Engenharia de Materiais (UACSA)

URI permanente desta comunidadehttps://arandu.ufrpe.br/handle/123456789/2913

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Produção de nanopartículas magnéticas aplicada ao processo de tratamento de efluentes oriundos das indústrias têxteis
(2018-08-27) Damasceno, Bárbara Souza; Araújo, Ana Cláudia Vaz de; http://lattes.cnpq.br/6861890992609511; http://lattes.cnpq.br/6533105269743189
Iron oxide magnetic nanoparticles (NPs) were synthetized by chemical coprecipitation method under ultrasound. Synthetized NPs were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, porosimetry and magnetometry. The crystalline phase of the obtained NPs was identified as maghemite and the crystallite average size was estimated by Scherrer equation around 31.5 nm. The FTIR spectra presented distinct absorptions bands at corresponding to intrinsic stretching vibrations of Fe–O bond at the iron oxides. Langmuir and BET surface areas of as-formed samples is 220,15 ± 19,81 m2 g-1 and 127,19 ± 4,94 m2 g-1 respectively. NPs samples present ferromagnetic behavior and saturation magnetization (SM) value of 46 emu g-1. Adsorption performances on synthetized and commercial nanoparticles were investigated and compared. The influences of parameters including pH, dye concentration, and agitation time have been investigated in order to find the optimum adsorption conditions. Parameters as pH 4.0, with 150 min of contact time and dye concentration of 20 mg L-1 were chosen. Adsorption results indicate that the isotherm and kinetics for dye adsorption on NPs obey Freundlich isotherm and pseudo-second-order kinetic, respectively. The maximum dye (20 mg·L-1) removal efficiency to maghemite NPs was found to be 43% and to commercial magnetite NPs was 33%. For the same experimental conditions, maghemite also had better application of the available area for adsorption than the magnetite NPs, presenting values of 8.80 mg g-1 and 6.12 mg g-1, respectively.
Aplicação de nanomateriais advindos de biomassa para tratamento de águas residuárias da indústria têxtil
(2019-01-25) Nascimento, Rizia Keila do; Araújo, Ana Cláudia Vaz de; http://lattes.cnpq.br/6861890992609511; http://lattes.cnpq.br/8972131109377770
The inadequate disposal of industrial effluents has caused serious problems of environmental contamination worldwide. In the textile pole of Pernambuco some cases of river pollution were reported due to the process of dyeing and washing of fabrics. In this work, the feasibility of the use of nanostructured carbonaceous materials (CN) in the adsorption of textile dyes is studied. To obtain the carbonaceous material sugarcane leaves were used, these were washed, dried, crushed and submitted to hydrothermal synthesis. The samples were characterized by X-ray diffractometry (XRD), infrared (IR) spectroscopy, thermogravimetric analysis (TGA) and porosimetric analysis. The synthesized materials were presented as finely divided dark powders. In adsorption analyzes of the indigo carmine and red congo dyes the nanomaterials showed to be promising adsorbents. It was possible to observe a favorable behavior in relation to the adsorption of the dyes in liquid medium. The Langmuir, Freundlich and Redlich- Peterson isotherm models were suitable for the studied materials. The kinetic adsorption analysis suggests a pseudo second order behavior. The adsorptive mechanism of the nanomaterials could be characterized as heterogeneous, with adsorbate / adsorbent interactions of a chemical nature, where adsorption in monolayers is carried out at low concentrations and in multilayers at high concentrations of dye.
Análise do processo adsortivo de corantes industriais por nanopartículas magnéticas de magnetita (Fe3O4)
(2019-07-08) Cabral, Ariane Nathália de Siqueira Souza; Araújo, Ana Cláudia Vaz de; http://lattes.cnpq.br/6861890992609511; http://lattes.cnpq.br/3246406733304902
Environmental degradation is an inevitable factor that accompanies the development of the population and unfortunately this has reached water systems, rivers and water sources. Among the agents that contribute to the contamination and degradation are the dyes from the textile and food industries that are discarded throughout the production processes. There are several methods being developed to eliminate the effluent dyes in rivers and springs, among which is the adsorption process. The magnetic nanoparticles of magnetite (Fe3O4) have been previously tested in the adsorption of dye residues from the textile and food industries. In this context, the objective of this work was to study the efficiency of magnetic nanoparticles of magnetite (NPs) in the adsorption process of some dyes present in industrial textile effluents, such as dyes, methyl orange (MEL) and methylene blue (AM) . A factorial design 2³ was established obtaining as factors studied time, pH and temperature, and for these factors its levels were analyzed. Analyzes were made for systems under ultrasound and under magnetic stirring, and for this, significant results were obtained for the two dyes. According to the results obtained for the ALM / NPs, factors such as time and pH with greater significance. It was observed that the most successful tests for adsorption were the tests 02 (11,362) and 06 (10,057), for the systems under ultrasound and under magnetic stirring, respectively. For the AM / NPs it was significant only the factor, time. The most favorable tests for the dye adsorption system were 04 (19,144) and 06 (21,457), for systems under ultrasound and under magnetic stirring, respectively.
Influência da tensão, velocidade de alimentação e DBCP na resistência à corrosão de revestimentos à base da liga inconel 625 depositada por MIG
(2019-07-09) Lima, Igor Jaloto de; Santos, Aureliano Xavier dos; http://lattes.cnpq.br/0810494477757052
Annually, high investments are made in the maintenance of pipelines used in the oil industry around the globe. Thus, solutions are sought that combine low cost, reproducibility and properties that are consistent, mainly against corrosion. One of these is the use of materials that have high mechanical and anticorrosive properties in the form of coatings, which could be deposited by welding. The objective of this study was to evaluate the effects of different welding parameters on the corrosion resistance of coatings based on the Inconel 625 alloy, deposited by MIG process in API 5L X70 steel. The parameters were optimized using the factorial experimental design and the results analyzed by the Response Surface Methodology (RSM). Three deposits with ½ overlap were performed by MIG welding process, followed by a cross section cut in the samples for analysis of the dilution, iron content and corrosion resistance by linear potentiodynamic polarization (PPL) through corrosion potential (Ecorr), corrosion current (Icorr) and polarization resistance (Rp). The coatings obtained presented values of the dilution ranging from 5.8% to 15.01%. The coating that presented lower dilution value, also was the one with lower Icorr and Fe, besides higher Rp and Ecorr, thus, greater corrosion resistance.
Síntese de nanomateriais de grafeno para utilização em nanocompósitos poliméricos
(2019-07-11) Nogueira, Nathália Maria Barbosa; Ghislandi, Marcos Gomes; http://lattes.cnpq.br/3409757365313853; http://lattes.cnpq.br/3264027755950807
Because of its unprecedented physical and chemical properties, graphene has attracted the attention of researchers searching to produce composite materials with unique properties. In this way, it has been studied the incorporation of graphene oxide loads into polymers and analyzed their influence on the mechanical, electrical and thermal behavior of the resulting composites. In this work, we present the preparation and the influence of the incorporation of graphene oxide (GO) on polyvinyl alcohol (PVOH). The mechanical reinforcement, by the incorporation of 0.5 wt%, 0.1 wt% and 1 wt% of graphene oxide into the polymer matrix, was estimated. The strategy involved the production of graphite oxide from graphite, using the modified Hummers method. The method was carried out by the addition of sulfuric acid (H2SO4), potassium permanganate (KMnO4) and hydrogen peroxide (H2O2), followed by the exfoliation of graphite oxide into sheets of graphene oxide by the use of ultrasound, and finally the preparation of the GO / PVOH nanocomposites by a simple solution mixing method. The synthesized materials were characterized by X-ray diffraction, Raman spectroscopy, and gravimetry. The analysis of the GO / PVOH films were carried out via tensile and UV-vis tests. Gravimetry showed that the solution of graphite oxide synthesized had a homogeneous concentration. X-ray diffraction (XRD) showed that the oxidative process of graphite precursor into graphite oxide was efficient. The stress-strain analysis confirmed the increase in mechanical strength of the polymeric film with the incorporation of graphene oxide load, while for the strain it was not possible to obtain conclusive data. The optical analysis showed a whitening of the film during the tensile test, indicating an alignment of the polymer chains and crystallization of the films. The UV-vis spectra showed that the pure PVOH film exhibited a high transparency, however, for the films with 0.1wt%, 0.5wt% and 1.0wt% GO this transparency decreased considerably.
Caracterização de matérias-primas cerâmicas utilizadas na produção de placas de revestimento em indústria do Cabo de Santo Agostinho
(2019-12-10) Silva, Renata Arcelino da; Diniz, Verônica Cristhina de Souza; http://lattes.cnpq.br/9239037374332331; http://lattes.cnpq.br/4639841941851252
Properties of ceramic products are related to initial characteristics of raw materials, so it is important to study them to obtain a quality product. In this study, aimed to evaluate clay composition and study physical-mechanical behavior of different raw materials used in production of ceramic tiles, allowing their analysis and processing in a simple, controlled and standard. Six unidentified raw materials donated by a ceramic coating industry from Cabo de Santo Agostinho were used. The samples were benefited and characterized per X-ray diffraction (XRD), Energy-dispersive X-ray spectroscopy (EDX) and sedimentary particle size. After, raw materials were uniaxial pressing and subjected to controlled burning at 1000 ºC/ 1h with rate of 5ºC / min. Then, properties were evaluated per of linear shrinkage, water absorption, apparent porosity and flexural strength. The samples presented crystalline phases of kaolinite, quartz, mica and smectite, besides of alkaline oxides. The mechanical properties of samples showed the highest plasticity index (18%) and maximum strength went MP1 and MP6, 18% and 20.45 MPa, respectively. Thus, the raw materials presented physical properties for use in various applications in ceramic tile, such as ceramic.
Influência da corrente e taxa de alimentação na resistência à corrosão de revestimento à base da liga INCONEL 625 depositada por PTA-P
(2019-12-10) Soares, Breno Luiz Santos; Santos, Aureliano Xavier dos; http://lattes.cnpq.br/0810494477757052
Nowadays, the oil exploration process is still greatly affected by pipeline failures, which delay the production schedule, creates high maintenance costs, and creates risks to the environment and health. Thus, the search for less costly alternatives to minimize these impacts is constant, especially against failures due to corrosion. One of these is the use of materials that have high mechanical and anticorrosive properties in the form of coatings, which could be deposited by welding. The objective of this study was to evaluate the effects of the welding current and feed rate on the corrosion resistance of coatings based on the Inconel 625 alloy, deposited by PTAP process in API 5L X70 steel. The parameters were optimized using the factorial experimental design and the results analyzed by the Response Surface Methodology (RSM). Three deposits with ½ overlap were performed by PTA-P welding process, followed by an analysis of the dilution, iron content and corrosion resistance by electrochemical measurements. The coatings obtained with lower welding current and feed rate values showed better anti-corrosion properties.
Síntese e caracterização de um nanocompósito de grafite magnético para adsorção dos corantes Reactive Black 5 (RB5) e Azul de Metileno (AM)
(2019-12-13) Damasceno, Bárbara Souza; Araújo, Ana Cláudia Vaz de; http://lattes.cnpq.br/6861890992609511; http://lattes.cnpq.br/6533105269743189
Magnetic graphite nanocomposite (NGM) based on magnetic nanoparticles (NPs) and graphite nanoplatelets has been synthesized by a novel hydrothermal synthesis route. NGM and its precursors were characterized by X-ray diffraction (XRD) and infrared spectroscopy (FTIR). The nanomaterial discoloration efficiency (%Ads) using reactive black 5 (RB5) and methylene blue (AM) textile dyes in aqueous solution as target pollutant were evaluated. The influence of adsorptive parameters on effluent discoloration efficiency responses was evaluated from a 23 factorial design and the response surface analysis of central rotational composite design. Adsorption parameters evaluated include: adsorbent mass, adsorbate concentration and agitation speed. It was observed that the parameters agitation speed (rpm) and concentration of adsorbate (mg L-1) are the factors more significant than any other combination and it is highly indicated that they should be parameterized in combination. NGM statistical results showed %Ads ~98% in the RB5 removal, extremely high adsorption velocity, since it reached the adsorption equilibrium within 10 minutes of contact with the adsorbate and it presented 99% adjustment for pseudo first and second order kinetics, besides it presented a maximum adsorptive capacity of ~93 mg g-1 for the adjustment of Langmuir model, predominant in this system. The %Ads of AM onto NPs and graphite was ~59% and 100%, respectively. The study shows that NGM can be magnetically separated from the aqueous solution without introduce any byproduct during adsorption and presented favorable adsorptive properties, which makes evident its applicability of use as environmental remediator. The application of this synthetic rout becomes of technological interest when, besides being unprecedented and low cost, NGM adsorptive properties are attractive to effectively discolor wastewater.
Resistência mecânica e térmica de compósitos reticulados de PVA/óxido de grafeno
(2019-12-19) Silva, Felipe de Andrade Oliveira; Ghislandi, Marcos Gomes; http://lattes.cnpq.br/3409757365313853; http://lattes.cnpq.br/0379100954556428
PVA composite films with citric acid and graphene oxide were synthesized via drop casting and crosslinked by heat treatment at 140° C for two hours. The influence of loads on mechanical, thermal and optical properties were characterized by tensile tests, thermogravimetry. and UV / VIS spectroscopy. The combined use of citric acid and graphene oxide proved to be very effective in promoting an increase in mechanical strength from 11.3 ± 1.4 MPa (pure PVA) to 37.1 ± 2.1 MPa (heat treated sample and 5% citric acid and 0.5% graphene oxide). However, there was a reduction in the maximum deformation from 333.0 ± 80.8% (pure PVA) to 84 ± 14%. The highest values obtained represent a 228% increase in mechanical strength and a 56% reduction in maximum deformation. The thermal stability of the films was analyzed by thermogravimetry; The addition of the fillers together with the heat treatment resulted in an increase in the degradation temperature from 269 ° C (pure PVA) to 325 ° C for the sample with 5% citric acid and 0.5 % graphene oxide. Optical properties were investigated by UV / VIS spectroscopy where yellowing due to heat treatment represented by a reduction in transmittance of 300-450 nm was observed. Keywords: Composites. Graphene. Cross-linking
Otimização da operação de britagem de peças de refugo no processo produtivo de uma empresa cerâmica
(2020-10-24) Silva, Robson de França; Fonseca, Juliana de Castro Macedo; http://lattes.cnpq.br/8869180950884002; http://lattes.cnpq.br/5901815548984027
Crushing is a unitary operation that aims at the fragmentation of a certain material, usually coming from mines, into smaller parts. This process is commonly used in the initial stages of production, but there are also ceramic industries that use the crusher as a means of transformation for the scrap of production to be used as a raw material. Therefore, this study aims to increase the efficiency of the crushing process of scrap parts in a ceramic industry. For this purpose, a brainstorming was done together with collaborators, and then data were created to size the operation (such as time to feed the crusher, time needed to crush a pallet with scrap parts, time needed to remove the scrap label, quantity of parts sent per day to the scrap, among others). With these data and parameters established, a study was made to know which factors were more harmful to the process, and it was discovered that the step of the removal of the indicative label of scrap was wasting a lot of time. Thus, the influence of the label material on the characteristics of the barbotine and part after sintering was studied. Rheological tests of barobotin and mechanical tests of compression, color, shrinkage and loss to the furnace of the sintered part were performed. It was verified that the label did not alter neither the properties of the casbutin nor the properties of the sintered part, being this step eliminated from the process and it was possible a 20% increase in the quantity of crushed pallets, besides a saving of almost 7 thousand reais per year.
Aumento da produtividade através da aplicação da metodologia World Class Manufacturing (WCM) com foco no pilar Workplace Organization (WO) em uma linha de montagem do setor automotivo de Pernambuco
(2020-11-04) Costa, Laís Martins Correia da; Figueiredo, José Fernando Dagnone; http://lattes.cnpq.br/0648307320706020; http://lattes.cnpq.br/5181183753810801
The Word Class Manufacturing (WCM) emerges as an efficient and effective management model, based on the concepts of zero waste, zero breaks, zero defects and zero stock, ensuring the safety of all employees, quality in all parts and high performance production. The main objective of this work was to show how to increase the productivity of a production line of the Industry of the automotive sector of Pernambuco with a focus on the application of the reactive and preventive concepts and tools of the pillar, Workplace Organization (Organization of the Workplace - WO), through the implementation of Kaizens referring to steps (steps) 1,2,3,4 and 5. The results obtained reveal that the objective was achieved and that the expansion of activities to similar production lines is possible, proving the efficiency of the method
Efeitos da temperatura no comportamento mecânico de matérias-primas utilizadas na produção de cerâmica de revestimento em indústria do Cabo de Santo Agostinho – PE
(2021-01-30) Silva, Renata Arcelino da; Diniz, Verônica Cristhina de Souza; http://lattes.cnpq.br/9239037374332331; http://lattes.cnpq.br/4639841941851252
The properties of ceramic tiles are dependent on their chemical composition and on the microstructure developed, mainly during the heat treatment to which they are developed. In this study, aimed to evaluate the influence of temperature on the mechanical behavior of ceramic raw materials of different compositions used in production of ceramic tiles, allowing their analysis and processing in a simple, controlled and standard. Six raw materials donated by a ceramic coating industry from Cabo de Santo Agostinho - Pernambuco were used. Samples of raw material were compacted by uniaxial pressing, then subjected to controlled sintering at 1000, 1100 and 1200 ° C for 1h, with a heating rate of 5ºC / min. Then, properties were evaluated per of linear shrinkage, water absorption, apparent porosity and flexural strength. The samples MP5 showed a good mechanical performance in relation to temperature variation, showed maximum strength, 45.27 MPa at 1100ºC, associated with low porosity (2.34% at 1100ºC) and the minimum concentration of internal cracks resulting from the low retraction of the part (6.34% at 1100ºC). Therefore, the raw materials presented physical properties for use in various applications in ceramic tile.
Adsorção de corantes em materiais híbridos obtidos de biomassa pirolisada com nanopartículas magnéticas
(2021-03-05) Nascimento, Rizia Keila do; Araújo, Ana Cláudia Vaz de; http://lattes.cnpq.br/6861890992609511; http://lattes.cnpq.br/8972131109377770
The adsorption of residues in aqueous medium is an effective process for treating effluents from the textile industry. Several materials have been developed for this purpose, and their adsorptive capacity has been thoroughly studied. In this work, a new adsorbent material was synthesized by a hydrothermal route. This hybrid material (named HB) is formed by biomass residue (sugarcane straw) and magnetite nanoparticles (NPs), an iron oxide. The magnetite cubic phase in HB was identified by X-ray diffraction. The Fe-O vibrational band, characteristic of iron oxide, was observed by infrared spectroscopy. HB presented a globular morphology, with a wide range of size (between 500 nm and 2 m). The performance of HB as an adsorbent was evaluated through the adsorption of the dyes Congo Red (VC) and Indigo Carmine (IC). The concentrations studied varied between 6.97 and 69.67 mg.L-1 for VC and between 4.66 and 46.64 mg.L-1 for IC. The adsorption kinetics curves showed that the saturation time of HB for both dyes was around 120 h. Most of the adsorption (around 71 % for the VC and 28 % for the IC) occurred in the first 24 h of contact between the adsorbent and the dyes. This indicates the feasibility of using HB on an industrial scale, mainly in the treatment of water contaminated by VC residues. The adsorption kinetics for both systems followed the Pseudo Second Order model, with 99% correlation for VC, and 82% for IC. For the adsorption isotherms, the Langmuir, Freundlich and Temkin models satisfactorily described the HB/VC system (above 95 % correlation) and the Freundlich and Temkin models described HB/IC (above 92 % correlation). The results presented show that HB has potential for adsorption of dyes in aqueous medium.
Aplicações de simulações computacionais para melhorias e redução de custos no processo de injeção de termoplásticos
(2021-07-14) Ribeiro, Rayanne do Nascimento Guerra Melo; Figueiredo, José Fernando Dagnone
The present project is intended to study the importance using computer simulations with the Inventor Moldflow 2019 software to study the main defects and the possibility of cost reduction in the thermoplastic injection process as a benefit of using industry 4.0 concepts. For this, thermoplastics High Density Polyethylene (HDPE or HDPE) and Polypropylene (PP) were studied to simulate the injection process of the plastic component of the domestic orange juice cone. The results induced that the injection parameters are influenced by the morphological properties of the polymers, with the crystallinity being directly induced in the contraction and injection pressure of thermoplastics. So, it was possible to show the potential of computer simulations as a tool for cost reduction in the thermoplastic injection process.
Avaliação do uso de politereftalato de etileno (PET) pós consumo na indústria de embalagens alimentícias
(2021-07-15) Silva, Bárbara Stefany Lima Da; Andrade, Daniela de Lourdes Anjos Coutinho Simões; http://lattes.cnpq.br/8149955436222196; http://lattes.cnpq.br/0185643398779242
The environmental appeals and the high percentage of Poly (Ethylene Terephthalate) - PET waste, discarded in nature, often inappropriately, drive the packaging market to seekalternatives for the use of post-consumer recycled PET (PET-PCR). In order to assist in this purpose, this work evaluated the feasibility of using 100% recycled PET as a raw material in the production of food packaging. For this purpose, PET-PCR was injected ina two-stage Husky injection molding machine with a 48-cavity mold. The results were compared with those of virgin PET (PET-V), a raw material already used, in order to evaluate the influence of the resin type used on the quality and viability of the preform for application in the packaging sector. The green coloring additive was added in both formulations, with 0.04% and 0.07%, by mass for PET-V and PET-PCR, respectively, to guarantee the color required in some types of carbonated beverages. According to the results obtained, the parameters established for the PET-PCR forming process did not cause injection defects or great divergences in relation to PET-V. Through intrinsic viscosity analysis, visual inspection, colorimetry and differential scanning calorimetry (DSC), it was noticed that PET-PCR is more susceptible to degradative hydrolytic fissionreactions, as expected, since it is a resin which has a thermal history, but these reactions do not make its use unfeasible in food packaging. The gas chromatography results show that the injection process used for PET-V provided higher acetaldehyde contents, this result was attributed to the more aggressive conditions during the extrusion step and, finally, the specific migration test showed that the PET- PCR is within the limits applicable according to the Brazilian Legislation for Carbonated Drinks (ANVISA - Technical Information No. 71 of February 11, 2016). Thus, PET-PCR can be used in theproduction of food packaging since the deviations found are purely esthetic and do not interfere with its quality and applicability.
Aplicação das ferramentas da qualidade para a redução das perdas de qualidade numa linha de fabricação de massas
(2021-07-15) Cabral, Ariane Nathália de Siqueira Souza; Araújo, Ana Cláudia Vaz de; http://lattes.cnpq.br/6861890992609511; http://lattes.cnpq.br/3246406733304902
The competition between companies that work with production in general, forces them to implement improvements in their management and control systems, aiming to reduce losses in production processes. This work was developed in a pasta factory located in the city of Jaboatão dos Guararapes in Pernambuco. The objective of this work was to diagnose and reduce losses in a pasta production line. A survey of losses was made in a production line of Ninho noodles, for a period of six months. The cost of existing losses was estimated, and the responsible sector stipulated a 40% reduction in this cost in the line under study. A study of the operation of this line was carried out. It was found that the main sites for reprocessing were in the press, in the drying tunnel, in the wire mat and in the elevator belt. Thus, from the 5 whys tool, the root causes of the problem were obtained: wire and elevator belt. From the application of the PDCA cycle, the actions were successfully carried out with a reduction of 61% of the non-conformity of the Reprocessing in the Nest-type noodle line. This loss reduction in the four months of the project due to Reprocessing, generated an annual gain of 25.1 ton/year, which means an annual gain of R$ 115,290.00 for the company.
Análise do tempo mínimo de cura de adesivo de poliuretano utilizado na laminação de filme de poliéster e polietileno
(2021-11-29) Brito, Venicius Leony de França; Fonsêca, Juliana de Castro Macêdo; http://lattes.cnpq.br/8869180950884002; http://lattes.cnpq.br/6624281780568416
A mixture of solvent-based polyurethane adhesive and ethyl acetate was prepared and applied to 12 μm polyester films with a coating machine, followed by an overlay with a 36 μm lowdensity polyethylene film of thickness. The obtained sample were conditioned in an oven at different temperatures in a humid environment, at intervals of 2, 4, 6, 8, and 24 hours. After this period, the variation of the adhesive cure as a function of temperature and time was endorsed through the analysis of Infrared spectroscopy with Fourier Transform using the Attenuated Total Reflectance technique (FIIR-ATR) with germanium crystal. Through analysis of 2270 cm-1 FTIR band. The aim of this work is to determine the shortest cure time for adhesives used in PET and PE lamination, using Fourier Transform infrared spectroscopy and Attenuated Total Reflectance technique.
Luminescência e estrutura dos nano cristais de LaF3:Ln3+ (Ln3+ = 5%Tb3+ ou 5%Eu3+): mistura de estado solido para obtenção de luz ajustável por cor no verde-vermelho
(2021-12-01) Assis Junior, Itamar Nunes de; Dousti, Mohammad Reza; http://lattes.cnpq.br/4499267719558750; http://lattes.cnpq.br/3435092289432408
Nanocrystals co-dated with the Tb3+ and Eu3+ ions have been of interest to many researchers for obtaining color-adjustable light from yellowish green to red-orange and for obtaining white light-emitting diodes in recent years. In these systems, the energy transfer between Tb3+ as an activator and Eu3+ as a sensitizer is exploited for the development of functional optical materials. In this work, the host, the LaF3 nanocrystal, is doped with 5% Tb3+ or 5% Eu3+ and heat-treated at 500°C for 3h [2] and mixed in proportions ranging from 15 to 85% of the rare earth. The mixtures were excited at 377 nm and their emissions spectra were investigated bymainly considering the emission bands at 548 nm of Tb3+ and 596 nm of Eu3+ which could be used to generate the adjustable light in the green to red spectral region which showed an excellent potential for emissions in this spectrum band with no evidence of radiative energy transfer and with transitions in levels. Moreover, the structures of the nanoparticles were investigated to confirm their monophasic crystalline nature and the effectiveness of the thermal treatment and it was found the formation of a nano particles with an average size of 15 nm and a surface free of pores and roughness. The lifetimes of the excited state were also measured for the proposed mixed systems, which remained with values between 53 to ≈ 93 µs for the 548 nm emission of Tb3+ and from ≈ 19 to ≈ 28 µs for the 596 nm emission of Eu3+, in order to investigate possible energy transfers between two rare earth species and to understand how this could affect the generation of color-adjustable light.
Análise da resistência a corrosão do aço API 5L X70 revestido com inconel 625 por soldagem plasma pó e por arco submerso
(2021-12-09) Ferreira, Beatriz Cândida de Farias; Santos, Aureliano Xavier dos; http://lattes.cnpq.br/0810494477757052; http://lattes.cnpq.br/8533374114394812
Annually, the oil industry invests large amounts in pipeline maintenance, mainly in anti- corrosion measures. Thus, solutions are sought that combine low cost, reproducibility and consistent properties. One of them is the use of materials that have high mechanical and anti- corrosive properties in the form of coatings that can be deposited by welding. This study aimed to evaluate the effects of different welding parameters on the corrosion resistance of inconel 625 alloy coatings deposited by API 5L X70 steel by the PTA welding process , evaluate samples with higher and lower dilution and use the parameters of these experiments to perform SAW submerged arc welding coating in order to compare the processes. The parameters were optimized through factorial experimental design and the results analyzed by the Response Surface Methodology (MSR). The samples were mainly evaluated by dilution (D), iron content (Fe) and resistance to corrosion by linear potentiodynamic polarization (PPL).
Estudo da influência da temperatura na alteração do revestimento permanente do fundo de uma panela de aço em uma aciaria elétrica
(2022-01-09) Diniz, Emilly Vithória Oliveira Rocha; Diniz, Verônica Cristhina de Souza; http://lattes.cnpq.br/9239037374332331; http://lattes.cnpq.br/4526803179109939
Steel is an iron-carbon alloy, which can be used in the most diverse sectors of the economy due to its low manufacturing cost and its chemical and mechanical properties. Refractory materials are part of the manufacture of steel through the composition of the internal lining in the equipment used in the manufacture of the same. Different types of refractory materials can be applied in these equipments, namely: dolomitic, magnesium, aluminous. In the present work, the modification of the thickness of the permanent coating of the steel ladle will be discussed in order to increase the weight of cast steel, performing the necessary measurements and comparisons to guarantee operational safety, obtaining results within the established limits, enabling the change.