Comparison of toxicity between lanthanum oxide nanoparticles and lanthanum chloride

Due to the wide application of rare earth elements,lanthanum(La) is gradually accumulated in our living environment.Lanthanum can enter the body through a variety of routes,which has a series of effects on various systems.As a consequence,the safety of lanthanum deserves our attention.This study aims to compare the toxicity of lanthanum oxide nanoparticles(La_(2)O_(3) NPs) and lanthanum chloride(LaCl_(3)) and enrich the toxicity evaluation of lanthanum.Therefore,a 30 d intragastal experiment was conducted.C57BL/6j mice were given by La_(2)O_(3) NPs solution and LaCl_(3) solution respectively at doses of 0,30,60 and120 mg/kg BW(lanthanum content).The results show that,compared with the control group,both La_(2)O_(3)NPs and LaCl_(3) can reduce the body weight of female mice in the high-dose group,but for male mice,the high-dose La_(2)O_(3) NPs solution can increase the body weight,while LaCl_(3) has the opposite effect.The coefficients of liver,kidney,heart,lung,uterine and ovaries increase first and then decrease with the exposure dose,but testes and epididymides coefficient keep increasing with the exposure of LaCl_(3) and La_(2)O_(3) NPs.La_(2)O_(3) NPs and LaCl_(3) can reduce the concentration of triglycerides(TG) and increase the level of low density lipoprotein(LDL),but the effect of La_(2)O_(3) NPs is more obvious.La_(2)O_(3) NPs and LaCl_(3) can reduce the concentration of malondialdehyde(MDA),increase the total antioxidant capacity(T-AOC)and enhance the activity of catalase(CAT),but LaCl_(3) has more obvious protective effects on oxidative stress.La_(2)O_(3) NPs and LaCl_(3) have potential risks to liver,and the toxicity of La_(2)O_(3) NPs might be higher than that of LaCl_(3).

Effect of La2O3 Addition on Sintering Properties of Magnesia

Light burned magnesia powders with different particle sizes were obtained by calcining crystalline magnesite.Sintered magnesia was prepared from the light burned magnesia powders by adding different amounts of La2O3.The effect of the La2O3 addition on the densification of magnesia was studied.The results show that the densification of sintered magnesia can be promoted both by reducing the particle size of the light burned powder and by adding small amounts of La2O3.The effect of the La2O3 addition is more significant:the maximum bulk density of the sintered magnesia can reach 3.49 g·cm-3 and the apparent porosity can be reduced to 0.33%.During sintering,Ca2+from the impurities enters La2O3 lattices,causing lattice distortion of La2O3 thus promoting the formation of La4.67(SiO4)3O phase and CaLa4(SiO4)3O phase,which fill the pores between the MgO grains and promote the densification of sintered magnesia.

Preparation and Characterization of La<SUB>2</SUB>O<SUB>3</SUB>Doped Ba<SUB>0.3</SUB>Sr<SUB>0.7</SUB>TiO<SUB>3</SUB>Perovskite Ceramics of Varied Sintering Temperature and Doping

In order to explore new application opportunities of Barium Strontium Titanate (BST) ceramic composite by modifying the conventional ferroelectric properties of BST through La2O3 doping in BST matrix sintered at different temperature was investigated in this current study. Unadulterated Ba0.3Sr0.7TiO3 (BST) matrix was prepared from BaTiO3 (99.95%) and SrTiO3 (99.95%) taken in stoichiometric extents which later doped by La2O3 (99.99%) in varying extents (0.05 g, 0.10 g and 0.15 g) exploiting solid state reaction route. Doping caused drag effect for the penetration of impurities and sintering temperature helped the impurities migration to BST. Dielectric constant gets lower with rising of frequency, as electrons do not get enough time to polarize at high frequency. Dielectric constant and conductance are found maximum for the sample (0.1 g La2O3 doped BST) sintered at 1460°C and reverse is found in impedance analysis. These electrical properties showed visible frequency dependent response irrespective of sintering temperature and doping.

Lithium incorporation enhanced resistive switching behaviors in lithium lanthanum titanium oxide-based heterostructure

Resistive switching devices with a high self-rectifying ratio are important for achieving the crossbar memristor array that overcomes the sneak current issue.Herein,we demonstrate a single amorphous lithium lanthanum titanium oxide(LLTO)layer based Pt/LLTO/Pt device possessing a self-rectifying ratio higher than 1 × 10^(4) that is comparable to the reported devices with complicated multi-layer stacking structures.Moreover,the device shows forming-free and highly uniform bipolar resistive switching(BRS)characteristic that facilitates the potential applications.The trap-controlled and trap-free space charge limited conductions are demonstrated to dominate the high and low resistance states of the device,respectively.The fast migration of lithium ions under external voltage accelerates the electron injection across the Pt/LLTO interface and also the space charge accumulation in the LLTO layer,and as a result,the high performance of the Pt/LLTO/Pt device was achieved.As demonstrated Pt/LLTO/Pt device sheds a light on the potential applications of the lithium ionic conductors in self-rectifying resistive switching devices.

LaO_(x)(OH)_(y) supported platinum catalysts for CO oxidation:Deactivation by formation of lanthanum carbonate

Platinum catalyst for CO oxidation has been studied for decades,due to its high activity and good stability.In this work,we prepared three different lantha num oxide or hydroxide supports(LaO_(x)(OH)_(y)),and deposited platinum(Pt) with 0.5 at% via an impregnation approach to synthesize Pt/LaO_(x)(OH)_(y) catalysts.However,we find that these catalysts perform a poor stability for the CO oxidation reaction.The fresh and used samples were comprehensively characterized by multiple techniques including power X-ray diffraction(XRD),X-ray absorption fine structure(XAFS),transmission electron microscopy(TEM),temperature-programmed reduction by carbon monoxide(CO-TPR) and thermogravimetric analysis(TGA),to demonstrate that the oxidized platinum atoms or clusters,without any component of Pt-Pt metallic bond,are highly dispersed on the surface of LaO_(x)(OH)_(y).Furthermore,the as-formed lanthanum carbonate(La_(2)O_(2)CO_(3)) during the exposure to ambient circumstances or in the reaction atmosphere of CO+O_(2),severely impair the reactivity of Pt/LaO_(x)(OH)_(y).On the basis of the obtained experimental results,we have drawn a conclusion that the oxidized P_(t)O_(x) atoms or PtxOy clusters are the active species for CO oxidation,while the formation of lanthanum carbonate is the origin of deactivation on reactivity.

Microstructure and mechanical properties of spark plasma-sintered La_(2)O_(3) dispersion-strengthened W-Ni-Fe alloy

An investigation of lanthanum oxide(La_(2)O_(3))addition to tungsten heavy alloy(WHA)with a ternary composition of W-7 Ni-3 Fe was reported in this study.The mixed powders were sintered using spark plasma sintering(SPS)technique.La_(2)O_(3)was added in increments of 0.25 wt%,0.50 wt%,0.75 wt%and 1.00 wt%to WHA,respectively.The sintered samples were characterized for microstructural evolution and mechanical properties.The influences of La_(2)O_(3)addition on density,grain size,hardness,ultimate tensile strength(UTS)and ductility on W-7 Ni-3 Fe system were discussed in this study.The highest relative sintered density of 87.95%was obtained for 0.25 wt%La_(2)O_(3)addition to W-7 Ni-3 Fe.The lowest grain size of 7.89μm was observed for 1.00 wt%La_(2)O_(3)addition.Similarly,the highest hardness and UTS of HV 533 and1110 MPa,respectively,were also obtained for the same composition.Scanning electron microscopy(SEM)and energy-dispersive spectroscopy(EDS)of the samples revealed homogenous distribution of La_(2)O_(3)in the alloy matrix.Fractography of the sintered alloy samples revealed W-W intergranular fracture.

Effects of preparation methods of support on the properties of nickel catalyst for hydrogenation of m-dinitrobenzene

Using tetraethyl orthosilicate(TEOS)as the pre-cursor of silica,the silica aerogel and xerogel,which were used as supports of nickel-based catalysts for liquid hydroge-nation of m-dinitrobenzene to m-phenylenediamine,were prepared by the sol-gel method combined with supercritical drying(SCD)and conventional drying,respectively.Then,a series of nickel-based catalyst samples supported on these supports were prepared by the incipient wetness impregna-tion method with an aqueous solution of nickel nitrate as well as lanthanum nitrate as impregnation liquids.Based on the characterization results of nitrogen adsorption-desorption(BET),X-ray diffraction(XRD),temperature programmed reduction(TPR),temperature-programmed desorption of hydrogen(H2-TPD),and catalytic activity evaluation,the physico-chemical properties and catalytic performances of the catalysts were investigated.The results show that the nickel crystallites on the binary nickel catalyst using silica aerogel as support are of smaller particle size.However,com-pared with the sample supported on silica xerogel,the nickel catalyst supported on the silica aerogel exhibits lower activity and selectivity for the hydrogenation of m-dinitrobenzene because it has a lesser amount of active sites and weaker absorption ability to reactants caused by sintering of the nickel crystallites.The addition of promoter La2O3 could increase the activity and selectivity of the catalysts.Among all the nickel-based catalyst samples prepared,the La2O3 promoted ternary nickel-based catalyst supported on silica xerogel exhibits the highest activity and selectivity for the hydrogenation of m-dinitrobenzene to m-phenylenediamine,which could be attributed to its highest active surface area and appropriate absorption strength to reactants.Over this prom-ising catalyst,the conversion of m-dinitrobenzene and the yield of m-phenylenediamine could reach 97.0%and 93.1%,respectively,under proper reaction conditions of hydrogen pressure 2.6 MPa,temperature 373 K,and reaction time 1 h.

Hierarchically 1D CdS decorated on 2D perovskite-type La_(2)Ti_(2)O_(7) nanosheet hybrids with enhanced photocatalytic performance

In this paper,a heterojunction of hierarchically one-dimensional(1D)cadmium sulfide(CdS)nanowires decorated on the two-dimensional(2D) La_(2)Ti_(2)O_(7) (LTO)has been fabricated by a simple two-step hydrothermal process.The structure,morphology and surface chemical composition of CdS/LTO were studied by a variety of characterizations,in which the X-ray photoelectron spectroscopy(XPS)results showed a strong interaction between CdS and LTO through S-O bonds.The typeⅡband alignment of CdS/LTO for favorable electron transfer from CdS to LTO and hole transfer from LTO to CdS was clarified by ultraviolet-visible(UV-Vis)diffuse reflectance spectroscopy and Mott-Schottky(M-S)plot measurements.In the absence of any co-catalyst,H2 production from water splitting and Rhodamine B(RhB)decomposition in aqueous solution were carried out to evaluate the photocatalytic activities,showing that the photocatalytic performance of CdS/LTO was superior to that of pure LTO and CdS under visible light and simulated sunlight.The optimal CdS content in the CdS/LTO system was determined to be 7.5 wt%.The present results show an effective pathway to design a 1D/2D heterojunction photocatalyst in the face of overwhelming problems of energy crisis and environmental pollution.