Ce Particles Research Articles

Simultaneous high tensile strength and high ductility in cast Ce-alloyed Ti

Addition of ∼3 wt% Ce to cast pure Ti induced formation of numerous fine Ce particles on the microstructure. The Ce-alloyed cast Ti had both high tensile strength and ductility, which are unattainable simultaneously in cast pure Ti. The mechanisms by which the Ce particles increased tensile properties were identified.

Effect of addition of Ce and accumulative roll bonding on structure-property of the Mg-Ce-Al hybrid composite and its prediction and comparison using artificial neural network (ANN) approach

Abstract Light alloys play a crucial role in realizing the national strategy for energy conservation and emission reduction, as well as promoting the upgrading of manufacturing industries. Mg/Al composite laminates combine the corrosion resistance and ductility of aluminium alloy with the lightweight characteristics of magnesium alloy. The addition of Ce (rare earth elements) can improve the mechanical properties of magnesium via grain refinement and improve the ductility of the hybrid composites. In the present work, an investigation on addition of Ce into the Mg/Al matrix through Accumulative Roll Bonding (ARB) has been presented. The Mg/Ce/Al hybrid composite consists of Mg-4%Zn alloy and Al 1100 alloy with 0.2% Ce particles added between the dissimilar layers. The changes occurred in the evaluation of microstructure, corrosion and mechanical properties of the Mg/Ce/Al hybrid composite as a result of deformation process and also the addition of Ce have been explicated. The ARB parameters: temperature, rolling speed, percentage reduction, and aging time, have been studied. An increase of about 2.36 times in strength and hardness of the hybrid composite, has been reported. Further, the structure–property relations in the Mg/Ce/Al hybrid composites were aslo predict and compare using machine learning models: Decision Tree and Multi-Layer Perceptron (MLP) models.

Diamond seed dependent luminescence properties of CVD diamond composite

Diamond-based X-ray luminescent composites are robust materials to be used in synchrotrons and free-electron lasers to detect and visualize high-intensity X-ray beams. Such composites consist of luminescent rare-earth (RE) particles embedded into an X-ray transparent diamond matrix. In this work, polycrystalline diamond composites with embedded particles of EuF3, SrF2:Eu and YAG:Ce were grown by microwave plasma CVD using diamond seeds with an average particle size difference of two orders of magnitude: from 5 nm up to 500 nm, with positive and negative zeta potentials. The structure, phase composition, and luminescent characteristics of the resulting composite films were investigated and analyzed. We found that various particle types can be better-suited for different composites, and the exact seeding should be selected on the case-by-case basis. The direct comparison of various diamond-based composites, grown in the identical CVD conditions but with various luminescent powders, show that YAG:Ce particles in diamond allow achieving a brighter photoluminescence (PL) in comparison to Eu-based fluorides. However, the set of fluoride powders doped with Eu3+ ions allow obtaining unusually narrow (FWHM = 0.9 nm) and intensive line near 611 nm in PL spectra, which might be better-suited for detection and characterization applications rather than a broad peak of Ce with FWHM ≈ 120 nm.

Yellow-white emitting phosphor-in-glass with LuAG:Ce and embedded CdS quantum dots

One-step sintering process was introduced to fabricate phosphor-in-glass (PiG) composite. Commercial cerium doped lutetium aluminum garnet (LuAG:Ce, Lu3Al5O12:Ce3+) phosphor was subjected to high-energy ball milling in a planetary ball mill. By controlling the milling time and velocity, the LuAG:Ce phosphors with average diameters from 0.5 to 10 μm was prepared. The effect of phosphor particle size on densification, final microstructure, thermal and optical properties of PiG was discussed. The results showed that the as-sintered PiG sample had amorphous phase and the LuAG:Ce phosphor particles uniformly distributed in glass matrix. LuAG:Ce particles were well preserved in silica glass matrix without any decomposition reaction. As the ball-milling process proceeded, the luminescent efficiency of phosphor was degraded owing to the low crystallinity of the surface of the LuAG:Ce particles. However, the sintering of LuAG:Ce with the glass and CdS QDs led to healing of the luminescence efficacy up to 23 % and shifting of chromaticity coordinates from green to yellow region. The improved value of correlated color temperature and the color rendering index of prepared PiG was achieved around 3100 K′ and 95, respectively. Moreover, the PiG with milled LuAG:Ce performs good laser output and can resist higher laser power owing to the effective heat dissipation.

Continuous supercritical hydrothermal synthesis of stabilized ZrO2 nanocomposites: Doping mechanism of typical metals and transition elements

In this study, Mg, Ce, Y and La-doped nano-zirconia particles were successfully obtained by continuous supercritical hydrothermal synthesis combined with nanotechnology and crystal stabilization technology. Through detailed characterization and analysis of the structure, crystal form, grain size of the particles and by-products, the doping amount of different element dopants was optimized, and the stable pathway of tetragonal and cubic phases was proposed. Moreover, the doping mechanisms of different elements and phase diagram of doped nano-zirconia were revealed. The results show that the crystal form is determined by the doping amount, ionic radius and intrinsic properties of ions. Y and Ce doping can completely stabilize the tetragonal or cubic phase without the formation of by-products. Mg and La doping produce by-products of Mg(OH)2 and La2O2CO3. As the ionic radius increases, the radius mismatch with Zr4+ leads to a stronger ability to stabilize the tetragonal or cubic phase. At the same time, minimum dopant for stable tetragonal or cubic phases will decrease.

In Situ TEM/STEM Investigation of Crystallization in Y3Al5O12:Ce at High Temperatures Inside a Transmission Electron Microscope.

Y3Al5O12:Ce (YAG:Ce) phosphors are extensively used in the field of white light-emitting diodes (LEDs) due to their efficient luminescent properties. To optimize the performance of YAG:Ce phosphors, a comprehensive understanding of their synthesis and structural evolution is essential. This paper presents a direct in situ transmission electron microscopy (TEM) /scanning TEM (STEM) investigation on the transformation process of a precursor comprising nanocrystalline CeO2 dispersed in an amorphous Y-Al oxide matrix into crystalline YAG:Ce particles. The study reveals that nanocrystalline CeO2 particles dissolve completely in the Y-Al oxide matrix at a temperature above 900 °C, while YAlO3 (YAP)-type crystalline particles with Al2O3 phase in grain boundaries are observed above 1000 °C. Finally, YAG:Ce-type crystalline particles are formed above 1180 °C. Atomic-resolution energy-dispersive X-ray spectroscopy (EDS) elemental mapping demonstrates that the doped cerium (Ce) atoms occupy the same atomic sites as yttrium (Y). Photoluminescence measurements validate the efficient luminescent properties of the obtained YAG:Ce phosphor.

MgF2-doped MgO-YAG:Ce composite ceramics prepared by pressureless vacuum sintering for laser-driven lighting

Laser-driven solid-state lighting has attracted much attention in recent years. However, the super-high luminous flux under high-power-density laser irradiation is accompanied by an enormous amount of heat. Here, to enhance the thermal robustness of phosphor converter materials, we prepared composite ceramics of YAG:Ce combined with high-thermal-conductivity MgO via simply vacuum sintering. 1.0 mol% MgF2 was employed as the liquid-phase sintering additive to accelerate the densification process. The optimum temperature proves to be 1400 °C, at which MgO-YAG:Ce composites exhibit highly dense composite structure, without obvious reaction between MgO and YAG phases. Additionally, low sinterability of commercial YAG:Ce particles dragged down the densification process, which limits the YAG:Ce content of the composites. As a result, MgF2-doped MgO-10 vol% YAG:Ce composite ceramic (MYF10) sintered at 1400 °C exhibits the highest relative density of 99.33 % and thermal conductivity of 42.05 W/(m·K). Under 34.06 W/mm2 blue laser excitation in a reflection mode, a stable laser-driven white light is obtained with the luminous flux of 2834 lm and luminous efficiency of 166 lm/W, respectively.

Crucial role of Ce particles during initial hydrogen absorption of AB-type hydrogen storage alloys

The hydrogen storage behavior and the microstructural features of AB-type Ti50Fe48V2 hydrogen storage alloys containing a small amount of cerium (Ce) were investigated to understand the effect of Ce addition during initial hydrogen absorption. The initial hydrogen absorption kinetics of the alloys improved significantly at room temperature with Ce addition, which exhibited no significant influence on the pressure-composition isotherms for hydrogen absorption and desorption. Fine spherical particles containing Ce, which were determined to be γ-Ce mixed with cerium oxide, were dispersed in the ordered body-centered cubic TiFe matrix. During the early stage of hydrogen absorption, small cracks were initiated around the Ce particles, likely caused by the volume expansion owing to the formation of ε-CeH2. Subsequently, many large cracks, believed to have formed owing to the hydrogenation of the TiFe matrix, propagated during further hydrogen absorption. Therefore, these Ce particles appear to play a crucial role by providing starting points for the initial hydrogenation, with this mechanism explaining the significant increase in the primary hydrogen absorption kinetics after Ce addition. Notably, some small pits were observed after partial hydrogen absorption, possibly attributed to the hydrogenation of Ce particles underneath the alloy surfaces.

Synthesis, characterization, and application of bio-templated Ni–Ce/Al2O3 catalyst for clean H2 production in the steam reforming of methane process

A mesoporous γ-alumina was successfully synthesized through an environmentally-friendly method using Fig leaves as a bio-template for the first time in this research. After confirming the formation of porous Al2O3 structure with different characterization techniques, it was used as a supporting material of Ni–Ce particles to effectively enhance the conversion of steam reforming of methane (SRM) process. For this purpose, we optimized Ni content, Ce content, and SRM temperature using bulk and porous structure of Ni–Ce/Al2O3 catalysts. The results of field emission scanning electron microscopy (FESEM), temperature-programmed desorption (H2-TPD), and N2 adsorption/desorption showed the formation of more dispersed Ni particles with smaller sizes on the mesoporous alumina (MAl), especially when they were promoted with CeO2. Besides the efficient influence of CeO2 on Ni particle dispersion, it was enhanced the Ni–Al interaction, increased the activity of the catalysts, and decreased the coke deposition on the catalysts during the SRM process. As a result, 20Ni-3.0Ce/MAl catalyst depicted the highest H2 yield of 96.02% and CH4 conversion of 90.20%, and the lowest produced CO2 to consumed CH4 of 0.52% at 700 °C SRM reaction. This is while the bulky catalyst with equal Ni and Ce contents had 86.09, 92.30, and 0.56 CH4 conversion, H2 yield, and CO2/CH4 molar ratio, respectively at this temperature. Besides, 20Ni-3.0Ce/MAl depicted the highest stability during 12 h continuous SRM reaction at 700 °C with the lowest reduction amounts of 3.97% and 5.12% for CH4 conversion and H2 yield, respectively.

Ce-doped SBA-15 supported Pd catalyst for efficient hydrogenation of 2-ethyl-anthraquinone

Hydrogenation of 2-ethyl-anthraquinone (EAQ) is a key reaction in the anthraquinone process for industrial production of H2O2, a green chemical with a variety of applications. Herein, Ce-doped SBA-15 was synthesized via a one-step hydrothermal method with ethylenediamine as pH regulator and explored as the support of Pd catalyst for EAQ hydrogenation. Part of Ce species was incorporated into SBA-15 framework and the rest existed as extra-framework Ce and fluorite phase CeO2 particles. The framework Ce species had a suppressing effect on the aggregation of Pd particles. Their amount increased with lowering Si/Ce molar ratio (SCA) from 50 to 20 and reached a plateau at 30. The content of Ce3+ and the number of oxygen vacancies showed the same trend as the amount of framework Ce with SCA, but monotonously increased with raising reduction temperature from 200 to 600 °C. In addition, hydrogen spillover from metal to support and an increase in the binding energy of Pd were observed. Compared with Pd/SBA-15, Ce-doped catalysts presented significantly improved catalytic performance. Among them, the catalyst with SCA of 30 and reduced at 400 °C exhibited the highest activity (3.8 times of Pd/SBA-15) and selectivity to 2-ethyl-anthrahydroquinone (94.2 % from 91.8 % over Pd/SBA-15).

Preparation and Performance of Carbon-Based Ce-Mn Catalysts for Efficient Degradation of Acetone at Low Temperatures.

Based on the porous carbon material from citric acid residue, catalysts of different Ce-Mn ratios were prepared with incipient-wetness impregnation (IWI) to delve into their acetone-degrading performance and relevant mechanisms. When the Ce-Mn molar ratio is 0.8, the prepared catalyst Ce0.8-Mn/AC shows abundant and uniformly dispersed Mn and Ce particles on the surface. The content of Mn and Ce on the Ce0.8-Mn/AC surface reaches 5.64% and 0.75%, respectively. At the acetone concentration of 238 mg/m3 (100 ppm), the laws of acetone degradation in different catalysts at different catalyzing temperatures and with various oxygen concentrations were studied, and we found that the rate of acetone degradation by Ce0.8-Mn/AC can exceed 90% at 250 °C. Cerium oxide and manganese oxide are synergistic in the catalytic degradation of acetone. Adding cerium to manganese-based catalysts can increase the oxygen migration rate in the catalysts and thus raise the reduction rate of lattice oxygen in manganese oxide. The results offer new ideas and approaches for the efficient and comprehensive utilization of bio-fermentation by-products, and for the development of cheap and high degradation performance catalysts for acetone.

Photoluminescent Plasma Electrolytic Oxidation Coatings Containing YAG: Ce Produced on 1050 Aluminum Alloy

In this work, we investigated the possible incorporation of YAG (yttrium aluminum garnet)-Ce particles into plasma electrolytic oxidation (PEO) coatings on 1050AA (aluminum alloy) in order to endow the surface with photoluminescent properties. Different treatment times and current modes (direct or pulsed) were tested as PEO process parameters using as electrolyte a silicates-containing solution. The microstructure of the samples was characterized by SEM and XRD measurements, the corrosion properties were determined by EIS tests, whereas the photoluminescence was evaluated with a proper spectrometer. The concentration of the YAG-Ce particles incorporated in the PEO coating was strongly influenced by the current mode, and in particular, it was higher with pulsed current mode. A higher content of YAG-Ce particles results in a better corrosion resistance and photoluminescent effect. PEO process in pulsed unipolar mode using an electrolyte containing YAG-Ce particles resulted an effective way to produce samples of 1050AA with a surface characterized by photoluminescent properties.

Influence of down-shifting particle’s size on monocrystalline silicon solar cells

The potential cerium doped yttrium aluminum garnet (YAG:Ce3+) phosphor particles of different sizes are mixed with ethylene-vinyl acetate (EVA) to make luminescent downshifting films, which are then utilized for packaging monocrystalline silicon solar cells. The luminescence of YAG:Ce particles with the different diameters (3–5 µm, 5–8 µm, 8–10 µm, 10–15 µm, 15–20 µm, and 20–30 µm), the transmission of the down-shifting EVA films with the phosphor particles and performance of the packaged solar cells have been investigated. Experimental results show that the particles with 15–20 µm have the highest luminescent intensity. When the mass ratio of phosphors to EVA is fixed, the films with 20–30 µm have the highest transmission. The most significant increase in solar cell conversion efficiency after packaging is due to the downshifting EVA films with 15–20 µm particles. This research could be useful in the selection of downshifting phosphors for solar cells in the future.

The Influence of Ce, La, and SiC Particles Addition on the Formability of an Al-Si-Cu-Mg-Fe SiCp-MMC.

Road transport and the associated fuel consumption plays a primary role in emissions. Weight reduction is critical to reaching the targeted reduction of 34% in 2025. Weight reduction in moving parts, such as pistons and brake disc rotors, provide a high-impact route to achieve this goal. The current study aims to investigate the formability of Al–Si alloys reinforced with different fractions and different sizes of SiCp to create an efficient and lightweight Al-MMC brake disk. Lanthanum (La) and cerium (Ce) were added to strengthen the aluminium matrix alloy and to improve the capability of the Al-MMC brake discs to withstand elevated temperature conditions, such as more extended braking periods. La and Ce formed intermetallic phases that further strengthened the composite. The analysis showed the processability and thermal stability of the different material’s combinations: increased particle sizes and broader size range mixture supported the formation of the SiCp particle interactions, acting as an internal scaffolding. In conclusion, the additions of Ce and La strengthened the softer matrix regions and resulted in a doubled compression peak strength of the material without affecting the formability, as demonstrated by the processing maps.

Self-sensing fluorescence polymer composites for chemical degradation protection and monitoring

The development of epoxy-based composites with the combination of protective and self-sensing capabilities continues to be a challenge in particular with respect to chemical and UV degradation. A promising approach is to fabricate these composites with phosphors particles, which provide the needed self-sensing characteristics. In this context, Y3Al5O12:Ce3+ (YAG:Ce) particles at different concentrations have been introduced into an epoxy polymer matrix, further placed in a laminate structure. The system was then exposed to specific degradation environments, including sulfuric acid and ultraviolet (UV) irradiation. The effects of these exposure treatments on the structural, mechanical, and optical properties of composites were investigated. A correlation between the variation of the physical-chemical parameters of the samples and the presence of YAG:Ce particles was observed, which demonstrate the self-sensing capabilities of the system. It is also demonstrated that fiberglass reinforced epoxy layered structures act as a good protective coating in sulfuric acid solution, while these layers degrade under UV irradiation. These findings provide a suitable platform for the development of coatings allowing to protect, detect and monitor corrosion in pipes and tanks under different industrial conditions.

Quantification and classification of engineered, incidental, and natural cerium-containing particles by spICP-TOFMS

Multi-elemental spICP-TOFMS is used to simultaneously classify mixtures of engineered, incidental, and natural Ce-containing nanoparticles based on conserved Ce : La and Ce : Nd ratios in natural Ce particles.

Organic and inorganic compounds as corrosion inhibitors to reduce galvanic effect for the hybrid structure AA2024-CFPR

The effect of the galvanic corrosion process taking place between aluminium alloy (AA2024-T3) and carbon fiber reinforced plastic (CFRP) immersed in 0.05 M NaCl was studied using organic and inorganic compounds as corrosion inhibitors. Electrochemical approaches such as electrochemical noise analysis (ENA) and electrochemical impedance spectroscopy (EIS) were carried out to evaluate efficiencies of 1,2,4-triazole (C2H3N3) and cerium nitrate hexahydrate (Ce(NO3)3·6H2O) as corrosion inhibitors. The highest efficiency was reached for Ce(NO3)3.6H2O, with some improvement observed by adding C2H3N3 in a mixed inhibitor solution. The noise resistance (Rn) and polarization resistance (Rp) values calculated from ENA and EIS data showed almost identical behavior with different magni­tudes but similar trends. Adsorption isotherm models estimated with fractional surface coverage (q) parameter were fitted better to Langmuir model for C2H3N3 and Temkin model for Ce(NO3)3·6H2O. The calculated values of Gibbs free energy suggested physi­sorption and chemisorption as spontaneous interactions between a metal surface and both inhibitors. Energy-dispersive X-ray spectroscopy (EDS) was carried out before and after immersing AA2024-T3 in the electrolyte, identifying rich zones in copper with cerium deposited over it and confirming the presence of rare-earth oxide deposition and oxide film products. The EDS analysis for CFRP revealed the deposition of Ce and Al particles over its surface after immersion in the electrolyte, especially in the areas rich in carbon.

Effects of rare earth Ce addition on the microstructure and shear property of Cu/In-50Ag/Cu composite solder joint

The microstructure and shear property of Cu/In-50Ag-xCe/Cu (x = 0, 0.3, 0.6, 1.2, 2 wt%) composite solder joints fabricated by transient liquid phase (TLP) bonding were investigated. The results showed that the appropriate amount of Ce particles refined the microstructure in the Cu/In-50Ag/Cu solder joint, and inhibited Cu2In phase formation at the Cu/solder interface. The refined Ag2In phases contribute to suppressing the formation of microstructural defects. The Ce particles can improve the microstructure uniformity of composite solder joint, the porosity of Cu/In-50Ag-0.6Ce/Cu solder joint is only 1.05%, and the excessive (1.2–2 wt%) Ce particles are harmful to the composite solder joints. Doping 0.3–0.6 wt% Ce particles can improve the shear strength of composite solder joints by reducing microstructural defects, refining Ag2In phases and improving the phase boundaries strength. The maximum shear strength value of the Cu/In-50Ag-0.6Ce/Cu composite solder joint reaches 17.58 MPa. The fracture mechanism is mainly brittle fracture, which occurs near the in-situ reaction zone. The Cu/In-50Ag-0.6Ce/Cu composite solder joint fabricated by TLP bonding with finer microstructure and higher mechanical properties is acceptable.

Palladium particles supported on porous CeMnO3 perovskite for catalytic oxidation of benzene

Since the traditional palladium based catalysts are susceptible to poisoning and deactivation, and they are expensive, which limits their practical application. The VOCs (volatile organic compounds) emissions are controlled by developing catalysts with low temperature activity and economical practicality. In this paper, the sol-gel method is combined to the impregnation method to synthesize Pd-CeMnO3 perovskite type catalyst. Pd-CeMnO3 (Pd %wt=0.5%wt) shows the T50% = 139 ℃ (the corresponding temperature required when the conversion rate reaches 50%) and T100% = 200 ℃ of removal rate, T50% = 162.5 ℃, and T100% = 220 ℃ of mineralization rate. According to XRD, XPS, H2-TPR, GC-MS and other characterization methods. Its activity benefits from the high dispersion of a certain amount of Pd on the surface of perovskite and the interaction with Ce particles accelerates the transfer of oxygen. The electron transfer of different Pd and Ce ions is beneficial to the generation of active oxygen, which activates the benzene ring into hydrocarbons while adsorbing oxygen to participate in the reaction. A series of heterogeneous reactions occurred and intermediate products such as benzaldehyde, benzaldehyde and phthalic anhydride were detected. Eventually it is oxidized to CO2 and H2O complying with the Mars-van-Krevelen mechanism.

Feasibility of cerium-doped LSO particles as a scintillator for x-ray induced optogenetics

Objective. Non-invasive light delivery into the brain is needed for in vivo optogenetics to avoid physical damage. An innovative strategy could employ x-ray activation of radioluminescent particles (RLPs) to emit localized light. However, modulation of neuronal or synaptic function by x-ray induced radioluminescence from RLPs has not yet been demonstrated. Approach. Molecular and electrophysiological approaches were used to determine if x-ray dependent radioluminescence emitted from RLPs can activate light sensitive proteins. RLPs composed of cerium doped lutetium oxyorthosilicate (LSO:Ce), an inorganic scintillator that emits blue light, were used as they are biocompatible with neuronal function and synaptic transmission. Main results. We show that 30 min of x-ray exposure at a rate of 0.042 Gy s−1 caused no change in the strength of basal glutamatergic transmission during extracellular field recordings in mouse hippocampal slices. Additionally, long-term potentiation, a robust measure of synaptic integrity, was induced after x-ray exposure and expressed at a magnitude not different from control conditions (absence of x-rays). We found that x-ray stimulation of RLPs elevated cAMP levels in HEK293T cells expressing OptoXR, a chimeric opsin receptor that combines the extracellular light-sensitive domain of rhodopsin with an intracellular second messenger signaling cascade. This demonstrates that x-ray radioluminescence from LSO:Ce particles can activate OptoXR. Next, we tested whether x-ray activation of the RLPs can enhance synaptic activity in whole-cell recordings from hippocampal neurons expressing channelrhodopsin-2, both in cell culture and acute hippocampal slices. Importantly, x-ray radioluminescence caused an increase in the frequency of spontaneous excitatory postsynaptic currents in both systems, indicating activation of channelrhodopsin-2 and excitation of neurons. Significance. Together, our results show that x-ray activation of LSO:Ce particles can heighten cellular and synaptic function. The combination of LSO:Ce inorganic scintillators and x-rays is therefore a viable method for optogenetics as an alternative to more invasive light delivery methods.