İsmail YILDIRIM, Alaeddin ARPACI

Basınçsız sinterlenmiş silisyum karbürde iç yapının kırılma tokluğuna etkisi

Bu çalışmada, farklı içerikte SiC karışımlar hazırlanmış, tek yönlü ve soğuk izostatik presleme tekniği ile preslenmelerdir. Şekillendirilen numunelerin yaş yoğunlukları tespit edilmiş, piroliz işlemi silisyum karbür numunelerde sinterleme öncesi ara işlem olarak kullanılmıştır. Numuneler, katı - katı ve katı - sıvı difüzyonu tekniği ile açık atmosfer ve argon gaz atmosferinde farklı sıcaklık ve sürelerde sinterlenerek üretilmişlerdir. Elde edilen numunelerin sinterleme sonrasında sahip oldukları, parazite, yoğunluk, sinterleme küçülmesi, sertlik ve kırılma tokluğu ölçümleri yapılmıştır. Elde edilen sonuçların literatürde verilen değerlerle uyum içinde olduğu belirlenmiştir

The microstructure effects on fracture toughness of pressureless sintered silicon carbide

In this study, eight group silicon carbide compositions were prepared and pressed using by uni-axially and cold isostatically pressing techniques. Green density has been observed for the pressed sample and Pyrolysing process is used as pro-process for carbonizing the Phenolic resins. Phenolic resins have been used to avoid the decomposition of silicon carbide and stabilize the structure. Solid state and liquid phase sintering techniques have been used for the sintering. Temperature and time are used as sintering parameters. Densities and porosity have been measured by Archimedes method and fracture toughness have been tested by indentation fracture toughness. CAB12 Coded composition (B4C + Al2O3+Y2O3 + carbon) sintered at 2150 °C. The density of samples has been measured as 3.02 gr/cm3 indentation fracture toughness were obtained 4.57 $MPa.m^{1/2}$ after sintering. CAJ09 Coded composition (HP1 SiC + Al2O3 + Y2O3 + carbon additives) has been sintered at 2000 °C. The density of sintered samples was measured as 3.12 gr/cm and 4,39 $MPa.m^{1/2}$ indentation fracture toughness values were obtained after sintering. Al2O3 and Y2O3 reaction resulted in a phase being Y5Al3 observed by XRD analysis. CAK01- CAK07 Coded compositions (#70 SiC + HP1 SiC + Al2O3 + Y2O3 + carbon additive) has been sintered at 2000 °C. The density of sintered samples was measured as 2.48 - 2.62 gr/cm3. Fracture toughness cannot be measured due to the 20.61 - 24.76 % porosity of the sample. Al2O3 and Y2O3 reaction resulted in a phase being Al5.Y3.O12 observed by XRD analysis. The obtained results have been observed in a good harmony compared to literature survey.

PDF

___

Sixta M. E., Zhang X. F., Jonghe L. C. D., (2001). Flexural Creep of in - Situ Toughened Silicon Carbide, Journal of American Ceramic Society, 84, 2022 - 2028.
Waye B. E., (1967). Introduction to Technical Ceramics, Maclaren Ltd., London
Neil, N. A., (1983). Raw materials for refractories SiC and Si3N4, Ceramic Engineering Science and Proceeding, 4 [1-2], 186-193.
Schwartz, M. M., (1992). Handbook of Structural Ceramics, McGraw - Hill Corp., ISBN 0-07-055719-5, America.
Chawla, K. K., (1993). Ceramic Matrix Composites, First Edition, Published by Chapman & Hall, SE 1 8HN, ISBN 0-412 36740-8, London.
Neil, N. A. ve Crowe, J. T., (1995). Silicon carbide, American Ceramic Society Bulletin, 74, 150-154. Saito, S., (1988). Fine Ceramics, Published by Elsevier, London.
Reed, J. S., (1995). Principles of Ceramic Processing Published by John Willey & Son Inc., ISBN 0-471 59721-X.
Wachman, B. J., (1989). Structural Ceramics, Published by Academic Press Inc., ISBN 0-12 341829-1.
Xu, H., Bhatia, T., Deshpande, S. A. ve Padtur, N. P., (2001). Microstructural evaluation in liquid phase sintered SiC: Part I, effect of started powder, Journal of American Ceramic Society, 84,1578-1584.
Prochazka, S., (1976). Sintering of silicon carbide, Mass Transport Phenomena in Ceramics, Edited by Cooper A.R., Heuer A.H., 421-431.
Prochazka, S. ve Charles, R. J., (1973). Strength of boron doped, hot-pressed SiC, American Ceramic Society Bulletin, 54, 885 - 892
Mulla, M. A. ve Crstic, V. D., (1991). Low temperature pressureless sintering of (3 silicon carbide with aluminium oxide and yttrium oxide additions, American Ceramic Society Bulletin, 70,439 - 442.
Van Dijen, F. K. ve Mayer, E., (1996). Liquid phase sintering of silicon carbide, Journal of the European Ceram. Soc, 16, 413-420.
Carneim T. J., Green D. J., (2001). Mechanical Properties of Dry - Pressed Alumina Green Bodies, Journal of American Ceramic Society, 84,1405 - 1410
Dean M. L., Bor W. L., Chen T. F., (1996). Porosity Dependence of Mechanical Strength and Fracture Toughness in SiC - A12O3 -Y2O3 Ceramics, Journal of Ceramic Society of Japan int. edition 103, 867 - 870
Hepworth, M. A., (1991). Processing, properties and application of structural silicon carbides, T & N Technology Ltd Report, 113-125.
Kim, D. H. ve Kim, C. H., (1990): Toughening behaviour of silicon carbide with additions of yttria and alumina, Journal of American Ceramic Society, 73, 1431 - 1434.
Ponton, C. B., Rawlings, R. D., (1989). Vickers indentation fracture test. Part 1 Review of literature and formulation of standardized indentation toughness equations, Materials Science and Technology, 5, 865 - 871.
Greil, P., (1995). Active filler controlled pyrolysis of preceramic polymers, Journal of American Ceramic Society, 78, 835-848.
Soraru, G. D., Babonneau, F. ve Mackenzie, J. D., (1990). Structural evaluations from polycar- bosilane to SiC ceramic, Journal of Material Science, 25, 3886 - 3893.
Tennery, V. J., (1989). Ceramic materials and components for engine, American Ceramic Society Bulletin, 68, 1480 - 1494.