I. Konyashin

A new carbon modification: ‘n-diamond’ or face-centred cubic carbon?

A new carbon modification having a face-centred cubic (fcc) structure has been obtained as a result of the transformation of a diamond surface during treatment in hydrogen plasma. The calculated density of electronic states of the fcc carbon phase provides evidence that it is a metallic form of carbon. The experimentally obtained crystal lattice parameter of the fcc carbon phase is found to be 0.3563 nm, which is close to that computed by the linear combination of atomic orbitals (LCAO) method. The fcc carbon phase has a characteristic edge offset in the electron energy loss spectrum distinguishing it from diamond, amorphous carbon and graphite. Here we show for the first time clear evidence for the existence of a carbon phase with the fcc crystal structure.

High quality diamond films on WC-Co surfaces

Abstract Diamond coatings chemically vapor deposited onto WC-Co cemented carbides by use of specially developed barrier underlayers are described. Preliminary seeding the barrier underlayers with nano-grain diamond particles by laser ablation allows obtaining fine-grained and uniform diamond coatings. The diamond coatings obtained in this way have high adhesion to the cemented carbide substrate due to enhanced interaction between the underlayer, nano-grained diamond nuclei and gas phase employed in their plasma-assisted chemical vapor deposition.

PACVD nano-crystalline BCN thin films obtained by use of an organoboron precursor

Abstract Thin films of the Bue5f8Cue5f8N system deposited by use of gas mixtures composed of a boron- and nitrogen-containing organic precursor, argon and hydrogen are investigated with the aid of a radiofrequency PACVD procedure. The structure and composition of these films are found to be strongly affected by the mole ratio between the organoboron precursor and hydrogen. The films obtained at high values of this ratio are amorphous: they become partially crystalline on decreasing this ratio. The deposit obtained at a relatively low value of this ratio is composed of a mixture of cubic boron nitride and boron carbide. Use of a considerable excess of hydrogen in the gas mixture is found to allow poorly crystalline and amorphous phases in the Bue5f8Cue5f8N system to be completely removed from the deposit.

The influence of excited hydrogen species on the surface state of sp2-hybridized boron nitride

Abstract The surface of sp2-hybridized boron nitride, namely well-crystallized hexagonal and poorly-crystallized turbostatic boron nitride, after its treatment in a hydrogen plasma was studied with the aid of high-resolution Auger spectroscopy. The surface state of both modifications of boron nitride is found to change due to interaction with excited hydrogen species. This interaction is thought to lead to termination of π (dangling) bonds of sp2-hybridized boron nitride by hydrogen atoms, which results in transformation of the sp2-hybridized state into the sp3-hybridized state on the surface of boron nitride.

Diamond films deposited on WC-Co substrates by use of barrier interlayers and nano-grained diamond seeds

Abstract Results on the structure, composition and properties of diamond films deposited onto WC-Co cemented carbides via special multilayer barrier interlayers preliminary seeded by nano-grained diamond particles are presented. The barrier interlayers comprise a layer adjacent to the substrate, which completely prevents substrate decarburization and Co diffusion from the substrate, and a diamond-bonding layer needed to obtain an enhanced adhesion of the PACVD diamond coating. Preliminary seeding the barrier interlayers with nano-grain diamond particles by use of a laser ablation technique allows a fine-grained, uniform and highly adherent diamond coating of high quality to be deposited by use of a conventional PACVD technique. Results on the nature of the interaction between the diamond nano-grained seeds and barrier interlayer are also presented.

A novel approach to deposition of cubic boron nitride coatings

Thin B-C-N and B-N films containing various proportions of cubic boron nitride (c-BN) have been obtained in the present study by plasma assisted chemical vapour deposition (PACVD) as a result of the in-situ decomposition of either dimethylamine borane (CH3)2NHBH3 or borane-ammonia BH3-NH3 in the hydrogen plasma. The structure and composition of the films are strongly affected by the precursor to hydrogen ratio in the gas phase. The films deposited at high values of the hydrogen excess contain c-BN and are free of sp 2 -hybridized boron nitride. The mechanism of depositing sp 3 -hybridized boron nitride is proposed, which includes the selective etching of sp 2 -hybridized BN and the formation of metastable BNHx species in the hydrogen plasma.

A technique for fabrication of coated TiCN-based cermets with functionally graded structure

Abstract A technique for fabrication of coated TiCN–Ni–Mo cermets with functionally graded microstructure and composition has been developed. A multilayer coating and the substrate near-surface zone with graded microstructure form as a result of interaction between the cermets and chromium vapour in vacuum. The coating consists of an upper layer of chromium carbide of about 10 μm in thickness and a thin interlayer of less than 1 μm composed of a Ni–Cr alloy between the carbide layer and the substrate. The wide near-surface zone of over 100 μm in thickness with graded microstructure and composition forming under the coatings has an increased Cr content in the Ni-based binder. This zone is characterised by enhanced corrosion- and oxidation-resistance.

The mechanism of cubic boron nitride deposition in hydrogen plasmas

Abstract Deposition of cubic boron nitride in hydrogen plasma is thought to proceed as a result of selective etching of sp2-hybridized boron nitride from the surface of the growing boron nitride film, the impact of hydrogen atoms or ions leading to formation of c-BN sp3 bonds on the surface and formation of metastable BNHx species in the gas phase. The mechanism of nucleation and growth of c-BN crystals in hydrogen plasmas is proposed.

Deposition of Cubic Boron Nitride in Hydrogen Plasma

Thin films of cubic boron nitride (c-BN) have great po-tential as hard protective coatings for wear applications orcomponents of electronic devices due to the outstandingproperties of c-BN, namely its unique combination of highhardness, high temperature oxidation and chemical stabil-ity, and excellent thermal conductivity. Only single-phasec-BN films are likely to be of practical importance sincethe difference between c-BN and hexagonal boron nitride(h-BN) is as significant as the difference between diamondand graphite. Until recently c-BN-containing films ob-tained by either physical vapor deposition (PVD) or plas-ma-assisted chemical vapor deposition (PACVD) have hadno practical significance due to their poor properties. PVDc-BN films typically have a very poor adhesion, contain aninterlayer of sp

Deposition of cubic boron nitride by laser ablation

Boron nitride films were obtained as a result of laser ablation of a nano-grained c-BN target. The films consist mainly of boron and nitrogen as well as some carbon and oxygen according to the results of Auger electron spectroscopy. The results of electron diffraction from the film indicate the presence of c-BN crystals in the deposit.