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1.
The nature of the B-site cation ordering and the associated defect process necessary to stabilize the ordered domains were investigated using the WO3-doped BaMg1/3Ta2/3O3 BMT system as a typical example of BaB1/3B2/3O3-type complex perovskites. It was shown that only the 1 : 2 long-range ordering of the B-site cation existed in both undoped and WO3-doped BMT perovskites. The atomic defect mechanism associated with the stoichiometric 1 : 2 long-range ordering was systematically investigated. It is concluded that the substitution of W6+ for Ta5+ in the WO3-doped BMT enhances the degree of the 1 : 2 long-range ordering and produces the positively charged W
Ta
sites with a concomitant generation of tantalum vacancies VTa and mobile oxygen vacancies V
O for the ionic charge compensation. 相似文献
2.
V. Ya. Pupko 《Journal of Engineering Physics and Thermophysics》1966,11(2):136-139
An examination is made of the use of adjoint functions in heat conduction and convection theory. Formulas of perturbation theory are obtained for steady and unsteady cases, an interpretation of the physical meaning of adjoint temperature is given, and some applications of the theory are discussed.Notation (r,)
thermal conductivity
- t(r,)
temperature
- t *(r,)
adjoint temperature
- qV(r,)
density of heat release sources
- p(r,)
a parameter of adjoint equation
- r
generalized coordinate
-
time
- (rs, )
heat transfer coefficient
- I
linear functional of temperature
- (r,;r0,0) and *(r,; r0,0)
Green's function for t(r, ) and t *(r, )
- C(r,)
volume specific heat
- W(r, )
vector distribution of flow velocities
- V, S
volume and surface areas of body
- R
radius of HRE
- r,
radial and angular coordinates
- Fin, Fout
inlet and outlet flow areas of channel 相似文献
3.
In the present work, the mechanism of martensitic transformation, the influence of -Fe particle size on the martensitic transformation induced by cold working, and the transformation of -Fe into -Fe by thermal treatment alone in a Cu-1.5 at% Fe alloy, was studied using field ion microscopy (FIM) and transmission electron microscopy (TEM). It has been found that -Fe precipitates smaller than about 10 nm did not transform martensitically to -Fe by cold working. Precipitates larger than 10 nm adopted a Kurdjumov-Sachs orientation relationship with the copper matrix; and the martensitically transformed -Fe precipitates were ellipsoidal in shape, with their major axes being oriented parallel to the 1 1 0 direction in the matrix. Dislocations were found in the matrix near the vicinity of transformed -Fe precipitates, giving support to the dislocation cutting mechanism proposed by other workers for the transformation. In thermally aged alloys, no transformation of -Fe to -Fe was observed during the coarsening of -Fe precipitates up to sizes as large as about 50 nm. These precipitates still remained coherent or semi-coherent with the copper matrix. 相似文献
4.
Crystallization of amorphous Fe78B13Si9 has been investigated using a combination of differential scanning calorimetry (DSC) and conventional and high-resolution transmission electron microscopy. The crystallization mechanisms and crystalline products are sensitive to the annealing temperature. At 450C, crystallization takes place by the growth of b c c -Fe (Si) dendrites, while at 510 and 515C there are three simultaneous reactions to form dendritic b c c -Fe (Si), elliptical crystals of b c t Fe3B and lamellar eutectic spherulites of b c c -Fe (Si) and b c t Fe3B. Quantitative TEM shows that the b c c -Fe (Si) dendrites and b c c -Fe (Si)-b c t Fe3B spherulites both form with constant nucleation and growth rates, in agreement with previous. DSC measurements of an Avrami exponent of 4. 相似文献
5.
B. R. Bergel'son A. S. Gerasimov 《Journal of Engineering Physics and Thermophysics》1979,37(5):1267-1274
A method is proposed for calculating the hydraulic characteristic and vapor content in a channel with underheated boiling.Notation H
heated length of channel
- dt
thermal diameter
- dh
hydraulic diameter
- t
thermal perimeter
- h
hydraulic perimeter
- s
through cross section
- N
power of channel
- q
heat flux
- G
weight flow rate
- W
velocity
-
coefficient of heat transfer
- t, T
temperatures
- t
temperature difference
- i
enthalpy
- P
pressure
- P
pressure drop
- x
weight vapor content
-
volumetric vapor content
- Cp
heat capacity
- r
heat of vaporization
-
coefficient of thermal conductivity
-
coefficient of surface tension
-
liquid density
-
vapor density
- g
acceleration of gravity
- o
coefficient of friction of liquid against the channel wall
-
shear stress
-
density of two-phase medium averaged over a channel cross section
-
dynamic viscosity
Indices s
on saturation line
- en
at channel entrance
-
l
liquid
- v
vapor
- w
wall
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, No. 5, pp. 784–792, November, 1979. 相似文献
6.
Tensile properties and plastic deformation modes of zirconium-niobium alloys were investigated at 290 and 77 K in the wide composition range from metastable to stable phase. Three types of plastic deformation modes, {332}113 twinning, {112}111 twinning and slip, were observed depending on alloy composition and temperature. {332}113 twinning, which occurs in metastable zirconium alloys, is related to the stability of phase to decomposition and leads to low yield stress and large elongation. On the other hand, {112}111 twinning, which appears in stable zirconium alloys, results from high critical stress for slip due to solution hardening and high Peierls stress and does not affect tensile properties significantly. The results obtained for zirconium-alloys are similar to those for titanium alloys, strongly suggesting that {332}113 twinning is an important plastic deformation mode which is common to phase alloys containing athermal phase. 相似文献
7.
K. A. Moler D. J. Baar Ruixing Liang W. N. Hardy A. Kapitulnik 《Journal of Superconductivity》1995,8(5):571-574
The total specific heat of YBa2Cu3O6.95 single crystals includes contributions from phonons and spin-1/2 particles, as well as electronic contributions. The electronic specific heat is described by a quadratic term T2 in zero field and a linear term [(0)+(H)]T which is increased when a magnetic field H is applied perpendicular to the CuO2 planes. In agreement with d-wave superconductivity, we find that n/Tc and (H)n(H/Hc2)1/2, where n is the coefficient of the normal-state linear term. The H1/2 dependence of the density of states at the Fermi level was predicted by G. Volovik for lines of nodes in the gap: the quasiparticles which contribute to this density of states are close to the nodes in momentum space and are located outside the vortex core. 相似文献
8.
J. H. Merkin 《Journal of Engineering Mathematics》1984,18(1):31-36
Summary The differential equation f + ff + f2 = 0 (where dashes denote differentiation with respect to the independent variable ) subject to the boundary conditions f(0)=0, f()=0 and either f(0)=1 or f(0)=–1 is considered. It is shown that by using pf as dependent variable and =C–f (where C=f()) as independent variable and then expanding in powers of , a very good approximation to the solution can be obtained using only a few terms in the expansion. 相似文献
9.
Mössbauer study on the magnetic state of iron particles in Fe-N and Fe-Zr-N soft magnetic thin films
T. Komatsu K. Shimagami K. Matusita K. Terunuma M. Miyazaki 《Journal of Materials Science》1995,30(21):5484-5489
The magnetic state of -Fe particles and the behaviour of nitrogen and zirconium during annealing in Fe96N4 and Fe85.6Zr7.6N6.8 magnetic thin films have been studied by conversion electron Mössbauer spectroscopy for 57Fe. The crystalline phases present in the Fe-N annealed films were -Fe and -Fe4N, and those in the Fe-Zr-N annealed films were -Fe and ZrN. In the Fe-N films annealed below 300°C, about 60% nitrogen is incorporated interstitially into -Fe and the rest is used for the formation of -Fe4N. In the Fe-N film annealed at 500°C, almost all nitrogen participates in the formation of -Fe4N, leading to the grain growth of -Fe particles and an increase in coercive force. The values (291–325 kOe) of internal magnetic field of iron sites in -Fe in the Fe-Zr-N films are much smaller than that (333 kOe) of the iron site in pure -Fe. Even if the Fe-Zr-N films were annealed at 500–700°C, some zirconium and nitrogen is still incorporated substitutionally and interstitially into -Fe, respectively. In particular, the substitutional zirconium depresses the grain growth of -Fe particles, perhaps due to a chemical interaction between zirconium and iron. 相似文献
10.
A. V. Ramana Reddy G. Ranga Mohan D. Ravinder B. S. Boyanov 《Journal of Materials Science》1999,34(13):3169-3176
The dielectric constant () and complex dielectric constant () of zinc substituted cobalt ferrites have been measured at room temperature in the high frequency range 100 kHz to 1 MHz. The values of dielectric loss tangent (tan ) have been computed from and . Plots of dielectric constant () versus frequency show a normal dielectric behaviour of the spinel ferrites. The frequency dependence of dielectric loss tangent (tan ) is found to be abnormal, giving a peak at certain frequency for all the ferrites under investigation. A qualitative explanation is given for the composition and frequency dependence of the dielectric constant and dielectric loss tangent. The dielectric constant for these mixed ferrites is approximately inversely proportional to the square root of the resistivity. A plot of dielectric constant versus temperature shows a transition near the Curie temperature. An attempt is made to explain the possible mechanism for this observation. 相似文献
11.
A. V. Kosterin 《Journal of Engineering Physics and Thermophysics》1980,39(1):769-771
Within the framework of the linear thermodynamics of irreversible processes, a general form is obtained for the equations of isothermal nonequilibrium filtration of an incompressible Liquid through a nondeforming porous matrix.Notation Q(e)
external heat flux
- Q
uncompensated heat
- U
interval energy
- S
entropy
- T
temperature
- dA(i)
elementary work of the internal surface forces
-
internal degrees of freedom
-
B
thermodynamic parameters conjugate to
-
dissipative function
- ij
stress tensor in the liquid
- vi
liquid-particle velocity
- V0
volume of the porous medium
- V
liquid volumes
- S0
surface of volume V0
- Se
liquid part of S0
- S1
liquid contact surface with the porous matrix inside V0
- P
mean (over Se) liquid pressure
- qi
filtration velocity
- s
Laplace-transform parameters
- t
time
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 1, pp. 77–80, July, 1980. 相似文献
12.
Two casts of type 316L(N) austenitic stainless steel have been solution treated for 1 h at 1070 C, air-cooled, then aged for up to 20 000 h at temperatures between 550 C and 750 C. Grain boundary precipitation of the M23C6 phase occurs, and the Cr composition profile normal to the grain boundaries has been determined at high resolution by an analytical electron microscope. The data have been fitted firstly to collector plate models, which indicated that some of the material was in the process of desensitization, or healing, indicated by a rise in the boundary Cr content. The data were then fitted to a model of the Cr profile as a function of ageing treatment in the healing regime, and a good correlation was obtained. 相似文献
13.
The electrical resistivity (T) of V-rich V3Si single crystals (T
c-11.4 K) was measured from 4.2 to 300 K along the directions of [1 0 0] and [1 1 1] before and after plastic deformation at 1573 K. Anisotropy of (T) was observed although V3Si has the cubic A15 structure. Plastic deformation does not affect the normal-state (T) behaviour but changes the normal-superconducting transition width Tc. At low temperatures (T
c<T 40 K), (T) varies approximately as T
n where n-2.5 and this behaviour does not contradict the (0)- phase-diagram plot proposed by Gurvitch, where is the electron-phonon coupling constant and (0) is the residual resistivity. 相似文献
14.
Summary This paper discusses the nature of an approximate solution for the hollow circular cylinder whose fixed ends are given a uniform relative axial displacement and whose cylindrical surfaces are free from traction. We shall take the solution of this problem to be given by a super-position of the following two problems: problem I considers a finite length cylinder whose ends are given a relative axial displacement, but are no longer fixed; problem II removes the radial displacement at the end of the cylinder obtained in problem I.Nomenclature a
mid-surface radius of cylinder
- c
half-height of cylinder
- E,
in-plane elastic moduli
- Et,
t, Gt
transverse elastic moduli
- z, , r
axial, circumferential, and normal strain
-
rz
transverse shear strain
- h
cylinder thickness
- z, , r
axial, circumferential, and normal stress
-
rz
transverse shear stress
- z, r
axial and radial coordinates
- uz, ur
axial and normal displacements 相似文献
15.
F. Branda G. Luciani A. Costantini P. Scardi L. Lanotte A. D'agostino 《Journal of Materials Science》2002,37(9):1887-1893
Thermal evolution of Fe62.5Co6Ni7.5Zr6Nb2Cu1B15 amorphous alloy prepared by one-roll melt-spinning technique was studied by XRD and DTA. The crystallisation process, occurring in several steps, can be summarised as follows: a a + -Fe a + -Fe + -Fe -Fe + -Fe + ZrB12, where a and a are amorphous phases, and a can be indexed as a -Fe (fcc) structure, with a crystalline order on an average distance of 8 Å. The metallic glass demixed on quenching, but component phases tended to mix by exchanging Fe atoms in a temperature range overlapped with the first crystallisation, which yields -Fe nanocrystals (27 Å). Higher temperature exo-peaks correspond mainly to a recrystallisation of the phases formed at lower temperature. It was found that this alloy has nanocrystalline structure also after heating at a well higher temperature than first crystallization. Even after the last exo-peak, the average crystallite size (D) was considerably smaller than that found in the literature for analogous metallic glasses; D values for our alloy were comparable to those of nanocrystalline phases of other systems heat treated below the temperature of exothermal DTA peaks. Extensive oxidation above 600°C, even at a low oxygen content (c
o
2 2 ppm), led to a marked modification of the surface layer: two zirconia polymorphs were identified on the surface of the ribbons, and the ratio of -Fe to -Fe content increased with respect to the bulk. Differences in thermal evolution between outer layer and bulk are attributed to a different phase composition and non-uniform distribution since the as-quenched stage. 相似文献
16.
Solidification behavior of Al-Si-Fe alloys and phase transformation of metastable intermetallic compound by heat treatment 总被引:1,自引:0,他引:1
Solidification behavior of Al-20 wt% Si-8 wt% Fe and Al-30 wt% Si-5 wt% Fe alloys during cooling with a cooling rate of 10 K/min has been studied using optical microscopy, X-ray diffractometry, differential thermal analysis, scanning electron microscopy and energy dispersive X-ray spectroscopy. In Al-20Si-8Fe alloy, metastable -Al4FeSi2 phase with tetragonal structure formed first from melt, followed by primary Si precipitation and then remaining liquid solidified finally into ternary eutectic of -Al, Si and phases. However, in Al-30Si-5Fe alloy, primary Si formed first, followed by the phase precipitation and then eutectic solidification. During isothermal heat treatment of as-solidified alloys, phase transformation from the phase to equilibrium phase began at the interface between phase and -Al matrix and progressed toward the inside of phase with co-precipitation of Si particles due to the difference in composition between -Al4FeSi2 and -Al5FeSi phases. 相似文献
17.
V. A. Gorodtsov 《Journal of Engineering Physics and Thermophysics》1980,39(4):1062-1065
Energy losses to radiation of internal waves during the vertical motion of a point dipole in two-dimensional and three-dimensional cases are computed.Notation o(z), po(z)
density and pressure of the ground state
- z
vertical coordinate
- v, p,
perturbed velocity, pressure, and density
- H(d 1n o/dz)–1
characteristic length scale for stratification
- N=(gH–1–g2c
o
–2
)1/2
Weisel-Brent frequency
- g
acceleration of gravity
- co
speed of sound
-
vertical component of the perturbed velocity
- V
vector operator
- k
wave vector
-
frequency
- d
vector surface element
- W
magnitude of the energy losses
- (t), (r) (x)(y)(z)
Dirac functions
- vo
velocity of motion of the source of perturbations
- d
dipole moment of the doublet
- o,l
length dimension parameters
- o
intensity of the source
Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 39, No. 4, pp. 619–623, October, 1980. 相似文献
18.
With the cohesive process zone representation of the micro-mechanistic processes that are associated with fracture as a basis, the author is involved in a wide-ranging research programme, the objective being to extend the fracture mechanics methodology for sharp cracks to blunt flaws, so as to take credit for the blunt flaw geometry. In earlier work, a Mode I fracture initiation relation has been derived, subject to the restriction that the process zone size s is small compared with the flaw depth (length) and any characteristic dimension other than the flaw root radius . The relation gives the critical elastic flaw-tip peak stress pcr, and has been derived using a two-extremes procedure, whereby the separate, and indeed exact, solutions for small and large s/ values are blended together to give an all-embracing relation that is valid for all s/ values. pcr is expressed in terms of the process zone material parameters and geometrical parameters but, for a wide range of flaw geometry parameters, pcr essentially depends on only one geometrical parameter . This paper provides underpinning for the general thrust of the two-extremes procedure by appealing to exact results for the complete spectrum of s/ values from analyses of appropriate Mode III models. Results obtained by applying the two-extremes procedure are shown to be in very good agreement with the exact results. 相似文献
19.
The mechano-chemical synthesis of thermoelectric material on the basis of -FeSi2 has been investigated. The mixture of FeSi and amorphous Si has been shown to be a optimum precursor to produce the thermoelectric ceramics. The ceramics properties (thermoelectric power , V/K, electrical conductivity 1/*cm) have been considerably improved by means of doping with superequilibrium quantity of 12% of aluminium (substitution of silicon) or 10% of cobalt (substitution of iron). The mechanical alloying in a high energy ball mill, under the acceleration of treating balls 800 m/sec2 produced homogeneous powder with a superequilibrium quantity of dopant, which conversed into thermoelectric ceramics after short annealing in vacuum at low temperature (780°C). The samples of ceramics with the maximum content of doping elements have increased thermoelectromotive force-up to 800 V/K. Mechanically alloyed ceramic is a promising material as a medium temperature thermoelectric with advanced properties for autonomous power supply units. 相似文献
20.
Single crystals of a Cu-Fe alloy, which contained spherical -Fe particles, were compressed up to shear strain of 0.17 in liquid nitrogen bath. In the process of straining the structural (optical and TEM) observations in as-deformed and post-deformation annealed samples were provided. The substructure of deformed samples was characterized by slightly developed cell structure and lack of distinct layer-like arrangements of dislocations. Three kinds of particles were found: coherent and semi-coherent f.c.c. -Fe and martensiticly transformed b.c.c. -Fe. The critical diameter for coherency loss was found to be 58 nm at the initial stage of deformation decreasing with strain to 50 nm. These values coincided with the theoretical estimations. It was suggested that relaxation of coherency strains around -Fe particles by the generation of interface dislocations might occur prior to the martensitic transformation. This assumption might explain the particle size dependency of martensitic transformation. 相似文献