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As a wide band gap semiconductor, alkaline-earth metal sulfides (AES) with low phonon energy, high laser damage threshold, and high transmittance in infrared, have wide application prospects in bioimaging, spectral conversion, and solid-state lighting. However, AES nanocrystals (NCs) suffer from the weak chemical-stability and low mechanical-stability, and can be easily oxidized in humidity and oxygen. Incorporation of AES NCs into inorganic glass is expected to overcome those inherent limitations. In this work, a new type of oxysulfide glass-ceramics containing CaS, SrS, BaS, Sr x Ba 1−x S, and Ca x Sr 1−x S NCs is developed, and average diameters of these AES NCs are tuned in the range of 3–18 nm. Precipitation of AES NCs not only improves the mechanical properties of glass, but also maintains high transmittance (˃60%) in the spectral range of 1–4.3 µm. Results reported in this work offer a new pathway for developing novel oxysulfide glass-ceramics for multi-functional optical devices. [ABSTRACT FROM AUTHOR]

In order to improve the filtration performance, silicon carbide porous ceramics with network cell wall were fabricated via the polyurethane foaming method using silicon carbide powder, alumina powder, polyether polyol, polymethylene polyphenyl polyisocyanate, dibutyltin dilaurate, triethylenediamine and silicone oil (foam stabilizer) as raw materials. The effects of the solid loadings of the slurry (45%, 50%, 55% and 60%, by mass) on the microstructure, physical properties and their filtration properties towards particu-late matters were studied. The result shows that: (1) with the increasing solid loading, the bulk density and cold compressive strength gradually increase, and the apparent porosity decreases; (2) the micropores generated during the polyurethane foaming process are distributed on the ceramic pore wall to form a network cell wall structure, which increases the collision probability between particles and the wall pores and improves the filtration efficiency; meanwhile, the network cell wall structure also improves the pore interconnectivity and reduces the press drop; (3) when the solid loading is 55%, the silicon carbide based porous ceramics have the bulk density of 0.57 g · cm-3, apparent porosity of 79.2%, cold compressive strength of 3.7 MPa, and the filtering efficiency of the paniculate matter of 91.2%, achieving good regeneration performance. [ABSTRACT FROM AUTHOR]

Reactive sintering has been widely utilized to densify ceramics. Although the technology has numerous advantages, the composition of as-sintered ceramics is hard to be adjusted unless additional products are added. In this work, a novel solid-state route based on the reactions among TiN, Al and B were proposed to consolidate TiB 2 -AlN- h BN ceramics (TAB) with tunable compositions (h BN ≤ 42 vol%, AlN ≤ 45 vol%). Dense TAB with high relative density, refined grain size and homogeneous microstructure were obtained via spark plasma sintering at 1800 °C and 60 MPa. It was found that exothermic reactions between the reactants could be ignited during heating, and the order of temperature at which the combustion process occurred was just opposite to the sequence of adiabatic temperature for individual reactions. Effects of h BN and AlN amounts on the densification, microstructure, mechanical properties, machinability and electrical resistivity of as-sintered ceramics were comprehensively investigated. Compared to AlN, h BN content played a more obvious role on those properties. As h BN contents increased from 0 to 42 vol%, the flexural strength, fracture toughness, Vickers hardness and modulus of TAB continuously decreased. TAB with h BN amounts ≥ 13 vol% exhibited better machinability with surface roughness lower than 2.9 µm after machining. Nevertheless, their electrical resistivity values at room temperature fluctuated in a narrow range between 43 μΩ·cm and 83 μΩ·cm, irrelevant with the h BN amounts. • TiB 2 -AlN- h BN ceramics with tunable compositions were reactively densified without adding external h BN or AlN at reduced temperature. • Relationships between the adiabatic temperature and the temperature when reactions occurred in the TiN-Al-B system were investigated. • TiB 2 -AlN- h BN ceramics with synergistically improved mechanical, electrical and machinability were achieved. [ABSTRACT FROM AUTHOR]

Designing high-performance ceramic adsorbent with a wide spectrum of properties such as regulatable pore structure, high surface area, ultrahigh organic dye removal efficiency and renewability in an affordable and rational approach is vital for real-life applications. However, integrating all these individual functionalities simultaneously into one bulky material is still challenging. Herein, hierarchical porous ceramic adsorbents with nanofibrous-granular composite structure were proposed via colloidal co-assembly of coal-containing kaolin waste and silicon to resolve the above conflicting demands. Such structure endows the resultant products with satisfactory surface area of 52 m2 g−1, ultrahigh malachite green removal efficiency of 97.6%, outstanding adsorption capacity of 97.6 mg/g, excellent renewability after calcining at 500 °C. Such ceramic adsorbent provides a sustainable and feasible strategy for fabricating water purification materials. [ABSTRACT FROM AUTHOR]

Summary: With the rapid development of electronic industry, the miniaturization and integration of components have become an irreversible development trend, which puts forward high requirements for lead‐free ceramic materials with excellent recoverable energy storage density and efficiency. In addition, it is also a great challenge to sustain excellent energy storage performance under different environmental conditions. In this work, a combined design strategy was proposed to induce polar nano regions and reduce grain size by introducing SrTi0.5Zr0.5O3 (STZ). The addition of STZ reduced the grain size to submicron level, accompanied by relaxation enhancement. The high energy storage properties (Wrec = 1.85 J/cm3, η = 65.92%) were achieved in 0.80Bi0.5Na0.5TiO3‐0.20SrTi0.5Zr0.5O3 (BNT‐STZ) ceramics at 150 kV/cm. Excellent temperature stability (40°C‐160°C) and frequency stability (1‐500 Hz) of energy storage performance have been obtained under 100 kV/cm, with the fluctuations below 8%. Importantly, A high power density of 3.64 MW/cm3 and a transitory discharge time (t0.9 ~ 0.632 μs) were achieved for 0.80BNT‐0.20STZ ceramic under 160 kV/cm. These characteristics indicate that 0.80BNT‐0.20STZ ceramic is expected to be applied in high‐power equipment. Highlights: A combined design strategy was proposed to induce polar nano regions and reduce grain size by introducing STZ.0.80BNT‐0.20STZ ceramic possesses a recoverable energy density of 1.85 J/cm3 and efficiency of 65.92%.0.80BNT‐0.20STZ ceramic exhibits good electrical stability in wide frequency (1‐500 Hz) and temperature range (40‐160°C).A high power density (PD) of 3.64 MW/cm3 and a transitory discharge time (t0.9 ~ 0.632 μs) can be achieved. [ABSTRACT FROM AUTHOR]

Gas-in-liquid foam templating is considered as a promising method for commercial-scale production of porous materials. However, Ostwald ripening occurs frequently during the preparation, which could bring about inhomogeneous bubbles with large sizes and deteriorate the performance of resultant products. To tackle this challenging task, we report a gelation network-triggered morphology-regulation strategy during the foaming process. As an exemplar, boehmite sol was incorporated into the andalusite suspension to stabilize the foam framework. After casting, the wet foam was able to maintain its overall shape, since andalusite particles were anchored onto the gas-liquid interface by the gelation network during mechanical frothing. The samples calcined at 1400°C feature homogeneous bubble with hierarchical porous architecture, smaller pore size with a mean value of 5.32 μm and robust compressive strength of 11.97MPa at a porosity level of 84 %. Our approach substantially broadens the design philosophy of high performance porous ceramics. [ABSTRACT FROM AUTHOR]

Preparation of ultralight ceramic foams via aqueous-based direct foaming method for practical application is a challenging task owing to Ostwald ripening of wet foam and unsatisfied mechanical strength of final products. To tackle these issues, the current work demonstrates the construction of alumina-mullite ceramic foams via gelation-assisted dual-phasic nanoparticle stabilized foams using boehmite sol and nanosilica as the raw materials. The gelation process of boehmite sol inhibits the Ostwald ripening and pore enlargement during drying. The highly active alumina powder derived from boehmite sol and nanosilica enables the reaction by forming mullite at 1200 °C. Consequently, the resultant products demonstrate a compressive of 3.9 MPa at a porosity level of 95.9 %, a bulk density of 0.18 g/cm3 and an ultralow thermal conductivity of 0.1043 W m−1 K−1 after firing at 1200 °C. The current strategy provides new insight for fabricating high-performance ceramic foams for multiple applications. [ABSTRACT FROM AUTHOR]

Compared to samples sintered from directly mixed powders, reactive sintering enables the production of denser ceramic materials with finer grains at even lower temperatures. However, there is a lack of quantitative comparisons between the two sintering approaches in terms of densification mechanisms and grain growth kinetics. In this work, taking two types of TiB 2 -SiC- h BN ceramics sintered from raw powders containing TiB 2 , SiC and h BN (TSB-M) and TiN, Si and B 4 C (TSB-R) as model materials, above mechanisms were quantitatively investigated using spark plasma sintering. Effects of dwell temperature and sintering pressure on the microstructure evolutions, densification kinetics as well as grain growth of TSB-R and TSB-M were thoroughly examined. The densification mechanisms for both samples under different conditions were revealed by calculating the effective stress exponent and apparent activation energy. According to regression coefficients for different grain growth exponents, the dominated growth mechanisms for SiC and TiB 2 grains were also explored. [ABSTRACT FROM AUTHOR]

In this study, novel porous LaPO 4 ceramics possessing closed spherical pores and thin pore walls have been firstly synthesized using the particle-stabilized foaming method. Affected by the calcination temperature together with solid loading, the obtained porous LaPO 4 ceramics exhibit high porosity (81.69–94.21 %), very low thermal conductivity (κ) (0.124–0.398 W m−1 K−1) and relatively high compressive strength (0.886–9.30 MPa). When the calcination temperature and solid loading are 1500 °C and 35 wt%, optimized porous LaPO 4 ceramics achieve a better balance between thermal conductivity (0.160 W m−1 K−1) and compressive strength (2.07 MPa). Based on this, the prediction model for the thermal conductivity is screened and the thermal insulating capability is further verified. This work suggests that porous LaPO 4 ceramics have the potential to be applied as thermal insulation material in the future. [ABSTRACT FROM AUTHOR]

The design and synthesis of new filtration materials for high-temperature particulate matter capture are of both technological and scientific importance but still remain a challenging task. In the current work, we presented an approach for the manufacturing of highly porous SiC cellular ceramics by combining polyether polyol-modified carbon black with polyurethane foaming method. Hydroxyl groups were introduced to the surface of carbon black to prevent agglomeration. As-obtained SiC cellular ceramic possed three-dimensional interconnected reticular architecture with the abundant micron-sized window on its cell wall. The resulting porous SiC ceramic exhibited a high removal efficiency (95.8%) with extremely low pressure drop (38 Pa). The successful fabrication of such fascinating material may provide new insights for high-temperature particulate matter filtration. [ABSTRACT FROM AUTHOR]

Engineering high performance cellular ceramics with both ultralow density and satisfactory compressive strength for practical applications still represents a grand challenge. Herein, alumina-based cellular ceramics bonded by in-situ formed mullite phase were constructed by Al 2 O 3 –Si-boehmite particle-stabilized foams. The gelation of boehmite sol improved the stability and harnessed the deformation of dried Al 2 O 3 –Si composite foam. The oxidation of silicon and further generation of in-situ mullite phase enhanced the chemical bond between alumina particles on cell walls, resulting in the superior mechanical properties. As an exemplar, the resulting cellular ceramic possessed the robust compressive strength of 2.26 MPa at a high porosity of 87.8%. The gelation-assisted Al 2 O 3 –Si particle-stabilized foams provide a facile and convenient strategy for construction of composite ceramic foams with high porosity and robust strength. [ABSTRACT FROM AUTHOR]

Cellular ceramics with 3D network architecture are attracting ever-increasing attention because of their great application potential in multiple fields. Unfortunately, a daunting challenge still remains for fabricating such materials. A novel methodology is provided in the current work to construct cellular ZrO 2 ceramics with such architecture by combining polyurethane foaming and chemical modification technology. Stearic acid grafted ZrO 2 powder with improved dispersibility allows the successful assembly into the polyurethane porous framework. The obtained cellular materials possess a three-dimensional network architecture with windows on the cell wall. The resulting ZrO 2 cellular ceramic with such unique structure exhibits a relatively high porosity (83.5%) and robust compressive strength (13.5 MPa), which outperforms most of the existing ZrO 2 -based counterparts. With above advantages, we envision that as-prepared products are promising for filter applications. [ABSTRACT FROM AUTHOR]

Ultralight ceramics with striking mechanical properties and improved pore connectivity could have wide applications in areas ranging from catalyst support to hot gas filtration. However, creating such materials has proven to be a challenging target. This work demonstrated a novel methodology to prepare porous MgAl 2 O 4 ceramics by calcining gelled MgO–Al 2 O 3 –SiO 2 particle-stabilized foams. The striking green strength of dried foams can be achieved as a consequence of MgO hydration and subsequent formation of gelled Mg(OH) 2 and MgO–SiO 2 –H 2 O skeleton. The decomposition of colloidal substance at elevated temperature resulted in the formation of small pores on the cell wall, thus forming the hierarchical porous architecture and improving the pore connectivity. The highly porous MgAl 2 O 4 ceramics fired at 1600°C possessed the integrated properties of ultrahigh porosity (87.0%), improved pore connectivity and satisfactory compressive strength (7.93 MPa), showing great potential to be used in multiple industrial fields. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Carbamate functional group was grafted onto carbon black surface. • Hierarchical PACs with 3D reticular architectures were fabricated. • PACs showed superior high-temperature particulate matter filtration. Abstract Porous ceramics with high porosity and extensive interconnected pores have great application potential in fields ranging from dye removal to high-temperature particulate matter (PM) capture. However, constructing these materials to achieve efficient filtration is extremely challenging. Herein, a novel strategy to create hierarchical-structured porous alumina ceramics (PACs) with three-dimensional (3D) reticular architecture is reported based on polyurethane (PU) foaming method. To ensure the efficient flow-through filtration, carbamate-grafted carbon black is used as the pore-forming agent and assembled into the porous PU framework. Submicron and micron-sized pores on the cell walls are observed in hierarchical-structured PACs. This unique structure enables a high PM removal efficiency (94.1%) at an ultralow pressure drop (20 Pa). Our work has demonstrated great application potentials of as-prepared PACs as an efficient high-temperature PM filter and provided new insights to develop highly effective filter. [ABSTRACT FROM AUTHOR]

Abstract A facile method for preparation of SiC nanofibrous network reinforced hierarchical structured porous Si 3 N 4 based ceramics via annealing Si-Si 3 N 4 binary particle-stabilized foam in coke bed is reported in this work for the first time. The atmosphere created by coke bed enables the fabrication of Si 3 N 4 based porous ceramics at 1450 °C without using sintering additives. As prepared specimens possess a relative high compressive strength due to the partial oxidation of Si 3 N 4 particles. This novel structure with three levels of hierarchy characterized by flexible SiC nanofibrous network, cell walls and unit cells can be characterized. The vaporization of silicon powder results in formation of Si(g), SiO(g) and allows subsequent generation of SiC nanofibrous network, leading to a considerable number of micro-pores on cell walls simultaneously. As-prepared porous ceramics contained 76.7% porosity and had compressive strength of 10.81 MPa. [ABSTRACT FROM AUTHOR]

We herein report a novel hierarchically porous ceramic foams derived from boehmite gel foams, which possess both high porosity and superior strength. The gel foams show excellent printability due to its predominant stability, high yield stress and storage modulus, which endows such foam material ideal ink for 3D printing lightweight and complex-shape materials via direct ink writing approach. The 3D printed ceramic foams possess programmable architecture assembled by porous filaments, uniform macro-pores with tunable size in the range of 4∼70 μm, as well as nanoscale pores in cell wall, after sintering at relatively low temperature of 1200–1300 °C. In this way, ceramic foams with high strength were achieved, attributed to the tiny grains, large amount of grain boundaries, uniform pores and hierarchical pore structure. Notably, the foams sintered below 1200 °C have significant advantage on specific surface area, which could reach up to 300-400 m2/g. [ABSTRACT FROM AUTHOR]

Constructing high-performance air filters for high-temperature particulate matter (PM) removal is of great importance but remains challenging. Here we demonstrate the ceramic foam-based filters via polyurethane (PU) foaming using diatomite and kaolin powder as the starting materials. Diatomite was grafted by dodecanedioic acid (DA) to improve the dispersity in the PU slurry. The calcined products demonstrated a hierarchical pore structure with multiple well-controlled micron-sized window pores on the cell wall of the sub-micron bubble. The resulting products exhibited a high removal efficiency (96.3%) at a pressure drop of 33 Pa. This research showed that as-prepared ceramic foams can be potentially used as new high-temperature filters for high-temperature PM removal. [ABSTRACT FROM AUTHOR]

The generation of PVA hydrogel through freeze-thaw technique has been utilized innovatively to complete the forming process of porous Si 3 N 4 ceramics in the present work. In comparison with gelcasting method, green body with comparable strength has been achieved by this novel forming process, which is owing to the strong function of PVA gel caused by the freeze-thaw cycles. Herein, Si 3 N 4 hollow spheres are employed as pore-forming agent in order to achieve closed pores. The morphology of green body illustrates that pores originate from both hollow spheres and the space occupied by ice crystals, and the latter gives rise to the increase of porosity around 10%. Studies on the mechanical, dielectric and thermal properties of porous Si 3 N 4 ceramics dependent on freeze-thaw cycle and freezing time have been performed. It is found that porous ceramics treated for freeze-thaw 2 cycles with freezing time of 24 h present excellent properties, which are promising to be applied as radome materials. [ABSTRACT FROM AUTHOR]