• Geomechanics and Engineering
• /
• v.10 no.1
• /
• pp.49-57
• /
• 2016

The high permeability-high strength concrete belongs to the typical of porous materials. It is mainly used in underground engineering for cold area, it can act the role of heat preservation, also to be the bailing and buffer layer. In order to establish a suitable model to predict the thermal conductivity and directly applied for engineering, according to the structure characteristics, the thermal conductivity predicting model was built by resistance network model of parallel three-phase medium. For the selected geometric and physical cell model, the thermal conductivity forecast model can be set up with aggregate particle size and mixture ratio directly. Comparing with the experimental data and classic model, the prediction model could reflect the mixture ratio intuitively. When the experimental and calculating data are contrasted, the value of experiment is slightly higher than predicting, and the average relative error is about 6.6%. If the material can be used in underground engineering instead by the commonly insulation material, it can achieve the basic requirements to be the heat insulation material as well.

• Korean Chemical Engineering Research
• /
• v.47 no.3
• /
• pp.368-372
• /
• 2009

A technique to measure the adsorption characteristic of surface area and pore size distribution is proposed and its performance is examined. While the existing equipment utilizes liquid nitrogen, the proposed uses carbon dioxide at the room temperature leading to the small measuring device with easy operation and short measurement time. The performance of the device has been examined with micro-particle carbon cryogel and bamboo activated carbon. The results from the proposed device compared with those of the adsorption apparatus indicate that the measurement of meso-porous material is comparable but micro-porous material gives some error.

• Journal of the Korean Ceramic Society
• /
• v.32 no.12
• /
• pp.1383-1391
• /
• 1995

Hexagonal $\delta$-FeOOH was coated with Ba-Sol, which was produced by hydrolizing Ba(OC2H5)2, Ba-Sol coated $\delta$-FeOOH spread on a stainless plate, dried at 8$0^{\circ}C$ and then heat-treated. In this way, Ba-ferrite fine particles were produced. although there was a difference in a degree of hydrolysis of Ba(OC2H5)2, crystalline phase of Ba-ferrite appeared around 617$^{\circ}C$, and Ba-ferrite single phase was obtained after heat treatment at 80$0^{\circ}C$ for 2 hr. When Ba-ferrite was made from Ba-Sol coated $\delta$-FeOOH, $\delta$-FeOOH was thermally decomposed to $\alpha$-Fe2O3 at $700^{\circ}C$, producing a porous structure which was observed by TEM photographs. But the porous structure was not observed at 80$0^{\circ}C$. Ba-ferrite, heat-treated at 80$0^{\circ}C$ for 2 hr, had mean particle size of 1000$\AA$, lattice parameter of a0=5.889243 $\AA$ and c0=23.214502 $\AA$, a saturation magnetization ($\sigma$8) of 45.3 emu/g and a coercive force (Hc) of 5200Oe.

• Korean Journal of Materials Research
• /
• v.28 no.2
• /
• pp.124-128
• /
• 2018

N-type porous silicon (PS) layers and thermally oxidized PS layers have been characterized by various measuring techniques such as photoluminescence (PL), Raman spectroscopy, IR, HRSEM and transmittance measurements. The top surface of PS layer shows a stronger photoluminescence peak than its bottom part, and this is ascribed to the difference in number of fine silicon particles of 2~3 nm in diameter. Observed characteristics of PL spectra are explained in terms of microstructures in the n-type PS layers. Common features for both p-type and n-type PS layers are as follows: the parts which can emit visible photoluminescence are not amorphous, but crystalline, and such parts are composed of nanocrystallites of several nm's whose orientations are slightly different from Si substrate, and such fine silicon particles absorb much hydrogen atoms near the surfaces. Light emission is strongly dependent on such fine silicon particles. Photoluminescence is due to charge carrier confinement in such three dimensional structure (sponge-like structure). Characteristics of visible light emission from n-type PS can be explained in terms of modification of band structure accompanied by bandgap widening and localized levels in bandstructure. It is also shown that hydrogen and oxygen atoms existing on residual silicon parts play an important role on emission stability.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.23 no.2
• /
• pp.126-131
• /
• 2011

Cyclone, a type of particle collector widely used in the field of ambient sampling and industrial particulate control, is the principal type of gas-solids separator that uses a centrifugal force. The goal of this study is to design and evaluate the cyclone that can be used for the household vacuum cleaners. A multi cyclone with a 1st cyclone and several 2nd cyclones is designed to improve dust collection efficiency. The dust collection efficiency and the suction power of 1st cyclone are evaluated. And the dust collection efficiency and the suction power of multi cyclone are evaluated according to various sizes of inlet and vortex finder. As a result, a cone shape porous filter has better dust collection efficiency than a cylinder shape porous filter. The dust collection efficiency of a multi cyclone is 3.5% greater than that of a single cyclone.

• Journal of the Korean Geotechnical Society
• /
• v.30 no.2
• /
• pp.19-32
• /
• 2014

Carbonate sand of Sabkha layer in the middle east was made of deposition of shell fragments and it consisted of porous particles containing inner void. Generally, at yield stress the soil structure begins to break down, so the porewater pressure and the settlement are increased rapidly. In carbonate sand, unlike quartz sand if particle crushing happens, the inner voids are exposed and porewater pressure can be decreased under yield stress. Porewater pressure can be determined as the sum of excess porewater pressure due to increase of relative density, inner void expose of particle under particle crushing stress and rearrangement of crushed particle fragments. The porewater pressure can be negative value in case of greater amount of inner void expose, so if particle crushing is bigger, the porewater pressure value is smaller. The negative value zone of porewater pressure from triaxial test result means particle crushing effect is bigger than outer void decrease effect and the particle crushing effect dominant zone size was 1.50∼3.46% from triaxial test result of Sabkha layer.

• Applied Chemistry for Engineering
• /
• v.17 no.2
• /
• pp.188-193
• /
• 2006

Synthesis of Boehmite particles were performed through the precipitation of aluminium nitrate ($Al_{3}(NO_{3})_3{\cdot}9H_{2}O$) with ammonia water ($NH_{4}OH$) by changing solution pH, mixing procedure, temperature, and feeding flux. The influence of the synthesis condition, which affected on the pH range of the Boehmite formation, particle morphology and pore property, was investigated. The Boehmite particles were formed in the reaction solution of pH 7.5~9. The particles prepared by P2jet type which maintained the pH uniformly during the precipitation resulted in homogeneous particles and pores because of the constant concentration of the reacted ion in the solution. It was resulted in the improvement of the specific surface area and pore volume of the particle at the same time. With the increasing of temperature and the decreasing of the feeding flux, it was occurred the large specific surface area and pore volume. Also it was presented the fibrillar shaped particles upper $60^{\circ}C$ of the reaction temperature. In this study, the optimal condition of the porous Boehmite was in P2jet type with $90^{\circ}C$ of reaction temperature and 2.5 mL/min of the feeding flux. At this time, the specific surface area, pore volume, and average pore size was $385.46m^2/g$, 1.0252 mL/g, 10 nm, respectively.

• Economic and Environmental Geology
• /
• v.37 no.1
• /
• pp.143-151
• /
• 2004

This study focused on examining the possibility of recycling mine solid waste as environmental materials, especially for porous media. Basic properties including mineralogical compositions, chemical compositions, and particle size distribution of the tailings from the Sangdong W mine were checked. The mineralogical and chemical compositions of the tailings samples were not much different in depth. According to Korean Standard Leaching Test for Wastes(KSLT), concentrations of heavy metals leached from the tailings were below the standard values. As a result of particle size analysis, the median diameter (d$_{50}$) of the tailings was in the range of 10 to 30 ${\mu}{\textrm}{m}$. The stable tailings slurry made up of 3 ${\mu}{\textrm}{m}$ in d$_{50}$ was prepared using Attrition Mill. The milling condition was 40 vol% in slurry concentration, 700 rpm in stirring speed, and 1 hour in milling time. PEI was added as dispersing agent. Concentrated slurry was extended to 3 times by foaming method. In the case of 3 times foamed slurry, the total and open porosity of ceramic supports sintered at 1,075$^{\circ}C$ for 90 minutes was about 80% and 72%, respectively. Pore size was in the range of 30∼350${\mu}{\textrm}{m}$. Therefore, the tailings could be recycled starting material for environmental materials such as macroporous ceramic support.

• Nuclear Engineering and Technology
• /
• v.48 no.4
• /
• pp.932-940
• /
• 2016

Pool boiling heat transfer of water saturated at atmospheric pressure was investigated experimentally on Cu surfaces with high-temperature, thermally-conductive, microporous coatings (HTCMC). The coatings were created by sintering Cu powders on Cu surfaces in a nitrogen gas environment. A parametric study of the effects of particle size and coating thickness was conducted using three average particle sizes (APSs) of $10{\mu}m$, $25{\mu}m$, and $67{\mu}m$ and various coating thicknesses. It was found that nucleate boiling heat transfer (NBHT) and critical heat flux (CHF) were enhanced significantly for sintered microporous coatings. This is believed to have resulted from the random porous structures that appear to include reentrant type cavities. The maximum NBHT coefficient was measured to be approximately $400kW/m^2k$ with APS $67{\mu}m$ and $296{\mu}m$ coating thicknesses. This value is approximately eight times higher than that of a plain Cu surface. The maximum CHF observed was $2.1MW/m^2$ at APS $67{\mu}m$ and $428{\mu}m$ coating thicknesses, which is approximately double the CHF of a plain Cu surface. The enhancement of NBHT and CHF appeared to increase as the particle size increased in the tested range. However, two larger particle sizes ($25{\mu}m$ and $67{\mu}m$) showed a similar level of enhancement.

• Journal of Biomedical Engineering Research
• /
• v.25 no.1
• /
• pp.1-4
• /
• 2004

On the background of general idea and technique of bioscience, medicine and engineering, tissue engineering aim at maintenance, improvement and repair of human body function through manufacturing and transplantation of artificial tissue and organ exchangeable human body. Basic material used in the area is scaffold that aid tissue and organ formation. Making scaffold, solvent-casting and particulate leaching technique is widely used in manufacturing of porous polymer scaffold. There are many types of particle including salt and gelatin. Salt is a most commonly used particulate because it is easily available and very easy to handle and gelatin particle is another candidate for this method because it is known as a material, which enhances cell attachment and proliferation. But there is no comparative study of two kinds of materials. In this study we compared the biocompatibility of the two scaffolds made from salt(salt scaffold) and gelatin particle (gelatin scaffold). These results demonstrated that gelatin scaffold showed better attachment of cells at the initial stage and better proliferation of cells. The better performance of gelatin scaffold is contributed to the better connection of pores in the same porosity.