In this study, Ni-Y2O3 powder was prepared by alloying recomposition oxidation sintering (AROS), solution combustion synthesis (SCS), and conventional mechanical alloying (MA). The microstructure and mechanical properties of the alloys were investigated by spark plasma sintering (SPS). Among the Ni-Y2O3 powders synthesized by the three methods, the AROS powder had approximately 5 nm of Y2O3 crystals uniformly distributed within the Ni particles, whereas the SCS powder contained a mixture of Ni and Y2O3 nanoparticles, and the MA powder formed small Y2O3 crystals on the surface of large Ni particles by milling the mixture of Ni and Y2O3. The average grain size of Y2O3 in the sintered alloys was approximately 15 nm, with the AROS sinter having the smallest, followed by the SCS sinter at 18 nm, and the MA sinter at 22 nm. The yield strength (YS) of the SCS- and MA-sintered alloys were 1511 and 1688 MPa, respectively, which are lower than the YS value of 1697 MPa for the AROS-sintered alloys. The AROS alloy exhibited improved strength compared to the alloys fabricated by SCS and conventional MA methods, primarily because of the increased strengthening from the finer Y2O3 particles and Ni grains.

In this study, we evaluated the effects of acid leaching on the properties of Cr powder synthesized using self-propagating high-temperature synthesis (SHS). Cr powder was synthesized from a mixture of Cr2O3 and magnesium (Mg) powders using the SHS Process, and the byproducts after the reaction were removed using acid leaching. The properties of the recovered Cr powder were analyzed via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), particle size analysis (PSA), and oxygen content analysis. The results show that perfect selective leaching of Cr is challenging because of various factors such as incomplete reaction, reaction kinetics, the presence of impurities, and incompatibility between the acid and metal mixture. Therefore, this study provides essential information on the properties under acidic conditions during the production of high-quality Cr powder using a self-propagating high-temperature synthesis method.

Powder flowability is critical in additive manufacturing processes, especially for laser powder bed fusion. Many powder features, such as powder size distribution, particle shape, surface roughness, and chemical composition, simultaneously affect the flow properties of a powder; however, the individual effect of each factor on powder flowability has not been comprehensively evaluated. In this study, the impact of particle shape (sphericity) on the rheological properties of Ti-6Al-4V powder is quantified using an FT4 powder rheometer. Dynamic image analysis is conducted on plasma-atomized (PA) and gas-atomized (GA) powders to evaluate their particle sphericity. PA and GA powders exhibit negligible differences in compressibility and permeability tests, but GA powder shows more cohesive behavior, especially in a dynamic state, because lower particle sphericity facilitates interaction between particles during the powder flow. These results provide guidelines for the manufacturing of advanced metal powders with excellent powder flowability for laser powder bed fusion.

In this paper, a durability study is presented to enhance the mechanical properties of an Fe-Si-Al powderbased magnetic core, through the addition of graphite. The compressive properties of Fe-Si-Al-graphite powder mixtures are explored using discrete element method (DEM), and a powder compaction experiment is performed under identical conditions to verify the reliability of the DEM analysis. Important parameters for powder compaction of Fe-Si-Algraphite powder mixtures are identified. The compressibility of the powders is observed to increase as the amount of graphite mixture increases and as the size of the graphite powders decreases. In addition, the compaction properties of the Fe-Si-Al-graphite powder mixtures are further explored by analyzing the transmissibility of stress between the top and bottom punches as well as the distribution of the compressive force. The application of graphite powders is confirmed to result in improved stress transmission and compressive force distribution, by 24% and 51%, respectively.

This study examined the quality characteristics of chicken breast emulsion-type sausages manufactured with different contents of Zanthoxylumschinifolium (Z.S.) powder (0, 1, 2 and 3%). The changes to the samples upon inclusion of Z.S. powder were monitored by measuring the proximate composition, pH, color, cooking yield, viscosity, texture profile analysis and protein solubility. The sausages manufactured with increasing amounts of Z.S. powder showed a decrease significantly in fat content (p<0.05), whereas the ash content increased. The pH of the cooked samples also decreased significantly with the increasing content of Z.S. powder (p<0.05). Before and after cooked lightness significantly decreased as the Z.S. powder content increased (p<0.05). The redness of the cooked samples also increased significantly with an increasing amount of Z.S. powder (p<0.05). Samples that contained 2% and 3% of Z.S. powder resulted in a significantly larger cooking yield compared to the control sample and the one containing 1% of Z.S. powder (p<0.05). The viscosity of the uncooked samples also increased with increasing amount of Z.S. powder. Furthermore, the samples containing 3% of Z.S. powder showed significantly lower levels of hardness and springiness than the control sample (p<0.05). In addition, the sample with 3% of Z.S. powder contained showed significantly higher total protein and myofibrillar protein levels than the other samples (p<0.05). Overall, the 3% of Z.S. powder chicken breast emulsion-type sausage performed well in most quality characteristic categories, and this formulation would be suitable for use in food manufacturing.

In this work, the electrical explosion of wire in liquid and subsequent spark plasma sintering (SPS) was introduced for the fabrication of Ni-graphite nanocomposites. The fabricated composite exhibited good enhancements in mechanical properties, such as yield strength and hardness, but reduced the ductility in comparison with that of nickel. The as-synthesized Ni-graphite (5 vol.% graphite) nanocomposite exhibited a compressive yield strength of 275 MPa (about 1.6 times of SPS-processed monolithic nickel ~170 MPa) and elongation to failure ~22%. The hardness of Nigraphite composite had a value of 135.46 HV, which is about 1.3 times higher than that of pure SPS-processed Ni (105.675 HV). In terms of processing, this work demonstrated that this processing route is a novel, simple, and low-cost method for the synthesis of nickel-graphite composites.

The objective of this study is to investigate the influence of powder shape and densification mechanism on the microstructure and mechanical properties of Ti-6Al-4V components. BE powders are uniaxially and isostatically pressed, and PA ones are injection molded because of their high strengths. The isostatically compacted samples exhibit a density of 80%, which is higher than those of other samples, because hydrostatic compression can lead to higher strain hardening. Owing to the higher green density, the density of BE-CS (97%) is found to be as high as that of other samples (BE-DS (95%) and P-S (94%)). Furthermore, we have found that BE powders can be consolidated by sintering densification and chemical homogenization, whereas PA ones can be consolidated only by simple densification. After sintering, BE-CS and P-S are hot isostatically pressed and BE-DS is hot forged to remove residual pores in the sintered samples. Apparent microstructural evolution is not observed in BE-CSH and P-SH. Moreover, BE-DSF exhibits significantly fine grains and high density of low-angle grain boundaries. Thus, these microstructures provide Ti-6Al-4V components with enhanced mechanical properties (tensile strength of 1179 MPa).

This study investigated the effects of Goami 2 on the properties of Garaetteok. The moisture, crude protein, crude lipid and crude ash contents of the rice were 16.02, 5.40, 1.87 and 0.77%, respectively. The amylose contents (32.16%) and total dietary fiber contents (9.03%) were the highest in Goami 2. The water binding capacity of Goami 2 (167.84%) was higher than general rice flour. Using a rapid visco analyzer (RVA), the initial pasting temperature of Goami 2 was found to be the highest; also, the peak viscosities of Goami 2 were higher than general rice powder. To assess the effect of Goami 2 on the quality characteristics of Garaetteok, the rice-cake was made by adding various amounts of Goami 2 (0, 10, 20, 30, and 40% w/w) to rice. It was observed that higher the amount of added Goami 2, lower were the grades. In terms of the color values of Goami 2 addition, the L-values of Garaetteok were lower with increasing amount of Goami 2; addition of 40% Goami 2 had the lowest value. The textural properties (hardness) also showed that tteok containing the greater amounts of Goami 2 were considerably harder compared with the control. Sensory preference tests revealed that addition of less Goami 2 had the highest scores for appearance, color and overall acceptability, and the Goami 2 added was lower than control. Therefore, as compared to others cultivars, rice flour proved the most acceptable for the preparation of Garaetteok with cultivar rice.

To investigate the adhesion effect of various kinds and contents of polymeric methylene diphenyl diisocyanates (pMDIs) on adhesion performance, wood adhesives (A-1~5) were synthesized and characterized. As results, when the amount of pMDI increased in adhesives, the dry tensile strength was found to be proportionally increased sustaining at around 16.0~21.6 kgf/cm2. The polyurethane (PU) resin, which used M11S as a source of pMDI showed the best wet tensile strength at 11.9 kgf/cm2 and cyclic boil tensile strength at 8.1 kgf/cm2, which satisfied the requirement of over 7 kgf/cm2. Thermal properties of the rice powder (RP) based polyurethane resins were characterized by differential scanning calorimetry (DSC) and Thermal gravimetric analysis (TGA). Thermal stability of polyurethane resins increased to 250℃ with adding pMDIs. The more pMDI (M5S) was added to adhesive, the higher thermal stability of the resin was observed by TGA.

MgB2 bulk superconductors are synthesized by the solid state reaction of (MgB4+xMg) precursors withexcessive Mg compositions (x=1.0, 1.4, 2.0 and 2.4). The MgB4 precursors are synthesized using (Mg+B) powders. Thesecondary phases (MgB4 and MgO) present in the synthesized MgB4 are removed by HNO3 leaching. It is found thatthe formation reaction of MgB2 is accelerated when Mg excessive compositions are used. The magnetization curves ofMg1+xB2 samples show that the transition from the normal state to the superconducting state of the Mg excessive sam-ples with x=0.5 and x=0.7 are sharper than that of MgB2. The highest Jc-B curve at 5 K and 20 K is achieved forx=0.5. Further addition of Mg decreases the Jc owing to the formation of more pores in the MgB2 matrix and smallervolume fraction of MgB2.

본 연구에서는 크기와 형상이 서로 다른 4가지 실버 파우더를 이용하여 감광성 실버 페이스트를 제조 하였다. 제조된 실버 페이스트의 레올로지 특성 및 터치패널용 전도성 미세패턴 구현을 검토하였다. 그리고 건조방식에 따른 전도성도 평가하였다. 그 결과 실버 파우더의 평균입자 크기는 D50=0.8∼1.0㎛이 가장 낮은 저항치를 얻을 수 있었고, 또한 패턴의 Sharpness도 가장 우수함을 알 수 있었다. 건조방식은 예비건조 및 후 건조를 IR/IR방식으로 진행한 것이 가장 낮은 저항치를 얻을수있었다.

In this study, nanocrystalline Cu-Ni bulk materials with various compositions were cold compacted by a shock compaction method using a single-stage gas gun system. Since the oxide layers on powder surface disturbs bonding between powder particles during the shock compaction process, each nanopowder was hydrogen-reduced to remove the oxide layers. X-ray peak analysis shows that hydrogen reduction successfully removed the oxide layers from the nano powders. For the shock compaction process, mixed powder samples with various compositions were prepared using a roller mixer. After the shock compaction process, the density of specimens increased up to 95% of the relative density. Longitudinal cross-sections of the shock compacted specimen demonstrates that a boundary between two powders are clearly distinguished and agglomerated powder particles remained in the compacted bulk. Internal crack tended to decrease with an increase in volumetric ratio of nano Cu powders in compacted bulk, showing that nano Cu powders has a higher coherency than nano Ni powders. On the other hand, hardness results are dominated by volume fraction of the nano Ni powder. The crystalline size of the shock compacted bulk materials was greatly reduced from the initial powder crystalline size since the shock wave severely deformed the powders.

Fe-Cr-Al powder porous metal was manufactured by using new electro-spray process. First, ultra-finefecralloy powders were produced by using the submerged electric wire explosion process. Evenly distributed colloid(0.05~0.5% powders) was dispersed on Polyurethane foam through the electro-spray process. And then degreasing andsintering processes were conduced. In order to examine the effect of cell size (200 µm, 450 µm, 500 µm) in process,pre-samples were sintered for two hours at temperature of 1450˚C, in H₂ atmospheres. A 24-hour thermo gravimetricanalysis test was conducted at 1000˚C in a 79% N₂ + 21% O₂ to investigate the high temperature oxidation behavior ofpowder porous metal. The results of the high temperature oxidation tests showed that oxidation resistance increased withincreasing cell size. In the 200 µm porous metal with a thinner strut and larger specific surface area, the depletion ofthe stabilizing elements such as Al and Cr occurred more quickly during the high-temperature oxidation compared withthe 450, 500 µm porous metals.

Stress-strain curves are fundamental properties to study characteristics of materials. Flow stress curves of the powder materials are obtained by indirect testing methods, such as tensile test with the bulk materials and powder compaction test, because it is hard to measure the stress-strain curves of the powder materials using conventional uniax- ial tensile test due to the limitation of the size and shape of the specimen. Instrumented nanoindentation can measure mechanical properties of very small region from several nanometers to several micrometers, so nanoindentation tech- nique is suitable to obtain the stress-strain curve of the powder materials. In this study, a novel technique to obtain the stress-strain curves using the combination of instrumented nanoindentation and finite element method was introduced and the flow stress curves of Fe powder were measured. Then obtained stress-strain curves were verified by the com- parison of the experimental results and the FEA results for powder compaction test.

알루미늄 테르밋 반응의 환원제로서 알루미늄 분말은 200 메쉬 이하의 미분이 필요하나, 알루미늄의 높은 인성과 분말 제조비 때문에 경제적으로 용이하지 않다. 그러므로 Mn3O4 분진 환원용 알루미늄 미분의 제조 코스트를 낮추기 위해, 알루미늄 합금분말의 제특성이 검토되었다. 망간을 다량 함유한 알루미늄 합금괴는 취성이 큰 금속간 화합물을 함유하고 있기 때문에 쉽게 파쇄할 수 있다. 또 망간은 망간 합금철의 주성분이다. Al-15%Mn 합금분말을 기계적 파쇄법으로 저렴하게 제조할 수 있다. Al 분말 대신에 Al-15%Mn 합금분말을 사용한 테르밋 반응 결과는 환원제로 순 알루미늄 분말을 사용한 경우와 같이 고순도 망간 합금철을 얻을 수 있었다. Al-15%Mn 합금분말를 이용한 Mn3O4 분진의 망간 회수율은 알루미늄 분말을 이용한 경우의 약 65% 보다 높은 약 70%의 높은 수준을 보였으며, 이는 비산이 적은 것에 기인한다.

In the present study, we systematically investigated the effect of Mn addition on nitrogenation behavior and magnetic properties of Sm-Fe powders produced by reduction-diffusion process. Alloy powders with only single phase were successfully produced by the reduction-diffusion process. The coercivity of powder rapidly increased during nitrogenation and reached the maximum of 637 Oe after 16 hours. After further nitrogenation, it decreased. In contrast, the coercivity of powder gradually increased during nitrogenation for 24 hours. The coercivity of powder was higher than that of powder at the same condition of nitrogenation. It was considered that the Mn addition facilitates the nitrogenation of powder and enhances the coercivity.

Sulgidduk is a kind of basic steamed rice cake in Korea. Multifunctional portable grinder was used for making sulgidduk and investigated the characteristic changes of rice powder for deciding the proper particle size of rice powder. Operation times for grinding the water absorbed swelled rice were 10, 20, 30 and 40 seconds. Moisture contents of rice powder and sulgidduk showed an increasing tendency with an increase of operation times for grinding. Springiness showed significant differences according to the operation times. Cohesiveness was decreased severely after 40 seconds grinding. Chewiness showed high after 20 seconds grinding in all groups; however, decreased after 40 seconds grinding and showed similar chewiness of the control group. Fracturability also showed severe increased tendency after 20 seconds grinding and decreased after 30 seconds grinding. Strength and hardness showed significant differences; they were increased until 30 seconds and severely decreased after 40 seconds grinding. L values showed significant differences in all the groups (p≤0.05). The a and b values did not show any differences in all groups. Overall sensory evaluations, such as colors, flavors and texture, were increased with operation times for grinding and showed significant differences among the groups (p<0.05). As a result of this study, 40 seconds grinding times were the best condition for making sulgidduk, using by multifunctional grinder.

Cold spray deposition using Titanium powder was carried out to investigate the effects of powder morphology and powder preheating on the coating properties such as porosity and hardness. The in-flight particle velocity of Ti powder in cold spray process was directly measured using the PIV (particle image velocimetry) equipment. Two types of powders (spherical and irregular ones) were used to manufacture cold sprayed coating layer. The results showed that the irregular morphology particle appeared higher in-flight particle velocity than that of the spherical one under the same process condition. The coating layer using irregular morphology powder represented lower porosity level and higher hardness. Two different preheating conditions (no preheating and preheating at ) were used in the process of cold spraying. The porosity decreased and the hardness increased by conducting preheating at . It was found that the coating properties using different preheating conditions were dependent not on the particle velocity but on the deformation temperature of particle. The deposition mechanism of particles in cold spray process was also discussed based on the experimental results of in flight-particle velocity.

Roll milled- and nano-powders were prepared from the freeze dried fruiting bodies of Hericium erinaceum and their hydration properties such as water solubility index, swelling capacity, water holding capacity, and water sorption isotherm were compared. Water content in freeze dried Nano-powder of Hericium erinaceum fruiting body was 8.17%. Nano-powder has higher water solubility index compared to roll mill powder by 58.41% and 39.06%, respectively. In the same way, swelling capacity of nano-powder was 10.21ml/g where as roll mill powder has only 4.42ml/g. In contrast, water holding capacity of nano-powder (3.87g/g) is lower than that of roll mill powder (6.81g/g). Water sorption isotherm of these powders was compared and the result shows no big difference at low relative humidity (below75%). However, a high relative humidity above 75%, these two kinds of powder showed comparable difference. At 84.34% relative humidity, roll mill powder has 30.41% of moisture content compared with 47.64% of nano-powder, and at the relative humidity of 97.3%, the moisture content of roll mill and nano-powder are 37.64% and 91.06% respectively.