The elimination of halon and frequent fire accidents have caused an urgent need for the development of high-efficient fire extinguishing agents. ABC dry powder has been paid much attention, and has become one of the most extensively used fire extinguishing agents nowadays owing to its wide applications in various fire protection fields. Therefore, to enhance the fire-extinguishing properties of ABC dry powder, ferrocene was used as the additive to develop a new composite ultrafine dry powder based on an ultrafine ABC dry powder product. Through flame inhibition tests, two performance indexes of the inhibition process, namely temperature drops and flame height variations, were adopted to measure the degree of flame suppression. The experimental results revealed that the temperature drops and flame height variations both increased and then decreased. Moreover, the composite ultrafine dry powder containing 0.7% ferrocene displayed the best inhibitory effect with the maximum temperature drop (152.9°C) and variation rate of flame height (14.01%). Thermogravimetric analysis and differential scanning calorimetry were used to analyze the thermal decomposition of the sample powders. Furthermore, based on the analysis results of the thermal decomposition temperature, weight loss, and other thermodynamic parameters of the sample powders, the reasons for performance advantages of composite ultrafine dry powder containing 0.7% ferrocene were clarified as the faster pyrolysis rate, more absorption of heat, stronger suffocation and chemical inhibition effect. Finally, possible speculations on the suppression mechanisms of composite ultrafine dry powder containing 0.7% ferrocene were proposed.
Laminar diffusion flame was used to study the effect of ethanol on n-heptane flame in terms of the morphology and microstructure of soot under atomization combustion. For the same carbon mass flux at the outlet of the burner, the ratio of ethanol doping in n-heptane was changed, and the soot was collected from the axial positions of the flame at different heights using the thermophoresis probe method. The results showed that the flame height increased significantly with the increasing ratio of ethanol doping. When the ratio of ethanol and n-heptane (CE/CN) was 1.5, the flame height increased by 10 mm compared with that of pure n-heptane flame. Besides, the temperature in the center of the flame decreased with the increasing ratio of ethanol doping, but the temperature in the low position was higher than that in the pure n-heptane flame, and the temperature in the high position was lower than that in the pure n-heptane flame. However, the flame temperature was the highest when the proportion of ethanol in the mixture was greater than that of n-heptane. The temperature at the flame center decreased with the increasing ratio of ethanol doping, while the temperature at the flame edge increased with the ratio. The primary particle size of soot (soot size hereafter) in all working conditions increased with the increase of flame height, which was in line with the general growth law of soot. Moreover, the soot size at the same height decreased with the increasing ratio of ethanol doping, and this trend was most obvious at the flame height of 20 mm and 30 mm. Compared with pure n-heptane, when CE/CN was 1.5, the soot size at 20 mm and 30 mm decreased by an average of 34.83%, indicating that ethanol could inhibit the surface growth of soot particle. Furthermore, the density of soot particles collected by a single copper net decreased significantly, indicating that ethanol could reduce the production amount of soot.
Jian Wang,Yaofeng Mao,Jie Chen,ZiJian Li,Jun Wang,Fude Nie
Boron (B) shows great potential applications in the military and aerospace industry due to its high calorific value. However, the reactivity is limited by the inert oxide layer (B 2 O 3 ) that covers the B particles. Herein, nano-Al, and Fluorographene (FG) are employed as coating materials to enhance the ignition and combustion efficiency of boron. When graphite fluoride (GF) was utilized as an oxidizer (the B/GF mass ratio is 1:9), the maximum heat release of B@nano-Al/GF (∼5.6 kJ/g) and B@FG/GF (∼5.4 kJ/g) were markedly higher than that of raw B/GF (∼2.5 kJ/g), ascribed to the self-activation effect of the coating layer. On this basis, the combustion experiments were performed and their performances were compared and studied. Specifically, the ignition delay time of B@nano-Al/GF and B@FG/GF was decreased to 320 ms 262 ms, respectively, compared with that of raw B/GF (380 ms) with 15 W laser power. This is consistent with the ignition burning test, where the B@6%nano-Al/GF and B@2%FG/GF have higher flame height than raw B/GF. However, the maximum pressure and pressurization rate decreased for B@6%nano-Al/GF and B@2%FG/GF because of the reduced amount of gas caused by decreased boron content. Additionally, the effects of the B/GF mass ratio (1:9, 2:8, 3:7, 4:6) on the combustion performances of composites were fully studied. The pressure output, combustion reaction, and ignition delay time are reduced with B/GF mass ratios increased. This work could provide a general approach to improve the ignition and combustion performance of boron.
危险品化学品经营许可证（带存储）