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Electromagnetic wave (EMW) absorbing materials have excellent potential for various applications in civil engineering and the military. In this study, siliconboron carbonitride (SiBCN) ceramics with excellent EMW absorption capability and oxidation resistance were obtained by adjusting the boron content. The results revealed that the graphite crystallite size in the SiBCN ceramics increased from 3.42 to 3.78 nm, whereas the thickness of the oxide layer decreased from 16.6 to 8.2 μm. The highest electrical conductivity and permittivity for the SiBCN ceramics were obtained when the boron content was 5%. The minimum reflection loss was −35.25 dB at 10.57 GHz and a ceramic thickness of 2.0 mm. At a temperature of 600 °C, the SiBCN ceramic exhibited excellent EMW attenuation ability; particularly, the minimum reflection loss reached −29.18 dB at 9.65 GHz and a ceramic thickness of 2.5 mm. The superior EMW absorption properties of the SiBCN ceramics at high temperatures can be ascribed to the synergistic effect of relaxation and conductivity. The results suggest that boron could enhance the transformation of amorphous carbon into crystalline graphite and increase the number of heterointerfaces and conductive paths. This work provides a method for obtaining SiBCN ceramics with excellent EMW absorption properties.

Polymer-derived SiBCN ceramics (PDCs-SiBCN) are promising ultrahigh-temperature ceramics owing to their excellent high-temperature oxidation resistance and electromagnetic wave (EMW)-absorbing capa...

In this study, a novel phosphate-based adhesive was prepared by using homemade aluminum phosphate as a matrix and by adding different fillers simultaneously. The effects of calcination temperature and filler composition on the bonding mechanism and high-temperature bonding strength of the adhesive for high-temperature alloys were studied. The results indicated that the crystalline transformation of AlPO4 occurred at 500 °C. AlPO4 has two crystalline forms at 500 °C: orthorhombic and hexagonal. The addition of CuO to the fillers resulted in the exchange of Fe and Cu at the substrate interface and enhanced the high-temperature bonding strength of the specimens. The maximum tensile strength of the specimens reached 3.9 MPa at 500 °C. These composites have potential applications in aviation, aerospace, and other fields.

The effect of nano-zirconia addition on the microstructure and properties of corundum castables was studied using corundum, kyanite, alumina powder, gel powder, and nano-ZrO2 as raw materials. The results showed that adding 1.2(wt)% nano-ZrO2 could reduce the median pore diameter of the castables from 480 to 200 nm at 110 °C. After the castables were heated at 1100 °C, the cold modulus of rupture increased by 29.95%, to 24.71 MPa, and the cold compressive strength increased by 50.32%, to 116.37 MPa. The hot modulus of rupture increased by 114.95%, to 3.59 MPa after being treatment at 1500 °C, the high surface energy of nano-ZrO2 can increase the interface energy and bonding strength between adjacent particles.

The work was to develop novel high temperature microwave absorbing material based MgZr4(PO4)6 (MZP) ceramic. The results show that thermal expansion process at higher temperature expand along c-axis while shrink along the a-axis. The conductivity of MZP ceramic was increased by 1000 orders due to the increase in magnesium ion mobility. In addition, the results indicates that the dielectric properties were dependent on temperature at all measured frequencies. The real and imaginary parts of dielectric constant increased from 4.0–5.2 and 0.024 to 0.4, respectively. The reflection loss varied with the change in thickness and the minimum reflection loss value was -26.66 dB at 800℃, suggesting that MZP ceramic was a promising novel high temperature microwave absorbing material.

The effects of in-situ synthesis columnar mullite and pore structure on the hot modulus of rupture (HMOR), thermal shock resistance and corrosion resistance of corundum castables have been investigated in this paper. When 2% nano silica was added, the pore diameters of castables could be decreased to 15 nm (at 110 °C), 1 μm (1100 °C) and 6 μm (1500 °C), respectively. The corresponding reducing magnitude of pore size is 98.5%, 83.3% and 33.3%. The HMOR of castables fired at 1500 °C increased by 110% to 3.64 MPa. Furthermore, after three thermal shock cycles, the residual strength ratio of castables increased from 5.2% to 15.3%. A large amount of cross-distributed columnar mullite was formed between nano silica and α-Al2O3 by the two-dimensional nucleation mechanism, which remarkably enhanced the high temperature properties. The penetration index reduced from 30.86% to 19.88%, suggesting that smaller pore size and higher viscosity had a great influence to the penetration process.

The effect of the particle size (50–325 mesh) and content (0–0.1 wt%) of metallic aluminum powder on the explosive spalling resistance of corundum-based refractory castables were investigated in this study based on air permeability, pore size distribution, heat release, fracture energy and microstructural analyses. The experimental results show that the addition of Al powder significantly improves their explosive spalling resistance. As observed, the explosive spalling resistance of the castables was mainly influenced by the permeability mechanism and the fracture energy. Permeable paths were generated in the microstructure of the sample during the overlapping period between the curing process and the H2 gas forming one, derived from the Al–H2O reaction. The highest permeability level was obtained when 0.075 wt % of Al powder with size of 100 mesh was incorporated into the corundum-based refractory castables. At the same time, the fracture energy of the castable samples was increased accordingly.

In this work, β-Sialon of different morphologies was generated using in situ morphological regulation and simulation. Their effects on the thermo-mechanical properties of Al2O3-C refractories were then investigated. The results indicate that columnar, plate-like, and hexagonal prism β-Sialon were formed from specimens without additives, with Fe2O3 as a catalyst, and with Ni as a catalyst, respectively. Transmission electron microscope (TEM) analysis results confirmed that the three morphologies of β-Sialon grow along with (110), (101), and (100), respectively. Density functional theory (DFT) results show that the addition of catalyst atoms could reduce the adsorption energy of gaseous Al2O on different crystal planes, which promotes the formation of β-Sialon. The formation of three different shapes of β-Sialon gave rise to materials with good mechanical strength. The cold modulus of rupture (CMOR) and cold crushing strength (CCS) of the specimen containing plate-like structure was slightly higher than those with a columnar and hexagonal prism, with maximum CMOR and CCS values of 27.2 MPa and 105.2 MPa, respectively. In addition, good thermal shock resistance was obtained due to the formation of β-Sialon; the residual strength ratio of the specimen with columnar β-Sialon was 78% after five thermal shock cycles, and those with plate-like and hexagonal prism reached 93% and 86%, respectively.

A new organic template, 1,3-cyclohexanedimethanamine (1,3-CDA), is found to be effective in directing the crystallization of ZSM-11 zeolite. Phase transformation from ZSM-11 to ZSM-5 was observed when varying the molar ratios of OH−/SiO2, Na+/SiO2 and SiO2/Al2O3. ZSM-11/ZSM-5 intergrowth zeolites with ZSM-5 contents from 10 to 100% were synthesized. The structural intergrowth was evidenced by TEM, and its formation may be ascribed to the competition between ZSM-11 and ZSM-5 zeolite in the system. The morphology of zeolite varies with the change of composition of the starting gel. The particle sizes of the products decrease with the increase of 1,3-CDA/SiO2 and Na+/SiO2 ratios. With the increase the OH−/SiO2 ratio, the sizes decrease at first and then increase. Meanwhile, the morphologies change from cross-like aggregates of orthotropic rods to aggregates of nano-rods, and then to irregular bulk crystals. With the decrease of SiO2/Al2O3 ratios from 100 to 40, the particle sizes decrease from 200 to about 50 nm, resulting in the formation of nanosized ZSM-11/ZSM-5 intergrowth zeolite.

Iron-containing siliconboron carbonitride (SiBCN) ceramics with multiple heterogeneous interfaces were fabricated using the microstructural design and polymer-derived ceramics (PDC) approach. The characterization results revealed the in-situ generation of nanocrystals, including graphite, belt-like silicon nitride (Si3N4), and silicon carbide (SiC) whiskers, in amorphous SiBCN matrix after annealing. At the same time, these dielectric lossy phases successfully constructed multiple heterogeneous interfaces and three-dimensional network structures. Consequently, the conductivity of the ceramics increased from 4.49 × 10−9 (annealed at 800 °C) to 0.67 × 10−4 S cm−1 (annealed at 1600 °C). The real part of permittivity improved from 4.57–3.36 (annealed at 800 °C) to 10.90–8.38 (annealed at 1600 °C) in the frequency range of 2–18 GHz. The formation of multiple heterogeneous interfaces caused interfacial polarization and increased the multiple relaxations, which ultimately led to a superior microwave absorption property with a minimum reflection loss (RLmin) of −34.28 dB and an effective absorption bandwidth (EAB) of 3.76 GHz (8.64–12.4 GHz).

β-Sialon with whisker-like, columnar, and plate-shaped structures was successfully synthesized with Al2O3–C refractory compositions. In the presence of a catalyst, the preferential growth face of columnar β-Sialon was (100), whereas plate-like β-Sialon preferred (101) and (111). DFT calculations demonstrated that the SiO adsorption energy on the (100), (101), and (111) faces of β-Sialon crystal were –34.95, –52.88, and –45.08 eV, respectively. Therefore, the (101) and (111) faces were more stable in Al-rich β-Sialon. With the increase in catalyst content, the Si-rich Si–Al–O–N liquid phases, which contributed to the generation of columnar β-Sialon, were converted into the Al-rich Al–Si–O–N system that was conducive to the formation of plate-like β-Sialon. Compared to the sample without the catalyst, the CMOR and HMOR of the specimen were increased by 45.07% and 60.47%, respectively, with the addition of Fe2O3. This was attributed to the formation of β-Sialon with a one- or two- dimensional shape.

The exploration of new strategies to fabricate phosphors with tunable luminescence and enhanced thermal stability has been pursued since a long time. In this study, we propose and demonstrate a novel methodology of coating g-C3N4 on phosphors by a vapor deposition method to synthesize core–shell phosphors with tunable luminescence and improved thermal stability. By this method, flaky g-C3N4 can be evenly coated on the surface of the precursors Y2O3:Eu3+,Tb3+ and Y2O3:Eu3+,Tb3+@SiO2 with a thickness of 8 nm. Under the excitation at 368 nm, the CIE coordinates can be adjusted from blue region (0.1713, 0.1887) to white (0.3074, 0.3232) and yellow (0.4565, 0.4703) regions by controlling the amount of g-C3N4. Moreover, the thermal stability of phosphors can be improved by the g-C3N4 coating shell at elevated temperatures due to the isolation of luminescence centers, modification of surface defects, and efficient energy transfer from g-C3N4; the emission intensity of Eu3+ at 398 K improved by 13% after coating with g-C3N4. The above-mentioned effects of g-C3N4 were also proved to work well on the Ca9.5Na2(PO4)7:Eu2+ yellow-green emitting phosphor, indicating that this methodology has general applicability for improving luminescent properties of phosphors.

Bio-inspired self-similar hierarchical honeycombs are multifunctional cellular topologies used for resisting various loadings. However, the crushing behavior under large plastic deformation is still unknown. This paper investigates the in-plane compressive response of selective laser melting (SLM) fabricated hierarchical honeycombs. The effects of hierarchical order, relative density as well as constituent material are evaluated. The results show that at small deformation, the AlSi10Mg alloy hierarchical honeycombs show great advantages over the elastic modulus and compressive strength than 316L steel hierarchical honeycombs. As the relative density and hierarchical order increase, the failure mechanism of AlSi10Mg alloy honeycombs gradually changes from a bending-dominated mode to a fracture-dominated mode, whereas all the 316L steel honeycombs fail due to the distortion of original unit cells. At large deformation, the AlSi10Mg alloy honeycombs behave with brittle responses, while the 316L steel honeycombs exhibit ductile responses, showing a negative Poisson’s ratio behavior and gradient deformation of hierarchical unit cells. The addition of unit cell refinements improves the elastic modulus of AlSi10Mg alloy honeycombs and advances the densification of 316L steel honeycombs. In addition, the effect of constituent material on the compressive response of hierarchical honeycombs has been discussed. This study facilitates the development and future potential application of multifunctional ultra-light sandwich structures.

In this paper, the effects of the matrix pore structure on the strength and corrosion resistance of corundum castables are reported. Pore diameters of castables fired at 110 °C could be decreased from 550 nm to 72 nm when 4% Al2O3-SiO2 gel powder was added. The pore diameter of the castables decreased from 850 nm to 500 nm after firing at 1100 °C, but increased from approximately 2 μm–8 μm after firing at 1500 °C. The strength of castables fired at 1500 °C increased remarkably with the addition of Al2O3-SiO2 gel powder. A maximum cold modulus of rupture (CMOR) of 62.34 MPa was obtained when 4% Al2O3-SiO2 gel powder was added. After slag corrosion, the penetration index fell from 16.6% to 4%, suggesting that a homogeneous pore size distribution and a smaller pore size played an important role in improving the penetration resistance.

β-Sialon bonded Al2O3–C refractories possess high strength and superior thermal shock performance. In this study, the growth of preferred β-Sialon (Si3Al3O3N5) and its effects on thermo-mechanical properties of Al2O3–C refractories were investigated via simulations and experiments. The results indicate that the additive Fe2O3 contributed to the formation of β-Sialon and helped its column structure become plate-like. Transmission electron microscopy confirmed that the (101) crystal plane was a growth plane of plate-like β-Sialon. The growth mechanism of β-Sialon was suggested by density functional theory; calculation results revealed that the key step for the formation and growth of β-Sialon was the adsorption of the gaseous molecule Al2O on the Si3N4 (101) crystal plane. It was found that the existence of Fe atoms could significantly reduce the adsorption energy. Additionally, Al2O3–C refractories containing plate-like β-Sialon possessed a high cold modulus of rupture and crushing strength, which increased by 40% and 15%, respectively, compared with the specimens containing column β-Sialon. It was also found that the formation of plate-like β-Sialon resulted in significantly better thermal shock resistance for the Al2O3–C refractory specimens, and the residual strength loss ratio of the sintered specimens was only 4% after five thermal shock cycles.

One-dimensional La3+-doped mullite of diameter 20–30 nm and length 2–3 μm was prepared by a molten salt method. The electrical properties of La(x)Al(6-x)Si2O13 (x = 0, 0.5%, 1.0%, 2.0%) can be effectively adjusted by the La3+ doping content. The electrical conductivity increased from 1.18 × 10−8 (x = 0) to 2.09 × 10−6 S cm−1 (x = 2.0%). The real part of permittivity was improved from 2.5 (x = 0) to 3.2 (x = 2.0%) in the frequency range 2–18 GHz. The presence of La3+ increased the dielectric loss types and improved the characteristic impedance matching, leading to excellent electromagnetic wave absorption with a minimum reflection loss of −18 dB. First-principles calculations revealed that La doping can decrease the band gap of mullite from 3.677 to 3.541 eV and induce the formation of local dipole moments, which can ultimately improve both the electrical conductivity and the dielectric polarization.

Several phosphate-bonded castables were prepared using corundum as a raw material and 48 wt.% phosphoric acid as a binder. The phase composition, microstructural evolution, and properties of the castables samples were analyzed, and a relationship between the microstructures and properties of the castables was established. The results revealed that the cold modulus of rupture of the specimens increased by 19 % to 33.02 MPa after firing at 1 100 °C when the alumina micropowder content increased from 10 % to 15 %. X-ray diffraction analysis revealed that corundum and AlPO4 were present in the castables fired at both 1 100 °C and 1 500 °C. The intensities of the AlPO4 diffraction peaks increased as the alumina micropowder content and sintering temperature increased. Scanning electron microscopy revealed that AlPO4 was tightly arranged and packed with particles.

Columnar β-Sialon bonding phases were in situ synthesised in Al2O3-C refractory composites and their growth mechanism was simulated based on first-principles calculations. The experimental results indicated that the addition of Fe2O3 as a catalyst accelerated the transformation of Si3N4 to β-Sialon, resulting in a well-developed columnar structure. The (100) facet was the primary surface for crystal growth during the transformation process of Si3N4 into β-Sialon. According to first-principles calculations, the surface energy of the (100) facet decreased greatly due to the substitution of (Si, N) pairs with (Al, O). The catalyst could promote the adsorption of gaseous phases on the (100) facet of Si3N4 and decreased the gas adsorption energy of both SiO and Al2O. Owing to the presence of in situ synthesised columnar β-Sialon bonding phases, the residual crushing strength of Al2O3-C refractory composites after 5 thermal shock cycles increased by 25.1%.

Fe-Mo catalyst with different molar ratios (1:0, 1:0.5, 1:1, 1:2, 1:3) were prepared by chemical co-precipitation method, and they were added to phenolic resin as catalysts. The microstructure and physicochemical properties of catalyst and crystalline carbon after phenolic resin pyrolysis were characterized by XRD, SEM, FT-IR, XPS and TEM. The results showed that the Fe/Mo molar ratio played a significant role in the graphitization of phenolic resin and the morphology of carbon nanotubes. The graphitization of the phenolic resin first increased and then decreased with the addition of Mo. When the Fe/Mo molar ratio was 1:2, the phenolic resin achieved the highest graphitization, and the formed carbon nanotubes had the highest crystallinity. The Fe atoms were in an electron-deficient state due to the electrons transferring from Fe to Mo, which enhanced the hydrocarbon compounds absorption on the surface of catalyst. And Mo was carbonized by carbon atoms to form α-MoC1-x, and then decomposed into β-Mo2C and graphite carbon, obtaining carbon atoms orderly arrangement and carbon nanotubes. Therefore, both the grain size and electron structure of catalyst significantly affect the catalytic properties of Fe-based catalyst.

A study of non-oxide bonding phases formed in situ by adding La2O3 to Al2O3-C refractories, and their influence on the thermo-mechanical properties, is presented. Calculations of the thermodynamics of the Al-Si-O-C-N system were thoroughly explored. Phase assemblage and microstructure were analyzed by means of X-ray diffraction and scanning electron microscopy. The results were that β-Sialon (Si3Al3O3N5) and 15R-Sialon (SiAl4O2N4) formed during sintering at 1400 °C. In addition, the presence of the rare earth oxide, La2O3, promotes columnar β-Sialon formation in a plate-like grain morphology, and this can improve the in situ synthesis of 15R-Sialon. The non-oxide bonding phases give rise to specimens with excellent strength and toughness. Increasing the La2O3 content from 0 wt% to 0.6 wt% enhanced the cold modulus of rupture and the cold crushing strength of the specimens fired from 31.1 MPa to 34.6 MPa, and from 101.3 MPa to 113.8 MPa, respectively. Meanwhile, the displacement was increased by 68% to 0.32 mm. The generation of plate-like β-Sialon and 15R-Sialon also had a positive effect on the hot strength and thermal-shock resistance. The hot modulus of rupture of the specimens fired improved by 21% compared to specimens without La2O3. After three thermal-shock cycles, the residual strength ratios of the specimens fired were above 88%.

The microstructural evolution and comprehensive properties of alumina refractory bonded with calcium aluminate cement and silica sol have been studied. Results have been correlated with the microstructural and phase evolutions using X-ray diffraction and scanning electron microscopy, as function of the pre-formed spinel powders. Matrix samples were obtained for phase and microstructural characterization in details, and the results were compared with those corresponding to the refractory castables. The room temperature and high temperature properties, including permanent of linear change, mechanical properties, hot modulus of rupture (HMOR) and slag resistance were measured. The castables exhibited a microstructural optimization and properties enhancement due to the addition of pre-formed spinel. A lot of secondary spinel and CA6 (CaO·6Al2O3) with small size were produced in the castables, and the contents of micro pores were greatly increased. As a result, the permanent of linear change of castables was decreased by 61%, while cold modulus of rupture (CMOR) and HMOR were increased more than 45% and 100%, respectively. The penetration indexes in the static slag resistance were decreased from 28.8% to 12.2%.

A novel nano-β-FeOOH/Fe3O4/biochar composite with enhanced photocatalytic performance and superparamagnetism was successfully fabricated via an environmentally friendly one-step method. The structural properties of the prepared composite were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and a vibrating sample magnetometer. The XPS spectrum of the as-prepared composites confirmed the presence of Fe-O-C bonds between β-FeOOH and biochar, which could be conducive to transfer photo-generated electrons. UV-vis spectroscopy confirmed the existence of an electron–hole connection between β-FeOOH and biochar, which promoted the rapid interface transfer of photogenerated electrons from β-FeOOH to biochar. These novel structures could enhance the response of biochar to accelerate the photoelectrons under visible light for more free radicals. Electron spin resonance analysis and free radical quenching experiments showed that •OH was the primary active species in the photodegradation process of methyl orange by nano-β-FeOOH/Fe3O4/biochar. In the synergistic photocatalytic system, β-FeOOH/Fe3O4/biochar exhibited excellent catalytic activity for the degradation of azo dye (methyl orange), which is 2.03 times higher than that of the original biochar, while the surface area decreased from 1424.82 to 790.66 m2·g−1. Furthermore, β-FeOOH/Fe3O4/biochar maintained a stable structure and at least 98% catalytic activity after reuse, and it was easy to separate due to its superparamagnetism. This work highlights the enhanced photocatalytic performance of β-FeOOH/Fe3O4/biochar material, which can be used in azo dye wastewater treatment.

This paper experimentally studied the dynamic mechanical and energy absorption responses of three types of samples: single-layer hexagonal aluminum honeycomb, and combined hexagonal aluminum honeycombs at two stacking angles (0° and 90°). The combined honeycombs are composed of two-layered and non-partitioned honeycombs. Dynamic experiments were conducted using a high-pressure gas-gun testing system at impact velocities of 30–70 m/s. Results showed that dynamic response of combined honeycombs mainly included cutting and buckling processes. The cutting plateau stress increased at a higher rate increased with impact velocity, but reached a lower final value in the 0°-layered honeycombs than in the 90°-layered honeycombs. The buckling plateau stress of the two combined honeycombs were almost equal, and approximately 1.5–2 times of their quasi-static values. Besides, a dimensionally consistent empirical formula was proposed to describe the effects of the honeycomb density and strain rate on the plateau stresses. It concluded that the energy absorption capacity was highest in the 90°-layered honeycombs and lowest in the single-layer honeycomb. Finally, the energy absorption mechanisms of the two combined honeycombs were discussed.

Limited studies were reported about energy absorption characteristics of combined honeycombs subjected to uniformly distributed explosive loading in air. In this paper, the cutting strain of the combined honeycomb core considering the effects of core diameter, explosive charge mass and scaled distance was first investigated through air explosion experiments. A full-scale finite element (FE) model and a homogenization method were then proposed and verified by comparing the numerical solutions with the experimental results. Based on the FE model, the individual effects of the peak overpressure and positive impulse on the cutting performance were revealed. The experimental results demonstrated that either a decreasing scaled distance or an increasing charge mass resulted in a larger cutting strain. The numerical solutions indicated that similar changing tendencies to cutting strain were observed for the cutting plateau stress and energy absorbed by the combined honeycomb. Based on the dimensional analyses, a semi-empirical formula was proposed for predicting the relationship between the absorbed energy and cutting plateau stress. In addition, a deformation mode map was developed. The map plotted the peak overpressure vs. the impulse and identified the dominant deformation mode for each application point in this space. The map can be used in combination with the semi-empirical formula, and then the cutting performance of the combined honeycomb can be determined easily and quickly.

ATS-type zeolite is used to be known as aluminophosphate or borosilicate. Its aluminosilicate analog was supposed to be a promising solid acid material, which is still of great challenges to synthesize directly. Herein, we report a new zeolite, SCM-39, as the first directly synthesized ATS aluminosilicate, using commercially available 4-pyrrolidinopyridine as OSDA. SCM-39 exhibits great hydrothermal stability and possesses a large amount of acid sites. In comparison with MOR zeolite, it showed better catalytic performances in the disproportionation of toluene and self-condensation of cyclohexanone.

Effects of laser shock peening (LSP) treatment on the creep properties and microstructural evolution of the surface of 7075 aluminum alloy were investigated in this work. The microstructures of the LSP-treated and untreated specimens before creep were characterized by transmission electron microscopy (TEM) and scanning electron microscope (SEM). Creep rupture was then investigated. After creep, electron backscatter diffraction (EBSD) was conducted to analyze the peaks of the misorientation angle for the as-machined and LSP-treated samples. SEM was performed to observe the fracture surface. Above results proved that LSP could enhance the steady-stage creep life by 97% at 350 MPa/200 °C, 307% at 350 MPa/200 °C, and 120% at 300 MPa/200 °C. The mechanism for the improved creep properties of 7075 aluminum alloy by LSP was analyzed by TEM observation. Moreover, the creep process and mechanism of the variation of their microstructures were discussed. LSP had a beneficial effect on the improvement of surface microstructure comprised of the increase of dislocation density and the refinement of dispersoids, which would hinder the dislocation movement, decrease the growth of tensile texture and cracks and lower the creep rate. So LSP can effectively enhance the creep resistance of 7075 aluminum at the elevated temperature and working stress.

In this paper, submicron spinel-containing calcium aluminate (SP-CA) cements were prepared at temperatures of 1200 °C (RA12), 1300 °C (RA13), and 1450 °C (RA14) using reactive alumina, magnesium hydroxide, and calcium carbonate as raw materials. The microstructural characteristics and high temperature properties of refractory castables bonded by SP-CA cement were investigated. The results indicated that the mineralogical compositions of SP-CA were spinel (MgAl 2 O 4 , MA) and CaAl 2 O 4 (CA). The spinel phases presented no definite borders or shapes, with average size ranging from 0.1 μm to 1.2 µm at different sintering temperatures. After heating alumina-spinel castables, the submicron spinel particles bonded with corundum and hibonite (CA 6 ) grains could strengthen the castable body. However, the large sized ( '''' of castable RA12 was 39.7 m, which is significantly higher than that of castable AS (19.8 m). The corrosion rate of castable RA12 was 5 mm 2 /min, which is significantly lower than that of castable AS (7.4 mm 2 /min). Small pore size and submicron spinel played relevant roles in corrosion behavior.

NiCoCrAlYSi coatings were prepared on the surface of nickel-based high-temperature alloys (Inconel 625) by laser cladding (LC) technique, and then the surface was modified by high current pulsed electron beam (HCPEB). The microstructural results indicate that metallurgical defects on the original surface, including micropores and elemental segregations were eliminated, and a remelted layer consisting of high density of cross slips and nanostructures was obtained. High-temperature oxidation resistance at 900 °C, 1000 °C and 1100 °C of the original coatings was investigated. When oxidized at 900 °C for 100 h, the original coating followed the linear growth law, and the TGO was mainly consisted of Al2O3. When oxidized at 1000 °C and 1100 °C for 100 h, the original coating followed the parabola law, and the TGO existed in a double-layer structure. After HCPEB irradiation, a rather stable, continuous, and slow-growing α-Al2O3 was formed on the surface after oxidation for 100 h at 1100 °C. The kinetic curves show that the growth rate of the TGO of the irradiated coatings was reduced by 43.9%, and the thickness was effectively decreased compared with the original sample. Thus, HCPEB technique is proved to be an effective method to improve the service life of laser cladding coatings.

Surface traveling waves (STWs) contribute greatly to non-specular scattering, but their scattering and attenuation characteristics in an absorbing coating are unclear. Thus, the scattering peak angular location and the electromagnetic (EM) loss of the STWs are calculated. The results show that the thickness of an absorbing coating should be appropriate to achieve a large EM loss in wide frequency bandwidth, and the magnetic loss is dominant in the attenuation constant. Moreover, radar cross section (RCS) features of the STW and the effect of EM parameters’ imaginary part on the RCS reduction of the STW at 6 GHz were investigated. The simulated results show that the wedge model can effectively excite the STW. Meanwhile, the permeability μ″ of the coating material has a more significant influence on the RCS reduction of the STW than the permittivity ɛ″. Furthermore, the simulated results were verified by the experimental results with an error of less than 20%.

Self-similar hierarchical honeycombs with complicated cellular topologies are promising cores for lightweight sandwich structures ascribed to superior structural efficiency in terms of mitigating damage. In this paper, the in-plane compressive characteristics of AlSi10Mg alloy hierarchical honeycombs, fabricated using Selective Laser Melting (SLM) methodology, under large deformation are reported. The results suggest that higher hierarchies enhance the elastic modulus of honeycombs significantly, whereas the compressive strength is improved negligibly. There is a failure mechanism transition from cell wall bending dominated to cell wall fracture dominated with the increase of relative density and hierarchical order, and the failure mechanisms are related to the wall thickness with critical value of 0.345 mm. It is concluded that the in-plane failure of hierarchical honeycombs is dominated by the bending, axial compression and shear deformation of original unit cell walls. Besides, the parent material without heat treatment contributes to more excellent mechanical properties of hierarchical honeycombs owing to higher tensile strength and elastic modulus. This work enables to facilitate the structural design and optimization of high-performance hierarchical honeycomb metamaterials with desired properties and functions.

Two series of experiments were conducted with different dimension and different masses of explosive. The failure processes of the side plate were recorded by using high-speed photography system. Damage features of the experimental results were analyzed. The results show that the damage degree increases with the increasing of TNT mass. In larger TNT mass cases, cracks produce in both the edge and the central of side plate, and some plates may eject out with relatively high launch velocity which are destructive to the adjacent cabins. During the deformation process, the edge and corner area of side plate may produce large deformation due to the intensified internal shock waves which is different from external explosion. Meanwhile, a number of numerical simulations were carried out by using the validated numerical method. Through analyzing the numerical and experimental results, three damage forms of cross-shaped damage, curve-shaped damage and sphere-shaped were observed. In cross-shaped damage form, six failure modes were concluded: plastic deformation (mode I); petalling in plates center (mode II* C ); Capping in plates center (mode II C ); corner shear failure (mode III in ); edge tearing (mode II); and shear failure over entire plate (mode III). In addition, the failure process and mechanisms of each mode were also analyzed.

The microstructure evolution and properties of Al 2 O 3 –SiC–C refractories with different Fe 2 O 3 content (0, 0.5, 1.0 wt%) heat-treated at 1400 °C were investigated. Also, the in-situ growth mechanism of diamond-shaped mullite platelets was discussed. The experimental results indicate that there were only mullite and SiC whiskers formed in the absence of the additive. However, both whisker-shaped and diamond-shaped mullite phases could be generated aside from SiC whiskers, which were satisfactorily correlated with Fe 2 O 3 addition. Interestingly, the introduction of Fe 2 O 3 changed the morphology of mullite whiskers from the curved structure (without additive) to the straight and elongated shape (with additive). Furthermore, these two-dimensional mullite platelets were better developed resulting in the larger size and higher yield with 1.0 wt% Fe 2 O 3 . XRD, SEM, TEM and HRTEM analyses reveal that with the addition of Fe 2 O 3 , mullite phases in refractory samples grew preferentially toward the crystal facets along (130) and (4 2 − 0) directions of mullite nanocrystals, thus, a diamond-shaped structure was generated. As the well-developed mullite platelets were formed, the cold modulus of rupture (CMOR) and the cold crushing strength (CCS) increased from 6.5 MPa to 10.3 MPa and from 38.7 MPa to 55.7 MPa, respectively. Meanwhile, after three thermal shock cycles, the CCS of samples containing 1.0 wt% Fe 2 O 3 only decreased by 2.6 MPa, and the residual strength ratio of CCS (CCSst) reached the maximum value of 95.3%. These results suggest that the in situ synthesized platelet-shaped mullite phase observably improved the thermal shock resistance of Al 2 O 3 –SiC–C refractories.

In this paper, using industrial alumina, calcined magnesite, ground calcium carbonate as raw materials, spinel-containing calcium aluminate cements (CMA) were prepared at 1500 °C with different calcine holding times (3 h and 6 h). The mineral composition and microstructural characteristics of prepared cement samples were studied using X-ray diffraction and scanning electron microscopy, and their hydration and rheological behavior were also investigated. The results indicated that increasing holding time can promote growth of CaAl2O4 grains and reduce setting time. The hydration mechanism of CMA follows the nucleation and crystal growth–diffusion (NG–D) process, and the hydration rate of CMA–3 h in the acceleratory period is higher than that of CMA–6 h, but there is no significant distinction in deceleration and stabilization periods. The slowdown of hydration rate directly affects the rheological behavior of CMA slurry, leading to decrease in yield stress, and thixotropic character. Also, the storage modulus (G') growth rate of CMA–3 h slurry is significantly higher than for CMA–6 h slurry, indicating the CMA synthesized at 1500 °C for 6 h possesses lower hydration activity.

Electromagnetic field (EMF) can promote the reaction between the Fe/Mn ion in slag and MgO-C refractories to form Mn-doped MgFe2O4 spinel. In order to further study the morphology and characteristics of Mn-doped MgFe2O4 spinel, the experiments were respectively carried out in medium-frequency induction furnace and resistance furnace. MgO-C refractories containing 6 wt.% carbon and iron-rich slag containing 53.62 wt.% Fe2O3 were used. The results show that the penetration layer in the slag line under EMF is obvious and the reduced Fe from FexO is distributed homogeneously in this layer. However in the resistance furnace having no EMF, there is not MgFe2O4 spinel but MgAl2O4 spinel formed. The iron content in Mn-doped MgFe2O4 spinels decrease dramatically from the erosion layer to penetration layer, while the manganese content in the spinel remains unchangeable.

Researchers are currently shifting their focus towards the synthesis of zeolites using new commercially available organic structure-directing agents (OSDA). Herein, we report for the first time the preparation of ITH-type zeolite with 2-(aminomethyl)-1-ethylpyrrolidine (AMEP), a simple and commercially available nonquaternary ammonium derivative of pyrrolidine. This work also explores the effects of various synthesis parameters on the product, which is key in the synthesis of a highly crystalline ITH-type zeolite in a wide range of Si/Ge molar ratios. Multiple techniques (XRD, SEM, FTIR, solid-state NMR and N2 physisorption) have been adopted to characterize the ITH-type zeolites with different Ge contents. Si and Ge elements are present in the different crystallographic positions. Particularly, Ge atoms preferentially occupy the double-four-ring (D4R) units. The ITH-type zeolites are characterized by high surface area and micropore volume. They are hydrothermally stable towards 700 °C 90% steam heating without significant loss of crystallinity and microporosity. Also, ITH-type zeolites demonstrate high cyclohexanone conversion, selectivity for the main product e-caprolactone and cycle use stability in the Baeyer–Villiger oxidation of cyclohexanone. Collectively, these features imply a wide application prospect of ITH-type zeolites in the conversion of ketones into valuable esters and lactones. This contribution presents a facile and low-cost synthesis of hydrothermally stable ITH-type zeolite and opens avenue to develop nonquaternary ammonium pyrrolidine derivatives as a novel OSDA family.

The Al 2 O 3 –SiC–C refractory samples were prepared from raw materials of calcined bauxite, brown fused alumina, tabular alumina, flake graphite, silicon carbide and metallic Si powders. The Fe 2 O 3 powders were used as additive and the phenolic resin was applied as binder. The effects of calcination temperature on microstructural evolution and thermo-mechanical properties of the samples had been studied. Thermodynamic calculation of Al–Si–O–C systems shows that both mullite and SiC were as equilibrium phases after coking at elevated temperatures. The experimental results indicate that the mullite whiskers with large aspect ratio were formed after fired at 1000 °C in a coke bed. When the temperature was raised to 1400 °C, a new phase of SiC whiskers was formed in addition to the mullite whiskers. Morever, a large number of the mullite platelets with diamond shape were generated. The property tests show that as the firing temperature rose from 1000 °C to 1400 °C, the value of cold modulus of rupture (CMOR) was increased by 57.1% to 8.2 MPa, and the cold crushing strength (CCS) was raised from 47.5 MPa to 54.8 MPa; also, the flexural modulus (FM) and load displacement were almost 30% and 20% increased respectively. It is also found that the hot modulus of rupture (HMOR) measured at 1400 °C reached the maximum value of 8.1 MPa after firing at 1000 °C. Furthermore, after three thermal shock cycles, the residual strength ratio of samples after cured at 200 °C was only 47.5% while the value rose to 96.4% after fired at 1400 °C. It is believed that the substantial enhancement in the thermo-mechanical properties of Al 2 O 3 –SiC–C refractory samples under room and elevated temperatures could be attributed to the synergistic effect of in-situ formed SiC whiskers, mullite whiskers and diamond-shaped mullite with plane structure.

In this paper, the alumina-based refractory castables were prepared using calcium aluminate cement (CAC) as binder. The phase composition and microstructural evolution of the castable samples during the heating process were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA), and thermal expansion analysis. The relationship between the microstructural characteristics of castables and the properties of elastic modulus was investigated. The results showed that, after the castables were cured at room temperature for 24 h and dried at 110 °C for 24 h, the main phases present after hydration were Al 2 O 3 , C 3 AH 6 , and AH 3 . C 3 AH 6 and AH 3 would be transformed into C 12 A 7 and AlO(OH) or Al 2 O 3 , as temperature increased from 110 °C to 800 °C, the microcrack caused by decomposition of the hydrates will led to the lower values of both the elastic modulus and strength of the castable samples. From 900 °C to 1000 °C, CA was recrystallized through the reaction between C 12 A 7 and A, resulting in an increase in elastic modulus and strength. Between 1100 °C and 1200 °C, CA 2 would be formed, which resulted in a volume expansion of the material and a slight increase in elastic modulus. Finally, the CA 6 phase was formed as the temperature increased to 1400 °C. The enhancement of the strength and elastic modulus of the castable samples could be attributed to their strong interlocking bonds between platelet CA 6 and matrix particles at high temperature.

The influence of the addition of Ni(NO3)2 · 6H2O on the microstructure and mechanical properties of low-carbon MgO–C refractory composites was investigated. The results indicated that MgO whiskers and carbon nanotubes could be generated in low-carbon MgO–C refractory composites with Ni(NO3)2 · 6H2O in a reducing atmosphere at 1 200 °C. The magnitudes of the cold crushing strength, the cold modulus of rupture, the fracture displacement, and the residual cold crushing strength are increased by 47 %, 66 %, 8 % and 26 %, respectively. The MgO–C refractory composites with the addition of 0.6 wt.% Ni(NO3)2 · 6H2O result in better overall properties. The MgO whiskers were generated via a dissolution–diffusion–precipitation mechanism, and their growth is in accordance with the vapour–liquid–solid model.

A series of high alumina refractory castables were prepared via casting with tabular alumina aggregates (0.088 – 5 mm), fine powders, and calcium aluminate cement as starting materials. The effect of the median diameter of alumina (D50 = 7.26 μm, 5.33 μm, 2.37 μm) on the thermo-mechanical properties of the refractory castables was investigated. The results indicate that the decrease in the alumina particle size from 7.26 μm to 2.37 μm has little influence on both the apparent porosity and bulk density of castables. However, the median pore size of castables fired after 1 600 °C decreased drastically from 4.7 μm to 2.4 μm correspondingly, which led to significant growth in the strength and thermal shock resistance of castables. The cold modulus of rupture and crushing strength were increased by 201 % and 120 %, respectively. At the same time, the hot modulus of rupture and elastic modulus were also increased by 143 % and 127 %, respectively. The residual elastic modulus was enhanced twice after three thermal cycles.

This research studied the effects of several dispersants on the morphologies of cement hydrates and properties of refractory castables. The results showed that the cement hydrate morphologies were closely related to the types of dispersants used. With naphthalene sulfonate formaldehyde condensate (FDN) and sodium tripolyphosphate (STPP) as dispersants, the cement hydrate of C 3 AH 6 obtained anomalistic shapes, and the AH 3 particles showed a diameter of not more than 1 μm. When propionic acid (PA) was added, C 3 AH 6 formed inerratic cubical grains, whereas AH 3 changed from particles to long column agglomerates; the ratio of the long radius increased with increasing PA concentrations. The addition of PA as dispersant generated CaCH 3 CH 2 CO 2 + , which resulted in a decrease in Ca 2+ concentration. Also, the relatively higher apparent porosity satisfied the space requirement for the growth of C 3 AH 6 , eventually resulting in larger inerratic cubical grains. The H + hydrolyzed from PA accelerated the growth on the (100) and (110) crystal planes of AH 3 ; thus, gibbsite stretched along the c -axis. The maximum values of CCS and CMOR for refractory castables prepared with PA as dispersant were 5.6 MPa and 46.6 MPa, respectively, which were higher than those for refractory castables with FDN and STPP. The observed excellent performance in strength might be related to the bridging effect resulting from the long-column AH 3 .

Combined aluminium honeycomb has been considered a promising structure in the protection field due to its excellent energy absorption capacity. To improve its application, it is crucial to understand the mechanical behaviour of combined honeycomb under explosion. Here, we examined the compression characteristics of combined honeycomb structure under explosion experimentally and through simulations. The effect of parameters, i.e. explosive scaled distance and slider thickness on compression depth and normalized compression stress were examined. Results showed that the energy absorption and compression strain decreased with the slider thickness and scaled distance. The normalized compression stress of the cutting stage remained unchanged and not sensitive to the slider thickness and scaled distance. Compared with other conventional honeycomb structures, the combined honeycomb structure exhibited promising application prospects in linear energy absorption structures. In addition, a semi-empirical formula was proposed to calculate the compression depth of two stack-up combined honeycomb, in which structural parameters and mechanics properties of the base material were considered. The predicted results were in good agreement with the experimental results.

The &ldquo, HOPE-I&rdquo, type high-current pulsed electron beam (HCPEB) equipment was used to irradiate the pure aluminum material with Zr coating preset by ball milling to realize the alloying of a Zr&ndash, Al coating surface. The microstructure and phase analysis were conducted by XRD, SEM, and TEM. The experimental results show that after Zr alloying on the Al surface by HCPEB, a layer of 15 &mu, m was formed on the surface of the sample, which was mainly composed of Zr and Al&ndash, Zr intermetallic compounds. A large number of Al3Zr (Ll2) particles was uniformly distributed in the alloyed layer, and the Al grains were obviously refined. In addition, the surface hardness and corrosion resistance of the samples were improved significantly after HCPEB irradiation.

MgZr4(PO4)6 (MZP) with Ce-doped content of 0%, 1%, 3% and 5% was synthesized by solid state reaction. The results showed that the oxygen octahedron would contract along the a-axis and expand along the b-axis and c-axis with Ce doping content increase. The electrical conductivity of MZP measured by impedance spectroscopy showed that Ce doping could enhance ionic conductivity of MZP from σ = 1.063 × 10−8 to 1.16 × 10−7 S/cm due to the bottleneck phenomenon in the magnesium ion migration channel. Moreover, the complex dielectric constant of MZP was measured by network analyzer, and the results showed that the real part of the permittivity increased from 3.2 to 4.1 in a frequency range of 2.0–18.0 GHz. The lowest reflection loss was −8 dB at 15.4 GHz when the doping content reaches 5%, which indicated that MZP was promising as a novel microwave absorbing material.

The quasi-static tests are conducted on three types of energy-absorption combined hexagonal aluminium honeycomb structures, i.e. traditional single-layer honeycomb, two-layer combined honeycombs at the stacking angles of 0° and 90°, and four-layer combined honeycombs to investigate the cutting properties at different stacking angles of combined honeycombs. The effects of stacking angles are discussed and the cutting mechanism between combined honeycombs is analyzed. It reports that the cutting stress of 90°-stacking honeycombs is 30% larger than that of 0°-stacking honeycombs. The absorbed energy of the cutting process accounts for about 30% of the total strain energy of honeycombs. The deformation sequence of different four-layer combined honeycombs can be controlled based on the difference of cutting stress at the stacking angles of 0° and 90°. Besides, a simplified theoretical model is proposed to obtain the relationship between the cutting stress and stacking angles, which is consistent with the experimental measurements.

The effect of colloidal silica (CS) on the hydrate phases and microstructure evolution of calcium aluminate cement (CAC) was investigated. Samples hydrated with CS were obtained and characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared spectroscopy (FT-IR), hydration heat measurement and Nuclear Magnetic Resonance (NMR). The results revealed that SiO2 nanoparticles may affect the hydrates crystallization process. There was a compact structure in the CAC paste with CS, while petal-shaped hydrates with a porous structure were formed in the pure CAC paste. The maximum value of electrical conductivity for CAC paste with CS suggested that the early stage of hydration for CAC was accelerated. However, the hydration heat curves revealed that the late stage of the CAC hydration process was inhibited, and the hydration degree was reduced, this result was in accordance with Thermogravimetry-Differential scanning calorimetry(TG-DSC) curves. The fitting results of hydration heat curves further showed that the hydration degree at NG (nucleation and crystal growth) process stage was promoted, while it was limited at the phase boundaries stage, and the diffusion stage in the hydration reaction was brought forward due to the addition of CS. According to these results and analyses, the differences in the hydration process for CAC with and without CS can be attributed to the distribution and nucleation effect of SiO2 nanoparticles.

Selective catalytic reduction of NOx with NH3 is one of the most widely used technologies in denitration. Vanadium-based catalysts have been extensively studied for the deNOx process. V2O5/WO3(MoO3)TiO2 as a commercial catalyst has excellent catalytic activity in the medium temperature range. However, it has usually faced several problems in practical industrial applications, including narrow windows of operation temperatures, and the deactivation of catalysts. The modification of vanadium-based catalysts will be the focus in future research. In this paper, the chemical composition of vanadium-based catalysts, catalytic mechanism, the broadening of the temperature range, and the improvement of erosion resistance are reviewed. Furthermore, the effects of four major systems of copper, iron, cerium and manganese on the modification of vanadium-based catalysts are introduced and analyzed. It is worth noting that the addition of modified elements as promoters has greatly improved the catalytic performance. They can enhance the surface acidity, which leads to the increasing adsorption capacity of NH3. Surface defects and oxygen vacancies have also been increased, resulting in more active sites. Finally, the future development of vanadium-based catalysts for denitration is prospected. It is indicated that the main purpose for the research of vanadium-based modification will help to obtain safe, environmentally friendly, efficient, and economical catalysts.

Transplant rejection is the key problem in organ transplantation and, in clinic, immunosuppressive agents such as tacrolimus are directly administered to the recipients after surgery for T-cell inhibition. However, direct administration of tacrolimus may bring severe side effects to the recipients. Herein, by rational design of two hydrogelators NapPhePheGluTyrOH (1) and Nap d-Phe dPheGluTyrOH (2), a facile method of immune responsive release of tacrolimus is developed from their hydrogels to overcome organ transplantation rejection. Upon incubation with protein tyrosine kinase, which is activated in T cells after organ transplantation, the tacrolimus-encapsulating Gel 1 or Gel 2 is disassembled to release tacrolimus. Cell experiments show that both Gel 1 and Gel 2 have better inhibition effect on the activated T cells than free drug tacrolimus. Liver transplantation experiments indicate that, after 7 days of treatment of same dose tacrolimus, the recipient rats in the Gel 2 group show significantly extended median survival time of 22 days while the recipients treated with conventional tacrolimus medication have a median survival time of 13 days. It is expected herein that this "smart" facile method of immune responsive release of tacrolimus can be applied to overcome organ transplantation rejection in clinic in the near future.

This study investigated the effect of the sintering temperature on the microstructural evolution and properties of Al2O3–C refractory samples, which were prepared using corundum, flake graphite, reactive alumina, Al and Si powders. The phenolic resin and nanometallic Ni were respectively applied as the binder and catalyst. The results indicate that hexagonal AlN particles, generated from the reaction of Al–N2 in Al2O3 refractories at 1000 °C, could transform into whiskers at 1200 °C. By increasing the sintering temperature to 1400 °C, a large number of plate-shaped β-Sialon could be generated. Under the action of Ni catalyst, the β-Sialon phases in refractories grew preferentially toward the crystalline facets (210) and (011) of AlN crystal and formed the plate-shape structure. When plate-shaped β-Sialon formed, the cold crushing strength (CCS) and cold modulus of rupture (CMOR) increased from 90.57 MPa to 148.67 MPa and from 22.83 MPa to 33.02 MPa, respectively. After two thermal shock cycles, the CCS of the refractories containing the plate-shaped β-Sialon had only decreased by 4.5 MPa. Thus, the in situ formation of plate-shaped β-Sialon could significantly improve the thermal shock resistance of Al2O3–C refractories.

Al2O3-C refractory samples were prepared using corundum, flake graphite, Al and Si powders and phenolic resin as raw materials. The in-situ synthesis mechanism of Al5O6N in Al2O3-C refractories was studied and the effect of adding nano metallic Fe on the formation and microstructure of Al5O6N phase was also investigated. Thermodynamic calculations show that Al5O6N can potentially be synthesized in a reducing atmosphere at 1600°C over a narrow range of N2 and CO pressures. Experimental results proved that Al5O6N phase was synthesized after 1600°C heat treatment when nano Fe was added to Al2O3-C refractories. As the content of nano Fe increases, Al5O6N particles show disappearance of oriented growth, with octahedron shapes turning into spherical agglomerations.