Several ternary Fe – Ge - C alloys with Ge contents ranging between 3 and 27 at. % have
been studied. The structure, anelastic, thermodynamic and kinetic phenomena in Fe - 3, - 12, -
19/21 and – 27 Ge have been examined by X-ray diffraction (XRD), heat flow (DSC), vibrating
sample magnetometry (VSM), optical-light and scanning electron microscopy, and internal friction
(IF) methods. The Fe - 3Ge and Fe - 12Ge alloys form b.c.c. solid solutions. A Snoek-type internal
friction (P1) peak is recorded in the Fe - 3Ge alloy with parameters similar to those for α-Fe:
Н = 0.86 eV, Δ = 0.015, β = 0.72 and τ0 = 2 × 10-15 s, showing that Ge atoms have little influence on
the diffusivity of carbon in iron. The Fe - 12Ge alloy, with a Curie point around 1008 K, has several
IF peaks: a broad Snoek-type (P1 and P2), the P3 peak caused by structural changes in as quenched
specimens during annealing, and a P4 (Zener) peak at higher temperature (Tm ≈ 773 K at f = 2 Hz,
β ≈ 0.7). The Fe - 21Ge alloy has bcc or bcc plus hexagonal structure depending on heat treatment.
The structure of the Fe3Ge-type alloy (Fe - 27Ge) consists mainly of hexagonal phases, i.e. hexagonal
ε (D019), β (B81), and cubic ε′ (L12), and exhibits corresponding magnetic ordering transitions
below 873 K which are not well-reflected in the common Fe - Ge phase diagrams. In particular a
high stability of the hexagonal ε phase at room temperature is noted. A broad internal friction relaxation
peak with Δ = 0.0036, H ≈ 1.8 eV and τ
0 = 2 ⋅ 10-17 s is found in Fe – 27 Ge and is classified
as a double Zener peak in the ε and β two-phase mixture.
Internal defects and strain in nanoparticles can influence their properties and therefore measuring these values is relevant. Powder diffraction techniques (neutron and synchrotron) are successfully used to characterize internal strain in the core-shell Ni(3)Si(Al)-SiO(x) nanoparticles having mean diameters of approximately 80 nm. The nanoparticles, which are strain-free after extraction from the bulk alloys, develop internal strain on heating. Both micro- and macro-strains can be measured from the analysis of Bragg peak shift and broadening. It is identified that differences in thermal expansion coefficient of the metallic core and the amorphous shell of the nanoparticles, as well as partial disordering of the L1(2) ordered core phase, are the main causes of strain evolution. Synchrotron measurements also detected partial crystallization of the amorphous silica shell.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.