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Short description: Allotrope of carbon

Q-carbon, short for quenched carbon, is a type of amorphous carbon, which is reported by its discoverers to be ferromagnetic, electrically conductive, harder than diamond,[1] and able to exhibit high-temperature superconductivity.[2][3][4][5] The original discoverers have published scientific papers on the synthesis and characterization of Q-carbon, but as of 2019, there is not yet any independent experimental synthesis or confirmation of these reported properties.

According to researchers, Q-carbon exhibits a random amorphous structure that is a mix of 3-way (sp2) and 4-way (sp3) bonding, rather than the uniform sp3 bonding found in diamonds.[6][7] Carbon is melted using nanosecond laser pulses, then quenched rapidly to form Q-carbon, or a mixture of Q-carbon and diamond. Q-carbon can be made to take multiple forms, from nanoneedles to large-area diamond films. Researchers also report the creation of nitrogen-vacancy nanodiamonds.[8]


In 2015, a research group led by Jagdish Narayan, a professor of materials science and engineering at North Carolina State University, and graduate student Anagh Bhaumik announced the discovery of Q-carbon.[2][4][9][10][11][12][13] They also announced the discovery of Q-boron nitride (Q-BN), and the conversion of carbon into diamond and h-BN into c-BN[14] at ambient temperatures and air pressures.[15]

The process started with Narayan's papers on laser annealing, published in Science,[16] and culminated in 2015–16 with another series of papers[17] and three United States patent applications: 62/245,108 (2015); 62/202,202 (2015); and 62/331.217 (2016). These have been licensed by Q-Carbon Inc[18] to commercialize products based on Q-carbon,[19][20][21] diamond,[22] Q-BN and c-BN.[23][24][25][26]


Typically, diamond is formed by heating carbon at very high temperatures (>5,000 K) and pressures (>120,000 atmospheres). However, Narayan and his group used kinetics and time control of pulsed nanosecond laser melting to overcome thermodynamic limitations and create a supercooled state that enables conversion of carbon into Q-carbon and diamond at ambient temperatures and pressures. The process uses a high-powered laser pulse, similar to that used in eye surgery, lasting approximately 200 nanoseconds. This raises the temperature of the carbon to approximately 4,000 K (3,700 °C; 6,700 °F) at atmospheric pressure. The resulting liquid is then quenched (rapidly cooled); it is this stage that is the source of the "Q" in the material's name. The degree of supercooling below the melting temperature determines the new phase of carbon, whether Q-carbon or diamond. Higher rates of cooling result in Q-carbon, whereas diamond tends to form when the free energy of the carbon liquid equals that of diamond.

Using this technique, diamond can be doped with both n- and p-type dopants, which is critical for high-power solid-state electronics. During rapid crystal growth from the melting, dopant concentrations can far exceed the thermodynamic solubility limit through a solute trapping phenomenon. This is necessary to achieve sufficiently high free carrier concentrations, since these dopants tend to be deep donors with high ionization energies.

It took researchers only 15 minutes to make one carat of Q-carbon. The initial research created Q-carbon from a thin plate of sapphire coated with amorphous (non-crystalline) carbon. Further studies have demonstrated that other substrates, such as glass or polymer, also work. This work was subsequently extended to convert h-BN into phase-pure c-BN.[27]


Q-carbon is non-crystalline, and while it has mixed sp2 and sp3 bonding, it is mostly sp3, which is offered as an explaination of its hardness[28] and its electrical, optical and magnetic properties. Q-carbon is harder than diamond by 48–70% because carbon is metallic in the molten state and gets closely packed, with a bond length smaller than that in diamond. Unlike all other known forms of carbon, Q-carbon is ferromagnetic, with a saturation magnetization of 20 emu/g and an estimated Curie temperature of approximately 500 K.[29][30]

Depending on the quenching rate from the supercooled state, Q-carbon can be a semiconductor or metallic. It glows more than diamond when exposed even to low levels of energetic radiation because of its stronger negative electron affinity.[31]

Boron-doped Q-Carbon exhibits BCS-type superconductivity at up to 57K.[32][33][34][35][21]

Some groups have provided theoretical explainations of the reported properties of Q-carbon, including the record high-temperature superconductivity, ferromagnetism and hardness.[36][37]

See also


  1. Narayan, Jagdish; Gupta, Siddharth; Bhaumik, Anagh; Sachan, Ritesh; Cellini, Filippo; Riedo, Elisa (2018). "Q-carbon harder than diamond" (in en). MRS Communications 8 (2): 428–436. doi:10.1557/mrc.2018.35. ISSN 2159-6859. 
  2. 2.0 2.1 Narayan, Jagdish; Bhaumik, Anagh (2015-12-07). "Novel phase of carbon, ferromagnetism, and conversion into diamond". Journal of Applied Physics 118 (21): 215303. doi:10.1063/1.4936595. ISSN 0021-8979. Bibcode2015JAP...118u5303N. 
  3. Roston, Brittany (Nov 30, 2015). "Researchers create diamond at room temperature". 
  4. 4.0 4.1 Bromwich, Jonah (2015-12-03). "New Substance Is Harder Than Diamond, Scientists Say". The New York Times. ISSN 0362-4331. 
  5. Ben Brumfield. "Q-carbon is harder, brighter than diamonds". 
  6. "Q-carbon is harder than diamond, incredibly simple to make | ExtremeTech". 
  7. "Researchers Find New Phase of Carbon, Make Diamond at Room Temperature". 
  8. Narayan, Jagdish; Bhaumik, Anagh (2016-11-02). "Novel synthesis and properties of pure and NV-doped nanodiamonds and other nanostructures" (in en). Materials Research Letters 5 (4): 242–250. doi:10.1080/21663831.2016.1249805. ISSN 2166-3831. 
  9. Crowell, Maddy (2015-12-03). "A replacement for diamonds? Scientists discover Q-carbon". Christian Science Monitor. ISSN 0882-7729. 
  10. Wei-Haas, Maya. "Weird New Type of Carbon Is Harder (and Brighter) Than Diamond". 
  11. Mack, Eric. "Scientists Create New Kind Of Diamond At Room Temperature". 
  12. "Q-carbon: A new phase of carbon so hard it forms diamonds when melted". 
  13. "Researchers find new phase of carbon, make diamond at room temperature". 
  14. Narayan, Jagdish; Bhaumik, Anagh (February 2016). "Research Update: Direct conversion of h-BN into pure c-BN at ambient temperatures and pressures in air" (in en). APL Materials 4 (2): 020701. doi:10.1063/1.4941095. ISSN 2166-532X. 
  15. Narayan, Jagdish; Bhaumik, Anagh; Gupta, Siddharth; Haque, Ariful; Sachan, Ritesh (2018-04-06). "Progress in Q-carbon and related materials with extraordinary properties" (in en). Materials Research Letters 6 (7): 353–364. doi:10.1080/21663831.2018.1458753. ISSN 2166-3831. 
  16. Science 204, 461 (1979) and Science 252, 416 (1991).
  17. APL Materials 3, 100702 (2015); APL Materials 4, 202701 (2016); J. Appl. Phys. 118, 215303 (2015); J. Appl. Phys. 119, 185302 (2016); Materials Res. Letters 2016; doi:10.1080/21663931.2015.1126865 ; Advanced Materials and Processes 174, 24 (2016).
  18. Q Carbon Inc
  19. Narayan, Jagdish; Bhaumik, Anagh (2016-02-03). "Q-carbon discovery and formation of single-crystal diamond nano- and microneedles and thin films" (in en). Materials Research Letters 4 (2): 118–126. doi:10.1080/21663831.2015.1126865. ISSN 2166-3831. 
  20. Gupta, Siddharth; Bhaumik, Anagh; Sachan, Ritesh; Narayan, Jagdish (2018-01-03). "Structural Evolution of Q-Carbon and Nanodiamonds" (in en). JOM 70 (4): 450–455. doi:10.1007/s11837-017-2714-y. ISSN 1047-4838. 
  21. 21.0 21.1 Gupta, Siddharth; Sachan, Ritesh; Bhaumik, Anagh; Pant, Punam; Narayan, Jagdish (June 2018). "Undercooling driven growth of Q-carbon, diamond, and graphite" (in en). MRS Communications 8 (2): 533–540. doi:10.1557/mrc.2018.76. ISSN 2159-6859. 
  22. Bhaumik, Anagh; Narayan, Jagdish (2018-01-03). "Synthesis and Characterization of Quenched and Crystalline Phases: Q-Carbon, Q-BN, Diamond and Phase-Pure c-BN" (in en). JOM 70 (4): 456–463. doi:10.1007/s11837-017-2712-0. ISSN 1047-4838. 
  23. Narayan, Jagdish; Bhaumik, Anagh (2016). "Discovery of Q-BN and Direct Conversion of h-BN into c-BN and Formation of Epitaxial c-BN/Diamond Heterostructures" (in en). MRS Advances 1 (37): 2573–2584. doi:10.1557/adv.2016.472. ISSN 2059-8521. 
  24. Narayan, Jagdish; Bhaumik, Anagh (2016). "Discovery of Q-BN and Direct Conversion of h-BN into c-BN and Formation of Epitaxial c-BN/Diamond Heterostructures". MRS Advances 1 (37): 2573–2584. doi:10.1557/adv.2016.472. ISSN 2059-8521. 
  25. Narayan, Jagdish; Bhaumik, Anagh; Xu, Weizong (2016-05-14). "Direct conversion of h-BN into c-BN and formation of epitaxial c-BN/diamond heterostructures" (in en). Journal of Applied Physics 119 (18): 185302. doi:10.1063/1.4948688. ISSN 0021-8979. 
  26. Narayan, Jagdish; Bhaumik, Anagh (2017), "Fundamental Discovery of Q-Phases and Direct Conversion of Carbon into Diamond and h-BN into c-BN", Mechanical and Creep Behavior of Advanced Materials (Springer International Publishing): pp. 219–228, doi:10.1007/978-3-319-51097-2_17, ISBN 9783319510965 
  27. APL Materials 4, 202701 (2016)
  28. Gupta, Siddharth; Sachan, Ritesh; Bhaumik, Anagh; Narayan, Jagdish (2018). "Enhanced mechanical properties of Q-carbon nanocomposites by nanosecond pulsed laser annealing" (in en). Nanotechnology 29 (45): 45LT02. doi:10.1088/1361-6528/aadd75. ISSN 1361-6528. PMID 30156561. 
  29. Bhaumik, Anagh; Nori, Sudhakar; Sachan, Ritesh; Gupta, Siddharth; Kumar, Dhananjay; Majumdar, Alak Kumar; Narayan, Jagdish (2018-02-06). "Room-Temperature Ferromagnetism and Extraordinary Hall Effect in Nanostructured Q-Carbon: Implications for Potential Spintronic Devices" (in EN). ACS Applied Nano Materials 1 (2): 807–819. doi:10.1021/acsanm.7b00253. ISSN 2574-0970. 
  30. Bhaumik, Anagh; Narayan, Jagdish (2018-05-28). "Electrochromic effect in Q-carbon" (in en). Applied Physics Letters 112 (22): 223104. doi:10.1063/1.5023613. ISSN 0003-6951. 
  31. Haque, Ariful; Narayan, Jagdish (June 2018). "Electron field emission from Q-carbon". Diamond and Related Materials 86: 71–78. doi:10.1016/j.diamond.2018.04.008. ISSN 0925-9635. 
  32. Bhaumik, Anagh; Sachan, Ritesh; Narayan, Jagdish (2017). "A novel high-temperature carbon-based superconductor: B-doped Q-carbon". Journal of Applied Physics 122 (4): 045301. doi:10.1063/1.4994787. Bibcode2017JAP...122d5301B. 
  33. Bhaumik, Anagh; Sachan, Ritesh; Narayan, Jagdish (2017-05-05). "High-Temperature Superconductivity in Boron-Doped Q-Carbon" (in EN). ACS Nano 11 (6): 5351–5357. doi:10.1021/acsnano.7b01294. ISSN 1936-0851. PMID 28448115. 
  34. Bhaumik, Anagh; Sachan, Ritesh; Gupta, Siddharth; Narayan, Jagdish (2017-11-10). "Discovery of High-Temperature Superconductivity (Tc =55 K) in B-Doped Q-Carbon" (in EN). ACS Nano 11 (12): 11915–11922. doi:10.1021/acsnano.7b06888. ISSN 1936-0851. PMID 29116751. 
  35. Bhaumik, Anagh; Sachan, Ritesh; Narayan, Jagdish (2018). "Magnetic relaxation and three-dimensional critical fluctuations in B-doped Q-carbon – a high-temperature superconductor" (in en). Nanoscale 10 (26): 12665–12673. doi:10.1039/c8nr03406k. ISSN 2040-3364. PMID 29946612. 
  36. Sakai, Yuki; Chelikowsky, James R.; Cohen, Marvin L. (2018-02-01). "Simulating the effect of boron doping in superconducting carbon". Physical Review B 97 (5): 054501. doi:10.1103/PhysRevB.97.054501. Bibcode2018PhRvB..97e4501S. 
  37. Sakai, Yuki; Chelikowsky, James R.; Cohen, Marvin L. (2018-07-13). "Magnetism in amorphous carbon". Physical Review Materials 2 (7): 074403. doi:10.1103/PhysRevMaterials.2.074403.