Tungsten diamond synthesis

Moissan, Ferdinand Frederic-Henri (1852-1907) is known in the field of ceramics for his unsuccessful attempts at diamond synthesis (he actually produced SiC). Moissan was awarded the 1906 Nobel Prize in Chemistry for isolating fluorine on June 26, 1886. It was in Moissan s laboratory at the University of Paris in France that tungsten carbide was first made. 

Nine compositions with the diamond concentration of 3, 5, 7, 9, 10, 12, 15, 20, 25 mass % were mixed with the charge Ti-C-Mo to produce multi-layered semi-products. The ready mixtures were placed layer-by-layer into a pressform in the following order diamondless layer weighing 25,5 g 3 mass % diamond layer, weighing 10 g 5 % layer -10 g 7 % layer - 10 g 9 % layer - 9,9 g 12 % layer - 9,9 g. After densification pellets were obtained 48 mm in diameter with the thickness of the layers 5.0, 2.0, 2.0, 2.0, 2.0, 2.0 mm correspondently. Multilayered pellets with the diamond concentration from layer to layer as much as 0, 5, 10, 15, 20, 25 % mass were prepared similarly. The final pellet was placed into a reactional mold. An SHS reaction was initiated from the lateral face of the cylindrical pellet by a tungsten spiral. After accomplishment of the combustion reaction and propagation of the combustion synthesis wave, the hot SHS-products were compacted in a hydraulic press at P > 400 MPa for no more than 10 s. The time of exposure to pressure was chosen dependent on the combustion temperature and reology of the products, e.g., on their plasticity and the amount of the liquid phase formed. Usually this time is 0.5 -4 2 sec. SHS-products were cooled at the room temperature. 

The belt apparatus (Fig. 7.3) provides an ideal high pressure-high temperature combination for solid-state synthesis. This apparatus was used for the synthesis of diamonds some years ago. It actually involves a combination of the piston-cylinder and the opposed anvil designs. The apparatus consists of two conical pistons made of tungsten carbide, which ram through a specially shaped chamber from opposite directions. The chamber and pistons are laterally supported by several steel rings,... 

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