In this study, we developed an innovative approach to achieving a higher sustainability in the experimentally guided combinatorial design of metal-matrix gradient structural composites. The titanium carbide of nano sizes or titanium diboride of submicron sizes were incorporated into the titanium matrix during the selective laser melting (SLM) process of Ti+(10, 15, 20 wt.%) TiC/TiB2 powder mixtures. Optimal regimes of 3D laser powder bed process were determined. We compared how the interfacial properties would change due to the composition differences in case of TiC and TiB2 reinforcing titanium matrix composites (TMC). Phase analysis of the fabricated TMC showed that the initial TiC and TiB2 particles dissolved with different velocities after remelting. Special attention was paid to carbon and boron dilution and secondary carbides and borides phase formation mechanisms when TiC/TiB2 were mixed with titanium. Microstructure, phase constitution and mechanical properties of the TMCs were investigated by the OM, SEM, XRD and microhardness measurement in order to validate the rapid alloy prototyping (RAP) concept in single technological approach.
In the present report, we demonstrate how Selective laser melting (SLM) process can contribute to a 4D manufacturing of functional and structural properties of shape memory alloys (SMAs) in-situ synthesized into Ni-Ti and Cu-Al-Ni powdered systems. Correlations of specific resistance and phase structure in Ni-Ti and Cu-Al-Ni intermetallic phases after the SLM were experimentally observed. It was shown that electrical resistivity of the phases studied (austenite, rhombohedral and martensite phases) increases with temperature but the slopes are quite different. Intermediate R-phase in nitinol (NiTi – intermetallide) shows generally higher electrical resistivity than the austenite phase, but its value grows with the decrease of temperature for laser melted samples. We explained this fact by an accumulation of dislocation with the continuous increase of the R-phase with the decrease of temperature. Hysteresis loop of the electrical resistivity and phase-structural properties of SL-Melted samples are correlated with conditions of SLM process, additional heating during the layerwise process, 3D part's porosity. It will be important for perspective 4D printed biomedical applications (bio-MEMS - sensors, drug delivery systems, implants, etc.) of fabricated self- self-initiating and self-fixing SMAs.
The conditions of selective laser melting (SLM) of tissue engineering scaffolds affect cell response and must be engineered to support cell adhesion, proliferation, and differentiation. In the present study, the influence of additional heating during SLM process on stem cell viability near biopolymer matrix reinforced by nanoceramics additives was carried out. We used the biocompatible and bioresorbable polymers (polyetheretherketone /PEEK/ and polycaprolactone /PCL/) as a matrix and nano-oxide ceramics - TiO2, Al2O3, ZrO2, FexOy and/or hydroxyapatite as a basis of the additives. The rate of pure PEEK and PCL bio-resorption and in mixtures with nano oxides on the matrix was studied by the method of mass loss on bacteria of hydroxylase and enzyme complex. The stem cellular morphology, proliferative MMSC activity, and adhesion of the 2D and 3D nanocomposite matrices were the subjects of comparison. Medical potential of the SLS/M-fabricated nano-oxide ceramics after additional heating as the basis for tissue engineering scaffolds and cell targeting systems were discussed.
In this paper, we discuss the issues relevant for the laser-machining process, including the precision and the material removal rate. We have investigated a surface morphology and a mass loss of technical rubber and plastic, industrial silicon and stainless steel ribbon after irradiation by microsecond laser pulses at different pulse energies, repetition rate and irradiation strategies. Laser milling with microsecond pulses (~ 10-5-10-6 s) is a thermal material removal process usually associated with detrimental effects such as heat affected zones, a recast layer and debris. It was shown, that process optimization can lead to considerable reduction of the above mentioned negative effects. The mass removal rates are analyzed depending on environment conditions and laser influence regimes. At the optimum operation parameters, have demonstrated that the experimental mass lost is significantly different from the theoretical estimations and this demands a future model improvement.
The deposition of nano-size copper particles was carried out by means of ink-jet printing on the ceramic substrate (silicon and faience) using Nd+3:YAG laser. Glycerin and aqueous based nano copper inks were prepared and were inkjetted in this study. The sintered copper film had a grainy structure with neck-like junctions. The microstructure and soldering properties were examined using XRD, SEM-EDX and optical microscopy. The dependence of the electrical resistance of the ink-jetted copper interconnection lines on the parameters of laser sintering regimes was estimated.
The objective of the investigation was to test the biocompatibility of 3D porous biopolymer matrices (tissue-cellular
scaffolds), made of biocompatible and bioresorbable polymers (polycarbonate, polyetheretherketone /PEEK/,
polycaprolactone), including the materials with biocompatible oxide ceramics additive (TiO2, Al2O3, ZrO2 and
hydroxyapatite) of micron and nano sizes, for tissue-engineering purposes. The porous samples were prepared via a
layer-by-layer SLS method. The surface microstructures and their roughness were analyzed by the optical microscopy
equipped with the cell analysis software. The cellular morphology, proliferative activity and adhesion of the polymeric
and ceramopolymeric matrices were the subjects for comparison. The study showed that all the tested materials posessed
biocompatible properties. The experimentally estimated cell duplication speed per day turned out to be maximal for
polycarbonate (0.279 duplications per day) and for PEEK + Al2O3 = 3:1 group (0.30 dupl/day) against 0.387 dupl/day for
the reference sample and 0.270 dupl/day for the group of cells placed close to the pure titanium samples.
The objectives of these researches were to investigate the technical fundamentals of synthesizing high-strength
biocompatible medical implants and tissue scaffolds made from nitinol or titanium using of Selective Laser
Sintering/Melting (SLS/M). In particular, we had been identify the processing parameters and procedures necessary to
successfully laser synthesize multi-material and functionally graded implants: the physical and mechanical properties,
microstructure, and corrosion behavior of the resulting structures; the shape memory effect in porous layered nitinol
structures made using laser synthesis.
The comparative morphological and histological results of Selective Laser Sintering of porous titanium and nitinol
implants are presented. Studies are conducted also on primary cultures of dermal fibroblasts and mesenchymal stromal
human cells of the 4-18 passages. The principle possibility of long cultivating a bone marrow on the porous carrier-incubator
from NiTi and titanium in vitro was determined.
Sufficient understanding of laser synthesized titanium and nitinol structures to determine their suitability for future use as
implants, resulting in superior tissue to implant fixation and minimally invasive surgical procedures, was developed.
Rapid prototyping (RP) and manufacturing (M) is a novel layer-by-layer fabrication technique which has become
increasingly popular due to its inherent flexibility for the manufacture of simple and complex 3D parts. Early we had
been shown opportunity of selective laser sintering (SLS) of different type powder systems (intermetallics, ceramics,
ferrites, high-temperature superconductors), traditional use for self-propagated high-temperature synthesis (SHS). The
non-thermal heating affect of an external electromagnetic field during SHS is related to the specific system under study
due to differences in movement of defects and ions at the 'plasma-like' molten combustion wave front. We have
developed and refined the testing scheme for electro-thermal phenomena studies which can directly influence on the SHS
combustion wave front. This work studies electromotive force (EMF) measurements across the front of combustion wave
during layer by layer surface laser sintering of exothermal powder compositions (Ni-Ti, Ni-Al). Analysis using an
analog-digital-analog computer converter allowed some control of the laser movement and hence some control of the
exothermal reaction - in so doing it provided near optimum conditions for forming layered 3D articles. Comparative
results of structural-phase transformation during laser control SHS in reaction-capable compositions are presented.
The main goal of the work was optimization of the phase and porous fine structures of filter elements and subsequent
laser synthesis by the method layer-by-layer Selective Laser Sintering (SLS) of functional devices, exploration of their
properties and requirements of synthesis. Common methodical approaches are developed by the searching optimal requirements of layer-by-layer synthesis usable to different powder compositions and concrete guidelines (conditions of sintering, powder composition, etc.) for SLS of filter elements (including anisotropic) from metal-polymer powder mixture - brass + polycarbonate{PC} = 6:1. As a result of numerical simulations it designed an original graph - numerical procedure and represented a computer program for definition of flow filter performances, as homogeneous (isotropic) as heterogeneous (anisotropic), having the cylindrical shape. Calculation of flow behavior for anisotropic filter elements allows predicting their future applications and managing its.
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.
In the present paper, on the basis of known earlier approaches, a continuous theoretical model was proposed, describing the behavior of viscoplastic porous powdered mixture (in general case made from some components) at high- speed laser heating, observed during SLS of a separate monolayer.
A method of layer by layer selective laser sintering is prosed to synthesize structural piezoelectric elements out of PZT ceramics. The dependence of density of sintered elements on the regimes of sintering was investigated. X-ray diffraction and x-ray phase analysis were performed. It is shown that phase content and lattice structure had changed as a result of laser treatment.
The process of controlled laser sintering for powdered SHS compositions with the bases Ni-Ti and Ni-Al was realized. The optimal parameters of laser effect, under which the reaction of SHS proceeds in controlled regime, were determined. The phase composition of the sintered structure was revealed by the x-ray phase analysis. In particular, it was shown, that the NiTi-material with shape memory effect, perspective for using in medical implantation, is the basis for forming intermetallic phase under laser sintering of Ni_Ti powder compositions.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.