Synergistic multi-doping effects on the Li7La3Zr2O12 solid electrolyte for fast lithium ion conduction.

Here, we investigate the doping effects on the lithium ion transport behavior in garnet Li7La3Zr2O12 (LLZO) from the combined experimental and theoretical approach. The concentration of Li ion vacancy generated by the inclusion of aliovalent dopants such as Al(3+) plays a key role in stabilizing the cubic LLZO. However, it is found that the site preference of Al in 24d position hinders the three dimensionally connected Li ion movement when heavily doped according to the structural refinement and the DFT calculations. In this report, we demonstrate that the multi-doping using additional Ta dopants into the Al-doped LLZO shifts the most energetically favorable sites of Al in the crystal structure from 24d to 96 h Li site, thereby providing more open space for Li ion transport. As a result of these synergistic effects, the multi-doped LLZO shows about three times higher ionic conductivity of 6.14 × 10(-4) S cm(-1) than that of the singly-doped LLZO with a much less efforts in stabilizing cubic phases in the synthetic condition

Characteristics of Ba(Zr0.1Ce0.7Y0.2)O3-δ nano-powders synthesized by different wet-chemical methods for solid oxide fuel cells

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2017R1A6A3A03004416) and (NRF-2015M1A2A2056833).Ba(Zr0.1Ce0.7Y0.2)O3-δ nano-particles were prepared by different wet-chemical synthesis, Pechini (BZCY(P)) and co-precipitation (BZCY(C)), respectively. The BZCY(C) powders have a particle size in range of about 50~150 nm, which is smaller than the BZCY(P) powders with about 500~900 nm. Both the BZCY materials show perovskite structures, but there are impurities in the BZCY (P). Moreover, the electrolyte density was higher in the BZCY (C) than the BZCY (P). The single cells with BZCY (C) electrolytes exhibited about 0.23 W cm−2 at 600 °C and about 0.31 W cm−2 at the same temperature were obtained when the anode-functional layer was introduced between the anode and electrolyte. Thus, the BZCY prepared by carbonate-derived co-precipitation method can be more favorable for high-purity and dense electrolytes in the solid oxide fuel cells than the BZCY prepared by Pechini method.PostprintPeer reviewe

Performance evaluation of the HepB Typer-Entecavir kit for detection of entecavir resistance mutations in chronic hepatitis B

Background/AimsMolecular diagnostic methods have enabled the rapid diagnosis of drug-resistant mutations in hepatitis B virus (HBV) and have reduced both unnecessary therapeutic interventions and medical costs. In this study we evaluated the analytical and clinical performances of the HepB Typer-Entecavir kit (GeneMatrix, Korea) in detecting entecavir-resistance-associated mutations.MethodsThe HepB Typer-Entecavir kit was evaluated for its limit of detection, interference, cross-reactivity, and precision using HBV reference standards made by diluting high-titer viral stocks in HBV-negative human serum. The performance of the HepB Typer-Entecavir kit for detecting mutations related to entecavir resistance was compared with direct sequencing for 396 clinical samples from 108 patients.ResultsUsing the reference standards, the detection limit of the HepB Typer-Entecavir kit was found to be as low as 500 copies/mL. No cross-reactivity was observed, and elevated levels of various interfering substances did not adversely affect its analytical performance. The precision test conducted by repetitive analysis of 2,400 replicates with reference standards at various concentrations showed 99.9% agreement (2398/2400). The overall concordance rate between the HepB Typer-Entecavir kit and direct sequencing assays in 396 clinical samples was 99.5%.ConclusionsThe HepB Typer-Entecavir kit showed high reliability and precision, and comparable sensitivity and specificity for detecting mutant virus populations in reference and clinical samples in comparison with direct sequencing. Therefore, this assay would be clinically useful in the diagnosis of entecavir-resistance-associated mutations in chronic hepatitis B

Evaluating the Nickel Content in Metal Alloys and the Threshold for Nickel-Induced Allergic Contact Dermatitis

Many patients are currently suffering from nickel (Ni)-induced allergic contact dermatitis (ACD). There have been few Korean studies dealing with the threshold of Ni-induced ACD and quantifying the total amount of Ni in the metal alloys. The aim of this study is to evaluate the amount of Ni leached from metal alloys and Ni contents in metal alloys, and to estimate the threshold of Ni-induced ACD. All the earrings we examined leached below 0.5 µg/cm2/week, the upper limit of European Union (EU) regulation, but the other metal alloys leached a much higher amount of Ni than the limit. Likewise, all the earrings we examined contained less than 0.05% Ni (500 µg/g), the upper limit of EU regulation, but the other metal alloys exceeded this limit. Twenty Ni-sensitive subjects, who were patch-tested with various concentrations of Ni sulphate, showed positive reactions to 5% and 1% Ni sulphate, 10 subjects showed positive reactions to 0.01%, and the most sensitive subject showed reaction even to 0.0001%. The subjects in this study were more sensitive to Ni than those in the previous studies done in Europe. Taken together, strictly regulating the Ni-containing alloys that are made in Korea is needed to lower the occurrence of Ni-induced ACD