Calcium phosphate-based bioceramics are highly valued in biomedical engineering for their remarkable biocompatibility and ability to promote bone regeneration. Hydroxyapatite (HAp) and zinc-doped R-tricalcium phosphate (xZn-TCP) have both been the subject of extensive research as biomaterials. However, the performance of composites combining these two materials still needs to be optimized. In this study, the HAp-and xZn-TCP-based composites, where x =3mol% and 5mol%, were carried out by mixing in water the two powders previously synthesized through a classical coprecipitation process. The stabilized slurries were slip cast on a plaster support to prepare thin pellets to be sintered. The study focused on two series of Zn-doped HAp/TCP composites containing HAp as the main phase (90 and 80 wt%) and xZn-TCP as the main phase (90 and 80 wt%). Structural analyses confirmed the presence of R-TCP with a rhombohedral structure and HA with a hexagonal structure. Zinc doping significantly improved sinterability, yielding relative densities of up to 99% at 1200 degrees C, particularly for the lower Zn content. Furthermore, zinc stabilized the R-TCP phase, resulting in an increase in the R-TCP -> a-TCP transition temperature to approximately 1420 degrees C. The mechanical study highlighted a positive relationship between increased sample density and optimization of material properties. Indeed, the composite made up of 80% (3 mol% Zn-TCP) and 20% HAp exhibited superior performance, showing the highest value of Young's modulus-135 GPa and the Vickers hardness-5.4 GPa. Along with these mechanical properties, cytotoxic tests performed by means of MTT assay on HEK293 cells showed that all compositions supported cell viability above 100%, thus indicating the absence of any cytotoxic effects. In addition to that, the ability to stimulate cell proliferation is another important property of these materials. Thanks to these unique properties, the materials under discussion have excellent prospects for usage in clinical practice, namely, as dental implants, spinal cages, and bone defect repair sites. (c) 2026 The Author(s). Published by Elsevier Espana, S.L.U. on behalf of SECV. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/ by-nc-nd/4.0/).

The nucleation and growth kinetics of mullite crystal structure prepared from Algerian natural phosphate (NP) and kaolin materials were studied by differential thermal analysis (DTA) and X-ray diffraction (XRD). The XRD patterns showed that mullite, hydroxyapatite and anorthite were the main crystal structures present in mixtures. From DTA results, several thermal characteristics including the crystallization peak temperature, activation energies, were calculated. The DTA results showed that the characteristics temperature and activation energies were reduced when the NP content was increased at the expense of kaolin material. Bulk crystallization was seen in samples with low/moderate and high NP amounts, respectively, with a fixed ( n=m=3 ) and growing ( n=3 and m=3 ) number of nuclei. As a result, it is possible to produce the mullite phase using Algerian kaolin raw material and natural phosphate that can be added as a structural modifier of the growth process.

Developing a nanocomposite that combines the stiffness of hydroxyapatite (HA), a bone-mimicking mineral, with the flexibility, and resorbability of polylactic Acid (PLA), a biodegradable polyester, presents significant potential in bone regeneration applications. The cold sintering process (CSP) offers a novel approach for consolidating HAPLA composite at low temperatures, addressing the co-sintering challenge posed by higher consolidation temperatures requirement for HA compared to PLA's compaction, or extrusion temperatures. This study investigates the effect of HA-to-PLA ratios and the plasticizing effect of PLA on the composite's consolidation behavior and mechanical properties, with a specific focus on HA consolidation within the PLA matrix under CSP conditions at 200 degrees C under 360 MPa pressure. Interestingly, the results revealed that the HA consolidation in composite matrix changes with PLA content and the plasticizing effect has a crucial role in enhancing this consolidation. An optimal HA-to-PLA weight ratio of 80:20 yielded superior HA consolidation and strong interfacial bonding between HA particles and HA and PLA, achieving an ideal mechanical strength and structural integrity balance. Overall, the HA-PLA composites exhibit mechanical strength comparable to human cortical bone, making them suitable for potential biomedical applications.

The field of bone tissue engineering is steadily being improved by novel experimental approaches. Nevertheless, microbial adhesion after scaffold implantation remains a limitation that could lead to the impairment of the regeneration process, or scaffold rejection. The present study introduces a methodology that employs laser-based strategies for the development of antimicrobial interfaces on tricalcium phosphate–hydroxyapatite (TCP-HA) scaffolds. The outer surfaces of the ceramic scaffolds with inner porosity were structured using a femtosecond laser (λ = 800 nm; τ = 70 fs) for developing micropatterns and altering local surface roughness. The pulsed laser deposition of ZnO was used for the subsequent functionalization of both laser-structured and unmodified surfaces. The impact of the fs irradiation was investigated by Raman spectroscopy and X-ray diffraction. The effects of the ZnO-layered ceramic surfaces on initial bacterial adherence were assessed by culturing Staphylococcus aureus on both functionalized and non-functionalized scaffolds. Bacterial metabolic activity and morphology were monitored via the Resazurin assay and microscopic approaches. The presence of ZnO evidently decreased the metabolic activity of bacteria and led to impaired cell morphology. The results from this study have led to the conclusion that the combination of fs laser-structured surface topography and ZnO could yield a potential antimicrobial interface for implants in bone tissue engineering.

Different bonding approaches were considered to develop layered composite ceramics of erbium doped yttrium aluminium garnet (Er:YAG/YAG) by Spark Plasma Sintering. More precisely three different strategies were envisaged, starting either from a stack of powders, pre-sintered or sintered ceramics. Highlighted by Electron Probe Micro Analysis (EPMA) analyses, these approaches led to different designs of interface i.e. doping profiles, linked to the different thermo-mechanical treatments applied, which have an influence on the grain boundary diffusion of erbium ions. The lengths of the diffusion were found to be of 12 mu m, 63 mu m and 140 mu m respectively for fully dense, powder and pre-sintered assembly approaches.

Hydroxyapatite is a well-known bioactive material widely employed in bone regeneration applications. Densifying hydroxyapatite at the nanoscale remains challenging with conventional sintering methods. This investigation focuses on the densification of commercially available nano-hydroxyapatite powders through the cold sintering process, utilizing water, acetic acid, and phosphoric acid solutions as transient liquids under 360 MPa pressure at 200 °C. The study systematically examines the influence of physical parameters of hydroxyapatite powder, liquid nature, and ionic concentrations of acid solutions on densification and microstructural characteristics. The relative density of consolidated samples varied with respect to the ionic concentration of the acid solution. Notably, a maximum relative density of 90% has been achieved for hydroxyapatite cold sintered using 2 M phosphoric acid solution without changing the original phase of hydroxyapatite. Overall, this study offers valuable insights into the impact of liquid chemistry on the densification of hydroxyapatite using the cold sintering technique.

Different bonding approaches were considered to develop layered composite ceramics of erbium doped yttrium aluminium garnet (Er:YAG/YAG) by Spark Plasma Sintering. More precisely three different strategies were envisaged, starting either from a stack of powders, pre-sintered or sintered ceramics. Highlighted by Electron Probe Micro Analysis (EPMA) analyses, these approaches led to different designs of interface i.e. doping profiles, linked to the different thermo-mechanical treatments applied, which have an influence on the grain boundary diffusion of erbium ions. The lengths of the diffusion were found to be of 12 μm, 63 μm and 140 μm respectively for fully dense, powder and pre-sintered assembly approaches.

Complex shapes pieces of Al2O3 can be rapidly shaped by SLA technology. However, debinding and sintering post-shaping steps still involve long working times. Sintering by microwave has been previously studied providing important time-saving in the fabrication processes and finer microstructures. However, debinding processes are still carried out by conventional methods which compromise the time-saving expectative. In this work, microwave debinding has been evaluated. Conventional and microwave debinding were carried out over pieces of Al2O3 shaped by SLA. The thermal cycle for microwave debinding has been optimized according to the organic species' thermal oxidation process limitations. In both cases, thermal treatments for sintering have been ended by conventional and microwave methods. The relative density, microstructure, hardness and Young modulus were measured and analyzed. Samples sintered by different methods show differences in these prop-erties due to the different temperatures that can be reached with the available experimental devices. However, no significant differences are found in any of those properties for samples treated with different debinding methods but after the same sintering process. For example, relative densities of 96% are achieved for conven-tionally sintered samples even if they were previously treated by conventional or microwave debinding. In such cases, hardness value was 20 +/- 7 and 19 +/- 2 GPa respectively and the Young Modulus value was 306 +/- 113 and 335 +/- 71 GPa respectively. According to these results, the microwave is a feasible method for debinding process.

Various efforts have been made to develop antibacterial biomaterials capable of also sustaining bone remodulation to be used as bone substitutes and reduce patient infection rates and related costs. In this work, beta-tricalcium phosphate (β-TCP) was chosen due to its known biocompatibility and use as a bone substitute. Metal dopants were incorporated into the crystal structure of the β-TCP, and disks were produced from this material. Magnesium and strontium, as well as copper and silver, were chosen as dopants to improve the osteogenic and antibacterial properties, respectively. The surface of the β-TCP samples was further modified using a femtosecond laser system. Grid and line patterns were produced on the plates’ surface via laser ablation, creating grooves with depths lower than 20 μm and widths between 20 and 40 μm. Raman and FTIR analysis confirmed that laser ablation did not result in the degradation or phase change of the materials, making it suitable for surface patterning. Laser ablation resulted in increased hydrophilicity of the materials, as the control samples (non-ablated samples) have WCA values ranging from 70° to 93° and become, upon laser ablation, superwicking surfaces. Confocal measurements show an increase in specific surface area of 50% to 200% compared to the control. Overall, the results indicate the potential of laser ablation to improve the surface characteristics of β-TCP, which may lead to an improvement in the antibacterial and osteogenic properties of the produced materials.

Tricalcium phosphate (Ca 3 (PO 4 ) 2 , TCP), is one of the most studied and used as material for bioresorbable implants. The β phase has a slower dissolution dynamic and ensures mechanical support for a longer time in biological environment, while a faster release of ions characterize the α phase that trigger a stronger biological response. In this work a femtosecond laser system was used to process β-TCP pellets surface. The femtosecond laser processing results in surface morphology modification, by turning the flat mirror polished surface into a rough and opaque one. The morphological and phisycochemical characteristics of material surface were studied by means of SEM, AFM, Raman, XRD and contact angle measurement. The processed surface showed the formation of micro and nano roughness alongside, furthermore a partial phase transformation from β-TCP to α-TCP was detected. A significant improvement in surface wettability for three different liquids (i.e.water, ethylene glycol and diiodo-methane) is reported. This implies an increase in surface free energy as well. The combination of α and β phase, together with the increased roughness obtained by laser processing, could positively affect the cell adhesion and metabolic activity.

beta-tricalcium phosphate (beta-TCP, beta-Ca-3(PO4)(2)) is an attractive biomaterial for bone repair applications. However, its sintering and mechanical properties are limited by a problematic phase transition to a-TCP. Cationic doping of beta-TCP is able to postpone the formation of a-TCP allowing higher sintering temperatures and better mechanical properties. The co-doping of beta-TCP with Mg2+ and S-r2+ has already been studied in detail, but the addition of antibacterial cations (Ag+ and Cu2+) on the Mg-Sr beta-TCP co-doped composition remains unexplored. Thus, two co-doped beta-TCP compositions were realized by aqueous precipitation technique without any secondary phase and compared with undoped beta-TCP: Mg-Sr (2.0-2.0 mol%) and Mg-Sr-Ag-Cu (2.0-2.0-0.1-0.1 mol%). Differential thermal analysis and dilatometry analyses showed a slight decrease of the beta-TCP. aTCP phase transition temperature for the Mg-Sr-Ag- Cu (2.0-2.0-0.1-0.1% mol) composition as compared to the Mg-Sr (2.0-2.0 mol%). However, both exhibited much higher transition temperatures than undoped beta-TCP. The addition of Ag+ and Cu2+ slightly reduces the grain size after sintering compared to the Mg-Sr (2.0-2.0 mol%) and the undoped compositions. The co-doped compositions also exhibited improved mechanical properties, specifically a higher Vickers hardness and elastic modulus. Finally, cell proliferation assays showed that the presence of dopants, even Ag+ and Cu2+, does not affect the survival and proliferation of cells. Thus, the use ofMg(2+), Sr2+, Ag+, andCu(2+) co-doped beta-TCP could be very promising for biomedical applications due to the improvements of these dopants on the thermal stability and mechanical and biological properties.

Neck formation and densification during sintering have strong effects on the thermal conductivity of a porous ceramic body. This has been described by an analytical model using grain conductivity, grain size, pore fraction and particle – particle contact area as input parameters. It has been tested on hydroxyapatite ceramics sintered with conventional, microwave and spark plasma techniques. The green bodies containing at least 40% porosity yield conductivity values in the range 0.24–0.29 Wm−1K−1. Neck formation in the initial stage of sintering increases the values to above 0.5 Wm−1K−1. Further increase is achieved by densification, well described by Landauer's relation as part of the model with close agreement to experiment for hydroxyapatite ceramics containing 40 to 5% porosity. An evaluation of thermal conductivity for 100% dense hydroxyapatite gives a value of 1.5 Wm−1K−1 which is almost constant between room temperature and 900 °C.

Among key factors determining the fate of biomaterials in vivo are their interactions with blood serum proteins, which can lead to either successful integration or rejection/encapsulation. Although there are a number of studies investigating the interactions between proteins and bioimplants, comparable data for different types of biomaterials are lacking. To fill this gap, the adsorption kinetics and binding interactions of bovine serum albumin (BSA) with calcium phosphates (CaPs), namely hydroxyapatite (HA) and calcium deficient apatite (CaDHA), different TiO2 nanomaterials (TiNMs) presenting various morphologies such as nanoparticles (TiNPs), nanoplatelets (TiNPls), nanotubes (TiNTs) and nanowires (TiNWs), as well as their composites with CaDHA (CaDHA/TiNMs) were investigated. The kinetics of BSA adsorption on all studied materials was best described by pseudo-second order kinetics. The rate coefficient values obtained for the composites were lower than those for CaDHA and the corresponding TiNMs, while the adsorption density was higher for the composites than for CaDHA, except for the composites with TiNTs. Adsorption on TiNWs, CaDHA and all composites involved intraparticle diffusion, which was the rate-limiting step only for CaDHA/TiNTs. Fluorimetric titration experiments revealed that the number of binding sites was in larger than 1, except for TiNTs and TiNWs, indicating positive binding cooperativity. Interestingly, the values of the binding constants were lower for the TiNMs with a higher adsorption rate coefficient. Overall, BSA adsorption on the studied materials proved to be a complex process, which depended on the different surface properties of the adsorbents. Which property had a dominant role depended on the chemical identity of the adsorbent. The obtained comparable data for different types of materials point to the way of modifying their protein adsorption and binding properties.

beta-tricalcium phosphate (beta-TCP, beta-Ca3(PO4)2) is one of the most attractive biomaterials for bone regeneration and beta-TCP macroporous scaffolds are very promising for both cell proliferation and mechanical support. The Additive Manufacturing (AM) process called Direct Ink Writing (DIW), based on the extrusion of a concentrated ceramic slurry, is particularly adapted to resolve the main drawbacks associated with conventional shaping of ceramic scaffolds. In this work, co-doped beta-TCP powders were synthetized and used to print macroporous scaffolds by DIW. Doped beta-TCP powders have been proved to exhibit higher thermal stability, densification and mechanical properties compared to undoped beta-TCP. Two co-doped compositions were produced via the aqueous precipitation technique combining magnesium, strontium, silver and copper cations: Mg-Sr (2.0-2.0 mol%) and Mg-Sr-AgCu (2.0-2.0-0.1-0.1 mol%). DIW slurries were optimized with undoped and co-doped beta-TCP with the use of a dispersant and a carboxymethylcellulose and polyethyleneimine mixture to obtain aqueous slurries filled with 42 vol% of powder. Complete rheological characterizations were realized to assess the suitability of the beta-TCP slurries for the DIW process (shear-thinning and thixotropic behaviour). The whole processing chain including printing, osmotic drying (PEG 10000) and sintering (1100 degrees C, 3 h) was optimized to successfully print co-doped beta-TCP macroporous scaffolds. Characterizations after sintering showed a reduction of macropores and microcracks using co-doped beta-TCP powders as well as improved compressive strengths and densities compared to undoped beta-TCP. A significant enhancement of compressive strength values was obtained compared to literature data.

To assess the application potential of novel biomaterials, their behaviour in model media and upon sterilization should be investigated, as well as the stability related to their storage conditions. Such data are lacking for Mg-substituted HAP (Mg-HAP). Therefore, the changes in the local structure of non-substituted and Mg-HAP after irradiation and immersion in corrected simulated fluid and saline solution for 28 days were followed by electron paramagnetic resonance (EPR) spectroscopy for the first time. To better understand the stability of radical species induced by sterilization, EPR spectra of samples kept for 2 h at temperatures up to 373 K were recorded to provide an insight into the stability of the sample storage conditions by the accelerated aging method. Samples were characterized by PXRD, FTIR, SEM, EDS, AAS and TGA. Results confirmed that irradiation does not induce changes in the composition or the structure of any of the investigated materials. Fading or the complete disappearance of radical signals in the EPR spectra after immersion in both media was accompanied by the disappearance of other phases formed as a minor byproduct in the synthesis of substituted HAP, as confirmed by PXRD and FTIR analysis. Obtained results confirm the great potential of Mg-HAPs for biomedical applications, although closer attention should be given to the processes related to sample storage stability at different temperatures.

Binder jetting (BJ) is an additive manufacturing process in which powder materials are selectively joined by a binder. BJ is plagued by its high sensitivity to both powder properties and process parameters which critically affect the quality of powder beds and final products. Alumina powder was used as a model material processed using different routes to obtain granules with various characteristics. Granule properties (particle size, morphology, flowability), characteristics of powder bed (roughness, packing density) and process parameters (binder saturation, layer thickness) were highly optimized in order to achieve the highest printed parts quality in terms of compressive strength and volume density. Optimized values reach 102.2 ± 11.1 MPa and 64.2 ± 1.9% T.D respectively which are close to expectations for this process. The paper serves as an aid in understanding the influence of powder properties and processing parameters and provides general guidelines to rapidly develop ceramic powders for conventional binder jetting process.

Infiltration of printed bodies with a ceramic suspension is a relevant approach to enhance density and properties of the porous binder-jetted parts. In the present work, significant improvements of alumina parts processed through this combination printing-infiltration was reported. The density of non-infiltrated (but sintered) samples only reached 55.3 +/- 1.1% of the theoretical density while it raised up to 87.9 +/- 0.5% after infiltration of a pre-consolidated body followed by sintering. Influence of multi-infiltration operations, pre-consolidation temperature, solids loading of suspensions and duration of infiltration on the final part density were discussed. Infiltration mechanism and porosity distribution have been carefully investigated. It was demonstrated that the ceramic suspension infiltrated the pre-consolidated ceramic skeleton mostly under the effect of gravity which may result in density heterogeneities of the infiltrated parts. The reported processing route can be straightforwardly applied to other ceramic systems and is particularly inexpensive, and it is believed to have industrial relevance.

This study was devoted to the understanding of the influence of MgAl2O4 ceramic properties on their ballistic performances. By modifying the processing parameters, ceramics with different microstructures were obtained. Among them, a transparent MgAl2O4 spinel with an in-line transmission between 77% and 83% in the visible range, an average grain size of 8.6 mu m and good mechanical properties (11.3 GPa in Knoop hardness and 2.5 MPa root m in fracture toughness) was produced. A thorough characterisation of the ceramics was accomplished in order to establish a link between microstructure, mechanical properties and ballistic protective performances against an armour piercing projectile of calibre 7.62x51 mm. The ballistic evaluation demonstrated the advantage of using a spinel layer as the strike face to stop a threat, while reducing drastically the thickness and the areal density of the transparent multilayer, compared to a simple glass armour. MgAl2O4 spinel with fine grains presented a better combination of mechanical properties compared to coarser microstructures, hence a better potential to damage a projectile at the impact.