• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.1
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• pp.24-28
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• 2018

Insulators used in overhead transmission lines are continuously exposed to a number of mechanical and electrical stresses owing to external environmental factors, resulting in corrosion, reduction in durability, and deterioration. Widely used porcelain insulators are fabricated with cement and porcelain and are especially common in Korea. Changes in the hardness and chemical reactivity of the cement increase the leakage and fault currents and increase the possibility of flashover due to insulation breakdown. Therefore, it is important to evaluate the durability and defects of porcelain insulators. Studies on the reliability of various evaluation methods are needed to prevent accidents by accurately determining the replacement timing and potential defects in porcelain insulators. In this study, the hardness of the cement part of the porcelain insulator was measured using the Vickers hardness test and its composition was analyzed by energy dispersive spectroscopy and X-ray diffraction analysis. The performance of the insulators was compared in two different regions with varying climatic conditions. This study presents an evaluation method of the defects in porcelain insulators by measuring humidity, which can also be used to assess the reliability of the insulators.

• Korean Journal of Materials Research
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• v.29 no.2
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• pp.106-115
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• 2019

Recently, metal cases are widely used in smart phones for their luxurious color and texture. However, when a metal case is used, electric shock may occur during charging. Chip capacitors of various values are used to prevent the electric shock. However, chip capacitors are vulnerable to electrostatic discharge(ESD) generated by the human body, which often causes insulation breakdown during use. This breakdown can be eliminated with a high-voltage chip varistor over 340V, but when the varistor voltage is high, the capacitance is limited to about 2pF. If a chip capacitor with a high dielectric constant and a chip varistor with a high voltage can be combined, it is possible to obtain a new device capable of coping with electric shock and ESD with various capacitive values. Usually, varistors and capacitors differ in composition, which causes different shrinkage during co-firing, and therefore camber, internal crack, delamination and separation may occur after sintering. In addition, varistor characteristics may not be realized due to the diffusion of unwanted elements into the varistor during firing. Various elements are added to control shrinkage. In addition, a buffer layer is inserted in the middle of the varistor-capacitor junction to prevent diffusion during firing, thereby developing a co-fired product with desirable characteristics.

• Journal of Powder Materials
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• v.28 no.3
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• pp.233-238
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• 2021

Iron-based amorphous powder attracts increasing attention because of its excellent soft magnetic properties and low iron loss at high frequencies. The development of an insulating layer on the surface of the amorphous soft magnetic powder is important for minimizing the eddy current loss and enhancing the energy efficiency of high-frequency devices by further increasing the electrical resistivity of the cores. In this study, a hybrid insulating coating layer is investigated to compensate for the limitations of monolithic organic or inorganic coating layers. Fe₂O₃ nanoparticles are added to the flexible silicon-based epoxy layer to prevent magnetic dilution; in addition TiO₂ nanoparticles are added to enhance the mechanical durability of the coating layer. In the hybrid coating layer with optimal composition, the decrease in magnetic permeability and saturation magnetization is suppressed.

• Corrosion Science and Technology
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• v.21 no.6
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• pp.487-494
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• 2022

Anodizing is a typical electrochemical surface treatment method that can improve the corrosion and insulating properties of aluminum alloys. The anodization process can obtain a dense structure. It can be used to artificially grow the thickness of an anodization film. Aluminum 3003 alloy used in this study is the most commonly used alloy for batteries due to its high strength and excellent formability as well as its weldability and corrosion resistance. Aluminum 3003 alloy was anodized at 0 ℃ with 0.3 M oxalic acid at 20 V, 40 V, or 60 V for 1 hour, 6 hours, or 12 hours. As a result of analyzing the composition of each specimen with an Energy Dispersive Spectrometer (EDS), aluminum was converted into an oxide film. The thickness of the formed anodization film increased when the applied voltage and anodization time increased. High corrosion potential values and low corrosion current density values were observed for the thickest oxide layer. The anodization film formed by anodization acted as a protective layer. The electrical resistance increased as the applied voltage and anodization time increased.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2001.06a
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• pp.73-73
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• 2001

Boron-containing materials have several excellent properties, such as superlnardness, insulation and non-Rinear optical property. Recently, oxynitride compounds, such as Si(ON), Ti(ON), became the promising materials applied in diffusion barrier layer and solar cell. With the expectation of obtaining the hybrid property, we have firstly grown the BON thin film by radio frequency (R.F.) plasma enhanced metalorganic chemical vapm deposition (PEMOCVD) with 100 kHz frequency and trimethyl borate precursor. The plasma source gases used in this study were Ar and $H_2$, and two kinds of nhmgen source gases, $N_2$ and <$NH_3$, were also employed. The as-grown films were characterized by XPS, IR, SEM and Knoop microlhardness tester. The relationship between the films hardness and the growth rate indicated that the hardness of the film was dependent on several factors such as nitrogen source gas, substrate temperature and film thickness due to the variation of the composition and the structure of the film. Both nitrogen and carbon content could raise the film hardness, on which nitrogen content did stronger effect than carbon. The smooth morphology and continuous structure was benefit of obtaining high hardness. The maximum hardness of BON film was about 10 GPa.

• Journal of Sensor Science and Technology
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• v.32 no.3
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• pp.187-193
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• 2023

Previous research has explored early expression of fire signs before the burning of insulation. To achieve this, typically, automatic inspections are used to detect gas emitted from odor capsules at electrical connection points; additionally, early fire signs can be expressed using visual inspection of changes in the appearance of temperature caps. However, early detection of electrical fire is often difficult because only specific inspections, which are not complex, are performed. Therefore, in this paper, we present complex inspection techniques, such as visual inspection, odor inspection, and automatic inspection, and propose a showing material of fire signs that can solve conventional problems. In addition, this study examines the conditions under which the candidate material for the showing material is designed, the composition of the candidate material selected based on the designed conditions, the manufacturing means used to produce the showing material considering the temperature for early expression of fire signs, and the performance of the produced showing material. Furthermore, we analyze various effects that can occur through the proposed display material.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.721-724
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• 2008

The present study was to develop a dry PFB method similar to the existing gypsum board construction method in order to apply the existing wet PFB method that uses fire.resistant adhesive. It was found that the existing wet method can produce concrete compressive strength of 80MPa and fire resistance of 3 hours with 30mm PF boards. The goal of development in this study was fire resistance of 3 hours through dry construction of 15mm fire resistant boards. The results of fire resistance test showed an increase in thermal durability and thermal strain. It is believed that inorganic fiber reduces thermal strain, and lowers heat insulation performance by 15% or less. This suggests that heat insulation performance was improved by the change in the inner composition of PF board resulting from the adjustment of Al:Si mol ratio, high temperature molding, and dry curing. According to the results of fire resistance test, when the dry PF method was applied, the temperature of the main reinforcing bar was 116$^\circ$C in 15mm, 103.8$^\circ$C in 20mm, and 94$^\circ$C in 25mm, and these results satisfied the current standards for fire resistance control presented by the Ministry of Land, Transport and Maritime Affairs. When a 3 hour fire resistance test was performed and the external properties of the specimen were examined, the outermost gypsum board hardly remained and internal PF board maintained its form without thermal strain.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.545-551
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• 2020

Cause analysis of surface pitting crack on a waterjet impeller was conducted. The waterjet impeller was made from stainless steel duplex 2205, which is more resistant to corrosion and local corrosion than typical stainless steel 316L and 317L, and has high mechanical strength, making it a useful material in various marine structures and seawater desalination facilities. The measurements were taken by scanning electron microscopy (SEM) and molecular ecological detection. The chemical composition of S was examined by SEM in the area of pitting corrosion. The dsrAB gene was detected on the sample of the pitting corrosion of the impeller through molecular ecological detection. Therefore, pitting corrosion on the surface of a waterjet impeller was caused by sulphite-reducing bacteria (SRB). To prevent the spread of SRB, management is required through high temperature treatments (over 65℃), pH management, or the insulation of a hull and waterjet.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.77-85
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• 2012

Production process of the flexible ceramic foamed body through the complexation with the fiberous sepiolite and expanded pearlite was researched. The processing of fibrillation of the inorganic mineral fiber sepiolite is the most important whole processing for manufacturing of the ceramic foamed body consisting of the expanded perlite and sepiolite. The fibrous sepiolite and expanded pearlite are blended and becomes the slurry phase. And this slurry phase is converted to a massive foamed body through the low temperature heat treatment process less than $300^{\circ}C$. The heat-treatment process of the slurry phase composite has to be designed to include the evaporation step of the moisture remaining among the slurry composition, foaming step by the decomposition of the foaming agent, and resolution removal step of the organic material which was added in the composite remained after the foaming step. The heat treatment process should be considered as significant factors in design of total process. As to the condition of heat treatment process and foaming agent, there was the a correlation. An organic type foaming agent like DSS (dioctyl sodium sulfosuccinte) was effective in foaming of the slurry compound consisting of the expanded perlite and sepiolite fiber.

• Korean Institute of Interior Design Journal
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• v.24 no.1
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• pp.178-188
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• 2015

This study has the main objective of being of help as a reference data for the application of the finishing materials when designing the interior of the chapel of the church space through analysis of the finishing materials against the chapels of church space which has complex function. As precedent studies for this, the composition of the function and concept of the church space was surveyed and the complex function of the church space was surveyed. The theoretical surveyed was performed according to the casual composition, behavior of the community and role and location of the duties of the church members. The case objects were 10 chapels constructed by 5 professional interior design companies. The content of the analysis was the finishing materials in the chapels and their application characteristics. The detailed considerations to be referred to when designing the interior of the chapels of church space in the future were proposed. The analysis result of the application of the finishing materials according to the locational function of the chapels of church space can be explained as follows. First, the platform area was the characteristic of applying finishing materials which induce visual immersion. As for the floor materials in the platform, in order to minimize the floor sound and vibration phenomenon occurring during movements, noise insulation and dust protection rubber sheet was place and on top of it the floor or the carpet was placed. Second, the Choir area had the difficult problem of having to consider the appropriate sound absorption occurring due to the proliferation of sound and performance of classical instruments at the same time. However, in the case, this problem was solved through the sculptures of convex shape. Third, since the scheelite is a space where many people move around, the finishing material which absorbs sound was mainly used. Fourth, the entrance area was composed of thick wall materials compared to other walls, and the sound absorption character was most significantly considered when applying the finishing material. Fifth, the broadcasting room was composed either in independent type or an open type and performed its function and the main finishing materials was transparent glass which was highest use frequency.