Effect of Environmental Conditions on the Dehydration and Performance of Fire-Protective Gels

During wildfire events fire-protective gels can be used as a line of defense to protect structures. The effectiveness of freshly applied gels in delaying ignition and flame growth on structures has been well established. However, in a real-world scenario there is a period between the application of the gel and the arrival of a spot fire or the fire-front. During this period, the gels are often exposed to extreme conditions consisting of high winds and low relative humidity. The effect of these weathering conditions on the performance of fire-protective gels is still poorly understood. This study examined the dehydration and performance of fire-protective gels following a range of weathering conditions. Two commercially available gels were applied to a 100-mm by 100-mm T1-11 plywood sample and then artificially weathered in an environmental chamber, with controlled temperature, relative humidity, and wind. The remaining mass of the gels was measured at selected intervals to determine the relationship between mass loss and dehydration related to weathering. A second series of tests was conducted on weathered T1-11 samples at specific mass loss states as well as on freshly applied gels using a 50 kW/m2 heat flux exposure utilizing a cone calorimeter. Results indicated that they dehydrated to the point where, after 3 h, fire performance was no better than the uncoated wood samples and the gels could facilitate ignition. This timeline suggests that gels should only be applied by first responders and homeowners should focus on evacuation related activities.

Fire-resistant hydrophobic nanocoated composite partition sheets

Composite partition sheets were prepared by vacuum infusion process using noncombustible glass fiber and waste nylon along with polyester matrix. The waste nylon materials obtained in the form of discarded fishing nets were reinforced in sheets with T90° orientation. They were then coated using two types of fumed silica nanopowders mixed in polyester resin. Two types of coated and corresponding bare hybrid composite samples were examined for their various properties. Appreciable values for mechanical properties were obtained for all the hybrid sheets which are more pronounced for the nanocoated sheets. Furthermore, horizontal flammability tests proved that the fumed silica-coated sheets have better flame-retardant characteristics. With constant heat flux of 50 W/m2, the specimens were investigated for the peak heat release rate (HRR) and fire reaction properties like total oxygen consumed, average specific mass loss rate, total smoke release, and average HRR which gave good results for the nanocoated sheets. Moreover, water-absorbing properties of the hybrid sheets were generally less and it was better in the case of hydrophobic fumed silica-coated samples. These low cost and less weight composite sheets were successfully developed and the results obtained were encouraging, which can be used as partition sheets in the construction of affordable buildings.

Synergistic effect of Al2O3/TiO2 reinforcements on slurry erosion performance of nickel-based composite coatings

Various aspects such as development, experimentation, and analysis have been covered in the present work to examine the behavior of test coatings under slurry erosion. The primary objective of the present study was to establish the specific mass loss from the test coatings under various slurry environmental conditions and highlights the importance of the addition of alumina in improving the slurry erosion resistance of Ni-TiO2 coating. To attain this objective, two powder compositions, viz. Ni-20TiO2 and Ni-15TiO2-5Al2O3 were deposited onto the CA6NM grade hydro-turbine steel using high velocity frame spray process. The microstructural characterization of the coatings was done by employing surface roughness tester, scanning electron microscope/energy-dispersive X-ray spectroscopy, and X-ray diffraction techniques, whereas mechanical analysis was carried out using micro-hardness and bond strength tester. The slurry erosion tests were performed using an indigenously fabricated high speed slurry erosion test rig at different levels of rotational speed, average particle size of erodent, and slurry concentration in order to explore their effects on slurry erosion performance of test coatings. The slurry erosion results, as well as scanning electron microscope observations of eroded specimens, revealed higher slurry erosion resistance of Ni-15TiO2-5Al2O3 coating in comparison with Ni-20TiO2 coating. Furthermore, each operational parameter was found to have a proportional effect on specific mass loss in case of both the coatings.

Theory of winds from cool stars

The goal of this paper is to provide a framework for thinking about the various physical processes that may play significant roles in driving the massive winds of cool, low-gravity stars. First, some general theoretical considerations involving mass, momentum, and energy balance are discussed. Next, the value of the solar wind as an analog for these late-type stellar winds and for related astrophysical flows is briefly examined. Finally, four specific mass-loss mechanisms are discussed, and the possible importance of each of these mechanisms for massive winds from cool, low-gravity stars is evaluated.