• 한국세라믹학회지
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• 제53권1호
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• pp.18-23
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• 2016

The development of a binder system with a lower carbon footprint as an alternative to Portland cement has been intensely researched. In the present study, alkali-activated fly ash exposed to carbon dioxide at an early age was characterized in compressive strength tests and by MIP, XRD and FT-IR analyses. The compressive strength of carbonated specimens experienced a dramatic increase in comparison to uncarbonated specimens. The microstructural densification of the carbonated specimens was evidenced by MIP. The XRD pattern showed peaks assigned to nahcolite, indicating that the pH was lower in the carbonated specimens. Under the carbon dioxide-rich environment, the aluminosilicate gel reached a more Si-rich state, which improved the mechanical properties of the alkali-activated fly ash.

• 한국세라믹학회지
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• 제52권4호
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• pp.264-268
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• 2015

Cu films were plated in an eco-friendly electroless bath (No-Formaldehyde) on Ni/screen printed Ag pattern/PET substrate. For electroless Cu plating, we used sodium-phosphinate ($NaH_2PO_2{\cdot}H_2O$) as reducing agent instead of Formaldehyde. All processes were carried out in electroless solution of pH 7 to minimize damage to the PET substrate. According to the increase of sodium-phosphinate, the deposition rate, the granule size, and rms roughness of the electroless Cu film increased and the Ni content also increased. The electroless Cu films plated using 0.280 M and 0.575 M solutions of sodium-phosphinate were made with Cu of 94 at.% and 82 at.%, respectively, with Ni and a small amount P. All electroless Cu plated films had typical FCC crystal structures, although the amount of co-deposited Ni changed according to the variation of the sodium-phosphinate contents. From these results, we concluded that a formation of higher purity Cu film without surface damage to the PET is possible by use of sodium-phosphinate at pH 7.

• 한국세라믹학회지
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• 제53권4호
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• pp.406-410
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• 2016

Carbon-coated sodium iron pyrophosphate ($Na_2FeP_2O_7$) was prepared by a simple and low-cost pyro-synthesis route for further use as the cathode for Na-ion batteries. The X-ray diffraction (XRD) pattern of the sample annealed at $650^{\circ}C$ confirmed the pure triclinic phase of $Na_2FeP_2O_7$. Electron microscopy studies revealed a cross linked plate shape morphology of the $Na_2FeP_2O_7$ sample. When tested for application in Na-ion battery, the $Na_2FeP_2O_7$ cathode showed two redox pairs in the potential window of 2.0-4.0 V. The cathode registered initial discharge and charge capacities of 80.85 and 90 mAh/g, respectively, with good cycling performance.

• 한국세라믹학회지
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• 제44권3호
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• pp.157-161
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• 2007

Line width under $100\;{\mu}m$ with good resolution is difficult to achieve using conventional thick-film process utilizing screen printing method. However combined with lithography technology finer line and space for miniaturization and highly integrated package is achievable. In this study, photosensitive Ag paste of optimum formulation used for thick film lithography technology was fabricated by various Ag powder, glass powder and additives. As the result, line width of $30\;{\mu}m$ with good definition and reduced mismatch during co-firing with LTCC substrate was acquired. Formulated Ag paste was used to pattern embedded fine line inductor with over 90% yield.

• 한국세라믹학회지
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• 제47권3호
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• pp.244-248
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• 2010

Porous calcium phosphates were successfully fabricated by using a cuttlefish bone. The cuttlefish bone, which is composed of $CaCO_3$, showed a special porous microstructure containing uniform-sized voids. In this study, the pre-forms infiltrated distilled phosphoric acid were sintered at $1200^{\circ}C$ in an air atmosphere. The porous microstructure of the pre-forms was kept their original pattern after sintering with a synthesis of calcium phosphate. The obtained porous calcium phosphate, sintered at $1200^{\circ}C$ for 3 h at 17% concentration of phosphoric acid, showed uniform open pores of 150 ${\mu}m$ in size and $\beta$-TCP phase in the XRD patterns. Above 16% concentration, CaO phase, derived from the decomposition of $CaCO_3$, decreased gradually in the sintered samples, and the measured Ca/P ratios of the samples prepared from 16% and 18% concentration were 1.67 and 1.43, which are close to stoichiometric HA (1.66) and $\beta$-TCP (1.50).

• 한국공작기계학회논문집
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• 제11권2호
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• pp.17-23
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• 2002

A cylindrical capacitance-type spindle displacement sensor was developed and its effectiveness as a system to monitor cutting forces during hard turning was tested in this research. The sensor was installed between the face of spindle cover and the chucking element and measured pure radial motion of the spindle under the condition with presence of roundness error at measured surface. To prove the effectiveness of the developed system hard aiming tests using ceramic inserts and tool steel as workpiece were conducted. The workpiece was hardened up to 65 Rc. The variations of pure radial motion of the spindle ware measured during the cutting tests. The signals from the sensor showed the same pattern of cutting force variations from the tool dynamometer due to the progress of tool wear. As the flank wear of the ceramic tool increased both static component of cutting forces and the amount of center shift of spindle orbit increased, Results from the research showed that the developed sensor could be utilized as an effective and cheap on-line sensing device to monitor cutting conditions and tool performance in the un-manned machining center.

• Journal of Advanced Marine Engineering and Technology
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• 제32권2호
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• pp.359-364
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• 2008

Using multi beam echo sounder, side scan sonar and scuba diving equipment, ceramic type, uneven type and semicircle-ramus type reefs into sandy bottom were ascertained, the depth of submersion in 7.2-10.3m on the coast of Gangneung, East of Korea, forty uneven type artificial reefs(AR) were totally buried into the sandy bottom. Two of five semicircle-ramus type ARs had only of their top area exposed. For most of the 45 ceramic reefs, only the upper 25-150cm of ARs were visible. The burial pattern is different in west and east side of the reefs, where the east side is deeply buried compared to the west side. From these results. it is recommended that sufficient analysis of bottom structure and materials especially in the sandy sea area should be undertaken in order to determine the best type of artificial reefs to be deployed and the best location for depoloyment.

• 한국세라믹학회지
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• 제44권1호
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• pp.32-36
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• 2007

Zinc gallate $(ZnGa_2O_4)$ thin film phosphors have been formed on ITO glass substrates by a sol-gel spinning coating method. For the formation of the film phosphors, the starting materials of zinc acetate dihydrate, gallium nitrate hydrate and 2-methoxyethanol as a solution were used. The thin films deposited were firstly dried at $100^{\circ}C$ and fired at $500^{\circ}C\;or\;600^{\circ}C$ for 30 min and then, annealed $500^{\circ}C\;or\;600^{\circ}C$ at for 30 min under an annealing atmosphere of 3% $H_2/Ar$. The thin films deposited on ITO glass plates showed the (220), (222), (400), (422), (511), and (440) peaks of spinel structure as well as the (311) peak indicating a standard powder diffraction pattern. The surface morphologies of the thin film phosphors were observed with a firing and an annealing condition. The $ZnGa_2O_4$ film phosphors showed the blue emission spectra around 410 nm as well as the emission spectra in the UV region (360-380 nm).

• 한국세라믹학회지
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• 제31권12호
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• pp.1501-1506
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• 1994

The precipitate of FeCl2.4H2O and NaOH, Fe(OH)2 was rapidly made to oxidize by H2O2 to prepare $\delta$-FeOOH. The particle size, surface and morphology of $\delta$-FeOOH, and the shape and structure of thermally decomposed $\delta$-FeOOH were investigated by the use of high resolution STEM. $\delta$-FeOOH prepared under the condition of reaction temperature of Fe(OH)2 at 4$0^{\circ}C$, [OH-][Fe2+]=5 and aging time of 2 hr Fe(OH)2, had 630$\AA$ mean particle size, 4~5 aspect ratio, 20.8 emu/g saturation magnetization and 210 Oe coercivity. The edges of $\delta$-FeOOH were inclined to (001) about 41$^{\circ}$, 60$^{\circ}$ and coincident with (102), (101) respectively. When $\delta$-FeOOH was thermally decomposed at 25$0^{\circ}C$ for 2 hr in vacuo, which had micropores of 0.9 nm thickness and crystallites of 2.4 nm thickness. (001)hex, [10]hex. of $\delta$-FeOOH parallel with (001)hex, [100]hex. of $\alpha$-Fe2O3 respectively. This showed three dimensional topotaxial structure transition, which was investigated by SADP (Selected Area Diffraction Pattern) of STEM.

• 한국세라믹학회지
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• 제29권3호
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• pp.195-201
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• 1992

It had been studied the structure and the magnetic properties of singel phase Co2Y(Ba2Co2Fe12O22) powder, one of the hexagonal ferrite. The material was successfully prepared by a commercially applicable coprecipitation method. Adding asqueous solution of BaCl2, CoCl2 and FeCl2(Ba2+:Co2+:Fe2+=1:1:6 in mole ratio) to a mixture of NaOH and hydrogen peroxide solution, coprecipitate was formed with rapid oxidation of ferrous to ferric ion. The coprecipitate transformed to single phase Co2Y powder at heat treatment temperatures as low as 900$^{\circ}C$. The shape of Co2Y particles obtained at 900$^{\circ}C$ was hexagonal plate-like (diameter∼$\mu\textrm{m}$, aspect ratio>10). The structure of the Co2Y was refined by a Rietveld analysis of the measured X-ray diffractogram. The lattice parameters are ao=5.8602${\AA}$ and co=43.512${\AA}$. Co2Y is a soft magnetic material with saturation magnetization 30 emu/g and coecivity 170 . A standard X-ray diffraction pattern for Co2Y is proposed as well.