Solid Freeform Fabrication from Gas Precursors Using Laser Processing

Table of Contents:

  1. Principal Investigator.
  2. Productivity Measures.
  3. Summary of Objectives and Approach.
  4. Detailed Summary of Technical Progress.
  5. Transitions and DOD Interactions.
  6. Software and Hardware Prototypes.
  7. List of Publications.
  8. Invited and Contributed Presentations.
  9. Honors, Prizes or Awards Received.
  10. Project Personnel Promotions.
  11. Project Staff.
  12. Multimedia URL.
  13. Keywords.
  14. Business Office.
  15. Expenditures.
  16. Students.
  17. Book Plans.
  18. Sabbatical Plans.
  19. Related Research.
  20. History.

Harris Marcus

Productivity Measures.

Summary of Objectives and Approach.

  1. Understanding of the fundamental processes in SALD and SALDVI deposition
  2. SALD Joining of ceramics, an extension of SALD to a participating substrate deposition situation
  3. Selection and use of materials for deposition

Detailed Summary of Technical Progress

The assembly and construction of the Solid Freeform Fabrication(SFF) laboratory, begun in late 1995, is essentially completed. Three operational SFF systems are in place with the appropriate ancillary equipment. The lab contains two SAL/SALDVI machines, one with a 4 inch by 4 1/2 inch working area powder delivery system(PDS) and the other with a 1 inch round diameter working area PDS, and a SALD joining machine, incorporating a rotational device designed to work with tube structures. Five lasers are available, including a brand new, power stability optimized 50 watt continuous wave Nd:YAG laser. Two new in-situ chemical analysis tools will be implemented on the SFF systems. The first is a residual gas analyzer, and the second is a four point sampling emission spectrometer.

The specific research programs at the UCONN SFF lab focus on ceramic fabrication from the gas-phase reactions. Fundamental understanding of the SALD and SALDVI processes are essential to applying the technology to real world applications. The SALDVI work focused on three main properties in the silicon carbide material system. The deposited shapes were composed of silicon carbide from tetramethylsilane(TMS) gas precursor infiltrating into silicon carbide powder. The intralayer density and interlayer bonding were the important structure properties to control, in addition to an interesting bubbling phenomenon was observed during the SALDVI process. The individual layer densities were improved to approximately 85% by tweaking such properties as powder size, scan speed, and the temperature field induced by the laser. Similarly, the bonding between successive layers was enhanced with this optimization approach, including the scan path of the laser beam in forming the shape. The bubbling phenomenon had not been noted before and was detected because of the video capabilities of the SFF systems. This effect is a bubbling of the powder particles at the edge of the deposited shape. It is believed to arise from the thermal expansion of the gas in the powder bed porosity. A new bed preheating approach is expected to diminish the bubbling effect. SALD research looked at multiple material deposition. Specifically, silicon nitride, from TMS and ammonia, and silicon carbide and carbon, from TMS and acetylene respectively, were examined. The silicon nitride was deposited as a thin film, and analyzed with respect to its insulative quality. The deposition was performed at low ammonia pressures, approximately 10 to 20 torr, using a carbon dioxide laser. The successful formation of the nitride layer countered previous notions of not being able to use ammonia gas precursors with a CO2 laser. Silicon carbide and carbon were deposited in line formations, with the resulting electrical properties coming under scrutiny. The line resistances and emf response to temperature changes were tested with respect to varied line widths(a function of scan speed and laser beam size) and deposition temperature field. These SALD/SALDVI investigations were applied to an embedded sensor project sponsored by DARPA. The DARPA program studied the feasibility to fabricate a ceramic matrix with an operational, in-situ thermocouple formed inside the matrix structure in one continuous process. An example of a SALD/SALDVI silicon carbide/carbon thermocouple in a silicon carbide matrix, along with its temperature and emf response, can be found at the UCONN website .

The second area of investigation in the SFF laboratory is ceramic joining by SALD, a patented process for substrate-involved SALD deposition. The joining of ceramic parts is accomplished by using a filler material deposited from the gas-phase reaction in SALD. In this manner, the ceramic joint can be tailored to match the material composition of the constituent ceramic part to be joined. The initial efforts focused on joining clay-bonded silicon carbide(approximate 75 to 80% density) tubes with silicon carbide deposited from TMS precursor. The adhesion of the SALD material to the tube is excellent. In fact, the interface between the SALD material and the tube is inconspicuous. The success of joints in this initial phase has been inconsistent. While the adhesion is outstanding, successful connective bonding of the SALD material across the joint has been challenging. An example of two clay-bonded silicon carbide tubes connected by the SALD joining method can be found at the UCONN website .

Transitions and DOD Interactions.

  1. Presentation on "Solid Freeform Fabrication at the University of Connecticut" at the ONR annual review meeting in Woods Hole, MA, June 16th , 1997
  2. Presentation of research programs and tour of the SFF laboratory for Dr. William Coblenz of DARPA, August 8th, 1997
  3. Dr. Marcus took a 4 day trip on the USS Tunney submarine from San Diego, CA to Seattle, WA, September, 1997

Software and Hardware Prototypes.

Thermocouple and Joining Samples

List of Publications.

  1. "Current and Future Trends in Solid Freeform Fabrication", by D.L. Bourell, J.J. Beaman, J.W. Barlow, R.H. Crawford, H.L. Marcus, and L.E. Weiss, SPIE Proceedings Volumer 2910, Rapid Product Development Technologies, Boston, MA, November, 1996. "Selective Area Laser Deposition of Titanium Oxide" by K.J. Jakubenas, Y.L. Lee, M.S. Shaarawi, H.L. Marcus, and J.M. Sanchez, Rapid Prototyping Journal, Vol. 3, No. 2, 1997, p. 66-70.
  2. "Recent Advances in SALD and SALDVI", by K. Jakubenas, B.R. Birmingham, S. Harrison, J.E. Crocker, J. Sanchez, and H.L. Marcus, Proceedings of the Seventh International Conference on Rapid Prototyping 1997, edited by R.P. Chartoff, A.J. Lightman, M.K. Agarwala, and F. Prinz, University of Dayton, p. 60-69.
  3. The following four papers are found in the Proceedings from the 1997 Solid Freeform Fabrication Symposium, edited by D.L. Bourell, J.J. Beaman, H.L. Marcus, R.H. Crawford, and J.W. Barlow, August, 1997, Austin, TX, to be published
  4. "Rapid Prototyping and Solid Free Form Fabrication", by J.G. Conley and H.L. Marcus, to be published in the Journal of Manufacturing Science and Engineering, November, 1997
  5. "Multiple Material Solid Free-Form Fabrication by Selective Area Laser Deposition" by K. J. Jakubenas, J.M. Sanchez, and H.L. Marcus, Materials & Design. Paper accepted and to be published.
  6. US Patent granted for "Joining Ceramics and Attaching Fasteners to Ceramics by Gas Phase Selective Beam Deposition, March 18, 1997, Patent #5,611,883

Invited and Contributed Presentations.

  1. "Recent Advances in SALD and SALDVI," Seventh International Conference on Rapid Prototyping 1997, San Francisco, March 31-April 3, 1997
  2. "Gas Phase Solid Freeform Fabrication at the University of Connecticut," MRS Annual Meeting, Solid Freeform Fabrication Session, San Francisco, March 31 - April 4, 1997
  3. "Selective Area Laser Deposition (SALD) of Titanium Oxide," 6th European Conference on Rapid Prototyping and Manufacturing 1997, Nottingham, UK, July 1-3, 1997
  4. Solid Freeform Fabrication Symposium 1997, Austin, TX , August 11-13, 1997, 4 presentations on the following topics: a) The Use of VRML to Integrate Design and Solid Freeform Fabrication, b) Gas Phase SFF Control System for Silicon Nitride Deposition by SALD/SALDVI, c) Fabrication of In-Situ SiC/C Thermocouples by Selective Area Laser Deposition, d) Net Shape Functional Parts Using Diode Laser
  5. "Selective Area Laser Deposition Joining of Silicon Carbide," American Ceramic Society 1997 Fall Meeting, San Francisco, October 12-15, 1997

Honors, Prizes or Awards Received.

Dr. Harris Marcus was elected to the Connecticut Academy of Science and Engineering(CASE) in 1997. The total membership is limited, by state statute, to 200.

Project Personnel Promotions.

Project Staff.

Multimedia URL.

  1. EOYL FY96
  2. QUAD FY96

Keywords.

  1. Gas-Phase Solid Freeform Fabrication
  2. Selective Area Laser Deposition (SALD)
  3. Selective Area Laser Deposition Vapor Infiltration (SALDVI)
  4. Embedded Thermocouple Fabricated by SALD/SALDVI
  5. Ceramic Joining by SALD
  6. Laser-induced Gas Reactions

Business Office

Expenditures

  1. Est. FY98: 100%
  2. FY97: 100%
  3. FY96: 100%
  4. FY95: 100%
  5. FY94: 100%

Current and Former Students

  1. Name: Mr. Shay Harrison
  2. Name: Mr. James E. Crocker
  3. : Name: Mr. Lianchao Sun
  4. : Name: Mr. Erik Geiss
  5. : Name: Mr. Yanshuo Wang

Book Plans

  1. Title: Proceeding of the Solid Freeform Fabrication Symposium 1997 edited by D.L. Bourell, J.J. Beaman, H.L. Marcus, R.H. Crawford, and J.W. Barlow
  2. Title: Solid Freeform Fabrication: A New Direction in Manufacturing by J.J. Beaman, J.W. Barlow , D.L. Bourell, R.H. Crawford, H.L. Marcus, and K.P. McAlea

Sabbatical Plans

Related Research

  1. The Concurrent Design and Manufacturing Simulation Laboratory (CDMS Lab), Dept. of Mechanical Engineering, University of Connecticut
  2. University of Texas at Austin
  3. Massachusettes Institute of Technology (MIT)
  4. Rutgers University
  5. Stanford University

History