Beta Transformation Research Articles

The effects of high pressure on the alpha /ai beta transformation in plutonium

The volume change during the β → α transformation in plutonium varies linearly with pressure according to the relationship Δ V V = 9.2−0.17 P , where Δ V V is the per cent change in unit volume and P is the applied pressure. The temperature hysteresis associated with the α /ai β transition is shown to be a function of internal transformation stress and applied pressure, decreasing from its maximum of 55° K at atmospheric pressure to 5° K at 25 kbar. The heat of transformation calculated from the Clausius Clapeyron equation and P- V- T data remains constant to pressures of 60 kbar.

Phase relations and structures in uranium-plutonium-fissium alloys

Alloys of U with 20 wt % Pu and various additions of a group of fission product elements termed “fissium” were investigated and their transformations, structures and melting points are reported. Additions of fissium, which was composed of the elements Ru, Mo, Pd, Te, Rh, Nb and Zr stabilized the gamma and beta uranium phases down to 555° C. At high fissium contents the beta transformation was entirely suppressed. Alpha uranium, gamma-prime and zeta were the stable phases at temperatures below 400° C. A primary phase “theta” with an unknown crystal structure was present in all the compositions studied. Lattice constants are given for alpha and gamma uranium and some intermetallic phases.

Kinetics of Structural Changes during Beta Transformation of Uranium

When uranium with preferred orientation is heat treated at low beta phase temperatures and cooled in air, grain coarsening proceeds at a more rapid rate than the loss of preferred orientation. Quenching into water from the beta temperature increases the rate of loss of preferred orientation and refines the grain size.To account for these effects, it is postulated that the transformation from the highly oriented alpha phase to the beta phase is incomplete in short times at low beta phase temperatures, and that during cooling the residual alpha grains serve as centers for retransformation to an oriented, large-grained alpha phase. Quenching increases nucleation from the beta phase, and results in a structure that is finer grained and more randomly oriented.

Nature de la transformation α → β de l'uranium au voisinage de l'equilibre

> It is well established that the transformations in weakly alloyed uranium are martensitic at low temperatures. On the other hand, the nature of the transformations in the neighborhood of equilibrium is very controversial. Of the two theses (transformation by germination and growth and martensitic transformation) argued, the thesis of germination and growth proves the alpha in equilibrium BETA transformation of uranium in the vicinity of equilibrium. The phase transformation kinetics show no martensitic transformation in the vicinity of the equilibrium temperature. (N.W.R.)

Eine neue Wertigkeitsstufe des Technetiums

By neutron irradiation of di-benzyl-molybdenum (O), a cation of technetium was obtained in carrier scale after beta transformation of the Mo/sup 99/. The cation is stable in air and 2 N acids and electrolytes. On the basis of its origin and its chemical properties, the cation complex is probably dibenzyl-technetium(I). (J.S.R.)

Phase diagram for the Zr-Be system: V. S. Emel'Yanov, Yu. G. Godin, A. I. Evstyukhin and A. A. Rusakov

Metallographic, thermal, and x-ray methods were used in qualitative phase analyses of beryllium- zirconium systems. Hardness measurements were taken, and the constitution diagram was plotted. The studies revealed four intermediate phases: ZrBe/sub 2/, ZrBe/sub 6/, ZrBe/sub 9/, and ZrBe/syb 13./. The first three form by peritectic reactions at an open maximum at 1645 deg C. A eutectic forms at 965 deg C and 5 wt.% Be between ZrBe/sub 2/ and zirconium. Additions of beryllium to zirconium reduce the temperature of alpha yields beta transformations and form eutectoids at 800 deg . Beryllium solubility in alpha zirconium is less than 0.1 wt.% and in beta zirconium less than 0.3 wt.%. Zirconium solubility in beryllium does not exceed 0.3 wt.%. (tr-auth)

Isomeric Effects in Fragmentation by Beta Decay: Monotritiated Propanes and Toluenes

The spectra of positively charged fragments from beta decay of tritium in primary and secondary monotritiated propane and in o-, m-, p-, and α-monotritiated toluene have been determined by mass spectrometric techniques. Although the number of products from decomposition of each molecule is quite large, the mass patterns from the two propanes are fairly similar while the four mass spectra from the isomeric tritiated toluenes are very nearly the same. These results suggest that the influence of the location of the radioactive atom in the molecule on the fragmentation following beta decay is often obscured by secondary processes, such as radiationless transitions, H-atom migration, and other rearrangements of the excited molecular ion before breakup. However, there are significant differences within the two groups of mass spectra. Some of the differences in the propane patterns are consistent with the greater stability of the secondary propyl structure as compared to that of the primary isomer. Energetically plausible decomposition schemes for the tritiated propanes are proposed. The distributions of excitation energies made available to the daughter molecular ions (C3H7He3)+ in the beta transformation of H3 to He3 are estimated.

X-Ray Diffraction Patterns and Alpha–Beta Transformation of a Protein extracted from the Human Epidermis

X-Ray Diffraction Patterns and Alpha–Beta Transformation of a Protein extracted from the Human Epidermis

The reality of neutrinos

In the year 1914 a young (at that time) British physicist, James Chadwick, who was sent to Germany to study the phenomena of radioactive decay, came across a rather interesting but, as it looked then, not very important discovery. He found that electrons emitted by radioactive substances in the process called beta transformation do not all possess the same velocity. In fact their velocities vary over a rather wide range.

The Beta′-Beta Transformation in Lithium-Lead Alloys

Measurements made by Grube and Klaiber in 1934 on the alloys of lithium and lead indicate that a transformation of peculiar character occurs in the beta-phase of these alloys. The behavior of this transformation under high hydrostatic pressure has been investigated by measurements of the electrical resistance. The results, together with those from rough thermal expansion measurements, indicate that the transition takes place gradually on heating from a phase of abnormally high energy and entropy content to a phase of more normal character. X-ray analyses suggest that the transition is accompanied by movements of the lithium atoms in the lattice to more orderly positions.

An x-ray study of the beta transformation in copper-zinc alloys

An x-ray study of the beta transformation in copper-zinc alloys