Plastic deformation mode of retainedβ phase inβ-eutectoid Ti-Fe alloys

Plastic deformation mode of-eutectoid Ti-Fe alloys has been investigated at 300 and 77 K in a retained single phase (containing athermal phase). Surface analysis and transmission electron microscopy show that {332}1 1 3 twinning and 1 1 1 slip appear to be dependent on orientation, composition and deformation temperature. The {3 3 2} 1 1 3 twinning appears only in metastable regions adjacent to the M_s curve in good agreement with previous work in-isomorphous alloys. Orientation dependence for occurrence of the preferential {332} 1 1 3 twinning among the twelve equivalent twinning systems can be explained in terms of the Schmid factor and the polarization of twinning shear. It is concluded that the {332} <1 1 3 twinning is common for-titanium alloys and related to the instability of the phase.     

The preparation of high transition temperature superconducting Pb-Bi-Ge alloy filaments using the method of glass-coated melt spinning

The melt spinning of Pb-Bi-Ge alloys with Pyrex glass was investigated as a means of producing a superconducting long filament with highT _c. Continuous filaments with maximumT _c of more than 10 K of Pb_100-x-y Bi _x Ge _y (15x37 and 725) were obtained from the molten state at 1500 K with a winding speed of 0.95 m sec^–1. The Pb₄₉Bi₃₃Ge₁₈ filament, which was 34×10^–6 m diameter and a ductile material with a tensile strength of 20 MPa and elongation of 2.7%, exhibited superconductivity at the highestT _c of 14.3 K. These filaments were found to be polycrystalline with a grain size of more than 5000×10^–10 m and had a mixed structure of germanium (diamond) (h c p) and bismuth phases. The germanium element distributed homogeneously in the filament.     

Temperature dependence of electrical resistivity of deformed and undeformed V-rich V3Si single crystals

The electrical resistivity (T) of V-rich V₃Si single crystals (T _c-11.4 K) was measured from 4.2 to 300 K along the directions of [1 0 0] and [1 1 1] before and after plastic deformation at 1573 K. Anisotropy of (T) was observed although V₃Si has the cubic A15 structure. Plastic deformation does not affect the normal-state (T) behaviour but changes the normal-superconducting transition width T_c. At low temperatures (T _c<T 40 K), (T) varies approximately as T ⁿ where n-2.5 and this behaviour does not contradict the (0)- phase-diagram plot proposed by Gurvitch, where is the electron-phonon coupling constant and (0) is the residual resistivity.     

Synthesis and dielectric properties of pyrochlore solid solutions in the Bi2O3-ZnO-Nb2O5-TiO2 system

Phase studies of solid solutions based on (Bi_1.5Zn_0.5)(Ti_1.5Nb_0.5)O₇ revealed extended regions of pyrochlore formation in the Bi₂O₃-ZnO-TiO₂-Nb₂O₅ system. At room temperature and 1 MHz (Bi_1.5Zn_0.5)(Ti_1.5Nb_0.5)O₇ has a high permittivity ( = 200), low dielectric loss (tan<1·10^–4) and a temperature coefficient of the permittivity, , = –1300ppm/K. Pyrochlore solid solutions based on (Bi_1.5Zn_0.5)(Ti_1.5Nb_0.5)O₇ can be formed with (Bi_2–xZn_x)(Ti_{2– x} Nb_x)O₇ (0.35x1.0) and with (Bi_1.5 Zn_0.5–y/3Ti_1.5+yNb_0.5–2y/3) O₇ (–1.5y0.75). Investigations of the dielectric characteristics showed that the high temperature dependence of the permittivity of (Bi_1.5 Zn_0.5)(Ti_1.5Nb_0.5)O₇ can be significantly modified by changing the composition of the pyrochlore within these regions of solid solubility. Below room temperature several of these compositions also exhibit a diffuse frequency dependent maximum in their permittivity characteristic of a transition to a relaxor type ferroelectric state. A third region of high permittivity pyrochlores with (Bi_1.5+2zZn_0.25–z Ti_2.25–z)O₇ (0.0z<0.15) was also identified in the Bi₂O₃-ZnO-TiO₂ sub system.     

Magnetic field dependence of the density of states of YBa2Cu3O6.95: Implications for the vortex structure

The total specific heat of YBa₂Cu₃O_6.95 single crystals includes contributions from phonons and spin-1/2 particles, as well as electronic contributions. The electronic specific heat is described by a quadratic term T² in zero field and a linear term [(0)+(H)]T which is increased when a magnetic field H is applied perpendicular to the CuO₂ planes. In agreement with d-wave superconductivity, we find that _n/T_c and (H)_n(H/H_c2)^1/2, where _n is the coefficient of the normal-state linear term. The H^1/2 dependence of the density of states at the Fermi level was predicted by G. Volovik for lines of nodes in the gap: the quasiparticles which contribute to this density of states are close to the nodes in momentum space and are located outside the vortex core.     

Submillimeter surface impedance and relaxation: A case study of quasi-two-dimensional YBa2Cu3Ox

Surface impedance measurements in the normal and superconducting state are an excellent method to study the conduction electron dynamics in metals. This holds especially in the relaxation range, i.e., for distances traveled in one r.f. periods= _F/(_f is the Fermi velocity) being smaller or of the order of the penetration depth and mean free pathl. For materials with _F<-10⁷ cm/sec the relaxation range is easily accessible forf>0.1 THz. Then, in the normal state, relaxation defines the surface impedance with a penetration depth approaching the London penetration depth _L, andR _0l/2 as surface resistance allowing a measure of _L and relaxation time (T, ). In the superconducting state the photon interaction scales with _F/_L=l/ ( _f is the dimension of Cooper pairs for l) and causes at low frequencies an absorption rate growing with, which is decreasing with _F/l. The rate increase proportional to turns to a decrease above 0.1 THz, being accompanied by a decrease of with frequency which is stronger for large and small _F/l. These characteristic dependences allow a measurement of material parameters, anisotropy, and dynamics of electrons. To evaluate the consequences of theâ, b, and-direction anisotropy, the integral kernels for normal and superconducting surface impedances in its nonintegrated, angle-dependent form are presented, analyzed, and compared with impedance measurements above 0.1 THz of YBa₂Cu₃O_x.     

Standard Gibbs' energies of formation of BaCuO2, Y2Cu2O5 and Y2BaCuO5

The Gibbs' energies of formation of BaCuO₂, Y₂Cu₂O₅ and Y₂BaCuO₅ from component oxides have been measured using solid state galvanic cells incorporating CaF₂ as the solid electrolyte under pure oxygen at a pressure of 1.01×10⁵ Pa BaO + CuO BaCuO₂ G _f,ox ^o (± 0.3) (kJ mol^–1)=–63.4–0.0525T(K) Y₂O₃ + 2CuO Y₂Cu₂O₂ G _f,ox ^o (± 0.3) (kJ mol^–1)=18.47–0.0219T(K) Y₂O₃ + BaO + CuO Y₂BaCuO₅ G _f,ox ^o (± 0.7) (kJ mol^–1)=–72.5–0.0793T(K) Because the superconducting compound YBa₂Cu₃O_7– coexists with any two of the phases CuO, BaCuO₂ and Y₂BaCuO₅, the data on BaCuO₂ and Y₂BaCuO₅ obtained in this study provide the basis for the evaluation of the Gibbs' energy of formation of the 1-2-3 compound at high temperatures.     

Hydraulic characteristics and vapor content in a channel with boiling of a liquid underheated up to the saturation temperature

A method is proposed for calculating the hydraulic characteristic and vapor content in a channel with underheated boiling.Notation H heated length of channel - d_t thermal diameter - d_h hydraulic diameter - _t thermal perimeter - _h hydraulic perimeter - s through cross section - N power of channel - q heat flux - G weight flow rate - W velocity - coefficient of heat transfer - t, T temperatures - t temperature difference - i enthalpy - P pressure - P pressure drop - x weight vapor content - volumetric vapor content - C_p heat capacity - r heat of vaporization - coefficient of thermal conductivity - coefficient of surface tension - liquid density - vapor density - g acceleration of gravity - _o coefficient of friction of liquid against the channel wall - shear stress - density of two-phase medium averaged over a channel cross section - dynamic viscosity Indices s on saturation line - en at channel entrance - l liquid - v vapor - w wall Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 5, pp. 784–792, November, 1979.     

Use of adjoint functions in investigations of heat conduction and transfer processes

An examination is made of the use of adjoint functions in heat conduction and convection theory. Formulas of perturbation theory are obtained for steady and unsteady cases, an interpretation of the physical meaning of adjoint temperature is given, and some applications of the theory are discussed.Notation (r,) thermal conductivity - t(r,) temperature - t *(r,) adjoint temperature - q_V(r,) density of heat release sources - p(r,) a parameter of adjoint equation - r generalized coordinate - time - (r_s, ) heat transfer coefficient - I linear functional of temperature - (r,;r₀,₀) and *(r,; r₀,₀) Green's function for t(r, ) and t *(r, ) - C(r,) volume specific heat - W(r, ) vector distribution of flow velocities - V, S volume and surface areas of body - R radius of HRE - r, radial and angular coordinates - F_in, F_out inlet and outlet flow areas of channel     

A high-resolution-electron-microscopy study of a γ/γ′-α directionally solidified eutectic alloy

The microstructure of a /- directionally solidified (DS) eutectic alloy with a nominal composition of Ni-30.26Mo-6.08Al-1.43V (wt%) was investigated by means of high-resolution electron microscopy (HREM) and analytical electron microscopy. The -fibres exhibited a typical morphology with a rectangular cross-section and they displayed the Bain orientation relationship (OR) with the / matrix; that is, [001][001] and (110)(010). Misfit dislocations and lattice strain fields existed at the / interface for different habit planes; that is, (110)(010) and (100)(110) were analysed. EDAX (Energy dispersive X-ray) analysis showed that the composition of the -phase was approximately Ni₄(Mo, Al, V); it contained 90° rotational domains of Ni₃(Mo, Al, V) with a DO₂₂ structure and Ni₂(Mo, Al, V) with a Pt₂Mo structure.     

Effect of BaO and SiO2 addition on PTCR BaTiO3 ceramics

The influence of Ba-excess and liquid phase sintering with SiO₂ on the electrical conduction and microstructure in PTCR BaTiO₃ has been investigated. Dense (95–96%), small grain (5–10 m) PTCR materials were obtained in Ba-excess (Ba/Ti=1.006) BaTiO₃. The materials exhibit low room temperature resistivity _RT (10⁰–10² ·cm) and high PTCR respond (more than 5 orders). Solid state sintering was found to inhabit the semiconducting and PTCR behavior in Ba-excess materials. Liquid phase sintering, using SiO₂ in the Ba-excess BaTiO₃, resulted in low _RT and significant PTCR response. Through domain observation, interior Polaron deficient zones were found in samples which exhibit limited liquid phase sintering, leading to non-uniform directional domains and low charge carrier mobility. Proper control of the SiO₂ concentration was found critical for obtaining uniform directional domain microstructures and low _RT.     

Electron diffraction study of superlattices and orientation variants in Ca3SrAl6SO16

Samples having the nominal composition of Ca₃SrAl₆SO₁₆ were sintered at 1380 °C and analysed by electron diffraction. The frequent appearances of forbidden and satellite reflections in this compound imply the presence of a number of basal and nonbasal superlattices so that the microstructure of this cement clinker was characterized by various superstructures including one-, two- and even three-dimensional superstructures along the 0 0 1, 1 1 0, 1 1 2, 1 1 4 or 2 2 1, 0 1 3 and 1 2 3 directions with repeat periods of two or three times of that of basic one, respectively, and intergrowth of these. Various domain structures with 90°, 120° and 48.2°, etc., orientation relationships were also detected in these superstructures and the total number of these orientation variants related to the symmetry elements lost in the process of phase transformation, can be predicted according to the conclusions of Van Tendeloo and Amerlinckx, or they are equal to the number of those unique planes in the matrix.     

Antiferromagnetic Order in the Ladder Compound SrCu2O3; Cu-NMR/NQR Measurements

We carried out the extensive Cu-nuclear magnetic and quadrupole resonance (NMR/NQR) experiments on the Zn(Ni)-doped ladder compound SrCu ₂ O ₃ (Sr123), Sr(Cu _1–x M _x ) ₂ O ₃ (M=Zn and Ni) with x 0.02 and the Ladoped Sr123, Sr _1–x La _x Cu ₂ O ₃ with x 0.03. A spin-correlation length _s /a (a: the lattice spacing between the Cu sites along the leg) of nonmagnetic impurity-induced staggered polarization (IISP) estimated from a quasi-one-dimensional (Q1D) IISP along the two legs in the 0.1–2 % Zn-doped Sr123 was found to be independent of temperature (T) and scaled to an mean impurity distance D _AV with the relation of _s /a = 2.5 + 0.1D _AV The _s /a's are much longer in x = 0.001 ( _s /a 50) and 0.005 ( _s /a 12) than an instantaneous spin-correlation length ₀ /a 3 – 8 in Sr123. The formula of Néel T, T _N (WC-Q1D)=J exp(–D _AV /(_s/a)) (J = 2000 K) based on the weakly interladder-coupled (WC) Q1D model explains the experimental T _N values quantitatively.     

Solid state phase transformation of BaB2O4 during the isothermal annealing process

Solid-state phase transformation of BaB₂O₄ during the isothermal annealing process for both to and to were investigated using a platinum crucible. For the -phase crystal at the -phase stable temperature (> 925 °C), the phase transforms to the phase perfectly below the melting temperature of 1100 °C. Meanwhile, for the -phase crystal at the -phase stable temperature (< 925 °C), the phase transforms to the phase perfectly above 800 °C. There is some difference in phase transformation behaviour between bulk-shape crystals and the powder, caused by thermal stress.     

Transport Properties of Untwinned YBa2Cu3O y Single Crystals and the Origin of the 60-K Plateau

Various transport properties, such as a- and b-axis resistivity ( _a and _b ), magnetoconductivity , Hall coefficient R _H, and a-axis thermopower S _a, are measured accurately in untwinned YBCO single crystals in a wide range of doping (6.35–7.00). The evolution of the transport properties upon changing oxygen content is described and a number of novel 60-K anomalies in the charge transport are summarized. Also, we present new evidence that weakening of superconductivity at the carrier concentration of 1/8 is responsible for the 60-K plateau.     

Ohm resistivity of electroless copper layers as a function of their thicknesses

The electric Ohm resistivity of electroless Cu depositions on dielectric substrates as a function of their thicknesses is studied. Substantial deviations (up to 10–20 times) from the standard resistivity ( = 1.7 cm^–1) below 0.5 (m thicknesses are observed. The experimental data show for the entire region of thicknesses (d 0.07–5 m) a power function between the relative resistivity changes (/) and the inverse thickness of depositions (d )–(/ (1/d )^0.8. This empirical relation is discussed as an effect of the porous structure of the metallic layers deposited on the substrate. A scanning electron micrography was applied in order to visualize the morphology of the depositions. The micrographs clearly show the evolution of the deposition profile: starting from separate islands at the very beginning of the process, and gradually covering the entire area with continuous but porous metal layers.     

Shear viscosity of the B phase of superfluid3He

The shear viscosity (T) in the Balian-Werthamer (BW) state of superfluid ³ He is calculated variationally throughout the region 0t 1(t=T/T _c) from the transport equation for Bogoliubov quasiparticles. Coherence factors are treated exactly in the calculation of the collision integral. The numerical result for =_s= _s(T)/_n(T_c) agree very well with experiment in the range 0.8t1.0. Analytic expressions = 0.577 (1–1.0008t) and =1–(23/64) [=(T)/k _B T] are obtained in the low-temperature region and in the vicinity ofT _c, respectively. From the numerical analysis it is shown that the latter equation is valid only in the temperature range 0.9997t1.0.Supported by the Research Institute for Fundamental Physics, Kyoto University.     

Texture development in Si3N4/BN fibrous monolithic ceramics

Preferred orientation was measured in Si₃N₄/BN fibrous monolithic ceramics using x-ray diffraction. The materials were manufactured by co-extrusion of polymer binder/ceramic blends which were subsequently pyrolized and then hot-pressed to produced a fully dense ceramic composite. A very strong modified wire texture was present in the BN with the basal planes aligned parallel to the axis of extrusion due to shear-induced reorientation of the platelet-shaped BN particles during co-extrusion. Texture was also observed in the Si₃N₄ and was attributed to a combination of co-extrusion and hot-pressing. After hot pressing, the basal planes of the rod-shaped -Si₃N₄ were observed to be preferentially aligned perpendicular to the extrusion direction. Measurements prior to hot-pressing revealed that a small amount (5%) of -Si₃N₄ was present in the -Si₃N₄ starting powder. Although texturing of the predominant -Si₃N₄ did not occur during co-extrusion, significant texturing of the -Si₃N₄ was observed. During subsequent hot-pressing, the pre-existing textured -Si₃N₄ particles appeared to act as seeds for transformation and preferred growth of rod-shaped grains parallel to the axis of extrusion.     

Stability of a moving interface in porous medium for non-newtonian displacing fluids and its applications in oil displacement mechanism

Summary In this paper a theoretical analysis regarding the rheological effects of non-Newtonian behavior of the displacing fluid on the stability of a moving interface in a porous medium. separating two immiscible and incompressible fluids, is performed. Conditions under which a piston-like displacement could be maintained in oil displacement mechanism with a non-Newtonian displacing fluid of power law are shown and discussed, with regard to the possibility of improving oil recovery from polymer flooding projects used in oil reservoir engineering.Nomenclature h layer thickness - H consistency index - k permeability - n rheological parameter for power law fluids - p pressure distribution - V interface velocity - v velocity - porosity - ₀ threshold gradient - viscosity - _ef effective viscosity - _ap apparent viscosity - ₀ yield stress - angle to the upward vertical     

Diffusional cubic-to-tetragonal phase transformation and microstructural evolution in ZrO2-Y2O3 ceramics

The diffusional cubic-to-tetragonal (c-t) phase transformation and microstructural evolution were studied on ZrO₂-Y₂O₃ ceramics with 4 to 6 mol% Y₂O₃ annealed in the two phase (c + t) region for longer periods of time. It was shown that in early stages of annealing a tweed structure of t-ZrO₂ was developed. With increasing annealing time this tweed structure becomes coarser and changes into internally twinned colony structure. The colonies can grow to large sizes but their twin-spacing remains almost constant. The effect of increasing annealing temperature was shown to be more obvious than prolonging annealing time in the transition from tweed to colony structure. The mechanism of the diffusional c-t transformation was discussed.