Lanthanum Cerium Research Articles

Yttria-stabilized zirconia and lanthanum cerate granules with YSZ whiskers prepared by spray drying for thermal barrier coatings

The aim of this study was to explore the effect of different solid phases and varied amounts of polyvinyl alcohol (PVA) on granule size of plasma-sprayable yttria-stabilized zirconia (YSZ) with YSZ whiskers (YSZ/W) and lanthanum cerate (La2Ce2O7, LC) with YSZ whiskers (LC/W) as composite powders. The initial phase of this study involved the preparation and optimization of a YSZ suspension using varying solid loadings of YSZ powder (ranging from 30-75 wt.%) and PVA serving as both a binder and dispersant. The suspension was subjected to rigorous optimization procedures to meet the required standards. The suspensions were spray dried, and the resulting granulates were examined using SEM to determine their shape and size. The particle size of YSZ granules increased with increasing solid loading of YSZ in the suspension. The optimum amount of dispersant was found to be 1 wt.% related to the weight of solid, while the solid loading was 75 wt.% of YSZ. In some cases, excessive YSZ solid loading and dispersant impaired the formation of spherical granules. Composite YSZ/W and LC/W granules were also prepared with spherical, lemon, or irregular shapes, with the whiskers embedded in the YSZ or LC powder.

High acid-base tolerance and long storage time lanthanum cerium co-doped carbon quantum dots for Fe3+ detection

In this paper, lanthanum and cerium co-doped carbon quantum dots (LaCe-CQDs) was firstly synthesized by one step hydrothermal method. The obtained LaCe-CQDs shown sable fluorescence properties with pH values from 3 to 9 and after 4 weeks of storage. The average particle size of LaCe-CQDs, with excitation and emission wavelengths of 350 nm and 446 nm, is 3.27 ± 0.12 nm. Selective analysis of various metal ions revealed the sensitivity of LaCe-CQDs towards Fe3+ ions. Within the 0–60 μM, the fluorescence intensity exhibits a strong linear correlation with the concentration of Fe3+. The limit of detection (LOD) was determined to be 0.753 μM. Additionally, the accuracy of LaCe-CQDs were demonstrated in natural water samples. Therefore, LaCe-CQDs are a promising sensor for Fe3+ detection.

Investigating Hot corrosion, CMAS, and Thermal Shock Behaviour of Double-layer YSZ/La2Ce2O7 + YSZ Thermal Barrier Coatings

AbstractIn this work, new double-layer YSZ/La2Ce2O7 (LC) + YSZ coatings were developed using air plasma spraying (APS). The surface of the prepared coatings was relatively smooth and consisted of melted and partially melted areas. Their resistance to hot corrosion, CaO-MgO-Al2O3-SiO2 (CMAS), and thermal shock were examined. YSZ was added to the upper layer to enhance the lanthanum cerate (La2Ce2O7, LC) properties. During the hot corrosion tests, the corrosion salt reacted with the upper layer, and the CeO2 phase and new corrosion products were identified. The main phase was LaVO4, and the secondary phases were CeVO4 and YVO4. SEM confirmed the formation of new, cuboidal-shaped corrosion products. The infiltration of CMAS led to the formation of additional new products: Ca4MgxAl4Si(6-x-γ)O14 and Ca2.8(LaxCe1-x).6(SiO4)O6-4x. SEM revealed CMAS infiltration through the upper layer in the form of islands. Following the thermal shock resistance tests, the upper layer gradually peeled off, and the coating survived 67 cycles. Possible failure mechanisms were identified, and failure was attributed to the spallation of the upper layer from the surface layer by layer. After all tests, the top layer showed partial spalling and delamination. This was mainly caused by the reaction of corrosive salt or CMAS with the top layer, which changed its composition, leading to the formation and propagation of cracks and, ultimately, the separation of part of the upper layer. Peeling of the upper layer through mainly horizontal cracks was observed after hot corrosion, CMAS and thermal shocks. The NiCrAlY bond coat and YSZ interlayer remained undamaged.

A simulation based analysis for enhancement of performances of turbine blades in turbo jet engines with thermal barrier coatings (TBCs)

The enhancement of turbine blade performance within turbo jet engines is crucial for prolonged engine life. Amidst various cooling strategies for turbine blades, thermal barrier coatings (TBCs) emerge as a highly effective method. Just as the choice of material for the turbine blade holds importance, so too do the materials comprising TBCs. The current research work aims to pursue finite element-based analyses of turbine blades with TBCs, an almost real complex-shaped geometric model comprising the blade body with a rabbet is essential, the stress generated during TGO growth which is crucial for analysis, to select the substrate from both a thermo-structural and cost perspective. In this research endeavor, TBCs were structured with a substrate, a bond coat (NiCoCrAlY), and a top coat of lanthanum cerate (La2Ce2O7) ceramic layers. A thermally grown oxide (TGO), namely α-Al2O3, forms between the bond coat and the top coat due to the elevated temperatures experienced. Two distinct substrates, Inconel 625 and Titanium-T6 alloy, were meticulously chosen as turbine blade materials. Commencing with NACA 4412 airfoil data, the turbine blade was meticulously designed using CATIA, followed by simulations conducted on ANSYS software through a static thermal structural model. The simulation aimed to determine the optimal top coat/thermally grown oxide (TC/TGO) and TGO/bond coat (TGO/BC) layer thicknesses to achieve minimal equivalent stress and total deformation in the turbine blade. The simulated results revealed that a combination of 400 µm TC/10 µm TGO and 10 µm TGO/100 µm BC provided the lowest equivalent stress and total deformation, thereby offering valuable insights for the current research.

Metal-organic decomposed lanthanum cerium oxide thin films: A study of chemical and surface properties

Lanthanum cerium oxide thin films have been deposited on n-type (100) silicon wafers using the spin coating technique. The post-deposition annealing was performed over spin-coated films. The compositional studies were conducted by performing Fourier transform infrared spectroscopy, Energy dispersive X-ray spectroscopy, and X-ray diffraction. Ellipsometry was used to determine the thickness and atomic force microscopy was performed to understand the surface morphology of the deposited thin films. The effect of rapid thermal annealing at different temperatures over the structural and chemical properties of the LaCeO2 thin films was observed. The FTIR spectra show the formation of silicates at the interface of the oxide and semiconductor, while XRD results show that the films become crystalline with increased annealing temperature. The refractive index was observed to be reduced with an increase in the annealing temperature and a minor reduction in the physical thickness as per the sample standard deviation of 0.2981[Formula: see text]nm.

Study on the thermal insulation property of lanthanum–cerium oxide coatings

Functional fillers with low thermal conductivity and high near-infrared reflectance play a vital role in high temperature thermal insulation coatings and make an outstanding contribution to achieving efficient comprehensive thermal insulation. In this work, the thermal insulation and bonding properties of lanthanum–cerium oxide (LCO) coatings were regulated by composition design. The effects of the La/Ce mole ratio on phase composition, the thermal conductivity and near-infrared reflectivity of LCO coatings were investigated systematically. The results showed that coating with a La/Ce mole ratio of 1:1 possess the excellent thermal insulation properties (ΔT ≈ 115°C) due to the formation of a LCO solid solution and a lanthanum phosphate mesophase with low thermal conductivity and high near-infrared reflectivity. In addition, the mortise and tenon structure was formed between the coating and the substrate, which led to the remarkable bonding properties. The LCO coating offers excellent thermal insulation properties and broad application prospects in the fields of high temperature and energy conservation.

Enhanced lanthanum and cerium removal of self-powered electro-membrane bioreactor (SPEMBR) using high-active bi-functional M-N-CNTs@Fe/Mo electrode

Lanthanum and cerium are widely used as important raw materials for energy storage batteries due to excellent natural electrical, magnetic, and optical properties. However, with the explosive growth of new energy generation and the environmental degradation-resistant of lanthanum and cerium, it is difficult to balance environmental sustainability and resource scarcity to achieve lanthanum-cerium removal by conventional chelate salt precipitation. Herein, a laboratory-scale self-powered electro-membrane bioreactor (SPEMBR), integrating high-active nitrogen-doped carbon nanotube-loaded iron and molybdenum bimetallic conductive composite electrode membrane (M−N−CNTs@Fe/Mo) by hydrothermal and phase inversion processes was successfully constructed and evaluated for removing lanthanum cerium from industrial wastewater. The prepared bi-functional M−N−CNTs@Fe/Mo5% electrode membrane exhibited a uniform morphology and excellent hydrophilicity, with nano pore lattice spacing only 0.2637 nm. Electrochemical test results demonstrated that the novel electrode indicated excellent redox properties (i0 = 8.35 × 10−3 A cm−2, Cdl = 1.13 mF cm−2) and efficient electron transfer efficiency (Rct = 4.69 Ω, n = 3.9). Based on optimized conditions (5)% doping ratio, pH = 10, C = 20 mg/L), the SPEMBR assisted by M−N−CNTs@Fe/Mo catalytic electrode membrane achieved approximately complete removal efficiency of lanthanum and cerium (>99.2 %), superior to most publicly available related studies (86.3 %-99.0 %), but with a calculation cost of only $8.54. Identification of membrane interface products and system precipitates demonstrated that the outstanding removal efficiency was attributed to the combined reaction mechanism of electroreduction, electrocoagulation and electromembrane filtration. This work provides a bright application prospect for low-cost and effective removal of lanthanum cerium metal based on electrode membranes.

Plasma-sprayed GNP/CNT reinforced lanthanum-cerate coatings: Hot corrosion assessment in Na2SO4-V2O5 environment

This study investigates the hot-corrosion behavior of Carbon nanotube/Graphene-nanoplatelets (CNT/GNP)-reinforced lanthanum cerate (LC) coatings in a Na2SO4–V2O5 molten salt environment at 1350 °C for varying durations. Coatings were prepared using APS and characterized using XRD, FESEM, Raman, XPS, etc., techniques. The CNT/GNP-reinforced LCGC hybrid composite coating exhibited superior hot-corrosion resistance compared to LC and LCG coatings. The uniform dispersion of GNPs/CNTs within the coating matrix and the creation of protective LC oxides enhanced corrosion resistance. These findings highlight the potential of GNP/CNT-reinforced coatings in protecting high-temperature components like combustion chambers and gas turbine engines from hot corrosion.

Lanthanum Cerate Microspheres for Efficient Fluoride Removal from Wastewater.

The performance of lanthanum cerate microspheres (LCM) at removing fluoride was analyzed in batch experiments after they were synthesized via the hydrothermal strategy. The ball-shaped microsphere morphology of LCM is confirmed by SEM and TEM. The synthesized LCM adsorbent showed excellent adsorption capacity in the pH range 3.0-7.0, with the optimal pH range being 3.5-4.5. The Langmuir adsorption model was more appropriate than the Freundlich model for describing the adsorption isotherm. The LCM adsorbent exhibited a significantly higher Langmuir adsorption capacity of 104.83 mg/g at pH 4.0, surpassing that of any other reported adsorbent. We investigated the adsorption of fluoride under a variety of conditions, including the presence of distinct anions. Furthermore, testing the adsorbent in actual groundwater demonstrated its high effectiveness in removing fluoride. Different useful analytical techniques were used for measurements and to learn and deduce the adsorption mechanism.

Phase stability and initial phase high-temperature corrosion behavior of non-stoichiometric lanthanum cerium oxide thermal barrier coatings

Three different compositions of lanthanum cerium oxide thermal barrier coatings with varied cerium oxide (1.8CeO2, 1.9CeO2 and 2.0CeO2) compositions were synthesized and plasma sprayed to achieve free-standing coatings. The phase stability studies showed that the coatings are stable at 1400 °C after 100 h. The high-temperature corrosion was performed in the presence of sulfate-vanadate (50 wt%Na2SO4+50 wt%V2O5) at 1000 °C for 4 h. The result depicts LaVO4 as the major corrosive product formed in all three compositions along with CeVO4, LaCeVO4 and CeO2. The hot corrosion test result gives information that the composition of CeO2 greatly influences the hot corrosion resistance. The increase in CeO2 percentage increases the resistance against the infiltration of molten sulfate-vanadate compounds. This investigation provides a feasible way to understand the coating composition for better hot corrosion resistance in sulfate-vanadate mixtures.

Single-step methane to methanol over lanthanum cerium oxide: The crucial role of surface reactive oxygen and carbonate species

The single-step conversion of methane to methanol (MTM) represents an attractive route for the valorization of low-concentration coalbed methane (CBM). In this work, the effects of surface reactive oxygen and carbonate species on the catalytic performance of LaCeOx materials for MTM reaction was investigated. Lanthanum cerium oxide with different crystal structure were prepared by adjusting the ratio of La to Ce. Under low methane concentration (8 vol.%), La5Ce1 sample with defective fluorite phase exhibited the best methanol site-time yield to 20 μmol gcat−1h−1. The more oxygen vacancies on defective fluorite phase promote the generation of reactive oxygen species. Moreover, it was also found that the incorporation of Ce weakened the adsorption of surface carbonate. The more moderately adsorbed carbonate on La2Ce1 sample enhanced the methanol selectivity. In-situ diffuse reflectance Fourier transform infrared spectroscopy (In-situ DRIFTS) further revealed the different methane to methanol pathway over La5Ce1 and La2Ce1 sample. Reactive oxygen species were attributed to the site for methane activation and CH3O* was the intermediate group of methanol. This study provides a new point that the oxygen species of lanthanum-cerium oxide could be regulated to promote their performance for MTM reaction, and we believed that the as-discussed oxide could be employed as the host materials for active phases as well.

Degradation of ofloxacin by lanthanum cerate perovskite activated bisulfite

In recent years, the extensive utilization of ofloxacin (OFX) has led to elevated concentration of OFX compound in the aquatic environment. At the same time, the inherent recalcitrance of OFX has presented a formidable challenge for OFX degradation. In this study, lanthanum cerium perovskite (LaCeO3) was prepared by citric acid sol–gel method to activate bisulfite (BS) for the effective degradation of OFX. The results revealed that the LaCeO3/BS system removed 87.5% of OFX within 180 min with a pseudo-first-order kinetic constant of 3 × 10−3 min−1. Radical quenching experiments and electron paramagnetic resonance (EPR) spectroscopy confirmed that sulfate radicals (SO4•_) and hydroxyl radicals (HO•) were the primary reactive species responsible for OFX removal in LaCeO3/BS system. The reaction mechanism indicated that Ce in LaCeO3/BS system served as the primary active site for BS activation, and a regenerating cycle involving ≡Ce(III)/≡Ce(IV) was present. Additionally, possible intermediate products were identified by a liquid chromatograph-mass spectrometer (LC-MS), revealing potential degradation pathways of OFX. Cycle tests and energy dispersive spectrometer (EDS) data demonstrated the favorable reusability and stability of LaCeO3.

Nanometric Cutting Mechanism of Cerium–Lanthanum Alloy

Cerium–lanthanum alloy is widely used in the green energy industry, and the nanoscale smooth surface of this material is in demand. Nanometric cutting is an effective approach to achieving the ultra-precision machining surface. Molecular dynamics (MD) simulation is usually used to reveal the atomic-scale details of the material removal mechanism in nanometric cutting. In this study, the effects of cutting speed and undeformed chip thickness (UCT) on cutting force and subsurface deformation of the cerium–lanthanum alloy during nanometric cutting are analyzed through MD simulation. The results illustrate that the dislocations, stacking faults, and phase transitions occur in the subsurface during cutting. The dislocations are mainly Shockley partial dislocation, and the increase of temperature and pressure during the cutting process leads to the phase transformation of γ-Ce (FCC) into β-Ce (HCP) and δ-Ce (BCC). β-Ce is mainly distributed in the stacking fault area, while δ-Ce is distributed in the boundary area between the dislocation atoms and γ-Ce atoms. The cutting speed and UCT affect the distribution of subsurface damage. A thicker deformed layer including dislocations, stacking faults and phase-transformation atoms on the machined surface is generated with the increase in the cutting speed and UCT. Simultaneously, the cutting speed and UCT significantly affect the cutting force, material removal rate, and generated subsurface state. The fluctuations in the cutting force are related to the generation and disappearance of dislocations. This research first studied the nanometric cutting mechanism of the cerium–lanthanum ally, providing a theoretical basis for the development of ultra-precision machining techniques of these materials.

Surface morphology of polycrystalline cerium–lanthanum alloy in nanometric cutting

Molecular dynamics simulation is carried out for the nanometric cutting of polycrystalline cerium–lanthanum alloy. By adjusting different grain orientations, the effects of slip direction on the alloy's surface morphology are studied at various undeformed chip thickness. The causes of the elastic deformation of the workpiece surface are clarified by analyzing the atomic motion trajectories. The grain boundary migration found during the simulation is also illustrated. Results show that slip deformation is the main influencing factor of plastic deformation in the processing, and the number of slip lines affects the surface step height of polycrystals.

Synthesis, Characterization, and Polishing Properties of a Lanthanum Cerium Fluoride Abrasive.

One kind of lanthanum cerium fluoride abrasive was prepared using the raw materials Ce2(CO3)3, La·Ce(CO3)3, and NH4F at temperatures of 400-1050 °C. The combined techniques of X-ray diffraction with Rietveld refinements, scanning electron microscopy, and X-ray photoelectron spectroscopy were employed to characterize the products. It was found that the materials are all made up of agglomerated irregular block-shaped particles with particle sizes in micrometer ranges. Below 850 °C, the product is a mixture of cubic CeO2 and trigonal LaF3, while above 900 °C, it is a mixture of cubic CeO2 and tetragonal LaOF. A higher calcination temperature suppresses the formation of the LaF3 phase but enhances the LaOF phase. The Ce in the prepared material is present in mixed states of Ce3+ and Ce4+, and the Ce4+/Ce3+ ratio increases with increasing calcination temperature. When the material prepared at 900 °C was used in the polishing test on K9 glass, the obtained polishing surface is very clean and flat, and the thickness difference before and after grinding is moderate, indicating its potential as an abrasive for polishing the surface of optical glass.

Increased high selectivity light aromatics and furans production by co-feeding methanol to catalytic pyrolysis of cellulose with Lanthanum–Cerium bimetallic modified MCM-41 catalysts

To develop a cost-effective La-based catalyst for conversion waste biomass into high valuable chemicals, bimetallic La–Ce modified MCM-41 catalysts with different La to Ce ratios were prepared by wet impregnation method, and successfully applied to catalytic pyrolysis of cellulose with methanol as hydrogen-donor. The synergistic effect, conversion pathway for promotion of furans and aromatic and deactivation mechanism were also evaluated in co-conversion process with different technologies. Results showed that, modified MCM-41 maintained mesoporous structure, and combination La, Ce-modified MCM-41 catalysts showed the best catalytic activity due to synergistic interaction of La–O species and Ce–O species with support as well as suitable mild strong acidity. Higher La content had remarkable advantage for advancing HCs and olefin content due to higher Brønsted acid intensity, and higher Ce content was facilitated to aromatic and furans conversion due to higher mesoporous volume. 1La–3Ce/MCM-41 demonstrated the most potential for furan formation (50.18%) and 1La–1Ce/MCM-41 exhibited best deoxygenation activity and obtained more than 61.16% HCs content and 35.15% MAHs selectivity via Diels-Alder reaction assist with acid centers and metal dispersion, furthermore, 1La–1Ce/MCM-41exhibited outstanding reusability and anti-coking performance, nearly 95% yield of HCs were still maintained after regeneration. Hence, catalytic pyrolysis vapor upgrading of waste biomass with La–Ce/MCM-41 had great potential to produce valuable fuels and chemical.

Thermal fatigue characteristics of 8Y2O3-ZrO2, La2Zr2O7, La2(Zr0.7Ce0.3)2O7 and La2Ce2O7 thermal barrier coatings in duplex, multilayer functionally graded and multilayer configurations

La2Zr2O7, La2(Zr0.7Ce0.3)2O7 and La2Ce2O7 pyrochlore plasma sprayable powders were synthesized and plasma spray coated on steel plates with NiCrAlY bond coat. Three different configurations were used: duplex, multilayer functionally graded and multilayer, with different combinations of commercial 8% yttria stabilized zirconia (8YSZ) and NiCrAlY (bond coat) layers. The prepared coatings were compared with the standard duplex 8YSZ thermal barrier coatings (TBCs) with a goal to study their suitability to serve as TBCs. TBCs? layer thicknesses and interfaces were studied via SEM on polished cross section metallographic samples removed from the spray coated TBCs. Thermal fatigue resistance was evaluated by directing a gas flame on the ceramic surface at 1200 and 1400 ?C, followed by its rapid withdrawal and forced cooling by pedestal fan. The maximum number of thermal shock cycles the coatings could withstand before failure was determined. The multilayered TBCs with lanthanum cerate composition stacked with 8YSZ exhibited the superior thermal fatigue resistance characteristics compared to all other studied TBCs. The findings were correlated with the crystalline phases of the ceramic coatings, obtained via XRD, and discussed in the light of existing literature.

Plasma-assisted cutting for impurity reconstruction of an as-cast cerium–lanthanum alloy

The high chemical activity and oxide impurities inside cerium–lanthanum (Ce–La) alloys make it difficult to achieve high surface finishing with diamond turning. Plasma-assisted cutting, in which the plasma is applied to regulate the longitudinal impurity distribution of the surface layer and improve its machinability in diamond turning, is proposed for machining as-cast Ce–La alloys. The effect of the rotational speed on built-up edge is discussed, and a surface with surface roughness of 6.5 nm in Sa is successfully achieved. Experimental results show that the machined modified alloy possesses good oxidation resistance, benefiting various applications in green energy.

Synthesis and characterization of pyrochlore-type lanthanum cerate nanoparticles: Electrochemical determination of antibiotic drug sulfadiazine in biological and environmental samples

In recent eras, antibiotic drugs are essential for humans and the veterinary health system. However, the improper discarding of their residues are simply contaminating the food products and environmental samples. Here, pyrochlore-type lanthanum cerate nanoparticles (LaCe NPs) were prepared through a simple co-precipitation route and used as effective electrocatalyst for the detection of antibiotic drug sulfadiazine (SDZ). The structural investigations of prepared material were carried out using XRD, FT-IR, XPS, SEM, HR-TEM, and EDX along with Elemental mapping analysis, which confirm the good formation of pyrochlore type LaCe in the form of particle-like morphology with well-crystalline nature. A nanosized LaCe revealed superior electrochemical activity towards SDZ owing to the large surface area, facilitating mass and ionic transport and chemical stability phenomena. The as-prepared LaCe NPs demonstrated an excellent electrochemical performance towards SDZ determination with a low LOD (50 nM), a wide dynamic range of 0.04–1525 μM, and an acceptable sensitivity of 1.92 μA μM−1 cm−2. Furthermore, the LaCe NPs/GCE revealed excellent reproducibility, storage stability, and selectivity parameters. Additionally, the proposed sensor achieves a good SDZ recovery in milk and human urine samples. The results strongly suggest that the rare earth metal oxide of lanthanum cerate is an efficient catalyst for portable detection of SDZ.

Plasma sprayed graphene/carbon nanotube reinforced lanthanum-cerate hybrid composite coating

Lanthanum cerate (LC: La2Ce2O7) is a potential material for thermal barrier coating, whose improved toughness is a crucial necessity for the pathway of its industrialization. Herein, we demonstrated a promising approach to develop graphene/carbon nanotube hybrid composite coating using a large throughput and atmospheric plasma spraying method. Graphene nanoplatelets (GNP: 1 wt %) and carbon nanotube (CNT: 0.5 wt %) reinforced lanthanum cerate (LCGC) hybrid composite coatings were deposited on the Inconel substrate. Addition of 1 wt % GNP and 0.5 wt % CNT in LC matrix has significantly increased its relative density, hardness, and elastic modulus up to 97.2%, 2–3 folds, 3–4 folds, respectively. An impressive improvement of indentation toughness (8.04 ± 0.2 MPa m0.5) was observed on LCGC coating, which is ∼8 times higher comparing the LC coating. The toughening was attributed to the factors: such as the distribution of GNPs and CNTs in the LC matrix, synergistic toughening offered by the GNPs and CNTs; (i) GNP/CNT pull-out, (ii) crack bridging and arresting, (iii) splat sandwiching, mechanical interlocking, etc. Finally, this improved toughness offered an exceptional thermal shock performance up to 1721 cycles at 1800 °C, without any major failure on the coating. Therefore, the GNP and CNT-reinforced LC hybrid composite coating can be recommended to open a path for turbine industries.