Abstract The physical and mechanical properties of foamed geopolymers were determined. The geopolymers were made with two different metakaolins (from Metacaulim do Brasil - MB, and Pantano Grande/RS - MPG) as precursors, with NaOH and Na2SiO3 as activators, and with the addition of foam, which was produced with the foaming agent diethanolamide of coconut fatty acid with a minimum of 80% concentration. Also, two times (2.5 and 4 h) were used for the calcination of MPG at 750 °C. The results showed that all factors (precursors type, alkali content, silica modulus, and foam content) had a significant influence on the response variables, which presented the following variations: compressive strength of 0.36 to 3.23 MPa; thermal conductivity from 0.22 to 0.42 W/(m.K); saturated bulk density from 1176 to 1364 kg/m3; dry bulk density of 619 to 864 kg/m3; air void from 46.4% to 62.5%; and water absorption from 55.7% to 95.4%. It was also concluded that the precursor type was the factor that had the most influence on the properties of foamed geopolymers, with MPG calcined for 4 h being the best, as greater compressive strength and low thermal conductivity were obtained.

Resumo O interesse no estudo de cigarras geralmente é despertado pela sua importância na agricultura. Entretanto, a possibilidade de que este grupo represente um pulso de nutrientes pode também implicar no sucesso de sobrevivência de espécies importantes num determinado bioma. O objetivo deste trabalho foi verificar o nível de proteínas solúveis e lipídios totais de Fidicina mannifera (Fabricius, 1803) e determinar se a espécie pode promover um pulso de nutrientes em duas fitofisionomias do Cerrado. Para avaliar o pulso de nutrientes, foram determinados os níveis de proteínas solúveis e lipídios totais de machos e fêmeas adultos de F. mannifera, e também a distribuição espacial de exúvias desta espécie, em duas fitofisionomias de Cerrado. A quantidade de proteínas disponibilizada por indivíduo não diferiu entre machos e fêmeas (p = 0,66), porém fêmeas apresentaram 40% mais lipídios do que machos (p = 0,05). Para mata de galeria F. mannifera ofertou 11,75 g/ha de proteína, 3,91 g/ha de lipídios, e no cerrado stricto sensu, 4,25 g/ha de proteína, e 1,41 g/ha de lipídio. Machos de cigarras possuem um abdômen oco, que abriga uma câmara de ressonância para a produção de som com o objetivo atração de fêmeas para acasalar, por outro lado as fêmeas armazenam maiores quantidades de lipídios, localizados principalmente na cavidade abdominal, onde a gordura corporal está diretamente ligada ao aparelho reprodutor para o desenvolvimento dos ovários, e produção de ovos após a emergência. A ocorrência em massa de F. mannifera no Cerrado, bem como a disponibilidade de proteínas e lipídios de fácil acesso, faz desta espécie um recurso alimentar que pode impactar diretamente na dieta de consumidores e detritívoros secundários, embora quantidade de nutrientes disponibilizados por F. mannifera não promova um pulso de nutrientes no local estudado.

Abstract Cicadas are usually studied regarding their importance in agriculture. However, the possibility of this group to represent a pulse of nutrients can also imply on the success of a given species in the biome. The aim of this study was to assess the level of total soluble proteins and lipids of Fidicina mannifera (Fabricius, 1803), and to determine whether the species can promote a pulse of nutrients in two vegetation classes of the Brazilian Cerrado. To assess the pulse of nutrients, it was concluded the determination of total soluble proteins and lipids from samples of males and adult females of F. mannifera, and the spatial distribution of exuviae of this species was also calculated in two vegetation classes of the Brazilian Cerrado. The amount of protein provided by each individual did not differ between males and females (p = 0.66) but females had 40% more lipids than males (p = 0.05). Regarding F. mannifera the gallery forest offered 11.75 g/ha of protein, 3.91 g/ha of lipids, and the Cerrado stricto sensu offered 4.25 g/ha of protein, and 1.41 g/ha of lipid. The male cicadas have a hollow abdomen, which houses a resonance chamber for sound production in order to attract females to mate, and females store larger amounts of lipids, mainly located in the abdominal cavity, where the body fat is directly linked to the reproductive system for the development of the ovaries and egg production after emergence. The mass occurrence of F. mannifera in the Brazilian Cerrado and the fast availability of proteins and lipids make this species a food resource that can directly impact the diet of secondary consumers and scavengers, although the amount of nutrients available by F. mannifera does not promote a pulse of nutrients in the study site.

Palygorskite is fibrous clay in which the structural tetrahedral and octahedral layers are organized in a way that structural channels are formed, leading to high surface area. However, impurities inside the channels and aggregated ones considerably reduce the available area. In order to increase the surface area, an activation treatment can be considered useful. The goal of this work is the activation of palygorskite from Guadalupe, Piauí, via sulfuric acid treatment using a two-level factorial design. The influence of three parameters (solution molarity, temperature and time) on BET surface area was determined. Moreover, samples were characterized via X-ray diffraction (XRD) and fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The largest surface area (282 m²/g) without considerable changes in clay structure and morphology was found in a sample treated with 5M H2SO4 at 70°C for 1h. The main parameters that favored the improvement of the surface area were the solution's molarity, temperature and their interaction.

Dentre as cerâmicas de uso biomédico destaca-se o fosfato tricálcico do tipo β (β-TCP). Pós cerâmicos são normalmente compactados e sinterizados em altas temperaturas para sua densificação e consequente aumento da resistência mecânica. Uma forma de otimizar a densificação de corpos cerâmicos é analisar a significância das variáveis de processamento por meio de um planejamento de experimentos. O objetivo deste trabalho foi determinar a significância dos seguintes parâmetros: pressão de compactação uniaxial (28 e 111 MPa); calcinação prévia do pó (como recebido - não calcinado e calcinado a 650 °C); temperatura e tempo de sinterização (respectivamente, 900 e 1150 °C, 2 e 4 h). As pastilhas produzidas foram caracterizadas por microscopia eletrônica de varredura, difração de raios X e espectroscopia no infravermelho, enquanto que a microdureza e a retração linear foram consideradas as respostas do planejamento. Observou-se que o aumento da pressão de compactação e da temperatura de sinterização foram os parâmetros mais importantes para a densificação das amostras. As pastilhas sinterizadas a 1150 °C apresentaram tamanho médio de grão entre 1 e 2 µm e retração linear máxima de aproximadamente 20%, bem superior à das amostras sinterizadas a 900 °C, que não apresentaram completa densificação. Não foram identificadas outras fases que não o β-TCP e também não foram observadas microtrincas nas amostras sinterizadas.

Among the ceramic materials for biomedical applications, tricalcium phosphate type β (β-TCP) can be highlighted. Usually, ceramic powders are pressed and densified at high temperatures in order to improve the mechanical strength. One way to optimize the densification of ceramic bodies is to analyze the significance of processing variables using an experimental design. The purpose of this work is to determine the significance of the following parameters: uniaxial pressure (28 and 111 MPa); previous thermal treatment of the powder (as-received -non-calcined and calcined at 650 °C); sintering temperature and time (900 and 1150 °C, 2 and 4 h, respectively). The produced tablets were characterized by scanning electron microscopy, X-ray diffraction and infrared spectroscopy, while linear shrinkage and microhardness results were considered as responses of the experimental design. It was observed that the uniaxial pressure and sintering temperature were the most important parameters for samples densification. The average grain size of the tablets sintered at 1150 °C was approximately 1-2 µm and maximum linear shrinkage of, approximately, 20%, well above the values found for the samples sintered at 900 °C, which did not present complete densification. Phases other than β-TCP were not present in the sintered samples and no cracking was observed.