Separation and Manipulation of Rare-earth Oxide Particles by Dielectrophoresis

A challenge in chemical engineering is the separation and purification of rare-earth elements and their compounds. We report the design and manufacture of a dielectrophoresis(DEP) microchip of microelectrode arrays. This microchip device is constructed in order to use DEP to capture micro-particles of rare-earth oxides in petro-leum. Dielectrophoretic behavior of micro-particles of rare-earth oxides in oil media is explored. The dielectropho-retic effects of particles under different conditions are investigated. It is showed that the prepared microchip is suit-able for use in the investigation of dielectrophoretic responses of the rare-earth oxides in oil media. The factors such as frequency,particle size and valence of rare-earth metal are discussed. When the frequency is fixed,the transla-tion voltage decreases as particle size increases. Lower frequencies are more effective for manipulation of inorganic particles in oil media. Particles of the same rare-earth oxide with different size,as well as particles of different rare-earth oxides,are captured in different regions of the field by regulating DEP conditions. This may be a new method for separation and purification of particles of different rare-earth oxides,as well as classification of particles with different size.

Preparation of Light-Emitting Ytterbium-Doped Tantalum-Oxide Thin Films Using a Simple Co-Sputtering Method

Light-emitting ytterbium-doped tantalum-oxide thin films were prepared using a simple co-sputtering method for the first time. Sharp photoluminescence peaks having a wavelength of around 980 nm were observed from films annealed from 700&degC to 1000&degC for 10 to 40 min. The strongest intensity of the 980-nm peak was obtained from a film deposited using three ytterbium-oxide pellets and annealed at 800&degC for 20 min. Such rare-earth doped tantalum-oxide sputtered films can be used as high-refractive-index materials of autocloned photonic crystals that can be applied to novel light-emitting devices, and they will also be used as both anti-reflection and down-conversion layers for realizing high-efficiency silicon solar cells.

Effects of Additives on the Microstructure and Tribology Performance of Ta-12W Alloy Micro-Arc Oxidation Coating

Oxide ceramic coatings were fabricated on tantalum alloys by micro-arc oxidation (MAO) to improve their hardness and tribological properties. The MAO coatings were manufactured in a mixed silicatephosphate electrolyte containing NaF and/or EDTA (ethylene diamine tetraacetic acid). The surface morphology,cross-sectional view, chemical composition, hardness, and wear performance of the coatings were analysed. As revealed by the scanning electron microscopy, silica-rich nodules appear on the MAO coating obtained in the silicate-phosphate electrolyte, but the formation of nodules is inhibited with NaF and/or EDTA in the electrolyte.Also, they reduce the roughness and improve the compactness of the coatings, which are composed of Ta_(2)O_(5),(Ta, O), and TaO. A thick and hard coating is obtained in the NaF-containing electrolyte, and the tribology performance is effectively improved. With additives, the nodule structure is detached from the coating surface and dissolved in the electrolyte. By using NaF as an electrolyte additive, the abrasion performance of the MAO coating is enhanced by decreasing the nodule structure, increasing the size of micropores, and improving the coating hardness.

Tunable structural color of anodic tantalum oxide films

Tantalum （Ta） oxide flhns with tunable structural color were fabricated easily using anodic oxidation. The structure, components, and surface valence states of the oxide films were investigated by using gazing incidence X-ray diffractometry, X-ray photoelectron microscopy, and surface analytical techniques. Their thickness and optical properties were studied by using spectroscopic ellipsometry and total reflectance spectrum. Color was accurately defined using L＊a＊b＊ scale. The thickness of compact Ta2O5 films was linearly dependent on anodizing voltage. The film color was tunable by adjusting the anodic voltage. The difference in color appearance resulted from the interference behavior between the interfaces of air-oxide and oxide metal.

Synthesis and X-Ray Diffraction Study of All Rare-Earth Series Oxides REE_2Ti_2O_7

The pyrochlore supergroup natural minerals are the oxides for formula A2-xB2O7. In this formula, A typically is Ca, Na, TR, Ba, Fe and Mn cation. B is Ta, Ti, Nb, W, Sb. The pyrochlore supergroup is divided into five groups basis of the atomic proportions of the B-site atoms Nb, Ta, Sb, Ti, and W. They are pyrochlore, microlite, roméite, betafite, and elsmoreite, respectively. Some of these minerals containing rare-earth elements species or synthetic oxides have important applications in materials, as for optical materials, light catalyst materials, magnetoelectric materials and radioactive waste treatment etc.

Photoluminescence Properties of Europium and Cerium Co-Doped Tantalum-Oxide Thin Films Prepared Using Co-Sputtering Method

We fabricated europium and cerium co-doped tantalum (V) oxide (Ta2O5: Eu, Ce) thin films using our co-sputtering method for the first time, and evaluated photoluminescence (PL) properties of the films after annealing at 600°C - 1100°C for 20 min. Four remarkable PL peaks at wavelengths of 600, 620, 700, and 705 nm were observed from the film annealed at 900°C. The intensities of the 700- and 705-nm peaks due to the 5D0 → 7F4 transition of Eu3+ were much stronger than those of the 600-nm (5D0 → 7F1) and 620-nm (5D0 → 7F2) peaks of the film annealed at 900°C. It seems that energy transfer from Ce3+ to Eu3+ occurs in the film, and much energy is selectively used for the 5D0 →7F4 and 5D0 →?7F1?transitions. Such a Ta2O5: Eu, Ce co-sputtered thin film seems to be used as a multi-functional coating film having both anti-reflection and down-conversion effects for realizing a high-efficiency silicon solar cell.

Photoluminescence and X-Ray Diffraction Properties of Europium and Silver Co-Doped Tantalum-Oxide Thin Films Deposited by Co-Sputtering

We fabricated europium and silver co-doped tantalum-oxide (Ta2O5:Eu, Ag) thin films using a simple co-sputtering method for the first time, and we evaluated their photoluminescence (PL) and X-ray diffraction (XRD) properties. We found that the most remarkable PL peak at a wavelength of 615 nm due to Eu3+ can be enhanced by Ag doping, and the strongest PL peak can be obtained from a Ta2O5:Eu, Ag thin film after annealing at 1000℃. Based on XRD measurements, we found that Ag2Ta8O21 crystalline phases produced by Ag doping are very important and Eu3TaO7 phases should be avoided in order to enhance the objective PL peak from our Ta2O5:Eu, Ag thin films.

High Performance Silicon Nitride-based Composite Materials with Rare-earth Oxides Additives

In the present paper,a silicon nitride-based composite processed with rare-earth oxidesadditives is presented.Its bend strength can be maintained at a value as high as 1000 MPafrom 1000 to 1370℃ and the fracture toughness measures 9-10 MPa·m1/2.The static fa-tigue behavior at 1370℃ of this material is also encouraging.Besides,two another α′/β′sialon composites doped with rare-earth oxides are also described.The effects of processingparameters on the microstructure and the properties of the materials are discussed in somedetails.

Enhancement of electrochemical performance in lithium-ion battery via tantalum oxide coated nickel-rich cathode materials

Nickel-rich cathode materials are increasingly being applied in commercial lithium-ion batteries to realize higher specific capacity as well as improved energy density.However,low structural stability and rapid capacity decay at high voltage and temperature hinder their rapid large-scale application.Herein,a wet chemical method followed by a post-annealing process is utilized to realize the surface coating of tantalum oxide on LiNi_(0.88)Mn_(0.03)Co_(0.09)O_(2),and the electrochemical performance is improved.The modified Li Ni_(0.88)Mn_(0.03)Co_(0.09)O_(2)displays an initial discharge capacity of~233 m Ah/g at0.1 C and 174 m Ah/g at 1 C after 150 cycles in the voltage range of 3.0 V–4.4 V at 45℃,and it also exhibits an enhanced rate capability with 118 m Ah/g at 5 C.The excellent performance is due to the introduction of tantalum oxide as a stable and functional layer to protect the surface of LiNi_(0.88)Mn_(0.03)Co_(0.09)O_(2),and the surface side reactions and cation mixing are suppressed at the same time without hampering the charge transfer kinetics.

Photoluminescence Properties of Thulium and Cerium Co-Doped Tantalum-Oxide Films Prepared by Radio-Frequency Co-Sputtering

We prepared thulium and cerium co-doped tantalum-oxide (Ta2O5 :Tm, Ce) thin films by radiofrequency co-sputtering of Tm2O3 and CeO2 pellets on a Ta2O5 disc for the first time, and photoluminescence (PL) properties of the films annealed at 700°C, 800°C, 900°C, or 1000°C for 20 min were evaluated. PL peaks around a wavelength of 800 nm due to Tm3+?were observed for films annealed at 900°C or 1000°C. The peak intensities of films prepared using one Tm2O3 pellet and one CeO2 pellet were much stronger than those of films prepared using one Tm2O3 pellet and two CeO2 pellets or films prepared using two Tm2O3 pellets and one CeO2 pellet. To obtain the strongest PL intensity from the film, the proper Tm concentration was estimated to be around 1.0 mol%, and the proper Ce concentration was estimated to be around 1.3 mol%. Such Ta2O5:Tm, Ce co-sputtered thin films can be used as high-refractive-index materials of autocloned photonic crystals that can be applied to novel light-emitting devices, and they will also be used as anti-reflection and downconversion layers for realizing high-efficiency silicon solar cells.

Fabrication of Erbium and Ytterbium Co-Doped Tantalum-Oxide Thin Films Using Radio-Frequency Co-Sputtering

An erbium and ytterbium co-doped tantalum-oxide (Ta2 O5:Er, Yb) thin film was fabricated using a simple co-sputtering method for the first time, and its photoluminescence (PL) spectrum was evaluated. Energy transfers between Er3+ and Yb3+ in the Ta2 O5:Er, Yb co-sputtered thin film were discussed by comparing between PL spectra of the Ta2 O5:Er, Yb film and Ta2 O5:Er or Ta2 O5:Yb films reported in our previous works. Such a Ta2 O5:Er, Yb co-sputtered film can be used as a high-refractive- index and light-emitting material of a multilayered photonic crystal that can be applied to a novel light-emitting device, and it will also be used as a multi-functional coating film having both anti-reflection and down-conversion effects for realizing a high-efficiency silicon solar cell.

Observation of Violet-Light Emission Band for Thulium-Doped Tantalum-Oxide Films Produced by Co-Sputtering

We prepared thulium-doped tantalum (V) oxide (Ta2O5:Tm) thin films using co-sputtering of two Tm2O3 pellets and a Ta2O5 disc, and we observed photoluminescence (PL) peaks not only around a wavelength of 800 nm due to the 3H4→3H6 transition of Tm3+ but also around a wavelength of 400 nm (violet) from the films after annealing for the first time. Comparatively narrow PL peaks around the wavelength of 400 nm were observed from the films annealed at 800°C and 900°C for 20 min. The peak intensity from the film annealed at 900°C was approximately four-times stronger than that from the film annealed at 800°C. The origin of the 400-nm peaks seems to be the same as our non-doped Ta2O5 thin films deposited using radio-frequency sputtering because we observe PL peaks around 400 - 430 nm from the Ta2O5 films. Such a Ta2O5:Tm co-sputtered thin film seems to be used as a multi-functional coating film having both anti-reflection and down-conversion effects for realizing a high-efficiency silicon solar cell.

Improvement of the light output and contact resistance of InGaN-based light-emitting diodes based on tantalum-doped indium tin oxide as p-type electrodes

This paper reports that highly transparent and low resistance tantalum-doped indium tin oxide （Ta-doped ITO） films contacted to p-type GaN have been prepared by the electron-beam evaporation technique. The Ta-doped ITO contacts become Ohmic with a specific contact resistance of $／sim 5.65／times 10^{ - 5}$$／Omega ／cdot$cm$^{2}$ and show the transmittance of $／sim $98% at a wavelength of 440nm when annealed at 500／du. Blue light emitting diodes （LEDs） fabricated with Ta-doped ITO p-type Ohmic contact layers give a forward-bias voltage of 3.21V at an injection current of 20mA. It further shows that the output power of LEDs with Ta-doped ITO contacts is enhanced 62% at 20mA in comparison with that of LEDs with conventional Ni/Au contacts

Effect of REs(Y,Nd)addition on high temperature oxidation kinetics,oxide layer characteristic and activation energy of AZ80 alloy

The oxidation behaviors of AZ80,AZ8O-0.32 Y and AZ8O-0.38 Nd(wt.%)alloys were researched at 413℃,420℃,427v and 433℃for up to 6 h in air environment via a high precision analytical balance,a laser confocal microscope,differential scanning calorimeter(DSC)analysis,X-ray diffraction(XRD)analysis,scanning electron microscope(SEM)observation,and X-ray photoelectron spectroscopy(XPS)analysis.The results show that the weight gain and oxidation rate of AZ80 are reduced significantly,the initiation form and propagation of cracks in oxide layer are changed.Compact and protective oxide layer forms on alloy surface with Y or Nd addition.And the activation energies of AZ80,AZ80-0.32Y and AZ8O-0.38Nd alloys calculated via Arrhenius equation are 82.556 kJ/mol,177.148kJ/mol and 136.738 kJ/mol,respectively.

Kinetic mechanism of anodic oxidation of tantalum in nitrate melts

The data of anodic oxidation of tantalum in high temperature nitrate melts were regressed according to 41 kinds of probable kinetic mechanism. The results show that the process follows the parabolic law α 2= kt , which means that the process of anodic oxidation of tantalum is limited by the movement of positive vacancies of tantalum ions. The voltage has an effect on the rate constant in prior period, which implies that the electromigration exists at the beginning of film growth. The breakdown of films exists in whole process. The films obtained are composed of orthorhombic β Ta 2O 5 and TaO y .[

Dehydration of sugars to 5-hydroxymethylfurfural and non-stoichiometric formic and levulinic acids over mesoporous Ta and Ta-W oxide solid acid catalysts

A series of mesoporous Ta and Ta-W oxides have been prepared and employed as solid acid catalysts for the dehydration of fructose and glucose to 5-hydroxymethylfurfural(HMF).Solid state 31 P MAS NMR spectroscopic results using trimethylphosphine(TMP)as a probe molecule show that the acid strength and the ratio of Br?nsted to Lewis acid sites increase gradually with the addition of tungsten in tantalum oxide.It is found that high sugar conversion and HMF selectivity are achieved over catalyst with relatively high ratios of Br?nsted to Lewis acid sites.Unexpected stoichiometric excess of formic acid relative to levulinic acid can be observed mainly because of direct decomposition of fructose over Lewis acid sites.The addition of 2-butanol leads to the increase of sugars conversion and the HMF selectivity,especially for the catalyst with high ratio of Br?nsted to Lewis acid sites.Among them,Ta7W3 oxide catalyst shows 54%HMF selectivity and good reusability with the addition of 2-butanol by extracting HMF from aqueous phase and removing humins deposed on the surface of the catalyst.

Sm_(2)Y_(1-x)Al_(x)TaO_(7)陶瓷材料的热物理性能

以高纯度Al_(2)O_(3)、Y_(2)O_(3)、Sm_(2)O_(3)和Ta_(2)O_(5)为原材料,采用高温烧结方法制备了Sm_(2)Y_(1-x)Al_(x)TaO_(7)系列陶瓷材料,对其晶体结构、显微组织、元素组成、热导率和热膨胀性能进行了系统研究。结果表明,除Sm_(2)Y_(0.5)Al_(0.5)TaO_(7)具有焦绿石结构之外,其余三种氧化物均具有单一的萤石晶体结构。其块体材料相对致密度均在90%以上,晶界清晰,各元素摩尔比与其化学式基本一致。由于Al^(3+)和Y^(3+)之间较大的离子半径和原子量差别,增大了对声子的散射,其热传导性能随着Al_(2)O_(3)含量的增加而降低。虽然Al_(2)O_(3)含量增加降低了其热膨胀系数,其大小与YSZ基本相当,所制备陶瓷在室温至1400℃范围内具有良好的相稳定性能。

Ta/Ta_(2)O_(5)/Cu结构制备及应用性能研究

介绍了以Ta/Ta_(2)O_(5)/Cu为结构的平板MIM电容器的制备方法和性能测试,探究金属Cu直接作为钽电解电容器阴极层的可行性。通过阳极氧化法在钽箔表面制备非晶态的Ta_(2)O_(5)薄膜,以化学镀铜、磁控溅射镀铜两种镀铜工艺制备Ta/Ta_(2)O_(5)/Cu结构,并对所得结构进行结构表征和性能测试。实验结果表明:不同镀铜方式制备的Ta/Ta_(2)O_(5)/Cu结构在电学性能测试过程中都没有表现出电容特性,正负极之间的电阻仅有0.7Ω;以金属Cu直接作为钽电容器的阴极层会导致金属铜在测试过程中被氧化成铜离子从而进入Ta_(2)O_(5)介质层中,进而导致Ta_(2)O_(5)的击穿,因此金属铜不适合直接作为钽电容的阴极层。

Temperature-sensing array using the metal-to-insulator transition of Nd_(x)Sm_(1-x)NiO_(3)

Rare-earth nickelates(RENiO_(3))show widely tunable metal-to-insulator transition(MIT)properties with ignorable variations in lattice constants and small latent heat across the critical temperature(TMIT).Particularly,it is worth noting that compared with the more commonly investigated vanadium oxides,the MIT of RENiO_(3)is less abrupt but usually across a wider range of temperatures.This sheds light on their alternative applications as negative temperature coefficient resistance(NTCR)thermistors with high sensitivity compared with the current NTCR thermistors,other than their expected use as critical temperature resistance thermistors.In this work,we demonstrate the NTCR thermistor functionality for using the adjustable MIT of Nd_(x)Sm_(1-x)NiO_(3)within 200–400 K,which displays larger magnitudes of NTCR(e.g.,more than 7%/K)that is unattainable in traditional NTCR thermistor materials.The temperature dependence of resistance(R–T)shows sharp variation during the MIT of Nd_(x)Sm_(1-x)NiO_(3)with no hysteresis via decreasing the Nd content(e.g.,x≤0.8),and such a R–T tendency can be linearized by introducing an optimum parallel resistor.The sensitive range of temperature can be further extended to 210–360 K by combining a series of Nd_(x)Sm_(1-x)NiO_(3)with eight rare-earth co-occupation ratios as an array,with a high magnitude of NTCR(e.g.,7%–14%/K)covering the entire range of temperatures.

Effect of Ta_(2)O_(5)nanoparticles on bioactivity,composition,structure,in vitro and in vivo behavior of PEO coatings on Mg-alloy

The present study investigates the physical and chemical characteristics,behavior in vitro and in vivo,and biocompatibility of coatings containing Ta_(2)O_(5),which are obtained by plasma electrolytic oxidation(PEO)on MA8 magnesium alloy.The obtained coatings demonstrate in vivo biocompatibility and in vitro bioactivity.Compared to the base PEO coating,the layers containing Ta_(2)O_(5)facilitate the development of apatite in simulated body fluid,suggesting that the inclusion of nanoparticles improves bioactivity of the coatings.It was found that incorporation of Ta_(2)O_(5)nanoparticles increases roughness and porosity of the formed layers by increasing particle concentration in electrolytes for the PEO process contributing to sufficient soft tissue ingrowth in vivo.Based on in vivo studies,these coatings also provide favorable tissue response and minimal inflammatory reaction in comparison with the bare magnesium alloy due to protection of living tissues from deleterious corrosion events of magnesium implant such as local alkalization and intense hydrogen evolution.The results obtained in the present study concluded biocompatibility,tissue integration of the PEO coatings containing Ta_(2)O_(5)nanoparticles making them a promising protective layer for biodegradable magnesium implants.