AUREA BEATRIZ CERQUEIRA GERALDO

AUREA BEATRIZ CERQUEIRA GERALDO

(Fonte: Lattes)

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Licenciada e bacharel em Química pela Universidade Federal do Paraná (1991), mestre em Físico-Química pela Universidade Estadual de Campinas (1993) e doutora em Engenharia Metalúrgica e de Materiais pela Universidade Federal do Rio de Janeiro (1998). Atualmente é tecnologista do Instituto de Pesquisas Energéticas e Nucleares. Atua principalmente nos seguintes temas: a) eletroquímica: eletroanalítica, eletrodissolução/eletrodeposição, b) materiais modificados por radiação: modificação e caracterização de materiais poliméricos, caracterização de materiais ligados a radioisótopos, estudo e caracterização de materiais para a produção de radioisótopos primários e c) ensino de química (Texto extraído do Currículo Lattes em 4 out. 2021)

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Mechanical evaluation of PVC films modified by electron beam irradiation
2011 - CARDOSO, J.R.; MOURA, E.; SOMESSARI, E.S.R.; SILVEIRA, C.G.; PAES, H.A.; SOUZA, C.A.; MANZOLI, J.E.; GERALDO, A.B.C.
The polyvinyl chloride (PVC) is a technological and low cost polymer. Although this polymer is weather resistant, it presents high sensitivity to high energy irradiation because of the weakness of carbon-chloride bond face to carbon-carbon and carbon-hydrogen bonds [1]. Upon exposure to high energy irradiation, some carbon-chloride bonds are broken to give rise radicals like chlorine and organic chloride that are initiators of two concurrent processes: degradation and crosslinking. The degradation process on PVC is macroscopically observed by discoloration effects, where the material tends to darken or to turn yellow, mainly at a typical sterilization dose of 25 kGy [2]; this process yields hydrogen chloride as a byproduct, it is autocatalytic and it continues after irradiation exposure. By other way, the crosslinking leads to an improvement in thermal resistance and mechanical properties. The aim of this work is to evaluate the mechanical properties of PVC irradiated by electron beam to verify the degradation process. Also, mechanical properties are investigated on styrene grafted PVC by electron beam irradiation using mutual and pre-irradiation methods to verify the mechanical resistance changes of obtained product if grafting process is applied from non-irradiated and from pre-irradiated substrates. The PVC commercial film samples with 210 jam thickness were cut into a dumbbell-shape (gauge length: 25 mm, width: 4.10 mm, area: 0.86 mm2). The grafting media was styrene /butanol-1 mixture in several monomer concentrations (from 10% to 100%). The samples were irradiated on a Job 188 Dynamitron® Electron Beam Accelerator with 1.5 MeV energy. All irradiation procedures were performed in atmosphere air and the irradiation conditions comprised doses from 10 kGy to 100 kGy and dose rates of 2.2 kGy/s and 22.4 kGy/s. The styrene grafted samples were analyzed by gravimetry to determinate the grafting yield; the final values have been averaged from a series of three measurements. The Mid-ATR-FTIR was the spectrophotometer technique used for qualitative/semi-quantitative analysis of grafted samples. The Young's module and tensile strength of pre-irradiated and grafted PVC samples at both methods were measured at a Lloyd LXR tensile tester at a crosshead speed of 10.00 mm/min. We observed the decrease of Young's module and tensile strength with the increase of absorbed dose at pre-irradiated PVC samples, that it indicates degradation process. These mechanical parameters results are discussed to styrene grafted PVC samples.
Effect of ionizing irradiation on tilapia (Oreochromis niloticus) skin
2011 - FROSE, C.A.P.; MOURA, E.; YAMAGUISHI, R.B.; SOMESSARI, E.S.R.; SILVEIRA, C.G.; LEME, E.; GERALDO, A.B.C.; MANZOLI, J.E.
The culture of tropical tilapia (Oreochomis niloticus), as a non-native freshwater fish specie in Brazil, have had importance in the last decade due its fast growing, fast reproduction characteristics, high tolerance of climate variations in our country and high disease resistance. The high demand of whole fish or fillets is related to its good taste. Althought, its skin, that represents from 4.5 % to14 % of fish weight, is a byproduct that is generally discared or sold at low cost to feed mills. The general animal skin composition comprises protein, water, minerals and fatty matter where the relative portions of these materials depends of upon animal specie, age, breed, feeding and other animal habits. The putrecible raw animal skins can be chemically and physically treated to make it in non-putrecible stabilized material; it results in a soft and flexible polymeric material. The chemical process to obtain this material generally involves a crosslinking of carboxyl groups or amino groups of skin proteins and the chemical reactive specie [1]. Also, physical process as UV irradiation have been successfully employed to crosslink collagenous biomaterials and thus, improved some mechanical characteristics [2]. The goal of this work was to study the tilapia skins exposed to ionizing irradiation from electron beams. The raw skins and the chemically degreased skins were the studied materials. The tensile strenght and elongation at break were the mechanical parameters evaluated. The optical microscopy was used to evaluate some histological characteristics in irradiated and non-irradiated samples. Also, the polymeric product obtained when skins are treated with oxidizing ions were used to compare some results. The tilapia raw skins were kindly available by APTA, a governmental agribusiness technological agency. These skins were scales free, slighted and frosted. The skins were irradiated in atmosphere air on a Job 188 Dynamitron® Electron Beam Accelerator with 1.5 MeV energy under comprised doses of 20 kGy and 40 kGy and dose rates of 2.2 kGy/s and 7.4 kGy/s. The mechanical parameters were measured at a Lloyd LXR tensile tester at a crosshead speed of 10.00 mm/min. Irradiated samples shows high integrity and high tensile strength in comparison to the polymeric product obtained by oxidizing ions reaction. These results are discussed.
Avaliação do teor de nitratos em águas potáveis por espectrofotometria Uv-vis
2021 - SILVA, MARIA E. da C.; GERALDO, AUREA B.C.
Study of Bixin oxidation by ionizing irradiation
2017 - FONSECA, THAIS N.; MOURA, EDUARDO de; GERALDO, AUREA B.C.
Brazil is the world's largest producer of annatto, followed by Kenya and Peru (CORLETT, 2007). The fruit of the annatto tree is constituted by a capsule containing external spines and internal seeds with reddish coloration, providing a natural pigment which is environmentally efficient, being able to replace synthetic pigments and dyes. The active substance of the pigment is Bixin, which is a type of carotenoid which constit utes a greater percentage of pigment in these seeds and has a lipo soluble character ( CUSTODIO , 2002 ). Bixin reacts with NaOH in a saponification reaction giving norbixin, which is water soluble. It is known that the destination of the dye extracted from t he fruit is intended for industry, especially the food industry. The culture of annatto tree brings prospects of development of agricultural programs for medium and small producers, which are able to use decadent areas of other crops. In addition to the fo od sector, new applications for the pigment helps the development of family farming (BERTOLIN, 2016). The pigment extracted from annatto undergoes a natural oxidation; this work aims to evaluate this phenomenon and also the oxidation of the pigment after the irradiation process. This work also evaluates of the how the oxidation process is affected by irradiation and the modifications introduced to irradiated pigments. Irradiated and non irradiated samples were characterized by UV vis s pectrophotometry a nd infrared spectroscopy (FTIR). The results are then discussed.
Irradiation of cellulosic waste from annatto seeds (Bixa orellana L.) for application in polymeric composites
2017 - TEIXEIRA, PAULA dos S.; MOURA, EDUARDO de; GERALDO, AUREA B.C.
The study o f natural vegetable, fiber reinforced polymeric composites became popular in the last decades since because this type of material enables the reduction of both the biomass waste and the cost of the final polymer product (MARINELLI, 2008). Plant fibers are plenty, low cost, they feature biodegradability and renewability. Moreover, cellulose polymer composites are more resistant to flection and impacts than the same base polymer material (FONSECA, 2005; HILLIG, 2008). Specifically, cellulose from annatto seed s is present in concentration at around 40 45%, which becomes important for industrial use (ANSELMO, 2008). In this work, the bagasse from annatto seeds after reddish pigment removal has being used to obtain high density polyethylene (HDPE) composites. T he original raw material underwent a pretreatment that extracted the components from seeds such as residue of remaining pigment, sugars, proteins and acid fats. The remaining fibers have been dried and mashed, and then submitted to electron beam irradiatio n with doses of 30 kGy, 50 kGy and 70 kGy to verify the effect of the radiation on the cellulose structure and its subsequent effect on the incorporation into polymer matrix. The study covered the extrusion of these fibers (irradiated and non irradiated) i n the ratio of 1 % to 5 % with HDPE. The sample characterization has been done by infrared spectrometry (FTIR), thermal degradation (TG) and mechanical tensile tests. The results are then discussed.
Effect of irradiation on the molar mass of chitosan from crab shells of Charybdis hellerii
2017 - FERREIRA, MAIARA S.; MOURA, EDUARDO de; GERALDO, AUREA B.C.
The importance of determining the molar mass of polymers is closely related to the size of the chain which is a controlling factor in the evolution of solubility, elasticity, fiber formation and mechanical strength properties. There are several methods used to determine the molar mass and they are divided into relative or absolute. Relative methods as viscosimetry require calibration with samples of molar mass known, whereas absolute methods as osmometry do not require it. The importance of molar mass determination is related to its high influence on the properties of chitosan, such as bacterial activity. There are some studies that show that the use of chitosan is more efficient in the inhibition of bacteria than the use of the oligomers that form the same (NO et al., 2002; HIRANO et al., 1989) and that the molar mass required for the inhibition of microorganisms should be greater than 10000 Da (SHAHIDI et al., 2000). The minimum inhibitory concentration of chitosan ranges from 0.005 - 0.1% and depends on the species of bacteria, the molar mass and the pH of the chitosan preparation (GUAN et al., 2001, NO et al., 2002). The method used in this work was the capillary viscosimetry because it is simple, fast and very efficient. For each sample, four dilutions were performed in order to make the extrapolation and determine the intrinsic viscosity. The average viscosity molar mass (Mw) was determined by the Mark-Houwink-Sakurada equation ([ƞ] = KMav). As one of the results it was observed that the chitosan coming from the crab shell is of low molar mass with a value correspondent about 10 times smaller when compared with the standard. The chitosan obtained with the use of electron beam irradiation also shows a decrease in the molar mass as a function of the increase of the absorbed radiation dose.
Crystallinity and mechanical properties of recycled, gamma irradiated HDPE/EPDM blends
2017 - GABRIEL, LEANDRO; MOURA, EDUARDO; GERALDO, AUREA B.C.
High Density Polyethylene (HDPE) is a commodity and its wide range of uses comprises several plastic processing in the industry due its conformability, high thermal and chemical resistance and a relative low cost [1]. Also, this material can be recycled many times, which is an important characteristic to decrease the environmental impact when plastic goods reach their end of life. EPDM is one of thermosetting elastomers widely applicated in automotive industry because of its high mechanical, thermal and ageing resistance [2]. The mixture of this both components generate a material with high impact resistance and tensile strength at break [3]. HDPE/EPDM blends are obtained by extrusion of these polymeric components with addition of compatibilizers agents to achieve a homogenous and compatible mixture [4]. In this work the High Density Polyethylene (HDPE) matrix has been recycled four times from original substrate and mixed to non-vulcanized EPDM rubber in proportions from 1 % to 10 % with no addition of compatibilizer agents. The gamma irradiation process was applied at 50 kGy and 100 kGy to both original and recycled blend samples. Characterization of samples was performed by X-ray diffraction and stress-strain assay. These results showed an increase of degree of crystallinity at recycled non-blended HDPE compared to this same parameter to pristine HDPE. It was also observed that crystallinity decreases as EPDM concentration increases. In irradiated samples, this parameter increase with high absorbed doses. The crystallite grain size increases in EPDM concentration from 1 % to 5 %; however, this parameter decreases in blends with 10 % of EPDM contents. This behavior suggests a co-crystallization effect on each polymeric component present in the blend and it may explain the miscibility and compability of both components in this material without addition of other agglutinative substances. The parameter stress at yield is high in pristine HDPE and low in recycled HDPE; this parameter decreases with as EPDM concentration increases in the non-irradiated polymeric blend. In irradiated blends the stress at yield increases in high doses. The irradiation process promotes blend crosslinking, and it is evident in blends with high EPDM concentration where high stress at 100 % strain is observed.
Solubilidade do PET em fenol
2019 - ARAUJO, BEATRIZ X.P. de; GERALDO, AUREA B.C.
Evaluation of ordered mesoporous silica SBA-15 dispersed in epoxy resin
2019 - VIRGINIO, SUELI; GERALDO, AUREA B.C.; MACHADO, LUCI D.B.; COSENTINO, IVANA C.; MATOS, JIVALDO do R.
To obtain the mesoporous nanostructured SBA-15 silica particles, a chemical reaction was perfomed using a template – a triblock copolymer (Pluronic 123®) - and a silica source - the tetraethyl orthosilicate - in acid medium. These silica particles were obtained by classical chemical reaction method and irradiation process (gamma rays from 60Co-Gammacell) at absorbed dose values of 0.5 kGy, 10 kGy and 25 kGy. Then, these silica particles were dispersed in epoxy resin Araldite® GY260 (diglycidyl ether of bisphenol A - DGEBA) and a cure agent. The particles dispersion was evaluated by two methodologies: a) Melt blending mode, where silica particles are dispersed in hot resin; b) Solvent-blended solution mode, where silica particles are dispersed in epoxy resin/acetone mixture in order to prevent the agglomeration of the inorganic phase. The silica particles had the specific surface area calculated from BET (Brunauer-Emmett-Teller) equation, while the BJH (Barrett- Joyner-Halenda) equation was used to determine pore volume and average diameter. Silica particles presented high surface area and pores arranged in hexagonal nanoscale diameter. The TEM images for irradiated silica particles have confirmed the hexagonal pore ordering in SBA-15 even using low gamma absorbed doses. The infrared absorption spectra (FTIR) confirmed that the added organic solvent has been effectively removed. Images of optical microscope revealed dispersion of the components by solvent-blended solution mode allows a better components interaction.
Ionizing radiation applied to one step conversion from different sources of chitin
2019 - FERREIRA, MAIARA S.; MOURA, EDUARDO; GERALDO, AUREA B.C.
Chitosan is a polyssacharide obtained from chitin’s molecule deacetylation which is the main constituent of some fungi species and the exoskeleton of crustaceans, insects and mollusks. Frequently the production of chitosan is from the crab shells and shrimps that are byproducts of the fishing industry, so it is highly dependent on seasonality. Therefore, finding new chitin’s sources become important. The amino groups present in chitosan give important biological properties such as biodegradability and biocompatibility, activity/immunological effects and antibacterial healing. The chitosan deacetylation process is an aggressive reaction since it requires the attack of chitineous substrate in hot and high concentrated alkalis solution by 1 to 17 hours. It is possible to reduce reagent concentration and time using high-energy irradiation (gamma rays and electron beam). The advantages of radiation use in high-energy include: the absence of chemical initiators, the process can be performed at room temperature and there is no need for the use of solvents. In this work, crab shell, shrimps, squid glads and blattaria were used in order to compare the quality of chitosan found in each animal source. After pretreatment, which include the steps of demineralization and deproteinization, the samples were irradiated at a dose of 20 kGy (gammacell) in order to reduce the deacetylation time. The chitosan from the used chitin sources was characterized by FTIR analysis and its degree of deacetylation was determined.