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Antioxidative Lithium Reservoir Based on Interstitial Channels of Carbon Nanotube Bundles
Cho, Seok-Kyu,Jung, Gwan Yeong,Choi, Keun-Ho,Lee, Jiyun,Yoo, JongTae,Kwak, Sang Kyu,Lee, Sang-Young American Chemical Society 2019 NANO LETTERS Vol.19 No.9
<P>Lithium (Li) metal has garnered considerable attention in next-generation battery anodes. However, its environmental vulnerability, along with the electrochemical instability and safety failures, poses a formidable challenge to commercial use. Here, we describe a new class of antioxidative Li reservoir based on interstitial channels of single-walled carbon nanotube (SWCNT) bundles. The Li preferentially confined in the interstitial channels exhibits unusual thermodynamic stability and exceptional capacity even after exposure to harsh environmental conditions, thereby enabling us to propose a new lithiation/delithiation mechanism in carbon nanotubes. To explore practical application of this approach, the Li confined in the SWCNT bundles is electrochemically extracted and subsequently plated on a copper foil. The resulting Li-plated copper foil shows reliable charge/discharge behavior comparable to those of pristine Li foils. Benefiting from the confinement effect of the interstitial channels, the SWCNT bundles hold great promise as an environmentally tolerant, high-capacity Li reservoir.</P> [FIG OMISSION]</BR>
Nonvolatile Resistance Switching on Two-Dimensional Electron Gas
Joung, Jin Gwan,Kim, Shin-Ik,Moon, Seon Young,Kim, Dai-Hong,Gwon, Hyo Jin,Hong, Seong-Hyeon,Chang, Hye Jung,Hwang, Jin-Ha,Kwon, Beom Jin,Kim, Seong Keun,Choi, Ji-Won,Yoon, Seok-Jin,Kang, Chong-Yun,Yoo American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.20
<P>Two-dimensional electron gas (2DEG) at the complex oxide interfaces have brought about considerable interest for the application of the next-generation multifunctional oxide electronics due to the exotic properties that do not exist in the bulk. In this study, we report the integration of 2DEG into the nonvolatile resistance switching cell as a bottom electrode, where the metal–insulator transition of 2DEG by an external field serves to significantly reduce the OFF-state leakage current while enhancing the on/off ratio. Using the Pt/Ta<SUB>2</SUB>O<SUB>5–<I>y</I></SUB>/Ta<SUB>2</SUB>O<SUB>5–<I>x</I></SUB>/SrTiO<SUB>3</SUB> heterostructure as a model system, we demonstrate the nonvolatile resistance switching memory cell with a large on/off ratio (>10<SUP>6</SUP>) and a low leakage current at the OFF state (∼10<SUP>–13</SUP> A). Beyond exploring nonvolatile memory, our work also provides an excellent framework for exploring the fundamental understanding of novel physics in which electronic and ionic processes are coupled in the complex heterostructures.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-20/am504354c/production/images/medium/am-2014-04354c_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am504354c'>ACS Electronic Supporting Info</A></P>
Biomimetic Superoxide Disproportionation Catalyst for Anti-Aging Lithium-Oxygen Batteries
Hwang, Chihyun,Yoo, JongTae,Jung, Gwan Yeong,Joo, Se Hun,Kim, Jonghak,Cha, Aming,Han, Jung-Gu,Choi, Nam-Soon,Kang, Seok Ju,Lee, Sang-Young,Kwak, Sang Kyu,Song, Hyun-Kon American Chemical Society 2019 ACS NANO Vol.13 No.8
<P>Reactive oxygen species or superoxide (O<SUB>2</SUB><SUP>-</SUP>), which damages or ages biological cells, is generated during metabolic pathways using oxygen as an electron acceptor in biological systems. Superoxide dismutase (SOD) protects cells from superoxide-triggered apoptosis by converting superoxide to oxygen and peroxide. Lithium-oxygen battery (LOB) cells have the same aging problems caused by superoxide-triggered side reactions. We transplanted the function of SOD of biological systems into LOB cells. Malonic acid-decorated fullerene (MA-C<SUB>60</SUB>) was used as a superoxide disproportionation chemocatalyst mimicking the function of SOD. As expected, MA-C<SUB>60</SUB> as the superoxide scavenger improved capacity retention along charge/discharge cycles successfully. A LOB cell that failed to provide a meaningful capacity just after several cycles at high current (0.5 mA cm<SUP>-2</SUP>) with 0.5 mAh cm<SUP>-2</SUP> cutoff survived up to 50 cycles after MA-C<SUB>60</SUB> was introduced to the electrolyte. Moreover, the SOD-mimetic catalyst increased capacity, <I>e</I>.<I>g</I>., more than a 6-fold increase at 0.2 mA cm<SUP>-2</SUP>. The experimentally observed toroidal morphology of the final discharge product of oxygen reduction (Li<SUB>2</SUB>O<SUB>2</SUB>) and density functional theory calculation confirmed that the solution mechanism of Li<SUB>2</SUB>O<SUB>2</SUB> formation, more beneficial than the surface mechanism from the capacity-gain standpoint, was preferred in the presence of MA-C<SUB>60</SUB>.</P> [FIG OMISSION]</BR>
Ho-Youn Park,Seok-Jung Kim,Yoo-Joon Sur,Jae-Woong Jung,Chae-Gwan Kong 대한견주관절의학회 2021 대한견주관절의학회지 Vol.24 No.2
Background: A midshaft clavicle fracture is a common fracture that typically responds well to open reduction and internal fixation (ORIF). However, refracture can occur after implant removal (IR). This study aimed to analyze the rate of refracture and related factors after removal of the locking compression plate (LCP) for displaced midshaft clavicle fractures. Methods: We retrospectively reviewed the medical records of 201 patients who had undergone ORIF with LCP for midshaft clavicle fractures after IR after bony union from January 2011 to May 2018 at our institute. We evaluated basic demographic characteristics and radiographic parameters. All patients were treated with an LCP for primary fracture. The patients were divided into two groups: a refracture group that experienced a second fracture within 1 year after IR and a no-fracture group. Results: There were four cases (1.99%) of refracture; three were treated conservatively, while one was treated surgically. All patients achieved bony union. The average interval between refracture and IR was 64 days (range, 6–210 days). There was a significant difference in classification of fractures (AO Foundation/Orthopaedic Trauma Association [AO/OTA] classification) between the two groups. However, other patient demographics and radiographic measurements between refracture and IR, such as bone diameter, showed no significant difference between the two groups. Conclusions: This study showed that one in 50 patients suffered from refracture after removal of the LCP. Thus, if patients desire IR, the surgeon should explain that there is a relatively higher possibility of refracture for cases with simple or segmental fractures than for other types of fracture.
Jun-Chul Park,Jong-Gwan Yook,Bong Hyuk Park,Namcheol Jeon,Kwang-Seok Seo,Dongsu Kim,Woo-Sung Lee,Chan-Sei Yoo IEEE 2013 IEEE transactions on microwave theory and techniqu Vol.61 No.12
<P>This paper presents a gallium nitride (GaN)-based hybrid current-mode class-S (CMCS) power amplifier (PA) using a bandpass delta-sigma modulator (BPDSM) for a 955-MHz LTE signal. To enhance the drain efficiency of the CMCS PA, the chip-on-board (COB) technique, which can reduce the external parasitic components of the packaged transistor and allow fast switching operation at high frequencies by minimizing distortion of the pulse waveform, is adopted. Also, GaN Schottky barrier diodes are fabricated in-house to protect the switching transistor against the high negative voltage swing. The differential output filter and balun composed of lumped LC resonators are integrated at the back of the switching transistor to extract amplified LTE signal from the output rectangular waveform, and the fabricated CMCS PA is measured and analyzed at four different states of BPDSM according to the coding efficiency from different input power level to obtain higher power and efficiency. Finally, a cavity bandpass filter (BPF) is added to the output circuit for a more accurate reduction of the harmonics and out-of-band noise signals to enhance system efficiency. From the measured results for an 8.5-dB PAPR 3 G LTE 10-MHz input signal, the proposed CMCS PA has a maximum average output power of 37.61 and 30.78 dBm, and the resulting drain efficiencies of 33.3% and 38.6% with the drain voltage of 19 and 7 V, respectively.</P>