Abstract: In this study, a trichloroethylene (TCE)-spill site was selected to assess the feasibility of enhanced in situ anaerobic bioremediation of TCE-contaminated groundwater using hydrogen as the electron donor produced from nanoscale zero-valent iron (nZVI). Results of hydrogen production experiments show that nZVI had a good efficiency on hydrogen production. Results of microcosm study show that indigenous microorganisms were capable of degrading TCE under anaerobic reductive dechlorinating conditions. Compared to the live control and autoclaved control microcosms, microcosms with hydrogen addition significantly enhanced the TCE removal rates. Results imply that nZVI can be applied as the source of hydrogen to bioremediate TCE-contaminated groundwater under anaerobic conditions. Except for the biotic mechanism, the supplied nZVI can also cause the TCE degradation via abiotic mechanism through oxidation-reduction process. For field application, if proper doses of iron nanoparticles can be applied in the mid- or downgradient areas, both chemical and biological mechanisms can enhance the removal of the contaminants and their byproducts. Knowledge and comprehension obtained in this study will be helpful in designing an enhanced in situ anaerobic bioremediation system for a TCE-contaminated site. The nZVI treatment scheme would be expected to provide a more cost-effective alternative to remediate chlorinated-solvent contaminated aquifers.
Abstract: Titanium dioxide (TiO2) nanotubes (TN) are an ideal nano-structured materials due to its promising applications in various scientific areas. Highly ordered TN arrays (TNAs) fabricated by electrochemical anodization proved to one of the exciting achievements during the past decades. In this paper, we did a series of experiments to investigate the influence of anodization parameters on the growth rate and morphology of the TNAs. And the results suggested that the anodization voltage, as well as the concentration of the anodization electrolyte, had a significant impact on the morphology of the TNAs. In-depth discussion for the TNAs was also presented.
Abstract: A micromechanical finite element model incorporated with molecular mechanics is employed to determine the mechanical properties of single-walled carbon nanotubes (SWCNT). The SWCNT is modelled as a space-frame structure. The bonds between the carbon atoms are simulated as beam members to carry the loads, while the carbon atoms are the joints of the members. The modified Morse potential is adopted to characterize the non-linear behavior of C-C bonds. In this work, the mechanical properties of SWCNT such as the Young’s modulus, ultimate strength and strain are investigated. To verify the proposed FE model and evaluate its performance, the effects of diameter and chirality on the mechanical properties of SWCNT are presented. It is found that both the Young’s modulus and ultimate strength of SWCNT increase monotonically with the increase of diameter. The Young’s modulus of armchair is larger than that of zigzag SWCNTs. These results are in good agreement with the existing numerical and experimental results.
Abstract: In this paper, some Ag-carried palygorskite nanocomposites P/Ag were prepared, their silver content were 1.3%, 4.61%, 9.54% separately. To investigate the effects of the silver content on tribological properties of 45 mild steel pairs, the P/Ag carried different Ag content were used as lubricant additive and their tribological properties were tested on the MMU-10G testing machine. The wear mass loss is used to assess the anti-wear properties of different additives. The surface topographies and main elements are analyzed through SEM and EDS after running for 30 hours. The results show that the friction coefficient and the wear mass loss significantly decrease along with the increase of silver content in the P/Ag: the average friction coefficient of the P/Ag with 9.54% silver reduces about 65% as much as the one with 1.3% silver, meanwhile, the wear mass loss decreases 57% likewise. The surfaces after rubbing 30 hours, some kind of auto-restoration films that contains sort of characteristic elements such as O, Si, Mg, Al, Ag etc. are formed on the surfaces. With the help of this kind of films, the anti-wear properties of the friction pairs are finally improved. The factors that cause the improvement of anti-friction properties of the friction pairs lie in the quality and the silver content of the auto-restoration films formed on the surfaces of friction pairs.
Abstract: The piezoelectric potential generated in a bent ZnO nanorod cantilever is analyzed by means of the first piezoelectric effect approximation. The results show that the piezoelectric potential in the nanorod is proportional to lateral force but is independent along the longitudinal direction. And the electric potential in the tensile area and that of compressive area are antisymmetric in cross section of the nanorod, which makes the nanorod become a "parallel plated capacitor" for piezoelectric nanodevices, such as nanogenerator. The investigation of the carriers influence on the piezoelectric potential in a bent ZnO nanorod reveals that the positive piezoelectric potential in stretched side of the bent nanorod is significantly screened by the carriers and the negative potential in compressed side is well preserved when considering a moderate carrier concentration of
Abstract: Uniform and monodisperse boehmite (γ-AlOOH) nanosheets with a thickness of less than 20 nm have been prepared by the hydrothermal treatment of amorphous boehmite. XRD and FTIR analysis showed that boehmite nanosheets have uniform and high degree of crystallinity. SEM micrographs indicated that boehmite has a leaf-like morphology with high anisotropy (with a length of 0.25～1 m and a width of 50～100 nm).
Abstract: Nanofluids containing Al2O3, ZnO, and MgO nanoparticles were prepared with distilled water as base fluid by violent stirring and ultrasonic dispersing. The forced convective heat transfer performances of the as-prepared nanofluids in tubular solar collector were investigated. The experimental results showed that the heat transfer efficiencies of Al2O3, ZnO, and MgO nanofluids were all increased in comparison to distilled water. For 1.0% vol. Al2O3, ZnO, and MgO nanofluids, the difference in temperature between nanofluids and distilled water all could exceed 3 °C in a day’s cycling. In daytime, from 6:00 a.m. to 18:00 p.m., the maximum differences in temperature of nanofluids and distilled water appeared at about 10:00 a.m., while the maximum temperatures were achieved at about 15:00 p.m. for both nanofluids and distilled water. In night, the temperatures of nanofluids still keep more than 1 °C higher than distilled water, which indicated that nanofluids could retain more heat energy. The viscosities and heat transfer efficiencies augmented with concentration increasing for ZnO nanofluids. Even at 0.2% vol. concentration, the difference in temperature between ZnO nanofluids and distilled could reach 2.55 °C. Based on low viscosity and excellent heat transfer performance, 0.2% vol. concentration ZnO nanofluid was an attractive option to be applied in solar energy utilization.
Abstract: Nitrogen-doped titania nanotubes (TiO2-xNx NTs) were synthesized by the soft chemical process, in which nitrogen-doped titania nanopowders (TiO2-xNx NPs) reacted with strong alkaline solutions (10M). The properties of TiO2-xNx NTs were examined. Experiments on the photodegradation of methylene blue (MB) and sulfosalicylic acid (SSA) were also carried out under visible light irradiation.
Abstract: The nanocrystalline orthorhombic LiMnO2 was successfully synthesized with the raw materials of MnO2, Mn (CH3COO)2 and LiOH by hydrothermal synthesis method, which has the properties of small size, less stacking faults and single phase. High resolution electron microscopy images show that along the b axis of the orthogonal LiMnO2, MnO6 and LiO6 octahedron arrange alternately and regularly. The orthorhombic LiMnO2 is proved to be p-type semiconductor by the Hall test. XPS tests indicate that the trivalent Mn in the o-LiMnO2 is in the high-spin state. And the magnetic study shows that there is reentrant spin glass behavior in o-LiMnO2. The contrast study of Raman spectroscopy and magnetic susceptibility shows that the characteristic mode softening of structural phase transition corresponds to the magnetic phase transition temperature, indicating a possible interaction between phonons and spin.