U.S. patent application number 15/222678 was filed with the patent office on 2018-02-01 for equipartition of nano particles in a metallic matrix to form a metal matrix composite (mmc).
The applicant listed for this patent is Gamma Technology, LLC. Invention is credited to Marco Curreli, William C. Harrigan, JR., Alfred W. Sommer.
Application Number | 20180029119 15/222678 |
Document ID | / |
Family ID | 61011952 |
Filed Date | 2018-02-01 |
United States Patent
Application |
20180029119 |
Kind Code |
A1 |
Curreli; Marco ; et
al. |
February 1, 2018 |
Equipartition of Nano Particles in a Metallic Matrix to Form a
Metal Matrix Composite (MMC)
Abstract
A metal matrix composite with a uniformly distributed ceramic
component is made by mixing nano size ceramic particles with a
surfactant and/or dispersing agent in a polar liquid to produce a
colloidal solution, blending the ceramic particles with micron or
sub-micron size metallic particles, and then compacting the blended
ceramic and metallic particles into a solid mass.
Inventors: |
Curreli; Marco; (Los
Angeles, CA) ; Harrigan, JR.; William C.; (Porter
Ranch, CA) ; Sommer; Alfred W.; (Valencia,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Gamma Technology, LLC |
Valencia |
CA |
US |
|
|
Family ID: |
61011952 |
Appl. No.: |
15/222678 |
Filed: |
July 28, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 3/17 20130101; B22F
2003/175 20130101; B22F 3/04 20130101; B22F 1/0074 20130101; C22C
1/1084 20130101; B22F 3/16 20130101; C22C 1/0416 20130101; B22F
2998/10 20130101; B22F 2999/00 20130101; B22F 2999/00 20130101;
C22C 1/1084 20130101; B22F 2201/01 20130101; B22F 2998/10 20130101;
C22C 1/1084 20130101; B22F 3/04 20130101; B22F 3/10 20130101; B22F
2998/10 20130101; C22C 1/1084 20130101; B22F 3/14 20130101; B22F
2998/10 20130101; C22C 1/1084 20130101; B22F 3/17 20130101; B22F
2998/10 20130101; C22C 1/1084 20130101; B22F 3/20 20130101; B22F
2998/10 20130101; C22C 1/1084 20130101; B22F 3/02 20130101; B22F
3/18 20130101 |
International
Class: |
B22F 1/00 20060101
B22F001/00; B22F 3/17 20060101 B22F003/17; B22F 3/04 20060101
B22F003/04; B22F 3/16 20060101 B22F003/16 |
Claims
1. A method of making a metal matrix composite comprising: mixing
ceramic particles with a surfactant in a polar liquid solvent to
produce a colloidal solution; blending metallic particles with the
ceramic particles in the colloidal solution; removing the solvent;
compacting the blended ceramic and metallic particles into a solid
mass.
2. The method of claim 1 wherein the ceramic particles are in the
range of approximately 5 to 1000 nanometers in diameter.
3. The method of claim 1 wherein the metallic particles are less
than approximately 2 microns in size.
4. The method of claim 1 wherein the polar liquid is an
alcohol.
5. The method of claim 4 wherein the polar liquid is isopropyl
alcohol.
6. The method of claim 1 wherein the surfactant is a phosphonic
acid.
7. The method of claim 6 wherein the surfactant is hexylphosphonic
acid.
8. The method of claim 1 further comprising adding a soluble
polymer dispersing agent to the polar liquid solvent.
9. The method of claim 8 wherein the soluble polymer dispersing
agent is poly vinyl pirrolidone.
10. The method of claim 1 wherein the ceramic and metallic
particles are blended ultrasonically.
11. The method of claim 1 wherein the ceramic and metallic
particles are blended in a dry state.
12. The method of claim 1 wherein the ceramic and metallic
particles are blended in a polar liquid.
13. The method of claim 12 wherein the ceramic and metallic
particles are blended with a high shear blender.
14. The method of claim 1 wherein the blended ceramic and metallic
particles are compacted by cold isostatic pressing and
sintering.
15. The method of claim 1 wherein the blended ceramic and metallic
particles are compacted by vacuum hot pressing.
16. The method of claim 1 wherein the blended ceramic and metallic
particles are compacted by hot powder forging.
17. The method of claim 1 further comprising extruding the solid
mass.
18. The method of claim 1 further comprising rolling the solid
mass.
19. The method of claim 1 wherein the metallic particles are
aluminum.
20. The method of claim 19 wherein the ceramic is alumina.
21. The method of claim 20 wherein the alumina particles are one of
alpha-phase, gamma-phase, or a combination of alpha-phase and
gamma-phase.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates generally to the field of
metal matrix composites. More particularly, the invention relates
to a method for uniformly distributing nanometer size ceramic
particles throughout a metal matrix.
Background
[0002] Many prior art methods exist to incorporate nano particles
into metallic matrices to form metal matrix composites (MMCs).
These include: (1) the heat treatment of supersaturated metallic
solid solutions to precipitate hard nano particles; (2) mechanical
alloying (or ball milling) of metallic powders with ceramic nano
particles followed by sintering/metal working at elevated
temperature and (3) the precipitation of nano ceramic particles
from liquid metal solutions, either as a result of a chemical
reaction or upon chilling the liquid. All three of these well-known
methods have their limitations.
[0003] Method (1) provides a very well distributed array of hard
nano precipitates in the solute depleted metal matrix. However,
these precipitated nano particles become unstable and dissolve back
into the metal matrix as the operating temperature of the MMC
approaches the aging thermal treatment temperature at which they
were formed. This limits the operating temperature of such
structural materials.
[0004] Method (2) suffers from the limitation that it is difficult
to create a uniform three-dimensional array of ceramic particles in
a metallic matrix without the use of expensive ball milling.
Moreover, the grinding media used in ball milling tends to
contaminate the nano powder as it is created. In many cases,
organic agents are introduced into the ball mill to suppress
flocculation of the newly formed nano particles. The
anti-flocculating agents tend to be trapped into the metallic
particles, which in turn embrittles the metallic matrix during
subsequent high temperature sintering and metal working
operations.
[0005] Method (3) is normally rather inexpensive to carry out, but
suffers from the fact that it is difficult to form a uniform array
of nano particles, and also from the fact that the microstructure
of the cast metal matrix is rather coarse and possesses low
mechanical strength.
[0006] A fourth method of creating a uniform array of nano ceramic
particles relies on the fact that metallic powder particles
naturally oxidize in air. The oxide layer is normally 1 nanometer
(nm) to 10 nm thick. Using powder metallurgy to make a solid
version of the oxidized particles, and extensive metal working
afterwards, leads to a uniform distribution of nano ceramic
particles throughout the solid. This approach to equipartition has
two limitations. First, the volume fraction of nano ceramic
particles that can be added to the MMC is directly related to the
surface area of the initial particle size of the metallic powder.
For example, in the case of aluminum powder, using this approach
with a 1.3 .mu.m average particle size as disclosed in U.S. Pat.
No. 8,323,373, one is limited to 2.4 volume % of distributed nano
aluminum oxide to the composite created. The second limitation is
that 1.3 .mu.m average particle size powder is very expensive and
difficult to find commercially.
SUMMARY OF THE INVENTION
[0007] Ceramic particles are normally electrical insulators and can
easily support electrical charges on their surfaces when immersed
in a polar liquid. With proper blending of a surfactant and the
nano particles in a polar liquid, one can create a colloid, at room
temperature, where each individual nano particle is physically kept
separated from all the others by electrostatic charges. Blending a
metallic powder with surfactant-treated nano particles allows one
to create a solid MMC with a uniform distribution of nano ceramic
particles employing conventional powder metallurgy followed by
extensive metal working.
[0008] Once the ceramic particles are uniformly distributed in the
metal matrix, they will remain in place until the metal matrix is
totally brought to a molten state thus removing the limitation
encountered with the prior art method (1) above. Creating a nano
particle dispersion by mixing surfactant treated nano ceramic
particles with metallic particles at room temperature eliminates
all the limitations noted for prior art methods (2) and (3) above.
The advantage that the method of the present invention has over
prior art method (4) above is that now we are able to incorporate
volumetric concentrations of nano particles quite inexpensively
well above the approximately 2% concentration limit available via
method (4).
[0009] The basic steps of the present invention comprise mixing
nano size ceramic particles with a surfactant in a polar liquid to
produce a colloidal solution, blending the ceramic particles with
micron or sub-micron size metallic particles, and then compacting
the blended ceramic and metallic particles into a solid mass. The
compacted material may be further worked by extruding or rolling to
a desired shape and size.
DETAILED DESCRIPTION
[0010] In the following description, for purposes of explanation
and not limitation, specific details are set forth in order to
provide a thorough understanding of the present invention. However,
it will be apparent to one skilled in the art that the present
invention may be practiced in other embodiments that depart from
these specific details. In other instances, detailed descriptions
of well-known methods and devices are omitted so as to not obscure
the description of the present invention with unnecessary
detail.
[0011] In one embodiment of the invention, a metal matrix composite
with a uniformly distributed ceramic component is made using a
process comprising several steps as described below. In this
particular example, the composite is an aluminum-alumina
(Al.sub.2O.sub.3) matrix; however, it is to be understood that the
invention is not limited in this regard and may be applied to any
other composite comprising a metal-ceramic matrix. Suitable ceramic
powders include, but are not necessarily limited to, oxides,
borides, carbides and nitrides.
[0012] First, mix a population of alpha-phase, nano-sized alumina
particles (approximately 5 nanometers to approximately 1000 nano
meters in diameter) in a polar liquid, such as isopropyl alcohol
(IPA, which is also referred to as 2-propanol or isopropanol), with
a surfactant and/or dispersing agent that is soluble in the polar
liquid, such as certain phosphonic acids, e.g., hexyl phosphonic
acid. Alternatively, the alumina particles may be gamma-phase or a
combination of alpha-phase and gamma-phase. The role of the
surfactant/dispersant is to facilitate wetting of the alumina nano
powder in the solvent of choice. For instance, hexyl phosphonic
acid rapidly and covalently binds to the surface of de-hydrated
alumina nanoparticles using its phosphonic acid group. The hexyl
group facilitates nanoparticle dispersion by providing an interface
that interacts with the solvent as well as with other dispersing
agents or stabilizers. Another advantage of creating a
"hexyl-capped" surface is to mitigate the strong pH-dependent
suspendability of charged alumina nanoparticles in organic
solvents. This is particularly useful for alumina nanoparticles,
which are known to have an isoelectric point close to pH 9.0. A
"hexyl-capped" surface is expected to have an isoelectric point
close to pH 7.0, facilitating dispersion in organic solvents, such
as IPA. Thus, de-hydrated alumina nanoparticles are added to a
stirring solution of hexyl phosphonic acid in IPA. A probe
sonicator (60 Hz) is also placed in the same solution to facilitate
full dispersion of the nanoparticles by ultrasonic agitation. As
large agglomerates are dispersed, phosphonic acid molecules rapidly
cap the surface of these nanoparticles preventing
de-agglomerations.
[0013] Second, during the dispersion process, the pH is adjusted to
the optimal value of isoelectric point, determined previously by
measurements of zeta potential. Addition of a dispersing polymer,
such as poly vinyl pirrolidone (PVP) and continuous ultrasonic
agitation helps keep the individual nanoparticles separated and
suspended in the organic solvent. The end result is the creation of
a stable colloidal alumina solution. Large agglomerates or certain
impurities (such as fused nanoparticles or alien material) may be
removed by centrifugation. Colloids can be formed at any
temperature that reasonably permits solubility of the surfactant
and dispersing polymer in the solvent. When IPA is used as a
solvent, the most convenient temperature range is between 15-75
degrees Celsius.
[0014] Third, once a stable colloidal solution is formed (for
example, by allowing the solution to stand for 6 hours or exposing
it to 20 g for 5 minutes such that no further sediments form and
all the nano alumina particles are in suspension), micron or
submicron size aluminum metallic particles are added while under
vigorous stirring and ultrasonic agitation. The solvent is then
removed by evaporation, forming a matrix of alumina nanoparticles
uniformly distributed among grains of micron or submicron size
aluminum particles.
[0015] Note that if the centrifuge step is not required, this
method may be used to create nano-alumina and micron-aluminum
matrix composites in a single step, in any desired concentration,
typically ranging from 1% to 40%. This is a significant advantage
over the traditional prior art methods for creating these MMCs
discussed above.
[0016] Fourth, in case other components are required in the final
MMC, such as boron carbide microparticles or other ceramic
microparticles, these components can be added after the addition of
the aluminum powder. These other components can be added in a
variety of concentrations, typically ranging from 0.1% to 20%.
[0017] Fifth, the blended powders from the foregoing step are
consolidated into a solid mass. This may be accomplished by cold
isostatic pressing, (CIP) and sintering, by vacuum hot pressing or
by hot powder forging.
[0018] In the case of CIP or hot vacuum pressing, the compacted
solids from the preceding step may then be either extruded or
rolled to the final shapes and sizes required by the end user. In
the case of extrusion, an extrusion ratio of at least 49:1 is
desirable to force the alumina nanoparticles inside the aluminum
grains.
[0019] It will be recognized that the above-described invention may
be embodied in other specific forms without departing from the
spirit or essential characteristics of the disclosure. Thus, it is
understood that the invention is not to be limited by the foregoing
illustrative details, but rather is to be defined by the appended
claims.
* * * * *