1. A catalyst obtained by:
a) preparing a spinel with the general formula AxA\u20321-xByB\u20322-yO4,
wherein A is selected from the group consisting of Co, Cu, Fe, Ni and combinations thereof;
wherein A\u2032 is Mn, of which up to two-thirds may be replaced by Mg, Zn and combinations thereof;
wherein B is selected from the group consisting of Co, Fe, Mn, and combinations thereof;
wherein B\u2032 is selected from the group consisting of Al, Cr, and combinations thereof;
wherein x and y are nonzero numbers less than 1 and represent the respective moles of A and B species;
wherein 0.25 is less than or equal to (1\u2212x+y)(2\u2212y); and wherein (1\u2212x+y)(2\u2212y) is less than 0.44; and wherein (1\u2212x+y)(2\u2212y) is greater than 0.52 and wherein (1\u2212x+y)(2\u2212y) is less than or equal to 0.60; and
b) activating the spinel in a reducing atmosphere to yield metal particles dispersed within andor on the spinel.
2. The catalyst of claim 1 wherein the metal particles have a composition selected from the group comprising A, B, and (A, B).
3. The method of claim 1 wherein the reducing atmosphere is hydrogen at temperatures between 800 and 1100 degrees Celsius.
4. The method of claim 1 wherein the activated catalyst may be oxidized at temperatures between 800 and 1100 degrees Celsius to yield the spinel.
5. A cermet catalyst material, comprising:
a spinel matrix defining at least one spinel grain; and
a plurality of metal particles at least partially embedded the at least one spinel grain;
wherein the spinel has a general formula
A
x
\u2062
A
1
–
x
\u2032
\u2061
B
y
\u2062
B
2
–
y
\u2032
\u2062
O
4
–
x
–
3
\u2062
y
2
;
wherein A is selected from the group including Co, Cu, Fe, Ni and combinations thereof;
wherein A\u2032 is selected from the group including Mg, Mn, Zn and combinations thereof;
wherein B is selected from the group including Co, Fe, Mn, and combinations thereof;
wherein B\u2032 is selected from the group including Al, Cr, and combinations thereof;
wherein when the at least one spinel grain is in a first oxidizing atmosphere and at a temperature above about 800 degrees Celsius the metal particles are absorbed into the spina matrix in the form of metal cations; and
wherein when the at least one spinel grain is in a reducing atmosphere and at a temperature between about 700 degrees Celsius and about 1100 degrees Celsius the metal cations emerge from the spinel matrix to yield a plurality of metal particles at least partially embedded in the at least one spinel grain.
6. The cermet catalyst material of claim 4 wherein the spinel matrix defines a plurality of spinel grains, and wherein the plurality of spinel grains are sintered together to define a spinel body.
7. The cermet catalyst material of claim 4 wherein the metal particles are between 1 nanometer and 100 nanometers across and wherein the metal particles are generally positioned at grain boundaries, grain surfaces and in intragranular pores.
8. The cermet catalyst material of claim 4 wherein 0.25 is less than or equal to (1\u2212x+y)(2\u2212y); and wherein (1\u2212x+y)(2\u2212y) is less than 0.44; and wherein (1\u2212x+y)(2\u2212y) is greater than 0.52 and wherein (1\u2212x+y)(2\u2212y) is less than or equal to 0.60; and wherein x and y represent the respective moles of A and B species.
9. A method for preparing a spinel cermet material, comprising:
mixing trivalent cations with divalent cations to define an admixture;
heating the admixture to yield a plurality of spinel grains defining a spinel matrix; and
generally evenly dispersing metal particles throughout the spinel matrix;
wherein the metal particles are positioned at grain boundaries, grain surfaces and in intragranular pores;
wherein the spinel matrix has a general formula
A
x
\u2062
A
1
–
x
\u2032
\u2061
B
y
\u2062
B
2
–
y
\u2032
\u2062
O
4
–
x
–
3
\u2062
y
2
;
wherein A is selected from the group including Co, Cu, Fe, Ni and combinations thereof;
wherein A\u2032 is selected from the group including Mg, Mn, Zn and combinations thereof;
wherein B is selected from the group including Co, Fe, Mn and combinations thereof;
wherein B\u2032 is selected from the group including Al, Cr and combinations thereof; and wherein x and y are both nonzero numbers less than 1;
wherein reducible metal cations may be absorbed into the spina structure at elevated temperatures in an atmosphere having a first oxygen partial pressure.
10. The method of claim 8 wherein absorbed metal cations are desorbed from the spinel structure upon exposure to elevated temperatures in an atmosphere having a second, lower oxygen partial pressure.
11. The method of claim 8 wherein 0.25 less than or equal to (1\u2212x+y)(2\u2212y); and wherein (1\u2212x+y)(2\u2212y) is less than 0.44; and wherein (1\u2212x+y)(2\u2212y) is greater than 0.52 and wherein (1\u2212x+y)(2\u2212y) is less than or equal to 0.60;
wherein x and y represent the moles of A and B species, respectively.
12. A cermet catalyst material, comprising:
a spinel matrix defining a spinel grain; and
a plurality of metal particles embedded in or on the spinel grain;
wherein when the spinel grain is in a environment the metal particles are absorbed into the spinel matrix in the form of metal cations;
wherein the first environment is defined as having an oxidizing atmosphere and a temperature in excess of about 800 degrees Celsius;
wherein when the spinel grain is in a second environment the metal cations emerge from the spinel matrix to yield a plurality of metal particles adhering to the spinel grain;
wherein the second environment is defined as having non-oxidizing atmosphere and at a temperature between about 600 and 1100 degrees Celsius,
wherein the spinel has a general formula AxA\u20321-xByB\u20322-yO4-x-(3y2);
wherein A is selected from the group consisting of Co, Cu, Fe, Ni and combinations thereof;
wherein A\u2032 is selected from the group consisting of Mg, Mn, Zn and combinations thereof;
wherein B is selected from the group consisting of Co, Fe, Mn, and combinations thereof;
wherein B\u2032 is selected from the group consisting of Al, Cr, and combinations thereof;
wherein x and y represent the respective moles of respective A and B species;
wherein the composition includes A, A\u2032, B and B\u2032 species; and
wherein 0.25 is less than or equal to (1\u2212x+y)(2\u2212y); and wherein (1\u2212x+y)(2\u2212y) is less than 0.44; and wherein (1\u2212x+y)(2\u2212y) is greater than 0.52 and wherein (1\u2212x+y)(2\u2212y) is less than or equal to 0.60.
13. The cermet catalyst material of claim 11 wherein the metal particles have a composition of A, B, andor (A, B).
14. The cermet catalyst material of claim 11 wherein A\u2032 and B species may desorb from the spinel matrix in the form of A\u2032O, BO, or (A\u2032, B)O and combinations thereof.
15. A catalyst material, comprising:
a spinel matrix defining a spinel grain; and
a plurality of metal particles embedded on the spinel grain;
wherein when the spinel grain is in a first oxidizing environment at a temperature above 800 degrees Celsius the metal particles are absorbed into the spinel matrix in the form of metal cations;
wherein when the spinel grain is in a second less oxidizing environment at a temperature between 600 degrees Celsius and 1100 degrees Celsius the metal cations emerge from the spinel matrix and to form a plurality of metal particles adhering to the spinel grain;
wherein the spinel has a general formula
A
x
\u2062
A
1
–
x
\u2032
\u2061
B
y
\u2062
B
2
–
y
\u2032
\u2062
O
4
–
x
–
3
\u2062
y
2
;
wherein A is selected from the group consisting of Co, Cu, Fe, Ni and combinations thereof;
wherein A\u2032 is selected from the group consisting of Mg, Mn, Zn and combinations thereof;
wherein B is selected from the group consisting of Co, Fe, Mn, and combinations thereof;
wherein B\u2032 is selected from the group consisting of Al, Cr, and combinations thereof;
wherein x and y represent the respective moles of A and B species;
wherein the spinel grain includes A, A\u2032, B and B\u2032 species; and
wherein 0.25 is less than or equal to (1\u2212x+y)(2\u2212y); and wherein (1\u2212x+y)(2\u2212y) is less than 0.44; and wherein (1\u2212x+y)(2\u2212y) is greater than 0.52 and wherein (1\u2212x+y)(2\u2212y) is less than or equal to 0.60.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A surgical apparatus for removing tissue from an interior portion of a body during a surgical procedure comprising:
a pouch assembly including a support and a pouch, said pouch including at least a first sac having a first diameter and a second sac having a second diameter, the first sac having an open distal end in fluid communication with an open proximal end of the second sac, the first diameter being greater than the second diameter and the second sac having a closed distal end, the pouch being dimensioned and arranged for receiving the tissue;
a drawstring operatively coupled to a proximal region of the first sac; and
an elongate tubular member for introducing the pouch, the pouch assembly being attached to the elongate tubular member.
2. The surgical apparatus of claim 1, wherein the first sac proximal end has a proximal sleeve for receiving a spring member supported by the elongate tubular member.
3. The surgical apparatus of claim 2, wherein the first sac has a distal sleeve disposed distally of the proximal sleeve.
4. The surgical apparatus of claim 3, further comprising a drawstring disposed in the distal sleeve.
5. The surgical apparatus of claim 4, wherein the first sac defines a weakened portion adjacent the support.
6. The surgical apparatus of claim 1, wherein the pouch is formed from a translucent material.
7. The surgical apparatus of claim 1, wherein the first sac has a substantially uniform diameter.
8. The surgical apparatus of claim 7, wherein the second sac has a substantially uniform diameter.
9. The surgical apparatus of claim 1, wherein the first sac has a tapered configuration.
10. The surgical apparatus of claim 9, wherein the second sac has a tapered configuration.
11. The surgical apparatus of claim 1, wherein the pouch has a reinforced band overlapping the first sac and the second sac.
12. The surgical apparatus of claim 1, wherein the elongate tubular member has a drive rod disposed therein, the pouch assembly being operably attached to the drive rod.
13. The surgical apparatus of claim 12, wherein the tubular member is sized so that the pouch assembly is received therein and the support is attached to the drive rod so that movement of the drive rod from a first position in which the pouch assembly is disposed within the tubular member to a second position in which the pouch assembly exits the tubular members.
14. The surgical apparatus of claim 13, wherein the drawstring is received in the tubular member and attached to a handle for pulling the drawstring proximally and thereby closing the pouch.
15. The surgical apparatus of claim 14, wherein the drive rod is attached to a handle for pulling the handle and moving the drive rod from the first position to the second position.