Acid Vapor Research Articles

Sintering of mixed Cu[sbnd]Ag nanoparticles pretreated by formic acid vapor for Cu[sbnd]Cu low temperature bonding

In this work, a CuCu low temperature bonding method by using mixed CuAg nanoparticles (NPs) paste was proposed. To remove the oxide on the surface of Cu NPs, formic acid vapor pretreatment process was applied to treat the mixed CuAg NPs paste at 180 °C for 30 min. After the 30-min pretreatment, the oxide on Cu NPs was effectively reduced and the bonding quality has significantly improved. A reliable CuCu bonding was successfully achieved at the temperature of 250 °C for 30 min under a low pressure of 5 MPa after the pretreatment of formic acid vapor and the average shear strength achieved approximately 60.5 MPa. For mixed CuAg NPs paste sintering at 250 °C, the average resistivity reached 39.7 μΩ·cm after the pretreatment. Besides, with the bonding temperature increasing, especially after the pretreatments of formic acid vapor, the bonding interfaces became more compact and the fracture surfaces exhibited more distinct ductile deformations, which further illustrates the high quality of bonding. According to the results, this bonding technology is promising to be widely used in power device packaging.

Development of pH sensitive turmeric dyed fabrics for detection of acetic acid vapours

A fabric sensitive to acidic vapors has been developed, using cationized cotton with eco-friendly pH-sensitive colorant turmeric. The fabric displays a color change in acidic and alkaline conditions on immersion and to acidic vapors. The fabrics show excellent reversibility on washing and can be used multiple times.

Acid-responsive Emission Color Changes of Diarylaminobenzylideneanilines

Emission color changes of 4-[bis(4-methylphenyl)amino]benzylideneaniline (BMBZA) and 4-[bis(9,9-dimethylfluoren-2-yl)amino]benzylideneaniline (BFBZA) in response to hydrochloric acid (HCl) vapor and solid organic acids, pentafluorobenzoic acid (PFBA) and benzoic acid (BA), have been investigated in their different solid states. Emission color of BMBZA crystals changed from greenish blue to reddish orange by exposure to HCl vapor, whereas the emission color of BFBZA crystals did not. However, powder sample obtained by grinding the BFBZA crystal exhibited emission color change by exposure to HCl vapor. Similar results of emission color changes of BMBZA and BFBZA crystals in response to PFBA were obtained. In the case of BMBZA–BA and BFBZA–BA systems, grinding of the crystalline mixtures allowed their emission color changes without change in their object colors.

Designing high efficiency graphite felt electrode via HNO3 vapor activation towards stable vanadium redox flow battery

A new method of preparing nitric acid vapor treated graphite felt for vanadium redox flow battery (VRFB) is developed. This method outperforms traditional impregnation methods in convenience, efficacy and controllability of fabrication process. A sequence reaction mechanism is proposed for nitric acid vapor treated graphite felt reactions occurring at 200 °C. The modified-graphite felt (m-GF) with excellent electrocatalytic redox reversibility toward VO2+/VO2+ and V2+/V3+ redox couples is prepared in the conditions of VHNO3/mpGF=0.45 mL g−1 at 200 °C in 300 min (m-GF-0.45). The nitric acid vapor reaction with graphite felts occurs preferentially on the surface of amorphous carbon and at defect sites in the graphitic structure, yields N2 and carbon-oxygen surface complexes, resulting in a higher double layer capacity (DLC) from 146 μF mg−1 (p-GF) to 1514 μF mg−1 (m-GF-0.45). Thus, the energy efficiency and discharge capacity of m-GF-0.45 electrode increases significantly by 8.7% and 100% at 150 mA cm−2, respectively.

Investigation of cation-assisted, chemically and thermally enhanced nitrogen-doped graphene nanofluid application as an efficient micro-emulsifier from EOR perspective

Innovatively designed additives have been introduced in last decade to make EOR processes more efficient under challenging conditions. However, nitrogen-doped graphene (NDG) is not known as such a stable efficient method to be injected into reservoir under harsh thermodynamic condition. Some treatment has been applied to molecular structure of commonly used nitrogen-doped graphene aqueous solution for improvement of stability and quality of aqueous solution. These treatments involve both nano-structure and the aqueous carrier fluid properties. Nano-structure modification has been conducted in three successive steps: oxidation with acid vapor and modified Hummers method, citric acid polymerization and heat treatment that succeed in NDG functionalization with carboxyl and hydroxyl groups and structure enhancement in molecular scale. Existing free mono- and divalent cations in aqueous carrier phase improve the emulsification dominant mechanism from Pickering unstable emulsion toward more stable micro-emulsion mechanism which appeared to be superior to conventional emulsifiers used in EOR process because of improved solubility and more facile transport through porous media. Zeta potential of solution has increased from −30 to −12.2 mV highlighting more emulsion stability. The interfacial tension between aqueous fluid containing 500 ppm APH-NDG11acidized, functionalized, heated nitrogen doped graphene. and free mono- and divalent cations and crude oil would be 50 % less in comparison to distilled water/crude oil IFT. Furthermore, APH-NDG, regardless of carrier aqueous type, causes a great decrease in contact angle and as a result, makes the rock surface become more water-wet.

Experience of Substantiation and Results of Monitoring of Priority Air Pollutants in Norilsk within the Federal Clean Air Project

Introduction: Long-term multicomponent ambient air pollution in residential areas is one of the serious threats to human health. The Federal Clean Air Project implemented within the National Ecology Project aims at fundamental improvement of the quality of life of the Russian population through reduction in emissions of priority (hazardous) pollutants posing the highest health risks. Objective: To substantiate the choice and to analyze the results of monitoring of priority air pollutants in the city of Norilsk included in the Project. Materials and methods: Priority chemicals were determined based on the results of a health risk assessment. The exposure was assessed on the basis of dispersion calculations using a consolidated database of stationary and mobile emission sources (1,970 sources from 110 enterprises and 175 sections of the urban road network) and the “Ecologist – City” 4.60.1 software with the “Average” calculation block, realizing atmospheric dispersion modeling techniques approved in the Russian Federation. The airborne pollutant accounting for at least 95 % of the unacceptable carcinogenic and/or non-carcinogenic risk was considered a priority. The estimates were then verified by the results of measuring ambient concentrations of 20 pollutants within socio-hygienic air quality monitoring in Norilsk for 2020–2021. Results: We established that both short- and long-term exposure to air pollutants posed unacceptable health risks to more than 180 thousand people affected. The list of priority contaminants subject to monitoring and priority regulation comprised ten chemicals, including nitrogen oxide and dioxide, sulfur dioxide, particulate matter, sulfuric acid, carbon oxide, copper oxide, nickel compounds, lead and its compounds, and benzene, of which seven were confirmed as such by the monitoring data. In fact, the measured concentrations of sulfur dioxide, particulate matter, copper and nickel compounds at a number of sites were significantly higher than those estimated by dispersion modeling. Vapors of sulfuric acid, carbon monoxide and nitrogen oxide were below the limit of detection. Conclusions: The health risk assessment methodology used for selecting priority air pollutants is an adequate and effective tool of environmental management. Verification of the lists of priority chemicals compiled on the basis of dispersion modeling using the merged database on the urban sources of air pollution is expedient and necessitates improvement of techniques and mechanisms for stocktaking of emission sources. A significant discrepancy between the estimated and measured data on pollution levels should be discussed by all interested parties and result in changes to the consolidated databases and an increase in the accuracy of subsequent hygienic assessments, including that of public health risks.

Comparative analysis of the effects of hydrogen and formic acid on the vacuum residue hydrocracking

The improvement of the existing technologies aimed at deeper processing of heavy oils and oil residues and development of new ones is an urgent task of modern oil refining. Experiments in a flow installation using a quartz reactor were performed to determine the formic acid decomposition pathway. The experiments showed that the formic acid decomposition over the Ni-Mo/Al2O3 catalyst predominantly yielded hydrogen and CO2. Therefore, in this study comparative experiments on the effects of hydrogen and formic acid on the vacuum residue hydrocracking in the presence of the Ni-Mo/Y-Al2O3 and Ni-Mo/Al2O3 catalysts were performed at 375–400 °C and 0.45 MPa pressure. The concentration of hydrogen or formic acid in argon was 10 vol%. The catalysts were prepared by impregnation of the corresponding supports with the aqueous solution obtained using nickel hydroxide, ammonium heptamolybdate and citric acid. Electron microscopy and XRD studies of the Ni-Mo/Y-Al2O3 and Ni-Mo/Al2O3 catalysts demonstrated that the active component in the studied catalysts was in a finely dispersed state. The size of Ni-Mo particles was 0.4–0.6 nm in the Ni-Mo/Y-Al2O3 catalyst and 0.3–0.6 nm in Ni-Mo/Al2O3. For both catalysts Ni-Mo/Y-Al2O3 and Ni-Mo/Al2O3 higher vacuum residue conversion to liquid products was observed in the presence of formic acid than in the presence of hydrogen. Hydrogen substitution for formic acid vapor during the vacuum residue hydrocracking also results in the lower sulfur content in the liquid reaction products. The use of formic acid as a hydrogen donor significantly simplifies the process hydrocracking.

Antibacterial, efficient and sustainable CS/PVA/GA electrospun nanofiber membrane for air filtration

Since the outbreak of the COVID-19 epidemic, a large number of disposable protective masks have been manufactured and used, and the abandonment of masks has caused enormous pollution. In this paper the chitosan (CS), polyvinyl alcohol (PVA), and water were used as raw materials and the nanofiber membranes were prepared by electrostatic spinning. The CS/PVA fiber membranes were crosslinked by glutaraldehyde hydrochloric acid vapour. The fiber morphology, hydrolysis resistance, antibacterial properties, chemical structure, thermal stability and filtration performance of nanofiber membranes were characterized. Results shows that the antibacterial performance of the crosslinked composite nanofibers exceeds 97%, the thermal stability is improved, and the fiber morphology is not destroyed. The hybridized fiber membrane has high filtration performance, excellent antibacterial and hydrolysis resistance, which broadening the PVA fiber membrane application. It is expected to replace traditional protective materials and relieve environmental pressure.

Scanning electron microscopy and X-ray microanalysis of the condition of concrete structures of a chemical enterprise with long-term corrosion in a sulfate environment

Long-term operation of premises in aggressive environments of chemical enterprises affects the surfaces of concrete structures and leads to the formation of destructive processes.
 The aim of the study was to determine changes in the structure and mineral composition of concrete during long-term operation in an aggressive sulfate environment at a chemical plant for the production of titanium dioxide using the sulfate method to predict the service life of concrete structures.
 It has been established that during the production of TiO2 pigment by the sulfate method, the ore is decomposed by sulfate acid at high temperature, accompanied by the release of H2SO4 vapor, sulfur dioxide SO2, hydrogen sulfide H2S and elemental sulfur. Studies have established that sulfate corrosion leads to the formation of sulfur and iron oxides on the concrete surface. Studies have revealed vast areas of the surface covered with crystals of elemental sulfur, the contents of which are confirmed by the results of X-ray microanalysis. The sizes of sulfur crystals in the image range from 12 to 180 µm, the shape corresponds to the rhombic allotropic modification S8. The penetration depth of iron sulfates into the thickness of concrete is about 50 microns. The microstructure of the surface is loose, with signs of corrosion.
 Exposure to a high concentration of sulphate acid vapors in the workshop of the enterprise led to the destruction of calcium carbonate and the formation of gypsum crystals in concrete. The formation of gypsum crystalline hydrates provokes sulfate corrosion of concrete, resulting in the formation of pores and microcracks in concrete with the formation of calcium hydrosulfoaluminate.
 The studies carried out using scanning electron microscopy and X-ray microanalysis make it possible to investigate the structural changes and mineral composition of concrete under the influence of long-term sulfate corrosion.

Prospective products of JSC «DINUR» for roofs of electric furnaces for vitrification of highly active waste

The results of researc work of «DINUR» refractory products for the roof of new melter EP-6 are presented. The acid resistance of the products at chemical attack of nitric acid vapor and nitric acid solution is determined. According to results of performed research work, mullite-silica castable МКРВ-53 grade was found to be optimal product for melter roof. Tab. 5.

Naked-Eye Optical Recognition of Ammonia Vapor and Melamine in Water Using a Fluorophore Appended Polymer Matrix.

The generation of solid-state emitters is a challenge due to the intrinsic aggregation-caused quenching feature of the fluorophores. A conformationally twisted pyridyl π-conjugate as a solid-state emitter is appended with well-known and inexpensive poly(methylmethacrylate) [PMMA] to afford a handy, portable, and reusable solid-state emitting polymer matrix. Entrapment of the probe is noticed through non-covalent interactions, resulting in a green-emitting platform. It quickly accepts a proton upon acid vapor exposure and switches emission from green to red with a significant 107nm redshift. This shift is reversible with red to green emissions while exposed to base vapor. Thus, polymer-blended, homogeneous red-emitting pyridyl salt is employed as potential material to detect various basic vapors optically. Among different bases, naked-eye detection of essential analytes such as ammonia vapor and melamine shows potential demands. Hence, we have established an easy detection of ammonia vapor and aqueous melamine as low as 2.5 and 0.126ppm, respectively, using this solid-state emitter that displays an emission color change with an enhancement of emission intensity even in an aqueous solution.

Organic Crystals with Response to Multiple Stimuli: Mechanical Bending, Acid-Induced Bending and Heating-Induced Jumping.

Multiple stimuli-responsive molecular crystals are attracting extensive attentions due to their potential as smart materials, such as molecular machines, actuators, and sensors. However, the task of giving a single crystal multiple stimuli-responsive properties remains extremely challenging. Herein, we found two polymorphs (Form O and Form R) of a Schiff base compound, which could respond to multiple stimuli (external force, acid, heat). Form O and Form R have different elastic deformability, which can be attributed to the differences in the molecular conformation, structural packing and intermolecular interactions. Moreover, both polymorphs exhibit reversible bending driven by volatile acid vapor, which we hypothesize is caused by reversible protonation reaction of imines with formic acid. In addition, jumping can be triggered by heating due to the significant anisotropic expansion. The integration of reversible bending and jumping into one single crystal expands the application scope of stimuli-responsive crystalline materials.

Investigation on SO3/sulfuric acid mist conversion in WFGD process

SO3 and sulfuric acid mist generated in coal-fired boilers and wet flue gas desulfurization (WFGD) processes can adversely affect boiler facilities, while detection and absorption is an important issue. Factors affecting the conversion of SO3 to sulfuric acid mist (SO3/sulfuric acid mist) during wet desulfurization were studied and evaluated in a simulated experimental system, including the effects of flue gas composition, temperature and humidity on the SO3/sulfuric acid mist conversion rate. The certain concentrations of SO3, water vapor, SO2, NO, NH3, O2 and N2 were mixed thoroughly to simulate the flue gas of WFGD under the special temperature conditions in this experiment. The sulfuric acid droplets, sulfuric acid vapor and sulfuric acid aerosol in the simulated flue gas were absorbed and intercepted by NaCl and quartz wool, gaseous SO3 was absorbed by isopropanol solution, and thorium-barium titration method was used to measure SO42− concentration. The results showed that the increase of temperature significantly decreased the SO3/sulfuric acid mist conversion rate, the increase of humidity significantly increased the SO3/sulfuric acid mist conversion rate, and O2 concentration had little effect on the SO3/sulfuric acid mist conversion rate. In addition, the increase concentration of NH3, NO and SO2 also improved the conversion rate of SO3/sulfuric acid mist to some extent.

Silver nanoparticulate antenna tracks sintered under carboxylic acid vapors for flexible radio-frequency identification tag application

Silver nanoparticulate antenna tracks sintered under carboxylic acid vapors for flexible radio-frequency identification tag application

Capturing Fleeting Intermediates in a Claisen Rearrangement Using Nonequilibrium Droplet Imbibition Reaction Conditions.

The Claisen rearrangement of aromatic allyl phenyl ether to 2-allyl phenol is known to be induced by heat, acid, and air-water interfacial (on-water) effects. In this work, we show that the combination of acid and interfacial effects in an "on-droplet" experiment accelerates this reaction even further (by a factor >10×). The reaction acceleration was achieved through a droplet imbibition mass spectrometry (MS) experiment that allows reactants to be deposited on rapidly moving (100 m/s), charged microdroplets while avoiding turbulent mixing. In this case, reactants are concentrated mainly at the surface of the short-lived microdroplets (microseconds), enabling enhanced interfacial effects. By doping n-butylamine in the spray solvent and subsequently exposing the resultant electrosprayed microdroplets to formic acid vapor, the ketone intermediate, 6-allylcyclohexa-2,4-dien-1-one, involved in this Claisen rearrangement was captured and characterized by tandem MS, successfully differentiating it from the corresponding isobaric reactant (allyl phenyl ether) and product (2-allyl phenol). Similar results showing rate acceleration and subsequent capture of the ketone intermediate via an instantaneous reaction with n-butylamine were demonstrated for p-methyl and p-nitro substituted allyl phenyl ether. Density functional theory calculations confirmed that the on-droplet reaction condition, with a high abundance of proton sources, is different from the neutral rearrangement. With a calculated free energy of activation of 5.2 kcal mol-1 for the protonated reactant, the on-droplet experimental condition provides a unique mechanism for catalyzing the Claisen rearrangement on the microsecond lifetime of the droplets. This experiment marks the first direct capture and detection of a short-lived ketone intermediate in the Claisen rearrangement, a task that is challenged by a thermodynamically favorable tautomerization step to give a more stabilized product (by 20 kcal/mol).

Synergistic effects of fresh garlic juice in cellulose based antimicrobial food packaging film

Development of cellulosic edible films and coatings enriched with garlic juice. • Novel cellulosic edible film enriched with fresh garlic juice was proposed. • The film was treated with glycerol and citric acid vapor to improve mechanical properties. • The films displayed excellent stretchability and optical clarity. • The films possessed excellent antifungal and antibacterial properties, thus retaining the food fresh. This article presented a novel food packaging film made from cellulose nanofibers (CNFs), raw garlic juice and glycerol. The film was made tough, strong, and barrier-resistant by treating the CNFs with glycerol and citric acid vapor, which performed as a plasticizer and cross-linking agent, respectively. Garlic juice was added as the antibacterial agent. The as-produced films exhibited 529, 47, and 59% higher extensibility, moisture resistance, and water vapor barrier, respectively than the pristine CNF film. The film also showed excellent antifungal and antibacterial resistance.

Airborne murine coronavirus response to low levels of hypochlorous acid, hydrogen peroxide and glycol vapors

Airborne murine coronavirus response to low levels of hypochlorous acid, hydrogen peroxide and glycol vapors

A fast-response visual indicator film based on polyvinyl alcohol/methylcellulose/black wolfberry anthocyanin for monitoring chicken and shrimp freshness

Natural anthocyanins are considered favorable indicators for new sensing materials because of their wide pH color range. Here, a smart visual indicator film was developed by introducing black wolfberry (BW) anthocyanins to a solid matrix composed of polyvinyl alcohol (PVOH) and methylcellulose (MC). Fourier transform infrared and X-ray showed that the introduction of BW anthocyanins enhanced hydrogen-bond interactions among the polymers and the anthocyanins were well fixed in the polymer matrix. 5 % BW could improve the stability of the PVOH/MC/BW and increase its tensile strength and breakage elongation by 63.2 % and 53.0 %, respectively. Optical observations and freshness monitoring suggested that the film loaded with 5 % BW could respond to acidic and basic vapors within 10 s and as low as 25 ppm NH3 in chicken and shrimp during storage at 4 °C. Therefore, PVOH/MC/BW-5% may potentially be used as a smart sensor to determine freshness in practical applications.

Design and Preparation of a Biobased Colorimetric pH Indicator from Cellulose and Pigments of Bacterial Origin, for Potential Application as Smart Food Packaging.

Nowadays, worldwide challenges such as global warming, pollution, unsustainable consumption patterns, and scarcity of natural resources are key drivers toward future-oriented bioeconomy strategies, which rely on renewable biobased resources, such as bacterial pigments and bacterial cellulose (BC), for materials production. Therefore, the purpose of this study was to functionalize bacterial cellulose with violacein, flexirubin-type pigment, and prodigiosin and test their suitability as pH indicators, due to the pigments’ sensitivity to pH alterations. The screening of the most suitable conditions to obtain the BC-pigment indicators was achieved using a full factorial design, for a more sustainable functionalization process. Then, the pH response of functionalized BC to buffer solutions was assessed, with color changes at acidic pH (BC-violacein indicator) and at alkaline pH (BC-violacein, BC-prodigiosin, and BC-flexirubin-type pigment indicators). Moreover, the indicators also revealed sensitivity to acid and base vapors. Furthermore, leaching evaluation of the produced indicators showed higher suitability for aqueous foods. Additionally, color stability of the functionalized BC indicators was carried out, after light exposure and storage at 4 °C, to evaluate the indicators’ capacity to maintain color/sensitivity. Thus, BC membranes functionalized with bacterial pigments have the potential to be further developed and used as pH indicators.

Thermally activated delayed fluorescence (TADF) emitters: sensing and boosting spin-flipping by aggregation.

Metal-free organic emitters with thermally activated delayed fluorescence (TADF) characteristics are emerging due to the potential applications in optoelectronic devices, time-resolved luminescence imaging, and solid-phase sensing. Herein, we synthesized two (4-bromobenzoyl)pyridine (BPy)-based donor–acceptor (D–A) compounds with varying donor size and strength: the emitter BPy-pTC with tert-butylcarbazole (TC) as the donor and BPy-p3C with bulky tricarbazole (3C) as the donor unit. Both BPy-pTC and BPy-p3C exhibited prominent emission with TADF properties in solution and in the solid phase. The stronger excited-state charge transfer was obtained for BPy-p3C due to the bulkier donor, leading to a more twisted D–A geometry than that of BPy-pTC. Hence, BPy-p3C exhibited aggregation-induced enhanced emission (AIEE) in a THF/water mixture. Interestingly, the singlet–triplet energy gap (ΔEST) was reduced for both compounds in the aggregated state as compared to toluene solution. Consequently, a faster reverse intersystem crossing rate (kRISC) was obtained in the aggregated state, facilitating photon upconversion, leading to enhanced delayed fluorescence. Further, the lone-pair electrons of the pyridinyl nitrogen atom were found to be sensitive to acidic protons. Hence, the exposure to acid and base vapors using trifluoroacetic acid (TFA) and triethylamine (TEA) led to solid-phase fluorescence switching with fatigue resistance. The current study demonstrates the role of the donor strength and size in tuning ΔEST in the aggregated state as well as the relevance for fluorescence-based acid–base sensing.