Study On The Characteristics Of Combustion Soot Of Typical Combustibles

Soot in fire scene has the advantages of simple extraction and complete preservation,which can reflect the image of the cause and spread of fire directly or indirectly.In the fire investigation,the soot can be comprehensively analyzed and reasonably inferred together with other evidences to form a strong evidence chain.Therefore,studying the changes of microscopic morphology and physicochemical properties of soot can provides new ideas and methods for the analysis and detection of combustion fumes in fire accident investigation.It is of great significance in tracing the origin of fire accidents.In this paper,Transmission Electron Microscopy(TEM),X-ray Photoelectron Spectroscopy(XPS)and Raman Spectroscopy(Raman)were used to comprehensively understand the soot under three single-factor conditions:fuel type,carrier type attached to soot and the different blending ratios of ethanol diesel.The chemical elements and functional groups in the samples were qualitatively and quantitatively analyzed by XPS.TEM was used to observe the micro-morphology of the samples.Raman could study the internal characteristics of carbon atoms in the samples.The main work and conclusions are as follows:In order to understand the physical and chemical characteristics of different types of combustible combustion fumes,five combustible soot were selected to study and analyze,such as gasoline,diesel,acetone,ethanol,polypropylene.The results show that the soot of five kinds of combustibles ontain the same functional groups,but the relative content of functional groups is different.The types of combustibles can be preliminarily determined by the characteristic functional groups.In addition,there have some differences in accumulation morphology,ordering degree,C-C bond length,particle size and interlayer spacing,which can be used to assist in judging the types of combustible species.The soot particles may react with the surface of the carrier adhering to the soot in the process of condensation collision.Different types of carriers may have some differences in the forensic analysis of the soot in the fire investigation.Four kinds of carriers were used to collect diesel fume.It was found that the types of carriers did not affect the qualitative identification results of diesel fuel,but the types of carriers have an effect on the adsorption capacity of each functional group.The micro-morphologies of the four carriers soot mainly show differences in agglomeration morphology,chain length and density.The type of carrier has a certain influence on the particle size,the average layer spacing of the carbon particles of the soot and the internal structural characteristics of the C atom.By changing the blending ratio of ethanol and diesel,the differences of combustion soot were compared and analyzed.As the proportion of ethanol blended diesel increases,the relative content of carbon-containing functional groups and oxygen-containing functional groups,the average particle size of basic carbon particles,and the interlayer spacing will be showing an increase or decrease trend.In a certain mixing ratio range,the relative intensities of the D and G peaks and ID/IG values increase as the blending ratio increases.