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报告题目:
Cold Gas Dynamic Spraying Process with Nano- and Micro-size Particles
　报告人:
 Tien-Chien Jen
Chair and Professor of Mechanical Engineering Department, 
University of Wisconsin, Milwaukee
报告时间:
 2010-04-14 10:00
报告地点:
 清华大学材料院学术报告厅（逸夫技术科学楼2－321）
主办单位:
 材料院《材料科学论坛》
　　简介:
清华大学材料科学与工程研究院《材料科学论坛》
 
 
Cold Gas Dynamic Spraying Process with Nano- and Micro-size Particles
 
Tien-Chien Jen, Ph.D
Chair and Professor of Mechanical Engineering Department
University of Wisconsin, Milwaukee
 
 
Abstract:
　　Nanostructured materials are typically defined as materials with grain sizes less than 100 nm. Nanostructured coatings and bulk parts are the most promising near-term structural applications of nanotechnology. For example, specialized coatings for corrosion, thermal, and/or chemical stability are extremely valuable for chemical, aerospace, semiconductor and other industries. Nanostructured bulk materials, which are defined as bulk solids with nanoscale or partly nanoscale structures, have a variety of potential applications for their unique properties, such as army components and automobile parts (superhard and superelastic properties), soft and permanent magnetic materials (magnetic properties), information storage, magnetoresistance spin valves, and magnetic nanocomposite refrigerants (ferromagnetic properties), and hydrogen storage medium for fuel cell technology (solubilities and diffusive properties).
       Nanoparticles with diameters between 1 and 100 nm are naturally the source materials or “building blocks” for making nanocrystalline solids and coatings. A direct fabrication technique for nanostructured coatings and bulk materials involve the deposition or the compaction of nanoparticles to form coatings or bulk parts without coarsening the nanoscale structure. Since the unique properties are very often limited to the finest grain sizes, methods must be found to stabilize the grain size (i.e. without coarsening) while attaining theoretical density and completing particulate bonding.
       One of the greatest challenges for nanostructured coatings and bulk materials is the fast turn-around and high throughput. The fundamental gateway for this is cost-effective nanoparticle production and nanostructure deposition and compaction. Although there are quite a wide variety of techniques for the fabrication of nanostructured coatings and bulk materials, the most current techniques are often limited to the laboratory scale and are high-temperature-related fabrication process which will cause most of the nanoparticle material oxidizing and coarsening so that the nanostructure coatings and bulk materials with required properties cannot be obtained. Therefore, developing innovative techniques without grain coarsening, melting temperature limitation, and contamination or oxidation for fabricating nanostructured coating and bulk materials inexpensively and quickly is an important area that requires substantial research. The main objective of this reseach is to develop a cost-effective low temperature nanostructure deposition and compaction technology to fulfill this challenge.
Here, we are developing a new, highly efficient, and low-cost technique of low temperature Electrostatic-force-assisted Cold Gas Dynamic Spray (ECGDS) with min-arc source nanoparticle production for the fabrication of nanostructured coatings and bulk materials. The ECGDS extends the conventional CGDS system for micro-sized particles to the nanoscale particle size spectrum. The basic idea is to combine the electrostatic field with the supersonic gas-particle two-phase dynamic flow field to provide sufficient momentum for nanoparticles to penetrate through the bow shock and then deposit on the target surface with sufficient kinetic energy.
A comprehensive numerical simulation for the gas-particle two phase flows with particle diameter ranging from 0.1μm to 50μm accelerated by carrier gas Nitrogen in a supersonic De-Laval-type nozzle, has been performed by our research group to provide the detailed information on the particles velocity development inside and outside supersonic nozzle. A Computational Fluid Dynamic (CFD) turbulent model based on continuum fluid mechanics hypothesis was developed to calculate the nitrogen carrier gas acceleration of copper and platinum particles with different diameters in a nozzle with a ratio of expansion of AE/A* = 28.4. The geometries of the nozzle are exactly the same as that of the test nozzle in the experimental apparatus, which has been established in our lab. In the calculations, copper and platinum particles are used with nitrogen as the process gas with an inlet pressure p0 = 2.0 MPa and an inlet temperature T0 = 773 K. The computational domain is composed of a De-Laval-Type (convergent-divergent) nozzle and the area between the outlet and substrate. The RNG k-ε turbulence model is chosen for modeling the turbulent flow in the pipe. The velocities distributions of the carrier gas, particles and shock distributions inside and outside of De-Laval nozzle are presented. The effect of particle sizes and distances between the substrate the nozzle exit on the impact velocity are also demonstrated. Initial experimental data on the effect of particle sizes on the coating efficiency is also presented for illustration purpose. A video will be shown to illustrate the actual experimental surface coating process
In addition, an electrostatic force is used to assist the particles when they are passing through the shocks. This approach, in fact, is to couple electrostatic force with the supersonic gas-particle two-phase dynamic flow. The purpose of this approach is to supply nanoparticles with enough momentum to pass through the bow shock and deposit on substrate with sufficient impact velocity. This innovative method for nano-scale particle deposition is called as Electrostatic-force-assisted Cold Gas Dynamic Spray (ECGDS) technique. Although a few works have been done on the simulation of CGDS particle behaviours inside and outside De-Laval nozzle, the transport characteristics of nano-scale charged particles in supersonic gas stream coupled with electrostatic field are still in the uncharted territory, in particular for the study of the interaction of nano-scale charged particles under the action of electrostatic field with the shocks outside supersonic nozzle. In this study, comprehensive numerical simulations were also conducted for the acceleration of the particles in supersonic nitrogen stream with the aide of the electrostatic force fields. The effects of particle sizes, the charge density, and the materials (particle density) are investigated in this study. This study also investigates the influence of charge density upon the velocity distribution of the particles. An initial design and set-up of the experiment is also shown in this presentation.
 
TIEN-CHIEN JEN
Chair and Professor
Department of Mechanical Engineering
College of Engineering and Applied Science
University of Wisconsin- Milwaukee
DEGREE
       March 1993  Ph.D., Mechanical and Aerospace Engineering, University
                     of California, Los Angeles
June 1987        M.S. Power Mechanical Engineering, National Tsing Hua University, 
                        Hsin-Chu, Taiwan
June 1982        B.S. Naval Architecture and Marine Engineering, National Cheng Kung
                        University, Tainan, Taiwan
ACADEMIC EXPERIENCE
Aug ’08 – present   Professor, University of Wisconsin, Milwaukee
July ’05 – present   Chairman, Mechanical Engineering Department
Aug ’01 – Aug ‘08 Associate Professor, University of Wisconsin, Milwaukee
Aug ’97 – July ‘01  Assistant Professor, University of Wisconsin, Milwaukee
 
PRIMARY AREA OF INTSRUCTIONAL INTEREST
     My primary area of instructional interest is in the thermal sciences area. I can teach pretty much all the courses related to thermal sciences. The courses I am constant teaching are: ME320 Introduction to Fluid Mechanics, ME321 Basic Heat Transfer, ME 415 Modern Thermomanufacturing Processes, ME 715 Numerical Methods for Engineering, ME 711 Thermal Radiation and Conduction, ME712 Convective Heat Transfer, ME721 Fundamental of Fluid Flows.
 
PRIMARY AREA OF RESEARCH/SCHOLARLY/CREATIVE INTEREST
     My  research/scholarly/creative focuses  are on Thermal Aspects of Machining Processes (e.g., grinding, turning, honing, milling, drilling, etc.), Cold Gas Dynamic Spraying (CGDS) Surface Coating Technology, Diffusion Bonding, Fuel Cells and Hydrogen Generation/Reforming Technology, Nano-Technology (thermal) in Materials Processing (ECGDS) and Biosensing Technology.
       Dr. Jen published over 45 journal papers in major journals, such as ASME Journal of Heat Transfer, International Journal of Heat and Mass Transfer, ASME Journal of Manufacturing Engineering and Sciences, etc.. Dr. Jen has also published and presented in professional conferences over 100 papers.
 
EXTRAMURAL FUNDING (over $1.5 million)—partial list
Principal Investigator, “A Feasibility Study on Metalworking Fluid and Solid Waste Elimination for Environmentally Benign Machining Processes,” EPA; 2007-2011, (EPA grant award number RD833357) $349,978.
Principal Investigator,” SGER/GOALI: Electrostatic-force-assisted Cold Gas Dynamic Spray of Nanoparticles- A New Low Temperature Process for Producing Nanostructured Coatings," National Science Foundation-CMMI program, NSF award # 0739503, 2007-2008, $51,023.
Principal Investigator, "Establishment of a Mechanical Engineering," 2007, GE Healthcare Technologies, 2/2007, $100,000.
Principal Investigator, "Analytical Studies of Drill Temperatures with Heat Pipe Cooling: A Novel Approach," 1999-2006, National Science Foundation GOALI (Grant Opportunity for Academic Liaison with Industry) Program, DMII 9908324, $439,992.
Principal Investigator, “Electrostatic-force-assisted Cold Gas Dynamic Spray of Nanoparticles: A New Low Temperature Process,” UW Systems Applied Research Grant; 2006-2007, $46,548.
Principal Investigator, “A Feasibility Study on Solid Waste Elimination for Environmentally Benign Machining Processes,” UW System Solid Waste Research Program, 2005-2006, $30,000.
Co-Principal Investigator, “ Environmentally Benign (Internal) Cooling of End Mills,” 2005-2006, UW System Applied Research Grant, $47,688 (PI: Frank Pfefferkorn, UW-Madison)
 
AWARD
1.      Graduate School/UWM Foundation Outstanding Research Award, in recognition of Outstanding and Creative Activity, November 2000.
2.      NSF GOALI Award, the first award of this kind been awarded from NSF to UWM, 1999-2006.
3.      Outstanding Research Award, CEAS, UWM, 2001.
4.      SME Research Initiation Award, SME Education Foundation, 1998-1999.
5.      SME Research Initiation Award, SME Education Foundation, 1997-1998.
6.      Best Paper Award, CIRP Annal paper title “Thermal Aspect Thermal Aspects of Grinding with CBN Wheels,” CIRP Annals, Vol. 38, No. 1, pp.557-560.
7.      Listed in Marquis Who’s Who in Science and Engineering (1994 - to date).
8.      Listed in Marquis Who’s Who in the World (1994 - to date).
9.      Listed in Marquis Who’s Who in America (1995 - to date).
10.  Listed in Lexington Who’s Who (1999 - to date).
 
PROFESSIONAL CONTRIBUTIONS
Administrative Service
·        Chair, Mechanical Engineering Department (07/05-present), has increased the department research funding from $84K (04-05) to $3.5 million (08-09)
·        Member, University Committee (08-11)
·        Vice Chair, Search and Screen Committee, College of Engineering and Science Dean’s Search, 2007, 2008
Professional Service
Editing of Journals
1.      Associate Editor for the International Journal of Transport Phenomena
       2. Regional Editor for the Far East Journal of Applied Mathematics
 3.   Regional Editor for the JP Journal of Heat and Mass Transfer
Refereeing of Articles, Books, and Grant Proposals
ASME Journal of Heat Transfer, ASME Journal of Fluid Engineering, ASME Journal of Tribology, ASME Journal of Manufacturing Science and Engineering, ASME Journal of Engineering for Industry, International Journal of Heat and Mass Transfer, AIAA Journal of Thermophysics and Heat Transfer, Solar Energy, Numerical Heat Transfer, Applied Thermal Engineering, Powder Technology, JP Journal of Heat and Mass Transfer, Far East Journal of Applied Mathematics, Journal of Manufacturing Systems, STLE Journal, IEEE Transactions on Systems, Man, and Cybernetics, International Journal of Transport Phenomena
Panel Participation
Panelist, National Science Foundation, participated  more than 30 panels for regular DMII, CBET, SBIR, STTR proposals review. (Small Business Innovative Research) Phase I on "Machine and Process Development" proposals review
Participation in Planning Professional Programs
Organized and co-chaired technical session on more than 30 sessions in ASME organized National Heat Transfer Conferences, and International Mechanical Engineering Congress and Exposition.  
 
联系人：张政军 老师 62779033
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