1,721,057 research outputs found
150 anni di immigrazioni a Roma capitale. Borgata Finocchio e dintorni.
No full textL'intervento della mia relazione, dal titolo "Aspetti socio-demografici delle comunità straniere del VI MUnicipio del comune di Roma" illustra le principali dinamiche migratorie del VI Municipio a partire dagli anni duemila ad oggi, l'evoluzione nel corso del tempo, il tipo di progetti migratori sul territorio, gli aspetti demografici del Municipio con il maggior numero di residenti (circa 50 mila) del Comune di Rome, la presenza delle diverse comunità straniere ed ulteriori aspetti utili ad inquadrare il tema in oggetto
Influence of the degradation medium on water uptake, morphology, and chemical structure of Poly(Lactic Acid)-Sisal bio-composites
No full textA series of poly(lactic acid) (PLA) and poly(lactic acid)-based bio-composites (sisal PLA) were prepared and studied by spectroscopic and microscopic techniques as such and after immersion at room temperature in different degradation mediums (i.e., distilled and natural sea water and solutions at pH = 2, 6, and 8). In these conditions, some of their macroscopic and microscopic properties were monitored during a period of 30 days. Water absorption increased with the increasing fiber content regardless of the immersion medium. The maximum water absorption was achieved at pH = 8 (~16%), indicating a more severe action of the alkaline mediums on the samples. The diffusivity, D, of PLA decreased with the addition of fibers and acidic mediums showed higher D, indicating higher diffusivity of water through the specimens with respect to those submerged in moderate or alkaline mediums. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis evidenced a weak interaction between the PLA matrix and the sisal fibers. Very limited degradation phenomena occur in our conditions: Despite some changes in the microstructure, the PLA backbone seems to be largely resistant to hydrolysis, almost regardless of the pH value and even at the highest sisal content
Ageing mechanisms on PdOx-based catalysts for natural gas combustion in premixed burners
No full textWater absorption behavior and physico-chemical and mechanical performance of PLA-based biopolymers filled with degradable glass fibers
No full textPoly(lactic acid) (PLA)-based biopolymers filled with degradable glass fibers were submitted to real life conditions, selected based on their potential applications as beverage containers, to evaluate the feasibility of their usage at the required operational conditions. To do so, several media (i.e., buffer solutions at pH = 3, 5, 7.5, 12 and alcoholic solution) and temperatures (25, 37, 55 and 70°C) were applied to mimic the storage of food, beverage, and detergents inside or in direct contact with the bio-based prototypes. Their mechanical, spectroscopic (FTIR) and morphological (SEM) features were evaluated and compared with samples after immersion. Water absorption increased with the increasing temperature, with maximum values achieved in alcoholic solutions indicating a more severe interaction of media with the functional groups of the samples. The diffusivity, D, increased with temperature, indicating faster water diffusion rate, especially in strong alkaline media. Treatments at pH 12 led to the most relevant degradation. This behavior was confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis that evidenced a strong decrease of the ester band at 1755 cm−1 and the dissolution of the external layer of the polymeric matrix, which became more evident at higher temperatures, where several glass fibers emerged from the bulk. Tensile and flexural tests indicated a softening of the material and an increase in the plasticity of the samples with the increasing temperature. Evident embrittlement of samples was observed at higher temperatures, suggesting an increase in the crystallinity degree of the biopolymer. The obtained results showed the suitability of the PLA-based biocomposites for applications that do not require high temperatures for long periods of time. Also, the tested materials were proved to resist washing with mild detergents. These results will help in the designing of the new improved PLA-based biocomposites to meet with the target objectives on their applications
Surface chemical studies of fresh and aged Pd/BaCeO3•ZrO2 catalyst for methane combustion
No full textEffect of large d0 cation doping on gamma-alumina's acid–base and catalytic properties
No full textBACKGROUND: Catalysts based on alumina-supported metal oxides are of crucial importance in the field of heterogeneous catalysis for several applications requiring tuning of surface acidity.
RESULTS: In this work, the effects of K+, Ca2+ and La3+ cation doping have been evaluated on a well-characterized commercial gamma-Al2O3 through morphological characterization and surface characterization (Brunauer–Emmet–Teller, X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared spectroscopy). The conversion of ethanol as a test reaction
was performed over these catalysts. The impregnated oxide species essentially remain at the surface, resulting in the partial poisoning of the strongest alumina Lewis acid sites. Moreover, oxide anions may increase basicity at the surface. The doping results in a significant decrease in catalytic activity in ethanol conversion to diethyl ether and to ethylene, which is shifted at higher temperatures. On the other side, higher activity in the formation of C4 olefins was detected, namely on the K-doped
alumina.
CONCLUSION: The partial poisoning of the strongest alumina Lewis acid sites and the presence at the surface of new more basic cation–anion couples result in significant changes in catalytic ethanol conversion
Effective Ce-based catalysts deposition on ceramic open cell foams
No full textIn this work, ceramic powder dispersion was achieved by using a glycerol/water solution as dispersion medium and polyvinyl alcohol as binder and rheology modifier. Five different powders were dispersed and they were deposited onto open cell ceramic foams: the bare carrier (i.e. cerium oxide) and four catalytically active powders (i.e. nickel, cobalt, iron and copper oxides supported on eerie). Catalysts powders have been extensively characterized and were demonstrated to be suitable samples candidates of model powders for the deposition onto open-cell foams. Rheological properties were found to be related to the dispersed powder, thus directly affecting washcoat load. Multiple depositions were performed by means of dip-coating on 20, 30 and 40 PPI Y-stabilized ZrO2 open cell foams. Depending on formulation and foam pore density, coating loads in the 6-30 % wt. range were obtained. Washcoat layers were found to be quite homogeneous and well adherent therefore suitable for catalytic applications, such as for instance the methane steam reforming synthesis for Ni-based catalysts
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