Effect Of Environmental Humidity Research Articles

The impact of environmental humidity on the mechanical property and microstructure of magnesium silicate hydrate cement

Environmental factors have a significant impact on the performance of cement-based materials. As a new type of low-carbon cementitious material, the performance of magnesium silicate hydrate cement (MSHC) under different environmental humidity conditions is crucial for its application. This study aimed to investigate the effects of environmental humidity on the hardening properties of MSHC. Compressive strength tests of MSHC were conducted under four different relative humidity (RH) conditions (RH of 33%, 58%, 75%, and 97%) and water curing (RH-w) condition. Microanalysis techniques were employed to reveal the strength mechanisms of MSHC under different environmental humidity conditions. The results showed that MSHC exhibited the optimal mechanical performance when RH was 75%, reaching 42.29 MPa. When RH was 58%, the compressive strength of MSHC was close to the optimal level, which was 41.02 MPa. However, under other humidity conditions (RH33, RH97, and RH-w), the compressive strength of MSHC was much lower than the optimal level, decreasing by 30.93%, 41.90%, and 63.66%, respectively. Pore structure analysis showed that the volume of detrimental pores (>100 nm) in the sample was the lowest when RH was 75%. Compared with RH75, the volume of detrimental pores in RH33, RH58, RH97, and RH-w increased by 20.47%, 9.83%, 36.77%, and 156.92%, respectively. In addition, the variation of environmental humidity resulted in different polymerization levels in the M-S-H gel, and higher degrees of polymerization were observed when RH was 58% and 75%.

Influence of Exposure to a Wet Atmosphere on the UV-Sensing Characteristics of ZnO Nanorod Arrays.

Zinc oxide is a promising material for the creation of various types of sensors, in particular UV detectors. In this work, arrays of ordered nanorods were grown by chemical vapor deposition. The effect of environmental humidity on the sensing properties of zinc oxide nanorod arrays was investigated, and a prototype UV sensor using indium as an ohmic contact was developed. UV photoresponses were measured for the samples stored in dry and wet atmospheres. The increase in sensitivity and response of the ZnO nanorod arrays was observed after prolonged exposure to a wet atmosphere. A model was proposed to explain this effect. This is due to the formation of hydroxyl groups on the surface of zinc oxide nanorods, which is confirmed by FTIR spectroscopy data. For the first time, it has been shown that after storage in a wet atmosphere, the sensory properties of the structure remain stable regardless of the ambient humidity.

Effect of environmental humidity on the creep behavior of flax fiber‐reinforced polymer composites

AbstractFlax fiber‐reinforced polymer (FFRP) composites are emerging popular environmental‐friendly construction materials. However, their significant creep properties have been a major concern for using FFRP in load‐bearing structures. This article presents an investigation of the effect of environmental humidity on the creep behavior of the FFRP. Samples with flax fiber in 0°, 90°, and ± 45° were manufactured, respectively, by the vacuum infusion method. Accelerated creep tests were conducted on samples in different relative humidities (RH), and the results were analyzed by the time–temperature superposition principle (TTSP). It is found the creep development of samples with 0° and 90° fiber increases with the RH, and their 30‐year total strain in 97% RH is about 10 times higher than that in 11% RH. The samples with ±45° fiber are found not obviously sensitive to the humidity change. The scanning electron microscope (SEM) check indicates the change in the fiber–matrix interface and cracks between microfibrils in a fiber bundle is the main reason for the change of creep behavior in high humidity. This study may benefit the design of structures made of natural fiber‐reinforced polymer composites, especially for load‐bearing structures working in high‐humidity environments.

Water Content-Controlled Formation and Transformation of Concomitant Pseudopolymorph Coordination Polymers.

Two concomitant pseudopolymorph coordination polymers {[Cd2L2(OAc)4]·2DMSO} n (1) and {[CdL(OAc)2]·2.75H2O} n (2) were synthesized by self-assembly of 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (L) and cadmium acetate in DMSO. Single-crystal X-ray diffraction confirmed that 1D ladder structural motifs exist for pseudopolymorphs 1 and 2 which contain DMSO and water guest molecules, respectively. Our study illustrated the active role of solvent water content in obtaining compound 2. We find that the presence of water as an impurity in the DMSO solvent creates the possibility of formation of concomitant pseudopolymorph coordination polymers which is a unique event. Furthermore, our analyses showed the effect of environmental humidity on the transformation of unstable compound 1. 1D ladder pseudopolymorphic compound 1 could be transformed to guest-free 1D linear compound [CdL(OAc)2(H2O)] n (3') (the powder form of single crystals of 3) through a scarce case of water absorption from air. Also, the crystalline material of coordination polymer 3 was transformed to coordination polymer 2 through the dissolution-recrystallization structural transformation process in DMF or DMSO. Our study clarified that the amount of water in the reaction container can control the formation of one of the compounds 2 or 3. In the presence of a significant amount of water, compound 3 (coordinated water) will be produced, whereas if a small amount of water is present, compound 2 (uncoordinated water) is prepared as an exclusive product.

Visual evaluation of warehousing humidity and time on bamboo performance

The inventories of Moso bamboo (Phyllostachys pubescens) resources are considered to be one of the most important strategic resources for economic construction and ecological building materials. Warehousing humidity is one of the objective factors that induce mold deterioration and quality deterioration of bamboo. To investigate the effect of environment humidity on the use value of bamboo, humidity levels of 45 %, 60 %, 75 % and 95 % and indoor environments were artificially simulated and regularly monitored for changes in quality during warehousing. During the 56-day storage period, with the increase of humidity in the warehousing environment, the dimensional expansion rate of the cortex side of bamboo was larger than that of the pith side and the cavity diameter ratio gradually decreased, Total color difference value, and mass density loss rate gradually decreased, and the peak compressive stress-strain displacement gradually increased, respectively. 95 % RH is beneficial to mold reproduction and only infect the surface, Fourier Transform Infrared Spectroscopy analysis showed that the quality changes during storage were more related to the decrease in the signal peak of the hemicellulose functional group of the material itself accompanied by the degradation of various monosaccharides, the lignin functional group corresponded to the decrease in L* and Total color difference, and the degree of pyrolysis tolerance was inversely proportional to the signal intensity of the cellulose functional group. Redundancy analysis showed that the positive contribution of humidity in the storage environment to the physical quality of bamboo was Bamboo pith linear > Width dimension > Bamboo cortex linear > Water content > Weight loss rate > Length Dimension > a*, and the storage time was closely related to the L* value and compression strength.

Humidity-induced direct modification of the optical response of plasmonic nanorod metamaterials

Plasmonic nanorod metamaterials are often used as a high-performance optical sensing platform for the detection of biochemical and gas species. Here, we investigate the effect of environmental humidity on their optical response. Due to the high refractive index sensitivity, a significant change in the transmission is observed with ΔT/T reaching values of more than 5% when the relative humidity is changed from 11% to 75%. This is the result of the condensation of water molecules on a rough surface of the gold nanorods. This finding reveals the importance of protecting plasmonic nanostructures from relative humidity variations in many practical applications. By coating the nanorods with a monolayer of poly-L-histidine, the fractional change of transmission is doubled due to the hydrophilic property of the monolayer, which can be used for the development of high-sensitivity relative humidity and dew condensation sensors.

An investigation of the effect of relative humidity on viscoelastic properties of flax fiber reinforced polymer by fractional-order viscoelastic model

As an environmental-friendly material with eligible mechanical properties, FFRP (Flax Fiber Reinforced Polymer) composites are being widely studied and used in the construction industry. This paper presents an investigation of the effect of environmental humidity on the viscoelastic properties of FFRP. Frequency sweep tests are conducted, and results are re-organized by the Time-Temperature Superposition Principle (TTSP). The Huet-Sayegh viscoelastic model is introduced to describe the relationship between viscoelastic properties and loading frequency. The fractional derivative is applied to the model for more accurate results. It is found both storage modulus and loss modulus decrease with the increase of relative humidity. However, the loss factor does not have a monotonical correlation with the relative humidity of the environment. In general, it can be concluded both the capacity of FFRP to store and dissipate the energy decreases over the hygroscopicity absorption in the air, but there is no specific relationship between the amount of their reduction.

Effect of Environmental Humidity on the Acoustic Vibration Characteristics of Bamboo

Bamboo musical instruments, such as bamboo flute and Ching-hu (Beijing opera fiddle), can generate a crisp and melodious sound closely related to the delicate multiscale pore structure of bamboo. Bamboo is a natural hydrophilic material, and its acoustic vibration characteristics are highly sensitive to changeable environmental humidity levels. Herein, we investigated the acoustic vibration characteristics of bamboo under three conditions: constant relative humidity (status I), changeable relative humidity (status II), and subjected to water extraction (status III). Three typical parameters were selected as evaluation indicators of bamboo acoustic vibration characteristics, namely, specific dynamic elastic modulus (E′/ρ), loss tangent (tanδ), and acoustical converting efficiency (ACE). The outer bamboos (OB) had higher E′/ρ and ACE but lower equilibrium moisture content (EMC) and tanδ than the inner bamboos (IB). Under status I, bamboo showed the maximum E′/ρ and ACE and the minimum tanδ at 35% RH (relative humidity) and about 6% MC. Compared with the bamboo under status II, the bamboo under status I retained higher E′/ρ and ACE and lower tanδ. However, the bamboo under status (III) reached the maximum E′/ρ and ACE and the minimum tanδ. The bamboo musical instrument is made of bamboo with proper removal of water-soluble extractives and high fiber volume fraction and stored in a stable relative humidity environment of 35%, which has suitable acoustic vibration characteristics.

Complex thermal analysis of supercapacitor by thermal impedance spectroscopy

Thermal impedance spectroscopy (TIS) measurement was developed for thermal analysis of supercapacitors. Compared with previously reported TIS measurement methods, the specific heat flux path through the supercapacitor device can be manipulated under the experimental system equipped with cold and heat sources. Using complex notation, the thermal impedance was defined as the ratio of the measured temperature difference across the tested device to the imposed heat flux. Different from the performance of Li-ion batteries, the thermal impedance spectra of the tested supercapacitor showed two semicircles with different diameters. The negative real part of the thermal impedance in the high frequency region could be considered as a frequencyrelated phase delay caused by the time response of the thermocouples in the temperature measurement. In addition, heat capacities and thermal resistances of the active materials and the casing of the tested supercapacitor were derived by equivalent thermal RC circuit. Furthermore, the effect of environmental humidity on the thermal characterization of active materials was isolated from the thermal impedance spectra.

4-tert-butyl pyridine additive for moisture-resistant wide bandgap perovskite solar cells

Perovskite solar cells fabrication process need inert or low humidity atmospheres. While highly efficient perovskite solar cells to overcome the photovoltaic marketing should be achieved stability at any environmental conditions. At high humidity, water molecules react with the perovskite layer and increase the degradation rate, leading to a drastic decrease in device performance and perovskite crystallinity. In this work, the effect of environmental humidity on photophysical parameters of wide bandgap, (WBG) perovskite layer and solar cells stability is systematically investigated and tBP is proposed as an additive in perovskite precursor to increase the moisture resistance and improve the crystallinity of the perovskite film, which is fabricated and kept at 80% RH. tBP act as a surface modification of the perovskite layer. According to SEM, XRD and water contact angle analysis, the crystallinity and hydrophobicity of the perovskite film improve by utilizing tBP. The stability and efficiency of the perovskite solar cells with tBP additive are higher than the perovskite solar cells without tBP. This work demonstrates that the engineering of the absorber precursor with a suitable additive could be a simple and low-cost strategy to reduce the effect of moisture in perovskite devices at high relative humidity.

Influence of moisture/water absorption on mechanical and thermal properties of polyamide6/boric oxide composites

PurposeThis paper aims to investigate the mechanical and thermal behavior, i.e. tensile strength, hardness, impact strength and glass transition temperatures of water-treated polyamide6/boric oxide (PA) composites.Design/methodology/approachThe PA6 and PA6/boric oxide composites were exposed to an open environment and immersed in water for 15 days to analyze the effect of environmental humidity and frequent water immersion conditions on the composite’s mechanical and thermal properties. The tensile strength, elastic modulus, hardness and impact strength of materials were measured to identify the mechanical properties. The scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) characterizations were used to see the effect of humidity/water absorption on microstructure, crystallinity and glass transition temperatures.FindingsThe testing results revealed the loss in strength, elastic modulus and hardness, while the impact resistance was improved after exposure of materials to humidity/water. SEM images clearly show the formation of voids and XRD graphs revealed the loss in crystallinity after water immersion. The DSC plots of water immersed materials revealed the loss of glass transition temperatures up to 15°C.Originality/valueThe mechanical and thermal behavior of PA composites varies according to the surrounding atmosphere. Experiments were performed to investigate the influence of water treatment on the PA6/B2O3 composite’s mechanical and thermal properties. Water treatment resulted in the bonding between PA and water molecules, which generated voids in the materials. These voids generations are found the main reason for the low strength and hardness of water-treated materials.

The Effect of Humidity on the Atomization Process and Structure of Nanopowder Designed for Extinguishment.

Increasingly, firefighting aerosols are being used to extinguish fires. It is assumed that the extinguishing mechanism involves breaking the chain of physicochemical reactions occurring during combustion by binding free radicals at ignition. The radicals are most likely formed from the transformation of water molecules, with the active surfaces of aerosol micro- or even nanoparticles. The aerosol extinguishing method is very effective even though it does not reduce oxygen levels in the air. In contrast to typical extinguishing powders, the aerosol leaves a trace amount of pollutants and, above all, does not adversely affect the environment by depleting the ozone layer and increasing greenhouse effects. Depending on how the firefighting generators are released, the aerosol can act locally or volumetrically, but depending on environmental conditions, its effectiveness can be variable. The article presents the influence of environmental humidity on the atomization of aerosol nanosize, which confirms the radical combustion mechanism. This paper presents the effect of environmental humidity on the atomization of aerosol superfine (nano) particles. The main focus was on the grain distribution and its effect on the surface activity of the FP-40C type firefighting aerosol. Changes in the characteristic parameters of the particle size distribution of RRSB (Rosin-Rammler-Sperling-Bennet) are presented.

Linear elastic and hyperelastic studies of equine hoof mechanical response at different hydration levels

Most simulation studies on equine hoof biomechanics employed linear elastic (LE) material models. However, the equine hoof wall's stress-strain relationship is nonlinear and varies with hydration level. Therefore, it is essential to investigate the accuracy of the LE model compared to more advanced material models, such as hyperelastic (HE) or viscoelastic models. The current research investigated performances of LE and three HE models (Mooney-Rivlin, Neo-Hookean, and Marlow) in describing equine hoof's mechanical behavior using finite element (FE) analysis. In the first attempt, a rectangular tissue specimen was simulated using the previously published experimental data. The Marlow HE model predicted the hoof wall stress-strain curve more accurately than the LE, Mooney-Rivlin, and Neo-Hookean models. The LE model accuracy, compared with the experimental results, varied within the reported range of the strain. However, the Marlow HE model perfectly matched the experimental data for a wide range of strains. In the second attempt, the entire hoof, including nine associated tissues, was modeled from computed tomography (CT) scans of an equine forelimb, and analyzed at trotting and standing modes of locomotion. The effect of environmental humidity on the hoof wall material properties was incorporated at four hydration levels; 0%, 53%, 75%, and 100%. The simulation results of the LE and HE models indicated that the minimum principal strain distribution on the hoof wall remained under 2% for various hydration levels and gait conditions. The numerical results of the Marlow HE model demonstrated better agreement with published experimental data compared to the LE, Mooney-Rivlin, and Neo-Hookean models. Higher hydration levels significantly increased the strains – a potential explanation could be the fact that the higher hydration levels decreased stiffness of the hoof wall tissues and ultimately increased strains. Higher ground reaction forces increased the von Mises stress at various points in the hoof wall, especially in the quarter regions and close to the coronet, where cracks and fractures are found more often in the physiological conditions.

Effects of Environmental Humidity on Microbial Community and Quality of Chilled Fresh Pork

Effects of Environmental Humidity on Microbial Community and Quality of Chilled Fresh Pork

An empirical model to evaluate the effects of environmental humidity on the formation of wrinkled, creased and porous fibre morphology from electrospinning

Controlling environmental humidity level and thus moisture interaction with an electrospinning solution jet has led to a fascinating range of polymer fibre morphological features; these include surface wrinkles, creases and surface/internal porosity at the individual fibre level. Here, by cross-correlating literature data of far-field electrospinning (FFES), together with our experimental data from near-field electrospinning (NFES), we propose a theoretical model, which can account, phenomenologically, for the onset of fibre microstructures formation from electrospinning solutions made of a hydrophobic polymer dissolved in a water-miscible or polar solvent. This empirical model provides a quantitative evaluation on how the evaporating solvent vapour could prevent or disrupt water vapor condensation onto the electrospinning jet; thus, on the condition where vapor condensation does occur, morphological features will form on the surface, or bulk of the fibre. A wide range of polymer systems, including polystyrene, poly(methyl methacrylate), poly-l-lactic acid, polycaprolactone were tested and validated. Our analysis points to the different operation regimes associated FFES versus NFES, when it comes to the system’s sensitivity towards environmental moisture. Our proposed model may further be used to guide the process in creating desirable fibre microstructure.

Functionalization of GaN Nanowire Sensors With Metal Oxides: An Experimental and DFT Investigation

The detection of NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> molecules by GaN nanowire sensors which were functionalized with various metal oxides have been comprehensively studied with device fabrication, characterization and modeling with first-principles calculations based on density functional theory (DFT). In this work, GaN nanowires were prepared on Si substrate by standard top-down fabrication process and then fabricated into resistor based chemical sensors. The surface of GaN nanowires were functionalized by three metal oxides: TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , ZnO and SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> for analysis. The UV illuminated device characterization results indicated that the devices with TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> functionalization exhibited the highest response toward NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas. It showed quick response (240s) and recovery (280s) process with strong NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> selectivity. In modeling, the oxide functionalized GaN in contact with NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> molecule was designed and geometrically optimized. Simulation results indicated that TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> functionalization enabled the most energy favorable surface for NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> adsorption among the three metal oxides. In addition, the electronic properties of these oxide functionalized GaN have been studied in terms of the total density of states (TDOS) and projected density of states (PDOS), indicating an excellent agreement with the above-mentioned experimental measurements. Furthermore, the effect of environmental humidity on the adsorbate-nanocomposite interaction has been simulated and studied. Overall, the metal oxide functionalization significantly enhances the performance of GaN gas sensors and selecting an appropriate oxide will optimize the detection.

Solubility considerations in relative block crystallization and morphology of PEO‐ b ‐PCL films

Poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) is a heavily investigated amphiphilic crystalline-crystalline diblock copolymer. Its macroscopic physical properties are influenced by the crystallization behavior, which is robust due to similar crystallization temperatures of PEO and PCL. As such, tailoring the crystallinity and crystalline morphology should be advantageous to achieving desired changes in film properties. One method to manipulate the crystallization, analyzed here, is the selective solvation of one block during solvent casting. By careful solvent selection, the crystallization of PEO and PCL during solvent evaporation led to changes in relative crystallinity and film morphology. The effect of environmental humidity on the crystallization mechanism and relative block crystallization was explored in detail using Fourier-transform infrared spectroscopy.

Effect of environmental humidity on the ionic transport of poly(ethylene oxide) thin films, investigated by local dielectric spectroscopy.

The effect of humidity on the ionic transport in the amorphous phase of poly(ethylene oxide) thin films has been studied by local dielectric spectroscopy. We explored a controlled humidity range between 15% RH and 50% RH. AFM-based local dielectric imaging allowed the thin film topography and the corresponding dielectric contrast maps to be obtained simultaneously. No humidity effect on the film topography was observed whereas large variation of the dielectric signal could be detected. In addition, we observed a clear dielectric contrast in different locations on the thin film surface. At selected regions with high contrast in the dielectric maps, we performed nanoDielectric Spectroscopy (nDS) measurements covering the frequency range from 5 Hz to 100 kHz. By modeling these spectroscopy results, we quantified the conductivity of the amorphous phase of the semicrystalline poly(ethylene oxide) films. The crystalline fraction of the PEO thin films was extracted and found to be about 36%, independently of humidity. However, the average conductivity increased by a factor of 25 from 2 × 10-10 to 5 × 10-9 S cm-1, by changing environmental humidity in the explored % RH range.

Parameterization of Entrainment Rate and Mass Flux in Continental Cumulus Clouds: Inference From Large Eddy Simulation

AbstractLarge eddy simulation with contrasting environmental humidity is used to study entrainment and detrainment rates and convective mass flux during the development stages of continental deep cumulus clouds. The cumulus clouds studied here are deeper than marine shallow cumulus or stratocumulus in the published literature. The main objective of the study is to parameterize the entrainment and detrainment rates in monsoon clouds during the break monsoon periods over land, useful for the large‐scale atmospheric models. A systematic decrease in cloud liquid water path is noted in drier environments as clouds become shallower due to the reduction of positive buoyancy in the cloud core. Updraft and downdraft velocities in the subcloud layers are strengthened in the drier environments, which are found to affect in‐cloud updraft strength. A most important finding of the present study is the effect of environmental humidity on the entrainment (and detrainment) rates and the convective mass flux. Many previous studies on this topic reported opposite results. The present study found that decreasing environmental humidity leads to a decrease in both the entrainment rate and the convective mass flux but an increase in the detrainment rate. The relationship of the entrainment parameters with the environmental relative humidity can be used for parameterization in the large‐scale models. The physical mechanism responsible for such response is identified as the strengthening of the subcloud updrafts compensated by the enhanced downdraft into the boundary layer in the drier environments, and this mechanism subsequently led to higher in‐cloud updraft velocity, resulting in lower entrainment rate.

Experiment on the Effect of Environmental Humidity on the Pool Fire in Confined Space

Experiment on the Effect of Environmental Humidity on the Pool Fire in Confined Space