U.S. patent application number 12/921945 was filed with the patent office on 2011-05-05 for nozzle configurations for abrasive blasting.
This patent application is currently assigned to ENBIO LIMITED. Invention is credited to John Gerard O'Donoghue, Leo Sexton.
Application Number | 20110104991 12/921945 |
Document ID | / |
Family ID | 40933529 |
Filed Date | 2011-05-05 |
United States Patent
Application |
20110104991 |
Kind Code |
A1 |
O'Donoghue; John Gerard ; et
al. |
May 5, 2011 |
NOZZLE CONFIGURATIONS FOR ABRASIVE BLASTING
Abstract
Disclosed herein are nozzle configurations for an abrasive
blasting system. The system can comprise multiple hoppers for
feeding separate powders streams to a fluid jet. The separate
powder streams can be mixed in a frustoconical or conical mixer
prior to delivery to the substrate surface. Also disclosed are
methods of texturizing the substrate surface by moving the
substrate or nozzle(s) during the delivery of dopant(s). Methods
for achieving a uniform distribution of dopant are also described.
Also disclosed herein are coaxial nozzle configurations having an
outer focusing stream to converge and/or mix with an inner particle
stream.
Inventors: |
O'Donoghue; John Gerard; (
Waterford, IE) ; Sexton; Leo; (Cork, IE) |
Assignee: |
ENBIO LIMITED
Carrigtwohill, Co. Cork
IE
|
Family ID: |
40933529 |
Appl. No.: |
12/921945 |
Filed: |
March 11, 2009 |
PCT Filed: |
March 11, 2009 |
PCT NO: |
PCT/IB09/05054 |
371 Date: |
January 18, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61035985 |
Mar 12, 2008 |
|
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|
61035982 |
Mar 12, 2008 |
|
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61038200 |
Mar 20, 2008 |
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Current U.S.
Class: |
451/36 ;
451/91 |
Current CPC
Class: |
C23C 4/02 20130101; B24C
11/00 20130101; B24C 3/02 20130101; B24C 5/02 20130101; B24C 5/04
20130101; C23C 24/04 20130101; B24C 1/10 20130101 |
Class at
Publication: |
451/36 ;
451/91 |
International
Class: |
B24C 1/00 20060101
B24C001/00; B24C 5/00 20060101 B24C005/00 |
Claims
1. An apparatus for abrasively blasting a substrate, comprising: at
least two hoppers for receiving at least two sets of particles
including a first set of particles comprising an abrasive and a
second set of particles comprising a dopant; a mixer for receiving
and mixing the at least two sets of particles from the at least two
hoppers to form a particulate mixture; and at least one fluid jet
for delivering the at least two sets of particles to the mixer, or
the particulate mixture to the substrate, the at least one fluid
jet being positioned downstream of the at least two hoppers.
2. The apparatus of claim 1, wherein the at least one fluid jet is
positioned at the base of the at least two hoppers.
3. The apparatus of claim 1, wherein the at least one fluid jet is
positioned at the base of the mixer.
4. The apparatus of claim 1, further comprising delivery tubes
connecting each of the at least two hoppers to the mixer.
5. The apparatus of claim 1, wherein each delivery tube is linear
and has an incident angle with respect to the vertical.
6. The apparatus of claim 5, wherein the delivery tube for the
first set of particles has an incident angle normal to the vertical
and the delivery tube for the second set of particles comprising
the dopant is delivered at an incident angle parallel to the
vertical.
7. The apparatus of claim 1, further comprising a second fluid jet
for delivering the second set of particles to the mixer.
8. An apparatus for abrasively blasting a substrate, comprising: a
first particle stream comprising an abrasive and a second particle
stream comprising a dopant; a conical or frustoconical mixer
comprising at least two channels penetrating through the mixer,
wherein the respective particle streams enter the channels
separately and exit the mixer to impact the substrate as a
particulate mixture of the first and second particle streams; and
at least one fluid jet to deliver at least one of the first and
second particle streams to the mixer, or to deliver the particulate
mixture to the substrate.
9. The apparatus of claim 8, wherein the two or more channels are
linear.
10. The apparatus of claim 9, wherein the block has a longitudinal
axis and each of the two or more channels has an incident angle
relative to the longitudinal axis ranging from 0.degree. to an
angle formed by the outer conical surface of the block, the
incident angle of each of the channels being the same or
different.
11. The apparatus of claim 8, wherein the at least one fluid jet is
positioned upstream of the mixer to deliver at least one of the
first and second particle streams to the mixer.
12. The apparatus of claim 8, wherein the at least one fluid jet is
positioned between the mixer and the substrate to deliver the
particulate mixture to the substrate.
13. The apparatus of claim 8, wherein the two ore more channels
merge into a single channel within the block.
14. An apparatus for abrasively blasting a substrate, comprising: a
coaxial nozzle for delivering a first set of particles comprising
at least one dopant and a second set of particles comprising an
abrasive, wherein an inner tubing of the nozzle delivers a particle
stream comprising a first set of particles, and an outer tubing
delivers a pressurized gas comprising the second set of particles
that encircles and converges inwardly toward the first set of
particles to mix and homogenize the first and second set of
particles, and wherein a resulting mixture of the first and second
particles bombard and impregnate and/or coat the substrate with the
at least one dopant.
15. The apparatus of claim 14, wherein the nozzle is a fluid
jet.
16. A method of modifying a substrate, comprising: delivering
substantially simultaneously a first set of particles comprising a
dopant and a second set of particles comprising an abrasive from at
least one fluid jet to a surface of the substrate to impregnate the
substrate with the dopant, each nozzle having an incident angle to
the vertical ranging from 0.degree. to 85.degree.; and moving the
substrate in a direction parallel to the substrate surface during
the delivering to deposit a track of the dopant on the substrate
surface.
17. A method of modifying a substrate, comprising: delivering
substantially simultaneously a first set of particles comprising a
dopant and a second set of particles comprising an abrasive from at
least one fluid jet to the substrate to impregnate the substrate
with the dopant, wherein the first and second set of particles
overlap at an area between the at least one fluid jet and the
substrate, and wherein a cross section of the overlap area has a
substantially homogeneous distribution of the first set of
particles.
18-57. (canceled)
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of priority under 35
U.S.C. .sctn.119(e) to U.S. Prov. App. 61/035,985, filed Mar. 12,
2008, U.S. Prov. App. 61/035,982, filed Mar. 12, 2008, and U.S.
Prov. App. 61/038,200, filed Mar. 20, 2008, the disclosures of
which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to apparatus and methods of
coating and/or impregnating and/or otherwise modifying surfaces
with dopants via abrasive blasting.
BACKGROUND OF THE INVENTION
[0003] The bombardment of metal surfaces with abrasive materials is
finding an increasing number of technical applications in recent
years. Techniques such as grit blasting, shot blasting, sand
blasting, shot peening and micro abrasion fall under this category
of surface treatment technique. In each of these techniques,
generally, an abrasive material, shot or grit, is mixed with a
fluid and delivered at high velocity to impinge the surface to be
treated. The technique used to deliver the abrasive material can be
classified as wet or dry depending on the choice of fluid medium
used to deliver the abrasive to the surface, usually water and air
respectively.
[0004] Applications of these technologies include metal cutting,
cold working metallic surfaces to induce desirable strain
characteristics and the pre-treatment of surfaces to induce
desirable texture (surface roughness) for the purposes of enhanced
adhesion of further coating materials. (See Solomon et al., Welding
research, 2003. October: p. 278-287; Momber et al., Tribology
International, 2002. 35: p. 271-281; Arola et al., J. Biomed. Mat.
Res., 2000. 53(5): p. 536-546; and Arola and Hall, Machining
science and technology, 2004. 8(2): p. 171-192.).
[0005] Abrasive blasting finds various applications industries,
such as the automotive, aerospace, construction, medical, and other
industries that involve surface texturing or smoothing. Due to the
variety of surfaces involved, including different material types,
textures, hardness, etc., a need remains for new nozzle
configurations for abrasive blasting.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1A shows an abrasive blasting system having multiple
hoppers for separate particle feeds that converge via a mixer;
[0007] FIG. 1B shows a mixer for separate particle streams;
[0008] FIG. 2A shows a frustoconical block mixer having inner
channels;
[0009] FIG. 2B shows another a frustoconical block mixer where the
channels have a different incident angle from those of FIG. 2A;
[0010] FIG. 3A shows a two-nozzle configuration where each nozzle
has an incident angle of 45.degree.;
[0011] FIG. 3B schematically depicts the "interaction zone overlap"
(IZO) of the configuration of FIG. 3A.
[0012] FIG. 3C shows a two-nozzle configuration in which the
incident angle is 5.degree.;
[0013] FIG. 3D schematically depicts the "interaction zone overlap"
(IZO) of the configuration of FIG. 3C;
[0014] FIG. 4A schematically depicts a dopant track deposited when
the substrate is moved horizontally;
[0015] FIG. 4B schematically depicts a dopant track deposited when
the substrate is moved horizontally in a direction opposite that of
FIG. 4A;
[0016] FIG. 4C schematically depicts two different dopant tracks
deposited on a single substrate when the substrate is moved in two
opposing directions;
[0017] FIG. 4D schematically depicts a dopant track comprising a
series of linear tracks;
[0018] FIG. 4E schematically depicts a dopant track comprising a
circular pattern;
[0019] FIG. 5A shows a cross-section of the width of a dopant track
that is non-uniformly distributed (weighted toward the middle);
[0020] FIG. 5B shows the Guassian distribution of the powder
density (y-axis) versus diameter of powder stream (x-axis) based on
the dopant track cross-section of FIG. 5A;
[0021] FIG. 5C shows a cross-section of the powder stream, showing
the non-uniform distribution of powder that results in the dopant
track of FIG. 5A;
[0022] FIG. 5D shows a cross-section of the width of a dopant track
that is uniformly distributed;
[0023] FIG. 5E shows a "top hat" distribution of the powder density
(y-axis) versus diameter of powder stream (x-axis) based on the
dopant track cross-section of FIG. 5D;
[0024] FIG. 5F shows a cross-section of the powder stream, showing
the uniform distribution of powder that results in the dopant track
of FIG. 5D;
[0025] FIG. 6A shows the extent of overlap ("O") of dopant tracks
required for a uniform surface coating based on the non-uniform
dopant track of FIG. 5A;
[0026] FIG. 6B shows the smaller extent of overlap ("O") of dopant
tracks required for a uniform surface coating based on the uniform
dopant track of FIG. 5D;
[0027] FIG. 7 shows a coaxial nozzle configuration having an outer,
focusing stream;
[0028] FIG. 8A shows a block mixer having a multiple nozzle
configuration with four side feed nozzles;
[0029] FIG. 8B schematically depicts the particle stream emanating
from the nozzle configuration of FIG. 8A;
[0030] FIG. 9A shows the mass flow rates of abrasive versus dopant
for increasing amounts of A to D;
[0031] FIG. 9B is an expanded area of interest of FIG. 9A, for
finer control of the dopent concentration; and
[0032] FIG. 10 shows a block mixer having a Y-shaped channel
configuration.
DETAILED DESCRIPTION
[0033] Disclosed herein are systems and treatment processes for
impregnating a surface, such as a metal surface, with a dopant. The
strength of the bond between the dopant and the surface and the
concentration of dopant achieved in or on the surface can be
improved over conventional methods of surface impregnation
techniques.
[0034] Abrasive blasting is typically used for cleaning or
stripping substrates of an outer surface. The present invention
employs the abrasive blasting technique to not only clean the outer
surface but to modify the surface with a dopant.
[0035] If a dopant material is delivered to the surface within a
high velocity fluid jet in the absence of an abrasive, no or
minimal surface modification will occur. Such circumstances can
arise for a number of reasons; the material may not have sufficient
particle size, or have sufficient density and hardness. It may also
be a consequence of the nature of the surface itself. For metal
surfaces, for example, the dopant material would require suitable
physical properties (e.g., density and/or hardness) to breech an
oxide layer to access the underlying metal surface.
[0036] One embodiment provides an apparatus for abrasively blasting
a substrate, comprising:
[0037] at least two hoppers for receiving at least two sets of
particles including a first set of particles comprising an abrasive
and a second set of particles comprising a dopant;
[0038] a mixer for receiving and mixing the at least two sets of
particles from the at least two hoppers to form a particulate
mixture; and
[0039] at least one fluid jet for delivering the at least two sets
of particles to the mixer, or the particulate mixture to the
substrate, the at least one fluid jet being positioned downstream
of the at least two hoppers.
[0040] In one embodiment, the at least one fluid jet is positioned
at the base of the at least two hoppers. In another embodiment, the
at least one fluid jet is positioned at the base of the mixer.
[0041] FIG. 1A shows one embodiment of a system 2 containing at
least two hoppers for delivering particulate material to a fluid
jet used for abrasively blasting a substrate. The apparatus of FIG.
1A contains multiple hoppers 4 (labeled hoppers 1, 2, 3 . . . n),
where each hopper 4 delivers a powder through individual delivery
tubes 5 leading to a common mixer. At least one of the hoppers
delivers an abrasive (A), such as Al.sub.2O.sub.3, for abrasively
blasting a surface of the substrate. For example, the substrate can
be a metal and the alumina can be used to abrasively blast the
oxide surface to expose the underlying metal surface. One
embodiment takes advantage of the removal of the oxide layer
overlying the metal substrate, and treating the newly exposed metal
beneath to add a new material (the dopant). Depending on the nature
of that added material, the surface properties of the metal article
can be tailored according to its intended functional
requirements.
[0042] At least one of the hoppers delivers the dopant that is
deposited on the metal surface underlying the metal oxide layer. In
the embodiment of FIG. 1A, at least two dopants can be deposited on
the metal surface, each dopant being delivered from individual
hoppers to the mixer. For example, hopper 1 can receive and deliver
the abrasive (A), hopper 2 can deliver a first dopant D1 (e.g.,
hydroxyapatite), and hopper three can deliver a second dopant D2
(e.g., a drug). It is readily appreciated that one or more dopants
may be delivered in combination with one or more abrasives, and one
of ordinary skill in the art can readily envision constructing
arranging multiple (n) hoppers to handle as many dopant/abrasive
types as needed.
[0043] Each powder type is delivered from the respective hopper to
a common mixer 8 where the particles can be mixed to form a more
homogeneous particulate mixture comprising the abrasive and
dopant(s). From the mixer 8, a powder stream of the abrasive and
one or more dopants is delivered to an interaction zone 10 (e.g., a
substrate surface).
[0044] To achieve abrasive blasting of the pressurized surface, a
fluid jet (not shown) delivers at least the abrasive (A) to and
from the mixer 8 to produce an accelerated powder stream that
bombards the substrate surface (enters interaction zone 10). The
fluid jet can deliver the powder stream via a pressurized fluid,
which can be a liquid or gas. In another embodiment, a fluid jet
also delivers the one or more dopants. The fluid jet(s) can be
positioned at the base of respective hoppers to accelerate
particles through the tubing 5 and to the mixer 8. The velocity of
the particles can enhance the mixing and the particles have
sufficient velocity to bombard the substrate surface and impregnate
it with dopant. In another embodiment, the fluid jet can be
positioned at the base of the mixer to accelerate particles from
the mixer to the substrate surface.
[0045] FIG. 1A shows the mixer having a conical shape, although a
frustoconical shape can be also applied. Various mixer shapes can
be envisioned so long as the shape allows the mixer to receive
multiple powder streams and to aggregate these streams into a more
homogeneous particulate mixture. FIG. 1B shows a detailed view of
mixer 18 comprising a feed section 22 leading to a cylindrical
section 24 that converges downwardly (toward the interaction zone
20) to a conical or frustoconical section 26. The feed section 22
contains apertures for the delivery tubes 18, allowing entry of the
abrasive (A) and dopant(s). After entry of the powders into the
mixer 18, the configuration of mixer 18 allows powder streams to
impact the side walls of the cylindrical section 22 and mix
throughout its length, potentially allowing greater mixing of the
powders. The embodiment of FIG. 1B also demonstrates the varying
angles from which the abrasive and dopant stream(s) can enter the
mixer 18 at feed section 22. The configuration of delivery tubes 15
in FIG. 1B has the abrasive powder stream pointed at an angle
90.degree. from the vertical toward the mixer. This abrasive stream
will collide in the mixer 18 with the dopant stream, which can
enter the mixer 18 at an angle at 0.degree. from the vertical
(e.g., dopant 1) or at another angle ranging between 0.degree. and
90.degree. (e.g., as with dopant 2). Upon collision with the
abrasive powder stream, the mixed powder stream can swirl in the
direction of arrow 28, allowing greater mixing of the powders. This
mixer design can provide increased and more efficient mixing. In
one embodiment, at least one abrasive stream is delivered with a
pressurized fluid such that the abrasive hits the dopant streams
with sufficient force to cause impregnation of the dopant on the
abrasive before the particles hit the substrate surface.
[0046] In one embodiment, the mixer is a funnel or funnel-like
structure, as in FIG. 1A. In another embodiment, the mixer can be
open at the top or can have a closed structure save for inlet holes
at the top for attaching tubing connecting the mixer to the
hoppers. One exit hole can be positioned at the bottom of the
mixer; alternatively, more than one exit hole can be provided,
resulting in a two, three, or multi-pronged junction where the
different particle streams meet at a point below the mixer. For
example, alumina can serve as the abrasive and hydroxyapatite can
serve as the dopant, where both sets of particles are fed to and
mixed in the mixer, allowing the particles to be delivered to the
interaction zone or substrate substantially simultaneously.
[0047] In one embodiment, the hopper contains a nozzle (fluid jet)
at its base and a source of pressurized fluid to emit a particle
stream to the mixer at high speed. In one embodiment, only the
abrasive is delivered to the mixer at high speed. One or more
dopants may or may not be delivered to the mixer at high speed. By
adjusting the respective flow rates of the abrasive and dopant(s),
the ratio of abrasive to dopant(s) can effectively be adjusted and
controlled while maintaining a constant overall mass flow rate.
[0048] Another embodiment provides an apparatus for abrasively
blasting a substrate, comprising:
[0049] a first particle stream comprising an abrasive and a second
particle stream comprising a dopant;
[0050] a conical or frustoconical mixer comprising at least two
channels penetrating through the mixer, wherein the respective
particle streams enter the channels separately and exit the mixer
to impact the substrate as a particulate mixture of the first and
second particle streams; and
[0051] at least one fluid jet to deliver at least one of the first
and second particle streams to the mixer, or to deliver the
particulate mixture to the substrate.
[0052] In one embodiment, the at least one fluid jet is positioned
upstream of the mixer to deliver at least one of the first and
second particle streams to the mixer. In another embodiment, the at
least one fluid jet is positioned between the mixer and the
substrate to deliver the particulate mixture to the substrate.
[0053] Another embodiment provides an apparatus for abrasively
blasting a substrate, comprising:
[0054] a first fluid jet for delivering a first particle stream
comprising an abrasive and a second fluid jet for delivering a
second particle stream comprising a dopant to be impregnated in the
substrate; and
[0055] a solid conical or frustoconical block positioned between
the fluid jets and the substrate or upstream of the fluid jets;
[0056] channels penetrating through the length of the block for
separate particle streams,
[0057] wherein the particle streams enter the channels from a top
surface of the block and exit from the bottom of the block before
impacting the substrate.
[0058] FIG. 2A shows one example of a mixer configured as a solid
block 30. Block 30 has a funnel shape where at its greatest width
(top of funnel), the block has a flat top surface 32. From the top
surface 32 the shape of the block converges to its smallest width
34 at the bottom. Block 30 has three channels 36 drilled from the
top surface 32 through the bottom 34 to allow a powder stream to
travel through the block. Optionally, a feed nozzle 33 stemming
from the channels 36 can provide an entry way for the respective
powders into block 30. Feed nozzle 33, although shown as a tube,
can alternatively be funnel-shaped, cup-shaped, or any other shape
known in the art to enhance optimal delivery of powder to block 30.
At a fixed distance "d1" from the bottom, the respective powder
streams reach a focal point at 38 prior to hitting the substrate
surface (not shown). Thus, block 30 comprises channels initiating
from the top (planar) surface of the conical or frustoconical mixer
and penetrating substantially the length of the mixer. As depicted
in FIG. 2A, the mixing occurs after the separate particle streams
have exited the mixer but before impacting the substrate
[0059] The distance "d1" can be varied depending on the incident
angle of the channels (with respect to the vertical), as in FIG.
2B. FIG. 2B shows a block 40 of a similar funnel shape to block 30
of FIG. 2A. Block 40 has a different incident angle of the channels
46 with respect to the longitudinal axis of the block, resulting in
the distance "d2" between the bottom 44 and focal point 48 being
greater than that of d1. In one embodiment, for a conical or
frustoconical block having a longitudinal dimension of about 50 mm
(the distance between the top surface and the bottom), the distance
between the exit point of the mixer and the focal point ("d1" or
"d2") can range from 10-20 mm, e.g., from 10-15 mm.
[0060] The blocks of FIGS. 2A and 2B can be used for fixed incident
angles in the situation where incident angles have been optimized
and their variation is not necessary. Blocks 30 and 40 provide a
more robust construction for delivery of multiple powder streams.
The nozzle block can be made from copper or tool steel. Two or more
channels can be readily envisioned, as demonstrated in FIGS. 2A and
2B.
[0061] FIG. 8A shows a block 50 having a multiple nozzle
configuration in which four side feed nozzles 53a (only two shown)
surround a central nozzle 53b positioned at top surface 52. In FIG.
8A, the central feed nozzle 53b delivers the abrasive A and the
four side feed nozzles 53a deliver one or more dopants (D1-D4),
which can be the same for each nozzle or different. The side feed
nozzles 53a are illustrated as delivering powder to channels 56 at
90.degree. radially relative to each other. With this arrangement,
the dopant powder can exit the bottom 54 and simultaneously arrive
at the focal point 58 of the powder stream along with the abrasive.
Multiple nozzles can improve the uniformity of the deposited layer
by impregnating the dopant from all angles.
[0062] FIG. 8B depicts a schematic side view of two of the dopant
powder streams 62a and 62b and abrasive stream "A" impinging
substrate 64. The entire nozzle arrangement can move in a direction
normal to the vertical as indicated by double arrow 66 (i.e.,
horizontally, or parallel to the substrate surface) while the
substrate 64 remains stationary. Alternatively, the substrate 64
can move horizontally (in a direction parallel to the substrate
surface) in the direction of double arrow 68 while the nozzle
configuration remains stationary. The movement of the
substrate/nozzles can affect the amount of dopant incorporation in
the substrate. For example, if the substrate 64 moves to the right
in FIG. 8B, then the dopant from powder stream 62b will be lightly
impregnated in the substrate due to some stripping from the
trailing abrasive stream A. Meanwhile, dopant emanating from powder
stream 62a may be incorporated in the substrate to a greater
extent.
[0063] In another embodiment, the block 50 of FIG. 8A can be
configured to deliver the dopants in an annular ring 57 surrounding
the central channel that delivers the abrasive stream. In one
embodiment, the annular ring is formed from a circular feed nozzle
(not shown). In another embodiment, the annular ring is formed from
multiple nozzles arranged in a circle surrounding the central
nozzle. Depending on the motion of the substrate or nozzle
apparatus, the amount of dopant delivered to the substrate can be
controlled.
[0064] The nozzle configurations of FIGS. 8A and 8B can deposit
dopant in gradients or in layers depending on the choice of dopant,
the position of the dopant stream with respect to the central
nozzle, the mass flow rate of dopant and abrasive, the velocity of
movement of the nozzle or substrate, etc. It will be readily
appreciated by one skilled in the art that any number of dopant
streams can be incorporated, as limited by the size of the block
50, the channels 56, etc.
[0065] Another embodiment of a block is depicted in FIG. 10. Block
200 comprises a conical shaped device with two openings 202 on the
top into which the dopant and abrasive are fed. More than two
openings can be constructed. Openings 202 lead to channels 204,
which merge to a single channel 206 around the center of the block
200. This Y-shaped pathway allows the powders to mix before they
exit through a single opening 208 at the bottom of the device.
[0066] FIG. 3A shows a two-nozzle configuration where both nozzles
72a and 72b are spaced a distance apart, and each nozzle having an
incident angle 74 from the normal (or angle of inclination) of
45.degree.. The two respective streams 76a and 76b first meet and
interact at a volume 78 above the substrate 80. An expanded view of
volume 78 is shown in FIG. 3B, and is also termed the "interaction
zone overlap" (IZO).
[0067] FIG. 3C illustrates another dual nozzle configuration in
which the nozzles 82a and 82b are maintained at the same distance
from the substrate as the nozzles in FIG. 3A but the incident angle
84 is changed to 5.degree.. The volume 88 for the nozzle
configuration of FIG. 3C is illustrated in FIG. 3D. It can be seen
that the IZO based on the volume 88 as shown in FIG. 3D (smaller
incident angle) is greater than the IZO of volume 78 of FIG. 3B, as
the base of the volumes are the same, but the height of the volume
88 increases as the incident angle 84 decreases.
[0068] A larger IZO provides a longer time period for the two
powder streams to interact with each other before hitting the
substrate, and thus, the efficiency of mixing is greater for an
embodiment such as FIGS. 3C and 3D, compared with the embodiment of
FIGS. 3A and 3B. In other embodiments, a shorter interaction time
period may be desired.
[0069] Another embodiment provides a method of modifying a
substrate, comprising:
[0070] delivering substantially simultaneously a first set of
particles comprising a dopant and a second set of particles
comprising an abrasive from at least one fluid jet to a surface of
the substrate to impregnate the substrate with the dopant, each
nozzle having an incident angle to the vertical ranging from
0.degree. to 85.degree.; and
[0071] moving the substrate in at least one horizontal direction
during the delivering to deposit a track of the dopant on the
substrate surface.
[0072] One embodiment of this method is demonstrated in FIG. 4A,
showing the abrasive (A) and dopant (D) (e.g., HA) particle streams
emanating from a two-nozzle configuration. In this embodiment, the
substrate 100 (e.g., a Ti coupon), is moved in a horizontal
direction (normal to the vertical) in the direction of arrow 102
(to the left) to create a track 104 of the deposited dopant. FIG.
4B shows the same particle streams and resulting patterns but for
the situation where the substrate 100 is moved horizontally in the
direction of arrow 108 (to the right), resulting in deposited track
106.
[0073] FIG. 4C shows the two line patterns 104 and 106 of deposited
dopant on the same substrate 100. It was unexpectedly discovered
that without changing the stream of abrasive and dopant, the track
texture differed depending on the direction of traverse of the
substrate, manifesting in a visual difference of the two substrate
surfaces. In one embodiment, the color of the Ti coupon layer can
vary depending on the direction of traverse of the substrate.
[0074] In one embodiment, the substrate is moved in more than one
horizontal direction. In this embodiment, the dopant can be
deposited on the substrate 110 in a pattern, as illustrated in
FIGS. 4D and 4E. FIG. 4D shows a continuous pattern 112 of linear
tracks where the direction of travel (see arrows 114) was changed
90.degree. from the previous direction. FIG. 4C shows a circular
direction of travel, resulting in a circular pattern 116.
[0075] Although FIG. 4D depicts a pattern created by twin nozzles,
each delivering a set of particles (abrasive "A" and dopant "D"
respectively), and FIG. 4E depicts a pattern created by either
coaxial nozzles or a single nozzle feeding both the abrasive "A"
and dopant "D," it would be readily understood by one skilled in
the art that the nozzle configurations can be reversed for FIGS. 4D
and 4E. For example, the pattern of FIG. 4D can be delivered by a
single nozzle or coaxial nozzles, while the circular pattern of
FIG. 4E can be delivered by twin nozzles having the same or unique
incident angles.
[0076] Another embodiment provides a method of controlling the
distribution of a track deposited by one or more particle streams
comprising an abrasive and dopant(s). FIG. 5A depicts a
cross-section of a deposited dopant track 122 on substrate 120. It
can be seen that the cross-section of track width 122 can have a
nonhomogeneous distribution, where a greater proportion of the
dopant is deposited in the middle of the track. The result is a
Gaussian distribution of dopant when plotting powder density
(y-axis) versus diameter of powder stream, as depicted in FIG. 5B.
FIG. 5C shows a cross-section of the dopant powder stream emanating
from the nozzle, indicating a greater dopant concentration in the
center of the particle stream cross-section, thereby producing the
nonhomogeneous deposit of FIG. 5A.
[0077] The effect of a nonhomogeneous distribution can be seen in a
layer formed from multiple overlapping parallel tracks. If each
track displayed a Gaussian distribution, a layer of uniform
thickness can be achieved but only with a large overlap between
adjacent, parallel tracks. In some instances, a nonhomogeneous
distribution may require an overlap ("O") between adjacent tracks
of about 70%, as schematically illustrated in FIG. 6A.
[0078] Accordingly, another embodiment provides a method of
improving the homogeneity of the distribution of a deposited track.
In one embodiment, a method of modifying a substrate,
comprises:
[0079] delivering substantially simultaneously a first set of
particles comprising a dopant and a second set of particles
comprising an abrasive from at least one fluid jet to the substrate
to impregnate the substrate with the dopant,
[0080] wherein the first and second set of particles overlap at an
area between the at least one fluid jet and the substrate, and
[0081] wherein a cross section of the overlap area has a
substantially homogeneous distribution of the first set of
particles.
[0082] FIG. 5D schematically depicts a cross-section of a deposited
track 124 on substrate 120. A plot of powder density (y-axis)
versus .phi. of powder stream would result in a uniform "top hat"
distribution, as schematically depicted in FIG. 5E. The resulting
cross-section of the powder stream would also be uniform, as
depicted in FIG. 5F. For a uniform distribution, the overlap ("O")
of adjacent tracks can be as low as 5-10% to result in uniform
surface coverage and thickness, as schematically illustrated in
FIG. 6B.
[0083] In one embodiment, a particle stream cross-section having a
uniform distribution of dopant(s) can be achieved with an apparatus
for abrasively blasting a substrate, comprising:
[0084] a coaxial nozzle for delivering a stream of particles,
[0085] wherein an inner tubing of the nozzle delivers a first
particle stream, and an outer tubing delivers a focusing stream
that encircles and converges inwardly toward the first particle
stream, and
[0086] wherein the stream of particles comprising the first
particle stream bombard and impregnate and/or coat the substrate
with the dopant.
[0087] FIG. 7 shows an embodiment of a coaxial nozzle 150, in which
a particle stream is emitted through an inner tubing 152 of the
nozzle 150. A focusing stream (F) can be delivered through an outer
coaxial tubing of the nozzle, resulting in the emission of a the
particle stream surrounded by the focusing stream.
[0088] In one embodiment, the inner tubing 152 delivers a first
particle stream comprising an abrasive and dopant (e.g., alumina
and hydroxyapatite), resulting in an emission of the two particle
types as a single particle stream. In one embodiment, the focusing
stream F is a pressurized gas delivered through an outer coaxial
tubing of the nozzle, resulting in the emission of a single
particle stream comprising abrasive and dopant surrounded by the
pressurized gas. The pressurized gas can cause the particles to
converge inwardly, resulting in additional mixing or homogenizing
of the two particle types. The resulting mixture can then bombard
and impregnate the surface of the dopant; because of the improved
mixing efficiency, a more uniform distribution of deposited dopant
can result.
[0089] FIG. 7 shows the particle stream entering the coaxial nozzle
in a direction parallel to the longitudinal axis of the nozzle
whereas the pressurized gas has an inlet normal to the longitudinal
axis. One of ordinary skill in the art can readily appreciate that
varying inlet angles for the gas or particles can be constructed as
alternative designs for the nozzle.
[0090] Another embodiment provides an apparatus for abrasively
blasting a substrate, comprising:
[0091] a coaxial nozzle for delivering a first set of particles
comprising at least one dopant and a second set of particles
comprising an abrasive,
[0092] wherein an inner tubing of the nozzle delivers a particle
stream comprising a first set of particles, and an outer tubing
delivers a pressurized gas comprising the second set of particles
that encircles and converges inwardly toward the first set of
particles to mix and homogenize the first and second set of
particles, and
[0093] wherein a resulting mixture of the first and second
particles bombard and impregnate and/or coat the substrate with the
at least one dopant.
[0094] In one embodiment, a particle stream cross-section having a
uniform distribution of dopant(s) can be achieved with an apparatus
for abrasively blasting a substrate, comprising:
[0095] a coaxial nozzle for delivering a first set of particles
comprising at least one dopant and a second set of particles
comprising an abrasive,
[0096] wherein an inner tubing of the nozzle delivers a particle
stream comprising a mixture of the first and second set of
particles, and an outer tubing delivers a pressurized gas that
encircles and converges inwardly toward the particle stream to mix
and homogenize the first and second set of particles, and
[0097] wherein a resulting mixture of the first and second
particles bombard and impregnate and/or coat the substrate with the
dopant.
[0098] Another embodiment provides a method of controlling the flow
rates of a particle mixture. By mixing the ratio of flow rates of
abrasive (A) to dopant (D) a map of dopant concentrations over a
range of flow rates can be created. FIG. 9A shows the mass flow
rates of A versus D for increasing amounts of A to D. By choosing a
range of mass flow rates from minimum (zero mass flow rate) to
maximum (determined by the powder feeder specifications) one can
impregnate a range concentrations of dopant into a surface. If an
area of interest was determined from analysis of this map then that
area of interest can be expanded and finer control of the dopant
concentration can be obtained, as depicted in FIG. 9B.
[0099] In certain embodiments, the dopant materials include but are
not limited to materials desired at an implant surface for the
purposes of steering and improving the body tissue-implant
interaction. The dopant can comprise materials such as polymers,
metals, ceramics (e.g., metal oxides, metal nitrides), and
combinations thereof, e.g., blends of two or more thereof.
[0100] Exemplary dopants include, modified calcium phosphates,
including Ca.sub.5(PO.sub.4).sub.3OH, CaHPO.sub.4.2H.sub.2O,
CaHPO.sub.4, Ca.sub.8H.sub.2(PO.sub.4).sub.6.5H.sub.2O,
.alpha.-Ca.sub.3(PO.sub.4).sub.2, .beta.-Ca.sub.3(PO.sub.4).sub.2
or any modified calcium phosphate containing carbonate, chloride,
fluoride, silicate or aluminate anions, protons, potassium, sodium,
magnesium, barium or strontium cations.
[0101] Other exemplary dopants include titania (TiO.sub.2),
zirconia, hydroxyapatite, silica, carbon, and chitosan/chitin.
[0102] In one embodiment, the dopant is a combination of an
agent-carrying media and at least one therapeutic agent (including
biomolecules and biologics). Potential carriers for therapeutic
agents including antibiotics, immuno suppressants, antigenic
peptides, bactericidal peptides, structural and functional proteins
have been disclosed in U.S. Pat. No. 6,702,850). Calcium phosphate
coatings as the drug carrier can also be used (see U.S. Pat. Nos.
6,426,114, 6,730,324, and U.S. Provisional Application No.
60/410,307, the disclosures of which are incorporated herein by
reference). Dopants that can act as agent-carrying media include
nanoporous, mesoporous, nanotubes, micro-particles of various
materials including hydroxyapatite, silica, carbon, and titania
(TiO.sub.2) capable of carrying therapeutic agents, biomolecules
and biologics. Particulates and powders (e.g. titania powder) can
be either adhesively bonded or covalently attached (tethered) to
the therapeutic agents, biomolecules and biologics.
[0103] Composites of media and carriers (e.g. sintered together),
and combinations of carriers can convey drugs and biologics and can
control elution profiles.
[0104] Other exemplary dopants include barium titanate, zeolites
(aluminosilicates), including siliceous zeolite and zeolites
containing at least one component selected from phosphorous,
silica, alumina, zirconia, calcium carbonate, biocompatible glass,
calcium phosphate glass. The dopant can also be a growth factor
consisting of epidermal growth factors, transforming growth factor
.alpha., transforming growth factor .beta., vaccinia growth
factors, fibroblast growth factors, insulin-like growth factors,
platelet derived growth factors, cartilage derived growth factors,
interlukin-2, nerve cell growth factors, hemopoietic cell growth
factors, lymphocyte growth factors, bone morphogenic proteins,
osteogenic factors or chondrogenic factors.
[0105] In one embodiment, the dopant is hydroxyapatite deposited on
a titanium surface. Both HA and TiO.sub.2 constitute excellent
biocompatible biointerfaces, both being biostable and safe in the
body. Both can be termed bioreactive in that they can induce
specific responses in certain tissues particularly bone tissue. The
surface resulting from the deposition of HA on titanium as
delivered by the micro-blasting technique combines the benefits of
both materials. The TiO.sub.2 is not fully covered by the dopant
(HA) and therefore still presents to the biological tissue, while
the HA affixed on and in the surface is not denatured by the
deposition process and therefore conveys its full benefit to the
surrounding tissue. In this manner the different benefits of both
biomaterials can brought to bear in the biointerface and when
further combined with the surface texture/morphology best suited to
intended functionality of the implant, and moreover the
availability of a drug delivery mechanism, can provide various
methods for tailoring the therapeutic, compositional and
morphological profile available to the patient end user.
[0106] In one embodiment, the dopant is a therapeutic agent. The
therapeutic agent can be delivered as a particle itself, or
immobilized inside or on a carrier material. In another embodiment,
the therapeutic agent is immobilized with the carrier material as a
homogeneous solid composition. Exemplary carrier materials include
any of the other dopants listed herein (those dopants that are not
a therapeutic agent) such as polymers, calcium phosphate, titanium
dioxide, silica, biopolymers, biocompatible glasses, zeolite,
demineralized bone, de-proteinated bone, allograft bone, and
composite combinations thereof.
[0107] Exemplary classes of therapeutic agents include anti-cancer
drugs, anti-inflammatory drugs, immunosuppressants, an antibiotic,
heparin, a functional protein, a regulatory protein, structural
proteins, oligo-peptides, antigenic peptides, nucleic acids,
immunogens, and combinations thereof.
[0108] In one embodiment, the dopant is a radio opaque material,
such as those chosen from alkalis earth metals, transition metals,
rare earth metals, and oxides, sulphates, phosphates, polymers and
combinations thereof.
[0109] In one embodiment, the carrier material is a biopolymer
selected from polysaccharides, gelatin, collagen, alginate,
hyaluronic acid, alginic acid, carrageenan, chondroitin, pectin,
chitosan, and derivatives, blends and copolymers thereof.
[0110] In one embodiment, the dopant is delivered in a gaseous
carrier fluid, such as nitrogen, hydrogen, argon, helium, air,
ethylene oxide, and combinations thereof. In another embodiment,
the dopant is delivered in a liquid carrier fluid. In one
embodiment, the liquid is also an etching liquid (basic or acidic)
In one embodiment, the dopant is delivered in an inert
environment.
[0111] Another embodiment relates to the chemical treatment of
metal surfaces for the purposes of adhesion. Good adhesion of
paints and polymeric coatings to metal surfaces is an area of
increasing technical importance. This technology can be used to
pre-treat a surface by impregnating it with compounds having
desired chemical functionality. These include but are not limited
to polymers or silica materials having siloxane groups.
[0112] The pretreatment can be used to lay down a very strongly
bound layer of seed polymer material on the surface. Further
polymer coatings could then be attached to this seed layer rather
than trying to attaching it directly to the surface of the
metal.
[0113] The dopant is not limited to one compound but could be any
combination of any of the materials listed or even any material(s)
that do(es) not have the necessary mechanical properties to
impregnate the surface if delivered singularly at high velocity to
the surface.
[0114] In one embodiment, the dopant can be any material so long as
it is passive, i.e., unreactive with the surface. It simply has to
be at the surface when the oxide layer is breeched by the abrasive
so that the oxide reforms around it.
[0115] In one embodiment, the dopant is nanocrystalline.
[0116] In one embodiment, the dopant is nanocrystalline
hydroxyapatite.
[0117] In one embodiment the abrasive has a suitable property
chosen from at least one of size, shape, hardness, and density to
break the oxide layer. In one embodiment, the abrasive has a modus
hardness ranging from 0.1 to 10, such as a modus hardness (Mohs)
ranging from 1 to 10, or a modus hardness ranging from 5 to 10. In
another embodiment, the abrasive has a particle size ranging from
0.1 .mu.m to 10000 .mu.m, such as a particle size ranging from 1
.mu.m to 5000 .mu.m, or a particle size ranging from 10 .mu.m to
1000 .mu.m.
[0118] Abrasive materials to be used in this invention include but
are not limited to shot or grit made from silica, alumina,
zirconia, barium titanate, calcium titanate, sodium titanate,
titanium oxide, glass, biocompatible glass, diamond, silicon
carbide, calcium phosphate, calcium carbonate, metallic powders,
carbon fiber composites, polymeric composites, titanium, stainless
steel, hardened steel, carbon steel chromium alloys, apatite grit
(e.g., MCD grit, Himed, N.Y.), and combinations thereof.
[0119] The pressure of the fluid jet will also be a factor in
determining the impact energy of the abrasive. The abrasive and
dopant(s) do not have to be delivered to the surface through the
same jet. They could be in any number of separate jets as long as
they deliver the solid components to the surface at the
substantially the same time, e.g., prior to reformation of the
oxide layer if the surface is a metal. This allows a large amount
of flexibility in optimizing the invention towards a specific need.
In one embodiment, the fluid jet is selected from wet blasters,
abrasive water jet peening machines, and wet shot peening machines.
In one embodiment, the at least one fluid jet operates at a
pressure ranging from 0.5 to 100 bar, such as a pressure ranging
from 1 to 30 bar, or a pressure ranging from 1 to 10 bar.
[0120] In another embodiment, the at least one fluid jet is
selected from dry shot peening machines, dry blasters, wheel
abraders, grit blasters), sand blasters(s), and micro-blasters. In
one embodiment, the at least one fluid jet operates at a pressure
ranging from 0.5 to 100 bar, such as a pressure ranging from 1 to
30 bar, or a pressure ranging from 3 to 10 bar.
[0121] In other embodiments, blasting equipment can be used in
conjunction with controlled motion such as CNC or robotic control.
The blasting can be performed in an inert environment.
[0122] In one embodiment, the article is an implantable medical
device. Exemplary medical devices include catheters, guide wires,
and baskets used in the removal of pathological calcifications. In
the case of biomedical devices it is desirable that the level of
impregnation of the abrasive itself in the surface is minimal. The
abrasive should further be biocompatible as it is likely that some
impregnation will occur.
[0123] In one embodiment, the article is a metal, such as those
metals chosen from pure metals, metal alloys, intermetals
comprising single or multiple phases, intermetals comprising
amorphous phases, intermetals comprising single crystal phases, and
intermetals comprising polycrystalline phases. Exemplary metals
include titanium, titanium alloys (e.g., NiTi or nitinol), ferrous
alloys, stainless steel and stainless steel alloys, carbon steel,
carbon steel alloys, aluminum, aluminum alloys, nickel, nickel
alloys, nickel titanium alloys, tantalum, tantalum alloys, niobium,
niobium alloys, chromium, chromium alloys, cobalt, cobalt alloys,
precious metals, and precious metal alloys. In one embodiment, the
metal is titanium.
[0124] In one embodiment the abrasive material is alumina (10 Mesh)
while the dopant is HA with a particle size range of 0.1 to 3
.mu.m. The mixed media is achieved by mixing the dopant and
abrasive between the ratio of 5:95 and 95:5 HA to Silica volume %
but more preferably between the ratio of 80:20 to 20:80 and most
preferably in the ratio range 60:40 to 40:60. The silica bead has a
Mohs hardness in the range of 0.1 to 10 but most preferably in the
range of 2 to 10 and most preferably in the range 5 to 10. This
mixed media is delivered to a titanium surface using a standard
grit blasting machine operating in the pressure range of 0.5 Bar to
20 Bar, such as a pressure range of 2 to 10 bar, or a pressure
range of 4 Bar to 6 Bar. The distance between the nozzle and the
surface can be in the range of 0.1 mm to 100 mm, such as a range of
0.1 mm to 50 mm, or a range of 0.1 mm to 20 mm. The angle of the
nozzle to the surface can range from 10 degrees to 90 degrees, such
as a range of 30 degrees to 90 degrees, or a range of 70 to 90
degrees.
[0125] In another embodiment the abrasive material is silica (10
Mesh) while the dopant is HA with a particle size range of 0.1 to 3
.mu.m. The mixed media is achieved by mixing the dopant and
abrasive between the ratio of 5:95 and 95:5 HA to alumina weight %
but more preferably between the ratio of 80:20 to 20:80 and most
preferably in the ratio range 60:40 to 40:60. The Alumina grit has
a Mohs hardness in the range of 0.1 to 10, such as a range of 2 to
10, or a range of 5 to 10. This mixed media can be delivered to a
titanium surface using a standard grit blasting machine operating
in the pressure range 0.5 Bar to 20 Bar, such as a pressure range
of 2 to 10 bar, a range of 4 Bar to 6 Bat. The distance between the
nozzle and the surface can range from 0.1 mm to 100 mm, such as a
range of 0.1 mm to 50 mm, or a range of 0.1 mm to 20 mm. The angle
of the nozzle to the surface can range from 10 degrees to 90
degrees, such as a range of 30 degrees to 90 degrees, or a range of
70 to 90 degrees.
[0126] One of ordinary skill in the art can appreciate the
influence of machine parameters including jet velocity, operating
pressure, venturi configuration, angle of incidence and surface to
nozzle distances on the extent of impregnation of the dopant in the
surface using these mixed media.
[0127] One of ordinary skill in the art can appreciate the effect
of the size, shape, density and hardness of the abrasive material
used on the extent of impregnation of the dopant in the surface
using these mixed media.
[0128] One of ordinary skill in the art can appreciate the effect
of the fluid stream itself, the blasting equipment using a gas
medium (typically air) the effects of using inert gases as a
carrier fluid e.g. N2 or noble gases such as Ar and He on the
extent of impregnation of the dopant in the surface using these
mixed media.
[0129] In the case of wet blasting equipment using a liquid as a
carrier fluid (normally water), One of ordinary skill in the art
can appreciate the effect of acidity and basicity on the extent of
impregnation of the dopant in the surface using these mixed
media.
[0130] As disclosed herein, the disclosed methods can be useful for
modifying the surfaces of medical devices. In the context of
medical device applications, dopants can be active (eliciting a
biological response) or passive (not eliciting a biological
response). Passive dopants can be conveyed to enhance lubricity or
render a substrate radio-opaque, of enhance wear characteristics or
enhance adhesion of an ad-layer, etc. Active agents can evoke a
response from the host tissue in vivo, enhancing the functionality
of the device or the surgery, or delivering a benefit as a
secondary function to the device.
EXAMPLES
Example 1
[0131] This Example describes the modification of titanium
substrates by delivering hydroxyapatite as the dopant in one
particle stream and alumina bead as the abrasive in a separate
particle stream using a twin nozzle ("twin blasting"). Table 1
summarizes the pre and post blasting methods.
TABLE-US-00001 TABLE 1 The experimental program to blast substrates
using various pre-blast and post-blasting combinations. Experiment
# Pre Blast Post Blast PH01 Twin blasting Al.sub.2O.sub.3 PH02 Twin
blasting Hydroxyapatite PH03 Twin blasting Twin blasting PH04
Hydroxyapatite Twin blasting PH05 Al.sub.2O.sub.3 Twin blasting
PH06 Hydroxyapatite Al.sub.2O.sub.3 PH07 Twin blasting 2 x n/a
speed
[0132] Experimental runs depositing various combinations of
Al.sub.2O.sub.3 and HA either with twin blasting or separately,
were carried out with a maximum of two blast passes--a per blast
pass and a post blast pass--on each experimental group. The powder
materials were stored in powder feeder hoppers, which formed part
of a Comco Accuflo Micro-blaster system. One hopper for each system
and at any one time two systems could be operated simultaneously.
Each micro-blaster system fed into a separate nozzle housed in a
Comco Advanced Lathe. Two nozzles were mounted on an adjustable
blast head configured to synchronize the flow from each nozzle to
the same point on the coupon's surface.
[0133] 100 micron particle size Alumina bead--Alox, (Mohs hardness
9,) was used in all test runs where twin blasting (HA and
Al.sub.2O.sub.3) or Al.sub.2O.sub.3 were run. The synthetic
Hydroxyapatite (lot #: 260-07205, Manufacturer: SAI, France) used
had a particle size range of 25 to 60 microns and was used in all
test runs where twin blasting (HA and Al.sub.2O.sub.3) or HA were
run.
[0134] In short both Accuflo micro-blasters are operating when the
twin blasting process is run and one or the other is turned off
when running the Al.sub.2O.sub.3 blast process (HA off) or the HA
blast process (Al.sub.2O.sub.3 off).
[0135] Five 15 mm square Grade 5 titanium coupons (Titanium 6AL-4V
Sheet Medical to ASTM F136 Spec) were treated for each test. The
surface of each was fully covered with in a raster fashion first
with the pre-blast treatment and then with the post-blast treatment
at a feed rate of 3.175 mmsec-1.
[0136] The blasting parameters were not varied, except to change
the blast head traverse speed for the final test.
[0137] The parameters were set as follows:
[0138] HA blast pressure: 60 PSI;
[0139] Alox blast pressure: 60 PSI;
[0140] HA nozzle ID: 0.030 inch;
[0141] Alox nozzle ID: 0.030 inch;
[0142] HA nozzle angle to surface: 80 degrees
[0143] Alox nozzle angle to surface: 80 degrees
[0144] Nozzle distance from surface: 0.5 inch
[0145] Following blasting, the coupons were subjected to a cleaning
treatment involving 20 minutes ultrasonic washing in isopropyl
alcohol to remove any material that was not intimately affixed to
the surface. After the ultrasonic cleaning the coupons were rinsed
with deionized water and air-dried in an oven at 40.degree. C. for
one hour.
[0146] Samples were submitted for XPS (X-Ray photoelectron
spectroscopy); FTIR (Fourier Transform Infrared Spectroscopy);
Surface Roughness analysis--Stylus Profilometry; to determine the
relative concentration of Ca, P, and Ti at the surface of each
sample in conjunction with the morphological characteristics of
each sample. Results for XPS analysis and stylus profilometry are
shown in Table 2.
TABLE-US-00002 TABLE 2 The XPS and Stylus Profilometry results of
the Ti substrates processed using various pre-blast and post-blast
combinations. Sample Mean Mean Mean Mean SD Sample No: Description
Ca/P % HA % Ti % Al Ra (nm) Ra (nm) PH01 1.sup.st twin blasting 1.8
5.4 4.66 9.30 549.67 35.91 2.sup.nd Al.sub.20.sub.3 only PH02
1.sup.st twin blasting 1.71 22.58 0.0 0 379.67 37.88 2.sup.nd HA
only PH03 1.sup.st twin blasting 1.73 19.52 1.54 0 437.17 72.85
2.sup.nd twin blasting PH04 1.sup.st Ha only 1.77 18.36 2.1 0
526.17 34.00 2.sup.nd twin blasting PH05 1.sup.st Al.sub.20.sub.3
1.79 17.27 1.74 2.10 494.17 23.34 2.sup.nd twin blasting PH06
1.sup.st Ha only 1.88 4.78 5.35 9.38 599.33 71.55 2.sup.nd
Al.sub.2O.sub.3 only PH07 Twin blasting 1.75 20.12 1.32 0 495.50
37.54 2 x speed
[0147] The data indicates that varying the pre-blast and post-blast
conditions as outlined in the experiment results in variation in
the % HA retaining on the surface, the introduction but also in
differences in the quantity and coverage of Hydroxyapatite on the
surface. Minimal variation in the Ca:P ratio occurs.
[0148] In the table it can be seen that when Al.sub.2O.sub.3 is
used as a separate blasting medium, some of it gets impregnated
into the surface of the Ti substrate. This can be seen in
experimental runs PH01, PH05 and PH06. The converse is also
true--when Al2O3 is not used as a separate medium but combined with
the twin blasting process, none of the Al2O3 particles get
impregnated into the Ti, and this can be seen in the remaining
samples, which are elaborated below. It should be noted that the
PH01 and PH06 groups demonstrate the highest roughness values of
all the groups, indicating that the post-blast with Al2O3 further
roughens a surface blasted with the twin blasting process and
giving rise to a dopant (HA) deposition.
[0149] This fact alone demonstrates that by varying the nature of
back to back micro-blasting operations, it is possible to either
incorporate or prevent the deposition of Al2O3 onto the Titanium
substrate. This implies that there is not a need to acid etch the
Ti after the treatment (to remove any Al2O3 particles impregnated
in the surface), as is the normal practice.
[0150] In sample PH02, pre-blasted with the twin blasting process
and post-blasted with the deposition of HA on its own, the % HA
retained on the surface is 22.5%, with respect to the other
elements, while displaying the least roughness of all the
experimental groups, indicating that the HA is filling up the
troughs on the surface created by the blasting processes. This is
further exemplified by the fact that there is no surface presence
of Titanium, as it is completely masked by the HA blanket
layer.
[0151] In sample PH03, pre-blasted and post-blasted with the twin
blasting process, in essence double blasting the substrate. This
revealed a similar % HA retained on the surface, i.e., 19.5%, with
a Titanium presence of 1.54%. The roughness is lower that other
twin blasting post-blasted groups (PH04 and PH05), indicating a
double filling of the troughs with HA in the Ti roughened surface
but not in the same manner as in PH03 where the HA blanket covers
all the Titanium substrate.
[0152] In sample PH04, the HA was deposited in the pre-blast step
followed then by the twin blasting process. It is known from
previous experimental work that the initial coating of HA is
loosely adherent on the substrate. The post-blast twin blasting
process further pummels this HA into the surface in conjunction
with depositing HA of its own. In either case 18.6% HA is manifest
on the surface, being consistent with previous twin blasting only
trials.
[0153] In group PH05, Al2O3 is deposited in the pre-blast step
followed then by the twin blasting process. There is a resultant
manifestation of 2.1 Aluminium on the surface from the Al2O3 only
pre-blast step, indicating that Al2O3 will anchor itself in
Titanium based substrates. All other aspects of this surface are as
one expects with the twin blasting process, i.e. Ti %, HA % Ca:P
ratio, surface roughness.
[0154] Group PH06 has a similar result to that of group PH01 and
this is because they both share a Al2O3 post-blast stet. Both
groups show high Aluminum % b retained on the surface and both have
high roughness values. The average Ti % and HA % on the surface is
the same for both indicating that irrespective of how the initial
step of placing HA on the surface is conducted, the post-blasting
with a abrasive-blast step only results in a burying of the HA deep
in the surface layer and high abrasive retention, while fresh
Titanium is churned up to the surface giving rise to an increase in
its manifestation over what would be expected.
[0155] Increasing the speed of the blast head traverse over the
titanium coupon has not had a detrimental effect on the levels of
HA deposited by the twin blasting only one step process. One would
have expected a less rough surface with less HA deposited and a
higher showing of Titanium on the surface. If anything there is a
slight improvement in the level of HA deposited on and in the
surface. This indicates that the twin blasting process for
depositing HA on a Titanium substrate is very robust and allow for
a doubling of the process speed with a consequent halving of the HA
quantity required to achieve the same surface result.
Example 2
[0156] A mixer (block) of FIG. 10 was used to deposit a dopant,
namely hydroxyapatite (HA), in the presence of an abrasive
(Al.sub.2O.sub.3) onto Grade V titanium.
[0157] The hydroxyapatite powder (from SAI, France) was loaded into
a power feeder unit (hopper) associated with a Comco Standard
Lathe. The abrasive (100 micron alumina, from Comco Inc, CA) was
loaded into a second powder feeder. Both powder feeders were
operating at a pressure of 90 psi and were connected to a mixer
device which consisted of a with two inlets and a single outlet
which ensured the two powder flows were blended together. The
output of the mixer was connected to a single microblast nozzle
inside the Comco Lathe. The output of this nozzle was used to blast
a 15 mm.times.15 mm CP titanium coupon (Titanium Sheet Grade 5
Medical). The nozzle to surface distance was 20 mm and the nozzle
was held at 90.degree. to the surface. The silicon carbide nozzle
had an orifice of 3.8 mm long by 1 mm wide and traversed the
surface at 1 cm per sec.
[0158] After blasting, the treated titanium samples were subjected
to an air blasting process operating at 120 psi to remove any
material that was not intimately affixed to the surface. Samples
were ultrasonically cleaned in iso-propyl alcohol for 5 minutes.
The sample was rinsed and then ultrasonically washed in isopropyl
alcohol for a further five minutes. Samples were then dried in air
and analysed using SEM-EDX to determine the relative concentration
of elements present at the surface of each coupon. This analysis
revealed a surface with 7.9% Ca, 5.7% P, 14.9% Ti and a large
amount of C and O. The high levels of Ca, P, C and O is consistent
with the deposition of a hydroxyapatite layer on the surface of the
titanium coupon.
Example 3
[0159] This Example describes a coaxial nozzle design of FIG. 7.
The coaxial nozzle included a first gas stream in the centre of the
device and second gas stream coaxially surrounding the first
stream. This allowed a gas flow to carry a first stream of
particles down the centre of the coaxial device. A second gas
stream flows outside of this and surrounds the first gas stream and
can transport a second set of particles. The second gas stream was
arbitrarily set at an incident angle of 14 degrees to the vertical.
This ensured that the second gas stream could converge with the
first gas stream, thereby focusing both sets of particles on to a
single zone on a substrate.
[0160] This coaxial nozzle was mounted on a Comco Standard Lathe
micro-blasting station and this was used to deposit a series of
hydroxyapatite (HA) coatings on to a titanium substrate (Grade V Ti
coupons, 15.times.15.times.1 mm dimensions). The substrates were
cleaned prior to coating by immersing in ultrasonically agitated
IPA for five minutes. Hydroxyapatite (SAI, France) was used as the
dopant and either MCD grit (Himed, N.Y.) or 100 um alumina (Comco,
Calif.) was used as an abrasive.
[0161] The coaxial nozzle was maintained 20 mm above the substrate
and moved at a speed of 13 mm/sec along the surface of the
substrates. The centre flow of particles was directed into a
microblast nozzle with 1.2 mm diameter outlet. The second outer
flow of particles was directed through a circular orifice with an
opening of 200 microns. All powders were flowed at a pressure of 90
psi.
[0162] The following coatings were deposited:
[0163] Sample 1: MCD was flowed through the first central opening
and HA was supplied through the second outer coaxial opening. This
deposited a coating onto the surface of the titanium. SEM-EDX
analysis determined that the HA level (Ca+P) was 16% (atomic weight
%).
[0164] Sample 2: The HA flow was turned off and the test was
repeated with only the MCD grit flowing through the centre. This
produced a HA level of 12%, due to the presence of microblasted
apatite MCD grit on the surface.
[0165] Sample 3. Alumina was introduced through the first central
channel and HA was again allowed to flow through the outer coaxial
channel. This produced a coating with 14% HA.
* * * * *