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For the accurate diagnosis of idiopathic pulmonary fibrosis (IPF), the presence of a definitive tomographic pattern of usual interstitial pneumonia (UIP) is of vital importance, in an appropriate clinical context. Targeted interrogation, the use of valid questionnaires, an acute rheumatologic evaluation and complementary examinations are important to rule out secondary causes such as hypersensitivity pneumonitis (HP), connective tissue diseases (CTD), drug toxicity and some pneumoconiosis that can mimic the radiological pattern and often hinder a clear diagnosis of IPF.

The corrosion and tribocorrosion behaviour of SLM-produced Ti6Al4V alloy was studied in comparison with its HP and commercial counterparts in 9 g/L NaClsolution at body temperature. Results showed that SLM processing route influenced the electrochemical response of the SLM-produced alloy by leading to a relatively lower quality for the passive film due to decreased beta phase and the formation of alpha' phase. However, after tribocorrosion, neither the total volume loss nor the volume loss under the influence of mechanical wear and wear accelerated corrosion showed any statistically significant difference between the processing routes., This study was supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 - Program Operacional Competitividade e Internacionalizacao (POCI) with the reference project POCI-01-0145-FEDER-006941, together with projects NORTE-01-0145-FEDER-000018-HAMaBICo and PTDC/EMS-TEC/5422/2014. The authors would also like to acknowledge Prof. Grata Minas for the provision of the profilometry.

Selective Laser Melting (SLM) is an extremely versatile technology especially suited for the manufacturing of thin-walled parts. Micro-sized parts are highly influenced and dependent on the SLM processing parameters; thus being indispensable to assess the influence of processing parameters on SLM fabrication, as isolated parameters but also their interactions. In this study, the influence of SLM laser power and scanning speed on Ti6Al4V micro-pillars and micro-plates thickness was assessed by applying response surface methodology (RSM). These analyses resulted in four models that exhibit complex correlations of SLM process parameters, with non-linear equations, having coefficients of determination that assess the quality of the models. These developed models are accurate tools that can be used to optimize the micro manufacture of Ti6A14V thin-walled parts by SLM., This work is supported by FCT - Fundacao para a Ciencia e a Tecnologia through the grant SFRH/BPD/112111/2015 and the projects PTDC/EMS-TEC/5422/2014 and NORTE-01-0145-FEDER-000018-HAMaBICo. Additionally, this work is supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 - Programa Operational Competitividade e Internacionalizacao (POCI) with the reference project POCI-01-0145-FEDER-006941.

SLM accuracy for fabricating porous materials is a noteworthy hindrance when aiming to obtain biomaterial cellular structures owing precise geometry, porosity, open-cells dimension and mechanical properties as outcomes. This study provides a comprehensive characterization of seventeen biomaterial Ti6Al4V-based structures in which experimental and numerical investigations (compression stress-strain tests) were carried out. Mono-material Ti6Al4V cellular structures and multi-material Ti6Al4V-PEEK cellular structures were designed, produced by SLM and characterized targeting orthopedic implants. In this work, the differences between the CAD design and the as-produced Ti6Al4V-based structures were obtained from image analysis and were used to develop predictive models. The results showed that dimensional deviations inherent to SLM fabrication are systematically found for different dimensional ranges. The present study proposes several mathematical models, having high coefficients of determination, that estimate the real dimensions, porosity and elastic modulus of Ti6Al4V-based cellular structures as function of the CAD model. Moreover, numerical analysis was performed to estimate the octahedral shear strain for correlating with bone mechanostat theory limits. The developed models can help engineers to design and obtain near-net shape SLM biomaterials matching the desired geometry, open-cells dimensions, porosity and elastic modulus. The obtained results show that by using these AM structures design it is possible to fabricate components exhibiting a strain and elastic modulus that complies with that of bone, thus being suitable for orthopedic implants., This work was supported by FCT (Fundacao para a Ciencia e a Tecnologia) through the grant SFRH/BD/128657/2017, the projects PTDC/EMS-TEC/5422/2014ADAPTPROSTHESIS, POCI-01-0145-FEDER-030353 (SMARTCUT), NORTE 010145_FEDER-000018-HAMaBICo and UID/EEA/04436/2019.

Focusing on implant surface design, aiming to improve implant primary stability, SLM technology was explored to produce dense and cellular structured Ti6Al4V specimens. The SLM specimens and also a commercial casted/forged Ti6Al4V group, were sandblasted and acid-etched to obtain a moderate surface roughness topography, typically used in implant manufacturing. Ti6Al4V-bone interaction and tribological performance were assessed by performing sliding tests aiming to replicate in some extension the insertion of a hip implant. The results shown a 24 and 32% higher kinetic friction coefficient values when comparing the cellular structures with the conventional casted/forged Ti6Al4V. These friction results together with a high amount of adhered bone are promising evidences of a higher efficiency of Ti6Al4V cellular structures for enhancing implant stability., This study was supported by FCT through the grants SFRH/BD/ 128657/2017 and SFRH/BPD/112111/2015, the project PTDC/EMS TEC/5422/2014 and also by project NORTE 01–0145_FEDER-000018. Furthermore, this work was supported by FCT with the reference pro ject UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145-FEDER-006941.

Acknowledgements: This work was supported by FCT through the grants SFRH/BD/128657/2017 and SFRH/BPD/112111/2015, the project PTDC/EMSTEC/5422/2014 and also by project NORTE 01-0145_FEDER-000018. Additionally, this work was supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145-FEDER-006941. A multi-material concept that gathers Ti6Al4V and PEEK properties in a cellular structured component was designed, fabricated and investigated targeting hip implants. SLM and pressure assisted injection techniques were used to obtain Ti6Al4V-PEEK multi-material structures. Aiming to reproduce to some extension the tribological phenomena occurring during and after hip implant insertion, five tribological tests were outlined and performed. The obtained results showed that the presence of PEEK on the Ti6Al4V-PEEK cellular structures led to a substantial improvement on the wear resistance (62% reduction in the mass loss) when compared to the material currently available on market for hip implants. The multi-material solution here investigated shows a good compromise between the primary stability after implant insertion and the wear performance. info:eu-repo/semantics/publishedVersion

This study is concerned with the influence of four metallic reinforcements on aluminum-silicon (AlSi) composites, with respect to wear behavior. AlSi-Ti; AlSi-Ti6Al4V; AlSi-1.4301 stainless steel and AlSi-Ni particulate reinforced composites were produced by a hot-pressing route. Microstructural characterization showed a uniform distribution of the reinforcing particles in the AlSi matrix. Reciprocating pin-on-plate wear tests were performed for AlSi and AlSi-based composites against gray cast iron plates. In order to compare the effect of different metallic particulates on the AlSi-based composites/gray cast iron tribopair wear performance, besides the pin, the counterface was also analyzed. The particle/matrix interface is analyzed in order to understand its influence on the tribopair behavior and on the controlling wear mechanisms. It was shown that the better compromise between both sliding surfaces performance was attained by AlSi-Ni/gray cast iron tribopair.

In order to enhance osteointegration, prostheses surfaces are usually coated with bioactive materials like hydroxyapatite (HA), material found in teeth and bones. Traditional HA coatings were proven adequate for obtaining high-quality coatings on metal substrates. However, due to the implantation process, these coatings can be detached from the metal surface. In this work, a new materials design that aims to avoid this coating detachment scenario is proposed, based on composites of Ti6Al4V alloy reinforced with HA powder, with materials gradation from bulk to surface of the prosthesis, where the titanium bulk provides toughness and the outer regions provide biological performance. In order to assess the mechanical and biological performance of the prosthesis outer region, Ti6Al4V-HA composites with different HA contents were produced and characterized regarding microstructure and mechanical properties. Shear tests were performed and fracture surfaces were analysed. EDS and XRD analysis were performed in order to assess HA possible decomposition due to processing temperature and pressure during the hot pressing route. This work shows that the combination of hot pressing technique and an FGM design approach is a promising solution for manufacturing prosthesis with improved bioactivity that can overcome the detachment problems of solutions based on HA coatings. Keywords: Ti6Al4V, Hydroxyapatite, Hot pressing, Functionally graded material, Composite, Biomedical applications

The aim of this paper was to study the interface reaction between an AlSi alloy reinforced with Ni coated Multi-Wall Carbon Nanotubes (MWCNTs). A powder metallurgy processing route was used to produce AlSi composites. SEM, DSC, XRD and TEM analysis showed the formation of Al3Ni due to the presence of Al from AlSi matrix and Ni from CNT coating. This contributes to stress transfer from matrix to CNT reinforcement and consequently to enhancement of mechanical properties of the composites. Also it was observed some dissolution of Ni to AlSi and that the CNTs are very stable as they maintain their integrity. The coating of CNTs seems to be a good solution for application of this reinforcement in commercial alloys.

Lightweight metal-matrix composites (MMC) are being applied in many fields such as aerospace and automotive, where detailed knowledge about their elastic and inelastic properties is required to make optimal design of the component. In this study the high-temperature damping capacity and dynamic Young’s modulus of hot-pressed AlSi-based hybrid composites reinforced with silicon carbide particles (SiC p ) and carbon nanotubes (CNTs) were experimentally measured and compared with AlSi–SiC p and AlSi–CNT composites. Results show that by reinforcing AlSi–SiC p with CNTs, the damping capacity is improved without reducing mechanical properties. The highest damping capacity value was attained by AlSi–(CNT–SiC p ) hybrid composite, for all the studied frequencies and temperatures, followed by AlSi–SiC p and AlSi–CNT composites. The possible damping mechanisms for all these produced composites are presented and discussed. Unlike to damping capacity, the dynamic Young’s modulus shows no substantial changes after adding CNTs to AlSi–SiC p . Results show that by using a proper combination of materials (including different types of reinforcements), scales (nano- and micro-sized reinforcements) and manufacturing processes, the design of a material with required damping capacity and mechanical properties is possible.

The effect of SiC particle size on the resultant damping capacity and dynamic modulus of aluminum metal matrix composites (AMMCs) was studied. Damping capacity, as well as dynamic Young's modulus, was measured at 1, 10 and 20 Hz, at room temperature. Image analysis and chemical composition were performed in order to investigate the AlSi–SiC interfacial reaction. The damping capacity of AlSi–SiCp composites, with three different particle size, was compared to AlSi unreinforced. The damping mechanisms involved were discussed in light of the results obtained from damping capacity. The results show that damping capacity and dynamic modulus of AlSi can be improved through the addition of SiC particles. Further, through a selection of specific sizes of SiC particles, it is possible to tailor the final composite stiffness and damping capacity.

The aim of this paper was to study the mechanical behavior of a hybrid AlSi–2 wt.%CNTs–5 wt.%SiCp composite. For comparison purposes the unreinforced AlSi alloy, AlSi–2 wt.%CNTs and AlSi–5 wt.%SiCp composites were used. A powder metallurgy processing route was used to produce the unreinforced AlSi alloy and AlSi composites. Tensile and fatigue tests were performed and the results showed that the hybrid composite AlSi–2 wt.%CNTs–5 wt.%SiCp proposed in the present paper, provided better overall properties than the single reinforcement composites. The improvement is attributed to the combined effects of two different reinforcements that act at different scales.

This work is concerned with understanding the influence of reinforcement mechanisms of carbon nanotubes (CNTs) on mechanical, wear, and fatigue tests on an Aluminium-Silicon (AlSi) alloy. The reinforcement mechanism is presented through the observation of fracture morphology of the different tests. Results of mechanical properties, fatigue life performance, and wear loss is presented and discussed. It is shown that the CNTs reinforcement effect is active simultaneously in all previous properties and the reinforcement physical mechanism seems to be essentially due to a reinforcement effect of the interface that seems to be similar in all mentioned mechanical solicitations.

In this study, the effect of the size of SiC particle on high temperature damping capacity and dynamic Young's modulus of hot-pressed AlSi–SiC composites has been investigated. SiC particles with sizes of 13 μm, 38.8 μm and 118 μm were added to AlSi matrix to prepare the hot-pressed AlSi–SiC composites. These composites were characterized using a dynamic mechanical analyser (DMA), over a temperature range of room temperature to 400 °C. Regarding damping capacity, all AlSi–SiCp composites exhibited higher damping capacity compared to unreinforced AlSi alloy (for all tested frequencies). AlSi–SiCp(118) composites exhibited the highest improvement in damping capacity. A damping peak was observed near 250 °C, as a result of a relaxation process. Regarding dynamic Young's modulus, it was observed that the addition of SiCp to the AlSi alloy improved the Young's modulus. It was also demonstrated that by increasing the SiCp size, a decrease in Young's modulus is attained, with the highest improvement in dynamic Young's modulus being obtained by AlSi–SiCp(13) composite. Keywords: Metal matrix composites, Powder metallurgy, Hot pressing, SiC

The aim of this paper was to develop a method of producing Functionally Graded Materials (FGMs) by powder metallurgy whose principle is similar to the solid freeform fabrication. According to required FGM design, different chemical compositions can be obtained as the mixture of the powders continuously deposited in the matrix is computer controlled. Afterward the powders are pressed followed by sintering. The main advantage of the developed method is the control over the produced gradient and furthermore does not require burning binder phase. The resulting FGMs have a great interest from the possibility of controlling the composition or structure and thus obtaining components with desired properties. The technique introduced in this research is innovative because it can be achieved a continuous variation of composition along a given axis of a sample, as well as a greater diversification of the types of produced gradients. Keywords: FGMs, SiC, Steel, Processing

Orthopedic implants are under incessant advancement to improve their interactions with surrounding bone tissue aiming to ensure successful outcomes for patients. A successful biological interaction between implant and surrounding bone depends on the combination of mechanical, physical and topological properties. Hence, Ti6Al4V cellular structures appear as very promising solutions towards the improvement of conventional orthopedic implants. This work addresses a set of fundamental tools that allow improving the design of Ti6Al4V cellular structures produced by Selective Laser Melting (SLM). Three-point bending tests were carried out to estimate the elastic modulus of the produced structures. Morphological analysis allowed to evaluate the dimensional differences that were noticed between the model CAD and the SLM structures. Finite element models (adjusted CAD) were constructed with the experimentally obtained dimensions to replicate the mechanical response of the SLM structures. Linear correlations were systematically found for the dimensions of the SLM structures as a function of the designed model CAD dimensions. This has also been observed for the measured porosities as a function of the designed CAD models. This data can be used in further FE analyses as design guidelines to help engineers fabricating near-net-shape SLM Ti6Al4V cellular structures. Besides, polished and sandblasted surface treatments performed on the Ti6Al4V cellular structures allowed to obtain suitable properties regarding roughness and wettability when compared to as-produced surfaces. The capillarity tests showed that all the analyzed Ti6Al4V structures are able to transport fluid along its structure. The cell viability tests demonstrate Ti6Al4V cellular structures SLM produced did not release toxic substances to the medium, indicating that these structures can assure a suitable environment for cells to proliferate and attach. This study proposes a design methodology for Ti6Al4V cellular structures, that owe suitable mechanical properties but also provide a proper combination of porosity, roughness, wettability, capillarity and cell viability, all of them relevant for orthopedic applications. A Ti6Al4V cellular structured hip implant prototype gathering the suitable features addressed in this study was successfully SLM-produced., This work was supported by FCT through the grants SFRH/BD/128657/2017 and SFRH/BPD/112111/2015, the projects PTDC/EMSTEC/5422/2014 (ADAPTPROSTHESIS) and POCI-01-0145-FEDER030353 (SMARTCUT) and also by project NORTE 01–0145_FEDER000018. Additionally, this work was supported by FCT with the reference project UID/EEA/04436/2019, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145- FEDER-006941.

PURPOSE The aim of this study was to characterize and compare the behavior of human osteoblasts and human gingival fibroblasts in contact with polyetheretherketone (PEEK), zirconia, and titanium implant surface materials. MATERIALS AND METHODS PEEK, yttria-stabilized zirconia (YTZP), and titanium discs were produced under appropriate and similar conditions to achieve controlled surface features. Human osteoblasts and human gingival fibroblasts were cultured on discs for 14 days. Cell viability and proliferation were evaluated using a resazurin-based method. Morphology and cellular adhesion were observed using field emission gun-scanning electron microscopy (FEG-SEM). Alkaline phosphatase (ALP) activity and bone cell mineralization were evaluated on osteoblasts. Confocal laser scanning microscopy (CLSM) images of fluorescent-stained fibroblasts were obtained at 7 and 14 days of the culture. Results were presented as mean and standard deviation (SD). Group comparisons were tested using analysis of variance (ANOVA) (Tukey's post hoc) with appropriate statistical software, and significance was set at P < .05. RESULTS Cell viability and proliferation were higher in PEEK and YTZP groups compared with titanium on osteoblast cells (P < .05, all time points) and on fibroblasts (P < .05, 7 and 14 days). All groups showed an increase in ALP activity over time, which was not significant. Mineralization patterns demonstrated an increase in mineral content over time, which was more apparent in the YTZP group. Cell spreading was more evident on PEEK and YTZP specimens. CONCLUSION The results suggest increased adhesion, viability, and proliferation of osteoblasts and gingival fibroblasts on zirconia and PEEK surfaces compared with titanium. These results are correlated with the increased wettability of these materials.

This work was supported by FCT through the grants SFRH/BD/128657/2017 and SFRH/BPD/112111/2015, the project PTDC/EMSTEC/5422/2014 and also by project NORTE 01–0145_FEDER-000018. Additionally, this work was supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01–0145-FEDER-006941. Ti6Al4V-alloy is commonly used in dental and orthopedic applications where tribochemical reactions occur at material/bone interface. These reactions are one of the main concerns regarding Ti6Al4V implants due to the generation of wear particles, linked to the release of metallic ions in toxic concentration which occurs when TiO2 passive film is destroyed by means of wear and corrosion simultaneously. In the present study, a multi-material Ti6Al4V-PEEK cellular structure is proposed. Selective Laser Melting technique was used to produce Ti6Al4V dense and cellular structured specimens, whilst Hot-Pressing technique was employed to obtain multi-material Ti6Al4V-PEEK structures. This study investigates the tribocorrosion behavior of these materials under reciprocating sliding, comparing them with commercial forged Ti6Al4V. Open-circuit-potential was measured before, during and after sliding while dynamic coefficient of friction was assessed during sliding. The results showed an improved wear resistance and a lower tendency to corrosion for the multi-material Ti6Al4V-PEEK specimens when compared to dense and cellular structures mono-material specimens. This multi-material solution gathering Ti6Al4V and PEEK, besides being able to withstand the loads occurring after implantation on dental and orthopedic applications, is a promising alternative to fully dense metals once it enhances the tribocorrosion performance. info:eu-repo/semantics/publishedVersion

This work was supported by FTC through the grant SFRH/BPD/112111/2015 and the project PTDC/EMS-TEC/5422/2014. Additionally, this work was supported by the project NORTE 01–0145_FEDER-000018 and by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalizaç~ao (POCI) with the reference project POCI-01-0145-FEDER-006941. In the present work, a new material design of Ti6Al4V-PEEK hybrid cellular structure with improved wear resistance is proposed. Samples with different dimensions of the open-cells (350, 400, 450, 500 μm) were fabricated by Selective laser melting (SLM) technology, while Hot pressing (HP) technology was employed to produce Ti6Al4V-PEEK hybrid cellular structures. The tribological tests were performed in Phosphate Buffered Saline solution at 37 ± 2 C. Results demonstrated that the addition of the biomedical PEEK protected the Ti6Al4V cellular structures, thus improving these hybrid structures wear resistance when increasing the amount of PEEK. The obtained results indicated that the Ti6Al4V-PEEK hybrid cellular structure with the dimensions of the opencells of 500 μm is a suitable structure for orthopedic implants, with improved properties. info:eu-repo/semantics/publishedVersion

This work presents a novel texture design for implants surface functionalization, through the creation of line-shaped textures on Ti6Al4V surfaces and subsequent sintering of hydroxyapatite (HAp) powder into the designated locations. HAp-rich locations were designed to avoid HAp detachment during insertion, thus guaranteeing an effective osseointegration. This process starts by creating textured lines using a Nd:YAG laser, filling these lines with HAp powder and sintering HAp using a CO2laser. The adhesion of HAp is known to be influenced by HAp sintering parameters, especially laser power and scanning speed and also by the textured lines manufacturing. Different laser parameters combinations were used to assess the sintering and adhesion of HAp to the textured lines. HAp adhesion was assessed by performing high energy ultrasonic cavitation tests and sliding tests mimicking an implant insertion, with Ti6Al4V/HAp specimens sliding against animal bone. The HAp content retained after these tests was measured and results showed that an excellent HAp sintering and adhesion was achieved when using a scan speed of 1 mm/s and laser power between 9 and 9.6 W. It is important to emphasize that results indicated that the HAp bioactivity was maintained when using these conditions, validating this functionalization process for the production of hip prosthesis with improved bioactivity., FEDER -Federación Española de Enfermedades Raras(POCI-01–0145-FEDER-006941), info:eu-repo/semantics/publishedVersion

The aim of this study was to analyze the osteogenic cell behavior on the surface of novel functionally graded titanium-based composites containing bioactive ceramics. Titanium grade V discs (8 × 3 mm) embedding gradual content of hydroxyapatite (TiAlV-HA) or beta-tricalcium phosphate (TiAlV-βTCP) were produced by hot-pressing technique. Titanium-ceramic composite discs and Ti grade V (control group) were placed in contact with human osteoblast culture assays. The morphology and adhesion of osteoblasts were inspected by field emission guns scanning electron microscopy (FEGSEM) while cell viability was assessed by fluorometric method. Alkaline phosphatase (ALP) activity and fluorescent microscopic analyses were used to evaluate mineralization on the test and control discs. FEGSEM images showed cells adhered to Ti6Al4V-ceramic and Ti6Al4V surfaces over a period of 24 h, and therefore, an intense proliferation of osteoblasts and spreading cells was noticed for 7 days. Cell viability increased with time on all the surfaces although TiAlV-βTCP revealed significant higher percentage of cell viability than that recorded for TiAlV-HA (p 0.01). TiAlV-βTCP also showed the highest hydrophilic character. ALP levels increased on the Ti6Al4V-ceramic surfaces when compared to the control group. Also, a qualitative analysis of mineralization evidenced an increase in mineral content on TiAlV-HA or TiAlV-βTCP groups. Novel functionally graded composites based on Ti grade V and hydroxyapatite or βTCP showed a higher bioactivity in presence of osteoblasts than that recorded on Ti grade V. Also, such functionally graded materials can prevent risks of failures by detachment of bioactive ceramic materials during implant placement. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1923-1931, 2018.

The aim of this paper was to examine the wear behaviour of a hybrid AlSi–2wt%CNTs–5wt%SiCp composite. For comparison purposes the unreinforced AlSi alloy, AlSi–2%wtCNTs and AlSi–5wt%SiCp composites were used. A powder metallurgy processing route was used to produce the unreinforced AlSi alloy and AlSi composites. Dry reciprocating pin-on-plate wear tests were performed and the results showed that the wear behaviour was improved for all produced composites when compared to the unreinforced AlSi alloy. However the best wear behaviour was achieved in the case of AlSi hybrid composite. This improvement is attributed to the combine effects of both constituent reinforcements. The dominant wear mechanisms were characterized by scanning electron microscopy with X-Ray Energy Dispersive Spectrometry analysis.

The aim of this work was to study, using the finite element method (FEM), the distribution of thermal residual stresses arising in metal–ceramic dental restorations after cooling from the processing temperature. Three different interface configurations were studied: with conventional sharp transition; one with a 50% metal–50% ceramic interlayer; and one with a compositionally functionally gradated material (FGM) interlayer. The FE analysis was performed based on experimental data obtained from Dynamic Mechanical Analysis (DMA) and Dilatometry (DIL) studies of the monolithic materials and metal/ceramic composites. Results have shown significant benefits of using the 50% metal–50% ceramic interlayer and the FGM interlayer over the conventional sharp transition interface configuration in reduction of the thermal residual stress and improvement of stress profiles. Maximum stresses magnitudes were reduced by 10% for the crowns with 50% metal–50% ceramic interlayer and by 20% with FGM interlayer. The reduction in stress magnitude and smoothness of the stress distribution profile due to the gradated architectures might explain the improved behavior of these novel dental restorative systems relative to the conventional one, demonstrated by in-vitro studies already reported in literature.

Carbon nanotube (CNT) incorporation in metal matrix composites is hampered by the development of attractive van der Waals forces, which lead to the formation of CNT agglomerates. Therefore, a detai...

The damage of piston rings is attributed first to wear, then to lubrication and fatigue. Their damage may be substantially mitigated by creating a FGM-Functionally Graded Material composite with optimized mechanical behavior. The aim of this paper was to produce an AlSi–CNTs functionally graded material (FGM) that can be considered for engine compression piston rings. The AlSi graded composites (reinforced with 0–2 wt.% CNT FGM approach) was obtained with a new equipment that was designed to produce FGMs by powder metallurgy (PM) processing route. SEM analysis showed that the produced FGMs have a gradual change in wt.% of reinforcement and on mechanical properties. Results of yield strength, ultimate tensile strength, tensile strain, fatigue limit performance and wear loss are presented and discussed. It is expected that the obtained AlSi–CNTs functionally graded composite developed for piston rings may have a global equilibrium of properties.

This study is concerned with the reactivity between SiC particles and 410L stainless steel alloy. An interval of sintering temperatures (900, 1000, 1100, and 1180℃) was scoped in order to study the temperature influence on the interface reaction under different compaction pressures (400, 800, and 1200 MPa). SiCp/410L SS composites were produced by powder metallurgy. Interface area fraction (%) results and microstructural characterization showed that the interface reaction is strongly dependent on temperature. At 900℃ no reaction SiCp/410L SS was found. At 1000℃ SiCp reacts with 410L SS matrix and with increasing temperature the extent of reaction becomes higher. However, at 1180℃ SiCp dissolves completely leading to specimen deformation. The higher interface area fraction was obtained at a sintering temperature of 1100℃ and a compaction pressure of 1200 MPa. This study presents an advantageous and original combination of materials and process that allows combining compaction pressure and sintering temperature in order to control the interface.

This experimental study is concerned with the influence of metallic (Ti) and ceramic (SiC) reinforcements in an aluminumfsilicon (AlSi) alloy, when regarding tensile properties and wear behavior. Several micron sized particulate reinforced composites were produced by hot-pressing technique: AlSi–SiC and AlSi–Ti composites and AlSi-(Ti–SiC) hybrid composites. Regarding tensile properties, all composites presented higher ultimate tensile strength (UTS) than the AlSi matrix, with the highest UTS being attained by a hybrid composite (AlSi-11.25%Ti–5%SiC). Regarding wear behavior, reciprocating pin-on-plate wear tests were performed for unreinforced AlSi; AlSi–Ti composites and AlSi-(Ti–SiC) hybrid composite against a gray cast iron (GCI) counterface. The wear mechanisms for all the tested tribopairs are presented and discussed. It was observed that the wear behavior of the AlSi–Ti/GCI and also AlSi-(Ti–SiC)/GCI tribopairs are improved when compared with the AlSi/GCI system. AlSi-11.25%Ti-5%SiC hybrid composite exhibited the highest improvement in wear rate.

The aim of this paper was to evaluate the effect of different dispersion methodologies on mechanical properties of the aluminum-silicon (AlSi) composites reinforced by multi-walled carbon nanotubes (MWCNTs) coated with Ni. Different mixing procedures of MWCNTs with AlSi powder were tested, and AlSi-CNT composites were produced by hot pressing—powder metallurgy technique. The shear tests were performed to get the mechanical properties. Scanning electron microscopy with x-ray energy dispersive spectroscopy analysis and thermal analysis was used to investigate the microstructure of AlSi-CNT composites, interface reactions, and fracture morphology after shear tests. The experimental results proved that an improvement of dispersion of CNTs was achieved by using a combination of different mixing processes.

Nickel particulate-reinforced aluminum-silicon composites, with 5, 12.5 and 20 wt%Nickel were produced by a hot pressing route. Microstructural characterization showed a uniform distribution of the Nickel particulates in the aluminum-silicon matrix. Ultimate tensile strength and hardness of the composites were found higher than for the aluminum-silicon alloy, while ductility suffered a decrease. Fracture surface analysis showed evidences of load transfer from the matrix to the reinforcement indicating the development of an effective interfacial bonding between Nickel particulates and aluminum-silicon matrix. Energy dispersive spectrometer and X-ray diffraction analyses performed in the particle/matrix interface revealed that it was formed by Al3Ni intermetallic. It was found that the amount of Al3Ni intermetallic has a paramount influence in the composites properties.

This study is concerned with the influence of Nickel, as reinforcement, in an aluminum–silicon (AlSi) alloy when regarding wear behavior. For these composites, the effect of Ni content, in the tribopair performance, was evaluated. For this purpose, the pin but also the counterface wear behavior was analyzed. Nickel particulate reinforced aluminum–silicon (AlSi) composites, with 5, 12.5 and 20 wt.% Ni were produced by a hot-pressing route. Microstructural characterization showed a uniform distribution of the Ni particulates in the AlSi matrix. EDS and XRD analyses revealed that the particle/matrix interface was formed by Al 3 Ni intermetallic. Reciprocating pin-on-plate wear tests were performed with AlSi and AlSi–Ni pins against a gray cast iron (GCI) counterface. It was observed that the wear behavior of the AlSi–Ni/GCI tribopair is improved when compared with the AlSi/GCI system.

The performance of dental restorations has been a concern of dentists and engineers. One of the topics that have concentrated most effort has been the study of the properties of the interface between the veneering porcelain to metallic or ceramic substrates, namely on the improvement of the adhesion between the two materials and its behaviour under oral conditions. This paper discusses the benefits of placing a composite interlayer (50% metal + 50% ceramic, vol.%) at interface between metal and ceramic in a dental restoration. The discussion covers the following aspects: performance of this system under thermomechanical fatigue conditions, thermal and mechanical properties of the composite interlayer, thermal residual stresses arising after porcelain sintering and technical feasibility on a prosthetic laboratory.

Titanium and its alloys have been widely used in many engineering areas due to their properties. Despite having a high implant-tissue osseointegration time, Ti6Al4V has been extensively used in prosthesis and articular implants. To promote a faster bone ingrowth and consequently reduce the implant fixation time, the addition of a bioactive phase to form a biocomposite seems to be an excellent solution. Because of their bioactivity and similarity in composition with the human bone, HAp and b-TCP are two of the most widely used calcium phosphates in biomedical applications. To guarantee a strong adhesion of the previous bioactive materials in the implants surface, samples of Ti6Al4V, Ti6Al4V1HAp (10 vol %) and Ti6Al4V+beta-TCP (10 vol %) TCP were processed by the hot pressing technique. Tribological tests against Al2O3, lubricated in PBS at 37 ºC were carried out on a ball-on-flat reciprocating sliding geometry. Loads in the range of 3 N to 30 N were applied and their effect on the friction behavior and wear resistance of the tested materials was evaluated. Values of the coefficient of friction as well as the wear rate tend to increase with the addition of a bioactive phase to the Ti alloy. Micrographs of the worn surfaces showed that abrasion and plastic deformation are the prevailing wear mechanisms in the studied tribosystems. For biocomposites, particularly in the case of Ti6Al4V+HAp, pull-out of bioactive particle clusters has a determinant role on the tribological response, increasing both the friction coefficient and the specific wear rate., Contract grant sponsor: FCT (Fundac¸ao para a Ci ~ encia e Tecnologia—Portugal); contract grant numbers: NORTE-01-0145-FEDER-000018; UID/EEA/04436/2013, info:eu-repo/semantics/publishedVersion

The development of new design approaches for biomedical applications using conventional and well accepted bio inert materials is an actual challenge. This study proposes a bilayered materials design approach obtained by hot pressing and is concerned with the influence of sintering pressure on the interface reaction between titaniumalloy (Ti6Al4V) and zirconia (ZrO2), on density and mechanical properties of the Ti6Al4V-ZrO2. For this purpose, different sintering pressureswere studied (P=5, 20 and 100MPa). Bilayered materialswere produced by hot pressing process, at T=1175 °C. Microstructural characterization showed that Ti6Al4V reacts with ZrO2 (for Pâ ¥20 MPa) and that the interface reaction is strongly dependent on pressure. Additionally, an oxygen-deficient ZrO2 â x black zirconia layer was obtained for specimens produced at P=20 and 100MPa as result of decreased O/Zr ratio due to Ti diffusion into ZrO2 side. Young's modulus and hardness properties were evaluated by nanoindentation test. The results showed that these properties are influenced by sintering pressure, increasing with an increase on sintering pressure, with the highest improvement for specimens produced at higher pressure., This work is supported by FTC through the grant SFRH/BD/112280/ 2015 and the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145- FEDER-006941, and NORTE-01-0145-FEDER-000018-HAMaBICo., info:eu-repo/semantics/publishedVersion

The Ti6Al4V alloy constitutes an alternative choice to the most common metal-polymer solutions for total hip arthroplasty (THA) due to good biocompatibility, optimal mechanical properties and high load bearing capacity. However, as Ti6Al4V is not bioactive in its conventional form, hydroxyapatite (HAp) and tricalcium phosphate (TCP) have been widely used as coatings of metal prostheses due to their osteogenic properties and ability to form strong bonds with bone tissue. A promising approach consists in creating a bioactive surface metal matrix composite Ti6Al4V+β-TCP or Ti6Al4V+HAp, obtained by hot pressing (HP) of powders. In this work, the tribological performance of Ti6Al4V+β-TCP and Ti6Al4V+HAp composites is studied to evaluate the frictional response and surface damage representative of prosthesis implantation, key factors in bone fixation. Biocomposites with 10vol% β-TCP and 10vol% Hap, as well as base titanium alloy, were prepared by HP with two surface finishing conditions - polished (Ra=0.3-0.5μm) and sandblasted (Ra=2.1-2.5μm) - for tribological testing against bovine cortical bone tissue. The static friction increases with surface roughness (from 0.20 to 0.60), whereas the kinetic regime follows an inverse trend for the biocomposites. In contrast with current knowledge, this study shows that an implant design solution based on Ti6Al4V+β-TCP or Ti6Al4V+HAp biocomposites with polished surfaces results in an improved primary stability of implants, when compared to traditional rough surfaces. Moreover, it is also expected that the secondary stability will improve due to the adhesion between bone and HAp/β-TCP, increasing the overall stability of the implant., This work has been supported by FCT (Fundação para a Ciência e Tecnologia - Portugal) in the scope of the project NORTE-01-0145-FEDER-000018 and UID/EEA/04436/2013., info:eu-repo/semantics/publishedVersion

Additive manufacturing (AM) technologies enable the fabrication of innovative structures with complex geometries not easily manufactured by traditional processes. Regarding metallic cellular structures with tailored/customized mechanical and wear performance aiming to biomedical applications, Selective Laser Melting (SLM) is a remarkable solution for their production. Focusing on prosthesis and implants, in addition to a suitable Young's modulus it is important to assess the friction response and wear resistance of these cellular structures in a natural environment. In this sense, five cellular Ti6Al4V structures with different open-cell sizes (100–500 μm) were designed and produced by SLM. These structures were tribologicaly tested against alumina using a reciprocating sliding ball-on-plate tribometer. Samples were submerged in Phosphate Buffered Saline (PBS) fluid at 37 °C, in order to mimic in some extent the human body environment. The results showed that friction and wear performance of Ti6Al4V cellular structures is influenced by the structure open-cell size. The higher wear resistance was obtained for structures with 100 μm designed open-cell size due to the higher apparent area of contact to support tribological loading., This work was supported by FTC project PTDC/EMS-TEC/5422/ 2014, by project NORTE 01-0145_FEDER-000018 and by the grant SFRH/BPD/112111/2015. Additionally, this work was supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01–0145-FEDER-006941., info:eu-repo/semantics/publishedVersion

The properties of parts produced by Selective Laser Melting (SLM) are highly influenced by the processing parameters. The calculation of the energy density is not enough for justifying the mechanical and physical properties, and understand the microstructures of Ti6Al4V samples produced by SLM. In fact, samples produced with the same energy density, but with different processing parameters, present distinct properties. In this sense, it is necessary to assess the influence of processing parameters on SLM fabrication, as isolated parameters but also their interactions.This work presents a study on the influence of several SLM processing parameters (laser power, scan speed and scan spacing) on density, hardness and shear strength of Ti6Al4V samples. The influence of these processing parameters on the final properties of SLM parts was obtained by using statistical analysis. Additionality, with the drive of finding the significant main factors and their interactions, analysis of variance (ANOVA) was performed. The influence of the above mentioned processing parameters on shear strength, hardness and density resulted in three models that can be used as predictive design tools for Ti6Al4V parts produced by SLM technology. Moreover, a study on the microstructures of the Ti6Al4V samples was performed and correlated with the obtained models. (C) 2016 Elsevier B.V. All rights reserved., This work is supported by FCT through the project with the reference EXCL/EMS-TEC/0460/2012 and the grant SFRH/BPD/112111/2015. This work is also supported by FCT with the reference project UID/EEA/04436/2013, by FEDER funds through the COMPETE 2020 Programa Operacional Competitividade e Internacionalizacao (POCI) with the reference project POCI-01-0145-FEDER-006941., info:eu-repo/semantics/publishedVersion

Selective Laser Melting (SLM) processing parameters are known to greatly influence 316L stainless steel final properties. A simple energy density calculation is insufficient for explaining mechanical and physical properties as well as microstructural characteristics, which are known to significantly influence these parts performance. In fact, parts produced by using different combinations of processing parameters, even presenting similar energy density, can display different properties. Thus, it is necessary to assess their influence as isolated parameters but also their interactions. This work presents a study on the influence of several SLM processing parameters (laser power, scanning speed and scanning spacing) on density, hardness and shear strength of 316L stainless steel. The influence of these processing parameters on the abovementioned properties is assessed by using statistical analysis. In order to find the significant main factors and their interactions, analysis of variance (ANOVA) is used. Furthermore, in order to assess the effect of the part building orientation, two different building strategies were tested. The influence of these processing parameters on shear strength, hardness and density were assessed for the two building strategies, thus resulting six different models that can be used as predictive design tools. The microstructures experimentally obtained were analyzed, discussed and correlated with the obtained models., This work was supported by the Portuguese Foundation of Science and Technology through the projects EXCL/EMS-TEC/0460/2012, UID/EEA/04436/2013 and by the FCT grant SFRH/BPD/112111/2015., info:eu-repo/semantics/publishedVersion

Au-50%Cu (at. %) alloy presents the shape memory effect (SME), which is dependent of the solid state transformation that happens during heating, after the introduction of an internal stress in the quenched state. The solid state phase transformation temperatures were determined by means of Differential Thermal Analysis (DTA), both in heating and cooling cycles. With the obtained DTA results, a sequence of high temperature X-ray diffraction (XRD) experiments were made, in order to confirm the presence of the solid state phase transformations and to determine their stable crystal structure and lattice parameters. These XRD results were compared with those obtained from the literature. The displacements of the lattice parameters were determined, for each equilibrium phase, for measurements at room temperature and at high temperature. The characteristics of the quenched samples were also studied in order to determine the phase transformations that are responsible for the shape memory effect in this alloy.

This study is concerned with the influence of sintering stage duration on the interface load transfer capacity between NiTi fibres and AlSi matrix alloy and thus in the final composite strength. Short-fibre-NiTi/AlSi composites were produced by a pressure-assisted sintering process, under vacuum, for sintering stages of 20, 25 and 60 min. All the obtained composites, with different sintering stages, have shown the occurrence of load transfer from the matrix to fibres, indicating the development of an effective interface between fibre and matrix. Performed shear tests have shown a decaying of shear strength with increasing sintering stage, in the selected range of sintering times, with the lowest sintering time leading to higher properties. It was also concluded that with increasing sintering stage, the interface volume around the fibres increases and the load transfer capacity decreases.

The present work is concerned with the ability of the incremental melting and solidification process to be used in a controlled way to produce functionally graded materials in industrial environments. For this purpose, the influence of the main process parameters, namely relative mould/coil rate and melt temperature, is evaluated in relation to the obtained final component chemical composition gradient. Several graded components of Cu–Sn alloys were produced. The effect of the process parameters on the final component gradient was quantified. It was verified that both the melt temperature and the relative mould/coil rate play a similar role in final component chemical composition gradient. Predictive equations for the gradient, namely the extension of chemical composition gradient zones, are proposed based on the two studied variables.

This paper is concerned in assessing the possibility of the use of a Directional Solidification (DS) process in order to produce functionally graded materials. It will be assessed the influence of the relative displacement rate between heating coil and mould, in order to evaluate the produced cooling rates along the casting and consequent metallurgical and mechanical properties on the obtained component. A copper-silver alloy, which is prompt to macro-segregation occurrence, will be used. Results demonstrate that the process, which is able to originate DS castings, may also be used for FGMs production.