Nickel Lattice Research Articles

Similarity of the Magnetization Distribution around Transition and Nontransition Element Impurities in Nickel

The magnetization distribution around a wide variety of impurities in nickel (Al, Ga, Si, Ge, Sn, Sb nontransition metals; Nb, Mo, Ru, Rh 4d; W, Re, Os 5d) has been measured. This work is an extension of the study initiated by Low and Collins1 of the 3d transition elements V, Cr, Mn, Fe dissolved in nickel. Two distinct kinds of magnetization distribution have been observed. In one category (Mn, Fe, Rh), the magnetic disturbance is confined to the impurity site. In the other category the magnetic disturbance is widespread, extending some 6 Å into the nickel lattice. With the exception of V, Ru, and Os, the individual scattering curves of the second class, when normalized at a single point, superpose. This leads to the conclusion that the spatial form of the moment disturbance in the nickel matrix is similar for Al, Ga, Si, Ge, Sn, Sb, Nb, Cr, Mo, W, and Re. This suggests that this wide variety of impurities affects the nickel matrix through the same mechanism. Differences between the impurities show up only in the strength of the disturbance. The normalization factor, which causes superposition of the scattering lengths, for a particular impurity appears to be proportional to the number of electrons outside closed shells in that impurity.

A study of the oxygen adsorption on nickel

Oxygen adsorption on nickel was studied in connection with the more general problem of determination of the number of surface metal atoms (the surface area) in multicomponent catalysts by the selective chemisorption method. Studies of the oxygen adsorption on samples of nickel powder at temperatures of 22–78 °C and −196 °C demonstrated that the amount adsorbed at 22 °C and −78 °C slowly and steadily increases with time. This phenomenon is explained by the oxygen incoporation into the crystal lattice of nickel. The processes connected with this incorporation become unmeasurably slow only at temperatures approaching that of the boiling point of nitrogen. At −78 °C no physical adsorption of oxygen occurs on nickel, whereas at −196 °C the major part of adsorbed oxygen is bound by physical adsorption. It was found during investigations on the thermal regeneration of the nickel surface coated by oxygen that this process does not occur to a greater extent up to temperatures exceeding 200 °C, as it is quoted in the literature, but it was also found that at lower temperatures, and even at −78 °C a certain part of the covered surface is regenerated in the vacuum. On the basis of the results obtained the choice of experimental conditions which are convenient for the determination of the nickel surface area in nickel catalysts by the selective oxygen adsorption on nickel is discussed.

Temperature Dependence of Internal Field at the Fe57 Nucleus in Nickel Lattice

Temperature Dependence of Internal Field at the Fe⁵⁷ Nucleus in Nickel Lattice

The effect of small additions of disperse alumina inclusions on some characteristics of sintered nickel

Materials containing 0.5, 1, 2, 3, 4, and 5 vol. % Al2O3 were obtained from mixtures of nickel oxide and alumina powder reduced with hydrogen. The apparent density of the reduced powder and the relative density of pressed compacts vary nonuniformly with increasing alumina content. The material with 1 vol. % Al2O3 has the maximum values of these characteristics. The sintering shrinkage and relative density of sintered specimens are minima for this composition. Disperse alumina inclusions appear to exert a dual effect on the shrinkage of contacts during sintering: On the one hand, they decrease shrinkage by disturbing contact between the nickel particles; on the other hand, they facilitate the evacuation of the water vapor forming during sintering. The disperse inclusions break up the nickel submicrograins and affect the microdistortions of the nickel lattice.

Lattice and Grain Boundary Self-Diffusion in Nickel

Lattice and grain boundary self-diffusion coefficients of radioactive nickel 63 into high purity nickel have been measured over the temperature range 650°–475°C. The lattice diffusion coefficients, measured by radioactive counting of the surface, are given by DL=1.9 exp(−66 800/RT) cm2sec−1in agreement with previous measurements at higher temperatures. The grain boundary diffusion coefficients, determined from activity-penetration data, are similarly given by DB=0.07 exp(−27 400/RT) cm2sec−1and found to be independent of grain diameter in the range of about 0.03 to 0.07 mm.

Interaction of Oxygen with (110) Nickel

The interaction of oxygen with a (110) nickel surface has been studied by photoelectric and low-energy electron diffraction techniques. With increasing exposure to O2, a sequence of oxygen—nickel structures is formed terminating in the NiO rocksalt structure which is oriented with the (100) face of the oxide parallel to the surface. It was possible to observe some of these structures in reverse order by heating the oxide-covered crystal in vacuum or subjecting it to brief argon ion bombardment. From the fact that the oxide was decomposed at only 200°C, and from the associated changes in work function and diffraction intensity, it is concluded that oxygen readily penetrates into the nickel lattice, occupying substitutional sites to form three-dimensional oxygen—nickel structures of increasing oxygen content until the composition of NiO is reached. This makes possible the correlation of the two-dimensional oxygen—nickel structures observed on different faces.

The influence of disperse alumina inclusions on some characteristics of sintered nickel

1. Curves of the relative density of Ni-Al2O3 specimens sintered in hydrogen at temperatures above 1475°K, plotted against aluminum oxide content, have maxima which correspond to 5% Al2O3 in the case of slow heating and 15% Al2O3 in the case of rapid heating. The presence of these maxima is attributed to the fact that, on the one hand, aluminum oxide promotes shrinkage by facilitating the removal of the water vapors formed during the reduction of oxides remaining in the powder; on the other hand, at high Al2O3 contents, shrinkage is reduced owing to disrupted nickel particle contacts. 2. The experimental curve of shrinkage vs. aluminum oxide content for specimens sintered in hydrogen at temperatures exceeding 1475°K lies much above the curve calculated with the aid of B. Ya. Pines' formula, which is also ascribed to facilitated removal of water vapors formed during the reduction of residual nickel oxides, from the compacts during sintering. 3. Aluminum oxide inclusions prevent the growth of nickel grains during sintering at temperatures up to 1475°K (for compositions with 5 and 10% Al2O3) and up to 1525°K (for compositions with 15 and 20% Al2O3). 4. Increasing the amount of aluminum oxide is accompanied by a decrease of submicrograin sizes attained during sintering. 5. Specimens sintered in hydrogen are characterized by the presence of microdistortions in the nickel lattice. The greater the density of the sintered specimens, the greater the microdistortions. The microdistortions are due to the evolution of hydrogen from nickel during cooling after sintering, brought about by the decreased solubility of hydrogen in nickel.

Paramagnetism and lattice parameters of iron-rich iron-germanium alloys

Paramagnetic and X-ray studies have been made on iron-rich iron-germanium alloys. The lower boundaries of the γ-loop have been determined from magnetic susceptibility measurements. The γ-loop extends to about 5·5 w o germanium. At high temperatures the paramagnetic behavior of iron-germanium solid solutions follows the Curie-Weiss law. These measurements show that germanium in solution in iron produces quantitatively different behavior in Curie point, Bohr magneton number, and lattice parameter than does silicon. Simple theoretical descriptions based on the Heisenberg model do not correctly describe the paramagnetism of binary iron alloys. The lattice spacings of solid solutions of germanium in iron, quenched from about 600°C, have been determined accurately as a function of atomic percentage of germanium. The plot of lattice constant vs. composition is a straight line to 10·45 a o germanium. The abrupt change to zero in the slope of this line establishes the α-phase boundary at that composition, at approximately 600°C. A new scheme is proposed for relating lattice parameter changes to atomic volume of the solute. Under the proposed assumptions, a linear relation of lattice parameter to atomic volumes of solvent and solute is found. They also serve equally well as a basis for the lattice dilation of the nickel lattice with germanium as the solute. Furthermore, the changes in volume per atom as a function of composition for the systems iron-germanium and nickel-germanium agree very well up to 5 a o germanium. The behavior of germanium as a solute in iron and nickel is in contrast to its behavior in the group 1B metals where the effect of valence difference is marked.

Degassing properties of nickel

The grades of nickel used in the electronic valve industry, containing magnesium, silicon and carbon among other impurities, have been found to have gas contents in the range 1.5 to 16 ml. torr g-1, the average value being about 5.0 ml. torr g-1. The total quantity of gas evolved is limited by the amount of oxygen present in the form of oxides of the impurities, particularly magnesium. These oxides have been found, both in wire and sheet, to be concentrated near the surface. In the case of sheet material 0.150 mm thick, 80% or more of the total gas content is in a skin 15μ thick. The diffusion constant of the gas desorbed from the nickel (largely carbon monoxide resulting from the reaction of carbon with the impurity oxides) has been measured in the temperature range 850° C to 975° C and, comparing the results with the diffusion of carbon in nickel, it is concluded that the evolution rate of carbon monoxide is largely controlled by the rate of carbon diffusion. In nickel which contains no stable impurity oxides the evolution of carbon monoxide proceeds at a slower rate and is controlled by the diffusion rate of the oxygen in the nickel lattice. The differences in evolution rate of carbon monoxide from the various grades of nickel can be explained in terms of the location of the oxygen in the nickel.

Une Nouvelle Forme du Nitrure de Nickel: Ni4N

The transformation of nickel lattices under the influence of nitrogen as an insertion impurity has been followed by electron diffraction after nitriding thin monocrystalline evaporated films of nickel in an atmosphere of ammoniac at different temperatures. As established previously, the nitriding process occurs as follows: Ni (f.c.c., a =3.52 Å)→ Ni 4 N (f.c.c., a =3.72 Å)→ Ni 3 N (hexagonal). In this work, a detailed study of some anomalous diffraction spots reported, but not interpreted in a previous work, has been undertaken. It has been found that these anomalous diffraction spots appear rather clearly on the specimens nitrided at 230–240°C and they belong to a new form of Ni 4 N which is no longer cubic but tetragonal. Its lattice parameters are: \begin{aligned} a{=}b{=}3.72\ \text{{\AA}}; c{=}2c^{*}{=}7.28\ \text{{\AA}} \end{aligned} These interpretations provide evidence of existence of two forms of Ni 4 N: one cubic: Ni N (I) and the other, tetragonal: Ni 3 N (II). The tetragonal form Ni 4 N (II) is derived from the cubic form Ni 4 N (I). This occurs as follows: Two elementary lattices of cubic Ni 4 N (I) join together after contraction along [ c ] axis (from c =3.72 Å to c * =3.64 Å) and form a unit cell of the tetragonal form. The two other axes [ a ] and [ b ] conserve their initial value of 3.72 Å ( c * / a =0.98).

Transformation des Reseaux Metalliques sous l'Influence des Elements d'Insertion : Transformation du Nickel sous l'Influence de l'Azote

Il est bien connu que certains metaux presentent des transformations allotropiques. L’existence de quelques-unes de ces formes allotropiques est actuellement de plus en plus contestee et on les attribue a des transformations s’effectuant sous l’influence d’elements d’insertion. Dans ce travail nous avons porte notre attention sur cette question en etudiant plus particulierement les transformations subies par le nickel sous l’influence de l’azote.

ON THE INTERNAL FRICTION PEAK ASSOCIATED WITH THE PRESENCE OF CARBON IN NICKEL

It is well-known that the stress-induced rotation of the magnetic domains in nickel gives rise to an internal friction peak (when internal friction is plotted as a function of temperature of measurement). An internal friction peak associated with the presence of carbon in nickel was recently observed in our laboratory. In this paper are described further experiments which demonstrate conclusively that this new internal friction peak is not connected with ferromagnetism of nickel but depends upon the amount of carbon in solid solution in nickel. More accurate determinations of the activation energy associated with this internal friction peak show that this activation energy is indeed very close to the activation energy for the diffusion of carbon in nickel. These experiments thus show that the new internal friction peak is associated with the stress-induced micro-diffusion of carbon in nickel.A brief discussion on the mechanism of this internal friction peak in terms of the existence of holes in the crystal lattice of nickel is given.

FERROMAGNETISM AND ORDER IN NICKEL MANGANESE ALLOYS

An investigation of ferromagnetism in nickel manganese alloys containing up to 40 atomic per cent manganese has been carried out. Twenty alloys within this composition range were subjected to heat treatments such that the atomic arrangement within the alloys varied from disorder to a high degree of long range order.The degree of order of Ni3Mn calculated from measured saturation magnetization using the atomic model of ferromagnetism was consistent with the value calculated from the ratio of measured integrated intensity of the (110) X-ray diffraction superlattice line to that of line (111).The relationship between saturation magnetization and concentration for the disordered alloys can be explained adequately by the existence of short range order. A value of 3.4 Bohr magnetons for the effective magnetic moment of manganese atoms in a nickel lattice was deduced.

半導体NiOの導電性に及ぼす酸素圧の影響

In the various oxygen pressures, we investigated the temperature dependency of the electrical conductivity (σ) of NiO. It changes from the form Aexp(−E⁄kT) to A′exp(−E⁄2kT) with the increase of oxygen pressure (P:10−3∼760 mmHg). From this change we can determine the unique value of the activation evergy E. E=1.25 eV. The dependency upon the oxygen pressure at a definite temperature can be expressed generally,by the formula, σ∞P\frac1x. If we assume, as usual, that when the oxygen pressure increases,the nickel ions moves towards the surface to react with oxygen and extend the lattice of NiO, leaving vacant lattice points on the nickel lattice of NiO, and that such vacant lattice points form the impurity levels, then we can obtain the relation σ∞P\frac14. Experimental value of x is 3.7 at 1000°,almost in accord with the above-mentioed result. But at lower temperatures we gain the smaller value of x,until finally it reaches to the relation σ∞P. And with such assumption,we cannot explain the change of the temperature dependence of the conductivity in the different oxygen pressures.So,we assume that the nickel ions which left the normal lattice points,partially extend the lattice NiO at the surface,and partially occupies the interstitial positions. Then, thenumber of the vacant lattice points (Nh) is proportional to \sqrtP,and the number of the interstitial nickel ions (Nf) is inversely proportional to\sqrtP.So the number of electrons at the imprurity levels,and of positive holes in the full band varies depending upon the oxygen pressure. Using these relations,we can derive the theory which may account for the experimental data.From our data,we get a constant δ=Nf⁄h\simeq2×10−3 at 1000°, P=760 mmHg, in which n denotes the number of free positive holes. This value of δ is very small, nevertheless the effect of this small value is very serious.

The Diffusion of Hydrogen Through Nickel

The diffusion of hydrogen through commercial and very pure anode nickel has been studied in a precision manner throughout the temperature interval 1100° to 150° Centigrade. It was found that the diffusion rates vary in a perfectly regular manner throughout this region, except for a discontinuity at the Curie point, namely near 360°C. A very exact agreement with the formula R = ATzpy ×exp (—b/T) was found in all cases. After long heat treatment with hydrogen the value of y in the above equation for anode nickel becomes +0.50±0.01 with the possible exception of a region within 3° of the Curie point. All the nickel used had isotherms whose slope at the start of observations was a maximum in the Curie region and markedly greater than 0.5, but which approached 0.5 as the heat treatment, ordinarily considered as having a decarburizing effect, progressed. The magnetic transition as shown by diffusion is abrupt, the isobars below the Curie region being quite as straight as above. There is always a sudden drop in the value of b as calculated from the simple equation R = A exp (—b/T) at the Curie point, the value changing in the purest nickel from 6600 to 5800 with rising temperature. No systematic breaks appear in the isobars at high temperatures, such as found in pure iron, but nevertheless the value of z indicates that the diffusing hydrogen possesses appreciable energy within the lattice. The Curie region shows marked hysteresis, and is similar to the Curie region of pure iron in this respect. Existing theories of ferromagnetism seem to require modification, inasmuch as the Curie transition in nickel appears to take place about as abruptly as the body-centered-face-centered transition in iron. The loss of magnetism at the Curie transition is essentially an atomic phenomenon and should not be associated primarily with conditions in aggregates of atoms or atomic domains. During the transformation for a finite time, there appears to be an additional electron in the valence shell of some nickel lattice points. A possible description of the process of the change from the ferromagnetic to the paramagnetic condition in the transition elements is that an electron is moved from the 3d shell to one of the 4 levels, followed more or less quickly by a drop of another 4-level electron back to such a 3d level as to result in the pairing of electron spins in the 3d shell.

An X-ray investigation of pure iron-nickel alloys. Part 4: the variation of lattice-parameter with composition

In this part of the paper the variations of lattice-parameter with the composition of the alloys is considered. Twenty alloys in the γ phase ranging in composition from 23 to 97 atomic per cent of nickel, and four alloys in the α phase ranging in composition from 3 to 16 atomic per cent of nickel were studied at different temperatures. At room-temperature, when iron is added to nickel the nickel lattice expands almost linearly with the atomic composition until the lattice-parameter reaches a maximum value of 3.5895 A. for an alloy the composition of which is 39 atomic per cent of nickel. On further addition of iron the lattice contracts. The variation of the parameter of the γ alloys with composition was examined at temperatures ranging up to 600°C. From the values of the lattice parameters the densities of pure iron-nickel alloys over the whole range of composition from pure iron to pure nickel were calculated.

X-ray investigation of pure iron-nickel alloys. Part I: thermal expansion of alloys rich in nickel

The thermal expansion of pure iron-nickel alloys having compositions ranging between 97 and 73 atoms of nickel per cent was measured by the X-ray method. Close agreement was found between the expansion of the crystal lattices and the expansion of specimens of material consisting of composite masses of crystals, such as were used by previous workers who employed the ordinary methods of measurement. For the alloys examined, which were all rich in nickel, the addition of iron to the nickel lattice was found to have two effects: (a) the nickel lattice expanded approximately in proportion to the amount of iron added, and (b) the temperature of the discontinuity in the thermal-expansion curve was raised with the addition of iron, but not in proportion to the amount of iron added. No change in structure took place at the temperature of magnetic transformation; the face-centred structure persisted from room-temperature through the transformation temperature up to 600°C., the highest temperature reached in the investigation. No ageing effect was observed with an alloy containing 94 atoms of nickel per cent, the lattice parameter showing no consistent change over a period of 15 months.