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Silicon oxycarbide (SiOC) ceramics have been used to fabricate microwave-absorbing metastructures, demonstrating impressive absorption capabilities. However, SiOC ceramic metastructures with excellent performance require simple fabrication processes and appropriate mechanical and electromagnetic properties. In this study, a solvent-free photosensitive polysiloxane preceramic was developed by blending methoxy/hydroxy polysiloxanes with acrylates, with a ceramic yield of over 60% after curing using a novel two-step ultraviolet (UV)/thermal method. The composition and microstructure of SiOC ceramics can be designed by controlling the preceramic composition. Dense, crack-free gyroid-shellular shaped triple periodic minimal surface (GS-TPMS) electromagnetic metastructures were fabricated using digital light processing (DLP) 3D printing technology. By designing the porosity of the GS-TPMS structure to 51%, an effective absorption bandwidth that covers the X-band can be achieved at a thickness of 3.1 mm. The honeycomb structure, with a geometric density of 0.69 g/cm3, exhibited a high compressive strength of 107.05 MPa. This paper presents an efficient approach for the prompt and customized fabrication of lightweight ceramic metastructures with outstanding microwave absorption properties. • A solvent-free polysiloxane/acrylate hybrid preceramics is developed for 3D printing. • The UV/thermal two-stage treatment achieved cross-linking curing of the preceramics. • Multiscale design of SiOC ceramics for enhanced microwave absorption properties. • SiOC ceramic metastructures with effective absorption in the X-band are prepared. [ABSTRACT FROM AUTHOR]

Due to the limitations of the Kramers-Kronig relationship, how to achieve ultra-wide effective absorption bandwidth remains a challenge for typical magnetic-dielectric absorbers. In the present work, we have explored the possibility of obtaining ultra-wide absorption bandwidth in FeSiAl composites with help of efficient electromagnetic (EM) simulation software-Computer Simulation Technology (CST). Flaky FeSiAl powders covered by CeO 2 have been prepared, in which EM parameters can be tuned by filling ratio of FeSiAl/CeO 2 in FeSiAl/CeO 2 -paraffin composites. The filling ratio has an effect on impedance matching and EM parameters by the arrangement of particles in the paraffin. The composite with 30 wt% flaky FeSiAl/CeO 2 achieves an effective absorption bandwidth (EAB) of 6.48 GHz and the optimal microwave absorption efficiency of 1499.3 dB GHz/(wt%⋅m) at 1.9 mm. Integrated with a macroscale honeycomb structural design, the FeSiAl/CeO 2 composites based metastructure exhibits broadband microwave absorption with an EAB of 14.224 GHz covering from 3.776 GHz to 18 GHz and reflection loss of-65.61 dB at 8.5 GHz. The excellent performances of the designed absorber are ascribed to multiple loss by integrating EM parameters of flaky FeSiAl/CeO 2 and the geometry parameters of honeycomb metasrtucture. The present work makes flaky FeSiAl/CeO 2 composites possible to achieve broadband microwave absorption. [ABSTRACT FROM AUTHOR]

Peculiarities of sintering of foamy ceramic filters based on submicron aluminum oxide powders with additions of titanium oxide and manganese dioxide nanopowders are considered. The processes of removal of polymeric and binder paraffin material during sintering have been studied. The physical and mechanical properties of the obtained porous permeable filters with a foamy structure were analyzed in details. At a sintering temperature in an air atmosphere of 1350 °C, sufficiently high physical and mechanical properties were obtained, which made it possible to use the developed filters as catalyst carriers for vehicle exhaust gases. Bench comparative tests have shown that ceramic filters with a foamed structure are promising catalysts for afterburning car exhaust gases instead of ceramic honeycomb blocks of catalyst carriers. The developed technology allows reducing the sintering temperature of porous foam ceramic filters to 1350 °C and replacing expensive high-temperature ceramic heaters with cheaper nickel-chromium ones. [ABSTRACT FROM AUTHOR]

A significant challenge in electrolyte-supported solid oxide fuel cells (SOFCs) pertains to the substantial thickness of the electrolyte, resulting in elevated operational temperatures that hinder commercial viability. In this research, we utilized digital light processing (DLP) 3D printing technology to fabricate ultra-thin honeycomb electrolyte-supported SOFCs and subsequently evaluated their performance. Through the use of ultraviolet absorbers, we achieved a shallow curing depth (60.3 μm), which facilitated the creation of ultra-thin electrolyte samples. We investigated the mechanical properties of electrolytes with various honeycomb structures, finding that the square honeycomb structure exhibited the highest mechanical integrity, with an average failure load of 1.01 N. Finally, we assessed the electrochemical performance, observing a substantial power density of 215.4 mW/cm2, representing a twofold increase compared to the 114 mW/cm2 achieved by the same method in a flat primary cell. [ABSTRACT FROM AUTHOR]

Porous honeycomb mullite ceramics were controllably fabricated in-situ using stereolithography 3D printing. The effects of the dispersant type and content on the rheological behavior of the mullite precursor slurry were investigated. Additionally, the influence of the debinding atmosphere (air and argon) on the quality of the samples and formation of cracks was also studied. The results indicated that oleic acid (OA), 3-glycidoxypropylthrimethoxysilane (KH560), and disperbyk (BYK111) displayed the capability to create low-viscosity and highly stable slurries. Among these KH560 was proved to be the most effective. The mullite precursor slurry containing 4 wt% KH560 dispersants exhibited a shear thinning behavior. It displayed a viscosity of 0.26 Pa·s at a shear rate of 30 s−1. The mullite ceramic parts displayed good a dimensional resolution at an exposure dose of 5.47 mJ/cm2. During the debinding process, the printed parts were susceptible to cracking and deformation in air, but remained devoid of defects in argon. When the samples were sintered at 1600 °C, the corundum phase transformed almost completely into the mullite phase. The linear shrinkage values were 5.81%, 6.33%, and 10.26% in the O-X, O–Y and O-Z directions, respectively. [ABSTRACT FROM AUTHOR]

In this study, Al 2 O 3 honeycomb sandwich structures with different core geometries (square, triangular, circular) have been fabricated through an additive manufacturing system based on the stereolithography (SLA) method. The debinding procedure was performed under both nitrogen and air atmospheres. The impacts of the debinding atmosphere and core geometry on the densification and mechanical properties were investigated. The stiffness and flexural strength of the ceramics were examined experimentally using an impulse excitation of vibration technique and a three-point bending test, respectively. The specific stiffness and specific strength of the ceramics were also evaluated, with the core geometries taken into consideration. The outcomes showed that higher densification was achieved when the ceramics were exposed to debinding in nitrogen. The stiffness values were found to be similar for the same debinding condition within the honeycomb sandwich structures, irrespective of the core geometry. Notably, the highest specific stiffness (98 MNm/kg) was achieved for the samples subjected to debinding in nitrogen with a square core geometry. Furthermore, ceramics with square cores for debinding in a nitrogen atmosphere also demonstrated the highest performance in terms of specific strength (110 kNm/kg) within the honeycomb structures. This study demonstrated that Al 2 O 3 honeycomb sandwich structures with square cores may be suitable candidates for lightweight-structure demanding applications. [ABSTRACT FROM AUTHOR]

Vitrified-bond diamond composites are materials commonly used for grinding wheels in the grinding process of silicon wafer production. In this study, the mechanism of the in situ honeycomb structure formation in the sintering process of composite materials was explored by changing the binder content without adding a pore-forming agent.The results show when the content of vitrified bond is 55 wt%, the in situ honeycomb structure forms, resulting in a porosity of 60.68 % and bending strength of 23.03 MPa.The X-ray diffraction (XRD), Raman spectroscopy (RS), and thermogravimetry-differential thermal analysis (TG-DTA) results show that no graphitization of diamond grain occurs during sintering. The bonding ability between the vitrified bond and diamond grain, along with the microstructure of vitrified-bond diamond composites, was studied using scanning electron microscopy (SEM). Moreover, the results of energy spectrum analysis (EDS) show that the diffusion and segregation of Na at the interface between the diamond particles and the vitrified bond improve the bonding strength, and the vitrified bond can effectively bond with the diamond particles. Finally, the formation mechanism of the honeycomb structure was elucidated using the surface and interface sintering theory. [ABSTRACT FROM AUTHOR]

Recrystallized SiC (R–SiC) honeycomb ceramics were prepared using Al 4 SiC 4 as additives through a two–step sintering process, consisting of pre–nitridation treatment at 1800 °C for 180 min, followed by heat treatment for 60 min at temperatures ranging from 2000 to 2200 °C. The influences of firing temperature on phase compositions, microstructures, porosity, and mechanical properties of honeycomb ceramics were evaluated. The results revealed that AlN, SiC, and C were formed in situ after nitriding at 1800 °C. As the subsequent heat treatment temperature increased from 2000 to 2200 °C, the sublimation rate of submicron SiC increased, as well as AlN solid solubility. AlN diffused into SiC lattice and formed the SiC–AlN solid solution, which accelerated the conversion of 6H–SiC to 4H–SiC. According to first–principles calculations, the formation of solid solution contributed to the sintering process, which performed through the reduction of the surface energy of the grains. In addition, the pore size of specimens increased with elevating the heating temperature, and the distribution transitioned from unimodal to bimodal. Simultaneously, AlN and C activated the SiC lattice and facilitated mass transfer rate. The SiC sintering necks were well–developed at 2200 °C, resulting in the optimized overall performance of SiC honeycomb ceramics with a porosity of 52.7% and compressive strength of 17.98 MPa. [ABSTRACT FROM AUTHOR]

Inspired by the double-helix structure of biological DNA, low-volume fraction and high-strength Al 2 O 3 twisted honeycomb structures with characteristics similar to those of helical structures in the z -axis were prepared by digital light processing 3D printing technology. As the twist angle increased, the compressive strength of the fabricated Al 2 O 3 structure decreased, and the deformation mechanism of the Al 2 O 3 structures gradually changed from stretching-dominated to bending-dominated, which can be predicted by the Gibson–Ashby model. The relationship between the effective elastic modulus and the volume fraction that can be modified by varying the wall thickness was described by the Pabst–Gregorova exponential relationship. The compressive strength of the Al 2 O 3 structure with a twist angle of 0° can reach 62.4 MPa at a volume fraction of 13.3%, providing guidance to optimize lightweight structures of ceramics. [ABSTRACT FROM AUTHOR]

Three metal-organic frameworks including Ce-BDC, In-BDC and In/Ce-BDC and corresponding derived CuO/ZnO/In 2 O 3 /CeO 2 catalysts were prepared. The catalyst-loaded cordierite honeycomb ceramic supports were applied in a microreactor for hydrogen production via methanol steam reforming. The In/Ce-BDC-derived catalyst exhibited a methanol conversion rate of 100%, a hydrogen yield of 0.336 mol/h and an energy efficiency of 54% at 300 °C and an inlet methanol flow rate of 0.112 mol/h. Moreover, CO with content lower than 1.5% and catalytic stability of 30 h was recorded. The high specific surface area and superior redox property of the In/Ce-BDC-derived catalyst were characterized. The increased contents of oxygen vacancies and surface oxygen, in collaboration with the improved solid solubility of CuO and ZnO, were associated with the charge exchange induced by the strong interaction between In 2 O 3 and CeO 2 , leading to the excellent catalytic performance of the In/Ce-BDC-derived catalyst. [ABSTRACT FROM AUTHOR]

Na 4 Mn 9 O 18 whiskers were prepared on the wall of cordierite honeycomb ceramics using the molten salt synthesis, and Na 4 Mn 9 O 18 whiskers were grew on channel surface of cordierite honeycomb ceramics to form hierarchical microstructure for catalytic combustion of soot. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were used to characterize the structural morphology and phase compositions. Na 4 Mn 9 O 18 whiskers with aspect ratio of 24.4 measured by statistics. It was found that the loading rate of the monolithic catalyst reaches 3.588% while the binding rate after sonication almost no change. Whiskers are tightly combined with the cordierite ceramic substrate by the binding strength experiments and EDS analysis. The oxygen temperature-programmed desorption (O 2 -TPD) measurements were performed to investigate the O 2 adsorption property. The catalytic performance of the samples were examined by semi-quantitative thermal gravimetric analysis (TG-DTG) and temperature-programmed oxidation (TPO). The catalyst performance study demonstrates that Na 4 Mn 9 O 18 whiskers decrease the soot combustion temperature apparently. Experiments show the characteristic temperature could be reduced by increasing the catalyst loading. The Na 4 Mn 9 O 18 decreased the ignition temperature of soot particles oxidation, and the cycle stability experiment confirmed that the sample (0h-m-k) has good structural stability and stable catalytic performance. The coarseness of the interface increased because Na 4 Mn 9 O 18 whiskers grew on the cordierite substrate, and the trapping ability improved. Na 4 Mn 9 O 18 is an important type of catalyst which is rarely studied in catalytic oxidation of soot. This catalyst displays good activity and stability in the soot catalytic oxidation. This unique microstructure has potential application in the DPF field. [ABSTRACT FROM AUTHOR]

In this research work, laser powder bed fusion (LPBF) based stainless steel 316L (SS316L) was fabricated and its corrosion behaviour was analysed for the oil-gas piping application. The Field Emission Scanning Electron Microscopy (FESEM) analysis of the LPBF SS316L specimen revealed the presence of 1–2 μ m size honeycomb structure and 2–10 μ m size tabular structures. Nano-size particles in the range of 100 nm–500 nm were formed between the two tabular cells as well as their boundary regions in the LPBF SS316L specimen. The energy-dispersive X-ray spectroscopy (EDS) analysis of the nanoparticle confirmed the presence of Si with a percentage of 1.4% along with 15.9% of Cr and 1.6% of Mo that have the characteristic of dispersion strengthening of the LPBF SS316L specimen. In addition, the δ-ferrite phase was observed in tabular structure boundaries and intercellular regions of solute in the LPBF SS316L specimen. Moreover, among the three crystallographic orientations {001}{101}and {111}, no domination behaviour was observed from the Electron Backscatter Diffraction (EBSD) study. The Transmission Electron Microscopy (TEM) analysis confirmed the presence of nano twin structures that had a span of several nm on the FCC austenite unit cell. These twins came under the {111} category twining that often occurred in FCC metals. A potentiodynamic polarization test was conducted on the LPBF SS316L specimen at five different time periods (i.e., 0, 7, 15, 34 and 56 h) and it was assessed that the 0 and 15 h immersion specimens exhibited superior corrosion resistance compared with other LPBF SS316L specimens. The Nyquist plot revealed that the 0 and 15 h immersion specimens offered the highest resistance value of 1846.1Ω and 1720.3 Ω, respectively against corrosion. The Bode plots of the LPBF SS316L specimen followed a similar trend as the Nyquist plots. [ABSTRACT FROM AUTHOR]

Microwave absorbing (MA) materials with yolk-shell structures have been extensively studied in impedance matching. However, the impedance matching achieved by the complementary effect of the core and the shell does not determine the reflection of the microwaves upon the occurrence at the first incidence. The interaction between the outer layer of materials and the electromagnetic waves significantly impacts the MA properties of materials. In this study, the impedance matching improvement method of the shell structure was further explored by preparing CoFe 2 O 4 @HCN (honeycomb carbon with N-doping) through the hydrothermal method followed by hydrolysis, polymerization, etching, and annealing. The resulting structure with heteroatoms doping provided the novel CoFe 2 O 4 @HCN with excellent impedance matching and multiple loss mechanisms contributing to MA process. The absorber with a filler loading of 40% exhibited an RL min of −68.03 dB with a matching thickness of 2.5 mm. The efficient absorbing bandwidth reached 5.92 GHz (a change from 11.92 to 17.84 GHz) at 1.99 mm thickness. Interestingly, these findings look promising for future synthesis and application of yolk-shell structure microwave absorbers. [ABSTRACT FROM AUTHOR]

Structural formations of metal-organic frameworks (MOFs) are predominately composed of empty space pockets inside a honeycomb structure assembled of organic linkers and metal ions, with the exception of a few small pockets of filled spaces. However, these extraordinary filled pockets provide a valuable resource as its applications when it comes through in various active areas. Recently, taking advantage of the rare combination of porosity, high surface area, and charge conductivity incorporated in MOFs applications such as electronic sensors, charge storage devices, electrocatalysts, and others previously outside the scope, but now has been developed. This review envisioned a scenario by presenting a piece of individual and collective established studies and investigations during the last few years for carbon dioxide reduction (CO 2 R) as MOF-based composites adjacent with semiconductor, photosensitizer, and conductive photo-electrocatalysts are discussed. Various strategies have been discussed to improve photo-electrocatalysts' performance by synthesis, bandgap engineering, and mobilizing the catalyst surface for optimizing yield. Moreover, the reaction mechanisms to drive the MOF, operational, improve stability, and evaluation approaches are summarized. To end with a discussion, actual limitations, future perspectives, and concerns are addressed in this review. [ABSTRACT FROM AUTHOR]

A novel network interlacing ZrC-VC ceramic coating was prepared by a pioneering spillover permeation. With the increase of Zr content in the blind vias, the content of ZrC in the coating and the density of the coating all decrease. The density of the coating on C/C–ZrC–SiC substrate is obviously higher than that on C/C substrate. The linear ablation rate of the novel ceramic coated C/C–ZrC–SiC composites was −0.06 μm/s with about 20 and 1.56 times reduction than C/C composites and C/C–ZrC–SiC composites respectively. The improved ablation resistance was attributed to a dense honeycomb ZrO 2 layer filled with liquid vanadium oxide in the ablation center and the improved thermal radiation. [ABSTRACT FROM AUTHOR]

To solve pollution problems caused by electromagnetic waves, advanced three-dimensional (3D) honeycomb Ag/Ti 3 C 2 T x hybrid materials were produced by a microwave hydrothermal method. The Ag/Ti 3 C 2 T x hybrid materials retained their hollow sphere structure after the polymethyl methacrylate (PMMA) template was removed by annealing. The hybrid materials changed from hydrophilic to hydrophobic and exhibited cross-surface heat insulation and reflection-dominant electromagnetic interference shielding (EMIS) performance owing to their special honeycomb structure. This study innovatively explored the influence of different particle sizes of honeycomb holes on EMIS performance. In particular, the Ag/Ti 3 C 2 T x 5 μm hybrid materials had an excellent average EMIS performance of 51.15 dB in the X-band and 56.64 dB in the K u -band. The superior performance was due to conduction loss, interface polarization, multi-reflection, and scattering caused by the 3D porous structure of the Ag/Ti 3 C 2 T x hybrid materials. In general, Ag/Ti 3 C 2 T x hybrid materials with honeycomb structures retained the advantages of lightweight, hydrophobicity, and EMIS performance, illustrating the great application prospects of these materials in high-end electronic equipment. [ABSTRACT FROM AUTHOR]

The current work describes the synthesis, structure, magnetic and optical properties of Cu1+ based delafossite oxides, Cu 3 (MFeSb)O 6 (M = Na, Li) synthesized by the topotactic ion-exchange reactions (around 400 °C) of CuCl with Na 4 FeSbO 6 and Na 3 LiFeSbO 6 in an inert argon atmosphere. The synthetic procedure is significant as the oxides could not be synthesized by the solid state methods. Chemical analysis coupled with energy dispersive spectral analysis confirmed the extent of replacement of Na+ ions by Cu+ ions. A complete exchange of alkali metal ion, Na+ by Cu1+ in the interlayers of these honeycomb oxides has been achieved using a ratio of 1:3 between Na 4 FeSbO 6 and CuCl. An additional exchange of approximately 70 % Na+ ions from the honeycomb arrays is possible by varying the ratio to 1:4. Rietveld refinements (space group C2/c) of the powder X-ray diffraction data have been carried out to ascertain the phase purity and to verify the structure formed by edge shared honeycomb arrays separated by Cu1+ in dumbbell configuration (O–Cu1+-O). X-ray photoelectron spectroscopy analysis confirmed the oxidation states of the constituent ions, specifically copper as Cu1+. A similar method is adopted to synthesize Cu 3 (LiFeSb)O 6 by reacting Na 3 (LiFeSb)O 6 and CuCl in the ratio 1:3 at 400 °C. These new delafossite oxides, Cu 3 (MFeSb)O 6 (M = Na, Li) and Cu 3 ((Cu 0.7 Na 0.3)FeSb)O 6, exhibit interesting magnetic properties which are significantly different from the rock salt based parent sodium analogs. Dominant antiferromagnetic interactions with a specific ordering temperature have been observed for these samples containing Fe3+ (d5) ions in the honeycomb. UV–visible diffuse reflectance measurements indicated the decrease in the band gap of Cu1+ based oxides. This study highlights the importance of low temperature ion-exchange reactions as an effective route to stabilize multifunctional materials of potential importance for various applications. [Display omitted] [ABSTRACT FROM AUTHOR]

An effective method to fabricate barium titanate (BTO)/carbonyl iron powder (CIP) composites with enhanced microwave absorption (MA) performance was prepared via multimaterial digital optical processing (DLP) 3D printing technique. The bilayer-gradient honeycomb structural absorber (BGHSA) with adjustable broadband can be obtained by leveraging of varying compositional and structural design (layered thickness ratios, and gradient structures). The optimal reflection loss (R L) value and effective bandwidth of BGHSA can reach −51 dB and 15.4 GHz, respectively, exhibiting a distinct improvement (R L increased by 32.4% and effective bandwidth by 42.9%) compared with the reference. The highly improved performances especially in the broadband absorption (15.4 GHz) were mainly attributed to the better impedance matching and waves multi-reflections. This work provides a promising strategy to fabricate functionally graded materials for potential application in the absorption of electromagnetic waves. [ABSTRACT FROM AUTHOR]

Al 2 O 3 and honeycomb skeleton-Al 2 O 3 composite coatings on Titanium alloy (Ti–6Al–4V) were prepared by atmospheric plasma spraying. A laser ablation experiment on as-sprayed coatings was performed. In this paper, the laser damage resistance, microstructure, phase composition of Al 2 O 3 coatings were examined. 3D Dimensional Confocal Microscopy, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Energy Dispersive Spectrometry (EDS) characterized the laser damage morphology, microstructure, phase composition, and element analysis, respectively. The influence of the honeycomb skeleton on the laser ablation damage on as-sprayed coatings was investigated by a comparative analysis of the laser damage morphology with different laser ablation times and gas flow. The results show that the honeycomb skeleton raises thermal conductivity and thermal diffusivity. Moreover, a "tower"-like dendrite was generated during the laser irradiation of the composite coating. The honeycomb skeleton refined the structure, suppressed crack propagation, and reduced the influence of gas flow on cracks. Under the same experimental laser ablation parameters, the laser damage area of the honeycomb skeleton-Al 2 O 3 composite coating was smaller than that of the Al 2 O 3 coating. It was demonstrated that the laser damage resistance of the honeycomb skeleton-Al 2 O 3 composite coating was superior to that of the Al 2 O 3 coating. [ABSTRACT FROM AUTHOR]

The turtle shell of biomass waste is used as raw material, and the natural inorganic salt contained in it is used as a salt template in combination with a chemical activation method to successfully prepare a high-performance activated carbon with hierarchical porous structure. The role of hydroxyapatite (HAP) and KOH in different stages of preparation was investigated. The prepared turtle shell-derived activated carbon (TSHC-5) has a well-developed honeycomb pore structure, which gives it a high specific surface area (SSA) of 2828 m2 g−1 with a pore volume of 1.91 cm3 g−1. The excellent hierarchical porous structure and high heteroatom content (O 6.88%, N 5.64%) allow it to have an ultra-high specific capacitance of 727.9 F g−1 at 0.5 A g−1 with 92.27% of capacitance retention even after 10,000 cycles. Excitingly, the symmetric supercapacitor assembled from TSHC-5 activated carbon exhibits excellent energy density and cycling stability in a 1 M Na 2 SO 4 aqueous solution. The energy density is 45.1 Wh·kg−1 at a power density of 450 W kg−1, with 92.05% capacitance retention after 10,000 cycles. Therefore, turtle shell-derived activated carbon is extremely competitive in sustainable new green supercapacitor electrode materials. [Display omitted] • Grass turtle shell contains heteroatoms and HAP for self-doping and as self-templates, respectively. • TSHC-5 has hierarchical porous structure with super high SSA (2828 m2 g−1) and pore volume (1.91 cm3 g−1). • Heteroatoms (O 6.88%, N 5.64%) can improve the wettability and conductivity of electrode materials. • TSHC-5 exhibits an ultra-high specific capacitance of 727.9 F g−1 at 0.5 A g−1. • The energy density of supercapacitor is 45.1 Wh·kg−1 at 450 W kg−1 using 1 M Na 2 SO 4 as electrolyte. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printing of ceramics has attracted increasing attention in various fields. However, the pyrolysis of organic components used for binding or polymerization in 3D printing commonly causes a large shrinkage (up to 30 %–40 %), high porosity, and cracking or deformation, severely limiting practical applications. In this study, 3D printing of Al 2 O 3 ceramic architectures with ultra-low shrinkage is realized by introducing inorganic binder aluminum dihydrogen phosphate (Al(H 2 PO 4) 3 , AP) as a ceramic precursor. Compared to organic binders, the inorganic AP binder can undergo crystallization conversion, which reduces mass loss during sintering at high temperatures, resulting in low shrinkage. Moreover, AP can be used as a rheological modifier to regulate the printability of the ceramic ink for direct ink writing of Al 2 O 3 ceramic architectures, such as wood-piled scaffolds, honeycomb structures, and tubes with high fidelity. The resultant Al 2 O 3 structural ceramics sintered at 1250 °C exhibit good mechanical performance and structural integrity. Most importantly, the linear shrinkage of the printed ceramics is less than 5 %, which is several times lower than that of ceramics with organic binders. This study provides a viable strategy for fabricating high-performance ceramic architectures with good dimensional fidelity for practical applications. ∙ Al 2 O 3 ceramics with aluminum phosphate binder were printed by using direct ink writing. ∙The resultant Al 2 O 3 ceramic exhibited ultra-low dimensional shrinkage owing to the inorganic binder. ∙Al 2 O 3 ceramics are programmable in size and shape, with good stability, reusability, and fidelity. [ABSTRACT FROM AUTHOR]

We have firstly studied the poling magnetic field dependence of magnetoelectric (ME) coupling in a honeycomb antiferromagnet Co 4 Nb 2 O 9 , and found that the ME susceptibilities do not increase monotonously with increasing the poling magnetic field strength (H Pole) as the usual case, but reach maxima around 10 kGs. This phenomenon results from opposite H Pole dependences of domain wall thickness and energitically preferred domain's proportion. More interestingly, if the sample returns to paramagnetic phase after being poled and then reenters antiferromagnetic phase without being poled, ME coupling still exists. This memory effect is attributed to the presence of ME domain nucleation centers in paramagnetic phase. [ABSTRACT FROM AUTHOR]

2.5D C f /SiC composite has been a key heat-resistant ceramic matrix composite (CMC) in aerospace field due to the special structure characteristics. Against the existing research almost focus on 'ablation behavior' in laser processing of CMC, this paper put forward the 'ablation evolution behavior' for the first time, and reveals the 'ablation evolution behavior' in micro-hole machining of 2.5D C f /SiC composites with millisecond laser. The results show that 0° fiber experiences the ablation evolution from filiform connection, flat ellipse, needle-like to convex structure. And the 90° fiber suffers the ablation evolution from cylindrical structure, lotus lead shape, bud-shape to closed shape. The core of the 90° fibers undergoes the topography structures from cylindrical protrusion, spherical protrusion to needle-like. Except for the honeycomb structure studied in existing research, four new recast layer structures, named transverse strip, longitudinal strip, shell structure, and multi-layer structure are found and analyzed. Further, the mechanism analysis reveals that the recast layer contains both oxidized characteristics and highly carbonized characteristics. In addition, the microstructural analysis shows that three types of particle topography adhere to the recast layer, that are spherical micro-protrusion (20–48 μm), bubble particles (5–15 μm), and sub-micron particles (<1 μm). [ABSTRACT FROM AUTHOR]

In this paper, a novel H 2 Ti 2 O 5 @MoS 2 @SiO 2 ternary composite material was prepared by a combination of dual hydrothermal method and controlled hydrolysis method, in which H 2 Ti 2 O 5 nanotubes are tightly combined with hierarchical molybdenum disulfide, and the unique structure of titanate nano whiskers, including the loosely bound alkali metal ions between the titanate layers with high dielectric constant and the large aspect ratio, which induce active response to the electric field. Flower-like molybdenum disulfide provides electrical conductivity, and silicon dioxide as a insulative coating layer can suppress excessive the electrical conductivity of the two-dimensional material. The morphological evolution was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results of showed that the sheet-shaped molybdenum disulfide coated with curved H 2 Ti 2 O 5 nanotubes showed a honeycomb structure with uniform size. Silicon oxide acts as a cladding layer to increase the thickness of the flakes. The existence of H 2 Ti 2 O 5 , molybdenum disulfide and silicon dioxide is confirmed by X-ray powder diffractometer (XRD) and Fourier transform infrared spectroscopy (FT-IR). The prepared product was confirmed by XPS, BET test and electrorheological rheometer. Core/shell nanoparticles not only exert the active response characteristics of titanate nanoparticles and molybdenum disulfide to electric field, but also inherit the excellent characteristics of a core-shell structure produced by the interface polarization and the synergistic effect of the polar groups on the surface of the two-dimensional material further enhance the electrorheological effect. [ABSTRACT FROM AUTHOR]

SiC honeycomb ceramic reinforced Al (SiC H /Al) composite with anisotropic microstructure was fabricated by spontaneous infiltration method, and the effect of SiC honeycomb reinforcement on the tribological performance of SiC H /Al composite in axial and radial directions was investigated. The SiC particle reinforced Al (SiC P /Al) composite with the same SiC content was prepared as a counterpart to reveal the effect of SiC reinforcement architecture on the tribological performance of the Al-matrix composites. Compared with the SiC H /Al composite in radial direction and the SiC P /Al composite, the SiC H /Al composite in axial direction shows the highest thermal conductivity of 140.96 W m−1 K−1 and hardness of 97.14 H V, which hinder the formation of oxidative wear and eroding of counter ball. Additionally, a mechanical mixed layer can be formed on the worn surface of SiC H /Al composite in axial direction during the friction process. As a consequence, the SiC H /Al composite in axial direction exhibits the optimal tribological performance with the lowest averaged friction coefficient (0.53) and wear rate (0.98 mm3 N−1 m−1). The results indicate that the SiC honeycomb reinforcement is a promising candidate to improve the tribological performance of metal-matrix composites, especially in their axial direction. [ABSTRACT FROM AUTHOR]

Nickel-based superalloys are favored because of high fatigue strength, corrosion resistance and oxidation resistance. However, the characteristics of high hardness, poor heat dissipation and sticking make the machinability of nickel-based superalloys poor, which is more serious for interrupted processing. Therefore, honeycomb ceramic tools are utilized to turn GH4169. Cutting and impact force, wear patterns and mechanism of honeycomb ceramic tools are analyzed. The results demonstrate that the impact force is greater than the average cutting force. Fractures, chipping and adhesion are the main wear characteristics of honeycomb ceramic tools. Furthermore, adhesive, abrasive and diffusion wear are the main wear mechanisms. [ABSTRACT FROM AUTHOR]

Different from traditional ceramic materials, three-dimensional (3D) porous ceramics have become a research hotspot in recent years due to combinative of light-weight and high strength. Meanwhile, the 3D printing technique, which can be used to design hierarchical porous structures by combining flexible design and advanced manufacturing procedures, is regarded as a revolutionary and attractive tool for the preparation of 3D porous ceramics. Herein, a novel road is reported for fabricating 3D porous ceramic lattices with excellent mechanical properties by bridging 3D printing and SiC chemical vapor infiltration. The effects of coordination number, rotation angle, hollow structure and sintering temperature on the performance of ceramic lattices were also investigated. As revealed by the results, the cubic lattices possess the highest compressive strength and fracture work, 41.93 MPa and 2126.7 kJ/m2, respectively. Among different hollow lattices, the stability and bearing capacity of triangular structures were superior to that of square and honeycomb structures. The compressive strength of the triangular hollow lattices can reach up to 31.20 MPa. And the fracture work of the 3D porous lattices without rotation can be 7 times that of the lattices with a rotation angle of 30° and 45°. Moreover, as the sintering temperature rises, the compressive strength of 3D porous ceramics gradually increases while the shrinkage tends to be more serious. Additionally, the fracture work of 3D porous ceramics reaches its peak at a sintering temperature of 1400 °C. The approach developed in this work provides a simple, economic, and effective way to fabricate 3D porous ceramics, which leads to promising applications in future functional devices. [ABSTRACT FROM AUTHOR]

Effects of glycerin and silica sol on the structure and performance of porous Si 3 N 4 ceramics that were prepared via freeze-drying were studied. Adding glycerol affected growth process of ice crystals, changed pore structural from bimodal peaks to triple peaks distribution, and formed regular honeycomb structure. This improved mechanical properties and electromagnetic wave transmission properties of Si 3 N 4 ceramics. Therefore, adding glycerol changed mesoscopic morphology of the material. For porous Si 3 N 4 ceramics with 72.5% porosity, flexural strength was 38 MPa, compressive strength was 42.6 MPa, and dielectric constant was 1.75 in the frequency range of 12.4–18 Hz as the amount of added glycerol increasing to 5 wt%. By reducing the sintering eutectic point of the system, the addition of silica sol promoted sintering shrinkage and formed new phases. Thus, pore size distribution was changed from bimodal to unimodal. Moreover, dielectric constant of samples increased from 2.25 to 3.5. Finally, structure and performance of porous Si 3 N 4 ceramics were controlled via addition of glycerol and silica sol. [ABSTRACT FROM AUTHOR]

Titanium honeycomb substrates having TiO 2 surface with nano- to micro-sized pores were prepared by electrochemical anodization and used to make Pt-based oxidation catalyst monoliths without conventional oxide-based washcoat layers for pre-turbocharger catalyst (PTC) applications exposed to harsh conditions under very high flow rates of exhaust gas and engine vibration. Adhesion strength and CO/C 3 H 6 oxidation performance of the catalysts were compared with conventional washcoated FeCrAl monolith catalysts. The intermediate porous TiO 2 layer formation by the anodization can dramatically enhance the catalyst adhesion strength without sacrificing the catalytic performance under GHSV (gas hourly space velocity) higher than 100,000 h−1 for PTC. [ABSTRACT FROM AUTHOR]

Three different alumina/aluminum bi-layer armors having different striking faces, i.e., monolithic alumina, mosaic alumina, and mosaic alumina enhanced by aluminum honeycomb, were fabricated and tested under the impact of the flat projectile. The ballistic performance of each armor type was also investigated using three-dimensional (3D) finite element (FE) simulations. Upon validating the FE simulation results with experimental measurements, the ballistic limit velocity and failure mechanisms for each type of armor, as well as the influence of ceramic tile size, impact position, border effect, and inter tile gap width were quantified. For the enhanced mosaic armor, the metallic honeycomb lattice performed as a cellular skeleton to confine the ceramic tiles and fragments, leading to enhanced ballistic resistance. Besides, the honeycomb enhanced mosaic armor was also found to have much improved multi-hit ballistic resistance in comparison with monolithic and mosaic alumina. The honeycomb preserved the structural integrity of the mosaic armor so that a high level of residual ballistic resistance remained even after impact. With the extended reliability calculation method, single shot ballistic data were used to estimate the performance of the honeycomb enhanced mosaic armor under multiple projectile impacts. [ABSTRACT FROM AUTHOR]

In this paper, the thermal shock resistance of an auxetic ceramic honeycomb plate is studied based on the fracture mechanics concept for the cases of a central crack or an edge crack. The transient temperature field and transient thermal stress field are obtained for both auxetic and non-auxetic structures. The relationship between the thermal stress intensity factor (TSIF) and the internal cell angle, crack length and time is determined and the critical temperature for the initiation of crack propagation is predicted. Results show that compared with the non-auxetic ceramic honeycombs which are at an internal cell angle of 30°, the critical temperature of the auxetic ceramic honeycombs whose cell are orientated at an angle of −30° increases by 78.5% and the TSIF at the crack tip decreases by 40%, respectively. Hence, the auxetic structures have better thermal shock resistance. This study indicates that auxetic ceramic honeycombs have significant potential applications in harsh temperature environments. [ABSTRACT FROM AUTHOR]

Wollastonite (CaSiO 3) based porous structures are useful in a wide range of applications including catalysis. Furthermore, the use of additive manufacturing techniques for the production of on-demand structures with controlled porosity are widely used for numerous materials. In the present work, CaSiO 3 was synthesized by co-precipitation method resulting in a fine CaSiO 3 –SiO 2 powder, which was processed to fabricate regular porous structures using the robocasting technique. Cylindrical structures of 10 mm in diameter and 10 mm in height were robocast following two different arrangement patterns, i.e., orthogonal and honeycomb with two different pore sizes (350 and 500 μm). In general, the orthogonal structures showed better geometrical and dimensional accuracy than honeycomb ones. The compression test showed that orthogonal structures were more reliable, while the honeycomb structures exhibited higher compressive strength. The reasons are on the differences in porosity and pore architecture between them. Additionally, the catalytic properties of the CaSiO 3 –SiO 2 powder were studied by the decomposition of isopropyl alcohol. The CaSiO 3 –SiO 2 showed strong selective basic catalytic properties, leading on the dehydrogenation of the alcohol producing acetone with a yield up to 92% at 350 °C. In summary, the CaSiO 3 –SiO 2 robocast structures have a significant potential for self-supporting catalytic reactors. [ABSTRACT FROM AUTHOR]

To avoid agglomeration of ultrafine diamond particles and to improve machining precision of silicon (Si) wafers, a combination of gel casting and pore-forming agent is introduced to fabricate vitrified-bonded ultrafine diamond grinding wheel with ultrahigh porosity (~75%), honeycomb structure, and homogeneous microstructure. Moreover, the as-prepared grinding wheel possesses uniformly distributed closed pores, which are highly desirable for chip removal, heat dissipation and extended service life. In addition, influences of sintering schedules on microstructure, porosity and bending strength of the as-prepared grinding wheel are systematically investigated. Because of the honeycomb structure, the as-fabricated grinding wheel renders superior self-sharpness, which is required for continuous grinding of Si wafers without dressing, and this subsequently enhances the working efficiency. Results reveal that the surface roughness and damaged layer of the ground Si wafers are approximately 5.0 nm and 0.21 μm, respectively. The current study provides a novel pathway for efficiently processing high-quality silicon wafers. [ABSTRACT FROM AUTHOR]

Herein, we fabricated honeycomb ceramics with different porosities and pore shapes via the layer-by-layer deposition of cordierite (2MgO·2Al 2 O 3 ·5SiO 2) particle ink, obtaining proper rheological properties using a direct-writing technology. No collapses as well as minimal cracking and bending were observed in the internal structure of the samples after calcination. We measured and compared the internal porosity and specific surface area of honeycomb ceramics with the same pore shape but different pore dimensions, as well as the same pore dimension but different pore shapes. The samples were both loaded with an γ-Al 2 O 3 washcoat and Pd-based catalyst using the same method for the catalytic combustion of toluene. The different porosity and pore shape influenced the catalytic efficiency. This study may provide some useful guidelines for fabrication of honeycomb ceramics by direct writing technology, which could be used to remove volatile organic pollutants(VOCs). [ABSTRACT FROM AUTHOR]

Abstract The size of the Field Effect Transistor (FET) has been decreasing exponentially each year to keep up with the demands of the microelectronic industry. However, this scaling is now reaching its limits due to the performance of the materials currently used in the FET. Specifically, the leakage through silicon dioxide, the current gate dielectric, is beginning to inhibit the FET's performance. Recently, attention has been turning towards two-dimensional materials for electronic devices. However, insulating is especially challenging for two-dimensional materials due to the short diffusion length for charge carriers. We consider several materials that have been shown to have a stable two-dimensional honeycomb structure. In order to characterize these materials, we use Density Functional Theory (DFT) to calculate key properties that determine performance, including the dielectric function, band gap, and effective mass. We check the compatibility of these materials with Molybdenum Disulfide (MoS 2), a two-dimensional material that has emerged as a promising candidate for the semiconducting channel of a FET. We have identified several promising candidates, including hBN, which is the common choice as a dielectric material, and LiF and BeO, which are materials that have not been used before as gate dielectrics. We anticipate that this study will contribute to advancing the development of transistors that are made completely of two-dimensional materials. Graphical abstract [ABSTRACT FROM AUTHOR]

Cordierite honeycomb with high loading and uniform coating of γ- Al 2 O 3 was prepared by a facile one-step dip coating strategy. The γ- Al 2 O 3 obtained loading, which was as high as 30%, could be calculated according to the different weight of bare and washcoated cordierite honeycomb. SEM micrographs showed that coarser surface and round channels were formed, demonstrating complete coverage of a γ-Al 2 O 3 layer on cordierite. The coating thickness was 30 µm, corresponding very well to the theoretical value, indicating a homogeneous coating of γ- Al 2 O 3 . Besides, no crack was observed on the surface or the corner of the channel wall. The washcoat exhibited excellent adherence with no significant weight loss after 3 h ultrasonic treatment, attributing to the “nail-like” strong interaction between the support and the washcoat. The derived PdCl 2 -CuCl 2 monolith catalyst showed excellent activity and stability for CO oxidation at room temperature in microreactor. The catalyst was also effective in pilot-scale test using the diesel exhaust as feed gas, presenting a great application prospect. [ABSTRACT FROM AUTHOR]

Ablation of C/C–ZrC composites in a solid rocket motor environment was investigated. The chemical compositions of the combustion gases were calculated using the principle of free energy minimisation. The chemical thermodynamics of the products of the reactions between the combustion gases and ZrC were studied using the FactSage software. The results show that H 2 O, CO 2 , and OH are the main oxidising species that consume ZrC/carbon, and the oxidation of ZrC reduces carbon consumption. In addition, melting and evaporation of ZrO 2 absorb heat from the combustion gases, relieving the erosive attack on carbon. The ablation of C/C–ZrC composites is controlled by both thermal chemical ablation and mechanical breakage. The cone-shaped fibres and shell-shaped, honeycomb matrix are attributed to thermal chemical ablation, whereas the carbon fragments result from mechanical breakage. [ABSTRACT FROM AUTHOR]

In this paper, the honeycombed top-porous/bottom-tubular TiO 2 nanotube arrays (TiO 2 NTs) were prepared by a facile two-step anodization method. The structural parameters of honeycombed TiO 2 NTs can be well controlled by adjusting the voltages in the second-step anodization process, and the honeycombed TiO 2 NTs showed much enhanced photocatalytic activity than the conventional 1-step TiO 2 NTs. [ABSTRACT FROM AUTHOR]

Abstract: We prepared titania films by aerosol deposition (AD), in which titania powder is supersonically accelerated for deposition onto a substrate. These AD titania films exhibited hydrophilicity and photocatalysis under UV exposure. However, after surface modification by CF4 plasma-etching, the films showed higher hydrophilicity and lower photocatalytic effect. After sufficient modification, they exhibited superhydrophilicity, which was induced by the presence of fluorine. This type of surface modification is useful for promoting hydrophilicity under no UV light exposure. [Copyright &y& Elsevier]

Honeycomb structures were extruded from MgAl2O4 spinel dough with optimum rheological properties. Extruded honeycombs are sintered at 1700°C followed by hot isostatic pressing (HIP) to achieve close to theoretical densities. Honeycombs have shown a density of 3.57g/cc along with the cellular properties such as wall thickness of 90µm, cell opening of 350×350µm2, cell density of 900 channels per square inch and relative density of 0.45. [ABSTRACT FROM AUTHOR]