• 한국재료학회지
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• 제14권5호
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• pp.368-373
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• 2004

To improve the conventional cathode-supported tubular solid oxide fuel cell (SOFC) from the viewpoint of low cell power density, expensive fabrication process and high operation temperature, the anode-supported tubular solid oxide fuel cell was investigated. The anode tube of Ni-8mol% $Y_2$O$_3$-stabilized $ZrO_2$ (8YSZ) was manufactured by extrusion process, and, the electrolyte of 8YSZ and the multi-layered cathode of $LaSrMnO_3$(LSM)ILSM-YSZ composite/$LaSrCoFeO_3$ were coated on the surface of the anode tube by slurry dip coating process, subsequently. Their cell performances were examined under gases of humidified hydrogen with 3% water and air. In the thermal cycle condition of heating and cooling rates with $3.33^{\circ}C$/min, the anode-supported tubular cell showed an excellent resistance as compared with the electrolyte-supported planar cell. The optimum hydrogen flow rate was evaluated and the air preheating increased the cell performance due to the increased gas temperature inside the cell. In long-term stability test, the single cell indicated a stable performance of 300 mA/$\textrm{cm}^2$ at 0.85 V for 255 hr.

• 한국염색가공학회지
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• 제32권1호
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• pp.65-71
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• 2020

Electrical energy is used for heating and cooling because electric cars do not have engines and cooling water. The downside is that when the heating and cooling system is applied to electric vehicles, about 40 percent of the energy is spent on heating and cooling, which is less efficient in winter. This has increased demand for electric vehicle battery efficiency. In this study, the condensation and dispersion of carbon nanotubes were controlled, and carbon fibers and composite slurry were manufactured without binders to manufacture paper. Manufactured by content showed the highest heat generation characteristic at 143℃ with a carbon fiber content ratio of 20wt% and confirmed that the heat temperature rises with increasing pressure. The plane heaters made through this study can be applied to a variety of products other than electric vehicles because they can be simplified by process and high temperature.

• 한국농공학회논문집
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• 제63권3호
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• pp.35-45
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• 2021

Digestate or slurry produced from anaerobic digestion is mostly applied to crop lands for its disposal and recovering nutrients. However, minimizing nitrogen losses following field application of the digestate is important for maximizing the plant's nitrogen uptake and reducing environmental concerns. This study was conducted to assess the effects of three different biogas digestate application techniques (sawdust mixed with digestate (SSD), the hole application method (HA), and digestate injected in the soil (SD)) on nitrate leaching potential in the soil. A pot laboratory experiment was conducted at room temperature of 25 ± 2 ℃ for 107 days. The experimental results showed that sawdust application method turned out to be appropriate for quick immobilization of surplus N in the form of microbial biomass N, reflecting its lower total nitrogen and NH₄-N contents and low pH. The NH₄-N and total nitrogen fate in the soil fertilized with manure showed no statistically significant (p > 0.05) differences between the different methods applied during the incubation time under room temperature. In contrast, NO₃-N concentration indicates significant reduction in sawdust treatment (p < 0.05) compared to the control and other application methods. However, the soil sawdust mixed with digestate was more effective than the other methods, because of the cumulative labile carbon contents of the amendment, which implies soil net N immobilization.

• 한국세라믹학회지
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• 제27권3호
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• pp.355-360
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• 1990

One of the possible ways to make a flexible wire of high-Tc superconductiong ceramics is the extrusion of a mixture slurry of superconducting powder with an appropriate polymer binder. The fabrication procedure for $YBa_2Cu_3O_{7-{\delta}}$ superconducting coils with this plastic mass is described. The major factors limiting the formation of extruded wire are the binder content, powder size, and entrapped gas in the mixture slurries. The optimum content of binder for both good flexbility and strength of wire was estimated to be 30wt%. The finer the powder size is, the more homogeneous structure the extruded wire has. The vacuum degassing before extrusion was necessary to remove the entrapped gas in as-extruded wire. The formability of wire depends greatly on the wire radius and binder content. After burning out the binder and the successive sintering, the contacts between the superconducting grains could be made. The resistivity vs. temperature behavior measured in the final wire showed the transition temperature of 90K with narrow transition width. However, the critical current densities of these wires are much lower in comparison to those of conventional bulk specimens.

• 한국주조공학회지
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• 제22권5호
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• pp.245-251
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• 2002

Cast AZ91 and extruded AM50 alloys were isothermally heated as solid/liquid coexistent temperatures, and semi-solid formed into sheets. Mold filling ability of semi-solid slurry with different liquid fractions was investigated in relation to process variables such as injection speed and mold temperature. Relatively uniform distribution of solid particle size and liquid fraction were observed throughout the semi-solid formed sheet. AZ91 alloy sheets were also manufactured by conventional die casting and compared with the semi-solid formed. It was found that the surface was more smooth and the dimensional accuracy was higher in case of the semi-solid formed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.60-63
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• 2003

Semi-solid forming is the process of stirring alloy during solidification, making the mixture of liquid and solid, solidifying it, reheating it to the solid-liquid coexistent temperature, and then injecting this semi solid slurry into dies. In the semi-solid die casting process, it is very important to find out the correlation of injection condition, microstructure and mechanical properties. Especially, an improper injection condition is the main cause of liquid segregation and non-homogeneous mechanical properties due to the difference of solid fraction according to the position of the products. To ensure the database requisite to the semi-solid die casting product, it is essential to acquire the mechanical properties considering liquid segregation to the injection condition. In this study, the effect of injection condition on liquid segregation, formability, microstructure and mechanical properties in a thin product was investigated.

• 한국정밀공학회지
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• 제20권1호
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• pp.85-90
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• 2003

Removal rate and Within Wafer Non-Uniformity (WIWNU), the most critical issues in Chemical Mechanical Polish (CMP) process, are related to the pressure distribution, wafer shape, slurry flow, mechanical property of pad and etc. Among them, wafer warp generated by other various manufacturing process of wafer may induce the deviation of pressure distribution on the backside of wafer. In the convex shaped wafer the pressure onto the backside of wafer is higher than that of perfectly flat shaped wafer. Besides, such an added pressure is in proportion to the curvature of wafer. That is, the bigger the curvature of wafer becomes the higher the removal rate goes. And the WIWNU is known to be directly related to the pressure distribution on the wafer as well. In other words, the deviation of pressure distribution is in proportion to the WIWNU. In this paper, it is found that the wafer shape may be modified through heating the backside of it and thus properly changed pressure onto the backside of it may improve the WIWNU.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.303-308
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• 2001

Recently, concrete structures have become larger and higher and are demanding high performance concrete with lower heat to prevent thermal cracking, far greater workability, high strength and durability, Application of low heat portland(Type IV) cement for the high performance concrete is the best solution to satisfied those requirements. Here are explained the effect on the properties of high flowing concrete using low heat portland cement by material and mixing variations. Variables for sensitivity test were selected items like finess modulus of aggregates, particle size of limestone powder, unit water, superplasticizer, viscosity agent and concrete temperature. The results of this study were be applied to slurry wall of #215 and #216 of underground LNG tank in Inchon.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.166-171
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• 2007

The characterization of monolithic SiC and SiCf/SiC composite materials fabricated by NITE and RS processes was investigated in conjunction with the detailed analysis of their microstructure and density. The NITE-SiC based materials were fabricated, using a SiC powder with average size of 30 nm. RS- SiCf/SiC composites were fabricated with a complex slurry of C and SiC powder. In the RS process, the average size of starting SiC particle and the blending ratio of C/SiC powder were $0.4\;{\mu}m$ and 0.4, respectively. The reinforcing materials for /SiC composites were BN-SiC coated Hi-Nicalon SiC fiber, unidirectional or plain woven Tyranno SA SiC fiber. The characterization of all materials was examined by the means of SEM, EDS and three point bending test. The density of NITE-SiCf/SiC composite increased with increasing the pressure holding time. RS-SiCf/SiC composites represented a great decrease of flexural strength at the temperature of $1000\;^{\circ}C.$

• 전자공학회논문지A
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• 제28A권11호
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• pp.880-886
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• 1991

Multi-layered chip inductors were prepared with good magnetic properties by sintering Ni-Zn-Cu ferrites at a lower temperature. A slurry with 49.5mol%Fe$_{2}O_{3}$, 20.5mol% ZnO, 20mol% NiO and 10nol% CuO was cast into tapes with 60-100\ulcorner of thickness with a doctor blade techniques. The tapes were screen-pronted with 100% silver electrodes, layered and pressed at 250kg/cm$^{2}$ and then sintered ant 900$^{\circ}C$ for 2h. Inductance with internal electrodes printed 5, 10, and 15 turns showed 4.9, 15 and 24$\mu$, respectively, at 1MHz.