Search

Two methyl-modified Al2O3/SiO2 xerogels, i. e. AIP-Al2O3/MSiO2 and ANN-Al2O3/MSiO2 xerogels, were prepared using aluminum isopropoxide and aluminum nitrate nonahydrate as the aluminum precursors, respectively. The appearance, density, viscosity, Gibbs activation energy for viscous flow and reaction rate constant of the sols were analyzed and compared. Their microstructures were characterized by means of powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and nitrogen adsorption–desorption measurements. The results show that the Al–O–Si bond is formed in the AIP-Al2O3/MSiO2 and ANN-Al2O3/MSiO2 xerogels. The ANN-Al2O3/MSiO2 sol has a smaller mean particle size and greater sol stability than the AIP-Al2O3/MSiO2 sol. Meanwhile, the ANN-Al2O3/MSiO2 xerogel has a smaller pore size and higher porosity. The total pore volume and specific surface area of the ANN-Al2O3/MSiO2 xerogel are 27.27% and 29.36% larger than those of the AIP-Al2O3/ MSiO2 sample, respectively. The saturated adsorption capacity of the ANN-Al2O3/MSiO2 xerogel to methylene blue is 7.15% larger than that of the AIP-Al2O3/MSiO2 xerogel.

With methyltriethoxysilane as hydrophobic precursors and aluminum isopropoxide as the aluminum source, the Al2O3/SiO2 sols and their gel materials were prepared. The effects of aluminum content (nA...

Titanium dioxide (TiO2) sol was prepared using tetrabutyl titanate as a precursor via an acid catalyzed sol-gel process. Investigation of the effects of acid content and annealing on the properties...

Improving proton conductivity is of great importance for the further application of metal–organic frameworks (MOFs) or metal–organic coordination polymers (MOCPs) in proton exchange membrane fuel cells. In this paper, we proposed a new approach to increase proton conductivities in MOCPs coming from organic ligands, e.g. coordination inducement and MOCP–cocrystal composite formation strategies, which is based on the potential function of organic ligands. By employing the approach, we have successfully synthesized and characterized three crystalline compounds, PPA (1), [Cu(PPA)I] (2) and [Co(PPA)2(BDC)(H2O)2·(PPA)2(H2BDC)2(H2O)] (3) (PPA = 4-(3-pyridinyl)-2-amino pyrimidine, H2BDC = 1,4-benzenedicarboxylic acid). These compounds show high water stabilities and different proton conducting behaviours, especially compound 3 with a proton conductivity of 2.29 × 10−4 S cm−1 at 325 K and ∼97% RH, which is higher than or comparable to those of some reported compounds. More importantly, a persistent increase in proton conductivity is observed from 1 to 3, which is about one order of magnitude. Furthermore, single crystal analyses show that coordination and hydrogen-bonding interactions play a crucial role in improving proton-conductive properties for these compounds. The study reveals that it is practical to boost the proton conductivity of crystal materials by means of their intrinsic merits and the strategy of molecular design.

A series of Al2O3 sols were prepared by HNO3 catalysis of aluminum isopropoxide (AIP), using different molar ratios of HNO3/AIP (nH). The changes in sol densities, viscosities, refractive i...

The Ag-loaded hydrophobic silica (Ag/M-SiO2) materials were prepared by sol-gel method with tetraethylorthosilicate (TEOS) as precursor and methyltriethoxysilane (MTES) as hydrophobic modifier. Contact angles, X-ray diffraction and X-ray photoelectron spectra were used to characterize the as-prepared Ag/M-SiO2 materials. The antibacterial properties of the Ag/M-SiO2 materials were evaluated against Escherichia coli and Staphylococcus aureus. The results indicated that the appropriate calcination temperature of keeping the hydrophobicity of Ag/M-SiO2 materials is 300∼500°C. Ag element exists in Ag/M-SiO2 materials as the elemental form and hydrophobic Si-CH3 groups have been successfully introduced into the Ag/M-SiO2 materials. The qualitative and quantitative antibacterial experiments showed that the antibacterial activity increased with the increase of silver content. When the molar ratio of Ag/TEOS is increased to 0.10, the Ag/M-SiO2 materials showed good antibacterial dissolution and broad-spec...

A large-transparent single crystal of 1-hexadecyl-3-methylimidazolium bromide monohydrate ([C16mim]Br·H2O) with 4-mm length was firstly obtained in the water–trichloromethane–toluene growth system (Vwater:Vtrichloromethane:Vtoluene = 0.1:1:2). The crystal structure was determined by single crystal X-ray diffraction method. It crystallizes in the triclinic system, space group P-1, with unit cell parameters a = 5.4962(15) A, b = 7.839(2) A, c = 27.279(8) A, α = 94.375°(4), β = 91.500°(5), γ = 101.999°(4), Z = 2, V = 1145.2(5)A3, Dc = 1.176 Mg/m3, μ = 1.804 mm− 1, F(000) = 436, the final R1 = 0.0497, wR2 = 0.1154. The 3D supramolecular structure is constructed through the weak interactions between imidazolium cations, Br− anions and lattice water molecules. The long alkyl chain to imidazolium ring and lattice water molecules play an important role in the self-assembled process. Moreover, it is proposed that [C16mim]Br has the aggregation behavior in water at the higher concentration and the possible self-assembled structure is the interdigitated pattern.

The microstructure of annealed Ti 50 Ni 24.9 Cu 25 Y 0.1 alloy was studied through X-ray diffraction (XRD) and transmission electron microscope (TEM) measurements. It has been shown that the microstructure was composed of the B19 martensite. The temperature, frequency and strain amplitude dependences of the internal friction (IF) in the Ti 50 Ni 24.9 Cu 25 Y 0.1 alloy were investigated by dynamic mechanical analyzer (DMA), as well as differential scanning calorimetry (DSC) measurement. The DSC results indicated that only a stage of the phase transformation took place and yttrium (Y) solid-solution narrowed the transformation hysteresis. The IF kept a high value in the stage of martensitic phase and the phase transformation due to the addition of Y element during nonisothermal process. The isothermal internal friction curves were observed in our work.