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Covalent cross-linked porous organic polymers (POPs) have shown great potential in adsorption and separation fields owing to their high surface areas, easy functionalization, and porous design using synthetic strategies. Herein, we report the facile preparation of two triphenylamine-based nitrogen-rich porous organic polyaminals (TPOAs), denoted as TPOA-F and TPOA-OH, from triphenylamine-based triazine-hexamine and commercially available fluorine- and hydroxyl-monoaldehydes, respectively via a amine–aldehyde condensation reaction without any catalyst addition. These two resulting TPOAs possessed large specific surface areas (1179 and 565 m2 g−1) and hierarchical pore distribution (0.58 to 5.20 nm). Owing to this, TPOAs exhibited highly promising application potential for natural gas purification (mainly light hydrocarbons and CO2 separation). Among them, TPOA-F shows the highest C3H8 uptake of 225 mg g−1, C2H6 uptake of 122 mg g−1, and CO2 uptake of 155 mg g−1 at 273 K/1 bar and C3H8 uptake of 187 mg g−1, C2H6 uptake of 93 mg g−1, and CO2 uptake of 95 mg g−1 at 298 K/1 bar. Then, the C3H8/CH4, C2H6/CH4, C3H8/C2H6, C3H8/CO2, C2H6/CO2, and CO2/CH4 gas mixture adsorption selectivities for TPOAs demonstrated the values of 68.7–78.8, 14.0–15.7, 4.9–5.0, 16.5–17.4, 3.4–3.5, and 4.2–4.5. Meanwhile, TPOAs also displayed considerable iodine capture performance up to 3.43 g g−1. In addition, this has surpassed many reported porous polyaminal materials for their abundant porosity and nitrogen active sites, which offer host–guest interactions due to the high electron density. This study would provide valuable guidance for the development and application of efficient POP-based adsorption and separation materials. [ABSTRACT FROM AUTHOR]

Two new zinc-triazole-carboxylate frameworks, namely [(CH3)2NH2][Zn2(DMTDC)2(tz)]·3DMF·5H2O (1) and [Zn2(DMTDC)(tz)2]·DMF·2H2O (2, H2DMTDC = 3,4-dimethylthieno [2,3-b]-thiophene-2,5-dicarboxylic acid, Htz = 1,2,4-triazole), were synthesized by using a thiophene-containing dicarboxylate and two different triazole ligands. In compound 1, the tz ligand is in situ generated from the deamination of 4-atz (4-atz = 4-amino-1,2,4-triazole) under solvothermal conditions. Single-crystal X-ray diffraction analyses show that compound 1 is a 3D anionic porous framework based on dinuclear Zn(II) tetracarboxylate paddlewheel SBUs and dinuclear [Zn2(tz)2] subunits whereas 2 is a neutral 3D framework and a pillared-layer structure based on the Zn–triazolate layers and dicarboxylate pillars. Both of the frameworks can be considered as pcu α-Po topologies, and exhibit irreversible solid-state structural transformations upon solvent removal/uptake. Gas adsorption experiments reveal that the two compounds display CO2-induced, gate-opening adsorption isotherms at 195 K. Dye adsorption tests indicate that compound 1 can selectively adsorb cationic dyes over the anionic and neutral dyes whereas 2 hardly adsorbs any selected dyes. [ABSTRACT FROM AUTHOR]

Ni-doped alumina nanoflakes are a potent sensing material for SO3 gas at 20–90 °C with moderate recovery. Herein, an economical synthesis of undoped and doped alumina for the experimental detection of SO3 target gas is reported. The Ni-doping results in an efficient fast response to all tested concentrations of the target gas and also showed good response at room temperature. However, the response increases enormously with the increase in temperature and reaches saturation at higher temperatures. Among the different temperatures, the sensor delivers a huge response at 90 °C and this temperature is optimum for sensor operation. The high Ni-doped sensor reveals an improved response of 12.40 towards 10 ppm SO3 and a response time of 9 s. The response shows a two-fold increase up to 60 ppm. The stability of the Ni-doped sensor is evaluated and validated under the ageing test over a 5 week period. Surprisingly, the sensor response shows a feeble decrease, maintaining an immense response. The sensor demonstrates ∼97% reproducibility, which assures the possibility for practical applications. Meanwhile, the Ni-dopant helps to increase oxygen adsorption and active sites. [ABSTRACT FROM AUTHOR]

Under the solvothermal condition, the reaction of 4,4′′-(1,3-phenylene)-bis[2,3′-bipyridine]-6-carboxylic acid (H2L1) with Mn(NO3)2·4H2O in dimethylacetamide (DMA) afforded a novel zero-dimensional (0D) metallomacrocycle, [Mn4(L1)4(H2O)8]·20H2O (1). However, in a similar solvothermal condition to 1, the reaction of H2L1 with Mn(OAc)2·4H2O in dimethylsulfoxide (DMSO) yielded one new three-dimensional (3D) metal–organic framework, [Mn(L1)]·4H2O·DMSO (2). Furthermore, other three 3D metal–organic frameworks, [M(L1)]·4H2O·DMSO (M = Cd (3), Cu (4) and Zn (5)), were obtained under the same solvothermal condition as 2, which are isostructural with 2. Interestingly, a novel two-dimensional (2D) metallomacrocycle network, [Zn2(L2)(H2O)3]·3H2O·DMA (6), was solvothermally synthesized through the reaction between 4,4′-(6,6′-([1,1′-biphenyl]-4,4′-diyl)bis(2-(4-carboxyphenyl)pyridine-6,4-diyl))dibenzoic acid (H4L2) and Zn(NO3)2·6H2O in DMA. 1–6 were fully characterized by infrared spectra, elemental analyses, thermogravimetric analyses, powder X-ray diffraction patterns, or single-crystal X-ray diffractions. The changes from 0D metallomacrocycle (1) to 3D isostructural metal–organic frameworks (2–5) are mediated by increasing solvent polarity (from DMA to relatively high polar DMSO) because the more polar DMSO solvent helps the coordination sites of L12− ligand to take part in coordination. More interestingly, 3, 5, and 6 achieve close to white-light emission upon excitation at 365 nm. The gas adsorption properties of 2–5 have also been investigated, and the results indicate that the CO2 adsorption capacities are relative to the framework stability of MOFs 2–5. The present work provides a promising approach to constructing novel metal–organic frameworks or metallomacrocycles and may open new perspectives for developing single-component white-light-emitting materials. [ABSTRACT FROM AUTHOR]

Stability is a key factor that restricts the practical applications of metal–organic framework (MOF) materials. In this work, we report an ultrastable three-dimensional cage-like MOF, SrCu(HC3N3O3)2, constructed by a polydentate cyanurate ligand and two kinds of different metal nodes. A high ratio of coordination sites in organic ligands, specific coordination of strong acid with a strong base and weak acid with a weak base and double independent completed coordination networks endow SrCu(HC3N3O3)2 with outstanding thermal stability (up to 300 °C) and acid/alkali resistance (pH = 2–14). Moreover, SrCu(HC3N3O3)2 possesses the highest porosity up to 36.7% among cyanuric acid-based MOF materials and exhibits differentiated adsorption of C3H4 (63 cm3 g−1) and C3H6 (51 cm3 g−1). The breakthrough experiment further verified that efficient C3H4/C3H6 separation can be achieved under dynamic conditions by SrCu(HC3N3O3)2. [ABSTRACT FROM AUTHOR]

Copyright of Technisches Messen is the property of De Gruyter and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

One-step evaporative jamming of colloidal silica particles in contact-free spray droplets resulted in well-defined powder micro-granules with interstitial nanopores. This paper reports the anomalous freezing behaviour of confined water in the microspheres synthesized using spray drying. It has been revealed that the freezing point of water in these microspheres gets significantly lowered (∼−45 °C) owing to the confinement effect. Thermoporometry results are corroborated with the structural details obtained using complementary techniques of gas adsorption measurements and small-angle x-ray scattering. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Coalbed methane (CBM) is an important resource of energy. For CBM recovery, sorption‐induced coal deformation can cause significant reservoir permeability change. Moisture content and coal pore morphology affect the gas adsorption capacity and can alter the coal deformation of the coal seam. Therefore, it is crucial to establish a coal gas moisture‐coupled model for CBM production prediction. However, there are currently insufficient data available for quantitative analyses. In this paper, a series of typical sorption‐induced strain experiments were carried out during methane adsorption and desorption on coal samples with different metamorphic degrees and moisture content. The pore morphology and adsorption capacity of coals were measured to analyze the reason for different deformation of coals with various pore structures and moisture. Results show that the adsorption capacity and deformation is corresponding to the specific surface area of micropore, which first decreases and then increases with coal ranks. The deformation and adsorption gas content of dried coals is greater than that of natural moisture coals, which means that moisture can reduce the sorption capacity of coals, resulting in the decrease of gas adsorption‐induced coal deformation. There is also residual deformation of coal samples after gas desorption caused by the residual adsorbed gas in coals. This paper quantitatively investigates the effects of pore characteristics and moisture on coal deformation and the internal mechanism. This work will provide essential information for building out a fully cross‐coupled model of coal gas‐moisture relationships for CBM production prediction. [ABSTRACT FROM AUTHOR]

In this paper, scanning electron microscopy, low-temperature N2 adsorption and CH4 isothermal adsorption experiments were performed on 11 coal samples with Ro,max between 0.98 and 3.07%. The pore structure characteristics of coals (specific surface area, total volume distribution) were studied to assess the gas adsorption capacity. The results indicate that there is significant heterogeneity on coal surface, containing numerous channel-like pores, bottle-shaped pores and wedge-shaped pores. Both Langmuir volume (VL) and Langmuir pressure (PL ) show a stage change trend with the increase of coalification degree. For different coalification stages, there exist different factors influencing the VL and PL values. For low-rank coals (Ro,max<1.1%), the increase of VL values and decrease of PL values are mainly due to the abundant primary pore and fracture within coal. For middle-rank coals (1.1%o,max<2.1%), the moisture content, vitrinite content and total pore volume are all the factors influencing VL, and the reduction of PL is mainly attributed to the decrease of moisture content and inertinite content. Meanwhile, this result is also closely related to the pore shape. For high-rank coals (Ro,max>2.1%), VL values gradually increase and reach the maximum. When the coal has evolved into anthracite, liquid hydrocarbon within pore begins pyrolysis and gradually disappears, and a large number of macropores are converted into micropores, leading to the increase of specific surface area and total pore volume, corresponding to the increase of VL. In addition, the increase of vitrinite content within coal also contributes to the increase of VL. PL, reaches the minimum, indicating that the adsorption rate reaches the largest at the low pressure stage. The result is mainly controlled by the specific surface area and total pore volume of coal samples. This research results will provide a clearer insight into the relationship between adsorption parameters and coal rank, moisture content, maceral composition and pore structure, and it is of great significance for better assessing the gas adsorption capacity. [ABSTRACT FROM AUTHOR]

Deep eutectic solvent (DES) is regarded as a new generation of green solvent due to its distinctive and tailorable physicochemical properties, such as low volatility, strong solubility, biodegradability, low-cost, environment-friendly, and feasibility of the structural design. As an alternative to traditional organic solvents and ionic liquids (ILs), DESs have been widely applied in many fields, such as organic chemical synthesis, electrochemical deposition, material preparation, biomass catalytic conversion, extraction and separation, detection and analysis, nanotechnology, gas absorption, and drug delivery. In this paper, through in-depth discussion on factors influencing the physicochemical properties of DESs, we summarized the relations between their composition, structure, and performance. Focusing on their solvent performance, we analyzed the latest research results of DESs with different physicochemical properties in various fields. It should be pointed out that designing and synthesizing DESs from the molecular structure aspect to regulate their physicochemical properties is the direction of accurately developing new functional applications of DESs. [ABSTRACT FROM AUTHOR]

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Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper describes a new gas optical depth parameterisation implemented in the most recent release, version 13, of the radiative transfer model RTTOV (Radiative Transfer for TOVS). RTTOV is a fast, one-dimensional radiative transfer model for simulating top-of-atmosphere visible, infrared, and microwave radiances observed by downward-viewing space-borne passive sensors. A key component of the model is the fast parameterisation of absorption by the various gases in the atmosphere. The existing parameterisation in RTTOV has been extended over many years to allow for additional variable gases in RTTOV simulations and to account for solar radiation and better support geostationary sensors by extending the validity to higher zenith angles. However, there are limitations inherent in the current approach which make it difficult to develop it further, for example by adding new variable gases. We describe a new parameterisation that can be applied across the whole spectrum, that allows for a wide range of zenith angles in support of solar radiation and geostationary sensors, and for which it will be easier to add new variable gases in support of user requirements. Comparisons against line-by-line radiative transfer simulations and against observations in the ECMWF operational system yield promising results, suggesting that the new parameterisation generally compares well with the old one in terms of accuracy. Further validation is planned, including testing in operational numerical weather prediction data assimilation systems. [ABSTRACT FROM AUTHOR]

To feature fast hydrogen detection, a new design of surface acoustic wave (SAW) based hydrogen sensor integrated with a micro-heater is proposed in this paper. A 200 MHz delay-line patterned SAW sensing chip coated Pd/Ni alloy hydrogen sensitive film and a micro-heater are prepared on a Y35oX quartz wafer. The hydrogen gas adsorption in Pd/Ni thin-film modulates the SAW propagation, and against the temperature interference, the corresponding changes in acoustic attenuation are collected as the sensor signal. The Micro-heater is designed to catalysis the gas-sensitive effect by regulating the working temperature, and the influence law of heating temperature towards response speed is revealed theoretically, allowing determination of the optimal working temperature. The experimental results verify the theoretical prediction. Fast response (t 90 < 2 s), lower power consumption (<1.35 W), and the low detection limit (<15 ppm) are achieved at low working temperature of 75 °C. Furthermore, very low crossed humidity sensitivity and excellent long-term stability are observed. • The novel design of SAW hydrogen sensor integrated with a micro-heater. • The influence law of heating temperature towards response speed is studied. • The optimal working temperature determined by the experiment is 75 °C. • The SAW sensor shows fast response of 2 s to 1% H 2 concentration. • The sensing system with small size and low power consumption is implemented. [ABSTRACT FROM AUTHOR]

A complete pore characteristic of the Indian Gondwana shale is studied by combining laboratory experiments and numerical modeling. Mercury injection capillary pressure (MICP), nitrogen gas adsorption (N2GA) and scanning electron microscopy (SEM) are the primary laboratory methods used to evaluate the pore characteristics. The N2GA and MICP were coupled to estimate the pore size distribution (PSD) of Indian Gondwana shale for the first time. The estimated PSD of Gondwana shale varies between 0.5 nm to 100 µm and most of the pores of the samples fall in the micropore and mesopore category. The porosity of Gondwana shale, measured using MICP, varies from 1.13 to 8.01%. The SEM micrographs and hysteresis pattern of isotherms reveal the presence of cylindrical, ink-bottle and slit shape pores in the samples. The BET (Brunauer-Emmett-Teller) surface area of pore for Gondwana shale varies from 3.42 m2/g to 21.5 m2/g. The FHH (Frenkel-Halsey-Hill) fractal model suggests that the Gondwana shale exhibits two types of fractal dimensions with highly complex pore geometry. The adsorption capacity of Gondwana shale is affected by the clay content. This paper attempted a different interpretation approach using experimental data and concluded that Indian Gondwana shale has high gas storage capacity. [ABSTRACT FROM AUTHOR]

The deformation of coal during the injection of sorptive gases can be classified into two types: deformation due to the pore pressure and the swelling deformation of the coal matrix induced by adsorption. These types of deformation have not been investigated separately in the previous researches. The main reason is that measuring the radial strain of the coal core directly and accurately is extremely difficult under triaxial stress. This paper demonstrates that by injecting both sorptive and non-sorptive gases into a coal sample with different pore pressures, while measuring the radial deformation of the coal sample with a high precision instrument (± 0.227 mm3), deformations due to the pore pressure and deformations induced by adsorption were separated from each other. The adsorption-induced deformations have an important influence on the effective stress. We studied the relationship between Biot coefficient and the swelling deformation due to the adsorption based on the Biot effective stress theory. The experimental results show that the Biot coefficient is the bilinear function in terms of the volumetric stress and pore pressure, shown as α = a + b Θ + c p + d Θ p . The data and results obtained in this experiment played a fundamental role in the applications of gas extraction, coal and gas outburst prevention and control, displacement of coalbed methane with CO2, and the establishment of the solid–fluid coupling model. [ABSTRACT FROM AUTHOR]

Iron-based catalysts can be used as de-NOx catalysts due to their good adsorption performance to gas molecules. However, the adsorption behaviours of NH3, NO, and O2 molecules on ferrous oxide surface are unclear. In this paper, the adsorption properties of NH3, NO, and O2 molecules over FeO (100) surface and oxygen-defected FeO (100) surface were studied by a density functional theory calculation. The Fe-top of the FeO (100) surface is the most active site. NH3 and NO can be adsorbed on the Fe-top sites by N terminal. The adsorption of O2 on the Hollow site of the FeO (100) surface has a larger adsorption energy. When oxygen-defected presents on the FeO (100) surface, the adsorption performances of NH3 and NO on the Fe-top sites are slightly decreased. NO and O2 can be adsorbed on the O-defected site, in which the adsorption energy of O2 is larger. For the adsorption of double molecules, O2 + NH3 or O2 + NO adsorbed on the FeO (100) surface have synergistic effects, respectively, which enhance the adsorption performance. Moreover, the co-adsorption behaviours of O2 + NH3 and O2 + NO on the O-defected FeO (100) surface also occur. [ABSTRACT FROM AUTHOR]

Due to their large surface areas and unique gas adsorption properties, mixed‐matrix membranes (MMMs) with metal–organic frameworks (MOFs) have been extensively studied in relation to various gas separations. In the present paper, we report the quick synthesis of MOF‐74 (M = Mg, Mn, Co, Ni) nanocrystals by microwave reactions and the fabrication of MMMs for use in CO2/N2 and O2/N2 separation. The scanning electron microscopy and energy dispersive X‐ray spectroscopy analysis revealed the homogenous distribution of the MOF‐74 nanocrystals within the polydimethylsiloxane (PDMS). The single gas permeation experiments showed the enhanced CO2/N2 and O2/N2 selectivity by adding the MOF‐74 nanocrystals to the PDMS. This enhanced CO2/N2 and O2/N2 selectivity may be due to the affinity of CO2 and O2 toward the Lewis acidic sites of the MOF‐74. [ABSTRACT FROM AUTHOR]

This paper studies the evolution of the pore size distribution of a fresh unconsolidated geopolymer paste between one day and a week, using thermoporometry. This was made possible by following a careful protocol for sample preparation and for analysis by differential scanning calorimetry. In contrast with nitrogen gas adsorption, this method quantifies directly the amount of water in pores. It also does not require heat and vacuum drying, thus maintaining the fragile pore structure of the unconsolidated paste. Moreover, it was found that, in a typical metakaolin‐based sodium geopolymer with a 10 to 20 hours workability period, the porosity gradually refines during the first week while the mesoporous volume is cut in half. This is probably due to the fact that the geopolymer network was still actively condensing from the activation solution. Part of the pore water never froze and, from mass balance, this residual water was attributed to the water bound in the hydration shell of the sodium counter ions. Only a minor occurrence of covalently bound protons as silanol groups was observed. The results presented here usefully complement data obtained by conventional techniques at later ages on consolidated geopolymers. It supports the growing body of literature on the structural evolution of geopolymers with time. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The selection of an optimized gas adsorption model is a quantitatively challenging task when characterizing shale gas reservoirs because every model has its own assumptions and mechanisms. In addition, excess when converting different models to absolute gas adsorption is reported in the literature, which differs due to variations in adsorbed phase density or volume. The roles of controlling factors change under various conditions and consequences, and it is hard to comprehend shale storage and production sources. Quantifying the contribution of adsorbed and absorbed gases to total gas storage is also challenging despite existing advanced techniques. This paper reviews gas adsorption in the light of applications, comparisons and challenges along with shale controlling factors, and it provides a better opportunity to comprehend shale storage and platforms to investigate further mechanisms of shale gas storage. It is revealed in this review that several crucial factors are found in shale that control and affect the gas adsorption capacity. Kerogen swelling and pore shrinkage, kerogen maturity, gas type and moisture content greatly influence gas adsorption capacity. The measurement of true adsorbed and bulk amount, selection of an optimized gas adsorption model, proper investigation of shale controlling factors, and accurate measurement of adsorbed and absorbed gases may enhance the accuracy of resource assessment and production performance predictions. [ABSTRACT FROM AUTHOR]

A study into the optimal deposition temperature for ultra-thin La2O3 and Y2O3/Ge gate stacks has been conducted in this paper with the aim to tailor the interfacial layer for effective passivation of the Ge interface. A detailed comparison between the two lanthanide oxides ( La2O3 and Y2O3) in terms of band line-up, interfacial features, and reactivity to Ge using medium energy ion scattering, vacuum ultra-violet variable angle spectroscopic ellipsometry (VUV-VASE), X-ray photoelectron spectroscopy, and X-ray diffraction is shown. La2O3 has been found to be more reactive to Ge than Y2O3, forming LaGeOx and a Ge sub-oxide at the interface for all deposition temperature studied, in the range from 44 °C to 400°C. In contrast, Y2O3/Ge deposited at 400 °C allows for an ultra-thin GeO2 layer at the interface, which can be eliminated during annealing at temperatures higher than 525 °C leaving a pristine YGeOx/Ge interface. The Y2O3/Ge gate stack deposited at lower temperature shows a sub-band gap absorption feature fitted to an Urbach tail of energy 1.1 eV. The latter correlates to a sub-stoichiometric germanium oxide layer at the interface. The optical band gap for the Y2O3/Ge stacks has been estimated to be 5.7±0.1 eV from Tauc-Lorentz modelling of VUV-VASE experimental data. For the optimal deposition temperature (400 °C), the Y2O3/Ge stack exhibits a higher conduction band offset (∼2.3 eV) than the La2O3/Ge °2 eV), has a larger band gap (by about 0.3 eV), a germanium sub-oxide free interface, and leakage current (°10°7 A/cm2 at 1V) five orders of magnitude lower than the respective La2O3/Ge stack. Our study strongly points to the superiority of the Y2O3/Ge system for germanium interface engineering to achieve high performance Ge Complementary Metal Oxide Semiconductor technology. [ABSTRACT FROM AUTHOR]

The full pore size distribution represents the integrated characteristics of micro‐nano pore‐throat systems in tight reservoirs. And it involves experiments of different scales to fully analyze the microscope properties. In this paper, we established a new approach for full pore size characterization through conducting the high‐pressure mercury intrusion (HPMI) experiments and low‐temperature nitrogen gas adsorption (LTN2GA) experiments. Meanwhile, we studied the petrology feature of the tight sandstones through X‐ray diffraction (X‐rD) and TESCAN Integrated Mineral Analyzer (TIMA). Then, we investigated the HPMI capillary pressure curves and pore size distribution characteristics, as well as the adsorption‐desorption isotherms features and BET‐specific surface area. Finally, the BJH, non‐local density functional theory (NLDFT) and the quenched solid density functional theory (QSDFT) are contrasted for analyzing the adsorption and pore size distribution characteristics. The HPMI method characterizes the macropores distribution accurately, and the micro/mesopores take up of 14.47% of the total pore spaces. The physisorption isotherms take on the combining shape of type II and IV(a), and the hysteresis loops are like type H3 combined with H4. The BET‐specific surface area is inversely proportional to permeability, and the constant of adsorption heat shows consistence with the analysis results of mineral content. QSDFT can characterize the pore size distribution of micro/mesopores more accurately than the BJH, HPMI, and NLDFT method. By combining the pores narrower than 34 nm calculated from QSDFT method and pores larger than 34 nm calculated from HPMI data with mercury intrusion pressure lower than 42.65 MPa, the full pore size distribution features of tight sandstones are accurately characterized. The micro/mesopores from the new combination method are 3.72% more than that calculated from the HPMI data, and it is of great significance for the accurate pore distribution evaluation and development of tight reservoirs. [ABSTRACT FROM AUTHOR]

CO2 enhanced shale gas recovery (CO2-ESGR) draws worldwide attentions in recent years with having significant environmental benefit of CO2 geological storage and economic benefit of shale gas production. This paper is aimed at reviewing the state of experiment and model studies on gas adsorption, competitive adsorption of CO2/CH4, and displacement of CO2-CH4 in shale in the process of CO2-ESGR and pointing out the related challenges and opportunities. Gas adsorption mechanism in shale, influencing factors (organic matter content, kerogen type, thermal maturity, inorganic compositions, moisture, and micro/nano-scale pore), and adsorption models are described in this work. The competitive adsorption mechanisms are qualitatively ascertained by analysis of unique molecular and supercritical properties of CO2 and the interaction of CO2 with shale matrix. Shale matrix shows a stronger affinity with CO2, and thus, adsorption capacity of CO2 is larger than that of CH4 even with the coexistence of CO2-CH4 mixture. Displacement experiments of CO2-CH4 in shale proved that shale gas recovery is enhanced by the competitive adsorption of CO2 to CH4. Although the competitive adsorption mechanism is preliminary revealed, some challenges still exist. Competitive adsorption behavior is not fully understood in the coexistence of CO2 and CH4 components, and more experiment and model studies on adsorption of CO2-CH4 mixtures need to be conducted under field conditions. Coupling of competitive adsorption with displacing flow is key factor for CO2-ESGR but not comprehensively studied. More displacement experiments of CO2-CH4 in shale are required for revealing the mechanism of flow and transport of gas in CO2-ESGR. [ABSTRACT FROM AUTHOR]

In the present paper, micro-mesoporous Fe-MIL-101/OAC composite using in situ incorporation of Fe-MIL-101 into oxidized activated carbon was synthesized and characterized by XRD, FT-IR, SEM, EDS, and BET techniques. The adsorption performances of toluene onto adsorbents in the gas phase were studied using a laboratory-scale dynamic adsorption system under moist ambience. The toluene adsorption capacity of Fe-MIL-101/OAC composite and Fe-MIL-101 were 127 and 97.6 mg g−1, severally. Results revealed that the larger pores in micro-mesoporous Fe-MIL-101/OAC enhanced the molecular diffusion rate. The findings indicated that micro-mesoporous structures played key roles in the capture of toluene molecules. The initial toluene concentration positively affected on toluene adsorption capacity while temperature and humidity negatively affected on toluene adsorption capacity. The Langmuir model and the pseudo-second-order kinetics model described better adsorption process of Fe-MIL-101/OAC composite. Thermodynamic findings determined that toluene adsorption over Fe-MIL-101/OAC was spontaneous, exothermic physisorption. The regeneration of the composite was still up to 72.6% after six cycles. The micro-mesoporous Fe-MIL-101/OAC composite proposes a promising support for the high toluene removal for future. [ABSTRACT FROM AUTHOR]

The exploration and development of unconventional resources have been of growing interest in the industry in recent years. It is widely known that the adsorption and desorption mechanisms of unconventional gas have great significance for gas accumulation and exploration. However, major researches based on the mechanism of solid-gas interface have failed to reveal it completely, which introduce large discrepancies between actual and predicted production. In this paper, the mechanism of solid-liquid-gas adsorption and desorption interface is enlightened to describe the characteristics of unconventional gas. The validity of the proposal was verified preliminarily by building a conceptual model which redefines the gas-water distribution. Furthermore, the possibility of production of gas trapped in micropores was first investigated. The findings of this study can help for better understanding of the adsorption, desorption, and production mechanisms and in unconventional gas system. Accordingly, the explanation of variation between experiment result and actual production rate even with physical parameters was reasonable in theory. Therefore, this work should provide a basis for improving the accuracy of production predictions in actual reservoirs and should assist analysts in determining reasonable unconventional gas target. [ABSTRACT FROM AUTHOR]

Pseudo-reservoir stimulation in horizontal well is an effective technique for indirectly extracting coalbed methane (CBM) in soft coal from the surrounding rocks (pseudo-reservoir). However, systematic studies of the theory and on-site application of this technique are still lacking, which severely hinders its application. In this paper, the technical principles of pseudo-reservoir stimulation are analyzed firstly, and then, the technical advantages are demonstrated by experimental tests and theoretical analysis. The results show that the pseudo-reservoir generally possesses considerable gas adsorption capacity, with the gas content of 1.56–4.22 cm3/g (avg. 2.51 cm3/g) in Well XC-01, which can be extracted as supplementary resources. The fracability of the pseudo-reservoirs is 0.73–0.92, which is much higher than that of the coal seam, i.e., 0.03–0.43. Meanwhile, the compressive and tensile strength and cohesion of the pseudo-reservoir are higher than those of the coal seam, indicating pseudo-reservoir stimulation is more conducive to forming fracture network, and maintaining wellbore stability and fracture conductivity. The technical feasibility of pseudo-reservoir stimulation is determined by the regional geological conditions, showing simple tectonic conditions and well-developed surrounding rocks with high fracability and mechanical strength but low permeability, water sensitivity and water content are beneficial for the technique application. Note that the fracture conductivity in pseudo-reservoir is more stable and higher than that in coal seam, pseudo-reservoir stimulation is beneficial for the CBM extraction from both hard and soft coal seams. By minimizing the gas diffusion distance, this technique overcomes the technical obstacles to the CBM commercialized production in soft coal. [ABSTRACT FROM AUTHOR]

Compared with porous solids, porous liquids have attracted more and more attention due to their unique physical‐chemical properties such as permanent porosity, fluidity, rapid heat and mass transfer. They have broad application prospects in the fields of gas adsorption and separation, homogeneous catalysis, and others. Porous liquids are generally divided into three categories that include type I, type II and type III according to the composition of the host system in porous liquids. In this paper, the research progress of porous liquids is briefly reviewed, the examples of synthesis, characterization and application of three types of porous liquids are illustrated in detail. Finally, the main issues and challenges faced by the development of porous liquids are summarized and prospected. [ABSTRACT FROM AUTHOR]

The zoning of the coal seam gas is zonal, which has a significant impact on the prominent prediction indicators, resulting in different prediction results for the same prominent prediction indicators in the same coal seam soft and hard coal. In this paper, the hard coal and soft coal in the coal seam are highlighted. The adsorption and desorption rules of the soft coal and hard coal in the outburst coal seam and its influence on the sensitivity of the outstanding prediction index are studied. The results show that: (1) the initial desorption of soft coal is larger than that of hard coal; (2) the outstanding prediction index has an exponential function relationship with gas pressure; (3) the sensitivity of prediction indicators is different. And concluded that: (1) the initial desorption rate of soft coal is faster than that of hard coal; (2) the outburst prediction index K1 and Δh2 increase with the increase of gas adsorption equilibrium pressure; (3) outburst prediction index K1 is more reliable than Δh2. [ABSTRACT FROM AUTHOR]

In study of gas migration process in coal seam, the permeability evolution rule with time has been one of hot topics in the area of coal seam for decades. At present, in view of the time-varying rule of coal seam permeability, the influence of microstructure parameters and adsorption effect are seldom considered simultaneously. In this paper, the fractal seepage model coupled with coal deformation, and the adsorption expansion effect of coal is proposed. A multi-field coupling model is established by considering the influence of matrix and fracture structure. The influence of structural parameters and adsorption constant of main fracture on the time-varying curve of macro permeability are analyzed, including: (1) fractal dimension for fracture lengths; (2) maximum fracture length; (3) Langmuir adsorption strain constant; (4) Langmuir adsorption pressure constant. The results show that, under the influence of in situ stress and adsorption effect, the permeability of coal seam decreases with time. The present results show that the permeability is proportional to the fractal dimension for fracture lengths and the maximum fracture length. The uniformity of permeability distribution is found to be directly proportional to the pressure constant of Langmuir and inversely proportional to the volume constant of Langmuir. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOF) are recently developed coordination porous materials, and their unique structures are very conducive to catalytic reactions. In this paper, p‐benzenedicarboxylic acid (PBA)‐Ni2+ MOF materials (denoted as PBA‐Ni‐x, where x represents the initial ratio of PBA to Ni2+) were synthesized by a hydrothermal method and characterized by X‐ray diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and N2 gas adsorption. H2 gas was produced using the synthesized MOF as a photocatalyst and Eosin Y as a photosensitizer. The dependence of the special surface area and thickness of the nanosheets of Ni‐MOF on the initial ratio of PBA to Ni2+ (PBA/Ni2+) was investigated. The BET surface areas of PBA‐Ni‐1 PBA‐Ni‐2 and PBA‐Ni‐3 are 11.00, 24.61 and 13.04 m2 g−1, respectively. And the thicknesses of nanosheets are approximately 600–1000, 200–500 and 300–700 nm. Among the three materials, PBA‐Ni‐2 has the thinnest sheet‐like structure and largest surface area. Thus, it displays the highest H2 evolution rate of 20.0 μmol h−1. The noble‐metal‐free hydrogen production system is valuable for the application of MOF materials in photocatalytic water splitting. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to predict total emissivity of CO near earth atmospheric conditions. Due to lack of total emissivity information in this temperature range, it was predicted from line data or spectral emissivity data. The results have been compared with several methods in this paper. The models compared are by Bliss [2], Hottel [4], Atwater and Ball [5, 7], wide band model by Edwards [6], Yamamoto and Sasamori [7, 8], and using HITRAN data base [12]. For spectral emissivity, the results by Yamamoto and Sasamori match well with predictions using HITRAN data base. For total emissivity, the deviations between models are rather large and sometimes more than about 0.05 at the upper bound value around 0.2. In general, for a given condition, the upper bound of total emissivity is given by Hottel, and lower bound is given by HITRAN. The predictions by Edwards are in between but near to those of Hottel. [ABSTRACT FROM AUTHOR]

Building on the ideas of the theoretical physicist David Bohm, this paper postulates that Cartesian Mechanism (CM), which is the current philosophical paradigm of modern science, is derived from a more fundamental paradigm - one that is based on undivided wholeness (UW). After a discussion on the nature of scientific theory, the paper contrasts the chief elements of CM, which postulates that an entity or a process (i.e., a whole) can be broken down into a certain number of fundamental parts (e.g., a photograph), against those of UW according to which the whole is primary while a part is a conceptual abstraction from the whole, which the part also contains (e.g., a hologram). The two worldviews are illustrated by simple examples. Two phenomena are then examined from the chemical engineering field. Mathematical models are presented for (a) unsteady-state physical gas absorption in a liquid, and (b) adsorption of a species in a single, spherical adsorbent pellet. The theoretical expressions for the instantaneous rates of absorption and adsorbate uptake exhibit holographic features, i.e., they contain or enfold the entire process history up to that instant. Only under special circumstances, e.g., when the turbulence level is high [case (a)] or at large times [cases (a) and (b)], they reduce or collapse into their standard, widely-used photographic forms (i.e., effect of past history is insignificant). Thus, the mechanistic (i.e., unfolded) order of everyday experience in which events appear to be separated in time and space may be a projection from a deeper (i.e., enfolded) order of reality. This has profound implications for the physical sciences and for present-day humanity that is rent by social divisions of various kinds. [ABSTRACT FROM AUTHOR]

Cationic exchange resins (CERs) are generally used for the purification and clarification processes of nuclear industry wastewater. The molten-salt oxidation method (MSO) can be effectively applied to the treatment of spent resins and the absorption of acid gas (such as SO2). In this study, the transformation of organic sulfur in resins in ternary molten carbonates was investigated. The FT-IR spectra proved that the existence of molten carbonates could promote the decomposition of the benzene ring, S–O and C–S bonds in the resin structure. The XRD pattern analysis revealed that organic sulfur in the sulfonic acid functional group of resins was fixed in spent salt in the form of sulfate. The XPS results showed the transformation of sulfur species into residues in the carbonate melt. The increase in temperature promoted the conversion of thiophene sulfur to sulfoxide sulfur and further to sulfones sulfur at over 550 °C in the carbonate melt. The retention rate of organic sulfur in spent salt was 82.55% at 800 °C. This study provides more theoretical guidance for the industrial treatment of spent resins and some technical support for the sustainable development of the nuclear industry. [ABSTRACT FROM AUTHOR]

Two structurally similar columnar ZnII-MOFs {[Zn8L4(TZ)4·0.5H2O]·4[Me2NH2]·6DMF·4H2O}n (Zn-MOF1) and {[Zn4L2(MT)2·H2O]·2[Me2NH2]·4DMF·4H2O}n (Zn-MOF2) were synthesized with irregular ligands, 2,2′-(pyridine-2,6-diyl) diterephthalic acid (H4L), 1,2,4-triazolium (TZ) and 1H-1,2,4-triazole-3-thiol (MT). Structural studies showed that both ZnII-MOFs had a similar 3D framework constructed with multiple SBUs and displayed an unusual (3,4,6)-connection topology. Furthermore, both ZnII-MOFs have high performance in gas adsorption and separation. The separation ratios of C2H2/CH4 and CO2/CH4 of Zn-MOF1 were 15.1 and 6.8, respectively, and those of Zn-MOF2 were 14.6 and 6.5, respectively. Moreover, Eu@Zn-MOF1 and Eu@Zn-MOF2 were successfully obtained by adding Eu3+ ions to the synthesis system. After a series of fluorescence tests, these two MOFs were found to have good fluorescence performance, and showed high selectivity and sensitivity to Fe3+ ions in aqueous solution with a low detection limit. [ABSTRACT FROM AUTHOR]

The electronic structure of hexasilaprismane (HSP) was examined with different computational techniques to elucidate the bonding features and the electrostatic surface potential of HSP. The carbon dioxide adsorption and separation capacities of metal-ion-decorated hexasilaprismane (HSP) were examined with DFT and CBS-QB3. Furthermore, the 1,2,3,4,5,6-hexaphenylprismasilane (HPPS) molecule was examined for its binding with metal ions and gas adsorption capacity. The Mg2+ ion complexed HPPS molecule adsorbs 15CO2 molecules with an average binding free energy of −0.98 eV per molecule. The calculated gravimetric densities of 45.1 and 48.4 wt% show that these systems can be employed for CO2 capture. The substantial difference in the affinity of the designed systems for CO2 gas molecules compared to N2 and CH4 molecules show the potential of the systems for CO2 separation from N2 and CH4 gas molecules. [ABSTRACT FROM AUTHOR]

A robust and porous titanium metal–organic framework (Ti-MOF; LCU-402) has been hydrothermally synthesized through combining a tetranuclear Ti2Ca2(μ3-O)2(μ2-H2O)1.3(H2O)4(O2C–)8 cluster and a tritopic 1,3,5-benzene(tris)benzoic (BTB) ligand. LCU-402 shows remarkable stability and permanent porosity for CO2, CH4, C2H2, C2H4, and C2H6 gas adsorption. Moreover, LCU-402 as a heterogeneous catalyst can smoothly convert CO2 under a simulated flue atmosphere into organic carbonate molecules by cycloaddition reactions of CO2 and epoxides, indicating that LCU-402 might be a promising catalyst candidate in practical applications. We are confident that the identification of a persistent titanium–oxo building unit would accelerate the development of new porous Ti-MOF materials. [ABSTRACT FROM AUTHOR]

An effective strategy is developed to synthesize a novel and stable layered Cu nanocluster using a one-pot reduction method. The cluster, with a molecular formula of [Cu14(tBuS)3(PPh3)7H10]BF4 which has been unambiguously characterized by single crystal X-ray diffraction analysis, exhibits different structures from previously reported analogues with core–shell geometries. In the absence of chiral ligands, the cluster displays intrinsic chirality owing to the non-covalent ligand–ligand interactions (e.g., C–H⋯Cu interactions and C–H⋯π interactions) to lock the central copper core. The interlacing of chiral-cluster enantiomers forms a large cavity, which lays the foundation for a series of potential applications such as drug filling and gas adsorption. Moreover, the C–H⋯H–C interactions of phenyl groups between different cluster moieties promote the formation of a dextral helix and realization of the self-assembly of nanostructures. [ABSTRACT FROM AUTHOR]

The distribution of gas and metals in the circumgalactic medium (CGM) plays a critical role in how galaxies evolve. The MUSE-ALMA Haloes survey combines MUSE, ALMA, and HST observations to constrain the properties of the multiphase gas in the CGM and the galaxies associated with the gas probed in absorption. In this paper, we analyse the properties of galaxies associated with 32 strong |${\rm H\, {\small I}}$| Ly-α absorbers at redshift 0.2 ≲ z ≲ 1.4. We detect 79 galaxies within ±500 kms−1 of the absorbers in our 19 MUSE fields. These associated galaxies are found at physical distances from 5.7 kpc and reach star formation rates as low as 0.1 M⊙ yr−1. The significant number of associated galaxies allows us to map their physical distribution on the Δ v and b plane. Building on previous studies, we examine the physical and nebular properties of these associated galaxies and find the following: (i) 27/32 absorbers have galaxy counterparts and more than 50 per cent of the absorbers have two or more associated galaxies, (ii) the |${\rm H\, {\small I}}$| column density of absorbers is anticorrelated with the impact parameter (scaled by virial radius) of the nearest galaxy as expected from simulations, (iii) the metallicity of associated galaxies is typically larger than the absorber metallicity, which decreases at larger impact parameters. It becomes clear that while strong |${\rm H\, {\small I}}$| absorbers are typically associated with more than a single galaxy, we can use them to statistically map the gas and metal distribution in the CGM. [ABSTRACT FROM AUTHOR]

Terahertz (THz) waves have been attracting much attention for a variety of technologies in recent years. However, only limited several experimental investigations on the terahertz characterization of plasmas have been reported. In this paper, a finite-difference time-domain method is applied to model the terahertz wave propagation in a high-temperature unmagnetized plasma. The rational polynomial function is established based on a hot plasma dispersion relation, and then, the relationship between D and E is deduced in the time domain. In the frequency domain, the reflection and transmission coefficients of terahertz waves through the hot unmagnetized plasma slab are computed, and their dependences on plasma frequency, plasma thickness, and collision frequency are studied. The results show theoretically that, when the terahertz wave passes through the plasma layer, its amplitude is obviously modulated by the electron density profile, the collision frequency, and the electron temperature. Finally, the potential application of terahertz waves in plasma diagnostics has been discussed. [ABSTRACT FROM PUBLISHER]

Coal seam is a sedimentary body with complex pore system. The gas adsorption property of coal is greatly determined by the adsorption‐pores (<100 nm), and the fractal dimension can be used an index to estimate the impact of the adsorption‐pores on the methane adsorption capacity of various rank coals. In this paper, low‐temperature N2 adsorption and H2O adsorption methods were used to study the adsorption‐pores structure and its fractal features. The results show that the development of adsorption‐pores closely depends on the coalification, and the degree of pore development exhibits a U‐shaped trend with increasing coal rank. Additionally, the pore size distributions of coal samples from N2 adsorption analysis and H2O adsorption analysis are similar, especially for samples LH7 and WLH8. Fractal analysis indicates that D2(N2) (0.5 < P/P0 < 1) can more accurately characterize the fractal features of adsorption‐pores than D2(H2O), which may be a result of the significant coal‐H2O interaction. Moreover, D2(N2) has stronger correlations with the coal pore parameters. With the increase in D2(N2), the Langmuir volume first decreases and then increases, which is probably associated with the competition effect of the pore structure and surface irregularity of coal. When D2(N2) < 2.7‐2.8, the pore structure plays a key role, while for D2(N2) > 2.7‐2.8, the influence of the specific surface area is more prominent. The equilibrium moisture content of the coal samples also has a positive correlation with D2, except for low‐rank coal sample YZG2 due to the presence of a large amount of oxygen‐containing functional groups, which increases its water‐holding capacity. [ABSTRACT FROM AUTHOR]

Summary: This paper presents the development of a discrete fracture model of fully coupled compressible fluid flow, adsorption and geomechanics to investigate the dynamic behaviour of fractures in coal. The model is applied in the study of geological carbon dioxide sequestration and differs from the dual porosity model developed in our previous work, with fractures now represented explicitly using lower‐dimensional interface elements. The model consists of the fracture‐matrix fluid transport model, the matrix deformation model and the stress‐strain model for fracture deformation. A sequential implicit numerical method based on Galerkin finite element is employed to numerically solve the coupled governing equations, and verification is completed using published solutions as benchmarks. To explore the dynamic behaviour of fractures for understanding the process of carbon sequestration in coal, the model is used to investigate the effects of gas injection pressure and composition, adsorption and matrix permeability on the dynamic behaviour of fractures. The numerical results indicate that injecting nonadsorbing gas causes a monotonic increase in fracture aperture; however, the evolution of fracture aperture due to gas adsorption is complex due to the swelling‐induced transition from local swelling to macro swelling. The change of fracture aperture is mainly controlled by the normal stress acting on the fracture surface. The fracture aperture initially increases for smaller matrix permeability and then declines after reaching a maximum value. When the local swelling becomes global, fracture aperture starts to rebound. However, when the matrix permeability is larger, the fracture aperture decreases before recovering to a higher value and remaining constant. Gas mixtures containing more carbon dioxide lead to larger closure of fracture aperture compared with those containing more nitrogen. [ABSTRACT FROM AUTHOR]

In this paper we have simulated the competitive adsorption of CO2, CH4, and N2 gases in deep coal seams by building a graphite supercell structure and discussed the impact of pressure, pore size, and multicomponent composition on CH4 desorption. The results show that the adsorption capacity of a single component gas changes is in the order of CO2 > CH4> N2. For the CH4/CO2 competitive adsorption, absorbed CO2 can reach saturation at low pressure conditions. CO2 has an adsorptive advantage compared with CH4. It is shown that CO2 can promote the CH4 desorption by the displacement mechanism. For CH4/N2competitive adsorption, the adsorption capacity of N2 is weaker than that of CH4, demonstrating that improvement in coalbed methane (CBM) production by N2 injection is achieved by reducing the partial pressure and creating flow channels. The presence of H2O has a greater impact on the gas with a stronger adsorption capacity in the binary component system. For the CH/CO2/N2 competitive adsorption, the CO2 adsorption is dominant in 1 nm slit pores, while CH4 adsorption is dominant in 2 nm slit pores. This indicates that when the pore diameter increases, the CO2/N2 injection does not promote CH4 desorption. H2O also has a significant impact on the competitive adsorption in the ternary component system. The strong interaction between H2O and CO2 weakens the CO2 adsorption capacity. [ABSTRACT FROM AUTHOR]

The seepage problem of coal-bed methane (CBM) has attracted increasing attention from the research and industry communities. Coal permeability, which is a key parameter for CBM production, has been extensively studied through both laboratory and field tests, mathematical modeling, and numerical simulations. However, relatively little work has been done to investigate the effect of matrix water content on coal permeability evolution. Because most coal seams contain water, it may have direct impact on the CBM seepage capacity. Therefore, in this paper, CBM seepage at different matrix water contents was investigated experimentally. Results demonstrate that coal permeability decreases with the increase in water content. It was also found that both pore pressure and water content can greatly affect CBM migration characteristics and that the sorption strain and permeability were mostly controlled by pore pressure. In addition, water can have an impact on gas adsorption and sorption-induced deformation, which can further affect seepage channel width, leading to change in coal permeability. In general, coal permeability was observed to decrease exponentially with the increase in water content and pore pressure. Moreover, a coal adsorption model and an adsorption-permeability model were established, considering water content and excess adsorption under constant external stress and triaxial strain conditions. The proposed permeability model showed good agreement with the experimental results. The present study provides for better understanding of coal permeability evolution in a water-bearing condition and for developing an improved model to simulate the CBM migration process under such condition more accurately. [ABSTRACT FROM AUTHOR]

A polarization-independent gas sensor based on crescent plasmonic dipole antenna loaded with graphene monolayer is introduced in this paper for environment monitoring applications. Single, dual, and four arms crescent dipoles are designed, analyzed and investigated. The proposed gas sensor has reconfigurable absorption characteristics in the wavelength range from 900 to 1600 nm which covers the different gases responses. A parametric study on the effect of the sensor dimensions and polarization of the illuminated waves on the total absorption of different gases is investigated. A graphene monolayer is used to enhance the gas molecule absorption in its unbiased state. An enhancement of the total absorption cross section (ACS) values for n = 1.4 is 1.028 × 105 nm2 for the unloaded sensor case and is 1.77 × 105 for the graphene loaded sensor case. The unloaded graphene sensor sensitivity is 630 nm/RIU, and for the graphene loaded case is 677.5 nm/RIU. Dual-polarized crescent dipole consists of two orthogonal arms is designed to maintain the same sensitivity for x- and y-polarized E-field illumination. A polarization independent gas sensor consists of four crescents dipole arms rotated with 45° is explained. An enhancement of gas absorption is achieved by using a sensor array of four-arm dipole sensor. Different array sizes loaded with graphene monolayer are investigated. The total ACS peak value is 7.84 × 106 nm2 for 6 × 6 dipole array is obtained. [ABSTRACT FROM AUTHOR]

The paper deals with the study of the effect of the morphology and structure of crystallites of p-Si layer on the adsorption of gas sensors. The porous layer was obtained by electrochemical anodization at anodizing current from10 to 60 mA and anodizing time from 5 to 30 min. The sensors were created as p-Si structures: PdAu-Si:GeAuNiAu by electron-beam evaporation. The porous layer surface was studied with optical microscopy, and the crystallite structure was examined with FTIR technique. It has been discovered that the anodization modes have a direct effect on the deformation vibrations of the SiHx group in wavenumbers from 700 to 950 cm - 1. At the boundaries of the crystallites, compressing stresses arise causing a decrease in Si-O-Si bond in wavenumbers from 1060 to 1160 cm - 1. It has been demonstrated the increasing effect of SiHn stretching bonds and SiOxHy complexes (absorption peaks at 2116 cm - 1 and 2340 cm - 1 respectively). The variation of anodizing time has a stronger effect on the structure of the porous layer than the variation of anodizing current. The adsorption sensitivity of the porous layer has been determined by the relative change in conductivity. The data obtained make it possible to conclude that the anodization mode affects the adsorption of gas sensors. This conclusion correlates with the data obtained with FTIR method in crystallites structure. [ABSTRACT FROM AUTHOR]

In this paper, an experimental study of the variation of resistivity of coal samples in different bedding directions at 1 MHz frequency was performed by establishing an experimental system for resistivity testing of coal under triaxial stress. The low-pressure nitrogen gas adsorption (LP-N2GA) experiment and scanning electron microscopy (SEM) were obtained to analyze the pore-fracture structural characteristics of coal samples and the influence on resistivity anisotropy. Furthermore, the fundamental cause of anisotropy of coal resistivity is expounded systematically. The results show that the resistivity of loaded coal decreased first before increasing. The ionic conductance and the high degree of metamorphism slow down the decrease of resistivity. The distribution of pore and fracture structures is anisotropic. The connected pores and fractures are mainly distributed along the parallel bedding direction. The weak plane of bedding, diagenetic fractures, and plane fracture structures of parallel bedding result in the increase of fractures in the direction of vertical bedding, so increasing the potential barrier. Therefore, the resistivity in the vertical bedding direction is higher than that of the parallel bedding. Loading coal resistivity anisotropy degree is a dynamic change trend; the load increases anisotropy significantly under axial pressure, and the degree of anisotropy has a higher discreteness under confining pressure. It is mainly the randomness of the internal pore-fracture compaction, closure, and development of the heterogeneous coal under the confining pressure; the more rapid the decline in this stage, the larger the stress damage degree. [ABSTRACT FROM AUTHOR]