Investigation of diamond biocompatible coatings for medical implants

Despite the advantages of diamond-like carbon fi lms that are used as wear-resistant coatings for implants, they may have a number of disadvantages such as the high level of internal tension, low adhesive durability and high sensitivity to environment conditions. These problems can be overcome by application of the new carbon nanocomposite coatings that can be deposited from C60 ionic beam. It was found that the proposed diamond-like nanocomposite coatings increase implant material resistance to electrochemical corrosion processes due to shift of its electrode potential to area of positive values, and also promote a complex of reparative and adaptation and compensatory reorganizations that will allow to accelerate processes of healing and postoperative adaptation of organism in zone of implant inputting.Незважаючи на переваги діамантоподібних вуглецевих покриттів, що використовуються в якості зносостійких захисних покриттів для імплантатів, вони можуть мати ряд недоліків, таких як високий рівень внутрішніх напружень, низька адгезійна міцність, висока чутливість до умов навколишнього середовища. Ці проблеми можуть бути подолані в разі застосування нових вуглецевих нанокомпозитних покриттів, нанесених з іонного пучка С60. Встановлено, що запропоновані діамантоподібні нанокомпозитні покриття підвищують опірність матеріалу імплантату до електрохімічних корозійних процесів за рахунок зміщення його електродного потенціалу в область позитивних значень, а також сприяють комплексу репаративних і адаптаційно-компенсаторних перебудов, що дозволить прискорити процеси загоєння та післяопераційної адаптації організму в зоні введення імплантату

Diamond biocompatible coatings for medical implants

New carbon (diamond-like) nanocomposite coatings deposited from a C60 ionic beam can be used as a wear-resistant protective coating for implants. It was found that these coatings enhance resistance to тelectrochemical corrosion processes due to a shift of the material’s electrode potential to a zone of positive values. They also promote a complex of reparative, adaptative and compensatory reorganization that accelerates the healing processes in the vicinity of the implant

Stimulation of calcium phosphate crystal formation by implant surfaces with electret properties

Oxide coatings with electret properties are investigated. The possibility of stimulation of the formation of calcium phosphate sediments near the electroactive surface is discussed. The exposure of implants with such coatings to solutions imitating blood plasma showed their high efficiency of biointegration due to activation of an exchange processes in living tissues by a negative superficial charge. The revealed effect amplifies with the growth of the thickness of the anodic oxide film

Features of medical implant passivation using anodic oxide films

The passivation ability of metals from groups IV and V of the Periodic Table is considered. Anodic treatment is able to neutralize the increase of metal hardening when comminuting grains to nanometre sizes. The deposition of metal oxide film coatings on a cobalt–chromium alloy surface results in substantial passivation of its surface and prevents cobalt and chromium accumulation in bone tissues. The decrease of surface activity of titanium implants can be achieved both by cleaning the surface during vacuum annealing before oxidation and by the increase of the anodic oxide film thickness, which limits mass and charge transfer through the implant surface. Recommended titanium implant treatment regimens are vacuum annealing at 650 °C and anodic oxidation to attain an oxide thickness less or equal to 300 nm

Properties of magnetron hydroxyapatite coatings deposited on oxidized substrates

Hydroxyapatite (HA) coating were formed on oxidized niobium surfaces by the highfrequency magnetron sputtering method using hydroxyapatite and tricalcium phosphate targets. The structure, substructure and mechanical properties of the Nb–Nb2O5–HA system were investigated by X-ray diffraction, atomic force microscopy and nanoindentation and the stress state was assessed. The synthesized hydroxyapatite film had the following characteristics: thermal expansion coefficient 10–5 K–1; modulus of elasticity 120 GPa; adhesive strength not less than 0.45 kg/mm2; density 2900 kg/m3. The stress magnitude in the metal oxide substrate was from 11 to 14 MPa after hydroxyapatite film deposition

Synthesis and characterization of hydroxyapatite-gelatine composite materials for orthopaedic application

The composite materials based on hydroxyapatite (HA) and gelatine (Gel) with addition of silver and zirconium oxide were obtained. The study investigates a combination of low powered ultrasonic irradiation and low concentration of gelatine in the co-precipitation synthesis. These composites have different weight ratios of organic/inorganic components and may be synthesized in two ways: simple mixing and co-precipitation. Both of which were compared. The estimation of porosity, in vivo testing, surface morphology and phase composition as well as the IR-analysis were provided. Hydroxyapatite was the main crystalline phase in obtained composites. While around powdered HA-Gel composite the connective tissue capsule is formed without bone tissue formation, HA-Gel-Ag porous composite implantation leads to formation of new bone tissue and activation of cell proliferation. Addition of silver ions into composite material allows decreasing inflammation on the first stage of implantation and has positive effect on bone tissue formation. Some of the obtained composite materials containing silver or ZrO2 are biocompatible. bio-resorbable and osteoconductive with high level of porosity (75e85%)

Synthesis and characterisation of nanocrystalline ZrN PVD coatings on AISI 430 stainless steel

The nanocrystalline films of zirconium nitride have been synthesized using ion-plasma vacuum-arc deposition technique in combination with high-frequency discharge (RF) on AISI 430 stainless steel at 150oC. Structure examinations X-ray fluorescent analysis (XRF), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) with microanalysis (EDS), and transmission electron microscopy (TEM), nanoidentation method – were performed to study phase and chemical composition, surface morphology, microstructure and nanohardness of coatings. The developed technology provided low-temperature coatings synthesis, minimized discharge breakdown decreasing formation of macroparticles (MPs) and allowed to deposit ZrN coatings with hardness variation 26.6…31.5 GPa. It was revealed that ZrN single-phase coatings of cubic modification with finecrystalline grains of 20 nm in size were formed

Study of natural convection development in narrow vertical channels

The process of heat transfer due to natural convection in narrow vertical water-filled pipes is considered. Experimental and simulation data are given. The mechanism of natural convection development is analysed. © Published under licence by IOP Publishing Ltd

Multiscale simulation models of Xe bubble formation in irradiated Mo

Multiscale simulation models for Xe bubble nucleation and growth in irradiated Mo were developed that consist Ab-initio calculations of the interatomic potentials for the Mo and Xe-Mo systems, atomistic MD simulations of the kinetic rate coefficients of radiation defects, and nucleation mechanisms of Xe bubbles in Mo. Simulations of various Xe concentrations, temperatures and pressures were carried out. A critical concentration of Xe atoms was determined at which the nucleation occurs spontaneously