In this study, TiO2 powders are synthesized from ammonium hexafluoride titanate (AHFT, (NH4)2TiF6) as a precursor by heat treatment. First, we evaluate the physical properties of AHFT using X-ray diffraction (XRD), particle size analysis (PSA), thermogravimetric analysis (TGA), and field-emission scanning electron microscopy (FESEM). Then, to prepare the TiO2 powders, is heat-treated at 300-1300oC for 1 h. The ratio of anatase to rutile phase in TiO2 is estimated by XRD. The anatase phase forms at 500oC and phase transformation to the rutile phase occurs at 1200oC. Increase in the particle size is observed upon increasing the reaction temperature, and the phase ratio of the rutile phase is determined from a comparison with the calculated XRD data. Thus, we show that anatase and rutile TiO2 powders could be synthesized using AHFT as a raw material, and the obtained data are utilized for developing a new process for producing high-quality TiO2 powder.

Using the ultrasonic pyrolysis method, spherical SiO2 powders were synthesized from aqueous SiO2 sol as a starting material. The effects of pyrolysis conditions such as reaction temperature, SiO2 sol concentration, and physical properties of precursor were investigated for the morphologies of the resulting SiO2 powders. The particle size, shape, and crystallite size of the synthesized SiO2 powders were demonstrated according to the pyrolysis conditions. Generally, the synthesized SiO2 particles were amorphous phase and showed spherical morphology with a smooth surface. It was revealed that increased crystallite size and decreased spherical SiO2 particle size were obtained with increases of the pyrolysis reaction temperature. Also, quantity of spherical SiO2 particles decreased with the decrease in the concentration and surface tension of the precursor.

Tin is one of the most promising anode materials for next-generation lithium-ion batteries with a high energy density. However, the commercialization of tin-based anodes is still hindered due to the large volume change (over 260%) upon lithiation/delithiation cycling. To solve the problem, many efforts have been focused on enhancing structural stability of tin particles in electrodes. In this work, we synthesize tin nano-powders with an amorphous carbon layer on the surface and surroundings of the powder by electrical wire explosion in alcohol-based liquid media at room temperature. The morphology and microstructures of the powders are characterized by scanning electron microscopy, Xray diffraction, Raman spectroscopy, and transmission electron microscopy. The electrochemical properties of the powder for use as an anode material for lithium-ion battery are evaluated by cyclic voltammetry and a galvanometric dischargecharge method. It is shown that the carbon-coated tin nano-powders prepared in hexanol media exhibit a high initial charge specific capacity of 902 mAh/g and a high capacity retention of 89% after 50 cycles.

Ni1/3Co1/3Mn1/3(OH)2 powders have been synthesized in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH using NH4OH as a chelating agent. The co-precipitation temperature is varied in the range of 30-80oC. Calcination of the prepared precursors with Li2CO3 for 8 h at 1000oC in air results in Li Ni1/3Co1/3Mn1/3O2 powders. Two kinds of obtained powders have been characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analyzer, and tap density measurements. The co-precipitation temperature does not differentiate the XRD patterns of precursors as well as their final powders. Precursor powders are spherical and dense, consisting of numerous acicular or flaky primary particles. The precursors obtained at 70 and 80oC possess bigger primary particles having more irregular shapes than those at lower temperatures. This is related to the lower tap density measured for the former. The final powders show a similar tendency in terms of primary particle shape and tap density. Electrochemical characterization shows that the initial charge/discharge capacities and cycle life of final powders from the precursors obtained at 70 and 80oC are inferior to those at 50oC. It is concluded that the optimum co-precipitation temperature is around 50oC.

Graphene oxide (GO) powder processed by Hummer's method is mixed with p-type Bi2Te3 based thermoelectric materials by a high-energy ball milling process. The synthesized GO-dispersed p-type Bi2Te3 composite powder has a composition of Bi0.5Sb1.5Te3 (BSbT), and the powder is consolidated into composites with different contents of GO powder by using the spark plasma sintering (SPS) process. It is found that the addition of GO powder significantly decreases the thermal conductivity of the pure BSbT material through active phonon scattering at the newly formed interfaces. In addition, the electrical properties of the GO/BSbT composites are degraded by the addition of GO powder except in the case of the 0.1 wt% GO/BSbT composite. It is found that defects on the surface of GO powder hinder the electrical transport properties. As a result, the maximum thermoelectric performance (ZT value of 0.91) is achieved from the 0.1% GO/BSbT composite at 398 K. These results indicate that introducing GO powder into thermoelectric materials is a promising method to achieve enhanced thermoelectric performance due to the reduction in thermal conductivity.

In this study, solid solution heat treatment of consolidated nickel-based superalloy powders is carried out by hot isotactic pressing. The effects of the cooling rate of salt quenching, and air cooling on the microstructures and the mechanical properties of the specimens are analyzed . The specimen that is air cooled shows the formation of serrated grain boundaries due to their obstruction by the carbide particles. Moreover, the specimen that is salt quenched shows higher strength than the one that is air cooled due to the presence of fine and close-packed tertiary gamma prime phase. The tensile elongation at high temperatures improves due to the presence of grain boundary serrations in the specimen that is air cooled. On the contrary, the specimen that is salt quenched and consists of unserrated grain boundaries shows better creep properties than the air cooled specimen with the serrated grain boundaries, due to the negative creep phenomenon.

This study was performed to evaluate physicochemical properties of model sausages with various levels of pressed cherry fruit extracts alone or in combination with tomato powders as a partial replacement of sodium nitrite. In study 1, physicochemical properties of model sausages were not affected by the addition of pressed cherry fruit extracts(p>0.05), except for Hunter L(lightness) and Hunter a(redness). Model sausages containing pressed cherry fruit extract(T1, 0.5% and T2, 1.0%) decreased lightness, whereas redness of REF(156 ppm sodium nitrite) was not different from T2(p>0.05). However, those with cherry fruit extract at 1% were proper to improve the hunter color values, especially redness values. In study 2, physicochemical properties of model sausages were not affected by the addition of pressed cherry fruit extract and tomato powders in selected nitrite contents, except for color and cooking loss(p>0.05). In color values, REF was the highest level, and T2, T4, and T5 was significantly low level in lightness (Hunter L). T2 was the highest value in cooking loss(%) among other treatments. The redness values(Hunter a) of T5(75ppm, nitrite, 1% pressed cherry fruit extract and 0.5% tomato powder) were not different from REF which had highest redness values(P<0.05). In conclusion, the combination of pressed cherry fruit and tomato powder might be considered as an alternative method to partially replace with sodium nitrite in pork model sausages.

Nickel powders were prepared under solvothermal condition by precipitation from metal nitrates with aqueous ammonium hydroxide. The powders were obtained at in a temperature range of 190-250 oC for 6h. The morphology and size of nickel powders were studied as a function of reaction temperature. The synthesis of nickel crystalline particles is possible under a solvothermal conditions in ethylene glycol solution. Characterization of the synthesized nickel powders were studied by XRD, SEM(FE-SEM) and TG/DSC. X-ray diffraction analysis of the synthesized powders indicated the formation of nickel structure after reaction. The average crystalline sizes of the synthesized nickel powders were in the range of 200-1000 nm; and the distribution of the powders was broad. The shape of the synthesized nickel particles was almost spherical. The morphology of synthesized nickel powders changed with reaction condition. It was possible to synthesize nickel powders directly in ethylene glycol without reducing agent.

Y2O3–H3BO3:Eu3+ powders are synthesized using a mechanical alloying method, and their photoluminescence (PL) properties are investigated through luminescence spectrophotometry. For samples milled for 300 min, some Y2O3 peaks ([222], [440], and [622]) and amorphous formations are observed. The 300-min-milled mixture annealed at 800°C for 1 h with Eu = 8 mol% has the strongest PL intensity at every temperature increase of 100°C (increasing from 700 to 1200°C in 100°C increments). PL peaks of the powder mixture, as excited by a xenon discharge lamp (20 kW) at 240 nm, are detected at approximately 592 nm (orange light, 5Do → 7F1), 613 nm, 628 nm (red light, 5Do → 7F2), and 650 nm. The PL intensity of powder mixtures milled for 120 min is generally lower than that of powder mixtures milled for 300 min under the same conditions. PL peaks due to YBO3 and Y2O3 are observed for 300-min-milled Y2O3–H3BO3 with Eu = 8 mol% after annealing at 800°C for 1 h.

As precursors of cathode materials for lithium ion batteries, Ni1/3Co1/3Mn1/3(OH)2 powders are prepared in a continuously stirred tank reactor via a co-precipitation reaction between aqueous metal sulfates and NaOH in the presence of NH4OH in air or nitrogen ambient. Calcination of the precursors with Li2CO3 for 8 h at 1,000°C in air produces dense spherical cathode materials. The precursors and final powders are characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size analysis, tap density measurement, and thermal gravimetric analysis. The precursor powders obtained in air or nitrogen ambient show XRD patterns identified as Ni1/3Co1/3Mn1/3(OH)2. Regardless of the atmosphere, the final powders exhibit the XRD patterns of LiNi1/3Co1/3Mn1/3O2 (NCM). The precursor powders obtained in air have larger particle size and lower tap density than those obtained in nitrogen ambient. NCM powders show similar tendencies in terms of particle size and tap density. Electrochemical characterization is performed after fabricating a coin cell using NCM as the cathode and Li metal as the anode. The NCM powders from the precursors obtained in air and those from the precursors obtained in nitrogen have similar initial charge/discharge capacities and cycle life. In conclusion, the powders co-precipitated in air can be utilized as precursor materials, replacing those synthesized in the presence of nitrogen injection, which is the usual industrial practice.

Porous W with spherical and directionally aligned pores was fabricated by the combination of sacrificial fugitives and a freeze-drying process. Camphene slurries with powder mixtures of WO3 and spherical PMMA of 20 vol% were frozen at −25 oC and dried for the sublimation of the camphene. The green bodies were heat-treated at 400 oC for 2 h to decompose the PMMA; then, sintering was carried out at 1200 oC in a hydrogen atmosphere for 2 h. TGA and XRD analysis showed that the PMMA decomposed at about 400 oC, and WO3 was reduced to metallic W at 800 oC without any reaction phases. The sintered bodies with WO3-PMMA contents of 15 and 20 vol% showed large pores with aligned direction and small pores in the internal walls of the large pores. The pore formation was discussed in terms of the solidication behavior of liquid camphene with solid particles. Spherical pores, formed by decomposition of PMMA, were observed in the sintered specimens. Also, microstructural observation revealed that struts between the small pores consisted of very fine particles with size of about 300 nm.

본 연구에서는 마늘 특유의 매운 맛과 냄새를 억제하고 대표성분인 alliin을 보호하기 위해 코팅물질과 건조방법을 달리하여 미세캡슐화하였다. 코팅물질은 말토덱스트린(MD), 분리유청단백질(WPI), 전지분유(WMP), 탈지분유(SMP)로 하고 건조방법은 분무건조(spray-drying)방법과 동결건조 (freeze-drying)방법을 이용하여 캡슐화 후 코팅물질 별, 건 조방법 별 alliin 보호특성, 관능특성 그리고 분산성을 알아 보았다. 코팅물질을 증류수에 완전히 분산시키기 위해 24 시간 동안 교반한 후 동결건조 마늘분말을 천천히 첨가하 였다. 1:1 비율의 동결건조마늘분말과 코팅물질을 혼합한 용액을 균질기를 이용하여 균질화하고, 분무건조기 또는 동결건조기를 이용하여 코팅물질을 달리하여 분말화하였 다. 미세캡슐화된 마늘분말의 추출물을 HPLC로 alliin 함 량을 정량 분석하였다. HPLC 분석결과 전지분유를 코팅물 질로 하고 분무건조방법으로 캡슐화한 마늘분말의 alliin함 량이 4.131 mg/g으로 최대함량을 보였으며, 관능평가 결과 로서 코팅물질을 분리유청단백질로 하고 분무건조방법으로 캡슐화한 마늘분말이 매운 맛과 냄새를 억제하는데 효과적 이었다. 또한 혼탁도 측정을 통한 캡슐화된 마늘 분말의 분산성을 측정했을 때, 전지분유로 캡슐화한 마늘분말의 안정성이 가장 높음을 확인할 수 있었다. 코팅물질 중 유 지방과 단백질이 황화합물에서 발생하는 특유의 매운맛과 냄새를 억제해주며 alliin의 보호에도 기여함을 알 수 있었 다. 본 실험결과, 지표물질 보호특성, 이취개선 등의 기초 자료는 기능성 식품 산업에 있어서 마늘 소재 개발을 위한 기초자료가 될 수 있을 것이다.

Fe-30 wt% TiC composite powders are fabricated by in situ reaction synthesis after planetary ball millingof (Fe, TiH2, Carbon) powder mixture. Two sintering methods of a pressureless sintering and a spark-plasma sinteringare tested to densify the Fe-30 wt% TiC composite powder compacts. Pressureless sintering is performed at 1100, 1200and 1300oC for 1-3 hours in a tube furnace under flowing argon gas atmosphere. Spark-plasma sintering is carried outunder the following condition: sintering temperature of 1050oC, soaking time of 10 min, sintering pressure of 50 MPa,heating rate of 50oC/min, and in a vacuum of 0.1 Pa. The curves of shrinkage and its derivative (shrinkage rate) areobtained from the data stored automatically during sintering process. The densification behaviors are investigated fromthe observation of fracture surface and cross-section of the sintered compacts. The pressureless-sintered powder com-pacts are not densified even after sintering at 1300oC for 3 h, which shows a relative denstiy of 66.9%. Spark-plasmasintering at 1050oC for 10 min exhibits nearly full densification of 99.6% relative density under the sintering pressure of50 MPa.

Fe-base superalloy powders with Y2O3 dispersion were prepared by high energy ball milling, followed by sparkplasma sintering for consolidation. High-purity elemental powders with different Fe powder sizes of 24 and 50mm were usedfor the preparation of Fe-20Cr-4.5Al-0.5Ti-O.5Y2O3 powder mixtures (wt%). The milling process of the powders was carriedout in a horizontal rotary ball mill using a stainless steel vial and balls. The milling times of 1 to 5 h by constant operation(350 rpm, ball-to-powder ratio of 30:1 in weight) or cycle operation (1300 rpm for 4 min and 900 rpm for 1 min, 15:1) wereapplied. Microstructural observation revealed that the crystalline size of Fe decreased with an increase in milling time by cyclicoperation and was about 15nm after 3 h, forming a FeCr alloy phase. The cyclic operation had an advantage over constantmilling in that a smaller-agglomerated structure was obtained. The milled powders were sintered at 1100oC for 30 min invacuum. With an increase in milling time, the sintered specimen showed a more homogeneous microstructure. In addition, ahomogenous distribution of Y-compound particles in the grain boundary was confirmed by EDX analysis.

본 연구는 돈육 중의 후지육을 이용하여 천연향신료인 생강 및 인삼분말을 첨가비율별로 처리(무처리 대조구), T1구(A-생강분말 0.1%첨가, B-인삼분말 0.1%첨가), T2구(A-생강분말 0.2%첨가, B-인삼분말 0.2%첨가), T3구(A-생강분말 0.3%첨가, B-인삼분말 0.3%첨가)하여 총 24점(4처리×2요인×3반복)의 돈육포를 제조한 후 저장기간에 따른 육포의 물리화학적 특성을 조사하였다. 돈육포의 수분활성도는 0.66∼0.80 정도였고, pH는 5.42∼5.75 범위로서 저장기간이 경과함에 따라 감소하여 통계적인 유의차를 나타내었다(p<0.05). 적색도(a값)에서는 대조구와 T1구가, 황색도(b값)은 T3구가 타 처리구보다 크게 높았다(p<0.05). 돈육포의 물성(texture)의 경우, 경도, 응집성 및 파쇄성은 대조구가 처리구보다 더 높았으나 검성과 탄력성의 경우에는 상반되게 오히려 더 낮게 나타났다. 총 유리아미노산은 처리구가 대조구보다 높은 경향이었고, 그 중에서도 T3-B구(50.06%)가 가장 높게 나타났다.

본 시험은 맥섬석과 한약제재 첨가급여가 한우거세우의 비육능력 및 혈액성상에 미치는 영향을 구명하기 위해 생후 13개월령의 거세한우 40두(4처리×5두×2반복)를 공시하여 사료용 첨가제로 1일 사료급여량의 0.5∼1.0% 수준으로 26개월령까지 시험하였다. 시험구 배치는 C(무첨가), T1구(맥섬석 0.5% 첨가), T2구(한약제재 0.5% 첨가), T3구(맥섬석 0.5%+한약제재 0.5% 첨가)로 구분하였다. 증체량의 경우 비육전기때 T1구(226.2kg)가, 비육후기 때는 T3구(162.1kg)가 가장 높게 나타났다(p<0.05). 혈중 총콜레스테롤 함량은 T3구가 다른 처리구보다 유의적으로 높았다(p<0.05). 또한 도체중은 T3구(439.00kg) > T2(425.80kg) > T1(420.50kg) > Control(413.00kg) 순으로 낮아졌다. 배최장근 단면적은 T3구가 107.00㎠로 다른 처리구보다 높았고(p<0.05), 도체등급에서 육질등급은 T2구와 T3구가 공히 3.25로서 크게 높았다(p<0.05). 한편 등심육의 지방산 조성에서 oleic acid 함량이 48.55∼50.90%로서 가장 많은 비율을 나타내었고, 불포화지방산은 T3구(57.94%)가 다른 처리구보다 유의적으로 높게 나타났다(p<0.05). 따라서 거세한우에게 각각 맥섬석과 한방제재를 혼합하여 첨가급여하면 도체등급, 관능검사 및 불포화지방산의 개선에 도움이 될 것으로 판단된다.

The sintering mechanisms of nanoscale copper powders have been investigated. A molecular dynamics (MD) simulation with the embedded-atom method (EAM) was employed for these simulations. The dimensional changes for initial-stage sintering such as characteristic lengths, neck growth, and neck angle were calculated to understand the densification behavior of copper nano-powders. Factors affecting sintering such as the temperature, powder size, and crystalline misalignment between adjacent powders have also been studied. These results could provide information of setting the processing cycles and material designs applicable to nano-powders. In addition, it is expected that MD simulation will be a foundation for the multi-scale modeling in sintering process.

Two sintering methods of a pressureless sintering and a spark-plasma sintering are tested to densify the Fe-TiC composite powders which are fabricated by high-energy ball-milling. A powder mixture of Fe and TiC is prepared in a planetary ball mill at a rotation speed of 500 rpm for 1h. Pressureless sintering is performed at 1100, 1200 and 1300oC for 1-3 hours in a tube furnace under flowing argon gas atmosphere. Spark-plasma sintering is carried out under the following condition: sintering temperature of 1050oC, soaking time of 10 min, sintering pressure of 50 MPa, heating rate of 50oC, and in a vacuum of 0.1 Pa. The curves of shrinkage and its derivative (shrinkage rate) are obtained from the data stored automatically during sintering process. The densification behaviors are investigated from the observation of fracture surface and cross-section of the sintered compacts. The pressureless-sintered powder compacts show incomplete densification with a relative denstiy of 86.1% after sintering at 1300oC for 3h. Spark-plasma sintering at 1050oC for 10 min exhibits nearly complete densification of 98.6% relative density under the sintering pressure of 50 MPa.

The synthesis of NiTi alloy powders by hydrogen reduction and dehydrogenation process of NiO and TiH2 powder mixtures is investigated. Mixtures of NiO and TiH2 powders are prepared by simple mixing for 1 h or ball milling for 24 h. Simple-mixed mixture shows that fine NiO particles are homogeneously coated on the surface of TiH2 powders, whereas ball milled one exhibits the morphology with mixing of fine NiO and TiH2 particles. Thermogravimetric analysis in hydrogen atmosphere reveals that the NiO and TiH2 phase are changed to metallic Ni and Ti in the temperature range of 260 to 290oC and 553 to 639oC, respectively. In the simple-mixed powders by heat-up to 700oC, agglomerates with solid particles and solidified liquid phase are observed, and the size of agglomerates is increased at 1000oC. From the XRD analysis, the presence of liquid phase is explained by the formation and melting of NiTi2 intermetallic compound due to an exothermic reaction between Ni and Ti. The simple-mixed powders, heated to 1000oC, lead to the formation of NiTi phase but additional Ni-, Ti-rich and Ti-oxide phases. In contrast, the microstructure of ball-milled powders is characterized by the neck-grown particles, forming Ni3Ti, Ti-oxide and unreacted Ni phase.

Spherical fine cobalt powders were fabricated by new liquid reduction method. Commercial cobalt sufate heptahydrate was used as raw material. Also ethylene glycol was used as solvent and hydrazine-sodium hypophosphite mixture was used as reduction agent for the new liquid reduction method. A plate shaped cobalt powders with an approximately 300 nm were prepared by a traditional wet ruduction method using distilled water as solvent and hydrazine. Spherical fine cobalt powders with an average size of 1-3 μm were synthesized by a new liquid reduction method in 0.3M cobalt sulfate and 1.5M hydrazine-0.6M sodium hypophosphite mixture at 333K.