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Ashless Antiwear and Antiscuffing (Extreme Pressure) Additives
Published in Leslie R. Rudnick, Lubricant Additives, 2017
Liehpao Oscar Farng, Tze-Chi Jao
Carbon nanodiamonds were first synthesized in 1962 by the detonation method in Russia [151]. Since then, various synthetic methods have been developed. They include ultrasonic cavitation of graphite, high-energy pulsed laser irradiation of graphite [152], and microplasma dissociation of ethanol vapor [153]. The majority of tribological studies on carbon nanodiamonds have used samples produced by the detonation method. The detonation nanodiamonds (DNDs) have a primary particle size of 3–5 nm. However, they form tightly bonded aggregates during detonation synthesis and purification processes. The size of aggregate particles ranges between 200 and 300 nm. The detonation reaction feedstock and conceptual structure of carbon nanodiamonds produced by detonation is shown in Figure 7.10. Various deagglomeration and fractionation procedures have been developed to reduce the aggregates to smaller sizes and even down to primary particle sizes for applications of carbon nanodiamonds as a lubricant additive [154].
Luminescent Diamond: A Platform for Next Generation Nanoscale Optically Driven Quantum Sensors
Published in Odireleng Martin Ntwaeaborwa, Luminescent Nanomaterials, 2022
Nicholas Nunn, Alexander I. Shames, Marco Torelli, Alex I. Smirnov, Olga Shenderova
There are two variants of the method: (1) detonation synthesis from explosives and (2) detonation shockwave compression of graphite to form diamond. Detonation synthesis mostly commonly refers the first method, where diamond forms directly from explosive materials during detonation. Typically, explosives such as TNT (2,4,6-trinitrotoluene) and RDX (Royal Demolition eXplosive or cyclonite/hexogen) are mixed such that the carbon content exceeds the oxygen content. Such a mixture is known as a ‘negative oxygen balanced’ composition. The explosives are detonated in sealed chambers with cooling provided by air, ice, or water. In fractions of microseconds after the detonation, pressures and temperatures are such that the carbon contained in the explosives liquifies (25–30 GPa, ~4000 K) (Fig. 1.2d). The expanding detonation shockwave causes a rapid drop in pressure and temperature, and the liquid carbon crystallizes into 3–5 nm diamond particles (Fig. 1.2c). The process eventually crosses into the regime where graphite is preferentially stabilized (Fig. 1.2d), leading to the growth of a graphitic network between the primary crystalline cores. The resulting detonation soot consists of 200–300 nm aggregates of the 3–5 nm primary particles, along with graphite and metal impurities that require additional purification procedures. Subsequent oxidation, purification, and disaggregation methods have been developed to isolate the 3–5 nm primary particles post synthesis [53, 62, 63]. Nanodiamonds produced via this method are referred to as detonation nanodiamonds (DNDs). The total nitrogen content in DND particles is on the order of 1 at % (10,000 ppm) [64], which is considerably higher than even most naturally occurring diamond. Moreover, nitrogen is distributed non-uniformly, mostly in clusters, along grain boundaries and as aggregates within the diamond lattice [65]. The high nitrogen content and non-uniform distribution are unsuitable in forming NV centers. However, we note that NV centers and their associated fluorescence can be detected in fractions of DND particles [65–67].
Improvements in the thread cutting torque for a 6082-T6 aluminum-based alloy with tapping tools utilizing diamond coating
Published in Machining Science and Technology, 2018
Hannu Korhonen, Arto Koistinen, Reijo Lappalainen
It is well known that a commercial powder of detonation nanodiamonds and their aqueous suspensions consist of 100–200 nm agglomerates of 4–5 nm crystalline diamond grains (Baidakova and Vul', 2007). To verify the deagglomeration of nanodiamonds and to separate the particles, the suspension was first ultrasonically jet streamed using Hielscher UPS 400 S -power ultrasonic equipment (Hielscher Ultrasonics GmbH, Teltow, Germany). After jet streaming the suspension was dosed in a cuvette and inserted into a polycarbonate folded capillary cell using a 2 ml syringe. Cuvette, cell and syringe were disposable. The cell is then capped and inserted into the measuring instrument. Finally, the original mean size of DND particles in aqueous solution was subsequently measured and revised by dynamic light scattering (DLS) method using a Zetasizer Nano ZS analyzer (Malvern Instruments Ltd, Worcestershire, UK). Size distributions into volume showed that 1.713 nm average diameter size particles dominated the volume 99.0%. In turn, the average sized 19.65 nm particles took 0.8% by volume. The rest of the volume 0.2% was 2370 nm averaged diameter aggregated particles. Thus, the suspension managed to meet quality requirements by the manufacturer (Carbodeon Ltd, Vantaa, Finland) to be used in the electrolyte bath.