Multi-shelled hollow nanomaterials with diverse compositions and architectures have garnered significant attention due to their unique structural advantages, including high surface-to-volume ratios, tunable inner cavities, and enhanced physicochemical properties. While single-shelled hollow structures have been extensively explored, multi-shelled architectures offer superior functionality, making them promising candidates for advanced applications. This review provides a comprehensive overview of recent advancements in the synthesis, classification, and biosensing applications of multi-shelled spherical nanomaterials. Various synthesis approaches, including hard templating, soft templating, sacrificial templating, and template-free methods, are critically analyzed with a focus on their advantages, limitations, and challenges. The potential of multi-shelled nanoparticles in biosensing is explored, particularly in electrode-based detection and surface-enhanced Raman scattering (SERS) techniques, enabling rapid, sensitive, and selective identification of harmful organisms, viruses, and contaminants. Furthermore, this review emphasizes the importance of developing greener, scalable, and cost-effective synthetic strategies to meet the growing demand for real-world applications. Future research directions are highlighted, including the integration of multi-shelled nanospheres into point-of-care diagnostic platforms, the design of multifunctional nanocomposites, and the enhancement of biosensing performance through novel hybrid materials. These advancements are expected to pave the way for next-generation biosensors capable of real-time, in vivo , and multiplexed detection, contributing significantly to healthcare, environmental monitoring, and food safety.
The reduction of HfO 2 to produce HfB 2 powder currently represents the most cost-effective synthesis method. However, reduction processes employing B 2 O 3 , B 4 C or elemental B invariably involve volatile B 2 O 3 species, which damage high-temperature furnaces. This work reports an alternative approach using BN/C as reductants in a spark plasma sintering (SPS) furnace to synthesize HfB 2 . The reaction mechanism involves two sequential steps: initial reduction of HfO 2 by C to form non-stoichiometric HfC 1- x , followed by reaction between HfC 1- x and BN to yield HfB 2 . At 1,600 °C, phase-pure HfB 2 powder with ultralow oxygen content (0.47 wt.%) was obtained. The synthesized powder exhibits submicron particle size ( d 50 = 0.184 μm) and a distinctive bimodal distribution pattern.
The investigation of novel, high-strength joining techniques for boron carbide ceramics and titanium alloys was posited to significantly improve the ballistic resistance of advanced ceramic–metal composite armor systems. Previous research pertaining to the brazing of ceramics and metals utilizing Ag–Cu–Ti filler alloys was conducted. Utilizing the Ag–Cu–Ti brazing system as the primary material facilitated the vacuum brazing process between B 4 C ceramics and TC4 titanium alloy. To alleviate the residual thermal stress within the B 4 C/TC4 joint, materials with a low thermal expansion coefficient, specifically tungsten (W), along with refractory metal foils such as Mo foil and Nb foil, were incorporated. A robust connection between B 4 C and TC4 was successfully established by implementing a composite brazing system comprising Mo foil, AgCuTi–W, AgCu foil, and Nb foil. The inclusion of 5 wt.% W content refined the intermediate layer, resulting in a denser organization. Upon the addition of 5 wt.% W, the shear strength attained its peak value of approximately 75 MPa, signifying an 87.5 % surge in comparison to the condition without the additive. Optimizing the mechanical performance of the B 4 C/TC4 joint was possible by prudently integrating suitable quantities of low expansion coefficient materials alongside intermediate brazing layers. Significantly, the combination system comprising nickel-plated B 4 C + Mo foil + AgCuTi-5 wt.% W + AgCu foil + Nb foil + TC4 displayed the utmost shear strength, approximately 101 MPa.
This study investigated the workability of copper-based hybrid composites. The copper composites with enhanced mechanical properties were fabricated using powder metallurgy to be reinforced with titanium dioxide (TiO 2 ) and molybdenum disulfide (MoS 2 ). Triaxial stress state conditions were used to evaluate the performance of the copper composites, such as true axial strain and stress, true hoop stress, true mean stress, true effective stress, strain hardening index, strength coefficient, and instantaneous strain hardening from the measurement obtained using cold upset testing. The relationships between various stresses and stress–strain ratios were plotted and analyzed. Results showed that the increased reinforcement contents in the copper matrix enhanced the mechanical properties of the copper composites, especially the true axial, the true hoop, and the true effective stresses. Furthermore, the combination of 5 wt.% of TiO 2 and 4 wt.% of MoS 2 in the copper matrix was identified as the optimum composition for the best workability.
This study investigates the surface cladding of AISI 1020 low-carbon steel using the arc-DED (direct energy deposition) process with Rockit (R) 431SR martensitic stainless-steel powder and AM 70 feedstock wire. The powder is overlaid onto the substrate surface and fused by the heat generated during the MIG (metal inert gas)-WAAM (wire arc additive manufacturing) process using AM 70 wire, forming a clad layer. The study evaluates the microhardness distribution, phase composition, residual stress, and electrochemical corrosion behavior of the Rockit (R) 431SR + AM 70 clad, comparing it with the AISI 1020 substrate and AM 70-clad AISI 1020 without powder addition. The results show that the Rockit (R) 431SR + AM 70 cladding significantly improves microhardness and corrosion resistance, making it a promising solution for industries requiring high wear and corrosion resistance. The findings include superior microhardness in the clad layers, compressive residual stress, and enhanced electrochemical properties, including higher corrosion potential and improved pitting resistance. It has been found that Rockit (R) 431SR + AM 70 cladding offers enhanced durability and corrosion resistance compared to AM 70-clad AISI 1020 and the AISI 1020 substrate, enhancing its applicability across the automotive, marine, and infrastructure sectors.
The objective of this study was to synthesize and partially stabilize tialite (beta-Al2TiO5), a refractory ceramic material recognized for its high thermal shock resistance, low thermal conductivity, and low wettability with molten non-ferrous metals. This was accomplished by combining high-energy milling with a two-step sintering approach to promote a fine-grained microstructure and controlled porosity. Three Al2O3:TiO2 molar ratios were investigated (55:35, 45:45, and 35:55), while maintaining a fixed addition of 10 mol.% MgO as a stabilizing agent. The results demonstrated that the composition with excess Al2O3 exhibited superior densification and mechanical performance compared to the other ratios. The optimized specimens presented high relative density (3.19 +/- 0.02 g cm(-3), 84.08 % relative density), low apparent porosity (05.50 +/- 0.04 %), great tensile strength (11.17 MPa), and a refined microstructure with an average grain size below 2 mu m. These findings highlight the effectiveness of combining high-energy milling and two-step sintering to produce stabilized tialite ceramics with enhanced structural integrity, providing a promising route for advanced refractory applications.
Failure at the bone-implant interface due to the difference in modulus is the primary cause of orthopaedic implant loosening. Multiple strategies are offered for enhancing osseointegration through tissue ingrowth with strong interfacial locking. The bioactive and bioresorbable metal-glass composite is designed for defect healing, which will ultimately be replaced by newly generated skeletal tissues. Conventional metallic biomaterials such as stainless steel, titanium, and cobalt-chromium alloys exhibit a substantially higher Youngs' modulus compared to that of natural bone. This pronounced stiffness mismatch in bioresorbable load bearing implants leads to an undesirable stress-shielding effect that compromises long-term implant performance and bone remodelling. Conversely, magnesium based alloys are lightweight and exhibit lower mechanical properties when utilised in a porous form compared to real bone. Nonetheless, its accelerated deterioration in the electrolytic environment of bodily fluids leads to adverse effects due to hydrogen accumulation in-vivo and void formation at the defect location. Bioglass, a bioactive osteoconductive substance with suboptimal mechanical characteristics, can be combined with magnesium to enhance mechanical properties and adjustable degradability. This study focused on the development of a bioactive glass-reinforced magnesium composite to enhance machinable strength, reduce effective Youngs' modulus, and improve in-vivo bioresorbability, serving as a template for skeletal tissue regeneration. X-ray diffraction and Fourier-transform infrared spectroscopy results show that the final product retains the essential physical features of both bioglass and magnesium. Energy-dispersive spectroscopy examination revealed the compositional distribution, while several microscopic analyses illustrated the microstructure of the synthesised composite. The developed material exhibits osteoconductivity and cytocompatibility; hence, the biocompatibility investigations may facilitate future applications.
In this study, the alkaline treatment of wood dust with the help of sodium hydroxide (NaOH) was performed and mixed with graphene nanoplatelets (GNPs) to prepare epoxy composites. The matrix system used was two-part standard epoxy araldite (AW106 & HV953) and the weight percentage of wood dust as well as GNPs was varied to investigate their effect on thermal and mechanical properties. The change in molecular architecture after alkali treatment on wood dust was examined with the help of Fourier transform infrared spectroscopy. Mechanical behavior was tested on a universal testing machine and thermal behavior was tested by thermo gravimetric analysis. The fracture surfaces were examined by field emission scanning electron microscope. Results indicate that addition of wood dust up to 2.5 wt.% concentration improves mechanical properties of epoxy composite and addition of GNPs up to 0.5 wt.% improves thermal as well as mechanical behaviour of the composite. The addition of GNPs provides good compatibility and surface structure to make uniform mixing of the nanoparticles. Hence, wood dust provides good option to make bio-composites with better and enhanced properties.
Microstructural and microprobe analyses of as-cast and annealed alloys (1,000 degrees C for 61 h) revealed a new congruently melting Hf0.45Ti0.55Ni2 compound in the Hf-Ti-Ni system. The compound forms two-phase equilibria with Hf7Ni10, Hf3Ni7, alpha HfNi3 and TiNi3 and exhibits a homogeneity range of 18-24 at.% Ti at 65 +/- 0.5 at.% Ni. Its crystal structure was determined by single-crystal and powder X-ray diffraction. Hf0.45Ti0.55Ni2 crystallizes in a derivative of the Co1.75Ge prototype exhibiting statistical mixture of hafnium and titanium atoms on 2d site and two 2a, 2c sites occupied by nickel atoms: PS hP6, SG P63/mmc, a = 4.225(2), c = 5.044(4) & Aring;. The Rietveld-refined composition, Hf0.482(2)Ti0.518(2)Ni2, is in close agreement with both the single-crystal X-ray diffraction data and the energy-dispersive X-ray analysis results. The homogeneity range of the compound Hf x Ti1-xNi2 has been refined from powder X-ray diffraction and energy-dispersive X-ray data: (0.55 <= x <= 0.72), variation of the lattice parameters is the following: a = 4.2045(3) - 4.185(1), c = 5.0055(4) - 5.000(1) & Aring;. The microstructure shows a characteristic twin morphology. The microhardness of the compound was measured as 1,160 +/- 20 and 1,140 +/- 60 H mu for single-phase as cast alloys containing 18 and 24 at.% Ti, respectively. Electronic structure calculations based on the LMTO method for the ordered model HfTiNi4 (P6/mmm) indicate a metallic behavior with significant Ti-Ni, Hf-Ni, and Ti-Hf bonding interactions. The analysis of DOS and COHP indicates strong covalent contributions alongside Ni-Ni antibonding states, suggesting a complex hybrid metallic-covalent bonding nature that stabilizes the Hf-Ti-Ni three-dimensional network.
The strength of parts produced by fused filament fabrication depends strongly on how the raster angles are arranged. While many studies have looked at conventional orientations such as 0 degrees, 90 degrees, and +/- 45 degrees, very little work has examined systematic groupings of angles or how such groupings influence strength. In this study, a multi-objective optimization framework is implemented that combines classical lamination theory, the Tsai-Hill failure criterion, the Heat Transfer Search algorithm, and the Technique for Order Preference by Similarity to Ideal Solution ranking method to identify effective raster angle configurations for improving tensile/shear and flexural/torsion performance. Tensile and bending experiments are carried out to establish the applied load values for optimization and to validate the methodology. The optimization produced both standard and non-standard symmetric raster angle configurations that improved strength. This includes [0 0 0 0 0 0 0 0]S for axial-bending, [1 1 1 1 86 86 86 86]S and [0 0 0 0 0 0 0 0]S for tensile-bending in the y-x direction, [45 -45 -45 -45 -45 45 45 45]S for shear-torsion, and [-15 14 -15 14 -15 14 -15 14]S for tensile-torsion. The raster angle grouping study also showed how different layer arrangements can create either smooth or abrupt stress transitions across the thickness, giving useful insight into inter-layer bonding. Taken together, these results demonstrate that the proposed framework can be used to systematically tune raster orientations to improve the strength of fused filament fabricated acrylonitrile butadiene styrene parts, and may be extended to other additively manufactured components.
This current contribution reports the absorption and emission behavior of the single walled carbon nanotube (SWCNT)-DNA conjugate integrated with cellulose extracted from Philippine endemic plants. Microscopy analysis reveals that pristine SWCNTs formed bundles and exhibited insolubility in water. With the addition of cellulose extracted from corn husk and coconut coir, dispersion of nanotubes is evidently observed due to hydrophilic-hydrophobic interactions of cellulose and nanotubes respectively. When SWCNT-DNA is integrated with cellulose, a membrane-like structure is formed attributed to the interaction of DNA and cellulose in nanotube surfaces. Interestingly, photoluminescence reveals the stability of this membrane formed on glass surface leading to bright PL images. This behavior can be attributed to the hydrogen bonding interaction of cellulose and DNA, van der Waals forces with nanotubes, and the ionic interactions between charged components of DNA in the suspension and the cellulose. These findings could lead to advancements in biosensing applications, leveraging the unique properties of cellulose from Philippine endemic plants.
The hot-deformation behavior and extrusion response of a rare-earth-containing Mg-4Y-2Nd-1Gd-1Ag-0.5Zr alloy were systematically investigated to establish processing guidelines for high-strength magnesium components. Cylindrical billets were homogenized, subjected to isothermal compression at 350-500 degrees C and strain rates of 0.001-1 s-1, and analyzed using a dynamic materials model to construct constitutive equations and hot-processing maps. The alloy exhibits an activation energy of similar to 229 kJ mol-1, close to the diffusion energy of Y in Mg, and a stress exponent n approximate to 5.0, confirming that high-temperature deformation is governed by dislocation glide and climb in the climb-controlled regime. Flow-stress curves reveal typical dynamic recrystallization (DRX) features, with higher temperatures and lower strain rates promoting extensive DRX and grain refinement. The instability regions predicted by the processing maps expand with strain from low-temperature/high-rate to high-temperature/high-rate conditions. Extrusion experiments validated the modelling results and identified an optimal processing window near 425 degrees C, yielding defect-free rods with a fine recrystallized grain size (similar to 4.4 & micro;m), a yield strength of 289 MPa, an ultimate tensile strength of 335 MPa, and an elongation of 10.6 %. These findings provide a mechanistic basis for the design of magnesium alloys combining high strength and ductility, and demonstrate the effectiveness of processing-map-guided extrusion for rare-earth-modified Mg systems.
The investigation of novel, high-strength joining techniques for boron carbide ceramics and titanium alloys was posited to significantly improve the ballistic resistance of advanced ceramic-metal composite armor systems. Previous research pertaining to the brazing of ceramics and metals utilizing Ag-Cu-Ti filler alloys was conducted. Utilizing the Ag-Cu-Ti brazing system as the primary material facilitated the vacuum brazing process between B4C ceramics and TC4 titanium alloy. To alleviate the residual thermal stress within the B4C/TC4 joint, materials with a low thermal expansion coefficient, specifically tungsten (W), along with refractory metal foils such as Mo foil and Nb foil, were incorporated. A robust connection between B4C and TC4 was successfully established by implementing a composite brazing system comprising Mo foil, AgCuTi-W, AgCu foil, and Nb foil. The inclusion of 5 wt.% W content refined the intermediate layer, resulting in a denser organization. Upon the addition of 5 wt.% W, the shear strength attained its peak value of approximately 75 MPa, signifying an 87.5 % surge in comparison to the condition without the additive. Optimizing the mechanical performance of the B4C/TC4 joint was possible by prudently integrating suitable quantities of low expansion coefficient materials alongside intermediate brazing layers. Significantly, the combination system comprising nickel-plated B4C + Mo foil + AgCuTi-5 wt.% W + AgCu foil + Nb foil + TC4 displayed the utmost shear strength, approximately 101 MPa.
By combining solid-state diffusion couple experiments with a numerical inverse method, the interdiffusion coefficients in NiAlCoCr/CoCrFeMn0.2Ni and NiAlCoCr/CoCrCu0.2FeNi diffusion couples were determined at 1,273-1,373 K, and their reliability was verified. The main interdiffusion coefficients on the NiAlCoCr alloy side were greater than those on the high-entropy alloy side at 1,273-1,373 K. The main interdiffusion coefficients followed the trend: D (Ni )(MnMn )> D-CuCu( Ni ) > D (Ni )(CrCr )> D Ni FeFe > D- Ni (CoCo) at 1,273 K. Tracer diffusion coefficients were calculated for both the CoCrFeMn0.2Ni/NiAlCoCr and CoCrCu0.2FeNi/NiAlCoCr diffusion couples at 1,273-1,373 K. Furthermore, the composition-dependent diffusion activation energies of the tracer diffusion coefficients were analyzed in the CoCrCu0.2FeNi/NiAlCoCr diffusion couple.
This study investigated the workability of copper-based hybrid composites. The copper composites with enhanced mechanical properties were fabricated using powder metallurgy to be reinforced with titanium dioxide (TiO2) and molybdenum disulfide (MoS2). Triaxial stress state conditions were used to evaluate the performance of the copper composites, such as true axial strain and stress, true hoop stress, true mean stress, true effective stress, strain hardening index, strength coefficient, and instantaneous strain hardening from the measurement obtained using cold upset testing. The relationships between various stresses and stress-strain ratios were plotted and analyzed. Results showed that the increased reinforcement contents in the copper matrix enhanced the mechanical properties of the copper composites, especially the true axial, the true hoop, and the true effective stresses. Furthermore, the combination of 5 wt.% of TiO2 and 4 wt.% of MoS2 in the copper matrix was identified as the optimum composition for the best workability.
The reduction of HfO2 to produce HfB2 powder currently represents the most cost-effective synthesis method. However, reduction processes employing B2O3, B4C or elemental B invariably involve volatile B2O3 species, which damage high-temperature furnaces. This work reports an alternative approach using BN/C as reductants in a spark plasma sintering (SPS) furnace to synthesize HfB2. The reaction mechanism involves two sequential steps: initial reduction of HfO2 by C to form non-stoichiometric HfC1-x, followed by reaction between HfC1-x and BN to yield HfB2. At 1,600 degrees C, phase-pure HfB2 powder with ultralow oxygen content (0.47 wt.%) was obtained. The synthesized powder exhibits submicron particle size (d(50) = 0.184 mu m) and a distinctive bimodal distribution pattern.
Industries require cost-effective, lightweight, and sustainable materials for various equipment fabrication purposes. Natural fiber composites are known to fulfill these criteria effectively. This study focused on the development of natural composites using Terminalia catappa fiber, Jujube fruit seed (J), and Neem seed (N), and evaluated their mechanical and wear properties. Composites were fabricated through the hand layup technique, maintaining a fixed resin-to-fiber ratio of 70:30 while varying Jujube fruit seed and Neem seed particle content from 1 to 3 wt.%. The JN (1:0) composite demonstrated superior hardness and tensile strength, measured at 92 Shore-D and 64.6 MPa, respectively. Additionally, this composite exhibited a minimal wear rate, wear loss, and coefficient of friction, recorded at 9 × 10 −5 g m −1 , 0.18 g, and 0.6, respectively. Thermal conductivity was also lowest for the JN (1:0) composite, at 0.11 W m −1 K −1 , attributable to the inclusion of Jujube fruit seed particles. Based on these findings, the JN (1:0) composite appears to be a promising material for applications in the automotive, packaging, and construction industries due to its notable mechanical strength and enhanced wear resistance.
Silicon nanowires were grown in-situ on the surface of basalt fibers (BFs) by a solution method. The mechanical properties and corrosion behavior of BFs before and after modification by hydrochloric acid (HCl) solution at room temperature, high-temperature, and high-temperature, high-pressure conditions were studied. The results showed that a high-temperature and high-pressure accelerated the corrosion of BF in HCl solution. The growth of silicon nanowires on the BFs improved the corrosion resistance of the BFs without greatly affecting their mechanical properties. After corrosion for 1 h in HCl at a high temperature and high pressure, the strength retention ratio of silicon nanowires modified BFs (PSN–BF) was 54 %, while that of unmodified BFs was 45 %. Upon increasing the modification time, the water contact angle on BFs increased from 138° at 4 h to 155° at 8 h. The higher contact angle indicated the greater hydrophobicity of the modified BFs, which reduced contact between BFs and the corrosive medium and improved their corrosion resistance. In addition, hydrogen ions (H + ) did not displace Si atoms in the silicon nanowires, and the tight wrapping of silicon nanowires protected the BF surface by preventing the reactions of metallic elements with H + .
Zn 1- x Mg x O ( x = 0, 0.03, 0.05, 0.07) nanoparticles were synthesized via solution combustion. Structural analysis confirmed a hexagonal wurtzite structure (space group P 6 3 mc). Crystallite sizes, calculated using the Debye–Scherrer formula, ranged from 55 to 75 nm. Fourier transform infrared spectra exhibited characteristic absorption peaks of wurtzite ZnO at 424 and 514 cm −1 , while Raman spectra revealed optical phonon modes associated with the wurtzite phase. Morphological and elemental analyses were performed using scanning electron microscope along with energy dispersive X-ray spectroscopy. Ultraviolet diffuse reflectance spectroscopy showed a blue shift in the band gap energy, increasing from 3.25 to 3.34 eV with higher Mg doping. Photoluminescence emission spectra indicated interstitial defects and oxygen vacancies, which significantly affected the electrical and optical properties. Impedance analysis revealed the presence of grains and grain boundaries, with total conductivity decreasing from 7.64 × 10 −8 S cm −1 to 1.03 × 10 −8 S cm −1 as Mg content increased. Mg-doped ZnO nanoparticles demonstrated improved charge carrier separation, enhancing photocatalytic activity. Photocatalytic studies on methylene blue (MB) dye degradation under UV light showed that Zn 0.93 Mg 0.07 O exhibited the highest photodegradation rate of 46 % after 180 min of irradiation.
This study investigates the influence of polyvinyl alcohol (PVA) treatment on bamboo long fibers to improve their performance in epoxy composites. Bamboo fibers were treated with PVA solutions at 1 %, 3 %, and 5 % and incorporated into epoxy matrices fabricated by hand lay-up. Microscopy revealed that 3 % PVA formed a uniform coating on fiber surfaces, enhancing adhesion with the matrix. Mechanical testing showed that PVA treatment improved tensile strength (from 32 to 39 MPa) and modulus (from 0.9 to 1.8 GPa), while impact resistance slightly decreased due to restricted fiber pull-out. Water absorption was also reduced, with 3 % PVA composites exhibiting the lowest uptake. Overall, PVA treatment is demonstrated as an effective and environmentally friendly modification method that enhances the mechanical strength and durability of bamboo/epoxy composites, making them more suitable for structural applications.
