Thermal Dilatation Research Articles

The investigation of the structural relaxation of Fe40Ni40B20 metallic glass by thermal dilatation measurements

High precision thermal dilatation measurements are used for the investigation of the structural relaxation and the crystallization process in amorphous Fe40Ni40B20 alloys obtained by the melt spinning technique. In the region of low temperature relaxation the thermal dilatation curves show an irreversible behaviour which is attributed to a change in the excess volume of the non-ideal glass. This process is quasi-continuous and results in about 0.15% length contraction for the quasi-isothermal annealing. In addition to this quasi-continuous densification two pronounced dilatation minima also occur which are probably due to compositional short range ordering before crystallization. The apparent activation energies (E) for the initial and further stages of crystallization are determined from the thermal dilatation curves obtained for the heating rates ranging from 1.5 to 160 K/min. Our E values of 3.1 and 3.6 eV (for the initial and further stages of crystallization, respectively) are in good agreement with those obtained independently from other measurements. The apparent contraction during crystallization is practically the same as that for low temperature relaxation.

An X-ray diffraction study of some hydrogen-heavy rare earth systems

Measurements of the lattice parameters of h.c.p. terbium, dysprosium and holmium containing 20 at.% H or 20 at.% D were made by X-ray diffraction between 20 and 800 °C. Information on the ratio c a and the thermal dilatation anisotropy α∥ α⊥ was obtained for the high temperature random solutions and is discussed. In the intermediate temperature range the heat H s of solution was determined. With regard to the existing results on hydrogen solutions of erbium, thulium and lutetium, the conditions for the appearance of the so-called α ∗ phase are discussed in terms of the heat of solution, which controls thermodynamically the ideal equilibrium state and of the hydrogen migration energy, which controls in practice the establishment of this equilibrium. A model is proposed.

Apparatus for thermal dilatation measurements of amorphous samples

An apparatus for high precision thermal dilation measurements of thin metallic amorphous ribbons is described. The arrangement is suitable for investigations in the temperature range from room temperature to 1400K and for heating rates from 2.5*10-2K s-1 to 2.5K s-1. The sample is fixed to a fused silica holder in a novel way and the thermal treatment is performed in a pure helium atmosphere. The resolution of the apparatus (limited by mechanical vibrations) is 10-7 m.

Magnetic properties of splat quenched Fe-Ni invar alloys

Recently, we proposed that the fcc phase of Fe-Ni Invar alloy has a tendency to be separated into two fcc phases. This idea is tested by comparing the magnetic properties and the thermal dilatation of splat quenched specimens with those of annealed specimens.

Elastic moduli and mode gammas of GaP: Their relationship to those of other isomorphic crystals and the high pressure structural-electrical transition

The transit times of ultrasonic waves associated with piezoelectrically inactive modes have been measured in sulfur-dope, n-type GaP using hydrostatic pressures up to 5 kbar. The velocities and elastic constants of most modes increase linearly with pressure but C S = 1 2 ( C 11− C 12) decreases slightly. The behavior of the elastic constants and their associated mode gammas are compared to those of other III–V compounds and of Si and Ge. We suggest that the behavior of C S is related to the occurrence of the structural-electrical transition which occurs at high pressure. A modified Born criterion for lattice stability developed by Demarest et al . is used to explain this relationship. The contribution of thermal dilatation to the temperature dependence of each elastic constant is deduced. Using it and data from the literature we find that the explicit thermal contribution to each elastic constant is significant and in the case of C 12 has an anomalous sign.

Beiträge zum thermischen Verhalten von Sulfaten, IV* Neues zum Verhalten von PbSO4 bei höherer Temperatur / Contributions to the Thermal Behaviour of Sulfates, IV* New Facts About the Behaviour of PbSO4 at Higher Temperature

Abstract Thermal Behaviour, Crystal Structures, Modifications Using the high temperature Guinier technique the transformation of the room temperature form N-PbSO4 to the cubic high-temperature form H-PbSO4 was observed. The nonquenchable H-PbSO4 modification crystallizes in the α-NaClO4-type with a(900°) = 7,23 Å, Z = 4 and dX-ray (900 °C) = 5,33 g/cm3 . The thermal dilatation of N-and H-PbSO4 was measured.

The stability, thermal dilatation and solidification properties of partially hydrogenated cottonseed oil emulsion in skim milk

SummaryThe stability of partially hydrogenated cottonseed oil in skim milk emulsion depended on the fat content and on the addition of emulsifier, being stable up to 50% fat. The thermal dilatation and the solid to liquid fat ratio were considerably affected by the fat content and the precooling treatment applied prior to dilatation. The total thermal dilatation, from 0 to 45°C, and the dilatation maxima increased with high fat content. Lower precooling temperature caused higher total dilatation, while longer precooling period led to high solid to liquid fat ratio up to 38°C.

A micropolar continuum theory for the flow of granular materials

The flow of granular materials at high deformation rates and low stress levels is described here using a micropolar continuum theory. The constitutive equations are obtained by statistical inference; the interparticle interactions are first studied, and constitutive relations of the continuum theory are deduced by statistical averaging. The material is assumed to consist of cohesionless rigid spheres of uniform size and the same mass, and the equivalence of the continuum description and the particle description is discussed. Particle fluctuations are regarded as macroscopic “heat”, and a thermodynamic analogy is developed. The “equations of state” are derived by assuming “local equilibrium”. “Entropy” is also introduced, and the law of “entropy” increase is proved. Two different regimes of flows—slow flows and fast flows—are analyzed, and such typical non-linear characteristics as the existence of the angle of repose and the “thermal dilatation” due to the particle fluctuations are shown to exist.

On Zero or Negative Thermal Dilatation of the Quenched Irreversible Fe–Ni Invar Alloys

The effect of quenching on the thermal dilatation of the Fe–Ni Invar alloys has been studied by absolute thermal dilatation measurements. It is well known that the reversible alloy with 36%Ni possesses the lowest coefficient of dilatation. The present study shows that the quenched irreversible alloy with 34%Ni also indicates zero or negative thermal dilatation. And apparent two A s -points are detected in the irreversible Invar alloys. These observations suggest that a stable state in the γ-phase region is not the perfect γ-phase. The measurements of magnetic susceptibility in the para-process and X-ray analyses indicate that the states produced by quenching have some similarities to those by cold-working, which can be ascribed to a transitional structure far from the perfect f.c.c. lattice.

Thermal variation of the apparent specific volume of polystyrenes in solution

A new approach to the polymer interactions inside and outside the coil is discussed and we explain the experimental variation of the apparent specific volume of polystyrene in good and in θ-solvents. In cyclohexane we define two very different regions above and below the θ-point. For the region above the θ point we calculate the thermal dilation coefficient, \\ ̄ ga, subtracting the intramolecular segment density effect. We relate \\ ̄ ga to the external degrees of freedom of the chain starting from the Prigogine theory of polymer solutions. We first considered the intramolecular segment interactions of the coil in the dilute solution.

Measurement of Thermal Expansion and Spontaneous Strain of Rochelle Salt

The thermal dilatations l j ( j =1, 2, 3) of Rochelle salt were carefully measured in a temperature range -40°C to +40°C by means of the air-capacitor method. The coefficients of linear thermal expansion exhibit a step-like behavior at both Curie points and their amplitudes agree fairly well with those estimated previously by the thermoelastic effect. The step in volume thermal expansion shows a positive sign at both Curie points. The spontaneous strains were separated from the l j by the method of least squares. The electrostrictive constants Q 1 j and Q 1 h (for volume) were obtained and it was found that the Q 13 shows an opposite sign to that given by Mason and a considerable temperature dependence which makes the sign of Q 1 h change in the ferroelectric region.

On Zero or Negative Thermal Dilatation and Phase Transformations in Cold-Worked Fe–Ni Invar Alloys

The effect of cold-swaging on the low thermal dilatation in the Fe–Ni Invar alloys, especially the negative dilatation of the 36%Ni alloy, was investigated by the X-ray and magnetic measurements as well as the thermal expansion measurements in the directions perpendicular and parallel to the swaging direction. Anomalies of the α→γ transformation were found in the irreversible alloy, which behaves as including higher A f -points or lower nickel contents. The γ-phase alloy after this transformation includes presumably lower Curie points. For the 36%Ni alloy, a swelling portion was found in the magnetic susceptibility in the para-process versus temperature curve in a lower temperature range, which is in agreement with the range of the negative dilatation. To explain such a state, a shear mechanism was discussed.

Thermal Dilatation in Pb(Zn1/3Nb2/3)O3 Crystal

The temperature dependence of the cell dimension of Pb(Zn1/3Nb2/3)03. crystal was investigated in the temperature range between liquid nitrogen temperature and 400°C by using an X-ray diffractometer and a thermal dilatometer of differential transformer type. The latticeconstant a increases with increasing temperature and the rhombohedral angle α approaches 90° at about 150°C. An anomaly in thermal dilatation was observed over a wide range of temperatures, corresponding to a diffuse transition from ferroelectric to paraelectric phase. The linear thermal expansion coefficient decreases with increasing temperature in the ferroelectric phase, reaches a minimum at about 120°C, and then gradually increases to a constant value(10.0×10-6K-1)in the higher temperature region.

Contribution of Lattice Dilation to the Temperature Shift of the Energy Gaps in Trigonal Selenium

AbstractThe influence of thermal lattice dilation on the temperature shift of some optical transitions has been studied. Below 100 K the shift of both the direct gap at H and the indirect gap is determined by the lattice dilation perpendicular to the hexagonal axis c, caused by acoustical phonons which leads to an increase of the gap energy with rising temperature. At higher temperatures the electron‐phonon coupling (mainly by optical phonons) gains importance and decreases the temperature coefficient of the gap energies. The energy of the direct gap at Z is less sensitive to the thermal dilation of the lattice.

A Focused-Beam Type Laser Interferometric Dilatometer

Using a laser beam focused near interferometer plates, an improved interferometric dilatometer has been developed. It has a couple of features, i.e. it has a much greater latitude in parallelism adjustment of the interferometer plates than that of the conventional Fizeau-type ones and enables, on the other hand, automatic recording with a simple device just composed of a solar cell and a recorder to measure reflected beams. Moreover, collimation of the optical system is very easy. Therefore, it is applicable even to routine determination of dilatation for quality control in a factory. The dilatometer is capable of determining the thermal dilatation of materials with low and/or negative expansion as well as those with transition, extremum or inflection point in expansion curves. Experimental results on some metallic, ceramic, semiconductor and glassy materials are presented.

Precision measurements of densities and thermal dilation of water between 5.deg. and 80.deg.

Precision measurements of densities and thermal dilation of water between 5.deg. and 80.deg.

Thermal dilatation and solidification properties of buffalo and cow creams

The thermal dilatation of cow cream, within a temperature range of -8° to 35° C, is considerably higher than that of buffalo cream, probably due to the difference in the degree of dispersion, in the saturation, and in the solidity of fat. The dilatation does not proceed regularly at the different temperatures. Cow cream shows one maximum dilatation, while buffalo cream shows three maxima, none of them is of the same height of cow maxima. Both creams contain the same solid fat percentage up to 16° C, afterwards, buffalo cream always contains higher percentage than cow cream at any temperature up to 30° C.

Thermodynamics of interacting continua with surfaces and creep analysis of concrete structures

Creep, shrinkage and delayed thermal dilatations of concrete have source mainly in the interaction with water of the internal surfaces of solids in the cement paste microstructure. This interaction is believed to consist in changes of thickness or mass content of mono- and multimolecular adsorbed water layers confined between two solid adsorbent surfaces. These changes are brought by diffusion of water and other molecules along the layers. In the present paper a consistent formulation of the above mechanism based on surface thermodynamics is presented and the isotropic macroscopic stress-strain relations are derived. These relations indicate the form of the dependence of material parameters on pore humidity and temperature, and restrict considerably the number of possible forms of constitutive equation that would have to be assumed on a purely phenomenological basis if the material were regarded as general interacting continua in which strains are general functionals of the history of water content and temperature. A viscoelastic material with time-dependent properties is obtained as the special case for constant humidity and temperature. A suitable, numerically stable algorithm of step-by-step time integration of stress and strain problems is also presented. Analysis of experimental data aimed at numerical determination of the material parameters is presently in progress at Northwestern University.

Cu-W複合材料の熱膨張について

The effects of annealing and subzero treatment on thermal dilatation of the W-fiber Cu composite were studied in relation to the residual stress and matrix yielding.For the composite annealed at 600°C for 1 hr, the heating curve forms a hysteresis loop with the cooling curve on the test up to 300°C, and a small region of inflection is observed on each curve.By the subzero treatment at −196°C for 10 min the inflection temperature on heating is lowered, but on cooling, it remains unchanged and no hysteresis loop is formed.In the temperature range which reaches the inflection region on heating and cooling tests, the fiber and the matrix undergo elastic deformation. The matrix begins to yield at the inflection. On the heating curve of the subzeroed composite, the inflection region is observed near room temperature corresponds to the matrix yielding.The temperature dependencies of expansion and contraction within the temperature range from the start to the inflection on heating and cooling tests below 300°C become smaller with increasing volume fraction of fiber (Vf). The coefficient can be simply estimated by the stress condition.The expansion coefficient beyond the temperature, at which the matrix starts the yielding, is independent of Vf and corresponds to the coefficient of the fiber. The average of the coefficient up to 300°C becomes smaller with the increase of Vf and coincides with the calculated value.

Evaluation of some physical quantities in the two phase region in cuprous selenide

The change of electrical conductivity and thermal dilatation of cuprous selenide at its phase transition was examined. The behaviour of these properties was explained considering a non-stoichiometric Cu 2− x Se sample as the binary system (Cu 2Se+copper deficit) and equating the concentration of deficit copper atoms with the concentration of holes. An experimentally attainable equilibrium process of phase transition in which both phases have different concentration of holes is discussed. The equations derived on the basis of this process describe the experimental curves with satisfactory agreement.