Diamond synthesis in aluminum matrix in molten alkali-halide at ambient pressure

• Diamond crystals synthesize in molten aluminum in molten alkali halides under air.
• Carbides of metals and non-metals used as a source of carbon
• Raman spectra, microhardness and EBSD confirm formation of perfect cubic diamonds.
• Diamond formation mechanism via carbon atom supersaturation has been proposed.
• Diamonds form under aluminum cooling under strongly non-equilibrium conditions.

The interaction of the molten aluminum with the carbon-containing admixture in a molten halide-alkali medium at atmospheric pressure with temperatures of 700–800 °С under strong non-equilibrium conditions is studied. Cubic diamond crystals of 2–100 μm and nanorods of 20–100 nm diameter and 5 μm lengths are first found forming inside the aluminum matrix under certain cooling regimes. The X-ray diffraction analysis, electron backscatter diffraction spectroscopy, electronic microscopy, Raman spectroscopy and microhardness detection register the perfect cubic diamond formation inside aluminum without applying of high temperature and high-pressure. Diamond formation mechanism is growing by carbon atom diffusion through an aluminum droplet. Diamond and nanodiamond synthesis conducted directly at the carbon ion interaction with the molten metal volume and subsequent cooling regimes.Prime novelty statementDiamond synthesis has been performed in molten aluminium via the interaction between molten aluminium and carbide-containing halide melt at 700–750 °C with ambient pressure.The X-ray diffraction analysis, electron backscatter diffraction spectroscopy, electronic microscopy, Raman spectroscopy and microhardness detection register the perfect cubic diamond formation inside aluminium without high temperatures and high-pressure regimes.

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