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1.
Non-destructive 14-MeV neutron activation analysis for silicon in steel has been applied with 56Mn as internal standard.56Mn is formed from the iron matrix via the 56Fe(n,p)56Mn reaction. Several methods of internal standardisation via56Mn are discussed. The 0.84-MeV photopeak of 56Mn is recommended if steel samples of about the same composition are to be analysed. Chemically analysed steel samples are used as silicon standards. A precision of 0.7% was obtained for an analysis plus standardisation time of 13 min. Special attention was paid to interferences produced by concentration changes of impurity elements. Several possible sources of errors were investigated. 相似文献
2.
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
3.
A rapid, nondestructive method for the determination of silicon in steels has been developed based on the measurement of the 1.77-MeV γ-line emitted by the proton inelastic scattering reaction 28Si(p,p')28Si For some of the determinations the 0.84-MeV γ-line from the reaction 56Fe(p,p')56Fe was used as internal standard. 相似文献
4.
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
5.
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
6.
R. J. Batra R. B. Lanjewar A. N. Garg 《Journal of Radioanalytical and Nuclear Chemistry》1986,104(2):115-125
Fast neutron-activation methods have been developed for the determination of iron and silicon in USGS and Indian standards and bauxites. Nuclear reactions56Fe/n, p/56Mn and28Si/n, p/28Al were carried out using241Am-Be neutron source and cutting off thermal neutrons with a Cd shield. For Si a cyclic method was adopted due to short half life of28Al /2.3 min/. The methods are non destructive, fast, economic and ideal for bulk analysis of rocks and process control.A part of this work was presented at the International Symposium on Nuclear Analytical Chemistry, Slowpoke Reactor Facility, Dalhousie University, Canada, June 5–7, 1985. 相似文献
7.
A method for the determination of oxygen based on the reaction16O(n, p)16N is suggested. The samples are irradiated in stainless steel capsules with fast neutrons. The total neutron flux passing
through the sample is proportional to the flux passing through the wall of the capsule. Therefore, the activity induced in
the capsule according to the reaction56Fe(n, p)56Mn can be used to monitor the neutron flux through the sample. Thus, the necessity of maintaining the sample in an exact position
during the irradiation is eliminated. 相似文献
8.
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
9.
S. A. Jonah M. O. A. Oladipo I. M. Umar N. Rabiu Y. U. Idris I. Y. Zakari 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(2):501-504
An irradiation procedure with fast and thermal neutrons from a 5 Ci Am-Be isotopic neutron source irradiation facility in
combination with a 3'3' NaI(Tl) detector system has been used to determine Al/Si weight ratios in alumino-silicates. Samples
were irradiated with and without Cd cover for 10 minutes and counted for 10 minutes after a waiting time of 1 minute. The
peak area analysis of the 1779 keV gamma-ray line of 28Al product radionuclide produced via 27Al(n,γ)28Al and 28Si(n,p)28Al reactions in combination with the neutron flux parameter at the irradiation site and nuclear data were used to determine
Al/Si ratios. Due to discrepancy in literature data, Am-Be neutron source spectrum averaged cross sections of (n,p) reactions
on 27Al, 28Si and 56Fe were determined by the activation technique using 115In(n,n')115mIn as the fast neutron flux monitor reaction. The method was tested using mixtures of high-purity Al2O3 and SiO2 with known weight ratios of Al/Si and validated by a certified reference material BCS-CRM 348 (Ball Clay). Results are presented
for bentonite, kaolin, bauxite, feldspar and ball clay samples from Nigeria. The method is non-destructive, rapid and suitable
for use in-situ for large-scale exploration works and industrial process control.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
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
11.
An instrumental neutron activation method for V, Mn and W in alloy steels with a 241 Am/Be isotopic neutron source is described. The samples were irradiated to induce the nuclear reactions 51V(n, γ) 52V, 55Mn(n, γ)56Mn, and 186W(n, γ)187W. The activities were measured with a NaI(TI) detector. Interferences on the measured photopeaks were shown to be negligible by measuring the half-lives of 62V, 56Mn and 187W.These thre elementes were determined in the range 1.5–12.9% in special steels; manganese in the range 0.5–1.6% was measured in cast irons. Calibration was done by comparison with results from wet chemistry and x-ray fluorescence spectrometry. The processing times for the vanadium, manganese and tungsten determinations were 11 min, 3 h and 26.3 h, respectively, but these were reduced greatly by intoruding a scheme wherein six samples were simultaneously irradiated and the 56Mn and 187W nuclides were measured sequentially for a series of 66 samples. The average processing time was reduced to 45 min for tungsten with a precision of 4.0% and accuracy of 3.4% and 22.8 min for manganese with a precision of 3.8% and accuracy of 3.1%. 相似文献
12.
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
13.
The fast neutron activation technique was applied to bulk samples (≈11 kg) of Australian black coal. The determination of alumina is based on the reaction 27Al(n,p)-27Mg by counting the 0.844-MeV peak (t = 9.4 min). Silica is determined by means of the reaction 28Si(n,p)28Al; the 1.78-MeV peak (t = 2.3 min) is counted and a correction for the interference from alumina is applied. The ash content is based on the correlation between ash and the sum of alumina and silica. The accuracies (1 SD) for the determination of alumina, silica and ash were 0.52% Al2O3, 0.79% SiO2 and 1.02% ash, respectively. The ash, alumina and silica contents of the samples were in the ranges 8.8–37.5%, 1.3–10.3% and 6.4–22%, respectively. 相似文献
14.
The paper describes an automatic equipment which allows to determine the silicon content of coal by neutron activation analysis. The technique is based on the measurement of gamma-ray intensity of the28Al radionuclide, which is the result of the fast neutron reaction28Si(n, p)28 Al. The Activation part includes a Pu-238/Be neutron source which is located in the middle of the sample container; the measuring part includes two NaI(Tl)-scintillation counters. The total time of the anlysis of one sample amounts to a few minutes; the standard deviation of a single determination is 0.2% SiO2. 相似文献
15.
The silicon content in an aluminum-silicon alloy was measured by nondestructive fast neutron activation analysis with fission spectrum neutrons. A boron nitride irradiation container reduced the flux of thermal and epithermal neutrons at the sample position, enhancing the29Si (n, p)29Al reaction. A detection limit of 0.4% silicon in a 0.5 g alloy sample was obtained. 相似文献
16.
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
17.
A method has been developed for determining silicon in aluminium by fast neutron activation. It is based on the separation
of two gamma lines by a Ge(Li) detector: the 1.73 MeV line from the product of27Al(n, α)24Na and the 1.78 MeV line from the28Si(n, p)28Al reaction. In the case of aluminium-silicon alloys 100 μg silicon can be determined, with an error of 10% in an aluminium
sample of 1 g.
This work was supported in part by the International Atomic Energy Agency. 相似文献
18.
Activation with fast neutrons from a Pu/Be source enables the 28Si(n, p)28 Al and 27Al(n p)27Mg reactions to be utilized. Seventy-two samples of pit coals with ash contents ranging from 3 to 40% were measured. The calibration function between ash content and both 1.78- and 0.84-MeV γ-ray counts was linear. The standard deviation was 0.9% for a 17% ash content and 1.4% over the whole range of ash contents. Comparison with other methods is discussed. 相似文献
19.
The determination of silicon via the 28Si(n,p)28 Al reaction by means of 14-MeV neutrons is applied to the analysis of pollution and natural aerosols. A Whatman 41 filter (40 cm2) on which airborne particulate material has been collected is compressed into a 3 × 12.7 mm pellet. Standards are prepared in the same way from clean filters spiked with a silicate solution. After a 50-s irradiation and a 75-s decay time, the sample is counted for 2 min with 5” × 5” NaI(Tl) well detector. The 1.779-MeV photopeak of 28Al is measured with a single channel sealer chain or with a multichannel analyser. The reproducibility, sensitivity and liability to interference from other elements were investigated for both counting systems. The homogeneity of the pellets and the filters was checked. The overall precision of one single-channel determination was estimated to be 3.5% after a 24-h high-volume sampling time. Samples collected in urban, industrial and remote areas with concentrations ranging from 0.05 to 15 μg Si m-3 air were analysed and the results are discussed. 相似文献
20.
To study the nature of ancient and modern pottery it is necessary to be able to determine the concentrations of the major
constituent elements. For such studies, mass balances calculated from these elemental concentrations cluster around 100% for
a silicate-silica matrix and around 80–90% in highly calcarious pottery which has a silicate-carbonate (silica) matrix. This
work requires experimental measurements with coefficients of variation wihtin approximately ±5%. The high concentrations of
silicon in pottery may reasonably be determined by neutron activation analysis using the nuclear reaction29Si(n, p)29 Al. Aluminium-29 has a half life of 6.56 minutes and a γ-ray energy of 1272 keV. Epithermal neutron irradiations of samples
in cadmium foil are required to minimize the quantities of thermal neutron induced radionuclides. The method of analysis developed
for the low flux SLOWPOKE reactor is described and the accuracy and precision of the technique is discussed by allusion to
analyses of standard reference materials. The application of this technique to two different archaeological problems is addressed.
The first is a case of carbonate dilution found in neolithic pottery from Iran and the second case is a problem of silica
dilution in Roman pottery from Germany. 相似文献