Abstract This report describes the photoacoustic and electron paramagnetic resonance investigations of Brazilian and Cuban zeolites. Photoacoustic optical absorption measurements indicate the presence of iron (Fe 3 +) ions with their respective transition bands for both zeolites. Two species of manganese (Mn 2 + and Mn 3 +) were identified in the Cuban sample and the electronic transitions assigned. Iron and manganese ions were confirmed through nonradiative relaxation ( τ) and characteristic diffusion ( τ β) times evaluation, whose values were found to be τ BRA = 5.40 ms, τ CUB = 4.60 ms, τ β BRA = 387 μs and τ β CUB = 305 μs. Crystal field (Dq- BRA/Dq- CUB = 1048 cm − 1/945 cm − 1) plus Racah (B- BRA/B- CUB = 457 cm − 1/813 cm − 1 and C- BRA/C- CUB = 3655 cm − 1/2496 cm − 1) parameters were assessed as well. Paramagnetic resonance corroborated Fe 3 + ions present in the Brazilian zeolite occupying sites showing axial and/or rhombic symmetry distortions. For the Cuban sample, results reveal the characteristic hyperfine sextet lines of Mn 2 + overlapping the Fe 3 + line. Values of Landé factor and isotropic hyperfine splitting constant were found to be 2.0 and 9.7 mT, respectively. This tells us that the Mn 2 + lies in octahedral symmetry probably replacing calcium ions and point towards an ionic bonding character of the Mn 2 + and its surroundings.

São apresentadas as propriedades físico-químicas de uma ocorrência sedimentar da Bacia do Parnaíba, Brasil, da zeólita estilbita, agregada a uma argila esmectítica. As amostras de diferentes sítios apresentam uma ampla variação do mineral zeolítico: entre 15% a 50%. A utilização de espirais concentradoras foi suficiente para obtenção de concentrados contendo até 67% do mineral. Ensaios laboratoriais do concentrado dopado com fertilizantes revelam taxas de liberação de nutrientes comparáveis aos obtidos com produtos comerciais similares.

This report describes the characterization of a sedimentary occurrence from the Parnaíba Basin, Brazil, containing the zeolite stilbite intertwined with smectitic clay mineral. The head samples from different sites present a wide content range of the zeolitic phase - 15% to 50%. The use of simple separation techniques - conventional gravitic treatments - yields concentrates containing about 67% of the zeolitic component. Assays with the amendments of these concentrates with plant nutrients yield release rates matching those reported for similar commercial products.

Para determinar a penetração da onda térmica na polpa do fruto do mamoeiro (Carica papaya L.), cv. Golden, a difusividade térmica foi obtida medindo a temperatura da polpa em quatro diferentes profundidades. As medidas foram realizadas inicialmente no estádio I de maturação do fruto, e as variações da difusividade térmica foram expressas em função do amadurecimento. Foi observada a diminuição da difusividade térmica no tempo. Propriedades químicas (pH, sólidos solúveis e acidez titulável) e física (firmeza da polpa) também foram determinadas, e os resultados, comparados com as variações da difusividade térmica.

In order to determine the penetration of the thermal wave in the papaya fruit pulp (Carica papaya L.), cv. Golden, thermal diffusivity of the pulp was obtained measuring temperature at four different depths. Measurements were carried out initially with the fruit on the first stage of maturity. The changes of the thermal diffusivity were expressed as a function of ripening. A temporal decrease of the thermal diffusivity was observed. Chemical (pH, soluble solids and total titratable acidity) and physical (pulp firmness) properties were measured as well and the results were compared to the thermal diffusivity change.

In this article, photothermal techniques were used in order to determine some thermal properties: diffusivity, conductivity, effusivity and specific heat capacity of WC-10 wt. (%) Co six samples subjected to different sintering processes. The samples were sintered using high pressure - high temperature (HPHT) sintering system. The open cell photoacoustic (OPC) used to measure thermal diffusivity is described in detail. The values of thermal properties here measured and evaluated are consistent to those previously reported in the literature.

Filmes densos de poli(3-hidrobutirato) e poli(3-hidroxibutirato-co-3-hidroxivalerato) com espessuras de 90 µm foram obtidos utilizando o método "casting" de deposição e caracterizados por espectroscopia de fotoelétrons, calorimetria diferencial e métodos fotoacústicos. As frações molares de hidroxivalerato utilizadas foram de 8, 14 e 22 % molar. Seguindo uma mesma tendência, a capacidade térmica específica e a temperatura de transição vítrea diminuem com o aumento da concentração de hidroxivalerato.

Poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) polymer dense films with thickness of 90 µm were obtained by the casting method and characterized using X-ray photoelectron spectroscopy, differential scanning calorimetric and photo-thermal methods. The HV molar fractions in the copolymer structure were 8, 14 and 22 mol %. The measured specific thermal capacity and the glass transition temperature of the P3(HB-co-x%HV) decrease for increasing hydroxyvalerate content following a similar trend.

Polyhydroxyalkanoates (PHAs) are polymers produced from renewable resources with biodegradability and biocompatibility, being therefore attractive for medical and pharmaceutical purposes. Poly (3-hydroxybutyrate) (PHB) is the most important polymer of this family by considering the biotechnology process of its synthesis. In the present study, dense films of PHB were prepared by casting from chloroform solutions (1% m/m). Permeability studies with water, methanol, ethanol and n-propanol were performed using the gravimetric method at different temperatures (from 50 ºC to 65 ºC). Results provide new data on permeability coefficients of PHB membranes.

The present work discuss the applicability of photothermal techniques for determining diffusion coefficients of oxygen and carbon dioxide of commercial low-density polyethylene (LDPE). The methodology involves the monitoring of diffused gas by a photoacoustic analyzer. Diffusion coefficients measured for CO2 and O2 were 2.77 x 10-8 cm²/s and 1.68 x 10-7 cm²/s, respectively. To support the gas diffusion results, thermal properties were studied using photoacoustic spectroscopy and crystallinity was determined using X-ray diffraction. Values obtained for thermal diffusivity and specific heat capacity were 1.65 x 10-3cm²/s and 2.33 J.cm-3K-1, which are in good agreement with values available in the literature for pure LDPE and thus assure reliability of diffusion coefficients values.

Propriedades termofísicas de copolímeros poli(3-hidroxibutirato-co-3-hidroxivalerato) poli(3HB-co-3HV) foram investigadas com o objetivo de entender a influência das unidades monoméricas de 3-hidroxivalerato (3HV) incorporadas durante a copolimerização aleatória. Os resultados mostram forte evidência de que uma plastificação interna é introduzida no copolímero pelas unidades de 3HV. Foi observado que a condutividade térmica do copolímero aumentou linearmente com a concentração de 3HV. Por outro lado, a difusividade térmica foi muito sensível as mudanças de composição do copolímero, apresentou um aumento brusco inicial e atingiu um platô de saturação. Os gráficos de amplitude contra frequência indicam a predominância de um mecanismo termoelástico. Neste trabalho é apresentando uma nova montagem fotoacústica para as medidas de efusividade térmica.

Basic data on thermophysical properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymers poly(3HB-co-3HV) were investigated with the aim of understanding the role of 3-hydroxyvalerate monomeric units (3HV) incorporated during random copolymerization. The results show strong evidence that internal plastification is produced by the introduction of 3HV units in the copolymer. It was observed that copolymer thermal conductivity increased approximately linearly with the 3HV content. On the other hand, thermal diffusivity was very sensitive to the change in the copolymer composition showing a sudden rise that attained a saturation plateau. Amplitude-frequency plots indicate that a thermoelastic bending mechanism is operating. In this paper a new photoacoustic arrangement for the measurement of thermal effusivity is presented.