Catalytic Combustion of Diesel Soot over K2NiF4-type Oxides La2-xKxCuO4

The K2NiF4 type oxides, La2-x KxCuO4 complex oxides with nanometric size were prepared by sol-gel method. The characters of these samples were analyzed by H2-TPR, XRD, FT-IR and SEM. The catalytic activity for soot combustion was evaluated by temperature-programmed reaction （TPO） technique. The results demonstrate that the substitution of K^＋ for La^3＋ at A-site will increase the catalytic activities of La2-xKxCuO4 to soot combustion greatly, and the substitution quantity affects the structure and catalytic activity obviously. The La1.8 K0.2 CuO4 complex oxides with tetrahedral structure has the best catalytic activity for soot removal reaction, the ignition temperature of soot combustion is decreased from 490 to 320℃.     

Thermodynamic properties of the MgAl2O4−MnAl2O4 spinel solid solution

The thermodynamic properties of the MgAl₂O₄−MnAl₂O₄ system are required for calculating the deoxidation equilibrium of molten iron and nickel containing magnesium, manganese, and aluminum. The thermodynamic properties of the MgAl₂O₄−MnAl₂O₄ spinel solid solution have been determined by equilibrating it with silver at known oxygen partial pressures. The free energy of formation of MnAl₂O₄ from its oxide components at 1673 and 1823 K was found to be −30.6 and −28.2 kJ/mol, respectively. It was observed that the MgAl₂O₄−MnAl₂O₄ spinel solid solution exhibited small negative deviations from ideal behavior at 1673 and 1823 K. The excess partial free energies of MgAl₂O₄, , and MnAl₂O₄, , at 1673 and 1823 K are expressed asG

Fluorescence Effect of SrAl_2O_4∶Eu and Diffuse Reflectivity of SrAl_2O_4∶Eu Based Ceramics

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Luminescence Properties of Eu^2 ＋ and Mn^2 ＋ Co-Doped CasMg（SiO4）4Cl2

The green phosphor for white LED, Ca8Mg(SiO4)4C12:Eu^2 , Mn^2 , was synthesized by high temperature solid state reaction under reducing atmosphere. During the process of the phosphor prepared, the excess CaC12 can improve the intensity of emission. The experimental results indicate that there is an effective energy transfer from Eu^2 to Mn^2 in Ca8Mg(SiO4)4Cl2 host. This kind of energy transfer may be due to resonance transfer, and this energy transfer is limited     

Effects of Cerium Oxide on Ni／Al2O3 Catalysts for Decomposition of CH4 and C2H4

Characteristics of carbon deposition of CH4 and C2H4 decomposition over supported Ni and Ni-Ce catalysts were studied by using a pulse reaction as well as BET, TPR, XPS and hydrogen chemisorption techniques. It is found that there is a metal-semiconductor interaction (MScI) in the Ni-Ce catalyst, and the effect of MScI on the carbon deposition of CH4 decomposition is opposite to that of C2H4. A novel model of carbon deposition of CH4 or C2H4 decomposition was proposed.     

Paramagnetic Anisotropy of CdGd2（WO4） 4-δ Single Crystal

CdGd2 （WO4）4 -δ single crystal was grown using the Czochralski＇s method. The crystal structure was tetragonal seheelite with lattice parameters a = b = 0.5203 nm and c = 1. 1359 nm. There were vacancies of （WO4）^2- , therefore, there were some Gd^2＋ ions. Langevin paramagnetism and anisotropy were observed from the δ-T curves at room temperature. The susceptibility X//was 3.5018×10^-3, and X⊥ was 3.4403× 10^-2. The anisotropy was also observed in the electron spin resonance （ESR） experiments. The anisotropic Land6 factors were g//= 2. 1333 and g~ = 2. 8411. The direction of easy magnetization was in the α-b plane. Anisotropic paramagnetic Curie constants C//and C⊥ were not only related to macroscopic a that was observed through the experiment, but were also related to J⊥ and J//, which were the microscopic quantum numbers of the Gd^2＋ and Gd^3｜ ions. Based on the detailed analyses, the proportion of 36.8% of Gd^3＋ ions to 63.2% of Gd^2＋ ions in the Gd ions of the CdGd2（WO4）4-δ crystal was calculated, and δ was 0.638 in the single crystal.     

Effect of Y2O3, CeO2 on Sintering Properties of Si3N4 Ceramics

The effect of rare earth oxides Y203 or Ce02 on sintering properties of Si3N4 ceramics was studied and the mechanism of assisting action during sintering was analyzed. The results in dicate that the best sintering properties appear in Si3N4 ceramics with 5% Y203 or 8% CeO2. Secondary crystallites are formed at grain boundaries after heat treatment,which decreases the amount of glass phase and contributes to the improvement of high-temperature mechanical properties of silicon nitride.     

Enhancement of photoluminescence of Ba2SiO4：Eu^2＋ by co-doping of La^3＋ or Y^3＋

Green light-emitting Ba2SiO4:Eu2+ phosphors co-doped with La or Y were synthesized by conventional solid-state reaction technique in reductive atmosphere (a mixture of 5% H2 and 95% N2). The results showed that the co-doping of La and Y could greatly enhance the fluorescence intensity of Ba2SiO4:Eu2+ phosphors. The optimum doping concentration expressed by the x value in (Ba0.985-1.5xREx)2SiO4: 0.03Eu2+ (RE=La or Y) was determined to be of 0.05. The excitation and emission peaks of all as-synthesized phosphors were wide bands. The excitation bands ranged from 250 to 400 nm, which matched well with the wavelength of near ultraviolet white light-emitting diodes (LED) chip and could be used as a potential candidate for the fabrication of white LED. The emission bands from 450 to 550 nm were typical 5d-4f transition emission of Eu2+ and displayed un-symmetry profiles because of the two substitution sites of Ba2+ with Eu2+.     

Luminescence and Preparation of LED Phosphor Ca8Mg （ SiO4）4Cl2 ： Eu^2＋

Calcium magnesium chlorosilicate doped by europium, Ca8Mg（SiO4）4Cl2： Eu^2＋, was prepared by the solid state reaction at high temperature. The compound obtained is pure Ca8Mg（SiO4）4Cl2 phase with cubic structure. Its average particle size is 5 μm, and it has good dispersity and morphological form. The excitation spectrum of Ca8Mg（SiO4）4Cl2： Eu^2＋ is a wide band, which covers from 270 to 480 nm. The emission spectrum is also a wide band peaked at 510 nm. The luminescent intensity reaches to the maximum when the concentration of Eu^2 ＋ is 2%. The wavelength of emission and excitation of the phosphor with various Eu^2 ＋ contents keeps constant. This spectrum range matches violet and blue LED chips very well, and its strong luminescence intensity is suitable for a green phosphor of tricolor phosphor of white light LED.     

Synthesis, Characterization and Luminescent Properties of Complexes of Rare Earth Nitrates with 2,2′:4′,4″:2″,2-Quaterpyridine

The rare earth nitrate complexes with 2,2′:4′,4″:2″,2-quaterpyridine (L) were prepared in ethylacetate. These new complexes with the general formula [RE(NO3)3L]*H2O (RE = La, Pr, Eu, Tb, Er, Y) were characterized by elemental analysis, IR spectra, thermal analysis and molar conductance measurements. The luminescence properties of these complexes were also studied.     

Synthesis, Characterization and Luminescent Properties of Complexes of Rare Earth Nitrates with 2,2′:4′,4″:2″,2- Quaterpyridine

Ｃｏｏｒｄｉｎａｔｉｏｎｃｏｍｐｌｅｘｅｓｃｏｎｔａｉｎｉｎｇｃｙ ｃｌｏｍｅｔａｌｌａｔｅｄｌｉｇａｎｄｓｈａｖｅｒｅｃｅｎｔｌｙｂｅｅｎｔｈｅｆｏｃｕｓｏｆｉｎｔｅｒｅｓｔｄｕｅｔｏｔｈｅｉｒｕｎｕｓｕａｌｐｈｏｔｏ ｐｈｙｓｉｃａｌａｎｄｅｌｅｃｔｒｏｃｈｅｍｉｃａｌｐｒｏｐｅｒｔｉｅｓ[1 ] .Ｓｏｍｅｏｆｔｈｅｃｏｍｍｏｎｅｓｔｒｅｃｅｎｔｅｘａｍｐｌｅｓａｒｅｂａｓｅｄｏｎｏｌｉｇｏｐｙｒｉｄｉｎｅａｎａｌｏｇｕｅｓ[2 ] .Ｔｈｅｒｅａｒｅａｎｕｍｂｅｒｏｆｒｅａｓｏｎｓｆｏｒｔｈｅｗｉｄｅ…     

Electronic structure of the SrAl2O4：Eu^2＋ persistent luminescence material

The electronic structure of the strontium aluminate (SrAl₂O₄:Eu²⁺) materials was studied with a combined experimental and theoretical approach. The UV-VUV synchrotron radiation was applied in the experimental study while the electronic structure of the non-optimized and optimized crystal structure were investigated theoretically by using the density functional theory. The structure of the valence and conduction bands as well as the band gap energy of the material together with the position of the Eu²⁺ 4f^{7 8}S_7/2 ground state were calculated. The calculated band gap energy (6.4 eV) agreed well with the experimental value of 6.6 eV. The valence band consisted mainly of oxygen states whereas the bottom of the conduction band of strontium states. In agreement with the experimental results, the calculated 4f^{7 8}S_7/2 ground state of Eu²⁺ lies in the energy gap of the host. The position of the 4f⁷ ground state depended on the Coulomb repulsion strength. The position of the 4f⁷ ground state with respect to the valence and conduction bands was discussed using theoretical and experimental evidence available.     

Luminescence Properties of Eu~(2 ) and Mn~(2 ) Co-Doped Ca_8Mg(SiO_4)_4Cl_2

The green phosphor for white LED, Ca8Mg(SiO4)4Cl2∶Eu2+, Mn2+, was synthesized by high temperature solid state reaction under reducing atmosphere. During the process of the phosphor prepared, the excess CaCl2 can improve the intensity of emission. The experimental results indicate that there is an effective energy transfer from Eu2+ to Mn2+in Ca8Mg(SiO4)4Cl2 host. This kind of energy transfer may be due to resonance transfer, and this energy transfer is limited.     

Multiple twins of τ2-Al13Co4 showing fivefold symmetry

The presence of a monoclinic Τ²-A1₁₃Co₄ phase, whosea andc are about Τ² = 2.618 (Τ = times greater than the respective parameters of the monoclinic Al₁₃Co₄, and its (100) and (001) twins has been reported earlier. Like its prototype structure, the monoclinic Al₁₃Fe₄/Al₁₃Co₄, this Τ²-A1₁₃Co₄ also shows a tendency to form multiple twins displaying five-fold symmetry. A transmission electron microscopic study of the twin mechanisms has been carried out. In addition to the well-known (001) and (100) glide twins, (20-1) glide twins have also been found. Alternate (100)-(20-l) or (100)-(001)-(100) twinning will yield twins display-ing fivefold symmetry. The distribution of Co atoms in the pentagonal layer in Τ²-A1₁₃Co₄ and the tessellation of pentagons in the (100) and (20-1) glide twins have also been studied by high-resolution electron microscopy.     

Effect of Ho^3＋ Ion on Luminescent Property of CaGaeS4：Eu^2＋

The afterglow luminescent property and thermo-luminescence (TL) of CaGa2S4：Eu^2 , Ho^3 were systemateally investigated. The afterglow of Eu and Ho Co-doped CaGa2S4 shows a broadband emission at 552 nm, which is the same as that of Eu doped CaGa2S4 only. And the decay behavior of CaGa2S4 Eu^2 , Ho^3 was investigated, which shows that CaGa2S4: Eu^2 , Ho^3 is a phosphor with long after-glow, whereas the CaGazS4:Eu^2 is a phosphor with-out long afterglow. Comparison of TL curves and 3D-TL emission spectra of CaGa2S4:Eu^2 ,Ho^3 and Ca-C, a2S4:Eu^2 show that a new trap center is produced at about 80℃, which is the basic reason of CaGazS4:Eu^2 ,Ho^3 with long afterglow.     

Morphological Variation of Eutectic Carbide in Twin-Roll Casting Strip of W9Cr4Mo2

Thetwin rollcastingisthatliquidmetaliscastdirectlyintosteelstripbetweentworotatingrollerscooledbywater[1-6] ,asshowninFig 1.Duetoveryrapidsolidificationspeed ,thelamellarspacingofeu tecticcarbideintwin rollcastinghighspeedsteelstripdecreasesenormouslyincontrasttothatincast inghighspeedsteelbillet[7] .Theeutecticcarbide ,however,stilldistributesincontinuousnetworkongrainboundary[8] ,whichwillleadtothehardnessincreaseofrollcastingstripwiththeresultthatthestripisdifficulttoprocesslater .Moreover …     

Study on Coke Formation and Stability of Nickel-Based Catalysts in CO2 Reforming of CH4

CO2 reforming of CH4 over nickel-based catalysts was investigated by using a fixed-bed reactor. Catalytic activity and amount of carbon deposition effects by nickel loading content, rare earth promoter and promoter contents were evaluated. It is found that nickel loading as well as reaction temperature can influence the activity and carbon deposition amounts, and with the addition of rare earth promoter, it can greatly improve the catalytic activity and exert a strong effect on the anticoking performance of the catalysts. The 5.0% (mass fraction)Ni-0.75% La BaTiO3 catalyst shows great resistance to coke formation and higher thermal stability as well as the catalytic activity.     

Influence of Y~(3 ) on Structure and Electrochemical Property of LiMn_2O_4

Influence of Y~(3 ) on Structure and Electrochemical Property of LiMn_2O_4     

Tempering Behavior of 45Cr-2W-0.25V Steel

 In this research the tempering behavior of a Cr-W-V steel was investigated. This new alloy with the composition of Fe-4.5Cr-2W-0.25V-0.1C was austenitized at 1000°C for 30 min and tempered at 500°C to 700°C for different times up to 100h. An OM analysis of the microstructure of air cooled and water quenched specimens before tempering showed that although in both conditions fully martensitic matrix formed, finer structure had formed in the water quenched specimens. The XRD and TEM results showed that the most stable carbides formed during tempering of the steel were M23C6 and M7C3, respectively. Other carbides such as M3C and M2C, formed in the first stages of tempering, and stable MC were also observed. The results showed that when the tempering time, temperature and cooling rate were increased, weight percent of extracted precipitates was increased. In addition, the formation rate of the stable carbides such as M23C6 and dissolution rate of the metastable carbides such as M3C and M2C were increased. The hardness results was revealed that tempering at 600°C and 700°C result in gradual decrease in hardness, but didn't observed significant changes in hardness at 500°C even for long tempering times.