Search Results (273)

Recent breakthroughs in materials science have driven transformative advancements in restorative dentistry. Advanced dental materials, such as bioactive materials, nanocomposites, and fibre-reinforced composites, are attracting attention. Bioactive materials, such as calcium silicate-based cements and bioactive glass, represent a paradigm shift by interacting with biological tissues to stimulate regeneration. They promote hydroxyapatite formation, accelerating mineralisation in hard and soft tissues, and are pivotal tools in minimally invasive procedures due to their functions of structural support and biological interaction. Nanomaterials, especially nanocomposites with embedded nanoparticles, effectively address polymerisation shrinkage and wear in traditional composites. With just 1.5% shrinkage, a flexural strength over 150 MPa, and 44–60% higher wear resistance than conventional composites, they offer significant improvements. Nanocomposites also provide enamel-like translucency and a bond strength of 27–38 MPa to dentin, ensuring excellent aesthetics and durability—making them ideal for direct restorations. Fibre-reinforced composites with glass or polymer fibres balance aesthetics with strength and are increasingly used in restorations. Their high fracture resistance, which closely approaches that of a natural tooth, enables clinicians to preserve more healthy teeth during restoration, in line with the principles of modern conservative dentistry. Overall, bioactive materials enhance tissue repair, nanocomposites optimise form and function, and fibre-reinforced composites deliver strength without compromising aesthetics. As these materials transition from research to clinical practice, they promise longer-lasting treatments, fewer complications, and higher patient satisfaction. This narrative review aims to explore three types of advanced dental materials and their role in improving clinical outcomes. Full article

Bone tissue engineering, as an important branch of regenerative medicine, integrates multidisciplinary knowledge from cell biology, materials science, and biomechanics, aiming to develop novel biomaterials and technologies for functional repair and regeneration of bone tissue. Hydrogels are among the most commonly used scaffold materials; however, conventional hydrogels exhibit significant limitations in physical properties such as strength, tensile strength, toughness, and fatigue resistance, which severely restrict their application in load-bearing bone defect repair. As a result, the development of high-strength hydrogels has become a research hotspot in the field of bone tissue engineering. This paper systematically reviews the latest research progress in this area: First, it delves into the physicochemical characteristics of high-strength hydrogels at the molecular level, focusing on core features such as their crosslinking network structure, dynamic bonding mechanisms, and energy dissipation principles. Next, it categorically summarizes novel high-strength hydrogel systems and different types of biomimetic hydrogels developed based on various reinforcement strategies. Furthermore, it provides a detailed evaluation of the application effects of these advanced materials in specific anatomical sites, including cranial reconstruction, femoral repair, alveolar bone regeneration, and articular cartilage repair. This review aims to provide systematic theoretical guidance and technical references for the basic research and clinical translation of high-strength hydrogels in bone tissue engineering, promoting the effective translation of this field from laboratory research to clinical application. Full article

Epoxy resins often require toughening to broaden their engineering applications, such as in durable concrete repair. This study addresses this need by developing high-performance polyurethane/epoxy (PU/EP) interpenetrating polymer networks (IPNs). The composites were synthesized via prepolymer and stepwise methods using polyether polyol (PPG-1000), isocyanate (MDI-50), and E51 epoxy. At an optimal PU prepolymer content of 15 wt%, the polyether-based IPNs achieved a balanced mechanical profile (tensile strength: 59.90 MPa; elongation at break: 6.46%; compressive strength: 69.99 MPa). Further tuning of the soft segment by introducing polyester polyol (PS-2412) yielded superior performance at a PS-2412/PPG-1000 ratio of 30/70. This formulation increased tensile and compressive strengths by 11.4% and 6.07% (to 66.74 MPa and 74.24 MPa), and dry and wet bond strengths by 12.1% and 36.3% (to 5.68 MPa and 4.62 MPa), respectively. The enhancement is attributed to the increased crosslinking density and more uniform network structure imparted by PS-2412, which improves stress distribution and interfacial adhesion. This work provides an effective soft-segment design strategy for fabricating toughened epoxy composites with robust mechanical and adhesive properties. Full article

Grouted sleeves are commonly used to connect prefabricated structural components, but construction defects can easily occur after installation, posing potential risks to the structure. This study conducts comparative uniaxial tensile tests on 39 grouted-sleeve specimens in 13 groups—including standard specimens, defective specimens, and specimens repaired with supplementary grouting. The strain distribution patterns under different grouting lengths and loading levels are analyzed to investigate the load-transfer mechanism between reinforcement bars and grouted sleeves, as well as the influence of various supplementary grouting amounts and material strengths on the mechanical performance of defective sleeves. In the uniaxial tensile test of grouted sleeves, with grout strengths of 85 MPa and 100 MPa and HRB400-grade steel bars, when the grouted anchorage length was 4 d, insufficient anchorage length resulted in low bond strength between the grout and the steel bar, leading to bond–slip failure. When the grouted anchorage length reached 6 d, steel bar fracture occurred inside the sleeve. When the total anchorage length formed by two grouting sessions reached 8 d, specimen slippage decreased, showing a trend where the strain growth rate of the sleeve gradually decreased from the grouted end to the anchored end, while the strain growth rate of the steel bar gradually increased. The longer the total anchorage length in the sleeve after grout repair, the stronger its anti-slip capability. The bearing capacity and failure mode of the specimens depend on the strength of the steel bars connected to the grouted sleeves and the strength of the threaded connection ends at the top. Experimental results show that the anchorage length and strength of high-strength grout materials have a significant reinforcing effect on defective sleeves. The ultimate bearing capacity of specimens with anchorage length of 6 d or more is basically the same as that of steel bars. Specimens with a total anchorage length of 8 d show approximately 10~20% less slippage than those with 6 d. The safe anchorage length for HRB400-grade steel bars in sleeve-grouted connections is 8 d, even though the bearing capacity of grouted sleeves with a 6 d anchorage length already meets the requirements. Bond strength analysis confirms that the critical anchorage length is 4.49 d. When the grouted anchorage length exceeds the critical length, the failure mode of the specimen is steel bar fracture. When the grouted anchorage length is less than the critical length, the failure mode is steel bar slippage. This conclusion aligns closely with experimental results. In engineering practice, the critical anchorage length can be used to predict the failure mode of grouted sleeve specimens. Based on experimental research and theoretical analysis, it is clear that using grout repair to reinforce defective grouted sleeve joints with a safe anchorage length of 8 d is a secure and straightforward strengthening method. Full article

Waterproofing systems frequently experience performance degradation during long-term service due to material aging and structural deformation, thereby necessitating localized repair interventions. The bonding interface between newly applied and existing membrane materials is a critical determinant of repair effectiveness. In this study, the aging-dependent repair performance of three representative waterproof membrane systems was systematically investigated using peel strength testing, low-temperature flexibility assessment, and interfacial morphology analysis under thermal–oxidative aging for 2, 5, 14, and 28 days. The results demonstrate that the homogeneous repair system based on ultra-thin reinforced self-adhesive polymer-modified bituminous membranes exhibits superior overall performance, maintaining the highest peel strength with only minor degradation even after 28 days of accelerated aging. In contrast, the polymeric butyl self-adhesive membrane subjected to homogeneous repair exhibited rapid adhesion degradation after 14 days, whereas the heterogeneous repair system showed improved stability during intermediate aging stages. Low-temperature flexibility testing further revealed that root-resistant bituminous membranes exhibited a slower aging rate, with a cracking temperature increase of 7 °C after 28 days, compared to a 10 °C increase observed for ultra-thin self-adhesive membranes. These quantitative findings provide clear guidance for the selection of appropriate repair membrane systems under varying aging conditions in waterproofing engineering, particularly for maintenance and rehabilitation applications. Full article

Anti-icing materials have attracted considerable research interest due to their potential applications in preventing ice accretion and growth. However, a major challenge in the field is how to enhance durability while maintaining anti-icing performance. This study proposes a facile fabrication method for anti-icing coatings with anti-aging and self-healing abilities. A three-dimensionally cross-linked block copolymer, synthesized from polydimethylsiloxane, 4-aminophenyl disulfide, and trimethylolpropane triglycidyl ether, yielded a coating with excellent anti-icing/de-icing performance, including a low ice adhesion strength (29.2 kPa) and a high icing delay time (1389 s). The introduction of 4-aminophenyl disulfide enables dynamic disulfide bond reorganization and aromatic framework formation, synergistically conferring the icephobic coating with self-repair mechanisms and an anti-aging function. The coating exhibited a rapid self-healing capability (within 4 h), which is facilitated by the dynamic exchange of its hydrogen and disulfide bonds. Furthermore, the material demonstrated outstanding durability against physical wear and ultraviolet radiation. After being subjected to a 1000-cycle abrasion test and ultraviolet aging, the coating successfully retained more than 70% of its original performance in both icing delay time and ice adhesion strength. This paper proposes a facile strategy for developing self-healing and anti-aging anti-icing coatings and proposes innovative strategies for multifunctional anti-icing coatings. Full article

To address brittle cracks in ceramic tools, an exogenous precursor ceramic repair agent was developed and applied to Al₂O₃/TiC/NiMo composite ceramic tools, which were treated by a two-step heat treatment process (heating at 3 °C/min to 300 °C for 60 min, heating the sample at 5 °C/min to 500, 600, 700, 800, and 900 °C, holding each for 60 min). The crack healing mechanism and temperature dependency of the repair agent were investigated. Cutting performance, including surface roughness, cutting force, and tool life, was optimized using an L9(34) orthogonal design. The results show that at 900 °C, the repair agent decomposed to form SiOC (Silicon Oxycarbide) amorphous phase and TiB₂ reinforced phase, filling the cracks and achieving atomic-level diffusion bonding. The flexural strength of the repaired sample recovered to 79.9% of the initial value (456.5 MPa), a 196.4% increase compared to the unrepaired sample. Optimal cutting parameters were found to be a cutting speed of 200 m/min, back draft of 0.1 mm, and feed of 0.1 mm/r. Under these conditions, surface roughness was 0.845 μm, cutting temperature was 258 °C, and stable tangential force was 70 N. The effective cutting distance of the repaired tool was increased from 1300 m to 1700 m. Wear was primarily abrasive and adhesive wear, and the SiOC phase formed by the repair agent helped to fill and repair the flank, thus extending tool life. Full article

Bone fractures are a serious health problem worldwide, and up to 10% of emergency department visits are related to such injuries. The development of effective materials for bone repair remains an urgent need of modern medicine. The aim of this study was to develop new scaffolds based on biopolymers (methyl cellulose and hydroxyethyl cellulose) modified with carbonate nanoparticles (CaCO₃, MgCO₃, ZnCO₃, MnCO₃, CuCO₃) for potential applications in bone tissue engineering. FTIR spectroscopy confirmed the successful formation of stable composite structures: characteristic absorption bands of the functional groups of the molecules that make up the scaffold, as well as specific fluctuations in metal-oxygen bonds (Ca–O, Zn–O, Cu–O), were revealed. Stability tests revealed the most stable samples when changing the pH and the ionic strength of the solution. The developed scaffold matrices had a high porosity in the range from 93.3% to 98.0%, and their moisture absorption capacity ranged from 858% to 1402%. Specific gravity measurements ranged from 0.050 g/cm³ to 0.067 g/cm³, indicating optimal material density for potential biomedical applications. Biological evaluation demonstrated different cytotoxic effects depending on the type of nanoparticles. Thus, matrices with minimal toxicity and promising biocompatibility (modified CaCO₃), as well as with significant toxic effects (modified ZnCO₃ and CuCO₃) were found. As a result, it was found that CaCO₃-modified scaffolds have the most favorable combination of structural, physical, and biological properties for potential applications in bone tissue engineering. The developed innovative materials are porous scaffolds in which nanoparticles of carbonates of osteotropic elements are embedded, which presumably contribute to the acceleration of bone tissue regeneration. However, this study provides encouraging preliminary data, and further in-depth biological and functional studies are needed to fully confirm the osteogenic potential and regenerative efficacy of the scaffolds. Full article

Concrete structure integrity is significantly compromised by the primary problem of cracking. Typically, surface cracking (predominantly shrinkage-induced and thermal microcracking) is rectified using costly and time-consuming repair methods involving mortar and other techniques. Research efforts have recently shifted towards developing smart materials to reduce concrete’s propensity for cracking, enhance its structural stability, and prevent damage to its framework. Concrete designs with self-healing capabilities can safeguard against degradation and enhance long-term durability. Despite extensive research, a consensus on the optimal preparation and mechanical properties of self-healing concrete has yet to be reached. Within self-healing concrete that utilizes microcapsules, repair agents are dispersed throughout the matrix to form a bond and seal cracks as damage develops. From the viewpoint of a sustainable society, this approach appears to promote the use of construction materials. This study examined the impact of Dawson/urea–formaldehyde microcapsule-based self-healing concrete using strength tests, where the effectiveness of different microcapsule quantities (0.5–2% microcapsule by weight of cement) was assessed. Following the data and data analysis, it becomes evident that among all samples, the 1% microcapsule sample yields outstanding results for both 7-day and 28-day compressive strength. Full article

Geothermal energy, recognized as a sustainable and clean resource, is playing an increasingly critical role in the global shift toward low-carbon energy systems. Nevertheless, the exploitation of fractured geothermal reservoirs is often impeded by severe lost circulation during drilling, where conventional plugging materials fail under high-temperature, high-salinity, and high-pressure conditions due to inadequate mechanical strength, poor thermal resistance, and lack of self-adaptive sealing behavior. In response, self-healing materials have emerged as an innovative strategy for developing intelligent lost circulation control technologies. Herein, we report a novel self-healing gel (XFFD) synthesized via inverse emulsion polymerization using acrylamide (AM), acrylic acid (AA), p-nitroblue tetrazolium (PNBT), and modified silica nanoparticles (PAS). The resulting material exhibits exceptional thermal stability, with decomposition onset above 356 °C, as determined by thermogravimetric analysis. Rheological and mechanical assessments reveal outstanding viscoelasticity, moderate swelling capacity (4.17-fold in deionized water), and a high self-recovery efficiency of 91.15%, accompanied by a bearing strength of 3.65 MPa. Mechanistic investigations indicate that the autonomous repair capability stems from dynamic non-covalent interactions—primarily hydrogen bonding and ionic associations—enabled by amide and carboxyl groups within the polymer network. Sand bed filtration tests under simulated geothermal conditions (150 °C, 8% salinity) demonstrate that XFFD forms a robust sealing barrier with significantly shallower invasion depth compared to conventional materials such as sulfonated asphalt and calcium carbonate. This work presents an effective self-healing gel system that ensures reliable wellbore strengthening and fluid loss control in challenging high-temperature, high-salinity geothermal drilling operations. Full article

Background/Objectives: Achieving durable intraoral repairs of fractured metal and zirconia restorations requires optimal adhesion. This in vitro study evaluated the effects of mechanical surface treatments and commercial repair systems on the shear bond strength (SBS) of composite resin to nickel–chromium (Ni-Cr) alloy and zirconia, including the influence of thermocycling aging. Methods: In this study, 144 Ni-Cr and zirconia discs (12 × 12 × 2 mm) were randomly assigned to three surface treatments: untreated control, airborne particle abrasion (50 µm Al₂O₃), and medium grit diamond bur grinding. Each group was further subdivided to assess two intraoral repair kits (GC Corp (Tokyo, Japan). and Bisco Inc. (Schaumburg, IL, USA)). Composite resin cylinders were bonded following the manufacturer’s instructions. Half of the specimens (n = 12/subgroup) underwent 5000 thermocycles (5–55 °C). Micro-shear bond strength testing was performed, and failure modes were analyzed. Data were analyzed using three-way ANOVA and post hoc tests (p < 0.05). Results: Air abrasion significantly increased SBS compared to control and bur grinding for metal (p < 0.001). For zirconia, both air abrasion and bur grinding yielded similarly improved SBS over the control (p < 0.001). The GC repair kit demonstrated significantly superior bond stability after thermocycling across both substrates. Aging significantly reduced SBS in all groups (p < 0.001), with the most substantial reductions observed in untreated controls and groups repaired with the Bisco system. Conclusions: Airborne particle abrasion combined with a HEMA-free, 10-MDP-containing universal adhesive achieved the strongest and most durable resin bonds to both metal and zirconia, supporting its clinical use for the intraoral repair of ceramic and metal restorations. Full article

This paper presents results from an extensive study on laminated timber beams manufactured without adhesives or metal fasteners. The use of such elements enables the implementation of the 4R principles in construction (Reduce, Reuse, Recycle, Repair). Prior to the testing of beam elements, tests were conducted on embedment strength of wooden dowels in comparison with conventional steel ones. The specimens varied in dowel diameter and in the angle of applied load relative to the grain direction. In addition to mechanically inserted dowels, an innovative dowel-welding method was examined. Welding enhances the bonding between lamellas, thereby improving overall mechanical performance. Further investigations involved beams with lamellas joined by dowels of different diameters, spacing, orientation, and installation methods. Experimental results were compared with analytical models for composite beams. The study showed that, except through the entire height of the beam section, it is possible to use dowels that connect only two lamellas, which is important for production. Dowels placed at 45° in relation to the lamella fibers showed approximately 20% greater capacity. It is also important to mention that study shows how welded dowels are only useful when they have larger diameters because then they achieve a significant level of cohesion. Full article

The bonding interface between repair materials and concrete substrate is the weakest link in the entire repair structure. If the interface bonding performance is insufficient, the repair material is prone to cracking or falling off, leading to repair failure. The shrinkage of repair materials is one of the primary factors affecting the bonding performance of these interfaces. In this study, sulphoaluminate cement (SAC) was used to improve the repair performance of ordinary Portland cement (OPC)–granulated blast furnace slag (GGBS) composite repair materials. The influence of SAC on the mechanical properties, bonding performance, expansion behavior, impermeability, and hydration heat of OPC-GGBS-SAC composite repair materials was investigated. The results demonstrate that the rapid hydration of SAC significantly improved the early strength and mechanical properties of the composite system at negative temperatures. The hydration products filled the pores within the concrete matrix, thereby enhancing the mechanical meshing effect at the interface. The early expansion effect of SAC formed a pre-stressor at the interface, which not only strengthened the bonding force between repair materials and the substrate, but also effectively inhibited the shrinkage of the composite system and prevented crack formation, thus significantly promoting the long-term reliability of the bonding interface. An appropriate amount of SAC can accelerate the hydration process of OPC-GGBS system, advance the exothermic peak, and promote the development of early strength. However, excessive incorporation will inhibit the later hydration of the composite system due to the way in which the hydration products wrap the cement particles. When the content of SAC was 5–10%, optimal comprehensive properties of the OPC-GGBS-SAC composite system were attained. Full article

The evaluation of interfacial bonds between polymeric cementitious composites (PCCs) and concrete is considered as a critical factor to determine structural safety, durability, and service life regarding the repair and strengthening of old concrete structures. Conventional evaluations of interfacial bond strength have primarily relied on destructive testing methods, such as the pull-off and slant shear tests. However, these methods inherently possess fundamental limitations, including localized damage, non-uniform stress distribution, and uncertainty in result interpretation. This review aims to provide a comprehensive overview of existing standards and methods for assessing interfacial bond strength. For this purpose, the evaluation methods and results for the interfacial bond strength between cementitious composites such as PCCs and concrete were systematically reviewed. It further examines the characteristics and sources of error of the representative destructive method (pull-off test), highlighting its inherent limitations. Furthermore, this study conducted an in-depth analysis of a hybrid evaluation strategy combining non-destructive testing (NDT) and artificial intelligence (AI) to overcome the limitations of conventional interfacial bond strength assessment methods and minimize prediction errors. The results demonstrated that the NDT–AI hybrid approach, based on an ANN–BFGS model, achieved the highest accuracy in bond strength prediction and was identified as the optimal method for quantitatively and non-destructively evaluating interfacial bond behavior. Full article

Hydrogels are three-dimensional polymeric networks capable of retaining large amounts of water. Polyvinyl alcohol (PVA)-based hydrogels exhibit autonomous self-healing through reversible physical interactions within the hydrogel matrix, including hydrogen bonding, crystallite formation, and dynamic crosslinking. However, their long self-healing times and low strength limit practical application. Herein, we propose an effective strategy to simultaneously achieve excellent self-repairing and high mechanical strength. The tensile strength of uncut PVA hydrogel was 1.21 MPa; after cutting and rejoining for 12 h at room temperature (RT), it recovered 94% of the original uncut strength. To accelerate self-healing, hydrogels were treated at 40, 50, and 60 °C for 20, 40, and 60 min. Under optimal conditions (60 °C for 60 min), 96% recovery was achieved. Mechanical properties were further improved by silica (Si) nanoparticles of various sizes (~12, ~85, and ~200 nm). Si-loaded hydrogels, particularly ~12 nm, demonstrated increased mechanical properties, reaching a tensile strength of 1.45 MPa and a self-healing recovery of 95% of the uncut hydrogel strength. Ultra-small (~12 nm) Si nanoparticles enhanced the overall mechanical properties by acting as an efficient nucleating agent and did not hinder the existing self-healing mechanism. The developed strategy will pave the way for novel techniques in hydrogel research and will advance applications such as soft robotics and wound dressing. Full article