The influence of preparation method on the physicochemical properties of titania–silica aerogels

A series of titania–silica aerogels with different compositions were prepared using four different preparation methods. The preparation steps were followed by a high temperature supercritical drying (HTSCD). It was found that application of ethanol and 2-propanol as the solvents for the titania precursor (with or without modification with acetyloacetone) resulted in materials with BET surface area up to 990 m²/g, total pore volume up to 5.6 cm³/g and density as low as 0.041 g cm⁻³. Obtained aerogels were mesoporous materials with the average pore diameter in the range 11–27 nm. It was stated that application of the I method (prehydrolysis) resulted in aerogels with higher average pore diameter than other preparation methods while aerogels with the lowest average pore diameter were obtained using the so-called IV, impregnation method. Anatase form of titania was found in all prepared samples. The prepared aerogels were being applied as catalysts in photodegradation of salicylic acid solution in water. The obtained results suggest a much higher catalytic efficiency of titania, which is present in aerogel than it is in the case of commercial P25 Degussa titanium dioxide.     

Effect of additive structure and size on SiO2 formation in polymer‐derived SiOC ceramics

Silicon oxycarbide (SiOC) ceramics with highly adjustable properties and microstructures have many promising applications in batteries, catalysis, gas separation, and supercapacitors. In this study, additive structures on the nucleation and growth of SiO₂ within SiOC ceramics are investigated by adding cyclic tetramethyl‐tetravinylcyclotetrasiloxane (TMTVS) or caged octavinyl‐polyhedral oligomeric silsesquioxane (POSS) to a base polysiloxane (PSO) precursor. The effects of the 2 additives on the polymer‐to‐ceramic transformation and the phase formation within the SiOC are discussed. POSS encourages SiO₂ nucleation and leads to more SiO₂ formation with significantly increased ceramic yield, which subsequently leads to higher specific surface of 1557 m²/g with a larger pore size of ～1.8 nm for the porous SiOC. High TMTVS content decreases both the specific surface area and pore volume of the resulting porous SiOCs. This study demonstrates a new approach of using Si‐rich additive POSS to increase the SiOC yield while maintaining or even increasing the specific surface area.     

Ion irradiation effect on spark plasma sintered silicon carbide ceramics with nanostructured ferritic alloy aid

Silicon carbide (SiC) is a promising material with excellent chemical and physical performance under irradiation for advanced nuclear applications. The addition of nanostructured ferritic alloy (NFA) has been proven beneficial for the densification of SiC ceramics based on our previous work. To understand their microstructural evolution and irradiation resistance, spark plasma sintered (SPSed) SiC ceramics with and without NFA aid (0 vol% NFA‐100 vol% SiC, 2.5 vol% NFA‐97.5 vol% SiC, and 5 vol% NFA‐95 vol% SiC) were exposed to 5 MeV Si⁺⁺ irradiation. The ion irradiation strongly modifies the surface morphology with isolated sand dune shaped structures, which can be explained by the Bradley‐Harper (B‐H) theory. SRIM simulation for both the pure SiC and NFA‐SiC predicts similar surface damage of ~45 dpa and peak damage of ~790 dpa at ~2.0 μm depth. For the actual samples, the SiC matrix is completely amorphous up to ~2.2 μm thickness (from the surface dune valley to the amorphous layer boundary), which is consistent with the SRIM predicted depth of ~2.3 μm. Reaction product (Fe,Cr)₃Si in the NFA‐SiC samples maintains a crystalline structure with dislocation loops. A defect rate model is applied to understand the fundamental difference in ion irradiation resistance between SiC and (Fe,Cr)₃Si.     

Effect of montmorillonite clay addition on the morphological and physical properties of Jatropha curcas L. and Glycine max L. protein concentrate films

Protein concentrates from jatropha (JPC) and soy seeds (SPC) were obtained by solubilization and acid precipitation of proteins. JPC and SPC films were prepared by the casting method, using two different montmorillonite (MMT) clay concentrations and plasticized with glycerol. Film properties were evaluated by scanning electron microscopy, transmission electron microscopy, X‐ray diffraction (XRD), Fourier transform infrared spectroscopy, thermogravimetric analysis, tensile properties, water retention, and water vapor transmission rate (WVRT). Typical tactoid microcomposite structures were found to be heterogeneously dispersed in the films containing MMT. A small XRD peak was found in films with MMT. Slight improvements in thermal stability and tensile strength were observed in the films with MMT. Reductions in water retention and WVRT were obtained when MMT was added into the films. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44459.     

The Use of Fractional Factorial Design for Atrium Fires Prediction

In order to mitigate the excessive computational cost of atrium fire simulations, a novel methodology based on the use of the Fractional Factorial Design technique to obtain an experimental validated tool, in the form of a surface response model, capable to predict fire induced conditions is proposed. This methodology is supported by results from a Design of Experiments benchmark, which consists of a set of FDS simulations in the present work. Specifically, a \(2^{6-2}_{IV}\) approach has been considered and applied to a 20 m cubic atrium. Thus, six factors have been considered, namely the fire Heat Release Rate (HRR) and location, the exhaust flow rate, the exhaust location and activation time, and the inlet vents area. Furthermore, the smoke temperature at the roof and 15 m high and the smoke layer height have been considered the variables of interest. Subsequently, a multiple linear regression analysis has been performed to predict and compare the steady and non-steady temperature profiles and the smoke layer drop with six novel full-scale atrium fire tests, and also with specific adjusted FDS models. In addition, this methodology has been extended successfully to predict the non-steady behaviour of the fire tests. At the steady state, the HRR and the exhaust flow rate have been found to be the most relevant factors. The results obtained with the proposed methodology show a good fit both with the fire tests and with the adjusted FDS models, with discrepancies mostly below 14%. For non-steady conditions, a time analysis of the influence of the six factors has been carried out. Again, remarkable good agreement with the time-dependent experimental results is achieved, with average discrepancies below 12%, being the larger differences found in the prediction of local effects, such as the smoke ceiling jet, for high HRR or when the make-up air influence is significant. The results turn this methodology into a powerful and useful tool for fire safety designs.     

Creating Inclusive Communities through Balancing Social Mix: A Critical Relationship or Tenuous Link?

This paper explores some fundamental assumptions being linked by State Housing Authorities to 'social mix' strategies in contemporary Australian public housing estate regeneration policy. Six case-study estates, two each in New South Wales, South Australia and Queensland form the basis for the empirical analysis. The two major ideas emerging from South Australian and Queensland projects are: first that lowering concentrations of public housing and developing more mixed income communities offers a means to reconnect socially excluded public housing tenants to mainstream society; second that a balanced social mix is a prerequisite for the development of 'inclusive', 'sustainable' and 'cohesive' communities. However, in light of the empirical findings that strong cohesive communities already exist on some estates prior to regeneration commencing, there is no evidence that a balanced social mix is a necessary condition for building inclusive communities. Coupled with findings in the projects of inadvertent negative consequences of implementing social mix policies, the paper questions whether policy makers are over-emphasising the extent to which social mix assists regeneration.     

Children's early interest-based activities in the home and subsequent information contributions and pursuits in kindergarten.

This study examined the early interests of 109 children and their subsequent information contributions and pursuits in kindergarten. Four groups of children with similar interests were identified on the basis of the children's profiles of activities in the home, tracked bimonthly for over a year. Activity patterns reflected conceptual, social, procedural, or creative interests. The role of early interests in understanding academic engagement was investigated, with gender, cognitive skill, and temperament statistically controlled. Observational data from throughout the school year revealed differences in the types of information that children contributed to discussions and pursued in class related to children's early interests. Findings enrich understanding of young children's academic behaviors and extend theoretical models of academic self-instruction behaviors such as information exchanges and pursuits in classrooms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Multi‐Material Tissue Engineering Scaffold with Hierarchical Pore Architecture

Multi‐material polymer scaffolds with multiscale pore architectures are characterized and tested with vascular and heart cells as part of a platform for replacing damaged heart muscle. Vascular and muscle scaffolds are constructed from a new material, poly(limonene thioether) (PLT32i), which meets the design criteria of slow biodegradability, elastomeric mechanical properties, and facile processing. The vascular–parenchymal interface is a poly(glycerol sebacate) (PGS) porous membrane that meets different criteria of rapid biodegradability, high oxygen permeance, and high porosity. A hierarchical architecture of primary (macroscale) and secondary (microscale) pores is created by casting the PLT32i prepolymer onto sintered spheres of poly(methyl methacrylate) (PMMA) within precisely patterned molds followed by photocuring, de‐molding, and leaching out the PMMA. Prefabricated polymer templates are cellularized, assembled, and perfused in order to engineer spatially organized, contractile heart tissue. Structural and functional analyses show that the primary pores guide heart cell alignment and enable robust perfusion while the secondary pores increase heart cell retention and reduce polymer volume fraction.     

An LNG release, transport, and fate model system for marine spills

LNGMAP, a fully integrated, geographic information based modular system, has been developed to predict the fate and transport of marine spills of LNG. The model is organized as a discrete set of linked algorithms that represent the processes (time dependent release rate, spreading, transport on the water surface, evaporation from the water surface, transport and dispersion in the atmosphere, and, if ignited, burning and associated radiated heat fields) affecting LNG once it is released into the environment. A particle-based approach is employed in which discrete masses of LNG released from the source are modeled as individual masses of LNG or spillets. The model is designed to predict the gas mass balance as a function of time and to display the spatial and temporal evolution of the gas (and radiated energy field).

LNGMAP has been validated by comparisons to predictions of models developed by ABS Consulting and Sandia for time dependent point releases from a draining tank, with and without burning. Simulations were in excellent agreement with those performed by ABS Consulting and consistent with Sandia's steady state results.

To illustrate the model predictive capability for realistic emergency scenarios, simulations were performed for a tanker entering Block Island Sound. Three hypothetical cases were studied: the first assumes the vessel continues on course after the spill starts, the second that the vessel stops as soon as practical after the release begins (3 min), and the third that the vessel grounds at the closest site practical. The model shows that the areas of the surface pool and the incident thermal radiation field (with burning) are minimized and dispersed vapor cloud area (without burning) maximized if the vessel continues on course. For this case the surface pool area, with burning, is substantially smaller than for the without burning case because of the higher mass loss rate from the surface pool due to burning. Since the vessel speed substantially exceeds the spill spreading rate, both the thermal radiation fields and surface pool trail the vessel. The relative directions and speeds of the wind and vessel movement govern the orientation of the dispersed plume.

If the vessel stops, the areas of the surface pool and incident radiation field (with burning) are maximized and the dispersed cloud area (without burning) minimized. The longer the delay in stopping the vessel, the smaller the peak values are for the pool area and the size of the thermal radiation field. Once the vessel stops, the spill pool is adjacent to the vessel and moving down current. The thermal radiation field is oriented similarly. These results may be particularly useful in contingency planning for underway vessels.