• Tribology and Lubricants
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• 제34권4호
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• pp.146-159
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• 2018

This paper presents a wear analysis procedure for calculating the wear of journal bearings of a four-strokes and four-cylinder engine operating at a constant angular crank shaft speed during firing conditions. To decide whether the lubrication state of a journal bearing is in the possible region of wear scar, we utilize the concept of the centerline average surface roughness to define the most oil film thickness scarring wear (MOFTSW) on two rough surfaces. The wear volume is calculated from the wear depth and wear angle, determined by the magnitude of each film thickness on a set of oil films with thicknesses lower than the MOFTSW at every crank angle. To calculate the wear volume at one contact, the wear range ratio during one cycle is used. The total wear volume is then determined by accumulating the wear volume at every contact. The fractional film defect coefficient, asperity load sharing factor, and modified specific wear rate for the application of the mixed-elasto-hydrodynamic lubrication regime are used. The results of this study show that wear occurs only at the connecting-rod big-end bearing. Thus, simulation results of only the big-end bearing are illustrated and analyzed. It is shown that the wear volume of each wear scar group occurs consecutively as the crank angle changes, resulting in the total accumulated wear volume.

• Journal of Information Display
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• 제6권2호
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• pp.25-29
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• 2005

The luminescent properties of $Eu^{3+}$ and $Sm^{3+}$ doped potassium tungstate phosphor are investigated. The $K_{4-3x}(WO_4)_2:Eu^{3+}\;_x,Sm^{3+}\;_y$ phosphor is produced by firing the mixed precursors, followed by re-firing with a flux. The re-firing process results in the defect-free surface and uniform growth of the particles. The strong absorption in the region of ultra violet light is observed due to the 4f-4f electron transitions of the $Eu^{3+}$ and $Sm^{3+}$ ions. The doping concentration of europium into potassium tungstate is relatively high, compared to other host materials. It is revealed that the crystal structure is a monoclinic with space group, C2/c. This crystal structure facilitated the $Eu^{3+}$ ions to be located with the Eu-Eu distance larger than 5 ${\AA}$ so that concentration quenching does not occur even at high doping concentration. The excitation spectrum could be adjusted by the introduction of the samarium. A small amount of the $Sm^{3+}$ ions that acts as a sensitizer increases the energy absorption peak around 405 nm.

• 한국세라믹학회지
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• 제53권3호
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• pp.362-366
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• 2016

In this study, humidity control ceramics with good adsorption/desorption capabilities and high strength were fabricated from drinking-water treatment sludge (DWTS) and Onggi soil. The DWTS powder heat-treated at $800^{\circ}C$ and Onggi soil were mixed at weight ratios of 40:60, 50:50, 60:40, and 70:30 and fired at $800-1000^{\circ}C$. With increasing DWTS content, density and flexural strength increased. For the sample with a DWTS:Onggi soil weight ratio of 70:30, porosity and specific surface area decreased with increasing firing temperature, attributed to densification and grain growth at high firing temperatures. From the results obtained, a firing temperature of $800^{\circ}C$ is the optimum condition for fabricating humidity control ceramics with good adsorption/desorption capabilities and strength. The maximum adsorbed amount for the sample fired at $800^{\circ}C$ was $439g/m^2$.

• Journal of Magnetics
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• 제5권2호
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• pp.40-43
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• 2000

Acicular $\alpha-FeOOH\; and\; Ba(OH)_2\cdot8H_2O$ are starting materials in this study. This paper presents the characteristics of the contents of citric acid and heating condition for preparing acicular barium ferrite powder. They control particle shape, crystalline phase, magnetic properties of acicular barium ferrite powder So the effects of the contents of citric acid and heating condition are studied. The experimental condition for starting materials were 800~1000$\circ C$ in firing and 0~40 wt% citric acid, respectively, Ba-ferrite particles fired at the range of 800 $\circ C$to 900 $\circ C$ were maintained as acicular particle shape, but there were mixed particles of acicular and round shape after fired at 950 $\circ C$. Ba-ferrite powder of the single phase was obtained in firing at 900~1000$\circ C$ and with 20 wt.% citric acid. There were unreacted phase of $\alpha-Fe_2O_3 \;and \; BaFe_2O_4$ phases as a second phase in case of sintering at below 850 $\circ C$. Acicular barium ferrite powder of single phase was also produced in firing at 900 $\circ C$ with 20 wt.% citric acid. The saturation magnetization of single phase of acicular $BaFe_12O_19$powder was about 51 emu/g and coercivity was about 4200 Oe.

• 한국세라믹학회지
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• 제33권9호
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• pp.1003-1011
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• 1996

Hydroxyapatite powder was synthesized by a citrate method, . Char-like precursor composed of Ca8(HPO4)2(PO4)4.5H2O (OCP) and CaCo3 was found via viscous resin-like intermediate by heating the mixed aqueous solution of Ca(NO3)2.4H2O(NH4)2HPO4 and citric acid. Resulted powder was transformed into hydroxyapatite phase by firing over 120$0^{\circ}C$-135$0^{\circ}C$ for 4 hr using the powder calcined at 90$0^{\circ}C$ for 10 hr composed of mostly single hydroxyapatite phase. The sintered densities increased with firing temperature up to 130$0^{\circ}C$ but the highest relative density was about 94% of theoritical value. indicating the presence of closed pores. The maximum 96 MPa of flexural strength was obtained at 120$0^{\circ}C$ firing but the flexural strength showed lower values over the above sintering condition. Vitro test was performed by immersing of two jointed specimens in SBF for seven days and adhesion was observed between two specimens.

• 한국세라믹학회지
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• 제17권2호
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• pp.96-100
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• 1980

The castable refractory, CaO.$2Al_2O_3$ is a useful alumina cement for iron, steel and cement for iron, steel and cement industries, however it is difficult to produce CaO.$2Al_2O_3$because of its high melting point(180$0^{\circ}C$) and narrow firing range. In this study, the coprecipitation method was used to produce CaO.$2Al_2O_3$ for lower temperature firing . This method involved the titration of mixed solution of calicum and aluminate which extracted from domestic kaolin with $NH4_OH$ solution under blowing $CO_2$ gas into the solution. The coprecipitate and its clacined products were analyzed by X-ray diffraction and DTA. The calcined products fired between 400 and 90$0^{\circ}C$ were amorphous, but at 100$0^{\circ}C$ the coprecipitate was converted into one compound, CaO$2Al_2O_3$. From those experimental results, it was found that we could synthesizze CaO.$2Al_2O_3$ at about 100$0^{\circ}C$ which is lower than conventional firing temperature by around 80$0^{\circ}C$. The refractoriness of this alumina cement was SK 34 and the compressive strength ( 1 day) was about 250kg/$\textrm{cm}^2$.

• 한국세라믹학회지
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• 제19권2호
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• pp.95-100
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• 1982

Instead of barium carbonate, domestic barite was used as the flux in manufacturing theinsulating porcelain. To avoid the problems arising from the decomposition of barite in the body during firing, BaO.$Al_2O_3$ was synthesized at $1300^{\circ}C$ for 5 hours. synthetic BaO.$Al_2O_3$ was mixed with other materials such as kaoline, alumina, clay, dolomite. The RO content (CaO. MgO. BaO) of the batches was varied from range of 4 to 14wt. % at 2wt. % - intervals, and firing temperature was varied from 1280 to 140$0^{\circ}C$-at 4$0^{\circ}C$ intervals The properties such as water absorption, bulk density. mechnical strength, specific resistance, and linear shrinkage were measured. The body containing 12 wt.% of RO content showed the satisfactory for the application in the Fixed Carbon Film Resistor.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.849-851
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• 2003

After multi-walled carbon nanotubes (MWNT) powder was crushed with ball milling process, it was mixed with organic vehicles. And then CNT paste was printed on ITO coated glass substrate. The field emission characteristics of CNT pastes fired in air atmosphere was better than that of CNT paste fired in Ar ambient due to less organic residues after firing.

• 대한조선학회논문집
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• 제41권1호
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• pp.82-87
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• 2004

The purpose of this paper is to obtain the data for manufacturing of microbe carriers as a method of FRP waste recycling technology. Since FRP waste is polymer, the experiment of the thermogravity analyzing was carried out to find thermal behavior. After that, microbe carriers were prepared from waste FRP powder, which had been decomposed, milled, and mixed with clay as a binder and CaCO3 as a flux and a loaming agent, respectively. finally it was made by filing of the sample up to 1,05$0^{\circ}C$. It was investigated how the variation of the additives and firing temperature effect apparent density, water absorption and micro structure.

• 한국세라믹학회지
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• 제37권1호
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• pp.1-5
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• 2000

Cathodoluminescence(CL) properties of ZnO:Zn green phosphor were investigated. ZnO:Zn phosphor was synthesized by varying reducing agents and firing temperatures. ZnS, charcoal and 5% H2 gas mixed with 95% N2 gas(5H2-95N2) were used as the reducing agent and atmosphere. The highest CL intensity of ZnO:Zn phosphor was observed under the condition of 5H2-95N2 atmosphere and firing temperature of 90$0^{\circ}C$ for 1h. Charocal and ZnO as reducing agents in the syntehsis of ZnO:Zn phosphor exhibited about 60% and 40%, respectively, of the CL intensity obtained with 5H2-95N2 atmosphere.