• Journal of the Korean Applied Science and Technology
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• v.33 no.2
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• pp.247-254
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• 2016

Since microzirconia has excellent thermal and mechanical properties with high chemical and electrical resistance, it can be used in various fields. When the surface of zirconia becomes hydrophilic, its dispersibility in water will be improved as well as the resistance to most hydrophobic contaminants will be increased. In this study, we investigated the introduction of a hydrophilic groups on the microzircornia surface through hydrolysis and condensation reactions with two different silanes containing hydrophilic functional groups, such as ${\gamma}$-aminopropyltrimethoxysilane (APS) and ${\gamma}$-ureidopropyltrimethoxysilane (UPS) at different pH and concentration conditions. A covalent bond formation between the surface hydroxyl groups of zirconia and that of hydrolyzed silanes was confirmed by ninhydrin test and FT-IR spectroscopy. However, the presence of Si on the surfaces of both silane modified microzirconias was unable to detect by SEM/EDS technique. In addition, particle size analysis results provide that the size of microzirconia was changed to smaller or bigger than that of original zirconia due to crushing and aggregation during the modification process. The water dispersibility was improved for only APS modifed zirconia (AS-2 and AS-3) under neutral pH condition, but the water dispersibility and stability for all cases of 0.5~2% UPS modifed zirconia (US series) were much improved.

• Journal of the Korean Geosynthetics Society
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• v.18 no.2
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• pp.37-44
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• 2019

The compressive strength of the soil stabilizer in the deep mixing method (DMM) depends on kinds of soil, particle size distribution, and water content. Because of this, Laboratory test has to perform to estimate the unit weight of binder to confirm the satisfaction of the design strength. In this study, uniaxial compression strength was measured by mixing the soil stabilizers developed in the previous study with clay in Busan, Yeosu, and Incheon area. And the strength enhancement effect was evaluated comparing with blast furnace slag cement (BFSC). Also, the relationship between the unit content of binder and uniaxial compressive strength was investigated in order to easily calculate the unit weight of binder required to ensure the stability of the ground at the field. As the results of the analysis, the relationship between the unit content of binder and the uniaxial compressive strength are ${\gamma}_B=(108.93+0.0284q_u){\pm}35$ when W/B is 70%, and ${\gamma}_B=(122.93+0.0270q_u){\pm}40$ when W/B is 80%.

• Journal of the Korean Institute of Gas
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• v.22 no.1
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• pp.26-36
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• 2018

Conventional nickel-based catalyst processes used for dry reforming reactions have high activation temperatures and problems such as carbon deposition and metal sintering on the active sites of the catalyst surface. In this study, the characteristics of butane dry reforming reaction were investigated by using DBD plasma combined with catalytic process and compared with existing catalyst alone process. The physical and chemical properties of the catalysts were investigated using a surface area & pore size analyzer, XRD, SEM and TEM. Using $10%Ni/{\gamma}-Al_2O_3$ at $580^{\circ}C$, in the case of the catalyst+plasma process, the conversion of carbon dioxide and butane were improved by about 30% than catalyst alone process. When the catalyst+plasma process, the conversion of carbon dioxide and butane and the hydrogen production concentration are enhanced by the influence of various active species generated by the plasma. In addition, it was found that the particle size of the catalyst is decreased by the plasma in the reaction process, and the degree of dispersion of the catalyst is increased to improve the efficiency.

• Journal of IKEEE
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• v.19 no.2
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• pp.193-200
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• 2015

In this paper, we propose the radiation measuring algorithm and the device composition using CMOS image sensor. The radiation measuring algorithm using CMOS image sensor is based on the radiation particle distinguishing algorithm projected to the CMOS image sensor and accumulated and average number of pixels of the radiation particles projected to dozens of images per second with CMOS image sensor. The radiation particle distinguishing algorithm projected to the CMOS image sensor measures the radiation particle images by dividing them into R, G and B and adjusting the threshold value that distinguishes light intensity and background from the particle of each image. The radiation measuring algorithm measures radiation with accumulated and average number of radiation particles projected to dozens of images per second with CMOS image sensor according to the preset cycle. The hardware devices to verify the suggested algorithm consists of CMOS image sensor and image signal processor part, control part, power circuit part and display part. The test result of radiation measurement using the suggested CMOS image sensor is as follows. First, using the low-cost CMOS image sensor to measure radiation particles generated similar characteristics to that from measurement with expensive GM Tube. Second, using the low-cost CMOS image sensor to measure radiation presented largely similar characteristics to the linear characteristics of expensive GM Tube.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.3
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• pp.428-436
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• 1997

Hexacelsian ($BaO{\cdot}Al_2O_3{\cdot}2SiO_2$) powder was prepared by a solution-polymerization route employing PVA solution as a polymeric carrier. A fine amorphous-type hexacelsian powder with an average particle size of 0.8 $\mu \textrm{m}$ and a BET specific surface area of $63 \textrm{m}^2$/g was made by a ball-milling the powder precursor for 12 h after calcination at $800^{\circ}C$ for :1 h. A densified hexacelsian was obtained through sintering at $1550^{\circ}C$ for 2 h under an air atmosphere. The $\alpha\longleftrightarrow\beta$ and $\beta\longleftrightarrow\gamma$ displacive phase transformation in polycrystalline hexacelsia,n was examined by using dilatometry and differential scanning calorimtry. The reconstructive transformation between hexacelsian and celsian was obtained by annealing at $1600^{\circ}C$ for 72h. Volume contraction of 5.6% was accompanied by the reconstructive transformation.

• Resources Recycling
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• v.9 no.5
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• pp.28-32
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• 2000

In this study, the new processing method to produce magnetite for mono-component black toner was studied using spray roaster. The produced magnetite is compared with TMB 125 made by Magnox, USA. When the weight ratio of the ferrous chloride and the ferric chloride is varied from 3:7~7:3 under $N_2$ atmosphere, the 100% major phase of magnetite is obtained. However, when the content of he ferrous chloride is higher than 70wt%, the content of FeO is increased. The phase of $\Gamma-Fe_2O_3$ is shown in th range of over 70wt% of the ferric chloride. The magnetite produced by spray roasting has a saturation magnetization of 80~85 emu/g and a coercivity of 110~130 Oe. The shape of the particle is irregular sphere and hte size of the magnetite is the range of $0.3~0.5\mu\textrm{m}$. It is shown that the magnetite made by spary roasting is enough to apply to the magnetic material of toner.

• Progress in Medical Physics
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• v.8 no.1
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• pp.69-79
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• 1997

Stability of the properties of magnetite particles in novel medicinal magnetic ointments of multipurpose application has been studied by M ssbauer spectroscopy. It has been found that the comparative analysis of the results obtained by model fitting of $^{57}$ Fe nuclei spectra with those known for the system Fe$_3$O$_4$-${\gamma}$-Fe$_2$O$_3$ allows to identify the phase composition of the particles. It is noted that this composition, as well as that of the initial pure component in the form of a highly dispersed fraction (~100$\AA$), differs noticeably from the stoichiometric one. From the magnetic hyperfine field despite small particle sizes, the particles exhibit no superparamagnetism (in the temperature range from 95 to 300K). Radiative sterilization of the ointments has no effect on the magnetic component composition.

• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1912-1920
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• 2011

The $SnO_2$ with a particle size of about 300 nm instead of Ni is used in this study to overcome rapid catalytic deactivation by the formation of a $NiAl_2O_4$ spinal structure on the conventional Ni/${\gamma}$-$Al_2O_3$ catalyst and simultaneously impregnated the catalyst with potassium (K). The $SnO_2-K_2O$ impregnated Zeolite Y catalyst ($SnO_2-K_2O$/ZY) exhibited significantly higher ethanol reforming reactivity that that achieved with $SnO_2$ 100 and $SnO_2$ 30 wt %/ZY catalysts. The main products from ethanol steam reforming (ESR) over the $SnO_2$-$K_2O$/ZY catalyst were $H_2$, $CO_2$, and $CH_4$, with no evidence of any CO molecule formation. The $H_2$ production and ethanol conversion were maximized at 89% and 100%, respectively, over $SnO_2$ 30 wt %-$K_2O$ 3.0 wt %/ZY at 600 $^{\circ}C$ for 1 h at a $CH_3CH_2OH:H_2O$ ratio of 1:1 and a gas hourly space velocity (GHSV) of 12,700 $h^{-1}$. No catalytic deactivation occurred for up to 73 h. This result is attributable to the easier and weaker of reduction of Sn components and acidities over $SnO_2-K_2O$/ZY catalyst, respectively, than those of Ni/${\gamma}$-$Al_2O_3$ catalysts.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.1
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• pp.5-11
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• 2001

Melting behavior and bridge phenomenon of solder paste, which is essential for surface mount technology in pachaging, were investigated. Solder paste of Sn-37%Pb was printed on Cu-pattern of PCB, and heated over melting point. Melting behavior of the paste was observed using CCD-camera. In order to modelize the melting and agglomeration phenomena of paste, two solder balls of 0.76 mm diameter were used. As experimental results, the paste start to melt from the margin of the printed shape. The height of the melted paste decreased from 270 $\mu\textrm{m}$ to 200 $\mu\textrm{m}$ firstly, and finally recovered to 250 $\mu\textrm{m}$ During the melting procedure, pores were evolved from the molted paste. Concerning melting model of solder ball, relationship between contact area of solder ball and soldering time was derived as $\chi^2/t=4r \; \gamma/\eta=7.56 m^2$/s at $280^{\circ}C$.

• Magazine of the Korea Concrete Institute
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• v.9 no.3
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• pp.149-156
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• 1997

In order to improve compressive strength of cement mortar, powder admixture(FAS) was mmufactured by mixing fly ash. Il-anhydite and silica hume, and superplasticizer was used for the control of fluidity reduction with the use of this admixture. Cement was substituted by 10, 20wt% of FAS respectively. At W/S = 0.40, the fluidity of' cement paste substituted by PAS was decreased. NSF and NT-2 were very effective fbr the control of fluidity reduction. As the particle size of U -anhydrite was fine, the fluidity of cement mortar was increased. The fluidity reduction of cement mortar substituted by 10wt% of FAS was controlled. The compressive strength of cement mortar substituted by 10wt% of FAS showed higher. value than that of 20wt%, expecially specimen(C1) substituted by 10wt% of $\gamma$ had the highest compressive strength value.