Avaliação das propriedades elétrica, dielétrica e piezoelétrica do compósito com conectividade 1-3 de poliuretano de óleo de mamona com bastões de PZT e MWCNT
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Data
2022-04-29
Autores
Costa, João Gustavo Leite
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Universidade Estadual Paulista (Unesp)
Resumo
Materiais capazes de alterar uma ou mais de suas propriedades quando submetido a um estímulo externo são classificados como inteligentes e entre essa ampla classe de materiais, destacam-se os compósitos piezoelétrico. Neste sentido, o presente trabalho objetiva obter compósitos piezoelétricos com conectividade 1-3 formados por uma matriz polimérica de poliuretano à base de óleo de mamona (PUR) e bastões de PZT, com e sem uma fase condutora (nanotubos de carbono de paredes múltiplas (MWCNT)). Para a obtenção das amostras foram obtidos bastões de PZT com diâmetro médio de 3 mm e foram utilizados 16 bastões para a obtenção das amostras sem e com a fase condutora (4,70% em volume de MWCNT). Para avaliar se a dispersão de MWCNT influenciou nas propriedades elétricas e piezoelétricas dos compósitos piezoelétricos 1-3, as amostras foram avaliadas por meio da técnica de impedância elétrica, medida de corrente dc e coeficiente piezoelétrico d33. A análise da condutividade elétrica dc (dc) e ac (’(f)) das amostras demonstrou que a dispersão de MWCNT não impactou na propriedade elétrica compósito 1-3, isso era esperado uma vez que a concentração de MWCNT está abaixo do limiar de percolação. Tais dados evidenciam que processo de condução foi realizado principalmente com movimento dos dipolos no interior dos bastões de PZT e do movimento de carga espacial. Tanto a condutividade relativa *(f) quanto a permissividade relativa (*(f)) dos compósitos 1-3 apresentaram comportamento dependente da frequência para toda faixa estudada; tal comportamento é característico de sólidos desordenados. A análise de MEV demonstrou que houve boa interação entre as fases matriz PUR e bastões de PZT. Já o coeficiente d33 demonstrou que adição de MWCNT na matriz melhorou a propriedade piezoelétrica do compósito trifásico PUR-MWCNT/PZT 1-3 em relação ao compósito bifásico PUR/PZT 1-3, cujo valor foi aproximadamente 210±12 pC/N contra 176±13 pC/N respectivamente. Por fim, os testes não-destrutivos por meio da técnica de emissão acústica, aplicando como fonte simuladora a queda de uma esfera maciça e a quebra da ponta do grafite, mostraram que ambas as amostras têm potencial para aplicação como sensor de saúde estrutural, no entanto, a amostra com a fase condutora apresentou melhor sinal, o que demonstra que a dispersão de MWCNT teve impacto positivo na captação do sinal gerado.
Materials capable of altering one or more of their properties when subjected to an external stimulus are classified as inteligent and among this wide class of materials stands out the piezoelectric composites. In this sense, the present work aimed to obtain piezoelectric composites with 1-3 connectivity formed by a polymeric matrix of polyurethane based on castor oil (PUR) and PZT rods, with and without a conductive phase (multi walled carbon nanotubes (MWCNT)). To obtain the samples, PZT rods with an average diameter of 3 mm were obtained, where 16 rods were used to obtain the samples without and with the conductive phase (4.70% in volume of MWCNT). To evaluate whether MWCNT dispersion influenced the electrical and piezoelectric properties of piezoelectric composites 1-3, the samples were evaluated using the technique of electrical impedance, dc current measurement and piezoelectric coefficient d33. The electrical conductivity analysis dc (dc) and ac (’(f)) samples demonstrated that MWCNT dispersion did not impact composite electrical property 1-3, this was expected once the Concentration of MWCNT is below the percolation threshold. This evidences that the conduction process is carried out mainly with movement of the dipoles inside the PZT rods and the space load movement. Both relative conductivity *(f) and relative permissiveness (*(f)) of the composites 1-3 presented frequency-dependent behavior for the entire studied range, such behavior is characteristic of disordered solids. MEV analysis showed that there was good interaction between the PUR matrix phases and PZT rods. The d33 coefficient showed that the addition of MWCNT in the matrix improved piezoelectric property of the three-phase composite PUR-MWCNT/PZT 1-3 in relation to the biphasic composite PUR/PZT 1-3, whose value was approximately 210±12 pC/N versus 176±13 pC/N respectively. Finally, non-destructive tests by means of acoustic emission technique, applying as a phantom source the fall of a massive sphere and the breaking of the graphite tip, showed that both samples have potential for application as a structural health sensor, however, the sample with the conductive phase showed better signal, which demonstrates that the dispersion of MWCNT had a positive impact on the capture of the generated signal.
Materials capable of altering one or more of their properties when subjected to an external stimulus are classified as inteligent and among this wide class of materials stands out the piezoelectric composites. In this sense, the present work aimed to obtain piezoelectric composites with 1-3 connectivity formed by a polymeric matrix of polyurethane based on castor oil (PUR) and PZT rods, with and without a conductive phase (multi walled carbon nanotubes (MWCNT)). To obtain the samples, PZT rods with an average diameter of 3 mm were obtained, where 16 rods were used to obtain the samples without and with the conductive phase (4.70% in volume of MWCNT). To evaluate whether MWCNT dispersion influenced the electrical and piezoelectric properties of piezoelectric composites 1-3, the samples were evaluated using the technique of electrical impedance, dc current measurement and piezoelectric coefficient d33. The electrical conductivity analysis dc (dc) and ac (’(f)) samples demonstrated that MWCNT dispersion did not impact composite electrical property 1-3, this was expected once the Concentration of MWCNT is below the percolation threshold. This evidences that the conduction process is carried out mainly with movement of the dipoles inside the PZT rods and the space load movement. Both relative conductivity *(f) and relative permissiveness (*(f)) of the composites 1-3 presented frequency-dependent behavior for the entire studied range, such behavior is characteristic of disordered solids. MEV analysis showed that there was good interaction between the PUR matrix phases and PZT rods. The d33 coefficient showed that the addition of MWCNT in the matrix improved piezoelectric property of the three-phase composite PUR-MWCNT/PZT 1-3 in relation to the biphasic composite PUR/PZT 1-3, whose value was approximately 210±12 pC/N versus 176±13 pC/N respectively. Finally, non-destructive tests by means of acoustic emission technique, applying as a phantom source the fall of a massive sphere and the breaking of the graphite tip, showed that both samples have potential for application as a structural health sensor, however, the sample with the conductive phase showed better signal, which demonstrates that the dispersion of MWCNT had a positive impact on the capture of the generated signal.
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Palavras-chave
MWCNT, PZT, Poliuretano à base de óleo de mamona, Compósitos, Sensor, Polyurethane based on castor oil, Composites, Sensor