2 research outputs found

    Avaliação de métodos de preparo de amostras de polietileno e polipropileno empregando decomposição assistida por radiação micro-ondas para posterior determinação de magnésio e titânio

    Get PDF
    Com o intuito de avaliar metodologias alternativas ao método de preparo de amostras de polietileno (PE) e polipropileno (PP) por decomposição por combustão em sistema aberto, métodos empregando decomposição assistida por radiação micro-ondas foram estudados. Foram avaliados os métodos de decomposição assistida por radiação micro-ondas (MW-AD), decomposição assistida por radiação micro-ondas combinada com radiação ultravioleta (MW-UV) e combustão iniciada por micro-ondas (MIC) para posterior determinação de Mg e Ti. Estes elementos foram determinados empregando espectrometria de emissão óptica com plasma indutivamente acoplado (ICP-OES), espectrometria de massa com plasma indutivamente acoplado (ICP-MS) e espectrometria de absorção atômica com chama (FAAS). O método de MW-AD foi realizado utilizando 5 mL de HNO3 concentrado e 1 mL de HCl concentrado para a decomposição de PE e 3,5 mL de HNO3 concentrado, 0,5 mL de HCl concentrado e 2,5 ml de solução de H2O2 30% para a decomposição de PP. Assim, até 450 mg de polímero foram decompostos e as soluções finais apresentaram teor de carbono residual (RCC) inferior a 6,0%. O estudo do método de MW-UV foi realizado com 250 mg de amostra e duas misturas ácidas foram avaliadas para cada polímero, sendo uma de composição idêntica a utilizada na MW-AD e uma segunda mistura com metade da concentração dos reagentes. As soluções finais apresentaram RCC inferior a 1,5%. No método de MIC uma solução absorvedora de HNO3 4 mol L-1 foi empregada e até 300 mg de polímero foram decompostas. As soluções finais apresentaram RCC inferior a 1,0%. Os três métodos de preparo de amostras foram considerados adequados para a decomposição de polímeros e as soluções finais obtidas foram adequadas para a determinação de Mg e Ti. Foi possível determinar Ti por ICP-OES e ICP-MS e Mg por ICP-OES e FAAS. De acordo com avaliação estatística dos dados obtidos para a determinação dos elementos, os resultados foram concordantes em um nível de confiança de 95%, conforme com o teste t-student empregado para comparar as técnicas de determinação e o teste ANOVA, utilizado para comparar os métodos de decomposição das amostras.In order to evaluate alternative methodologies for the preparation of samples of polyethylene (PE) and polypropylene (PP) by decomposition by open system combustion, methods employing microwave assisted decomposition were studied. The methods of microwave-assisted digestion (MW-AD), microwave-assisted ultraviolet digestion (MW-UV) and microwave-induced combustion (MIC) for further determination of Mg and Ti. These elements were determined using inductively coupled plasma optical emission spectrometry (ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS) and flame atomic absorption spectrometry (FAAS). The MW-AD method was performed using 5 mL of concentrated HNO3 and 1 mL of concentrated HCl for the PE decomposition and 3.5 mL of concentrated HNO3, 0.5 mL of concentrated HCl and 2.5 ml of 30% H2O2 solution for the PP decomposition. Thus, up to 450 mg of polymer were decomposed and the final solutions had residual carbon content (RCC) of less than 6.0%. The study of the MW-UV method was carried out with 250 mg of sample and using two different acid mixtures for each sample, one of composition identical to that used in the MW-AD and a second mixture with half the concentration of the reagents. The final solutions presented RCC less than 1.5%. In the MIC method using 4 mol L-1 HNO3 as absorbing solution a quantitative recoveries were obtained for Mg and Ti. In addition, it was possible to digest up to 300 mg of polymer. The final solutions presented RCC less than 1.0%. All three methods of sample preparation were considered suitable for the decomposition of polymers and the final solutions obtained were suitable for the determination of Mg and Ti. It was possible to determine Ti by ICP-OES and ICP-MS and Mg by ICP-OES and FAAS. According to a statistical evaluation of the data obtained for the determination of the elements, the results were concordant at a 95% confidence level, according to the t-student test used to compare the determination techniques and the ANOVA test used to compare the methods of decomposition of samples

    Lunar Gravitational-Wave Antenna

    Get PDF
    Monitoring of vibrational eigenmodes of an elastic body excited by gravitational waves was one of the first concepts proposed for the detection of gravitational waves. At laboratory scale, these experiments became known as resonant-bar detectors first developed by Joseph Weber in the 1960s. Due to the dimensions of these bars, the targeted signal frequencies were in the kHz range. Weber also pointed out that monitoring of vibrations of Earth or Moon could reveal gravitational waves in the mHz band. His Lunar Surface Gravimeter experiment deployed on the Moon by the Apollo 17 crew had a technical failure rendering the data useless. In this article, we revisit the idea and propose a Lunar Gravitational-Wave Antenna (LGWA). We find that LGWA could become an important partner observatory for joint observations with the space-borne, laser-interferometric detector LISA, and at the same time contribute an independent science case due to LGWA's unique features. Technical challenges need to be overcome for the deployment of the experiment, and development of inertial vibration sensor technology lays out a future path for this exciting detector concept.Comment: 29 pages, 17 figure
    corecore