Multiscale Characterization Method Research Articles

Polyaluminum enhanced dehydrated cement paste activated slag: Mechanical performance and microstructural analysis

Dehydrated cement paste (DCP) activated slag offer a promising sustainable alternative to traditional Portland cement, but their inadequate mechanical strength limits practical applications. This study investigates the potential of polyaluminum chloride (PAC) to enhance the performance of DCP activated slags, utilizing multi-scale characterization methods. Results demonstrate that PAC incorporation significantly promotes strength development, enabling the binder to meet requirements for most engineering applications. PAC accelerates Ca(OH)2 consumption, and facilitates additional hydration product formation that refines the pore structure, leading to the densification of samples. These improvements in strength and microstructure are attributed to the modified slag dissolution and the enhanced polymerization of the C-A-S-H gel. Furthermore, the underlying role of PAC on the hydration, mechanical performance and microstructural development of DCP activated slags are discussed.

The mechanism for annealing-induced ductile to brittle transition in a high-temperature titanium alloy and its mitigation

By investigating the relation between microstructure evolution and tensile responses of a BTi6431S alloy at room temperature and 700 °C, this study finds an annealing-induced ductile-to-brittle transition phenomenon in the near-α titanium alloy. The high strength of the as-received BTi6431S alloy is rooted in the high dislocation density and collective dislocation behavior in the α phase. However, after annealing at 650 °C, the alloy exhibits brittle fracture at room temperature. Using multiscale characterization methods, we attribute this phenomenon to the presence of brittle precipitates and the change of dislocation structures near the surface of BTi6431S titanium alloy. Silicides are generated in the vicinity of the surface region due to the relatively high dislocation density on the surface after the rolling process. The room temperature ductility can be restored by removing the near-surface area. When the alloy is tested at 700 °C, most of the near-surface brittle silicides and dislocations can be eliminated, because the deformation is mainly affected by dislocation behavior and dynamic recrystallization at high temperature. The findings in this study can advance the understanding of alloying effects on the mechanical behavior of high-temperature titanium alloy. The results suggest that inhibiting silicide formation and controlling the environmental temperature during service are potential approaches for maintaining the mechanical performance of this near-α titanium alloy.

Investigation on creep behavior and microstructural features of an additively manufactured Ti2AlNb alloy upon isothermal deformation at elevated temperature

In this work, we investigated the creep behavior of a SLM-printed Ti2AlNb alloy and systematically examined the corresponding microstructural features using multi-scale characterization methods. A single β-phase matrix is produced in the alloy due to the extremely fast solidification process. A new O phase transformation is triggered by the applied external stress following the crystallographic relation of (101) B2//(001) O, compared with the aged counterpart in which only the conventional β-to-O phase transformation with a (110) B2//(020) O relation occurs. This phase transformation contributes to improving the creep resistance of printed specimen test applied with creep stress of 150 MPa at 923 K, suggesting a final steady strain rate of ∼5 × 10–8/s. This work further elucidates the mechanisms of the microstructural evolution of SLM-printed Ti2AlNb-based alloys on creep and offers valuable insights for the future development of high creep-resistance alloys.

Toughening mechanism and delayed fracture analysis of 4145H steel under intercritical quenching heat treatment process

Tuning thermal treatment schedule has been confirmed as an effective technical route for achieving optimum properties of steels. In the present work, the intercritical quenching tempering(IQT) process was applied to steel 4145H for oil drilling tools, and the performance enhancement and delayed fracture mechanism of the IQT process were comprehensively elucidated using multiscale characterization methods and various mechanical tests. Compared with the quenching and tempering(QT), the IQT process results in a separate island ferrite plus finely tempered sostenite organization, which reduces the dislocation density in the tempered organization and increases the proportion of recrystallized grains. Due to the grain refinement effect of multiple quenching, the pristine austenite grains were refined by 58 %. At the same time, the proportion of large-angle grain boundaries increased from 68.6 % to 80.3 %. The results of the mechanical property tests show that the intercritical 790 °C quenching treatment and tempering at 600 °C exhibits a tensile strength of 1087 MPa, a high elongation of 21.72 %, and a high impact work of 104 J compared to QT. The improved impact toughness is mainly attributed to the grain refinement effect of multiple quenching and the large-angle grain boundaries provided by the composite ferrite organization and M23C6 carbides. The impact of different ratios of large-angle grain boundaries on crack extension was also evolved by means of the crystal phase field, and the delayed fracture effect of large-angle grain boundaries was verified.

Development of durable engineered cementitious composites using local ingredients

Environmental and economic concerns impel large volume construction materials to employ as many local ingredients as feasible while maintaining high performance. In this research, durable Engineered Cementitious Composites (ECC) are developed using local desert sand from Saudi Arabia, polypropylene/polyethylene fibers, and crystalline admixture. Multi-scale characterization methods were utilized, including compressive/uniaxial tensile tests, self-healing tests, permeability tests, and micro/chemical analyses. Mercury intrusion porosimetry, X-ray diffraction, and scanning electron microscopy were employed to interpret the mechanisms underlying the observed macroscopic behavior. The developed ECC possesses the highest ductility (8.6 %) and lowest crack width (below 63 μm) among desert sand ECCs in the literature. The crystalline admixture produces additional C-S-H gel and crystalline Ca(OH)2 precipitates, endowing the desert sand ECC with enhanced self-healing ability. The self-healed ECC demonstrates improved durability with reduced permeability and enhanced mechanical properties recovery. The localized durable ECC holds promise for both rehabilitating aging infrastructures and newly constructed facilities in regions with large supplies of desert sand.

Elucidating degradation mechanisms of Co-free high-Ni layered oxide cathodes for Li-ion batteries via advanced X-ray-based characterization methods

High-Ni layered oxide cathodes without Co are being investigated as potential cathode materials for Li-ion batteries with high energy density. By decreasing the Co content, these cathodes not only boost energy density but also alleviate concerns about the supply instability and fluctuating cost of Co raw materials. However, the elevated Ni content in the layered oxides causes distinct chemo-mechanical degradation mechanisms that inhibit their commercial application. In order to gain insight into the degradation process at various scales, from the atomic to the particle and the electrode levels, and to devise ways to prevent degradation, multi-scale characterization methods are essential. In this review, we critically evaluate the role of Co substitution in high-Ni layered oxides and the impact of Co content on the chemo-mechanical degradation process. Furthermore, the use of advanced X-ray-based characterization methods, which have helped shed light on the degradation mechanisms of high-Ni cathodes, is also discussed.

Enhanced strength-ductility synergy in a new 2.2 GPa grade ultra-high strength stainless steel with balanced fracture toughness: Elucidating the role of duplex aging treatment

Tuning thermal treatment schedule has been confirmed as an effective technical route for achieving optimum properties of steels. In the present work, the role of a unique duplex aging process on the enhanced strength-ductility synergy in a newly designed 2.2 GPa grade martensitic ultra-high strength stainless steel (UHSSS) was fully elucidated utilizing multi-scale characterization methods and various mechanical tests. Compared with the first aging-treated steel, the strength and ductility are synergistically enhanced after the second aging treatment due to increased volume fractions of Laves phase and reversed austenite as well as intensification of spinodal decomposition. Specifically, nanoprecipitates not only act as “obstacles” for dislocation movements, but also delay the deformation localization and necking instability, resulting in the dramatic increase of both strength (359 MPa for yield strength) and ductility (17% for reduction of area). The second aging-treated steel exhibited an impressive combination of mechanical properties: yield strength ∼ 1876 MPa, ultimate tensile strength ∼ 2259 MPa, elongation to fracture ∼ 11.5%, reduction of area ∼ 52%, and fracture toughness ∼ 43 MPa·m0.5 at ambient temperature. As revealed by the microstructural characterization, the aged steel is primarily strengthened by three distinct types of nanoprecipitates, including M2C, Laves phase, and α’Cr domains. The strengthening contributions of these precipitates were quantitatively estimated in terms of Orowan dislocation looping or cutting mechanisms. It is found that Laves phase contributed the maximum strength increment induced by precipitation hardening. An accessible pathway consisting of duplex aging treatment and co-precipitation of multiple nanoprecipitates is thus validated to exploit high-performance UHSSSs.

Optimization of the Evaluation Indexes for Asphalt UV Aging Behaviors based on Multi-scale Characterization Methods: from the Evolution of Their Physical-Chemical Properties and Microscope Morphology

Aiming to propose some suitable evaluation indexes to quantitatively characterize the UV aging resistance of asphalt binders, firstly, effects of UV aging on asphalt’s properties were comprehensively explored from the multiple scales, including their physical rheological properties, chemical compositions and microscope morphology. The above properties of asphalt binders before and after UV aging were respectively measured with the conventional physical properties tests, dynamic shear rheometer (DSR) test, thin-layer chromatography test (TLC) test, gel permeation chromatography (GPC) test and atomic force microscopy (AFM) test. Subsequently, based on some principles for establishing evaluation indexes, such as discrimination, regularity and consistency, the optimal evaluation indexes were proposed to quantitatively characterize the UV aging resistance of asphalt binders. Finally, relationships between the physical properties, chemical compositions and micro morphology of asphalt binders were discussed with the Pearson correlation coefficient method. Test results show that UV aging has a significant effect on physical rheological properties of asphalt, and ranking of aging resistances among asphalt binders evaluated by different macro indices are nearly consistent. Among these macro indexes, the G-R parameter aging index are proved to be the evaluation index with the highest discrimination degree, followed by complex shear modulus G* aging index (60 °C, 10 rad/s, 1 %) and zero shearing viscosity ZSV aging index (60 °C). Chemical composition test results demonstrate that with the growth of UV aging degree, resins components in asphalt increase gradually, while aromatics components decrease, which results in the proportion of larger molecular size (LMS) in asphalt gradually increases. And AFM test results show that UV aging will cause the number of the “bee structure” and roughness values of asphalt gradually decrease, thus promoting the transformation of the asphalt micro structure to smooth. Pearson correlation analysis indicates the compared with the roughness Ra, the Gel index Ic and LMS possesses higher correlation with G-R and G*, whose R values both exceed 0.8. Thus, it may be appropriate to adopt some chemical composition evaluation indexes (such as Ic, LMS) to characterize the UV aging degree of asphalt binders from the microscope perspective.

Mechanical properties and microstructure evolution of additive manufactured 316L stainless steel under dynamic loading

Stainless steel 316L alloy with a complete austenite phase was manufactured using the Laser Engineered Net Shaping (LENS) technique. The microstructure of LENS-316L from the sub-millimeter to nanometer domains was analyzed using multi-scale characterization methods. The dynamic behavior of LENS-316L was studied by the Split Hopkinson Pressure Bar (SHPB) test. In this study, the dominating strengthening mechanism of the microstructure in LENS-316L was the dislocation strengthening mechanism, providing approximately 153 MPa. The molten pool deforms significantly after the material was dynamically compressed. When the strain rate reached 5000 s−1, the material exhibited an adiabatic shear phenomenon and formed adiabatic shear bands. The width of the shear band decreased with the increase in the strain rate. When the strain rate increases from 3000 s−1 to 4000 s−1, the dislocation density increases, the number of twins increases, and the twin thickness decreases. The effect of varying strain rates (3000, 4000, 5000, 6000 s−1) and varying temperatures (20, 150, 272, 450, 620 °C), on the stress–strain curves of the material were studied through the SHPB test. Additionally, the traditional Johnson–Cook (JC) constitutive model was modified. The modified constitutive model considers the effects of the strain rate and temperature softening coefficients in the strain hardening stage to predict the mechanical behavior of LENS-316L at high temperature and strain rates. Model predictions were in agreement with the experimental data. This study provides important insights for applying the LENS-316L complex construction in a dynamic load impact environment.

New insights into the recrystallization behavior of large-size Mo–3Nb single crystal based on multi-scale characterization

The occurrence of recrystallization will cause catastrophic damage to the structure of metallic single crystal, which can be avoided by choosing crystal orientation reasonably. In this work, the effect of crystal orientation on the recrystallization behavior of single crystal is investigated using multi-scale characterization method. The electron backscattered diffraction analysis shows that in mesoscopic scale, the recrystallization behavior of Mo–3Nb single crystal exhibits a strong orientation dependence, which the new recrystallization grains are produced in the <111>-oriented single crystal, while the single crystal structure is still retained in other orientations. At the micro scale, the elongated dislocation cells with certain misorientations appear in the <111>-oriented single crystal, while only the dislocation walls and parallel dislocation cells distribute on the single crystal with the <110> and <112> orientations, respectively. The length of dislocation lines in deformed single crystal with <111> orientation is calculated using molecular dynamics to be 3491.22 Å, which is much longer than that of the <112> orientation (1133.27 Å) and the <110> orientation (2862.68 Å), suggesting a higher crystal distortion and easier recrystallization in the <111> orientation. In addition to the coalescence mechanism of discontinuous sub-grains, the shear band also plays an important role in promoting recrystallization nucleation. This work provides reference value for the secondary processing of molybdenum single crystal, so as to obtain more excellent products and expand its potential application.

Evolution of dislocation cellular pattern in Inconel 718 alloy fabricated by laser powder-bed fusion

The dislocation cellular pattern (DCP) is a predominant microstructure in laser-based additively manufactured metals. Understanding the evolution of DCP paves the way for optimizing the laser-produced microstructure, which can ultimately modify the mechanical properties. In this work, we combined tensile test and multiscale characterization methods to systematically study the development of DCP in deformed Inconel 718 alloy that was processed with laser powder-bed fusion technique. Although the DCP has a similar appearance as the deformation-induced dislocation cell, the wall of DCP consists of solute atoms and small precipitates, which are absent in the conventional dislocation cell. The development of DCP during plastic deformation was independent of crystal orientation. The evolution process of DCP can be divided into two stages. At a tensile strain lower than 10%, the size of DCP was independent of flow stress. At higher strain levels, the DCP size decreased; however, the maximum reduction obtained at the strain-to-failure was only ~27% of the undeformed DCP size. The geometrically necessary dislocation density at DCP boundaries increased as increasing strain. Because of the interactions of dislocation tangles, solute atoms, and precipitates in the DCP wall, the DCP configuration is stabilized, and its role in deformation was neither like that of the dislocation cell nor that of the grain boundary.

Stability and thinning behaviour of aqueous foam films containing fluorocarbon and hydrocarbon surfactant mixtures

The stability and thinning behaviour of the liquid foam film containing fluorocarbon and hydrocarbon surfactant mixtures were investigated quantitatively by using the optical interferometry technique. Multiscale characterization methods were employed to study the relationships between foam stability, film thinning behaviour, and bulk and interfacial properties. The results show that the liquid film from the SDS solution is unstable with rapid marginal regeneration. Adding fluorocarbon surfactant FC1157 can significantly enhance film stability and slow down liquid drainage rates of the liquid film. For the SDS film with mobile surfaces, the film thinning process follows a power-law behaviour and the thinning exponent becomes less negative by increasing FC1157 concentrations. At very high FC1157 concentrations, the film surface becomes relatively immobile and the thicknesses profile is close to the theoretical prediction of a rigid film. It should be emphasized that the bulk aggregation and surface adsorption behaviours of surfactants affect the thinning rate and stability of the liquid film. Large aggregates assembled from FC1157 molecules produce a viscous solution that offers high resistance to liquid motion. Due to low compression velocities at the film border, the film containing SDS/FC1157 mixtures with relatively immobile surfaces has larger marginal regeneration wavelengths than that of the mobile film stabilized by SDS alone. In addition, foam stability results indicate that there is a qualitative relationship between the macroscale foam and microscale single film in terms of their lifetime.

Multiscale Characterization of Photovoltaic Modules—Case Studies of Contact and Interconnect Degradation

The current popularity of photovoltaic (PV) systems is due in large part to their exceptional reliability and significantly lower cost than other energy sources. Studying cell and module degradation is key to promote further development in the state of the art. Fielded oraccelerated aged modules exhibit different failure modes, of which metallization degradation (contacts and interconnections) is prevalent. In this work, we discuss how multiscale characterization methods can be applied to a variety of module technologies that have been field exposed and have undergone accelerated age testing. These methods include performing characterization on the module level, cell level, and finally the materials level. The observed performance losses from the module- and cell-level characterization can be correlated with materials properties to find out the root cause of degradation. We recommend an initial nondestructive characterization suite, including module- and cell-level current–voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$I\text{--}V$</tex-math></inline-formula> ), Suns– <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OC</sub> , photoluminescence and electroluminescence imaging, quantum efficiency, ultraviolet fluorescence imaging, and thermal infrared imaging. Samples are then extracted from particularly degraded regions of the module and prepared for materials characterization techniques, such as top-down and cross-sectional scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, secondary ion mass spectrometry, Raman spectroscopy, and transmission electron microscopy, allowing a deeper look into the mechanism behind the metallization degradation. This article serves as an instructional review to introduce the different multiscale characterization methods and how they can be effectively applied to perform PV degradation studies. We also share some of our examples and discuss the strengths, limitations, and best practices for each of the characterization techniques.

Effects of tribo-film on wear resistance of additive manufactured cobalt-based alloys during the sliding process

Cobalt-based alloys are widely used in the fields of aerospace and automobile, whereas poor tribological performances under low-load sliding conditions limit their applicability. In the present study, three cobalt-based alloys with Al and Ni additions were fabricated by direct laser deposition, and their tribological properties were investigated. The friction tests were carried out by sliding specimens against GCr15 balls in the same conditions. The lowest coefficients of friction and wear loss were observed during friction tests of the 2Al alloy, but the 2Al25Ni alloy had inferior performances. Multiscale characterization methods were performed and revealed that the tribo-films are comprised of nano-scale oxides and amorphous structures, forming on the worn surfaces of the 2Al and 2Al25Ni alloys. Meanwhile, the amorphous structure generated on the top of the interface was observed to retain debris, which was helpful for the tribo-film generation. Compared with the CoCrW alloy, due to the high oxidation capacity, the tribo-film on the worn surface of the 2Al alloy was beneficial for lubrication and wear resistance. Although the thick tribo-film was formed on the 2Al25Ni alloy, the coefficients of friction and material loss increased, owing to the film was generated by high temperature. This work gives a better understood of the tribo-film formation and influences on wear and friction behavior, getting an effective method to improve wear resistance of cobalt-based alloys.

On the microstructure and tensile properties of Inconel 718 alloy fabricated by selective laser melting and conventional casting

In this work, we investigated the microstructure and tensile properties of Inconel 718 alloy processed by selective laser melting (SLM) and conventional casting technique using multiscale characterization methods. Results indicated that a columnar grain structure containing cellular structure units with submicron size was the major feature in the as-printed Inconel 718 alloy. At the cellular structure boundaries, the high-density dislocation tangles, segregation of Nb/Mo atoms and nano-sized Laves phases were found. Meanwhile, we also observed dislocation pile-ups and stacking faults in the interior of the cellular structure. In contrast, in the as-cast Inconel 718 alloy, both the grains and Laves phases were much coarser. Discrete dislocations, dislocation tangles and [Formula: see text]” precipitates were locally observed in the grains. Tensile results showed the as-printed Inconel 718 alloy had a higher strength and a lower elongation in comparison with those in the as-cast alloy. Based on the experimental results, the formation mechanism of the cellular structure was discussed.

Investigation of the influences of ternary Mg addition on the solidification microstructure and mechanical properties of as-cast Al–10Si alloys

A hypoeutectic Al–10Si-2.0 Mg ternary alloy with high strength and high ductility was developed for as-cast service conditions. The effects of eutectic-forming element Mg on the primary α-Al dendrites, eutectic Si structure, Mg2Si intermetallic compound, mechanical properties and fracture behavior were systematically investigated via multiscale characterization methods. Interestingly, the results demonstrated that with the increasing Mg content, the secondary dendrite arm spacings of the primary α-Al dendrites were significantly reduced, and the grain size was refined, while the flaky eutectic Si structure was fully modified into a coral-like morphology. Additionally, the size of the Mg2Si intermetallic phase sharply decreased, and it was distributed much more uniformly in the interdendritic/intergranular eutectic regions. In contrast with the binary Al–10Si alloy, the yield strength, the ultimate tensile strength and the fracture strain were substantially enhanced to 159.4 MPa, 275.3 MPa and 14.1%, respectively, which correspond to improvements of 131.0%, 70.4% and 27.0%, respectively. The underlying mechanisms that were responsible for the evolution of the microstructure and mechanical properties are explicitly discussed.

Multiscale characterization of pore structure and connectivity of Wufeng-Longmaxi shale in Sichuan Basin, China

By combining the micro-CT, SEM, FIB-SEM and FIB-HIM, a multiscale characterization method was explored to study the pores in Wufeng-Longmaxi shale, Sichuan Basin, China. This method extends the previous test scale so that the sub-10 nm pores can be visualized in both 2D and 3D. In order to consider the homogeneity or heterogeneity and verify the representativeness of samples, REV and REA (representative elementary volume and area) was determined. Pores in shale were classified as organic pore, inorganic pore and micro-fracture based on SEM, and their surface porosity and pore size distribution were calculated. By 3D reconstruction of FIB-SEM and FIB-HIM, the pore networks were visualized down to sub-10 nm, and the connect patterns of pores through throats were carefully investigated. Results show that, REV and REA are different at different scale. The cube and square growing pattern, grain size, feature distribution and imaging accuracy can affect REV and REA in different degree. SEM quantification results indicate that, the surface porosities of OM particles (ϕS OM) of two 1st member of Longmaxi samples are larger than those of Wufeng samples, indicating the organic pores of 1st member of Longmaxi samples are more developed than Wufeng samples. The size of inorganic pores of Wufeng samples are larger than those of Longmaxi samples. The permeability shows a positive correlation with surface density of micro-fractures. The 3D pore network analysis of FIB-SEM further shows the interconnectivity of 1st member of Longmaxi samples are better than Wufeng samples. The interconnected pores are mainly between 10 and 30 nm, and the throats are concentrated between 0 and 30 nm for both 1st member of Longmaxi samples and Wufeng samples. This is further refined by FIB-HIM, in which, the interconnected pores and throats are concentrated below 10 nm. FIB-HIM also provides clear 3D images of how organic pores can be connected by throats, which is a great progress in shale pore characterization.

Research progress on multiscale structural characteristics and characterization methods of iron ore sinter

At present, blast furnace ironmaking is still the main process for producing molten iron, and sinters are the main raw material for blast furnace ironmaking. A sinter with good metallurgical performance can not only ensure smooth operation of the blast furnace but also reduce the blast furnace fuel ratio and increase the molten iron production. Structure is the most important factor affecting the metallurgical properties of the sinter. Thus, the research progress of sinter pore and mineral phase structures was reviewed and the mechanism by which they influence sinter properties was expounded. Multiscale characterization methods for the sinter and their advantages and disadvantages were introduced, and the future research direction of sinter was discussed.

A comprehensive characterization of North China tight sandstone using micro-CT, SEM imaging, and mercury intrusion

A clear understanding of pore structure of tight oil reservoirs is essential for reservoir evaluation and enhanced oil recovery. This paper presents a multiscale characterization method using a combination of pressure-controlled porosimetry (PCP), micro-computed tomography (micro-CT), and scanning electron microscopy (SEM). Four tight sandstone samples from Chang 7 Formation in the Ordos Basin were collected for petrophysical characterization. Pore-throat size distributions (PTSDs) for these samples were measured via PCP. A high-resolution micro-CT scan (1 μm/pixel) was used to acquire 3D volumetric images of small core plugs to evaluate pore connectivity of these samples. Additionally, high-resolution digital images were obtained through SEM to identify different pore types. SEM analysis shows that pores in tight sandstones could be classified into four types, i.e., residual interparticle pores, grain dissolution pores, clay pores, and micro-fractures. Residual interparticle pores are often coated by fibrous illite and chlorite. Grain dissolution pores are mainly deduced from the dissolution of grain minerals, among them the feldspar dissolution pore is the primary type. According to the PCP experiments, these samples exhibit multiscale pore structures with a wide range of PTSD from 9.2 nm to 500 μm dominated by nanopores. Average mercury intrusion saturation and permeability contribution value of the dominating nanopores are 63.61% and 80%, respectively. Given the unresolved nanopores, CT images were segmented into three phases, including pore space, grain phase, and clay minerals. The results of connectivity analysis demonstrate that macroscopic pores are mostly connected by clay phases, implying that nanopores provide the critical flow paths. This novel multiscale characterization approach provides us a better understanding of complex pore structures of tight sandstones.

Multiscale characterization method for line edge roughness based on redundant second generation wavelet transform

We introduce a multiscale characterization method for line edge roughness (LER) based on redundant second generation wavelet transform. This method involves decomposing LER characteristics into independent bands with different spatial frequency components at different scales, and analyzing the reconstructed signals to work out the roughness exponent, the spatial frequency distribution characteristics, as well as the rms value. The effect of noise can be predicted using detailed signals in the minimum space of scale. This method was applied to numerical profiles for validation. Results show that according to the line edge profiles with similar amplitudes, the roughness exponent R can effectively reflect the degree of irregularity of LER and intuitively provide information on LER spatial frequency distribution.