Spin‐polarized charge transfer at the interface between a ferromagnetic (FM) metal and a molecule can lead to ferromagnetic coupling and to a high spin polarization at room temperature. The magnetic properties of these interfaces can not only alter those of the ferromagnet but can also stabilize molecular spin chains with interesting opportunities toward quantum computing. With the aim to enhance an organic spintronic device's functionality, external control over this spin polarization may thus be achieved by altering the ferromagnet/molecule interface's magnetic properties. To do so, the magnetoelectric properties of an underlying ferroelectric/ferromagnetic interface are utilized. Switching the ferroelectric polarization state of a PbZr0.2Ti0.8O3 (PZT) bottom layer within a PZT/Co/FePc‐based (Pc ‐ phthalocyanine) device alters the X‐ray magnetic circular dichroism of the Fe site within the phthalocyanine molecular top layer. Thus, how to electrically alter the magnetic properties of an interface with high spin polarization at room temperature is demonstrated. This expands electrical control over spin‐polarized FM/molecule interfaces, which is first demonstrated using ferroelectric molecules, to all molecular classes. 相似文献
This paper investigates shortcomings that limit the performance of optical code division multiple access (OCDMA) systems including the low cardinality and data rate as well as the high power at reception. The main drawback for such systems known as multiple access interference accompanying by phase induced intensity noise is also investigated to effeciencly propose a novel two dimensional cyclic shift (2D-CS) code to be implemented in non-coherent OCDMA systems. The developed code is based on a one dimensional cyclic shift (1D-CS) code previously provided by research works processing spectral amplitude coding for optical code division multiple access (SAC-OCDMA) systems. Numerical results obtained by this study are therefore compared to previous studies employing different codes like two dimensional extended double weight (2D-EDW), two dimensional flexible cross correlation/modified double weight (2D-FCC/MDW), two dimensional perfect difference (2D-PD), two dimensional diluted perfect difference (2D-DPD), two dimensional multi service (2D-MS) and two dimensional zero cross correlation/multi diagonal (2D-ZCC/MD) codes. Accordingly, it is demonstrated that the proposed 2D-CS code outperforms all codes given previously in terms of system capacity where the small increasing percentage is about 40% compared to 2D-ZCC/MD and 2D-MS. Systems using 2D-CS code can support until 203 simultaneous users with a total code length equal to 171. System performance investigation leads to a BER and Q-Factor closely to1.0E?12 and 1.0E?27, and 6.6 dB and 10.6 dB at 20 km of single mode fiber length using white light source and Laser, respectively. Furthermore, such a code can be easily adopted by OCDMA systems for a long distance up to approximately 55 and 100 km.
A series of modified zeolite catalysts (HYM) was prepared by ion-exchange of a commercial faujasite Y by various cations (M=Ni, Cr, Fe, Li, Ce). The exchange level was calculated from the chemical analysis results. The acidity of the samples was
determined by ammonia adsorption calorimetry which allowed the simultaneous determination of the number and strength of the
acid sites. The order of acidity obtained was the following: HYCr>HY>HYNi>HYLi>HYFe>HYCe.
These catalysts were tested in the dry reforming reaction of methane by carbon dioxide in the 400–700°C domain, under atmospheric
pressure. The best catalytic performances were observed with the HYNi sample which displayed methane and dioxide conversions
of 74,1 and 78,5% respectively.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
A series of nickel-exchanged catalysts based on ZSM-5, USY, and Mordenite zeolites has been prepared by the ionic exchange method. The NiZeol catalysts have been characterized by XRD and BET. The exchange levels and nickel contents of the catalysts have been determined by chemical analysis. The acidity of the zeolite supports has been investigated using NH3 adsorption microcalorimetry. The number of acidic sites was found to decrease according to the following sequence: HUSY > HZSM-5 > HMOR. The temperature programmed reduction studies showed that the most reducible catalyst is NiZSM-5. The Ni-exchanged zeolites presented good catalytic performance in the methane reforming by CO2. At a temperature of 650°C, CH4 conversions of 71 and 54% were achieved on NiUSY and NiZSM-5 respectively. At 400°C, CO2 FTIR adsorption has shown that CO2 decomposes into CO and oxygen on NiZSM-5 which explains its reactivity at such a low temperature, while no decomposition of this probe molecule was observed on the NiUSY catalyst. The catalytic performance was found to vary in the following sequence at 650°C: NiUSY > NiZSM-5 > NiMOR. Moreover, the catalytic performances were found to depend strongly on the CO2/CH4 ratio in the feed and were markedly improved for CO2/CH4 greater than 1. 相似文献
Antimony-containing mesoporous SBA-15 with different Si/Sb ratio has been synthesized using a post-treatment procedure with
an aqueous solution of SbCl3 and characterized by elemental analysis, XRD method, N2 adsorption measurements (BET and BJH theory) and FTIR spectroscopy. The benzylation of aromatics by benzyl chloride has been
investigated over these solids. Indeed, the antimony-containing mesoporous SBA-15 showed both high activity and high selectivity
for this reaction. More interesting is the observation that Sb-SBA-15 (35) catalyst is active and selective for large molecules
like naphthenic compounds such as 2-methylnaphthalene and it can also be reused in the benzylation of benzene for several
times. Kinetics of the benzene benzylation over these catalysts have also been investigated.
Published in Russian in Kinetika i Kataliz, 2009, vol. 50, no. 3, pp. 428–433.
The article is published in the original. 相似文献
The benzylation of benzene and the substituted benzenes reaction employing benzyl chloride as the alkylating agent over a
series of zinc-containing mesoporous silicas with different Zn contents have been investigated. These materials (Zn-HMS-n) have been characterized by chemical analysis, BET, and XRD. The mesoporous zinc-containing materials showed both high activity
and high selectivity for benzylation of benzene. The activity of these catalysts for the benzylation of different aromatic
compounds is in the following order: benzene > toluene > p-xylene > anisole. The kinetics of the benzene benzylation over these catalysts has also been investigated.
Published in Russian in Kinetika i Kataliz, 2007, Vol. 48, No. 3, pp. 421–425. 相似文献
The benzylation of benzene by benzyl chloride to diphenylmethane over FeCl3, InCl3, GaCl3, ZnCl2, CuCl2 and NiCl2 supported on mesoporous SBA-15 at 353 K has been investigated. The redox property due to the impregnation of the SBA-15 by transition metal chloride seems to play a very important role in the benzene benzylation process. Among the catalysts, the FeCl3/SBA-15 showed both high conversation and high selectivity for the benzylation of benzene. The activity of these catalysts for the benzylation of different aromatic compounds is in the following order: benzene > toluene > p-xylene > anisole. More interesting is the observation that this catalyst is always active and selective for large molecules like naphthenic compounds such as methoxynaphthalene and he can also be reused in the benzylation of benzene for several times. Kinetics of the benzene benzylation over these catalysts have also been investigated. 相似文献
Silica-, alumina- and titania-supported Co catalysts with different metal loadings were tested for selective citral hydrogenation in liquid phase. Temperature programmed desorption of hydrogen (H2-TPD) indicated that the catalysts with the highest unsaturated alcohols selectivities present particular H-Co species. Electron diffraction and XRD measurements revealed that these species would be linked to the presence of Co0 hexagonal phase. According to the results obtained by TEM and cyclohexane dehydrogenation, these two properties would be present on large Co particles. 相似文献