Heat capacity and electrical resistivity of POCO AXM-5Q1 graphite in the range 1500–3000 K by a pulse-heating technique

Measurements of the heat capacity and electrical resistivity of POCO AXM-5Q1 graphite in the temperature range 1500–3000 K by a subsecond-duration pulse-heating technique are described. The results for heat capacity may be represented by the relation $$C_{{\text{p }}} = 19.438 + 3.6215 \times {\text{10}}^{{\text{ - 3}}} {\text{ }}T - 4.4426 \times {\text{10}}^{{\text{ - 7}}} {\text{ }}T^2$$ where C _p is in J · mol^?1 · K^?1 and T is in K. The results for electrical resistivity vary with the density (d) of the specimen material and, therefore, are represented by the following relations: for d=1.709, $$\rho = 1084.6 - 1.9940 \times {\text{10}}^{{\text{ - 1}}} {\text{ }}T + 1.6760 \times {\text{10}}^{{\text{ - 4 }}} T^{2{\text{ }}} - 2.0310 \times {\text{10}}^{{\text{ - 8 }}} T^3$$ and for d= 1.744, $$\rho = 943.1 - 1.3836 \times {\text{10}}^{{\text{ - 1}}} {\text{ }}T + 1.3776 \times {\text{10}}^{{\text{ - 4 }}} T^{2{\text{ }}} - 2.0310 \times {\text{10}}^{{\text{ - 8 }}} T^3$$ where ρ is in μΩ · cm, T is in K, and d (at 20°C) is in g · cm ^?3. The maximum uncertainties in the measured properties are estimated to be 3% for heat capacity and 1 % for electrical resistivity.     

Specific heat capacity and electrical resistivity of a carbon-carbon composite in the range 1500–3000 K by a pulse heating method

Measurements are described of specific heat capacity and electrical resistivity of a 2-2-3 T-50 carbon-carbon composite in the temperature range 1500–3000 K by a subsecond duration pulse heating technique. The results are represented by the relations 1 $$C\rho = 1.691 + 2.598{\text{x10}}^{{\text{ - 4}}} T - 2.691{\text{x10}}^{{\text{ - 8}}} T^2 $$ 2 $$\rho = 733.0 + 6.594{\text{x10}}^{{\text{ - 2}}} T$$ where c _p is in J · g^?1 · K^?1, ρ is in ΜΩ · cm, and T is in K. Inaccuracy of specific heat capacity and electrical resistivity measurements is estimated to be not more than ±3%.     

The ductile-brittle transition in a polyethylene copolymer

The ductile-brittle transition of an ethylene-hexene copolymer was measured from 80 to 24° C. The basic curves of stress against time to failure could all be unified in terms of a single equation based on normalizing the stress relative to the transition stress between the ductile and brittle regions and using a single thermal activation parameter. This unity is based on the observations which show that the ductile and brittle failure processes are both associated with a shear process. The unifying equation is $$\left( {\frac{\sigma }{{\sigma _{\text{c}} }}} \right)^n = \left( {\frac{{t_{\text{R}} }}{{t_{\text{f}} }}} \right){\text{ exp }}\left[ {{\text{85 500/}}R\left( {\frac{1}{T} - \frac{1}{{T_{\text{R}} }}} \right)} \right]$$ where σ _c is the minimum stress for ductile failure at an arbitrary temperature, T _R; t _R is the time to failure at an arbitrary reference temperature T _R; n equals 34 and 3.3 for the ductile and brittle regions, respectively and R is in J mol^?1 K^?1.     

Luminescence of SrAl<Subscript>2</Subscript>O<Subscript>4</Subscript>:Cr<Superscript>3+</Superscript>

Samples of SrAl₂O₄ and SrAl₂O₄:Cr³⁺ were prepared by mixing the powder materials SrCO₃, Al₂O₃, and Cr₂O₃. The crystal structures of the undoped and doped samples were analyzed by X-ray diffraction (XRD) measurements. The diffraction patterns reveal a dominant phase, characteristic of the monoclinic SrAl₂O₄ compound and another unknown secondary phase, in small amount, for doped samples. The data were fitted using the Rietveld method for structural refinements and lattice parameter constants (a, b, c, and β) were determined. Luminescence of Cr³⁺ ions in this host is investigated for the first time by excitation and emission spectroscopy at room temperature. Emission spectra present a larger band and a smaller structure associated to the and electronic transitions, respectively. The obtained results are analyzed by crystal-field theory and the crystal-field parameter, Dq, and Racah parameters, B and C, are determined from the excitation measurements.     

Transient interferometric technique for measuring thermal expansion at high temperatures: Thermal expansion of tantalum in the range 1500–3200 K

The design and operational characteristics of an interferometric technique for measuring thermal expansion of metals between room temperature and temperatures in the range 1500 K to their melting points are described. The basic method involves rapidly heating the specimen from room temperature to temperatures above 1500 K in less than 1 s by the passage of an electrical current pulse through it, and simultaneously measuring the specimen expansion by the shift in the fringe pattern produced by a Michelson-type polarized beam interferometer and the specimen temperature by means of a high-speed photoelectric pyrometer. Measurements of linear thermal expansion of tantalum in the temperature range 1500–3200 K are also described. The results are expressed by the relation: $$\begin{gathered} (l - l_0 )/l_0 = 5.141{\text{ x 10}}^{ - {\text{4}}} + 1.445{\text{ x 10}}^{ - {\text{6}}} T + 4.160{\text{ x 10}}^{ - {\text{9}}} T^2 \hfill \\ {\text{ }} - 1.309{\text{ x 10}}^{ - {\text{12}}} T^3 + 1.901{\text{ x 10}}^{ - {\text{16}}} T^4 \hfill \\ \end{gathered}$$ where T is in K and l₀ is the specimen length at 20°C. The maximum error in the reported values of thermal expansion is estimated to be about 1% at 2000 K and not more than 2% at 3000 K.     

Cation distribution investigation of the system Li0.5Fe x Ga2.50-xO4 by X-rays,electrical conductivity and Mossbauer studies

Structural, electrical and Mossbauer studies were carried out for the system Li_0.5Fe _x Ga_2.50-xO₄. All the compounds with 0 ? x? 2.5 crystallised with cubic spinel structure. Lattice constant values calculated from XRD analysis were found to increase with increasing x. X-ray intensity calculations indicated that Li¹⁺ occupies only the octahedral site and Ga³⁺ and Fe³⁺ ions occupy both octahedral and tetrahedral sites. Activation energy and thermoelectric coefficient values decreased with increasing values of x. All the compounds studied were p-type semiconductors and possess low mobility values of 10^?7-10^?9 cm²V^?1 s^?1. Mossbauer data show the presence of iron in the Fe³⁺ state and the isomer shift values for all the compositions of the system are within the range of high spin ferric compounds. The probable ionic configuration for the system is suggested as: $${\text{Ga}}_{{\text{1 - }}\alpha }^{{\text{3 + }}} {\text{Fe}}_\alpha ^{{\text{3 + }}} [Li_{0.5}^1 {\text{Fe}}_{{\text{x - }}\alpha }^{{\text{3 + }}} {\text{Ga}}_{{\text{2}}{\text{.5 - x + }}\alpha }^{\text{3}} ] {\text{O}}_{\text{4}}^{{\text{2 - }}} $$      

Thermal expansion of rhodium,iridium, and palladium at low temperatures

Coefficients (α) of linear thermal expansion of Rh, Ir, and Pd are reported to be respectively 8.45, 6.65, and 11.78×10^?6 ° K^?1 at 238°K, and 3.50, 3.43, and 6.21×10^?6 °K^?1 at 75°K. At temperatures below 10°K, α may be represented by $$\begin{gathered} 10^{10} \alpha = 20{\rm T} + 0.052{\rm T}^3 (Rh) \hfill \\ 10^{10} \alpha = 9{\rm T} + 0.070{\rm T}^3 (Ir) \hfill \\ 10^{10} \alpha = 40.5{\rm T} + 0.435{\rm T}^3 (Pd) \hfill \\ \end{gathered} $$ TheT andT ³terms are identifiable with electron and lattice vibrational components, respectively. Corresponding Grüneisen parameters are γ (electron)≈2.8, 2.7, and 2.22 for Rh, Ir, and Pd, and γ ₀ (lattice)≈2.0, 2.3, and 2.25.     

Thermophysical measurements on tungsten-3 (wt %) rhenium alloy in the range 1500–3600 K by a pulse heating technique

Simultaneous measurements of the specific heat capacity, c _p, electrical resistivity, ρ, and hemispherical total emittance, ε, of tungsten-3 (wt%) rhenium alloy in the temperature range 1500–3600 K by a subsecond-duration pulse heating technique are described. The results are expressed by the relations $$\begin{gathered} c_{\text{P}} = 0.30332 - 2.8727 \times 10^{ - 4} {\text{ }}T + 1.9783 \times 10^{ - 7} {\text{ }}T^2 \hfill \\ {\text{ }} - 5.6672 \times 10^{ - 11} {\text{ }}T^3 + 6.5628 \times 10^{ - 15} {\text{ }}T^4 , \hfill \\ \rho = - 24.261 + 8.1924 \times 10^{ - 2} {\text{ }}T - 3.7656 \times 10^{ - 5} {\text{ }}T^2 \hfill \\ {\text{ + 1}}{\text{.1850}} \times {\text{10}}^{ - 8} {\text{ }}T^3 - 1.3229 \times 10^{ - 12} {\text{ }}T^4 , \hfill \\ \varepsilon = 0.1945 + 5.881 \times 10^{ - 5} {\text{ }}T, \hfill \\ \end{gathered} $$ where T is in K, c_p is in J·g^?1·K^?1, and ρ is in μΩ·cm. The melting temperature (solidus temperature) was also measured and was determined to be 3645 K. Uncertainties of the measured properties are estimated to be not more than ±3 % for specific heat capacity, ±1 % for electrical resistivity, ± 5 % for hemispherical total emittance, and ±20 K for the melting temperature.     

Heat capacity and electrical resistivity of palladium in the range 1400 to 1800 K by a pulse heating method

Measurements of heat capacity and electrical resistivity of palladium in the temperature range 1400–1800 K by a subsecond duration pulse heating technique are described. The results are expressed by the relations: 1 $$C_p = 32.19 - 5.966{\text{x10}}^{{\text{ - 3}}} T + 4.440{\text{x10}}^{{\text{ - 6}}} T^2 $$ 1 $$p = 15.42 + 1.840{\text{x10}}^{{\text{ - 2}}} T$$ where C _p is in J · mol^?1 · K^?1, ρ in μΩ · cm, and T in K. Estimated maximum inaccuracies of the measured properties are: 3% for heat capacity and 1% for electrical resistivity.     

Phase relations in the system Cu-La-O and thermodynamic properties of CuLaO2 and CuLa2O4

Phase relations in the system Cu-La-O at 1200 K have been determined by equilibrating samples of different average composition at 1200 K, and phase analysis of quenched samples using optical microscopy, XRD, SEM and EDX. The equilibration experiments were conducted in evacuated ampoules, and under flowing inert gas and pure oxygen. There is only one stable binary oxide La₂O₃ along the binary La-O, and two oxides Cu₂O and CuO along the binary Cu-O. The Cu-La alloys were found to be in equilibrium with La₂O₃. Two ternary oxides CuLaO₂ and CuLa₂O₄₊ were found to be stable. The value of varies from close to zero at the dissociation partial pressure of oxygen to 0.12 at 0.1 MPa. The ternary oxide CuLaO₂, with copper in monovalent state, coexisted with Cu, Cu₂O, La₂O₃, and/or CuLa₂O₄₊ in different phase fields. The compound CuLa₂O₄₊, with copper in divalent state, equilibrated with Cu₂O, CuO, CuLaO₂, La₂O₃, and/or O₂ gas under different conditions at 1200 K. Thermodynamic properties of the ternary oxides were determined using three solid-state cells based on yttria-stabilized zirconia as the electrolyte in the temperature range from 875 K to 1250 K. The cells essentially measure the oxygen chemical potential in the three-phase fields, Cu + La₂O₃ + CuLaO₂, Cu₂O + CuLaO₂ + CuLa₂O₄ and La₂O₃ + CuLaO₂ + CuLa₂O₄. Although measurements on two cells were sufficient for deriving thermodynamic properties of the two ternary oxides, the third cell was used for independent verification of the derived data. The Gibbs energy of formation of the ternary oxides from their component binary oxides can be represented as a function of temperature by the equations:

Sublimation study of BiBr3

Steady-state sublimation vapour pressures of anhydrous bismuth tribromide have been measured by the continuous gravimetric Knudsen-effusion method from 369.3 to 478.8 K. Additional effusion measurements have also been made from 435.4 to 478.6 K by the torsion—effusion method. Based on a correlation of Δ_sub H ₂₉₈ ⁰ and Δ_sub S ₂₉₈ ⁰ , a recommended p(T) equation has been obtained for BiBr₃(s) $$\alpha - {\rm B}i{\rm B}r_3 :log{\text{ }}p = - C\alpha /T - 12.294log{\text{ }}T + 5.79112 \times 10^{ - 3} {\text{ }}T + 47.173$$ with Cα=(Δ _subH ₂₉₈ ⁰ +20.6168)/1.9146×10^-2 $$\beta - {\rm B}i{\rm B}r_3 :log{\text{ }}p = - C\beta /T - 23.251log{\text{ }}T + 1.0492 \times 10^{ - 2} {\text{ }}T + 77.116$$ with Cβ=(Δ _subH ₂₉₈ ⁰ +46.2642)/1.9146×10^-2 where p is in Pa, T in Kelvin, Δ _sub H ₂₉₈ ⁰ in kJ mol^?1. Condensation coefficients and their temperature dependence have been derived from the effusion measurements.     

Thermal expansion of molybdenum in the range 1500–2800 K by a transient interferometric technique

The linear thermal expansion of molybdenum has been measured in the temperature range 1500–2800 K by means of a transient (subsecond) interferometric technique. The molybdenum selected for these measurements was the Standard Reference Material SRM 781 (a high-temperature enthalpy and heat capacity standard). The results are expressed by the relation where T is in K and l ₀ is the specimen length at 20°C. The maximum error in the reported values of thermal expansion is estimated to be about 1% at 2000 K and not more than 2% at 2800 K.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Thermophysical measurements on low carbon 304 stainless steel above 1400 K by a transient (subsecond) technique

Simultaneous measurements, by a subsecond duration transient technique, to determine the specific heat capacity, c _p , the electrical resistivity, ρ, and the hemispherical total emittance in the temperature range 1400–1700 K, and the melting point and the radiance temperature at the melting point, of AISI type 304L stainless steel are described. The results are expressed by the relations: $$c_p = 1127{\text{ }} - {\text{ }}7.265{\text{ }} \times {\text{ }}10^{ - 1} {\text{ }}T{\text{ }} + {\text{ }}2.884{\text{ }} \times {\text{ }}10^{ - 4} {\text{ }}T^2$$ $$\rho = 75.59{\text{ }} + {\text{ }}4.695{\text{ }} \times {\text{ }}10^{ - 2} {\text{ }}T{\text{ }} - {\text{ }}9.592{\text{ }} \times {\text{ }}10^{ - 6} {\text{ }}T^2$$ where c _p is in J · kg^?1 · K^?1, ρ is in ΜΩ · cm, and T is in K. The value of the hemispherical total emittance is 0.37 in the range 1700–1900 K. The melting point and the radiance temperature (at 653 nm) at the melting point are 1707 and 1590 K, respectively, yielding a value of 0.385 for the normal spectral emittance at the melting point. Estimated inaccuracies of the measured properties are: 3% for the specific heat capacity, 2% for electrical resistivity, 5% for hemispherical total emittance, and 8 K for melting point and radiance temperature at the melting point.     

Surface and grain-boundary energies of cubic zirconia

Using the multiphase equilibration technique for the measurement of contact angles, the surface and grain-boundary energies of polycrystalline cubic ZrO₂ in the temperature range of 1173 to 1523 K were determined. The temperature coefficients of the linear temperature function obtained, are expressed as $$\frac{{{\text{d}}\gamma }}{{{\text{d}}T}}({\text{ZrO}}_{\text{2}} ){\text{ }} = {\text{ }} - 0.431{\text{ }} \times {\text{ }}10^{ - 3} {\text{ }} \pm {\text{ }}0.004{\text{ }} \times {\text{ }}10^{ - 3} {\text{ Jm}}^{ - {\text{2}}} {\text{ K}}^{ - {\text{1}}} $$ and $$\frac{{{\text{d}}\gamma }}{{{\text{d}}T}}({\text{ZrO}}_{\text{2}} - {\text{ZrO}}_{\text{2}} ){\text{ }} = {\text{ }} - 0.392{\text{ }} \times {\text{ }}10^{ - 3} {\text{ }} \pm {\text{ }}0.126{\text{ }} \times {\text{ }}10^{ - 3} {\text{ Jm}}^{ - {\text{2}}} {\text{ K}}^{ - {\text{1}}} $$ respectively. The surface fracture energy obtained with a Vickers microhardness indenter at room temperature is found to be γ _F=3.1 J m^?2.     

Experimental Study of the Thermodynamic Properties of Diethyl Ether (DEE) at Saturation

The isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\), saturation densities (\({\rho _{\rm S}^{\prime}}\) and \(({\rho_{\rm S}^{\prime\prime})}\)), vapor pressures (P _S), thermal-pressure coefficients \({\gamma_V=\left({\partial P/\partial T}\right)_V}\), and first temperature derivatives of the vapor pressure γ _S = (dP _S/dT) of diethyl ether (DEE) on the liquid–gas coexistence curve near the critical point have been measured with a high-temperature and high-pressure nearly constant-volume adiabatic piezo-calorimeter. The measurements of \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) were made in the liquid and vapor one- and two-phase regions along the coexistence curve. The calorimeter was additionally supplied with a calibrated extensometer to accurately and simultaneously measure the PVT, C _V VT, and thermal-pressure coefficient, γ _V , along the saturation curve. The measurements were carried out in the temperature range from 416 K to 466.845 K (the critical temperature) for 17 liquid and vapor densities from 212.6 kg · m^?3 to 534.6 kg · m^?3. The quasi-static thermo- (reading of PRT, T ? τ plot) and baro-gram (readings of the tensotransducer, P ? τ plot) techniques were used to accurately measure the phase-transition parameters (P _S ,ρ _S ,T _S) and γ _V . The total experimental uncertainty of density (ρ _S), pressure (P _S), temperature (T _S), isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\), and thermal-pressure coefficient, γ _V , were estimated to be 0.02 % to 0.05 %, 0.05 %, 15 mK, 2 % to 3 %, and 0.12 % to 1.5 %, respectively. The measured values of saturated caloric \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) and saturated thermal (P _S, ρ _S, T _S) properties were used to calculate other derived thermodynamic properties C _P , C _S, W, K _T , P _int, ΔH _vap, and \({\left({\partial V/\partial T}\right)_P^{\prime}}\) of DEE near the critical point. The second temperature derivatives of the vapor pressure, (d² P _S/dT ²), and chemical potential, (d² μ/dT ²), were also calculated directly from the measured one- and two-phase liquid and vapor isochoric heat capacities \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) near the critical point. The derived values of (d² P _S/dT ²) from calorimetric measurements were compared with values calculated from vapor–pressure equations. The measured and derived thermodynamic properties of DEE near the critical point were interpreted in terms of the “complete scaling” theory of critical phenomena. In particular, the effect of a Yang–Yang anomaly of strength R _μ on the coexistence-curve diameter behavior near the critical point was studied. Extended scaling-type equations for the measured properties P _S (T), ρ _S (T), and \({({C_{V1}^{\prime}} ,{C_{V1}^{\prime\prime}},{C_{V2}^{\prime}},{C_{V2}^{\prime\prime}})}\) as a function of temperature were developed.     

Determination of standard Gibbs energies of formation of ternary oxides in the system Co-Sb-O by solid electrolyte emf method

An isothermal section of the phase diagram of the system Co-Sb-O at 873 K was established by isothermal equilibration and XRD analyses of quenched samples. The following galvanic cells were designed to measure the Gibbs energies of formation of the three ternary oxides namely CoSb₂O₄, Co₇Sb₂O₁₂ and CoSb₂O₆ present in the system.

Electrical transport studies on heavy rare-earth tungstates

This paper reports the measurement of thermoelectric-power (S) at different temperatures (800–1100 K) and electrical conductivity (σ) as a function of electric field strength, time, ac signal frequency and temperature (650–1200 K) for pressed pellets of heavy rare-earth tungstates (HRET) with a general formula RE₂(WO₄)₃ [where RE = Tb, Dy, Ho, Er, Tm and Yb]. These tungstates are typical insulating compounds with room-temperature σ value less than 10^?10 ohm^?1 cm^?1 and become semiconductors at elevated temperature with σ values of the order of 10^?5 ohm^?1 cm^?1 at 1200 K. The S vs T^?1 and log σ vs T^?1 plots are linear, but a change in the slope of straight lines occurs at a temperature (T_B) which lies between 900–1025 K for different tungstates. These break temperatures are the same for both S and σ plots. It has been found that HRET are mixed ionic-electronic conductors. Above T_B the electronic conduction dominates over the ionic conduction, but below T_B both become comparable. The electronic conduction above T_B is intrinsic with large polaron holes as the principal charge carriers; they conduct via a band mechanism. The energy band gap lies in the range 3.2 to 4.0 eV, and the charge carrier mobility in the range 3.8×10^?2 to 2.5 cm²/V-Sec for the different tungstates. Below T_B both electronic and ionic conduction are extrinsic. The electrons conduct via a thermally activated hopping mechanism with an activation energy lying in the range 0.87 to 1.30 eV, and the holes via a diffusion process with an activation energy lying in the range 0.88 to 1.23 eV for the different tungstates.     

An approximate approach for the calculation ofM s in iron-base alloys

Having estimated the critical driving force associated with martensitic transformation,ΔG ^α→M, as $$\Delta G^{\alpha \to M} = 2.1 \sigma + 900$$ whereσ is the yield strength of austenite atM _s, in MN m^?2, we can directly deduce theM _s by the following equation: $$\Delta G^{\gamma \to {\rm M}} |_{M_S } = \Delta G^{\gamma \to \alpha } + \Delta G^{\alpha \to M} = 0.$$ The calculatedM _s are in good agreement with the experimental results in Fe-C, Fe-Ni-C and Fe-Cr-C, and are consistent with part of the data in Fe-Ni, Fe-Cr and Fe-Mn alloys. Some higher “M _s” determined in previous works may be identified asM _a,M _s of surface martensite or bainitic temperature. TheM _s of pure iron is about 800 K. TheM _s in Fe-C can be approximately expressed as $$M_S (^\circ {\text{C}}) = 520 {\text{--- }}\left[ {{\text{\% C}}} \right]{\text{ }}x 320.$$ In Fe-X, the effect of the alloying element onM _s depends on its effect onT ₀ and on the strengthening of austenite. An approach for calculation of ΔG ^γ→α in Fe-X-C is suggested. Thus dM _s/dx _c in Fe-X-C is found to increase with the decrease of the activity coefficient of carbon in austenite.     

Multiple Andreev Reflections Spectroscopy of Two-Gap 1111- and 11 Fe-Based Superconductors

Using the “break-junction” technique, we prepared and studied superconductor–constriction–superconductor (ScS) nanocontacts in polycrystalline samples of Fe-based superconductors CeO_0.88F_0.12FeAs (Ce-1111; $T_{C}^{\mathrm{bulk}} = 41 \pm1~\mathrm{K}$ ), LaO_0.9F_0.1FeAs (La-1111; $T_{C}^{\mathrm{bulk}} = 28 \pm1~\mathrm {K}$ ), and FeSe ( $T_{C}^{\mathrm{bulk}} = 12 \pm1~\mathrm{K}$ ). We detected two subharmonic gap structures related with multiple Andreev reflections, indicating the presence of two superconducting gaps with the BCS-ratios 2Δ _L /k _B T _C =4.2÷5.9 and 2Δ _S /k _B T _C ～1?3.52, respectively. Temperature dependences of the two gaps Δ _L,S (T) in FeSe indicate a k-space proximity effect between two superconducting condensates. For the studied iron-based superconductors, we found a linear relation between the gap Δ _L and magnetic resonance energy, E _res≈2Δ _L .