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221.
Daniela C.L. Vasconcelos Fernando G. Brandão Eduardo H.M. Nunes Lecino Caldeira Manuel Houmard Ana P. Musse Sueli A. Hatimondi Jaílton F. Nascimento Wilson Grava Wander L. Vasconcelos 《Journal of Non》2012,358(18-19):2663-2666
Materials with hierarchical porous structures have attracted great attention over the past years since they have been widely used in many industrial applications. Starch stands out among the materials commonly used as sacrificial templates in environmentally friendly applications. In addition, starch is inexpensive, easy to process, and readily available. In this work we present a structural characterization of sponges prepared by freezing and thawing of a starch gel. Samples obtained in this study were examined by scanning electron microscopy (SEM) and X-ray microtomography (μ-CT). SEM tests revealed that these samples show an open macroporous framework with continuous walls. μ-CT tests revealed that it is possible to tailor the pore structure of these materials by changing the starch concentration in gels used in their processing. We noticed that increasing starch concentration from 15 wt.% to 60 wt.% leads to sponges with porosities ranging from about 28% to over 65%. It was also observed that the higher the starch concentration, the greater the mean pore size of the prepared sponge. 相似文献
222.
J.?Serrado?Nunes A.?Wu J.?Gomes V.?Sencadas P.?M.?Vilarinho S.?Lanceros-Méndez 《Applied Physics A: Materials Science & Processing》2009,95(3):875-880
The piezoelectric and pyroelectric properties of PVDF mainly depend on its β-phase.
This work reports the study by scanning force microscopy in a piezoresponse mode of the variations in the topological morphology
and piezoelectric surface response of β-PVDF prepared by the main preparation methods of this phase. Clear differences in the poled region distribution and size,
as well as in the local piezoactivity, have been identified. The piezoelectric activity at a mesoscale reflects the semicrystalline
phase of the polymer. 相似文献
223.
S. Firmino?Mendes C. M. Costa V. Sencadas J. Serrado?Nunes P. Costa R. Gregorio J. L. Gomez Ribelles S. Lanceros-Méndez 《Applied Physics A: Materials Science & Processing》2009,96(4):1037-908
In this work, poly(vinilidene fluoride)/Pb(Zr0.53Ti0.47)O3([PVDF]1−x
/[PZT]
x
) composites of volumetric fractions x and (0–3) type connectivity were prepared in the form of thin films. PZT powder of crystallite size of 0.84, 1.68, and 2.35
μm in different amounts of PZT (10, 20, 30, and 40%) was mixed with the polymeric matrix. The crystalline phase of the polymeric
matrix was the nonpolar α-phase and the polar β-phase.
Dielectric and dynamic mechanical (DMA) measurements were performed to these composites in order to evaluate the influence
of particle size and the amount of PZT filler with respect to the PVDF matrix. The inclusion of ceramic particles in the PVDF
polymer matrix increases the complex dielectric constant and dynamical mechanical response of the composites. A similar behavior
is observed for the α- or β-phase of the polymeric matrix indicating that the PVDF polymer matrix is not particularly relevant for the composite behavior.
On the other hand, ceramic size and especially content play the major role in the increase of the dielectric response and
the room temperature storage modulus. In particular, the storage modulus increases with increasing PZT concentration, but
this increase is more pronounced, in terms of maximum value, for the sample with 2.35 μm particle size; DMA reveals two main
relaxations in the analyzed samples. A low-temperature process maximum at ca. −40°C, usually labeled by β or α
a
associated to the T
g
of the polymer and the α-relaxation at temperatures above 30°C. The β-relaxation is also observed in the dielectric measurements.
The models used to asses the dielectric behavior of the samples with increasing PZT concentration indicate that the particle–matrix
interaction plays a relevant role, as well as the particle asymmetry and relative orientation, being the Yamada model the
most appropriate to describe the composite behavior.
An erratum to this article can be found at 相似文献
224.
Sérgio A. Saraiva Patrícia V. Abdelnur Rodrigo R. Catharino George Nunes Marcos N. Eberlin 《Rapid communications in mass spectrometry : RCM》2009,23(3):357-362
A tiny droplet of typical samples of fabric softeners from different commercial brands placed on a smooth paper surface was subjected to easy ambient sonic‐spray ionization mass spectrometry (EASI‐MS). With no need for sample‐preparation or pre‐separation procedures, EASI‐MS and EASI‐MS/MS identify nearly instantaneously the main surfactants and the homologous series employed in their formulations. Adulterated and low quality samples containing no or less efficient softeners are also easily recognized. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
225.
Ellery R. Garbelini Manfredo Hörner Vinícius F. Giglio Aline H. da Silva Andersson Barison Fábio S. Nunes Prof. Dr. 《无机化学与普通化学杂志》2009,635(8):1236-1241
Pale‐green crystals of the title complex were prepared by reaction of 2‐formylpyridine semicarbazone (HCSpy) and nickel(II) perchlorate in boiling ethanol. The crystals are triclinic with the nickel ion in an octahedral arrangement, coordinated by two nitrogen atoms and one oxygen donor atom from each ligand molecule. The effect of coordination on bond lengths and angles was explored by comparison with the single‐crystal structure data of the free ligand HSCpy, which was collected as well. The assumed coordination mode was supported by 1H and 13C NMR spectroscopic data. A detailed analysis of the electronic properties, including semi‐empirical quantummechanical calculations is presented. Furthermore, the data obtained from magnetic susceptibility and EPR measurements are in accordance with a low‐spin d8 nickel(II) complex. 相似文献
226.
Vapour–liquid equilibrium measurements for binary and ternary (carbon dioxide + β-myrcene and carbon dioxide + β-myrcene + hydrogen) systems have been carried out at 323.15 K and pressures in the range from 7 MPa to the critical pressure of the binary mixture and at pressures from 10 to 14 MPa for the investigated ternary systems. Samples from the coexisting phases were taken, and compositions were determined experimentally. Results were correlated using the Peng–Robinson and the Soave–Redlich–Kwong equations of state with the Mathias–Klotz–Prausnitz mixing rule. The set of interaction parameters for the employed equations of state and applied mixing rule for the system of CO2 + β-myrcene and of CO2 + β-myrcene + H2 were obtained. Additionally, the volume expansion of the liquid phase for the binary mixtures (carbon dioxide + β-myrcene and carbon dioxide + limonene) were measured at 323.15 K and at pressures from 4 MPa up to very close to the critical pressure of the mixture. The ratio of liquid phase total volumes at the given pressure and at 4 MPa was calculated. 相似文献
227.
228.
229.
Annabel Fernandes Maria Joo Nunes Ana Sofia Rodrigues Maria Jos Pacheco Lurdes Ciríaco Ana Lopes 《Molecules (Basel, Switzerland)》2021,26(16)
Complex wastewater matrices present a major environmental concern. Besides the biodegradable organics, they may contain a great variety of toxic chemicals, heavy metals, and other xenobiotics. The electrochemically activated persulfate process, an efficient way to generate sulfate radicals, has been widely applied to the degradation of such complex effluents with very good results. This review presents the fundamentals of the electro-persulfate processes, highlighting the advantages and limitations, followed by an exhaustive evaluation on the application of this process for the treatment of complex industrial effluents. An overview of the main relevant experimental parameters/details and their influence on the organic load removal is presented and discussed, having in mind the application of these technologies at an industrial scale. Finally, the future perspectives for the application of the electro-persulfate processes in the treatment of complex wastewater matrices is outlined. 相似文献
230.
Neftali L. V. Carre?o Michael R. Nunes Irene T. S. Garcia Marcelo O. Orlandi Humberto V. Fajardo Elson Longo 《Journal of nanoparticle research》2009,11(4):955-963
Several types of carbon nanostructures (amorphous and graphitic), for the coating of SnO2 nanobelts and nanoparticles were obtained by a single catalytic process, during methane, natural gas, and methanol decomposition
using the reactivity of surface-modified SnO2 nanostructure as a nanotemplate. The nanostructured catalyst templates were based on transition metal nanoparticles supported
on SnO2 nanobelts previously prepared by a carbothermal reduction process. Carbon-coated SnO2 nanopowders were also successfully synthesized for the fabrication of carbon spheres. The carbon coating process and yield,
along with the nature of the nanostructured carbon, are strongly influenced by the chemically modified surface of the SnO2 nanostructure template and the chemical reaction gas composition. The preliminary catalytic activity and gas-sensing properties
of these novel materials based on metal nanoparticles and carbon-coated SnO2 were determined. 相似文献