La2O3 Phase Research Articles

Boosting bio-lipids hydrodeoxygenation via highly dispersed and coking-resistance bimetallic Ni-La/SiO2 catalyst

A highly dispersed and coking-resistance bimetallic Ni-La/SiO2 catalyst was prepared for the selective hydrodeoxygenation (HDO) of fatty acid methyl esters (FAMEs) and non-edible bio-lipids to hydrocarbon compounds. Under optimum conditions, full conversion of methyl palmitate (MP) and 97.6% selectivity for pentadecane (PD) were achieved. The catalyst also exhibited high conversion and excellent desired product selectivity for the HDO of various model FAMEs, fatty acids, trilaurin, jatropha oil (JO) and waste cooking oil (WCO). Multiple characterizations show that the embedding effect (metal−support or metal−metal interaction) associated with the introduction of metallic La not only contributes to the formation of well-dispersed Ni particles and abundant active Niδ+−OV−LaOx species, but also prevents the migration and sintering of metallic Ni particles at high temperatures. Furthermore, the mutual transformation of the La2O3 and La2O2CO3 crystal phases effectively inhibits coke deposition on the catalyst surface during the reaction process, resulting in remarkable stability and reusability of the catalyst. A plausible reaction network and mechanism for the catalytic HDO of MP over Ni-La/SiO2 catalyst were proposed. This method of constructing a catalytic system can provide a basis for the development of efficient catalysts for the HDO of non-edible bio-lipids.

Green synthesis of La2O3–LaPO4 nanocomposites using Charybdis natator for DNA binding, cytotoxic, catalytic, and luminescence applications

Abstract A one-step biosynthetic pathway for the fabrication of La2O3–LaPO4 nanocomposites (NCs) was developed, employing Charybdis natator. The structure and phase changes of the NCs were confirmed, and their diverse applications were explored. The peaks at 206, 332, and 442 nm in UV-DRS studies confirmed the formation of La2O3–LaPO4 NCs. Fourier transform infrared spectral analysis revealed La–O stretching at 716 cm−1 and the presence of PO 4 3 − {\text{PO}}_{4}^{3-} bands at 532, 560, 578, and 618 cm−1. X-ray diffraction patterns showed a hexagonal phase of La2O3 with peaks at 2θ 11.04 and 28.57 and monoclinic LaPO4 phases at 2θ = 18.79 and 41.88. X-ray photoelectron spectroscopy data showed binding energy peaks at 836.04 and 852.77 eV, corresponding to 3d5/2 and 3d3/2 of the lanthanum. The average particle size from HR-TEM analysis was 28.95 nm after annealing at 800°C and SAED patterns confirmed their crystalline nature. The high affinity of the NCs towards ctDNA was established by a binding constant value of 2.08 (mg·mL−1)−1. Under UV exposure, 96% degradation efficiency for methyl orange within 120 min at pH 4 was displayed, with a rate constant of 2.72 × 10−2 min−1 affirming their photocatalytic potential. Their biocompatibility was assessed through MTT assay and luminescence characteristics were evaluated.

Biosynthesis of lanthanum oxide-cerium phosphate as luminescent materials using a marine soft coral for cytotoxic, photocatalytic and photometric applications

Researchers created a single-step biosynthetic method using marine soft coral to produce La2O3–CePO4 (LCP) nanocomposites. The structure and phase transitions of the nanocomposites were verified, and various potential applications were investigated. The UV-DRS study peaks supported the evidence of La2O3–CePO4 formation. Analysis using FT-IR spectroscopy showed the La–O bonds and PO43− bands. The XRD analysis revealed the presence of the hexagonal phase of La2O3 and the monoclinic CePO4 phases. The average particle size of La2O3–CePO4 nanocomposites was 25.81 nm. Absorption spectroscopy indicates that the La2O3–CePO4 nanocomposites interact with the DNA groove. Under UV light exposure, a degradation efficiency of 90.12 % was achieved for alizarin yellow within 100 min at a pH of 4. The rate constant of 0.0151 min−1 confirmed the photocatalytic capabilities of the material. Their compatibility with living organisms was evaluated using the MTT assay, while their luminescence properties were examined closely. These result paves a way for manufacturing innovation.

Improved toughness and oxidation resistance of Nb[sbnd]Si based ultra-high temperature alloys by in-situ generated La2O3 phase

The effects of in-situ rare earth oxide phase La2O3 on the microstructure and properties of NbSi based ultrahigh temperature alloys were investigated. The NbSi based alloys were doped with varying amounts of La (0.05, 0.1, 0.2, 0.4 and 0.8 at.%). The La2O3 phase forms in situ during the melting process. The fracture toughness is greatly improved by the La2O3 phase, and the KQ value of the 0.4La alloy is 27.1% higher than that of the base alloy. The improvement of fracture toughness is due to these three aspects: first, the high-melting-point La2O3 phase (TmLa2O3= 2588 K) precipitates first and effectively refines the microstructure. As a result, the frequency of secondary cracking and crack bridging increases. Second, the formation of the La2O3 phase significantly reduces the issue of oxygen contamination. Third, the high-hardness La2O3 phase separates during the fracture process, reducing the constraints on the deformation of NbSi based alloys. Additionally, La2O3 has the lowest Gibbs free energy among all possible formed oxides. During the oxidation process, the continuous oxidation behavior of the La2O3 phase reduces the degree of oxidation inside the alloy. Therefore, the oxidation resistance is significantly improved.

Hydrogen-rich syngas production from acetic acid as bio-oil model compound: Effect of intermediate phases (La2NiO4, La2O3 and Ni) of LaNiO3 catalyst

In biomass gasification, bio-oil is the main component of the condensable by-products. It is considered an attractive source for H2 production via steam reforming. This study conducted acetic acid as a bio-oil model compound with LaNiO3 perovskite catalyst due to its high oxygen vacancies and active sites. However, the perovskite structure of LaNiO3 catalysis can be destroyed by produced H2 gas, forming additional phases, including La2NiO4, La2O3 and Ni. The LaNiO3 and different phases were synthesized via a sol-gel method to probe its contribution and interaction with the H2 gas produced from steam reforming of acetic acid. Through 300 min of reaction in steam to carbon (S/C) ratio of 3, the results showed that reduced-LaNiO3 has stable H2 gas production, while the other phases decrease with time. In particular, CH4 is the main composition with the La2O3 phase. A series of characterization techniques, such as XRD, BET, XPS, SEM, TG, H2-TPR and (CO2 and O2)-TPD, were utilized to investigate fresh and used samples. The results showed that the LaNiO3-reduced phase has high oxygen storage capacity, oxygen mobility, oxygen vacancies and surface area, preventing coke deposition. In contrast, the LaNiO3 and La2NiO4 phases have poor coke deposition resistance.

Improved high-temperature sintering resistance and light alkanes oxidation activity by La modification on Co3O4 nanocatalyst

In order to improve low-temperature activity and high-temperature sintering resistance of cobalt-based catalyst in catalytic degradation of emitted light alkanes, a strategy of lanthanum modification on Co3O4 nanocrystalline is proposed in this work, aiming at efficiently degrading methane emitted from the oil and natural gas industry. The La-Co3O4 nanocatalysts were prepared by co-precipitation method, and the effects of La-doping on the structural features and catalytic activity of Co3O4 catalyst for methane oxidation were investigated. The results show that the addition of lanthanum forms a composite catalyst containing La2O3 phase and Co3O4 phase, and the interaction increases the active species, which can significantly improve the low-temperature activity of the catalyst. Among them, 5 % La-Co3O4-F catalyst shows the best catalytic activity with 48 °C decrease of the temperature of 90 % methane conversion (T90) compared with pure Co3O4. Furthermore, with thermal ageing treatment at 750 °C for 100 h, Lanthanum modification can significantly slow down the agglomeration growth and the decrease of specific surface area of cobalt oxide in long-term running, and the formation of perovskite structure (LaCoO3) on Co3O4 nanocrystal surface increases the mobility of lattice oxygen, further inhibiting the sintering deactivation of Co3O4 catalyst. The catalyst doped with 5 % La still showed better performance after thermal ageing, which is 127 °C lower than T90 of pure Co3O4. Moreover, this advantage of La doping can also be observed in the catalytic oxidation of other typical hydrocarbons such as ethane and propane. This work provides a promising strategy toward the design of advanced non-precious metal oxide catalysts for practical catalytic oxidation application with excellent high-temperature sintering resistance.

Effect of Mn content on the structure, electromagnetic properties, and electromagnetic wave absorption characteristics in La0.7Sr0.3Mn1+xO3

The perovskite manganese oxide, La0.7Sr0.3Mn1+xO3 (x = −0.4, −0.2, 0, 0.2, 0.4, 0.6, 0.8, 1.0), was synthesized using the solid-state reaction method. A single-phase perovskite structure was obtained at the stoichiometric composition (x = 0). However, with an increase in Mn excess (x > 0), secondary phases of Mn2O3 and Mn3O4 formed and increased, while La2O3 and Sr-rich phases emerged when Mn is deficient (x < 0). The electrical conductivity, permittivity, and permeability of the samples showed significant variations with x, as both charge transport and magnetism originate from the presence of Mn. Complex permittivity (ε', ε") and permeability (μ', μ") spectra were utilized to calculate RL maps based on a transmission line theory. For samples with x ≥ 0, which exhibited relatively high values of ε' and ε", there was no significant absorption of electromagnetic (EM) waves within the measured frequency range (0.1 ≤ f ≤ 18 GHz) due to high EM wave reflection. Conversely, the Mn-deficient samples (x = −0.2, −0.4) demonstrated excellent EM wave absorption properties in the GHz range. This can be attributed to their favorable impedance matching characteristics, resulting from significantly reduced ε' and ε" values in the Mn-deficient samples. Notably, the sample with x = −0.2 exhibited the most outstanding EM wave absorption characteristics, with an RL value of −56 dB at a frequency of 2.33 GHz and a thickness of 7.59 mm. Additionally, it achieved an RL value of −50 dB at 9.8 GHz and 2.90 mm thickness.

Understanding La2NiO4-La0.5Ce0.5O2 Oxygen Electrode Phase Evolution in a Solid Oxide Electrolysis Cell

This work aims to understand the decomposition mechanism of a La2NiO4 phase in La2NiO4-La0.5Ce0.5O2 (LNO-LDC) oxygen electrodes after testing in a solid oxide electrolysis cell (SOEC) at 800oC. Scanning/transmission electron microscopy (S/TEM) examination of LNO-LDC electrode at atomic level before and after testing was undertaken. Pure LNO and LDC phases as well as a low density of lanthanum phosphate (LPO) grains were detected in the as prepared (untested) oxygen electrode. P enrichment, a potential constituent in some of the synthesis additives, was found as small, nanometer scale, deposits along all grain boundaries which is suggested to poison the LNO phase during SOEC operation. Mild to aggressive decomposition of La2NiO4-La0.5Ce0.5O2 (LNO-LDC) oxygen electrode was observed after SOEC operating at 800 °C at 1.3V for 920 hours. Detailed microstructural and microchemical characterization of the decomposed regions was performed using an aberration (CS) corrected JEM-ARM200CF transmission electron microscope operated at 200 kV. The evolution of the LNO phase decomposition was noted beginning with the expulsion of Ni into the surrounding LNO matrix and grain boundaries, forming La-rich and Ni-rich phases in the LNO correspondingly. An acicular La2O3 phase was always noted initiating at either the LNO/LDC or LNO/LNO interfaces, growing and eventually intersecting one another, especially in aggressively decomposed regions. Initial decomposition exhibited single layers of Ni atoms along (004) plane of LNO, followed by gradual formation of La3Ni2O7, LaNiO3, and fine NiO (several nanometer in size) phases during moderate to aggressive decomposition. In addition, NiO was noted at LDC/LDC grain boundaries ranging from a few to several tens of nanometers thick. This presentation will demonstrate how P contamination may affect the stability of SOEC cells.

Methane conversion to syngas by chemical looping on La0.8Sr0.2FexCo1-xO3 (x = 0, 0.25, 0.50, 0.75) perovskites with CO2 co-feeding

Partial oxidation of methane (POM) by chemical looping with CO2 co-feeding on La0.8Sr0.2FeO3 (LSF) perovskite catalyst yielded a highly selective operation and enabled to extend the duration of reduction cycle. In this work, the conversion of methane to syngas was studied on La0.8Sr0.2Fe(x)Co(1-x)O3 (x = 0, 0.25, 0.5, 0.75) perovskites in chemical-looping mode, co-feeding CO2 and methane. The reaction was conducted at 850 °C, 15 min reduction (10% methane in N2, 0–3% CO2), and 10 min oxidation (10% O2 in N2) cycles. The perovskites activity decreased with increasing Co content, in the absence of CO2, due to intensified coke deposition on the catalyst. Addition of CO2 during the reduction step (1–3%) reduced coke accumulation. A run conducted on La0.8Sr0.2CoO3 (LSC) with continuous feeding of CO2 and periodical (on–off) methane feeding indicated that CO2 reacts with the accumulated coke in reverse-Boudouard reaction, increasing CO selectivity without affecting the methane conversion. XRD analysis of reduced Co-containing perovskites indicates a decreasing perovskite content. Metallic Co and La2O3 phases increased as the Co content in the fresh perovskite increased, increasing coke deposition. As the Co content increased, the process shifts from POM with oxygen replenishment (LSF) to cracking followed by reverse-Boudouard reaction (LSC).

Reset-First and Multibit-Level Resistive-Switching Behavior of Lanthanum Nickel Oxide (LaNiO3-x) Thin Films.

The resistive random-access memory (RRAM) with multi-level storage capability has been considered one of the most promising emerging devices to mimic synaptic behavior and accelerate analog computations. In this study, we investigated the reset-first bipolar resistive switching (RS) and multi-level characteristics of a LaNiO3-x thin film deposited using a reactive magnetron co-sputtering method. Polycrystalline phases of LaNiO3 (LNO), without La2O3 and NiO phases, were observed at similar fractions of Ni and La at a constant partial pressure of oxygen. The relative chemical proportions of Ni3+ and Ni2+ ions in LaNiO3-x indicated that it was an oxygen-deficient LaNiO3-x thin film, exhibiting RS behavior, compared to LNO without Ni2+ ions. The TiN/LaNiO3-x/Pt devices exhibited gradual resistance changes under various DC/AC voltage sweeps and consecutive pulse modes. The nonlinearity values of the conductance, measured via constant-pulse programming, were 0.15 for potentiation and 0.35 for depression, indicating the potential of the as-fabricated devices as analog computing devices. The LaNiO3-x-based device could reach multi-level states without an electroforming step and is a promising candidate for state-of-the-art RS memory and synaptic devices for neuromorphic computing.

ISOTHERMAL SECTION OF THE Al2O3–TiO2–La2O3 PHASE DIAGRAM AT 1400 °C

Isothermal section of the Al2O3–TiO2–La2O3 phase diagram at 1400 °C is constructed for the first time. It is the part of systematic investigations of Al2O3–TiO2–Ln2O3 (Ln = lanthanides, Y) systems. The 1400 °C was taken as the temperature, at which no liquid is expected in the system. Samples were prepared by a chemical method. Samples were annealed in air at 1400 °C for 80 hour sand cooled in the furnace. Phases in the samples were determined by XRD analysis. New phases and appreciable homogeneity regions based on components and binary compounds were not found. Isothermal section consists of six narrow two-phase and seven three-phase regions. Triangulation of the system is determined by the phase La2Ti2O7, which is in equilibrium with compounds Al2TiO5, LaAlO3 and system components TiO2 and Al2O3. Formation of phases La4Ti9O24, La2Ti3O12 and La2TiO5 in binary boundary system TiO2–La2O3 causes the appearance of partially quasibinary sections Al2TiO5–La4Ti9O24, Al2TiO5–La2Ti3O12 and LaAlO3–La2TiO5. The obtained results make a significant contribution to the understanding of interactions between the components in the system studied. The system includes binary compounds with high electro-optical, ferroelectric, piezoelectric, photocatalytic properties, mikrowave dielectric ceramic. In addition, in the system we expects the existence of new three-phase and two-phase eutectics, which can be obtained in the form of high-temperature structural materials by the directional solidification. This fact opens up the possibility to find and establish the coordinates of new three-phase and two-phase eutectics for directional solidification and to obtain new high-temperature structural materials in the Al2O3–TiO2–La2O3 system.

Facile Synthesis and Enhanced Photocatalytic Properties of La2O3/SrSn(OH)6 Nanorods

Background: The efficient removal of the environmental organic pollutants using the photocatalytic technology catalyzed by the semiconductors has attracted great research interest in recent years. La2O3/SrSn(OH)6 nanorods show enhanced photo-catalytic activity towards crystal violet (CV). Objective: The aim is to obtain La2O3/SrSn(OH)6 nanorods by a simple hydrothermal route using lanthanum acetate and SrSn(OH)6 nanorods, and research the photo-catalytic properties for the CV degradation. Methods: La2O3/SrSn(OH)6 nanorods were obtained by a hydrothermal route using lanthanum acetate and SrSn(OH)6 nanorods and characterized by X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy (DRS), photoluminescence (PL) and photo-catalytic experiments. Results: The composite nanorods are comprised of hexagonal SrSn(OH)6 and cubic La2O3 phases. Some nanoscale particles attach to the surface of the nanorods with the diameter and length of about 100 nm and longer than 1 μm, respectively. La2O3/SrSn(OH)6 nanorods show lower band gap value than that of the SrSn(OH)6 nanorods. The photocatalytic reaction rate constant for the CV degradation using 15wt.%-La2O3/SrSn(OH)6 nanorods is 3 times higher than that of the pure nanorods. Conclusion: La2O3/SrSn(OH)6 nanorods possess good reusability and stability for the CV removal. The photo-catalytic activity for the CV removal of the SrSn(OH)6 nanorods can be greatly enhanced by the La2O3.

The Microstructure and Properties of Ni-Si-La2O3 Coatings Deposited on 304 Stainless Steel by Microwave Cladding

In this investigation, microwave radiation was used alongside a combination of Ni powder, Si powder, and La2O3 (Lanthanum oxide) powder to create surface cladding on SS-304 steel. To complete the microwave cladding process, 900 W at 2.45 GHz was used for 120 s. "Response surface methodology (RSM)" was utilized to attain the optimal combination of microwave cladding process parameters. The surface hardness of the cladding samples was taken as a response. The optimal combination of microwave cladding process parameters was found to be Si (wt.%) of 19.28, a skin depth of 4.57 µm, irradiation time of 118 s, and La2O3 (wt.%) of 11 to achieve a surface hardness of 287.25 HV. Experimental surface hardness at the corresponding microwave-cladding-process parameters was found to be 279 HV. The hardness of SS-304 was improved by about 32.85% at the optimum combination of microwave cladding process parameters. The SEM and optical microscopic images showed the presence of Si, Ni, and La2O3 particles. SEM images of the "cladding layer and surface" showed the "uniform cladding layer" with "fewer dark pixels" (yielding higher homogeneity). Higher homogeneity reduced the dimensional deviation in the developed cladding surface. XRD of the cladded surface showed the presence of FeNi, Ni2Si, FeNi3, NiSi2, Ni3C, NiC, and La2O3 phases. The "wear rate and coefficient of friction" of the developed cladded surface with 69.72% Ni, 19.28% Si, and 11% La2O3 particles were found to be 0.00367 mm3/m and 0.312, respectively. "Few dark spots" were observed on the "corroded surface". These "dark spots" displayed "some corrosion (corrosion weight loss 0.49 mg)" in a "3.5 wt.% NaCl environment".

Characterization and evaluation of the therapeutic benefits of pure and lanthanides mono- and co-doped zinc oxide nanoparticles

The effect of Lanthanides-doping on the structural, optical, morphological, antibacterial and anticancer properties of zinc oxide (ZnO) nanoparticles was investigated. Pure ZnO, Zn0.9La0.1O, Zn0.9Ce0.1O, and Zn0.9La0.05Ce0.05O were fabricated through the chemical co-precipitation route. The structural and morphological properties were studied using the X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The optical properties were analyzed by photoluminescence spectroscopy (PL). The inhibitory effect of the synthesized nanoparticles (NPs) was assessed against six bacterial strains using the agar well diffusion and broth micro-dilution methods. The anticancer potential of the synthesized NPs was assessed against two human colon cancer cell lines Caco-2 and HCT-116. The appearance of the La2O3 and CeO2 secondary phases upon doping La3+ and Ce3+ ions induced structural and morphological changes. The large distorted hexagonal morphology of pure ZnO is transformed into small sized distorted hexagonal form. The photoluminescence spectra revealed the point defects resulting from Lanthanum (La) and cerium (Ce) doping. The prepared NPs significantly inhibited the growth of the six investigated bacteria and induced cytotoxic effects and morphological changes against Caco-2 and HCT-116 cell lines. This study showed that doping ZnO with lanthanide ions such as La3+ and Ce3+ provide promising biological applications. These NPs showed a potent antibacterial and anticancer effect towards the investigated bacterial strains and colon cancer cell lines. These findings point to the importance of the biological applications of NPs, and the possibility of investigating other biomedical applications for NPs.

Effect of LaB6 on the microstructure evolution and mechanical properties of Ti-45Al-8Nb alloy

High-Nb-containing TiAl alloys have been considered an excellent candidate for demanding high-temperature structural components due to their attractive mechanical properties and low density. However, the intrinsic brittleness at room temperature remains a great barrier limiting its processability. Here a novel alloy design strategy was introduced to improve its ductility from the perspective of grain refinement and removal of oxygen within the matrix. A minor content of LaB6 was introduced into Ti-45Al-8Nb alloy prepared by vacuum arc melting. La2O3 and TiB ceramic phases were in-situ synthesized owing to the decomposition of LaB6 additive. The effect of LaB6 addition on the microstructure and compressive properties of TiAl-based alloys was investigated. The LaB6 inoculation not only refines the lamellar colonies but also promotes the generation of single γ phases, contributing to the transformation from coarse full-lamellar to refined near-lamellar and even dual-phase colonies. The major fracture mode transformed from inter-lamellar to trans-lamellar to inter-granular with LaB6 addition increasing. With 0.4 wt% LaB6 addition, both the ultimate compress strength and fracture strain increased from 1065 MPa and 17.1 % to 1503MPa and 26.98 % respectively.

MgO-La2O3mixed metal oxides heterostructure catalysts for photodegradation of dyes pollutant: synthesis, characterization and artificial intelligence modelling.

In the present work, we prepared MgO-La2O3-mixed-metal oxides (MMO) as efficient photocatalysts for degradation of organic pollutants. First, a series of MgAl-%La-CO3-layered double hydroxide (LDH) precursors with different contents of La (5, 10, and 20 wt%) were synthesized by the co-precipitation process and then calcined at 600°C. The prepared materials were characterized by XRD, SEM-EDX, FTIR, TGA, ICP, and UV-vis diffuse reflectance spectroscopy. XRD indicated that MgO, La2O3, and MgAl2O4 phases were found to coexist in the calcined materials. Also, XRD confirms the orthorhombic-tetragonal phases of MgO-La2O3. The samples exhibited a small band gap of 3.0-3.22eV based on DRS. The photocatalytic activity of the catalysts was assessed for the degradation of two dyes, namely, tartrazine (TZ) and patent blue (PB) as model organic pollutants in aqueous mediums under UV-visible light. Detailed photocatalytic tests that focused on the impacts of dopant amount of La, catalyst dose, initial pH of the solution, irradiation time, dye concentration, and reuse were carried out and discussed in this research. The experimental findings reveal that the highest photocatalytic activity was achieved with the MgO-La2O3-10% MMO with photocatalysts with a degradation efficiency of 97.4% and 93.87% for TZ and PB, respectively, within 150min of irradiation. The addition of La to the sample was responsible for its highest photocatalytic activity. Response surface methodology (RSM) and gradient boosting regressor (GBR), as artificial intelligence techniques, were employed to assess individual and interactive influences of initial dye concentration, catalyst dose, initial pH, and irradiation time on the degradation performance. The GBR technique predicts the degradation efficiency results with R2 = 0.98 for both TZ and PB. Moreover, ANOVA analysis employing CCD-RSM reveals a high agreement between the quadratic model predictions and the experimental results for TZ and PB (R2 = 0.9327 and Adj-R2 = 0.8699, R2 = 0.9574 and Adj-R2 = 0.8704, respectively). Optimization outcomes indicated that maximum degradation efficiency was attained under the following optimum conditions: catalyst dose 0.3g/L, initial dye concentration 20mg/L, pH 4, and reaction time 150min. On the whole, this study confirms that the proposed artificial intelligence (AI) techniques constituted reliable and robust computer techniques for monitoring and modeling the photodegradation of organic pollutants from aqueous mediums by MgO-La2O3-MMO heterostructure catalysts.

Influence of impurity gas seeding into deuterium plasma on the surface modification, sputtering erosion and deuterium retention in W and W-La2O3 alloy

Surface modification, sputtering erosion and deuterium (D) retention were investigated of tungsten (W) and W-1 wt.% La2O3 (WL10) that were exposed to pure D plasma and D plasma with different impurities (He, N2, Ar). After the plasma exposure, the surface of WL10 is covered by blisters with various shapes, and their size and density increase with D fluence. When the fluence was higher than 8.6 × 1024 D m−2, the blister rupturing occurred causing a partially- and/or fully-opened lid features. The phase interface between La2O3 grains and W matrix was served as the nucleation sites for blistering and large-scale crack propagation near the surface. Small blisters were preferentially appeared on the grains with surface orientation of nearly (111) and that originated from the intra-granular crack at depths much closer to the sample surface. Micro-sized pits were formed on the WL10 surface after exposure to high fluence plasma, which was due to a higher sputtering rate of La2O3 grains during plasma exposure. For both materials, seeding He in D plasma can effectively inhibit the blister formation, and most serious blistering occurs with N seeding in D plasma. When exposed to Ar + D plasma, sparse small blisters were visible and most of blisters were ruptured for W, whereas there are some big blisters with long strip shape for WL10. The difference in blistering behavior between W and WL10 was attributed to the differences in microstructure, composition as well as ductility due to the presence of La2O3 phases. The sputtering yields increased slightly with He seeding in D plasma. N2 and Ar seeding in D plasma leaded to a significant increase in sputtering yields. As compared to the W, the WL10 exhibits a better sputtering erosion resistance in terms of the sputtering yield. The D retention in WL10 increases with D fluence and that was equal to or lower than that in W when exposed to the same conditions.

The Ni Catalyst Supported on the FSP-made Transition Metal (Co, Mn, Cu or Zn) Doped La2O3 Material for the Dry Reforming of Methane

The transition metal (Co, Mn, Cu or Zn) doped La2O3 material was prepared by flame spray pyrolysis (FSP) technique. The 2 wt.% Ni catalyst supported on this material was characterized by XRD, N2 physisorption, TPR, H2 chemisorption and TGA, and evaluated by the dry reforming of methane (DRM). The perovskite structure was certainly formed when either Co or Mn was introduced. The Cu can generate the La2CuO4 spinel phase while the Zn showed a mixed phase of La2O3, ZnO and La(OH)3. The Ni/Co-La2O3 catalyst was more active for the DRM because of high amount of active dual sites of Ni and Co metals dispersed on the catalyst surface. The formation of La2O2CO3 during the reaction can inhibit the coke formation. The cooperation of La2O2CO3 and MnO phases in the Ni/Mn-La2O3 catalyst was promotional effect to decrease carbon deposits on the catalyst surface. The partial substitution of Co for Mn with a small content of Mn can enhance the catalytic activity and the product yield. The Ni/Mn0.05Co0.95-La2O3 catalyst showed the highest CH4 conversion, H2 yield and H2/CO ratio. The Mn inserted into the perovskite structure of LaCoO3 was an important player to change oxygen mobility within the crystal lattice to maintain a high performance of the catalyst. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Tunning Ce valence and optimizing intergranular phase to prepare high abundance (La, Ce, Pr)-Fe-B permanent alloys with excellent properties

The regulation of Ce valence and the optimization of intergranular phase can effectively improve magnetic properties, which is beneficial in promoting the application of high abundance rare earth in permanent magnets. In this work, [(La0.3Ce0.7)xPr1-x]17Fe78B6 (x = 0.1–0.7) melt-spun alloys are prepared. The results illustrate that, Ce shows the mixed valency consisting of Ce3+ and Ce4+ configuration, and when x = 0.3, the alloy possesses the highest Ce3+ ratio. Meanwhile, the highest Ce4+ ratio can be determined in x = 0.1 alloy. TEM characterization demonstrates that, the intergranular rare earth oxides including CeO2 phase, Pr2O3 phase, (Pr, Ce)2O3 as well as La2O3 phase can be determined, among which CeO2 phase, existed in x = 0.3 alloy, is more beneficial in elevating the coercivity. Thus, the optimum comprehensive magnetic properties with the remanence of 6.5 kG and the coercivity of 14.9 kOe can be obtained in x = 0.3 alloy. In addition, due to more uniform microstructure of melt-spun alloy with x = 0.3, higher thermal stability can be obtained. Elemental metallurgical behavior reveals that La, Ce and Pr elements are enriched in intergranular phase, and main phase region is rich for Fe element.

Phase equilibria in the La2O3-Y2O3-Gd2O3 system at 1500°C

The phase equilibria in the ternary La2O3-Y2O3-Gd2O3 system at 1500?C were studied by X-ray diffraction, petrography and electron microscopy in the overall concentration range. The samples of different compositions have been prepared from nitrate acid solutions by evaporation, drying and calcination at 1100 and 1500?C. The solid solutions based on various polymorphous forms of constituent phases and ordered phase of LaYO3 were revealed in the system. The isothermal section of the phase diagram for the La2O3-Y2O3-Gd2O3 system has been developed. It was established that in the ternary La2O3-Y2O3-Gd2O3 system fields of solid solutions exist based on hexagonal (A) La2O3 phase, monoclinic (B) modifications of La2O3 and Gd2O3, cubic (C) modification of Y2O3, as well as perovskite-type structure of LaYO3 (R) with rhombic distortions. The systematic study that covered the whole compositional range excluded the formation of new phases. The refined lattice parameters of the unit cell and the boundaries of the homogeneity fields for solid solutions were determined.