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Showing papers on "Transition temperature published in 1977"


Journal ArticleDOI
TL;DR: In this article, the authors used the multidetector D1B at the I.L. high flux reactor to measure neutron diffraction diagrams, above and below the transition temperature of 3.8 K. At 1.9 K, they found very weak magnetic reflections corresponding to an antiferromagnetic structure sinusoǐdally modulated, according to the propagation vector.

167 citations


Journal ArticleDOI
TL;DR: It is found that the characteristic band pattern, corresponding to monoclinic symmetry in multilamellar liposomes of these phospholipids, is observed only in freeze-fracture electron microphotographs when samples are quenched from temperatures intermediate between the chain melting transition temperature and the pretransition temperature of the membrane.

120 citations


Journal ArticleDOI
TL;DR: The second order phase transition in biphenyl has been monitored using some lines unique to the Raman spectrum of the low temperature phase as discussed by the authors, and a 33 cm − 1 interval observed in the crystal at 4.2 K is estimated to be about 40 cm −1.

97 citations


Journal ArticleDOI
TL;DR: In this article, a phase diagram is constructed which is consistent with both calorimetric and neutron scattering results, and a formula relating the domain size to the shift in transition temperature gives r = 50' A for the mean radius of the domains.

96 citations


Patent
26 May 1977
TL;DR: A coupling for tubes, pipes or the like, fabricated of heat recoverable metal that is treated so that it will contract when heated above its transition temperature spontaneously expand when cooled to the transition temperature to permit it to be installed or removed from the pipes as mentioned in this paper.
Abstract: A coupling for tubes, pipes or the like, fabricated of heat recoverable metal that is treated so that it will contract when heated above its transition temperature spontaneously expand when cooled to its transition temperature to permit it to be installed or removed from the pipes.

93 citations


Journal ArticleDOI
TL;DR: In this paper, the elastic modulus and viscoelastic properties of styrene-butadiene-styrene (SBS) block copolymers were measured as a function of temperature (80-170°C) and frequency using the eccentric rotating disc geometry.
Abstract: Dynamic viscosity and elastic modulus for a low molecular weight styrene-butadiene-styrene (SBS) block copolymer ate measured as a function of temperature (80-170°C) and frequency using the eccentric rotating disc geometry These linear properties are superimposed to yield master curves each of which exhibits two branches below different (critical) reduced frequencies At lower temperatures, the non-Newtonian behavior characteristic of SBS block copolymers is observed In contrast, Newtonian response occurs at higher temperatures As a consequence, plots of the viscoelastic properties vs temperature exhibit discontinuities below the critical frequencies, reflecting a narrow transition at about 142°C Above this temperature, it is inferred, consistent with the equality of dynamic and steady state viscosities, that the polystyrene (S) blocks, existent in dispersed domains at low temperatures, exceed a critical degree of compatibility with the continuous polybutadiene phase The activation energies indicate that the S blocks affect the temperature dependence of the dynamic properties in proportion to their presence in an interphase which is assumed to continuously grow in size as temperature is raised to the transition temperature Below the critical reduced frequencies, it is inferred that S domain disruption may increasingly occur in conjunction with the observed property enhancement due to these domains, relative to the miscible blocks, as reduced frequency is lowered However, above these frequencies, the presence of frequency-temperature superposition implies that the S domains and the miscible blocks are equivalent in their effects on properties At still higher reduced frequencies, the domains present at the low temperatures studied are assumed to remain intact, but plateau behavior similar to the response characteristic of homopolymers is observed

82 citations


Journal ArticleDOI
TL;DR: In this article, an x-ray diffraction study of Nylon 11 was carried out at high pressures and high temperatures, and the authors found that the triclinic structure (α phase) changing to a pseudohexagonal structure.
Abstract: An x‐ray diffraction study of Nylon 11 was carried out at high pressures and high temperatures. Careful measurements made on both wet and dry samples at atmospheric pressure indicated that the structure of Nylon 11 suggested by Slichter was not quite correct. Some distortion of the planar conformation causes a shortening of the c repeat distance from the value required for a fully extended conformation. The compressibility of the crystal lattice at higher pressures up to 20 kbar was studied and related to the anisotropic bonding present in the structure. A crystal transition at atmospheric pressure previously unreported was observed to occur at 95 °C, the triclinic structure (α phase) changing to a pseudohexagonal structure. The influence of pressure on this transition was studied. It was found that the increase in transition temperature with pressure dTt/dP (∼15 K/kbar) was greater than the melting temperature increase with pressure dTm/dP (∼9 K/kbar). A pressure‐temperature phase diagram for Nylon 11 wa...

79 citations


Journal ArticleDOI
TL;DR: In this article, a review of the available data on the yield stress of Ll2 ordered alloys, alloys with the Cu3Au structure, is presented, showing that the anomalous yield strength increase with increasing temperature is compatible with a solid solution strengthening, model, although the data are still insufficient.

79 citations


Journal ArticleDOI
TL;DR: X-ray diffraction experiments of a single crystal of magnetite at 84 K were carried out to investigate the crystal symmetry below the transition temperature as discussed by the authors, and a new lattice deformation which makes crystal symmetry lower than rhom-bolaedral was clarified.
Abstract: X-ray diffraction experiments of a single crystal of magnetite at 84 K were carried out to investigate the crystal symmetry below the transition temperature. A new lattice deformation which makes the crystal symmetry lower than rhom-bolaedral was clarified. The extra reflections which appear in the low temperature phase were observed for the first time with X-ray diffraction. The extinction of (4, 4, \(\pm\frac{1}{2}\)) reflections, which was found by Iizumi and Shirane by means of neutron diffraction, was also confirmed. All the experimental results can be explained reasonably by assuming that the low temperature phase of magnetite has monoclinic symmetry, and the space group is either C s 4 - C c or C 2 h 6 - C 2/ c .

77 citations


Journal ArticleDOI
TL;DR: In this article, the structure, phase diagram and compression behavior of polyethylene are studied by X-ray diffraction up to 11 kbar and 300°C, revealing conformational disorder of the molecule.
Abstract: The structure, phase diagram and compression behavior of polyethylene are studied by X-ray diffraction up to 11 kbar and 300°C. Distinct diffuse scattering on the non-equatorial line is first observed for the hexagonal phase of oriented polyethylene, revealing conformational disorder of the molecule. The phase diagram determined shows that the hexagonal phase exists in a temperature range which increases with increasing pressure up to 11 kbar. It is found that the compressibility of the hexagonal phase takes higher values on the lower pressure side, and approaches the value for the orthorhombic phase with increasing pressure. A simple relation between the lattice parameters of the orthorhombic phase, ao/bo=1.57-1.58, is found to hold at the transition temperature to the hexagonal phase irrespective of pressure.

69 citations


Journal ArticleDOI
TL;DR: In this paper, the structure and electronic properties of polymeric superconductor (SNBr/sub 0/sub.//sub 4/)/sub x/ have been reported and the first chemical modification of the polymeric Superconductor has been performed.
Abstract: We report the structure and electronic properties of (SNBr/sub 0//sub .//sub 4/)/sub x/ and the first chemical modification of of the polymeric superconductor (SN)/sub x/. Its dc conductivity at 300 K is ten times greater than that for (SN)/sub x/ and the thermoelectric power is positive rather than negative. The plasma energy and the superconductivity transition temperature are essentially unchanged. These results suggest that a small displacement of the Fermi level and a large increase in scattering time occur upon bromination.

Journal ArticleDOI
TL;DR: In the transition between the CsCl-type and NaCl -type structures, caesium chloride retains a definite orientation relation of [110] (CsC1) || [100] (NaC1), and [001] (CC 1 ) || [011](NaCl) as discussed by the authors, and the closest packing planes of both structures are retained in the transition and have an approximately equal density of ions at the transition temperature.
Abstract: In the transition between the CsCl-type and NaCl-type structures, caesium chloride retains a definite orientation relation of [110] (CsC1) || [100] (NaC1) and [001] (CsC1) || [011] (NaCl). The closest-packing planes of both structures are retained in the transition and have an approximately equal density of ions at the transition temperature. A uniaxial expansion (or shrinkage) parallel to one of the twofold axes in the CsCl-type structure (or the fourfold axes in the NaCl-type structure) attending the transition was observed under the optical microscope. The amount of the uniaxial expansion is about 15% of the size of the low- temperature form, and the volume change of about 17% in the transition is mostly due to this uniaxial expansion. The transition mechanism is explained as being due to a combination of two systematic movements of ions: intralayer rearrangement and interlayer translation.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the temperature and orientation dependence of Ni3(Al, W) slip properties and found that the peak strength of the slip system changes largely depending on the orientation of the compression axis.
Abstract: The temperature and orientation dependence of the mechanical behavior of Ni3(Al, W) was investigated by compression tests on single crystal specimens. It was found that at low temperatures {111} slips operate, whereas at elevated temperatures {100} slips operate, and also that the positive temperature dependence of the yield strength occurs only in the temperature range of the {111} slips. The peak-strength temperature (transition temperature of the slip system) changes largely depending on the orientation of the compression axis. The critical resolved shear stress of the primary (111)[10] slip is also orientation dependent in a similar way to that of Ni3Ga and Ni3Ge; it increases as the stress component of the (010)[10] cross-slip increases.

Journal ArticleDOI
TL;DR: In this paper, the influence of defects on structural transition temperature on structural transitions is studied. At the local transition temperature T l c, a localized phonon condenses and the resulting cluster couples linearly to the band phonons and gives a central peak.

Journal ArticleDOI
TL;DR: In this article, the authors achieved critical current densities of over 1.8×106 A/cm2 at 4.2°K and 150 kG in Nb3Al tapes rapidly quenched from the liquid state at rates of 105-106°C/sec.
Abstract: Critical current densities of over 1.8×106 A/cm2 at 4.2 °K and 150 kG have been achieved in Nb3Al tapes rapidly quenched from the liquid state at rates of 105–106 °C/sec. The superconducting transition temperature is about 16 °K, indicating a relatively high degree of order, and increases to 18.4 °K upon annealing at 750 °C. The observed microstructure depends sensitively on the quenching rate and consists of small submicron grains surrounded by a thin boundary layer of different composition. The grain size is roughly inversely proportional to the temperature gradient during quenching. The quoted critical current densities, the highest observed to date in any superconductor, should be regarded as a lower limit of the material critical value imposed by the heating problems due to the contact resistance.

Journal ArticleDOI
TL;DR: In this article, it was found that the iodine content in the complex TTT2I3 may be varied from 1.5 to ≈ 1.55 atoms per molecule of TTT.
Abstract: It is found that the iodine content in the complex TTT2I3 may be varied from 1.5 to ≈ 1.55 atoms per molecule of TTT. Increasing of the iodine concentration in the complex gives rise to an increase in the degree of incommensurability of the TTT and the I sublattices and also the degree of disordering associated with losing the correlation in arrangement of different one-dimensionally ordered iodine chains. It results in the change of conducting and magnetic properties of the complex. The temperature of the conductivity maximum moves down as the iodine concentration is increased in the complex, and the maximum is the higher, the lower its temperature. It is found that a phase transition of the metal-insulator type exists in TTT2I3 with a transition temperature depending on the iodine content. [Russian Text Ignored].

Journal ArticleDOI
TL;DR: In this paper, the fracture surface energy was determined using the double cantilever beam (DCB) technique and crack lengths were determined by compliance calibration, and the fracture strength was measured in 3-point bending, independent of the thermal treatments.
Abstract: Zirconium oxide-zirconium 2-phase alloys with composition 40 at.% Zr-60 at.% O (23 vol% metal phase) were prepared by hot-pressing mixtures of the oxide and the metal powders. The microstructure consisted of oxide grains completely surrounded by the metal phase. The effective fracture surface energy, γeff, was determined using the double cantilever beam (DCB) technique and crack lengths were determined by compliance calibration. Rapidly cooled specimens, in which the tetragonal to monoclinic phase transition would cause residual stresses, exhibited γeff values as much as 70% greater than stress-relieved specimens (65 J/m2 and 38 J/m2, respectively). A shift in the tetragonal ⇋ monoclinic transition temperature in the as-hot-pressed and the rapidly cooled specimens, compared to the stress-relieved specimens, confirmed the existence of residual stresses. The fracture strength, σeff, measured in 3-point bending, was found to be independent of the thermal treatments. Scanning electron microscopy and optical microscopy revealed that the fracture is transgranular.

Journal ArticleDOI
TL;DR: In this article, a Langevin equation for the order parameter is derived, which is appropriate for the nonequilibrium steady-state process under consideration, and which explains the observed discontinuous phase transition.
Abstract: Recent observations of radiation-stimulated superconductivity above the thermodynamic transition temperature reveal the existence of a first-order phase transition between a normal and a superconducting state In this Letter, a Langevin equation for the order parameter is derived, which is appropriate for the nonequilibrium steady-state process under consideration, and which explains the observed discontinuous phase transition

Journal ArticleDOI
TL;DR: In this paper, Nb3Ir polycrystalline films with the A15 structure deposited on sapphire were used as substrates for the epitaxial growth of nb3Ge because of the favorable lattice parameter match.
Abstract: Nb3Ir polycrystalline films with the A15 structure deposited on sapphire were used as substrates for the epitaxial growth of Nb3Ge because of the favorable lattice parameter match. The experimental results clearly show that epitaxial growth indeed occurs and helps to extend the range of homogeneity of the A15 phase up to 26.3 at.% Ge as compared with the thermodynamic equilibrium boundary at 19 at.% Ge. Furthermore, epitaxy results in a considerable rise in the superconducting transition temperature for Ge‐rich samples together with a reduction in the transition width.

Journal ArticleDOI
TL;DR: The temperature dependence of all elastic constants of cubic NaCN, measured by ultrasonic methods at ca 15 MHz from the transition point at 10.55 to 200°C, exhibits a similar anomalous thermoelastic behaviour to cubic KCN as discussed by the authors.
Abstract: The temperature dependence of all elastic constants of cubic NaCN, measured by ultrasonic methods at ca 15 MHz from the transition point at 10.55 to 200°C, exhibits a similar anomalous thermoelastic behaviour to cubic KCN. Within a wide temperature range all elastic wave velocities increase with higher temperature. The most characteristic feature of the anomalous behaviour is the softening of the shear constant c44 approaching the transition temperature. It is given by c44(T) ≃O.2144(T- T0)/T0 (1011dyn cm-2) with T0 = 255.4 K. The extremely small velocity of the elastic transverse wave connected with c44 makes NaCN highly suited for acousto-optical deflector devices.

Journal ArticleDOI
TL;DR: Magnetic susceptibility, specific heat and 133Cs magnetic resonance measurements in a single crystal of CsNiBr3 are reported in this paper, revealing two magnetic transitions separating the paramagnetic phase from the antiferromagnetic ground state.

Journal ArticleDOI
TL;DR: In this article, tunneling measurements of amorphous transition-metal based superconductors are found to be 3.5±0.1 in agreement with the BCS theory in the weak-coupled limit.

Journal ArticleDOI
TL;DR: In this article, Alloy compositions spanning the A15 phase field and the adjacent two phase fields were arc melted and cast as rods for the study of metallurgical processing, resulting microstructures and superconductivity of V3Ga.
Abstract: Alloy compositions, spanning the A15 phase field and the adjacent two phase fields, were arc melted and cast as rods for the study of metallurgical processing, resultant microstructures and superconductivity of V3Ga. In cast materials, dendritic segregation was observed by metallographic examination and a radial Ga gradient was revealed by inductive super conducting transition temperature measurement. A brief heat treatment at temperatures in the bcc-phase field eliminated the dendritic segregation, decreased the radial Ga gradient, and produced very similar microstructures in the full range of compositions. The fine scale segregation generated in the bcc-to-A15 transformation was removed by an anneal at 1000 to 1150°C. The series of annealed specimens were uniform in microstructure and also in hardness. The lattice parameter-composition plot defined two lines intersecting near the stoichiometric composition. These data and density measurements show that the compositional adjustment is by substitution of V and Ga atoms on lattice sites. The superconducting transition temperature drops rapidly from a maximum as the composition deviates from stoichiometry. Measured values of the zero field transition temperature are somewhat higher than theT o determined by extrapolating low fieldT c measurements to zero field.

Journal ArticleDOI
TL;DR: In this article, the temperature dependence of the TMPD photoionization energy threshold, I, in a set of eight hydrocarbon solvents has been systematically studied, from room temperature down to 77 K.
Abstract: The temperature dependence of the TMPD photoionization energy threshold, I, in a set of eight hydrocarbon solvents has been systematically studied, from room temperature down to 77 K. For this purpose ion-pair formation is detected either by measuring the photocurrents in the liquid phase or by measuring the recombination luminescence intensity in the solid phase. It is found that I(liquid) increases linearly when the temperature is decreased down to the liquid–solid transition temperature. At this temperature I undergoes an abrupt increase of 0.2–0.6 eV depending on the hydrocarbon and the nature of the phase transition. Any subsequent solid–solid phase change is accompanied by a new shift towards higher energy. In the low temperature phase of all the studied crystals, I(solid) has a constant value down to 77 K. Glass-forming liquids have a very different behavior: I varies linearly in the liquid and the straight line extrapolates to the I(glass) value at 77 K. The applicability of the two methods is dis...

Journal ArticleDOI
15 Jul 1977
TL;DR: In this paper, the cooling and warming curves of pure and mixed-crystal biphenyl near the paramagnetic resonance transition temperature were measured, and a first order phase transition in pure fiphenyl at 42.4 ± 0.3 K was reported, for which Δ H ≈ 70 cal mole −1.
Abstract: Previously reported single discontinuities in the zero-field splittings of triplet phenanthrene- d 10 and naphthalene- d 8 in biphenyl near 40 K are further characterized. The transition leading to these discontinuities in the mixed crystals is shown to set in at 42.0 ± 0.4 K upon lowering the temperature, and to occur over a temperature range of a few degree. Cooling and warming curves of pure and mixed-crystal biphenyl near the paramagnetic resonance transition temperature were measured, and a first order phase transition in pure fiphenyl at 42.4 ± 0.3 K is reported, for which Δ H ≈ 70 cal mole −1 . A second prominent feature in the temperature dependences of the zero-field splittings in these mixed crystals, which was not previously reported, has been shown to occur near 15 K. Although this second feature is only partially characterized by the present data, it is tentatively assigned as due to a transition intrinsic to pure biphenyl.

Journal ArticleDOI
TL;DR: In this paper, a phase transition connected with the occupation of two inequivalent octahedra complexes GeF 2−6 positions was discovered and studied by means of ESR.


Journal ArticleDOI
TL;DR: The superparamagnetic behavior of very small particles of metallic iron (ca 1.5 nm), with about half of their atoms at the surface, is changed reversibly by adsorption and desorption of hydrogen below thesuperparamagnetic transition temperature.
Abstract: The superparamagnetic behavior of very small particles of metallic iron (ca 1.5 nm), with about half of their atoms at the surface, is changed reversibly by adsorption and desorption of hydrogen below the superparamagnetic transition temperature. The change after adsorption implies a lowering of the anisotropy energy barrier for the magnetic relaxation of iron and is ascribed to a change in crystalline shape. No such changes are observed for larger particles of iron (ca 8 nm) with about 10% of their atoms at the surface.

Journal ArticleDOI
TL;DR: In this paper, the effect of the enhanced acoustic mode softening at T c on the wave velocity and Young's modulus surfaces is discussed, as well as the effects of the acoustic phonon branch with wave vector (110), particle displacement (110) near the Brillouin zone center.
Abstract: Indium rich, In-Cd alloys undergo a f.c.c. to f.c.t. structural phase transition which the presence of a cubic invariant in the Hamiltonian renders first order. Ultrasonic wave velocity measurements have been made in single crystals of both the f.c.c. and f.c.t. phases, emphasis being placed on behaviour near the phase transition. The shear modulus ½(C 11-C 12) tends to very small values in both phases as the transition temperature T c is approached: the onset of instability is manifested as softening of the acoustic phonon branch with wave vector (110), particle displacement (110) near the Brillouin zone centre. However, in contrast to its behaviour in the In-Tl alloys, ½(C 11-C 12) does not go to zero in the In-Cd alloys. This finding corresponds to the more recognizable first-order character of the transition in the In-Cd compared to that in In-Tl alloys. The effect of the enhanced acoustic mode softening at T c on the wave velocity and Young's modulus surfaces is discussed. In addition to the...

Journal ArticleDOI
TL;DR: In this paper, the superconducting transition temperature and its dependence on hydrostatic pressure to 22 kbar have been determined for a series of (La, Ce)Ru2 alloys.