Professor Office: SH 465 Tel: (216) 523 7342 Email: s.tewari@csuohio.edu Ph.D., Chemical Engineering Purdue University

Materials Processing-Structure-Properties Relationships, Convection Effects in Solidification Processing, NDE-Thermal/Environmental Barrier Coatings, Nano/microporous materials

• Research Projects
• Recent Publications
• Recent Graduate Students and Post Doctoral Associates

Research Projects

• Non destructive in-situ atomic emission spectroscopy technique to identify the onset of failure in environmental/thermal barrier coatings on hot stationary or rotating components in gas turbine engines.
• Thermal/environmental barrier coating for silicon based ceramics, such as, silicon carbide and silicon nitride for elevated temperature applications.
• Nano and meso-porous ceramic membrane materials (Co-PI: Dr. Orhan Talu).
• Relationship between adherence and proliferation of cells and macro/micro/ and nano-surface texture in titanium alloys for orthopedic implant applications.Projects supported by NASA, and DOE.

Recent Publications

1. “Mushy Zone Characteristics and Macrosegregation during Directional Solidification”, S.N.Ojha and S.N. Tewari, Trans. Indian Inst. Met., vol. 57[5], (2004), 475-483.

2. “Structural Difference in the Cortical Bone of Turkey Tibia”, Yu-Shuiuan, C. Ramachandra and S.N. Tewari, J. Materials Science, 39[1], (2004), 207-214.

3. “A Comparison Between Growth Morphology of “Eutectic” Cells/Dendrites and Single-Phase Cells/Dendrites”, S. N. Tewari, S.V. Raj and I.E. Locci, Metallurgical and Materials Transactions A, 35A, (2004), 1632-1635.

4. “Spectroscopic Non Destructive Evaluation of Environmental Barrier Coating Failure on Silicon-based Ceramics”, C. Ramachandra, K.N. Lee, S.N. Tewari and W. DeGroot, J. American Ceramic Society, vol. 87, (2004), 1117-1121.

5. “Mushy Zone Rayleigh Number to Describe Macrosegregation and Channel Formation in Directionally Solidified Metallic Alloys”, S.N. Tewari, R. Tiwari and G. Magadi, Metallurgical and Materials Transactions A, 35A, (2004), 2927-2934.

6. “Durability of TBCs with a Surface Environmental Barrier Layer under Thermal Cycling in Air and in Molten Salt”, C. Ramachandra, K.N. Lee and S.N. Tewari, Surface & Coatings Technology, 172 (2-3), (2003), 150-157.

7. “A Mushy Zone Rayleigh Number to Describe Interdendritic Convection During Directional Solidification of Hypoeutectic Pb-Sb and Pb-Sn Alloys’, S.N. Tewari and R. Tiwari, Metallurgical and Materials Transactions A, 34A, (2003), 2365-2376.

8. “Effect of Crucible Diameter Reduction on the Convection, Macrosegregation and Dendritic Morphology During Directional Solidification of Pb-2.2 wt pct Sb Alloy”, Jun Chen, S.N. Tewari, G. Magadi and H.C. De Groh III, Metallurgical and Materials Transactions A”, 34A[12], (2003), 2985-2990.

9. “Directional Solidification and Convection in Small Diameter Crucibles”, J. Chen, P.K. Sung, S.N. Tewari, D.R. Poirier, and H. C. DeGgroh III, Material Science and Engineering A, 357[1,2], (2003), 397-405.

10. “Compressive Properties of Zone-Directionally Solidified Beta-NiAl and its Off-Eutectic Alloys with Cr and W”, R. Asthana, R. Tiwari and S.N. Tewari, Materials Science and Engineering A, 336[1-2],(2002), pp. 99-109.

11. “Reaction Bonded Silicon Carbide by Reactive Infiltration”, P. Sangsuwan, J.A. Orejas, J.E. Gatica, S.N.Tewari and M.Singh, Ind. Eng. Chem.. Res., 40, (2001), pp. 5191-5198.

12. “Wear and Friction Behavior of Pressure Infiltration Cast Copper-Carbon Composite”, G. Goller, D. Koty and S.N. Tewari, M. Singh and A. Tekin, SCAND J METALL, 30[2], 2001 pp.77-83.

13. “Effect of Growth Rate on macrosegregation during directional solidification of a Pb-Sb alloy”, S.N. Ojha and S.N. tewari, Int. J. Cast Metals Res., 13, 2000, 207-213.

14. “Directional solidification microstructure in diffusive and convective regimes”, R. Trivedi, H. Miyahara, P. Mazumder, E. Simsek and S.N. Tewari, Journal Crystal Growth, 222, (2000), 365-379.

15. “Interface Response to Solidification in Sapphire-Reinforced Ni-Base Composites”, R. Asthana and S.N. Tewari, Adv. Composite Mater., vol. 9 , No. 4, (2000), 265-308.

16. “Mushy Zone Morphology during Directional Solidification of Pb-5.8 wt% Sb Alloy”, L.Yu,, G. L.Ding, J. Reye, S.N. Ojha and S.N. Tewari, Metallurgical and Materials Transactions A, 31A, (2000), 2275-2283.

17. Y. He, K. N. Lee, R. A. Miller and S. N. Tewari, "Development of Refractory Silicate-YSZ Dual Layer TBCs," NASA TM-1999-209079; Journal of Thermal Spray technology, 9[1], (2000), 59-67.

18. “Degradation of Aluminum Alloy-Carbon Composites due to Humidity”, H. Song, S.N. Tewari and M. Singh, Journal of Materials Science Letters, 19, (2000), 209-211.

19. "Reactive Infiltration of Silicon Melt through Microporous Amorphous Carbon Preforms", P. Sangsuwan, S.N. Tewari, J.E. Gatica, M. Singh and R. Dickerson, Metallurgical and Materials Transactions B, 30B, (1999), 933-944.

20. "Copper Alloy Impregnated Carbon-Carbon Hybrid Composites for Electronic Packaging Applications", S.K. Datta, S.N. Tewari, J.E. Gatica, W. Shih and L. Bentsen, Metallurgical and Materials Transactions A, 30A, (1999), 175- 181.

21. “Strength Degradation of Sapphire Fibers during Pressure Infiltration Casting of Sapphire-Reinforced Ni-base Superalloys”, R. Asthana, S.N. Tewari and S. Draper, Metallurgical and Materials Transactions-A, 29A, (1998), 1527-30.

22. "Dynamic Analysis of Unidirectional Pressure Infiltration of Porous Preforms by Pure Metals", D.K. Biswas, J.E. Gatica and S.N. Tewari, Metallurgical and Materials Transactions A, 29A, (1998), 377-388.
    

Recent Students and Post Doctoral Associates

Graduate Students:

• “Channel Segregate Formation and Macrosegregation during Directional Solidification”, Manik K. Sharma, M.S., Cleveland State University, 2000.

• “Cellular Array Morphology during Directional Solidification” Yi Hsuan Weng, M.S., Cleveland State University, 2001.

• “Morphology of Directionally Solidified Pb-Sb Alloys”, Lu Yu, Doctor of Engineering, Cleveland State University, 2001.

• “Dendrite Morphology During Directional Solidification of Metallic Alloy: Steady-State Growth and History Dependence”, Yushi Chen, M.S.. Cleveland State University, 2001.

• Cellular/Dendritic Tip Radii of Pb-Sb Alloys During Directional Solidification”, Sachin Sanghavi, M.S., Cleveland State University, 2001.

• “Observational Study on the Haversian System in a Turkey Tibia at Microstructural and Ultrastructural Levels”, Yu-Shiuan Chen, M.S., Cleveland State University, 2002.

• “Primary Dendrite Spacing During Directional Solidification of Binary Metallic Alloys, its History Dependence and Influence of Interdendritic Convection”, Jun Hui, Doctor of Engineering, Cleveland State University, 2003.

• “Dendritic Array Morphology: Effect of Reducing Crucible Diameter and Role of Solid-Liquid Surface Energy”, Jun Chen, Doctor of Engineering, Cleveland State University, 2004.

• “Rayleigh Number to Describe Effect of Convection on Microstructure Development and Defect Formation”, Ritesh K. Tiwari. M.S., Cleveland State University, 2004.

• “Convection due to Changing Cross-section during Directional Solidification of Alloys and its Influence on the Dendritic Array Morphology and Macrosegregation”, Kunal Pandit, M.S., Cleveland State University, 2004.

• “Effect of Crucible diameter reduction on dendrite morphology during directional solidification of Pb-2.2 wt pct Sb alloy”, Surender Dass Adepu, M.S., Cleveland State University, 2005.

• “Directional solidification of succinonitrile-1.9% acetone in bulk crucibles”, Rajaylakshmi Anantatmukula, M.S., Cleveland State University, 2005.

Post Doctoral Associates:

1. Dr. G. Ding, “Cellular/Dendritic Microstructures” (1997-2001).
2. Dr. M. Gopal Krishna, “Cellular/Dendritic Microstructures” (1998-2001).
3. Dr. Yi-Rong He, “Thermal Barrier Coatings” (1998-2000).
4. Dr. C. Ramachandra, “Thermal Barrier Coatings” (2000- 2003).
5. Dr. X. Wu, “Cellular/Dendritic Morphology” (2001- 2003).
6. Dr. Guofeng Chen, “Spectroscopic In-Situ Non-Destructive Evaluation to Monitor the Health of Thermal Barrier Coatings”, 2003- 2006.