Jean-Christophe Sangleboeuf

Casting method for producing low-loss chalcogenide microstructured optical fibers

We report significant advances in the fabrication of low loss chalcogenide microstructured optical fiber (MOF). This new method, consisting in molding the glass in a silica cast made of capillaries and capillary guides, allows the development of various designs of fibers, such as suspended core, large core or small core MOFs. After removing the cast in a hydrofluoric acid bath, the preform is drawn and the design is controlled using a system applying differential pressure in the holes. Fiber losses, which are the lowest recorded so far for selenium based MOFs, are equal to the material losses, meaning that the process has no effect on the glass quality.

Surface damage of soda–lime–silica glasses: indentation scratch behavior

Abstract Contact mechanics problems are of fundamental interest both to understand the process of surface damage and matter removal in brittle materials, and to develop a method to evaluate their scratch resistance. In order to get insight into these problems in the case of soda–lime–silica glasses, a classical indentation apparatus was used, and an original scratch experimental setup was designed, allowing for a monotonic loading (or unloading) of the indenter combined with a controlled sliding of the specimen beneath the indenter. The influences of the normal load, the moisture level and the glass composition have been studied, and clear relationships were established between the glass compositions and the indentation-scratching behavior. The indentation and scratching characteristics such as the critical-crack-initiation loads and the transition loads between the different scratch regimes were correlated and interpreted in the light of the brittleness index and structural considerations.

The creep mechanism of ceramic matrix composites at low temperature and stress, by a material science approach

Abstract This paper deals with the creep mechanism for ceramic matrix composites reinforced by long ceramic fibers in a ceramic or glass-ceramic matrix, tested at low stresses (

Development of a chalcogenide glass fiber device for in situ pollutant detection

AbstractInfraredopticalfibersbasedonchalcogenidesareinvestigatedtooptimizetheirresponseandtheyareusedforinsitudetection of pollutant in groundwater. The pilot scale measurements proved that a Te 2 As 3 Se 5 (TAS) glass fiber permitsaccess to the absorption line positions of classic pollutants like tetrachloroethylene or dichlorobenzene. Moreover, ithas been shown that the original design of the fiber enables detection of weak concentrations of pollutants down to1 ppm. For experiments in real world conditions, optical fibers must be durable under various natural workingconditions in ground water. The preliminary mechanical tests demonstrate that efforts have to be done while drawingthe fiber to improve their resistance. Nevertheless, at this time, a polymer coated TAS glass fiber is already a useful toolto collect some infrared spectra in landfill. 2003 Elsevier B.V. All rights reserved. PACS:61.43.Fs; 42.81.)i; 62.20.)x; 89.60.+x 1. IntroductionA new generation of optical fibers has beendeveloped based on the large transparency domainof an original family of IR chalcogenide glassestransmitting from 2 to 14 lm. These fibers canbe used as chemical sensors in many fields of ap-plication: biology, medicine, food, environment

A synthetic aragonite-based bioceramic: influence of process parameters on porosity and compressive strength

We investigate the influence of process parameters such as weight fraction and particle size of pore-former, and isostatic pressure, on porosity and compressive strength of non-sintered porous calcium carbonate biomaterials compacted at high pressure in uniaxial or isostatic mode. Experiment design and results analysis are performed according to a two-level 2k factorial design method (FDM). Results indicate that only the weight fraction of pore-former (wt fpf) influences significantly the porosity and the compressive strength. The porosity P, is described by a linear function of wt fpf, and the compressive strength sigma(comp), by an exponential one. For materials compacted under uniaxial pressing: P (vol%) = 33.7 + 85.4 (wt fpf) and sigma(comp) (MPa) = 28.8e(-9.2(wt fpf)) with 0.1 < or = wt fpf < or = 0.3. For materials compacted in isostatic mode: P (vol%) = 33.9 + 82.1 (wt fpf) and sigma(comp) (MPa) = 24.0e(-7.0(wt fpf)) with 0.15 < or = wt fpf < or = 0.35. The pore-former particle size has no significant influence on both properties. The increase in isostatic pressure provides slightly lower porosity and better compressive strength. For a fixed fraction of pore-former, isostatic pressing leads to a better compressive strength than uniaxial pressing. This study indicates that, for a constant amount of pore former, the size of macropores can be adjusted to reach optimal bone-ingrowth without change in compressive strength.

Indentation-induced densification of soda-lime silicate glass

Abstract Glass is densified under a sharp diamond indenter. The densification is not a volume conservative process, and does not contribute to the volume strain around the indentation. This means that densification affects residual stresses around the indentation impression. In order to estimate the densification volume, three-dimensional images of Vickers indentations on soda-lime silicate glasses were obtained before and after annealing. Only the densified volume can be recovered by annealing. After annealing at around glass transition temperature, large volume recovery (55 – 80 %) of Vickers indentation was observed for soda-lime silicate glass. The volume recovery is much larger than the recoveries of indentation diagonal and depth. It is found that the densification of glass under the sharp indenter cannot be ignored for evaluating crack initiation and brittleness of glass. In addition, the residual stresses around the indentation impression were also estimated from the plastically deformed volume and the size of plastic zone around the indentation.

Understanding of the creep behavior of SiCf-SiBC composites

Abstract This paper deals with some creep results on a new generation of a ceramic matrix composite with a self-healing matrix. This investigation is based on the creep curves, the observation of damages and their quantification by image analysis, and the application of the damage mechanics approach. The results obtained herein illustrate the concept of the damage-creep mechanism.

SiCf–SiBC composites: microstructural investigations of the as-received material and creep tested composites under an oxidative environment

SiCf–SiBC composites fabricated by Snecma Propulsion Solide (St Médard en Jalles, France) were investigated by SEM and HRTEM in the as‐received state and after creep tests performed in air, in a temperature range 1423–1573 K, under 170 and 200 MPa. These composites are reinforced by Hi‐Nicalon fibres (Nippon Carbon). A pyrocarbon interphase was first deposited on the fibres. The matrix was then deposited on the fibrous preform by several chemical vapour infiltrations (CVI). As a result the matrix is multilayered and based on the Si–B–C ternary system. This matrix is self‐sealing: this is due to the presence of boron inducing the formation of a sealant glass if the material is heated in an oxidative environment. This glass will protect fibres and fibre/matrix interphases against oxidation. Hi‐Nicalon fibres as well as the different matrix layers were studied by HRTEM and EDX. Some investigations were carried out on the creep‐tested specimens in order to characterize modifications observed in the different constituents of the composites, particularly at the interfaces between the matrix layers and at the fibre/matrix interface. It was shown that several matrix layers crystallized during the creep tests. Moreover, a thin silica layer was observed at the pyrocarbon/matrix interfaces. Differences between the behaviour of the same type of material creep tested under neutral atmosphere are discussed.

Thermal behaviour of composites aluminosilicate-calcium phosphates

A new type of aluminosilicate matrix calcium phosphate crystallites composites (ACPC) was synthesized and studied for osseous bone applications. The room temperature synthesis of the aluminosilicate matrix and composites was described. Thermal treatments of compounds allowed the adaptability of some parameters (pH, porosity and mechanical properties). Structure of heat treated composites were characterized by XRD and FTIR. The influence of thermal treatment on the mechanical properties, the porosity and the pH was studied for two temperatures (250 and 500°C). Results evidenced the ability to control the pH, the high level of porosity (»70%) and the good mechanical properties, allowing to consider that ACPC are potential biomaterials for osseous bone application.

Influence of Grinding Parameters on Glass Workpieces Surface Finish Using Response Surface Methodology

Surface finish determines service life of glass workpieces. Therefore, an extensive polishing phase is usually performed to limit the local irregularities. In this paper, we propose to investigate the influence of the grinding parameters on the surface finish of glass samples in order to limit the damages at the earlier stage of the machining process. A central composite design of experiments has been used to define experimental tries that consist of up-grinding or down-grinding glass samples with various feed rate, depth of cut, and wheel speed values. Roughness parameters derived from the Abbott-Firestone curve R(k), R(vk), and the material ratio 100-Mr2 have been used to characterize the surface finishes of the ground glass samples. Using the design of experiments, surface responses have been modeled for each roughness parameter to investigate the influence of the cutting parameters. Abbott-Firestone parameters allow a relevant characterization of the glass samples surface finishes. Feed rate increase led to deeper valleys, thus providing a rough surface finish that could potentially shorten workpieces service life. On the contrary, increasing depth of cut tend to reduce valley depth. Wheel speed has shown minor influence on the surface finish. Up-grinding could help obtain less deep valleys than with a down-grinding. However, up-grinding also increases the cutting forces and induces vibrations that led to an increase of the core roughness and eventually to the fracture of the glass sample during the machining. In a material removal context-in opposition with polishing-feed rate should be carefully chosen since it is the most influential parameter on the surface finish. To maximize productivity while obtaining low-valleys surface finishes, an appropriate strategy would consist in down-grinding with a low feed rate, a high depth of cut, and a high wheel speed. [DOI: 10.1115/1.4004317]