Co‐doped silica sol solutions with varying Co composition (Co/(Si+Co)=10–50 mol%) were prepared from tetraethoxysilane and Co(NO3)2·6H2O. Subsequently, these solutions were used in the preparation of hydrogen separation microporous membranes with enhanced hydrothermal stability at 500°C under a steam pressure of 300 kPa. At Co concentrations >33%, the XRD pattern and peak intensity of the Co‐doped silica preparations were similar and were not dependent on Co composition, suggesting that Co was incorporated into the silica network. The best H2 permeation performance in a steam atmosphere (500°C; steam pressure, 300 kPa) was obtained using silica doped with approximately 30 mol% Co. Co‐doped silica membranes (Co 33 mol%) fired at 600°C under a steam partial pressure of 90 kPa showed stable gaseous permeances and a H2 permeance of approximately 2.00–4.00 × 10−6 m3(STP)·(m·s·kPa)−1 with a selectivity of 250–730 (H2/N2), even after 60 h of exposure to steam (steam pressure, 300 kPa) at 500°C.

The crystallization behavior of organometallic-precursorderived amorphous Si-C-N ceramics was investigated under N 2 atmosphere using X-ray diffractometry (XRD), transmission electron microscopy (TEM), and solid-state 29 Si nuclear magnetic resonance (NMR) spectroscopy. Amorphous Si-C-N ceramics with a C/Si atomic ratio in the range of 0.34 -1.13 were prepared using polycarbosilane-polysilazane blends, single-source polysilazanes, and single-source polysilylcarbodiimides. The XRD study indicated that the crystallization temperature of Si 3 N 4 increased consistently with the C/Si atomic ratio and reached 1500°C at C/Si atomic ratios ranging from 0.53 to 1.13. This temperature was 300°C higher than that of the carbon-free amorphous Si-N material. In contrast, the SiC crystallization temperature showed no clear relation with the C/Si atomic ratio. The TEM and NMR analyses revealed that the crystallization of amorphous Si-C-N was governed by carbon content, chemical homogeneity, and molecular structure of the amorphous Si-C-N network.

Silica and cobalt-doped silica membranes that showed a high permeance of 1.8 Â 10 À7 mol m À2 s À1 Pa À1 and a H 2 /N 2 permeance ratio of $730, with excellent hydrothermal stability under steam pressure of 300 kPa, were successfully prepared. The permeation mechanism of gas molecules, focusing particularly on hydrogen and water vapor, was investigated in the 300-500 C range and is discussed based on the activation energy of permeation and the selectivity of gaseous molecules. The activation energy of H 2 permeation correlated well with the permeance ratio of He/H 2 for porous silica membranes prepared by sol-gel processing, chemical vapor deposition (CVD), and vitreous glasses, indicating that similar amorphous silica network structures were formed. The permeance ratios of H 2 /H 2 O were found to range from 5 to 40, that is, hydrogen (kinetic diameter: 0.289 nm) was always more permeable than water (0.265 nm).

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Recently, researchers spare no efforts to fabricate desirable vanadium dioxide (VO2) film which provides simultaneously high luminous transmittance and outstanding solar modulation ability, yet progress towards the optimization of one aspect always comes at the expense of the other. Our research devotes to finding a reproducible economic solution-processed strategy for fabricating VO2-SiO2 composite films, with the aim of boosting the performance of both aspects. Compare to VO2 film, an improvement of 18.9% (from 29.6% to 48.5%) in the luminous transmittance as well as an increase of 6.0% (from 9.7% to 15.7%) in solar modulation efficiency is achieved when the molar ratio of Si/V attains 0.8. Based on the effective medium theory, we simulate the optical spectra of the composite films and the best thermochromic property is obtained when the filling factor attains 0.5, which is consistent with the experimental results. Meanwhile, the improvement of chemical stability for the composite film against oxidation has been confirmed. Tungsten is introduced to reduce the phase transition temperature to the ambient temperature, while maintain the thermochromism required for application as smart window. Our research set forth a new avenue in promoting practical applications of VO2-based thermochromic fenestration.

V1−xWxO2(M/R) nanorods with superior doping efficiency (103 °C per at% W) and thermochromic property (Tvis = 60.6%, ΔTsol = 10.3%) were synthesized using a one-step hydrothermal method.

We have performed molecular dynamics simulations of amorphous Si 3 N 4 containing boron (Si-B-N). We have examined short-range atomic arrangements and self-diffusion constants of amorphous Si-B-N systems with various boron contents. Our simulations show that boron atoms are threefold coordinated by nitrogen atoms and that nitrogen atoms are bonded to both silicon and boron atoms in the amorphous network of Si-B-N. Also, the self-diffusion constant of nitrogen in Si-B-N is much decreased compared with that in amorphous Si 3 N 4 . This suggests that boron is important in decreasing the mobility of atoms in amorphous Si-B-N, which may explain the improved thermal stability of amorphous Si-B-N relative to amorphous Si 3 N 4 observed experimentally.

Nickel (Ni) nanoparticle-dispersed amorphous silica (Si-O) powders were synthesized from chemical solution precursors. The high-temperature hydrogen adsorption property of the precursor-derived composite powders was investigated in comparison with the amorphous Si-O and Ni at 773 K. Among the three powder samples, Ni nanoparticle-dispersed amorphous Si-O exhibited a unique reversible hydrogen adsorption property that was hardly detected on the amorphous Si-O and Ni. The increase amount of the reversibly adsorbed hydrogen was the highest for the composite samples at around the Ni content with a Ni/(Si1Ni) ratio of 0.2-0.3. The results strongly suggested that when the composite material is used in the form of a gas separation membrane, the reversibly adsorbed hydrogen property is thought to contribute to the additional increase in the number of solubility sites for hydrogen, which leads to a selective enhancement in the high-temperature hydrogen permeance at 773 K.