Yip-Wah
Chung
Department
of Materials Science and Engineering
Northwestern
University
2220
N. Campus Drive, Evanston, IL 60208
Email:
ywchung@northwestern.edu
My
research is primarily in the area of surface science, thin films and tribology.
1.
Protective Overcoats for Hard Disks
As
the industry moves to higher density magnetic recording, one needs to bring the
read/write head closer to the disk surface. The industry goal is to
develop hard disk systems with areal density of 1 Tb/in2
program. At this areal density, the protective overcoat cannot be thicker
than 1 nm that must provide the necessary protection against occasional
head-disk contacts and corrosion protection for the underlying media. The
overcoat material must therefore be wear-resistant, continuous (no pinholes),
thermally stable and compatible with the lubricant. We are currently exploring new overcoat materials with these
objectives.
Representative Publication
D.
J. Li, M. U. Guruz, Yip-Wah Chung, and C. S. Bhatia, “Ultrathin CNx overcoats
for 1 Tb/in2 hard disk systems”, Applied Physics Letters 81, 1113-1115 (2002)
2. Low-Friction Coatings
While
many coatings are available with excellent solid lubrication properties, they
tend to work under inert environments, e.g., without oxygen or water
vapor. We are exploring ways to design coatings with ultralow friction
properties in a normal air ambient. Preliminary experiments showed that
we can obtain coatings with coefficient of friction less than 0.01 in
laboratory air (25% relative humidity). These coatings may find
applications requiring low energy consumption and minimal adhesion at contacts.
Representative Publication
Christina Freyman, Yanfeng Chen, and Yip-Wah
Chung, “Synthesis of carbon films with ultra-low friction in dry and humid
air”, Surface and Coatings Technology 201, 164-167 (2006)
3.
High-Temperature Nanotribology
The
goal of our research is to understand scientific phenomena occurring at the
nanometer scale that may affect friction and wear. Most of the current
studies in this field are conducted at ambient temperatures. However,
most of the important engineering problems associated with friction and wear occur
at elevated temperatures (e.g., power train components). We are equipped
with a nanoindentator-friction instrument that can operate up to 500 C.
This provides us with the unique capability to investigate nanoscale
tribological phenomena at elevated temperatures.
Representative Publication
H.
Yu, S. Liu, J. Wang, and Yip-Wah Chung, “Influence of temperature-dependent
yield strength on thermomechanical asperity contacts”, Tribology Letters 17,
155-163 (2004)
4. Nanostructured Materials with Enhanced
IR Reflectivity
The
goal of this new research program is to develop materials that can be tuned to
reflect infrared light with high efficiency. One potential application is to reduce heat load in
buildings, cars and planes due to solar irradiation. If successful, this can reduce energy consumption and
improve overall fuel efficiency in transportation.
Awards
Fellow,
Society of Tribologists and Lubrication Engineers (2005)
Innovative
Research Award, ASME Tribology Division (2002)
Fellow,
American Vacuum Society (2000)
Advisory
Professor, Fudan University, China (1999)
National
Storage Industry Consortium Technical Achievement Award (1999)
Fellow,
ASM International (1998)
Visiting
Fellow, Japan Society for Promotion of Science
Ralph
A. Teetor Engineering Educator Award (1991)
ASME
Tribology Division Best Paper Award (1990)
Faculty
Honor Roll (1990)
Teacher
of the Year in MSE (1986, 1991)
Professional Activities
Program
Director, Surface Engineering and Materials Design, Civil and Mechanical
Systems Division, Directorate for Engineering, National Science Foundation
(2003-5)
Chair,
AVS Advanced Surface Engineering Division (2004)
Guest
Editor, MRS Bulletin (March 2003)
American
Vacuum Society Board of Directors, 1/98 - 12/99
Associate
Editor, ASME Journal of Tribology, 1997-2003
Editorial
Board, Tribology Letters
AVS
Prairie Chapter Executive Committee
Hong
Kong Research Grants Council (1993-)
Department
Chair (1992-98)
Director,
NSF/IUCRC Center for Engineering Tribology (1987-1992)
Some Statistics
From
1991 to 2001, our group graduated ten PhD students. The average time for
completion is 4.25 years. Three are in government labs, and the other seven
are in industry. On average, each student published 4 papers by the time
of thesis completion. The average group size (students+postdoc+visitors)
is between five and six.
Recent
Publications (* = invited)
2003
167. *(with William Sproul), “Superhard
coating materials”, MRS Bulletin 28, 164-5 (2003)
168. (with Kitty Lee, C. Y. Chan, I. Bello,
S. T. Lee, A. Karimi, J. Patscheider, M. P. Delplancke-Ogletree, Dehua Yang, B.
Boyce and Thomas Buchheit), “An international round-robin experiment to evaluate
the consistency of nanoindentation hardness measurements of thin films”,
Surface and Coatings Technology 168, 57-61 (2003)
169. (with De-Jun Li), “Ultrasmooth CNx
overcoats for next-generation hard disks”, IEEE Transactions on Magnetics 39,
765-768 (2003)
170. (with Yanfeng Chen), “The role of
hydrogen diffusion and desorption in moisture-induced embrittlement in
intermetallics doped with alloyed elements”, Intermetallics 11, 551-4 (2003)
171. (with Dejun Li, Yanfeng Chen and F.
Lazaro Freire, Jr.), “Metrology of 1-10 nm thick CNx films:
thickness, density and surface roughness measurements”, JVST A21, L19-21 (2003)
172. *(with Mark Hersam), “Detecting elusive
surface atoms with atomic force microscopy”, Proceedings of the National
Academy of Sciences 100, 12531-2 (2003).
2004
173. (with Kitty W. Lee, Yu-Hsia Chen and
Leon M. Keer), “Hardness, internal stress, and thermal stability of TiB2/TiC
multilayer coatings synthesized by magnetron sputtering with and without
substrate rotation”, Surface and Coatings Technology 177/178, 591-596 (2004)
174. (with Sulin Zhang , Greg Wagner, Sergey
N. Medyanik, Wing-Kam Liu and Yuan-Hsin Yu), “Experimental and molecular
dynamics simulation studies of friction behavior of hydrogenated carbon films”,
Surface and Coatings Technology 177/178, 818-823 (2004)
175. (with Yanfeng Chen), “The effect of Fe
on the moisture-induced embrittlement in (Ni,Fe)Ti alloys”, Intermetallics 12,
815-819 (2004)
176. (with H. Yu, S. Liu, and J. Wang),
“Influence of temperature-dependent yield strength on thermomechanical asperity
contacts”, Tribology Letters 17, 155-163 (2004)
177. *(with Ken Chong), “Advice on Acquiring
NSF Funding in Nanomechanics and Surface Engineering”, JOM October 2004, p.
36-37.
178. (with T. G. Nieh, C. Iwamoto, Y.
Ikuhara and K. W. Lee), “Comparative studies of crystallization of a bulk
Zr-Al-Ti-Cu-Ni amorphous alloy”, Intermetallics 12, 1183-1189 (2004)
179. (with M. T. Siniawski, S. J. Harris, Q.
Wang and C. Freyman), “Effects of thickness and roughness variations on the
abrasiveness of a thin boron carbide coating”, Tribology Letters 17, 931-937
(2004)
2005
180. (with
Kitty W. Lee, Chad Korach and Leon M. Keer), “Tribological and dry machining
evaluation of superhard TiB2/TiC multilayer coatings deposited on
Si(001), M2 steel, and C3 WC cutting tool inserts using magnetron sputtering”,
Surface and Coatings Technology 194, 184-189 (2005)
2006
181. (with
Yanfeng Cheng and Shu-You Li), “Boron carbide and boron carbonitride thin films
as protective coatings in ultra-high density hard disk drives”, Surface and
Coatings Technology 200, 4072-4077 (2006)
182. (with Christina Freyman and Yanfeng Chen), “Synthesis of carbon films with ultralow friction in dry and humid Air”, Surface and Coatings Technology 201, 164-167 (2006)
183. (with
Christina Freyman, Bo Zhao and Yanfeng Chen), “Water adsorption and desorption
on ultra-low friction sulfur-doped hydrogenated carbon films”, Journal of
Physics Condensed Matter 18, S1721-1726 (2006)
2007
185. (with Yanfeng Chen and Hongmei Wen”, “Moisture-induced
embrittlement mechanism for (Ni,Fe)Ti alloys”, Intermetallics 15, 288-293
(2007)
Textbooks:
“Practical Guide to
Surface Science and Spectroscopy”, Academic Press (2001)
“Introduction
to Materials Science and Engineering”, CRC Press/ Taylor and Francis Group
(2006)
Instructional
materials for “Introduction to Materials Science and Engineering”
Last
updated: May 2007