Results 1 - 10 of 16539
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[en] SiOCH ULK films with k-value from 2.5 to 2.1 and porosity from 24 to 40% were etched in CHF3, CHF3 + Ar, CF4 and CF4 + Ar plasmas at +15…−120 °C with and without bias being applied. It was shown that the presence of Ar in gas mixture can significantly increase the damage of unetched ultra low-k (ULK) material (at sidewalls) due to the removal of −CH3 groups from the film by VUV photons. It was also shown that etching and damage of the sidewalls by F atoms can be partially prevented by lowering the temperature of the sample. (paper)
[en] Zeolite with trimodal porosity can be synthesized by desilication of zeolite nanocrystal aggregate. In the desilication process, the originally existed intercrystalline mesopores of zeolite nanocrystal aggregate were enlarged into large mesopore, and the new small intracrystalline mesopore channel was created, thus the Zeolite with trimodal porosity was formed. The structure of resulted zeolite, both on aggregate and mesopore level can be fine tuned by the desilication degree. - Graphical abstract: The Si from the edges and boundary of nanocrystals was first removed resulted the surface roughness and enlarges of the originally existed intercrystalline mesopores. As the degree of alkali-treatment increasing, the Si species inside zeolite nanocrystals was also removed, leading to further enlarges the intercrystalline mesopores and the formation of small intracrystalline mesopores. In case the alkali-treatment is serve enough to completely dissolve the bridges between zeolite nanocrystals, zeolite nanocrystals were exfoliated from the aggregate. Highlights: ► Zeolite with trimodal porosity by desilication of zeolite nanocrystals aggregate. ► The original intercrystalline mesopores were enlarged into large mesopore. ► The new intracrystalline mesopores were created as the inside Si extracted out. ► The aggregate structure, crystallinity and acidity of parent zeolite remained. ► Desilication is start on the edges then in the inner part of zeolite.
[en] In order to overcome the difficulty of choosing appropriate grading parameters of filling material for mines which are using filling mining method, the fractal theory is introduced, and a fractal equation of grading is built to represent gradation. Meanwhile taken Dahongshan copper mine as an example to discuss the relationship between fractal dimension and porosity, cementing strength under different parameters. A prediction model of cementing strength is built based on the experimental data, and the results show that the optimal grading parameters of Dahongshan copper mine is fractal dimension = 2.82. The optimized grading parameters of filling material in Dahongshan run steady, which greatly reduced the filling cost. (paper)
[en] In this work, we model the biofilm growth at the microscale using a rectangular pore network model in 2D and a cubic network in 3D. For the 2D network, we study the effects of bioclogging on porosity and permeability when we change parameters like the number of nodes in the network, the network size, and the concentration of nutrients at the inlet. We use a 3D cubic network to study the influence of the number of nodes in the z direction on the biofilm growth and on upscalability. We show that the biofilm can grow uniformly or heterogeneously through the network. Using these results, we determine the conditions for upscalability of bioclogging for rectangular and cubic networks. If there is uniform biofilm growth, there is a unique relation between permeability and porosity, K ∼ ϕ2, this relation does not depend on the volume of the network, therefore the system is upscalable. However, if there is preferential biofilm growth, the porosity-permeability relation is not uniquely defined, hence upscalability is not possible. The Damköhler number is used to determine when upscalability is possible. If the Damköhler number is less than 101, the biofilm grows uniformly and therefore the system is upscalable. However, if the Damköhler number is greater than 103, the biofilm growth exhibits a deviation from uniform biofilm growth and heterogeneous growth is observed, therefore upscalability is not possible. There is a transition from uniform growth to preferential growth if the Damköhler number is between 101 and 103.
[en] The development of the process to obtain porous pieces with specific pore size distribution by powder metallurgy has been described with reference to gas absorbers (getters). The evolution of the pressing and sintering procedures have been described. Specific characteristics of porosity distribution have been obtained by controlling the process variables and by the addition of pore forming substances. (author)
[en] Modeling of dring of capillary porous media is difficult due to the complex and coupled heat and mass transfer that occur at dynamic liquid-gas-sold interface. Thus far, drying was simulated using either continuum models or pore-network models, both of which have limitations. In this work, the Lattice Boltzmann Method (LBM) is used to simulate the drying in porous media. The LBM is ideal for such simulations as it can incorporate complex effects in a simple way to exhibit realistic fluid-gas interface during drying of capillary porous media. (Author)
[en] Self compacting concrete (SCC) seem to be a very promising materials for construction thanks to their properties in a fresh state. Studying of the influence of the parameters of specific designed mixes to their mechanical, physical and chemical characteristics in a state hardened is an important stage so that it can be useful for new-to-the-field researchers and designers (worldwide) beginning studies and work involving self compacting concrete. The objective of this research is to study the durability of self compacting concrete. The durability of concrete depends very much on the porosity; the latter determines the intensity of interactions with aggressive agents. The pores inside of concrete facilitate the process of damage, which began generally on the surface. We are interested to measure the porosity of concrete on five SCC with different compositions (w/c, additives) and vibrated concrete to highlight the influence of the latter on the porosity, thereafter on the compressive strength and the transfer properties (oxygen permeability, chloride ion diffusion, capillary absorption). (author)
[en] This work deals with the theoretical study of the asphalt based solids leaching. A unified descriptive model has been developed in order to take advantage of the available knowledge and to propose an evolution of the model to leaching conditions the most general possible (series of free swelling phases and of forced swelling phases). The proposed approach consists to answer analytically and numerically the model for two limit cases (free swelling and initially forced), in order to reveal the influence parameters and to explain why it is expected that the phenomenologies differ. (O.M.)
[en] Microporosities play important biologic and mechanical roles on health. One of the side effects caused by some chemotherapy drugs is the induction of amenorrhea, temporary or not, in premenopausal women, with a consequent decrease in estrogen production, which can lead to cortical bone changes. In the present work, the femur diaphysis of rats treated with chemotherapy drugs were evaluated by 3D morphometric parameters using synchrotron radiation microtomography. Control animals were also evaluated for comparison. The 3D tomographic images were obtained at the SYRMEP (SYnchrotron Radiation for MEdical Physics) beamline at the ELETTRA Synchrotron Laboratory in Trieste, Italy. Results showed significant differences in morphometric parameters measured from the 3D images of femur diaphysis of rats. - Highlights: • Changes in cortical bone porosity due to chemotherapeutic drugs. • 3D morphometric parameters with synchrotron radiation microtomography. • Chemotherapy induced bone loss in rats.