Navegando por Palavras-chave "Compósitos cerâmicos"

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    Análise das propriedades dielétricas e da estabilidade térmica da matriz compósita 𝑭𝒆𝑵𝒃𝑶𝟒(fno) - 𝑪𝒂𝑻𝒊𝑶𝟑(cto) para uso em antenas ressoadoras dielétricas
    (Universidade Federal Rural do Semi-Árido, 2021-07-26) Queiroz, Stefany Kariny dos Santos de Souza; Queiroz Júnior, Idalmir de Souza; 63510731468; http://lattes.cnpq.br/8047604543096116; Sombra, Antônio Sérgio Bezerra; 11420618334; http://lattes.cnpq.br/6034251420222926; Silva, Isaac Barros Tavares da; 09660918410; http://lattes.cnpq.br/7304355962395872; Silva, Ronaldo Santos da; 96979941534; http://lattes.cnpq.br/4548331237405072
    Over the years, the growing development in telecommunications systems has resulted in the need to develop wireless communication technologies using electromagnetic waves. The use of ceramic materials in electrical and electronic systems is becoming more and more constant, as they often provide viable solutions to many of the problems that need to be resolved. Currently, Iron Niobate (𝐹𝑒𝑁𝑏𝑂􀬸) has been widely used as a photoanode in converters, gas sensors and electronic devices. Calcium Titanate (𝐶𝑎𝑇𝑖𝑂􀬷) has interesting characteristics for technological applications, such as multilayer capacitors, thermistors, dielectric resonators and miniaturization of electronic devices. This work presents the structural and dielectric characterization of composites formed by mixing 𝐹𝑒𝑁𝑏𝑂􀬸(FNO) and 𝐶𝑎𝑇𝑖𝑂􀬷 (CTO), as well as a study on the thermal stability of the new synthesized matrix. The solid state reaction was used to obtain pure FNO and ceramic composites obtained by adding CTO at 20%, 40%, 50% and 80% by weight. X-ray diffraction was used in the structural characterization of these compounds. For the characterization of the dielectric properties, the dielectric permittivity and the loss tangent were measured. A study of the antenna parameters of the samples was also carried out, namely: S11, Smith's Chart and Antenna Gain. Both the dielectric properties and the antenna parameters were obtained through the techniques of Hakki-Coleman, Monopolo and Microstrip Line. Finally, the measurement of the Resonance Frequency Temperature Coefficient (τf) was performed to verify the thermal stability of the material. In the study of this parameter, one looks for materials with the temperature coefficient of the resonance frequency as close to zero as possible, which gives greater thermal stability to the material. It was found that the thermal stability improves with the application of 𝐶𝑎𝑇𝑖𝑂􀬷 with values ranging from -1293 ppm°C􀬿􀬵 to 850 ppm°C􀬿􀬵. The 60% concentration of 𝐶𝑎𝑇𝑖𝑂􀬷 in the sample is the closest to τf equal to zero. In the dielectric characterization, in general, it was observed that the addition of CTO increased the permittivity of the composite matrix and decreased the loss tangent value. The samples working as antennas presented a very satisfactory performance, with a low S11 value and good impedance matching. When compared the measured and simulated results, they showed good agreement and uniformity between them
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    Projeto de antena do tipo patch sobre substrato dielétrico baseado em cério e bismuto
    (2023-05-20) Melo, Ingryd Kely Cosme; Silva, Isaac Barros Tavares da; Silva, Isaac Barros Tavares da; Queiroz Júnior, Idalmir de Souza; Holanda, Samanta Mesquita de
    Este trabalho teve por objetivo a produção de substrato dielétrico de estrutura silenita, baseado em bismuto e cério, para dispositivos de comunicação. O sistema bismuto-cério foi sintetizado em diferentes proporções (1:1 a 5:1 de Bi:Ce) em estrutura cristalina de silenita a partir da rota sol-gel/combustão e calcinado a 650° C, posteriormente, resfriado de forma natural. O material foi submetido à caracterização estrutural através da Difratometria por Raios-X (DRX), juntamente com o refinamento Rietveld, para análise das fases formadas. Os materiais resultantes foram prensados a 5 MPa em prensa hidráulica com matriz cilíndrica por aproximadamente 1 h. A caracterização dielétrica do material foi realizada para frequências de 1,0 a 8,5 GHz. A validação dos materiais para aplicação em dispositivos deu-se com a simulação e construção de antenas de microfitas do tipo circular, estas ressoando em frequências entre 6,5 e 8,5 GHz. As medições apresentaram boa concordância com as antenas simuladas, com erro máximo de 1,3% na medida de frequência de ressonância e de 0,074% para coeficientes de reflexão ( , ), em escala linear.