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The increasing electromagnetic hazards including electromagnetic interference and electromagnetic pollution, which were stemmed from massive usage of electromagnetic technology, have triggered widespread concerns. To cope with this challenge, electromagnetic wave absorbing materials with high performance are greatly needed. Composite construction has been widely applied in electromagnetic (EM) wave absorbing materials to achieve high permittivity, high permeability and impedance matching. However, high-temperature stability, oxidation and corrosion resistance are still unignorable issues. Herein, high entropy hexaborides/tetraborides (HE REB6/HE REB4) composites with synergistic dielectric and magnetic losses were designed and successfully synthesized through a one-step boron carbide reduction method. The five as-prepared (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)B6/(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)B4, (Y0.2Nd0.2Sm0.2 Er0.2Yb0.2)B6/(Y0.2Nd0.2Sm0.2Er0.2Yb0.2)B4, (Y0.2Nd0.2Eu0.2Er0.2Yb0.2)B6/(Y0.2Nd0.2Eu0.2Er0.2Yb0.2)B4, (Nd0.2Sm0.2Eu0.2Er0.2Yb0.2)B6/(Nd0.2Sm0.2Eu0.2Er0.2Yb0.2)B4 and (Y0.2 Sm0.2Eu0.2Er0.2Yb0.2)B6/(Y0.2Sm0.2Eu0.2Er0.2Yb0.2)B4 contain two phases of HE REB6 and HE REB4. Among them (Y0.2Nd0.2Sm0.2Eu0.2 Er0.2)B6/(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)B4 (HE REB6/HE REB4-1) and (Y0.2Nd0.2Sm0.2Er0.2Yb0.2)B6/(Y0.2Nd0.2Sm0.2Er0.2Yb0.2)B4 (HE REB6/HE REB4-2) exhibit excellent EM wave absorption properties. The optimal minimum reflection loss (RLmin) and effective absorption bandwidth (EAB) of HE REB6/HE REB4-1 and HE REB6/HE REB4-2 are –53.3 dB (at 1.7 mm), 4.2 GHz (at 1.5 mm) and –43.5 dB (1.3 mm), 4.2 GHz (1.5 mm), respectively. The combination of conducting HE REB4 with magnetism into HE REB6 as a second phase enhances dielectric and magnetic losses, which lead to enhanced EM wave absorption performance. Considering superior high-temperature stability, oxidation and corrosion resistance of HE REB6 and HE REB4, HE REB6/HE REB4 composite ceramics are promising as a new type of high-performance EM wave absorbing materials.

The SiC fibers were coated with Ti3SiC2 interphase by dip-coating. The Ti3SiC2 coated fibers were heat-treated from 900 °C to 1100 °C in vacuum and argon atmospheres to comparatively analyze the effect of temperature and atmosphere on the microstructural evolution and mechanical strength of the fibers. The results show that the surface morphology of Ti3SiC2 coating is rough in vacuum and Ti3SiC2 is decomposed at 1100 °C. However, in argon atmosphere, the surface morphology is smooth and Ti3SiC2 is oxidized at 1000 °C and 1100 °C. At 1100 °C, Ti3SiC2 oxidized to form a thin layer of amorphous SiO2 embedded with TiO2 grains. Meanwhile, defects and pores appeared in the interphase scale. As a result, the fiber strength treated in the argon was lower than that treated in vacuum. The porous Ti3SiC2 interphase fabricated under vacuum was then employed to prepare the SiCf/SiC mini composite by chemical vapor infiltration (CVI) combined with precursor infiltration pyrolysis (PIP), and can effectively improve the toughness of SiCf/SiC mini composite. The propagating cracks can be deflected within the porous interphase layer, which promotes fiber pull-outs under the tensile strength.

Carbon species incorporation and carbon deposits are common in the manufacture process and application of yttria-stabilized zirconia (YSZ) ceramics, while the potential corrosion induced by the resultant carburization is unclear. The 3YSZ hollow fiber membranes were prepared by wet spinning method. A sintering procedure at 1300–1450 °C under 0.02 MPa oxygen partial pressure, and thereafter an oxidation treatment at 800 °C were applied to investigate the carbothermal reaction and carburization corrosion mechanism. It was found that the trace carbon species of 1.0–2.2 mol% derived from polymeric precursors triggered the carburizing strengthening of porous YSZ membranes without sacrificing porosity and deformability. However, the carburization corrosion also occurred at the mild oxidation treatment, resulting in deterioration in bending strength and integrated structure converting into fine grains. Raman spectra, XPS bands and HR-TEM images confirmed that the in-situ synthesized ZrCxOy oxidized into monoclinic ZrO2, and micro-cracking formed along grain boundaries, which led to substantial mechanical strength loss.

Ceramic electrospun nanofibrous membranes (ENMs) are ideal candidates for ultrafiltration applications in harsh environments. However, it has been a great challenge to fabricate ceramic ENMs with sufficient strengths to withstand the water pressure duo to their intrinsic brittleness. In this study, we report an ultra-strong Y3Al5O12-Al2O3 ENM employing graphene oxide (GO) as a sacrificing additive for the first time. The optimized membrane exhibits tensile strengths of 5.63 ± 0.31 MPa after sintering at 900 °C and 3.48 ± 0.44 MPa at 1000 °C. The high strength of the membrane ensures it to be used independently under a pressure up to 160 K Pa. An excellent nano-particle filtration performance is achieved with a high permeation flux of 5718–8494 L m−2 h−1 bar−1 and high rejection efficiencies above 99.75 % in both neutral and acidic water conditions. The work demonstrates a facile route for effective strengthening of ceramic ENMs with their great potential in harsh-environment self-standing ultrafiltration applications.

A dense HfC(Si, O)-HfB2(Si, O) composite was fabricated by reactive spark plasma sintering using HfC and SiB6 as starting reactants. The best ablation resistance was obtained with the composite fabricated with the addition of 15 vol.% SiB6. After ablation under an oxyacetylene flame for 60 s, the mass and linear ablation rates of this composite were −0.007 mg cm−2 s−1 and −0.233 μm s−1, respectively. The negative ablation rates are the result of a slight mass gain/thickness increase, which indicate that the oxidation process was stable and mechanical scouring was limited during ablation. This enhanced ablation resistance was attributed to a unique double-layered oxide formation, which possessed lower oxygen permeability and better mechanical strength. The solid solution nature of the composite and its appropriate phase composition were responsible for the stable oxide structure formation.

Ablation behavior of 3D-Cf/SiBCN composites with (PyC/SiC)3 multi-layers as interphase was investigated in plasma ablation flame at a heat flux of 4.02 MW m−2. During ablation, amorphous SiBCN matrix is firstly oxidized and forms a borosilicate glass, in which B2O3 is volatilized as the ablation going on. At the ablation center with higher temperature, SiC and Si3N4 grains are precipitated from the amorphous SiBCN matrix. And then, these SiC and Si3N4 grains are oxidized, forming a certain viscous silica rich protective coating on the sample surface. Moreover, it is revealed that the SiC layers in (PyC/SiC)3 multi-layers interphase can protect the carbon fibers from ablation damage effectively. Compared with the Cf/(PyC)SiBCN composites, much improved ablation resistance is achieved for the Cf/(PyC/SiC)3SiBCN composites. The linear and mass recession rates of the Cf/(PyC/SiC)3SiBCN composites are as low as 1.7 ± 0.4 μm s−1 and 0.0427 ± 0.0053 mg mm−2s−1, which are ∼43 % and ∼21 % lower than those of Cf/(PyC)SiBCN.

Scheelite coating was deposited on SiC fiber tows from various liquid-phase precursors followed by heat treatments between 900 °C and 1100 °C in different atmospheres. The tensile strength was fully retained for the coated fibers treated at 900 °C in vacuum. Subsequent heat treatment at 1100 °C in Ar had little effect on the fiber strength, which is explained by the excepted good thermal stability between the scheelite coating and SiC fiber. However, larger strength degradation and poor spool ability of coated fibers prepared in Ar/air were found. Assisted oxidation of SiC fiber by calcium salts is suggested to be responsible for the much larger strength degradation of fibers prepared in Ar/air.

The oxide scales of hafnium carbide (HfC) typically exhibit a porous structure after oxidation/ablation due to the release of gas oxidation products, which allows oxygen penetration to promote the rapid oxidation of the HfC matrices. Here, we report that the oxidation/ablation resistance of HfC was enhanced by the incorporation of amorphous silicon carbonitride (SiCN). HfC-SiCN ceramics with 10 vol. % SiCN showed a significant improvement in the oxidation/ablation resistance compared with pure HfC. The HfC-10 vol. % SiCN ceramic has a higher density with good mechanical properties. After being oxidized at 1500 °C for 2 h, a dense and homogeneous HfO2-HfSiO4 layer with low oxygen permeability is formed. The ablation resistance of the HfC-10 vol. % SiCN ceramic is improved due to the formation of the triple-layer structure oxide with good thermal stability and mechanical scouring resistance. After ablation under an oxyacetylene flame for 60 s, the mass and linear ablation rates of HfC-10 vol. % SiCN ceramic are -0.019 mg cm−2 s−1 and -0.156 μm s−1, respectively.

HfC-HfB2 composite ceramics were successfully reactively spark plasma sintered with a unique SiB6 additive. The incorporation of the SiB6 not only promotes the densification of HfC (up to ~99%), but also significantly enhances the toughness from 4.3 ± 0.5 MPa m1/2 to 14.2 ± 1.4 MPa m1/2. The flexural strength of the HfC-HfB2 composite ceramics was simultaneously improved to 529 ± 48 MPa, which is about 1.4 times higher than that of HfC. This improvement is attributed to the dense composite microstructure comprising an in-situ formed HfB2 and a solid solution of Si and O in HfC and HfB2 grains.

Scheelite coating was deposited on SiC fiber tows from various liquid-phase precursors at 1100℃. Strength degradation of SiC fiber was found after fiber coating which was found to be caused by the stress corrosion as a result of gases generated from the decomposition of by-products remaining in the coating. A new and simple method of low temperature pre-heat treatment was adopted to eliminate the stress corrosion in the fiber coating process and to isolate the effect of different types of gases on the stress corrosion cracking of fibers. The tensile strength and fractography of samples with and without pre-heat treatment were compared. Furthermore, the effect of gas composition on the strength degradation of SiC fiber was also investigated through the control experiments.

A flexible and robust YAG-Al2O3 composite nanofibrous membrane was fabricated by a combination of sol-gel and electrospinning methods, then a sintering at 900 °C. The effects of Al2O3 on the microstructure and mechanical performance of YAG nanofibrous membranes were investigated. The YAG nanofibrous membrane is brittle but the composite membranes exhibit a brittle-to-flexible transformation as the Al2O3 content reaches 30 wt.%, which can be attributed to an optimized dense hybrid microstructure consisting of finer YAG grain size surrounded by amorphous Al2O3. The YAG-30 wt.% Al2O3 nanofibrous membrane sintered at 900 °C shows a tensile strength of 3.52±0.31 MPa, three times of that of pure Al2O3 sintered at the same temperature. The membrane still presents a decent flexibility with a tensile strength of 0.75±0.25 MPa after sintering at 1000 °C, which is at least 100 °C higher than the sintering temperature of most reported ceramic nanofibrous membranes.

Continuous alumina fiber-reinforced yttria-stabilized zirconia (YSZ) composites with a LaPO4 fiber coating were fabricated by slurry infiltration and spark plasma sintering (SPS). The LaPO4 coating was deposited on the reinforcement alumina fabrics by a modified sol-gel method. The YSZ slurry with good dispersion and stability was prepared by optimizing the pH value, dispersant addition and ball milling time. The fabricated composite with a high density of ∼ 92 % has a good flexural strength of 277 ± 43 MPa, and a superior fracture toughness of 15.93 ± 0.75 MPa·m1/2 exhibiting a non-brittle failure behavior. It was found that the LaPO4 coating reduced the residual stress near the fiber/matrix interface to 131 ± 41 MPa, which was 369 ± 63 MPa in the composite without the fiber coating. The LaPO4 coating renders a weak interphase to improve the composite toughness by activating several toughening mechanisms including crack deflection, fiber debonding and pullout, and delamination behavior.

Yttrium aluminum garnet (YAG) fibers were prepared by a sol-gel method, and then sintered in air or nitrogen atmosphere, respectively. The effects of sintering atmosphere on the densification process and microstructure of YAG fibers were investigated. No obvious difference can be found in the fibers sintered below 800 °C. At 1100 °C, the grain size of YAG fibers sintered in nitrogen is much smaller than in air. This difference is much clearer at the higher temperature of 1200 °C. The fine grains are explained by the existence of residual carbon in YAG fibers, which can be trapped at the grain boundaries to hinder the movement of grain boundary. Meanwhile, the densification degree of fibers sintered in nitrogen is higher than in air at 1200 °C, due to the smaller grain size and higher oxygen vacancy concentration generated in the nitrogen atmosphere, which leads to a higher fiber densification rate.

Cartilage, especially articular cartilage, is a unique connective tissue consisting of chondrocytes and cartilage matrix that covers the surface of joints. It plays a critical role in maintaining joint durability and mobility by providing nearly frictionless articulation for mechanical load transmission between joints. Damage to the articular cartilage frequently results from sport-related injuries, systemic diseases, degeneration, trauma, or tumors. Failure to treat impaired cartilage may lead to osteoarthritis, affecting more than 25% of the adult population globally. Articular cartilage has a very low intrinsic self-repair capacity due to the limited proliferative ability of adult chondrocytes, lack of vascularization and innervation, slow matrix turnover, and low supply of progenitor cells. Furthermore, articular chondrocytes are encapsulated in low-nutrient, low-oxygen environment. While cartilage restoration techniques such as osteochondral transplantation, autologous chondrocyte implantation (ACI), and microfracture have been used to repair certain cartilage defects, the clinical outcomes are often mixed and undesirable. Cartilage tissue engineering (CTE) may hold promise to facilitate cartilage repair. Ideally, the prerequisites for successful CTE should include the use of effective chondrogenic factors, an ample supply of chondrogenic progenitors, and the employment of cell-friendly, biocompatible scaffold materials. Significant progress has been made on the above three fronts in past decade, which has been further facilitated by the advent of 3D bio-printing. In this review, we briefly discuss potential sources of chondrogenic progenitors. We then primarily focus on currently available chondrocyte-friendly scaffold materials, along with 3D bioprinting techniques, for their potential roles in effective CTE. It is hoped that this review will serve as a primer to bring cartilage biologists, synthetic chemists, biomechanical engineers, and 3D-bioprinting technologists together to expedite CTE process for eventual clinical applications.

Bone is a dynamic organ with high regenerative potential and provides essential biological functions in the body, such as providing body mobility and protection of internal organs, regulating hematopoietic cell homeostasis, and serving as important mineral reservoir. Bone defects, which can be caused by trauma, cancer and bone disorders, pose formidable public health burdens. Even though autologous bone grafts, allografts, or xenografts have been used clinically, repairing large bone defects remains as a significant clinical challenge. Bone tissue engineering (BTE) emerged as a promising solution to overcome the limitations of autografts and allografts. Ideal bone tissue engineering is to induce bone regeneration through the synergistic integration of biomaterial scaffolds, bone progenitor cells, and bone-forming factors. Successful stem cell-based BTE requires a combination of abundant mesenchymal progenitors with osteogenic potential, suitable biofactors to drive osteogenic differentiation, and cell-friendly scaffold biomaterials. Thus, the crux of BTE lies within the use of cell-friendly biomaterials as scaffolds to overcome extensive bone defects. In this review, we focus on the biocompatibility and cell-friendly features of commonly used scaffold materials, including inorganic compound-based ceramics, natural polymers, synthetic polymers, decellularized extracellular matrix, and in many cases, composite scaffolds using the above existing biomaterials. It is conceivable that combinations of bioactive materials, progenitor cells, growth factors, functionalization techniques, and biomimetic scaffold designs, along with 3D bioprinting technology, will unleash a new era of complex BTE scaffolds tailored to patient-specific applications.

The CeO2, Y2O3 and HfO2 doped β-NiAl coatings with controlled concentrations were fabricated on Hastelloy substrates using spark plasma sintering. The effects of reactive element oxide (REO) species and concentrations on the isothermal oxidation of the β-NiAl coatings were investigated. It was found that the addition of Y2O3 and HfO2 improved the oxidation performance of β-NiAl coatings, but CeO2 with high concentrations (0.5 at.%) had a detrimental effect. At low concentration (0.05 at.% and 0.1 at.%), HfO2 was less effective in improving the oxidation resistance of β-NiAl compared with Y2O3 and CeO2, while HfO2 at higher concentration of 0.5 at.% was the most effective among the three. The effects of REO species and concentrations on the NiAl oxidation behavior were further discussed in related to the intrinsic properties of the REOs and the chemical compositions of the substrate.

La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) solid oxide fuel cell cathodes were poisoned by Cr at different temperatures and polarization conditions with a Cr-Fe alloy as the interconnect. Cr induced degradation was analysed by electrochemical impedance spectroscopy (EIS) focusing on the electrochemical resistance (R chem ) that reflects the cathode electrochemical properties. It was found that R chem increased more with increasing temperatures. However cathodic polarization exhibited a synergistic effect with the temperature, which accelerated the LSCF cathode degradation at 800 °C while lowering the degree of degradation at 900 °C. By correlating complementary micro- and nano-scale microstructure characterization with the impedance analysis, the degradation mechanisms were investigated. A new Cr incorporation mechanism involving preferential formation of nanometre size Fe-Co-Cr-O spinel particles within the cathode up to the cathode/electrolyte interface was found to be responsible for the reduced degradation at 900 °C combined with cathodic polarization. The new mechanism reveals that the activity of B site elements in LSCF and possibly other perovskite cathodes plays an important role under certain combined temperature and polarization conditions, therefore future research in designing Cr resistant perovskite cathode materials may consider strategies that utilize the exsolution of B site elements for the formation of beneficial spinel phases.

The third octave sound absorption coefficient testing is conducted to compare the sound absorption properties metal foam and flexible cellular materials, by using sound absorption tester with the method of trasfer function sound absorption tester with the method of trasfer function. The sound absorption mechanisms are discussed by changing the parameters of sound absorption structure, such as the thickness of matrix materials and the thickness of cavity. The results show that pearl wool and glass wool exhibited excellent sound absorption properties. The peak value of sound absorption coefficient for pearl wool reaches to 0.991, and for glass wool, 0.985. The average sound absorption coefficient for pearl wool is 0.729, and for glass wool, 0.679. Among of three metal foams, the foamed aluminum material exhibited optimum sound absorption properties, and is superior to flexible sound absorption materials. The peak value of sound absorption coefficient reaches to 0.993, and the average value reaches to 0.781. This can be attributed to the flow resistance, porosity, thickness, cavity and structure factor, which influence the sound absorption of open cell materials.

The interfacial bonding at protective coatings and Zr alloy substrates could have a significant effect on the corrosion behaviors of the coatings. In this work, FeCrAl-Zr couples were fabricated at 900 °C by spark plasma sintering (SPS), and the interfacial bonding of the couples was modified through the addition of Si and/or thermal diffusion at 1100 °C–1300 °C. Uphill diffusion of silicon occurred during SPS. The corrosion resistance of the couples in 400 °C/10.3 MPa steam, and the effects of the interfacial bonding characteristics were studied. Due to the presence of ZrSi2 in the interfacial layer, the interfacial bonding of the FeCrAl/Si-Zr couple had a better corrosion resistance than that of the FeCrAl-Zr couple, withstanding 14 days of corrosion in steam compared to 7 days for the FeCrAl-Zr couple. The results also suggested that bimetallic effect could accelerate the oxidation of Zr alloy at the interface of the couples, and galvanic corrosion significantly contributed to the serious corrosion of the interface of the diffusion bonded couples with thermal diffusion. The influence of oxide growth stress around interface on the bonding lifetime of the couples was also discussed.

SiC structures with porosities ranging between 20-60% have been fabricated using two methods emulsification and freeze casting. While emulsification results in foam-like isotropic materials with interconnected pores, freeze casting can be used to fabricate highly anisotropic materials with characteristic layered architectures. The parameters that control the pore size and final porosity have been identified (solid content in the initial suspensions, emulsification times or speed of the freezing front). We have found that liquid state sintering (suing Al2O3 and Y2O3 as additives) at 1800°C on a powder (SiC/Al2O3) bed provides optimum consolidation for the porous structures. The mechanical strength of the materials depends on their density. Freeze casted materials fabricated with bimodal particle size distributions (a controlled mixture of micro and nanoparticles) exhibit higher compressive strengths that can reach values of up to 280MPa for materials with densities of 0.47.

Novel organic-inorganic composites were in-situ synthesized by using TriSilanolPhenyl polyhedral oligomeric silsesquioxane (SO-POSS) as fillers and poly(2,5-benzimidazole) (ABPBI) as polymer matrix. The uniformly dispersed 3% SO-POSS particles in ABPBI matrix increased the thermal stability of the composite membranes. It was found that both the water and H3PO4 uptakes were increased significantly with the addition of SO-POSS due to the formation of hydrogen bonds between the POSS and H2O/H3PO4, which played a critical role in the improvement of the conductivity of the composite membranes at temperature over 100 °C. Proton conductivities of H3PO4 doped with 3wt% SO-POSS contained ABPBI membranes increased with the increase of H3PO4 absorbance, reaching the maximum proton conductivity of 2.55 × 10-3 S·cm-1 at 160 °C, indicating that the ABPBI/SO-POSS composite membrane could be a promising candidate for mid-temperature PEMFCs.

The current lifestyles, increasing population, and limited resources result in energy research being at the forefront of worldwide grand challenges, increasing the demand for sustainable and more efficient energy devices. In this context, additive manufacturing brings the possibility of making electrodes and electrical energy storage devices in any desired three-dimensional (3D) shape and dimensions, while preserving the multifunctional properties of the active materials in terms of surface area and conductivity. This paves the way to optimized and more efficient designs for energy devices. Here, we describe how three-dimensional (3D) printing will allow the fabrication of bespoke devices, with complex geometries, tailored to fit specific requirements and applications, by designing water-based thermoresponsive inks to 3D-print different materials in one step, for example, printing the active material precursor (reduced chemically modified graphene (rCMG)) and the current collector (copper) for supercapacitors or anodes for lithium-ion batteries. The formulation of thermoresponsive inks using Pluronic F127 provides an aqueous-based, robust, flexible, and easily upscalable approach. The devices are designed to provide low resistance interface, enhanced electrical properties, mechanical performance, packing of rCMG, and low active material density while facilitating the postprocessing of the multicomponent 3D-printed structures. The electrode materials are selected to match postprocessing conditions. The reduction of the active material (rCMG) and sintering of the current collector (Cu) take place simultaneously. The electrochemical performance of the rCMG-based self-standing binder-free electrode and the two materials coupled rCMG/Cu printed electrode prove the potential of multimaterial printing in energy applications.

In this study, zein-protein based cryogels were synthesized by solution-based graft copolymerization of acrylic acid monomers onto zein protein backbones in the presence of an acrylamide crosslinker and initiators (sodium bisulfite and potassium persulfate). The grafting was confirmed by Fourier transform infrared spectroscopy. The thermal properties of the cryogels were assessed by thermogravimetric analysis and their morphology was studied by scanning electron microscopy and Brunauer–Emmett–Teller surface analysis. It was found that freezing the materials using liquid nitrogen at −196 °C before drying increased the surface area of the cryogels as compared to freezing at −20 °C. Dynamic mechanical analysis tests revealed that cryogels with increased acrylic acid content captured ambient moisture more quickly. The absorption capacity tests were performed in water and in diesel fuel. The highest equilibrium swelling of cryogels in distilled water reached 119.5 g/g of cryogel after 1 h while the highest equilibrium swelling in diesel fuel reached 49.8 g/g of cryogel in 15 min.

Superabsorbent hydrogels were synthesized by solution-based graft copolymerization of acrylic acid monomers on the hydrolyzed zein protein backbones in the presence of an acrylamide crosslinker, sodium bisulfite and potassium persulfate as initiators. The grafting was confirmed by Fourier transform infrared spectroscopy and the morphology was studied by scanning electron microscopy. A loose structure was observed in the hydrolyzed zein protein-g-polyacrylic acid. Moreover, differential scanning calorimetry and swelling tests were performed to evaluate the effect of the formulations on the thermal and swelling properties of the hydrogels. The highest equilibrium swelling value in distilled water reached 239.6 g/g of hydrogel. The potential of these materials as heavy metal ions chelator was also assessed. The preliminary results showed that the hydrogels had a good copper ion chelation capacity (maximum of 208 mg/g at pH 4.5), probably due to the presence of a large number of functional groups from the polyacrylic acid and the hydrolyzed zein protein.

In this study, we report a type of ultra oxidation and spallation resistant Y/Hf-doped AlCoCrFeNi high-entropy alloy (HEA). The alloy exhibits a significantly lower oxidation rate at 1100 °C with a kp value of about 1.9 × 10−13 g2 cm-4s-1, which is one magnitude lower than those of the conventional NiCoCrAlY alloys. Additionally, the alloy shows a strong resistance to the oxide scale spallation. The superior oxidation performance for the Y/Hf-doped HEA can be attributed to the fast establishment of exclusive α-Al2O3 scale, the beneficial reactive element effect and the large columnar grain size (width) in the oxide scale.

An approach to improve the sintering ability and the fracture toughness of hafnium carbide (HfC) ceramic by designing a unique composite structure is reported. The uniform and ultra-fine HfC nanoparticles (~300 nm) are synthesized at 1450°C by vacuum carbonization reaction with the glucose-derived hydrothermal precursor as a carbon source and template. HfC ceramic sintered with a SiCN sintering aid of 15 vol. % possesses a beneficial three-dimensional network microstructure composed of inter-penetrating phases of carbon, SiC and HfC with varied stoichiometry at multi-length scales. The obtained HfC exhibits a higher fracture toughness of 5.5 MPa m1/2, which can be attributed to the unique composite structure able to promote stress releases in the crack tip and enhance the resistance to crack propagation.

The soft sensing system has drawn huge enthusiasm for the application of soft robots and healthcare recently. Most of them possess thin-film structures that are beneficial to monitoring strain and pressure, but are unfavorable for measuring normal displacement with high linearity. Here we propose soft tactile sensors based on uniform-strength cantilever beams that can be utilized to measure the normal displacement and force of soft objects simultaneously. First, the theoretical model of the sensors is constructed, on the basis of which, the sensors are fabricated for testing their sensing characteristics. Next, the test results validate the constructed model, and demonstrate that the sensors can measure the force as well as the displacement. Besides, the self-fabricated sensor can have such prominent superiorities as follows—it is ultra-soft, and its equivalent stiffness is only 0.31 N·m−1 (approximately 0.4% of fat), it has prominent sensing performance with excellent linearity (R2 = 0.999), high sensitivity of 0.533 pF·mm−1 and 1.66 pF·mN−1 for measuring displacement and force, its detection limit is as low as 70 μm and 20 μN that is only one-tenth of the touch of a female fingertip. The presented sensor highlights a new idea for measuring the force and displacement of the soft objects with broad application prospects in mechanical and medical fields.

In this study, the oxidation behavior of AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) with/without Y doping at 1000 °C and 1100 °C was reported. The doping of minor Y is crucial to improving the Al2O3 scale adhesion and achieving its durability at high temperatures. The oxidation rates of Y-doped AlCoCrFeNi2.1 EHEA at 1000 °C and 1100 °C are comparable and even lower compared with conventional Al2O3-forming NiCoCrAlY/CoNiCrAlY alloys. The superior oxidation resistance and highly stable eutectic lamellar structure after high-temperature oxidation make Y-doped AlCoCrFeNi2.1 EHEA show a tremendous potential in high-temperature application.

Proteins are renewable resources rich in animals and plants and can be extracted from the agricultural and breeding industry byproducts and wastes. Collagen, keratin, zein and soy proteins are found in these byproducts and are extensively studied for protein-based hydrogels, which are especially attractive as a promising biomaterial due to their excellent biocompatibility, biodegradability, nontoxicity and low immune response. In recent years, hydrogels have been playing an increasingly important role in tissue engineering, drug delivery, nutrient encapsulation, controlled release of pesticides and other fields. The diversity of the amino acid composition of proteins leads to significant differences in their processing strategies, and the properties of the resultant hydrogels. This review covers the extraction methods for collagen, keratin, zein and soy proteins from various industrial byproducts, the synthesis of hydrogels from these protein sources, as well as their potential applications.

Phosphoric acid doped polybenzimidazoles are among the most interesting proton exchange membrane materials for high temperature proton exchange membrane fuel cell applications. As a major challenge the proton conducting decline due to free phosphoric acid leaching during the long term fuel cell operation is addressed by fixing overmuch phosphoric acid in the polymer matrix. Novel organic-inorganic composite membranes are prepared via in situ synthesis of poly(2,5-benzimidazole) (ABPBI) and OctaAmmonium POSS (AM-POSS) hybrid composites (ABPBI/AM-POSS) following phosphoric acid doping and membrane casting procedures. Compared with the pristine ABPBI membrane, the introduction of AM-POSS into ABPBI polymer membrane caused water and phosphoric acid absorbilities increasing dramatically, resulting in the significant increase of proton conductivities at whether hydrous or anhydrous condition. ABPBI/3AM composite membranes with phosphoric acid uptake above 250% showed best proton conductivities from room temperature to 160 °C, indicating these composite membranes could be excellent candidates as a polymer electrolyte membrane for low and intermediate temperature applications.

© 2016 American Chemical Society.The degradation of intermediate temperature solid oxide fuel cell (ITSOFC) cathodes has been identified as a major issue limiting the development of ITSOFCs as high efficiency energy conversion devices. In this work, the effect of Cr poisoning on (La0.6Sr0.4)0.95(Co0.2Fe0.8)O3-δ (LSCF6428), a particularly promising ITSOFC cathode material, was investigated on symmetrical cells using electrochemical impedance spectroscopy and multiscale structural/chemical analysis by advanced electron and ion microscopy. The systematic combination of bulk and high-resolution analysis on the same cells allows, for the first time, direct correlation of Cr induced performance degradation with subtle and localized structural/chemical changes of the cathode down to the atomic scale. Up to 2 orders of magnitude reduction in conductivity, oxygen surface exchange rate, and diffusivity were observed in Cr poisoned LSCF6428 samples. These effects are associated with the formation of nanometer size SrCrO4; grain boundary segregation of Cr; enhanced B-site element exsolution (both Fe and Co); and reduction in the Fe valence, the latter two being related to Cr substitution in LSCF. The finding that significant degradation of the cathode happens before obvious microscale change points to new critical SOFC degradation mechanisms effective at the nanometer scale and below.

Cr poisoning has been identified as a critical issue for solid oxide fuel cell (SOFC) cathodes degradation when metallic alloys are used for intermediate temperature SOFCs. In addition, Mo is also a common alloying element in ferritic stainless steel or Ni based alloys considered as interconnect materials and molybdenum trioxide is very volatile, raising concerns on Mo poisoning to the cathodes. In this work, the intrinsic reactivity of Cr with a porous (La0.6Sr0.4)0.95(Co0.2Fe0.8)O3 − δ cathode (LSCF6428) with and without the presence of Mo was investigated by transmission electron microscopy (TEM) in order to reveal the nanoscale incorporation and evolution behavior of Cr and/or Mo in LSCF. Cr incorporation was identified with formation of Cr containing phases including chromium oxide and SrCrOx with sizes of as small as ~ 100 nm, suggesting that the poisoning can take effect with subtle changes at the very small scale. Co-poisoning of Mo with Cr significantly changes the pattern of Cr behavior. CrCo2Fe3Ox spinel becomes the main reaction product in addition to chromium oxide as a result of Sr reacting preferentially with Mo to form SrMoO4. The LSCF grain boundary was found to be rich in Cr and deficient in Co. These results suggest that potential Mo poisoning effects should be considered when developing metallic interconnects containing Mo.

Ablation behavior and thermal damage mechanisms of Cf/SiBCN composites were investigated in plasma ablation flame under a heat flux of 4.02 MW/m2, simulating a hypersonic service environment at ∼2200 °C. Oxide layer formed on the composites surface effectively protects internal Cf/SiBCN composites from further ablation. However, the internal Cf/SiBCN composites endure severe thermal damage and complex reactions, leading to decomposition of SiBCN matrix and formation of α/β-SiC, β-Si3N4 grains, amorphous C layer and ring-like SiC layer. Based on detailed microstructure and phase composition analysis, thermal damage and microstructure evolution mechanisms of Cf/SiBCN composites during plasma ablation are clarified.

There is a growing interest in the development of composites with complex structures designed to generate enhanced mechanical properties. The challenge is how to implement these structures in practical materials with the required degree of control. Here we show how freeze casting of ceramic preforms combined with metal infiltration can be used to fabricate Al 2 O 3 /Al-4wt% Mg micro-laminated composites. By manipulating the solid content of the suspension and the morphology of the ceramic particles (from platelets to round particles) it is possible to access a range of structures with layer thickness varying between 1 and 30 μm and metallic contents between 66 and 86 vol%. The mechanical response of the materials is characterized by combining bending tests with observation of crack propagation in two and three dimensions using different imaging techniques. These composites are able to combine high strength and toughness. They exhibit a rising R-curve behaviour although different structures generate different toughening mechanisms. Composites fabricated with Al 2 O 3 particles exhibit the highest fracture resistance approaching 60 MPa m 1/2 , while laminates prepared from Al 2 O 3 platelets exhibit higher strengths (above 700 MPa) while retaining fracture resistance up to ∼40 MPa m 1/2 . The results provide new insights on the effect of structure on the mechanical properties in metal-ceramic composites as well as on the design of appropriate testing procedures.

TriSilanolPhenyl oligomeric silsesquioxane (SO-POSS) are embedded into poly(2,5-benzimidazole) (ABPBI) matrix via in-situ synthesis and ionic liquid (IL) [BMIM]BF4 are added as proton conductor to fabricate tri-component composite membranes. The proton conductivity of ABPBI/SO-POSS/IL reaches 57 ms cm-1 at 100 °C, which is significantly higher than that of Nafion, indicating that the composite membranes could be a promising candidate for high temperature PEMFCs.

Phosphoric acid doped polybenzimidazole membranes with good electrochemical properties at high temperature have been under increasing study in recent years for application in high temperature polymer electrolyte membrane fuel cell (HT-PEMFC). The disadvantages associated with these types of membranes include reduced proton conductivity due to acid leaching under continuous usage. The aforementioned drawbacks can be partly overcome by the addition of modified inorganic particles. This work reports the synthesis of poly (2,5-benzimidazole)/sulfonated sepiolite composite membrane (ABPBI/S-Sep) via in-situ method following by phosphoric acid doping procedure. The sulfonation modification of Sep was successfully characterized by XRD and contact angle test. SEM shows that S-Sep particles are well dispersed in the ABPBI matrix. The introduction of S-Sep into ABPBI helps to improve the water uptake, phosphoric acid doping level and proton conductivity of the composite membrane compared to the virgin ABPBI. With the similar phosphoric acid doping level, the proton conductivity of the composite membrane exhibits the highest value of 2.31mS/cm at 90oC which is four times of phosphoric acid doped pristine ABPBI membranes, indicating that the sulfonated sepiolite modified ABPBI composite membrane could be a prospective candidate applying in PEMFC to extend its operating temperature ranges.

Acceptor-doped LaNbO4 is a promising electrolyte material for proton-conducting fuel cell (PCFC) applications. As charge transfer processes govern device performance, the outermost surface of acceptor-doped LaNbO4 will play an important role in determining the overall cell performance. However, the surface composition is poorly characterized, and the understanding of its impact on the proton exchange process is rudimentary. In this work, the surface chemistry of 1 atom % Sr-doped LaNbO4 (La0.99Sr0.01NbO4-d, denoted as LSNO) proton conductor is characterized using LEIS and SIMS. The implication of a surface layer on proton transport is studied using the isotopic exchange technique. It has shown that a Sr-enriched but La-deficient surface layer of about 6–7 nm thick forms after annealing the sample under static air at 1000 °C for 10 h. The onset of segregation is found to be between 600 and 800 °C, and an equilibrium surface layer forms after 10 h annealing. A phase separation mechanism, due to the low solubility of Sr in LaNbO4, has been proposed to explain the observed segregation behavior. The surface layer was concluded to impede the water incorporation process, leading to a reduced isotopic fraction after the D216O wet exchange process, highlighting the impact of surface chemistry on the proton exchange process.

The solar-assisted oxidation of water is an essential half reaction for achieving a complete cycle of water splitting. The search of efficient photoanodes that can absorb light in the visible range is of paramount importance to enable cost-effective solar energy-conversion systems. Here, we demonstrate that atomically thin layers of MoS2 and WS2 can oxidize water to O2 under incident light. Thin films of solution-processed MoS2 and WS2 nanosheets display n-type positive photocurrent densities of 0.45 mA cm–2 and O2 evolution under simulated solar irradiation. WS2 is significantly more efficient than MoS2; however, bulk heterojunctions (B-HJs) of MoS2 and WS2 nanosheets results in a 10-fold increase in incident-photon-to-current-efficiency, compared to the individual constituents. This proves that charge carrier lifetime is tailorable in atomically thin crystals by creating heterojunctions of different compositions and architectures. Our results suggest that the MoS2 and WS2 nanosheets and their B-HJ blend are interesting photocatalytic systems for water oxidation, which can be coupled with different reduction processes for solar-fuel production.

The Fe and Pt modified β-NiAl overlay coatings with controlled concentrations were firstly fabricated on Hastelloy substrates using spark plasma sintering. The effects of Fe, Pt and their concentrations on the isothermal oxidation of the β-NiAl coatings were investigated. The unmodified NiAl coatings showed the worst spallation resistance, both Fe and Pt addition could significantly improve the oxidation performance of β-NiAl coatings. The mechanisms of Fe, Pt and their concentrations on the NiAl oxidation behavior were further discussed in related to the transformation of θ-Al2O3 to α-Al2O3, void formation at scale/coating interface and impurities (S and C) segregations. It is proposed that Fe could be a cheap alternative for Pt, though it was less effective than Pt to improve the oxidation resistance of β-NiAl coatings.

This paper describes the fabrication of hybrid ceramic/carbon scaffolds in which carbon nanofibres and multi-walled carbon nanotubes fully cover the internal walls of a microporous ceramic structure that provides mechanical stability. Freeze casting is used to fabricate a porous, lamellar ceramic (Al2O3) structure with aligned pores whose width can be controlled between 10 and 90 μm. Subsequently, a two step chemical vapour deposition process that uses iron as a catalyst is used to grow the carbon nanostructures inside the scaffold. This catalyst remains in the scaffold after the growth process. The formation of the alumina scaffold and the influence of its structure on the growth of nanofibres and tubes are investigated. A set of growth conditions is determined to produce a dense covering of the internal walls of the porous ceramic with the carbon nanostructures. The limiting pore size for this process is located around 25 μm.

Optimising the properties of platelet reinforced composites requires the strength of the reinforcing phase to be known, however strength measurements at such small scales are difficult and therefore data is sparse. In this work the flexural strength and Weibull modulus of microscopic, alumina platelets has been measured as 5.3 ± 1.3 GPa and 3.7 respectively, using an in-situ micro 3-point bend test. A general approach to correct for the effect of variation in sample size on the Weibull modulus is presented, and the internal structure of the platelets is revealed by TEM.

The properties of graphene open new opportunities for the fabrication of composites exhibiting unique structural and functional capabilities. However, to achieve this goal we should build materials with carefully designed architectures. Here, we describe the fabrication of ceramic-graphene composites by combining graphene foams with pre-ceramic polymers and spark plasma sintering. The result is a material containing an interconnected, microscopic network of very thin (20–30 nm), electrically conductive, carbon interfaces. This network generates electrical conductivities up to two orders of magnitude higher than those of other ceramics with similar graphene or carbon nanotube contents and can be used to monitor ‘in situ' structural integrity. In addition, it directs crack propagation, promoting stable crack growth and increasing the fracture resistance by an order of magnitude. These results demonstrate that the rational integration of nanomaterials could be a fruitful path towards building composites combining unique mechanical and functional performances., Micro- and nanostructures found in nature can be adopted to new uses and materials in engineered composites. Here authors demonstrate large enhancements in toughness and electrical conductivity in a ceramic upon addition of graphene at low (1 volume %) levels.

Oxidation of silicon melt infiltrated SiC/SiC ceramic matrix composites (CMC) was studied in air at 1200–1400 °C for 1, 5, 24 and 48 h. Weight gain and oxide layer thickness measurements revealed the oxidation follows parabolic reaction kinetics with increase in temperature and time. XRD showed the extent of oxide layer (SiO2) formation was greatest after 48 h at 1400 °C: an observation confirmed by X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM) analyses. Oxide layer thickness varied from 1 μm after 48 h at 1200 °C to 8 μm after 48 h at 1400 °C. Oxidation of SiC/SiC composites is both temperature and time dependent with an activation energy of 619 kJ mol−1. BN coatings around SiC fibres showed good resistance to oxidation even after 48 h at 1400 °C.

Releasing a bimaterial system, which consists of a pre-stretched dielectric elastomer membrane attached on a flexible frame, transforms a planar structure into a 3D structure through buckling. The buckled structure can deform further upon applying of a voltage, giving rise to the so-called dielectric elastomer minimum-energy structures (DEMES). Simple and easy-to-use theory and model would simplify the tedious trial-and-error designing process. We describe an extended model accounting for nonlinear rubber elasticity, pre-stretch, and the concentrated transverse load of a bending beam DEMES actuator. We design and fabricate a petal-shaped actuator with three petals. Elevation of a 1-g mass upward 7 mm is demonstrated upon application of 7000 V. Good correlation is achieved between model prediction and experimental measurement.

Ultra-light porous networks based on nano-carbon materials (such as graphene or carbon nanotubes) have attracted increasing interest owing to their applications in wide fields from bioengineering to electrochemical devices. However, it is often difficult to translate the properties of nanomaterials to bulk three-dimensional networks with a control of their mechanical properties. In this work, we constructed elastomeric graphene porous networks with well-defined structures by freeze casting and thermal reduction and investigated systematically the effect of key microstructural features. The porous networks made of large reduced graphene oxide flakes (>20 μm) are superelastic and exhibit high energy absorption, showing much enhanced mechanical properties than those with small flakes (

© 2014 Rebecca J. Nicholls, Published by Wiley-VCH Verlag GmbH and Co. KGaA. Zirconium-based alloys are used in water-cooled nuclear reactors for both nuclear fuel cladding and structural components. Under this harsh environment, the main factor limiting the service life of zirconium cladding, and hence fuel burn-up efficiency, is water corrosion. This oxidation process has recently been linked to the presence of a sub-oxide phase with well-defi ned composition but unknown structure at the metal-oxide interface. In this paper, the combination of first-principles materials modeling and high-resolution electron microscopy is used to identify the structure of this sub-oxide phase, bringing us a step closer to developing strategies to mitigate aqueous oxidation in Zr alloys and prolong the operational lifetime of commercial fuel cladding alloys.