In the present work,the effect of pre-calcination on carbonation conversion and cyclic stability of modi fied CaObased sorbent was investigated by thermogravimetric analyzer(TGA).The modi fied CaO-based sorbents with ...In the present work,the effect of pre-calcination on carbonation conversion and cyclic stability of modi fied CaObased sorbent was investigated by thermogravimetric analyzer(TGA).The modi fied CaO-based sorbents with CaAc_2 as precursor were respectively doped with different elements(Mg,Al,Ce,Zr and La).The speci fic surface area,pore volume and pore size distribution were tested by N_2 isothermal adsorption measurements.The phase compositions of sorbents were characterized by X-ray diffraction(XRD).The results showed that the cyclic stabilities of the sorbents were improved by pre-calcination.The pre-calcination was conducted at 900°C for 5 h in air by the muf fle furnace.With pre-calcination,the cyclic stabilities of sorbents could be as high as 96% after 22 cycles,such as CaO-Al,CaO-Ce and CaO-La.After contact with air,the carbonation conversions of spent sorbents with pre-calcination suddenly increased by about one-sixth due to the change of channel structure by hydration.Both the cyclic stability of sorbent and the durability of reactivation were related to the structural stability of sample,especially the stability of mesopores between 2 nm and 5.5 nm.The present work also provided an easy and low-cost method for reactivating the spent CaO-based sorbents.展开更多
HfO2 films are deposited by atomic layer deposition（ALD） using tetrakis ethylmethylamino hafnium（TEMAH） as the hafnium precursor,while O3 or H2O is used as the oxygen precursor.After annealing at 500℃ in nitrogen...HfO2 films are deposited by atomic layer deposition（ALD） using tetrakis ethylmethylamino hafnium（TEMAH） as the hafnium precursor,while O3 or H2O is used as the oxygen precursor.After annealing at 500℃ in nitrogen,the thickness of Ge oxide＇s interfacial layer decreases,and the presence of GeO is observed at the H2 O-based HfO2 interface due to GeO volatilization,while it is not observed for the O3-based HfO2.The difference is attributed to the residue hydroxyl groups or H2 O molecules in H2 O-based HfO2 hydrolyzing GeO2 and forming GeO,whereas GeO is only formed by the typical reaction mechanism between GeO2 and the Ge substrate for O3-based HfO2 after annealing.The volatilization of GeO deteriorates the characteristics of the high-κ films after annealing,which has effects on the variation of valence band offset and the C-V characteristics of HfO2 /Ge after annealing.The results are confirmed by X-ray photoelectron spectroscopy（XPS） and electrical measurements.展开更多
There are four types of Mg–Al–Si–O inclusions observed in the Mg-treated Al-deoxidized ultra-low-carbon steel con-taining trace Si,including SiO_(2),2MgO·SiO_(2),3Al_(2)O_(3)·2SiO_(2),and 2MgO·Al_(2)...There are four types of Mg–Al–Si–O inclusions observed in the Mg-treated Al-deoxidized ultra-low-carbon steel con-taining trace Si,including SiO_(2),2MgO·SiO_(2),3Al_(2)O_(3)·2SiO_(2),and 2MgO·Al_(2)O_(3)·5SiO_(2)and their composite inclusions.Using FactSage,the phase relationship of Mg–Al–Si–O system at 1473–2073 K was calculated using FactSage software,and the change in Si content can change the stable region range of different Mg–Al–Si–O-based inclusions.Based on the types of inclusions observed experimentally,the formation pathways of inclusions were predicted and a kinetic model was established to describe the formation process of the xMgO·yAl_(2)O_(3)–Mg–Al–Si–O and xAl_(2)O_(3)·ySiO_(2)–Mg–Al–Si–O inclusions.展开更多
Model catalysts approach is widely adopted in fundamental studies of complex heterogeneous cataly-sis.Traditional model catalysts are single crystal-based model catalysts,whose results,however,some-times suffer from t...Model catalysts approach is widely adopted in fundamental studies of complex heterogeneous cataly-sis.Traditional model catalysts are single crystal-based model catalysts,whose results,however,some-times suffer from the"material gap"and"pressure gap"when applied to working catalysts.Recently,uniform catalytic nanocrystals with well-defined structures have emerged,and we have put forward a concept of nanocrystal-based model catalysts for fundamental studies of complex heterogeneous ca-talysis under conditions approaching working catalysts as closely as possible.In this perspective,we summarize our research progresses on Cu_(2)O-based nanocrystal model catalysts.Following a brief in-troduction,we summarize controlled synthesis of uniform Cu_(2)O nanocrystals with various morpholo-gies,morphology-dependent surface compositions and structures and surface chemistry of uniform Cu_(2)O nanocrystals,and heterogeneous catalysis of Cu_(2)O-based nanocrystals.Finally,we conclude the concept of nanocrystal-based model catalysts and outlook that uniform nanocrystals can act not only as model catalysts but also as efficient catalysts.展开更多
基金Supported by Capture CO2 and Storage Technology Jointly Studied by USA and China(2013DFB60140-04)Key Program of National Natural Science Foundation of China(No.21536009)
文摘In the present work,the effect of pre-calcination on carbonation conversion and cyclic stability of modi fied CaObased sorbent was investigated by thermogravimetric analyzer(TGA).The modi fied CaO-based sorbents with CaAc_2 as precursor were respectively doped with different elements(Mg,Al,Ce,Zr and La).The speci fic surface area,pore volume and pore size distribution were tested by N_2 isothermal adsorption measurements.The phase compositions of sorbents were characterized by X-ray diffraction(XRD).The results showed that the cyclic stabilities of the sorbents were improved by pre-calcination.The pre-calcination was conducted at 900°C for 5 h in air by the muf fle furnace.With pre-calcination,the cyclic stabilities of sorbents could be as high as 96% after 22 cycles,such as CaO-Al,CaO-Ce and CaO-La.After contact with air,the carbonation conversions of spent sorbents with pre-calcination suddenly increased by about one-sixth due to the change of channel structure by hydration.Both the cyclic stability of sorbent and the durability of reactivation were related to the structural stability of sample,especially the stability of mesopores between 2 nm and 5.5 nm.The present work also provided an easy and low-cost method for reactivating the spent CaO-based sorbents.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60976068 and 61076097)the Cultivation Fund of the Key Scientific and Technical Innovation Project of the Ministry of Education of China (Grant No. 708083)
文摘HfO2 films are deposited by atomic layer deposition（ALD） using tetrakis ethylmethylamino hafnium（TEMAH） as the hafnium precursor,while O3 or H2O is used as the oxygen precursor.After annealing at 500℃ in nitrogen,the thickness of Ge oxide＇s interfacial layer decreases,and the presence of GeO is observed at the H2 O-based HfO2 interface due to GeO volatilization,while it is not observed for the O3-based HfO2.The difference is attributed to the residue hydroxyl groups or H2 O molecules in H2 O-based HfO2 hydrolyzing GeO2 and forming GeO,whereas GeO is only formed by the typical reaction mechanism between GeO2 and the Ge substrate for O3-based HfO2 after annealing.The volatilization of GeO deteriorates the characteristics of the high-κ films after annealing,which has effects on the variation of valence band offset and the C-V characteristics of HfO2 /Ge after annealing.The results are confirmed by X-ray photoelectron spectroscopy（XPS） and electrical measurements.
基金The authors are grateful to the National Natural Science Foundation of China(Grant No.51874170)the Union Foundation of State Key Laboratory of Marine Equipment and Applications-University of Science and Technology Liaoning(SKLMEA-USTL-201706)for supporting this work.
文摘There are four types of Mg–Al–Si–O inclusions observed in the Mg-treated Al-deoxidized ultra-low-carbon steel con-taining trace Si,including SiO_(2),2MgO·SiO_(2),3Al_(2)O_(3)·2SiO_(2),and 2MgO·Al_(2)O_(3)·5SiO_(2)and their composite inclusions.Using FactSage,the phase relationship of Mg–Al–Si–O system at 1473–2073 K was calculated using FactSage software,and the change in Si content can change the stable region range of different Mg–Al–Si–O-based inclusions.Based on the types of inclusions observed experimentally,the formation pathways of inclusions were predicted and a kinetic model was established to describe the formation process of the xMgO·yAl_(2)O_(3)–Mg–Al–Si–O and xAl_(2)O_(3)·ySiO_(2)–Mg–Al–Si–O inclusions.
基金supported by the National Natural Science Foundation of China(Nos.21525313,U1930203,and 22102146)the Chinese Academy of Sciences,and the Changjiang Scholars Program of the Chinese Ministry of Education.
文摘Model catalysts approach is widely adopted in fundamental studies of complex heterogeneous cataly-sis.Traditional model catalysts are single crystal-based model catalysts,whose results,however,some-times suffer from the"material gap"and"pressure gap"when applied to working catalysts.Recently,uniform catalytic nanocrystals with well-defined structures have emerged,and we have put forward a concept of nanocrystal-based model catalysts for fundamental studies of complex heterogeneous ca-talysis under conditions approaching working catalysts as closely as possible.In this perspective,we summarize our research progresses on Cu_(2)O-based nanocrystal model catalysts.Following a brief in-troduction,we summarize controlled synthesis of uniform Cu_(2)O nanocrystals with various morpholo-gies,morphology-dependent surface compositions and structures and surface chemistry of uniform Cu_(2)O nanocrystals,and heterogeneous catalysis of Cu_(2)O-based nanocrystals.Finally,we conclude the concept of nanocrystal-based model catalysts and outlook that uniform nanocrystals can act not only as model catalysts but also as efficient catalysts.
