Some features of pilling formation on carpeting from synthetic texturized new types of yarns

Conclusions It has been found that pilling formation does not take place on carpet items made from pneumotexturized polyamide or matrix-fibrillar yarns.On prolonged abrasion of carpet specimens from yarns of the matrix-fibril type, fibrillation of the yarns is observed, accompanied by an increase in the surface density of the carpet pile mass.Translated from Khimicheskie Volokna, No. 5, pp. 35–36, September–October, 1985.     

Heterogeneous asymmetric reactions. 23. Enantioselective hydrogenation of ethyl pyruvate over cinchonine- and α-isocinchonine-modified platinum catalysts

The enantioselective hydrogenation of ethyl pyruvate to (S)-ethyl lactate over cinchonine- and -isocinchonine-modified Pt/Al₂O₃ catalysts was studied as a function of modifier concentration and reaction temperature. The maximum enantioselectivities obtained under the applied mild conditions were 89% ee using cinchonine (0.014 mmoldm^–3, 1 bar H₂, 23°C, 6% AcOH in toluene), and 76% ee in the case of -isocinchonine (0.14 mmoldm^–3, 1 bar H₂, –10°C, 6% AcOH in toluene). Since -isocinchonine of rigid structure exists only in anti-open conformation these data provide additional experimental evidence to support the former suggestion concerning the dominating role of anti-open conformation in these cinchona-modified enantioselective hydrogenations.     

Preparation of crimped synthetic yarns directly during the spinning process

Conclusions The practical possibility of preparing yarns with an adequate crimp directly during the spinning process without expensive operations to give yarns a crimp by mechanical means has been demonstrated experimentally.Yarn crimp is achieved by using spinnerets having holes of variable cross-section; this ensures obtaining yarns with a head-tail cross-sectional profile.The authors express their thanks to K. H. Gaitel, a specialist in the Schwartz (East Germany) man-made fibre company and to F. Dolke and G. Tuschan, specialists in the spinneret manufacturing plant in Grebzig (East Germany) for help in carrying out this work.Translated from Khimicheskie Volokna, No. 2, pp. 40–42, March–April, 1985.     

Shock‐Wave Deformation and Fracture of Zirconium Dioxide Ceramics of Various Fractional Composition and Porosity

The paper reports results from measurements of freesurface velocity profiles of shockloaded zirconium dioxide ceramics with a porosity of 16–22% produced from compositions with a size of the coarse fraction of 0.5–2.0 mm. Shockwave loading of ZrO₂ samples 5–20 mm thick was performed by aluminum impactors 3–12 mm thick with a velocity of 10–100 m/sec. The measured freesurface velocity profiles were used to assess the dynamic compressive and tensile strengths of the ceramics and thedamping properties of the ceramics.     

Crystal structure and morphology of electrodeposited zinc-iron binary alloys

Deposits of zinc-iron alloy have been prepared galvanostatically from a sulphate bath and the crystal structure has been determined by X-ray diffraction and transmission electron microscopy measurements. The electrodeposited zinc-iron alloys have metastable structures and the individual phases coexist over wide composition ranges. The phases are identified as (10073 at % zinc), (8748 at % zinc), ₁(7862 at % zinc) and (620 at % zinc). Thec andc/a in the h.c.p. lattice of the -phase decrease continuously with decrease of zinc concentrations, and the latter changes from 1.86 to 1.60 (a andc are the lattice constants of the -phase in the direction of thea- andc-axes, respectively). The -phase particles exhibit a hexagonal plate-like morphology which is thin in the direction of thec-axis. The morphology of the electrodeposits changes from plate-like to pyramidal shape when fine -phase particles (100 nm) start to form surrounding the -phase platelets, and then to lenticular or granular in the /₁ duplex region. The -phase forms in the low zinc concentration region and changes the electrodeposits to a fine cuboidal morphology.     

Life of silicon carbide heaters in argon at high temperatures

Conclusions The electrical heating elements made from silicon carbide in argon age slowly and may operate for more than 300 h at a temperature on the surface of 1700C and more than 200 h at 1800C.The service life of the heating elements made from silicon carbide at 2000C in argon is less by a factor of 20 than at 1800C. At 2000C sublimation of the SiC from the heating element is observed.The presence in the argon atmosphere of up to 11% oxygen does not have a marked influence on the rate of oxidation of the heating elements at 1600C at the surface.Translated from Ogneupory, No. 3, pp. 33–36, March, 1967.     

Preparation of crimped synthetic fibres directly in the spinning process

Conclusions In the preparation of crimped polyamide yarns without the use of texturing devices, it has been found that in yarns of complex profile, of the head-tail type, the two parts of the yarn cross-section interact in accordance with the bimetallic plate rule. The crimp can be described satisfactorily by the Brand-Backer equation.Dependences of the degree of crimp on the ratio of the head and tail lengths, birefringence, and spinning speed have been obtained for selected variants of yarn profile; this makes it possible to find an optimum regime for yarn preparation.Translated from Khimicheskie Volokna, No. 3, pp. 32–33, May–June, 1985.     

Study of the change in morphological structure of UHM yarns on storage by the polarization interferometry method

Conclusions Dependences of birefringence of the radial coordinate have been obtained for old and relatively fresh UHM yarns using the polarizing interference microscope.Storage of UHM yarns in air leads to increased strength and elongation at break in microplastics and correspondingly to an increase in the birefringence close to the yarn surface and on it.Translated from Khimicheskie Volokna, No. 4, pp. 43–44, July–August, 1989.     

Diffusion-controlled current distributions near cell entries and corners

This paper reports experimental work undertaken to explore diffusion-controlled current distributions immediately downstream of sudden changes in flow cross-sectional area such as may occur at the entry to electrochemical flow cells. Nozzle flows expanding into an axisymmetric circular duct and into a square duct have been investigated using the reduction of ferricyanide ions on nickel micro-electrodes as the electrode process. The spanwise distribution of current has also been studied for the case of the square cell where secondary corner flows are significant.Nomenclature A electrode area (cm²) - c bulk concentration of transferring ions (mol dm^–3) - D cell diameter (cm) - D Diffusion coefficient (cm₂s^–1) - F Faraday number (96 486 C mol^–1) - I limiting electrolysis current (A) - k mass transfer coefficient (cm s^–1) - N nozzle diameter (cm) - u mean fluid velocity (cm s^–1) - x distance downstream from point of entry to cell (cm) - z number of electrons exchanged - electrolyte viscosity (g s^–1 cm^–1) - electrolyte density (g cm^–3) - (Re)_D duct Reynolds number,Du/ - (Re)_N nozzle Reynolds number,Nu/ - (Sc) Schmidt number,/D) - (Sh) Sherwood number,kD/D)     

Cooperative inclusion of sodium 1-pyrenesulfonate by γ-cyclodextrin

Summary The interaction of -cyclodextrin(-CD) with sodium 1-pyrenesulfonate(PS) was studied spectrophotometrically. -CD was found to cause much larger decrease in the absorption maxima of PS than -CD. The fluorescence spectra of PS in the presence of -CD showed excimer emission, while those of PS with -CD showed only monomer emission, indicating that -CD forms 12 (-CDPS) complexes in which two PS molecules are included in the -CD cavity in a face-to-face fashion. The binding isotherm showed a sigmoidal curve. The association constants were estimated by computer simulation of the binding curve. The 12 (CDPS) complex was found to be much more stable (K=10⁶ M^–1) than the 11 complex (K=1 M^–1). At high concentration of -CD another -CD cooperates in binding two PS molecules, resulting in the formation of a 22 complex.     

Characteristics of Microscale Combustion in a Narrow Heated Channel

The characteristics of microscale combustion were investigated by using a microchannel heated by an external source. The inner diameter of the channel was 2 mm, which was slightly smaller than the quenching distance of the stoichiometric methane–air mixture under normal conditions. The effects of the equivalence ratio and the averaged flow velocity on the characteristics of combustion in the microchannel were examined. At a channelwall temperature of 1000°C, flames could be stabilized at equivalence ratios of 0.05–1.9 and mixture velocities up to 150 cm/sec in a Ushaped quartzglass channel. At moderate equivalence ratios and lower velocity conditions within the flammability region, oscillatory combustion was observed. A simple analytical model predicting flame oscillations on the basis of the linear analysis of steady solutions is proposed.     

Performance and impedance studies of thin,porous molybdenum and tungsten electrodes for the alkali metal thermoelectric converter

Columnar, porous, magnetron-sputtered molybdenum and tungsten films show optinum performance as AMTEC electrodes at thicknesses less than 1.0 m when used with molybdenum or nickel current collector grids. Power densities of 0.40 W cm^–2 for 0.5 m molybdenum films at 1200 K and 0.35 W cm^–2 for 0.5 m tungsten films at 1180 K were obtained at electrode maturity after 40–90 h. Sheet resistances of magnetron sputter deposited films on sodium beta-alumina solid electrolyte (BASE) substrates were found to increase very steeply as thickness is decreased below about 0.3–0.4 m. The a.c. impedance data for these electrodes have been interpreted in terms of contributions from the bulk BASE and the porous electrode/BASE interface. Voltage profiles of operating electrodes show that the total electrode area, of electrodes with thickness <2.0 m, is not utilized efficiently unless a fairly fine (1×1mm) current collector grid is employed.     

Structure of the Reaction Zone of a Steady Detonation Wave in Dinitrodiazapentane

The massvelocity profiles in 2,4dinitro2,4diazapentane samples of different densities were registered by a laser interferometer and the electromagnetic technique. The reaction time was shown to reach 300 nsec and weakly depend on density, while the pressure in the chemical spike can be twice as high as that at the Chapman–Jouguet point. No special features due to diamond formation were observed in the massvelocity profiles registered in the chemical reaction zone.     

Machining temperature in grinding refractory materials with a diamond wheel

Conclusions When machining an electrically nonconducting material with a diamond wheel the machining temperature can be measured by means of two imbedded contiguous electrodes (the 2ICE method) which give temperature readings from small volumes in the contacting layers of the tool and the machined material. The time constant of the method is negligibly small and the readings stable, and the method permits temperature measurements even when use is made of a coolant.The hot thermocouple junction of the two imbedded electrodes formed by the cutting action of the diamond grain is 10–15 times smaller in volume than a wire thermocouple with electrodes of the same diameter.The temperature functions derived in this investigation are reduced to a convenient exponential equation which covers the most advantageous range of machining parameters for refractory materials.Translated from Ogneupory, No. 6, pp. 15–18, June, 1977.     

Specific features of the phase transformations occurring during the sintering process of the beta-alumina based ceramics and their properties

Conclusions During the sintering process of beta-alumina obtained using the method of plasmochemical synthesis, the structural transformation occurs and it is accompanied by the separation of the excess Na₂O and the formation of an intergranular meltlike phase that is saturated with sodium and is characterized by high dielectric properties.The quantity of the meltlike phase and the magnitude of the /( + ) ratio determine the degree of stabilization (stability) and the final resistivity of the material and depend on the initial chemical composition and the heating rate maintained during the sintering process.It was shown that when the duration of residence of the material in the hot zone of the furnace is increased or when the specimens sintered maintaining high heating rates are subjected to additional heat treatment, one observes the occurrance of the reverse structural transformation that is characterized by an increase of the phase ratio /( + ) 1, a reduction in the quantity of the meltlike phase right up to its complete disappearance, and a decrease of the electrical resistivity of the material.In the materials having a large excess quantity of sodium oxide, the process of crystallization of the intergranular NaAlO₂ phase occurs simultaneously with the second phase transformation.The best ceramic and electrophysical parameters were obtained when sintering the material contained 7.9% Na₂O.Translated from Ogneupory, No. 3, pp. 13–18, March, 1990.     

The role of Ni2+ diffusion on the reducibility of NiO/MgO system: A combined TRP-XPS study

The progressive dissolution of nickel ions in the lattice of MgO matrix, promoted by the calcination temperature, has been monitored using XPS. The reducibility of Ni/MgO catalysts is affected by the modification of the surface chemical composition. TPR peaks have been correlated with several NiO forms. Both XPS and TPR results indicate a different behaviour pattern for the supported and physically mixed NiO/MgO systems, and this has been attributed to the different available contact area between NiO and MgO. The formation of both NiO rich and MgO rich NiO-MgO solid solutions, with the tendency to evolve towards the bulk solid solution, has been invoked to explain the substantial changes in the TPR pattern of the different air calcined systems.     

Lamellar Thickness of a Syndiotactic Polystyrene Determined from Small-angle X-ray Scattering and Transmission Electron Microscopy

Extensive morphological studies on a syndiotactic polystyrene (sPS) sample prepared from compression molding were carried out using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). SAXS was conducted at 25C as well as at 150C to enhance the scattering contrast in order to obtain more reliable morphological parameters. The compression-molded sample was crystallized into a orthorhombic crystal lattice characterized by wide-angle X-ray diffraction (WAXD). A similar weight fraction of crystallinity, ca. 0.37, was obtained from both WAXD and differential scanning calorimetry measurements.In addition to the scattering peak at a scattering vector of ca. 0.36 nm^–1 attributable to the presence of lamellar/amorphous layers, anomalous scattering at the zero angle was found from the SAXS intensity profiles. Based on the Debye–Bueche theory, the scattering profile of this peculiar zero-angle scattering was deduced and was subtracted from the raw intensity profile to obtain the intensity profile exclusively associated with the lamellar/amorphous structure. A consistent long period was obtained for SAXS measured either at 25 or 150C, provided that the appropriate subtraction of intensities due to the zero-angle scattering was conducted. Moreover, the lamellar thickness deduced from the one-dimensional correlation function was in good agreement with TEM results. A difference scattering pattern derived from SAXS measured at 150 and 25C was obtained and a comparison of the morphological parameters was provided as well.     

Combustion Modes of a Strongly Diluted Ti + 2B System

Combustion modes of a Ti + 2B system with a high mass content of copper and iron (63–83%) are studied for various initial temperatures and compositions of the specimens and the particle sizes of the reagents. The parametric domains of existence of highvelocity and lowvelocity layerbylayer and spin combustion modes are found.     

Synthesis of statistical polydiene networks by reaction of liquid polyenes with telechelic siloxanes

The present investigation concerns the synthesis of statistical networks similar to vulcanized rubber. We have used liquid precursor polymers: polybutadiene (PB) and polyisoprene (PI) with telechelic siloxanes. The reactivity of the polydienes can be classified as follows: PB units 1,2 PI units 3,4 PI units 1,4 0. The network formation is a function of the ratio R = nb, of pendent double bonds/nb. of SiH. For R 1 the networks are rather hard and brittle, for 8 R 10 they are soft and elastic, whereas for R 16 the gels obtained are very soft and sticky.     

Properties ofSrMO 3-δ(M=Fe,Co) as oxygen electrodes in alkaline solution

Strontium ferrates and cobaltates with compositions SrFeO_3- (0.060.40) and SrCoO_3- (0.040.30) were synthesized. The dependence of the oxygen electrode properties on the value was examined in 1 mol dm^–3 KOH solution. In the SrFeO_3- series, the samples with 0.24<<0.29, showed the highest activity in both oxygen evolution and reduction reactions. In contrast, no strong dependence on the value was observed in SrCoO_3-, which also showed a high catalytic activity for oxygen evolution.