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- 저자 : 장기훈 (검색결과 88 건)
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Carbon nanotubes/nickel-cobalt hydroxide nanorods composite for supercapacitor applictation
장기훈,안희준 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Supercapacitors have intrigued researchers because of their greater energy density compared to conventional capacitors and their greater power density than batteries, as well as their long cycle life. However, for high power applications, a major disadvantage is that they have unsatisfactory energy density compared to batteries. To increase the energy density of supercapacitors, increasing the potential range is an effective approach. Carbon can complement or replace batteries in electrical energy storage and harvesting applications, where high power delivery and wide potential range are needed. Among them, CNTs are an attractive solution for energy storage devices due to their unique properties such as high chemical stability, high aspect ratio, strong mechanical strength, and high activated surface area. Alternative pseudocapacitive materials have proven to be promising materials for supercapacitor applications. Among these other metal oxides/hydroxides, nickel- and cobalt-based materials are considered the most promising for the next generation of supercapacitors because of their high specific capacitances, cost effectiveness, and natural abundance. Herein, multi-walled carbon nanotube (MWCNT) and nickel-cobalt binary metal hydroxide nanorod hybrids have been developed through the chemical synthesis of binary metal hydroxide on a MWCNT surface. These hybrids show enhanced supercapacitive performance and cycling ability. In this study, we report on the synthesis of nickel-cobalt hydroxide and CNT composites on a stainless steel substrate with promising charge storage performance. These electrodes yield a significantly high capacitance of 502 F/g with a high energy density of 69 Wh/kg at a scan rate of 5 mV/s. The film is stable up to 5000 cycles with greater than 80% capacitance retention.
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장기훈,유성일,안희준 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1
Transition metal oxides have received tremendous interests in supercapacitors over the last decade due to their fast and reversible Faradaic redox reactions which is known as pseudo-capacitance. Several methods have been used to synthesize metal oxide nanostructures including chemical bath deposition, hydroxide decomposition, thermal decomposition of carbonates, nanocasting, electrodeposition, combustion, coprecipitation and the sol-gel method. Many of these have drawbacks in that they are energy consuming, lengthy and involve multiple steps. Especially, all methods require calcinations/heat treatment at 200-600°C for 1-24 hrs. Therefore, faster, more facile and energy efficient methods for metal oxide nanostructure production are of interest. Here we report an agile and facile method for the preparation of high-performance supercapacitive cobalt oxide nanoflakes by using an intense pulsed light (IPL) technology. By this method, the cobalt oxide formation can be accomplished within milliseconds by irradiating the broad wavelength light with high energy density on cobalt oxide precursor, which is exceptionally faster than other metal oxide formation methods. We have fabricated cobalt oxide nanoflakes on Ni-foam substrate by using the IPL technique. The as-prepared substrates are further utilized as a supercapacitor electrode, and their supercapacitive performance will be discussed in the presentation.
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장기훈,김준성,조현진,김권천 朝鮮大學校 附設 醫學硏究所 2006 The Medical Journal of Chosun University Vol.31 No.1
The thyroid gland has been considered as an infrequent metastasis site. However, the incidence of thyroid involvement in reported autopsy series varies from 1.25% to 24%. In most autopsy series, breast and lung cancers have been the most frequent metastatic diseases to the thyroid gland, In contrast, renal cell carcinoma is the most frequent source of metastasis in clinical series. Many reports suggested that ultrasonography and subsequent ultrasonography-guided FNAB are mostly best suited for diagnosis of thyroid metastasis. Metastasis to the thyroid gland is associated with a poor prognosis and the prognosis depends essentially on the primary cancer. Surgery may prolong survival in a patient in whom the thyroid metastasis isolated, and thus early diagnosis and aggressive treatment should be performed in patients with the history of cancer.
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