Repair Applications Research Articles

Characterization of thin-walled self-healing microcapsules reinforced with multi-walled carbon nanotubes

This study presents a novel approach to fabricating thinner shells and significantly enhancing the fracture strength of melamine-urea-formaldehyde (M-U-F) microcapsules reinforced with multi-walled carbon nanotubes (MWCNTs). Unlike previous studies that primarily focused on single-walled carbon nanotubes (SWCNTs) or MWCNTs in polyurea-formaldehyde (PUF) shells, this research advances microcapsule technology by exploring MWCNT reinforcement in M-U-F shells. We employed a dual experimental-numerical approach, combining the precision of micro-compression tests with the predictive capabilities of finite element analysis (FEA) to determine the elastic modulus of MWCNT-reinforced M-U-F microcapsules. This method offers new insights into the mechanical behavior of these microcapsules. Our findings indicate an 8.8% increase in fracture load and a 14.6% reduction in fracture displacement for MWCNT-reinforced microcapsules compared to conventional M-U-F microcapsules. Additionally, FEA confirmed the results of the micro-compression tests, showing that MWCNT-reinforced microcapsules had the best correlation with an elastic modulus of 4.00 GPa. Conventional M-U-F microcapsules corresponded to an elastic modulus of 2.25 GPa. These results provide a comprehensive understanding of how nano-reinforcement influences the structural properties of thin-walled microcapsules, with potential applications in composite damage repair and beyond.

Role of Ti3AlC2 MAX phase in regulating biodegradation and improving electrical properties of calcium silicate ceramic for bone repair applications

Calcium silicate ceramic is a promising bioceramic for various biomedical applications, but its high biodegradation rate and low strength restrict its clinical utility. As a result, the study devised an innovative solution to address these issues by utilizing the titanium aluminum carbide phase, potentially for the first time in biological applications, in conjugation with hydroxyapatite. Then, using powder metallurgy technology, they added these phases to calcium silicate to create nanocomposites. After soaking in simulated body fluid for ten days, the produced nanocomposites were assessed for bioactivity and biodegradability using scanning electron microscopy, inductively coupled plasma-atomic emission spectroscopy, and weight loss assays. Their electrical and dielectric properties were also measured before and after soaking in the simulated body fluid solution. Furthermore, the tribo-mechanical properties of all sintered samples were measured. Interestingly, adding 40% hydroxyapatite nanoparticles to calcium silicate reduced the porosity from 12 to 6%. However, adding five vol% of the titanium aluminum carbide phase to the same sample increased the porosity to 8%. Importantly, these recorded percentages of porosity were comparable to those of compact bone porosity, which range from 5 to 13%. The addition of hydroxyapatite and titanium aluminum carbide phase significantly improved the rapid biodegradation of calcium silicate, albeit with a slight decrease in its bioactive properties, as evidenced by the incomplete surface coverage of the samples with the hydroxyapatite layer in the scanning electron microscopy images. The electrical properties of the nanocomposites were better with the addition of hydroxyapatite and titanium aluminum carbide phase, which helped the bone heal faster. The addition of a titanium aluminum carbide phase significantly improved the mechanical properties of the resulting nanocomposites. For example, the calculated values for compressive strength of all examined samples were 131, 115, 105, 147, and 135 MPa. Based on the results, the prepared samples can be used in orthopaedic and dental applications.

Neurotrophic extracellular matrix proteins promote neuronal and iPSC astrocyte progenitor cell- and nano-scale process extension for neural repair applications.

The extracellular matrix plays a critical role in modulating cell behaviour in the developing and adult central nervous system influencing neural cell morphology, function and growth. Neurons and astrocytes, play vital roles in neural signalling and support respectively and respond to cues from the surrounding matrix environment. However, a better understanding of the impact of specific individual extracellular matrix proteins on both neurons and astrocytes is critical for advancing the development of matrix-based scaffolds for neural repair applications. This study aimed to provide an in-depth analysis of how different commonly used extracellular matrix proteins- laminin-1, Fn, collagen IV, and collagen I-affect the morphology and growth of trophic induced pluripotent stem cell (iPSC)-derived astrocyte progenitors and mouse motor neuron-like cells. Following a 7-day culture period, morphological assessments revealed that laminin-1, fibronectin, and collagen-IV, but not collagen I, promoted increased process extension and a stellate morphology in astrocytes, with collagen-IV yielding the greatest increases. Subsequent analysis of neurons grown on the different extracellular matrix proteins revealed a similar pattern with laminin-1, fibronectin, and collagen-IV supporting robust neurite outgrowth. fibronectin promoted the greatest increase in neurite extension, while collagen-I did not enhance neurite growth compared to poly-L-lysine controls. Super-resolution microscopy highlighted extracellular matrix-specific nanoscale changes in cytoskeletal organization, with distinct patterns of actin filament distribution where the three basement membrane-associated proteins (laminin-1, fibronectin, and collagen-IV) promoted the extension of fine cellular processes. Overall, this study demonstrates the potent effect of laminin-1, fibronectin and collagen-IV to promote both iPSC-derived astrocyte progenitor and neuronal growth, yielding detailed insights into the effect of extracellular matrix proteins on neural cell morphology at both the whole cell and nanoscale levels. The ability of laminin-1, collagen-IV and fibronectin to elicit strong growth-promoting effects highlight their suitability as optimal extracellular matrix proteins to incorporate into neurotrophic biomaterial scaffolds for the delivery of cell cargoes for neural repair.

Cohesion Regulation of Polyphenol Cross‐Linked Hydrogel Adhesives: From Intrinsic Cross‐Link to Designs of Temporal Responsiveness

AbstractPolyphenol hydrogels have found widespread application in wound healing, bone repair, drug delivery, and biosensors due to their robust wet adhesion, high ductility, and excellent self‐healing ability. However, these hydrogels often exhibit low intrinsic cohesion, which limits their overall adhesive strength. Enhancing cohesion is critical for improving both the adhesion and mechanical properties of the hydrogels, thereby expanding their utility in biomedical fields. This review begins by exploring strategies to enhance the cohesion of polyphenol hydrogel adhesives, detailing modifications that act individually or synergistically. The importance of temporally regulating cohesion is emphasized to accommodate various applications and environmental conditions. Finally, this paper discusses remaining challenges in cohesion regulation and outlines prospects for future research. It is hoped that this comprehensive review will provide new insights into the development of advanced polyphenolic hydrogel adhesives and contribute to the design of “smart adhesives” for increasingly complex needs in biomedical applications.

Application of hydrogel-loaded dental stem cells in the field of tissue regeneration.

Mesenchymal stem cells (MSCs) are highly favored in clinical trials due to their unique characteristics, which have isolated from various human tissues. Derived from dental tissues, dental stem cells (DSCs) are particularly notable for their applications in tissue repair and regenerative medicine, attributed to their readily available sources, absence of ethical controversies, and minimal immunogenicity. Hydrogel-loaded stem cell therapy is widespread across a variety of injuries and diseases, and has good repair capabilities for both soft and hard tissues. This review comprehensively summarizes the regenerative and differentiation potential of various DSCs encapsulated in hydrogels across different tissues. In addition, the existing problems and future direction are also addressed. The application of hydrogel-DSCs composite has gained substantial progress in the field of tissue regeneration and need in-depth study in the future.

Numerical Investigation of Polymer-based Biomaterials for Artificial Hip Joint with Diverse Boundary Conditions

Background: Hip suffering is a serious concern for human health, which may be caused by arthritis, accidents, and childhood disorders; hence, man-made joints are the only option for restoring the function of natural hips and ensuring a comfortable life. To design an effective hip joint is a challenging task; there are myriads of novel designs continuously patented over the last two decades. Methods: The finite element approach was utilized in this extensive investigation to assess selfmated polymer-based biomaterials (PTFE, UHMWPE, and PEEK) with different boundary conditions. The numerical analysis was performed to find the stress intensity and deflection of the femoral head and the acetabular components; the evaluation was done critically with a 10-node quadratic tetrahedron element and different mesh intensities. Results: The detailed outcome showcases that the bare PEEK mated GO-PEEK has good load resistance and is affected by minimum stress and deflection, which is quantified at 20.89% less than the PTFE with GO-PEEK (M3) combination. This stress and deflection are quite higher than those of metal implants (Ti6Al4V) but comparatively more prominent materials for human cortical bone. Conclusion: This investigation proved the polymer-on-polymer combination effectively eliminates stress shielding and metal ion emission, reducing revision surgery and elevating implant longevity. Therefore, it was identified that PEEK-based polymer composites are the best-suited alternative substance for hip repair applications.

Silver Nanoparticles and Simvastatin-Loaded PLGA-Coated Hydroxyapatite/Calcium Carbonate Scaffolds.

The need to develop synthetic bone substitutes with structures, properties, and functions similar to bone and capable of preventing microbial infections is still an ongoing challenge. This research is focused on the preparation and characterization of three-dimensional porous scaffolds based on hydroxyapatite (HA)-functionalized calcium carbonate loaded with silver nanoparticles and simvastatin (SIMV). The scaffolds were prepared using the foam replica method, with a polyurethane (PU) sponge as a template, followed by successive polymer removal and sintering. The scaffolds were then coated with poly(lactic-co-glycolic) acid (PLGA) to improve mechanical properties and structural integrity, and loaded with silver nanoparticles and SIMV. The scaffolds were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), ATR FT-IR, and silver and SIMV loading. Moreover, the samples were analyzed by Brillouin and Raman microscopy. Finally, in vitro bioactivity, SIMV and silver release, and antimicrobial activity against Staphylococcus aureus and Staphylococcus epidermidis were evaluated. From the Brillouin spectra, samples showed characteristics analogous to those of bone tissue. They exhibited new hydroxyapatite growth, as evidenced by SEM, and good antimicrobial activity against the tested bacteria. In conclusion, the obtained results demonstrate the potential of the scaffolds for application in bone repair.

Towards Strength–Ductility Synergy in Cold Spray for Manufacturing and Repair Application: A Review

Cold spray is a solid-state additive manufacturing technology and has significant potential in component fabrication and structural repair. However, the unfavourable strength–ductility synergy in cold spray due to the high work hardening, porosity and insufficient bonding strength makes it an obstacle for real application. In recent years, several methods have been proposed to improve the quality of the cold-sprayed deposits, and to achieve a balance between strength and ductility. According to the mechanism of how these methods work to enhance metallurgical bonding, decrease porosity and reduce dislocation densities, they can be divided into four groups: (i) thermal methods, (ii) mechanical methods, (iii) thermal–mechanical methods and (iv) optimisation of microstructure morphology. A comprehensive review of the strengthening mechanism, microstructure and mechanical properties of cold-sprayed deposits by these methods is conducted. The challenges towards strength–ductility synergy of cold-sprayed deposits are summarised. The possible research directions based on authors’ research experience are also proposed. This review article aims to help researchers and engineers understand the strengths and weaknesses of existing methods and provide pointers to develop new technologies that are easily adopted to improve the strength–ductility synergy of cold-sprayed deposits for real application.

Development and Biocompatibility Assessment of Decellularized Porcine Uterine Extracellular Matrix-Derived Grafts.

Biomaterials derived from biological matrices have been widely investigated due to their great therapeutic potential in regenerative medicine, since they are able to induce cell proliferation, tissue remodeling, and angiogenesis in situ. In this context, highly vascularized and proliferative tissues, such as the uterine wall, present an interesting source to produce acellular matrices that can be used as bioactive materials to induce tissue regeneration. Therefore, this study aimed to establish an optimized protocol to generate decellularized uterine scaffolds (dUT), characterizing their structural, compositional, and biomechanical properties. In addition, in vitro performance and invivo biocompatibility were also evaluated to verify their potential applications for tissue repair. Results showed that the protocol was efficient to promote cell removal, and dUT general structure and extracellular matrix composition remained preserved compared with native tissue. In addition, the scaffolds were cytocompatible, allowing cell growth and survival. In terms of biocompatibility, the matrices did not induce any signs of immune rejection invivo in a model of subcutaneous implantation in immunocompetent rats, demonstrating an indication of tissue integration after 30 days of implantation. In summary, these findings suggest that dUT scaffolds could be explored as a biomaterial for regenerative purposes, which is beyond the studies in the reproductive field.

Synergetic effect of bioglass and nano montmorillonite on 3D printed nanocomposite of polycaprolactone/gelatin in the fabrication of bone scaffolds

Nowadays, bone injuries and disorders have increased all over the world and can reduce the quality of human life. Bone tissue engineering repair approaches require new biomaterials and methods to construct scaffolds with the required structural properties as well as improved performance. As potential therapeutic strategies in bone tissue engineering, 3D printed scaffolds have been developed. Polycaprolactone/Ceramic composites have attracted considerable attention due to their cytocompatibility, biodegradability, and physical properties. In this study, a 3D printing process was used to create polycaprolactone (PCL)-Gelatin (GEL) scaffolds containing varying concentrations of Bioglass (BG) and Nano Montmorillonite (MMT). This mixture was then loaded into a 3D printer, and the scaffolds were printed layer by layer. After constructing the scaffolds, they were then examined for their physical, chemical, and biological characteristics. Surface appearance was analyzed with a scanning electron microscope (SEM), which revealed that NC increased the diameter of pores from 465 to 480 μm. The elements in the scaffolds were evaluated by EDX analysis, and a uniform dispersion of nano montmorillonite particles was observed. The compressive strength reached 76.43 MPa for PCL/G/35 %MMT/15 %BG scaffold. Also, the rate of water absorption, biodegradability and bioactivity of PCL-GEL scaffolds increased significantly in the presence of NC. According to the MTT cell test results, adding BG and NC increased cell proliferation, adhesion and cell viability to 127.7 %. These findings indicated that the 3D printed PCL/G/35 %MMT/15 %BG scaffold has promising strategies for bone repair applications. Also, polynomial curve fitting shows that scaffold degradability after soaking in PBS can be predicted using the initial weight and soaking time. Adding more variables and data could improve prediction accuracy, reducing the need for experiments and conserving resources.

Development of IN718 Coating for Repair Applications by High-Pressure Cold Spraying Followed by Heat Treatment

Development of IN718 Coating for Repair Applications by High-Pressure Cold Spraying Followed by Heat Treatment

Mechanical and tribological assessment of PEEK and PEEK based polymer composites for artificial hip joints

Abstract Human hip failure remains a significant issue, and constructing artificial joints is imperative for affected individuals. This study examined the mechanical and wear behavior of polyether ether ketone (PEEK) polymers, including bare PEEK (BP), HA (Hydroxyapatite)-infused PEEK (HA-PEEK), and GO (Graphene oxide)-infused HA-PEEK (GO-HA-PEEK). The samples were prepared using compression molding, and wear characteristics were evaluated using a linear reciprocating tribo-tester against a stainless-steel counterface under a load 50 N, frequency 5 Hz, stroke length 20 mm, and time 30 min. The 10 % w/w HA inclusions slightly elevate the PEEK’s tensile strength from 29.85 ± 1.11 MPa (BP) to 34.23 ± 1.09 MPa, and the 0.5 % w/w GO with 10 % w/w HA encapsulations have significantly improved tensile properties (65.10 ± 1.12 MPa), which is 2.2 fold higher than the BP. However, the attained impact properties fall below the satisfactory level. Coefficient of friction and wear rate are significantly reduced. The wear rate reduced from 3.39 × 10−6 mm3 N−1 m−1 (BP) to 2.54 × 10−6 mm3 N−1 m−1 on HA-PEEK, and more than two times reduction (1.69 × 10−6 mm3 N−1 m−1) with 0.5 % w/w GO incorporating HA-PEEK. The results show that the reinforcements significantly reduced wear and improved the mechanical strength of PEEK polymers. Unlike BP and HA with lowered impact resistance, GO integrated HA-PEEK exhibited outstanding mechanical and wear performance. Therefore, HA and GO-infused PEEKs are suitable alternatives for hip repair applications.

Comparative Analysis of Serum and Serum-Free Medium Cultured Mesenchymal Stromal Cells for Cartilage Repair.

Mesenchymal stromal cells (MSCs) are promising candidates for cartilage repair therapy due to their self-renewal, chondrogenic, and immunomodulatory capacities. It is widely recognized that a shift from fetal bovine serum (FBS)-containing medium toward a fully chemically defined serum-free (SF) medium would be necessary for clinical applications of MSCs to eliminate issues such as xeno-contamination and batch-to-batch variation. However, there is a notable gap in the literature regarding the evaluation of the chondrogenic ability of SF-expanded MSCs (SF-MSCs). In this study, we compared the in vivo regeneration effect of FBS-MSCs and SF-MSCs in a rat osteochondral defect model and found poor cartilage repair outcomes for SF-MSCs. Consequently, a comparative analysis of FBS-MSCs and SF-MSCs expanded using two SF media, MesenCult™-ACF (ACF), and Custom StemPro™ MSC SFM XenoFree (XF) was conducted in vitro. Our results show that SF-expanded MSCs constitute variations in morphology, surface markers, senescence status, differentiation capacity, and senescence/apoptosis status. Highly proliferative MSCs supported by SF medium do not always correlate to their chondrogenic and cartilage repair ability. Prior determination of the SF medium's ability to support the chondrogenic ability of expanded MSCs is therefore crucial when choosing an SF medium to manufacture MSCs for clinical application in cartilage repair.

Tissue engineering of Cornea via Type 1 Collagen Biomaterials – A perspective

Engineering corneal tissue has advanced significantly in recent years. Engineering a biocompatible, mechanically stable, and optically clear tissue presents significant engineering hurdles. Two fundamental strategies have been explored by scholars to address these issues: cell-based methods for controlling cells their own extracellular matrix and scaffold-based methods for supplying dense, transparent matrices for cell growth. Both approaches have had some level of success. Additionally, new developments in innervating a tissue-engineered construct have been developed. Future research must concentrate on enhancing the mechanical stability of engineered constructions and the host reaction to implantation. Type 1 Collagen Biomaterial has been used for the construction of scaffolds or implantation for the cornea repair. Various methods for fabrication of the scaffolds have been described and mentioned tissue engineering application for cornea repair and regeneration. Given this correspondence, the type 1 collagen was a potential biomaterial for tissue engineering scaffold fabrication for effective regeneration of cornea.

Fabrication of novel polysaccharides and glycerol monolaurate based camellia oil composite oleogel: Application in wound healing promotion

In this study, a novel camellia oil composite oleogel (SX@G-CO) was prepared by a combination of direct dispersion and emulsion-templated methods using polysaccharides (sodium alginate and xanthan gum, ratio in 4:6) as oleogelators and glycerol monolaurate (GML, 7 wt%) as gel-enhancer. The comparative experiments revealed that the polysaccharides could effectively enhance the densification of the three-dimensional network structure of the oleogel through hydrogen bonding and electrostatic interactions, and significantly improve its thermal stability, rheological properties (adhesive strength 49,243.6 mPa•s, viscosity recovery rate 94.6 %) and oil binding capacity (80.6 %). The introduction of GML further enriched the crystal diversity of the oleogel and imparted excellent antimicrobial ability (nearly 100 % inhibition effect on E.coli). Furthermore, the in vitro experiments demonstrated that the synergistic effect of polysaccharides and GML significantly enhanced the anti-inflammatory, antioxidant, cell migration and proliferation abilities of SX@G-CO oleogel compared with GML-CO and SX-CO oleogels. In addition, SX@G-CO oleogel has also been demonstrated to effectively promote full-thickness burn healing in mice by reducing bacterial infection and inflammatory response, regulating free radical levels, and promoting neovascularization in vivo, with effects comparable to marketed ointment. SX@G-CO oleogel as a bioactive molecule-polysaccharides composite has potential clinical application in burn wound repair.

Incorporation of small extracellular vesicles in PEG/HA-Bio-Oss hydrogel composite scaffold for bone regeneration

Stem cell derived small extracellular vesicles (sEVs) have emerged as promising nanomaterials for the repair of bone defects. However, low retention of sEVs affects their therapeutic effects. Clinically used natural substitute inorganic bovine bone mineral (Bio-Oss) bone powder lacks high compactibility and efficient osteo-inductivity that limit its clinical application in repairing large bone defects. In this study, a poly ethylene glycol/hyaluronic acid (PEG/HA) hydrogel was used to stabilize Bio-Oss and incorporate rat bone marrow stem cell-derived sEVs (rBMSCs-sEVs) to engineer a PEG/HA-Bio-Oss (PEG/HA-Bio) composite scaffold. Encapsulation and sustained release of sEVs in hydrogel scaffold can enhance the retention of sEVs in targeted area, achieving long-lasting repair effect. Meanwhile, synergistic administration of sEVs and Bio-Oss in cranial defect can improve therapeutic effects. The PEG/HA-Bio composite scaffold showed good mechanical properties and biocompatibility, supporting the growth of rBMSCs. Furthermore, sEVs enhancedin vitrocell proliferation and osteogenic differentiation of rBMSCs. Implantation of sEVs/PEG/HA-Bio in rat cranial defect model promotedin vivobone regeneration, suggesting the great potential of sEVs/PEG/HA-Bio composite scaffold for bone repair and regeneration. Overall, this work provides a strategy of combining hydrogel composite scaffold systems and stem cell-derived sEVs for the application of tissue engineering repair.

Predictions of mechanical properties of Fiber Reinforced Concrete using ensemble learning models

Fiber Reinforced Concrete (FRC) significantly improves the tensile, crack resistance, and durability of concrete by adding fiber materials, making it highly promising for applications in structural reinforcement, repair and new construction projects. The strength of FRC is a crucial indicator of its mechanical properties. This study utilizes ensemble learning techniques to predict and analyze the compressive strength, splitting tensile strength, and flexural strength of FRC. A total of 1589 sets of compressive strength data, 1137 sets of splitting tensile strength data, and 1061 sets of flexural strength data were collected from existing literature. Four ensemble models (GBDT, Xgboost, LightGBM, RF) were used to establish prediction models and analyze influencing factors for these three FRC mechanical properties, and the results were compared with traditional models. The results show that the ensemble models can effectively solve the FRC strength prediction problems compared to traditional models. The GBDT regression model performed best in predicting compressive and flexural strength, with R2 values of 0.939 and 0.867, respectively. The Xgboost regression model performed best in predicting splitting tensile strength, with an R2 value of 0.944. Further analysis using SHAP revealed that cement and water significantly impact FRC strength. The inclusion of fibers significantly affects the splitting tensile strength and flexural strength of FRC but has a minimal impact on compressive strength. The study not only demonstrates the feasibility of using machine learning algorithms for FRC strength prediction but also provides a fast and reliable means for FRC strength prediction, offering more reliable data support for the design and application of FRC materials, aiding practical engineering applications.

Evaluating EHS parastomal hernia classification for surgical planning: a retrospective analysis of 160 consecutive cases in a single center.

Parastomal hernia (PH) is a prevalent complication following ostomy formation, presenting significant challenges in surgical management. This study aims to validate the European Hernia Society classification for PH through the application of the Hybrid Parastomal Endoscopic Repair (HyPER) method. The study focuses on establishing the practical utility of the European Hernia Society classification in a clinical setting, particularly in guiding surgical approaches and improving patient outcomes. This retrospective observational study aimed to assess the utility of the European Hernia Society classification in planning surgical strategies for parastomal hernias. The validation of the classification of PH was based on the experience involving 160 patients in single center. Patients were classified according to the European Hernia Society criteria, and data were collected on patient demographics, clinical presentations, and surgical outcomes. Main goal was to assess the consistency and applicability of the European Hernia Society classification in predicting surgical challenges and outcomes. The study found a predominance of complex Type III and IV hernias. The European Hernia Society classification was effective in categorizing PH, aiding in surgical planning and highlighting the increased complication rates associated with more complex hernia types. This study represents the largest single-center cohort treated for PH by a single team, providing a controlled evaluation of the HyPER technique's effectiveness. The validation of the European Hernia Society classification in this study is a significant advancement in the standardization of PH management. The findings demonstrate the classification's utility in enhancing surgical planning and patient-centered care. The study also opens avenues for further research into standardized approaches and techniques in PH treatment.

Electrochemical corrosion behavior and passive film properties of Fe2Ni2CrV0.5Nbx (x=0.2, 0.4, 0.6, 0.8) eutectic high-entropy alloy coating prepared by laser cladding

The phase composition, microstructure morphology, and corrosion behavior of Fe2Ni2CrV0.5Nbx (x=0.2, 0.4, 0.6, 0.8) eutectic high-entropy alloy (EHEA) coatings produced via laser cladding were investigated. The research delved into discerning the phase structures and microstructural variations of the EHEA coatings concerning differing Nb compositions. The findings highlighted a direct correlation between Nb content and the volume fraction of the eutectic structure, specifically the FCC/Laves phases. Electrochemical evaluations, including diverse tests such as potentiodynamic polarization, electrochemical impedance spectroscopy, cyclic polarization, Mott-Schottky measurements, and X-ray photoelectron spectroscopy, revealed distinct corrosion behaviors among the EHEA variants. Notably, the Fe2Ni2CrV0.5Nb0.2 coating exhibited relatively superior corrosion resistance compared with Fe2Ni2CrV0.5Nbx (x=0.4,0.6,0.8) coatings, attributed to its lower corrosion current density (Icorr) and the formation of a thicker passive film with prolonged passivation duration. Conversely, the Fe2Ni2CrV0.5Nb0.8 coating, characterized by increased eutectic structures and grain boundary density, yielded a thicker yet non-uniform passive film with higher vacancy defects. This comprehensive exploration into the corrosion behavior and passive film properties of these EHEA coatings provides a reference for designing materials that hold promising implications for future corrosion-resistant material development in industrial parts repair applications.

The mechanical performance evaluation of fly-ash derived geopolymer mortar for concrete patch repair

The utilization of fly-ash-based geopolymers as a primary material in patch repair mortar technology represents a significant advancement in replacing conventional cement mortar, known for its high carbon emissions. This study employs Class C fly-ash with various proportions of activators to evaluate the resulting mechanical properties of the geopolymer mortar. The research includes trial and error for mix design, selection of an effective curing temperature, fresh properties, and hardened properties of mortar. Class C fly-ash was chosen due to its high-temperature resilience, essential for geopolymerization. An effective curing temperature of 60°C was identified. The activator solution comprised NaOH and Na2SiO3 with a 14 M molarity. Results indicate the highest compressive strength at a fly-ash to activator ratio of 60:40, achieving 70.80 MPa, while the highest average flexural strength was at a 70:30 ratio, achieving 12.19 MPa. The highest splitting tensile strength was also at a 70:30 ratio, measuring 26.33 MPa. These findings suggest that fly-ash-based geopolymer mortar is suitable for use in patch repair applications for corrosion damage.