Fabrication of Glass Ceramic Fibres for High Temperature ...
Ceramic Fibres
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Transcript of Ceramic Fibres
Vikas Singh IIT Delhi .
CONTENTS Introduction1. Ceramic vs glass2. Classification3. Need Basic terminology1. Porcelain2. Feldspar,kaolinite3. Clay4. Mullite5. Sintering & Pyrolisis
Fibre production Alumina fibre by sol gel process Recent developments Pros and cons Conclusion
Vikas Singh IIT Delhi .
INTRODUCTIONCeramic fibre is a collective term used for all the inorganic non-metallic fibres that are mostly crystalline.(Trade names- Nextel, Nicalon,Tyarnno,Sylramic etc)
Glass fibre is confined to those made from solidifying glass melts and mostly amorphous.
NEED- Polymeric fibres degrade before 400 0C Glass fibres before 700 0C Carbon fibre before 450 0C (oxidative conditions) Ceramic fibres upto 1500 0C or above !!!!!
Vikas Singh IIT Delhi .
# Key features stiffness, strength & high temperature performance– AEROSPACE application at earliest.
# commercial reality are Silicon carbide (SiC) and Alumina fibre (∝-Al2O3)
# SiC stable upto 700 0C Al2O3upto 1400 0C
Vikas Singh IIT Delhi .
FibresInorganic Organic
Carbon fibre
Polymeric
Metallic Non metallic
Ceramic Glass & mineral
OxideNon
oxide
Ceramic fibres under classification
Vikas Singh IIT Delhi .
TERMINOLOGYPorcelain- An aluminosilicate from clay. Similar in microstructure to brick, pottery etc.
Mullite- silicate mineral (a ceramic type) present in porcelain. 3Al2O32SiO2 or 2Al2O3 SiO2
Vikas Singh IIT Delhi .
Feldspar and Kaolinite- Feldspar is a mineral that gives Kaolinite (platelets) on weathering.
Source- wikipedia
Vikas Singh IIT Delhi .
Clay- mixture of kaolinite etc and pottery is made of it.
Common Ceramic- clay+water. Water helps in pliability so that kaolite pletelets can slide over. Its removal leads to crystalline structure.
Pyrolysis- pyr "fire" and lysis "separating“. Organic matter in absence of oxygen. Why CROSSLINKING important ?? (monomer,shape)
Vikas Singh IIT Delhi .
Sintering- process of producing objects from powders. Principle of atomic diffusion. Ice cubes in water !!!
(Powder compacting sintering cannot be in fibres)
Bulk ceramic Vs ceramic fibre (finer microstructure, less flaws and reduced large sized defects)
Vikas Singh IIT Delhi .
FIBRE PRODUCTIONDirect process – spun to form“green fibre” (intermediate).
Spinning dope based on1. Molecularly dispersed– molecular level
(ions)--additives2. Colloidally dispersed- sol gel3. Coarse ceramic powders- slurry process4. Inorganic polymers- precursor polymer
process
Vikas Singh IIT Delhi .
Precursor system
(brittle , flaws)
Solvent/melt spinning
Green fibre
Pyrolysis/SinteringCeramic fibre
Fibre before and after sinteringSource-Materials Letters 65 (2011) 2717–2720
Vikas Singh IIT Delhi .
Indirect process –
1. CVD- gas phase deposition of ceramic material
2. Relic process- cellulose in salt solution---burnt off---ceramic
percursor deposited on the surface or fibre is soaked in pre ceramic precursor-
pyrolysis
Vikas Singh IIT Delhi .
CVD & SOL GELCVD- Chemical vapour deposition Diameter and flexibility….. 10 micron vs 100 micron Oldest process for non oxide ceramic fibres Eg. SiC vapour deposition on Tungsten, Molybdenum or carbon fibre. Role of interface ??
Source-Composites Science andTechnology 32 (1988) 31-55
Vikas Singh IIT Delhi .
Vertical 2 m reactorTemperature 1400-1500 C1-2 min residence time ReactionCH3SiCl3 SiC + 3HCl
AdvantagesHigh deposition rateIsotropic and dense coating
DisadvantageHigh deposition temperatureGases may be corrosive or explosivesCostly process
Vikas Singh IIT Delhi .
Sol gel-used for Alumina
Advantages-Low temperature of processingHomogenity of productUniform diameter
Source- http://www.gitam.edu/
Vikas Singh IIT Delhi .
OXIDE VS NON OXIDE FIBRES
OXIDE-Al2O3, SiO2, mullite
basedoxidisableProne to creep at 1100 0CLess complicated process
NON OXIDE- SiC, SiCN basedStable upto 1500 0CLess creepMainly amorphous
Source- Fibers for Ceramic Matrix CompositesBernd Clau ß
Vikas Singh IIT Delhi .
SiC and Alumina based commercial fibres
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ALUMINA BY SOL GELAluminiumtrisopropoxide+water 1M solution100 ml taken added 10%,15%,20% hydroxyethylcellulose (HEC) for spinnability sol spun to gel in ammonia solution drying at room temp sintering at 1600 0C for 2 hoursCharacterizationDTA,TGA,Viscometry of dope
Vikas Singh IIT Delhi .
TGA analysisDTA analysis
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Viscocity is high for thehigher organic content
Vikas Singh IIT Delhi .
ADDITIONAL Si gives flexibility but creep. So minimum Si (Zr,Ce)O2stablized zirconium fibre better than Y203 stablized. Melt spinning Vs sol gel. (Stiochiometry) Acetylacetone (acac)-chelating agent, drying control-DMF
Constant DMF-to-Zr ratio of 2.
Source-Materials Science and Engineering, A 189 (1994) 311-317
Vikas Singh IIT Delhi .
RECENT DEVELOPMENTS Green fibre morphology
Variable dia fibresSource- ICFT website
Vikas Singh IIT Delhi .
Si-B-N fibre – 1500-1800 0CPolymeric precursor-crosslinking problem…New route by condensation polymerisation of((CH3NH)4Si) and ((CH3NH)3B) Si/B ratio variation gives different performance
Electrospinning !!
Electrospun alumina fibre (SEM image)
Vikas Singh IIT Delhi .
DISADVANTAGES Most ceramic fibres only on laboratory scale Even sophesticated techniques cannot make 100% oxygen free fibres Carcinogenicity Dust problem
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WHAT WE LEARNT...... Mainly used for high temperature applications (even upto 2000 0C) Silicon carbide and Alumina are used commercially Can be melt, dry or wet spun, former gives better economy and homogenity Sol gel and CVD techniques are still very useful Oxide containing ceramic fibres degrades early Ceramic fibre’s dust can be carcinogenic
Vikas Singh IIT Delhi .
REFERENCES1. X.Wang et l, Materials research bulletin 46 (2011)
2398-24022. H.Yu et al, Materials letter 74 (2012) 247-2493. X.Chen et al, Journal of Non-Crystalline Solids 355
(2009) 2415–24214. X. Zhao et al, Materials Letters 65 (2011) 2717–
27205. Bio-inorganic Hybrid Nanomaterials. Edited by E.
Ruiz-Hitzky, K. Ariga, Y. M. Lvov6. http://ntp.niehs.nih.gov/go/roc127. P.K. Chakrabarty et al. / Journal of the European
Ceramic Society 21 (2001) 355-3618. G. Emig et al. / Sol-gel process for spinning of
continuous (Zr, Ce) O2 fibers
Vikas Singh IIT Delhi .
9. M. Balasubramanian / Journal of Materials Processing Technology 173 (2006) 275–28010. Chem. Mater., Vol. 8, No. 8, 1996 205711. V.M.Kikko et al, Scripta mater. 44 (2001) 249–25512. www.wikipedia.org/sintering13. www.wikipedia.org/pyrolysis14. Xi Zhao, et al, Materials Letters 65 (2011) 2717–2720
Vikas Singh IIT Delhi .
tHANK YOU(Queries…???)