arXiv subjects

Sylvain Deville

Publications and source records attributed to Sylvain Deville.

At least 55 records · Page 3Linked to original sources

arXiv2017

Atomic force microscopy study of the tetragonal to monoclinic transformation behaviour of silica doped yttria-stabilized zirconia

The tetragonal to monoclinic phase transformation of zirconia has been the subject of extensive studies over the last 20 years [1-4]. The main features of the transformation have been identified and its martensitic nature is now widely recognised [5-8]. More specifically, the relevance of a nucleation and growth model to describe the transformation is widely accepted. Recent fracture episodes [9] of zirconia hip joint heads were reported, failures related to the t-m transformation degradation. Among the materials solutions considered for decreasing the sensitivity to t-m phase transformation, the possibility of adding silica as a dopant appears as an appealing one. Previous studies have revealed the beneficial effect of silica addition by the formation of a glassy phase at the grain boundaries and triple points. This glassy phase has been proven to reduce the residual stresses level [10], slowing down the transformation kinetics. Preliminary quantitative investigations by XRD have shown these materials are less susceptible to transformation. However, the mechanism by which the transformation propagated has still to be assessed.

cond-mat.mtrl-sci↗

arXiv2017

Atomic force microscopy of transformation toughening in ceria-stabilized zirconia

We demonstrate in this paper that atomic force microscopy can be successfully used to gain further insights into the understanding of transformation toughening in ceria stabilized zirconia. Transformation was induced by stresses accumulated in the region surrounding propagating cracks in double torsion samples. The resolution provided by AFM at the surface of the samples made it possible to observe the formation of self accommodated martensite pairs in the near crack areas. The potential for transformation is found to decrease with increasing alloying addition, and is totally suppressed for 16 mol.% CeO2-TZP samples. A statistical analysis of the martensite pair orientation is performed, and the relationship with the applied stress and strain fields is discussed. The contribution to transformation toughening by transformation-induced plasticity occurring in the formation of martensitic variant pairs with small net shear is demonstrated. The influence of alloying addition content on the potential for transformation toughening and fracture toughness values is finally discussed.

cond-mat.mtrl-sci↗

arXiv2017

Microstructural investigation of the aging behavior of $(3Y-TZP)-Al_2O_3$ composites

The low temperature autoclave aging behavior of zirconia toughened alumina composites processed by a classical powder mixing processing route was analyzed using atomic force microscopy (AFM), scanning electron microscopy and X-Ray diffraction. The transformation was evaluated in terms of nucleation and growth, assessed by XRD. The time-temperature equivalency of the transformation was used to measure an apparent activation energy of the nucleation stage of the transformation of 78kJ/mol. The microstructural features influencing the transformation were identified, and the influence of the alumina matrix on the transformation was investigated. Transformation progression grain by grain was observed by AFM. Transformation does not only occur in zirconia agglomerates but also in isolated zirconia grains. The matrix could partially inhibit the transformation. This behavior could be rationalized considering the constraining effect of the alumina matrix, shape strain accommodation arguments and microstructural homogeneity effects.

cond-mat.mtrl-sci↗

arXiv2017

In Situ X-Ray Radiography and Tomography Observations of the Solidification of Alumina Particles Suspensions. Part I: Initial Instants

This paper investigates by in situ high-resolution X-ray radiography and tomography the behaviour of colloidal suspensions of alumina particles during directional solidification by freezing. The combination of these techniques provided both qualitative and quantitative information about the propagation kinetic of the solid/liquid interface, the particles redistribution between the crystals and a particle enriched phase and the 3D organisation of the ice crystals. In this first part of two companion papers, the precursor phenomena leading to directional crystallisation during the first instants of solidification is studied. Mullins-Sekerka instabilities are not necessary to explain the dynamic evolution of the interface pattern. Particle redistribution during these first instants is dependent on the type of crystals growing into the suspension. The insights gained into the mechanisms of solidification of colloidal suspensions may be valuable for the materials processing routes derived for this type of directional solidification (freeze-casting), and of general interest for those interested in the interactions between solidification fronts and inert particles.

cond-mat.mtrl-sci↗

arXiv2017

In Situ X-Ray Radiography and Tomography Observations of the Solidification of Alumina Particles Suspensions. Part II: Steady State

This paper investigates the behaviour of colloidal suspensions of alumina particles during directional solidification, by in situ high-resolution observations using X-ray radiography and tomography. This second part is focussed on the evolution of ice crystals during steady state growth (in terms of interface velocity) and on the particles redistribution taking place in this regime. In particular, it is shown that diffusion cannot determine the concentration profile and the particles redistribution in this regime of interface velocities (20-40 microns/s); constitutional supercooling arguments cannot be invoked to interpret particles redistribution. Particles are redistributed by a direct interaction with the moving solidification interface. Several parameters controlling the particles redistribution were identified, namely the interface velocity, the particle size, the shape of the ice crystals and the orientation relationships between the crystals and the temperature gradient.

cond-mat.mtrl-sci↗

arXiv2017

A critical comparison of methods for the determination of the ageing sensitivity in biomedical grade yttria stabilized zirconia

Since the recent failure events of two particular series of zirconia femoral heads for total hip replacement prosthesis, a large decrease in the use of zirconia ceramics for orthopaedic implants has been observed. In spite of the biomedical success of this material during the last ten years, this was required for safety reasons, until the cause of the failures is known. It has been shown that these failures were related to the low temperature hydrothermal degradation (also known as ageing). Thus it is crucial to better understand the ageing behaviour, in order to be able to assess its importance and then control it if required. In this paper, various techniques relevant to assess the hydrothermal degradation sensitivity of biomedical grade yttria stabilized zirconia are discussed and compared. The expected outputs of conventional methods, i.e. X-Ray diffraction and scanning electron microscopy are examined. More recent methods like optical interferometry and atomic force microscopy are presented, with their respective benefits and drawbacks. An up to date comparison of these different techniques is provided, and their use for ensuring the long term reliability of a particular batch of zirconia in terms of ageing degradation is demonstrated.

cond-mat.mtrl-sci↗

arXiv2017

Ice-templated porous alumina structures

The formation of regular patterns is a common feature of many solidification processes involving cast materials. We describe here how regular patterns can be obtained in porous alumina by controlling the freezing of ceramic slurries followed by subsequent ice sublimation and sintering, leading to multilayered porous alumina structures with homogeneous and well-defined architecture. We discuss the relationships between the experimental results, the physics of ice and the interaction between inert particles and the solidification front during directional freezing. The anisotropic interface kinetics of ice leads to numerous specific morphologies features in the structure. The structures obtained here could have numerous applications including ceramic filters, biomaterials, and could be the basis for dense multilayered composites after infiltration with a selected second phase.

cond-mat.mtrl-sci↗

arXiv2017

Freeze casting of hydroxyapatite scaffolds for bone tissue engineering

Although extensive efforts have been put into the development of porous scaffolds for bone regeneration, with encouraging results, all porous materials have a common limitation: the inherent lack of strength associated with porosity. Hence, the development of porous hydroxyapatite scaffolds has been hindered to non-load bearing applications. We report here how freeze-casting can be applied to synthesize porous hydroxyapatite scaffolds exhibiting unusually high compressive strength, e.g. up to 145 MPa for 47% porosity and 65 MPa for 56% porosity. The materials are characterized by well-defined pore connectivity along with directional and completely open porosity. Various parameters affecting the porosity and compressive strength have been investigated, including initial slurry concentration, freezing rate, and sintering conditions. The implications and potential application as bone substitute are discussed. These results might open the way for hydroxyapatite-based materials designed for load-bearing applications. The biological response of these materials is yet to be tested.

cond-mat.mtrl-sci↗

arXiv2017

Modeling the aging kinetics of zirconia ceramics

Yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) with different microstructures were elaborated. The isothermal tetragonal to monoclinic transformation was investigated at 134 °C in steam by X-ray diffraction, Atomic Force Microscopy (AFM) and optical interferometry. The aging kinetics were analyzed in terms of nucleation and growth, using the Mehl-Avrami-Johnson (MAJ) formalism. Numerical simulation of the aging of zirconia surfaces was also conducted, and the results were used to better fit the aging kinetics. The simulation shows that the exponent of the MAJ laws is controlled not only by the nucleation and growth mechanisms, but also - and mainly - by their respective kinetic parameters. Measurements of nucleation and growth rates at the surface, at the beginning of aging, and the use of numerical simulation allow the accurate prediction of aging kinetics.

cond-mat.mtrl-sci↗

arXiv2017

Martensitic relief observation by atomic force microscopy in yttria stabilized zirconia

The tetragonal to monoclinic (t-m) phase transformation of zirconia has been the object of extensive investigations of the last twenty years, and is now recognised as being of martensitic nature. However, martensitic transformation has only been observed by transmission electron microscopy or indirect methods. Though the benefit on the fracture toughness and crack resistance was the main interest, the transformation is now considered for its consequences on the degradation of the material. The use of AFM reported here allowed the observation of the first stages of martensite relief growth and of new martensitic features.

cond-mat.mtrl-sci↗

arXiv2017

Atomic force microscopy study and qualitative analysis of martensite relief in zirconia

A recent report [S. Deville et al., J. Am. Ceram. Soc., 86(12), 2225 (2003)] has shown the new possibilities offered by atomic force microscopy (AFM) to investigate martensitic transformation induced relief in zirconia. In this paper, we studied qualitatively the surface relief resulting from martensitic tetragonal to monoclinic phase transformation in yttria and ceria-doped zirconia by AFM. AFM appears as a very powerful tool to investigate martensite relief with a great precision. The phenomenological theory of martensitic crystallography could be succesfully applied to explain all the observed features. The formation conditions of the martensite are discussed, as well as ways of accommodating locally the transformation strain, i.e. self-accommodating variant pairs and microcracking. Variants growth sequences are observed. These observations bring new insights and explanations on the transformation initiation and propagation sequences.

cond-mat.mtrl-sci↗

arXiv2017

Freeze-Casting of Porous Ceramics: A Review of Current Achievements and Issues

Freeze-casting, the templating of porous structure by the solidification of a solvent, have seen a great deal of efforts during the last few years. Of particular interest are the unique structure and properties exhibited by porous freeze-casted ceramics, which opened new opportunities in the field of cellular ceramics. The objective of this review is to provide a first understanding of the process as of today, with particular attention being paid on the underlying principles of the structure formation mechanisms and the influence of processing parameters on the structure. This analysis highlights the current limits of both the understanding and the control of the process. A few perspectives are given, with regards of the current achievements, interests and identified issues.

cond-mat.mtrl-sci↗

arXiv2017

Architectural control of freeze-cast ceramics through additives and templating

The freezing of concentrated colloidal suspensions is a complex physical process involving a large number of parameters. These parameters provide unique tools to manipulate the architecture of freeze-cast materials at multiple length scales in a single processing step. However, we are still far from developing predictive models to describe the growth of ice crystals in concentrated particle slurries. In order to exert reliable control over the microstructural formation of freeze-cast materials, it is necessary to reach a deeper understanding of the basic relationships between the experimental conditions and the microstructure of the growing solid. In this work, we explore the role of several processing variables (e.g., composition of the suspension, freezing rate, and patterning of the freezing surface) that could affect the formulation strategies for the architectural manipulation of freeze-cast materials. We also demonstrate, using freeze-cast lamellar structures, how reducing the lamellar thickness by less than half increases compressive strength by more than one order of magnitude.

cond-mat.mtrl-sci↗

arXiv2017

Dispersion of Boron Nitride Powders in Aqueous Suspensions with Cellulose

The dispersion of nitride and carbide ceramic particles in water is difficult, due to the absence of hydroxyl groups on their surface. Boron nitride is not an exception and despite its numerous applications, no effective dispersant has been identified so far. We demonstrate here the dispersion properties of two cellulose derivatives for hexagonal boron nitride powders, hydroxyl ethyl cellulose and methyl cellulose. The effect of particle sizes and cellulose concentration was investigated. The adsorption of cellulose onto the surface of the BN particles was confirmed by isotherm adsorption. Zeta potential measurements shows a charge screening effect of the cellulose The suspensions obtained were highly loaded and stable versus pH, and thus could lead to homogeneous codispersion of BN particles and sintering additives.

cond-mat.mtrl-sci↗

arXiv2017

Freezing as a path to build complex composites

Materials that are strong, ultra-light weight and tough are in demand for a range of applications, requiring architectures and components carefully designed from the micrometer down to nanometer scales. Nacre-a structure found in many molluscan shells-and bone are frequently used as examples for how nature achieves this through hybrid organic-inorganic composites. Unfortunately, it has proven extremely difficult to transcribe nacre-like clever designs into synthetic materials, partly because their intricate structures need to be replicated at several length scales. We demonstrate how the physics of ice formation can be used to develop sophisticated porous and layered-hybrid materials, including artificial bone, ceramic/metal composites, and porous scaffolds for osseous tissue regeneration with strengths up to four times higher than those currently used for implantation.

cond-mat.mtrl-sci↗

arXiv2017

Reply to the correspondence: "On the fracture toughness of bioinspired ceramic materials"

This is a reply to the correspondence of Prof. Robert Ritchie: "On the fracture toughness of bioinspired ceramic materials", submitted to Nature Materials, which discusses the fracture toughness values of the following papers: Bouville, F., Maire, E., Meille, S., Van de Moortèle, B., Stevenson, A. J., & Deville, S. (2014). Strong, tough and stiff bioinspired ceramics from brittle constituents. Nature Materials, 13(5), 508-514 and Le Ferrand, H., Bouville, F., Niebel, T. P., & Studart, A. R. (2015). Magnetically assisted slip casting of bioinspired heterogeneous composites. Nature Materials, 14(11), 1172-1172.

cond-mat.mtrl-sci↗

arXiv2017

The lure of ice-templating: recent trends and opportunities for porous materials

Ice-templating is a simple materials processing and shaping route where the growth of crystals from a solvent template the porosity. Although the principles of ice-templating were established a long time ago, it has lured considerable attention over the past 5 years to become a well-established processing route for porous materials of all kinds. In this viewpoint, I summarize the current status and recent trends of ice-templating studies. I then review the unique assets of ice-templating and propose a roadmap of the most promising or pressing questions and opportunities in this domain.

cond-mat.mtrl-sci↗

arXiv2017

Interaction of multiple particles with a solidification front : from compacted particle layer to particle trapping

The interaction of solidification fronts with objects such as particles, droplets, cells, or bubbles is a phenomenon with many natural and technological occurrences. For an object facing the front, it may yield various fates, from trapping to rejection, with large implications regarding the solidification pattern. However, whereas most situations involve multiple particles interacting with each other and the front, attention has focused almost exclusively on the interaction of a single, isolated object with the front. Here we address experimentally the interaction of multiple particles with a solidification front by performing solidification experiments of a monodisperse particle suspension in a Hele-Shaw cell, with precise control of growth conditions and real-time visualization. We evidence the growth of a particle layer ahead of the front at a close-packing volume fraction and we document its steady state value at various solidification velocities. We then extend single particle models to the situation of multiple particles by taking into account the additional force induced on an entering particle by viscous friction in the compacted particle layer. By a force balance model, this provides an indirect measure of the repelling mean thermomolecular pressure over a particle entering the front. The presence of multiple particles is found to increase it following a reduction of the thickness of the thin liquid film that separates particles and front. We anticipate the findings reported here to provide a relevant basis to understand many complex solidification situations in geophysics, engineering, biology, or food engineering, where multiple objects interact with the front and control the resulting solidification patterns.

cond-mat.soft↗