In the present work blends of polystyrene (PS) with sepiolites have been produced using a melt extrusion process. The dispersion degree of the sepiolites in the PS has been analyzed by dynamic shear rheology and X-ray micro-computed tomography. Sepiolites treated with quaternary ammonium salts (O-QASEP) are better dispersed in the PS matrix than natural sepiolites (N-SEP) or sepiolites organo-modified with silane groups (O-SGSEP). A percolated network is obtained when using 6.0 wt% of O-QASEP, 8.0 wt% of N-SEP and 10.0 wt% of O-SGSEP. It has been shown that multiple extrusion processes have a negative effect on the polymer architecture. They produce a reduction in the length of the polymeric chains, and they do not lead to a better dispersion of the particles in the polymer matrix. Foams have been produced using a gas dissolution foaming process, where a strong effect of the dispersion degree on the cellular structure of the different foams was found. The effects on the cellular structure obtained by using different types of sepiolites, different contents of sepiolites and different extrusion conditions have been analyzed. The foams produced with the formulations containing O-QASEP present the lowest cell size and the most homogeneous cellular structures. 相似文献
A theoretical approach for the interpretation of the kinetics of simultaneous stable and metastable phase precipitation in
a binary system is proposed. The model, based on the nucleation and growth theory, defines a critical size different for each
phase. The size of the clusters evolves by adding or substracting a single atom one at a time. A set of coupled differential
equations is obtained for the chemical rate whose solution reproduces the kinetics of thermoelectric power measurements in
the Fe-C multiphase system. Suppositions about the growing and dissolution rate constants reduce the size of the equation
system with a gain in computation time. 相似文献
Consumers demand organic products because they believe that the organic products are more flavorful and respectful to the
environment and human health. The effects of organic farming on the minerals contents and aroma composition of Clemenules
mandarin juices were studied. Minerals (Fe, Cu, Mn, Zn, Ca, Mg, K, and Na) were quantified using atomic absorption-emission
spectroscopy, while volatile compounds were extracted using the dynamic headspace technique and were identified and quantified
by GC–MS. In general, organic farming produced a mandarin juice with a higher quality than that produced by conventional agricultural
practices. Higher concentrations of both minerals and positive volatile compounds were found in the organic juice, while the
formation of off-flavors was higher in the conventional juice, although threshold values were not reached. 相似文献
This article proposes a scheme for the on-line adjustment of three mode controller settings based on experimental measurements of closed-loop performance. It uses a recently developed heuristic tuning procedure to identify estimated process parameters. This method may give rise to conflicting estimates. Fuzzy Set theory is applied to manage the situation in terms of a fuzzy conjunction to combine the various estimates. PID control was chosen because of its wide use in the industrial environment due to driving simplicity and robustness. The article shows design, development, and computer simulation aspects. 相似文献
Optimal solutions in environmental catalysis require a well-coordinated development of catalysts and of process design. This contribution is devoted to energy integrated design concepts for fuel reforming and for automotive exhaust purification. The examples presented demonstrate the importance of an innovative process design for optimal utilization of existing catalysts and show the potential of future developments.
New concepts for steam reforming through the efficient coupling of the endothermic reforming reaction with an exothermic combustion reaction are discussed in the first part. These concepts have been implemented for methanol steam reforming in a counter-current reactor with distributed side feed of burner gas and for methane steam reforming in a modular reactor with a co-current reaction section for the endothermic and the combustion reaction and attached counter-current heat exchangers. Both applications employ the so-called folded sheet reactor design, which ensures an excellent heat transfer between the reforming and combustion channels and efficient heat recovery.
A similar design solution is introduced for the apparently different case of automotive exhaust purification. The proposed concept aims at decoupling exhaust after-treatment from engine control. Its main component is a counter-current heat exchanger with integrated purification stages for HC-oxidation, NOX storage and reduction and soot filtering. A small catalytic burner at the hot end of the heat exchanger provides both heat and oxidizing or reducing agents on demand. A new soot filter design allows for safe soot filter regeneration. 相似文献