Igor Shishkovsky

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.

The synthesis of a biocomposite based on nickel titanium and hydroxyapatite under selective laser sintering conditions

The conditions of synthesis of a nickel titanium based biocomposite material with hydroxyapatite added to the initial Ni-Ti powder mixture were studied. The material was obtained by a method based on the combination of laser-controlled selective sintering and self-propagating high-temperature synthesis. The data of X-ray diffraction and electron microscopy indicate that the high-rate laser heating induces the interaction of hydroxyapatite with nickel titanium, which results in the formation of additional intermetallic phases (NiTi2, Ni3Ti).

Synthesis of functional gradient parts via RP methods

Discusses the prospects of integration of functionally graded materials coating methods and computer modelling methods, which developed independently earlier. It is shown that combining these two approaches will result in the development of a powerful technology that can draw on the experience gained from MicroElectroMechanical Systems (MEMS). A goal of this review paper is to emphasise the main problems and to discuss already known examples of functionally graded tool synthesis based on rapid prototyping methods.

Shape memory effect in porous volume NiTi articles fabricated by selective laser sintering

The shape memory effect in porous nickel titanium (NiTi) articles obtained by means of layered synthesis using selective laser sintering (SLS) technology was studied by measuring the temperature dependence of the electric resistivity of the material. For the porous NiTi samples synthesized from Ni and Ti powders, the interval of probable appearance of the shape memory effect falls within the temperature interval from −50 to 0°C. In a porous material synthesized by laser sintering from a commercial NiTi powder of the PV N55T45 grade, this effect falls in the interval from +25 to +50°C. Prospects for the use of porous NiTi articles as medicinal implants are discussed.

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.

Laser-induced combustion synthesis of 3D functional materials: computer-aided design

Selective Laser-induced Sintering (SLS) of mixed powders of Ni + Ti; Ni + Al; Ti + Al; TiO2 + ZrO2 + PbO; Al(Al2O3) + Zr(ZrO2); BaO2 + Fe2O3 + Cr2O3 + Fe and Li2O2 + Fe2O3 + Cr2O3 + Fe is presented. Optimization of the process using computer-aided 2D and 3D movement of the laser beam enabled porous monoliths to be prepared of chosen net shape.

Manufacturing three-dimensional nickel titanium articles using layer-by-layer laser-melting technology

Specific features of layer-by-layer synthesis of three-dimensional (3D) nickel titanium (NiTi, nitinol) articles by selective laser melting (SLM) technology have been studied. Nonporous 3D nitinol articles have been obtained for the first time in a single technological cycle. A necessary condition was that the NiTi powder medium was heated to 500°C during sintering. The structure and composition of intermetallic phases in SLM-synthesized samples have been studied by optical metallography, microhardness measurements, scanning electron microscopy, X-ray diffraction, and energy-dispersive x-ray analysis techniques. Optimum SLM regimes for manufacturing NiTi articles and promising medical applications of this material are considered.

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-controlled intermetallics synthesis during surface cladding

In this chapter the suitability of laser cladding (LC) process of exothermic powders, traditionally used in the self-propagating high-temperature synthesis (SHS) technology, is described. On site, the synthesis of new intermetallic phases and the overlapping of SHS and LC processes makes it possible both to obtain more durable parts of complex shape and to enlarge the functional resource of these coatings. The numerical simulation of thermal fields in the powder mixtures (Ni-Al, Ti-Al, Fe-Al) during the SHS and LC processes is examined in the last paragraph of this chapter and based on the experimental description of the thermal fields in the exothermal reaction wave front.

Laser synthesis of functional graded filter elements from metal-polymer powder compositions

Perspectives of laser synthesis of functional graded materials (FGM) with controlled pores and chemical mixture are discussed. Filter elements from metal-polymer powder compositions were fabricated by the selective laser sintering method. It was shown that physical properties of the composited 3D part can change from layer to layer and have no nature analogy. In particular, permeability and porosity coefficients of synthesized 3D parts were determined depending on laser influence parameters and a polymer quantity. Wide opportunities of preliminary computer modeling of the porous space structure, the forecast filtration characteristics are discussed.