Fluorine-doped tin oxide (FTO) has been used as a representative transparent conductive oxide (TCO) in various optoelectronic applications, including light emitting diodes, solar cells, photo-detectors, and electrochromic devices. The FTO plays an important role in providing electron transfer between active layers and external circuits while maintaining high transmittance in the devices. Herein, we report the effects of substrate rotation speed on the electrical and optical properties of FTO films during ultrasonic spray pyrolysis deposition (USPD). The substrate rotation speeds were adjusted to 2, 6, 10, and 14 rpm. As the substrate rotation speed increased from 2 to 14 rpm, the FTO films exhibited different film morphologies, including crystallite size, surface roughness, crystal texture, and film thickness. This FTO film engineering can be attributed to the variable nucleation and growth behaviors of FTO crystallites according to substrate rotation speeds during USPD. Among the FTO films with different substrate rotation speeds, the FTO film fabricated at 6 rpm showed the best optimized TCO characteristics when considering both electrical (sheet resistance of 13.73 Ω/□) and optical (average transmittance of 86.76 % at 400~700 nm) properties with a figure of merit (0.018 Ω-1).

Lithium-ion batteries (LIBs) are powerful energy storage devices with several advantages, including high energy density, large voltage window, high cycling stability, and eco-friendliness. However, demand for ultrafast charge/discharge performance is increasing, and many improvements are needed in the electrode which contains the carbon-based active material. Among LIB electrode components, the conductive additive plays an important role, connecting the active materials and enhancing charge transfer within the electrode. This impacts electrical and ionic conductivity, electrical resistance, and the density of the electrode. Therefore, to increase ultrafast cycling performance by enhancing the electrical conductivity and density of the electrode, we complexed Ketjen black and graphene and applied conductive agents. This electrode, with the composite conductive additives, exhibited high electrical conductivity (12.11 S/cm), excellent high-rate performance (28.6 mAh/g at current density of 3,000 mA/g), and great long-term cycling stability at high current density (88.7 % after 500 cycles at current density of 3,000 mA/g). This excellent high-rate performance with cycling stability is attributed to the increased electrical conductivity, due to the increased amount of graphene, which has high intrinsic electrical conductivity, and the high density of the electrode.

Tungsten disulfide (WS2), a typical 2D layerd structure, has received much attention as a pseudocapacitive material because of its high theoretical specific capacity and excellent ion diffusion kinetics. However, WS2 has critical limits such as poor long-term cycling stability owing to its large volume expansion during cycling and low electrical conductivity. Therefore, to increase the high-rate performance and cycling stability for pseudocapacitors, well-dispersed WS2 nanoparticles embedded in carbon nanofibers (WS2-CNFs), including mesopores and S-doping, are prepared by hydrothermal synthesis and sulfurizaiton. These unique nanocomposite electrodes exhibit a high specific capacity (159.6 F g−1 at 10 mV s−1), excellent high-rate performance (81.3 F g−1 at 300 mV s−1), and long-term cycling stability (55.9% after 1,000 cycles at 100 mV s−1). The increased specific capacity is attributed to well-dispersed WS2 nanoparticles embedded in CNFs that the enlarge active area; the increased high-rate performance is contributed by reduced ion diffusion pathway due to mesoporous CNFs and improved electrical conductivity due to S-doped CNFs; the long-term cycling stability is attributed to the CNFs matrix including WS2 nanoparticles, which effectively prevent large volume expansion.

Carbon supports for dispersed platinum (Pt) electrocatalysts in direct methanol fuel cells (DMFCs) are being continuously developed to improve electrochemical performance and catalyst stability. However, carbon supports still require solutions to reduce costs and improve catalyst efficiency. In this study, we prepare well-dispersed Pt electrocatalysts by introducing titanium dioxide (TiO2) into biomass based nitrogen-doped carbon supports. In order to obtain optimized electrochemical performance, different amounts of TiO2 component are controlled by three types (Pt/TNC-2 wt%, Pt/TNC-4 wt%, and Pt/TNC-6 wt%). Especially, the anodic current density of Pt/TNC-4 wt% is 707.0 mA g−1 pt, which is about 1.65 times higher than that of commercial Pt/C (429.1 mA g−1 pt); Pt/TNC-4wt% also exhibits excellent catalytic stability, with a retention rate of 91 %. This novel support provides electrochemical performance improvement including several advantages of improved anodic current density and catalyst stability due to the well-dispersed Pt nanoparticles on the support by the introduction of TiO2 component and nitrogen doping in carbon. Therefore, Pt/TNC-4 wt% may be electrocatalyst a promising catalyst as an anode for high-performance DMFCs.

Because of their excellent stability and highly specific surface area, carbon based materials have received attention as electrode materials of electrical double-layer capacitors(EDLCs). Biomass based carbon materials have been studied for electrode materials of EDLCs; these materials have low capacitance and high-rate performance. We fabricated tofu based porous activated carbon by polymer dissolution reaction and KOH activation. The activated porous carbon(APC-15), which has an optimum condition of 15 wt%, has a high specific surface area(1,296.1 m2 g−1), an increased average pore diameter(2.3194 nm), and a high mesopore distribution(32.4 %), as well as increased surface functional groups. In addition, APC has a high specific capacitance(195 F g−1) at low current density of 0.1 A g−1 and excellent specific capacitance(164 F g−1) at high current density of 2.0 A g−1. Due to the increased specific surface area, volume ratio of mesopores, and surface functional groups, the specific capacitance and high-rate performance increased. Consequently, the tofu based activated porous carbon can be proposed as an electrode material for high-performance EDLCs.

In the present study, vanadium oxide(V2O5) films for electrochromic(EC) application are fabricated using sol-gel spin coating method. In order to optimize the EC performance of the V2O5 films, we adjust the amounts of polyvinylpyrrolidone(PVP) added to the solution at 0, 5, 10, and 15 wt%. Due to the effect of added PVP on the V2O5 films, the obtained films show increases of film thickness and crystallinity. Compared to other samples, optimum weight percent(10 wt%) of PVP led to superior EC performance with transmittance modulation(45.43 %), responding speeds(6.0 s at colored state and 6.2 s at bleached state), and coloration efficiency(29.8 cm2/C). This performance improvement can be mainly attributed to the enhanced electrical conductivity and electrochemical activity due to the increased crystallinity and thickness of the V2O5 films. Therefore, V2O5 films fabricated with optimized amount of PVP can be a promising EC material for high-performance EC devices.

Nb-doped TiO2(NTO) coated NiCrAl alloy foam for hydrogen production is prepared using ultrasonic spray pyrolysis deposition(USPD) method. To optimize the size and distribution of NTO particles based on good physical and chemical stability, we synthesize particles by adjusting the weight ratio of the Nb precursor solution(5 wt%, 10 wt% and 15 wt%). The morphological, chemical bonding, and structural properties of the NTO coated NiCrAl alloy foam are investigated by X-ray diffraction(XRD), X-ray photo-electron spectroscopy(XPS), and Field-Emission Scanning Electron Microscopy(FESEM). As a result, the samples of controlled Nb weight ratio exhibit a common diffraction pattern at ~25.3o , corresponding to the(101) plane, and have chemical bonding(O-Nb=O) at 534 eV. The NTO particles with the optimum weight ratio of N (10 wt%) show a uniform distribution with a size of ~18.2-21.0 nm. In addition, they exhibit the highest corrosion resistance even in the electrochemical stability estimation. As a result, the introduction of NTO coated NiCrAl alloy foam by USPD improves the chemical stability of the NiCrAl alloy foam by protecting the direct electrochemical reaction between the foam and the electrolyte. Thus, the optimized NTO coating can be proposed for excellent protection of NiCrAl alloy foam for hydrocarbon-based steam methane reforming(SMR).

To improve the performance of carbon nanofibers as electrode material in electrical double-layer capacitors (EDLCs), we prepare three types of samples with different pore control by electrospinning. The speciments display different surface structures, melting behavior, and electrochemical performance according to the process. Carbon nanofibers with two complex treatment processes show improved performance over the other samples. The mesoporous carbon nanofibers (sample C), which have the optimal conditions, have a high sepecific surface area of 696 m2 g−1, a high average pore diameter of 6.28 nm, and a high mesopore volume ratio of 87.1%. In addition, the electrochemical properties have a high specific capacitance of 110.1 F g−1 at a current density of 0.1 A g−1 and an excellent cycling stability of 84.8% after 3,000 cycles at a current density of 0.1 A g−1. Thus, we explain the improved electrochemical performance by the higher reaction area due to an increased surface area and a faster diffusion path due to the increased volume fraction of the mesopores. Consequently, the mesoporous carbon nanofibers are demonstrated to be a very promising material for use as electrode materials of high-performance EDLCs.

High performance lithium-ion batteries (LIBs) have attracted considerable attention as essential energy sources for high-technology electrical devices such as electrical vehicles, unmanned drones, uninterruptible power supply, and artificial intelligence robots because of their high energy density (150-250 Wh/kg), long lifetime (> 500 cycles), low toxicity, and low memory effects. Of the high-performance LIB components, cathode materials have a significant effect on the capacity, lifetime, energy density, power density, and operating conditions of high-performance LIBs. This is because cathode materials have limitations with respect to a lower specific capacity and cycling stability as compared to anode materials. In addition, cathode materials present difficulties when used with LIBs in electric vehicles because of their poor rate performance. Therefore, this study summarizes the structural and electrochemical properties of cathode materials for LIBs used in electric vehicles. In addition, we consider unique strategies to improve their structural and electrochemical properties.

Since the late 19 century, the Choseon dynasty forcibly opened the door to western countries, including Japan. In addition, cultural propagation called ‘modernity’ caused subtle changes in dietary life. Based on the theory of colonial dual society, this study examined the dietary modernity in Kyungsung (mid 1930s~early 1940s) when 50 years had passed since the Open-Door policy. Three films, <Turning point of the youngsters>(1934), <Sweet Dream>(1936) and <Spring of Korean Peninsula>(1941) (those made in 1930s~1940s) were analyzed. Twenty six scenes [14 scenes from <Turning point of the youngsters>, five scenes from <Sweet Dream>, and seven scenes from <Spring of Korean Peninsula>] related to the dietary life from films were chosen and classified according three criteria (degree of modernization, main influential countries, and benefit groups from modernization). The degree of modernization of all films was more than 80%. The average proportion of the countries that affected modernization were western (35%), western-Japan (28%) and Japan (20%). Approximately 33, 53 and 14% of the upper, middle, lower classes, respectively, benefited from diet modernization. The main places where modernized dietary culture could be enjoyed were cafes, western restaurants, tea rooms, and hotels. The main food or beverages that were considered as modernized dietary culture were liquor (especially beer), coffee, and western meals. People in Kyungsung in the mid 1930s~early 1940s experienced modernity in dietary life differently according to the social classes and these culture changes were generally accepted as a symbol of modernity.

The design of non-precious electrocatalysts with low-cost, good stability, and an improved oxygen reduction reaction(ORR) to replace the platinium-based electrocatalyst is significant for application of fuel cells and metal-air batteries with high energy density. In this study, we synthesize iron-carbide(Fe3C) embedded nitrogen(N) doped carbon nanofiber(CNF) as electrocatalysts for ORRs using electrospinning, precursor deposition, and carbonization. To optimize electrochemical performance, we study the three stages according to different amounts of iron precursor. Among them, Fe3C-embedded N doped CNF-1 exhibits the most improved electrochemical performance with a high onset potential of −0.18 V, a high E1/2 of −0.29 V, and a nearly four-electron pathway (n = 3.77). In addition, Fe3C-embedded N doped CNF-1 displays exellent long-term stabillity with the lowest ΔE1/2= 8 mV compared to the other electrocatalysts. The improved electrochemical properties are attributed to synergestic effect of N-doping and well-dispersed iron carbide embedded in CNF. Consequently, Fe3C-embedded N doped CNF is a promising candidate for non-precious electrocatalysts for high-performance ORRs.

구상나무는 아고산대에 한정되어 생육하는 것으로 알려져 있는데 최근 국립공원 내에서 고사하는 개채가 많이 발견되고 개체 수 또한 줄어들고 있는 실정이다. 따라서 본 연구는 쇠퇴 현상을 보이고 있는 구상나무 군락의 토양 환경 특성 파악을 통하여 추후 국립공원 내 구상나무 군락의 보전방안 마련 및 관리를 위한 기초자료를 제공하고자 수행되었다. 국립공원 내 구상나무군락의 토양 환경 특성을 파악하기 위하여 소백산 비록봉(1지점), 덕유산 서봉(1지점), 향적봉(4지점) 그리고 지리산 노루목(1지점), 돼지평전(1지점), 반야봉(2지점), 벽소령(1지점), 세석평전(1지점), 영신봉(1지 점), 임걸령(1지점), 장터목(1지점), 제석봉(2지점)에 존재 하는 구상나무 군락을 조사 대상지로 선정하였다. 토양의 물리적 특성을 분석한 결과 평균 토심은 소백산에서 68cm, 덕유산에서 41cm 그리고 지리산에서 44cm로 나타났으며, 특히 지리산 돼지평전과 벽소령 지역 내 구상나무군락의 경우에는 10cm 이하로 매우 낮게 조사되어 매우 열악한 토양 환경을 보이고 있었다. 0~10cm 깊이에서 가비중 평균은 소백산에서 0.38g/㎤, 덕유산에서 0.48g/㎤, 지리산에서 0.62g/㎤로 분석되어 우리나라 산림토양(정진현 등, 2002) A층 평균 0.88g/㎤ 그리고 B층 평균 1.01g/㎤보다 낮은 수준을 보이고 있었으며, 토심이 깊어질수록 가비중은 증가하는 경향을 보이고 있었다. 토양 수분함량의 경우에는 0~10cm 깊이에서 평균 39.69%~47.57%로 나타났다. 토양의 화학적 특성을 분석한 결과 토양 산도(pH)는 소백산에서 평균 4.90, 덕유산에서 4.59 그리고 지리산에서 4.69로 우리나라 산림의 토양 산도(pH) A층 평균 5.48 그리고 B층 평균 5.52보다 매우 낮게 나타났다. 토양 내 유기물 함량은 소백산에서 평균 9.08%, 덕유산에서 12.92% 그리고 지리산에서 12.68%로 양호한 수준이었으며, 모든 조사 지점에서 우리나라 산림토양 내 A층 유기물 평균 4.49%, B층 평균 2.03% 보다도 높은 함량을 보이고 있었다. Miller and Donahue(1990)에 의하면 유기물은 토양 중 양이온 치환용량(C.E.C.)의 30~70%를 제 공하며 부식으로 인하여 양이온치환 입지가 제공되는 것으로 알려져 있는데, 본 연구대상지의 양이온 치환용량을 분석한 결과 유기물 함량이 상대적으로 높았던 덕유산과 지리산에서 각각 22.05cmolc･kg-1과 19.69cmolc･kg-1로 높게 나타났다. 그리고 유기물 함량이 상대적으로 낮았던 소백산에서 17.58cmolc･kg-1로 조사되었는데, 이는 우리나라 산림토양 내 A층 양이온 치환용량 평균 12.5cmolc･kg-1, B층 평균 10.7cmolc･kg-1 보다는 높은 수준을 보이고 있었다. 유기물과 밀접한 관계를 가지고 있는 전질소 함량의 경우에도 소백 산에서 평균 0.52%, 덕유산에서 0.58% 그리고 지리산에서 0.59%로 조사되어 우리나라 산림토양 내 A층 전질소 평균 0.19%, B층 평균 0.09% 보다도 높은 함량을 보이고 있었다. 치환성양이온 K+은 덕유산과 지리산 조사 지역에서 평균 0.20cmolc･kg-1로 조사되어 우리나라 산림토양 A층 평균 0.22cmolc･kg-1, B층 평균 0.21cmolc･kg-1과 유사한 수치를 보였으나, 소백산 구상나무림의 경우에는 0.10cmolc･kg-1으로 다소 낮은 수치를 보였다. 하지만 치환성 양이온 Na+, Ca2+, Mg2+의 경우에는 우리나라 산림토양과 비교하여 매우 낮은 수치를 보이고 있었으며, 김창환(2012)이 보고한 지리 산 국립공원 내 구상나무림의 토양 조사 결과와 비교하여도 다소 낮은 수준이었다. 따라서 본 조사 대상지인 지리산, 덕유산, 소백산 국립공원 내 구상나무 임분의 건전한 생육을 위해서는 토양 산도의 개선과 치환성 양이온 부족 문제에 대한 개선 대책이 필요할 것으로 판단된다.

Although milk, which is a representative western food, has a more than 100-year history in Korea, the preference is controversial. This study examined the milk history of Choseon in 1884~1938. This period was divided into 4 periods regarding the westerner’s records and advertisements. Westerners who visited Choseon in 1884~1895 (1st period) recorded the eating habits of Choseon,i.e., no milk consumed, even in insufficient food situation. Among the westerners, medical missionaries began to show or/and recommend condensed milk for sick children. In 1896~1909 (2nd period) newspapers, general shops in Hanseong for westerners showed advertisements of dairy products. In the 1900s, condensed and raw milk were advertised through newspapers. Domestic ranching systems to produce raw milk were established at that time mainly by Japanese. In the 1910s (3rd period), raw milk and condensed milk were advertised in newspapers. Since the mid-1920s (4th period), dairy products were bisected into condensed and powdered (dried) milk. Moreover, many Japanese manufacturers appeared in the advertisement in the 1920s. These results suggest that milk has been recognized as a symbol of an enlightenment food in Korea since the late 1900s, but the old negative wisdom, unfamiliar taste, and high price of milk at that time limited its appeal.

Tungsten oxide(WO3) films with uniform surface morphology are fabricated using a spin-coating method for applications of electrochromic(EC) devices. To improve the EC performances of the WO3 films, we control the heating rate of the annealing process to 10, 5, and 1 oC/min. Compared to the other samples, the WO3 films fabricated at a heating rate of 5 oC/min shows superior EC performances for transmittance modulation(49.5 %), response speeds(8.3 s in a colored state and 11.2 s in a bleached state), and coloration efficiency(37.3 cm2/C). This performance improvement is mainly related to formation of a uniform surface morphology with increased particle size without any cracks by an optimized annealing heating rate, which improves the electrical conductivity and electrochemical activity of the WO3 films. Thus, the WO3 films with a uniform surface morphology prepared by the optimized annealing heating rate can be used as a potential candidate for performance improvement of the EC devices.

Needle-like NiO protecting layers on NiCrAl alloy foam, used as support for hydrogen production, are introduced through electroplated Ni and subsequent microwave annealing. To improve the stability of the NiCrAl alloy foam, oxygen concentration of microwave annealing to form a needle-like NiO layer with good chemical stability and corrosion resistance is controlled in a range of 20 and 50 %. As the oxygen concentration increases to 50 %, needle-like NiO forms a dense coating layer on the NiCrAl alloy foam; this layer formation can be attributed to accelerated growth of the (200) plane. In addition, the increased oxygen concentration causes increased NiO/Ni ratio of the resultant coating layer on NiCrAl alloy foam due to improved rate of the oxidation reaction. As a result, the introduction of dense needle-like NiO layers formed at 50 % oxygen concentration improves the chemical stability of the NiCrAl alloy foam by protecting the direct electrochemical reaction between the electrolyte and the foam. Thus, needle-like NiO can be proposed as a superb protecting layer to improve the chemical stability of NiCrAl alloy form.

Nitrogen (N)-doped protein-based carbon as platinum (Pt) catalyst supports from tofu for oxygen reduction reactions are synthesized using a carbonization and reduction method. We successfully prepare 5 wt% Pt@N-doped protein-based carbon, 10 wt% Pt@N-doped protein-based carbon, and 20 wt% Pt@N-doped protein-based carbon. The morphology and structure of the samples are characterized by field emission scanning electron microscopy and transmission electron micro scopy, and crystllinities and chemical bonding are identified using X-ray diffraction and X-ray photoelectron spectroscopy. The oxygen reduction reaction are measured using a linear sweep voltammogram and cyclic voltammetry. Among the samples, 10 wt% Pt@N-doped protein-based carbon exhibits exellent electrochemical performance with a high onset potential of 0.62 V, a high E1/2 of 0.55 V, and a low ΔE1/2= 0.32 mV. Specifically, as compared to the commercial Pt/C, the 10 wt% Pt@N-doped proteinbased carbon had a similar oxygen reduction reaction perfomance and improved electrochemical stability.

Sb-doped SnO2 (ATO) transparent conducting films are fabricated using horizontal ultrasonic spray pyrolysis deposition (HUSPD) to form uniform and compact film structures with homogeneously supplied precursor solution. To optimize the molar concentration and transparent conducting performance of the ATO films using HUSPD, we use precursor solutions of 0.15, 0.20, 0.25, and 0.30 M. As the molar concentration increases, the resultant ATO films exhibit more compact surface structures because of the larger crystallite sizes and higher ATO crystallinity because of the greater thickness from the accelerated growth of ATO. Thus, the ATO films prepared at 0.25 M have the best transparent conducting performance (12.60±0.21 Ω/□ sheet resistance and 80.83% optical transmittance) and the highest figure-of-merit value (9.44±0.17 × 10-3 Ω-1). The improvement in transparent conducting performance is attributed to the enhanced carrier concentration by the improved ATO crystallinity and Hall mobility with the compact surface structure and preferred (211) orientation, ascribed to the accelerated growth of ATO at the optimized molar concentration. Therefore, ATO films fabricated using HUSPD are transparent conducting film candidates for optoelectronic devices.