Hygroscopic Effects Research Articles

Hygroscopic effects on sound absorption of multiscale bio-based porous materials

Hygroscopicity is the tendency of a material to absorb moisture from the surrounding environment. This work investigates hygroscopic effects on the sound absorption properties of multiscale bio-based materials. It is shown how moisture can significantly alter their acoustic performance as well as how to recover their original dry-material performance by means of heat treatment, akin to thermal reactivation commonly used in the chemical engineering industry. The results of an experimental campaign, conducted over an extended period of time, is reported. Possible theoretical explanations on the reduced acoustic performance of activated carbons by hygroscopic effects and the achieved improvement, obtained after heat treating the material, are also presented. The results of this work provide useful insights on the long-term acoustic behaviour of multiscale bio-based materials for noise control applications.

Effect of hygroscopicity of typical powder solid wastes on their radon exhalation characteristics

The characteristics of radon exhalation in the hygroscopic properties of powder solid wastes are immensely significant for environmental safety and their transportation, storage, and landfill. This study detected the radon concentration of superfine cement and five kinds of powder solid waste: fly ash, silica fume, coal gangue, S95 mineral powder, and molybdenum tailing powder, at different hygroscopic times for 1–5 d under 95 % relative humidity. Additionally, the influence of particle size and porosity of solid waste on radon exhalation characteristics was analyzed using a laser particle size analyzer and nitrogen adsorption technology. The results show that the radon exhalation rate of the solid waste was at a low level in dry conditions. Although the presence of water due to the increased moisture absorption rate inhibited the radon exhalation to a certain extent, it was higher than that in dry conditions. The reciprocal of the moisture absorption rate had a strong linear relationship with the ratio between the radon exhalation rate after hygroscopy and radon exhalation rate from dry materials. The pore structure has a significant effect on the exhalation rate of radon, and the macropores inhibits the exhalation rate of radon. The results of this study have guiding significance for the reuse of solid waste and the prevention of radiation risk of radon exhalation during transportation.

Modified cotton gauze with high hemostatic efficacy due to controllable hygroscopicity and wet tissue adhesiveness

AbstractIn circumstances of severe traumatic bleeding, urgent bleeding control is vital to the wellness and life of the wounded person. Among many hemostatic measures, gauze is widely used because of cost‐effectiveness, safety and efficiency. However, it may suck a large amount of blood before bleeding stops. Thus, advanced hemostatic gauzes less blood loss and quick hemostatic rate and is greatly demanded. Herein, a novel tissue adhesive gauze (TA‐gauze) is developed by coating a thin layer of polyethyleneimine/poly(acrylic acid) (PEI/PAA) on the plain cotton gauze. This TA‐gauze has a reduced hydrophilicity and gets a new trait of wet tissue adhesiveness from the PEI/PAA coating layer. The TA‐gauze shows much improved hemostatic performance in the rat injury models, that is, its blood loss in the rat femoral artery model is just 13% that of the cotton gauze, due to it can retard the blood movement in the gauze and at the seam of gauze/tissue through a synergistic effect of tissue adhesion and hygroscopicity. It is biocompatible and on‐demand detachable. The simple preparation procedure and high hemostatic efficiency of the TA‐gauze may promise a bright future for an ideal hemostatic dressing for bleeding control.

A study of thermal and safety behaviour of potassium nitrate in flash powder after surface modification for prevention of self-decomposition due to hygroscopic effect

A study of thermal and safety behaviour of potassium nitrate in flash powder after surface modification for prevention of self-decomposition due to hygroscopic effect

Driving mechanisms and hydro‐chemical variation for assessing salt‐induced weathering of sandstone in grotto relics

AbstractSalt weathering is considered as one of the most damaging processes acting on cultural heritage sites and salt crystallization significantly contributes to the deterioration of natural sandstone in grotto relics. A laboratory partial immersion experiment was carried out to elucidate how humidity influences the salt‐induced weathering in grotto relics. Field environmental observations at the Yungang Grottoes were conducted to evaluate the differences between experimental endeavours and field observations. Superficial salt accumulation was characterized by hydro‐chemical and quantitative atomistic analysis. It revealed the co‐existence of calcium sulphate and magnesium sulphate, with a Ca/Mg molar ratio of 0.27 at RHam and 4.13–18.15 at a constant RH. An average increase of 165 mg/L in Na+ concentration and 120.7 mg/L in Mg2+ concentration in the groundwater was detected after immersion, which was attributed to the dissolution of the sandstone rock. The reduction of 322.5 mg/L in the SO42− concentration in the groundwater after partial immersion shows that capillary forces influence the migration of SO42− from the immersion solution. Calcium sulphate and magnesium sulphate accumulation with a Ca/Mg molar ratio of 0.03–0.17 in the field environment is strongly correlated with the occurrence of salt efflorescence. The upward transport of soluble salt was driven by capillary forces after partial immersion in the groundwater collected from the Yungang Grottoes. It then migrated from the interior to the exterior of the sandstone specimen due to evaporation. Salt efflorescence formed on the upper exposed stone close to the capillary fringe owing to the combined effects of condensation, hygroscopicity and evaporation. These processes were driven by wetting–drying and dissolution–crystallization cycles in response to fluctuating environmental conditions. These results contribute to a better understanding the mechanism of salt‐induced weathering and provide a basis for future conservation to mitigate the harmful impact of salts in heritage sites.

Behavior of Self‐Disintegrating Microparticles at the Air/Mucus Interface

In recent years, highly specialized nanoscopic drug carriers have been developed, which can, e.g., traverse biological barriers, protect drugs against harsh physiological conditions, and release such drugs in a controlled manner. However, for the delivery of particles via the respiratory pathway, aerodynamic diameters in the range of several micrometers are required to achieve good lung deposition and biodistribution. To combine the favorable properties of inhalable, micron‐sized particles with the advantages of nanosized drug carriers, herein, dry‐powder, hybrid microparticles (h‐μPs), which disintegrate upon contact with moist surfaces (as present in the lung) to release the embedded nanoparticles into the mucosa, are introduced. Furthermore, a microfluidic setup, which mimics the air–gel interface of the mucosal airway epithelium, is presented. With this setup, the interaction of airborne h‐μPs with the mucosal interface on a microscopic level is investigated. In detail, the influence of the h‐μP charge on their deposition efficiency is tested and it is found that this process is governed by a combination of electrostatic interactions between the mucosal surface and the h‐μPs as well as hygroscopic effects. Thus, this approach can help to optimize inhalable drug carriers to increase the efficiency of pulmonary drug administration via the respiratory pathway.

Hygroscopicity in Epoxy Powder Composites

Epoxy powders offer a low-cost way of manufacturing thick-section composite parts, such as those found in wind and tidal turbines. Currently, their processing cycle includes a lengthy drying stage (≥15 h) to remove ambient moisture. This drying stage prevents void defect formation and, thereby, a reduction in mechanical properties; however, it constitutes up to 60% of the processing time. Little research has been published which studies the drying stage or its optimisation. In the present work, experimental and simulated analyses are used to investigate the effects of hygroscopicity in epoxy powder composites. Tests are performed to quantify the void content of dried and undried laminates and to measure its impact on transverse flexural strength. Dynamic vapour sorption analysis is used to study the sorption behaviour of the epoxy powder. It is shown that the epoxy powder is slightly hygroscopic (1.36 wt%) and exhibits sorption behaviour that is characteristic of glassy polymers. This results in up to 4.8% voids (by volume) if processed in an undried state, leading to a 43% reduction in transverse flexural strength. A modified linear driving force model is fitted to the desorption data and then implemented in existing process-simulation tools. The drying of a thick epoxy powder composite section is simulated to investigate the influence of powder sintering on the duration of the drying stage. Process simulations reveal that a standard drying cycle prematurely sinters the powder, which inhibits moisture release. By maintaining the powder state, simulations show that the drying cycle can be reduced to 5 h.

Minimizing pathogen transmission through indoor environment optimization using central composite design of experiment

The human respiratory emission mechanism generates virus particles such as the COVID-19 virus that exists in both aerosols and water droplets form. Trajectories of airborne pathogens transmitted from coughing are influenced by the air flow pattern surrounding the transmission source, making it challenging to predict. ANSYS Fluent 2022 R1 is employed in this study to visualize the airborne pathogen transmission in indoor space of different environmental conditions with steady-state and periodic wind velocity. The effect of five different indoor parameters on airborne transmission is studied, which include wind velocity, air temperature, relative humidity of the air, particle residence time after emission, and the physical distancing of 3 feet, 6 feet, and 10 feet between two humans. The characteristics between airborne transmission and varying indoor conditions have motivated this study to correlate their dynamic relationship. Due to the limitation in controlling indoor conditions, obtaining optimum indoor conditions with minimal airborne transmission remains challenging. Simulation-based design of experiment of central composite design type yields optimum indoor condition with a wind velocity of 4.337 m/s, air temperature of 24.26 °C, and relative humidity of 40.14% showed 58.14% reduction in deposited particle mass relative to the base condition at a similar physical distancing of 3 feet. Surrounding air with higher relative humidity leads to a larger mean diameter of particles due to the hygroscopic growth effect. In comparison, the evaporation effect dominates in lower air humidity, leading to particle shrinkage. Particle deposition from human to human is lower with longer distances between humans, with comparable behaviour of particle transmission at each successive time step, suggesting prolonged exposure risk of the healthy individual as time progresses. This research focuses on adopting engineering simulation to find optimum indoor conditions with minimal human-to-human airborne transmission to strengthen safety and health judgement during a pandemic.

Experimental study on the influence of electrical conductivity of hygroscopic compounds on the performance of a hygroscopic cycle

Dry climate conditions and the risk of desertification have increased significantly due to the effects of climate change. This fact, combined with the growing energy demand, leads to the need of research focused on improving the performance and efficiency of power plants. In the Hygroscopic Cycle Technology, recently implemented at industrial scale, steam condensation is performed in an absorber using solutions of hygroscopic compounds in water. Hygroscopic effects increase the condensing temperature for a given pressure, allowing the implementation of dry coolers at high ambient temperatures and eliminating cooling water consumption. In this work, due to their relevance in the cycle performance and control, the influence of the concentration of hygroscopic salts in the cycle has been studied, providing insight into proper operational ranges and key parameters. An experimental study of the influence of make-up water quality, with the concentration of impurities measured by water electrical conductivity and cycle mass flow ratio values has been performed in a pilot plant. The results, used to validate a mass and species conservation model, have allowed to obtain operational charts of the cycle and may help to reduce the amount of instrumentation required for cycle control. It was found that the decrease in electrical conductivities with boiler blowdowns in the cycle stabilized at a boiler blowdown ratio of 5%. Blowdown ratios above 10% did not result in substantially lower boiler Cycles Of Concentration in comparison with the increase of thermal energy losses and pumping power (0.42 kJ/kg for each additional 1% of blowdown). It was also found that the ratio between the cooling reflux and turbine steam conductivity had to be higher than 1.1 for condensation by absorption to occur, and that a minimum blowdown ratio of 0.04% was required to avoid using a droplet separator to control live steam quality. Hence, a compromise in the boiler blowdown ratio must be found for each particular application. Finally, hygroscopic effects in condensing pressure and temperature have been experimentally verified at pilot plant scale, leading to potentially higher cycle power output values and higher temperatures in the cooling stream of industrial power cycles, which may make it easier to reject heat from the cycle.

A method to quantify and account for the hygroscopic effect in stem diameter variations

Dendrometers recording stem diameter variations (SDV) at high-resolution are useful to assess trees' water relation since water reserves are stored in the elastic tissue of the bark. These tissues typically shrink during the day as they release water when evaporative demand is high and swell during the night as they are replenished when evaporative demand is low, generating the typical SDV profile known as the diel SDV cycle. However, similar SDV cycles have been observed on dead trees due to the hygroscopic shrinking and swelling of the dead bark tissues. In order to remove this hygroscopic effect of the bark, dendrometers are applied as close as possible to the living bark tissues by removing the outer dead layer, however with questionable success. In this study, we used SDV time series from 40 point dendrometers applied on dead-bark-removed mature trees to assess and quantify the remaining hygroscopic effect on individual trees. To do so, we checked SDV behavior in the cold season and explored the relation between the diel SDV cycle and changes in relative humidity (RH). Our results showed that (a) the hygroscopic effect in SDV can be well-detected based on the amplitude of the diel SDV cycle (diel SDVampl) and the correlation between SDV and RH during both the cold and the warm season; (b) the level of the hygroscopic effect varies strongly among individuals; (c) diel SDVampl is proportional to both changes in RH and transpiration so that the hygroscopic effect on the diel SDV cycle can be quantified using a linear model where (diel SDVampl) is a function of RH changes and transpiration. These results allow the use of the model to correct the amplitude of the diel SDV cycles and suggest that this method can be applied to other ecological relevant water-related SDV variables such as tree water deficit.

Hygroscopic Tunable Multishape Memory Effect in Cellulosic Macromolecular Networks with a Supramolecular Mesophase

Tunable multishape memory polymers offer intriguing opportunities for memorizing multiple temporary shapes with tunable transition temperatures from one material composition. However, such multishape memory effects have been exclusively correlated with the thermomechanical behaviors of polymers, significantly limiting their applications in heat-sensitive scenarios. Here we report a nonthermal tunable multishape memory effect in covalently cross-linked cellulosic macromolecular networks, which spontaneously organize into supramolecular mesophases by water evaporation induced self-assembly. The supramolecular mesophase endows the network with a broad, reversible hygromechanical response combined with a unique moisture memory effect at ambient temperature, enabling diverse multishape memory behaviors (dual-, triple-, and quadruple-shape memory) under highly tunable and independent control of relative humidity (RH) alone. Significantly, such a hygroscopic tunable multishape memory effect readily extends the implications of shape memory polymers beyond the conventional thermomechanical regimes with potential advantages for biomedical applications.

Hygroscopic analysis and tribo-mechanical characterization of biocompatible PP/PA6/Boron sesquioxide composite

PurposeThe purpose of this study is to look into the hygroscopic and tribo-mechanical properties of a polypropylene/polyamide-6 (PP/PA6) blend and a PP/PA6/Boron sesquioxide composite.Design/methodology/approachThe hygroscopic behaviour of the PP/PA6 blend and PP/PA6/Boron sesquioxide composite was studied using a water contact angle goniometer in this study. To validate the hygroscopic behaviour of the blend and composite, water contact angles and surface energy of the materials were investigated. Tensile strength and hardness tests were used to determine mechanical characteristics, and tribological experiments on a pin-on-disc tribometer were used to demonstrate the friction and wear rates of dry and water-conditioned blends and composites. The melting temperature of dry and water-conditioned composites was determined using DSC analysis.FindingsThe hygroscopic effect of the PP/PA6 blend was found to be minimal in the experiment, while it was relatively dominating in the PP/PA6/Boron sesquioxide composite. Tensile strength was found to be somewhat lower in blend and composite compared to virgin PP, whereas hardness was found to be higher in both blend and composite. The composite’s tribological testing findings were fairly outstanding, with the coefficient of friction (COF) and wear rates significantly reduced due to boron sesquioxide reinforcement. The reaction between boron sesquioxide and water molecules produced boric acid, which increased the tribological characteristics of the composite even further. Following 30 days of water conditioning, the weight of the blend increased by 3.64% and the weight of the composite increased by 6.45% as compared to the dry materials. After water conditioning, tensile strength reduced by 0.8% for the blend and 14.16% for the composite. Hardness was determined to be the same in the dry state and after water-conditioning for blend but dropped 1% for composite. As compared to blend, the COF and wear resistance of composite were 15.52% and 25.16% higher, respectively. After absorbing some water, the results increased to 28.57% and 34.9%, respectively.Originality/valueThe mechanical and thermal behaviour of polymer composites (particularly polyamide composites) vary depending on the surrounding environment. Tests were carried out to explore the effect of water treatment on the tribo-mechanical and thermal characteristics of PP/PA6/Boron sesquioxide composite. Water treatment caused polyamides to bind with water molecules, resulting in voids in the material. The interaction between boron sesquioxide and water molecules produced boric acid, which increased the tribological characteristics of the composite.

A global evaluation of daily to seasonal aerosol and water vapor relationships using a combination of AERONET and NAAPS reanalysis data

Abstract. The co-transport of aerosol particles and water vapor has long been noted in the literature, with a myriad of implications such as air mass characterization, radiative transfer, and data assimilation. Here, the relationship between aerosol optical depth (AOD) and precipitable water vapor (PW) is evaluated to our knowledge for the first time globally, at daily to seasonal levels using approximately 20 years of NASA Aerosol Robotic Network (AERONET) observational data and the 16-year Navy Aerosol Analysis Prediction System (NAAPS) reanalysis v1.0 (NAAPS-RA) model fields. The combination of AERONET observations with small uncertainties and the reanalysis fields with global coverage is used to provide a best estimate of the seasonal AOD and PW relationships, including an evaluation of correlations, slope, and PW probability distributions for identification of statistically significant differences in PW for high-AOD events. The relationships produced from the AERONET and NAAPS-RA datasets were compared against each other and showed consistency, indicating that the NAAPS-RA provides a realistic representation of the AOD and PW relationship. The analysis includes layer AOD and PW relationships for proxies of the planetary boundary layer and the lower, middle, and upper free troposphere. The dominant AOD and PW relationship is positive, supported by both AERONET and model evaluation, which varies in strength by season and location. These relationships were found to be statistically significant and present across the globe, observed on an event-by-event level. Evaluations at individual AERONET sites implicate synoptic-scale transport as a contributing factor in these relationships at daily levels. Negative AOD and PW relationships were identified and predominantly associated with regional dry-season timescales in which biomass burning is the predominant aerosol type. This is not an indication of dry-air association with smoke for an individual event but is a reflection of the overall dry conditions leading to more biomass burning and higher associated AOD values. Stronger correlations between AOD and PW are found when evaluating the data by vertical layers, including the boundary layer and the lower, middle, and upper free troposphere (corresponding to typical water vapor channels), with the largest correlations observed in the free troposphere – indicative of aerosol and water vapor transport events. By evaluating the variability between PW and relative humidity in the NAAPS-RA, hygroscopic growth was found to be a dominant term to (1) amplify positive AOD–PW relationships, particularly in the midlatitudes; (2) diminish negative relationships in dominant biomass burning regions; and (3) lead to statistically insignificant changes in PW for high-AOD events for maritime regions. The importance of hygroscopic growth in these relationships indicates that PW is a useful tracer for AOD or light extinction but not necessarily as strongly for aerosol mass. Synoptic-scale African dust events are an exception where PW is a strong tracer for aerosol transport shown by strong relationships even with hygroscopic effects. Given these results, PW can be exploited in coupled aerosol and meteorology data assimilation for AOD, and the collocation of aerosol and water vapor should be carefully taken into account when conducting particulate matter (PM) retrievals from space and in evaluating radiative impacts of aerosol, with the season and location in mind.

Bond durability between BFRP bars and seawater coral aggregate concrete under seawater corrosion environments

The combination of fiber-reinforced polymer (FRP) composites with seawater coral aggregate concrete (CAC) in offshore construction contributes to reduced construction costs and avoids the corrosion problems related to steel-reinforced concrete structures. However, the durability for FRP-reinforced CAC members during service in marine environments is not well understood, which greatly hinders their application in offshore construction. In this paper, accelerated aging tests were employed for investigating the bond performance between the basalt-FRP (BFRP) bars and the CAC under seawater drying-wetting cycle and immersion environments. The effects of various exposure temperatures and exposure times on bond characteristics were considered, and scanning electron microscopy (SEM) was adopted to characterize microstructure changes at the cross-section of BFRP bars subjected to seawater exposure environments. The experimental results revealed that after being exposed to seawater corrosion conditions, the slope in the rising stage of the curves (i.e., initial bond stiffness) appeared to increase somewhat due to the hygroscopic expansion effect of the FRP bars, but the bond strength and its corresponding slip value demonstrated a gradual decrease. After being subjected to seawater drying-wetting cycle conditions at 45 °C and 60 °C for 12 months, the bond strength of BFRP bars in CAC declined by approximately 6.5 % and 12.0 %, respectively. This deterioration in the bond strength was related to the degradations in the mechanical properties of the FRP bars and the CAC, as well as the interfacial performance between the FRP bars and the CAC.

Transport and deposition of beclomethasone dipropionate drug aerosols with varying ethanol concentration in severe asthmatic subjects

This study aims to assess the effects of varying an ethanol co-solvent on the deposition of drug particles in severe asthmatic subjects with distinct airway structures and lung functions using computational fluid dynamics. The subjects were selected from two quantitative computed tomography imaging-based severe asthmatic clusters, differentiated by airway constriction in the left lower lobe. Drug aerosols were assumed to be generated from a pressurized metered-dose inhaler (MDI). The aerosolized droplet sizes were varied by increasing the ethanol co-solvent concentration in the MDI solution. The MDI formulation consists of 1,1,2,2-tetrafluoroethane (HFA-134a), ethanol, and beclomethasone dipropionate (BDP) as the active pharmaceutical ingredient. Since HFA-134a and ethanol are volatile, both substances evaporate rapidly under ambient conditions and trigger condensation of water vapor, increasing the size of aerosols that are predominantly composed of water and BDP. The average deposition fraction in intra-thoracic airways for severe asthmatic subjects with (or without) airway constriction increased from 37%±12 to 53.2%±9.4 (or from 20.7%± 4.6 to 34.7%±6.6) when the ethanol concentration was increased from 1 to 10%wt/wt. However, when the ethanol concentration was further increased from 10 to 20%wt/wt, the deposition fraction decreased. This indicates the importance of selecting appropriate co-solvent amounts during drug formulation development for the treatment of patients with narrowed airway disease. For severe asthmatic subjects with airway narrowing, the inhaled aerosol may benefit from a low hygroscopic effect by reducing ethanol concentration to penetrate the peripheral region effectively. These results could potentially inform the selection of co-solvent amounts for inhalation therapies in a cluster-specific manner.

Effect of Indoor Condition with Cross Ventilation on Deposition of Airborne Droplets Emitted from Human Cough

Prediction of airborne transmission in different environmental condition remains as the research challenge in the field. This has motivated the present study to obtain the direct impact of flow field to the physical nature of transmission. ANSYS Fluent 2022 R1 software is utilised in this research to numerically investigate and visualize flow pattern in a closed environment with cross ventilation and its effect to the emitted droplets deposition. The effect of different indoor parameters towards airborne transmission are investigated, which include wind velocity, air relative humidity (RH), and exposure time after emission. Simulation result revealed increasing wind velocity according to Beaufort wind scale of 1.0 to 3.9 m/s, increases transmission rate due to enhanced convection effect. Surrounding air with higher RH leads to a larger mean diameter of particles due to hygroscopic growth effect, while evaporation effect dominates in lower air RH, leading to particle shrinkage. In a light wind breeze, droplet mass of 5.15 mg deposited on receiver body within 0.5 s of transmission when RH is 40%, while only 3.29 mg droplets reached receiver in RH of 99.5%. Droplet particles settle on the floor within 1.50 s revealed 0.66 mg deposited mass in higher RH, while 0.26 mg of droplets deposited in lower RH. Deposition at transmitter body is possible due to recirculation effect of incoming wind generated between transmitter and receiver, leading to 3.7 times higher deposited mass in lower RH as compared to in higher RH. This research highlights application of Euler-Lagrange model to represent the trajectory of cough droplets influenced by indoor condition with horizontal wind, in the effort to strengthen safety and health judgement in the event of a pandemic.

Effects of hygroscopicity on aerosol optical properties and direct radiative forcing in Beijing: Based on two-year observations.

The influence of relative humidity on aerosol properties and the direct radiative forcing of PM10 and PM1 were investigated in Beijing from January 2018 to December 2019. The annual mean scattering hygroscopic growth factor at RH = 80 % [f(80 %)] of PM10 and PM1 were 1.60 ± 0.24 and 1.58 ± 0.22, respectively. The variation of aerosol hygroscopic growth factors of PM10 and PM1 aerosols was similar, which is mainly due to the fact that aerosol scattering in Beijing is dominated by fine particles. The seasonal mean f(80 %) of PM10 from spring to winter were 1.66 ± 0.23, 1.71 ± 0.25, 1.51 ± 0.20, 1.49 ± 0.16, respectively, which were higher in spring and summer, and lower in autumn and winter. The diurnal variation of f(80 %) was relatively higher from 12:00 to 18:00, which could be related to the formation of secondary aerosols by photochemical reactions. f(80 %) shows a strong positive relationship with both the scattering Angström exponent (SAE) and the single scattering albedo (ω0) under dry conditions; therefore, the scattering hygroscopic growth factor could be estimated using these two parameters. The upscatter fraction (β) and single scattering albedo, which are the key aerosol optical properties for the calculation of direct radiative forcing, are also RH-dependent. As RH increases, the upscatter fraction (backscatter fraction) decreases and ω0 increases. The aerosol radiative forcing at RH 80 % was 1.48 times as that in the dry state. The sensitivity experiment showed that the variation in the scattering coefficient with relative humidity had the greatest influence on radiation forcing, followed by β and ω0. The seasonal variation of ΔF(80 %)/ΔF(dry) coincides with that of the aerosol hygroscopic growth factor. Our study suggests that understanding the influence of relative humidity on aerosol properties and direct radiative forcing is important for accurately estimating the radiative forcing of aerosols.

습식 성장한 ULSD 입자상 물질의 물리적 및 화학적 특성 분석에 관한 연구

Condensation of water can affect the morphology of particulate matter (PM) produced from burning hydrocarbon fuel and thus their refractive index, eventually altering the light scattering properties of particles. Optical characteristics of PMs released in the air is an essential research to reduce uncertainty in terms of environmental and climate models. However, research results on the effect of hygroscopicity of particulate matter on optical properties are relatively insufficient. Therefore, in this study, optical characteristics were studied through physical and chemical analysis of Ultra Low Sulfur Diesel (ULSD) PM produced under different relative humidity conditions. While Transmission Electron Microscope(TEM) analysis was performed to confirm the physical shape, Raman spectra & total carbon analysis were performed to elucidate the degree of graphitization of carbon of PM. Results obtained from series of analyses clearly indicate that ULSD PM reacted with water to collapse the agglomerate structure into a compact form, thus resulting in an increase in the light scattering effect.

Sustainable Hierarchical-Pored PAAS-PNIPAAm Hydrogel with Core-Shell Structure Tailored for Highly Efficient Atmospheric Water Harvesting.

As an effective way to obtain freshwater resources, atmospheric water harvesting (AWH) technology has been a wide concern of researchers. Therefore, hydrogels gradually become key materials for atmospheric water harvesters due to their high specific surface area and three-dimensional porous structure. Here, we construct a core-shell hydrogel-based atmospheric water harvesting material consisting of a shell sodium polyacrylate (PAAS) hydrogel with an open pore structure and a core thermosensitive poly N-isopropylacrylamide (PNIPAAm) hydrogel with a large pore size. Theoretically, the mutual synergistic hygroscopic effect between the core layer and the shell layer accelerates the capture, transport, and storage of moisture to achieve continuous and high-capacity moisture adsorption. Simultaneously, the integration of polydopamine (PDA) with the hydrogel realizes solar-driven photothermal evaporation. Therefore, the prepared core-shell hydrogel material possesses great advantages in water adsorption capacity and water desorption capacity with an adsorption of 2.76 g g-1 (90% RH) and a desorption of 1.42 kg m-2 h-1. Additionally, the core-shell structure hydrogel collects 1.31 g g-1 day-1 of fresh water in outdoor experiments, which verifies that this core-shell hydrogel with integrated photothermal properties can capture moisture in a wide range of humidity without any external energy consumption, can further sustainably obtain fresh water in remote water-shortage areas.

Improved design of available atmospheric corrosion monitoring sensor with a higher sensitivity to low NaCl deposition

• A novel sensor that monitors the corrosion behavior of material was designed. • The sensor shows good responses to surface wetting and electrolyte development. • The sensor shows high resolutions in corrosion detection under low NaCl conditions. • The sensor provides perspectives on current atmospheric corrosion sensor design. The development of electrochemistry-based sensors is central to in-situ atmospheric corrosion monitoring of materials under conditions of both outdoor and indoor exposures. In this work, an improved design with an exposed Cu teeth height in the two member electrodes of the traditional EIS-based atmospheric corrosion sensor makes the sensor more sensitive under the thin electrolyte layer. With the noble design, the improved sensor exhibits a high sensitivity in surface electrolyte generation when the NaCl deposition is higher than 20 mg/m 2 , and a good corrosion rate response to NaCl deposition as low as 2 mg/m 2 . The grooves between adjacent exposed Cu teeth facilitate the formation of electrolyte layer under the hygroscopic effect of NaCl deposition, and thus improve sensitivity of the sensor to low NaCl deposition. Therefore, the improved sensor has broad potential applications in field conditions to monitor low NaCl deposition induced thin electrolyte layer evolution and corrosivity assessment of the atmosphere.