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Showing papers on "Phase (matter) published in 1975"


Journal ArticleDOI
TL;DR: In this article, the conditions for the retention of a zirconia-rich tetragonal phase at ambient temperature were established and the existence of a miscibility gap, closed below the solidus temperature, in the yttria-rich solid solution region was proposed.
Abstract: Metastable and equilibrium phase relationships in the system ZrO2:YO1.5 have been studied by X-ray diffraction. The conditions for the retention of a zirconia-rich tetragonal phase at ambient temperature are established. The existence of a miscibility gap, closed below the solidus temperature, in the yttria-rich solid solution region is proposed. Some evidence for partially ordered phases is presented.

1,170 citations


Journal ArticleDOI
P. E. Cladis1
TL;DR: The nematic phase occurs at both a higher and a lower temperature than the smectic phase as mentioned in this paper, and measurements of the bend elastic constant as a function of concentration are presented.
Abstract: The nematic-smectic-$A$ transition temperature of mixtures of HBAB {$p$-[($p$-hexyloxybenzylidene)-amino]benzonitrile} and CBOOA [N-$p$-cyanobenzylidene-$p\ensuremath{-}n$-octyloxyaniline] becomes multivalued with increasing concentration of HBAB. The nematic phase occurs at both a higher and a lower temperature than the smectic phase. Measurements of the bend elastic constant as a function of concentration are presented.

321 citations


Journal ArticleDOI
TL;DR: In this article, phase diagrams representing lateral phase separations in the plane of lipid bilayer membranes have been determined for binary mixtures containing dielaidoylphosphatidylcholine together with dimyristoyl-phosphate-derived spin labels.
Abstract: Phase diagrams representing lateral phase separations in the plane of lipid bilayer membranes have been determined for binary mixtures containing dielaidoylphosphatidylcholine together with dimyristoylphosphatidylcholine, dipalmitoylphosphatidylcholine, distearoylphosphatidylcholine, dioleoylphosphatidylcholine, and dipalmitoylphosphatidylethanolamine. The phase diagrams were deduced from observations of the temperature dependence of the paramagnetic resonance spectra of low concentrations of spin-labels incorporated in these bilayer membranes. In one case, the binary mixture of dipalmitoylphosphatidylethamine and dielaidoylphosphatidylcholine, evidence has been obtained for fluid-fluid immiscibility, in specified temperature and compoistion ranges. This immiscibility could give a lateral phase separation into fluid domains in the plane of the membrane, and/or a transverse phase separation into an asymmetrical bilayer membrane, and/or possibly disco ntinuous bilayer membranes of different composition. An asymmetrical bilayer membrane can be expected on theoretical grounds to form a nonplanar membrane.

297 citations



Journal ArticleDOI
TL;DR: In this paper, the effects of fabrication variables on the high-temperature strength of hot-pressed Si3N4 containing 5 wt% Y2O3 were studied.
Abstract: The effects of fabrication variables on the high-temperature strength of hot-pressed Si3N4 containing 5 wt% Y2O3 were studied. Materials containing a crystalline grain-boundary phase, formed as a consequence of a high-temperature presintering heat treatment and identified as Si3N4·Y2O3, had high-temperature strengths significantly superior to those observed for materials containing a glass phase.

230 citations


Journal ArticleDOI
TL;DR: The panel discussed the question of a developmental phase of parenthood in an epigenetic context, and the suggestion that those with residual partial failures in the resolution of their earlier intrapsychic conflicts have an opportunity for new and better solutions.
Abstract: Dr. Irwin Marcus introduced the Panel members, noting that Therese Benedek, in a presentation to this Association in 1958, parented the title and theme of this Panel. Marcus set the question of a developmental phase of parenthood in an epigenetic context. He observed that all our basic psychoanalytic concepts, from their inception by Freud, are developmental. Beyond the Oedipus complex, Freud detailed a puberty and climacterium. Of the subsequent contributions in expansion of Freud’s original formulation, Marcus could touch on the work of only a few. Spitz refers to phases of development in terms of critical periods and organizers. His theories explicate Freud’s theory of the complemental series and of furation, and generate implications for prevention and therapy. Mahler’s formulations of the normal autistic, symbiotic, and separation-individuation phases of development have stimulated a series of panels on “The Experience of Separation-Individuation in Infancy and its Reverberations Through the Course of Life.” Moving another step ahead on the continuum into.adolescence, Blos has described four developmental tasks of that phase of development: the second individuation, achievement of ego continuity, integration of a sexual identity, and mastery of residual trauma. Marcus noted that progressive and regressive aspects of developmental phenomena occur throughout the life cycle. The achievement and maintenance of an adult ego identity cannot be regarded as a permanent, unalterable state. Zetzel considered it a basic fact of life that every important maturational challenge presents significant regressive threats. She believed that those with limited symptomatology during a developmental crisis have greater potential for genuine maturity than those who have consolidated regressite defenses in their definitive character structure. Marcus saw in this postulate the suggestion that those with residual partial failures in the resolution of their earlier intrapsychic conflicts have an opportunity for new and better solutions.

230 citations


Journal ArticleDOI
TL;DR: In this paper, the early stages of spinodal decomposition in age hardening Cu-Ti alloys have been studied by electron microscopy, and a sequence of microstructures was used to show that continuous phase separation was the mechanism of decomposition.

229 citations



Journal ArticleDOI
TL;DR: In this article, a review of phase equilibria in glass-forming systems is presented together with a discussion of the thermodynamic behaviour of systems exhibiting liquid-liquid immiscibility.
Abstract: This review is concerned with the process of liquid-phase separation in glass-forming systems. In the first part a general account of phase equilibria is presented together with a discussion of the thermodynamic behaviour of systems exhibiting liquid-liquid immiscibility. The estimation of free energies from phase-boundary data and the location of the spinodal boundary are briefly considered. The origin of immiscibility in silicate solutions is discussed from a thermodynamic approach. The importance of association, particularly in silicate systems, is stressed. In the second part of the review, an outline of the theories of homogeneous nucleation and spinodal decomposition is given and a review of recent theoretical developments. The intersecting growth model is discussed and also the laterstage coarsening of both droplet and interconnected structures. The theories are compared with experimental results (including electron microscope and small-angle X-ray scattering data) for various systems. The effects of phase separation on crystallization processes in glasses and on the physical and chemical properties of glasses are outlined. Although the results considered are for oxide systems where sufficient data are available, much of the discussion is applicable to glass-forming systems in general.

169 citations


Journal ArticleDOI
TL;DR: In this paper, the phase behavior at low temperature, in particular the critical and tricritical properties, of liquid 3He4He mixtures and certain types of metamagnets, such as FeCl2 etc., is investigated.

159 citations


Journal ArticleDOI
TL;DR: The microstructure of a complex multicomponent varistor ceramic based on ZnO with small additions of antimony, bismuth, cobalt, manganese, and tin oxides has been elucidated using a variety of structural techniques as mentioned in this paper.
Abstract: The microstructure of a complex multicomponent varistor ceramic based on ZnO with small additions of antimony, bismuth, cobalt, manganese, and tin oxides has been elucidated using a variety of structural techniques. Three crystalline phases are found to coexist in the sintered material. The bulk phase consists of a polycrystalline matrix of ZnO doped with Co(II). The ZnO grains are separated from one another by a Bi2Zn4/3Sb2/3O6 pyrochlore phase which forms a three−dimensional threadlike network, indicative of a liquid phase at high temperatures. A Zn(Zn4/3Sb2/3)O4 spinel constitutes the third phase and forms well−faceted octahedral crystals located frequently at grain boundaries between the ZnO and occasionally within the grains. This phase acts as a grain growth moderator for ZnO by anchoring the boundaries during sintering, but plays no role in the nonlinear characteristic of the varistor. A quasiequilibrium between the pyrochlore and spinel has been established such that formation of the spinel is favored at high temperatures. The over−all varistor microstructure may be described as a three−dimensional series−parallel network of ZnO−pyrochlore junctions.

Journal ArticleDOI
TL;DR: Amorphous Ge x Se 1− x compounds have been prepared and carefully characterized in the range 0.15 ⩽ x ¼ 0.30 by heating samples from the amorphous phase, the crystallization process has been investigated for 0.43 (density and micro-hardness measurements and DTA experiments as discussed by the authors ).
Abstract: Amorphous Ge x Se 1− x compounds have been prepared and carefully characterized in the range 0 ⩽ x ⩽ 0.43 (density and micro-hardness measurements and DTA experiments). By heating samples from the amorphous phase, the crystallization process has been investigated for 0.15 ⩽ x ⩽ 0.30. An immiscibility gap in the vitreous region is determined by optical microscopy, from phase-separation observations; moreover, a new metastable crystalline phase appearing as an intermediate step between phase separation and stable GeSe 2 is described.

Journal ArticleDOI
TL;DR: In this article, the transformation behavior of roller-quenched amorphous Pd 0.165 alloys, after rapid heating to temperatures near to or above T g, is reported.
Abstract: The transformation behavior of roller-quenched amorphous Pd 0.82− x Au x Si 0.18 and Pd 0.835− x Au x Si 0.165 alloys, where x ⩽ 0.10, after rapid heating to temperatures near to or above T g , is reported. The calorimetrically determined glass ( T g ) and kinetic crystallization ( T c ) temperatures both increased with x up to x ≈ 0.04. With increasing x , at x ⩾ 0.04, T c decreased rapidly while T g varied little. Binary Pd 0.82 Si 0.18 alloys crystallized to an fcc phase without apparent composition segregation. The tendency to phase separate at T near T g , as manifested by small- (SAXS) and large-angle X-ray scattering and calorimetry, increased with increasing Au substitution. Pd 0.8 Au 0.035 Si 0.165 alloy apparently phase separated by a nucleation and growth mechanism, with a growth rate limited by the melt viscosity, to form an fcc phase dispersed in an amorphous phase which later crystallized. Pd 0.74 Au 0.08 Si 0.18 alloy phase separated initially to two melts, each of which later crystallized in turn. The initial separation behavior was generally consistent with the predictions of the spinodal theory but with some deviation from Cahn's linear relation.

Journal ArticleDOI
TL;DR: In this paper, the diffusion coating of nickel with aluminum was studied by a two-step aluminizing pack process involving initially an influx of aluminum at the surface (step 1) and later a partial honiogenization of the aluminum-rich region under conditions of zero surface flux (step 2).
Abstract: The diffusion coating of nickel with aluminum was studied by a two-step aluminizing pack process involving initially an influx of aluminum at the surface (step 1) and later a partial honiogenization of the aluminum-rich region under conditions of zero surface flux (step 2). The process was studied in the temperature range from 870 to 1000°C. Step 1 was characterized mainly as the rapid, parabolic growth (after an initial transient period) of the Ni2Al3 phase (γ) as a surface layer with concurrent growth of a thinner NiAl (δ) layer. Step 2 was characterized mainly as the rapid loss of the aluminum gradient in the γ layer followed by parabolic growth of the δ layer primarily by the solution of they phase. Mathematical models were developed, in which numerical methods and computer techniques as well as closed-form solutions were utilized. The models yielded growth rate predictions in agreement with the experimental data and were used to define the critical parameters controlling growth kinetics for the aluminide layers formed during this process.


Journal ArticleDOI
TL;DR: In this paper, the energy of solid neutron matter configurations in which layers of parallel spin neutrons with spin direction perpendicular to the plane of the layer are stacked such that neutrons in adjacent layers have antiparallel spins was investigated.

Journal ArticleDOI
TL;DR: In this article, Tungsten spheres of uniform size were coated with copper and then heated above the melting point of copper for four minutes, and by direct comparison of the presintered and the liquid phase sintered condition the movements of individual particles could be measured as a function of the amount of liquid, wetting angle and packing density.

Journal ArticleDOI
TL;DR: The temperature dependence curve of chlorophyll a fluorescence in intact cells, membrane fragments, and extracted lipids of Anacystis cells suspended in a buffer solution showed that the fluorescence yield became maximum near the phase transition temperatures, suggesting that chlorophyh a in the thylakoid membrane works as a native fluorescence probe for the detection of phase transition.
Abstract: The transition of the physical phase of lipids in membrane fragments of a blue-green alga Anacystis nidulans was studied by a spin labeling technique. The maximum hyperfine splitting of the electron spin resonance spectrum of the N-oxyl-4', 4'-dimethyloxazolidine derivative of 5-ketostearic acid plotted against the reciprocal of the absolute temperature gave a discontinuity point that was characteristic of a transition of the physical phase of the hydrocarbon region of membrane lipids. The phase transition appeared at approximately 13 or 24 C in the organisms grown at 28 or 38 C, respectively.The temperature dependence curve of chlorophyll a fluorescence in intact cells, membrane fragments, and extracted lipids of Anacystis cells suspended in a buffer solution showed that the fluorescence yield became maximum near the phase transition temperatures. These findings suggest that chlorophyll a in the thylakoid membrane works as a native fluorescence probe for the detection of phase transition.The temperature dependence of photosynthetic electron transport reactions was studied by measuring the oxidoreductive reactions of P700 and by measuring O(2) evolution. Each of the Arrhenius plots of the reaction rates was composed of two straight lines with a break near the phase transition temperatures. The activation energy was always lower above than below the transition temperatures. It is proposed to explain these phenomena that a reaction involving plastoquinone is influenced by the physical state of membrane lipids.The shift between the pigment state 1 and state 2 measured by fluorescence transients also showed a characteristic break in the Arrhenius plots near the phase transition temperatures; below the transition temperatures the shift almost disappeared. This suggests that the configurational change of the thylakoid membrane related to the state 1 and state 2 shift is dependent on the physical state of membrane lipids. In the chloroplasts of lettuce and spinach, on the other hand, there was no break in the Arrhenius plot of the electron transport reactions or of Mg(2+)-induced changes of chlorophyll a fluorescence.It is suggested that the transitions of the hyperfine splitting of the ESR signal, electron transport, and the configurational change, as well as the appearance of the maximum of chlorophyll a fluorescence, in the thylakoid membranes of Anacystis nidulans are all related to the transition of the physical phase of membrane lipids between the liquid crystalline state and the mixed liquid crystal-solid state.

Journal ArticleDOI
TL;DR: In this article, a region of coupled growth, in which modified eutectic alone grows, has been delineated and the effect of strontium level on the shape of this region determined.

Journal ArticleDOI
TL;DR: In this paper, the decomposition tie line of a quenched and aged alloys along the composition line was studied by electron diffraction and microscopy, and it was suggested that for the symmetrical alloy, the structure of the Cu3Al-rich particles varies with decomposition temperature.

Journal ArticleDOI
L.L. Ting1
01 Sep 1975-Wear
TL;DR: In this article, the authors analyzed the engagement behavior of two annular disks covered with a layer of porous material, and the engagement model dealt with was postulated to consist of three phases: squeeze film phase, mixed asperity contact phase and consolidating contact phase.

Journal ArticleDOI
TL;DR: In this article, a two-phase material with cylindrical phase boundaries is considered and the generators of the phase boundaries are parallel to the z axis and the x and y axes are the principal axes of the effective conductivity tensor.
Abstract: A two−phase material in which the phase boundaries are cylindrical surfaces is considered. The generators of the phase boundaries are parallel to the z axis and the x and y axes are the principal axes of the effective conductivity tensor. If the two phases have conductivities σ1 and σ2, then the effective conductivity σx* (σ1,σ2) (in the x direction) of the material and the effective conductivity σy* (σ2,σ1) (in the y direction) of the material obtained by interchanging the two phases are related by σx* (σ1,σ2) σy* (σ2,σ1) =σ1,σ2. For a statistically isotropic material σx* (σ1,σ2) =σy* (σ1,σ2) =σ* (σ1,σ2). If, in addition, the material is statistically symmetric so that interchange of the two phases yields again the same material, then σ* (σ1,σ2) =σ* (σ2,σ1) = (σ1σ2)1/2.

Journal ArticleDOI
TL;DR: The phase equilibria in the FeFe2O3Y 2O3 system have been established at 1200°C and the standard free energies of formation of yttria, hematite, magnetite, wustite, metallic iron, yttrium-iron perovskite, and a new phase YFe 2O4 belonging to a rhombohedral crystal system were determined in this article.

Journal ArticleDOI
TL;DR: It is demonstrated that a clinical concentration of an inhalation anesthetic produces changes in both the phase transition temperature of pure lipid bilayers and the lateral phase separation temperature of mixed dipalmitoyl- and dimyristoylphosphatidylcholine bilayers of a magnitude sufficient to influence protein function.
Abstract: Several workers have shown that phase transition-related changes in membrane lipids have a profound effect on membrane-solvated protein function. This phase transition temperature dependence has been explained as resulting from the formation of lateral phase separations within the membrane bilayer. The present study demonstrates that a clinical concentration of an inhalation anesthetic produces changes in both the phase transition temperature of pure lipid bilayers and the lateral phase separation temperature of mixed dipalmitoyl- and dimyristoylphosphatidylcholine bilayers of a magnitude sufficient to influence protein function. It is further shown that pressure is able to antagonize the effect of the anesthetic on these transition temperatures. It is proposed that anesthetic action within nerve membranes may be the result of changes in the lateral phase separation-controlled environment of the membrane-solvated proteins essential to nerve function.

Journal ArticleDOI
TL;DR: In this article, the Percus-Yevick equation for a multicomponent system of adhesive spheres is solved exactly and the phase behavior is determined by the number and nature of zeros of a system of m (m + 1) 2 quadratic equations.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the kinetics of adsorption and desorption to the air/water surface in submicellar surfactant solutions by means of a dynamic technique in which the surface is subjected to small amplitude sinusoidal compression and expansion.
Abstract: The kinetics of adsorption and desorption to the air/water surface in submicellar surfactant solutions has been studied by means of a dynamic technique in which the surface is subjected to small amplitude sinusoidal compression and expansion. In all cases studied so far a diffusion controlled mechanism was found, characterised by a frequency dependent surface tension variation and a phase difference between applied area change and resulting surface tension change of at most 45°. When such experiments are carried out above the critical micellar concentration a characteristically different behaviour is observed with a much steeper frequency dependence of the surface tension change and with phase differences between 45 and 90°.Experiments of this type, carried out for solutions of some nonionic surfactants can be quantitatively interpreted on the basis of a model in which the diffusional exchange of monomers between surface and bulk and the exchange between monomers in the intermicellar solution and micelles are consecutive processes. It is shown that establishment of micellar equilibrium under certain conditions can be a fairly slow process with relaxation times of the order of seconds, although the actual exchange of monomers with micelles could well be several orders of magnitude faster.Some implications of the presence of micelles on the general nature of dissipative processes near a surface are discussed.

Journal ArticleDOI
TL;DR: In this article, the poling of certain compositions of PLZT ceramic is shown to cause a phase transition (α→β) in a single−grain thickness, where the polar β phase can be rhombohedral, tetragonal, or orthorhombic depending upon composition.
Abstract: The poling of certain compositions of PLZT ceramic is shown to cause a phase transition (α→β). The polar β phase can be rhombohedral, tetragonal, or orthorhombic depending upon composition, while phase α is always cubic. Characteristic subgrain domain structure is observed in the β phase for orthorhombic and rhombohedral compositions. Phase α is shown to be optically isotropic in a single−grain thickness. Identification of these phases and the observed domain structure enables the phase transitions

Journal ArticleDOI
TL;DR: In this article, it was shown that the amount of Fe that can be oxidized in the forsterite phase is directly related to the excess Si present, either incorporated in the structure, or available from another phase richer in SiO 2 such as pyroxene.

Journal ArticleDOI
TL;DR: Introduction of cholesterol leads to a reduction in fluorescence intensity, most readily explained by a 1:1 lipid:cholesterol interaction with exclusion of monomeric, fluorescent, chlorophyll a.

Journal ArticleDOI
TL;DR: In this paper, the triple point (γ, ǫ, l) of iron has been located at 0.94±0.20 Mbar and 2970 ± 200°C by means of extrapolations of recent data on the melting temperature of the γ phase of iron to 200 kbar and of the revised γ -ǫ phase boundary.
Abstract: Summary The triple point (γ, ɛ, l) of iron has been located at 0.94±0.20 Mbar and 2970 ± 200°C by means of extrapolations of recent data on the melting temperature of the γ phase of iron to 200 kbar and of the revised γ - ɛ phase boundary. The slope for the ɛ - l boundary is calculated to be 1.4±0.3 deg/kbar at the triple point. For a core composition dominated by iron and for all realistic estimates of the slope of the γ - ɛ phase boundary, the ɛ phase appears to be the appropriate iron phase for the inner core. Using the linear relationship between melting temperature and volume compression of the solid phase proposed by Kraut and Kennedy, the melting temperature of the ɛ iron at a pressure corresponding to the mantle-core boundary is calculated to be 3500 ± 200°C and that at a pressure corresponding to the inner-outer core boundary to be 4650 ± 500°C. The present calculated melting temperature difference throughout the outer core is more than twice as great as that estimated by Higgins and Kennedy who have not considered the effect of the γ - ɛ transformation on the melting curve. Hence, the obstacle preventing adiabatic convection in the liquid outer core has been removed without resort to the suggestions of other investigators.