Microstructure Composition Research Articles

A green inorganic binder for material extrusion of ultra-low shrinkage and relatively high strength metakaolin ceramics at low sintering temperature

Ultra-low shrinkage and relatively high strength metakaolin ceramics printed by material extrusion were innovatively fabricated using inorganic aluminum dihydrogen phosphate (Al(H2PO4)3) as a binder and low sintering temperature. The optical microscopy, scanning electron microscopy (SEM), electronic vernier caliper, three-point bending test, Archimedes method and X-ray diffraction (XRD) were used to measure and evaluate the surface morphology, microstructure, dimensional shrinkage, flexural strength, porosity and phase composition of the printed ceramics sintered at different temperatures. The results showed that when the mass ratio of metakaolin, Al(H2PO4)3 and deionized water was 17:6:2, the rheological characteristic of the purely green inorganic ceramic slurry was very suitable for material extrusion additive manufacturing, and the corresponding printed ceramic green bodies possessed high-quality formability. The ceramic samples sintered at 750 °C possessed the best whiteness, the lowest shrinkage (<2%), relatively high flexural strength (9.02 MPa). As the sintering temperature increased, Al(H2PO4)3 transformed to aluminum metaphosphate Al(PO3)3, and then decomposed into aluminum phosphate (AlPO4) and phosphorus pentoxide gas (P2O5), which caused pores and reduced strength, and alumina oxide (Al2O3) and silicon oxide (SiO2) in metakaolin gradually transformed to mullite and cristobalite with more stable structure and higher strength.

A study on influence of sintering temperature, diameter and volume fraction of metal hollow spheres on the mechanical properties of metal hollow spheres composites

The structural parameters (the sintering temperature, diameter, and volume fraction of the hollow spheres) have a considerable influence on the mechanical properties of metal hollow sphere composites (MHSCs). Hence, the influence laws of the structural parameters on the mechanical properties of MHSCs possess certain research significance. To obtain these laws, MHSCs with different structural parameters were fabricated using a pressure casting method. Subsequently, the density of the MHSCs was determined through the direct measurement method. Meanwhile, X-ray diffraction and scanning electron microscopy were employed to conduct in-depth analyses of the phase composition and microstructure of the MHSCs. Additionally, the compression performance of the MHSCs was measured with the assistance of a universal mechanical testing machine. The analysis of the microstructure and phase composition results revealed that MHSCs consisted of γ-Fe, Al, Si, Fe₂Al₇Si, Fe₂Al₄Si, and Al₈Si₆Mg₃Fe phases, with the transition layer composed of the Fe₂Al₇Si phase. The results of the compression performance indicated that the compression performance of MHSCs increased with the rise of the sintering temperature and decreased with the increase of the volume fraction. However, as the diameter of MHS increased, the yield strength of MHSCs declined while the deformation strength of MHSCs increased. When the diameter of the MHSs was 2.55mm and the volume fraction was 40%, the compression performance of the MHSCs reached its optimum. At that point, the yield strength was 113.65±3.37 Mpa, and the average deformation strength was 81.26±5.45 Mpa.

Elevating alloy performance: the role of bioactive glass in Mg-9Al-Zn matrix composites through friction stir back extrusion

ABSTRACT This study investigates the impact of friction stir back extrusion (FSBE) parameters on the microstructure and mechanical properties of magnesium matrix composites reinforced with bioactive glass particles. Higher rotational speeds (1600 rpm) generate more heat and stirring, promoting finer grains and better particle dispersion, while lower speeds lead to larger grains. Conversely, slower extrusion speeds allow more time for heat dissipation and better mixing, contributing to smaller grains and a more uniform particle distribution. Key findings show that increasing the bioactive glass content enhances both hardness and ultimate tensile strength (UTS), with optimal mechanical properties achieved at 1600 rpm rotational speed, 48.97 mm/min extrusion speed, and 5 vol.% bioactive glass. The introduction of bioactive glass particles restricts grain growth and improves load transfer, thereby reinforcing the composite. Additionally, the study identifies a gradient microstructure in the composite wire, with smaller grains near the surface due to higher plastic strain and temperature, in contrast to the core, which exhibits larger grains.

Impact of hBN Content on the Tribological Behavior and Thermal Diffusivity of HVOF-Sprayed Cr3C2-NiCr Coatings

Considering the significant health risks posed by hard chrome plating during its application, thermally sprayed Cr3C2-NiCr cermet coatings represent a suitable alternative. Incorporating hexagonal boron nitride (hBN) as a dry lubricant into the feedstock powder can further enhance wear resistance and thermal conductivity, crucial for preventing premature failure caused by inadequate lubrication. In this study, the mass fraction of hBN was varied between 0 and 15 wt.% to assess its influence on the tribological performance of the coatings using pin-on-disk tests. The coating’s hardness was measured via the Vickers method, and its cracking tendency at the coating/substrate interface was evaluated. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to analyze the microstructure and phase composition, while thermal diffusivity was determined using the laser flash method. The findings revealed that the inclusion of hBN, at concentrations of up to 10 wt.%, leads to an improvement in thermal diffusivity and a reduction in the coefficient of friction. However, exceeding this threshold leads to a decrease in hardness and increased crack formation tendency, highlighting the trade-off between frictional and mechanical properties.

Characterization of oil body microstructure, accumulation level and chemical composition in walnut fruit during growth

Oil body (OB) is composed of phospholipids, proteins and neutral lipids. However, the changes of these components in walnut OB (WOB) during walnut growth have not been studied. In this paper, CLSM, TEM and LC-MS/MS were used to observe and quantify the microstructure, accumulation level and biochemical composition of WOB during the growth of walnut (Wen 185 cultivar). The results showed that WOB accumulated near the cell wall on day 60 and then toward the center of cell until it occupied the entire cell on day 88. Afterwards, the WOB began to grow and fuse. Analysis of the chemical composition of WOB indicated that phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylinositol, and phosphatidylserine and oleosins, caleosins, and steroleosins made up the WOB membrane. The core of the WOB consisted of 22 free fatty acids and monoacylglycerol, diglyceride, triglyceride. Phosphatidylcholine, triglyceride and oleosin contents continued to increase. The contents of phosphatidylglycerol, unsaturated fatty acids, caleosins and steroleosins continued to decline. The content of phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine remained basically unchanged. These findings provided a basis for understanding the dynamic pattern of WOB bioaccumulation in walnut kernel at different developmental stages.

Direct graphene growth on low-alloy and mild steel surfaces controlled by carbon solubility and surface microstructural transformations during chemical vapor deposition

This study demonstrates for the first time, graphene grown directly on the iron-rich surfaces of bulk 8620 low-alloy and 1018 mild steel by chemical vapor deposition, a key step toward developing thin graphene coatings with strong graphene-steel bonding. Low growth temperatures of 660 °C–680 °C, were used to manipulate the steel's carbon solubility, confining carbon diffusion and microstructural transformations to the surface regions, with the bulk relatively unchanged. For 1018, a growth temperature of 680 °C resulted in a multilayer graphene coating with 80 % coverage. The alloying elements in 8620 improved graphene formation by influencing the surface microstructure transformations at these growth temperatures, with graphene coverage up to 95 %. The surface microstructure for 8620 affected graphene formation, seen in growths at 660 °C where a few-layer graphene coating formed from a cementite surface layer, and for growths at 680 °C where multi-layer graphene covered a pearlite dominant surface microstructure. Contact angle measurements confirmed the hydrophobicity of the graphene coating and electrochemical testing by potentiodynamic polarization and electrochemical impedance spectroscopy confirmed the 101 mV improvement to corrosion potential and an increase in impedance up to 18.23 kΩ. These detailed results regarding the direct growth of graphene as a coating layer on highly oxidation-sensitive steel surfaces suggest that this process is achievable through manipulating carbon solubility at the steel's surface by controlling temperature, alloy composition and surface microstructure transformations. These methods could be leveraged in developing protective graphene coatings for various iron-based alloys.

Corrosion resistance and biocompatibility of silica coatings on AZ31 magnesium alloy via magnetron sputtering

Magnesium alloys have promising prospects in biodegradable implants, but premature degradation is the main factor limiting their application. We prepared silicon coatings of different thicknesses on the surface of AZ31 magnesium alloy using the RF magnetron sputtering method. The phase, microstructure, and elemental composition of the coatings were characterized by XRD, SEM, and EDS, respectively. The corrosion resistance of the coatings in simulated body fluids was tested using immersion corrosion and electrochemical corrosion tests. Results showed that the silicon coating sputtered for 3 hours had the best corrosion potential and current, with a corrosion current density of 6.5614E-6 (A/cm2), which is two orders of magnitude lower than that of the AZ31 substrate. The extract of the sample in RPMI-1640 medium was co-cultured with human umbilical vein endothelial cells (HUVEC), and its cytotoxicity was evaluated by the CCK-8 assay. It was found that the silicon coating sputtered for 3 hours had the least toxicity, and the endothelial cells had a high proliferation rate. Therefore, the magnetron sputtered Si coating on AZ31 magnesium alloy exhibits good corrosion resistance and biocompatibility.

Construction of NiCo2O4/NiCoO2 co-embedded porous bio-carbon with rich heterogeneous interfaces for excellent bacteriostatic microwave radiation protection

To attain the stable protection against electromagnetic radiation pollution in complex bacterial environment, herein the NiCo2O4 and NiCoO2 co-embedded porous bio-carbon (PBC) with outstanding microwave absorption and anti-bacterial ability was successfully obtained via facile carbonization and immersion-annealing route. The component and microstructure of composites are both tightly affected by the synthetic temperature, which also influences the oxygen vacancy content and defect density within them. The strong interface polarizations from plentiful heterogeneous interfaces and dipole polarizations generated by defects and vacancies contribute greatly to the dielectric absorption, while the eddy-current loss and magnetic resonances have a certain effect as well. Under the matched impedance from magnetic-dielectric balance, the optimized absorption strength of prepared composite achieves −38.2 dB at 2.0 mm thickness with broad absorbing bandwidth of 7.01 GHz for only 2.31 mm. Moreover, the plentiful oxygen vacancies induced reactive oxygen species (ROS) together with heavy metal ions from nickel-cobalt ferrites can suppress the reproduction of Gram negative Escherichia coli (E. coli) and Gram positive Staphylococcus aureus (S. aureus) with anti-bacterial rates of 92.4 % and 93.2 %, respectively. The paper offers a novel insight to design dual-functional microwave absorber with excellent bacteriostatic performance for long-term using in complex bacterial environment.

Experimental Periodontitis Increases Anxious Behavior and Worsens Cognitive Aspects and Systemic Oxidative Stress in Wistar Rats.

Periodontitis (PD) has the potential to induce systemic changes that affect both physical and behavioral aspects. These alterations may be associated with changes in both the inflammatory profile and the oxidative stress status of individuals with PD. Therefore, we aimed to evaluate the effects of PD on oxidative stress, as well as on behavioral parameters and cognitive impairment, in a preclinical model. Twenty-four male Wistar rats were randomly assigned to PD and sham groups. PD was induced by the ligature protocol for 14 days. Behavioral tests were initiated on the 9th day of the experiment to evaluate anxious behavior and cognition (learning and memory). After euthanasia, oxidative stress was evaluated in the gums, blood, hippocampus, and amygdala. Alveolar bone loss, bone microstructure, and elemental compositions of the mandibular bone were also assessed. PD increased alveolar bone loss, reduced the calcium and phosphorus content in the mandibular bone, and increased anxiety-like behavior and cognitive decline (p < 0.05). Furthermore, PD significantly affected the redox balance, as evidenced by increased total antioxidant capacity (TAC) in the gingiva and hippocampus (p < 0.05). It also led to increased lipid peroxidation in the gingiva and erythrocytes (p < 0.05), decreased antioxidant defenses in erythrocytes (superoxide dismutase) and the hippocampus (catalase), and increased antioxidant activity (catalase) in the amygdala (p < 0.05). PD resulted in cognitive alterations, including impairments in spatial learning and memory, as well as increased anxious behavior, likely due to redox imbalance in rats.

Synthesis, characterization and application of MWCNT/TiO2 composite for photocatalytic reduction of benzophenone to benzopinacol

Photocatalytic reactions are widely investigated as a green chemistry approach towards organic molecule synthesis. Herein, we fabricated (MWCNT/TiO2) composite materials which are beneficial in the photocatalytic synthesis of benzopinacol on irradiation with UV–visible light. The precursor-layer-coating (PLC) method was successfully employed to produce a series of composite materials, X%-MWCNT/TiO2, where (X = 2, 4, 6, and 8 % w/w). The XRD confirmed major-anatase and minor-brookite TiO2 along with MWCNT in the composite. FE-SEM, HR-TEM, and EDAX revealed the expected composite microstructure, morphology, and compositional details. The nanosized (10 ̶30 nm), spherically shaped TiO2 particles were seen integrated to the MWCNT surface. The BET-surface area of the mesoporous composites enhanced from 83.77 to 114.39 m2/g as the MWCNT loading increased from 2 % to 8 %. The optical studies indicated a marginal shift in absorption edge towards longer wavelength with % MWCNT loadings. The band gap (Eg) was reduced and the charge pair recombination rate retarded. The PL, Raman and XPS studies supported the heterojunction formation at the interface. The photocatalytic activity was evaluated based on the % conversion efficiency of benzophenone to benzopinacol in the presence of light and composite as a photocatalyst. The 6 %-MWCNT/TiO2 demonstrated the highest photoactivity with an additional 34 % and 25 % yield in UV and sunlight respectively compared to bare TiO2. The effective light absorption, electronic excitation, charge pair separation and transfer mechanism at the MWCNT/TiO2 interface were responsible for enhanced photoactivity. The current investigation provided a promising strategy to produce hybrid photocatalytic material for organic molecule synthesis.

Mechanical and microstructural characteristics of Al-Li2099-graphene MMCs for aerospace applications

ABSTRACT Aluminium-Lithium (Al-Li) alloys are known for its properties that are superior to conventional ones. The inclusion of graphene reinforcements to the metal matrix improved strength, stiffness, density reduction, tensile properties, wear, creep, and fatigue resistance. This study examined the combined result of graphene nanoparticles (GNP) and the Al-Li2099 alloy with an ultrasonic-aided stir-casting process. The nano-particulate metal matrix composites with various weight percentages (wt. %) of GNP were fabricated and investigated for physical, mechanical, and microstructural properties. The nanocomposites’ mechanical properties were examined in detail, and significant improvements in hardness, tensile, and compressive strength were observed with higher wt. % of GNP. Theoretical and empirical densities were measured, revealing that the nanocomposite’s densities decrease with the increase in wt. % of nano-reinforcements. Material characterisation of the composites was carried out using XRD, EDAX, SEM, and Fourier-Transformation Infrared Spectroscopy (FTIR). SEM and EDAX confirmed the presence of GNP particulates in the matrix microstructure and elemental composition. The XRD results confirmed the presence of GNP particulates in the Aluminium Alloy (AA) 2099 and the composite, and no other intermetallic elements were detected. The results demonstrated that the GNP addition to the AA2099 significantly enhanced the mechanical and microstructural characteristics of the nanocomposite.

Faience beads excavated from Laolongtou cemetery, Yanyuan: new evidence of the cultural exchange between the south‐western and north‐western parts of China

AbstractAncient Chinese beads provide important evidence of cultural exchanges. This study used a scanning electron microscope with an energy‐dispersive spectrometer to analyse the microstructure and chemical composition of faience beads excavated from Laolongtou cemetery in Yanyuan county, China. Based on the analysis results, two glazing methods (efflorescence and cementation) and two bead types (high‐Pb and high‐K beads) were identified. A comparison of the chemical compositions of samples unearthed at the Laolongtou cemetery and samples from north‐western China indicated close regional contact. Bronze wares and burial customs in Laolongtou cemetery also revealed that the Yanyuan region might be a significant node in the Southern Silk Road between the south‐western and north‐western parts of China and even in Southeast Asia.

Effect of Ti2AlC on the microstructure and properties of Cu-graphite composites

Cu-graphite composites (CGCS) find extensive applications in electrical contact components. However, due to insufficient wetting between Cu and graphite, their bonding remains weak. Additionally, the Cu coating on the surface of graphite in Cu-coated graphite particles used to fabricate CGCS tends to segregate during sintering, which leads to defects such as porosity. To address these issues, this study incorporated Ti2AlC into CGCS sintered at 980 °C using a pneumatic sintering process. Subsequently, the microstructure and properties of the composites were examined and analyzed. The findings indicated that incorporating Ti2AlC prevented severe segregation of the Cu coating on the graphite surface during sintering, maintaining complete coverage of the graphite particles by the Cu matrix. In addition, the development of a TiC layer increased the interface bonding strength between the Cu matrix and graphite from 0.40 GPa to 5.00 GPa. Besides, CGCS with Ti2AlC exhibits better mechanical properties and tribological properties; their hardness, compressive strength, and wear rate are 64.5 HV, 269 MPa, 1.378×10-5 mm3/N·m, respectively.

Influence of the graphene oxide-coated steel fiber on the microstructure optimization of UHPC

Benefiting from its superior mechanical properties, large specific surface area and abundant oxygen-containing functional groups, graphene oxide (GO) can generate nucleation and pore-infilling effects to optimize the microstructure of the cementitious composites, thus reinforcing the mechanical performance and durability of cement-based materials. However, due to the dispersion issues and relatively high cost, the widespread use of GO in the cement industry has not yet been realized. In the present study, we applied three different methods to coat industrial GO nanosheets on the steel fiber’s surface and reinforce the UHPC microstructure. The proposed coating method effectively disperses GO within the ultra-high-performance concrete (UHPC) matrix and targets its enhancement effects on the interfacial transition zone (ITZ), which has the weakest pore structure in UHPC. The result presents that the three-step dip method of GO coating on the steel fiber demonstrates higher effectiveness in reinforcing the microstructure of UHPC, the porosity of the matrix is 1.88 %, with a relative decrease of 37.1 ∼ 60.3 %. In addition, the average distance of ITZ after GO enhanced UHPC is about 3.7 µm, about 37.3 %-68.1 % shorter, and the ITZ porosity is 3.8 %, which is 15.6 %-65.5 % lower. With the assistance of the metal intrusion technique, backscattered electron characterization and deep learning-based analysis, the pore structure features of UHPC were extracted with a classification recognition accuracy of 88.5 %, and the pore intrusion volume inside the characteristic region of the UHPC matrix increased by 1.89–2.14 times. The extraction characteristics illustrated that the GO strengthening on steel fibers was more effective in ITZ, with an optimization efficiency of about 8.1 % higher than in other regions. We expect that the findings of this study could provide deep insights into GO modification for cementitious composite reinforcement applications and open new pathways for affordable alternatives to nano-enhanced composites.

Effect of grain size on tensile deformation behavior of nano-polycrystalline Al and Al–Mg alloys with grain boundary segregation of Mg

Mg is easily segregated to the grain boundary of the Al–Mg alloy, which affects the mechanical properties of the alloy. In order to reveal the role of Mg element at grain boundaries in Al–Mg alloys, molecular dynamics simulation was used to study the tensile deformation behavior of nano-polycrystalline Al and Al–Mg alloys with different grain sizes. The results show that the elastic modulus and tensile strength of Al and Al–Mg alloys have a clear grain size dependence. The critical grain size at which the elastic modulus decreases as the grain size decreases is independent of Mg. As the Mg content increases to 3 at. %, the critical grain size for the transition from the Hall-Petch relationship to the inverse Hall-Petch relationship increases. The appropriate content of Mg segregation at the grain boundary can increase the elastic modulus, strength and plasticity of the alloy, and inhibit the grain boundary cracking. This result provides important theoretical support for the composition design and microstructure regulation of high-performance Al–Mg alloys.

Nanostructure-induced functional combination of vanishing magnetostriction and magnetic softness in ferromagnetic (GaNi)xCoCrFe (x = 0.4–1.6) high-entropy alloys

Searching for high-entropy alloys with functional properties that emerge from their multi-scale structure, we have investigated the (GaNi)xCoCrFe (x = 0.4–1.6) system. We have characterized structure, microstructure, nanostructure and chemical composition of the individual phases in the multi-phase alloys and determined their magnetic, magnetostrictive and electrical properties. We found that the alloys are ferromagnetic and exhibit functional combination of magnetic softness and vanishing magnetostriction, classifying them as energy-efficient “supersilent” materials (inaudible to a human ear) for alternating-current (AC) electromagnetic applications in the audio-frequency range. The alloys develop a two-phase structure, a face-centered cubic (fcc) and a body-centered cubic (bcc), where the fcc phase fraction decreases, while the bcc fraction increases with the increasing (GaNi)x content. Ferromagnetism of the alloys originates from the highly nanostructured bcc phase, with the ferromagnetic Curie temperatures in the range TC = 750–700 K, depending on x. The fcc phase is not nanostructured and is paramagnetic at room temperature, but undergoes a spin glass transition at Tf≈6.4 K. The magnetic softness and vanishing magnetostriction of the alloys are both nanomagnetic phenomena. The magnetic-softness and magnetostriction parameters of the x = 1.3 and 1.6 alloys make them relevant for supersilent AC applications at low frequencies.

Solid-liquid phase microextractive adsorption of bio-lactic acid by a novel microextractor immobilizing ionic liquid A336

The separation of biochemicals poses significant challenges, such as complex product composition, strong hydrophilicity, and high boiling point, which leads to laborious procedures, low yield, and high energy consumption. These obstacles have become bottlenecks for the industrialization of biochemicals. To enhance the efficient separation of bio-lactic acid, a novel microextractor, PS-A336, was synthesized through the copolymerization of ionic liquid (IL) A336 onto a polystyrene (PS) skeleton and further employed to investigate the solid–liquid phase microextractive adsorption (SLPMA). Extensive analysis of PS-A336 microstructure and chemical composition demonstrated its exceptional performance with a rapid (< 20 min) adsorption capacity (1150 mg/g) for LA in the batch system, which is the highest value reported and 11.0 times higher than that of the pristine supports. PS-A336 maintained its stability even after 15 cycles of column chromatography. Its adsorption behavior also fits the common thermodynamic and kinetic models, and it is better for the SLPMA kinetic model established on Fick diffusion law. Additionally, PS-A336 exhibited high adsorption capacity and selectivity for LA from the fermentation broth, achieving above 98 % removal ratios to proteins, inorganic salts, and pigments. The double hydrogen bonds between PS-A336 and LA were identified as the primary driving forces for SLPMA following theoretical and structural investigations. Notably, the immobilized IL in PS-A336 exhibited a remarkable microextraction effect, i.e., an increase in extractive capacity at least 16.6 times due to 59.8-fold improvement in the interface area compared with the bulk IL, which is 28.6 times higher than the adsorption capacity of PS skeleton. Our findings provided new insights into the combination of extraction and adsorption, as well as valuable guidance for the efficient separation of bio-based chemicals.

Morphological and microstructural evolution of mesophase-pitch-based carbon-fiber-reinforced carbon matrix composite under Ar ions irradiation

Carbon/carbon (C/C) composites are critical structural materials for advanced reactors, including molten salt reactors. However, the irradiation mechanisms, particularly the differences in irradiation-induced damage between fibers and matrices, remain inadequately understood. In this study, the irradiation behavior of mesophase-pitch-based carbon-fiber-reinforced carbon matrix composites was investigated under 1.8-MeV Ar-ion irradiation at a dose of 3 × 1016 ions/cm2 at room temperature. Following irradiation, both the carbon fiber and matrix underwent amorphization and exhibited significant changes in surface morphology, the matrix exhibiting pronounced volumetric shrinkage compared to the fiber. Additionally, irradiation resulted in the degradation of the ordered graphite layers and closure of the initial cracks within the fiber and matrix. Notably, the matrix contained a greater number of initial cracks and crack closure was more pronounced during irradiation compared to the fiber. The differential shrinkage observed between the fiber and matrix is primarily attributed to the differences in the irradiation-induced closure behavior of the initial cracks in each component. These findings provide insights into enhancing the irradiation performance of C/C composites by adjusting the microstructural composition of the fiber and matrix.

Effect of Rotational Speed on Microstructure and Properties of Al‐Based Composite Reinforced with High‐Entropy‐Alloy Particles Fabricated by Friction Stir Processing

In the present investigation, the production of composites based on 7075Al is involved, reinforced with particles of high‐entropy alloy (AlCoCrFeNi), using the friction stir processing (FSP) technique. The primary objective is to examine how varying the rotational speed during processing affects the uniformity of the composite microstructure, the strength of the bonding between different materials, and the mechanical properties of the composite. In these findings, it is indicated that higher processing rotational speeds lead to enhanced homogeneity of the composite material and promote strong bonding with the matrix. The Al13Co4 phase is generated at the interface before the formation of the Al5Co2 phase. The microhardness of the composites exhibits an increase in hardness of 78%, 84%, 86%, and 83% compared to the hardness of the 7075Al. Similarly, the tensile strength is enhanced by 26%, 36.7%, 49%, and 40%, respectively. The broken surface shows an even spread of particles with many small depressions, which is a clear sign of a common type of fracture that can stretch without breaking. The primary processes that enhance the strength of the FeCoNiCrAl/7075Al composite manufactured by FSP include the load‐transfer effect, dispersion strengthening, grain refinement strengthening, and thermal mismatch strengthening.

Deep learning based segmentation of binder and fibers in gas diffusion layers

Gas diffusion layers (GDLs) are vital parts for the performance of proton-exchange membrane fuel cells (PEMFCs). In many cases, they are made of Carbon-Carbon Composite Paper (CCCP), which consists of carbon fibers and a carbonized binder material. The distribution of the fibers and binder in the GDL strongly influences the performance of a PEMFC. Synchrotron scans are a great way to obtain information about the microstructural composition of carbon paper GDLs (Figure 2), but there is one major obstacle. Binder and fibers tend to have the same attenuation and, consequently, the same gray values in the scans. To overcome this, we introduce a machine learning-based method that segments fibers and binder from the local morphology of a CCCP. The training data is generated using FiberGeo, a module in the GeoDict software for fibrous microstructure generation. FiberGeo creates fibers based on stochastic geometry and adds binder using morphological opening and closing operations. We applied the machine learning-based method to four Scans of samples of Toray Carbon Paper with varying amounts of binder in them. The result is the quantification of individual voxels as fiber or binder material that can be used, for example, in performance simulations of property simulations in PEMFCs [1–4]. Here, we focus on the differences in the spatial distribution of the binder both in the through-plane and in-plane directions.