Идентификация NV-центров в синтетических флуоресцентных наноалмазах и контроль дефектности кристаллитов методом электронного парамагнитного резонанса

A 100 nm synthetic diamond particle with a large (> 4 ppm) amount of nitrogen vacancy (NV) centers has been studied. The latter exhibit lines associated with forbidden Delta m_s = 2 and allowed Delta m_s = 1 transitions in the electron paramagnetic resonance (EPR) spectra of the ground state of the NV(-) center. The luminescence intensity of particles in the range 550-800 nm increases with an increase in the irradiation dose of 5 MeV electrons and correlates with the integrated intensity of the EPR line with a g-factor g = 4.27.This value is used to estimate the concentration of NV(-) centers and to select diamond powders with the highest fluorescence intensity. The dependence of the EPR signal intensity of the Delta m_s = 2 transition of the NV(-) center on the microwave power has the form of a curve with saturation and subsequent decay, and rather well characterizes the crystal quality of the local environment of the centers under study in these particles. The intensity of the x,y Delta m_s = 1 transition (at ~281.2 mT, 9.444 GHz) turns out to be more sensitive to changes in particle size in the submicron range and the appearance of near-surface defects obtained during mechanical processing.

Integration of Fluorescent, NV-Rich Nanodiamond Particles with AFM Cantilevers by Focused Ion Beam for Hybrid Optical and Micromechanical Devices

In this paper, a novel fabrication technology of atomic force microscopy (AFM) probes integrating cantilever tips with an NV-rich diamond particle is presented. Nanomanipulation techniques combined with the focused electron beam-induced deposition (FEBID) procedure were applied to position the NV-rich diamond particle on an AFM cantilever tip. Ultrasonic treatment of nanodiamond suspension was applied to reduce the size of diamond particles for proper geometry and symmetry. The fabricated AFM probes were tested utilizing measurements of the electrical resistance at highly oriented pyrolytic graphite (HOPG) and compared with a standard AFM cantilever performance. The results showed novel perspectives arising from combining the functionalities of a scanning AFM with optically detected magnetic resonance (ODMR). In particular, it offers enhanced magnetometric sensitivity and the nanometric resolution.

Machining the Surface of Orthopedic Stent Wire Using a Non-Toxic Abrasive Compound in a Magnetic Abrasive Finishing Process

The orthopedic stent wire is one of the critical medical components, which is mainly used for the replacement of physically damaged parts in the human body. Therefore, a smooth surface and lack of toxic substances on the surface of this component are highly demanded. In this study, a magnetic abrasive finishing (MAF) process was carried out using a non-toxic abrasive compound (a mixture of iron powder, diamond particles, cold cream, and eco-friendly oils) to achieve high-quality surface finishing of orthopedic stent wire. The surface roughness (Ra) of the stent wire was investigated according to various processing parameters: different rotational speeds (500, 1000, and 2000 rpm), diamond particle sizes (1.0 µm), and three eco-friendly oils (olive oil: C98H184O10; grapeseed oil: C18H32O2; and castor oil: C57H104O9) within 300 s of the finishing time. The results showed that the surface roughness of the wire was reduced to 0.04 µm with a rotation speed of 1000 rpm and a diamond particle size of 1 µm when using grapeseed oil. SEM microimages and EDS analysis showed that the MAF process using a non-toxic abrasive compound could improve the surface quality of orthopedic Ni-Ti stent wire with a lack of toxic substances on the surface finish.

New Abrasive Coatings: Abraded Volume Measurements in Ceramic Ball Production

Technological progress in hybrid bearings developed high wear and abrasion resistant materials for rolling elements. The manufacturing process of bearing balls presents new challenges, as nowadays, it requires time-consuming and costly processes. In this frame, the bearing manufacturing industry is demanding improvements in materials, geometry, and processes. This work aims to investigate new abrasive coatings for grinding wheels for Si3N4 ball manufacturing. Tribological pin on disk tests are performed on samples of grinding materials (disk) versus a Si3N4 ball (pin). Two samples of specimens coated with an electrodeposited diamond and diamond-reinforced metal matrix composite are examined to measure the abrasion rate and the wear resistance of Silicon Nitride Si3N4 balls, considering the influence of sliding speed and the effect of coating deposition on diamond particle density and granulometry. The measurements estimated the specific wear coefficient k, the height wear surface h, and the wear rate u of the Si3N4 balls. The results pointed out that by increasing the sliding speed, the abraded volume increases for both the coatings. The parameters affecting the abrasion effectiveness of both the coatings are the surface roughness, the abrasive particle dimension, and the sliding speed.

Features of the physicochemical properties of narrow fractions of aggregates of diamond nanopowders modified with iron ions

The paper presents the results of a study of the physical and chemical properties of narrow fractions of diamond nanopowders with a low content of non-diamond carbon grade ASUD-99. Six fractions with different average diameters of diamond particle aggregates from 28.785 to 3.891 μm were obtained by separating a 0.2 % aqueous suspension of the initial powders by the sedimentation method. It has been found that the smallest aggregates consist of larger particles with a smaller specific surface area and a lower interaction energy between them. This conclusion is confirmed by a decrease in the porosity of the obtained aggregates. So, if the pore volume in the largest aggregates of diamond particles is 0.859 ml/g, then in the smallest 0.550 ml/g, while the pore radius of diamond aggregates in different fractions changes insignificantly. Separation in a magnetic field at different currents of diamond nanopowders with a specific magnetic susceptibility of 0.52×10-8 m3 kg, treated with a solution of 5 % iron chloride, made it possible to obtain five fractions that differ from each other in specific magnetic susceptibility (c) – from magnetic fractions with c = 4.30×10-8 m3/kg to diamagnetic – with c = –0.11×10-8 m3/kg. It is shown that the modification of diamond nanopowders with iron ions increases the separation selectivity and makes it possible to isolate diamagnetic powders.

A Thermomechanical Model of Retention of a Diamond Particle in Matrices Based on Fe

The aim of this paper was to determine the influence of the mechanical and thermal parameters of the matrix materials on their retentive properties. The term ‘matrix retention’ denotes the capacity of a metallic matrix material to retain diamond particles at the surface of a diamond tool during working. The bonding is obtained during cooling after the hot pressing process. Proper mechanical bonding depends on elastic and plastic properties of the matrix. The model of a diamond particle embedded in a metallic matrix was created using Abaqus software. The analysis has indicated the mechanical parameters that are responsible for the retention of diamond particles in a matrix.