Showing papers by "Philippe Belleville published in 2005"

Applications of hybrid organic–inorganic nanocomposites

Abstract: Organic–inorganic hybrid materials do not represent only a creative alternative to design new materials and compounds for academic research, but their improved or unusual features allow the development of innovative industrial applications. Nowadays, most of the hybrid materials that have already entered the market are synthesised and processed by using conventional soft chemistry based routes developed in the eighties. These processes are based on: a) the copolymerisation of functional organosilanes, macromonomers, and metal alkoxides, b) the encapsulation of organic components within sol–gel derived silica or metallic oxides, c) the organic functionalisation of nanofillers, nanoclays or other compounds with lamellar structures, etc. The chemical strategies (self-assembly, nanobuilding block approaches, hybrid MOF (Metal Organic Frameworks), integrative synthesis, coupled processes, bio-inspired strategies, etc.) offered nowadays by academic research allow, through an intelligent tuned coding, the development of a new vectorial chemistry, able to direct the assembling of a large variety of structurally well defined nano-objects into complex hybrid architectures hierarchically organised in terms of structure and functions. Looking to the future, there is no doubt that these new generations of hybrid materials, born from the very fruitful activities in this research field, will open a land of promising applications in many areas: optics, electronics, ionics, mechanics, energy, environment, biology, medicine for example as membranes and separation devices, functional smart coatings, fuel and solar cells, catalysts, sensors, etc.

MgO insulating films prepared by sol–gel route for SiC substrate

Abstract: Silicon carbide (SiC) is a wide bandgap semiconductor suitable for high-voltage, high-power, and high-temperature devices from dc to microwave frequencies. However, the commercialization of advanced SiC power devices remains limited due to performance limitation of the SiO2 dielectric among other issues. Indeed, SiO2 has a dielectric constant 2.5 times lower than that of SiC, which means that at critical field for breakdown in SiC, the electric field in the adjoining SiO2 becomes too high for reliable operation. This removes the main advantage of using SiC power devices if the ten times higher breakdown field for SiC in comparison to Si cannot be exploited. Therefore, alternative dielectrics having a dielectric constant higher than or of the same order as that of SiC (ɛr ≈ 10) should be used to reduce the electrical field in the insulator. Among alternative dielectrics to silicon dioxide (SiO2), magnesium oxide (MgO) seems to be a good candidate regarding its bulk properties: large bandgap, high thermal conductivity and stability, and a suitable dielectric constant (ɛr ≈ 10). In order to evaluate such promising candidate, the sol–gel process appears to be a convenient route to elaborate this kind of coatings. By selecting appropriate precursor solution and optimizing the curing conditions of the films, MgO films could be obtained under various crystallization states: non-oriented and preferred 〈1 1 1〉 orientation. MIM structures have been used to investigate the insulating potentialities of the sol–gel MgO films. The dielectric strength of the films was found to be microstructure dependent, and reached 5–8 MV/cm at room temperature. Leakage currents were measured from 25 °C up to 250 °C.

Nanosturctured Coating and Coating Method

Abstract: The present invention relates to a method of coating a surface with nanoparticles, to a nanostructured coating that can be obtained by this method, and also to a device for implementing the method of the invention. The method is characterized in that it comprises an injection of a colloidal sol of said nanoparticles into a plasma jet that sprays them onto said surface. The device ( 1 ) comprises: a plasma torch ( 3 ); at least one container ( 5 ) containing the colloidal sol ( 7 ) of nanoparticles; a device ( 9 ) for fixing and for moving the substrate(S); and a device ( 11 ) for injecting the colloidal sol into the plasma jet ( 13 ) of the plasma torch. The present invention has applications in optical, electronic and energy devices (cells, thermal barriers) comprising a nanostructured coating that can be obtained by the method of the invention.

Nanostructured coating and coating method

Abstract: The invention relates to a method for coating a surface with nanoparticles, to a nanostructured coating that can be obtained by using this method, and to a device for carrying out the inventive method. The method is characterized in that it involves an injection of a colloidal sol of these nanoparticles into a plasma jet that projects these onto the surface. The device (1) comprises plasma torch (3), at least one reservoir (5) containing the colloidal sol (7) of nanoparticles; a device (9) for fixing and displacing the substrate (S), and; an injection system (11) for injecting the colloidal sol into the plasma jet (13) of the plasma torch. The invention can be used in optical, electronic, and energy (battery, thermal barrier) devices comprising a nanostructured coating that can be obtained by using the aforementioned method.

Mgo-Based Coating for Electrically Insulating Semiconductive Substrates and Production Method Thereof

Abstract: The present invention relates to a magnesium oxide-based (MgO) inorganic coating intended to electrically insulate semiconductive substrates such as silicon carbide (SiC), and to a method for producing such an insulating coating. The method of the invention comprises the steps of preparing a treatment solution of at least one hydrolysable organomagnesium compound and/or of at least one hydrolysable magnesium salt, capable of forming a homogeneous polymer layer of magnesium oxyhydroxide by hydrolysis/condensation reaction with water; depositing the treatment solution of the hydrolysable organomagnesium compound or of the hydrolysable magnesium salt, onto a surface to form a magnesium oxide-based layer; and densifying the layer formed at a temperature of less than or equal to 1000° C.

Process for preparing piezoelectric materials

Abstract: The invention concerns a method for preparing a material based on piezoelectric ceramic oxide(s) comprising the following steps: a) wet deposition on at least one surface of a substrate of a layer of a dispersion comprising a piezoelectric ceramic oxide powder and a piezoelectric ceramic oxide precursor sol-gel solution identical to or different from the piezoelectric oxide constituting the powder; b) repeating a) once or several times, so as to obtain a stack of at least two layers; c) heat-treating said layers so as to transform them into corresponding ceramics; d) wet-shrink impregnation of the stack obtained at c) with a sol-gel solution identical to the one used in step a); e) optionally repeating step d) once or several times; f) heat-treating said stack, so as to transform the sol-gel impregnating the stack into the corresponding piezoelectric ceramics.

Process for producing thin photosensitized semiconducting films

Abstract: The invention relates to a process for producing thin, semiconducting films photosensitized by one or more chromophores, which comprises at least one cycle comprising, in succession, the following steps: a) a step of depositing, on a support, at least one film of a solution obtained by sol-gel polymerization of one or more precursors of a semiconducting oxide or semiconducting oxides, said semiconducting oxide or oxides being chosen from metal oxides, metalloid oxides and mixtures thereof; b) a drying step carried out on the film obtained at a); c) an acid, basic or neutral treatment step carried out in liquid or gaseous medium on the film obtained at b); and d) a step of photosensitizing the film obtained at c) by one or more chromophores, by bringing this film into contact with a solution containing the chromophore(s). Application to the production of electrodes for photovoltaic cells and to light-emitting diodes.

Revetement nanostructure et procede de revetement

Abstract: La presente invention se rapporte a un procede de revetement d'une surface par des nanoparticules, a un revetement nanostructure susceptible d'etre obtenu par ce procede, ainsi qu'a un dispositif de mise en oeuvre du procede de l'invention. Le procede se caracterise en ce qu'il comprend une injection d'un sol colloidal desdites nanoparticules dans un jet de plasma qui les projette sur ladite surface. Le dispositif (1) comprend une torche a plasma (3) ; au moins un reservoir (5) contenant le sol colloidal (7) de nanoparticules ; un dispositif de fixation et deplacement (9) du substrat (S) ; et un systeme d'injection (11) du sol colloidal dans le jet de plasma (13) de la torche a plasma. La presente invention trouve une application dans des dispositifs optique, electronique, energetiques (pile, barriere thermique) comprenant un revetement nanostructure susceptible d'etre obtenu par le procede de l'invention.

Mgo-base coating for electrically insulating semi-conductor substrates and production method

Abstract: The invention relates to an inorganic magnesium oxide-based coating (MgO) for electrically insulating semi-conductor substrates such as a silicon carbide (SiC) and to a method for producing said insulating coating. The inventive method consists in preparing a treating solution of at least one type of water-soluble organomagnesium and/or of at least one type of a water-soluble magnesium salt for forming a homogenous polymer magnesium oxide/hydroxide layer by a hydrolysis-condensation reaction with water, in applying the treating water-soluble organomagnesium or water-soluble magnesium salt solution to a surface for forming a magnesium oxide-base layer and in densifying the thus formed layer at a temperature equal to or less than 1000 °C.

Production of a ceramic oxide based coating conforming with the geometry of a substrate with raised designs, using a sol-gel technique with a precursor solution of the ceramic oxide

Abstract: Production of a ceramic oxide conformable coating on a substrate having raised designs comprises: (a) deposition of a sol-gel solution layer, as a precursor of the ceramic, on the substrate; (b) heat treatment of the layer to form the ceramic; (c) optional repetition of these steps; (d) the sol-gel solution is prepared by contacting metal molecular precursors of the ceramic in a diol solvent and possibly aliphatic monoalcohol, allowing the solution to rest to obtain an essentially constant viscosity and diluting the solution with a diol solvent.

Procede de fabrication de couches minces semi-conductrices photosensibilisees

Abstract: L'invention a trait a un procede de fabrication de couches minces semi-conductrices photosensibilisees par une ou plusieurs substances chromophores, qui comprend au moins un cycle comprenant successivement les etapes suivantes : a) une etape de depot sur un support d'au moins une couche d'une solution obtenue par polymerisation par voie sol-gel d'un ou plusieurs precurseurs d'oxyde(s) semi-conducteur(s), ledit ou lesdits oxyde(s) semi-conducteurs etant choisi(s) parmi les oxydes de metaux, les oxydes de metalloide et les melanges de ceux-ci ; b) une etape de sechage de la couche obtenue en a) ; c) une etape de traitement acide, basique ou neutre en milieu liquide ou gazeux de la couche obtenue en b) ; d) une etape de photosensibilisation de la couche obtenue en c) par une ou plusieurs substances chromophores par mise en contact de cette couche avec une solution comprenant la ou les substance(s) chromophore(s). Application a la fabrication d'electrodes de cellules photovoltaiques et aux diodes electroluminescentes.

Method for preparing piezoelectric materials

Abstract: The invention concerns a method for preparing a material based on piezoelectric ceramic oxide(s) comprising the following steps: a) wet deposition on at least one surface of a substrate of a layer of a dispersion comprising a piezoelectric ceramic oxide powder and a piezoelectric ceramic oxide precursor sol-gel solution identical to or different from the piezoelectric oxide constituting the powder; b) repeating a) once or several times, so as to obtain a stack of at least two layers; c) heat-treating said layers so as to transform them into corresponding ceramics; d) wet-shrink impregnation of the stack obtained at c) with a sol-gel solution identical to the one used in step a); e) optionally repeating step d) once or several times; f) heat-treating said stack, so as to transform the sol-gel impregnating the stack into the corresponding piezoelectric ceramics.

Preparation of a stable sol-gel solution precursor of a ceramic oxide containing lead, titanium, zirconium and a metal lanthanide for electronic applications calling for a high dielectric constant

Abstract: The preparation of a stable sol-gel solution precursor of a ceramic oxide comprises: (A) preparing a sol-gel solution from molecular precursors of lead, titanium, zirconium and a metal lanthanide with a diol solvent and possibly an aliphatic mono-alcohol; (B) resting the solution for sufficient time to obtain an essentially constant viscosity; and (C) diluting the solution to a determined level with an identical diol solvent or a miscible solvent. Independent claims are also included for: (A) the sol-gel solution obtained from this method of preparation; (B) the preparation of a ceramic material using the sol-gel solution; and (C) the ceramic oxide material produced.

Method for production of photosensitised thin layer semiconductors

Abstract: The invention relates to a method for production of thin layer semiconductors, photosensitised by one or more chromophore substances with at least one cycle, comprising the following successive steps: a) a step of deposition on a support of at least one layer of a solution, obtained by sol-gel polymerisation of one or more precursors of semiconductor oxide(s), said semiconductor oxide(s) being selected from metallic oxides and mixtures thereof, b) a drying step for the layer obtained in a), c) an acid, basic or neutral treatment step in a liquid or gaseous medium of the layer obtained in b), d) a photosensitisation step of the layer obtained in c) using one or more chromophore substances, by bringing said layer into contact with a solution comprising the chromophore substance(s). The above is of application in the production of electrodes for photovoltaic cells and electroluminescent diodes.