Partial oxidation of methane on Ni/CeO2-ZrO2/γ-Al2O3 prepared using different processes

The influences of CeO2-ZrO2 and γ-Al2O3 mixing methods on the catalytic activity and stability of partial oxidation of methane （POM） were investigated over Ni/Ce0.7Zr0.3O2-Al2O3 catalysts. The catalysts were characterized by XRD, TPR, H2-chemsorption, and TG-DTA. For fresh catalysts, the results showed that the salt precursor mixing catalyst （ATOM） presented better performance than the catalysts prepared by the precipitator mixing method （MOL） and the powder mechanically mixing method （MECH）. The result of XRD suggested that the interaction between CeO2-ZrO2 and Al2O3 in ATOM sample was stronger than the others, which led to more lattice defects and thereby better initial activity. Moreover, the MECH sample had the best stability and the least coke deposition in 24 h stability tests. The results of TPR and H2-chemsorption indicated that the intimate contact of Ni-Al in MECH sample enhanced the ability of resisting coke deposition and metal sintering.     

NiO-Ce0.5Zr0.5O2 catalysts prepared by citric acid method for steam reforming of ethanol

NiO-Ce0.5Zr0.5O2 catalysts were prepared by citrate method and used for hydrogen production from steam reforming of ethanol （SRE）. The effect of nickel content and space velocity on the catalytic performance was investigated. The prepared catalysts were characterized with XRD and thermal analysis techniques. 20%NiO-Ce0.5Zr0.5O2catalyst was very active and selective for hydrogen production via SRE, in which ethanol conversion of 100% could be obtained with feed component of 20% （H2O＋EtOH） and 80% N2, water/ethanol of 3/1 in molar ratio at 350 ℃. Also, the catalyst showed good stability for anti-sintering and carbon-resistance. The XRD illuminated that both NiO and Ce0.5Zr0.5O2 crystal sizes were very small in NiO-Ce0.5Zr0.5O2 catalyst, and Ce0.5Zr0.5O2 solid solution was formed.     

Study on photodegradation of Azo dye by polyoxometalates/polyvinyl alcohol

A series of photocatalysts, K11[Ln(PW11O39)2]/PVA (Ln=La, Ce, Pr, Nd, Sm) were prepared by K11[Ln(PW11O39)2] (Ln=La, Ce, Pr,Nd, Sm) containing five kinds of lanthanides and polyvinyl alcohol as the support. The catalysts obtained were characterized by Fourier trans-form infrared spectra, UV-vis spectra, powder X-ray diffraction, and scanning electron microscopy, indicating that the structure of K11[Ln(PW11O39)2] and polyvinyl alcohol remained intact, respectively. The photocatalysts exhibited efficient catalytic activity to degrade methyl orange, Congo Red, Ponceau 2R. The maximal degradation conversions of the three kinds of dyes were 99.58%, 47.61%, 72.42%, respectively.     

Nanoscratch behaviors of La0.7Sr0.3MnO3＋δ thin films

The nanoscratch behaviors of La0.7Sr0.3MnO3＋δ films, which were deposited with ratio of O2/（O2＋Ar）, ranging from 4.4% to 45.6% by DC magnetron sputter, were investigated by a nanoindentation technique. The results indicated that the friction coefficient between the films and the diamond tip depended on the loading critical load. The friction coefficient was about 0.08-0.12 when the loading normal load was less than the loading critical load. The films displayed excellent elastic recovery after unloading. When the loading load was larger than the loading critical load, plastic deformation and ploughing appeared for the films. The friction coefficient was about 0.43 when the film was damaged completely. The suitable decrease in ratio of O2/（O2＋Ar） could improve the nanoscratch resistance of the films. The film deposited with O2/（O2＋Ar）=25% possessed better scratch resistance due to good elastic recovery, high nanohardness, and critical load. The loading critical load of the film was larger than 80 raN.     

Zirconia modified monolithic macroporous Pt/CeO2/Al2O3 catalyst used for water-gas shift reaction

Monolithic macroporous Pt/CeO2/Al2O3 and zirconia modified Pt/CeO2/Al2O3 catalysts were prepared by using concentrated emulsions synthesis route. The catalytic performances over the platinum-based catalysts were investigated by water-gas shift (WGS) reaction in a wide temperature range (180-300 oC). The samples were characterized with thermogravimetry (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and temperature programmed reducti...     

La2O2CO3 supported Ni-Fe catalysts for hydrogen production from steam reforming of ethanol

La2O2CO3 was prepared by calcination of La2 (CO3)3 in the air. Catalysts Ni-Fe/La2O2CO3 with different mole ratios of Ni to Fe, Ni/La2O2CO3 and Fe/La2O2CO3 were prepared by impregnation method. The catalytic properties were evaluated on steam reforming of ethanol (SRE) from 300 to 700 ℃ under atmospheric pressure and the samples were characterized by Brunauer-Emmett-Teller method (BET), X-ray diffraction (XRD) and temperature programmed reduction (TPR). The results showed that Ni-Fe bimetallic catalysts exh...     

Luminescence properties of Eu2＋ -doped Ba3Si6O12N2 green phosphor： concentration quenching and thermal stability

The efficient Eu2+ -doped Ba3 Si6O12N2 green phosphors were prepared by a traditional solid state reaction method under N2 /H2 atmosphere at a temperature up to 1350 oC for 12h. Photoluminescence (PL) properties showed a broad emission band with a peak of 525 nm and the full width of half-emission maximums (FWHM) of 70 nm under 460 nm light irradiation. The X-ray diffraction patterns (XRD) and scanning electron microscope (SEM) images of the synthesized powder demonstrated its pure phase and excellent crystallization. Quenching concentration in this phosphor was found to be 0.3. The mechanisms of concentration quenching and redshift of emission peak with increasing concentration of Eu2+ were studied. The temperature dependence measurement of this green phosphor revealed excellent thermal quenching property compared to silicate green phosphor. It is believed that Ba3 Si6O12N2 :Eu2+ is an excellent green phosphor for UV or blue chip based white LEDs.     

Synthesis of Al2O3/TiCN-0.2%Y2O3 Composite by Hot Pressing

Al2O3/TiCN composites were synthesized by hot pressing.The influences of components and HP temperature on mechanical properties,such as bending strength,breaking tenacity and Vickers hardness were investigated.The results showed that the mechanical properties of Al2O3/TiCN composite increased with temperature when hot pressing temperature is below 1650 ℃.The mechanical properties reached their maximums when the composites were sintered at 1650 ℃ for 30 min under hot pressing pressure of 35 MPa,the value of bending strength,breaking tenacity and Vickers hardness was 1015 MPa,6.89 MPa·m1/2,and 20.82 MPa,respectively.When hot pressing temperature was above 1650 ℃,density decreased because of decomposition with increased temperature,and mechanical properties dropped because of rapid growth of grains in size at high temperature.Microstructure analysis showed that the addition of Y2O3 led to the formation of YAG phase so as to inhibit the growth of crystals.This helped to improve breaking tenacity of the composites.TiCN particles with diameters of 1 μm dispersed at Al2O3 grain boundaries,inhibited grain growth and enhanced mechanical properties of the composites.SEM study of the propagation of indentation cracks showed that the bridge linking behavior between matrix and strengthening phase might lead to the formation of the coexisted field of crack deflection,branching and bridge linking.The mechanism of this phenomenon was that the addition of Y2O3 improved the dispersion of TiCN particles so as to enhance the tenacity of the composites.The breaking tenacity was changed from 5.94 to 6.89 MPa·m1/2.     

Highly nonlinear property and threshold voltage of Sc2O3 doped ZnO-Bi2O3-based varistor ceramics

A series of ZnO-Bi2O3-based varistor ceramics doped with 0-0.4 mol.% Sc2O3 were prepared by high-energy ball milling and sintered at temperatures between 1000 and 1150oC. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were applied to characterize the phases and microstructure of the varistor ceramics. A DC parameter instrument for varistor ceramics was applied to investigate the electronic properties and V-I characteristics. The results showed that there were no changes in crystal structure with Sc2O3-doped varistor ceramics and that the average size of ZnO grain increased first and then decreased. The best electronic characteristics of the varistor ceramics prepared by high-energy ball milling were found in 0.3 mol.% Sc2O3-doped ZnO-Bi2O3 -based ceramics sintered at 1000 oC, which exhibited a threshold voltage of 821 V/mm, nonlinear coefficient of 62.1 and leakage current of 0.16 μA.     

Synthesis of ZrO2-HfO2-Y2O3-Sc2O3 Nano-Particles by Sol-Gel Technique in Aqueous Solution of Alcohol

Zirconium dioxide is a significant material withgood physicochemical characteristics . It is used inmanyfields such as energysources ,material and envi-ronment . Cubic phase zirconium dioxide doped withyttria (YSZ) is alreadyin wide use in solid oxygenfu-…     

Study on Sulfation of CeO2/γ-Al2O3 Sorbent in Simulated Flue Gas

It is well known that sulfur dioxide(SO2) , morethan50%of which arise fromcombustion of fossil fu-els ,are precursors of acidrain andtheir emission pos-es a global threat tothe atmosphere .Environmental a-gencies have ,therefore ,regulated emissions of SO…     

Effect of Metal Oxide Doping into Ce0.5Zr0.5O2 on Catalytic Activity of MnOx/γ-Al2O3/Ce0.45Zro.45M0.1Ox （M = Y, La, Mn） Honeycomb Catalysts

This article showed that the catalytic activity of MnOx/γ-Al2O3/Ce0.5Zr0.5O2 monolithic catalyst toward the catalytic combustion of ethanol in a fixed bed reactor could be greatly improved by doping three metal oxides into Ce0.5Zr0.5O2. The catalytic activity of MnOx/γ-Al2O3/Ce0.45Zr0.45M0.1 Ox （M = Y, La, Mn） is better than that of MnOx/γ-Al2O3/Ce0.5 Zr0.5O2. The order of activity of the catalysts is as follows： MnOx/γ-Al2O3/Ce0.45Zr0.45Y0.1Ox 〉 MnOc/γ-Al2O3/Ce0.45 Zr0.45La0.1Ox 〉 MnOx/γT-Al2O3/Ce0.45Zr0.45Mn0.1Ox 〉 MnOx/y-Al2O3/Ce0.5Zr0.5O2. The influence of the loading amount of manganese oxide in enhancing the catalytic activity of MnOx/γ-Al2O3/Ce0.45Zr0.45Y0.1 Ox was investigated. The results showed that when MnO2 loading amount was 10% （mass fraction）, the MnOx/Al2O3/Ce0.45Zr0.45Y0.1Ox catalyst recorded the highest activity.     

Catalytic combustion of toluene over Pd-based monolithic catalysts with a novel washcoat Ce0.8Zr0.15La0.05Oδ

Two novel washcoats Ce_0.8Zr_0.15La_0.05O_δ and Ce_0.8Zr_0.2O₂ was prepared by an impregnation method, which acted as a host for the active Pd component to prepare Pd/Ce_0.8Zr_0.15La_0.05O_δ/substrate and Pd/Ce_0.8Zr_0.2O₂/substrate monolithic catalysts for toluene combustion. The washcoats was characterized by X-ray diffraction (XRD), Raman spectroscopy, Brunauner-Emmett-Teller (BET), and H₂-temperature-programmed reduction (H₂-TPR). The result indicated that both the washcoats had strong vibration-shock resistance according to ultrasonic test. Doping La³⁺ into CeO₂-ZrO₂ solid solution could generate more oxygen vacancies, and could inhibit the sinter of CeO₂-ZrO₂ solid solution when calcined at high temperatures (800, 900 and 1000 °C). The washcoat Ce_0.8Zr_0.15La_0.05O_δ had much better redox properties. The reductive temperature of Ce⁴⁺ species shifted to low temperature by 60 °C when the washcoats calcined at high temperatures (800, 900 and 1000 °C). The Pd/Ce_0.8Zr_0.15La_0.05O_δ/substrate monolithic catalyst calcination at 500 °C had the best catalytic activity and the 95% toluene conversion at a temperature as low as 190 °C. When calcined at low temperature (500 and 700 °C), the catalytic activity has little improvement, however, when calcined at high temperature, the catalytic activity of Pd/Ce_0.8Zr_0.15La_0.05O_δ/substrate monolithic catalysts had significant improvement. As catalyst washcoat, the Ce_0.8Zr_0.15La_0.05O_δ had better thermal stability than the washcoat Ce_0.8Zr_0.2O₂, the developed Pd/Ce_0.8Zr_0.15La_0.05O_δ/substrate monolithic catalyst in this work was promising for eliminating Volatile organic compounds.     

Visible luminescence of lanthanide ions in Ca3Sc2Si3O12 and Ca3Y2Si3O12

The crystalline materials Ca₃Sc₂Si₃O₁₂ and Ca₃Y₂Si₃O₁₂ were characterized by different crystal structures, as the former is a cubic garnet, while the latter is an orthorhombic compound. We investigated the optical spectroscopy of these materials doped with several trivalent lanthanide ions and compared the results for the two hosts. Polycrystalline samples were prepared by solid state reaction, both undoped and doped with the trivalent lanthanide ions Eu³⁺, Tb³⁺ and Sm³⁺. Emission, excitation and Raman spectra of these materials were measured at temperatures ranging from 300 to 10 K. The optical spectra were assigned and discussed, and the effects of the crystal structure of the host on the spectroscopic behaviour were addressed. The technological potential of these compounds in the field of optical materials and devices was discussed.     

Preparation and Characterization of Gd3Sc2Ga3O12 Polycrystalline Material by Co-Precipitation Method

Gd3Sc2Ga3O12 polycrystalline material for single crystal growth was prepared with Ga, Gd2O3 and Sc2O3 as starting materials and aqueous ammonia as the precipitator by co-precipitation method. The precursors sintered at various temperatures were characterized by infrared spectra （IR）, X-ray diffractometry （XRD） and transmitted electron microscopy （TEM）. The results showed that pure GSGG phase could be obtained at 900 ℃. The sintered powders were well-dispersed and less-aggregated in the sintered temperature range of 900 - 1000 ℃. XRD and TEM show that the polycrystalline particle sizes of the polycrystalline powders were about 20 - 50 nm. Compared with the method that Ga2O3, Gd2O3 and Sc2O3 were mixed directly and sintered to get polycrystalline materials, the synthesized temperature was lower and sintered time was shorter. Thus co-precipitation was a good method to synthesize GSGG polycrystalline material.     

Investigation on pumping oxygen characteristics of （Bi2O3）0.73（Y2O3）0.27 solid electrolyte

（Bi2O3）0.73（Y2O3）0.27 fine powders prepared by wet chemical precipitation method were cold isostatically pressed to form solid electrolyte tubes, and sintered at 900 ℃ for 10 h in the air. Their pumping oxygen characteristics in non-dehydrated Ar gas were investigated, where a ZrO2 （Y2O3 stabilized） oxygen sensor was used to measure the oxygen partial pressure Po2. The results showed that the Po2 value reached magnitudes of 1×10^-2-1×10^-10 Pa at the applied pumping oxygen voltage of 0.5 V, 1×10^-37-1×10^-27 Pa at 1.0 V and 1×10^-53-1×10^47 Pa at 2.0 V within the temperature range from 550 to 650 ℃. Moreover, no cracks were found in the tested solid electrolyte tubes. Thus, the Bi2O3-Y2O3 system might be used in solid electrolyte oxygen pump for purifying gases.     

Luminescent properties of amorphous phosphor 1.4YeO3·2.5Al2O3·0.1Tb2O3 prepared by sol-gel method

Amorphous phosphor 1.4YeO3·2.5Al2O3·0.1Tb2O3 （the same composition as Y2.8Tb0.2Al5O12） was prepared via a sol-gel method at relatively low temperature （i.e., below 650℃）, which is much lower than that for the preparation of polycrystalline Y3Al5O12：Tb^3＋ （above 1400℃）. The amorphous phosphor prepared in the optimized conditions showed a bright green-yellowish luminescence, the intensity of which was comparable with that of polycrystalline sample and the emissions of which were assigned to 5D4 → 7Fj transitions of Tb^3＋. Besides the emissions of Tb^3＋, the amorphous samples prepared at temperatures below 500 ℃ presented a weak blue emission band around 420 nm.     

Catalytic wet oxidation of N,N-dimethyl formamide over ruthenium supported on CeO2 and Ce0.7Zr0.3O2 catalysts

A series of Ru supported on CeO₂ and Ce_0.7Zr_0.3O₂(CeZrO) was prepared by incipient-wet impregnation method and investigated in the catalytic wet oxidation of N,N-dimethyl formamide (DMF) in batch reactor. The physicochemical property of the catalysts was characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), H₂ temperature-programmed reduction (H₂-TPR), X-ray photoelectron spectroscopy (XPS) and thermogravimetry (TG). Compared with 3%Ru/CeO₂, 3%Ru/Ce_0.7Zr_0.3O₂ catalyst exhibits much higher performance for DMF degradation due to the promotion of Ru dispersion and the transfer of active oxygen, and 99% DMF conversion and 97% COD elimination are obtained at 453 K, 2.5 MPa oxygen pressure after 5 h. The reaction mechanism of DMF degradation was suggested. The carbonaceous species deposition and oxidation of Ru can be responsible for catalyst deactivation. And the catalyst activity can be recovered by air calcination and H₂ reduction.     

Electrical Transport and Giant Magnetoresistance in （ 1 - x ） La0.67 Ca0.33 MnO3/x CuO Composites

Samples with nominal composition of （1 - x）La0.67Ca0.33MnO3 （LCMO）/xCuO （x = 0%, 2%, 4% and 20% ） were made using a special experimental method. The temperature dependence of the resistivity （ρ） of the composites was investigated in the temperature range of 10 - 300 K and different magnetic fields of H = 0, 0.1, 0.3, 0.5, 1.0 and 3.0 T. The results showed that CuO percentage x had important effects on metal-insulator transition temperature （Tp）, zero field peak resistivity （ρmax）, and magnetoresistance （MR） properties of the composites. Tp shifted sharply towards low temperature with the increase of x in the range of x ≤4%, but was almost independent of x at high level of CuO content. Composites with x = 4 % and 20 % exhibited similar electrical transmission behavior. Compared with pure LCMO, enhanced magnetoresistance could be clearly observed even in a quite low magnetic field of 0.3 T. For x =4% and 20% samples, the MR value at 0.3 T could reach as high as - 88% and - 90%, respectively. XRD and SEM analysis showed that the substantial enhancement of MR, especially near Tp, was because of local spin disorder between contiguous LCMO ferromagnetic particles caused by the addition of CuO.     

Influence of Different Subsistence States of CeO2-ZrO2 Mixed Oxides in Catalyst Coating on Catalytic Properties

The metallic substrate-catalysts with different subsistence states of CeO2-ZrO2 mixed oxides were prepared and the catalytic properties were investigated. The studies on CeO2-ZrO2-V2O5-CuO mixed oxides which were prepared by coprecipitation, show that the doping of V5 and Cu2 in CeO2-ZrO2 mixed oxides can enhance the catalytic activity and thermal stability of coating materials. Moreover, different additives were doped in slurries of γ-Al2O3 to investigate the influence of additives on oxidation activity of catalysts. The mixture of ceria-zirconia, alkali metals and other rare earths acting as additives exhibits promotion effect on oxidation activity by optimizing the distribution of oxygen on the surface and in the bulk of ceria species. This mentioned mixture was mixed with γ-Al2O3 and a newly proposed active component to prepare a new catalyst. Afterward, the influence of thermal treatment on the new catalyst were investigated by calcinations at 500, 650, 750, 800, 850 and 900 ℃ for 2 h. The light-off curves of CO and HC show that after being treated at 650～750 ℃, catalysts present the best activity. XRD patterns show that ceria and zirconia species in the newly proposed active component form a phase of extra CeO2-ZrO2 mixed oxides on the surface of catalysts after the thermal treatment at 750 ℃, which has practical value for improving the preparation process and promoting the catalytic properties. Moreover, XPS results imply the existence of Ce1-xPdxO2-σ and Ce1-xPtxO2-σ on the surface of these treated samples, which may show influence on the catalytic activities.