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NANOSIZED FINE PARTICLES AND FIBRES AS REINFORCING MATERIALS SYNTHESISED FROM SEPIOLITE

NANOSIZED FINE PARTICLES AND FIBRES AS REINFORCING MATERIALS SYNTHESISED FROM SEPIOLITE. Dr. Ali Osman KURT Sakarya University Engineering Faculty, Esentepe Campus, SAKARYA - TURKEY. NATO-ASI Conference - Antalya 1-12 Sept. 2003. Contents. Introduction Sepiolite clay mineral

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NANOSIZED FINE PARTICLES AND FIBRES AS REINFORCING MATERIALS SYNTHESISED FROM SEPIOLITE

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  1. NANOSIZED FINE PARTICLES AND FIBRES AS REINFORCING MATERIALS SYNTHESISED FROM SEPIOLITE Dr. Ali Osman KURT Sakarya University Engineering Faculty, Esentepe Campus, SAKARYA - TURKEY NATO-ASI Conference - Antalya 1-12 Sept. 2003

  2. Contents • Introduction • Sepiolite clay mineral • Chemical and mineralogical features • Purification • Intercalation • Current and potential Uses • Silicon Nitride (Si3N4) powders • Carbothermal reduction - nitridation • Pyrolysis of Sepiolite - Polyacrylonitrile • Conclusions

  3. Sepiolite clay mineral- properties • Light (2-2.5 g.cm-3) • Soft (2-2.5 Mohs) • High specific surface area (400 ext. + 500 int. = 900 m2.g-1theoretical) (250 - 300 m2.g-1 N2-BET) • Fibres (L: 3-5m, W: 100-300nm) • Cation exchange capacity (3-45 meq/100g)

  4. Sepiolite reserves - ores in the World • Somalia (50-100 m.tonne), Tanzania, Kenya, Mexico. • Madagascar, Morocco, Persia, USA (Nevada), China, Spain (15-20 m.ton)… • Turkey (above 100 m.tonne. (1.5 m.tonne >%50 rich in mineral) • Location: Eskişehir (Sivrihisar, Mihalıççık-Yunusemre), Çanakkale, Bursa, Kütahya, Isparta ve Konya-Yunak.

  5. Sepiolite clay mineral- processing • A single fibre constitutes several fibres bundled together. Under ultrasonic shaking bundles could be apart to single fibres in an aqueous solution.

  6. Sepiolite clay mineral- processing • Theoretically possible to have fibres of ten to fifteen angstrom (Å) thick and a few micron long by dissolving sepiolite framework structure leaving selective intercalated materials within the channels of the fibres.

  7. Sepiolite - purification • As-received mineral constitutes approx. 20 wt.% of dolomite “MgCa (CO3)2” impurity. • Magnesium silicate + Dolomite+ Diluted HCl solution (0.21M at 60oC for 1.5h.) = Pure Sepiolite

  8. Sepiolite:Its Use • Thickener in polyesters, paints and grease • Papermaking and cosmetics industry • As fillers in the pharmaceutical, rubber and plastic industry • As a toughener in the rubber industry • As filters and clarifiers in chemical processes • Used in drilling mud • Additives in refractory and insulating materials.

  9. Production of Si3N4 Sepiolite:Its Use: High-Tech Ceramics I. Method, Carbothermal Reduction Nitridation (CRN) II. Method, Pyrolysis of Sepiolite-Polyacrylonitrile (Sep-PAN)

  10. Production of Si3N4 from sepiolite:I.Method: CRN Process • CRN Process Sep. + C + N2*Si3N4 + CO *(Mg2SiO4, MgSiN2,Si2N2O,Fe2Si, AlFeO3) • Conversion of Fosterite to Si3N4 3Mg2SiO2 + N2 + 12C  Si3N4 + 6Mg + 12CO • Formation of -Si3N4 (11.5m2.g-1)

  11. Production of Si3N4 from sepiolite:II.Method: Pyrolysis of Sepiolite-Polyacrylonitrile (Sep-PAN) sep + AN Polymerisation  stabilisation (24h) (60C,12h) (225C,20h)  pyrolysis  product (1350oC,4h) (Si3N4)

  12. Si3N4Its Use: • An inexpensive synthesis method using cheap and readily available raw materials were used to produce Si3N4 powders. • The product may have applications where high purity is not an essential requirement such as thermocouple protection sheaths, riser and delivery tubes in low-pressure diecasting operations and cutting edges for scissors. • Whiskers could be used in metal matrix composites as a reinforcing material. • -phase silicon nitride powders could be utilised as reinforcement in a glass matrix, ceramic matrix or metal matrix composites.

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