Aqueous Alkali Solution Research Articles

How Thick Aqueous Alkali Should be Better for Aluminum-Air Batteries at Sub-Zero Temperatures: A Critical Anti-Freezing Concentration.

The application of portable aluminum-air batteries (AABs) in extreme environments is an inevitable demand for future development. Aqueous electrolytefreezing is a major challenge for low-temperature operations. Conventionally, enlightened by the organic system in metal ion batteries, blindly increasing the concentration is regarded as an efficient technique to reduce the freezing point (FP). However, the underlying contradiction between the adjusting mechanism of the FP and OH- transportation is ignored. Herein, the aqueous alkali solution of CsOH is researched as a prototype to disclose the intrinsic conductive behavior and related solvent structure evolution. Different from these inorganic electrolyte systems, the concept of a critical anti-freezing concentration (CFC) is proposed based on a specific temperature. The relationship between hydrogen bond reconstruction and de-solvation behavior is analyzed. A high conductivity is obtained at -30°C, which is also a recorded value in an intrinsic aqueous AAB. The homogenous dissolution of the Al anode is also observed. As a general rule, the CFC concept is also applied in both the KOH and NaOH systems.

WO3 nanostructures produced from tungsten welding electrode scraps: Temperature influence on optical and morphological characteristics

Methods to produce WO3 nanostructures have become important due to the possibility of using this material in a wide range of technological applications. In this context, a hydrated WO3.2H2O structure was produced by the electrochemical dissolution of welding electrode scraps in an alkali aqueous solution, followed by acid precipitation. The thermal treatment of this precursor structure at 550, 700, 850, and 1000 °C was able to produce γ phase WO3 materials with a monoclinic crystalline structure at all the temperatures used, as demonstrated by XRD and RAMAN characterization. However, different treatment temperatures can yield materials with diverse morphologies and optoelectronic properties. For example, the material produced at 1000 °C presented an elongated nanorod shape, with dimensions, from the base, ranging between 50 and 500 nm, a length of about 4 μm, and the lowest Eg value. The spectroscopic characterization also demonstrated that above 700 °C, the thermal treatment could eliminate the crystallization water and create oxygen vacancies, mainly at 850 and 1000 °C; explaining the decrease in the Eg values with increased temperature. As proof of concept, photocatalytic degradation of the Reactive Black 5 dye demonstrated that the material produced at 1000 °C was able to discolor ca. 50% of the initial color. Broad DFT analyses were performed, carefully describing the surface properties and the influence of morphology on the material properties. Therefore, we demonstrated that a simple, fast and low-cost two-step process was successfully developed aiming at a noble reuse of residues of this important material.

ALIGNMENT OF FINGERING PATTERN INDUCED BY AN INTERFACIAL NEUTRALIZATION REACTION

In this paper, we numerically study buoyancy-driven chemoconvective instabilities in a vertically oriented Hele-Shaw cell. At the beginning, the cavity is filled with a homogeneous aqueous solution of a strong inorganic alkali, and this system is statically stable. We assume that the upper boundary is free, and a fixed value of the concentration of a strong inorganic acid is set there. After bringing the reactants into contact, density stratification quickly becomes unstable due to a neutralization reaction, resulting in density fingering. The mathematical model includes the effect of producing a new amount of solvent (water). We show that this effect is a reason for the sudden alignment of salt fingers that we previously observed in experiments. In this work, we carry out a formal parametric study of the system with a change in the dimensionless parameter responsible for the intensity of water production. One can interpret this variation as a sequential consideration of substances from the homologous series of alkalis. We show that there exists a critical value of the parameter, crossing which one can observe a spontaneous transition from an irregular fingering pattern to cellular chemoconvection. The latter looks like a system of fingers tightly pressed against each other with tips aligned along a horizontal line. The lower boundary of the vortices uniformly moves down. We found that instead of the usual coarsening of the structure, one observes an increase in the aspect ratio of vortices. We investigate the dynamics of the lower boundary of the fingering pattern and changes in the pattern wavelength. Complex rearrangements of the reaction front, which include the processes of plume creation and coalescence, are illustrated using space-time diagrams.

Polysaccharide content and composition analysis in the herb <i>Astragalus albicaulis</i> DC

Aim – to isolate and analyze the polysaccharides content in the herb Astragalus albicaulis.
 Material and methods. The object of the study was the herb Astragalus albicaulis harvested in the Kursk region in 2022 during the period of mass flowering. To isolate the polysaccharide complex, polyphenolic compounds were previously removed from the raw material. After drying, a water-soluble polysaccharide complex, pectin substances, hemicellulose A and hemicellulose B were sequentially isolated from the extraction cake. As extractants, purified water was used to isolate the water-soluble polysaccharide complex, a mixture of 0.5% solutions of oxalic acid and ammonium oxalate (1:1) was used for pectin substances extraction, to obtain hemicelluloses – a 10% aqueous solution of alkali followed by neutralization with acetic acid. The composition of the obtained substances was analyzed after acid hydrolysis using paper chromatography.
 Results. It was found that the yield of water-soluble polysaccharides from the herb Astragalus albicaulis was 9.41% ± 0.46%, pectin substances – 17.49% ± 0.62%, hemicellulose A – 0.86% ± 0.04%, hemicellulose B – 5.36% ± 0.25%. After acid hydrolysis, 5 monosaccharides were found in the complex of water-soluble polysaccharides: rhamnose, xylose, arabinose, galactose, and glucuronic acid, of which arabinose and galactose were predominant. The monosaccharide composition of pectin substances was represented by xylose, arabinose, glucose, galactose and galacturonic acid, galacturonic acid predominated. As a result of the identification of hydrolysis products of hemicellulose A and B, rhamnose, xylose and glucose were found, the predominant monosaccharide was xylose.
 Conclusion. For the first time, complexes of polysaccharides – water-soluble polysaccharides, pectin substances, hemicellulose A and B – were isolated and studied by fractions from the herb Astragalus albicaulis, their qualitative composition was registered. The data obtained indicates that the herb Astragalus albicaulis can be used as a source of natural polysaccharides.

STUDY OF THE EFFICIENCY OF USING THE EXPERIMENTAL BIOCIDE SANDEZ FOR THE SANITATION OF THE POULTRY WATER SUPPLY SYSTEM

Ensuring the maximum level of biosecurity in farms that grow poultry without the use of antibiotics is a prerequisite for epizootic well-being. The article presents data on the development of an ecologically safe method of sanitation treatment of the water supply system of poultry houses. For sanitation treatment of the water supply system, the alkaline detergent and disinfectant "Sandez" was used, which is an aqueous solution of alkali, does not contain anti-corrosion substances and compounds that create a potential threat of negative impact on the environment. The active substance of the drug "Sandez" - sodium hydroxide causes denaturation of protoplasmic proteins of microbial cells. In the experiment, the water supply system of the poultry house was filled with a 1.5% solution of "Sandez" disinfectant and left filled with this solution for after standing for 1 hour, the aqueous solution was drained and the pipelines were washed with clean tap water. In the control, sodium hypochlorite with a concentration of 75–100 mg/dm3 of active chlorine was used to disinfect the water supply network. Environmentally safe disinfectant "Sandez" ensures compliance of water quality and safety indicators with the requirements of state sanitary standards and regulations. "Sandez" product has an excellent washing effect with water hardness up to 8 mg-eq/l, has a low corrosive effect on metal structures of technological equipment. The method of sanitation treatment of the water supply network of poultry houses in the system of veterinary and sanitary measures during poultry farming is based on the use of a 1.5% solution of the ecologically safe alkaline detergent and disinfectant "Sandez" has high disinfectant properties, provides a bactericidal effect on pathogenic microorganisms E. coli, S. enteritidis, Enterococcus spp., P. aeruginosa, microbial contamination is 24% less than a similar pokahnik in the control control.The use of this method in the system of veterinary and sanitary measures during poultry farming provides a high sanitizing effect, control of microbiological indicators of the safety of drinking water, a long-lasting antiseptic effect, prevents the emergence of resistance of microorganisms to the action of disinfectants and does not create a negative impact on the environment.

Thermodynamic characterization of aqueous solutions of NaCl, KCl, MgCl2 and CaCl2: volumetric, acoustic, viscometric and computational analysis

The volumetric and acoustic properties of alkali and alkaline earth metal salts are ubiquitous in numerous biological and non-biological processes and accurate formulation of their thermophysical properties is a fundamental prerequisite for complete exploration of their diverse applications. To meet this purpose, in this investigation, we herewith report the systematic data of densities ρ, speed of sound u and viscosity η of aqueous binary solutions of the prominent alkali and alkaline earth metal salts viz. NaCl, KCl, MgCl2, and CaCl2 at seven different temperatures T = (288.15–318.15 K) and ambient pressure over the wide concentration range of (0.002–1) mol∙kg−1.These experimental data have been further employed to obtain some important thermodynamic parameters, viz, the apparent molar volume of solute Vϕ, limiting apparent molar volume of solute Vϕ0, isentropic compressibility of solution κS, apparent molar isentropic compression of the solute KS,ϕ, limiting apparent molar isentropic compression of solute KS,ϕ0 and apparent molar expansibility Eϕ0. Further, the coefficient of thermal expansion α*, the second-order derivative of limiting apparent molar volume ∂2Vϕ0/∂T2, Jones-Dole equation viscosity A, B, D coefficients, temperature derivative of B coefficient i.e. dB/dT, activation parameters for viscous flow and hydration number nH have also been computed. The results obtained have been used to elucidate different interactions taking place in the aqueous electrolytic solutions. To corroborate the experimental results, quantum chemical calculations were performed using density functional theory (DFT) by Gaussian software package. The calculations included an analysis of molecular orbitals, with particular emphasis on the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO).

Self-Assembly of Alkanethiols on an Oxide-Free Surface of a Copper Electrode from Alkaline Solutions under Electrochemical Control

Using voltammetry and chronoamperometry, the formation process and properties of insulating nanofilms of alkanethiols with different chain lengths (butane-, octane-, dodecanethiol) obtained on an oxide-free copper surface were studied. The electrochemical method for modifying the copper surface includes the removal of the oxide layer by its cathodic reduction, the adsorption of a thiol under electrochemical control, followed by studying the properties of the resulting nanofilm by voltammetry in one solution. It is shown that, with this approach, a dense thiol film is formed, with its blocking properties depending on the adsorption potential, the time of contact of the electrode with the thiol-containing solution, the thiol concentration, and the presence of dissolved oxygen in the solution. The introduction of ethanol into an aqueous alkali solution leads to a significant acceleration of the process of self-assembly of dodecanethiol, but greatly inhibits the process of self-assembly of butanethiol. The approach proposed in this work makes it possible to use aerated low-concentration thiol-containing solutions to obtain alkanethiol films on the Cu surface with good blocking properties.

Highly Stretchable yet Degradable and Recyclable Conductive Composites with Liquid Metal Nanodroplets as Physical Crosslinks

AbstractLiquid metal (LM) droplet‐embedded polymer composites with exceptional thermal, electrical, and mechanical characteristics are attractive for applications in soft electronics and thermal management. Generally, a high volume fraction of LMs is required for desirable thermal and electrical properties, and thus recycling of LMs is favorable and cost effective. However, recycling LMs from composites remains a formidable challenge because the LM droplets are typically dispersed into a permanent covalently crosslinked polymer matrix. Here, a facile synthesis of LM‐polymer composites with high electrical conductivity (1800 S cm−1), high stretchability (1400% tensile strain), as well as degradability and recyclability is reported. The composite comprises a poly(2‐hydroxyethyl acrylate) hydrogel that is physically crosslinked by LM nanodroplets as a polymer matrix and either LM microdroplets or silver microflakes as a conductive filler. A postdrying process improves the mechanical performance of the composite while creating percolating pathways via the rearrangement of the conductive fillers, imparting high electrical conductivity to the composite. Moreover, the composites are readily degraded and dissolved in aqueous alkali solutions at room temperature thanks to the reactive nature of LM crosslinks, enabling high recycling efficiency of ≈80% and 95% for composites with LM microdroplets and silver microflakes as conductive fillers, respectively.

Efficient separation of o-, m-, and p-cresols from simulated coal-based products using eco-friendly amine ionic liquids: Algae toxicity assessment, extraction, and mechanism exploration

Three cresol isomers (o-, m-, and p-cresols) derived from coal-based products are valuable compounds mainly used in the fine chemical and pharmaceutical industries. For the clean production of cresols without using strong acid and alkali aqueous solutions, liquid-liquid extraction was adopted, and four eco-friendly amine ionic liquids (AILs) were synthesized and characterized as extractants. The toxicity of AILs was evaluated using an algal toxicity assessment. The results showed that AILs can be considered practically nonharmful. The effects of stirring time, mAILs:mmixtures, extraction temperature, and initial content for extraction of cresols were investigated. The results showed that the AILs exhibited better performance for the extraction of the three cresol isomers. At the initial cresol content of mcresol:moil = 1:10, the AIL N,N,N′,N′-tetramethylguanidine acetate ([N-tmg][Ac]) could extract cresols with an extraction efficiency of more than 97% under the optimal extraction conditions mAILs:mmixtures = 1:5, stirring time of 30 min, temperature of 25 °C. In addition, the intermolecular interactions were analyzed using quantum chemistry calculations. The results demonstrated that the hydrogen bonds (H-bonds) formed between the anions in the AILs and the phenolic hydroxyl groups of cresols were the major driving forces for the extraction of cresols. Finally, the reusability of the [N-tmg] [Ac] and [TEA] [Ac] AILs was explored, and the recovered AILs were confirmed by proton nuclear magnetic resonance (1H NMR) spectroscopy. Compared with traditional technologies that utilize strong acid and alkali aqueous solutions, the proposed method can avoid the discharge of acid and alkali wastewater, providing a promising route for the cleaner production of cresols from coal-based products.

Acetylcellulose Recovery from Waste Residual for Attenuating Reactive Dye from Aquaculture Waste as a Fascinating Synergistic Ecology Effect

Waste valorization is attracting not only the scientific world but also the world. Acetylcellulose wastes from cigarette filter residuals are signified as the largest global impact of solid waste. Acetylcellulose recycling for desired products is a promising way for environmental management. In this regard, the current investigation is dealing with the immersion of residual filters sequentially into aqueous solutions of alkali and ethanol before water washing, which converts them into a superhydrophobic acetylcellulose adsorbent material. The morphology and characteristics of the acetylcellulose fiber were characterized using a Scanning Electron Microscope (SEM) and Fourier-Transform infrared spectroscopy (FTIR). The adsorption tendency was checked for Levafix Blue dye compromised in an aqueous stream as a model textile polluted effluent. The experimental results exposed that the acetylcellulose fiber displayed a sensible textile dye elimination from the dying stream. Langmuir isotherm is well fitting the adsorption matrix and the reaction follows the 1st-order kinetic model. The so-obtained acetylcellulose fiber showed tremendous efficiency for dye removal from aqueous effluent. The attained maximum monolayer adsorption capacity was recorded as 4.8 mg/g at pH 3.0 and an adsorbent dose of 1 g/L through the isotherm time of 2 h. Also, temperature elevation could increase the adsorption capacity to 5.7 mg/g. Due to this excellent affinity to adsorb dye at an economic wise rate is shown as a promising candidate for textile dye elimination form aqueous effluent.

INFLUENCE OF TECHNOLOGICAL PARAMETERS ON THE FORMATION OF AN EMULSION EXTRACT OF WOODY GREENS OF SCOTS PINE

The present study is devoted to the analysis of extracts obtained from pine tree greens by the emulsion method and to increasing the efficiency of extraction of extractive substances. Coniferous tree greens are a rich source of compounds that have surface-active properties (resin and fatty acid salts, phospholipids, glycerides, etc.), which makes it possible to obtain emulsion extracts. The influence of the concentration of an aqueous solution of alkali, hydromodulus and duration of extraction on the formation of an emulsion and its quality (particle size of the dispersed phase and their distribution) was determined. Extracts were analyzed by optical microscopy. It has been established that the concentration of an aqueous solution of alkali is 3%, the hydromodulus is 1/8, and the duration of extraction is 30 min, which contributes to the formation of an oil-in-water emulsion with an average particle size of the dispersed phase of 2.5 μm, uniformly distributed throughout the volume of the dispersion medium. In the set parameters, a high-quality emulsion is formed and the lipophilic neutral components of the studied raw materials are effectively extracted.

Study of electrochemical behaviour of binder-free nickel metal-organic framework derived by benzene-1,3,5-tricarboxylic acid for supercapacitor electrode

In this work, the Metal-Organic Framework (MOF) is derived from the metal nickel (Ni) and organic linker benzene-1,3,5-tricarboxylic acid (H3BTC). H3BTC is used because it is inexpensive and BTC3- builds multi-dimensional frameworks with metal centers that facilitate three carboxylate groups.Ni-MOF has been synthesized using a one-step hydrothermal technique. The synthesized product has been examined structurally and optically using Thermogravimetric Analysis, X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and UV–Vis spectroscopy. XRD and FTIR results suggest the formation pattern of Ni-MOF. The band gap value of Ni-MOF calculated by UV–Vis spectroscopy comes out to be 3 eV which confirms the creation of nanoparticles. Surface morphology is examined with the help of the Field Emission Scanning Electron Microscopy technique showing the spherical shape of nanoparticles. The specific surface area is calculated by using the Brunauer-Emmett-Teller technique and the calculated value is 35.405 m2g−1. The electrochemical response of the synthesized product has been tested in 3 different alkali aqueous electrolytes (1 M LiOH, 1 M NaOH, and 1 M KOH) with the help of cyclic voltammetry (CV), galvanic charge-discharge (GCD) technique & electrochemical impedance spectroscopy (EIS) to achieve the most appropriate combination of electrode-electrolyte for improved electrochemical results. The prepared Ni-MOF shows the highest specific capacitance (573 F g − 1) in 1 M KOH alkali electrolyte in comparison to 1 M LiOH (535 F g − 1) & 1 M NaOH (308 F g − 1) at the low scan rate value of 5 mV s−1 which reveals that the compatibility of Ni-MOF synthesized electrode material with 1 M KOH aqueous solution. Also the Ni-MOF shows excellent cycling stability (∼ 154% capacitance retention after 1000 cycles) in 1 M KOH alkali aqueous solution. All the results explain that the synthesized Ni-MOF can give the best electrochemical performance with 1 M KOH and hence can be used as an effective material for the electrode of a supercapacitor.

Molecular modeling and simulation of aqueous solutions of alkali nitrates.

A set of molecular models for the alkali nitrates (LiNO3, NaNO3, KNO3, RbNO3, and CsNO3) in aqueous solutions is presented and used for predicting the thermophysical properties of these solutions with molecular dynamics simulations. The set of models is obtained from a combination of a model for the nitrate anion from the literature with a set of models for the alkali cations developed in previous works of our group. The water model is SPC/E and the Lorentz-Berthelot combining rules are used for describing the unlike interactions. This combination is shown to yield fair predictions of thermophysical and structural properties of the studied aqueous solutions, namely the density, the water activity and the mean ionic activity coefficient, the self-diffusion coefficients of the ions, and radial distribution functions, which were studied at 298K and 1bar; except for the density of the solutions of all five nitrates and the activity properties of solutions of NaNO3, which were also studied at 333K. For calculating the water the activity and the mean ionic activity coefficient, the OPAS (osmotic pressure for the activity of selvents) method was applied. The new models extend an ion model family for the alkali halides developed in previous works of our group in a consistent way.

The thermodynamics of enhanced dope stability of cellulose solution in NaOH solution by urea

The addition of urea in pre-cooled alkali aqueous solution is known to improve the dope stability of cellulose solution. However, its thermodynamic mechanism at a molecular level is not fully understood yet. By using molecular dynamics simulation of an aqueous NaOH/urea/cellulose system using an empirical force field, we found that urea was concentrated in the first solvation shell of the cellulose chain stabilized mainly by dispersion interaction. When adding a glucan chain into the solution, the total solvent entropy reduction is smaller if urea is present. Each urea molecule expelled an average of 2.3 water molecules away from the cellulose surface, releasing water entropy that over-compensates the entropy loss of urea and thus maximizing the total entropy. Scaling the Lennard-Jones parameter and atomistic partial charge of urea revealed that direct urea/cellulose interaction was also driven by dispersion energy. The mixing of urea solution and cellulose solution in the presence or absence of NaOH are both exothermic even after correcting for the contribution from dilution.

회전자력 작용에 의한 이온 수송에 관한 실험적 연구

Hydrogen production using water electrolysis is generally a well-known phenomenon. Hydrogen produced using the water electrolysis method is an environment-friendly energy source called ‘green hydrogen’ that does not emit any environmental pollutants when using renewable energy as an energy source. This study aims to improve the efficiency of hydrogen production by using the ion transportation effect induced by a rotating magnetic force. For this purpose, the experimental conditions for ion transport were determined through an experiment using a copper wire and the rotating magnetic force for water electrolysis was applied using an alkali aqueous solution. Based on the results, an increase in the number of bubbles generated by the rotating magnetic force increased was observed. It is assumed that the efficiency of hydrogen production using water electrolysis can be improved by the rotating magnetic force.

Alkaline Carbonization of Polyacrylonitrile for the Preparation of Microporous Carbon Materials

A method has been proposed for the synthesis of activated carbon materials (ACMs) based on polyacrylonitrile (PAN) by activation with potassium hydroxide under the action of IR heating. Two approaches to the chemical activation of the polymer precursor were presented: formation of ACM based on PAN preliminarily heat-treated at 200°C and based on PAN carbonized at 700°C by impregnation with an aqueous alkali solution followed by heating to 800°C. Due to the use of IR radiation, the heating can be performed at a rate of 50 K/min, and the exposure time at a given temperature can be reduced to 2 min. The dependence of the specific surface area and porosity of ACM according to BET on the synthesis conditions was studied. The proposed approaches lead to the formation of ACMs with specific surface areas of 1091 and 2121 m2/g, respectively.

Alkali resistant epoxy binders for pultrusion

Alkali-resistant hot-curing epoxy binders based on ED-20 and new amine hardeners “Amikrost” have been developed, intended for the production of glass-composite fittings for construction purposes. The rheological properties of epoxy compositions were determined, using differential scanning calorimetry and thermogravimetric analysis, the temperature dynamics of the curing process of epoxy compositions and the thermal-oxidative resistance of cured samples were studied. The alkali resistance of cured epoxy compositions and specimens of composite reinforcement in 40% alkali aqueous solution was evaluated. It is shown that the developed amine hardeners provide high alkali resistance of composite reinforcement in comparison with the currently used anhydride hardener iso-MTHPA, which is especially important for reinforcing buried and hydraulic concrete.

Corrosion of steel rebars embedded in One-part Alkali activated concrete mixes

To reduce CO2 emissions and turn a variety of industrial/agricultural wastes into valuable cementitious products, alkali-activated materials (AAM) are recognized as suitable substitutes for regular Portland cement (OPC). However, the concentrated aqueous alkali solutions used in conventional two-part alkali activated materials are highly corrosive, viscous, and are difficult to handle in direct field applications. As a result, the potential for developing so-called "just add water" type one-part AAMs, as compared to traditional two-part AAM, is being explored, particularly in cast-in-situ applications. In the present study on corrosion of reinforcing steel bars in fly ash-slag (FA-GGBS) based one-part AAC mixtures, three parameters—the total binder content, the relative proportions of GGBS and Fly-ash and the percentage of sodium oxide (Na2O) - are recognized as the key factors in determining the strength and durability performance (including corrosion of rebars embedded in it) of a given AAC mix. Accordingly, experiments were conducted on AAC mixes with three binder contents (440, 460, and 480 kg/m3), three Slag/FA ratios (80/20, 70/30 and 60/40, by volume) and three alternate Na2O percentages (5, 6, and 7%, by weight of total binder content). Prismatic cylindrical test specimens of reinforced geopolymer concrete were prepared and half-cell potential and corrosion rate measurements were made after 28-, 56-, and 90 days of continuous exposure to 3% of NaCl solution, to accelerate the corrosion process. Measured corrosion current density and corrosion rates using a Electro-chemical Corrosion Analyser have indicated that the AAC mixture having a total binder content 440 kg/m3, GGBS/FS ratio of 70/30 and 6% Na2O content, exhibits best corrosion resistance amongst the various mixes tested herein, as measured up to the end of 90-days.

Fabrication of High-Performance Colorimetric Membrane by Incorporation of Polydiacetylene into Polyarylene Ether Nitriles Electrospinning Nanofibrous Membranes.

Polyarylene ether nitrile (PEN) is a novel high-performance engineering plastic with various applications, particularly in thermoresistance-required fields. In this study, a well-known stimuli-response polydiacetylene monomer, 10, 12-pentacosadiynoic acid (PCDA), was encapsulated within electrospun PEN nanofibers to fabricate a colorimetric membrane with satisfactory thermal and corrosion resistance. To optimize the compatibility with PCDA, two PENswith distinct molecular chains were utilized: PEN-PPL and PEN-BPA. The chemical structure and elemental mapping analysis revealed that the PCDA component was successfully incorporated into the PEN fibrous. The PCDA bound significantly better to the PEN-PPL than to the PEN-BPA; due to the carboxyl groups present on the side chains of PEN-PPL, the surface was smooth and the color changed uniformly as the temperature rose. However, owing to its poor compatibility with PEN-BPA, the PCDA formed agglomerations on the fibers. The thermal analysis demonstrated that the membranes obtained after PCDA compounding maintained their excellent heat resistance. The 5% weight loss temperatures of composite nanofibrous membranes manufactured by PEN-PPL and PEN-BPA were 402 °C and 506 °C, respectively, and their glass transition temperatures were 219 °C and 169 °C, respectively, indicating that the blended membranes can withstand high temperatures. The evaluation of application performance revealed that the composite membranes exhibited good dimensional stability upon high thermal and corrosive situations. Specifically, the PEN-P-PCDA did not shrink at 170 °C. Both composite membranes were dimensionally stable when exposed to the alkali aqueous solution. However, PEN-P-PCDA is more sensitive to OH-, exhibiting color transition at pH > 8, whereas PEN-B-PCDA exhibited color transition at high OH- concentrations (pH ≥ 13), with enhanced alkali resistance stability owing to its nanofibrous architecture. This exploratory study reveals the feasibility of PEN nanofibers functionalized using PCDA as a desirable stimulus-response sensor even in high-temperature and corrosive harsh environments.

Nucleation and Growth of Methane and Carbon Dioxide Hydrates on Wetting Liquid Films

The results of visual studies of the growth of methane and carbon dioxide hydrates from highly dilute aqueous solutions of acids and alkalis, as well as from the same solutions with the addition of 0.1 wt % sodium dodecyl sulfate, are presented. It was found that in addition to the growth of hydrate films at the water–gas interface (for solutions without sodium dodecyl sulfate) and the growth of a loose mass of hydrate on the walls of the reactor in the case of solutions with sodium dodecyl sulfate, there is also growth of the hydrate film on the free walls of the reactor. We speculate what these hydrate films form from the wetting water films located on the walls. In addition, growth of relatively large hydrate agglomerates on the reactor walls was observed. They look like “growing directly from the wall”. Presumably, this is due to the possibility of film transfer of water between the formed hydrate films and the walls of the reactor. Possible features of the hydrate formation process caused by the formation of hydrates on wetting films are also discussed.