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Micromechanical properties of C70 single crystals in the temperature range 77–350 K
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10.1063/1.3693580
/content/aip/journal/ltp/38/3/10.1063/1.3693580
http://aip.metastore.ingenta.com/content/aip/journal/ltp/38/3/10.1063/1.3693580
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Real (a) and theoretical (b) morphology of C70 crystals. The image of an unfolded crystal (c) shows indenter imprints in the basal (0001), pyramidal {1101}, and prismatic {1010} planes; in the last two planes near the indentations applied at P = 0.05 N the gliding steps, parallel to the lines of intersection of planes of observation with the basal plane, can be seen.

Image of FIG. 2.
FIG. 2.

Microstructure of habit planes of the C70 single crystal: basal (0001) (a, b, d) and pyramidal (1101) (c); before (a, b, c) and after (d) heating to temperature, exceeding phase transition temperature DHCP → HCP T γ″–γ′ = 348 K.

Image of FIG. 3.
FIG. 3.

Indentation in the habit planes of C70 single crystals: the pyramid plane (1101) (P = 0.05, 0.02, and 0.01 N for the three top imprints) (a), the prism plane (1010) (P = 0.05 N) (b). T ≈ 290 K. The smaller diagonal of rhombic imprints is parallel to the imprint in the basal plane (0001).

Image of FIG. 4.
FIG. 4.

Dependence of the anisotropy coefficient of microhardness of the first kind K I = (a 2/a 1)2 for the pyramid plane (1101) of C70 single crystal on the load of the indenter when T = 291 K (a) and on the temperature when P = 0.05 N (b); 2а 1 and 2а 2 are the lengths of the shorter and the longer diagonals of the imprint. Inset in (b) shows imprints obtained for P ≈ 0.05 N at T= 291 K and T = 77 K; the horizontal plane of the imprint is parallel to the imprint in the basal plane (0001).

Image of FIG. 5.
FIG. 5.

Dependence of anisotropy coefficients of microhardness of the first type K I = (a 2/a 1)2 in the prism plane (1010) of the Zn single crystal on the load on the indenter at room temperature (a) and on temperature when P = 1 N (b), the angle between the smaller diagonal and the imprint in the basal plane (0001) equals zero and 25° for the data given in (a) and (b), respectively; 2а 1 and 2а 2 are the lengths of the shorter and longer diagonals of the imprint.

Image of FIG. 6.
FIG. 6.

Dependence of the square of the length of the indentation diagonal in the basal plane (0001) (a) and in the pyramid plane (1101) (b), (1 and 2 are the shorter and longer diagonals, respectively) on the indenter load. T ≈ 290 K. The dotted line shows the linear approximation of the initial part of the dependences. The magnitude of microhardness determined by the initial portion of the curve equals HV  ≈ 65 MPa (in the basal plane (0001)), and HV  ≈ 80 MPa (in the pyramid plane (1011), curve 2, long diagonal).

Image of FIG. 7.
FIG. 7.

Temperature dependence of microhardness of the C70 microcrystal, obtained by indentation of the basal plane (0001) (load P = 0.05 N). The data obtained by the low-temperature hardness meter (dark symbols) for decreasing temperature and with a Neophot microscope with a special attachment with increasing temperature (light symbols). T 1 = T γ″–α = 276 K is the phase transition temperature for DHCP → monoclinic lattice, T 2 = T γ′–γ″ = 308 K is the phase transition temperature for HCP → DHCP (upon cooling), T 3 = T γ″–γ′ = 348 K is the phase transition temperature for DHCP → HCP (upon heating).

Image of FIG. 8.
FIG. 8.

Temperature dependences of microhardness of C70 fullerite single crystals (1 is for the basal plane; 2 is for the pyramidal plane; values of HV are calculated for the long diagonal of the imprint) and C60 (3 is for the cubic plane (100)) (Ref. 14). Dependence 1 agrees with that given in Fig. 7. T 1 = T γ″–α = 276 K, T 2 = T γ′–γ″ = 308 K, T 3 = T γ″–γ′ = 348 K.

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/content/aip/journal/ltp/38/3/10.1063/1.3693580
2012-03-27
2014-04-25
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Micromechanical properties of C70 single crystals in the temperature range 77–350 K
http://aip.metastore.ingenta.com/content/aip/journal/ltp/38/3/10.1063/1.3693580
10.1063/1.3693580
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