High-temperature corrosion characteristics of yttria-stabilized zirconia material in molten salts of LiCl-Li2O and LiCl-Li2O-Li

The isothermal and cyclic corrosion behavior of yttria (Y₂O₃)-stabilized zirconia (ZrO₂) in a LiCl-Li₂O molten salt were investigated at 650 °C in an argon atmosphere. During isothermal and cyclic corrosion tests in the molten salt of LiCl-Li₂O for 168 h and 7 thermal cycles, the corrosion rate was very low, whereas under the molten salt of LiCl-Li₂O-Li for 168 h, the corrosion rate was almost 10 times higher than that in the molten salt of LiCl-Li₂O. No corrosion product was detected until 168 h for the isothermal corrosion test, however, after 7 thermal cycles, a very-low-intensity Li₂ZrO₃ peak was detected at the beginning stage of the chemical reaction between ZrO₂ and Li₂O. Additionally, in the molten salt of LiCl-Li₂O-Li for 168 h, a large amount of Li₂ZrO₃ was formed, with evidence of marked cracks, pores, and spallations on the corroded surface. The introduction of Y₂O₃-stabilized ZrO₂ was beneficial in increasing the hot corrosion resistance of the structural materials used to handle molten salts containing Li₂O at elevated temperature without forming a lithium at the cathode during the electrolytic reduction process.     

Formation and Microwave Dielectric Properties of the Mg2V2O7 Ceramics

The formation process and microwave dielectric properties of the Mg₂V₂O₇ ceramics were investigated. The MgV₂O₆ phase that was formed at around 450°C interacted with remnant MgO above 590°C to form a homogeneous monoclinic Mg₂V₂O₇ phase. Finally, this monoclinic Mg₂V₂O₇ phase was changed to a triclinic Mg₂V₂O₇ phase for the specimen fired at 800°C. Sintering at 950°C for more than 5 h produced high-density triclinic Mg₂V₂O₇ ceramics. In particular, the Mg₂V₂O₇ ceramics sintered at 950°C for 10 h exhibited the good microwave dielectric properties of ɛ_r=10.5, Q × f =58 275 GHz, and τ_f=−26.9 ppm/°C.     

Effect of Bi2O3 Addition on the Sintering Temperature and Microwave Dielectric Properties of Zn2SiO4 Ceramics

Bi₂O₃ was added to a nominal composition of Zn_1.8SiO_3.8 (ZS) ceramics to decrease their sintering temperature. When the Bi₂O₃ content was <8.0 mol%, a porous microstructure with Bi₄(SiO₄)₃ and SiO₂ second phases was developed in the specimen sintered at 885°C. However, when the Bi₂O₃ content exceeded 8.0 mol%, a liquid phase, which formed during sintering at temperatures below 900°C, assisted the densification of the ZS ceramics. Good microwave dielectric properties of Q × f =12,600 GHz, ɛ_r=7.6, and τ_f=−22 ppm/°C were obtained from the specimen with 8.0 mol% Bi₂O₃ sintered at 885°C for 2 h.     

Fabrication and characterization of a Ni-YSZ anode support using high-frequency induction heated sintering (HFIHS)

Ni-YSZ cermet anode supports solid oxide fuel cells (SOFCs) were fabricated by high-frequency induction heated sintering (HFIHS) under 60 MPa pressure with powders synthesized by the glycine nitrate process (GNP) as well as mechanically mixed commercial powders. The HFIHS method created a uniformly porous microstructure without abnormal grain growth compared to the conventional sintering method. Samples sintered by HFIHS show higher strength and electrical conductivity than conventionally sintered samples, even though they have similar porosity.     

Electrochemical performance of Ni1−xFex–Ce0.8Gd0.2O1.9 cermet anodes for solid oxide fuel cells using hydrocarbon fuel

Ni_1?xFe_x bimetallic-based cermet anodes were investigated for hydrocarbon-fueled solid oxide fuel cells. Ni_1?xFe_x–Ce_0.8Gd_0.2O_1.9 cermet anodes were synthesized using a glycine nitrate process, and their electrical conductivity and the amount of carbon deposits were found to decrease with increasing Fe content. The anode polarization resistance for the CH₄ fuel was significantly reduced by Fe alloying, which was strongly related to the carbon deposition behavior. The maximum power density of the single cell with Ni_0.85Fe_0.15–Ce_0.8Gd_0.2O_1.9 in CH₄ at 800 °C was 0.27 W/cm². Fe alloying significantly improved the electrochemical performance of solid oxide fuel cells in CH₄ fuel by suppressing carbon deposition.     

Reactivity of bio-sorbent prepared by waste shells of shellfish in acid gas cleaning reaction

Acid gas cleaning activity of bio-adsorbent prepared by waste shell of different shellfish species was investigated in a fixed bed reactor to evaluate its feasibility as an acid gas cleaning agent. The physicochemical properties of prepared adsorbents were measured using ICP, BET, SEM-EDX and XRD. The results showed that active chemical species of bio-sorbent are comparable to that of commercial limestone and lime. SO2/NOx removal capacity of waste shell of shellfish was higher than that of commercial limestone due to the enhanced physical properties. In particular, the desulfurization activity of clam based adsorbent was the best among the tested waste shells because of both higher calcium content and more specific surface area. These lead to the conclusion that commercial limestone can be substituted for bio-sorbent prepared by waste shell of clam.     

Electrochemical properties related to the thickness control of the solid oxide fuel cell component layer using decalcomania paper

We fabricated anode-supported solid oxide fuel cells using decalcomania paper. To investigate the changes in thickness of the component layer and electrical properties in a unit cell, the number of layers of cathodes and the electrolyte decalcomania paper is changed. As a result, the thickness of the electrolyte and cathode layer regularly increases with an increase in the number of decalcomania papers attached. In addition, when only one electrolyte decalcomania paper is attached to an anode support, a tight and dense 8 μm electrolyte layer is obtained. A unit cell with a cathode thickness of 120 μm to which decalcomania paper is attached nine times is shown to have an open circuit voltage (OCV) of 1.08 V and a maximum power density (MPD) of 902 mW cm^?2 at 800 °C.     

Synthesis of β-silicon carbide nanofiber from an exfoliated graphite and amorphous silica

Silicon carbide (SiC) nanofibers were synthesized from exfoliated graphite containing silica particles at 1425 °C in a 25% H₂/Ar atmosphere. Two types of SiC nanofibers with different morphologies were formed depending on the silica content. A higher silica content led to straight nanofibers with a regular diameter size. The SiC nanofibers derived from the exfoliated graphite/40 wt% SiO₂ powder mixture contained a large number of stacking faults and grew along the [1 1 1] direction. A gas–gas reaction mechanism was proposed to explain the formation of SiC nanofibers.     

Numerical analysis of the effect of injection pressure variation on free spray and impaction spray characteristics

Compression ignition direct injection diesel engines employed a high pressure injection system have been developed as a measure to improve a fuel efficiency and reduce harmful emissions. In order to understand the effects of the pressure variation, many experimental works have been done, however there are many difficulties to get data in engine condition.