Neutron diffraction analysis of the microstructure of dispersion-hardening steels

Neutron diffraction was employed in order to determine microdeformations in samples of stainless austenitic dispersion-hardened steels subjected to the action of high temperatures (to 700°С) during different times (up to 12 h). Experiments were conducted on a high-resolution neutron diffractometer using the timeof- flight method. The analysis performed showed systematic changes in the parameters and microdeformations of the crystal lattice. The high level of the diffractometer resolving power made it possible to reveal some important additional details of the microstructure of dispersion-hardened steels as compared to the results obtained earlier on a diffractometer with monochromatic neutron beam.     

Micro- and macroscopic thermal expansion of stabilized aluminum titanate

The lattice expansion of aluminum titanate (AT) obtained by firing a mixture of alumina, rutile, strontium and calcium carbonate and silica was measured using neutron and laboratory X-ray diffraction. The microscopic data are compared with macroscopic measurement completed by dilatometry.A powder and a compact rod sample were compared to assess the influence of micro residual stresses locked into the solid structure at grain level, which could possibly be relieved upon grinding.Results show good correlation between neutron and X-ray diffraction techniques. They also show that a compact material behaves differently than a powder, contrary to what happens for other porous ceramics such as cordierite. The integrity factor model was used to rationalize the results and predict grain level stresses in all crystal directions and all phases (AT, Strontium aluminum silicate, alumina and residual glass). Calculation show that the AT c-axis is always under compression while all other crystal directions and phases are under tension. Those micro-stresses do not undermine the macroscopic mechanical properties of the material and confer to it its interesting properties like low thermal expansion and enhanced strain tolerance.     

Phase Transformations of a CeCo3-Based Intermetallic Hydride at Temperatures from 200 to 950°C

Inorganic Materials - Samples obtained by heating a CeCo3-based intermetallic hydride with a low hydrogen content (1.0 H/FU) to a high temperature in an inert atmosphere have been characterized by...     

High damping in Fe-Ga-La alloys: Phenomenological model for magneto-mechanical hysteresis damping and experiment

Ferromagnetic high damping (FHA) alloys with a wide temperature range from-150 ℃ to 300 ℃ have unique application value in extreme environments.In the present work,the damping behaviors of Fe21Ga-xLa (x =0.12 wt.％,0.24 wt.％,0.47 wt.％,1.18 wt.％,and 2.33 wt.％La) alloys have been studied in detail,and a new phenomenoiogical model has been proposed.With the increase of La content,the Laves phase (LaGa2) in the matrix increases gradually,and the resistance opposing the domain movement increases as well.Combined with the results of synchrotron radiation X-ray diffraction,neutron diffraction,and magnetic domain observation,the resistance mainly comes from three parts: the average stress related to the lattice distortion of the matrix,the average stress related to the increasing area energy of domain walls (DWs),and the average stress related to the increasing demagnetization energy induced by the Laves phase.Different from the traditional method of reducing internal stress through annealing to improve the damping capacity,the proper internal stress barriers are necessary to Barkhausen jumps to dissipate energy.Therefore,proper doping to balance resistance and mobility of DWs is a reliable way to improve damping capacity.Meanwhile,for Fe-Al and Fe-Cr based Alloys,the new model also has a good fitting effect.This study provides a theoretical and experimental reference for improving the functional properties of ferromagnetic alloys.     

Interrelation among superstructural ordering,oxygen nonstoichiometry and lattice strain of double perovskite Sr2FeMoO6−δ materials

Journal of Materials Science - Double perovskite ceramics Sr2FeMoO6?δ having different amount of antisite disordering and oxygen content are prepared by the solid-phase reaction method...     

Structure of thermally desorbed CeNi<Subscript>3</Subscript>-based hydrides

CeNi₃H _x (x = 0.7, 0.8, 1.0, 1.8, 3.4, 3.8) hydrides have been prepared through hydrogen desorption from CeNi₃ hydrogenated at low (p _{H 2} = 0.01 GPa) and high (p _{H 2} = 0.2 GPa) hydrogen pressures. Using X-ray and neutron diffraction, the hydrides are shown to be isostructural with CeNi₃ (sp. gr. P6₃/mmc, no. 194). The lattice parameters of the hydrides vary appreciably with hydrogen content. The sequence of hydrogen release from different interstices in the desorption process is shown to be opposite to that of hydrogen uptake in the hydrogenation process. The solid-solution range in the desorbed hydrides is much broader than that upon hydrogenation. The extent of the solid solution is influenced by the phase composition of the parent intermetallic compound.     

Synthesis and structure of CeNi<Subscript>3</Subscript>D<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>

We describe the synthesis of CeNi₃D _x deuterides at normal and high deuterium pressures. X-ray and neutron diffraction techniques were used to identify the position and determine the positional parameters of the metal and deuterium atoms. The deuterides are isostructural with the parent compound CeNi₃ but have a larger unit cell. Increasing the deuterium content to the composition CeNi₃D_5.2 leads to partial amorphization of the material. The variation in unit-cell volume observed at low and high deuterium contents indicates that the metal-deuterium bonds are partially ionic and partially metallic.     

Hydriding of TiMo alloys at high hydrogen pressures

We studied the interaction of Ti_0.40Mo_0.60 and Ti_0.34Mo_0.66 alloys with hydrogen and obtained hydrogen desorption isotherms at pressures of up to 250 MPa. At high hydrogen pressures, we observed the formation of Ti_0.40Mo_0.60Н_1.1 and Ti_0.34Mo_0.66Н_0.8 hydride phases. According to X-ray diffraction data, the hydrides consisted of phases with a body-centered cubic and face-centered cubic (CaF₂ structure) lattices. The structure of the deuteride based on the Ti_0.40Mo_0.60 alloy was studied by neutron diffraction. We identified the sites occupied by deuterium atoms and determined their occupancies.     

Temporal characterization of static CMOS RAM,compiled by Subμm design rules

Temporal characterization is considered of ready circuit topological variants of RAM compilers. Their number may reach 0.5–10⁶. The problem is an inappropriate combination of accuracy-speed indicators of all known algorithms and software for calculating signal delays, if the specified calculation is performed for each case directly in the compiler. A number of conceptually related principles are proposed to consider the precision-performance ratio within acceptable limits.