U.S. patent application number 12/700702 was filed with the patent office on 2010-08-12 for method and apparatus for electrodeposition in metal acoustic resonators.
This patent application is currently assigned to Impulse Devices, Inc.. Invention is credited to Brant James CALLAHAN, Dario Felipe Gaitan, Corey Scott.
Application Number | 20100200417 12/700702 |
Document ID | / |
Family ID | 42539499 |
Filed Date | 2010-08-12 |
United States Patent
Application |
20100200417 |
Kind Code |
A1 |
CALLAHAN; Brant James ; et
al. |
August 12, 2010 |
Method and Apparatus for Electrodeposition in Metal Acoustic
Resonators
Abstract
Methods and systems for electrodeposition of Indium, Gallium, or
other metals within a metal acoustic resonator chamber are
provided, including for electrodeposition of Indium or Gallium as a
strike layer on an interior surface of a cavitation chamber. The
resultant strike layer affords an accommodating wetting surface for
subsequent filling with a liquid metal and performing cavitation
therein. In some embodiments, this allows for the use of liquid
metal in an acoustic resonator without the damping effects inherent
with oxide boundaries or other defects.
Inventors: |
CALLAHAN; Brant James;
(Grass Valley, CA) ; Gaitan; Dario Felipe; (Nevada
City, CA) ; Scott; Corey; (Grass Valley, CA) |
Correspondence
Address: |
Intrinsic Law Corp.
235 Bear Hill Road, Suite 301
Waltham
MA
02451
US
|
Assignee: |
Impulse Devices, Inc.
Grass Valley
CA
|
Family ID: |
42539499 |
Appl. No.: |
12/700702 |
Filed: |
February 4, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61206661 |
Feb 4, 2009 |
|
|
|
Current U.S.
Class: |
205/210 ;
205/205 |
Current CPC
Class: |
C25D 7/00 20130101; C25D
3/54 20130101; C25D 5/36 20130101 |
Class at
Publication: |
205/210 ;
205/205 |
International
Class: |
C25D 5/34 20060101
C25D005/34 |
Goverment Interests
STATEMENT OF GOVERNMENT SPONSORED RESEARCH
[0002] The present work was facilitated at least in part by U.S.
government support under Contract No. W9113M-07-C-0178, which was
awarded by the U.S. Space and Missile Defense Command and
subcontracted to the present assignee. Accordingly, the government
may have certain rights herein.
Claims
1. A method for treating an acoustic resonator, comprising:
providing a metallic acoustic resonator body having at least an
interior surface thereof; cleaning said interior surface of
contaminants; placing a chemically-suitable electroplating bath in
contact with said interior surface; providing an electrical current
to an electrode within said bath so as to cause an
electrodeposition of a substance onto said interior surface of said
acoustic resonator; and stopping said electrodeposition when
sufficient deposition to allow proper wetting of said interior
surface by a liquid metal in said acoustic resonator has been
achieved.
2. The method of claim 1, further comprising cleaning said interior
surface with a solvent before electrodeposition.
3. The method of claim 2, said cleaning comprising cleaning with a
solvent comprising an acid solution.
4. The method of claim 3, further comprising rinsing off said acid
solution before electrodeposition.
5. The method of claim 1, further comprising rinsing said
electroplating bath after electrodeposition is complete.
6. The method of claim 1, said interior surface comprising an
interior surface of a portion of a whole acoustic resonator, and
further comprising repetition of the cleaning and electrodeposition
on other portions of said acoustic resonator, and further
assembling the portions of the acoustic resonator to one
another.
7. The method of claim 1, placing said chemically-suitable
electroplating bath comprising placing a bath containing a
sulfamate solution in contact with said interior surface.
8. The method of claim 1, providing said electrical current to said
electrode comprising providing an electrical current to an anode
disposed within said electroplating bath.
9. The method of claim 8, providing said electrical current to said
anode comprising providing said electrical current to an anode
comprising Indium disposed within said electroplating bath.
10. The method of claim 8, providing said electrical current to
said anode comprising providing said electrical current to an anode
comprising Gallium disposed within said electroplating bath.
11. A method for achieving cavitation in a liquid metal medium,
comprising: cleaning an interior surface of a substantially
enclosed acoustic resonator with a solvent; at least partially
filling said resonator with a chemically-suitable electroplating
solution; applying a current to an electrode disposed within said
acoustic resonator until a desired amount of electrodeposition has
occurred onto said interior surface of said acoustic resonator;
rinsing said acoustic resonator to substantially clear out said
electroplating solution; substantially filling said acoustic
resonator with a liquid metal substance that wets against said
interior surface of said acoustic resonator; and providing acoustic
driving force to said acoustic resonator so as to cause cavitation
within said liquid metal substance.
Description
RELATED APPLICATIONS
[0001] This application incorporates by reference and claims the
priority and benefit of U.S. Provisional Patent Application
61/206,661, under 35 U.S.C. Sec. 119(e), filed on Feb. 4, 2009.
BACKGROUND
[0003] Gallium is an element that is used in semiconductor and
other industries and more recently in acoustics research. Gallium
is generally recovered as a by-product from Bayer-process liquors
containing sodium aluminate. Although electrodeposition is a common
method to recover bulk Ga out of basic or acidic solutions, or to
purify bulk Ga, there have not been many applications for this
material where thin films were deposited with controlled
uniformity, morphology and thickness. Therefore, only a few
electroplating bath chemistries and processes were developed and
reported for the deposition of thin layers of Ga on substrates for
electronic applications. For example, Ga-chloride solutions with pH
values varying between 0 and 5 were evaluated by S. Sundararajan
and T. Bhat (J. Less Common Metals, vol. I 1, p. 360, 1966) for
electroplating of Ga films.
Technical Field
[0004] The present application relates to treatment of surfaces of
acoustic resonators such as would be used to cause cavitation in a
liquid or liquid metal medium, including the wetting and
electrodeposition of materials onto a surface of said
resonators.
[0005] The above-mentioned methods and plating baths reportedly
achieved Ga film deposition. There are, however, some common
problems associated with the prior-art electrochemical deposition
processes. These problems include, low cathodic deposition
efficiency due to excessive hydrogen generation, poor repeatability
of the process, partly due to the poor cathodic efficiency, and the
poor quality of the deposited films such as their high surface
roughness and poor morphology. These issues may not be important
for bulk Ga electroplating or for Ga films deposited for the
purpose of investigating scientific topics such as deposition
mechanisms. Poor film morphology or inadequate thickness control
may also not be important for the electrically inactive
applications of Ga layers, such as their use as lubricating
coatings etc. However, properties of the Ga films become important
for certain new acoustic applications where Ga film plays a role in
forming an active boundary layer of an acoustic device, such as a
resonator.
[0006] Prior-art Ga electroplating techniques utilizing simple
electrolytes operating under acidic or basic pH values are not
suitable for the above mentioned applications for a variety of
reasons, including that they result in poor plating efficiencies
and films with rough morphology (typically surface roughness larger
than about 20% of the film thickness). Gallium is a difficult metal
to deposit without excessive hydrogen generation on the cathode
because Ga plating potential is high. Hydrogen generation on the
cathode causes the deposition efficiency to be less than 100%
because some of the deposition current gets used on forming the
hydrogen gas, rather than the Ga film on the substrate or
cathode.
[0007] Hydrogen generation and evolution also causes poor
morphology and micro defects on the depositing films due to the
tiny hydrogen bubbles sticking to the surface of the depositing
film, masking the micro-area under them, and therefore impeding
deposit on that micro-area. This causes micro-regions with less
than optimum amount of Ga in the film stack. Poor plating
efficiencies inherently reduce the repeatability of an
electrodeposition process because hydrogen generation phenomenon
itself is a strong function of many factors including impurities in
the electrolyte, deposition current densities, small changes on the
morphology or chemistry of the substrate surface, temperature, mass
transfer etc. As at least one of these factors may change from run
to run, hydrogen generation rate may also change, changing the
deposition efficiency.
[0008] Furthermore, electrodeposition of Ga out of low pH aqueous
electrolytes or solutions may suffer from low cathodic efficiencies
arising from the presence of a large concentration of H+ species in
such electrolytes. Therefore, hydrogen gas generation may be
expected to lessen at higher pH values. However, as the pH is
increased in the solution, Ga forms oxides and hydroxides, which
may precipitate and lead to adverse acoustical or mechanical or
chemical conditions.
[0009] Another problem is with which the electroplating art in
general is concerned is the necessity for preparing the surface on
which an initial layer or strike of metal is to be deposited. In
particular, the deposition of an initial nickel or gold strike on a
stainless steel surface usually requires preliminary pretreatment
of the surface to prepare it to accept similar Group IV metals.
[0010] It has not been possible or practical in the prior art to
achieve large acoustic standing waves and high Q's in acoustic
resonators.
SUMMARY
[0011] Aspects of the present disclosure are directed to a
composition providing an aqueous bath for electrodeposition of
Indium and Gallium on a substrate, and with a method of preparing
the composition. The invention finds particular application,
although it is not necessarily limited thereto, to the provision of
an aqueous bath composition for the electrodeposition of Indium and
Gallium strike upon a stainless steel substrate.
[0012] Indium is a soft (modified Brinell 0.9 to 1) silvery white
metal with a brilliant metallic luster. It has a low melting point
(156.7.degree. C.) and a relatively high boiling point
(2080.degree. C.), therefore resulting in a low vapor pressure. It
is ductile, malleable, crystalline and diamagnetic. In the
electromotive series, it lies between iron and tin.
[0013] Indium will generally plate from either acid or alkaline
solutions. Acid plating formulations include sulfate, sulfamate,
fluoborate and EDTA or NTA complexed acidic baths. Alkaline
formulations include the cyanide bath and non-cyanide alkaline
baths complexed with ammonium tartrate.
[0014] In some aspects, the present invention to provide a novel
bath composition for an aqueous bath which may be prepared for
electroplating Indium or Gallium by a simple and efficient method
without the necessity for crystallization, precipitation or
filtration.
[0015] Further aspects hereof are directed to a novel Indium or
Gallium electroplating bath composition, which is particularly
suited to provide an initial strike Indium or Gallium on an
untreated stainless steel surface.
[0016] In a specific embodiment, a method for preparation of the
base metallization for the acoustic resonator includes the steps
of: 1) Cleaning and activation. The cleaning step removes oils,
grease and other soils from the base metallization surface. The
activation step removes oxides from the base metallization surface,
which improves electro-deposition. The base metal may be cleaned
either by ultrasonic solvent vapor degreasing or by immersion in a
commercial alkaline cleaning bath operated at, e.g., 80-90.degree.
C. for a time, e.g., 10-15 minutes, followed by a hot water rinse.
2) The base metal then is acid activated by immersion in about a
10-15 percent by volume of sulfuric or hydrochloric acid solution
at room temperature for about 3-5 minutes, followed by a quick cold
water spray rinse. The quantitative examples provided herein are
given for the sake of illustration only, and are not intended to be
bounds on the possible embodiments hereof or limitations of the
same.
[0017] In an exemplary multistep plating process there may be an
intermediate plate or strike, it is necessary to remove the drag-in
from the previous process. Immediately following the acid
activation or strike plate, the base metal should then be immersed
in a 5 percent by weight solution of sulfamic acid solution for 1-3
minutes. This is to ensure that the pH of the base metallization
surface remains acidic so no reformation of oxide occurs and also
to protect the indium sulfamate plating bath from drag-in of
activator chemicals. If there is no intermediate process (ionic
contaminates) then a cold-water rinse to remove any activation
process products will suffice. The substrate is now ready for
indium plating.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] For a fuller understanding of the nature and advantages of
the present invention, reference is be made to the following
detailed description of preferred embodiments and in connection
with the accompanying drawings, in which:
[0019] FIG. 1 illustrates an exemplary resonator prepared for
electrodeposition with an Indium or Gallium source;
[0020] FIG. 2 illustrates an exemplary electrodeposition process in
an acoustic resonator;
[0021] FIG. 3 illustrates other exemplary aspects of a process for
preparing an acoustical resonator for cavitation of a metal
fluid;
[0022] FIG. 4 illustrates another exemplary resonator cross section
after being prepared and filled with a liquid metal filler; and
[0023] FIG. 5 illustrates another embodiment for treating a portion
of an acoustic resonator body.
DETAILED DESCRIPTION
[0024] As discussed above, it is useful to have a proper surface to
allow wetting of the surface for use in an acoustic resonator. For
example, in the case of a metal (e.g., stainless steel) acoustic
resonator having substantially an interior and an exterior surface
thereof, it is useful to properly prepare the wall of the interior
surface so that minimal contamination, oxidation, delamination,
shape deformities, gas bubble trapping, and other undesirable
effects take place during acoustic resonance. Specifically, in the
case of enclosures used for acoustic cavitation of a metal liquid,
it can be useful to have the enclosures sealed and filled with the
liquid metal to achieve the highest quality factor (Q) for the
resonator or cavitation chamber.
[0025] Referring to FIG. 1, an acoustic resonator 100 is provided.
The resonator includes a metal (e.g., stainless steel) shell 110,
which can be spherical in general shape, but is not limited to such
a geometry. The shell can be made to resonate using acoustic
drivers coupled to shell 110. The resonators can be driven in a
manner known to those skilled in the art, and can be driven at a
main frequency and power level as desired to cause vibration,
oscillation, movement, or other mechanical and acoustic modes in
shell 110.
[0026] The shell 110 has an outer or exterior surface 112 and an
inner or interior surface 114 substantially defining an enclosure
or enclosed volume of the resonator 100. In one or more
embodiments, it is desired to electroplate or treat the interior
surface 114 to optimize or improve the ability to wet the interior
of the shell 110 and achieve a good acoustic coupling to the
cavitation fluid within the shell 110.
[0027] Accordingly, in some embodiments, a plating solution 150 is
provided within shell 110. The plating fluid is a fluid material
having certain desired properties and chemical composition as is
discussed further herein.
[0028] In addition, an activation element or source 130 is
positioned within the shell 110. The source 130 may be positioned
at or near the center of the volume of the resonator 100. In a
spherically-shaped resonator, source 130 may be placed at the
geometric center of the sphere. The source 130 may comprise Indium
in some embodiments. In other embodiments, the source may comprise
Gallium. The source 130 may be in the form of a small spherical
source or mass suspended by a platinum wire 120 or similar
conducting element. The platinum wire 120 is in turn coupled to a
copper wire with a sleeve portion 125. The wires penetrate into the
resonator 100 through a port 115 provided at a chosen spot in the
shell 110 and allowing penetration of the anode through the shell
110. The port 115 may be sealed around copper wire sleeve 125 in a
way that preserves the plating solution or fluid 150 inside
resonator 100.
[0029] The electrical plating process is facilitated by an
electrical source 140, which may be a DC current source or voltage
source or other driver. The electrical source 140 can have a
positive and a negative end to develop an electromotive force to
sustain the plating process. In some embodiments, one end 142 of a
circuit comprising the electrical source 140 is coupled to a spot
on the exterior surface 112 of resonator shell 110. Current is then
driven through the circuit to achieve the desired plating onto the
interior surface 114 of shell 110.
[0030] Once the interior surface 114 is sufficiently plated it is
treated to other steps as described below and the resulting
resonator may be more suited for taking on and cavitating a metal
fluid within the resonator. In one embodiment, the electrodes are
conductive wires providing a low resistive electrical pathway
between the current source and the anode and cathode. In some
embodiments, the electrodes can be any suitable conducting conduit
or trace.
[0031] The preparation of the electrode/anode junction for the
plating operation may be designed for optimal effect, as the
plating bath can be poisoned by ions from other metals, e.g.,
nickel or copper. In some embodiments, the assembly may be coated
with a chemically resistant epoxy/insulator to prevent
contamination of the plating bath.
[0032] In one embodiment, the current source 140 is one sufficient
to support current densities of 10-20 Amps (Amperes) per square
foot of the cathode substrate to be plated. Current densities of
100 Amps per square foot may be used, and the temperature of the
plating bath may be maintained between 20-25.degree. C. The use of
cooling coils may help to keep the bath at this temperature when
operating at higher current densities in some embodiments.
Excessive current densities might cause the constituents of the
plating bath to break down, and as a result, the current source can
be replaced with a battery or any other suitable power supply if
desired in some embodiments.
[0033] In the current embodiment of the present invention, the
cathode/substrate is a 17-4 stainless steel acoustic resonator in
the shape of a spherical shell 110. In other embodiments, the bulk
can be made of other steels, such as 304 or 316 steels. However,
one skilled in the art will appreciate that the invention is not
limited to stainless steel and that any suitable substrate can be
used.
[0034] The present discussion also illustrates one or more methods
for achieving the instant electroplating and surface preparation
for acoustic resonator chambers. For example, an Indium sulfamate
electrolytic solution 150 may be used in the manner below allowing
the use of standard plastic or plastic lined plating tanks with
continuous filter pump agitation. The plating bath may be operated
at room temperature; therefore, no immersion heaters are necessary
in some embodiments.
[0035] In some embodiments, sulfamic acid may be used to control
the bath pH. The bath may have a pH of 1-3.5 (and more
specifically, e.g., a pH of 1.5-2.0). In the present embodiment,
26.4 grams per liter is used. The pH can be adjusted by making
additions of sulfamic acid. If the pH gets too high the indium will
precipitate out in the form of Indium hydroxide, which causes the
solution to assume a milky-white appearance. Over time, the pH of
the bath will rise. The pH is frequently monitored using a pH
meter. The pH is maintained within this range by small additions of
a 10% solution of sulfamic acid dissolved in distilled or deionized
water.
[0036] The bath 150 may be further prepared by addition of Indium
sulfamate at a concentration of 105 grams per liter of solution.
Because the anode efficiency is 100% and the cathode efficiency is
90%, the Indium concentration tends to rise over time, leveling off
at about 200-250 g/l. This is a normal situation and the rise in
Indium concentration does not necessarily affect the operation of
the bath except perhaps for excessive driving currents, which may
cause the hydrolysis of water at the anode and oxygen gas to
evolve.
[0037] The bath 150 may further include other constituents such as
150 grams per liter of Sodium sulfamate, 46 grams per liter of
Sodium Chloride, 8 grams per liter of Dextrose, and 2.3 grams per
liter of Triethanolamine. These are used to increase bath
conductivity and buffers, respectively.
[0038] In some embodiments, it is preferable to have the surface
area of the anode be approximately equal to or greater than the
surface area of the work pieces.
[0039] The following describes a preferred embodiment, provided for
the purpose of illustration, but not by way of limitation. As an
example, the base metal of the shell 110 may be cleaned either by
ultrasonic solvent vapor degreasing or by immersion in a commercial
alkaline cleaning bath operated at 80-90.degree. C. for about 10-15
minutes, followed by a thorough hot water rinse. The base metal
then should be acid activated by immersion in a 10-15 percent
volume of sulfuric or hydrochloric acid solution at room
temperature for 3-5 minutes, followed by a quick cold water spray
rinse. The concentrations and times given are illustrative in
nature and can be modified as desired for a given purpose.
[0040] Following the acid activation, the base metal may be
immersed in a 5 percent by weight solution of sulfamic acid
solution for 1-3 minutes. Depending on the vessel or the work
piece, the work piece is filled or placed in the sulfamate plating
bath 150.
[0041] The anode source 130 is lowered into the bath 150 to the
proper height in the center of the sphere. Current is applied via
the current source in accordance with the current density
boundaries. Time dictates the amount of Indium deposited at the
rate of 20 amps per square foot resulting in an exemplary rate of
deposition of Indium of 0.001486 inches deposited per hour.
[0042] Following deposition, the anode and solution are removed
from the sphere. The interior of the sphere is given a thorough
rinse in deionized water and air dried in an inert environment
(e.g., argon, etc.). Gallium metal is now applied to the surface of
the bulk in the form of liquid. In another embodiment, the Gallium
is in a solid form. In either event, the Gallium mixes with the
Indium creating a Ga/In alloy producing a mirror-like wetted
surface at room temperature. The resonator 100 can now be filled in
an inert environment with liquid Gallium with no threat or reduced
threat of oxide boundary layers with inhibit acoustic resonation or
cavitation within the resonator 100.
[0043] In other embodiment, the Indium anode source 130 may be
replaced with one of Gallium and using a high alkaline plating
solution 150 instead of the sulfamate bath. It should be noted that
at highly alkaline pH values oxides or hydroxides may dissolve as
soluble Ga species. Therefore, it may be possible to electrodeposit
Ga in a bath of pH greater than 14 containing Ga salts using high
concentrations of KOH and NaOH in the bath formulation. High
concentrations of alkaline species, however, may cause corrosion of
the equipment as well as the cathode material itself. A limit on
the amount of Ga that can be dissolved in the form of acidic Ga
salts (GaCl3, Ga(NOa)3 etc) in such solutions before Ga starts to
precipitate may exist in some embodiments. Accordingly, the pH may
be adjusted again by further addition of alkaline species such as
NaOH and KOH. As pointed out above, solutions comprising a large
molar amount of caustics may be difficult to handle and may also
have high viscosity. Therefore, the viscosity and caustic content
may be controlled in some embodiments. High viscosity can cause
hydrogen bubbles formed on the cathode may adhere more to the
cathode making it difficult to remove them by stirring or other
means of mass transfer. Such gas bubbles on the cathode surface
increase defectivity of the deposited Ga layer. The present
techniques take these effects into consideration, and embodiments
hereof reduce and resolve these issues so that bubbles are removed
or reduced in the system.
[0044] The electrodeposition of Ga, or other suitable materials of
similar chemical and/or mechanical, acoustic, hydrodynamic, or
electrical property, is performed in a similar manner as described
in the above embodiments. Gallium plates to the stainless steel
sphere interior 114 resulting in an improved wetting surface for
liquid Ga when applied. This effects a boundary layer devoid of
oxides which impede transference of acoustic power from the shell
and drivers (not shown) to the bulk of the liquid metal.
[0045] Once properly treated, the resonator 100 is better suited to
provide cavitation within the resonator, especially for metallic
substances or liquid metals such as Gallium, Indium or others.
[0046] By way of overview, FIG. 2 illustrates an exemplary and
simplified process 200 for electrodeposition and preparation of an
interior surface of a metal acoustic resonator.
[0047] At step 202 the resonator is provided consistent with the
needs of a specific application, and can include for example
providing a spherical or cylindrical or other shape of metal walled
resonator.
[0048] At step 204 the interior surface of the resonator is cleaned
as described above. The cleaning 204 may be followed by a rinsing
step 206, which can include rinsing with water or with another
inert or suitable fluid.
[0049] At step 208 the surface is activated and prepared for
electrodeposition at step 210.
[0050] Now referring to FIG. 3, an exemplary process 300 for
electroplate deposition onto a metal resonator is provided. As
before, a metal shell resonator having an interior surface and
volume thereof is provided. At least the interior surface is
cleaned at step 302. This is followed by a rinse, such as a hot
water rinse in step 304. It should be appreciated that the rinse
may be done using another fluid or gas and does not necessarily
need water for said rinsing step.
[0051] At step 306, the surface being treated is inserted into an
acid solution, such as to activate the surface as discussed above.
This is followed by another optional rinsing step 308, which an be
in the form of a cold water rinse.
[0052] The resonator is filled or substantially filled with the
plating bath solution, which is typically a fluid as described
above, at step 310.
[0053] The anode source is inserted into the volume of the
resonator being treated at step 312.
[0054] Current or electromotive drive is applied at step 314 to
achieve the electroplating process and coat the interior surface of
the acoustic resonator as needed. The process of electrodeposition
is continued as needed, and is stopped at step 316 based on a
criterion or set of criteria. The criteria for stopping the
electrodeposition may include a predetermined length of time, an
integrated time-current calculation, a thickness of deposited
material, a temperature preset, a predetermined electrical property
of the system, or other criteria.
[0055] FIG. 4 illustrates an exemplary cross-section of a treated
resonator 400. The metal shell 406 of the resonator is for example
stainless steel. The shell 406 is coated with an electroplated
layer 404 as described above. The fluid 402 then wets along the
surface of electroplated layer 404 and substantially fills any
voids so that cavitation or other acoustical effects can take place
in fluid 402.
[0056] FIG. 5 illustrates an exemplary embodiment 500 whereby a
portion of a resonator body 502 is treated by electrodeposition as
described above. The body portion 502 comprises for example a
partial spherical (e.g., hemispherical) portion. The system for
treating the resonator includes a DC power supply 504 that provides
electromotive driving force for the plating steps.
[0057] A cathode 506 is provided in an electro-polish solution 508
and the process plates the interior surface of portion 502 until
sufficient treatment or deposition has taken place. The other
portions of the system may be similarly treated, and afterwards,
the system may be assembled using the plurality of treated
portions. So for example, two halves of a substantially spherical
acoustical resonator may be treated as described above, and the
halves may then be welded, joined, bolted, threaded, adhered, or
otherwise coupled to form the resultant acoustic resonator
apparatus or cavitation chamber.
[0058] The present invention should not be considered limited to
the particular embodiments described above, but rather should be
understood to cover all aspects of the invention as fairly set out
in the attached claims. Various modifications, equivalent
processes, as well as numerous structures to which the present
invention may be applicable, will be readily apparent to those
skilled in the art to which the present invention is directed upon
review of the present disclosure. The claims are intended to cover
such modifications.
* * * * *