Inert Gas Research Articles

Effect of Heat Treatment on the Supramolecular Structure of Copolymers Based on Poly(propylene glycol fumarate phthalate) with Acrylic Acid

Previous studies investigating the thermal decomposition of p-PGFPh:AA copolymers in an inert atmosphere have provided only a general understanding of the changes that occur during thermolysis. Comprehensive studies are required to gain a better understanding of these processes [1]. The most comprehensive information on the influence of various factors on both the kinetics and the supramolecular structure of the resulting products can be obtained by combining the method of thermal analysis with IR, mass spectrometry, and scanning electron microscopy. The compounds studied have two different compositions, namely p‑PGFPh:AA 6.77:93.23 mol % and p-PGFPh:AA 86.67:13.33 mol %. These compounds were then subjected to a thermolysis process, which resulted in the emission of gases and a decrease in sample weight. The degradation process can be divided into three stages: 1) Depolymerization of the main chain; 2) Depolymerization of the side chain; 3) Final decomposition. These processes occur sequentially at different temperature ranges. According to TG- and DTG studies, complete decomposition of p-PGFPh:AA copolymers occurred at Tterm = 340–350 °C. In this temperature range, a slight loss of sample mass (less than 10 wt %) was observed along with a slight gas evolution. The main gaseous products from the transformation of the studied samples were CO and CO2. This was supported by IR-CO (2000–2200 cm−1) and CO2 (2310–2370 cm−1) as well as mass spectrometric observations. The final products resulting from the thermolysis of p-PGFPh:AA copolymers were examined under an electron microscope. The results showed a similar morphological pattern of mesostructures with sizes ranging from 0.3–1.5 μm, which were observed depending on the porous structure of the initial polymer material. Based on the experimental data, it can be concluded that the p-PGFPh:AA copolymers (in proportions of 6.77:93.23 mol % and 86.67:13.33 mol %) have a relatively high degree of resistance to heating and do not undergo any changes in chemical composition, particle size and shape. In conclusion, the results clearly indicate that the selection of conditions for pyrolysis plays a crucial role in increasing the thermal stability of polymeric materials. This method allows for purposeful changes in the structure and properties of polymers.

Self-Modification of Defective TiO2 under Controlled H2/Ar Gas Environment and Dynamics of Photoinduced Surface Oxygen Vacancies.

In recent years, defective TiO2 has caught considerable research attention because of its potential to overcome the limits of low visible light absorption and fast charge recombination present in pristine TiO2 photocatalysts. Among the different synthesis conditions for defective TiO2, ambient pressure hydrogenation with the addition of Ar as inert gas for safety purposes has been established as an easy method to realize the process. Whether the Ar gas might still influence the resulting photocatalytic properties and defective surface layer remains an open question. Here, we reveal that the gas flow ratio between H2 and Ar has a crucial impact on the defective structure as well as the photocatalyic activity of TiO2. In particular, transmission electron microscopy (TEM) in combination with electron energy loss spectroscopy (EELS) revealed a larger width of the defective surface layer when using a H2/Ar (50 %-50 %) gas mixture over pure H2. A possible reason could be the increase in dynamic viscosity of the gas mixture when Ar is added. Additionally, photoinduced enhanced Raman spectroscopy (PIERS) is implemented as a complementary approach to investigate the dynamics of the defective structures under ambient conditions which cannot be effortlessly realized by vacuum techniques like TEM.

High-Pressure Molecular Sieving of High-Humidity C2H4/C2H6 Mixture by a Hydrophobic Flexible Metal-Organic Framework.

Molecular sieving is an ideal separation mechanism, but controlling pore size, restricting framework flexibility, and avoiding strong adsorption are all very challenging. Here, we report a flexible adsorbent showing molecular sieving at ambient temperature and high pressure, even under high humidity. While typical guest-induced transformations are observed, a high transition pressure of 16.6 atm is observed for C2H4 at 298 K because of very weak C2H4 adsorption (~16 kJ mol-1). Also, C2H6 is completely excluded below the pore-opening pressure of 7.7 atm, giving single-component selectivity of ca. 300. Quantitative high-pressure column breakthrough experiments using 1:1 C2H4/C2H6 mixture at 10 atm as input confirms molecular sieving with C2H4 adsorption of 0.73 mmol g-1 or 32 cm3(STP) cm-3 and negligible C2H6 adsorption of 0.001(2) mmol g-1, and the adsorbent can be completely regenerated by inert gas purging. Furthermore, it is highly hydrophobic with negligible water adsorption, and the C2H4/C2H6 separation performance is unaffected at high humidity.

Modular Assembly of Pyrrolo[3,4-c]isoquinolines through Rh-Catalyzed Cascade C-H Activation/Annulation of O-Methyl Aryloximes with Maleimides.

An efficient and practical strategy for the construction of pyrrolo[3,4-c]isoquinolines via Rh(III)-catalyzed cascade C-H activation and subsequential annulation process from easily available O-methyl aryloximes and maleimides has been disclosed. This facile protocol does not require any inert atmosphere protection with good efficiency in a low loading of catalyst and exhibits good functional group tolerance and broad substrate scope. Notably, the as-prepared products show potential photophysical properties.

Radon Exhalation Rate: A Metrological Approach for Radiation Protection.

Radon, a radioactive inert gas that comes from the decay of naturally occurring radioactive species, poses a substantial health risk due to its involvement in lung cancer carcinogenesis. This work proposes a metrological approach for determining radon exhalation rates from diverse building materials. This methodology employs an electrostatic collection chamber for alpha spectrometry of radon isotopic decay products. Experimental evaluations were conducted particularly focusing on volcanic gray tuff from Sant'Agata de' Goti (Campania region, Italy), a material commonly utilized in construction, to assess radon exhalation rates. The study aligns with Legislative Decree 101/2020, a transposition of European Directive 59/2013/Euratom, highlighting the need to identify materials with a high risk of radon exhalation. Moreover, this work supports the goals of the Italian National Radon Action Plan related to the aforementioned decree, aiming to develop methodologies for estimating radon exhalation rates from building materials and improving radioprotection practices.

Inert Gas Element as Active Infrared‐Absorption Source and Donor in Silicon for Forbidden‐Wavelength Sensing

AbstractIntrinsic silicon (Si) is forbidden for infrared (IR) sensing at the communication wavelength like 1.31 or 1.55 µm due to the well‐known bandgap limitation. In this work, an unexpected physical picture of using argon (Ar) is identified, which is usually inert to the surrounding chemical environment and used as a protective agent in semiconductor processing, to overcome the IR‐sensing‐forbidden problem in Si. Here, it is shown by an analysis of a dynamic secondary ion mass spectrometer that such a Si, when exposed to laser pulse in Ar gas, can contain a very high dose of Ar up to 1020 cm−3 even after 1300 days. First‐principles calculations, molecular dynamics, and Hall effect measurements reveal that, due to both steric and dynamic repulsions by Ar orbitals to Si dangling bonds, the Ar‐filled‐vacancy produces a much wider defect band inside the gap, which is not only responsible for strong infrared absorption, but also causes a significant increase in n‐type conductivity, both in line with experiments. The study proves that originally inert elements in fact can act as active impurities in semiconductors for advanced applications, which updates the current knowledge of defect physics.

Exploration and Frontier of Coal Spontaneous Combustion Fire Prevention Materials

Mine fires have always been one of the disasters that restrict coal mining in China and endanger the life safety of underground workers. The research and development of new fire prevention materials are undoubtedly important to ensure the safe and efficient production of modern mines. At present, the main inhibiting materials used are grout material, inert gas, retarding agent, foam, gel, and so on. In order to explore the current situation of coal spontaneous combustion (CSC) fire prevention, the existing fire prevention materials were reviewed and prospected from three aspects: physical, chemical, and physicochemical inhibition. The results show that, at present, most of the methods of physicochemical inhibition are used to inhibit CSC. Antioxidants have become popular chemical inhibitors in recent years. In terms of physical inhibition, emerging biomass-based green materials, including foams, gels, and gel foams, are used to inhibit CSC. In addition, CSC fire-fighting materials also have shortcomings, including incomplete research on the mechanism of material action, poor stability of inhibitory properties, low efficiency, and economic and environmental protection to be improved. The future research direction of fire-fighting materials will be based on theoretical experiments and numerical simulation to study the mechanism and characteristics of CSC and develop new directional suppression materials with physicochemical synergies. These findings have extremely important implications for improving materials designed to prevent CSC.

Synthesis, Characterization, Thermal and conductivity Study for 1,4-dimethyl-2,5-bis(tellurocyanatomethyl)benzene

The new Tellurium compound is prepared in two steps. In the first step, p-xylene was reacted with formaldehyde and hydrochloric acid to give 1,4-bis(chloromethyl) -2,5-dimethylbenzene, which was added in the second step to Tellurium powder added to the potassium cyanide compound under an inert atmosphere of argon to give the new compound and diagnosed by infrared, elemental analysis, visible and ultraviolet rays, mass spectrometry, and nuclear magnetic resonance spectroscopy. At the same time, a thermogravimetric analysis of the compound was carried out to evaluate the thermal stability, and by using the thermal analysis data, the values of the kinetic and thermodynamic functions were extracted, as well as the conductivity at different temperatures was studied.

Fire suppression using a self-activating extinguisher based on carbon dioxide hydrate

Artificial and natural gas hydrates have a great potential as environmentally friendly fire suppressants. In this research, we have developed a novel self-activating hydrate extinguisher and tested it in different types of fires. The extinguisher stops the flame combustion at the moment of activation due to the shock wave produced by its burst. Then the gas hydrate spreads over the surface of the burning fuel, its ice shell melts, thus reducing the temperature in the seat of the fire and releasing the inert gas, which displaces the oxidizer from the combustion zone. The experiments have shown that the extinguisher response time can be adjusted by varying such parameters as the mass of hydrate and the volume of the free space in the extinguisher, the amount of added water, and the type of mechanical impact on the extinguisher. We have also developed a conceptual framework for the production of self-activating hydrate extinguishers and their delivery to the seat of the fire. Overall, the research findings pave the way for improving the efficiency of firefighting means by making them more environmentally friendly, less damaging to the equipment, and as suitable as possible to the world of today.

Experimental study of the effect of the temperature of inert gases on the intensity of thermal decomposition of rubber

THE PURPOSE. An experimental method is used to evaluate the effect of the temperature of inert gases on the rate of thermal decomposition of waste rubber products (fragments of a car tire) upon their direct contact.METHODS. The research was carried out on a test firing stand at a stationary mode of gas movement in the temperature range from 300 °C to 500 °C. The initial weight of the rubber was 4 grams. The thermal decomposition of rubber was carried out due to the thermal energy of inert gas released during the combustion of a propanebutane mixture with air at α = 1.1...1.15. The consumption of fuel and oxidizer remained constant, the change in gas temperature was carried out by heat exchange of hot gases and water in the heat exchanger.RESULTS. Metodology of conducting experiments, the object of research under the study, results of the research and their analysis are described in the article. The main parameters were selected: the rate of decrease in rubber mass depending on the temperature of the gases, the limiting value of the gas temperature at which sulfur in solid form remains in the decomposed part of the rubber.CONCLUSION. It was found that with increasing temperature of the inert gas, the rate of thermal decomposition of rubber increases. When rubber is in a gaseous environment in the temperature range from 450 0C to 500 0C, the sulfur content in the solid residue remains practically unchanged. The average rate of pyrolysis was 0.02 kg/h, which is 6 times higher than the rate of pyrolysis in the retort (0.003 kg/h).

Hydrothermal Hot Isostatic Pressing (HHIP)-Experimental Proof of Concept.

A new hydrothermal hot isostatic pressing (HHIP) approach, involving hydrothermal water conditions and no usage of inert gas, was hypothesized and tested on 3D-printed Al-10%Si-0.3%Mg (%Wt) parts. The aluminum-based metal was practically inert at the applied HHIPing conditions of 300-350 MPa and 250-350 °C, which enabled the employment of a long (6-24 h) HHIP treatment with hardly any loss of material (the overall loss due to corrosion was mostly <0.5% w/w). Applying the new approach on the above-mentioned samples resulted in an 85.7% reduction in the AM micro-pores, along with a 90.8% reduction in the pores' surface area at a temperature of 350 °C, which is much lower than the 500-520 °C applied in common argon-based aluminum HIPing treatments, while practically maintaining the as-recieved microstructure. These results show that better mechanical properties can be expected when using the suggested treatment without affecting the material fatigue resistance due to grain growth. The proof of concept presented in this work can pave the way to applying the new HHIPing approach to other AM metal parts.

Redox Stability and Electrical Properties of a Series of Novel Quadruple Dopant BIMEVOX: Bi2V1−4x(CuNiNbTi)xO5.5−δ

Bi2VO5.5‐based materials are well‐known oxide ion conductors owing to their exceptionally high ionic conductivity. However, their poor phase and redox stabilities under a reducing atmosphere hinder their practical application as electrolytes for solid oxide fuel cells. Here, a series of novel quadruple metal‐doped bismuth vanadium system materials Bi2V1−4x(CuNiNbTi)xO5.5−δ (0 ≤ x ≤ 0.1) are prepared through a traditional solid state reaction method, aiming to enhance the phase and redox stability under reducing atmosphere. The results reveal that multiple‐metal‐doping can stabilize the tetragonal phase of Bi2VO5.5 to room temperature and show good phase and structural stabilities under inert or high oxygen partial pressure atmospheres, as well as pure oxide ion conduction which is slightly lower than that of the parent material. However, under a reducing environment, the Bi2V1−4x(CuNiNbTi)xO5.5−δ materials would still undergo a phase decomposition, yielding elemental bismuth impurity, and introducing strong electronic conduction. Thus, how to improve the phase and redox stabilities under the reducing atmosphere of the Bi2VO5.5‐based materials is still the endeavor direction in the future.

Predictive modeling and multi-parametric optimization of catalytic pyrolysis of disposable face mask using a combinational approach of response surface methodology and machine learning: Insights into the influence of waste-derived catalyst

The current study aims to model and optimize the catalytic pyrolysis of face masks incorporating a waste-derived catalyst to analyze the effect of process parameters (temperature, feed-to-catalyst ratio, and inert gas flow rate) on the oil yield of the process. An integrated approach of response surface methodology (R2-0.95) and machine learning (decision trees regression, R2-0.83) demonstrated a higher prediction accuracy and lower error margins. Explainable artificial intelligence tools spotlighted temperature to be the predominant parameter followed by feed-to-catalyst ratio. Experimental oil yield (13.5%) obtained at optimized parameters (516 °C temperature, 3:1 feed-to-catalyst ratio, and 163 mL/min inert gas flow rate) was compared with those predicted through response surface methodology (13.7%) and decision trees regression (13.12%), showcasing an absolute error range of 0.2–0.4 wt%. Gas chromatography-mass spectroscopy analysis of oil highlighted the presence of silica compounds that can be extracted as value-added chemicals. Further, the overall percentage of naphthene's, paraffins, and olefins in the oil were approximated to be around 40.5% based on the peak area. The presence of hydrocarbons in oil having carbon numbers predominantly in the range of gasoline and diesel as well as a high heating value of 36.56 MJ/kg demonstrated its potential to be used as a fuel. The present study demonstrates the feasibility of valorizing the face mask into energy-dense oil comparable to commercial range fuel using a spent adsorbent based catalyst.

Prevention of weld decay in TIG-welded AISI 304 steel pipes

Weld decay occurs due to chromium carbide precipitation at grain boundaries in the heat-affected zone (HAZ) during tungsten inert gas (TIG) welding of austenitic stainless steels. This issue is particularly significant concerning the welding of AISI 304 steels, commonly used in the food industry. Although this problem can be overcome with different methods, there are some restrictions. A novel technique for welding AISI 304 steel pipes is introduced to reduce weld decay and improve their mechanical properties. The use of this technique, which includes faster cooling after welding, significantly minimizes the time of precipitation of chromium carbide. Temperature measurements and microstructural analyses monitored precipitation, and the impact of the technique on the mechanical characteristics of AISI 304 steel pipes was assessed through hardness and hoop tensile tests. There was a 6% increase in hardness values observed in the HAZ region, as well as a 16.7% increase in maximum load and a 127.4% increase in elongation. The reduction in chromium carbide precipitation observed in the microstructural analysis was confirmed through the double-loop electropotentiokinetic reactivation test, specifically for assessing intergranular corrosion. With the novel method, there were a 25% increase in corrosion resistance in the HAZ and a 40% increase in the weld zone.

Preparation and Experimental Research of Temperature Sensitive Expansion Gel Material for Fire Prevention and Extinguishing in Coal Mines

ABSTRACT In order to solve the problems of high viscosity at room temperature, easy dehydration and shrinkage of phase change gel, and poor plugging effect of traditional mine gel, a new type of temperature-sensitive expansion gel was developed by using hydroxypropyl methyl cellulose, chitosan, guar gum and sodium bicarbonate as raw materials, using orthogonal test and response surface analysis. The structural characterization, characteristics, fire prevention, and extinguishing performance of the temperature-sensitive expansion gel were tested. The experimental results show that the optimal ratio of temperature-sensitive swelling gel is 0.75 wt % chitosan, 0.5 wt % acetic acid, 2.5 wt % hydroxypropyl methyl cellulose, 0.4 wt % sodium bicarbonate, and 0.15 wt % guar gum. The phase transition temperature (LCST) of this ratio is 67°C. After standing at room temperature for 6 h, the gel viscosity is 5852 mpa·s, the expansion ratio is 0.846, and the strength is 319.525 N/m2. During the heating process of the coal sample after adding the temperature-sensitive expansion gel, the gel will undergo phase change and expansion in the high-temperature area of the coal, and the viscosity will increase. It can stay in the high-temperature area, wrap the coal block, and isolate the oxygen from entering, thus effectively inhibiting the coal spontaneous combustion process. In addition, the gel also produces inert gas carbon dioxide, which effectively suffocates the flame. Therefore, compared with the conventional inhibitor solution, the temperature-sensitive expansion gel has better fire extinguishing effect.

Analyzing and modeling of CO purging for high-temperature proton exchange membrane fuel cells

Purging offers a straightforward and cost-effective means of eliminating inert gases that accumulate in high-temperature proton exchange membrane fuel cells (HT-PEMFC) operating in dead-end anode (DEA) mode. Nevertheless, earlier studies primarily concentrated on inert gases, overlooking the significant challenge posed by the strong adsorption of CO within HT-PEMFC, complicating the use of inert gas methods for CO purification. This paper presents an analytical model that was validated experimentally. Leveraging this model, the paper analyzes the crucial parameter of CO concentration within the anode and deduces theoretical extreme values. Subsequently, it proposes purging strategies tailored to different operational conditions. The findings indicate that the minimum CO concentration within HT-PEMFC is influenced by current, feed gas flow rate, and feed gas CO concentration. Additionally, the maximum CO concentration is affected by the off-duration of the purge valve in addition to these factors. Specifically, under the operating condition of 473.15 K, adopting a CO concentration threshold purge strategy is recommended, whereas under the operating condition of 448.15 K, voltage drop and CO concentration threshold purge strategies should be respectively implemented above and below the cutoff line based on the current. This research contributes to mitigating the issue of CO accumulation in DEA mode.

Combined Gas Tungsten Arc Welding and Shielded Metal Arc Welding Processes for Joining Tube to Tubesheet in Shell and Tube Heat Exchangers

Abstract Flawless tube and tubesheet joints are necessary for shell and tube heat exchanger with high leakproof ability and durability. The consequence of mixing of transfer fluids due to the defective welded or expanded tube-to-tubesheet joint results in complete malfunctioning of the heat exchange process. In this case, there is a high demand for quality assessment of the fabricated tube-to-tubesheet joints (TTS) based on the international standards. Additionally, the literature on assessing the mechanical and metallurgical characteristics of tube-to-tubesheet joints using any one welding technique is available; however, articles dealing with the use of multiple welding techniques are scanty. In the current work, the quality assessment of strength welded and light expanded (3%) tube-to-tubesheet joints followed by light expansion was performed whereas for welding, combined gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW) as root pass and cap pass were adopted in the fabrication stage. Quality and sound tube-to-tubesheet joints were produced using welding and tube expansion process. Linear and circular indications representing the cracks were absent on the developer in the liquid penetration test. The minimum leak path (MLP) was greater than the two-third of tube wall thickness. The results strongly qualify the use of combined gas tungsten inert gas and shielded metal arc welding process for manufacturing of tube-to-tubesheet joints. The methodology and results in the current article are beneficial for researchers and industrialists working close to shell and tube heat exchangers and boilers.

Quantum chemistry study on inhibition of coal spontaneous combustion based on anti-gastric acid bionics: Na+, Mg2+ inhibition and CO2 inerting

In view of the limitations of single means of inhibiting coal spontaneous combustion and the lack of research on the joint mechanism of different inhibition means, this paper constructed a joint oxygen shielding structure based on the bionic principle that gastric mucosa and gastric mucus cooperate with each other to resist gastric acid and prevent gastric acid from eroding the gastric wall, and studied the microscopic mechanism of joint inhibition of coal spontaneous combustion by using Na+, Mg2+ blocking and CO2 inerting at the same time. In this paper, the change of CO2 adsorption strength before and after ionic inhibition is used to demonstrate that the two have a synergistic effect of inhibiting coal spontaneous combustion, and the micro-mechanism of the combination of these two means is not seen in related studies. In addition, this paper also made detailed quantum chemistry simulation calculations on the water absorption of ions, the existence of coordination bonds, and the chemical stability of coal molecules after inhibition, which is a refinement and supplement to the theory of coordination inhibition. The results showed that the coal molecules themselves were attractive to water, with an adsorption energy of -12.43 kJ/mol; the adsorption strength of coal molecules to water after Na+ inhibition was more than four times of that before the inhibition, at -53. 65 kJ/mol, and the effect of Mg2+ was even better, with the adsorption energy to water increasing to -180.98 kJ/mol, and from the point of view of adsorption of water, the ions exhibited a positive coal spontaneous combustion inhibition effect. The inhibitory effect of Na+ on aldehyde group is stronger than that of Mg2+; the initial adsorption energy between CO2 and coal molecules was -12.34 kJ/mol, and the adsorption energy between the coal molecular structure and CO2 after ionic inhibition was -18.12 kJ/mol ∼ -28.62 kJ/mol, which was significantly enhanced compared with that before the inhibition, suggesting that the combination of the two means can synergistically inhibit spontaneous combustion of coal, and the synergistic effect of Mg2+ with inert gases is stronger than that of Na+.

Investigation of effectiveness of KOH-activated olive pomace biochar for efficient direct air capture of CO2

The capture of CO2 directly from the air is one of the most promising methods under investigation in recent years to reduce the environmental concentration of this pollutant in order to mitigate its effects on climate change. In this work, the activation of olive pomace biochar with potassium hydroxide, KOH, has been studied for its use as a CO2 adsorbent. The effectiveness of biochar activated with KOH at 750 °C in an inert N2 atmosphere was evaluated, using different mass ratios of biochar/KOH, 1:0.5, 1:1, and 1:2. Various characterisation analyses of the biochar were performed to determine its chemical composition, specific surface area, pore size and volume, structure, morphology, and functional groups. The adsorption isotherm was determined at atmospheric pressure and a temperature of 10 °C. The experimental equilibrium results were fitted to the Langmuir, Freundlich, and Temkin models. Additionally, the kinetic behavior of biochar/KOH as an adsorbent was studied, and dynamic experiments were conducted at atmospheric pressure and 10 °C. The experimental data were fitted to various kinetic models (pseudo-first order, pseudo-second order, Avrami, and Elovich). Furthermore, the mass transfer mechanism during the adsorption process was evaluated using the intra-particle diffusion model. Finally, biochar regeneration was investigated for its subsequent reuse as an adsorbent. For this purpose, complete desorption of the captured CO2 in the biochar was easily carried out by modifying the temperature.

Influence of Welding Parameters on Strength of Metal Inert Gas Welded Mild Steel Joints

Influence of Welding Parameters on Strength of Metal Inert Gas Welded Mild Steel Joints