[en] The structure-microstructure and color parameters of the Mg_1-xYb_(2/3)x□_(1/3)xS (0≤x≤0.45) (□: cation vacancy) were investigated. The samples present exclusively the NaCl-type average structure up to x=0.35, when a phase with spinel-type structure is observed. Its composition, measured with X-ray energy dispersive spectroscopy (XEDS), corresponds to an intermediate phase between the NaCl-type (MgS) and the normal spinel (MgYb₂S₄) structures. The selected area electron diffraction patterns (SAEDPs) show diffuse scattering attributed to short-range order (SRO) in the cation sublattice. Extended defects along <1 1 1>_NaCl (x=0.30) and along <1 1 1>_spinel (x=0.35 and x=0.45) have been observed both in the SAEDPs and in the corresponding high resolution transmission electron microscopy (HRTEM) images. The samples yellow color variation was characterized with reflectance spectra in the visible region. This system has possible applications as inorganic pigments in plastics and paints due to its high color quality

[en] Highlights: • Strain behaviour of EUROFER97-2 under low cycle fatigue tests at room temperature and 550 °C. • Softening behaviour is not observed at low strain at RT and is very low at low strain and 550 °C. • Microstructure characterization by means of STEM on as-received and after fatigued tests. • Different damage deformation mechanism detected depending on the strain range and temperature. -- Abstract: Low cycle fatigue (LCF) behaviour of EUROFER97 version 2 was studied in normalized plus tempered conditions within a wide total strain range of 0.4–1.8% at room temperature (RT) and 550 °C. At the lowest strain (0.4%) EUROFER97-2 shows very low softening behaviour at both temperatures. However, by increasing the strain amplitude, the material showed an instant hardening followed by a sharp softening up to rupture and fatigue life was reduced. In-depth microstructural characterization by STEM in thin foils and also in a carbon extraction replica was performed on selected samples strained at 0.4, 0.8, 1 and 1.8% at both RT and 550 °C. The microstructural development is based on the rearrangement and/or annihilation of dislocations, which lead to a sub-grain formation and eventually growth, specially enhanced at 550 °C. The microstructural modifications, in regard to dislocations and sub-grain structures, are more intense as the strain amplitude applied is increased. No significant changes in composition, size, and distribution of M23C6 and MX precipitates were observed. Consequently, it is demonstrated that the fatigue life of EUROFER97-2 at room temperature and at 550 °C is strongly dependent on dislocation evolution.

[en] Pure EFDA Iron was irradiated under triple ions beam (Fe + He + H) at 350 °C, 450 °C and 550 °C respectively to a nominal 40 dpa with a uniform He concentration of ∼14 appm He/dpa and H content of ∼50 appm H/dpa at depth between 1 and 2 μm. Cavity characteristics (size, morphology, distribution and population) at each irradiation temperature have been thoroughly studied by TEM using FIB lamellae, showing bubble formation at all irradiation temperatures with several differences between one to another experimental condition. At 350 °C homogeneous distribution of small cavities with sizes in the range of 2–4 μm was observed. However, irradiations at 450 °C and 550 °C led to non-homogeneous distribution of cavities with a wide range of sizes. Additionally, it was detected at these temperatures, preferential nucleation of bubbles within the ferritic grains exhibiting rounded and faceted shapes. Faceted cavities with sizes larger than 16 nm were detected at 450 °C and 550 °C.

[en] Highlights: • Influence of chemical composition tuning on secondary phases • Role of the V and N content on M₂X precipitation • C and N contents on MX and M₂X The composition of new eigth 9% Cr reduced activation ferritic/martensitioc steels (RAFMs) has been finely tuned in order to increase the amount of fine MX precipitates and reduce coarse M₂₃C₆ carbides through the application of thermomechanical treatments. The microstructural investigations by TEM/STEM and EELS have shown M₂₃C₆, M₂X (Cr₂N), and MX (Ta, V, and Ti-rich) precipitates after tempering at 750 °C/2 h. Higher N contens (0.04–0.03 wt%) seems to favored M₂X precipitation over MX with V contents round 0.2 wt%. MX-Ti rich presents sizes larger than MX (Ta or V rich). EELS anlysis have shown that the MX (Ta, V and Ti rich) precipitated after tempering at 750 °C/2 h are mainly carbo-nitrides. Composition, size, number density and carbon and nitrogen content on MX and M₂X is discussed in terms of the composition of each Alloy.

[en] In the Sb–Nb–S system four new misfit layer phases have been found and carefully investigated via Transmission Electron Microscopy (TEM). Their structures are of composite modulated structure type with stoichiometries that can be formulated as (SbS)_1_+_δ(NbS_2)_n; for n=1, δ~1.14 and 1.19; for n=2, δ~1.18 and for n=3, δ~1.19. Selected Area Electron Diffraction (SAED) patterns show an almost commensurate fit between the pseudo-tetragonal (SbS) and the pseudo-orthohexagonal (NbS_2)_n subcells along the misfit direction a, with 3(SbS)≈5(NbS_2), being b the same for both sub-lattices and c the stacking direction. For n=1, a commensurate phase with 4a_S_b_S=7a_N_b_S_2 has also been observed. In addition to the characteristic misfit and associated modulation of the two sub-structures, a second modulation is also present which appears to be primarily associated with the (SbS) sub-structure of both the n=1 and n=2 phases. High Resolution Transmission Electron Microscopy (HRTEM) images show ordered stacking sequences between the (SbS) and (NbS_2)_n lamellae for each of the four phases, however, disordered intergrowths were also occasionally found. Most of the crystals showed different kinds of twinning defects on quite a fine scale. Many crystals showed curled up edges. In some cases the lamellar crystals were entirely folded giving rise to similar diffraction patterns as found for cylindrical crystals. - Graphical abstract: Idealized structure models of the first three members of the homologous series (SbS)_1_+_δ(NbS_2)_n. - Highlights: • Transmission Electron Microscopy study of misfit layer sulfides (SbS)_1_+_δ(NbS_2)_n. • The structures consist of a (SbS) layer interleaved between n (NbS_2) layers. • Two different members n=1, one n=2 and one n=3 have been studied. • Twinning, intergrowths and different modulations in the (SbS) substructure

[en] Highlights: • Development by thermomechanical treatment of new generation of RAFM steels for fusion applications. • Effects of tempering on secondary precipitation (M₂₃C₆, M₂X, and MX) and martensite transformation. • Influence of alloy chemistry refinement on amount, distribution, and size of precipitates.

[en] The structures of two intercalation compounds, Ge_∼0.2NbSe₂ and Ge_∼0.3NbS₂ were investigated by single crystal X-ray diffraction and electron microscopy (selected area electron diffraction (SAED), high resolution electron microscopy (HRTEM) and X-ray microanalysis by energy dispersive spectroscopy (XEDS)). Crystal structure determinations of the average structure of the intercalation compounds 2H-Ge_0.217NbSe₂ and 4H-Ge_0.288NbS₂ are reported: the selenide compound crystallizes in the space group P6₃/mmc with a = 3.4560(9) A and c = 12.966(3) A and adopts the 2H-NbSe₂ structure-type, while the sulfide compound crystallizes in the P6₃mc space group, with a = 3.3392(9) A and c = 25.404(7) A with a structure-type 4H_c-NbS₂ which it is known for TaSe₂. In both structures the germanium atoms are located in the empty octahedral positions of the van der Waals gap between the NbX₂ (X = S, Se) layers. Electron diffraction patterns from several Ge_xNbSe₂ crystal flakes show different superstructures and exhibit diffracted diffuse intensity: weak satellites corresponding to a₀√(3)xa₀√(3) and 2a₀ x 2a₀ superstructures were observed for x ∼ 0.15 (a₀ is the basal lattice parameter of the host structure). For x ∼ 0.25-0.33, the same type of satellite is observed with a stronger intensity. For x ∼ 0.5 only satellites corresponding to the a₀√(3)xa₀√(3) superstructure were present. In the case of Ge_xNbS₂, with 0.10 < x < 0.25, the germanium atoms are ordered in domains with an a₀√(3)xa₀√(3) superstructure. In some crystals disorder along the c-axis has been observed.

[en] In the Sb-Nb-S-Se system, a new misfit layer compound (MSL) has been synthesized and its structure was determined by combining single crystal X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. It presents a composite crystal structure formed by (SbS_1-xSe_x) slabs stacking alternately with double NbS₂ layers and both can be treated as separate monoclinic subsystems. The (SbS_1-xSe_x) slabs comprise a distorted, two-atom-thick layer with NaCl-type structure formed by an array of {SbX₅} square pyramids joined by edges (X: S, Se); the NbS₂ layers consist of {NbS₆} trigonal prisms linked through edge-sharing to form sheets, just as in the 2H-NbS₂ structure type. Both sublattices have the same lattice parameters a = 5.7672(19) A, c = 17.618(6) A and β = 96.18(3)^o, with incommensurability occurring along the b direction: b₁ = 3.3442(13) A for the NbS₂ subsystem and b₂ = 2.8755(13) A for the (SbS_1-xSe_x) subsystem. The occurrence of diffuse scattering intensity streaked along c^* indicates that the (SbS_1-xSe_x) subsystem is subjected to extended defects along the stacking direction.