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  2. Pesquisar por Orientadores

Navegando por Orientadores "REIS, Marcos Allan Leite dos"

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    Código de resposta rápida nanoestruturado impresso em 3D
    (Universidade Federal do Pará, 2023-07-12) OLIVEIRA, Dhonata Sebastião Caldas; REIS, Marcos Allan Leite dos; http://lattes.cnpq.br/8252507933374637; https://orcid.org/0000-0003-2226-2653
    Due to the Fourth Industrial Revolution, also known as Industry 4.0, factories increasingly have systems dependent on the Internet and communication technologies, which guarantees them unprecedented efficiency, but makes them vulnerable to cyber attacks. For this reason, cybersecurity it is an increasingly relevant topic, with technologies such as blockchain and quantum cryptography based on physically unclonable functions (PUFs) presenting themselves as alternatives in this area. In this sense, this work presents the synthesis of poly(acrylonitrile-butadiene-styrene) (ABS) nanocomposites with respectively 1 and 2 % by mass of carbon nanotubes (CNTs) for the 3D printing of the so-called NanoCodecs, which present Raman spectral signatures, classified as PUFs, which can be used as cryptographic keys generated by a code built in the Python programming language. For this, two solutions were prepared, the first with multi-walled CNTs functionalized with carboxylic acid in acetone, and the other with pure ABS pellets in this same solvent. After mixing these solutions and ultrasonic baths, the acetone was evaporated and ABS/NTC1%m/m and ABS/NTC2%m/m pellets were produced, which were used for the production of nanostructured filaments in an extruder. Then NanoCodecs as quick response code (QR code) and as round/square stamps were 3D printed. The electrical characterization of samples printed with nanostructured filaments showed a reduction in electrical resistance with an increase in the percentage by mass of CNTs. Despite this, the morphological characterization by Scanning Electron Microscopy showed that there is a low concentration of nanotubes on the surface of the samples, which indicates that they are dispersed throughout the volume of the samples. The vibrational characterization by Raman spectroscopy was used to identify the characteristics of pure materials, both ABS and NTCs, and compare with the Raman spectrum of the ABS/NTCs nanocomposite. As a result, there was an overlap of the vibrational modes of both materials, with emphasis on the shift to the right of the sub-band 𝐺𝑒𝑥𝑡 in 8 𝑐𝑚−1, which indicates that the nanotubes are compressed in the polymeric matrix. Finally, using nanocomposites as PUFs, it was possible to generate keys from the main vibrational modes of these materials: the D, G and 2D bands of nanotubes and the bands named as 1001-PS and 2239-PAN of ABS. Therefore, the results obtained indicate that NanoCodecs can be used as elements of ybersecurity in Industry 4.0, through cryptographic keys generated by the spectral analisys of the nanocoposite used for produtction of the NanoCodecs.
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    ItemAcesso aberto (Open Access)
    Desenvolvimento de termocélulas nanoestruturadas do tipo em camadas e coplanar
    (Universidade Federal do Pará, 2021-08-10) PINHEIRO, Paula Fabíola Pantoja; REIS, Marcos Allan Leite dos; http://lattes.cnpq.br/8252507933374637; https://orcid.org/0000-0003-2226-2653
    Environmental problems accentuated by fires and fossil fuels reflect the need to develop more accurate environmental monitoring systems, as well as the reuse of waste heat in thermoelectric conversion in industrial processes. Thus, in this research, thermocells based on Buckypaper (BP) were developed in two arrangements: layered and coplanar. BP was produced by vacuum filtration of functionalized Carbon Nanotubes (f-CNTs) through a filter paper with 14 μm pores. Scanning Electron Microscopy showed a BP consisting of cellulose fibers impregnated with agglomerated f-CNTs. By measuring two-point, a BP tape (1.0 cm2) showed an electrical resistance of 0.92 kΩ at 300 K. When heated in the range of 300-337 K, the BP reduced on average 22.39% of its electrical resistance, characterized as a thermoresistor. In the layered thermocell, keeping the copper electrode at room temperature while the BP electrode (active area: 5.5 cm2 ) was thermally excited generated a thermoelectric power (α) of 26.33 mV/K for ΔT = 3.0 K. This result is superior to that reported in nanostructured thermoelectrochemical cells and is close to that obtained by commercial silicon. In the coplanar thermocell, the BP was connected between two copper electrodes that acted as hot and cold sides (cooled by a heatsink) and reached α = -0.06 mV/K for ΔT = 19 K. This result was inferior to that obtained for Bi2Te3 and superior to that obtained by a free-standing BP based on nitrogen-doped CNTs.
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    Desenvolvimento de termosensores nanoestruturados impressos em 3D
    (Universidade Federal do Pará, 2023-06-26) SANTOS, Leandro José Sena; REIS, Marcos Allan Leite dos; http://lattes.cnpq.br/8252507933374637; https://orcid.org/0000-0003-2226-2653
    The market for temperature sensors and other related devices has grown significantly in recent years. It is estimated that there will be an annual growth rate of 11% between 2019 and 2026. This growth has sparked interest in studies focusing on alternative nanosensors that offer better portability, sustainability, and may contribute to achieving the Sustainable Development Goals (SDGs). This work presents the development of four sensors based on Poly (lactic acid) - PLA and Carbon Nanotubes - CNTs, produced using additive manufacturing. These sensors are designed for monitoring body temperature (35 to 45ºC) and cold room temperatures (5°C to -40°C), covering an active area of 15cm2. One of these sensors was developed using only PLA as a control sample, while the others were nanostructured by adding two different types of inks containing CNTs. The synthesis of these sensors was performed through 3D printing using Fused Deposition Modeling (FDM) technology, with a specific synthesis method for each sensor. Through morphological, vibrational, and electrical characterizations, the devices/sensors exhibited thermoresistive and thermoelectric responses to temperature variations. Electronic microscopy and vibrational Raman spectroscopy analyses of the nanocomposite samples revealed the successful incorporation of CNTs into the PLA matrix, as evident from their characteristic vibrational spectra. The sensors demonstrated a Seebeck coefficient of 1.33μV/K under temperature gradients of 300K, and a maximum thermoresistive response of -4.35± 0.15% at approximately 45°C. Thus, such developed devices exhibited the behavior of thermistors and thermocouples, making them a promising alternative for implementation in cold rooms and Home Health systems.
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    ItemAcesso aberto (Open Access)
    Eletrodeposição pulsada e caracterização de revestimentos de cobre/nanotubos de carbono em ligas de alumínio 3003 e 1350
    (Universidade Federal do Pará, 2025-06-25) SILVA, Alberto Solary da; SOUSA, Mário Edson Santos de; http://lattes.cnpq.br/4761512397509247; HTTPS://ORCID.ORG/0000-0002-7605-2371; REIS, Marcos Allan Leite dos; http://lattes.cnpq.br/8252507933374637; https://orcid.org/0000-0003-2226-2653
    The demand for more efficient and sustainable electrical systems has driven research toward innovative materials that enhance the properties of electrical conductors. Aluminum (Al) and its alloys are widely used in power transmission and distribution due to their low density and good electrical conductivity. The pursuit of improved electrical properties has led to the development of coatings that increase conductivity without compromising the lightweight nature of the material. This study presents an investigation into the anodization of Al substrates as a preparation step for nanostructured coatings, combined with pulsed current electrodeposition of a copper (Cu) and multi-walled carbon nanotube (MWCNT)-based nanocomposite, focusing on the correlation between electrical properties and microstructure. Experiments were conducted on Al 3003 alloy sheets, and on wires and cables made from Al 1350 alloy. Optimized anodization parameters were established using 100% H₂SO₄, direct current of 3 A, and 10 V applied for 2 hours. For the pulsed current electrodeposition, a concentration of 1 mg/mL of MWCNTs, an 80% duty cycle, 2 A, and 10 V were applied for 1 hour. Field Emission Gun Scanning Electron Microscopy (FEG-SEM) micrographs confirmed the formation of a uniform and porous aluminum oxide (Al₂O₃) layer, essential for coating adhesion, and revealed the homogeneous and effective distribution of the nanocomposite over the anodized surface. Energy Dispersive Spectroscopy (EDS) verified the presence of Cu and carbon (C) elements distributed throughout the coating layer. Raman spectroscopy identified characteristic vibrational modes of MWCNTs: D, G, and G′ bands, showing variations in intensity and bandwidth due to structural modifications induced by electrodeposition. X-ray Diffraction (XRD) analysis revealed the crystalline phases present in the coating and structural changes resulting from the surface treatment, confirming the integration of the nanocomposite into the metallic substrate. Electrical conductivity tests using the four-point Kelvin probe method, before and after coating, demonstrated a significant increase in electrical conductivity (σ), indicating improved charge transport efficiency due to the synergy between Cu and MWCNTs. Among the results, a ∼ 52.33% increase in surface electrical conductivity (σₛ) of the Al sheets and an increase in IACS from 67.76% to ∼ 73.5% in the coated wires stood out. Similarly, the average resistance of the coated cable decreased from 4.88×10⁻⁴ Ω to 1.934×10⁻⁴ Ω, a reduction of ∼ 60.37% compared to the uncoated cable. Statistical analyses supported these findings and confirmed their significance. Joule heat dissipation and ampacity calculations confirmed the superior performance of the coated material and its potential for application in power transmission and distribution systems. Therefore, the Cu-MWCNT nanocomposite coating obtained via pulsed current electrodeposition on anodized surfaces represents a promising approach for improving the electrical properties of Al-based conductors.
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    Influência dos parâmetros de preenchimento, forma e reforço nanoestruturado em matriz polimérica de PLA impressos em 3D
    (Universidade Federal do Pará, 2024-04-08) FARIAS, Dorivane Cohen; REIS, Marcos Allan Leite dos; http://lattes.cnpq.br/8252507933374637; https://orcid.org/0000-0003-2226-2653
    With the advancement of Additive Manufacturing and its applications in various industrial sectors, it becomes increasingly important to investigate the processability parameters associated with this technology. Thus, the present study aimed to investigate the influence of shape (solid and honeycomb), infill patterns (concentric, hexagons, and triangles), and concentrations of Carbon Nanotubes - CNTs (1 and 2 wt%) in a polymeric matrix of Poly (Lactic Acid) - PLA. The material was fabricated using the Fusion Deposition Modeling - FDM technique. The CNTs, PLA, and nanocomposites were characterized by Scanning Electron Microscopy - SEM, X - Ray Diffraction (XRD), and Raman Spectroscopy. Mechanical properties were analyzed through tensile, compression, and Charpy impact tests. The results of the SEM analysis before and after mechanical testing show: voids, CNTs, cracks, pores, and fractures. XRD analysis reveals two diffraction peaks for CNTs at 2θ: 30.01° and 2θ: 50.03°, while PLA and nanocomposites exhibit predominantly amorphous phases. In Raman characterization, the vibrational bands of CNTs, PLA, and nanocomposites were deconvoluted into subbands. CNTs showed the following subbands: DL, DR, DLO, Dmiddle, Gout, Ginn, D', 2DL, 2DR, DL + Gout, and DR + Ginn, in PLA the most prominent subbands are associated with symmetric and asymmetric vibrations of CH3. In nanocomposites, the subbands manifest as overlap of the vibrational modes of their respective constituents (PLA and CNTs). The mechanical analyses of tensile, compression, and Charpy impact tests indicate that infill patterns, shapes, and nanoreinforcement influence the mechanical properties. In tensile testing, the concentric infill pattern exhibited better performance for both shapes, with 40.75 MPa for the solid shape and 9.76 MPa for the honeycomb shape. The nanocomposites in tensile testing showed lower performance compared to the matrix. In compression testing, the triangular infill pattern showed better performance, with 52.8 MPa for the solid shape and 20.8 MPa for the honeycomb shape. In compression testing, the nanocomposites exhibited higher strengths than the matrix, with the PLA/2%CNTs nanocomposite showing the best performance in the solid shape at 73.5 MPa, and in the honeycomb shape, the PLA/1%CNTs nanocomposite performed the best at 33.2 MPa. In Charpy impact testing for the solid shape, the infill patterns did not differ in performance. However, in the honeycomb shape, the hexagon pattern stood out, with 2.88 J/m. For the nanocomposites, in both shapes, the PLA/2%CNTs fraction showed better performance, with 3.8 J/m for the solid shape and 2.98 J/m for the honeycomb shape.
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    ItemAcesso aberto (Open Access)
    Prototipagem de sistema de alarme de incêndio baseado em sensor nanoestruturado integrado a IoT
    (Universidade Federal do Pará, 2021-06-29) FREITAS, Luís Gustavo Oliveira de; REIS, Marcos Allan Leite dos; http://lattes.cnpq.br/8252507933374637
    The improvement of remote sensing systems for the detection of forest fires or industrial plants is fundamental to the development of industry 4.0, and it is becoming increasingly important for many countries where forest fires occur frequently. Therefore, it is necessary to design and explore a device that has a quick response, that has remote monitoring in real time and can generate warning signs that precede major fires in indoor (indoor) and outdoor (outdoor) environments, this nanostructured sensor based on buckypaper that it consists of carbon nanotube films and has thermal sensitivities that can be measured in short response times. In the prototyping of the fire alert sensor, thermal tests were carried out to evaluate the effectiveness. Furthermore, it was integrated with IoT (Internet of Things) using the NodeMCU architecture together with the MQTT (Message Queuing Telemetry Transport) protocol, thus enabling the sending of the alert message to the end user through an Android application. Preliminary results show that this nanostructured sensor can be effective at distances of less than 1 meter from the fire source, for example at 20 cm, generating a thermovoltage of 2.3 mV over 80 seconds with a heat source at 240 ° C. This work shows the entire development process of this prototype with real-time monitoring with the function of issuing an early fire alert.
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    Reforço superficial em alumínio fundido por nanotubos de carbono via tratamento de solubilização
    (Universidade Federal do Pará, 2021-10-14) BRITO, Paulo Roberto de Oliveira; REIS, Marcos Allan Leite dos; http://lattes.cnpq.br/8252507933374637
    Carbon nanotubes (CNTs) are noteworthy, as they reinforce the metallic matrix, due to mechanical properties, such as the ~ 1.0 TPa Young module. To improve the maintenance of the commercially pure aluminum surface, multi-walled carbon nanotubes (MWCNTs) were incorporated into the aluminum surface with heat treatment by solid solubilization, in order to improve the surface properties of aluminum. The aluminum samples were subjected to chemically attacked with the Keller reagent, for a period of 30, 60 and 120 seconds, and soon after the roughness assessment was carried out, and then they were placed in a container containing NTCs, being subjected to a 640°C for one hour. Afterwards, the morphology was evaluated in the scanning electron microscope, where an aggregate of NTCs was observed, the DRX was performed to evaluate the addition of the NTCs in the matrix, and the Raman Spectrum that evaluated the charge transfer to the matrix. Microhardness was performed to evaluate the result of the incorporation of the NTCs in the matrix. The results obtained show that the incorporation of CNTs in the aluminum matrix increases the hardness in approximately 20% of the surface, in comparison with the control sample. The process of incorporating CNTs into the aluminum matrix by solubilization is a promising, simple and inexpensive alternative to improve the durability of the aluminum surface.
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    Síntese e caracterização de cerâmicas bifásicas de fosfatos de cálcio (HA / β-TCP) a partir de nanocelulose do tegumento do açaí (Euterpe oleracea Mart.)
    (Universidade Federal do Pará, 2018-10-31) VALENTIM, Rachel Margalho Barreira; DIAS, Carmen Gilda Barroso Tavares; http://lattes.cnpq.br/2113791118142177; REIS, Marcos Allan Leite dos; http://lattes.cnpq.br/8252507933374637
    The remnants of the açaí agribusiness (Euterpe Oleracea Mart) are sources of lignocellulosic materials. The extraction of nanocellulose from the açaí integument constitutes viable raw material for the synthesis of biphasic ceramics (HA / β-TCP) by acid hydrolysis. After the fruit pulp is obtained a biomass that is divided into three fractions: sludge (parenchyma), fiber (monostelo) and endocarp. The integument is analyzed by MEV / EDS, through the endocarp of açaí of terra firme and of várzea presenting essential nutrients, to obtain ceramics of phosphates of calcium. The biocomposite (NC / HA / β-TCP) was characterized by MEV, presenting crystalline species on the surface of the nanocellulose; X-ray diffraction presenting HA nucleation attributed to type I cellulose and tricalcium phosphate (β-TCP) on the surface of cellulose type II; showing the growth of HA crystals on the surface of the nanocellulose. The FTIR analysis showed characteristic peaks of PO4-3, C1-H glycosidic deformation at 897 cm -1 attributed to cellulose, strong C-C conjugate binding at 1609 cm -1 attributed to lignin showing a decrease in content during the process. The results of particle size are in the nanometric dimension showing 643.50 nm as the most common value related to the results of the zeta potential presenting unstable particles producing particles aggregation and stable particles with modulus value greater than 20 mV. Due to the characteristics presented by the biphasic ceramic synthesized in this work it is suggested its application as biomaterial.
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