Formation Of Ce Research Articles

Comparative analysis of enhanced adsorption and thermal decomposition of oil-borne PFAS using CeO2 nanoparticles and activated carbon

Per- and poly-fluoroalkyl substances (PFAS) are widely used as surfactants in the oil and gas industry, presenting significant environmental and health risks due to their persistence and mobility. While prevailing research primarily targets PFAS removal from aqueous environments, this study explores the efficacy of nanosized cerium oxide nanoparticles (CeO2 NPs) and traditional activated carbon (AC) in removing PFAS from organic media via adsorption and thermal degradation. Both adsorbents exhibited robust adsorption capabilities; however, their interaction mechanism with PFAS differ significantly. CeO2 NPs primarily engage in chemical adsorption with PFAS, whereas AC relies on hydrophobic interactions. Additionally, CeO2 NPs outperformed AC in thermal degradation experiments, achieving approximately 95 % decomposition of PFOS at 400 °C, compared to only 52 % with AC. Furthermore, the formation of stable Ce−F bonds at high temperatures significantly reduced fluoride ion release from CeO2 NPs, underscoring their potential to minimize environmental impact. This study is the first to apply both AC and CeO2 NPs for PFAS removal from organic media and to elucidate their distinct adsorption and thermal decomposition mechanisms, highlighting the superior performance of CeO2 NPs in environmental remediation of PFAS.

Fe doping enhanced Cr(VI) adsorption efficiency of cerium-based adsorbents: Adsorption behaviors and inner removal mechanisms

Cerium-based adsorbents possessed unique advantages of valence variability and abundant oxygen vacancies in hexavalent chromium (Cr(VI)) adsorption, but high cost and unstable properties restricted their application in Cr(VI) contained wastewater treatment. Herein, a series of bimetallic adsorbents with different cerium/iron ratios (CeFe@C) were prepared by adding inexpensive Fe into Ce-based adsorbents (Ce@C), and the effect of Fe doping on adsorption properties of Ce@C for Cr(VI) was investigated thoroughly. Compared with pristine Ce@C, CeFe@C exhibited excellent removal performance for Cr(VI), and the improved maximum adsorption capacity reached 75.11 mg/g at 25℃. Benefiting from Fe doping, CeFe@C had good regeneration property, with only 25 % decrease after five adsorption–desorption cycles. Contents of trivalent cerium (Ce(III)) and oxygen vacancies (Ov) in bimetallic adsorbents were positively correlated with divalent iron (Fe(II)) doping, indicating that the formation of Ce(III) and surface defects on Ce@C could be effectively regulated by Fe doping. Density functional theory (DFT) calculation results further proved that the doped Fe enhanced the electron transfer effectively and lowered the energy barriers of Cr(VI) adsorption onto Ce@C surface, strengthening the reduction and complexation to Cr(VI). This study provides new insights for improving the Cr(VI) removal performance by modified Ce-based adsorbents, and further promotes the utilization potentiality of low-cost and low-toxicity Ce-based adsorbents in Cr(VI)-containing wastewater treatment.

Improvement of chemical mechanical polishing performance by introducing N–Si bond via external coating of cerium oxide with ZIF-8

Cerium oxide (CeO2) nanoparticles are widely used as abrasives in chemical mechanical polishing (CMP), an essential process for obtaining Si wafers with excellent surface quality. While CeO2 nanoparticles form Ce–O–Si bonds, which exhibit good CMP performance, their low activity results in a low removal rate. To address this issue, a two-step ultrasonic dispersion method was employed to prepare a uniform nuclear@shell CeO2@ZIF-8. The process of chemical bond generation in CMP was studied using spherical aberration-corrected transmission electron microscopy and X-ray photoelectron spectroscopy. In comparison to pure cerium oxide, the formation of Ce–O–Si bond was observed, and notably, the emergence of N–Si bond originating from the N of the ZIF-8 shell was identified. Coupled with the increased Ce3+ content, these developments enhanced CMP performance. The material removal rate (MRR) of the CeO2@ZIF-8 abrasives was 151.507 nm/min, which is 89.72 % higher than that of the pure CeO2 abrasives. Moreover, the surface roughness, as determined via AFM testing, was reduced to 0.231 nm within the confines of a 5.0 × 5.0 μm² region. Therefore, this study introduces a novel concept for CMP research by developing a CeO2@ZIF-8 compound abrasive to create a new N–Si bond.

Ammonia and toluene oxidation: Mutual activating effect of copper and cerium on catalytic efficiency

Copper and cerium containing hydrotalcite-like precursors Cux-Cey-Mg-Al were synthesized by mutual co-precipitation followed by calcination at 800 °C. The obtained mixed metal oxides were studied as catalysts for selective ammonia oxidation (NH3-SCO) and toluene combustion. Various techniques, such as temperature-programmed reduction with hydrogen, temperature-programmed desorption of toluene, scanning electron microscopy and reactive frontal chromatography were used to characterize the catalysts. Series 800-Cux-Ce2.5 showed the highest catalytic efficiency in both reactions, allowing complete NH3 and C7H8 conversion below 350 °C and 500 °C, respectively. CeO2 crystallites (12–18 nm), as well as dispersed CuO oxide forms were found in the most active samples. Both phases affect pollutants conversion, however, for ammonia oxidation the occurrence of Cu2+ is essential, while for toluene oxidation, the formation of Ce4+ is sufficient. Over the most active sample (800-Cu5-Ce2.5) the complete conversion in mutual oxidation of NH3 and toluene was achieved below 450 °C.

Nanocrystalline Ce(OH)4-based materials: ruthenium selective adsorbent for highly alkaline radioactive liquid waste

Abstract Cerium hydroxide, Ce(OH)4 (Ce), has been synthesised and assessed as a Ru-selective adsorbent for treating alkaline radioactive liquid waste. Infrared spectroscopy, thermal analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy investigations confirmed the successful formation of nanocrystalline Ce from Ce(NO3)3·6H2O. Selective removal of 106Ru from the ion-exchange effluent of intermediate-level liquid waste (ILW) by Ce was assessed using a high-pure germanium (HPGe) gamma-ray spectrometer. The calculated average distribution coefficient (k D) was ∼200 mL/g. The percentage removal of 106Ru using Ce by varying time, [106Ru] and [Ce] was calculated. The adsorption of 106Ru on Ce follows pseudo-second-order and Freundlich isotherms. The calculated Q max was 93,584 Bq/g. Accelerated leaching studies of the Ru-laden Ce cement product were carried out and found suitable for transport and disposal. Further, Ce-Polyether sulphone (Ce-PES) and Ce-Chitosan (CeC) composites were prepared and assessed for their Ru-uptake capacity for engineering scale application.

Colloidal Aziridinium Lead Bromide Quantum Dots.

The compositional engineering of lead-halide perovskite nanocrystals (NCs) via the A-site cation represents a lever to fine-tune their structural and electronic properties. However, the presently available chemical space remains minimal since, thus far, only three A-site cations have been reported to favor the formation of stable lead-halide perovskite NCs, i.e., Cs+, formamidinium (FA), and methylammonium (MA). Inspired by recent reports on bulk single crystals with aziridinium (AZ) as the A-site cation, we present a facile colloidal synthesis of AZPbBr3 NCs with a narrow size distribution and size tunability down to 4 nm, producing quantum dots (QDs) in the regime of strong quantum confinement. NMR and Raman spectroscopies confirm the stabilization of the AZ cations in the locally distorted cubic structure. AZPbBr3 QDs exhibit bright photoluminescence with quantum efficiencies of up to 80%. Stabilized with cationic and zwitterionic capping ligands, single AZPbBr3 QDs exhibit stable single-photon emission, which is another essential attribute of QDs. In particular, didodecyldimethylammonium bromide and 2-octyldodecyl-phosphoethanolamine ligands afford AZPbBr3 QDs with high spectral stability at both room and cryogenic temperatures, reduced blinking with a characteristic ON fraction larger than 85%, and high single-photon purity (g(2)(0) = 0.1), all comparable to the best-reported values for MAPbBr3 and FAPbBr3 QDs of the same size.

Exclusive ion recognition using host-guest sandwich complexes.

Ion recognition in porous aqueous media utilizing polyethers involves the formation of 1 : 1 and higher-order host-guest complexes. The effectiveness of these interactions relies on the optimal size of the host cavity to encapsulate the guest ions. While liquid/liquid extraction based on host-guest interactions offers higher specificity in metal ion extraction, it results in the co-extraction of unwanted coordinating solvents and counter-anions. Therefore, an improved protocol is required by which the ion can be selectively trapped within the host cavity and simultaneously decrease the guest coordination with the outside environment. This study delves into the microscopic mechanisms underpinning the exclusive ion recognition through the formation of 2 : 1 host-guest sandwich complexes, which reduce metal coordination with solvent or counter-ions, ensuring selectivity. Our analysis shows that ions with a radius larger than the host cavity, such as cesium (Cs+), form stable host-guest sandwich complexes at elevated host concentrations. In this study, we performed molecular dynamics simulations to investigate the microscopic details of Cs+ interactions with open-chain and preorganized polyethers, namely podand, crown, and cryptand in electrolyte media. Our findings reveal that the formation of stable Cs+-crown sandwich complexes significantly reduces Cs+ coordination with H2O and NO3-. This loss of solute coordination leads to exclusivity in bound metal ions, offering a potential strategy for efficient solvent extraction.

Discovery and In Situ Crystallization Studies of Cerium-Based Metal-Organic Frameworks with V-Shaped Linker Molecules.

We report the discovery and characterization of two porous Ce(III)-based metal-organic frameworks (MOFs) with the V-shaped linker molecules 4,4'-sulfonyldibenzoate (SDB2-) and 4,4'-(hexafluoroisopropylidene)bis(benzoate) (hfipbb2-). The compounds of framework composition [Ce2(H2O)(SDB)3] (1) and [Ce2(hfipbb)3] (2) were obtained by using a synthetic approach in acetonitrile that we recently established. Structure determination of 1 was accomplished from 3D electron diffraction (3D ED) data, while 2 could be refined against powder X-ray diffraction (PXRD) data using the crystal structure of an isostructural La-MOF as the starting model. Their framework structures consist of chain-like inorganic building units (IBUs) or hybrid-BUs that are interconnected by the V-shaped linker molecules to form framework structures with channel-type pores. The composition of both compounds was confirmed by PXRD, elemental analysis, as well as NMR and IR spectroscopy. Interestingly, despite the use of (NH4)2[CeIV(NO3)6] in the synthesis, cerium ions in both MOFs occur exclusively in the + III oxidation state as determined by X-ray absorption near edge structure (XANES) and X-ray photoelectron spectroscopy (XPS). Thermal analyses reveal remarkably high thermal stabilities of ≥400 °C for the MOFs. Initial N2 sorption measurements revealed the peculiar sorption behavior of 2 which prompted a deeper investigation by Ar and CO2 sorption experiments. The combination with nonlocal density functional theory (NL-DFT) calculations adds to the understanding of the nature of the different pore diameters in 2. An extensive quasi-simultaneous in situ XANES/XRD investigation was carried out to unveil the formation of Ce-MOFs during the solvothermal syntheses in acetonitrile. The crystallization of the two Ce(III)-MOFs presented herein as well as two previously reported Ce(IV)-MOFs, all obtained by a similar synthetic approach, were studied. While the XRD patterns show time-dependent MOF crystallization, the XANES data reveal the presence of Ce(III) intermediates and their subsequent conversion to the MOFs. The addition of acetic acid in combination with the V-shaped linker molecule was identified as the crucial factor for the formation of the crystalline Ce(III/IV)-MOFs.

Magnetically separable and reusable Fe3O4/chitosan nanocomposites green synthesized utilizing Moringa oleifera extract for rapid photocatalytic degradation of methylene blue

This study focused on the green synthesis of Fe3O4/Chitosan (Cs) nanocomposites using Moringa oleifera leaf extract, which showed good photocatalytic activity when exposed to ultraviolet (UV) irradiation. X-ray diffraction spectrum of Fe3O4/Cs informs the cubic inverse spinel and has crystallite size in the 10.1 – 11.7 nm range. The crystallite size also increased with the increase of Cs mass. The morphology of Fe3O4 and Fe3O4/Cs was nearly spherical. The transmission electron microscope showed the most uniform size of nanocomposites at around 17.1 nm. The Fourier transform infrared spectrophotometer result identified Fe-O in the 576–583 cm−1 range, indicating that Fe3O4 successfully bonded to Cs. Other functional groups, including O–H, C–H, C–O, C–O–C, and NH2, were also found, indicating that the formation of Cs was effective. The element composition of Fe3O4 is Fe (70.9 %) and O (29.1 %). Meanwhile, Fe3O4/Cs (4:4) is 47.9 %, 36.4 %, 11.3 %, and 4.4 % for Fe, O, C and N, respectively. The hysteresis curve indicated that Fe3O4 and Fe3O4/Cs nanocomposites have soft ferromagnetic properties. Meanwhile, the saturation magnetization of Fe3O4 and Fe3O4/Cs (4:2) nanocomposites are 54.0 and 42.3 emu/g, respectively. Peaks are seen in the UV–visible absorption spectrum of Fe3O4 and Fe3O4/Cs nanocomposites between wavelengths 365–377 nm. The optical band gap energy (Eg) of Fe3O4 and Fe3O4/Cs (4:2) are 3.4 and 3.0 eV, respectively. As the mass of Cs increases, the band gap energy decreases. Under UV light irradiation, 50 mg of Fe3O4 and Fe3O4/Cs were analyzed on 7 ppm of methylene blue, pH = 4. The maximum photocatalytic activity Fe3O4/Cs (4:3), achieved an impressive degradation rate of 94.7 % after 120 min of irradiation. The magnetically separable capability means nanocomposites can be recycled and reused five times with high degradation. Furthermore, Fe3O4/Cs has the potential to be a low-cost and environmentally friendly reusable photocatalyst for rapid wastewater degradation.

High-performance Pt/CeO2-ZrO2 catalysts for selective hydrogenation of α,β-unsaturated aldehydes to unsaturated alcohols under mild reaction conditions: “Giant” hydrogen spillover behind the activity enhancement

Pt supported on CeO2-ZrO2 mixed oxide showed unusually high activity and regioselectivity compared to common commercial hydrogenation catalysts in hydrogenation of α,β-unsaturated aldehydes to unsaturated alcohols. DRIFTS-CO, TEM, XPS, TPR-H2 studies demonstrated that the CeO2-ZrO2 support stabilizes Pt as small clusters, especially for the catalysts with ultra-low Pt loadings < 0.1 % wt. Interaction of Pt clusters with the easily reducible CeO2-ZrO2 mixed oxide leads to intense low-temperature hydrogen spillover effect, which in turn is responsible for active hydrogen species generation on Pt and their transfer to the support leading to reduction of CeO2 with the formation of Ce3+, where the carbonyl bond can be adsorbed and activated. According to the results of EPR studies of hydrogen species generated on the catalyst surface, we assume that hydrogen on a Pt/CeO2-ZrO2 catalyst can undergo heterolytic dissociation with the formation of hydride ions, which provide selective carbonyl bond hydrogenation, but not with the predominant formation of radical type (H●) species that lead to unselective hydrogenation of both C = O and C = C bonds. A careful 1H magic angle spinning solid-state NMR (1H MAS SS NMR) study of hydrogen adsorbed on Pt/CeO2-ZrO2 and Pt supported on non-reducible oxide (SiO2) confirmed the formation of hydride on Pt/CeO2-ZrO2, whilst only molecular hydrogen was detected on the Pt/SiO2 sample.

Luminescence and photoconversion properties of Ce-doped Ca3Sc2Si3O12 crystal

This work is dedicated to investigation of the luminescent properties of the prospective photoconversion material based on the crystal of Ce3+ doped Ca3Sc2Si3O12 (CSSG) garnet. The GSSG:Ce crystal was grown using the micro-pulling-down (μPD) method. The CSSG:Ce crystal exhibited an intensive photoluminescence (PL) emission band with two sub-bands peaked at 504 and 545 nm, corresponding to 5d-4f (2F5/2;7/2) transitions. Furthermore, we have investigated also the formation of cerium multicenters in the GSSG:Ce crystal using analyses of the structure of Ce3+ photoluminescence emission and excitation spectra under excitation of the luminescence of this crystal by synchrotron radiation. The formation of Ce3+-multicenters in CSSG:Ce garnet is caused by the local inhomogeneity of the dodecahedral sites of garnet lattice due to localization of the hetero-valent Sc3+ and Si4+ cations in the octahedral and tetrahedral positions of the garnet host. The existence of Ce3+ multicenters resulted in a significant enhancement of the Ce3+ emission band in the red range and improving the performance of conventional YAG:Ce phosphor. The next task of our work was to evaluate the possibility of application of the GSSG:Ce crystal as a light phosphor-converter (pc) for white light-emitting diodes (WLEDs). In the frame of this task, we have successfully developed a prototype of WLED by employing the CSSG:Ce crystal as a phosphor-converter (pc) with blue 450 emitting LED as well as investigated the color characteristics of this pc-WLED.

Constructing Ce–Mn/Al2O3 with different active components for low temperature catalytic degradation of chlorobenzene in soil

Soil remediation containing numerous organic contaminants is of great significance to ecological environment. Herein, the synergetic effects of Ce–Mn/Al2O3 with different active components on catalytic thermal desorption of chlorobenzene in soil were investigated. The optimized Ce–Mn/Al2O3 drastically enhance the desorption efficiency of chlorobenzene, and the corresponding conversion reaches 100% within 1 h at a low temperature of 120 °C. The superior performance is ascribed to the formation of Ce–Mn solid solution during the calcination process, resulting in a certain lattice change to the generation of abundant oxygen vacancies and acidic sites. Combining with the analysis of in-situ diffuse reflectance infrared spectroscopy and gas chromatography-mass spectrometry, the final products of chlorobenzene are decomposed into CO2, H2O, Cl2 and HCl. This work sheds light on the rational design of highly-active catalysts for practical applications of sustainable soil remediation.

Effect of acetate ions and pH on the morphology of cerium oxide nanoparticles

Cerium oxide nanoparticles (CeNPs) are recognized as functional materials with suitability in diverse applications. Conventional synthesis of CeNPs involves direct addition of alkaline solutions and/or precipitating agents to cerium solutions. Rapid changes in solution concentrations and ligand introduction result in less control over particle size and dispersity. Here, we report a simple hydrothermal synthesis of cubic shaped CeNPs through homogenous precipitation, achieved by introduction of acetate molecules. A distinct trend in CeNPs transitioning from octahedral to cubic morphologies was observed through a series of experiments. Results from experimental and computational studies have demonstrated that acetate plays an important role in directing the morphological transition of CeNPs and providing a pH-buffered environment. The formation of Ce(IV)-acetate complexes not only stabilizes aqueous Ce(IV) but also inhibits its hydrolysis in conditions of lower pH. The stabilization of Ce(IV) ions is also favorably weakened during the hydrothermal treatment, leading to successful homogeneous precipitation and the formation of mono-dispersed cubic-shaped CeNPs.

(Digital Presentation) GDC/YSZ Bilayer Electrolyte Fabrication by In-situ Hydrothermal Growth

GDC (gadolinia-doped ceria) can be used as barrier layer between the high-performance LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) cathode and YSZ (8% mol yttria stabilized zirconia) electrolyte, to prevent chemical incompatibility and elements diffusion. However, the GDC layer is difficult to achieve as high density as the YSZ electrolyte, especially under low sintering temperatures. While, increase sintering temperature over ~1200 ℃ could induce the formation of (Ce,Zr)O2 solid solution.In this work, we report a highly dense bilayer GDC/YSZ electrolyte prepared at low sintering temperature. Specifically, the as-sintered anode supported SOFC half-cell with already-dense YSZ electrolyte was immersed in solution of Gd(NO3)3·6H2O and Ce(NO3)3·6H2O, followed by a hydrothermal treatment at 180 ℃ (accounts for steam pressure of ~1 MPa) for 36 h. This yielded a dense GDC layer growth on YSZ electrolyte with thickness of ~200 nm. Then, the cells were sintered at 1100, 1150 and 1200 ℃, respectively. Afterwards, the hydrothermal treatment was repeated once, to grow an additional GDC layer. This post-grown GDC was then co-sintered with the screen printed LSCF cathode at 1075 ℃.Results show that, the GDC/YSZ bilayer electrolyte is successfully fabricated under low sintering temperature below 1200 ℃, with overall GDC layer as thick as ~540 nm and ultra-high density as the YSZ electrolyte. The single cell with 1200 ℃ sintered GDC, named as GDC-1200, shows the best output performance, i.e. maximum power density of ~0.96 W/cm2 at 780 ℃. Moreover, the cell runs stably at 720 ℃ for 300 hours, showing decent durability.Fig. 1 (a) j-V-P curves of bilayer electrolyte SOFCs with varied GDC sintering temperature; (b) operation voltage versus time for GDC-1200 cell under constant current mode; (c) SEM images and (d) EDS mapping of single cell (GDC-1200) fracture Figure 1

From Ce(OH)3 to Nanoscaled CeO2: Identification and Crystal Structure of a Cerium Oxyhydroxide Intermediate Phase

Cerium oxide is a pivotal compound in catalysis, both as a support and as an active phase. However, its fine features, such as the Ce(III) to Ce(IV) ratio, strongly depend on the protocol used to prepare it. While the literature contains tens of protocols to prepare cerium oxide nanoparticles from Ce(III) precursors, there is still an open question regarding the time at which the cerium oxidation occurs and the role of hydroxide phases in this process. This article identifies an oxyhydroxide phase of Ce(IV) as a key intermediate and proposes a crystal structure for it. For this purpose, phase-pure cerium trihydroxide (Ce(OH)3) nanorods (<20 nm) were first prepared by hydrothermal treatment of a cerium nitrate salt (Ce(NO3)3·6H2O) in the presence of KOH. Aging of this phase in air was monitored by X-ray absorption spectroscopy, which confirmed the formation of an intermediate Ce(IV) crystalline compound, unreferenced so far. Based on X-ray and neutron powder diffraction experiments combined with DFT calculations, we propose that this new phase is a cerium oxyhydroxide of the chemical formula CeO(OH)2, for which a structural model is proposed. Thermodiffraction experiments finally established that this compound is an observable intermediate in the synthesis of cerium dioxide CeO2 by calcination of Ce(OH)3 in air.

Electrospun Ce–Mn oxide as an efficient catalyst for soot combustion: Ce–Mn synergy, soot-catalyst contact, and catalytic oxidation mechanism

Increasing the contact efficiency and improving the intrinsic activity are two effective strategies to obtain efficient catalysts for soot combustion. Herein, the electrospinning method is used to synthesize fiber-like Ce–Mn oxide with a strong synergistic effect. The slow combustion of PVP in precursors and highly soluble manganese acetate in spinning solution facilitates the formation of fibrous Ce–Mn oxides. The fluid simulation clearly indicates that the slender and uniform fibers provide more interwoven macropores to capture soot particles than the cubes and spheres do. Accordingly, electrospun Ce–Mn oxide exhibits better catalytic activity than reference catalysts, including Ce–Mn oxides by co-precipitation and sol-gel methods. The characterizations suggest that Mn3+ substitution into fluorite-type CeO2 enhances the reducibility through the acceleration of Mn–Ce electron transfer, improves the lattice oxygen mobility by weakening the Ce–O bonds, and induces oxygen vacancies for the activation of O2. The theoretical calculation reveals that the release of lattice oxygen becomes easy because of a low formation energy of oxygen vacancy, while the high reduction potential is beneficial for the activation of O2 on Ce3+-Ov (oxygen vacancies). Due to above Ce–Mn synergy, the CeMnOx-ES shows more active oxygen species and higher oxygen storage capacity than CeO2-ES and MnOx-ES. The theoretical calculation and experimental results suggest that the adsorbed O2 is more active than lattice oxygen and the catalytic oxidation mainly follows the Langmuir-Hinshelwood mechanism. This study indicates that electrospinning is a novel method to obtain efficient Ce–Mn oxide.

Phase evolution in the UO2–CeO2 system under oxidizing and reducing conditions: X-ray diffraction and spectroscopic studies

The solid-solution formation mechanism and defect dynamics in U1-xCexO2±δ solid solutions have been investigated by means of X-ray diffraction (XRD) analysis, Raman spectroscopy, and X-ray absorption near-edge structure (XANES) spectroscopy. Diffraction studies have revealed the formation of single-phase solid solutions with a fluorite-type structure at x ≤ 0.2 and a single-phase fluorite-type structure with broadened diffraction peaks, attributed to inhomogeneity in the O/M ratio, at 0.3 ≤ x ≤ 0.8 under reducing conditions. Oxidizing conditions result in the formation of single-phase solid solutions with fluorite-type structure at x ≥ 0.4. Upon the formation of Ce3+ in solid solutions at x ≤ 0.2 under reducing conditions, charge neutrality is achieved through oxygen vacancy creation and formation of higher oxidation states of uranium through a charge compensation mechanism. Lattice parameter–composition relationships for fluorite-type phases synthesized under oxidizing conditions show a decrease in lattice parameters as compared to their stoichiometric counterparts due to the oxidation of U4+ to U5+/U6+. XANES studies provide direct experimental evidence of the presence of Ce3+ in solid solutions, despite synthesis under oxidizing conditions.

Degradation analysis of perovskite solar cells doped with MABr3 via electrochemical impedance

In this study, perovskite solar cells with a structure CsyFA1-xMAxCS0.05Pb(I1.05-xBrx)3, with X = 0 (no doping was added to the base structure CsFAPbI3) and X = 0.085 (CsFAPbI3 was doped with 8.5% MABr3) were prepared and were subjected to a 60 days ageing process (15 days under vacuum conditions followed by 45 days under room conditions) to study their stability. J-V curves showed that after the 60 days, the cells with no MABr3 only had 50.32% of the original efficiency remaining, while the samples with 8.5% MABr3 had 92.89% of the original efficiency, being the Jsc the main parameter that was affected during the ageing period. IPCE measurements suggest the formation of Cs segregates, that maintain or even increase the Jsc. According to electrochemical impedance studies, these segregates could be promoted by the lower ionic movement resistance in the 8.5% MABr3 samples, which may allow to re-arrange the atoms of the crystalline structure in a benefic way. This work is of great importance because it helps to understand how the doping affects the degradation processes, while showing how Impedance Spectroscopy can be used to characterize the changes in the electrical and ionic dynamics of the solar cells.

Surface hardening of extreme ultraviolet(EUV) photoresist by CS2 plasma for highly selective and low damage patterning

Extreme ultraviolet (EUV) lithography has the advantage of implementing a finer pattern by using a wavelength of 13.5 nm light source with a higher resolution value than the existing ArF light source. However, there are several issues regarding EUV photoresist (PR), such as low etch resistance due to thin thickness and pattern mismatch during subsequent processing/deterioration of electrical characteristics of the device due to increase in line edge roughness (LER). In this study, the effect of CS2 plasma treatment and/or followed annealing at 80 °C on the EUV PR properties was investigated to improve PR characteristics such as LER, etch resistance, etc. during the etching by CF4 plasma. The CS2 plasma treatment and followed annealing improved the PR characteristics such as decreased ΔLER, decreased ΔCritical dimension, and decreased ΔThickness of the PR after the etching compared to the reference and/or annealed PR. Especially, the PR treated by CS2 plasma + annealing showed the improvement of etch resistance of ∼ 70 % compared to the reference PR. The X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy showed that the improvement of EUV PR properties were related to the formation of CS, OS bonds on the surface of PR by the CS2 plasma treatment + annealing.

Effect of cerium on the primary carbides and inclusions in electroslag remelted M35 high speed steel

To restrain the formation of primary carbides in M35 high speed steel, the present work investigated the effect of cerium on the microstructure, primary carbides and inclusions in electroslag remelted M35 high speed steel based on experimental characterizations and thermodynamic calculations. The primary carbides in M35 high speed steel are M2C-type carbides with orthorhombic crystal structure and MC-type carbides with FCC crystal structure. M2C-type carbides are the dominant carbides, whose precipitation is prior to the MC-type carbides. With adding cerium content to 0.0230wt%, the evolutionary process of inclusions is: MgO∙Al2O3→Ce2O3, CeAlO3 and Ce2O2S→Ce2O3, Ce2O2S and Ce2O3 core surrounded by Ce–As–P layer. Adding cerium content from 0 to 0.0230wt% causes the secondary dendrite arm spacing to decrease from 36.8 μm to 29.4 μm, as the heterogeneous nucleation of Ce2O3, Ce2O2S and CeAlO3 inclusions, as well as the effect of dissolved cerium including the increase in the constitutional undercooling and the drag on the migration of liquid–solid interface. Ce2O3, Ce2O2S and CeAlO3 are the less effective heterogeneous nucleation cores for M2C-type and MC-type primary carbides precipitation than MgO∙Al2O3 inclusions, which is conducive to the decrease in the area fraction of primary carbides with adding 0.0067wt% cerium. Further increasing cerium content to 0.0230wt%, the formation of Ce–As–P inclusions surrounding Ce2O3 promotes the precipitation of M2C-type primary carbides, causing the increase in the area fraction of primary carbides.