Determinations de traces dans les semi-conducteurs par activation neutronique

Résumé On décrit la détermination de traces dans le germanium, le silicium et le sélénium. En appliquant des techniques gamma spectrométriques, précédées ou non de séparations chimiques il est possible de doser les éléments suivants dans (1) germanium: As, Cu, Au, Ga, Zn, Hg, Cr, Sn, Sb, Co, In, Ni, Ir, Se, Sc, Ag, Ta, Hf et U; (2) silicium: P, Au, Sb, Ga, Fe, K, Cr, Mo, Sn, As, Co, In, Zn, Cu, W, Ta, Na, Eu, Sm, La, Sc et T1; (3) sélénium: Cl, Br, I, P, S, Te, Na, K, Cr, Fe, Co, Cu, Zn, Ga, Sc, Ag, Cd, La, W, Au et Tl. Les concentrations et ou limites de détections varient de quelques parties par million à 10⁻³ parties par milliard.     

Substoichiometric and non-destructive determination of trace impurities in high-purity optical glasses by neutron activation analysis

A method of radioactivation analysis has been developed for the determination of 17 elements as impurities in high-purity optical glasses. The substoichiometric extraction of platinum with dithizone was studied and a simple procedure was proposed for the determination of platinum. Copper and manganese were also determined substoichiometrically by the extractions with dithizone and with thenoyltrifluoracetone, respectively. The non-destructive γ-ray spectrometry using a Ge(Li) detector has been applied for the determination of the other 14 elements (Ag, Co, Cr, Eu, Fe, Ir, Sc, Zn, Cs, Hf, Rb, Sb, Ta and Tb). Impurity elements at the ppb level were analysed by the proposed method and it is shown that the method is reliable for the determination of trace impurities in high-purity optical glasses.     

Considerations about the226Ra gross alpha counting determination

Chemical elemental compositions of some silicate, magnetic and glass spherules were investigated with INAA. The elements determined include Os, Ir, Ni, Co, Fe, Cr, Au, La, Ce, Sm, Eu, Yb, Lu and Sc etc. The elemental correlation, as well as their enrichment (or depletion) factors relative to Cl chondrite were examined. The high concentrations of the refractory siderophile elements contained in these spherules support the proposal that they originate from extraterrestrial substances. Some useful chemical criteria for identifying the sources of silicate, magnetic and glass spherules are put forward.     

Instrumental neutron activation analysis of a sulfide ore and some ore benefication products

Samples of a pyritic lead-zinc ore and some benefication products were examined by instrumental activation analysis using Ge(Li) gamma-spectrometry. The following elements were determined using thermal neutron activation: Sc, Cr, Co, Zn, As, Se, Ag, Sb, Ir, Au and Th. The technique is especially favourable for the determination of cobalt, arsenic, antimony and gold, but selenium, silver and thorium can also be determined in most fractions. Activation with epithermal neutrons will improve conditions for the determination of As, Sb, Se, Ag, Au and Th.     

Detection limits in epithermal neutron activation analysis of geological material

The improvement of detection limits for trace elements in geological samples by epithermal neutron activation analysis is examined. The relative merits of cadmium, boron and composite cadmium+boron filters are compared for trace elements Ni, As, Pd, Cd, Sb, W, Ir, Pt and Au, and interfering elements Na, K, Sc, Cr, Fe, Co and Cu. A boron filter gives optimum sensitivity for the trace elements based on interference from⁴⁶Sc, but the detection limits are only improved 2–5 times. Ma imum possible improvement, which is shown by Ni, gives sensitivities 5 times better under cadmium and 15 times under boron.     

Expert system for nuclide identification and interpretation of gamma-spectrum analysis

Trace element data (Sc, Cr, Co, Hf, Ta and Th) are reported for a weathering profile of gabbroic rocks located near Serpa, Portugal. The results obtained for the whole rock samples showed that: (i) Co and Sc contents decrease upwards the profile. Co appears to be mobilized in the soil probably as soluble cation; (ii) Cr tends to remain in the profile; and (iii) Hf and Th concentrate in the upper horizons. Trace element distribution in different size fractions of the upper horizons revealed: (i) Sc, Cr and Co have a more uniform distribution than Hf, Ta and Th; (ii) Hf and Ta are concentrated in the intermediate fractions; and (iii) Th is concentrated in the finer fractions, probably due to incorporation in weathering resistant minerals, specially in the initial stages of weathering.     

Instrumental neutron activation analysis of limestone and associated calcite samples from Abakaliki,lower Benue Trough,Nigeria

Twenty four elements: Fe, Al, Ca, Mg, K, Na, Sc, Sr, Co, Cr, Zn, V, Hf, Ir, W, REE (La, Ce, Nd, Sm, Eu, Tb, Yb, Lu) and Th were determined in limestone and associated calcite from Abakaliki, South-Eastern Nigeria, by instrumental neutron activation analysis (INAA) technique. The USSG reference materials BCR-1 and AGV-1 were included in the analysis to assure quality control of the accumulated data. Hitherto, there is very little work of this type on the deposits in the region being studied. This study, therefore, provides baseline data for the deposit.     

Instrumental neutron activation analysis of trace elements in quartz

A scheme for INAA of 32 elements (As, Au, Ba, Br, Ca, Cd, Ce, Co, Cr, Cs, Eu, Fe, Hf, Hg, Ir, K, La, Lu, Mn, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, W. Yb, Zn) in quartz glass is proposed. The accuracy of the procedure is evaluated by the analysis of two NBS standard reference materials (SRM-1571 and SRM-1632-a). The method is convenient for routine work. The method was used for the determination of impurities in laboratory quartz glass. Dedicated to the 60th birthday of acad. prof. g. bliznakov     

Trace characterisation of lithium niobate by neutron activation analysis

Summary Coprecipitation behaviour of As, Au, Co, Cr, Cu, Eu, Fe, Ir, La, Lu, Mn, Mo, Nb, Ni, Pd, Pt, Sb, Sc, Ta, W, Zn and Zr during precipitation of hydrous oxide of niobium from lithium niobate was investigated. The matrix was dissolved in HF-HNO₃, evaporated to dryness and niobium was precipitated from HNO₃-H₂O₂ medium. The recovery studies were made using radiotracers. A radiochemical separation scheme based on group precipitation has been developed for the determination of Au, Co, Cr, Cu, Fe, Mn, Ni, Pd, Pt, Zn, Zr and rare earth elements. The method was applied to the analysis of lithium niobate. This analysis has provided fruitful information for improving the quality of the crystal.     

Determination of arsenic,scandium, chromium,cobalt and nickel in asbestos by neutron activation analysis

Arsenic, scandium, chromium, cobalt and nickel were determined by neutron activation analysis in various Chrysolite-Asbestos from Canada, Russia, Italy in an asbestos plate, and in dry, as well as in wet manufactured asbestos. Following concentration values were found: for As 0.01–5.5 ppm, for Sc 5.4–14.80 ppm, for Cr 79.5–918.8 ppm, for Co 10.8–80.9 ppm, for Ni 148–1786 ppm. Statistically significant differences /t=0.05/ in contents of As, Sc, Cr, Co and Ni were detected in the different samples of asbestos. The concentration of As and Cr in Italian asbestos were considerably higher than in Canadian chrysolite.     

Accumulation and distribution of elements in rice /seed,brand layer,husk/ by neutron activation analysis

Various rice samples /seed, brand layer, husk/ from Vietnam were analyzed for Se, Hg, Cr, Ni, Sc, Rb, Fe, Zn and Co by neutron activation analysis. The concentration values found /seed/ were the following: Se 0.04–0.07 ppm, Hg 0.02–0.07 ppm, Cr 2.13–8.65 ppm, Ni 1.56–4.95 ppm, Sc 0.02–0.06 ppm, Rb 0.84–2.71 ppm, Fe 26.31–96.07 ppm, Zn 10.65–27.39 ppm and Co 0.02–0.15 ppm. The values were reported in ppm /dry weight/. Statistical analysis /t-test, t=0.05/ showed that the content of elements varies between sorts of rice; the content of Rb, Fe, Ni, Cr of rice husk was significantly higher than in rice seed and brand layer.     

Multielemental determination in platinum rocks by nondestructive neutron activation analysis

Na, Zn, Re, Sc, Ir, Ru, Pt, Fe and Co have been determined in Pt-rock samples from different parts of the state by thermal neutron-activation analysis followed by nondestructive analysis on a MCA. The accuracy and precision of the method have been determined.     

Determination of major components and trace elements in ancient silver by thermal neutron activation analysis

Thermal neutron activation of minute samples of ancient silver objects has provided useful information concerning their silver, copper and gold content. The results of such analysis of eighteen Sasanian silver objects are discussed together with consideration of the sampling problems involved. In order to extend these measurements to include other elements, an isotopic exchange system has been developed to separate other activities present in irradiated silver specimens quantitatively from the silver, copper and gold activities. Following exchange with cuprous and silver iodides it has been possible to count quantitatively the activity of fourteen additional elements: As, Br, Co, Cr, Fe, Hg, Ir, K, Mn, Na, Sb, Sc, Se and Zn. Research supported in part by the U. S. Atomic Energy Commission.     

Radioanalytical methods for the non-destructive analysis of lunar samples

The elemental compositions of Apollo 11 and Apollo 12 lunar soil samples 10084,141 and 12070,83 and Apollo 12 rock fragment 12063,73 were determined by non-destructive radioanalytical methods. Main mineral fractions and glasses separated from these samples were analyzed as well. Instrumental neutron activation analysis (INAA) was used to determine Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zr, Cs, Ba La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, Lu, Hf, Ta, W, Ir, Au, Th and U. A method of delayed neutron counting was used for the determination of uranium, and non-dispersive radioisotopic X-ray fluorescence analysis was applied to the determination of Ti, Fe, Sr, Y and Zr.     

Electronic and magnetic properties of all 3d transition‐metal‐doped ZnO monolayers

Stable geometries, electronic structures, and magnetic properties of the ZnO monolayer doped with 3d transition‐metal (TM) (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) atoms substituting the cation Zn have been investigated using first‐principles pseudopotential plane wave method within density functional theory (DFT). It is found that these nine atomic species can be effectively doped in the ZnO monolayer with formation energies ranging from ?6.319 to ?0.132 eV. Furthermore, electronic structures and magnetic properties of ZnO monolayer can be modified by such doping. The results show that the doping of Cr, Mn, Fe, Co, Ni, and Cu atoms can induce magnetization, while no magnetism is observed when Sc, Ti, and V atoms are doped into the ZnO monolayer. The magnetic moment is mainly due to the strong p–d mixing of O and TM (Cr, Mn, Fe, Co, Ni, and Cu) orbitals. These results are potentially useful for spintronic applications and the development of magnetic nanostructures. © 2013 Wiley Periodicals, Inc.     

Radiochemical multielement neutron activation analysis of niobium via medium- and long-lived radionuclides

Two radiochemical neutron activation analysis techniques capable for the determination of Ag, Au, Cd, Co, Cr, Cs, Cu, Fe, Hf, Ir, K, Mn, Mo, Na, Ni, Pd, Pt, Rb, Sc, Se, Ta, Th, Sn, W, Zn, and Zr in niobium via medium- and long-lived indicator radionuclides were developed. They involve two different irradiation and cooling times as well as two different group separation schemes based on extraction and ion exchange. The achievable limits of detection are between 10⁻⁷ g/g and 10⁻¹³ g/g. The techniques were applied to analysis of niobium of different purity grades. For a number of elements, the results of these techniques are compared with those of other techniques. This work was supported by Bundesministerium für Forschung und Technologie, Bonn.     

Use of INAA and ICP-MS for the assessment of trace element mass fractions in adult and geriatric prostate

The variation with age of the mass fraction of 54 trace elements (Ag, Al, As, Au, B, Be, Bi, Br, Cd, Ce, Co, Cr, Cs, Dy, Er, Eu, Fe, Ga, Gd, Hf, Hg, Ho, Ir, La, Li, Lu, Mn, Mo, Nb, Nd, Ni, Pb, Pd, Pr, Pt, Rb, Re, Sb, Sc, Se, Sm, Sn, Ta, Tb, Te, Th, Ti, Tl, Tm, U, Y, Yb, Zn, and Zr) in intact nonhyperplastic prostate of 65 healthy 21–87 year old males was investigated by instrumental neutron activation analysis with high resolution spectrometry of long-lived radionuclides and inductively coupled plasma mass spectrometry. This work revealed that there is a significant tendency for an increase in Bi, Cd, Co, Fe, Hg, Sc, Sn, Th, U, and Zn (p < 0.0014) mass fraction in normal prostate from age 21 years to the sixth decade. In the sixth to ninth decades the mass fractions of almost all chemical elements investigated in nonhyperplastic prostates were maintained at approximately stable levels. Our finding of correlation between pairs of prostatic chemical element mass fractions indicates that there is a great disturbance of prostatic chemical element relationships with increasing age.     

Solid state NMR spectroscopy as a probe of structure and bonding in the carbides Sc3TC4 (T = Co,Ni, Ru,Rh, Os,Ir)

Scandium transition metal carbides having the formula Sc₃TC₄ (T = Co, Ni, Ru, Rh, Os, Ir) have been structurally characterized by solid state ¹³C and ⁴⁵Sc nuclear magnetic resonance spectroscopy. In all the compounds investigated, well-resolved signals are observed for crystallographically distinct carbon and scandium sites, confirming the formation of superstructures in the Rh and Ir compounds at ambient temperature. ⁴⁵Sc NMR spectra are dominated by anisotropic broadening due to second-order quadrupolar perturbations. The nuclear electric quadrupolar coupling parameters (the coupling constant C_Q and the asymmetry parameter η) are generally found in good agreement with values calculated theoretically from the crystal structure using the WIEN2k program. Furthermore, the spectra reveal large isotropic resonance shift differences between inequivalent Sc sites in a given compound and between sites of the same type for different compounds. Altogether the results illustrate that ⁴⁵Sc NMR is a sensitive method for detecting isotropic and anisotropic local electron density variations in the Sc₃TC₄ family.     

Determination of iridium in mafic rocks by atomic absorption

Iridium is determined in mineralized mafic rocks by atomic absorption after fire-assay concentration into a gold bead. Inter-element interferences in the atomic-absorption determination are removed and Ir sensitivity is increased by buffering the solutions with a mixture of copper and sodium sulphates. Substantial amounts of Ag, Al, Au, Bi, Ca, Cd, Co, Cr, Fe, Ho, Hg, K, La, Mg, Mn, Mo, Ni, Pb, Te, Ti, V, Y, Zn and platinum metals can be tolerated in the atomic-absorption determination. The sensitivity and detection limits are 3.2 and 0.25 ppm of Ir, respectively.     

Elemental content in wheat products of Al-Qusim region, Saudi Arabia using the INAA technique

Wheat is one of the most grown crops in Saudi Arabia. It is grown in various regions of the country. Accurate knowledge of the elemental concentrations in wheat and its products (bran and flour) is of great importance from a nutritional point of view. Wheat samples were obtained from the Al-Qusim region, 300 km northwest of Riyadh, and analyzed. Up to 50 elements (Al, Sb, As, Ba, Br, Cd, Ca, Cs, Cl, Cr, Co, Cu, Ga, Au, Hf, In, I, Ir, Fe, Mg, Mn, Hg, Mo, Ni, K, Rb, Sc, Se, Ag, Na, Sr, Ta, Te, Th, Sn, Ti, W, U, V, Zn, Zr, Ce, Dy, Eu, La, Lu, Nd, Sm, Tb and Yb) were determined in the wheat products. It was observed that the elemental content of bran was much higher than that of white flour.