Nanoconfinement degradation in NaAlH4/CMK-1

An ordered mesoporous carbon scaffold (CMK-1) has been synthesized and infiltrated with NaAlH₄ nanoparticles by solvent- and melt-infiltration techniques. Small angle X-ray scattering (SAXS), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM) and energy dispersive spectroscopy (EDS) are used to characterize the structure, composition and morphology before and after thermal treatment. This study illuminates some of the problems that can be associated with nanoconfinement of hydrogen storage materials including scaffold contamination, residual solvent contamination, sample morphology changes after heating, and other factors that can be detrimental to the application of these systems. Of particular interest is the expulsion of NaAlH₄ decomposition products from the scaffold after heating beyond its melting point under vacuum. This results in the surface of mesoporous carbon particles having arrays of multi-micron-long Al filaments that are >100 nm in diameter.     

Wettability of carbon surfaces by pure molten alkali chlorides and their penetration into a porous graphite substrate

The wettability of graphite and glassy carbon surfaces by pure molten alkali chlorides (NaCl, KCl, RbCl, CsCl) was measured by the sessile drop method. The contact angle was found to decrease with increase of the cation radius of the chloride. Using our measured and available literature data, a new, semi-empirical model is established to estimate the adhesion energy between the 20 alkali halide molten salts and graphite (or glassy carbon). The adhesion energy is found to increase with square of the radius of the cation, and the inverse of the radius of the anion of the salt. The minimum possible value for the surface energy of graphite (and glassy carbon) was found as 150 ± 30 mJ/m². The critical contact angle of spontaneous penetration (infiltration) of the molten chlorides into a porous graphite substrate was found experimentally below 90°, in the interval between 31° and 58°. This is explained by the inner structure of the porous graphite.     

Model for Coupled Liquid Water Flow and Heat Transport with Phase Change in a Snowpack

The flow of liquid water in a snowpack is complex because of the coupled processes involved, including the phase change between liquid and solid, and the latent and sensible heat transfer processes. To properly describe the details of spatial and temporal changes in a snowpack it is necessary to include these coupled processes. This paper presents a numerical model of coupled liquid water flow and heat transport in a snowpack. The model is intended to quantify infiltration into a snowpack, and evaluate the potential for the formation of distinct heterogeneities in liquid water and heat transport properties in a snowpack. The numerical model solves the two-dimensional form of the governing coupled equations using a finite difference scheme. The governing equations assume thermodynamic equilibrium between the solid and liquid phases in the snowpack. Equations describing the metamorphosis of ice grains during liquid water flow are applied within the model, and the heat and liquid water transport properties of the snow are treated with relations identical to those used for mineral porous media. Sample solution results for an alternative formulation taken from the literature are used to test the present solution, and it is found that the present model yields similar results but with some distinct differences. The effect of direct coupling of the temperature with the liquid water pressure is presented in a simple horizontal freezing simulation, which is compared with the Stefan problem where liquid water is not redistributed. Overall the direct coupling and water redistribution is found to lead to greater front penetration in comparison to the Stefan formulation. For infiltration with gravity it is shown that grain size growth during infiltration leads to increased wetting front penetration.     

Using Compost to Increase Infiltration and Improve the Revegetation of a Decomposed Granite Roadcut

Decomposed granite (DG) soils are very erosive and, when disturbed, are difficult to revegetate. Sediment eroding from DG roadcuts can severely impact nearby drainage basins. Two ways of reducing surface erosion are to increase the surface saturated hydraulic conductivity (Ksat) of the soil and to stabilize the surface with vegetation. This study examined the ability of unscreened yard waste compost to increase the Ksat of these soils and facilitate revegetation. A compost application rate of 24% by volume increased postconstruction Ksat of a DG roadcut to levels comparable to a revegetated reference site. The establishment of vegetation was important to maintain the initial increase in Ksat associated with tillage and compost amendment. By the second year, above-ground biomass significantly increased with increasing compost amendment rate. There was also a significant increase in soil Ksat in the 12 and 24% compost treatments in the second year compared to the first year, indicating the strong influence of plant growth on soil surface hydrology.     

Quantifying the contribution of ambient and indoor‐generated fine particles to indoor air in residential environments

Indoor fine particles (FPs) are a combination of ambient particles that have infiltrated indoors, and particles that have been generated indoors from activities such as cooking. The objective of this paper was to estimate the infiltration factor (F_inf) and the ambient/non‐ambient components of indoor FPs. To do this, continuous measurements were collected indoors and outdoors for seven consecutive days in 50 non‐smoking homes in Halifax, Nova Scotia in both summer and winter using DustTrak (TSI Inc) photometers. Additionally, indoor and outdoor gravimetric measurements were made for each 24‐h period in each home, using Harvard impactors (HI). A computerized algorithm was developed to remove (censor) peaks due to indoor sources. The censored indoor/outdoor ratio was then used to estimate daily F_infs and to determine the ambient and non‐ambient components of total indoor concentrations. F_inf estimates in Halifax (daily summer median = 0.80; daily winter median = 0.55) were higher than have been reported in other parts of Canada. In both winter and summer, the majority of FP was of ambient origin (daily winter median = 59%; daily summer median = 84%). Predictors of the non‐ambient component included various cooking variables, combustion sources, relative humidity, and factors influencing ventilation. This work highlights the fact that regional factors can influence the contribution of ambient particles to indoor residential concentrations.     

Infiltration of SOFC Stacks: Evaluation of the Electrochemical Performance Enhancement and the Underlying Changes in the Microstructure

Experimental SOFC stacks with 10 SOFCs (LSM‐YSZ/YSZ/Ni‐YSZ) were infiltrated with CGO and Ni‐CGO on the air and fuel side, respectively in an attempt to counter degradation and improve the output. The electrochemical performance of each cell was characterized (i) before infiltration, (ii) after infiltration on the cathode side, and (iii) after the infiltration of the anode side. A significant performance enhancement was observed after the infiltration with CGO on the cathode, while the infiltration of the anode side with Ni‐CGO had no significant effect on the electrochemical performance. After testing the cells were characterized by SEM and TEM/EELS. A thin layer of CGO nanoparticles around the LSM‐YSZ back bone structure was found after infiltration. On the anode side nano sized Ni particles were found embedded in a CGO layer formed around the Ni‐YSZ structure. EELS analysis showed that the oxidation state of the Ce ions is identical on the air and the fuel side.     

Hollow polymeric microcapsules: Preparation, characterization and application in holding boron trifluoride diethyl etherate

A novel method was proposed to prepare boron trifluoride diethyl etherate ((C₂H₅)₂O·BF₃)-loaded microcapsules. To protect the high activity of (C₂H₅)₂O·BF₃, hollow microcapsules were prepared via UV-initiated polymerization in emulsion with the aid of CO₂ microbubble templates, evacuation, and immersion in (C₂H₅)₂O·BF₃ allowing infiltration of the chemical. The selected photo-initiator induced rapid curing of the oil layer in the CO₂/oil/water emulsion, ensuring production of the desired hollow capsules. Structure, geometry, morphology and properties of the resultants were carefully studied in relation to their synthesis conditions and loading behavior in liquid (C₂H₅)₂O·BF₃. The results indicated that the amount of (C₂H₅)₂O·BF₃ filled in the capsules can be adjusted by changing the shell composition. Having been encapsulated, (C₂H₅)₂O·BF₃ maintained its reactivity with epoxy.     

Overview of pressure coefficient data in building energy simulation and airflow network programs

Wind pressure coefficients (C_p) are influenced by a wide range of parameters, including building geometry, facade detailing, position on the facade, the degree of exposure/sheltering, wind speed and wind direction. As it is practically impossible to take into account the full complexity of pressure coefficient variation, building energy simulation (BES) and Airflow network (AFN) programs generally incorporate it in a simplified way. This paper provides an overview of pressure coefficient data and the extent to which they are currently implemented in BES–AFN programs. A distinction is made between primary sources of C_p data, such as full-scale measurements, reduced-scale measurements in wind tunnels and computational fluid dynamics (CFD) simulations, and secondary sources, such as databases and analytical models. The comparison between data from secondary sources implemented in BES–AFN programs shows that the C_p values are quite different depending on the source adopted. The two influencing parameters for which these differences are most pronounced are the position on the facade and the degree of exposure/sheltering. The comparison of C_p data from different sources for sheltered buildings shows the largest differences, and data from different sources even present different trends. The paper concludes that quantification of the uncertainty related to such data sources is required to guide future improvements in C_p implementation in BES–AFN programs.     

界面合金化制备WC_P颗粒增强钢基复合材料

采用真空实型负压铸渗工艺,通过在预制复合层中添加适量钼铁粉进行界面合金化,成功制备出了WCP颗粒增强钢基表面复合材料。结合OM、SEM、XRD和显微硬度计等分析手段对复合层物相组成、显微结构与性能进行了测试。结果表明,添加16.67%(质量分数)的钼铁粉有效改善了复合层界面组织及力学性能的连续性,改善了复合材料的铸渗效果,增加了铸渗层厚度,合金碳化物含量增加,复合层基体硬度约是基材的2倍,提高了复合材料的耐磨性。     

Data-mining analysis of in-sewer infiltration patterns: seasonal characteristics of clear water seepage into Brussels main sewers

Parasitic clear water infiltration is known to increase the waste water volumes in most sewerage systems. Amongst others, a problem arising from that is a significant variation of waste water pollutant concentration over time, which complicates the purification process and increases its cost. Capitalizing on new extensive databases, we propose a new method for the identification of clear water infiltration rates based on data-mining and data consolidation of long time data series. Based on a straightforward anthropogenic tracer, together with a simple but rigorous water budget, the infiltrated volumes are quantified day-by-day for the entire zone treated by a major waste water treatment plant. Brussels city is used as an example of the applicability of the method over several years, demonstrating the significant seasonal changes in sewer infiltration rates in the area and the progress achieved so far by structural sewer repair.