Project

ADITIMAT "Additive Manufacturing: from Material to Application"

Goal: R&D Programme funded by the Regional Government of Madrid and the European Union, focused on Additive Manufacturing (Reference S2018/NMT-4411).

The Programme involves 6 research groups from public Universities and research centers in Madrid (URJC, UCM, UC3M, UPM and CSIC) and 5 laboratories that provide technical support.

Date: 1 January 2019 - 31 December 2022

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Project log

Javier Bedmar
added 2 research items
Aluminum matrix composites reinforced with carbon fiber have been manufactured for the first time by infiltrating an A413 aluminum alloy in carbon fiber woven using high-pressure die casting (HPDC). Composites were manufactured with unidirectional carbon fibers and with 2 × 2 twill carbon wovens. The HPDC allowed full wetting of the carbon fibers and the infiltration of the aluminum alloy in the fibers meshes using aluminum at 680 °C. There was no discontinuity at the carbon fiber-matrix interface, and porosity was kept below 0.1%. There was no degradation of the carbon fibers by their reaction with molten aluminum, and a refinement of the microstructure in the vicinity of the carbon fibers was observed due to the heat dissipation effect of the carbon fiber during manufacturing. The mechanical properties of the composite materials showed a 10% increase in Young's modulus, a 10% increase in yield strength, and a 25% increase in tensile strength, which are caused by the load transfer from the alloy to the carbon fibers. There was also a 70% increase in elongation for the unidirectionally reinforced samples because of the finer microstructure and the load transfer to the fibers, allowing the formation of larger voids in the matrix before breaking. The comparison with different mechanical models proves that there was an effective load transference from the matrix to the fibers.
Sandra Cifuentes
added a research item
Magnesium scaffolds are biodegradable, biocompatible, bioactive porous scaffolds, which find applications within tissue engineering. The presence of porosity increases surface area and enhances cell proliferation and tissue ingrowth. These characteristics make Mg scaffolds key materials to enhance the healing processes of tissues such as cartilage and bone. However, along with the increment of porosity, the corrosion of magnesium within a physiological environment occurs faster. It is, therefore, necessary to control the degradation rate of Mg scaffolds in order to maintain their mechanical properties during the healing process. Several studies have been performed to increase Mg scaffolds’ corrosion resistance. The different approaches include the modification of the Mg surface by conversion coatings or deposited coatings. The nature of the coatings varies from ceramics such as hydroxyapatite and calcium phosphates to polymers such as polycaprolactone or gelatin. In this work, we propose a novel approach to generating a protective bilayer coating on the Mg scaffold surface composed of a first layer of naturally occurring Mg corrosion products (hydroxide and phosphates) and a second layer of a homogeneous and biocompatible coating of polylactic acid. The Mg scaffolds were fabricated from Mg powder by means of powder metallurgy using ammonium bicarbonate as a space holder. The size and amount of porosity were controlled using different size distributions of space holders. We addressed the influence of scaffold pore size on the conversion and deposition processes and how the coating process influences the in vitro degradation of the scaffolds
Javier Bedmar
added a research item
The presence of defects like porosity and lack of fusion can negatively affect the properties of the materials manufactured by Selective Laser Melting (SLM). The optimization of the manufacturing conditions allows reducing the number of defects, but there is a limit for each manufacturing material and process. To expand the manufacturing envelope, a remelting after every layer of the SLM process has been used to manufacture Ti6Al4V alloy samples using an SLM with a CO2 laser. The effect of this processing method on the microstructure, defects, hardness, and, especially, the corrosion properties was studied. It was concluded that the laser remelting strategy causes an increment of the α and β phases from the dissolution of metastable α'. This technique also provokes a decrease in the number of defects and a reduction of the hardness, which are also reduced with lower scanning speeds. On the other hand, all the corrosion tests show that a low scanning speed and the laser remelting strategy improve the corrosion resistance of the Ti6Al4V alloy since parameters like the Open Circuit Potential (OCP) and the Polarization Resistance (Rp) are nobler and the mass gain is lower.
Javier Bedmar
added a research item
In additive manufacturing (AM), the technology and processing parameters are key elements that determine the characteristics of samples for a given material. To distinguish the effects of these variables, we used the same AISI 316L stainless steel powder with different AM techniques. The techniques used are the most relevant ones in the AM of metals, i.e., direct laser deposition (DLD) with a high-power diode laser and selective laser melting (SLM) using a fiber laser and a novel CO2 laser, a novel technique that has not yet been reported with this material. The microstructure of all samples showed austenitic and ferritic phases, which were coarser with the DLD technique than for the two SLM ones. The hardness of the fiber laser SLM samples was the greatest, but its bending strength was lower. In SLM with CO2 laser pieces, the porosity and lack of melting reduced the fracture strain, but the strength was greater than in the fiber laser SLM samples under certain build-up strategies. Specimens manufactured using DLD showed a higher fracture strain than the rest, while maintaining high strength values. In all the cases, crack surfaces were observed and the fracture mechanisms were determined. The processing conditions were compared using a normalized parameters methodology, which has also been used to explain the observed microstructures.
Antonio Javier Sánchez-Herencia
added a research item
To soften the extreme sintering conditions of Tungsten Carbide (WC), a 3 wt.% of metallic nickel (Ni) was added to the starting powders. To ensure a fair distribution of the second phase and an intimate mixture of the phases, the colloidal process was adopted. A commercial Ni and a in-house synthesised nanosized nickel were used as sintering aids. Rheological studies allowed a high dispersion of the nickel in the final composite powders. Sintering studies by Hot-Pressing route (HP) proved the great benefices of Ni as a sintering aid, decreasing the maximum temperature necessary to achieve full densification, from 1900 to 1450 °C and dwell times from 20 to 7 min. Among all the materials obtained, the best results in terms of density, microstructure and properties were obtained for WC-nNi, which achieved hardness of 14.8 GPa and toughness comparable to conventional cermets with much higher content of metallic phase.
Juan José Moreno Labella
added a research item
In Blister-Actuated Laser-Induced Forward Transfer (BA-LIFT), a laser pulse generates a blister in an intermediate polyimide layer to push away the fluid. In this work, a Phase Field model has been proposed to study the transference mechanisms. Simulations and experimental shadowgraphy images for BA-LIFT of water-glycerol mixtures have been compared. The transference mechanism in BA-LIFT is ideally only mechanical and does not explain some secondary effects in the jet expansion that have already been described in other LIFT techniques and associated with the cavitation of a thermally generated vapor bubble. The numerical model can reproduce the expansion of the main jet. The addition of a second push at 9 μs delay allows reproducing the secondary effects. Four possible causes of the second push have been studied: absorption of the laser pulse in the fluid, thermal conduction through the polyimide layer, a mechanical rebound of the elastically deformed blister, or pressure fall due to fluid velocity. After the analysis, the first three explanations have been rejected, and a hypothesis is proposed: the velocity field generated by the blister produces a cavitation bubble in the interface between the polyimide layer and the fluid, whose effects would be the same than the cavitation of the vapor bubble in other LIFT techniques.
Sandra Cifuentes
added 2 research items
This chapter is focused on some of the most important polymers used for preparing hybrid materials applied in biomedicine. The work is divided into two parts: Non-degradable polymers used for hybrid materials in implants and degradable polymers employed to fabricate biomedical implants and devices. Each part describes the main characteristics of these structures, followed by a list of the most significant polymers and derivatives. This brief introduction could be useful for industry, students, or people interested in the recent advances of biomedical applications where polymers play an important role.
The potential of bioresorbable metals to revolutionize current and future medical devices fascinates researchers. Magnesium, iron, and zinc have been thoroughly studied for the treatment of cardiovascular diseases or to repair fractures. Iron was the first type of metal being researched and introduced in biomedical applications. Magnesium is the most studied one, it has been tested by clinical trials and commercially available products have been already developed. The interest in zinc has recently emerged and is continuously growing. This chapter offers an overview of the role that Mg, Fe, and Zn are playing advancing the evolution of bioresorbable implants.
Antonio Javier Sánchez-Herencia
added 6 research items
A heterocoagulation route is proposed to prepare Reduced Graphene Oxide-Nickel Oxide (RGO/NiO) hybrid structures for their application as supercapacitor electrodes. The RGO intercalation among the NiO nanoplatelets was carried out by electrostatic interactions of the synthetized particles which were previously dispersed and stabilized in aqueous media to improve the assembly between both materials forming core-shell structures. The electrophoretic deposition (EPD) was used to shape the composite onto 3D collector (Ni foams) controlling their growth and homogeneity. Electrodes were thermal treated at 325 °C during 1 h to improve the electrochemical response since the formation of ceramic necks among NiO semiconductor nanoparticles preserves the microstructural integrity to enhance their connectivity avoiding the employment of binders, while RGO contributes with the electrochemical double layer effect to step up the specific capacitance by reducing the charge transfer resistance. FESEM results confirmed that RGO nanosheets were full-covered by the NiO nanoplatelets and suggested that ∼1 mg of the electroactive composite homogeneously covers the Ni foam and it is the optimum among of electroactive material to avoid microstructural defects that produce ohmic drops limiting the capacitance. The electrochemical characterization of the resulting binder-free RGO/NiO electrodes was compared with the bare-NiO electrode. The hybrid composite exhibited excellent performance with a high specific capacitance of 940 F g ⁻¹ at 2 Ag ⁻¹ and a higher rate capability.
Titanium oxide-based photocatalytic filters were produced by Fused Deposition Modelling (FDM) using biopolymers obtained from renewable biomass resources. The thermoplastic route allows shaping composites through the immobilization of photoactive TiO 2 nanoparticles in an environmentally friendly bioplastic such as the polylactic acid (PLA). Composites with an inorganic charge of 30 wt% of TiO 2 nanoparticles (NPs) exhibit a 100% methyl orange (MO) degradation after 24 h of light exposition due to the extremely uniform dispersion of the nanophase within the polymer matrix in the FDM feedstock. Surface modification of TiO 2 NPs allows the optimization of the colloidal dispersion and stabilization of the inorganic charge in a PLA solution and hence, the optimal distribution of nano-photoactive points in the TiO 2 /PLA filaments and scaffolds. The proposed new route of processing improves the dispersion of nano-charges comparing with the traditional thermo-pressing routes used for mixing thermoplastics based composites, avoiding the thermal degradation of the polymer and providing a customised product. In this manuscript the evolution of photodegradation with the increase of TiO 2 content in the composite and the variation of the filter geometry was evaluated.
The formulation, development and optimization of water-based inks of platelet-like nanoparticles are the main objective of this work. As-synthesized Ni(OH) 2 nanoparticles were dispersed and stabilized in aqueous suspension by PEI addition. The combination of DEG (cosolvent) with H 2 O shows the ideal values of surface tension and viscosity for piezoelectric inkjet printing, which exhibits a homogeneous jetting flow of the nanoplatelets suspension. The printed nanostructure was sintered at low temperature (325 °C) and the electrochemical overview of NiO electrode behavior was described. These printable pseudocapacitors tested by a three-electrode cell have showed a competitive specific capacitance, leading 92% and 78% of capacitance retention for 2000 cycles at scan rates of 1 and 2 A/g respectively, and a coulombic efficiency of 100%. The initial performance of this printed NiO pseudocapacitor can be compared with others prepared by conventional methods. This new finding is expected to be particularly useful for the designing of micro-pseudocapacitors.
Sandra Cifuentes
added a research item
Prosthetic Joint Infections (PJI) are one of the most dangerous and devastating complications following total joint replacement, with important implications for patient health and high costs for Public Health. Fungi infections are a concern for the orthopedic community due to their recent increasing incidence and their resistance to antifungals. Nowadays, these infections are prevented by the prophylactic administration of antifungals. In this research, we propose an alternative to this approach through the local prevention of the infections using coatings deposited on the implants and loaded with antifungals. In this manner, new biodegradable coatings were synthesized with antifungals incorporation for the drug local release. Coatings were prepared using sol-gel technology based on 3-(trimethoxysilyl)propyl methacrylate (MAPTMS) and tetramethyl orthosilicate (TMOS). Two different fungicides (fluconazole and anidulafungin) were separately introduced at different concentrations. Coatings were deposited on powder metallurgical titanium (TiPM) substrates by dip-coating technique. After determination of the optimal synthesis parameters to obtain homogeneous films, coatings were physicochemically characterized by Scanning Electron Microscopy (SEM), ²⁹Si Nuclear Magnetic Resonance (²⁹Si NMR), Thermogravimetric analysis (TGA), Contact Angle measurements and Electrochemical Impedance Spectroscopy (EIS) tests. Studies of drug release, cytotoxicity, biofilm inhibitory capacity, and hydrolytic degradation were also performed. This study demonstrated that the release of the physically-trapped in the polysiloxane network antifungals is proportional to the degradation of the coatings. In addition, the degradation kinetics in fluconazole-laden coatings were different from those loaded with anidulafungin and depended on the chosen precursors and their molar ratio and the molecular weight and concentration of the incorporated drug. Synthesized coatings loaded with anidulafungin are presented as an alternative to prevent PJI since in vitro tests performed demonstrated their non-cytotoxicity accompanied by antifungal effectiveness.
Eduardo Tabares
added a research item
MAX phases exhibit excellent combination of ceramic and metallic-like properties. In this work, MAX phase Ti3SiC2 powder was synthesized starting-off with different combinations of elemental powders and carbides. The powders used were Ti, Si, C, SiC and TiC in different combinations, molar ratios and powder size. Powders were heat treated on a vacuum furnace for different times and temperatures for in situ production of the Ti3SiC2 MAX phase. High purity synthesized samples were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) in order to identify and quantify the different phase constituents present. The main phase constituents in the powders produced were Ti3SiC2 and TiSi2. Up to 94% of Ti3SiC2 MAX phase was obtained using Ti:SiC:C as starting powders in a molar ratio of 3:1.5:0.5. Different phase constitution was observed on the surface and the centre of the samples. An optimal starting powder composition, molar ratio, heat treatment temperature and time is proposed for the formation of high purity Ti3SiC2 MAX phase. Selected mixture was studied thermodynamically and a reaction mechanism of formation of the MAX phase is proposed.
Marta Muñoz
added 3 research items
This work aims to develop polymer/magnesium composites as new biodegradable and bioresorbable materials for osteosynthesis implants. The polymeric matrix will benefit from the higher strength and modulus of the Mg particles, whereas Mg will benefit from the surrounded protective polymeric matrix that will control its degradation rate. To provide a proof of concept a set of specimens were processed by combining solvent casting of PLLA (poly-I.-lactic acid) loaded with 30 wt% of Mg particles and further molding by compression. Mechanical characterization reveals that reinforcing the polymer matrix with Mg particles improves its mechanical properties (hardness up to 340 MPa and yield strength up to 100 MPa). Interestingly, Young's modulus determined by ultramicroindentation increases up to 8 GPa. From the DSC analysis it follows that the unloaded and loaded polymer has similar crystallinity, which indicates that the improvement in mechanical properties is purely the effect of particle reinforcement.
Stainless steel coatings were deposited by high velocity oxy fuel (HVOF) technique on ZE41 magnesium alloy substrates. Different coatings with different thicknesses were sprayed on the magnesium alloy without causing any degradation on its microstructure and without modifying its mechanical properties. The wear behavior of the 316L stainless steel coatings was tested using the ball-on-disk configuration technique in dry conditions. Bulk 316L stainless steel and ZE41 magnesium alloys were also tested for comparative purposes. In the best conditions, the coatings provided up to 93% more wear resistance than uncoated ZE41 (at low loads and speeds) and only 11% below bulk 316L stainless steel (at high loads and speeds). The number of the layers that formed the coatings brings a change in the predominant wear mechanism through the appearance of a mechanical mixing layer (MML) that significantly reduces the wear rate.
This study shows that the use of polylactic acid polymer (PLA) coatings deposited by dip-coating on AZ31 magnesium alloy can increase the integrity of the system and the fracture toughness of magnesium substrates treated by plasma electrolytic oxidation (PEO). This provides a novel and promising use of a multilayered system made of fully biocompatible materials. The maximum adhesion strength value for PLA coatings on AZ31 was >50% higher than the maximum one for AZ31/PEO/PLA, while the maximum bending strain tripled. The limitations observed in the AZ31/PEO system arise from the brittle nature of the oxides formed during PEO treatments; their negative impact is reduced when incorporating a PLA layer that is capable of filling the pores and sealing the cracks of the PEO layer. PLA coatings reduce corrosion of AZ31 and maintain the corrosion protection provided by the PEO treatments. The characteristics of the PLA coatings on AZ31 Mg alloy and on AZ31/PEO systems were evaluated by using a Taguchi design of experiment (DOE) method using the following processing parameters: (i) number of layers, (ii) withdrawal speed and (iii) polymer concentration. The effect of these three degrees of freedom and, the surface treatment has been evaluated with regards to different properties desired for the coatings, i.e., adhesion, thickness, roughness, and corrosion resistance.
Maria Verde
added a project goal
R&D Programme funded by the Regional Government of Madrid and the European Union, focused on Additive Manufacturing (Reference S2018/NMT-4411).
The Programme involves 6 research groups from public Universities and research centers in Madrid (URJC, UCM, UC3M, UPM and CSIC) and 5 laboratories that provide technical support.