Low Relative Humidity Environment Research Articles

Integrating self-hygroscopic hydrogel electrolyte and porous electrode for supercapacitor operating in variable humidity environments

The application of supercapacitors (SCs) based on the conventional polyvinyl alcohol‑potassium hydroxide (PVA-KOH) polymer electrolyte is challenged in variable humidity environments, especially in low relative humidity (RH) environments. Herein, taking advantage of the high ionic conductivity and strong hygroscopicity of highly concentrated KOH solutions, we have prepared a hygroscopic hydrogel polymer electrolyte composed of sodium alginate (SA)/PVA/poly(acrylic acid) (PAA)-KOH. The SA/PVA/PAA-KOH gel electrolyte exhibits high ionic conductivity, superior water retention and even water adsorption capability. A three-dimensional CoCu-layered double hydroxide/zeolitic imidazole framework-67 (CuCo-LDH/ZIF-67) porous electrode has also been prepared for the construction of the high-performance SC operating in variable RH environments. The CuCo-LDH/ZIF-67 porous electrode allows deep penetration of the self-hygroscopic electrolyte, facilitating electron/ion diffusion and providing fast water transport channels. As a result, our asymmetric SC show significantly improved electrochemical performance than that of SC based on conventional PVA-KOH electrolyte under different RH environments. This integration strategy can advance the practical application of SC in extreme environments.

Investigation of the effect of relative humidity on micro lime consolidation of degraded earthen structures

Micro lime, hydrated lime (Ca (OH)2) with particle sizes of 1-3μ dispersed in isopropanol, can be used to reinforce deteriorated earthen structures. The consolidation effect depends on the amount of moisture present in the structure or in the ambient air. This study investigates the influence of different levels of relative humidity (RH) on the consolidation effect of micro lime on earthen structures, the chemical processes responsible for the consolidation and the physical changes to the structure. The aim is to gain a deeper understanding of the underlying chemical reactions and to identify a potential limit to the applicability of this consolidation method in low RH environments. The fact that many of these sites are located in arid climates greatly influences the practical application of micro lime in the conservation of historical earthen structures. To characterize the consolidation effect of micro lime, unconfined compressive strength and exposure to wet and dry cycles were used. The properties of the reaction products and the bonding between soil particles and micro lime were investigated using thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). At RH levels of 25%, 45%, 65% and 90%, the unconfined compressive strength (UCS) and the modulus of deformation at 50% strength (E50) of the micro lime-reinforced specimens demonstrated an increase with humidity. This led to a significant improvement in their ability to resist the effects of dry–wet cycles. Results from thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) indicate that micro lime interacts with the soil matrix via carbonation, with the reaction rate increasing with humidity. At 25% RH, vaterite was produced and residual free lime was observed, whereas at humidity levels of 45% and above, the reaction yielded vaterite and aragonite. The lime treatment did not significantly alter the pore structure of the soil specimens. The total porosity of the specimens was only slightly reduced, with the main effect of the lime treatment being a reduction in the number of large pores.

Phosphonate poly(vinylbenzyl chloride)-Modified Sulfonated poly(aryl ether nitrile) for Blend Proton Exchange Membranes: Enhanced Mechanical and Electrochemical Properties.

Blend proton exchange membranes (BPEMs) were prepared by blending sulfonated poly(aryl ether nitrile) (SPAEN) with phosphorylated poly(vinylbenzyl chloride) (PPVBC) and named as SPM-x%, where x refers to the proportion of PPVBC to the weight of SPAEN. The chemical complexation interaction between the phosphoric acid and sulfonic acid groups in the PPVBC-SPAEN system resulted in BPEMs with reduced water uptake and enhanced mechanical properties compared to SPAEN proton exchange membranes. Furthermore, the flame retardancy of the PPVBC improved the thermal stability of the BPEMs. Despite a decrease in ion exchange capacity, the proton conductivity of the BPEMs in the through-plane direction was significantly enhanced due to the introduction of phosphoric acid groups, especially in low relative humidity (RH) environments. The measured proton conductivity of SPM-8% was 147, 98, and 28 mS cm-1 under 95%, 70%, and 50% RH, respectively, which is higher than that of the unmodified SPAEN membrane and other SPM-x% membranes. Additionally, the morphology and anisotropy of the membrane proton conductivities were analyzed and discussed. Overall, the results indicated that PPVBC doping can effectively enhance the mechanical and electrochemical properties of SPAEN membranes.

Biomineralisation to improve properties of polymer modified concrete for chloride environments

This research compares the performance of three types of polymer-modified concrete (TPE, LDPE/EVA, and PCL) if bacteria-based solutions are used for reinforced concrete (RC) structures designed for a compressive strength higher than 50 MPa in chloride environments. The aim is to understand the impact on mechanical and durability performance of concrete. These recyclable polymers' use is crucial to increasing the strength at 28 and 60 days. At 60 days, all polymer-modified concrete reached a compressive strength higher than 60 MPa. The use of bioproducts is crucial to lowering the open porosity values to 4%. However, the use of bioproducts tends to delay the increase of concrete's compressive strength with time, especially until the 14 days. The existence of tetrahedron and pyramid structures in polymer-modified bio concrete indicates that calcite is present, and the quantity of calcium carbonate in the polymer-modified bio concrete is significantly higher than in plain bio-concrete or even plain. The bioproduct plays a dominant role in the capillary control and prevents water migration more effectively in comparison to the use of different polymers in concrete. The bioproduct substantially minimise the migration of chlorides to 7 × 10−12 m2/s, a water-soluble ion in wet/humid concrete porous medium environments, but also at low relative humidity environments, as it happens when the concrete is exposed to capillary suction. The highest electrical resistivity values have been recorded in TPE bio-concrete.

Toward Improved Polymer Electrolyte Membranes in a High Temperature, Low Relative Humidity Environment

Previous studies on Polymer Electrolyte Membranes have shown that sulfonated polymers exhibit high thermal stability and mechanical properties. The proton conductivity of the sulfonated polymer is strongly dependent upon the degree of sulfonation, where it increases with increasing degree of sulfonation. Also, some observations suggest that densely packed sulfonate groups confer some advantages in allowing more mobile water and protons in the low water content range. In this study bisphenol-based polymers were modified by adding sulfone-amides to form a ball of sulfonates (BOS). Thin, ductile films of the membrane are fabricated by the solution casting method, which resulted in membranes with a thickness of approximately 50 mm. The synthesized copolymers and membranes are characterized by 1 H NMR, FT-IR, ion exchange capacity, water uptake, specific density and proton conductivity measurements. The water uptake and proton conductivity of the membranes are analyzed to determine the impact of varying degrees of sulfonation and side -chains groups within the modified Bisphenol based membranes. Conductivity was tested over a range of temperatures and relative humidity levels simulating potential operating conditions. Water sorption was tested over a range of relative humidity levels to gain an understanding of how relative humidity affects membrane hydration, which is one of the primary factors determining the rate of proton transport in the membrane. In addition, specific density was also measured as density offers insight into membrane hydration and polymer morphology and allows assessment of the mobility of the charge carriers. By studying membranes in this fashion, their performance can be objectively assessed in a controlled environment prior to testing in PEM fuel cells.

Resistive Switching of Self‐Assembled Silver Nanowire Networks Governed by Environmental Conditions

AbstractPercolating networks formed by coated metallic nanowires have recently shown to exhibit memristive properties, opening a path for the development of neuromorphic systems. In this work, the resistive switching phenomena occurring in percolative networks of silver nanowires (AgNWs) coated with a thin layer of polyvinylpyrrolidone is studied. By performing voltage‐driven excursions, the highly‐conductive pristine state irreversibly changes to a higher resistance state. Such an electroforming procedure enables the switching among multiple resistance states. The stability and controllability of the resistance levels are found to be highly dependent on the initial state and the environmental conditions. In low relative humidity environments, the system displays the most controlled switching operation, while in high humidity environments the system shows a high conductance level. Samples with hysteretic response display sharp and spontaneous transitions to different resistance states, exhibiting multilevel memory device features. Both behaviors can be associated with regions of high local concentration of AgNWs that can couple or decouple from the conduction paths according to external stimuli. Conductivity is determined at a fundamental level by electrochemical processes at critical junctions in which water molecules play a key role. These results are relevant for the development of AgNWs‐based electronics and in‐hardware neuromorphic computing.

Effects and Interaction of Meteorological Parameters on Influenza Incidence During 2010-2019 in Lanzhou, China.

BackgroundInfluenza is a seasonal infectious disease, and meteorological parameters critically influence the incidence of influenza. However, the meteorological parameters linked to influenza occurrence in semi-arid areas are not studied in detail. This study aimed to clarify the impact of meteorological parameters on influenza incidence during 2010–2019 in Lanzhou. The results are expected to facilitate the optimization of influenza-related public health policies by the local healthcare departments.MethodsDescriptive data related to influenza incidence and meteorology during 2010–2019 in Lanzhou were analyzed. The exposure-response relationship between the risk of influenza occurrence and meteorological parameters was explored according to the distributed lag no-linear model (DLNM) with Poisson distribution. The response surface model and stratified model were used to estimate the interactive effect between relative humidity (RH) and other meteorological parameters on influenza incidence.ResultsA total of 6701 cases of influenza were reported during 2010–2019. DLNM results showed that the risk of influenza would gradually increase as the weekly mean average ambient temperature (AT), RH, and absolute humidity (AH) decrease at lag 3 weeks when they were lower than 12.16°C, 51.38%, and 5.24 g/m3, respectively. The low Tem (at 5th percentile, P5) had the greatest effect on influenza incidence; the greatest estimated relative risk (RR) was 4.54 (95%CI: 3.19–6.46) at cumulative lag 2 weeks. The largest estimates of RRs for low RH (P5) and AH (P5) were 4.81 (95%CI: 3.82–6.05) and 4.17 (95%CI: 3.30–5.28) at cumulative lag 3 weeks, respectively. An increase in AT by 1°C led to an estimates of percent change (95%CI) of 3.12% (−4.75% to −1.46%) decrease in the weekly influenza case counts in a low RH environment. In addition, RH showed significant interaction with AT and AP on influenza incidence but not with wind speed.ConclusionThis study indicated that low AT, low humidity (RH and AH), and high air pressure (AP) increased the risk of influenza. Moreover, the interactive effect of low RH with low AT and high AP can aggravate the incidence of influenza.

Relative humidity control during shiitake mushroom (Lentinus edodes) hot air drying based on appearance quality

A relative humidity (RH) control method was proposed based on changes of shiitake mushroom ratio of wrinkled surface area (RWSA) obtained by computer vision technology (namely 30 %-RWSA) during which dehumidification fan was turned on with a sudden increase of RWSA. Three other RH control methods of continuous fanning, setting constant target RH (namely Whole process 30 %) and controlling RH based on RH change (namely 30 %-RH) were also carried out for comparison. Drying time of 30 %-RWSA group was significantly (p ≤ 0.05) shortened, while shrinkage, RWSA, rehydration ratio were insignificantly different from (p > 0.05) those of 30 %-RH group. The cell aspect ratio of continuous fanning group was the lowest. The results showed that the qualities of shiitake mushrooms could not be improved by shortening RH keeping time, shiitake mushroom should be dried in low RH environment. The Gaussian process regression (GPR) model was effective for on-line prediction of RWSA.

The importance of correct mineral identification for the determination of appropriate specimen storage conditions in geological museum collections

Many minerals are susceptible to environmental conditions; for example, several sulfates are prone to dehydration under low relative humidity. As such, the appropriate storage conditions required by minerals are species-specific. In an example presented here, stalactitic specimens previously thought to have been melanterite (a hydrated iron sulfate) from the South Wales Coalfield in the collections at National Museum Cardiff (NMC) were recently identified as being dominated by magnesium and aluminium sulfate species of various hydration states. The presence of epsomite in the majority of the analysed specimens indicates that it, rather than melanterite, was likely the initial predominant phase of the stalactites. Whilst the stability limits of hydrated iron sulfates markedly differ compared to those of magnesium and aluminium, all will dehydrate if stored under low relative humidity, as evidenced in the example provided here. Specimen storage in fluctuating and low relative humidity environments resulted in the dehydration of the magnesium and aluminium sulfates to lesser hydrated sulfates, and consequently resulted in partial loss of the original specimens. As storage environments affect long-term preservation and appropriate storage conditions for minerals are species-specific, the accurate identification of mineral specimens is imperative for the determination of appropriate storage conditions.

Effect of Exposure Conditions and Internal Curing on Pore Water Potential Development in Cement-Based Materials

Moisture availability is a crucial factor for ongoing hydration reactions and controlling capillary pore water potential (PWP) development in cement-based mixtures. Harsh exposure conditions (such as low relative humidity, high temperature, or high wind speed) or incorporating fine cementitious materials may increase the mixture susceptibility to PWP development, and thus, early-age shrinkage. This study aims to investigate PWP and electrical conductivity development in cement paste and mortar mixtures with various water-to-cement ratios (from 0.25 to 0.4), silica fume substitutions, and internal curing in both sealed and harsh exposure conditions (ambient temperature from 10 to 35°C and relative humidity from 25% to 75%). The results indicate that high ambient temperature and silica fume incorporation substantially accelerate moisture loss and PWP development. The outcome of this study also shows the capability of internal curing using lightweight fine aggregate to delay PWP development in mixtures containing silica fume or exposure to low relative humidity and high-temperature ambient environments.

High-Performance Humidity Sensor Based on Urchin-Like Composite of Ti3C2 MXene-Derived TiO2 Nanowires.

Humidity sensors have broad applications in health monitoring, environmental protection and human-machine interface, and robotics. Here, we developed a humidity sensor using alkali oxidation method to grow in situ TiO2 nanowires on two-dimensional Ti3C2 MXene. With an order of magnitude larger surface area compared to pure Ti3C2 or TiO2 materials, the urchin-like Ti3C2/TiO2 composite demonstrates a record high sensitivity in a low relative humidity (RH) environment (∼280 pF/% RH from 7% RH to 33% RH). Complex impedance spectroscopy and Schottky junction theory were employed to understand the underlying sensing mechanisms of the Ti3C2/TiO2 composite under various humidity conditions. We demonstrate the application of humidity sensors made with the Ti3C2/TiO2 composite for noncontact detection of the presence of various liquids as well as human fingers.

Shrinkage and creep strains of concrete exposed to low relative humidity and high temperature environments

Creep and shrinkage of concrete is influenced by many factors including relative humidity and temperature. The combined effect of low relative humidity (<20%) and high temperature (38 °C) on creep and shrinkage of concrete is uncertain as limited tests have been conducted in this domain. Also unknown is the ability of the fib MC2010 model code in predicting the shrinkage and creep at the environment. This paper presents the results of experiments conducted in which concrete was cast and exposed to the aforementioned environmental conditions. The shrinkage and creep behaviour of the concrete was observed for 110 days, and experimental results were compared with predicted values using fib MC2010 model code.

Evaluating the feasibility of a personal particle exposure monitor in outdoor and indoor microenvironments in Shanghai, China

ABSTRACTExisting particulate matter (PM) monitors have too low spatiotemporal resolution to properly characterize individual exposure doses. In order to support health impact assessment, it is essential to develop a better method to assess individual exposure by taking account of varied environments in which people spend their time. Compact light-scattering PM monitors can potentially fill this need. This study was conducted to evaluate feasibility of a low-cost PM monitor (Plantower PMS 7003) in indoor and roadside outdoor microenvironments compared to research-grade instruments in Shanghai, China. The monitors exhibited excellent performance with a high linear response and low bias values both in outdoor and indoor tests. The monitors also showed little confounding bias in low relative humidity environments. Taking into account the accessibility and portability of this monitor, the monitors were able to detect the dynamic nature of individual exposures and provide data and knowledge about human exposure assessments.

Temperature Dependent Photodegradation on Urethane Coatings for Building Materials in a Low Relative Humidity Environment

Temperature Dependent Photodegradation on Urethane Coatings for Building Materials in a Low Relative Humidity Environment

Relative Breakthrough Time (RBT) of Organic Vapor in Activated Carbon Small Beds in Low Relative Humidity Environment

Relative Breakthrough Time (RBT) of Organic Vapor in Activated Carbon Small Beds in Low Relative Humidity Environment

Randomized Trial of Desktop Humidifier for Dry Eye Relief in Computer Users.

Dry eye is a frequently reported problem among computer users. Low relative humidity environments are recognized to exacerbate signs and symptoms of dry eye, yet are common in offices of computer operators. Desktop USB-powered humidifiers are available commercially, but their efficacy for dry eye relief has not been established. This study aims to evaluate the potential for a desktop USB-powered humidifier to improve tear-film parameters, ocular surface characteristics, and subjective comfort of computer users. Forty-four computer users were enrolled in a prospective, masked, randomized crossover study. On separate days, participants were randomized to 1 hour of continuous computer use, with and without exposure to a desktop humidifier. Lipid-layer grade, noninvasive tear-film breakup time, and tear meniscus height were measured before and after computer use. Following the 1-hour period, participants reported whether ocular comfort was greater, equal, or lesser than that at baseline. The desktop humidifier effected a relative difference in humidity between the two environments of +5.4 ± 5.0% (P < .001). Participants demonstrated no significant differences in lipid-layer grade and tear meniscus height between the two environments (all P > .05). However, a relative increase in the median noninvasive tear-film breakup time of +4.0 seconds was observed in the humidified environment (P < .001), which was associated with a higher proportion of subjects reporting greater comfort relative to baseline (36% vs. 5%, P < .001). Even with a modest increase in relative humidity locally, the desktop humidifier shows potential to improve tear-film stability and subjective comfort during computer use.Trial registration no: ACTRN12617000326392.

Highly compressed water structure observed in a perchlorate aqueous solution

The discovery by the Phoenix Lander of calcium and magnesium perchlorates in Martian soil samples has fueled much speculation that flows of perchlorate brines might be the cause of the observed channeling and weathering in the surface. Here, we study the structure of a mimetic of Martian water, magnesium perchlorate aqueous solution at its eutectic composition, using neutron diffraction in combination with hydrogen isotope labeling and empirical potential structure refinement. We find that the tetrahedral structure of water is heavily perturbed, the effect being equivalent to pressurizing pure water to pressures of order 2 GPa or more. The Mg2+ and ClO4− ions appear charge-ordered, confining the water on length scales of order 9 Å, preventing ice formation at low temperature. This may explain the low evaporation rates and high deliquescence of these salt solutions, which are essential for stability within the low relative humidity environment of the Martian atmosphere.

Impedance Spectroscopy Study of the Effect of Environmental Conditions on the Microstructure Development of Sustainable Fly Ash Cement Mortars.

Today, the characterisation of the microstructure of cement-based materials using non-destructive techniques has become an important topic of study, and among them, the impedance spectroscopy has recently experienced great progress. In this research, mortars with two different contents of fly ash were exposed to four different constant temperature and relative humidity environments during a 180-day period. The evolution of their microstructure was studied using impedance spectroscopy, whose results were contrasted with mercury intrusion porosimetry. The hardening environment has an influence on the microstructure of fly ash cement mortars. On one hand, the impedance resistances R1 and R2 are more influenced by the drying of the materials than by microstructure development, so they are not suitable for following the evolution of the porous network under non-optimum conditions. On the other hand, the impedance spectroscopy capacitances C1 and C2 allow studying the microstructure development of fly ash cement mortars exposed to those conditions, and their results are in accordance with mercury intrusion porosimetry ones. Finally, it has been observed that the combined analysis of the abovementioned capacitances could be very useful for studying shrinkage processes in cement-based materials kept in low relative humidity environments.

Estimation of the probability of bacterial population survival: Development of a probability model to describe the variability in time to inactivation of Salmonella enterica

Despite the development of numerous predictive microbial inactivation models, a model focusing on the variability in time to inactivation for a bacterial population has not been developed. Additionally, an appropriate estimation of the risk of there being any remaining bacterial survivors in foods after the application of an inactivation treatment has not yet been established. Here, Gamma distribution, as a representative probability distribution, was used to estimate the variability in time to inactivation for a bacterial population. Salmonella enterica serotype Typhimurium was evaluated for survival in a low relative humidity environment. We prepared bacterial cells with an initial concentration that was adjusted to 2 × 10n colony-forming units/2 μl (n = 1, 2, 3, 4, 5) by performing a serial 10-fold dilution, and then we placed 2 μl of the inocula into each well of 96-well microplates. The microplates were stored in a desiccated environment at 10–20% relative humidity at 5, 15, or 25 °C. The survival or death of bacterial cells for each well in the 96-well microplate was confirmed by adding tryptic soy broth as an enrichment culture. The changes in the death probability of the 96 replicated bacterial populations were described as a cumulative Gamma distribution. The variability in time to inactivation was described by transforming the cumulative Gamma distribution into a Gamma distribution. We further examined the bacterial inactivation on almond kernels and radish sprout seeds. Additionally, we described certainty levels of bacterial inactivation that ensure the death probability of a bacterial population at six decimal reduction levels, ranging from 90 to 99.9999%. Consequently, the probability model developed in the present study enables us to estimate the death probability of bacterial populations in a desiccated environment over time. This probability model may be useful for risk assessment to estimate the amount of remaining bacteria in a given sample.

Real-Time Nanoscale Open-Circuit Voltage Dynamics of Perovskite Solar Cells

Hybrid organic-inorganic perovskites based on methylammonium lead (MAPbI3) are an emerging material with great potential for high-performance and low-cost photovoltaics. However, for perovskites to become a competitive and reliable solar cell technology their instability and spatial variation must be understood and controlled. While the macroscopic characterization of the devices as a function of time is very informative, a nanoscale identification of their real-time local optoelectronic response is still missing. Here, we implement a four-dimensional imaging method through illuminated heterodyne Kelvin probe force microscopy to spatially (<50 nm) and temporally (16 s/scan) resolve the voltage of perovskite solar cells in a low relative humidity environment. Local open-circuit voltage (Voc) images show nanoscale sites with voltage variation >300 mV under 1-sun illumination. Surprisingly, regions of voltage that relax in seconds and after several minutes consistently coexist. Time-dependent changes of the local Voc are likely due to intragrain ion migration and are reversible at low injection level. These results show for the first time the real-time transient behavior of the Voc in perovskite solar cells at the nanoscale. Understanding and controlling the light-induced electrical changes that affect device performance are critical to the further development of stable perovskite-based solar technologies.