Styrene–Acrylic Emulsion with “Transition Layer” for Damping Coating: Synthesis and Characterization

In order to study the dynamic mechanical properties of styrene–acrylic latex with a core/shell structure, a variety of latexes were synthesized by semi-continuous seeded emulsion polymerization based on “particle design” with the same material. The latexes were characterized by rotary viscosimeter, dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), dynamic mechanical analysis (DMA), and universal testing machine. The effects of difference at the glass transition temperature (Tg) of core and shell and the introduction of the “transition layer” on the damping and mechanical properties of latex film were studied. The results indicate that as the Tg of core and shell gets closer, the better the compatibility of core and shell, from phase separation to phase continuity. Furthermore, the introduction of the “transition layer” can effectively improve the tensile strength and tan δ (max) of the latex film. The tensile strength and maximum loss factor (f = 1 Hz) of latex with the “transition layer” increased by 36.73% and 29.11% respectively compared with the latex without the “transition layer”. This work provides a reference for the design of emulsion for damping coating

Solvothermal Synthesis, Structural Characterization and Optical Properties of Pr-Doped CeO2 and Their Degradation for Acid Orange 7

Pr-doped CeO2 with different doping levels was prepared from Ce(NO3)3∙6H2O and Pr(NO3)3∙6H2O by solvothermal method without any additional reagents, in which the mixed solution of ethylene glycol and distilled water was employed as a solvent. The influences of Pr-doping on phase composition, crystal structure and morphology were investigated, as well as Pr valence and oxygen vacancy defects. The Pr cations entered into the CeO2 crystal lattice with normal trivalence and formed a Pr-CeO2 solid solution based on the fluorite structure. The larger trivalent Pr was substituted for tetravalent Ce in the CeO2 crystal and compensated by oxygen vacancy defects, which caused the local lattice expansion of the crystal lattice. Moreover, the Pr-doped CeO2 solid solutions exhibited visible color variation from bright cream via brick red to dark brown with the increasing of Pr contents. The degradation of AO7 dye was also investigated using a domestic medical ultraviolet lamp; the removal efficiency of AO7 by 1% and 2% Pr-doped CeO2 approached 100%, much higher than 66.2% for undoped CeO2

Water uptake and hygroscopicity of perchlorates and implications for the existence of liquid water in some hyperarid environments

The existence of liquid water is a prerequisite for habitability. Deliquescence of perchlorates under subsaturated conditions has been proposed to explain the occurrence of liquid water in some hyperarid environments on the earth and on the Mars. However, the amount of liquid water associated with perchlorates under different conditions is not well understood yet. In this work, we have measured deliquescence relative humidity (DRH) of three perchlorates at different temperatures from 278 to 303 K. DRH decreases from (42.8 +/- 0.6)% at 278 K to (40.5 +/- 0.5)% at 303 K for Mg(ClO4)(2)center dot 6H(2)O, and from (18.5 +/- 0.5)% at 278 K to (15.5 +/- 0.5)% at 303 K for Ca(ClO4)(2)center dot 4H(2)O; in contrast, deliquescence of KClO4 did not occur even when RH (relative humidity) was increased to 95%. In addition, we have determined the amount of water taken up by Ca(ClO4)(2)center dot 4H(2)O and Mg(ClO4)(2)center dot 6H(2)O as a function of RH (0-90%) and temperatures (278-298 K). It is found that when both salts are deliquesced, more water (similar to 10% on average) is associated with Mg(ClO4)(2)center dot 6H(2)O than Ca(ClO4)(2)center dot 4H(2)O on the per mole ClO4- base. Overall, this work would significantly improve our knowledge in hygroscopicity of perchlorates, and thus may provide fundamental insights into the hydrologic cycles in some hyperarid regions on the earth and on the Mars

Impacts of methanesulfonate on the cloud condensation nucleation activity of sea salt aerosol

Methanesulfonate, an important oxidation product of dimethyl sulfide, is abundant in marine aerosol particles. However, its impact on the cloud condensation nucleation (CCN) activity of marine aerosol is yet to be elucidated, largely because the CCN activity of methanesulfonate has been seldom investigated. In this work, we measured the CCN activities of three common methanesulfonates, and the single hygroscopicity parameters (kappa) were determined to be 0.46 +/- 0.02 for sodium methanesulfonate (NaMS), 0.37 +/- 0.01 for calcium methanesulfonate, and 0.47 +/- 0.02 for potassium methanesulfonate, respectively. In addition, we explored the effect of NaMS on the CCN activities of NaCl and synthetic sea salt. It was found that if presented with a mass ratio of 1:1, NaMS would significantly reduce the CCN activities of NaCl and sea salt, and the K values of binary mixtures could be estimated using the simple mixing rule. Nevertheless, if only presented with a mass ratio of 1:10 (an environmentally relevant value), the effect of NaMS on the CCN activities of NaCl and sea salt was found to be small. Overall, we conclude that from our experimental data and its levels found in the troposphere, methanesulfonate may only have minor impacts on the CCN activity of marine aerosol

Intermediate‐Volatility Organic Compounds Observed in a Coastal Megacity:Importance of Non‐Road Source Emissions

Intermediate‐volatility organic compounds (IVOCs) are among the most important precursors to secondary organic aerosol (SOA), yet their sources and contributions to SOA in ambient air are poorly constrained. In this study, IVOCs were collected with sorption tubes in a coastal city in southern China during September–October 2019 and were analyzed by gas chromatography‐mass selective detector after thermo‐desorption. The measured average concentration of IVOCs was 25.0 ± 0.95 μg m−3 (mean ± 95% C.I.), and residual unresolved complex mixtures shared 79.8% ± 1.91% of IVOCs. The estimated SOA production, even only from speciated IVOCs and unspeciated branch‐alkane IVOCs, reached 2.44 ± 1.46 μg m−3, approximately five times that from VOCs during the photochemically active period (12:00–15:00 local time). Based on the positive matrix factorization model with a photochemical‐age‐based parameterization, diesel‐related emission was the largest contributor (46.6%) of IVOCs, followed by ship emission (23.0%), gasoline exhaust (16.8%), and biomass/coal burning (13.6%). Non‐road diesel engines accounted for a dominant part in diesel‐related emission. Ship emission was found to contribute SOA formation potentials (SOAFPs) comparable to that of diesel‐related emission, while biomass/coal burning showed higher SOAFPs than gasoline exhaust. Our results revealed that non‐road sources, such as ship emission, non‐road diesel engines, and biomass/coal burning contributed substantially to IVOCs, and will be of greater importance in producing ambient SOA with the increasingly stringent control on emissions from on‐road vehicles

Interactions of organosulfates with water vapor under sub- and supersaturated conditions

Organosulfates (OSs) are important constituents of secondary organic aerosols, but their hygroscopic properties and cloud condensation nucleation (CCN) activities have not been well understood. In this work we employed three complementary techniques to characterize interactions of several OSs with water vapor under sub- and supersaturated conditions. A vapor sorption analyzer was used to measure mass changes in OS samples with relative humidity (RH, 0 %-90 %); among the 11 organosulfates examined, only sodium methyl sulfate (methyl-OS), sodium ethyl sulfate (ethyl-OS), sodium octyl sulfate (octyl-OS) and potassium hydroxyacetone sulfate were found to deliquesce as RH increased, and their mass growth factors at 90 % RH were determined to be 3.65 +/- 0.06, 3.58 +/- 0.02, 1.59 +/- 0.01 and 2.20 +/- 0.03. Hygroscopic growth of methyl-, ethyl- and octyl-OS aerosols was also studied using a humidity tandem differential mobility analyzer (H-TDMA); continuous hygroscopic growth was observed, and their growth factors at 90 % RH were determined to be 1.83 +/- 0.03, 1.79 +/- 0.02 and 1.21 +/- 0.02. We further investigated CCN activities of methyl-, ethyl- and octyl-OS aerosols, and their single hygroscopicity parameters (kappa(cnn)) were determined to be 0.459 +/- 0.021, 0.397 +/- 0.010 and 0.206 +/- 0.008. For methyl- and ethyl-OS aerosols, kappa(cnn) values agree reasonably well with those derived from H-TDMA measurements (kappa(gf)) with relative differences being < 25 %, whereas kappa(cnn) was found to be similar to 2.4 times larger than kappa(gf) for octyl-OS, likely due to both the solubility limit and surface tension reduction

Impacts of methanesulfonate on the cloud condensation nucleation activity of sea salt aerosol

Methanesulfonate, an important oxidation product of dimethyl sulfide, is abundant in marine aerosol particles. However, its impact on the cloud condensation nucleation (CCN) activity of marine aerosol is yet to be elucidated, largely because the CCN activity of methanesulfonate has been seldom investigated. In this work, we measured the CCN activities of three common methanesulfonates, and the single hygroscopicity parameters (kappa) were determined to be 0.46 +/- 0.02 for sodium methanesulfonate (NaMS), 0.37 +/- 0.01 for calcium methanesulfonate, and 0.47 +/- 0.02 for potassium methanesulfonate, respectively. In addition, we explored the effect of NaMS on the CCN activities of NaCl and synthetic sea salt. It was found that if presented with a mass ratio of 1:1, NaMS would significantly reduce the CCN activities of NaCl and sea salt, and the K values of binary mixtures could be estimated using the simple mixing rule. Nevertheless, if only presented with a mass ratio of 1:10 (an environmentally relevant value), the effect of NaMS on the CCN activities of NaCl and sea salt was found to be small. Overall, we conclude that from our experimental data and its levels found in the troposphere, methanesulfonate may only have minor impacts on the CCN activity of marine aerosol

Water Soluble Organic Nitrogen (WSON) in Ambient Fine Particles Over a Megacity in South China: Spatiotemporal Variations and Source Apportionment

Organic nitrogen aerosols are complex mixtures and important compositions in ambient fine particulate matters (PM2.5), yet their sources and spatiotemporal patterns are not well understood particularly in regions influenced by intensive human activities. In this study, filter-based ambient PM2.5 samples at four stations (one urban, two rural, plus one urban roadside) and PM samples from combustion sources (vehicle exhaust, ship emission, and biomass burning) were collected in the coastal megacity Guangzhou, south China, for determining water soluble organic nitrogen (WSON) along with other organic and inorganic species. The annual average WSON concentrations, as well as the ratios of WSON to water soluble total nitrogen, were all significantly higher at rural sites than urban sites. Average WSON concentrations at the four sites during the wet season were quite near each other, ranging from 0.41 to 0.49g/m(3); however, they became 2 times higher at the rural sites than at the urban sites during the dry season. Five major sources for WSON were identified through positive matrix factorization analysis. Vehicle emission (29.3%), biomass burning (22.8%), and secondary formation (20.2%) were three dominant sources of WSON at the urban station, while vehicle emission (45.4%) and dust (28.6%) were two dominant sources at the urban roadside station. At the two rural sites biomass burning (51.1% and 34.1%, respectively) and secondary formation (17.8% and 30.5%, respectively) were dominant sources of WSON. Ship emission contributed 8-12% of WSON at the four sites. Natural vegetation seemed to have very minor contribution to WSON