Phase composition,conductivity,and sensor properties of cerium-doped indium oxide

The hydrothermal synthesis of In_(2)O_(3)and CeO_(2)–In_(2)O_(3)is investigated as well as the properties of sensor layers based on these compounds.During the synthesis of In_(2)O_(3),intermediate products In(OH)_(3)and InOOH are formed,which are the precursors of stable cubic(c-In_(2)O_(3))and metastable rhombohedral(rh-In_(2)O_(3))phases,respectively.A transition from c-In_(2)O_(3)to rh-In_(2)O_(3)is observed with the addition of CeO_(2).The introduction of cerium into rh-In_(2)O_(3)results in a decrease in the sensor response to hydrogen,while it increases in composites based on c-In_(2)O_(3).The data on the sensor activity of the composites correlate with XPS results in which CeO_(2)causes a decrease in the concentrations of chemisorbed oxygen and oxygen vacancies in rh-In_(2)O_(3).The reverse situation is observed in composites based on c-In_(2)O_(3).Compared to In_(2)O_(3)and CeO_(2)–In_(2)O_(3)obtained by other methods,the synthesized composites demonstrate maximum response to H_(2)at low temperatures by 70–100℃,and have short response time(0.2–0.5 s),short recovery time(6–7 s),and long-term stability.A model is proposed for the dependence of sensitivity on the direction of electron transfer between In_(2)O_(3)and CeO_(2).

Toxic Effects of Lanthanum, Cerium, Chromium and Zinc on Potamogeton Malaianus

The toxic effects of rare earth elements such as lanthanum, cerium and heavy metal elements such as chromium, zinc on Potamogeton malaianus Miq. were studied. The results show that the contents of chlorophyll and soluble protein increase to a certain degree and then decrease under La3+ Ce3+ Zn2+ stress, while there is a constantly dropping tendency under Cr6+ stress. The four ions have different effects on protective enzyme systems of Potamogeton malaianus. They can induce rises of the activities of catalase (CAT) and peroxides (POD) at lower concentration, however, with the increase of ions concentration, the activities decline. The change of SOD activity is exactly opposite to that of CAT and POD activity. It falls at first and rises later. An increasing tendency of MDA content appears with the increasing concentration. The toxicities of La3+, Zn2+, Ce3+ and Cr6+ become more serious in the order. The lethal concentration of Cr6+ to Potamogeton malaianus ranges from 0.5 to I mg(-1) that of Ce3+ and Zn2+ ranges from 3 to 5 mg(-1) and that of La3+ ranges from 7 to 10 mg(.)L(-1). The toxic mechanism of La3 + and Ce3+ is similar to that of Cr6+ and Zn2+.

Behaviors of Lanthanum and Cerium on Grain Boundaries in Carbon Manganese Clean Steel

The behaviors of La and Ce on gram boundaries in carbon manganese clean steel were investigated by high-reso- lution transmission elecetron microscope （HRTEM）, scanning elecetron microscopy（SEM ）, energy dispersive spectrometer （EDS） and X-ray diffraction（XRD） analysis. The existing forms of rare earths （RE） in clean steel were as follows： dissolved in sohd solution, forming inclusion or second phase containing RE （RE-Fe-P, La-P, Fe-La eutectic and Fe-Ce phase）. The dissolved La or Ce segregated at grain boundaries. The segregation of both S and P at gram boundaries was reduced with suitable RE content. The impact toughness of the steel was improved obviously. La and Ce had effecets on purifying molten steel and modifying inclusions in clean steel, whereas with excessive La or Ce, La-Fe-P, La-P and Fe-La eutecetic phase or Ce-Fe-P and Fe-Ce intermetallic compound would form along grain boundaries, causing the impact energy to decrease significantly.

Effects of Lanthanum and Cerium on Acid Phosphatase Activities in Two Soils

To evaluate the security of using thulium, comparision between effects of La and those of Ce on acidic phosphatase activities in red soil and yellow soil in Zhejiang district was studied under conditions of ambient temperature and humidity. Results show that the acid phosphatase from different soil respondes to La and Ce differently. The activity of acid phosphatase in soil 1 declines with the increase of the concentration of La and Ce. The maximum inhibitory ratio of La and Ce reaches 69.8% and 71.0% respectively. But La and Ce have stimulative effect on the activity of acid phosphatase in soil 2. Under the effect of same concentration of the thulium, the acid phosphatase in two soils increases with the extending of culture time.

Effect of Lanthanum-praseodymium-cerium Mischmetal on Mechanical Properties and Microstructure of Mg-A1 Alloys

The effects of lanthanum-praseodymium-cerium mischmetal （LPC） on the microstructure and mechanical properties of Mg-Al alloy were investigated. With the addition of LPC, an additional rod-like Al11La3 phase was deposited in the alloy. LPC greatly improves the tensile strength of cast Mg-Al alloys but negatively affects the elongation of cast alloys above 473 K. Cast alloys are strengthened by both precipitation strengthening and dispersion strengthening at ambient temperature. When the temperature exceeds 473 K, only the dispersion operates as a strengthening mechanism.

Cerium and Lanthanum Modified Pd/Al_2O_3 Catalysts for Methanol Decomposition

CeO 2 improves the activity and selectivity of Pd/Al 2O 3 catalyst for methanol decomposition. The interaction between Pd and CeO 2 was then proposed to result in the promoting effect. The selectivity of CO and H 2 is significantly improved by addition of La 2O 3 to either Pd/Al 2O 3 or Pd/CeO 2/Al 2O 3 catalysts. Moreover, a synergistic promotion between CeO 2 and La 2O 3 on γ Al 2O 3 supported Pd catalysts was observed for the catalytic activity towards methanol decomposition into CO and H 2.

Mechanism of chlorinating lanthanum oxide and cerium oxide with ammonium chloride

Using ammonium chloride （NH4Cl） as a chlorinating agent, the effects of chlorinating temperature, chlorinating time and NH4Cl dosage on chlorination of La2O3 and CeO2, and the thermal decomposition of LaCl3·7H2O and CeCl3·7H2O were investigated. The results show that 80% of both La2O3 and CeO2 can be chlorinated at 300 ℃ for 90 min, and have no advantage to chlorination of lanthanum and cerium oxides at higher temperature. The thermal decomposition of LaCl3 and CeCl3 is carried out to explore the mechanism of chlorinating lanthanum and cerium oxides. At the same time, the chlorination of lanthanum and cerium oxides is not devoted to the HCl decomposed from NH4Cl, but to NH4Cl directly taking part in the chlorination of La2O3 and CeO2. The lanthanum and cerium oxides in chlorination firstly form intermediate LaOCl and CeOCl, and then transfer to LaCl3 and CeCl3, finally to La2O3 and CeO2, respectively. The thermal decomposition analyses of LaCl3·7H2O and CeCl3·7H2O further prove the existence of the intermediates LaOCl and CeOCl. Therefore the chlorinating temperature and time should strictly be controlled when the lanthanum oxide and cerium oxide are chlorinated with NH4Cl. And over-dosage of NH4Cl should be also applied in the process of chlorination.

Effect of Potassium on Sol-Gel Cerium and Lanthanum Oxide Catalysis for Soot Combustion

The catalytic activity in the soot combustion is reported for a series of potassium-promoter alumina supported catalysts prepared by the sol-gel method to be used in the catalytic combustion of soot. The studied systems correspond to CeO2-Al2O3 and La2O3-Al2O3 with charges of 3 and 5 wt% of CeO2 and La2O3. Potassium impregnation is performed to reach 3 atoms of K per nm2 of the mixed oxide. The effect of the potassium incorporation increases its reducibility, decreases the surface area and forms a new type of oxygen that is stronger than the oxygen in mixed oxides with similar chemical nature. The existence of potassium oxides, K2O and oxygen responsible for the vacancies and/or lattice defects (O2−) are related to good catalytic activity. Additionally, the presence of alkali affects the structural and textural characteristics of the catalyst, promoting the catalytic activity in soot combustion.

Complete Oxidation of Methane over Palladium Supported on Alumina Modified with Calcium,Lanthanum,and Cerium Ions

The activity and thermal stability of Pd/Al2O3 and Pd/（Al2O3＋MOx） （M=Ca, La, Ce） palladium catalysts in the reaction of complete oxidation of methane are presented in this study. The catalyst supports were prepared by sol-gel method and they were dried either conventionally or with supercritical carbon dioxide. Then they were impregnated with palladium nitrate solution. The catalysts with unmodified alumina had a high surface area. The activity and thermal stability of the aluminasupported catalyst was also very high. The introduction of calcium, lanthanum, or cerium oxide into alumina support caused a decrease of the surface area in the way dependent on the support precursor drying method. These modifiers decreased the activity of palladium catalysts, and they required higher temperatures for the complete oxidation of methane than unmodified Pd/Al2O3. The improvement of the palladium activity by lanthanum and cerium support modifier was observed only at low temperatures of the reaction.

Different Influences of Lanthanum and Cerium on Stability of Y Zeolite and Their DFT Calculations

In this paper,the different influences of lanthanum (La) and cerium (Ce) species on the stability of Y zeolite were studied by X-ray diffractometry (XRD),X-ray photoelectron spectroscopy (XPS),and multinuclear (27Al,29Si) solidstate nuclear magnetic resonance spectroscopy (NMR).It was found that the stability of Y zeolite could be enhanced by the introduction of La or Ce species;however,the former effect was more remarkable than the latter.These results were also confirmed theoretically by density functional calculations.There was a strong interaction between the rare earth (La or Ce) species and Y zeolite clusters,which restrained the formation of extra-framework aluminum and enhanced evidently the stability of Y zeolite.Furthermore,the interaction between La species and Y zeolite was stronger than that of Ce species with Y zeolite.

Solvent extraction of lanthanum and cerium ions from hydrochloric acidic aqueous solutions using partly saponified 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester

In order to clarify the extraction process with saponified extractant, the solvent extraction experiments of rare earth elements(REEs), lanthanum and cerium, by using partly saponified 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester(EHEHPA, HL) from hydrochloric acidic solutions have been performed. The concentration of initial aqueous rare earth ion was in a range of 0.0010–0.1000 mol·L^(-1); EHEHPA in a range of 0.2877–0.8631 mol·L^(-1) with saponification rate of 0.3(mole fraction), and the initial aqueous p H in a range of 1.00–4.00. Firstly, the extracted species were determined by the saturation extraction capacity method. Secondly, according to the equilibrium aqueous pH values, the extraction processes were divided into three different categories: extraction with saponified EHEHPA, extraction with un-saponified EHEHPA, and hydrolysis process. Finally, for the first two processes, in order to predict the distribution ratio, two semi-empirical calculation models were developed with.The calculation results are in good agreement well with the experimental data.

Study on Aldol Condensation of HCHO and CH_3CHO over MgO Catalysts Modified by Lanthanum and Cerium

Aldol condensation of HCHO and CH_3CHO over MgO, modified MgO and Al_2O_3 with rare earth oxides, was studied. The measurement of adsorption of pyrrole on catalysts by in-situ FT-IR and NH_3 TPD indicated that the addition of elements La or Ce into MgO increased the acidity of the solid. In-situ FT-IR showed that the activation of-C=O in HCHO adsorbed on CeO-MgO and La_2O_3-MgO occurred. The measurement of catalytic activity implied that the modified catalysts can promote the formation of pentaerythritol, dipentaerthritol and tripentaerythritol.

Photoluminescence of Cerium(Ⅲ)in Lanthanum Strontium Halophosphates

La_(1.5)Sr_(7.0)Na_(1.5)(PO_4)_6X′X″(X′and X″stand for two identical or different halide ions F^-,Cl^-,and Br^-)is a new kind matrix of phosphors.X-ray analysis shows that these crystals belong to the apatite structure of hexagonal system with a space group of p6_(3/m).Their lattice parameters have been obtained.Subsolidus phase relationship in the double halophosphate systems were determined by lattice parameter method.It has been proved that in the Br-Cl and F-Cl systems there exist complete and continuous solid solutions.In the F-Br sys- tem there appears a two phase region with the bromide composition 0.75<Br<1.25. The variation of emission intensity of Ce^(3+)with the change of halogen composition has been observed. Fluorescence spectroscopic study unraveled that there exist two types of luminescent center in Ce^(3+)activated La_(1.5)Sr_(7.0)Na_(1.5)(PO_4)_6X′X″crystals.The temperature dependence of the peak wavelength was determined.As temperature is raised,emission bands shift towards blue.

Effect of Lanthanum and Cerium on Expression of RSCU-PA-32k Gene in Saccharomyces Cerevisiae

Lanthanum chloride can promote expression efficiency of rscu-PA-32k gene in yeast. 2 and 5 mmol·L -1 LaCl 3 increase the activities of the expression product by 13% and 20% (from 14.6 to 16.5 and 17.5 U·ml -1). Cerium chloride can decrease the activity of expression product. 2 and 5 mmol·L -1 CeCl 3 decreases the activities of the expression product by 21% and 33% (from 14.6 to 11.5 and 9.8 U·ml -1).

Effects of Lanthanum and Cerium on Chlorophyll Content, Yield and Components of Soybean in Northeast China

In this paper,three soybean varieties with different qualities were used as experimental materials for potted plants.In the seedling stage and the flowering stage,different concentrations of lanthanum and cerium(120,150 and 180 mg·L^-1 LaCl3;30,60 and90 mg·L^-1 CeCl3;30,40 and 60 mg·L^-1 LaCl3+30,40 and 60 mg·L^-1 CeCl3)were sprayed to study the effects of lanthanum and cerium on soybeans(leaf photosynthetic pigment content,yield and the constituent factors).The results showed that chlorophyll contents of different qualities soybean leaves reached the maximum under 120 mg·L^-1 LaCl3 treatment.The yield of high protein soybean was the highest under 60 mg·L^-1 CeCl3 treatment,the yield of high fat soybean was the highest under 30 mg·L^-1 CeCl3 treatment.Therefore,the lanthanum and cerium solutions had the effect of"low promotion and high inhibition"on chlorophyll content of soybeans,and the cerium solution could increase the yields of different quality soybeans.

Effects of Rare Earth Lanthanum and Cerium on Antioxidant Enzyme Activities in Soybean Leaves

Rare earth has a long history of agricultural use and can improve the yield and quality of agricultural by-products,but its regulation mechanism is still unclear.The aim of the study was to investigate the effects of lanthanum and cerium on the activities of peroxidase,catalase and ascorbate peroxidase in leaves of soybeans[Glycine max(L.)Merr].Soybean varieties of Dongnong 42,Dongnong 47 and Dongnong 52 from Northeast China were used as experimental materials.The samples were tested by spraying different concentrations of LaCl3(120,150 and 180 mg·L-1),CeCl3(30,60 and 90 mg·L-1)and LaCl3+CeCl3(30,40 and60 mg·L-1 mix)solutions on the leaves at the seedling stage and the early flowering stage of soybeans.The results showed that the suitable species and concentrations of lanthanum and cerium could increased the activities of antioxidant enzymes in soybean leaves,but the effects of lanthanum and cerium on different varieties of soybeans were also different.For Dongnong 42,the optimum lanthanum and cerium treatment was 60 mg·L-1 LaCl3+CeCl3,and the activities of peroxidase,catalase and ascorbate peroxidase increased by 11.36%(p<0.05),13.89%(p>0.05)and 50.00%(p<0.05)compared with those of CK.The optimal lanthanum and cerium treatment of Dongnong 47 was40 mg·L-1 LaCl3+CeCl3.Compared with those of CK,the above three enzyme activities increased by 15.80%(p<0.05),51.52%(p<0.05)and 20.75%(p>0.05).The optimal lanthanum and cerium treatment of Dongnong 52 was 60 mg·L-1 LaCl3+CeCl3,which increased the activities of the three enzymes by 33.49%(p<0.05),19.23%(p>0.05)and 23.53%(p<0.05)compared with those of CK.

Effects of Lanthanum and Cerium on Seeds Fatty Acid Composition in Soybean

Soybean Dongnong 42 from northeast of China was used as an experimental material.The samples were tested by spraying different concentrations of LaCl3,CeCl3 and LaCl3+CeCl3 solutions on the leaves at the seedling stage and the early flowering stage of the soybeans.Gas chromatography was used to determine the fatty acid content and ratio of the soybean seeds at the maturity stage.The fatty acid ratio of soybean seeds were evaluated by calculating saturated fatty acid(SFA),monounsaturated fatty acid(MUFA),polyunsaturated fatty acid(PUFA),unsaturated fatty acids(UFA),UFA/SFA,index unsaturated fatty acid(IUFA)and double bond index(DBI).(MUFA+PUFA)/SFA was used to study the effects of rare earths on the quality of soybean seeds.The results showed that spraying the rare earth solution could significantly optimize the fatty acid distribution ratio of soybean seeds.Compared with the control group(CK),stearic acid was reduced by 5%and linolenic acid was reduced by 3.72%.Except for La10,the oleic acid content increased significantly by 2.22%.Under the treatment of 30 mg·L^(−1) CeCl3,UFA,UFA/SFA and DBI were 83.56,5.08 and 9.47,respectively,which were the highest in each group.Under the treatment of 150 mg·L^(−1) LaCl3,(MUFA+PUFA)/SFA was 4.89,the closest meal to the recommended ratio.The above results showed that spraying appropriate concentrations of rare earth at the seedling stage and the early flowering stage could optimize the fatty acid ratio of soybean seeds and improve dietary fatty acid ratios.

Ultra-precision machining of cerium-lanthanum alloy with atmosphere control in an auxiliary device

Cerium–lanthanum alloys are the main component of nickel–metal hydride batteries,and they are thus an important material in the greenenergy industry.However,these alloys have very strong chemical activity,and their surfaces are easily oxidized,leading to great difficulties in their application.To improve the corrosion resistance of cerium–lanthanum alloys,it is necessary to obtain a nanoscale surface with low roughness.However,these alloys can easily succumb to spontaneous combustion during machining.Currently,to inhibit the occurrence of fire,machining of this alloy in ambient air needs to be conducted at very low cutting speeds while spraying the workpiece with a large amount of cutting fluid.However,this is inefficient,and only a very limited range of parameters can be optimized at low cutting speeds;this restricts the optimization of other cutting parameters.To achieve ultraprecision machining of cerium–lanthanum alloys,in this work,an auxiliary machining device was developed,and its effectiveness was verified.The results show that the developed device can improve the cutting speed and obtain a machined surface with low roughness.The device can also improve the machining efficiency and completely prevent the occurrence of spontaneous combustion.It was found that the formation of a build-up of swarf on the cutting tool is eliminated with high-speed cutting,and the surface roughness(Sa)can reach 5.64 nm within the selected parameters.Finally,the oxidation processes of the cerium–lanthanum alloy and its swarf were studied,and the process of the generation of oxidative products in the swarf was elucidated.The results revealed that most of the intermediate oxidative products in the swarf were Ce^(3+),there were major oxygen vacancies in the swarf,and the final oxidative product was Ce^(4+).

Cerium Methacrylate Assisted Preparation of Highly Thermally Conductive and Anticorrosive Multifunctional Coatings for Heat Conduction Metals Protection

Preparing polymeric coatings with well corrosion resistance and high thermal conductivity(TC)to prolong operational life and ensure service reliability of heat conductive metallic materials has long been a substantive and urgent need while a difficult task.Here we report a multifunctional epoxy composite coating(F-CB/CEP)by synthesizing cerium methacrylate and ingeniously using it as a novel curing agent with corrosion inhibit for epoxy resin and modifier for boron nitride through"cation-π"interaction.The prepared F-CB/CEP coating presents a high TC of 4.29 W m^(−1)K^(−1),which is much higher than other reported anti-corrosion polymer coatings and thereby endowing metal materials coated by this coating with outstanding thermal management performance compared with those coated by pure epoxy coating.Meanwhile,the low-frequency impedance remains at 5.1×10^(11)Ωcm^(2)even after 181 days of immersion in 3.5 wt%NaCl solution.Besides,the coating also exhibits well hydrophobicity,self-cleaning properties,temperature resistance and adhesion.This work provides valuable insights for the preparation of high-performance composite coatings with potential to be used as advanced multifunctional thermal management materials,especially for heat conduction metals protection.

Cerium-tungsten oxides supported on activated red mud for the selective catalytic reduction of NO_(x)

Activated red mud(RM)has been proved to be a promising base material for the selective catalysis reduction(SCR)of NOx.The inherent low reducibility and acidity limited its low-temperature activity.In this work,molybdenum oxide,tungsten oxide,and cerium oxide were used to reconfigure the redox sites and acid sites of red mud based catalyst.When activated red mud was reconfigured by cerium-tungsten oxide(Ce-W@RM),the NOx conversion kept above 90%at 219-480℃.The existence of Ce^(3+)/Ce^(4+) redox electron pairs provided more surface adsorbed oxygen(O_(α)) and served as a redox cycle.Positive interactions between Ce,W species and Fe oxide in red mud occurred,which led to the formation of unsaturated chemical bond and promoted the activation of adsorbed NH_(3) species.WO_(3) and Ce_(2)(WO_(4))_(3)(formed by solid-state reaction between Ce and W species)could provide more Brønsted acid sites(W-O modes of WO_(3),W=O or W-O-W modes of Ce_(2)(WO_(4))_(3)).CeO_(2) species could provide more Lewis acid sites.The Langmuir-Hinshelwood(L-H)routes and Eley-Rideal(E-R)routes occurred in the low-temperature SCR reaction on the Ce-W@RM surface.NH_(4)^(+) species on Brønsted acid sites,NH_(3) species on Lewis acid sites,bidentate nitrate and bridging nitrate species were key active intermediates species.