Search

The research was focused on alternative treatment techniques, separating immediate and long-term reconstruction stages. The work involved development of ceramic materials dedicated to reconstruction of the temporomandibular joint area. They were based on alumina (aluminum oxide) and characterized by varying porosities. A broad spectrum of studies was conducted to test the proposed material and determine its suitability for mandibular reconstruction. They compared the effects of substrate properties of ceramic materials in terms of biocompatibility, microbiology and systemic toxicity in in vivo studies. Finally it was concluded that Alumina LithaLox 350D is best suited for jawbone implants.

This paper presents the results of biocompatibility testing performed on several biomaterial variants for manufacturing a newly designed petal valve intended for use in a pulsatile ventricular assist device or blood pump. Both physical vapor deposition (PVD) and plasma-enhanced chemical vapor deposition (PECVD) were used to coat titanium-based substrates with hydrogenated tetrahedral amorphous carbon (ta-C:H) or amorphous hydrogenated carbon (a-C:H and a-C:H, N). Experiments were carried out using whole human blood under arterial shear stress conditions in a cone-plate analyzer (ap. 1800 1/s). In most cases, tested coatings showed good or very good haemocompatibility. Type a-C:H, N coating proved to be superior in terms of activation, risk of aggregation, and the effects of generating microparticles of apoptotic origin, and also demonstrated excellent mechanical properties. Therefore, a-C:H, N coatings were selected for further in vivo studies. In vivo animal studies were carried out according to the ISO 10993 standard. Intradermal reactivity was assessed in three rabbits and sub-acute toxicity and local effects after implantation were examined in 12 rabbits. Based on postmortem examination, no organ failure or wound tissue damage occurred during the required period of observation. In summary, our investigations demonstrated high biocompatibility of the biomaterials in relation to thrombogenicity, toxicity, and wound healing. Prototypes of the petal valves were manufactured and mounted on the pulsatile ventricular assist device. Hydrodynamic features and impact on red blood cells (hemolysis) as well as coagulation (systemic thrombogenicity) were assessed in whole blood., Highlights Thin coatings.Biocompatibility.Haemocompatibility.In vio test.Intradermal reactivity.Sub-acute toxicity.

Direct oesteointegration between a polymeric implant made of a polymer such as a PEEK and host tissues involves direct connection via surface energy, which can be increased by plasma surface modification. Thin coatings are preferably produced by deposition from the gaseous phase (CVD - chemical vapour deposition). In the frame of this research study, PEEK substrates were modified by the PTFE + SiO2/organic silicone multilayer structures that were designed via a biomimetic concept based on algae shell structures. The coatings exhibited mechanical wear resistance and ensured adequate human fibroblast cell proliferation. The proliferation was characterized using confocal microscopy. The analysis together with detailed microstructural characterization with transmission electron microscopy techniques (TEM) established a complex correlative microscopy characterization and allowed the determination of the mechanical and biological features of the coatings. High-resolution TEM (HRTEM) observations revealed possibilities of gas circulation in between the substrate material and the outside environment without making direct contact.

The process of modern cardiovascular device fabrication should always be associated with an investigation of how surface properties modulate its hemocompatibility through plasma protein adsorption as well as blood morphotic element activation and adhesion. In this work, a package of novel assays was used to correlate the physicochemical properties of thin ceramic coatings with hemocompatibility under dynamic conditions. Different variants of carbon-based films were prepared on polymer substrates using the magnetron sputtering method. The microstructural, mechanical, and surface physicochemical tests were performed to characterize the coatings, followed by investigation of whole human blood quality changes under blood flow conditions using the "Impact R" test, tubes' tester, and radial flow chamber assay. The applied methodology allowed us to determine that aggregate formation on hydrophobic and hydrophilic carbon-based coatings may follow one of the two different mechanisms dependent on the type and conformational changes of adsorbed blood plasma proteins.

The main purpose of the work was to assess the haemocompatible properties of polyurethane discs with a modified surface dedicated to cardiovascular system regeneration. They were coated with acrylic acid-based material to inhibit the activation of the blood coagulation cascade. This coating improved the wettability of the material, leading to the prevention of protein adsorption on the surface. The blood-material interaction was analyzed in dynamic conditions with a specially designed tester, which helps to control blood-material interaction under high shear stress conditions. The corresponding numerical model of the tester was also developed by finite volume method (FVM). The 3D FVM model allows the determination of shear stresses applying different flow and boundary conditions representing blood-material interactions. The haemocompatibility analyses were performed through in vitro tests using a blood flow simulator. They revealed a low probability of activation of blood coagulation and low leukocyte activation. The original mechanical set-up to test the blood-material interaction helped to prove that acrylic acid-based coatings expressed good haemocompatible properties.

Minimizing of the life-threatening thrombo-emboli formation in pulsatile heart assist devices by a new biomimetic heart valve design is presently one of the most important problems in medicine. As part of this work, an original valve structure was proposed intended for pneumatic, extracorporeal ventricular assist devices. The valve design allows for direct integration with other parts of the pulsating blood pump. Strengthening in the form of the titanium or steel frame has been introduced into the polyurethane lagging, which allows for maintaining material continuity and eliminating the risk of blood clotting. The prototype of the valve was made by the injection molding method assisted by numerical simulation of this process. The prototype was introduced into a modified pulsating, extracorporeal heart assist pump ReligaHeart EXT (developed for tilting disc valves) and examined in-vitro using the &ldquo, artificial patient&rdquo, model in order to determine hydrodynamic properties of the valve in the environment similar to physiological conditions. Fundamental blood tests, like hemolysis and thrombogenicity have been carried out. Very low backflow through the closed valve was observed despite their slight distortion due to pressure. On the basis of immunofluorescence tests, only slight activation of platelets was found on the inlet valve and slight increased risk of clotting of the outlet valve commissures as a result of poor valve leaflets assembling in the prototype device. No blood hemolysis was observed. Few of the clots formed only in places where the valve surfaces were not smooth enough.

The future and development of science are in interdisciplinary areas, such as biomedical engineering. Self-assembled structures, similar to stem cell niches, inhibit rapid cellular division processes and enable the capture of stem cells from blood flow. By modifying the surface topography and stiffness properties, progenitor cells were differentiated towards the formation of endothelial cell monolayers to effectively inhibit the coagulation cascade. Wrinkled material layers in the form of thin polymeric coatings were prepared. An optimized surface topography led to proper cell differentiation and influenced the appropriate formation of endothelial cell monolayers. Blood activation was decelerated by the formed endothelium.

In addition to high bonding between bone and implant, suppressing bacterial infection at the implant site is an extremely high surgical request. For spinal implants the effects of infection can be much worse due to risks for the patient by nerve damage resulting in paralysis. The main problem of nosocomial multiresistant bacteria is connected to biofilm formation, which efficiently protects against infiltration of pharmaceutical antibiotic drugs. In such a case, a fast revision surgery for exchange of the implant is mandatory, because osseointegration is stopped by bacterial endotoxins. Mostly silver is used on the market, possessing a wide spectra of anti-microbial activity for the majority of nosocomial bacteria and viruses at very low ppb concentration by destroying their cell walls. In this study, it is aimed to improve the antibacterial behavior of PEEK implants by developing a layered, biofunctional coating which consists of titanium as a stiff and osteoconductive base layer, magnesium as bioresorbable intermediate layer to increase the bioactivity and silver as an antibacterial top layer. Platinum is doped to silver to increase the release of silver. XRD, SEM/EDS and AFM, ultra-micro hardness indentation test and immersion tests are carried out to identify the coating properties. In order to clarify the release mechanism, electrochemical tests are also performed. Results reveal that doping Pt increases the mechanical properties of the coating whereas it decreases the release of silver by enhancing its passivation behavior. (C) 2016 Elsevier B.V. All rights reserved.

Surface functionalization of medical devices made of polyaryletheretherketone (PEEK) is an essential requirement when a direct osteointegration between implants and host tissues is desired. The main objective of the work was to improve bio-activity and tribological properties of advanced polymer PEEK type materials through development of biomimetic, smart polytetrafluorethylene (PTFE) composite coatings. The optimal biological (fibroblasts cell proliferation) and tribological (micro-hardness, scratch adhesion) properties of the PTFE coating were found for porous, nano-composite, multi-layered structures. Coatings were more porous on the surface what made it prone for fibroblast cell proliferation, and more dense close to the PEEK substrate, what positively influenced on their tribological properties.

The paper presents an influence of the surface mechanical properties of thin-film materials on blood cell adhesion under shear stress conditions. Physical vapour deposited (PVD) coatings i.e. hydrogenated amorphous carbon (a-C:H) doped with nitrogen or silicon have been investigated. The mechanical properties of materials, namely their microhardness and Young’s modulus were measured using indentation test with Rockwell indenter. The adhesion efficiency of blood cells in dynamic conditions were analysed using a radial flow chamber. Red blood cells (RBC) were used as representative cells to analyse cell–material interactions. The biomaterial examinations were performed under physiological flow conditions at the single-cell level. The 3D FVM (finite volume method) model of multi-phase radial flow test was developed to reproduce the physical test and to predict distributions of shear stresses and velocity during blood washout with PBS. Cell–material interactions were found to be strongly associated with the mechanical properties of the thin-film material. The decrease in the hardness of the coatings translated into a weaker cell – material interactions.

Selective laser sintering (SLS) is an additive manufacturing process which nowadays receives abundant attention from industry sectors. However, the number of materials which can be processed by SLS is still very limited and requires further research. The present work aims to contribute to this topic by investigating the mechanical properties of neat and short carbon fibre reinforced polyamide 1212 processed by SLS. The specimens were built in different spatial alignments to obtain ample details on the tensile behaviour. The detailed examinations of the fractured specimens were performed by means of optical microscopy, scanning electron microscopy and X-ray computed tomography. The comprehensive analysis revealed that most of the fibres (85 – 95%) were oriented in the plane of the powder layer and here, the majority along the direction of the moving roller coater, which distributes the powder on the powder bed of the SLS machine. It was shown that this effect has a direct impact on the strength and stiffness of the printed tensile bars and thus on the mechanical behaviour of SLS printed parts. Furthermore, the analysis results indicate the possibility to control this mechanical anisotropy through a systematic alignment of the components in the powder cake.

Ex situ and in situ scanning and transmission electron microscopy studies (SEM and TEM respectively) of the wear mechanisms in Ti/TiN with silver nanoparticles were performed herein. Two types of wear mechanisms occur the in multilayer coatings that consist of the layer-by-layer removal of the coating and deformation localization through the formation of shear bands. The shifting of the layers in the shear band area is equal to the layer repetition period, where a period consists of one metallic and one ceramic layer. It is confirmed that the angle in between the c-axis of the parent lattice and twin lattice is approximately 35°, which indicates the operation of the tensile twining mode T2 in the individual Ti crystallites.

In case of benign and malignant tumours affecting the maxillofacial region, the resection of jawbone reflects the standard therapy in more than 5.000 cases per year within the European Union. The resulting large bone defects lead to scarred, mangled facial appearance, loss of mastication and probably speech, requiring aesthetic and functional surgery as a basis for physical and physiological rehabilitation. Although autologous vascularized bone autografts reflect the current golden standard, the portion of bone available for the procedure is limited and subsequent high-dose anti-cancer chemo-/radiotherapy can lead to local tissue necrosis. Autologous vascularized bone from fibular or iliac-crest autografts is current golden standard in jawbone resection post-treatment, however, the portion of transplantable bone is limited and subsequent high-dose anti-cancer chemo-/radiotherapy often results in tissue necrosis Our research focuses on alternative treatment techniques: tissue reconstruction via novel patient-specifically manufactured maxillofacial implant that stimulates bone tissue growth. The planned neoformation of vascularized bone in such implants within the patient's own body as "bioreactor" is the safest approach in tissue engineering. The works described herein included the design of the metallic substrate of the implant with the use of computed tomography basing on real patients scans and then 3D-printing the substrates from the Ti6Al7Nb powder. The metal core was then evaluated in terms of structural characteristic, cytotoxicity and gene expression through the in vitro tests. Further experiments were focused on fabrication of the biocompatible coating for outer surface of the bone implant that would enhance the healing process and accelerate the tissue growth. Functional polymeric granulate dedicated for osteoconductive, osteoinductive and osteogenesis properties were elaborated. Another approach including the coating for the implant surface with two-phase biocompatible layer including polymeric microspheres and hydrogel carrier, which would provide long-time release of bone and cartilage growth factors around the implant were also done. The polymeric granulate containing βTCP improved bone cells growth, but it some modification has to be done in order to improve structural pores to ensure for better osteoconductivity. The biocompatible coating including PVP hydrogel and polymeric microspheres is still in the development process.

Purpose: The main goal of this work was to develop haemocompatibile thin film materials dedicated to novel flexible mechanical heart valves intended for pulsatile ventricle assist devices. Methods: The studies performed have led to the selection of a material for the surface modification of the metallic scaffold. Haemocompatible, biofunctional, ultra-elastic, thin carbon-based coatings were proposed. The surface was designed to eliminate thrombogenic and microbial construction by a reduction in turbulence and sufficient washing of the biofunctional-adapted surfaces, thus allowing for extended use for temporary heart support. The article presents the influence of the mechanical properties of coatings and their influence on the haemocompatibility. In this study, we investigated a simplified model of the whole blood shear stress based on a cone and plate rotational viscometer. Several indices of platelet activation were analysed, including platelet and granulocyte-platelet aggregates, platelet activation markers and platelet-derived microparticles. Results: The shear stress induced a platelet aggregate count in the range from 2% to 30% of the CD61 positive cells. For polyurethane (PU), the average value of platelet aggregates was on the level of 7%. The analyses have demonstrated that the cytometric methods of the direct determination of platelet-derived microparticles in plasma are reproducible and reliable. Considering the generation of microparticles on the tested coatings under hydrodynamic conditions, the best properties were observed for the coating a-C:H,N. Conclusion: The results indicate that a-C:H-based coatings with the thickness of 110 nm do not induce an immune response and do not influence the origin of platelet microparticle formation; thus, these type of coatings are the most promising for the parts which are planned to withstand blood contact under the high value of shear stress.

Nowadays the demands of high reliability, high mechanical properties under fatigue loading and ultra-light-weight design are topics of pressing needs in different industry applications. Additive manufacturing technique has great potential to meet such demands and Selective Laser Sintering (SLS) is the dominantly used one due to its versatility in material design, construction and the much higher achievable mechanical strength compared to its competing technologies like fused filament fabrication. In this study, it is aimed to give an insight to the fracture behaviour of SLS produced lattice structure with macro-porosity under compression load. The stress type and distribution on the lattice structure under compression load are anisotropic because of the unit cell topologies and the anisotropic processing condition. Therefore, different kinds of fracture types are evident depending on the region of the fractured struts.

PEEK is a medical grade material which is increasingly used instead of titanium in osteosynthesis and joint replacement. However, its surface properties of PEEKlack on an adequate osteoconductivity. In this study, two coatings with different architectures composed of Ti, Mg and Ag were prepared by physical vacuum deposition to be used in spinal implants. The mechanical durability of the coatings is investigated in terms of their tribological behaviour.

Requirements for tribological protective coatings for medical tools, which would increase their wear and corrosion resistance, are very high. The presented paper deals with novel nano-composite, multilayer protective coatings for tissue interaction elaboration and their diagnosis on metallic substrates. A hybrid pulsed laser deposition system was used for coating deposition. In the presented work, nano-composite Cr/CrN + [Cr/a-C : H implanted by metallic nanocrystals] multilayer coatings were developed for surface protection. The mechanical properties of the coatings were investigated by means of micro-hardness and elasticity modulus measurements. Bio-medical tests were conducted using eukaryotic cells. Microstructural analysis by means of transmission electron microscopy indicated that chromium which was implanted into a-C : H layers reacted with carbon forming chromium carbides.

Cr/CrN multilayers with a bilayer period λ = 62 ÷ 1000nm, were investigated. They were deposited by PLD technique on austenitic and ferritic stainless steel substrates. Coating hardness and adhesion to substrates were measured by nanoindentation and scratch testing. Multilayer properties were compared with single Cr and CrN coatings. The 2xCr/CrN and 4xCr/CrN multilayers exhibited hardness slightly lower than the hardness of a single CrN coating, while the critical load of the 4xCr/CrN multilayer, measured in the scratch test, was two times higher than for CrN. Furthermore, the character of coating failure also indicates the higher fracture toughness of multilayers than ceramic ones. The highest scratch resistance of the hardest multilayer with a bilayer period λ = 250nm is extremely interesting. The measured values of the critical loads LC1and LC2of all coatings were higher for harder ferritic than austenitic substrates. However, analysis of scratch track geometry indicated that coating failure occurred under the same deformation of the coating-substrate system, while the higher values of critical load for coatings on ferrite derived from the higher hardness of the substrate.

The aim of this study was to determine the mutagenic and thrombogenic potential of a material composed of a thin coating deposited on a polymeric substrate. In this work, a surface was modified in a manner that would mimic the function of cellular niches. Finally, the surfaces should actively capture and differentiate progenitor cells from the blood stream. Thin films with 10 to 500nm thicknesses were deposited by unbalanced, pulsed DC magnetron sputtering on smooth polyurethane. Such high energy conditions led to a stiffening of the polymer surface layers by pseudodiffusion during the initial stages of film growth. Both the high intrinsic film stress due to high energy film growth and the huge difference in the elastic properties of the films and polymer substrates resulted in hierarchical and self-adapting nanowrinkling. Surface modifications of synthetic materials for future use in regeneration of the circulatory system must be tested in terms of their thrombogenicity and mutagenicity. Point mutations in many cases can lead to many serious haematologic complications. Genotoxicity was determined by testing for reverse histidine mutations in selected strains of Salmonella typhimurium. The analysis was performed in the presence and absence of metabolic activation system S9 containing liver microsomal fraction of rats. Based on these results, no mutagenicity of the tested material was observed. The interaction of blood and the material under dynamic conditions was described. Blood from above the analysed surface was collected after the test, and the quality of the blood was assessed along with the type of cellular response to the surface. In the obtained results of the coagulation processes, it was found that the tested material reduced the process of platelet activation under hydrodynamic conditions in comparison to the control material, polyurethane.

The current work explains the influence of the polymer substrate on the topography formation of nano-wrinkled thin titanium films. Similar to the biomimetic antetype of human skin, this wrinkling phenomenon increases the elastic deformability of hard materials under tensile loading by flattening the wrinkled waves before high tensile stresses occur. Low energetic plasma deposition in direct current magnetron sputtering leads to smoother films with equiaxed domed wrinkle topography without a distinct preferred orientation on polymers (polyethylene terephthalate, polycarbonate, thermoplastic polyurethane). These domes are at least one order of magnitude larger than the commonly found topography on stiff silicon and correlates to the size of crystalline spherulites and segments in the applied semi- and pseudo-crystalline polymers. High energetic plasma deposition in pulsed laser deposition results in denser films with stretching of wrinkles. Higher intrinsic stresses require for relaxation deformation of deeper regions of the polymer below the surface. Because the width of these sinusoidal wrinkles is quite similar to sputtered films and the preferred stretching orientation correlates to the main direction of the polymer chains, the change in the wrinkle shape can only be explained by stress relaxation due to mechanical anisotropy by extrusion-based manufacturing.

The tribological protection of stiff technical polymers like epoxy resins, being main component in fiber strengthened composites (CFC), gains increasing interest to enable their use in mechanical engineering applications. Besides hardening of the surfaces to achieve similar properties like low carbon steels, smooth surfaces are essential in sliding contact. However, the conditions of film growth during magnetron sputtering including thermal stresses result in high intrinsic film stresses, which trigger the formation of distinct surface topography. Especially chromium nitride (CrNx) single layer coatings show a fragmentation of the coating by cracking during film growth. Preferential growth of crystallites in subsequent deposition closes these cracks, provides complete covering of the surface, and bulged topographical features. Goal of this work is describing the mechanisms of formation of these topographical features as well as emphasizing influences of higher film toughness by Cr-CrNx multilayer coatings on the density and height of the bulges.

The coating deposition inside tubes becomes increasingly important for fluidic applications, in which inner surfaces are chemically and mechanically strained by the flowing liquid and by scratching of particles. The developed process for tube coating, presented in this work, is based on the discharge in the precursor gas atmosphere between two mesh electrodes at the ends of the tube. The gas mixture is introduced on one end and pumped through the electrode on the other end. Igniting plasma inside the tube, the tube walls are the barrier to the atmosphere. Especially pulsed DC discharges for plasma polymerization in this alignment lead to good coating results, which is shown in this work focusing on deposition in pure and mixed hexamethyldisiloxane, ethyne, and oxygen atmospheres. Chemical binding, wetting, and ageing are strongly influenced by the choice of the gas mixtures. Sufficient oxygen partial pressure in the deposition atmosphere leads to hydrophilic behavior of the SiO2-like polymer-like carbon coatings, all other applied atmospheres to generally hydrophobic behavior of pure and Si-doped plasma polymers, respectively.

Six types of diamond-like carbon (DLC) coatings with zirconium (Zr)-containing interlayers on titanium alloy (Ti-6Al-4V) were investigated for improving the biotribological performance of orthopedic implants. The coatings consist of three layers: above the substrate a layer stack of 32 alternating Zr and ZrN sublayers (Zr:ZrN), followed by a layer comprised of Zr and DLC (Zr:DLC), and finally a N-doped DLC layer. The Zr:ZrN layer is designed for increasing load carrying capacity and corrosion resistance; the Zr:DLC layer is for gradual transition of stress, thus enhancing layer adhesion; and the N-doped DLC layer is for decreasing friction, squeaking noises and wear. Biotribological experiments were performed in simulated body fluid employing a ball-on-disc contact with a Si3N4 ball and a rotational oscillating motion to mimic hip motion in terms of gait angle, dynamic contact pressures, speed and body temperature. The results showed that the Zr:DLC layer has a substantial influence on eliminating delamination of the DLC from the substrates. The DLC/Si3N4 pairs significantly reduced friction coefficient, squeaking noise and wear of both the Si3N4 balls and the discs compared to those of the Ti-6Al-4V/Si3N4 pair after testing for a duration that is equivalent to one year of hip motion in vivo.

The paper presents the results of mechanical and tribological tests of new TiN/a-C:H multilayer coatings, which were compared with the properties of single TiN and a-C:H coatings. The effects of the bilayer period and thickness ratio of ceramic and carbon layers on the hardness, resistance to scratching, fracture, wear and coefficient of friction, of such coatings were analyzed. The optimal properties were exhibited by coatings with a 125 nm bilayer period and a TiN/a-C:H thickness ratio of 1:1 and 1:2. The test results showed that there is no reason to reduce the multilayer period to 30 nm and increase the amount of carbon layers to a 1:4 ratio, because such coatings are brittle and exhibit poor adhesion to the substrate. On the other hand, coatings with a higher ratio of ceramic layers have a higher coefficient of friction.

Multilayers of alternate Ti/TiN coatings deposited on X20Cr13 ferritic stainless steel by pulsed laser deposition (PLD) method have been tested using instrumented indentation. The effect of bilayer period and metal/ceramic thickness ratio were studied.

The paper reports about a biomimetic based comparison of deformation in magnetron sputtered multilayer coatings based on titanium (Ti), titanium nitride (TiN) and diamond-like carbon (DLC) layers and the deformation mechanisms in nacre of mollusc shells. Nacre as highly mineralized tissue combines high stiffness and hardness with high toughness, enabling resistance to fracture and crack propagation during tensile loading. Such behaviour is based on a combination of load transmission by tensile stressed aragonite tablets and shearing in layers between the tablets. Shearing in these polysaccharide and protein interlayers demands hydrated conditions. Otherwise, nacre has similar brittle behaviour to aragonite. To prevent shear failure, shear hardening occurs by progressive tablet locking due to wavy dovetail-like surface geometry of the tablets. Similar effects by shearing and strain hardening mechanisms were found for Ti interlayers between TiN and DLC layers in high-resolution transmission electron microscopy studies, performed in deformed zones beneath spherical indentations. 7 nm thin Ti films are sufficient for strong toughening of the whole multi-layered coating structure, providing a barrier for propagation of cracks, starting from tensile-stressed, hard, brittle TiN or DLC layers.

Despite the numerous applications of tribological coatings, a methodology that estimates the load-bearing capacity of coating–substrate systems has not yet been developed. In this paper, the allowable loads for coated surfaces were determined using spherical indentation tests with a 20–500 μm range of indenter tip radius. Titanium nitride (TiN) coatings, 0.7–2.4 μm thick, deposited on steel substrates by the pulsed laser deposition (PLD) technique were tested. Indentation results allow to draw the map of deformation of this coating–substrate system and estimate the allowable loads, into avoid the destruction of the system by the substrate yield and coating fracture. Tribological studies, carried out in the ball-on-disc contact, showed a completely different character of wear of the systems for loads below and above the permissible level. The wear process was analyzed by transmission electron microscopy (TEM) on thin films prepared from wear tracks by the focus ion beam technique (FIB).

Chromium/chromium nitride multilayer coatings consisting of a stack of alternating 82 nm thick chromium and 168 nm thick CrNx sublayers with a total thickness of 4 μm were deposited on silicon wafers by magnetron sputtering below 70 °C. X-ray diffraction revealed for the as-deposited state a significant fraction of material in amorphous state. The effect of subsequent heat treatment on the formation of the crystalline phases Cr and Cr2N, on the coherent diffracting length of the occurring crystallites, as well as the correlated variations of the lattice cell parameters was studied by in-situ high temperature X-ray diffraction techniques. Ex-situ observations of the crystallographic texture showed the presence of a fibre texture parallel to the [1 0 0] direction for the Cr-phase and a fibre texture parallel to the [1 1 2] direction for the Cr2N phase.

Microscale interpretation of tribological phenomena in Ti/TiN soft-hard multilayer coatings on soft austenite steel substratesThe mechanical and tribological behavior of physical vapor deposited coatings on soft substrate materials gains increasing interest due to economical and environmental aspects - e.g. substitution of steels by light-weight metals or polymers in transport vehicles. Nevertheless, such soft materials require surface protection against wear in tribological contacts. Single layer hard coatings deposited at room temperature are brittle with a relatively poor adhesion. Therefore, they should be better substituted by tough multilayer coatings of soft-hard material combinations. However, the mechanics of such multilayer coatings with several 10 nm thick bilayer periods is difficult and yet not well described. The presented work tries to fill the gap of knowledge by focusing both on mechanical investigations of hardness, adhesion, and wear and on microscopic elucidation of deformation mechanisms. In the paper 1 μm thick Ti/TiN multilayer stacks were deposited by magnetron sputtering on soft austenitic steel substrates at room temperature to prevent distortion of functional components in future applications. High hardness was found for 8 and 16 bilayer films with modulation ratio Ti: TiN = 1:2 and 1:4. This was attributed (with use of transmission electron microscopy) to stopping the crack propagation in thin Ti layers of the multilayer systems by shear deformation combined with different fracture mechanisms in comparison with that for the TiN single layers (edge cracks at the border of the contact area and ring cracks outside, respectively).

The development of the model of the multistep nanoindentation test with Berkovich indenter, accounting for the residual stress distribution, is one of the aims of the present paper. The specimen is unloaded in the intervals between the deformation steps. Substrate, which is composed of a ferritic steel and biocompatible pulsed laser deposition TiN coating, is considered. The selection of the TiN was inspired by its perspective application as the coating for a constructional element of the heart prosthesis (blood chamber and aortic valves). Sensitivity analysis of the model predictions with respect to its parameters is presented in the present paper. The theory of elastic–plastic deformations is used in the finite element model, which simulates both loading and unloading phases, accounting for the real geometry of the indent. The main goal of the present paper was to inversely analyse the tests for coating/substrate system. Square root error between measured and predicted forces is the objective function in the analysis. Results of the inverse calculations, which are presented in the present paper, may be helpful in simulations of the behaviour of TiN deposited on substrate in various applications as bionanomaterials.

State-of-the-art non-thrombogenic blood contacting surfaces are based on heparin and struggle with the problem of bleeding. However, appropriate blood flow characteristics are essential for clinical application. Thus, there is increasing demand to develop new coating materials for improved human body acceptance. Materials deposited by vacuum coating techniques would be an excellent alternative if the coating temperatures can be kept low because of the applied substrate materials of low temperature resistance (polymers). Most of the recently used plasma-based deposition techniques cannot fulfill this demand. However, adequate film structure and high adhesion can be reached by the pulsed laser deposition at room temperature, which was developed to an industrial-scaled process at Laser Center Leoben. Here, this process is described in detail and the resulting structural film properties are shown for titanium, titanium nitride, titanium carbonitride, and diamond-like carbon on polyurethane, titanium and silicon substrates. Additionally, we present the biological response of blood cells and the kinetic mechanism of eukaryote cell attachment. In conclusion, high biological acceptance and distinct differences for the critical delamination shear stress were found for the coatings, indicating higher adhesion at higher carbon contents.

Developing soft and elastic coating materials is one of the future challenges in research on new coating materials for vacuum deposition processes. This development direction is in its infancy and fully contrary to the thin film research mainstream. Such coatings – tailor-made with gradients in hardness and elastic modulus – could work as adhesive and load-supporting layers on polymers bridging the properties from soft substrate to the stiff, wear-resistant hard top coating. In this work we used the approach of a chemical vapour deposition process with plasma assistance from an unbalanced RF (13.56 MHz) powered magnetron sputtering cathode in planar parallel plate arrangement. The characterization of the amorphous hydrogenated and polymer-like carbon films showed a high influence of the used precursor gas (acetylene, butane) on hardness and elasticity. The elastic moduli were found to be between 2 and 35 GPa for the fully amorphous films with a-C:H structure. Specific growth structures were found in HR-TEM imaging of the amorphous coatings. All coatings adhere strongly on a rubber-like polymer (thermoplastic polyurethane).

The pre-treatment of work-piece surfaces is decisive for improved adhesion of tribological, decorative, sensor, biocompatible, etc. coatings subsequently deposited by vacuum coating techniques. Most current industrial techniques (mainly glow discharges) miss the requirements for activating temperature-sensitive and electrically insulating materials. Gridless plasma sources like the linear anode layer ion source are an excellent alternative due to their low investment and operating costs and scalability to many industrial applications, and also due to the measured plasma characteristics (low surface charging, broad energy distribution). The appreciable increase of adhesion by anode layer source plasma pre-treatment and the effects of ion energy and gas composition are presented for room temperature sputtered titanium nitride coatings polyamide, polycarbonate, and poly(ethyleneterephtalate). For these polymers, the oxygen-based functionalization (chain-scissoring and cross-linking) strongly influence the wetting behaviour and improve the adhesion by suppressing adhesive cracking at low scratching loads. Low O2 contents in Ar–O2 discharge of ∼400 eV average ion energy lead to best coating adhesion.

The aim of the current work is the transfer of multilayer design knowledge on the Pulsed Laser Deposition (PLD) technique for industrially-scaled room-temperature growth of titanium - titanium nitride (Ti-TiN) structures. Because almost all PVD and CVD coating techniques require substrate temperatures > 200°C for sufficiently adhering and dense coatings, there is high demand for the development of large-area and high-rate low-temperature vacuum deposition process like the PLD, e.g. for the coating of temperature-sensitive or shape- distortion-sensitive materials and substrates. A pulsed Nd:YAG laser (wavelength: 1064 nm) was used for depositing alternately Ti and TiN layers in Ar and N2 atmosphere, resp., forming nearly particulate-free, very smooth and dense 1 μm thick coatings. Starting from single layers, in multilayers with thicker individual layers hardness and scratch resistance (critical load in scratch tests) is decreased, but this trend is reversed in multilayers of very thin (< 100 nm) individual layers. In contrast, the compressive growth stress is dropping down continuously in the multilayers of increasing period numbers.

The current work explains the influence of semi-crystalline polymers on the topography formation of nano-wrinkled thin diamond-like carbon films. The nano-wrinkling effect is based on relaxation of high intrinsic thin film stresses by a common deformation of a soft substrate surface and a hard thin film. Wrinkles form either in domed or in sinusoidal topography, which is mainly influenced by the polymer substrate, especially the orientation of macromolecular chains. High energetic deposition conditions, like in direct deposition from ion sources, result in high compressive film stresses. While crystalline segments in amorphous polymeric matrix in polyethylene terephthalate favors the formation of sinusoidal wrinkle shape under high energetic conditions, film growth on mostly amorphous polymers (like polycarbonate) is influenced by linear stretching of polymer chains, occurring during polymer manufacturing by foil extrusion. Low energetic deposition conditions, being found in pulsed direct current magnetron sputtering, lead to much lower intrinsic film stress. The lower depth of interaction with the polymer macromolecules for stress relaxation shifts the main influence on wrinkling from the bulk structure to the surface inhomogeneities (like micro-scratches).

The microstructure of the Cr/CrN and Ti/TiN multilayers coatings deposited with the pulsed laser deposition (PLD) technique was studied using transmission electron microscope Philips CM20 TWIN (200 kV). It was found that the metallic buffer layers are characterized by the smallest columnar crystallite size and the highest defect density; this might rise their hardness but compromise the coating adhesion. The intermediate metallic layers showed a larger and less defected columnar structure as compared with the nitride layers, what should improve the coatings toughness. The scratch test performed with a Rockwell penetrator of 200 μm diameter loaded from 0.03 N up to 20 N indicated that the switching from a single layer to a multilayered metal/nitride coating of the same thickness improved the resistance to scratch test in case of Ti/TiN from 16.4 N for a TiN single layered to 22.9 N for a 32 layered coating and Cr/CrN from 4.4 N for a CrN single layered to 6.6 for a 32 layered ones.

Titanium-based compounds are widely used as coating materials for mechanical, tribological, electrical, optical, catalytic, sensoric, micro-electronical applications due to their exceptionally physical and chemical properties. Recently, the trend of using temperature-sensitive materials like polymers and tool steels with the highest hardness demands new low-temperature coating techniques for protective surface finishing as well as for surface functionalization, but up to now there is lack of industrially scaled vacuum coating techniques at temperatures below 50 °C. An alternative for overcoming this problem is the pulsed laser deposition (PLD) technique, which was up-scaled for industrial demands at Laser Center Leoben of JOANNEUM RESEARCH Forschungsgesellschaft mbH. The current paper summarizes the application of the industrially-scaled PLD technique on the deposition of the presently most important Ti-based coatings: metallic titanium, titanium nitride (TiN), titanium oxide (TiO2) and titanium carbonitride (TiCN). PLD coating allows, even at room temperature, the formation of film structures of Zone-T type of Thornton's structure zone model, both on substrates aligned normal and parallel to the incident vapor flux. The high-energetic deposition conditions are revealed by the occurrence of (2 2 0) textures for the fcc TiN-based films. The dense grown structure affects advantageously the tribological behavior—generally, low wear rates and (for TiCN) very low friction coefficients were found. For TiO2 coatings, growing as a mixture of β -TiO2 and amorphous phases, the easily reproducible change of deposition parameters in the room-temperature PLD allows large differences in the optical transmission and electrical resistance.

The aim of the present work was the improvement of titanium–aluminium nitride (TiAlN) coating by the solid-solution hardening with carbon atoms leading to titanium–aluminium carbonitride (Ti,Al)CxN1−x coatings with varying carbon (x) and nitrogen contents. The request of low deposition temperatures which are indispensable for the coating of heat-sensitive materials like tool steels of high hardness and polymers was reached by the application of the room temperature pulsed laser deposition (PLD) technique. A Nd:YAG laser of 1064 nm wavelength operated at two different laser pulse energies was used in the ablation experiments of pure TiAl targets (50 at.% Al) in various C2H2–N2 gas mixtures. The results reveal a strong dependency of the gas mixture on the C and N content of the coatings. Furthermore, the different pulse energies change the ratio of Ti/Al atoms in the grown coatings. The crystallization was influenced too by the pulse energy and, thus, the energy and distribution of the atoms, ions and clusters. For the hardness and elastic moduli, two distinct stages in dependency on the crystallinity were found: High carbon contents lead due to the formation of pure carbon precipitations, found in the Raman investigations, to the destruction of the crystallin structure and, thus, to up to 60% lower hardnesses and elastic moduli. A low friction behaviour was found for coatings of the higher Al contents deposited at lower laser pulse energies due to the formation of carbon rich transfer layers on both the coatings and the Al2O3 counterparts.

Titanium carbonitride (TiC x N 1− x ) hard coatings possess excellent tribological behavior in metal punching and forming as well as high biocompatibility. Because almost all PVD and CVD coating techniques for TiC x N 1− x coatings require substrate temperatures higher than 150–200 °C for reaching sufficient adhesion strength to the substrate surface, there is high demand in the development of large-area and high-rate low-temperature vacuum deposition processes. In the present work, this call was fulfilled by the application of the room temperature pulsed laser deposition (PLD) for TiC x N 1− x coating with various carbon ( x ) and nitrogen contents. A pulsed Nd:YAG laser (wavelength: 1064 nm) was used for the vaporization of pure titanium targets in low-pressure N 2 /C 2 H 2 atmospheres. The highly ionized metal vapor was deposited onto polished substrates (molybdenum, AISI D2 steel), forming a nearly particulate-free, very smooth and dense film structures, which can be hardly reached by using other PVD techniques. The variation of the gas flow during deposition causes a change of the chemical composition and the microstructure of the nearly particulate-free coatings, and, consequently, of the mechanical and tribological properties. The solid solution hardening of the fcc TiN lattice by low contents of carbon increases the hardness and elastic modulus, while higher carbon contents decrease this effect. Furthermore, the maximum in hardness and elastic modulus correspond with the minima in the friction coefficients (∼0.2) and wear rates of both the coated disc and the counterparts (AISI 52100 (DIN 100Cr6) ball-bearing steel balls).

The high hardness and the low-wear rates characterize the outstanding tribological behaviour of titanium nitride (TiN) making it to the most widespread material for hard coatings, which were deposited industrially in recent years by employing various deposition methods. For coating of heat sensitive materials and machine parts at low temperatures down to room temperature, only a few deposition techniques can be applied. One of these is the pulsed laser deposition (PLD) method. In this work a multi-spot PLD system with four Nd:YAG laser beams (1064-nm wavelength) was applied to vaporize titanium targets in low-pressure N 2 atmospheres at room temperature. For the deposition of the TiN coatings, high speed tool steel (AISI M2) and corrosion resistant steel (AISI 630 HT) substrates were used. To investigate the differences of film growth in dependency of the target–substrate arrangement, the substrate surfaces were situated parallel (on-axis) and rectangular (off-axis) to the target. The coatings were examined by light-microscopy, scanning electron microscopy, X-ray diffraction, nanoindentation and pin-on-disc tests against ball-bearing steel (DIN 100Cr6/AISI 52100) and alumina (Al 2 O 3 ) counterparts. The results indicate a high influence of the target–substrate arrangement on the textures, residual stresses and hardnesses of the TiN coatings. In spite of these differences all coatings on both on-axis and off-axis placed substrates possess excellent adhesion and high-wear resistance.

Titanium oxide (TiOx) coatings exhibit extraordinary optical, electrical and tribological properties, but very less is known about coatings deposited at room temperature. In the present work this gap was closed by employing the room temperature pulsed laser deposition (PLD) technique. In order to simulate different deposition conditions, the substrate (AISI M2, molybdenum) surfaces were situated parallel (‘on-axis’ geometry) and perpendicular (‘off-axis’) to the pure titanium targets ablated by the Nd:YAG lasers with a wavelength of 1064 nm. The combination of a four-beam PLD evaporator with a suitable movement of the substrates resulted in a high-rate film growth on large surfaces. The coating structure investigated by X-ray diffraction consists of a mixture of monoclinic β-TiO2 and amorphous TiOx phase. The ratio of the amount of the phases, the hardness and the elastic constants strongly depend on the O2 gas pressure and the target–substrate arrangement applied for deposition. Owing to the very high adhesion and their very smooth surfaces, the TiOx coatings exhibit friction coefficients of approximately 0.55 and wear rates of lower than 10−15 m3 N−1 m−1, turning out that titanium oxide coatings deposited by means of PLD are very promising candidates for wear protection applications.