F.A. Schmidt

Electrotransport of interstitial atoms in yttrium

Abstract The electrotransport velocities of carbon, oxygen and nitrogen in yttrium were determined in the temperature range of 1235 to 1460°C. Diffusion coefficients and effective charges were calculated for these elements for the same temperatures. Yttrium metal purified by the electrotransport method showed a decrease in oxygen content from 780 to 90 p.p.m. and an increase in the resistance ratio from 12 to 45.

ELECTROTRANSPORT OF CARBON, NITROGEN, AND OXYGEN IN GADOLINIUM.

Abstract The electrotransport velocities of carbon, nitrogen and oxygen were measured in both the alpha and beta crystalline forms of gadolinium. Measurements were made at 1050, 1125, 1200 and 1265 °C. All three solutes migrated in the same direction as the electron flow but much higher mobilities were observed in the β (b.c.c.) form. Diffusion coefficients and effective valences were calculated for these elements at the same temperatures. Electrotransport was shown to be an effective method of purifying a small amount of gadolinium as indicated by resistance ratio measurements.

The yttrium-germanium system

Abstract The yttrium-germanium system has been investigated by thermal, microscopic, chemical and X-ray analyses. Germanium lowers the transformation temperature of yttrium from 1473 °C to 1460 °C by an inverse peritectic reaction. There is a eutectic reaction at 12 at. % germanium and 1280 °C between yttrium and the compound Y5Ge3, which melts congruently at 1965 °C. Another eutectic occurs at 88 at. % germanium and 820 °C between germanium and YGe3.5, which forms peritectically at 860 °C. There are six additional compounds in the system that result from peritectic reactions, namely, Y5Ge44 at 1945 °C; Y11Ge10 at 1900 °C; YGe at 1730 °C; Y2Ge3 at 1460 °C; YGe1.7 at 910 °C and YGe2 at 880 °C. The compound Y2Ge3 undergoes a polymorphic transformation at 1430 °C. New evidence concerning the crystal structures of Y2Ge2 and YGe1.7 which involve the A1B2 defect and the ThSi2 defect structure types, respectively, was obtained. The compounds YGe2 and YGe3.5 decompose eutectoidally at 760 °C and 710 °C, respectively, and their crystal structures are discussed.

ELECTROTRANSPORT OF CARBON IN NIOBIUM AND TANTALUM.

The electrotransport velocity of carbon in niobium and tantalum was measured at temperatures above 1900 °C using 14C as a tracer. In both metals carbon was found to migrate in the opposite direction to the electron flow. The diffusion coefficients and effective charge were also calculated for this solute at the same temperatures. n nA least-squares treatment was made of the combined diffusion data of this study and that obtained at lower temperatures by other investigators. Values of D0 and ΔH in the equation D = D0 exp (-gDH/RT), were determined for the extended temperature range and are as follows; niobium tantalum.

Purification of rare-earth metals by electrotransport

Abstract The principles of the electrotransport purification process are described, together with those variables that affect the degree of purity attainable. Experiments on the purification of yttrium, lutetium and gadolinium with respect to carbon, nitrogen and oxygen are described and the results compared with those predicted from theory. Metal purities were evaluated by resistance ratio measurements and chemical analyses.

PREPARATION OF HIGH PURITY THORIUM AND THORIUM SINGLE CRYSTALS.

Abstract Ultra-high purity thorium has been prepared using electrotransport as the refining method. This metal has a total impurity content of less than 50 p.p.m. and a resistance ratio of greater than 1000. A procedure was also developed by which single crystals of the high purity thorium could be prepared by repeated heating of the specimen through its alpha to beta phase transformation followed by prolonged heating just below the transformation temperature.

Yttrium-tin alloy system☆

Abstract A phase diagram is proposed for the yttrium-tin system based on thermal, microscopic and X-ray evidence. Tin additions lower the transformation temperature of pure yttrium from 1465 ° to 1360 °C by an inverse peritectic reaction while yttrium additions decrease the melting point of tin from 232 ° to 229 °C by a eutectic reaction. There is also a eutectic at 11.5 at.% tin and 1260 °C between yttrium and the compound Y 5 Sn 3 , which melts congruently at 1940 °C. There are four additional compounds in the system which result from peritectic reactions. The compositions of these compounds were determined to be Y 5 Sn 4 Y 11 Sn 10 , YSn 2 and YSn 3 . Horizontals associated with the decomposition of these compounds occur at 1790 °; 1600 °, 1140 ° and 515 °C, respectively.

Yttrium-antimony alloy system☆

Abstract A phase diagram is proposed for the yttrium-antimony system based on thermal, microscopic, chemical and X-ray analyses. An inverted peritectic reaction develops as a result of antimony additions, lowering the 1475° C transformation temperature of yttrium to 1462° C. Eutectic reactions occur at 14.5 at. % antimony and 1220° C, and greater than 99.0 at.% antimony and 629° C. There are four compounds in the system. The compound YSb melts congruently at 2310° C while Y 3 Sb and Y 5 Sb 3 result from peritectic reactions at 1240° and 1690° C. The fourth compound, Y 4 Sb 3 , forms peritectically at 2120° C, but decomposes by a eutectoid reaction at 1660° C.

The effect of low percentage alloying additions on the ductility of iodide chromium

Abstract The ductility of binary chromium-base alloys containing 0.1, 0.5, 1.5, and 3.0 wt. % of 34 different metals was evaluated from bend tests on arc-melted specimens. The results of this investigation indicate that the brittle-ductile transition temperature of chromium-base alloys is dependent primarily on the atomic size of the alloying addition. The transition temperature of iodide chromium is decreased by the addition of solute atoms that form solid solution alloys and have atomic diameters larger than chromium but not exceeding the 15% size limit. Those elements with atomic diameters between 2 and 10% larger produce the maximum decrease in the brittle-ductile transition temperature. Those alloying additions which exhibit little or no solid solubility in chromium and have atomic diameters that exceed the 15% limit all raise the transition temperature of high purity chromium. Additions of those metals that form carbides, nitrides, and oxides that are more stable than the corresponding chromium compounds increase the brittle-ductile transition temperature rather sharply, which is the converse of what has previously been observed on chromium of lesser purity.

The yttrium-bismuth alloy system☆

Abstract The yttrium-bismuth alloy system was studied using microscopic, X-ray, thermal, and chemical analyses. An inverted peritectic reaction develops as a result of bismuth additions lowering the 1475 °C transformation temperature of yttrium to 1460 °C. Eutectic reactions occur at 18.5 at.% Bi and 1145 °C, and greater than 99.9 at.% Bi and 209 °C. There are only two intermetallic compounds in the system. The compound YBi melts congruently at 2020 °C and Y 5 Bi 3 results from a peritectic reaction at 1530 °C. The crystal structure of this second compound is discussed.