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Nunes J.M.A.,Campus Universitario Ministro Petronio Portella | Espinosa J.W.M.,UFG | Gurgel M.F.C.,UFG | Pizani P.S.,Federal University of São Carlos | And 3 more authors.
Ceramics International | Year: 2012

Lead zirconate powders, obtained by the polymeric precursor method, were annealed for 2 h at temperatures from 300 to 800°C. The effect of heat treatment on structural defects and photoluminescent behavior was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Fourier transform Raman spectroscopy (FT-Raman), scanning electron microscopy (SEM), and photoluminescence spectroscopy (PL). XRD patterns and FT Raman spectra showed that the structure of the PbZrO 3 powders was orthorhombric. FT-IR spectra exhibited absorption bands at 450 and 860 cm -1. These were ascribed to ZrO bands and indicate the ZrO 6 octahedral group. SEM micrographs suggested that the annealing temperature allowed structural morphology changes in the samples. PbZrO 3 powders emitted green photoluminescence at room temperature and at lower annealing temperatures but no photoluminescence was observed from the ordered structure. This optical behavior was attributed to structural evolution from disordered to ordered as a function of PbZrO 3 powder annealing. The intensity of the green PL component increased after annealing at 300°C. © 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Leite L.F.C.,Embrapa Meio Norte | Galvao S.R.S.,Embrapa Meio Norte | Neto M.R.H.,FAEM UFPel | Araujo F.S.,University of Campinas | Iwata B.F.,Campus Universitario Ministro Petronio Portella
Revista Brasileira de Engenharia Agricola e Ambiental | Year: 2010

No-tillage adoption has been considered a viable alternative for sustainable soil use. This work aimed to evaluate the influence of no-tillage system with different times of adoption and conventional tillage on chemical attributes and carbon stocks in an Oxisol of the savannah of Piauí in Northeastern Brazil. Soil samples in the 0-5, 5-10, 10-20 and 20-40 cm layers were collected in conventional tillage (CT) no-tillage (NT) with 2 (NT2), 4 (NT4) and 6 (NT6) years of adoption and native forest (NF). The following chemical properties were evaluated: pH, extractable P, exchangeable cations, Al, potential acidity (H+Al), total organic carbon (TOC) and microbial biomass carbon (Cmic). NT adoption increased pH, extractable P and exchangeable cations contents. Compared to conventional tillage, TOC and Cmic stocks increased 34 and 99% (NT2), 47 and 92% (NT4) and 61 and 108% (NT6), respectively, in the superficial layer (0-20 cm). No-tillage adoption improves chemical attributes and increases total organic carbon and microbial carbon and its continuous use contributes to soil quality in savannah soils of Piaui state.

Iwata B.F.,Federal University of Ceará | Leite L.F.C.,Embrapa Meio Norte | Araujo A.S.F.,Campus Universitario Ministro Petronio Portella | Nunes L.A.P.L.,Campus Universitario Ministro Petronio Portella | And 2 more authors.
Revista Brasileira de Engenharia Agricola e Ambiental | Year: 2012

This study aimed to quantify the effects of agroforestry systems (AFS), with different periods of adoption, and slash and burn agriculture (SB) on the chemical attributes of an Ultisol in the 'Cerrado' of Piaui State, Brazil. In two distinct climatic seasons (dry and rainy) four systems were studied: AFS with six (AFS6) and thirteen years (AFS13) of adoption, an area under SB and a native forest (NF), as a reference. In the AFS, in all depths, higher reduction in the Al3+ and H+ + Al3+ contents were observed as well as an increase of pH value and contents of nutrients (N, P, Ca, Mg and K) and organic carbon in soil. In the soil under SB, only in superficial layers, the ash deposited on the soil caused an increase in contents of nutrients, except for P, which was higher in all the depths. There was significant seasonal effect in the contents of nutrients, reducing in the rainy season. Agroforestry systems promoted increase in the nutrient contents of an Ultisol and can be considered useful to improve soil chemical quality in areas of 'Cerrado' of Piauí State, Brazil.

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