In the present work, a new hydrogen added argon heat treatment process that prevents the formation of hydrides and eliminates the dehydrogenation step, is developed. Dissolved hydrogen has a good effect on sintering properties such as oxidation resistance and density of greens. This process can also reduce costs and processing time. In the experiment, commercially available Ti-6Al-4V powders are used. The powders are annealed using tube furnace in an argon atmosphere at 700oC and 900oC for 120 min. Hydrogen was injected temporarily during argon annealing to dissolve hydrogen, and a dehydrogenation process was performed simultaneously under an argon-only atmosphere. Without hydride formation, hydrogen was dissolved in the Ti-6Al-4V powder by X-ray diffraction and gas analysis. Hydrogen is first solubilized on the beta phase and expanded the beta phases’ cell volume. TGA analysis was carried out to evaluate the oxidation resistance, and it is confirmed that hydrogen-dissolved Ti-6Al-4V powders improves oxidation resistance more than raw materials.

Ni-based oxide dispersion strengthened (ODS) alloys have a higher usable temperature and better hightemperature mechanical properties than conventional superalloys. They are therefore being explored for applications in various fields such as those of aerospace and gas turbines. In general, ODS alloys are manufactured from alloy powders by mechanical alloying of element powders. However, our research team produces alloy powders in which the Ni5Y intermetallic phase is formed by an atomizing process. In this study, mechanical alloying was performed using a planetary mill to analyze the milling behavior of Ni-based oxide dispersions strengthened alloy powder in which the Ni5Y is the intermetallic phase. As the milling time increased, the Ni5Y intermetallic phase was refined. These results are confirmed by SEM and EPMA analysis on microstructure. In addition, it is confirmed that as the milling increased, the mechanical properties of Ni-based ODS alloy powder improve due to grain refinement by plastic deformation.

This study examines paraelectric Bi1.5Zn1.0Nb1.5O7 (BZN), which has no hysteresis and high dielectric strength, for energy density capacitor applications. To increase the breakdown dielectric strength of the BZN film further, poly(vinylidene fluoride) BZN-PVDF composite film is fabricated by aerosol deposition. The volume ratio of each composition is calculated using dielectric constant of each composition, and we find that it was 12:88 vol% (BZN:PVDF). To modulate the structure and dielectric properties of the ferroelectric polymer PVDF, the composite film is heat-treated at 200 oC for 5 and 30 minutes following quenching. The amount of α-phase in the PVDF increases with an increasing annealing time, which in turn decreases the dielectric constant and dielectric loss. The breakdown dielectric strength of the BZN film increases by mixing PVDF. However, the breakdown field decreases with an increasing annealing time. The BZN-PVDF composite film has the energy density of 4.9 J/cm3, which is larger than that of the pure BZN film of 3.6 J/cm3.

A powder mixture of 70 wt% Al2O3 and 30 wt% hydroxyapatite (HA) is sintered at 1300 ℃ or 1350 ℃ for 2 h at normal pressure. An MgF2-added composition to make HA into fluorapatite (FA) is also prepared for comparison. The samples without MgF2 show α & β-tricalcium phosphates (TCPs) and Al2O3 phases with no HA at either of the sintering temperatures. In the case of 1,350 ℃, a CaAl4O7 phase is also found. Densification values are 69 and 78 %, and strengths are 156 and 104MPa for 1,300 and 1,350 ℃, respectively. Because the decomposition of HA produces a H2O vapor, fewer large pores of 5-6 μm form at 1,300 ℃. The MgF2-added samples show FA and Al2O3 phases with no TCP. Densification values are 79 and 87%, and strengths are 104 and 143 MPa for 1,300 and 1,350 ℃, respectively. No large pores are observed, and the grain size of FA (1-2 μm) is bigger than that of TCP (0.7 μm ≥) in the samples without MgF2. The resulting TCP/Al2O3 and FA/Al2O3 composites fabricated in situ exhibit strengths 6-10 times higher than monolithic TCP and HA.

This study examined the quality characteristics of dumpling shells prepared with 0, 2, 4, 6, and 8% mulberry leaf powder. According to the amylograph data, the composite of mulberry leaf powder-wheat flour samples reduced the gelatinization temperatures, viscosities at 95oC, and maximum viscosity with increasing mulberry leaf powder content. The lightness (L) and redness (a) values decreased with increasing mulberry leaf powder content, whereas the yellowness (b) value increased. In addition, the weight, volume, and turbidity increased after cooking. In terms of the textural characteristics, addition of mulberry leaf powder increased the hardness, springiness, cohesiveness, chewiness, and adhesiveness. The DPPH free radical scavenging activity of the dumpling shells increased significantly (p<0.05) with increasing levels of mulberry leaf powder. The taste, chewiness and texture of the dumpling shells prepared with added 4% mulberry leaf powder were preferred. The sensory evaluation showed that the overall preference of the dumpling shell with the addition of 4% mulberry leaf powder was more effective than the control.

High performance lithium-ion batteries (LIBs) have attracted considerable attention as essential energy sources for high-technology electrical devices such as electrical vehicles, unmanned drones, uninterruptible power supply, and artificial intelligence robots because of their high energy density (150-250 Wh/kg), long lifetime (> 500 cycles), low toxicity, and low memory effects. Of the high-performance LIB components, cathode materials have a significant effect on the capacity, lifetime, energy density, power density, and operating conditions of high-performance LIBs. This is because cathode materials have limitations with respect to a lower specific capacity and cycling stability as compared to anode materials. In addition, cathode materials present difficulties when used with LIBs in electric vehicles because of their poor rate performance. Therefore, this study summarizes the structural and electrochemical properties of cathode materials for LIBs used in electric vehicles. In addition, we consider unique strategies to improve their structural and electrochemical properties.

The gas sensor is essential to monitoring dangerous gases in our environment. Metal oxide (MO) gas sensors are primarily utilized for flammable, toxic and organic gases and O3 because of their high sensitivity, high response and high stability. Tungsten oxides (WO3) have versatile applications, particularly for gas sensor applications because of the wide bandgap and stability of WO3. Nanosize WO3 are synthesized using the hydrothermal method. Asprepared WO3 nanopowders are in the form of nanorods and nanorulers. The crystal structure is hexagonal tungsten bronze (MxWO3, x =< 0.33), characterized as a tunnel structure that accommodates alkali ions and the phase stabilizer. A gas detection test reveals that WO3 can detect acetone, butanol, ethanol, and gasoline. This is the first study to report this capability of WO3.

In this study, the effects of powder size and composition on the reflectance of Al-Si based alloys are presented. First, the reflectance of Al-Si bulk and powder are analyzed to confirm the effect of powder size. Results show that the bulk has a higher reflectance than that of powder because the bulk has lower surface defects. In addition, the larger the particle size, the higher is the reflectance because the interparticle space decreases. Second, the effect of composition on the reflectance by the changing composition of Al-Si-Mg is confirmed. Consequently, the reflectance of the alloy decreases with the addition of Si and Mg because dendrite Si and Mg2Si are formed, and these have lower reflectance than pure Al. Finally, the reflectance of the alloy is due to the scattering of free electrons, which is closely related to electrical conductivity. Measurements of the electrical conductivity based on the composition of the Al-Si-Mg alloy confirm the same tendency as the reflectance.

In aluminum brazing processes, corrosive flux, which is used in preventing oxidation, is currently raising environmental concerns because it generates many pollutants such as dioxin. The brazing process involving noncorrosive flux is known to encounter difficulties because the melting temperature of the flux is similar to that of the base material. In this study, a new brazing filler material is developed based on aluminum and non-corrosive flux composite powder. To minimize the interference of consolidation aluminum alloy powder by the flux, the flux is intentionally embedded in the aluminum alloy powder using a mechanical milling process. This study demonstrates that the morphology of the composite powder can be varied according to the mixing process, and this significantly affects the relative density and mechanical properties of the final filler samples.

In this study, a method to remove residual powder on a multi-layered graphene and a new approach to transfer multi-layered graphene at once are studied. A graphene one-step transfer (GOST) method is conducted to minimize the residual powder comparison with a layer-by-layer transfer. Furthermore, a residual powder removing process is investigated to remove residual powder at the top of a multi-layered graphene. After residual powder is removed, the sheet resistance of graphene is decreased from 393 to 340 Ohm/sq in a four-layered graphene. In addition, transmittance slightly increases after residual powder is removed from the top of the multi-layered graphene. Optical and atomic-force microscopy images are used to analyze the graphene surface, and the Ra value is reduced from 5.2 to 3.7 nm following residual powder removal. Therefore, GOST and residual powder removal resolve the limited application of graphene electrodes due to residual powder.

In this study, porous Mo-5 wt% Cu with unidirectionally aligned pores is prepared by freeze drying of camphene slurry with MoO3-CuO powders. Unidirectional freezing of camphene slurry with dispersion stability is conducted at -25℃, and pores in the frozen specimens are generated by sublimation of the camphene crystals. The green bodies are hydrogen-reduced at 750℃ and sintered at 1000℃ for 1 h. X-ray diffraction analysis reveals that MoO3- CuO composite powders are completely converted to a Mo-and-Cu phase without any reaction phases by hydrogen reduction. The sintered bodies with the Mo-Cu phase show large and aligned parallel pores to the camphene growth direction as well as small pores in the internal walls of large pores. The pore size and porosity decrease with increasing composite powder content from 5 to 10 vol%. The change of pore characteristics is explained by the degree of powder rearrangement in slurry and the accumulation behavior of powders in the interdendritic spaces of solidified camphene.

본 연구는 섬초 분말 1%, 3%, 5%, 7% 첨가비율에 따른 식빵의 품질 특성을 연구하였다. 반죽의 pH는 첨가량이 증가할수록 낮아졌으며, 7% 첨가에서 낮게 나타났다. 반죽의 발효 팽창력은 1차 발효와 2차 발효에서 첨가량이 증가할수록 낮아졌으며, 첨가량에 따라 반죽의 발효시간이 지날수록 감소하는 것으로 나타났다. 식빵의 수분함량은 첨가량이 증가할수록 낮아졌으며, 식빵의 부피는 1% 첨가> 3% 첨가> 5% 첨가> 7% 첨가 순으로 나타났다. 비용적은 첨가량이 증가할수록 제품의 부피는 낮게 나타났으며, 비용적이 낮을수록 부피는 감소하였다. 내부색도는 첨가량이 증가할수록 명도, 적색도는 감소하였으며, 황색도는 증가하는 걸로 나타났다. 총 구성아미노산 함량은 첨가량이 증가할수록 높게 나타났으며, glutamic acid가 높게 나타났다. 총 유리아미노산 함량은 첨가량이 증가할수록 높게 나타났으며, 5% 첨가와 7% 첨가에서 cystine이 가장 높게 나타났다. 식빵의 조직감은 대조구에 비하여 탄력성과 응집성이 낮게 나타났으며, 씹힘성, 부서짐성, 경도는 대조구에 비하여 높게 나타났다. 부착성은 7% 첨가에서 나타났다.

본 연구는 아질산나트륨 및 비타민 C의 대체로 첨가한 수벌번데기 분말이 유화형 소시지의 이화학적 품질 특성에 미치는 영향을 구명하고자 하였다. 시료는 아질산염, 비타민 C 및 수벌번데기 분말의 첨가 수준에 따라 각각 아질산나트륨 150 ppm+비타민 C 200 ppm(대조구), 아질산나트륨 75 ppm+ 비타민C 100 ppm+수벌번데기 분말 6.015%(T1) 또는 수벌번데기 분말 12.03%(T2)을 첨가하여 제조한 후 4℃에 30일 동안 저장하였다. pH는 수벌번데기 분말의 첨가 수준이 증가함에 따라 현저하게 감소하였다(p<0.05). 일반성분 함량은 수벌번데기 분말의 첨가 수준이 높은 소시지에서 낮은 수분 및 조단백질 함량과 높은 조지방 및 조회분 함량을 보였다 (p<0.05). 지방산 조성은 T1과 T2가 대조구에 비해 포화지방산 함량이 높았으나(p<0.05), 불포화지방산 및 다가불포화지 방산 함량은 낮았다(p<0.05). 색깔은 T1과 T2가 대조구보다 현저하게 낮은 명도(L*) 및 적색도(a*)와 높은 황색도(b*) 및 hue-angle(h°)을 보였으며(p<0.05), T2의 경우 가장 낮은 chroma(C*)를 나타내었다(p<0.05). 지방산화물(TBARS) 함량은 T2가 가장 높았으며(p<0.05), 특히, 대조구보다 2배 이상 높았다. 조직감은 T1과 T2가 저장기간 동안 대조구에 비해 단단한 특성을 보였다(p<0.05). 따라서 유화형 소시지에서 수벌번데기 분말의 첨가는 색깔, 지방산화안정성 및 조직감에 부정적인 영향을 미치는 것으로 나타나, 아질산나트륨 및 비타민 C 대체 효과가 없었다

With the recent remarkable improvements in the average speeds of contemporary trains, a necessity has arisen for the development of new friction modifiers to improve adhesion characteristics at the wheel-rail interface. The friction modifier must be designed to reduce slippage or sliding of the trains’ wheels on the rails under conditions of rapid acceleration or braking without excessive rolling contact wear. In this study, a novel composite material consisting of metal, ceramic, and polymer is proposed as a friction modifier to improve adhesion between wheels and rails. A blend of Al-6Cu-0.5Mg metallic powder, Al2O3 ceramic powder, and Bakelite-based polymer in various weight-fractions is hot-pressed at 150oC to form a bulk composite material. Variation in the adhesion coefficient is evaluated using a high-speed wheel-rail friction tester, with and without application of the composite friction modifier, under both dry and wet conditions. The effect of varying the weighting fractions of metal and ceramic friction powders is detailed in the paper.

Despite numerous advances in the preparation and use of GaN, and many leading-edge applications in lighting technologies, the preparation of high-quality GaN powder remains a challenge. Ammonolytic preparations of polycrystalline GaN have been studied using various precursors, but all were time-consuming and required high temperatures. In this study, an efficient and low-temperature method to synthesize high-purity hexagonal GaN powder is developed using sub-micron Ga2O3 powder as a starting material. The sub-micron Ga2O3 powder was prepared by an ultrasonic spray pyrolysis process. The GaN powder is synthesized from the sub-micron Ga2O3 powder through a nitridation treatment in an NH3 flow at 800℃. The characteristics of the synthesized powder are systematically examined by X-ray diffraction, scanning and transmission electron microscopy, and UV-vis spectrophotometer.

PURPOSES : The purpose of this study is to analyze not only the strength but also the durability and abrasion resistance of concrete pavements as increasing the cases of domestic concrete pavement damage which do not meet the service years. METHODS: The bottom layer of a two-lift concrete pavement was paved with original Portland cement (OPC) with 20~23 cm thickness. On the other hand, the top-layer, which is directly exposed to the environment and vehicles, was paved with high-performance concrete (HPC) with 7~10 cm thickness. For the optimal mixed design of the top-layer material of a two-lift concrete pavement, silica fume and polymer powder were mixed. Furthermore, it analyzes abrasion resistance of concrete as follow‘ ASTM C 779’which is dressing wheel abrasion test method. RESULTS : As a result, abrasion resistance is improved with increasing the silica fume ratio. When the polymer powder is mixed, abrasion resistance of concrete is much improved. However, the effect of mixing ratio is not significant. It is very effective that adding both silica fume and polymer powder occur 20~40% of abrasion comparing with OPC variables. CONCLUSIONS : The concrete strength and durability increased with silica fume and polymer powder. In particular, it is significant increasing strength of polymer powder under the flexural strength. In the abrasion resistance side, it is also significant when the silica fume and polymer powder used together.