• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.527-531
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• 2010

The optimized sheet for EMI shielding was prepared by metal power with Fe series. Then various metal powders were deposited on the sheet by PVD method. Moreover, the PVdF nanofiber membrane was used to compare the characteristic of EMI shielding efficiency of various metal powders. The electrical property was measured by the 4-point probe method. The result from EDS confirmed that the metal powder existed on the sheet. EMI shielding efficiency was analysed by EMI shielding measurement apparatus. The lowest electrical resistance, $641.95{\Omega}{wcdot}cm$, was obtained with $1000\;{\AA}$ deposition of Cu on the sheet. It was revealed that the EMI shielding efficiency increased with increase of the metal deposition thickness. The sheet deposited by Cu with $1000\;{\AA}$ showed the highest EMI shielding efficiency, 32.5 dB.

• Journal of Navigation and Port Research
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• v.35 no.7
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• pp.569-573
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• 2011

In this paper, we developed a Smart Heat Radiating Sheet(SHRS) having the absorption ability of more than 15 dB, and thermal conduction rate more than 20 W/mk for port logistics RFID(Radio Frequency IDentification) system by using AMP(Amorphous Metal Powder) and shielding sheet. Firstly, the EM(Electro_Magnetic) wave absorber samples were fabricated by using AMP and CPE (Chlorinated Polyethylene) with different composition ratios of 80 : 20 wt.% and 85 : 15 wt.%, respectively. Secondly, we fabricated the Smart Heat Radiating Sheet using the shielding sheet to attach EM Wave Absorber. As a result, the Smart Heat Radiating Sheet with absorption ability of 16 dB at 433 MHz and thermal conduction rate is 24 W/mk has been developed with the composition ratio of Amorphous Metal Powder : CPE = 85 : 15 wt.% and thickness of 5.5 mm.

• Korean Journal of Materials Research
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• v.29 no.9
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• pp.532-541
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• 2019

Information and communication technologies are developing rapidly as IC chip size becomes smaller and information processing becomes faster. With this development, digital circuit technology is being widely applied to mobile phones, wireless LANs, mobile terminals, and digital communications, in which high frequency range of GHz is used. In high-density electronic circuits, issues of noise and EMC(Electro-Magnetic Compatibility) arising from cross talk between interconnects or devices should be solved. In this study, sheet-type electromagnetic wave absorbers that cause electromagnetic wave attenuation are fabricated using composites based on soft magnetic metal powder and silicon rubber to solve the problem of electromagnetic waves generated in wireless communication products operating at the frequency range of 2.4 GHz. Sendust(Fe-Si-Al) and carbonyl iron(Fe-C) were used as soft magnetic metals, and their concentrations and sheet thicknesses were varied. Using soft magnetic metal powder, a sheet is fabricated to exhibit maximum electromagnetic attenuation in the target frequency band, and a value of 34.2dB(99.9 % absorption) is achieved at the target frequency.

• Korean Journal of Materials Research
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• v.29 no.6
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• pp.363-370
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• 2019

The recent development of information and communication technologies brings new changes to automobile traffic systems. The most typical example is the advancement of dedicated short range communication(DSRC). DSRC mainly consists of an intelligent transportation system(ITS), an electronic toll collection system(ETCS) and an advanced traveler information system(ATIS). These wireless communications often cause unnecessary electromagnetic waves, and these electromagnetic waves, in turn, cause frequent system malfunction. To solve this problem, an absorber of electromagnetic waves is suggested. In this research, various materials, such as powdered metal and iron oxides, are used to test the possibility for an effective absorption of the unnecessary electromagnetic waves. The various metal powders are made into a thin sheet form by compositing through processing. The electromagnetic characteristics(complex permittivity, complex permeability) of the fabricated sheet are measured. As a result, we achieve -6.5 dB at 940 MHz(77.6 % absorption rate) with a 1.0 mm-thickness electromagnet wave absorber, and -9.5 dB at 940 MHz(88.8 % absorption rate) with a 2.0 mm-thickness absorber.

• Design & Manufacturing
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• v.16 no.1
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• pp.43-49
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• 2022

As technologies in various industrial fields develop, high-quality parts are required. In the past, precision parts were produced by the contact machining method, but the contact machining method has clear limitations. In order to solve this problem, research on a non-contact processing method has been conducted, and laser processing and electric discharge processing are representative. However, the non-contact method has a problem in that productivity is insufficient, and there is a problem that it takes a lot of time to continuously process microholes. Researchers have developed an electron beam drilling equipment for continuous processing of fine holes, and a vaporization amplification sheet to increase the processing efficiency of the equipment. In this study, a cylindrical vaporization amplification sheet using room temperature curing type silicon was fabricated, and the metal distribution and thickness uniformity of the produced sheet were analyzed. In order to manufacture a cylindrical vaporization amplification sheet, an equipment capable of using centrifugal force was developed, and a sample in which metal powder was evenly distributed and a constant thickness was produced.

• Korea-Australia Rheology Journal
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• v.14 no.2
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• pp.71-76
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• 2002

Metal thin films, which are indispensable constituents of ULSI (Ultra Large Scale Integration) circuits, have been fabricated by physical or chemical methods. However, these methods have a drawback of using expensive high vacuum instruments. In this work, the fabrication of tungsten metal film by spin coating was investigated. First of all, inorganic peroxopolytungstic acid (W-IPA) powder, which is soluble in water, was prepared by dissolving metal tungsten in hydrogen peroxide and by evaporating residual solvent. Then, the solution of W-IPA was mixed with organic solvent, which was spin-coated on wafers. And then, tungsten metal films, were obtained after reduction procedure. By selecting an appropriate organic solvent and irradiating UV, the sheet resistance of the tungsten metal film could be remarkably reduced.

• Journal of Powder Materials
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• v.25 no.2
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• pp.120-125
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• 2018

Boron nitride nanotubes (BNNTs) are receiving great attention because of their unusual material properties, such as high thermal conductivity, mechanical strength, and electrical resistance. However, high-throughput and high-efficiency synthesis of BNNTs has been hindered due to the high boiling point of boron (${\sim}4000^{\circ}C$) and weak interaction between boron and nitrogen. Although, hydrogen-catalyzed plasma synthesis has shown potential for scalable synthesis of BNNTs, the direct use of $H_2$ gas as a precursor material is not strongly recommended, as it is extremely flammable. In the present study, BNNTs have been synthesized using radio-frequency inductively coupled thermal plasma (RF-ITP) catalyzed by solid-state ammonium chloride ($NH_4Cl$), a safe catalyst materials for BNNT synthesis. Similar to BNNTs synthesized from h-BN (hexagonal boron nitride) + $H_2$, successful fabrication of BNNTs synthesized from $h-BN+NH_4Cl$ is confirmed by their sheet-like properties, FE-SEM images, and XRD analysis. In addition, improved dispersion properties in aqueous solution are found in BNNTs synthesized from $h-BN+NH_4Cl$.

• Proceedings of the Korean Magnestics Society Conference
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• 2003.06a
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• pp.30-31
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• 2003

• Journal of Powder Materials
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• v.27 no.3
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• pp.256-267
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• 2020

Metal additive manufacturing (AM) technologies are classified into two groups according to the consolidation mechanisms and densification degrees of the as-built parts. Densified parts are obtained via a single-step process such as powder bed fusion, directed energy deposition, and sheet lamination AM technologies. Conversely, green bodies are consolidated with the aid of binder phases in multi-step processes such as binder jetting and material extrusion AM. Green-body part shapes are sustained by binder phases, which are removed for the debinding process. Chemical and/or thermal debinding processes are usually devised to enhance debinding kinetics. The pathways to final densification of the green parts are sintering and/or molten metal infiltration. With respect to innovation types, the multi-step metal AM process allows conventional powder metallurgy manufacturing to be innovated continuously. Eliminating cost/time-consuming molds, enlarged 3D design freedom, and wide material selectivity create opportunities for the industrial adoption of multi-step AM technologies. In addition, knowledge of powders and powder metallurgy fuel advances of multi-step AM technologies. In the present study, multi-step AM technologies are briefly introduced from the viewpoint of the entire manufacturing lifecycle.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.887-888
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• 2006

The present study describes the wear and mechanical behaviour of carbide composites in cyclic loading applications (blanking of sheet metal). Adhesive wear as well as fatigue endurance were tested, complemented by XRD studies. It was found that the blanking performance of a carbide composite is controlled by its resistance to adhesion wear and fatigue sensitivity. XRD studies revealed that fatigue damage is preceded by plastic strain in both phases of the composites