Development of methods for controlling the change in the functional cover and the energy composition of the surface of detonation synthesis diamond nanopowders is necessary to create stable suspensions and materials from them. The aim of this work is to study changes in the electrokinetic and electrophysical characteristics of the powder as a result of the modification of detonation synthesis diamond nanopowders using a liquid-phase thermochemical treatment. Diamond nanopowders of grades ASUD-75 - ASUD-99 with different sp2-hybridization carbon content, manufactured at the V.I. Bakul National Academy of Sciences of Ukraine from the product of detonation synthesis of diamond from the company "ALIT" (Zhytomyr) investigated. Diamond nanopowders of ASUD-90 grade after their modification by means of liquid-phase thermochemical treatment using: a melt of alkalis, a mixture of nitric and sulfuric acids, a mixture of chromic and sulfuric acids were investigated by electrophoresis using a device "Dzeta-potential-analizer" company "Mikromeritiks". Electrokinetic characteristics of diamond nanopowders: the magnitude and sign of the electrokinetic potential, electrophoretic mobility are determined. The methods were used to study the physicochemical characteristics of nanopowders: electrical resistivity, carbon content of sp2-hybridization, mass fraction of impurities in the form of an incombustible residue, and specific surface area. In this work, it was established by electrophoresis that the value of the electrokinetic potential and electrophoretic mobility of the powder decrease by 2-10 times with a decrease in the mass fraction of sp2-hybridization carbon from 23.6 to 0 wt%. Using the ASUD-90 nanopowder as an example, it is shown that the modification of the nanopowder by the liquid-phase method using thermochemical treatment with mixtures of oxidants leads to a decrease in the values of electrophoretic mobility by 1.1-7.5 times and electrokinetic potential by 1.1-7.3 times. It was found by dielectric measurement that the tangent of the dielectric loss angle of diamond nanopowders of grades ASUD-90 - ASUD-99 is in the range 0.3046 - 0.3146. Modification of the ASUD-90 grade nanopowder using a liquid-phase thermochemical treatment leads to a change in the interval of the dielectric loss tangent, namely 0.2450-0.3249. According to the degree of increase in the ratio of the dielectric loss tangent from 0% humidity to 100% humidity, the methods for modifying nanopowders can be arranged as follows: modifying using a melt of alkalis (ASUD-90-1 sample, S = 12.8%) <mixture of chromic and sulfuric acids (sample ASUD-90-3, S = 13.8%) <mixture of nitric and sulfuric acids (sample ASUD-90-2, S = 20.8 %).
Physical and mechanical properties of carbon nanotube (CNT) powders depend on the method of their synthesis and chemical refinement. In order to create new composite materials that contain CNT powders as a filler, it is necessary to achieve functionalization of powder surface. Functionalization of MWCNT-A brand CNT powder surface using pulse processing by high voltage electric discharges (HVED) in liquid leads to changes in distribution of its particles by size, a decrease in amorphous carbon content and in powder thermostability. Sedimentation separation of powder after HVED processing leads to formation of powder in three size ranges (0.118-0.139, 2.639-20.895 and 2.44-33.701 µm). Thermochemical modification of CNT powders leads to an increase in specific surface area, total volume of pores and micropores, their mean radii, a decrease in impurities content, changes in distribution of its particles by size, a decrease in amorphous carbon content and in powder thermostability. Electrochemical reconstruction of the surface of specimens of initial MWCNT-A brand CNT powder allows decreasing impurities content, free energy of surface saturation by water vapor, specific magnetic susceptibility, electrokinetic potential as well as increasing specific surface area, pores total volume and hydrogen adsorption. Consecutive application of these methods leads to a decrease in impurities content in MWCNT-A brand CNT powder and to changes of its physical and chemical characteristics. Mass share of impurities decreases 3.7 times, mass share of soluble impurities decreases 7 times, specific magnetic susceptibility increases 5.2 times, electrokinetic potential increases 7.8 times. Specific electric resistivity increases 1.3 times, which leads to changes of adsorption and structural characteristics of powder: specific surface area increases 1.4 times and free energy of surface saturation by water vapor decreases by 11.9 %, which means that surface becomes more hydrophobic. As a result of such changes, rate of hydrogen adsorption on powders surface increases by 46 % and the current density at the potential of-0.6 V increases by 50 %.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.