• Research Paper

    Enhancing Structural Integrity of Composite Sandwich Beams Using Viscoelastic Bonding with Tapered Epoxy Reinforcement
    Rajesh Lalsing Shirale, Surekha Anil Bhalchandra
    Composite laminates are used in a wide range of applications including defense, automotive, aviation and aerospace, marine, wind energy, and recreational sporting … + READ MORE
    Composite laminates are used in a wide range of applications including defense, automotive, aviation and aerospace, marine, wind energy, and recreational sporting goods. These composite beams still exhibit problems such as buckling, local deformations, and interlaminar delamination. To overcome these drawbacks, a novel viscoelastic autoclave bonding with tapered epoxy reinforcement polyurethane films is proposed. In existing laminates, compression face wrinkling and interlaminar delamination is caused in the sandwich beam. The unique viscoelastic autoclave spunbond interlayer bonding is designed to prevent face wrinkling and absorb and distribute stresses induced by external loads, thereby eliminating interlaminar delamination in the sandwich beam. Also, the existing special reinforcement causes stress concentrations, and the core is not effectively connected, which directly affects the stiffness of the beam. To address this, a novel tapered epoxy polyurethane reinforcement adhesive film is proposed, whose reinforcement thickness gradually tapers as it enters the core material. This minimizes stress concentrations at the interface, preventing excessive adhesive squeeze-out during the bonding process, and improves the stiffness of the beam. Results indicate the proposed model avoids the formation of micro cracks, interlaminar delamination, buckling, and local deformations, and effectively improves the stiffness of the beam. - COLLAPSE
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    27 March 2024

  • Research Paper

    Synthesis and Properties of Ni-CNT Nanocomposites Using Electrical Explosion of Wire in Different Conditions
    Maithili Biswas, Jin-Chun Kim
    Ni-CNT nanocomposites were synthesized via the electrical explosion of wire (EEW) in acetone and deionized (DI) water liquid conditions with different CNT … + READ MORE
    Ni-CNT nanocomposites were synthesized via the electrical explosion of wire (EEW) in acetone and deionized (DI) water liquid conditions with different CNT compositions. The change in the shape and properties of the Ni-CNT nanopowders were determined based on the type of fluids and CNT compositions. In every case, the Ni nanopowder had a spherical shape and the CNT powder had a tube shape. However, the Ni-CNT nanopowders obtained in DI water exhibited irregular shapes due to the oxidation of Ni. Phase analysis also revealed the existence of nickel oxide when using DI water, as well as some unknown peaks with acetone, which may form due to the metastable phase of Ni. Magnetic properties were investigated using a Vibrating Sample Magnetometer (VSM) for all cases. Nanopowders prepared in DI water conditions had better magnetic properties than those in acetone, as evidenced by the simultaneous formation of super paramagnetic NiO peaks and ferromagnetic Ni peaks. The DI water (Ni:CNT = 1:0.3) sample revealed better magnetic results than the DI water (Ni-CNT = 1:0.5) because it had less CNT contents. - COLLAPSE
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    27 March 2024

  • Research Paper

    Formation of Magnetic Structures for Trapping of Breast Cancer Cell
    Alaa Alasadi, Ali Ghanim Gatea Al Rubaye
    This work focuses on the fabrication of excellent magnetic structures for trapping breast cancer cells. Micro-magnetic structures were patterned for trapping cancer … + READ MORE
    This work focuses on the fabrication of excellent magnetic structures for trapping breast cancer cells. Micro-magnetic structures were patterned for trapping cancer cells by depositing 30 nm of permalloy on a silicon substrate. These structures were designed and fabricated using two fabrication techniques: electron beam lithography and laser direct writing. Two types of magnetic structures, rectangular wire and zig-zagged wire, were created on a silicon substrate. The length of each rectangular wire and each straight line of zig-zagged wire was 150 µm with a range of widths from 1 to 15 µm for rectangular and 1, 5, 10 and 15 µm for zigzag, respectively. The magnetic structures showed good responses to the applied magnetic field despite adding layers of silicon nitride and polyethylene glycol. The results showed that Si + Si3N4 + PEG exhibited the best adhesion of cells to the surface, followed by Si + Py + Si3N4 + PEG. concentration of 5-6 with permalloy indicates that this layer affected silicon nitride in the presence of Polyethylene glycolPEG. - COLLAPSE
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    27 March 2024

  • Research Paper

    Development of Eco-Friendly Ag Embedded Peroxo Titanium Complex Solution Based Thin Film and Electrical Behaviors of Resistive Random Access Memory
    Won Jin Kim, Jinho Lee, Ryun Na Kim, Donghee Lee, Woo-Byoung Kim
    In this study, we introduce a novel TiN/Ag embedded TiO2/FTO resistive random-access memory (RRAM) device. This distinctive device was fabricated … + READ MORE
    In this study, we introduce a novel TiN/Ag embedded TiO2/FTO resistive random-access memory (RRAM) device. This distinctive device was fabricated using an environmentally sustainable, solution-based thin film manufacturing process. Utilizing the peroxo titanium complex (PTC) method, we successfully incorporated Ag precursors into the device architecture, markedly enhancing its performance. This innovative approach effectively mitigates the random filament formation typically observed in RRAM devices, and leverages the seed effect to guide filament growth. As a result, the device demonstrates switching behavior at substantially reduced voltage and current levels, heralding a new era of low-power RRAM operation. The changes occurring within the insulator depending on Ag contents were confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Additionally, we confirmed the correlation between Ag and oxygen vacancies (Vo). The current-voltage (I-V) curves obtained suggest that as the Ag content increases there is a change in the operating mechanism, from the space charge limited conduction (SCLC) model to ionic conduction mechanism. We propose a new filament model based on changes in filament configuration and the change in conduction mechanisms. Further, we propose a novel filament model that encapsulates this shift in conduction behavior. This model illustrates how introducing Ag alters the filament configuration within the device, leading to a more efficient and controlled resistive switching process. - COLLAPSE
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    27 March 2024

  • Research Paper

    Selective Atomic Layer Deposition of Co Thin Films Using Co(EtCp)2 Precursor

    Co(EtCp)2프리커서를 사용한 Co 박막의 선택적 원자층 증착

    Sujeong Kim, Yong Tae Kim, Jaeyeong Heo

    김수정, 김용태, 허재영

    As the limitations of Moore’s Law become evident, there has been growing interest in advanced packaging technologies. Among various 3D packaging techniques, … + READ MORE
    As the limitations of Moore’s Law become evident, there has been growing interest in advanced packaging technologies. Among various 3D packaging techniques, Cu-SiO2 hybrid bonding has gained attention in heterogeneous devices. However, certain issues, such as its high-temperature processing conditions and copper oxidation, can affect electrical properties and mechanical reliability. Therefore, we studied depositing only a heterometal on top of the Cu in Cu-SiO2 composite substrates to prevent copper surface oxidation and to lower bonding process temperature. The heterometal needs to be deposited as an ultra-thin layer of less than 10 nm, for copper diffusion. We established the process conditions for depositing a Co film using a Co(EtCp)2 precursor and utilizing plasma-enhanced atomic layer deposition (PEALD), which allows for precise atomic level thickness control. In addition, we attempted to use a growth inhibitor by growing a self-assembled monolayer (SAM) material, octadecyltrichlorosilane (ODTS), on a SiO2 substrate to selectively suppress the growth of Co film. We compared the growth behavior of the Co film under various PEALD process conditions and examined their selectivity based on the ODTS growth time. - COLLAPSE
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    27 March 2024

  • Research Paper

    Enhancing Die and Wire Bonding Process Reliability: Microstructure Evolution and Shear Strength Analysis of Sn-Sb Backside Metal

    다이 및 와이어 본딩 공정을 위한 Sn-Sb Backside Metal의 계면 구조 및 전단 강도 분석

    Yeo Jin Choi, Seung Mun Baek, Yu Na Lee, Sung Jin An

    최여진, 백승문, 이유나, 안성진

    In this study, we report the microstructural evolution and shear strength of an Sn-Sb alloy, used for die attach process as a … + READ MORE
    In this study, we report the microstructural evolution and shear strength of an Sn-Sb alloy, used for die attach process as a solder layer of backside metal (BSM). The Sb content in the binary system was less than 1 at%. A chip with the Sn-Sb BSM was attached to a Ag plated Cu lead frame. The microstructure evolution was investigated after die bonding at 330 °C, die bonding and isothermal heat treatment at 330 °C for 5 min and wire bonding at 260 °C, respectively. At the interface between the chip and lead frame, Ni3Sn4 and Ag3Sn intermetallic compounds (IMCs) layers and pure Sn regions were confirmed after die bonding. When the isothermal heat treatment is conducted, pure Sn regions disappear at the interface because the Sn is consumed to form Ni3Sn4 and Ag3Sn IMCs. After the wire bonding process, the interface is composed of Ni3Sn4, Ag3Sn and (Ag,Cu)3Sn IMCs. The Sn-Sb BSM had a high maximum shear strength of 78.2 MPa, which is higher than the required specification of 6.2 MPa. In addition, it showed good wetting flow. - COLLAPSE
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    27 March 2024

  • Research Paper

    Effect of Silica Particle Size and Aging Time on the Improvement of Mechanical Properties of Geopolymer-Fiber Composites

    실리카의 입자 크기와 Aging 시간이 지오폴리머 섬유 복합체의 기계적 물성 향상에 미치는 효과

    Yoonjoo Lee, Seokhun Jang, Minkyeong Oh, Dong-Gen Shin, Doo Hyun Choi, Jieun Lee, Chang-Bin Oh

    이윤주, 장석훈, 오민경, 신동근, 최두현, 이지은, 오창빈

    Geopolymer, also known as alkali aluminum silicate, is used as a substitute for Portland cement, and it is also used as a … + READ MORE
    Geopolymer, also known as alkali aluminum silicate, is used as a substitute for Portland cement, and it is also used as a binder because of its good adhesive properties and heat resistance. Since Davidovits developed Geopolymer matrix composites (GMCs) based on the binder properties of geopolymer, they have been utilized as flame exhaust ducts and aircraft fire protection materials. Geopolymer structures are formed through hydrolysis and dehydration reactions, and their physical properties can be influenced by reaction conditions such as concentration, reaction time, and temperature. The aim of this study is to examine the effects of silica size and aging time on the mechanical properties of composites. Commercial water glass and kaolin were used to synthesize geopolymers, and two types of silica powder were added to increase the silicon content. Using carbon fiber mats, a fiber-reinforced composite material was fabricated using the hand lay-up method. Spectroscopy was used to confirm polymerization, aging effects, and heat treatment, and composite materials were used to measure flexural strength. As a result, it was confirmed that the longer time aging and use of nano-sized silica particles were helpful in improving the mechanical properties of the geopolymer matrix composite. - COLLAPSE
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    27 March 2024
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