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In this work, the oxidation properties of austenitic 316L stainless steel powder and sintered porous support were investigated at the temperature range of ~600-750 䨽 for 100 hours in ambient air. Oxidation kinetics was determined by continuous thermogravimetry and analyzed employing parabolic rate law. It was observed that oxidation leads to the formation of an oxide scale, with substantial oxidation occurring at = 650 ℃ in the powder. The porous steel support was fabricated using the tape casting method with two distinct pore former concentrations. The microstructural features of both the powder and support were investigated by X-ray diffractometry and scanning electron microscopy coupled with energy-dispersive X-ray analysis. The mechanical properties of the metal support were examined before and after oxidation via a microhardness test. The effect of porosity on the resulting properties of the metal support was also highlighted. In summary, 316L stainless steel support suits SOCs applications below 600 ℃. [ABSTRACT FROM AUTHOR]

Oxygen-defective metal oxides, e.g., acceptor-doped CeO2, demonstrate exceptionally large electrostrictive responses compared to state-of-the-art electromechanically active ceramic materials. Recent investigations focus on trivalent acceptor (A3+) doped ceria and surmise that giant electrostriction on these compounds depends on the electroactive polarizable elastic dipoles associated with electronic defects in the lattice, e.g., oxygen vacancies and polarons. Similarly, to relaxor piezoelectrics, electromechanical responses in doped-ceria strictly depend on the applied field frequency, i.e., time-dependent, revealing a complex interplay between the electro-chemo-mechanic effect in the materials and a loss of properties above 1–10 Hz. This work demonstrates the electromechanical properties of divalent (A2+) calcium-doped ceria (CDC) polycrystalline ceramics with various doping levels (Ce1−xCaxO2−x, x = 0.025–0.15). All the CDC compounds illustrate a steady and high electrostrictive strain coefficient (M33) value exceeding 10−18 m2 V−2 across frequencies between 10−1 and 103 Hz. Notably, the M33 is slightly influenced by the nominal oxygen vacancy concentration, CaO segregation, and the microstructure. These key findings unveil a new form of electromechanical effects in calcium-doped ceria that are rigorously stimulated by the strong electro-steric interaction of pairs. [ABSTRACT FROM AUTHOR]

In the customary way of clay brick production by burning soil in Bangladesh and other developing countries, a good number of bricks (approximately 13%) are severely overburnt due to uncontrolled distribution of temperature in the kiln. These bricks are dark red in color, severely distorted, and swollen. These bricks are considered totally useless and are not allowed in any construction work. In this study, the feasibility of utilizing these overburnt bricks as coarse aggregates in highway pavement projects was explored. Routine laboratory tests such as the Los Angeles abrasion, water absorption, specific gravity, and unit weight, were used to compare the properties of the overburnt bricks with the best possible quality picked or pick-Jhama (Type A) bricks from the same stockyards in Bangladesh. It was found that overburnt brick aggregates are much stronger, less absorptive, and denser in general than the ones from the picked or pick-Jhama (Type A) bricks. Therefore, these bricks may be conveniently and economically used as highway pavement coarse aggregates. Manufacturers may also be encouraged to produce such high strength brick with adequate quality control measures. CE Database subject headings: Bricks; Aggregates; Pavements; Absorption; Gravity.

We couple the spark plasma sintering (SPS) technique with the ball mill process to fabricate a new electro-chemo-mechanical functional carbon–metal oxide hybrid material. Graphene oxide (GO) or carbon nanotubes (CNT) carbon allotropes are mechanically mixed with gadolinium-doped ceria (CGO). SPS allows consolidating dense carbon–metal oxide hybrids with uniform morphology and high crystallinity. The carbon allotropes and SPS lead to highly reduced CGO. The metal oxide presents a chemically tuned grain boundary with highly oxygen defect concentration at the near-grain boundary region. The hybrid interface can hinder chemical oxidation at high-temperature depending on the carbon allotropy. As a result, the hybrid materials with CNT display high ionic conductivity and activation energy, reducing the space charge layer and charge distribution. This feature enhances the electromechanical properties at room temperature. We especially disclose electrostriction in the CNT-based hybrids superior to the pure CGO and follow a non-Newnham relation. Notably, integrating carbon materials with metal oxides using the SPS can generally be applied to synthesising a range of functional metal oxide composite. [ABSTRACT FROM AUTHOR]

Oxygen-defective ceria, e.g. Gd-doped ceria, shows giant electromechanical properties related to a complex local rearrangement of its lattice. Although they are not entirely identified, the electroactive mechanisms arise from cation and oxygen vacancy (VO) pairs (i.e. Ce–VO), and the local structural elastic distortion in their surroundings. Here, we study the geometry and behaviour of Ce–VO pairs in a grain boundary-free bulk Ce0.9Gd0.1O1.95 single crystal under an AC electric field of ca. 11 kV cm−1. The analysis was carried out through X-ray absorption spectroscopy (XAS) techniques at the Ce L-III edge. Using Density Functional Theory (DFT) calculations, we investigated the effects of the strain on density of states and orbitals at the valence band edge. Our research indicates that electrostriction increases at low temperatures. The electromechanical strain has a structural nature and can rise by one order of magnitude, i.e., from 5 × 10−4 at room temperature to 5 × 10−3 at −193 °C, due to an increase in the population of the electrically active pairs. At a constant VO concentration, the material can thus configure heterogeneous pairs and elastic nanodomains that are either mechanically responsive or not. [ABSTRACT FROM AUTHOR]

Mass diffusion controls material structuring from the atomic to the macro-scale defining properties and functionalities. We show here that surface energy in Ce0.9Gd0.1O3-d shaped nanocrystals, i.e. nanocubes, nanorods and spherical nanoparticles, can control solid state diffusion mechanisms over a long range, leading to extreme microstructural diversity. [ABSTRACT FROM AUTHOR]

Sun exposure is the main cause of squamous ( SCC) and basal cell carcinoma ( BCC) although pattern and amount differ by cancer type, and sun sensitivity is the major host risk factor. Our study investigated risk factors and residential ambient UV in a population-based sample of Australian 45 and Up Study participants: 916 BCC cases, 433 SCC cases, 1224 controls. Unconditional logistic regression models adjusting for key covariates demonstrated 60% increased BCC risk and two-fold increased SCC risk with sun sensitivity, and three- and four-fold increased risk, respectively, with solar keratoses. BCC but not SCC risk increased with higher early-life residential UV in all participants (odds ratio ( OR) = 1.54; 95% CI 1.22-1.96 for intermediate; OR = 1.31; 95% CI 1.03-1.68 for high UV at birthplace) and similarly in Australian-born participants ( P-values < 0.05). Risk of SCC but not BCC increased with long-term cumulative sun exposure assessed by self-reported outdoor work ( OR 1.74, 95% CI 1.21-2.49). In conclusion, sun sensitivity is important for both cancers, early-life UV but not cumulative UV appears to increase BCC risk, the former an apparently novel finding, and SCC risk appears only to be related to long-term cumulative sun exposure. [ABSTRACT FROM AUTHOR]

Electrical conductivity and acoustic loss Q−1 of single crystalline Li(Nb,Ta)O3 solid solutions (LNT) are studied as a function of temperature by means of impedance spectroscopy and resonant piezoelectric spectroscopy, respectively. For this purpose, bulk acoustic wave resonators with two different Nb/Ta ratios are investigated. The obtained results are compared to those previously reported for congruent LiNbO3. The temperature dependent electrical conductivity of LNT and LiNbO3 show similar behavior in air at high temperatures from 400 to 700 °C. Therefore, it is concluded that the dominant transport mechanism in LNT is the same as in LN, which is the Li transport via Li vacancies. Further, it is shown that losses in LNT strongly increase above about 500 °C, which is interpreted to originate from conductivity-related relaxation mechanism. Finally, it is shown that LNT bulk acoustic resonators exhibit significantly lower loss, comparing to that of LiNbO3. [ABSTRACT FROM AUTHOR]

Compositionally complex oxides (CCOs) or high-entropy oxides (HEOs) are new multielement oxides with unexplored physical and functional properties. In this work, we report fluorite structure-derived compositionally complex zirconia with composition Zr 1- x (Gd 1/5 Pr 1/5 Nd 1/5 Sm 1/5 Y 1/5 ) x O 2-δ ( x = 0.1 and 0.2) synthesized in solid-state reaction route and sintered via hot pressing at 1350 °C. We explore the evolution of these oxides' structural, microstructural, mechanical, electrical, and electromechanical properties regarding phase separation and sintering mechanisms. Highly dense ceramics are achieved by bimodal mass diffusion, composing nanometric tetragonal and micrometric cubic grains microstructure. The material exhibits an anomalously large electrostriction response exceeding the M 33 value of 10 -17 m 2 /V 2 at room temperature and viscoelastic properties of primary creep in nanoindentation measurement under fast loading. These findings are strikingly similar to those reported for doped ceria and bismuth oxide derivates, highlighting the presence of a large concentration of point defects linked to structural distortion and anelastic behavior, which are characteristics of nonclassical ionic electrostrictors.