Papers by Keyword: Nanoporous

Abstract: In this paper, an experimental examination of defects in anodization of aluminum of the industrial grade A7E is presented. A two-step method of anodizing was used in an electrolyte containing 20% wt. % sulfuric acid at 0 ° C at constant voltage. Micro-video recording was carried out in both anodizing stages to examine anodizing process on a micrometer scale, and to determine the corresponding macro-scale effects indicating incorrect anodization process. Macro-scale effects in the form of gas evolution were detected. Subsequently confirmed on the surface of the coating from which it occurred, using scanning electron microscopy. Methods for preparing samples subject to anodization are proposed to reduce the number of defects. The results should lead to industrial implementation of inexpensive and high-quality nanoporous anode materials with a variety of applications.

Abstract: The affinity of nanoporous biochars functional groups for immobilization Cu, Zn, and Pb in aqueous solution has been studied. BET results revealed the nanoporous structure of the chars. Batch experiments have been designed and performed.The results indicated remarkable sorption capacity in case of each char: in a multi-metal system, B1, B2, and B3 adorbed 24.39, 23.61, 35.69 mg/g copper, 63.36, 90.96, 95.36 mg/g lead, and 20.16, 21.26, and 25.44 mg/g zinc, respectively. To find out the sorption mechanism with a post-sorption FTIR analysis over the biochars has been made. The results suggest the possible competitive immobilization mechanism as Cu being mainly organically bounded to amino, hydroxyl and carboxyl functional groups, Pb forming insoluble hydroxide, phosphate or carbonate, and Zn being mostly sorbed in the residual fraction.

Abstract: Elongated iron oxide nanopores (FNPs) were fabricated by anodisation of iron in fluoride-ethylene glycol (EG) added to it 1 ml, 1 M KOH electrolyte at three different voltages: 30 V, 40 V and 50 V. It was observed regardless of the voltage applied; the nanopores seem to be separated from one to another at the bottom part of the anodic film forming rather discreet nanotubular structure at this region. X-ray diffraction (XRD) was used to evaluate the phases present within the anodic layer. γ-FeOOH, Fe (OH)₂, and FeF₅.H₂O were detected in all samples. However, when the anodisation voltage was increased, peaks from the FeF₅.H₂O are more intense indicating either more F^- insertion in the anodic layer or crystallization of this phase at higher voltage. After annealing, XRD detected only hematite; α-Fe₂O₃ and magnetite; Fe₃O₄ indicative of phase formation or transformation had occurred during the annealing process. The annealed samples displayed an ability to adsorb Cr (VI) with almost 30 % reduction of the Cr (VI) concentration after 5 hours of exposure to the nanoporous anodic film.

Abstract: In this paper, we report the experimental results on the synthesis of low-density tetraethoxysilane (TEOS)-based silica aerogels prepared under ambient pressure. The drying control chemical additive N, N-Dimethylformamide (DMF) was introduced to the experiments. Before dring, the water within alcogel was exchanged with ethanol and n-hexane. Trimethylchlorosilane (TMCS) was used to modify the hydrophilic gel surface to make sure the final aerogel is hydrophobic. The effects of solvent EtOH and DMF on the properties of the resulting aerogels were investigated. The microstructure, morphology and other properties of the aerogels were studied by FT-IR, TEM and BET measurement. The resulting aerogels have a well-developed mesoporous structure (mean pore size of ~15 nm) with low density (0.08g/cm³), a high specific surface area (1267m²/g) super hydrophobicity (Ө=165^o) and high transmissivity (~90%).

Abstract: Anodisation of iron foil was done to produce anodic film with nanoporous structure. The effect of anodic voltage on the morphology of the anodic oxide formed was investigated. Anodic film formed on iron foil anodised at 10 V is rather compact no obvious pores. Pores can be detected on oxide anodised at 30 V despite not very uniform. For foil anodised at 50 V, 1.8 µm thick anodic layer which consisted of uniform circular pores is observed. This film was then annealed at 450°C for 3 h in air as to induce crystallinity. The annealed nanoporous film exhibits a light illuminated photocurrent of 0.45 mA in 1 M NaOH + H₂O₂ solution.

Abstract: Nanoporous materials with organic frameworks (3PDVB/MA-1) have been successfully synthesized in the microchannel through solvothermal polymerization of divinylbenzene and methacrylic acid in the presence of tetrahydrofuran. The material has (3PDVB/MA-1) disordered mesopores with uniform pore size (~50 nm) and high BET surface area (415 m²g^-1). In the adsorption of heavy metal cations Co²⁺ in wastewater, the mesoporous resins exhibit superior performances, and thus have great potential in water treatments.

Abstract: Building insulation is an important part of building energy conservation. The heat insulation coating preapred from modified expanded perlite has been a potential building thermal insulation material. In this paper, aerogel was filled into the pores of expanded perlite by vacuum impregnation method to produce aerogel-modified expanded perlite at ambient pressure. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2 adsorption–desorption techniques. The results revealed that aerogel could be well filled into the pores of expanded perlite, and the resultant aerogel-modified expanded perlite possessed nanoporous structure with higher specific surface area of 196 m2·g-1, and low thermal conductivity of 0.063 W·m-1·K-1 less than that of expanded perlite by 13.3%. Heat insulation coatings prepared from aerogel-modified expanded perlite had good thermal insulation effect, indicating that the product showed potential aplication in the field of building energy conservation.

Abstract: The bionic structure nanoporous TiO₂ materials were prepared using aquatic plants as biological templates. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), nitrogen adsorption method and ultraviolet-visible light spectrometer were employed to characterize the structure of samples and the degradation performance of methylene blue solution under the visible light. The results showed that TiO₂ sample inherited the porous structure of original template. Such bionic material was composed of ultra-thin piece layers which were full of TiO₂ nanoparticles with size of about 10 nm. The product was studded with piled pores which had a few to dozens of nanoaperture. The material was doped with a small number of bionic legacy elements which can enhance the absorption of 400-800 nm range of the visible light, thus the bionic nanoporous TiO₂ materials had better photocatalytic degradation effects of methylene blue solution in the sun.

Abstract: Carbon nanotube (CNT) is one of the most attractive materials for the potential applications of nanotechnology due to its excellent mechanical, thermal, electrical and optical properties. We demonstrated the fabrication of carbon nanotube and carbon nanofiber (CNF) inside the pore and at the surface of anodic aluminum oxide (AAO) membrane by chemical vapor deposition method at atmospheric pressure. Ethanol was used as a hydrocarbon source and Co–Mo as catalyst. CNT was synthesized at different temperature. High graphitic multiwall carbon nanotube (MWCNT) was found at 750°C, while CNF was found at 800°C and above temperature analyzing by Raman spectroscopy.

Abstract: When thickness of a membrane reduces its mechanical properties go down but thinner the membrane better the performance of the membrane in terms of filtration. In this research we fabricated a fluid filtration system with a very thin anodic aluminum oxide (AAO) membrane. The system consists of microchannels at one side of membrane while other side is flat. For both sides inlet and outlet are given. The system can facilitate two types of fluid to flow at two sides of membrane for filtration. The membrane thickness achieved was 4 μm. The average pore diameter was 50 nm. The nanopores inside the membrane are highly straight and perpendicular to the surface. The fabricated channel and wall width was 200 µm and 100 µm successively. The pillars in between microchannels hold the membrane which is termed as partial freestanding alumina (PFA) and thereby retain desired mechanical properties of the membrane. The system was tested for diffusion between DI water and salted water. The DI water was flowed in channels and salted water on other side of membrane. The pH value of DI water changed after flow. Due to channel walls, AAO membrane fabricated in this system can tolerate more pressure which leads it to be used for convective flow by applying higher pressure gradient.