Papers by Keyword: Surface Area

Abstract: Sintering involves several interactions as particles bond and enable microstructure evolution toward a minimized energy condition, resulting in a complex interplay of measurement parameters. Overriding the evolution is energy minimization, and from that perspective some simple relations emerge. The natural progression is determined by energy reduction, measured by surface area, density, and grain boundary area (grain size). Contrary to the usual sintering analysis that starts with atomic level mass transport mechanisms, presented here is an approach that links to global energy reduction during sintering to simple monitors. Initially sintering converts surface area into lower energy grain boundary area. Subsequently grain growth annihilates grain boundary area. Thus, grain boundary area peaks at intermediate sintered densities, while surface area continuously declines. The trajectory follows a straightforward dependence on density as illustrated using data for a wide variety of materials and consolidation conditions.

Abstract: The microstructure, specific surface area, and pore size distribution of nickel oxide–samarium doped ceria carbonate (NiO–SDCC) composite anodes were investigated with respect to wt.% NiO. Four types of composite anode powders were prepared by mechanically mixing NiO with SDCC electrolytes at different wt.% (50:50, 60:40, 70:30 and 80:20). XRD results demonstrated that the crystalline phase structure of NiO and SDCC does not show any phase change, but only exhibits the NiO and SDCC interface within the NiO–SDCC composite anode powder. SEM and BET results show that wt.% NiO considerably influenced the particle connectivity between NiO and SDCC, particle size, specific surface area, and pore size distribution. Specific surface area, and pore size increased whereas particle size decreased with an increase in wt.% NiO. The highest surface area (11.9 m²/g) and the largest pore volume (0.14 cm³/g) were obtained for NiO–SDCC (60:40) composite anode powder. Therefore, the composite anode with large specific surface area displays the highest catalytic activity and the lowest interfacial polarization resistance at the anode/electrolyte interface.

Abstract: This study examines two things about a dye sensitized solar cell (DSSC) to improve power conversion efficiency. One is how to make ZnO-coated TiO2 electrode. The other is how to make carbon nanotube (CNT) electrode. First, we considered the process of making the ZnO-coated TiO₂ electrode of the DSSC. This ZnO coating of the DSSC is important for the increase of power conversion efficiency. The fabrication method of the ZnO-coated TiO₂ electrode was simple dip coating. This method uses the immerse of the zinc acetate dehydrate [Zn (CH₃COO₂)・2H₂O] solution. This method can make the cheap ZnO-coated TiO₂ electrode. However, this method has a slightly negative effect, which is filling in holes of the porous TiO₂ layer. We tried to improve this negative effect. We changed the concentration of a zinc acetate dehydrate solution from low to high. Also, we changed the immersing time of the zinc acetate dehydrate solution. We did the control of the band gap of ZnO-coated TiO₂ electrode of DSSC for increasing power conversion efficiency. Second, we substituted CNT for counter electrodes to improve the performance of DSSC. As a manufacture method of CNT electrode, we used electrophoretic deposition (EPD). After that, we baked this CNT electrode and measured its specific surface area. We tried to improve specific surface area by changing baking temperature.

Abstract: Selection of suitable activation agent is important in order to produce high surface area of activated carbon. The present study was undertaken to develop high surface area of durian shell activated carbon (DSAC) using different chemical activation agents which were potassium hydroxide (KOH) and phosphoric acid (H₃PO₄). Surface porosity and surface area were directly measured from scanning electron microscopy (SEM) and surface area analyzer, respectively. For the optimum condition, it showed that H₃PO₄ treated DSAC had the highest surface area which was 257.50 m²/g compared to KOH treated DSAC which was 13.10 m²/g. H₃PO₄ treated DSAC also showed the highest micropore surface area, external surface area and total pore volume with 191.22 m²/g, 66.28 m²/g and 0.149 cm³/g, respectively. SEM result showed that H₃PO₄ treated DSAC had a well pronounce porosity than durian shell char. Surface area and surface porosity were important in an adsorption process.

Abstract: Mesoporous carbonated hydroxypatite (CHA) is a promising drug delivery agent for disease treatment and could be a carrier for different types of drugs and antibiotics. It is still a challenge to introduce pores to carry drugs within the mesoporous CHA and obtain high surface area nanoparticles. This study investigates the effect of different types of nonionic surfactant and carbonate concentration on the pore characteristic of mesoporous CHA. Mesoporous CHA is synthesised through the coprecipitation technique using nonionic surfactants as pore templates i.e., P123 and F127 with different carbonate concentration. The axial view of transmission electron microscopy (TEM) images shows the pores formed within the particles are distributed randomly, while the parallel view demonstrates that nanopore channels are developed within the CHA particles. Nitrogen adsorption analysis provides the surface area and Pore Size Distribution (PSD) of the nanoparticles. The PSD shows that CHA synthesis with P123 and F127 has similar pore size, around 28.9 nm, but different surface area. The results confirm the different types of surfactant templates has a positive effect on the pore characteristic, while carbonate precursor concentration does not significantly change surface area and pore size.

Abstract: Alumina aerogels were prepared from aluminum sect-butoxide via sol-gel process and supercritical drying. The influence of Ethyl acetoacetate (Etac) on the aerogel properties, microstructure, and thermal stability was systematically studied. At the same time, reaction mechanism was also investigated. The results show that, without and with Etac addition, the alumina aerogels are consisted of crystalline boehmite and amorphous network, respectively. When n_Etac/n_Al molar ratio is 0.01~0.15:1, Al₂O₃ aerogels have larger surface area (71~98 m²/g) than pure alumina aerogel (61m²/g) after heated at 1200°C, a proper ratio of Etac is helpful to increases the gelation time and stability of alumina sol, and is useful to improve the thermal stability of Al₂O₃ aerogels.

Abstract: Interface adsorption of gases and liquid on a clean solid surface could be due to the physical or chemical adsorption. In this study, the activated carbon was prepared from sugar cane husk (powder and granular form) using phosphoric acid (H₃PO₄) as activating agent. Sample was activated at 500°C for two hours in the furnace and washed using vacuum method. Besides, surface area of activated carbon was defined using Single Point Brunauer-Emmett-Teller (BET) Nitrogen Gas. The physico-chemical characteristics of the prepared activated carbon were characterized by Fourier-Transformed Infrared Spectroscopy (FTIR), gravimetric method, and Field Emission Scanning Electron Microscopy (FESEM). The adsorption study by surfactants, namely CTAB (cationic) and TX-100 (non-ionic) were investigated. The experimental results showed that a good activated carbon was prepared from sugar cane husk granular (SCH-G) gave the highest BET surface area of 860.18 m²/g and the adsorption capacity of SCH-G activated carbon at 25°C using TX-100 (205.81 mg g^-1) was greater compared to the CTAB (108.20 mg g^-1). This study has shown that the sugar cane husk was a good activated carbon and has potential to be used as adsorbent for the removal of surfactants from aqueous solutions.

Abstract: In the present work porous clay ceramic pellets (porosity ≤ 30 %) are investigated for the wastewater purification technologies. Calcareous and non-calcareous illite containing clays with different content of fine clay fraction (particle size ≤ 0.005 mm) are used. Sawdust in amount of 3 wt% for the increasing of porosity and surface area is used. Non-calcareous clays are also used for the production of ceramic materials with porosity ≥ 50 %. Pores are formed in result of chemical reaction in clay suspension of aluminium paste with water. After sintering of dry samples the sorption ability of covalent (iodine) and ionic (ammonia) compounds are determined. Sorption ability depends on many factors such as chemical composition of clay, sintering temperature, pore size distribution in the ceramic materials, surface area, pH of water after immersion of pellets and adsorbable substances.

Abstract: This paper presents 4-D high resolution electrical resistivity tomography study for slope monitoring using two optimized (modified) arrays of the Wenner-Schlumberger and Pole-Dipole. These optimized resistivity arrays give a total of 2052 number of datum points from each data acquisition set. These two optimized were used because they have more datum points compared to their original arrays. Perhaps these optimized arrays were able to resolve the subsurface structures from surface areas. Inversion results from the computer (mathematical models) suggested that these optimized arrays were able to give in imaging the Earth’s subsurface structures and characterization at different period of time. Furthermore, in this paper, we are presented merging data levels in order to give high resolution in electrical resistivity tomography. Even though the time taken for data acquisition using this technique is twice, the outcome is compromised and reliable which helpful in the Earth’s subsurface interpretation.

Abstract: Nanomaterials are playing a more and more important role in all fields, leading to increasing its release into the environment. Nanomaterials may pose a potential threat to environment and human health. Thus, there is a growing need for adaptable methods and technologies to analyze and characterize the properties of nanoparticle for purpose of understanding and minimizing the potentially unforeseen health or environmental hazards. Nuclear Magnetic Resonance (NMR) method, as a powerful analytical tool which based on the theory of solvent relaxation, breaks through some limitations of conventional methods, making it feasible in analysis and characterization of nanoparticles in aqueous phase. This paper has sketched recent research about specific surface area determination and competitive adsorption between components on the surface of nanoparticles. It also pointed out the pros and cons of NMR and conventional methods. As a result, NMR solvent relaxation will be a promising application in future.