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Li G.,Zhejiang University | Kuang Y.,Zhejiang University | Hu S.,Science and Technology on Scramjet Laboratory
Shiyou Xuebao, Shiyou Jiagong/Acta Petrolei Sinica (Petroleum Processing Section) | Year: 2015

The formation process and mechanism of ZSM-5 coating on stainless steel substrate prepared by using in-situ hydrothermal synthesis were studied. The influences of several factors on the preferential orientation of the crystals in the coating were discussed. The results showed that a-oriented ZSM-5 coating was formed on the upward side, while no continuous coating formed on the downward side of stainless steel substrate, when it rested in the autoclave at an angle. Under the same hydrothermal conditions, randomly oriented crystals were formed on the substrate which was positioned horizontally at the bottom of the autoclave, and after ultrasonic washing in deionized water for 20 min, however, some a-oriented crystals also appeared. Continuous a-oriented ZSM-5 coating was successfully obtained on the horizontally positioned substrate, when a reaction mixture with a small amount of ethanol was employed. a-Oriented ZSM-5 coating was shown to be transformed from an amorphous coating on the substrate in two steps, in which b-oriented crystals were first formed from the amorphous coating, followed by the formation of a-oriented crystals on the (010) face of these b-oriented crystals. On the horizontally positioned substrate, a-oriented ZSM-5 coating was also formed first, and then was covered subsequently with randomly oriented crystals which were formed in the solution. ©, 2015, Science Press. All right reserved. Source

Wang C.-A.,Tsinghua University | Wang M.-F.,Science and Technology on Scramjet Laboratory
Frontiers of Materials Science | Year: 2013

The thermal shock behavior of ZrB2-SiC ceramics was studied with water, air and methyl silicone oil as quenching media, respectively. The temperature of all coolants was room temperature (25°C) and the residual strength of the ceramics after quenching was tested. The strength of the ceramics after water quenching had an obvious drop when the temperature difference, ΔT, was about 275°C, while the residual strength of the specimens quenched by air and silicone oil only varied a little and even increased slightly when the temperature difference was higher than 800°C. The different thermal conductive coefficient of the coolants and surface heat transfer coefficient resulted in the differences in the thermal shock behavior. The formation of oxidation layer was beneficial for improving the residual strength of the ceramics after quenching. © 2013 Higher Education Press and Springer-Verlag Berlin Heidelberg. Source

Wei B.,Beihang University | Xu X.,Beihang University | Yan M.,Beihang University | Shi X.,Science and Technology on Scramjet Laboratory | Yang Y.,Beihang University
Journal of Propulsion and Power | Year: 2012

Experimental and numerical study of a novel integrated flush-wall aeroramp injector/gas-pilot flame has been conducted in a scramjet combustor. The aeroramp injector consisted of four flush-wall holes. Downstream of it, the gas-pilot flame as located as igniter and flame holder. The experiment's facilities can deliver a continuous supersonic flow of Mach number 2.0 with a total temperature of 1200 K. In the cold flow tests, schlieren and surface oil-flow visualization pictures in the vicinity of injectors were taken to obtain a qualitative assessment of the injectors flowfields. The detailed characteristics of cold flowfields were numerically simulated, which agreed well with the experimental results. Some important parameters, such as mixing efficiency, penetration depth, and maximum concentration decay, were investigated to analyze the mixing performance. In the hot flow tests, ethylene was injected into the mainstream at jet-to-freestream momentum flux ratios q between 1.2 and 3.9. One-dimensional performance analysis of the test data indicates combustion efficiencies as high as 90% in all cases. This was the first time that the integration of an aeroramp injector/gas-pilot flame for supersonic combustion was studied. The results show that this novel injection and flame holding configuration for supersonic combustion is feasible. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. Source

Na J.,Tianjin University of Technology | Liu G.,Tianjin University of Technology | Zhou T.,Tianjin University of Technology | Ding G.,Tianjin University of Technology | And 2 more authors.
Catalysis Letters | Year: 2013

ZSM-5/MCM-41 zeolite composites with varying mesopore sizes were prepared through alkali-desilication and surfactant-directed recrystallization with different chain length of alkyltrimethylammonium bromide. XRD and TEM revealed that the composites possessed the characteristics of both ZSM-5 and mesoporous MCM-41 with hexagonal symmetry. N2-adsorption-desorption, 27Al MAS NMR, NH3-TPD and in situ FT-IR results suggested that the sizes of the mesopores and the accessibility of acid sites could be affected greatly by the chain length of alkyltrimethylammonium bromide used. Catalytic cracking of n-dodecane over ZSM-5/MCM-41 composites was studied in the form of coatings on the inside of a tubular reactor at 550 °C and 4 MPa. The conversion of n-dodecane increased gradually with increasing the mesopore sizes of ZSM-5/MCM-41 composites, implying a positive effect of the mesopores on the diffusion inside pore channels and the accessibility of acid sites by the reactants. © 2013 The Author(s). Source

Yuan F.,Zhejiang University | Li G.,Zhejiang University | Hu S.,Science and Technology on Scramjet Laboratory
Shiyou Xuebao, Shiyou Jiagong/Acta Petrolei Sinica (Petroleum Processing Section) | Year: 2014

ZSM-5 films were prepared on the surface of stainless steel plates or tubes by means of in-situ growth method. The influence of alkali treatment on structure and catalytic performance of ZSM-5 films were studied. The results showed that the treatment of ZSM-5 films in 0.2 mol/L NaOH solution with long time or high temperature caused formation of cracks in the film, which could affect the adhesion strength between the film and the substrate. Under appropriate conditions of alkali treatment, the formation of cracks in the film could be avoided. The mesopores could not be produced in the film under the conditions at which mesopores could be formed in the powdery sample. The amorphous materials presented on the film surface were dissolved during alkali treatment, thus the catalytic performance of the film would be improved. Source

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