High hardness cubic boron nitride with nanograin microstructure produced by high‐energy milling

Abstract

High‐energy shaker milling of hexagonal boron nitride (hBN) powders was used to produce powders rich in sp3 bonding. The powders contained up to 68% sp3 bonding and were found to nucleate nanosize cBN grains during consolidation at 5.5 GPa and 1400°C. The effect of hBN starting particle size, milling time, and powder‐to‐milling ball ratio were studied. The amount of sp3 bonding for milled hBN powders was determined, using 11B solid‐state NMR. The milled material was also analyzed by XRD, Raman spectroscopy, and HRTEM. The results indicate that the material has a nanosized microstructure comprised of a disordered hBN matrix and cBN nuclei in the form of sp3‐rich domains. Eight different milled powders were produced and consolidated at pressures of either 5.5 or 6.5 GPa and temperatures of either 1400°C or 1450°C into 12 mm diameter and 5 mm thick pellets. Consolidated pellets formed from milled hBN with 68% sp3 bonding had Vickers hardness of 42 ± 1 GPa and fracture toughness 3.8 ± 0.1 MPa.m1/2. Vickers hardness of 49 ± 1 GPa and fracture toughness of 4.6 ± 0.1 MPa.m1/2 was achieved with a precursor that contained milled hBN and 50 vol. % of 0.5 μm diameter cBN crystals.

Tribological and anti-corrosion performance of epoxy resin composite coatings reinforced with differently sized cubic boron nitride (CBN) particles

“…4(a). It was observed that the hardness of the composite coatings decreased along with the content of micro-CBN (the coating CBN-EP-1 exhibited the highest hardness, which was as high as 19.80 HV, increased by 98.0% compared with 10 HV of neat EP. The coating CBN-EP-4 showed the lowest hardness as low as 13.76 HV, which represents an increase of 37.6% compared with neat EP).…”

“…As a new type of micro/nanomaterial, boron nitride possesses a variety of crystalline structures, such as hexagonal and cubic [18][19][20][21]. Cubic boron nitride (CBN), whose hardness is second only to diamond, has been widely used in the field of wear resistance.…”

Properties and device performance of BN thin films grown on GaN by pulsed laser deposition

“…6 However, our Raman sepctra matches quite well with the reported literature for disordered h-BN. 35 Thus, although the BN film is most likely the disordered/amorphous nature (without any long-range atomic ordering, as shown later by HRTEM), however it may not be "completely" disordered/amorphous. In that case, sp 2 -bonded regions may exist within the film that gives rise to the observed E2g mode, along with the E1u one.…”

“…We also observed another peak at 1600 cm -1 that we attributed to the longitudinal optical (LO) E1u infrared active mode caused by the disorder-induced breaking of surface symmetry (related to grain boundaries, edges, disorder, or vacancies) in the BN film. [33][34][35] Fundamentally, the E2g peak is related to the sp 2 -bonded modes (long-range B-N ordered) in h-BN. 6 However, our Raman sepctra matches quite well with the reported literature for disordered h-BN.…”

High-strength composite materials based on aluminum reinforced by micro and nanostructures (mini review)

“…Al-КМ были опробованы следующие типы нанодобавок: Al 2 O 3 , AlN, SiC, CuO, B 4 C, Li 3 N, CНТ, BNНЧ, BNНТ и др [15,18,22,24,29,[34][35][36][37][38][39][40][41][42]…”