WO2008145182A1 - Procédé de fabrication de préformes de verre à structure de précision - Google Patents

Procédé de fabrication de préformes de verre à structure de précision Download PDF

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Publication number
WO2008145182A1
WO2008145182A1 PCT/EP2007/055237 EP2007055237W WO2008145182A1 WO 2008145182 A1 WO2008145182 A1 WO 2008145182A1 EP 2007055237 W EP2007055237 W EP 2007055237W WO 2008145182 A1 WO2008145182 A1 WO 2008145182A1
Authority
WO
WIPO (PCT)
Prior art keywords
sol
glass
gel
structured
mould
Prior art date
Application number
PCT/EP2007/055237
Other languages
English (en)
Inventor
Lorenzo Costa
Andreas RÜCKEMANN
Original Assignee
Degussa Novara Technology S.P.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Degussa Novara Technology S.P.A. filed Critical Degussa Novara Technology S.P.A.
Priority to PCT/EP2007/055237 priority Critical patent/WO2008145182A1/fr
Priority to TW097119536A priority patent/TW200911712A/zh
Publication of WO2008145182A1 publication Critical patent/WO2008145182A1/fr

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
    • C03B37/01—Manufacture of glass fibres or filaments
    • C03B37/012—Manufacture of preforms for drawing fibres or filaments
    • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
    • C03B37/016—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by a liquid phase reaction process, e.g. through a gel phase
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2203/00—Fibre product details, e.g. structure, shape
    • C03B2203/10—Internal structure or shape details
    • C03B2203/14—Non-solid, i.e. hollow products, e.g. hollow clad or with core-clad interface
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2203/00—Fibre product details, e.g. structure, shape
    • C03B2203/42—Photonic crystal fibres, e.g. fibres using the photonic bandgap PBG effect, microstructured or holey optical fibres

Definitions

  • the invention concerns a method to produce precision structured performs of glass. These performs can be used to prepare micro-structured optical fibers.
  • Structured preforms are important for the preparation of micro-structured optical fibres.
  • Micro-structured optical fibres typically are characterized by an array of air columns embedded within a silica matrix and extended along the z-axis of fibre.
  • the interest in the micro-structured optical fibres is motivated as a promising option for alternative products to the conventional optical fibre.
  • the new product is based on different optical principles, that consent wave-guiding under different conditions, like photonic band gap guidance.
  • Several new properties were observed and reported for wave-guiding under these conditions, among others are super-continuum generation, high birefringence, endlessly single moded behaviour and low bend-loss. (Sol-gel derived micro-structured fibres fabrication and characterization (Ryan T. Bise and Dennis J. Trevor, OWL 6)).
  • Micro-structured optical fibres have been fabricated first using conventional optical components like glass tubes and rods, bundling them together and drawing into fibres.
  • EP 1 172 339 B 1 is specifically directed to the, so called, "alkaline sols", well defined in the two, previously quoted, technical patents.
  • EP 1 172 339 Bl states how to use the mould with the alkaline sol; claim 1, step b) , states: "Filling at least a portion of said vessel with a silica-containing sol, and permitting or causing said sol to gel, such that a gel body with said multiplicity of elongated elements results" its teaching is consistent with the use of alkaline sols, that are "silica containing sols"; it is silent about alkoxydes, that are not present in the formulation of such sols, (defined in US 5.240.488 and US 5.379.364) . No example of sol preparation is given, consistently with the dependence on the sol formulation defined in the previously quoted us patents. For sake of clarity, in those patents the sol is prepared exclusively with silica, at "alkaline pH” (Sol - pH over 12) .
  • the subject of the invention is a method to produce precise structured preforms of glass for pulling micro-structured optical fibers, using the known sol-gel process, which characterized in, that the sol is poured into a mould which is equipped with a number of inserts and the inserts are extracted before the syneresis of the aquagel takes place.
  • the invention has discovered that the precision required for fine-structured pre-forms for high-performing micro- structured optical fibres is achievable by Sol-Gel advantageously through a very different sol-formulation and a different moulding procedures with respect to previous art .
  • the process according to the invention is based on composite sol, gelation under acid conditions and supercritical drying of the aquagel, that, under specific conditions, can be characterized by thermo-mechanical ideal isotropy, maintained also through thermal densification to glass.
  • thermo-mechanical ideal isotropy maintained also through thermal densification to glass.
  • the sol used according to the invention for the precision replication of the mould inner volume can be a composite sol, derived from the combination of silicic acid from silicon alkoxide, hydrolyzed under acid pH and, non- hydrolysable under such conditions fumed silica, in the proper proportions.
  • the acidic hydrolysis of the silicon-alkoxide is dictated by the need of acidic conditions for gelation to produce a porous network structured down to the lowest dimensions.
  • Alkaline gelation tends, instead toward aggregation of massive, non-porous, globular components of sizable dimensions, (C. Jeffrey Brinker, George W. Scherer, SOL-GEL SCIENCE, pages 99-107) .
  • the sol preparation can be based on the specific procedure described in the following:
  • Acid catalyzed hydrolysis of silicon alkoxide/alkoxides in water can be between 4 and 48.
  • pH of water before hydrolysys can be from 1,0 to 3,0; preferred condition can be from 1,5 to 2,5.
  • Silicon dioxide as "fumed -silica" present during hydrolysis can be not in excess of 4/1 molar ratio silicon dioxide/silicon alkoxide.
  • Total silicon dioxide present in the sol can be not in excess of 4/1 molar ratio silicon dioxide/silicon alkoxide.
  • the optional extraction of liquid phase can be done by reduced pressure-distillation. This can be done completely or partially.
  • a mechanical and/or ultrasonic homogenization of sol can be done.
  • Degassing of sol can be done by ultra-sonic and/or reduced pressure, and/or helium bubbling. The degassing steps can help to remove the bubbles from the sol.
  • a optionally centrifuging the sol at 550 to 650 "g" can be done if extra uniformity is needed.
  • the centrifugation is not essential to the process of the invention. Therefore this step can be done optionally. But, if done, it results in a smother surface.
  • the pH-value of the sol can be stuffed into the range of 3.5 to 4.1, preferred 3.65 to 3.80 in order to start the gelation.
  • the stuffing can be done by adding a free base.
  • the sol can be filled into moulds prepared for the desired precision-structured aquagel.
  • the moulds can be prepared as follows: A proper cylindrical container ("tubular") , equipped with proper number of inserts (inner moulds), is prepared providing the necessary anti adesion character of the mould critical surfaces, by proper choice of materials or by proper surface-treatments of the same.
  • the method for precision structuring cylindrical aqua-gels with series of columns, parallel to the aquagel axial direction can be based on a series of elongated elements, protruding into the gel, and extractable before the syneresis of the aquagel takes place.
  • the internal volume of the mould is characterized by the same symmetry of the aquagel programmed.
  • the inner mould can be made of plastic, natural hydrophobic material, glass or metal with specific hydrophobic surface treatment.
  • the plastic can be used without any surface treatment .
  • the sol After the sol is poured into the mould it can be properly monitored to determine its gelation time (typically less then 2 hrs) ; After gelation water can be poured over the gel .
  • the inner mould can be extracted before they can be blocked by the process of "syneresis".
  • Syneresis is the phenomenon observed in sol-gel after the gelation and moderate aging of the gel. It is observable typically from 6 hours of aging of the gel. It manifests itself with a small withdrawing of the gel mass from the external mould. It typically results in an advantage for extracting the gel body from the external mould, but in a serious problem of compression on any evential inner mould.
  • the syneresis is explained with a model of crosslinking of silanol groups facing each other in micropores from opposite positions.
  • the structured gel can remain in the external, cylindrical container and go through the process of aging (about 48 hrs) , the process of neutralization (about 72 hrs) , the process of solvent exchange (10-15 days), the process of supercritical drying (24-36 hrs) and an aero-gel, bearing the identical structure of the aquagel, but for the light, isotropic shrinkage due to the syneresis, is produced.
  • the aero-gel can be removed from the original container and entered the densification oven, were it is subjected to a known process of thermo-densification at temperature below 1400 0 C to become an optical fibre preform of the purest silica glass.
  • the process according to the invention shows the advantage that precise forms of isotropic glass can be made.
  • the precision is better than one part per thousand.
  • An acid sol was prepared as it follows:
  • the resulting homogeneous, composite sol was conditioned for gelation in about 1 h by rising its pH to a value of 3.71.
  • the mould was filled with sol and sealed.
  • the inner moulds were extracted using a precision extractor and adding enough water to balance the volume of the extracted inner-moulds.
  • the structured gel was left in the external mould, properly sealed and aged for 48 hrs, then the bottom closure of the mould was replaced with the "solvent-exchange" type of closure and a light fluxing of distilled water / acetone started to gradually dehydrate the liquid surrounding the gel and filling its porosity.
  • the process of solvent- exchange was completed after 11 days, when the concentration of water in the liquid surrounding the gel was less than 0.5 %.
  • the gel was set for drying in autoclave, immerged in acetone. The temperature and the pressure were programmed for 280 0 C and 55 bars. After the autoclave cycle the sample was extracted from the original container as aerogel. The aero-gel was extracted from the original container and densified to glass in the known densification cycle that include decarbonisation, dehydration and purification from traces of metals. A pure silica glass was obtained, perfectly structured as programmed, without defects or deformations to a precision of 1 part / thousand.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Glass Melting And Manufacturing (AREA)
  • Manufacture, Treatment Of Glass Fibers (AREA)

Abstract

L'invention porte sur un procédé de fabrication de préformes de verre à structure de précision par le procédé sol-gel connu, le sol étant versé dans un moule équipé d'inserts et les inserts étant extraits avant que la synérèse de l'aquagel n'ait lieu. Les préformes de verre peuvent être utilisées pour la traction de fibres optiques microstructurées.
PCT/EP2007/055237 2007-05-30 2007-05-30 Procédé de fabrication de préformes de verre à structure de précision WO2008145182A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/EP2007/055237 WO2008145182A1 (fr) 2007-05-30 2007-05-30 Procédé de fabrication de préformes de verre à structure de précision
TW097119536A TW200911712A (en) 2007-05-30 2008-05-27 Method to produce precision structured preforms of glass

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2007/055237 WO2008145182A1 (fr) 2007-05-30 2007-05-30 Procédé de fabrication de préformes de verre à structure de précision

Publications (1)

Publication Number Publication Date
WO2008145182A1 true WO2008145182A1 (fr) 2008-12-04

Family

ID=39032203

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2007/055237 WO2008145182A1 (fr) 2007-05-30 2007-05-30 Procédé de fabrication de préformes de verre à structure de précision

Country Status (2)

Country Link
TW (1) TW200911712A (fr)
WO (1) WO2008145182A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11884550B2 (en) 2016-09-02 2024-01-30 3M Innovative Properties Company Shaped gel articles and sintered articles prepared therefrom

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5240488A (en) * 1992-08-14 1993-08-31 At&T Bell Laboratories Manufacture of vitreous silica product via a sol-gel process using a polymer additive
EP1172339A1 (fr) * 2000-07-11 2002-01-16 Lucent Technologies Inc. Procédé de fabrication d'une fibre optique microstructurée par un procédé sol-gel
EP1199581A1 (fr) * 2000-10-20 2002-04-24 Lucent Technologies Inc. Fibre multimode microstructurée
EP1283195A1 (fr) * 2001-08-01 2003-02-12 Novara Technology S.R.L. Procédé sol-gel pour la fabrication de préformes pour fibres optiques
EP1661866A1 (fr) * 2004-11-27 2006-05-31 Degussa AG Procédé de fabrication de gels de silice à base d'eau

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5240488A (en) * 1992-08-14 1993-08-31 At&T Bell Laboratories Manufacture of vitreous silica product via a sol-gel process using a polymer additive
EP1172339A1 (fr) * 2000-07-11 2002-01-16 Lucent Technologies Inc. Procédé de fabrication d'une fibre optique microstructurée par un procédé sol-gel
EP1199581A1 (fr) * 2000-10-20 2002-04-24 Lucent Technologies Inc. Fibre multimode microstructurée
EP1283195A1 (fr) * 2001-08-01 2003-02-12 Novara Technology S.R.L. Procédé sol-gel pour la fabrication de préformes pour fibres optiques
EP1661866A1 (fr) * 2004-11-27 2006-05-31 Degussa AG Procédé de fabrication de gels de silice à base d'eau

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11884550B2 (en) 2016-09-02 2024-01-30 3M Innovative Properties Company Shaped gel articles and sintered articles prepared therefrom

Also Published As

Publication number Publication date
TW200911712A (en) 2009-03-16

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