The purpose of this study is to investigate the catalytic effects of alkali and alkaline earth metallic species （AAEM） on char conversion during the gasification in steam and the changes in ex-situ char reactivity i...The purpose of this study is to investigate the catalytic effects of alkali and alkaline earth metallic species （AAEM） on char conversion during the gasification in steam and the changes in ex-situ char reactivity in oxygen after the gasification in steam using different forms （i.e. H-form, Na-form） of Shengli brown coal. The surface area, AAEM concentration and carbon crystallite of chars were obtained to understand the change in char reactivity. It was found that not only Na concentration and carbon structure were the main factors governing the char reactivity in the atmosphere of steam and oxygen, but also they interacted each other. The presence of Na could facilitate the formation of disordering carbon structure in char, and the amorphous carbon structure would in turn affect the distribution of Na and thus its catalytic performance. The surface area and pore volume had very little relationship with the char＇s reactivity. Addi- tionally, the morphology of chars from different forms of coals were observed using scanning electron microscope （SEM）.展开更多
Lanthanum oxide impregnated large-pore zeolite catalysts were prepared. The catalysts were characterized by XRD （X-ray diffraction）, PSA （particle size analysis）, TPD （temperature programmed desorption） and SEM ...Lanthanum oxide impregnated large-pore zeolite catalysts were prepared. The catalysts were characterized by XRD （X-ray diffraction）, PSA （particle size analysis）, TPD （temperature programmed desorption） and SEM （scanning electron microscope）. The performances of the catalysts were investigated using the alkylation reaction of naphthalene with methanol. Under comparable conditions, the La-impregnated β-zeolite catalyst showed the highest catalytic activity among all the catalysts tested. The lower reaction temperature is favorable for the formation of 2,6-dimethyl naphthalene.展开更多
In this study,the thick AlGaN epilayers have been grown on the c-plane sapphire substrate and the free-standing GaN substrate using low-temperature AlN nucleation layers by low-pressure metal-organic chemical vapor de...In this study,the thick AlGaN epilayers have been grown on the c-plane sapphire substrate and the free-standing GaN substrate using low-temperature AlN nucleation layers by low-pressure metal-organic chemical vapor deposition(LPMOCVD).High resolution X-ray diffraction(HRXRD),atom force microscopy(AFM),scanning electron microscopy(SEM),photoluminescence(PL) and Raman scattering measurements have been employed to study the crystal quality,threading dislocation density,surface morphology,optical properties and phonon properties of thick AlGaN epifilms.The results indicate that AlGaN epifilms crystal quality can be improved greatly when grown on the free-standing GaN substrate.We calculated the threading dislocation density and found that thick AlGaN epifilm grown on the free-standing GaN substrate is much lower in total threading dislocation density than that grown on the sapphire substrate,although the surface morphology is rougher than that of sapphire substrate.展开更多
文摘The purpose of this study is to investigate the catalytic effects of alkali and alkaline earth metallic species （AAEM） on char conversion during the gasification in steam and the changes in ex-situ char reactivity in oxygen after the gasification in steam using different forms （i.e. H-form, Na-form） of Shengli brown coal. The surface area, AAEM concentration and carbon crystallite of chars were obtained to understand the change in char reactivity. It was found that not only Na concentration and carbon structure were the main factors governing the char reactivity in the atmosphere of steam and oxygen, but also they interacted each other. The presence of Na could facilitate the formation of disordering carbon structure in char, and the amorphous carbon structure would in turn affect the distribution of Na and thus its catalytic performance. The surface area and pore volume had very little relationship with the char＇s reactivity. Addi- tionally, the morphology of chars from different forms of coals were observed using scanning electron microscope （SEM）.
文摘Lanthanum oxide impregnated large-pore zeolite catalysts were prepared. The catalysts were characterized by XRD （X-ray diffraction）, PSA （particle size analysis）, TPD （temperature programmed desorption） and SEM （scanning electron microscope）. The performances of the catalysts were investigated using the alkylation reaction of naphthalene with methanol. Under comparable conditions, the La-impregnated β-zeolite catalyst showed the highest catalytic activity among all the catalysts tested. The lower reaction temperature is favorable for the formation of 2,6-dimethyl naphthalene.
基金supported by the National Key Science and Technology Special Project,China(Grant No.2008ZX01002-002)the Major Program and State Key Program of the National Natural Science Foundation of China(Grant Nos.60890191 and 60736033)the Fundamental Research Funds for the Central Universities,China(Grant No. JY10000904009)
文摘In this study,the thick AlGaN epilayers have been grown on the c-plane sapphire substrate and the free-standing GaN substrate using low-temperature AlN nucleation layers by low-pressure metal-organic chemical vapor deposition(LPMOCVD).High resolution X-ray diffraction(HRXRD),atom force microscopy(AFM),scanning electron microscopy(SEM),photoluminescence(PL) and Raman scattering measurements have been employed to study the crystal quality,threading dislocation density,surface morphology,optical properties and phonon properties of thick AlGaN epifilms.The results indicate that AlGaN epifilms crystal quality can be improved greatly when grown on the free-standing GaN substrate.We calculated the threading dislocation density and found that thick AlGaN epifilm grown on the free-standing GaN substrate is much lower in total threading dislocation density than that grown on the sapphire substrate,although the surface morphology is rougher than that of sapphire substrate.
