Strong yet flexible ceramic aerogel.

Ceramic aerogels are highly efficient, lightweight, and chemically stable thermal insulation materials but their application is hindered by their brittleness and low strength. Flexible nanostructure-assembled compressible aerogels have been developed to overcome the brittleness but they still show low strength, leading to insufficient load-bearing capacity. Here we designed and fabricated a laminated SiC-SiOx nanowire aerogel that exhibits reversible compressibility, recoverable buckling deformation, ductile tensile deformation, and simultaneous high strength of up to an order of magnitude larger than other ceramic aerogels. The aerogel also shows good thermal stability ranging from -196 °C in liquid nitrogen to above 1200 °C in butane blow torch, and good thermal insulation performance with a thermal conductivity of 39.3 ± 0.4 mW m-1 K-1. These integrated properties make the aerogel a promising candidate for mechanically robust and highly efficient flexible thermal insulation materials.

Anti-Shedding Nickel-Protection-Layer Boosting an Ultrahigh Loading Carbon Fiber@Co-NiSx Electrode to Deliver Superior Areal/Volumetric/Gravimetric Capacitance.

Challenges remain to show good capacitive performance while achieving high loadings of active materials for supercapacitors. Trying to realize this version, a nickel-protecting carbon fiber paper@Co-doped NiSx (Ni-CP@Co-NiSx) electrode with high specific gravimetric, areal, and volumetric capacitance is reported in this work. This free-standing electrode is prepared by an electroplating-hydrothermal-electroplating (EHE) three-step method to achieve a high loading of almost 26.7 mg cm-2. The cobalt-doping and nickel-protection strategies effectively decrease the impedance and inhibit the active material dropping from the electrode resulting from the expansion stress, which endows the Ni-CP@Co-NiSx electrode with a high rate and good cycling performance, especially with an ultrahigh specific areal/volumetric/gravimetric capacitance of 53.3 F cm-2/2807 F cm-3/1997 F g-1 at 5 mA cm-2, respectively. Employing activated carbon functionalized with riboflavin (AC/VB2) as a negative electrode, the asymmetric supercapacitor device delivers a very high energy density of up to 60.4 W h kg-1. This work demonstrates that electrodes with a high loading density and excellent performance can be obtained by the combination of the EHE method to adjust the internal conductivity and external structural stability.

Characterization of Bacterial Community Structure Dynamics in a Rat Burn Wound Model Using 16S rRNA Gene Sequencing.

Burns destroy the skin barrier and alter the resident bacterial community, thereby facilitating bacterial infection. To treat a wound infection, it is necessary to understand the changes in the wound bacterial community structure. However, traditional bacterial cultures allow the identification of only readily growing or purposely cultured bacterial species and lack the capacity to detect changes in the bacterial community. In this study, 16S rRNA gene sequencing was used to detect alterations in the bacterial community structure in deep partial-thickness burn wounds on the back of Sprague-Dawley rats. These results were then compared with those obtained from the bacterial culture. Bacterial samples were collected prior to wounding and 1, 7, 14, and 21 days after wounding. The 16S rRNA gene sequence analysis showed that the number of resident bacterial species decreased after the burn. Both resident bacterial richness and diversity, which were significantly reduced after the burn, recovered following wound healing. The dominant resident strains also changed, but the inhibition of bacterial community structure was in a nonvolatile equilibrium state, even in the early stage after healing. Furthermore, the correlation between wound and environmental bacteria increased with the occurrence of burns. Hence, the 16S rRNA gene sequence analysis reflected the bacterial condition of the wounds better than the bacterial culture. 16S rRNA sequencing in the Sprague-Dawley rat burn model can provide more information for the prevention and treatment of burn infections in clinical settings and promote further development in this field.

Highly Stretchable, Crack-Insensitive and Compressible Ceramic Aerogel.

Ceramic aerogels are attractive candidates for high-temperature thermal insulation, catalysis support, and ultrafiltration materials, but their practical applications are usually limited by brittleness. Recently, reversible compressibility has been realized in flexible nanostructures-based ceramic aerogels. However, these modified aerogels still show fast and brittle fracture under tension. Herein, we demonstrate achieving reversible stretch and crack insensitivity in a highly compressible ceramic aerogel through engineering its microstructure by using curly SiC-SiOx bicrystal nanowire as the building blocks. The aerogel exhibits large-strain reversible stretch (20%) and good resistance to high-speed tensile fatigue test. Even for a prenotched sample, a reversible stretch at 10% strain is achieved, indicating good crack resistance. The aerogel also displays reversible compressibility up to 80% strain, ultralow thermal conductivity of 28.4 mW m-1 K-1, and excellent thermal stability even at temperatures as high as 1200 °C in butane blow torch or as low as -196 °C in liquid nitrogen. Our findings show that the attractive tensile properties arise from the deformation, interaction, and reorientation of the curly nanowires which could reduce stress concentration and suppress crack initiation and growth during tension. This study not only expands the applicability of ceramic aerogels to conditions involving complex dynamic stress under extreme temperature conditions but also benefits the design of other highly stretchable and crack-resistant porous ceramic materials for various applications.

Ultralight, Recoverable, and High-Temperature-Resistant SiC Nanowire Aerogel.

Ultralight ceramic aerogels with the property combination of recoverable compressibility and excellent high-temperature stability are attractive for use in harsh environments. However, conventional ceramic aerogels are usually constructed by oxide ceramic nanoparticles, and their practical applications have always been limited by the brittle nature of ceramics and volume shrinkage at high temperature. Silicon carbide (SiC) nanowire offers the integrated properties of elasticity and flexibility of one-dimensional (1D) nanomaterials and superior high-temperature thermal and chemical stability of SiC ceramics, which makes it a promising building block for compressible ceramic nanowire aerogels (NWAs). Here, we report the fabrication and properties of a highly porous three-dimensional (3D) SiC NWA assembled by a large number of interweaving 3C-SiC nanowires of 20-50 nm diameter and tens to hundreds of micrometers in length. The SiC NWA possesses ultralow density (∼5 mg cm-3), excellent mechanical properties of large recoverable compression strain (>70%) and fatigue resistance, refractory property, oxidation and high-temperature resistance, and thermal insulating property (0.026 W m-1 K-1 at room temperature in N2). When used as absorbents, the SiC NWAs exhibit an adsorption selectivity of low-viscosity organic solvents with high absorption capacity (130-237 g g-1). The successful fabrication of such an attractive material may provide promising perspectives to the design and fabrication of other compressible and multifunctional ceramic NWAs.

Super-strong dislocation-structured high-carbon martensite steel.

High-carbon martensite steels (with C > 0.5 wt.%) are very hard but at the same time as brittle as glass in as-quenched or low-temperature-tempered state. Such extreme brittleness, originating from a twin microstructure, has rendered these steels almost useless in martensite state. Therefore, for more than a century it has been a common knowledge that high-carbon martensitic steels are intrinsically brittle and thus are not expected to find any application in harsh loading conditions. Here we report that these brittle steels can be transformed into super-strong ones exhibiting a combination of ultrahigh strength and significant toughness, through a simple grain-refinement treatment, which refines the grain size to ~4 µm. As a result, an ultra-high tensile strength of 2.4~2.6 GPa, a significant elongation of 4~10% and a good fracture toughness (K1C) of 23.5~29.6 MPa m1/2 were obtained in high-carbon martensitic steels with 0.61-0.65 wt.% C. These properties are comparable with those of "the king of super-high-strength steels"-maraging steels, but achieved at merely 1/30~1/50 of the price. The drastic enhancement in mechanical properties is found to arise from a transition from the conventional twin microstructure to a dislocation one by grain refinement. Our finding may provide a new route to manufacturing super-strong steels in a simple and economic way.

catena-Poly[[[diaqua-diformato-cobalt(II)]-µ-1,4-bis-(1H-benzimidazol-1-yl)benzene] dihydrate].

In the title coordination polymer, {[Co(CHO(2))(2)(C(20)H(14)N(4))(H(2)O)(2)]·2H(2)O}(n), the Co(II) atom (site symmetry [Formula: see text]) is coordinated by two formate O atoms, two water O atoms and two N atoms from two 1,4-bis-(1H-benzimidazol-1-yl)benzene ligands (L), resulting in a distorted trans-CoN(2)O(4) octa-hedral coordin-ation environment. The complete L ligand is generated by crystallographic inversion symmetry and serves to bridge the cobalt ions into a chain propagating in [1[Formula: see text][Formula: see text]]. The dihedral angle between the central benzene ring and the imidazole ring system is 38.48 (12)°. O-H⋯O hydrogen bonds involving both the coordinated and uncoordinated water mol-ecules occur and help to link the chains together.