• 한국결정성장학회지
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• 제30권6호
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• pp.226-231
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• 2020

전기방사 공정을 이용하여 니켈, 아연, 철 전구체를 포함하는 Polyvinyl pyrrolidone 나노 섬유를 제조하였다. 이를 전자기파 차폐에 사용할 수 있는 Ni0.5Zn0.5Fe2O4 산화물 나노 섬유로 전환하기 위하여 열처리 조건을 제어하였다. 비정질 카본 블랙이나 의도치 않은 제2상 등을 배제하고 1차원 미세구조를 유지하면서 산화물 나노 섬유로 만들기 위하여 열처리 중 실시간으로 샘플을 채취해 공정 중 샘플 변화를 추적하였다. X-ray diffraction(XRD) 분석 결과 결정화된 Ni0.5Zn0.5Fe2O4의 회절 패턴은 300℃부터 나타나기 시작하였으나, energy dispersive spectroscopy(EDS) 결과 상 카본 블랙이 대부분 사라지기 위해서는 500℃ 이상의 열처리를 필요로 하였다. 650℃ 이상의 온도부터는 본격적으로 결정 핵 성장이 진행되어 섬유 표면 상태가 매끄럽지 않아지므로, 적용 분야에 따라 선택적으로 열처리 조건을 결정해야 함이 확인되었다.

• 한국건설순환자원학회논문집
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• 제8권4호
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• pp.467-474
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• 2020

탄소나노튜브는 뛰어난 역학적 성능 및 기능성으로 다양한 분야에서 활용되고 있는 나노소재이다. 탄소나노튜브를 건설재료 분야에 활용하는 연구는 현재의 화두 중 하나로, 예전에 비해 점차 많은 연구가 진행되고 있으나, 탄소나노튜브의 혼입률이 시멘트 페이스트의 압축강도 및 유변학적 물성에 미치는 영향을 검증한 문헌은 상대적으로 부족한 것으로 나타났다. 본 연구에서는 Polyvinyl Pyrrolidone을 사용하여 수용액 분산된 다중벽 탄소나노튜브를 이용하여 시멘트 페이스트를 제조하고, 이의 유변학적 물성 및 압축강도 특성을 확인하고자 하였다. 본 연구의 결과에 따르면, 탄소나노튜브의 혼입률이 증가할수록 소성점도 및 소성항복응력의 증가가 발생하였으며, 물시멘트비가 낮은 경우에 이러한 경향이 더욱 뚜렷하게 드러나는 것이 확인되었다. 탄소나노튜브 혼입 시멘트 페이스트의 압축강도는 물시멘트비가 0.30인 경우 탄소나노튜브 혼입률 0.1wt%에서, 물시멘트비가 0.40인 경우에는 혼입률 0.2wt%에서 최대가 되는 것으로 나타났다.

• 한국미생물·생명공학회지
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• 제16권4호
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• pp.303-309
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• 1988

Cellulose를 이용할 수 있는 Cellulomonas속 균주의 종간 세포의 융합방법을 확립하기 위해 원형질체 재생 및 융합조건에 대해 검토하였다. Cellulomonas속 균주의 원형질체는 osmotic stabilizer를 포함하는 재생배지에서 유동성 한천배지로 중층하여 재생시켰고 재생 확인은 주사전자현미경으로 하였다. 원형질체 융합은 항생물질 내성과 영양요구성 돌연변이주의 유전자 표지에 확인하였다. Lysozyme을 처리하여 형성된 C. flavigena 원형 질체의 세포벽 재생은 osmotic stabilizer로 0.4M sorbitol을 포함하는 재생배지에서 약 15% 수준이었으며 여기에 Polyvinyl Pyrrolidone(PVP) 3% 첨가로 재생율을 약 3배정도 증가시킬 수 있었다. Cellulomonas속 균주의 변이주간의 원형질체 융합은 융합유도제로 PEG 6000을 취하여 최적농도 40% (w/v), 치적 처리시간 15분, Ca농도 25mM에서 약 2.0$\times$$10^{-4}$ - 4.0$\times$$10^{-4}$의 융합빈도를 얻을 수 있었다.

• Asian-Australasian Journal of Animal Sciences
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• 제27권11호
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• pp.1571-1576
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• 2014

Nutritive values of green and black tea by-products and anti-nutritive activity of their tannins were evaluated in an in vitro rumen fermentation using various molecular weights of polyethylene glycols (PEG), polyvinyl pyrrolidone (PVP) and polyvinyl polypyrrolidone as tannin-binding agents. Significant improvement in gas production by addition of PEG4000, 6000 and 20000 and PVP was observed only from black tea by-product, but not from green tea by-product. All tannin binding agents increased $NH_3$-N concentration from both green and black tea by-products in the fermentation medium, and the PEG6000 and 20000 showed relatively higher improvement in the $NH_3$-N concentration. The PEG6000 and 20000 also improved in vitro organic matter digestibility and metabolizable energy contents of both tea by-products. It was concluded that high molecular PEG would be suitable to assess the suppressive activity of tannins in tea by-products by in vitro fermentation. Higher responses to gas production and $NH_3$-N concentration from black tea by-product than green tea by-product due to PEG indicate that tannins in black tea by-product could suppress rumen fermentation more strongly than that in green tea by-product.

• 한국약용작물학회지
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• 제14권3호
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• pp.130-133
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• 2006

더덕 종자의 파종시 산파에 의한 종자 손실이 클 뿐만 아니라 입모 후 잡초 발생에 의한 제초 관리가 어려워 재배 농가에서 어려움이 많아 발아 미세환경을 개선시킬 수 있을 뿐만 아니라 기계화 점파 및 멀칭 재배가 가능하고 제초문제를 해결할 수 있는 더덕 종자 펠렛팅 연구를 실시하였던 바 그 결과를 요약하면 다음과 같다. 다양한 피복물질을 이용한 펠렛팅 종자의 발아율은 PID처리가 가장 높았으며 Illite, PIT, Diatomite, BT 순으로 높게 나타났다. 접착물질은 PVP 처리가 가장 발아율이 높았으며 PVA, XG, CMC, AG 순으로 높게 나타났다. 펠렛팅 종자의 피복소재별 성형율, 강도는 PID 가 가장 좋았으며, 발아율에 가장 좋은 물리적 특성은 수분 접촉시 split형의 1/2 균열이 생기고 수분 흡수력은 S자형의 흡수 양상을 보였다. 토양함수량에 따른 발아율은 50% 조건에서 PID처리가 가장 좋았으며, 수분함수량이 높을수록 펠렛팅 종자의 발아율은 증가되는 경향이었다.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1993-1996
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• 2010

Silver nanoparticles has been prepared by the $\gamma$-irradiation and in situ reduction methods. Based on the Raman spectra, TEM images, X-ray Diffraction (XRD) patterns and UV-vis spectra, the in situ reduction method is more stable and the average size of the silver nanoparticles is also smaller than by the $\gamma$-irradiation reduction method. It is identified that the silver ions interacting with nonbonding electrons of oxygen atom in the carbonyl group of polyvinylpyrrolidone (PVP) by the in situ reduction method. It is also found advantages of the in situ reduction method including no additional reducing agents, without $\gamma$-irradiations treatment and the room temperature treatment suitability.

• 한국재료학회지
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• 제24권11호
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• pp.578-584
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• 2014

To synthesize Sn nanoparticles (NPs) less than 30 nm in diameter, a modified polyol process was conducted at room temperature using a reducing agent, and the effects of different pH values of the initial solutions on the morphology and size of the synthesized Sn NPs were analyzed. tin(II) 2-ethylhexanoate, diethylene glycol, sodium borohydride, polyvinyl pyrrolidone (PVP), and sodium hydroxide were used as a precursor, reaction medium, reducing agent, capping agent, and pH adjusting agent, respectively. It was found by transmission electron microscopy that the morphology of the synthesized Sn NPs varied according to the pH of the initial solution. Moreover, while the size decreased to 11.32 nm with an increase up to 11.66 of the pH value, the size increased rapidly to 39.25 nm with an increase to 12.69. The pH increase up to 11.66 dominantly promoted generation of electrons and increased the amount of initial nucleation in the solution, finally inducing the reduced-size of the Sn particles. However, the additional increase of pH dominantly induced a decrease of PVP by neutralization, which resulted in acceleration of the agglomeration by collisions between particles.

• 한국작물학회지
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• 제43권4호
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• pp.214-222
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• 1998

These experiments were conducted to investigate water uptake, electrical conductivity, germination percentage, seedling growth, and seedling establishment rate in direct seeding cultivation of rice. The rice seeds of six japonica type varieties were coated with 12 kinds of polymers in a standard concentration of 0.2% using seed coating machine. The water absorption of the polymer-coated seeds under saturation conditions was not different among varieties, and was the highest in kulcel, maltrin, and waterlock on the polymer-coated seeds. The electrical conductivity with waterlock (55.0 $\mu scm^{-1}g^{-1}$) was higher than the control plot (45.6 $\mu scm^{-1}g^{-1}$) and other treatments. The germination of the polymer-coated seeds was 95.9% at control plot, 92.7% at low temperature and 35.7% at high temperature. The total dry weight of seed decreased in the order of low temperature, control plot, and high temperature, and was effective in pvp (polyvinyl pyrrolidone), opadry, and sacrust. The seedling establishment rate in direct seeding cultivation ranged from 74.9 to 81.0% in flooded paddy surface, and ranged from 64.7 to 76.6% in dry paddy. In both cases, it decreased in the order of early, medium and medium-late varieties, but was enhanced in daran 8600, sepirect, and sacrust. According to this study the recommended polymers for direct seeding cultivation of rice are daran 8600, sepirect, and sacrust.

• Environmental Analysis Health and Toxicology
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• 제30권
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• pp.3.1-3.6
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• 2015

Objectives This study aims to evaluate the size-dependent toxicity of spherical silver nanoparticles (Ag NPs) to an endemic benthic organism, Glyptotendipes tokunagai. Methods Ag nanoparticles of three nominal sizes (50, 100, and 150 nm) capped with polyvinyl pyrrolidone (PVP-Ag NPs) were used. Their physicochemical properties, acute toxicity (48 hours), and bioaccumulation were measured using third instar larvae of G. tokunagai. Results The aggregation and dissolution of PVP-Ag NPs increased with exposure time and concentration, respectively, particularly for 50 nm PVP-Ag NPs. However, the dissolved concentration of Ag ions was not significant compared with the median lethal concentration value for $AgNO_3$ (3.51 mg/L). The acute toxicity of PVP-Ag NPs was highest for the smallest particles (50 nm), whereas bioaccumulation was greatest for the largest particles (150 nm). However, larger PVP-Ag NPs were absorbed and excreted rapidly, resulting in shorter stays in G. tokunagai than the smaller ones. Conclusions The size of PVP-Ag NPs significantly affects their acute toxicity to G. tokunagai. In particular, smaller PVP-Ag NPs have a higher solubility and stay longer in the body of G. tokunagai, resulting in higher toxicity than larger PVP-Ag NPs.

• 한국분무공학회지
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• 제20권1호
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• pp.53-58
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• 2015

In this study, we prepare the Ag nanofluids synthesized by the chemical reduction method and measure the extinction coefficient of those nanofluids at a wavelength of 632.8 nm. The Ag nanofluids are synthesized by the chemical reduction method using silver nitrate ($AgNO_3$) and sodium borohydride ($NaBH_4$) in water and ethylene glycol (EG). For stable dispersion of Ag particles in the base liquids, polyvinyl pyrrolidone (PVP) is added as a surfactant. The extinction coefficient of manufactured Ag nanofluids is measured by an in-house developed measurement system at the wavelength of 632.8 nm. The results show that the extinction coefficient of water-based and EG-based Ag nanofluids is linearly increased with respect to the particle loadings. Moreover, it is shown that the extinction coefficient of EG-based Ag nanofludis is higher than that of water-based Ag nanofluids. Finally we compare the experimental results with both the Maxwell-Garnett model and Rayleigh scattering approximation model, and they demonstrate that the Rayleigh scattering approximation model is reasonably predict the extinction coefficient of Ag nanofluids using hydraulic diameter of silver nanoparticle.