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In this paper, we study the elastic properties of the entropy-stabilized oxide (Mg, Co, Ni, Cu, Zn)O using experimental and first principles techniques. Our measurements of the indentation modulus on grains with a wide range of crystallographic orientations of the entropy-stabilized oxide revealed a high degree of elastic isotropy at ambient conditions. First principles calculations predict mild elastic anisotropy for the paramagnetic structure, which decreases when the system is considered to be non-magnetic. When the antiferromagnetic state of CoO, CuO, and NiO is accounted for in the calculations, a slight increase in elastic anisotropy is observed, suggesting a coupling between magnetic ordering and the orientation dependent elastic properties. Furthermore, an examination of the local structure reveals that the isotropy is favored through local ionic distortions of Cu and Zn—due to their tendencies to form tenorite and wurtzite phases. The relationships between the elastic properties of the multicomponent oxide and those of its constituent binary oxides are reviewed. These insights open up new avenues for controlling isotropy for technological applications through tuning composition and structure in the entropy-stabilized oxide or the high-entropy compounds in general. [ABSTRACT FROM AUTHOR]

The physical and mechanical properties of two barium alkali silicate glasses were determined as a function of temperature. Their Young's modulus and Poisson's ratio were determined by resonant ultrasound spectroscopy; their viscosity, thermal expansion, and glass transition temperature were determined using a thermomechanical analyzer. The wetting behavior of the two glasses on alumina and 8 mol% yttria stabilized zirconia (8 YSZ) substrates was determined by measuring contact angles in air as a function of temperature and time. Values of Young's modulus for both glasses were in good agreement with those predicted by the Makishima and MacKenzie model. The physical and mechanical properties of these glasses are discussed in the context of their potential use for sealing applications in solid-oxide fuel cells. [ABSTRACT FROM AUTHOR]

Effective models of the mechanical behavior of thermoelectric materials under device conditions require knowledge of temperature-dependent elastic properties. Between room temperature and 600 K, resonant ultrasound spectroscopy measurements of three skutterudite thermoelectric materials, i.e. n-type Co0.95Pd0.05Te0.05Sb3 (both with and without 0.1 at.% cerium dopant) and p-type Ce0.9Fe3.5Co0.5Sb12, showed that the Young's and shear moduli decreased linearly with temperature at a rate of −0.021 GPa/K to −0.032 GPa/K, and −0.011 GPa/K to −0.013 GPa/K, respectively. In contrast, the Poisson's ratio was approximately 0.22 for the three materials and was relatively insensitive to temperature. For temperatures >600 K, the elastic moduli decreased more rapidly and resonance peaks broadened, indicating the onset of viscoelastic behavior. The viscoelastic relaxation of the moduli was least for Ce-doped n-type material, for which grain boundary precipitates may inhibit grain boundary sliding which in turn has important implications concerning creep resistance. In addition, powder processing of the n- and p-type materials should be done cautiously since submicron-sized powders of both the n- and p-type powders were pyrophoric. [ABSTRACT FROM PUBLISHER]

Test procedures for the mechanical evaluation of diesel particulate filter (DPF) substrate materials have been developed and applied for the characterization of porous cordierite under ambient conditions. Specifically the double-torsion test method was employed to characterize fracture toughness and slow crack behavior while resonant ultrasound spectroscopy (RUS) was used to determine the elastic properties of the substrate walls. A dry grinding procedure was developed to fabricate test specimens for these tests. The fracture behavior of porous cordierite was related to the pore structure inside the filter wall. Implications of the test results on the mechanical reliability of DPFs are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Amorphous and crystalline β-eucryptite (LiAlSiO4) specimens were prepared with controlled grain sizes and varying levels of microcracking, and their elastic moduli were determined using resonant ultrasound spectroscopy. It was found that the relationship between Young’s modulus, Poisson’s ratio and degree of microcracking in these materials can be described well with fracture-mechanics-based models. It was also found that if glassy β-eucryptite is considered to be a microcracked medium in which broken Si–O bonds, with respect to the crystalline material, constitute microcracks, then its elastic properties can be described equally well by these models. Such considerations are explained by noting the differences in atomic bond density among the different states of the material and by accounting for differences in strain energy release rate measurements on glass and ceramic specimens. [Copyright &y& Elsevier]

Abstract: The thermoelectric material PbTe has been used in a wide variety of power generator applications. However, there is limited mechanical property data available for PbTe for temperatures above room temperature. This paper reports dynamic elastic moduli measured via resonant ultrasound spectroscopy on undoped and PbI2-doped polycrystalline PbTe between room temperature and 773K; in addition, the room temperature carrier concentration was measured by a Hall effect experiment. The Young’s modulus and shear modulus of PbTe decreased linearly with temperature above room temperature, while the Poisson’s ratio exhibited either monotonic increase or decrease with temperature. The Young’s modulus and shear modulus values obtained during heating and cooling agreed to within 1%. The dynamic elastic moduli data obtained in this study compared well in general with literature data. The difference observed between the current study and other literature studies is explained in terms of the carrier concentration effect on elastic moduli. [Copyright &y& Elsevier]

Mechanical properties, namely tensile and flexural strengths and elastic modulus, of polyphenylene-sulfide (PPS) bonded Nd–Fe–B magnets have been studied from −40 to 180 °C. The ultimate tensile strength (Sut) of PPS bonded magnets decreases with increasing temperature. The tensile strength of PPS bonded Nd–Fe–B magnets was reduced significantly above 100 °C. At 180 °C, the PPS bonded magnets still exhibit a Sut of 16–18 MPa. For bonded magnets with about 60% volume fraction of Nd–Fe–B powder, the PPS bonded magnet shows about twice the tensile strength and half the ultimate strain compared to that of Nylon bonded magnet. At room temperature, the flexural strength is, in general, comparable to the tensile strength. Dynamic elastic modulus measured using the impact resonance method was in good agreement with the elastic modulus obtained from tensile tests. Scanning Electron Microscopy analyses of the fractured surfaces revealed two distinct failure mechanisms. Debonding along the Nd–Fe–B particle and PPS interface is the main cause for failures at 100 and 180 °C. The fracture of Nd–Fe–B particle was observed on the fracture surface of specimens tested at −40 and 23 °C. [Copyright &y& Elsevier]