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SiCN(Fe) ceramics with excellent electromagnetic wave (EMW) absorption performance were successfully prepared from a preceramic polymer doped with ferrocene. Additive manufacturing (Digital Light Processing), providing enhanced structural design ability, was employed to fabricate samples with complex architectures. During pyrolysis, ferrocene catalyzed the in-situ formation of a large amount of turbostratic carbon, graphite and SiC nanosized phases, which formed carrier channels in the electromagnetic field and increased the conductivity loss. Meanwhile, it also increased the dipole polarization, interface polarization and the dielectric properties of the material, which finally enhanced the EMW absorption capacity of SiCN(Fe) ceramics. When containing 0.5 wt% ferrocene, the material showed good performance with EAB 4.57 GHz at 1.30 mm, and RL min −61.34 dB at 2.22 mm. The RL min of 3D-SiCN-0.5 ceramics was −6 dB, and the RL of the X-band was lower than −4 dB at 2 mm. [ABSTRACT FROM AUTHOR]

The PDCs (polymer-derived ceramics)-SiCN(Ni) fibers with multiple loss mechanisms were prepared by electrospinning. Influenced by the in-situ formed CNTs and Ni 2 Si at the high treatment temperature, the impedance matching performance of fibers was enhanced obviously. In addition, the electromagnetic wave (EMW) absorbing performance was further improved by unique one-dimensional structure of fibers, interfacial polarization, dipole polarization and magnetic loss. Because of good impedance matching and multiple losses, fibers possessed admirable EMW characteristic with strong absorbing ability of the minimum reflection loss (RL) reaching −44.88 dB and the widest effective absorption band (EAB) reaching 4.8 GHz (13.2–18 GHz) at 1.42 mm. Hence, SiCN(Ni) ceramics prepared had a wide application in the field of electromagnetic absorption. [ABSTRACT FROM AUTHOR]

The electromagnetic waves (EMW) absorption properties of SiOC ceramics synthesized by polymer-derived method were investigated, and additive manufacturing was employed to obtain the integration of structure and functions. The presence of free carbon and β-SiC nanocrystallites increased the internal relaxation interfacial polarization, which improved the EMW absorption properties significantly. In particular for the sample pyrolyzed at 1200 °C, the effective absorption bandwidth (EAB, RL<-10 dB) and minimum reflection loss (RL)were 4.9 GHz (at a thickness of 1.58 mm) and -23.5 dB, respectively, indicating the excellent EMW absorption properties of this SiOC material. In addition, we 3D printed two typical porous structures (a log-pile grid and a gyroid) in which the thickness of solid element corresponded to the one providing optimal absorption. Additive Manufacturing of designed structures will enable to improve and further optimize the selection and control of the absorbing material in practical applications. [ABSTRACT FROM AUTHOR]

The SiCN(Fe) fibers with excellent one-dimensional microstructure and electromagnetic wave (EMW) absorption performance were synthesized by combining polymer-derived ceramics (PDCs) method and electrospinning. The in-situ generation of Fe 3 Si and CNTs by adding ferric acetylacetonate (FA) into the raw materials effectively improved the dielectric properties, magnetic properties and the impedance matching performance of the SiCN(Fe) fibers. The EMW absorption performance of SiCN(Fe) fibers were mainly based on dipole polarization loss, interface polarization loss and eddy current loss. The RL min value of SiCN(Fe) fibers reached −47.64 dB at 1.38 mm and the effective absorption band (EAB, RL ≤ −10 dB) reached 4.28 GHz (13.72–18 GHz, 1.35 mm). [ABSTRACT FROM AUTHOR]

The Fe/C/SiCN composite ceramics were synthesized by polymer-derived method to obtain the integration of structure and functions. The electromagnetic waves (EMW) absorption properties at X and Ku bands were investigated. The addition of nano-sized Fe particles improved the magnetic loss and impedance matching, and the carbon nanotubes generated by the iron in-situ catalysis increased the internal relaxation polarization and interfacial polarization, which together improved the EMW absorption properties significantly. In particular, the Fe/C/SiCN-9 showed the optimum reflection loss (RL) of −31.06 dB at 10.03 GHz with an effective absorption bandwidth (EAB, RL < −10 dB) of 3.03 GHz at 2.51 mm, indicating the excellent EMW absorption properties of Fe/C/SiCN composite ceramics. [ABSTRACT FROM AUTHOR]

The PDCs-SiCN(Fe) ceramics with negative permeability and permittivity (double-negative properties) were synthesized by polymer-derived method with ferric acetylacetonate as additive. The phase composition, microstructure, carbon crystalline state and electromagnetic properties of PDCs-SiCN(Fe) ceramics were analyzed. The results indicated that the double-negative properties of PDCs-SiCN(Fe) ceramics were controlled by the amount of Fe. The minimum reflectivity value (RL min) of PDCs-SiCN(Fe) ceramics with 7 wt% Fe reached −54 dB in the double-negative frequency range (13.85–14.15 GHz) with 2 mm (thickness). In addition, the peak of the RL min moved to the low frequency as the thickness increased, indicating the effective absorption band of PDCs-SiCN(Fe) ceramics can be broadened by adjusting the thickness. [ABSTRACT FROM AUTHOR]

The amino-hydroxyapatite (HAP-NH2) was synthesized by grafted amino functional groups onto hydroxyapatite. The uranium adsorption performance of HAP-NH2 was studied under different conditions. The results indicated that HAP-NH2 possessed high adsorption capacity (96 mg g−1), wide pH values range (2-8) and fast adsorption rate (20 min). The adsorption kinetic and adsorption isotherm models of HAP-NH2 revealed that the uranium adsorption process was belonged to chemical adsorption. Furthermore, the main forces between uranium ions and HAP-NH2 were attributed to hydroxyl, amino and phosphorous functional groups. [ABSTRACT FROM AUTHOR]

Carbon-containing polymer-derived SiCN ceramics (PDCs-SiCN-C) were successfully fabricated with multi-layer graphene (MLG) and multiwalled carbon nanotubes (MWCNTs) as additives at 1100 °C. The effects of MLG and MWCNTs on the microwave absorption properties of PDCs-SiCN-C ceramics were analyzed. The imaginary permittivity and loss tangent of SiCN-MLG and SiCN-MWCNTs were about 3.4, 0.67 at 11.2 GHz and 3.1, 0.57 at 10.6 GHz, respectively. The minimum reflection loss of SiCN-MLG and SiCN-MWCNTs at 3 mm was − 54 dB and − 48 dB with the effective absorption bandwidth (RL ≤ −10 dB, >90% absorption) about 1.5 GHz and 0.9 GHz in X-band. [ABSTRACT FROM AUTHOR]

Nickel-containing polymer-derived SiCN ceramics (PDC-SiCN (Ni) ceramics) were prepared with different adding amounts of Ni nanopowders by a polymer-derived method. The compositions, microstructure, electromagnetic (EM) properties and microwave absorption properties of the PDC-SiCN (Ni) ceramics in the 2–18 GHz frequency range were investigated. Results showed that the Ni nanoparticles were distributed in the SiCN amorphous matrix. Moreover, the electromagnetic properties could be tuned by varying the Ni adding amounts. The best absorption properties with a maximum reflection loss (R L ) of − 39 dB at 17.2 GHz was obtained in the PDC-SiCN (Ni) ceramics with 10 wt% adding amount and the effective absorption width (R L < −10 dB) was 1.7 GHz with a thickness of 2 mm. Thus the synergetic effect of both the dielectric and magnetic loss endowed the PDC-SiCN (Ni) ceramics with excellent microwave absorption performance. [ABSTRACT FROM AUTHOR]

PDCs-SiCN(Fe) ceramics were successfully fabricated with different content of ferric acetylacetonate (FA) by polymer-derived method. The effects of FA on the phase composition, microstructure, resistivity, dielectric properties, magnetic properties and microwave absorption properties of PDCs-SiCN(Fe) ceramics in the range of 2–18 GHz were investigated. The samples presented amorphous structure with a few crystalline phases of α-Fe and free carbon in the gaps, which were expected to be good soft magnetic materials. The average real permittivity and imaginary permittivity of PDCs-SiCN(Fe) ceramics with 50 wt% FA was about 14.1 and 5.3 respectively. Furthermore, the PDCs-SiCN(Fe) ceramics with 50 wt% FA addition content showed the broad absorption bandwidth in the 5.1–8.4 GHz with RL ≤ −10 dB (> 90% absorption) at 4 mm. [ABSTRACT FROM AUTHOR]

A series of nickel-containing polymer-derived SiCN ceramics (PDC-SiCN (Ni) ceramics) were successfully prepared from different nickel sources following a polymer-derived method. The scanning electron microscopy (SEM) and transmission electron microscope (TEM) were used to peruse the microstructure of the ceramics. The electromagnetic and microwave absorption properties of PDC-SiCN (Ni) ceramics in the 2–18 GHz range were investigated. Results showed that the Ni nanoparticles in ceramics were dispersed in the amorphous SiCN matrix and the synergetic effect of dielectric and magnetic loss enhanced electromagnetic attenuation of the materials. The optimal reflection loss (R L ) was found for the PDC-SiCN (Ni) ceramics with Ni powders as nickel source, being −78.6 dB at 17.1 GHz when the thickness was 3.5 mm and the bandwidth of RL below −10 dB (90% absorption) was 1.6 GHz. It meant that the PDC-SiCN (Ni) ceramics might exhibit a promising prospect as microwave absorbing materials. [ABSTRACT FROM AUTHOR]

A novel and efficient sorbent: phosphoryl multiwalled carbon nanotubes (PS-MWCNTs) were synthesized by modifying MWCNTs with phosphoryl functional groups. PS-MWCNTs possessed excellent uranium adsorption capacity (194.17 mg g−1) with a wide range of pH values (> 2) and short adsorption equilibrium time (10 min). The isotherm models revealed that the U(VI) adsorption mechanism of PS-MWCNTs mainly belonged to chemical adsorption. Furthermore, the XPS analysis showed that the main forces between uranium ions and PS-MWCNTs were attributed to the phosphoryl functional groups. [ABSTRACT FROM AUTHOR]

The polymer-derived SiCN ceramics were synthesized at different annealing temperature (900 ∼ 1400 °C). The XRD, SEM, FT-IR, Raman and XPS were used to analyze the phase composition and microstructure. The result indicated that the crystallization degree and content of free carbon gradually improved with the increase of annealing temperature. The resistivity, dielectric and microwave absorption properties of the samples were studied at 2 ∼ 18 GHz. The resistivity decreased gradually as the annealing temperature rose. The dielectric constant of sample decreased with the increase of frequency in 1 ∼ 5 MHz. The existence of free carbon could improve the dielectric properties of polymer-derived SiCN ceramics at high frequency. The reflectance of the sample synthesized at 1100 °C was below −10 dB (> 90% absorption) in a wide frequency range of 6 ∼ 16 GHz and the maximum value of dielectric loss angle tangent was about 0.6 at 16 GHz. [ABSTRACT FROM AUTHOR]

The SiCN precursor was prepared by cross-linking process using polysilazane (PSZ) as raw materials. The cross-linking behavior and dielectric properties of SiCN precursor were analyzed. The results indicated that the main reactions during cross-linking process were double bond addition reaction, hydrosilylation reaction, dehydrogenation coupling reaction and transamination reaction. The SiCN precursor was made up of Si-C-N network structure and the main chemical bonds were Si-C, Si-N and C-C. The appropriate cross-linking temperature of SiCN precursor was 600 °C. Furthermore, the increasing content and crystallization degree of free carbon could improve the dielectric properties of SiCN precursor. [ABSTRACT FROM AUTHOR]

The effect of ZrO 2 addition on the mechanical properties of B 4 C ceramics prepared by pressureless sintering was investigated. Submicron B 4 C powders, phenolic resin as binders and submicro-sized ZrO 2 as sintering aids were used. Results show that the addition of ZrO 2 improves the relative density and mechanical properties of B 4 C remarkably. The highest relative density was 96.7%, meanwhile bending strength and Vickers hardness of 365.4 MPa and 34.2 GPa, respectively were measured for specimens added with 15 wt% ZrO 2 and pressureless sintered at 2100 °C for 60 min. [ABSTRACT FROM AUTHOR]

Dy 2 TiO 5 powders were synthesized by molten salt and solid-state methods. The influences of molten medium on phase compositions and microstructures were analyzed. The addition of molten salt lowered significantly the synthesis temperature and resulted in uniform powders. Green bodies compacted from the prepared powders were pressureless sintered at 1600 °C. Sinterability, mechanical properties and neutron absorption performance of the sintered pellets were studied. Results showed that molten salt synthesis resulted in materials with higher fracture toughness and bending strength, excellent hardness and neutron adsorption performance compared to the solid-state process. The neutron absorption rate reached 86.6% for 8 cm thick pellets. [ABSTRACT FROM AUTHOR]

The SiBCN composite fibers with strong electromagnetic wave (EMW) absorption performance were successfully prepared via polymer-derived ceramics (PDCs) and electrospinning methods at relatively lower preparation temperature. The results showed that the in-situ generated free carbon which existed in the matrix in the form of simple substance and was characterized by low crystallinity. The graphite carbon improved the dielectric loss and properties of SiBCN composite fibers. In particular for the SiBCN composite fibers pyrolyzed at 1300 °C, the in-situ generated nano β-SiC crystallization increased the EMW absorption performance significantly. The minimum reflection loss (RL min) of the SiBCN-3 reached − 54.91 dB at 2.35 mm and the effective absorption band (EAB, RL ≤ −10 dB) reached 4.72 GHz (13.28–18 GHz, 1.75 mm). Hence, the SiBCN fibers prepared at relatively lower temperature give good absorption performance and predict a broader application prospect in the field of EMW absorption materials. • SiBCN fibers with excellent EMW absorption performance were successfully prepared. • The in-situ generated free carbon improved the dielectric loss and properties of SiBCN fibers. • The minimum reflection loss (RL min) of SiBCN-3 reached − 54.91 dB at 2.35 mm. • The effective absorption band (EAB, RL ≤ −10 dB) of SiBCN-3 reached 4.72 GHz (13.28–18 GHz) at 1.75 mm. [ABSTRACT FROM AUTHOR]

Porous BN p /Si 3 N 4 ceramics were prepared by gas pressure sintering method as a candidate wave-transparent material. The effects of BN particle additions ranging from 0 wt% to 15 wt% on the phase compositions, microstructures, mechanical performance and dielectric properties were investigated. With the increase of BN content, the apparent porosity of the BN/Si 3 N 4 ceramics increased greatly from 2.3% to 21.2%. Although the mechanical properties were partially weaken, the dielectric performance of the porous BN/Si 3 N 4 was largely enhanced at the same time. For the 10% BN/Si 3 N 4 porous composite ceramics, the permittivity and dielectric loss was 33.5% and 62.2% lower than that of the porous Si 3 N 4 without BN content, respectively. Specifically, when 10% BN particles were added, the porous BN p /Si 3 N 4 has a porosity of 20.5% and the permittivity and dielectric loss were 5.14 and 0.0085 respectively with bending strength of 190.1 MPa and fracture toughness of 4.16 MPa m 1/2 , which can meet the required value of wave transparent materials. [ABSTRACT FROM AUTHOR]

In this paper, the electromagnetic wave (EMW) absorption properties of SiCN ceramics with a shellular structure prepared by 3D printing technology (DLP) at different pyrolysis temperatures were investigated. The research shows that polarization loss and multiple reflections are the principal reasons for the improvement in sample absorption performance. The shellular structure is favorable for the multiple reflections and scattering of electromagnetic wave inside the material. The turbostratic carbon, graphitic carbon and SiC generated by pyrolysis are conducive to improving the dielectric loss of the sample, adjusting its impedance matching performance and improving its absorption performance. The RL min of SiCN-1200 reaches − 21.12 dB (3.22 mm), and the effective band width is 4.20 GHz, covering the whole X-band. The excellent EMW absorption performance of DLP-SiCN ceramics, together with additive manufacturing, enable the integration of material, structure and function within a single component. [ABSTRACT FROM AUTHOR]

Grain boundary resistance is one of the main factors inhibiting the electrical properties of BaZr 0.1 Ce 0.7 Y 0.2 O 3-δ (BZCY) proton conduction electrolytes for solid oxide fuel cells (SOFCs). The Cu-doping strategy is applied to improve the electrical performance of grain boundary by promoting the grain growth and reducing the grain boundary blocking effect. For BaZr 0.1 Ce 0.7 Y 0.2-x Cu x O 3-δ (BZCYCu x , x = 0, 0.025, 0.050, 0.075, 0.100), the largest average grain size is 11.64 μm, which is approximately 5 times that of the BZCY electrolyte without Cu doping (2.13 μm). The optimized electrical performance is 1.64 × 10−2 S cm−1 at 700 °C in moist air, which is twice that of BZCY. This is mainly attributed to the enhanced grain boundary conductivity by appropriate Cu doping, while BZCYCu 0.075 has the highest w / d g (0.733) and a relative low Δ φ (0) (0.201). The anode-supported cell shows a peak power density of 810 mW cm−2 at 700 °C in moist H 2 (as fuels) and ambient air (as oxidants). • Large grain sized BZCY electrolytes (∼11.64 μm) is prepared by Cu doping. • The cleaning effect on grain boundaries reduces the impurity blocking effect. • The optimized electrical conductivity is 1.64 × 10−2 S cm−1 at 700 °C in moist air. • The peak power density reaches 810 mW cm−2 at 700 °C. [ABSTRACT FROM AUTHOR]

SiBCN ceramic materials are widely studied in electromagnetic wave (EMW) absorption. However, their practical application is limited due to the problem of poor impedance matching. In this study, SiBCN (Ni) fibers were successfully prepared by doping magnetic metal Ni, and the absorption properties of the samples were systematically investigated at different high-temperature treatments (1200 °C–1500 °C). The results showed that the doping of Ni contributed to the formation of carbon nanotubes (CNTs), which could enhance the improvement of conductive loss performance. Additionally, the catalytic effect of Ni promoted the formation of various crystals, including Ni 2 Si, β-SiC, Si 3 N 4 , and Si 2 N 2 O, resulting in the presence of multiple heterogeneous interfaces and excellent polarization loss capability. The Ni 2 Si particles acted as magnetic loss units, thereby enhancing the impedance matching of the fibers. Consequently, the SiBCN (Ni) sample prepared at 1300 °C exhibited a minimum reflection loss (RL min) of −21.38 dB and an effective absorption band (EAB) of 3.68 GHz. In addition, SiBCN (Ni) fibers coating proved effective in reducing Radar Cross Section (RCS) signals. Therefore, these findings suggest that SiBCN (Ni) fibers have the potential to serve as EMW absorbers in military radar and satellite communication. [Display omitted] [ABSTRACT FROM AUTHOR]

BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb) as a potential candidate for protonic ceramic fuel cells (PCFCs) electrolytes, often suffers from its high sintering temperature, making it deviate from the stoichiometric ratio and present a poor electrochemical performance than expected. Here, we reported a Ba evaporation inhibition strategy to fabricate stoichiometric BZCYYb electrolyte. By using this strategy, Ba evaporation and Y 2 O 3 /Yb 2 O 3 segregation can be effectively suppressed. The electrolyte's average grain size is ∼5.29 μm, significantly promoting grain growth. An improvement of 60 % in total conductivity is accomplished at 700 °C in humid air, approaching 2.7 × 10−2 S cm−1. By constructing the proton transport model, the reasons for the enhanced electrochemical performance are explained from both bulk and grain boundary. Finally, at 700 °C, an anode-supported single cell with stoichiometric BZCYYb electrolyte demonstrates a maximum power density of 0.65 W cm−2, showing that the barium evaporation inhibition strategy is a powerful tool to fabricate PCFCs with high performance. • Stoichiometric BZCYYb electrolyte is obtained by a Ba evaporation inhibition strategy. • Large grain size (∼5.29 μm) of BZCYYb electrolyte is obtained. • Enhanced electrical conductivity reaches to 2.7 × 10−2 S cm−1 at 700 °C in humid air. [ABSTRACT FROM AUTHOR]

For the sake of enhance the sinter ability and electrical conductivity of BaZr0.1Ce0.7Y0.2O3‐δ (BZCY) electrolytes, a modified aqueous gel‐casting method was applied to synthesize high sintering active and high conductive BZCY nano‐powders. The new approach makes it easy to obtain pure perovskite. The highly sintering active purity‐phase of BZCY nano‐powder (particle size of 50∼100 nm) was obtained by calcining at 1100°C for 2 h. Nano‐powders effectively reduce the sintering densification temperature and successfully prepare BZCY electrolyte with relative density > 96 % at 1450°C, and promote grain growth with an average grain size of 2.36 μm. Benefiting from this, improved electrical conductivities (e.g., 12.4×10−3 S cm−1 at 700°C, in wet air) are obtained. The NiO‐BZCY/BZCY/LSCF‐BZCY anode‐supporting single cell shows a peak power density of 0.75 W cm−2 at 700°C while taking ambient air as oxidants and wet H2 (∼3 vol.% H2O) as fuels. [ABSTRACT FROM AUTHOR]

Dy 2 TiO 5 ceramics with small grain size range of 1.5–3 μm were successfully prepared by microwave sintering method. The phase composition, microstructure, thermal expansion, stability, corrosion resistance and neutron absorption properties of Dy 2 TiO 5 ceramics were investigated. The results show that Dy 2 TiO 5 ceramics possess high mechanical properties due to the small grain size, with a microhardness of 12.26 GPa. The addition of Mo significantly reduces the thermal expansion phenomenon of the sample. The oxide film formed on the surface of the Dy 2 TiO 5 ceramic enhances its excellent corrosion resistance. In addition, the Dy 2 TiO 5 ceramic shows excellent neutron absorption with 87.34% neutron absorption and over 94% thermal neutron absorption in 8 cm thick particles. [ABSTRACT FROM AUTHOR]

The biomass porous carbon (BPC)/polymer-derived composite ceramics with lightweight and efficient electromagnetic waves (EMW) absorbing performance was prepared by using sorghum straw as the absorbing matrix and combining the magnetic precursor acetylacetone nickel (NA) with polysilazane (PSZ). The results showed that when the doped content of NA was 2% and the filler content was 30%, the sample exhibited strong response to EMW. The minimum reflection loss (RL min) reached − 69.44 dB at the thickness of only 1.33 mm, and the effective absorption bandwidth (EAB) at 1.49 mm was 4.27 GHz (13.73–18 GHz). In addition, the RL min at 4.22 m was −45.80 dB at low frequency. The EAB between 4.20 mm and 5 mm remained above 2.4 GHz and the widest reached 2.48 GHz. The in-situ generated Ni 2 Si effectively adjusted the impedance matching of the sample, and jointly regulated the conductivity with graphite carbon. The biomass porous carbon material matrix with large specific surface area, CNTs and Ni 2 Si provided large numbers of heterogeneous interfaces, which promoted interfacial polarization and dipole polarization. In addition, the introduction of Ni endowed magnetic loss, and a variety of loss mechanisms improved the EMW absorbing properties of the Ni/PDCs/BPCs composites. [Display omitted] [ABSTRACT FROM AUTHOR]

Ferreous polymer-derived SiCN ceramics (PDCs-SiCN(Fe)) were successfully synthesized by precursor conversion method. The phase composition and microstructure of the obtained products were investigated by XRD, SEM and TEM. The result indicated a mainly amorphous structure with a few α-Fe,and graphite phases in the gaps. The conductivity, electromagnetic parameters and wave absorbing properties of the prepared ceramics were studied at the frequency band from 2 to 18 GHz. The reflectance of PDCs-SiCN(Fe) was about −10 dB (> 90% absorption) in the range of 4–16 GHz with 25 wt% nano-Fe 2 O 3 addition at the thickness 8 mm. The maximum value of dielectric and magnetic loss angle tangent was about 1.5, indicating PDCs-SiCN(Fe) ceramics possessed good absorption performance. [ABSTRACT FROM AUTHOR]

BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 O 3-δ (BZCYYb), one kind of promising electrolyte materials for proton-conducting solid oxide fuel cells (H+-SOFCs), generally suffers from the poor sinterability, leading to poor electrochemical performances lower than expected. Herein, a facile method, modified room temperature solid-state reaction (M-RTSSR) was proposed for synthesizing highly active BZCYYb nanopowders. Pure perovskite BZCYYb powders can be obtained at a low calcination temperature of 950 °C and a short dwelling time of 3 h. The highly active character allows the sintering temperature of BZCYYb electrolytes decrease from 1550 °C to 1450 °C, thus effectively suppressing the Ba evaporation and promoting the grain growth. The electrical conductivity measured at 700 °C in wet air is 2.6 × 10−2 S cm−1, which mainly benefits from the improvement of grain boundary conductivity. According to the analysis based on space charge layers, the enhanced electrical performance can be ascribed to their lower space charge potential (Δ φ (0)) and higher impurity blocking item (ω/d g). Finally, the anode-supported single cell with such BZCYYb electrolytes reaches a peak power density of 0.54 W cm−2 at 700 °C while taking humid H 2 (∼3 vol% H 2 O) as fuels and ambient air as oxidants. • A facile method is firstly proposed to synthesize highly active BZCYYb nanopowders. • The calcination temperature of pure BZCYYb nanopowders is decreased to 950 °C. • The sintering temperature of densified BZYCCb electrolytes is decreased by 100 °C. • The electrical conductivity of 2.6 × 10−2 S cm−1 at 700 °C in wet air is achieved. • The mechanism of enhanced electrical performances is clarified. [ABSTRACT FROM AUTHOR]

The SiCN/Fe/Ni ceramics codoped with iron acetylacetonate (FA) and nickle acetylacetonate (NA) was synthesized by polymer-derived ceramics (PDCs) method in this study. The microstructure, phase composition and electromagnetic wave (EMW) absorption properties of the samples were analyzed. The polarization loss and conduction loss of materials were analyzed by the direct current (DC) multimeter and the contribution rate of polarization loss was more than 94% in the whole frequency band. The results showed that C, SiC, Fe 2 Si, Ni 3 Si, γ- (Fe, Ni) and CNTs were formed after pyrolysis which provided lots of heterogeneous interface and enhanced the interfacial polarization. Meanwhile, Ni could enter the lattice of Fe and formed a unique electronic configuration, which reinforced the conductivity and stability of Fe. In addition, the in-situ generated Fe 2 Si and Ni 3 Si provided magnetic loss and conduction loss. The RL min value of SiCN/Fe/Ni-3 ceramic was −52.06 dB at 1.54 mm and the effective absorption band (EAB, RL ≤ −10 dB) reached 4.21 GHz (13.79–18 GHz, 1.43 mm). [Display omitted] [ABSTRACT FROM AUTHOR]

By utilizing polymer-derived ceramics (PDCs) method and electrospinning technology, SiCN(Ni) fibers with 1 wt% nickel content at different calcination temperatures (1000–1300 °C) were synthesized. The properties of PDCs-SiCN(Ni) fibers were tested by XRD, SEM, TEM, Raman spectroscopy, XPS and vector network analyzer. The results showed that the addition of nickel acetylacetonate (NA) promoted the in-situ formation of CNTs and Ni 2 Si at high temperatures, which could adjust the impedance matching performance and improve the electromagnetic wave (EMW) absorption properties. The minimum reflection loss (RL) of SiCN(Ni) fibers was −47.55 dB (4.2 mm), and the effective absorption band (EAB, RL ≤ −10 dB) was 3.6 GHz (14.4–18 GHz) under the ultra-thin thickness of 1.24 mm. [ABSTRACT FROM AUTHOR]

La 0·6 Sr 0·4 Co 0·2 Fe 0·8 O 3-δ (LSCF), one kind of state-of-art solid oxide fuel cells (SOFCs) cathodes, often suffers from the chromium poisoning in the operating condition with Cr-based stainless steel interconnects, resulting in deteriorating cell performances. A simple electroless silver plating method was used to modify the surface of LSCF cathodes (named LSCF-Ag), and the anti-chromium stability of LSCF cathodes was studied. After the Cr treatment for 40 h, the polarization resistance (R p) of LSCF cathodes changes from 0.26 Ω cm2 to 0.62 Ω cm2 at 700 °C, while that of LSCF-Ag cathodes shows nearly no change (from 0.24 Ω cm2 to 0.26 Ω cm2 at 700 °C). In LSCF-Ag cathodes, the formation of AgCrO 2 instead of SrCrO 4 avoids the lack of excessive Sr in the A site of LSCF, and AgCrO 2 has an electronic conductivity two orders of magnitude greater than SrCrO 4 , thereby exhibiting significant survivability to Cr. The single cell with LSCF-Ag cathodes after Cr treatment shows a stable peak powder density of 288 mW cm−2 at 700 °C while taking wet hydrogen and air as fuel and oxidizer. As a comparison, the peak power density of single cells with blank LSCF cathodes drops by 12%. It is suggested that the simple electroless silver plating on LSCF cathodes is an effective method to suppress cathode chromium poisoning. [Display omitted] • Ag modified LSCF cathodes are synthesized by the simple electroless plating. • Ag loaded on the LSCF cathode can preferentially react with Cr to form AgCrO 2. • Ag modified LSCF cathodes show excellent resistance and stability to chromium. [ABSTRACT FROM AUTHOR]

Faced with severe electromagnetic wave (EMW) pollution, the development of high-performance EMW absorbers remains a formidable challenge. In this study, SiBCN/Ni fibers containing uniformly dispersed Ni 2 Si nanoparticles were synthesized by electrospinning method with polymer-derived ceramics method, and their electromagnetic properties were evaluated. The low permeability threshold of the fibers ensures sufficient conduction loss effect. The in situ grown Ni 2 Si nanoparticles provide a magnetically coupled network, which is more conducive to obtaining excellent impedance matching. Furthermore, the presence of β-SiC, SiO 2 , and Si 2 N 2 O generates numerous heterogeneous interfaces (e.g., C-SiC and C-Ni 2 Si), leading to enhanced interfacial polarization through the accumulation of charges. As a result, the prepared SiBCN/Ni fibers exhibit impressive EMW absorption properties. At a Ni content of 1 wt%, the effective absorption band (EAB) is 4.32 GHz (13.68–18 GHz). At a Ni content of 1.5 wt%, the minimum reflection loss (RL min) is −52.98 dB, and the sample has excellent radar scattering capabilities, which is verified by CST Microwave Studio simulations. Therefore, SiBCN/Ni fibers are promising as excellent EMW absorbing materials in practical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Polyhedral oligomeric silsesquioxanes (POSS) and γ-glycidoxy propyl trimethoxy silane (KH560) were applied to modify boron nitride (BN) and boron nitride whisker (BNw), and modified BN (m-BN) and modified BNw (m-BNw) were added as thermally conductive fillers to polybenzoxazine (PBz) matrix to synthesize m-BN/m-BNw/PBz composite by hot press. The research results indicate that the modification of BN and BNw and the synergistic effect between m-BN and m-BNw can significantly improve the thermal conductivity of PBz composite. The thermal conductivity of PBz composite with 25 wt % m-BN and 25 wt % m-BNw reached to 1.27 W/mK, which is 35% higher than PBz composite with 50 wt % m-BN (0.94 W/mK), 76% higher than PBz composite with 50 wt % BN (0.72 W/mK), and also display excellent electrical insulation performance. The corresponding dielectric constant (ε) and dielectric loss (tan δ) were 3.83 and 0.0078, respectively. Besides, the Theat-resistance index (THRI) of PBz composite with 25 wt % m-BN and 25 wt % m-BNw is 242.26 °C, and the thermal degradation temperature at 30% weight loss (T30) is 557.72 °C, are higher than PBz matrix (224.46 and 498.88 °C). And the tensile strength of PBz composites with 25 wt % m-BN and 25 wt % m-BNw is 47.71 MPa. [ABSTRACT FROM AUTHOR]

In order to enhance the electrochemical performance of cobalt-free Bi 0.7 Sr 0.3 FeO 3-δ (BSFO) cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs), a composite cathode consisting of BSFO and La 0.8 Sr 0.2 MnO 3-δ (LSM) is developed. The optimized polarization resistance of the composite cathode (0.11 Ω cm2 at 800 °C) is found to be only 61 % that of pure BSFO (0.18 Ω cm2 at 800 °C), indicating a significant improvement in performance. The first-principles calculation indicates that the enhanced electrochemical performance is mainly due to the domain of low oxygen vacancy formation energies of BSFO-LSM-L interfaces (E vac , −3.63 eV) and LSM (E vac , −3.11 eV). The anode-supported single cell of NiO-SDC/SDC/BSFO－LSM shows a peak power density of 825.83 mW cm−2 at 800 °C using wet H 2 (∼3 vol% H 2 O) as fuels and ambient air as oxidants. In addition, the single cell exhibits a good stability at the electric current density 400 mA cm−2 for 50 h measured at 650 °C. • BSFO-LSM composite cathode is developed for IT-SOFCs application. • The polarization resistance of BSFO dramatically decreases by introducing LSM. • The electrochemical property is explained by the first-principles calculation. • The single cell shows a peak power density of 825.83 mW cm−2 at 800 °C. [ABSTRACT FROM AUTHOR]

In this work, novel and efficient SiBCN(Fe) nanofibers were successfully prepared by electrostatic spinning and polymer-derived ceramic (PDCs) methods, and their electromagnetic wave (EMW) absorption properties were investigated after pyrolysis at 1100–1500 °C. Notably, SiBCN(Fe) nanofibers exhibit the best EMW absorption performance after pyrolysis at 1400 °C, with a minimum reflection loss (RL min) of −72.87 dB at 3.6 GHz and an effective absorption bandwidth (EAB, RL≤ −10 dB) of 4.34 GHz at 1.44 mm. Its excellent EMW absorption performance is attributed to its fiber structure, which facilitates the multi-level reflection and scattering of EMW. Meanwhile, the doping of Fe facilitates the in-situ generation of substances such as Fe 3 Si, which can impart SiBCN(Fe) nanofibers with magnetic loss and perfect impedance matching performance. The simulated radar cross-section (RCS) results show that the optimized SiBCN(Fe) nanofibers can effectively achieve the attenuation of EMW in a practical environment. Compared with many previously reported magnetic hybrid composites, SiBCN(Fe) nanofibers exhibit excellent electromagnetic absorption properties with a simpler preparation process, which have the potential to be used as lightweight, ultra-strong radar-absorbing materials. [Display omitted] [ABSTRACT FROM AUTHOR]

The SiC nanotubes were synthesized on porous Si 3 N 4 matrix by polysilazane immersion-pyrolysis. The β-SiC and free C contents increased with the increasing dipping times, which cause some clear vibration and loss peaks of the dielectric constant patterns emerged at around 12.9 GHz and 14.7 GHz in the samples of 20 wt% and 30 wt% benzoic acid, respectively. The reflectivity of the obtained ceramics were −7dB ∼ −10dB from the frequency of 8 GHz–18 GHz, which means that the amount of 80%–90% electromagnetic wave could be attenuated. The ceramics containing 40 wt% benzoic acid showed the high loss, low reflectivity and a wide absorbing band, indicating the high absorbing efficiency and good dielectric properties. Image 1 • The SiC NTs were synthesized. • 80%-90% EMI was attenuated for 10GHz. • The low R values means good absorbing ability. [ABSTRACT FROM AUTHOR]

Abstract Nickel-doped polymer derived SiCN ceramics (PDCs-SiCN (Ni)) were successfully prepared via a polymer-derived method from polysilazane and nickel oxide, and pyrolyzed at 900°C-1400 °C. The effects of pyrolysis temperatures on phase composition, microstructure and microwave absorption properties of PDCs-SiCN (Ni) were investigated. Results showed that the polymer-to-ceramic conversion was completed at around 800 °C. Besides carbon nanotubes were formed in the pore area of SiCN matrix through the catalysis of Ni. The electromagnetic (EM) parameters varied with the different pyrolysis temperatures. When the PDCs-SiCN (Ni) pyrolyzed at 1200 °C, the minimum reflection loss value reached −48.5 dB at 15.1 GHz, exhibiting the best EM wave absorption properties. Highlights • PDCs-SiCN(Ni) were prepared from polysilazane and NiO, and pyrolyzed at 900–1400 °C. • Carbon nanotubes were formed in the SiCN matrix through the catalysis of Ni. Carbon nanotubes could improve ε' values. • The SiCN matrix could reduce agglomeration and oxidation of Ni nanoparticles. • The PDCs-SiCN(Ni) pyrolyzed at 1200 °C exhibited the best wave absorption properties. [ABSTRACT FROM AUTHOR]

Zirconium diboride (ZrB 2 ) powders were synthesized by carbothermal reduction with ZrO 2 , HBO 2 , and carbon black as raw materials. The effects of reaction temperature and HBO 2 content on the phase and morphology of ZrB 2 powders were investigated. The phase composition was characterized by X-ray diffraction (XRD) and the micromorphology was observed by scanning electron microscope (SEM). The thermodynamic reaction process was studied. When the amount of HBO 2 was 60 wt%, pure ZrB 2 powders could be obtained, as indicated by XRD results. Hexagonal ZrB 2 particles ranging from 1 to 2 µm could be successfully prepared at 1600 °C in Ar atmosphere while adding 30 wt% NaCl. [ABSTRACT FROM AUTHOR]

In recent years, electromagnetic wave (EMW) absorbing materials derived from biomass materials have been widely concerned because of their light weight and high efficiency. Here, Ni/PDCs/biomass ceramic composites absorbing material was prepared by a simple suspension impregnation-in-situ reduction carbonization process and polymer-derived ceramics (PDCs) with peanut shell as the absorbing matrix and NiO doped in polysiloxane as the precursor solution. The synergistic effect of Ni/PDCs could effectively adjust the impedance matching of the composite, and the BET results shown that the prepared Ni/PDCs/biomass ceramic composites had a hierarchical porous structure, which could not only provide a large number of heterogeneous interfaces, but also enhance the interface polarization, dipole polarization and multiple reflection loss of the absorbing material. The sample of NPP-1 possessed good EMW absorbing performance when the content of NiO was 1 % and the filler was 50 %, the minimum reflection loss (RL min) reached − 66.38 dB at 1.74 mm, and the effective absorption bandwidth (EAB) was 3.54 GHz (14.46–18 GHz) at 1.45 mm. In this work, the electromagnetic parameters of biomass materials were adjusted by polymer conversion ceramics and metal oxides, which provided another feasible scheme for enhancing the absorbing properties of biomass materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Er 0.2 Bi 0.8 O 1.5 (ESB), the oxide with the best oxygen conduction ability, is introduced to modify the electrical performance of Y 0.16 Zr 0.84 O 1.92 (YSZ) electrolytes for solid oxide fuel cells, and the electrical property and grain boundary conduction mechanism of xESB-YSZ (x = 0, 5, 10, 15, and 20 mol.%) are investigated. The introduction of ESB effectively promotes densification during sintering and improves the electrical performance of YSZ. At the addition of 20 mol.% ESB (20ESB-YSZ), the electrolyte allows a decrease of 500 °C for sintering temperature due to the low melting point of ESB, and ∼4 times higher electrical conductivity (0.093 S cm−1 at 750 °C) than that of YSZ (0.021 S cm−1 at 750 °C) without extra electronic conduction. Basing on the Motte-Schottky model, the enhance electrical performance is mainly attribute to two aspects. One is the lower space charge potential (0.014 V for 20ESB-YSZ, 0.207 V for YSZ), and the other is the higher impurity blocking term (0.97 for 20ESB-YSZ, 0.928 for YSZ). X-ray photoelectron spectroscopy analysis of composite electrolytes reveals that the oxygen vacancies content increase with the increased addition amount of ESB. The 20ESB-YSZ electrolyte-supported single cell with Ag-Sm 0.2 Ce 0.8 O 1.9 as electrodes exhibits a power density of 0.572 W cm−2 at 750 °C. • 20ESB-YSZ exhibits ∼4 times higher electrical conductivities than that of YSZ. • Grain boundary barrier of 20ESB-YSZ is ∼20 times lower than that of YSZ. • The impurity blocking effect of 20ESB-YSZ is reduced. • The electrolyte-supported single cell shows a maximum power density of 0.572 W cm−2 at 750 °C. [ABSTRACT FROM AUTHOR]

This article concerns a hot-press sintered Sialon ceramic using Si 3 N 4 and AlN as raw materials, Y 2 O 3 and La 2 O 3 as additives. The influences of AlN adding amount (5~30 wt.%) on the sintered densification, phase compositions and microstructures are discussed. Results showed that the β-Sialon ceramic could be obtained by hot-press sintering of 95~80 wt.% Si 3 N 4 , 5~20 wt.% AlN and extra 5 wt% Y 2 O 3 -La 2 O 3 additives, while the excess of 25 wt.% AlN would lead to the transformation from β-Sialon to α-phase. The relationships of AlN contents with bending strength and thermal conductivity of the sintered composites were also involved in the study. For the composition of 80 wt.%Si 3 N 4 -20 wt.%AlN, the sintered sample showed the fracture strength of 408 MPa and the highest thermal conductivity of 34 W/(m·K) which is 44.7% higher than that of the sample at an adding AlN content of 5 wt.%. [ABSTRACT FROM AUTHOR]