Search Results (45)

In order to solve various problems in traditional roads and extend their service life, new road materials have become a research hotspot. Polyurethane prepolymers (PUPs) and ceramic fibers (CFs), as materials with unique properties, were chosen due to their synergistic effect: PUPs provide elasticity and gel-like behavior, while CFs contribute to structural stability and high-temperature resistance, making them ideal for enhancing asphalt performance. PUPs, a thermoplastic and elastic polyurethane gel material, not only enhance the flexibility and adhesion properties of asphalt but also significantly improve the structural stability of composite materials when synergistically combined with CF. Using response surface methodology, an optimized preparation scheme for PUP/CF composite-modified asphalt was investigated. Through aging tests, dynamic shear rate (DSR) testing, bending rate (BBR) testing, microstructure scanning (MSCR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and infrared spectroscopy (IR), the aging performance, rheological properties, permanent deformation resistance, microstructure, and modification mechanism of PUP/CF composite-modified asphalt were investigated. The results indicate that the optimal preparation scheme is a PUP content of 7.4%, a CF content of 2.1%, and a shear time of 40 min. The addition of the PUP and CF significantly enhances the asphalt’s aging resistance, and compared with single-CF-modified asphalt and base asphalt, the PUP/CF composite-modified asphalt exhibits superior high- and low-temperature rheological properties, demonstrating stronger strain recovery capability. The PUP forms a gel network structure in the material, effectively filling the gaps between CF and asphalt, enhancing interfacial bonding strength, and making the overall performance more stable. AFM microscopic morphology shows that PUP/CF composite-modified asphalt has more “honeycomb structures” than matrix asphalt and CF-modified asphalt, forming more structural asphalt and enhancing overall structural stability. This study indicates that the synergistic effect of PUP gel and CF significantly improves the macro and micro properties of asphalt. The PUP forms a three-dimensional elastic gel network in asphalt, improving adhesion and deformation resistance. Using response surface methodology, the optimal formulation (7.4% PUP, 2.1% CF) improves penetration (↓41.5%), softening point (↑6.7 °C), and ductility (↑9%), demonstrating the relevance of gel-based composites for asphalt modification. Full article

The development of symmetrical solid oxide fuel cells with identical cathode and anode is beneficial for thermal matching and reducing the cost. Herein, proton-conducting electrolyte and novel high catalytic activity electrode material for symmetrical solid oxide fuel cells are proposed. Ni-doping at the B-site of (Sr_0.8Ce_0.2)_0.95FeO_3−δ (SCF) indicates reduced cell edge lengths, cell volume, and a more porous honeycomb structure. The B-site elements in oxide tend to have a high oxidation state via Ni-doping. Simple doping modification in SCF causes better thermal matching between the electrode and electrolyte and form more oxygen vacancies at the operating temperature. At the anode side, Ni-doping improves the stability of the symmetric electrode in reducing the atmosphere. The polarization resistance of symmetrical cells for new electrode material is half of the original both in oxidation and reduction atmosphere, which indicates boosted electrochemical performance for the cathode and anode. At the same time, Ni-doping reduces the impedance activation energy of the anode reaction in symmetric cells. The output performance of the cell is 210.4 mW·cm⁻² at 750 °C and the thickness of the electrolyte is 400 μm, achieving a highly efficient symmetrical electrode in proton ceramic fuel cells. The new finding of materials provides a novel high efficiency symmetrical electrode and proposes guidance for the improvement of solid oxide fuel cells at a reduced temperature. Full article

In order to improve the strength and toughness-matching of metal matrix composites and enhance the mechanical properties of ceramic-reinforced iron matrix composites with a honeycomb architecture, TiCp/H13 steel composites with a honeycomb architecture were successfully prepared using squeeze-infiltration technology, in which the composite region was the honeycomb wall and the steel matrix was the honeycomb core. The effects of the composite-region fraction and TiCp content in the composite region on the compressive mechanical properties of the composites were studied, and the fracture mode and cracking behavior were analyzed. The results show that TiCp was evenly distributed in the composites region, and the interface of TiCp/H13 steel was tightly bonded without obvious defects. With the same TiCp content, the compressive strength of honeycomb-architecture composites first increased and then decreased with the increase in the composite-region volume fraction, and the highest strength was obtained at 50 vol.% of the composite region. The influence factor of the composite-region volume fraction on the strength was −38.3 MPa/%. Meanwhile, the fracture strain of the architecture composites decreased gradually. The influence factor of the composite-region volume fraction on plasticity was −0.25%/%. With the same composite-region fraction, both the compressive strength and plasticity of the composite decreased gradually with the increase in TiCp content (35 vol.%, 50 vol.%, and 65 vol.%). The influence factor of TiCp content on the strength was −21.4 MPa/%, and its influence factor on plasticity was −0.34%/%. The maximum compressive strength (2288.1 MPa) was obtained in the architecture composite with 50 vol.% of the composite region and 35 vol.% of TiCp, and the highest plasticity (25.9%) was obtained for the architecture composite, with 35 vol.% of the composite region and 35 vol.% of TiCp. Compared to those of common ZTA/iron honeycomb-architecture composites, the comprehensive mechanical properties of the TiCp/H13 steel matrix honeycomb-architecture composites were greatly improved. It showed good energy-absorption characteristics during compression. Full article

This work aims to study the influence of the material and geometric parameters that characterize re-entrant hexagonal honeycomb auxetic structures in the maximum transverse static deflection of beams. In addition, this study considers the composition of the material through the thickness results from the mixture of a metallic phase and one of four different selected ceramics, using the exponential volume fraction law. The first-order shear deformation theory within an equivalent single-layer approach is used to assess the material and geometric parameters’ influence on the structures’ deflection. Considering this theoretical approach, the impact of the material and geometric parameters on the shear correction factors, calculated for each specific case, is also analyzed. The results allow us to conclude how the shear correction factors and the structures’ maximum static deflection are affected by the re-entrant hexagonal honeycomb auxetic cells’ aspect ratios, by the angle associated with the direction of the inclined members of the hexagonal cells and the use of materials with differentiated Poisson’s ratios. Full article

This study aimed to evaluate the effect of ceramic type, firing tray, and firing substrate on the density, shrinkage, biaxial flexural strength, Martens’ hardness, and elastic indentation modulus of zirconia veneering ceramics. Disk-shaped specimens were fabricated from a high-fusing (HFZ) and a low-fusing (STR) zirconia veneering ceramic. These specimens were then divided into 10 groups according to firing trays (round, small honeycomb-shaped, cordierite [RSC]; round, large honeycomb-shaped, aluminum oxide [RLA]; rectangular, plane, silicon nitride [RCPS]; round, plane, silicon nitride [RPS]; and rectangular, plane, calcium silicate [RCPC]) and firing substrates (firing cotton and platinum foil) used (n = 12). The density, shrinkage, biaxial flexural strength, Martens’ hardness, and indentation modulus were measured, and analyzed with generalized linear model analysis (α = 0.05). The interaction between the ceramic type and firing substrate affected density (p < 0.001), and the other outcomes were affected by the interaction among all main factors (p ≤ 0.045). Higher density was observed with HFZ or platinum foil (p ≤ 0.007). RSC and RLA led to a higher density than RCPS within HFZ and led to the lowest density within STR (p ≤ 0.046). STR had a higher shrinkage (p < 0.001). RSC mostly led to a lower shrinkage of HFZ (p ≤ 0.045). The effect of ceramic type and firing substrates on the biaxial flexural strength, Martens’ hardness, and indentation modulus was minimal while there was no clear trend on the effect of firing tray on these properties. Ceramic type, firing tray, and firing substrate affected the mechanical properties of the tested zirconia veneering ceramics. Firing the tested zirconia veneering ceramics over a round and small honeycomb-shaped cordierite firing tray with firing cotton mostly led to improved mechanical properties. Full article

Although bioceramic materials exhibit good biocompatibilities and bone conductivities, their high brittleness and low toughness properties limit their applications. Zirconia (ZrO₂)/resin composites with idealized structures and properties were prepared by fused deposition modeling (FDM) combined with a vacuum infiltration process. The porous structure was prepared using the FDM three-dimensional printing technology, with granular zirconia as the raw material, and the relationship between the pore shape, pore size, and deformation was discussed. The results showed that square pores were more suitable than honeycomb pores for printing small pore sizes, and the resolution was high. Scanning electron microscopy observations showed that the superposition of multiple printing paths promoted the emergence of hole defects. The effects of the resin and the pore shape on the compressive strengths of the composites were studied. It was found that the compressive strengths of the honeycomb pore ZrO₂/resin composites and porous ceramics were superior to those of the square pore samples. The introduction of the resin had a significant effect on the compressive strengths of the composites. The compressive strength increased in the direction perpendicular to the pores, while it decreased in the direction parallel to the pores. Full article

The porous TiCO ceramic was synthesized through a one-step sintering method, utilizing phenolic resin, TiO₂ powder, and KCl foaming agent as raw materials. Ni(NO₃)₂·6H₂O was incorporated as a catalyst to facilitate the carbothermal reaction between the pyrolytic carbon and TiO₂ powder. The influence of Ni(NO₃)₂·6H₂O catalyst content (0, 5, 10 wt.% of the TiO₂ powder) on the microstructure, compressive strength, and thermal conductivity of the resultant porous TiCO ceramic was examined. X-ray diffraction and X-ray photoelectron spectroscopy results confirmed the formation of TiC and TiO in all samples, with an increase in the peak of TiC and a decrease in that of TiO as the Ni(NO₃)₂·6H₂O content increased from 0% to 10%. Scanning electron microscopy results demonstrated a morphological change in the pore wall, transforming from a honeycomb-like porous structure composed of well-dispersed carbon and TiC-TiO particles to rod-shaped TiC whiskers, interconnected with each other as the catalyst content increased from 0% to 10%. Mercury intrusion porosimetry results proved a dual modal pore-size distribution of the samples, comprising nano-scale pores and micro-scale pores. The micro-scale pore size of the samples minorly changed, while the nano-scale pore size escalated from 52 nm to 138 nm as the catalyst content increased from 0 to 10%. The morphology of the pore wall and nano-scale pore size primarily influenced the compressive strength and thermal conductivity of the samples by affecting the load-bearing capability and solid heat-transfer conduction path, respectively. Full article

This analysis investigated the impact wave response and propagation on a composite sandwich shell when subjected to a low-velocity external shock, considering hygrothermal effects. The sandwich shell was crafted using face layers composed of functional gradient metal–ceramic matrix material and a core layer reinforced with negative Poisson’s honeycomb. The honeycomb layer consisted of a combination of viscoelastic polymer material and elastic material. The equivalent parameters for the functional gradient material in the face layers were determined using the Mori–Tanaka and Voigt models, and the parameters for the negative Poisson’s ratio honeycomb reinforcement core layer were obtained through Gibson’s unit cell model. Parameters relevant to a low-velocity impact were derived using a modified Hertz contact law. The internal deformations, strains, and stress of the composite sandwich shell were described based on the higher-order shear deformation theory. The dynamic equilibrium equations were established using Hamilton’s principle, and the Galerkin method along with the Newmark direct integration scheme was employed to calculate the shell’s response to impact. The validity of the analysis was confirmed through a comparison with published literature. This investigation showed that a multilayer negative Poisson’s ratio viscoelastic polymer material honeycomb-cored structure can dissipate impact wave energy swiftly and suppress shock effectively. Full article

A multilayer liquid-containing protective structure is composed of a liquid tank, ceramic, a honeycomb sandwich and homogeneous steel. This structure has superior resistance to combined blast wave and fragment loading. Due to the relatively complicated construction of the structure, the inner damage, energy absorption and the protection characteristics of the multilayer liquid-containing protective structure need to be further studied. In this paper, a multilayer liquid-containing structural model is constructed, the dynamic response process of multilayer liquid-containing structure under combined blast wave and fragment loading is analyzed, and the damage and energy absorption characteristics of each layer structure are investigated. In addition, the effects of the charge mass and fragment form on the structural failure modes and energy absorption characteristics are discussed. The results indicate that different modes of damage occur in each layer structure. The front plate of the liquid tank sustains the most damage and absorbs the most energy, and the honeycomb sandwich absorbs the second most energy. The damage area of the front plate and the degree of compression collapse of the honeycomb sandwich increase with increasing charge mass. When the charge mass is small, the damage mode of the multilayer liquid-containing structure is greatly affected by fragments, and the damage effect of the blast wave increases with increasing charge mass. For a constant charge mass, the degree of damage to the protective structure is minimally impacted by the fragment weight, and the degree of damage can be substantially reduced by reducing the number of fragments. Full article

The expansion of renewable energy sources and sustainable infrastructures for the generation of electrical and thermal energies and fuels increasingly requires efforts to develop efficient technological solutions and holistically balanced systems to ensure a stable energy supply with high energy utilization. For investigating such systems, a research infrastructure was established within the nationally funded project Energy Lab 2.0 including essential components for generation, conversion and storage of different energy sources. One element includes a thermal energy storage (TES) system based on solid materials, which was supplemented by an electrically heated storage component. Hereby, the overall purpose is to efficiently generate and store high-temperature heat from electrical energy with high specific powers during the charging period and provide thermal energy during the discharging period. Today’s solutions focus on convective electrical heating elements, creating, however, two major challenges for large-scale systems: limited load gradients due to existing systemic inertias and limited operating temperatures of 700 °C in the MW scale. To overcome such restrictions, a novel electrically heated storage component with dual operating modes was developed. The central component of this solution is a ring-shaped honeycomb body based on an SiC ceramic with electrical heating registers on the inside and outside. This configuration allows, in storage operation, instantaneous direct heating of the honeycomb body via thermal radiation. At the end of systemic start-up procedures, an operational change toward a convective heating system takes place, whereby the high-temperature heat previously stored is transferred to downstream components. The simulation studies performed for such a component show, for both operating modes, high operating temperatures of over 800 °C with simultaneous high electrothermal efficiencies of up to 90%. Experimental investigations on a 100 kW scale at the DLR test facility HOTREG in Stuttgart confirmed the feasibility, performance and good agreement with simulation results for a selected honeycomb geometry with a mass of 181 kg. With its successful testing and good scalability, the developed component opens up high use case potentials in future Power-to-Heat-to-Power applications, particularly for Brayton process-based Carnot batteries and adiabatic compressed air energy storage systems. Full article

A novel approach for manufacturing porous materials, foreseen as solar receivers for concentrated sun radiation, used in the power tower technology is presented. In such applications, materials are subjected to steep thermal gradients and thousands of cycles. Yet, materials consisting of honeycombs and ceramic foams showed insufficient thermal performance. By using the fused filament fabrication process, one can design printed parts meeting the requirements for solar receivers, namely dark color and high solar absorptance. This exploratory study unveils data on the retained crushing strength of newly developed 3D-printed porous Black Zirconia cubes after thermal cycling under similar conditions to those experienced by volumetric receivers and catalyst substrates for solar fuels (H₂ and/or CO) production via the thermochemical cycle. Unlike dense ceramics, the resistance to thermal shock of 3D-printed cubes underwent a gradual decrease with the increase in the thermal gradient. The thermal shock cycles were performed between 800 °C and 1100, 1200, and 1300 °C, corresponding to a ΔT of 300, 400, and 500 K, respectively. Additionally, water quenching tests were performed at ΔT = 300 K up to 400 K. Crushing strength measurements carried out to evaluate the retained mechanical strength after exposure up to 100 cycles showed that the Black Zirconia cubes can withstand thermal gradients up to at least 400 K. Full article

Ceramic components require very high energy consumption due to synthesis, shaping, and thermal treatment. However, this study suggests that combining the sol–gel process, replica technology, and stereolithography has the potential to produce highly complex geometries with energy savings in each process step. We fabricated light-frame honeycombs of Al₂O₃, Ba_0.85Ca_0.15Zr_0.1Ti_0.9O₃ (BCZT), and BaTiO₃ (BT) using 3D-printed templates with varying structural angles between −30° and 30° and investigated their mechanical and piezoelectric properties. The Al₂O₃ honeycombs showed a maximum strength of approximately 6 MPa, while the BCZT and BaTiO₃ honeycombs achieved a d₃₃ above 180 pC/N. Additionally, the BCZT powder was prepared via a sol–gel process, and the impact of the calcination temperature on phase purity was analyzed. The results suggest that there is a large energy-saving potential for the synthesis of BCZT powder. Overall, this study provides valuable insights into the fabrication of complex ceramic structures with improved energy efficiency and enhancement of performance. Full article

In recent years, there have been increasing research interests in investigating the compression and ballistic responses of metal-ceramic hybrid structures, mainly making use of the synergistic effects of conventional metal honeycomb structures and infilled ceramic matrix materials. In this paper, a novel hybrid auxetic re-entrant metal-ceramic lattice is designed and manufactured to overcome the intrinsic conflicts between the strength and toughness of architected mechanical metamaterials, synergistic effects of auxetic re-entrant metal honeycombs and infilled ceramic materials are experimentally and numerically studied, and auxetic deformation features and failure modes are characterized with the digital image correlation (DIC) technique as well. It was found that (1) the infilled ceramic matrix of conventional honeycomb frames only endure longitudinal compression or impact loading along the external loading direction, while auxetic metal re-entrant honeycomb components endure both longitudinal and transverse loading due to the negative Poisson′s ratio effect and (2) the collaborative effects of infilled auxetics and the constraint frames’ hybrid structure dramatically moderate the stress concentration state and improve the impact resistance of single-phase ceramic materials. Our results indicate that the auxetic hybrid design exhibits promising industrial application potentials for blast protection engineering. Full article

The synthesis of Co and Ce oxide nanoparticles using precipitation of precursor salt solutions in the form of microdroplets generated with a nebulizer proved to be an efficient, fast and inexpensive method. Different morphologies of single oxides particles were obtained. Ceria nanoparticles were almost cube-shaped of 8 nm average size, forming 1.3–1.5 μm aggregates, whereas cobalt oxide appeared as rounded-edged particles of 37 nm average size, mainly forming nanorods 50–500 nm. Co₃O₄ and CeO₂ nanoparticles were used to generate structured catalysts from both metallic (stainless steel wire mesh monoliths) and ceramic (cordierite honeycombs) substrates. Ceria Nyacol was used as a binder to favor the anchoring of catalytic particles thus enhancing the adhesion of the coating. The resulting structured catalysts were tested for the combustion of diesel soot with the aim of being used in the regeneration of particulate filters (DPFs). The performance of these structured catalysts was similar to or even better than that exhibited by the catalysts prepared using commercial nanoparticles. Among the catalysts tested, the structured systems using ceramic substrates were more efficient, showing lower values of the maximum combustion rate temperatures (T_M = 410 °C). Full article

Volatile organic compounds (VOCs) in indoor environments have typical features of multiple components, high concentration, and long duration. The development of gas sensors with high sensitivity to multiple VOCs is of great significance to protect human health. Herein, we proposed a sensitive ZnO/WO₃ composite chemi-resistive sensor facilely fabricated via a sacrificial template approach. Based on the transferable properties of self-assembled monolayer colloidal crystal (MCC) templates, two-dimensional honeycomb-like ordered porous ZnO/WO₃ sensing matrixes were constructed in situ on commercial ceramic tube substrates with curved and rough surfaces. The nanocomposite thin films are about 250 nm in thickness with large-scale structural consistency and integrity, which facilitates characteristic responses with highly sensitivity and reliability. Furthermore, the nanocomposite sensor shows simultaneous responses to multiple VOCs that commonly exist in daily life with an obvious suppression sensing for traditional flammable gases. Particularly, a detection limit of 0.1 ppm with a second-level response/recovery time can be achieved, which is beneficial for real-time air quality assessments. We proposed a heterojunction-induced sensing enhancement mechanism for the ZnO/WO₃ nanocomposite film in which the formation of abundant heterojunctions between ZnO and WO₃ NPs significantly increases the thickness of the electron depletion layer in the bulk film and improves the formation of active oxygen species on the surface, which is conducive to enhanced responses for reducing VOC gases. This work not only provides a simple approach for the fabrication of high-performance gas sensors but also opens an achievable avenue for air quality assessment based on VOC concentration detection. Full article