Physical Properties of Nickel

The colour of nickel is silver-white with a grey tinge, and, when electrodeposited, the metal may be bright and lustrous, or, as pointed out by J. M. Merrick, dark and matte. Nickel can take a high polish so that it reflects a large proportion of the light falling on a polished surface. This makes the metal valuable for electroplating. A. W. Wright found that thin films of nickel viewed in transmitted light appear grey or brownish-grey; and G. T. Beilby said olive-green, or blue. W. L. Dudley observed that the incandescent vapour appears bluish-green. E. van Aubel discussed the colour and transparency of nickel. W. T. Brandt compared the decolorizing power of nickel, zinc, and tin on copper:

Copper (per cent.)	Cu-Ni Alloy	Cu-Sn Alloy	Cu-Zn Alloy
95	Paler than copper	Red (golden) yellow	Almost copper-red
90	Light copper-red	Reddish-grey-yellow	Yellowish-reddish
85	Pale red	Reddish-yellow	Reddish-yellow
80	White pink tinge	Reddish-grey	Reddish-yellow
78	Nearly white	Yellowish-grey	Reddish-yellow
75	Nearly white	Reddish-white	Pale yellow
70	Silver-white	White	Yellow

G. Rose observed that the crystalline fracture shows that the crystals belong to the cubic system, though S. Kalischer was unable to establish this by corrosion figures. R. M. Bozorth and F. E. Haworth, and H. H. Potter and W. Sucksmith studied the corrosion figures. G. J. Sizoo, and C. H. Mathewson discussed the twinning of the crystals; and A. Schrader and E. Weiss observed no twinning of the crystals, nor did they find any twinning or grain-growth develop during annealing. F. C. Thompson and W. E. W. Millington, and J. A. Ewing and W. Rosenhain observed slip-bands and twinning lamellae in nickel. A. Schrader and E. Weiss studied the twinning of nickel. G. T. Beilby observed that the polished metal has a transparent glass-like skin which may pass into minute scales or granules. W. G. Burgers and W. Elenbaas studied the zone-like structure of electrolytic nickel. The microstructure after etching the polished surface is fairly typical of polycrystalline metals. E. S. Davenport discussed the sub-crystalline boundaries. The microstructure of nickel was studied by W. Velguth, and R. Yogel. According to P. D. Merica and R. G. Waltenberg, nickel oxide or sulphide, and manganese sulphide are sometimes visible; if over 0.4 per cent, of carbon is present, it usually occurs as graphite. The intercrystalline brittleness was shown by H. S. Rawdon and co-workers to be due to the oxidation or sulphurization of the grains so that their cohesion is destroyed. G. Tammann studied the effect of annealing on the adsorption of dyes by nickel wires; and G. Tammann and A. Ruhenbeck, the welding power of nickel. H. C. H. Carpenter examined the effect of the imprisoned gas.

The etching of the metal was studied by J. Czochralsky, and H. S. Rawdon and co-workers. According to W. A. Mudge, the microstructure can be developed by etching with 5 to 100 per cent, nitric acid - say, by diluting a soln. of the 50 to 75 per cent, acid with commercial 50 per cent, acetic acid. H. S. Rawdon and M. G. Lorentz recommended conc. hydrochloric acid; or a soln. of ferric chloride acidified with hydrochloric acid; and for electrolytic etching, a current density of 0.01 amp. per sq. cm. and an electrolyte of sulphuric acid, 22 parts by vol., 3 per cent, hydrogen dioxide, 12 parts by vol., and 66 per cent, of water by vol.; or else, as electrolyte, a 5 per cent. soln. of a mixture of nitric and sulphuric acids, 3:1.

A. H. Hull reported that the X-radiograms of nickel correspond with both a face-centred and a body-centred cubic lattice, and that the lattice constant length of edge of cube of the face-centred form is a=3.54 Å. F. Wever found no evidence of the existence at ordinary temp, of two forms of nickel with different space- lattices. The atomic arrangement is uniformly that of a body-centred, cubic lattice with a parameter a=519×l0^-8 cm. Impurities may increase the distances between the atoms. Non-magnetic or β-nickel, like β-iron, cannot be regarded as an allotropic form with a lattice structure different from that of ordinary or α-nickel. S. B. Hendricks and co-workers could detect no evidence of any allotropic change in nickel up to 101.5°, and the body-centred form has not been detected by other observers, but the lattice constant of the face-centred form was found by W. P. Davey, and G. L. Clark and co-workers, to be 3.499 A.; F. Wever, and L. W. McKeehan, 3.51 Å.; H. Lange, 3.518 Å.; A. Osawa, 3.508 Å.; L. Mazza and A. G. Nasini, 3.514 Å.; S. Holgerson, 3.52 Å.; H. Bohlin, and L. Yegard and H. Dale, 3.53 Å.; A. Westgren and A. Almin, 3.519 Å.; W. C. Phebus and F. C. Blake, 3.521 Å.; Z. Jeffries and R. S. Archer, E. C. Bain, A. W. Hull, R. W. G. Wyckoff, and A. Sacklowsky, 3.54 Å.; R. G. Kennedy, 3.525 Å. For 99.94 per cent, nickel; F. Wever, 3.51 Å.; L. W. McKeehan, 3.510 Å.; and E. A. Owen and J. Iball gave a=3.5179 Å.; and they calculated the closest approach of the atoms to be 2.487 Å. The subject was discussed by R. Brill and H. Pelzer, M. I. Gen and co-workers, A. O. Jung, E. Piwowarsky, R. Riedmiller, P. Rontgen and W. Koch, J. E. L. Jones and B. M. Dent, W. Biissem and F. Gross, H. Karlsson, E. A. Owen and E. L. Yates, H. Kersten and J. Maas, K. Becker, E. R. Jette and F. Foote, and E. C. Bain. G. L. Clark and co-workers observed that nickel catalysts prepared in different ways, and with different activities, all gave identical lattices with a=3.536 Å. W. P. Jesse found the length of the edge of the cubic lattice of nickel at:

Temperature	20°	900°	1000°	1100°	1200°
α Å	3.518	3.568	3.575	3.583	3.592

L. Mazza and A. G. Nasini, G. Hagg and G. Funke, H. Bohlin, R. M. Bozorth, N. Uspensky and S. Konobejewsky found that nickel obtained by electrodeposition, by the decomposition of nickel carbonyl, and by the reduction of the oxide, crystallizes in face-centred cubes. The dimensions of the crystal particles are 10^-2 to 10^-5 cm. The length of the elementary cell is 3.514 Å. L. H. Germer said that with single crystals of nickel, the X-radiograms show patterns due (i) to the face- centred cubic space-lattice of the crystal; (ii) the first or outermost layer of nickel atoms; (iii) a monatomic layer of adsorbed gas; and (iv) an outer thicker layer of absorbed gas. S. Dembinska, and W. Bussem and F. Gross studied the crystal structure of thin films. W. Hume-Rothery studied the relations amongst the lattice constants of nickel, and other elements.

G. Greenwood discussed the fibrous texture of nickel wires. The unit face- centred, cubic lattice of cold-drawn nickel wire has the edge a=3.515 Å.; and the crystals are arranged so that the (111) and (100)-faces are parallel with the axes of the fibres. G. Tammann found that in rolling nickel, the icositetrahedral and octahedral planes tend to form parallel to the surface. W. A. Wood studied the distortion of the lattice with electrodeposited nickel; C. B. Hollabaugh and W. P. Davey, the orientation of the crystals by cold-rolling; S. T. Konobejewsky, and E. van Aubel studied the distortion of the space-lattice by mechanical work; and F. von Goler and G. Sachs, F. Krau, G. Tammann and co-workers, W. A. Wood, E. Schmid, M. Bonzel, G. W. Brindley and F. W. Skiers, W. E. Schmid and E. A. W. Miiller, S. T. Konobejewsky, and C. B. Hollabaugh and W. P. Davey, the effect of cold-rolling on the lattice structure.

Pure, cold-drawn nickel, after various heat-treatments, although sometimes showing peculiar re-crystallization effects, always crystallizes in face-centred, cubic crystals; the re-crystallization cannot be detected by X-ray analysis for temp, up to 940°; the appearance of characteristic re-crystallization structures is observed only when the metal has been annealed at temp, upwards of 1000°. A prolonged annealing at 1200° for 30 hrs. produces coarse grains, irregularly oriented, giving rise to a marked reduction of ductibility and tensile strength. Quenching does not produce any change in the lattice structure. II. Schottky and H. Jungbluth said that the first signs of re-crystallization occur at 500°; and G. Wazau, and Z. Jeffries and R. S. Archer gave 600° for the temp, of re-crystallization, and the theory of the subject was studied by J. A. M. van Liempt. F. Sauerwald discussed the grain-growth of nickel during sintering. G. Tammann and W. Salge gave 200° to 220° for the beginning of re-crystallization.

G. Bredig and R. Allolio said that some samples of electrolytic nickel deposited in an atm. of hydrogen at a few tenths of a mm. press., seemed to have a close- packed, hexagonal structure when that of electrodeposited nickel is a typical face- centred cube, with a=3.514 Å. According to G. Wazau, the structure of electrolytic metal usually consists of parallel lines of crystals packed in layers parallel to the surface of the cathode. After annealing at 600°, in the absence of air, the metal shows signs of re-crystallization characterized by a widening of the lines, and their separation into elongated crystals. After annealing at 900°, the re-crystallization is complete, and the new crystals are the smaller the greater is the press, to which the metal has been previously subjected. The hardness rapidly falls on the annealing temp, changes from 500° to 700°, and it thereafter falls more slowly. Annealing does not reduce the brittleness due to occluded hydrogen. The orientation of the electrodeposited crystals was studied by G. L. Clark and P. K. Frolich, C. Upthegrove and E. M. Baker, G. W. C. Kaye, R. Glocker and E. Kaupp, A. K. Graham, R. M. Bozorth, D. J. Macnaughtan and co-workers, and G. E. Gardam and D. J. Macnaughtan.

L. R. Ingersoll and J. D. Hanawalt found that the film of nickel formed by spluttering the metal in hydrogen is non-magnetic, and it is initially amorphous, or else the crystals are too small to detect. It then crystallizes with a lattice like that of the massive metal, or else the lattice may be more or less distended. The distorted lattice is face-centred and cubic, being about 6 per cent, larger than that of ordinary nickel. If the film be de-gassed by heating it to about 400°, normal crystals are formed. If the nickel be spluttered in nitrogen, a non-magnetic, metallic film is produced, and it has a face-centred, tetragonal lattice with a=3.994 Å., and c=3.760 Å., so that the axial ratio a:c is 1:0.92. Nickel en masse has a face-centred, cubic lattice with a=3.517 A. W. P. Jesse observed no new form of nickel between 450° and 1200°. S. Valentiner and G. Becker observed a normal, face-centred, cubic lattice, with edge a=3.51 A., in all nickel films obtained by spluttering in hydrogen. G. P. Thomson said that films of nickel deposited by spluttering on rock-salt, in an atm. of argon, exhibit a hexagonal structure with a lattice having a=4.06 Å., and c=8.86 Å. This result is different from that observed by G. Bredig and R. Allolio, but G. Bredig and E. Schwarz von Bergkampf found that nickel spluttered from a cathode hydrogen gives a non-magnetic mirror of the metal with a hexagonal lattice, and that if the mirror be heated in hydrogen, the metal then has the ordinary cubic lattice. E. Rupp examined the effect of adsorbed hydrogen on the space-lattice; and O. Werner, the diffusion of radium emanation. V. Kohlschutter and co-workers, M. I. Gen and co-workers, G. D. Preston, M. Miwa, W. Biissem and F. Gross, and S. Dembinska studied the crystal structure of thin films; and H. Reininger, the structure of sprayed films.