Room temperature ferromagnetic gadolinium silicide nanoparticles
A particle usable as T 1 and T 2 contrast agents is provided. The particle is a gadolinium silicide (Gd 5 Si 4 ) particle that is ferromagnetic at temperatures up to 290 K and is less than 2 μm in diameter. An MRI contrast agent that includes a plurality of gadolinium silicide (Gd 5 Si 4 ) particles that are less than 1 μm in diameter is also provided. A method for creating gadolinium silicide (Gd 5 Si 4 ) particles is also provided. The method includes the steps of providing a Gd 5 Si 4 bulk alloy; grinding the Gd 5 Si 4 bulk alloy into a powder; and milling the Gd 5 Si 4 bulk alloy powder for a time of approximately 20 minutes or less.
1. A ferromagnetic material, comprising:
a gadolinium silicide (Gd 5 Si 4 ) particle, wherein the Gd 5 Si 4 particle is ferromagnetic at temperatures up to 290 K and wherein the Gd 5 Si 4 particle is less than 2 μm in diameter.
2. The material according to claim 1 , wherein the Gd 5 Si 4 particle remains ferromagnetic at temperatures up to 310 K.
3. The material according to claim 1 , wherein the Gd 5 Si 4 particle is less than 1 μm in diameter.
4. The material according to claim 1 , wherein the Gd 5 Si 4 particle is less than 500 nm in diameter.
5. The material according to claim 1 , wherein the Gd 5 Si 4 particle includes 5 wt % or less Gd 5 Si 3 .
6. An MRI contrast agent, wherein the MRI contrast agent comprises:
a plurality of gadolinium silicide (Gd 5 Si 4 ) particles, wherein the Gd 5 Si 4 particles are less than 1 μm in diameter wherein the Gd 5 Si 4 particles are ferromagnetic at temperatures up to 290 K.
7. The MRI contrast agent according to claim 6 , wherein the Gd 5 Si 4 particles are ferromagnetic at temperatures up to 310 K.
8. A method for creating the ferromagnetic material of claim 1 comprising the steps of:
providing a Gd 5 Si 4 bulk alloy;
grinding the Gd 5 Si 4 bulk alloy into a Gd 5 Si 4 bulk alloy powder; and
milling the Gd 5 Si 4 bulk alloy powder for a time of approximately 20 minutes or less.
9. The method of claim 8 , wherein the grinding and milling steps further comprise using an inert atmosphere.
10. The method of claim 8 , wherein the using an inert atmosphere step further comprises using a noble gas atmosphere.
11. The method of claim 8 , wherein the milling step further comprises ball milling.
12. The method of claim 11 , wherein the ball milling step further comprises using a milling media with a mass ratio of milling media to Gd 5 Si 4 bulk alloy powder of between 2:1 and 10:1.
13. The method of claim 12 , wherein the using a milling media step further comprises using stainless steel balls having two different sizes.
14. The method of claim 13 , wherein the step of using stainless steel balls having two different sizes further comprises using a first size stainless steel balls with a diameter of 11.1 mm and using a second size of stainless steel balls with a diameter of 6.3 mm.
15. The method of claim 14 , further comprising the step of providing a ratio of the second size of stainless steels balls to the first size of stainless steel balls of 2:1.
16. The method of claim 8 , wherein the step of providing a Gd 5 Si 4 bulk alloy further comprises providing a pure phase alloy.
17. The method of claim 8 , wherein the providing a Gd 5 Si 4 bulk alloy step further comprises the steps of:
supplying a stoichiometric quantity of at least 99.9% purity gadolinium metal;
supplying a stoichiometric quantity of at least 99.999% purity silicon;
melting the gadolinium and silicon together in an inert atmosphere at least once; and
cooling the mixture of gadolinium and silicon at a rate fast enough to avoid neighboring phases.
18. The method of claim 17 , wherein the melting step is performed at least four times.
19. The method of claim 17 , wherein the melting step further comprises using an electric arc furnace on a water-cooled copper hearth to melt the gadolinium and silicon.