• The Journal of Advanced Prosthodontics
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• v.15 no.5
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• pp.227-237
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• 2023

PURPOSE. This study aimed to assess and compare the color stability, flexural strength (FS), and surface roughness of occlusal splints fabricated from heat-cured acrylic resin, milled polymethyl methacrylate (PMMA)-based resin, and 3D-printed (PMMA) based-resin. MATERIALS AND METHODS. Samples of each type of resin were obtained, and baseline measurements of color and surface roughness were recorded. The specimens were divided into three groups (n = 10) and subjected to distinct aging protocols: thermomechanical cycling (TMC), simulated brushing (SB), and control (without aging). Final assessments of color and surface roughness and three-point bending test (ODM100; Odeme) were conducted, and data were statistically analyzed (2-way ANOVA, Tukey, P <.05). RESULTS. Across all resin types, the most significant increase in surface roughness (Ra) was observed after TMC (P < .05), with the 3D-printed resin exhibiting the lowest Ra (P < .05). After brushing, milled resin displayed the highest Ra (P < .05) and greater color alteration (∆E₀₀) compared to 3D-printed resin. The most substantial ∆E₀₀ was recorded after brushing for all resins, except for heat-cured resin subjected to TMC. Regardless of aging, milled resin exhibited the highest FS (P < .05), except when compared to 3D-printed resin subjected to TMC. Heat-cured resin exposed to TMC demonstrated the lowest FS, different (P < .05) from the control. Under control conditions, milled resin exhibited the highest FS, different (P < .05) from the brushed group. 3D-printed resin subjected to TMC displayed the highest FS (P < .05). CONCLUSION. Among the tested resins, 3D-printed resin demonstrated superior longevity, characterized by minimal surface roughness and color alterations. Aging had a negligible impact on its mechanical properties.

• Korean Journal of Materials Research
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• v.17 no.9
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• pp.453-457
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• 2007

Interest in use of ink-jet printing for pattern-on-demand fabrication of metal interconnects without complicated and wasteful etching process has been on rapid increase. However, ink-jet printing is a wet process and needs an additional thermal treatment such as an annealing process. Since a metal ink is a suspension containing metal nanoparticles and organic capping molecules to prevent aggregation of them, the microstructure of an ink-jet printed metal interconnect 'as dried' can be characterized as a stack of loosely packed nanoparticles. Therefore, during being treated thermally, an inkjet-printed interconnect is likely to evolve a characteristic microstructure, different from that of the conventionally vacuum-deposited metal films. Microstructure characteristics can significantly affect the corresponding electrical and mechanical properties. The characteristics of change in microstructure and electrical resistivity of inkjet-printed silver (Ag) films when annealed isothermally at a temperature between 170 and $240^{\circ}C$ were analyzed. The change in electrical resistivity was described using the first-order exponential decay kinetics. The corresponding activation energy of 0.44 eV was explained in terms of a thermally-activated mechanism, i.e., migration of point defects such as vacancy-oxygen pairs, rather than microstructure evolution such as grain growth or change in porosity.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.207-210
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• 2009

According to the recent demand for materials for use in various displays and solid state lightings, new phosphors with improved performance have been pursued consistently. Multi objective genetic algorithm assisted combinatorial material search (MOGACMS) strategies have been applied to various multi-compositional inorganic systems to search for new phosphors and to optimize the properties of phosphors.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.16.2-16.2
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• 2009

Developing a low cost printing material that can replace silver for the formation of a conducting pattern is an important issue in printed electronics. We report a novel approach using a non-oxidized copper material during the printing and sintering process under ambient conditions, which was previously considered unachievable. An attempt was made to understand the conversion process of cuprous oxide nanoparticle aggregates on metallic copper crystals through chemical reduction in the solution phase. The detailed mechanism for this conversion, including the role of the surfactant and crystal growth, was examined.

• Composites Research
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• v.36 no.3
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• pp.193-198
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• 2023

Currently, there are many discussions about composite materials and 3D printed composite material to weight reduction of ships. A test was conducted to confirm the applicability of the 3D printed composite material to ships and offshore structures by linking the 3D printing technology with excellent productivity and the composite material with corrosion resistance and lightweight characteristics in salt water environments. In order to apply the 3D printed composite material used in this paper to ships and offshore structures, the temperature environmental effects that can be exposed in the marine environment should be considered. Therefore, the tensile test was conducted with specimen of Carbon + Onyx, Carbon + Nylon, HSHT glass + Onyx, HSHT glass + Nylon material in low temperature (-50℃), room temperature (20℃), and high temperature (50℃) environments that can be exposed to the marine environment. As a result of the tensile test, the carbon + onyx specimen showed the highest tensile strength and the HSHT glass + onyx specimen showed the highest tensile strain. In addition, by analyzing the tested specimens, the failure mode of the 3D printed composite material specimens exposed to various temperature environments was analyzed.

• Korean Journal of Materials Research
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• v.24 no.11
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• pp.632-638
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• 2014

We investigated the effects of DMAB (Borane dimethylamine complex, C2H10BN) in electroless Ni-B film with addition of DMAB as reducing agent for electroless Ni plating. The electroless Ni-B films were formed by electroless plating of near neutral pH (pH 6.5 and pH 7) at $50^{\circ}C$. The electroless plated Ni-B films were coated on screen printed Ag pattern/PET (polyethylene terephthalate). According to the increase of DMAB (from 0 to 1 mole), the deposition rate and the grain size of electroless Ni-B film increased and the boron (B) content also increased. In crystallinity of electroless Ni-B films, an amorphization reaction was enhanced in the formation of Ni-B film with an increasing content of DMAB; the Ni-B film with < 1 B at.% had a weak fcc structure with a nano crystalline size, and the Ni-B films with > 5 B at.% had an amorphous structure. In addition, the Ni-B film was selectively grown on the printed Ag paste layer without damage to the PET surface. From this result, we concluded that formation of electroless Ni-B film is possible by a neutral process (~green process) at a low temperature of $50^{\circ}C$.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.8
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• pp.426-431
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• 2015

The advantages of a printed circuit heat exchanger (PCHE) are the compactness and efficiency derived from its heat-transfer characteristics; furthermore, a PCHE for which a diffusion bonding method was used during production can be applied to extreme environments such as a cryogenic condition. In this study, a micro-channel PCHE fabricated by diffusion bonding was investigated in a cryogenic environment regarding its thermal performance and the pressure drop. The test rig consists of an LN2 storage tank, vaporizers, heaters, and a cold box, whereby the vaporized cryogenic nitrogen flows in hot and cold streams. The overall heat-transfer coefficients were evaluated and compared with traditional correlations. Lastly, we suggested the modified heat-transfer correlations for a PCHE in a cryogenic condition.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.6
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• pp.610-615
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• 2022

BaTiO₃ is one of the ferroelectric materials with excellent dielectric properties such as high dielectric constant, low dielectric loss, and is widely used for the manufacturing of capacitors, piezoelectric converters, microsensors, and ferroelectric memories. Inkjet printing is a technology which uses digital and contactless methods which significantly improves flexibility associated with material and structural design, reducing manufacturing costs. Therefore, the top and bottom electrodes, BaTiO₃ ink, and photocurable resin were all printed by an inkjet to produce a BaTiO₃ capacitor. The properties of the printed thin film were analyzed. It was confirmed that the photocurable resin ink was well-infiltrated between the BaTiO₃ powder particles printed by inkjet. The dielectric properties of the capacitor such as dielectric constant which varies in accordance with frequency, polarization and tunability that changes with voltage, were measured.

• Corrosion Science and Technology
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• v.22 no.3
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• pp.153-163
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• 2023

Two types of accelerated tests, Water Drop Test (WDT) and Temperature-Humidity-Bias Test (THBT), can be used to evaluate the susceptibility to electrochemical migration (ECM). In the WDT, liquid water is directly applied to a specimen, typically a patterned conductor like a printed circuit board. Time to failure in the WDT typically ranges from several seconds to several minutes. On the other hand, the THBT is conducted under elevated temperature and humidity conditions, allowing for assessment of design and life cycle factors on ECM. THBT is widely recognized as a more suitable method for reliability testing than WDT. In both test methods, localized corrosion can be observed on the anode. Composition of dendrites formed during the WDT is similar to that formed during THBT. However, there is a lack of correlation between the time to failure obtained from WDT and that obtained from THBT. In this study, we investigated the relationship between electrochemical parameters and time to failure obtained from both WDT and THBT. Differences in time to failure can be attributed to actual anode potential obtained in the two tests.

• Korean Journal of Materials Research
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• v.17 no.12
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• pp.676-681
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• 2007

According to progress rapidly digitalization, networked and mobilization of electronics industry, there are demands for being smaller, thinner, more light, and more efficient complex functions of electronic devices which are wireless devices, semi-conductors, packages and mobile devices. Therefore, the solder resist on a printed circuit board have been required with the high resolution and the eco-friendly materials in the surface treatments such as high heating process and coating process with electrolysis. In this study, the photoinitiator initiator and monomers of the solder resist were prepared with their contents for reducing the occurrence of the under-cut. We investigated the sample surface by UV/VIS spectrometer, FT-IR, OM after HASL and ENIG process. From our results, it is possible to get a high adhesion of resist with optimal contents between the photoinitiator initiator and monomers after surface treatments.