A series of Ferrierite(FER)zeolites were prepared via hydrothermal synthesis in the absence of organic templates with the aid of sodium-type FER zeolite(NaFER)or NaFER suspensions(NaFERsus)acquired by NaOH solution tr...A series of Ferrierite(FER)zeolites were prepared via hydrothermal synthesis in the absence of organic templates with the aid of sodium-type FER zeolite(NaFER)or NaFER suspensions(NaFERsus)acquired by NaOH solution treatment as seeds.The differences in the structures and acid sites of the obtained FER zeolite catalysts arising from the choice of seed were investigated,and the catalytic performances of the obtained FER zeolites were evaluated in the skeletal isomerization of n-butene.The results indicate that the samples synthesized using NaFERsus feature more Br?nsted acid sites(BAS)in the 10-membered-ring(10-MR)at the expense of strong acid and Lewis acid sites(LAS),compared with samples derived from NaFER.Therefore,the FER samples synthesized using NaFERsus outperformed the NaFER counterparts as the BAS in 10-MR and LAS were the main active sites,while BAS in 8-MR and LAS were responsible for side reactions,such as polymerization,cracking,and carbon deposition in n-butene isomerization.The optimized FER catalyst was continuously used for 720 h at 350℃ at 0.1 MPa under an n-butene space velocity of 2.0 h^(-1),during which the n-butene conversion remained at>40%,and the isobutylene yield was>37.5%.展开更多
In the Yangtze river aera,the first crop of indi-ca rice is sown in late Mar to early Apr andtransplanted in early May.Usually,seedlingsperish when abnormal low temperature of 6-10℃ lasted for 3 d or longer.The effec...In the Yangtze river aera,the first crop of indi-ca rice is sown in late Mar to early Apr andtransplanted in early May.Usually,seedlingsperish when abnormal low temperature of 6-10℃ lasted for 3 d or longer.The effect ofsocking seed with urea solution on increasingthe cold tolerance at the seedling stage was展开更多
Well-crystallized high-silica NaY zeolites (Si/Al〉2.5) were prepared from a reaction mixture consisting of metakaolin, sodium silicate solution and seed solution via optimization of the mixture composition and reac...Well-crystallized high-silica NaY zeolites (Si/Al〉2.5) were prepared from a reaction mixture consisting of metakaolin, sodium silicate solution and seed solution via optimization of the mixture composition and reaction conditions. The transformation from kaolin to high-silica NaY zeolite was confirmed by XRD, SEM and IR techniques. Subsequently, the influence of synthesis parameters, i.e. initial SIO2/Al2O3, initial Na2O/SiO2, initial H2O/SiO2, aging time of the seed solution, crystallization temperature and crystallization time, on the NaY growth was investigated in terms of crystallinity and Si/Al ratio. The results showed that the effects of initial SiO2/Al2O3, initial Na2O/SiO2 and initial H2O/ SiO2 on the crystaIlinity and Si/Al ratio of NaY zeolite are similar to those observed in the conventional syntheses of NaY zeolites only using sodium silicate solution as silicon source. However, due to the use of metakaolin as the main silicon and aluminum sources in the present study, a long crystallization induction period of 20 h was achieved, which can be attributed to the dissolution of metakaolin. In addition, different from the conventional syntheses of zeolite NaY, pure NaY zeolites (i.e. without NaP zeolite impurity) were still obtained even at 120℃ because of the use of a large quantity of seed solution (23 wt%) in the reaction mixture. As the aging time of the seed solution increased from 3.5 h to 22 h, the relative crystallinity of the NaY zeolite first increased sharply and then reached a plateau, while the Si/Al ratio first increased rapidly up to a maximum value of 2.75 corresponding to an aging time of 6.5 h, and then decreased sharply with the aging time.展开更多
Through analysing the exact solution of some nonlinear models, the role of the variable separating method in solving nonlinear equations is discussed. We find that rich solution structures of some special fields of th...Through analysing the exact solution of some nonlinear models, the role of the variable separating method in solving nonlinear equations is discussed. We find that rich solution structures of some special fields of these equations come from the nonzero seed solution. However, these nonzero seed solutions is likely to result in the divergent phenomena for the other field component of the same equation. The convergence and the signification of all field components should be discussed when someone solves the nonlinear equation using the variable separating method.展开更多
In this paper,ferroelectric tetragonal tungsten bronze type potassium lithium niobate(KLN)crystal with a size of 20mm×8mm×43mm was grown from a melt with a composition of 32mol% K 2CO 3,24mol% Li 2CO 3 and 4...In this paper,ferroelectric tetragonal tungsten bronze type potassium lithium niobate(KLN)crystal with a size of 20mm×8mm×43mm was grown from a melt with a composition of 32mol% K 2CO 3,24mol% Li 2CO 3 and 44mol% Nb 2O 5 by the top seeded solution growth (TSSG)method.The KLN crystal as grown along [110]axis has a perfect crystal melt interface dominated by {110} and {210} facets.Lattice constants were measured by X ray diffraction (XRD) analysis performed on {001}and {110}natural faces of single crystal samples.The anisotropic thermal expansion behavior of the crystal was also studied along [001] and [110] axes,respectively by using a Shimadzu TMA 50 thermomechnical analyzer.For the purpose of crystal poling,the dependence of crystal capacitance vs.temperature in both heating and cooling cycles was measured and the ferroelectric Curie temperature was determined to be 514℃.The crystal was poled at 506℃ with a dc field of about 250 V/cm along the c axis of the sample,for a time corresponding to about 1.5 h/cm.The blue second harmonic generation (SHG)characteristics of the KLN crystal were investigated by using a 3900s Ti∶sapphire CW tunable laser.Blue laser light at wavelength 432nm was obtained by the non critical phase matching (NCPM)SHG at room temperature.Based on the wavelength and temperature tuning curves for the NCPM SHG,the wavelength acceptance and temperature acceptance of this KLN crystal were measured.The crystal property homogeneity along the <110>growth axis was also studied by measuring the room temperature NCPM wavelength at different growth positions.展开更多
The growth of polycrystalline silicon layers on glass from tin solutions at low temperatures is presented.This approach is based on the steady-state solution growth of Si crystallites on nanocrystalline seed layers, w...The growth of polycrystalline silicon layers on glass from tin solutions at low temperatures is presented.This approach is based on the steady-state solution growth of Si crystallites on nanocrystalline seed layers, which are prepared in a preceding process step. Scanning electron microscopy and atomic force microscopy investigations reveal details about the seed layer surfaces, which consist of small hillocks, as well as about Sn inclusions and gaps along the glass substrate after solution growth. The successful growth of continuous microcrystalline Si layers with grain sizes up to several ten micrometers shows the feasibility of the process and makes it interesting for photovoltaics.展开更多
Formamidine(FA)-based perovskite solar cells(PSCs)are promising candidates for photoelectric conversion devices due to their excellent optoelectronic properties.However,the instability of perovskites,especially moistu...Formamidine(FA)-based perovskite solar cells(PSCs)are promising candidates for photoelectric conversion devices due to their excellent optoelectronic properties.However,the instability of perovskites,especially moisture instability,remains one of the biggest obstacles to the commercialization of perovskite devices.Therefore,it is very important to explore and target the effect of moisture on FA-based perovskites to prevent this effect and improve device stability.Herein,we studied the degradation process of commonly used FA-based perovskite films by X-ray diffraction and scanning electron microscopy characterization and analyzed the reasons for their humidity-induced degradation.Subsequently,we further adopted a strategy by adding methylammonium bromine powder into a PbI_(2) precursor solution to prepare a seed solution in a two-step preparation process to enhance the performance and stability of FA-based PSCs.Finally,the degradation rate of the obtained perovskite film was significantly slowed down under high humidity compared to that of perovskite films prepared by a two-step method without applying a seed solution.The corresponding device achieved a remarkable power conversion efficiency of 23.22%,and the efficiency of this device showed no attenuation after 900 h of exposure to air.展开更多
基金the funding of the project by the CNPC Corporation (2018B-1907)。
文摘A series of Ferrierite(FER)zeolites were prepared via hydrothermal synthesis in the absence of organic templates with the aid of sodium-type FER zeolite(NaFER)or NaFER suspensions(NaFERsus)acquired by NaOH solution treatment as seeds.The differences in the structures and acid sites of the obtained FER zeolite catalysts arising from the choice of seed were investigated,and the catalytic performances of the obtained FER zeolites were evaluated in the skeletal isomerization of n-butene.The results indicate that the samples synthesized using NaFERsus feature more Br?nsted acid sites(BAS)in the 10-membered-ring(10-MR)at the expense of strong acid and Lewis acid sites(LAS),compared with samples derived from NaFER.Therefore,the FER samples synthesized using NaFERsus outperformed the NaFER counterparts as the BAS in 10-MR and LAS were the main active sites,while BAS in 8-MR and LAS were responsible for side reactions,such as polymerization,cracking,and carbon deposition in n-butene isomerization.The optimized FER catalyst was continuously used for 720 h at 350℃ at 0.1 MPa under an n-butene space velocity of 2.0 h^(-1),during which the n-butene conversion remained at>40%,and the isobutylene yield was>37.5%.
文摘In the Yangtze river aera,the first crop of indi-ca rice is sown in late Mar to early Apr andtransplanted in early May.Usually,seedlingsperish when abnormal low temperature of 6-10℃ lasted for 3 d or longer.The effect ofsocking seed with urea solution on increasingthe cold tolerance at the seedling stage was
基金supported by Beijing Natural Science Foundation (Grant No.2093043)the National Natural Science Foundation of China (Grant No.20606038)
文摘Well-crystallized high-silica NaY zeolites (Si/Al〉2.5) were prepared from a reaction mixture consisting of metakaolin, sodium silicate solution and seed solution via optimization of the mixture composition and reaction conditions. The transformation from kaolin to high-silica NaY zeolite was confirmed by XRD, SEM and IR techniques. Subsequently, the influence of synthesis parameters, i.e. initial SIO2/Al2O3, initial Na2O/SiO2, initial H2O/SiO2, aging time of the seed solution, crystallization temperature and crystallization time, on the NaY growth was investigated in terms of crystallinity and Si/Al ratio. The results showed that the effects of initial SiO2/Al2O3, initial Na2O/SiO2 and initial H2O/ SiO2 on the crystaIlinity and Si/Al ratio of NaY zeolite are similar to those observed in the conventional syntheses of NaY zeolites only using sodium silicate solution as silicon source. However, due to the use of metakaolin as the main silicon and aluminum sources in the present study, a long crystallization induction period of 20 h was achieved, which can be attributed to the dissolution of metakaolin. In addition, different from the conventional syntheses of zeolite NaY, pure NaY zeolites (i.e. without NaP zeolite impurity) were still obtained even at 120℃ because of the use of a large quantity of seed solution (23 wt%) in the reaction mixture. As the aging time of the seed solution increased from 3.5 h to 22 h, the relative crystallinity of the NaY zeolite first increased sharply and then reached a plateau, while the Si/Al ratio first increased rapidly up to a maximum value of 2.75 corresponding to an aging time of 6.5 h, and then decreased sharply with the aging time.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10675065, 90503006 and 10735030) and the K.C.Wong Magna Fund in Ningbo University.Acknowledgement The author would like to thank the helpful discussion of Prof. Sen-Yue Lou.
文摘Through analysing the exact solution of some nonlinear models, the role of the variable separating method in solving nonlinear equations is discussed. We find that rich solution structures of some special fields of these equations come from the nonzero seed solution. However, these nonzero seed solutions is likely to result in the divergent phenomena for the other field component of the same equation. The convergence and the signification of all field components should be discussed when someone solves the nonlinear equation using the variable separating method.
文摘In this paper,ferroelectric tetragonal tungsten bronze type potassium lithium niobate(KLN)crystal with a size of 20mm×8mm×43mm was grown from a melt with a composition of 32mol% K 2CO 3,24mol% Li 2CO 3 and 44mol% Nb 2O 5 by the top seeded solution growth (TSSG)method.The KLN crystal as grown along [110]axis has a perfect crystal melt interface dominated by {110} and {210} facets.Lattice constants were measured by X ray diffraction (XRD) analysis performed on {001}and {110}natural faces of single crystal samples.The anisotropic thermal expansion behavior of the crystal was also studied along [001] and [110] axes,respectively by using a Shimadzu TMA 50 thermomechnical analyzer.For the purpose of crystal poling,the dependence of crystal capacitance vs.temperature in both heating and cooling cycles was measured and the ferroelectric Curie temperature was determined to be 514℃.The crystal was poled at 506℃ with a dc field of about 250 V/cm along the c axis of the sample,for a time corresponding to about 1.5 h/cm.The blue second harmonic generation (SHG)characteristics of the KLN crystal were investigated by using a 3900s Ti∶sapphire CW tunable laser.Blue laser light at wavelength 432nm was obtained by the non critical phase matching (NCPM)SHG at room temperature.Based on the wavelength and temperature tuning curves for the NCPM SHG,the wavelength acceptance and temperature acceptance of this KLN crystal were measured.The crystal property homogeneity along the <110>growth axis was also studied by measuring the room temperature NCPM wavelength at different growth positions.
基金Project supported by the German Research Foundation(DFG)(No.BO 1129/5-1)
文摘The growth of polycrystalline silicon layers on glass from tin solutions at low temperatures is presented.This approach is based on the steady-state solution growth of Si crystallites on nanocrystalline seed layers, which are prepared in a preceding process step. Scanning electron microscopy and atomic force microscopy investigations reveal details about the seed layer surfaces, which consist of small hillocks, as well as about Sn inclusions and gaps along the glass substrate after solution growth. The successful growth of continuous microcrystalline Si layers with grain sizes up to several ten micrometers shows the feasibility of the process and makes it interesting for photovoltaics.
基金the support from the National Natural Science Foundation of China(Nos.52025028 and 52002258)the Ministry of Science and Technology of China(No.2021YFA1500803)+2 种基金the Natural Science Foundation of Jiangsu Province(Nos.BK20200877 and BK20210728)“Shuangchuang”Program of Jiangsu Provincethe Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions.
文摘Formamidine(FA)-based perovskite solar cells(PSCs)are promising candidates for photoelectric conversion devices due to their excellent optoelectronic properties.However,the instability of perovskites,especially moisture instability,remains one of the biggest obstacles to the commercialization of perovskite devices.Therefore,it is very important to explore and target the effect of moisture on FA-based perovskites to prevent this effect and improve device stability.Herein,we studied the degradation process of commonly used FA-based perovskite films by X-ray diffraction and scanning electron microscopy characterization and analyzed the reasons for their humidity-induced degradation.Subsequently,we further adopted a strategy by adding methylammonium bromine powder into a PbI_(2) precursor solution to prepare a seed solution in a two-step preparation process to enhance the performance and stability of FA-based PSCs.Finally,the degradation rate of the obtained perovskite film was significantly slowed down under high humidity compared to that of perovskite films prepared by a two-step method without applying a seed solution.The corresponding device achieved a remarkable power conversion efficiency of 23.22%,and the efficiency of this device showed no attenuation after 900 h of exposure to air.