Er Particles Research Articles

A novel coarse-grained modeling and simulation for microstructure and shear evolution of induced dipole dominant electrorheological fluid

Induced dipole dominant electrorheological fluid (ID-ERF) is a new type of ERF. After high energy ball milling (HEBM) process, dielectric particles produce a large number of oxygen vacancies, and the dipoles formed by the polarization of these oxygen vacancies provide excellent ER properties. ID-ERF has the advantages of high shear stress, low current density, long service life, anti-sedimentation, simple preparation method, etc. It should be a new generation of ERF material suitable for practical application. In this work, facing at the shortcomings of traditional particle MD simulation of ERF system, a coarse-grained molecular dynamics (CGMD) model is constructed. The evolution of ID-ERF is simulated under the conditions of no electric field and 5 kV/mm electric field. Proves that there is an adsorption layer of carrier liquid on the surface of ER particles, and shows BCT lattice arrangement under electric field. The sinusoidal shear strain is applied to the model, and calculate the variation of strain amplitude, loss factor, storage modulus and loss modulus. In addition, we prepared ID-ERF and tested its performance to compare with the simulation results.

A highly homogeneous electrorheological fluid with potential applications in optics

A new type of electrorheological fluid (ERF) with high ER efficiency, low zero-field viscosity and high uniformity was synthesized by a hydrolysis method, based on modified titanium and succinic acid. The electro-responsive performance of ERF under electric field 0–3 kV mm−1 were studied in detail. In addition to traditional research methods to explore the morphology of the ER particles, we also utilized optical diffraction imaging to study the uniformity of the chain-like structure formed by the ER particles. Due to the relatively uniform size, the particles aggregate into a periodic spatial modulation structure parallel to the electric field direction and similar to a grating on the macroscopic scale, which can further manufacture liquid controllable gratings. The observed diffraction spots, up to six levels, indicate the ERFs have potential applications in the field of optics.

Upconversion Luminescence Response of a Single YVO4:Yb, Er Particle.

We present the results of the luminescence response studies of a single YVO4:Yb, Er particle of 1-µm size. Yttrium vanadate nanoparticles are well-known for their low sensitivity to surface quenchers in water solutions which makes them of special interest for biological applications. First, YVO4:Yb, Er nanoparticles (in the size range from 0.05 µm up to 2 µm), using the hydrothermal method, were synthesized. Nanoparticles deposited and dried on a glass surface exhibited bright green upconversion luminescence. By means of an atomic-force microscope, a 60 × 60 µm2 square of a glass surface was cleaned from any noticeable contaminants (more than 10 nm in size) and a single particle of 1-µm size was selected and placed in the middle. Confocal microscopy revealed a significant difference between the collective luminescent response of an ensemble of synthesized nanoparticles (in the form of a dry powder) and that of a single particle. In particular, a pronounced polarization of the upconversion luminescence from a single particle was observed. Luminescence dependences on the laser power are quite different for the single particle and the large ensemble of nanoparticles as well. These facts attest to the notion that upconversion properties of single particles are highly individual. This implies that to use an upconversion particle as a single sensor of the local parameters of a medium, the additional studying and calibration of its individual photophysical properties are essential.

Microstructure, superplasticity, and mechanical properties of Al–Mg–Er–Zr alloys

Minor additions of rare-earth elements improve the mechanical properties of aluminum-based alloys due to precipitation strengthening, increased recrystallization resistance, and grain refinement effects. This study investigated the microstructure, room temperature mechanical properties, and superplasticity of Al–Mg–Z–Er alloys with the Mg content in a range of 2.1–4.9 wt%. The alloys' microstructure was presented by an Al-based solid solution matrix enriched with Mg, the (Al,Mg) 3 Er phase of solidification origin, and nanoscale secondary precipitates of the Al 3 (Er,Zr) L1 2 –structured phase. The Al 3 (Er,Zr) precipitates provided the Orowan strengthening mechanism, led to a strong recrystallization resistance and the Zener pinning effect during elevated temperature deformation. An increase of the Mg solute resulted in a solid solution strengthening and facilitated dynamic recrystallization at elevated temperatures. In the alloy with 4.9%Mg, a combined effect of fine L1 2 precipitates, high solute Mg, and (Al,Mg) 3 Er particles led to a fine-grained structure formation and superplasticity with the maximum strain rate sensitivity m of 0.51 and the elongation-to-failure of 550–600% at the constant strain rates of (0.8–1) × 10 −2 s −1 . The mechanical properties at room temperature were studied after the post-deformation annealing of the thermomechanically treated alloys and after the superplastic deformation. The developed Arrhenius-type mathematical model of superplastic deformation behavior showed excellent predictability for the studied alloys with different solute Mg. • Microstructure and tensile properties for thermomechanical-treated Al–Mg–Er–Zr alloys were studied. • A L1 2 -Al 3 (Er,Zr) precipitates parameters were studied after annealing of as-cast and rolled samples. • Increase in Mg solute improved solid solution strengthening and superplastic properties. • Model with excellent predictability of the superplastic deformation behavior was developed.

Upconversion Nanocrystals with High Lanthanide Content: Luminescence Loss by Energy Migration versus Luminescence Enhancement by Increased NIR Absorption

AbstractLanthanide‐doped upconversion nanoparticles (UCNPs) have attracted a lot of interest due to their benefits in biological applications: They are not suffering from intermittence and provide nearly background‐free luminescence. The progress in synthesis nowadays enables access to complex core‐shell particles of controlled size and composition. Nevertheless, the frequently used doping ratio dates back to where mostly core‐only particles of relatively large size have been studied. Especially at low power excitation as needed in biology, a decrease in particle size leads to a drastic decrease in the upconversion efficiency. An enhancement strategy based on an increased absorption rate of near‐infrared light provided by an increase of the sensitizer content, together with the simultaneous blocking of the energy migration pathways to the particle surface, is presented. NaYbF4(20%Er) particles of 8.5 nm diameter equipped with an about 2 nm thick NaYF4 shell show significantly enhanced upconversion luminescence in the red (660 nm) compared to the most commonly used particles with only 20% Yb3+ and 2% Er3+. The impact of size, composition, and core‐shell architecture on photophysical properties are studied. The findings demonstrate that an increase in doping rates enables the design of small, bright UCNPs useful for biological applications.

Influence of erbium addition on the defects of selective laser-melted 7075 aluminium alloy

ABSTRACT Selective laser-melted (SLMed) 7075 aluminium alloy is prone to cracking. Erbium (Er) could modify the aluminium alloys to prevent cracking in traditional manufacturing processes. In the present study, Er-modified 7075 aluminium alloy powders are prepared to investigate the influence of Er element on crack reduction in SLM. The evolution of Er is characterised by a scanning electron microscope (SEM), a X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM). The results show that the crack density is reduced with Er addition, but the porosity increases, a new discovery. Based on the SEM and TEM results, Er addition exists in the form of unmelted particles and Al3Er of sub-micrometer scale. The Er particles in the molten pool deteriorate the fluidity and result in higher porosity. The coherency between aluminium matrix and Al3Er favours the grain refinement, therefore the crack reduction.

Designing particle size of aminated polyacrylonitrile spheres to enhance electrorheological performances of their suspensions

The influence of particle size and functional group as one of the pivots for particle interaction that enhances electrorheological performance were studied by varying the particles to micron and nanometer-sized polyacrylonitrile (PAN) spheres for rheological comparability analysis. Emulsion polymerization and catalytic amination with diethylene triamine (DETA) were used to successfully synthesize ER particle samples and then dispersed in silicon oil for suspension analysis. Micron-sized particles presented a large surface electron density for high conversion of nitrile groups with DETA than in nano. Polar groups from DETA improved particle polarization which enhanced ER effect by increasing yield strength by more than 10 folds on raw PANs. However, small sized nano particle exhibited relatively reduced ER effect owing to aggregation by Brownian motion pronouncing aminated micro PAN with the best ER activity followed by the aminated nano PAN, micro PAN and nano PAN as follows.

3D - Multi Phase-Field Simulation of Stress, Strain, and Concentration Field Due to Al 3X (X = Sc, Zr, Er) Particle Growth in Al Matrix

3D - Multi Phase-Field Simulation of Stress, Strain, and Concentration Field Due to Al ₃X (X = Sc, Zr, Er) Particle Growth in Al Matrix

Particle source and radial electric field shear as the factors affecting the LH-transition possibility and dynamics in a tokamak

Numerous theoretical and experimental studies have proved the important role of radial electric field inhomogeneity, or shear, in LH-transition initiation, and established heating power threshold for transition, although some experiments provide the observation of LH-transition dependency on particle source. It is necessary to apply a concerted approach to describe LH-transition initiation possibility and dynamics, considering Er shear, particle source and turbulence properties as the main factors responsible for LH-transition initiation.

Construction of a novel pitaya-like CsxWO3@NaYF4:Yb, Er particles with simultaneous colour tuning and upconversion luminescence enhancement

In order to further improve the luminescence of NaYF4:Yb,Er, we successfully constructed pitaya-like Cs0·3WO3@NaYF4:Yb, Er particles, in which Cs0·3WO3 particles were encapsulated in NaYF4:Yb, Er particles. This structure enhanced the intensity of 407, 527, 542 and 657 nm emission peaks by 10.1, 5.9, 5.5 and 1.8 times, respectively. Through calculated, the Commission Internationale de l’Eclairage (CIE) chromaticity coordinates changed from (0.28, 0.71) to (0.25, 0.73), indicating that the emission colour was tuned from yellow to green. The construction mechanism of this structure and the mechanism of upconversion (UC) luminescence enhancement were discussed. By studying the different luminescence mechanisms of NaYF4:Yb, Er excited by 1550 and 980 nm laser, we found that the UC luminescence enhancement and colour tuning of NaYF4:Yb, Er were due to the localized surface plasmon resonance (LSPR) effect of Cs0·3WO3, which can absorb more excited photons and transfer them to the Er3+ ion 4I11/2 level. Given that the transition process of green light emission is easier than red light emission, the redundant photons are more inclined to achieve emitting green light and show UC luminescence enhancement and emission colour tuning. Overall, the as-prepared novel pitaya-like Cs0·3WO3@NaYF4:Yb, Er particles exhibit strong UC luminescence enhancement and colour tuning, thus having great application prospect in the field of luminescent displays.

Effect of non-axisymmetric perturbations on the ambipolar Er and neoclassical particle flux inside the ITER pedestal region

The transport dynamics of impurities in the pedestal region of ITER plasmas is of crucial interest since this regulates the penetration of impurities from the edge into the core plasma, where an excessive accumulation of impurities can degrade their fusion performance. In the pedestal region of H-mode tokamak plasmas, anomalous transport is highly reduced and impurity transport is found to be well described by the neoclassical theory. Under these conditions, perturbations to the axisymmetric tokamak geometry can strongly affect both the radial electric field and particle transport. In this work, we describe the results of numerical studies performed to quantify the effects on the pedestal ambipolar electric field and radial particle fluxes of the non-axisymmetric fields, associated with both the intrinsic toroidal field ripple and extrinsic fields applied for ELM control, for ITER Q = 10 plasma conditions with emphasis on high Z impurity transport. It is found that the effect of the ITER toroidal field ripple on high Z impurity transport is negligible. On the contrary, extrinsic three-dimensional fields applied for ELM control cause a strong modification of the pedestal ambipolar electric (to less negative values) and the appearance of multi-valued solutions for the pedestal electric field, analogue to core stellarator transport significantly increasing the outward character of neoclassical pedestal transport for both the main plasma ions (D and T in ITER) and high Z impurities, suggesting a strong modification of the background plasma profiles. Finally, it is found that for the Z impurity, its quantitative evaluation has uncertainties (with important implications for the radial flow direction) associated with the high poloidal Mach number ~ 1, due to the high pedestal electric field and large ion mass, which renders the first order neoclassical theory questionable. Detailed ITER MHD 3D equilibria and a benchmark of SFINCS against NEO and NCLASS codes has also been obtained.

Dependence of the luminescent properties of thermostabilized upconversion NaYF4:Yb, Er particles on the excitation power and temperature

The excitation power dependence of upconversion luminescence intensity and temperature sensing characteristics are investigated in the NaYF4 : Er3 + , Yb3 + @ SiO2 particles synthesized in-house using a hydrothermal method. The effect of laser-induced heating of the upconversion particles is shown, which introduces distortions in the measured power and temperature dependences of the upconversion luminescence. We propose a technique for calibrating the temperature dependence of upconversion particle luminescence, which should improve the accuracy of temperature measurements. The technique is based on the stabilization of upconversion particles temperature, which provides the suppression of laser-induced heating of upconversion particles.

APPLICATION OF OPEN BOUNDARIES WITHIN A TWO-WAY COUPLED SPH MODEL TO SIMULATE NON-LINEAR WAVE-STRUCTURE INTERACTIONS

A two-way coupling between the fully non-linear potential flow (FNPF) solver OceanWave3D and the Smoothed Particle Hydrodynamics (SPH) solver DualSPHysics is presented. At the coupling interfaces within the SPH domain, an open boundary formulation is applied. An inlet and outlet zone are filled with bu er particles. At the inlet, horizontal orbital velocities and surface elevations calculated with OceanWave3D are imposed on the bu er particles. At the outlet, horizontal orbital velocities are imposed, but the surface elevation is extrapolated from the fluid domain. Velocity corrections are applied to avoid unwanted reflections in the fluid domain. The SPH surface elevation can be coupled back to OceanWave3D, where the original solution is overwritten. The coupling methodology is validated using a 2-D test case of a floating box. Additionally, a 3-D proof of concept is shown where overtopping waves are acting on a heaving cylinder. The 2-way coupled model proofs to be capable of simulating wave propagation and wave-structure interaction problems with an acceptable accuracy with RMSE values remaining below the smoothing length h.

Enhanced Upconversion Luminescence of Metal-Capped NaGd0.3 Yb0.7 F4:Er Submicrometer Particles.

Metallic nanostructures are often used to enhance photoluminescence of nanomaterials based on local field enhancement with plasmons at metal surfaces. Here upconversion luminescence (UCL) enhancement of submicrometer-size NaGd0.3 Yb0.7 F4 :Er particles in cap-like metal cavities, formed by deposition of a silver film on the particles dispersed on glass substrates, is studied. UCL of the particles is shown to be influenced by not only the plasmon-enhanced local field but also the cavity modes. By varying the cavity size and location of the particles in the cavities, fluctuant variations of the UCL enhancement and electronic depopulation rate are observed in experiments. Typically, a maximum of 12-fold enhancement of the UCL intensity is obtained. Combining the results with numerical simulations, the phenomenon is ascribed to effects of metal quenching, plasmonic field enhancement, and the cavity modes for the excitation and emission photons. Finally it is verified that, for the cap-like submicrometer metal cavities, allocating the particles at the open mouths of the cavities is more advantageous to obtaining stronger enhancements of the particles' UCL. And the demonstrated structure is also convenient to fabricate for applications, e.g., in solar cells.

Effect of Er on Microstructure and Hardness of Al-Zn-In Alloy

A new sacrificial Al-5Zn-0.03In-Er alloy was developed with improved microstructure consisting of Er rich phase and refined α-Al. This paper focused on the influence of Er as alloying element on the microstructure and hardness of Al-5Zn-0.03In alloy. With the increase of Er content, the α-Al was refined and the hardness was improved, at the same time a amount of Er rich phases and particles also appeared. The segregation of Er in the front of the solidification interface results in the refining of α-Al. The higher hardness of the Er containing alloy make it possilbe to apply the alloy under a complicated enviorment where the mechanical property is requred. It is concluded that 4 wt% Er is optimum to obtain the refined microstructure and proper hardness.

Microstructure and mechanical properties of ZK60-Er magnesium alloys

The effects of Er addition on the microstructure and mechanical properties of ZK60 alloy were investigated. Cast ZK60-Er (0, 0.5, 1, 2 and 4wt%) ingots homogenized at 350°C were extruded at 400°C. It was found that Er primarily existed in the form of Mg–Zn–Er intermetallic particles instead of Er-containing α-Mg solid solution. Due to the formation of Mg–Zn–Er particles, the dissolution of Zn solutes in homogenized billets decreased with increasing Er modification. Typical fiber textures along with dynamically precipitated spherical Mg–Zn compounds were developed during the extrusion process. Mg–Zn precipitates gradually decreased with the increasing Er level. Er addition slightly decreased the elongation and scarcely increased the tensile strength of the extruded bars. The extruded alloys with different Er contents shared similar microstructural evolutions in the subsequent heat treatment. No Er-bearing precipitates were found in the heat treated bars. Mechanical strengths decreased but the plasticity increased by increasing the solutionization time from 1.5h to 12h at 400°C. Upon further aging at 200°C for 10h, there was no significant change in the optical microstructure while Mg–Zn compounds statically precipitated. The plasticity could be compensated by the decrease of defects caused by the static precipitation of Mg–Zn compounds.

Nanoparticulate coatings with efficient up-conversion properties.

Nanoparticulate films with high up-conversion emission (UC) properties were prepared by spray-deposition of nanometer-sized YVO4:Yb,Er particles. The optical properties of YVO4:Yb,Er were optimized upon annealing before the film deposition in order to get the highest possible UC signal in the considered type of system. Thanks to a simple model and some time-resolved spectroscopic investigations, the contribution of the scattering to the UC signal could be separated from the intrinsic properties (crystallinity, surface defects) of the material. The films obtained by this technique present the advantages of having both high UC and good transparency.

Synthesis of β-Phase NaYF4:Yb,Er Upconversion Nanocrystals and Nanorods by Hot-Injection of Small Particles of the α-Phase

Abstract β-NaYF4:Yb,Er upconversion nanocrystals are synthesized by a hot-injection method employing purified α-NaYF4:Yb,Er particles with a size of approximately 2–3 nm as single-source precursor. The method allows to prepare either spherical nanoparticles with different sizes or nanorods by simply controlling the addition rate of the solution of α-phase particles and performing the synthesis either in the absence or in the presence of seed particles. The luminescence properties of the different particles are compared also including core-shell particles.

Size-dependent luminescence of spherical Y2O3:Er nanoparticles

Spherical nanocrystalline Y2O3:Er particles differing in composition and size, with a scatter in the range 10–15%, have been prepared through the low-temperature thermolysis of an amorphous precursor. We have studied the luminescence, diffuse reflectance, and photoluminescence excitation spectra of Y2O3:Er nanoparticles differing in shape. The intensity of the visible luminescence bands of erbium-doped yttria has been shown to depend on sphere diameter. The resonance wavelengths of coupled photons have been determined as functions of Y2O3:Er phosphor nanosphere size.

Ostwald-ripening and particle size focussing of sub-10 nm NaYF₄ upconversion nanocrystals.

We have studied the growth behaviour of sub-10 nm NaYF₄ upconversion nanocrystals of the hexagonal β-phase and the cubic α-phase. Ostwald-ripening of such particles in oleic acid/octadecene solvent results in broadening of the particle size distribution if the colloid contains particles of one crystal phase only. Narrow size distributions are formed only if β-phase particles grow in the presence of an excess of α-phase particles. Such binary mixtures of α-phase and β-phase particles form intrinsically when colloids of α-phase particles are heated for a sufficiently long time, because seeds of the β-phase nucleate in the solution after some time at high temperatures. Since the number of seeds determines the final size of the β-phase product, control of the nucleation is crucial for controlling the final particle size. We show that the number of β-phase seeds strongly depends on the composition of the α-phase known to form solid solutions Na₁-xYF₄-x in the range from x = 0 to x = 4/9. Sodium-deficient α-phase particles form a negligible number of β-phase seeds whereas α-phase particles with high sodium content yield a very large number of seeds. By taking advantage of this dependence and modifying the synthesis of the α-phase particles accordingly, small phase-pure β-NaYF₄:Yb,Er particles with a size smaller than 6 nm can be prepared in oleic acid/octadecene just as well as much larger particles.