The adsorption of water vapor on nanodiamond (ND) powders of detonation synthesis with various chemical states of the particle surface is investigated. The specific surface, porosity, and isotherms of water-vapor adsorption by ND powders are determined. It is shown that ND surface chlorination leads to a decrease of concentration of the primary adsorption centers determining the amount of water adsorbed. The data on the influence of the water vapor relative pressure on electrical conductivity G and dielectric permeability ɛ of the powders before and after chemical modification of ND are obtained. The interconnection between the amount of adsorbed water and ND electrical parameters is considered within percolation theory. It is shown that water-vapor adsorption leads to a giant increase in the dielectric permeability value and significant rise of conductivity near percolation threshold.

The effects of water adsorption on the conductivity (G) and the dielectric constant (epsilon) of detonation nano diamond powders were studied. The relationship between water quantity and electrical parameters of the system nano diamond-adsorbed water is analyzed in the framework of percolation theory. The epsilon values for wet powders exceed epsilon for dry samples by 10(4)-10(5) times (the giant dielectric polarization phenomenon). It was shown that the chemical modification of diamond surface causes the change in percolation threshold.

The frequency dependencies of conductivity, G(f), and permittivity, ϵ(f), in the frequency range 1 Hz–1.6 MHz at different water vapor pressures were measured for hydrophilic and hydrophobic of detonation nanodiamond powders (∼300 m2/g). It was shown that a sharp increase of G (percolation threshold) was observed at p/ps = 30% for hydrophilic and 60% for hydrophobic samples. The G value changed from 10−12 to 10−5 Ohm−1·cm−1 at relative humidity range from 0% to 95%. The obtained conductivity data were analyzed using the information on quantity water adsorption within the framework of percolation theory and primary adsorption centers of nanodiamond surfaces. It was determined that in low frequency range f < 100 Hz at different water pressure permittivity ϵ has giant value 103–106 associated with surface polarization processes in studied heterogeneous system.

In the present work, the temperature dependence of the static G(dc)(T) and dynamic conductivity G(ac)(T, f) of detonation nanodiamond powders in the frequency range 25-10(6) Hz and 300<T<800 K have been studied. Data on G(dc)(T) and G(ac)(T, f) were obtained for the initial and aminated samples. It has shown that the value of electroconductivity for the intial and amianted nanodiamond powders differs by 2,5 order. A value of activation energy decreases compared to the original and equals 0.46 eV. Data on the effect of ammonia adsorption on G(dc)(T), G(ac)(T, f) and the frequency dependence of dielectric permeability (e) were obtained for powders of DND at room temperature. The effect of giant dielectric permeability increase at low frequencies was found. After exposure to ammonia within 48 hours, the dielectric permeability changes from 15 to 2,1.10(5) for initial sample at a 25 Hz, and at 1 kHz from 11 to 1.6.10(3) for UDD-SP,.

Polycrystalline diamond films were obtained by a chemical crystallization from an electricity activated vapor phase. Films were grown on polycrystalline tungsten substrates. The temperature dependence /sigma/(T) of the electrical conductivity in the diamond films was measured normal to the film thickness using dc and a two-electrode method. The tungsten substrate served as one of the electrodes. The conductivity of the polycrystalline diamond films indicates an activation process. The conductivity is described by two activation energies for low and high temperatures.