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IntroductionCeramic vs glass Classification Need

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Basic terminologyPorcelain Feldspar,kaolinite Clay Mullite Sintering & Pyrolisis

Fibre production Alumina fibre by sol gel process Recent developments Pros and cons Conclusion Vikas Singh IIT Delhi .

Ceramic fibre is a collective term used for all the inorganic nonmetallic 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 .

Inorganic

Fibres Organic

Carbon fibre Metallic Non metallic Polymeric Ceramic

Glass & mineral

Oxide

Non oxide

Ceramic fibres under classificationVikas Singh IIT Delhi .

Porcelain- 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 matterin absence of oxygen. Vikas Singh IIT ?? Why CROSSLINKING importantDelhi . (monomer,shape)

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 .

Direct process spun to formgreen fibre (intermediate).Spinning dope based on 1. Molecularly dispersed molecular level (ions)--additives 2. Colloidally dispersed- sol gel 3. Coarse ceramic powders- slurry process 4. Inorganic polymers- precursor polymer process

Vikas Singh IIT Delhi .

Precursor system (brittle , flaws)

Solvent/melt spinning

Green fibre

Fibre before and after sintering Source-Materials Letters 65 (2011) 27172720

Ceramic fibreVikas Singh IIT Delhi .

Pyrolysis/Sintering

Indirect process percursor deposited on the surface or fibre is soaked in pre ceramic precursor-

pyrolysis

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CVD- gas phase deposition of ceramic material Relic process- cellulose in salt solution---burnt off--ceramicVikas Singh IIT Delhi .

CVD- 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 ??

Vikas Singh IIT Delhi .

SourceComposites Science and Technology 32 (1988) 31-55

Vertical 2 m reactor Temperature 1400-1500 C 1-2 min residence time Reaction CH3SiCl3 SiC + 3HCl

Advantages High deposition rate Isotropic and dense coating

Disadvantage High deposition temperature Gases may be corrosive or explosives Costly process Vikas Singh IIT Delhi .

Sol gelused for Alumina

AdvantagesLow temperature of processing Homogenity of product Uniform diameter

Source- http://www.gitam.edu/

Vikas Singh IIT Delhi .

OXIDE-Al2O3, SiO2, mullite based oxidisable Prone to creep at 1100 0C Less complicated process NON OXIDE- SiC, SiCN based Stable upto 1500 0C Less creep Mainly amorphousSource- Fibers for Ceramic Matrix Composites Vikas Singh IIT Delhi . Bernd Clau

SiC and Alumina based commercial fibresVikas Singh IIT Delhi .

Aluminiumtrisopropoxide+water 1M solution 100 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 hours Characterization DTA,TGA,Viscometry of dopeVikas Singh IIT Delhi .

DTA analysis

TGA analysis

Vikas Singh IIT Delhi .

Viscocity is high for the higher organic content

Vikas Singh IIT Delhi .

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 .

Green fibre morphology

Variable

dia fibres

Source- ICFT website

Vikas Singh IIT Delhi .

Si-B-N fibre 1500-1800 0C Polymeric precursor-crosslinking problem New route by condensation polymerisation of ((CH3NH)4Si) and ((CH3NH)3B) Si/B ratio variation gives different performance

Electrospinning !!

Vikas Singh IIT Delhi Electrospun alumina fibre (SEM image).

Most ceramic fibres only on laboratory scale Even sophesticated techniques cannot make 100% oxygen free fibres Carcinogenicity Dust problem

Vikas Singh IIT Delhi .

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 fibres dust can be carcinogenic

Vikas Singh IIT Delhi .

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X.Wang et l, Materials research bulletin 46 (2011) 23982402 H.Yu et al, Materials letter 74 (2012) 247-249 X.Chen et al, Journal of Non-Crystalline Solids 355 (2009) 24152421 X. Zhao et al, Materials Letters 65 (2011) 27172720 Bio-inorganic Hybrid Nanomaterials. Edited by E. RuizHitzky, K. Ariga, Y. M. Lvov http://ntp.niehs.nih.gov/go/roc12 P.K. Chakrabarty et al. / Journal of the European Ceramic Society 21 (2001) 355-361 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) 275280 10. Chem. Mater., Vol. 8, No. 8, 1996 2057 11. V.M.Kikko et al, Scripta mater. 44 (2001) 249255 12. www.wikipedia.org/sintering 13. www.wikipedia.org/pyrolysis 14. Xi Zhao, et al, Materials Letters 65 (2011) 27172720

Vikas Singh IIT Delhi .

tHANK YOU(Queries???)Vikas Singh IIT Delhi .