Self‐Assembled Pd@CeO2/γ‐Al2O3 Catalysts with Enhanced Activity for Catalytic Methane Combustion

Pd@CeO₂/Al₂O₃ catalysts are of great importance for real applications, such as three‐way catalysis, CO oxidation, and methane combustion. In this article, the Pd@CeO₂ core@shell nanospheres are prepared via the autoredox reaction in aqueous phase. Three kinds of methods are then employed, that is, electrostatic interaction, supramolecular self‐assembly, and physical mixing, to support the as‐prepared Pd@CeO₂ nanospheres on γ‐Al₂O₃. A model reaction of catalytic methane‐combustion is employed here to evaluate the three Pd@CeO₂/γ‐Al₂O₃ samples. As a result, the sample Pd@CeO₂‐S‐850 prepared via supramolecular self‐assembly and calcined at 850 °C exhibits superior catalytic performance to the others, which has a far lower light‐off temperature (T₅₀ of about 364 °C). Moreover, almost no deterioration of Pd@CeO₂‐S‐850 is observed after five sequent catalytic cycles. The analysis of H₂‐TPR curves concludes that there exists hydrogen spillover related to the strong metal–support interaction between Pd species and oxides. The strong metal–support interaction and the specific surface areas might be responsible for the catalytic performance of the Pd@CeO₂ samples toward catalytic methane combustion.     

Einfluß des Gefügezustandes auf die mechanischen Eigenschaften von (α + β)- Titanlegierungen

Influence of Microstructure on Mechanical Properties of (α + β)-Ti-Alloys The amount of α- and β-phase in (α + β)-Titanium alloys for example in the alloy TiAl6 V4 may be altered to a large extend by annealing procedures. In the alloy TiAl6 V4 each temperature corresponds to a certain amount of each of these phases, the composition of which is also dependent on annealing temperature. Above about 970 °C the homogeneous β-phase appears. Additions of Iron, Oxygen, Nitrogen and Hydrogen have a great influence on the transition temperature and the distribution of the α- and β-phase. There is a great influence of the distribution of the phases on the mechanical properties. The β-phase and the α-solid solution can be quenched from high temperature and decomposed at a lower temperature, so that intermediate phases as ω from β and α₂ from α may be precipitated. The α-solid solution is anisotropic so that texturized samples have different properties in various directions. Based on these fundamental aspects it is shown to what extend these microstructures may influence the mechanical properties especially the fatigue behaviour of (α + β)-Ti-alloys.     

Evidence for mixed-phase crystalline β-C3N4 and c-BN films

In this paper strong experimental evidence is presented suggesting that we have synthesized the β-C₃N₄ phase. This is a material predicted by theory to have comparable property to diamond. The films containing mixed-phase crystalline β-C₃N₄ and c-BN were deposited on steel substrate Ck 35 by a hot filament assisted r. f. plasma CVD method using organo-metallic precursor. The crystal structure of these mixed-phases was identified by X-ray diffraction (XRD) as well as transmission electron diffraction analysis (TED).     

The Standard Model and the neutron β-decay

This article reviews the relationship between the observables in neutron β-decay and the accepted modern theory of particle physics known as the Standard Model. Recent neutron-decay measurements of various mixed American–British–French–German–Russian collaborations try to shed light on the following topics: the coupling strength of charged weak currents, the universality of the electroweak interaction and the origin of parity violation.     

Poly(β-Styryl)-(1,2-Methanofullerene-C60)-61-Formo Hydroxamic Acid for the Solid Phase Extraction, Separation and Preconcentration of Rare Earth Elements

A new fullerene derivatives poly(β-styryl)-(12-methanofullerene-C₆₀)-61-formo hydroxamic acid has been synthesized and applied for the solid phase extraction, separation, preconcentration and ICP-MS determination of Ce, La, Pr, Nd, Sm and Gd. The introduction of the fullerene moiety into poly(β-styryl)-hydroxamic acid enhances its reactivity, chemical stability and recycled for their determination. The various parameter, viz. kinetics of sorption, breakthrough studies, effect of eluents, etc., have been studied. The influence of several diverse ions is also discussed. The proposed method has been applied for the sequential chromatographic separation of rare earths in the presence of each from rocks, monazite sand and in environmental samples.     

Inclusion Complexes of Tolnaftate with β-Cyclodextrin and Hydroxypropyl β-Cyclodextrin

Tolnaftate, an antifungal agent, was found to form inclusion complexes with both β-cyclodextrin (β-CD) and hydroxypropyl β-cyclodextrins (HPBCDs) with two different degrees of substitution [HPBCD(A)-8% and HPBCD(B)-3%]. Complex formation in the solution state was studied using phase solubility and spectral shift methods. Solid complexes were prepared by the coprecipitation method. Solubilities and dissolution rates were determined for each solid complex, its corresponding physical mixture, and free drug. The increase in solubility of tolnaftate with added HPBCD was found to be significantly greater than with added β-CD. For both HPBCD(A) and HPBCD(B), over the concentration range 0-0.05 M. 1:1 complexes with stability constants of 1460 ± 139 M^-1 and 1860 ± 165 M^-1 were observed, respectively. Over the β-CD concentration range 0-0.02 M, a 1:1 complex with a stability constant of 1190 ± 105 M^-1 was observed. At higher HPBCD concentrations, the increase in solubility was observed to show a positive deviation from linearity (type A_p phase diagram). Using the spectral method, in a 2 5% v/v methanol in water system, the stability constants were determined to be 1020 ± 150 M^-1 1110 ± 120 M^-1 and 1100 ± 260 M^-1 for HPBCD(A), HPBCD(B) and β-CD, respectively. The solid complexes prepared showed improved dissolution over physical mixtures and free drug.     

Characterization and investigation of the mesogenic, thermo-morphologic and thermotropic properties of new chiral (S)-5-octyloxy-2-[{4-(2-methylbuthoxy)-phenylimino(methyl]phenol liquid crystalline compound

Synthesis, characterization and investigation of the mesogenic, thermo-morphologic and thermotropic properties of a new chiral liquid crystalline compound are presented in this work. This new compound has prolate molecules and exhibits the chiral smectic C* mesophase in a sufficiently large temperature interval. Two types of solid crystalline phases have been found in this compound. Typical textures and temperatures of the direct and reverse phase transitions, taking place in the compound, are given. Typical peculiarities for the first-order transition between the smectic C* mesophase and isotropic liquid have been observed.     

Gas- und Plasmanitrieren der (α + β)- Titanlegierung TiAl6V4. Vergleichende Untersuchungen zu Schichtaufbau und Schichteigenschaften

The usually low wear resistance of titanium materials can be increased by the thermochemical surface treatment nitriding. In result of comparative investigations of gas and plasma nitriding it will be shown that it is possible to obtain a specific variation of the properties in the highly stressed case by means of these both technologies on example of the (α + β) alloy Ti-6Al-4V. Gas and plasma nitriding was carried out in the temperature range from 650 to 800°C over 4 to 48 h in different gas atmospheres, i. e. 100% NH₃ (gas), 100% N₂ (gas and plasma), 20% H₂ + 80% N₂ and 20% Ar + 20% H₂ (plasma). The temperature range was fixed in the middle of (α + β) region, because the core properties are influenced negative in the field of β-transustemperature. The relations between the applied nitriding technologies, the layer structure (chemical, phases, geometrical) and selected layer properties (microroughness, microhardness, fracture and wear behaviour) are described.     

固体超强酸SO42-/TiO2-Al2O3的制备及其催化合成冰片

采用溶胶-凝胶法和浸渍法制备了系列SO_4~(2-)/TiO_2-Al_2O_3固体超强酸催化剂,运用XRD、NH_3-TPD、FT-IR、PyFTIR、XPS、SEM等技术手段,研究了复合催化剂材料的结构与性质,初步探讨了固体超强酸SO_4~(2-)/TiO_2-Al_2O_3催化剂的构效关系,得到适宜的催化剂制备条件为:n(TiO_2)/n(Al_2O_3)=1∶2、硫酸浸渍浓度1mol/L、催化剂焙烧温度500℃。考察了物料物质的量比、催化剂用量、反应时间等对催化合成冰片的影响。结果表明,在物料物质的量比为1∶0.4,催化剂用量为α-蒎烯质量的7%,采用程序升温方式(65℃-1h,75℃-4h,90℃-1h)加热的条件下,固体超强酸SO_4~(2-)/TiO_2-Al_2O_3催化剂的催化活性最高,α-蒎烯的转化率高达100%,龙脑的收率高达59.74%,SO_4~(2-)/TiO_2-Al_2O_3固体超强酸催化剂在重复使用6次的条件下,α-蒎烯的转化率均不变,龙脑的收率下降2.99%,催化剂的重复使用性良好。     

Comparative determination of the α/β phase fraction in α+β-titanium alloys using X-ray diffraction and electron microscopy

A comparison is made between the measured α/β phase fractions in Ti-6246 using X-ray diffraction (XRD) and electron microscopy. Image analysis of SEM and TEM images was compared to the phase fraction estimate obtained using electron backscattered diffraction, lab and high-energy synchrotron XRD. There was a good agreement between the electron microscopic and diffraction techniques, provided that the microstructural parameters of grain size and texture are estimated correctly when using quantitative Rietveld refinement.     

On the giga cycle fatigue behaviour of two-phase (α2+γ) TiAl alloy

Fatigue crack initiation behaviour is investigated at room temperature in the (α₂-Ti₃Al and γ-TiAl) alloy. High cycle fatigue tests ranging up to 10¹⁰ cycles are carried out on the powder metallurgy (P/M) bar specimens under different loading conditions with a stress ratio of R=0.1 and R=0.5. Microstructural characterization and fracture surface analysis are also investigated by optical (OM) and scanning electron microscopy (SEM). Ti–Al alloy studied here shows two phases in microstructure (nearly refined lamellar thickness) composed of α₂-Ti₃Al and γ-TiAl (hereafter called γ+α₂ alloys) and fracture mechanism is explained with different plastic incompatibilities between the two phases.     

Phase diagrams of the ternary liquid systems [Ce(NO3)3(TBP)3]-C10H22-[UO2(NO3)2(TBP)2] and [Ce(NO3)3(TBP)3]-C10H22-[Th(NO3)4(TBP)2] and of the quaternary liquid system [Ce(NO3)3(TBP)3]-C10H22-[UO2(NO3)2(TBP)2]-[Th(NO3)4(TBP)2]

The phase diagrams of the ternary liquid systems [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[UO₂(NO₃)₂(TBP)₂] and [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[Th(NO₃)₄(TBP)₂] and of the quaternary liquid system [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[UO₂(NO₃)₂(TBP)₂]-[Th(NO₃)₄(TBP)₂] at T = 298.15 K are constructed. The phase diagrams are characterized by areas of homogeneous solutions and of two-phase liquid systems (systems with phase separation), with one phase (I) enriched in [Ce(NO₃)₃(TBP)₃], [Th(NO₃)₄(TBP)₂], and [UO₂(NO₃)₂(TBP)₂], and the other phase (II), in C₁₀H₂₂. Using the data on the mutual solubility of the components in the systems under consideration and equations of the NRTL model, the parameters of intermolecular interactions and the excess Gibbs energies (G ^ex) were calculated for the binary, ternary, and quaternary systems. Passing from the ternary system [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[Th(NO₃)₄(TBP)₂] to the quaternary system [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[UO₂(NO₃)₂ (TBP)₂]-[Th(NO₃)₄(TBP)₂] does not appreciably affect the distribution of C₁₀H₂₂ between phases I and II, but leads to the redistribution of [Ce(NO₃)₃(TBP)₃] into phase II and of [Th(NO₃)₄(TBP)₂] into phase I.