Sr2SiO4∶Eu 3+ ,Bi 3+ and SrSiO 3∶Eu 3+ ,Bi 3+ samples were synthesized at high temperature and high pressure. The effect of high pressure on the structure and luminescence properties of the samples were ...Sr2SiO4∶Eu 3+ ,Bi 3+ and SrSiO 3∶Eu 3+ ,Bi 3+ samples were synthesized at high temperature and high pressure. The effect of high pressure on the structure and luminescence properties of the samples were studied. As a comparison, the samples were also prepared by the method of sol-gel at high temperature and atmospheric pressure. The SrSiO 3∶Eu 3+ ,Bi 3+ prepared at atmosphere has a hexagonal phase structure; in the pressure range of 2 34-4 10 GPa, it is transformed into a pseudo-orthorhombic structure(monoclinic), and in the pressure range of 4 10-4 15 GPa, the structure change of Sr 2SiO 4∶Eu 3+ , Bi 3+ has not been observed, it maintains the monoclinic structure of the samples synthesized at an atmospheric pressure. High pressure makes the luminescence properties of the samples changed obviously. The intensity and the relative quantum luminescent efficiency decrease, the half-width increases obviously and the red shift occurs. The changes of the luminescence properties result from the pressure-induced changes of the crystal structures.展开更多
The preparing method,rolling technology and mechanical properties of low chromium semi-steel grinding ball by cross rolling were studied.The results show that when the low chromium semi-steel bar is forged from55mm to...The preparing method,rolling technology and mechanical properties of low chromium semi-steel grinding ball by cross rolling were studied.The results show that when the low chromium semi-steel bar is forged from55mm to50mm,cross-rolled into grinding ball at 1 000-1 050℃,air cooled and tempered at 550℃for 2h,the best mechanical properties,especially the abrasive resistance under the action of hard abrasive,can be obtained.展开更多
In this paper, the properties of carbon deposited on hexaaluminateLaNiAl_(11)O_(19) catalyst were characterized by X-ray photoelectron spectroscopy (XPS), and in themeantime, the amount of carbon deposited on the cata...In this paper, the properties of carbon deposited on hexaaluminateLaNiAl_(11)O_(19) catalyst were characterized by X-ray photoelectron spectroscopy (XPS), and in themeantime, the amount of carbon deposited on the catalyst, after both CH_4 decomposition and CO_2reforming of CH_4, was determined by means of thermogravimetric analysis (TGA), respectively. Therates of carbon deposited on the catalyst were also investigated and the apparent kinetic equationof CO_2 reforming of CH_4: ν_c = kp^(0.72)(CH_4)·p^(-0.55)(CO_2), was established by analyzing therelation between the rates of deposited carbon and the pressure ratio of CH_4 and CO_2.展开更多
The effect of cooling rate on structure and properties of wear-resistant low chromium cast iron after 40% hot deformation was investigated by metallographic and scanning electron microscope. The results show that the ...The effect of cooling rate on structure and properties of wear-resistant low chromium cast iron after 40% hot deformation was investigated by metallographic and scanning electron microscope. The results show that the cooling rate is closely related to the structure and properties, and for the cast iron, the best comprehensive mechanical properties were obtained by forced air cooling with a cooling rate as about 7 ℃/s. The reason and regularity for the change of mechanical properties were analyzed.展开更多
The effects of the incorporated oxygen and the different buffer layers on the optical properties and surface morphology of GaN were studied. The results show that the decrease of the concentration of the incorporated ...The effects of the incorporated oxygen and the different buffer layers on the optical properties and surface morphology of GaN were studied. The results show that the decrease of the concentration of the incorporated oxygen has no effect on the surface morphology, but improves the optical properties. While the introduction of the AlN buffer layer makes not only the surface morphology but also the optical properties improve. Both the oxygen contamination from the nitrogen source and the resulted morphology are directly related to the line width of the low-temperature photoluminescence(PL) spectra.展开更多
A Raman study was carried out for LiMn 2O 4, which was synthesized via the mixture of Mn 3O 4 and LiNO 3 sintered at different temperatures. It is shown that there are two kinds of Raman spectra for LiMn 2O ...A Raman study was carried out for LiMn 2O 4, which was synthesized via the mixture of Mn 3O 4 and LiNO 3 sintered at different temperatures. It is shown that there are two kinds of Raman spectra for LiMn 2O 4 at different sintering temperatures, while the X-ray diffraction patterns of LiMn 2O 4 sintered at different temperatures are the same. Five Raman bands observed for the materials sintered below 500 ℃ are consistent with the theoretical prediction for spinel structure based on the group theory. Only two Raman bands were observed for the materials sintered at temperatures higher than 500 ℃. The best preparation condition for obtaining a good spinel LiMn 2O 4 is suggested based on the Raman study.展开更多
A series of GaN layers was grown on sapphire (0001) substrates under various growth conditions by means of the molecular beam epitaxy(MBE) method, the optical characteristics and surface morphologies of the samples we...A series of GaN layers was grown on sapphire (0001) substrates under various growth conditions by means of the molecular beam epitaxy(MBE) method, the optical characteristics and surface morphologies of the samples were studied. The results show that the line width of the GaN emission gradually decreases and the peak shifts under the Ga-rich condition by increasing the Ga-flux on keeping all other growth conditions unchanged. It has been also found that the resulted morphology is directly related to the Ga-flux.展开更多
Let G be a graph which contains exactly one simple closed curve.We prove that a continuous map f:G→G has zero topological entropy if and only if there exist at most k■[(Edg(G)+End(G)+ 3)/2]different odd numbers n_1,...Let G be a graph which contains exactly one simple closed curve.We prove that a continuous map f:G→G has zero topological entropy if and only if there exist at most k■[(Edg(G)+End(G)+ 3)/2]different odd numbers n_1,...,n_k such that Per(f)is contained in ∪_i^k=1 ∪_j~∞=0 n_i2~j,where Edg(G) is the number of edges of G and End(G)is the number of end points of G.展开更多
基金Supported by the Science and Technology Bureau of Jilin Province( No. 2 0 0 2 0 6 15 ) and the Overseas- back Scholar Pro-gram of Ministry of Personnel of China
文摘Sr2SiO4∶Eu 3+ ,Bi 3+ and SrSiO 3∶Eu 3+ ,Bi 3+ samples were synthesized at high temperature and high pressure. The effect of high pressure on the structure and luminescence properties of the samples were studied. As a comparison, the samples were also prepared by the method of sol-gel at high temperature and atmospheric pressure. The SrSiO 3∶Eu 3+ ,Bi 3+ prepared at atmosphere has a hexagonal phase structure; in the pressure range of 2 34-4 10 GPa, it is transformed into a pseudo-orthorhombic structure(monoclinic), and in the pressure range of 4 10-4 15 GPa, the structure change of Sr 2SiO 4∶Eu 3+ , Bi 3+ has not been observed, it maintains the monoclinic structure of the samples synthesized at an atmospheric pressure. High pressure makes the luminescence properties of the samples changed obviously. The intensity and the relative quantum luminescent efficiency decrease, the half-width increases obviously and the red shift occurs. The changes of the luminescence properties result from the pressure-induced changes of the crystal structures.
基金Item Sponsored by Guiding Program of Science and Technology Research of Hebei of China(94122123)
文摘The preparing method,rolling technology and mechanical properties of low chromium semi-steel grinding ball by cross rolling were studied.The results show that when the low chromium semi-steel bar is forged from55mm to50mm,cross-rolled into grinding ball at 1 000-1 050℃,air cooled and tempered at 550℃for 2h,the best mechanical properties,especially the abrasive resistance under the action of hard abrasive,can be obtained.
文摘In this paper, the properties of carbon deposited on hexaaluminateLaNiAl_(11)O_(19) catalyst were characterized by X-ray photoelectron spectroscopy (XPS), and in themeantime, the amount of carbon deposited on the catalyst, after both CH_4 decomposition and CO_2reforming of CH_4, was determined by means of thermogravimetric analysis (TGA), respectively. Therates of carbon deposited on the catalyst were also investigated and the apparent kinetic equationof CO_2 reforming of CH_4: ν_c = kp^(0.72)(CH_4)·p^(-0.55)(CO_2), was established by analyzing therelation between the rates of deposited carbon and the pressure ratio of CH_4 and CO_2.
文摘The effect of cooling rate on structure and properties of wear-resistant low chromium cast iron after 40% hot deformation was investigated by metallographic and scanning electron microscope. The results show that the cooling rate is closely related to the structure and properties, and for the cast iron, the best comprehensive mechanical properties were obtained by forced air cooling with a cooling rate as about 7 ℃/s. The reason and regularity for the change of mechanical properties were analyzed.
文摘The effects of the incorporated oxygen and the different buffer layers on the optical properties and surface morphology of GaN were studied. The results show that the decrease of the concentration of the incorporated oxygen has no effect on the surface morphology, but improves the optical properties. While the introduction of the AlN buffer layer makes not only the surface morphology but also the optical properties improve. Both the oxygen contamination from the nitrogen source and the resulted morphology are directly related to the line width of the low-temperature photoluminescence(PL) spectra.
基金SupportedbytheNational NaturalScienceFoundation of China( No.5 0 2 72 0 2 3),the Special Funds for Major State Ba-sic researchProject of China under( No.2 0 0 2 CB2 1180 2) and the Research Grant for Ph.D Programs from Ministry ofEduca-tion( No.2 0 0 10
文摘A Raman study was carried out for LiMn 2O 4, which was synthesized via the mixture of Mn 3O 4 and LiNO 3 sintered at different temperatures. It is shown that there are two kinds of Raman spectra for LiMn 2O 4 at different sintering temperatures, while the X-ray diffraction patterns of LiMn 2O 4 sintered at different temperatures are the same. Five Raman bands observed for the materials sintered below 500 ℃ are consistent with the theoretical prediction for spinel structure based on the group theory. Only two Raman bands were observed for the materials sintered at temperatures higher than 500 ℃. The best preparation condition for obtaining a good spinel LiMn 2O 4 is suggested based on the Raman study.
基金the Science and Technology Bureau of Jilin Province(No.2 0 0 2 0 6 15 ) and The Overseas- back ScholarProgram of Ministry of Personnel of China
文摘A series of GaN layers was grown on sapphire (0001) substrates under various growth conditions by means of the molecular beam epitaxy(MBE) method, the optical characteristics and surface morphologies of the samples were studied. The results show that the line width of the GaN emission gradually decreases and the peak shifts under the Ga-rich condition by increasing the Ga-flux on keeping all other growth conditions unchanged. It has been also found that the resulted morphology is directly related to the Ga-flux.
基金Project supported by NSF (10171034) of ChinaNSF (970395) of Guangdong province
文摘Let G be a graph which contains exactly one simple closed curve.We prove that a continuous map f:G→G has zero topological entropy if and only if there exist at most k■[(Edg(G)+End(G)+ 3)/2]different odd numbers n_1,...,n_k such that Per(f)is contained in ∪_i^k=1 ∪_j~∞=0 n_i2~j,where Edg(G) is the number of edges of G and End(G)is the number of end points of G.
