The Study On The Flash Ignition And Combustion Of Iron And Aluminum Nanoparticles And Their Complexes

The flash as a new non-contact ignition method has attracted lots of interest from researchers.Different from the spark ignition,plasma ignition and laser ignition,the flash ignition can successfully achieve distributed ignition in quite short time.Most materials with higher energy density could be ignited by flash.such as aluminum nanoparticles,carbon nanotubes,graphene oxide and porous silicon.There were rare researches about Fe nanoparticles ignited by the flash.To compare the differences between different nanometer metal materials,Fe nanoparticles,Al nanoparticles and their composite materials were studied to analyze the characteristic and factors of flash ignition.First,Fe NPs and A1 NPs were ignited by the flash and the results were record by the high speed camera.By observing the burning images,the combustion mode was studied and the burning temperature distributions were calculated.And the microstructure of these two nanometer materials was measured to analyze the oxidation mechanism of the flash ignition.By changing the mass and the diameter of the samples,the MIE and the conversion was measured to analyze the factors on the ignition process.By using different filters,the ignition phenomenon of these materials was record to investigate the wavelength of flash light on the flash ignition.The results were made of two parts,the first part was the flash ignition of Fe NPs.It showed that the combustion of Fe NPs contained the ignition process and burning process.The temperature of ignition process with several milliseconds was of 2000K,and the temperature of burning process with several seconds was of 800K.The MIE of Fe NPs decreased and the conversion increased with the increasing mass of the samples.Also the MIE decreased and the conversion increased with the increasing particles numbers on unit area.The second part was the flash ignition of Al NPs.It showed that Al NPs burned with bright light and the burning temperature of Al NPs was of 1000K.The MIE and the conversion of A1 NPs were larger than the MIE of the Fe NPs.The MIE of Al NPs did not change much with different mass.The conversion of the A1 NPs increased with the increasing mass of the samples.The oxidation mechanism of two nanometer materials was all attributed to the black body effect that the nanoparticles absorbed the light energy and achieved to the ignition point in a really short time.The light energy absorbed from the flash was influenced by wavelengths but the conversion of nanoparticles was only related to the packing mass.Secondly,appropriate amount of carbon nanotubes mixed with Fe NPs and Al NPs to form different mixtures respectively.Two mixtures were ignited by the flash and the ignition images were record by the camera to study the combustion characteristic and calculate temperature distribution.The MIE of two mixtures was measured to analyze the factors on the ignition process.The microstructure was measured to analyze the oxidation mechanism of the flash ignition.The results showed that the mixture of Fe NPs and CNTs burned with slight red light and the temperature level was of 900K.When the mass ratio of CNTs was in the range of 0～20%,the MIE of the mixture decreased greatly;when the mass ratio of CNTs was in the range of 20～80%,the MIE did not change much;when the mass ratio of CNTs was in the range of 80～100%,the MIE increased again.On the other hand,the mixture of Al NPs and CNTs burned with giant flame,and the temperature of the mixture was of 1000K.The highest point was in the central part of the flame.The MIE of the mixture decreased with the increasing mass ratio of CNTs.Finally,appropriate amount of catalyst was added to the two metal nanoparticles to form the composite material.The ignition phenomenon of two mixtures was record by the camera and the temperature distribution was calculated by using two-color method.The MIE of two mixtures with different TiO2 mass ratio and mass was measured to analyze the method to decrease the MIE.The results showed that the addition of appropriate TiO2 as catalyst in the Fe NPs did not affect the combustion phenomenon.The temperature still maintained in the level of 850K.The MIE of the mixture increased with the increasing TiO2 mass ratio.On the other hand,an obvious explosion occurred when the TiO2 was added to the Al NPs.In the exposure process,the temperature level was of 2400K.When the mass ratio of TiO2 was in the range of 0-20%,the MIE of the mixture with TiO2 and A1 NPs decreased greatly;when the mass ratio of TiO2 was in the range of 20～40%,the MIE did not change much;when the mass ratio of TiO2 was higher than 60%,the MIE increased to the largest point gradually.