U.S. patent application number 16/986596 was filed with the patent office on 2022-02-10 for waterless electrically operated propellant.
The applicant listed for this patent is RAYTHEON COMPANY. Invention is credited to Lauren Brunacini, Thomas M. Deppert, David Hardy, Frederick B. Koehler.
Application Number | 20220041522 16/986596 |
Document ID | / |
Family ID | |
Filed Date | 2022-02-10 |
United States Patent
Application |
20220041522 |
Kind Code |
A1 |
Deppert; Thomas M. ; et
al. |
February 10, 2022 |
WATERLESS ELECTRICALLY OPERATED PROPELLANT
Abstract
An electrically operated propellant includes an electrolyte
source. The electrolyte source is an ionic liquid, a
polyelectrolyte, or a combination thereof. The electrically
operated propellant also includes a polymeric binder. The
electrically operated propellant is substantially waterless with a
water content of less than 10 wt. % water based on total weight of
the electrically operated propellant.
Inventors: |
Deppert; Thomas M.;
(Gilbert, AZ) ; Brunacini; Lauren; (Tucson,
AZ) ; Koehler; Frederick B.; (Tucson, AZ) ;
Hardy; David; (Sahuarita, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RAYTHEON COMPANY |
Waltham |
MA |
US |
|
|
Appl. No.: |
16/986596 |
Filed: |
August 6, 2020 |
International
Class: |
C06B 45/10 20060101
C06B045/10; C06B 29/00 20060101 C06B029/00 |
Claims
1. An electrically operated propellant comprising: an electrolyte
source, the electrolyte source being an ionic liquid, a
polyelectrolyte, or a combination thereof; and a polymeric binder;
wherein the electrically operated propellant is substantially
waterless with a water content of less than 10 wt. % water based on
total weight of the electrically operated propellant.
2. The electrically operated propellant of claim 1, wherein the
ionic liquid is a salt that melts into a liquid without decomposing
or vaporizing.
3. The electrically operated propellant of claim 1, wherein the
electrically operated propellant is waterless with a water content
of 0 wt. % water.
4. The electrically operated propellant of claim 1, further
comprising a perchlorate oxidizer.
5. The electrically operated propellant of claim 1, wherein the
electrolyte source is a perchlorate-based electrolyte source.
6. The electrically operated propellant of claim 1, wherein the
polyelectrolyte is a polycation, a polyanion, a polyampholyte, or a
combination thereof.
7. The electrically operated propellant of claim 1, wherein the
ionic liquid comprises a metal.
8. The electrically operated propellant of claim 1, wherein the
ionic liquid is 1-(2-hydroxyethyl)-3-methylimidazolium chloride;
1-butyl-3-methylimidazolium perchlorate; 1-alkyl-3-methyl
imidazolium tetrafluoroborate; 4-amino-1-butyl-1,2,4-triazolium
nitrate or any combination thereof.
9. An electrically operated propellant comprising: an electrolyte
source, the electrolyte source being a polymer comprising a
plurality of electrolyte groups; and a polymeric binder; wherein
the electrically operated propellant is substantially waterless
with a water content of less than 10 wt. % water based on total
weight of the electrically operated propellant.
10. The electrically operated propellant of claim 9, wherein the
electrically operated propellant is waterless with a water content
of 0 wt. % water.
11. The electrically operated propellant of claim 9, further
comprising a metal fuel.
12. The electrically operated propellant of claim 9, wherein the
polymer comprising the plurality of electrolyte groups is a
polymerized ionic liquid.
13. The electrically operated propellant of claim 9, wherein the
polymer comprising the plurality of electrolyte groups is a
polycation, a polyanion, a polyampholyte, or a combination
thereof.
14. The electrically operated propellant of claim 9, further
comprising a perchlorate oxidizer.
15. A method of making an electrically operated propellant, the
method comprising: combining an electrolyte source and a polymeric
binder to form a propellant composition, the electrolyte source
being an ionic liquid, a polyelectrolyte, or a combination thereof;
and forming the propellant composition into a solid propellant
configuration; wherein the electrically operated propellant is
substantially waterless with a water content of less than 10 wt. %
water based on total weight of the electrically operated
propellant.
16. The method of claim 15, wherein the ionic liquid is a salt that
melts into a liquid without decomposing or vaporizing.
17. The method of claim 15, wherein the ionic liquid is a
polymerized ionic liquid.
18. The method of claim 15, wherein the polyelectrolyte is a
polycation, a polyanion, a polyampholyte, or a combination
thereof.
19. The method of claim 15, further comprising combining a metal
fuel with the electrolyte source and the polymeric binder.
20. The method of claim 15, wherein the electrically operated
propellant is waterless with a water content of 0 wt. % water.
Description
BACKGROUND
[0001] Missiles and rockets burn propellants within combustion
chambers to generate pressurized gases. The pressurized gases are
directed through a nozzle to provide thrust and accordingly propel
the body of the missile or rocket.
[0002] Solid rocket propellants are formed with a solid oxidizer,
for instance ammonium perchlorate, fuels, additives, and binders.
Ignition systems that elevate the temperature of the solid rocket
propellant to the point of combustion are used to ignite the solid
rocket fuel.
[0003] After ignition of a solid rocket motor, the reaction
generally cannot be interrupted until the fuel is completely
consumed, and solid rocket propellant burns according to the shape
of the propellant grain the propellant burn rate and its operating
pressure, which is dictated by the nozzle throat size. Thus, the
burn rate of the fuel proceeds according to a set of predefined
parameters that generally cannot be changed during launch and/or
flight.
[0004] Some solid propellants can be electrically controlled
propellants that are ignitable and extinguishable under a variety
of conditions, including under high pressures within a rocket motor
combustion chamber. Such electrically operated propellants can be
selectively ignited and extinguished over a broad range of
conditions, which facilitates the selective generation of thrust
for a variety of applications, for example, to control to a vehicle
without consuming the entirety of the propellant at one time.
SUMMARY
[0005] According to embodiments of the present invention, an
electrically operated propellant includes an electrolyte source.
The electrolyte source is an ionic liquid, a polyelectrolyte, or a
combination thereof. The electrically operated propellant also
includes a polymeric binder. The electrically operated propellant
is substantially waterless with a water content of less than 10 wt.
% water based on total weight of the electrically operated
propellant.
[0006] According to other embodiments of the present invention, an
electrically operated propellant includes an electrolyte source.
The electrolyte source is a polymer with a plurality of electrolyte
groups. The electrically operated propellant further includes a
polymeric binder. The electrically operated propellant is
substantially waterless with a water content of less than 10 wt. %
water based on total weight of the electrically operated
propellant.
[0007] Yet, according to other embodiments of the present
invention, a method of making an electrically operated propellant
includes combining an electrolyte source and a polymeric binder to
form a propellant composition. The electrolyte source is an ionic
liquid, a polyelectrolyte, or a combination thereof. The method
further includes forming the propellant composition into a solid
propellant configuration. The electrically operated propellant is
substantially waterless with a water content of less than 10 wt. %
water based on total weight of the electrically operated
propellant.
[0008] Additional features and advantages are realized through the
techniques of the present invention. Other embodiments and aspects
of the invention are described in detail herein and are considered
a part of the claimed invention. For a better understanding of the
invention with the advantages and the features, refer to the
description and to the drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0009] For a more complete understanding of this disclosure,
reference is now made to the following brief description, taken in
connection with the accompanying drawings and detailed description,
wherein like reference numerals represent like parts:
[0010] FIG. 1 is a cross-sectional view of a gas generation
assembly including an electrically operated propellant; and
[0011] FIG. 2 is a flow diagram showing a method of making an
electrically operated propellant.
DETAILED DESCRIPTION
[0012] Electrically operated propellants can be controlled
(ignited, extinguished, and throttled) using an electrical signal
provided by one or more configured electrodes. For example,
applying a voltage across the electrodes ignites the propellant,
and conversely, the interrupting the voltage extinguishes the
propellant. In a rocket motor, it may be desirable to throttle or
interrupt the burn of the electrically operated propellant during
vehicle flight in order to control the rocket motor burn during
different flight events in order to accomplish a desired mission in
a variable environment.
[0013] Generally, electrically operated solid propellants include a
perchlorate oxidizer, a metal fuel, a polymeric binder, and a
solvent. Water has most commonly been used to solubilize the
polymeric binder and form an aqueous solution with the additional
propellant ingredients.
[0014] One challenge of using electrically operated propellants, in
a significantly cold space propulsion application scenario, for
example, is that the water used to form aqueous solutions can boil,
due to the pressure drop, or freeze, due to the low temperatures,
if exposed directly to a space environment. Even if the water in
the propellant is not directly exposed to the space environment,
the included water ingredient poses an overall issue due to the
significantly high and/or low temperature and pressure exposure in
space. Risks of the water in the electrically operated propellants
include potentially rendering the propellant inoperable are
therefore undesirable for space applications.
[0015] Similarly, the water in electrically operated propellants
that are used in other applications, such as in airbag inflators,
presents challenges because including volatile components in the
formulation that could be labile are problematic. This volatility
makes using electrically operated propellants with significant
quantities of water challenging, as water content verification and
continuous absorption and loss of water despite manufacturing,
storage, and use in controlled environments pose additional water
related issues.
[0016] Additionally, long term storage of an electrically operated
propellant with a water ingredient is challenging, as water may
interact with other materials, the propellant, rocket motor, and/or
flight vehicle. Further, water presents challenges with respect to
with propellant relaxation out of the desired propellant shape,
oxidations, as well as material compatibility with additional
materials used in the rocket motor build.
[0017] Accordingly, one or more aspects of the present invention
address the above-described shortcomings by providing electrically
operated propellants and methods of making and using electrically
operated propellants, which are substantially waterless in some
embodiments, and waterless in other embodiments. In one or more
aspects of the present invention, the electrically operated
propellants include an electrolyte source, a metal fuel, a
polymeric binder, and optionally, a perchlorate oxidizer, with the
electrolyte source being an ionic liquid, a polyelectrolyte, or a
combination thereof. In other aspects of the present invention, the
electrically operated propellants include an electrolyte source, a
metal fuel, a polymeric binder, and optionally, a perchlorate
oxidizer, with the electrolyte source being a polymer with a
plurality of electrolyte groups.
[0018] Aspects of the present invention provide various advantages.
Water is reduced or completely eliminated in electrically operated
propellant compositions. Further, any aqueous solvents, such as
water, which are required for water soluble binders (e.g., casein,
methyl cellulose, polyethylene oxide, polyvinyl acetate, and
polyvinyl alcohol) are replaced by a non-aqueous solvent(s), which
includes one or more of an ionic liquid, polyelectrolyte, or
polymer with a plurality of electrolyte groups. The non-aqueous
compositions eliminate the risk of water rendering the propellant
inoperable when exposed directly or indirectly to a space
environment in a space propulsion application (e.g., a rocket
motor). Eliminating volatile water also allows the electrically
operated propellant to be used in other non-space applications
where water loss or absorption is undesired, for example, in airbag
inflators.
[0019] The term "substantially waterless" or "non-aqueous" and
variations thereof is used in this detailed description to mean a
water content of less than 10 weight % (wt. %) water, less than 5
wt. % water, or less than 0.1 wt. % water. In some aspects,
substantially waterless means completely waterless, with 0 wt. %
water present in the composition.
[0020] The term "ionic liquid" and variations thereof are used in
this detailed description to mean a salt that melts into a liquid
without decomposing or vaporizing.
[0021] The term "polyelectrolyte" and variations thereof are used
in this detailed description to mean a polymer that includes a
plurality of electrolyte groups (cations, anions, or a combination
thereof).
[0022] The term "electrolyte source" and variations thereof are
used in this detailed description to mean a substance that produces
an electrically conducting solution of ions when dissolved in a
suitable solvent.
[0023] As described above, electrically operated propellants
described herein include, but are not limited to, an electrolyte
source, a metal fuel, a polymeric binder, and optionally a
perchlorate oxidizer, with the electrolyte source being an ionic
liquid, a polyelectrolyte, a polymer comprising a plurality of
electrolyte groups, or a combination thereof. The electrically
operated propellants are substantially waterless and include a
water content of less than 10 weight % (wt. %) water, less than 5
wt. % water, or less than 0.1 wt. % water. In some embodiments,
substantially waterless electrically operated propellants are
waterless, with 0 wt. % water.
[0024] Ionic liquids in the electrically operated propellants are
salts that melt into a liquid without decomposing or vaporizing. In
some aspects, ionic liquids are liquid at a temperature below
100.degree. C. The ionic liquids are "energetic" or "nonenergetic"
ionic liquids. The term "energetic" and variations thereof is
intended to describe a substance with a neutral or positive oxygen
balance. Ionic liquids are salts in the liquid state, which in some
embodiments, have a melting point below 25.degree. C. Ionic liquids
melt without decomposing or vaporizing. Ionic liquids are also be
referred to as liquid electrolytes, ionic melts, ionic fluids,
fused salts, liquid salts, and ionic glasses.
[0025] Non-limiting examples of ionic liquids for the electrically
operated propellants include 1-(2-hydroxyethyl)-3-methylimidazolium
chloride; 1-butyl-3-methylimidazolium perchlorate; 1-alkyl-3-methyl
imidazolium tetrafluoroborate; 4-amino-1-butyl-1,2,4-triazolium
nitrate or any combination thereof.
[0026] In some aspects of the present invention,
1-(2-hydroxyethyl)-3-methylimidazolium chloride functions as a
plasticizer that improves processing. In other aspects of the
present invention, 1-butyl-3-methylimidazolium perchlorate is
included in the electrically operated propellants to function as
both the electrolyte source and an oxidizer, as it is a
perchlorate-based electrolyte. Other perchlorate-based ionic
liquids can be used in the electrically operated propellants.
[0027] In one or more aspects of the present invention, the ionic
liquid in the electrically operated propellant is a polymerized
ionic liquid. Polymerized ionic liquids include a liquid ionic
species (electrolyte group) in each repeating monomeric unit.
Polymerized ionic liquids provide advantages in the electrically
operated propellants, including enhanced stability, improved
processability, flexibility, and durability, among others. In other
aspects of the present invention, the ionic liquid includes a metal
(a metal ionic liquid).
[0028] Polyelectrolytes are polymers that include a plurality of
electrolyte groups (cations, anions, or a combination thereof).
Non-limiting examples of polyelectrolytes include polycations,
polyanions, polyampholytes, or a combination thereof.
[0029] The amount of the electrolyte source present in the
electrically operated propellant varies depending on the type of
electrolyte source and end propellant/application. According to
some aspects of the present invention, the electrically operated
propellant includes the electrolyte source in an amount of about 20
to about 90 percent of the total weight of the electrically
operated propellant. According to other aspects of the present
invention, the electrically operated propellant includes the
electrolyte source in an amount of about 30 to about 80 percent of
the total weight of the electrically operated propellant.
[0030] In some aspects of the present invention, the electrolyte
source can also function as the oxidizer, and the electrically
operated propellants do not include additional oxidizers. Yet, in
other aspects of the present invention, the electrically operated
propellants include a separate perchlorate oxidizer, in addition to
the electrolyte source.
[0031] Non-limiting examples of perchlorate oxidizers include
perchlorate oxidizers such as aluminum perchlorate, ammonium
perchlorate, barium perchlorate, calcium perchlorate, lithium
perchlorate, magnesium perchlorate, perchlorate acid, strontium
perchlorate, sodium perchlorate, or any combination thereof.
[0032] The amount of the perchlorate oxidizer present in the
electrically operated propellant varies depending on the type of
oxidizer and end propellant/application. According to some aspects
of the present invention, the electrically operated propellant
includes a perchlorate oxidizer in an amount of about 30 to about
90 percent of the total weight of the electrically operated
propellant. According to other aspects of the present invention,
the electrically operated propellant includes a perchlorate
oxidizer in an amount of about 45 to about 75 percent of the total
weight of the electrically operated propellant.
[0033] The electrically operated propellant further includes,
optionally, a metal fuel. The metal fuel assists propellant
operation in several ways, including but not limited to,
facilitating the application of an electrical signal or by
increasing the density of the propellant. Non-limiting examples of
the metal fuel include tungsten, magnesium, copper oxide, copper,
titanium, aluminum, or any combination thereof.
[0034] The amount of the metal fuel present in the electrically
operated propellant varies depending on the type of fuel and end
propellant/application. According to some aspects of the present
invention, the electrically operated propellant includes a metal
fuel in an amount of about 0 to about 40 percent of the total
weight of the electrically operated propellant. When included, the
electrically operated propellant includes less than 40 percent
weight of the total weight of the electrically operated propellant.
According to other aspects of the present invention, the
electrically operated propellant includes a metal fuel in an amount
of about 0 to about 30 percent of the total weight of the
electrically operated propellant.
[0035] The electrically operated propellant further includes a
polymeric binder. The polymeric binder is a water-soluble binder, a
water insoluble polymeric binder, or a combination thereof.
[0036] Non-limiting examples of water-soluble polymeric binders
include casein, methyl cellulose, polyethylene oxide, polyvinyl
acetate, polyvinyl alcohol, or any combination thereof.
[0037] Non-limiting examples of water insoluble polymeric binders
include polymer electrolytes, water insoluble copolymers, or a
combination thereof.
[0038] A polymer electrolyte is an electrically conducting solution
of a salt in a polymer. Solid or gel polymer electrolytes are
blends containing an electrically conductive polymer, a metal salt,
a finely divided inorganic filler material, and a finely divided
ion conductor. The polymer electrolyte is a solid polymer
electrolyte, a gel polymer electrolyte, a dry solid polymer
electrolyte, or a composite polymer electrolyte.
[0039] The water insoluble polymeric binder is also a copolymer,
such as a copolymer binder system. A non-limiting example of a
water insoluble copolymer is polyurethane.
[0040] The amount of the polymeric binder present in the
electrically operated propellant varies depending on the type of
water insoluble polymeric binder and end propellant/application.
According to some aspects of the present invention, the
electrically operated propellant includes a polymeric binder in an
amount of about 10 to about 50 percent of the total weight of the
electrically operated propellant. According to other aspects of the
present invention, the electrically operated propellant includes a
polymeric binder in an amount of about 15 to about 30 percent of
the total weight of the electrically operated propellant.
[0041] The electrically operated propellant can be used in a
variety of applications, such as a gas generation system of a
rocket motor. Other applications for the electrically operated
propellant include, but are not limited to, other forms of gas
generations systems used in place of traditional solid or liquid
rocket motor solutions, such as orbit maintenance systems,
divert/attitude control systems, and ignition systems, in
additional to as a replacement for traditional and smart air bag
inflator systems, as well as ejection systems.
[0042] The polymeric binder cooperates with the electrolyte source,
metal fuel, and optional perchlorate oxidizer to combine these
components into a solid fuel propellant shapeable into any
configuration such as the cylindrical configurations provided in
FIG. 1, which is described in further detail below. The
electrically operated propellant has a storage modulus sufficiently
high to allow for the maintenance of the shape the propellant is
molded into at manufacture. For instance, the electrically operated
propellant has a storage modulus of 300 psi or greater at ambient
temperature that accordingly allows the propellant in the
configurations shown in FIG. 1 or other configurations to maintain
its shape through dynamic conditions including, but not limited to,
pressurization, launch and flight. The propellant with a consistent
shape accordingly maintains a predictable performance profile as
the shape and surface area of the propellant are relatively static
during operation. The electrically operated propellant is thereby
formable (e.g., can be cast or molded) into any number of grain
configurations and reliably perform with a desired performance
profile (thrust dictated at least in part by the grain surface
area) even when subject to dynamic conditions.
[0043] FIG. 1 depicts a cross-sectional view of a gas generation
assembly including an electrically operated propellant according to
aspects of the present invention. It is to be noted that the gas
generation system with electrically operated propellant shown in
FIG. 1 is but one example, and the electrically operated propellant
can be used in other configurations, applications, and gas
generation systems.
[0044] The gas generation system 100 is shown as part of an overall
assembly, such as a rocket motor 102. In one example, the gas
generation system 100 includes the rocket motor 102. The gas
generation system 100 includes the electrically operated propellant
108, configured to provide thrust through a rocket nozzle 112.
[0045] The gas generation system 100 includes a combustion chamber
of 104 having the electrically operated propellant 108 positioned
therein. Two or more electrodes 110 extend into the electrically
operated propellant 108 within the combustion chamber 104. The
electrically operated propellant 108 fills a portion of combustion
chamber 104 and has a predetermined grain shape. In another
example, the electrically operated propellant 108 fills
substantially the entirety of the combustion chamber 104. That is
to say, the electrically operated propellant 108 extends from the
position shown in FIG. 1 toward a position in close proximity to
the nozzle 112. Accordingly, the two or more electrodes 110
similarly extend through the electrically operated propellant 108
toward the nozzle 112.
[0046] The electrically operated propellant 108 includes a
formulation that allows for the igniting and extinguishing of the
propellant in a variety of conditions according to the application
(and interruption of the application) of electricity through the
electrodes 110. For instance, the electrically operated propellant
108 is configured to ignite with the application of voltage across
the electrodes 110. Conversely, the electrically operated
propellant 108 is extinguished with the interruption of the voltage
at a range of pressures (e.g., from 0 psi to 2,000 psi). For
instance, where the combustion chamber 104 is part of the rocket
motor 102, and the motor is in the process of generating thrust,
the pressure within the combustion chamber 104 is greater than 200
psi, for instance from 200 to 2,000 psi. In this condition, it may
be desirable to interrupt the burn of the electrically operated
propellant, for example, in order to provide changing levels of
thrust for a mission with variable requirements. In such a
circumstance the voltage applied across the electrodes 110 is
interrupted. Despite the pressurized environment of the combustion
chamber 104, subjecting the electrically operated propellant 108 to
a pressure greater than 200 psi, for instance pressures approaching
2,000 psi, the interruption of voltage to the electrodes 110 allows
the electrically operated propellant 108 to extinguish. With the
electrically operated propellant 108 extinguished, the generation
of thrust is halted and the propellant is preserved for future use.
The gas generation systems 100 is configured for ignition and
extinguishing during operation. Importantly, even with ambient or
high pressures within the combustion chamber 104, such as
atmospheric pressure, pressures greater than 200 psi, 500 psi,
1,000 psi, 1,500 psi and up to 2,000 psi, the electrically operated
propellant 108 is extinguished with the interruption of electricity
(e.g., voltage or current) applied across the electrodes 110.
[0047] FIG. 2 is a flow diagram showing a method 200 of making an
electrically operated propellant according to some aspects of the
present invention. As shown in box 202, an electrolyte source, an
optional metal fuel, and a polymeric binder are combined to form a
propellant composition. The metal fuel is optional, and in some
embodiments, the metal fuel is not included in the propellant
composition. As shown in box 204, any additional formulation
components are added into the propellant composition. As shown in
box 206, the propellant composition is machine processed for a
specified time, under specified conditions (temperature, pressure,
machine settings, etc.), depending on the particular propellant and
configuration. As shown in box 208, the machine processed
composition is formed into a solid propellant configuration. The
propellant composition is moldable, extrudable, castable,
pressable, or a combination thereof, depending on the application.
As shown in box 210, the solid propellant configuration is set for
a specified amount of time in a controlled environment
(temperature, pressure, humidity, etc.), depending on the
particular propellant and application.
[0048] Various embodiments of the present invention are described
herein with reference to the related drawings. Alternative
embodiments can be devised without departing from the scope of this
invention. Although various connections and positional
relationships (e.g., over, below, adjacent, etc.) are set forth
between elements in the following description and in the drawings,
persons skilled in the art will recognize that many of the
positional relationships described herein are
orientation-independent when the described functionality is
maintained even though the orientation is changed. These
connections and/or positional relationships, unless specified
otherwise, can be direct or indirect, and the present invention is
not intended to be limiting in this respect. Accordingly, a
coupling of entities can refer to either a direct or an indirect
coupling, and a positional relationship between entities can be a
direct or indirect positional relationship. As an example of an
indirect positional relationship, references in the present
description to forming layer "A" over layer "B" include situations
in which one or more intermediate layers (e.g., layer "C") is
between layer "A" and layer "B" as long as the relevant
characteristics and functionalities of layer "A" and layer "B" are
not substantially changed by the intermediate layer(s).
[0049] The following definitions and abbreviations are to be used
for the interpretation of the claims and the specification. As used
herein, the terms "comprises," "comprising," "includes,"
"including," "has," "having," "contains" or "containing," or any
other variation thereof, are intended to cover a non-exclusive
inclusion. For example, a composition, a mixture, process, method,
article, or apparatus that comprises a list of elements is not
necessarily limited to only those elements but can include other
elements not expressly listed or inherent to such composition,
mixture, process, method, article, or apparatus.
[0050] Additionally, the term "exemplary" is used herein to mean
"serving as an example, instance or illustration." Any embodiment
or design described herein as "exemplary" is not necessarily to be
construed as preferred or advantageous over other embodiments or
designs. The terms "at least one" and "one or more" are understood
to include any integer number greater than or equal to one, i.e.
one, two, three, four, etc. The terms "a plurality" are understood
to include any integer number greater than or equal to two, i.e.
two, three, four, five, etc. The term "connection" can include an
indirect "connection" and a direct "connection."
[0051] References in the specification to "one embodiment," "an
embodiment," "an example embodiment," etc., indicate that the
embodiment described can include a particular feature, structure,
or characteristic, but every embodiment may or may not include the
particular feature, structure, or characteristic. Moreover, such
phrases are not necessarily referring to the same embodiment.
Further, when a particular feature, structure, or characteristic is
described in connection with an embodiment, it is submitted that it
is within the knowledge of one skilled in the art to affect such
feature, structure, or characteristic in connection with other
embodiments whether or not explicitly described.
[0052] For purposes of the description hereinafter, the terms
"upper," "lower," "right," "left," "vertical," "horizontal," "top,"
"bottom," and derivatives thereof shall relate to the described
structures and methods, as oriented in the drawing figures. The
terms "overlying," "atop," "on top," "positioned on" or "positioned
atop" mean that a first element, such as a first structure, is
present on a second element, such as a second structure, wherein
intervening elements such as an interface structure can be present
between the first element and the second element. The term "direct
contact" means that a first element, such as a first structure, and
a second element, such as a second structure, are connected without
any intermediary conducting, insulating or semiconductor layers at
the interface of the two elements.
[0053] The terms "about," "substantially," "approximately," and
variations thereof, are intended to include the degree of error
associated with measurement of the particular quantity based upon
the equipment available at the time of filing the application. For
example, "about" can include a range of .+-.8% or 5%, or 2% of a
given value.
[0054] The flowchart and block diagrams in the Figures illustrate
possible implementations of fabrication and/or operation methods
according to various embodiments of the present invention. Various
functions/operations of the method are represented in the flow
diagram by blocks. In some alternative implementations, the
functions noted in the blocks can occur out of the order noted in
the Figures. For example, two blocks shown in succession can, in
fact, be executed substantially concurrently, or the blocks can
sometimes be executed in the reverse order, depending upon the
functionality involved.
[0055] The corresponding structures, materials, acts, and
equivalents of all means or step plus function elements in the
claims below are intended to include any structure, material, or
act for performing the function in combination with other claimed
elements as specifically claimed. The description of the present
invention has been presented for purposes of illustration and
description, but is not intended to be exhaustive or limited to the
invention in the form disclosed. Many modifications and variations
will be apparent to those of ordinary skill in the art without
departing from the scope and spirit of the invention. The
embodiments were chosen and described in order to best explain the
principles of the invention and the practical application, and to
enable others of ordinary skill in the art to understand the
invention for various embodiments with various modifications as are
suited to the particular use contemplated.
[0056] While the preferred embodiments to the invention have been
described, it will be understood that those skilled in the art,
both now and in the future, may make various improvements and
enhancements which fall within the scope of the claims which
follow. These claims should be construed to maintain the proper
protection for the invention first described.
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