Median Pore Diameter Research Articles

선탄경석(選炭硬石)과 광산화물(鑛酸化物)로 제조(製造)한 담체(擔體)의 중금속(重金屬) 불용화(不溶化) 특성연구(特性硏究)

Abstract Porous pellets for immobilizing heavy metals were manufactured from coal tailings and iron oxide powder. Coal tailings waspulverized and mixed with iron oxide powder. The mixed powder was granulated into spherical pellets and roasted. Over 1100 o C,residual coal in coal tailings reduced iron oxide to ZVI(Zero-Valent Iron). The pellets have 34.63% of porosity, 1.31 g/mL ofbulk density, and 9.82 µ m median pore diameter. The pellets were reacted with synthetic solutions containing each heavy metals:arsenic(V), copper(II), chrome(VI), and cadmium(II), respectively. On the test of immobilizing heavy metal, the pellets madeat 1100 o C were superior to the other pellets made under 1000C. Immobilizing over 99.9% of 10ppm heavy metal solutionsrequired 1 hour for arsenic, 2 hours for chrome, and 4 hours for copper. However, immobilizing capacity of cadmium was infe-rior to that of the other metals and it was decreased in reversely proportion to initial concentration of the solutions. Key words: Coal tailings, Iron oxide, Immobilization, Heavy metals

Hydrothermal synthesis and characterization of alkali-activated slag–fly ash–metakaolin cementitious materials

In the present work, the alkali-activated slag–fly ash–metakaolin cementitious materials were prepared by hydrothermal method. The as-synthesized products were characterized by X-ray diffraction (XRD), fourier transform-infrared spectrum (FT-IR), scanning electron microscopy (SEM), mercury porosimetry and universal testing machine. The results showed that the main mineral phases of the products were zeolite NaP1, analcime and aluminosilicate gel (zeolite precursor) when Si/Al/Ca molar ratio of the starting materials was 1.7:1.0:0.25. While Si/Al/Ca molar ratio of the system changed to 2.3:1.0:0.45, zeolite NaP1 transformed to analcime, and a tobermorite phase appeared. The quantities and types of zeolites synthesized depended on the Si, Al and Ca molar ratio of starting materials. The average compressive strength of the products was more than 60MPa after hydrothermal process. And the products exhibited a porosity of less than 36% and a median pore diameter (area) of approximately 12nm. The reaction degree results indicated that about 75% of starting materials transformed to zeolitic structure and aluminosilicate gel after alkaline activation and hydrothermal process.

Ultrafine silver(II) oxide particles decorated porous ceramic composites for water treatment

Ultrafine silver(II) oxide particles-decorated porous ceramic composites have been prepared directly by chemical oxidation, with diatomite-based porous ceramics as the carrier. The prepared composites were characterized by mercury intrusion method, XRD, XPS, FT-IR, SEM, AAS and shake-flask method. The results show that silver(II) oxide decorated diatomite-based porous ceramic composites possess crystal structure and are composed of tetragonal cristobalite, monoclinic silver(II) oxide and cubic silver(I) oxide. The silver(II) oxide weight percentage content of the composites prepared is 8.5% and the average pore diameter, median pore diameter, apparent density and porosity of the composites are 3.862 μm, 0.354 μm, 1.794 g mL −1, and 57.985%, respectively. The composite can release silver in water solution, with a release rate of 7.420 × 10 −3 mg L −1 h −1. The composites show the strong bactericidal activity. When the contact time with Staphylococcus aureus and Escherichia coli exceeds 20 min, the bactericidal rates reach up to 99.9%.

Preparation and characterization of activated carbons for SO2 adsorption from Taixi anthracite by physical activation with steam

Taixi anthracite was used as a precursor to prepare activated carbons (AC) for SO2 adsorption from flue gas. In this work the activated carbons were prepared by physical activation with steam. Specifically, the effects of activation temperature and burn-off degree on the physico-chemical properties of the resulting AC samples were comparatively studied. The different types of pore volumes, pore size distributions and surface chemistries of the activated carbons on the SO2 adsorption were also analyzed. The results show that the increasing burn-off leads to samples with continuous evolution of all types of pores except ultramicropore. The ultramicropore volume increases to a maximum of 0.169 cm3/g at around 50% burn-off and then decreases for 850 °C activation. At higher activation temperature, the micropore volume decreases and the mesopore structure develops to a certain extent. For all the resulting AC samples, the quantities of the basic surface sites always appear much higher than the amount of the acidic sites. The activated carbon prepared with higher micropore volume, smaller median pore diameter and higher quantities of the basic surface sites represents better SO2 sorption property.

Effect of Aggregate Size and Gradation on the Ceramsite Sound-Absorbing Materials

In this paper, the effect of ceramsite aggregate size and gradation on the sound absorption and mechanical properties of the materials were studied and the relationship between material’s pore structure and its sound absorption were discussed. It can be found from the results that the sound absorption and mechanical properties of the ceramsite sound-absorbing materials increase with the content of the fine ceramsite increased due to the decrease of the median pore diameter of the ceramsite sound-absorbing materials where the improvement of the sound absorption at the high frequency band is more significant suggesting that fine pores have a better sound-absorbing effect for high-frequency noise. Higher effective porosity doesn’t mean better sound absorption, because materials with coarse pores have shorter internal routes for sound waves and less friction during sound waves passing through pores, which conversely decreases the material’s sound absorption. Ceramsite with higher internal porosity and more uniform pore diameter distribution can produce materials with better sound absorption.

Synthesis of mesoporous alumina using a recyclable methylcellulose template

Mesoporous alumina was synthesized from AlCl 3 and NaAlO 2 using methylcellulose (MC) as the template. The MC could be recycled by exploiting its phase changes with temperature, and 63.48% of the template was recovered after the synthesis. The mesoporous γ-alumina produced was in short-range order, with moderately strong acidity, a narrow pore-size distribution and a median pore diameter of 3.7 nm. The mesoporous alumina was thermally stable up to 650 °C and hydrothermally stable. Mesoporous silica was also successfully synthesized using the MC template. This economical and green synthesis could be applied to prepare other mesoporous or porous materials.

Hydrogen Adsorption on Metal-Organic Framework MOF-177

This review summarizes the recent literature on the synthesis, characterization, and adsorption properties of meal-organic framework MOF-177. MOF-177 is a porous crystalline material that consists of Zn4O tetrahedrons connected with benzene tribenzoate (BTB) ligands. It is an ideal adsorbent with an exceptionally high specific surface area (BET>4500 m 2/g), a uniform micropore size distribution with a median pore diameter of 12.7 Å, a large pore volume (2.65 cm 3/g), and very promising adsorption properties for hydrogen storage and other gas separation and purification applications. A hydrogen adsorption amount of 19.6 wt.% on MOF-177 at 77 K and 100 bar was observed, and a CO 2 uptake of 35 mmol/g on MOF-177 was measured at 45 bar and an ambient temperature. Other hydrogen properties (kinetics and heat of adsorption) along with adsorption of other gases including CO 2, CO, CH 4, and N 2O on MOF-177 were also be discussed. It was observed in experiments that MOF-177 adsorbent tends to degrade or decompose when it is exposed to moisture. Thermogravimetric analysis showed that the structure of MOF-177 remains intact at temperatures below 330°C under a flow of oxygen, but decomposes to zinc oxide at 420°C.

Thermoresponsive poly(N-vinylcaprolactam) cryogels: synthesis and its biophysical evaluation for tissue engineering applications

The thermoresponsive poly(N-vinylcaprolactam) (PVCl) based cryogel network were synthesized and characterized with respect to physical and biological properties. The PVCl cryogel crosslinked with polyethylene glycol-diacrylate (PEGda) was synthesized in 1% dimethyl sulfoxide containing aqueous medium at -12°C for 12-14 h. The cryogel synthesized in this manner were highly spongy in nature and can absorb water in its porous network. These polymeric cryogel networks have good physical morphology as confirmed by scanning electron microscopy. The estimated porosity of these cryogels was 90% as demonstrated by various methods based on absorption of water and cyclohexane. The median pore diameter and surface area was 30 μm and 2.0253 m(2)/g, respectively as confirmed by analysis on mercury porosimeter. These materials can interact with biological system without any cytotoxic effects. Change in temperature influenced the adsorption of fetal bovine serum (FBS) on PVCl scaffold which showed maximum protein adsorption at 37°C, as compared to that at 25°C. Furthermore, the fibroblast cell adhesion studies showed the potential of these PVCl based cryogels as tissue engineering scaffolds.

Preparation and Characterization of Inorganic Silica-Organic Polymer Mixture Based C16 Capillary Monolithic Column

Abstract A novel inorganic silica-organic polymer mixed-based capillary electrochromatography monolithic column was prepared by using precursor 3-(trimethoxysilyl) propyl methacrylate with double-functional group hydrolysis/polycondensation in acidic aqueous solution, followed by double-bond co-polymerization with organic monomer hexadecyl mathacrylate under the thermal initiated condition, and the combination of preparation of silica-based monolithic column and organic polymer monolithic column was suggested. A simple operation of controlling sol mixture using mercury infusion when the mixture infused into capillary was raised to acquire smooth interface of stationary phase. The preparation conditions of monolithic column were optimized. The structure of the monolithic columns was characterized by SEM images and nitrogen absorption method, and the results showed that the median pore diameter of the materials was in the range of 3 to 7 nm with average surface area of 103.4 M2 g−1. The influence of buffer concentration, pH value, and organic modifier content on electroosmotic flow (EOF) velocity has been investigated. Seven neutral aromatic hydrocarbons were baseline separated with column efficiency of naphthalene up to 54000 plates m−1. The reproducibility for separation time and retention factor was given in terms of RSD values at 0.9% and 0.6% (n = 5) for run-to-run injections and 1.2% and 0.8% (n = 3) for day-to-day operations. The RSD values of separation time and capacity factor of different columns (n = 3) were 8.7 and 5.7%, respectively. The studies on performance of columns indicated that the columns possess typical reverse retention mechanism.

Fabrication, Structure and Properties of Porous SiC Ceramics with High Porosity and High Strength

Porous SiC ceramics with high porosity and high strength were fabricated by gelcasting, with tert-butyl alcohol (TBA) as solvent, acrylamide (AM) as monomer, and in-situ reaction bonding with a-Al2O3 as sintering additive. SiC suspension with 10 vol% solid loading was successfully solidified by gel-casting to form high strength green body. The results showed that the compressive strength of the porous SiC ceramics increased with sintering temperature from 1300 to 1450°C, but porosity had little change, due to formation of more volume of cristobalite and mullite phases on the surface of SiC grains, accompanied by a large volume expansion effect. Very narrow single-peak distributions with about 2 mm median pore diameter could be found for the porous SiC ceramics. The porosity and compressive strength of the porous SiC ceramics sintered at 1450°C were 71.21 % and 12.14 MPa, respectively.

Accelerated Formation of THF−H2 Clathrate Hydrate in Porous Media

Porous media were used to control the hydrogen clathrate particle size in order to accelerate its formation kinetics. Stoichiometric tetrahydrofuran-hydrogen binary clathrate hydrates with approximately 1 wt % hydrogen loading formed in the mesopores of four porous media with median pore diameters of 49, 65, 100, and 226 A at 270 K and hydrogen pressure of 65 bar. The minimum formation time for the tetrahydrofuran-hydrogen binary clathrate hydrates was 27 min in a porous medium with a median pore diameter of 49 A, which is 6-22 times faster than the tetrahydrofuran-hydrogen binary clathrate hydrates formed in the bulk ice. The clathrate formation time was found to increase with pore size of the porous media. A modified shrinking core kinetic model was used to calculate the diffusivity of hydrogen in the tetrahydrofuran-hydrogen binary clathrate hydrates. Hydrogen diffusivities in the tetrahydrofuran-hydrogen binary clathrate hydrates were found to be on the order of 10(-18)-10(-19) m(2)/s and decrease with increasing pore size or clathrate particle size.

Effect of ZrO 2 addition on crystallization behaviour, porosity and chemical–mechanical properties of a CaO–TiO 2–P 2O 5 microporous glass ceramic

2–6 mol% ZrO 2 was added to a base glass composition of P 2O 5 31.25, CaO 43.75, TiO 2 25 (mol%) at the expense of TiO 2. The prepared glasses were crystallized to bulk glass ceramics containing the major phases of β-Ca 3(PO 4) 2 and CaTi 4(PO 4) 6. DTA was utilized to determine the appropriate phase separation–nucleation and crystallization temperatures. The crystalline products and resulting microstructures were examined by XRD and SEM. The β-Ca 3(PO 4) 2 phase was dissolved out by leaching the resulting glass ceramics in HCl, leaving a porous skeleton of CaTi 4(PO 4) 6. It was shown that ZrO 2 addition resulted in reduction of volume porosity and mean pore diameter while the specific surface area was increased. The smallest median pore diameter and largest surface area were 8.6 nm and 32 m 2 g −1 respectively obtained for the specimen containing 6 mol% ZrO 2. The ZrO 2 addition also improved the chemical durability and bending strength of porous glass ceramics.

Formation of dense silicon carbide by liquid silicon infiltration of carbon with engineered structure

Fully dense and net-shaped silicon carbide monoliths were produced by liquid silicon infiltration of carbon preforms with engineered bulk density, median pore diameter, and chemical reactivity derived from carbonization of crystalline cellulose and phenolic resin blends. The ideal carbon bulk density and minimum median pore diameter for successful formation of fully dense silicon carbide by liquid silicon infiltration are 0.964 g cm−3and approximately 1 μm. By blending crystalline cellulose and phenolic resin in various mass ratios as carbon precursors, we were able to adjust the bulk density, median pore diameter, and overall chemical reactivity of the carbon preforms produced. The liquid silicon infiltration reactions were performed in a graphite element furnace at temperatures between 1414 and 1900 °C and under argon pressures of 1550, 760, and 0.5 Torr for periods of 10, 15, 30, 60, 120, and 300 min. Examination of the results indicated that the ideal carbon preform was produced from the crystalline cellulose and phenolic resin blend of 6:4 mass ratio. This carbon preform has a bulk density of 0.7910 g cm−3, an actual density of 2.1911 g cm−3, median pore diameter of 1.45 μm, and specific surface area of 644.75 m2g−1. The ideal liquid silicon infiltration reaction conditions were identified as 1800 °C, 0.5 Torr, and 120 min. The optimum reaction product has a bulk density of 2.9566 g cm−3, greater than 91% of that of pure β–SiC, with a β–SiC volume fraction of approximately 82.5%.

Porosities and pore sizes in coralline calcium carbonate

Coral is a material that recently has gained increased attention as a potential bone graft substitute material. The porosity and pore size distribution of the exoskeleton of eight different coral species were investigated by mercury intrusion and microscopy. A classification was established comprising two groups according to porosity: L-type, having low porosity (< 20 vol.%), and H-type, having high porosity (> 20 vol.%). According to literature, this value of 20 vol.% seems to be a lower porosity limit for successful surgical applications as bone graft substitution material. Pore size distributions are well-defined in three H-type species, each one having a different order of magnitude for the median pore diameter: Porites (order 2), Millepora (order 1), and Manicina (order 0). Tubular and slit pore geometries were suggested after microscopy.

Hydrogen reduction of preoxidised ilmenite in fluidised bed and packed bed reactors

The kinetics of fluidised bed hydrogen reduction of preoxidised ilmenite concentrates was studied as a function of the different operating parameters of gas velocity, pressure and temperature. The reduction kinetics is controlled by gas starvation at typical fluidised bed flowrates and pressures. Gas starvation was found to dominate at H2 flowrate to ilmenite ratios less than 2 L min−1 g−1. At higher ratios, a form of attenuated gas starvation exists due to the small equilibrium constant for ilmenite reduction. This leads to large variations in the kinetic driving force for small variations in water vapour in the bed. Within the gas starvation region, there is an apparent linear dependence of reduction rate on pressure when a constant fluidising velocity is used. However if the supply of hydrogen to the reactor is kept constant, then the reduction rate is independent of gas pressure above 1 bar. At hydrogen supplies above 2 L min−1 g−1 the reduction rate increases with pressure but the relationship is not linear. An important contributing factor to reduction mechanisms is the very fine intrapore diameters (median pore diameter <0·15 μm) in reduced ilmenite grains, which lead to Knudsen gas diffusion in the pores and a build up of water vapour pressure within the grains.

Nonsurfactant route of fatty alcohols decomposition for templating of mesoporous silica

Mesoporous silica with wormhole-like channel networks were successfully prepared in a direct synthesis method by a modified two-step base–acid catalyzed nonsurfactant carbon templating route at room temperature. This new method allows direct decomposition of palm oil derived fatty alcohols onto silica sources generating the required carbon template in situ to induce mesoporosity. Carbon templating using palm oil-derived fatty alcohols are renewable and environmental friendly. Furthermore, this method was carried out in a simple manner and the porosity of the resulting materials could be controlled successfully. The resulting materials had high surface area of 505 m 2/g and pore volume of 1.4 mL/g, respectively. The median pore diameter estimated by the BJH method was at ca. 7.8 nm to 13 nm. Moreover, pH functionalized mesoporous silica materials exhibited stable absorbances for more than ten cycles at ca. 560 nm.

나노구체의 자기조립 성질과 표면장력을 이용한 나노유체필터 및 나노포어 마이크로믹서

We present a simple and an inexpensive method for the fabrication of a nano-fluidic filter and a nano-pore micromixer using self-assembly of nano-spheres and surface tension. Colloid-plug was formed by surface tension of liquid in a microchannel to fabricate nanofluidic filter. When colloid is evaporated, nano-spheres in a colloid are orderly stacked by a capillary force. Orderly stacked nano-spheres form 3-D nano-mesh which can be used as a mesh structure of a fluidic filter. We used silica nano-sphere whose diameter is , and silicon micro-channel of -diameter. Fabricated nano-fluidic filter in a micro-channel has median pore diameter of 158nm which was in agreement with expected diameter of the nano-pore of . A nano-pore micromixer consists of micro-channel and self-assembled nano-spheres. In the nano-pore micromixer, two different fluids had no sooner met together than two fluids begin to mix at wide region. From the experimental study, we completely apply self-assembly of nano-spheres to nano-fluidic devices.

Preparation and Characterization of Cordierite-Bonded Silicon Carbide Porous Ceramics

Cordierite-bonded silicon carbide porous ceramics were prepared by a reactive process, in which kaolin, talc, and alumina powders were mixed with silicon carbide powders and graphite powder was used as a pore former. The mixture was heated in air so that graphite was burned out and silicon carbide particles were bonded by reaction-derived cordierite. Open porosity and strength of porous ceramics were strongly dependent on the volume fraction of graphite and cordierite. A three-point bending strength of 13.9 MPa was achieved at a open porosity of 38.5 %, exhibiting coefficient of thermal expansion of 7.28 × 10-6/oC at the range of 25 – 800oC. Increase of cordierite volume in SiC matrix indicated mechanical improvement of the porous ceramics due to the increase of neck area among the SiC particles. Porous ceramics sintered at 1450oC possessed higher open porosity and median pore diameter than those of samples sintered at 1250 and 1350oC, since pore generated by the transport of dissolved talc materials as increasing temperature.

Synthesis of open porous emulsion-templated monoliths using cetyltrimethylammonium bromide

In recent years, open porous materials (polyHIPEs) have attracted more and more attention because of their specific properties and applications in biological tissue scaffolds, catalysis supports and ion-exchange resin. However, the surfactants used in this type material were limited to nonionic surfactants or the mix of nonionic surfactant and ionic surfactant. In this work, firstly well-defined polyHIPEs were synthesized by W/O emulsions with ionic surfactant alone (e.g., CTAB). Furthermore, the polyHIPEs with much higher pore volume (14.7 cm 3 g −1), uniform pore diameter and cell size were obtained by this method. Both the median pore diameter and average cell size of the polyHIPEs rose with increase of DVB concentration and/or water fraction.

Porous hydroxyapatite tablets as carriers for low-dosed drugs

The present study evaluated an innovative technique for the manufacturing of low-dosed tablets. Tablets containing hydroxyapatite and a pore forming agent (50% (w/w) Avicel PH 200/20, 37.5% and 50% corn starch/37.5% sorbitol) were manufactured by direct compression followed by sintering. The influence of pore forming agent (type and concentration), sinter temperature and sinter time on tablet properties was investigated. Sintering (1250 °C) revealed tablets with an acceptable friability (<1%). Using 50% (w/w) Avicel PH 200 as pore forming agent resulted in tablets combining the highest porosity (50%) and the highest median pore diameter (5 μm). Aqueous drug solutions (metoprolol tartrate, riboflavin sodium phosphate) were spiked on the tablet surface. The maximum volume of drug solution absorbed was limited (2 × 100μl), revealing that these porous carriers were ideal for low dosed formulations. Drug release from the tablets was slow, independent of the drug. To accelerate drug release, tablets were manufactured using a modified gelcasting technique yielding tablets with a median pore size of 60 and 80 μm. Release from these tablets was drastically increased indicating that the permeability of the tablets was influenced by the pore size, shape and connectivity of the porous network. Changing and controlling these parameters made it possible to obtain drug delivery systems providing different drug delivery behaviour.