Papers by Keyword: Specific Surface Area

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Authors: Mohamad Deraman, Rusli Daik, Sepideh Soltaninejad, Najah Syahirah Mohd Nor, Awitdrus, Rakhmawati Farma, Nurul Fatin Mamat, Nur Hamizah Basri, Mohd Amir Radhi Othman
Abstract: Interest in research of supercapacitor has been in increasing trend because of high demand of supercapacitor application as energy storage device in both systems that require low and high power-energy usage. For supercapacitor using porous carbon electrodes, the energy storage mechanism involves the electrolyte ions in electrodes pores and electronic charges in electrodes to form electric double layers at the electrode-electrolyte interface without undergoes any chemical reaction. The specific surface area of porous electrodes, which affect the performance of supercapacitor, have been widely investigated by many researchers using the nitrogen adsorption-desorption measurement. However, despite its simplicity the X-ray diffraction method is rarely found being used to determine the specific surface area of porous electrodes. Therefore, in the present paper, we propose a new equation which expressed the specific surface area of electrodes as a function the electrode structural parameters obtained from the X-ray diffraction data, and duration of activation time employed during the electrode preparation. This equation is found to produce a satisfactory result and is expected to be beneficial for studying supercapacitor electrode materials.
Authors: Kyung Hoon Lee, Kwang Suk You, Ji Whan Ahn, Bong Chan Ban
Abstract: The present study examined the effect of the activation properties of granulated blast furnace slag according to the type of alkaline activator, the specific surface area of blast furnace slag, and the amount of ordinary Portland cement substituted on the compressive strength of the cement containing blast furnace slag. For activators, Na2SiO3, Na2CO3, NaOH, and Na2SO4 were used. Na2SiO3, Na2CO3, and Na2SO4 were converted into Na2O, to which 1 wt.%, 3 wt.%, 5 wt.%, and 7 wt.% were added, and subjected to experimentation, with the W/S (water/solid) ratio = 0.5. The principal hydration products were C-S-H, C4AH13, Aft (ettringite), and Al(OH)3. Na2CO3 exhibited the largest slag hydration rate. Consequently, the present study used Na2CO3 as the alkaline activator. The compressive strength of blast furnace slag cement mortar was then measured according to the amount of Na2CO3 added (2.5 wt.% and 5.0 wt.%), the specific surface area of blast furnace slag (4,000 cm2/g, 6,000 cm2/g, and 8,000 cm2/g), and the substitution rate (30 wt.%, 50 wt.%, and 70 wt.%) of the blast furnace slag in terms of ordinary Portland cement. The results are as follows: at the ages of 1 day and 3 days, respectively, the early strength increased as the specific surface area of blast furnace slag and the amount of alkaline activator added increased; at the age of 7 or more days, the compressive strength increased as the amount of alkaline activator added decreased and as the specific surface area of blast furnace slag increased.
Authors: Chun Ping Tang
Abstract: Aiming at the characteristics of phosphate repairing materials, the influences of retarder, specific surface area of magnesium oxide and content of fly ash on the dry-shrinkage performance of phosphate cement were studied in this paper. The results showed that greater content of retarder would result in greater dry-shrinkage value within a certain range, greater specific area of magnesium oxide would result in greater dry-shrinkage value while the increase of content of fly ash would cause the dry-shrinkage value to be decreased correspondingly within a certain range.
Authors: Prashant Kumar, Frédéric Topin
Abstract: The thermo-physical behavior of open-celled metal foams depends on their microscopic structure. Various ideal periodic isotropic structures of tetrakaidecahedron shapes with constant cross section of the ligament having circular, square, diamond, hexagon and star strut shapes with various orientations are studied. We have proposed a generalized analytical model in order to obtain geometrical parameters correctly and various relationships between different geometrical parameters and porosities (60-95%) are presented. We have also studied the flow parameters namely permeability and inertia coefficient for different strut shapes and various Reynolds number (0.00001<Re<3000). The range of solid to fluid phase conductivity ratios (λsf) studied is from 10 to 30000 for different porosities in local thermal equilibrium condition and an analytical correlation is proposed comprising geometrical parameters of foam structure.
Authors: W. M. Abdel-Wareth, Xu Xu
Abstract: Effects of various grain sizes (10~390 µm) under heating rate of 40 °C/min on ammonium perchlorate (AP) decomposition characteristic parameters, the decomposition thermal behavior and kinetic parameters (activation energy and pre-exponential factor), were investigated by simultaneous DSC/TGA in a dynamic nitrogen atmosphere. In addition, the specific surface areas were measured by the BET-method. Moreover, the kinetic parameters were determined by a simplified approach based on the isoconversional method. The results showed that, the higher the AP particle size the lower the determined decomposition kinetic parameters. In addition, the results were in acceptable agreements with some important literatures. Moreover, it was highly recommended to apply the higher agreeable heating rates for AP samples to determine that parameters more accurately.
Authors: Ji Yi Luan, Xue Mei Wu, Gui Fu Wu, Dong Wei Shao
Abstract: In this paper, the chars of wood dust, corn straw, rice husk and coal pulverized were obtained at different residual time of various pyrolysis temperature (1173 K, 1273 K and 1373 K) during the process of flash pyrolysis in the drop tube furnace (DTF). In order to obtain the parameters of porous structure which included specific surface area, pore volume and fractal dimension of char, low-temperature nitrogen adsorption method was employed to obtain nitrogen adsorption isotherm of chars sample. For the four chars, the corn straw char had the biggest specific surface area and pore volume, the rice husk in second place, the wood dust in third place, and the pulverized coal char in the last one. By taking Frenkel-Halsey Hil (FHH) method to analyze the fractal character of char surface structure, we found that the fractal dimension of biomass except wood char is higher than those of pulverized coal char.
Authors: Vita Zalite, Janis Locs
Abstract: In current research three different prepared calcium deficient hydroxyapatite samples were evaluated for dental application. Lyophilized (lyoCDHAp), spray dried (spCDHAp) powders and wet precipitates (pCDHAp) were characterized by XRD, FTIR, SEM and BET analysis. Results showed, that various drying processes did not affect initial crystallinity, phase and chemical composition of samples. Small agglomerates (up to 2 μm) beside separated particles for lyoCDHAp and spCDHAp were observed in SEM analysis. LyoCDHAp and spCDHAp powders could be used as desensitizing component in the dentifrice, while pCDHAp could be more resorbable due to smaller particle size and induce remineralization of caries sites in the enamel.
Authors: Ratni Nurwidayati, Muhammad Bahrul Ulum, Januarti Jaya Ekaputri, Triwulan, Priyo Suprobo
Abstract: The effect of loss of ignition, specific gravity, fineness, specific surface area and soluble fly ash to compressive strength of geopolymer paste were studied. Six fly ashes from two different sources and different time of collection were evaluated. Sodium hydroxide and sodium silicate were used as alkali activator. Concentration of sodium hydroxide and mass ratio of sodium hydroxide to sodium silicate were fixed 14M and one respectively. The result indicated that the improvement in compressive strength of geopolymer paste was more influenced by fineness, specific surface area and soluble content of fly ash. Soluble content of fly ash greatly affected the compressive strength of geopolymer paste compare to the compressive strength of cement paste with 20% fly ash replacement.
Authors: Dan Xi Li, Quan Xiao Liu
Abstract: On the base of the former research of mercerization of pulp fibers, SEM, XRD and Automated Surface Area & Pore Size Analyzer were used to characterize surface morphology, crystalline property, and specific surface area and the pore size distribution of fibers. The results show that the fiber cell wall swelling, degree of crystallinity decrease and specific surface area and pore size distribution increase after mercerization.
Authors: T. Miramond, Pascal Borget, Serge Baroth, Daculsi Guy
Abstract: Physico-chemical characteristics impact directly or indirectly the bioactive properties of biomaterials, it is then essential to correlate it with their effect in vivo. A panel of biomaterials available on the market, based on Hydroxyapatite (HA) and Tricalcium phosphate (β-TCP) is studied in terms of surface area, hydrophilicity, porosity, zeta potential, crystalline phases and density. This study highlights the dispersity of commercial calcium phosphates (CaP) properties, and demonstrates how the quality criteria required for such bone substitute based on biomimicry concept, whose pores distribution is certainly the more relevant, are often incompletely or not respected according to literature.
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