A. Vehanen

IR spectra of detonation nanodiamonds modified during the synthesis

IR-spectra of a great number of samples of detonation nanodiamonds (DND) obtained under different conditions (with dopants added or with the use of reducing agents) have been analyzed for the first time. The quantity and type of incombustible impurities have been found to have no effect on the pattern of IR spectra. It is shown that in the IR-spectral range there exist some narrow frequency ranges where the majority of DND exhibit absorption regardless of the synthesis conditions (829, 1365, 1558, 1628, 1732, 2341, 2858, 2928 cm−1). IR-spectra confirm the presence of nitrogen impurity centers in new DNDs and of the functional groups NO2, CH, NO3, CH2, OH, C=O on the DND surface.

A possible mechanism of nanodiamond formation during detonation synthesis

A new mechanism of formation of nanodiamond particles during detonation synthesis has been put forward. It includes the following steps: (a) decomposition of trinitrotoluene (TNT) molecules into basic radicals-a radical-like dimer C2 and CO3, decomposition of hexogen molecules into C2 and of benzotrifuroxane molecules into C2; (b) formation of cyclohexane from C2 or immediately of radical adamantane molecules; (c) interaction of diamond-like core (adamantane radical) with methyl and other monocarbon radicals; and (d) growth of detonation nanodiamond particles like in a CVD process. It is shown that the nucleation of a radical-like adamantine molecule occurs within a range between the center of the chemical peak zone and the Chapman-Jouguet plane, the growth of diamond particles takes place at the same time and comes to an end at an early stage of isoentropic (Taylor) expansion of detonation gases entrapping solid carbon particles.

Purification of detonation nanodiamond material using high-intensity processes

New procedures were developed for chemical treatment of detonation nanodiamonds and diamond-containing detonation blend to remove water-insoluble metal-containing impurities. The detonation nanodiamond material is treated with complexing agent solutions under cavitation conditions and at high temperature and pressure. Sodium 2,3-dimercaptopropanesulfonate (Unithiol), disodium dihydrogen ethylenediaminetetraacetate, thiourea, potassium thiocyanate, dicyandiamide, and hexamethylenetetramine are used as complexing agents. The complexing agent concentration in solution is 0.5–20 wt % at the nanodiamond material to complexing agent weight ratio higher than 0.2. The use of aqueous solutions of the complexing agents at high temperatures and pressures appeared to be the most efficient.

The influence of aqueous armor composition for TNT–RDX explosive charge on the yield and quality of detonation nanodiamond and diamond-containing soot in detonation synthesis

The paper addresses the detonation synthesis factors that govern the yield of nanodiamonds and diamond-containing soot, and their quality. The effect of such an important factor as the composition of armor (shell) of the explosive charge is described. The authors discuss three different methods of initiating an explosive charge, which involve the use of gas, water, or ice, respectively, and their advantages and disadvantages. The influence of the composition of mixtures of aqueous solutions of various substances (organic and inorganic) on the outcome of the detonation synthesis is shown in detail.

Electrochemical chromium-diamond coating

The paper addresses the basic mechanism of deposition of electrochemical chromium-diamond coatings and shows the results of producing such coatings with detonation nanodiamonds of various types and static-synthesis nanodiamonds. The process kinetics and the state of nanodiamonds in a universal chromium plating solution are studied; the paper shows the influence of nanodiamonds on micro- and macrostructure, physical-mechanical properties of the chromium-diamond coatings and surface morphology of the coatings; usability of modified diamond-containing soot is demonstrated. Chromium plating processes involving detonation nanodiamonds from various manufacturers are compared; microhardness is shown to reach 1400 kgf/mm2, wear resistance to increase six-fold, corrosion resistance to increase by a factor of more than 8.

Deep purification of detonation nanodiamond material

The paper presents new alternative procedures of chemical purification of detonation nanodiamonds and diamond-bearing detonation soot to remove water-insoluble metal-containing impurities through a high-temperature treatment using solutions of complexons of concentration 0.5 to 20 wt %, where the ratio between the detonation nanodiamond material and the complexon is above 0.2. The following substances can be used as complexons: sodium 2,3-dimercaptopropanesulfonate, disodium dihydrogen ethylenediaminetetraacetate (Trilon), thiocarbamide, potassium rhodanate, dicyandiamide, hexamethylenetetramine. Purification of detonation nanodiamonds can be also performed by exposing them to an ultrasonic action. A combination of the ultrasonic treatment and treatment with complexon solutions has proved most efficient, significantly reducing the amount of metal-containing impurities.

A study of defects and impurities in doped detonation nanodiamonds by EPR, Raman scattering, and XRD methods

Samples of detonation nanodiamonds modified during the synthesis by adding doping elements in various ways have been studied by spectroscopic methods (electron paramagnetic resonance, Raman scattering, and X-ray diffraction). For the first time, the presence of P1 centers in detonation nanodiamond crystals has been indirectly demonstrated. The authors discuss the nature and distribution of spins as observed by the electron paramagnetic resonance, the composition of phases and size of the coherent scattering region, and crystal density (calculated by the X-ray method) of the detonation nanodiamond samples at hand.

Effect of Armoring Composition on the Yield of Nanodiamonds and Content of Impurities

Efficiency of using detonation nanodiamonds is strongly affected by the amount and elemental composition of impurities. The study considers the possibility of affecting the yield of detonation nanodiamonds and diamond-containing stock and the content and composition of incombustible impurities in the stock and diamonds by varying the composition of the water armor (shell) of the classical TNT–hexogen (50/50) charge. As compounds affecting the above parameters were used hydrazine, urotropin, ammonia, urea, Trilon B (disodium salt of ethylene diamine tetraacetic acid), aminotetrazole, and boric acid. It was found that using urotropin was the optimal as regards a whole set of parameters. In this case, the maximum yield of detonation nanodiamonds (6.9%) and diamond-containing stock (13.4%) was obtained. A close yield of the diamond-containing stock and detonation nanodiamonds was provided by using hydrazine and urea in the armor. Use of boric acid in the armor can substantially diminish the variety of impurity elements in the diamond-containing stock and detonation nanodiamonds at an acceptable yield of the diamond-containing stock (11.1%) and detonation nanodiamonds (6.13%). Use of pure water as the armor is inefficient.

Oxidation of aluminum in the presence of nanodiamond additives

The study of the kinetics of aluminum oxidation process in the presence of modified nanodiamonds and diamond-containing soot (DND-TAN and DCS-boron, respectively) shows their impact on the growth and quality of anodic films: the film thickness and the current efficiency have increased by 13 % at 2 A/dm2 and using DCS-boron; the number of pores has been reduced two-fold using nanodiamond additives; no pinholing has been detected; micro-hardness of the oxide coating has increased 1.5 to 1.6 times (up to 1020 kg/mm2).

The process of electrochemical deposition of zinc in the presence of boron-doped detonation nanodiamonds

The influence of detonation of nanodiamonds doped with boron during the detonation synthesis (DND-boron) on the process of electrochemical deposition of zinc from a zincate electrolytic solution is investigated. It is shown that the throwing power (the coating uniformity) increases 2to 4-fold depending on the DND–boron concentration, the electrolytic conductivity remains unchanged, the corrosion resistance (as measured by the corrosion currents) of the Zn–DND-boron coating grows 2.6 times when tested in the 3% NaCl solution and 3 times in the climatic chamber.