Phase diamond

In the case of the graphite-to-diamond transformation, thermodynamic results predict that graphite is the stable allotrope at a fixed temperature at all pressures below the transition pressure and that diamond is the stable aUotrope at all pressures above the transition pressure. But diamond is not converted to graphite at low pressures for kinetic reasons. Similarly, at conditions at which diamond is the thermodynamically stable phase, diamond can be obtained from graphite only in a narrow temperature range just below the transition temperature, and then only with a catalyst or at a pressure sufficiently high that the transition temperature is about 2000 K. 

Figure 8.8 Phase diagram for epitaxial PbTiOa thin films on SrTiOs. Circles no satellites, paraelectric phase P. Triangles ferroelectric stripe phase Diamonds ferroelectric stripe phase Fp. Squares ferroelectric monodomain phase If.

Figure 24. Variation in the percentage of the different phases of Ndo.5-SrasMnOj with temperature FMM phase (diamonds) orbitally ordered A-type AFM phase (circles) charge-ordered CE-type AFM phase (squares) (from Woodward et al.50),...

At the conditions when the rate Hmiting step is crystallization of the target carbon phase (diamond) from the energy saturated primary carbon atoms C generated by the methane pyrolysis, the stepwise process can be written as a series of steps ... 

The known presolar/circumstellar phases diamond, silicon carbide, and graphite each contain a distinct noble-gas component which, like the major (except perhaps for carbon in diamonds), minor, and other trace elements in these phases, is radically anomalous compared to normal solar-system composition. These components are listed in Table 2 and illustrated in Figure 5. In the exploratory studies in which an understanding of these components was being developed, a variety of more-or-less complicated names, typically an acronym for some descriptive phrase or arbitrarily selected alphabetic characters (not all from the Latin alphabet), have been used. Some... 

Identification of vapor grown diamond is accomplished by X-ray diffraction or electron diffraction using a transmission electron microscope (TEM) and by Raman spectroscopy. Diamond coatings show the characteristic first-order Raman peak for diamond at 1332cm [59]. In many cases, an additional peak located at 1550cm occurs in the Raman spectrum which is attributed to a highly disordered carbon phase (diamond-like carbon) [60]. This diamond-like carbon contains sp and sp hybridized C-atoms which do not coincide with graphite. 

FUonenko VP, Davydov VA, Zibrov IP et al (2010) High pressure synthesis of new heterodiamond phase. Diamond Relat Mater 19 541-544... 

Pokropivny AV (2006) Structure of the boron nitride E-phase diamond lattice of B12N12 fullerenes. Diamond Relat Mater 15 1492-1495... 

Figures. Phase diagram ofthe Yoshida-Kamakura potential for a = 3.3. PandT areinreduced units. Full dots are two-phase coexistence points. Open dots are points of density maximum in the fluid phase. Diamonds and triangles denote points of —S2 maxima and D minima, respectively (D being the self-diffusion coefficient), giving the left boundary of the regions of structural and diffusion anomaly (the right boundaries, which are defined by —52 minima and D maxima, are out of the T range shown). Data are from Ref. [88].

In the past years there have been an increasing number of studies identifying the primary gas-phase diamond growth precursor [65, 67, 80-87] in CVD techniques, which have been the subject of controversy. The growth rate and film quahty of materials synthesized by CVD processes depend critically on the composition of the species generated. 

CVD (vapor-phase) diamond, potentially important but still basically at the laboratory stage withfew applications in production (reviewed in Ch. 13). 

The low-pressure vapor-phase process is based on chemical vapor deposition (CVD) and the material is often referred to as Vapor-phase diamond, diamond coating, or CVD diamond . CVD diamond will be used in this book. 

Figure 7.18. Results of local thermal analysis on the polymer blend shown in Fig. 7.17 occluded phase (diamonds) continuous phase (squares) (reproduced with permission of Anasys Instruments Inc.).

The Clapeyron equation can be applied to substances under extreme conditions of temperature and pressure, because it can estimate the conditions of phase transitions—and therefore the stable phase of a compound—at other than standard conditions. Such conditions might exist, say, at the center of a gas giant planet like Saturn or Jupiter. Or, extreme conditions might be applied in various industrial or synthetic processes. Consider the synthesis of diamonds, which normally occurs deep within the earth (or so it is thought). The phase transition from the stable phase of carbon, graphite, to the unstable phase, diamond, is a viable target for the Clapeyron equation, even though the two phases are solids. 

Fig. 7 Eneintiomer retention factors obtained on the Chirobiotic T column (teicoplanin selector) plotted versus the oiganic modifier content in the mobile phtise. a, c, and d RPLC mode with ethanol/pH 4 buffer mobile phases b normal-phase mode with ethanol/hepttme mobile phases. Diamonds and thick line LSER calculated retention factors using system parameters [48] and Table 5 solute descriptors squares experimental retention factors of the first eluting entmtiomer triangles experimenUil retention factors of the last eluting enantiomer...

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