Phase diagram with a region of liquid carbon-diamond metastable states

Basharin, A. Yu.; Dozhdikov, V. S.; Kirillin, A. V.; Turchaninov, M. A.; Fokin, L. R.

doi:10.1134/s1063785010060210

Cited by 13 publications

(10 citation statements)

References 9 publications

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“…[3] Figure 2 shows variation of Gibbs free energy as a function of temperature for graphitic carbon (G g ), liquid carbon (G liq ), and diamond (G d ) near our ambient temperature of processing [7] . According to this free energy diagram, amorphous Q-carbon is formed at the highest undercooling T q , and diamond is nucleated at slightly higher temperature of T d .…”

Section: A Modified Carbon Phase Diagrammentioning

confidence: 99%

RETRACTED ARTICLE: Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

Narayan

2016

Metall Mater Trans A

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We review the discovery of new phases of carbon (Q-carbon) and BN (Q-BN) and address critical issues related to direct conversion of carbon into diamond and hBN into cBN at ambient temperatures and pressures in air without any need for catalyst and the presence of hydrogen. The Q-carbon and Q-BN are formed as a result of quenching from super undercooled state by using high-power nanosecond laser pulses. We discuss the equilibrium phase diagram (P vs T) of carbon, and show that by rapid quenching, kinetics can shift thermodynamic graphite/diamond/liquid carbon triple point from 5000 K/12 GPa to super undercooled carbon at atmospheric pressure in air. Similarly, the hBN-cBN-Liquid triple point is shifted from 3500 K/9.5 GPa to as low as 2800 K and atmospheric pressure. It is shown that nanosecond laser heating of amorphous carbon and nanocrystalline BN on sapphire, glass, and polymer substrates can be confined to melt in a super undercooled state. By quenching this super undercooled state, we have created a new state of carbon (Q-carbon) and BN (Q-BN) from which nanocrystals, microcrystals, nanoneedles, microneedles, and thin films are formed depending upon the nucleation and growth times allowed and the presence of growth template. The large-area epitaxial diamond and cBN films are formed, when appropriate planar matching or lattice matching template is provided for growth from super undercooled liquid. The Q-phases have unique atomic structure and bonding characteristics as determined by high-resolution SEM and backscatter diffraction, HRTEM, STEM-Z, EELS, and Raman spectroscopy, and exhibit new and improved mechanical hardness, electrical conductivity, and chemical and physical properties, including room-temperature ferromagnetism and enhanced field emission. The Q-carbon exhibits robust bulk ferromagnetism with estimated Curie temperature of about 500 K and saturation magnetization value of 20 emu g À1 . We have also deposited diamond on cBN by using a novel pulsed laser evaporation of carbon and obtained cBN/diamond composites, where cBN acts as template for diamond growth. Both diamond and cBN grown from super undercooled liquid can be alloyed with both p-and n-type dopants. This process allows carbon to diamond and hBN to cBN conversions and formation of useful nanostructures and microstructures at ambient temperatures in air at atmospheric pressure on practical and heat-sensitive substrates in a controlled way without need for any catalysts and hydrogen to stabilize sp 3 bonding for diamond and cBN phases.

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Section: A Modified Carbon Phase Diagrammentioning

confidence: 99%

RETRACTED ARTICLE: Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

Narayan

2016

Metall Mater Trans A

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“…According to this free energy diagram, amorphous Q-carbon is formed at the highest undercooling T q , and diamond is nucleated at slightly higher temperature of T d . It should be mentioned that Basharin et al 28 FIG. 17.…”

Section: Discussionmentioning

confidence: 97%

“…Basharin et al 28,29 have estimated the temperature dependence of Gibbs free energy of graphite, metastable liquid carbon and diamond at a low pressure of 0.012 GPa of helium and found that free energy of liquid carbon can be equal to that of diamond at 4160 6 50 K; this is considerably lower than melting point of liquid graphite at a pressure of 0.012 GPa of helium. Fig.…”

Section: Discussionmentioning

confidence: 99%

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Novel phase of carbon, ferromagnetism, and conversion into diamond

Narayan

Bhaumik

2015

Journal of Applied Physics

140

131

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We report the discovery of a new phase of carbon (referred to as Q-carbon) and address fundamental issues related to direct conversion of carbon into diamond at ambient temperatures and pressures in air without any need for catalyst and presence of hydrogen. The Q-carbon is formed as result of quenching from super undercooled state by using high-power nanosecond laser pulses. We discuss the equilibrium phase diagram (P vs. T) of carbon and show that by rapid quenching kinetics can shift thermodynamic graphite/diamond/liquid carbon triple point from 5000 K/12 GPa to super undercooled carbon at atmospheric pressure in air. It is shown that nanosecond laser heating of diamond-like amorphous carbon on sapphire, glass, and polymer substrates can be confined to melt carbon in a super undercooled state. By quenching the carbon from the super undercooled state, we have created a new state of carbon (Q-carbon) from which nanodiamond, microdiamond, microneedles, and single-crystal thin films are formed depending upon the nucleation and growth times allowed for diamond formation. The Q-carbon quenched from liquid is a new state of solid carbon with a higher mass density than amorphous carbon and a mixture of mostly fourfold sp 3 (75%-85%) with the rest being threefold sp 2 bonded carbon (with distinct entropy). It is expected to have new and improved mechanical hardness, electrical conductivity, chemical, and physical properties, including room-temperature ferromagnetism (RTFM) and enhanced field emission. Here we present interesting results on RTFM, enhanced electrical conductivity and surface potential of Q-carbon to emphasize its unique properties. The Q-carbon exhibits robust bulk ferromagnetism with estimated Curie temperature of about 500 K and saturation magnetization value of 20 emu g À1. From the Q-carbon, diamond phase is nucleated and a variety of micro-and nanostructures and large-area single-crystal diamond sheets are grown by allowing growth times as needed. Subsequent laser pulses can be used to grow nanodiamond into microdiamond and nucleate other nanostructures of diamond on the top of existing microdiamond and create novel nanostructured materials. The microstructural details provide insights into the mechanism of formation of nanodiamond, microdiamond, nanoneedles, microneedles, and single-crystal thin films. This process allows carbon-to-diamond conversion and formation of useful nanostructures and microstructures at ambient temperatures in air at atmospheric pressure on practical and heat-sensitive substrates in a controlled way without need for any catalysts and hydrogen to stabilize sp 3 bonding for diamond formation. V

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“…After melting, the system undergoes cooling, because the melt graphite is in thermal contact with the bulk graphite and surrounding water, and temperature and pressure decrease abruptly. Cooling velocity of the melted graphite is expected to be as high as 10 10 –10 11 K/s (as usual with nanoseconds laser pulses) and, in this conditions, within a few nanoseconds and in undercooling state, the system is brought into the region of stability of diamond or metastability of graphite, where the nucleation of a solid stable phase (diamond) is favored 39 40 .…”

Section: Resultsmentioning

confidence: 99%

On the thermodynamic path enabling a room-temperature, laser-assisted graphite to nanodiamond transformation

Gorrini

Cazzanelli

Bazzanella

et al. 2016

Sci Rep

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Nanodiamonds are the subject of active research for their potential applications in nano-magnetometry, quantum optics, bioimaging and water cleaning processes. Here, we present a novel thermodynamic model that describes a graphite-liquid-diamond route for the synthesis of nanodiamonds. Its robustness is proved via the production of nanodiamonds powders at room-temperature and standard atmospheric pressure by pulsed laser ablation of pyrolytic graphite in water. The aqueous environment provides a confinement mechanism that promotes diamond nucleation and growth, and a biologically compatible medium for suspension of nanodiamonds. Moreover, we introduce a facile physico-chemical method that does not require harsh chemical or temperature conditions to remove the graphitic byproducts of the laser ablation process. A full characterization of the nanodiamonds by electron and Raman spectroscopies is reported. Our model is also corroborated by comparison with experimental data from the literature.

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Phase diagram with a region of liquid carbon-diamond metastable states

Cited by 13 publications

References 9 publications

RETRACTED ARTICLE: Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

RETRACTED ARTICLE: Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

Novel phase of carbon, ferromagnetism, and conversion into diamond

On the thermodynamic path enabling a room-temperature, laser-assisted graphite to nanodiamond transformation

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