Abstract: EXAFS technique was used to quantitatively determine the local structure evolutions of Ni-B and Ni-Ce-Bultrafine amorphous alloys prepared by chemical reduction during the annealed process. The results show that the average bond length R_j, coordination number N, thermal disorder factor σ_Tand static disorder factor σ_Sare 0.275 nm, 11.9, 0.0069 nm, 0.034 nm; 0.215 nm, 2.7, 0.0055 nm, 0.0038 nm, and 0.276 nm, 12.4, 0.0067 nm, 0.035 nm; 0.214 nm, 2.9, 0.0058 nm, 0.0042 nm for the Ni-Ni and Ni-Bfirst neighbor shells of Ni-Band Ni-Ce-Bultrafine amorphous alloys, respectively. It is indicated that the σ_Sof Ni-Ni shell is rather larger, about four or five times as large as that of σ_T, and one order larger than that of σ_Sof Ni-Bshell. Ni-Bsample is crystallized after being annealed at 300 ℃, and its R_Ni—Ni as well as σ_Sare 0.254 nm and 0.011 nm, respectively. However, the crystallization temperature of Ni-Ce-Bsample increases about 100 ℃ due to the addition of 0.3% Ce element. The local structure around Ni atom for the Ni-Bsample annealed at 500 ℃ is fully similar to that of Ni foil. For the Ni-Ce-Bsamples annealed at 500 ℃, the σ_Sof Ni-Ni shell is 0.0073 nm and the N of Ni-Bshell is 1.2. It implies that the Ni lattice produced from the crystallization of Ni-Ce-Bamorphous alloys is significantly distorted and the interaction between Ni and Batoms is strongly increased by the effect of Ce element.

Key words: EXAFS, Ni-B, Ni-Ce-B, Ultrafine amorphous alloy