Title: SYNTHESIS AND FABRICATION OF REFRACTORY URANIUM COMPOUNDS. Summary Report, January 1, 1961-March 15, 1962
Abstract: It was concluded that the completeness of the reaction of UO/sub 2/ and carbon to form UC in vacuum furnacing probably depends upon the activity of the specific UO/sub 2/ and carbon, the intimacy of mixing, and the size of pellets heated, as well as time and temperature of heating. Under the conditions of the experiments, there appeared to be no advantage in heating to temperatures higher than 1600 deg C for periods longer than 75 minutes. The product obtained by synthesizing at higher temperatures for longer periods was no purer and was somewhat less sinterable. With the specific UC prepared by synthesis in vacuum at 1600 deg C the optimum conditions for sintering in vacuum appeared to be heating at 1940 deg C for about 80 minutes, Equivalent results were obtained by sintering at atmospheric pressure in flowing helium for 4 hours at 1800 deg C. Average densities were about 90% theoretical. The additives UO/sub 2/ (5%), UO/ sub 2/ (5%), and UN (10%) had but little effect on the bulk density of UC when sintered in vacuum or in helium under the above conditions. The following additives, in powder form, promoted densification of the UC powder used inmore » this investigation: uranium, iron, and nickel. Uranium metal is effective only if the sintering is done under conditions which prohibit its carbonization or oxidation, both of which take place quite readily. Iron is less effective than nickel and appears to promote more rapid grain growth. Nickel was also superior to uranium metal as a densification aid. About 0.1 to 0.2% nickel appeared to be an optimum amount, with an optimum temperature of about 1525 deg C when sintering in helium at atmospheric pressure. The presence of appreciable amounts of iron, uranium metal, and free carbon decreased somewhat the effectiveness of nickel. However, the presence of UO/sub 2/, UO/sub 2/, or UN did not affect the efficiency of nickel, and densities in excess of 95% theoretical were obtained even though these impurities were present in amounts of 5 to 10%. Nickel, in amounts of 0.1 to 0.2%, appeared to promote the formation of U/sub 2/C/sub 3/ when UC powders were sintered at 1525 deg C. Metallographic examinatlon indicated that specimens sintered under the above conditions usually contained at least 15% of a second phase believed to be U/sub 2/C/sub 3/. Chemical analysis indicated that an accurate control of impurity content of specimens prepared for irradiation was not achieved. (auth)« less
Publication Year: 1962
Publication Date: 1962-05-01
Language: en
Type: article
Access and Citation
Cited By Count: 2
AI Researcher Chatbot
Get quick answers to your questions about the article from our AI researcher chatbot