Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-02-21T21:14:12Z No. of bitstreams: 1 AnaPaulaPereiraFulco_TESE.pdf: 5611369 bytes, checksum: 90dd17509ac9fc7af5b3bb30ec9b9fd9 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-02-22T20:47:30Z (GMT) No. of bitstreams: 1 AnaPaulaPereiraFulco_TESE.pdf: 5611369 bytes, checksum: 90dd17509ac9fc7af5b3bb30ec9b9fd9 (MD5) / Made available in DSpace on 2018-02-22T20:47:30Z (GMT). No. of bitstreams: 1 AnaPaulaPereiraFulco_TESE.pdf: 5611369 bytes, checksum: 90dd17509ac9fc7af5b3bb30ec9b9fd9 (MD5) Previous issue date: 2017-11-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Materiais comp?sitos de matriz polim?rica refor?ados com fibras de carbono utilizados em estruturas aeron?uticas e aeroespaciais est?o frequentemente sujeitos ? carregamentos c?clicos e condi??es ambientais de temperatura e umidade, que podem provocar degrada??o e at? a falha do componente. O objetivo deste trabalho foi estudar os efeitos do envelhecimento sob exposi??o a temperatura at? 160?C e ? umidade nos mecanismos de dano de comp?sitos carbono/ep?xi submetidos a carregamento c?clico. Um estudo preliminar de envelhecimento acelerado foi inicialmente realizado em comp?sitos unidirecionais AS4/8552 com ciclo exposi??o de 8 h de radia??o UVA-340 a 80?C seguidas de 4 h de condensa??o a 50?C, at? atingir o tempo total de 2.160 h. Os efeitos do envelhecimento do material foram evidenciados pela perda de massa, exposi??o das fibras, altera??es qu?micas, aumento da densidade de trincas em testes de cisalhamento interlaminar e flambagem das fibras em amostras fraturadas em testes de compress?o, embora n?o tenham sido observadas altera??es significativas nas propriedades mec?nicas do material. Com base neste trabalho preliminar, um estudo foi realizado em laminados [02/902]s do mesmo material, utilizando ciclo de exposi??o de 8 h a 160 ?C seguidas de 4 h com umidade relativa de 80% a 70 ?C, at? atingir o tempo total de 2.880 h. Em seguida, as amostras foram submetidas a ensaios de fadiga com controle de carga, com raz?o de tens?es R = 0,1 e frequ?ncia de 5 Hz. Os comp?sitos foram caracterizados por espectroscopia de infravermelho com transformada de Fourier (FTIR), an?lise din?mico mec?nica (DMA), microscopia eletr?nica de varredura (MEV) e varia??o de massa, antes e ap?s a exposi??o higrot?rmica. Amostras de ep?xi puro 8552 foram tamb?m expostas as mesmas condi??es de envelhecimento e caracterizadas por microscopia ?tica (MO), espectroscopia FTIR e varia??o de massa. A partir dos diagramas de vida em fadiga, uma fun??o de deslocamento (shift) foi proposta para a previs?o de n?mero de ciclos para falha de comp?sitos envelhecidos com base em dados de testes de fadiga em comp?sitos n?o envelhecidos. O estudo tamb?m mostrou que a falha por fratura pode n?o ser o melhor par?metro para avalia??o do efeito do envelhecimento higrot?rmico na vida em fadiga de materiais comp?sitos de matriz polim?rica refor?ados com fibras de carbono. Outros par?metros como delamina??o e satura??o de trincas s?o tamb?m essenciais para avaliar a durabilidade desses materiais comp?sitos. / Carbon fiber reinforced polymer (CFRP) composites used in aeronautic and aerospace structures are often exposed to cyclic loading and environmental effects such as temperature and humidity, which can lead to degradation and failure of the component. The objective of this work was to study the effects of aging under exposure to temperature up to 160?C and humidity on the damage mechanisms of carbon/epoxy composites subjected to cyclic loading. Initially, a preliminary accelerated aging study was conducted with unidirectional AS4/8552 samples using an exposure cycle of 8 h of UVA-340 at 80 ?C followed by 4 h of condensation at 80 ?C, for a total exposure period of 2,160 h. The effects of aging were evidenced by weight loss, fiber exposure, chemical changes, increased crack density in interlaminar shear strength tests, and fiber buckling in fractured samples after compression tests, even though no significant changes mechanical properties were observed. Based on this preliminary work, a study was conducted on [02/902]s laminates of the same material, using an exposure cycle of 8 h at 160 ?C followed by 4 h of 80% relative humidity at 70 ?C, for a total exposure period of 2,880 h. Afterwards, stress-controlled tension-tension fatigue tests were conducted using a stress ratio R = 0.1 and frequency of 5 Hz. Composites were characterized using Fourier transform infrared spectroscopy (FTIR), Dynamic Mechanical Analysis (DMA), Scanning Electron Microscopy (SEM) and weight change, before and after hygrothermal exposure. Samples of plain epoxy 8552 were also exposed to the same aging conditions and characterized by optical microscopy (OM), FTIR spectroscopy and weight change. Based on the fatigue life diagrams, a shift function was proposed for the prediction of number of cycles to failure of aged composites based on data from unaged specimens. The study also showed that failure by fracture may not be the best parameter to evaluate the effect of hygrothermal aging on fatigue life of carbon fiber reinforced polymer composites. Other parameters such as delamination and crack saturation are also essential to assess durability of these composites.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-03-12T13:28:19Z No. of bitstreams: 1 RenanSavioDeAlmeidaCoelho_DISSERT.pdf: 6989070 bytes, checksum: 02ffff122848bc43e7d1a9ef1bef5171 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-03-14T19:12:58Z (GMT) No. of bitstreams: 1 RenanSavioDeAlmeidaCoelho_DISSERT.pdf: 6989070 bytes, checksum: 02ffff122848bc43e7d1a9ef1bef5171 (MD5) / Made available in DSpace on 2018-03-14T19:12:58Z (GMT). No. of bitstreams: 1 RenanSavioDeAlmeidaCoelho_DISSERT.pdf: 6989070 bytes, checksum: 02ffff122848bc43e7d1a9ef1bef5171 (MD5) Previous issue date: 2017-07-28 / As propriedades ?nicas do comp?sito de matriz met?lica de cobre (Cu) refor?ada por dispers?o de part?culas de carboneto de tungst?nio (WC) s?o de grande import?ncia para v?rias aplica??es industriais, devido a sua excelente resist?ncia sob alta temperatura, boa resist?ncia ? corros?o e ? fratura. O comp?sito Cu-WC ? quimicamente e termicamente est?vel, al?m de possuir excelentes propriedades de condutividade t?rmica e el?trica. Tais caracter?sticas o tornam um promissor material para fabrica??o de contato el?trico de alta pot?ncia, eletrodos para soldagem, condutores de campo magn?tico pulsado, dispositivos de gerenciamento t?rmico e el?trico. Este trabalho investiga o efeito da moagem de alta energia na densifica??o e microestrutura dos comp?sitos WC-20%Cu e WC-18%Cu-2%Nb, bem como a influ?ncia da adi??o do ni?bio como inibidor de crescimento de gr?o. O efeito da press?o de compacta??o e da temperatura de sinteriza??o dos p?s preparados por moagem e mistura mec?nica na densidade tamb?m foram estudados. P?s de WC, Cu e Nb, na raz?o de 80, 20 e 2 por cento em massa, respectivamente, foram preparados por moagem e, tamb?m, por mistura mec?nica. A moagem dos p?s comp?sitos foi realizada a seco sob atmosfera ambiente com um recipiente e bolas de metal duro em um moinho attritor. Os p?s foram mo?dos a 900 rpm durante 90 minutos e sob uma raz?o de massa p? para bolas de 1:100. Compactos de p?s com forma cil?ndricas foram prensados a 200, 400 e 600 MPa em uma matriz de a?o uniaxial de 8 mm de di?metro. Os corpos verdes foram sinterizados nas temperaturas de 1030 ?C e 1150 ?C por 60 min. em forno tubular resistivo sob atmosfera de nitrog?nio. A microestrutura dos corpos sinterizados foi analisada por microscopia eletr?nica de varredura. Para analisar a presen?a de impurezas nos p?s elementares e mo?dos, an?lises qu?micas de FRX e EDS foram realizadas. A an?lise de DRX foi usada para detectar as fases presentes. Uma significativa diminui??o dos cristalinos e amorfiza??o das fases Cu e WC foi exibida pelos p?s mo?dos. Assim como, um menor tamanho de gr?o foi alcan?ado pelas microestruturas sinterizadas dos p?s comp?sitos Cu-WC com adi??o de Nb. Os compactos de p?s submetidos a maior press?o de compacta??o e temperatura de sinteriza??o tamb?m alcan?aram as maiores densifica??es. / The unique properties of copper metal matrix composite reinforced by dispersion tungsten carbide particles (WC) are of great importance for several industrial applications, due to their excellent high temperature strength and good corrosion and fracture resistance. This composite is chemically and thermally very stable at high temperatures, as well as having excellent thermal and electrical conductivity properties. These promising features make for the manufacture of high-power electrical contact parts, welding electrodes, magnetic field conductors, thermal and electrical management devices. This work investigates the effect of high energy milling on the densification and microstructure of the composites WC-20% Cu and WC-18% Cu-2% Nb as well as an influence of the addition of niobium as a grain growth inhibitor. The effect of the compacting pressure and the sintering temperature of the powders prepared by milling and mechanical mixing in the density were also studied. WC, Cu and Nb powders in the ratio of 80, 20 and 2 percent by mass, respectively, were prepared by milling and also mechanical mixing. The powder mixture were mechanically alloyed in a attritor ball mil in a dry environment. The powders were milled at 900 rpm, with a mass to powder ratio of 1: 100 balls for 1.5 hours, and pressed at 200, 400 and 600 MPa in a uniaxial matrix with 8mm diameter. The green bodies were sintered at temperatures of 1030 ?C and 1150 ? C for 60 min in a resistive tubular oven under a nitrogen atmosphere. A microstructure of sintered bodies for analysis by scanning electron microscopy. To analyze a presence of impurities in the initial powder and the as-milled powders, chemical analyzes of XRF and EDS were performed. A XRD analysis was used to detect as structure of crystalline. Amortization of the Cu and WC phases occurred, with a decrease in the crystalline phase due to milling, and inhibition of grain growth, both at temperatures, in the samples with Nb. Higher compaction pressure and higher sintering temperature show better results for densification of the material.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-04-02T12:49:22Z No. of bitstreams: 1 GiorgioAndreBritoOliveira_DISSERT.pdf: 3458330 bytes, checksum: 434d48526b1ff4a3e12b0d1b440b6198 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-04-04T14:49:22Z (GMT) No. of bitstreams: 1 GiorgioAndreBritoOliveira_DISSERT.pdf: 3458330 bytes, checksum: 434d48526b1ff4a3e12b0d1b440b6198 (MD5) / Made available in DSpace on 2018-04-04T14:49:23Z (GMT). No. of bitstreams: 1 GiorgioAndreBritoOliveira_DISSERT.pdf: 3458330 bytes, checksum: 434d48526b1ff4a3e12b0d1b440b6198 (MD5) Previous issue date: 2018-02-09 / Os materiais comp?sitos s?o um novo destaque no avan?o tecnol?gico, impondo novas pesquisas relacionadas ao assunto devido a sua crescente demanda nas mais diversas ?reas. Dentre essas pesquisas surgem as que tem como objetivo facilitar as aplica??es desses materiais, atrav?s de uma r?pida apura??o das suas propriedades mec?nicas sem a necessidade de procedimentos experimentais, sendo essa fator primacial na prepara??o de projetos. Assim surgiram os modelos micromec?nicos, que ganharam destaque devido a sua praticidade, como exemplo das equa??es da Regra das Misturas e das equa??es de Halpin-Tsai. Recentemente, novos modelos computacionais vem combinando modelos micromec?nicos e aperfei?oando-os para se ter a m?xima acur?cia, como por exemplo as redes neurais artificiais (RNAs). Com base nisso, este trabalho visa a cria??o de arquiteturas de RNAs capazes de modelar o m?dulo de cisalhamento (G12) e a tens?o ?ltima de tra??o longitudinal (Xt) de comp?sitos unidirecionais. Com as RNAs treinadas e testadas, essas v?o servir como ferramentas computacionais, semelhante a fun??es, em que fornecendo as entradas teremos uma sa?da desejada. Para isso, fez-se necess?rio uma coleta de dados da literatura, que foram divididos em um conjunto de treino e um conjunto de teste, para realiza??o da valida??o cruzada. Se desenvolveram sete tipos de arquiteturas diferentes, tr?s para o G12 e quatro para o Xt, na qual essas possuem entre duas, tr?s e quatro entradas. Dentre esses modelos tr?s deles s?o considerados modelos mistos, que combina valores da sa?da da RNA com os valores obtidos vindos de modelos micromec?nicos, como o modelo de Halpin-Tsai. Ap?s o treinamento das RNAs, foi realizada uma an?lise comparativa dos valores vindos da RNA e dos valores experimentais, e ainda an?lises quantitativas e qualitativas com base no modelo de compara??o (modelo de Halpin-Tsai e modelo da Regra das Misturas), apresentando maiores valores de coeficiente de correla??o e menores valores de erro quadr?tico m?dio. / The composite materials are a new highlight in the technological advancement, consequently leading to the development of new researches due to its growing demand in the most diverse areas. Among these researches, arise those that have the objective to facilitate the application of these materials, through a fast estimation of its mechanical properties, without the need for experimental procedures, with this being the main factor in the projects preparation. Thus the micromechanical models appeared, which gained importance due to its practicality, such as the Mix Rule and the Halpin-Tsai equations. Recently, new computational models are combining micromechanical models and perfecting them to obtain maximum accuracy, as for instance in the Artifical Neural Networks application. Therefore, this work aims to create an Artificial Neural Network (ANN) architecture capable of modeling the shear modulus and ultimate longitudinal stress of unidirectional composites. When the ANN?s are trained and tested, they will serve as computational tools, similar to functions, where an input is supplied to obtain a desired output. To achieve this goal, it was necessary a collection of data in literature, which were divided in a training group and a testing group, with the cross validation between them being performed. Seven different types of architectures were developed, three for the G12 and four for the Xt, each of these with two, three and four inputs. Among these models, three of them are considered mixed models, which combines values from the output of the ANN with values obtained from the micromechanical models, such as the Halpin-Tsai. After the ANN training, a comparative analysis was performed between the values from the ANN and the experimental values, with quantitative and qualitative analysis being performed with the Halpin-Tsai model as a base for comparison, presenting higher values for the correlation coefficient and smaller values for the root mean square error.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2018-04-11T19:34:25Z No. of bitstreams: 1 LucasRicardoFernandesFigueiredo_TESE.pdf: 6637394 bytes, checksum: 61ae8caa80c576775c523ad68f0527cc (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-04-12T22:55:55Z (GMT) No. of bitstreams: 1 LucasRicardoFernandesFigueiredo_TESE.pdf: 6637394 bytes, checksum: 61ae8caa80c576775c523ad68f0527cc (MD5) / Made available in DSpace on 2018-04-12T22:55:55Z (GMT). No. of bitstreams: 1 LucasRicardoFernandesFigueiredo_TESE.pdf: 6637394 bytes, checksum: 61ae8caa80c576775c523ad68f0527cc (MD5) Previous issue date: 2017-12-13 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / ?Adesivos verdes? t?m despertado grande interesse cient?fico e tecnol?gico como alternativa aos produtos comerciais convencionais, que em geral, liberam subst?ncias t?xicas e levam um longo per?odo de tempo para degradar. Entretanto, as propriedades mec?nicas limitadas e a r?pida degrada??o de alguns pol?meros biodegrad?veis limitam seu uso na maioria das aplica??es pr?ticas. No presente trabalho, comp?sitos foram preparados usando pol?meros biodegrad?veis e nanowhiskers de celulose (NWC) visando sua utiliza??o como adesivos para madeira. O objetivo da pesquisa foi estudar o efeito da adi??o dos nanowhiskers de celulose (NWC) nas propriedades mec?nicas e na degrada??o dos pol?meros. Os pol?meros biodegrad?veis sintetizados por policondensa??o ? base de glicerol e ?cidos foram poli (adipato de glicerol) - PGA, poli (maleato de glicerol) - PGM, poli (citrato de glicerol) - PGC, poli (ftalato de glicerol) - PGPh, poli (succinato de glicerol) PGSu e poli (sebacato de glicerol) - PGS. Al?m desses, copol?meros poli (glicerol succinato-co-maleato) - PGMSu, poli (glicerol succinato-co-adipato) - PGASu e poli (glicerol adipato-co-maleato) - PGMA foram tamb?m sintetizados. Nanowhiskers de celulose (NWC) foram adicionados aos pol?meros para avalia??o dos seus efeitos na melhoria das propriedades mec?nicas e no controle da taxa de degrada??o. Os materiais foram produzidos com a adi??o de 0, 5, 10 e 20% em peso de NWC. Os pol?meros puros e os comp?sitos foram analisados por Calorimetria Diferencial de Varredura (DSC), An?lise termogravim?trica (TGA), difra??o de Raios X (DRX) e espectroscopia Infravermelho por transformada de Fourier (FTIR). Juntas adesivas foram produzidas em corpos de prova de pinus (Pinus elliottii) e angelim (Vatairea heteroptera Ducke) e submetidas a degrada??o por envelhecimento acelerado e testes de cisalhamento sob tra??o. Juntas coladas produzidas com adesivos ? base de acetato de polivinila - PVAc e cianoacrilato foram tamb?m testadas, nas mesmas condi??es, para fins de compara??o. As an?lises t?rmicas indicaram que a maioria dos pol?meros biodegrad?veis ? base de glicerol testados s?o est?veis at? aproximadamente 260?C e a adi??o de NWC aumentou a estabilidade t?rmica (Tonset) de alguns pol?meros em 26?C at? 48?C, enquanto outros n?o foram afetados. As an?lises de superf?cie de fratura por microscopia eletr?nica de varredura (MEV) ap?s os testes de cisalhamento sugerem redu??o de ductilidade com a incorpora??o de NWC ao adesivo. As medidas de ades?o indicaram que os adesivos verdes desenvolvidos a partir de pol?meros de glicerol com 10 e 20% em peso de NWC apresentaram resist?ncia ao cisalhamento superior ao adesivo comercial ? base de PVAc. Os melhores resultados e resist?ncia ao cisalhamento foram obtidos para PGASu com 20% em peso de NWC (2,57 ? 0,36 MPa) e PGM com 20% em peso de NWC (2,33 ? 0,43 MPa), enquanto que a resist?ncia ao cisalhamento do acetato de polivinila - PVAc foi de 1,58 ? 0,18 MPa. O envelhecimento resultou em maior resist?ncia ao cisalhamento de alguns adesivos. A melhoria mais significativa foi obtida para PGMA com 20% em peso de NWC, que atingiu (3,89 ? 0,74 MPa) ap?s 250 h de envelhecimento, portanto, maior que a resist?ncia ao cisalhamento do cianoacrilato (3,12 ? 0,53 MPa). Em ?ltima an?lise, os resultados apresentados neste trabalho sugerem que a adi??o de nanowhiskers de celulose (NWC) ? uma abordagem vi?vel para ajustar as propriedades mec?nicas e degrada??o dos pol?meros biodegrad?veis. / ?Green adhesives? are of great scientific and technological interest as an alternative to conventional commercial products, which often release toxic substances and take long time to degrade. However, the poor mechanical properties and fast degradation of some biodegradable polymers limit their use in most practical applications. In the present work, novel biodegradable composites were prepared using biodegradable polymers and cellulose nanowhiskers (CNW) for their use as wood adhesives. The goal of the investigation was to study the effect of the addition of CNW on the mechanical properties and degradation of the polymers. The biodegradable polymers synthesized by polycondensation based on glycerol and acids were poly(glycerol adipate) - PGA, poly(glycerol maleate) - PGM, poly(glycerol citrate) - PGC, poly(glycerol phthalate) - PGPh, poly(glycerol succinate) - PGSu and poly(glycerol sebacate) - PGS. In addition, the copolymers synthesized were poly(glycerol succinate-co-maleate) - PGMSu, poly(glycerol succinate-co-adipate) ? PGASu and poly(glycerol adipate-co-maleate) ? PGMA. Cellulose nanowhiskers (CNW) were added to the polymers as an approach for improving the mechanical properties and controlling the degradation rate. Composites were produced with the addition of 0, 5, 10 and 20 wt.% of CNW. The neat polymers and composites were analyzed by Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). Adhesively bonded joints were produced in test specimens of slash pine (Pinus elliottii) and angelim (Vatairea heteroptera Ducke) and subjected to accelerated aging and tested under shear by tensile loading. Bonded joints produced with polyvinyl acetate - PVAc and cyanoacrylate based adhesives were also tested under the same conditions for comparison purposes. Thermal analyses indicated that most of the biodegradable glycerol-based polymers tested are stable up to about 260?C and the addition of CNW increased the thermal stability (Tonset) of some polymers by 26?C up to 48?C, while others were not affected. Analyses of the fracture surfaces after the shear tests by Scanning Electron Microscopy (SEM) suggest less ductile fracture with the incorporation of CNW to the adhesive. The shear strengths of the green adhesives developed from glycerol with 10 and 20 wt.% CNW were greater than that of the commercial PVAc based adhesive. The best results of shear strengths were obtained for PGASu 20 wt.% CNW (2.57 ? 0.36 MPa) and PGM 20 wt.% CNW (2.33? 0.43 MPa), while the shear strength for polyvinyl acetate - PVAc was 1.58 ? 0.18 MPa. Aging improved the shear strength of some adhesives. The best result was obtained for PGMA 20 wt.% CNW, which reached (3.89 ? 0.74 MPa) after 250h of aging, thus greater than the shear strength of cyanoacrylate (3.12 ? 0.53 MPa). Ultimately, the results presented in this work suggest that the addition of cellulose nanowhiskers (CNW) is a viable approach to tailor mechanical properties and degradation of biodegradable polymers.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-03-28T19:32:55Z No. of bitstreams: 1 MiguelCabralDeMacedoNeto_TESE.pdf: 9317764 bytes, checksum: d6388f1f4587c23e99a96ddc982ae840 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-03-29T19:48:43Z (GMT) No. of bitstreams: 1 MiguelCabralDeMacedoNeto_TESE.pdf: 9317764 bytes, checksum: d6388f1f4587c23e99a96ddc982ae840 (MD5) / Made available in DSpace on 2017-03-29T19:48:43Z (GMT). No. of bitstreams: 1 MiguelCabralDeMacedoNeto_TESE.pdf: 9317764 bytes, checksum: d6388f1f4587c23e99a96ddc982ae840 (MD5) Previous issue date: 2016-10-10 / O surgimento de materiais comp?sitos tem o objetivo de se encontrar propriedades especificas desejadas para determinadas aplica??es, como melhor resist?ncia mec?nica, materiais mais leves, economicamente vi?vel, materiais recicl?veis e etc.Nessa perspectiva estudou-se a viabilidade do uso da palha de a?o para a obten??o de um comp?sito de matriz polim?rica. Foram testadas tr?s formula??es, com 10%, 15% e 20% de fibras do comp?sito. Para a caracteriza??o do comp?sito foram determinadas propriedades t?rmicas (condutividade, capacidade t?rmica, difusividade e resistividade), mec?nicas (tra??o e flex?o) e fisioqu?micas (MEV, DRX, densidade, absor??o e degrada??o). O comp?sito, em suas tr?s formula??es, apresentou resist?ncia mec?nica superior a quase totalidade dos comp?sitos j? estudados no laborat?rio LMHES. Essa maior capacidade de resist?ncia mec?nica esteve associada a utiliza??o de um fibra met?lica. No que diz respeito as propriedades t?rmicas, o comp?sito estudado apresentou uma menor capacidade de isolamento t?rmico que os outros comp?sitos anteriormente estudados. O comp?sito apresentou maior viabilidade para a absor??o de umidade e resist?ncia mec?nica. o pior resultado deu-se para aplica??es t?rmica onde sua condutividade t?rmica est? acima da maioria dos comp?sitos polim?rico mostrados pela literatura, em fun??o da utiliza??o de uma fibra met?lica. Foram realizados ensaios mec?nicos, t?rmicos dentre outros, apresentando ?timos resultados devido as propriedades espec?ficas do comp?sito proposto como resist?ncia a flex?o, e boa resist?ncia ? absor??o de meios aquosos. As propriedades do comp?sito pode ser utilizado para a fabrica??o de estruturas que n?o requeiram significativa resist?ncia mec?nica na tra??o, como por exemplo, prot?tipos solares e e?licos, como fornos e fog?es solares e p?s de aerogeradores. / Composite materials arise from the need of finding desired properties for certain applications, such as better mechanical resistance, lighter materials, cost-effectiveness, recyclable material, etc. The difficulties of disposal, recycling or reuse are now environmental concerns and therefore subject matter of much research. In this perspective we studied the feasibility of using steel wool for obtaining a polymeric matrix composite. Three formulations were tested, 10%, 15% and 20% of composite fibers. For the characterization of the composite were determined thermal properties (conductivity, heat capacity, diffusivity and resistivity), mechanical properties (traction and bending) and physiochemical properties (SEM, XRD, density, absorption and degradation). The composite in its three formulations had higher mechanical strength compared to almost all composites that have already been studied in the laboratory LMHES. This greater mechanical resilience was associated with the use of a metallic fiber. Regarding the thermal properties, the composite studied had a lower thermal insulation than other composites studied previously. The composite showed higher viability for humidity absorption and mechanical resilience. The worst result was in thermal applications where its thermal conductivity is above of most polymeric composites found in the literature, due to the use of a metallic fiber. Some tests were made, such as mechanical, thermal, among other tests, showing excellent results because of the specific properties of the composites proposed, namely flexural strength, and good resistance to absorption in aqueous environment. The properties of such composite can be used to make structures that do not require significant mechanical resilience in traction, for instance in solar and wind prototypes, such as ovens and solar powered cookers and wind generator blades.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-08-01T11:55:03Z No. of bitstreams: 1 AndreyJoseMoraesDeLima_DISSERT.pdf: 2671095 bytes, checksum: 5c9ecacd56db46c55bf4d3ca78559cc9 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-08-02T13:26:05Z (GMT) No. of bitstreams: 1 AndreyJoseMoraesDeLima_DISSERT.pdf: 2671095 bytes, checksum: 5c9ecacd56db46c55bf4d3ca78559cc9 (MD5) / Made available in DSpace on 2017-08-02T13:26:05Z (GMT). No. of bitstreams: 1 AndreyJoseMoraesDeLima_DISSERT.pdf: 2671095 bytes, checksum: 5c9ecacd56db46c55bf4d3ca78559cc9 (MD5) Previous issue date: 2016-03-31 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Eletr?litos comp?sitos constitu?dos por uma matriz cer?mica de c?ria (CeO2) ou c?ria-gadol?nia (Ce0,9Gd0,1O2-?, CGO) e misturas eut?ticas de Na2CO3/Li2CO3 ou LiCl/KCl permitem reduzir a temperatura de funcionamento de c?lulas a combust?vel de 600 - 800 ?C para a faixa entre 400 e 600 ?C. Neste trabalho, eletr?litos comp?sitos ? base de c?ria e sais fundidos (misturas eut?ticas de carbonatos ou cloretos) foram obtidos pelo m?todo citrato. A rota qu?mica adotada possibilitou a s?ntese em simult?neo das duas fases dos comp?sitos, com um controle preciso de composi??o e microestrutura, promovendo uma substancial intera??o qu?mica entre fases. O estudo avaliou os efeitos da composi??o (teor de carbonato ou cloreto em matriz de c?ria ou CGO) e do processamento (temperatura de sinteriza??o) na microestrutura e propriedades de transporte dos comp?sitos. A caracteriza??o estrutural por difra??o de raios X revelou que os carbonatos e cloretos existem como fases amorfas. Apesar das baixas densidades relativas (entre 52 e 75%), decorrentes das reduzidas temperaturas de sinteriza??o (c?ria/carbonatos a 690 ?C e c?ria/cloretos entre 400 e 600 ?C), observou-se que a fus?o das fases amorfas atua como um selo que pode evitar o fluxo de gases atrav?s das amostras. A correla??o entre a composi??o e o comportamento el?trico, recorrendo ?s t?cnicas de espectroscopia de infravermelho, microscopia eletr?nica de varredura e espectroscopia de imped?ncia, permitiu ampliar o conhecimento existente sobre as novas caracter?sticas destes materiais relativamente aos eletr?litos convencionais. / Solid electrolyte is the part of the fuel cell has three essential functions: separate reagents, blocking electronic current and have high ionic conductivity of the elements that compose it. Composite electrolytes consisting of a ceria (CeO2) or ceria-gadolinia (Ce0,9Gd0,1O2, CGO) ceramic matrix and eutectic mixtures of Na2CO3/Li2CO3 or LiCl/KCl allow reducing the operating temperature of ceramic fuel cells from 600 - 800?C to 400 ? 600 ?C. In this paper, composite electrolytes based on ceria and molten salts (eutectic mixtures of carbonates and chlorides) were obtained by the citrate method. The adopted chemical route enabled the simultaneous synthesis of the two phases, with precise control of composition and microstructure, providing substantial chemical interaction between phases. The study evaluated the effects of composition (carbonate or chloride content in the ceria based matrix) and processing (sintering temperature) on microstructure and transport properties of the composites. The structural characterization by X-ray diffraction showed that the carbonates and chlorides exist as amorphous phases. Despite the low relative densities (between 52 and 75%), as a result of reduced sintering temperatures (ceria/carbonate at 690?C and ceria/chloride between 400 and 600?C), it was observed that the fusion of the amorphous phase acts as a seal that can prevent the flow of gases through the samples. The correlation between the composition and the electrical behavior, using the infrared spectroscopy techniques, scanning electron microscopy and impedance spectroscopy, has observed a homogeneous microstructural distribution between phases, indicating the formation of a ceramic skeleton based on ceria, surrounded by a mixture of amorphous salts, obtaining a conductivity of 0.079 S cm-1 and 0,058 cm-1 S for the ceria composite and carbonates at 600 ? C and 0.0016 S cm-1 and 0.0011 S cm-1 for composites ceria and chlorides at 450 ? C.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-08-10T11:35:31Z No. of bitstreams: 1 RobertoKleciusMendoncaFernandes_TESE.pdf: 9615422 bytes, checksum: cd708447bea2bf643fce86924f5bbab0 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-08-11T10:55:04Z (GMT) No. of bitstreams: 1 RobertoKleciusMendoncaFernandes_TESE.pdf: 9615422 bytes, checksum: cd708447bea2bf643fce86924f5bbab0 (MD5) / Made available in DSpace on 2017-08-11T10:55:04Z (GMT). No. of bitstreams: 1 RobertoKleciusMendoncaFernandes_TESE.pdf: 9615422 bytes, checksum: cd708447bea2bf643fce86924f5bbab0 (MD5) Previous issue date: 2017-05-15 / O mancal seco ? um elemento estrutural presente na maioria dos sistemas mec?nicos das ind?strias dos setores eletrodom?sticos, agropecu?rios, aeroespacial, aeron?utico e automotivo. Este trabalho d? continuidade a uma linha de pesquisa iniciada no Grupo de Estudos de Tribologia e Integridade Estrutural (GET) da Universidade Federal do Rio Grande do Norte (UFRN) e tem o objetivo de investigar tribologicamente comp?sitos polim?ricos com matriz de politetrafluoretileno (PTFE) e carga de rejeito de scheelita para aplica??o em mancais secos, visando reduzir custo e aumentar a vida em servi?o destes elementos. O rejeito de scheelita, origin?rio da extra??o da scheelita utilizada para produ??o do tungst?nio, ? um res?duo mineral composto de ?xidos, como os de sil?cio, c?lcio, alum?nio, ferro, magn?sio, tungst?nio, dentre outros. O rejeito de scheelita foi caracterizado na condi??o como adquirido, atrav?s de an?lises de MEV e EDS, e peneirado para tamanho de part?cula inferior a 45 ?m. O PTFE foi analisado por DRX. PTFE e rejeito de scheelita foram misturados mecanicamente, moldados por compress?o a quente, num molde projetado envolto por uma resist?ncia el?trica, atrav?s de uma prensa hidr?ulica. Investigou-se o desempenho tribol?gico dos comp?sitos submetidos a cargas (1) em movimento linear alternado (reciprocating) e (2) com indenta??es repetidas. As superf?cies novas e ensaiadas foram analisadas por Microscopia de For?a At?mica (AFM) no que concerne aos par?metros de rugosidade peri?dica e n?o peri?dica. Verificou-se que a varia??o no teor de rejeito de scheelita e a frequ?ncia do movimento alternado influenciaram no desempenho tribol?gico e na resist?ncia do comp?sito, relacionados ao coeficiente de atrito, ? rugosidade, ao desgaste e ? indenta??o. Os comp?sitos polim?ricos desenvolvidos e ensaiados demonstraram se constituir em novos materiais adequados para aplica??o de mancais secos, notadamente o comp?sito com 80% de PTFE e 20% de rejeito de scheelita que, mostrando-se como de melhor desempenho tribol?gico, apresenta-se como uma alternativa vi?vel e de custo mais baixo que o PTFE puro. / Dry rubbing journal bearing is a structural part that is present in the most of mechanical systems of industries from home appliances, agricultural, aerospace, aeronautic and automotive sectors. This work gives continuity to a research started in Group of Studies in Tribology and Structural Integrity (GET) at Federal University of Rio Grande do Norte (UFRN) and has objective to investigate, tribologically, a scheelite tailings- filled PTFE composites to dry rubbing journal bearings application, to reduce cost and extend life service of this parts. The tailing of scheelite, obtained from scheelite mining to produce tungsten, is a mineral spoilage composed of oxides, as a silicon oxides, calcium, aluminum, iron, magnesium, tungsten and others. The tailing of scheelite was analyzed as acquired through SEM and EDS analysis, and sieved to get a particle size less than 45 ?m. PTFE was analyzed through XRD. PTFE and scheelite tailings was mechanically mixed, hot compression molding in a designed mold involved by a electrical resistance and compressed by a hydraulic press. It was investigated tribological performance of composites subject to loads (1) in reciprocating movement and (2) repeated indentations. The new and tested surfaces were analyzed through Atomic Force Microscope (AFM) to collect periodic and non periodic roughness parameters. It was verified that scheelite tailing content and frequency of reciprocating influenced tribological performance and strength of composites, related to coefficient of friction, roughness, wear and indentation. The developed and tested polymeric composites showed to constitute a new materials suitable to dry rubbing journal bearings applications, notably 80% of PTFE and 20% scheelite tailing composite content that was the best tribological performance composite and being introduced as a viable alternative and lower cost than pure PTFE.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-09-19T19:40:39Z No. of bitstreams: 1 AdrianoLincolnAlbuquerqueMattos_TESE.pdf: 27478075 bytes, checksum: 07d8b83bd142d721fba0a56eaf59e772 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-09-19T22:36:46Z (GMT) No. of bitstreams: 1 AdrianoLincolnAlbuquerqueMattos_TESE.pdf: 27478075 bytes, checksum: 07d8b83bd142d721fba0a56eaf59e772 (MD5) / Made available in DSpace on 2017-09-19T22:36:46Z (GMT). No. of bitstreams: 1 AdrianoLincolnAlbuquerqueMattos_TESE.pdf: 27478075 bytes, checksum: 07d8b83bd142d721fba0a56eaf59e772 (MD5) Previous issue date: 2017-06-28 / As fibras lignocelul?sicas t?m se tornado alternativas econ?micas e ecol?gicas para uso como refor?os ou cargas em comp?sitos com pol?meros virgens ou reciclados. O presente trabalho foi subdividido em tr?s artigos que abordaram diferentes aspectos do desenvolvimento de comp?sitos. O primeiro envolveu a modifica??o de part?culas lignocelul?sicas, utilizando o l?quido da casca da castanha de caju (LCC) como fonte de cardanol, tendo por objetivo o incremento da degradabilidade de comp?sitos de polipropileno (PP) com diferentes tipos de part?culas lignocelul?sicas. Ensaios de termooxida??o e an?lises do comportamento mec?nico, da composi??o qu?mica e das propriedades f?sicas das amostras, permitiram a verifica??o de que os comp?sitos produzidos com part?culas modificadas com o LCC se degradaram na metade do tempo dos comp?sitos convencionais. O segundo artigo objetivou a otimiza??o da metodologia de modifica??o qu?mica da superf?cie de part?culas lignocelul?sicas com LCC, que tamb?m pode ser utilizada como etapa intermedi?ria na funcionaliza??o das part?culas lignocelul?sicas, pois introduz em sua superf?cie s?tios de maior reatividade. A efici?ncia das metodologias de modifica??o qu?mica foi avaliada com o uso de t?cnicas de microscopia eletr?nica de varredura (MEV), espectroscopia de infravermelho por transformada de Fourier (FTIR), termogravimetria (TG) e ?ngulo de contato. Tamb?m foi avaliado o comportamento das part?culas modificadas em comp?sitos com polipropileno. As propriedades dos comp?sitos obtidos foram avaliadas por ensaio de tra??o e an?lise t?rmica din?mico mec?nica (DMTA). O terceiro artigo abordou a produ??o de comp?sitos de PP com farinha de madeira de cajueiro e farinha de folha de carna?ba. As propriedades f?sicas, mec?nicas e morfol?gicas foram avaliadas por TG, calorimetria explorat?ria diferencial (DSC), DMTA, e MEV. Comp?sitos obtidos com fibras in natura, mercerizadas e compatibilizadas com anidrido maleico foram comparados, tendo sido observados os melhores desempenhos nos comp?sitos com o uso do anidrido maleico e farinha da folha de carna?ba. / Lignocellulosic fibers have become an economical and ecological alternative for use as reinforcements and fillers in composites made of virgin or recycled polymers. The present work was subdivided in three papers that focus different aspects of the development of composites. The first one had involved the modification of lignocellulosic particles, using the cashew nut shell liquid (CNSL) as the source of cardanol. The objective was increasing in the degradability of polypropylene (PP) composites made of different types of lignocellulosic particles. Thermo-oxidation tests and analyzes of the mechanical behavior, chemical composition and physical properties of the samples allowed the verification that composites produced with CNSL-modified particles degraded in half the time of the conventional ones. The second article aimed at optimizing the methodology of chemical modification of lignocellulosic particles surface with CNSL that can also be used as an intermediary step in further functionalization of lignocellulosic particles, as it introduces upon its surface higher reactivity sites. The efficiency of the chemical modification methodologies was evaluated with the use of scanning electron microscopy (SEM), infrared spectroscopy (FTIR), thermogravimetry (TGA) and contact angle. The behavior of composites made of the modified particles in polypropylene matrix was also evaluated by mechanical tests and dynamic mechanical thermal analysis (DMTA). The third paper dealt with the production of PP composites made of cashew wood flour and carnauba leaf flour. The physical, mechanical and morphological properties were evaluated by TGA, differential scanning calorimetry, mechanical tensile and flexural tests, and SEM. Composites made of bulk fibers, mercerized and coupled with maleic anhydride were compared and the best performances were observed in the composites using maleic anhydride as coupling agent and carnauba fibers.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-10-02T23:44:18Z No. of bitstreams: 1 MicaelaDeFreitasAndrade_DISSERT.pdf: 2178407 bytes, checksum: c7e3c6bd92127a3aa87e92fb7d2fc5e4 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-10-09T21:08:28Z (GMT) No. of bitstreams: 1 MicaelaDeFreitasAndrade_DISSERT.pdf: 2178407 bytes, checksum: c7e3c6bd92127a3aa87e92fb7d2fc5e4 (MD5) / Made available in DSpace on 2017-10-09T21:08:28Z (GMT). No. of bitstreams: 1 MicaelaDeFreitasAndrade_DISSERT.pdf: 2178407 bytes, checksum: c7e3c6bd92127a3aa87e92fb7d2fc5e4 (MD5) Previous issue date: 2017-07-28 / O uso de materiais comp?sitos tem crescido principalmente daqueles que apresentam res?duos na sua composi??o, uma vez que os impactos ambientais gerados com o mau destino desses materiais t?m preocupado a sociedade. Este trabalho apresenta o estudo e caracteriza??o de um material comp?sito obtido da mistura de matriz polim?rica de resina poli?ster e res?duos da casca de ovo de galinha. As cascas recolhidas foram secas e quebradas para a obten??o de tr?s granulometrias (fina, m?dia e grossa). As matrizes utilizadas foram ?s resinas poli?ster ortoft?lica e tereft?lica, escolhendo-se o percentual de res?duo de 100% em massa em rela??o ? matriz, em fun??o de testes preliminares para o diagn?stico da satura??o do comp?sito. Os corpos de prova foram constru?dos e submetidos a testes para caracteriz?-los atrav?s de suas propriedades t?rmicas (condutividade t?rmica, capacidade t?rmica, difusividade e resistividade), mec?nicas (resist?ncias ? tra??o, flex?o e impacto) e f?sicas (densidade, absor??o de umidade e envelhecimento). Como esperado, o comp?sito proposto apresentou menor resist?ncia mec?nica do que a matriz, caracterizando o res?duo como carga de enchimento. Desta forma, todas as formula??es do comp?sito apresentaram-se aplic?veis em estruturas que n?o requerem resist?ncia a grandes esfor?os. O comp?sito apresentou condutividade t?rmica superior ?s resinas matrizes para todas as formula??es, com condutividade t?rmica superior a 0,21 W/m.K, classificando-se como condutor t?rmico. A densidade aparente dos comp?sitos n?o apresentou varia??o significativa em rela??o ? resina. A maior qualidade do comp?sito estudado foi a diminui??o da quantidade de resina a ser utilizada, uma vez que a carga de p? de res?duo pode alcan?ar 100% em rela??o ? matriz, diminuindo-se o custo do material obtido para a fabrica??o de estruturas diversas. / The use of composite materials has grown mainly from those that present residues in their composition, since the environmental impacts generated by the bad destiny of these materials have worried society. This work presents the study and characterization of a composite material obtained from the mixture of polymer matrix of polyester resin and residues of chicken eggshell. The collected shells were dried and broken to obtain three granulometries (fine, medium and coarse). The matrices used were the orthophthalic and terephthalic polyester resins, being chosen the percentage of residue of 100% in mass in relation to the matrix, as a function of preliminary tests for the diagnosis of composite saturation. The test specimens were constructed and subjected to tests to characterize them through their thermal properties (thermal conductivity, thermal capacity, diffusivity and resistivity), mechanical (tensile strength, flexural and impact strength) and physical properties (density, moisture absorption and aging). As expected, the proposed composite presented lower mechanical resistance than the matrix, characterizing the residue as filling load. In this way, all the formulations of the composite were applicable in structures that do not require resistance to great efforts. The composite presented superior thermal conductivity to the matrix resins for all the formulations, with thermal conductivity superior to 0,21 W/m.K, being classified as thermal conductor. The apparent density of the composites did not show significant variation in relation to the resin. The higher quality of the composite studied was the reduction of the amount of resin to be used, since the residue dust load can reach 100% in relation to the matrix, reducing the cost of the material obtained for the manufacture of diverse structures.

Submitted by Celso Magalhaes (celsomagalhaes@ufrrj.br) on 2017-06-22T11:26:06Z No. of bitstreams: 1 2016 - B?rbara Magalh?es Neto.pdf: 3282939 bytes, checksum: a4ead0ff5e7307971c24940b1bea36a3 (MD5) / Made available in DSpace on 2017-06-22T11:26:06Z (GMT). No. of bitstreams: 1 2016 - B?rbara Magalh?es Neto.pdf: 3282939 bytes, checksum: a4ead0ff5e7307971c24940b1bea36a3 (MD5) Previous issue date: 2016-07-19 / Among the many existing methods for removing heavy metals off the effluents, the adsorption process stands out for being considered most effective, at lower cost. The phenomenon of adsorption consists in a process of the transfer of one or more constituents of a fluid phase to a surface of a solid phase. The adsorption process depends on physical and chemical characteristics, as: structural properties of the adsorbent (porosity, functional groups), adsorbate (ionic radius and coordination number), interaction between adsorbent and adsorbed. New technologies have emerged with focus returned to the use of biological materials with adsorbing properties for the treatment of effluents, in particular, removal and recovery of heavy metals, showing good performance. The main advantages of using natural adsorbents (biosorbents) in the process of sorption are: low waste generation, easy recovery of metals, the possibility of reuse of the adsorbent and lower operating costs, depending on the adsorbent material used in the process. From the foregoing this research used tablets of composite material, formed of recycled low density polyethylene (LDPErec) as polymer matrix and adsorbent materials (coconut fibber FC, chitosan Qui or clay B) and a comparative study using such tablets as adsorbents, to removal of the chromium (III), in order to determine which tablet has a better adsorption of chromium (III).To this end, there were realized three experimental design, where they were evaluated the influence of the size of coconut fibber particles, the composition of LDPErec/Fc, LDPErec/B, LDPErec/Qui, LDPErec/FC/Qui and LDPErec/B/Qui, the concentration of chromium (III) adsorbate and the exposure time of the tablets in the chromium (III) solution. With the results can conclude that the models used in the experimental design were valid for the evaluation of significant variables of this work, as the best chromium (III) removal conditions. That happened to the composition values of 40/60% to the tablets of LDPErec/FC1, LDPErec/FC3 and LDPErec/B. The particle size range of coconut fibber that proved more favourable was smaller particle size (100-120 mesh) in the composition of 40/60 %. The conductivity has been used to predict a chromium (III) sorption model but it proved not to be good parameter / Entre os muitos m?todos existentes para a remo??o de metais pesados em efluentes, o processo de adsor??o destaca-se por ser considerado um dos mais efetivos, com menor custo. O fen?meno da adsor??o consiste em um processo de transfer?ncia de um ou mais constituintes de uma fase fluida para a superf?cie de uma fase s?lida. O processo de adsor??o depende de caracter?sticas f?sicas e qu?micas, como: propriedades estruturais do adsorvente (porosidade, grupos funcionais), do adsorvato (raio i?nico, n?mero de coordena??o) e intera??es entre o adsorvente e o adsorvato. Novas tecnologias t?m surgido com o foco voltado para a utiliza??o de materiais biol?gicos com propriedades adsorventes para tratamento de efluentes, e particularmente, na remo??o e recupera??o de metais pesados, apresentando bom desempenho. As principais vantagens de utiliza??o de adsorventes naturais (biossorventes) no processo de sor??o s?o: baixa gera??o de res?duos, f?cil recupera??o dos metais, a possibilidade de reutiliza??o do adsorvente e menor custo operacional, dependendo do material adsorvente que ? utilizado no processo. A partir do exposto essa pesquisa utilizou pastilhas de materiais comp?sitos, formadas por polietileno de baixa densidade reciclado (PEBDrec) como matriz polim?rica e materiais adsorventes (fibra de coco-FC, quitosana-Qui ou argila-B) e realizar um estudo comparativo utilizando essas pastilhas como adsorventes, na remo??o de cromo (III), a fim de determinar qual apresenta uma melhor adsor??o de cromo. Com esta finalidade, foram realizados tr?s planejamentos experimentais, onde foram avaliadas a influ?ncia da granulometria das part?culas de fibra de coco, a composi??o das pastilhas de PEBDrec/FC, PEBDrec/B, PEBDrec/Qui, PEBDrec/FC/Qui e PEBDrec/B/Qui, a concentra??o do adsorvato de cromo (III) e o tempo de exposi??o das pastilhas a solu??o de cromo (III). Com os resultados p?de-se concluir que os modelos usados nos planejamentos experimentais foram v?lidos para a avalia??o da signific?ncia dessas vari?veis, como para as melhores condi??es de remo??o do cromo (III), as quais aconteceram nos valores de composi??o de 40/60% das pastilhas de PEBDrec/FC1, PEBDrec/FC3 e PEBDrec/B. A faixa granulom?trica da fibra de coco que se mostrou mais favor?vel foi de menor granulometria (100-120 mesh) na composi??o de 40/60%. Utilizou-se a t?cnica de condutividade para predizer um modelo de sor??o de cromo (III), por?m nas condi??es do estudo, a condutividade n?o demonstrou ser um bom par?metro