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In this work, the microstructure and microwave dielectric properties of novel MgTiO3-x wt% MgAl2O4 (x = 5, 10, 15, 20) composite ceramics were investigated. MgTiO3 and MgAl2O4 compounds were synthesized by conventional solid-state reaction method and the composites were fabricated by wet mixing, pressing in die and sintering in the temperature range of 1200–1350 oC for 5 h in air. X-ray analysis of the sintered sample proved that no reaction occurred between the two phases during sintering process. The results proved that sinter-ability of MgTiO3 is improved by adding MgAl2O4 second phase up to 10 wt% and for more than it, sintered density of the fabricated composite decreased due to higher refractoriness of MgAl2O4 phase. Dielectric constant of the fabricated composites decreases from around 16.4 to 15 by increasing the amount of secondary phase from 0 to 20 wt% and nearly follow a linear relation in semi logarithmic scale. The temperature coefficient of resonant frequency became more negative by increasing the amount of used MgAl2O4. The quality factors values were determined in the range of 140,000–160,700 GHz, reaching the maximum of 160,700 GHz for the composite includes 10 wt% of MgAl2O4 second phase. [ABSTRACT FROM AUTHOR]

In the present study, feasibility of aluminothermic reduction of molybdenum oxide by microwave oven was studied. Furthermore, the effect of compaction pressure and the amount of used Al and CaO as flux on aluminothermic reduction of molybdenum oxide were investigated. Thermodynamic analysis of the corresponding reaction indicated that, aluminothermic reduction of MoO3 was possible at all temperatures. XRD patterns and thermodynamic investigation of reaction products indicated that aluminothermic reduction of molybdenum oxide progressed through the formation of intermediate phases such as Al2 (MoO4)3 and MoO2 where the final products were elemental Mo and Al2O3. Results revealed that by increasing the compaction pressure of the pellet, undesired phases of molybdenum dioxide (MoO2) and aluminum molybdate Al2(MoO4)3 can be detected among the final products. By increasing the amount of Al more than stoichiometric ratio, the intermediate phases, such as MoO2, were produced. The results indicated that by adding CaO to the MoO3-Al system, the unwanted molybdenum dioxide (MoO2) and aluminum molybdate (Al2 (MoO4)3) compounds were successfully reduced to Mo. In the present work, metallic molybdenum could easily and successfully be separated from Al2O3 slag, as the side product of the reaction, in molten phase, based on the difference in their densities. [ABSTRACT FROM AUTHOR]

A novel cathode material of (Nd0.9La0.1)1.6Sr0.4Ni0.75Cu0.25O3.8 (NLSNC4), is synthesized by solid state reaction and is further investigated in combination with samarium doped ceria (SDC) as composite cathodes including 0, 10, 30, 50, and 70 of SDC electrolyte phase. The X‐ray diffraction analysis showed that NLSNC4 was produced in pure phase and was chemically compatible with SDC electrolyte. Electrical conductivities of single phase and composite cathode materials along with their electrochemical performances on SDC electrolytes in symmetric cells were measured by DC four‐probe method and electrochemical impedance spectroscopy (EIS), respectively. Results indicated that the maximum electrical conductivity is 135.56 S cm−1 at 350 °C, measured for single phase NLSNC4, sintered at 1,300 °C. Polarization resistance of pure NLSNC4 cathode was 2.71 Ω cm2 at 800 °C, and NLSNC4‐x wt.% SDC composite cathodes displayed Rp value of 0.35, 0.14, 0.12, and 0.32 Ω cm2 at 800 °C, for x = 10, 30, 50, and 70, respectively. [ABSTRACT FROM AUTHOR]

In this study, the microhardness, wear and corrosion resistance of electroless deposited Ni-W-P-B4C, Ni-P-B4C, Ni-W-P and Ni-P coatings on AZ91D magnesium alloy were investigated. The hardness of the Ni-W-P-B4C and Ni-P-B4C composite coatings was more than that of the Ni-P and Ni-W-P coatings. The Pin on disk wear test results showed that the Ni-W-P-B4C and Ni-P-B4C composite coatings have a better wear resistance in comparison to the Ni-W-P and Ni-P coatings. The worn surfaces exhibited a change in the wear mechanism from adhesive for the Ni-P coating to abrasive for the Ni-W-P and Ni-W-P-B4C coatings and combination of adhesive and abrasive for the Ni-P-B4C composite coating. Tafel test has been used to assess corrosion performance of the specimens; the Ni-W-P coatings exhibited the best corrosion resistance while the Ni-W-P-B4C and Ni-P-B4C composite coatings showed less corrosion performance than the Ni-W-P and Ni-P coatings respectively. [ABSTRACT FROM AUTHOR]

The current work assesses the impact of structural differences between stable and metastable ZrO2 precursors on the mechanochemical preparation of BaZrO3. Monoclinic (m-ZrO2) and tetragonal (t-ZrO2) zirconia polymorphs were prepared without stabilizing additives by slow alkaline precipitation. Highenergy milling of the individual ZrO2 precursors induced different partial transformations in each case. The as-synthesized m-ZrO2 powders showed partial conversion to the tetragonal polymorph on mechanical activation, reaching about 10% t-ZrO2 after 420 min accompanied by increases in strain. In contrast, the as synthesized t-ZrO2 powders underwent the inverse transformation to the monoclinic phase, producing about 50% m-ZrO2 after 120 min with the liberation of strain. The t-ZrO2 precursor was shown to exhibit the higher reactivity with barium peroxide, yielding significantly earlier formation of barium zirconate under room-temperature mechanosynthesis. The progress of the mechanochemical formation of BaZrO3 has been discussed with respect to the differing behaviour of the ZrO2 precursors upon mechanical activation and associated thermodynamic perspectives. [ABSTRACT FROM AUTHOR]

Crystal structure and oxide ion conductivity of a series of Ti and Ti-Cu double substituted Bi4V2O11 compounds, Bi2V(1-x)TixO(11-x)/2 (0.085 ≤ x ≤ 0.15), and Bi2V0.9Cu(0.1-x)TixO5.35+x (0 ≤ x ≤ 0.1), were investigated using X-ray powder diffraction and ac impedance spectroscopy in the temperature and frequency range of 100–700°C and 10-2–107 Hz, respectively. Structural phase transitions, α → β and β → γ, occur as a function of composition in Ti substituted compounds for which the γ is evidenced to be stable at room temperature when x exceeds 0.125. For all Ti-Cu double substituted compounds studied, the room temperature phase was identified to be γ phase. The required amount of Ti for γ phase stabilization at room temperature was significantly reduced and the conductivity improved when Cu substituted a part of Ti. Therefore, for the Bi2V0.9Cu(0.1-x)TixO5.35+x (0 ≤ x ≤ 0.075) compounds the ionic conductivity increased and activation energy decreased with decreasing x. At low temperature, the highest ion conductivity was obtained for Bi2V0.9Cu0.1O5.35. At high temperature (T>500°C), a different behavior was observed. The total conductivity increased at first with decreasing x values down to x = 0.05 and then decreased. The maximum conductivity was obtained for Bi2V0.9Cu0.05Ti0.05O5.4, and the activation energy decreased with decreasing x values, such as what happened at low temperature. [ABSTRACT FROM AUTHOR]

Crystal structure and oxide ion conductivity of a series of Ti and Ti-Cu double substituted Bi4V2O11 compounds, Bi2V(1-x)TixO(11-x)/2 (0.085 ≤ x ≤ 0.15), and Bi2V0.9Cu(0.1-x)TixO5.35+x (0 ≤ x ≤ 0.1), were investigated using X-ray powder diffraction and ac impedance spectroscopy in the temperature and frequency range of 100–700°C and 10-2–107 Hz, respectively. Structural phase transitions, α → β and β → γ, occur as a function of composition in Ti substituted compounds for which the γ is evidenced to be stable at room temperature when x exceeds 0.125. For all Ti-Cu double substituted compounds studied, the room temperature phase was identified to be γ phase. The required amount of Ti for γ phase stabilization at room temperature was significantly reduced and the conductivity improved when Cu substituted a part of Ti. Therefore, for the Bi2V0.9Cu(0.1-x)TixO5.35+x (0 ≤ x ≤ 0.075) compounds the ionic conductivity increased and activation energy decreased with decreasing x. At low temperature, the highest ion conductivity was obtained for Bi2V0.9Cu0.1O5.35. At high temperature (T>500°C), a different behavior was observed. The total conductivity increased at first with decreasing x values down to x = 0.05 and then decreased. The maximum conductivity was obtained for Bi2V0.9Cu0.05Ti0.05O5.4, and the activation energy decreased with decreasing x values, such as what happened at low temperature. [ABSTRACT FROM AUTHOR]

This report describes characteristic features and clinical presentation of six young patients (ranging in age from five to 25 years) with various congenital forms of pulmonary arteriovenous fistulas as well as one 21-year old patient with traumatic intrapulmonary arteriovenous fistula. The former six patients were cyanotic, had clubbing of the digits and exertional dyspnea; two, additionally, had telangiectasia. All patients underwent cardiac catheterization and pulmonary angiography. None had pulmonary hypertension. Angiographically, four had diffuse arteriovenous fistulas in both lungs (Figures 1 and 3 to 5) and two had arteriovenous fistulas localized in one pulmonary segment. Four patients were additionally studied with radionuclide angiography and pulmonary perfusion scintigraphy. In three of these, substantial right-to-left shunt in the region of the lungs was detected; the diagnosis could not be established in only one of the latter with a small traumatic intrapulmonary arteriovenous shunt of less than 10%. While noninvasive methods provide adjunctive diagnostic support, pulmonary angiography is still required to assess, with certainty, the nature and localization of the lesion. In cyanotic patients with no evidence of cardiac disease, differential diagnostic consideration should be given to pulmonary arteriovenous fistulas.