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排序方式: 共有182条查询结果,搜索用时 125 毫秒
1.
Laurie Pesant Joseph Matta Cuong Pham-Huu François Garin Pierre Bernhardt Charlotte Pham Marc-Jacques Ledoux 《Topics in Catalysis》2004,(1):281-286
Platinum catalyst supported on a medium surface area -SiC was successfully used for the catalytic combustion of model carbon particles and compared to a catalyst supported on a low surface area -SiC. The -SiC-based catalyst showed no deactivation as a function of cycling tests while a strong deactivation was observed on the -SiC-based catalyst. This deactivation was attributed to the progressive encapsulation of the platinum particles by a layer of silica which built up during the combustion cycle. These results render possible the use of Pt/-SiC catalyst as a diesel carbon particle catalytic filter with continuous regeneration. 相似文献
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Viet Hung Pham Thanh Truong Dang Tran Viet Cuong Seung Hyun Hur Byung-Seon Kong Eui Jung Kim Jin Suk Chung 《Korean Journal of Chemical Engineering》2012,29(5):680-685
We report the effect of temperature on the extent of graphene oxide reduction by hydrazine and the dispersibility of the resulting
chemically converted graphene (CCG) in polar organic solvents. The extent of graphene oxide reduction at high temperatures
was only slightly higher than at low temperatures (30–50 °C), while the dispersibility of the resulting CCG in organic solvents
decreased markedly with increasing temperature. The low dispersibility of CCGs prepared at high temperatures was greatly affected
by reduction and influenced by the formation of an irreversible agglomerate of CCG at high temperatures. The reduction of
graphene oxide at low temperatures is necessary to prepare highly dispersible CCG in organic solvents. CCG prepared at 30
°C is dispersible in N-methyl-2-pyrrolidone concentrations as high as 0.71 mg/mL. The free-standing paper made of this CCG
possessed an electrical conductivity of more than 22,000 S/m, one of the highest values ever reported. 相似文献
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Influence of the preparation conditions on the synthesis of high surface area SiC for use as a heterogeneous catalyst support 总被引:2,自引:0,他引:2
N. Keller C. Pham-Huu S. Roy M. J. Ledoux C. Estournes J. Guille 《Journal of Materials Science》1999,34(13):3189-3202
The influence of different parameters (temperature, duration and SiO source) on the synthesis of silicon carbide SiC according to the gas-solid reaction between SiO vapors and activated charcoal was investigated. The material obtained retained the general shape of the activated charcoal, which is an advantage because of the difficulty in post shaping SiC, due to the high strength of the material. High temperature (>1250 °C) and long reaction duration led to a high C* SiC conversion but with a relatively low surface area (20–25 m2 · g–1) due to sintering via the surface diffusion phenomenon. The combination of a lower reaction temperature (1200 °C), longer reaction duration (15 h) and high (Si + SiO2)/C* weight ratio allowed SiC to be obtained with a surface area of around 50 m2 · g–1, which can be used as a support material for heterogeneous catalysis. 相似文献
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ZnO structures were synthesised on the sapphire (112?0) substrate by a vapour transport method in a gas flowing furnace. The influence of the oxygen content in the gas mixture on the morphology and luminescent properties of ZnO structures grown on a strip-like substrate was investigated, with all other growth parameters being kept nominally identical. Integrated electron microscopy and cathodoluminescence analysis shows gradual variations of structural and optical emission properties for ZnO structures grown on the long substrate. Defect-related green luminescence of ZnO is found to be highly dependent on the oxygen vapour in the growth region of the furnace. Our findings demonstrate that the green luminescence is associated with oxygen deficiency in ZnO. 相似文献
8.
Marc J. Ledoux Cuong Pham-Huu Nicolas Keller Jean-B. Nougayr de Sabine Savin-Poncet Jacques Bousquet 《Catalysis Today》2000,61(1-4):157-163
Very high activity and selectivity could be achieved for the direct oxidation of H2S into elemental sulfur at low reaction temperature (40–60°C), on nickel sulfide supported SiC catalyst. The heterogeneous nature of the support surface (hydrophilic and hydrophobic areas) could explain the important role played by water to maintain a high and stable H2S conversion level. The formation of a very active superficial nickel oxysulfide phase was proposed in order to explain the activation period necessary at reaction temperatures <60°C. Total selectivity for sulfur was attributed to the very low reaction temperature and the absence of any microporosity in the support. 相似文献
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We present a unified approach to the construction of multidimensional trellis codes that have small constellation expansion ratio (CER) and small peak-to-average power ratio (PAR) and hence are of high bandwidth efficiency. In the approach, we extend Wei's (1987) construction to dimensionalities other than a power of two and propose a low-complexity encoder. We also present a general partition technique that gives geometrically uniform partitions with a good distance profile. The proposed method can generate many good codes including previously reported Ungerboeck codes, Gallager-Calderbank-Sloane codes, and Wei codes with quadrature amplitude modulation signals. Some newly discovered six-dimensional trellis codes are compared with these known codes on their CER, PAR, effective coding gain, and encoder/decoder complexities. 相似文献
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