Direct synthesis and characterization of the Fe3+ analogue of Naβ″-alumina

A new isomorphic analogue of-alumina, a potassium-free Na-ferrite (Na₂O · 5 (Al_0.10Fe_1.90)O₃, referred to as Na-ferrite), has been synthesized and is characterized using X-ray powder and single crystal diffraction, wet chemical analysis, and transmission electron microscopy (TEM). In addition, Na-aluminate-gallate-ferrate phases were also successfully synthesized, but were not characterized in detail. Na-ferrite grew in a slowly cooling melt or partial melt from 1250° C in air using Na₂CO₃ and Fe₃O₄ (magnetite) as starting materials. The compound was also synthesized using-Fe₂O₃ instead of Fe₃O₄ under the same conditions, but its abundance was much less and-Fe₂O₃ and NaFeO₂ were the dominant phases. The new material (cell dimensionsa = 0.5955,c = 3.5623 nm) is reversibly hygroscopic, andc increases 2% after hydration. TEM images dearly show the 1.19 nm lattice spacing corresponding to the ionic conduction planes, and these planes are observed to be both straight and curled. The origin of the curled lattice planes, the existence of which is also evident in the single crystal precession photographs, is not clear, although we believe it may involve a structural misfit between the ferric oxide spineI block and soda layer.     

Electrochemical determination of rusted steel surface stability

The stability of a rusted steel surface exposed to a 0.11 M sodium sulphate solution has been studied. Electrochemical impedance spectroscopy, polarization resistance and atomic absorption analysis techniques were used in conjunction with mild steel specimens rusted in a rural atmosphere and treated with different concentrations of phosphoric acid. Since most of the impedance diagrams obtained differ from the typical semicircle, it is not clear how to obtain kinetic information on the corrosion process. The polarization resistance technique gives more useful data.     

Abrasion Resistance of Field-Assisted Ion-Exchanged Glass

The fracture strength of HF-etched samples was measured as a function of field-assisted K-Na ion exchange depth, as well as the severity of abrasion. As expected, the more severe the abrasion, the greater the depth required to make the strength insensitive to abrasion. An abrasion-independent weakening mechanism that increased with exchange depth was also found to be operative.     

Toughening by Metallic Lamina in Nickel/Alumina Composites

Tape casting and hot-pressing were used to produce metal/ alumina laminate composites. The mechanical behavior of these laminates was characterized. The strength and toughness of the laminates were greatly improved in comparison to that of monolithic alumina. Indentation strength values of the laminates remained approximately constant for indent loads between 10 and 100 N. Thus, this type of laminate appears to be a good candidate for damage-tolerant composite material design.     

HEAT TRANSFER IN PARTIALLY MISCIBLE TERNARY SYSTEMS

In the study of mass transfer between partially miscible liquids, temperature perturbations have been found to have an important effect in the generation of interfacial activity. Micro- and macro-generated interfacial convection usually occurs in combination with one another even in fairly simple heat or mass transfer events. These combinations are responsible for the enhancement of mass transfer rates. In an effort to acquire a better understanding of the heat transfer effects in ternary liquid-liquid systems, temperature difference profiles were measured when contacting two partially miscible phases. A vertical and a rotational transfer cell were designed to contact the partially miscible phases without inducing external disturbances. Five thermocouples were immersed in the bottom liquid phase at predetermined positions below the interface. In order to understand the influence of the convection generated, the vertical cell was designed to hinder convection in one phase, while the rotational cell permits convection in both phases. The experimental results showed larger temperature differences in the rotational cell after the contact of the phases. Also, systems which were initially unsaturated presented larger heat effects than those in which the partially miscible solvents were initially saturated. Several parameters indicating the importance of heat effects in the ternary systems studied are reported.     

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.     

Processing and Properties of Particulate Composites from Coated Powders

A method is described for sintering of highly loaded (≤20 vol%) alumina matrix/silicon carbide whisker or platelet composites to closed porosity. The method uses controlled heterogeneous precipitation in a suspension of whiskers or platelets. The suspension-coated particles are calcined to produce a free-flowing composite powder which can be hot-pressed or free-sintered to high density. The results of consolidation and mechanical property testing are reported.     

Effect of eicosa-5,8,11,14-tetraynoic acid on fatty acid composition of selected organs in the rat

Eicosa-5,8,11,14-tetraynoic acid or arachidonic acid or no supplement (controls) was given orally to rats maintained on a fat free diet and the fatty acid composition of total lipids of several organs determined. No changes were noted in the total fatty acid concentrations of the organs examined in the various groups. A decrease in the amount of arachidonic acid, 22∶4ω6 and 22∶5ω6 (as percent of total fatty acids), and an increase in the amount of 20∶3ω6 and linoleate were observed in total lipids of several organs. In the group receiving the arachidonate supplement, there was less linoleate and 20∶3ω6 and more arachidonate than in the controls. Both eicosa-5,8,11,14-tetraynoic acid and arachidonate supplements resulted in a decrease in 20∶3ω9 in most organs studied. Generally, the most marked changes were seen in liver but, of the other organs examined (heart, kidney, testis, brain, and adrenals), only the adrenals failed to show any significant differences between the controls and each of the two supplemented groups. Although the experimental conditions preclude conclusive interpretation of the changes observed, it is suggested that eicosa-5,8,11,14-tetraynoic acid was effective in inhibiting the conversion of linoleate to arachidonate and the conversion of arachidonate to 22∶4 and 22∶5.     

Suitability of commercial cottonseed for producing edible high protein flours by liquid classification

The 1976 and 1977 crops of glanded cottonseed from oil mills located in 7 major U.S. cottonbelt growing areas were evaluated as to their suitability for processing into edible, high-protein flours. Both the physical and chemical characteristics of fuzzy seed samples were studied. Ginned seed samples were hulled, dried, comminuted, slurried with hexane and liquid classified by both a laboratory differential settling test (DST) and pilot plant liquid cyclone process (LCP). Liquid cyclone operating data and extensive analytical data of the kernels, flour and meals produced are shown. A free gossypol level of 1.10% or less in full fat kernels was the determining factor for producing edible flours from glanded seed by the LCP. The Lower Rio Grande Valley area was the only area from which liquid classified cottonseed flour consistently exceeded the current maximal free gossypol standard of 450 ppm. Ca. 94% of the total U.S. cottonseed production is suitable for producing edible, high-protein flours by liquid classification.     

Separation and identification of phenolic acids and related compounds by gas chromatography and fourier transform infrared spectroscopy

Phenolic acids and related compounds were separated by gas chromatography using three separate columns. One of these columns was coupled to a Fourier transform infrared spectrometer. The trimethylsilyl derivatives could be separated and identified by comparing the relative retention times of the three different columns. However, where there was overlap, the accompanying infrared data clearly distinguished between the questionable derivatives, thus enabling characterization of all derivatives.The use of trade, firm, or corporation names in this article is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture or the Forest Service of any product or service to the exclusion of others that may be suitable.