Jérôme Chevalier

• Managing Director at Institut National des Sciences Appliquées de Lyon

In this work, the impact resistance of three zirconia ceramics was investigated: two yttria-stabilized zirconia (3Y-TZP and 1.5Y-TZP) and a ceria-stabilized-zirconia (Ce-TZP) composite. The impact resistance was evaluated through drop-ball impact tests on disk-shaped samples. The results are discussed in terms of the materials’ transformability, wh...

We conventionally assume that ceramics are brittle. The risks induced by this structural behaviour do not cancel the undeniable need for ceramics in applications with extreme environmental demands. These constraints could be a high working temperature or wear, where metals cannot be used, or in contact with the human body, where the inherent chemic...

We investigate the rheological properties of ceramic slurries designed for laser stereolithography manufacturing in relation to their formulation, including the powder morphology, their volume fraction, and the concentration of dispersing agent. By combining dynamic strain sweep and Small‐Angle X‐ray Scattering (SAXS) experiments, we first illustra...

Additive manufacturing (AM) is increasingly employed in orthopedics to manufacture patient-specific prostheses and orthoses while reducing time and production costs compared to traditional thermoforming. Nowadays, an ankle–foot orthosis (AFO) can be manufactured by material extrusion with various polymers and designs. The objective of this work is...

Nowadays, about 15% of people living in post-war countries needing prosthetic and orthotic equipment they have access due to their long, high costs and complex manufacturing processes. In recent years, additive manufacturing (AM) is increasingly popular in the rehabilitation centers as an alternative since prototypes can be manufactured without res...

Development of restorative materials capable of mimicking optical and mechanical performance of natural teeth is a quest in aesthetic density. Yttria-Stabilized Zirconia (YSZ) ceramics represent one of the most popular choices for dental restorations, owing to their biocompatibility, white colour, and the possibility to use CAD-CAM technologies. In...

We study the shear rheological behavior of a commercial stereolithography paste containing ≈50 vol. % of zirconia particles (diameter ≈ 100 nm) with the aim to clarify physical mechanisms occurring during the “scraping” step of this yield stress fluid. Beyond a flow curve characterized by a high zero-shear viscosity accompanied with an overall shea...

In this work, the mechanical response and the damage process during compressive loading tests of hydroxyap-atite scaffolds processed by stereolithography and designed for biomedical applications were investigated. Damage is followed by acoustic emission monitoring, Scanning Electron Microscopy observations at different loading stages and by In-situ...

Alumina (α‐Al2O3) is one of the major ceramic oxides commonly used for its advanced mechanical properties. Since recently, nanoscale α‐Al2O3 requires more in‐depth characterization related to ceramic powder compaction and sintering as well as for applications in the field of biomedical engineering. In this study, we use classical molecular dynamics...

Our current study concerns the structural analysis and mechanical properties under compressive loading of a new developed additive-manufactured hydroxyapatite (HA) scaffolds, designed for bone tissue engineering. Structural evaluation was performed by X-ray computed tomography (X-CT) and the compressive strength was determined by uniaxial testing m...

The additive manufacturing of composite structures can open possibilities in the design and fabrication of devices but also demands new approaches. In this work, we use thermally reversible pastes to fabricate ceramic matrix (Al2O3) composites reinforced with continuous metallic fibres (steel). The approach is based on the micro-extrusion of cerami...

Robocasting, or Direct Ink Writing, can be used to create dense mono- or multi-materials ceramic parts using micro-extrusion of ceramic pastes through needles, whose position is controlled in 3D. Rheological properties of the ceramic pastes, printing parameters and thermal post processes (drying, debinding and sintering) are key parameters to contr...

Additive manufacturing of ceramic materials has been rapidly expanding for several years. Robocasting (sometimes referred to as Direct Ink Writing) is one of the few additive manufacturing techniques that allows processing multiple materials simultaneously as multiple cartridges can be loaded in the machine and used to print a single part. Thanks t...

A commercial composite powder was used to develop a new paste for stereolithography processing (SLA) of dense 11Ce-TZP-based composites containing 8 vol.% of alumina and 8 vol.% of strontium aluminate. The same powder was used to prepare reference ceramics by conventional Cold Isostatic Pressing (CIP) and sintering. The use of SLA gave rise to a mi...

To decrease the light scattering caused by birefringence of the tetragonal phase of dental Yttria-Stabilized Zirconia (YSZ), two main strategies are followed: 1) increasing Y2O3 content to have a larger amount of non-birefringent cubic phase or 2) decreasing grain size below 100 nm to reduce their scattering coefficient. Both strategies might affec...

Objective To evaluate the manufacturing accuracy of zirconia four-unit fixed dental prostheses (FDPs) fabricated by three different additive manufacturing technologies compared with subtractive manufacturing. Methods A total of 79 zirconia FDPs were produced by three different manufacturing technologies, representing additive (one stereolithograph...

This work describes the development of transparent high-strength Yttria-Stabilized Zirconia (YSZ) ceramics with ultra-fine grain size utilizing conventional pressure-less densification. Starting with nanoparticles with diameter <10 nm, it was possible to achieve full densification (>99.5% of theoretical density) at a sintering temperature of 1100–1...

Ti40Cu36Zr10Pd14 metallic glass is often considered a promising candidate for biomedical applications, in particular for the manufacturing of small size dental implants. Nevertheless, its processing and limited glass-forming ability leads to the appearance of crystalline spheres called “spherulites”. These spherulites play a major role in the defor...

Aluminum oxide (α-Al2O3) is known as one of the major ceramic oxide and is currently used for its advanced mechanical properties. Nowadays, it requires a more in-depth description at small-scales especially for applications in the fields of nanocrystalline ceramic fabrication and nanomechanics. In this study, we investigate the transferability of s...

One of the limitations to the use of certain bulk metallic glasses is related to the formation of crystalline zones or defects, often called “spherulites”, during the casting process. In the case of Ti40Zr10Cu36Pd14 (at %) metallic glass, which is a candidate for biomedical applications, spherulites of diameter up to few hundreds of microns were pr...

The present invention relates to the synthesis of highly translucent/transparent high-strength yttria stabilized zirconia (3-8 mol%) with ultra-fine grain size in bulk form via a simple technique. These ceramics can be used ,in particular, in the dental field.

Two‐photon lithography is a potential route to produce high‐resolution 3D ceramics. However, the large shrinkage due to the elimination of an important organic counterpart of the printed material during debinding/sintering remains a lock to further development of this technology. To limit this phenomenon, an original approach based on a composite r...

Poly(L-lactide-co-D,L-lactide) PDLA/45S5 Bioglass® (BG) composites for medical devices were developed using an original approach based on a thermal treatment of BG prior to processing. The aim of the present work is to gain a fundamental understanding of the relationships between the morphology, processing conditions and final properties of these b...

Different kinds of interactions between the restorative material and mineralized dental tissues result in secondary caries around dental composites. Of these, the mechanical interactions have to be carefully investigated. Due to the elastic mismatch between dental tissues and the composite restoration, complex stresses and strains develop at their...

Objectives: Ceramics are an alternative to titanium for aesthetic and metal-free solutions in dental implantology. However, several reports of fractures of 3Y-TZP implants in clinical studies further motivate the search for alternative ceramic materials. Tri-phasic oxide materials based on Ceria-doped zirconia (Ce-TZP) were developed recently to be...

Objective Healing of soft tissues and improvement of aesthetics have become major research objectives in implantology and renewed the interest for ceramics implants. The aim of this study was to evaluate the pre-clinical performance of screw-shaped sandblasted-etched implants processed from an innovative zirconia-based ceramic composite, in compari...

Magnesium oxide nanocubes are compressed along the [001] direction in situ in the transmission electron microscope. Incipient plasticity in the smaller samples is characterized by the nucleation of few $ \raise.5ex\hbox{$\scriptstyle 1$}\kern-.1em/\kern-.15em\lower.25ex\hbox{$\scriptstyle 2$} {\lt}110{\gt} \{{110} \} $ 1/2<110>{110} dislocations wh...

Long-term, reliable operation of Solid Oxide fuel and electrolysis Cell (SOCs) necessitates cells with high strength and resistance to mechanical degradation. In this work, strength, Young’s modulus and Low-Temperature Degradation (LTD) of several zirconia-based SOCs supports are studied. The study shows that replacing 3YSZ with a tetragonal zircon...

Osteomalacia is a pathological bone condition consisting in a deficient primary mineralization of the matrix, leading to an accumulation of osteoid tissue and reduced bone mechanical strength. The amounts, properties and organization of bone constituents at tissue level, are known to influence its mechanical properties. It is then important to inve...

3Y-TZP discs were coated using 5Y-PSZ and 12Ce-TZP suspensions. Samples were evaluated in terms of roughness (Ra, Rq, Rz and Rsk), B3B flexural resistance, hardness, Young's modulus by instrumented indentation and surface damage resistance and Vickers hardness by impress Vickers measurements. Coatings with thickness of ~7 μm were obtained. 3Y-TZP u...

Transformation-induced plasticity in a ceria-stabilized-zirconia based composite was studied in four-point bending, with particular emphasis on nucleation and growth of tetragonal-to-monoclinic transformation bands. They initiated on the side in tension at a given value of stress and grow in size and number with increased applied load. The spacing...

In this work, the effect of substituting Cu with small amounts of Sn and Si on the passive behavior and pitting resistance of the bulk metallic glass Ti40Zr10Cu36Pd14 was investigated. The Sn/Si substitution promoted homogenization of the solid solution and limited the presence of casting defects. In addition, unlike the heterogeneous passive film...

Zirconia implants are appreciated in some clinical indications in light of their aesthetic appearance and good biocompatibility. The aim of this work was to evaluate the performance of a newly developed two-piece zirconia/polyether ketone ketone (PEKK) implant-abutment combination after long-term cyclic loading in a hydrothermal environment, using...

Due to its excellent properties, yttria-stabilized tetragonal zirconia ceramics (Y-TZP) are considered to be an appropriate choice for advanced dental applications. However, the long-term surface stability of these materials in a humid environment is still a matter of discussion. In the present work, two commercial and one in-house prepared 3Y-TZP...

Further development and upscaling of the Solid Oxide fuel and electrolysis Cell (SOCs) technologies would significantly benefit from improvement of their mechanical robustness. In this work, microstructure, crystalline phase composition, fracture toughness and susceptibility to low- and high-temperature degradation of six different Ni(O)‒Zirconia f...

Meso-porous γ-alumina ceramics used as catalyst supports are characterized by high porosity fraction (>70%) and specific surface area (>200 m²/g) targeted to ensure high catalytic performances, but at the expense of the mechanical strength. The aim of this work is to link the mechanical properties of three different catalyst supports with their mic...

Individual platelets in nacre‐like ceramics are able to locally withstand stress levels many times larger than the strength of larger specimens made of the same materials. This size effect, usually reported as being relative to the size of pre‐existing defects, is described by considering both stress and energy failure conditions. We show that ther...

In this work 3 mol.% yttria-stabilized zirconia (Y-TZP) disks were pressed and subsequently coated, aiming at producing reliable protective coatings to avoid Low Temperature Degradation (LTD) of Y-TZP. Suspensions of 12Ce-TZP or 5Y-PSZ (5 mol.% yttria stabilized zirconia) powders with different solid contents were used as coatings. Accelerated agin...

Objectives The presentin vitro study evaluated the effect of LTD (Low Temperature Degradation) on microstructural properties, phase transformation and micro-crack formation of 5 commercially and non-commercially available Zirconia dental implant systems. Methods Accelerated ageing at 134 °C and 2 bar pressure for 30 h was completed. Focused Ion Be...

Thin, porous zirconia-based ceramic components are of high interest in energy application devices where they are used as structural ceramics. Mechanical reliability of such devices is not only dependent on the fracture toughness of the ceramic components, but also on their sensitivity to slow crack growth (SCG). In this work, the fracture toughness...

Toughness, strength, creep resistance, and fatigue behavior of ceramics can be improved by using roughly equiaxed reinforcements. This can be obtained through the addition of transformable (zirconia) particles, whiskers, carbon nanotubes, graphene, or short fibers. Different toughening mechanisms are then possible and can act independently or in sy...

This article updates and expands the previous one “Zirconia in Orthopedics: An Open Issue” written fifteen years ago, which covered the knowledge on orthopedic zirconia up to 2005. This update includes advances in this topic, responds to some of the questions that were left open on the use of zirconia in orthopedics and analyzes how such yttria-sta...

Forty years ago, Garvie and his Australian co‐workers reported that the stress‐induced transformation of metastable tetragonal zirconia grains to the monoclinic symmetry could give rise to a powerful toughening mechanism. Their results even led them to consider zirconia systems as analogues of certain steels. This seminal paper generated extraordin...

Composites of 8 mol.% yttria-stabilized zirconia (8YSZ) with graphene nanoplatelets (GNP) have been pointed as alternative interconnectors in SOFC due to their mixed ionic-electronic conduction. Here we show that GNP addition provides rising crack-resistance behavior, with long crack toughness up to 78% higher than that of 8YSZ, also improving its...

Ceria-Yttria co-doped tetragonal zirconia is an attractive class of materials having high strength, toughness and thermal stability. In this study, several co-doped zirconia powders with different stabilizers contents were synthesized via continuous hydrothermal flow synthesis (CHFS). The CHFS was concluded as a suitable method in synthesizing ultr...

Ceramics and their composites are in general brittle materials because they are predominantly made up of ionic and covalent bonds that avoid dislocation motion at room temperature. However, a remarkable ductile behavior has been observed on newly developed 11 mol.% ceria-stabilized zirconia (11Ce-TZP) composite containing fine alumina (8 vol.% Al2O...

Objectives: To evaluate two-body wear of three zirconia ceramics stabilized with 3, 4 and 5mol% yttria and to compare their wear behavior with that of a lithium-disilicate glass-ceramic. Methods: Sixteen rectangular-shaped specimens made from three grades of zirconia ceramics and a lithium-disilicate glass-ceramic were polished and dynamically l...

The market share of zirconia (ZrO2) dental implants is steadily increasing. This material comprises a polymorphous character with three temperature-dependent crystalline structures, namely monoclinic (m), tetragonal (t) and cubic (c) phases. Special attention is given to the tetragonal phase when maintained in a metastable state at room temperature...

This study aims to investigate the influence of different laser surface texturing parameters on Low-Temperature Degradation and mechanical properties of Yttria-tetragonal zirconia polycrystals (3Y-TZP), focused on biomedical applications. The roughness resulted from laser irradiation was characterized by Ra, Rt, Rsk and Rku parameters, as well by S...

The objective of this paper is to review the current knowledge on the development of nanostructured zirconia-based ceramics and composites suitable for application in dentistry. Isi Web of Science, Science Direct, Scientific.net databases, and Google were searched electronically for the period of 1980 to the present, matching the keywords “nano” wi...

Objective: To evaluate the effect of artificial aging on the mechanical resistance and micromechanical properties of commercially and noncommercially available zirconia dental implants. Methods: Scanning electron microscopy (SEM) and X-ray computed tomography (X-CT) were performed on implant systems including: Z-systems®, Straumann®, Zibone® and...

Resorbable ceramics used as porous bone substitutes are designed to favor bone in-growth and to be gradually replaced by natural tissues after in vivo resorption. However, a lack of experimental techniques to quantitatively monitor the evolution of their mechanical properties during resorption is noted. In this paper, we propose to use spherical in...

Ceramic-on-ceramic bearings in total hip replacement have shown the potential to provide low wear solutions in hip replacement. Assessing the tribological performance of these materials is important to predict their long-term performance in patients. In this study, a methodology was devised to assess the tribological in vitro behaviour of composite...

X-ray Computed Tomography (XCT) analysis was applied to identify and quantify typical defects in dense 3Y-TZP zirconia processed by the Lithography-based Ceramic Manufacturing (LCM) technique. XCT derived strengths were anticipated from the XCT data and compared to experimental measurement. A good agreement between XCT data, bending strength measur...

High strength and translucency are generally not coincident in one restorative material and there is still a continuous development for a better balance between these two properties. Zirconia and lithium-disilicate glass-ceramics are currently the most popular alternatives for monolithic restorations. In this work, the mechanical properties and mor...

The efficiency of calcium phosphate (CaP) bone substitutes can be improved by tuning their resorption rate. The influence of both crystal orientation and ion doping on resorption is here investigated for beta-tricalcium phosphate (β-TCP). Non-doped and Mg-doped (1 and 6 mol%) sintered β-TCP samples were immersed in acidic solution (pH 4.4) to mimic...

Scaffolds for bone tissue engineering require a combination of bioactivity and bioresorption at the sample surface and high mechanical properties in the bulk. This work presents a novel calcium phosphate (CaP)/polycaprolactone (PCL) scaffold with graded composition and porosity fraction. The scaffold is made of (i) a dense hydroxyapatite (HA)/β-tri...

etragonal Zirconia Polycrystals (TZP) is attractive for structural biomedical applications because of their excellent mechanical properties at room-temperature, which include high strength, fracture toughness and wear resistance. In this work, zirconia stabilized with Y or Yb or Yb+Nd, all containing 0.5 vol.% Al2O3, were prepared by hot-pressing (...

Objectives The purpose of this work is a proof of concept to introduce a new quantitative 3D-analysis of dental erosion obtained by focused ion beam (FIB) tomography associated with silver nitrate penetration into porosities in etched enamel. Methods One sample selected was sound enamel after removal of the aprismatic surface. The other was studie...

Slow crack growth (SCG) behavior of four zirconia-based composites reinforced with 40 vol% WC, TiC, NbC or TiCN were studied by means of double-torsion testing. Compared to monolithic zirconia, the composites had a higher resistance to fast fracture, i.e., higher fracture toughness. The extent of toughening depended on the reinforcement type, shift...

Conventional composites often do not represent true synergy of their constituent materials. This is particularly evident in biomaterial applications where devices must interact with cells, resist cyclic loads and biodegrade safely. Here we propose a new hybrid system, with co-networks of organic and inorganic components, resulting in unprecedented...

This review paper focuses on dislocations and plastic deformation in magnesium oxide crystals. MgO is an archetype ionic ceramic with refractory properties which is of interest in several fields of applications such as ceramic materials fabrication, nano-scale engineering and Earth sciences. In its bulk single crystal shape, MgO can deform up to fe...

Oxide ceramics are sensitive to slow crack growth because adsorption of water can take place at the crack tip, leading to a strong decrease of the surface energy in humid (or air) conditions. This is a major drawback concerning demanding, long-term applications such as orthopaedic implants. Here we show that a specific nanostructuration of ceramic...

Atomic force microscopy (AFM) can be used to characterise several aspects of the surface degradation and reinforcement mechanisms of zirconia based ceramics, such as crack propagation, martensitic relief formation, grains pull-out and transformation toughening. AFM can also be used to quantify precisely the transformation and provide reliable param...

Alumina-zirconia nano-composites were recently developed as alternative bearing materials for orthopedics. Previous, preliminary reports show that such alumina-zirconia nanocomposites exhibit high crack resistance and low wear rate. In this paper, additional information is given in terms of wear, crack resistance and ageing behaviour: femoral heads...

Though the martensitic transformation in zirconia has been the object of a very large number of studies for the last decades, qualitative and quantitative observations of the formation and growth of relief induced by low temperature treatments has hardly ever been reported. In the first part of the study, we have demonstrated the excellent agreemen...

Recently, several episodes of fracture of zirconia ceramic femoral heads of total hip prostheses have alarmed the medical and scientific community regarding aging problems in zirconia prostheses. Such fractures cause immediate local tissue reactions, which require urgent medical intervention to prevent further complications. As a result, it has bee...

Changes in crystalline phases resulting from low-temperature ageing of different yttria doped and non-doped zirconia-toughened alumina composites and nanocomposites were investigated under controlled humidity and temperature conditions in autoclave. A classical powder mixing processing route and a new modified colloidal processing route were used t...