In graphite furnace atomic absorption spectrometry (GF-AAS), the atomization process of lead occurring in graphite atomizers with/without a platform plate was investigated when palladium was added to an iron-matrix sa...In graphite furnace atomic absorption spectrometry (GF-AAS), the atomization process of lead occurring in graphite atomizers with/without a platform plate was investigated when palladium was added to an iron-matrix sample solution containing trace amounts of lead. Absorption profiles of a lead line were meas- ured at various compositions of iron and palladium. Variations in the gas temperature were also estimated with the progress of atomization, by using a two-line method under the assumption of a Boltzmann distribu- tion. Each addition of iron and palladium increased the lead absorbance in both the atomizers, indicating that iron or palladium became an effective matrix modifier for the determination of lead. Especially, palladium played a significant role for controlling chemical species of lead at the charring stage in the platform-type atomizer, to change several chemical species to a single species and eventually to yield a dominant peak of the lead absorbance at the atomizing stage. Furthermore, the addition of palladium delayed the peak after the gas atmosphere in the atomizer was heated to a higher temperature. These phenomena would be because the temperature of the platform at the charring stage was elevated more slowly compared to that of the furnace wall, and also because a thermally-stable compound, such as a palladium-lead solid solution, was produced by their metallurgical reaction during heating of the charring stage. A platform-type atomizer with palladium as the matrix modifier is recommended for the determination of lead in GF-AAS. The optimum condition for this was obtained in a coexistence of 1.0 × 10–2 g/dm3 palladium, when the charring at 973 K and then the atomizing at 3073 K were conducted.展开更多
In this paper, the general calculation formulas of radial matrix elements for relativistic n-dimensional hydrogen atom of spin S=0 are obtained, and the recurrence relation of different power order radial matrix eleme...In this paper, the general calculation formulas of radial matrix elements for relativistic n-dimensional hydrogen atom of spin S=0 are obtained, and the recurrence relation of different power order radial matrix elements are also derived.展开更多
The effects of four types of graphite tube and five matrix modifiers on the determination of selenium by graphite furnace atomic absorption spectrometry were compared.The results show that platform thermolysis coat gr...The effects of four types of graphite tube and five matrix modifiers on the determination of selenium by graphite furnace atomic absorption spectrometry were compared.The results show that platform thermolysis coat graphite tube and magnesium nitrate and cobaltco as matrix modifer can get a high sensitivity and a good recovery.The optimized working conditions and interference in the determination were invesigated.This result is consistent with that of XRF.The recovery is from 100.8 % to102.2 %,the relative standard deviation is from 3.47% to 5.56 % (n=9),and the detection limit of selenium is 378 pg (C=44.5μg/g to 97.3μg/g.).The proposed method can be applied to the rapid determination of selenium in electrolytic manganese.展开更多
A method is described for the direct determination of iron in high purity sodium fluoride using graphite furnace atomic absorption spectrometry. Interferences caused by the matrix are investigated. It is shown that th...A method is described for the direct determination of iron in high purity sodium fluoride using graphite furnace atomic absorption spectrometry. Interferences caused by the matrix are investigated. It is shown that the ashing temperature can be increased to 1 400°C and matrix interferences eliminated, the sensitivity of iron increased in 1. 27 fold by the addition of nickel nitrate. The method is applied to the determination of iron in sodium fluoride and satisfactory results are obtained.展开更多
Atomic oxygen （AO） is considered the most erosive particle to spacecraft materials in low earth orbit （LEO）. Carbon fiber, car-bon/carbon （C/C）, and some modified C/C composites were exposed to a simulated AO en...Atomic oxygen （AO） is considered the most erosive particle to spacecraft materials in low earth orbit （LEO）. Carbon fiber, car-bon/carbon （C/C）, and some modified C/C composites were exposed to a simulated AO environment to investigate their behaviors in LEO. Scanning electron microscopy （SEM）, AO erosion rate calculation, and mechanical property testing were used to characterize the material properties. Results show that the carbon fiber and C/C specimens undergo significant degradation under the AO bombing. According to the effects of AO on C/C-SiC and CVD-SiC-coated C/C, a condensed CVD-SiC coat is a feasible approach to protect C/C composites from AO degradation.展开更多
Temperature-dependent Embedded-Atom-Method (EAM) functions of hcp titanium have been determined by fitting to the lattice constants and elastic constants, measured at various temperatures as well as by considering the...Temperature-dependent Embedded-Atom-Method (EAM) functions of hcp titanium have been determined by fitting to the lattice constants and elastic constants, measured at various temperatures as well as by considering the universal Rose's relation. The EAM functions thus obtained satisfy the stable structure requirement and Cauchy discrepancy. The results show that the EAM functions do have temperature-dependence, and in the meanwhile it also provides EAM functions of titanium for the study of Ti-based metallic materials at various temperatures. (Author abstract) 16 Refs.展开更多
文摘In graphite furnace atomic absorption spectrometry (GF-AAS), the atomization process of lead occurring in graphite atomizers with/without a platform plate was investigated when palladium was added to an iron-matrix sample solution containing trace amounts of lead. Absorption profiles of a lead line were meas- ured at various compositions of iron and palladium. Variations in the gas temperature were also estimated with the progress of atomization, by using a two-line method under the assumption of a Boltzmann distribu- tion. Each addition of iron and palladium increased the lead absorbance in both the atomizers, indicating that iron or palladium became an effective matrix modifier for the determination of lead. Especially, palladium played a significant role for controlling chemical species of lead at the charring stage in the platform-type atomizer, to change several chemical species to a single species and eventually to yield a dominant peak of the lead absorbance at the atomizing stage. Furthermore, the addition of palladium delayed the peak after the gas atmosphere in the atomizer was heated to a higher temperature. These phenomena would be because the temperature of the platform at the charring stage was elevated more slowly compared to that of the furnace wall, and also because a thermally-stable compound, such as a palladium-lead solid solution, was produced by their metallurgical reaction during heating of the charring stage. A platform-type atomizer with palladium as the matrix modifier is recommended for the determination of lead in GF-AAS. The optimum condition for this was obtained in a coexistence of 1.0 × 10–2 g/dm3 palladium, when the charring at 973 K and then the atomizing at 3073 K were conducted.
文摘In this paper, the general calculation formulas of radial matrix elements for relativistic n-dimensional hydrogen atom of spin S=0 are obtained, and the recurrence relation of different power order radial matrix elements are also derived.
文摘The effects of four types of graphite tube and five matrix modifiers on the determination of selenium by graphite furnace atomic absorption spectrometry were compared.The results show that platform thermolysis coat graphite tube and magnesium nitrate and cobaltco as matrix modifer can get a high sensitivity and a good recovery.The optimized working conditions and interference in the determination were invesigated.This result is consistent with that of XRF.The recovery is from 100.8 % to102.2 %,the relative standard deviation is from 3.47% to 5.56 % (n=9),and the detection limit of selenium is 378 pg (C=44.5μg/g to 97.3μg/g.).The proposed method can be applied to the rapid determination of selenium in electrolytic manganese.
文摘A method is described for the direct determination of iron in high purity sodium fluoride using graphite furnace atomic absorption spectrometry. Interferences caused by the matrix are investigated. It is shown that the ashing temperature can be increased to 1 400°C and matrix interferences eliminated, the sensitivity of iron increased in 1. 27 fold by the addition of nickel nitrate. The method is applied to the determination of iron in sodium fluoride and satisfactory results are obtained.
基金financially supported by the Major International(Regional)Joint Research Project under the National Natural Science Foundation of China(No.50820145202)the Major State Basic Research Development Program of China(No.2011CB605806)
文摘Atomic oxygen （AO） is considered the most erosive particle to spacecraft materials in low earth orbit （LEO）. Carbon fiber, car-bon/carbon （C/C）, and some modified C/C composites were exposed to a simulated AO environment to investigate their behaviors in LEO. Scanning electron microscopy （SEM）, AO erosion rate calculation, and mechanical property testing were used to characterize the material properties. Results show that the carbon fiber and C/C specimens undergo significant degradation under the AO bombing. According to the effects of AO on C/C-SiC and CVD-SiC-coated C/C, a condensed CVD-SiC coat is a feasible approach to protect C/C composites from AO degradation.
文摘Temperature-dependent Embedded-Atom-Method (EAM) functions of hcp titanium have been determined by fitting to the lattice constants and elastic constants, measured at various temperatures as well as by considering the universal Rose's relation. The EAM functions thus obtained satisfy the stable structure requirement and Cauchy discrepancy. The results show that the EAM functions do have temperature-dependence, and in the meanwhile it also provides EAM functions of titanium for the study of Ti-based metallic materials at various temperatures. (Author abstract) 16 Refs.
