Catalytic synthesis of segmented carbon filaments via decomposition of chlorinated hydrocarbons on Ni-Pt alloys

A series of micro-disperse Ni1-xPtx alloys with the sponge-like structure was prepared by a simultaneous precipitation method with subsequent sintering of the sediment in H-2 atmosphere at 800 degrees C. The formation of single-phase solid solution Ni1-xPtx was confirmed by powder XRD analysis for entire range of Pt concentrations (1.3-75.9 wt.%). The synthesized samples were studied in a process of catalytic decomposition of C2H4Cl2 at 600 degrees C. In situ kinetic studies of the carbon deposition process were carried out in a flow gravimetric setup equipped with McBain balances. Interaction of Ni-Pt alloys with reaction mixture is characterized by an induction period (18-32 min) followed by rapid disintegration of the bulk alloys with intensive growth of carbon fibers. The stage of the induction period was explored in detail by means of XRD and SEM techniques. According to XRD data, the interaction of Ni-Pt alloys with C2H4Cl2 vapors is accompanied by formation of Ni1-xPtxC delta interstitial solution due to entry of carbon into the crystal lattice of the alloy. The effect of Pt addition on catalytic activity of Ni in CCVD process was also studied. It was found that the yield of carbon product depends extremely on Pt concentration with a maximum at C-Pt = 4.3 wt.% (26 g/g(Ni) for 120 min). The impact of Pt concentration upon morphology and structural features of the produced carbon fibers was investigated by SEM and TEM techniques.