Microstructural Changes Research Articles

Recycling devulcanized EPDM to improve engineering properties of SBR rubber compounds

Ethylene propylene diene rubbers (EPDM) have gained substantial attention in automotive and industrial applications owing to their exceptional resistance against weathering and heat. Despite their advantages, the elastomeric nature of EPDM poses challenges in its recycling due to the presence of crosslinks in their chemical structure, preventing them from melting. To overcome this issue, devulcanized EPDM (EPDMd) has been developed, characterized by the effective breaking of these crosslinks. Our study focuses on common composites that include Styrene Butadiene Rubber (SBR), EPDM and silica, but with the incorporation of devulcanized EPDM (EPDMd).We have studied the mechanical, thermal, structural and dielectric properties of SBR composites containing EPDMd at variable compositions (0, 20, 40, 50, 60 phr). Employing techniques such as Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectropy (FTIR), and Scanning Electronic Microscopy (SEM), we have explored the microstructural changes driving the macroscopic effects on the measured properties.The results show that incorporating EPDMd improves the crosslinking degree and, at optimal 40 phr loading, significantly increases the mechanical properties of SBR matrix. The addition of SiO2, in general, reduce tensile strength and elongation, while increasing the Young's modulus, except for compositions around 40 phr EPDMd. The dielectric measurements are in concordance with the previous data, showing a moderation of the Maxwell–Wagner–Sillars (MWS) effect due to SiO2 in highly filled EPDMd composites at 40 phr EPDMd.

Dependence of the mechanical properties of nylon-carbon fiber composite on the FDM printing parameters

Nylon-based polymer reinforced with short carbon fibers (PA-CFs), fabricated using the Fused Deposition Modeling (FDM) 3D printing process, has been proposed for various applications. However, the mechanical performance of these materials as a function of printing parameters, including wall thickness at infill contents < 100 %, has yet to be reported in the literature. This paper focuses on the effects of infill percentage, nozzle temperature, and wall thickness on the porosity content, microstructure, and mechanical properties of PA-CF specimens. Employing a Taguchi (L9 − 3^3) design of experiments, tensile and flexural testing were conducted to assess their mechanical response. The printing temperature induces microstructural changes, promoting interlayer debonding due to voids and pores at wall- and skin-core interfaces. Wall thickness significantly impacts tensile strength and can be maintained between 0.8 and 1.35 mm for maximum flexural strength, while maximal tensile strength can only be achieved with a wall thickness between 1.15 and 1.5 mm.

Study of bainite and martensite tempering in a medium C high Si steel. microstructural disparities and equilibrium convergence

This study investigates the tempering behavior of bainite and martensite in a medium carbon, high silicon steel, with a focus on the microstructural evolution and the attainment of equilibrium, over a temperature range of 200–650 °C. The dissimilarities between the characteristics of the two initial microstructures, both comprising a C-saturated tetragonal ferrite matrix and retained austenite, are reflected in the differences observed in their evolution towards equilibrium as the tempering temperature increases. Therefore, while retained austenite plays a pivotal role in the bainitic microstructure, in the martensitic microstructure it is the ferritic matrix, which is highly dislocated and enriched in carbon, that plays a determinant role. The findings demonstrate that while both bainite and martensite can converge towards the same equilibrium state upon high-temperature tempering (600–650 °C), the pathway to this convergence is markedly different, with bainite exhibiting a slower transformation rate. This path to equilibrium has been characterised by means of high-resolution dilatometry, scanning electron microscopy and detailed X-ray diffraction analysis. This has provided a dynamic and detailed picture of the most relevant microstructural changes and tempering mechanisms in high silicon steels. It has also provided a foundation for tailoring heat treatment processes to optimise the mechanical properties of advanced bainitic and martensitic steels.

Effects of heating media on microstructure and chemical composition of heat-treated Pometia pinnata

Changes of microstructure, crystallization, chemical composition, and equilibrium moisture content (EMC) of heat-treated wood (HTW) were investigated to explore the effects of heating media (saturated steam, superheated steam, air) and heat treatment (HT) temperature on HTWs. The results showed that the saturated steam induced more severe cell wall destruction than the other two media. Although the porosity slightly increased with the increasing HT temperature, superheated steam and air HT still decreased the porosity compared to that of control, whereas saturated steam HT increased the porosity. The HT increased both relative crystallinity and crystal size of HTWs. The increasing HT temperature slightly increased the relative crystallinity but decreased the crystal size. The highest crystallinity (55.0%) was observed after saturated steam HT. Leaching led to the increase of crystal size of HTW treated in saturated steam (about 0.15 nm), while those treated in unsaturated steam and air decreased. The increase in relative amount of lignin and cellulose due to the hemicellulose degradation were the main chemical changes of HTWs. Further lignin condensation reaction only occurred after saturated steam HT. Although saturated steam HT induced increased porosity, its lowest EMC (5.91%) indicated the decrease of hydroxyl groups.

Microstructural changes in the welding of titanium-stabilized steels

Abstract At the Central Institute for Engineering, electronics, and Analytics (ZEA-1 by its acronym in German) of the Jülich Research Center GmbH, a cryostat was developed for the European Spallation Neutron Source (ESS) and manufactured from a titanium-stabilized austenitic stainless steel alloy (EN 1.4571). After tungsten inert gas welding, the welds exhibited a black, patchy discoloration. After materialographic preparation, the phenomena were examined using microscopic methods to assess their impact on the strength of the weld and thus on the usability of the cryostat. Not only could the impact on the cryostat operation be assessed, but the formation mechanism could be elucidated and suitable measures could be outlined to avoid the black, patchy discoloration.

Microstructures of iron meteorites

Abstract Meteorites originate from the early phase of our solar system and are wonderfully undefined and inhomogeneous. In terms of its composition and microstructure, one single meteorite has quite a few surprises in store. The iron meteorite microstructure depends essentially on the initial solidification of the melt in a larger asteroid or minor planet. The solidification process itself is a function of local element concentrations and the very slow cooling rate. Various collisions in space resulted in the fragmentation of the asteroids and the deformation of the microstructure. However, whether visible microstructural changes occur or not depends on the microstructure itself. And finally, corrosion may also occur in the Earth’s atmosphere. An attempt is made to explain the different microstructures on the example of three iron meteorites, namely those found in Canyon Diablo, Gebel Kamil, and Dronino.

Valorization of ladle furnace slag and functional enhancement of post-adsorption materials

Carbonating metallurgical slags plays a pivotal role in achieving efficient mineral CO2 sequestration and waste valorization.This research introduces a novel integrated approach that combines the carbonation of Ladle Furnace Slag (LFS) with the simultaneous degradation of Methyl Orange (MO) in synthetic water. The comprehensive characterization of LFS was conducted using X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), Brunauer-Emmett-Teller (BET) analysis, and Scanning Electron Microscopy (SEM). The adsorption experiments reveal the high LSF capacity for MO degradation (149.25 mg/g) following pseudo-second-order kinetics (R2 = 0.99) and Langmuir isotherm (R2 = 0.98). The adsorption process was primarily governed by chemical and electrostatic interactions. Analysis of LFS-loaded MO indicated a reduction in Ca(OH)2phases, responsible for CO2mineralization and the formation of calcite (CaCO3). Furthermore, the study explored the reusability of LFS-MO composites through chemical and thermal modifications. Pyrolysis of carbonated LFS with KOH impregnation exhibited potential for regenerating Ca(OH)2phases, while thermal modification induced significant mineral and microstructural changes, creating new active sites at various temperatures. Additionally, the Fenton-like reaction followed by thermal modification resulted in a highly organized and microporous LFS structure with enhanced surface area and porosity. Moreover, modification with ZnSO4followed by thermal activation promoted the formation of ZnO nanoxides on the LFS surface. This research proposes an innovative carbonating approach for metallurgical slags and wastewater treatment, extending their utility and enhancing industrial sustainability. Carbonated LFS-MO composites hold promise for applications in construction, CO2capture, and wastewater treatment, thereby fostering sustainable industrial practices with ongoing research and development efforts.

Early age accelerated carbonation of cementitious materials surface in low CO2 concentration condition

Accelerated carbonation curing contributes to the carbon sequestration effect of cementitious materials and enhances surface density. However, in large-scale applications, traditional high CO2 concentration conditions (>5 % CO2) are constrained by economic costs. This study traces the early-stage accelerated carbonation process of cement mortar under low CO2 concentration (3 % CO2) condition from the perspectives of the evolution of CaCO3 crystal types, phase transformations, and microstructural changes, and compares the results with those under the 20 % CO2 condition. The results show that the carbonation depth of mortar specimens cured under the 3 % CO2 condition is shallower, but the cumulative concentration of CaCO3 within the surface 3 mm is not significantly lower than that under the 20 % CO2 condition; The carbonation zone generates more low-crystalline forms of CaCO3; The accelerated carbonation process does not affect the formation of CH and ettringite. Microscopic results indicate that under the 3 % CO2 condition, the synergistic effects of hydration and carbonation are better, and appropriately extending the curing time helps to refine the pore structure of the carbonation zone and improve the density of the substrate surface.

Determining of the effect of reinforcing microrelief guides on the efficiency of folding integrated covers

The object of research is the processes of strengthening the working surfaces of profile folding strips made of stainless steel AISI 347 and carbon steel AISI 1005 using laser formation of microrelief guides. The analytical and experimental studies are based on the technique of laser microrelief formation by pulsed laser effects. The main assumption of the study is that the use of laser microrelief formation could increase the hardness and wear resistance of the folding strips, improving the process of folding integrated covers. Analyzing the effect of different hardening methods on the mechanical properties and wear resistance of the working surfaces of folding strips is necessary to achieve this goal. A methodology for assessing microstructural changes and their impact on the mechanical properties of folding strips during laser hardening has been proposed. It has been shown that the formation of microrelief guides by laser pulse exposure reduces the thermal load on the material, increases the uniformity of hardening and wear resistance. The revealed wear rates calculated for carbon steel AISI 1005 are 0.875, and for stainless steel AISI 347 – 0.345. To improve the accuracy and efficiency of the folding process, a methodology has been devised for calculating the quantitative formation of microrelief guides on the working surface of profile folding strips. This will not only improve the wear resistance and mechanical properties of the strips but also optimize production processes. Differences in the results of hardening for stainless steel AISI 347 and carbon steel AISI 1005 were found: the hardness values for AISI 347 are 3,088–4,904 MPa at a load of 50–350 g with a deviation of 37.1 %, and for AISI 1005 – 2141–1665 MPa with a deviation of 22.3 %

Effects of Ultrasonication in Water and Isopropyl Alcohol on High-Crystalline Cellulose: A Fourier Transform Infrared Spectrometry and X-ray Diffraction Investigation.

This paper investigates the effects of ultrasonication on cellulose microparticles in different conditions. FTIR (Fourier transformed infrared spectrometry) and XRD (X-ray diffraction) analyses were used to compare the changes in the cellulose microstructure caused by the following various ultrasonic treatment conditions: time, amplitude of generated ultrasound waves, output power converted into ultrasound, the liquid medium (water and isopropyl alcohol) used for ultrasonication, and the shape of the vessel used for sonication. The cumulative results lead to an increase in the crystalline region directly proportional to the condition of sonication. Also, the total crystallinity index varied from 1.39 (pristine cellulose) to 1.94 for sonication in alcohol to 0.56 for sonication in water. The crystallinity index varied from 67% (cellulose) to 77% for the sample with 15 min of sonication in isopropyl alcohol and 50.4% for the sample with 15 min of sonication in water.

Atmosphere toward regulation of MoO3 microstructure for lactic acid hydrodeoxygenation to propionic acid

Regulation of MoO3 microstructure was explored at different atmospheres, which was further evaluated for catalytic performance on lactic acid hydrodeoxygenation. Catalyst structure was characterized by XRD, FT-IR, HRTEM, and oxygen vacancies were measured by EPR and XPS spectra. It was found that the direct H2-Ar treatment generated an obvious change in MoO3 microstructure to form rich oxygen vacancies in MoO3-H, and the succedent H2-Ar treatment had negligible influence in MoO3-A-H, indicating that the non-crystallizing MoO3 is effortless to generate oxygen vacancy with H2-Ar atmosphere treatment. Correspondingly, MoO3-H achieved 58.6 % of lactic acid conversion and 64.7 % of propionic acid selectivity much higher than MoO3-A-H with 41.7 % of lactic acid conversion and 56.9 % of propionic acid selectivity, which also outperformed most of the LA hydrodeoxygenation catalysts in propionic acid selectivity. This work demonstrates that the calcined atmospheres can efficiently regulate MoO3 microstructure to form rich oxygen vacancies for lactic acid hydrodeoxygenation to propionic acid.

What has brain diffusion magnetic resonance imaging taught us about chronic primary pain: a narrative review.

Chronic pain is a pervasive and debilitating condition with increasing implications for public health, affecting millions of individuals worldwide. Despite its high prevalence, the underlying neural mechanisms and pathophysiology remain only partly understood. Since its introduction 35 years ago, brain diffusion magnetic resonance imaging (MRI) has emerged as a powerful tool to investigate changes in white matter microstructure and connectivity associated with chronic pain. This review synthesizes findings from 58 articles that constitute the current research landscape, covering methods and key discoveries. We discuss the evidence supporting the role of altered white matter microstructure and connectivity in chronic primary pain conditions, highlighting the importance of studying multiple chronic pain syndromes to identify common neurobiological pathways. We also explore the prospective clinical utility of diffusion MRI, such as its role in identifying diagnostic, prognostic, and therapeutic biomarkers. Furthermore, we address shortcomings and challenges associated with brain diffusion MRI in chronic primary pain studies, emphasizing the need for the harmonization of data acquisition and analysis methods. We conclude by highlighting emerging approaches and prospective avenues in the field that may provide new insights into the pathophysiology of chronic pain and potential new therapeutic targets. Because of the limited current body of research and unidentified targeted therapeutic strategies, we are forced to conclude that further research is required. However, we believe that brain diffusion MRI presents a promising opportunity for enhancing our understanding of chronic pain and improving clinical outcomes.

Macro–micro correlation analysis on the loess from Ili River Valley subjected to freeze–thaw cycles

The Ili River Valley in Xinjiang, China, is a typical seasonal frozen area where loess landslide disasters have become increasingly common during the freeze–thaw periods in recent years. This study analyzed the macroscopic mechanical strength and microstructure changes of the Ili loess under different freeze–thaw cycles (FTCs) through the post-freeze–thaw triaxial compression test on the unsaturated soil in laboratory. Apart from the scanning electron microscopy (SEM), and the nuclear magnetic resonance (NMR), the macro–micro correlation analysis and the cluster-principal component analysis were applied for the theoretical discussion. The results indicated that the cohesive force of the loess exhibits an initial decreases, followed by the increases, and eventually keep stable after various FTCs, while the internal friction angle showed the opposite developing trend before the final constant. Similar to the strong correlation between the cohesive force and the particle abundance, the internal friction angle is also closely related to the abundance and orientation fractal dimension of the loess particles. However, the principal component analysis results showed that cohesive force strongly correlates with the average maximum pore size and the pore size fractal dimension, for which the internal friction angle most strongly affected by the average maximum particle size. The possible reason is that the extracted principal components represent a class of microscopic parameters with the same or similar change trend, although there may be a certain offset between them. The mechanical deterioration of loess is attributed to the repeated frost heaving force and the migration potential caused by FTCs. The alterations of the microstructure accelerated the deterioration of the macroscopic mechanical properties of the loess, which further widens the understanding of the mechanism behind the deterioration of loess mechanical strength in the Ili River Valley under FTCs, and contributes to the prevention and management of the local landslide disasters.

Texture and lattice strain evolution in a pearlitic steel during shear deformation: An in situ synchrotron X-ray diffraction study

In-situ synchrotron X-ray diffraction experiments were conducted on the pearlitic steel sample with a carbon content of 0.74% by weight. Specimens were subjected to uniaxial loading that induced shear deformation and two-dimensional diffraction patterns were acquired. The evolution of the lattice microstrain and the strain-resolved crystallographic texture development of both ferrite (α-BCC) and cementite (θ-orthorhombic) phases were followed. The analysis revealed that the texture changed from {110}<113>α to {113}<121>α component and then, stabilized at {013}<uvw>α orientations. The θ phase exhibited a weak texture in the {100, 010, and 001}θ family planes. Additionally, it was revealed that the nucleation of interfacial defects at the α/θ interface promotes the amorphization of cementite and the activation of slip systems in less densely packed {310}α planes. The influence of microstructural changes on mechanical properties is discussed.

Effect of Continuous Electrolysis on the Power Generation Performance of a Microtubular Oxide Fuel Cell Using Intermediate Ring‐Shaped Collector

An anode‐support microtubular solid oxide fuel cell (MTSOFC) using an intermediate ring‐shaped electrode collector is simulated using COMSOL Multiphysics software to investigate current density distribution and mass transfer in both power generation and electrolysis modes. The cell is converted to power generation mode during continuous electrolysis, and the electrochemical performance of MTSOFC is tested to study the effect of electrolysis on the power generation performance. The power density output of the MTSOFC decreases from 250 to 150 mW cm−2 after only 40 h of continuous electrolysis. The microstructural changes in different regions during operation are observed through posttest analysis conducted on the fuel inlet, electrochemical reaction concentration region, and fuel outlet of the microtubular cell. The local agglomeration of nickel occurs in the concentrated region of the electrochemical reaction, while the coarsening of nickel oxidation mainly takes place at the fuel inlet and outlet.

Exploring the reinforcing mechanism of graphene oxide in cementitious materials through microstructural analysis of synthesised calcium silicate hydrate

Graphene oxide (GO) has been shown to enhance the mechanical properties and durability of cementitious materials, although the exact reinforcement mechanism is not fully understood. Given the critical role of calcium silicate hydrate (CSH) in determining these materials' properties, this study investigates the microstructural changes in CSH with the incorporation of GO. Using a co-precipitation method, CSH samples with and without GO were synthesised and characterised through thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and nuclear magnetic resonance (29Si NMR and 1H NMR). The results demonstrated that GO incorporation enhances the polymerisation and crystallinity of CSH, as evidenced by TGA and XRD. FTIR and SEM analyses indicated that the CSH structures became more ordered and denser with GO addition. NMR analysis further confirmed improved structural order and reduced interlayer spacing. Overall, incorporating GO into CSH significantly increases crystallite size and promotes a more ordered CSH structure. These effects collectively result in enhanced load transfer, improved crystal interlocking, and a synergistic improvement in the mechanical properties and durability of cementitious materials.

Investigations on the influence of hot rolling on the creep characteristics of additively manufactured Mg-5Ag alloy

The requirement for lightweight materials that can survive increasingly severe conditions for aerospace components has fueled the research on magnesium alloys. The current work investigates the influence of hot rolling on the creep characteristics of the Mg-5Ag alloy that is fabricated through a selective laser melting process. The creep properties of parent material (PM) and hot-rolled specimens (HRA) are determined by indentation creep tests at 250 °C, 275 °C, and 300 °C. The microstructural evolution, phase transformation kinetics, and texture evolution were deduced using instrumental analysis, including SEM, EBSD, TEM, and XRD. The specimen PM features α-Mg grains with intermetallic Mg-Ag particles along grain boundaries and random grain orientations with low-angle boundaries. However, specimen HRA has a more fraction of Mg-Ag precipitates, a dominant (0001) grain orientation, and higher peak intensity from the (002) plane. The HRA specimen also demonstrates higher apparent activation energies, attributed to microstructural changes from hot rolling. The results show that the creep resistance of the hot rolled Mg-5Ag alloy is superior to as-fabricated Mg-5Ag alloy based on the creep velocity, stress exponent, and apparent activation energy.

Whey protein and maltodextrin conjugated foam-mat dried honey powder: Functional, physicochemical, structural, rheological and thermal characterization

Honey in its natural form possesses considerable challenges in mass production and transportation owing to its viscosity and stickiness, making it prone to crystallization over time. Dried honey powder makes it convenient for handling and processing. In this study, foam mat dried powder (FMDP) was obtained by foam mat drying technique in which whey protein isolate (WPI) and maltodextrin (MD) were used as foaming agent and foam stabilizer, respectively. The obtained FMDP was characterized in terms of physical, chemical, functional, phytochemical, rheological and structural properties to study the impact of foaming agents. WPI was found to improve the functionality, stability and glass transition temperature and on the other hand, MD was found to enhance the stability, crystallinity and the color of the FMDP. FTIR helped in understanding the changes in the functional groups attributed to the foaming agents. The crystallinity and the microstructural changes in the FMDP were observed from X-ray diffractograms and SEM micrographs, respectively. The rheological characterization confirmed the viscous nature of honey. The study confirmed the interaction between proteins and polysaccharides, which subsequently improved the heat stability, functional properties, solubility, emulsifying capacity, antioxidant properties, and solubility. The dried honey samples demonstrated minimal caking, low cohesiveness (Hausner ratio: 1.16 ± 0.027–1.29 ± 0.041), good and fair flowability (ranging between 14.25 ± 2.02–22.52 ± 2.25). Therefore, it can be concluded that during this study, protein and polysaccharide conjugate FMDP was obtained with better quality attributes, which can be further incorporated during various product development in food industries.

The developing hippocampus: Microstructural evolution through childhood and adolescence.

The hippocampus is a structure in the medial temporal lobe which serves multiple cognitive functions. While important, the development of the hippocampus in the formative period of childhood and adolescence has not been extensively investigated, with most contemporary research focusing on macrostructural measures of volume. Thus, there has been little research on the development of the micron-scale structures (i.e., microstructure) of the hippocampus, which engender its cognitive functions. The current study examined age-related changes of hippocampal microstructure using diffusion MRI data acquired with an ultra-strong gradient (300 mT/m) MRI scanner in a sample of children and adolescents (N=88; 8-19 years). Surface-based hippocampal modelling was combined with established microstructural approaches, such as Diffusion Tensor Imaging (DTI) and Neurite Orientation Dispersion Density Imaging (NODDI), and a more advanced gray matter diffusion model Soma And Neurite Density Imaging (SANDI). No significant changes in macrostructural measures (volume, gyrification, and thickness) were found between 8-19 years, while significant changes in microstructure measures related to neurites (from NODDI and SANDI), soma (from SANDI), and mean diffusivity (from DTI) were found. In particular, there was a significant increase across age in neurite MR signal fraction and a significant decrease in extracellular MR signal fraction and mean diffusivity across the hippocampal subfields and long-axis. A significant negative correlation between age and MR apparent soma radius was found in the subiculum and CA1 throughout the anterior and body of the hippocampus. Further surface-based analyses uncovered variability in age-related microstructural changes between the subfields and long-axis, which may reflect ostensible developmental differences along these two axes. Finally, correlation of hippocampal surfaces representing age-related changes of microstructure with maps derived from histology allowed for postulation of the potential underlying microstructure that diffusion changes across age may be capturing. Overall, distinct neurite and soma developmental profiles in the human hippocampus during late childhood and adolescence are reported for the first time.

Fracture toughness and microstructural analysis of rotary friction welded S355J2 and SS316L steels for critical applications

Dissimilar metal welding is seeing growing adoption across industries to enhance structural functionality and efficiency. Achieving high-quality, defect-free dissimilar weld joints requires a comprehensive understanding of the interrelationships between the welding-induced microstructural changes and the material's performance characteristics, particularly its fracture-related properties. This study investigates the impact of microstructural changes on the fracture toughness of dissimilar welds between structural low-carbon steel (S355J2) and austenitic stainless steel (SS316L) prepared using the Rotary Friction Welding (RFW) technique. Welding preforms were created from respective pipe pup pieces. The evaluation involves microstructural analysis, tensile testing, hardness testing, and fracture toughness testing using compact tension specimens derived from various zones of the weld joints. Results revealed significant microstructural differences across the weld joint. The weld region exhibited stable hardness with a maximum of 208 HV1 in S355J2′s thermo-mechanically affected zone (TMAZ). High tensile strength (Ultimate Tensile Strength 540 MPa, Yield Strength 367 MPa) with failures mainly on the S355J2 side. The fracture toughness (KQ) matched parent metal values, with the RFW weld centre line (WCL) showing superior crack tip opening displacement (CTOD) of 0.35 mm. Fractography generally indicates ductile failure.