Diamond phase diagram

Figure 15.6 The (graphite + diamond) phase diagram, including the pressure-temperature region for diamond synthesis with ferrous metals and their alloys as solvent catalysts. Reproduced with permission from H. M. Strong, Early Diamond Making at General Electric , Am. J. Phys., 57, 794-802 (1989). Published by the American Association of Physics Teachers.

Figure Al.3.23. Phase diagram of silicon in various polymorphs from an ab initio pseudopotential calculation [34], The volume is nonnalized to the experimental volume. The binding energy is the total electronic energy of the valence electrons. The slope of the dashed curve gives the pressure to transfomi silicon in the diamond structure to the p-Sn structure. Otlier polymorphs listed include face-centred cubic (fee), body-centred cubic (bee), simple hexagonal (sh), simple cubic (sc) and hexagonal close-packed (licp) structures.

Fig. 1. Carbon-phase diagram where A, solvent-cataly2ed diamond growth B—G, diamond formation direcdy from graphite C, graphite formation from diamond, D, approximate region where formation of Lonsdaleite occurs from weU-ordered graphite crystals (7,8). To convert GPa to atm, multiply by...

Elucidation of the phase relationships between the different forms of carbon is a difficult field of study because of the very high temperatures and pressures that must be applied. However, the subject is one of great technical importance because of the need to understand methods for transforming graphite and disordered forms of carbon into diamond. The diagram has been revised and reviewed at regular intervals [59-61] and a simplified form of the most recent diagram for carbon [62] is in Fig. 5. 

Figure 8.4 Phase diagram of carbon showing regions of importance for the production of synthetic diamond. ...

The phase diagram for carbon, shown here, indicates the extreme conditions that are needed to form diamonds front graphite, (a) At 2000 K, what is the minimum pressure needed before graphite changes into diamond (b) What is the minimum temperature at which liquid carhon can exist... 

Use the phase diagram for carbon in Exercise 8.14 (a) to describe the phase transitions that carbon would undergo if compressed at a constant temperature of 2000 K from 100 atm to 1 X 106 atm (b) to rank the diamond, graphite, and liquid phases of carbon in order of increasing density. 

Figure 1. Phase diagrams of the systems M0-H20 (Adapted from ref. 1) and MO-DOPC-H20 (at 28 C, Adapted from ref. 2), respectively. G (gyroid) and D (diamond) are cubic phases with similar structures to the type shown schematically in the figure (Adapted from ref. 18).

Fig. 5 Magnetic phase diagram of [Mn(Cp )2][Pt(tds)2] M(T) (filled diamonds) M(H) (//] (filled triangles), H (filled inverted triangles), x (T) (open circles) x (H) (open squares) Tt is the tricritical temperature I denotes the first-order MM transition II denotes a second-order transition (AF-PM phase houndary) and III denotes a higher order transitions (from a PM to a FM like state). From [45]...

Figure 5.4 The phase diagram of carbon showing the two solid-state extremes of diamond and graphite. Graphite is the thermodynamically stable form of carbon at room temperature and pressure, but the rate of the transition C iamond) — C aphite) is virtually infinitesimal...

Carbon phase diagram. This diagram (and especially the boundary lines of the diamond phase) is very interesting and important. 

An interesting application of this method is the preparation of diamond films which may be obtained from a precursor such as CH4, C2H2 and H2 activated by heating, microwaves, etc. typically at 600-1000°C at a reduced pressure. The direct deposition from the gas to the surface results in the formation of metastable diamond whereas, according to the phase diagram (see Fig. 5.37), the production of stable bulk diamond requires very high pressure and temperature. Kinetically, the... 

For carbon, the diamond-type structure is metastable at room conditions it is stable at high pressure. See the phase diagram of carbon shown in Fig. 5.37. 

R. Boehler, D. Errandonea, and M. Ross, The laser-heated diamond cell High P-T phase diagrams, in High Pressure Phenomena Proceedings of the International School of Physics Enrico Fermi, Course CXLVII, R. J. Hemley, G. L. Chiarotti, M. Bernasconi, and L. Ulivi, eds., lOS Press, Amsterdam, 2002, p. 55. 

Fig. 2. Phase diagram approximation of carbon, indicating pressure-temperature parameters favoring yield of graphite and diamond. See also phase diagram in the article on Carbon...

Fig. 6.22 Phase diagram for blends of PE and PEP homopolymers (A/j, - 392 and 409 respectively) with a PE-PEP diblock (iVc = 1925) (Bates et al. 1995). Open and filled circles denote experimental phase transitions between ordered and disordered states measured by SANS and rheology respectively. Phase boundaries obtained from self-consistent field calculations are shown as solid lines. The diamond indicates the Lifshitz point (LP), below which an unbinding transition (UT) separates lamellar and two-phase regions in mean field theory.

Fig. 6.31 Results from SCFI calculations for diblock/homopolymer blends (Matsen 1995b). (a) The dimensionless Helmholtz free energy Fu() as a function of homopolymer volume fraction at y X = 12, / = 0.45 and /3 = The dashed line shows the double tangent construction used to locate the binodal points denoted with dots. The dotted line is the free energy of non-interacting bilayers, (b) Phase diagram obtained by repeating this construction over a range of %N. The dots are the binodal points obtained in (a), and the diamond indicates a critical point below which two-phase coexistence does not occur. The disordered homopolymer phase is labelled dis, and the lamellar phase lam.

Fig. 6.33 Similar to Fig. 6.31, but for ft = (Matsen 19956). In this case the Helmholtz free energy curve indicates that macrophase separation does not occur, and so an unbinding transition occurs at the composition indicated by the dot. In the phase diagram, the diamond shows where the stability line for microphase separation meets the unbinding transition (Lifshitz point). 

The successful conversion of graphite to diamond involves crystallizing the diamond from a liquid melt. The solvent most often used is nickel metal, or alloys of nickel with other ferrous metals. The reason for this success can be seen by referring to Figure 15.7, the binary (solid + liquid) phase diagram for (nickel + carbon).u8 We note from the figure that (Ni + C) forms a simple... 

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