Low Gas Concentrations Research Articles

Low cost ternary metal oxide based nanocomposites as a room temperature formaldehyde sensor

To protect human health from hazardous gases, it is necessary to rapid detection of toxic gases utilizing gas sensors. Though there are various gas sensors, despite that, they endure inaccuracy in selectivity and sensitivity in the real-time monitoring of the low concentration of gases. In this context, the practical design for developing a cost-effective formaldehyde (HCHO) sensor using a hetero-type ternary nanocomposite ZnO/CdO/CuO (ZCCO) metal oxide (MOX) materials with porous structure is an ideal choice. In this study, ZCCO heterostructures demonstrated rapid selectivity towards HCHO compared with other volatile organic compounds and exhibited excellent long-term stability for up to 80 d. The sensor capability has been further improved with the heterostructures’ porous morphology, greater specific surface area, huge reaction sites, and electron sensitization effects of highly dispersed nanocomposite material. This work reports the Lowest Detection Limit (LDL) towards HCHO at room temperature as 250 ppb. These heterostructures enable the charge transport mechanism between the interparticle ZnO/CdO (n–n junctions) and the ZnO/CuO (n–p junctions) that can simultaneously enhance the sensitivity of the gas molecule’s reactions.

Evolution from gas outburst to coal outburst: An analysis from the perspective of asynchronous transfer difference of gas mass and coal deformation

Considering that coal and gas outburst is a highly complex nonlinear process, the synchronous energy criterion based on the gas expansion energy and the coal deformation potential energy is often adopted to evaluate the hazard. However, the synchronous energy criterion without considering the transfer difference of gas mass and coal deformation has defects in describing the evolution characteristics of coal-rock gas dynamic disasters. Hence, it is necessary to investigate the asynchronous characteristics of the gas expansion energy and the coal deformation potential energy. In this study, the deformation characteristics of coal injected with He and CH4 were measured respectively with the aid of a self-developed device for observing the asynchronous characteristics of effective stress and adsorption-induced deformation. Besides, the differentiated propagation characteristics of gas pressure and adsorption-induced deformation were obtained, and the asynchronous propagation starting point and propagation rate difference between them were analyzed and determined. Furthermore, based on the calculation formula of gas expansion energy and coal deformation potential energy, the values and propagation differences of the two types of energy at different times were revealed. Finally, the typical outburst phenomena were explained using the energy asynchronous theory. The following research findings were yielded. The adsorption-induced expansion process lasts longer than the gas pressure reduction process, which is the reason for asynchronous propagation of gas expansion energy and coal deformation potential energy. The coal deformation potential energy can be further divided into mechanical compression strain energy and desorption shrinkage strain energy. In the initial stage of outburst, the main sources of energy are free gas expansion energy and mechanical compression strain energy. As time progresses, the effect of desorption gas expansion energy and desorption shrinkage strain energy gradually strengthens. From the perspective of energy asynchrony, outburst occurrence at a low gas concentration in deep regions and delayed outburst in cross-cut coal uncovering can be explained as the result of dynamic load instability in surrounding stopes brought about by lagging superimposed deformation disturbances after gas desorption, or the result of self-induced lagging shrinkage deformation formed under special boundary conditions. The findings of this study are helpful to guide the design and connection of the prevention and control methods of deep coal-rock gas dynamic disasters.

Fabrication of selective and highly sensitive triethylamine gas sensor using In2O3–SnO2 hollow nanospheres in room temperature activated by UV irradiation

Introducing a groundbreaking solution, a room-temperature (RT, 25 °C) gas sensor addresses complexities in conventional sensors, promising enhanced performance. Synthesized through hydrothermal and thermal calcination processes, SnO2 hollow nanospheres (HNs) are integrated with In2O3 components to bolster sensing capabilities. The sensor detects triethylamine (TEA) gas upon UV light irradiation, owing to its unique surface properties and SnO2–SnO2 and SnO2–In2O3 homo- and heterojunctions. This results in unparalleled sensitivity to TEA gas (Ra/Rg = 34–100 ppm) and an exceptional limit of detection (3.98 ppt), attributed to photo-ionized O2− ions' heightened reactivity. The study proposes superior sensors backed by comprehensive analyses, demonstrating their performance improvements and underlying mechanisms. The optimized sensor design, based on In2O3-appended SnO2 HNs, presents exceptional selectivity, pattern recognition for low TEA gas concentrations, humidity resistance, and reliability under UV irradiation.

Au- or Ag-Decorated ZnO-Rod/rGO Nanocomposite with Enhanced Room-Temperature NO2-Sensing Performance.

To improve the gas sensitivity of reduced oxide graphene (rGO)-based NO2 room-temperature sensors, different contents (0-3 wt%) of rGO, ZnO rods, and noble metal nanoparticles (Au or Ag NPs) were synthesized to construct ternary hybrids that combine the advantages of each component. The prepared ZnO rods had a diameter of around 200 nm and a length of about 2 μm. Au or Ag NPs with diameters of 20-30 nm were loaded on the ZnO-rod/rGO hybrid. It was found that rGO simply connects the monodispersed ZnO rods and does not change the morphology of ZnO rods. In addition, the rod-like ZnO prevents rGO stacking and makes nanocomposite-based ZnO/rGO achieve a porous structure, which facilitates the diffusion of gas molecules. The sensors' gas-sensing properties for NO2 were evaluated. The results reveal that Ag@ZnO rods-2% rGO and Au@ZnO rods-2% rGO perform better in low concentrations of NO2 gas, with greater response and shorter recovery time at the ambient temperature. The response and recovery times with 15 ppm NO2 were 132 s, 139 s and 108 s, 120 s, and the sensitivity values were 2.26 and 2.87, respectively. The synergistic impact of ZnO and Au (Ag) doping was proposed to explain the improved gas sensing. The p-n junction formed on the ZnO and rGO interface and the catalytic effects of Au (Ag) NPs are the main reasons for the enhanced sensitivity of Au (Ag)@ZnO rods-2% rGO.

Hydrogen sulfide removal from low concentration gas streams using metal supported mesoporous silica SBA-15 adsorbent

The removal of hydrogen sulfide (H2S) from gas mixtures is paramount as it can cause environmental damage, corrosion, and catalyst poisoning even at low concentration levels (100–200 mg/L). In this work, a series of Fe-Cu oxides supported SBA-15 materials were prepared using the wet incipient impregnation method with different Fe and Cu atomic ratios to evaluate the H2S removal performance. It was found that the H2S adsorption capacity generally increases with an increase in the CuO loading, with a Cu-Fe atomic ratio of 1.0:0.3 displaying the highest breakthrough H2S adsorption capacity of 74.08 mg H2S/g-sorbent. Through the XPS results, the adsorbent existed in the form of sulfate, sulfide, and elemental sulfur after reacting with H2S. In particular, it was confirmed that Fe2O3 helps to improve the H2S removal performance by creating an alkaline environment. The material with superior performance showed high capacity at low concentration compared to several published reports.

Carbon emission reduction accounting method for a CCUS-EOR project

It is difficult to quantify and certify the greenhouse gas (GHG) emission reduction in the entire process of a project of carbon capture, utilization and storage (CCUS)-enhanced oil recovery (EOR). Under the methodological framework for GHG voluntary emission reduction project, the carbon emission reduction accounting method for CCUS-EOR project was established after examining the accounting boundaries in process links, the baseline emission and project emission accounting methods, and the emission and leakage quantification and prediction models, in order to provide a certification basis for the quantification of GHG emission reduction in the CCUS-EOR project. Based on the data of energy consumption, emission and leakage monitoring of the CCUS-EOR industrial demonstration project in Jilin Oilfield, the net emission reduction efficiency is determined to be about 91.1% at the current storage efficiency of 80%. The accounting and prediction of carbon emission reduction for CCUS-EOR projects with different concentrations and scales indicate that within the project accounting boundary, the certified net emission reduction efficiency of the low-concentration gas source CCUS-EOR projects represented by coal-fired power plants is about 37.1%, and the certified net emission reduction efficiency of the high-concentration gas source CCUS-EOR projects represented by natural gas hydrogen production is about 88.9%. The proposed method is applicable to the carbon emission reduction accounting for CCUS-EOR projects under multiple baseline scenarios during the certification period, which can provide decision-making basis for the planning and deployment of CCUS-EOR projects.

Biosensor development for low-level acetaldehyde gas detection using mesoporous carbon electrode printed on a porous polyimide film

Acetaldehyde, which is an intermediate product of alcohol metabolism, is known to induce symptoms, including alcohol flushing, vomiting, and headaches in humans. Therefore, real-time monitoring of acetaldehyde levels is crucial to mitigating these health issues. However, current methods for detecting low-concentration gases necessitate the use of complex measurement equipment. In this study, we developed a low-cost, low-detection-limit, enzyme-based electrochemical biosensor for acetaldehyde gas detection that does not require sophisticated equipment. The sensor was constructed by screen-printing electrodes onto a porous polyimide film, using grafted MgO-templated carbon (GMgOC) as working electrode material, carbon for the counter electrode, and silver/silver chloride for the reference electrode. Pyrroloquinoline-quinone-dependent aldehyde dehydrogenase was immobilized on the working electrode, and a chamber was attached to the electrode chip and filled with 1-methoxy-5-methylphenazinium methyl sulfate solution. The sensor can be used to measure acetaldehyde gas concentrations from 0.02 to 0.1 ppm, making it suitable for monitoring human skin gas. This low detection limit was achieved by delivering the analyte through the porous polyimide film on which the electrodes were printed and accumulating acetaldehyde in the mesoporous GMgOC of the working electrode. This mechanism suggests that this sensor design can be adapted to develop other low-detection limit gas sensors, such as those for screening skin gas biomarkers.

Zinc-aluminum layered double hydroxide and double oxide for room-temperature oxidation of sulfur dioxide gas

Sulfur dioxide (SO2) gas at trace levels challenges the consumption of fuel gases and cleaning of flue gases originating from diverse anthropogenic sources. We have demonstrated Zn–Al layered double hydroxide (LDH) and layered double oxide (LDO) as low-cost and effective adsorbents in removing lowly concentrated SO2 gas at room temperature. Water in the adsorbent bed significantly improved the performance, where the maximum adsorption capacity of 38.0 mg g−1 was achieved for LDO. Based on the spectroscopic findings, the adsorbed gas molecules were oxidized to surface-bound sulfate/bisulfate species, showing complete mineralization of SO2 molecules. By employing an inexpensive NaOH–H2O2 solution-based regeneration strategy, we successfully regenerated the spent LDO, significantly restoring its gas uptake capacity. The regenerated oxide exhibited an increased gas uptake capacity ranging from 38.0 to 98.5 mg g−1, highlighting the practicality and economic feasibility of our approach. LDH/LDO materials are promising regenerable adsorbents for removing low concentrations of SO2 gas in ambient conditions.

ZnO-Loaded Graphene for NO2 Gas Sensing.

This paper investigates the effect of decorating graphene with zinc oxide (ZnO) nanoparticles (NPs) for the detection of NO2. In this regard, two graphene sensors with different ZnO loadings of 5 wt.% and 20 wt.% were prepared, and their responses towards NO2 at room temperature and different conditions were compared. The experimental results demonstrate that the graphene loaded with 5 wt.% ZnO NPs (G95/5) shows better performance at detecting low concentrations of the target gas than the one loaded with 20 wt.% ZnO NPs (G80/20). Moreover, measurements under dry and humid conditions of the G95/5 sensor revealed that the material is very sensitive to ambient moisture, showing an almost eight-fold increase in NO2 sensitivity when the background changes from dry to 70% relative humidity. Regarding sensor selectivity, it presents a significant selectivity towards NO2 compared to other gas compounds.

Effect of Gas-Phase Passivation Technology on Spontaneous Combustion Characteristic Stage and Reaction Kinetics of FeS During Particle Size Fragmentation

ABSTRACT To investigate the mechanism of inhibition of spontaneous combustion of reactive FeS by gas-phase passivation, this paper used liquid-phase synthesis to prepare reactive FeS which were divided into five particle size ranges by crushing and grinding and then passivated those by low-oxygen gas. This paper analyzed the effect of gas-phase passivation on the characteristic parameters of the characteristic stages of crushed FeS from the perspective of thermodynamics, and used the KAS and FWO methods to calculate the apparent activation energy of the different characteristic stages of the FeS oxidation heating process. Inhibition mechanism of FeS spontaneous combustion reaction kinetics during particle size fragmentation by gas-phase passivation was revealed. The results indicate that in the spontaneous combustion stage at room temperature (RT), the exothermic heat of passivated FeS was significantly reduced to below 5 J/g, and the apparent activation energy rose up to 116 kJ/mol, which was significantly increased by about 50% compared to the activated FeS. The essence of gas-phase passivation is that the low oxygen concentration gas reacts with FeS to produce a passivation protective film, blocking the reaction and pushing the oxidation process backwards as a whole. In the weight gain stage of oxygen absorption, the weight gain of passivation FeS is reduced to less than 2.2%, and the heat release is reduced to 2.8J/g. The particle size of the passivated FeS decreased, and the apparent activation energy increased by 20 kJ/mol in the decomposition and combustion stage. With the decrease of FeS particle size, the gas-phase passivation is more effective and the inhibition effect of spontaneous combustion of FeS is more obvious.

Using a Photoacoustic Cell for Spectroscopy of Toxic Air Pollutants including CO2, SO2 and NO Gases

Due to the rise in global temperature and climate change, the detection of CO2, SO2 and NO pollutants is important in smart cities. In this paper, an H-shaped photoacoustic cell is utilized for the detection of low-concentration gases. The geometry of the cell is miniaturized and designed with specific parameters in order to increase its efficiency and performance. The designed cell eliminates problems such as bulkiness and cost, which prevent the use of sensors in detecting greenhouse gases. The simplicity of the design expands the application rate of the cell in practice. In order to consider the viscosity and thermal effects, the cell is formulized by fully linearized Navier–Stokes equations, and various parameters, such as acoustic pressure, frequency response, sound speed (sound velocity) and quality factor, are investigated for the mentioned gases. The performance of the system is frequency-based, and the target gases can be detected by using a microelectromechanical resonator as a pressure sensor. Quality factor analysis expresses that CO2, SO2 and NO gases have quality factors of 27.84, 33.62 and 33.32, respectively. The performance of the cell in the resonance state can be expressed by the linear correlation between the results. The background noise generated in the photoacoustic research has been removed by miniaturization due to the obtained resonance, and the proposed cell provides a proper signal-to-noise ratio. The results of the proposed system represent the increase in the quality factor, which reduces the losses and thus increases the sensitivity of the system in the study of greenhouse gases.

Research on controlling gas overrun in a working face based on gob-side entry retaining by utilizing ventilation type “Y”

To determine the characteristics of air leakage concerning a “Y” type ventilation in gob-side entry retaining with roof cutting, pressure relief, and the law of a resulted gas accumulation (GA), research is conducted by employing the CFD simulation incorporated with the gauged parameters of working face (WF) mining to analyze the air leakage of “Y” type ventilation. For this purpose, the 1201 fully mechanized coal mining face in the south Wu mining location of the Daxing coal mine is taken as an illustrative example to study the air leakage in the “Y” type ventilation. So, the gas concentration (GC) issue surpassing the limit in the upper corner of the goaf was simulated. The results show that the goaf is formed into an open space when roof cutting and pressure relief technology along the goaf is implemented. The air pressure at the upper corner of the WF would be the lowest, which is only 1.12 Pa. The airflow of air leakage under a pressure difference would move from the gob-side entry retaining to the goaf. Moreover, the simulation of mine ventilation indicates that the volume of air leakage positively correlates with the length of gob-side entry retaining. When the WF is advanced 500 m ahead, the maximum volume of air leakage would reach 247 m3/min within the range of 500–1300 m, and then the rate of air leakage gradually would decrease. When the WF is advanced at 1300 m, the air leakage would become the smallest, which is 175 m3/min. When gas control is under consideration, the effect of gas extraction would be best with the buried pipe whose depth and diameter are set to 4.0 m and 400 mm, respectively. So, the GC in the upper corner would become 0.37%. After the high-level borehole with a 120 mm diameter is mined, the GC in the deep goaf decreased to 3.52%, and the GC at the upper corner became further reduced to 0.21%. While the high-level borehole gas is extracted by employing the extraction system of the high-concentration gas, the extraction system of low-concentration gas is utilized to extract the upper corner gas of the WF, thus, the problem of gas overrun was resolved satisfactorily. During the recovery period of the mining, the GC at each gauging point was less than 0.8%, which effectively guided the secure production in the Daxing coal mine and provided a theoretical foundation to control gas overrun during the mining process.

Effect of Salt Content and Operating Temperature on the Nitrogen Dioxide Gas Sensing Performance of Sodium-Ion Conducting Solid Polymer Electrolyte

Sodium-ion conducting solid polymer electrolyte (Na-SPE) films based on polyvinyl alcohol (PVA) with various weight percentages of sodium iodide (NaI) were prepared using the casting technique. The films’ structural, morphology and electrical conductivity were examined to understand the sensing mechanism of the as-prepared Na-SPE films. The X-ray diffraction (XRD) and atomic force microscopy (AFM) data, respectively, showed the amorphous and homogeneous granular structure of Na-SPE films due to the high dissociation of NaI in the PVA matrix for all concentrations. The changes in the FTIR vibrational modes of Na-SPEs provide evidence of interactions between cations and functional groups of the host matrix. The effect of salt content, operating temperature and gas concentration on the performance of the Na-SPE sensor towards NO2 were investigated. In contrast to the pure PVA film, which did not respond to NO2 gas at low concentrations, Na-SPE films exhibit higher sensitivity to NO2 gas with faster response and recovery times. At low NO2 gas concentration (50 ppm), a sample containing 20 wt.% of NaI exhibits the highest sensitivity at the operating temperature of 200 °C. In comparison, at a high NO2 gas concentration (550 ppm), a sample containing 40 wt.% of NaI exhibits a maximum sensitivity at 150 °C. These findings suggest that Na-SPE films would be suitable for gas sensor applications. HIGHLIGHTS Na-SPEs films based on PVA with various salt contents have been prepared using the casting method The Hall effect data confirm the n-type conductivity of the Na-SPEs Na-SPE structure exhibits high sensitivity towards NO2 with rapid response/recovery times SPE film has a maximum sensitivity of 127.3 % at low NO2 gas concentration and a maximum sensitivity of 126 % at high gas concentration These results imply that this compound would be suitable for environmental and industrial uses GRAPHICAL ABSTRACT

Surface geochemical anomaly pattern of medium-to-high temperature geothermal systems in South China and its application

The existence of thermal storage will correspondingly increase the temperature of surrounding strata and promote the continuous expansion, volatilization, upward migration, and loss of gas in the strata. As a result, a low-concentration gas field will be formed in the strata above geothermal reservoirs. Geothermal reservoirs could in turn heat formation water and increase the solubility of soluble inorganic salts in the surrounding rocks and the total dissolved solids (TDS) content in the formation water. Since water can strongly wet and permeate strata, the dissolved inorganic salts migrate into upper strata along with water, giving rise to the formation of a high-concentration inorganic salt field in the strata above geothermal reservoirs. A higher geothermal reservoir temperature corresponds to more significant characteristics mentioned above. Therefore, a medium-to-high temperature geothermal system has a surface geochemical anomaly pattern of high inorganic salt concentrations and low gas concentrations (also referred to as the high-salt and low-gas pattern). This pattern is applied to the surface geochemical exploration of the two geothermal fields in Guangdong Province, i.e., the Huangshadong geothermal field in Huizhou City and the Xinzhou geothermal field in Yangjiang City, revealing low-concentration gas fields above both. The application results also show that the exposed thermal spring water in both geological fields has higher concentration of dissolved inorganic salt than the surface water and nearby seawater, forming high-amplitude anomalies on the surface above geothermal reservoirs. These characteristics, as well as the measured temperature at known geothermal wells, verify the validity of the high-salt and low-gas pattern of medium-to-high temperature geothermal systems proposed in this study. Moreover, the high-salt and low-gas pattern proposed predicts three favorable medium-to-high temperature geothermal zones in the surface geochemical exploration of the Shiba Basin near the Huangshadong geothermal field.

Rapid detection of ppb level electrolyte leakage of lithium ion battery（LIB）by WO3 hollow microsphere gas sensor

As known, the leakage of lithium battery (LIB) electrolyte is an important cause for runaway failure of LIB, so it has great significance to develop an approach for electrolyte leakage detection with low detection limit and fast response. In this work, we developed a Pd-doped WO3 gas sensor, taking the main component of electrolyte Ethyl Methyl Carbonate (EMC) as the target gas. The sensor has a hollow microsphere structure assembled by nano-particles, and the sensor with Pd doping ratio of 1.5% has the best gas sensing performance. At 275 ℃, the response to 10 ppm EMC is 17.8, and still 45% to EMC as low as 100 ppb. Furthermore, the response time is fast as 19 s to 10 ppm EMC. In addition, the sensor also shows novel stability and gas selectivity, the fluctuations of baseline resistance and response just were 0.77% and 4.6%, respectively. The results show that the sensor can detect extremely low concentration of EMC gas with fast response, and has great application potential in the field of lithium battery safety.

Highly sensitive gas optical sensing in a multicavity based quasi-parity-time-symmetric structure

A multicavity based quasi-parity-time (PT) symmetric structure is theoretically investigated for realizing highly sensitive gas detection. In the PT-symmetric broken phase, the singular pole effect can be achieved with much enhanced transmission, based on which low concentration of gas in the air can be efficiently sensed. In addition, the sensing signal is directly recorded by the change of the transmittance (T) of the sensor, real-time monitoring can be realized in our proposed structure. The sensitivities of -ΔT/ΔnD can reach 79437.2602 RIU−1 and 24753.7366 RIU−1 for benzene and methane, respectively. Such high sensitivity just occurs in the low concentration range. Our structures show great promise in constructing sensitive gas sensors to detect various harmful gases, such as volatile organic compounds (VOC) etc.

Cu-doped flower-like SnO2 architecture toward promoting SO2 detection: Fast equilibrium and low trace monitoring

Design of practical tin oxide (SnO2) semiconductor gas sensors is fundamental strategy to detect hazardous gases such as SO2. However, challenges remain in the detection of SO2 gas at low concentration and slow equilibrium between gas adsorption and desorption. Herein, the superior performance of nanostructured of Cu-doped flower-like SnO2 architecture via feasible hydrothermal method demonstrated for the detection of SO2 gas at low concentration (1–20 ppm) and fast gas adsorption and desorption equilibrium (14 s) towards 5 ppm SO2. Furthermore, the as fabricated 3 mol% Cu-doped SnO2 shows an outstanding gas response (∼ 4.05–20 ppm SO2) at the working temperature of 300 ℃. The Cu-doping strategy may pave the way to ultrasensitive SO2 gas sensor possessing low trace monitoring and fast equilibrium ability to satisfy the increasing demand for toxic SO2 gas detection.

Explosion and vented explosion behaviors of low-concentration gas in large-scale pipes

The extraction, transmission, and use of low-concentration gas in coal mines are often challenged by potential accidents due to proximity to the combustion and explosion concentration limit. Water sealing of fire barriers and explosion venting devices guarantee the safe transmission of low-concentration gas. The propagation and venting of gas explosion under different concentrations are experimentally investigated in a DN500 mm pipe explosion propagation test system. The water sealing of fire barrier vented explosion field evolution of methane-air mixture at the stoichiometric concentration (9.5 vol%) is examined through Fluent numerical simulation to reveal the water sealing of fire barrier further vented explosion pattern of gas transmission pipelines under low concentrations. The explosion overpressure and flame propagation of low-concentration gas in pipes are observed and correlated. Based on their coupling relationship, the design basis for the installation location of the explosion venting device is derived. The vented explosion characteristics of low-concentration gas during pipe transmission are summarized, proving that this explosion venting technique enhances both the explosion venting device and explosion parameters. Our observations and analysis can offer useful clues to underground gas explosion and prevention in coal mines.

Evolutionary Model and Experimental Validation of Gas-Bearing Coal Permeability under Negative Pressure Conditions.

Coal bed methane drainage is the main approach to lower risks of coal seam while raising the efficiency in natural resource utilization. The negative pressure used for extraction in coal mines is largely determined empirically due to a lack of experimental research on how coal permeability changes under the combined influence of effective stress and negative pressure. This results in low gas extraction efficiency and concentration. In this paper, to study the effect law of complex stress and extraction on coal permeability during coal and gas co-mining, a test system was specially designed to determine the gas flow and coal permeability of coal samples under different stress paths and negative pressure conditions in the lab. The study analyzed the correlation between coal permeability, effective stress, and negative pressure and subsequently developed a permeability evolution model for gas-bearing coal under negative pressure conditions. The results showed that the permeability of coal increases with the increase in negative pressure and decreases with the increase in effective stress; the permeability of coal can be abruptly changed by changes in stress loading patterns; the established model of permeability evolution of gas-bearing coal can better reflect the correlation between permeability, effective stress, and negative pressure. The research outcomes offer a valuable theoretical foundation for the efficient extraction and utilization of methane in coal mines.

ガスセンサ・ニオイセンサに向けた酸化スズナノマテリアルの創製

Expectations for the sensing of very small amounts of gases and odors are increasing in many fields such as medicine, healthcare, and mobility. In recent years, nanomaterials with various forms such as needle-like, belt-like, sheet-like, and dendrite-like have been developed. These nanomaterials have been used to detect very small amounts of gas with a semiconductor gas sensor. In addition, detection of various gases and odor molecules has been realized using these gas sensors. In particular, in the field of ceramics, which requires high-temperature firing at several hundred degrees Celsius, the realization of “cold crystallization”, which has been a long-standing issue, has had a great impact. Nanomaterials with high surface area, unique shape, metastable crystal facets, etc. have been developed with cold crystallization of ceramics. These nanomaterials have improved the low-concentration gas detection characteristics of gas sensors and odor sensors. In this review, I would like to introduce the fabrication of new SnO2 nanomaterials and the development of gas and odor sensors using the SnO2 nanomaterials.