5L-Scale Magnesio-Milling Reduction of Nanostructured SiO2 for High Capacity Silicon Anodes in Lithium-Ion Batteries.

Nanostructured silicon (Si) is useful in many applications and has typically been synthesized by bottom-up colloid-based solution processes or top-down gas phase reactions at high temperatures. These methods, however, suffer from toxic precursors, low yields, and impractical processing conditions (i.e., high pressure). The magnesiothermic reduction of silicon oxide (SiO2) has also been introduced as an alternative method. Here, we demonstrate the reduction of SiO2 by a simple milling process using a lab-scale planetary-ball mill and industry-scale attrition-mill. Moreover, an ignition point where the reduction begins was consistently observed for the milling processes, which could be used to accurately monitor and control the reaction. The complete conversion of rice husk SiO2 to high purity Si was demonstrated, taking advantage of the rice husk's uniform nanoporosity and global availability, using a 5L-scale attrition-mill. The resulting porous Si showed excellent performance as a Li-ion battery anode, retaining 82.8% of the initial capacity of 1466 mAh g-1 after 200 cycles.

Estimation of spontaneous waste ignition time for prevention and control of landfill fire.

Openmunicipal solid waste(MSW) dumpsites in India are significant hotspots of spontaneous fire and associated air and ground water pollution. Unscientific dumping of MSW poses a major threat to the surrounding environment and human health. One-year-old biodegradable waste components comprised of paper, cardboard, newspaper, textile, wood, grass leaves and coconut shell were analyzed for the determination of the moisture content (MC), smoldering temperature, ignition temperature, and ignition time. Principal component analysis of the old waste components revealed that cardboard, paper, newspaper and leaves are most susceptible waste components for spontaneous ignition. In contrast, MC was the most influential parameter for resulting changes in ignition temperature (0C) on ignition time (min). A numerical equation was developed to estimate the time required for the spontaneous waste ignition at MSW dumpsite. The results of the study showed that the aged waste (age ≥ 3 year) having MC below 6 % and initial surface temperature of 78 0C might smolder and ignite during the hottest time of the day in âˆ¼ 6 and âˆ¼ 26 days, respectively. Estimates showed that the time required for spontaneous waste ignition of aged waste is moderately dependent on waste MC (∼5-55 %), surface temperature (∼40-100 0C), monthly pattern of average high temperature (∼36.6-42.6 0C), biodegradable waste components having smoldering temperature ≤ 150 0C and ignition temperature ≤ 270 0C. The present study also showed that the occurrence of landfill fire events at MSW dumpsites is more prominent during the pre-monsoon season i.e. during the elevated temperature level.

Experimental Study of Oriented Strand Board Ignition by Radiant Heat Fluxes.

Wood and composite panel materials represent a substantial part of the fuel in many building fires. The ability of materials to ignite when heated at elevated temperatures depends on many factors, such as the thermal properties of materials, the ignition temperature, critical heat flux and the environment. Oriented strand board (OSB) without any surface treatment in thicknesses of 12, 15 and 18 mm were used as experimental samples. The samples were gradually exposed to a heat flux of 43 to 50 kW.m-2, with an increase of 1 kW.m-2. At heat fluxes of 49 kW.m-2 and 50 kW.m-2, the ignition times are similar in all OSB thicknesses, in contrast to the ignition times at lower heat fluxes. The influence of the selected factors (thickness and distance from the heat source) was analysed based on the experimentally obtained data of ignition time and weight loss. The experimentally determined value of the heat flux density was 43 kW.m-2, which represented the critical heat flux. The results show a statistically significant effect of OSB thickness on ignition time.

Determination of ignition temperature of municipal solid waste for understanding surface and sub-surface landfill fire.

Open dumping of municipal solid waste (MSW) is a common practice in India which leads to a number of problems like non-uniform compaction, slope failure, percolation of water during rainy seasons, abrupt leachate generation and stability issues. It also leads to various other issues, such as manual scavenging and deliberate waste burning. During the waste degradation process, an enormous amount of heat and landfill gases (LFGs) like carbon dioxide (CO2) and methane (CH4) are generated. Biological and chemical reactions happening at the surface and inside the landfill contribute to the heat generation. Initiation of waste ignition is a major cause of spontaneous landfill fire. The risk posed by landfill fires is high in India as most of the landfills are non-engineered. The present study aims to determine the ignition temperature of waste dumped at Bhandewadi dumpsite located at Nagpur, India which will enable a better understanding of the initiation of fires in non-engineered landfill (surface and sub-surface fires), especially in Indian condition. The results of the present study showed that ignition temperature is directly proportional to the moisture content of MSW for its values ranging from 5 to 55% by mass. The correlation of smoldering time (Ts) and ignition time (Ti) of MSW with its age under gradual temperature rise in a muffle furnace (i.e., 3 °C/min) were also studied and it was found that Ts and Ti are directly proportional to the age of MSW and the values ranged from 23 to 34 min for Ts and 27 to 48 min for Ti.