Preparation of finely dispersed nanographite

We have developed a convenient single-step method for producing stable nanographite dispersions from natural graphite in various solvents using high-power sonication. Nanographite dispersions in water are shown to be stable for several weeks, and aqueous nanographite dispersions containing a surfactant are stable for several months. Nanographite samples prepared from aqueous nanographite dispersions have been characterized by various physicochemical techniques (including X-ray diffraction and Raman spectroscopy). Interference microscopy, transmission and scanning electron microscopy, and atomic force microscopy have been used to examine the morphology and determine the size of nanographite particles. The nanographite platelets are 300–500 nm in lateral size and 20–40 nm in thickness, which corresponds to 30–50 graphene layers.     

Preparation and properties of Fe-B-Si-C amorphous alloys

The crystallization temperatures, magnetic properties, and density of amorphous alloys of FexBySizCzare reported for72 < x < 88, 16 < y < 28, and0 < 2z < 12. The peak value of 4 ± Msis 17 kG in the as-cast state and occurs in the region of Fe82B13Si2.5C2.5. The crystallization temperatures, Curie temperatures, saturation magnetization, and density all appear to be average values of the ternary Fe-B-Si and Fe-B-C properties.     

Rheological properties of finely dispersed suspensions

The influence exerted by the physical interaction of particles, their Brownian motion, and the fluctuations in porosity on the effective viscosity of suspensions and colloids is evaluated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 57, No. 6, pp. 923–929, December, 1989.     

Upper critical field and related properties of superconducting amorphous alloys Zr-Si

The upper critical fieldH _c2 has been measured for the superconducting amorphous alloys Zr_100–x Si _x withx=13, 15, and 17 over a wide temperature range down to 50 mK. Measurements for related properties, such as the depinning current densityJ _p , pinning force densityF _p , and flux flow resistivity _f , reveal that these systems are well characterized as typically soft and dirty type II superconductors with an extremely lowJ _p of 1 A/cm² andF _p of 1.5×10⁴ N/m³ ath (H/H _c2)=0.5 andt (T/T _c )=0.5. The temperature dependence ofH _c2 is well fitted by a curve of the Werthamer-Helfand-Hohenberg theory with Maki parameter =1.7–1.5 and spin-orbit interaction parameter _so=1–2.4. These results indicate that the Pauli spin-paramagnetic effect plays an important role in the low-temperature behavior ofH _c2 in these low-T _c and high-H _c2 amorphous superconductors. Corrections of the electron-phonon coupling (_ep=0.6) to the Pauli spin-paramagnetic limiting field lead to a reduced importance of the spin-orbit interaction effect, with _so less than 1.0. A discussion is given of the structural inhomogeneities in an amorphous phase, which are sensitively reflected in the strength of the fluxoid line pinning interaction (J _p ,F _p ) and are intimately related to the nonintrinsic anomaly, observed in many amorphous alloys, thatH _c2 depends linearly on temperature even at low temperatures, exceeding the theoretically allowedH _c2 values.     

Interaction of finely dispersed particles with the column of a constricted arc

It is shown that when particles of powder interact with the column of a constricted arc, repulsive forces are created.Translated from Inzhenerno-Fizicheskii Zhurnal Vol. 43, No. 2, pp. 303–306, August, 1982.     

Distribution of finely dispersed particles with respect to residence time in a vortex chamber

The motion of finely dispersed particles is described statistically with the use of the Fokker-Planck equation. An expression is obtained for the particle distribution function with respect to residence time. Results of the calculation illustrate the dependence of the average particle residence time in the apparatus on the process parameters.Notation A constant - C' parameter characterizing the intensity of random forces - d _p particle diameter, m - K drying rate coefficient - r radial coordinate of the particle, m - R ₀ radius of the outlet orifice, m - R radius of the chamber, m - u,u _in,u _eq instantaneous, initial, and equilibrium moisture contents of the particle, kg/kg - V _r radial gas velocity, m/sec - W tangential velocity of the particle, m/sec - x=r/R dimensionless variable - dynamic viscosity, Pa·sec - _p, _g density of the particles and gas, kg/m³ - time, sec - angular velocity of gas suspension, sec^–1 Academic Scientific Complex A. V. Luikov Heat and Mass Transfer Institute, Academy of Sciences of Belarus, Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 4, pp. 552–558, July–August, 1995.     

全金属组元铁基块体非晶的制备与性能研究

为了获得良好的玻璃形成能力,通常在铁基非晶合金中添加类金属元素(P、C、B、Si等),但这些铁基非晶合金大多室温塑性很差,且其脆性与其类金属元素的种类、含量以及分布有密切关系,因而本文选取全金属组元铁基非晶合金(Fe_(0.52)Co_(0.3)Ni_(0.18))_(73)Cr_(17)Zr_(10),通过旋淬甩带与铜模喷铸的方法分别制备了条带与块体试样,并采用X射线衍射仪(XRD)、差示扫描量热仪(DSC)、万能试验机等进行了相关性能研究.研究表明:(Fe_(0.52)Co_(0.3)Ni_(0.18))_(73)Cr_(17)Zr_(10)的临界尺寸在1～2 mm,玻璃转变温度为482℃,过冷液相区达到70℃;直径为1 mm的非晶棒材的屈服强度为2 190 MPa,断裂强度达到2 800 MPa,塑性应变量为3.6%.全金属成分中更多的金属-金属键合方式可能是其拥有较好塑性的原因.     

Microstructure and superconducting properties of rapidly-quenched copper-based alloys containing immiscible lead and bismuth elements

Copper-based superconducting alloys including finely dispersed f c c lead or h c p (Pb- Bi) particles in f c c copper matrix have been obtained by rapid quenching (Cu-M)_100-x Pb_x and (Cu-M)_100-x (Pb_0.6Bi_{0.4 x} (M = aluminium, silicon or tin;x < 10 at%) alloys containing immiscible elements such as lead and bismuth. The particle size and interparticle distance were about 30 to 130 nm and 20 to 200 nm for had particles and about 30 to 60 nm and 30 to 150 nm for (Pb- Bi) particles. The transition temperature,T _c, was in the range of 3.2 to 5.5 K for the Cu-M-Pb alloys and 6.2 to 6.3 K for the Cu-M-Pb-Bi alloys. Critical magnetic field,H _c2, and critical current density,J _c, for the later alloys were 0.47 to 0.93T at 4.2 K and 1.1 × 10⁵ to 2.7 × 10⁵ Am^–2 at zero applied field and 4.21 K. The mechanism of the appearance of such a soft-type superconductivity for the rapidly quenched copper-based alloys was discussed, and inferred to be due to the formation of a percolation path of a superconducting lead or Pb-Bi phase along the grain boundaries, sub-boundaries and/or tangled dislocations where the lead or Pb-Bi phase precipitated preferentially, rather than the proximity effect based on lead or Pb-Bi particles.     

Rheological properties of homogeneous finely dispersed suspensions. Steady flows

Expressions are obtained for the rheological parameters (effective viscosity, force of interphase interaction, etc.) of a moderately concentrated suspension of spherical particles. The equations of motion of the suspension and of its phases are written.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 33, No. 5, pp. 872–879, November, 1977.     

Preparation and crystallization of chromium-based amorphous alloys

The glass formability of the Cr₇₂ (B, Si, C)₂₅Al₃ system has been investigated. Samples were prepared by rapid quenching from the melt by the melt spinning technique. Of the compositions investigated, only Cr₇₂B₁₀C₁₀Si₅Al₃ and Cr₇₁ C₁₇Si₈Al₃ formed fully amorphous alloys. These showed crystallization temperatures of 997 and 990 K, respectively, among the highest reported for transition metal-metalloid amorphous alloys. The crystallization products have been found to be Cr₇C₃ and Cr₃(Si, B) for Cr₇₂B₁₀C₁₀Si₅Al₃ and Cr₇C₃ and Cr₃Si for Cr₇₂C₁₇Si₈Al₃. The effects of substituting iron in place of chromium in Cr₇₂C₁₇Si₈AI₃ have been investigated. For up to 20 at% Fe the crystallization products are (Cr, Fe)₇C₃ and Cr₃Si. An alloy with 30 at% Fe crystallizes into (Cr, Fe)₇C₃ and hexagonal Cr-Si-C.     

Photochromic behavior of nanocomposite hybrid films of finely dispersed phosphotungstic acid particles into polyacrylamide

A series of nanocomposite hybrid films consisting of phosphotungstic acid (PW12) and polyacrylamide (PAM) were prepared. TEM images showed that PW12 particles with average diameter of tens of nanometer were finely dispersed in the film. FT-IR results suggested that the Keggin geometry of PW12 was still preserved inside the matrix and a charge-transfer bridge was built between PW12 and PAM through hydrogen bonds. Under UV irradiation, PW12 was reduced photochemically to yield various mixed-valency colored species (heteropoly blues or heteropoly browns). The extent of photoreduction was concerned with the concentration of PW12 and irradiation time. The presence and diffusion of oxygen played an important role in reversibility of photochromism.     

Convective heat-transfer mechanism in two-phase flows for high concentrations of finely dispersed solid particles

A model is proposed for convective heat transfer and an analytic solution is obtained for the energy equation for a two-phase flow in vertical tubes with high concentrations of finely dispersed solid particles.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 6, pp. 926–932, June, 1985.     

Preparation of Pt dispersed porous carbon particles from polyimide particles

We investigated the preparation of Pt and Pt/Ru bimetallic fine particles dispersed in polyimide particles by precipitation from various polyamic acid solutions containing Pt and Ru complexes, followed by the carbonization of the resulting polyimide particles. As Pt complexes, platinum(II) acetylacetonate [Pt(acac)₂], trimethylplatinum iodide [PtIMe₃], and (trimethyl) methylcyclopentadienylplatinum [Pt(MeCp)Me₃] were used. As Ru complexes, ruthenium(III) acetylacetonate [Ru(acac)₃], acenaphthylene heptacarbonyl triruthenium [(C₁₂H₈)Ru₃(CO)₇], and tetracarbonylbis(-cyclopentadienyl)diruthenium [Ru₂(CO)₄Cp₂] were used. Bow tie-like polyimide particles containing Pt or Pt/Ru bimetallic particles could be obtained from pyromellitic dianhydride /m-phenylenediamine (PMDA/MPD) polyamic acid containing Pt and Ru complexes. Sheaf-like polyimide particles were obtained by using 4,4-oxydianiline(ODA) as diamine. The morphologies of polyimide particles strongly depend on the kind and the concentration of Pt and Ru complexes. We could obtain Pt or Pt/Ru bimetallic fine particles dispersed in porous carbon particles, which morphologies are the same as the polyimide particles used as carbon precursors, by heat-treatment of the obtained polyimide particles. Pt and Pt/Ru fine particles in the range of 310 nm were contained in bow tie-like or sheaf-like carbon particles. The addition of Ru complexes to polyamic acid solutions decreased the sizes of Pt particles in carbon particles.     

Calculations of turbulent jets with finely dispersed solid admixtures

We suggest a computational-experimental method for determining the hydrodynamic characteristics of a dust-laden gas jet. The method is based on Prandtl-Mieses generalized variables. For this case we obtain an algebraic model of turbulence which allows us to take into account the mutual effect of phases and the initial conditions at the nozzle outlet. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 6, pp. 919–923, November–December, 1997. Original article submitted     

Computation of steady-state radial distribution of finely dispersed particles in a vertical turbulent gas flow

The technique and results of computation of the radial distribution of the concentration of solid particles suspended in an axisymmetric stabilized turbulent flow are discussed for different types of interaction of the particle flux with the walls of the channel.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 32, No. 6, pp. 965–971, June, 1977.     

Penetration of a magnetic field into superconducting lead and lead-indium alloys

The temperature dependence of the magnetic field penetration depth of superconducting lead and lead-indium alloys has been studied over the temperature range between about 2 K andT _c. Data are analyzed in terms of the microscopic theory. The difficulties of a unique analysis of the penetration data are pointed out and a strategy for the best analysis is discussed. The penetration depth atT=0 K for pure lead is determined as 525 Å. This value, though higher than the previously accepted value for lead, is nevertheless consistent with the strong coupling character of lead.