High Melting Point Metals Research Articles

The glide of single crystals of molybdenum

As pointed out in the paper by Andrade and Tsien, the situation as regards body-centred crystals is such that further information as to the glide element of crystals of this class is needed. In particular, there is considerable uncertainty as to the glide plane, different crystallographic planes being, apparently, operative with different metals. It is possible that with body-centred crystals the planes on which glide takes place depend upon the temperature with reference, say, to the melting point of the metal, since with certain hexagonal crystals such as magnesium, fresh planes have been found to come into operation at high temperatures. Molybdenum, which crystallizes in the body-centred system, has an extremely high melting point, about 2630° C., and so offers a wide range of temperature for experiment. In the following pages work on the glide elements in the temperature range 20 -1000° is described, and it is shown that while the glide plane at the lower temperatures is (112), at high temperature it is (110). The glide direction is in all cases [111], thus confirming the rule that the glide direction is the most closely packed direction. It is hoped later to extend the determinations to higher temperatures. 2—Preparation of the Crystals The crystals were prepared by the method devised by Professor Andrade for metals of high melting point, in which the wire is maintained at a high temperature by a current passing through it, and a local temperature gradient, which slowly travels down the wire, is obtained by a small subsidiary furnace surrounding the wire. For this method it is desirable not to use too thick a wire, and the metal used was 0∙25 mm. in diameter, supplied by the Tungsten Manufacturing Company. If such a wire be maintained by the passage of a current at a temperature some 1000° C. below its melting point, the individual crystallites grow, until the appearance shown in fig. 1, Plate 4 is obtained, where some of the crystals extend right across the wire. The crystal boundaries in this picture have been revealed by etching with dilute nitric acid.

Positive Ray Analysis of Ions from a High Frequency Spark

This paper gives the analysis by the Thomson parabola method of the positive rays of various materials produced by the high frequency spark method developed by Dempster. The spark materials investigated may be classified into three groups, i.e., metals of high melting point, metals of low melting point and minerals. It was found that almost all the ions obtained were atomic and that most of the elements gave multiply charged ions. The change of charges during the passage from the accelerating field to the analyzing field was also observed. Ions of the elements which exist ordinarily in the gaseous state were obtained from the solid compounds of which these elements form constituents. Helium ions were obtained from the radioactive mineral, cleveite (U${\mathrm{O}}_{2}$\ifmmode\cdot\else\textperiodcentered\fi{}U${\mathrm{O}}_{3}$\ifmmode\cdot\else\textperiodcentered\fi{}PO\ifmmode\cdot\else\textperiodcentered\fi{}Th${\mathrm{O}}_{2}$). From the experiments thus far performed, the high frequency spark method has been shown to be able to give strong sources of multiply charged ions of almost all the elements.

SMALL CAST THORIUM OXIDE CRUCIBLES*

ABSTRACTCrucibles were made from thorium oxide by casting from a slip made according to ceramic practice. The presence of cryolite in the slip insured its successful use. These were fired to 1885°C in a gas furnace of special construction. The addition of zirconium oxide makes a crucible easier to manufacture. The finished crucibles were successfully used in vacuum‐induction furnaces to melt pure metals to 2300°C. No contamination of the metals resulted.Expansion curves indicate a peculiar action of the crucibles made with zirconium oxide in the 700 to 900° region. The mean coefficient of expansion of fused thoria is found to be 93 × from 0 to 600°C.These crucibles are found to be (a) fairly resistant to chemical reagents, but not enough so for chemical work and (b) resistant to wetting of molten metals of high melting point.

Obituary notices

The death of Mr. C. T. Heycook, which took place oil June 3, removes from among us one who has gained the affection of generations of Cambridge men and who was a pioneer in an important branch of inorganic chemistry. Heycock was the younger son of Frederick Heycock, of Braunston, Oakham, and was born on August 21, 1858; he received his early education at the Grammar Schools of Bedford and Oakham, and entered King's College, Cam-bridge, as an Exhibitioner in 1877, taking the Natural Sciences Tripos in 1880. For many years he taught Chemistry, Physics and Mineralogy for the Cambridge examinations and in 1895 he was elected to a Fellowship at King’s College, becoming a College lecturer and Natural Sciences Tutor in the following year, lie was elected a Fellow of the Royal Society in 1895 and was awarded the Davy Medal in 1920 for his work on alloys. His original work on the metals attracted the attention of the Goldsmiths Company who endowed a Readership in Metallurgy at Cambridge; he was appointed to this office in 1908 and held it until his retirement in 1928. He was admitted to the Livery of the Gold-smiths Company in 1909 and to the Court in 1913; he acted as Prime Warden during the year 1922-1923 and took a been interest in the work of the Company’s Assay Office. Notwithstanding the exacting character of his work as a Cambridge coach, Heycock joined with his lifelong friend, F. H. Neville, F.R.S., in a comprehensive study of the metals and their alloys; this partnership, which was only dissolved by the death of Neville in 1915, led to a remarkable series of papers in which novel directions of investigation were mapped out and developed. Before entering upon this joint work, Heycock had had some experience as an investigator; in 1876 he published a not on the spectrum of indium in conjunction with Mr. A. W. Clayden, M. A., and in 1882 he contributed a paper on the atomic weight of rubidium at the British Association meeting. Heycock and Neville’s first joint paper was published in 1884 and described a redetermination of the molecular weight of ozone by the diffusion method. The first of the series of papers on the metals was published in 1889 and dealt with the depression of the freezing points of metals brought about by others dissolved therein; in this, and later papers, it was shown that the addition of small amounts of a second metal depresses the freezing point of the first to an extent (1) directly proportionate to the weight, of metal added, and (2) in rough inverse proportion to the atomic or molecular weight of the added metal. Raoult’s law for ordinary solutions was thus extended to alloys and a method indicated for calculating the latent heat of fusion of a metal by the application to the freezing point depressions of the now well-known van't Hoff equation. At the outset mercury thermometers were used in the temperature measurements and only alloys of low melting points could be studied: the introduction by H. L. Callendar of the platinum resistance pyrometer made it possible to extend the scope of the investigation to metals of high melting point. At that time the melting points of silver, gold and copper were not known with any degree of accuracy, partly because of the difficulty of making the physical measurements, partly because the necessity for using metals of high chemical purity and for protecting them from contamination during melting had not been recognised. A number of fixed points on the platinum resistance pyrometer had to be established before the study of alloys of high melting points was undertaken; these fixed points were determined with the aid of Dr. E. H. Griffiths, F. R. S., and with such accuracy that the results obtained by their use have not since been seriously affected. Thus, Heycock and Neville determined the melting point of Levol’s alloy as 778.7° C. and used this constant as a secondary fixed point; a very recent determination by the Washington Bureau of Standards gives the melting point as 779.4°.

Excitation Processes in the Hollow Cathode Discharge

The low potential gradients in the negative glow in a hollow cathode discharge in a rare gas make it a favorable source for the excitation of metallic spark spectra. The metal studied forms the cathode, and is brought into the discharge by cathode sputtering or evaporation. The excitation is limited by collisions of the second kind between gas and metal atoms and ions. The spectroscopic data of all the available cases have been examined to see what determines the processes occurring. In general only those processes occur in which the metal can be excited to some term in the spark spectrum with gain or loss of only a small amount of kinetic energy to balance the reaction equation. High melting point metals or those which sputter poorly cathodically enter the discharge in helium in the normal state or in a low metastable state of the atom. With low boiling points metals appreciable numbers of metal ions enter the reactions. In intermediate cases or in argon or neon, it is not always possible to predict if metal ions will enter the reaction or not. The conditions which determine the results are discussed.

Process of Refining Lead and Lead Alloys

This invention relates to a method of improving the mechanical properties of lead and lead alloys and more particularly to a method of alloying certain high melting-point metals with lead or lead alloys at comparatively low temperatures. A certain kind of commercial pig lead, such as Southeastern...