DESORPTION OF IMPURITIES FROM DETONATION NANODIAMOND DURING THE SYNTHESIS OF INTERMATALLIC COMPOUNDS OF THE Ni-Al SYSTEM

Abstract

The results of modification of the impurity subsystem of detonation nanodiamonds (DND) (from the “Altai” Federal Research and Production Center (Biysk)) with active metals and mixtures of nickel and aluminum metals are presented. Samples made from three different metal-diamond mixtures were investigated: 1) 70 wt % of DND and 30 wt % of Al, 2) 50 wt % of DND and 50 wt % of mixture of nickel and aluminum in NiAl stoichiometry, 3) 70 wt % of DND and 30 wt % of mixture of nickel and aluminum in Ni3Al stoichiometry. The heating of samples of nanodiamonds in a vacuum volume (VUP-5) is accompanied by thermal desorption of volatile compounds. Analysis of the samples using differential scanning calorimetry and mass-spectrometry (DSC - on STA 409 PC Luxx NETZSCH, MS - on QMS 403 D Aeolos NETZSCH) allowed us to study the kinetics of desorption and the molecular composition of volatile compounds desorbed by heating nanodiamonds. Annealing of the charge with aluminum is accompanied by a nonmonotonic change in the weight of the sample during heating. Heating mixtures of nanodiamond with nickel and aluminum is accompanied by an almost monotonic decrease in weight. Weight loss at up to 950 °C annealing can reach 20%. When samples are heated to 950 °C, H2O (up to 200 °С), O2 (up to 60 °С), H2S (up to 700 °С), CO2 (up to 600 °С), SO2 (up to 450 °С), N2 (up to 60 °С) evaporate from the surface of the samples. Endo- and exo-effects indicate the occurrence of chemical reactions between impurities and metals. The cleaning process most actively takes place during the annealing of the metal-diamond mixture containing Ni and Al in Ni3Al stoichiometry.