• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.6
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• pp.861-868
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• 2021

To confirm the influence of modified starch on frozen storage stability, the microstructure and sensory characteristics of fish cakes, called Eomuk in Korea, by using seven varieties of starch, including native starch (NS), physically treated corn starch (MS) and modified starch [treatment with acetate (SA-1, SA-2 and SA-3), hydroxypropyl (HS), and acetylated distarch adipate (ADA)] were evaluated. Scanning electron microscopy (SEM) photographs showed fish cakes with NS had a finer and denser network structure than those made with modified starches. During frozen storage, fish cakes with HS and ADA exhibited a stable structure, as evaluated by porosity and rough surface. The results of the sensory evaluation showed that modified starch, including HS, SA-2 and ADA, increased the taste and firmness of the fish cakes, while NS, MS and the modified starch SA-3 resulted a decrease in the sensory properties during storage. Therefore, HS, SA-2 and ADA are suitable additives to improve the sensory quality of frozen fish cakes.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.6
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• pp.295-302
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• 2022

The present study aims to investigate the effect of Al content on microstructure and hardness of discontinuous precipitates (DPs) formed by continuous cooling (CC) in Mg-8%Al and Mg-9.5%Al alloys. The DPs had a wide range of (α+β) interlamellar spacings, which may well be attributed to the different transformation temperatures during CC. The higher Al content gave rise to the higher level of interlamellar spacings of the DPs, and thicker and larger amount of β phase layer in the DPs. It is noticeable that the Mg-9.5%Al alloy exhibited higher hardness of the DPs than the Mg-8%Al alloy, but the ratio of increase in hardness of the DPs compared to that of the as-cast state was similar regardless of the Al content. The reason was discussed based on the differences in microstructures of the DPs for the Mg-8%Al and Mg-9.5%Al alloys.

• Advances in concrete construction
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• v.14 no.5
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• pp.341-354
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• 2022

Treatment of solid waste building materials is a crucial method of disposal and an area of ongoing research. New standards for the treatment of solid waste building materials are necessary due to multisource features, huge quantities, and complicated compositions of solid waste. In this research, sustainable nanomaterial mixtures containing nano-paper waste (NPW) and nano-metakaolin (NMK) were used as a substitute for Portland cement. Portland cement was replaced with different ratios of NPW and NMK (0%, 4%, 8%, and 12% by weight of cement) while the cement-to-water ratio remained constant at 0.4 in all mortar mixtures. The fresh properties had a positive effect on them, and with the increase in the percentage of replacement, the fresh properties decreased. The results of compressive strength at 7 and 28 days and flexural strength at 28 days show that the nanomaterials improved the strength, but the results of NMK were better than those of NPW. The best replacement rate was 8%, followed by 4%, and finally 12% for both materials. The combination of NMK and NPW as a replacement (12% NMK + 12% NPW) showed less shrinkage than the others because of the high pozzolanic reactivity of the nanomaterials. The combination of NMK and NPW improved the microstructure by increasing the hydration volume and lowering the water in the cement matrix, as clearly observed in the C-S-H decomposition.

• Journal of Surface Science and Engineering
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• v.34 no.2
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• pp.97-104
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• 2001

($Ti_{ 1-x}$$Al_{ x}$)N has been deposited on high speed steel (HSS) substrate using PECVD from the gas mixture of $TiC1_4$, $AlC1_4$, $NH_3$, $H_2$, and Ar. The correlation between the microstructure and the mechanical properties was investigated. ($Ti_{1-x}$$Al_{ x}$)N showed single phase NaCl-structure up to X=0.87, while a mixed phase of NaCl Type (Ti, Al) N and wurtzite structure AlN was observed for 0.87$Ti_{1-x}$ $Al_{x}$ )N became by degrees as increasing X, which made the hardness of the coating higher by Al addition. When the coating was composed of a mixed phase, however, the hardness decreased abruptly due to the effect of soft AlN phase. The wear volume of the coatings could be obtained as the concentration of the coating was varied, and the relation between the wear volume and hardness or the adhesion strength was discussed.

• Journal of Powder Materials
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• v.30 no.2
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• pp.116-122
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• 2023

Because magnets fabricated using Nd-Fe-B exhibit excellent magnetic properties, this novel material is used in various high-tech industries. However, because of the brittleness and low formability of Nd-Fe-B magnets, the design freedom of shapes for improving the performance is limited based on conventional tooling and postprocessing. Laser-powder bed fusion (L-PBF), the most famous additive manufacturing (AM) technique, has recently emerged as a novel process for producing geometrically complex shapes of Nd-Fe-B parts owing to its high precision and good spatial resolution. However, because of the repeated thermal shock applied to the materials during L-PBF, it is difficult to fabricate a dense Nd-Fe-B magnet. In this study, a high-density (>96%) Nd-Fe-B magnet is successfully fabricated by minimizing the thermal residual stress caused by substrate heating during L-PBF.

• Structural Engineering and Mechanics
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• v.82 no.4
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• pp.543-556
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• 2022

Fly ash (FA) is the main additive to concretes currently produced. This substitute of ordinary Portland cement (OPC) have a positive effect on the structure and mechanical parameters of mature concrete. Unfortunately, the problem of using FA as the OPC replacement is that it significantly reduces the performance of concretes in the early stages of their curing. This limits the possibility of using this type of concrete, e.g., in the prefabrication, where it is required to obtain high strength composites after short periods of their curing. In order to minimize these negative effects, research has been undertaken to increase the early strength of the concretes with FA through the application of a specially dedicated chemical nanoadmixture (NA) in the form of seeds of the C-S-H phase. Therefore, this paper presents results of tests of modified concretes both with the addition of FA and with NA. The analyses were carried out based on the results of the macroscopic and microstructural tests in 5 time periods, i.e. after: 4, 8, 12, 24 and 72 hours. The greatest increase in mechanical strength parameters and rapid development of the basic matrix phases in composites in the first 12 hours of composites curing was observed.

• Composites Research
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• v.36 no.2
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• pp.86-91
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• 2023

Thermoplastic polyurethane (TPU) is a material whose mechanical properties change according to the phase separation of its unique internal microstructure and is therefore used in various industries. Use of TPU as composites helps in improving the desirable characteristics and properties in accordance with usage. Eco-friendly fillers one of the fillers are on the rise and those are mostly used for reinforcing role. Suberin, which can be extracted from cork, is the main component of cork. It is known to serve high damping property of elastomer composite. The original chemical structure of Suberin is an aliphatic polyester aggregate. In this research, Suberin is obtained after depolymerization into an oligomer having 2 or 3 ester bonds through alkaline hydrolysis. The extracted suberin was added to the matrix which is thermoplastic polyurethane as an eco-friendly filler for improving vibration damping property. As a result, when 10 wt% of suberin was added into thermoplastic polyurethane the existing trade-off relationship was overcome. And it is attained the elastic modulus and damping factor at room temperature improving 92 and 59%, respectively, compared to the original matrix. Those results are from the interaction between the microstructure of TPU and suberin.

• Transactions of Materials Processing
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• v.31 no.3
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• pp.117-123
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• 2022

In this study, a commercial AZ61 magnesium alloy is extruded at 300 ℃ and 400 ℃ and the microstructures, mechanical properties, and high-cycle fatigue properties of the extruded materials are investigated. Both extruded materials have a fully recrystallized microstructure with no Mg₁₇Al₁₂ precipitates. The average grain size and maximum basal texture intensity of the extruded material increase with increasing extrusion temperature. The material extruded at 400 ℃ (AZ61-400) has higher tensile yield strength and lower compressive yield strength than the material extruded at 300 ℃ (AZ61-300) because of the stronger basal texture of the former. Because of coarser grain size, the tensile elongation of AZ61-400 is lower than that of AZ61-300. Despite the differences in microstructures and tensile/compressive properties, the two extruded materials have the same fatigue strength of 110 MPa. This is because the finer grain size of AZ61-300 causes an increase in fatigue strength, but its weaker texture causes a decrease in fatigue strength. In both extruded materials, fatigue cracks initiate at the surface of fatigue specimens at all stress amplitudes tested.

• Archives of Metallurgy and Materials
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• v.64 no.2
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• pp.623-626
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• 2019

Rare earth Nd-Fe-B, a widely used magnet composition, was synthesized in a shape of powders using gas atomization, a rapid solidification based process. The microstructure and properties were investigated in accordance with solidification rate and densification. Detailed microstructural characterization was performed by using scanning electron microscope (SEM) and the structural properties were measured by using X-ray diffraction. Iron in the form of α-Fe phase was observed in powder of about 30 ㎛. It was expected that fraction of Nd₂Fe₁₄B phase increased rapidly with decrease in powder size, on the other hand that of α-Fe phase was decreased. Nd-rich phase diffused from grain boundary to particle boundary after hot deformation due to capillary action. The coercivity of the alloy decreased with increase in powder size. After hot deformation, Nd₂Fe₁₄B phase tend to align to c-axis.

• Archives of Metallurgy and Materials
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• v.66 no.4
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• pp.1033-1036
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• 2021

Laser cladding is a method that can be applied to repair the crack and break on the mold and die surfaces, as well as generate new attributes on the surface to improve toughness, hardness, and corrosion resistance. It is used to extend the life of the mold. It also has the advantages of superior bonding strength and precision coating on a local area compared with the conventional thermal spraying technology. In this study, we investigated the effect of cladding on low carbon alloy steel using 18%Cr-2.5%Ni-Fe powder (Rockit404), which showed high hardness on the die surface. The process conditions were performed in an argon atmosphere using a diode laser source specialized for 900-1070 nm, and the output conditions were 5, 6, and 10 kW, respectively. After the cladding was completed, the surface coating layer's shape, the hardness according to the cross-section's thickness, and the microstructure were analyzed.