• Journal of the Semiconductor & Display Technology
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• v.12 no.1
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• pp.23-28
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• 2013

Epoxy resins are widely used in microelectronics packaging such as printed circuit board and encapsulating for semiconductor manufacturing. Water can diffuse into and through the epoxy matrix systems and moisture absorption at boarding interfaces of matrix resin systems can lead to a hydrolysis at the interfaces resulting in delamination of encapsulating materials. In the study, the changes of diffusion coefficient and moisture content ratio of epoxy resin systems with nano-sized fillers according to the change of liquid type epoxy resins were investigated. RE-304S, RE-310S, RE-810NM and HP-4032D as a epoxy resin, Kayahard AA as a hardener, and 1B2MI as a catalyst were used in these epoxy resin systems. After curing, moisture content ratios were measured with time under the 85 and 85% relative humidity condition using a thermo-hydrostat. The maximum moisture absorption ratio and diffusion coefficient of EMC decrease with the filler content. It can be seen that these decreases are due to the increase of filler surface area and the decrease of moisture through channel with the content of nano-sized filler.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.29-29
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• 2010

Engineering plastics have excellent electrical properties, mechanical strength and various characteristic which include chemical resistance, environmental resistance, weatherability at a wide temperature range. It has good characteristic(light weight, good productivity) as compare with epoxy or porcelain insulators. However, engineering plastics not suited to outdoor insulator because it isn't hydrophobic. Therefore, to over come these critical problems, we improve the surface insulation characteristics of engineering plastic by coating micro-, nano- size inorganic fillers added to RTV-SIR(Room temperature vulcanized-silicone rubber) at this plastic surface. The effect is analyzed through salt-fog test, tracking test. In conclusion, the engineering plastic coated RTV with micro-$Al_2O_3$20[phr], nano-Al(OH)3 1 ~ 3[phr] improved much better than the others.

• Carbon letters
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• v.15 no.4
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• pp.268-276
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• 2014

Recently, methods that usea carbon-based filler, a conductive nanomaterial, have been investigated to develop composite fillers containing dielectric materials. In this study, we added geometric changes to a carbon fiber, a typical carbon-based filler material, by differentiating the orientation angle and the number of plies of the fiber. We also studied the electrical and electromagnetic shield characteristics. Based on the orientation angle of $0^{\circ}$, the orientation angle of the carbon fiber was changed between 0, 15, 30, 45, and $90^{\circ}$, and 2, 4, and 6 plies were stacked for each orientation angle. The maximum effect was found when the orientation angle was $90^{\circ}$, which was perpendicular to the electromagnetic wave flow, as compared to $0^{\circ}$, in which case the electrical resistance was small. Therefore, it is verified that the orientation angle has more of an effect on the electromagnetic interference shield performance than the number of plies.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.355-363
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• 2015

HVDC technology has become popular as an economic mode of bulk power transmission over very long distances. Polymeric insulators in HVDC power transmission lines are affected by surface tracking and erosion problems due to contamination deposit, which pose a greater challenge in maintaining the reliability of the HVDC system. In addition, polymeric insulators are also naturally affected by aging due to various environmental stresses, which in turn accelerates the surface tracking and erosion problems. Research works towards the improvement of tracking and erosion resistance of polymeric insulators by adding nano-sized fillers in the base material are being carried out worldwide. However, surface tracking and erosion performance of nano-filled aged polymeric insulators for HVDC applications are not well reported. Hence, in the present work, tracking and erosion resistance of the nano $Al(OH)_3$ filled silicone rubber insulation material has been evaluated under DC voltages at different filler concentrations and aged conditions, as per IEC 60587 test procedures. Leakage current and contact angle measurements were carried out to understand the surface hydrophobicity. Moving average technique was used to analyze the trend followed by leakage current. Water aged specimen shows less tracking resistance when compared with thermal aged specimen. It is observed that nano-filler concentration of 5% is even sufficient to get better tracking/erosion resistance under DC voltages.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.1027-1034
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• 2010

Effects of inorganic nano-powders on the polymerization and thermal degradation kinetics as well as the mechanical properties of polyurethane nano-composites were studied by both the measurement of polymerization temperature as a function of time and non-isothermal thermogravimetric analysis (TGA) as well as the Instron test. As the results from polymerization studies, the reaction rates of MMT-filled PU composites were faster than those of Ce500-filled ones, and moreover, the activation energies using Kissinger method for the thermal degradation of composites were calculated as 139.34 kJ/mol for the Ce500-filled PU composites and 91.12 kJ/mol for MMT-filled one, respectivel, exhibiting that MMT nano-powder seemed to be acting as the catalyst for both polymerization and degradation of PU composites. UTM result, however, showed that tensile strength at break of MMT-filled composites was much higher than that of Ce500-filled ones above the concentrations range of 5 phr in the composites.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.25 no.2
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• pp.98-108
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• 2016

In recent days, perhaps the biggest driver in new material development is the desire to improve restorations esthetics compared to the traditional metal substructure based ceramics or all-ceramic restorations. Each material type performs differently regarding strength, toughness, effectiveness of machining and the final preparation of the material prior to placement. For example, glass ceramics are typically weaker materials which limits its use to single-unit restorations. On the other hand, zirconia has a high fracture toughness which enables multi-unit restorations. This material requires a long time sintering procedure which excludes its use for fast chair side production. Hybrid ceramic material developed for CAD/CAM system is contained improved nano ceramic elements. This new material, called a Resin Nano Hybrid Ceramic is unique in durability of function and aesthetic base compositions. The new nano-hybrid ceramic material is not a composite resin. It is also not a pure ceramic. The material is a mixture of both and consists of nano-ceramic fillers. Like a composite, the material is not brittle and is fracture resistant. Like a glass ceramic, the material has excellent polish retention for lasting esthetics. The material is easily machined by chair side or in a dental lab side, could be an useful restorative option.

• The Journal of Advanced Prosthodontics
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• v.13 no.4
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• pp.226-236
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• 2021

PURPOSE. This study aimed to evaluate the effect of incorporating zirconium oxide nanoparticles (nano-ZrO₂) in polymethylmethacrylate (PMMA) denture base resin on flexural properties at different material thicknesses. MATERIALS AND METHODS. Heat polymerized acrylic resin specimens (N = 120) were fabricated and divided into 4 groups according to denture base thickness (2.5 mm, 2.0 mm, 1.5 mm, 1.0 mm). Each group was subdivided into 3 subgroups (n = 10) according to nano-ZrO₂ concentration (0%, 2.5%, and 5%). Flexural strength and elastic modulus were evaluated using a three-point bending test. One-way ANOVA, Tukey's post hoc, and two-way ANOVA were used for data analysis (α = .05). Scanning electron microscopy (SEM) was used for fracture surface analysis and nanoparticles distributions. RESULTS. Groups with 0% nano-ZrO₂ showed no significant difference in the flexural strength as thickness decreased (P = .153). The addition of nano-zirconia significantly increased the flexural strength (P < .001). The highest value was with 5% nano-ZrO₂ and 2 mm-thickness (125.4 ± 18.3 MPa), followed by 5% nano-ZrO₂ and 1.5 mm-thickness (110.3 ± 8.5 MPa). Moreover, the effect of various concentration levels on elastic modulus was statistically significant for 2 mm thickness (P = .001), but the combined effect of thickness and concentration on elastic modulus was insignificant (P = .10). CONCLUSION. Reinforcement of denture base material with nano-ZrO₂ significantly increased flexural strength and modulus of elasticity. Reducing material thickness did not decrease flexural strength when nano-ZrO₂ was incorporated. In clinical practice, when low thickness of denture base material is indicated, PMMA/nano-ZrO₂ could be used with minimum acceptable thickness of 1.5 mm.

• Advances in nano research
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• v.16 no.1
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• pp.11-26
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• 2024

In this study, free vibration analysis of FG porous spherical cap reinforced by graphene platelets resting on Winkler-type elastic foundation has been surveyed for the first time. Three different types of porosity patterns are considered for the spherical cap whose two types of porosity patterns in the metal matrix are symmetric and the other one is uniform. Besides, five GPL patterns are assumed for dispersing of GPLs in the metal matrix. Tsai-Halpin and extended rule of the mixture are used to determine the Young modulus and mass density of the shell, respectively. Employing 3D FEM elasticity in conjunction with Hamilton's Principle, the governing motion equations of the structure are obtained and solved. The impact of various parameters including porosity coefficient, various porosity distributions in conjunction with different GPL patterns, the weight fraction of graphene Nano fillers, polar angles and stiffness coefficient of elastic foundation on natural frequencies of FG porous spherical cap reinforced by GPLs have been reported for the first time.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.95-99
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• 2018

High thermal conductivity films with electrically insulating properties have a great potential for the effective heat transfer as substrate and thermal interface materials in high density and high power electronic packages. There have been lots of studies to achieve high thermal conductivity composites using high thermal conductivity fillers such alumina, aluminum nitride, boron nitride, CNT and graphene, recently. Among them, hexagonal-boron nitride (h-BN) nano-sheet is a promising candidate for high thermal conductivity with electrically insulating filler material. This work presents an enhanced heat transfer properties of ceramic/polymer composite films using h-BN nano-sheets and PVA polymer resins. The h-BN nano-sheets were prepared by a mechanical exfoliation of h-BN flakes using organic media and subsequent ultrasonic treatment. High thermal conductivities over $2.8W/m{\cdot}K$ for transverse and $10W/m{\cdot}K$ for in-plane direction of the cast films were achieved for casted h-BN/PVA composite films. Further improvement of thermal conductivity up to $13.5W/m{\cdot}K$ at in-plane mode was achieved by applying uniaxial compression at the temperature above glass transition of PVA to enhance the alignment of the h-BN nano-sheets.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.357-357
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• 2006

Many industrial sources of proteins can be used as raw materials to produce films, molded materials, and various hollow items either by "casting" techniques or by "thermoplastic processing". Combining proteins with natural fibbers, paper or biodegradable polyesters is very promising to form biodegradable composites witch take advantage of the barrier and mechanical properties of each component. Using nano-fillers to form nanocomposites has also been shown to be interesting to improve properties. Production, with low transformation cost, of protein based materials to form biodegradable materials with controlled functional properties for food uses, medical uses, packaging, agriculture, controlled release systems, etc. is discussed.