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Novel highly foldable HAp ceramic paper with fire retardancy but without fiber was fabricated via novel non-solvent displacement nonaqueous precipitation strategy. The obtained HAp ceramic paper, characterized by highly smooth and glossy, is characterized via X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), curlability test, moisture absorbency and Pb2+ removal performance test. The results show that the ceramic paper is very straight, uniform, and smooth with high curlability and low moisture absorption. No fiber is detected in the ceramic paper. No defect is either detected except for at the edge area. The HAp ceramic paper is grown along the (002) crystal plane of the hydroxyapatite phase from hexagonal plate like single crystal sheets. The ceramic paper loaded for four times has formed a clear four-layer-structured, with a total thickness of about 832 nm. The thickness of each layer is very uniform, with an average thickness of about 208 nm per layer. HAp ceramic paper has excellent Pb2+ ions removal performance, curling performance, moisture absorption performance and flame retardant performance. These performances confirm this novel HAp ceramic paper has superior properties over the traditional ceramic paper with fibers and shows great application prospect in various fields. [ABSTRACT FROM AUTHOR]

This paper describes the fabrication and characterization of porous SiC ceramics derived from highly-filled preceramic papers. The SiC ceramics were obtained by spark plasma sintering of stacked preceramic papers at temperatures of 2100 and 2200 °C under pressures of 5–60 MPa for 10 min. The microstructure and phase composition were analyzed by scanning electron microscopy and X-ray diffraction, respectively. Gas permeation tests were performed using hydrogen permeation cell at room temperature. It is revealed that the porosity of sintered SiC can be varied from 9 to 45 % depending on the sintering parameters. The shrinkage of the materials during spark plasma sintering occurs in four stages. The linear shrinkage value of the material increases from 7 to 47 % at 2100 °C and from 20 to 50 % for the samples sintered at 2100 and 2200 °C, respectively. Correlation dependencies between porosity and mechanical properties of the fabricated SiC were established. The obtained porous SiC ceramics exhibit high bending strength of 165 MPa and gas permeation flux of 78 molH 2 /m2/s at the porosity of 36 % that make it suitable for ceramic-based membranes. [ABSTRACT FROM AUTHOR]

In this study, continuous carbon reinforced C f /(Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C–SiC high entropy ceramic matrix composites were additively manufactured through paper laminating (PL), direct slurry writing (DSW), and precursor infiltration and pyrolysis (PIP). (Ti 0.2 Zr 0.2 Hf 0.2 Nb 0.2 Ta 0.2)C high entropy ceramic (HEC) powders were synthesized by pressureless sintering and ball milling. A certain proportion of HEC powder, SiC powder, water, binder, and dispersant were mixed to prepare the HEC-SiC slurry. Meanwhile, BN coating was prepared on the 2D fiber cloth surface by the boric acid-urea method and then the cloth was cut into required shape. Additive manufacturing were conducted subsequently. Firstly, one piece of the as-treated carbon fiber cloth was auto-placed on the workbench by paper laminating (PL). Then, the HEC-SiC slurry was extruded onto the surface of the cloth by direct slurry writing (DSW). PL and DSW process were repeated, and a C f /HEC-SiC preform was obtained after 3 cycles. At last, the preform was densified by precursor infiltration and pyrolysis (PIP) and the final C f /HEC-SiC composite was prepared. The open porosity of the C f /HEC-SiC composites, with the HEC volume fractions of 15, 30 and 45%, were 7.7, 10.6, and 11.3%, respectively. And the density of the C f /HEC-SiC composites, with the HEC volume fractions of 15, 30 and 45%, were 2.9, 2.7 and 2.3 g/cm3, respectively. The mechanical properties of the C f /HEC-SiC composites increased firstly and then decreased with the HEC content increase, reaching the maximum value when the HEC volume fraction was 30%. The mechanical properties of the C f /HEC-SiC composites containing 45, 30 and 15% HEC were as follows: flexural strength (180.4 ± 14 MPa, 183.7 ± 4 MPa, and 173.9 ± 4 MPa), fracture toughness (11.9 ± 0.17 MPa m1/2, 14.6 ± 2.89 MPa m1/2, and 11.3 ± 1.88 MPa m1/2), and tensile strength (71.5 ± 4.9 MPa, 98.4 ± 12.2 MPa, and 73.4 ± 8.5 MPa). From this study, the additive manufacturing of continuous carbon fiber reinforced high entropy ceramic matrix composites was achieved, opening a new insight into the manufacturing of ceramic matrix composites. [ABSTRACT FROM AUTHOR]

My comments concern the significant error in the crystallographic part of the commented papers. It was discovered that the studied nanocrystals are of sillenite type and the correct formula should be Bi 25 FeO 39 :Co,Ti and Bi 25 FeO 39 :Ni,Ti instead of BiFeO 3. Moreover, the type of unit cell is not correct. Due to the doping the new type of unit cell, previously unknown, was proposed for such crystals. It was found that the studied sample contains two slightly different phases of the sillenite type. The actual chemical composition of the studied crystals is not known. [ABSTRACT FROM AUTHOR]

Abstract: Powders obtained from coal fly ash and paper mill sludge were milled alone or in mixture, pressed into specimens and sintered. Fired materials were characterized by density, water absorption, shrinkage on firing, crystal structure, microstructure, strength, hardness and toughness. Samples made with paper mill sludge alone had a high sintering temperature, contained extended fractures after sintering and were not further studied. All the other compositions, sintered between 1130 and 1190°C, showed low water absorption, density below 2.6g/cm3, fair mechanical properties and contained several phases. More in particular, the material containing 25wt% of coal ash and 75wt% of powder from paper sludge displayed the best overall behaviour. [Copyright &y& Elsevier]

Abstract: Glass-ceramics were prepared from mixtures of wastes generated from refining of silica sand and kaolin clay (Kira) and paper sludge ash. Kira and paper sludge ash were mixed in mass ratios of 55/45. The mixtures were melted at 1400°C and quenched in water to obtain glasses. The quenched glasses were ground to <48 mesh and used to prepare glass-ceramics. Crystallization of the parent glass occurred above 950°C, producing quartz solid solution at 1000°C and cristobalite at 1100°C as the major crystalline phases. The color of the glass-ceramics is white or slightly pale yellow. The four-point bending strengths of the as-fired glass-ceramics range from 63 to 66MPa and the Vickers microhardness values from 6.0 to 6.4GPa. The average linear thermal expansion coefficients of the glass-ceramics range from 6.3×10−6 /°C to 8.1×10−6 /°C (30–380°C) and show non-linearity around the phase transition temperatures of quartz and cristobalite. The chemical durability of the resulting glass-ceramics is excellent in alkali but poor in acid solution. The glass-ceramics show rather better performance than commercial glass-ceramics even when prepared solely from wastes starting materials. [Copyright &y& Elsevier]

To address the difficulties of continuous adjustment of visible transmittance of amorphous porous ceramics and their anti-fogging without treatment, this paper delicately combined "hydrochromism" and porous ceramics, and prepared water-induced SiO 2 transparent porous ceramics (TPCs) with high strength and adjustable transparency. The effects of adding solvents to the silica sol on their visible transmittance, integrity and porosity were studied, and their multifunctional applications were also investigated. Results showed that the addition of EG, ammonia and acetonitrile mainly affected the gel integrity, the porosity of amorphous TPCs, and their gelation time and light transmittance, respectively. The compressive strength, porosity, visible transmittance after drying and water absorption of the optimal TPCs prepared at 600 °C by adding the above three solvents were 23.95 MPa, 54.7 %, 43 % and 81 %, respectively. The transparency of TPCs could be adjusted from 3 % to 81 % by controlling their water content, and they had excellent thermal insulation and anti-fogging ability without any treatment, and the excellent anti-fogging performance is related to their hydrophilicity and uniform nanopore structures. Overall, this paper provides new strategies for lightweighting, anti-fogging, and continuous adjustment of visible transmittance of transparent ceramics, and the resulting lightweight TPC is an ideal candidate for applications in daylighting design, as well as thermal insulation and anti-fogging in high humidity environments. [Display omitted] • Water-induced highly transparent SiO 2 -based TPCs were prepared for the first time. • Controlling water content in TPCs has realized its continuous cycle from transparent to opaque. • TPCs possess the anti-fogging ability without any treatment. • TPC is an ideal candidate for applications in daylighting design, thermal insulation and anti-fogging. [ABSTRACT FROM AUTHOR]

The paper presents an original method for synthesizing high-density composite ceramics with a Mo 2 C/Mo 3 Co 3 C composition using the technology of high-speed Spark Plasma Sintering (SPS) of a mechanically activated powder mixture of Mo 2 C-10 wt%Co. The activated homogeneous starting mixture was obtained by wet milling/activation of the initial powders of Mo 2 C and Co in an anhydrous isopropanol medium. The ceramic samples were consolidated by SPS under vacuum (10−5 atm.) at 1000, 1100, 1150, and 1200 °C with a heating rate of 87.3 °C·min−1 under constant external uniaxial pressing pressure of 50 MPa. The sintering kinetics were studied, the twofold nature of sintering was established, and the temperature range of active densification was determined. The ceramic synthesis is accompanied by a reactive interaction of the components, resulting in the formation of the Mo 3 Co 3 C phase and a change in the crystal lattice of the non-stoichiometric Mo 2 C x compound. The ceramic obtained in the temperature interval of the isothermal sintering stage of 1150–1200 °C is homogeneous in the distribution of Mo and Co, consists of a Mo 2 C/Mo 3 Co 3 C phase mixture, has a density value of 98.13 ± 0.5 % theoretical density, and has an average Vickers hardness value of ∼1526 HV. Increasing the sintering temperature to 1200 °C results in the formation of almost monolithic structures in the samples, but also induces the formation of large defects due to the collective consolidation of pores within the bulk material and increases the susceptibility of the ceramic to cracking. The paper presents preliminary results from electrochemical testing. The proposed method for synthesizing Mo 2 C/Mo 3 Co 3 C ceramics has potential for use in optimizing the composition and production methods of electrode materials for the realization of active components in heterostructured electrodes used for hydrogen evolution. [ABSTRACT FROM AUTHOR]

3D printed ceramic parts often have defects due to their inherent brittleness. These defects are of various scale sizes. Detecting these defects, especially with multiple sizes, is a challenging task in the field of detection. Furthermore, there is a lack of surface defect real-time detection systems suitable for industrial applications in this field. Based on this, this paper makes two contributions: the design and development of a real-time defect detection system, and the proposal of a multiscale defect detection method for 3D printed ceramic surfaces within this system. Firstly, the paper establishes the overall structure of the real-time detection system for surface defects on 3D printed ceramic components, and describes the hardware and software components of the system. On this basis, a dataset of ceramic surface defect images is collected and constructed. Then, experimental analyses point out the shortcomings of the You Only Look Once version-5 (YOLOv5) model for multiscale defect detection. To address the shortcomings, the YOLOv5 model is optimized from three aspects, resulting in the Deep separable convolution + residual network-SKNetwork-Efficient Channel Attention Network-YOLOv5 (DepRes-SK-ECA-YOLOv5) model for multiscale defect detection. This model improves the ability to extract and fuse features of defects at different scales. The experimental results show that the DepRes-SK-ECA-YOLOv5 model can achieve 93.5 %, 91.6 %, 94.3 %, and 0.198 s for Precision, Recall, mAP, and Speed for the test set, respectively. Finally, the paper designs the workflow for the system software. The system hardware and system software are integrated to form a real-time detection system. The performance of the detection system is verified through experiments. [ABSTRACT FROM AUTHOR]

Friction and wear are two critical tribological factors that instigate unavoidable failures of moving components in the mechanical system. Additionally, these factors have a huge impact on global energy consumption, economy, and CO 2 emissions. Minimization of friction and wear in mechanical systems is rather challenging, however, significant advancement has been achieved in the development of new techniques to mitigate these tribological issues. Surface coating is one of the most commonly used techniques to reduce/eliminate tribological failures. Though a wide range of hard and anti-wear coating materials (metallic alloys, carbon, metallic glasses, polymers, ceramics, and composites) have been developed in the last few decades, however, ceramic coatings have always been a prime interest to researchers owing to their outstanding hardness, wear resistance, corrosion resistance, and damping capacity. Specifically, nitride ceramic coatings have been passed a long journey as hard and wear-resistance protective coatings in multiple industries such as manufacturing, automobile, aerospace, etc. This article reviews the journey of the development of nitride coatings for tribological applications. These developments include first-, second-, and third-generation nitride ceramic coatings, which include binary, ternary, multi-elemental as well as multi-layered coating compositions. This review paper sheds light on the available literature, merits, demerits, and applications of all nitride ceramics coatings for tribological applications. Recently, an innovation in nitride ceramic coatings has been reported, which is the utilization of the high entropy concept in these coatings, which has been reported to improve their tribological properties tremendously. This review paper also delivers a comprehensive review of high-entropy nitride ceramic coatings (both equimolar and non-equimolar compositions) for tribological applications, which is the latest and hot topic for researchers working on ceramics coatings and tribology. At last, this review paper identifies the gaps and provides the future possibilities of research in this area. [ABSTRACT FROM AUTHOR]

In this study, lithium–zinc ferrite (LZF) ceramics were prepared by spark plasma sintering. Problem of carbon pollution was effectively resolved by annealing decarburization, formation of BN-coated carbon paper, and formation of protective layer of different metal foils (Ti, Mo, W, and Ta). The effects of carbon pollution and different protective layers on microstructure and dielectric and magnetic properties of LZF ceramics were studied comprehensively. Results reveal that annealing decarburization and BN-coated carbon paper could significantly improve resistance and saturation magnetization (M s) of LZF, while real part of dielectric constant (ε′) and dielectric loss (tanδ) were significantly reduced. X-ray diffraction patterns indicate that all selected protective layers can provide good spinel-phase LZF ceramics. The utilization of metallic foil as protective layer can effectively reduce carburization, improve the resistance of LZF ceramics, and reduce ε′ and tanδ values. X-ray photoemission spectroscopy and Raman spectroscopy results reveal that cations with the highest valence state replace Fe3+ at B-site. The use of metal foil protective layer leads to the infiltration of metal ions into LZF lattice, leading to the increase in the lattice constant and decrease in the M s value. This study deepens the understanding of carburization during SPS, providing a reference scheme for future applications. [ABSTRACT FROM AUTHOR]

Formulation of black ceramic ink and its ink-jet printability on a glass substrate were investigated. The thermal and chemical stabilities of CoFe 2-x Cr x O 4 and Ni 0.925 Mn 0 .075 Fe 1.875-x Cr x Mn 0.125 O 4 black inorganic pigments were analyzed with various amounts of Cr substitutions. The ceramic ink was prepared using the pigment composition that demonstrated color stability during the high temperature glazing process with a minimal Cr substitutional amount. After the dispersion stability and rheological property were optimized, the ceramic ink was suitably jetted from a print head as a single sphere-shaped droplet without satellite droplets. To improve the printability of the ceramic ink, the glass substrate was treated with a perfluorooctyl trichlorosilane (PFTS) solution. As a result, the PFTS surface treatment increased the contact angle of the ceramic ink droplets on the glass substrate and effectively minimized the ink spreading phenomena. [ABSTRACT FROM AUTHOR]

Due to its excellent strength and high thermal conductivity, beryllium oxide (BeO) is widely used as a fuel matrix material and neutron moderator in nuclear reactors. In the preparation of bulk BeO materials, previous research on the hot-pressing sintering methods is insufficient. This paper mainly introduces the process of hot-pressing sintering, and uses orthogonal experiments with different process parameters to explore their influences on the grain size and porosity of the products, and how to affect their flexural strength and thermal conductivity as well. Molecular dynamics simulations have also been used to study the growth of the amorphous phase in BeO ceramics. In addition, a relatively optimized preparation scheme, that is, holding at 1500 °C for 30 min and pressure of 20 MPa can be obtained. Under the optimized parameter, the flexural strength of the product can reach 244.74 MPa, and its thermal conductivity can reach 179 W/(m*K) at 200 °C, and 31 W/(m*K) at about 1000 °C. It provides a reference for the preparation of high performance BeO ceramics. [ABSTRACT FROM AUTHOR]

Currently, the lattice oxygen is the key factor affecting the thermal conductivity of AlN ceramics. In this paper, three methods are proposed to limit lattice oxygen, namely reducing the original powder oxygen content, changing the debinding atmosphere, and extending the sintering time. The results show that the low powder oxygen content and protective debinding atmosphere alter the carbon and oxygen content, and further promote the formation of the Y 4 Al 2 O 9 (YAM) phase. The generated YAM phase can effectively reduce the lattice oxygen in terms of thermodynamics. Prolonged high temperatures can provide kinetic conditions to reduce the lattice oxygen to 0.0343 wt%. In addition, morphological changes of the phase at the grain edges and their influence on the mechanical properties were noted. Finally, AlN ceramics with a thermal conductivity of 220 W m−1 K−1 and a flexural strength of 340 MPa were obtained. This study can provide a valuable reference for the industrial production of AlN ceramics. [ABSTRACT FROM AUTHOR]

The conventional solid-phase sintering method for the preparation of Ln 2 Ti 2 O 7 ceramics using oxides as reactants generally requires higher temperature, larger pressure, and greater energy consumption. In this paper, we synthesize a Eu 2 Ti 2 O 7 ceramic powder in relatively low-temperature molten salt (KCl–NaCl) using Eu 2 O 3 powder and TiO 2 powder as reactants at 1000 °C. The results of XRD, SEM, and element mapping indicate that the product have high phase purity, good crystal morphology and uniform chemical composition. Moreover, Eu 2 Ti 2 O 7 -based glass-ceramics are obtained by sintering with different contents of borosilicate glass. The SEM images of glass-ceramic show that almost no obvious defects or voids are found on the surface of the samples. The values of water absorption for all glass-ceramic waste forms are less than 0.5 %. With the increase of ceramic embedding rate, the hardness of the glass-ceramics first increases and then decreases, while the density gradually increases. When the embedding rate increased to 30 wt%, the hardness of glass-ceramic reaches a maximum of 19.53 GPa. The glass-ceramic waste form embedded with 30 wt% Eu 2 Ti 2 O 7 exhibits very stable chemical durability with a low leaching rate of 1.42 × 10−8 g m−2 d−1 at 90 °C even after 28 days. [ABSTRACT FROM AUTHOR]

Ceramics is a promising material that has been widely used as artificial bones. However, most available investigations were devoted to new material development and implant structure design, while few of studies focused on innovative hybrid implants that can act not only as implants but also as surgery tools for solving specific health issues. This paper innovatively designed and additively-manufactured a zirconia ceramic surgery tool, which can not only act as a drilling tool, but also retain itself in the drilled hole after the surgery as bone scaffold, at the meantime delivery active ingredient (Vitamin C) for fast recovery. To achieve early intervention, the proposed zirconia ceramic tool was additively manufactured with inter-connected pore structures that can benefit the recovery. The zirconia ceramic surgery tools (with 50 %, 70 % and 80 % porosity) showed the required mechanical properties to act as a drilling tool. The tool also showed drug releasing function with the different diffusion rates based on drug diffusion experiments. The zirconia ceramic tool with Vitamin C coating also showed enhanced cell adhesion and accelerated cell growth based on the osteoblast induction assessment. Based on above, the proposed zirconia ceramic tool is expected to bring new possibilities for wide applications of ceramic tools in surgeries. [ABSTRACT FROM AUTHOR]

This paper explores the important impact of Fe 2 O 3 on the synthesis, structure, hardness, and radiation shielding characteristics of Apatite–Wollastonite (AW) glass ceramics for bone implantation and shielding application. The prepared studied samples were prepared and the effects of Fe 2 O 3 addition on the synthesis process, density, and different physical and structural parameters comprehensively investigated. Additionally, the radiation shielding properties were determined by using PHITS simulation code and XCOM calculations for all samples. The results reveal that there is a significant impact of Fe 2 O 3 addition on density, hardness, and radiation shielding of AW glass ceramics. The Vickers hardness values were calculated as 547, 598, and 621 Hv in measurements under 0.1 kg load., the density values are found to be as 2.87, 3.07 and 3.28 g/cm3 for AW, Aw -1Fe, and Aw -2Fe, respectively. The highest linear attenuation coefficient in the AW- 2Fe is 0.096 cm−1, Aw -1Fe showed 0.084 cm−1 and AW gave 0.072 cm−1 at 6 MeV. This study underscores the pivotal role of Fe 2 O 3 as a multifaceted modifier in tailoring the properties of AW glass ceramics for bone implantation and other diverse applications extending from medical imaging to radiation and charged ions shielding. [ABSTRACT FROM AUTHOR]

Vat photopolymerization 3D printing provides a novel approach for preparing broadband wave-transparent Si 3 N 4 /β-SiAlON composite ceramics. This paper oxidized raw powder to introduce low dielectric phases (SiO 2) and overcome the low curing depth of α-Si 3 N 4. The solid content of oxidized α-Si 3 N 4 was increased to 50 vol% for the first time by modification with dispersant. The selected print thickness of 50 μm was the highest known for Si 3 N 4 vat photopolymerization 3D printing, greatly improving printing efficiency. Finally, Si 3 N 4 /β-SiAlON composite ceramics were sintered in the range of 1600-1800 °C, and the mechanical and dielectric properties were systematically studied. The composite ceramics sintering at 1780 °C had a maximum bending strength of 236 ± 16 MPa, and the real permittivity was 4.83. At 1800 °C the porosity increased resulting in bending strength decreased to 109 ± 4 MPa, and the real permittivity to 3.23. This study filled the gap in the post-treatment of oxidized α-Si 3 N 4 and guided the application of Si 3 N 4 /β-SiAlON composite ceramics in the field of wave-transparent. [ABSTRACT FROM AUTHOR]

Electrocaloric refrigeration shows the merits of environmental safeguarding, large efficiency, easy combination, and miniaturization as a novel solid-state refrigeration technique. In this paper, Sn4+ is doped into the B site of BLNT ceramics. By adjusting the doping content, the T-C phase transition peak was successfully shifted to room temperature and promoted the formation of relaxor ferroelectrics, resulting in a wider operating temperature range (T span) and improved adiabatic temperature change (ΔT). A comprehensive study was conducted on the crystal structure, surface morphology, dielectric properties, ferroelectricity, and electrical properties of BLNTS ceramics with varying levels of Sn4+ doping. Wherein, when the doping amount is 5Sn, a maximum adiabatic temperature change value (ΔT max) of 1.14 K was obtained, and the temperature span (T span) reached 45 °C (T span is defined as ΔT ≥ 80 % ΔT max). This work proposes a high-performance environmentally friendly electrocaloric effect (ECE) material suitable for solid-state cooling applications. [ABSTRACT FROM AUTHOR]

Zirconia ceramics have become an important material for the manufacture of key components in aerospace, military, energy, and other fields due to their excellent mechanical properties. However, their inherent high hardness and brittleness make them difficult to machine with high efficiency and low damage, resulting in poor surface integrity. Inspired by the ribbed groove structure of shark skin and the fractal structure of insect wing veins, two zirconia ceramics with different bionic textures are designed in this paper, and zirconia ceramic surfaces are bionically textured by using an ultrafast picosecond pulse laser. The effects of the special bionic textures on the grinding behavior of zirconia ceramics, specifically surface morphology, surface roughness, edge morphology, and subsurface damage, were investigated. The experimental results show that the surface integrity of the bionic textured zirconia ceramics is better compared to the untextured surface. In particular, the bionic insect wing veins texture exhibits the best surface quality with the least sub-surface damage, and the surface roughness S a is reduced by a maximum of 21.46 %, and S z is reduced by a maximum of 18.87 %. However, the best edge morphology is exhibited by the bionic shark skin texture. Additionally, bionic texturing improves grinding lubrication and cooling conditions. The results confirm that applying bionic texturing to zirconia ceramics effectively enhances grinding performance and improves grinding surface integrity. [ABSTRACT FROM AUTHOR]

The cleaning of traditional ceramics consumes much water and detergents. It is valuable to consider how to endow the ceramics with self-cleaning character. In this paper, titanic-based-crystallites (CaTi(SiO 5) or TiO 2) superhydrophilic glazes with superior self-cleaning properties were in situ prepared by a simple one-time firing method. There is no any extra treatment involved in the preparation process. It was found that the precipitation of titanic-based crystallites in the glaze could be adjusted by controlling the cooling system. The transformation mechanism of the phase was analyzed based on the phase separation state. Stress conditions of a dirt cell on surfaces with different roughness were discussed. The correlation between geometric structure and self-cleaning performance demonstrated that the multi-level structure is vital for self-cleaning performance. The self-cleaning mechanism of the superhydrophilic glaze was proposed. The titanic-based crystallite glazes possess superhydrophilic characteristics (<8.0 °), high hardness (642.44–707.85 kgf·mm−2), and excellent self-cleaning performance to oily ink stamps and relatively good performance to human fecal simulacrum, the miso sauce, due to the multi-level structure with nano-scale surface roughness, showing a good application potential on the self-cleaning domain, i.e. glass and traditional ceramic, etc. [ABSTRACT FROM AUTHOR]

The current paper reports on the crystal structure, microwave dielectric properties as well as the antenna parameters of (1-x)MgTiO 3 - xSrTiO 3 (abbreviated as (1-x)MT-xST) for x = 0.025, 0.05, 0.075, 0.1 ceramic based dielectric resonator antennas (DRAs). The (1-x) MT - xST samples have been prepared with the help of a solid-state reaction route. The SrTiO 3 was introduced to MgTiO 3 as a τ f compensator for developing a tunable τ f material. Rietveld refinement results of X-ray diffraction data suggest that all the samples exhibit a combination of two crystallographic phases i.e., rhombohedral (R-3) + cubic (Pm-3m). The SEM micrographs show clear and well-defined grains for (1-x)MT - xST (for x = 0.025–0.1) ceramics. The modes of vibration of the crystal structures of the materials have been identified by the Raman spectroscopy method. The bond strength, bond valency, bond energy, and tolerance factor have been determined for (1-x)MT - xST (for x = 0.025–0.1) materials. The microwave dielectric performances of ceramics have been analyzed over a frequency band of 1–10 GHz. It has been found that the dielectric constant is almost constant along the microwave frequency range. The behavioral change of tuned temperature coefficient of resonant frequency (τ f) along with quality factor have been reported. Besides, DRAs have been formed using all ceramic compositions, and simulations were performed to determine the various antenna properties, such as efficiency, input impedance, radiation properties, gain, and reflection coefficient. This study supports the use of microwave dielectric ceramics in antenna fields and highlights the enormous potential of (1-x)MT - xST for (x = 0.05) materials in communication systems. [ABSTRACT FROM AUTHOR]

Binder jetting (BJ) additive manufacturing has the advantages of high precision, fast forming speed, and no need for supporting structure, which is especially suitable for the forming of metallic and ceramic components with complex structures. In this paper, SiC ceramic parts were obtained by BJ additive manufacturing and precursor impregnation pyrolysis (PIP) cycles. It has been observed that the thickness of the printing layer significantly affects the strength of the SiC green body. The SiC green body exhibited the highest bending strength (3.1 ± 0.2 MPa) and lower dimensional deviation (0.47–1.64 %) when printed with a layer thickness of 50 μm. However, the bending strength of the SiC ceramics (after densification) had little variations when different printing layer thicknesses were utilized. In the subsequent densification process, the density, hardness, and bending strength of SiC ceramics increase as the number of PIP cycles increases obviously, and the flexural strength reached 228.7 ± 14.2 MPa after 9 PIP cycles, while the shrinkage rates in the X, Y, and Z direction were 1.9 %, 2.8 %, and 1.2 %, respectively. In addition, the influence mechanism of printing parameters on the strengths of the green bodies and SiC ceramics was also discussed. Specifically, it was found that with the layer thickness increase, the strengths of SiC ceramics also increase. [ABSTRACT FROM AUTHOR]

3D printing of ceramics is a novel technology that allows for the rapid preparation of complex ceramic structures, with potential applications in various industrial fields. However, the high porosity often observed in ceramics prepared via 3D printing can negatively affect their mechanical properties. In this paper, a novel process for manufacturing silicon carbide ceramics reinforced with short carbon fibers (C f /SiC) is proposed. The process employs direct ink writing (DIW) and solid-phase sintering technology, leading to a substantial improvement in the mechanical properties of ceramics and a shorter preparation cycle. Bending properties and fracture toughness of C f /SiC ceramics were evaluated by a series of mechanical tests, including three-point bending and single-edge notched beam tests. The findings showed that the bending strength and fracture toughness of the ceramics were 446.0 MPa and 6.021 MPa•m1/2, respectively. Moreover, a theoretical model was developed to predict the strength of symmetrically distributed laminated beams with different fiber orientation, prepared by varying the printing direction. Simulation results on bending strength from the theoretical model are in good agreement with experimental result with prediction difference less than 11.41 %. [ABSTRACT FROM AUTHOR]

Addressing the challenge of existing insulation materials struggling to achieve the synergy of lightweight construction, high strength, and low thermal conductivity, this paper presents a method based on multi-material assembly technology to achieve a controlled composite of a three-dimensional continuous silicon carbide network and graphite matrix. Following an examination of the impact of various forming densities and the addition of expandable graphite on the thermal conductivity and compressive strength of graphite/SiC composites, the study explored the effects of different "enhancement network" topologies on the properties of these composites. The investigation demonstrates that adjusting the forming density and incorporating expandable graphite enable regulation of both the porosity and closed porosity of the composites, thereby controlling their compressive strength and thermal conductivity. Additionally, the construction of a three-dimensional continuous SiC network structure within the graphite matrix significantly enhances the compressive strength of the composites, with only a slight increase in thermal conductivity. A graphite/SiC composite thermal insulation material was ultimately developed, boasting a density of merely 1.1 g/cm³, a low thermal conductivity of 1.847 W/m·K, and an impressive compressive strength reaching 15.627 MPa. Its overall performance surpasses that of water-glass sand, making it a promising candidate for various applications in the foundry industry as a thermal insulation material. [ABSTRACT FROM AUTHOR]

In this paper, cordierite ceramics with high far-infrared emission properties are synthesized by a high-temperature solid-phase method using molybdenum tailings and vanadium-titanium magnetite tailings. The microstructure, physical properties and far-infrared emission mechanism of ceramics are investigated. The results show that the ceramics synthesized with 10 wt% molybdenum tailings and 30 wt% vanadium-titanium magnetite tailings have a flexural strength of 67 MPa, a bulk density of 2.531 g/cm3 and a maximum far-infrared emissivity of 0.958 when the sintering temperature is 1200 °C. The crystal phase of the ceramic are 21.4 % cordierite and 58.7 % magnesia-alumina spinel. In the sintering process, the Fe3+ in vanadium-titanium magnetite tailings doped into the cordierite to substitute the Mg2+, which has the similar ionic radius with Fe3+, to form a substitutional solute. Ionic substitution causes the lattice parameters of cordierite larger, reducing the symmetry of the lattice vibrations and leading to lattice distortion. In addition, the composition of a large amount of magnesia-aluminum spinel is attributed to the far-infrared emission properties of ceramics. [ABSTRACT FROM AUTHOR]

The AlN/BN composite ceramic, fabricated via hot-press sintering, exhibits obvious anisotropy due to the establishment of directional alignment of h-BN. However, the variation and influence mechanisms of bending strength (σ) and thermal conductivity (λ) are remain unclear in different directions, which greatly limit the application of AlN/BN composite ceramics. In this paper, the effects of h-BN content on phase composition, microstructure and anisotropy of AlN/BN composite ceramics are discussed in detail. The results reveal that AlN/BN composite ceramics have three directions: perpendicular (⊥), longitudinal parallel (∥), and lateral parallel (≡) to the hot-pressing direction. The content of h-BN is a crucial factor affecting the anisotropy of AlN/BN composite ceramics. h-BN enhances the thermal conductivity in the ∥ and hinders the thermal conductivity in the ⊥. With the increase in h-BN amount, λ ∥ rises gradually, while λ ⊥ gradually falls. When the mass percentage of h-BN and AlN is 25 % (AB25), the λ ∥ is as high as 90 W m−1 K−1, which is about 2.25 times that of λ ⊥. In terms of mechanical properties, σ ≡ and σ ⊥ first increase and then decrease, while σ ∥ only decreases. This is attributable to h-BN being effective in enhancing mechanical properties by inhibiting crack propagation in the ⊥ and ≡ direction, while the promotion of crack propagation leads to a decrease in mechanical properties in the ∥ direction. σ ≡ reaches the highest values (σ ≡ = 460.2 MPa) at an h-BN amount of 10 % (AB10), which is about 1.19 and 2.04 times that of σ ⊥ and σ ∥ , respectively, and 22.1 % higher than that of AB0. [ABSTRACT FROM AUTHOR]

Polymer-derived ceramics (PDCs) are increasingly recognized as promising materials for high-temperature thin/thick film sensors (HTTFSs). However, a large linewidth and poor dimensional accuracy have severely restricted the practical application of PDCs HTTFSs. Our study employed a picosecond laser to precisely pattern the polymer-derived ceramic (PDC) thick film while applying no obvious damage to the interface between ceramic and substrate. Through parameters optimization, the laser-affected area was minimized to 6 μm wide, and a minimum feature size of about 30 μm was achieved. Furthermore, 7 rounds of high-temperature tests of the patterned film revealed good temperature-resistance repeatability within a temperature range of up to 800 °C. To demonstrate practical application potential, we successfully fabricated a heat flux sensor, and it exhibited a sensitivity of 1.32 mV/(kW/m2), a response time of 600 ms, and excellent repeatability over a range of 0–75.4 kW/m2. In summary, this paper proposes a novel approach toward miniaturizing the linewidth of the polymer-derived ceramics thick film sensor, showing significant potential for precise measurements in extreme environments. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper presents the preparation and characterization of transparent oxyfluoride glass ceramics (GCs) that contain nanocrystals of K 3 YF 6 co-doped with Dy3+ and Sm3+. The study investigates the luminescence characteristics, the process of energy transfer (ET) and the behavior of the ratio-metric temperature sensing. The formation of well-defined nanocrystals of K 3 YF 6 in the glass substrate was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). By varying Sm3+ concentration, a tunable emission ranging from pale yellow to orange-red was observed. Energy transfer from Dy3+ to Sm3+ ions was confirmed through fluorescence spectra and decay curves. Sample K 3 YF 6 , containing 0.5 mol%Dy3+/1.2 mol%Sm3+, showed an absolute sensitivity (S a) of 0.635 % K−1 and relative sensitivity (S r) of 0.401 % K−1. These findings underscore the promising applications of K 3 YF 6 : Dy3+, Sm3+ GCs in multicolor displays and high-performance temperature sensing devices. [ABSTRACT FROM AUTHOR]

Solar energy absorption and storage of integrated ceramic materials is both the absorption of sunlight and storage of sunlight into thermal energy functional materials. In this paper, the effect of Fe 2 O 3 on the solar absorptivity, thermal storage properties, sintering temperature, and physical properties of mullite-based thermal storage ceramics was investigated. The results show that the absorptivity and thermal storage density of the sample AF4 (Bauxite:50 wt%, Clay:50 wt%, Fe 2 O 3 :11 wt%) after sintering at 1420 °C are 87.2% and 1116.5 kJ kg−1, respectively; and the unit volume of the AF4 sample can provide the power grid with 918.01 kW h of electricity, save 112.91 kg of coal, and reduce 361.33 kg of CO 2 emission. This study systematically elucidated the mechanism of the enhancement of sample absorption caused by Fe3+ doping-induced changes in substrate color, reduction in material forbidden bandwidth, and lattice anharmonic vibration effect, in addition to comprehensively evaluating the feasibility of the optimal AF4 sample for use in solar energy absorbing and storing integrated ceramic materials. [ABSTRACT FROM AUTHOR]

The laser direct fusion welding of SiO 2 ceramics was a global challenge in the manufacture of radome. The paper explored the laser direct fusion welding of SiO 2 ceramics, investigated the influence of filling powder addition and welding material composition on the formation of weld. The findings revealed that the addition of welding material effectively addressed the issue of weld formation in laser direct fusion welding SiO 2 ceramic. However, the abundance of internal bubbles within the weld emerged as a significant impediment to further enhancing weld strength. The addition of SiO 2 /Al 2 O 3 mixed powder not only significantly reduced the quantity and size of internal bubbles within the weld but also generated the strengthening phase Al 2 SiO 5 , leading to a substantial increase in weld shear strength, reaching a maximum of 106 % of the base material. The research results provided a new solution for direct melting welding of ceramics. [ABSTRACT FROM AUTHOR]

CaBi 2 Nb 2 O 9 (CBN) with the Aurivillius phase has a high Curie temperature (T C) and remarkable fatigue resistance, which has great potential for application as high-temperature sensors. However, due to its low piezoelectric properties, its practical application remains a great challenge. In this paper, Ca 1- x Ce x Bi 2 Nb 2 O 9 ceramics were prepared by the direct reaction sintering (DRS) and conventional preparation (CP) methods, respectively. The experimental results indicate that Ce doping can increase the piezoelectric coefficient d 33 of CBN ceramics by about two times. Among them, the grain size of the samples prepared by the DRS method is finer and more uniform, and the d 33 value of DRS samples is about 3.6–9.4 % higher than that of CP samples. The DRS sample Ca 0·97 Ce 0·03 Bi 2 Nb 2 O 9 has a d 33 value of 18.9 pC/N, a T C of 948 °C, and a resistivity of 1.1 × 105 Ω cm at 600 °C. This study shows that DRS method is an effective densification method, which can prepare CBN-based ceramics with excellent comprehensive properties, and provides an innovative preparation route to explore CBN-based ceramics with excellent piezoelectric properties. [ABSTRACT FROM AUTHOR]

The bandwidth adaptation factor (BAF), which is calculated as BW • (λ L - λ H): (d • f r), is a crucial evaluation parameter for designing ultrathin broadband absorbers. In this paper, a high BAF absorber is designed by utilizing an impedance frequency selective surface (FSS), which includes a six pinnacles FSS, a La-doped mullite ceramic dielectric layer and a metal backplane. The optimal numbers of pinnacled FSS is determined through comparison and optimization, and the power monitor results indicate that the main loss modes are electrical and ohmic loss. Subsequently, the impedance analysis reveals that the favourable absorption performance is attributed to good impedance matching and high loss coefficient. Furthermore, the observation of the current distribution on the surface confirms that the primary loss appears at the pinnacles. The proposed absorber has below −10 dB reflectivity in 12.26–18.00 GHz. Meanwhile, the BAF is 3.36 and the thickness is only 0.061 λ L (1.5 mm). The measured results are in good agreement with the simulation results, demonstrating an excellent BAF characteristic. [ABSTRACT FROM AUTHOR]

In this work we successfully synthesize CsPb(Br x I 1-x) 3 perovskite nanocrystals with different Br/I ratio in a borogermanate glass matrix. The XRD studies show cubic perovskite phase peaks shift as the Br/I ratio changes. The formed nanocrystals have mean size of about 17 nm based on the calculations from the absorption spectra. The smooth change of the Br/I ratio in perovskite nanocrystals allow to obtain luminescence in the range 500–750 nm with quantum yield up to 35 %. The luminescence quantum yield and lifetime of the mixed-halide nanocrystals steadily increase with iodine concentration. Practical application of perovskite glass-ceramics as a radiation converter is shown in the paper. [Display omitted] [ABSTRACT FROM AUTHOR]

The effect of Ru-substitution (5–15 %) on the charge ordering of Y 0.5 Ca 0.5 MnO 3 has been investigated in this paper. Ru, existing in different oxidation states such as Ru4+ and Ru5+, plays an immense role in causing ferromagnetic (FM) superexchange interactions with Mn3+ ions. This, combined with the FM double-exchange interactions between Mn3+ and Mn4+ ions, destroys charge ordering. The development of ferromagnetism in Ru-substituted compounds is understood experimentally through the remarkable enhancement of dc magnetization with a simultaneous shift of T C from 57 K to 95 K with increasing Ru content from x = 0.05 to x = 0.15. The appearance of hysteresis for higher doping concentrations further confirms the FM nature. Concomitant with the favorable impact on the magnetic nature, there is also a development of magnetocaloric properties upon Ru-substitution. The maximum magnetic entropy change for x = 0.05 to 0.15 that was found to peak at T C ranges from 1.08 J/kg/K to 2.8 J/kg/K respectively for a field change of 9 T. The corresponding relative cooling power (RCP) increases from 76 J/kg to 324 J/kg indicating a significant growth of RCP with Ru substitution. These salient features of Ru-doped Y 0.5 Ca 0.5 MnO 3 would make it a suitable candidate for magnetic refrigeration. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of the properties of Poletaevsky kaolin with the aim of using it in the ceramic industry. Based on the results of determining the chemical, mineral and granulometric composition. The mineral composition of Poletaevsky kaolin is kaolinite 80–85 wt %, muscovite and illite 10–15 wt %, quartz up to 10–15 wt %. It has been established that the Hinckley index for Poletaevsky kaolin is 0.68, compared to 1.38 for Glukhovetsky one. The ratio of highly ordered kaolinite to low ordered kaolinite for Poletaevsky kaolin is 22 : 78, for Glukhovetsky kaolin the ratio of highly ordered kaolinite to low-ordered kaolinite is 57 : 43. It was established that Poletaevsky kaolin can be used in the production of ceramic materials by plastic or semi-dry molding. The determined low content of high-ordered kaolinite and the insignificant content of particles less than 2 μm according to the results of laser diffraction analysis can lead to the production of an unstable slip. When firing samples of Poletaevsky kaolin, a minimum water absorption of 5.5 % was achieved at a firing temperature of 1450 °C. In this case, the resulting maximum apparent density was 2.17 g/cm3, the maximum mullite content was 38 %, and the maximum compressive strength was 32 MPa. [Display omitted] [ABSTRACT FROM AUTHOR]

3D printing is an excellent choice for manufacture of ceramic cores; however, the inter-layer structures in 3D printed sample leads to anisotropy in microstructure and properties. In this paper, silica-based ceramic cores were prepared by digital light processing, and metallic Si powder was employed as mineralizer to relieve the anisotropy. The metallic Si powder converts into SiO 2 in oxidation reaction with significant volume expansion, which inhibits the shrinkage rate and partly fills the interlayer gaps of the ceramic core. Meanwhile, the metal Si powder leads to lower curing thickness in 3D printing, and thicken the interlayer gaps. Due to the cooperation of the oxidation reaction and decreased curing thickness by the metallic Si powder, the 0.4 wt% of metallic Si powder reduced the anisotropy in structure and mechanical property due to the alleviated inter-layer structure and the interlayer and intralayer strengths show optimal values of 11.4 MPa and 17.2 MPa at room temperature, respectively. This work inspires new guidance to 3D printing of ceramic cores with uniform microstructure and excellent mechanical properties. [ABSTRACT FROM AUTHOR]

Many factors impact the formability of single phase high-entropy pyrochlore ceramics (HEPCs) which become a research hotspot owing to their excellent properties. To investigate the effect of size disorder, two combinations with same mixing entropy and different size disorder were designed, thermodynamic analysis of first-principles calculations and experimental research were conducted in this paper. The calculation results reveal that the enthalpy change decreases significantly with the decrease of size disorder, promoting the synthesis of single-phase high-entropy pyrochlore. The experimental results prove that the combination with lower size disorder leads to single-phase HEPCs, and the prepared material exhibits low thermal conductivity (1.68 W/(m·K)) and low theoretical density (5.73 g/cm3). [ABSTRACT FROM AUTHOR]

In this research, the authors explore the structural, dielectric, electrical insulating, electromechanical, and piezoelectric characteristics of ceramics that have been modified using BaTiO 3 and (K 0.5 Bi 0.5)TiO 3.as key components. Specifically, they explore the composition (1-x-y)(Na 0.5 Bi 0.5)TiO 3 -xBaTiO 3 -y(K 0.5 Bi 0.5)TiO 3 , where x (mol.%) varies between 0, 6, and NBT, and y (mol.%) varies between 0, 18, and KBT. These ceramics were fabricated using a solid-state synthesis technique. The optimized calcination temperature for achieving a pure perovskite phase was determined to be 1000 °C for a duration of 4 h. The research involves a comprehensive analysis of the composition, microstructure, electrical insulating, and electromechanical characteristics of the ceramics. Rietveld analysis of X-ray diffraction (XRD) data was employed to accurately ascertain the morphotropic phase boundary (MPB) within this material. In this paper, we discuss the impact of crystallite size on the shifts in Raman band frequencies. Sintering at 1100 °C for 4 h was found to enhance densification, with scanning electron microscopy (SEM) images illustrating a nearly uniform distribution of compact grains. Electrical insulating assessments demonstrate that each of the ceramics displays a scattered phase transition around the temperature T m , with a diffusivity ranging from 1.4 to 1.8, and a shift of T m towards elevated temperatures. Exceptional piezoelectric properties were observed at the morphotropic phase boundary (MPB), including a d 33 value of 149 pC/N and electromechanical coupling factors kp of 0.297. These findings are attributed to the coexistence of rhombohedral and tetragonal phases, as well as precise grain size control. This research presents a novel approach to enhancing lead-free ferroelectric materials based on the composition 0.76(Na 0.5 Bi 0.5)TiO 3 -0.06BaTiO 3 -0.18(K 0.5 Bi 0.5)TiO 3. [ABSTRACT FROM AUTHOR]

High-entropy perovskite oxides (HEPOs) have attracted considerable attention as dielectric ceramics. However, the energy-storage performance of these HEPOs still requires improvement. In this study, a series of (1- x)(Bi 0. 4 Ba 0. 2 K 0. 2 Na 0.2)TiO 3 - x NaNbO 3 high-entropy ceramics were designed and prepared using a high-entropy strategy. The introduction of antiferroelectric NaNbO 3 into the (Bi 0. 4 Ba 0. 2 K 0. 2 Na 0.2)TiO 3 medium-entropy matrix increased the configurational entropy and cationic disorder, resulting in improved energy storage performance. The ceramic with an optimal composition of 0.775(Bi 0. 4 Ba 0. 2 K 0. 2 Na 0.2)TiO 3 -0.225NaNbO 3 achieved a high recoverable energy density (W rec) of 2.523 J/cm3 and a high efficiency (η) of 83.7% at an electric field of 220 kV/cm. Furthermore, the material demonstrated good temperature and frequency stability, as well as good anti-fatigue properties. This paper presents a dielectric ceramic suitable for energy storage under low to moderate electric fields. [ABSTRACT FROM AUTHOR]

In this paper, polycrystalline Lu 1- x Dy x Fe 0.5 Cr 0·5 O 3 (0 ≤ x ≤ 0.15) perovskite ceramics were synthesized via a conventional solid-state-reaction technique. Structural and magnetic properties of the samples were experimentally studied. The cell volume of the lattice expands with the rise in Dy3+ amount. The measuring of magnetic properties shows that the undoped sample exhibits a negative magnetization effect with a compensation temperature of 231.1 K, while the Dy-doped samples display negative magnetization effects between two compensation temperatures. The magnetic switch experiment demonstrates the significant potential for practical applications through stable and repeatable switching of magnetization state by adjusting the external magnetic field between 50 Oe and 300 Oe. Besides, the presence of two compensation temperatures which can be regulated by changing the doping content or external magnetic field provides more possibilities for application. Moreover, based on the comprehensive analysis of the experimental results, it is believed that the negative magnetization effect originates from the competition of magnetic moments in different directions. Meanwhile, the second compensation temperature occurs in low temperature region might be attributed to the additional positive magnetic moment contributed by the paramagnetic Dy3+ ions. [ABSTRACT FROM AUTHOR]

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]

The electrochemical discharge machining (ECDM) is an advanced and promising technology for fabricating micro structures. This method is effectively applicable for non-conductive hard and brittle materials micromachining, such as glass and ceramics. However, the ceramics high melting point and intense heat exchange effects during microchannel fabrication lead to the easy dissipation of thermal energy and the difficulty in processing. To address this issue and expanded the ECDM processing range. This paper dedicated to the investigation of the material removal mechanism and process characteristics for the alumina ceramic surfaces microchannels preparation. Firstly, this study explained the difference of the ECDM critical applied voltage and gas film generation mechanism by analyzing the volt-ampere characteristic curve of 20 wt% NaOH electrolyte with a tool immersed depth of 2 mm and 10 mm respectively. Then, a thermal removal finite element model (FEM) for ECDM was developed. The heat cumulative and intermittent cooling effects applied on the alumina ceramic surface dominated the materiel removal. Additionally, it can be found that the microchannel machining accuracy and bottom surface quality depended on the Gaussian heat source characteristics, gas film formation mechanism, heat accumulation effect, and temperatures spatial and temporal distribution. And a series of single factor experiments for evaluating the parametric studies such as the effect of discharge frequency, applied voltage, duty ratio and tool feed rate on the fabricated microchannel performance are executed. Finally, the complex three-dimensional structures of cross microchannel grid and zigzag microchannel array with variable depth were successfully fabricated on aluminum oxide ceramic surface. Notably, the results highlighted and enriched the ECDM stability, consistency and applicability for alumina ceramic surface microchannel fabrication. [ABSTRACT FROM AUTHOR]

In this paper, a series of Ba 1-x Mn x Al 2 O 4 (x = 0.00 0.02 0.05 0.10 0.15 0.20) green high NIR reflective pigments were prepared by solution gel method and applied to ceramic glaze for thermal insulation evaluation. The experimental results show that Mn2+ ions successfully replace Ba2+ ions without changing the morphology of the phase structure of the materials. The Ba 1-x Mn x Al 2 O 4 morphology shows nanowire-like shape as detected by SEM. The absorption of Mn2+ ions in the visible region changes the color of the materials from white to green, and with the a* values in the range of −20.28 to −58.17, the materials have excellent coloring properties. The near-infrared reflectivity of the material in the range of 700–2500 nm is 47.35%–68.07%, which is significantly higher than other materials of the same color. In the heat insulation application experiment, the inner surface temperature of ceramic glazes with Ba 1-x Mn x Al 2 O 4 materials was reduced by 16.17%–23.87% compared to ordinary ceramic samples. [ABSTRACT FROM AUTHOR]

A creative way to overcome the general problem of high-porosity ceramic foams with low intensity has been proposed here. For the first time, zirconia toughened alumina (ZTA) ceramic foams with a large number of intragranular structures have been prepared by particle-stabilized foams using boehmite sol and ZrO 2 sol as raw materials. The grain boundary mobility of alumina in ceramic foams is much higher than that of zirconia due to the extremely high sintering activity of the boehmite nanoparticles, and then a typical intragranular structure of alumina grains wrapping around zirconia grains is formed. Based on the strengthening effects of intragranular zirconia grains, the as-prepared ZTA foams have excellent mechanical properties, with ultra-high compressive strength of 10.3–88.0 MPa and high porosity of 91.0–79.1 %. This paper provides a novel strategy for the preparation of high-performance ceramic foams. [ABSTRACT FROM AUTHOR]

This paper presents the synthesis of multifunctional ceramics, represented as Sr 2- x Sm x Ag 0.2 Na 0.8 Nb 5- x Ti x O 15 , through the solid-state reaction method. Smaller ions in both A and B sites were co-substituted, resulting in a notable relaxation behavior, which was analyzed to determine the contributing factors for underlying structural mechanisms. Introducing Sm3+ and Ti4+ not only transformed the structure from Im 2 a to Bbm 2 symmetry and then eventually to paraelectric P 4/ mbm phase, but also induced the evolution of incommensurate structure and the formation of nano-domains to modulate relaxation behavior. Notably, the enhanced energy storage properties (W rec ∼ 3.38 J/cm3, η ∼ 84.5 %) and desirable red-orange emission performance (λ em = 610 nm) were obtained for Sr 1.7 Sm 0.3 Ag 0.2 Na 0.8 Nb 4.7 Ti 0.3 O 15 ceramics. Moreover, the multifunctional ceramics exhibited high power and current densities (P D ∼ 116.38 MW/cm3, C D ∼ 1026.43 A/cm2) together with a prolonged decay life (745 μs). Therefore, the proposed materials may be suitable for potential applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this paper, Bi 2 O 3 doped BaTiO 3 -0.01MgO-0.01Nb 2 O 5 ceramics are designed to increase dielectric constant, reduce dielectric loss and improve temperature dielectric stability through inducing defects, and are prepared by flash sintering method to inhibit the volatilization of Bi element and ensure the element ratio. The microstructure, polarization mechanisms, dielectric properties and conduction mechanism of the ceramics are studied. The doping of Bi 2 O 3 can enhance the relaxation behavior and dielectric properties. The defects evolution in BaTiO 3 -0.01MgO-0.01Nb 2 O-0.01Bi 2 O 3 ceramics are studied. The results show that the BaTiO 3 ceramics doped with different amounts of Bi 2 O 3 can form defect dipoles { [ Bi Ba ∙ ‐ Mg Ti ″ ‐ Bi Ba ∙ ] ×, [ Nb Ti ∙ ‐ V Ba ″ ‐ Nb Ti ∙ ] ×, [ Mg Ti ″ ‐ V O ∙ ∙ ] ×} and oxygen vacancy, which enhance the short-range transition within the grain and inhibit the movement of free electrons at the grain boundary. The ceramics have excellent room temperature properties, high dielectric constant (ε r = 2894) and low dielectric loss (tan δ < 0.03). The ceramics have superior temperature stability and satisfying the EIA X8R (Δ ε r / ε 25 ≤ ±15 %, over the temperature range from −55 °C to 150 °C). It is found that flash sintering can effectively guarantee the stoichiometric concentration of bismuth element and obtain good properties of ceramics. This study demonstrates the potential of Bi 2 O 3 doped BaTiO 3 -based ceramics synthetized by flash sintering as high-performance electronic device materials. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of different forming processes on the surface morphology and dimensional accuracy of zirconia ceramics, and selects the optimal forming process for mechanical property analysis. A laboratory-built ceramic laser 3D printer was used to carry out the forming experiments on the specimens. Under the condition that only the forming process of the experimental target is changed, the effects of powder layering process, scanning spacing and scanning strategy on the surface morphology and properties of zirconia ceramics are investigated. The use of two powder spreading and scanning forming processes in the sample forming process effectively improved the forming defects of zirconia ceramics caused by powder splattering, and the zirconia ceramics had a better forming effect. Under this condition, the dimensional accuracy of the specimens increases and then decreases with the decrease of the scanning spacing, where the highest dimensional accuracy is obtained when the scanning spacing is 0.158 mm; among different scanning strategies, the best surface morphology is obtained by forming specimens with the island scanning strategy. In addition, the mechanical properties of the ceramics formed from zirconia showed that the Young's modulus and Vickers hardness of the samples increased by approximately 53.6 % and 15.7 %, respectively, compared to the traditional forming process. [ABSTRACT FROM AUTHOR]