Detonation nanodiamonds simultaneously purified and modified by gas treatment

The gas phase method of simultaneous purification and modification of detonation nanodiamond has been developed that allows producing nanodiamonds of the superior quality and with high stability of suspensions. The technology uses a fluidized bed reactor fed with an air enriched with oxygen or ozone. In the reactor, the non-diamond by-products of detonation synthesis, mostly graphite, are reacted to ozone at the elevated temperature and converted to CO₂ or CO. Simultaneously the surface of detonation nanodiamonds is depleted of non-diamond carbonaceous by-products of the detonation synthesis and enriched with oxygen-containing chemical groups. The technology is an attractive alternative to a commonly used method of detonation soot treatment with concentrated acids or other strong liquid oxidizers. In this paper, we report on the reactor, method and physical chemical properties of nanodiamonds processed from soot by treatment in air enriched with ozone. The technology is environmentally friendly and may find wide application in industry.     

Where and when are nanodiamonds formed under explosion?

The formation of nano-sized diamonds during the detonation of a TNT/RDX explosive with 50/50 composition was investigated experimentally in situ by means of small-angle X-ray scattering using synchrotron radiation with nanosecond time resolution. No nanodiamonds were observed immediately after the detonation front, as only the nucleation of nanodiamonds takes place at this moment. The increase in small-angle X-ray scattering which was observed during 2 μs was the cause of the dynamic growth of nanodiamonds. The inclusion of a very thin shell around the explosive causes a significant increase in this time, because the kinetic of nanodiamonds growth was changed.

In another set of experiments, the nanodiamonds were artificially introduced into different explosives before explosion. The nanodiamonds were not destroyed in RDX immediately after the detonation front, but burned in an oxidants with some delay. In TNT, the nanodiamonds were not destroyed at all.     

Detonation of nanosized explosive: New mechanistic model for nanodiamond formation

While nanodiamonds are synthesized by detonation of microstructured explosives since 50 years ago, we developed a novel approach to synthesize these particles by using nanostructured explosives. This new synthesis method leads to novel results not only in the control of the size, but also in the understanding of the nanodiamond synthesis and the detonation mechanisms. The use of explosive particles with size down to 40 nm results in the formation of detonation nanodiamonds with a mean size of 2.8 nm. In the light of these experiments, a model based on the size of the material involved during the detonation process has been developed to explain the size of the obtained nanodiamond. According to hypotheses based on the number of the nanodiamond nucleation sites, the experimental results are in favor of a decrease in the size of the nanodiamonds formed when the size of the explosive particles used during detonation is decreased.     

Infrared absorption study of surface functional groups providing chemical modification of nanodiamonds by divalent copper ion complexes

Infrared (IR) absorption data evidence the presence of multiple carboxyl and anhydride groups together with hydroxyl and C(sp³)-H groups in the dried copper-modified detonation nanodiamonds (DND). Insignificant differences in IR spectra of initially purified and copper-modified nanodiamonds indicate that in the ion exchange process Cu²⁺ ions substitute protons just in a small fraction of the entire amount of carboxyl groups on the DND surface. Surface anhydride groups appear as the result of mutual conversion of the neighboring carboxyl groups into the anhydride ones. The observation of specific shape of IR absorption spectrum of DND is a good practical rule for primary selection of detonation nanodiamonds with oxygen-containing functional groups well suitable for targeted surface modification by double-charged metal ions.     

Using the tracer method to study detonation processes

The tracer method was used to study the synthesis of nanodiamonds during detonation of composite explosives. Alloys of TNT with RDX, HMX, PETN, and benzotrifuroxan were studied. It was shown that, in all cases, most nanodiamonds were formed from TNT carbon. It was concluded that during the chemical reaction in the detonation wave propagating in heterogeneous explosives, equilibrium parameters were not established. In homogeneous TNT/PETN mixtures, individual components react with each other to form common products. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 6, pp. 92–98, November–December, 2008.     

Cold plasma functionalization of nanodiamond particles

Functionalization of three different types of detonation nanodiamonds was performed using a cold plasma discharge generated with fluorine containing gas. The chemical bonds formed between the reactive species generated in the plasma and nanodiamond particle surfaces were confirmed by FTIR and XPS analysis. From results of FTIR and XPS characterization, it was concluded that initial type of nanodiamond has little overall effect on the degree of fluorination. Fluorination of nanodiamonds allowed for the previously unavailable colloidal suspension in anisole.     

Preparation of composite electrochemical nickel–diamond and iron–diamond coatings in the presence of detonation synthesis nanodiamonds

In the work it is shown that addition of individual pure detonation synthesis nanodiamonds to nickel- and iron-plating electrolytes results in an increase in microhardness (2–3.5 times) and wear-resistance (3–6 times) and a decrease in porosity (3–4 times) of a coating. The use of nanodiamonds as a component of diamond-containing blend (a semi-product of synthesis of the nanodiamonds) results in deterioration of all of the above properties for a nickel–diamond coating and great improvement of the same properties for an iron–diamond coating.     

Specific Features of Synthesis of Detonation Nanodiamonds

It is demonstrated that the Chapman-Jouguet parameters for high explosives used in nanodiamond synthesis are located in the region of liquid nanocarbon; therefore, the chemical reaction zone of the detonation wave involves formation of carbon nanodroplets, which are later crystallized into nanodiamonds on the segment of the isentrope of expansion of detonation products, passing through the region of stability of nanodiamonds in the pressure range of 16.5–10 GPa and the temperature range of 3400–2900 K. Soot in the resultant mixture is the product of amorphization of nanodroplets rather than graphitization of ultrafine diamonds. The influence of detonation conditions of high-explosive charges in an explosive chamber on nanodiamond synthesis is analyzed. __________ Translated from Fizika Goreniya i Vzryva, Vol. 41, No. 5, pp. 104–116, September–October, 2005.     

Surface electronic structure of detonation nanodiamonds after oxidative treatment

X-ray absorption spectroscopy has been used for comparative study of electronic structure of detonation nanodiamonds (ND) purified using different oxidative treatments. The treatment of detonation soot with a mixture of nitric and sulphuric acids followed by ion exchange and ultrafiltration of hydrosol obtained was found to result in developing of ND surface coverage consisting of oxidized carbon species, which electronic state is close to that of strongly oxidized graphite. The deeper purification of ND was demonstrated to allow cleaning of ND particles from most of the oxidized carbon contaminations.     

Pressure induced changes in fractal structure of detonation nanodiamond powder by small-angle neutron scattering

The results of the experiments on small-angle neutron scattering from the industrial detonation nanodiamond powder under a pressure in the range of up to 1000 MPa are reported. It is shown that at a scale of 10–100 nm the scattering is determined by the fractal pore structure within aggregates of nanodiamonds. Its fractal dimension monotonously decreases with pressure from 1.8 to 1.2, which indicates the recombination of pores as a result of mobility of nanodiamonds in the powder under pressure. The mean pore size under the highest pressure (6 nm) is close to the characteristic size of nanodiamonds in the sample (5 nm) found from the width of X-ray diffraction peaks. The difference can be explained by the existence of a non-diamond carbon shell around diamond crystallites.     

Influence of HMX particle size on the synthesis of nanodiamonds in detonation waves

The effect of the particle size of HMX in alloys with TNT on the synthesis of nanodiamonds in a detonation wave was studied experimentally. Mixtures with a TNT content of 40 to 90% and the specific surface area of HMX varied in the range of 5–510 m²/kg were investigated. For all mixtures, an increase in the particle size of HMX was found to lead to an increase in the yield of nanodiamonds with the maximum yield shift toward alloys with increased TNT content. The results are explained using a model based on the absence of thermodynamic equilibrium between the components of the heterogeneous explosive during detonation. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 79–84, March–April, 2008.     

Obtaining of Detonation Diamonds from Individual Explosives

Combustion, Explosion, and Shock Waves - A method of obtaining detonation nanodiamonds from tetryl by means of blasting the latter in a water shell with the explosive/water mass ratio of...     

Electrochemical codeposition of Sn–Pb–metal alloy along with detonation synthesis nanodiamonds

In this work, it is shown that the addition of detonation nanodiamonds into electrolytes for electrochemical deposition of the alloy of Sn–Pb results in considerable improvement of coating properties such as microhardness, microporosity, soldering ability and throwing power of the electrolytes.     

Nanodiamonds as Carriers for Address Delivery of Biologically Active Substances

Surface of detonation nanodiamonds was functionalized for the covalent attachment of immunoglobulin, and simultaneously bovine serum albumin and Rabbit Anti-Mouse Antibody. The nanodiamond-IgG^I125 and RAM-nanodiamond-BSA^I125 complexes are stable in blood serum and the immobilized proteins retain their biological activity. It was shown that the RAM-nanodiamond-BSA^I125 complex is able to bind to the target antigen immobilized on the Sepharose 6B matrix through antibody–antigen interaction. The idea can be extended to use nanodiamonds as carriers for delivery of bioactive substances (i.e., drugs) to various targets in vivo.     

The effects of surface oxidation on luminescence of nano diamonds

In this work we quantify and characterise the effects of air-oxidation on nitrogen-vacancy defect luminescence in both high-temperature-high-pressure and detonation synthesized nanodiamonds using Raman and luminescence spectroscopies. We find that oxidation treatments result in an increased nitrogen-vacancy centre excited state lifetime from 13 ns to 25 ns and in 5-nm diamonds the intensity of this luminescence increases by at least 5-fold. At the same time, in 5-nm diamonds, short lived surface-defect related luminescence is reduced by 10-fold. Furthermore we find that air oxidation reduces the sp² and disordered carbon fraction of nanodiamonds by up to 5-fold in 5-nm nanodiamonds. Based on these results, the authors suggest that the disordered-carbon and graphite shell of 5-nm nanodiamonds quenches nitrogen-vacancy luminescence, and that this quenching can be partially reduced by surface oxidation. These findings provide useful insights into the role of the graphite and disordered carbon shell in quenching luminescence, and have implications for the applicability of 5-nm nanodiamonds to bio- and quantum physics applications.     

Extraterrestrial,terrestrial and laboratory diamonds — Differences and similarities

Characterization tools such as confocal Raman micro-spectroscopy, Laser Ablation (LA-ICP-TOF-MS) and SEM-EDS were used to characterize meteorites: primitive achondrite — not classified NWA XXX ureilite found in 2006 in Morocco and the graphite nodula from the Canyon Diablo iron meteorite. The presence of diamond was confirmed in both samples.There are two kinds of meteoritic diamonds: diamonds of the sizes of microns up to millimeters are most probably of impact origin, nanodiamonds of the sizes of 1–3 nm, called presolar diamonds because of the isotopic anomalies, are believed to be formed before our Solar System was formed. There are many theories concerning presolar diamonds formation, among them: impact shock metamorphism driven by supernovae or chemical vapor deposition (CVD) from stellar outflows.We examined the properties of diamond nanopowders obtained by the PA CVD and detonation methods. Nanodiamonds obtained by the detonation method, called ultradispersed detonation diamonds (UDD), are of the same range of sizes as presolar diamonds.The results show both differences and similarities among meteoritic, terrestrial and laboratory diamonds. The comparison will help to understand the processes during presolar nanodiamonds formation.     

Structural properties of nanocomposites based on resole-type phenol-formaldehyde oligomers and detonation nanodiamonds

Using the methods of infrared spectroscopy (IRS) and X-ray photoelectron spectroscopy (XPS), it was shown that short-term high-energy machining of detonation nanodiamonds (DND) leads to structural changes in the crystal structure and functional composition of the surface layer on particles. The possibility of spontaneous formation for stable colloidal systems with a narrow size distribution of mechanically activated DND in phenol-formaldehyde oligomers (PFO) was established. By molecular spectroscopy it was revealed that π → π* interactions of the aromatic rings of PFO are caused by orientational phenomena as a result of hydrogen bonds between an activated DND surface and functional groups of PFO. The effect of DND concentration on the curing reaction parameters ofpsgr the phenol-formaldehyde oligomer was determined by differential scanning calorimetry (DSC). The concentration effect of mechanically activated nanodiamonds on the physical and mechanical characteristics of a composite material based on phenol-formaldehyde binder and polyamide paper (Nomex) was studied. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48582.     

Onion-like carbon for terahertz electromagnetic shielding

It is demonstrated that onion-like carbon (OLC) provides efficient attenuation of the electromagnetic spectrum over the wavelength range 12–230 THz as compared to detonation nanodiamonds (DND) at similar or higher concentrations. Some characteristics of OLC important for the processing of polymer composites such as surface functional groups, zeta-potentials and agglomerate sizes are reported.     

An efficient purification method for detonation nanodiamonds

This article reports the purification process of detonation soot to obtain pure nanodiamond powder. Nanodiamonds are synthesized by detonation using a high explosive mixture composed of trinitrotoluene and hexogen. The detonation of the charge leads to a powder containing nanodiamonds as well as metallic impurities and sp² carbon species. Further, to remove metallic particles, an unusual acidic treatment (hydrofluoric/nitric acids; i.e. fluorinated aqua regia) was set up. To eliminate sp² carbon species such as graphite and amorphous carbon, a thermal oxidation treatment was performed at 420 °C under air in a furnace during several hours. Transmission Electronic Microscopy, Raman spectroscopy, X-ray diffraction and Thermo-Gravimetric Analysis showed that this purification process is very efficient. From TGA measurements, a model of the carbon grain combustion was developed by considering graphitic shells surrounding the nanodiamond particles, and was used to demonstrate that the selective oxidation of graphite was experimentally realistic. Moreover, another model was set up from specific area measurements to evaluate the thickness of the functional groups surrounding the nanodiamonds after the oxidation of sp² carbonaceous species. The treatment described herein was achieved on several tens of grams of product and could be easily adapted to the industrial scale.     

Coagulation of carbon clusters in a detonation wave

The effect of the parameters of a charge of TNT/RDX alloys and their detonation conditions on the coagulation of carbon on the isentrope of the detonation products is analyzed. In the region of liquid nanocarbon, coagulation occurs by coalescence of nanodroplets and in the region of solid nanocarbon, by their joining (sintering) simultaneously with crystallization. Therefore, the specific surface area of nanodiamonds calculated from their sizes is always larger than the measured value. Separation of nanodroplets in detonation products accelerates their coagulation and cooling due to the flow of cooler products around them. Evaluation of the distance between the surfaces of nanodroplets in various TNT/RDX alloys shows that they are small, smaller than nanodroplets. The conditions of rapid coalescence of nanodroplets during different deceleration of the products by rigid barriers are analyzed. An increase of up to five orders of magnitude in the size of diamond particles was established experimentally. The factors responsible for the change in the coagulation rate with the transition from heterogeneous to homogeneous TNT/RDX alloy with decreasing size of TNT/RDX particles are discussed.