Mechanochemical synthesis of Co-C materials

Synthesis of large-sized spherical Co–C alloys with soft magnetic properties though a high-pressure solid-state metathesis reaction

“…6,22,[60][61][62][63] The decomposition enthalpy of metastable Co 3 C is relatively high (−DH = 23 kJ mol −1 ). 3,6 In an isobaric environment, the variation in Gibbs free energy (DG) can be expressed as DG = DH − TDS, where DH represents enthalpy change, and DS represents entropy change. When Co 3 C decomposes into Co and C, an increase in internal disorder is observed within the system, leading to a positive DS (>0).…”

“…It has been reported that metastable Pnma Co 3 C, decomposes into fcc Co and graphite at certain temperatures. 6,22,60–63…”

“…2d illustrates the atomic lattice of fcc Co, Pnma Co 3 C and fcc Co 1− x C x (solid solution). Due to the good solubility (above 7 at%) of C in Co, 6 C atoms preferentially occupy octahedral interstitial positions within the fcc Co lattice, displaying a higher electron affinity for metals. In contrast, N atoms face challenges in diffusing within the Co lattice, hindering the formation of metal nitrides.…”

“…These alloy compounds can exhibit a diverse range of crystal structures and properties, which are contingent upon the composition, 1 proportions of elements, [2][3][4][5] and the arrangement of the crystal lattice. [6][7][8] A noteworthy observation lies in the dependence of the magnetic moment on the unit cell volume. 9 This imbues them with substantial potential applications in the realm of materials science.…”

“…5,[14][15][16][17][18][19][20][21][22] Experimental and theoretical studies have conrmed its notable magnetization strength and coercivity, suggesting that it could serve as an ideal rare-earth-free permanent magnet material with promising developmental prospects. 5,14 Co 3 C nanoparticles have been synthesized using methods like wet chemical synthesis, 5,23,24 mechanical alloying, 3,6,25 ion irradiation, 26 and the one-pot template-free solvothermal approach. 27 P. V. Marshall et al utilized a DAC (diamond anvil cell) device with a size of 300 mm to synthesize microscale Co 3 C under conditions of 5-15 GPa and 1200 K. 28 However, stable carbides are not present in the Co-C system.…”