Zukünftige Aufgaben der Verfahrenstechnik im Wasser- und Kohlenstoffkreislauf unserer Erde

Future Tasks of Processing Technology in Water and Carbon Cycle of the Earth The consumption of water and energy is very high in the modern industrial society. Energy is produced mostly from fossil fuels. From the material viewpoint, the planet earth is a system with closed cycles. One must therefore ask about the consequences of such high consumption on this cycle. Several contributions of processing technology to intensification of water and carbon cycle are shown. These solutions are compared with processes that have been developed for the maintenance of important cycles in spacecrafts.     

Isolation of two nitrogen-free toxins from tung kernels

Summary A procedure is described for isolating two nitrogen-free toxins from tung kernels and from press cake. Chick-feeding tests were used to determine which fraction was toxic at every separation. Both substances were highly toxic as 10-mg. doses killed 4-day old chicks. These substances were shown by chromatography on glass paper to be different and chromatography homogeneous, but also unstable. The elementary composition, hydroxyl content, saponification value, and specific rotation for the two toxins are given. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U, S. Department of Agriculture.     

Plastic Deformation and the Fracture Surface Energy of Sodium Chloride

A correlation between plastic deformation at crack tips in sodium chloride and the measured value of the fracture surface energy is presented. Plastic deformation can either aid or hinder crack growth, depending on the mode of deformation at the crack tip. If plane-stress deformation occurs, crack motion is hindered by step formation, dislocation generation, and plastic blunting of the crack tip. If plane-strain deformation occurs, crack motion is aided by stress fields that arise from the deformation. The specific surface free energy of sodium chloride, {100} plane, is estimated to be less than 0.37 J/m².     

Structural Aspects of the Lattice Thermal Expansion of Hexagonal Cordierite

The mechanism of lattice thermal expansion in pure hexagonal cordierite prepared by glass devitrification was investigated by time-of-flight neutron powder diffraction at temperatures from 22° to 750°C under vacuum. Full matrix least-squares refinement of the diffraction spectra was carried out in space group P6/mcc using the Rietveld method. The structural data from the refinements were resolved into components parallel and normal to the c axis. The negative c axis expansion results from two effects: (1) increasing distortion of the T₂ tetrahedral (ring tetrahedra) with temperature, primarily due to displacement of the T₂ cations toward the c-axis channels in the structure; (2) decreasing distortion of the T₁/M tetrahedra/ octahedra with increasing temperature, due to octahedral I (M-O₁) bond expansion and an associated decrease in torsional distortion of the T₁ tetrahedra.     

Reciprocating flow ion exchange part II: Application to saline water softening

The “hardness” components in sea water can be considerably reduced by means of a new economical fixed bed technique called “Reciprocating Flow Ion Exchange”, when used in conjunction with a closed cycle exchanger-evaporator system. Removal of 87.9% of the calcium and 54.5% of the magnesium in sea water has been obtained with an overall flow rate of 5.0 U. S. g. p. m./sq. ft. Results from bench scale and a 5,000 g. p. d. pilot plant were identical. The virtually continuous cyclic steady-state process requires a small amount of exchanger (0.5 to 2% of the usual ion exchange methods, such as conventional fixed beds or fluidized beds). The effects of variation in operating parameters are discussed.     

Blackening in yttria stabilized zirconia due to cathodic processes at solid platinum electrodes

The DC cathodic voltage current density (V-J) characteristics at the contact between a solid disc Pt-13% Rh electrode and yttria stabilized zirconia (YZr) electrolyte were investigated to evaluate the conditions under which blackening occurred in the anionic conductor. Polycrystalline and single crystal samples have been studied using oxygen-argon mixtures between 10⁰ and 10^–3 atm oxygen and at temperatures in the range 800 to 1450°C. It is shown that the rate determining step of the overall cathodic reaction, O₂(g)+2Vö+4ear2O _o ^x under low field, ohmic conditions is the first electronation step, but true activation polarization at higher fields is masked by mass transfer limitations. The limiting current density in the polycrystalline material was directly proportional to the oxygen partial pressure whereas at low temperatures, below 1000°C, in the single crystal.The former behaviour is attributed to a flux limit in the ambient oxygen gas, whereas the regime is believed to be a consequence of molecular dissociation, coupled with surface exchange, onto the mobile interfacial layer. It is further shown that blackening is a consequence of thermionic emission of electrons across the cathodic interface into anion vacancy traps and the cathodicV-J characteristics of the blackened material saturate to obey aJV ² law above about 2 V, indicative of a space charge limited current. A tentative model is proposed.     

Influence of Hydrostatic Pressure and Humidity on Superplastic Ductility of Two β-Spodumene Glass-Ceramics

The extent of superplastic deformation in two lithium aluminosilicate glass-ceramics was found to be limited either by intergranular cavitation or by the initiation and growth of surface cracks. Tensile tests were performed under a superimposed hydrostatic pressure to distinguish between the two failure mechanisms. Two materials, one with a high flow stress and the other with a low flow stress, were studied. Cavitation was substantially suppressed by hydrostatic pressure in both materials. The strain-to-fracture, however, was enhanced only in the material with the lower flow stress. (In at least one instance the tensile ductility became almost infinite.) In the material with the higher flow stress, failure was caused by the initiation and propagation of cracks from the surface. The crack-propagation mode of failure was found to be sensitive to humidity, raising the possibility of stress-corrosion cracking at high temperatures in glass-ceramic materials.