Navegando por Assunto "Casting"

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Acesso aberto (Open Access)
Aplicação da tecnologia supercrítica e de fndição na obtenção de embalagens ativas de gelatina de peixe (Cynoscion acoupa) com óleo essencial piper divaricatum
(Universidade Federal do Pará, 2021-10-27) ALBUQUERQUE, Gilciane Américo; CARVALHO JÚNIOR, Raul Nunes de; http://lattes.cnpq.br/5544305606838748; JOELE, Maria Regina Sarkis Peixoto; http://lattes.cnpq.br/2618640380469195
Active films produced with gelatin from the skin of hake fish (Cynoscion acoupa) and essential oil (EO) Piper divaricatum were obtained by two techniques: impregnation by supercritical CO2 (scCO2) and casting. Initially, the process of impregnating the EO in the gelatin film was carried out using CO2 as a supercritical solvent, in an autoclave at 35 º C, at pressures of 100, 150 and 200 bar and times of 60, 90 and 120 min. The active film that showed the highest percentage of inhibition of antioxidant activity (IAA%) was obtained at 100 bar and 60 min (41.63±1.6%). Scanning electron microscopy (SEM) showed that the EO presented heterogeneous distribution in the film, confirming the impregnation. The scCO2 impregnation resulted in a film with lower tensile strength and thermal stability, greater flexibility and opacity when compared to the control, indicating the potential of this technique to obtain active packaging for food products. After determining the best parameter of the impregnation process, the concentrations of 10%, 20% and 30% of the EO in the gelatin film were compared by the casting and impregnation techniques by scCO2. The films obtained with the addition of 20% (71.97±1.71) and 30% (79.17±1.01) of EO produced by casting showed the highest retentions of the IAA%. Films made by scCO2 impregnation showed lower antioxidant activity, but this was improved with increasing EO content from 20% (23.57±1.45) to 30% (33.66±2.42). Through scanning electron microscopy (SEM) images, oil droplets with heterogeneous distribution were observed in films impregnated by scCO2 and homogeneous surface by the casting technique. The films impregnated with scCO2 proved to be transparent, resistant to traction, elastic and with greater thermal stability. Meanwhile, the films produced by casting showed greater resistance to moisture and greater protection from UV light. The casting technique showed greater potential for the production of active packaging, as the film showed better antioxidant potential with the incorporation of EO and the use of emulsifier in the film solution. Impregnation by scCO2 showed potential to obtain the active film, however further studies should be carried out to improve the limitations of oil retention in the film found in this
Acesso aberto (Open Access)
Desenvolvimento de ligas de alumínio nanoestruturadas para a utilização em cabos elétricos
(Universidade Federal do Pará, 2023-03-15) PRAZERES, Emerson Rodrigues; SOUZA, José Antônio da Silva; http://lattes.cnpq.br/6157348947425968; BRAGA, Eduardo de Magalhães; http://lattes.cnpq.br/4783553888547500
Aluminum nanocomposites demonstrate the ability to improve mechanical properties, thermal and electrical conductivity. For aluminum, the incorporation of multi-walled carbon nanotubes (NTCPM) using conventional melting methods is an old problem, due to disintegration of the walls of carbon nanotubes when subjected to high temperatures. In this study, aluminum nanocomposites were manufactured by the conventional casting method, using stainless steel powder (304LSS), nanostructured silicon and nickel. The carbon nanotubes were treated with hydrogen peroxide, allowing adhesion by polar interaction with the particles of the metallic powders. The nanostructured compounds were added to the aluminum matrix by means of conventional casting. After obtaining the material as a melt, it went through the machining process to a diameter of 18.5 mm and then through the cold working process until a diameter of 3.0 mm was obtained. The alloys were characterized mechanically through tensile and microhardness tests, electrically through electrical resistance tests, using a 2-point kelvin bridge, and structurally through macrostructure and microstructure analyses. The 304LSS powder added alloying elements, refined the grains and the NTC improved electrical conductor performance, with electrical conductivity gains in the range of 10%. Associates associated with carbon-associated components not linked to chains of protein chains are compounds of carbon, associated with proteins, aggregates, associated with carbon, associated with proteins, associated with significant proteins in the LRT. The alloys with Ni and carbon nanotubes contributed to significant gains in electrical conductivity and LRT, with the alloy with 2% nickel and 0.1% NTC showing gains of approximately 8% in electrical and mechanical properties. Nanostructured alloys were also superior in terms of electrical and mechanical properties than commercial alloys.