410 research outputs found
Interaction of Sodium Titanate Nanotubes with Organic Acids and Base: Chemical, Structural and Morphological Stabilities
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This work reports the interaction of sodium titanate nanotubes (Na-TiNT) with aqueous solutions of benzoic and phenylphosphonic acids and of aniline. The Na-TiNT were obtained from hydrothermal treatment of TiO(2) in aqueous NaOH solution. The results obtained from FTIR, XRD, TEM and elemental analyses showed that the chemical, structural and morphological stability of the nanotubes is related to the medium (acidic or basic) and to the treatment conditions (temperature and contact time). A titanium(IV) alpha-phenylphosphonate phase was obtained from interaction between Na-TiNT and phenylphosphonic acid. The amount and crystallinity of the new phase were dependent of the contact time and temperature, respectively. On the other hand, TiO(2) or proton-rich titanate nanotubes were formed, depending on treatment conditions, from interaction between Na-TiNT and benzoic acid. When Na-TiNT interacted with aniline, no chemical, morphological or compositional change was observed.21713411348Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq
Synthesis of titanate nanostructures using amorphous precursor material and their adsorption/photocatalytic properties
This paper reports on a new and swift hydrothermal chemical route to prepare
titanate nanostructures (TNS) avoiding the use of crystalline TiO2 as starting
material. The synthesis approach uses a commercial solution of TiCl3 as
titanium source to prepare an amorphous precursor, circumventing the use of
hazardous chemical compounds. The influence of the reaction temperature and
dwell autoclave time on the structure and morphology of the synthesised
materials was studied. Homogeneous titanate nanotubes with a high
length/diameter aspect ratio were synthesised at 160^{\circ}C and 24 h. A band
gap of 3.06\pm0.03 eV was determined for the TNS samples prepared in these
experimental conditions. This value is red shifted by 0.14 eV compared to the
band gap value usually reported for the TiO2 anatase. Moreover, such samples
show better adsorption capacity and photocatalytic performance on the dye
rhodamine 6G (R6G) photodegradation process than TiO2 nanoparticles. A 98%
reduction of the R6G concentration was achieved after 45 minutes of irradiation
of a 10 ppm dye aqueous solution and 1 g/L of TNS catalyst.Comment: 29 pages, 10 figures, accepted for publication in Journal of
Materials Scienc
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The contribution of tropical cyclones to the atmospheric branch of Middle America's hydrological cycle using observed and reanalysis tracks
Middle America is affected by tropical cyclones (TCs) from the Eastern Pacific and the North Atlantic Oceans. We characterize the regional climatology (1998-2016) of the TC contributions to the atmospheric branch of the hydrological cycle, from May to December. TC contributions to rainfall are quantified using Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA) product 3B42 and TC tracks derived from three sources: the International Best Track Archive for Climate Stewardship (IBTrACS), and an objective feature tracking method applied to the Japanese 55-year and ERA-Interim reanalyses. From July to October, TCs contribute 10-30% of rainfall over the west and east coast of Mexico and central Mexico, with the largest monthly contribution during September over the Baja California Peninsula (up to 90%). TCs are associated with 40-60% of daily extreme rainfall (above the 95th percentile) over the coasts of Mexico. IBTrACS and reanalyses agree on TC contributions over the Atlantic Ocean but disagree over the Eastern Pacific Ocean and continent; differences over the continent are mainly attributed to discrepancies in TC tracks in proximity to the coast and TC lifetime. Reanalysis estimates of TC moisture transports show that TCs are an important moisture source for the regional water budget. TC vertically integrated moisture flux (VIMF) convergence can turn regions of weak VIMF divergence by the mean circulation into regions of weak VIMF convergence. We discuss deficiencies in the observed and reanalysis TC tracks, which limit our ability to quantify robustly the contribution of TCs to the regional hydrological cycle
INVENTORY OF MOSQUITOES (DIPTERA: CULICIDAE) IN CONSERVATION UNITS IN BRAZILIAN TROPICAL DRY FORESTS
Priority for the Worse Off and the Social Cost of Carbon
The social cost of carbon (SCC) is a monetary measure of the harms from carbon emission. Specifically, it is the reduction in current consumption that produces a loss in social welfare equivalent to that caused by the emission of a ton of CO2. The standard approach is to calculate the SCC using a discounted-utilitarian social welfare function (SWF)—one that simply adds up the well-being numbers (utilities) of individuals, as discounted by a weighting factor that decreases with time. The discounted-utilitarian SWF has been criticized both for ignoring the distribution of well-being, and for including an arbitrary preference for earlier generations. Here, we use a prioritarian SWF, with no time-discount factor, to calculate the SCC in the integrated assessment model RICE. Prioritarianism is a well-developed concept in ethics and theoretical welfare economics, but has been, thus far, little used in climate scholarship. The core idea is to give greater weight to well-being changes affecting worse off individuals. We find substantial differences between the discounted-utilitarian and non-discounted prioritarian SCC
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