RESUMO
In this work, we present a temperature-dependent behavior of monoclinic silver dimolybdate (m-Ag2Mo2O7) microrods using in situ Raman scattering. The m-Ag2Mo2O7 microrods were obtained by the conventional hydrothermal method at 423 K for 24 h. The structural and morphological characterization of the sample has been done by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Temperature-dependent Raman scattering measurements were performed on m-Ag2Mo2O7 microrods, and the results show an irreversible first-order structural phase transition at 698 K-723 K and the melting process at 773 K. Changes in the Raman spectra confirm the phase transition from the P21/c monoclinic structure to the P-1 triclinic structure. No morphological changes were observed during the structural phase transition of the sample at 723 K. Time-dependent optical microscopy at 773 K showed the growth of nanowires on the Ag2Mo2O7 microrods in the triclinic structure.
RESUMO
It is estimated that the planting of pinus in Brazil exceeds 2 million hectares comprising mainly two species Pinus taeda and P. elliottii. Due to the expansion of this culture and the often inappropriate cultural methods, this crop became increasingly susceptible to pest insects (Zaleski et al., 2005). Among these the aphids are outstanding due to their characteristics such as high fertility, presence of both wingless and winged forms, thus facilitating dispersal, parthenogenetic reproduction that coupled to the favorable Brazilian climatic conditions make them one of the most important pests of Pinus spp. plantations (Penteado et al., 2004).(AU)