Numerical Simulation of Ignition of a Condensed Substance by a Particle Heated to High Temperatures

The problem of ignition of a condensed substance by single particles heated up to high temperatures is solved within the framework of the twodimensional heattransfer model. Numerical studies are performed for typical materials: polyvinyl nitrate and carbonic particles. Regimes of ignition of a condensed substance by a single particle at relatively low temperatures are adequate in terms of the ignition delay to regimes of heating of the condensed substance by a gas flow without particles; at high temperatures, they correspond to regimes of heating by a metal plate with a fixed temperature. In a certain (rather narrow) range of particle temperatures, the use of the twodimensional heattransfer model yields ignitiondelay values substantially different from other regimes.     

Iron species incorporated over different silica supports for the heterogeneous photo-Fenton oxidation of phenol

Iron-containing catalysts have been prepared following different synthesis routes and silica supports (amorphous, zeolitic and mesostructured materials). Activity and stability of these materials were assessed on the photo-Fenton degradation of phenolic aqueous solutions using near UV irradiation (higher than 313 nm) at room temperature and initial neutral pH. Their catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversions. Aromatic compounds and carboxylic acids as by-products coming from incomplete mineralization of phenol as well as the efficiency of each catalytic system in the use of the oxidant were also studied. Stability of the materials throughout the photo-Fenton reaction was evaluated in terms of metal leachibility. Activity and stability depend on the environment of iron species and features of silica support. The evolution of pH with the reaction time and their relationship with TOC degradation and leaching degree has been discussed. A nanocomposite material of crystalline iron oxides supported over mesostructured SBA-15 material is shown the most successful catalyst for degradation of phenolic aqueous solutions by photo-Fenton processes, achieving an outstanding overall catalytic performance accompanied with a noteworthy stability.     

Formation of carbon nanofibers via carbon monoxide disproportionation

Experimental results suggesting that carbon nanofibers are formed from amorphous carbon released at several compact active sites are reported. It was shown that the sites in question are catalyst crystal lattice defects formed at the crystallite contact boundaries.     

The Determination of Surface Development in Cement Pastes by Nuclear Magnetic Resonance

Pulsed proton NMR was used to determine the specific surface of hydrating cement pastes. The method is based on the fact that the measured proton spin-lattice relaxation rate (l/ T₁ ) of water in cement pastes is (in view of the fast exchange between water molecules in the adsorbed and bulk phase) proportional to the fraction of water molecules covering the solid surface and thus proportional to the NMR surface of the newly grown hydration products. In general, the method can be used for powders, fibrous and porous materials in contact with liquid water, or other fluids containing protons.     

Lipids of seven cereal grains

Grain samples of representative varieties of barley, corn, oats, rye, sorghum, triticale, and wheat grown commercially in the north central US were analyzed. Chemical constituents of the varieties studied are presented to provide an overview of their characteristics. Lipids of the milled grain samples were solvent extracted, classified by silicic acid column chromatography, and separated by thin layer chromatography. Fatty acid composition of the total lipid was determined by gas liquid chromatography and the fatty acid content was determined by saponification and extraction. Total lipid content of the grains ranged from 2.3% for ‘Polk’ wheat to 6.6% for ‘Chief’ oats. Lipid composition varied considerably. The row crops, corn and sorghum, have a high neutral lipid and low glycolipid content. The small grain varieties have a more balanced distribution among neutral lipids, glycolipids, and phospholipids. Fatty acid composition of the total lipid was similar for all grains. Minor qualitative differences were noted among the lipid classes of the 7 cereals.     

Mortars for zirconia refractories

Conclusions The composition was developed for a mortar based on zirconium dioxide and orthophosphoric acid intended for laying zirconia refractories. The filler should be stabilized ZrO₂ powder of a particle size below 0.5 mm with 10% monoclinic fine-grain ZrO₂ mixed with orthophosphoric acid added in the proportion of 2–4% in terms of P₂O₅.The mortar was tested with zirconia refractory linings and gave satisfactory results.Owing to its low water retention capacity and short setting time Ca₇Al₆ZrO₁₈ cement cannot be recommended for a zirconia base mortar.Translated from Ogneupory, No. 8, pp. 52–59, August, 1973.     

Kinetik der Fetthärtung und Vergleich verschiedener Katalysatoren

Kinetics of Edible Oil Hydrogenation and Comparison of Different Catalysts The kinetics of selective hydrogenation of edible oils were investigated giving special consideration to geometrical isomerization. The reaction was carried out in a stirred semibatch pressure vessel under constant hydrogen pressure and isothermal conditions. Tests with different catalysts such as nickel, palladium, platinum, rhodium and copper chromite showed considerable differences in selectivity and isomerization behaviour. It could be shown that the major part of the elaidic acid (trans) is formed during the saturation of the linoleic acid to the monoenoic acid. Kinetic measurements with the system soybean oil/copper chromite showed that the hydrogen pressure has the biggest effect on selectivity and isomer distribution. All observed phenomena of the hydrogenation system could be described using a modified Langmuir-Hinshelwood type model. Using this model, observed conversion curves for different oils like rape seed, olive, soybean, sunflower seed and thistle oil could be simulated with good accuracy.     

Impact thermoplastics: Combined role of rubbery phase volume and particle size on toughening efficiency

A relationship has been found for OSA (olefin-acrylonitrile-styrene) polymers between normalized Izod impact strength (ΔI/N) or yield stress (Δσy/N) with mean particle radius. These normalized functions (which analytically include radius and rubbery phase volume) are representative of the toughening effect of a single particle with respect to the styrene-acrylonitrile (SAN) rigid matrix. ΔI/N and Δσy/N increase exponentially as a function of the radius. This approach, for Izod, was also applied to HIPS and toughened nylon reported in the literature and similar results were obtained. In the case of nylon, however, the ΔI/N values are split in two different curves related to the tough-brittle transition described in that literature. Referring to OSA, three samples (with the largest radii more than 0.22 μm) fail in a brittle manner and do not fit the curve of ΔI/N: they fit, however, that of Δσy/N. Further work must be done in order to investigate a decisive role either of interfacial adhesion (eventual lack for these three materials) or of tough-brittle transition mentioned before for shear-yielding deforming materials. In fact, OSA has behavior intermediate between that of nylon and HIPS which deforms by crazing.     

Strength after heating of unfired refractories containing chemical bonding agents

Conclusions Out of all the experimental bonding agents used in the production of unfired magnesite and magnesite-chromite refractories: SDW; MgSO₄,· 7H₂O; MgSO₄·7H₂O + H₃BO₃; (NaPO₃)_n, the greatest strength on heating is provided by the addition of 2% (NaPO₃)_n.An addition of boric acid to the refractories using the MgSO₄,·7H₂O bonding agent helps to strengthen the refractories in the 500–900°C interval; at a higher temperature the refractories with the magnesium sulfate plus boric acid bonding have no advantages in their strength properties over the articles with the magnesium sulfate bonding agent only.The magnesite-chromite articles with the chemical bonding agent have better strength in the 1000–1400°C interval than the magnesite articles. This is explained by the spinelformation reactions which occur at these temperatures.On the basis of these studies (NaPO₃)_n and also MgSO₄,· 7H₂O with an addition of H₃BO₃ can be recommended as chemical bonding agents for unfired magnesite-chromite refractories.Translated from Ogneupory, No. 1, pp. 48–52, January, 1979.     

Photoisomerization of antiaggregation pheromone verbenone: Biological and practical implications with respect to the mountain pine beetle,Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae)

Release of the antiaggregation pheromone, verbenone, at 3.8 mg/ day from a concentrated source within a multiple-funnel trap completely inhibited response by the mountain pine beetle (MPB),Dendroctonus ponderosae Hopkins, to attractive semiochemical lures. When aerial applications were simulated and verbenone was released at the same rate from beads lying in a 2×2-m area on the forest floor 15–35 cm below a trap, the response of the MPB was inhibited by only 50%. This reduced inhibition may be explained in part by the photoisomerism of verbenone. When exposed to full sunlight on two occasions, the times required for 50% of verbenone vapors to be converted to chrysanthenone were 75 and 100 min, respectively. Trap and tree-baiting experiments indicated no biological activity of chrysanthenone. Rapid photoisomerization could reduce the concentration of verbenone below biologically active levels and would allow the MPB to colonize trees close to already occupied hosts, contributing to the characteristic clumped distribution of MPB attack. The rate of verbenone photoisomerization may vary according to geographic location, stand elevation and density, and should be considered before verbenone is applied to control the MPB and other bark beetles.