Reaction Of Nitrides And Oxide With Bath Metals In Gas Analysis In Metals

Abstract

Reactions of two nitrides, an oxide (α-SiaNi, A1N and α-AI2O3) and bath metals (platinum, iron and tin) in graphite capsules were investigated in vacuum fusion analysis by measuring gas extraction curves with a quadrupole mass spectrometer which can simultaneously measure nitrogen and carbon monoxide from the furnace. From the characteristic gas extraction patterns of each bath metals, gas release reaction mechanisms and their temperatures were studied.     

Determination of nitrogen in boron carbide by instrumental photon activation analysis

Boron carbide is widely used as industrial material, because of its extreme hardness, and as a neutron absorber. As part of a round-robin exercise leading to certification of a new reference material (ERM-ED102) which was demanded by the industry we analysed nitrogen in boron carbide by inert gas fusion analysis (GFA) and instrumental photon activation analysis (IPAA) using the ¹⁴N(γ,n)¹³N nuclear reaction. The latter approach is the only non-destructive method among all the methods applied. By using photons with energy below the threshold of the ¹²C(γ,n)¹¹C reaction, we hindered activation of matrix and other impurities. A recently installed beam with a very low lateral activating flux gradient enabled us to homogeneously activate sample masses of approximately 1 g. Taking extra precautions, i.e. self-absorption correction and deconvolution of the complex decay curves, we calculated a nitrogen concentration of 2260 ± 100 μg g⁻¹, which is in good agreement with our GFA value of 2303 ± 64 μg g⁻¹. The values are the second and third highest of a rather atypical (non-S-shape) distribution of data of 14 round-robin participants. It is of utmost importance for the certification process that our IPAA value is the only one not produced by inert gas fusion analysis and, therefore, the only one which is not affected by a possible incomplete release of nitrogen from high-melting boron carbide. Figure Twin-Detector system for analyzing spatially extended samples     

Quantitative analysis of trace bulk oxygen in silicon wafers using an inert gas fusion method.

This paper describes a method for removing oxide film from the surface of silicon wafers using an inert gas fusion impulse furnace and precise determination of bulk oxygen within the wafer. A silicon wafer was cut to about 0.35 g (6 x 13 x 2 mm) and dropped into a graphite crucible. The sample was then heated for 40 s at 1300 degrees C. The wafer's oxide film was reduced by carbon and removed as carbon monoxide. The treated silicon sample was taken out of the graphite crucible and maintained again with the holder of the oxygen analyzer. The graphite crucible was then heated to 2100 degrees C. The treated silicon sample was dropped into the heated graphite crucible and the trace bulk oxygen in the wafer was measured using the inert gas fusion infrared absorption method. The relative standard deviations of the oxygen in silicon wafer samples with the removed surface oxide film were determined to be 0.8% for 9.8 x 10(17) atoms/cm3, and 2.7% for 13.0 x 10(17) atoms/cm3.     

Beitrag zur Sauerstoffbestimmung in Urancarbiden

Zusammenfassung Es wurden vergleichbare Versuche über die Bestimmung von Sauerstoff in Urancarbiden nach der Heißextraktionsmethode sowohl unter Vakuum als auch mit Hilfe des Trägergasverfahrens durchgeführt. Dabei zeigte es sich, daß für unsere Zwecke die Vakuumextraktion der Trägergasmethode überlegen ist. Von den untersuchten Badmetallen Eisen, Kobalt und Nickel lieferte das Kobalt bei Temperaturen von 1900 und 2000° C die besten Ergebnisse. Das Analysengut wurde in Stückchen in die Bäder gegeben. Die Verwendung von Pulvern erwies sich als ungünstig. Durch metallographische und autoradiographische Untersuchungen konnte dieses Verhalten u. a. durch Graphitausscheidungen in den Bädern erklärt werden. Thermodynamische Abschätzungen stimmten mit den Experimenten überein.

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Summary Comparable experiments on the analysis of oxygen impurities in uranium carbides by vacuum-fusion and inertgas-fusion methods have been performed, using various temperatures and bath compositions (iron, cobalt, and nickel). The latter fusion method proved to be unsatisfactory. Best results were obtained by the vacuum-fusion method, using a cobalt bath at 1900–2000° C. Thermodynamic evaluations were in good agreement with the experimental results. Metallographic and autoradiographic investigations explained that the unfavourable behaviour of powdered samples compared to massive samples was above all due to the increasing graphite precipitation in the bath.

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Fräulein U. Haarmann und Frau E. Popien danken wir für die tatkräftige Mithilfe bei der Durchführung der experimentellen Arbeiten.     

Bestimmung von Sauerstoff in Urancarbiden nach einer neuen badfreien Tr?gergasmethode

Zusammenfassung Es wird über die Sauerstoffbestimmung in Urancarbiden berichtet, die nach einer neuen, badfreien Heißextraktionsmethode im Stickstoffstrom durchgeführt wurde. Der Stickstoff spielt hierbei nicht nur als Trägergas eine Rolle, sondern ermöglicht als Reaktionspartner durch Bildung stabiler Nitride bzw. Carbonitride einen schnellen und vollständigen Abbau der als UO₂ bzw. U(C, O) in den Urancarbiden vorliegenden Sauerstoffverunreinigungen. Die Brauchbarkeit der neuen Methode wurde experimentell durch die Ergebnisse mehrerer Analysenserien bestätigt, die unter vergleichbaren Bedingungen mit Hilfe des Vakuumheiß-extraktionsverfahrens und der Argon-Trägergasmethode gewonnen wurden. Die aus thermodynamischen Berechnungen erhaltene Aussage über den Reaktionsmechanismus bei der O₂-Entgasung von UC-Proben durch badfreie Heißextraktion sowohl im Stickstoffstrom als auch im Vakuum konnte experimentell durch chemische, röntgendiffraktometrische und metallographische Untersuchungen an entgasten Proben bestätigt werden.Da man bei der N₂-Trägergasmethode ohne Badmetall arbeitet, bieten sich gegenüber den anderen Heißextraktionsverfahren folgende Vorteile: 1. Der störende Einfluß der Graphitausscheidung in der Badflüssigkeit auf die Probenlösungs- und Entgasungsvorgänge entfällt. 2. Verluste an Analysengas durch Getterung an verdampftem Badmetall werden vermieden. 3. Sowohl die Möglichkeit mehrfacher Benutzung der Graphittiegel als auch der Verzicht auf Kapsel- und Badmaterialien wirkt sich bei Serienuntersuchungen kostensparend aus.Die Anwendungsmöglichkeit dieser Methode ist nicht nur auf die Sauerstoffanalyse in Uranverbindungen beschränkt. Alle Elemente, deren Oxide mit Kohlenstoff im Stickstoffstrom unter Bildung beständiger Nitride bzw. Carbonitride und CO reagieren, lassen sich auf diese Weise analysieren.

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Summary A report is given on the determination of oxygen in uranium carbide by a new method of hot extraction in a stream of nitrogen replacing the molten bath of the vacuum fusion method. The nitrogen is not only used as a carrier gas but also as a chemical reactant, which — by the formation of stable nitrides and carbonitrides — removes the oxygen impurities present as UO₂ and U(C,O) in the uranium carbide. The utility of the new method has been demonstrated by the results of several series of determinations which have been obtained under comparable conditions by vacuum fusion and by the use of argon as carrier gas. The results of thermodynamic calculations on the reaction mechanism of the removal of oxygen from UC-samples by hot extraction without fusion using a stream of nitrogen carrier gas as well as vacuum could be confirmed by chemical, X-ray diffraction, and metallographical analysis of outgassed samples.By avoiding the use of a molten-metal bath the nitrogen carrier gas method presents the following advantages over the other fusion methods: 1. The troublesome influence of graphite precipitations in the liquid metal bath on the process of dissolution and outgassing is avoided; 2. Losses of the gas by gettering on vapourised metal are avoided; 3. Both the possibility to use the graphite crucible several times and the saving of capsules and bath materials reduce the cost of series determinations.The applicability of this method is not limited to the determination of oxygen in uranium compounds. All elements the oxides of which react with carbon in a stream of nitrogen and form stable nitrides or carbonitrides and CO may be analysed by this method.

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Die vorstehende Arbeit ist entstanden im Rahmen des THTR-Associationsvertrages zwischen Europäischer Atomgemeinschaft, Brown Boveri/Krupp Reaktor-bau GmbH und Kernforschungsanlage Jülich des Landes Nordrhein-Westfalen e.V.     

Influence of carbon dioxide in the determination of oxygen in copper by reduction fusion

It has been reported that copper melted in a graphite crucible at high temperature will give off its oxygen content mainly as CO and partially as CO(2). Thus if oxygen in copper is determined by means of apparatus designed to measure only CO as the reaction product, the results are obviously liable to error. Methods of suppressing formation of CO(2) during the fusion process are proposed. When the oxygen is determined by gas chromatography, formation of CO(2) can be suppressed by adding a 0.5% Si-1.5% NiCu bath-alloy together with the copper sample or by inserting a spectrographically pure carbon rod into the graphite crucible used for the fusion. When the oxygen is determined by coulometry, formation of CO(2) can be suppressed by the addition of the SiNiCu bath-alloy or by appropriate modification of the graphite crucible to obtain an optimum working temperature. The results obtained by either method are in agreement with those obtained by a modified vacuum fusion method in which CO and CO(2) can both be measured. These methods have been validated by analysis of two standard reference materials.     

Tin atom formation in a graphite furnace atomizer

Absorbance measurements resolved in time and space are presented for tin vaporized under various conditions in a graphite furnace. Mass spectroscopie studies coupled with temporal and spatial absorbance measurements indicate that oxygen entrained in the inert sheath gas significantly attenuates the free atomic tin population through the rapid formation of SnO. Addition of 10% hydrogen to the sheath gas and enclosure of the atomizer, substantially reduce the effect of entrained oxygen. Similar release mechanisms are postulated with and without hydrogen, but it is suggested that the concentration of elemental tin on the surface at the time of vaporization is greater when hydrogen is included. The effects of added sulfate salts were also studied and it was concluded that the formation and prevolatilization of SnS is responsible for the extreme depressions reported in the literature.     

Zur Stickstoff- und Sauerstoffbestimmung in Uranverbindungen nach dem Vakuumhei?extraktionsverfahren

Zusammenfassung Die Einsatzfähigkeit eines Routine-Hochvakuumheißextraktionsgerätes auf dem Gebiet der Analyse von Stickstoff und Sauerstoff in Uranverbindungen wird durch Vergleich mit anderen Methoden überprüft. Es zeigt sich, daß ein solches Gerät auf diesem Gebiet mit Erfolg eingesetzt werden kann. Sauerstoff und auch Stickstoff werden bei Anwendung von Graphitkapseln von 0,14 bzw. 0,3 cm³ Rauminhalt in Gegenwart von Reinst-Nickel als Badmetall bei 2000° C quantitativ extrahiert. Es werden genaue Arbeitsvorschriften für die Bestimmung von Stickstoff und Sauerstoff in UN, UCN und UC gegeben.

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Determination of nitrogen and oxygen in uranium compounds using the vacuum hot extraction method

The possibility of using a standard high-vacuum hot extraction equipment in the analysis of nitrogen and oxygen contained in uranium compounds was verified by comparison with other methods. The use of such an equipment in this field proved to be successful. Oxygen and nitrogen are extracted quantitatively at 2000° C in the presence of very pure nickel as the bath metal with the use of graphite capsules of 0.14 and 0.3 cm³ capacity, respectively. Precise instructions are given for the determination of nitrogen and oxygen in UN, UCN, and UC.

     

The thermal analysis of lipids isolated from various tissues of deers and does

TG analysis of lipids is a suitable analytical method that offers the possibility to correlate kinetic parameters of thermal degradation (activation energy) and lipid composition. For this purpose, an inert (nitrogen) or oxidising atmosphere (oxygen) was applied during the thermal treatment (30–220°C) of lipids isolated from intramuscular and fatty tissues (L-IMT and L-FT) of deers and does. Prior to investigation, the extracted samples of lipids were kept at –24°C or +4°C for nine months, thus enabling detection of the influence of storage temperature on the thermal behaviour of the lipids.     

Determination of micro amounts of oxygen in silicon by inert-gas fusion

A chromatographic inert-gas fusion method using an Ni-Sn fusion bath and helium as carrier gas has been developed for determining micro amounts of oxygen in silicon. With the Ni-Sn bath, the oxygen determination can be done at lower temperatures (1650-1700 degrees ) in a heated graphite crucible than in an empty crucible (with no molten metal bath) in which the sample is directly in contact with the carbon. Four samples can be analysed in succession in a single crucible with a relatively short time for oxygen extraction (5 min). Careful control of experimental conditions, and the use of a water-cooled quartz tube and a small unshielded graphite crucible have resulted in a lower blank (0.1 mug of oxygen), and better reproducibility, enabling oxygen in silicon to be determined down to 1 ppm. A calibration curve for determining oxygen in single crystals of silicon by measuring the infrared absorption at 9 mum has been constructed and gives results agreeing with those obtained by alpha-particle activation analysis.     

Determination of oxygen and Hydrogen in tungsten and other metals by a vacuum-fusion gas-chromatographic method

A gas-chromatographic method has been developed for the analysis of gas evolved from tungsten and tungsten-base alloys in the vacuum-fusion process. The method is suitable for determining 5–3,000 p.p.m. of oxygen and 0.2–300 p.p.m. of hydrogen, and can be applied to other metals. Above 50 p.p.m. of oxygen and 3 p.p.m. of hydrogen, the values found compare favourably with those obtained by alternative methods; below these levels, no reliable alternative procedures are readily available. In the proposed method, the sample is submitted to vacuum fusion in a molten platinum bath in a graphite crucible, and an aliquot of the evolved gas is transferred by means of a specially modified Drallim valve, to a stream of high-purity helium. The components are separated on a column of molecular-sieve 5A at 100° and detected with a radioactive-type ionization detector. Calibration and operation of the system are described in detail, and the effects of variables are discussed. Evidence was obtained that hydrogen recoveries by the conventional vacuum-fusion method are sometimes slightly low, because of methane formation. An important advantage of the method is that the evolved gases are positively identified by their retention volumes.     

Zur Bestimmung kleinster Sauerstoffgehalte in Metallen nach dem Heißextraktionsverfahren. III

Zusammenfassung Bei der Bestimmung von Gasgehalten in Metallen nach dem Vakuumheißextraktionsverfahren können systematische Fehler durch Getterung von freigesetztem Probengas an Filmen aus verdampftem und in der Apparatur wieder abgeschiedenem Metall auftreten. Dieser Gettereffekt tritt bei der Bestimmung sehr kleiner Gasgehalte in besonderem Maße auf. Zu seiner direkten Messung wird ein auf der Isotopenverdünnungsanalyse basierendes Meßverfahren beschrieben. Die Anwendung auf die Bestimmung weniger ppm Sauerstoff in Eisen und Molybdän führte zu folgenden Ergebnissen. Bei optimalen Analysenbedingungen (Extraktionstemperatur von 1600° C für Fe bzw. 2200° C für Mo, Entgasung jeder Probe in einem leeren Tiegel) treten keine durch den Gettereffekt verursachten Fehler auf. Bei anderen Analysenbedingungen wurden Gasverluste von mehr als 50% gemessen.

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On the determination of very small oxygen contents in metals by the vacuum fusion method. III

Summary The determination of gases in metals by vacuum fusion extraction can be affected with systematic errors due to the gettering of the gases to be analyzed on metal films in the apparatus arising from the evaporation and redeposition of sample or flux metal. The errors become increasingly severe with decreasing gas contents.By the method described it is possible to follow up the gettering effect in a quantitative manner. The method is based on an isotopic dilution technique. Its application to the determination of few ppm of oxygen in iron and molybdenum led to the following results. At optimum analytical conditions (extraction temperature of 1600° C for Fe and of 2200° C for Mo, resp.; degassing of each sample in a blank crucible), no errors due to the gettering effect occure, but otherwise losses of oxygen up to 50% and more could be observed.

     

Recovery of plutonium from graphite crucibles generated in inert gas/vacuum fusion technique

A simple and rapid method has been developed for the separation and purification of plutonium from solid analytical waste (containing uranium, plutonium, nickel and graphite) generated during the analysis of the nuclear fuels for their oxygen and nitrogen contents by inert gas fusion technique. The method is based on crushing the graphite crucibles, electromagnetic separation of plutonium-nickel alloy, dissolution in nitric acid and ion exchange purification of plutonium. Recovery of plutonium is better than 98%. The method may be extendable for the recovery of any other valuable materials from such analytical waste.     

Investigation of physicochemical properties of biooils produced from yellow poplar wood (Liriodendron tulipifera) at various temperatures and residence times

Fast pyrolysis of yellow poplar wood (Liriodendron tulipifera) was performed under different temperature ranges and residence times in a fluidized bed reactor to maximize the yield of biooil. In this study, the pyrolysis temperature ranged from 400 °C to 550 °C, and the residence time of pyrolysis products was controlled between 1.2 and 7.7 s by inert nitrogen gas flow. The results revealed that the distribution of thermal degradation products (biooil, biochar, and gas) from the woody biomass was heavily influenced by pyrolysis temperature, as well as residence time. The highest yield of biooil was approximately 68.5 wt% (wet basis), with pyrolysis conditions of 500 °C and 1.9 s of residence time. Water content of the biooils produced at different temperatures was 25-30 wt%, and their higher heating values were estimated to be between 15 MJ/kg and 17 MJ/kg. Using GC/MS analysis, 30 chemical components were identified from the biooil, which were classified into 5 main groups: organic acids, aldehydes, ketones, alcohols, and phenols. In addition, biochar was produced as a co-product of fast pyrolysis of woody biomass, approximately 10 wt%, at temperatures between 450 °C and 550 °C. The physicochemical features of the biochar, including elemental analysis, higher heating values, and morphological properties by SEM, were also determined.     

Reactions of antioxidants with molecular oxygen. Part I. 2,2′-methylene-bis(4-methyl-6-tert-butylphenol) in silicone matrix

The reaction of 2,2′-methylene-bis(4-methyl-6-tert-butylphenol) stabiliser with oxygen was studied in an inert substrate at 80-120 °C temperature under 0.02-3.0 MPa oxygen pressure ranges. UV/VIS spectrophotometry and Gel Permeation Chromatography were used to follow the antioxidant consumption and the formation of oxidation products. A simplified mechanistic model of stabiliser oxidative transformation was proposed and corresponding kinetic parameters were determined and compared with the kinetic values obtained by other authors.     

Mechanism for the formation of tin oxide nanoparticles and nanowires inside the mesopores of SBA-15

The formation of polycrystalline tin oxide nanoparticles (NP) and nanowires was investigated using nanocasting approach included solid-liquid strategy for insertion of SnCl₂ precursor and SBA-15 silica as a hard template. HR-TEM and XRD revealed that during the thermal treatment in air 5 nm tin oxide NP with well defined Cassiterite structure were formed inside the SBA-15 matrix mesopores at 250 °C. After air calcination at 700 °C the NP assembled inside the SBA-15 mesopores as polycrystalline nanorods with different orientation of atomic layers in jointed nanocrystals. It was found that the structure silanols of silica matrix play a vital role in creating the tin oxide NP at low temperature. The pure tin chloride heated in air at 250 °C did not react with oxygen to yield tin oxide. Tin oxide NP were also formed during the thermal treatment of the tin chloride loaded SBA-15 in helium atmosphere at 250 °C. Hence, it is well evident that silanols present in the silica matrix not only increase the wetting of tin chloride over the surface of SBA-15 favoring its penetration to the matrix pores, but also react with hydrated tin chloride according to the proposed scheme to give tin oxide inside the mesopores. It was confirmed by XRD, N₂-adsorption, TGA-DSC and FTIR spectra. This phenomenon was further corroborated by detecting the inhibition of SnO₂ NP formation at 250 °C after inserting the tin precursor to SBA-15 with reduced silanols concentration partially grafted with tin chloride.     

Some observations on the thermal behaviour of curcumin under air and argon atmospheres

The TG, DTG and DTA curves of curcumin(I) have been recorded in static air and inert dynamic argon atmosphere over the range between ambient temperature and 600°–700°C using a Netzsch thermal analyser STA 429. Careful examination of these curves reveals appreciable differences in the behaviour of I under either atmospheres, which are easily recognized by comparing the profiles of their thermal curves, particularly in the melting point, thermalL stability of intermediates, percent weight loss and exothermicity of the chemical processes. Gaschromatographic analysis of volatile pyrolysates trapped during thermal analysis indicates the formation of (CH₃)₂CO, CH₃COH and C₆H₅OCH₂COOH (phenyl oxyacetic acid). However, in static air CO₂ and H₂O were identified as well. X-ray diffractometry reveals the formation of amorphous carbon as a final product in argon and a mixture of amorphous carbon and graphite in air. It seems that the relatively high mass of argon plays an important role in the reactions and stability of intermediates. In either atmospheres curcumin is thermally stable up to 249°C withm.p. of 176.4°–177.5°C. The unique shape of the DTA curve of I could be used forits identification.     

The determination of oxygen in brass and zinc by a vacuum carbon-reduction techniques

A vacuum carbon-reduction technique for the determination of oxygen in brass and zinc has been studied. As a preliminary, zinc is removed from the samples, sealed in predegassed graphite capsules, in a silica furnace maintained at ca. 850°C under vacuum in a vacuum fusion instrument. The residual contents of the capsules are then analysed in sequence at 1450°C in the main furnace of the apparatus, to which they are transferred without breaking the vacuum. The procedure developed affords a detection limit of 0.5–1 ppm of oxygen for samples weighing ca. 1.5 g.     

Determination of total tin in silicate rocks by graphite furnace atomic absorption spectrometry

A method is described for the determination of total tin in silicate rocks utilizing a graphite furnace atomic absorption spectrometer with a stabilized-temperature platform furnace and Zeeman-effect background correction. The sample is decomposed by lithium metaborate fusion (3 + 1) in graphite crucibles with the melt being dissolved in 7.5% hydrochloric acid. Tin extractions (4 + 1 or 8 + 1) are executed on portions of the acid solutions using a 4% solution of trioctylphosphine oxide in methyl isobutyl ketone (MIBK). Ascorbic acid is added as a reducing agent prior to extraction. A solution of diammonium hydrogenphosphate and magnesium nitrate is used as a matrix modifier in the graphite furnace determination. The limit of detection is > 10 pg, equivalent to > 1 μg l^?1 of tin in the MIBK solution or 0.2–0.3 μg g^?1 in the rock. The concentration range is linear between 2.5 and 500 μg l^?1 tin in solution. The precision, measured as relative standard deviation, is < 20% at the 2.5 μg l^?1 level and < 7% at the 10–30 μg l^?1 level of tin. Excellent agreement with recommended literature values was found when the method was applied to the international silicate rock standards BCR-1, PCC-1, GSP-1, AGV-1, STM-1, JGb-1 and Mica-Fe. Application was made to the determination of tin in geological core samples with total tin concentrations of the order of 1 μg g^?1 or less.     

Mikroanalytische Bestimmung des Sauerstoffes in fluor-, phosphor- und metall-organischen Verbindungen mit dem Balzers Exhalograph® EAO-202

Zusammenfassung Zur Bestimmung des Sauerstoffes in fluor-, phosphor- und metall-organischen Verbindungen wird die Probe — zusammen mit Schmelzzuschlägen in eine Alu-Kapsel gasdicht eingeschlossen —in einer Graphitkapsel unter Vakuum durch Impulsheizung aufgeschmolzen und der als CO freiwerdende Sauerstoff von einer Gassammelpumpe in die Meßkammer eines Infrarot-Analysators gedrückt und dort gemessen.

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Determination of oxygen in organic fluorine- and phosphorous- or metal-organic compounds

Summary The sample is enclosed together with fusion aiding material in a capsule of aluminium and pyrolyzed under vacuum in a graphite capsule by pulse current heating at high temperature over a short period. The oxygen in the sample is converted to carbon monoxide which is transferred into the cuvette of an IR-analyzer by means of a collector pump and therein determined quantitatively.

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Herrn Prof. Dr. Hans Lieb zum 90. Geburtstag in Verehrung und Dankbarkeit gewidmet.