Study of the reduction of UO2 by magnesium or calcium dissolved in molten chlorides

The reduction of solid UO₂ to uranium by magnesium or calcium dissolved in their molten chlorides has been studied. The rate of reduction per unit area of UO₂ surface, at constant temperature and concentration of reductant in the molten chloride, was found to increase with time to a constant value. The rate of reduction per unit area was observed to be proportional to the concentration of reductant in the molten salt. The small increase observed in the reaction rate over the temperature range 750° to 850°C, suggests that the reduction is controlled by transport of the reductant to the reaction site. Solidified salt, containing UO₂ pellets which had been partially reduced, was sectioned, polished, and examined microscopically. The products of the reduction reaction form concentric layers around the UO₂ pellets. Layers of metallic uranium and oxide containing small amounts of dispersed salt alternated with layers of salt containing small amounts of metallic uranium and oxide. The layers ruptured, presumably because the volume of the products, uranium and oxide, is greater than the volume of the UO₂. Therefore, an impervious layer did not form on the oxide surface to inhibit the reduction reaction.     

Review of Toward a Psychology of the Scientist.

Reviews the book, Toward a Psychology of the Scientist by Sonja C. Graver (1981). The major themes of this highly condensed 92 page book are that all sciences are philosophic and that psychological research provides insight into how scientists formulate and revise theories. The author further contends that the development of science would be enhanced if all scientists (including psychologists) understood the primary importance of the role of theory, imagination and creativity in experimentation. The scientific model suggested is that progress in science occurs by way of reformulations of arbitrary world views, and that scientific activities would be enhanced if the subjective and psychological, particularly cognitive, aspects were stressed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An improved numerical interconversion for creep compliance and relaxation modulus

An imporved method for the numerical evaluation of the convolution integral in the relationship between creep compliance and relaxation modulus is discussed. The better approximation is obtained by the assumption that both functions can be assumed to be linear within a series of increasing time intervals which do not change as the calculation progresses. The calculation is carried out on both hypothetical and real examples which substantiates its applicability and accuracy.     

Thermodynamics of cadmium- and zinc-rich alloys in the Cd−La,Cd−Ce,Cd−Pr,Zn−La,Zn−Ce and Zn−Pr systems

The thermodynamics of the cadmium- and zinc-rich alloys in the Cd?La, Cd?Ce, Cd?Pr, Zn?La, Zn?Ce, and Zn?Pr systems have been studied with a high-temperature galvanic cell method. The values of the standard free energy of formation (kcal per mole) of the intermetallic compounds are given by the equations: $$\begin{gathered} (LaCd_{11} ), \Delta Gf^ \circ = - 72.3 + 43.6 \times 10^{ - 3} T (670^ \circ to 804^ \circ K) \hfill \\ (CeCd_{11} ), \Delta Gf^ \circ = - 70.5 + 44.6 \times 10^{ - 3} T (638^ \circ to 884^ \circ K) \hfill \\ (PrCd_{11} ), \Delta Gf^ \circ = - 69.1 + 44.8 \times 10^{ - 3} T (635^ \circ to 825^ \circ K) \hfill \\ (LaZn_{11} ), \Delta Gf^ \circ = - 92.6 + 48.0 \times 10^{ - 3} T (705^ \circ to 793^ \circ K) \hfill \\ (CeZn_{11} ), \Delta Gf^ \circ = - 87.9 + 45.0 \times 10^{ - 3} T (710^ \circ to 1018^ \circ K) \hfill \\ (PrZn_{11} ), \Delta Gf^ \circ = - 85.3 + 42.7 \times 10^{ - 3} T (696^ \circ to 875^ \circ K) \hfill \\ \end{gathered} $$ Equations are also given for the partial molar excess free energies of the lanthanide in dilute solutions of the lanthanide in liquid cadmium or zinc. The enthalpy of formation of the intermetallic compounds is discussed in terms of the crystalline structure of these intermetallic compounds. It is shown that the enthalpy of formation is a linear function of the ration/V _c , wheren is the number of zinc or cadmium atoms which are near-neighbors of the lanthanide atom andV _c is the volume of the cage formed by the near-neighbor cadmium or zinc atoms. A linear dependence of the enthalpy of formation onn/V _c is also found for the intermetallic compounds in several other binary systems. These empirical correlations are discussed in terms of a model which involves localized bonds between the lanthanide and zinc or cadmium atoms.     

Catalytic Synthesis of Chemicals from Coal

Abstract

While the oil and gas needed for the production of chemicals in the United States is only a small percentage of the total oil and gas consumed, the manufacture and use of chemicals from these hydrocarbons has a tremendous impact on the economy of the country. A study by A. D. Little, Inc. [1] in 1973 showed that the impact of a 15% decline in production of organic chemicals could result via a “multiplier” effect in a loss of over 1,700,000 jobs and a $65 to 70 billion loss in the production value of goods. One need only look around to see how pervasive and ubiquitous chemicals from petroleum products are in everyday life; our clothes, our food (fertilizers), all sorts of polymers, plastics, drugs and medicinal, tires, tubing, building materials, automobile interiors-the list is long and verge important to the economic health and growth of the country.     

Infrared Reflection Spectroscopy and Effective Medium Modeling of As-Anodized and Oxidized Porous Silicon Carbide

We present a study of the infrared reflectance of porous silicon carbide (PSC) formed by the electrochemical dissolution of silicon carbide substrates of both 6H and 4H polytypes. The reflectance from n-PSC, both as-anodized and passivated, is reported for the first time. The passivation of PSC has been accomplished using a short thermal oxidation. Fourier transform infrared (FTIR) reflectance spectroscopy is employed ex situ after different stages of the thermal oxidation process. The characteristics of the reststrahlen band normally observed in bulk SiC are altered by anodization; further changes in the reflectance spectra occur following oxidation for different periods of time. An effective medium theory model that includes air, SiC and SiO₂ as component materials is shown to characterize the observed changes in the reflectance spectra after different stages of PSC oxidation.