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Solovyov L.A.,RAS Institute of Chemistry and Chemical Technology
Acta Crystallographica Section B: Structural Science | Year: 2012

A revision is presented of the restrained Rietveld analysis of the crystal structure of magnesium perchlorate tetrahydrate, Mg(ClO 4) 2·4H 2O, recently published by Robertson & Bish [(2010), Acta Cryst. B66, 579-584]. The actual symmetry of the material is shown to be C2/m. The corrected structure model is refined by the derivative difference method [Solovyov (2004). J. Appl. Cryst. 37, 743-749], anisotropically for all non-H atoms and isotropically for two independent H atoms without restraints. © 2012 International Union of Crystallography Printed in Singapore - all rights reserved.

Kozlova S.A.,RAS Institute of Chemistry and Chemical Technology | Kirik S.D.,Siberian Federal University
Microporous and Mesoporous Materials | Year: 2010

The influence of different types of post-synthetic treatment (exposure at calcination, at boiling treatment in neutral, acidic and alkaline aqueous solutions, treatment in hydrofluoric acid) on the state of the silanol surface of the mesostructured mesoporous silicate materials MCM-41 and SBA-15 has been studied. The material alteration has been monitored by X-ray diffraction, IR-spectroscopy, thermal analysis and nitrogen adsorption. It has been shown that post-synthetic treatment changes the concentration of silanol groups on the material surface. The limit value has been established by experiment: about 3-4 OH/nm 2 for MCM-41 and 5-6 OH/nm 2 for SBA-15, with its excess resulting in the material destruction. The distribution of the re-formed Si-OH groups over the surface is of irregular focal nature. In spite of the destruction, the specific characteristics of the material (inner surface, volume, and lattice parameter) remain the same. The treatment type and medium content influence the material destruction rate, but not the limit density of the silanol covering. Based on the molecular model of MCM-41 and percolation theory an interpretation has been proposed due to the mechanism of fragmentary material decay. Fragments of the surface with the concentration of the OH-groups exceeding the limit eliminate from material because the concentration of OH-groups is correlated with concentrations of the broken silaxane bonds (Si-O-Si), which responsible for the surface connectivity. © 2010 Elsevier Inc. All rights reserved.

Gottesman R.,Institute of Nanotechnology and Advanced Materials | Shukla S.,Institute of Nanotechnology and Advanced Materials | Perkas N.,Institute of Nanotechnology and Advanced Materials | Solovyov L.A.,RAS Institute of Chemistry and Chemical Technology | And 2 more authors.
Langmuir | Year: 2011

Colloidal silver has gained wide acceptance as an antimicrobial agent, and various substrates coated with nanosilver such as fabrics, plastics, and metal have been shown to develop antimicrobial properties. Here, a simple method to develop coating of colloidal silver on paper using ultrasonic radiation is presented, and the coatings are characterized using X-ray diffraction (XRD), high resolution scanning electron microscope (HRSEM), and thermogravimetry (TGA) measurements. Depending on the variables such as precursor concentrations and ultrasonication time, uniform coatings ranging from 90 to 150 nm in thickness have been achieved. Focused ion beam (FIB) cross section imaging measurements revealed that silver nanoparticles penetrated the paper surface to a depth of more than 1 μm, resulting in highly stable coatings. The coated paper demonstrated antibacterial activity against E. coli and S. aureus, suggesting its potential application as a food packing material for longer shelf life. © 2010 American Chemical Society.

Solovyov L.A.,RAS Institute of Chemistry and Chemical Technology
Chemical Society Reviews | Year: 2013

Ordered mesostructured mesoporous materials, combining nano-organization with atomic disorder, are both attractive and challenging objects of investigation by X-ray and neutron diffraction. The development of diffraction mesostructure analysis methods and their applications in studies on structural characterization, formation processes and physisorption phenomena in these advanced materials are summarized in this tutorial review. The focus here is on the techniques that allow extracting mesostructure parameters and peculiarities of density distribution in the materials from the Bragg reflection positions and intensities. The investigations of mesoporous silicates, their nonsilica replicas and composites are discussed including the combined use of diffraction with electron microscopy and physisorption. The small-angle scattering curve analysis, which is also an important methodology in the field, is out of the scope of this review. © The Royal Society of Chemistry 2013.

Tsyganova S.I.,RAS Institute of Chemistry and Chemical Technology
Wood Science and Technology | Year: 2013

In this work, different activated carbons were prepared from composites based on birch sawdust and coal-tar pitch by chemical activation with zinc chloride, phosphoric acid, and potassium hydroxide followed by carbonization. The influence of different chemical agents (ZnCl2, KOH, and H 3PO4), final temperature of carbonization and media on yield and structural properties of the carbonic product was studied. It was shown that chemical agents allow increasing yield of carbonic residue. Composite modification by H3PO4 or ZnCl2 facilitates the formation of molded porous carbonic residue during the carbonization process. However, addition of KOH to the composite leads to formation of powder-like carbonic residue having a specific surface area of 1,600 m2 g -1 at 800 C. It was established that all samples aged in air medium at 800 C have higher values of specific surface area in comparison with the same samples aged in argon medium at similar conditions. © 2012 Springer-Verlag.

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