Yu. G. Morozov

Porous biocompatible implants and tissue scaffolds synthesized by selective laser sintering from Ti and NiTi

An investigation of the technical aspects of producing sufficiently high strength porous biocompatible medical implants and tissue scaffolds from nitinol or pure titanium using selective laser sintering/ melting (SLS/M) is presented. In particular, the necessary processing parameters and procedures for successful laser synthesis of functionally graded implants have been established. Physical and mechanical properties, microstructure, corrosion behavior of the synthesized structures, as well as shape memory in porous layered nitinol structures made using laser synthesis are reported. Comparative morphological and histological results of SLS of porous titanium and nitinol made implants are also presented. Investigations were carried out on primary cultures of dermal fibroblasts and mesenchymal stromal human cells. The possibility of cultivating bone marrow on the porous carrier-incubator made from NiTi and pure titanium in vitro was determined. Sufficient understanding of the nature of laser synthesized titanium and nitinol structures was developed in order to determine their suitability for use as functional implants. This resulted in superior tissue to implant fixation and the development of minimally invasive surgical procedures.

Magnetic ordering in hydrofullerite C60H24

Abstract Hydrofullerites C 60 H x synthesised at hydrogen pressures of 0.6 and 3 GPa were found to possess ferromagnetic properties at room temperature. The magnitude of magnetisation varied from sample to sample and reached 0.001–0.16 Bohr magnetons per C 60 molecule at H =10 kOe. The coercivity of all the samples was about 100 Oe. The hydrofullerites had either an fcc or bcc lattice formed of C 60 H x units. The maximum values of magnetisation were observed for the fcc hydrofullerites with x ≈24.

Preparation of nickel nanoparticles for catalytic applications

Spherical oxidized nickel particles 15 to 200 nm in average size have been produced by a crucibleless aerosol method involving metal vapor condensation in an inert gas flow and oxidation processes. The particles have been characterized by scanning electron microscopy, X-ray microanalysis, X-ray diffraction, BET surface area measurements, and vibrating-sample magnetometry. The process parameters have been optimized for the preparation of particles with tailored size, specific surface area, and saturation magnetization. A dc electric field applied to the condensation zone during the oxidation process reduces the size and increases the extent of oxidation of the particles. We have studied low-temperature oxidation of carbon monoxide and propane on nickel nanopowders differing in particle size and extent of oxidation. The nanoparticles with optimized characteristics have been shown to have a marked catalytic effect on these processes.

Electric field-assisted levitation-jet aerosol synthesis of Ni/NiO nanoparticles

Ni/NiO powdered nanoparticles with average sizes 10–30 nm were prepared by a levitation-jet method involving the condensation of Ni metal vapour in a mixture of helium with various amounts of air or oxygen. The process was undertaken with the application of a DC electric field up to 6.5 kV cm−1. The particles were characterized by X-Ray diffraction, transmission electron microscopy, BET adsorption and vibrating sample magnetometry. It was found that the intensity of the applied electric field and partial oxygen pressure correlated with the main structural and magnetic parameters of the nanoparticles, such as average particle size, residual ratio of nickel, coercivity and maximum magnetisation. The specific surface area of the particles correlated with the magnitude of the external electric field. Room-temperature hysteresis loops of weakly oxidized nanoparticles show ferromagnetic-like behaviour, whereas the strongly oxidized ones exhibit a low-field ferromagnetic feature superimposed to a paramagnetic signal, regardless of the particle size. Magnetic measurements allowed for the estimation of the residual metal Ni content in the powdered nanoparticles, which can be as low as 0.04 at.% depending on oxygen partial pressure and external electric field strength.

Porous titanium and nitinol implants synthesized by SHS/SLS: Microstructural and histomorphological analyses of tissue reactions

The comparative microstructural analyses and histomorphological studies of tissue reactions to porous titanium and nitinol implants synthesized by Selective Laser Sintering (SLS) are presented for a rat model for bone implants. It was discovered that the surface of porous pegs of titanium and nitinol made by SHS/SLS has a significantly favorable structure to the mechanical interlocking with bone and soft tissues. Histological analysis of decalcified paraffin sections after implant removal could only show that trabecular bone structures and marrow cavities were observed around the porous implants. In the connective tissue of the remaining implant beds the following cells: macrophages, fibroblasts, adipocytes and lymphocytes are discernible. It was shown that the nitinol synthesized by combined SHS/SLS technique has a developed and ordered microstructure.

C60H18, C60H36 and C70H36 Fullerene Hydrides: Study by Methods of IR, NMR, XPS, EELS and Magnetochemistry

Abstract Fullerene hydrides of C60H18, C60H36 and C70H36 are studied by using IR, 1H and 13C NMR, X-ray photoelectron and electron energy loss spectroscopies, and magnetochemistry. The comparison of IR and solid state 1H and 13C NMR data for C60H36 with the theoretical ones allows the suggestion that fullerene hydride has a T symmetric structure and contains 4 isolated benzenoid rings located at tetrahedral positions on the surface of a closed skeleton of the molecule. The EELS revealed that the transition from fullerene to the hydride is accompanied by the decrease of the density of valence electrons. Magnetization measurements showed C60H36 to be a ferromagnet. The hydrogenated fullerenes were prepared by transfer hydrogenation procedures involving 9,10-dihydroanthracene. The compositions of the hydrides are determined by field desorption mass-spectral analysis.

Fragmentation of adenine and uracyl molecules through electron captures in collisions with ions

The time-of-flight mass spectrometry method is used to study processes occurring when 36-keV multiply charged Ar ions (Ar6+) capture electrons from adenine and uracyl molecules. Adenine and uracyl constitute one of two base pairs entering into the RNA composition. The fragmentation scheme of resulting molecular ions is derived by analyzing correlations between the detection times of all fragment ions. Fragmentation patterns for molecular ions resulting from molecule ionization by photons, electrons, protons, and multiply charged ions are compared.

Design of Three-Dimensional Functional Articles via Layer-by-Layer Laser Sintering of Exothermic Powder Mixtures

Three-dimensional parts with a wide range of properties were synthesized by combining together self-propagating high-temperature synthesis (SHS) and selective laser sintering (SLS). Different powder mixtures were investigated for producing piezoceramics, ferrites, and the high-temperature superconductor. Changing the structure, volume fraction, phase, and pore-distribution within the composite optimized the physical properties. The optimum regime for laser synthesis and some of their associated electro-physical properties were determined by changing the laser parameters, as well as, by conducting the reactions in an applied dc magnetic field. The mechanical properties and the ability to influence the Shape Memory Effect in synthesized porous NiTi were also studied. Stress-strain, X-ray, scanning electronic microscopy (SEM), and energy dispersive analysis by X-rays (EDAX) characterization data were shown to be dependent on laser irradiation parameters. A comparative study of bone-integration with porous NiTi implants was conducted.

Laser synthesis and comparative testing of a three-dimensional porous matrix of titanium and titanium nickelide as a repository for stem cells

The paper discusses the prospects of layer-by-layer synthesis of porous tissue scaffolds (matrices) of titanium and NiTi (nitinol) as a repository for stem cells. The experiments are performed on primary cultures of human dermal fibroblasts of 4–18 passages. The culture of dermal fibroblasts is obtained from the skin and muscle tissue of 6 to 10-week abortuses with the method of primary explants. The role of surface morphology of porous matrices of these materials in cell adhesion and proliferation is examined in comparison with cast dental titanium. The surface microstructure and roughness are analyzed with optical and scanning electron microscopy before and after experiments in vitro. The elemental analysis is used to determine the biochemical composition of post-experimental porous matrix structures. The results show high chemotaxis of cells to the samples and effect of the matrix composition on the development of cell culture.

Characteristic features of the vaporization mechanism in the crucible-free production of aerosol particles

Abstract The mechanism of vaporization of a liquid metal drop in the crucible-free method for the production of aerosol particles was investigated. By using different metals (such as Ni and Cd) it was established that during vaporization in an inert gas flow, the liquid metal drop becomes partially hollow. Evaporation of metal atoms from the inner cavity of the drop is more intense as compared to that from the surface. The process is followed by the condensation of small metal particles. The aerosol particles obtained by these routes differ in their size distribution. A scheme of the processes under study is suggested.