双金属镍-锰/γ-Al2O3催化剂对甲烷二氧化碳重整反应的影响 (cited: 1)

用浸渍法制备γ-Al₂O₃负载的Ni-Mn双金属催化剂．在500～700 oC按照17:17:2的CO₂/CH₄/N₂比例,以36 mL/min的载气流速进行甲烷二氧化碳重整反应, 利用甲烷二氧化碳的转化率、生成的合成气H₂/CO比例以及长期稳定性等指标评价了催化剂的催化性能． 实验表明, 添加Mn提高催化性能并使双金属催化剂的稳定性更高, 比单金属催化剂更好地抑制焦炭生成,Mn最合适的添加量0.5wt％ ．通过BET、CO2-TPD、TGA、XRD、SEM、EDX和FTIR各种技术对催化剂进行了表征．     

Reactions of 1,3,5-triazinylnitroformaldoximes 3*. Interaction of 1,3,5-triazinylnitroformaldoximes with malonic acid esters

The reaction of 6-R-4-methoxy-1,3,5-triazin-2-ylnitroformaldoximes with dimethyl malonate gives the zwitterionic 4-methoxycarbonyl-3-(4-R-6-methoxy-1,3,5-triazin-2-yl)-4,5-dihydroisoxazol-5-ones. X-ray structural analysis has been carried out on the zwitterionic 4-methoxycarbonyl-3-(4-methoxy-6-piperidino-1,3,5-triazin-2-yl)-4,5-dihydroisoxazol-5-one.     

Effect of Nano‐support and Type of Active Metal on Reforming of CH4 with CO2

Two series of Co and Ni based catalysts supported over commercial (ZrO₂, CeO₂, and Al₂O₃) nano supports were investigated for dry reforming of methane. The catalytic activity of both Co and Ni based catalysts were assessed at different reaction temperatures ranging from 500—800 °C; however, for stability the time on stream experiments were conducted at 700 °C for 6 h. Various techniques such as N₂ adsorption‐desorption isotherm, temperature‐programmed reduction (H₂‐TPR), temperature‐programmed desorption (CO₂‐TPD), temperature‐programmed oxidation (TPO), X‐ray diffraction (XRD), thermogravimetric analysis (TGA) were applied for characterization of fresh and spent catalysts. The catalytic activity and stability tests clearly showed that the performance of catalyst is strongly dependent on type of active metal and support. Furthermore, active metal particle size and Lewis basicity are key factors which have significant influence on catalytic performance. The results indicated that Ni supported over nano ZrO₂ exhibited highest activity among all tested catalysts due to its unique properties including thermal stability and reducibility. The minimum carbon deposition and thus relatively stable performance was observed in case of Co‐Al catalyst, since this catalyst has shown highest Lewis basicity.     

Experimental estimation of the surface roughness distribution parameters in nanochannels

A statistical model of surface roughness is developed to calculate the molecular flows in nanosystems. In this model, surface asperities are represented by a set of flat microareas connected by edges with each other and having normals that differ from the normal to the mean level. A Solver PRO-M atomic force microscope is used to measure the following two parameters of the microscopic roughness of a hard disk: the slope along a scan line and the asperity height. A large experimental sample from the measured values of these parameters is used to obtain a distribution function density for the angle of inclination and conditional distributions (with parameters dependent on this angle) for the asperity height and the area of the triangle formed by the height and the sides of the angle. The latter conditional exponential distribution turns out to be more convenient for calculating random quantities. The results can be employed to simulate boundary conditions when calculating molecular flows by statistical Monte Carlo methods and to estimate the properties of new materials for protective surface coatings in the nanosystems containing gas flows.     

Increase in the average radiation power of a plasma relativistic microwave generator

The operation of a pulse-periodic plasma relativistic microwave generator with a pulsed power of 50 MW was experimentally studied. A change in the shapes of the electron collector and output unit allowed a significant increase in the average emission power. The microwave pulse duration was increased from 30 to 70 ns, and the repetition rate of microwave pulses was increased from 5 to 50 Hz.     

Photoluminescence of germanium quantum dots grown in silicon on a SiO<Subscript>2</Subscript> submonolayer

The photoluminescence of quantum dots in Si/Ge/SiO₂/Si and Si/Ge/Si structures is investigated as a function of temperature. The low activation energies for the temperature quenching of photoluminescence of germanium quantum dots in both structures are explained in terms of the thermally stimulated capture of holes from quantum dots to the energy levels of defects localized in their vicinity.     

Neutron activation analysis of IAEA proposed certified reference material IAEA-407 (North Sea Fish Homogenate)

The proposed reference material from the International Atomic Energy Agency, namely IAEA-407 (Fish Homogenate) was analyzed using instrumental neutron activation analysis (INAA). 15 elements, Al, As, Cl, Co, Cr, Fe, Hg, Mg, Mn, K, Na, Sb, Se, V and Zn, were determined using two irradiations (5 minutes and 5 hours) and four countings. IAEA-MA-A-1/TM (Copepoda Homogenate), NIST-SRM-1566 (Oyster Tissue), NIST-SRM-1572 (Citrus Leaves) and NIST-SRM-1577a (Bovine Liver) were utilized as standards in the quantification step.     

Formation of ultrasmall germanium nanoislands with a high density on an atomically clean surface of silicon oxide

The experimental results of an investigation into the initial stages of growth of a germanium film on an atomically clean oxidized silicon surface are reported. It is shown that the growth of the germanium film in this system occurs through the Volmer-Weber mechanism. Elastically strained nanoislands with a lateral size of less than 10 nm and a density of 2 × 10¹² cm^?2 are formed on the oxidized silicon surface. In germanium films with a thickness greater than 5 monolayers (ML), there also arise completely relaxed germanium nanoislands with a lateral size of up to 200 nm and a density of 1.5 × 10⁹ cm^?2.     

Defect-induced increase in the phonon energy involved in the formation of Urbach tail in Cu-ternaries

From a combined analysis of the stoichiometric composition and Urbach tail in samples of CuInSe₂, CuInTe₂, and CuGaTe₂ of the I-III-VI₂ family of chalcopyrite semiconductors, it is found that the energy hν_p involved in the electron/exciton-phonon interaction is a linear function of a parameter Δz which is the sum of the deviations from ideal molecularity Δx and anion to cation ratio Δy. It gives evidence that in the copper ternaries hν_p is associated to the structural defects caused by cation-cation, cation-anion, and other intrinsic disorders. The high value of hν_p found in the studied samples, higher than the highest optical mode, is shown to come from the contribution of the additional phonon energy due to structural defects. This is in agreement with recently proposed models of the temperature dependence of the Urbach energy.