École Nationale Supérieure de Céramique Industrielle

Inkjet printing is emerging at the forefront of biosensor fabrication technologies. Parallel advances in both ink chemistry and printers have led to a biosensor manufacturing approach that is simple, rapid, flexible, high resolution, low cost, efficient for mass production, and extends the capabilities of devices beyond other manufacturing technologies. Here we review for the first time the factors behind successful inkjet biosensor fabrication, including printers, inks, patterning methods, and matrix types. We discuss technical considerations that are important when moving beyond theoretical knowledge to practical implementation. We also highlight significant advances in biosensor functionality that have been realised through inkjet printing. Finally, we consider future possibilities for biosensors enabled by this novel combination of chemistry and technology.

The influence of grain boundaries on heat transfer through polycrystalline alumina has been investigated between 20° and 500°C. The thermal conductivities of small‐grained porous ceramics and large‐grained dense ceramics have been measured using the laser‐flash technique. Two methods have been developed to assess the average thermal resistance of a grain boundary. The first method is based on the comparison of room‐temperature thermal conductivities for dense ceramics that have various average grain sizes. This method yields a value of 0.9 × 10 −8 m 2 ·K·W −1 . The second method, particularly suitable for porous ceramics, is based on the extrapolation of the inverse of the thermal conductivity versus temperature to give an intercept with the axis at T = 0 K. This value is attributed to the thermal resistance of grain boundaries. By taking into account the influence of the pore content using an effective medium theory, the average thermal resistance of a grain boundary has been evaluated to be 1.3 × 10 −8 m 2 ·K·W −1 in dense alumina and 2.2 × 10 −8 m 2 ·K·W −1 in alumina containing a pore volume fraction of 0.3.

Although many thermal plasma processes have been developed for industrial applications, the wide acceptance as a manufacturing technology is prevented due to economical and competitive reasons, and/or reproducibility and reliability aspects. This paper is devoted to an assessment of the present knowledge in the following topics: (1) plasma torch and performance of blown arc (dc or ac), transferred arc and radio frequency torches; (2) established industrial applications with special emphasis on cutting, welding, spraying, transferred arc reclamation, reheating and purification, reheating metal melts, smelting reduction, chemical operations, and waste destruction; (3) recent developments in the knowledge of fundamental processes in plasma torches with power sources, cathodes (hot and cold), anodes (static and dynamic behavior), and torch components; (4) modeling-thermodynamic and transport properties, plasma flow with and without the Maxwell's equations; (5) measurement techniques including emission and absorption spectroscopy, laser scattering, enthalpy probes, video cameras, spectral analysis, shadowgraphy, and particle diagnostics either in flight with statistical measurements and those giving characteristics of a single particle upon flattening on a substrate; and (6) plasma-processing development in the presently used industrial processes and also in prospective processes with surface hardening, ultrafine powder production, plasma-assisted CVD, and plasma-fluidized or spouted bed reactors.

Lead magnesium sniobate, Pb(Mg 1/3 Nb 2/3 )O 3 (PMN), was prepared by a sol‐gel technique using alkoxide precursors. The hydrolysis‐condensation mechanism leads to a translucent gel which is dried under hypercritical conditions to avoid collapse of the porous texture. After drying, the aerogel exhibits a B‐deficient pyrochlore structure which progressively inserts magnesium oxide when the temperature increases. Near 700°C, this pyrochlore phase completely transforms into the PMN‐perovskite phase. Above 1000°C, the loss of lead oxide leads to the destabilization of the PMN‐perovskite with formation of an A‐deficient pyrochlore phase.

Abstract To estimate the contribution of all major components to the thermal properties of natural hemp fiber bundles, the thermal decomposition of hemp fibers following several chemical treatments was studied by the differential thermogravimetric analysis (DTA/TGA). Contrary to what was observed with measurements conducted under air, the thermal degradation of all major hemp fiber components (pectins, hemicellulose, cellulose, and lignin principally) could be easily detected and deconvoluted under inert atmosphere. The intensity of the TGA peaks observed at 235°C (characteristics of pectin) and at 265°C (characteristics of hemicellulose) decreased after all fiber chemical treatments. This resulted in an overall increase of the cellulose percentage. Based on the onset temperature of DTA, it was found that the thermal stability decreased in the following order: NaOH‐treated fibers, silane‐treated fibers, solvent extracted fibers (water/ethanol mixture, 20/80 v/v), and untreated hemp fibers. Moreover, the difference of the mass loss (%) between TGA under argon of silane‐treated fibers and untreated fibers showed that some silane molecules were chemically attached to hemp fiber bundles. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Among transition metal nitrides, molybdenum nitrides have been much less studied even though their mechanical properties as well as their electrical and catalytic properties make them very attractive for many applications. The δ-MoN phase of hexagonal structure is a potential candidate for an ultra-incompressible and hard material and can be compared with c-BN and diamond. The predicted superconducting temperature of the metastable MoN phase of NaCl-B1-type cubic structure is the highest of all refractory carbides and nitrides. The composition of molybdenum nitride films as well as the structures and properties depend on the parameters of the process used to deposit the films. They are also strongly correlated to the electronic structure and chemical bonding. An unusual mixture of metallic, covalent and ionic bonding is found in the stoichiometric compounds.

Ceramic three‐dimensional parts can be produced by a stereolithography (SL) process using a ceramic suspension containing alumina powder, UV curable monomer, diluent, photoinitiator and dispersant. The monomer reacts to UV radiation (argon ionized laser) and is transformed into a solid polymer which is then removed by thermal treatment (debinding). Subsequent sintering of green parts leads to dense ceramic parts. The effect of each component on the rheology of the alumina suspensions has been studied first. Both the addition of dispersant and diluent and the increase in temperature allow a significant decrease of the viscosity of the suspensions. The highly loaded (more than 55 vol. per cent), homogeneous and stable suspensions have a shear thinning behaviour which is favourable for casting the layers. Adequate cured depth (above 200μm) and satisfactory transversal resolution have been obtained and these allow the production of ceramic parts, which demonstrates the feasibility of the process. Sintering at 1,580°C leads to dense ceramic parts with homogeneous microstructure. The process still needs to be optimized to improve even more the mechanical properties.

Among the different rapid prototyping technologies, solid freeform fabrication (SFF) is the most suitable for ceramics. Here a stereolithographic technique is presented that allows the usage of pastes composed of ceramic particles dispersed in a photocurable resin for the fabrication of alumina pieces. They exhibit a similar flexural strength than alumina parts made by classical techniques like pressing.

Abstract Natural hemp fibers were chemically modified using silane coupling agents to reduce their hydrophilic character. The existence of a chemical bond between coupling agents and hemp fibers was confirmed by ATR‐FTIR spectroscopy, 29 Si Nuclear Magnetic Resonance (NMR), thermogravimetric analysis (TGA), energy dispersive spectroscopy (EDS), and BET surface area measurements. It was shown that the initial concentration and the chemical structure of the organosilane coupling agent have an effect on the grafted quantity on the hemp fiber surfaces. The grafted quantity increased proportionally to the initial concentration of silane molecules. The presence of polar amino end group (NH 2 ) in silane structure can cause an increase in the grafted quantity, compared with results obtained in the case of silane molecules containing methacryloxy groups. This effect is attributed to the formation of hydrogen bonds between NH 2 and unreacted hydroxyl groups of hemp fibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Si 3 N 4 /SiC composites are ceramic materials that exhibit excellent performance for high‐temperature applications. Prepared from an ultrafine amorphous Si‐C‐N powder, sintered materials are constituted mainly of a β ‐Si 3 N 4 matrix with SiC inclusions and have a very small grain size (less than 1 μm). Such a microstructure is propitious for superplastic forming. Superplasticity has been studied in tension, from 1550° to 1650°C, under nitrogen atmosphere. Elongations over 100% have been achieved. In many cases, at the highest temperatures and slowest strain rates, materials are damaged by different processes, including microcracking, cavitation, and chemical decomposition. A map of the most suitable (strain‐rate/temperature) domain has been established. It allows the prevention of any structural alteration by selecting carefully the testing conditions. Since specimens suffered considerable strain‐induced hardening, sources for this phenomenon are examined. Although the experiments have involved high temperature and extensive strain, neither static nor dynamic grain growth has occurred. Crystallization of the amorphous grain‐boundary phase, which is reported in most cases, may be invoked. However, based on microstructural observations, it is not the unique origin for flow hardening.

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This topical review presents an overview of the formulation, characterisation and range of applications for polymer nanocomposites. After explaining how material properties at the nanometre scale can vary compared to those observed at longer length scales, typical methods used to formulate and characterise nanocomposites at laboratory and industrial scale will be described. The range of mechanical, electrical and thermal properties obtainable from nanocomposite materials, with examples of current commercial applications, will be outlined. Formulation and characterisation of nanoparticle, nanotube and graphene composites will be discussed by reference to nanoclay-based composites, as the latter are presently of most technological relevance. Three brief case studies are presented to demonstrate how structure/property relationships may be controlled in a variety of polymer nanocomposite systems to achieve required performance in a given application. The review will conclude by discussing potential obstacles to commercial uptake of polymer nanocomposites, such as inconsistent protocols to characterise nanocomposites, cost/performance balances, raw material availability, and emerging legislation, and will conclude by discussing the outlook for future development and commercial uptake of polymer nanocomposites.

Fracture toughness of ZrO 2 ‐toughened alumina could he increased by macroscopic interfaces, such as those existing in laminated composites. In this work, tape casting was used to produce A/A or A/B laminates, where A and B can be Al 2 O 3 , Al 2 O 3 /5 vol% ZrO 2 , and Al 2 O 3 /l0 vol% ZrO 2 . An increase of toughness is observed, even in the Al 2 O 3 /Al 2 O 3 laminates.

Partitioning and transmutation (P&T) of minor actinides (MA) is currently studied to reduce the nuclear waste inventory. In this context, the fabrication of MA bearing materials is of great interest to achieve an effective recycling of these highly radioactive elements. To ensure the in-pile behavior, nuclear oxide fuels have to respect several criteria including preservation of the fluorite structure and defined oxygen to metal ratio (O/M). In the case of Am bearing materials, such as U(1-y)Am(y)O(2±x) (y = 0.10, 0.15, 0.20), the O/M determination is quite challenging using conventional methods (TGA, XRD) because of the particular thermodynamic properties of Am. Despite the lack of experimental data in the U-Am-O system, thermodynamical models are currently developed to effectively assess the O/M ratio. In this work, the O/M ratios were calculated for various oxygen potentials using the cation molar fraction determined by XAS measurements. These results are an important addition to the experimental data available for the U-Am-O system. Moreover, XRD and XAS indicated that the fabrication of fluorite U(1-y)Am(y)O(2±x) solid solution was achieved for all Am content and oxygen potentials investigated. On the basis of the molar fraction, a description of the solid solution was proposed depending on the considered sintering conditions. Finally, the occurrence of an unexpected charge compensation mechanism was pointed out.

Nitrogen sorption and small- and wide-angle X-ray and neutron scattering techniques were used to study the porous structure of geopolymers, inorganic polymers synthesized by reaction of a strongly alkaline solution and an aluminosilicate source (metakaolin). The effects of aging and the use of alkali activators (Na + , K + ) of different sizes were investigated at room temperature. The influence of aging time on the microstructure of both geopolymer matrixes was verified in terms of pore volume and specific surface area. The results suggested a refinement of the porosity and therefore a reduction in the pore volume over time. Regardless of the age considered, some characteristics of the porous network such as pore size, shape and distribution depend on the alkali activator used. Whatever the technique considered, the potassium geopolymer has a greater specific surface area than the sodium geopolymer. According to the scattering results, the refinement of the porosity can be associated with, first, a densification of the solid network and, secondly, a partial closure of the porosity at the nanometre scale. The kinetics are much slower for the sodium geopolymer than for the potassium geopolymer in the six months of observation.

The aggregation process of a two-component dilute system (3 vol %), made of alumina submicrometer particles and silica nanoparticles, is studied by Brownian dynamics simulations. Alumina and silica particles have very different sizes (diameters of 400 and 25 nm, respectively). The particle-particle interaction potential is of the DLVO form. The parameters of the potential are extracted from the experiments. The simulations show that the experimentally observed aggregation phenomena between alumina particles are due to the silica-alumina attraction that induces an effective driving force for alumina-alumina aggregation. The experimental data for silica adsorption on alumina are very well reproduced.

This paper deals with the role of epitaxial strain on the structure and electronic transport properties of metastable SmNiO3 layers grown by metal-organic chemical vapor deposition onto SrTiO3 and LaAlO3 substrates. The characterization of these layers is carried out by high resolution x-ray diffraction and four-probe resistivity measurements. It is found that the SmNiO3 phase is stabilized by in-plane compressive strain whereas in-plane tensile strain induces the creation of oxygen vacancies that induces an annihilation of the metal-insulator transition and a huge increase of the resistivity.

-HA) porous ceramics were processed to obtain a similar microstructure and surface physico-chemical properties (grain size, porosity ratio and pore size, surface roughness and zeta potential). The biological behavior was studied using MC3T3-E1 pre-osteoblastic and RAW 264.7 monocyte/macrophage cell lines. Chemical dissolution in the culture media and resorption lacunae produced by osteoclasts occur with both HA and CHA ceramics, but CHA exhibits much higher dissolution and greater bioresorption ability. CHA ceramics promoted a significantly higher level of pre-osteoblast proliferation. Osteoblastic differentiation, assessed by qRT-PCR of RUNX2 and COLIA2, and pre-osteoclastic proliferation and differentiation were not significantly different on CHA or HA ceramics but cell viability and metabolism were significantly greater on CHA ceramics. Thus, the activity of both osteoclast-like and osteoblastic cells was influenced by the carbonate substitution in the apatite structure. Furthermore, CHA showed a particularly interesting balance between biodegradation, by osteoclasts and chemical dissolution, and osteogenesis through osteoblasts' activity, to stimulate bone regeneration. It is hypothesized that this amount of 4.4 wt% carbonate substitution leads to an adapted concentration of calcium in the fluid surrounding the ceramic to stimulate the activity of cells. These results highlight the superior biological behavior of microporous 4.4 wt% A/B CHA ceramics that could beneficially replace the commonly used HA of biphasic calcium phosphates for future applications in bone tissue engineering.

The actual ambiguity in the interpretation of the Raman-active vibrations of tetragonal ${\mathrm{ZrO}}_{2}$ is discussed as a factor impeding progress in long-standing investigations of the polymorphism of zirconia. The reliable symmetry assignment of these vibrations is proposed by analyzing a polarized light scattering from single-crystal grains of epitaxial films of pure $t\ensuremath{-}{\mathrm{ZrO}}_{2}$ grown on monocrystalline ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ samples. The interrelations between the Raman spectrum of $t\ensuremath{-}{\mathrm{ZrO}}_{2}$ and the relevant phonons of $c\ensuremath{-}{\mathrm{ZrO}}_{2}$ are considered, implying the ${A}_{1g}$ vibration as a soft mode driving the tetragonal-cubic transformation.

The sol–gel method has been developed for the preparation of pure Ba(Mg 1/3 Ta 2/3 )O 3 ceramics. This involves the reaction of the heterometallic alkoxide Ta 2 Mg(OEt) 12 with hydrated barium hydroxide Ba(OH) 2 ·8H 2 O. Complete crystallization of the sol–gel‐derived powder is achieved at 600°C, leading to a cubic perovskite type phase. After sintering at 1400°C (2–5 h), a trigonal cell arises from Mg–Ta ordering (the degree of order is greater than 0.9), and about 98.5% of the theoretical density is obtained. Preliminary microwave dielectric measurements show that the dielectric constant and the unloaded Q u of the ceramics are 24.2 and 6750, respectively, at 7.7 GHz.