Multiscale Morphology Research Articles

Multiscale deformation processes during cold sintering of nanovaterite compacts

Cold sintering is a promising route towards the manufacturing of dense ceramics at mild processing conditions, but our poor understanding of the process has prevented the wider spread of this attractive densification approach. Using nanovaterite powders with well-defined multiscale morphology, we perform in-situ X-Ray tomography on compacts subjected to controlled mechanical load and quantify the multiscale deformation processes responsible for the water-assisted cold sintering of this powder with the help of instrumented indentation experiments at the micro- and nano-scale. Our results reveal the crucial effect of water in promoting the macroscopic densification process and highlight the dominant role of the nanoparticle network inside agglomerates in controlling the cold sintering of compacts at high mechanical loads. By providing new insights into the deformation processes responsible for the densification effect, this study can potentially guide the discovery of novel chemical compositions and particle morphologies that can be more easily densified through room-temperature cold sintering with water.

Faster Islanding Detection of Microgrid Based on Multiscale Mathematical Morphology

Faster and reliable islanding detection of microgrid is necessary to protect the equipment and maintenance personnel. Voltage and frequency are two important parameters needs to be controlled in microgrid; Voltage and frequency stability of microgrid depends merely on main grid during grid connected mode and depends on individual controllers during islanding mode. This research proposes a time domain technique based on multi-scale mathematical morphology (MMM) for islanding detection. The proposed technique uses multiscale dilation-erosion difference filter (MDEDF) with peak value of the signal. The performance of the proposed technique is validated in IEEE-13bus system with different cases such as mismatch in real power, reactive power, load switching, motor switching; L-G fault .The results validate the accuracy and efficacy of the proposed technique and also compared with recently published work.

Fault Feature Extraction and Degradation State Identification for Piezoelectric Ceramics Cracking in Ultrasonic Motor Based on Multi-Scale Morphological Gradient

Piezoelectric ceramics cracking is one of the main faults of the ultrasonic motor. According to the morphological mathematics and information entropy, a method based on multi-scale morphological gradient was proposed for ceramics fault feature extraction and degradation state identification. To solve the problem that traditional multi-scale morphology spectral (MMS) entropy cannot exactly describe the performance degradation of the piezoelectric ceramics, multi-scale morphology gradient difference (MMGD) entropy was proposed to improve the sensitivity to the fault. Furthermore, multi-scale morphology gradient singular (MMGS) entropy was presented to reduce the system noise interference to the useful fault information. The disturbance analysis of temperature, load, and noise for MMGD entropy and MMGS entropy was also given in this paper. Combining the advantages of the above two entropies, a standard degradation mode matrix was built to distinguish the degradation state via the grey correlation analysis. The analysis of actual test samples demonstrated that this method is feasible and effective to extract the fault feature and indicate the degradation of piezoelectric cracking in ultrasonic motor.

Automatic Microseismic Events Detection Using Multiscale Morphological Characteristic Function

Surface-acquired microseismic events are commonly unpredictable and appear as weak signals with low signal-to-noise ratios (SNRs), which present a significant challenge in microseismic data analysis and events detection. We have developed the multiscale morphology method for automatically detecting microseismic events. The technique is based on the fact that the effective signal and noise have different features in the multiscale morphological section. According to these characteristics, the effective signal can be identified by waveform consistency analysis. The microseismic data are first decomposed into different scales by multiscale morphology decomposition. Then the multiscale morphology characteristic function is calculated by waveform cross correlation approach and the potential microseismic events are evaluated using the peak value of the multiscale morphology characteristic function. Applications of the proposed method on the synthesized data and field data have been explored in this article. Various examples demonstrate that the proposed method has the advantage of suppressing the effect of Gaussian noises adaptively. Furthermore, it is excellent in automatically detecting the low SNR signal so that more microseismic events can be identified. In addition, the method could be applied to other fields, such as in the identification of earthquake signals.

Role of Multivalent Interactions in Dynamic-Template-Directed Assembly of Conjugated Polymers

Dynamic-template-directed assembly is a promising method to enhance molecular ordering and electronic properties of solution-coated polymer semiconductor thin films over large area. In this work, we establish that multicomponent dynamic templates of complimentary chemistries can promote polymer crystallization through cooperative multivalent interactions. We investigate this phenomenon using a combination of templating substrates including a fluoropolymer, a hydrogen-bonded liquid and an ionic liquid. Template-dependent multiscale morphology is studied by a comprehensive set of characterization techniques to understand how introducing diverse chemical moieties modulates polymer assembly. Our results clearly confirm synergistic effect between components of complimentary chemistries constituting the dynamic template. The relative degree of crystallinity is improved by 50-150% for films deposited on multicomponent dynamic templates compared to their neat constituents. In addition, macroscopic alignment is increased significantly (2 to 5 times) compared to single-component templates. As a result, highly anisotropic charge transport is observed with apparent hole mobilities up to 3.6 cm2V-1s-1. In contrast, such synergistic effect is not observed when using multicomponent dynamic template of comparable chemistries (i.e. ionic liquid and polymerized ionic liquid). We elucidate the origin of this synergistic effect through a combination of attenuated total reflectance Fourier transform infrared spectroscopy and isothermal titration calorimetry. When the dynamic template is comprised of two or more components interacting with complementary binding sites on the conjugated polymer (esp. backbone vs. side chain), the template-polymer interactions is significantly enhanced compared to the sum of single component contributions. These results provide valuable insights on surface-directed conjugated polymer crystallization during large-area solution coating. Template dynamics is rarely studied, and represents a new opportunity for guiding assembly of soft functional matter.

Multiscale pore structure analysis of nano titanium dioxide cement mortar composite

The effects of nano-Ti O2 (NT) on the multiscale pore system and morphology of cement mortars were studied by X-ray computed tomography (X-CT), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) method. The obtained results from X-CT showed that microscale pores (from 20 μm to 200 μm) of mortars mixed with 2.5 wt% NT were significantly refined. When the content of NT is more than 2.5 wt%, the total pore volume and the number of pores begin to increase. However, when the amount of NT exceeds the optimal value, e.g., (2.5 < NT < 5%), the recorded 2D porosity (void area fraction), are still lower than the reference sample. Meanwhile, the microscopy results proved that, by adding 2.5 wt% NT, the pores of cement mortars were best filled, resulting in a more homogenous morphology. At the nanoscale, the BET results revealed a clear trend of increasing surface area and pore volume of the NT cement mortars, over the entire range of NT percentages, i.e., from 0 wt% to 10 wt%. This could stem from the formation of nanosized needle-shaped products in the presence of the nanoparticles. Further, the permeability of NT cement mortars was measured using a high-pressure core holder and the results showed that 2.5 wt% NT inclusions could reduce the permeability of the cement mortars by 32%. However, adding more NT (>2.5 wt.%) led to higher permeability. This is in line with the microscale pore analysis from X-CT. It can be concluded that adding a certain amount of NT (around 2.5 wt%) can modify the pore structure of cement mortars by changing the harmful microscale pores (permeability related) to the nano-sized benign pores, leading to a much stronger durability of cement-based materials.

Fault diagnosis for rolling element bearing using variational mode decomposition and l1 trend filtering

In order to extract the faint fault features of bearings in strong noise background, a method based on variational mode decomposition and l1 trend filtering is proposed in this study. In the variational model, the mode number κ is determined difficulty, thus l1 trend filtering is applied to simplify the frequency spectrum of the original signals. In this case, this parameter can be defined easily. At the same time, a criterion based on kurtosis is used to adaptively select the regularization parameter of l1 trend filtering. The combined approach is evaluated by simulation analysis and the vibration signals of damaged bearings with a rolling element fault, an outer race fault and an inner race fault. The results demonstrate that the hybrid method is effective in detecting the three bearing faults. Moreover, compared with another approach based on multiscale morphology and empirical mode decomposition, the proposed method can extract more bearing fault features.

Morphologically bioinspired hierarchical nylon 6,6 electrospun assembly recreating the structure and performance of tendons and ligaments

Reconstructions of ruptured tendons and ligaments currently have dissatisfactory failure rate. Failures are mainly due to the mechanical mismatch of commercial implants with respect to the host tissue. In fact, it is crucial to replicate the morphology (hierarchical in nature) and mechanical response (highly-nonlinear) of natural tendons and ligaments. The aim of this study was to develop morphologically bioinspired hierarchical Nylon 6,6 electrospun assemblies recreating the structure and performance of tendons and ligaments. First, we built different electrospun bundles to find the optimal orientation of the nanofibers. A 2nd-level hierarchical assembly was fabricated with a dedicated process that allowed tightly joining the bundles one next to the other with an electrospun sheath, so as to improve the mechanical performance. Finally, a further hierarchical 3rd-level assembly was constructed by grouping several 2nd-level assemblies. The morphology of the different structures was assessed with scanning electron microscopy and high-resolution X-ray tomography, which allowed measuring the directionality of the nanofibers in the bundles and in the sheaths. The mechanical properties of the single bundles and of the 2nd-level assemblies were measured with tensile tests. The single bundles and the hierarchical assemblies showed morphology and directionality of the nanofibers similar to the tendons and ligaments. The strength and stiffness were comparable to that of tendons and ligaments. In conclusion, this work showed an innovative electrospinning production process to build nanofibrous Nylon 6,6 hierarchical assemblies which are suitable as future implantable devices and able to mimic the multiscale morphology and the biomechanical properties of tendons and ligaments.

In Operando Monitoring of Dynamic Recovery in 3D-Printed Thermoset Nanocomposites by XPCS.

Extrusion-based additive manufacturing methods, such as direct-write of carbon fiber-reinforced epoxy inks, have become an attractive route toward development of structural composites in recent years, because of emerging techniques such as big area additive manufacturing. The development of improved materials for these methods has been a major focus area; however, an understanding of the effects of the printing process on the structural and dynamic recovery in printed materials remains largely unexplored. The goal of this work is to capture multiscale and temporal morphology and dynamics within thermosetting composite inks to determine the parameters during the printing process that influence the recovery of the printed material. Herein, we use X-ray photon correlation spectroscopy in small-angle scattering geometry to reveal both morphology and recovery dynamics of a nanoparticle (layered-silicate Cloisite 30B) in a thermoset epoxy resin (EPON 826) during the printing process in real time. Our results show that the dynamics of the layered silicate particles during recovery are anisotropic and slow down to behavior which ischaracteristic of aging in colloidal clay suspensions around tage ≈ 12 s. The dynamics and alignment of the particles during recovery were tempo-spatially mapped, and the recovery post printing was shown to be strongly influenced by the deposition onto the build plate in addition to the extrusion through the print head. Our in operando results provide insight into the parameters that must be considered when optimizing materials and methods for precisely tailored local properties during 3D printing.

Edge detection on terahertz pulse imaging of dehydrated cutaneous malignant melanoma embedded in paraffin

Terahertz pulse imaging of cutaneous malignant melanoma dehydrated by ethanol and embedded in paraffin was carried out across a frequency range of 0.2–1.4 THz. First, the tissue images based on the time-domain electric-field amplitude information were acquired. Then the areas of normal and cancerous tissues were determined using multi-scale, multi-azimuth and multi-structural element mathematical morphology. The physical meaning of the image was analyzed by calculation of the refractive index and absorption coefficient of cutaneous malignant melanoma in different areas. The refractive index of both normal and cancerous tissues showed anomalous dispersion. The refractive index of cancerous tissues tended to vary between 0.2 and 0.7 THz, while that of normal and fat tissues remain almost unchanged. The absorption of cancerous tissues was higher, with a maximum at 0.37 THz. We concluded that both the refractive index and absorption coefficient differ considerably between normal and cancerous tissues, and the areas of normal and abnormal tissues can be identified using THz pulse imaging combined with mathematical morphology. The method for edge detection of terahertz pulse imaging of cutaneous malignant melanoma provides a reference for the safe surgical removal of malignant tumors.

Finite element modeling of porous polymer pipeline coating using X-ray micro computed tomography

Offshore pipelines are designed to sustain impact from fish trawl equipment and anchors, but due to component complexity, insulating coating solutions are often neglected in mechanical capacity estimates. In this work, efforts are made to predict the mechanical behavior of a typical polymeric insulating coating solution using the finite element method. To do so, the multi-scale morphology of porous polymer coating specimens was mapped using X-ray Micro Computed Tomography (XRMCT) and Differential Scanning Calorimetry (DSC). XRMCT-based finite element models were then derived, analyzed and evaluated against compression tests and the DSC results. The modeling approach produced good correspondence with experimental tests.

Trimetallic Metal–Organic Framework Derived Carbon‐Based Nanoflower Electrocatalysts for Efficient Overall Water Splitting

AbstractSearching desirable cost‐effective electrocatalysts for overall water splitting is of great importance for the hydrogen production industry. Here a facile synthesis of trimetallic carbon nanoflower electrocatalysts is reported which are derived from Co2+/Fe2+/Ni2+ ratio adjustable metal–organic frameworks (MOFs). The unique nanosheet‐assembled multiscale nanoflower morphology can enlarge the catalyst/electrolyte contact area, and the synergistic electronic effects between trimetallic components endow the trimetallic carbon nanoflower electrocatalysts with more oxygen vacancies and a higher degree of graphitization of carbon, thus showing excellent activity. The optimized Co0.2Fe0.8Ni‐OCNF reaches a current density of 10 mA cm−2 at low overpotential of 291 mV with a very small Tafel slope of 36.1 mV dec−1 and 1.65 V@10 mA cm−2 for a two‐electrode water electrolysis in an alkaline solution, outperforming the commercial IrO2 electrocatalysts. The results may pave the way to the development of more efficient multicomponent nanosheet‐assembled multiscale nanomaterials for various catalytic applications.

Separation Mechanism and Construction of Surfaces with Special Wettability for Oil/Water Separation.

Oil leakage and the discharge of oil/water mixtures by domestic and industrial consumers have caused not only severe environmental pollution and a threat to all species in the ecosystem but also a huge waste of precious resources. Therefore, the separation of oil/water mixtures, especially stable emulsion, has become an urgent global issue. Recently, materials containing a special wettability feature for oil and water have drawn immense attention because of their potential applications for oil/water separation application. In this paper, we systematically summarize the fundamental theories, separation mechanism, design strategies, and recent developments in materials with special wettability for separating stratified and emulsified oil/water mixtures. The related wetting theories that unveil the physical underlying mechanism of the oil/water separation mechanism are proposed, and the practical design criteria for oil/water separation materials are provided. Guided by the fundamental design criteria, various porous materials with special wettability characteristics, including those which are superhydrophilic/underwater superoleophobic, superhydrophobic/superoleophilic, and superhydrophilic/in-air superoleophobic, are systemically analyzed. These superwetting materials are widely employed to separate oil/water mixtures: from stratified oil/water to emulsified ones. In addition, the materials that implement the demulsification of emulsified oil/water mixtures via the ingenious design of the multiscale surface morphology and construction of special wettability are also discussed. In each section, we introduce the design ideas, base materials, preparation methods, and representative works in detail. Finally, the conclusions and challenges for the oil/water separation research field are discussed in depth.

The effect of multiscale morphology on electrical conduction characteristics of isotactic polypropylene ultrathin films

With a modified solution-processing method, isotactic polypropylene (iPP) ultrathin films (∼160 nm) are fabricated and investigated, which reveals a multiscale morphological effect of intramolecular interaction, lamellar orientation and intra-spherulite structure on the macroscopic carrier transport process. The morphology of ultrathin films is tuned by annealing under various temperatures (Ta) from 140 °C to 170 °C. It is found that when Ta < 160 °C, the lamella has a more flat-on like orientation. The spherulite size grows steadily with Ta. However, when Ta ≥ 160 °C, the morphology varies dramatically from spherulite-like to seaweed-like with lamella oriented edge-on. Depending on the microstructure, the electrical conduction characteristics of iPP ultrathin film changes, correspondingly. The conductivity is estimated from the long-term polarization current, which follows a hopping mechanism with a hopping distance about 1.5 nm and a critical field about 100 MV/m. It is proposed that the morphological changes with Ta result in more structural disorders, smaller inter-spherulite weak regions, and well-developed microstructure, which greatly suppress the electrical conductivity of iPP ultrathin films over one order. The present work reveals the essential role of multiscale morphology on the electrical property, which is of help for establishing the structure-property relation.

Globular bundles and entangled network of proteins (CorA) by a coarse-grained Monte Carlo simulation

Using a coarse-grained model, self-organized assembly of proteins (e.g., CorA and its inner segment iCorA) is studied by examining quantities such as contact profile, radius of gyration, and structure factor as a function of protein concentration at a range of low (native phase) to high (denature phase) temperatures. Visual inspections show distinct structures, i.e., isolated globular bundles to entangled network on multiple length scales in dilute to crowded protein concentrations. In native phase, the radius of gyration of the protein does not vary much with the protein concentration while that of its inner segment increases systematically. In contrast, the radius of gyration of the protein shows enormous growth with the concentration due to entanglement while that of the inner segment remains almost constant in denatured phase. The multi-scale morphology of the collective assembly is quantified by estimating the effective dimension D of protein from scaling of the structure factor: collective assembly from inner segments remains globular (D~3) at almost all length scales in its native phase while that from protein chains shows sparsely distributed morphology with D ≤ 2 in entire temperature range due to entanglement except in crowded environment at low temperature where D~2.6. Higher morphological response of chains with only the inner-segments due to selective interactions in its native phase may be more conducive to self-organizing mechanism than that of the remaining segments of the protein chains.

Laser surface texturing of copper and variation of the wetting response with the laser pulse fluence

We report an experimental investigation on laser surface texturing of copper targets by Ti:Sa femtosecond laser pulses addressing their wetting response to water droplets. In particular, fs laser surface processing is used to developed hierarchical surface structures by writing parallel micro-trenches with a period of 50 μm at different laser pulse fluences. The laser irradiation simultaneously induces both the formation of laser induced periodic surface structures (LIPSS), in form of periodic ripples, and the random decoration with nanoparticles, resulting in the formation of a multiscale surface morphology. The morphological features of the samples are investigated and correlated with their wetting response through static contact angle measurements. Our findings evidence a progressive increase of the contact angle with the laser pulse fluence. The combination of the microscale trenches, written by laser line scanning, with the ripples patterns and the random nanoparticles decoration, formed on the surface, allow developing highly hydrophobic copper samples with contact angles reaching values around 160°, presenting potential interest for wettability applications.

Color image enhancement based on adaptive multi-scale morphological unsharpening filter

In order to overcome the problem in Retinex algorithm that it is possible to cause image detail loss by using Gauss function to estimate illumination, in this paper, we propose a color image enhancement algorithm based on multi-scale morphology unsharp method combined with Retinex. Firstly, the color image is converted from RGB space to HSV space. Then, the S component is enhanced by adaptive logarithmic transformation to improve its visual characteristics and make it consistent with human visual system. The method of multi-scale morphological unsharpening is adopted to estimate the V component, and the multi-scale weights are adaptively selected according to the features of the image. The V component is enhanced according to the Retinex principle. Finally, the H and the enhanced S and V components are recombined and reflected into RGB space to achieve the purpose of image enhancement. The experimental results showed that the algorithm is superior to the traditional SSR, MSR and MSRCR algorithms in terms of entropy, average gradient and sharpness, and outperforms those based on Gauss function estimation.

Mode II fracture toughness of carbon–epoxy bonded joints with femtosecond laser treated surfaces

Mode II fracture toughness of carbon–epoxy bonded joints considering laser treated surfaces was evaluated using the End-Notched Flexure (ENF) test. Four different surface preparations were performed using distinct processing conditions before bonding the specimen arms. The Resistance-curves of the fracture tests were obtained considering an equivalent crack length based procedure. The influence of the different surface treatments on the mode II fracture behaviour was assessed comparing the average values of the fracture toughness. It was verified that a laser treatment employing two interfering laser beams, which produces a complex multi-scale surface morphology free of contaminants, is the best surface preparation regarding higher values of the mode II fracture energy. A cohesive zone analysis was used aiming to validate the followed procedures. The excellent agreement obtained between numerical and experimental results reveals that the used techniques are sound.

Generation of realistic sand particles with fractal nature using an improved spherical harmonic analysis

Based on X-ray micro-computed tomography images of natural sand particles, a set of spherical harmonic descriptors and an associated fractal dimension were introduced to characterise the multi-scale particle morphology. Based on the statistics of the fractal dimensions for different types of sands, this study proposed a practical method to generate realistic sand particles with the major morphological features of their mother sands. To validate this method, two virtual sand assemblies were generated, whose 3D printing and shape parameters were compared with those of real sand particles. Furthermore, these generated particle morphologies were incorporated into DEM simulations of granular column collapse.

Research on the multi-scale microstructure of polyacrylonitrile precursors prepared by a dry-jet wet spinning process

An understanding of the properties of polyacrylonitrile (PAN) precursors is an essential precondition for manufacturing high-performance carbon fibres, and the structure of the precursors has a direct and profound effect on the performance of carbon fibres. In this study, PAN precursors, formed in a multistage coagulation bath, were spun by a dry-jet wet spinning process, and the multi-scale microstructure and morphology of the precursors were investigated by separating the fibrils from the precursors. Scanning electron microscopy and high-resolution transmission electron microscopy were employed to examine the surface morphology, cross-sectional morphology and microstructure of the precursors. X-ray diffraction was used to characterize the crystal structure. The micropore sizes of the precursors were determined with nitrogen adsorption experiments; the adsorption increased after ultrasonic etching and decreased with an increase in the treated concentration. All the results demonstrated that the PAN precursors had a multi-scale microstructure, the precursors consisted of fibrils with diameters of 80–200 nm and the fibrils consisted of some microfibrils with diameters of 20–40 nm, including the periodic tissues with thicknesses of 16–30 nm perpendicular to the fibre axis.