Determination of some trace elements in the industrial process of aluminium production

Some trace elements in samples from the aluminium industry (Aluminium Kombinat, Titograd, Yugoslavia) were determined by instrumental neutron activation analysis. Samples characteristic for alumina production (bauxite, red sludge), reduction cell components (alumina, anode, AlF₃, cryolite) and aluminium produced (purity 99.5–99.7%) have been analyzed. 10 trace elements were determined under a given set of working conditions and followed through the routine production.     

Determination of uranium and thorium at the sub-ng/g-level in high-purity aluminium by radiochemical neutron activation analysis

Summary A radiochemical neutron activation analysis technique for the determination of uranium und thorium in highpurity aluminium via the indicator radionuclides ²³⁹Np and ²³³Pa, respectively, has been developed. The separation procedure is based on the removal of ²⁴Na on hydrated antimony pentoxide followed by ion-exchange on Dowex-1X8 from HCl/HF and HCl medium. The eluate fraction being of interest for the determination of uranium and thorium contains > 99% of ²³⁹Np and ²³³Pa and, in addition, 11±2% of hafnium and 29±5% of zirconium, and non-detectable fractions of other radionuclides. For a 3-day irradiation of a 100 mg sample at a thermal neutron flux of 10¹⁴cm^–2s^–1 and a decay time of 5 days, the attainable detection limit for both elements is 0.05 ng/g. The method was applied to the analysis of different high-purity aluminium samples, and the results are compared with those obtained in other laboratories.

---

Bestimmung von Uran und Thorium in hochreinem Aluminium im sub-ng/g-Bereich durch radiochemische Neutronenaktivierungsanalyse

     

Analytical study of two diazotization-coupling reactions. Application to the determination of nano-amounts of nitrite in water

Aluminium has been determined in various standard rocks by 14-MeV neutron activation analysis. The induced ²⁷Mg activity (1.01-MeV photopeak) was counted with a multichannel analyser, equipped with Barto?ek's dead-time stabilizer system. Aluminium standards were prepared by mixing silica and alumina. Correction was made for the interfering reaction ³⁰Si(n,α)²⁷Mg by counting the 1.78-MeV peak, 10 min after irradiation. The mean coefficient of variation on a single determination was 2.8% at the 6–10% aluminium level.     

Cation distribution in Ni-substituted Mn-ferrites by Mössbauer technique

The neutron spectra of one outer (#10) and two inner (#2 and #3) sites of the Dalhousie University SLOWPOKE-2 reactor (DUSR) have been calibrated for the k ₀-based neutron activation analysis (k ₀-NAA). The parameters determined include the cadmium ratio (R _Cd), epithermal neutron flux shape factor (), subcadmium-to-epithermal neutron flux ratio (f), thermal-to-fast neutron flux ratio (f _F), modified spectral index r()(T_n/T₀)^1/2, Westcott g _Lu(T _n)-factor, and absolute neutron temperature (T _n). The a-values of -0.0098±0.0045 and -0.0425±0.0047 and -0.0422±0.0053 and f-values of 57.1±2.2 and 18.8±0.4 and 18.9±0.4 were obtained for the sites #10, #2 and #3, respectively. The modified spectral index (MSI), g _Lu(T _n)-factor, and T _n have been determined for the handling of non 1/v (n,) reactions. The accuracy of the method was evaluated by analyzing reference materials.     

Determination of the silver content of ancient silver coins by neutron activation analysis

A reactor neutron activation analysis procedure for the determination of the silver content of silver coins is described. The samples are irradiated for 1 s, cooled for 85 s and measured for 60 s with a Ge-detector. The analysis is based on the measurement of¹¹⁰Ag and¹⁰⁸Ag. Aluminium is used for flux monitoring and pulse pile-up correction. A calibration curve is prepared by irradiating and measureing a series of discs with known silver contents. An average precision of ±2.1% is obtained. The analysis of coins with known silver contents shows good agreement with the given values. The analysis time is 2.5 minutes per sample.     

Validation experiment for large-sample prompt-gamma neutron activation analysis

A method is proposed for the implementation of large-sample prompt-gamma neutron activation analysis (LS-PGNAA). The method was tested with four different sample materials at the thermal PGNAA facility at JAERI, Japan. The macroscopic scattering cross section (Σ _s) and absorption cross section (Σ _a) of the samples were determined by monitoring the neutron flux in four positions just outside the sample container. With the Σ _s and Σ _a determined, the spatial neutron density distribution [n(r)] inside the sample material was derived. Taking n(r) and the gamma-ray self-absorption into account simultaneously, the effective geometric gamma-ray detection efficiency for large samples as a function of gamma-ray energy was calculated. Taking silicon as test element, the concentrations found agreed to within 7% with the known concentrations in the four sample materials examined, both when using relative standardization and with absolute standardization.     

Calibration of sputtering yields for AES depth profiling of oxide layers on aluminium by means of carrier-gas heat extraction analysis

Summary For the purpose of obtaining suitable reference materials for technical coatings on aluminium, the feasibility of calibration of oxide layers by means of heat extraction was studied. Oxide layers were prepared on aluminium sheets by immersion in water of 50 or 80 ° C and annealing at 500 or 600 °C in argon atmosphere. The layer thickness was calculated from the oxygen content of the sample as measured by carrier-gas heat extraction analysis.The total sputtering yield of aluminium oxide layers was obtained via the correlation of AES depth profiling with heat extraction analysis results. This was demonstrated for high purity (99.9%) and technical purity (98.5%) aluminium with its original roughness from the rolling process, on which 20 to 1,000 nm thick oxide layers had been grown.The sputtering yields for the oxide layers prepared were found to be 3.9±0.8 atoms/ion, i.e., about four times higher than that for -Al₂O₃. Calibration of depth profiling on such technical quality oxide layers on aluminium was found to be feasible with a relative precision of 10 to 20%.

---

Kalibrierung der Ionenzerstäubung zur AES-Tiefenprofilanalyse von Oxidschichten auf Aluminium durch Trägergas-Heißextraktion

---

On leave from the Institute of Photographic Chemistry, Academia Sinica, Beijing, People's Republic of China     

Half-life of <Superscript>97</Superscript>Zr,re-measured

Summary The half-life of ⁹⁷Zr, used for the calculation of thermal/epithermal neutron flux ratio in k₀-NAA, is re-determined using three measurement systems with different pulse processing principles. The result of 16.755±0.013 hours clarifies the discrepancy between two widely used literature values, 16.744±0.011 and 16.90±0.05 hours. Different dead-time correction methods used on various measurement systems are evaluated. Factors influencing precise measurement of relative peak counting rates are discussed in time-series measurements over a dynamic range of 1000-fold radioactive intensities (10 half-lives).     

COHN analysis: Body composition measurements based on the associated particle imaging and prompt-gamma neutron activation analysis techniques

The measurement of the body’s carbon (C), oxygen (O), hydrogen (H), and nitrogen (N) content can be used to calculate the relative amounts of fat, protein, and water. A system based on prompt-gamma neutron activation analysis (PGNAA), coupled with the associated particle imaging (API) technique, is being developed for this purpose. A compact D, T neutron generator (∼10⁷ n/s output) with an internal alpha-particle detector is used. The counting system consists of 6 shielded bismuth germanate (BGO) detectors (10.2 cm × 10.2 cm × 10.2 cm) operated with fast-timing electronics to detect only gamma-rays within a 100 ns time window following a trigger pulse generated by the alpha detector. The body can be scanned from the shoulders to the knees within about 30 min, with the equivalent whole-body dose <0.4 mSv. The cumulative gamma-ray spectra in the 2 MeV to 8 MeV region is collected and analyzed for multiple peaks attributed to body C,O,H, and N. Measurement precision for each element, based on tissue-equivalent phantoms, are in the 2–5% range, which are sufficient for population studies in adults. Further improvements are needed to extend the measurements to pediatric clinical research studies.     

Influence of the effective mass on the relative neutron density distribution inside a large sample in prompt-gamma neutron activation analysis

A Monte Carlo study was carried out to determine the influence of the effective scattering mass (M _e) of the atoms on the neutron density profile inside and outside the sample illuminated by a thermal neutron beam as in large-sample prompt-gamma neutron activation analysis (LS-PGNAA). From theory it is known that the spatial neutron density distribution (n(r)) inside a large sample is not the same for atoms with the same macroscopic scattering and absorption cross-section (Σ _s and Σ _a) but different M _e, due to anisotropic scattering at low M _e. The probability of neutron absorption in the sample was found to be the same for materials with equal Σ _s and Σ _a but different M _e, even though the neutron density distribution in the sample was found to change slightly. In view of typical sample, collimator and detector dimensions, it is concluded that M _e does not need to be taken into account in a correction method for neutron self-shielding in LS-PGNAA.     

Influence of aluminium precursor on physico-chemical properties of aluminium hydroxides and oxides

An attempt to obtain aluminium hydroxide that could give aluminium oxides of increased thermal stability was made. Aluminium hydroxide was precipitated during a hydrolysis of aluminium chloride in ammonia medium. The influence of preparative conditions, such as a dosing rate of aluminium precursor, pH, duration of the precipitate refluxing and temperature of calcination, on the properties of obtained hydroxides and oxides was investigated. The materials were studied with the following methods: thermal analysis, IR spectroscopy, low-temperature nitrogen adsorption and adsorption–desorption of benzene vapours. Precipitated boehmites had high values of S _BET determined from nitrogen adsorption (220–300 m²g^–1), good sorption capacity for benzene vapours, developed mesoporous structure and hydrophilic character. It has been proved that a high pH value during the precipitation of aluminium hydroxide favoured better crystallisation of boehmite structure, higher temperature of its dehydroxylation into γ-Al₂O₃, and delayed transformation of γ phase into α-Al₂O₃. Aluminium oxides derived from the hydroxides precipitated at a high pH were the most stable at high temperatures, and were characterised with the best surface properties. The online version of the original article can be found at     

Über basische Aluminiumsalze und ihre Lösungen. XIX. Zur Art der Al-Kationen in hochbasischen,hochkonzentrierten Aluminiumchloridlösungen

Basic Aluminium Salts and their Solutions. XIX. Nature of Aluminium Cations in Highly Basic Highly Concentrated Aluminium Chloride Solutions It is shown that in highly concentrated basic aluminium chloride solutions (c_Al ≈ 7.7 mol · l^?1; r = OH/Al = 2.48), prepared by dissolving aluminium metal in substoichiometric quantities of hydrochloric acid, polymeric aluminium cations (Al_poly) dominate. By dilution of these solutions also increasing amounts of monomeric cations (Al_mono) occur. On aging Al_mono reacts with Al_poly forming small portions of tridecameric Al₁₃O₄₀ cations (Al₁₃). On the basis of these results literature data, after which corresponding commercial basic aluminium chloride solutions contain essentially Al₁₃ cations, are critically discussed.     

Nuclear data measurements for zirconium isotopes used for activation analysis and neutron metrology

In order to establish more accurate nuclear data for the zirconium isotopes⁹⁴Zr and⁹⁶Zr, joint experimental work has been conducted in three different reactor types. After carefully calibrating the neutron spectra in the irradiation channels used, nuclear constants k₀ and Q₀ were remeasured and found to be The relevant effective resonance energies have been recalculated using the latest BNL neutron resonance parameters yielding . The epithermal neutron shielding factor G_e has been experimentally determined as a function of foil thickness. The results gave G_e(⁹⁴Zr)=0.983 (±0.3%) and G_e(⁹⁶Zr)=0.973 (±0.4%) for the most frequently used 0.125 mm foil thickness. Finally the half life of the⁹⁷Zr isotope has also been remeasured to give T_1/2(⁹⁷Zr)=16.744±0.011 h with 1 limit.     

Analysis of inclusions in aluminium by dissolution of the samples in hydrochloric/nitric acid

Summary A new method has been developed for the analysis of oxides, borides and Al₃Ti in aluminium. 20 g samples are dissolved in hydrochloric acid — nitric acid solution. The solution is filtered and the silicon in the residue is removed by means of hydrofluoric acid. The undissolved phases were identified by X-ray diffraction and Scanning Electron Microscopy; the composition of the particles was determined by use of emission spectrography and X-ray fluorescence and the size distribution of the inclusions by use of the Coulter Counter.An aluminium — 5 wt% titanium — 1 wt% boron alloy investigated contains 6.4 wt% TiAl₃ and 3.4 wt% TiB₂. The results obtained with the new method were in agreement with standard optical analysis of the alloy material.Five aluminium ingots investigated contain 6–10 ppm oxides as determined by neutron activation analysis. The new method gave similar, but lower oxide values. The differences in results was explained by assuming that a small portion of the oxides went into solution in the acids and that the samples analyzed by neutron activation had a surface oxide layer.The main weight fraction of the oxides was found to consist of particles larger than 5 m in spherical diameter.

---

Analyse von Einschlüssen in Aluminium durch Lösen der Proben in Salz/Salpeter-Säure

Zusammenfassung Zur Analyse von Oxiden, Boriden und Al₃Ti in Aluminium wurde eine neue Methode entwickelt, bei der 20 g-Proben in einer HCl/HNO₃-Mischung aufgelöst werden. Nach Filtern der Lösung wird das Silicium im Rückstand mit Flußsäure (HF) entfernt. Die ungelösten Phasen werden mit Hilfe von Röntgenbeugung und REM identifiziert, die Partikel-zusammensetzung mit Hilfe von Emmissionsspektrographie und Röntgenfluorescenz bestimmt und die Größenverteilung der Einschlüsse mit Coulter Counter ermittelt.Für eine Al — 5% Ti — 1% B-Legierung haben wir 6.4% TiAl₃ und 3.4% TiB₂ ermittelt. Die mit Hilfe der neuen Methode gefundenen Resultate stimmten mit den Werten der optischen Standardanalyse überein.Fünf durch Neutronenaktivierung untersuchte AlGußstücke enthielten 6–10 ppm Oxide. Die neue Methode gab ähnliche aber niedrigere Oxidwerte. Die Unterschiede lassen sich durch kleine Oxidmengen erklären, die in den Säuren in Auflösung gehen; außerdem besaßen die mit Neutronenaktivierung analysierten Proben eine Oberflächenoxidschicht.Den hauptsächlichen Gewichtsanteil der gefundenen Oxide bildeten Partikel mit mehr als 5 m Durchmesser.

     

Analysis of intermetallic particles in aluminium by dissolution of the sample in butanol

Summary A new method for the quantitative analysis of intermetallic particles in aluminium has been developed. 0.3–5 g samples are dissolved in absolute 1-butanol. The content, the chemical composition, the structure, the shape and the size distribution of the undissolved particles have been determined by means of a series of methods including weight measurements, X-ray fluorescence, inductively coupled argon plasma spectrometry, Coulter Counter analysis and X-ray diffraction. The materials investigated were samples of 99.999 wt% aluminium, 99.5 wt% aluminium and aluminium — 0.4 wt% magnesium — 0.4 wt% silicon — 0.2 wt% iron alloy. Cast samples of the latter alloy contained mainly -AlFeSi and samples homogenized at 580°C - AlFeSi and 1-AlFe(Ni,Cu)Si. Al₁₃Fe₄-particles were dominant in the intermetallic phase present in the 99.5 wt% aluminium samples investigated. The results have been compared and found in agreement with emission spectrometric measurement of the alloys' chemical composition, transmission electron microscopy of the intermetallic phases of thin foils and light microscopy analysis of particles in polished samples.

---

Analyse intermetallischer Partikel in Aluminium durch Auflösung der Probe in Butanol

Zusammenfassung Zur Analyse wurden 0,3–5 g der Probe in absolutem 1-Butanol gelöst. Gehalt, chemische Zusammensetzung, Struktur, Form und Größenverteilung der ungelösten Partikel wurden mit Hilfe verschiedener Methoden bestimmt (Gewichtsmessungen, Röntgenfluorescenzanalyse, ICP, Coulter Counter-Analyse, Röntgendiffraktion). Die untersuchten Proben waren 99,999%iges Al, 99,5%iges Al sowie Al-Legierung mit 0,4% Mg, 0,4% Si und 0,2% Fe. Gußproben dieser Legierung enthielten hauptsächlich -AlFeSi, bei 580° C homogenisierte Proben -AlFeSi und 1-AlFe(Ni,Cu)Si. In der intermetallischen Phase der 99,5%- igen Al-Probe überwogen Al₁₃Fe₄-Partikel. Die erhaltenen Ergebnisse stimmen überein mit emmissionsspektrometrischen Bestimmungen der chemischen Zusammensetzung, mit transmissions-elektromikroskopischen Messungen der intermetallischen Phasen dünner Folien sowie der lichtmikroskopischen Analyse der Partikel in polierten Proben.

     

Recoil128I atoms in iodine pentoxide under /n, γ/ process

An attempt js made to study the behaviour of recoil¹²⁸I atoms in neutron irradiated I₂O₅ at ambient temperature. The initial retention is found to be 44±2%. However, a substantial increase /57±2%/ in the value is observed upon heating the sample at 473 K for 1 h prior to irradiation. A kinetic study of post-recoil thermal annealing of neutron irradiated material is also presented. Effect of pre-heat treatment results in a decrease of rate constants and saturation retention values at respective temperatures while the E_act for the overall process remains almost unaltered.     

Rapid continuous determination of aluminium in copper-base alloys by flow-injection spectrophotometry

Summary A flow-injection spectrophotometric method has been developed for the rapid, continuous determination of aluminium in copper-base alloys. The system consists of the masking of copper, zinc, iron, etc. with a combined use of thiourea, ascorbic acid and EDTA and the measurement of light absorption of aluminium-Xylenol Orange complex at 506 nm. With appropriate standardization satisfactory results are obtained in spite of sluggish reaction of aluminium and Xylenol Orange. The system allows the analysis of solutions of copper-base alloys for aluminium to be conducted at a rate of 50 determinations per hour without any carryover. The results obtained for standard brasses and aluminium bronze (Al 1.43–10.2%) agreed well with the certified values. The precision (rsd) ranges are 0.2–0.3%.

---

Kontinuierliches Schnellverfahren zur Bestimmung von Aluminium in Kupferlegierungen mit Hilfe der Flow-Injection-Spektralphotometrie

Zusammenfassung Bei dem empfohlenen Verfahren werden Cu, Zn, Fe und andere Störelemente mit Hilfe von Thioharnstoff, Ascorbinsäure und EDTA maskiert und der Al-Xylenolorange-Komplex bei 506 nm gemessen. Mit Hilfe eines geeigneten Eichverfahrens werden trotz der trägen Reaktion von Al mit Xylenolorange zufriedenstellende Werte erhalten. 50 Bestimmungen können innerhalb von 1 h ohne jedes Verschleppen durchgeführt werden. Bei der Analyse von Messing und Al-Bronze (1,43–10,2% Al) wurde gute Übereinstimmung mit zertifizierten Werten erzielt. Die Standardabweichungen lagen im Bereich von 0,2–0,3%.

     

Über basische Aluminiumsalze und ihre Lösungen. VII. Zum Einfluß der Herstellungsbedingungen,der Konzentration und der Alterungszeit auf die Zusammensetzung von Lösungen basischer Aluminiumsalze

Basic Aluminium Salts and their Solutions. VII. Influence of Preparation, Concentration, and Aging on the Constitution of Solutions of Basic Aluminium Salts 0.1 to 4 molar basic aluminium chloride solutions – prepared by dissolving aluminium metal in substoichiometric quantities of hydrochloric acid and 10^?4 to 0.2 molar basic solutions of aluminium chloride and perchlorate – prepared by adding alkali to the solutions of the neutral salts were investigated for the kinetics of their reactions with ferrone and by ²⁷Al NMR spectroscopy. In all solutions the contents of polymeric species decreases at equal basicity with increasing aluminium concentration. On the other hand the Al₁₃O₄₀ complex is only formed in solutions prepared by addition of alkali. The differences of composition are confirmed by the aging behaviour of the solutions.     

In vivo total body chlorine measurements using prompt-gamma neutron activation analysis

Total body chlorine (TBC1) provides an estimate of extracellular water. We have examined the feasibility of measuring TBC1 using the 5.6, 6.1, and 8.6 MeV C1 peaks produced during in vivo prompt-gamma neutron activation (dose<0.3 mSv). In subjects, background interference permitted the use of only the 8.6 MeV peak in C1 analysis. Preliminary analyses of the prompt-gamma spectra for 33 healthy females (ages: 24–40 yr) provided a mean estimate of 0.85 g C1 per kg body weight. It is therefore feasible to measure TBC1 concurrently with body nitrogen using relatively low-dose prompt-gamma neutron activation analysis.     

Measurement of low concentrations of hydrogen in small samples by intermediate neutron moderation

An improved method based on the moderation of intermediate neutrons for the measurement of hydrogen in small samples is described. With the aid of boron and cadmium filters, a space shielded from slow neutrons is set up close to an isotopic neutron source shrouded by water moderator. A BF₃ proportional counter enclosed with a sample cell is placed in this space. The neutron count rate of the counter increases when a hydrogen-containing material is introduced into the cell, due to the moderation of intermediate neutrons passing through the filters. With a 1.3 μg²⁵²Cf neutron source, the lower limit of hydrogen detection for 200 ml samples in 10 min count time is 0.01 wt.%. This method is suitable for measuring the H₂O content of heavy water.