D.V. Shtansky

Structure and properties of CaO- and ZrO2-doped TiCxNy coatings for biomedical applications

Abstract In the present work multicomponent thin films based on the systems Ti–Ca–C–O–N and Ti–Zr–C–O–N have been deposited and evaluated. TiC 0.5 +10% CaO and TiC 0.5 +10% ZrO 2 targets were manufactured by means of the self-propagating high-temperature synthesis (SHS) method. The synthesized targets were subjected to DC magnetron sputtering in an atmosphere of argon or in a gaseous mixture of argon and nitrogen. The films were characterized in terms of their structure, surface topography, mechanical properties and tribological behavior. The films deposited on Si substrates under optimal conditions showed high hardness in the range of 36–40 GPa, low Youngs modulus 260–300 GPa and high percentage of elastic recovery 70–75%. The CaO- and ZrO 2 -doped Ti–C–N films showed significantly lower friction coefficient and wear rate against WC+6% Co alloy in comparison to conventional magnetron–sputtered TiC and TiN films. The biocompatibility of the films was evaluated by both in vitro and in vivo experiments (in mice). In vitro studies involved the investigation of the proliferation of fibroblasts Rat-1 and epithelial cells IAR-2 at the tested films and morphometric analysis of the cells cultivated on the films. Fibroblasts and epithelial cells were seeded on the coverslips, coated with examined films and incubated at 37 °C for 24, 48 and 72 h. We did not detect statistically significant differences in the attachment, spreading and proliferation of cultured cells on the coated and the uncoated substrata. The adhesion and proliferation of cells was good at all investigated films. We also did not observe any inflammatory reactions on the implants, inserted under the mouse skin.

The Structure and Properties of Ti–B–N, Ti–Si–B–N, Ti–Si–C–N, and Ti–Al–C–N Coatings Deposited by Magnetron Sputtering Using Composite Targets Produced by Self-Propagating High-Temperature Synthesis (SHS)

The microstructures and compositions of multicomponent Ti–B–N, Ti–Si–B–N, Ti–Si–C–N, and Ti–Al–C–N films deposited by reactive magnetron sputtering using composite targets and produced by self-propagating high-temperature synthesis (SHS) have been investigated by means of transmission electron microscopy. Auger spectroscopy, and X-ray diffraction. Depending on the chemical composition of the film deposited, different single-phase crystalline films were observed. The sputtering process included sputter cleaning prior to the DC magnetron sputter deposition of Ti and TiN interlayers prior to DC magnetron sputter deposition of the multicomponent films from multicomponent targets. The films produced were characterized in terms of their microhardness, wear resistance, high-temperature oxidation conducted in air. and corrosion resistance in a solution of 5NH2SO4 at room temperature.

Self-propagating high-temperature synthesis of advanced materials and coatings

ABSTRACT Self-propagating high-temperature synthesis (SHS) or combustion synthesis (CS) is a rapidly developing research area. SHS materials are being used in various fields, including mechanical and chemical engineering, medical and bioscience, aerospace and nuclear industries. The goal of the present paper is to provide a comprehensive state-of-the-art review and to analyse a critical mass of knowledge in the field of SHS materials and coatings. We also briefly discuss the history and scientific foundations of SHS along with an overview of the technological aspects for synthesis of different materials, including powders, ceramics, metal-ceramics, intermetallides, and composite materials. Application of CS in the field of surface engineering is also discussed focusing on two main routes for applying SHS to coating deposition: (i) single-step formation of the desired coatings and (ii) use of SHS-derived powders, targets or electrodes in the coating deposition processes.

Localized deformation of multicomponent thin films

A comparative analysis of fracture for various films is presented. Films of Cr–B, Ti–Si–N, Ti–B–N and Ti–Cr–B–N were deposited by DC magnetron sputtering of composite targets. The indentation of the as-deposited films on ( 001 ) Si substrates was made using Vickers microhardness tester at a load of 10, 25 and 50 g. The scanning electron microscopy and atomic force microscopy studies were fulfilled to investigate the film behavior during localized deformation. Both homogeneous and localized inhomogeneous deformations of the fracture surface were observed and described. Isolated particles located within the area of deformation were frequently observed. The films were characterized in terms of their structure, hardness, elastic modulus, elastic recovery and surface topography. The H yE ratio (i.e. resistance to plastic deformation ) was proposed to be a ranking parameter 32 for the prediction of shear banding under the localized deformation. The correlation between the surface roughness, surface relief inside indentations and columnar fracture morphology was outlined. It was suggested that column sliding is the dominant fracture mechanism resulting in the formation of breaking-away particles under unloading. 2002 Elsevier Science B.V. All rights reserved.

Optimization of PVD Parameters for the Deposition of Ultrahard Ti–Si–B–N Coatings

Multicomponent Ti–Si–B–N coatings were deposited on high-speed steel (HSS) substrates by reactive magnetron sputtering using a SHS TiB + 20 wt% Si target. The influences of the substrate temperature, bias voltage, and nitrogen partial pressure on the structure and the elemental compositions of the films were studied. The films were characterized by high-resolution transmission electron microscopy (HRTEM), Auger spectroscopy (AES), and X-ray diffraction (XRD). The results of HRTEM analysis indicated the formation of an ordered–disordered structure with fine crystalline grains of hexagonal Ti(B,N)x phase and amorphous integrain layers. The stoichiometry of the Ti(B,N)x phase was strongly affected by PVD process parameters. The films were characterized in terms of their microhardness and wear resistance. The reasons for the high value of microhardness appear to be the result of stoichiometric phase composition, compressive residual stress, and dense and fine microstructure of the Ti–Si–B–N coatings. The tribological wear test results indicated the superior wear-resistant properties of Ti–Si–B–N coatings compared to TiN and Ti(C,N) coatings.

Structure and Properties of Ti–B–N, Ti–Cr–B–(N), and Cr–B–(N) Coatings Deposited by Magnetron Sputtering of Targets Prepared by Self-Propagating High-Temperature Synthesis

Transmission and scanning electron microscopy, x-ray phase analysis, x-ray photoelectron spectroscopy, and atomic-force microscopy were used to study the structure and surface topography of Ti-B-N, Ti-Cr-B-(N), and Cr-B-(N) thin films. Physical, mechanical, and tribological characteristics of coatings were comparatively analyzed, including determination of the hardness, elastic modulus, elastic recovery, critical load, friction coefficient, and wear rate. It was shown that Ti-B-N and Ti-Cr-B-N coatings are superior to conventional TiN-and Ti-C-N-based coatings in terms of their physicomechanical and tribological properties. Ti-B-N and Ti-Cr-B-N coatings deposited under optimum conditions were characterized, accordingly, by a hardness of 31–34 and 40–47 GPa, an average elastic modulus of 378 and 506 GPa, a friction coefficient of 0.49–0.60 and 0.45–0.52, a dry-wear rate of (3.4–4.6) × 10−7 and (6.0–6.8) × 10−7 mm3 N−1 m−1, and a largest critical load of 50 and 22 N. Features in the determination of the physicomechanical properties of films during nanoindentation and their wear properties are discussed.

Boron Nitride Nanoparticles with a Petal-Like Surface as Anticancer Drug-Delivery Systems

Nanoparticles (NPs) have a great potential as nanosized drug-delivery carriers. Such systems must safely deliver the drug to the site of the tumor without drug leakage, effectively penetrate inside cancer cells, and provide intracellular drug release. Herein we developed an original and simple method aimed at the fabrication of spherical boron nitride NPs (BNNPs), 100-200 nm in diameter, with peculiar petal-like surfaces via chemical vapor deposition. Such structures were found to be able to absorb a large amount of antitumor drug-killing tumor cells. They revealed low cytotoxicity and rapid cellular uptake. BNNPs were saturated with doxorubicin (DOX) and then dispersed. The BNNPs loaded with DOX (BNNPs-DOX) were stable at neutral pH but effectively released DOX at pH 4.5-5.5. MTT assay and cell growth testing showed that the BNNPs-DOX nanocarriers had been toxic for IAR-6-1 cells. BNNPs loaded with DOX penetrated into the neoplastic IAR-6-1 cells using endocytic pathways, and then DOX released into the cytoplasm and cell nuclei and resulted in cell death.

Adhesion, Friction, and Deformation Characteristics of Ti-(Ca,Zr)-(C,N,O,P) Coatings for Orthopedic and Dental Implants

This paper reports on the results of a comparative investigation into the physical, mechanical, and tribological characteristics of Ti-(Ca,Zr)-(C,N,O,P) coatings. The hardness, elastic modulus, elastic recovery, adhesion strength, friction coefficient, and wear rate of the coatings are determined. The specific features revealed in the deformation and fracture of the coatings deposited on various substrates in the course of adhesion tests are described. It is shown that the critical loads responsible for different types of adhesion and cohesion failure of the coatings can be determined from a set of parameters obtained during their scratching. The features observed in the behavior of the friction characteristics of the coatings during tribological tests in air and in a physiological solution are discussed.

Boron nitride nanotube growth via boron oxide-assisted chemical vapor transport-deposition process using LiNO3 as a promoter

High-purity straight and discrete multiwalled boron nitride nanotubes (BNNTs) were grown via a boron oxide vapor reaction with ammonia using LiNO3 as a promoter. Only a trace amount of boron oxide was detected as an impurity in the BNNTs by energy-dispersive X-ray (EDX) and Raman spectroscopies. Boron oxide vapor was generated from a mixture of B, FeO, and MgO powders heated to 1,150 °C, and it was transported to the reaction zone by flowing ammonia. Lithium nitrate was applied to the upper side of a BN bar from a water solution. The bar was placed along a temperature gradient zone in a horizontal tubular furnace. BNNTs with average diameters of 30–50 nm were mostly observed in a temperature range of 1,280–1,320 °C. At higher temperatures, curled polycrystalline BN fibers appeared. Above 1,320 °C, the number of BNNTs drastically decreased, whereas the quantity and diameter of the fibers increased. The mechanism of BNNT and fiber growth is proposed and discussed.

Self-propagating high-temperature synthesis of ceramic materials based on the Mn + 1AXn phases in the Ti-Cr-Al-C system

Compact ceramic materials based on the Mn + 1AXn phases in the Ti-Cr-Al-C system are produced by forced self-propagating high-temperature synthesis (SHS) compaction. The mechanisms of the structure and phase formation in synthetic products, as well as the combustion macrokinetics of the SHS mixture, are studied. Complex investigations of the structure, phase composition, and physical and mechanical properties of new Ti2 − xCrxAlC ceramic materials synthesized at different charging parameters (x = 0, 0.5, 1, 1.5, and 2) are performed. The highest content (96–98%) of the Mn + 1AXn phase in the composition of synthetic products is found to be in samples where just one of the host elements (titanium (x = 0) or chromium (x = 2)) is present. The produced materials have a high heat resistance, and the increase in the chromium concentration is favorable to an appreciable growth in resistance to high-temperature oxidation.