Table 1.
Proximate analysis and ultimate analysis of anthracite from Huyan Mountain.
Table 2.
High-temperature simulation experimental scheme.
Table 3.
XRD parameter analysis result table.
Fig 1.
(a) XRD diffraction pattern; (b) Evolution curve of d002. With the elevation of temperature, the (002) peak demonstrates a trend of approaching the peak position of the standard graphite peak (2θ = 26.6°). Concurrently, its peak intensity enhances, and the full width at half maximum (FWHM002) diminishes. Notably, the HC sample exhibits a more acutely defined peak shape. When the temperature reaches 2700 °C, the rate of graphitization decelerates conspicuously. The (002) peak arrests its development at 2θ = 26.44°, with no discernible changes thereafter. Utilizing the Bragg equation to compute the interlayer spacing d002 of the carbon layers, it is revealed that within the temperature range of 2100–2400 °C, as the temperature ascends, the d002 value declines rapidly, approaching the interlayer spacing of standard graphite, which is 0.3354 nm. The HC sample possesses a lower d002 value, indicative of a higher degree of graphitization. However, as the temperature nears 2700 °C, the rate of d002 development gradually attenuates until it ceases. Ultimately, both the HR and HC samples reach an identical d002 value of 0.3368 nm.
Fig 2.
Curves of microcrystalline parameters vary with temperature.
(a) Evolution curve of Lc; (b) Evolution curve of La.
Table 4.
Raman parameter analysis result table.
Fig 3.
Peak-fitting diagram of Raman spectra.
Concomitant with the elevation in the temperature, the intensity of the G peak (graphite peak) escalates, and its peak position drifts towards 1580 cm−¹. The intensity of the D peak (defect peak) dwindles, where in-plane defects (D1) and interlayer defects (D2) are preponderant. The second-order Raman peak, the S2 peak, vanishes completely, and the three - dimensional structure of graphite is subject to a process of incremental improvement.
Fig 4.
Curves of Lattice parameters vary with temperature.
(a) Evolution curve of R2; (b) Evolution curve of R3.
Fig 5.
HRTEM characterization between 2100 °C and 2400 °C.
(a) HR-1 at 2100 °C; (b) HR-2 at 2400 °C; (c) HC-1 at 2100 °C; (d) HC-2 at 2400 °C. Wrinkled graphite stage, the number of stacked carbon layers is relatively meager. The graphite laminae present an abundance of imperfections. A substantial quantity of disordered carbon layers is discernible.
Fig 6.
HRTEM Characterization between 2700 °C and 3000 °C.
(a) HR-3 at 2700 °C. In the transitional regime from wrinkled graphite to flat graphite, the malleability of the graphite laminae augments. The external orientation becomes markedly pronounced, while the internal configuration remains tortuous and chaotic; (b) HR-4 at 3000 °C. In the transitional regime from wrinkled graphite to flat graphite, in comparison to the state at 2700 °C, the graphite lamellae experience further evolution. The orientation becomes more pronounced with the number of stacked carbon layers escalates, and the quantity of disordered carbon layers dwindles; (c) HC-3 at 2700 °C. Flat graphite stage, the edges of the graphite lamellae manifest a remarkable degree of regularity. The orientation is highly conspicuous, and the quantity of stacked layers is relatively scant, spanning approximately 3 to 5 layers. Intrinsically, disordered carbon layers endure; (d) HC-4 at 3000 °C. Flat graphite stage, the structural order experiences a further augmentation. The amount of disordered carbon layers dwindles substantially, and the number of stacked layers ascends to upwards of ten layers.
Fig 7.
SEM characterization between 2700 °C and 3000 °C.
(a) HR-3 at 2700 °C; (b) HR-4 at 3000 °C; (c) HC-3 at 2700 °C; (d) HC-4 at 3000 °C.
Fig 8.
Microscopic component images of anthracite from Huyan Mountain.
(a) Fusinite, oil-immersion reflected light; (b) Fusinite, cellular structure, oil-immersion reflected light.