Oxide-dispersion-strengthened (ODS) ferritic alloys are fascinating materials for future high temperature energy production technologies. MgAl2O4 ODS alloy incorporating nanoscale oxide particles were produced by mechanical milling (MM) followed by hot isostatic pressing (HIP). The MgAl2O4 nanoscale oxide particles were formed during the HIP process by the addition of MgO and Al2O3 to the Fe–Cr matrix. Microstructural evolution of ODS alloys was structurally characterized at each step of the elaboration processes by means of scanning electron microscope (SEM), transmission electron microscope (TEM), and x-ray diffraction (XRD). The observations of structure of the mixed powders in ODS alloys after MM indicated that the initial powders, coupled with the original MgO and Al2O3 powders, got fractured by severe plastic deformation and ultrafine bcc grains (∼17 nm) of the matrix and amorphous phase composed of Mg, Al, and O were formed during MM. The main driving force for the formation of amorphous phase comes from the increase of volume fraction of bcc Fe grain boundary and the increase of interfacial energy due to the decrease in the size of MgO and Al2O3 powders. The MgAl2O4 nanoscale oxide particles formed at 1173 K which was far below the traditional sintering temperature of the raw material. And the structures of MgAl2O4 nanoscale oxide particles were observed by TEM.

Cu(In,Ga)Se2 (CIGS) semiconductors were prepared by arc melting and the vacuum solid reaction. CIGS nanoparticles were synthesized by the mechanical alloy method. The influences of various ball-milling speeds on phase structures for CIGS nanoparticles were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystal structures and unit-cell parameters of CIGS nanoparticles were determined using TREOR program and the least squares method. A Rietveld structural refinement was used to determine the atomic occupations and atomic numbers of CIGS prepared under various ball-milling speeds. The least size of agglomerated CIGS nanoparticles should be around 200 nm. CIGS nanoparticles milled at various milling speeds with a tetragonal chalcopyrite structure were obtained according to XRD analyses. However, Ga content in CIGS depends on milling speeds. Based on the structural refinements, the unit-cell parameters are a = 5.693(8)–5.744(9) Å and c = 11.334(9)–11.524(4) Å with gallium content ranging from 0.3 to 0.5. The atomic occupations are corresponding to the 4a crystal site for Cu atoms, the 4b site for In and the 8d site for Se. Ga prefers to occupy the 4b crystal site.

Nanostructured WC-Co powders obtained by mechanical milling were investigated by combination of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) techniques. HRTEM image analysis shows that in the as-milled nanostructured powder, many WC grains contain stacking faults lying on the plane{10.0}. Analysis of phase images showed that these defects were nearly periodically ordered along the [10.0] direction. Based on these observations, a structural model is proposed for the WC grains with ordered stacking faults, which is in fact equivalent to a superstructure of WC with space group Amm2. When this model is introduced together with the normal WC structure (space group P6m2) into the Rietveld refinement, a much better agreement between the calculated and experimental XRD profiles is obtained. This study allowed obtaining the lattice parameters, grain size, microstrain and other structural information on the as-milled powders.