• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.132-139
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• 2005

Sintering behavior of $BaO-Nd_{2}O_3-TiO_2$ with a Pb-based glassceramics frit were investigated in order to understand an effect of glassceramics as a low temperature sintering agent on dielectric ceramics. A green sheet form was fabricated through tape casting method with the glassceramic fut added $BaO-Nd_{2}O_3-TiO_2$. The dispersion properties, rheological properties and final density of dielectric composit slurry as a function of amount and composition of organic additives was examined. The dispersants' addition was effective in controlling dispersion of the ceramics in solution. The addition of excessive dispersant showed adverse effect on dispersion. The prepared slurries, containing ceramic : powders, glass-ceramics and various kinds of organic viechles, exhibited typical shear thinning behavior. The best properties of tape casting appeared powder to solvent ratio 65 : 35 and amount of the binder 6 wt$\%$ and plasticizer 3 wt$\%$. The viscosity of the slurry was 677 cps and green/sintered density in the tape was $3.3 g/cm^3,\;5.56 g/cm^3$ respectively.

• KCI Concrete Journal
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• v.14 no.3
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• pp.121-129
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• 2002

This study investigates experimentally into the design factors and quality variations having an effect on the properties of the combined high flowing concrete to be poured in the slurry wall of Inchon LNG in-ground receiving terminal. Especially, high belite cement and lime stone powder as cementitious materials and viscosity agent in order to improve self-compaction and hydration heat are used in this study. Water-cement ratio(W/C), fine aggregate volume ratio(Sr) and coarse aggregate volume ratio(Gv) as design factors of the combined high flowing concrete are applied to determine the optimum mix design proportion. Also quality variations for sensitivity test are selected items as followings. (1)Surface moisture(5cases) and (2)Fineness modulus of fine aggregate(5cases), (3)Concrete temperature(3cases), (4)Specific surface(3cases) and particle size of lime stone powder. As experimental results, water-cement ratio, fine and coarse aggregate volume ratio are shown as the optimum range 51%, 43% and 53% separately considering site condition of slurry wall. Also quality factors by sensitivity test should be controlled in the following ranges. (1) Surface moisture :to.67% and (2)Fineness modulus 2.6$\pm$0.2 of fine aggregate, (3)Concrete temperature l0-20t, (4) Specific surface 6,000$\textrm{cm}^2$/g and particle size 9.7$\pm$1.0${\mu}{\textrm}{m}$ of lime stone powder. Based on the results of this study, the optimum mix design proportion of the combined high flowing concrete are selected and poured successfully in the slurry wall of LNG in-ground tank.

• Tribology and Lubricants
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• v.35 no.6
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• pp.323-329
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• 2019

Sapphire is currently used as a substrate material for blue light-emitting diodes (LEDs). The market for sapphire substrates has expanded rapidly as the use of LEDs has extended into various industries. However, sapphire is classified as one of the most difficult materials to machine due to its hardness and brittleness. Recently, a lap-grinding process has been developed to combine the lapping and diamond mechanical polishing (DMP) steps in a single process. This paper studies, the effect of wafer surface roughness on the chemical mechanical polishing (CMP) process by pressure and abrasive concentration in the lap-grinding process of a sapphire wafer. In this experiment, the surface roughness of a sapphire wafer is measured after lap-grinding by varying the pressure and abrasive concentration of the slurry. CMP is carried out under pressure conditions of 4.27 psi, a plate rotation speed of 103 rpm, head rotation speed of 97 rpm, and slurry flow rate of 170 ml/min. The abrasive concentration of the CMP slurry was 20wt, implying that the higher the surface roughness after lapgrinding, the higher the material removal rate (MRR) in the CMP. This is likely due to the real contact area and actual contact pressure between the rough wafer and polishing pad during the CMP. In addition, wafers with low surface roughness after lap-grinding show lower surface roughness values in CMP processes than wafers with high surface roughness values; therefore, further research is needed to obtain sufficient surface roughness before performing CMP processes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.10
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• pp.865-871
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• 2016

In recent years, traditional scaffold fabrication techniques such as gas foaming, salt leaching, sponge replica, and freeze casting in tissue engineering have significantly limited sufficient mechanical property and cell interaction effect due to only random pores. Fused deposition modeling is the most apposite technology for fabricating the 3D scaffolds using the polymeric materials in tissue engineering application. In this study, 3D slurry mould was fabricated with a blended biphasic calcium phosphate (BCP)/Silica/Alginic acid sodium salt slurry in PCL mould and heated for two hours at $100^{\circ}C$ to harden the blended slurry. 3D dual-pore BCP/Silica scaffold, composed of macro pores interconnected with micro pores, was successfully fabricated by sintering at furnace of $1100^{\circ}C$. Surface morphology and 3D shape of dual-pore BCP/Silica scaffold from scanning electron microscopy were observed. Also, the mechanical properties of 3D BCP/Silica scaffold, according to blending ratio of alginic acid sodium salt, were evaluated through compression test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.68-69
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• 2005

BTO ($BaTiO_3$) thin film is one of the high dielectric materials for high-density dynamic random access memories (DRAMs) due to its relatively high dielectric constant. It is generally known that BTO film is difficult to be etched by plasma etching, but high etch rate with good selectivity to pattern mask was required. The problem of sidewall angle also still remained to be solved in plasma etching of BTO thin film. In this study, we first examined the patterning possibility of BTO film by chemical mechanical polishing (CMP) process instead of plasma etching. The sputtered BTO film on TEOS film as a stopper layer was polished by CMP process with the self-developed $BaTiO_3$- and $TiO_2$-mixed abrasives slurries (MAS), respectively. The removal rate of BTO thin film using the$ BaTiO_3$-mixed abrasive slurry ($BaTiO_3$-MAS) was higher than that using the $TiO_2$-mixed abrasive slurry ($TiO_2$-MAS) in the same concentrations. The maximum removal rate of BTO thin film was 848 nm/min with an addition of $BaTiO_3$ abrasive at the concentration of 3 wt%. The sufficient within-wafer non-uniformity (WIWNU%)below 5% was obtained in each abrasive at all concentrations. The surface morphology of polished BTO thin film was investigated by atomic force microscopy (AFM).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.101-102
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• 2006

BTO ($BaTiO_3$) thin film is one of the high dielectric materials for high-density dynamic random access memories (DRAMs) due to its relatively high dielectric constant, It is generally known that BTO film is difficult to be etched by plasma etching, but high etch rate with good selectivity to pattern mask was required. The problem of sidewall angle also still remained to be solved in plasma etching of BTO thin film. In this study, we first examined the patterning possibility of BTO film by chemical mechanical polishing (CMP) process instead of plasma etching. The sputtered BTO film on TEOS film as a stopper layer was polished by CMP process with the sell-developed $BaTiO_3$- and $TiO_2$-mixed abrasives slurries (MAS). respectively. The removal rate of BTO thin film using the $BaTiO_3$-mixed abrasive slurry ($BaTiO_3$-MAS) was higher than that using the $TiO_2$-mixed abrasive slurry ($TiO_2$-MAS) in the same concentrations. The maximum removal rate of BTO thin film was 848 nm/min with an addition of $BaTiO_3$ abrasive at the concentration of 3 wt%.

• Journal of the Mineralogical Society of Korea
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• v.23 no.3
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• pp.191-197
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• 2010

Fine nickel metal powder of uniform morphology, narrow size distribution, and high purity was prepared from high purity metal solution. Slurry reduction method for the synthesis of metal powder was applied with a special interest in their fine and spherical shape. The products were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Well dispersed ultrafine nickel powder with the particle size range of 100~200 nm was produced from Ni-hydrazine precursor using hydrazine as a reductant for 90 min reaction in 4.5 M NaOH solution.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1C
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• pp.1-5
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• 2010

The river maintenance processing has revealed that the river beds in Korea have been significantly polluted in various ways for the last two decades. Thus, the dredging, transportation and landfilling of these contaminated materials are attracting public attention these days. In this study, electrokinetic method was applied in order to accelerate the settling processes of clay particles in suspension and evaluate the factors affecting the settling behaviour. It has been found from the testing results that the settling velocity under the influence of electrokinetics was much faster than the gravitational one, and the water content of slurry soil reduced significantly after the electrokinetic processing. The initial water content of slurry soil should be one of the important factors affecting the settling behaviour as well as variation of water content, and hence the electrokinetic processing would be the cost-effective method for the field application.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.2
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• pp.63-68
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• 2007

A number of process problems should be solved in the multi-layered ceramic devices such as EMI filter. In particular, it is essential to control the sintering shrinkage in co-firing of different materials for obtaining defect-free samples such as crack, camber, and delamination which usually occur near the surface and interface. We studied the effect of the powder properties of ferrite on the co-firing behavior of green ceramic layers composed of ferrite and varistor. Three kind of ferrite powder samples as a function of milling time (24, 48, and 72 hr) were prepared. Varistor and ferrite ceramic green sheet were made by means of doctor blade process using slurry (ceramic powder and binder solution). Here, slurry was prepared by mixing 55 wt% powder with 45wt% binder solution. Varistor and ferrite green sheets were laminated at $80 kg/cm^2$, and co-fired at $900^{\circ}C$ and $1000^{\circ}C$ for 3 hr. We obtained the camber-free and co-fired ferrite/varistor layer structure by controlling the milling time and sintering temperature.

• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.446-449
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• 1999

본 연구에서는 기존의 자성 웨지의 제조공정을 대체하여 제조 공정이 단순하고, 그의 정밀성이 우수한 tape casting-lamination법에 의한 자성 웨지의 제조 공정의 적용 가능성에 대한 연구를 수행하였다. 철 분말과 에폭시 slurry는 우수한 tape casting 특성을 보여주었으며, 이렇게 얻어진 green tape과 유리 섬유를 적층하여 자성 웨지를 얻었다. 이러한 과정을 거쳐서 얻어진 제품의 품질 특성을 평가한 결과, 기존의 제조 공정으로 얻어진 제품에 비하여 품질의 균일성이 우수하며, 제조 공정을 혁신적으로 단축하는 것이 가능한 것을 보여주고 있다.