Preparation of La0.9RE0.1MnO3 Ultra-fine Particles Used for CH4 Oxidation

Ｐｅｒｏｖｓｋｉｔｅ ｔｙｐｅｏｘｉｄｅｓ (ｇｅｎｅｒａｌｆｏｒｍｕｌａＡＢＯ3 )ｈａｖｅｂｅｅｎａｔｔｒａｃｔｉｎｇｍｕｃｈａｔｔｅｎｔｉｏｎｆｏｒｍｏｒｅｔｈａｎｔｗｏｄｅｃａｄｅｓｄｕｅｔｏｔｈｅｉｒｐｏｔｅｎｔｉａｌｃｏｍｍｅｒｃｉａｌａｐｐｌｉｃａｔｉｏｎｓａｓｃａｔａｌｙｓｔｓｆｏｒｖａｒｉｏｕｓｒｅａｃｔｉｏｎｓ :ｏｘｉｄａｔｉｏｎｏｆＣＯ[1～ 3 ] ａｎｄｌｉｇｈｔｈｙ ｄｒｏｃａｒｂｏｎｓ[4～ 7] ,ｃｏｍｂｕｓｔｉｏｎｏｆｎａｔｕｒａｌｇａｓｏｒＣＨ4 [8～ 1 1 ] (ｔｏｃｏｎｔｒｏｌＮ…     

Effect of tourmaline additive on the crystal growth and activity of LaCoO3 for catalytic combustion of methane

LaCoO3/tourmaline was prepared as catalysts on the methane catalytic combustion. As additive tourmaline, its effect on crystal growth and catalytic activity of LaCoO3, were investigated via X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), H2-temperature programmed reduction(H2-TPR) and catalyst evaluation techniques. SEM and TEM indicated that the spontaneous polarizability of tourmaline made LaCoO3 particles grow dispersedly on tourmaline, alleviated the agglomeration and exposed more reactive sites. It was a main influence leading to the improvement of catalysts activity, exposed via catalyst evaluation device. Among the different additive proportion of compound samples, the 2% tourmaline added LaCoO3 showed an obvious enhancement activity compared to non-tourmaline sample—the light-off temperature was 454 °C and CH4 reached the full conversion at 563 °C.     

Influence of preparation method on performance of a metal supported perovskite catalyst for combustion of methane

A different method was employed for the preparation of a metal supported perovskite catalyst for the catalytic combustion of methane.The prepared metallic catalysts were characterized by means of X-ray diffractometer(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and also by ultrasonic and thermal shock tests and catalytic activity.It was found that the process factors during the preparation,e.g.the preparation of the catalyst precursor and the coating slurry,the calcination te...     

Preparation and Physicochemical Characterization of La1-xCexCoO3+δ Perovskite Catalyst and Its Methane Catalytic Combustion

Perovskite oxide LaCoO3 methane catalytic material was synthesized with citric acid complexation and bubbling method.The effect of doped cerium was studied on the series of La1-xCexCoO3 δ materials by means of BET,XRD and SEM techniques.Their catalytic behaviors were studied with methane catalytic complete combustion as probe reaction.The results show that doped cerium has great effect on crystal phase formation.When doped cerium is less than 0.3 (molar ratio),the crystal phase of oxide has little changed.When doped cerium is up to 0.5,Co3O4 phase is obviously discovered and the perfectibility of LaCoO3 perovskite crystal phase is deteriorated.When x is over 0.7,perovskite crystal phase is weakened or completely disappeared.Considering the crystal phase of oxides,the optimum doped cerium is about 0.3.The perovskite oxides can be formed at a low calcinations temperature of 700 ℃.When x is 0.3,the highest catalytic activity of T10% (390 ℃) and T90% (603 ℃) is obtained on the series of La1-xCexCoO3 δ materials calcined at 800 ℃.     

稀土双掺杂锰氧化物La0.5Dy0.2Sr0.3MnO3的磁性质

采用固相反应法制备了La0.5Dy0.2sr0.3MnO3样品,通过M-T曲线、M-H曲线、ESR曲线研究了样品的磁性质.结果表明:在rc处样品经历了顺磁到铁磁的转变;当r相似文献   

Synthesis and Electrical Properties of La0.8Sr0.2-xCaxCo0.9Fe0.1O3-δ

Ａｎｉｍｐｏｒｔａｎｔｇｏａｌｉｎｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｓｏｌｉｄｏｘ ｉｄｅｆｕｅｌｃｅｌｌｓ (ＳＯＦＣｓ)ｉｓｔｏｒｅｄｕｃｅｔｈｅｏｐｅｒａｔｉｎｇｔｅｍ ｐｅｒａｔｕｒｅｏｆｔｈｅｆｕｅｌｃｅｌｌｓｔａｃｋｆｒｏｍ 10 0 0℃ｔｏｂｅｌｏｗ85 0℃ｓｏａｓｔｏｇｅｔａｎｏｐｔｉｍｕｍｔｒａｄｅ ｏｆｆｂｅｔｗｅｅｎｐｅｒ ｆｏｒｍａｎｃｅａｎｄｌｉｆｅｔｉｍｅｏｆｔｈｅｓｔａｃｋａｎｄｔｏｒｅｄｕｃｅｔｈｅｏｖｅｒａｌｌｓｙｓｔｅｍｃｏｓｔ[1] .Ｔｏａｃｈｉｅｖｅｔｈｉｓｄｅｓｔｉｎａｔ…     

Thermoelectric properties of Sr0.9La0.1TiO3 and Sr2.7La0.3Ti2O7 with 15%Ag addition

15%Ag-added cubic perovskites Sr0.9La0.1TiO3 and Ruddlesden-Popper （RP） phases Sr2.7La0.3Ti2O7 were fabricated via hydrothermal synthesis, cold pressing and high-temperature sintering. The structure and thermoelectric properties were also investi-gated for all samples. The results indicated that Ag precipitated as a second phase. Ag addition made electrical conductivity and ab-solute Seebeck coefficient enhanced, as a result, the ZT values were enhanced both for two series. Compared with cubic perovskite, RP phase was subjected to smaller impact by Ag addition. The reasons for enhancing ZT value and the different impact for two series by Ag addition were also discussed.     

Catalytic performance for methane combustion of supported Mn-Ce mixed oxides

A series of supported Mn-Ce mixed oxide catalysts were prepared by the impregnation method and used for the oxidation of methane. The catalysts were characterized by N2 adsorption （BET）, X-ray diffraction （XRD）, laser Raman spectrum （LRS）, and temperature programmed reduction （TPR） techniques. The XRD and LRS results confirmed the high dispersion of active components or formation of solid solution between manganese and cerium oxides in the bulk and on the surface of mixed oxide catalysts. The reducibility was remarkably promoted by the stronger synergistic interaction between the two oxides from H2-TPR measurements. As expected, all the experimental mixed oxide catalysts showed excellent activity for methane combustion at low temperature. Especially, for the catalyst with Mn-Ce ratio 3：7, methane conversion reached 92% at a temperature as low as 470 ℃.     

Effects of sol-gel method and lanthanum addition on catalytic performances of nickel-based catalysts for methane reforming with carbon dioxide

The nickel-based catalysts were prepared by the sol-gel method and used for the CH4 reforming with CO2. The effects of the sol-gel method on the specific surface area, catalytic activity, desorption, and reduction performances of catalysts were investigated with BET, TPR, and TPD. Compared with the catalyst prepared by the impregnation method, the results indicated that the catalysts prepared by the sol-gel method had larger specific surface area, showing higher catalytic activities and exhibiting perfect desorption and reduction performances. In addition, the modification effects of adding La were studied, and it was found that the 0.75NLBT catalyst constituted of 5wt.%Ni-0.75wt.%La was optimal.     

Magnetocaloric Effect in Colossal Magnetoresistance Material（ La0.6 Dy0.1 ） Sr0.3 MnO3

The magnetocaloric effect was discovered in 1881by Warburg[1]. When a magnetic field is applied to amagnetic material, the unpaired spins are aligned par allel to the magnetic field, which lowers the magneticentropy and causes the sample to heat up. I…     

镱的高掺杂对La0.67Sr0.33MnO3体系磁电性质的影响

研究了La0.67-xYbxSr0.33MnO3(x=0.40,0.50,0.60)体系的M-T曲线、M-H曲线、ρ-T曲线和MR-T曲线.实验结果表明:随着Yb掺杂的增加,体系从长程铁磁有序向自旋团簇玻璃态和反铁磁状态转变;高掺杂时的输运行为在其磁背景下发生异常,Yb掺杂引起的磁结构的变化将导致CMR效应.     

Preparation and properties of nanocrystal SmBO3 by nitrate-citrate sol-gel combustion method

Nanocrystal SmBO3 powders were synthesized by nitrate-citrate sol-gel combustion method. The phase evolution, morphologies and absorbency of the synthesized powders were characterized by X-ray diffraction (XRD), Field emission scanning electronic microscope (FESEM), Fourier transform infrared spectroscopy (FTIR) and UV-3101PC spectrophotometer (UVPC), respectively. XRD and FESEM re-sults showed that pure SmBO3 phase was obtained at 750 ℃, with an average original particle size of about 100 nm. FTIR showed that there were apparently concentrated absorbent peaks between 500 and 1400 cm-1. Moreover, the reflectivity of the powders apparently decreased at the wavelength between 1.05 and 1.15 μm. Therefore, SmBO3 might be a kind of absorbent material for infrared laser.     

La0.9Sr0.1MnO3微波合成和晶格热膨胀系数的研究

采用微波法合成固体氧化物燃料电池负极材料La0.9Sr0.1MnO3,并用动态高温粉末X射线衍射技术,对微波合成的产物La0.9Sr0.1MnO3从室温到1200℃之间的晶格热膨胀系数进行了测定。实验结果表明:在测试温度范围内,La0.9Sr0.1MnO3的晶格膨胀系数与温度呈线性关系。微波法合成的La0.9Sr0.1MnO3的晶格热膨胀系数为:△a/a0△T=8.9×10-6/℃、△c/c0△T=11.2×10-6/℃和△V/V0△T=29.3×10-6/℃。在实验温度区间内未发现样品有明显的相变或结构转变现象。     

Magnetic Properties and Colossal Magnetoresistance of La0.7Sr0.3MnO3 Materials Doped with Fe

Ｔｈｅｄｉｓｃｏｖｅｒｙｏｆｔｈｅｃｏｌｏｓｓａｌｍａｇｎｅｔｏｒｅ ｓｉｓｔａｎｃｅｉｎｐｅｒｏｖｓｋｉｔｅｍａｎｇａｎｉｔｅｓｄｅｒｉｖｅｄｆｒｏｍＬａＭｎＯ3 ｈａｓａｒｏｕｓｅｄｍｕｃｈｉｎｔｅｒｅｓｔｏｗｉｎｇｔｏｉｔｓｐｏｔｅｎｔｉａｌａｐｐｌｉｃａｔｉｏｎａｎｄｔｈｅｏｒｅｔｉｃａｌｒｅｓｅａｒｃｈｖａｌｕｅｓ .Ｔｈｅｓｕｂｓｔｉｔｉｏｎｏｆｍｅｔａｌｅｌｅｍｅｎｔ,ｓｕｃｈａｓＣａ ,Ｓｒ,Ｂａ ,ｆｏｒＬａｉｎＬａＭｎＯ3 ,ｏｆｔｅｎｌｅａｄｓｔｏａｎｉｎｓｕｌａｔｏｒ ｍｅｔａｌｔｒａ…     

Magnetic Coupling in La0.67 Ca0.33 MnO3／La0.67 Sr0.33 CoO3／La0.67 Ca0.33MnO3 Trilayer Films

The perovskite La0.67 Ca0.33 MnO3/La0.67 Sr0.33 CoO3/La0.67 Ca0.33 MnO3 trilayers were fabricated by a facing-target sputtering technique and their magnetotransport properties were investigated. The magnetoresistance is dependent on spacer thickness and dramatically decreases when La0.67 Sr0.33 CoO3 layer is thick enough because of its short-circuiting effect. Different from La0.67 Ca0.33 MnO3 single layer, trilayer films with thin La0.67 Sr0.33 CoO3 spacer have the enhanced metal-semiconductor transition temperature (TMS) of La0.67 Ca0.33 MnO3 layers. The magnetic coercivity Hc shows a nonmonotonic behavior with changing the spacer layer thickness at 230 K. The waist-like hysteresis indicates that there is an indirect exchange coupling between the top and bottom Lao.67 Ca0.33 MnO3 layers across the spacer La0.67 Sr0.33 CoO3 layer.     

Dy和Sm部分替代La对La0.7Sr0.3MnO3磁电行为的影响

通过对La0.7-xTxSr0．3MnO3(T=Dy，Sm)系列样品的红外透射谱，激光拉曼谱，M-T曲线和ρ-T曲线的测量，研究了该样品的磁电行为。结果发现，随着掺入量的增加，样品的顺磁-铁磁相变温度逐渐降低，磁结构从顺磁向自旋团簇玻璃态、反铁磁状态转变，样品的磁电阻迅速增加。有趣的是在较低温度下，Dy掺杂M-T曲线出现比较奇特的尖峰，而Sm掺杂M-T曲线比较变化较平坦。对Dy，Sm掺杂的作用可以用晶格效应和额外磁性的竞争来解释。     

Study on catalytic combustion of benzene over cerium based catalyst supported on cordierite

A series of MnCeOx catalysts supported on cordierite honeycomb (Cord) were prepared by a combustion synthesis method using Mn(NO3)2 , Ce(NO3 )2·6H2O and citric acid. The effect of the molar ratio of Mn/Ce, calcination time, the amount of citric acid and the effect of water vapor on the catalytic properties for the complete oxidation of benzene were investigated. These catalysts were characterized by X-ray diffraction (XRD), H 2 temperature-programmed reduction (H2 -TPR), O2 temperature programmed desorption (O2 -TPD) and scanning electron microscopy (SEM) techniques. The results indicated that the MnCeOx /Cord catalyst with Mn/Ce molar ratio of 1:1, calcining for 7h and M n+ /(citric acid) molar ratio of 6 exhibited the highest catalytic activity. When the concentration of benzene was 1500 ppm and the gaseous hourly space velocity was 20000h -1 , the conversion of toluene was 99.1% at the reaction temperature of 300 oC.     

Electrical Properties and Microwave Synthesis of Mixed Rare Earth Oxide Ln0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ

In order to lower the raw materials cost and develop a novel cathode materials for intermediate temperature solid oxide fuel cell(ITSOFC), using mixed rare earth replacing the expensive pure La2O3 as the raw materials, the powders of Ln0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ (Ln=the mixed rare earth, x=0.05, 0.10, 0.15) for the applications as the cathode materials were prepared by microwave sintering process. The crystal structure and the particles morphology of the obtained powders were characterized by XRD and SEM, the electrical conductivity of all samples sintered at 1200 ℃ for 3 h was also measured as the function of the temperature from 100 to 800 ℃ by DC four-probe method in air. The experimental results show that due to the influence of mixed rare earth the powders of Ln0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ synthesized at 1200 ℃ for 0.5 h with the mean particle size of 1～20 μm was of perovskite and cubic fluorite phase as well a little SrO phase, the electrical conductivity of the samples decreases with the adding Ca2+ content, and are all higher than 100 S·cm-1 from 500 to 700 ℃ when x≤0.10. Ln0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ. Can meet the demand of the electrical properties for the cathode materials in ITSOFC.     

Electric properties of La0.8Sr0.2CoO3 nanoceramics

The electric measurements were carried out for La_0.8Sr_0.2CoO₃ nanoceramics by using impedance spectroscopy methods. The resistance of sample was practically independent of frequency in measurement range. Its dependence on reciprocal temperature showed quite complicated mechanism of conduction. The most striking property of investigated sample was its resistance decreasing with increasing applied polarization.