Face-centered cubic structure alloy particles and method of manufacturing same
View Patent ↗Alloy particles of an alloy having a face-centered cubic structure comprise at least one selected from Fe and Co and at least one selected from Pt and Pd as principal components. The alloy particles have a TEM-measured average grain size (D TEM ) of not more than 50 nm, and a single crystallinity (D TEM )/(D X ) that is less than 1.50, where (D X ) is X-ray crystallite size. These alloy particles can be advantageously manufactured by using the polyol process to synthesize the alloy particles in the presence of a complexing agent.
1. Alloy particles of an alloy having a face-centered cubic structure, comprising:
T and M in such a composition ratio that, when T is one or two selected from Fe and Co, and M is one or two selected from Pt and Pd, X in formula T x M 1-x is within the range of 0.3 to 0.7, and, with respect to (T+M), no more than 30 atomic percent (including zero percent) of metallic elements other than T and M, with the remainder being unavoidable impurities,
the alloy particles having a TEM-measured average grain size (D TEM ) of not more than 50 nm, and a single crystallinity (D TEM )/(D x ) that is less than 1.50, where (D x ) is X-ray crystallite size,
in which 90 or more out of 100 particles satisfy the equation (1) below and equation (2) below is satisfied,
0.90X av ≦X 1 , X 2 , . . . X 100 ≦1.10X av (1)
Standard deviation σ of X 1 , X 2 , . . . X 100 ≦20% (2)
provided that with respect to the value of X in the formula T x M 1-x , X av represents a measured particle value (value of X in the mean constituent of a particle assemblage), and of X 1 , X 2 , . . . X 100 represents the measured X value of each of 100 particles arbitrarily selected when the measurement field of view contains 1000 or more particles.
2. The alloy particles according to claim 1 , wherein primary particles comprise up to five crystal grains.
3. The alloy particles according to claim 1 , wherein the particles are spaced apart in a distributed state.
4. The alloy particles according to claim 1 , wherein junction between particles is suppressed by mutual reaction.
5. The alloy particles according to claim 1 , wherein a surface active agent is adhered to the surface of each particle.
6. The alloy particles according to claim 1 , wherein a coupling agent or modified coupling agent is adhered to the surface of each particle.
7. The alloy particles according to claim 1 , wherein TEM-based observation shows almost no surface pitting of particles.
8. The alloy particles according to claim 1 , wherein heat treatment is used to effect phase change from a face-centered cubic structure to a face-centered tetragonal structure.
9. The alloy particles according to claim 1 , wherein the metallic elements other than T and M are at least one selected from the group Au, Ru, Rh, Os and Ir.
10. The alloy particles according to claim 1 , wherein the metallic elements other than T and M are at least one selected from the group Au, Ag, Cu, Sb, Bi and Pb.