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1.
Silicon as silicon dioxide in iron and steel-making slags and fluorspars was analyzed by 14 MeV neutron activation high-resolution
γ-ray spectrometry. Silicon was detected by measuring the 1.78 MeV γ-ray of28Al, the product of the28Si(n, p) reaction, using a 30 cm3 coaxial Ge(Li) detector. A modified TPA method was used for the calculation.28Al is also produced from phosphorus by the31P(n,α) reaction, and from aluminium by the27Al(n,γ) reaction. The contribution from the former reaction could be corrected experimentally when the P2O5 content of the sample was known, while the latter reaction could be neglected in this neutron energy region. The experimental
correction coefficient for phosphorus agreed well with the theoretical value calculated from the nuclear properties of silicon
and phosphorus. Yields of28Al from SiO2, P2O5 and Al2O3 of the same weight percentages were calculated as 1, 0.426 (experimentally 0.44) and 0.0022, respectively. The results of
this method agreed well with the results of the usual chemical methods. The limit of detection of SiO2 in iron and steel-making slags and fluorspars was calculated as 0.07%. The coefficient of variation of repeated experiments
was compared with the statistical one. 相似文献
2.
Silicon in cast iron was analyzed by 14 MeV neutron activation—high-resolution γ-ray spectrometry. Silicon was detected as28Al, the product of the28Si(n, p)28Al reaction. Interference of56Mn was separated using a Ge(Li) detector and a biased amplifying system. The 1. 81 MeV gamma-radiation of56Mn, which is the product of the56Fe(n, p)56Mn reaction of the matrix of cast iron, was used as an internal standard and for correction of the self-absorption of the
1. 78 MeV gamma-radiation of28Al by the sample. The interferences of aluminum, phosphorus and manganese could be neglected according to the results calculated
from their nuclear properties and contents in the cast iron of this experiment.
The results of this method agreed well with the results of the usual chemical method, with errors less than 5% of the results,
and the precision of the method was satisfactory with a C. V. of less than almost 6% for rapid analysis of silicon in cast
iron. The analytical line through the origin with a slope of the mean value of the repetition experiments could be used as
the analytical line with almost the same precision and accuracy of the results as for the analytical line calculated by the
least squares method. 相似文献
3.
V. Cercasov 《Journal of Radioanalytical and Nuclear Chemistry》1979,52(2):399-410
The 14 MeV neutron activation facility of the Hohenheim University is described and the calculated determination limits for
20 elements are presented. The determination of aluminium via the27Al(n, p)27Mg reaction and of silicon by the28Si(n, p)28Al reaction is applied to the analysis of atmospheric aerosols. A running program for routine analyses was elaborated. The
method was checked with the aid of an intercomparison sample. 相似文献
4.
R. Van Grieken A. Speecke J. Hoste 《Journal of Radioanalytical and Nuclear Chemistry》1970,6(2):385-398
A fast (10 min), non-destructive simultaneous determination of silicon and phosphorus in cast iron and steel by 14 MeV neutron
activation was developed. The 1.78 MeV28Al activity (T=2.24 min) induced by the reaction28Si(n, p)28Al is counted on a NaI(Tl) detector. Two measurements are made to correct for the 1.81 MeV56Mn activity (T=2.58 hr) from the iron matrix. However,28Al is also produced via31P(n, α)28Al. By (n, 2n) reaction, phosphorus yields also30P (T=2.6 min), the 0.511 MeV annihilation radiation of which is counted by two opposite NaI(Tl) detectors in coincidence.
Again, two successive coincidence measurements are carried out in order to take into account the53Fe activity (β+; T=8.9 min) from54Fe(n, 2n)53Fe. The28Al measurement is appropriately corrected via the computed phosphorus content. An oxygen flux monitor was used to normalize
to the same flux. Nuclear interferences have been examined. Special attention has been paid to the presence of copper. The
standard deviation for phosphorus being as high as ca. 0.09% P for a single determination, this technique can only be practical
as an independent phosphorus analysis for high phosphorus cast irons. The precision on the28Al measurement is 5% relative for 0.2% Si and 2.5% above 1% Si.
Aspirant of the N.F.W.O. 相似文献
5.
J. D. Jones P. B. Kaufman W. L. Rigot 《Journal of Radioanalytical and Nuclear Chemistry》1979,50(1-2):261-275
Silicon has been found to be an essential element for the growth and development of many ecomomically important plants such
as sugarcane, rice, oats, and wheat. A method is described for the quantitative determination of silicon in plant samples.
Measurements were made with two Ge(Li) detectors matched with a multiplexing unit to provide a single amplified signal to
a computerized analyzer system. For those materials containing greater than 0.5 weight percent silicon, the reaction29Si(n, p)29Al (1273 keV) provides a direct measurement of the quantity of silicon provided the irradiation is done in a special boron
nitride capsule to reduce interferences from thermal neutron reactions and a correction is made for the single escape line
from28Al (1268 keV). For lesser quantities of silicon, a technique which utilizes the fast neutron reaction28Si(n, p)28Al is preferred. Corrections for the interference produced by the presence of phosphorus31P(n, α)28Al are made by determining the phosphorus content following the instrumental analysis using a unique application of neutron
activation analysis, i. e., measurement of tungsten in tungstomolybdophosphoric acid produced when molybdate and tungstate
ions are added to dissolved samples of the plant material containing phosphorus. Aluminum, which may also produce an interference
by thermal neutron reaction27Al(n, γ)28Al, is determined directly from the original activation data after subtracting out the effect of the phosphorus. Thus, three
irradiations in the pneumatic sample irradiator are necessary; one short irradiation (1 min) without thermal neutron shielding,
a longer irradiation (6 min) in the boron capsule, and a final irradiation of the tungstomolybdophosphoric acid provide all
data required to accurately determine silicon in plant materials. A computer program has been developed that provides rapid
reduction of the data in final report format. Elements such as sodium, chlorine, calcium, manganese, potassium, and magnesium
extrinsic to the analysis for silicon are also determined by this method. The method has been tested on a large number of
samples and reliable results are obtained with less than 0.2 g of sample.
This work was supported by Grant 533 from the Michigan Memorial—Phoenix Project. 相似文献
6.
I. E. Stamatelatos K. Katopodis Y. Bersos J. A. Kalef-Ezra G. Lefkopoulos K. Siamopoulos 《Journal of Radioanalytical and Nuclear Chemistry》1999,241(3):483-486
Serum aluminum levels were determined by instrumental neutron activation analysis in 31 patients undergoing long-term haemodialysis.
Aluminum-28 1.778 MeV (T
1/2=2.24 min) γ-rays produced by the thermal neutron reaction27Al(n,γ)28Al were detected. Successive irradiation of the samples at epithermal neutron fluence was performed to correct for the interference
from the fast neutron reaction31P(n,α)28Al. Serum aluminum level in this group of subjects was adequately represented by a lognormal distribution with a mean and
variance of 16.5 μg/l and 16.8 μg/l, respectively. The results obtained were found to be in agreement with serum aluminum
determination performed by electrothermal atomic absorption spectrophotometry (r
2=0.97). Instrumental neutron activation can provide a rapid technique to routinely monitor long-term haemodialysis patients
in order to identify individuals at greater risk to develop aluminum toxicity. 相似文献
7.
E. Santner 《Journal of Radioanalytical and Nuclear Chemistry》1971,7(2):271-280
Three experimentally different methods for analysing silicon in steel by activation with fast neutrons are described. By bombardment of28Si with fast neutrons28Al is obtained after a (n, p) reaction.28Al emits a γ-radiation of 1.78 MeV. The difficulty lies in discriminating the 1.78 MeV peak out of the emitted radiation. The first method consists in determining the ratio of the 1.8 MeV peak to the 2.1 MeV peak of an activated iron sample. From this ratio one can deduct the contribution of28Al to the 1.8 MeV peak of a silicon containing sample. The other method of separation makes use of the different half-lives of the 1.78 MeV γ-rays from28Al and the 1.81 MeV γ-rays from56Mn. The direct separation of the peaks with a Ge(Li) detector is the third method. This paper illustrates the possibilities of activation analysis with fast neutrons. For this reason the values measured are compared with the results of chemical analyses. 相似文献
8.
Conclusion Dans une première partie, l’étude des réactions engendrées par les neutrons rapides de pile sur douze éléments a montré que
certaines de celles-ci pouvaient être utilisées pour un dosage quantitatif.
Dans une seconde partie, nous proposons un dosage radiochimique du silicium par la réaction28Si(n, p)28Al qui a, dans nos conditions de travail, sa limite de détermination à 620 μg. A titre de comparaison, signalons que cette
limite se situe par irradiation avec des neutrons de 14 MeV, produits au moyen d’un accélérateur (flux de 5·108 n·cm−2·sec−1), à environ 10 μg.
Le dosage non destructif du silicium dans le diméthylpolysilane est décrit.
In the first part, the fast-neutron flux available in reactor cores was utilized to define experimentally the sensitivity for the determination of 12 different elements, based on fast-neutron nuclear reactions. The fluxes available with our AGN-201 P reactor are in the range of 109–1010 n·cm−2·sec−1 in the 1–4 MeV region. A good sensitivity was obtained for27Al,52Cr,56Fe,28Si,23Na [by (n, p) reaction],27Al,31P,89Y [by (n, α) reaction] and197Au,183W,89Y [by (n, n′) reaction]; the elements Cl, Ca, Pb failed to give reactions. In the second part, a non-destructive method for the determination of silicium based on the reaction28Si(n, p)28Al is proposed. The limit of determination is about 0.6 mg for a neutron flux of 109 n·cm−2·sec−1. As an example, Si in dimethylpolysilane was determined.相似文献
9.
Kathryn R. Williams 《Journal of Radioanalytical and Nuclear Chemistry》1996,212(5):361-371
A new method for the determination of aluminum and silicon has been developed for zeolite catalysts. In contrast to previous methods, thermal neutrons are used for the analysis of both elements, and cadmium absorbers are not needed. The silicon determination utilizes a one-hour irradiation to observe the31Si produced by the (n, ) reaction of30Si. A 15-second irradiation is used for the27Al(n, )28Al reaction. The28Al activity is corrected for the contribution from the28Si(n,p)28Al reaction by using the analyzed weight of silicon in the sample and the data for a silicon standard irradiated simultaneously with the zeolite and the aluminum standard. The quantitation limits are 0.012 g for silicon and 3.3×10–5 g for aluminum. Sodium presents a significant interference, but this element can be removed by taking advantage of the ion exchange properties of these materials. 相似文献
10.
A fast (2–5 min) non-destructive determination of silicon in steel by 14-MeV neutron activation is described. The 1.78-MeV 28Al activity, induced by the reaction 28Si(n,p)28Al, is counted on a NaI(Tl) detector. An oxygen flux monitor is used to normalise to the same neutron flux.Two methods are described to correct for the 56Mn activity (2.58 h), induced into the iron matrix via 56Fe(n,p)56Mn. Nuclear interferences of phosphorus and aluminium have been examined. Special attention has been paid to stainless steels. A sensitivity of 0.02 to 0.05% of silicon is obtained. The precision is 2 to 3% for steels containing above 1% silicon, and 7% for 0.1% of silicon. 相似文献
11.
C. Friedli M. Rousseau P. Lerch 《Journal of Radioanalytical and Nuclear Chemistry》1981,64(1-2):239-247
In order to determine traces of boron, silicon and sulfur, B(18O, x)27Mg, Si(18O, x)43Sc and S(18O, x)47V reactions have been investigated between 15 and 44MeV. At 34 MeV, only a few of the systematically identified nuclear interferences
produce27Mg and the detection limit is 30ng boron for a 10 minute irradiation with a 0.3μA·cm−2 oxygen-18 beam. Silicon analysis has shown nuclear interferences from Al, P and K; interference-free detection limit is 80
ng silicon for an hour irradiation with a 0.4 μA·cm−2 beam at 39 MeV. There is no nuclear interference for the sulfur determination and the detection limit is 5 ng sulfur for
a 30 minutes irradiation with a 0.5 μA·cm−2 beam at 39 MeV. Thus a selective and sensitive sulfur determination can be achieved. 相似文献
12.
B. Wierczinski J. Alstad K. Eberhardt J. V. Kratz R. Malmbeck M. Mendel A. Nähler J. P. Omtvedt G. Skarnemark N. Trautmann N. Wiehl 《Journal of Radioanalytical and Nuclear Chemistry》1998,238(1-2):193-197
The nucleus23Na has been investigated by studying the primary γ-rays emitted from 53 keV neutron capture in it using a high resolution
and high efficiency (100%) HPGe detector and NaI(T1) detector for anti-Compton. 24 primary γ-rays were placed in the24Na, in which 3 primary γ-rays were new ones from a (n, γ) reaction, and reported for the first time. In order to obtain an
exact energy calibration within 7 MeV,56Fe(n,γ)57Fe reaction was used at thermal neutron energy. Intensity calibration was obtained from the27Al(p,γ)28Si reaction atE
p=2046 keV. The neutron binding energy of24Na was determined to be 6959.75 keV. 相似文献
13.
Chromium and silicon are determined simultaneously in steel by 14-MeV neutron activation analysis. The activities of 52V(Eγ=1.43 MeV,T=3.76 min) from 52Cr(n,p)52V and 28Al (Eγ=1.78 MeV; T=2.24 min) from 28Si(n,p)28Al are evaluated by mixed γ-ray spectrometry. The influence of manganese and phosphorus, the main interfering elements, is negligible for most stainless steels. The count rate should be limited, to avoid 52V pulse pile-up effects interfering in the 28Al energy region. Precisions in the 2-10% range are reached, depending on the concentrations, for a 10-min analysis time. Results for a series of steel samples are compared with industrial analyses. 相似文献
14.
R. Vlastou C. T. Papadopoulos M. Kokkoris G. Perdikakis S. Galanopoulos M. Serris A. Lagoyannis S. Harissopulos 《Journal of Radioanalytical and Nuclear Chemistry》2007,272(2):219-222
The neutron facility at the 5.5 MV tandem T11/25 Accelerator of NCSR “Demokritos” can deliver monoenergetic neutron beams
in the energy range from thermal to 450 keV, 4–11.5 MeV and 16–20.5 MeV via the 7Li(p,n), 2H(d,n) and 3H(d,n) reactions, respectively. The flux variation of the neutron beam is monitored by using a BF3 counter and a liquid scintillator BC501A detector. The 232Th(n,2n)231Th and 241Am(n,2n)240Am as well as (n,2n), (n,p) and (n,α) reactions on natural Ge and Hf isotopes, have been investigated from threshold up to
11.5 MeV, by using the activation method. The cross section values have been determined relative to the 197Au(n,2n)196Au, 27Al(n,α)24Na and 93Nb(n,2n) reference reaction cross sections. 相似文献
15.
P. Holmberg M. Hyvönen M. Tarvainen 《Journal of Radioanalytical and Nuclear Chemistry》1978,42(1):169-175
Samples of compact bone, bone marrow and spongiosa of cow femur have been irradiated in vitro with 14 MeV neutrons. The Ca/P
ratio for compact bone was found to be 2.16±0.24. The suitability of using 14 MeV neutrons and the31P(n, α)28Al reaction for studying the bone mineral composition in vitro is discussed. 相似文献
16.
R. Weinreich S. M. Qaim H. Michael G. Stöcklin 《Journal of Radioanalytical and Nuclear Chemistry》1976,30(1):53-66
The advantages of high energy cyclotrons as compared to small compact cyclotrons for the production of special radionuclides
are outlined. The routine production of123I (T=13.3 h) and28Mg (T=21.1 h) by means of high energy nuclear reactions at the Jülich Isochronous Cyclotron is described. The reaction127I(d,6n)123
123I at 78 to 64 MeV is used for the production of123I with thick target yields of 8 mCi/μAh and high radionuclidic purity. The practical experience in the application of this
process, which is well suited for the production of Na123I and for123Xe-exposure labelling techniques, is reported.28Mg is produced by the27Al(α, 3p)28Mg reaction at Eα=140 to 30 MeV with thick target yields of 40 μCi/μAh. The carrier-free28Mg is separated from the matrix activities by coprecipitation and anion exchange with chemical yields of 80%. 相似文献
17.
A method is described for the determination of sodium and phosphorus using the NG-160 neutron generator and an automated pneumatic
transport device. The reactions23Na (n, p)23Ne and31P(n, α)28 Al are utilized for the determination of sodium and phosphorus, respectively. For the determination of sodium, hermetically
sealed vials are indispensable. The time required for one determination is 6 to 8 min. A rapid method for the determination
of macro-amounts of sodium against a phosphorus background is also described, leading to the general conclusion that isotopes
with γ-quantum energies close to 0.51 MeV can be determined against a background of positron radiation sources in a well-type
crystal. 相似文献
18.
A. Kacperek C. J. Evans J. Dutton W. D. Morgan A. Sivyer 《Journal of Radioanalytical and Nuclear Chemistry》1987,114(1):165-172
Neutron activation analysis, using inelastic scattering, provides a quantitative, non-invasive technique of studying silica burdens and is potentially useful as a screening procedure for occupationally exposed workers. In this method, silicon is measured using the fast neutron inelastic scattering reaction28Si(n,n )28Si which emits 1779 keV -rays. The method requires a source of fast neutrons (> 2MeV). A 2MV Van de Graaff generator has been developed to produce a pulsed beam of 5.2 MeV neutrons. The pulsed beam has the advantage of improving measurement sensitivity by separating in Bone the inelastic scattering -rays from those due to thermal-neutron capture reactions. The incident neutron energy was chosen to maximise the silicon -ray count rate, while keeping the signal from the competing reaction31P(n,)28Al negligible. 相似文献
19.
A non-destructive method has been developed for the determination of silicon in steel alloys by reactor fast neutron activation analysis using the 29Si(n,p) 29Al reaction. An iron sample and a comparator of pure metallic silicon powder are irradiated in a cadmium case. In order to obtain the net counting rate of the 1273.4 keV peak from 29Al, background activities are corrected carefully to avoid peaks of 1268.0 keV from 28Al single-escape and 1266.2 keV from 31Si. The present method is superior to the method using the 28Si(n,p) 28Al reaction. 相似文献
20.
H. V. Kazemi J. S. Morris S. H. Anderson C. J. Gantzer G. A. Buyanovsky 《Journal of Radioanalytical and Nuclear Chemistry》1998,235(1-2):249-254
In soil science (ca. 1970), bromide ion (Br−) in various forms (e.g., KBr, NaBr, SrBr2) was introduced as a non-reactive stable tracer in solute transport studies normally moving freely with the flux of water
without substantial chemical or physical interactions with the soil. Typically, Br− is extracted from soil and quantified using either a bromide selective electrode (sensitivity is ≈10μg/ml) or by high-performance
liquid chromatography (sensitivity is ≈0.010 μg/ml). Where the sensitivity is adequate, the selective conductivity method,
which is simple, affordable and fast, is preferred. More recently (ca. 1990), workers have reported that 20% of Br− tracers, at low groundwater pH, may be adsorbed by iron oxides and kaolinite when present in the alluvial aquifer. We investigated
the use of Epithermal Neutron Activation Analysis (ENAA) as a means of measuring Br− directly in soil samples without an extraction. ENAA was chosen because of its high theoretical advantage factor over aluminum
(i.e. ≈20), the principal interfering soil constituent, calculated for the79Br(n,γ)80Br reaction compared to27Al(n, γ)28Al. Br− was measured (sensitivity is ≈0.050 μg/g) in one gram soil samples from a 5 s irradiation (φepi=2.5·1012 n·cm-2·s-1) using a BN capsule. 相似文献