Process Developments And Applications Around The Powder In Tube Technique

The purpose of this presentation is to give an overview of techniques available to produce original optical fibers and application dedicated. Some alternative fabrication solutions to the well-know stack and draw technique will be developed, following by the interest to join the stack and draw technique to other ones like Repusil® Technique, Rod in Tube and finally the Powder in Tube methods, first described by the Bell Lab in the seventies and up to date since some years by several groups in the world. Realization of performing optical devices such as light sources or optical sensors can be purposed by this two last original ways

High-performance shape-engineerable thermoelectric painting

Output power of thermoelectric generators depends on device engineering minimizing heat loss as well as inherent material properties. However, the device engineering has been largely neglected due to the limited flat or angular shape of devices. Considering that the surface of most heat sources where these planar devices are attached is curved, a considerable amount of heat loss is inevitable. To address this issue, here, we present the shape-engineerable thermoelectric painting, geometrically compatible to surfaces of any shape. We prepared Bi2Te3-based inorganic paints using the molecular Sb2Te3 chalcogenidometalate as a sintering aid for thermoelectric particles, with ZT values of 0.67 for n-type and 1.21 for p-type painted materials that compete the bulk values. Devices directly brush-painted onto curved surfaces produced the high output power of 4.0 mW cm(-2). This approach paves the way to designing materials and devices that can be easily transferred to other applications.ope

Modified powder-in-tube technique based on the consolidation processing of powder materials for fabricating specialty optical fibers

The objective of this paper is to demonstrate the interest of a consolidation process associated with the powder-in-tube technique in order to fabricate a long length of specialty optical fibers. This so-called Modified Powder-in-Tube (MPIT) process is very flexible and paves the way to multimaterial optical fiber fabrications with different core and cladding glassy materials. Another feature of this technique lies in the sintering of the preform under reducing or oxidizing atmosphere. The fabrication of such optical fibers implies different constraints that we have to deal with, namely chemical species diffusion or mechanical stress due to the mismatches between thermal expansion coefficients and working temperatures of the fiber materials. This paper focuses on preliminary results obtained with a lanthano-aluminosilicate glass used as the core material for the fabrication of all-glass fibers or specialty Photonic Crystal Fibers (PCFs). To complete the panel of original microstructures now available by the MPIT technique, we also present several optical fibers in which metallic particles or microwires are included into a silica-based matrix

Selective laser sintering of porcelain

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Fabrication and optical properties of transparent fine-grained Zn1.1Ga1.8Ge0.1O4 and Ni2+ (or Cr3+)-doped Zn1.1Ga1.8Ge0.1O4 spinel ceramics

International audienceFor the first time, a Zn1.1Ga1.8Ge0.1O4 transparent spinel ceramic has been fully densified by spark plasma sintering. XRD measurements show that this ceramic is composed of a pure cubic spinel phase. SEM analysis revealed a homogeneous and dense microstructure with the average grain size being 200 ± 100 nm. The transmittance of these fine-grained ceramics reached 70 % in the visible range and is very close to 80 % at 2 µm, thus close to the Tmax value deduced from the measurement of the refractive index. The ceramics exhibit excellent mechanical properties with a Young modulus of 222 GPa, a Vickers hardness of 14.25 GPa and a thermal conductivity of 7.3 W.m−1. K−1. By doping with Cr3+ ions, transparent Zn1.1Ga1.8Ge0.1O4 ceramics present both a red luminescence and a long-lasting afterglow during several minutes. Moreover, a near infrared broadband emission at 1.3 µm is also achieved with Ni2+ ions

Highly transparent bismuth borotellurite glass-ceramics: Comprehension of crystallization mechanisms

International audienceUnderstanding the mechanism at play during the partial crystallization of a parent glass remains crucial for controlling the optical properties of the final glass-ceramics. In this work, we study the crystallization of bismuth borotellurite glasses, where a specific investigation on the 60TeO2–20B2O3–20Bi2O3 composition is reported. Under adapted heat treatment conditions, highly transparent glass-ceramics can be obtained: the crystallization of the unique anti-glass Bi2Te4O11 phase is evidenced by X-ray diffraction and Raman spectroscopy data confirm its disordered nature. While the quenched glass appears homogeneous, the observation of the early stages glass-ceramic samples by transmission electron microscopy reveals the formation of isolated polycrystalline Bi2Te4O11 entities scattered in a predominant glassy matrix. However, longer heat-treatment of samples induce some chemical demixtion of the residual glass matrix, where two separate amorphous regions of a different composition coexist. The resulting material is finally constituted of the aforementioned Bi2Te4O11 polycrystalline clusters dispersed within a majority of regions with a Te/Bi ratio larger than the nominal 1.5 ratio, separated by tiny “venules” strongly impoverished in tellurium and also likely containing boron element. Photoluminescence properties of Eu3+-doped samples indicate that tiny spectral and temporal modifications happen with the crystallization, reflecting the persistent disordered surrounding of the rare-earth ions. © 202

Fibres optiques vitrocéramiques par le procédé «powder in tube ».

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