Pd nanoparticles of well-defined shapes with face centered cubic structure were grown electrochemically on silicon substrates with high degree of reproducibility. As direct application of these electrochemically grown Pd nanostructures they have been used as catalyst for the growth of multi wall carbon nanotube (MWCNT). It is observed that the MWCNTs are filled with a Pd based material during growth by microwave plasma enhanced chemical vapor deposition (MPECVD) technique. High-resolution transmission electron microscopy, used to study the material inside MWCNT suggests the formation of PdH0.649 or Pd2Si during the growth of carbon nanotube. Raman spectroscopy has been used to study the structure of the MPECVD grown carbon nanotubes. 相似文献
The effects of the volume and pH of the impregnation solution and of the calcination conditions were examined on the physicochemical and catalytic properties of a 13 wt% MoO3/Al2O3 extrudate catalyst. The Al2O3 support and drying procedures (static conditions without flowing air) were fixed in the preparations. In the present series of catalysts, the amount of crystalline MoO3 was marginally small. It was found that the dispersion of Mo oxide species increased as the volume of the impregnation solution increased, gradually approaching a maximum value. The increase in pH (2–8) of the impregnation solution was found to reduce the dispersion of Mo oxide species. The Mo dispersion increased slightly for the impregnation catalysts as the calcination temperature increased (673–873 K), whereas it decreased for the equilibrium adsorption catalysts. The effects of the calcination atmosphere (with or without flowing air, or with flowing humid air) were very small on the dispersion of Mo oxide species under the present preparation conditions. On the other hand, the methanol oxidation activity of MoO3/Al2O3 was sensitive to the preparation parameters examined here. It was demonstrated by means of EPMA and XPS that a considerable migration of Mo took place during the calcination.
In the present study on the preparation of a 13 wt% MoO3/Al2O3 catalyst, an impact index is proposed to measure the magnitude of the effects of the respective parameter(s) on the physicochemical and catalytic properties. With the Mo dispersion, the effects of the preparation parameter decreased in the order, surface area of the support >> drying process > volume of the impregnation solution > pH, calcination temperature and atmosphere. The size of the impact index for the dispersion of Mo sulfide species is 70–75% of that for the Mo oxide species. The HDS activity of the catalyst was less affected by the preparation parameters than the Mo sulfide dispersion. The preparation parameters affected the segregation of Mo on the outer surface of extrudates in a decreasing order: drying process > volume of the impregnation solution > pH, calcination conditions. It was found that the oxidation of methanol was affected most intensely by the drying procedures. The volume of the impregnation solution, calcination conditions and pH of the impregnation solution also strongly affected the oxidation activity. The impact index suggests that the sensitivity to the preparation variables of the physicochemical and catalytic properties of MoO3/Al2O3 decreases in the order, methanol oxidation activity > surface Mo segregation > Mo oxide dispersion > Mo sulfide dispersion > HDS activity. 相似文献
K(Ta,Nb)O3 (KTN) thin films have been prepared by the chemical solution deposition method. KTN precursors consisted of a uniform mixture of K[Ta(OC2H5)6] and K[Nb(OC2H5)6] with interaction at the molecular level. Perovskite KTN thin films with the desired composition (Ta/Nb = 65/35, 50/50, and 35/65) were synthesized from the precursor solutions by the dip coating method. KTN thin films with (100) preferred orientation were successfully synthesized on MgO(100) and Pt(100)/MgO(100) substrates. X-ray pole figure measurements showed that grains of KTN films had a prominent three-dimensional regularity on MgO(100) and Pt(100)/MgO(100) surfaces. The Curie temperatures of KTN films decreased with increasing Ta/Nb ratio. Typical P-E hysteresis loops were observed for KTN thin films of three compositions on Pt(100)/MgO(100) substrates. The values of remanent polarization ( P r) of KTN films increased as the Ta/Nb ratio changed from 65/35 to 35/65. 相似文献
A novel repeated batch operation mode was proposed for ethanol fermentation, where the fermenter beer was periodically exchanged between the fermenter with biomass recycle and the distillation unit, to promote the selective removal of ethanol. Using the mathematical model developed, as based on the experimental results, the optimal operation of the proposed method was shown to attain high performance, with a productivity of about 12 g dm−3 h−1 and a product concentration of 400 g dm−3. 相似文献
To understand the role of Cu film texture in grain growth at room temperature (RT) in relation to twin boundary formation Cu films were deposited on various barrier materials and the Cu film texture was investigated by X-ray diffraction. Cu grain growth was rapid on a barrierless SiO2/Si substrate and very slow on a Ta barrier due to strong (1 1 1) texture. The growth rate and the average grain diameter after being kept at RT for up to ∼60 days were maximum at a (2 0 0)Cu peak to (2 2 2)Cu peak area ratio of ∼1.0, where {1 1 1}, {1 0 0} and {5 1 1} grains coexisted. Such coexistence of three or more orientations of grains is essential in facilitating Cu grain growth at RT. Similarly, the average twin boundary (TB) density was maximum when Cu grain growth was facilitated. TB formation in nano-sized Cu grains was not controlled by grain size, but due to grain growth. The TB could be annealing twins caused by irregularities in the stacking sequence during relatively fast grain growth. The Cu film texture is concluded to be determined at the beginning of deposition, and the wettability of various barrier materials by the Cu films plays a key role in determining the film texture. 相似文献
Prostate cancer is one of the most common malignant neoplasms in men with an overall incidence of approximately 15 per cent during the normal life span. Androgen-deprivation therapy (hormone therapy) is an effective treatment of this disease when progressed to an advanced stage. Despite impressive responses, such treatment when applied on a continuous basis is not curative and eventually culminates in androgen-independent disease. On the other hand, intermittent androgen suppression (IAS) was first conceived as a potential way of delaying progression to androgen-independence, in addition offering the possibility of reducing adverse effects and improving the quality of life. Although the validity of this approach has been confirmed in several clinical studies, the optimal scheduling of the cycles of on- and off-treatment remains to be explored. In the present article, we show that IAS lends itself to mathematical modelling with hybrid dynamical systems and that the model we have developed can be used to select the best strategy for keeping prostate cancer in an androgen-dependent state as long as possible. Our results also suggest that the current way of using IAS exceeds what is necessary for optimal control; in fact, we have found that to achieve optimal control, the amount of therapy (dose and duration of drugs) can be reduced by a factor of one half. 相似文献
This study investigated whether the disengagement of attention from facial expression is modulated by gaze direction in infants. To this end, we measured the saccadic reaction time required for the 10-month-olds to disengage their attention from angry and happy expressions combined with either straight or averted gaze. The 10-month-olds' disengagement of their attention from happy faces was modulated by gaze direction. This finding indicates that gaze direction strongly influences infants' allocation of attention to facial expressions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
Diamond powders were attempted to be consolidated at elevated temperature using an explosive compaction technique employing
a cylindrical configuration. A compacted diamond sample recovered from the center of a cylinder, close to the end plug made
of stainless steel showed high hardness and tight interparticle bonding between the diamond powders. The sample was characterized
on the basis of X-ray diffraction patterns. No graphitization was observed due to heating or compaction, and the hot compacted
sample was highly strained by intensive deformation at elevated temperature. 相似文献
Organosilyl aluminophosphates (AlPOs) were prepared by using organosilyl agents such as methyltriethoxysilane and ethyltriethoxysilane, and characterized by XRD, TG, ICP, CHN elemental analysis, NMR, SEM, and TEM, and gas adsorption properties of them were investigated. The organosilyl agents formed amorphous phases on the AlPO crystal surfaces. The amorphous phases play two roles; changing the size of pore and forming the new pore spaces. The change of pore size induces molecular sieving phenomenon for small molecules. The pore in the amorphous phase is more effective for i-butane than toluene molecules, although they have the similar molecular sizes each other. 相似文献
Titanium dioxide (TiO2) bulk with pure anatase phases was fabricated by an explosive compaction technique using an underwater shockwave. Dynamic shock pressure of 6 GPa was used to consolidate anatase TiO2 powders. Its microstructural, crystalline structural and photocatalytic characteristics were observed and measured by various techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and photocatalytic activity measurement system. It was confirmed that the relative density of anatase TiO2 compact is about 96% (3.73 g/cm3) of the theoretical density (3.89 g/cm3) and a strong surface bonding between particles is formed by a shock energy. In X-ray diffraction analysis, high purity anatase phases, broadened peaks due to lattice defects and decreased crystallite size were found. For the photocatalytic activities, the anatase TiO2 compact was quite excellent compared to the commercial sintered TiO2 bulk. 相似文献