Associate Professor Alfred Tok

Email: miytok@ntu.edu.sg
Phone: (+65) 6790 4935
Office: N4.1-02-23
Related Links:
1) http://www.ntu.edu.sg/home/miytok
2) Research Areas
3) FYP 2011/2012 Project Titles

Current Research Interests
He leads the Rare Earth Nano-Materials Group that focuses on the synthesis, processing, consolidation and applications of rare earth nano-particles. The group developed various methods to synthesize these nano-particles in the oxide, nitride and carbide forms. These methods include sol gel, precipitation (direct, co-Precipitation, gel Precipitation, polyol), plasma Spraying (DC & RF), flame Spraying (hydrolysis & pyrolysis) and electrostatic atomisation. Several consolidation / application methods are also being studied and developed, and these include tape casting (aqueous & non-aqueous), spray drying, sputtering, dip coating and spin coating.

Typical research areas include gadolinium oxide-doped cerium oxide nano-particles for mid-temperature solid oxide fuel cells, ITO nano-particles for OLED and sputtering target, Y/Eu nano-particles for plasma displays, nano-phosphors for RGB and white LEDs, Boron-Neodymium for magnets, and barium sulphate and boron carbide nano-particles for medical and defence applications respectively. Rare earth nano-particles for applications in MLCCs and MLCPs for microelectronics are currently being studied. Research is also ongoing on aluminum nitride as a high thermal conductivity substrate.

The group collaborates actively with AMR Technologies Inc. (Canada), Defence Science & Technology Agency (DSTA), University of California Los Angeles (UCLA) and University of Cambridge, UK.

Biographical Information
Alfred Tok obtained his Bachelor of Engineering (1st Class Honours) from the Queensland University of Technology, Australia in 1995. He was also awarded the Dean's Award for Excellence. He then worked as a Mechanical Engineer at Singapore Technologies Aerospace Engineering Pte Ltd, Singapore. In 1997, he pursued his PhD in Mechanical Engineering from Nanyang Technological University and graduated in 2000. He worked as a Research Fellow in the School of Materials Engineering, NTU from 2000 to 2002. In 2003, he took up the position of Assistant Professor in the School of Materials Science & Engineering, NTU.

Teaching

• MS2011 Mathematics II
• MS7001 Materials Laboratory Techniques

Selected Publications

A.I.Y. Tok, F.Y.C. Boey & K.A. Khor, "Tape Casting of High Dielectric Ceramic Composite Substrates for Microelectronics Application," Journal of Materials Processing Technology, Vol. 89 (1999), p.508-512.

F.Y.C. Boey, X.L. Song, Z. Gu & A.I.Y. Tok, "ALON Phase Formation in a Tape Cast Al2O3/AlN Composite," Journal of Materials Processing Technology, Vol. 89 (1999), pp. 478-480.

A.I.Y. Tok, F.Y.C. Boey & K.A. Khor, "Tape Casting of High Dielectric Ceramic Substrates for Microelectronics Application," Journal of Materials Engineering & Performance, Vol. 8(4) (1999), pp. 469-472.

A.I.Y. Tok, F.Y.C. Boey & Y.C. Lam, "Non-Newtonian fluid flow model for ceramic tape casting," Materials Science & Engineering A, Vol. A280 (2000), pp. 282-288.

F.Y.C. Boey, A.I.Y. Tok, Y. Long & H.Y. Yeong, "Properties of Porous AlN Multi-layered Ceramic Sandwich Substrates," Journal of Materials Research, Vol. 17(5) (2001), pp. 1061-1068.

F. Boey, L. Cao, K.A. Khor & A.I.Y. Tok, "Phase reaction & sintering behavior of a Al2O3-20wt%AlN-5wt%Y2O3 system," Acta Materialia, Vol. 49 (2001), pp. 3117-3127.

S.C. Joshi, Y.C. Lam, F.Y.C. Boey & A.I.Y. Tok, "Power Law Fluids and Bingham Plastics Flow Models for Ceramics Tape Casting, Journal of Materials Processing Technology, Vol. 120 (2002), pp. 215-225.

F.Y.C. Boey, A.I.Y. Tok, Y.C. Lam & S.Y. Chew, "On the effects of secondary phase on thermal conductivity of AlN ceramic substrates using a microstructural modeling approach," Materials Science & Engineering A, Vol. 335 (2002), pp. 281-289.

F.Y.C. Boey, A.I.Y. Tok & W.J. Clegg, "Porous reaction-sintered AlN tapes for High Performance Microelectronics Application," Journal of Materials Research, Vol. 17(2) (2002), pp. 306-314.

F.Y.C. Boey & A.I.Y. Tok, “Porous AlN ceramic substrates by reaction sintering,” Journal of Materials Processing Technology, Vol. 140 (2003), pp. 413-419.

F.Y.C. Boey, X.L Zhao & A.I.Y Tok, "Synthesis of Al2O3/AlN composite powders by plasma processed Al2O3 with various additives," Journal of Materials Research, Vol. 19 (5) (2004), pp. 1356-1363.

A.I.Y Tok, L.H. Luo & F.Y.C. Boey, "Carbonate Co-precipitation of Gd2O3-doped CeO2 solid solution nano-particles," Materials Science & Engineering A, Vol. 383 (2004) pp. 229-234.

A.I.Y. Tok, L. Luo, F.Y.C. Boey & S.H. Ng, “Consolidation and Properties of Gd0.1Ce0.9O1.95 Nano-Particles for SOFC Electrolytes.” Journal of Materials Research, Vol. 21 (2006), pp. 119-124.

A.I.Y Tok, F.Y.C. Boey, S. Du & B.K Wong, “Flame Spray Synthesis of ZrO2 Nanoparticles using liquid precursors,” Materials Science & Engineering B, Vol. 130 (2006) pp. 114-119.

L.H. Luo, A.I.Y. Tok, F.Y.C Boey & S.H. Ng, “Aqueous Tape Casting of 10 mol%-Gd2O3-doped-CeO2 Nanosized Powders”, Materials Science & Engineering A, Vol. 429 (1-2) (2006), pp. 266-271.

A.I.Y Tok, F.Y.C. Boey & X.L. Zhao, "Novel Synthesis of Al2O3 Nano-Particles by Flame Spray Pyrolysis," Journal of Materials Processing Technology, Vol. 178 (2005), pp. 270-273.

L.T. Su, A.I.Y. Tok, F.Y.C. Boey & J. Woodhead, “Chemical Gelation of Cerium (III) doped Y3Al5O12 Single Crystal Nanoparticles,” Journal of Materials Research, Vol. 21 (10) (2006), pp. 2510 to 2515.

X.L. Sun, A.I.Y. Tok, R. Huebner & F.Y.C. Boey, “Phase transformation of ultrafine rare earth oxide powders synthesized by radio frequency plasma spraying,” Journal of the European Ceramic Society, Vol. 27 (2007), pp. 125-130.

W. Wang, S.P. Jiang, A.I.Y. Tok & L. Luo, “GDC-impregnated Ni Anodes for Direct Utilization of Methane in Solid Oxide Fuel Cells,” Journal of Power Sources, Vol. 159 (2006) pp. 68-72.

Happy, A.I.Y. Tok, F.Y.C. Boey, R. Hubner & S.H. Ng, “Synthesis of Dysprosium Oxide by Homogeneous Precipitation,” Journal of Electroceramics, Vol. 17 (2006), pp. 73-76.

X.L.Sun, A.I.Y. Tok, F.Y.C. Boey & R. Huebner, “RF Plasma Processing of Ultrafine Sm-Lu Mixed Oxide Powders,” International Journal of Nanoscience, Vol. 5 No. 4 & 5 (2006), pp. 487-491.

Happy, A.I.Y. Tok, L.T. Su, F.Y.C. Boey & S.H. Ng, “Homogeneous Precipitation of Dy2O3 Nano-Particles – Effects of Synthesis Parameters,” Journal of Nanoscience & Nanotechnology, Vol. 7 (2007), pp. 1-9.

Y.L. Wu, A.I.Y. Tok, F.Y.C. Boey, X.T. Zeng & X.H. Zhang, “Chemical Synthesis of ZnO Nanocrystals,” Applied Surface Science, Vol. 253 (2007), pp. 5473-5479.

X.L. Sun, A.I.Y. Tok, F.Y.C. Boey, C.L. Gan & M.K. Shreyer, “Solvent and Plasma Gas Influence on the Synthesis of Y2O3 Nanoparticles by Suspension Plasma Spraying,” Journal of Materials Research, Vol. 22(5) (2007), pp. 1306-1313.

Y.L. Wu, C.S. Lim, S. Fu, A.I.Y. Tok, H.M. Lau, F.Y.C. Boey & X.T. Zeng, “Surface Modifications of ZnO Quantum Dots for Bio-Imaging,” Nanotechnology, Vol. 18 (2007), pp. 1-9.

A.I.Y. Tok, F.Y.C. Boey, Z. Dong & X.L Sun, “Hydrothermal Synthesis of CeO2 Nano-Particles,” Journal of Materials Processing Technology, Vol 190 (1-3) (2007), pp. 217-222.

A.I.Y. Tok, S.W. Du, F.Y.C. Boey & W.K. Chong, “Hydrothermal Synthesis and Characterization of Rare-Earth Doped Ceria Nanoparticles,” Materials Science & Engineering A, Vol. 466 (1-2 (2007)), pp. 223-229.

Y.D. Zhen, A.I.Y. Tok, S.P. Jiang & F.Y.C. Boey, “La(Ni,Fe)O3 as a Cathode Material with High Tolerance against Cr Poisoning for Solid Oxide Fuel Cells,” Journal of Power Sources, Vol. 170 (1) (2007), pp. 61-66.

S.P. Jiang, Y. Zheng, S. Zhang, A.I.Y Tok & P. Wu, “An Electrochemical Method to Assess the Chromium Volatility of Chromia-Forming Metallic Interconnect for SOFCs" Journal of the Electrochemical Society, Vol. 153 (11) (2006), pp. A2120-A2125.

L.Y.L. Wu, A.I.Y. Tok, F.Y.C. Boey, X.T.Zeng & Z.H. Zhang, “Chemical Synthesis of ZnO Nanocrystals,” IEEE Transactions on Nanotechnology, Vol. 6 (5) (2007), pp. 497-503.

X.L. Sun, A.I.Y. Tok, F.Y.C. Boey, S.L. Lim, C.W. Kang & H.W. Ng, “Combustion-aided Suspension Plasma Spraying of Y2O3 Nanoparticles—Synthesis and Modeling,” Journal of Applied Physics, Vol. 103 (2008), pp. Online Version.

L.T. Su, A.I.Y. Tok, F.Y.C. Boey, X.H. Zhang, J.L Woodhead & C.J. Summers, “Photoluminescence phenomena of Ce3+-doped Y3Al5O12 nanophosphors,” Journal of Applied Physics, Vol. 102 (2008), pp. Online Version.

Y.D. Zhen, A.I.Y. Tok, S.P. Jiang & F.Y.C. Boey, “Fabrication & Performance of GDC-based intermediate-temperature Solid Oxide Fuel Cells,” Journal of Power Sources, Vol. 178 (2008), pp. 69-74.

Y.D. Zhen, A.I.Y. Tok, F.Y.C. Boey & S.P. Jiang, “Development of Cr-tolerant cathodes of solid oxide fuel cells", Electrochemical and Solid-State Letters, Vol. 11 (3) (2008), pp. B42-B46.

X.L. Sun, A.I.Y. Tok, F.Y.C. Boey, S.L. Lim, C.W. Kang & H.W. Ng, “Combustion-aided Suspension Plasma Spraying of Y2O3 Nanoparticles—Synthesis and Modeling,” Virtual Journal of Nanoscale Science & Technology, Vol. 17 (8) (2008), Online Version