• 전기화학회지
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• 제2권1호
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• pp.5-12
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• 1999

PVA-전구체법을 사용하여, 리튬전지의 양극물질인 $Li_xNi_{1-y}Co_yO_2$의 다결정성 분말을 합성하였다. 합성된 분말을 양극물질로 사용하여 리튬이온전지를 제조하여 전지의 전기화학적 성질을 측정하였다. PVA와 금속이온간의 상대적 양, PVA의 농도 및 중합도, 열처리조건, 금속의 조성비 등 여러 다른 합성조건을 변화시키면서, 그러한 합성상의 조건 변화가 리튬이온전지의 전지특성과 어떠한 상호관계를 갖는지 조사하였다. 전지의 초기성능에 관한 한, PVA-전구체법으로 합성한 $Li_xNi_{1-y}Co_yO_2$의 경우, 최적의 조성은 x=1.0, y=0.26인 것으로 관찰되었다. PVA-전구체법으로 합성할 경우, 전구체에 남는 잔여탄소로 인해 형성되는 $Li_2CO_3$가 전지의 성능을 저하시키는 것으로 관찰되었다. 이를 제거하기 위해 건조 공기의 흐름 속에서 열처리를 하거나, 합성 후 2차 열처리 과정에서 $500^{\circ}C$의 온도에서 건조공기의 흐름을 유지하며 annealing 처리를 하는 것이 전지의 특성을 크게 개선하는 것으로 관찰되었다.

• 한국재료학회지
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• 제7권2호
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• pp.140-144
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• 1997

은 튜브에 장입되기 전의 초기 분말의 입자 크기가 Ag/Bi-2223초전도 선재의 미세구조와 상전이, 임계 전류 밀도등에 미치는 영향에 대해 고찰하였다. 분말의 입자 크기는 하소 분말을 볼밀을 이용하여 0-48 시간 동안 분쇄하여 조절하였다. 열처리 후 최종 초전도 선재의 전기적 성질은 초기 분말의 입자 크기에 영향을 받는 것으로 나타났으며 분말의 분쇄에 의한 반응성의 증가에 의해 열처리시 2223 상으로의 상전이가 빠르게 일어났고 이차상의 크기와 분율이 감소된 미세구조를 얻을 수 있었다. 그러나 과다한 분쇄에 의한 반응성의 증가에 의해 열처리시 2223상으로의 상전이가 빠르게 일어났고 이차상의 크기와 분율이 감소된 미세구조를 얻을 수 있었다. 그러나 과다한 분쇄는 분말의 비정질화를 유발하여 2223 상으로의 전이를 방해함으로써 선재의 임계 전류 밀도를 감소시키는 결과를 나타내었다.

• 한국분말재료학회지
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• 제22권5호
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• pp.350-355
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• 2015

Perforated polygonal cobalt oxide ($Co_3O_4$) is synthesized using electrospinning and a hydrothermal method followed by the removal of a carbon nanofiber (CNF) template. To investigate their formation mechanism, thermogravimetric analysis, field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy are examined. To obtain the optimum condition of perforated polygonal $Co_3O_4$, we prepare three different weight ratios of the Co precursor and the CNF template: sample A (Co precursor:CNF template- 10:1), sample B (Co precursor:CNF template-3.2:1), and sample C (Co precursor:CNF template-2:1). Among them, sample A exhibits the perforated polygonal $Co_3O_4$ with a thin carbon layer (5.7-6.2 nm) owing to the removal of CNF template. However, sample B and sample C synthesized perforated round $Co_3O_4$ and destroyed $Co_3O_4$ powders, respectively, due to a decreased amount of Co precursor. The increased amount of the CNF template prevents the formation of polygonal $Co_3O_4$. For sample A, the optimized weight ratio of the Co precursor and CNF template may be related to the successful formation of perforated polygonal $Co_3O_4$. Thus, perforated polygonal $Co_3O_4$ can be applied to electrode materials of energy storage devices such as lithium ion batteries, supercapacitors, and fuel cells.

• 한국전기전자재료학회논문지
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• 제19권12호
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• pp.1092-1098
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• 2006

The influence of the concentration of precursor solution and the number of solution coatings on the densification of the $Pb(Zr_xTi_{1-x})O_3$ (PZT) thick films was studied. PZT powder and PZT precursor solution were prepared by3 sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The composition of powder and precursor solution were PZT(70/30) and PZT(30/70), respectively. The PZT precursor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5 to 2.0 mol/L[M] and the number of coating was repeated from 0 to 6. The XRD patterns of all PZT thick films shelved typical perovskite polycrystalline structure. The porosity of the thick films was decreased with increasing the number of coatings and 6-time coated films with 1.5 M showed the dense microstructure and thickness of about $60{\mu}m$. The relative dielectric constant of the PZT thick film was increased with increasing the number of solution coatings and the thick films with 1.5 M, 6-time coated showed the 698. The remanent polarization the 1.5 M and 6-time coated PZT thick films was $38.3{\mu}C/cm^2$.

• Bulletin of the Korean Chemical Society
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• 제18권6호
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• pp.612-618
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• 1997

$LiMn_2O_4$ powders were prepared by burning and subsequent calcination of PEG-metal nitrate precursor. After the burning stage of the precursor, some minor phases such as $Mn_2O_3$ (or $Mn_3O_4$), MnO, and carbonate were formed and single phases of $LiMn_2O_4$ were obtained by further calcinations above 400 ℃. From thermal analysis of the precursor, a violent thermal decomposition, which was indicated by a drastic weight loss accompanied by a sharp and strong exothermic peak, was observed and probably caused by an oxidation-reduction reaction between oxidizer and fuel. The formation of the minor phases could be explained in terms of the burning behavior of the precursor by employing valence concepts of propellant chemistry. The calcined powders were composed of submicron-sized but highly agglomerated particles and showed very broad particle size distribution.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2001년도 추계학술강연 및 발표대회
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• pp.10-10
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• 2001

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.486-486
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• 2006

• 한국해양공학회지
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• 제24권6호
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• pp.86-91
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• 2010

Superconductor material $Bi_2Sr_2Ca_2Cu_3O_x$(Bi-2223) powders were synthesized by ultrasonic spray pyrolysis method. It is clear that Bi-2223 phase more than Bi-2212 phase was acquired at sufficient synthesized time. Best condition for Bi-2223 phase was synthesizing temperature at $860^{\circ}C$. We also investigated the effects for concentrations and viscosities of starting liquid precursor as well as temperature distribution of reacting furnace. The size of synthesized powder was decreased by decreasing the concentration of starting liquid precursor. Modified reacting furnace with four different temperature heating zones gave us successful results for desirable nano-powder including $Bi_2Sr_2Ca_2Cu_3O_x$ phase. Citric acid addition to starting liquid precursor showed increasing of the size for synthesized powder. Bi-2223 single phase was acquired from Bi2223 and Bi-2212 mixed phases through heat treatment in box furnace at 24 hours.

• 한국세라믹학회지
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• 제42권3호
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• pp.205-210
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• 2005

Tetraethyl Orthosilicate(TEOS)를 $SiO_2$ 전구체 용액으로 사용하여 Polyacrlamide gel 방법으로 나노 실리카 분말을 합성하였다. 이 gel 공정법은 비교적 간단한 중합법이며, 고분자 망상구조가 $SiO_2$의 응집을 억제하므로 비교적 낮은 하소온도에서 나노입자를 합성할수 있었다. $SiO_2$ 분말입자의 크기는 gel 전구체중의 ammonium persulphate와 N,N'-methylene-bis-acryamide(BIS)의 농도에 영향을 받았다. 실리카 입자의 크기는 ammonium persulphate의 농도가 증가할수록 작아졌으며 그 농도가 0.01M일때 가장 작은 10nm크기의 입자를 얻었다. 또한 그 입자의 크기는 BIS의 농도가 증가할수록 작아졌으며 그 높도가 0.05M일때 입자의 크기는 5nm였다.

• Progress in Superconductivity
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• 제12권1호
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• pp.6-11
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• 2010

The milling effects of a precursor $Y_2BaCuO_5$ (Y211) powder having 1 wt.% $CeO_2$ on the microstructure and critical current density ($J_c$) of liquid infiltration growth (LIG) processed $YBa_2Cu_3O_{7-y}$ (Y-123) bulk superconductors were investigated. The microstructure analysis revealed that the Y211 size in the final Y-123 products decreased with increasing the milling time and a relatively high density and uniform distribution of Y211 inclusions were observed in the sample prepared using 8 h milled powder. However, the unexpected Y211 particles coarsening was observed from the 4 h milled sample which was further increased for 10 h milled sample. Critical current density ($J_c$) of the LIG processed Y-123 bulk superconductors was found to be dependent on the milling time of the Y211 precursor powder. The $J_c$ increased with the increase of milling time and reached up to a maximum at 8 h in the self field while 10 h milled sample showed lower $J_c$ at the same field which might be due to the exaggerated growth and non-uniform distribution of Y211 particles.