• Transactions on Electrical and Electronic Materials
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• v.14 no.3
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• pp.133-138
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• 2013

Acrylonitrile-butadiene-styrene (ABS) plastic is a polymer material extensively used in electrical and electronic applications. Nickel (Ni) thin film was deposited on ABS by electroless plating, after its surface was treated and modified with atmospheric plasma generated by means of dielectric barrier discharges (DBDs) in air. The method in this study was developed as a pre-treatment for electroless plating using DBDs, and is a dry process featuring fewer processing steps and more environmentally friendliness than the chemical method. After ABS surfaces were modified, surface morphologies were observed using a scanning electron microscope (SEM) to check for any physical changes of the surfaces. Cross-sectional SEM images were taken to observe the binding characteristics between metallic films and ABS after metal plating. According to the SEM images, the depths of ABS by plasma are shallow compared to those modified by chemically treatment. The static contact angles were measured with deionized (DI) water droplets on the modified surfaces in order to observe for any changes in chemical activities and wettability. The surfaces modified by plasma showed smaller contact angles, and their modified states lasted longer than those modified by chemical etching. Adhesion strengths were measured using 3M tape (3M 810D standard) and by 90° peel-off tests. The peel-off test revealed the stronger adhesion of the Ni films on the plasma-modified surfaces than on the chemically modified surfaces. Thermal shock test was performed by changing the temperature drastically to see if any detachment of Ni film from ABS would occur due to the differences in thermal expansion coefficients between them. Only for the plasma-treated samples showed no separation of the Ni films from the ABS surfaces in tests. The adhesion strengths of metallic films on the ABS processed by the method developed in this study are better than those of the chemically processed films.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.545-549
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• 2001

Glass-ceramics were prepared and evaluated for the properties to expand the scope of application of the rare earth aluminosilicate glasses, A glass-ceramic added with $TiO_2$as a nucleating agent, which was crystallized internally and it was characterized for physical, thermal and mechanical properties of crystal and residual glass in the glass-ceramic, X-ray diffractometer reveals an unknown crystal as $Nd_{4.6}Si_{7.6}Al_{4.0}Ti_{2.4}O_{32}$ which was found in surface and internal crystals dependent on composition and heat treatments. The thermal expansion coefficients of glass-ceramics were $5.4~6.2{\times}10^{-6}/^{\circ}C$, which increased with increasing crystal growth. Considering that the hardness and the elastic constant of crystal in glass-ceramics are 12GPa and 220GPa, respectively, the application of the glass-ceramics would be applicable for structural materials at elevated temperature.

• Composites Research
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• v.31 no.6
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• pp.371-378
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• 2018

In this study, the thermoelastic properties of poly lactic acid (PLA) based nanocomposites are predicted by molecular dynamics (MD) simulation and a micromechanics model. The stereocomplex mixed with L-lactic acid (PLLA) and D-lactic acid (PDLA) is modeled as matrix phase and a single walled carbon nanotube is embedded as reinforcement. The glass transition temperature, elastic moduli and thermal expansion coefficients of pure matrix and nanocomposites unit cells are predicted though ensemble simulations according to the hydrolysis. In micromechanics model, the double inclusion (D-I) model with a perfect interface condition is adopted to predict the properties of nanocomposites at the same composition. It is found that the stereocomplex nanocomposites show prominent improvement in thermal stability and interfacial adsorption regardless of the hydrolysis. Moreover, it is confirmed from the comparison of MD simulation results with those from the D-I model that the interface between CNT and the stereocomplex matrix is slightly weak in nature.

• Journal of Adhesion and Interface
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• v.18 no.2
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• pp.68-74
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• 2017

Epoxy resins are widely used in various fields due to their excellent thermal, mechanical and chemical properties. In order to improve the mechanical properties of the epoxy composition after curing, various materials are mixed in the epoxy resin. Among the nano materials, CNT is the most widely used. However, CNT has limitations in terms of manufacturing process and manufacturing cost. Therefore, there is a growing interest in naturally occurring HNTs having similar structure to that of CNT. In this study, the thermal and mechanical properties of epoxy compositions containing HNTs treated with two types of silane compounds were investigated. The mechanical properties of silane-treated HNT were measured by using a universal testing machine. The differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and thermomechanical analysis (TMA) were used to measure thermal properties. As a result of the above tests, when the HNT was surface-treated with aminosilane, the tensile strength of the epoxy composition containing the HNT was higher than that of the epoxy composition containing epoxy silane treated HNT. The linear thermal expansion coefficients (CTE) obtained from the thermomechanical analysis of the two epoxy compositions for the comparison of dimensional stability showed that the HNT composition treated with aminosilane showed a lower value of CTE than that of epoxy composition including the pristine HNT.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.2
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• pp.245-253
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• 2010

The reliability problems of flip chip packages subjected to temperature change during the packaging process mainly occur due to mismatches in the coefficients of thermal expansion as well as features with time-dependent material properties. Resin molding compounds like glass fiber reinforced epoxy composites used as the dielectric layer in printed circuit boards (PCB) strongly exhibit viscoelastic behavior, which causes their Young's moduli to not only be temperature-dependent but also time-dependent. In this study, the stress relaxation and creep tests were used to characterize the viscoelastic properties of the glass fiber reinforced epoxy composite. Using the viscoelastic properties, finite element analysis (FEA) was employed to simulate thermal loading in the pre-baking process and predict thermal warpage. Furthermore, the effect of viscoelastic features for the major polymeric material on the dielectric layer in the PCB (the glass fiber reinforced epoxy composite) was investigated using FEA.

• Composites Research
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• v.16 no.1
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• pp.1-12
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• 2003

This study developed SiC$_{p}$/A1$_2$O$_3$$_{f}$/Al composites for electronic packaging to which reinforcements were added with the volume fractions of 49%, 56% and 63% by the squeeze casting method. 0.8 wt. % of the inorganic binder as well as the A1$_2$O$_3$ fiber and SiC Particles with the volume fraction of 1:10 were added to the composites, which were produced in the newly designed mold. For the produced SiC/Al composites, the CTEs (coefficients of thermal expansion) were measured from 30 to 300 and compared with the FEM numerical simulation to analyze the temperature dependent properties. The experiment showed the CTEs of SiC$_{p}$/A1$_2$O$_3$$_{f}$/Al composites that were intermediate values of those of Rule of Mixture and Turner's Model. The CTEs were close to Turner's Model in the room temperature and approached the Rule of Mixture as the temperature increases. These properties analyzed from the difference of the average stress acting between the matrix and the reinforcements proposed in this study.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.524-532
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• 1997

ffects of radiation on the thermal and mechanical properties of modified epoxy resin and hydrogenated bisphenol-A type epoxy resin based neutron shielding materials to be used for radioactive material shipping and storage casks have been investigated. The onset temperatures of the shielding materials of KNS(Kaeri Neutron Shield)-201 and KNS-302 increased with the radiation dose, but those of KNS-202 and KNS-301 decreased at radiation dose above 0.5 MGy. In addition, the radiation dose rarely affected the change of weight of shielding materials with the variation in temperature. At radiation dose up to 0.1 MGy, thermal conductivities of shielding materials were not affected. The thermal expansion coefficients of the shielding materials of KNS-301 and 302 were affected to a less extent than those of KNS-201 and 202 by radiation. At radiation dose up to 0.1 MGy, the tensile strength, compressive strength and flexural strength of the shielding materials of KNS-202 and KNS-301 and 302 increased with the radiation dose. In contrast, those of KNS-201 decreased with an increase in the radiation dose. In addition, the amount of radiation dose on the shielding materials did not result in a measurable loss of specific gravity, weight and hydrogen content.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.32 no.5
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• pp.212-217
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• 2022

Large thermal stress due to the difference between silicon carbide and graphite's coefficients of thermal expansion could be formed during crystal growing process of silicon carbide (SiC) at high temperature. The large thermal stress could separate the SiC seed crystals from graphite components, which bring about the drop of the seed crystal during crystal growth. However, the bonding properties of SiC seed crystal module has hardly reported so far. In this study, SiC and graphite were bonded using 3 types of bonding agents and a three-point bending tests using a mixed-mode flexure test were conducted for the bonded samples to evaluate the bonding characteristics between SiC and graphite. Raman spectroscopy, X-ray Photoelectron Spectroscopy, and X-ray Computed Tomography were used to analyze the bonding characteristics and the microstructures of the SiC-graphite interfaces bonded with the bonding agents. As results, an excellent bonding agent was chosen to fabricate SiC seed crystal module with 50 mm in diameter. An SiC single crystal with 50 mm in diameter was successfully grown without falling out during top seeded solution growth of SiC at high temperature.

• Applied Chemistry for Engineering
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• v.9 no.6
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• pp.884-888
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• 1998

Effects of heating time under high temperature on the thermal and mechanical properties of neutron shielding materials based on modified (KNS-102), hydrogenated(KNS-106) bisphenol-A type epoxy resin and phenol-novolac(KNS-611) type epoxy resin for radioactive material shipping casks have been investigated. At early stages, the initial decomposition temperatures of the shielding materials of KNS-102, KNS-106 and KNS-611 increased with the heating time under high temperature, but it was rarely affected by the heating time in the later stages. In addition, the thermal conductivities of KNS-102 and KNS-106 decreased with heating time, but that of KNS-611 increased with the heating time. On the contrary, the thermal expansion coefficients of neutron shielding materials decreased with increase of heating time. At the high temperature, the tensile strength and flexural strength of the shielding materials of KNS-102 and KNS-611 increased with heating time, but those of KNS-106 decreased with increase of heating time. And the heating time under high temperature on the neutron shielding materials did not show measurable loss of weight and hydrogen content.

• Korean Journal of Materials Research
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• v.8 no.5
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• pp.457-463
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• 1998

New neutron shielding materials, KNS-201, KNS-301 and KNS-601 have been fabricated to be used for radioactive material shipping and storage cask. The base materials are a modified and a hydrogenated bisphenol- A type and novolac type epoxy resin, and aluminium hydroxide and boron carbide are added. These shielding materials offer good fluidity at processing, which makes it possible to form this resin shield into complicated geometric shapes such as radioactive material shipping and storage cask. Several measurements were made for the shielding materials to evaluate the thermal and mechanical properties and radiation resistance. The properties of the shielding materials are as follows: onset temperatures 2S7~28$0^{\circ}C$, thermal conductivities 0.9S~1.14W/m. K, thermal expansion coefficients 0.77~1.26x$10_{-6}{\circ}C_{-1}$, combustion characteristics < 80$0^{\circ}C$, ATB(average time of burning) < 5sec, AEB(average extent of burning) < 5mm, tensile strengths 2.5~3.2kg/$\textrm{mm}^2$, compressive strengths 13.2~1S.2kg/$\textrm{mm}^2$, flexural strengths 5.2 -6.4kg/$\textrm{mm}^2$. In general, the concerned properties of KNS-201, KNS-301 and KNS-601 were revealed to be better than those of NS-4- FR. foreign neutron shielding material. It is also observed that the radiation resistance of KNS- 601 was better than those of KNS-201 and KNS-301.