Dry Hydrogen Atmosphere Research Articles

High resistance ratio antimony

Abstract We have zone-refined antimony in a dry hydrogen atmosphere and have obtained a resistance ratio P 300°K/ P 4.2°K of around 6x10 3 for nearly 75% of thr ingot. This is the highest figure yet recorded. Further measurements at 1.6°K show a ratio P 300°K/ P 1.6° of around 13x10 3 .

Developing a method and producing a batch of experimental corundum insulating brick

A rational technology was developed for making corundum insulating material for service in oxidizing and reducing atmospheres at 1500–1550°C. Prolonged operation of the corundum lightweight lining of a test furnace used to anneal transformer steel in a dry hydrogen atmosphere at the Novolipets Metallurgical Factory showed that the use of such refractories substantially improves the quality of the steel.

Effect of Silicon on the Low-Induction Permeability of 4-Molybdenum Permalloy

Using 350-g arc-melted button heats, measurements have been made of the effects of residual silicon on the initial permeability (μ40B) of 4-Moly Permalloy. Cooling rates in the atomic ordering range (1200°–600°F) were varied between 70° and 4750°F/h. Silicon has a considerable effect on cooling rate response, its effect being similar to molybdenum in that it slows down the cooling rate (CRopt) required to develop the best permeability. Since minor variations in nickel and molybdenum content also affect CRopt, it cannot be stated unequivocally that silicon is good or bad for properties. It is demonstrated that if the cooling rate is too fast for a given base composition, silicon is detrimental, while the reverse is true if the cooling rate is too slow for the base composition. However, in the latter case, the benefit of silicon is dependent upon maintaining a dry hydrogen atmosphere during the final anneal; with a −30°F dew-point hydrogen, the improvement is lost due to oxidation of the silicon. Some further effects of dew-point variations during the final anneal on magnetic properties are described in relation to residual silicon and aluminum.

Kinetics of uranium-dioxide sintering between 950°C and 1500°C in dry hydrogen atmosphere

The kinetics of sintering of UO 2 compacts prepared from ammonium diuranate and calcined at 800°C have been studied in the temperature range 950–1500°C, in dry hydrogen atmosphere. The bulk density D s achieved at a desired period, has been determined by measuring the change in the volume of the pellets. At all temperatures studied, the bulk density and the sintering period t have been related by the expression D s = C log t + X, where C and X are constants. From these results the activation energy of the process has been evaluated and the mean value has been found to be 102 ± 10 kcal/mole.

Some techniques for obtaining iron-manganese cermet compounds

1. Some methods for obtaining carbon-free iron-manganese alloys were described. 2. The iron-manganese alloys obtained by sintering powder mixtures contain oxides which cannot be reduced by sintering in a very dry hydrogen atmosphere. 3. It is shown that the method of thermodiffusion infiltration produces porous iron-manganese alloys containing no oxides; these powders can be used for producing poreless compounds. 4. The relationship has been established between the degree of infiltration of iron pressings and iron powder by manganese and the process temperature, porosity, time, and the thickness of the powder layer.

Creep of urania base solid solutions

Sintered uranium dioxide specimens containing soluble additions of CaO, Y 2O 3, ZrO 2 or insoluble additions of SiO 2 were subjected to creep-in-bending tests at temperatures from 1200–1450 °C in a dry hydrogen atmosphere. The soluble additions decreased and SiO 2 additions increased the plasticity of UO 2. Activation energies for steady state creep were determined. Grain boundary sliding and migration occurred during creep of all these materials. Additions of CaO, Y 2O 3 and SiO 2 increased the tendency towards formation of intercrystalline cracks during creep of UO 2.

Anisotropy in Rolled Permalloy Tape

The anisotropy induced in gold-doped Permalloy by cold rolling and subsequent heat treatments has been investigated using a recording torque magnetometer. The material was cold rolled from 0.014 in. to 0.000125 in. and then heat treated for 2 hr in a dry hydrogen atmosphere. The torque curves obtained could be decomposed into a hard and soft component. For fields below 200 oe, the torque curves due to the hard component have a tangent-like shape with the peak a few degrees from the hard direction, while the torque curves due to the soft component have the regular shape corresponding to uniaxial magnetocrystalline anisotropy. Both components are uniaxial with the easy direction along the roll direction. The hard component is independent of the heat treatments up to about 900°C and has an equivalent anisotropy field of the order of several hundred oersteds. The high apparent anisotropy of the hard component and its independence of the heat treatment suggest that this component arises from a magnetostatic effect. By etching the tape it has been shown that the hard component is due to the surface structure of the tape. The surface structure is probably the result of the rolling process. The soft component is strongly dependent upon the heat treatment subsequent to the cold work and almost vanishes at an annealing temperature of about 650°C. This decrease is consistent with the ordered pair mechanism suggested by Chikazumi. The small residual soft component at high annealing temperatures is very sensitive to the rate of quenching. This behavior may indicate the presence of partial ordering and some degree of crystal orientation. The value of the anisotropy field due to the soft component is approximately equal to the measured value of the threshold for rapid rotational flux reversal.

A Study of the Mechanism of Sintering of Metallic Particles

An investigation has been carried out on the mechanism of sintering of metallic particles. Single layers of spherical copper particles have been sintered under varying conditions of time and temperature in a dry hydrogen atmosphere. Analysis of the rate of interface contact between the particles has shown metallic sintering to be a diffusion process, in agreement with the theory of Kuczynski. The heat of activation of self-diffusion of copper has been calculated and found to be 55,000 cal./mole. This is in close agreement with Kuczynski and also values obtained by other workers using the radioactive tracer method.