Showing papers on "Phase (matter) published in 1970"
TL;DR: In this paper, the authors discussed the properties of small elongated particles suspended in a nematic or cholesteric phase, with low concentrations, and found that in most cases the particle axis should be locked and parallel to the local nematic axis n(r).
Abstract: The present paper discusses some properties of small, elongated particles suspended in a nematic or cholesteric phase, with low concentrations (typical volume fraction occupied by the particle f ≊ 10-3). We find that in most cases the particle axis should be locked and parallel to the local nematic axis n(r). If such colloidal suspensions could be made successfully with magnetic grains, it should be possible to prepare « ferronematics » or « ferrocholesterics », where locally all particles are magnetized in one direction (colinear to n), and also « compensated » materials with no spontaneous magnetization. These three types of samples should all show remarkable distorsions and phase changes in low external fields H. Similar effects are expected under electric fields with colloidal suspensions of polar rod molecules such as helical polypeptides.
553 citations
TL;DR: In this article, the authors have observed a divergence of the magnetic birefringence, and a critical increase and slowing of the fluctuations in order in the isotropic phase of a nematic liquid crystal.
Abstract: We have observed a divergence of the magnetic birefringence, and a critical increase and slowing of the fluctuations in order in the isotropic phase of a nematic liquid crystal. Our results are quantitatively described by a mean-field model except for a critical region close to the ordering temperature where the fluctuations are so large that the meanfield approximation fails.
290 citations
TL;DR: Monolayer results indicate that the molecular area occupied by the higher melting component becomes larger because of the increased configurational freedom of its chains, particularly with respect to the effect of temperature on lipids and membranes.
279 citations
01 Jan 1970
TL;DR: Two phase mixtures thermally induced flow oscillations, discussing scaling criteria, phase change numbers and stability boundaries were discussed in this paper, where the phase change number and scaling criteria were discussed.
Abstract: Two phase mixtures thermally induced flow oscillations, discussing scaling criteria, phase change numbers and stability boundaries
199 citations
176 citations
01 Jan 1970
175 citations
167 citations
TL;DR: In this paper, a random phase model is used to calculate conductivity, thermopower, and optical absorption of amorphous semiconductors, and an upper limit of 10 17 eV −1 cm −3 can be put on the density of states in the middle of the energy gap, for some bulk semiconducting glasses.
Abstract: A model is studied which assumes that, in the conduting states of an amorphous semiconductor, the phase of the probability amplitude for finding an electron on a particular atomic site varies randomly from atom to atom. This “random phase model” is used to calculate the conductivity, thermopower, and optical absorption. Experimental data on conductivity and thermopower are analyzed for three chalcogenide compositions. There is an upper limit on the mobility of about 20 cm 2 /V sec. The matrix element for an optical transition from conducting states to conducting states is shown to be equal to that from conducting states to localized states. Therefore an upper limit of the order of 10 17 eV −1 cm −3 can be put on the density of states in the middle of the energy gap, for some bulk semiconducting glasses. Measurement of optical absorption of low magnitude in the infrared would make it possible to deduce the density of states as a function of energy in the gap.
152 citations
TL;DR: In this article, phase relations in the system CaO-cobalt oxide in air have been determined in the temperature range of approximately 800-1500°C, where the only crystalline phases existing in equilibrium with liquids are lime solid solution and CoO solid solution; eutectic temperature in air is 1350°C.
150 citations
TL;DR: In this article, the authors used conoscopic observation and circularly polarized light to estimate the C phase temperature dependent tilt angle of liquid crystal smectic C-particle tilt angle.
Abstract: Liquid crystal smectic C phase temperature dependent tilt angle, using conoscopic observation and circularly polarized light
134 citations
TL;DR: In this article, it was suggested that there may be three types of nematic phases: skewed cybotactic, normal and classical nematic phase, in which no regular arrangement between neighboring molecules exists.
Abstract: It is suggested that there may be three types of nematic phases: the skewed cybotactic phase, in which the molecules are arranged in groups in such a way that the centers of the molecules in each group lie in a plane making an angle α (significantly different from 90°) with the mean direction of the molecules in that group; the normal cybotactic phase, similar to the skewed one but with α close to 90°; and the classical nematic phase, in which no regular arrangement between neighboring molecules exists Three means of distinguishing between these phase types are discussed: the X-ray diffraction pattern, the type of the preceding smectic phase, and the microscopic textures It is shown that the application of the last two methods to literature data yields support for the concept of different types of nematic phases
TL;DR: In this paper, the effects of applied fields on the phase transition of isotropic-nematic phase transition in liquid crystals were investigated. But the phase-transition was not shown to be second order.
Abstract: The molecular-field description of the isotropic-nematic phase transition in liquid crystals is investigated. It is found that the effects of fluctuations may be observable, and the first corrections due to fluctuations to the light scattering and magnetic birefringence in the isotropic phase are determined. The effects of applied fields on the phase transition are investigated. It is found that if the molecules prefer to line up transverse to an applied field there is a critical field above which the phase transition is second order.
TL;DR: In this paper, the thermal expansion behavior of two duplex systems, lead-fused silica and aluminum-silicon, has been investigated experimentally above and below room temperature, and the role of microplastic yielding in high-inclusion-content composites is discussed.
Abstract: The thermal expansion behavior of the two duplex systems, lead‐fused silica and aluminum‐silicon, has been investigated experimentally above and below room temperature. The microstructure in the first case consisted of fused silica particles in a lead matrix, while silicon constituted the dispersed phase in the second. The expansion coefficients always fell below those predicted by the simple rule of mixtures. A model is proposed and a new formula for the calculation of the thermal expansion coefficient of duplex materials is derived. The new formula fits experimental results better than Turner's formula. The role of microplastic yielding in high‐inclusion‐content composites is discussed.
TL;DR: In this paper, two different Widmanstatten morphologies have been observed in nominally similar Zircaloy-4.5, showing that some of the particles are NaCl cubic structure with a lattice parameter of 5.25 A which corresponds to zirconium phosphide.
TL;DR: In this paper, a general theoretical investigation of 3-wave interaction in the well-defined phase description with special regard to nonlinear explosive instabilities in the presence of linear damping or growth is presented.
Abstract: The paper presents a general theoretical investigation of 3‐wave interaction in the well‐defined phase description with special regard to nonlinear explosive instabilities in the presence of linear damping or growth.
TL;DR: In this article, the formation of the omega and alpha phases on quenching and aging and of martensite under an applied stress has been studied in binary, isomorphous titanium alloys containing molybdenum, niobium and vanadium.
TL;DR: The ternary phase fields of three tetragonal tungsten-bronze type structures have been located as mentioned in this paper, and only one of these structures is a Ternary compound; it is located along the binary join, extending from 20 to 80 m/o, and melts congruently near 50%.
Abstract: Phase equilibria in the binary system and the ‐rich region of the ternary system were investigated by DTA, x‐ray diffraction, strip heater, and Curie temperature measurement techniques. The ternary‐phase fields of three tetragonal‐tungsten‐bronze type structures have been located, Only one of these structures is a ternary compound; it is located along the binary join, extending from 20 to 80 m/o , and melts congruently near 50% . The ternary solubility extends from about 4% excess to about 1% excess . This phase possesses observable orthorhombic distortion in the ‐rich region of the solid solution. The implications of the phase diagram for the crystal growth of these compounds are briefly discussed.
TL;DR: In this paper, a curve relating composition of synthetic pentlandite with interplanar spacing was determined experimentally as follows: d115 ǫ = 1.9407 − 0.0077x2, where x represents the iron to nickel we...
Abstract: A curve relating composition of synthetic pentlandite with interplanar spacing was determined experimentally as follows: d115 = 1.9407 – 0.0023x + 0.0077x2, where x represents the iron to nickel we...
01 Oct 1970
TL;DR: In this article, the phase diagram of octaoxyethylene dodecylether vs. water system has been determined and the thermodynamic aspects and the dissolution mechanism of nonionic surfactant-water systems are discussed.
Abstract: The phase diagram of octaoxyethylene dodecylether vs. water system has been determined. On the basis of these results as well as of published thermodynamic data, the thermodynamic aspects and the dissolution mechanism of nonionic surfactant-water systems are discussed. Unlike ordinary solutions, an aqueous solution of nonionic surfactant resembles, in principle, a fine dispersion of the two phases. One is the water phase containing a very small amount of nonionic surfactant (0.02 wt %), and the other is the swollen surfactant phase. The thermodynamic properties agree with such a model. The mechanism of the dissolution of biopolymers and polysoaps can be explained similarly.
TL;DR: In this article, the temperature of mesomorphic-isotropic phase changes and of transitions between mesophases may be markedly shifted by manageable electric fields, and experiments demonstrating such a shift in the nematicisotropic transition of $p$-ethoxybenzylidene-${p}^{\ensuremath{'}}$-aminobenzonitrile are reported.
Abstract: It is proposed that the temperature of mesomorphic-isotropic phase changes and of transitions between mesophases may be markedly shifted by manageable electric fields. First experiments demonstrating such a shift in the nematic-isotropic transition of $p$-ethoxybenzylidene-${p}^{\ensuremath{'}}$-aminobenzonitrile are reported.
TL;DR: In this paper, a ternary phase diagram was constructed between UO 2 -U 3 O 8 and CeO 2 −CeO 1·818 for all concentrations of Ce and for temperatures between room temperature and 600°C, from results obtained using a high-temperature X-ray powder diffraction camera.
TL;DR: In this paper, the phase relations in the ZrO2Sc2O3 system have been investigated by the methods of high-temperature X-ray analysis, dilatometry, differential thermal analysis, and electrical conductivity measurements in the composition range 3 −40 mol % Sc 2O3 and the temperature range 20 −2000°C.
01 Jan 1970
TL;DR: In this paper, the phase transformation of the metastable β phase has been found to proceed through a transition reaction leading to the formation of two bcc phases rather than through the precipitation of the ω phase as has been previously reported.
Abstract: The phase transformations which occur in the all-β titanium alloy Ti-13V-llCr-3Al at temperatures below ∼ 500°C have been studied by transmission electron microscopy, X-ray diffraction, and electrical resistivity techniques. The decomposition of the metastable β phase has been found to proceed through a transition reaction leading to the formation of two bcc phases rather than through the precipitation of the ω phase as has been previously reported. An interpretation of the observed decomposition sequence, based on thermodynamic reasoning, is presented. The decomposition characteristics of the Ti-13V-llCr-3Al alloy have been compared with those of a Ti-13V-llCr alloy to determine the influence of aluminum on the transformation behavior.
TL;DR: In this paper, the Curie temperatures, magneto-optical, and magnetic properties of MnBi films at the quenched high-temperature phase were measured and compared with those of the normal low-Temperature phase.
Abstract: Manganese bismuth films can exist in two crystallographic phases. The Curie temperatures, magneto‐optical, and magnetic properties of films prepared at the quenched high‐temperature phase were measured and compared with those of the films at the normal low‐temperature phase. The low Curie temperature of 180°C makes the quenched films more attractive for optical memory applications. Laser Curie‐point writing experiments have been performed on both types of films at various operating temperatures. The results can be explained on the basis of the physical properties of the two phases of MnBi films.
TL;DR: In this article, an additional lower temperature liquid crystalline phase is observed with chloro-substituted compounds for n-alkoxy chain lengths of C8 and longer and with the methyl substituted compounds for chain length of C10 and longer.
Abstract: Bis-(4′-n-alkoxybenzal)-2-chloro-1, 4-phenylenediamines and bis- (4′-n-alkoxybenzal)-2-methyl-1, 4-phenylenediamines with different alkoxy groups have been synthesized. Similar compounds with fluoro, bromo and chloro groups replacing the alkoxy groups have also been prepared. All the compounds show a nematic liquid phase. An additional lower temperature liquid crystalline phase is observed with chloro-substituted compounds for n-alkoxy chain lengths of C8 and longer and with the methyl substituted compounds for chain lengths of C10 and longer. This lower temperature phase can show a threaded texture very similar to the nematic phase. Furthermore, both phases can be uniformly oriented by surface action and can assume a twisted structure. We suppose that the lower temperature phase has a layered structure in which the molecules are inclined to the layers, and that it corresponds to a smectic liquid crystal classified by Sackmann and Demus as smectic C.
TL;DR: The results have shown the presence of liquid crystalline phases and the pronounced influence of these on the properties of emulsions in water-oil-emulsifier systems.