Synthesis and thermal decomposition of magnesium dicarbide

Abstract

The conditions of formation of magnesium dicarbide from magnesium and acetylene were investigated; the optimum temperature, reaction period, and acetylene flow rate were sought so as to achieve high yields of dicarbide and minimize the free carbon deposit. The porosity of the magnesium dust was found to have a pronounced effect upon the yield; a considerable improvement was achieved by pressing the dust into pellets with controlled porosity. The powder X-ray diffraction patterns of MgC2 samples were studied. The intense reflection could be indexed for the bet symmetry (a = 392.9 ± 0.6 pm, c = 503.7 ± 1.2 pm), but as the intensity calculations for dicarbide models with different arrangements of the C22- groups indicate, the symmetry of the MgC2 lattice will be lower than tetragonal. The thermal decomposition of the dicarbide leading to sesquicarbide was examined in dependence on time and temperature by hydrolyzing the samples and analyzing the gaseous products by GLC. Due to the thermal decomposition, traces of sesquicarbide appear even during the dicarbide synthesis. The decomposition process was approximated by kinetic equations. The Arrhenius equation constants, in the temperature region of 485-560 °C, are AA = 4.97 . 1012 s-1, EA = 257 kJ mol-1.

Synthesis of β-Mg2C3: A Monoclinic High-Pressure Polymorph of Magnesium Sesquicarbide

“…An MA synthesis experiment using 13 C amorphous carbon (99% of isotope purity) was performed at 9 GPa and 1700 K (outside of the formation region of Mg 2 C) to further investigate the states of carbon in the new phase using 13 C NMR (Figure 2b). While multiple peaks exist in the spectrum due to multiphase synthesis, two clear groupings occur near δ = 50 and 175 ppm, in an approximate 2:1 ratio.…”

“…All solid state NMR experiments were run on a Chemagnetics Infinity Solid State NMR system. The static field of this instrument is 7.05 T yielding Larmor frequency for 13 C of 75 MHz. Direct polarization with magic angle spinning (ω 1 /2π = 11 kHz) was employed using 5 mm inner diameter zirconia rotors and a doubly tuned MAS RF probe.…”

“…Direct polarization with magic angle spinning (ω 1 /2π = 11 kHz) was employed using 5 mm inner diameter zirconia rotors and a doubly tuned MAS RF probe. Boron nitride inserts were employed around the sample to negate 13 C background from within the rotor. As the amount of sample was very small the issue of background signal from Vespel components of the stator in proximity to the RF coil is significant.…”

Carbon‐fibre reinforced magnesium alloys: nanostructure and chemistry of interlayers and their effect on mechanical properties

“…In the chemical literature ( Irmann, 1948; Schneider & Cordes, 1955; Hájek et al ., 1983a , 1983b), the system C/Mg is treated as a chemically non‐reactive one. This is because the two binary magnesium carbides MgC 2 and Mg 2 C 3 are endothermic compounds which start to decompose at about 500 °C and 650 °C, respectively.…”

Microstructural analysis of a carbon fibre reinforced AZ91D magnesium alloy composite

“…The two possible magnesium carbides-MgC 2 and Mg 2 C 3 -are highly reactive and thermally unstable. 13,14 The carbide MgC 2 has been reported in a carbon-fibre-reinforced pure Mg composite 15 but this has been questioned by Viala et al, 4 who report that carbon fibres exhibit an almost complete inertness to pure Mg between 700 and 1000 K.…”