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Djalma de Albuquerque Barros Filho

Bio: Djalma de Albuquerque Barros Filho is an academic researcher. The author has contributed to research in topics: Colloidal crystal & Scanning electron microscope. The author has an hindex of 2, co-authored 4 publications receiving 6 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the absence of N2 and surfactant will result in colloidal particles with high affinity to agglomerate forming two kinds of nanostructured assemblies: colloidal crystals and nanowires.
Abstract: The conditions of chemical synthesis can be crucial for polymerization of styrene in such a way that it can be produced latex beads at nanometric range (ϕ < 400nm). In this work, it will be analyzed how the absence of N2 and surfactant will result in colloidal particles with high affinity to agglomerate forming two kinds of nanostructured assemblies: colloidal crystals and nanowires. Four syntheses were realized and four parameters were changed: temperature, impeller speed, and initiator and styrene concentrations. The dispersion was filtered and coated on glass slides by evaporation induced self-assembly (EISA) process. Morphology and topography were observed at Scanning Electron Microscopy (SEM) and Atomic Force Microscope (AFM) respectively. They show how the synthesis conditions play a vital a role on the formation of self assembly nanostructures that can be applied as templates for sensors and biomaterials devices.

3 citations

Journal ArticleDOI
TL;DR: In this paper, it is discussed how it is possible to produce latex films by evaporation induced self-assembly (EISA) process, which can be used for generation of functional devices like sensors, solar cells and biomaterials.
Abstract: It will be discussed in this work how it is possible to produce latex films by evaporation induced self-assembly (EISA) process. Latex beads were synthesized in a cylindrical flask without N2 flow. The polymerization process of styrene happens at water as solvent and with the presence of persulfate potassium as initiator. The final product was a dispersion of spherical nanometric particles (ɸ = 0.47 ± 0.06μm) whose concentration can be changed from 0.5 to 10% (V/Vo). These dispersions were spread on glassy substrates at 50°C over a square area (~1cm2) with control of solvent evaporation. The films are transparent and they show the formation of nanowire structures by scanning electron microscopy (SEM) characterization. Such structures were associated to high affinity of latex beads particles to form cylindrical arrangements due to presence of O2 during their synthesis. It has been concluded that this self-assembly structure can be very worthy for generation of functional devices like sensors, solar cells and biomaterials.

2 citations

Journal ArticleDOI
TL;DR: In this paper, the synthesis and formation of mesoporous titania films by latex beads templating was analyzed by Scanning Electron Microscopy (SEM) measurements.
Abstract: This article deals with the synthesis and formation of mesoporous titania films by latex beads templating The infiltration of latex template by titanium precursor solution resulted in compact films that generated an inverted pore network resulting from the latex removal as it was observed by Scanning Electron Microscopy (SEM) measurements The goal of this work is to analyze the deposition of latex beads on glassy substrates and eventual infiltration by precursor solution of mesoporous titania The final product was bulky films with porosity in the micrometric scale defined by latex beads The synthesis of latex beads was carried out in the absence of N2 and the titania precursor solution was obtained from the ternary system: HCl/P-123/1 Butanol The characterization of films by SEM was carried out after the removal of latex template by calcination in a tubular oven The appearance of films was compact for 30% V/Vo dispersion concentration and there was a well-defined pore network observed in the SEM characterization associated with the presence of latex beads that assembles by Solvent Controlled Evaporation (SCE) technique SEM characterization showed that latex beads coated on glass substrates and formed a network structure that could be applied to functional devices like solar cells, catalizers and batteries It is necessary to decrease the concentration of the dispersion to form films with homogeneous monolayers that become transparent to visible light KEYWORDS: Nanotechnology, semiconductor oxide, self-structured materials

1 citations

Journal ArticleDOI
TL;DR: In this article, the formation of nanocrystalline films of titania on metallic surfaces was characterized by scanning electron microscopy (SEM) and it was observed that the nature of the substrate directly influences the topography of the mesoporous titania, which is no longer hexagonal with ordered pores but lamellar allowing the production of self-cleaning membranes with direct application in civil construction.
Abstract: Improvement of porous materials has been one of the goals of nanotechnology. There is an increasingly real need to understand the mechanisms that generate self-structured materials specifically those that originate from colloidal particle templates such as: polymers, silica, titania and silicon. These templates are important to produce devices with industrial applications such as: solar cells, desalinizers, batteries and photonic crystals. One of the main difficulties encountered in the application of colloidal particles is to produce them on a large scale with uniform size and deposit them on flat surfaces so that they can homogeneously cover a substrate forming crystallographic domains on a micrometric scale. The objective of this work is to analyze the formation of nanocrystalline films of titania on metallic surfaces that were characterized by scanning electron microscopy (SEM). The metallic substrates were commercial steel plates found in hardware stores. The substrate was covered with latex beads infiltrated by a precursor solution of titania and subsequently heat treated in a tubular oven at 600 oC for one hour. It is observed that the metallic substrate influences the topography of the mesoporous titania film resulting in a lamellar structure in which interaction with the external environment is suitable. These results show that the nature of the substrate directly influences the topography of the mesoporous titania, which is no longer hexagonal with ordered pores but lamellar allowing the production of self-cleaning membranes with direct application in civil construction. KEYWORDS: Colloidal particles, Metallic substrates, Lamelar structure.

Cited by
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Journal ArticleDOI
TL;DR: M. floribunda bloomed irregularly throughout the year, concentrating flowering in two periods of the year with the greatest peaks in March and August, while the greatest fruiting peaks were observed in April and September.
Abstract: Myrciaria floribunda is a species native to the restinga areas of the Atlantic Forest that presents great phenotypic variation in fruits, great socioeconomic importance in regions of natural occurrence and high productive potential. The characterization of heterogeneous populations is crucial for plant selection and breeding programs, since it allows the distinction of superior individuals. The aim of this study was to characterize the reproductive structure of M. floribunda accessions, and to observe the influence of climate and environment on its reproductive process, through floral biology, floral morphoanatomy and reproductive phenology. Apis mellifera and Trigona spinipes are the main floral visitors of cambui. Stigma receptivity lasts up to 5 hours after flower opening and pollen viability was above 90%. Regarding the flower structure, the female sexual organ is monocarpic, the ovary is efferent, bilocular, with two ovules per locule, the inflorescence is fascicle-like and consists of small white flowers, actinomorph symmetry, heteroclamid and monoclines. Plants bloomed irregularly throughout the year, concentrating flowering in two periods of the year with the greatest peaks in March and August, while the greatest fruiting peaks were observed in April and September.

6 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used facilitated support membranes containing Ag+ ions to separate paraffins and olefins without water and achieved high selectivity of ethene against ethane in separation processes using inorganic-organic hybrid membranes containing silver(I) ions.
Abstract: Silver in Hybrid Membranes Facilitates Separation of Ethene and Ethane Researchers at the Osaka National Research Institute in Japan have achieved good selectivity of ethene against ethane in separation processes using inorganic– organic hybrid membranes containing silver(I) ions. The organic poly(N-vinylpyrrolidone) (PVP) part increased the flexibility of the inorganic network and immobilized the silver ions, which can function as olefin carriers. The membranes showed higher selectivity at higher temperatures, as thermal energy enhances the decomplexation rate of the silver olefin complexes. Separation of paraffins and olefins is usually carried out by cryogenic distillation. Among the alternatives that were investigated to replace this energy-intensive process, the use of facilitated support membranes containing Ag+ ions seemed to be promising. While supported liquid membranes and ion-exchange membranes require saturation of the feed gas with solvent, silver polymer membranes can be used to separate paraffins and olefins without water. The limitation of these membranes to low temperatures has now been overcome by replacing the pure polymer membrane with an organic–inorganic hybrid membrane as reported in the March issue of the Journal of the American Ceramic Society. The hybrid membranes were prepared via a sol-gel route using tetraethoxysilane, propyl triethoxysilane, water, and HNO3. After several hours of stirring, PVP and later AgBF4 were added. Membranes were produced by dip-coating on a porous aluminum tube. Two membranes containing ~10 wt% PVP, one with and one without silver, as well as a membrane containing ~20 wt% PVP and silver ions, were prepared. Fourier transform infrared spectrophotometry measurements suggested that the silver ions were bound to the amide group of the PVP segments. The silica matrix gave the membranes enhanced thermal stability; the PVP made the inorganic network more flexible and nonporous. While the membrane without silver ions showed little selectivity for ethene, both of the silver-containing membranes gave PC2H4 /PC2H6 ratios that increased with increasing temperature. At 423 K, values of 1.9 and 2.3 were observed for the membranes containing 10 wt% and 20 wt% PVP, respectively. The researchers said that selectivity of the membranes could be improved by, “(1) raising the temperature to increase the decomplexation rate of C2H4 from Ag+ and (2) increasing the PVP content.” The researchers attribute the latter effect to the ability of the PVP to increase the flexibility of the inorganic framework and the immobilization of Ag+ in the polymer segments. CORA LIND

1 citations

Journal ArticleDOI
TL;DR: In this paper, the synthesis and formation of mesoporous titania films by latex beads templating was analyzed by Scanning Electron Microscopy (SEM) measurements.
Abstract: This article deals with the synthesis and formation of mesoporous titania films by latex beads templating The infiltration of latex template by titanium precursor solution resulted in compact films that generated an inverted pore network resulting from the latex removal as it was observed by Scanning Electron Microscopy (SEM) measurements The goal of this work is to analyze the deposition of latex beads on glassy substrates and eventual infiltration by precursor solution of mesoporous titania The final product was bulky films with porosity in the micrometric scale defined by latex beads The synthesis of latex beads was carried out in the absence of N2 and the titania precursor solution was obtained from the ternary system: HCl/P-123/1 Butanol The characterization of films by SEM was carried out after the removal of latex template by calcination in a tubular oven The appearance of films was compact for 30% V/Vo dispersion concentration and there was a well-defined pore network observed in the SEM characterization associated with the presence of latex beads that assembles by Solvent Controlled Evaporation (SCE) technique SEM characterization showed that latex beads coated on glass substrates and formed a network structure that could be applied to functional devices like solar cells, catalizers and batteries It is necessary to decrease the concentration of the dispersion to form films with homogeneous monolayers that become transparent to visible light KEYWORDS: Nanotechnology, semiconductor oxide, self-structured materials

1 citations