Pore Spacing Research Articles

Macro-micro structure engineering of bio-spore-derived hard carbon as an efficient anode in sodium ion batteries

Elucidating the macro–micro structures of hard carbon is critical to address the issues of deficient Na+ storage capacity at the anode in Na+ ion batteries. Herein, hard carbon materials with various macro–micro structures were synthesized by pyrolyzing the spores of Calvatia Gigantea (SCG) as precursors treated by a coupling strategy with a dehydration process via concentrated H2SO4 treatment and the removal of inherent Si species by NaOH. Research results demonstrate that the process of concentrated H2SO4 pretreatment can induce the collapse of original hollow spheres of SCG to form specific hard carbon hollow hemispheres, while the NaOH leaching treatment can further modulate the microstructures of hard carbon. Attributed to the unique characteristics of specific hollow hemi-spherical morphology, ultra-low surface area, rich closed pore and appropriate layer spacing, the hard carbon not only exhibits outstanding specific capacity up to 500 mA h g−1 with a high initial Coulombic efficiency of 90.23 % for Na+ storage, but also presents excellent high-rate capability with 254.88 mA h g−1 at 5 A/g and cycling stability with a capacity retention rate of ≥80 % after 4102 cycles. The outstanding performance exceeds the vast majority of reported hard carbons for Na+ storage. Theoretical analysis further reveals that increasing closed pores constructed by distorted graphite-like layers together with proper lattice distance and curvature in hard carbon is essential to improve Na+ storage capacity. The coupling strategy of tuning the morphologies and microstructures of spore-derived hard carbon in the work provides new insights for developing advanced hard carbon with efficient Na+ storage performance.

Interaction effect of adjacent pores on plasma generation inside pores of porous catalysts

A study on the influence of pore characteristics on the microdischarge plasma inside pores of catalyst is important for understanding plasma catalysis mechanism. This article focuses on the effect of pore interaction on plasma production in pores including electron density, electron temperature, and total ion density, etc. These parameters are calculated by solving the electron energy density conservation equation, electron convection diffusion equation, heavy species conservation equation and Poisson equation. The numerical simulation results show that the distribution of electron density, electron temperature and electric field in and near a pore is apparently affected by the adjacent pore, namely, the time-averaged electron density, total ion density and ionization rate in a pore increase with the pore spacing in the range of 8–150 μm because the loss of electrons to the wall due to the adjacent pore decreases with the increasing pore spacing, but there is an opposite law for the time-averaged electron temperature and electric field in a pore; moreover, the pore spacing presents more apparent effect on the plasma generation in a smaller pore and at higher applied voltage, indicating stronger interactions between pores at these conditions. The simulation results show that the pore characteristics of porous catalysts including pore spacing and pore diameter may affect the degradation of pollutants in plasma catalysis processes. The study is important for understanding the plasma catalysis mechanisms, especially the influence mechanism of pore interaction on microdischarge in porous catalysts.

Challenges in porosity characterization of thin films: Cross-evaluation of different techniques

The review article provides an overview of the most important and popular techniques for evaluating the porosity of thin films developed for various applications. These methods include ellipsometric porosimetry (EP), positron annihilation (lifetime) spectroscopy (PAS/PALS), and grazing incidence small-angle x-ray scattering (GISAXS). Special attention is given to the challenges associated with interpreting the measured data and the inherent limitations of each method. It is demonstrated that EP, GISAXS, and PALS are all informative for studying the pore structure in thin films, with each method offering unique insights. GISAXS, in particular, allows for the evaluation of three-dimensional mesostructures, including pore arrangement, pore spacing, and structural order. On the other hand, PALS has a unique advantage in its capability to analyze extremely small isolated pores (free volume). The advantage of EP lies in its simplicity and the possibility to analyze multiple properties from the same set of measurements. The cross-evaluation of different methods offers important insights into the complex pore structure of materials, highlighting the significance of appropriate modeling and interpretation of data.

Liverwort bHLH transcription factors and the origin of stomata in plants

Stomata are distributed in nearly all major groups of land plants, with the only exception being liverworts. Instead of having stomata on sporophytes, many complex thalloid liverworts possess air pores in their gametophytes. At present, whether stomata in land plants are derived from a common origin remains under debate.1,2,3 In Arabidopsis thaliana, a core regulatory module for stomatal development comprises members of the bHLH transcription factor (TF) family, including AtSPCH, AtMUTE, and AtFAMA of subfamily Ia and AtSCRM1/2 of subfamily IIIb. Specifically, AtSPCH, AtMUTE, and AtFAMA each successively form heterodimers with AtSCRM1/2, which in turn regulate the entry, division, and differentiation of stomatal lineages.4,5,6,7 In the moss Physcomitrium patens, two SMF (SPCH, MUTE and FAMA) orthologs have been characterized, one of which is functionally conserved in regulating stomatal development.8,9 We here provide experimental evidence that orthologous bHLH TFs in the liverwort Marchantia polymorpha affect air pore spacing as well as the development of the epidermis and gametangiophores. We found that the bHLH Ia and IIIb heterodimeric module is highly conserved in plants. Genetic complementation experiments showed that liverwort SCRM and SMF genes weakly restored a stomata phenotype in atscrm1, atmute, and atfama mutant backgrounds in A.thaliana. In addition, homologs of stomatal development regulators FLP and MYB88 also exist in liverworts and weakly rescued the stomatal phenotype of atflp/myb88 double mutant. These results provide evidence not only for a common origin of all stomata in extant plants but also for relatively simple stomata in the ancestral plant.

Simulation of crack nucleation in materials with regularly arranged spherical pores under multiaxial loading conditions

A numerical study of the initial stage of crack growth in a material containing spherical pores under multiaxial compression (constrained conditions) has been carried out using the finite element method. The influence of the pore spacing and the mechanical properties of the material on the fracture localization and the direction of crack growth has been analyzed. Both brittle and ductile materials were studied. It has been established that material properties and the mutual arrangement of defects have a significant influence on the direction of propagation of cracks arising on the stress concentrators (structure defects), up to mutually perpendicular directions (for uniaxial of the characteristic sizes of the region of influence of spherical pores on each other, beyond which the stress fields of the neighboring elements of the structure do not overlap. The dependences of the sizes of this area on the elastic characteristics of the matrix material are shown. The obtained results are relevant for obtaining numerical estimates of the duration of the initial stages of quasi- brittle fracture of ceramic-based heterophase materials, refractories in particular. Ill. 6. Ref. 26. Tab. 1.

Simplified Method of Estimating the A300 Micropore Content in Air-Entrained Concrete

It is well known that the most important parameters for predicting the frost resistance of pavement concrete are the air pore spacing factor, L, and the micropore content, A300. The A300 parameter requires complex calculations with the estimation of the air-void size in a 3D space. The procedure is based only on one-dimensional chord lengths. The air-void distribution is used only to determine the content of micropores and has no other practical application. Based on the results of the analysis, it was found that there is a simpler way to estimate the A300 parameter without the tedious calculations described in the EN 480-11 Standard. The presented approach is based on the existing linear correlation between the A300 parameter and the number of chords in 28 length classes. The developed function includes only a few coefficients (eight classes) because only chord lengths of 10-350 µm are statistically significant. This fact is important not only for the simplification of calculations but may also have consequences for the methodology of testing parameters characterizing the structure of air-entrained concrete using the 2D method. The presented function allows the estimation of A300 with a standard error not exceeding 0.02%, so it is useful for practical use.

Study on the Shadow Effect of the Stress Field around a Deep-Hole Hydraulic-Fracturing Top-Cutting Borehole and Process Optimization

The clean utilization and green development of coal resources have become a research focus in recent years. Underground hydraulic fracturing technology in coal mines has been widely used in roof pressure relief, top coal pre-splitting, gas drainage, roadway pressure relief and goaf disaster prevention. Different in situ stress types cause great differences in the stress field around the boreholes, the critical pressure of the fracture initiation, and the direction of the fracture expansion trend; in addition, the stress shadow effect generated by the superposition of stress fields between boreholes relatively close together has a mutual coupling effect on the evolution of the stress field, the development of the plastic zone, and the crack propagation of the rock mass. Therefore, an effective method to solve the problem is to establish a mechanical model of hydraulic fracturing in boreholes for theoretical calculation, determine the influence mechanism of the crack shadow effect, and design a numerical simulation experiment of the equivalent stress fluid–solid coupling of hydraulic fracturing under different pore diameters and spacings. In addition, combining rock mechanics and fracture mechanics to analyze the influence of the shadow effect of the stress field between cracks on the evolution of the equivalent stress and the plastic zone is one of the important advances in this paper. Considering the engineering background of the site, the geological conditions and the requirements of general regulations, it is considered that the parameter selection of roof fracturing hydraulic fracturing technology in the Yushen mining area is more suitable when 0.12 m hole diameter and 3.5 m hole spacing are selected.

Twelve Months of Denosumab and/or Alendronate Is Associated With Improved Bone Fatigue Life, Microarchitecture, and Density in Ovariectomized Cynomolgus Monkeys.

Prolonged use of antiresorptives such as the bisphosphonate alendronate (ALN) and the RANKL inhibitor denosumab (DMAb) are associated with rare cases of atypical femoral fracture (AFF). The etiology of AFF is unclear, but it has been hypothesized that potent osteoclast inhibitors may reduce bone fatigue resistance. The purpose of this study was to quantify the relationship between antiresorptive treatment and fatigue life (cycles to failure) in bone from ovariectomized cynomolgus monkeys. We analyzed humeral bone from 30 animals across five treatment groups. Animals were treated for 12 months with subcutaneous (sc) vehicle (VEH), sc DMAb (25 mg/kg/month), or intravenous (iv) ALN (50 μg/kg/month). Another group received 6 months VEH followed by 6 months DMAb (VEH-DMAb), and the final group received 6 months ALN followed by 6 months DMAb (ALN-DMAb). A total of 240 cortical beam samples were cyclically tested in four-point bending at 80, 100, 120, or 140 MPa peak stress. High-resolution imaging and density measurements were performed to evaluate bone microstructure and composition. Samples from the ALN (p= 0.014), ALN-DMAb (p= 0.008), and DMAb (p< 0.001) groups illustrated higher fatigue-life measurements than VEH. For example, at 140 MPa the VEH group demonstrated a median ± interquartile range (IQR) fatigue life of 1987 ± 10593 cycles, while animals in the ALN, ALN-DMAb, and DMAb groups survived 9850 ± 13648 (+395% versus VEH), 10493 ± 16796 (+428%), and 14495 ± 49299 (+629%) cycles, respectively. All antiresorptive treatment groups demonstrated lower porosity, smaller pore size, greater pore spacing, and lower number of canals versus VEH (p< 0.001). Antiresorptive treatment was also associated with greater apparent density, dry density, and ash density (p≤ 0.03). We did not detect detrimental changes following antiresorptive treatments that would explain their association with AFF. In contrast, 12 months of treatment may have a protective effect against fatigue fractures. © 2022 American Society for Bone and Mineral Research (ASBMR).

Analysis of the Relationship between Mechanical Properties and Pore Structure of MSW Incineration Bottom Ash Fine Aggregate Concrete after Freeze-Thaw Cycles Based on the Gray Theory

The destruction of concrete building materials in severely cold regions of the north is more severely affected by freeze-thaw cycles, and the relationship between the mechanical properties and pore structure of concrete with fine aggregate from municipal solid waste (MSW) incineration bottom ash after freeze-thaw cycles is analyzed under the degree of freeze-thaw hazard variation. In this paper, the gray correlation method is used to calculate the correlation between the relative dynamic elastic modulus, compressive strength, and microscopic porosity parameters to speculate on the most important factors affecting their changes. The GM (1,1) model was established based on the compressive strength of the waste incineration ash aggregate concrete, the relative error between the simulated and actual values in the model was less than 5%, and the accuracy of the model was level 1, indicating that the GM (1,1) model can well reflect the change in the compressive strength of the MSW incineration bottom ash aggregate concrete during freeze-thaw cycles. Using the gray correlation method, the correlation between the relative dynamic elastic modulus, compressive strength, air content, specific surface area, pore spacing coefficient, and pore average chord length was calculated, and the pore spacing coefficient and pore average chord length were determined to be highly correlated with each other. This determination can help analyze and infer the deterioration mechanism of concrete subject to freeze-thaw cycles. These results can provide a theoretical basis for guiding the engineering practice of concrete with fine aggregates of household bottom ash in the northern cold region.

Effect of pore design on the mechanical properties of nanoporous high-entropy alloys

To reveal the dependence of mechanical properties upon the pore design, we perform molecular dynamics simulations to investigate the tensile responses of nanoporous Cantor high-entropy alloys (HEAs), considering the effects of pore size, pore distribution, pore shape, pore spacing, and pore density. Decreasing the pore spacing promotes the transition of fracture mechanism from shear banding to necking. Depending on the pore distribution in the heterostructures, the deformation induced by multiple shear bands and the transition of FCC phase to HCP phase are observed, which is conducive to the homogeneous plastic flow and the enhanced ductility. Pore shape dictates the stress distribution and accumulation closely related to failure mechanisms and mechanical properties of nanoporous HEAs, such as the bending-dominated signature of circle pore and the stretching-dominated signature of ellipse pore producing enhanced modulus and strength. With constrained geometries, “smaller is stronger” is observed in the size effect of neck width. The scaling laws of modulus and strength versus relative density and neck width are derived and developed. The investigation further clarifies the structure–property relationship of nanoporous HEAs and highlights a new strategy for enhanced plasticity by the pore design.Subject Areas: material science, computational material.

Effect of Fly Ash Content on the Microstructure and Strength of Concrete under Freeze–Thaw Condition

To understand the influence of fly ash (FA) content on the microstructure and strength of concrete under freeze–thaw cycles (FTCs), four groups of concrete with different FA contents (0–30%) were tested under FTC condition. Mass loss rate, relative dynamic modulus of elasticity (RDME), splitting tensile strength and other damage indicators were selected to describe the impact of macro properties. The micro physical changes, porosity and pore size distribution parameters were obtained through scanning electron microscope (SEM) and nuclear magnetic resonance (NMR) experiments. The influence mechanism of FA content on the frost resistance durability of concrete under FTC was discussed from the macro and micro perspectives. The results show that under the action of FTC, the addition of FA fills the pores, reduces the pore spacing, improves the strength of concrete, and makes the RDEM and splitting tensile strength of concrete increase first and then decrease. Among them, 20% FA concrete has the best frost resistance. The pore structure parameters show that the content of pores smaller than 100 nm has a great impact on the frost resistance durability of FA concrete, and increasing the content of these pores can improve the frost resistance durability of concrete.

Porous Aluminum Oxide for Medical Applications Including Targeted Drug Delivery

A comprehensive review of the current level of research in the development of intelligent hybrid nanosystems based on porous inorganic materials, in particular porous alumina, has been carried out. Porous materials are of great interest for the development of controlled drug delivery platforms due to their high effective surface area and controlled pore size. One of the main determinants of the overall pore drug loading and release profile is pore geometry. Three-dimensional pore structures with complex pore geometries and increasing surface area are promising platform designs for sustained drug release. But there are certain structural and financial difficulties in their manufacture. Porous anodic alumina, which is easily and economically produced by electrochemical anodization, allows complex and reproducible three-dimensional pore geometries to be obtained. The unique physical and chemical properties of porous anodic alumina make this material a promising platform for controlled drug release. Porous anodic alumina has a highly ordered pore distribution, and its well-known electrochemical fabrication methods allow precise control of pore spacing, diameter, length, and pore geometry. The purpose of this work is to analyze the current level of research in the development of intelligent hybrid nanosystems based on porous alumina with different characteristics for use in medicine. The presented works have shown interesting opportunities for the development of intelligent, multifunctional optical devices with a microchip design. The design of implantable biosensors with the ability to monitor biological systems in vivo and in real time is promising for the use of porous anodic alumina immunosensors.

Development and implementation of a micromechanically motivated cohesive zone model for ductile fracture

Gaining popularity after its coupling with the finite element method, cohesive zone modeling has been used extensively to model fracture, especially in delamination problems. Its constitutive relations, i.e. traction-separation laws, are mostly derived phenomenologically without considering the underlying physical mechanisms of crack initiation and propagation. The approach could potentially be used for ductile fracture as well where the micromechanics of the phenomenon is explained by nucleation, growth and coalescence of pores. In this context, the objective of this work is to develop and implement a physically motivated cohesive zone modeling framework for ductile fracture in metallic materials. In order to accomplish this, a micromechanically motivated traction-separation relation which considers the growth of a physical pore is developed. Tractions are directly represented as a function of pore fraction, and its evolution is driven by separations. The model is implemented as an intrinsic cohesive zone element in a two-dimensional setting. Implementation steps and methodology including the finite element framework are presented in detail for mode-I, mode-II and mixed-mode fracture cases. The derivation of the mixed-mode case leads to a novel yield function representation of tractions and separations, instead of an explicit expression. Hence, an incremental implicit elasto-plastic numerical integration scheme is utilized to solve mixed-mode system of equations required for crack initiation and propagation. The framework is implemented as a user element subroutine in Abaqus (UEL) and the numerical simulations are conducted with compact tension (CT) and single edge notch (SEN) specimens to test the implementation and influence of the micromechanical parameters such as pore size, shape and spacing on the ductile crack initiation and propagation. The work is concluded by presenting an outlook for the capability of the model to predict crack path.

Patches of patches: Spatial fluctuations of elastic turbulence in porous media

Polymer solutions are often injected in porous media for applications such as oil recovery and groundwater remediation. As the fluid navigates the tortuous pore space, elastic stresses build up, causing the flow to become unstable at sufficiently large flow rates—a phenomenon often known as “elastic turbulence”. However, what physical factors determine the onset of this instability, and what its spatial and temporal characteristics are, remain unknown. In this talk, I describe some of our work using direct visualization in model porous media to address this gap in knowledge. First, we show that the spacing between pores strongly influences the flow: when the pore spacing is sufficiently small, the unstable flow in the different pores exhibits a surprising bistability due to the interplay between elongation and relaxation of polymers as they are advected through the pore space (Browne et al., J. Fluid Mech. 2020). Second, using experiments in full three-dimensional porous media, we show that the onset of unstable flow in each pore is akin to a second-order phase transition, arising due to the persistence of discrete patches of instability. Thus, unstable flow is patchy across the different pores of the medium. Guided by these findings, we directly link the energy dissipated by pore-scale fluctuations to the flow resistance through the entire medium, enabling prediction of the macroscopic transport behavior (Browne and Datta, Science Advances 2021). Together, these results reveal the rich array of behaviors that can arise during the unstable flow of polymer solutions through porous media, and provide a general framework by which flow fluctuations can be predicted and controlled.

Acoustic transmission loss and noise from Kevlar wind tunnel walls

In this paper we will develop a model for the acoustic transmission loss and self-noise generated by a Kevlar wind tunnel wall. It is shown that the porosity of the fabric is the most important controlling factor of the transmission loss, and the effect of wind tunnel flow speed is to increase the losses, as observed in experiments. In addition, a model is developed for the weave noise generated by a Kevlar wind tunnel wall, which is found to be caused by the pumping of the fluid through the pores in the Kevlar and depends on their open area ratio. The mechanism for this sound generation is similar to the roughness noise mechanism for a turbulent boundary layer in that the pore spacing couples with the small wavelength disturbances in the boundary layer to cause acoustic radiation at the sum and difference frequencies.

Double-sided polishing photonic crystal fiber biosensor based on surface plasmon resonance for cancer single cell detection

In this paper, we propose a high sensitivity double-sided polishing photonic crystal fiber biosensor based on surface plasmon resonance. The performance of the sensor was analyzed by the finite element method, including the influence of different pore sizes and positions, polishing depth, pore spacing, metal thickness, refractive index (RI), and manufacturing error (5%) on the sensing performance. And the performance of practical application in cancer detection was analyzed. The use of a double-sided polishing structure and coating with a gold layer not only increases the contact area between the analyte and gold layer but also provides a large-enough space for the analysis channel, which is conducive to the actual manufacture and use. The sensor has a detection range of 1.35–1.39, maximum wavelength sensitivity of 21,500 nm/RIU, average wavelength sensitivity of 9550 nm/RIU, amplitude sensitivity of − 1057.1756 RIU − 1 , R 2 of 0.98265, figure of merit of 250, and maximum resolution of 4.68 × 1 0 − 6 , which can be used in cancer detection and other biological areas.

Effect of defects on the constant-amplitude fatigue behavior of as-built Ti-6Al-4V alloy produced by laser powder bed fusion process: Assessing performance with metallographic analysis and micromechanical simulations

The influence of various process parameters on the mechanical behavior (including tensile strength, strain-to-failure and constant-amplitude fatigue performance) of as-built Ti-6Al-4V alloy, produced via laser powder bed fusion (L-PBF) process, is demonstrated using complementary information obtained from mechanical (uniaxial tensile and fatigue) tests, fractography analysis, metallographic analysis and micromechanical simulations. Four different build conditions were considered such that the laser power and velocity were varied for each build while holding the build orientation, hatch spacing, layer thickness, laser spot size and hatch rotation constant. The volumetric energy densities (E) of the four unique builds were: 33 J/mm3, 66 J/mm3, 130 J/mm3 and 180 J/mm3, respectively. Two coupons per build were subjected to constant-amplitude fatigue loading while one coupon per build was subject to uniaxial tensile loading at room temperature. Coupons belonging to Builds 1 and 2 (corresponding to E values of 33 J/mm3 and 66 J/mm3, respectively) had considerably longer fatigue lives compared to coupons from Builds 3 and 4 (corresponding to E values of 130 J/mm3 and 180 J/mm3, respectively).To reconcile the relative lifing capability of the four builds, fractography, two-dimensional (2D) pore analysis, and multiscale finite-element simulation campaigns are detailed. Collectively, these exercises underscore the centrality of pore clustering on the fatigue performance of the builds. Moreover, they highlight the role that microstructural character (viz. grain orientation with respect to loading) plays on the accumulation of plastic strain in the vicinity of pores. Specifically, it is demonstrated that a pore embedded in a grain favorably oriented for slip accumulates a significant amount of plastic strain compared to one embedded in a grain not favorably oriented for slip. Comparing the relative performance and defect character of the four builds, this study suggests that both pore spacing and relative grain hardness act in concert with other fatigue-limiting characteristics including pore size, shape and distance to free surface.

Pore spacing gradient can direct endothelial cell migration in microphysiological systems

Porous membranes are one of the main components of microphysiological systems. They can compartmentalize different cell types and establish physiologically relevant cell-cell communication between co-cultured cells. We previously showed that porous membranes' characteristics can modulate cell-substrate interactions and guide cell responses. Pore spacing is a major characteristic that can control cell-substrate interaction since it provides the required area for the development of ECM and adhesive components.

From the outside to the inside: Elucidation of the mechanism of pseudomorphic transformation of SBA-15 into MCM-41 by following its time-resolved conversion

Pseudomorphic transformation of silica materials is a versatile approach for the fabrication of porous phases in which the particle morphology and pore structure can be controlled independently from each other. It has been applied already for a wide variety of different parent silica materials, however, there is still a controversy about the details of the mechanism, about the manner of how the transformation proceeds through the body of the particles. The pure homogeneous distribution model on the one hand, and the core-shell model, on the other hand, are the so-to-speak extreme poles in this controversy, not excluding that a mixed-mode model can be valid for a particular parent silica phase. Herein, the detailed mechanism for the pseudomorphic transformation of ordered mesoporous SBA-15 into MCM-41 is elucidated by following the time-resolved conversion of the parent silica material. Upon pseudomorphic transformation, the characteristic morphology of the parent SBA-15 particles remains unchanged, whereas the original pore structure undergoes a successive restructuring in the presence of hexadecyl-trimethylammonium ions as a structure-directing agent. The inflow of the alkaline transformation solution within the pore system of SBA-15 initiates undirected dissolution and re-condensation processes of the pristine pore walls, resulting in an undulation, a slight shrinkage and a partial obstruction of the original mesopores. Simultaneously small domains of MCM-41 with various spatial orientations are formed on the external particle surface, restricting the access to the undulated mesopores within the particle core. The resulting core-shell structure of the partially transformed materials provides interesting gas physisorption hysteresis phenomena, caused by a cavitation mechanism during the evaporation of adsorbate from partially blocked SBA-15 pores. PXRD reflections that can be assigned to the characteristically large pore spacing of SBA-15 were found within patterns even for materials with a supposedly complete conversion. The occurrence of these reflections can be attributed to inaccessible pore domains of SBA-15. With proceeding transformation, a reduction of the amount of inaccessible SBA-15 pores was observed, finally leading to a material with typical MCM-41 characteristics but with a slightly less pore ordering due to the abrasively conditions during the long hydrothermal treatment. • Time-resolved pseudomorphic transformation of ordered mesoporous SBA-15 into MCM-41. • Original particle morphology of SBA-15 remained unchanged after transformation. • Bimodal mesoporous core-shell structures obtained by partial transformation. • Hysteresis phenomena in partially transformed samples caused by cavitation. • Inaccessibility of SBA-15 pore domains at partially transformed samples proven by nitrogen physisorption and PXRD.

Preparation and characteristic analysis of nanofacula array

The development of nanofacula array is an effective methods to improve the performance of Near-field Scanning Optical Microscopy (NSOM) and achieve high-throughput array scanning. The nanofacula array is realized by preparing metal nanopore array through the "two etching-one development" method of double-layer resists and the negative lift-off process after metal film coating. The shading property of metal film plays important rules in nanofacula array fabrication. We investigate the shading coefficient of three kinds of metal films (gold–palladium alloy (Au/Pd), platinum (Pt), chromium (Cr)) under different coating times, and 3.5 min Au/Pd film is determined as the candidate of the nanofacula array fabrication for its lower thickness (about 23 nm) and higher shading coefficient (≥ 90%). The nanofacula array is obtained by irradiating with white light (central wavelength of 500 nm) through the metal nanopore array (250/450 nm pore diameter, 2 μm pore spacing and 7 μm group spacing). Moreover, the finite difference and time domain (FDTD) simulation proves that the combination of nanopore array and microlens array achieves high-energy focused nanofacula array, which shows a 3.2 times enhancement of electric field. It provides a new idea for NSOM to realize fast super-resolution focusing facula array.