U.S. patent application number 09/878075 was filed with the patent office on 2001-10-25 for method of coating three dimensional objects with molecular sieves.
This patent application is currently assigned to Board of Regents, The University of Texas System. Invention is credited to Balkus, Kenneth JR., Kinsel, Mary E., Scott, Ashley S..
Application Number | 20010033951 09/878075 |
Document ID | / |
Family ID | 23228552 |
Filed Date | 2001-10-25 |
United States Patent
Application |
20010033951 |
Kind Code |
A1 |
Balkus, Kenneth JR. ; et
al. |
October 25, 2001 |
Method of coating three dimensional objects with molecular
sieves
Abstract
A method of coating a substrate with an oriented film. A target
is ablated to create a plume. The substrate is manipulated, which
may be by vibration, in the plume to coat the substrate with a
film. The film is heated in a synthesis gel of the target to form
the oriented film.
Inventors: |
Balkus, Kenneth JR.; (The
Colony, TX) ; Kinsel, Mary E.; (Arlington, TX)
; Scott, Ashley S.; (Richardson, TX) |
Correspondence
Address: |
Michael C. Barrett
FULBRIGHT & JAWORSKI L.L.P.
Suite 2400
600 Congress Avenue
Austin
TX
78701
US
|
Assignee: |
Board of Regents, The University of
Texas System
|
Family ID: |
23228552 |
Appl. No.: |
09/878075 |
Filed: |
June 7, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09878075 |
Jun 7, 2001 |
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09316322 |
May 21, 1999 |
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6274207 |
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Current U.S.
Class: |
428/702 |
Current CPC
Class: |
C23C 14/28 20130101;
Y10T 428/2996 20150115; C23C 14/5806 20130101; Y10T 428/2998
20150115; Y10T 428/29 20150115; C23C 14/223 20130101; Y10T 428/2913
20150115; Y10T 428/2993 20150115; Y10T 428/2995 20150115; Y10T
428/2982 20150115; Y10T 428/2991 20150115 |
Class at
Publication: |
428/702 |
International
Class: |
B32B 009/00 |
Goverment Interests
[0001] The government may own rights in the present invention
pursuant to grant number 009741-055, UTD Account No. 2-23206, from
Texas Higher Education Coordinating Board-Advanced Technology
Program.
Claims
What is claimed is:
1. A method of coating a substrate, comprising: providing a target;
ablating material from said target to create a plume; manipulating
the substrate in said plume to coat said substrate with a film; and
heating said film in a synthesis gel of said target.
2. The method of claim 1, wherein heating said film forms an
oriented film.
3. The method of claim 2, wherein said oriented film comprises
crystals normal to the surface of said substrate.
4. The method of claim 1, wherein said target comprises a
zeolite.
5. The method of claim 4, wherein said zeolite comprises at least
one of UTD-1, ZSM-5, Beta, Mordenite, NaX, NaA, SSZ-33, SSZ-31,
SSZ-42, MCM-22, or a mixture thereof.
6. The method of claim 1, wherein said target comprises a
phosphate.
7. The method of claim 6, wherein said phosphate comprises an
aluminum phosphate.
8. The method of claim 7, wherein said aluminum phosphate comprises
at least one of VPI-5, AlPO.sub.4-5, AlPO.sub.4-8, or a mixture
thereof.
9. The method of claim 6, wherein said phosphate comprises a
silicon aluminum phosphate.
10. The method of claim 9, wherein said silicon aluminum phosphate
comprises at least one of SAPO-5, SAPO-37, SAPO-42, or a mixture
thereof.
11. The method of claim 6, wherein said phosphate comprises a metal
aluminum phosphate.
12. The method of claim 12, wherein said metal aluminum phosphate
comprises at least one of MAPO-39, MAPO-5, MAPO-11, UCSB-6, UCSB-7,
or a mixture thereof.
13. The method of claim 1, wherein said target comprises a
mesoporous molecular sieve.
14. The method of claim 13, wherein said mesoporous molecular sieve
comprises at least one of MCM-41, MCM-48, SBA-15, SBA-16, Nb-TMS-1,
Ti-TMS-1, Ta-TMS-1, or a mixture thereof.
15. The method of claim 1, wherein said ablating comprises
subjecting said target to pulsed radiation from an excimer
laser.
16. The method of claim 15, wherein said laser comprises a KrF*
laser operating between about 70 and about 200 mJ/pulse with a
repetition rate between about 1 and about 50 Hz.
17. The method of claim 1, wherein manipulating comprises moving
said plume relative to said substrate.
18. The method of claim 1, wherein said manipulating comprises
vibrating said substrate.
19. The method of claim 1, wherein said heating comprises heating
between about 1 hour and about 200 hours.
20. The method of claim 1, further comprising adjusting a
background pressure of said substrate to between about 150 mTorr
and about 350 mTorr.
21. The method of claim 20, wherein said background pressure
comprises a background pressure of O.sub.2.
22. The method of claim 1, wherein said substrate comprises a
zeolite crystal, glass, metal, metal oxide, or plastic.
23. The method of claim 1, wherein said substrate comprises a
porous substrate.
24. The method of claim 1, wherein a largest dimension of said
substrate is between about 10 nm and about 10 mm.
25. The method of claim 1, wherein said substrate is spherical.
26. The method of claim 1, further comprising washing or calcining
said oriented film.
27. A coated substrate made by the method of claim 1.
28. A method of coating a substrate with an oriented film,
comprising: providing a target comprising Cp*.sub.2Co.sup.+ or
Cp.sub.2Fe; laser ablating material from said target to create a
plume; vibrating the substrate in said plume to coat a film on said
substrate; and heating said film in a synthesis gel of said target
to form the oriented film.
29. The method of claim 28, wherein said laser ablating comprises a
first stage and a second stage, said first stage ablating material
at a first laser power and said second stage ablating material at a
second laser power, and wherein said first laser power differs from
said second laser power.
30. A coated substrate made by the method of claim 28.
31. A method of coating a substrate with an oriented film,
comprising: providing a target comprising Cp*.sub.2Co.sup.+ or
Cp.sub.2Fe; directing pulsed laser radiation having an energy
between about 70 mJ/pulse and about 200 mJ/pulse at a repetition
rate of between about 1 Hz and about 50 Hz to said target to create
a plume; heating said substrate; maintaining a pressure between
about 150 mTorr and about 350 mTorr about said substrate; vibrating
said substrate within said plume to coat a film on said substrate;
and heating said film in a synthesis gel of said target to form the
oriented film.
32. The method of claim 31, further comprising washing or calcining
said oriented film.
33. A coated substrate made by the method of claim 31.
Description
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of coating three
dimensional and non-uniform objects with molecular sieves using
pulsed laser deposition.
[0004] 2. Description of Related Art
[0005] There are a variety of methods for fabricating molecular
sieves into thin films. A popular approach is the seed method,
which involves the deposition of colloidal suspensions of zeolite
nanosols onto a flat substrate followed by a controlled secondary
growth of the nanoparticles. The resulting films are generally
continuous and sometimes oriented. It appears, however, that the
seed method works best with only a few types of zeolites,
especially those with crystal morphologies that efficiently pack on
the substrate surface such as zeolite NaA or ZSM-5. This also
implies that this method works best on flat surfaces. Consequently,
there are relatively few examples of zeolite films and no examples
of oriented films on non-planar surfaces.
[0006] The deposition-during-synthesis technique has been used to
grow zeolite Beta onto macroporous alumina spheres with a 4%
loading by immersing the support in the synthesis mixture.
Analogously, metal and ceramic monoliths have also been coated with
zeolite Beta, Mordenite, and ZSM-5 utilizing this technique.
Molecular sieve films prepared by the direct deposition of crystals
from solution, however, often suffer from defects and poor
adhesion. Furthermore, controlling the film thickness and
orientation can be quite a challenge.
SUMMARY OF THE INVENTION
[0007] In one respect, the invention is a method of coating a
substrate. A target is provided. Material is ablated from the
target to create a plume. The substrate is manipulated in the plume
to coat the substrate with a film, and the film is heated in a
synthesis gel of the target. In another respect, the invention is a
coated substrate made by this method.
[0008] In other aspects, the heating of the film forms an oriented
film. The oriented film may include crystals normal to the surface
of the substrate. The target may include a zeolite. The zeolite may
include at least one of UTD-1, ZSM-5, Beta, Mordenite , NaX, NaA,
SSZ-33, SSZ-31, SSZ-42, MCM-22, or a mixture thereof. The target
may include a phosphate. The phosphate may include an aluminum
phosphate. The aluminum phosphate may include at least one of
VPI-5, AlPO.sub.4-5, AlPO.sub.4-8, or a mixture thereof. The
phosphate may include a silicon aluminum phosphate. The silicon
aluminum phosphate may include at least one of SAPO-5, SAPO-37,
SAPO-42, or a mixture thereof. The phosphate may include a metal
aluminum phosphate. The metal aluminum phosphate may include at
least one of MAPO-39, MAPO-5, MAPO-11, UCSB-6, UCSB7, or a mixture
thereof. The target may include a mesoporous molecular sieve. The
mesoporous molecular sieve may include at least one of MCM-41,
MCM-48, SBA-15, SBA-16, Nb-TMS-1, Ti-TMS-1, Ta-TMS-1, or a mixture
thereof The ablating may include subjecting the target to pulsed
radiation from an excimer laser. The laser may include a KrF* laser
operating between about 70 and about 200 mJ/pulse with a repetition
rate between about 1 and about 50 Hz. The manipulating may include
moving the plume relative to the substrate. The manipulating may
include vibrating the substrate. The heating may include heating
between about 1 hour and about 200 hours. The method may also
include adjusting a background pressure of the substrate to between
about 150 mTorr and about 350 mTorr. The background pressure may
include a background pressure of O.sub.2. The substrate may include
a zeolite crystal, glass, metal, metal oxide, or plastic. The
substrate may include a porous substrate. The largest dimension of
the substrate may be between about 10 nm and about 10 mm. The
substrate may be spherical. The method may also include washing or
calcining the oriented film.
[0009] In another respect, the invention is a method of coating a
substrate with an oriented film. A target including
Cp*.sub.2Co.sup.+ or Cp.sub.2Fe is provided. Material is laser
ablated from the target to create a plume. The substrate is
vibrated in the plume to coat a film on the substrate, and the film
is heated in a synthesis gel of the target to form the oriented
film. In another respect, the invention is a coated substrate made
by this method.
[0010] In other aspects, the laser ablating may include a first
stage and a second stage. The first stage ablates material at a
first laser power and the second stage ablates material at a second
laser power, the first laser power being different than the second
laser power.
[0011] In another respect, the invention is a method of coating a
substrate with an oriented film. A target including
Cp*.sub.2Co.sup.+ or Cp.sub.2Fe is provided. Pulsed laser radiation
having an energy between about 70 mJ/pulse and about 200 mJ/pulse
at a repetition rate of between about 1 Hz and about 50 Hz is
directed to the target to create a plume. The substrate is heated.
A pressure between about 150 mTorr and about 350 mTorr about the
substrate is maintained. The substrate is vibrated within the plume
to coat a film on the substrate, and the film is heated in a
synthesis gel of the target to form the oriented film. In another
respect, the invention is a coated substrate made by this
method.
[0012] In other aspects, the method may also include washing or
calcining the oriented film.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The following drawings form part of the present
specification and are included to further demonstrate certain
aspects of the present invention. The invention may be better
understood by reference to one or more of these drawings in
combination with the detailed description of specific embodiments
presented herein.
[0014] FIG. 1A. Schematic diagram of 3-D objects manipulated in a
laser ablation plume by vibration.
[0015] FIG. 1B. Side view schematic of an apparatus for vibrating
objects in a laser ablation plume.
[0016] FIG. 1C. Top view schematic of an apparatus for vibrating
objects in a laser ablation plume.
[0017] FIG. 2. Scanning electron micrograph of pulsed-laser
deposited (PLD) glass bead after a multi-staged deposition time of
35 min.
[0018] FIG. 3A. Scanning electron micrograph of post hydrothermally
treated PLD glass beads after a multi-staged deposition time of 35
min.
[0019] FIG. 3B. Higher magnification scanning electron micrograph
of post hydrothermally treated PLD glass beads after a multi-staged
deposition time of 35 min.
[0020] FIG. 4. Cross section of post hydrothermally treated PLD
glass beads after a multi-staged deposition time of 35 min.
[0021] FIG. 5. Higher magnification scanning electron micrograph of
hydrothermally treated PLD glass beads after sonicating for one
hour in deionized water.
[0022] FIG. 6. Scanning electron micrograph of hydrothermally
treated PLD glass beads after calcining in air at about 550.degree.
C. for about 6 hours.
[0023] FIG. 7. Cross-section of PLD UTD-1 film covering a metal
bead fabricated with about a 13 minute deposition time and about a
70 mJ/pulse laser power.
[0024] FIG. 8A. Scanning electron micrograph of a post
hydrothermally treated PLD metal bead.
[0025] FIG. 8B. Higher magnification scanning electron micrograph
of a post hydrothermally treated PLD metal bead.
[0026] FIG. 9. Cross section of a post hydrothermally treated PLD
metal bead.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0027] Laser ablation offers a distinct advantage of being able to
coat non-planar surfaces by manipulating an object in a laser
ablation plume or by manipulating the direction of the plume. Using
the disclosed methods, the utility of pulsed laser deposition (PLD)
may be extended to include microscale objects such as catalyst
particles and catalyst supports. In order to evenly coat
three-dimensional objects by PLD, one may move the objects in the
ablation plume or may likewise move the plume relative to the
object. Mechanical manipulation may not always be feasible on small
length scales. However, a method of vibrating an object in a laser
ablation plume sufficiently manipulates an object to ensure that it
is coated in three-dimensions.
[0028] In one disclosed embodiment, a pancake vibrator may provide
sufficient motion for small substrates, such as metal or glass
beads, in an ablation plume to be evenly coated with zeolites,
phosphates, mesoporous materials, or other materials. For example,
the presently disclosed methods may be used to coat three
dimensional objects with a molecular sieve coating. A three
dimensional substrate may be placed in or on a vibrating apparatus
and may be subjected to a plume generated by laser ablation of a
target. The vibrating medium may rotate and generally, manipulate,
the substrate, exposing, over time, its entirety to the plume to
form a laser-deposited film covering the substrate. The substrate
may then be hydrothermally treated to form an oriented coating.
[0029] In one embodiment, post hydrothermal treatment includes
heating PLD coated substrates in a synthesis gel of the material
used as a target during ablation. Thus, in embodiments utilizing a
UTD-1 target, post hydrothermal treatment may include heating UTD-1
PLD substrates in a UTD-1 synthesis gel, while for MAPO-39 coatings
a MAPO-39 synthesis gel may be used. Heating times, temperatures,
and conditions may be varied to achieve an oriented film. In a
particular UTD-1 embodiment, however, heating may be at about
175.degree. C. for about 72 hours.
[0030] In one embodiment, crystals may be oriented so that
one-dimensional channels may be normal to the substrate. A detailed
discussion of methods used to form oriented films using laser
ablation may be found in co-pending U.S. patent application Ser.
No. ______ filed May 21, 1999 and entitled, "Preparation Of Laser
Deposited Oriented Films And Membranes" by Kenneth J. Balkus, Jr.,
Mary E. Kinsel, and Lisa L. Washmon, which is incorporated herein
by reference in its entirety.
[0031] In one embodiment, small (about 75 .mu.m) beads may be
coated with an oriented film via laser ablation. The coating may be
with UTD-1 molecular sieves, but it will be understood with the
benefit of the present disclosure that a variety of other materials
including, but not limited to, zeolites such as ZSM-5, Beta,
Mordenite , NaX, NaA, SSZ-33, SSZ-31, SSZ-42, MCM-22, aluminum
phosphates such as VPI-5, AlPO.sub.4-5, AlPO.sub.4-8; silicon
aluminum phosphates such as SAPO-5, SAPO-37, SAPO-42; metal
aluminum phosphates such as MAPO-39, MAPO-5, MAPO-11, UCSB-6,
UCSB-7; mesoporous molecular sieves such as MCM-41, MCM-48, SBA-15,
SBA-16, Nb-TMS-1, Ti-TMS-1, and Ta-TMS-1 may be used as a coating
as well. Thus, although description herein may be directed to, for
example, UTD-1 coatings for convenience, those having skill in the
art will understand that description herein applies to many other
coating materials as well including, but not limited to, the
coatings listed above. Targets used in methods described herein may
include an ultraviolet absorbing material including, but not
limited, to, the organometallic cobalticinium ion CP*.sub.2Co.sup.+
or the related ferrocene Cp.sub.2Fe to facilitate ablation. It will
be understood that other UV absorbing materials suitable for aiding
in ablation may be substituted therewith.
[0032] Substrates may be various materials and may include, but are
not limited to, zeolite crystals, glass, metal, metal oxide, or
plastics. Substrates may be of various configurations including,
but not limited to, flat substrates or substrates having a
nonplanar topology. Substrates may be of any shape and/or size
suitable for applying a coating by the methods described herein. In
one embodiment, substrates may include fibers, such as optical
fibers.
[0033] In one embodiment, about 0.025 g (which may be equivalent to
about 100 small spherical beads) may be loaded into a substrate
holder, configured to vibrate, without any pretreatment. The
vibrating substrate holder allows the beads to move and rotate
freely in a UTD-1 laser ablation plume. In this embodiment, the
laser ablation of an assynthesized UTD-1 target for about 5 minutes
at a power of about 159 mJ/pulse results in coated beads as shown
in FIG. 2.
[0034] When high laser power of about 100 to about 150 mJ/pulse is
used, the laser beam may tend to eject some large fragments of the
UTD-1 target material onto the surface of the substrate. Thus, a
lower laser power from about 50 to about 80 mJ/pulse may be used to
achieve less target splashing on the surface.
[0035] Other embodiments achieving an ablated film that is
continuous and thick enough to provide a protective covering for a
glass substrate may involve increasing deposition time from between
about 5 to about 25 minutes, followed by an additional 10 minutes
to provide a PLD film of greater than about 1.75 .mu.m.
[0036] In such an embodiment, the first coating may be done
utilizing low laser power (about 69 mJ/pulse) that provides a
tight, densely packed uniform film with less splashing of the
target material. A second coating may be applied utilizing a higher
laser power (about 138 mJ/pulse) for about 10 minutes during which
some splashing may occur. In this embodiment, the glass beads may
be completely coated with a thick PLD film.
[0037] FIG. 2 shows an SEM image of a multi-staged PLD glass bead
that was coated for about 25 minutes at low laser power, and for
about 10 minutes at high laser power. This image shows no evidence
of any discontinuity on the surface of the substrate. The larger
fragments from splashing may be seen dispersed around the entire
glass bead surface. It appears that the large fragments from
splashing are sitting on top of the thin layer of the laser
deposited zeolite film.
[0038] A post hydrothermal treatment may be applied to the thickly
coated film as described herein. FIG. 3A shows an SEM image of a
glass bead after post hydrothermal treatment, and it may be noted
that the original size of the glass bead here was not diminished.
In fact, the diameter of the glass bead increased from about 75
.mu.m to about 90 .mu.m. Random crystal aggregates obtained from a
synthesis gel used in the post hydrothermal treatment may be seen
in the background of the image. UTD-1 crystals appear to be
attached to the glass beads radiating up from the glass bead
surface.
[0039] FIG. 3B shows an SEM image taken at a higher magnification
of the hydrothermally treated glass bead. The UTD-1 crystals may be
seen radiating up from the laser deposited surface with plank-like
morphology. The crystals appear to be normal to the surface of the
spheres, creating a preferred orientation of the UTD-1 crystals in
which the one-dimensional channels run in parallel along the length
of the planks. Loosely attached random crystals may also be seen on
the surface of the oriented crystals. X-ray diffraction analysis
confirms the phase identity of UTD-1.
[0040] A cross section of the UTD-1 PLD film may be taken in order
to obtain a film thickness of a post hydrothermally treated PLD
film. FIG. 4 shows an SEM image in which UTD-1 crystals may be seen
radiating up from the surface of the glass bead. The crystals also
appeared to be densely packed, which is consistent with the theory
that as the fragments reorganize they are forced to grow
substantially vertically. The film appears to be in the range of
about 7 to about 9 microns thick. This is consistent with the
increase in diameter of the glass bead substrate shown in FIG.
3A.
[0041] The preferred orientation of the reorganized film is also
comparable to thick films (about 11 .mu.m) that have been formed on
flat substrates after pulsed laser deposition (PLD). However,
crystals on flat substrates have appeared to be more densely packed
at the surface due to the planar morphology of the substrate.
Additionally, the crystals from the glass beads appeared to be
smaller than the crystals generated from the flat substrates, while
being larger than the crystals generated in the bulk gel
synthesis.
[0042] It appeared that the crystals may be strongly adhered to the
surface of the substrate since there was no loss of film upon
handling. Glass substrates used herein were too small to under go a
scratch test to confirm film adhesion. Retention of the film after
sonication may, however, be supporting evidence for the strong
adhesion of the film to the substrate. Therefore, glass beads may
be subjected to a one-hour sonication in deionized water to test
the adhesion of the films.
[0043] FIGS. 5 shows an SEM image of glass beads after such
sonication. In FIG. 5, the UTD-1 hydrothermally treated film
appeared to still be attached to the glass beads after sonication.
FIGS. 5 illustrates a consequence of a static hydrothermal
treatment. Some of the glass beads in the figures appeared to have
oriented themselves in a close-packing arrangement, and it appeared
that they were held together by inter-grown crystals. Also, FIG. 5
shows the effect of the beads resting in the bottom of the reactor,
where flat spots may be seen. In light of this, a re-growth step
may benefit from a stirred or rotated system so the beads may
remain dispersed in the post hydrothermal treatment. This image
reveals the UTD-1 crystal radiating themselves around the glass
beads. The sonication test supported the proposition that the
hydrothermally treated films were well adhered to glass
substrates.
[0044] Thermal stability of films prepared in accordance with the
present disclosure may be tested by calcining glass beads in air at
about 550.degree. C. for about 5 hours. After calcination, the film
may change from a yellow color to a gray color upon decomposition
of bis(pentamethylcyclopentadienly)cobalt (III) ion
Cp*.sub.2Co.sup.+ template in the post hydrothermal treatment gel.
The SEM image of FIG. 6 revealed that an oriented UTD-1 film may
still remain on a glass bead even after thermal stress. In FIG. 9,
there were some randomly oriented crystals on the surface of the
oriented crystals that were probably deposited from the bulk
gel.
[0045] The above data provided evidence that post hydrothermally
grown films on 3-D objects may become well adhered to a substrate
and that they may be thermally stable up to temperatures of at
least about 550.degree. C.
[0046] In one embodiment, PLD films may be grown on
three-dimensional metal substrates. Metal spheres, including steel
spheres, may be used as substrates. In one embodiment, spherical,
zinc galvanized coated steel buck shot pellets measuring about 0.5
mm in diameter may be used as substrates. In one embodiment,
untreated metal beads (such as six to eight untreated metal beads)
may be loaded into a vibrating substrate holder. Heating the
substrates in an oxygen atmosphere may promote adhesion to the
interface where the energetic particles form covalent bonds with
the metal surface. An oxide linkage at the surface/film interface
may account for strong adhesion of the film as shown by the
retention of the film to the metal bead after an etching test with
a diamond scribe.
[0047] In one embodiment, the metal sphere is a fairly smooth
non-planar substrate with some imperfections across the surface. It
is possible that such scattered defects that are present on the
surface may promote film adhesion by providing crevices for the
crystals to nucleate. In one example, after pulsed laser deposition
of UTD-1 for about 10 minutes at a laser power of about 123
mJ/pulse, a film may be achieved.
[0048] Splashing may result in larger fragments on the surface. The
UTD-1 fragments from splashing, some as large as a micron, may be
evenly dispersed around the surface of the bead. In order to obtain
less splashing, a laser power of about 70 mJ/pulse may be used.
With the exception of a lower laser power, the deposition
parameters may be analogous to the conditions required for flat
pulsed laser deposited UTD-1 films as disclosed for example, in
co-pending U.S. patent application Ser. No. ______ filed May 21,
1999 and entitled, "Preparation Of Laser Deposited Oriented Films
And Membranes" by Kenneth J. Balkus, Jr., Mary E. Kinsel, and Lisa
L. Washmon. By decreasing the laser power, however, a uniform
well-adhered thin deposited film may be achieved on the substrate
where the PLD fragments were small, tightly packed, and uniform
throughout the entire surface of the bead.
[0049] FIG. 7 shows a cross section of the PLD film. The film was
estimated to be about 900 nm thick, which corresponds to a
deposition rate of about 70 nm/min. This film was thin compared to
the PLD film required for glass beads because the metal beads may
better withstand high pH conditions present in the hydrothermal
treatment gel. There appeared to be no exposed areas on the surface
of the substrate after PLD. The film was still well-adhered to the
substrate even after etching the surface with the diamond scribe. A
loosely bound film most likely would have flaked off the surface
when subjected to such a test.
[0050] PLD films from a UTD-1 target were mostly amorphous to
x-rays, which is consistent with results obtained with glass beads.
In one embodiment, the PLD UTD-1 film coating metal substrates may
be hydrothermally treated as previously described by placing the
metal balls in a Teflon lined Parr reactor containing the UTD-1
synthesis gel mixture for, in one embodiment, about 72 hours at
about 175.degree. C. under static conditions.
[0051] FIG. 8A and FIG. 8B show SEM images at different
magnifications of resulting post hydrothermally treated metal
spheres. FIG. 8A shows what appeared to be a new, thick layer
surrounding the metal sphere that was not present before
hydrothermal treatment. The post hydrothermally treated film was
continuous, and covered the entire surface of the bead with no
observable voids on the surface. A closer inspection of the thick
layer revealed highly crystalline film that was confirmed as UTD-1
by powder x-ray diffraction (XRD).
[0052] FIG. 8B shows the UTD-1 crystals having a plank-like
morphology radiating up from the substrate surface. The crystals
appeared to be normal to the surface of the spheres, creating a
preferred orientation of the UTD-1 crystals in which the
one-dimensional channels run in parallel along the length of the
planks. A cross section of the post hydrothermal PLD film was taken
by scratching the film with a diamond scribe.
[0053] FIG. 9 shows a scanning electron micrograph of the cross
section in which the reorganized film was determined to be about 14
.mu.m thick. The increased reorganized film thickness of the metal
beads may be explained with the increased PLD film associated with
the metal beads. Also, as seen in the glass beads, the crystals
generated on the metal beads appeared to be smaller than crystals
obtained from flat substrates, while being larger than crystals
generated from the bulk gel.
[0054] The cross section view in FIG. 9 provided a better view of
the densely packed crystals growing upwards from the substrate
surface. It may be seen that the plank-like morphologies of the
crystals preferred to grow perpendicular to the substrate because
of the dense crystal packing. There were also some broken random
crystal observed on the bead surface, which may be caused by the
etching of the film and the crystals that were generated by the
bulk gel. These scattered crystals were loosely bound and may be
removed by simply blowing air across the substrate.
[0055] As a control study, blank beads may also be subjected to a
hydrothermal treatment. In this case, UTD-1 crystals are randomly
scattered over the surface of the substrate. Such crystals do not
radiate perpendicular from the surface as in the case of the PLD
crystals. Such crystals were, instead, similar to crystals found in
a bulk gel synthesis. Furthermore, the crystals were loosely bound
to the bead's surface, as they tended to detach when blowing air
over the surface or even when washing with water. This unsuccessful
attempt to prepare oriented crystals by direct deposition from the
gel indicates that the uniform pulsed laser deposited film may be
essential to the formation of well-adhered, continuous, and
oriented coatings, including UTD-1 coatings.
[0056] In contrast to glass beads which may need a PLD film of
about 1.75 .mu.m, the stability of metal spheres to high pH may
allow for oriented growth from PLD films as thin as about 0.9
.mu.m. The larger metal sphere substrate may generate thicker films
than their smaller glass bead counterparts during the crystal
reorganization process in the post hydrothermal treatment. The
metal beads may have a reorganized crystal growth of about 14
.mu.m, in contrast to the approximate 9 .mu.m reorganized crystal
growth of the smaller glass beads. Increased crystal growth may be
a linear relationship with the size of the substrate. With metal
spheres described herein being about 66% larger than the glass
beads described herein, more material may be needed to effectively
coat the metal spheres, which may give rise to more nucleation
sites.
[0057] Applications for the presently disclosed methods are vast.
Using pulsed laser ablation to coat three dimensional and
non-uniform objects may be applied commercially in areas such as,
but not limited to, separations, catalysis and chemical sensors.
The methods may be used to coat one molecular sieve onto another to
enhance catalytic and size-selective properties. Another
application may be utilizing molecular sieve coated glass beads to
pack HPLC columns which, in turn, may enhance selectivity and
separation properties of the column.
[0058] The following examples are included to demonstrate specific
embodiments of the invention. It should be appreciated by those of
skill in the art that the techniques disclosed in the examples
which follow represent techniques discovered by the inventors to
function well in the practice of the invention, and thus may be
considered to constitute specific modes for its practice. However,
those of skill in the art should, in light of the present
disclosure, appreciate that many changes may be made in the
specific embodiments which are disclosed and still obtain a like or
similar result without departing from the spirit and scope of the
invention.
EXAMPLE 1
Zeolite UTD-1 Coating on Buck Shot Pellets
[0059] Zeolite UTD-1 was synthesized using
bis(pentamethylcyclopentadienly- )cobalt (III) hydroxide,
Cp*.sub.2CoOH, as the template. The substrates in this Example were
spherical, zinc galvanized coated steel buck shot pellets measuring
about 0.5 mm in diameter and glass beads (Supleco) measuring about
75 .mu.m in diameter.
[0060] A 2.5 cm in diameter pressed pellet of the as-synthesized
UTD-1 was mounted in a controlled atmosphere chamber at about a
60.degree. C. angle about 2.5 cm above the substrate holder as
shown in FIGS. 1A-1C. The glass or metal beads were then loaded
into a glass dish (about 2.5 cm in diameter and about 1 cm deep)
attached to an 8.25.times.3.2 cm steel plate. The substrate holder
sat directly on top of a MOTOROLA.RTM. pancake pager vibrator that
was controlled by an on/off single speed switch powered by a AA
battery. The directional nature of the laser-generated plume
allowed substrates to vibrate in the plume and to become evenly
coated. Typical experimental conditions were as follows: laser
power was about 70 to about 156 mJ/pulse, repetition rate was about
10 Hz, substrate temperature ranged from about 25 to about
60.degree. C., vacuum chamber pressure was about 150 mTorr, and
deposition rate was about 70 nm/min at about 70 mJ/pulse on the
non-planar metal bead surface.
[0061] The PLD UTD-1 coated beads were placed in a 23 ml Teflon
lined Parr reactor containing a UTD-1 synthesis gel having a molar
ratio of SiO.sub.2:Na.sub.2O:CP*.sub.2Co.sup.+:H.sub.2O of about
1:0.05:0.1:60. The reactor was heated at about 175.degree. C. for
about 72 hours under static conditions. The beads were then
separated from the gel by gravity filtration, washed with deionized
water, and dried at room temperature. The beads were then calcined
in air at about 550.degree. C. for about 6 hours to remove the
template.
EXAMPLE 2
Zeolite UTD-1 Coating on Glass Beads and Buck Shot Pellets
[0062] 75 micron glass beads and galvanized coated stainless buck
shot pellets have been coated with UTD-1 by pulsed laser ablation
(248 .mu.m, KrF*). Typical experimental conditions were as follows:
laser power was about 70 to about 156 mJ/pulse, repetition rate was
about 10 Hz, substrate temperature was about 25 to about 59.degree.
C., background pressure was about 150 mTorr with O.sub.2 deposition
rate was about 130 nm/min, deposition time was about 5 minutes to
about 13 minutes. The beads or pellets having a UTD-1 coating were
placed in a high temperature Teflon liner reactor along with the
UTD-1 synthesis gel. A post hydrothermal treatment was then carried
out on these laser deposited substrates for about 72 hours in an
autoclave at about 175 degrees C. resulting in a continuous highly
oriented UTD-1 membrane.
EXAMPLE 3
Zeolite UTD-1 Coating on Glass Beads and Buck Shot Pellets
[0063] Glass beads having a diameter of about 75 microns and
galvanized coated stainless steel buck shot pellets have been
coated with UTD-1 by pulsed laser ablation (248 nm, KrF*). The
substrate was placed inside a shallow glass dish, about 2.5 cm in
diameter and about 1.21 cm deep, as shown in FIG. 1. The glass dish
was mounted on a 8.25".times.3.20 cm steel plate, and sat directly
on top of a pancake vibrator that was surrounded by a foam ring.
The vibrator was controlled by an on/off switch attached to the
steel plate, and was powered by a AA battery. The vibrator
apparatus was mounted on a 15.24.times.7.62 cm stainless steel pipe
(not shown) that allowed for the substrate to be placed about 2.5
cm from the target. FIG. 1C shows the top view of the vibrator
apparatus. Typical experimental conditions were as follows: laser
power was about 70 to about 156 mJ/pulse, repetition rate was about
10 Hz, substrate temperature was about 25 to about 59.degree. C.,
background pressure was about 150 mTorr with O.sub.2 and deposition
rate was about 130 nm/min. With the vibrator turned on, the pellets
vibrated in the plume, allowing the UTD-1 to be deposited uniformly
onto the substrates.
[0064] A post hydrothermal treatment was then carried out on these
laser deposited films by placing the pellets in a gel having a
molar patio of SiO.sub.2:Na.sub.2O:CP*.sub.2Co+:H.sub.2O of
0.05:0.1:60 for about 72 hours in an autoclave at about 175.degree.
C. resulting in a continuous highly oriented UTD-1 membrane.
EXAMPLE 4
CoAPO-5 Crystals
[0065] CoAPO-5 crystals were coated onto MAPO-39 crystals by pulsed
laser ablation (248 nm, KrF*). The experimental conditions were as
follows: laser power was about 71.2 mJ/pulse, repetition rate was
about 10 Hz, substrate temperature was about 25.degree. C.,
background pressure was about 150 mTorr with O.sub.2 deposition
rate was about 130 nm/min, deposition time was about 7 minutes and
30 seconds. A coating of CoAPO-5 was obtained on the MAPO 39
crystals.
EXAMPLE 5
FeAPO-5 Crystals
[0066] FeAPO-5 crystals were coated on MAPO-39 crystals by pulsed
laser ablation (248 mn, KrF*). The experimental conditions were as
follows: laser power was about 71.2 mJ/pulse, repetition rate was
about 10 Hz, substrate temperature was about 25.degree. C.,
background pressure was about 150 mTorr with O.sub.2 deposition
rate was about 130 nm/min, and deposition time was about 7 minutes
and 30 seconds. A coating of FeAPO-was also achieved on MAPO-39
crystals.
[0067] While the invention may be adaptable to various
modifications and alternative forms, specific embodiments have been
shown by way of example and described herein. However, it should be
understood that the invention is not intended to be limited to the
particular forms disclosed. Rather, the invention is to cover all
modifications, equivalents, and alternatives falling within the
spirit and scope of the invention as defined by the appended
claims. Moreover, the different aspects of the disclosed
compositions and methods may be utilized in various combinations
and/or independently. Thus the invention is not limited to only
those combinations shown herein, but rather may include other
combinations.
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