Research ArticleMATERIALS SCIENCE

Pressure-induced shear and interlayer expansion in Ti3C2 MXene in the presence of water

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Science Advances  12 Jan 2018:
Vol. 4, no. 1, eaao6850
DOI: 10.1126/sciadv.aao6850
  • Fig. 1 Humidity-dependent XRD of uniaxially pressed discs.

    XRD (Cu Kα radiation) of Ti3C2Tx equilibrated at various RHs. (A) Powders directly after equilibration (all reflections are {00l}). (B) Same powders, after uniaxial pressing to 300 MPa to form discs. Asterisks denote {00l} reflections, and squares denote (111) reflections from a small amount of TiC impurity. (C) Initial wet paste directly after preparation (bottom), after pressing to 300 MPa to form a disc (middle), and after drying the disc over P2O5 for 48 hours (top). All reflections are {00l}.

  • Fig. 2 Pressure-dependent in situ XRD.

    (A) XRD patterns (Mo Kα radiation) of Ti3C2Tx collected in DAC at various pressures up to ≈5 GPa using water as pressure-transmitting medium (that is, a large excess of water). The red asterisk (*) denotes the (002) reflection of a small amount of residual Ti3AlC2. All other reflections are MXene {00l}. (B) Basal spacing d001 as a function of external pressure for Ti3C2Tx in two experiments with different amounts of water: excess H2O (blue circles) and a small amount of H2O (black triangles). Note that the maximum expansion here is almost 2 Å smaller than those reported in Fig. 1.

  • Fig. 3 Depth-profile XRD of pressed discs.

    XRD (Cu Kα radiation) of Ti3C2Tx pressed into discs at 300 MPa. (A and B) Powders were equilibrated at 0% RH (A) or 100% RH (B) before pressing. In each case, further XRD was taken after indicated approximate depths of material had been removed from the surface by scraping to obtain an approximation of the depth profile. All reflections are {00l}.

  • Fig. 4 SEM images of pressed-disc surfaces.

    SEM images of various pressed discs made with powders that had been equilibrated, before pressing, at various labeled RHs. (A and B) Images from the surface (A) and interior (B) of the same disc. Examples of multilayered particles at various states of shear are labeled with green arrows; regions of extreme shear are labeled with red arrows. Scale bars, 4 μm.

  • Fig. 5 Humidity-dependent ex situ XRD after K+ intercalation.

    Effect of K+ ions intercalated into Ti3C2Tx. (A) XRD of Ti3C2Tx discs pressed at 300 MPa from powders that were equilibrated at various relative humidities. All reflections are MXene {00l}. (B) SEM micrograph of the top surface of the 100% RH disc, showing no evidence of major nanosheet slipping.

  • Table 1 Comparison of basal spacings of Ti3C2Tx made by different methods.
    Etching systemProcessingBasal spacing (Å)Δd001 (Å)*Reference
    10% HFUndisturbed multilayered stacks, dry~100(6, 22)
    10% HFUndisturbed multilayered stacks, still wet13.53.5(9)
    10% HFDelaminated and restacked15.15.1(9)
    HCl + LiFDisc (pressed at 300 MPa)15.05(12)
    HCl + LiFSpray-coated film (from delaminated suspension)14.754.75(25)
    HCl + LiFThick film via filtration of delaminated suspension15.25.2(26)
    HCl + LiFSpincoating (single- to few-layer flakes)15 ± 2§5(27)
    10% HFDisc (pressed at 300 MPa)155This work

    *Measured as the expansion from fully collapsed dry structure with d001 = 10 Å.

    †Pressed-disc data not included in published report.

    ‡From reported d(002)/2.

    §Monolayer with H2O via atomic force microscopy.

    • Table 2 Compilation of basal spacings of pressure-induced expansion in materials in the literature.
      MaterialΔd001 (Å)Pressure (GPa)Reference
      Ti3C2Tx2.5*/50.3 (uniaxial, ex situ)This work
      0.16*/2.660.32 (quasi-hydrostatic)§
      0.69*/3.19After unloading from 4.98 (quasi-hydrostatic)
      Na-fluorohectorite (a clay mineral)2*2.5 (hydostatic)§(34)
      Kaolinite1.5*/2.40.1 (hydrostatic, over 65 hours)§(35)
      GO2.5*/6.91.25 (hydrostatic)§(1)

      d defined as difference between the phase after pressure is applied and highest d spacing observed from ambient-pressure hydration.

      †Δd defined as difference between pressure-hydrated phase and dried, fully collapsed structure.

      ‡Maximum pressure applied (ex situ experiments).

      §Pressure at which the expansion was observed to occur.

      Supplementary Materials

      • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/1/eaao6850/DC1

        fig. S1. Full diffraction pattern of Ti3C2Tx compressed in excess H2O at a pressure of 2 GPa.

        fig. S2. Full diffraction pattern of Ti3C2Tx compressed in excess H2O at a pressure of 3 GPa.

        fig. S3. Analysis of material ejected from the side of the die.

      • Supplementary Materials

        This PDF file includes:

        • fig. S1. Full diffraction pattern of Ti3C2Tx compressed in excess H2O at a pressure of 2 GPa.
        • fig. S2. Full diffraction pattern of Ti3C2Tx compressed in excess H2O at a pressure of 3 GPa.
        • fig. S3. Analysis of material ejected from the side of the die.

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