Determination of traces of nitrogen in refractory metals and alloys by hydrofluoric acid-phosphoric acid-potassium dichromate decomposition and indophenol photometry

Kallmann, Silve; Hobart, Everett W.; Oberthin, Hans.; Brienza, Walter C.

doi:10.1021/ac60258a051

Cited by 25 publications

(5 citation statements)

References 8 publications

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“…Oxygen, nitrogen, carbon, and hydrogen were determined by inert-gas fusion, modified Kjeldahl (ref. 7), combustion, and hydrogen extraction methods, respectively. Metallic impurities were determined by either mass or optical spectrographic methods.…”

Section: Methodsmentioning

confidence: 99%

Observation of oxide particles below the apparent oxygen solubility limit in tantalum

Stecura

1974

Metall Trans

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The apparent solubility of oxygen in polycrystalline tantalum as determined by the X-ray diffraction lattice parameter technique is about 1.63 atomic percent at 820° C. However, oxide particles were identified in samples containing as low as 0.5 atomic percent of oxygen. These oxide particles were present at the grain boundaries and within the grains. The number of , oxide particles increased with increasing oxygen concentration in tantalum. The presence of oxide particles suggests that the true solubility of oxygen in the polycrystalline tantalum metal is probably significantly lower than that reported in the literature. SUMMARYThe distribution of oxygen in high purity poly crystalline tantalum containing up to 3.0 atomic percent of oxygen was studied by X-ray diffraction, microhardness measurements, extraction in methanol-bromine solution, polarized light optical microscopy, and electron microscopy.X-ray diffraction and microhardness measurements indicated a uniform oxygen distribution in all oxygen-doped samples. From the X-ray diffraction lattice parameter study, it was concluded that the apparent solubility of oxygen in poly crystalline tantalum at 820° C is about 1.63 atomic percent. Neither method disclosed the presence of tantalum oxides on the surface or in the matrix of the tantalum metal.However, tantalum oxides were extracted from the samples containing less than 1. 63 atomic percent oxygen. The extracted oxides were identified by X-ray diffraction as TagO, Ta.O, Ta2O, TaOg, and TagOg. Particles assumed to be oxides were seen by electron microscopy in the samples containing about 0. 5 atomic percent oxygen. Electron microscopy investigations further indicated that these particles were present at the grain boundaries and within the grains. Furthermore, investigations by polarized light optical microscopy indicated that the number of particles in tantalum increases with the increase of oxygen concentration in tantalum.The presence of tantalum oxides below the oxygen solubility limits reported in the literature and determined in this study suggests that the true solubility of oxygen in the polycrystalline tantalum metal may be significantly lower than reported in the literature. Segregation of oxygen at the grain boundaries is believed to be primarily responsible for the observed behavior. The determination of the solubility of oxygen in the tantalum metal might be determined by the X-ray diffraction technique provided that the amount of oxygen combined in the form of oxides can be determined.

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Section: Methodsmentioning

confidence: 99%

Observation of oxide particles below the apparent oxygen solubility limit in tantalum

Stecura

1974

Metall Trans

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“…Stevenson (10) noted that the difficulties of obtaining satisfactory nitrogen determinations in igneous rocks and silicate materials are further increased by the fact that the small amount of nitrogen ordinarily present is so intimately combined with the mineral phases that prolonged periods of digestion are required for its liberation. Kallmann et al (11) noted that among the most exasperating obstacles for determining trace quantities of nitrogen in refractory-like materials have been the inability to dissolve the samples and the relatively high operational blanks. The technique of inert carrier-gas fusion extraction overcomes both problems.…”

Section: Resultsmentioning

confidence: 99%

Inert carrier-gas fusion determination of total nitrogen in rocks and meteorites

Gibson¹,

Moore²

1970

Anal. Chem.

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“…The divergence from the actual value equals the scatter of the sensitivity factor-24%-which definitely exceeds the corresponding percentages incident to conventional techniques at relatively high nitrogen concentrations. On the other hand, a signal advantage of the new method is that it requires the use of a mere 0.1 mg of the substance, which compares with 5 grams needed for the chemical (12), 0.05 to 1 gram for the physicochemical (13,14), and 1.6 mg for the physical (ultraviolet spectroscopic) (15) procedures. Accordingly, it lends itself particularly well to the determination of nitrogen in very thin iron deposits (16), and to a study of the scatter of nitrogen content in the sample.…”

Section: Discussionmentioning

confidence: 99%

“…wt. ppm-i.e., one equivalent to those obtained by conventional chemical(12), physicochemical(13,14), and physical…”

mentioning

confidence: 96%

Quantitative determination of nitrogen in iron by spark source mass spectrometry

Vidal¹,

Galmard²,

Lanusse³

1970

Anal. Chem.

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Determination of traces of nitrogen in refractory metals and alloys by hydrofluoric acid-phosphoric acid-potassium dichromate decomposition and indophenol photometry

Cited by 25 publications

References 8 publications

Observation of oxide particles below the apparent oxygen solubility limit in tantalum

Observation of oxide particles below the apparent oxygen solubility limit in tantalum

Inert carrier-gas fusion determination of total nitrogen in rocks and meteorites

Quantitative determination of nitrogen in iron by spark source mass spectrometry

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