Navegando por Autor "Sousa, Rômulo Ribeiro Magalhães"
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Artigo Study of High-Density Polyethylene (HDPE) kinetics modification treated by Dielectric Barrier Discharge (DBD) plasma(MDPI, 2020-10-21) Feitor, Michelle Cequeira; Medeiros Neto, João Freire de; Souza, Ivan Alves de; Targino, Talita Galvão; Diniz, Gutembergy Ferreira; Libório, Maxwell Santana; Sousa, Rômulo Ribeiro Magalhães; Costa, Thércio Henrique de CarvalhoIn this work, the plasma was used in the dielectric barrier discharge (DBD) technique for modifying the high-density polyethylene (HDPE) surface. The treatments were performed via argon or oxygen, for 10 min, at a frequency of 820 Hz, voltage of 20 kV, 2 mm distance between electrodes, and atmospheric pressure. The efficiency of the plasma was determined through the triple Langmuir probe to check if it had enough energy to promote chemical changes on the material surface. Physicochemical changes were diagnosed through surface characterization techniques such as contact angle, attenuated total reflection to Fourier transform infrared spectroscopy (ATR-FTIR), X-ray excited photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Plasma electronics temperature showed that it has enough energy to break or form chemical bonds on the material surface, impacting its wettability directly. The wettability test was performed before and after treatment through the sessile drop, using distilled water, glycerin, and dimethylformamide, to the profile of surface tensions by the Fowkes method, analyzing the contact angle variation. ATR-FTIR and XPS analyses showed that groups and bonds were altered or generated on the surface when compared with the untreated sample. The AFM showed a change in roughness, and this directly affected the increase of wettabilityArtigo Surface modification of PET fabric by plasma pre-treatment for long-lasting permethrin deposition(Wiley, 2020-05-18) Feitor, Michelle Cequeira; Badaro, Adair Divino da Silva; Libório, Maxwell Santana; Souza, Flaviane camara de; Sousa, Rômulo Ribeiro Magalhães; Santos, Rayane Saory Medeiros dos; Costa, Thércio Henrique de Carvalho; Naeem, Muhammad; Iqba, JavedThe mosquito-transmitted diseases are of serious concern and are affecting several millions of peoples worldwide. Instead of medication afterward the disease initiated, self-protection against the mosquito's is preferable, specifically in endemic areas. For this purpose, the permethrin coated clothing is a suitable choice to avoid mosquitos' bites. Unfortunately, the permethrin coating on fabrics is not long-lasting, and its laundering resistance is very low on hydrophobic fabric. In this study, the effect of plasma surface modification of PET fabric on the adhesion of permethrin and its laundering resistance are evaluated. The plasma processing is carried out in nitrogen, oxygen, and nitrogen–oxygen mixture plasma. The samples are analyzed using Fourier Transform Infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscope and chromatography. The results show that the oxygen plasma pre-treated samples exhibit the higher residual contents of permethrin after 60 wash cycles as compared with other gasses. Without plasma pre-treatment, the 95% loss, whereas the sample with oxygen plasma pre-treatment shows that only 22% loss of initial concentration of permethrin occurs after washing. This study shows that plasma pre-treatment is valuable to improve the absorption of permethrin in PET and its laundering-resistance. As plasma treatment is a cost-effective technique, it needs less processing time and eco-friendly, thus it is a great choice to deposit long-lasting permethrin coating by plasma pre-treatment, instead of conventional binding agents. Remarkably, the plasma treatment technique is a well-established and industrially acceptable technique, thus expected to be of noteworthy importance for insecticide garments manufacturersArtigo Triple langmuir probe, optical emission spectroscopy and lissajous figures for diagnosis of plasma produced by dielectric barrier discharge of parallel plates in atmospheric pressure(IOS Press, 2020-06-08) Feitor, Michelle Cequeira; Souza, Ivan Alves de; Medeiros Neto, João Freire de; Nascimento, Igor Oliveira; Matamoros, Efrain Pantaleon; Fernandes, Fernanda Melo; Sousa, Rômulo Ribeiro Magalhães; Costa, Thércio Henrique de CarvalhoThis work aimed to characterize a Dielectric Barrier Discharge (DBD) plasma equipment through optical and electrical measurements, seeking to obtain a greater knowledge of the plasma production process and how it behaves through the adopted parameters, such as frequency and voltage applied between electrodes, at a fixed distance of 1.7 mm. In order to measure them, three different characterization techniques were applied. The first method was the Lissajous figures, a technique quite effective for a complete electrical characterization of DBD equipment. The second technique used was the Optical Emission Spectroscopy, a tool used for the diagnosis of plasma, being it possible to identify the excited species produced in discharge in diffuse and filamentary regime in the plasma. And finally, the triple Langmuir probe technique was used to obtain the electron temperature and electron density. Based on this study, it was possible to identify the equipment efficiency in different regimes. The electron temperature measurement for both systems analyzed were 27.96 eV and 20.69 eV to the filamentary and diffuse regimes, respectively. The density of electrons number to these regimes were 1.09 × 1021m−3 and 1.56 × 1021m−3