• 한국재료학회지
• /
• 제22권11호
• /
• pp.569-574
• /
• 2012

Large single grain $Gd_{1.5}Ba_2Cu_3O_{7-y}$ (Gd1.5) bulk superconductors were fabricated by a top-seeded melt growth (TSMG) process using an $NdBa_2Cu_3O_{7-y}$ seed. The seeded Gd1.5 powder compacts with a diameter of 50 mm were subjected to the heating cycles of a TSMG process. After the TSMG process, the diameter of the single grain Gd1.5 compact was reduced to 43 mm owing to the volume contraction during the heat treatment. The superconducting transition temperature ($T_c$) of the top surface of the single grain Gd1.5 sample was as high as 93.5 K. The critical current densities ($J_cs$) at 77 K and 1T and 1.5 T were in ranges of 25,200-43,900 $A/cm^2$ and 10,000-23,000 $A/cm^2$, respectively. The maximum attractive force at 77 K of the sample field-cooled using an Nd-B-Fe permanent magnet (surface magnetic field of 0. 527 T) was 108.3 N; the maximum repulsive force of the zero field-cooled sample was 262 N. The magnetic flux density of the sample field-cooled at 77 K was 0.311T, which is approximately 85% of the applied magnetic field of 0.375 T. Microstructure investigation showed that many $Gd_2BaCuO_5$ (Gd211) particles of a few ${\mu}m$ in size, which are flux pinning sites of Gd123, were trapped within the $GdBa_2Cu_3O_{7-y}$ (Gd123) grain; unreacted $Ba_3Cu_5O_8$ liquid and Gd211 particles were present near the edge regions of the single grain Gd1.5 bulk compact.

• 생명과학회지
• /
• 제25권2호
• /
• pp.206-213
• /
• 2015

선식은 웰빙식, 건강식으로 아시아인들에게는 인기있는 식품이지만 외국인들에게는 생소한 식품이다. 이에 본 연구는 외국인들의 선호도를 높이기 위하여 선식을 스무디 형태로 제조하고, 그의 특성을 연구하였다. 효소활성을 지니는 선식 제조를 위해서 흑미와 현미는 발아시켜 사용하였는데, 실온에서 24시간 침지시킨 후, 24시간 $30^{\circ}C$에서 발아시켰다. 알파아밀라아제 효소역가는 발아 전후로 약 13~15배 증가하였다. 현미는 발아 전 9.16 CU/g에서 152.63 CU/g로 증가하였고, 흑미는 7.47 CU/g에서 97.96 CU/g으로 증가하였다. 또한 발아현미분말을 엿기름으로 당화시킨 후, 토마토 30 g과 미강 1.5 g을 첨가하여 유산균을 배양하였다. 이때의 최고균체농도가 $1.1{\times}10^9CFU/ml$ 이었고, 이를 동결건조하여 선식에 첨가하였다. 선식음료제조 후 농도가 $1.3{\times}10^5CFU/ml$로 요구르트 스무디 제조를 위한 스타터 농도로 충분하였다. 이를 이용하여 배양한다면, 선식 요구르트 스무디를 제조가 가능하다. 관능평가결과, 선식 음료의 최적 조건으로는 우유 200 ml에 선식 30 g를 혼합한 것을 가장 선호하였다. 이때의 색도는 L 값 : $63.50{\pm}0.41$, a 값 : $-0.35{\pm}0.06$, b 값 : $8.85{\pm}0.19$로 나타났고, 점도는 $5.97{\pm}1.2$ centipoise 이었다.

• Korean Chemical Engineering Research
• /
• 제44권2호
• /
• pp.160-165
• /
• 2006

니켈 분말을 이용하여 제조된 다공성 니켈 지지체 위에 팔라듐-구리-니켈 합금 수소 분리막을 제조하였다. 다공성 니켈 지지체는 열적안정성과 수소취성에 강한 모습을 나타내었으며, 다공성 니켈 지지체에 기존의 습식 방식인 염산에 의한 표면 전처리 방식을 건식 방식인 플라즈마 표면개질로 대체하였다. 다공성 니켈 지지체의 기공을 매립하기 위해 전해도금방식으로 $2{\mu}m$의 두께로 코팅하였으며, 그 후 니켈 도금된 지지체 위에 스퍼터 방식으로 팔라듐을 $4{\mu}m$, 구리를 $0.5{\mu}m$의 두께로 코팅하였다. 이와 같이 제조된 시편을 $700^{\circ}C$에서 1시간 구리 리플로우를 통해 미세기공이 없는 매우 치밀한 팔라듐-구리-니켈 합금 분리막을 제조하였다. 그 결과 팔라듐-구리-니켈 합금 수소분리막은 다공성 니켈지지체와 좋은 접착성을 가지고 있으며 수소-질소 혼합가스에서 무한대의 분리도 값을 나타내었다.

• 한국식품영양과학회지
• /
• 제32권8호
• /
• pp.1278-1284
• /
• 2003

본 연구에서는 김 분말을 첨가하여 기능성 스폰지 케이크를 제조하였을 때의 반죽특성 및 제품의 물리화학적 변화와 상품화 가능성을 조사하였다. 김 스폰지 케이크의 수분함량은 대조구와 김 분말 2,4,6% 첨가시는 차이를 나타내지 않았으나, 8 및 10% 첨가시에는 증가하였으며, 단백질함량, 회분함량도 각각 유의적으로 증가하였다. 비중은 김의 첨가량이 증가할수록 증가하였으며, 김분말 10% 첨가시에는 0.674로서 케이크의 부피가 크게 감소함을 알 수 있었다. 무기질은 Ca와 Na 성분이 가장 많았다. Crust의 L, a, b값은 모두 대조구에 비하여 감소하였으며, crumb의 L과 b값도 유의 적으로 감소하였다. 유리아미노산의 함량은 김분말 첨가량이 증가함에 따라 높게 나타났으며, L-glutamic acid, L-alanine, L aspartic acid 및 L-leucine등의 순으로 검출되었다. 경도(hardness), 탄력성(springiness), 응집성(cohesiveness), 점성(gumminess), 씹힘성(chewiness), 복원성(resilience)은 김분말 첨가량이 증가할수록 높은 값을 나타내었고, 스폰지 케이크의 외관은 작아졌으며, 주사현미경 관찰 결과 기공이 작아지고 큰 입자의 air cell이 나타났다 또한 부착성, 냄새, 입에서의 느낌, 촉촉함 및 종합적인 관능검사 항목으로 보아 스폰지 케이크의 김분말 최적 첨가량은 2%가 적당하였다.

• Journal of Microbiology and Biotechnology
• /
• 제23권12호
• /
• pp.1757-1764
• /
• 2013

Trichoderma harzianum ZF-2 producing laccase was isolated from decaying samples from Shandong, China, and showed dye decolorization activities. The objective of this study was to optimize its culture conditions using a statistical analysis of its laccase production. The interactions between different fermentation parameters for laccase production were characterized using a Plackett-Burman design and the response surface methodology. The different media components were initially optimized using the conventional one-factor-at-a-time method and an orthogonal test design, and a Plackett-Burman experiment was then performed to evaluate the effects on laccase production. Wheat straw powder, soybean meal, and $CuSO_4$ were all found to have a significant influence on laccase production, and the optimal concentrations of these three factors were then sequentially investigated using the response surface methodology with a central composite design. The resulting optimal medium components for laccase production were determined as follows: wheat straw powder 7.63 g/l, soybean meal 23.07 g/l, $(NH_4)_2SO_4$ 1 g/l, $CuSO_4$ 0.51 g/l, Tween-20 1 g/l, $MgSO_4$ 1 g/l, and $KH_2PO_4$ 0.6 g/l. Using this optimized fermentation method, the yield of laccase was increased 59.68 times to 67.258 U/ml compared with the laccase production with an unoptimized medium. This is the first report on the statistical optimization of laccase production by Trichoderma harzianum ZF-2.

• 한국환경농학회지
• /
• 제15권3호
• /
• pp.391-398
• /
• 1996

The pretreatment of bark powder with sodium hydroxide and formalin showed the most excellent adsorption ratio, but this method could not practically be used because of the occurrence of dark-colored pigments in filtrates during pretreatment. Instead, acid and formalin were the most affirmative and effective among the pretreatment methods tested, and could be used for this purpose. Among tested species, Quercus acutissima and Robinia pseudo-accacia showed the largest amount of metal adsorption, and $Pb^{2+}$ was the best(83 to 96%) among the four heavy metals tested. The order of adsorption ratios other metals was as follows; $Cu^{2+}$ > $Zn^{2+}$ > $Cd^{2+}$, and the ratio was approximately 45 to 55%. In addition, as the substrate amount increased, the amount of adsorbed heavy metals in subtrates gradually increased, but the adsorbed amount was not proportional to the substrate amount. The order of heavy metal adsorption was as follows; $Pb^{2+}$ > $Cu^{2+}$ > $Cd^{2+}$ > $Zn^{2+}$. Depending on flow rate and column size, pine bark power adsorbed more heavy metals in the 5ml/min flow rate and 3.5cm column size rather than the 10ml/min and 2.0cm. However, oak bark power showed contrary results compared with pine bark powder. The adsorption of $Pb^{2+}$ occurred rapidly in the incipient stagte. Even though bark powders were repeatedly used three times, there was no change in the adsorption ratio(45%), but after four times, the adsorption ratio was significantly reduced to 35%.

• 한국표면공학회지
• /
• 제45권6호
• /
• pp.248-256
• /
• 2012

A Pd-based hydrogen membranes for hydrogen purification and separation need high hydrogen perm-selectivity. The surface roughness of the support is important to coat the pinholes free and thin-film membrane over it. Also, The pinholes drastically decreased the hydrogen perm-selectivity of the Pd-based composite membrane. In order to remove the pinholes, we introduced various surface pre-treatment such as alumina powder packing, nickel electro-plating and micro-polishing pre-treatment. Especially, the micro-polishing pretreatment was very effective in roughness leveling off the surface of the porous nickel support, and it almost completely plugged the pores. Fine Ni particles filled surface pinholes with could form open structure at the interface of Pd alloy coating and Ni support by their diffusion to the membrane and resintering. In this study, a $4{\mu}m$ surface pore-free Pd-Cu-Ni ternary alloy membrane on a porous nickel substrate was successfully prepared by micro-polishing, high temperature sputtering and Cu-reflow process. And $H_2$ permeation and $N_2$ leak tests showed that the Pd-Cu-Ni ternary alloy hydrogen membrane achieved both high permeability of $13.2ml{\cdot}cm^{-2}{\cdot}min^{-1}{\cdot}atm^{-1}$ permation flux and infinite selectivity.

• 한국자기학회지
• /
• 제2권1호
• /
• pp.44-49
• /
• 1992

단롤법 급속응고기술을 이용하여 $Nd_{12}Fe_{80}B_{6}(Nb,\;M)$ (M=Ti/Cu/Ga) 리본을 제작하고 이의 자기특성 및 미세조작에 관한 연구를 하였다. X-선 회절 및 TEM을 이용한 미세조직 조사 결과, 리본의 이방화에 Ga이 효과적이며, 디스크표면속도 17.9 m/s로 제작한 $Nd_{12}Fe_{80}B_{6}(Nb,\;Ca)$ 리본은 약 30 nm의 미세한 결정립으로 구성되고 자유표면이 이방화된 조직으로 형성됨을 알았다. 이 리본을 분쇄하여 자장중에서 정렬시킨 분말의 잔류자속밀도는 0.87 T의 높은 값을 보였으며, 분쇄하기전 리본의 잔류자속밀도에 비하여 약 5% 정도 높았다. 이상의 결과로 부터 리본의 자유표면은 이방화가 되고 나머지 부분은 HIREM 특성을 나타내는 새로운 형태의 고특성 급속응고리본의 제조가 가능할 것으로 사료된다.

• 열처리공학회지
• /
• 제4권1호
• /
• pp.13-18
• /
• 1991

The formation of high $T_c$ phase is very sluggish and c parameter of unit cell of high $T_c$ phase is about $37{\AA}$. High $T_c$ oxide superconductor with a $T_c$ above 100 K has been successfully prepared by solid state reaction method in BiSrCaCuO system by Pb adding. The microstructure related to the formation of the high $T_c$ phase has been investigated. As compared with YBCO compound, the formation reaction of the high $T_c$ requires long time heat treatment. It is due to the transformation from the low $T_c$ phase to high $T_c$ phase. The sintering just below the melting point of the calcined powder mixture is effective on the formation of the high $T_c$ phase in Pb-added BiSrCaCuO system. The growth of the high $T_c$ superconducting phase has a thin plate shape, which is characterized by the c parameter of $37{\AA}$. The formation of the high $T_c$ phases is delayed by the excessive addition of Pb. The lattice parameter(c) of the unit cell (both the low and high $T_c$ phases) is increased with increase of Pb.

• 한국분말재료학회지
• /
• 제22권6호
• /
• pp.408-412
• /
• 2015

This study attempts to manufacture a Ni-Cr-Al-Y coating layer using a kinetic spray process and investigates the microstructure and physical properties of the manufactured layer. The Ni-22Cr-10Al-1Y (wt.%) composition powder is used, and it has a spherical shape with an average diameter of $23.7{\mu}m$. Cu plate is used as the substrate. Optical microscope, X-ray diffraction, scanning electron microscope and Vickers hardness test are carried out to characterize the macroscopic properties of the coating layer. Furthermore, the coating layer underwent vacuum heat treatment at temperatures of $400^{\circ}C$ and $600^{\circ}C$ for 1 hour to check the effect of heat treatment temperature on the properties. The manufactured coating layer is 1.5 mm thick, and featured identical phases to those found in the powder. The porosity of the coating layer is measured at 2.99%, and the hardness is obtained at $490.57H_v$. The layer shows reduced porosity as heat treatment temperature increased, and hardness is reduced at $400^{\circ}C$ but shows a slight increase at $600^{\circ}C$. Based on the findings described above, this study also discusses possible manufacturing methods for a Ni-Cr-Al-Y coating layer using the kinetic spray process.