Laser-engineered heavy hydrocarbons: Old materials with new opportunities

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Science Advances  24 Apr 2020:
Vol. 6, no. 17, eaaz5231
DOI: 10.1126/sciadv.aaz5231
  • Fig. 1 Schematic of laser ablation of natural HH (coal, MO pitch, and tar).

    (A) HH materials: tar, MP, and coal. (B) Laser-ablated stochastic graphitic system from HH. (C) TEM image of laser-ablated steam cracked tar. (D) TEM image of laser-ablated LvB coal (DECS 19). (E) TEM image of laser-ablated MP pitch. Arrows point to graphitic fringe stackings. Scale bars, 5 nm (C to E). Insets of (C) and (D): Profiles of highlighted lines. The average interlayer spacing of ablated tar is ~4.3 Å, and that of ablated coal is ~3.4 Å. (F) MD simulation result of sp2 carbon change in tar, coal, and pitch after laser ablation. (G) MD simulation results of H:C ratio change in tar, coal, and MP pitch after laser ablation. (H) Schematic of how naturally occurring PAHs are stitched to larger graphitic clusters when ablated by CO2 laser. A.U., arbitrary units.

  • Fig. 2 Raman analysis of HHs, oxidized HHs, and laser-ablated HHs.

    (A) Raman spectrum of laser-ablated HHs. Raman spectrum of laser-ablated MP with different additives. The increased 2D peak and narrowed G peak indicate a better aromatic stacking in laser-ablated MP with additive alkane and small aromatic fragment. Raman spectra of laser-ablated oxidized tar and MP thin films showing a strong 2D peak compared to the near-zero 2D peak in ablated nonoxidized films. (B) ID/IG ratio, FWHM, and G peak position analysis of Raman spectra. The numbers in each data point indicate a different sample. Ox, oxidized; Asphal, asphaltene; a-C, amorphous carbon; nc, nanocrystalline. (C) Fitted in-plane crystallite size La from ID/IG.

  • Fig. 3 Conductivity and electrical transportation of HH.

    (A) Conductivity of laser-ablated natural polyaromatic hydrocarbon (NPAH) thin films and their hybrid thin films compared to the conductivities of synthetic carbon materials. (B) Temperature-dependent conductivity of laser-ablated NPAHs.

  • Fig. 4 Conductivity optimization of laser-ablated tar.

    (A) Optical images of laser-ablated tar thin film. The scanning speed is fixed at 127 mm/s, while defocus and laser power vary as labeled on the image. Optical absorption analysis of laser-ablated tar. Photo credit: Xining Zang, Massachusetts Institute of Technology. (B) Visible light (2 to 3 eV) absorption of tar and ablated tar, from which Urbach tail is derived in (C). The slope of (B) can be used to derive H:C ratio and aromatic content following the method in (20). (D) H:C ratio and aromatic content change in response to different laser power at the same defocus setting at 0.14 inches. (E) Raman spectrum of laser-ablated tar with different power at a defocus distance of 0.14 inches. (F) Conductivities of ablated tar, which shows a tentative linear response to power/defocus. In (E) and (F), the full-range power is 30 W. Percentage is used to record the parameter tuned in the software interface. The real power numbers can be calculated accordingly.

  • Fig. 5 Applications of laser-treated tar in electronics and additive manufacturing.

    (A) Fabrication schematics of laser-printed devices, including patterning, washing, and transfer process. (B) Laser-printed tar-based devices including a transparent heater, an interdigit supercapacitor, and a flexible strain sensor transferred onto PDMS. Details of performance are shown in the Supplementary Materials. (C) Heating responses under different bias. Temperature will plateau after ~20 s, and the saturated temperature increases with input bias voltage. Heating temperature can reach up to 300°C under 60-V bias. (D) Optical image of laser-printed supercapacitor and strain sensor. (E) Performance of strain sensor made of laser-ablated tar. (F) Performance of strain sensor made of laser-ablated MP-asphaltene composite. (G) Comparison of gauge factors of strain sensor in (E) and (F). Photo credit: Xining Zang, Massachusetts Institute of Technology.

Supplementary Materials

  • Supplementary Materials

    Laser-engineered heavy hydrocarbons: Old materials with new opportunities

    X. Zang, C. Jian, S. Ingersoll, Huashan Li, J. J. Adams, Z. Lu, N. Ferralis, J. C. Grossman

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    • Figs. S1 to S8
    • Tables S1 and S2

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