Microstructural Analysis Research Articles

Experimental investigations on physico-mechanical properties of kaolinite clay soil stabilized at optimum silica fume content using clamshell ash and lime

This investigation examines the effect of clamshell ash (CSA) and lime additives on the physico-mechanical characteristics of kaolinite clay soil stabilized at the optimum silica fume content. Laboratory tests were performed to assess plasticity, shrink-swell characteristics, compaction characteristics, unconfined compressive strength (UCS), shear strength characteristics, mineralogical and morphological microstructure characteristics of stabilized soil specimens. The kaolinite clay soil was stabilized at its optimum silica fume content (6%) to produce the highest strength and was altered with three non-identical proportions of clamshell ash and lime (3%-9%). Cylindrical soil specimens, 76 mm in height and 38 mm in diameter, were moulded and treated for curing periods of 1, 7, 14, and 30 days to examine the strength of the altered soil. The findings revealed that, adding clamshell ash and lime significantly alters the plasticity, shrink-swell, maximum dry unit weights, and optimum moisture contents of the silica fume-stabilized soil. In terms of strength, the beneficial effects of CSA and lime additives were found to be more significant with more extended curing periods. Incremental increases in curing periods resulted in further enhancements in UCS, cohesion, and internal friction angle, indicating continued strength development over time. Microstructural analysis using field emission scanning electron microscopy and X-ray diffraction provided insights into the interparticle bonding mechanisms and microstructural changes induced by the addition of CSA and lime. The emergence of cementitious phases and pozzolanic responses between soil particles and stabilizers contributed to the densification and strengthening of the stabilized soil matrix. The findings of this study provide valuable insights into the potential of clamshell ash and lime additives to enhance the engineering properties of kaolinite clay soil stabilized with silica fume. These results have implications for sustainable soil stabilization practices, offering a promising approach to improve the performance of soils for various engineering applications, including construction and geotechnical projects.

Development of Mg-Sb-Sn and Mg-Sb-Ca Magnesium Alloys for Automotive Applications: Microstructure, Mechanical Properties, and Corrosion Behavior Analysis

Development of Mg-Sb-Sn and Mg-Sb-Ca Magnesium Alloys for Automotive Applications: Microstructure, Mechanical Properties, and Corrosion Behavior Analysis

Impact of coating and microstructure on wear resistance of tool steels for wood cutting: a novel approach to quantification and analysis of wear-related damages

Squaring, a wood transformation process, is an operation which consists of introducing the logs into a squaring machine which then uses sharp tools to cut the wood into pieces with high surface quality. Tool steels used in this process experience significant wear, damaging the wood surface and hence leading to substantial scrape rate. This study investigates the wear resistance of three tool steels specifically designed for wood cutting applications: modified AISI A8, modified steels with 0% and 1% tungsten, and powder metallurgy prepared W360 steel. Furthermore, the influence of a PVD coating on the wear resistance of the three alloys was investigated. ASTM G65 abrasive wear tests were conducted using the dry sand/rubber wheel abrasion test. A methodology using a non-contact 3D measurement system and specialized software was developed, allowing for a thorough quantitative assessment of the wear of these steels. The results revealed that the coated A8mod + 1%W steel exhibits the best resistance among the coated steels. Despite the excellent intrinsic resistance of W360 steel, the coating did not provide a significant improvement for this steel, showing only a 10% reduction in wear. Microstructural analysis revealed that the predominant wear mechanisms were abrasion and impact. The relative performance of each steel was quantified and is reported. Field trials conducted under actual cutting conditions, indicate the superiority of W360 steel in terms of resilience to wear and impacts compared to other tested alloys, while confirming the effectiveness of surface treatments in mitigating material wear. However, A8 steel modified with 1% tungsten exhibits increased wear under coating.

Heat Input Effects on Microstructural and Mechanical Analysis of AA2014 Alloy in Friction Stir Welding: Influence of Rotational and Traverse Speed

Heat Input Effects on Microstructural and Mechanical Analysis of AA2014 Alloy in Friction Stir Welding: Influence of Rotational and Traverse Speed

Analysis of phase, microstructure, and mechanical characteristics of selective laser melted AlSi10Mg alloy after post-heat treatment

Analysis of phase, microstructure, and mechanical characteristics of selective laser melted AlSi10Mg alloy after post-heat treatment

Prebiotic membrane structures mimic the morphology of alleged early traces of life on Earth

Elucidating compositions of the first cell membranes requires experiments with molecules and chemical conditions representative of early Earth. The molecules used are described as ‘prebiotically plausible’, i.e., they could have formed through abiotic reactions before the emergence of biology. Similarly, the chemical properties of solutions in which these membranes are formed (e.g., pH, temperature, ionic strength) must represent early Earth environments. Here, using confocal and transmission electron microscopy combined with population morphometry, we show that prebiotically plausible molecules, in solutions representative of Hadean submarine alkaline hydrothermal vents, form microstructures with substantial morphological diversity. The microstructures hold the potential for use as analogues of prebiotic processes in the rock record. Additionally, many of the structures are morphologically similar to purported early microfossils, highlighting limitations of morphological interpretation in these studies. Detailed analyses of abiotic microstructures are essential for understanding the earliest life on Earth, and for interpretation of potential biosignatures from extra-terrestrial bodies.

Clpf encodes pentatricopeptide repeat protein (PPR5) and regulates pink flesh color in watermelon (Citrullus lanatus L.).

The gene controlling pink flesh in watermelon was finely mapped to a 55.26-kb region on chromosome 6. The prime candidate gene, Cla97C06G122120 (ClPPR5), was identified through forward genetics. Carotenoids offer numerous health benefits; while, they cannot be synthesized by the human body. Watermelon stands out as one of the richest sources of carotenoids. In this study, genetic generations derived from parental lines W15-059 (red flesh) and JQ13-3 (pink flesh) revealed the presence of the recessive gene Clpf responsible for the pink flesh (pf) trait in watermelon. Comparative analysis of pigment components and microstructure indicated that the disparity in flesh color between the parental lines primarily stemmed from variations in lycopene content, as well as differences in chromoplast number and size. Subsequent bulk segregant analysis (BSA-seq) and genetic mapping successfully narrowed down the Clpf locus to a 55.26-kb region on chromosome 6, harboring two candidate genes. Through sequence comparison and gene expression analysis, Cla97C06G122120 (annotated as a pentatricopeptide repeat, PPR) was predicted as the prime candidate gene related to pink flesh trait. To further investigate the role of the PPR gene, its homologous gene in tomato was silenced using a virus-induced system. The resulting silenced fruit lines displayed diminished carotenoid accumulation compared with the wild-type, indicating the potential regulatory function of the PPR gene in pigment accumulation. This study significantly contributes to our understanding of the forward genetics underlying watermelon flesh traits, particularly in relation to carotenoid accumulation. The findings lay essential groundwork for elucidating mechanisms governing pigment synthesis and deposition in watermelon flesh, thereby providing valuable insights for future breeding strategies aimed at enhancing fruit quality and nutritional value.

Curcumin-loaded food-grade nano-silica hybrid material exhibiting improved photodynamic effect and its application for the preservation of small yellow croaker (Larimichthys polyactis)

Two types of curcumin-loaded food-grade nano-silica (F-SiO2) hybrid materials were successfully synthesized using the rotary evaporation method (F-SiO2@Cur) and the adsorption method (Cur@F-SiO2). The microstructure and spectral analyses confirmed that the curcumin in F-SiO2@Cur was loaded within the nanopores in a non-aggregate form rather than being adsorbed onto the surface (Cur@F-SiO2). Additionally, F-SiO2@Cur exhibited remarkable water solubility (1510 ± 50.33 µg/mL) and photostability (a photodegradation ratio of only 59.22 %). Importantly, F-SiO2@Cur obtained a higher capacity for the generation of singlet oxygen (1O2) compared to control groups. Consequently, F-SiO2@Cur-mediated photodynamic inactivation (PDI) group attained the highest score in sensory evaluation and the best color protection effect in PDI experiment of small yellow croaker (Larimichthys polyactis) at 4 °C. Moreover, F-SiO2@Cur could effectively controlled total volatile basic nitrogen (TVB-N) content, pH, and total viable count (TVC), thereby prolonging the shelf life. Therefore, F-SiO2@Cur-mediated PDI is an effective fresh-keeping technology for aquatic products.

Static and dynamic strength properties of highly structured clay-rich diatomite in Shengzhou, China

Diatomite is a widespread geological substance found in coastal and lake areas worldwide. Although diatomites are increasingly used in geotechnical engineering construction, a significant knowledge gap exists regarding their mechanical responses to static and dynamic loadings, particularly in high-speed railway projects. This study investigates the static and dynamic behaviors of diatomites through extensive experiments, considering both natural and remolded states. It focuses on representative diatomite specimens obtained from the Shengzhou region in China, an area intersected by the Hang-Shao-Tai high-speed railway. The results of uniaxial compression and undrained triaxial shear tests show that the structural degradation of diatomite significantly impacts its stress-strain responses, failure patterns, and mechanical parameters under static and dynamic loading conditions. The structural effects of natural diatomite tend to degrade as the confining pressure level increases, resulting in corresponding changes in its mechanical parameters. Undrained triaxial shear tests conducted on natural diatomite reveal that the inclinations of the shear band closely correspond to those predicted by the Mohr-Coulomb solution. Additionally, we present a modified hyperbolic-type model to evaluate the damping ratio of diatomites. Furthermore, a power-law model based on Hardin's formula was used to predict the maximum shear modulus of diatomites under varying stress levels and void ratios. Microstructural and chemical analyses were conducted using scanning electron microscopy and X-ray diffraction to gain insights into the observed structural effects at the microscale.

High critical current properties of multi-filamentary MgB2 superconducting wires fabricated by an internal Mg diffusion method

Abstract Although both mass density and grain connectivity of MgB2 superconducting layers can be greatly improved through an internal Mg diffusion (IMD) process, poor structure uniformity and low MgB2 filling factor of IMD wires limit further enhancement of their superconducting performance. Herein we prepared 19-filament and 37-filament IMD-MgB2 superconducting wires by a combination of optimizing the component structure and introducing the intermediate annealing process. The microstructure analysis suggests that well structure uniformity and high layer density have been achieved in multi-filamentary MgB2 wires; and the MgB2 filling factor reaches up to 9.3-11.0%. The magnetic superconducting transition of MgB2 wires is relatively sharp and the onset Tc is around 37 K. Remarkably, there is no magnetic flux jump for 37-filament wires in low field region at 5 K. At 4.2 K and 4 T, the transport layer Jc values of 19-filament and 37-filament MgB2 wires are as high as 1.5×105 A/cm2 and 2.2×105 A/cm2, respectively, and accordingly engineering Je of 1.7×104 A/cm2 and 2.0×104 A/cm2. These results indicate that the performance of multi-filamentary IMD-MgB2 wires can compete with the traditional PIT-MgB2 wires as applied in the industry.

Strength and Durability Properties of High-Volume Fly Ash (HVFA) Binders: A Systematic Review

South Africa is endowed with a wealth of coal-fired power stations that can produce extremely high volumes of fly ash per year exceeding 34 million tonnes. The use of high-volume fly ash (HVFA) binders in the construction sector has the capacity to significantly reduce greenhouse gas emissions associated with traditional cement production and offset the carbon footprint of Eskom. The excessive production of fly ash by Eskom warrants the need for developing ultra-high-volume fly ash binders (UHVFA, fly ash/binder > 60 wt%). Nonetheless, fly ash (FA) replacement of cement is still largely limited to 35% regardless of more ambitious research indicating the potential to surpass 60%. In view of the urgent need for South Africa to offset and reduce its carbon footprint, this work reviews and summarises the literature on the performance of HVFA binders with a focus on two specific areas: (i) strength and (ii) durability. On HVFA binder strength, the focus is drawn on work that analysed the compressive strength, flexural strength, and split tensile strength. This review focuses on the extant literature analysing the durability of HVFA binders using various tests, including sorptivity, resistivity, permeability, tortuosity, rapid chloride penetration tests, resistance to sulphate attack, and microstructural analysis. As the FA content increases towards optima, i.e., 50–80%, the most indicative composite characteristics of the strength and durability properties are UCS (30–90 MPa) and permeability (low). This review reveals the leading methodologies, instrumentation, findings, challenges, and contradictions.

Enhancing Mechanical Properties and Microstructures of Mass-Manufactured Sand Concrete by Incorporating Granite Powder

The production of manufactured sand and stone processing can cause dust pollution due to the generation of a significant amount of stone powder. This dust (mainly granite powder) was collected and incorporated as a cement replacement into mass-manufactured sand concrete in order to enhance the mechanical properties and microstructures. The heat of the hydration was measured by adding the granite powder into the cementitious material system. The mechanical properties, autogenous shrinkage, and pore structures of the concrete were tested. The results showed that the mechanical strength of the concrete increased first and then decreased with the increase in granite powder content. By replacing the 5% cement with the granite powder, the 28 d compressive and flexural strength increased by 17.6% and 20.9%, respectively. The autogenous shrinkage was mitigated by the incorporation of the 10% granite powder and decreased by 19.7%. The mechanism of the granite powder in the concrete was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP). The porosity decreased significantly within the 10% granite powder. A microstructure analysis did not reveal a change in the type of hydration products but rather that the granite powder played a role in the microcrystalline nucleation during the hydration process.

Performance Assessment of Quenchants on Mechanical Properties of Steel Grade A1046

The main aim of the study is to assess the performance of ghee oil, coconut oil and sea water quenchants on mechanical properties of A1045 steel. The procedures comprise the production of tensile steel specimens, heat-treat them into electrical oven at 850°C for one hour, quench them in ghee oil, coconut oil and sea water separately. The quenched samples were again tempered separately at the temperature of 400°C. Then all the specimens taken for the mechanical tests such as hardness, tensile, impact test and also to calculate the percentage of elongation, having completion of tests, microstructural analysis had conducted to view the structures contain in each specimen. The results obtained on these processes determine whether these oils can be used as local industrial quenchants. The facilities required for the research is include material testing laboratory, heat treatment workshop, machine shop and metallographic laboratory to mentioned but a few. The material selection is steel grade A1045, that have been normally utilize in metal industries for the production of machine parts and structural components

Effects of Er addition on the hot deformation behavior and microstructure evolution of AZ31 alloy

AZ31 magnesium alloys typically have poor room temperature ductility after initial deformation. To address this disadvantage, rare earth element Er is introduced to regulate the structure, weaken texture, and promote non-basal slip to achieve plasticization. In this study, the deformation behavior and microstructure evolution during the hot compression process of Er added AZ31 alloy were systematically investigated. Hot compression stress-strain curves showed that the addition of Er reduced the deformation resistance. The constitutive equation and processing map were established. By combining the processing map with the microstructure analysis and texture evolution, an optimal processing area was determined to be 350–400 °C at a strain rate of 0.01 s−1. The influence of Er addition on the twinning behavior, recrystallization mechanism, and slip system of the AZ31 alloy were discussed. During the deformation process, the twinning behavior violates the maximum SF criterion, which is related to severe local stress. Continuous dynamic recrystallization, discontinuous dynamic recrystallization, and twinning induced recrystallization are all detected in the alloy. Through the in-grain misorientation axis and transmission electron microscopy, it can be confirmed that the addition of Er promoted the occurrence of pyramidal <c+a> slip. This is related to the modification of stacking fault energy by Er and the hindrance effect of the second phase containing Er on the basal dislocation.

Improved structure and enhanced properties of detonation sprayed W coating via hot isostatic pressing

Tungsten has garnered significant attention for its superior performance as a plasma-facing material in tokamak devices. However, its hardness and high ductile-to-brittle transition temperature present challenges for its application in plasma-facing components. To address these issues, this study employs the detonation spraying (DS) technique to prepare tungsten coatings on a TZM alloy substrate and further optimizes their properties through hot isostatic pressing (HIP) treatment. Advanced characterization techniques were utilized to conduct a detailed microstructural and compositional analysis of the coatings. The results indicated that the HIP treatment significantly reduced the porosity of the coatings, improving their density and overall quality. Additionally, HIP treatment led to a decrease in internal stress, a reduction in dislocations, and the grain growth within the coatings. The study also discussed how the HIP process improved the microstructure of the DS tungsten coatings through these mechanisms, thereby enhancing the coatings' thermodynamic properties. Mechanical property tests revealed that the coatings treated with HIP exhibited higher bonding strength and lower hardness, attributed to the increase in grain size and the reduction in dislocation density within the coatings. Thermal property tests demonstrated that the HIP-treated coatings possessed higher thermal diffusivity and specific heat capacity in the temperature range of 100 to 500 °C. Furthermore, the performance of the coatings under transient high heat flux conditions was significantly improved after the HIP treatment, showing better resistance to the thermal shock and cracking. These findings are of great importance for understanding the performance enhancement of DS tungsten coatings in nuclear fusion reactor applications via HIP, especially as candidate materials for the first wall of tokamak devices.

Influence of Post-processing and Build Direction on the Wear Behaviour of Laser Powder Bed Fused Maraging Steel

Abstract Present study investigates the effect of post processing (heat treatment: solutionising at 850°C for 2 hr with aging at 490°C for 3 hr and cryogenic treatment at -196°C for 24 hr) and the effect of build direction (along the build direction (BD) and perpendicular to the build direction (PBD)) on the wear behavior of maraging steel fabricated by Laser powder bed fusion (LPBF). The results are also compared with conventional hot-forged samples. The pin on disc equipment was used to conduct the wear experiments with an EN31 steel disk as the counter body. Heat treatment decreased the wear rate of LPBF material by 54.78% and 83.84% in BD and PBD, respectively. This is due to the restriction of grain expansion by the Ni-based precipitants in age hardening treatment. The cryogenic treatment further decreased the wear rate of LPBF material by 87.84% and 90.9% in BD and PBD, respectively. This significant reduction can be attributed to the change of phase to martensite, as confirmed through microstructure and X-ray diffraction (XRD) analysis. Moreover, hot forged material also obtained a reduced wear rate after heat and cryogenic treatments. The highest wear resistance was found with the LPBF cryo-treated BD sample due to increased hardness from 388 HV to 640 HV. The worn surface of test samples was examined by using scanning electron microscopy (SEM), energy dispersive X-ray (EDX), 3D profilometer, and XRD analysis. Oxidation wear, adhesive wear, and abrasive wear are the predominant wear mechanisms identified using SEM.

Catalyst-regulated conversion of p-phenylenediamine-based carbon dots from red to deep-blue emission

Deep-blue emission (＜450 nm) is significant in high-density information storage, solid-state lighting, and vivid displays. However, the carbon dots (CDs) obtained from p-phenylenediamine (pPD) have only red fluorescence, which greatly limits the application and development of pPD-based CDs. As we all know, a catalyst is a substance that can change the rate and pathway of a chemical reaction. Herein, we designed to add a catalyst to realize the conversion of pPD-based CDs from red to deep-blue fluorescence. The emission peak of obtained deep-blue CDs was 440 nm, and the full-width at half-maximum (FWHM) was only 58 nm, with a high color purity. In addition, through in-depth analysis of microstructure and photoluminescence (PL) properties, it is found that the decrease of the sp2-conjugated domain and the graphite N content and the increase in pyridinic N content were the main reasons for the blue shift of the spectra. Based on this, the formation process and mechanism of red and deep-blue CDs were further elucidated. This work not only efficiently realized the design of the deep-blue CDs but also provided a new idea for the luminescence regulation of CDs without changing the raw materials and reaction conditions.

Investigating the role of steel and polypropylene fibers for enhancing mechanical properties and microstructural performance in mitigating conversion effects in calcium aluminate cement

Fiber reinforcement is widely employed in numerous industries due to its exceptional mechanical properties; however, its specific role in enhancing the strength of calcium aluminate cement (CAC) composites remains inadequately understood. This study investigates the influence of fiber addition on the mechanical characteristics of CAC composites during curing. Two types of fibers, steel and polypropylene, were incorporated into CAC composites, and their mechanical properties, chemical composition, and microstructural performance were evaluated using various methods. Assessments including flowability, bulk density, volume of permeable voids, water absorption, and mechanical strength tests were conducted, alongside X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), and Field Emission Scanning Electron Microscopy (FESEM) analysis. Results reveal a significant enhancement in mechanical strengths with the inclusion of fibers in CAC composites. The addition of 1% fibers to the composites resulted in significant improvements. Steel fibers (SF) led to notable enhancements of approximately 19.7%, 68%, and 26.4% in compressive, direct tensile, and flexural strengths, respectively, while polypropylene fibers (PF) resulted in enhancements of 1.9%, 20%, and 16.7%, respectively. Microstructural analysis revealed that SF and PF contribute to pore refinement, enhancing strength and durability. Findings suggest that SF addition effectively mitigates strength loss induced by the conversion effects of stable phase C3AH6 in CAC, thereby fostering the development of an environmentally friendly, quick-setting, high-performance concrete system. This research offers valuable insights for the design and potential enhancement of CAC-based composites to improve performance and durability under severe conditions.

Advancing soy protein isolate-ulvan film physicochemical properties and antioxidant activities through strategic high-pressure homogenization technique

Soy protein-based films often exhibit poor properties, including limited mechanical strength, stability, and bioactivity, which hinder their extensive application in the food industry, particularly in edible packaging. To enhance the properties of soy protein-based films, we employed high-pressure homogenization (HPH) to modify the soybean protein isolate (SPI) molecules and sought to cross-link SPI with ulvan polysaccharide, which possesses distinctive bioactivities. The results confirmed that soluble ulvan polysaccharides were incorporated into the cross-linking system through hydrogen bonding. Results indicated that HPH treatment enhanced SPI's solubility and surface hydrophobicity (H0), promoting hydrogen bonding and hydrophobic interactions between SPI and ulvan, as evidenced by ζ-potential and turbidity measurements. Structural and microstructural analyses of both individual SPI and composite films, using FT-IR, XRD, CD and SEM, demonstrated a high compatibility between HPH-treated SPI and ulvan. The incorporation of ulvan reduced the films' tensile strength (TS), but higher pressure significantly improved it (p < 0.05). Post-HPH modification, the films exhibited increased contact angle and swelling capacity (p < 0.05), indicating enhanced hydrophobicity. Higher pressure treatments resulted in more opaque and yellowish films, thereby diminishing ultraviolet light transmission. Thermal stability analyses, via TGA-DSC, showed that U-HSPI films had improved thermal stability compared to pure SPI films. Moreover, ulvan inclusion boosted the antioxidant capacity of SPI films, especially after HPH treatment. Overall, this study confirms that HPH modification substantially influences the properties and activities of SPI-based films, and the complex films based on SPI and ulvan with improved physicochemical and antioxidant properties exhibit a great potential in the food packaging field.

Ni / GDC Fuel Electrode for Low-Temperature SOFC and its Aging Behavior Under Accelerated Stress

Abstract The microstructural integrity of Ni-based fuel electrodes is important for long-term solid oxide fuel cell (SOFC) operation. Degradation due to microstructural changes such as Ni-agglomeration, coarsening, and densification must be prevented by an appropriate microstructure. Here, the performance of four types of nickel-ceria-based fuel electrodes, which differ concerning layer sequence and manufacturing processes, was evaluated by electrochemical impedance spectroscopy at the nominal operating temperature of 600°C. Electrodes produced through screen-printed GDC exhibited an acceptable polarization resistance (0.260 Ωcm²), whereas electrodes with an additional printed Ni/GDC layer demonstrated inferior performance (0.550 Ωcm²). Electrodes formed through infiltration of GDC into the printed GDC-layer displayed unreproducible performance values ranging from 0.16 to 1.20 Ωcm² despite similar processing. Conversely, electrodes with an extra layer of GDC infiltrated into the Ni-backbone exhibited good performance (0.195 Ωcm²) and stability. Accelerated degradation tests under OCV at increased operating temperatures of 700 and 900°C were performed on the sample based on a GDC infiltrated Ni-backbone that performed best among reproducible samples. The polarization resistance at 600°C recorded at the beginning and the end of life increased by up to 100%. Microstructural analysis of the electrodes at different aging states revealed strong microstructural changes of fine-infiltrated GDC structures and Ni agglomeration at higher operating temperature