Electron Microscopy Investigations Research Articles

Superior Piezo-/Ferro-Electricity in Antiferroelectric AgxNbO3-δ Thin Films by Nanopillar Local Structure Design.

Antiferroelectrics are fundamental mother compounds critical in developing innovative lead-free piezoelectrics and ferroelectrics and hold great promise for wide-ranging applications in energy conversion and electronic devices. However, harnessing their superior properties presents a significant challenge due to the delicate balance required between their various states. In this study, through the unique design of nanopillar structures to alleviate the local polar heterogeneity, we have achieved significantly improved piezo-/ferro-electricity in classic lead-free antiferroelectric AgxNbO3-δ (x = 1, 0.9, and 0.8) epitaxial thin films. The effective piezoelectric coefficient reaches 440 pm V-1, 1 order of magnitude larger than the stoichiometric AgNbO3, rivaling classic lead zirconate titanate piezoelectrics. Atomic-scale electron microscopy investigations unravel the underlying mechanisms. The nanopillars, characterized by antisite occupancy of both Ag and Nb atoms and forming out-of-phase boundaries with the matrix, reduce the local crystal symmetry via interphase strain. This leads to the creation of flexible multinanodomain structures that significantly facilitate polarization rotation, thus substantially enhancing the piezoelectric performance. This study demonstrates the feasibility of engineering local heterogeneity through nanopillar design, offering a generally applicable method for property improvement of a wide range of antiferroelectrics.

Histological and scanning electron microscopy investigation of the effects of titanium surface modifications on osseointegration in rabbits.

This study aimed to compare the novel Estaş Medical Anodization (EMA) surface treatment technique with the techniques commonly used in the literature and to examine their effects on osteointegration in the rabbit tibia. A total of 24 rabbits used in this study were divided into 3 groups, with 8 rabbits in each group. Using both tibias of all rabbits in the study, screws belonging to the control group were placed in the left tibia, and the right tibia belonging to the experimental group were placed. In the first 8 rabbits, a single experimental group in the right tibia were used; in the second 8 rabbits, 2 different experimental groups in the right tibia were used; and in the last 8 rabbits, 2 different experimental groups in the right tibia were used. Thus, 5 different experimental groups with 8 screws in each group and a separate control group were formed for each of them. EMA-treated surfaces were named 200-800 nm iris oxidation and 800-1200 nm gray oxidation according to the TiO2 layer thickness. Group 1 was implanted with mini-screws prepared with chemical etching+EMA iris oxidation, while group 2 was implanted with sandblasted, large-grit and acid-etched (SLA) mini screws treated with EMA gray oxidation. Group 3 was implanted with mini-screws treated with EMA gray oxidation, group 4 was implanted with mini-screws treated with chemical etching+micro-arc oxidation, and group 5 was implanted with mini-screws treated with chemical etching+EMA gray oxidation. The control group was implanted with mini-screws prepared with pure titanium. At the end of 6 weeks, osseointegration percentages were calculated and compared using histological and scanning electron microscope (SEM) analyses. The histological results confirmed the increase in osseointegration percentages in all experimental groups compared to those that received pure titanium implants (P values control group vs group 1=.005, control group vs group 2, 3, 4, 5=.001). The comparison between the groups revealed that the chemical etching+EMA gray oxidation modification technique (group 5) significantly increased osseointegration compared to the SLA+EMA gray oxidation technique (group 5 vs group 2 P=.016) and the chemical etching+EMA iris oxidation technique (group 5 vs group 1 Pp=.001). The EMA gray oxidation technique (group 3) significantly increased osseointegration compared to the chemical etching+EMA iris oxidation technique (group 1) (group 3 vs group 1 P=.043). The results of the SEM analysis showed that osseointegration was significantly increased in all experimental groups compared to that in the pure titanium (control) group (P values control group vs group 1, 2, 3=.001, control group vs Group 4,5=.006). The mean osseointegration percentage in the experimental groups was the highest in group 5, followed by group 4, group 3 and group 1 equally, and group 2. However, the differences among the experimental were not significant (group 1, group 2, group 3, group 4 vs group 5 P=.408). The EMA titanium surface modification techniques we developed significantly increased osseointegration compared to the pure titanium surface. The EMA gray oxidation technique seems to result in higher osseointegration rates than the EMA iris oxidation technique, and similar rates can be found with the SLA and chemical etching techniques. N/A.

Determination of the average crystallite size and the crystallite size distribution: the envelope function approach EnvACS.

A procedure is presented to exactly obtain the apparent average crystallite size (ACS) of powder samples using standard in-house powder diffraction experiments without any restriction originating from the Scherrer equation. Additionally, the crystallite size distribution within the sample can be evaluated. To achieve this, powder diffractograms are background corrected and long-range radial distribution functions G(r) up to 300 nm are calculated from the diffraction data. The envelope function f env of G(r) is approximated by a procedure determining the absolute maxima of G(r) in a certain interval (r range). Fitting of an ACS distribution envelope function to this approximation gives the ACS and its distribution. The method is tested on diffractograms of LaB6 standard reference materials measured with different wavelengths to demonstrate the validity of the approach and to clarify the influence of the wavelength used. The latter results in a general description of the maximum observable average crystallite size, which depends on the instrument and wavelength used. The crystallite site distribution is compared with particle size distributions based on transmission electron microscopy investigations, providing an approximation of the average number of crystallites per particle.

Annealing Behavior of a Mg-Y-Zn-Al Alloy Processed by Rapidly Solidified Ribbon Consolidation.

Mg-Y-Zn-Al alloys processed by the rapidly solidified ribbon consolidation (RSRC) technique are candidate materials for structural applications due to their improved mechanical performance. Their outstanding mechanical strength is attributed to solute-enriched stacking faults (SESFs), which can form cluster-arranged layers (CALs) and cluster-arranged nanoplates (CANaPs) or complete the long-period stacking ordered (LPSO) phase. The thermal stability of these solute arrangements strongly influences mechanical performance at elevated temperatures. In this study, an RSRC-processed Mg-0.9%, Zn-2.05%, Y-0.15% Al (at%) alloy was heated at a rate of 0.666 K/s up to 833 K, a temperature very close to melting point. During annealing, in situ X-ray diffraction (XRD) measurements were performed using synchrotron radiation in order to monitor changes in the structure. These in situ XRD experiments were completed with ex situ electron microscopy investigations before and after annealing. At 753 K and above, the ratio of the matrix lattice constants, c/a, decreased considerably, which was restored during cooling. This decrease in c/a could be attributed to partial melting in the volumes with high solute contents, causing a change in the chemical composition of the remaining solid material. In addition, the XRD intensity of the secondary phase increased at the beginning of cooling and then remained unchanged, which was attributed to a long-range ordering of the solute-enriched phase. Both the matrix grains and the solute-enriched particles were coarsened during the heat treatment, as revealed by electron microscopy.

Exploring the structural, optical, dielectric and magnetic properties of rare earth samarium doped Ca-Mg based Ca0.5Mg0.5Fe12−xSmxO19 ferrite nanoparticles

The emergence of M-type hexaferrite presents an encouraging alternative to rare earth magnets, due to its economic feasibility and outstanding magnetic properties. This makes it a viable option for applications in the electric automotive and magnetic industry applications. In this study, we utilized a sol–gel auto-combustion technique to synthesize a series of samarium (Sm) doped calcium-magnesium (Ca-Mg) hexaferrite samples having chemical formula Ca0.5Mg0.5Fe12−xSmxO19 (x = 0.00, 0.05, 0.10, 0.15, and 0.20). The XRD analysis confirmed the crystal structure of the synthesized materials, revealing a consistent magneto-plumbite phase across all samples. Scanning electron microscopy (SEM) investigations further confirmed the homogeneous distribution and agglomeration of nanostructures. FTIR analysis identified the presence of two primary absorption bands in Ca-Mg hexaferrites with both bands exhibiting a shift towards lower frequency ranges with increasing doping levels. The dielectric loss (ε″) and dielectric constant (ε′) were higher at lower frequencies but decreased as the frequency increased. Additionally, higher concentrations of samarium resulted in further reductions in both dielectric loss (ε″) and dielectric constant (ε′). Notably, saturation magnetization (Ms) and remanence (Mr) values demonstrated an increasing trend with higher degrees of Sm+3 substitution, while coercivity (Hc) values exhibited relative stability. Our findings indicate that these materials possess promising magnetic parameters falling within the ranges of 31.52–37.77 emu·g−1 for Ms, 18.16 – 21.53 emu·g−1 for Mr, and 2.088–2.243 kOe for Hc, suggesting their potential utility across diverse applications including permanent magnets used in electric vehicle motors, storage devices, microwave components, and electromagnetic radiation absorbers.

Natural Synthesis, Characterisation, and Photocatalytic Performance of Nanoparticles made of Manganese Dioxide using Manganese Acetate Tetrahydrate as Precursor

Abstract: This study describes a straightforward, effective, and environmentally benign method for producing manganese dioxide nanoparticles (MnO2 NPs) using Nyctanthes arbor-tristis leaf extract. It was discovered by Fourier-transform infrared spectra that the plant extract contributed to the creation of MnO2 NPs. The band gap of the synthesised MnO2 NPs was identified as the source of the absorption peaks observed in the UV–visible absorption spectra at 412 nm. X-ray diffraction analysis was used to identify the crystal phase of the MnO2 NPs and validate the development of crystalline MnO2 NPs. According to the X-ray diffraction pattern, MnO2 NPs have crystalline nature. Furthermore, the synthesised MnO2 NPs' was revealed by field emission scanning electron microscopy investigation with EDS which gives Information about Compositional elements. MnO2 NPs have the ability to degrade MB dyes in the UV-Visible light spectrum by photocatalysis. Using Methylene Blue as an organic pollutant, the photocatalytic activities for the dye degradation of MnO2 NPs were assessed

Antimicrobial and Molecular Docking Studies of 1,3,4-Thiadiazole Tethered Sulfa-Azo Derivatives via Hydrazono-Methyl Bridge

A new series of 1,3,4-thiadiazole linked to sulfa-azo derivatives via hydrazono-methyl bridge were synthesized via the reaction of methyl ((E)-(sulfa-derivatives)diazenyl) benzylidene)hydrazine-1-carbodithioates 1a-e with ethyl ester and acetyl hydrazonyl halides 2a-d. The chemical structures of the newly 1,3,4-thiadiazoles 3a-t have been clarified considring their elemental and spectral analysis. Antimicrobial activity of the newly 1,3,4-thiadiazoles was determined for Staphylococcus aureus, Escherichia coli, Candida albicans, as well as Aspergillus niger using the cup agar plate diffusion method. Out of the twenty compounds, compounds 3j, 3k, 3l, and 3s with isoxazole sulfonamides were selected for MIC assay. Compound 3j was equipotent with neomycin control drug against all tested strains, while compound 3k was 4-fold higher than neomycin against S. aureus, E. coli, and C. albicans with MIC values of 9.77, 19.53, and 19.53 μg/mL, respectively. Compound 3l was equipotent with neomycin against S. aureus and C. albicans, while it was 2-fold higher than neomycin against E. coli with MIC of 39.06 μg/mL. For 3s, it was less potent than neomycin against all tested microbs with 2-fold and 4-fold less potent. Further scanning electron microscopy (SEM) investigation has been studied to reveal the disruption effect of the selected potent antimicrobial compound (3k) on the intact cells of tested microbs S. aureus, E. coli in addition to C. albicans. Results showed that 3k exhibited a noticeable effect on destroying microbial cell walls. Furthermore, molecular docking study has been done to assess the binding behavior of two most effective compounds 3k and 3l with the target crystal structure of dihydropteroate synthase (PDB: 6CLV for S. aureus) and (PDB: 5U14 for E. coli). Compound 3k was shown to be able to form stable complexes with both target enzymes of dihydropteroate synthase through hydrogen bonding and hydrophobic interactions.

Analysis of fiber post–resin cement interfacial adaptation at different post regions using field emission scanning electron microscopy

Abstract Introduction: An ideal interfacial adaptation between fiber posts and resin cement is critical for optimum retention and good scenario. Therefore, this research was designed to estimate the interfacial adaptation at fiber post–resin cement interfaces using field emission scanning electron microscopy (FESEM) investigation. Materials and Methods: Forty-five extracted human lower premolars with sole and round canal were classified into three groups (n = 15) following the fiber post types. Each tooth was decoronated and implanted in acrylic resin-filled polyvinyl chloride mold. Roots were undergone endodontic management and post space preparations. Then, each group was classified into three subdivisions (n = 5) according to the resin cement types. After cementation, each post space was marked into apical, middle, and coronal thirds and sectioned horizontally into three 2 mm disc thickness for each third. After that, each disc in each sub-group was then subjected to FESEM analysis to evaluate the gaps width at fiber post–resin cement interface in µm. The data were recorded and statistically evaluated and compared using two-way analysis of variance and Duncan’s multiple range tests at P ≤ 0.05. Results: The everStick post with the RelyX U-200 cement group showed significantly the least gap width mean, while the glass fiber post with the TOTAL C-RAM cement has statistically the greatest gap width mean along the coronal, middle, and apical thirds of fiber post at P ≤ 0.05. The apical third of fiber post showed significantly the greatest mean of gap width, while the middle third showed the least gap width mean at P ≤ 0.05. Conclusion: Different brands of fiber post and resin cement can influence the interfacial adaptation at post–cement interface.

Incorporation of CuS nanorods in polyelectrolyte multilayer microcapsules improved cancer cell cytotoxicity and signal intensity in ultrasound imaging

The fabrications of hollow microcapsules (MCs) with new architecture and ability to incorporate different nanomaterials have received great interest for targeted cancer therapy. Recently, CuS based nanomaterials have been demonstrated to possess the ability to mimic Fenton-like activity in tumor environment and inducing cancer cell apoptosis by generating highly reactive oxygen species (ROS). In this study, we have developed poly(allylamine) hydrochloride (PAH)/dextran sulfate (DS) polyelectrolyte MCs capable of carrying doxorubicin (DOX) for targeted cancer therapy and ultrasound imaging. The electron microscopy investigations showed the formation of polymeric MCs of 3 µm in size with incorporated CuS NRs in their interior structure. The surface modification of MCs with folic acid (FA), and encapsulation of model hydrophilic molecules in MCs was studied by UV–Visible (UV–Vis) spectroscopy, Fourier transform infra-red (FTIR) spectroscopy and confocal laser scanning microscopy. The encapsulation efficiency of DOX was found to be 56 % and the release was found to be linear at pH 5.5 and 7.4 in the absence of ultrasound exposure. The ultrasound exposure resulted in sudden rupture of MCs at 1 MHz and 1 W/cm2 and caused burst release of DOX at both pH conditions. The FA decorated PAH/DS/CuS NR MCs exhibited improved anti-cancer activity against MDA-MB-231 cancer cells due to the synergistic effects of ultrasound mediated burst release of chemotherapeutic drug (DOX), glutathione-stimulated ROS and targeted cancer therapy. Further, the capsules showed better echogenicity than that of control PAH/DS MCs when imaged under medical ultrasound-scanning system. Hence, the MCs demonstrated in this study have huge potential for targeted cancer theranostics by offering an option to image the cancer cells during the treatment period.

A study of the spinodal decomposition of AgC[sbnd]u alloy films using in situ transmission electron microscopy

We performed in situ transmission electron microscopy (TEM) investigations to understand spinodal decomposition in AgCu alloy thin films. The decomposition of a homogeneous nanocrystalline morphology into a heterogeneous two-phase structure when annealed in situ from room temperature to 400 °C was investigated with different imaging modes in the TEM. These studies reveal phase transformation proceeds in stages: between 180 and 200 °C, onset of phase separation via spinodal decomposition is observed. Then, prominent phase separation occurs between 200 and 250 °C with minimal grain growth. Next, between 250 and 300 °C, grain growth primarily occurs via coalescence, with no apparent phase separation. From 300 to 350 °C, we observe significant phase separation and Ostwald Ripening. Finally, between 350 and 400 °C, further coarsening occurs via coalescence. STEM-HAADF mode reveals the onset of phase separation from domains as small as 5 nm and these results are also supported by electron diffraction and compositional mapping.

In Situ Formation of SnSe2/SnSe Vertical Heterostructures toward Polarization Selectable Band Alignments.

2D van der Waals (vdW) layered semiconductor vertical heterostructures with controllable band alignment are highly desired for nanodevice applications including photodetection and photovoltaics. However, current 2D vdW heterostructures are mainly obtained via mechanical exfoliation and stacking process, intrinsically limiting the yield and reproducibility, hardly achieving large-area with specific orientation. Here, large-area vdW-epitaxial SnSe2/SnSe heterostructures are obtained by annealing layered SnSe. These in situ Raman analyses reveal the optimized annealing conditions for the phase transition of SnSe to SnSe2. The spherical aberration-corrected transmission electron microscopy investigations demonstrate that layered SnSe2 epitaxially forms on SnSe surface with atomically sharp interface and specific orientation. Optical characterizations and theoretical calculations reveal valley polarization of the heterostructures that originate from SnSe, suggesting a naturally adjustable band alignment between type-II and type-III, only relying on the polarization angle of incident lights. This work not only offers a unique and accessible approach to obtaining large-area SnSe2/SnSe heterostructures with new insight into the formation mechanism of vdW heterostructures, but also opens the intriguing optical applications based on valleytronic nanoheterostructures.

Physics and chemistry from parsimonious representations: image analysis via invariant variational autoencoders

Electron, optical, and scanning probe microscopy methods are generating ever increasing volume of image data containing information on atomic and mesoscale structures and functionalities. This necessitates the development of the machine learning methods for discovery of physical and chemical phenomena from the data, such as manifestations of symmetry breaking phenomena in electron and scanning tunneling microscopy images, or variability of the nanoparticles. Variational autoencoders (VAEs) are emerging as a powerful paradigm for the unsupervised data analysis, allowing to disentangle the factors of variability and discover optimal parsimonious representation. Here, we summarize recent developments in VAEs, covering the basic principles and intuition behind the VAEs. The invariant VAEs are introduced as an approach to accommodate scale and translation invariances present in imaging data and separate known factors of variations from the ones to be discovered. We further describe the opportunities enabled by the control over VAE architecture, including conditional, semi-supervised, and joint VAEs. Several case studies of VAE applications for toy models and experimental datasets in Scanning Transmission Electron Microscopy are discussed, emphasizing the deep connection between VAE and basic physical principles. Python codes and datasets discussed in this article are available at https://github.com/saimani5/VAE-tutorials and can be used by researchers as an application guide when applying these to their own datasets.

Invited: Mimicking Biological Synapse Activity with LDH-Based Memristor

Memristors, mimicking biological synapse response, are believed to have a great potential for use as an adaptive memory unit in future neuromorphic computing systems. Here we report on fabrication of two-dimensional memristor comprised of layered double hydroxide (LDH) material, covered with graphene layer, serving as a terminal for connecting to electrodes. We demonstrated nonvolatile resistive switching of LDH memristor. Device performance is studied upon replacing graphene semimetal with alternative 2D materials. Comprehensive characterization of the memristor materials was performed with correlated Raman, Electron, and Scanning Probe Microscopy methods.ACKNOWLEDGMENTThis work was supported by the US Department of Defense (Contract #W911QY2220006), 2DCC-MIP NSF cooperative agreement DMR-2039351. Work was performed at JSNN, a member of the Southeastern Nanotechnology Infrastructure Corridor (SENIC) and National Nanotechnology Coordinated Infrastructure (NNCI), which is supported by the NSF (ECCS-1542174)

(Invited) Electron Microscopy Investigation of PEM Electrolyzer Degradation at Low Iridium Loadings

The employment of hydrogen as an energy carrier provides a promising solution toward zero carbon emission and battling climate change. To meet the DOE’s Hydrogen Shot goal of $1 per kilogram of hydrogen by 2031, proton exchange membrane (PEM) water electrolysis is a key technology of hydrogen production from renewable energy sources. Successful deployment of PEM electrolyzers requires reducing cost while simultaneously improving performance and lifetime. While cost reduction is expected from a variety of strategies including scaling up, operation optimization, and advanced manufacturing, it remains vital to reduce the use of noble-metal catalyst due to its scarcity and vulnerable supply chain subject to market disturbance. [1]Reducing the loading of iridium catalyst on the anode while maintaining electrolyzer performance and durability is of great challenge. In this talk, we discuss issues in PEM electrolyzer component development and advanced manufacturing of electrode layers related to catalyst loading reduction with an emphasize on analytical electron microscopy which provides valuable insight on materials morphology, crystalline structure, and chemical compositions. The batch-to-batch variance of catalyst morphology and elemental composition/distribution from commercial suppliers will be examined for catalyst down-selection. We then analyze the effect of reducing Ir loading on the electrode layer structure and ionomer distribution. These results are correlated with electrochemical measurements in the electrolyzer cell, which help elucidate the effect of low catalyst loading on electrolyzer performance. Morphologies of degraded low-loading anode catalyst layer and gas recombination layers will be investigated, and the dissolution and migration of iridium will be studied. We will also examine impact of different roll-to-roll manufacturing strategies for low-loading catalyst layers and on electrolyzer durability. Last but not least, we analyze MEAs subject to cation contamination and recovery procedure with electron microscopy. [2]References[1] Alia, S.M., Current Opinion in Chemical Engineering 2021, 33:100703.[2] Funding for this work was provided by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office through the H2NEW Consortium. Electron microscopy research conducted as part of a user project at the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory.

Adapting Conductivity and Mechanical Properties through Layer Thickness Variation in Copper Niobium Laminated Metallic Composites

Cu/Nb laminated metallic composites (LMCs) exhibit extraordinary mechanical strength while electrical conductivity is maintained at a high level. In this research, Cu‐based LMCs with varying volume fraction of niobium are produced via accumulative roll bonding (ARB) and additionally cold‐rolled and heat‐treated to identify the role of these heterogeneous phase boundaries on the overall sheet properties. Deformation structures in these layered materials are studied through scanning transmission electron microscopy investigations. The existence of an interface‐affected zone at the phase boundaries and mechanical intermixing is attributed to decreasing electrical and increasing mechanical properties, especially in very thin layered LMCs. Atom probe tomography measurements show that mechanical alloying occurs due to severe plastic deformation during ARB processing of the laminates. An additional subsequent heat treatment leads to chemical demixing at the interfaces of the phase boundaries.

Comparison of kink-band structures and specificities of cell wall polysaccharides in modern and ancient flax fibres

Flax (Linum usitatissimum L.) is a plant of industrial importance, its fibres being presently used for high-value textile applications, composite reinforcements as well as natural actuators. Human interest in this fibre-rich plant dates back several millennia, including to Ancient Egypt where flax was used extensively in various quotidian items. While the recent technical developments of flax fibres continue to diversify through scientific research, the historical use of flax also has rich lessons for today. Through careful examination of ancient Egyptian and modern flax fibres, this study aims to conduct a multi-scale characterization from the yarn to the fibre cell wall scale, linking differences in structure and polysaccharide content to the mechanical performance and durability of flax. Here, a multi-scale biochemical study is enriched by scanning electron microscopy and nanomechanical investigations. A key finding is the similarity of cellulose features, crystallinity index and local mechanical performances between ancient and modern fibres. Biochemically speaking, monosaccharides analysis, deep-UV and NMR investigations demonstrate that ancient fibres exhibit less pectins but a similar hemicellulosic content, especially through uronic acids and galactose, suggesting the sensitivity of these non-crystalline components.

Microstructural and mechanical properties of Al-Al2O3 micro and nanocomposite fabricated by stir casting

ABSTRACT The current study examines the relationship between the microstructure and tribological characteristics of Al-Si alloy composites reinforced by secondary phase nano SiC particulates synthesis via the stir casting process. The results of wear testing of stir-cast SiC metal matrix composites including up to 12 weight percent fine (75–100 µm) and coarse (125–150 µm) size particles were obtained from cast aluminium alloy. It was discovered via microstructural investigation that the aluminium alloy and SiC particles have good interface bonding. However, at greater amounts (12 wt.%) of fine size reinforcement, clustering of reinforced particles is observed. In addition, results state that finer size particles agglomerate more in the matrix than coarser size particles at greater reinforcement levels. In addition, increasing the amount of SiC particles in the matrix enhanced the hardness of the base alloy. However, when the size of the SiC particles was reduced, the hardness of the composite increased dramatically. Better wear resistance was observed for higher SiC reinforcement levels, while higher forces were also associated with a corresponding increase in wear rate. A combined mode of adhesive and abrasive wear mechanisms is responsible for composite wear, according to a scanning electron microscopy (SEM) investigation of worn surfaces.

Compressive behavior of thermoplastic polyurethane with an active agent foaming for 3D-printed customized comfort insoles

The primary objective of this study was to investigate the compressive behavior of 3D-printed specimens made of a thermoplastic polyurethane filament, specifically colorFabb varioShore TPU, which incorporates a foaming agent. The foaming technology makes it possible to manipulate 3D prints' properties by adjusting process parameters that affect the level of expansion, such as printing temperature, printing speed or flow ratio. This capability opens new possibilities for 3D-printed personalized foot orthotics or for static comfort-oriented applications by tailoring the stiffness of the print based on the application requirements. Since infill density and infill pattern also affect the compressive characteristics of 3D prints, this research took these two parameters into account as independent variables, alongside the printing temperature. Thus, the specimens with printing temperatures set at 190 °C, 220 °C, and 240 °C, gyroid and honeycomb patterns, and infill variations from 10 % to 35 % in 5 % increments were experimentally investigated in compression testing. The evaluation was conducted to determine the influence of these factors on the stiffness of prints at 10 % and 20 % strains, in accordance with established standard. The findings had an important practical value as they provide data for adjusting the variable stiffness based on peak plantar pressure measurement data when developing tailored foot orthoses (insoles), which was the second objective of the research. The most influential factor affecting the compressive strength was the printing temperature, followed by infill density and pattern type. The difference in compression modulus between 10 % and 20 % strains did not exhibit statistical significance. Moreover, the main effects plots indicated minimal variations in compression modulus effects at 220 °C and 240 °C, whereas an important difference was observed at 190 °C printing temperature, which was confirmed by scanning electron microscopy investigations showing foamed layers at 220 °C and unfoamed layers at 190 °C. Furthermore, interaction plots revealed no significant interaction effect among the studied variables. Additionally, a comparison of samples’ sizes and densities before and two months after testing indicated no observable modifications When applied to custom orthotics (five pairs of insoles were customized and tested), the experimental findings documented variations in the reduction and distribution of peak plantar pressure based on the infill variability.

Atomistic phase transition mechanism of zero-strain electrode material: Transmission electron microscopy investigation of Li4Ti5O12 spinel lattice upon lithiation

The lithiation mechanism of electrode materials is important for understanding the basic reactions in Li-ion batteries. In particular, zero-strain materials have garnered interest owing to their stable charge–discharge performances. In this study, we investigated the atomistic phase transition mechanism of spinel Li4Ti5O12, a well-known zero-strain material, using high-resolution transmission electron microscopy. A single-crystalline Li4Ti5O12 (100) specimen was prepared and observed in situ at a lattice resolution under electron-beam-assisted lithiation. The lattice fringes originating from the Li plane of the spinel crystal were anisotropically altered during phase transition, suggesting the asymmetrical site shifting of Li atoms during lithiation. This spontaneous symmetry-breaking mechanism for the phase transition is considered essential for the lithiation of spinel lattice.

Teak leaf biochar production for sustainable forest waste management at low temperatures

This study investigates the possibilities of producing biochar from teak leaves as an environmentally beneficial approach to managing forest waste in a sustainable manner. Teak leaves, a readily available forest by-product, were converted into biochar through a low-temperature pyrolysis process using a top-lit updraft mechanism. The results demonstrate the efficiency of this approach, yielding a substantial biochar output of 37.4 wt%, with its thermal field modelled perfectly via Levenberg-Marquardt algorithm in ANN topology. Elemental analysis of the teak leaf biochar revealed a high carbon content of 64.40%, positioning it as a valuable carbon-rich material suitable for various applications. Textural properties analysis indicated a significant surface area of 371.78 m2/g and a total pore volume of 0.175 cm³/g, enhancing its potential for various applications. Scanning Electron Microscopy (SEM) investigations showed a diverse network of pores and a rough surface structure, reinforcing the biochar’s versatility. This study shows the environmental benefits of low-temperature teak leaf biochar production, because it provides a carbon-content-preserving, sustainable alternative for handling forest wastes.