Influence of silicon on the growth of barrier-type anodic films on titanium

Amorphous anodic titania, stabilised by incorporation of silicon species, is shown to grow to high voltages on sputter-deposited, single-phase Ti-Si alloys during anodizing at a constant current density in ammonium pentaborate electrolyte. The films comprise two main layers, with silicon species confined to the inner layers. An amorphous-to-crystalline transition occurs at ∼60 V on the Ti-6 at.% Si alloy, while the transition is suppressed to voltages above 140 V on alloys with 12 and 26 at.% silicon. The crystalline oxide, nucleated at a depth of ∼40% of the film thickness, is associated with the presence of a precursor of crystalline oxide in the pre-existing air-formed oxide. The modified structure of the air-formed oxide due to increased incorporation of silicon species suppresses the amorphous-to-crystalline transition until the onset of dielectric breakdown. The transport numbers of cations and anions during growth of the anodic oxides are independent of the concentration of silicon species in the inner layer, despite the marked change in the field strength.     

Pro- und Antioxydantien auf dem Fettgebiet XVII: Fette und Fettstoffwechsel der Winterschläfer, 1. Mitteilung: Der Siebenschläfer (Glis glis L.)

Pro- and Antioxidants in the Field of Fats XVII: Fats and Fat-metabolism of Hibernating Animals I. The Seven Sleepers. (Glis glis L.) After a short review of the literature about hibernation, the analysis of the lipids of the seven sleepers (Glis glis L.) is given. The problem, whether the yellow lipochrome results from the autoxidation of polyenoic fatty acids because of the decrease in biological antioxidants, especially vitamin E, could not be completely explained. The brown tissue, the socalled “sleep gland” contains substances which are insoluble in fat solvents and probably formed by the reaction of polyenes with proteins or by the autoxidation of lipoproteins which contain them.     

Thermal Conductivity/Diffusivity of Silicon Carbide Whisker Reinforced Mullite

The thermal conductivity and diffusivity of silicon carbide whisker reinforced mullite was shown to increase with whisker content. This effect was much greater for vapor-liquid-solid (VLS) whiskers than for rice-hull (RH) whiskers. This suggests that the thermal conductivity for the VLS whiskers was significantly higher than for the RH whiskers. Due to preferred orientation of the whiskers, thermal conductivity and diffusivity of the composite samples exhibited significant anisotropy.     

Cure kinetics of neat and graphite-fiber-reinforced epoxy formulations

An investigation was carried out into the cure kinetics of neat and graphite fiber-reinforced epoxy formulation, composed of tetraglycidyl 4,4′-diaminodiphenyl methane (TGDDM) resin and diaminodiphenyl sulfone (DDS) curing agent. Two experimental techniques were employed: isothermal differential scanning calorimetry (IDSC) and dynamic differential scanning calorimetry (DDSC). An autocatalytic mechanism with the overall reaction rate order of 2 was found to describe adequately the cure kinetics, of the neat resin and the composite. All kinetic parameters, including reaction rate constants, activation energies and preexponential factors, were calculated and reported. The presence of graphite fibers in the composite had only a very small initial effect on the kinetics of cure.     

Mechanical properties of moist agglomerates in relation to granulation mechanisms part I. Deformability of moist,densified agglomerates

The mechanical properties of moist samples of fine, polydisperse powders are investigated by measuring the tensile strength by a diametrical compression test and the stress—strain relationship of samples exposed to uniaxial compression. The strengths determined by the two methods correlate well. The strength of moist samples compressed to porosities comparable to the level of intragranular porosities achieved by granulation in high-speed mixers is shown to be influenced significantly by particle interactions in addition to mobile liquid bondings. For a particular material the strength is controlled mainly by porosity and liquid saturation. It is shown that the effect of a growing liquid saturation is to reduce particle interactions and thus to facilitate densification during granulation. The deformability of moist samples, which is dependent on strength and deformation behaviour, is assessed for lactose and dicalcium phosphate.     

Secondary products from high pressure hydrogenation of crambe oil

Hydrogenation of crambe oil, mainly an α,α’-dierucoyl triglyceride, in the presence of cadmium promoted copper-chromite provides long chain waxes being sought as sperm whale oil replacements. Gas liquid chromatography and gas chromatography-mass spectrometry analyses of secondary products indicate, however, that reduction proceeds rather differently from Adkins-type hydrogenations of triglycerides over copper-chromium oxide catalysts. Monoand diunsaturated alkenes ranging from C₁₆-C₂₄, odd chain lengths included, constitute ca. 1% of the product. Esters of crambe acids with methyl, ethyl, n-propyl, and isopropyl alcohols account for less than 5%. These alcohols and traces of 1,2-propanediol from the hydrogenolysis of glycerol occur in either the head gas or the reaction mixture or both. In contrast to published results for Adkins-type hydrogenations of triglycerides, n-propyl alcohol is far more abundant than isopropyl alcohol or 1,2-propanediol. Isopropyl esters of C-18 acids are not present, and those of C-22 acids constitute no more than 2% of the total esters. Low proportion of isopropyl esters and enrichment of C-22 acids in the secondary products compared with C-18 acids suggest that the acyl substituent at the β-position of glycerol is eliminated during hydrogenation of crambe oil with a Cd−Cu−Cr catalyst. Presented at the AOCS Meeting, Mexico City, April 1974. ARS, USDA.     

Analysis and monitoring oftrans-isomerization by IR attenuated total reflectance spectrophotometry

Attenuated total reflectance for IR determination oftrans-isomers in fats appears to have distinct advantages over procedures currently used. The AOCS standard method CD 14-61 requires weighing and quantitative dilution of a sample with carbon disulfide before spectrophotometric analysis at 10.3 μm. In contrast, according to the attenuated total reflectance analytical procedure, one neither weighs nor dilutes but merely fills the cell with oil and reads at 10.3 μm. In addition to analyses fortrans-isomers in liquid oils, margarines and shortenings, attenuated total reflectance enables one to monitortrans-development continuously during hydrogenation. The presence of catalyst in unfiltered hydrogenated oils does not interfere with attenuated total reflectance measurements in contrast to classical transmission measurements. Unfiltered oil from the hydrogenator can be circulated through the attenuated total reflectance cell to recordtrans-isomerization during the reaction. ARS, USDA.     

Characterization of branched chain fatty acids from subcutaneous triacyglycerols of barley-fed lambs

The fatty acids of subcutaneous triacylglycerols (containing ca. 11% of branched chain components) from lambs fed on barley-rich diets were fractionated by treatment with mercuric acetate and by urea adduct formation to yield concentrates rich in the branched chain components, all of which were saturated. The concentrates were subjected to analysis by high resolution gas liquid chromatography in conjunction with mass spectrometry. The branched chain fatty acids consisted of a complex mixture of mono-, di-, and trimethyl substituted components. The greater part of the mixture comprised monomethyl substituted acids of chain length 10–17 carbon atoms. Within each of these molecular species, a number of positional isomers was identified, notably in respect of methyltetradecanoic acid (methyl substituent on carbon 2, 4, 6, 8, 10, and 12) and methylhexadecanoic acid (methyl substituent on carbon 2, 4, 6, 8, 12, and 14). Homologous series also could be recognized of one of which all eight members from 4-methyldecanoic acid to 4-methylheptadecanoic acid were identified; together they accounted for ca. 39% of the branched chain fatty acids which were sampled for mass spectrometry. The dibranched acids identified consisted of five members of a homologous series, ranging in chain length from 11–15 carbon atoms and with substituent methyl groups at positions 4 and 8. Though the identity of only one tribranched acid (2,6,10-trimethyltetradecanoic acid) was established, others also apparently were present in the mixture. The probable involvement of methylmalonate in the biosynthesis of these branched chain acids is discussed briefly, with particular reference to the availability of vitamin B₁₂ in relation to the activity of methylmalonyl coenzyme A mutase.