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Fig. 9 (a) Electron diffraction intensity distributions determined for the films with Mn contents of 50 at%; (b) and 70 at%, highlighting carbide formation a-Mn phase disappears and carbide phases form. As the that appear at 400 °C, a list of candidate phases was made

Figure 9 (a) Electron diffraction intensity distributions determined for the films with Mn contents of 50 at%; (b) and 70 at%, highlighting carbide formation a-Mn phase disappears and carbide phases form. As the that appear at 400 °C, a list of candidate phases was made

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Fig. 1 Heating profile used in the in-situ experiments The films were in-situ annealed and examined by TEM in a Philips CM-20 electron microscope operated at 200 kV. The temperature range of in-situ annealing was 20-600 °C. The temperature was increased in steps of 50 °C and at every stage the samples were held at the set temperature for 5 min. The heating profile is shown in Fig. 1. The vacuum conditions during annealing were set temperature for 5 min. The heating profile 1s shown of 50 °C and at every stage the samples were held at the
Fig. 1 Heating profile used in the in-situ experiments The films were in-situ annealed and examined by TEM in a Philips CM-20 electron microscope operated at 200 kV. The temperature range of in-situ annealing was 20-600 °C. The temperature was increased in steps of 50 °C and at every stage the samples were held at the set temperature for 5 min. The heating profile is shown in Fig. 1. The vacuum conditions during annealing were set temperature for 5 min. The heating profile 1s shown of 50 °C and at every stage the samples were held at the
Fig. 2 Changes in the microstructure of the films with Mn contents of 50 at% ((a)—(h)) and 70 at% ((i)—(p)) during annealing in bright field TEM images ((a), (1) 20 °C; (b), (j) 250 °C; (©), (kK) 300 °C; (d), (1) 350 °C; (e), (m) 400 °C; (f), (n) 450 °C, (g), (0) 500 °C; (h), (p) 600 °C) observed at each temperature up to 600 °C (Fig. 3(e)—(h) and (m)-(p)). For better view they are marked with quad- rants on Fig. 4 (an enlarged version of Fig. 3(m)). In addi- tion to the changes in phases, the intensity of surface oxi- dation increases with increasing temperature (Fig. 3(e)—(h) and (m)—(p)) and above 400 °C substantial grain growth can be observed (Fig. 2(e)—(h) and (m)—(p)). which is essential for the exact measurement of the posi-
Fig. 2 Changes in the microstructure of the films with Mn contents of 50 at% ((a)—(h)) and 70 at% ((i)—(p)) during annealing in bright field TEM images ((a), (1) 20 °C; (b), (j) 250 °C; (©), (kK) 300 °C; (d), (1) 350 °C; (e), (m) 400 °C; (f), (n) 450 °C, (g), (0) 500 °C; (h), (p) 600 °C) observed at each temperature up to 600 °C (Fig. 3(e)—(h) and (m)-(p)). For better view they are marked with quad- rants on Fig. 4 (an enlarged version of Fig. 3(m)). In addi- tion to the changes in phases, the intensity of surface oxi- dation increases with increasing temperature (Fig. 3(e)—(h) and (m)—(p)) and above 400 °C substantial grain growth can be observed (Fig. 2(e)—(h) and (m)—(p)). which is essential for the exact measurement of the posi-
Fig. 4 SAED pattern obtained for the 70 at% Mn film at 400 °C. The quadrants denote the diffraction rings corresponding to the new phases
Fig. 4 SAED pattern obtained for the 70 at% Mn film at 400 °C. The quadrants denote the diffraction rings corresponding to the new phases
Fig. 3 SAED patterns of the films with Mn contents of 50 at% ((a)—(h)) and 70 at% ((i)—(p)) during annealing ((a), (1) 20 °C; (b), (j) 250 °C; (c), (k) 300 °C; (d), (1) 350 °C; (e), (m) 400 °C; (f), (n) 450 °C, (g), (0) 500 °C; (h), (p) 600 °C)
Fig. 3 SAED patterns of the films with Mn contents of 50 at% ((a)—(h)) and 70 at% ((i)—(p)) during annealing ((a), (1) 20 °C; (b), (j) 250 °C; (c), (k) 300 °C; (d), (1) 350 °C; (e), (m) 400 °C; (f), (n) 450 °C, (g), (0) 500 °C; (h), (p) 600 °C)
Fig. 5 The internal calibration of camera constant presented on the 70 at% Mn film at 600 °C. The quadrants denote the diffraction rings of the SAED pattern corresponding to the MnO phase, i.e. the internal standard. The triangles mark the MnO diffraction maxima on the electron diffraction intensity distribution
Fig. 5 The internal calibration of camera constant presented on the 70 at% Mn film at 600 °C. The quadrants denote the diffraction rings of the SAED pattern corresponding to the MnO phase, i.e. the internal standard. The triangles mark the MnO diffraction maxima on the electron diffraction intensity distribution
Fig. 6 (a) Electron diffraction intensity distributions for the films with Mn contents of 50 at%; (b) and 70 at% at different temperatures during in-situ heat treatment in solute concentration. By separating the effect of these mechanisms, the composition of solid solutions may be cal- culated. Thermal expansion can be calculated based on the lattice parameter for pure components at room temperature (a,,, = 3,6149A [15] and a, ,,, = 8,9125A [16]) and their thermal expansion coefficients (a,, = 1.65 x 10° 1/K [15] and a,,,= 2.17 x 10° 1/K [16]) using Eq. (1). For compari- son, the temperature dependence of pure lattice parameters is shown in Fig. 7 with dotted lines. The difference between the measured curves and the curves calculated for thermal expansion originates from the lattice distortions caused by solute atoms. To determine the composition of solid solu- tions, the dissolution limit of each possible solute element should be considered. a-Mn can dissolve up to 10 at% Cu under non-equilibrium conditions [9], 5 at% °C in the tem- perature range of 0-400 °C [17], and a negligible amount of O [18]. Thus, the a-Mn-based solid solution can be com- posed of Mn, Cu and C atoms. As it is not possible to sepa- rate the lattice distortions caused by substitutional Cu atoms and interstitional C atoms, we cannot calculate the compo- sition of the a-Mn-based solid solution and its changes in the temperature range of 300-400 °C. By contrast, Cu can dissolve 20-45 at% Mn in the temperature range of 300- 600 °C [12], and negligible amounts of C and O [19, 20]. Thus, the Cu-based solid solution is composed of Cu and Mn atoms, i.e. it is a Cu(Mn) solid solution and its compo- sition can be calculated. Czigany et al. [21] measured the effect of composition on the Cu(Mn) lattice parameter as: a= a,, + 0.322c, where c is the Mn concentration in the Cu(Mn) solid solution in at%. To consider the effect of ther- mal expansion we modified this equation as follows.
Fig. 6 (a) Electron diffraction intensity distributions for the films with Mn contents of 50 at%; (b) and 70 at% at different temperatures during in-situ heat treatment in solute concentration. By separating the effect of these mechanisms, the composition of solid solutions may be cal- culated. Thermal expansion can be calculated based on the lattice parameter for pure components at room temperature (a,,, = 3,6149A [15] and a, ,,, = 8,9125A [16]) and their thermal expansion coefficients (a,, = 1.65 x 10° 1/K [15] and a,,,= 2.17 x 10° 1/K [16]) using Eq. (1). For compari- son, the temperature dependence of pure lattice parameters is shown in Fig. 7 with dotted lines. The difference between the measured curves and the curves calculated for thermal expansion originates from the lattice distortions caused by solute atoms. To determine the composition of solid solu- tions, the dissolution limit of each possible solute element should be considered. a-Mn can dissolve up to 10 at% Cu under non-equilibrium conditions [9], 5 at% °C in the tem- perature range of 0-400 °C [17], and a negligible amount of O [18]. Thus, the a-Mn-based solid solution can be com- posed of Mn, Cu and C atoms. As it is not possible to sepa- rate the lattice distortions caused by substitutional Cu atoms and interstitional C atoms, we cannot calculate the compo- sition of the a-Mn-based solid solution and its changes in the temperature range of 300-400 °C. By contrast, Cu can dissolve 20-45 at% Mn in the temperature range of 300- 600 °C [12], and negligible amounts of C and O [19, 20]. Thus, the Cu-based solid solution is composed of Cu and Mn atoms, i.e. it is a Cu(Mn) solid solution and its compo- sition can be calculated. Czigany et al. [21] measured the effect of composition on the Cu(Mn) lattice parameter as: a= a,, + 0.322c, where c is the Mn concentration in the Cu(Mn) solid solution in at%. To consider the effect of ther- mal expansion we modified this equation as follows.
Fig. 7 (a) Lattice parameters measured for Cu-based; (b) and a-Mn-based solid solutions in the temperature range of 300—600 °C Table 1 Data used for calculating Mn concentration in the Cu(Mn) solid solution. The error of Mn concentration due to the error of lattice parameter measurement is 5 %. Iree energy. however, the stability of phases also depends on the concentration. To predict if another oxide can form alongside MnO, we need to examine the Mn-O phase dia- gram [18] (shown in Fig. 8(b)). The Mn-O phase diagram shows that up to 0.5 mole fraction of O two phases are in equilibrium: a-Mn and Mn,_O. In our case the O orig- inates from the residual atmosphere in the microscope column (1 x 10% Pa at 600 °C), so the mole fraction of O is very low and only MnO can form. Considering car- bides, Cu does not form carbide phases [19], but several Mn carbides exist [17] and Mn carbide formation is an expected reaction at the Cu-Mn/C interface. According to the Mn-C phase diagram (Fig. 8(c)) three carbide phases can form in the temperature range of 20-600 °C depend- ing on the concentration. The C substrate of our samples can be regarded as an infinite source of C atoms and C
Fig. 7 (a) Lattice parameters measured for Cu-based; (b) and a-Mn-based solid solutions in the temperature range of 300—600 °C Table 1 Data used for calculating Mn concentration in the Cu(Mn) solid solution. The error of Mn concentration due to the error of lattice parameter measurement is 5 %. Iree energy. however, the stability of phases also depends on the concentration. To predict if another oxide can form alongside MnO, we need to examine the Mn-O phase dia- gram [18] (shown in Fig. 8(b)). The Mn-O phase diagram shows that up to 0.5 mole fraction of O two phases are in equilibrium: a-Mn and Mn,_O. In our case the O orig- inates from the residual atmosphere in the microscope column (1 x 10% Pa at 600 °C), so the mole fraction of O is very low and only MnO can form. Considering car- bides, Cu does not form carbide phases [19], but several Mn carbides exist [17] and Mn carbide formation is an expected reaction at the Cu-Mn/C interface. According to the Mn-C phase diagram (Fig. 8(c)) three carbide phases can form in the temperature range of 20-600 °C depend- ing on the concentration. The C substrate of our samples can be regarded as an infinite source of C atoms and C
Fig. 8 Data used for creating a list of candidate phases to identify the phases forming in the temperature range of 400-600 °C; (a) Standard free energies of Cu and Mn oxides in the temperature range of 20-600 °C. (All free energy values are normalized to 1 mol O,.) [22-24]; (b) Mn-O equilibrium phase diagram in the temperature range of 227-927 °C [18]; (c) Mn-C equilibrium phase diagram in the temperature range of 0-650 °C [17] can be regarded as an infinite source of C atoms and C Cu ones at all temperatures. Thus, Mn oxidizes more read- ily than Cu and the formation of Cu oxides can be ruled rr re ry, a. a ily than Cu and the formation of Cu oxides can be ruled
Fig. 8 Data used for creating a list of candidate phases to identify the phases forming in the temperature range of 400-600 °C; (a) Standard free energies of Cu and Mn oxides in the temperature range of 20-600 °C. (All free energy values are normalized to 1 mol O,.) [22-24]; (b) Mn-O equilibrium phase diagram in the temperature range of 227-927 °C [18]; (c) Mn-C equilibrium phase diagram in the temperature range of 0-650 °C [17] can be regarded as an infinite source of C atoms and C Cu ones at all temperatures. Thus, Mn oxidizes more read- ily than Cu and the formation of Cu oxides can be ruled rr re ry, a. a ily than Cu and the formation of Cu oxides can be ruled
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