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Magnetic Power of Nickel

Nickel becomes non-magnetic when heated above about 350°. J. Plucker observed that the magnetic power of nickel is five times smaller at 350° than it is at 50°. E. Becquerel added that the magnetic power of nickel is completely lost at 400°. Whilst iron undergoes transformations at about 890° and 770° - vide iron - cobalt undergoes a magnetic transformation at about 1143°, and nickel at about 340°, when magnetic, or a-nickel passes into the non-magnetic, or β-nickel. The corresponding transformation with iron is lowered continuously by increasing proportions of nickel up to 25 per cent., so that C. E. Guillaume suggested that α-iron and α-nickel are isomorphous. Similarly, the behaviour of iron alloyed with higher proportions of nickel led F. Osmond, F. Osmond and G. Cartaud, and W. Guertler and G. Tammann to assume that γ-iron and β-nickel form isomorphous mixtures - vide infra, iron-nickel alloys. The magnetic change is often regarded as an allotropic change, but E. C. Bain, and F. Wever found that the space-lattice of nickel at 500° is the same as it is at ordinary temp., and therefore the magnetic change is not due to a rearrangement of the atoms. J. Hopkinson found that an impure sample becomes non-magnetic at 310°, and H. E. J. T. du Bois found 300° for another impure sample. J. M. Gaugain gave 350° for the transition temperature; and, for nickel free from cobalt, of a high degree of chemical purity, and melted in hydrogen, H. Copaux obtained 340°. The point is depressed by the presence of impurities. Various observations, with more or less pure samples, were made by W. Guertler and G. Tammann, 325°; J. Hopkinson, 310°; T. P. Harrison, 374°; P. Curie, 340°; H. Pecheux, 335° to 345°; 1.1. Schukoff, and H. le Chatelier, 340°; E. Janecke, 347° to 360°; P. Weiss and R. Forrer, 357°; P. Weiss and co-workers, 363°; A. Krupkowsky, 368-3°; H. Masumoto, 376°; H. Copaux, 340°; B. Stark and D. Tararczenko, 370°; D. and H. E. Hanson, 348° and 393° respectively obtained from the cooling and heating curves; A. L. Baikoff, 360.80°; K. Honda, 348° to 351°; K. Honda and H. Takagi, 370°; L. Tieri, 355°; W. F. Colby, 280° to 310° for commercial nickel, and 370° to 380° for electrolytic nickel; M. Werner, 352°; R. L. Sanford, and L. Jordan and W. H. Swanger, 370° to 380°, for 99.94 per cent, nickel; J. Dorfman and R. Jaanus, 356.5° to 359.5°; B. V. Hill, 355° for hard nickel, and 340° for annealed nickel; and M. Werner obtained by different methods values ranging from 352° to 360°.

W. del Regno said that the transformation takes place over a range of temp, of 100° between 300° and 400°, M. F. Angell observed that the magnetic transformation temp, of nickel carbide shifted 130° by heat treatment; annealing from high temp, gives a low value, and abrupt cooling produced a value as high as 420°. J. Hopkinson observed no trace of the phenomenon of recalescence as nickel changes from the non-magnetic to the magnetic state in cooling past 310°, but A. L. Baikoff observed a slight break in the differential cooling curve at 360° in agreement with the magnetic transformation of the metal. M. Garvin and A. M. Portevin also studied the cooling curves of nickel. H. C. Cross observed a break in the heating curve of 99.94 per cent, nickel beginning at 351° to 353°, and ending at 357° to 359°; and in the cooling curve beginning at 332° and 351°, and ending at 316° and 342°. There is therefore a thermal transformation at about 350°. A. Perrier and F. Wolfers observed kinks in the heating curve of nickel at 480° and 880°. Observations were also made by M. Faraday, S. Bidwell, A. Heydweiller, C. Drucker, A. Schulze, C. H. M. Jenkins and M. L. V. Gayler, R. Ruer and co-workers, H. A. Rowland and L. Bell, J. A. Ewing and G. C. Cowan, and K. Honda and S. Shimizu. Lord Kelvin discussed the bearing of the phenomenon on the law of the transformation of energy - vide iron. A change at about 700° was observed by C. Tomlinson, T. P. Harrison, W. Schlett, I. I. Schukoff, E. J. Janitzky, M. Werner, E. Cohen, E. Janecke, and P. N. Laschtschenko. According to M. Copisarow, the change variously reported to occur between 345° and 365° is the Curie point which he represents by β⇔γ and that which occurs at about 700° corresponds with the γ⇔δ change in iron. If the A2-arrest is the Curie point of iron the change at about 350° is to be represented as α⇔β change; and the second will be equivalent to the β⇔γ change of iron. C. L. Utterback observed a break in the total radiation of nickel between 1127° and 1170°, indicating some kind of allotropic or internal change.

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