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Abstract The internal sediment release is a key factor controlling eutrophication processes in large, shallow lakes. Sediment resuspension is associated with the wave and current induced shear stress in large, shallow lakes. The current study investigated the wind field impacts on sediment resuspension from the bottom at Meiliang Bay of large, shallow Lake Taihu. The impacts of the wind field on the wave, current, and wave-current combined shear stresses were calculated. The critical wind speed range was 4–6 m/s after which wave and current shear stress started to increase abruptly, and onshore wind directions were found to be mainly responsible for greater shear stress at the bottom of Lake Taihu. A second order polynomial fitting correlation was found between wave (R 2 0.4756) and current (R2 0.4466) shear stresses with wind speed. Wave shear stress accounted for 92.5% of the total shear stress at Meiliang Bay. The critical wave shear stress and critical total shear stress were 0.13 N/m2 for sediment resuspension whereas the current shear stress was 0.019 N/m2 after which suspended sediment concentrations (SSC) increased abruptly. A second order polynomial fitting correlation was found between wave (R 2 0.739), current (R 2 0.6264), and total shear stress (R2 0.7394) with SSC concentrations at Meiliang Bay of Lake Taihu. The sediment resuspension rate was 120 to 738 g/m2/d during 4–6 m/s onshore winds while offshore winds contributed ≥ 200 g/m2/d. The study results reveal the driving mechanism for understanding the role of the wind field in sediment resuspension while considering wind speed and direction as control parameters to define wave and current shear stresses. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) constitutes a substantial portion of the global carbon cycle and serves as the largest reservoir of reactive carbon on Earth. Studying DOM's sources, molecular compositions, and reactivity is central to understanding the fate and environmental effects of organic carbon, yet, links between DOM composition and reactivity remain to be established. In this study, stable carbon isotopic composition and ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) were combined with degradation experiments to comprehensively study DOM's properties in the major rivers across the Pearl River Delta (PRD) in South China. The increasing δ13C-DOC along the Pearl River at the PRD suggests that terrestrial DOM from upstream was gradually diluted by local processes. Although affected by different interaction patterns of multiple sources, a major component of DOM, enriched in CHO and lignins, is molecularly indistinguishable in different rivers (molecular Bray-Curtis dissimilarity of 15%–31%). The photo-degradation removed 34% (PDOC%) of initial DOM within 14 days, twice that by biodegradation (BDOC%). In contrast to earlier research, the distinctive integration of molecular characterization with DOM degradation kinetics indicates that both regional (common shared molecules) and local (partial shared and unique molecules) derived DOM play a collective role in governing the bio-degradation kinetics of DOM, while the photo-degradation kinetics of DOM are barely correlated to molecular composition. The thorough investigation of DOM molecular composition and its correlation with bulk DOM properties in the PRD region, though requiring further investigation into its mechanisms, offers valuable insights into the role of riverine DOM in coastal hypoxia and the global carbon cycle. [Display omitted] • Lignin-enriched terrestrial dissolved organic matter (DOM) dominates at all sites. • Heteroatom- and proteins-enriched DOM is introduced at the Pearl River Delta. • DOM bio-degradation has higher rate, lower removal proportion, and wider reactivity. • Photo-degradation of DOM is barely correlated to the molecular composition. • The results have novel implications for coastal hypoxia and the global carbon cycle. [ABSTRACT FROM AUTHOR]

Wind induced flow velocity patterns and associated thermal destratification can drive to hypoxia reduction in large shallow lakes. The effects of wind induced hydrodynamic changes on destratification and hypoxia reduction were investigated at the Meiling bay (N 31° 22′ 56.4″, E 120° 9′ 38.3″) of Lake Taihu, China. Vertical flow velocity profile analysis showed surface flow velocities consistency with the wind field and lower flow velocity profiles were also consistent (but with delay response time) when the wind speed was higher than 6.2 m/s. Wind field and temperature found the control parameters for hypoxia reduction and for water quality conditions at the surface and bottom profiles of lake. The critical temperature for hypoxia reduction at the surface and the bottom profile was ≤24.1C° (below which hypoxic conditions were found reduced). Strong prevailing wind field (onshore wind directions ESE, SE, SSE and E, wind speed ranges of 2.4–9.1 m/s) reduced the temperature (22C° to 24.1C°) caused reduction of hypoxia at the near surface with a rise in water levels whereas, low to medium prevailing wind field did not supported destratification which increased temperature resulting in increased hypoxia. Non-prevailing wind directions (offshore) were not found supportive for the reduction of hypoxia in study area due to less variable wind field. Daytime wind field found more variable (as compared to night time) which increased the thermal destratification during daytime and found supportive for destratification and hypoxia reduction. The second order exponential correlation found between surface temperature and Chlorophyll-a (R 2 : 0.2858, Adjusted R-square: 0.2144 RMSE: 4.395), Dissolved Oxygen (R 2 : 0.596, Adjusted R-square: 0.5942, RMSE: 0.3042) concentrations. The findings of the present study reveal the driving mechanism of wind induced thermal destratification and hypoxic conditions, which may further help to evaluate the wind role in eutrophication process and algal blooms formation in shallow water environments. Outcome Wind field is the key control factor for thermal destratification and hypoxia reduction. 24.1C° is the critical/threshold temperature for hypoxia, Chlorophyll-a and NH 3 -N concentrations of the shallow freshwater lake. [ABSTRACT FROM AUTHOR]

Dust aerosol effect on the retrievals of dusty cloud top height (DCTH) are analyzed over Northwest China using cloud products from MODerate Resolution Imaging Spectroradiometer (MODIS) on Aqua, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and CloudSat for the Spring season of March–May over the years 2007–2011. An excellent agreement is found between CloudSat and CALIPSO derived DCTHs for all cloud types, suggesting that the effect of dust aerosols plays a small role in DCTHs determination for lidar and radar measurements. However, the presence of dust aerosols greatly affects the retrievals of DCTHs for MODIS compared with pure clouds and the active sensors derived results. The differences of DCTHs retrieving from CloudSat and MODIS range from −2.30 to 6.8 km. Likewise, the differences of DCTHs retrieving from CALIPSO and MODIS range from −2.66 to 6.78 km. In addition, the results show that the differences in DCTHs for active and passive sensors are dependent on cloud type. On the whole, dust aerosols have the largest effect on cloud top heights (CTH) retrieved of nimbostratus (Ns), followed by altocumulus (Ac) and altostratus (As), the last is cirrus (Ci) over Northwest China. Our results also indicate that the accuracy of MODIS-derived retrievals reduces accompanied with a decrease of height. [ABSTRACT FROM AUTHOR]

Despite a large amount of work have been carried out to prepare polymer/graphene hybrid nanocomposites, preparing rubber composites filled with graphene oxide via layer-by-layer (LBL) electrostatic self-assembly has not yet been reported. In this work, free-standing conductive multilayer film of (PEI/XNBR/PEI/GO) 30 (30 is referred to the number of deposition cycles) was fabricated on glass substrate through alternative LBL self-assembly with graphene oxide (GO), carboxylic acrylonitrile butadiene rubber (XNBR) latex, and polyethyleneimine (PEI). During the self-assembly process, negatively charged carboxyl groups on XNBR latex and GO sheets can be electrostatically bound by positively charged amino groups from PEI molecules. After thermal treatment, XNBR latex particles in each layer are gradually mixed together and became a continuous rubber film layer, and partial ionic bonds among XNBR latex, PEI and GO sheets are changed into covalent amide bonds. The formation of the multilayer XNBR/graphene film with ordered arrangement of GO sheets and XNBR latex layers was demonstrated by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The obtained XNBR/graphene film exhibited a significant improvement in mechanical properties, namely, 192% increase of the tensile strength and 215% increase of the elastic modulus. Besides, electrical conductivity of the prepared multilayer film reached 8.2E-03 S cm −1 after thermal reduced reaction. Hopefully, this prepared multilayer film may be potentially used as an elastomeric conductive material. [ABSTRACT FROM AUTHOR]

Abstract: A heavy dust storm that occurred in Northwestern China during April 24–30 2010 was studied using observational data along with the Fu–Liou radiative transfer model. The dust storm was originated from Mongolia and affected more than 10 provinces of China. Our results showed that dust aerosols have a significant impact on the radiative energy budget. At Minqin (102.959°E, 38.607°N) and Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL, 104.13°E, 35.95°N) sites, the net radiative forcing (RF) ranged from 5.93 to 35.7Wm−2 at the top of the atmosphere (TOA), −6.3 to −30.94Wm−2 at surface, and 16.77 to 56.32Wm−2 in the atmosphere. The maximum net radiative heating rate reached 5.89K at 1.5km on 24 April at the Minqin station and 4.46K at 2.2km on 29 April at the SACOL station. Our results also indicated that the radiative effect of dust aerosols is affected by aerosol optical depth (AOD), single-scattering albedo (SSA) and surface albedo. Modifications of the radiative energy budget by dust aerosols may have important implications for atmospheric circulation and regional climate. [Copyright &y& Elsevier]

Abstract: A biomimetic method for the preparation of highly conductive silver-plated polyethylene terephthalate (PET) fiber was demonstrated. First, the PET fibers were functionalized with a bio-inspired polydopamine (PDA) coating, simply by being dispersed in a dopamine solution under mild stirring at room temperature. Electroless plating of silver was then carried out on the surface of the PET-PDA fiber. An aqueous solution of silver nitrate and glucose was used as silver precursor and reducing reagent, respectively. The overall procedure is fast, simple, efficient, nontoxic, as well as controllable. The PDA layer on the PET surface was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and contact angle measurement. The crystalline structure of the modified PET fiber was studied by X-ray diffraction (XRD). The morphology of the PET-PDA and the PET-Ag fiber was observed by scanning electron microscopy (SEM). SEM results showed that the silver layer coated on PET-PDA was continuous, uniform, and compact. The as-prepared PET-Ag fibers have good electrical conductivity, with surface resistivity as low as 0.4mΩcm. The binding force between the silver layer and PET-PDA fiber was strong enough that the silver layer remained compact and continuous after the PET-PDA/Ag fiber was rinsed under ultrasound for 4h. [Copyright &y& Elsevier]

• Water plays a different role in coal spontaneous combustion before and after the critical temperature. • CO and C 2 H 4 can be selected as the index gases. • The gas production during coal oxidation is related to the relative content of functional groups. To explore the influence of long-term water immersion on the spontaneous combustion characteristics of coal, temperature-programmed test system and In-situ Fourier transform infrared spectroscopy (In-situ FTIR) were used. Differences in gas production of soaked coal and raw coal showed that the process of long-term water immersion played a different role before and after critical temperature. In the stage of surface oxidation, moisture could inhibit the spontaneous combustion of coal, when the critical temperature point was exceeded, it played a promoting role instead. As an explanation in support of the above arguments, the relative contents of active functional groups in raw and soaked coal were compared, which indicated that the process of water immersion could affect relative contents of hydroxyl, aromatic hydrocarbon, aliphatic hydrocarbon and oxygen-containing functional groups, giving rise to an acceleration in the reaction process of coal oxygen and exhibiting higher tendencies toward spontaneous combustion. A practical consequence of this finding is the soaking mechanism should not be neglected in any precautionary or preventive measures to avoid potential spontaneous combustion in overlying goaf of shallowly buried and close distance coal seams. [ABSTRACT FROM AUTHOR]

The disappearance of submerged aquatic vegetation caused by the use of purse seine in productive fishery has aroused the attention of the national government. In order to restore aquatic vegetation, the government has removed the seine nets on the Huayanghe Lake's surface. Here, fourteen cruises were conducted in the Huayanghe Lakes from 2016 to 2019 to study the response of water quality and phytoplankton communities to rapidly recovering aquatic vegetation. The results showed that the restoration of aquatic vegetation increased the Secchi depth (from 65.36 to 105.52 cm) and dissolved oxygen (from 8.98 to 12.17 mg/L), while the concentration of total nitrogen (from 0.98 to 0.53 mg/L), and total phosphorus (from 0.04 to 0.02 mg/L) decreased, resulting in a 35.3% and 11.6% reduction in the total phytoplankton density and chlorophyll ɑ , respectively. In addition, the restoration of aquatic vegetation significantly increased Shannon–Wiener diversity, Margalef richness indices by 51.6% and 40.1%. We also observed that phytoplankton density exhibited significant changes based on nonmetric multidimensional scaling analysis (NMDS). In Lake Huangda, the coverage of aquatic vegetation was as high as 80%. We also observed that after the restoration of aquatic vegetation, the proportion of cyanobacteria decreased significantly by 21%. Our study emphasizes that aquatic plants can alleviate eutrophication and increase the diversity of phytoplankton, thus providing guidance for the restoration and protection of water ecosystems in the lakes connected to the Yangtze River. Unlabelled Image • The restoration of aquatic vegetation alleviates eutrophication. • The restoration of aquatic vegetation considerably enhanced phytoplankton diversity. • The restoration of aquatic vegetation reduced the dominance of cyanobacteria. • The restoration of aquatic vegetation reduced the total phytoplankton density. [ABSTRACT FROM AUTHOR]

In recent years, aramid nanofibers (ANFs) have been widely used in polymer reinforcement and toughening fields, due to their large specific surface area, high aspect ratio and retaining the excellent strength, modulus and high temperature resistance of aramid micron fibers (AMFs). It is considered that ANFs have excellent reinforcement effects for polymer composites and much attention has been focused on them. ANFs have excellent water dispersibility, which provides convenience for their reinforced polymers. ANF-reinforced polymers could also impart excellent properties such as high temperature resistance, flame retardancy, and tear resistance. Therefore, it is necessary to find a simple and efficient preparation method of ANFs. However, there is almost no literature review on the research progress of the fabrication of ANFs and ANF-reinforced polymer composites. This article reviews the recent research progress of the preparation of ANFs and the advantages and disadvantages of different preparation methods, and presents the applications in reinforcing various polymer matrices such as epoxy, rubber and composites. Finally, we proposed our own opinions on the issues of ANF-reinforced polymers. [ABSTRACT FROM AUTHOR]

In this paper, the synergistic effect of co-gasification for coal gangue and pine sawdust was studied on a self-made two-stage gasification fixed bed experimental device. The results indicated that there was synergistic effect between coal gangue and pine sawdust. With the gasification temperature was 850 °C, the catalytic reforming temperature was 900 °C, the steam flow was 2 ml/min and the mixing ratio of coal gangue and pine sawdust was 1:1. The co-gasification synergistic effect yields the best results, the H 2 volume fraction reached its highest value of 37.2%, with a synergistic coefficient of 0.22. Under this condition, the number of mesopores in co-gasification char was the largest and the absorbance of the hydroxyl (-OH) functional group was the smallest. The alkali metal (K, Ca) content reached a maximum of 22.18%, which was conducive to the formation of hydrogen. • Relationship between gas composition and physiochemical properties was observed. • With a mixing ratio of 1:1, the synergistic effect was the greatest. • The alkali metals K and Ca had a catalytic effect on the decomposition of –OH. [ABSTRACT FROM AUTHOR]

Dust aerosols from the desert areas of China can be lifted to the upper troposphere and transported eastward by the westerly, affecting regional and local air pollution process. In this paper, we analyzed the long-range transport of dust and its impact on the haze-fog process that occurred in Tianjin from 23 November to 5 December 2018. Satellite and ERA5 reanalysis data revealed that dust from northwestern China was transported to eastern China by the westerly flow behind the troughs, which subsequently enhanced the air pollution in Tianjin area. On 26 November and 2 December, the visibility was less than 2 km with a relative humidity (RH) over 90%, indicating there was fog weather in Tianjin. The dust influx from the northwest direction mixed with ground pollutants, increased the PM 2.5 and PM 10 mass concentrations and enhanced the air pollution with the cumulative peak value of the PM 2.5 mass concentration reaching over 300 μg/m3 on 26 November. On 27 November and 3 December, the wind speed increased and large dust particles were transported to Tianjin, the PM 10 mass concentration exceeded a much higher value of 550 μg/m3 whereas the PM 2.5 mass concentration decreased to its lowest value, indicating dust weather followed the typical haze-fog pollution period in Tianjin. The ground lidar observations indicated that a large amount of non-spherical dust aerosols transmitted to Tianjin at 1.5~2.5 km height and settled down near the ground, which substantially affected the aerosol optical characteristics and air quality over the area. The influx of dust successive after the haze-fog weather, aggravated the air pollution process in Tianjin area, make it lasting for 153 h. • Long-range transport of dust and its effects on air pollution in Tianjin were studied. • The process of air pollution includes haze, fog and dust weather. • Dust alternates with haze-fog, make the duration of pollution lasting for 153 h. [ABSTRACT FROM AUTHOR]

Dust aerosols play important roles in marine ecosystems and carbon export once they are deposited and dissolved in the ocean. The effect of dust aerosols on chlorophyll-a (Chl-a) concentrations and particulate organic carbon (POC) in the subarctic North Pacific Ocean (SNPO) received particular attention due to their influence on air-sea carbon flux. However, significant uncertainties remain in understanding the long-range transport, atmospheric process and deposition of dust/polluted dust aerosols and their impacts on oceans. A trans-Pacific dust/polluted dust episode from 12 to 17 March 2015 was analyzed using satellite data and the WRF-Chem model. Both results confirmed that dust/polluted dust aerosols were transported from the Taklimakan Desert to the SNPO in 4–5 days under the effect of the westerly jet system. Anthropogenic aerosol mixed with dust aerosol during atmospheric process. The total deposition of dust aerosols based on model results over the research region (40°-50°N, 150°-155°E) in the SNPO from 16 to 18 March 2015 was 6.8 mg m−2. Both Chl-a concentrations and POC increased nearly 50% after the dust deposition. Dust deposition might leads to an increase in phytoplankton by iron fertilization effect. In addition, polluted dust deposition might be an important source of POC in the surface ocean. • Anthropogenic and dust aerosol mixed during transport. • Polluted dust deposition provides particulate organic carbon to the surface ocean. • A trans-Pacific polluted dust and its effect on ocean productivity were studied. [ABSTRACT FROM AUTHOR]

It is very important to improve the electrical conductivity of polymer nanocomposites (PNCs), which can be used under the external field. In this work, by employing a coarse-grained molecular dynamics simulation, the effect of the external fields (tensile field and shear field) on the conductive probability of PNCs has been investigated in details by tuning the nanofiller shape. By carefully analyzing the conductive network, compared with the rod filler and the sphere filler, the Y filler and the X filler can protect the conducive networks well from their breakage perpendicular to the external fields, which thus can significantly enhance the conductive probability under the external fields. In other words, compared with under the quiescent state, the decrease or the increase of the conductive probability under the external fields depends on the nanofiller shape. Meanwhile, it is interesting to find that both the directional conductive probabilities parallel to the shear field and perpendicular to the shear field increase with the shear rate for the Y fillers, which further reflects their high conductive probability under the shear field. The reason can be attributed to two aspects: (1) the gradual aggregation of Y fillers under the external field; (2) the multi-arm structures of Y fillers. In summary, this work presents some further understanding how to improve the electrical conductivity of PNCs under the external fields by tuning the nanofiller shape. Image 1 [ABSTRACT FROM AUTHOR]

A novel procedure was demonstrated for the preparation of carbon nanotubes (CNTs) decorated with silver nanoparticles through poly(dopamine) (PDA) surface functionalization and ultraviolet (UV) irradiation. The CNT surfaces were first functionalized by a bio-inspired PDA layer. X-ray photoelectron spectroscopy (XPS) results showed that PDA layer with thicknesses in nanometers were formed on the outer surfaces of the CNTs. With the immersion of the PDA-coated CNTs (CNTs-PDA) into a silver plating bath, the silver ions attached to the CNTs-PDA surfaces were reduced in situ to silver nanoparticles by using the N-containing groups and reducing ability of PDA. The dense silver nanoparticles were further decorated on the CNTs-PDA surfaces under UV irradiation. High-resolution transmission electron microscopy (HRTEM) images showed that the spherical silver nanoparticles were about 3–4 nm in diameter and uniformly distributed on the outer surfaces of the CNTs. The distance between the nanoparticles was less than 10 nm. The as-prepared silver-decorated CNTs-PDA nanocomposites had excellent electrical conductivity, with a surface conductivity of up to 340 S/cm. [ABSTRACT FROM AUTHOR]

The soluble fractions of iron (Fe S) and manganese (Mn S) in atmospheric aerosols potentially impact human health and ocean ecosystems. This study investigated a persistent haze-to-dust process observed in winter Qingdao, a coastal city in Northern China, focusing on the aerosol sources and acidification process affecting the dissolution of Fe and Mn. It was found that Fe S in PM 2.5 peaked during the intermingling of dust plumes with local haze, while other species of Fe and Mn reached their maximal levels coinciding with PM 10. Positive Matrix Factorization (PMF) analysis determined that aged dust was the main source of Fe S in PM 2.5 , accounting for 44.0%, while fresh dust contributed just 1.9%. Conversely, fresh dust played a more significant role in PM 10 , contributing 8.9% to Fe S. Similar trends were observed in the initial dust and dust swing periods, aged dust was the dominant contributor to Fe S , but fresh dust accounted for a higher fraction in PM 10 (11.5%) than in PM 2.5 (4.9%). In contrast, Mn S levels, with high solubility (%Mn S), were mainly from fresh dust (27.9% and 63.2% in PM 2.5 and PM 10 , respectively). The PMF estimated %Mn S in fresh dust at 17.0% for PM 2.5 and 19.4% for PM 10 , considerably higher than Fe solubility (%Fe S) at 0.3% and 0.1% in the corresponding particulate sizes. Additionally, %Fe S correlated more strongly with sulfate and nitrate per unit Fe mass (R2 = 0.68 and 0.79 in PM 2.5 and PM 10) than %Mn S (R2 = 0.49 and 0.50), suggesting a more profound impact of acidification on Fe dissolution. Further analysis suggests liquid water content rather than pH played a more critical role during the acidification process within fine particles. This study successfully estimated the solubility of Fe and Mn within various aerosols, providing valuable information and advancing our understanding of their dissolution and potential health and ecosystem impacts. [Display omitted] • The fresh and aged dust were successfully distinguished during a haze-to-dust event via a refined PMF model. • Soluble Fe in both PM 2.5 and PM 10 mainly from aged dust, with more fresh dust in PM 10 ; soluble Mn mainly from fresh dust. • Solubilities of Fe and Mn from fresh and aged dust aerosols estimated via PMF analysis generally resemble the observed data. • The acidification process exerts a more pronounced impact on the dissolution of Fe than on Mn. • Liquid water content rather than pH played a more critical role during the acidification process within fine particles. [ABSTRACT FROM AUTHOR]

Electromagnetic interference (EMI) shielding materials with favorable flexibility, robustness, and multipurpose capabilities are urgently desired for smart wearable devices. Herein, flexible PDMS/cellulose nanofiber/Ag nanowire composite films with sandwich structures were successfully fabricated by a facile method. First, silver nanowires (AgNWs) were uniformly stacked in the upper part of the cellulose gel using a controlled two-step vacuum-assisted filtration; next, AgNWs were tightly embedded in the cellulose matrix by a hot-pressing strategy; finally, a hydrophobic protective layer, PDMS, was introduced. The water contact angle (WCA) of composite films could reach 121°. Compared with uniformly mixed films, AgNWs deposited only on the surface of the matrix allowed the conductivity to reach 381 S/cm at a low weight fraction of AgNWs (6 wt%). Thanks to such excellent conductivity, the composite films exhibited superior EMI shielding effectiveness (49 dB) at only 40 μm thickness, and Joule heating performance, i.e., the surface temperature reached 111.3 °C at 1.5 V driving voltage. It was worth noting that after bending and peeling damage, the WCA and EMI shielding effectiveness of composite films were not significantly impacted due to the hot-pressing strategy and hydrophobic surface protection. The robust composite films show huge application potential in the wearable electronics field. [Display omitted] • AgNWs deposited only on the surface of the matrix allowed high conductivity (381 S/cm) at a low weight fraction of AgNWs (6 wt%). • The composite films were more robust due to the protection of hydrophobic surfaces. • The composite films exhibited superior EMI shielding effectiveness and Joule heating performance at only 40 μm thickness. [ABSTRACT FROM AUTHOR]

The antibacterial and barrier properties of natural rubber used as gloves are very important for the safety of medical staffs. In this research, the silver (Ag) particles were loaded on the surface of graphene oxide (GO) first modified by polydopamine (PDA). Then, the complex particles (Ag-PDA-GO) were introduced into the natural rubber (NR) latex, and the Ag-PDA-GO/NR film composites were obtained by the dipping method. Results showed that a fine dispersion of Ag-PDA-GO in NR film was obtained due to the isolation effect of Ag and PDA between GO sheets. Compared with those of pristine NR composite, when the GO content was only 0.2 phr, the tensile strength, tear strength and modulus at 100% and 300% strains of the composites increase by 66.7%, 128%, 37.7% and 30.7%, respectively, compared with the pure NR. The gas diffusion coefficient was reduced by 15.6% due to the strong interface interaction between GO and NR macromolecules. When the GO content was only 0.1 phr, the minimum inhibitory concentrations (MIC) of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were 16 and 32 μg/mL, respectively. These results are of great significance for improving the barrier and antibacterial properties of medical rubber products. [ABSTRACT FROM AUTHOR]

Abstract: Novel silica/poly(dopamine)/silver (from inner to outer) (denoted as SiO2/PDA/Ag) conductive micro-particles were first synthesized by biomimetic poly(dopamine) coating. These micro-particles were then coated with a poly(dopamine) layer to form core/shell-structured particles, with silica/poly(dopamine)/silver core and poly(dopamine) shell (denoted as SiO2/PDA/Ag/PDA). This multilayer core/shell micro-particles were confirmed by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscope. Polymer composites were then prepared by mechanical blending of poly(dimethyl siloxane) and the core/shell-structured particles. It was found that the silver layer and the poly(dopamine) shell had good adhesion with substrate and they kept intact even under violent shearing stress during mechanical mixing. The effect of the thickness of outermost poly(dopamine) shell as well as the loading amount of this filler on the dielectric and electrical properties of the composites was further studied. The results showed that the dielectric constant, dielectric loss, and conductivity of the composites decreased with increasing shell thickness (10–53nm) at the same loading level. And the maximal dielectric constant of composites was achieved in the composites filled with SiO2/PDA/Ag/PDA (with 10–15nm PDA shell) particles, which was much larger than that of the composite filled with SiO2/PDA/Ag particles without insulative PDA shell. At the same time, the composites can change from conductor into insulator by controlling the shell thickness of core/shell-structured conductive particles. This simple and controllable biomimetic method may be applied to construct many other conductive filler in order to realize controllable dielectric and electrical performance of polymer composites. [Copyright &y& Elsevier]

Due to the chemical inertness of the polyester (PET) fiber surface, it often needs to be immersed in a traditional resorcinol-formaldehyde-latex (RFL) dipping solution before it can be used in rubber composite. However, the RFL dipping system contains toxic components, resorcinol and formaldehyde, and is gradually banned. In this article, a novel resorcinol-formaldehyde-free environmentally friendly adhesion promoter for dipping treatment of PET fiber was synthesized. Specifically, water soluble ethylene glycol diglycidyl ether (EGDE) and diethylenetriamine (DETA) were introduced into the new dipping solution to replace the toxic ingredients of resorcinol and formaldehyde in RFL dipping system. We use polyester fabrics to study the effects of reaction conditions, chemical structures and interfacial adhesion mechanism on the treatment results to achieve the level of conventional RFL treatment. The surface chemical compositions of modified PET fabrics were characterized by attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The results showed that the fabric surface was successfully coated with the dipping layer. In addition, interfacial adhesive properties between modified PET fabrics and rubber were studied. The results showed that the peel adhesive strength between the modified PET fabric and the rubber was 17 N/mm, which was comparable to the RFL dipping system. • A novel resorcinol-formaldehyde-free environmentally friendly adhesion for dipping treatment of fibers was synthesized. • Interfacial adhesive properties between modified polyester (PET) fabrics and rubber matrix were studied. • The peel adhesive strength between the modified PET fabric and the rubber matrix was 17 N/mm. [ABSTRACT FROM AUTHOR]

A plasma-assisted surface modification method was introduced to enhance the interfacial adhesion of rubber composites reinforced with ultra-high molecular weight polyethylene (UHMWPE) fibers. First various reactive monomers were grafted onto the fiber surface via a plasma-assisted radical polymerization reaction. Subsequently, the grafted fibers underwent RFL (resorcinol-formaldehyde-latex) dipping process to bolster their interfacial adhesion with rubber. Compared with the original UHMWPE fibers, the modified fiber-reinforced rubber composites showed an increase in H pull-out force by 105.3 %–165.7 N and peel strength by 145.2 % to 10.3 N/mm, reaching the level of general-purpose fabric-core conveyor belt (≥4.5 N/mm). After the modification, the dynamic fatigue life and aging stability of the fiber-reinforced rubber composites were significantly improved, thereby enhancing the service life and safety of the composites. The results show that this method greatly improves the chemical activity, hydrophilicity, and surface roughness of UHMWPE fibers with minimal damage, rendering it a promising choice for industrial applications. [Display omitted] • A new strategy for UHMWPE fiber modification applicable to rubber matrix was provided. • A rubber material that can be quickly vulcanized at low temperatures for use in textile core conveyor belts was prepared. • The H pull-out force between the modified UHMWPE fiber and rubber reached 165 N, which reached the application level. • The interfacial bonding mechanism and chemical reaction processes between modified fibers and rubber are elucidated. [ABSTRACT FROM AUTHOR]

This work simulates the real harsh service conditions of Fiber-reinforced polymer composites (FRPC), and the dynamic adhesion and failure mechanism of nylon 66 (PA66)-reinforced natural rubber (NR) composites under large deformation and wide temperature range are deeply studied by comprehensive analysis of the interfacial adhesion evolution, microstructure and failure damage location of the composites, interfacial heating rate, and modulus ratio of PA66/NR. The failure mechanism of PA66/NR composites is interfacial debonding at −20 °C, 25 °C and 80 °C, whereas that at 120 °C is matrix cracks. Interestingly, at −20 °C, the crack expansion at the interface is slow, and the samples show two-stage damage during fatigue, resulting in the highest fatigue life. At 80 °C, the interface heating rate and modulus ratio of the PA66/NR composites is the lowest, and thus the fatigue life is higher than that at 25 °C and 120 °C. Keywords: fiber reinforced polymer composites, fatigue life, failure mechanism. [Display omitted] • The test method for fatigue life under wide temperature range was established. • They show the highest fatigue life at −20 °C and the lowest one at 120 °C. • The failure location was studied by distribution of characteristic elements. • The fatigue failure mechanisms under wide temperature range were revealed. [ABSTRACT FROM AUTHOR]

Upon the effect of atmospheric stability on air pollution, this study highlights the weakened diurnal evolution of atmospheric boundary layer (ABL), which is crucial to the formation of regional fog-haze and air pollution episodes over eastern China (ECN). The decrease of atmospheric visibility (Vis) during 1973–2012 is found to be related to the more stable ABL with weakened diurnal evolution that is characterized by a concurrent weakening of surface wind, a decrease in ABL height, and a reduction of diurnal temperature range (DTR, – 0.26 and – 0.092 °C/10-years in the winter and summer, respectively). With a general synchronous variation, the increase in both aerosol loading and cloud cover might work in concert to reduce solar radiation reaching the surface, stabilize ABL and weaken the diurnal ABL evolution, thereby weakening the turbulent mixing of pollutants and enhancing air pollution. This conjecture of “aerosol, cloud – ABL – air pollution” feedback, with particular emphasis on the effect of cloud (in addition to the effect of aerosol) on the ABL evolution, is supported by our analysis of 40 years trends in the cloud, Vis and DTR from surface observation, the aerosol optical depth from MODIS, and the validated MERRA-2 reanalysis aerosol, cloud and boundary layer height (by surface observation and routine radiosonde sounding). Regarding the linkage between fog-haze and diurnal evolution of the ABL, the result emphasizes the effect of a persistent high relative humidity (RH), which is found to be important to the formation of regional persistent fog-haze episodes and must be carefully considered in future study. Therefore, a chain of processes is suggested to interpret the occurrence of regional persistent fog-haze episodes over ECN. First, during a polluted day, because of aerosol radiative effects, the high ABL stability and high RH can persist throughout the day, and consequently, favoring the accumulation of pollutants as well as the secondary formation and hygroscopic growth of aerosol. Second, the maintenance of such more stable, humid and polluted ABL is in contrast to a clear day when the ABL is more convective in the afternoon and facilitates the diffusion and dilution of pollutants. Third, under a persistent stable synoptic system, the increase of air pollution associated with the weakened diurnal evolution of ABL due to the “aerosol, cloud – ABL – air pollution” feedback, as described above, can be further strengthened, thereby renders more persistent and severe air pollution events. The DTR variation in relationship with the aerosol, cloud, ABL and air pollution is also discussed. [ABSTRACT FROM AUTHOR]

With the rapid depletion of fossil fuels and the associated environmental issues, solar energy is identified as one of the most promising pollution-free and renewable resource. Herein, we prepared a novel Ag-Paraffin@Halloysite microsphere with the integrated abilities of storing solar energy and catalytic function by self-assembly method. The results show that Ag-Paraffin@Halloysite microsphere has a core-shell structure with paraffin as core and halloysite as shell, and Ag nanoparticles are dispersed uniformly on the surface of the microspheres. The high thermal storage capability, encapsulation ratio and encapsulation efficiency of Ag-Paraffin@Halloysite indicate that it can be used as an ideal heat storage material. Compared with pure paraffin, Ag-Paraffin@Halloysite has higher thermal conductivity, excellent thermal storage capacity, and faster transient thermal response. After heat storage, Ag-Paraffin@Halloysite shows much better catalytic activity (95.3% of conversion in 6 min) compared with the one without heat storage (71.1% of conversion in 6 min) for catalytic reduction of 4-nitrophenol. This result suggests its potential to be used as a self-heating catalyst for storing/releasing thermal energy during catalytic reactions. This work may offer a general and innovative approach to couple phase change materials with catalyst and open up a new avenue for utilization of solar energy in the fields of chemistry and chemical engineering. [ABSTRACT FROM AUTHOR]

Lake Taihu was chosen as a case for parameter uncertainty and sensitivity analysis of water quality simulation in large shallow lakes. Forty parameters in Environmental Fluid Dynamic Code model (EFDC) were filtered and analyzed. The results showed that parameters had a considerable influence on simulation and three groups of parameters related to algal kinetics (i.e. PMc, BMRc and PRRc), light (KeChl) and temperature (KTG1c) were very sensitive. For shallow lakes with frequent algal blooms, light extinction due to Chlorophyll- a is also a sensitive parameter. While the temperature effect coefficient for algal growth is sensitive for lakes with seasonal temperature variation. Sensitive parameters and their relevant uncertainty varied spatially. For high nutrients and algae concentration subareas, temperature was more likely to be a limiting factor, whereas sensitive factors could be light in lower concentration subareas. Since most sensitive parameters were related to algae, uncertainty in simulation increased with increasing algal kinetic processes over time and varied in different subareas. Lower nutrients and algae concentration subareas were more easily influenced by model parameters while nearshore areas were highly influenced by boundary conditions. For better simulation of water quality, variable stoichiometry phytoplankton models should be considered and zooplankton need to be integrated into the model explicitly rather than a fixed predation rate. [ABSTRACT FROM AUTHOR]

Carbon nanotube bundles (CNTB) with one-dimensional orientation arrangement structure were grafted a layer of polyacrylic acid (PAA) through plasma induced polymer grafting in this study. Thus, we blended these modified CNTB (CNTB-PAA) into natural rubber (NR) matrix through the silane in-situ modification-dispersion technique achieved by mechanical blending method. In this process, carboxyl groups in large quantities distributed in the surface of CNTB-PAA could be subjected to dealcoholization reaction with silicon hydroxyl (Si-OH) generated from the hydrolysis of silane coupling agent (Si69), and a single sulfur bond of Si69, meanwhile, could participate in the curing reaction of rubber. The ultimate nanocomposites had a significantly decreased network effect of fillers and an improved interfacial bonding between CNTB and rubber matrix. The tensile and dynamic-mechanical tests revealed a strong enhancement in the tensile stress and a marked reduction in the dynamic hysteresis loss of the nanocomposites. [ABSTRACT FROM AUTHOR]

In this work, a novel strategy to avoid the blooming of antioxidants and improve the aging-resistance of styrene-butadiene rubber (SBR) was proposed by using carbon nanotubes (CNTs) loaded with antioxidant N-(1, 3-dimethyl) butyl-N′-phenyl-p-phenylenediamine (4020) as filler. The sustained release of antioxidant from carbon nanotubes extends its action time. The amount of antioxidant in the rubber composites allows for a concentration of 2.0 wt.% without causing blooming by encapsulating antioxidant into carbon nanotubes. The aging resistance of SBR/CNTs composites was studied by comparing the mechanical properties before and after thermal-oxidative and ozone aging. A fifteen-day thermal-oxidative aging test at 100 °C shows preservation of mechanical properties and a twenty-four-hour ozone aging test shows no cracks. Furthermore, due to the present of thermal and electrical conductive carbon nanotubes, the rubber composites emerge thermal conductivity of 0.303 W/m·K and electrical conductivity of 4.74 × 10 7 Ω·cm which can be extended for many potential applications, such as long service life tires and antistatic conveyer belts. This loading and sustained release approach can be extended to antimicrobial, antifouling, and other application. [ABSTRACT FROM AUTHOR]

Considering the rapidity and lesser sample amount required, the Fourier Transform Infrared Spectra (FTIR) was often used to quantitatively determine the rubber content of Russian dandelion, guayule, etc. This is because their chemical structure are cis -1,4-polyisoprene (CPI) which has a unique and isolate skeleton stretching vibration peak at 835 cm −1 band, and is convenient for determining the rubber content. However, this method is not suitable for Eucommia Ulmoides (EU) gum which will crystallize easily at room temperature due to the regular chemical structure of trans -1,4-polyisoprene (TPI), that will restrict the skeleton stretching vibration of TPI greatly. As a result, its FTIR spectrum only shows a very small peak at 845 cm −1 band hiding among a number of crystalline peaks around nearby, thus it cannot be used to determine the rubber content of Eucommia ulmoides oliv ( E. ulmoids ) directly. Actually, these crystalline peaks could be eliminated easily by elevating the temperature over 60 °C, and a unique and isolate skeleton stretching vibration characteristic band at 845 cm −1 was left alone in the TPI's FTIR spectrum which can be used expediently to determine the content of EU gum. At the present paper, the Variable Temperature Fourier Transform Infrared Spectroscopy (VTFTIR) was used to determine the rubber content of E. ulmoides . The results indicate that the rubber content of E. ulmoides samples (1–40, 5–35, 22–11) provided by Northwest Agriculture and Forestry University (NAFU) are 4.66%, 4.04%, 4.32% respectively, and the errors of average value were less than 5% compared with Soxhlet Extraction. [ABSTRACT FROM AUTHOR]

A facile and efficient mussel-like inspired modification method was developed to improve the interfacial adhesion of aramid fibers/rubber composites. The surfaces of aramid fibers were pre-deposited by poly(catechol/polyamine) (PCPA) layer, which was formed via the oxidation polymerization of catechol/polyamine (CPA) under UV irradiation. Then, the PCPA-coated fibers were further grafted with ethylene glycol diglycidyl ether (EGDE) to introduce epoxy groups onto aramid fibers surface. The kinetics of catechol oxidation was investigated by UV–vis measurements, suggesting that UV irradiation accelerated the polymerization process of CPA. The effects of EGDE concentration and grafting time on the adhesion force between aramid fibers and rubber matrix were evaluated by pull-out test, and a maximum increase of 85.6% in adhesion force was achieved, even better than that by dopamine in our previous study (a 67.5% improvement). Compared with the method based on dopamine chemistry, this method has advantages of lower cost (less than 1% of the price of dopamine) and shorter reaction time (3 h less in pre-deposition time). This study provides a new efficient strategy for fibers surface functionalization, which has promising application in rubber industry. [ABSTRACT FROM AUTHOR]

We studied the effect of the microstructure of multiwalled carbon nanotubes (MWCNTs) on interfacial interaction in seven kinds of MWCNT/natural rubber (NR) composites. Unexpectedly, the degree of defects (I D /I G ) of MWCNTs was found to play a key role in the interfacial interaction of MWCNT/NR composites. The content of bound rubber (BR) of the composites almost linearly increased with the increase in the I D /I G of MWCNTs. Then we studied the interfacial interaction between MWCNTs with high degree of defects and NR. Interestingly, the BR of the composites consisted of loosely adsorbed BR (LBR) and tight BR (TBR). TBR occupied about half of the total BR, and cannot be removed by extraction in hot toluene for 48 h. Meanwhile, the mobilities of macromolecules in TBR were more restricted than those in LBR. We discussed in depth the molecular origin of the interfacial interaction between defected MWCNTs and NR, and then proposed that LBR was topologically confined by the steps-like structure of defected MWCNTs whereas TBR was principally chemically bonded to MWCNTs. This study provided new insight on the interfacial interaction between MWCNTs and NR and thus provides guidance for the preparation of high-performance elastomer composites with strong interfacial interaction. [ABSTRACT FROM AUTHOR]

Fiber-reinforced rubber composites (FRRC) are widely used in automobile, aero tires, and conveyor belts, etc. In order to obtain high performance of FRRC, strong interfacial adhesion between fibers and rubber is a key. Resorcinol-formaldehyde-rubber latex (RFL) as the widely used dipping system in industry can do harm to human health and environment because of the release of resorcinol and formaldehyde in air. In this study, a new kind of eco-friendly dipping system for PA66 fibers was designed and successfully prepared, especially to meet the harsh service environment of aero tires. Such new dipping system is composed of the first coating of tea polyphenols (TP) on fiber surface through the hydrogen bonding between TP and PA66 fibers followed by the second coating with the mixture of glycerol triglycidyl ether (GTE), 2-ethyl-4-methylimidazole (MZ) and styrene-butadiene-vinyl-pyridine (VP) latex, in which the covalent bonding between TP and GTE, the crosslinking of GTE and the co-crosslinking of VP and NR matrix result in the formation of a solid transition bridge between PA66 fibers and NR matrix. By using such eco-friendly dipping system with optimized ratio of MZ/GTE, PA66 fibers/NR composites exhibit equivalent interfacial adhesion and aging stability as that using RFL system, while maintaining the strength and safety of composites. More importantly, PA66 fibers using the eco-friendly dipping system exhibit even better fatigue stability of interfacial adhesion after 46800 times of cyclic fatigue than that using RFL system. The relationship between the dipping layer structure and the interfacial adhesion of the composites was established. [Display omitted] • A new kind of eco-friendly dipping system for PA66 fiber cords was developed. • The new dipping system shows equivalent adhesion effect as that using RFL. • The new dipping system exhibits better fatigue stability than that using RFL. • The dipping layer structure and interfacial adhesion relationship was established. [ABSTRACT FROM AUTHOR]

Sulfate and nitrate formed on dust aerosols can considerably affect particles' physicochemical properties due to their high hygroscopicity. Dust reverse-transport (DRT) events can occur in eastern China when dust plumes undergo a distinct turn caused by Asian highs or cyclones, resulting in the re-appearance of the dust plume in one place but with anthropogenic pollutants mixed in. In this study, three DRT events were identified at a coastal city, Qingdao. The secondary sulfate and nitrate in PM 2.5 collected during the DRT events were estimated according to the mass concentration of water-soluble ions and dust tracer metal. Several key factors, including heterogeneous reactions on aerosols, photochemical conversions in the air, and precursors' abundance in dust plumes, affected the aging of dust plumes. In the presence of adequate ammonium and high-level oxidants in the air, sulfate and nitrate were efficiently produced under moderate/high humidity conditions when DRT events occurred to the south of Qingdao. The proportions of the secondary sulfate/nitrate in total concentrations exceeded 90%, in which 20.8%–43.1% of secondary nitrate was formed on dust particles. In contrast, when the DRT occurred to the north of Qingdao with low relative humidity and low [NH 4 +]/[SO 4 2−] ratio, the growth of sulfate and nitrate was small. This study reveals a manner of efficient sulfate and nitrate formation in dust plumes in the continental atmosphere. • Dust reverse-transport phenomena were used to study the aging process of dust plumes. • East Asian dust plumes were prone to aging when transported to the south of Qingdao. • Secondary sulfate/nitrate formation was strongly influenced by the precursors' concentrations on dust transport pathways. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) attract considerable scientific and engineering interest because of their excellent mechanical, electrical and thermal properties. Today, when manufacturers use CNTs, purification, chemical modifications and dispersion techniques are usually applied rendering them cost-effective in large-scale applications. Our research shows that multi-wall CNTs bundles (MWCNTBs) with the same alignment, orientation and high surface defects for each CNT can be directly incorporated into the elastomer matrix through melt compounding. A uniform dispersion of CNTs and strong interfacial interactions between elastomers and CNTs due to the silane-coupling agent can be simultaneously produced. The resulting elastomer/MWCNTBs nanocomposites demonstrate excellent mechanical properties, high thermal conductivity and low volume resistivity. Note that this nanocomposite is achieved using common compounding equipment that is easy to industrialize. Through further scale-up, we confirmed that this elastomer/MWCNTBs nanocomposite has the most optimized comprehensive performance with practical applications for fuel-savings and engineering tires. These advantages include fuel efficiency, anti-static electricity and long-time fatigue resistance. In light of the large number of tires used worldwide, this work is promising for future large-scale industrial applications of CNTs. [ABSTRACT FROM AUTHOR]

The reaction mechanism and the interfacial modulus gradient of the interfacial transition layer between the environmentally friendly dipping system (PAL) and the rubber have not been fully studied. In order to better understand the chemical structures and nano-mechanical properties of the interface between the dip layer and the rubber, we used advanced atomic force microscope (AFM) and nanoscale Fourier transform infrared spectroscopy (nano-FTIR) to perform detailed analysis in this article. The characterization of interfacial nano-mechanical properties and chemical structures is very significant for the illustration of interfacial adhesion mechanism. AFM can effectively characterize the detailed interfacial modulus gradient and the thickness of interface, while nano-FTIR can comprehensively measure the interfacial chemical structures and the distribution of chemical bonds. The results suggest that the thickness of the interface between the PAL dip layer and the rubber matrix is 175 nm, and the crosslinking density of the interfacial layer is high, which explains that the failure location of fiber/rubber composites after pull-out tests occurs on the side of the rubber matrix. Similarly, the microstructure of resorcinol-formaldehyde-latex (RFL) system was also characterized, and the preparation of RFL usually requires carcinogenic and toxic substances such as formaldehyde and resorcinol. [Display omitted] • The reaction mechanism and interfacial modulus gradient of the PAL and the rubber have been fully studied. • Nano-FTIR can measure the interfacial chemical structures and the distribution of chemical bonds. • The thickness of the interfacial transition layer between the PAL and the rubber is about 175 nm. [ABSTRACT FROM AUTHOR]