• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1065-1069
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• 1998

This study was investigated to improve peformance of carbon negative electrode for lithium ion secondary battery. The carbon electrode was prepared by mixing with graphitic carbon material, natural graphite, and nongraphitic carbon material, petroleum cokes, which was heat-treated at $700^{\circ}C$ for l hour. Its electrochemical and charge-discharge characteristics were tested according to mixing ratio of different two types of carbon material. The carbon electrode prepared with various mixing ratio showed both charateristcs of two different types of carbon materials and the best characteristics as carbon electrode was demonstrated at mixing ratio of 1:1.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.25-28
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• 1998

Lithiated cobalt and nickel oxides are becoming very attractive as active cathode materials for secondary lithium ion secondary battery. $LiCoO_2$ is easily synthesized from lithium cobalt salts, but has a relatively high oxidizing potential on charge. LiNiOz is synthesized by a more complex procedure and its nonstoichiometry significantly degraded the charge-discharge characteristics. But $LiNiO_2$ has a lower charge potential which increases the system stability. Lithiated cobalt and nickel oxides are iso-structure which make the preparation of solid solutions of $LiNi_{1-x}Co_xO_2$ for O$LiCoO_2 and LiNiO_2$ electrode. The aim of the presentb paper is to study the electrochemical behaviour, as weU as the possibilities for practical application of layered Iithiated nickel oxide stabilized by $Co^{3+}$ substitution as active cathode materials in lithium ion secondary battery.

• Journal for History of Mathematics
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• v.33 no.4
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• pp.237-257
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• 2020

In this paper, we classify the mathematical terms in Korean Standard Unabridged Dictionary into four groups; ① group 1 consists of the terms which coincide with the mathematical terms in the 2015 Editing Material, ② group 2 consists of the terms which are synonyms or old terms or inflection forms of the mathematical terms in the Editing Material, ③ group 3 consists of the terms which do not belong to group 1 or group 2, but relate to the elementary or secondary school mathematics, ④ group 4 consists of the terms which do not relate to the elementary or secondary school mathematics. And then we make a comparative study with the mathematical terms in the Editing Material. In this study, we find out the mathematical terms in the Editing Material, but not in Korean Standard Unabridged Dictionary. And by using synonyms and old terms of the mathematical terms in the Editing Material we guess the rough tendency which terms belong to the Editing Material. By investigating the terms in group 3 and 4, we find out the mathematical terms which may belong to the Editing Material. We also find out the wrong or inconsistent explanations in Korean Standard Unabridged Dictionary.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.8 no.1
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• pp.76-82
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• 1999

Zinc phosphate cement has long been the material of choice for permanent luting of cast restorations, and through many years of use has been considered effective to retain castings. However, cast restorations cemented with this material have been susceptible to secondary caries. Glass ionomer luting agents become available in the late 1970s. These material s, through release of fluoride, show considerable promise as a means of reducing secondary caries. Other favorable traits include significantly less disintegration in vivo than zinc phosphate cements, a film thickness comparable to that of zinc phosphate cement, and adhesion to tooth structure. Compomer materials were created in 1993 as a filling material for deciduous teeth, cervical lesions, and class III cavities. In the meantime, compomer have been developed as chemical hardening cements for cast gold restorations. The aim of this paper is to review the articles on luting cements to help the choice of dental cements.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.1
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• pp.11-25
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• 2024

Lithium-ion batteries (LIBs) have attracted great attention as the common power source in energy storage fields of large-scale applications such as electrical vehicles (EVs), industries, power plants, and grid-scale energy storage systems (ESSs). Insertion, alloying, and conversion reactions are the main electrochemical energy storage mechanisms in LIBs, which determine their electrochemical properties and performances. The electrochemical reaction mechanisms are determined by several factors including crystal structure, components, and composition of electrode materials. This article reviews a new strategy to compensate for the intrinsic shortcomings of each reaction mechanism by introducing the material systems to form a single compound with different types of reaction mechanisms and to allow the simultaneous hybrid electrochemical reaction of two different mechanisms in a single solid solution phase.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.1
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• pp.207-212
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• 2024

Recently, with the strengthening of environmental regulations, there has been an increasing interest in eco-friendly energy sources, leading to a trend of the increasing scale of Cargo Containment Systems (CCS) for Liquefied Natural Gas (LNG) carriers. Among these systems, membrane tanks have gained popularity in LNG transport vessels due to their superior spatial utilization and competitiveness. However, due to high initial investment costs and the difficulty in repair in case of damage, a safety layer, the secondary barrier, must be installed without fail. In this study, in order to apply a new secondary barrier to the existing membrane-type LNG CCS, tests were conducted on the fiberglass layer previously used in the Triplex-Flexible Secondary Barrier (FSB), substituting it with basalt fiber. Tensile and vertical tensile tests were performed to assess the newly applied material. Environmental tests were conducted at room temperature (25℃) and extremely low temperatures (-170℃), considering the temperatures to which substances may be exposed during LNG vessel operations. The basalt-FSB produced in this study demonstrated superior results compared to the specifications of the existing product, confirming its potential applicability for implementation.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.202-206
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• 1990

The existing batteries such as lead acid battery and Nicad battery have been at serious issue, because heavy metal such as Pb and Cd give rise to environmental pollution. Therefor, when these material is changed over polymeric electroactive material, we expect environmental pollution will be prevented. We decided to develop 2025 coin type PAn/Li-Al secondary battery for goal of memory back-up battery. This report is concerned with manufacturing of 2025 coin type PAn/Li -Al secondary battery.

• Carbon letters
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• v.11 no.4
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• pp.343-346
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• 2010

The various expanded graphites (EGs) was prepared and applied as anode material for high power Li-ion secondary battery (LIB). By changing the processing conditions of EG, a series of EG with different structure were produced, showing the changed electrochemical properties. The charge-discharge test showed that the initial reversible capacity of EG anodes prepared at the suitable conditions was over 400 mAh/g and the charge capacity at 5 C-rate was 83.2 mAh/g. These values demonstrated the much improved electrochemical properties as compared with those for the graphite anode of 360 mAh/g and 19.4 mAh/g, respectively, showing the possibility of EG anode materials for high power LIB.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.1
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• pp.1-6
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• 2009

Air core based transformers have been designed, simulated and fabricated by using micromachining process for the application of wireless power transmission with the range of frequency from 1 GHz to 20 GHz. Fabricated transformers are the types of solenoid transformers with primary and secondary coils. the size of fabricated transformer is $1.1{\times}1.5{\sim}2.15\;mm$ including ground shield. Transformers have been measured by dividing two groups based on the turns ratio between primary coil and secondary coil which are 1:1 transformers(the number of turns of primary coil and secondary coil: 3/3, 5/5, 7/7) and l:n transformers(the number of turns of primary coil and secondary coil: 3/3, 3/6, 3/9). As a result of the measurement, the lowest insertion loss of transformers ranged from 2 dB to 2.8 dB according to the number of turns between primary coil and secondary coil. And the lowest insertion loss from the transformers was measured at the frequency from 7 GHz to 11 GHz according to the number of turns between primary coil and secondary coil. Based on the measurement data from the microfabricated transformers, the transformer with the 3/3 turns in the primary coil and secondary coil showed best performance compared to others in terms of lowest insertion loss, lowest insertion loss frequency and bandwidth.

• Korean Journal of Materials Research
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• v.33 no.6
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• pp.257-264
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• 2023

To develop a high capacity lithium secondary battery, a new approach to anode material synthesis is required, capable of producing an anode that exceeds the energy density limit of a carbon-based anode. This research synthesized carbon nano silicon composites as an anode material for a secondary battery using the RF thermal plasma method, which is an ecofriendly dry synthesis method. Prior to material synthesis, a silicon raw material was mixed at 10, 20, 30, 40, and 50 wt% based on the carbon raw material in a powder form, and the temperature change inside the reaction field depending on the applied plasma power was calculated. Information about the materials in the synthesized carbon nano silicon composites were confirmed through XRD analysis, showing carbon (86.7~52.6 %), silicon (7.2~36.2 %), and silicon carbide (6.1~11.2 %). Through FE-SEM analysis, it was confirmed that the silicon bonded to carbon was distributed at sizes of 100 nm or less. The bonding shape of the silicon nano particles bonded to carbon was observed through TEM analysis. The initial electrochemical charging/discharging test for the 40 wt% silicon mixture showed excellent electrical characteristics of 1,517 mAh/g (91.9 %) and an irreversible capacity of 133 mAh/g (8.1 %).