No abstract

A major component of fire investigation is tracking the cause of fire, finding of which help to strengthen the physical evidence, especially in case of arson with accelerants. When metallic substances are exposed to fire at high temperature, they undergo oxidation. Accelerants at the fire scene impart some oxidative characteristics on metallic materials. For instance oxides and substrates found on metal surfaces provide valuable information for determining the characteristics of fire, such as exposure temperature, duration and involvement of a liquid accelerant. In this study, we investigated the oxidation behavior of carbon steel at high temperature in a simulated flame environment using ethanol combustion. After oxidation, the morphological and microstructural features of the samples were characterized by observation, scanning probe microscope, X-ray diffractions and scanning electron microscopy with energy-dispersive spectroscopy analysis. The results showed that elemental carbon was deposited on the samples surface, which were ascribed to the incomplete combustion of ethanol. An oxide with a mesh-like pattern appeared on the samples, which was ascribed to the complex oxidation conditions of the fire scene. The properties of the oxides were strongly dependent on the oxidation duration, temperature and atmosphere. These results provide reference information for determining the presence of combustion accelerants at the fire scene.

High performance mixed potential type NO2 sensors using porous yttria-stabilized zirconia (YSZ) layers doped with different concentration graphite as solid electrolyte and LaFeO3 as sensing electrode were fabricated and characterized. LaFeO3 was prepared by a typical citrate sol–gel method and characterized using XRD. The surface morphology and porosity of porous YSZ layers were characterized by field emission scanning electron microscope (FESEM). The sensor doped with 3 wt% graphite shows the highest response (−76.4 mV to 80 ppm NO2) and the response is linearly dependent on the logarithm of NO2 concentration in the range of 10–200 ppm. The sensor measurement results also present good repeatability and cross-sensitivity.

With methyl vinyl silicone (MVQ) as the base rubber, filled with self-synthesized carbon coated aluminum nanoparticles, the high thermal conductive composite was prepared by using the method of mechanical blending. The effect of carbon coated aluminum nanoparticles on thermal conductivity and coefficient of thermal expansion (CTE) of the silicone rubber were investigated, and it was found that thermal conductivity of the composite increased with increasing carbon coated aluminum nanoparticles content during the process of thermal conductive network initially formed to throughout the whole composite, the thermal conductivity began to decrease when the filling content reached 250phr,the optimum filling amount of carbon coated nanoparticles was 250phr.The Y-Agrai model was employed to investigate the thermal conductivity of the thermal conductive composite, results indicated that when the filling content was less than 200phr,theoretical value was coincided with measured value. While the filling content was more than 200phr, theoretical value was gradually less than measured value. While the carbon coated aluminum nanoparticles content increased, the coefficient of thermal expansion (CTE) of composite decreased significantly.

The polyethylene/montmorillonite (PE/MMT) nanocomposites were prepared by melt blending the organic MMT with the ternary-monomer graft copolymers of polyethylene (GPE) which were prepared by solid phase grafting maleic anhydride, methyl methacrylate and butyl acrylate onto PE. Fourier transform infrared spectroscopy was used to characterize the structure of GPE. X-ray diffraction patterns and transmission electron microscopy were used to characterize the morphology of GPE/MMT nanocomposites. Results showed that GPE was an outstanding polymeric material to prepare an exfoliated polymer/layered silicates nanocomposites due to the high polarity of GPE and high graft degree. Most layered silicates still maintain the exfoliated and well dispersed state even at 40 phr OMMT content. The exfoliation of layered silicates was attributed to the well intercalation and easy wetting of the grafted oligomers.