Kinetic Analysis of the Chemical Structure of Filtration-Combustion Waves in Fuel-Lean Gases

On the basis of skeleton diagrams and sensitivity analysis, the structure of the heat-release region, special features of formation of radicals, and methane-oxidation dynamics under conditions of filtration combustion of an ultralean methane–air mixture are considered in detail. It is shown that the exothermal region consists of two consecutive peaks, the first one due to oxidation of hydrocarbons and hydrogen by OH radicals and the other due to the CO oxidation reaction. Several specific regions are identified in the wave, depending on the prevailing reactions of branching of radical chains. The main chain mechanism of formation of radicals is the reaction CH₃ + O₂ = CH₃O + O in the region of low temperatures, the reaction HO₂ + CH₃ = CH₃O + OH in the transitional region, and the reaction H +O₂ = O + OH in the region of high temperatures. Two former regions correspond to the preheating zone, and the latter corresponds to the reaction zone of the wave of filtration combustion of gases.     

Deposition of nanocrystals on flat supports by spin-coating

Monodisperse particles can be evenly distributed over flat supports by spin-impregnation. In this way Cu precursors have been deposited onto Si wafers. The effects of the rotation frequency and the concentration of the impregnation solution have been investigated. The mean diameter of the deposited particles can be varied from several nanometers upto several micrometers as is shown by microscopy images. Spin-impregnation appears a useful tool to prepare well-defined flat model catalysts, which are readily accessible both to quantitative characterisation and to catalytic testing.     

Dynamics and self-organization of catalytic systems

The kinetics of a catalytic reaction is frequently formulated in terms of simple concepts of the Langmuir type. Apart from limitations arising from the non-uniformity of the catalyst's surface and from the coverage dependence of the rate constants, several other complications may come into play. These may arise on the quantum level where energy flow between the various degrees of freedom may cause failure of simple transition state theory, as well as on the continuum level where formulation of rate equations in terms of coupled non-linear differential equations may give rise to a rich scenario of spatio-temporal self-organization, including kinetic oscillations, chaos, and formation of concentration patterns. Several of these phenomena are illustrated by selected examples.     

The efficient synthesis of poly(silapropynylenes) via condensation of NaCэCNa with R1R2SiCL2 activated by pyridine

Summary To efficiently prepare poly(silapropynylenes), the condensation of NaCCNa with R₁R₂SiCl₂ activated by pyridine were investigated. The condensation produced tactable polymers(Mw ca. 2100–9000) with significantly higher yields of 80–97% than those from R₁R₂SiCl₂ itself and also gave rise to much more improvement in the yields and molecular weight than with acetylenic di Grignard or di lithium salts. The activation of R₁R₂SiCl₂ by pyridine accelerated the condensation reaction, which resulted in production of macrocyclic polymers as well as linear polymers.     

Effect of chemical crosslinking on molecular mobility in swollen polystyrenes

Summary Proton relaxation time measurements of chemical crosslinked polystyrenes swollen in protonated and deuterated benzene have been done in order to get informations on the microdynamic behaviour of polystyrene as well as of benzene molecules under the influence of the polymeric network. By means of additional T_1d-measurements further evidences for a slow anisotropic motion could be obtained, which cause a T₂-plateau in the high temperature region. The results are compared with those of MAR-experiments.Presented at the 22nd Microsymposium, Characterization of Structure and Dynamics of Macromolecular Systems by NMR Methods, Praque, CSSR, July 20–23, 1981     

The evaluation of castor oil effect on stress-cracking resistance of polyethylene sheets by means of a practical device

Summary The occurrence of stress cracking failure in polyethylene films caused by a chemical was checked by means of a device, such as a big jack support. In this work, castor oil was used as the reagent and polyethylene films of different origins were tested. The samples used were cut out of polymer films just like those used in stress-strain study, i. e., dogbones. The stress applied in testing was caused by the dislocation of the big jack parallel plates. The test was run at room temperature and at 60°C, in presence and in absence of castor oil. Tendency of failure is favored by presence of stress when the specimen is in contact with castor oil. Higher temperatures enhance the tendency of failure.     

Fireclay deposits in Kimovsk Coalfields

Conclusions The Kimovsk clays occurring in alternation with coal seams as well as the underclays are suitable for the production of grade B and to a certain extent of grade A chamotte.As a result of considerable losses on ignition only part of these clays is added to the bond in preparing mixtures for grade B refractories.In order to increase the homogeneity of refractories, employ local Kimovsk clays and more rationally possibly launch grade A production on their basis, it is necessary to forego the use of Suvorovsk and Latnaya clays and plan necessary to forego the use of Suvorovsk and Latnaya clays and plan selective mining at the Kimovsk coal fields.The planning of simultaneous but separate fireclay and coal mining at Kimovsk Coal fields is an urgent problem that calls for an expeditious solution.     

Interactions between pheromone traps with different strength lures for the pine beauty moth,Panolis flammea (Lepidoptera: Noctuidae)

Catches of malePanolis flammea in traps baited with lures containing 25 g of sex attractant are enhanced when in the proximity of traps baited with 125-g lures. The degree of enhancement is increased as the intertrap distance is decreased, and when the low-dose trap is upwind of the high-dose one. The patterns of alteration in trap catch suggest that moths initially attracted by one lure may divert into other traps, which may be either upwind of the original trap (overshooting), or downwind (undershooting). Overshooting can result in up to fivefold increases in catch and may provide a useful method for estimating the attractant zone of particular lure/trap combinations.     

On the preparation and properties of CuZSM-5 catalysts for NO decomposition

Equilibrium exchange isotherms were determined for the exchange of Cu²⁺ with NaZSM-5 at varying Cu(Ac)₂ concentrations in solutions of constant volume and zeolite weight. At low Cu²⁺ levels the solid scavenged all the copper ions. When copper could be detected in the equilibrated solutions, overexchange was observed. The extent of overexchange was higher at pH 6 than at pH 4. These results were analyzed in relation to catalytic activity.On leave from the Central Institute for Chemistry, Hungarian Academy of Sciences, H1525 Budapest, Hungary.     

Ultradrawing of “springy” polypropylene films

Summary It is demonstrated that in the process of ultradrawing of semicrystalline polypropylene the morphology of the initial material plays major role. Extremely high draw ratios are obtained (_max50) when drawing hard elastic polypropylene films perpendicular to their initial molecular orientation. This behaviour is explained by the molecular processes of plastic deformation.     

Molecular mechanics studies of model polysilanes

A molecular mechanics study of a homologous series of di-substituted polysilane model compounds investigates the effect ofn-alkyl side-chain substituent length on overall polymer conformation. Using the recently released MM3 program to probe backbone and side-chain energetics, the results suggest that an off-trans (160°) backbone structure is optimal in both longer-side chain (i.e., di-n-hexyl) and shorter-side chain (di-ethyl) polysilanes. Also a chair-like conformation for side-chain dihedral angles is preferred.This paper is from the Second International Topical Workshop, Advances in Silicon-Based Polymer Science.     

High-durability plugs for the ladles of continuous steelcasting plant

Conclusions The Krasnyi Oktyabr refractories plant has produced SP-14 and SP-11 type conical chamotte plugs containing 39.77% Al₂O₃ + TiO₂.The SP-14 plugs were tested in the main ladles of the continuous steelcasting equipment of the Novo-Lipetsk metallurgical plant, the SP-11 type in pony ladles at the Sarkanais Metallurgs plant.The tests demonstrated the superiority of these plugs, i.e., they reduced the proportion of unregulated castings from 23.2 to 3.4% in the main ladles and lowered wear in the pony ladles by 8–9%. These conical chamotte plugs can be recommended, therefore, for use in the main and pony ladles of continuous steelcasting equipment.Translated from Ogneupory, No. 6, pp. 3–4, June, 1974.     

Oviposition deterrent from eggs ofCallosobruchus maculatus: Spacing mechanism or artifact?

Females ofCallosobruchus maculatus (F.) avoid ovipositing on host seeds already bearing conspecific eggs, and thus distribute eggs evenly among seeds. This behavior was presumed to be mediated by an ether-soluble oviposition marker that is deposited with the egg and can be extracted from egg-laden artificial hosts (glass beads). Ablation experiments revealed that the true factors promoting an even dispersion of eggs were perceived by the maxillary and labial palpi. In contrast, receptors on the antennae were largely responsible for avoidance of seeds treated with oviposition marker. Taken together, these results suggest that a careful distinction should be drawn between factors that promote spacing of eggs under natural conditions and general oviposition deterrents that may be isolated from both sexes.     

Preparation effects on the activity of Cu-ZSM-5 catalysts for NO decomposition

Effects of Cu-ZSM-5 catalyst preparation on the activity of over-exchanged copper for NO decomposition are reported. The Cu-ZSM-5 catalysts were prepared by incorporating Cu²⁺ cations into ZSM-5 zeolites from an aqueous cupric acetate solution adjusted to different pH values by adding either acetic anhydride or aqueous ammonia in the solution. The Cu²⁺ exchange levels increased with increasing pH level. STEM/EDX analysis identified CuO particles (5–6 nm) on the zeolite surface for the materials exchanged at pH>6. Conversion and kinetics measurements of NO decomposition to N₂ over these catalysts showed that the over-exchanged copper was not active. Short-time wash with aqueous ammonia removed this copper. The catalyst activity correlated very well with the amount of copper remaining in the ZSM-5 channels.     

Convective Regime of Filtration Combustion of Energetic Materials in a Cocurrent Flow of Their Combustion Products

The convective regime of filtration combustion of energetic materials in a cocurrent flow of their combustion products is studied using a model with extremely simplified kinetics and heat transfer, which shows instability of the process. It is shown that the more accurate twotemperature model describes a steadystate regime. In this regime, the gas temperature on the hot boundary of the heating zone is well below the combustion temperature, and the solidphase temperature is well below the temperature proposed in recent studies on this topic. It is pointed out that the twotemperature approach is unjustified and intragranular nonisothermicity must be taken into account for convective regimes. It is shown that the threetemperature model, which takes into account this effect, does not give a stable steadystate solution.     

Synthesis of new metal-containing side-chain monomers and polymers

New metal-containing vinyl monomers, hexyl-6-oxy-{4-[4-(4-carboxy cyclopentadienyl manganese tricarbonyl phenyl)phenyl]benzoyloxy}methacrylate and hexyl-6-oxy-{4-[4-(4-ferrocenoyl phenyl)phenyl]benzoyloxy}methacrylate, and the corresponding homopolymers and random copolymers with hydroxy monomer hexyl-6-oxy-{4-[4-(4-hydroxyphenyl)phenyl]benzoyloxy}methacrylate were synthesized. The compounds were characterized by¹H NMR; their thermal behavior was investigated by means of differential scanning calorimetry. Monomers and polymers containing the ferrocene unit melt at lower temperatures than those derived from the cyclopentadienyl managanese tricarbonyl moiety. The melting temperatures of the monomers and polymers ranged from 399 to about 515 K, Both monomers and polymers failed to exhibit mesogenic behavior. Values ofM _n,M _w,M _w/M _n, and degree of polymerization were obtained by gel permeation chromatography. TheM _n ranged from 16,500 for the copolymer containing hexyl-6-oxy-{4-[4-(4-ferrocenoyl phenyl)phenyl] benzoyloxy}methacrylate and hydroxy monomer hexyl-6-oxy-{4-[4-(4-hydroxyphenyl)phenyl]benzoyloxy}methacrylate at a 1:3 ratio to 26,000 for the copolymer containing hexyl-6-oxy-{4-[4-(4-carboxy cyclopentadienyl manganese tricarbonyl phenyl)phenyl]benzoyloxy}methacrylate and hydroxy monomer hexyl-6-oxy-{4-[4-(4-hydroxyphenyl)phenyl]benzoyloxy}methacrylate at a 1:3 ratio.M _w/M _n ranged from 1.6 in the case of the copolymer containing hexyl-6-oxy-{4-[4-(4-carboxy cyclopentadienyl manganese tricarbonyl phenyl)phenyl]benzoyloxy}methacrylate and hydroxy monomer hexyl-6-oxy-{4-[4-(4-hydroxyphenyl)phenyl]benzoyloxy}methacrylate at a 1:3 ratio to 2.2 in the case of poly(hexyl-6-oxy{4-[4-(4-carboxy cyclopentadienyl manganese tricarbonyl phenyl)phenyl]benzoyloxy}methacrylate).     

Prediction of Reverse Relaxation and Deformation—Recovery Processes in Synthetic Fibres

Use of force and geometric deformation variants of the nonlinear-hereditary viscoelasticity equation for prediction of complex processes by calculation is examined on the example of deformation-recovery and reverse relaxation processes in Lavsan synthetic fibres. A comparison of the calculated and measured values allows recommending the method of calculated prediction in which an elementary function — the normalized arctangent of the logarithm of the reduced time serves as the normalized relaxation or creep function.     

Ethynylene-disilanylene copolymers

Polymers of structure (SiR₂SiR₂-C C-SiR₂SiR₂-C C) _n , in which ethynylene units alternate with disilylene units, have been prepared by two routes: (a) condensation of dichlorodisilanes with dilithium derivatives of 1,2-diethynyldisilanes and (b) ring-opening polymerization of strained cyclic disilanylene-acetylnes, (SiR₂SiR₂C C)₂. The polymers display UV absorption near 240 nm indicative of – conjugation between the Si₂ and the C C moieties. Polymers with R=R=n-Bu or R=n-Bu, R=Ph, undergo solid-state transitions to form liquid crystalline mesophases resembling those observed for many poly(silylenes). Single crystals were obtained for the polymer with R=R=CH₃, by precipitation from dilute cyclohexane solution. The solid-state properties and structures of this family of polymers are discussed.This paper was presented at the Second International Topical Workshop, Advances in Silicon-Based Polymer Science.     

“Roughness” of the Gasless Combustion Front

Concepts of local curvatures of the combustion front (roughnesses) caused by penetration of the melt into the heating zone are developed. Based on the estimates of characteristic times and scales of individual stages, different combustion modes and their relation with the structural parameters of the initial mixture are revealed.     

Water vapor absorption and aqueous retention of hydrolyzed starch polyacrylonitrile graft copolymers — “superabsorbent starch”

Summary Starch copolymers with polyacrylonitrile grafts were prepared using the Mn³⁺ initiation method and different amounts of acrylonitrile. The product was hydrolyzed in aqueous alkali (nitrile groups to amide and carboxyl groups) to enhance the hydrophilic character of the copolymer and achieve superabsorbent properties. At relative humidities (RH) up to 95–97 % the modified starch shows normal water vapor absorption like cellulose and other polysaccharides. When in contact with liquid distilled water, the modified starch forms a superabsorbent gel which retains very large amounts of water (up to 800 g/g). At low and high pH and in aqueous salt solutions (NaCl, CaCl₂ and synthetic urine) the water retention is strongly reduced. This is interpreted as due to the ionic strength (salt effect) and for Ca²⁺ ions probably also crosslinking by salt formation with carboxyl groups on adjacent chains or chain segments.