Estudo de massa cerâmica triaxial visando à otimização do ciclo de queima da indústria de cerâmica estrutural

Over recent years the structural ceramics industry in Brazil has found a very favorable market for growth. However, difficulties related to productivity and product quality are partially inhibiting this possible growth. An alternative for trying to solve these problems and, thus, provide the pottery industry the feasibility of full development, is the substitution of firewood used in the burning process by natural gas. In order to contribute to this process of technological innovation, this paper studies the effect of co-use of ceramic phyllite and kaolin waste on the properties of a clay matrix, verifying the possible benefits that these raw materials can give to the final product, as well as the possibility of such materials to reduce the heat load necessary to obtain products with equal or superior quality. The study was divided into two steps: characterization of materials and study of formulations. Two clays, a phyllite and a residue of kaolin were characterized by the following techniques: laser granulometry, plasticity index by Atterberg limits, X-ray fluorescence, X-ray diffraction, mineralogical composition by Rietveld, thermogravimetric and differential thermal analysis. To study the formulations, specifically for evaluation of technological properties of the parts, was performed an experimental model that combined planning involving a mixture of three components (standard mass x phyllite x kaolin waste) and a 23 factorial design with central point associated with thermal processing parameters. The experiment was performed with restricted strip-plot randomization. In total, 13 compositional points were investigated within the following constraints: phyllite ≤ 20% by weight, kaolin waste ≤ 40% by weight, and standard mass ≥ 60% by weight. The thermal parameters were used at the following levels: 750 and 950 °C to the firing temperature, 5 and 15 °C/min at the heating rate, 15 and 45min to the baseline. The results showed that the introduction of phyllite and/or kaolin waste in ceramic body produced a number of benefits in properties of the final product, such as: decreased absorption of water, apparent porosity and linear retraction at burn; besides the increase in apparent specific mass and mechanical properties of parts. The best results were obtained in the compositional points where the sum of the levels of kaolin waste and phyllite was maximal (40% by weight), as well as conditions which were used in firing temperatures of 950 °C. Regarding the prospect of savings in heat energy required to form the desired microstructure, the phyllite and the residue of kaolin, for having small particle sizes and constitutions mineralogical phases with the presence of fluxes, contributed to the optimization of the firing cycle.

Efeitos da respiração em freno-labial sobre os volumes pulmonares e o padrão de hiperinsuflação dinâmica em pacientes com asma

Objectives: To evaluate how to develop dynamic hyperinflation (DH) during exercise, the influence of pursed-lip breathing in (PLB) on breathing pattern and operating volume in patients with asthma. Methods: We studied 12 asthmatic patients in three moments: (1) anthropometry and spirometry, (2) submaximal incremental cycle ergometer test in spontaneous breathing and (3), submaximal incremental test on a cycle ergometer with PLB using the Opto-electronic plethysmography. Results: Evaluating the end-expiratory lung volume (EEV) during submaximal incremental test in spontaneous breathing, patients were divided into euvolume and hyperinflated. The RFL has increased significantly, the variation of the EEV group euvolume (1.4L) and decreased in group hyperinflated (0.272L). In group volume observed a significant increase of 140% in Vt at baseline, before exercise, comparing the RFL and spontaneous breathing. Hyperinflated group was observed that the RFL induced significant increases of Vt at all times of the test incremental baseline, 50%, 100% load and 66% recovery, 250%, 61.5% and 66% respectively. Respiratory rate decreased significantly with PLB at all times of the submaximal incremental test in the group euvolume. The speed of shortening of inspiratory muscles (VtRcp/Ti) in the hyperinflated increased from 1.6 ± 0.8L/s vs. 2.55 ± 0.9L/s, whereas in the RFL euvolume group ranged from 0.72 ± 0.31L/s vs. 0.65 ± 0.2L/s. The velocity of shortening of the expiratory muscles (VtAb/Te) showed similarity in response to RFL. In group hyperinflated varied vs. 0.89 ± 0.47 vs. 0.80 ± 0.36 and ± 1.17 ± 1L vs. 0.78 ± 0.6 for group euvolume. Conclusion: Different behavior in relation to EEV in patients with moderate asthma were observed, the HD and decreased EEV in response to exercise. The breathing pattern was modulated by both RFL performance as at home, making it more efficient