The specific heat of lithium from 20 to 300 °K: the martensitic transformation

1960 ◽  
Vol 254 (1279) ◽  
pp. 444-454 ◽  
Keyword(s):  
Martensitic Transformation ◽  
Specific Heat ◽  
Atomic Weight ◽  
Phase Region ◽  
Two Phase ◽  
Self Diffusion ◽  
Debye Temperatures ◽  
Order Of Magnitude ◽  
Two Phases ◽  
Heat Of Transformation

Measurements on lithium of atomic weight 6·945 are reported. A thermal study of the martensitic transformation showed a large specific-heat anomaly in the reversion region and a specific heat dependent upon thermal history in the two-phase region. The high-temperature end of the reversion anomaly shows time effects which suggest that the process here is controlled by a spectrum of activation energies of the same order of magnitude as that for self diffusion. With some assumptions the heat of transformation from hexagonal closepacked to body-centered cubic lithium is deduced to be about 14 cal/g atom and the Debye temperatures of the two phases at 60 °K are 390 and 371 °K respectively. The entropy at 298·15 °K is 6·95 ±0·04 cal/°K g atom.

The specific heat of sodium from 20 to 300 °K: the martensitic transformation

1960 ◽  
Vol 254 (1279) ◽  
pp. 433-443 ◽  
Keyword(s):  
Martensitic Transformation ◽  
Specific Heat ◽  
Phase Region ◽  
Two Phase ◽  
Cast Sample ◽  
Hexagonal Close Packed ◽  
Debye Temperatures ◽  
Significant Difference ◽  
Two Phases ◽  
Heat Of Transformation

Measurements on a cast sample and an extruded sample are reported. There is no significant difference in behaviour. No anomaly of the type reported by Dauphinee et al. (1954) was found. A thermal study of the martensitic transformation showed a large specific-heat anomaly in the reversion region and a specific heat dependent on thermal history in the two-phase region. The heat of transformation from hexagonal close-packed to body-centred cubic sodium is deduced to be about 10 cal/g atom and the Debye temperatures of the two phases at 20 °K to be 160 and 153 °K respectively. The entropy at 298.15 °K is 12.24 ± 0.12 cal/°K g atom.

Anomalous phase composition in the two-phase region of DyFe3−xAlx (x≤1.0)

2010 ◽  
Vol 25 (4) ◽  
pp. 349-354 ◽  
Author(s):  
Y. Q. Chen ◽  
J. K. Liang ◽  
J. Luo ◽  
J. B. Li ◽  
G. H. Rao
Keyword(s):  
Phase Region ◽  
Hexagonal Structure ◽  
Unit Cell Parameters ◽  
Two Phase ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Two Phases ◽  
Xrd Patterns ◽  
Phase Relationships

The structure transitions and phase relationships of DyFe3−xAlx compounds have been investigated by X-ray powder diffraction. Our XRD results show that each of the compounds with x≤0.45 crystallizes in the rhombohedral PuNi3-type structure with space group R3¯m and Z=9; for the 0.8≤x<1.0 compounds, each has a hexagonal structure of the CeNi3 type with space group P63/mmc and Z=6; and each of the samples with 0.45<x<0.8 is a two-phase mixture of the PuNi3- and CeNi3-type structures. The calculated XRD intensities of the DyFe3−xAlx compounds with x=0.2, 0.33, 0.4, and 0.45 indicate that Dy occupies the 3a and 6c sites, Fe and Al distribute randomly on the 18h site, and the 3b and 6c sites are exclusively occupied by Fe, which agrees well with those of our experimental XRD patterns. The XRD intensities of the DyFe3−xAlx compounds with x=0.8 and 1.0 have also been calculated and found to agree with the experimental results with Dy on the 2c and 4f sites, Fe and Al at the 12k site, and Fe at the 2a, 2b, and 2d sites. In the two-phase region with x=0.45–0.8, the values of unit-cell parameters and phase compositions are linearly dependent on the value of x, indicating that the two phases are constituted by the same composition x with different stacking arrangements. This abnormal two-phase equilibrium is further confirmed by the structural analysis of the DyFe2.33Al0.67 (or x=0.67) sample. The samples with x=1.1 and 1.2 were also analyzed, and each found to be a mixture of more than two phases.

scholarly journals Evolution of Ferromagnetism in LaMnO3+δ

1999 ◽  
Vol 52 (2) ◽  
pp. 205 ◽  
Author(s):  
Michihito Muroi ◽  
Robert Street
Keyword(s):  
Low Temperature ◽  
Hysteresis Loops ◽  
Magnetic Ordering ◽  
Extensive Study ◽  
Ferromagnetic Phase ◽  
Two Phase ◽  
Order Of Magnitude ◽  
Inverse Susceptibility ◽  
Two Phases ◽  
Minor Hysteresis Loops

An extensive study has been made of the magnetic properties of LaMnO3+δ with finely tuned hole concentrations, x (=2δ), ranging between 0·08 and 0·15. As x increases in the range studied, the spontaneous magnetisation at low temperature increases from only about 20% to almost 100% of the value for full polarisation of Mn spins, and the coercivity Hc decreases by more than an order of magnitude, e.g. from 4·2 kOe to 120 Oe at 5 K. The magnetic ordering temperature Tc takes a minimum at x = xc ~ 0·12. For x < xc, the inverse susceptibility shows a marked decrease as Tc is approached from above. Measurements of minor hysteresis loops for the sample with x = 0·08 show that magnetisation is reversible with respect to field changes except near Hc. These observations are discussed in terms of a two-phase exchange coupling (TPEC) model in which it is assumed that at low temperature the system separates into two phases, a hole-free antiferromagnetic phase and an optimally doped ferromagnetic phase, and the two phases are coupled through superexchange interactions at the interface.

Unsteady Analysis of Particle-Laden Gas Flows When Hit by a Moving Shock Wave

2001 ◽  
Author(s):  
Jun Sung Park ◽  
Seung Wook Baek
Keyword(s):  
Shock Wave ◽  
Specific Heat ◽  
Mechanical Characteristics ◽  
Mass Density ◽  
Particle Mass ◽  
Tvd Scheme ◽  
Two Phase ◽  
Energy Conversion Systems ◽  
Successful Design ◽  
Two Phases

Abstract A successful prediction of the thermo-fluid mechanical characteristics of gas and particles is very crucial and imperative for the successful design and operation of rocket nozzles and energy conversion systems. This paper describes an interaction phenomenon when a moving shock wave hits a two-phase medium of gas and particles. A particle-laden gas is considered to be located along a ramp so that numerical integration is accomplished from the tip of ramp for a finite period. For the numerical solution, a fully conservative unsteady implicit 2nd order time-accurate sub-iteration method and a 2nd order Total Variation Diminishing (TVD) scheme are used with the finite volume method (FVM) for gas phase. For particle phase, the Monotonic Upstream Schemes for Conservation Laws (MUSCL) as well as the solution of the Riemann problem for the particle motion equations is used. Transient development of thermo-fluid mechanical characteristics is calculated and discussed by changing the particle mass density and particle specific heat. Major results reveal that when the particle mass density is smaller, there is a stronger interaction between two phases so that the velocity and temperature differences between two phases more rapidly decrease. When the particle specific heat is varied, only a thermal effect (temperature difference between gas and particles) is observed while the other effects (variations of particle concentration and velocity fields) are minor.

Dynamics of Volume Expansion of De-Mixing Liquids after Pulsed IR Heating

2011 ◽  
Vol 64 (9) ◽  
pp. 1274 ◽  
Author(s):  
Jonathan Hobley ◽  
Sergey Gorelik ◽  
Yutaka Kuge ◽  
Shinji Kajimoto ◽  
Motohiro Kasuya ◽  
...  
Keyword(s):  
Volume Change ◽  
Volume Expansion ◽  
Mixed Volume ◽  
Phase Region ◽  
Water Mixture ◽  
Two Phase ◽  
Nanosecond Pulsed Laser ◽  
Two Phases ◽  
The One ◽  
Laser Heated

Triethylamine (TEA)–water mixtures have a critical-temperature (Tc). Below Tc the mixture exists as one phase and above Tc it exists in two phases. The de-mixed volume is different to the mixed volume. A nanosecond pulsed-laser heated a TEA–water mixture so that it de-mixed. The resulting dynamics of volume expansion were monitored using interferometry. For T-jumps within the one phase region the dynamics of volume change were limited by the speed of sound. However, T-jumps between the one and two phase regions also manifested a slower volume change associated with the de-mixing process. After 150 ns, the volume of the de-mixed TEA–water was consistent with the equilibrium volume change. This suggests that, within 150 ns, the system had split into phase-domains having equilibrium compositions of TEA and water. Subsequently the phase domains would simply merge and grow resulting in no further volume change to reduce surface tension between the phases.

Formation and morphology of Kurnakov type D022 compound in disordered face-centered cubic γ–(Ni, Fe) matrix alloys

2006 ◽  
Vol 21 (1) ◽  
pp. 21-26 ◽  
Author(s):  
Akane Suzuki ◽  
Masao Takeyama
Keyword(s):  
Strain Ratio ◽  
Misfit Strain ◽  
Phase Region ◽  
Partial Replacement ◽  
Invariant Line ◽  
Face Centered Cubic ◽  
Two Phase ◽  
Two Factors ◽  
Face Centered ◽  
Two Phases

Formation and morphology of D022 compound Ni3V in γ face-centered cubic (fcc) matrix phase were investigated to understand fundamentals for controlling microstructure of alloys strengthened by Kurnakov-type geometrically close-packed (GCP) intermetallics. The D022 phase with plate-shaped morphology coherently precipitates in the γ + D022 two-phase region above the T0 line in Ni–V binary alloys. Due to the negative and positive lattice misfits along the a-axis and the c-axis of D022 (δa < 0 < δc), an invariant line exists between the two phases, and the morphology of D022 phase is changeable by controlling the two factors; the misfit strain ratio δc/δa is a decisive factor to determine the habit plane defined by the invariant line and one of the a-axes of D022, whereas the magnitude of |δa| is responsible for the shape of D022 phase with either prism or plate. These findings were extended to Ni–Fe–Nb–V system by partial replacement of Ni and V with Fe and Nb, respectively.

PHONON SPECIFIC HEAT NEAR THE MARTENSITIC TRANSFORMATION IN A CUBIC CuZnAl ALLOY

1978 ◽  
Vol 39 (C6) ◽  
pp. C6-1033-C6-1034 ◽  
Author(s):  
D. Abbe ◽  
R. Caudron ◽  
P. Costa
Keyword(s):  
Martensitic Transformation ◽  
Specific Heat

THE MECHANISM OF RAISING AND QUANTIFICATION OF SPECIFIC HEAT FLUX AT BOILING OF NANOFLUIDS IN FREE CONVECTION CONDITIONS

2017 ◽  
pp. 25-34
Author(s):  
V.N. Moraru
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Capacity ◽  
Specific Heat ◽  
Chemical Properties ◽  
Heating Surface ◽  
Physical Models ◽  
Superheated Liquid ◽  
Two Phase ◽  
Boiling Process

The results of our work and a number of foreign studies indicate that the sharp increase in the heat transfer parameters (specific heat flux q and heat transfer coefficient _) at the boiling of nanofluids as compared to the base liquid (water) is due not only and not so much to the increase of the thermal conductivity of the nanofluids, but an intensification of the boiling process caused by a change in the state of the heating surface, its topological and chemical properties (porosity, roughness, wettability). The latter leads to a change in the internal characteristics of the boiling process and the average temperature of the superheated liquid layer. This circumstance makes it possible, on the basis of physical models of the liquids boiling and taking into account the parameters of the surface state (temperature, pressure) and properties of the coolant (the density and heat capacity of the liquid, the specific heat of vaporization and the heat capacity of the vapor), and also the internal characteristics of the boiling of liquids, to calculate the value of specific heat flux q. In this paper, the difference in the mechanisms of heat transfer during the boiling of single-phase (water) and two-phase nanofluids has been studied and a quantitative estimate of the q values for the boiling of the nanofluid is carried out based on the internal characteristics of the boiling process. The satisfactory agreement of the calculated values with the experimental data is a confirmation that the key factor in the growth of the heat transfer intensity at the boiling of nanofluids is indeed a change in the nature and microrelief of the heating surface. Bibl. 20, Fig. 9, Tab. 2.

Solution Properties and Phase Behavior of Ammonium Hexylene Octyl Succinate in Water and Water-Oil System

1970 ◽  
Vol 3 (1) ◽  
Author(s):  
Md. Hamidul Kabir ◽  
Ravshan Makhkamov ◽  
Shaila Kabir
Keyword(s):  
Critical Micelle Concentration ◽  
Phase Behavior ◽  
Liquid Crystalline ◽  
Carbon Number ◽  
Phase Region ◽  
Solution Properties ◽  
Middle Phase ◽  
Two Phase ◽  
Lamellar Liquid Crystal ◽  
Drug Ingredient

The solution properties and phase behavior of ammonium hexylene octyl succinate (HOS) was investigated in water and water-oil system. The critical micelle concentration (CMC) of HOS is lower than that of anionic surfactants having same carbon number in the lipophilic part. The phase diagrams of a water/ HOS system and water/ HOS/ C10EO8/ dodecane system were also constructed. Above critical micelle concentration, the surfactant forms a normal micellar solution (Wm) at a low surfactant concentration whereas a lamellar liquid crystalline phase (La) dominates over a wide region through the formation of a two-phase region (La+W) in the binary system. The lamellar phase is arranged in the form of a biocompatible vesicle which is very significant for the drug delivery system. The surfactant tends to be hydrophilic when it is mixed with C10EO8 and a middle-phase microemulsion (D) is appeared in the water-surfactant-dodecane system where both the water and oil soluble drug ingredient can be incorporated in the form of a dispersion. Hence, mixing can tune the hydrophile-lipophile properties of the surfactant. Key words: Ammonium hexylene octyl succinate, mixed surfactant, lamellar liquid crystal, middle-phase microemulsion. Dhaka Univ. J. Pharm. Sci. Vol.3(1-2) 2004 The full text is of this article is available at the Dhaka Univ. J. Pharm. Sci. website

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