• Journal of Environmental Science International
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• v.15 no.5
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• pp.431-438
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• 2006

The strength, water permeability, and photo-degradation efficiency of NOx of porous concrete with a new concept were studied in this paper. The porous concrete was comprised of coarse aggregate of maximum size 40 mm, cement, silica fume, water and air-entraining(AE) water reducing agent. The strength of porous concrete was strongly related to its matrix proportion and compaction energy. An experimental test was carried out to study the parameters of cement proportions and silica fume content for pavement applications of porous concrete which were paving a footpath, a bikeway, a parking lot, and a driveway. The regressed equations of relation-ships between compressive strength and flexural strength, and coefficient permeability and void ratios were indicated as y=7.69x+71.74 and $y=0.42e^{0.28x}$. A method of making an air purification-functioning road, which was spraying a mixture of a photocatalyst, cement, and water onto the surface of the road, was suggested.

• Journal of the Korea Concrete Institute
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• v.12 no.6
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• pp.91-98
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• 2000

Porous concrete having continuous voids is gaining more interest as an ecological material. It has several useful functions such as water and air permeability, sound absorption, etc. Its strengths are considerably lower than those of conventional concrete due to the large and continuous voids in it. This study has been carried out to investigate the influence of mix factors and mixture proportion of aggregate on the strengths and water permeability of porous concrete. And it has been carried out to investigate the evaluation of void of porous concrete by the ultra-sonic pulse velocity. The results f this study are as follows: 1) The theoretical void ratio has greater influence than any other factor on the strengths and water permeability of porous concrete. And it is a little affected by the replacement proportion of silica-fume and mixture proportion of aggregate. 2) Because the coefficients of correlation between the void ratio and ultra-sonic pulse velocity were relatively high, it will be possible that the void ratio is predicted by the ultra-sonic pulse velocity.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.223-228
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• 2006

Pore-size controlled porous carbons for the catalyst supports of the direct methanol fuel cell were prepared from the mesophase pitch by using the silica spheres with different sizes. Pitch solution in THF and spheres were mixed, carbonized and etched by 5 M NaOH to make porous carbon. Specific surface area of the porous carbons was $14.7{\sim}87.7m^2/g$ and average pore diameter was 50~550 nm which were dependent on the size of silica spheres. Aqueous reduction method was used to load 60 wt% PtRu on the prepared porous carbon supports. The electro-oxidation activity of the supported 60 wt% Pt-Ru catalysts was measured by cyclic voltammetry and unit cell test. For the 60 wt% Pt-Ru/porous carbon synthesized by 50 nm silica, current density value in the cyclic voltammetry test was $123mA/cm^2$ at 0.4 V and peak power density in the unit cell test were 105 and $162mW/cm^2$ under oxygen at 60 and $80^{\circ}C$, respectively.

• Membrane Journal
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• v.15 no.2
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• pp.105-113
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• 2005

Silica membranes were prepared on a porous metal sheet by ultrasonic spray pyrolysis method for gas separation at high temperatures. In order to improve the permselectivity, silica was deposited in the sol-gel derived $silica/\gamma-alumina$ intermediate layer by pyrolysis of tetraethyl orthosilicate (TEOS) at 873 K. The pyrolysis with forced cross flow through the porous wall of the support was very effective in plugging mesopores, Knudsen diffusion regime, that were left unplugged in the membranes. At permeation temperature of 523 K, the silica/alumina composite membrane showed $H_2/N_2$ and water/methanol selectivity as high as 17 and 16, respectively, by molecular sieve effect.

• KIEAE Journal
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• v.17 no.3
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• pp.107-112
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• 2017

Purpose: Both silica gel and activated carbon black particles were adopted for use as PCM absorbed porous media applicable as construction materials. To investigate usable methods for absorbing PCM into the media, they were soaked into PCM and also tested for enhancement of PCM absorption into them. Method: To test PCM absorption into some porous media such as both ${\varphi}1{\sim}2mm$ and $10{\mu}m$ silica gels, and $50{\mu}m$ activated carbon black, $43^{\circ}C$ PCM was used as a laten heat material. The method, soaking into PCM was applied to this study, and the media were moderately rotated by centrifuge to have the extra PCM flow out. DSC analysis was conducted to investigate the melting and solidifying of the PCM absorbed into the porous media. Result: It was found that PCM was absorbed into the porous media by over 85 wt% of all particles. In addition, it was noted that the ultrasonic vibrator was accelerating the PCM absorption into the particles to three times higher speed than simple soaking. Centrifuge was adopted to remove extra PCM sticking on the particle surfaces and extra PCM was moderately removed from the surfaces of the particles. DSC analysis indicated that the latent heat of the absorbed PCM particles was 160 J/g, and the melting temperature was approximately $40^{\circ}C{\sim}50^{\circ}C$.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.185-197
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• 2019

Deactivation of porous photocatalytic materials was studied using three types of microstructured particles: macroporous titania particles, titania microspheres, and porous silica microspheres containing CNTs and $TiO_2$ nanoparticles. All particles were synthesized by emulsion-assisted self-assembly using micron-sized droplets as micro-reactors. During repeated cycles of the photocatalytic decomposition reaction, the non-dimensionalized initial rate constants (a) were estimated as a function of UV irradiation time (t) from experimental kinetics data, and the results were plotted for a regression according to the exponentially decaying equation, $a=a_0\;{\exp}(-k_dt)$. The retardation constant ($k_d$) was then compared for macroporous titania microparticles with different pore diameters to examine the effect of pore size on photocatalytic deactivation. Nonporous or larger macropores resulted in smaller values of the deactivation constant, indicating that the adsorption of organic materials during the photocatalytic decomposition reaction hinders the generation of active radicals from the titania surface. A similar approach was adopted to evaluate the activation constant of porous silica particles containing CNT and $TiO_2$ nanoparticles to compare the deactivation during recycling of the photocatalyst. As the amount of CNTs increased, the deactivation constant decreased, indicating that the conductive CNTs enhanced the generation of active radicals in the aqueous medium during photocatalytic oxidation.

• Advances in nano research
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• v.15 no.5
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• pp.423-439
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• 2023

The aim of this paper is to investigate the free vibration behavior of the micro sandwich beam composing of five layers such as functionally graded (FG) porous core, nanocomposite reinforced by carbon nanotubes (CNTs) and piezomagnetic/piezoelectric layers subjected to magneto electrical potential resting on silica aerogel foundation. The effect of foundation has been taken into account using Vlasov model in addition to rigid base assumption. For this purpose, an iterative technique is applied. The material properties of the FG porous core and FG nanocomposite layers are considered to vary throughout the thickness direction of the beams. Based on the Timoshenko beam theory and Hamilton's principle, the governing equations of motion for the micro sandwich beam are obtained. The Navier's type solution is utilized to obtain analytical solutions to simply supported micro sandwich beam. Results are verified with corresponding literatures. In the following, a study is carried out to find the effects of the porosity coefficient, porous distribution, volume fraction of CNT, the thickness of silica aerogel foundation, temperature and moisture, geometric parameters, electric and magnetic potentials on the vibration of the micro sandwich beam. The results are helpful for the design and applications of micro magneto electro mechanical systems.

• Steel and Composite Structures
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• v.47 no.5
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• pp.633-644
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• 2023

Taking a look at the previously published papers, it is revealed that there is a porosity index limitation (around 0.35) for the mechanical behavior analysis of the functionally graded porous (FGP) structures. Over mentioned magnitude of the porosity index, the elastic modulus falls below zero for some parts of the structure thickness. Therefore, the current paper is presented to analyze the vibrational behavior of the FGP Timoshenko beams (FGPTBs) using a novel refined formulation regardless of the porosity index magnitude. The silica aerogel foundation and various hydrothermal loadings are assumed as the source of external forces. To obtain the FGPTB's properties, the power law is hired, and employing Hamilton's principle in conjunction with Navier's solution method, the governing equations are extracted and solved. In the end, the impact of the various variables as different beam materials, elastic foundation parameters, and porosity index is captured and displayed. It is revealed that changing hygrothermal loading from non-linear toward uniform configuration results in non-dimensional frequency and stiffness pushing up. Also, Al - Al2O3 as the material composition of the beam and the porosity presence with the O pattern, provide more rigidity in comparison with using other materials and other types of porosity dispersion. The presented computational model in this paper hopes to help add more accuracy to the structures' analysis in high-tech industries.

• Membrane Journal
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• v.19 no.2
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• pp.122-128
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• 2009

We prepared monodispersed spherical silica microgels by controlling various conditions of emulsification procedure using a lab-scale membrane emulsification system equipped with SPG (Shirasu porous glass) porous membrane having pore size of $1.5{\mu}m$. We determined the effects of process parameters of membrane emulsification (ratio of dispersed phase to continuous phase, sodium silicate concentration, emulsifier concentration, dispersed phase pressure, stirring speed) on the mean size and size distribution of silica microgels. The increase of the ratio of dispersed phase to continuous phase, dispersed phase pressure and sodium silicate concentration led to the increase in the mean size of microgels. On the contrary, the increase in emulsifier concentration and stirring speed of the continuous phase caused the reduction of the mean size of microgels. Through controlling these parameters, monodisperse spherical silica microgels with about $6{\mu}m$ of the mean size were finally prepared.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.2519-2525
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• 2014

WeI have studied the process for synthesizing porous silica with a specific surface area of minimum $800m^2/g$ by adding surfactant [Poly Etylene Glycol(PEG) and Hydroxy Propyl Cellulose(HPC)] to the sol-gel reaction between sodium silicate and hydrochloric acid. NaCl, the by-product of the sol-gel reaction, was water cleaned and removed; when 200 ml of water was used to clean 50 g of silica gel, NaCl remaining in the silica gel was reduced to maximum 0.81wt%. The appropriate level of surfactant for silica gel synthesizing proved to be below 5%. As a result of the experiment, for the silica synthesized by adding surfactant of HPC(2.5%)+PEG(2.5%), the surfactant area was $860m^2/g$ and grain size was $20-50{\mu}m$. From this study, we have concluded that it is of industrial significance that specific surface area is improved and silica of a regular grain size is obtained just by adding surfactant in the gel process or drying process of silica.