PPGEM - Doutorado em Engenharia Mecânica

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Efeito da técnica de preparação de pó e da adição de Nb na densificação e microestrutura dos compósitos WC-Cu-Nb sinterizados com fase líquida
(Universidade Federal do Rio Grande do Norte, 2023-03-20) Coelho, Renan Sávio de Almeida; Costa, Franciné Alves da; http://lattes.cnpq.br/8698567925323942; http://lattes.cnpq.br/4429205296751509; Silva, Angelus Giuseppe Pereira da; Dias, Avelino Manuel da Silva; https://orcid.org/0000-0001-8974-5137; http://lattes.cnpq.br/1142442322601442; Mashhadikarimi, Meysam; Araújo Filho, Oscar Olimpio de; Gomes, Uilame Umbelino
WC-Cu composites are used as electrical contacts in high power circuit breakers and electrical resistance welding electrodes. This is due to the high thermal and electrical conductivity and excellent workability of copper associated with the high resistance to wear and erosion by electric arc of tungsten carbide. However, the low wettability of liquid copper on tungsten carbide particles and the mutual insolubility of the constituents make it difficult to densify this composite. This work investigates the effect of adding 5 and 10% by mass of Nb to the WC-20%Cu composite and the influence of the powder preparation technique on the microstructure, densification and properties of WC-Cu-Nb composites sintered in liquid phase. The crystallite size of the WC-20%Cu- 5%Nb composite powders ground for 5 h in an attritor mill reached 11.0, 11.2 and 26.9 nm for the respective WC, Cu and Nb phases. In contrast, the crystallite size of the same composite powders milled for 10 h in a planetary mill reached only 15.0 and 16.3 nm for the respective WC and Cu phases, but the Nb phase amorphizes or goes into solid solution in Cu. Although the attrition mill produced a greater reduction of crystallites and greater dispersion of the hard WC phase in the soft Cu and Nb phases, contamination by Fe, from the grinding body and chromed steel container, promoted less densification of the powder compacts of the composite. WC-20%Cu-5%Nb, as the compacts of these composite powders ground for 5 h in an attritor mill reached a density of only 71.39 ± 3.38% of the theoretical density, while the compacts of the same composite powders ground for 10 h in a planetary mill, also with chrome steel grinding bodies, reached a density of 81.43 ± 2.7% of the theoretical density. On the contrary, when grinding was carried out in a planetary mill with carbide grinding media, no contamination was detected and the density reached 93.25 ± 3.16%. The addition of Nb contributes to the densification of the WC-Cu composites, as the powder compacts of the WC-20%Cu composite with zero, 5 and 10% by mass of Nb prepared in a planetary mill reached a density, respectively, 77.62 ± 1, 0.65%, 81.43 ±2.70%, 84.34 ± 1.37% of theoretical density when sintered at 1150 °C for 1 hour. Furthermore, the microstructure of the sintered compacts of WC-20%Cu powders with a higher amount of Nb exhibit smaller grain size, confirming their efficiency in inhibiting the grain growth of the sintered composites. Brinell hardness increases with milling time reaching values of 101 HB and decreases with decreasing WC mass. The electrical conductivity increases with the addition by mass of Nb, reaching 2.27% IACS when the amount of 10% by mass of Nb is added to the WC-20%Cu composite.
Obtenção e caracterização de compósitos com matriz de resina poliéster, resíduos do sabugo de milho e fibras de juta e de vidro tipo E
(Universidade Federal do Rio Grande do Norte, 2023-02-28) Oliveira, Mariana Lima de; Souza, Luiz Guilherme Meira de; http://lattes.cnpq.br/0801747108308706; http://lattes.cnpq.br/4244867517148720; Moutinho, Daniel Joaquim da Conceição; Nascimento, José Heriberto Oliveira do; Souza, Luiz Guilherme Vieira Meira de; Batista, Salomão Sávio
The search for new materials as an alternative to the use of iron, wood and synthetic materials has stimulated countless researches. From this perspective, the appropriate disposal of waste and the reduction of its discard in nature have contributed to the emergence of new materials that meet the increasingly specific needs of the population and industry. In this work are addressed the processes of obtaining and characterizing composites of hybrid and non-hybrid polymer matrix and loading / reinforcement of residues of corn cob and fiber of jute and of glass type E. In order to obtain the bran, the corn was dried in a solar dryer and then crushed in forage, obtaining the desired granulometry of the sieving. Will be described the processes of treatment and processing of waste and the fibers as well as the production of composites. It is intended to study the proportions between the constituent elements of the composites, determining the most appropriate for manufacturing laminates and structures of solar equipment. Thus, it is desired to characterize the mechanical and physical properties of the developed composites, thus determining their possible applications. Previous work has shown that the main advantage of the polymer composite with corn cob residue was its low density, around 1.06 kg / m 3, but with a low mechanical resistance. Preliminary results showed that the hybridization of these composites gave an improvement in its mechanical resistance.
Obtenção e caracterização de um compósito de matriz de resina poliéster e pó de resíduo de aço
(Universidade Federal do Rio Grande do Norte, 2022-12-24) Spinelli, Mário César de Oliveira; Souza, Luiz Guilherme Meira de; http://lattes.cnpq.br/0801747108308706; http://lattes.cnpq.br/8554099162501861; Moutinho, Daniel Joaquim da Conceição; Nascimento, José Heriberto Oliveira do; https://orcid.org/0000-0001-6804-2854; http://lattes.cnpq.br/7033735079037677; Souza, Luiz Guilherme Vieira Meira de; Batista, Salomão Sávio
The growing use of organic products and varied processes of environmental processing of products and their consequences for human and varied health of the planet. Among the material machining processes, it is produced by machining processes, which are more harmful to human health, and that cause environmental concern. The processes for obtaining and characterizing deposits with polyester resin (RP) and iron powder filler (PRA) were studied. Composites and resins were determined by the resin mass ratio 1.0 RP + 0.50 PRA, 1.0 RP + 1.0 PRA and 1.0 RP + 1.5 PRA. The base fabrication method or closed bond molding was done cold. As proposed composite configurations. All designed formulations can be processing. Such compounds were properties characterized by the determination of their mechanical, thermal, electromagnetic, density, water absorption and aging. The composites obtained will be used for electromagnetic shielding. The composite with the highest economic viability was 1.0 RP + 1.5 PRA. It was found that the PRA was composed of 98% iron and that it had the function of filling and flexing load and reinforcement for impact, where the composite had its most promising result. The composite achieved a shielding factor of approximately 23 decibels at the 9 GHz frequency, in the X-band, its capability for electromagnetic shielding.
Caracterização da cortiça de Calotropis Procera como potencial aplicação em materiais sustentáveis
(Universidade Federal do Rio Grande do Norte, 2022-08-29) Silva, Anaxmandro Pereira da; Ladchumananandasivam, Rasiah; Silva, Kesia Karina de Oliveira Souto; https://orcid.org/0000-0002-9705-6750; http://lattes.cnpq.br/4712628443097348; https://orcid.org/0000-0002-0810-8433; http://lattes.cnpq.br/8553209522282182; http://lattes.cnpq.br/7643374686458188; Zille, Andrea; Nascimento, José Heriberto Oliveira do; Fangueiro, Raul Manuel Esteves Sousa
The cork industry throughout the world has stood out for its innovation and constant growth. Today, cork is used in different industrial segments and in the most varied products such as raw cork, boards, coatings, insulation, and composites, among others. The peculiar properties of cork of lightness, elasticity, compression with elastic memory, resistance to friction and hypoallergenic characteristics, among others, associated with advances in research and development in the area, make possible several uses of this 100% natural and renewable raw material. The objective of this work was to develop an ecomaterial obtained from the cork of the Calotropis Procera plant, for potential industrial application and evaluating its mechanical property of tensile strength. The suberose material showed potential cortical characteristics according to the micrograph, confirmed by BET analysis, amorphous structure in its xray diffraction spectroscopy, low density with an average of 0.24 kg/dm³, thermal stability and FTIR peaks characteristic of a cortical material. The average contact angle of the in natura sample presented an average of 139.3º, which characterizes it as hydrophobic. After grinding and compaction of the sample in a mold, it maintained being hydrophobic, with a hydrophilic tendency and a decrease in its contact angle to around 89.4º. The material composed of GreenPoxy (GP) resin and cork was submitted to mechanical tensile strength tests to compare it with the GP. The results of the of GP and samples of GP with cork showed an average fracture resistance in the ratio of around 29% in tensile strength and 26% less in elongation in relation to GP samples and 0.6% less weight. In XPS, EDS and FRX can be confirmed in the amount of C and O as their main constituents. In view of the results, it can be concluded that cork can be used as a filler in thermoset composites.
Funcionalização de tecidos de malhas e filmes de quitosana com Ximenia Americana L. para o uso antimicrobiano
(Universidade Federal do Rio Grande do Norte, 2022-06-28) Costa, João Batista Sousa; Alves, Salete Martins; Nascimento, José Heriberto Oliveira do; http://lattes.cnpq.br/8550161853747323; https://orcid.org/0000-0002-2659-4746; http://lattes.cnpq.br/3682962930509154; Rocha, Brismark Goes da; Morais, João Paulo Saraiva; Deus, Katherine Carrilho de Oliveira
Currently, the demand for functional textiles, such as fabrics and antimicrobial polymeric films, which are environmentally safer, has been increasing. Thus, chemical compounds that pose risks to the environment and to man can be replaced by natural products. As these products are safe and non-toxic, they are an alternative of great importance especially for textiles in the medical and health fields. Therefore, in view of the various plants used in popular medicine, Ximenia americana L. and chitosan are cited. These substances have the properties of biodegradability, biocompatibility and antibacterial action. The present work aims at the functionalization of knit fabrics and polymeric chitosan films with American ximenia for antimicrobial use. Functionalization in the meshes was performed using two methods: exhaustion (alt) and impregnation (padding). In the process of exhaustion, the mesh remains under agitation in contact with the ximenia extract, and in the impregnation, the fabric passes through pressure rollers so that the extract is forced to penetrate it. The polymeric chitosan films were produced by the solvent evaporation method, known as the solvent casting method. All functionalized materials were characterized by several techniques, namely scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (Tg), color strength, tensile strength, and antimicrobial activity. For polymeric films, measurements of thickness, humidity and opacity were made, in addition to the characterizations already mentioned. Regarding antimicrobial characterization, all functionalized tissues were shown to be bactericidal for Staphylococus aureus bacteria (S. aureus), as they formed inhibition halos, showing that the bacteria did not proliferate. In the chitosan films with ximenia, there were larger halo formations demonstrating that these have better properties. In view of the results, we conclude that functionalization proved to be effective for the purposes of this work, since all textiles (fabrics and films) had a bactericidal character.
Estudo experimental de tensões residuais aplicados em superfícies usinadas em elementos de máquinas
(Universidade Federal do Rio Grande do Norte, 2020-11-30) Carvalho Filho, Eugênio Teixeira de; Medeiros, João Telesforo Nóbrega de; http://lattes.cnpq.br/3206952338356447; http://lattes.cnpq.br/3722989676510159; Oliveira, Adilson José de; https://orcid.org/0000-0001-6104-569X; http://lattes.cnpq.br/3158071963293362; Alves Júnior, Clodomiro; Macedo, Daniel Araújo de; Souza, Juliana Ricardo de; Martinez, Luís Gallego
This thesis is structured based on consolidated results and organized from five articles produced during the period of scientific investigation. Initially, an Interlaboratory study was carried out in order to understand the possible sources of measurement uncertainty and to create a methodology for reliable quantification by the X-ray diffraction technique using an Ishikawa diagram; going through an investigation on the influence of the mechanical properties of the materials and interferences that each phase acts on the measurements of the residual stresses in experiments with analysis of AISI 316L steel and duplex steel (austeno-ferritic); The thesis is not limited only to the development of the methodology but also to practical applications for assessing the tribological behavior of mechanical components and studies on better machining conditions. The study of residual stresses has huge importance for the evaluation of a component or engineering structure, considering that all manufacturing processes promote a new condition of this elastic response. One of the studies evaluated the influence of turning conditions on residual stresses in AISI 1045 steel. Another article evaluated the effects of different grades of carbide coatings and lubrication cooling techniques on tool life and surface residual stress. milled HCWCI; Concluding with the comparative study of the evolution of wear associated with residual stresses in AISI 52100 and Carbon Steel steels tested in a cam follower system. The work emphasized the importance of a well-defined methodology for carrying out residual stress measurements as well as the relevance of measures in processes involving the wear of metallic components. According to the study carried out in this thesis, the values of residual techniques measured by the X-ray diffraction are mainly steps influenced by all scales of measurement parameters and are associated with the material processing steps, with the greatest contribution being the last one.
Efeito das propriedades físicas, químicas e morfológicas na redução de arrasto do Sylgard 184 modificado por plasma no escoamento laminar
(Universidade Federal do Rio Grande do Norte, 2022-07-08) Lima, Luiz Henrique Pinheiro de; Costa, Thercio Henrique de Carvalho; Bessa, Kleiber Lima de; http://lattes.cnpq.br/3825553608740400; https://orcid.org/0000-0001-7429-4273; http://lattes.cnpq.br/3647710047561421; http://lattes.cnpq.br/3732022226834668; Feitor, Michelle Cequeira; https://orcid.org/0000-0002-4850-9493; http://lattes.cnpq.br/4011909474871656; Ortiz, Jayme Pinto; Libório, Maxwell Santana
Obtenção de revestimento cerâmico a partir da mistura de argila plástica com resíduos do caulim, da esmeralda, chamote de telha e cinza vegetal
(Universidade Federal do Rio Grande do Norte, 2012-10-11) Oliveira, Celso Luis Evangelista de; Nascimento, Rubens Maribondo do; Paskocimas, Carlos Alberto; http://lattes.cnpq.br/2365059843175411; Pontes, Luiz Renato de Araujo; http://lattes.cnpq.br/4820371851760936; http://lattes.cnpq.br/8671649752936793; http://lattes.cnpq.br/3045786915775991; Silva, Gilson Garcia da; http://lattes.cnpq.br/8681275097040450; Silva, Jaquelígia Brito da
Mineral exploration and ceramic industry cause changes in the environment natural characteristics. Mineral extraction generates mountains of waste that are discarded nearby ore beds. The production of red ceramics is developed without any concern for workers’ health and environment, generating the disposal of badly burned products and / or out of specification. In addition, wood is used as fuel, contributing to the desertification of semi-arid and caatinga regions. The ash generated is thrown nearby pottery factories, causing the contamination of soil, water and air and respiratory problems to the surrounding population. With the objective of minimizing the harmful effects to the environment, adding commercial and technological value to materiais discarded by kaolin and emerald mining industries and by potteries, this study proposed the development of products for ceramic coating based on formulations made with waste from the Processing of kaolin, emerald, tile manufacturing waste, vegetal ash and illitic clay. The raw materiais were characterized by X-ray fluorescence, X-ray diffraction, thermal analysis (thermomechanical, thermogravimetry, differential thermo analysis and termoderivative), particle size analysis and plasticity. The formulations were developed taking into consideration literature, which recommend the manufacturing of 192 specimens with 8% moisture, 13 g mass, using uniaxial pressing at 45 MPa. The specimens were dried in electric oven at 110 ° C for 24 h, sintered at temperatures of 1000, 1025, 1050, 1100, 1125 and 1150°C at a heating rate of 5 ° C / min, being submitted to technological tests and analysis of their microstructure by SEM. According to standard NBR 13817:1997, it was found that all formulations studied have produced products for ceramic coating, being classified as sandstone, semi-sandstone, semi-porous and porous porcelain, with water absorption ranging from [(0; 00 ± 0.06) to (27.97 ± 1.47)%], tensile strength from [(6.90 ± 0.66) to (51.76 ± 4.62)] MPa, depending on formulation and firing temperature.
Análise de propriedades mecânicas de pastas de cimento aditivadas com Óxido de Magnésio e Látex SBR
(Universidade Federal do Rio Grande do Norte, 2022-03-18) Ramalho, Ramón Victor Alves; Alves, Salete Martins; Freitas, Júlio Cézar de Oliveira; https://orcid.org/0000-0003-1324-9705; http://lattes.cnpq.br/2357217530716519; https://orcid.org/0000-0002-2659-4746; http://lattes.cnpq.br/8550161853747323; http://lattes.cnpq.br/4464923939795989; Santiago, Rodrigo César; http://lattes.cnpq.br/6823966481089536; Costa, Bruno Leonardo de Sena; http://lattes.cnpq.br/8841158786789727; Pereira, Dennys Salvino Sérgio
Leaks through the cement sheath have been a persistent and chronic problem in the oil industry for decades. Thus, several additives are used to strengthen the cement matrix and provide better adaptation of the slurry to the well scenario. Drying shrinkage caused by water loss and gel consolidation is a serious disadvantage of Portland cement. This shrinkage is capable of creating microcracks when the stresses are greater than the tensile strength of the cement, which significantly increases the permeability of this material. Magnesium Oxide (MgO) is an additive able of reducing drying shrinkage through structural substitutions in the cement matrix. SBR Latex is a widely used additive to prevent gas migration as it reduces fluid loss, increases acid resistance and improves the microstructural bonds of cement. Based on this, this work evaluates the influence of MgO and SBR latex additives using experimental design. The results confirm the effects of MgO and SBR latex in reducing scenarios favorable to leaks and point to a strong influence of MgO in reducing drying shrinkage and gel formation. They indicate that MgO has low influence on compressive strength in the early stages of curing but has an important influence throughout curing and also has a strong influence on the shear strength of the slurry. They show that SBR Latex is an additive able of reducing compressive strength by increasing the elasticity of the slurry and that it has little practical influence on the shear stresses. From the results obtained it's possible establish better conditions for formulating slurries that use MgO and/or SBR látex applicable in oil well cementing operations.
Estudo do efeito do teor de SiC e da moagem de alta energia na microestrutura e nas propriedades mecânicas e físicas do compósito Cu-SiC
(Universidade Federal do Rio Grande do Norte, 2021-02-05) Câmara, Nailton Torres; Costa, Franciné Alves da; Gomes, Uílame Umbelino; https://orcid.org/0000-0002-4074-0762; http://lattes.cnpq.br/9858094266525225; http://lattes.cnpq.br/8698567925323942; http://lattes.cnpq.br/4265029671192367; Silva, Angelus Giuseppe Pereira da; http://lattes.cnpq.br/1435330862718379; Silva, Ariadne de Souza; http://lattes.cnpq.br/5623381698478389; Silva, Elialdo Chiberio da; http://lattes.cnpq.br/5426129339908081; Mashhadikarimi, Meysam; http://lattes.cnpq.br/9422624675887080
The Cu-SiC composite combines high thermal and electrical conductivity and good copper ductility with good thermal conductivity, low density and high abrasion resistance of SiC. Such characteristics allow this composite to be applied as electrical contacts and heat sinks, however, the mutual insolubility of both phases difficulty to obtain by sintering. Several studies use high energy milling (HEM) to prepare powders from immiscible systems with low wettability, as it produces greater sinterability of the material through the reduction of tehe particle size and homogenization of the phases. In this work, Cu-SiC composite powders with 2, 10 and 15% of SiC were prepared by mechanical mixing and MAE. The mechanical mixing was carried out to manually mix the powders in a plastic package. The WEM of the powders was carried out in a planetary mill pulverisette 7 with pool and metal grinding hard in liquid medium of alcohol - 99.5% at 400 rpm for 2, 10, 20 and 30 hours. The mass ratio of poder/ball used was 1: 5. Cu-SiC powder compacts were pressed at 500 MPa in a uniaxial cylindrical matrix. The green compacts were sintered in a tubular resistive oven and with a dilatometric record at 1000 oC for 1 h under an argon atmosphere. The heating rate used was 10 oC / min. Analyzes of FRX, DRX, MEV and EDS were used to characterize both powders and sintered compacts. The crystallite size and the microdeformation of the Cu and SiC phases of the Cu-SiC powders were determined using the TOPAS software. Particle size distribution measurements of elementary powders (Cu and SiC) and Cu-SiC composite were performed by laser diffraction. The density of green and sintered compacts was obtained using the geometric method, and the Archimedes principle. Eletrolytic corrosion measurements were performed on the sintered compacts of mixed powders and milled for 30 h. The corrosion resistance of the Cu-SiC composite decreases significantly to a contente above 2% by mass of SiC. The density values of the sintered compacts decrease with the increase in the SiC content (0, 2, 10 and 15% w) and the grinding time (2, 10, 20 and 30 h). The sintered compacts of mixed powders Cu-2% SiC reached 77.2% relative density, while the compacts of Cu-2% SiC powders milled for 2 and 30 h obtained a relative density of 72.7 and 65.4%. The compacts of Cu-SiC powders with 10 and 15% by weight of SiC milled for 2 h obtained a density of 64.9 and 58.2%, respectively. The HV values of the sintered compacts increase with an increase in the SiC content and the highest values were obtained by compacts of Cu-SiC powder ground for 10 h. The microhardness values of these compacts of powders milled for 10 h with 2, 10 and 15% by mass of SiC reached 50.9, 83.7 and 115.6 HV, respectively. The microstructures of the sintered compacts of milled Cu-SiC powders are more homogeneous than that of mixed powders.
Estudo da densificação e microestrutura do compósito cobregrafite preparado por moagem de alta energia e sinterizado por SPS
(Universidade Federal do Rio Grande do Norte, 2020-08-28) Nunes, Evanildo Vicente de Oliveira; Costa, Franciné Alves da; http://lattes.cnpq.br/8698567925323942; http://lattes.cnpq.br/7215349710716825; Mashhadikarimi, Meysam; http://lattes.cnpq.br/9422624675887080; Torres, Marco Antônio Morales; http://lattes.cnpq.br/0091292234916055; Gomes, Uilame Umbelino; http://lattes.cnpq.br/9858094266525225; Silva, Ariadne de Souza; http://lattes.cnpq.br/5623381698478389; Macedo, Daniel Araújo de; http://lattes.cnpq.br/1027496814443777; Silva, Angelus Giuseppe Pereira da; http://lattes.cnpq.br/1435330862718379
Cu-graphite composite is a material used as electrical contacts. In this work, the effect of high energy milling on the production of Cu-graphite composite powders was investigated. The influence of the preparation of these powders on the densification and microstructure of the sintered samples was also the object of investigation, in addition to the effect caused on the electrical conductivity of this composite. The powders were prepared by manual mechanical mixing and high energy milling in the Pulveriseatte 7 and SPEX 8000D planetary mills. Cu powders and graphite in the proportion of 5 wt.% Of graphite were placed to milling in a Pulveriseatte 7 planetary mill with container and carbide balls and in a SPEX 8000D mill with container and stainless steel balls. In the planetary mill, the milling was carried out at 400 rpm under a high purity argon atmosphere for 50 h. During this time, samples of powders were collected after 2, 10, 20, 30 and 40 h of milling. The mass ratio of ball powder used was 1:5. The same argon atmosphere and mass ratio of powder to balls were used for milling in SPEX mill. Two powders were prepared at 400 rpm for 1 and 2 h of milling. Powder compacts prepared by milling and mechanical mixing were sintered by pulsed plasma (SPS) at 650, 700 and 950 °C for 5 minutes and under a pressure of 25, 40 and 50 MPa in a graphite cylindrical matrix and under a vacuum chamber. The heating rate used was 100°C/min. The SEM images associated with the EDS showed that the increase in the milling time caused a good dispersion and homogenization between the phases, as well as, a good refinement of the milled powders. The diffractograms revealed that the evolution of the milling promoted a reduction in the size of the crystallite in the copper phase. The sintered samples of the mixed powders showed higher density.
Obtenção, caracterização e viabilidade de aplicação de um compósito com matriz de resina poliéster e carga de fibras do caroço do açaí
(Universidade Federal do Rio Grande do Norte, 2018-12-21) Vieira, Ana Paula Nascimento Batista; Souza, Luiz Guilherme Meira de; http://lattes.cnpq.br/0801747108308706; http://lattes.cnpq.br/3102483476799704; Lima, Flávio Anselmo Silva de; http://lattes.cnpq.br/7506532088253804; Marques, Marcelo de Souza; http://lattes.cnpq.br/8876575945576374; Santos, Natanaeyfle Randemberg Gomes dos; http://lattes.cnpq.br/0174046631340409; Santos Júnior, Zulmar Jofli dos
New materials are being developed by adding relevant characteristics and properties, examples being the composite materials that cover different fields of engineering. This research presents the processes of obtaining and manufacturing a composite matrix of terephthalic polyester resin and loading of residues of açaí kernel fibers. Preliminary tests demonstrated the feasibility of obtaining the composite for a maximum load of 15%. The mass proportions of residues, relative to the polyester resin matrix, corresponding to 5, 10 and 15% were thus chosen. Two configurations were chosen for the composite: with treated and untreated fibers. The treatment of the fibers was carried out in order to remove impurities in hot water, for a period of thirty minutes. With the selected formulations, test specimens were produced, according to the pertinent norms, and determined the properties that characterized the composites, traction, flexion, impact, density, water absorption, aging mass loss, thermogravimetric (TG) and Electron Microscopy Scanning MEV. For all formulations the fiber residues presented satisfactory results when applied to panels for the fabrication of parts and structures, since they presented mechanical properties as described in the standard NBR 15316-3.
Modificação, caracterização de superfície de titânio CP tratado por plasma de H2 - N2 - O2 e avalição da biotividade da superfície tratada
(Universidade Federal do Rio Grande do Norte, 2021-08-10) Vitoriano, Jussier de Oliveira; Alves Júnior, Clodomiro; http://lattes.cnpq.br/7441669258580942; http://lattes.cnpq.br/6988558607381011; Moura, Carlos Eduardo Bezerra de; http://lattes.cnpq.br/4717410137206021; Amorim Filho, Jayr de; http://lattes.cnpq.br/2319345508519050; Nascimento, José Heriberto Oliveira do; http://lattes.cnpq.br/7033735079037677; Pessoa, Rodrigo Sávio; http://lattes.cnpq.br/3318707277023349
Currently, the study of oxynitrided surfaces emerges as one of the most promising ways to obtain improvements in several properties of titanium and expand its applications. In this context, the plasma-assisted surface modification technique stands out due to its versatility, low impact on the environment and for being economically viable. Thus, samples were subjected to plasma treatment for surface modification. Six study conditions were established for this doctoral work, where thermochemical treatments were carried out in plasma atmospheres containing mixtures of H2 – N2 – O2. Grazing X-ray diffraction (GIDRX), X-ray induced photoelectron spectroscopy (XPS), Raman spectroscopy and energy dispersive spectroscopy (EDS) were used for chemical composition analyses. To assess the bioactivity, the samples were immersed in a simulated body solution for 7 days. The surface energy and contact angle were obtained by the sessile drop method. The results showed that the fluxes used in the pretreatment and treatments were adequate to oxynitrite the titanium surface in a predominantly diffusive process with about 6 µm thickness. In wettability, there is a direct relationship between an increase in nitrogen flux in the working atmosphere with an increase in the contact angle and a reduction in the polar coordinate and surface tension of the treated surfaces. In the results referring to hydroxyapatite nucleation, the highest degree of bioactivity is highlighted under the experimental conditions of maximum oxygen flow and lower oxygen flow, in intermediate conditions and absence of oxygen flow, a behavior equivalent to a control sample is observed.
Obtenção de sistemas nanométricos do tipo O/A de óleos Cymbopogon Winterianus Jowitt e Azadirachta Indica A. Juss para aplicações em materiais têxteis na área da saúde
(Universidade Federal do Rio Grande do Norte, 2020-10-26) Sá, Christiane Siqueira de Azevedo; Ladchumananandasivam, Rasiah; Silva, Késia Karina de Oliveira Souto; 0000-0002-9705-6750; http://lattes.cnpq.br/4712628443097348; http://lattes.cnpq.br/8553209522282182; http://lattes.cnpq.br/0563573712770423; Nascimento, José Heriberto Oliveira do; http://lattes.cnpq.br/7033735079037677; Silva, Iris Oliveira da; http://lattes.cnpq.br/3890585112132451; Zille, Andrea; http://lattes.cnpq.br/5170871954635708; Rossi, Cátia Guaraciara Fernandes Teixeira; http://lattes.cnpq.br/0103853142184734
Technical and functional textile materials have been extensively researched and developed for being used in many areas of science, environment and technological materials. In this context, the objective of this work was to develop a functional textile material with antimicrobial properties for various applications. Natural polymers with various properties and infinite applications in the textile area were used. It is known that fibrous materials require surface modification to confer different chemical and physical properties in order to become multifunctional materials. With the advent of nanotechnology, the techniques have been developed as being essential tools to qualitatively characterize these new materials. Essential oils have long been used by the industry, but today they are also widely used for functional finishes due to their efficacy without harming the final effects of textile materials. In this way, microemulsions are mainly used due to their higher solubilization, furthermore, for their numerous applications in chemical reactions, drug delivery and nanomaterials preparation. In this work, citronella (Cymbopogon Winterianus Jowitt) and neem (Azadirachta Indica A. Juss) oils were used as solubilized antimicrobial agents, in the form of microemulsions, for textile materials. Chitosan is a bioactive natural polymer and has a wide variety of applications due to its properties, also has antimicrobial properties and in this work, its function as textile fabric surface modifying agent, where a soybean cloth was used. The commercially available essential oils were, reduced into microemulsions. Two types of emulsifiers, a surface-active agent, “tween 80,” and a vegetable surface active agent were prepared using neem oil, a surface-active agent and co-taut, with distilled water, under constant stirring. The particle sizes of the microemulsions, were in the order between 7.21 and 7.52 nm. The emulsions exhibited very good chemical stability and considerable antimicrobial properties. Through TEM analysis, the formation of droplets in the microemulsions was confirmed. The vegetable surfactants demonstrated better solubility and pH recommended for their application as surfactants, and for antimicrobial activities, which were tested against the bacteria Escherichia Coli. The clothes were treated with PI and PII microemulsions, and tested for antimicrobial activity against Staphylococcus aureus and Escherichia coli, where their growth was inhibited, considering, the bacterial activity being satisfactory, which helped in promoting its use in the surfactants to be employed in hospital environments.
Pontos quânticos de grafeno dopado/TiO2 nanoparticulado: síntese e caracterização de têxteis fotoluminescentes multifuncionais
(Universidade Federal do Rio Grande do Norte, 2020-11-30) Felipe, Brenno Henrique Silva; Nascimento, José Heriberto Oliveira do; Ladchumananandasivam, Rasiah; 0000-0002-0810-8433; http://lattes.cnpq.br/8553209522282182; http://lattes.cnpq.br/7033735079037677; http://lattes.cnpq.br/4520242315652155; Carvalho, Bruno Ricardo de; http://lattes.cnpq.br/6214643115504976; Silva, Kesia Karina de Oliveira Souto; http://lattes.cnpq.br/4712628443097348; Carastan, Danilo Justino; http://lattes.cnpq.br/7462836318959519; Zille, Andrea; http://lattes.cnpq.br/5170871954635708; Fechine, Pierre Basilio Almeida; http://lattes.cnpq.br/1184349463710551
Nitrogen-Doped Graphene Quantum Dots (N-GQDs) and TiO2 nanoparticles were applied on textile fibers to obtain new multifunctional materials with UV protection, self-cleaning and photoluminescence properties. The N-GQDs were synthesized by means of citric acid and urea pyrolysis. The TiO2 nanoparticles were synthesized via sol-gel process using titanium isopropoxide as a precursor. Cotton fabrics were coated with the nanoparticles in a hydrothermal process using polyvinyl alcohol (PVA) as a binding agent. The N-GQDs were characterized by Fourier Transform Infrared (FTIR), High Resolution Transmission Electron Microscopy (HRTEM), X-ray Diffracion (XRD), UV-vis and photoluminescence spectroscopy. TiO2 was characterized by HRTEM and XRD. The nano-coated fabrics were characterized by diffuse reflectance spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), UV-vis spectroscopy, X-ray Excited Photoelectron Spectroscopy (XPS), Atomic Force Microscopy (AFM) and XRD. Self-cleaning activity was assessed by measures of intensity of discoloration of cationic dye in the functionalized fabrics. An association between N-GQDs and TiO2 resulted in an efficiency of 91.1% in the presence of UV light in the photocatalysis of the dye. UV protection was assessed using an Australian standard and it was observed that both N-GQDs and TiO2 nanocoated fabrics as well as N-GQDs / TiO2 resulted in a level of protection classified as excellent. Thus, a new hybrid textile material was obtained.
Utilização de pós de bambu e de rejeitos de lentes oftálmicas na obtenção de compósitos poliméricos
(Universidade Federal do Rio Grande do Norte, 2021-02-05) Batista, Salomão Sávio; Souza, Luiz Guilherme Meira de; ; http://lattes.cnpq.br/7682385778883770; ; http://lattes.cnpq.br/6568697391562456; Leite, Amanda Melissa Damião; ; http://lattes.cnpq.br/3077817092155432; Moutinho, Daniel Joaquim da Conceição; ; http://lattes.cnpq.br/5956394362169556; Nascimento, José Heriberto Oliveira do; ; http://lattes.cnpq.br/7033735079037677; Santos, Natanaeyfle Randemberg Gomes dos; ; http://lattes.cnpq.br/0174046631340409
The environment has been suffering due to the indiscriminate use of natural resources and their environmental impacts. The main attacks on environmental sustainability are caused by synthetic materials and their waste. This work combines two materials that aim to contribute to this problem; one of natural origin, natural bamboo fiber of the Bambusa Vulgaris Schrad (PB) species and one of discard, ophthalmic lens waste (PRLO), both without defined application, produced in large quantities and the waste discarded irregularly in landfills. Bamboo and tailings powders were produced, with 2.07 mm and 1.14 mm granulometries, respectively. The amounts by weight of 10 and 15% PB, 15 and 40% PRLO and a hybrid composition with 5% PB and 20% PRLO were used to obtain the desired composites. The composite plates were manufactured by the cold compression wet molding process in closed mold. In the characterization it was verified the decrease of the mechanical strength of the composite in comparison to the matrix, concluding that the bamboo powders and lens rejects had a filling load function. The most expressive result of the composites was the impact resistance, corresponding to 0.55 J / cm2 for PRLO 40%, 39.6% higher than the polyester resin matrix. As a practical application, two table tops and bench tops were manufactured, using the most economically and ecologically viable composites, C4 and C2.
Obtenção de superfície seletiva do tipo armadilha ótica via oxidação por plasma eletrolítico
(Universidade Federal do Rio Grande do Norte, 2020-03-20) Silva, Hugo Fernandes Medeiros da; Alves Júnior, Clodomiro; Costa, Franciné Alves da; ; http://lattes.cnpq.br/8698567925323942; ; http://lattes.cnpq.br/7441669258580942; ; http://lattes.cnpq.br/9696293343662583; Alves, Salete Martins; ; http://lattes.cnpq.br/8550161853747323; Gomes, Uilame Umbelino; ; http://lattes.cnpq.br/9858094266525225; Rangel, Elidiane Cipriano; ; http://lattes.cnpq.br/6885205382275380; Cruz, Nilson Cristino; ; http://lattes.cnpq.br/7157327220048138
High performance solar collectors are those with selective surfaces, with high absorption of solar radiation and lower reflectance of heat radiation. One of the new strategies to improve this performance involves modifying its surfaces to obtain an optical trap structure. In this work, the plasma treatment technique called Plasma Electrolytic Oxidation (PEO), was tested to produce porosity on aluminum surfaces by a controlled manner. For this, we used a pulsed square wave voltage power supply applied at the following frequency 10 kHz. The applied current densities were 0.12, 0.15 and 0.17 A / cm2 . In addition to these variables, the duty cycle was also changed by 30, 50 and 70%. And each treatment was performed for different times duration, 2, 4 and 6 min. After the treatments, the surfaces were evaluated for their microstructure, chemical composition and optical properties. Porous aluminum oxide surfaces were produced, which are capable of absorbing radiation in the UV-Vis-NIR range. Among all treated samples, the sample treated for 6 minutes, with 70% duty cycle and 1 A applied current, was the sample that showed the most efficient absorption of solar radiation for application in the manufacture of solar collectors.
Estudo do efeito da moagem com a adição da alumina no metal duro
(Universidade Federal do Rio Grande do Norte, 2020-04-29) Leal, Erisson Aparecido de Deus; Costa, Franciné Alves da; ; http://lattes.cnpq.br/8698567925323942; ; http://lattes.cnpq.br/7599101450686139; Silva, Angelus Giuseppe Pereira da; ; http://lattes.cnpq.br/1435330862718379; Tavares, Elcio Correia de Souza; ; http://lattes.cnpq.br/4400396552273448; Alves, Salete Martins; ; http://lattes.cnpq.br/8550161853747323; Gomes, Uilame Umbelino; ; http://lattes.cnpq.br/9858094266525225
The WC-Co (carbide) composite, as well as the ceramic alumina are widely used as cutting tools in the metal-mechanic and petroleum, mining and civil construction industries due to their high hardness, high resistance to abrasion and under high temperature .This work investigates the addition of 1, 2, 5 and 10% by weight of Al2O3 to a cemented carbide powder (WC-Co) with 10% by weight of Co, the effect of preparing the composite powders by manual mixing and high energy milling and in addition, the influence of the sintering temperature on the density and microstructure of the sintered compacts. A high-energy powder 7 planetary mill was used to prepare all powders using a container with carbide balls and 99% ethyl alcohol at 400 rpm for 50 h, except for the WC-10%Co powder with 5% by weight of Al2O3 which also had a powder charge milling for 30 h. Powder samples were collected after 2, 6, 10, 20 and 30 h during milling and by manual mixing to serve as a reference. Green compacts with 5.04 ± 0.2 mm in diameter were pressed to 200 MPa in a uniaxial cylindrical stainless-steel matrix. These were sintered in a dilatometer at 1400 °C and 1550 °C for 1 h under an argon atmosphere and a heating rate of 10 °C/min. All powders and sintered compacts were characterized using particle size distribution techniques, XRD, SEM, EDS, measures of density, densification, dilatometric contraction and Vickers hardness. The compacts of composite powders WC-10% CoAl2O3 with addition of 5 and 10% of Al2O3 exhibit higher density and densification under higher temperature, however the maximum density achieved was 70% of the theoretical density both when milling for 50 h and for mixed for 10 minutes. However, compacts of composite powders WC-10%Co-5%Al2O3 milling for 30 h sintered at 1550 °C exhibit denser microstructures with a density of 91% and a densification of 87%, in addition to a hardness of 500 HV.
Desenvolvimento de ferramentas de corte autolubrificantes compostas por WC-Co e lubrificantes sólidos
(Universidade Federal do Rio Grande do Norte, 2021-02-26) Albano, Wendell; Alves, Salete Martins; Filgueira, Marcello; ; ; ; http://lattes.cnpq.br/4444267211330113; Melo, Anderson Clayton Alves de; ; Silva, Angelus Giuseppe Pereira da; ; Ventura, Carlos Eiji Hirata;
There is currently a trend in the industry that aims to reduce or eliminate the use of cutting fluid in machining operations. The use and disposal of this material at the end of its life, harms the environment. In order to reduce environmental damage, dry cutting techniques have been employed in some machining operations. This work aims to develop self-lubricating cutting tools for machining, and its application in dry machining operations. The tools will be produced through the technique Spark Plasma Sintering (SPS), which has the characteristics of consolidating powder structures through the simultaneous application of pressure and temperature. The solid lubricants studied to insert self-lubricating characteristics in the tools were Molybdenum Disulphide (MoS2) and Graphite (C). Samples with different compositions were sintered in a cylindrical format to investigate the effect of adding solid lubricants on their properties of hardness, compressive strength and wear resistance. The compositions with the best results were selected for a second stage, the sintering of cutting tools with commercial geometry. The compositions with MoS2 did not stand out in the initial characterizations, and were not selected for the second stage. With the results, tools with SNGN 12 04 12 geometry were manufactured composed of WC - 10% Co and Graphite. and then were evaluated in dry turning tests. Then, these inserts were evaluated in dry turning tests of the aluminum alloy 6351 T6, having produced results considered satisfactory, in order to characterize the tools as self-lubricating.
Dinâmica não linear e controle de osciladores inteligentes
(Universidade Federal do Rio Grande do Norte, 2020-10-05) Freitas Neto, Felipe Rodrigues de; Bessa, Wallace Moreira; ; http://lattes.cnpq.br/3256782908311485; ; http://lattes.cnpq.br/0320581384445966; Zachi, Alessandro Rosa Lopes; ; http://lattes.cnpq.br/3410411498624892; Savi, Marcelo Amorim; ; http://lattes.cnpq.br/1224532648969159; Araújo, Marcio Valério de; ; http://lattes.cnpq.br/0827462439273599; Freire Júnior, Raimundo Carlos Silverio; ; http://lattes.cnpq.br/1042806990155996
Problems involving mechanical vibrations are common in virtually all branches of industry. In order to try to suppress or control these vibrations, several methods and techniques have been developed over the last decades and continue today, mainly due to the growing needs of engineering. Among the techniques used can be cited the use of intelligent materials and smart structures. These materials exhibit a non-linear behavior, and depending on the parameters of the dynamic system that employ them, they may present periodic, almost periodic and chaotic responses. Given this wealth of responses, there is an increase in the complexity of predicting their behavior and applying an effective control technique. The present work presents a study of the nonlinear dynamics of an oscillator with intelligent materials and seeks to bring the system to a desired state using a robust control technique aided by an Radial-Basis Function Networks. A demonstration of the robustness of the technique is presented using Lyapunov’s theory of stability and Barbalat’s lemma. Before applying this control technique, a prior study of the static behavior of Shape Memory Alloys Composites (SMAC) is carried out, followed by a dynamic study where tools such as the Bifurcation Diagram and the Largest Lyapunov Exponent are explored to extract more information about the dynamics presented by oscillators with such materials. Specific cases are presented to verify the effectiveness of the control technique, which must be robust, capable of learning, adapting and predicting. As a result, the control technique used was able to control oscillators with Shape Memory Alloys (SMA) and Shape Memory Alloy Composites in the face of non-linearities such as hysteresis, dead-zone and saturation, with fluctuations in the parameters and and the lack of system dynamics. The control technique was also able to control the chaotic oscillator responses.

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