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Surface mercury release is an important source of atmospheric mercury, and asphalt pavement occupies a high proportion. However, the current characteristics of mercury exchange flux on asphalt ground are unclear, which is not conducive to assessing the contribution of surface mercury release to atmospheric mercury. Therefore, the dynamic flux chamber method was used to measure the variation characteristics of mercury exchange flux on the underlying surface of typical artificial asphalt in Qingdao in four seasons. The average mercury exchange flux of the asphalt ground surface was 0.12±0.38 ng/(m2•h). The mercury flux was mainly released in spring, summer, and autumn, the highest in summer was twice that in spring, and the deposition occurred mainly in winter. Under the influence of meteorological factors and atmospheric mercury concentration, the mercury exchange flux reached its peak value when the light intensity and surface temperature were the highest in spring and autumn, while the peak value in summer occurred after the maximum light intensity and reached its maximum peak value at the highest surface temperature.

A kind of composite propellant based on a click-chemistry binder, the propargyl-terminated ethylene oxide-tetrahydrofuran copolyether (PTPET), and ammonium perchlorate (AP), aluminum (Al) were studied with ammonium dinitramide (ADN), hexahydro-1,3,5-trinitro-s-triazine (RDX) and hexanitroisowurtzitane (CL20), respectively. Thermogravimetric analysis (TG) and energy calculation of the composite propellants containing ADN and CL20 were carried out. The burning rates of the composite propellants were measured in the pressure range of 3–17 MPa with measurement system of Charge Coupled Device (CCD) line scan camera and high-pressure chamber. Scanning electron microscopy was used to characterize the quenched surfaces of the burning propellants. Microscopic high-speed photography was used to record the flame structure and dynamic burning surface of the propellants in the argon atmosphere. The replacement of RDX with CL20 had less effect on the thermal decomposition of the components in the propellant, but increased the burning rates of the propellant. The replacement of AP with ADN could significantly accelerate the thermal decomposition of the plasticizer A3, AP and PTPET binder, so that the burning rates under high pressure was raised obviously. For the propellants containing ADN and CL20, there were dense and thick molten layer of ADN on the burning surface. The propellants containing ADN and CL20 exhibited characteristic flame different from the propellant containing only AP and RDX. These results were considered to correlate with the early thermal decomposition of ADN and higher burning rate of the propellants. [ABSTRACT FROM AUTHOR]

The combustion process of Al particles in an aluminised solid propellant containing organic fluoride (SOF) has been investigated in comparison to that of a normal solid propellant (Sn). The agglomeration process of ignited Al particles on the burning surface was recorded by means of microscopic high-speed photography. The records showed that the ignited Al particles in propellant Sn tended to form large, homogeneous agglomerates on the burning surface, whereas the ignited Al particles in propellant SOF tended to form distinct, coherent yet discrete agglomerates with a flocculent structure. The combusting agglomerates were quenched with cold acetone to obtain the burning-interrupted agglomerates, and morphological and surface element distribution analyses were performed on these quenched agglomerates by SEM with EDX. The results showed the quenched agglomerates from Sn to be large (50–100 µm) and to have an obvious 'cap–core' structure, with the 'cap' and 'core' consisting mostly of aluminum oxide (Al2O3) and unreacted aluminum (Al), respectively. In contrast to those from Sn, the quenched agglomerates from SOF were spherical and much smaller (5–20 µm), with uniform dispersal of Al, O, and F on their surfaces. The solid agglomerate products from complete combustion of the propellants in an oxygen bomb were collected and further analysed by TEM, selected area electron diffraction (SAED), and XRD. The results indicated that the propellant Sn tended to form solid combustion products with a dense crystalline structure, whereas the propellant SOF tended to form solids with a more irregular inner structure of low crystallinity. The above results suggested that the ignition/agglomeration/combustion process of Al in SOF did not obey the prototypical model for aluminised solid propellants. The effect of fluoridation on Al particles during the combustion process of the solid propellant containing organic fluoride has been confirmed and is considered to be a crucial factor in giving rise to the observed phenomena. [ABSTRACT FROM AUTHOR]

A series of activated Al-Co3O4 powders were prepared by high-energy ball milling, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC). The properties of these activated Al-Co3O4 powders reacting with the water steam were systematically investigated at 700°C, 800°C, and 900°C. Morphologies and phases of their reaction products with water steam were characterized by SEM, XRD, and the residual metal aluminum content in products was also measured. The results showed that the reaction properties of the Al-Co3O4 powders with the water steam were closely related to the milling time. The Al-Co3O4 powder experiencing 3 h milling showed the finer particle size, lower initial oxidation temperature, earlier autoignition, and longer combustion in the water steam at high temperature than the other samples. The Co2Al9 alloy was detected in the reaction products of Al-Co3O4 powders with water steam. The investigation demonstrated that the activated Al-based powders could be prepared with the Al and Co3O4 through high-energy milling process. [ABSTRACT FROM AUTHOR]

Octaphenylsilsesquioxane (OPS), polyphenylsilsesquioxane (PPSQ), and octavinylsilsesquioxane (OVP) have been incorporated into ethylene propylene diene terpolymer (EPDM) in order to study their effects on the ablative properties of the respective EPDM composites. The results show that PPSQ and OVP serve as effective ablative additives for EPDM composites. The linear ablation rates of EPDM composites with 4.4 wt % OVP or PPSQ were reduced by 21 or 16.5%, respectively, compared with the control sample. Moreover, OVP and PPSQ also improved the flame retardancy and suppressed smoke emission. The heat release rate of EPDM composite with 4.4 wt % OVP was measured as 90.6 kW m−2, 17% lower than that of the control sample, and the same amount of PPSQ reduced the total smoke release from 1946 to 1497 m2 s−1. Thermogravimetric analysis results showed EPDM/OVP composite to leave a higher residual mass than the calculated value. Besides, scanning electron microscopy, cone calorimetry (CONE), and BET tests showed that the chars formed during the ablation of EPDM composites containing OVP and PPSQ had better structural stability and thermal stability owing to the fact that they were denser and more homogeneous. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48365. [ABSTRACT FROM AUTHOR]