reduced the number and size of Cr2O3/Co-40Cr inteffacial defects.
基金supported by National Natural Science Foundation of China(No.52104305)the Science and Technology Innovation Project of Shanghai Lingang New Area(No.SH-LG-GK-2020).
文摘The titanium alloys with highly chemical activity require stable crucible refractories that can withstand the erosion of alloy melts.The phase composition and microstructure are crucial factors that affect the stability of the refractory crucible.The effect of Y_(2)O_(3) on the composition and microstructure of BaZrO_(3) crucible was systematically investigated,and the improved mechanism of the stability of BaZrO_(3)/Y_(2)O_(3) crucible was clarified in comparison with the BaZrO_(3) crucible.The results showed that the erosion layer thickness of the BaZrO_(3)/Y_(2)O_(3) crucible was only 63μm,which was far less than that in the BaZrO_(3) crucible(485μm),and the erosion layer in the BaZrO_(3)/Y_(2)O_(3) crucible also exhibited a higher density than that in the BaZrO_(3) crucible.During the sintering,Y_(2)O_(3) could improve the densification of the BaZrO_(3) crucible due to the solid solution effect between Y_(2)O_(3) and ZrO_(2),which also caused the evaporation of BaO,resulting in the generation of a Y_(2)O_(3)(ZrO_(2))film on the surface of the crucible.Furthermore,the Y_(2)O_(3)(ZrO_(2))had higher thermodynamic stability than Y_(2)O_(3),confirming that the BaZrO_(3)/Y_(2)O_(3) crucible with high density exhibited a superior erosion resistance to titanium alloys.This dual-phase structure provides a strategy to design a long-life and stable refractory for melting titanium alloys.
基金supported by the National Natural Science Foundation of China(52071065)the Fundamental Research Funds for the Central Universities(N2007007)+1 种基金the National Key R&D Program of China(2016YFB-0301201)the Ten Technology Research Projects of Hunan Province(No.2022GK1050).
文摘A porous yttrium oxide crucible with both thermal shock resistance and erosion resistance was developed by structural optimization.The structure-optimized yttrium oxide crucible was proved to be suitable for melting highly reactive titanium alloys.Low-cost(TiB+Y2O_(3))-reinforced titanium matrix composites were prepared by vacuum induction melting using the prepared crucible.The thermal deformation behavior and microstructure evolution of(TiB+Y2O_(3))-reinforced tita-nium matrix composites were investigated at deformation temperatures of 900-1100℃with strain rates of 0.001-1 s-1.The results showed that the prepared yttrium oxide crucible had both thermal shock and erosion resistance,the low-cost titanium matrix composites could be prepared by the developed yttrium oxide crucibles which were homogeneous in composition and highly sensitive to strain rate and deformation temperature,and the peak and theological stresses decreased with increasing deformation temperature or decreasing strain rate.In addition,the average thermal deformation activation energy of the composites was calculated to be 574.6 kJ/mol by establishing the Arrhenius constitutive equation in consideration of the strain variables,and the fitting goodness between the predicted stress value and the measured value was 97.624%.The calculated analysis of the hot processing map showed that the best stable thermal deformation zone was located in the deformation temperature range of 1000-1100℃and strain rate range of 0.001-0.01 s^(-1),where the peak dissipation coefficient wasη=71%.In this zone,the deformation of the reinforcement and matrix was harmonious,the reinforcement was less likely to fracture,dynamic recrystallization occurred more fully and the alloy exhibited near steady rheological characteristics.
文摘Y2O3-doped ZnO-based varistor ceramics were prepared using high-energy ball milling （HEBM） and low-temperature sin- tering technique, with voltage-gradient of 1934-2197 V/mm, non-linear coefficients of 20.8-21.8, leakage currents of 0.59-1.04 μA, and densities of 5.46-5.57 g/cm3. With increasing Y2O3 content, the voltage-gradient increases because of the decrease of ZnO grain size; the non-linear coefficient and the leakage current improve but the density decreases because of more porosity; the donor con- centration and density of interface states decrease, whereas the barrier height and width increase because of the acceptor effect of Y2O3 in varistor ceramics.
文摘Y 2O 3/TiO 2 samples were prepared by sol-gel process and characterized by means of X-ray diffraction (XRD), laser Raman spectra (LRS), UV-visible diffuse reflectance spectra (DRS), specific surface area (BET), and transmission electron microscopy (TEM). The results show that the relative intensity of 101 peak of anatase and 002 peak of rutile, the mean crystal diameter and mean particle diameter of Y 2O 3/TiO 2 samples decrease while specific surface area increases owing to doping Y 2O 3. Y 2O 3/TiO 2 samples have a larger specific surface area and higher thermal stability. Owing to quantum size effect, the reflectance of Y 2O 3/TiO 2 samples is larger than that of pure TiO 2 in the range of 380～460 nm and the position of Raman peaks varies slightly. Being a model reaction, the photo-catalytic degradation of methylene blue (MB) with positive charge and methyl orange (MO) with negative charge was investigated in TiO 2 and Y 2O 3/TiO 2 nanopowder suspension irradiated by high-pressure mercury lamp. As a result, the addition of Y 2O 3 to TiO 2 is detrimental to photo-activity of TiO 2 for MB photo-degradation and photo-catalytic behavior is enhanced due to 5%, 10% Y 2O 3 deposited on TiO 2 for the photo-degradation of MO. And the relationship between photo-physical properties and photo-activity was discussed.
文摘Nanostructured Y203 was successfully prepared via a two-step and template-free method. Firstly, yttrium hydroxide precursor was galvanostatically grown on the steel substrate from chloride bath by direct and pulse current deposition modes. Direct cunent deposition was carried out at the constant current density of 0.1 A/dm2 for 600 s. The pulse current was also performed at a typical on-time and off-time （ton=l S and Germ s） with an average current density of 0.05 A/dm2 （la=0.05 A/din2） for 600 s. The obtained hydroxide films were then scraped from the substrates and thermally converted into final oxide product via heat-treatment. Thermal behaviors and phase transformations during the heat treatment of the hydroxide powder samples were investigated by differential scanning calorimetry （DSC） and thermogravimetric analysis （TGA）. The final oxide products were characterized by means of X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR） and scanning electron microscopy （SEM）. The results showed that the well-crystallized Y203 with brainand sphere-like morphology were achievable via pulse and direct deposition modes, respectively. It was concluded that pulse current cathodic electrodeposition offered a facile route for preparation ofnanostructured Y203.
基金financially supported by National Natural Science Foundation of China (No. 50875144)
文摘The pH value and viscosity of Y2O3-SiO2 （Y-Si） slurry made by Y2O3 powders and silica sol for the face coat of Ti-6Al-4V investment casting were measured. The thermal behavior of the shell made by the Y-Si face coat system was investigated by differential scanning calorimeter （DSC）, thermal gravimetric （TG） analysis combined with mass spectrometry （MS）, and the phase transformations were determined by X-ray diffraction （XRD）. Hot strength, residual strength, linear expansion coefficient, and wearing resistance performance of the shell were also tested. The microstructure and elements distri- bution of the interaction layer were studied by scanning electron microscope （SEM） and energy-dispersive spectrometer （EDS）, respectively. The microhardness tester was applied for the microhardness. The results showed that the slurry was stable for at least 60 h. A very small amount of YZrO3 was formed below 1050℃ and Y2SiO5 was formed around 1450℃. The shell made by Y-Si system had good mechanical property which could reduce cracks during the procedure of dewaxing and inclusions during pouring. Some Al volatilized from the melt, permeated the surface of the face coat shell, and formed the black reaction layer, which blocked the permeation of O so that O penetration was limited to 5μm. The depth of Si penetration was about 60 μm. The hard layer was also around 60 μm.
