Nitrogen In Solid Solution Research Articles

Untersuchungen im System Niob-Stickstoff: I. Eigenschaftsänderungen von Niob durch gelösten Stickstoff

The electrical resistance, the lattice parameter, the hardness and the internal friction of niobium-nitrogen solid solutions were determined as a function of nitrogen content in the range 0 – 1.5 at % N. These properties largely vary in a linear manner with solute content. 1 at % nitrogen in solid solution in previously degassed niobium raises the electrical resistance at 10° C from 14.1 to 18.2 μΩ·cm, the lattice parameter at 20° C from 3.300 0 to 3.304 1 Å and the microhardness under 50 g load at 20° C from 63 to 245 kg/mm 2. The nitrogen damping peak at 260° C (frequency 0.73/sec) for 0.5 at % N reaches a level of θ = 560 × 10 −4 . The activation energy of the simple relaxation process is 33.8 kcal/mol. The property changes induced in niobium by dissolved nitrogen were compared with the corresponding values for the solid solution systems niobium-oxygen, tantalum-oxygen, tantalum-nitrogen, vanadium-nitrogen and vanadium-oxygen.

Optical absorption features associated with paramagnetic nitrogen in diamond

Abstract A survey of the optical and E.P.R. absorption in a large number of diamonds revealed that most natural diamonds contain substitutional nitrogen exclusively in non-paramagnetic, platelet form. These diamonds are classified as Type I a. A small group of transparent natural diamonds contain dispersed, paramagnetic nitrogen. The optical properties of these diamonds are unlike those of other diamond types and were hitherto unknown. It is proposed that these diamonds be classified as Type I b. The absorption continuum in the ultra-violet and visible region and the infra-red bands in the region of single single-phonon absorption, characteristic of Type I b diamonds, are shown to be due to paramagnetic nitrogen in solid solution. Synthetic diamonds are found to be generally of Type I b, whereas natural Type I b diamonds are rare exceptions. This is attributed to the growth history of the specimens.

Strain-aging effects of nitrogen in vanadium

Specimens were strained in tension from room temperature to 550°C at strain rates in the range of 10 −3–10 −4/sec on iodide vanadium containing varying amounts of nitrogen in solid solution. Maxima in the tensile strength, yield strength, and strain-hardening coefficient, a minimum in the strain-rate sensitivity and the occurrence of serrated stress-strain curves were observed in the temperature range of 300° to 450°C. The activation energy for strain aging in vanadium was found to be 37.3 ± 3.7kcal/mole from the strain rate dependence of the strain-aging peak and 36.2 ± 4.5kcal/mole from a return-of-yield point method. These values agree well with those reported for the diffusion of nitrogen in vanadium as determined by other methods. Thus, the results of this investigation indicate that nitrogen is associated with many of the strain-aging effects observed in vanadium.

Magnetic Investigation of Pure Manganese and of Several of its Alloys

Arrott, Coles, and Goldman have shown that a parasitic ferromagnetism can be induced at low temperatures in antiferromagnetic α manganese by pickling in nitric acid, and that this effect can be subsequently removed by a vacuum anneal. We have confirmed this result. Furthermore, we have eliminated as possible sources for this effect the presence of hydrogen or nitrogen in solid solution and the formation of nitrides or hydrides. However, strains arising upon transforming from the β phase to the α phase can induce this parasitic ferromagnetism. These results fit well with Li's hypothesis of antiferromagnetic domain boundaries giving rise to parasitic ferromagnetism. According to Li, strains should serve well to stabilize the domain boundaries.

Some internal friction studies in columbium

Carbon has been found to diffuse in columbium at a slightly more rapid rate than nitrogen. At 1 cps, that internal friction peak which arises from the stress-induced ordering of carbon in columbium is found at 268°C while the nitrogen peak occurs at 285°C. The diffusion coefficients are: D=0.0046 exp (—33,300/RT) for carbon in columbium and D=0.0072 exp (—34,800/RT) for nitrogen in columbium. The carbon peak in columbium is very unstable, the height declining rapidly with time in contrast to the nitrogen peak. The ratio of the height of the nitrogen peak to the concentration of nitrogen in solid solution (expressed in wt pct) was found to be 0.33, in good agreement with previous work. The internal friction in high purity columbium was found to be a sensitive function of the strain amplitude at which the damping was measured.

The influence of pressure on the mean time of stay of interstitial nitrogen in iron

Abstract The influence of the hydrostatic pressure on the mean time of stay of interstitial carbon atoms in α-iron was determined by measuring the time decrease of permeability. This influence was found to be very small at temperatures from 239°K up to 253°K. The corresponding activation volume is negligible. It is concluded that Keyes' semi-empirical relationship between activation energy and activation volume does not hold for this case, no more than for solid solutions of nitrogen in α-iron.

Mechanism of the Reaction of Hydrogen with Zirconium: I . Role of Oxide Films, Pretreatments, and Occluded Gases

Previous studies have shown the reaction of zirconium with hydrogen to be sensitive to surface preparation, surface films, heat treating cycles, cold working of the metal, and nonmetallic impurities.Experiments were made on the rate of reaction of high purity zirconium with pure hydrogen using a sensitive microbalance method, and an all glass and ceramic vacuum system to minimize contamination.The effect of a preliminary vacuum heating cycle on rate of reaction with hydrogen at 150°C was studied by varying the temperature of the vacuum heating cycle from 150° to 700°C. Samples having the room temperature oxide present showed only a slow rate of reaction, while samples heated to 700°C for one hour showed a rate of reaction 7700 times as great. Results also showed that the oxide film was effectively removed by heating in a vacuum for one hour at 500°C.A study was made of the thickness and nature of the oxide film. Thus, the film formed in air at room temperature was more resistant to hydrogen attack than thicker oxides formed at higher temperatures. Studies on the effect of small quantities of oxygen and nitrogen in solid solution indicate only minor effects. Results suggest that considerable revision is necessary in concepts of the mechanism of the hydrogen reaction on metals.

Some Properties of Columbium Containing Nitrogen

Quench aging of supersaturated solid solutions of nitrogen in columbium takes place in reasonable times in the temperature range 300° to 500°C. Changes in internal friction, hardness, and electrical resistivity are found to accompany this change.

Precipitation phenomena in the solid solutions of nitrogen and carbon in alpha iron below the eutectoid temperature

Precipitation phenomena in the solid solutions of nitrogen and carbon in alpha iron below the eutectoid temperature

X-Ray Studies on the Nitrides of Iron

IN the preliminary report under the above title, published in NATURE of May 26, p. 826, the conclusion is drawn that the cubic γ-phase is a solid solution of nitrogen in γ-Fe. A further study of the photograms, however, makes a correction of this assumption necessary, for there are in the photograms two very weak lines which indicate that the nitrogen atoms have definite places in the lattice.

X-ray Studies on the ‘Nitrides’ of Iron

EXPERIMENTS made by Fowler, Baur and Voermann, White and Kirschbraun, and Tschischewski show that iron ‘nitrides’ with a maximum amount of about 11 per cent nitrogen are formed when ammonia is led over heated iron. The most favourable temperature for the reaction seems to be about 450° C. Some of the authors are of the opinion that definite chemical compounds, that is, nitrides, are formed, while others consider the products to be solid solutions of nitrogen in iron. Studying the ironitrogen system by means of X-rays, I have found the latter opinion to be the correct one.