A NOTE ON THE REDUCED EFFICIENCY OF THE INDUSTRIAL CYCLONE

In this paper a theoretical investigation into the basis of the reduced efficiency of a conical cyclone is performed. By considering the flow in a region where viscosity is unimportant an analytical solution to the problem is obtained. From this model the performance of the cyclone is evaluated and this can be expressed in terms of three operating and design parameters. One of these parameters is the split ratio, that is the proportion of the volume of fluid entering the cyclone which goes to the underflow. It is demonstrated mathematically that the empirical formula for the reduced efficiency at present in common use is a very good absolute measure of the separating ability of a cyclone.     

Fracture mechanics studies on concrete compounds

An experimental and analytical investigation was conducted to determine fracture mechanics characteristics of hardened cement paste, aggregates and aggregate-cement paste interfaces. For this the fracture toughness K_Ic was determined on wedge loaded CT-specimens. It was found that hardened cement paste, aggregates and interfaces exhibit unique K_Ic values which are independent of the initial crack length. In additional test series the ductility of various model concretes tested in flexure was determined. The ductility depends primarily on the fracture toughness toughness of the aggregate-hardened cement paste interfaces and is less affected by the fracture toughness of the hardened cement paste.     

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.     

Photodegradation of ethylene–propylene copolymer and ethylene–propylene–ethylidenenorbornene terpolymer

Significant progress has been made in recent years regarding the photooxidation of olefin copolymers, but questions still remain. This paper reviews the progress and probes the photooxidative chemistry of ethylene–propylene (EP) and ethylene/propylene/diene monomer (EPDM) copolymers. Both stabilized and unstabilized polymer plaques were irradiated in a xenon are and the surface chemistry followed using infra-red spectroscopy. Model compounds were used to help elucidate the chemistry caused by unique structural features present in the copolymers. Volatile products evolved during photooxidation were determined giving valuable insight into the degradation chemistry.     

Dislocation Structures in Creep-Deformed Polycrystalline MgO

Secondary creep of polycrystalline MgO with grain sizes of 100 and 190 μm was investigated at 1300° to 1460°C under compressive loads of 2.5 to 5.5 kgf/mm². The dependence of creep rate on load follows a power law with an exponent of 3.2±0.3. The process is thermally activated, with an activation energy of 76 ± 12 kcal/mol. The creep rate is independent of grain size. The dislocation structure was investigated by transmission electron microscopy. The total dislocation density follows the relation, σ= bG √ρ, commonly found for metals. The dislocations form a 3-dimensional network in which many dislocation segments lie in their slip or climb planes. On the basis of this structure, a model is proposed in which glide is the principal cause of deformation but the rate-limiting process, i.e. annealing of the network, is diffusion-controlled. Theoretical estimates and experimental results agree within 1 order of magnitude.     

Leaching of Polyphase Nuclear Waste Ceramics: Microstructural and Phase Characterization

The leaching of complex polyphase nuclear waste ceramics is described in the context of the geochemically established dissolution behavior of the constituent phases. Static leach tests conducted on ceramic monoliths in deionized water, in simulated silicate, and in brine groundwaters, conforming to Materials Characterization Center standards and an accelerated, microscopic leach test, were used to identify the processes. Dissolution and formation of surface passivation layers are discussed in terms of hydrolysis and the adsorption of the metal hydroxocomplexes onto the monolith surface. The factors observed to affect dissolution are pertinent to the leaching of other polyphase nuclear waste ceramics.     

Habit Changes of Sapphire Grown from PbO-PbF2, and MoO3-PbF2 Fluxes

Single crystals of Al₂O₃ (sapphire) were grown from PbO-PbF₂ and MoO₃-PbF₂ fluxes; they varied from flat plates (PbF₂-rich melts) to equidimensional crystals (PbO- or MoO₃-rich melts). The primary growth planes are basal {0001}, first-order rhombohedral {1011}, and second-order rhombohedral {0112}. The habit change is interpreted on the basis of F^- contamination and Pb²⁺ surface adsorption. Possible ion species in the melts and their relative importance on crystal growth from these systems are discussed.     

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.