Littérature scientifique sur le sujet « Adsorption induced deformation »

Abstract Adsorption-induced deformation is a change in geometrical dimensions of an adsorbent material caused by gas or liquid adsorption on its surface. This phenomenon is universal and sensitive to adsorbent properties, which makes its prediction a challenging task. However, the pure academic interest is complemented by its importance in a number of engineering applications with porous materials characterization among them. Similar to classical adsorption-based characterization methods, the deformation-based ones rely on the quality of the underlying theoretical framework. This fact stimulates the recent development of qualitative and quantitative models toward the more detailed description of a solid material, e.g. account of non-convex and corrugated pores, calculations of adsorption stress in realistic three-dimension solid structures, the extension of the existing models to new geometries, etc. The present review focuses on the theoretical description of adsorption-induced deformation in micro and mesoporous materials. We are aiming to cover recent theoretical works describing the deformation of both ordered and disordered porous bodies.

A newin situsetup combining small-angle neutron scattering (SANS) and dilatometry was used to measure water-adsorption-induced deformation of a monolithic silica sample with hierarchical porosity. The sample exhibits a disordered framework consisting of macropores and struts containing two-dimensional hexagonally ordered cylindrical mesopores. The use of an H2O/D2O water mixture with zero scattering length density as an adsorptive allows a quantitative determination of the pore lattice strain from the shift of the corresponding diffraction peak. This radial strut deformation is compared with the simultaneously measured macroscopic length change of the sample with dilatometry, and differences between the two quantities are discussed on the basis of the deformation mechanisms effective at the different length scales. It is demonstrated that the SANS data also provide a facile way to quantitatively determine the adsorption isotherm of the material by evaluating the incoherent scattering contribution of H2O at large scattering vectors.

This thesis has presented a fundamental study of simple gas adsorption and adsorption-induced deformation in carbonaceous materials including both graphite and porous carbon. Monte Carlo simulation was conducted to obtain the behaviours of adsorption and adsorption-induced solid deformation that are comparable to experimental studies including the adsorption isotherm, the strain isotherm and the isosteric heat, as well as the relevant microscopic properties that facilitate the understanding of underlying mechanisms.

Ce travail contient deux parties portant sur l'élaboration de matériaux microporeux. Dans la première partie, nous abordons la synthèse en trois étapes (dans l'ordre : polymérisation radicalaire en masse, fonctionnalisation et hyper-réticulation via une réaction d'alkylation de Friedel-Crafts) de polymères hyper-réticulés fonctionnalisés et fluorés (HCP) à partir de trois unités monomères fonctionnelles : le divinylbenzène, le chlorure de vinylbenzyl et le pentafluorostyrene. Les propriétés texturales des HCP se sont révélées fortement influencées par le rapport initial des monomères. Par conséquent, ce dernier a été optimisé afin de trouver un compromis raisonnable entre les propriétés texturales et le degré de fonctionnalisation. Une méthode de fonctionnalisation sélective, rapide et économe en énergie, la réaction para-fluoro-thiol, a été utilisée pour fonctionnaliser le cycle pentafluorobenzene avec une série de thiols accessibles, portant divers groupes chimiques (sulfonate, alkyle, amine et hydroxyle), aboutissant à des HCP fonctionnalisés avec des groupements chimiques variés. Les performances d'adsorption de CO2 à haute pression des matériaux ont été évaluées par manométrie. Les résultats ont montré les différences induites par la présence des groupements chimique à pression ambiante et ont mis en évidence l'importance des propriétés texturales, et en particulier celle du volume microporeux, envers les performances d'adsorption à haute pression, avec une contribution probable du gonflement des HCP induit par adsorption.La deuxième partie de ce travail concerne la synthèse de films de silice microporeux à partir de composés organosilane dipodaux. Après avoir évalué une série de techniques, notamment l'autoassemblage assisté par électrochimie (EASA), le dépôt par solution de Stöber et l'autoassemblage induit par évaporation (EISA), cette dernière méthode a été retenue pour produire des films uniformes et sans fissures. Ces films serviront de matériau modèle simple pour la première étape de validation expérimentale d'un modèle de poromécanique. Tout d'abord, une série de films a été élaborée à partir de cinq précurseurs organosilane dipodaux par coulée de solvant afin d'identifier les précurseurs et le protocole adaptés à l'obtention de films nanoporeux. Trois de ces précurseurs organosilane dipodaux ont permis d'obtenir des films nanoporeux avec une dispersité variable de la PSD, comme l'a révélé la porosimétrie à l'argon. En conséquence, ces derniers ont été sélectionnés pour élaborer des films minces par dépôt par trempage. Deux types de substrats ont été considérés (PVC et wafer de silicium), et la vitesse de retrait a été ajustée afin d'obtenir des films uniformes et sans fissures. Les films déposés sur wafer de silicium dans le régime de drainage ont été choisis pour réaliser des études de déformation induite par adsorption d'eau à l'aide de la porosimétrie environnementale par ellipsométrie (EEP). Au cours de quatre cycles continus d'adsorption/désorption, les résultats ont révélé que la chimisorption de l'eau entraînait un changement progressif des propriétés d'adsorption et de déformation de tous les matériaux entre les cycles. Un gonflement monotone a été observé pour deux des matériaux, tandis qu'une contraction suivie d'un gonflement, typique d'une condensation capillaire, a été observée pour un film
This work contains two parts dealing with the elaboration of microporous materials. In the first part, we address the three-step synthesis (in order: bulk radical polymerization, functionalization, and hypercrosslinking via Friedel-Crafts alkylation reaction) of functionalized fluorinated hypercrosslinked polymers (HCP) starting from three functional monomer units: divinyl benzene, vinylbenzyl chloride, and pentafluorostyrene. The textural properties of the HCPs were found to be strongly influenced by the initial monomer ratio. Therefore, the latter was optimized for a reasonable compromise between textural properties and functionalization degree. A selective, rapid, and energy-efficient functionalization route known as the para-fluoro-thiol reaction is utilized in order to functionalize the pentafluorobenzene ring with a series of widely available thiols bearing various chemical groups (sulfonate, alkyl, amine, and hydroxyl), yielding functionalized HCPs with diverse chemical moieties. The high-pressure CO2 adsorption performance of the materials was assessed using manometry. The results showed the discrepancies brought by the presence of functional groups at ambient pressure. They underlined the importance of textural properties, particularly of microporous volume, for high-pressure sorption performances, with a probable contribution of adsorption-induced swelling of the HCP.The second part of this work deals with the synthesis of microporous silica films from dipodal organosilane compounds. After assessing a series of techniques including electrochemically assisted self-assembly (EASA), Stöber solution deposition, and evaporation-induced self-assembly (EISA), the latter was chosen for producing uniform and crack-free films. These films will serve as a straightforward model material for the initial step of the experimental validation of a poromechanics model. First, a series of films have been elaborated from five dipodal organosilane precursors by solvent-casting in order to identify the suitable precursors and protocol for the obtention of nanoporous films. Three of these dipodal organosilane precursors yielded nanoporous films with variable PSD dispersity, as evidenced by Ar porosimetry. Consequently, the latter were selected to elaborate thin films by dip-coating-coating. Two types of substrates were considered (PVC and Si wafer) and the withdrawal speed was adjusted to obtain crack-free and uniform films. Films deposited on Si wafers in the draining regime were selected to conduct water sorption-induced deformation studies using environmental ellipsometry porosimetry (EEP). Over four continuous adsorption/desorption cycles, the results revealed that the chemisorption of water led to a gradual change of the adsorption and deformation properties of all the materials between the cycles. A monotonous swelling was observed for two of the materials while a contraction followed by swelling, typical of a capillary condensation, was observed for one film

碩士
國立臺灣大學
土木工程學研究所
96
Microcantilever-based biosensors are rapidly becoming an enabling sensing technology for a variety of label-free biological applications due to their wide applicability, versatility and low cost. It is thus imperative for us to reveal the physical origin of adsorption-induced deformation, and to further analyze its implication of microscopic mechanisms on macroscopic deformation. The objective of this work is to develop a multi-scale theory that can analyze deformation of micro-cantilever beam subjected to bio-adsorption mechanisms calculated by ab- initio simulation and classical molecular dynamics. The multi-scale theory developed herein has successfully correlated atomistic information (the mechanism of bio-adsorption) and continuum description (bending behavior of a cantilever beam). We have studied the adsorption mechanisms of bio-molecules for SAM (self-assembly monolayer, alkanethiolic molecular for n=1~14) adsorbed on gold through ab-initio and molecular dynamics simulation. The ab-initio simulation results are in a good agreement with the literature, and the error of calculated absorption energy is less than 13％. We then extend to longer SAM simulation by molecular dynamics and the calculated absorption energy is less than 7％ when comparing with the ab-initio results. Adsorption-induced stresses for different SAMs (for n=4, 6, 8, 12 and 14) are calculated by the multi-scale method. Calculated deflection based on the adsorption-induced stress agrees well with experimental measurements. Physical origin of adsorption induced deformation is revealed through the change of atomic positions and forces.

The goal of this work is to improve the understanding of adsorption-induced deformation in nanoporous (and in particular microporous) materials in order to explore its potential for material characterization and provide guidelines for related technical applications such as adsorption-driven actuation. For this purpose this work combines in-situ dilatometry measurements with in-depth modeling of the obtained adsorption-induced strains. A major advantage with respect to previous studies is the combination of the dilatometric setup and a commercial sorption instrument resulting in high quality adsorption and strain isotherms. The considered model materials are (activated and thermally annealed) carbon xerogels, a sintered silica aerogel, a sintered hierarchical structured porous silica and binderless zeolites of type LTA and FAU; this selection covers micro-, meso- and macroporous as well as ordered and disordered model materials. All sample materials were characterized by scanning electron microscopy, gas adsorption and sound velocity measurements. In-situ dilatometry measurements on mesoporous model materials were performed for the adsorption of N2 at 77 K, while microporous model materials were also investigated for CO2 adsorption at 273 K, Ar adsorption at 77 K and H2O adsorption at 298 K. Within this work the available in-situ dilatometry setup was revised to improve resolution and reproducibility of measurements of small strains at low relative pressures, which are of particular relevance for microporous materials. The obtained experimental adsorption and strain isotherms of the hierarchical structured porous silica and a micro-macroporous carbon xerogel were quantitatively analyzed based on the adsorption stress model; this approach, originally proposed by Ravikovitch and Neimark, was extended for anisotropic pore geometries within this work. While the adsorption in silica mesopores could be well described by the classical and analytical theory of Derjaguin, Broekhoff and de Boer, the adsorption in carbon micropores required for comprehensive nonlocal density functional theory calculations. To connect adsorption-induced stresses and strains, furthermore mechanical models for the respective model materials were derived. The resulting theoretical framework of adsorption, adsorption stress and mechanical model was applied to the experimental data yielding structural and mechanical information about the model materials investigated, i.e., pore size or pore size distribution, respectively, and mechanical moduli of the porous matrix and the nonporous solid skeleton. The derived structural and mechanical properties of the model materials were found to be consistent with independent measurements and/or literature values. Noteworthy, the proposed extension of the adsorption stress model proved to be crucial for the correct description of the experimental data. Furthermore, it could be shown that the adsorption-induced deformation of disordered mesoporous aero-/xerogel structures follows qualitatively the same mechanisms obtained for the ordered hierarchical structured porous silica. However, respective quantitative modeling proved to be challenging due to the ill-shaped pore geometry of aero-/xerogels; good agreement between model and experiment could only be achieved for the filled pore regime of the adsorption isotherm and the relative pressure range of monolayer formation. In the intermediate regime of multilayer formation a more complex model than the one proposed here is required to correctly describe stress related to the curved adsorbate-adsorptive interface. Notably, for micro-mesoporous carbon xerogels it could be shown that micro- and mesopore related strain mechanisms superimpose one another. The strain isotherms of the zeolites were only qualitatively evaluated. The result for the FAU type zeolite is in good agreement with other experiments reported in literature and the theoretical understanding derived from the adsorption stress model. On the contrary, the strain isotherm of the LTA type zeolite is rather exceptional as it shows monotonic expansion over the whole relative pressure range. Qualitatively this type of strain isotherm can also be explained by the adsorption stress model, but a respective quantitative analysis is beyond the scope of this work. In summary, the analysis of the model materials' adsorption-induced strains proved to be a suitable tool to obtain information on their structural and mechanical properties including the stiffness of the nonporous solid skeleton. Investigations on the carbon xerogels modified by activation and thermal annealing revealed that adsorption-induced deformation is particularly suited to analyze even small changes of carbon micropore structures
Ziel dieser Arbeit ist es, dass Verständnis der adsorptionsinduzierter Deformation von nanoporösen (insbesondere mikroporösen) Materialien zu erweitern, um ihr Potenzial für die Materialcharakterisierung zu erforschen. Zusätzlich sollen Orientierungshilfen für technische Anwendungen, wie z.B. adsorptionsgetriebene Aktuatoren, bereitgestellt werden. Hierfür kombiniert diese Arbeit in-situ Dilatometriemessungen und detaillierte Modellierung der gemessenen adsorptionsinduzierten Dehnungen. Der wesentliche Vorteil dieser Arbeit gegenüber vorherigen Studien ist die Kombination des dilatometrischen Messaufbaus mit einer kommerziellen Gasadsorptionsanlage, was die Messung qualitativ hochwertiger Adsorptions- und Dehnungsisothermen erlaubt. Die betrachteten Materialsysteme sind (aktivierte und geglühte) Kohlenstoffxerogele, ein gesintertes Silica-Aerogel, ein gesintertes, hierarchisch strukturiertes, poröses Silica und binderlose Zeolithe der Typen LTA und FAU. Diese Auswahl umfasst mikro-, meso- und makroporöse ebenso wie geordnete und ungeordnete Modellmaterialien. Alle Modellmaterialien wurden mit Rasterelektronenmikroskopie, Gasadsorption und Schallgeschwindigkeitsmessungen charakterisiert. In-situ Dilatometriemessungen an mesoporösen Modellsystemen wurden für N2-Adsorption bei 77 K durchgeführt, während alle mikroporösen Modellsysteme zusätzlich bei CO2-Adsorption (273 K), Ar-Adsorption (77 K) und H2O-Adsorption (298 K) untersucht wurden. Der verfügbare Messaufbau für in-situ Dilatometrie wurde im Rahmen dieser Arbeit weiterentwickelt, um Auflösung und Reproduzierbarkeit der Messungen von kleinen Dehnungen zu verbessern, was insbesondere für mikroporöse Materialien von Bedeutung ist. Die experimentellen Adsorptions- und Dehnungsisothermen des hierarchisch strukturierten, porösen Silicas und des mikro-makroporösen Kohlenstoff-Xerogels wurden mit dem adsorption-stress-Modell quantitativ ausgewertet. Hierfür wurde das adsorption-stress-Modell, ursprünglich eingeführt von Ravikovitch et al., für die Verwendung von anisotropen Porengeometrien erweitert. Während die der Deformation zu Grunde liegende Adsorption im Fall des mesoporösen Silicas gut mit der klassischen und analytischen Theorie von Derjaguin, Broekhoff und de Boer beschrieben werden konnte, erforderte die Adsorption in den Kohlenstoffmikroporen umfassende Berechnungen mittels nichtlokaler Dichtefunktionaltheorie. Um die adsorptionsinduzierten Spannungen mit entsprechenden Dehnungen zu korrelieren, wurden zusätzlich mechanische Modelle für die untersuchten Materialien entworfen. Das resultierende theoretische Konstrukt aus Adsorptions-, adsorption-stress- und mechanischem Modell wurde auf die ermittelten experimentellen Daten angewandt und strukturelle und mechanische Eigenschaften der Modellmaterialien bestimmt, d.h. Porengröße bzw. Porengrößenverteilung sowie die mechanischen Module der porösen Matrix und des unporösen Festkörperskeletts. Es konnte gezeigt werden, dass die ermittelten Materialeigenschaften konsistent mit unabhängigen Messungen und/oder Literaturwerten sind. Hierbei ist zu beachten, dass sich die Erweiterung des adsorption-stress-Modells für eine korrekte Auswertung der experimentellen Daten als zwingend erforderlich erwies. Des Weiteren konnte gezeigt werden, dass die adsorptionsinduzierte Deformation von ungeordneten mesoporösen Aero-/Xerogelstrukturen qualitativ denselben Mechanismen folgt, die für das geordnete, hierarchisch strukturierte, poröse Silica identifiziert wurden. Die entsprechende quantitative Modellierung erwies sich allerdings als schwierig, da die Poren in Aero-/Xerogelstrukturen geometrisch schlecht zu fassen sind. Gute Übereinstimmung zwischen Modell und Experiment konnte nur für das Stadium gefüllter Poren und den relativen Druckbereich der Monolagenbildung erzielt werden. Der Zwischenbereich der Multilagenadsorption erfordert ein komplexeres Modell, um die Spannung quantitativ korrekt zu beschreiben, die sich auf Grund der gekrümmten Adsorbat-Adsorptiv-Grenzfläche im Material ausbildet. Mit Hinblick auf mikro-mesoporöse Kohlenstoffxerogele konnte gezeigt werden, dass sich dort Deformationsmechanismen von Mikro- und Mesoporen überlagern. Die Dehnungsisothermen der Zeolithe wurden nur qualitativ ausgewertet. Das Ergebnis für den Zeolithen vom Typ FAU stimmt gut mit anderen in der Literatur beschriebenen Experimenten und dem theoretischen Verständnis überein, das sich aus dem adsorption-stress-Modell ergibt. Im Gegensatz dazu ist die gemessene Dehnungsisotherme des Zeolithen vom Typ LTA eher ungewöhnlich, da sie monotone Expansion des LTA-Zeolithen über den gesamten Druckbereich zeigt. Qualitativ kann dieses Ergebnis ebenfals mit dem adsorption-stress-Modell erklärt werden, aber eine detaillierte, quantitative Analyse übersteigt den Rahmen dieser Arbeit. Insgesamt erweist sich die Analyse der adsorptionsinduzierten Dehnungen der Modellmaterialien als geeignetes Mittel, um Informationen über deren strukturelle und mechanische Eigenschaften zu erlangen, was auch die Steifigkeit des unporösen Festkörperskeletts miteinschließt. Desweiteren zeigen Untersuchungen an aktivierten und geglühten Kohlenstoffxerogelen, dass adsorptionsinduzierte Deformation insbesondere geeignet ist, um kleine Änderungen an Mikroporenstrukturen zu analysieren

AbstractLarge lightweight alloy skin panels are extensively utilized in the aerospace industry and serve as crucial components constituting the outer shells of aircraft, launch vehicles, manned spacecraft, and other equipment. However, due to their thin-walled nature and limited stiffness, they are susceptible to clamping deformation and machining-induced deformations. Vacuum adsorption technology is widely employed in aircraft manufacturing to mitigate part deformation during machining through the utilization of profiling molds. However, to achieve the milling and drilling tasks in a single clamping process, it is necessary to reserve drilling positions in the vacuum adsorption mold. Unfortunately, this leads to significant deformation of the aircraft skin at the reserved drilling positions during processing. This article utilizes finite element simulation technology to analyze the deformation of the aircraft skin during the vacuum adsorption clamping process. The simulation results indicate that the maximum deformation reaches 5.602 mm, which primarily occurs at the middle hole of the vacuum adsorption mold. To address this issue, the article proposes a solution of adding sealing strips around the reserved holes. This solution effectively reduces the deformation of the skin during the processing stage.

In chapter 8, we applied the bracket formalism to the relatively old problem of incompressible and isothermal viscoelastic fluids. In addition to these assumptions concerning the state of the fluid medium, we therein assumed that the polymer concentration (in the case of polymer solutions) was constant. Although even in this case we were able to find some new results, it is through new applications altogether that the major advantages of this technique will be applied to the fullest extent. Thus, in this chapter we wish to study three new applications of the generalized bracket to outstanding problems concerning viscoelastic fluids. The first section of this chapter is concerned with the complications induced in viscoelastic-fluid modeling by considering compressible and non-isothermal systems. In the second section, we present the analysis of simultaneous concentration and deformation changes associated with the bulk flow of dilute polymer solutions in a form also suitable for the description of flow-induced phase separation. In the third and final section we focus our attention on the solid-surface/polymer interactions which may lead to an apparent “slip velocity” or “adsorption layer” at the interface. We consider §9.3 as the culmination of chapters 8 and 9, and therefore we present it last despite the fact that the natural order for chapter 9 would have been the reverse of what is given below, going from the simplest to the most complex. This last section is the perfect example of our theme of consistently abstracting microscopic information to the macroscopic level of description. Because of the abundance and variety of thought on the issue of flow-induced polymer migration, §9.2 is very inconclusive at this point in time. Its presence here is solely to stimulate additional thought upon this issue. In industrial applications involving polymers, rarely does the engineer deal with an isothermal, and, consequently, incompressible fluid. Most processes are performed at extremely high temperatures, and much heating and cooling design goes into the successful process. Indeed, even if industrial processes were performed at constant temperature, one would still need to handle non-isothermalities since polymers produce large degrees of viscous heating during flow.

Microcantilever-based biosensors are rapidly becoming an enabling sensing technology for a variety of label-free biological applications due to their wide applicability, versatility and low cost. It is thus imperative for us to reveal the physical origin of adsorption-induced deformation, and to further analyze its implication of microscopic mechanisms on macroscopic deformation. In the paper, we study adsorption-induced surface stresses and microcantilever motion in alkanethiolate SAMs on Au surface. We develop a multiscale method that can analyze deformation of micro-cantilever beam subjected to bio-adsorption mechanisms calculated by ab-initio simulation and classical molecular dynamics. The adsorption mechanisms of different SAMs adsorbed on Au(111) surface, in the dry and liquid phase, are studied by ab-initio simulation and the adsorption-induced stresses are calculated through the multiscale method. The results give insight into the atomic forces and positions that play a key role in producing adsorption-induced surface stresses and resultant mechanical bending of microcantilevers.

A 1 cm × 1 cm biosensor chip for analyzing DNA hybridization is developed by CMOS process. The sensor chip has 6 measurement regions, each region with 3 pairs of parallel microcantilever of 125 × 60 × 0.75μm. The microcantilever is a 4-layer structure composed of an immobilized surface layer, a top insulation layer, an embedded piezoresistive layer, and a bottom insulation layer to measure the nano-deformation induced by the surface-assemble monolayer of alkanethiols on Au. By the Langmuir adsorption model, the estimated adsorption rate of the ssDNA is 0.005sec−1. The design has intrinsic sensitivity needed in biochemical applications such as detecting nucleotide polymorphism and single base mutation to sequence DNA. The capability of in-situ, multipoint measurement promise many frontiers to be explored.

Abstract A thermodynamically rigorous constitutive model is used to describe the full coupling among the nonlinear processes of transport, sorption, and solid deformation in organic shale where the pore fluid is the binary mixture of carbon dioxide and methane. The constitutive model is utilized in a numerical solution that simulates injection of carbon dioxide in shale before producing carbon dioxide and methane from the same. The solution considers advection and diffusion as viable mechanisms of pore fluid transport where the latter comprises molecular, Knudsen, and surface diffusion in ultralow permeability shale. Results indicate that complete or partial exclusion of the coupling between sorption and solid phase deformation from the solution would result in underestimation of carbon dioxide storage capacity and natural gas recovery factor of the rock. In this aspect, sorption-induced deformation and strain-induced changes in gas sorption capacities are all conducive to both outcomes.

Abstract This paper presents the design and testing of a bioinspired compliant suction cup with tunable elastic stiffness using shape memory alloy (SMA). We embedded SMA wires into a compliant suction cup for stiffness tuning. When the voltage is input, it increases the stiffness of the suction cup body and helps prevent deformation. Further, a bending moment is applied to the suction cup lip in contact with the surface, which reduces the probability of gas leakage as well as the risk of adsorption failure. In the experiment, suction cups with and without embedded SMA are tested respectively. The maximum pull-off forces and adsorption time are measured via an MTS tester, and the pressure values induced by SMA’s tuning effect on the cup lip are recorded by membrane sensors. Results show that under the same preloading forces, the adsorption force is almost identical, while the adsorption maintaining time of the suction cup with embedded SMA is increased by 365% at the maximum compared with that without SMA. The force generated by the bending moment applied to the lip increases by 360% at the maximum when the SMA is activated. The strain of the sample embedded with SMA is 186% less than that of the sample made of pure soft material at 20kPa stress. The results indicate that the embedded SMA can help increase the stiffness, reduce the deformation of the suction cup body, and enhance adsorption maintenance ability.

ABSTRACT: CO2 sequestration along with enhanced coalbed methane (ECBM) has received considerable attention for energy recovery and CO2 storage. CO2 injection not only reduces permeability due to the swelling effect but modifies the temperature field, resulting in coupled thermo-mechanical coal deformations. Limited efforts have been devoted towards the understanding of thermo-mechanical deformations in the coalbed methane (CBM) industry. This study proposed a theoretical model of thermal expansion coefficients through energy principle. Direct measurements of coal deformations with variations in temperature and pressure were carried out. The results indicate that thermo-induced deformation linearly correlates with temperature variations with estimated thermo-deformative coefficients between 8×10-5/K to 10×10-5/K, falling within the theoretical bounds. Additionally, the coal matrix retains its elastic properties after thermal cycling. The mechanical compression at different temperatures exhibits similar trends, increasing linearly with pressure. The matrix bulk modulus increases with pressure cycles at elevated temperatures, indicating that the coal becomes stiffer due to residual strain and gradually increases with pressure depletion. Anisotropic matrix deformation was observed when the temperature was above 273.15 K. The deformation of the coal can have significant implications on the evolution of effective stress, permeability, and localized failure, ultimately controlling CO2 sequestration and long-term CBM production. 1. INTRODUCTION CBM is an unconventional natural gas resource stored within coal seams. Over the past four decades, CBM has developed rapidly and become an important energy source in the United States, Canada, Australia, China, et al. (Yang & Liu, 2021). CBM is known for its relatively low risk associated with low costs due to the maturity of CBM exploration, drilling, completion, and stimulation processes (Flores, 2013). In the United States, CBM production peaked at 1.97 trillion cubic feet (TCF) in 2008, and as of 2022, it still contributes 0.72 TCF, accounting for 2% of the overall U.S. natural gas production (U.S. Department of Energy, 2022, 2023). ECBM was first proposed by Puri (Puri & Yee, 1990) to address the inefficiencies resulting from the reservoir pressure reduction during the late time reservoir depletion. More recent attention has focused on the CO2-ECBM technology and CO2 storage, as depicted in Figure 1 (a) (Jessen, Tang, & Kovscek, 2008; Lin, Ren, Cheng, & Nemcik, 2021; Mazzotti, Pini, & Storti, 2009). CO2 can displace methane attributed to its higher affinity for coal, effectively enhancing methane recovery, particularly in low-permeability CBM reservoirs (White, Strazisar, Granite, Hoffman, & Pennline, 2003). Furthermore, this innovative process has a long-term environmental benefit of sequestering and storing CO2 within underground coal seams. The storage potential of CO2 in unminable coal seams is considerable, with estimated capacities ranging from 3 to 200 GtCO2, making it a relevant option for mitigating anthropogenic CO2 emissions (Mazzotti et al., 2009; Metz, Davidson, De Coninck, Loos, & Meyer, 2005). Many researchers have considered that during the CO2 injection process, CO2 adsorption can induce a significant matrix swelling (Figure 1 (b)), resulting in cleat closure and reduction in permeability (Pekot & Reeves, 2002; J.-Q. Shi & Durucan, 2005; Siriwardane, Gondle, & Smith, 2009; G. X. Wang, Wei, Wang, Massarotto, & Rudolph, 2010; White et al., 2005). This reduction in permeability limits the CO2 injection rate, which is critical for the success of CO2-ECBM (Bai et al., 2022; Lu & Connell, 2008; Zhang & Ranjith, 2019). Indeed, in addition to sorption-induced strain, the coal deformation can also be influenced by fluid composition, temperature, and water saturation, as demonstrated in Figure 1 (c), (d), and (e).

Abstract Recently short-term laboratory primary creep i.e., time-dependent deformation under triaxial in situ stress condition of ultra-low permeable gas shales have been utilized to work out geomechanical impacts of field development cycle such as modification of in situ stress state, prediction of production induced deformation, and understanding of fracture closure mechanism. However, obtaining creep data from the laboratory method is tedious, time-consuming, and costly. A simple power law model as a function of time involving instantaneous elastic compliance of the studied material B, and time dependent component n is used to describe creep and stress relaxation owing to the superposition principle of linear viscoelastic materials. Gas shales usually have a large specific surface area (SSA) because of the dominance of clay minerals (Illite, Smectite, Kaolinite, and Chlorite) and/or total organic carbon (TOC). Low-pressure nitrogen gas adsorption is a quick and cost-effective method to derive specific surface area value SN2 on powdered gas shale samples. From the observed strong empirical correlation between creep parameters and SN2value as well as with weak phase fraction ClayTocPHI (combination of clay, porosity, and TOC), a novel indirect approach is proposed to predict primary creep constitutive parameters either from the specific surface area (SSA) value SN2 or weak phase fraction ClayTocPHI of multiple gas shales at deeper subsurface formations (Figure 1). These gas shales cover a broad range of mineralogy, maturity, porosity, and depositional history. Through a case study, empirically derived creep parameters from SN2 are utilized to predict the least principal stress Shmin magnitude at depth of a six lithological layered gas shale formation with a viscoelastic stress relaxation approach. Direct field measurement validated the layered variation of the predicted Shmin magnitude.