• Korean Journal of Materials Research
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• v.29 no.1
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• pp.23-29
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• 2019

Three-dimensional(3D) printing is a process for producing complex-shaped 3D objects by repeatedly stacking thin layers according to digital information designed in 3D structures. 3D printing can be classified based on the method and material of additive manufacturing process. Among the various 3D printing methods, digital light processing is an additive manufacturing technique which can fabricate complex 3D structures with high accuracy. Recently, there have been many efforts to use ceramic material for an additive manufacturing process. Generally, ceramic material shows low processability due to its high hardness and strength. The introduction of additive manufacturing techniques into the fabrication of ceramics will improve the low processability and enable the fabrication of complex shapes and parts. In this study, we synthesize silica composite material that can be applied to digital light processing. The rheological and photopolymeric properties of the synthesized silica composite are investigated in detail. 3D objects are also successfully produced using the silica composite and digital light processing.

• Elastomers and Composites
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• v.58 no.1
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• pp.44-56
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• 2023

Additive manufacturing (AM) or three-dimensional (3D) printing of metals has been drawing significant attention due to its reliability, usefulness, and low cost with rapid prototyping. Among the various AM technologies, fused deposition modeling (FDM) or fused filament fabrication is receiving much interest because of its simple manufacturing processing, low material waste, and cost-effective equipment. FDM technology uses metal-filled polymer filaments for 3D printing, followed by debinding and sintering to fabricate complex metal parts. An efficient binder is essential for producing polymer filaments and the thermal post-processing of printed objects. This study involved an in-depth investigation of and a fabrication route for a novel multi-component binder system with steel alloy powder (45 vol.%) ranging from filament fabrication and 3D printing to debinding and sintering. The binder system consisted of polyvinyl pyrrolidone (PVP) as a binder and thermoplastic polyurethane (TPU) and polylactic acid (PLA) as a carrier. The PVP binder held the metal components tightly by maintaining their stoichiometry, and the TPU and PLA in the ratio of 9:1 provided flexibility, stiffness, and strength to the filament for 3D printing. The efficacy of the binder system was examined by fabricating 3D-printed cubic structures. The results revealed that the thermal debinding and sintering processes effectively removed the binder/carrier from the cubic structures, resulting in isotropic shrinkage of approximately 15.8% in all directions. The scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) patterns displayed the microstructure behavior, phase transition, and elemental composition of the 3D cubic structure.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.4
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• pp.1-7
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• 2023

The ability of 3D/4D printing technology to create arbitrary 3D structures provides a greater degree of freedom in the design of printed structures. This capability has influenced the field of electronics and biomedical applications by enabling the trends of device miniaturization, customization, and personalization. Here, the current state-of-the-art knowledge of 3D printed electronics and biomedical applications with the unique and unusual properties enabled by 3D/4D printing is reviewed. Specifically, the review encompasses emerging areas involving recyclable and degradable electronics, metamaterial-based pressure sensor, fully printed portable photodetector, biocompatible and high-strength teeth, bioinspired microneedle, and transformable tube array for 3D cell culture and histology.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.391-396
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• 2020

In this study, we developed a phosphor film screen that can be applied to radiographs during non-destructive testing using Gd₂O₂S:Tb phosphor compounds. The image uniformity of the fabricated phosphor screen film was analyzed by FE-SEM, RMS and RDS analysis. In addition, the tensile strength, elongation, and modulus of elasticity of the Gd₂O₂S:Tb phosphor screen were evaluated by measuring the stress-strain characteristic curve. As a result, it was evaluated that the RSD value had an excellent image uniformity within 10% of the evaluation criteria. In addition, as a result of evaluation of physical properties, the tensile strength was 1.1760 N/㎟, the tensile strength at break was 1.1515 N/㎟. These results suggest that the Gd₂O₂S:Tb phosphor screen fabricated using the room temperature gel-printing method could be applied to digital radiography detectors for radiography.

• The Journal of Advanced Prosthodontics
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• v.15 no.4
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• pp.189-201
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• 2023

PURPOSE. The aim of this study was to investigate the mechanical properties of three-dimensional (3D) printed denture base resin incorporating microcapsules containing plant essential oils. MATERIALS AND METHODS. Denture base specimens containing up to 3% w/v essential oil microcapsule powders (MCPs), i.e., eucalyptus, geranium, lavender, menthol, and tea tree, in two resins (Detax and NextDent 3D+) were 3D printed using two printers (Asiga and NextDent 5100). The dispersion and interaction of the MCPs in the resin were assessed by SEM while the mechanical properties of the incorporated denture base including flexural strength (MPa), flexural modulus (MPa), Vickers hardness (VHN), and surface roughness (Ra) were also subsequently evaluated. Statistical analysis of any differences in mean values was determined using a two-way ANOVA with Tukey's post hoc testing (α = .05). RESULTS. The spherical shape of the MCPs was maintained during the mixing and polymerization/printing process. However, the Detax-Asiga group showed significant agglomeration of the MCPs even at the lowest MCP concentration levels (0.5% w/v). Overall, as the microcapsule concentration increased, the mean flexural strength decreased, though the menthol MCP groups remained compliant with the ISO standard. The flexural modulus and harness remained relatively unchanged, and the flexural modulus complied with the ISO standard regardless of the MCP concentration. Surface roughness increased with the addition of the MCPs but also remained below that required for clinical acceptance. CONCLUSION. Incorporation of microencapsulated plant essential oils into 3D printed denture base resin was successfully achieved. While incorporation negatively influenced flexural strength and surface roughness, little effect on flexural modulus and Vickers hardness was demonstrated.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.4
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• pp.56-62
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• 2006

Various kinds of rapid prototyping processes are available, such as stereo-lithography apparatus(SLA), fused deposition modeling(FDM), selective laser sintering(SLS), 3 dimensional printing(3DP), and laminated object manufacturing(LOM). In this study, benchmark tests are carried out to obtain detailed informations about surface roughness and mechanical properties of those parts. Although the patterns and roughness averages of part surface are dependent on the surface direction, the roughness of SLA part is the best and that of FDM or 3DP part is the worst. It is shown that FDM part has an advantage in impact strength, SLS(or EOS) part in compressive strength, and LOM part has an advantage in tensile strength and heat resistance, but the change of building direction in FDM and LOM processes severely weakens the tensile and impact strengths.

• Journal of Forest and Environmental Science
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• v.23 no.2
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• pp.119-122
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• 2007

Actually, about 45% of total costs for wastewater treatment in a papermaking mill is spent for sludge disposal and the cost of chemicals used to improve the dewaterability of sludge takes much part of it. In order to reduce sludge disposal cost and to improve the efficiency of sludge treatment, it is necessary to minimize the amount of water contained within the sludge and hence to improve the dewaterability of the sludge. The objective of this study was to elucidate the way of improving the dewaterability of sludge. Three types of wastewater from a tissue paper mill, a printing paper mill and a newsprint mill were used and two types of high molecular weight flocculants (anionic PAM and cationic PAM) were used to treat the wastewater. Dewaterability of sludge was evaluated by measuring floc strength.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.3
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• pp.373-376
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• 2021

Tested the flexural strength and maximum load of two types of dental 3 D printed temporary tooth materials of the DLP method. The average flexural strength was 206.98 MPa in the test group and 139.77 MPa in the control group. The average flexural strength of the experimental group was 67.21 MPa higher than that of the control group. In the maximum load experiment, an average of 44.16N in the experimental group and 37.31N in the control group were measured. The average value of 6.85N was higher in the experimental group, and the durability of the artificial tooth restoration was improved.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.193-198
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• 2021

In this study, the rheological characteristics and of 3D printing composite materials and the compressive strength characteristics according to the lamination patterns were evaluated. As a result of rheology test, rapid material change was observed after 60 minutes of extrusion, yielding stress 1.4 times higher than immediately after mixing, and plastic viscosity was 14.94-25.62% lower. The compressive strength of the specimens manufactured in the mold and the laminated specimens were compared, and the lamination pattern of the laminated specimens were 0°, 45°, and 90° as variables. The compressive strength of the mold casting specimen and the laminated specimen from 1 to 28 days of age showed similar performance regardless of the lamination pattern. In particular, at the age of 28 days, the modulus of elasticity, maximum compressive strength, and strain at maximum stress of all specimens were almost the same. In order to analyze the interface of the laminated specimens, X-ray CT analysis of the specimen whose compressive strength were measured was performed. Through CT analysis, it was confirmed that cracks did not occur at the lamination interface, which can be judged that the interface in the laminated specimen behaved in an integrated manner.

• The Journal of Korean Academy of Prosthodontics
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• v.52 no.2
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• pp.67-73
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• 2014

Purpose: The purpose of present study is to compare mechanical properties and microstructural characteristics of fractured surface for cast, 3-D printing laser sintered and CAD/CAM milled cobalt-chromium (Co-Cr) alloy specimens and to investigate whether laser sintered technique is adequate for dental applications. Materials and methods: Thirty six flat disc shape Co-Cr alloy specimens were fabricated for surface hardness test and divided into three groups according to the manufacturing methods; 12 specimens for casting (n=12), 12 specimens for laser sintered technology (n=12) and 12 specimens for milled technology (n=12). Twelve dumbbell shape specimens for each group were also fabricated for a tensile test. Statistical comparisons of the mechanical properties for the alloys were performed by Kruskal-Wallis test followed by Mann-Whitney and Bonferroni test. The microstructural characteristics of fractured surfaces were examined using SEM. Results: There were significant differences in the mean Vickers hardness values between all groups and the cast specimen showed the highest (455.88 Hv) while the CAD/CAM milled specimen showed the lowest (243.40 Hv). Significant differences were found among the three groups for ultimate tensile strength, 0.2% yield stress, elongation, and elastic modulus. The highest ultimate tensile strength value (1442.94 MPa) was shown in the milled group and the highest 0.2% yield strength (1136.15 MPa) was shown in the laser sintered group. Conclusion: Different manufacturing methods influence the mechanical properties and microstructure of the fractured surfaces in Co-Cr alloys. The cast Co-Cr alloy specimens showed the highest Vickers hardness, and the CAD/CAM milled specimens revealed the highest tensile strength value. All alloys represent adequate mechanical properties satisfying the ISO standards of dental alloy.