Sintering of Powdered Copper
Brendan Short, Brendan Barrett, Jason Gamble
Engineering 45, SRJC Fall 2011
Sintering Overview
What is Sintering?
How does Sintering Work?
What Materials can be Sintered?
What are the advantages of
sintering?
What is Sintering
 Sintering is a metallurgical process in which a powdered material is
compressed and heated to form a solid part in the desired shape
In more detail:
Solid state sintering is the process of taking metal in the form of a powder and placing it into a mold or die. Once compacted into the mold the material is placed under a high
heat for a long period of time. Under heat, bonding takes place between the porous aggregate particles and once cooled the powder has bonded to form a solid piece.
Sintering can be considered to proceed in three stages. During the first, neck growth proceeds rapidly but powder particles remain discrete. During the second, most
densification occurs, the structure recrystallizes and particles diffuse into each other. During the third, isolated pores tend to become spheroidal and densification continues at
a much lower rate. The words Solid State in Solid State Sintering simply refer to the state the material is in when it bonds, solid meaning the material was not turned molten to
bond together as alloys are formed.[11]
One recently developed technique for high-speed sintering involves passing high electrical current through a powder to preferentially heat the asperities. Most of the energy
serves to melt that portion of the compact where migration is desirable for densification; comparatively little energy is absorbed by the bulk materials and forming machinery.
Naturally, this technique is not applicable to electrically insulating powders.
To allow efficient stacking of product in the furnace during sintering and prevent parts sticking together, many manufacturers separate ware using Ceramic Powder Separator
Sheets. These sheets are available in various materials such as alumina, zirconia and magnesia. They are also available in fine medium and coarse particle sizes. By matching
the material and particle size to the ware being sintered, surface damage and contamination can be reduced while maximizing furnace loading.
Source: Todd, Robert H., Allen, Dell K., Alting, Leo, "Manufacturing Processes Reference Guide", 1st Edition, Industrial Press Inc., New York 1994, ISBN 0-8311-3049-0
How Does Sintering Work?
 Sintering works by atomic diffusion of powdered
materials which is greatly accelerated at high
temperatures
In more detail:
Sintering is a method used to create objects from powder. It is
based on atomic diffusion. Diffusion occurs in any material above
absolute zero, but it occurs much faster at higher temperatures. In
most sintering processes, the powdered material is held in a mold
and then heated to a temperature below the melting point. The
atoms in the powder particles diffuse across the boundaries of the
particles, fusing the particles together and creating one solid
piece. Because the sintering temperature does not have to reach
the melting point of the material, sintering is often chosen as the
shaping process for materials with extremely high melting-points
such as tungsten and molybdenum.
Source: "Materials Science and Engineering: R: Reports :
Consolidation/synthesis of materials by electric current
activated/assisted sintering". ScienceDirect. Retrieved 2011-0930.
What Can be Sintered?
 Most Metals, Ceramics, and Plastics
In more detail:
Most, if not all, metals can be sintered. This applies especially to pure metals produced in vacuum
which suffer no surface contamination. Sintering under atmospheric pressure requires the usage of a
protective gas, quite often endothermic gas. Many nonmetallic substances also sinter, such
as glass, alumina, zirconia, silica, magnesia, lime, ice, beryllium oxide, ferric oxide, and
various organic polymers. Sintering, with subsequent reworking, can produce a great range of
material properties. Changes in density, alloying, or heat treatments can alter the physical
characteristics of various products. For instance, the Young's Modulus En of sintered iron powders
remains insensitive to sintering time, alloying, or particle size in the original powder, but depends
upon the density of the final product:
Plastic materials are formed by sintering for applications that
require materials of specific porosity. Sintered plastic porous
components are used in filtration and to control fluid and gas
flows. Sintered plastics are used in applications requiring
wicking properties, such as marking pen nibs. Sintered ultra
high molecular weight polyethylene materials are used
as ski and snowboard base materials. The porous texture
allows wax to be retained within the structure of the base
material, thus providing a more durable wax coating.
Source: "Materials Science and Engineering: R: Reports :
Consolidation/synthesis of materials by electric current activated/assisted
sintering". ScienceDirect. Retrieved 2011-09-30.
What are the advantages of Sintering
 Very high and uniform purity can be easily achieved
 The simple fabrication process retains purity
 Grain size is easily controlled
 No deformation is needed to produce directional elongation of grains
 Void density can be controlled
 Objects can be created in any shape
 Shapes can be produced that not be made by any other process
Project Materials and Preparation
 99.63% atomized pure copper powder with spherical particles with a
range of sizes from 45 to 75 micrometers was used
 Hydraulic Press
 Cylindrical Mold
 High Temperature Ovens
 Ceramic Oven Cups
 Microscope with digital imaging
 Polishing and sanding tools
 Scale
 Gloves and protective eyewear
 Bandages for Younes
Project Procedure
1. Weigh out 10 gram amounts of copper powder for pellets
2. Copper powered compressed to cylindrical pellets under
10,000 psi with hydraulic press
3. Samples put into ovens at temperatures of 900 and 1500
degrees Fahrenheit
4. Samples pulled from oven at 10 minutes (only 1500 degree),
30 minutes, 60 minutes, 90 minutes (only 900 degree), and
6 hours
5. Samples sanded, polished, and examined under microscope
at 40x lens magnification and 30x camera magnification for
around 1200x total magnification
Project Results:
Photographs of Un-sintered copper pellets
Photographs of 900 degree sintered copper
Photographs of 1500 degree sintered copper
Our Results Clearly show the diffusion of the
copper particles over time
Oxidation on a Sample
Non-Sintered Copper
Non-Sintered Copper
900 Degrees for 30 minutes
900 Degrees for 60 minutes
900 Degrees for 90 minutes
900 Degrees for 6 Hours
1500 Degrees for 10 min
1500 Degrees for 30 min
1500 Degrees for 1 hour
1500 Degrees for 6 hours
900 Degree Progression
30 min
90 min
60 min
6 hr
1500 Degree Progression
10 min
60 min
30 min
6 hr
Expected Results:
References:
"Materials Science and Engineering: R: Reports : Consolidation/synthesis of materials by electric current activated/assisted
sintering". ScienceDirect. Retrieved 2011-09-30.
Todd, Robert H., Allen, Dell K., Alting, Leo, "Manufacturing Processes Reference Guide", 1st Edition, Industrial Press Inc.,
New York 1994, ISBN 0-8311-3049-0
“The Ultimate Source for Information on Copper and Copper Alloys” http://www.copper.org
Mepco (The Metal Powder Company Limited) Materials Safety and Information Sheet