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.     

Detonation nanodiamonds as UV radiation filter

The attenuation of ultraviolet radiation (UVR) by detonation nanodiamonds (DND) can be significant, depending on the concentration, composition of DND surface, size of DND particles and content of nitrogen defects in DND. The ability of DND to attenuate efficiently UVA (320–400 nm), UVB (290–320 nm) and UVC (190–290) radiation via absorption and scattering makes them attractive broad-spectrum UV-protecting agents. The studied DND exhibited red photoluminescence presumably due to the nitrogen-vacancy centers.     

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.     

Locating inherent unpaired orbital spins in detonation nanodiamonds through the targeted surface decoration by paramagnetic probes

Detonation nanodiamond (DND) produced by explosive method has been successfully modified by divalent copper ions via their exchange with protons of neighboring carboxyl groups in water suspension. These ions interact magnetically with all diamond defect sites (both surface and bulk) causing changes in parameters of electron paramagnetic resonance (EPR) signal originating from spins (S = 1/2) of dangling C-C bonds — i.e. unpaired lone orbital paramagnetic centers (PC). EPR on the series of well purified aggregated and disintegrated DND samples in powders and suspensions showed that EPR parameters of PC in DND are unique features characterizing the nanodiamond particle as an isolated object. Surface Cu²⁺ ions located on the DND surface have been used for probing the location of PC. Double component analysis of PC's EPR spectra showed quasilinear dependence of line broadening for both EPR spectra components on probe concentration. The concentration changes for the broader component were found to be more prominent than that for the narrower one. It allows attributing PC characterized by the broader and narrower components to different types of defects located closer to the DND surface and deeper towards the diamond core. The estimated depths of occurrence for two types of intrinsic PC are ~ 0.8 nm and ~ 1.5 nm from the DND surface for the shallow and deeper PC, respectively.     

Absorption and scattering of light in nanodiamond hydrosols

Scattering and absorption of optical radiation in hydrosols of detonation nanodiamonds (DND) have been studied. Experimental data are presented on the spectral response of the optical density of DND hydrosols prepared by different techniques and in different concentrations. The size distribution of DND particles in these hydrosols was investigated by dynamic light scattering (DLS). The experimental data are compared with calculations. The calculations were performed on models including both the structure of a single DND particle made up of a diamond core and a thin graphite-like shell and the size distribution of the DND particles. A comparison of experiments with the calculation provided a possibility of refining the model of the DND particle and gaining insight into the nature of particle aggregation. It is demonstrated that the combined use of two methods of investigation, which deal with the spectral response of optical density and dynamic light scattering, offers valuable information on the nature of DND hydrosol coloring and the results of particle size determination.     

Effect of nanodiamond surface functionalization using oleylamine on the scratch behavior of polyacrylic/nanodiamond nanocomposite

Addition of hard particles such as nanodiamonds to polymers to improve their physical and mechanical properties is very common. However, nanodiamonds are usually hydrophilic so their tendency to form agglomerates in a polymeric matrix is quite strong. In this study, the effect of nanodiamond surface modification on its uniform dispersion in a polymeric matrix such as polyacrylic-base polymer clear coat was investigated. For this purpose, detonation nanodiamond (DND) with an average particle diameter of 4–6 nm was used. To improve dispersion of as-received DND (AR-DND) in the polymeric matrix, the surfaces of the particles were modified by heat treatment (oxidation) in air and followed by functionalization using oleylamine (OLA) as surfactant. So, nanocomposites with different contents of AR-DND, HT-DND and OLA treated HT- DND (OLA-HT-DND) particles were produced. Their characterizations were investigated by employing many analytical methods such as: Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and thermo-gravimetry analysis (TGA). Scratch resistance test and study of coating surfaces, using scanning tunneling microscopy (STM), were carried out on the polymeric nanocomposites. The results showed that the surface-functionalized nanodiamonds are highly dispersive and stable in the polymeric matrix. In addition, scratch resistance was increased with the addition of nanoparticles.     

Chemical-mechanical polishing performance of core-shell structured polystyrene@ceria/nanodiamond ternary abrasives on sapphire wafer

Driven by electrostatic attraction, Ce⁴⁺ ions or/and positively charged detonation nanodiamond (DND) particles can absorb onto negatively charged polystyrene (PS) spherical colloids. Three types of core-shell structured composite abrasives, PS@CeO₂, PS@DND and PS@CeO₂/DND, can thus be assembled. When PS@CeO₂ and PS@DND were used to polish sapphire wafer at pad rotating speed of 120–150 r/min and load pressure of ~3 kg, the material removing rate (MRR) exceeded 1.0 μm h⁻¹, 10–20 % higher than unitary abrasives. The surface profile roughness (Ra) for wafer polished by these two composite abrasives was respectively 1.25 and 0.63 nm, which is superior to CeO₂ (Ra = 1.38 nm) and DND (Ra = 1.29 nm). When using PS@CeO₂/DND, the polishing interface area can be increased owing to the combined effect of elastic PS spheres and intensively coated CeO₂ and DND. Meanwhile, the synergistic mechanism of sapphire-CeO₂ chemical reaction and the strong mechanical abrasion of DND particles benefit the polishing efficiency. MRR for this ternary composite abrasive attained 1.4–1.7 μm h⁻¹ while sapphire can be smoothed to a sub-nanoscale roughness.     

Grain-boundary heat conductance in nanodiamond composites

Sintering of detonation nanodiamonds (DND) has been studied at a pressure of ～ 7 GPa in the 700–2000 °C temperature range. The X-ray coherent-scattering regions in DND have been found to grow with increasing sintering temperature. It is shown that diamond crystallites grow by the oriented attachment mechanism. It is demonstrated that the increase of thermal conductivity of the composites thus obtained is initiated by variation of the heat conductance of the boundaries separating DND crystallites.     

Structural study of detonation nanodiamonds

The structure of spherical hollow detonation nanodiamonds (DND) previously ground in a planetary mill for 10 min has been studied by synchrotron radiation diffraction. The interference contribution of the diffraction pattern from DND calculated using different structural parameters has been compared with the experimental pattern of DND after mechanical treatment. It was shown that after mechanical treatment of spherical hollow DND (r_inner=19.94 A, r_outer=25.47 A), two kinds of particles were observed: one was non-hollow spheres of r=13.9 A size at the same lattice parameters a=b=3.85 A, c=3.45 A and the others, of the size 5a×13b×5c at the parameters a=c=3.567 A, b=3.85 A, were particles of non-spherical shape.     

Strong pinning effect of alumina/nanodiamond composites obtained by pulsed electric current sintering

A small fraction (5 vol.%) of detonation nanodiamonds, or DND, acts as a remarkably effective boundary pinning agent in alumina throughout a wide sintering temperature range (from 1200 up to 1700 °C). This is the first time that such a strong grain growth inhibitory effect is observed for any of the alumina based composites of similar characteristics reported in the literature. These nanocomposites were consolidated by pulsed electric current sintering (PECS) and present bending strength (550 MPa) and toughness (5.2 MPa m^1/2) values significantly higher than the ones corresponding to alumina compacts obtained under the same sintering conditions.     

Nuclear spin-lattice relaxation in nanocarbon compounds caused by adsorbed oxygen

Nuclear spin-lattice relaxation measurement is an effective tool for studying electronic structure and magnetic properties of nanosized compounds. The present work deals with the effect of oxygen molecules, adsorbed onto the surface of carbon nanoparticles - in which the number of surface atoms is comparable with that in the sample's volume - on nuclear spin-lattice relaxation rate of the carbon nuclei. We measured ¹³C spin-lattice relaxation in as-prepared (air rich) and out-gassed samples of detonation nanodiamond (DND), activated carbon fibers (ACF) and glassy carbon (GC) samples having multishell onion-like structure.Our measurements showed that the paramagnetic oxygen molecules (the only magnetic agent in ambient air), being physisorbed onto the surface and in structural voids of ACF and GC, create an additional relaxation channel and definitely affect the ¹³C spin-lattice relaxation as do the unpaired electrons of the internal dangling bonds. Air removal results in 1.5-2 times elongation in T₁. In contrast, the relaxation time is nearly the same for as-prepared and out-gassed DND samples. The reason is that in DND oxygen molecules have access only to the surface carbon nuclei whereas the rest of carbons remain unaffected by oxygen. Thus the main relaxation agents in DND particles are dangling bonds with unpaired electron spins, which mask the relaxation effect of paramagnetic oxygen. These findings are in a good agreement with our EPR data, which show that oxygen affects the inherent paramagnetic defects in the aforementioned nanocarbons.     

Deposition of detonation nanodiamonds by Langmuir–Blodgett technique

Langmuir–Blodgett technique, which classically allows preparing monomolecular films, was here used to deposit a film of detonation nanodiamond particles.We proceeded to the functionalization of the nanodiamond (nD) particles so as to obtain hydrophobic nanodiamonds. Cetyltrimethylammonium chloride (C₁₉H₄₂ClN) (CTAC) was used for this purpose in order to form an ionic complex ND–COO^?(NH₃)⁺–R with the functional groups of the nanodiamonds.Compressions with various strengths (10 to 30 mN/m) were performed on the Langmuir–Blodgett device in order to prepare different types of deposits on mica substrates. Atomic Force Microscopy was used to characterize these deposits. It was shown that compressions with low intensity result in discontinuous distributions of the particles on the surface. Conversely, very dense and continuous deposits were observed for higher compression strengths. By optimizing the nD/CTAC ratio in the suspension, a very regular deposit with a monoparticle height was obtained.     

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.     

IR spectroscopy approach for the study of interactions between an oxidized aluminium surface and a poly(propylene-g-acrylic acid) film

In this paper, we report the study of the interactions between a poly(propylene-g-acrylic acid) and an oxidized aluminium surface by IR spectroscopy. A deposit of a pure poly(acrylic acid) on the same surface is used as a model. Under free acid form (COOH) we demonstrate the formation of hydrogen bondings between the acrylic carboxyl groups and OH functions located at the surface of alumina. This is characterized by an IR absorption [v_(c?o)] at 1733 or 1743 cm^?1 when we observe the metal surface either after peeling of a PPg(OH) film initially pressed on it or after a deposit of PAA(OH). Under the carboxylate form (COO^?), we observe two modes of interaction, the one purely ionic between COO^? and Al³⁺ with an absorption located near 1550 cm^?1 and the other of complex form between COO^? and Al³⁺ giving a band near 1610 cm^?1. The water molecules can play a major part, in particular in the first case (COOH) where they destroy hydrogen bondings in favor of the formation of ? COO^? groups, interacting with the metal surface according to ionic or complex modes as above. © 1993 John Wiley & Sons, Inc.     

Seeding slurries based on detonation nanodiamond in DMSO

Identification of a solvent where nanodiamond particles form stable colloids is very important for a variety of applications including seeding of a substrate for diamond film growth. Dimethyl sulfoxide (DMSO) is one of the most powerful readily available organic solvents. We demonstrated that using DMSO as a solvent for detonation nanodiamonds (DND) provides significant advantages in achieving resistance to sedimentation in colloidal suspensions for DND with positive zeta potentials. Colloidal stability of DND with negative zeta potentials in DMSO, however, is low. Using DMSO allows for the effective fractionation of a variety of DNDs including those that cannot be fractionated using DI water, for example, as a solvent. We also present seeding results using different DMSO/alcohol seeding slurry compositions. Combination of DMSO and alcohol as a seeding slurry allows removal of the solvent without damaging uniformity of the seeds after their distribution over a substrate.     

Thermochemistry of nanodiamond terminated by oxygen containing functional groups

The standard enthalpies of formation at 25 °C of nanodiamonds terminated by oxygen containing functional groups have been investigated by high-temperature oxidation calorimetry. Depending on the amount of oxygen containing functional groups, the nanodiamonds (plus oxygen and hydrogen as represented in the surface functional groups) can be up to 52 kJ mol⁻¹ more stable in enthalpy than graphite, which means that less heat is evolved during oxidation of nanodiamonds terminated by oxygen containing functional groups, since their surface carbon is already partially oxidized. The stability of the nanodiamonds terminated by oxygen containing functional groups increases (enthalpy of formation becomes more negative) with increasing surface area within the studied range, reflecting the dominant effect of higher content of surface functional groups over the destabilizing effect of higher surface-to-volume ratio typical for nanoparticles.     

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.     

Studies on syntheses and permeabilities of special polymer membranes. XLVII. Active transport and selective transport of metal ions through membranes from poly(isobutylene-alternative co-maleic anhydride) and poly(vinyl alcohol)

When a cation exchange membrane having carboxyl groups, made of poly(isobutylene-alternative co-maleic anhydride) and poly(vinyl alcohol), was set in a diaphragm type cell, in which one side of the solution was adjusted to be acidic and the other side alkaline, metal ions were actively transported from the alkaline side to the acidic side across the membrane against the concentration gradient of metal ions between both sides. The driving force of the transport of metal ions was the difference in H⁺ ion concentration between both sides. It was presumed that the active transport was carried out chemically and physically. In the selective transport of metal ions, the selectivity was dependent on both the hydrated ionic radius for the metal ions and the affinity between the carrier fixed to the membrane, the carboxyl group, and the metal ions.     

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.     

Direct sector field ICP-MS determination of metal impurities in detonation nanodiamond

A simple, rapid, sensitive and accurate method for the determination of metal impurities in detonation nanodiamond (DND), based upon the direct aspiration of aqueous suspensions of nanodiamond into a sector field inductively coupled plasma mass spectrometer (ICP-MS) is proposed. Quantitative release, atomisation and ionisation of the nanodiamond coated and encased elements, within the plasma, and their detection free from spectral interference, was confirmed by comparing results obtained from the direct ICP-MS analysis of aqueous suspensions with results from the ICP-MS analysis of the acidic digests of pre-ashed DND, obtained through DND combustion in air at 723 K for 48 h. The developed direct method was capable of the quantification of more than 30 elements at concentration levels of 10⁻⁸ wt.%, with acceptable levels of precision and accuracy, from an aqueous suspension of just 0.1 mg mL⁻¹ DND.