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Two unique polyoxometalate (POM)-encapsulated tubular materials with the formula K(H2O)6[M6(btp)6(H2O)22](P2W18O62)3(Hbtp)5(btp)3·52H2O [M = Mn (1) and Co (2); btp = 2,6-bis(1,2,4-triazol-1-yl)pyridine] were designed and synthesized based on the Dawson POM and V-type btp ligand, as confirmed by IR, X-ray diffraction (XRD), and element analysis. Single-crystal XRD analyses of compound 1show that two kinds of remarkable metal–organic supramolecular nanotubes, including trigonal and hexagonal nanotubes, are constructed along the c-axis direction via π···π-packing interactions between {Mn3(btp)3} rings and the btp ligands, of which [α-P2W18O62]6–anions are confined in channels, making the entire structure extraordinarily stable. Meanwhile, the coordinated [α-P2W18O62]6–anion within the hexagonal channel makes the channel highly hydrophilic and attracts a number of guest water molecules to fill in the free space, conducive to proton transport. Therefore, the single-crystal sample of 1exhibits a high proton conductivity of 6.39 × 10–3S cm–1along one-dimensional channels, 30 times higher than that of a pellet sample at 358 K and 98% relative humidity.

Hydrogen-bonded organic frameworks (HOFs) with inherent well-defined hydrogen-bond networks are promising proton conduction materials. Herein, four three-dimensional HOFs were controllably assembled from 1,2,4,5-benzenetetracarboxylic acid and guanidinium of different chain lengths with certain ratios, in which GC-1 has undergone a water-induced single-crystal-to-single-crystal (SCSC) transformation to a more stable GC-2 with successive π–π stacking interactions. Notably, the ideal single-crystal sample of GC-2 exhibits an ultrahigh proton conductivity of 1.78 × 10–2S cm–1along the [100] direction at ambient temperature and 98% RH. This sample is highly anisotropic with 3–5 orders of magnitude higher than those along the [010] and [001] directions, which is closely related to favorable proton-transfer paths of 1D highly hydrophilic channels formed by the consecutive hydrogen-bonded network between protonated guanidinium cations and carboxylic acid anions along the a-axis direction. Compared with the pelletized samples of GC-2, GC-3, and GC-4, their composite membranes with Nafion show significant enhancement of proton conduction with remarkable values of 1.33 × 10–1, 1.92 × 10–1, and 1.98 × 10–1S cm–1at 338 K and 98% RH, indicating great application potential.

ZrO2impurity phase was examined by means of X-ray diffraction and scanning electron microscopy in reactive-sintered ZrB2–SiC–ZrC composites hot-pressed at 1600°C and 1800°C. An analytical electron microscopy study further revealed solid-solution of both Zr and O in the ß-SiC phase: Zr:Si ratios were measured to be 1.83 ± 0.17 × 10-2and 1.91 ± 0.16 × 10-2respectively for each sample, while O:Si ratios were in the range of 2.3 ~ 2.8 × 10-2. Common co-existence of ZrO2grains and SiC grains containing Zr–O solutes indicates that this oxide plays a significant role in the sintering process, which substantially modifies the reactive phase relations. Observation of an intergranular Si–Zr–C–O glassy phase suggests the presence of a similar sintering liquid as a fast or even dominant diffusion path to promote the reactive sintering.

Multi-walled carbon nanotubes (MWNT) were successfully chemically modified (MWNT-COOH) and reacted with polyethylene glycol (PEG) to prepare nanocomposites. As- prepared kinds of functionalized MWNT (MWNT-g-PEG) were characterized with FTIR, TGA and TEM. Nonisothermal crystallization kinetics of MWNT-g-PEG composites was investigated by differential scanning calorimeter (DSC). The kinetics was analyzed using the Ozawa and Avrami equation modified by Jeziorny. The results showed that the Ozawa approach failed to describe the crystallization behavior of nanocomposites, whereas the modified Avrami analysis could explain the behavior of MWNT-g-PEG nanocomposite only. It is observed that the presence of MWNT hindered the mobility of PEG chains and decreased the overall crystallization rate. It was found that the crystallization behavior of MWNT-g-PEG nanocomposite was strongly affected by the incorporation of MWNT. The data for the nonisothermal crystallization could be analyzed properly by the Avrami equation modified by Jeziorny. The results showed that the presence of MWNT decreased the overall nonisothermal crystallization rate of the PEG chains which were grafted onto the MWNT due to MWNT might act as physical hindrances retarding the mobility of PEG chains and decreased the crystallinity.

Current high temperature ceramics, such as ZrO2, Si3N4 and SiC, cannot be used at temperatures over 1600°C due to their low melting temperature or dissociation temperature. For ultrahigh temperature applications over 1800°C, materials with high melting points, high phase composition stability, high thermal conductivity, good thermal shock and oxidation resistance are needed. The transition metal diborides, mainly include ZrB2 and HfB2, have melting temperatures of above 3000°C, and can basically meet the above demands. However, the oxidation resistance of diboride monolithic ceramics at ultra-high temperatures need to be improved for the applications in thermal protection systems for future aerospace vehicles and jet engines. On the other hand, processing science for making high performance UHTCs is another hot topic in the UHTC field. Densification of UHTCs at mild temperatures through reactive sintering is an attracting way due to the chemically stable phase composition and microstructure as well as clean grain boundaries in the obtained materials. Moreover, the stability studies of the materials in phase composition and microstructures at ultra high application temperatures is also critical for materials manufactured at relatively low temperature. Furthermore, the oxidation resistance in simulated reentry environments instead of in static or flowing air of ambient pressure should be evaluated. Here we will report the concept, advantages and some recent progress on the reactive sintering of diboride–based composites at mild temperatures.

ZrB2-SiC based composites with 0,5 and 15 vol% addition of ZrC were synthesized via reactive hot pressing at 1800°C using Zr, Si and B4C as raw materials. The mechanical properties of the composites were investigated. The composite of ZSC15 that contained 15 vol% of ZrC has the highest hardness. ZSC5 with 5 vol% of ZrC owns a most homogenous microstructure and the highest fracture toughness and flexural strength.

Data on treatable traits (TTs) in different populations are limited.