With the advancement of Additive Manufacturing and its applications in various industrial segments, it becomes increasingly important to investigate the processability parameters associated with this technology. Thus, the present study aimed to investigate the influence of the form (solid and honeycomb), infill patterns, and concentrations of Carbon Nanotubes (CNTs) (1.0 and 2.0% m/m) in a polymeric matrix of Poly (Lactic Acid) (PLA). The material was produced through Additive Manufacturing using the Fused Deposition Modeling-FDM technique, adopting three infill patterns: concentric, hexagonal, and triangular. The CNTs used as reinforcements, the matrix, and the nanocomposite were characterized by Scanning Electron Microscopy – SEM, X-Ray Diffraction and Raman Spectroscopy. The mechanical properties of the nanocomposites were determined through Tensile (ASTM D638-22), Compression (ASTM D695-15), and Charpy Impact tests (ASTM D6110-18). The results of the morphological analysis conducted before and after the mechanical test on the matrix and nanocomposites show elements such as: voids, detachments, cracks, pores, compacted zones, structural ruptures and the presence of CNTs. The X-ray Diffraction analysis for the CNTs exhibit characteristic diffractions, while for PLA before and after 3D Printing, a predominance of the amorphous phase was observed. The PLA/1%CNTs and PLA/2%CNTs nanocomposites evidenced only little alterations, attributed to functionalization and low dimensionality of CNTs clusters. Regarding Raman characterization for the CNTs, the D band was deconvoluted into three sub-bands, two designated as DL at 1305 and 1347 cm -1 , and one as DR at 1360 cm-1 . The G band was similarly deconvoluted into three sub-bands, Gout, Ginn, and D’, located at 1580, 1605, and 1620 cm-1 , respectively. For PLA, the band corresponding to the symmetric vibration of CH3 was deconvoluted into two sub-bands at 1448 and 1460 cm-1 , while the asymmetric vibration was identified at 1387 cm-1 . In nanocomposites, the bands manifest as overlays of the vibrational modes of their constituents (PLA and CNTs). The mechanical analyses of tensile, compression, and Charpy impact reveal that infill patterns, geometries, and nanoreinforcement directly influence the mechanical properties of printed parts. In the tensile mechanical analysis for solid samples, the infill pattern that showed the highest average tensile strength was concentric, at 40.75 MPa. Conversely, for honeycomb-shaped samples, the best average tensile strength was attributed to the sample with concentric infill pattern, at 9.76 MPa. Nanocomposites exhibited inferior tensile performances compared to the matrix. In the compression mechanical analysis, for solid samples, the triangular pattern stands out, presenting an average compression strength of 52.8 MPa. For honeycomb-shaped samples, the triangular pattern also stands out, with an average strength of 20.8 MPa. Nanocomposites showed superior compression performances compared to the matrix, with the solid form (PLA/2%CNTs) exhibiting better performance, at an average strength of 73.5 MPa. In the honeycomb form, the nanocomposite (PLA/1%CNTs) showed better performance, reaching 33.2 MPa. In the Charpy impact analyses, the hexagonal pattern demonstrates the best average performance. In the solid configuration, its average impact resistance is 3.44 J/m, while in the honeycomb form, it registers 2.88 J/m. Nanocomposites in the solid configuration exhibit higher average impact resistance than the matrix, with the PLA/2%CNTs nanocomposite standing out, reaching 3.8 J/m. Conversely, in the honeycomb configuration, values of 2.72 J/m are observed for the PLA/1%CNTs nanocomposite and 2.98 J/m for the PLA/2%CNTs nanocomposite, respectively. This study investigates the effect of three variables (infill patterns, geometries, and nanoreinforcement) on the mechanical properties of PLA. The results highlight the significant influence of these factors under various mechanical loading conditions, thereby emphasizing the importance of this research, which investigates such conditions and contributes to a deeper understanding of 3D printed FDM products when subjected to different mechanical analyses.

A engenharia de tecidos atua como uma alternativa para substituir órgãos e tecidos do  sistema biológicos que foram afetados por alguma enfermidade, sem estimular reações adversas  no paciente. Ao usar a junção entre células do próprio paciente, fatores de crescimento e  scaffolds tridimensionais (biomateriais), é possível criar uma estrutura, com propriedades  otimizadas, que vai favorecer a regeneração do local lesionado. Para isso, então, torna-se  necessário estudar com profundidade o tipo de material que será usado como scaffold. Entre os  materiais nessa área, destacam-se os polímeros e hidrogéis (Poli (ε-caprolactona) (PCL) e poli  (2-hidroxietil metacrilato) (pHEMA), respectivamente). A PCL é biorreabsorvível,  biodegradável, atóxica e biocompatível, no entanto é hidrofóbica. Por outro lado, o pHEMA é  biocompatível, atóxico, hidrofílico, mas não apresenta boa degradabilidade. Sendo assim, ao  unir as propriedades desses dois materiais, usando uma estrutura de redes semi-interpenetrantes  (semi-IPN), pode-se ter um produto novo, com efeito sinérgico dos polímerosindividuais. Além  disso, é possível intercalar compostos bioativos, através do uso de óleos vegetais amazônicos, nessas estruturas para potencializar, ainda mais, a regeneração do tecido e combater possíveis  infecções por microrganismos. Visto isso, portanto, esse trabalho objetiva a obtenção e  caracterização de redes semi-IPN de PCL-pHEMA-copaíba para uso como scaffolds na  engenharia de tecidos, usando a técnica de rotofiação. Os resultados demonstraram com sucesso  o processamento de fibras PCL (com e sem óleo de copaíba) e a possível formação de redes  semi-IPN PCL-pHEMA. O espectro de FTIR mostrou interações dos grupos funcionais dos  materiais, confirmando a incorporação do óleo na estrutura do PCL e a formação de redes semi interpenetrantes. As micrografias revelaram microfibras emaranhadas e desorganizadas em  todas as amostras, com diferentes diâmetros e porosidades. A análise do ângulo de contato  demonstrou que a adição do hidrogel à estrutura do PCL otimizou as propriedades hidrofílicas  do material. Os termogramas confirmaram que o material não sofreu alteração significativa na  estabilidade térmica com a adição do hidrogel e do óleo. Testes microbiológicos confirmaram  a ação antimicrobiana do óleo de copaíba contra bactérias gram-positivas. Espera-se, por fim,  que um novo biomaterial seja desenvolvido para uso na engenharia de tecidos valorizando o  uso de recursos naturais amazônicos.

This research reports the evaluation of essential oils (OEs) such as those from the plant Piper divaricatum and Clove (button) Eugenia caryophyllus, as green inhibitors of protection in metallic materials precisely in this work, carbon steel. Resistance tests were carried out in corrosive media such as 1M HCl and 3.5% NaCl, the concentrations used for both essential oils were 0.5g/L; 1g/L; 2g/L and 4g/L, for periods of time such as 24h and 7 days. The method used to evaluate the efficiency of the oils was gravimetric (weight loss). The Scanning Electron Microscopy technique of the field emission gun type (MEVFEG) was conducted to investigate the surface of the specimen, while its chemical composition was treated through Electron Dispersion Spectroscopy (EDS). In this work, several aspects were discussed, such as the efficiency in relation to the time the specimen is exposed to corrosive media and factors such as the adsorption isotherm of oils on the metal surface, in addition to studies of the corrosion rate of the specimens in the absence and presence of inhibitors and their relationship with the oil concentrations used. The studies indicated that the essential oils of Piper divaricatum and Clove (Eugenia caryophyllus) showed excellent results in an acid medium of up to 98.3% for the concentration of 2g/L of Piper divaricatum EO in 24h, and 89.5% for the concentration of 1g/L of Eugenia caryophyllus EO in 7 days. In the neutral medium, the highest percentages of progress were 61.1% for the concentration of 0.5g/L of the EO of Piper divaricatum in 24h, and 83.3% for the concentration of 1g/L of the EO of Eugenia caryophyllus in 24h. the isotherms of the oils followed the Langmuir adsorption model, where both oils adsorbed on the metal surface forming a monolayer, the best results of isotherms were for the acid medium, for the neutral medium due to the high variability of the data it was not possible to establish a consistent following. In view of the proposed results, it was possible to conclude that the essential oils of P. divaricatum and E. caryophyllus have the potential to be used as resistance inhibitors, mainly in the acid medium, thus providing new alternatives, in order to reduce the toxicity of this process in comparison to inhibitors already on the market.

The emergence of smart factories based on Industry 4.0 increases the automation and optimization of industrial processes in production chains. In this context, the integration between physical and digital systems depends on intelligent sensors, with greater sensitivity and integrated by the Internet of Things (IoT). The literature indicates that piezoresistive sensors can be produced by additive manufacturing (AM) and nanostructured with
carbon nanotubes (NTCs), which generate a nanoelectromechanical system (NEMS) after its dispersion in the material. Thus, this work presents the development of a low-cost piezoresistive nanoelectromechanical sensor, produced by applying layers of NTCs on poly(acrylonitrile-butadiene-styrene) (ABS) parts printed by fused deposition modeling (FDM), integrable to the Industry 4.0 via IoT through ESP32 microcontrollers. For this, a diaphragm-type sensor device with dimensions 17.8, 17.8 and 5.5 𝑚𝑚 was developed, whose sensor element deformation occurs by pressing a button. After MA printing of the device parts, carboxylic acid functionalized multi-walled CNTs (MWCNT-COOH) were dispersed by ultrasonic bath in a solution with a concentration of 1 𝑚𝑔/𝑚𝑙 of acetone and dimethylformamide, in a ratio of 1 ∶ 1 in volume, for coating the sensor elements in successive layers with an aerograph. After the deposition of five layers of CNTs on the polymeric substrate, measurements of electrical resistance obtained with a picoammeter showed the percolation of the material in the second layer, with initial values above 10 𝑇 Ω and final values below 100 𝑘 𝑂𝑚𝑒𝑔𝑎 after the fifth layer, which occurs by the formation of conduction channels originating from the random arrangement of CNTs on the ABS surface, as observed by Field Emission Scanning Electron Microscopy (FEG-SEM). After that, the electrical resistance was measured during pressure cycles with progressive load and with maximum load, in which the sensor elements presented an operating range of 139.97 ± 0.46 to 363.25 ± 0.39 𝑘𝑃 𝑎. In the first test, the minimum sensitivity of 0.1 % and maximum sensitivity of 1.16 %. In the second, the highest average sensitivity was 0.63 ± 0.04 % and the lowest average response and recovery times were 0.55 ± 0.29 𝑠 and 12.29 ± 1.44 𝑠, respectively. Raman spectroscopy showed the overlapping of the signals of each material, in particular the ABS band at 1447 𝑐𝑚 −1 which appears prominently between the NTCs 𝐷 and 𝐺 bands. Based on the piezoresistive response that the material presented from the NEMS generated by the deposition of NTCs on ABS, this concept of a load cell can be integrated into an ESP32 microcontroller board, making it an intelligent device with potential application in industrial systems. 4.0.

The market for temperature sensors and other related sensors has grown in recent years. It is  estimated that it will have an annual growth of 11% per year between 2019 and 2026, and this  has sparked interest in studies focusing on more portable nanosensors. Thus, this work presents  the development of four sensors based on Poly (lactic acid) - PLA and Carbon Nanotubes - CNTs, produced by additive manufacturing and aimed at temperature monitoring, including  negative temperatures. One of these sensors was developed only in PLA and the others were  nanostructured by adding two different types of inks, containing CNTs. These were synthesized  by 3D printing using Fused deposition modeling (FDM) technology, in addition to adopting  different standards and methodologies for each one. Through morphological, vibrational, and  electrical characterizations, the devices/sensors demonstrated thermoresistive and  thermoelectric responses to the applied temperature variations. In this case, the morphology, as  analyzed by electron microscopy and vibrational Raman spectroscopy obtained from the  nanocomposite samples, showed the incorporation of CNTs in the PLA matrix, as well as their  vibrational spectra obtained with characteristic signatures of the materials used. The  manufactured devices have an active area of 15 cm2and presented a Seebeck coefficient at 1.33  µV/K under temperature gradients of 300K, in addition to presenting a maximum response of - 4.35± 0.15% for approximately 45 °C, for thermoresistive analysis. Thus, the developed devices  exhibited the behavior of thermistors and thermocouples, which promote these to excellent  temperature sensors.

The civil construction industry is one of the sectors of the economy that consume the most  natural resources, from the production of inputs to the execution of the work, which can  significantly affect the environment and the quality of life of the population. Geopolymers are  inorganic polymers with great ecological potential, produced from aluminosilicates and  synthesized by alkaline solutions, providing the material with better mechanical resistance.  Geopolymeric cement is a high-tech material developed using clay minerals, with  characteristics such as durability, mechanical resistance, strong adhesion, heat resistance, in  addition to being easily mixed and applied. The present study sought, through a correct  proportion of the components that constitute the geopolymer, the production of a Geopolymeric  Synthetic Aggregate (ASG), making variations with percentages of blast furnace slag and  variations in the alkaline concentration of sodium hydroxide (NaOH). Soon after, physical tests  were carried out on the powdered materials to verify the fineness index, loss on fire and  moisture content of kaolin, metakaolin and blast furnace slag. The samples underwent  characterization and the main analyzes involved in the process were: X-ray diffraction (DRX),  infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and EDS. A compression  test was also carried out on the geopolymer synthetic aggregate specimen. The results of the  compressive strength test indicated that the specimen with a percentage of 35% blast furnace  slag and an alkaline concentration of sodium hydroxide at 10 molar presented better results. In  the analysis of the microstructure of the paste, a dense morphology was observed, which gives  the material high resistance to compression.

In the last decades, the search for ecologically clean materials has become increasing, i.e., materials that are able to aggregate sustainable aspects and high mechanical performance. In the context of sustainability, the use of waste for the production of new materials has become frequent, because the incorporation of this waste can represent a solution for its environmentally correct disposal. The use of natural fibers in the production of new materials has increased a lot in recent years. The tururi fibrous tissue comes from the Ubuçu palm tree. The tissue is responsible for wrapping the fruits of the palm. Part of the fibrous tissue from the collection of the fruits is used in handicrafts and rudimentary activities such as covering houses. However, a large amount of this waste is discarded in inadequate places, thus generating environmental
damage. In this context, the use of tururi fabric as a reinforcement agent in polymer matrix composites appears as a viable alternative for the sustainable disposal of this waste. The use of natural fibers as reinforcement in composites of polymeric matrix is already well consolidated, because some fibers have high mechanical performance and good thermal stability, two highly attractive properties in composite materials. The composites reinforced with natural fibers have a wide field of application, and can be used in civil construction, aerospace, and automotive industries, among others. In this context, the present study aims to characterize the tururi fibrous tissue by means of optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR), as well as to determine physical properties such as weight, specific mass and moisture content of the tissue. Consequently, to evaluate the mechanical behavior of polyester matrix composites reinforced with tururi fibrous fabric. The composites will be made with 2.5, 5.0 and 7.5 % in mass of fibrous reinforcement. After the confection of the composites these will be tested in traction, flexion and Charpy impact. Moreover, the morphology of the composites will be analyzed by scanning electron microscopy at the point of fractures of the aforementioned tests, in order to verify the adhesion between matrix and reinforcement and understand the type of fracture. The mechanical tests will be performed in order to verify the possibilities of application of these composites in automotive, ballistic and civil construction areas