• Title/Summary/Keyword: Filler

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Study on the Thermomechanical Properties of Epoxy-Silica Nanocomposites by FTIR Molecular Structure Analyses (FTIR 분자구조 해석을 통한 에폭시-실리카 나노복합소재의 열기계적 물성 연구)

  • Jang, SeoHyun;Han, Yusu;Hwang, DoSoon;Jung, Juwon;Kim, YeongKook
    • Journal of the Microelectronics and Packaging Society
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    • v.28 no.2
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    • pp.51-57
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    • 2021
  • This paper analyzed the effects of the concentration of nano-silica particles contained in epoxy resin on the thermomechanical properties of the composite materials. The 12nm sized nanoparticles were mixed with epoxy polymer by 5 different weight ratios for the test samples. The glass transition temperature, stress relaxation, and thermal expansion behaviors were measured using dymanic mechanical analyzer (DMA) and thermomechanical analyzer (TMA). It was shown that the nano particle mixing ratios had significant influences on the viscoelastic behaviors of the materials. As the content of the silica particles was increased, the elastic modulus was also increased, while the glass transition temperatures were decreased. Fourier Transform Infrared Spectroscopy (FTIR) results played an important role in determining the causes of the property changes by the filler contents in terms of the molecular structures, enabling the interpretations on the material behaviors based on the chemical structure changes.

A Study on the Mechanical Properties of Duplex Stainless Steel Weldment According to Mo Contents

  • Bae, Seong Han;Lim, Hee Dae;Jung, Won Jung;Gil, Woong;Jeon, Eon Chan;Lee, Sung Geun;Lee, Hyo Jong;Kim, In Soo;Lee, Hae Woo
    • Korean Journal of Metals and Materials
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    • v.50 no.9
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    • pp.645-651
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    • 2012
  • This study investigated changes in phase fraction caused by the addition of Mo, as well as the subsequent behaviour of N and its effect on the mechanical properties of welded 24Cr-N duplex stainless steel weld metals. Filler metal was produced by fixing the contents of Cr, Ni, N, and Mn while adjusting the Mo content to 1.4, 2.5, 3.5 wt%. The delta ferrite fraction increased as the Mo content increased. In contrast, the ${\gamma}$ fraction decreased and changed from a round to an acicular shape. Secondary austenite (${\gamma}^{\prime}$) was observed in all specimens in a refined form, but it decreased as the Mo content increased to the extent that it was nearly impossible to find any secondary austenite at 3.5 wt% Mo. Both tensile and yield strengths increased with the addition of Mo. In contrast, the highest value of ductility was observed at 1.41 wt% Mo. At all temperatures, impact energy absorption showed the lowest value at 3.5 wt% Mo, at which the amount of ${\delta}$-ferrite was greatest. There was no significant temperature dependence of the impact energy absorption values for any of the specimens. As the fraction of ${\gamma}$ phase decreased, the amount of N stacked in the ${\gamma}$ phase increased. Consequently, the stacking fault energy decreased, while the hardness of ${\gamma}$ increased.

A Study on the Insulation Characteristics of Epoxy Composites Using Electric Field Simulation

  • Lee, Deok-Jin
    • Journal of the Korea Society of Computer and Information
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    • v.26 no.2
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    • pp.53-60
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    • 2021
  • In this paper, we aimed to identify the insulation characteristics and reliability of Epoxy composites, which are widely used as insulation material for electrical & electronic components and electric appliance. To this end, it was necessary to predict variations of electric field due to the distribution of fillers that must be added by economic and mechanical factors. So, we verified the result using an electric field analysis Simulator. Furthermore, under the condtion of DC voltage application, an dielectirc breakdown test was performed according to ambient temperature changes and the distribution of fillers, and the changes were observed. Three types of specimens were manufactured by adding 0, 50 and 100[phr] filling to Epoxy resin. In all specimens, as temperature was increased, the strength of the dielectric strength was decreased. When comparing the simulation results with the actual dielectric breakdown test results, we was able to confirm the technical applicability required for Insulation design of electric appliance.

Efficient Management of the pH of the Wet Scrubber Washing Water for Risk Mitigation (리스크 완화를 위한 Wet Scrubber 세정수 pH의 효율적 관리)

  • Joo, Dong-Yeon;Seoe, Jae Min;Kim, Myung-Chul;Baek, Jong-Bae
    • Journal of the Korean Society of Safety
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    • v.35 no.6
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    • pp.85-92
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    • 2020
  • Wet Scrubber reacts the incoming pollutant gas with cleaning water (water + absorbent) to absorb pollutants and release the clean air to the atmosphere. Wet scrubbers and packed tower scrubbers using this principle are widely used in businesses that emit acid gases. In particular, in the etching process using hydrochloric acid (HCl), alkaline washing water (NaOH) having a pH of about 8 to 11 is used to absorb a large amount of acid gas. However, These salts are attached to the injection nozzle (nozzle), filling material (packing), and the demister (Demister), causing air pollution, human damage, and inoperability due to clogging and acid gas discharge. Therefore, In this study, an improvement plan was proposed to manage the washing water with pH 3~4 acidic washing water. The test method takes samples from the Wet Scrubber flue measurement laboratory twice a month for 1 year. Hydrogen chloride (HCl) concentration (ppm) was measured, and nozzle clogging and scale conditions were measured, compared, and analyzed through a differential pressure gauge and a pressure gauge. As a result of the check, it was visually confirmed that the scale was reduced to 50% or less in the spray nozzle, filler, and demister. In addition, the emission limit of hydrogen chloride in accordance with the Enforcement Regulation of the Air Quality Conservation Act [Annex 8] met 3 ppm or less. Therefore, even if the washing water is operated in an acidic pH range of 3 to 4, it is expected to reduce air pollution and human damage due to clogging of internal parts, and it is expected to reduce maintenance costs such as regular cleaning or replacement of parts.

A Study on the Possibility of Bulk Graphite Manufacturing using Coal Tar as a Binder and an Impregnant (콜타르를 결합재 및 함침재로 이용한 벌크 흑연 제조)

  • Lee, Sang-Min;Lee, Sang-Hye;Kang, Dong-Su;Roh, Jae-Seung
    • Composites Research
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    • v.34 no.1
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    • pp.51-56
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    • 2021
  • This paper studied the possibility of manufacturing bulk graphite using coal tar, a precursor of coal tar pitch, as a binder and impregnant. Carbonization was conducted after mixing and molding with natural graphite as a filler and coal tar as a binder. Impregnation-recarbonization was performed five times after carbonization. Coal tar used as impregnant. Measuring density, porosity, compressive strength, and anisotropy ratio was conducted. The maximum density of bulk graphite specimen was 1.76 g/㎤ and the minimum porosity was 15.6% which could be controlled by process control. The highest compressive strength was 20.3 MPa. Then the maximum anisotropic ratio of bulk was shown 0.34 through XRD analysis. Therefore, it was confirmed that it was possible to manufacture artificial graphite in a bulk form by using coal tar as a binder and an impregnant.

Vibration analysis of sandwich sector plate with porous core and functionally graded wavy carbon nanotube-reinforced layers

  • Feng, Hongwei;Shen, Daoming;Tahouneh, Vahid
    • Steel and Composite Structures
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    • v.37 no.6
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    • pp.711-731
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    • 2020
  • This paper deals with free vibration of FG sandwich annular sector plates on Pasternak elastic foundation with different boundary conditions, based on the three-dimensional theory of elasticity. The plates with simply supported radial edges and arbitrary boundary conditions on their circular edges are considered. The influence of carbon nanotubes (CNTs) waviness, aspect ratio, internal pores and graphene platelets (GPLs) on the vibrational behavior of functionally graded nanocomposite sandwich plates is investigated in this research work. The distributions of CNTs are considered functionally graded (FG) or uniform along the thickness of upper and bottom layers of the sandwich sectorial plates and their mechanical properties are estimated by an extended rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The core of structure is porous and the internal pores and graphene platelets (GPLs) are distributed in the matrix of core either uniformly or non-uniformly according to three different patterns. The elastic properties of the nanocomposite are obtained by employing Halpin-Tsai micromechanics model. A semi-analytic approach composed of 2D-Generalized Differential Quadrature Method (2D-GDQM) and series solution is adopted to solve the equations of motion. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. Some new results for the natural frequencies of the plate are prepared, which include the effects of elastic coefficients of foundation, boundary conditions, material and geometrical parameters. The new results can be used as benchmark solutions for future researches.

Clinical and radiographic features of facial cosmetic materials: A systematic review

  • Alsufyani, Noura;Aldosary, Reem;Alrasheed, Rasha;Alsufyani, Mohammed
    • Imaging Science in Dentistry
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    • v.52 no.2
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    • pp.155-164
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    • 2022
  • Purpose: The aim of this study was to systematically screen the literature for studies reporting cosmetic material in the oral and maxillofacial complex to shed light on the types of cosmetic materials, their radiographic appearance, and possible complications. Materials and Methods: Five electronic databases were reviewed for eligible studies. The general search terms were "cosmetic," "filler," "face," and "radiograph." Demographics, material types, clinical and radiographic presentation, and complications were recorded. Results: Thirty-one studies with 53 cases met the inclusion criteria. The mean age was 52.6±15.4 years with a 4 : 3 female-to-male ratio. The most common material was calcium hydroxyapatite (CaHa) (n=14, 26.4%), found incidentally. The materials were generally located within the upper cheek and zygoma (n=35, 66.0%), radiographically well-defined (n=44, 83%), and had no effects on the surrounding structures (n=27, 50.9%). The internal structure was radiopaque (calcification, hyperdensity) for gold wires, CaHa, bone implants, and secondary calcification or ossification. Outdated cosmetic materials or non-conservative techniques were infiltrative, had effects on the surrounding structures, and presented with clinical signs, symptoms, or complications. Conclusion: Conventional radiography, cone-beam computed tomography, and multi-detector computed tomography are useful to differentiate several cosmetic materials. Their magnetic resonance imaging appearance was highly variable. The infrequent inclusion of cosmetic materials in the differential diagnosis implies that medical and dental specialists may be unfamiliar with the radiographic appearance of these materials in the face.

Effect of the Alignment of Milled Carbon Fiber Dispersed in Various Solvents (Solvent 별 분산에 따른 Milled Carbon Fiber의 배열성 연구)

  • Lee, Sung-Kwon;Choi, Sung-Woong
    • Composites Research
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    • v.35 no.1
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    • pp.47-51
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    • 2022
  • In order to efficiently control the heat generation of electronic devices, many research has been conducted on thermally conductive composite materials. In this study, milled carbon fiber was dispersed in four solvent to investigate the relationship of carbon fiber alignment according to dispersion by solvents, and carbon fiberreinforced composite material(CFRP) was manufactured using vacuum filtration. To evaluate the arrangement of CFRP the arrangement of the prepared specimen was observed under an optical microscope, and thermal conductivity was measured by Laser Flash Analysis. The Through-plane thermal conductivity of CFRP using NMP and Ethanol was 10.79 W/mK and 10.57 W/mK respectively, which were improved by 218% and 209% compared to the In-plane thermal conductivity. The high viscosity of the solvent greatly affects the shear of the fluid, and it seemed to determine the alignment of the filler.

A Conductive-grid based EMI Shielding Composite Film with a High Heat Dissipation Characteristic (전도성 그리드를 활용한 전자파 흡수차폐/방열 복합소재 필름)

  • Park, Byeongjin;Ryu, Seung Han;Kwon, Suk Jin;Kim, Suryeon;Lee, Sang Bok
    • Composites Research
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    • v.35 no.3
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    • pp.175-181
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    • 2022
  • Due to the increasing number of wireless communication devices in mmWave frequency bands, there is a high demand for electromagnetic interference (EMI) shielding and heat dissipating materials to avoid device malfunctions. This paper proposes an EMI shielding composite film with a high heat dissipation characteristic. To achieve this, a conductive grid is integrated with a polymer-based composite layer including magnetic and heat dissipating filler materials. A high shielding effectiveness (>40 dB), low reflection shielding effectiveness (<3 dB), high thermal conductivity (>10 W/m·K), thin thickness (<500 ㎛) are simultaneously achieved with a tailored design of composite layer compositions and grid geometries in 5G communication band of 26.5 GHz.

Weld Characteristic Analysis for Weld Process Variables of Tip-Rotating Arc Welding in Butt Joint of Shipbuilding Steels (조선용 강재의 맞대기 이음에서 팁회전 아크 용접의 공정 변수에 따른 용접 특성 분석)

  • Lee, Jong Jung;Ahn, Sang Hyun;Park, Young Whan
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.20 no.7
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    • pp.105-112
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    • 2021
  • Reduction of weld distortions and increase in productivity are some of the major goals of the shipbuilding industry. To address these issues, many researchers have attempted to apply new welding processes. In the shipbuilding industry, steel is the candidate material of choice owing to its good weldability. However, conventional welding techniques are not feasible for avoiding welding problems. Tip-rotating arc welding is one of the high-efficiency welding process that has several advantages, such as high welding speed, high melting rate, low heat input, and less distortion. The present study investigates the influence of the welding variables on the weld characteristics of tip-rotating arc welding. Welding was performed using EH36 as the base metal and SM-70s as the filler metal, which are widely used in shipbuilding. Basic experiments were conducted to understand the effects of the major welding variables, such as welding and tip-rotating speeds. The distortion and mechanical properties of the optimal welding conditions were used to evaluate the tip-rotating arc welding performance. Consequently, the feasibility of the tip-rotating arc welding process for joining steel components was investigated, so that the optimized welding conditions could be applied directly to ship body welding to enhance the quality of the welded joints.