Search

Piezoelectric, ferroelectric and electromechanical properties were studied at macroscopic and local scale level in stannum doped (Ba0.88Ca0.12)(SnxZr0.1-xTi0.9)O3 ceramics, with an objective to explore the effect of low content (0  x  0.5 at%) of the substituent (Sn) on the functional properties. The results exemplified that the substitution had an influence on the crystal lattice and microstructure that affected the dielectric, ferroelectric, and electromechanical properties. Enhancement in electrical/electromechanical properties were observed with stannum substitution. Optimal electrical properties were obtained in the composition with Sn = 0.3 at% that exhibited maximum piezoelectric constant d33 = 405 pC/N, planar electromechanical coupling factor kp ~ 0.41, and saturation polarization Ps =12.1 μC/cm2 . The same composition showed an electric-field strain response, Smax ~ 0.08% and a converse piezoelectric coefficient, 𝑑33 ∗ of ~ 525 pm/V. Local scale characterization via piezoresponse force microscopy technique revealed complex domain patterns comprising stripe-like macro-domains and featureless nanosized domains. Energy harvesting and energy storage performance were evaluated for exploring their suitability in energy applications published

Publisher Copyright: © 2022 The Author(s) Laser surface texturing (LST) is a powerful technique for creating high quality micro-textured patterns with different shapes and sizes on metallic biomaterials. Textured surfaces may improve the interaction between bone and implant by increasing the surface contact area and thus promoting bone regeneration. The goal of this study was to explore Nd:YAG laser potential for texturing micro-scale pillars with pyramid geometry, with dimensions in a selected range, in a reproducible way. First, the design and texture of grooves were addressed, then proceeding to pillars. Two laser machining and marking strategies were investigated, and the consecutive laser processing strategy and continuous marking mode were selected due to the resultant smoother grooves. Then, a cross-hatched pattern was designed to texture a pillar pattern with targeted dimensions. Given the direct effect of the LST drawing and laser parameters on the texture dimensions, three mathematical models, one for each texture dimension (groove width, pillar width and pillar depth) were developed. These models are accurate tools for predicting the texture dimensions in the selected range and this LST approach was effective on creating well-defined, uniform and equally spaced surface textures on Ti6Al4V parts, in a reproducible way. A combination of drawing and laser parameters was selected for the target dimensions, also considering suitable wettability and roughness for biomedical applications.

Powder bed fusion (PBF) technologies have gained increased attention in the automotive sector for the manufacturing of mould tooling and inserts. These technologies can expressively reduce lead time and waste of material, while allowing extraordinary freedom to design new geometries. The performance of the produced parts is highly dependent on processing parameters. In this work, 18Ni300 maraging steel, a widely used material in mould and tooling industries, was selected to be transformed by Selective Laser Melting (SLM) using a previous defined framework of SLM variables, among them laser power (Lp), point distance (Pd), exposure time (Et) and hatch distance (Hd). The experimental results demonstrated that these parameters have vital importance to produce fully dense and micro-hardness improved parts. Furthermore, results showed that the energy density per se does not explain the final properties of 18Ni300 produced by SLM. Maximized density (99.99%) was achieved using (Lp, Pd, Et, Hd) (275.0 W, 60 μm, 65.0 μs, 110 μm), corresponding to 2.71 J/mm2 planar energy density, while maximized micro-hardness (350 HV2) was achieved using (Lp, Pd, Et, Hd) (337.5 W, 70 μm, 52.5 μs, 95 μm), corresponding to 2.66 J/mm2 planar energy density. The statistical relationship between SLM parameters and final density and micro-hardness of the parts was established using the so-called Response Surface Methodology (RSM), resulting in two predictive models, for density and micro-hardness. The most influential (single and combined factors), for both models, were then determined using analysis of variance (ANOVA). The outcomes of the ANOVA analysis revealed a predicted coefficient of determination, R2(pred.), of 93.73% and 98.98% for density and micro-hardness models, respectively, revealing that the developed models have high accuracy for the prediction of both properties on 18Ni300 steel parts produced by SLM.

Zirconia is a very popular material among implants and prosthesis, due to its antibacterial activity, corrosion resistance and hardness properties. For these purposes, zirconia is to be sintered beforehand to obtain good dimensional and geometrical accuracy and then machined. However, the machining of sintered zirconia has always been a troublesome proposition, attributable to its extreme hardness. The excellent properties of zirconia were applied in this study to the cutlery design. Nowadays, cutlery/flatware designs are constantly changing. However, for manufacturing, the traditional molding process remains widely popular, despite having huge limitations regarding aesthetic and design flexibility. In the present study, we explore a new horizon of cutlery design by patterning using laser surface modification. Blocks were laser machined from zirconia green compacts, which solved the machining problems associated with sintered zirconia, and then inserted into stainless-steel cutlery grooves to produce a novel aesthetical cutlery design. This study addresses the parametric optimization of laser parameters (power, scanning speed and number of passages) to produce cavities in zirconia green compacts. Material removal, depth of cut, geometry and surface roughness were taken as output variables. For the analyses, a full factorial design of experiments was adopted. Moreover, this study provides the optimum parameters for the laser machining of zirconia green compacts to produce blocks with accurate dimensions and geometries. After laser machining the zirconia blocks, sintering was performed to achieve the desired dimensions. published

Dynamic and fast-changing designs for cutleries or flatware are one important nature of this production business. Globalized hospitality merchandise, the demanding nature of modern customers, throat-to-throat competition of manufacturing industries, and the modernization of the manufacturing processes are some of the major challenges for the cutlery (silverware) manufacturing industry. So far, traditional methods of moulding and shaping are considered to be the best to provide static designs and trademark patterns of the organisation. Preparing a designed mould for a fixed blueprint of cutlery and then producing it in bulk is the sole purpose of existing methods. However, with the invention of laser engraving and design systems, the entire business of cutlery production has revolutionized. Allowing for different designs for different cutleries to set without changing the whole production line was the aim of this study. As shown in Figure 1, AISI-304 stainless steel, which is the general flatware material selected for laser engraving, was evaluated with three most vital input parameters (power, scanning speed and loops or number of passes) followed by the analysis of geometry, roughness, and volume removed/material removal (MR) as output variables. This study will provide insight into the know-how situation involving the processing of cutleries and introduction of different ceramic materials to the surface to define desired patterns. We produced different design patterns by laser and ingrained ceramic blocks on the silverware. This approach is much more flexible and adoptable for pattern changes. Besides that, there is no need to prepare a mould for each design. Belo Inox, Portugal supplied the silverware as per the collaborative project agreement. published

During machining processes, a high temperature is generated in the cutting zone due to plastic deformation, resulting in an increase of wear and consequently reducing the lifetime of cutting tools. The addition of well-defined patterned surfaces with random or regular microfeatures to cutting tools can improve its wettability, providing an enhanced lubrication effect, a reduced tool-chip friction and a lower tool wear rate. In this sense, this work proposes a laser surface texturing approach of WC-Co green compacts to obtain different cross-hatched micropatterns, for enhancing these tools wettability. Results showed that laser surface texturing allowed to produce well-defined, reproducible and equally spaced cross-hatched micropatterns in WC-Co green compacts. A contact angle of 33.5° was obtained for the experiment with a groove and peak width of 250 μm and 3 laser passages, resulting in a 27% reduction, when compared with an untextured cutting tool (45.8°). This approach was found effective to improve the wettability of WC-Co cutting tools.

Magnesium (Mg) and its alloys are promising materials for a wide range of biomedical applications due to its biodegradability. Nevertheless, their rapid corrosion dictates the need to develop strat...

Cubic boron nitride is becoming an alternative cutting tool material for machining under demanding conditions, displaying superior wear performance and machined parts with higher quality. The current need to reduce the cobalt content in these tools led to this study and focused on alternative binder materials for cubic boron nitride cutting tools. This work addresses several nickel–cobalt-based materials, regarding their microstructure, mechanical (hardness and shear strength), and tribological performance. The best results were attained when adding tungsten carbide to nickel–cobalt, once nickel–cobalt–tungsten carbide was found to display the higher mechanical properties, together with the higher wear resistance.

As one of the most important additive manufacturing (AM) techniques, laser metal deposition (LMD) has been extensively studied specially during the last few years. Similar to other AM techniques, the quality of LMD parts is highly dependent on the processing parameters that need to be optimized so as to obtain geometrically accurate parts as well as favorable microstructures and, thus, mechanical properties. The present review paper therefore aims to present a critical analysis and overview of the relationship between processing parameters, microstructure, and mechanical properties of LMD components made from the Ti–6Al–4V alloy. Moreover, we discuss the applications of LMD parts in the aerospace and biomedical industries as well as the potential of LMD techniques for fabrication of more complex parts such as cellular structures. The paper concludes with a summary of the most important findings and suggestions for future research.

This study intends to develop a novel zirconia scaffold design with a significantly lower Young's Modulus than zirconia bulk material (210 GPa) aiming to match this elastic property with that of the host bone, for application as endosseous implants. This scaffold with a complex interconnected structure can allow bone ingrowth, vascularization and provide a good initial stability. This novel thin-walled zirconia scaffold was manufactured by green machining and afterwards furnace sintered. The obtained YM of this zirconia scaffold was found significantly lower than zirconia bulk material due a less stiff geometry with small (walls and floors) dimensions. Insertion replication tests were performed for evaluating the fixation at the initial moment of implantation, being experimentally verified a high static initial coefficient of friction. The capillarity of these scaffolds was also assessed, revealing a very high rising speed of water inside these structures. This study proved that this novel ceramic scaffold design can be fabricated for several dimensions for obtaining desired elastic properties. The proposed fabrication strategy allows the fabrication of thin-walled structures unachievable by conventional machining.

Acknowledgments This work was supported by Fundação para a Ciência e Tecnologia (FCT), Portugal through the grants SFRH/BD/140191/2018, 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 is supported by FCT with the reference project UID/EEA/04436/2019. The following study proposes a multi-material solution in which Ti6Al4V cellular structures produced by Selective Laser Melting are impregnated with bioactive materials (hydroxyapatite or β-tricalcium phosphate) using press and sintering technique. To assess the tribological response of these structures, an alumina plate was used as a counterpart in a flat-on-flat reciprocating sliding test. Ti6Al4V cellular structures impregnated with bioactive materials displayed the highest wear resistance when compared with the unreinforced structures. Among the bioactive structures, Ti6Al4V cellular structures impregnated with βTCP were the ones with higher wear resistance, having the lowest weight loss. Hence, these structures are promising multifunctional solutions for load-bearing applications by gathering suitable mechanical properties (strength and stiffness); bioactive properties and in addition an improved wear performance. info:eu-repo/semantics/publishedVersion

Nowadays, conventional machining of WC-Co green compacts is used in industries in order to achieve desired dimensions, complex geometries and good surface quality. However, conventional machining presents some problems, namely tool wear, tool breakage, chatter, vibration and deflection besides mechanically induced damage to the compact. Laser machining is a promising approach to machine WC-Co green compacts, since it is performed without contact and allows great flexibility for producing several geometries, high material removal rate, good surface quality and precision, also for complex shapes. It also allows the production of details smaller than 0.2 mm, hardly manufactured by conventional machining, due to the brittle nature of cutting tools of very small dimensions. Due to the abovementioned reasons, laser machining presents a great potential for lowering the production costs of cemented carbide tools. This work addresses the laser machining of WC-Co green compacts, using a Nd:YAG laser and performing different strategies and combinations of laser parameters to obtain different types of profiles (grooves, areas and specific geometries). Results showed that an effective laser machining of WC-Co green compacts is attained when using laser power of 3 W, scan speed of 128 mm/s, 8 passages and line spacing of 0.08 mm. These parameters were effective for obtaining around 800 μm depth geometries, where the addition of a finishing step (1.5 W, 256 mm/s and 8 passages) improved the quality of the edge of the machined geometry. The laser machined compacts were sintered using a SinterHIP process and no undesirable phases were detected, as eta-phase or graphite.

Although hydroxyapatite coatings have been proven effective for obtaining uniform and continuous coatings on metallic endosseous implants, the detachment of these coatings during implantation can critically compromise the hydroxyapatite bioactive role. In order to overcome this problem, this work proposes a new integrated approach, starting with the laser machining of the Ti6Al4V implant, followed by the allocation of the hydroxyapatite and its subsequent laser sintering. In this study two different powder compaction/laser sintering methods were tested. Hydroxyapatite sinterability and adhesion to the metal was assessed for both methods, considering several conditions. Hydroxyapatite possible degradation due to the temperatures achieved during this process was also evaluated by means of Energy Dispersive Spectrometry (EDS) and X-ray diffraction (XRD). The better solution assured a significant retained volume of non-degraded hydroxyapatite. This work proves that laser technology is a promising approach for the manufacturing of implants with improved bioactivity sites that can overcome the detachment problems of coating-based solutions.

Load-bearing implants success is strongly dependent on several physical and chemical properties that are known to drive cellular response. In this work, multi-material β-TCP-Ti6Al4V cellular structures were designed to combine Ti6Al4V mechanical properties and β-Tricalcium Phosphate bioactivity, in order to promote bone ingrowth as the bioactive material is being absorbed and replaced by newly formed bone. In this sense, the produced structures were characterized regarding roughness, wettability, β-TCP quantity and quality inside the structures after fabrication and the pH measured during cell culture (as consequence of β-TCP dissolution) and those aspects were correlated with cellular viability, distribution, morphology and proliferation. These structures displayed a hydrophilic behavior and results showed that the addition of β-TCP to these cellular structures led to an alkalization of the medium, aspect that significantly influences the cellular response. Higher impregnation ratios were found more adequate for lowering the media pH and toxicity, and thus enhance cell adhesion and proliferation., FCT (Fundação para a Ciência e Tecnologia) through the grants SFRH/BD/140191/2018; SFRH/BPD/112111/2015, SFRH/BD/128657/2017, SFRH/BD/141056/2018; SFRH/BPD/97701/2013, PD/BDE/127836/2016, and the projects PTDC/EMS-TEC/5422/2014_ADAPTPROSTHESIS and NORTE-01-0145-FEDER-000018-HAMaBICo. 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

This work was supported by FCT (Fundação para a Ciência e Tecnologia) through the grants SFRH/BPD/112111/2015, SFRH/BD/128657/2017, PD/BDE/127836/2016, SFRH/BPD/97701/2013, SFRH/ BD/141056/2018, SFRH/BD/140191/2018 and the projects PTDC/EMSTEC/5422/2014 and NORTE-01-0145-FEDER-000018-HAMaBICo. 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. Multi-material Ti6Al4V cellular structures impregnated with 45S5 bioactive glass were designed and produced using Selective LaserMelting (SLM), an additive manufacturing technique, combinedwith Press and Sintering focusing on load bearing components like hip implants. These structures were designed to combine Ti6Al4V mechanical properties and promote bone ingrowth into the structure as the bioactive material (45S5) is being absorbed and replaced by newly formed bone. The influence of these structures design on some of the physical and chemical aspects that drive cellular response was assessed. Roughness, wettability, bioactive glass quantity and quality on the structures after processing and the pH measured during cell culture (as a consequence of bioactive glass dissolution) were evaluated and correlated with cellular viability, cellular distribution, morphology and proliferation on the surface and inside the structures. info:eu-repo/semantics/publishedVersion

Ti6Al4V sub-millimetric cellular structures arise as promising solutions concerning the progress of conventional orthopedic implants due to its ability to address a combination of mechanical, physical and topological properties. Such ability can improve the interaction between implant materials and surrounding bone leading to longterm successful orthopedic implants. Selective Laser Melting (SLM) capability to produce high quality Ti6Al4V porous implants is in great demand towards orthopedic biomaterials. In this study, Ti6Al4V cellular structures were designed, modeled, SLM produced and characterized targeting orthopedic implants. For that purpose, a set of tools is proposed to overcome SLM limited accuracy to produce porous biomaterials with desired dimensions and mechanical properties. Morphological analyses were performed to evaluate the dimensional deviations noticed between the model CAD and the SLM produced structures. Tensile tests were carried out to estimate the elastic modulus of the Ti6Al4V cellular structures. The present work proposes a design methodology showing the linear correlations found for the dimensions, the porosity and the elastic modulus when comparing the model CAD designs with Ti6Al4V structures by SLM., This work was supported by FCT through the grant SFRH/BD/ 128657/2017 and the projects PTDC/EMS-TEC/5422/2014_ADAPT PROSTHESIS, NORTE-01-0145-FEDER-000018 – HAMaBICo and UID/ EEA/04436/2019.

In this study, a multi-material NiTi-PEEK cellular structured solution was designed, produced and characterized targeting orthopedic applications. For that purpose, Selective Laser Melting (SLM) technique was used to produce NiTi cellular structures with different open-cell sizes and wall thicknesses. Hot Pressing (HP) technique was used to introduce PEEK in the open-cells of NiTi structures to obtain multi-material components. Morphological characterization showed that the selected SLM processing parameters were suited to achieve high-quality parts without significant defects. Tribological characterization proved an enhanced wear resistance to the multimaterial specimens when compared with the mono-material NiTi structures. These multi-material structures are a promising solution for providing a customized stiffness and superior wear resistance to NiTi structures to be integrated in innovative orthopedic designs., This work was supported by FCT (Fundação para a Ciência e a Tecnologia) through the grant SFRH/BD/140191/2018 and by project NORTE 01–0145_FEDER-000018-HAMaBICo. Additionally, this work is supported by FCT with the reference project UID/EEA/04436/2019.

The number of patients undergoing joint replacement surgery has progressively increased worldwide due to world population ageing. In the Unites States, for example, the prevalence of hip and knee replacements has increased more than 6 and 10 times, respectively, since 1980. Despite advances in orthopaedic implant research, including the development of novel implantable biomaterials, failures are still observed due to inadequate biomechanical compliance at the bone-implant interface. This comprises static and dynamic mechanical mismatch between the bone and the implant surface. The importance and robustness of biomechanical cues for controlling osteogenic differentiation of mesenchymal stem cells (MSC) have been highlighted in recent studies. However, in the context of bone regenerative medicine, it remains elusive how mechanobiological signals controlling MSC osteogenic differentiation dynamics are modulated in their interaction with the bone and with implants. In this review, we highlight recent technological advances aiming to improve host bone-implant interactions based on the osteogenic and mechanoresponsive potential of MSC, in the context of joint replacement surgery. First, we discuss the extracellular and intracellular mechanical forces underlying proper receptivity and stimulation of physiological MSC differentiation and linked osteogenic activity. Second, we provide a critical overview on how this knowledge can be integrated towards the development of biomaterials for improved bone-implant interfaces. Third, we discuss cross-disciplinarily which contributes to the next generation design of novel pro-active orthopaedic implants and their implantation success. Graphical Abstract.

The aim of this study was to characterize the mechanical properties of a bioactive-modified polyetheretherketone (PEEK) manufacturing approach for dental implants and to compare the in vitro biological behavior with titanium alloy (Ti6Al4V) as the reference. PEEK, PEEK with 5% hydroxyapatite (HA), PEEK with 5% beta-tricalcium phosphate (βTCP), and Ti6Al4V discs were produced using hot pressing technology to create a functionally graded material (FGM). Surface roughness values (Ra, Rz), water contact angle, shear bond strength, and Vickers hardness tests were performed. Human osteoblasts and gingival fibroblasts bioactivity was evaluated by a resazurin-based method, alkaline phosphatase activity (ALP), and confocal laser scanning microscopy (CLSM) images of fluorescent-stained fibroblasts. Morphology and cellular adhesion were confirmed using field emission gun-scanning electron microscopy (FEG-SEM). Group comparisons were tested using analysis of variance (Tukey post hoc test), α = .05. All groups presented similar roughness values (P > .05). Ti6Al4V group was found to have the highest contact angle (P < .05). Shear bond strength and Vickers hardness of different PEEK materials were similar (P > .05); however, the mean values in the Ti6Al4V group were significantly higher when compared with those of the other groups (P < .05). Cell viability and proliferation of osteoblast and fibroblast cells were higher in the PEEK group (P < .05). PEEK-βTCP showed the highest significant ALP activity over time (P < .05 at 14 days of culture). An enhanced bone and soft-tissue cell behavior on pure PEEK was obtained to the gold standard (Ti6Al4V) with equivalent roughness. The results substantiate the potential role of chemical composition rather than physical properties of materials in biological responses. The addition of 5% HA or βTCP by FGM did not enhance PEEK mechanical properties or periodontal cell behavior.

Adding a biological apatite layer to the implant surface enhances bone healing around the implant. Objective This study aimed to characterize the mechanical properties and test human gingival fibroblasts behavior in contact with Zirconia and Titanium bioactive-modified implant materials. Methodology 6 groups were considered: Titanium (Ti6Al4V), Ti6Al4V with 5% HA and 5% ßTCP, Zirconia (YTZP), YTZP with 5% HA and 5% ßTCP. For each group, we produced discs using a novel fabrication method for functionally graded materials, under adequate conditions for etching and grit-blasting to achieve equivalent surface microroughness among the samples. Surface roughness (Ra, Rz), water contact angle, shear bond strength, and Vickers hardness were performed. Human gingival fibroblasts immortalized by hTERT gene from the fourth passage, were seeded on discs for 14 days. Cell viability and proliferation were assessed using a resazurin-based method, and cellular adhesion and morphology using field emission gun scanning electron microscopy (FEG-SEM). After 3 days of culture, images of fluorescent nucleic acid stain were collected by confocal laser scanning microscopy (CLSM). Results Results were presented as mean ± standard deviation (SD). We compared groups using one-way ANOVA with Tukey’s post-hoc test, and significance level was set at p

Osseointegration is defined by a stable and functional union between bone and a surface of a material. This phenomenon is influenced by the geometric and surface characteristics of the part where the bone cells will attach. A wide variety of studies proves that ceramic materials are strong competitors against conventional metals in the scope of bone tissue engineering. Ceramic scaffolds, porous structures that allow bone ingrowth, have been studied to enhance the osseointegration phenomenon. Geometric and dimensional parameters of the scaffold have influence in its performance as mechanical and structural supporter of bone growth. However, these parameters are conditioned by the manufacturing process by which these scaffolds are obtained. Several studies focusing on the production process of ceramic scaffolds have been developed, using 3D printing, stereolithography, selective laser sintering, green machining, robocasting, and others. The main purpose of this work is to evaluate and compare the different manufacturing processes by which ceramic scaffolds can be produced. This comparison addresses scaffold parameters like pore size, pore shape, porosity percentage, roughness, and so forth. Additionally, the different materials used in different manufacturing processes are also mentioned and discussed given its influence on a successful osseointegration while simultaneously displaying adequate mechanical properties. After making a screening on the available ceramic scaffolds manufacturing processes, several examples are presented, proving the potential of each of these manufacturing process for a given scaffold geometry.

Nickel-titanium (NiTi) cellular structures are a very promising solution to some issues related to orthopaedic implant failure. These structures can be designed and fabricated to simultaneously address a combination of mechanical and physical properties, such as elastic modulus, porosity, wear and corrosion resistance, biocompatibility and appropriate biological environment. This ability can enhance the modest interaction currently existing between metallic dense implants and surrounding bone tissue, allowing long-term successful orthopaedic implants. For that purpose, NiTi cellular structures with different levels of porosity intended to reduce the elastic modulus were designed, modelled, selective laser melting (SLM) fabricated and characterized. Significant differences were found between the CAD design and the SLM-produced NiTi structures by performing systematic image analysis. This work proposes designing guidelines to anticipate and correct the systematic differences between CAD and produced structures. Compressive tests were carried out to estimate the elastic modulus of the produced structures and finite element analyses were performed, for comparison purposes. Linear correlations were found for the dimensions, porosity, and elastic modulus when comparing the CAD design with the SLM structures. The produced NiTi structures exhibit elastic moduli that match that of bone tissue, which is a good indication of the potential of these structures in orthopaedic implants., This work was supported by FCT (Fundação para a Ciência e Tecnologia) through the grant SFRH/BD/128657/2017 and the projects POCI-01-0145-FEDER-030353 (SMARTCUT), NORTE 01–0145_FEDER000018-HAMaBICo, UID/EEA/04436/2019 and UID/Multi/04044/2019.

The high temperatures generated in the cutting zone during machining processes results in an increase of wear mechanisms, reducing the lifetime of cutting tools. In this sense, cutting tools industry is constantly looking for new ways to reduce this temperature. This work proposes a novel cemented carbide cutting tool design and fabrication process for enhancing these tools thermal conductivity. This design incorporates copper heat sinks in designated strategic locations, fabricated using innovative laser green compacts machining. A thermal conductivity of 127 W/m.K was obtained for WC-Co/Cu, considerably higher than that of WC-Co (36 W/m.K). This approach for obtaining WC-Co/Cu cutting tools was found effective for increasing locally the thermal conductivity, especially in the cutting zone vicinity., This work was supported by FCT (Fundação para a Ciência e a Tecnologia) through the project POCI-01-0145-FEDER-030353 (SMARTCUT) and also by the project NORTE 01-0145, FEDER-000018 (HAMaBICo). Additionally, this work is supported by FCT with the reference project UID/EEA/04436/2019. The authors would like to thank Miguel Ângelo Neto and Filipa Oliveira from University of Aveiro for helping in the 3D optical profilometry analysis.

The amount of hip revision surgeries is significantly increasing due to the loss of fixation between implant and bone, that leads to implant failure. The stiffness mismatch between Ti6Al4V hip implants and bone tissue, the non-uniform implant-bone contact pressure, and the poor wear resistance of Ti6Al4V are pointed as three critical issues that contribute to these implant's failure. In this study, a multi-material design and fabrication concept was exploited aiming to change traditional manufacturing paradigms, by allocating different biomaterials in a single component targeting a multi-functional hip implant. Selective Laser Melting technology was explored to fabricate NiTi-Ti6Al4V multi-material cellular structures with a Ti6Al4V inner region and a NiTi outer region. This work was focused on the SLM fabrication and processing parameters validation on a commercial SLM equipment. The morphological analyses allowed to assess a successful solidification and bond between NiTi and Ti6Al4V materials in the transition region. The shear tests revealed a high bond strength of the transition region with an average strength of 33 MPa. The nano-indentation results showed that the Ti6Al4V region exhibits a higher hardness and elastic modulus when compared with the NiTi region. This work is a part of a broader objective that aims to create a NiTi-Ti6Al4V multi-material and cellular structured hip implant capable to provide customized stiffness, superior wear resistance and a controlled NiTi outer region volume change., This work was supported by FCT (Fundação para a Ciência e a Tecnologia) through the grant SFRH/BD/128657/2017 and the projects PTDC/EMS-TEC/5422/2014_ADAPTPROSTHESIS and UID/EEA/04436/2019.

In the present study, mono- and multi-material laser textured Ti6Al4V implants are manufactured and characterized in vivo to explore their applicability in orthopedic implants. Laser surface texturing is used for manufacturing grooved Ti6Al4V implants while a pressure-assisted sintering technique is employed to impregnate beta-tricalcium phosphate into grooves for an improved bioactivity. After implantation into Sprague Dawley rat's femur for 4 and 12 weeks, bone-implant fixation and osseointegration are assessed, by performing push-out tests and histological characterization. Histological characterization showed bone formation around all implants, characterized by immature bone at 4 weeks of implantation and a more mature bone after 12 weeks. The maximum push-out forces are higher for the textured and multi-material solution, when compared to non-textured implants right after 4 weeks of implantation (p < 0.05). After 12 weeks, multi-material implant displayed higher fracture energy when compared to non-textured implants (p < 0.05). Results revealed that laser surface texturing and bioactive multi-material solutions are highly effective to promote bone regeneration and enhance bone-implant fixation for further application in orthopedic implants. published

In today’s manufacturing, selective laser melting (SLM) enables the production of 3D metal parts with innovative designs. However, this technique is still limited to certain materials due to residual stresses and cracking. The ultra-low carbon maraging steel 18Ni300 is a proven steel for SLM processing, while H13 steel still presents some challenges due to cracking and low wettability. These two steels are currently used in mould making due to their mechanical properties. Aiming to compare and better understand the behaviour of these two steels manufactured by selective laser melting, their mechanical performance and dry sliding wear were investigated. Both steels processed by SLM exhibited the expected yield stress and tensile strength values, suitable for mould making. Dry sliding wear tests performed using a pin-on-disc apparatus, where pins of steel were pressed against discs of polypropylene reinforced with 40 wt% short E-glass fibres, showed that the H13 steel had a specific wear rate two orders of magnitude lower than the 18Ni300 steel (0.11 × 10-7 mm3 /m.N). The wear mechanism of the 18Ni300 steel is abrasion, while fatigue plays the main role in the H13 steel. The results of this work allow to establish a correlation between the obtained microstructure, mechanical behaviour and tribological performance of both steels under the tested conditions and show that the H13 steel, processed by SLM, can be a good choice for the critical zones of moulds where a higher wear resistance is required. published

The development of new approaches to improve the implant integration and subsequently its long-term maintenance is an actual challenge. In this way and trying to mimic natural bone composition, HAp-functionalized zirconia surfaces were produced by means of hybrid laser technique combining additive (laser sintering) and subtractive (laser machining) processes. Nd:YAG laser-generated textures were created to improve mechanical interlocking of hydroxyapatite (HAp) powder and consequently enhance its adhesion to zirconia surface. Different laser parameters and also different approaches were tested to optimize the textured line-patterning of zirconia surface. The created microtextures were characterized by Scanning Electron Microscopy (SEM). Furthermore, textured zirconia surfaces were functionalized with HAp by means of CO2 laser. Different power and scan speed laser parameters were tested to promote HAp retention inside of line-patterning. The results showed that it is possible to design the textured surface by changing energy density and atmosphere. Furthermore, high amount of retained and sintered bioactive material was found when high laser power and low scan speed were performed.

Bioactive ceramic coatings have been proposed to improve the bioactivity of zirconia although the coating detachment can occur during implant placement. The main aim of this study was to enhance bioactivity and strength of the implant surface by using a gradated bioactive zirconia structure. Zirconia discs (8 × 3 mm) embedding gradual content of hydroxyapatite (YTZP-HA) or beta-tricalcium phosphate (YTZP-βTCP) were produced by hot-pressing technique. Specimens were initially studied regarding hardness, roughness, wettability, and shear bond strength of the gradated zone. Functionally gradated ceramic discs and zirconia (control group) were placed in contact with human osteoblast culture for 1, 3, 7, and 14 days. Field emission guns scanning electron microscopy (FEGSEM) was used to assess the morphology and adhesion of osteoblasts while cell viability was assessed by fluorometric method. The mineralization on the test and control discs was evaluated by Alkaline phosphatase (ALP) activity and fluorescent microscopy. Shear strength mean values of the outer layer bioactive ceramic and zirconia bulk were recorded at 150 MPa. Mechanical assays demonstrated that the novel design and manufacturing approach proposed for producing gradated zirconia embedding bioactive ceramics resulted in significantly higher mechanical strength as compared to monolithic zirconia. Also, cell viability and ALP levels increased on gradated zirconia containing HA or βTCP over time. Gradated zirconia containing hydroxyapatite revealed an increased viability, bioactivity, and mineralization of human osteoblasts when compared to conventional zirconia surface, without substantial loss of strength.

Made available in DSpace on 2020-12-12T01:09:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-12-01 Ti6Al4V cellular structures were produced by selective laser melting (SLM) and then filled either with beta-tricalcium phosphate (β-TCP) or PEEK (poly-ether-ether-ketone) through powder metallurgy techniques, to improve osteoconductivity and wear resistance. The corrosion behavior of these structures was explored considering its importance for the long-term performance of implants. Results revealed that the incorporation of open cellular pores induced higher electrochemical kinetics when being compared with dense structures. The impregnation of β-TCP and PEEK led to the creation of voids or gaps between the metallic matrix and the impregnated material which also influenced the corrosion behavior of the cellular structures. Center for Micro Electro Mechanical Systems (CMEMS) University of Minho (UMinho) MIT Portugal Program School of Engineering University of Minho Centre for Rapid and Sustainable Product Development Polytechnic Institute of Leiria Rua General Norton de Matos IBTN/Br – Brazilian Branch of the Institute of Biomaterials Tribocorrosion and Nanomedicine UNESP Campus de Bauru Av. Eng. Luiz Edmundo Carrijo Coube, 14-01 IBTN/Br – Brazilian Branch of the Institute of Biomaterials Tribocorrosion and Nanomedicine UNESP Campus de Bauru Av. Eng. Luiz Edmundo Carrijo Coube, 14-01

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.

Nano and micro-sized metal particles are interesting solutions for several applications, from electronics to biomedical fields. In recent years, MgO has been gaining attention due to its nontoxicity and antibacterial activity, making this an interesting material for implants coating for instance. This study aims the fabrication/preparation of nanoparticles by laser ablation in liquid from the Mg bulk. The influence of liquid media and laser energy on the morphology, size and properties of the obtained nanoparticles was assessed. A Nd:YAG nanosecond laser of 1064 nm of wavelength at different laser energies was employed to irradiate Mg target in three environments (distilled water+SDS, ethanol and propanol). Ultraviolet–visible (UV–vis) absorption spectrophotometry, scanning electron microscopy with a transmission electron detector (STEM) and transmission electron microscopy (TEM) were used for characterizing the obtained particles, viz. particles’ mean size and size distribution. The composition of the obtained nanoparticles was analyzed by SAED patterns. The results showed that the characteristics of the obtained nanoparticles were prominently influenced by varying laser energy and liquid medium. The smaller particles are obtained when using ethanol and propanol (having 16.7 nm and 15.3 nm respectively), as compared to distilled water+surfactant.

Orthopaedic implants for load-bearing applications are usually composed of titanium-based materials. Aiming to propose a strategy able to improve the bone-implant interface on these implants, commercially pure titanium and Ti6Al4V alloy were subjected to anodic oxidation, hydrothermal treatment and to anodic oxidation followed by hydrothermal treatment and the produced oxide film was investigated. In addition, different mechanical (as-received vs mechanical polished) and chemical pre-treatments (alcohol cleaning vs acidic pre-treatment) were studied. No significant differences were found between the chemical pre-treatments, whereas upon different surface treatments the TiO2 layer presented different characteristics, namely regarding its crystallinity, roughness, thickness and wettability. The hydrothermal treatment followed by immersion for 24 h in 5XPBS was effective in creating a potentially bioactive oxide film, given the presence of anatase and rutile phases, and a hydrophilic layer for both Ti materials. Ti grade 2 subjected to alcohol cleaning and hydrothermal treatment resulted in a surface roughness of 226.7 ± 3.1 nm and water contact angle of 67.2 ± 8.7°, whereas for the Ti grade 5 subjected to the same surface treatment, Ra was equal to 20.4 ± 1.7 nm and the water contact angle to 83.5 ± 4.7°. In this context, the hydrothermal treatment is proposed as a simple treatment capable of improving the characteristics of the implant surface, thereby promoting osteoconductivity.

Cobalt is nowadays the most used binding material for diamond cutting tools (DCTs), once it grants a suitable retention of diamond particles during in-service conditions. However, cobalt is an expensive and toxic material, being thus necessary to find effective alternatives that suit the requirements of this tool. In this context, this study focuses on the production of different nickel-cobalt-based materials, aiming to decrease cobalt content in cutting tools. Unreinforced Ni-Co-based materials (Ni-Co; Ni-Co-WC; Ni-Co-Cr3C2) and also Ni-Co-based materials reinforced with 4 wt% of diamond particles were produced by hot pressing, with a sintering temperature of 900 °C, under a pressure of 70 MPa, during 15 min. These materials were characterized regarding their microstructure, hardness, and shear strength. In order to assess these materials, tribological properties, and cutting performance, pin-on-disc wear tests, with the diamond-reinforced Ni-Co-based materials serving as pin and a stone serving as disc, were also performed. Results revealed that the best cutting performance was displayed by diamond-reinforced Ni-Co-WC, having the highest disc/pin wear ratio among the produced materials.

This work presents a comprehensive study on the influence of three different processing technologies (Selective Laser Melting, Hot Pressing and conventional casting) on the microstructure, mechanical and wear behavior of an austenitic 316L Stainless Steel. A correlation between the processing technologies, the obtained microstructure and the mechanical and wear behavior was achieved. The results showed that the highest mechanical properties and tribological performance were obtained for 316L SS specimens produced by Selective Laser Melting, when compared to Hot Pressing and conventional casting. The high wear and mechanical performance of 316L Stainless Steel fabricated by Selective Laser Melting are mainly due to the finer microstructure, induced by the process. In this sense, Selective Laser Melting seems a promising method to fabricate customized 316L SS implants with improved mechanical and wear performance.

The current trend to replace cobalt in diamond cutting tools (DCT) for stone cutting has motivated the study of alternative materials for this end. The present study characterizes several copper-nickel-based materials (Cu-Ni; Cu-Ni-10Sn, Cu-Ni-15Sn, Cu-Ni-Sn-2WC and Cu-Ni-Sn-10WC) for using as matrix material for diamond cutting tools for stone. Copper-nickel-based materials were produced by hot pressing, at a temperature of 850 °C during 15 min and under an applied pressure of 50 MPa. The mechanical properties were evaluated though the shear strength and hardness values. The microstructures and fracture surfaces were analyzed by SEM. The wear behavior of all specimens was assessed using a reciprocating ball-on-plate tribometer. The hot pressing produced compacts with good densification. Sn and WC promoted enhanced mechanical properties and wear performance to Cu-Ni alloys. Cu-Ni-10Sn and Cu-Ni-10Sn-2WC displayed the best compromise between mechanical and wear performance.

The aim of this work was to study the influence of the processing route on the microstructural constituents, hardness and tribological (wear and friction) behavior of Ti6Al4V biomedical alloy. In this sense, three different processing routes were studied: conventional casting, hot pressing and selective laser melting. A comprehensive metallurgical, mechanical and tribological characterization was performed by X-ray diffraction analysis, Vickers hardness tests and reciprocating ball-on-plate wear tests of Ti6Al4V/Al 2 O 3 sliding pairs. The results showed a great influence of the processing route on the microstructural constituents and consequent differences on hardness and wear performance. The highest hardness and wear resistance were obtained for Ti6Al4V alloy produced by selective laser melting, due to a markedly different cooling rate that leads to significantly different microstructure when compared to hot pressing and casting. This study assesses and confirms that selective laser melting is potential to produce customized Ti6Al4V implants with improved wear performance.

The current trend to replace cobalt in diamond cutting tools (DCTs) for stone cutting has motivated the study of alternative materials for this end. The present study evaluated the performance of several diamond-reinforced copper–nickel composites as regard to their suitability for serving as stone cutting materials. Cobalt (Co) and copper–nickel composites (Cu–Ni; Cu–Ni–10Sn, Cu–Ni–15Sn, Cu–Ni–Sn–2WC, and Cu–Ni–Sn–10WC) reinforced with 4 wt% of diamond particles were produced by hot pressing, at a temperature of 850 °C during 15 min and under an applied pressure of 50 MPa. The obtained specimens were characterized in terms of Vickers hardness and shear strength. The microstructure was analyzed by the means of SEM/EDS. A pin-on-disc wear test, with the composite serving as pin and a stone serving as disc, was performed in order to assess the tribological properties and cutting performance. Cu–Ni–Sn–10WC showed to be the material with the best cutting properties, with the highest disc/pin wear ratio registered among the remaining competing materials. This material arises as a promising alternative to be used in the stone cutting industry.

This study is concern with tribocorrosion behaviour of Ti6Al4V-HA biocomposites. The Ti6Al4V composites reinforced with different contents of hydroxyapatite (HA) particles 5–15%, vol%) were produced by hot pressing technique. The tribocorrosion tests were performed by using a ball-on-plate configuration in artificial saliva at 37 °C. The tests were carried out under open circuit potential (OCP), with a sliding duration of 1800 s, 1 N normal load and 1 Hz frequency. The open circuit potential and wear mechanisms for all tested biocomposites are presented and discussed. The results suggest that HA plays a relevant role on tribocorrosion behaviour of Ti6Al4V-HA composites. All composites samples presented better wear resistance and also a relatively lower tendency to corrosion with increasing HA content.

The development of high damping materials for noise reduction and attenuation of vibration on structural applications, such as automotive and aerospace industries, has been investigated. This experimental study is concerned with the damping capacity (tan delta) and dynamic Young's modulus (|E*|) of Silicon carbide (SiC) reinforced aluminium (Al) matrix composite. AlSi-SiCp composite was produced by hot pressing technique. Damping capacity and dynamic Young's modulus of composite and unreinforced AlSi alloy were studied using a dynamic mechanical analyser (DMA), over a temperature range of room temperature-400 °C (during heating and cooling phases), at 1 and 20 Hz. AlSi-SiCp composite showed higher damping capacity and dynamic Young's modulus than the AlSi unreinforced alloy. Furthermore, damping capacity was found to increase with temperature, while modulus decreases. The possible damping mechanisms are presented and discussed.

Aluminum-silicon (AlSi) composite reinforced with 20 wt% Ni particulates was produced by hot pressing and characterized using nanoindentation. Energy dispersive spectrometry and X-ray diffraction analyses showed that Al3Ni intermetallic was formed in the interface between Ni particulates and AlSi matrix. Chemical composition, hardness, and elastic modulus were studied along the interface from inner (near Ni) to outer (near AlSi) regions. A uniform composition was found throughout the interface, having 805.6 HV hardness and elastic modulus of 185.4 GPa. Interface properties have a crucial influence on the composite performance and their assessment is of paramount importance on composite properties estimation using predictive models.