U.S. patent application number 14/086619 was filed with the patent office on 2014-03-20 for spinel ceramics via edge bonding.
This patent application is currently assigned to The Government of the United States of America, as represented by the Secretary of the Navy. The applicant listed for this patent is Ishwar D. Aggarwal, Shyam S. Bayya, Robert E. Miklos, Jasbinder S. Sanghera, Guillermo R. Villalobos. Invention is credited to Ishwar D. Aggarwal, Shyam S. Bayya, Robert E. Miklos, Jasbinder S. Sanghera, Guillermo R. Villalobos.
Application Number | 20140079909 14/086619 |
Document ID | / |
Family ID | 46577592 |
Filed Date | 2014-03-20 |
United States Patent
Application |
20140079909 |
Kind Code |
A1 |
Sanghera; Jasbinder S. ; et
al. |
March 20, 2014 |
Spinel Ceramics Via Edge Bonding
Abstract
A spinel ceramic made from the process comprising the steps of
polishing one edge of a first spinel part to a surface roughness of
less than 1 nm, polishing one edge of a second spinel part to a
surface roughness of less than 1 nm, joining the polished edge of
the first spinel part to the polished edge of the second spinel
part, heating the first and second spinel parts to about
1000-1200.degree. C., and maintaining said heating for about 3-6
hours resulting in bonded spinel parts.
Inventors: |
Sanghera; Jasbinder S.;
(Ashburn, VA) ; Bayya; Shyam S.; (Ashburn, VA)
; Villalobos; Guillermo R.; (Springfield, VA) ;
Aggarwal; Ishwar D.; (Charlotte, NC) ; Miklos; Robert
E.; (La Plata, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sanghera; Jasbinder S.
Bayya; Shyam S.
Villalobos; Guillermo R.
Aggarwal; Ishwar D.
Miklos; Robert E. |
Ashburn
Ashburn
Springfield
Charlotte
La Plata |
VA
VA
VA
NC
MD |
US
US
US
US
US |
|
|
Assignee: |
The Government of the United States
of America, as represented by the Secretary of the Navy
Washington
DC
|
Family ID: |
46577592 |
Appl. No.: |
14/086619 |
Filed: |
November 21, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
13354143 |
Jan 19, 2012 |
|
|
|
14086619 |
|
|
|
|
61437880 |
Jan 31, 2011 |
|
|
|
Current U.S.
Class: |
428/141 ;
156/308.2 |
Current CPC
Class: |
B32B 37/14 20130101;
C04B 2235/6562 20130101; C04B 2235/963 20130101; Y10T 428/24355
20150115; C04B 2237/76 20130101; C04B 2235/6565 20130101; Y10T
156/1064 20150115; C04B 37/001 20130101; C04B 35/645 20130101; C04B
2237/704 20130101; C04B 2237/343 20130101; B32B 18/00 20130101;
Y10T 428/24967 20150115; C04B 2237/52 20130101; C04B 2235/6567
20130101 |
Class at
Publication: |
428/141 ;
156/308.2 |
International
Class: |
B32B 18/00 20060101
B32B018/00; B32B 37/14 20060101 B32B037/14 |
Claims
1. A spinel ceramic made from the process comprising the steps of:
polishing one edge of a first spinel part to a surface roughness of
less than 1 nm; polishing one edge of a second spinel part to a
surface roughness of less than 1 nm; joining the polished edge of
the first spinel part to the polished edge of the second spinel
part; heating the first and second spinel parts to about
1000-1200.degree. C.; and maintaining said heating for about 3-6
hours resulting in bonded spinel parts.
2. The spinel ceramic of claim 1 wherein the bonded spinel parts
form a spinel ogive dome.
3. The spinel ceramic of claim 2 wherein the spinel ogive dome is a
monolithic part with an almost invisible bondline.
4. The spinel ceramic of claim 1 wherein said spinel ceramic
comprises a monolithic spinel ogive dome with a nearly invisible
bondline wherein said spinel (MgAl.sub.2O.sub.4) is a rugged, hard
and strong ceramic material which transmits from the UV to the
infrared in the range of from about 0.2 to about 5 .mu.m.
5. A spinel ceramic made from the process comprising the steps of:
polishing a first edge of a first spinel transparent tile, having
dimensions of about 3''.times.3''.times.1/2'' thick, wherein said
polishing results in less than 1 nm surface roughness; polishing a
first edge of a second spinel transparent tile, having dimensions
of about 3''.times.3''.times.1/2'' thick, wherein said polishing
results in less than 1 nm surface roughness; joining the polished
edges; applying a load to the tiles; heating the tiles up to
1100.degree. C. at 5.degree. C./min and holding for 6 hours; and
cooling slowly to room temperature at 1.degree. C./min resulting in
bonded spinel tiles.
6. The spinel ceramic of claim 5 wherein the spinel ceramic
exhibits optical transparency from the UV to 5 .mu.m, similar to
the first spinel transparent tile and the second spinel transparent
tile prior to bonding.
7. A spinel ceramic made from the process of claim 5 wherein said
spinel ceramic comprises a monolithic spinel ogive dome with a
nearly invisible bondline wherein said spinel (MgAl.sub.2O.sub.4)
is a rugged, hard and strong ceramic material which transmits from
the UV to the infrared in the range of from about 0.2 to about 5
.mu.m.
Description
[0001] This application claims priority to and benefit of U.S.
patent application Ser. No. 61/437,880 filed Jan. 31, 2011 and U.S.
patent application Ser. No. 13/354,143 filed on Jan. 19, 2012 the
entirety of each is herein incorporated by reference.
BACKGROUND
[0002] This application concerns a method of making transparent
ceramic spinel windows, domes and other complex shapes.
BRIEF SUMMARY OF THE INVENTION
[0003] Spinel (MgAl.sub.2O.sub.4) is a rugged, hard and strong
ceramic material which transmits from the UV to the infrared (0.2
to 5 .mu.m). The ceramic is made by densifying powder at elevated
temperatures.
[0004] Spinel can be achieved by hot pressing powders or by vacuum
sintering a pre-shaped green body. This leads to greater than 90%
density. Subsequent hot isostatic pressing (HIP) eliminates
residual porosity to leave a fully dense ceramic.
[0005] The sintering process relies on very monodisperse
nano-powder and proper cold shaping prior to sintering at elevated
temperatures. This process has proved very difficult to make
transparent spinel ceramic and leads to warping of larger parts or
complex shapes due to non-uniform densification.
[0006] The hot pressing has been demonstrated by us to be
reproducible since the die design dictates the final ceramic
part.
[0007] This has been very successful to make flat spinel parts but
leads to problems when trying to make complex shapes such as domes
and ogives. The unique aspect ratio of domes and especially ogive
domes makes it very difficult to hot press without inducing
excessive stresses which cause premature mechanical failure during
hot pressing under typical loads (2-8 kpsi).
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 illustrates a geometric shape of an ogive.
[0009] FIG. 2(a) illustrates two spinel ceramic tiles prior to
diffusion bonding and (b) illustrates after diffusion bonding.
[0010] FIG. 3 illustrates an edge bonded approximately
hemispherical spinel ceramic dome.
[0011] FIG. 4 illustrates two ogive dome halves and a fully bonded
transparent ogive made from spinel ceramic.
DETAILED DESCRIPTION
[0012] This disclosure teaches a method of making transparent
ceramic spinel windows, domes and other complex shapes.
[0013] This disclosure teaches a method that overcomes the current
issues and fabricates crack-free high optical quality spinel
ceramic parts such as domes and even larger flats.
[0014] This disclosure is based on edge bonding two halves of a
part together to make a transparent article. The bondline is
invisible after the bonding process and the final part has the same
properties as the original spinel including optical and mechanical
properties.
[0015] Spinel (MgAl.sub.2O.sub.4) is a rugged, hard and strong
ceramic material which transmits from the UV to the infrared (0.2
to 5 .mu.m). The ceramic is made by densifying powder at elevated
temperatures. This can be achieved by hot pressing powders or by
vacuum sintering a pre-shaped green body. This leads to greater
than 90% density. Subsequent hot isostatic pressing (HIP)
eliminates residual porosity to leave a fully dense ceramic.
[0016] The sintering process relies on very monodisperse
nano-powder and proper cold shaping prior to sintering at elevated
temperatures. This process has proved very difficult to make
transparent spinel ceramic and leads to warping of larger parts or
complex shapes due to non-uniform densification.
[0017] The hot pressing has been demonstrated by us to be
reproducible since the die design dictates the final ceramic part.
This has been very successful to make flat spinel parts but leads
to problems when trying to make complex shapes such as domes and
ogives. The unique aspect ratio of domes and especially ogive domes
makes it very difficult to hot press without inducing excessive
stresses which cause premature mechanical failure during hot
pressing under typical loads (2-8 kpsi).
[0018] An ogive dome's size and shape, including sharpness are
defined in FIG. 1. The sharpness of an ogive dome is expressed by
the ratio of its radius to the diameter of the cylinder; a value of
one half being a hemispherical dome, and larger values being
progressively more pointed. The more pointed the dome, the more
difficult it is to make.
[0019] Two spinel parts can be polished to a surface roughness of
better than 1 nm. This is critical since larger surface roughness
leads to trapped voids after the bonding process.
[0020] The two parts are then brought together and heated to about
2/3 (1000-1200 C) of the hot pressing temperature (1500 C) for
several hours to effectively bond the two parts together.
[0021] The joined part can be further polished to the desired
finish.
[0022] This method is very effective at tiling spinel ceramics
together and diffusion bonding to make larger panels. Similarly, a
custom, yet simpler die is needed to make a half dome and with much
reduced stresses.
[0023] After polishing and edge bonding the parts together, only
one monolithic part remains with an almost invisible bondline. This
is a successful method to make spinel ogive domes.
[0024] EXAMPLES
Example 1
[0025] Two spinel 3''.times.3''.times.1/2'' thick transparent tiles
were edge polished to <1 nm surface roughness (FIG. 2(a)). The
samples were brought together and held under slight load, heated up
to 1100 C at 5 C/min and held for 6 hours, and then cooled slowly
to room temperature at 1 C/min. The final part was polished to
remove surface debris and artifacts.
[0026] FIG. 2(b) shows the final part which exhibits excellent
optical transparency from the UV to 5 .mu.m, similar to the parts
prior to bonding.
Example 2
[0027] A die was designed for the hot press to make half
hemispherical domes from spinel ceramic. The two halves were given
a superpolish to provide a surface roughness of <1 nm and edge
bonded similar to the process shown in Example 1. The final dome
was surface polished and is shown in FIG. 3.
Example 3
[0028] This example demonstrates the fabrication of an ogive dome
using two halves previously hot pressed in a custom die. The edges
are superpolished to <1 nm surface roughness and then edge
bonded together, similar to process used in Example 1. The ogive
dimensions will dictate the design of custom dies for use in the
hot press to make the halve ogives.
[0029] This new edge bonding process has the capability to make
complex shapes, such as domes, and especially ogive domes that
cannot be made any other way with transparent spinel ceramic. It
also enables scale up to larger samples, which could be complex
shapes or just flat windows.
[0030] Many modifications and variations of the present invention
are possible in light of the above teachings. It is therefore to be
understood that the claimed invention may be practiced otherwise
than as specifically described. Any reference to claim elements in
the singular, e.g., using the articles "a," "an," "the," or "said"
is not construed as limiting the element to the singular.
* * * * *