A new direction in the creation of ceramic materials with a specified phase composition and structure. Part I. Preparation of binders for ceramics production by the sol-gel method. 2. Preparation of ethylsilicate binders and their modification1

The problem of obtaining ethylsilicate binders by hydrolysis of ethylsilicate in an acid medium with various amounts of water is considered. The difference in the polycondensation of different hydrolysis products is discussed. It is suggested that the silica binder be carbonized by introducing a water-soluble substance into the hydrolyzate. The preceding paper of the series has been published in Nos. 1–2, 1999.     

A new direction in the creation of ceramic materials with a specified composition and structure. Part 1. Manufacturing binders for the ceramic industry by the solgel method. 5. Preparation and physicochemical properties of ethylsilicate binders for ceramic and refractory production

Compositions and methods for preparing various ethylsilicate binders for the production of ceramics and refractories are presented. The physicochemical features of the transformations of the created binders recommended for cast and pressed articles, unshaped mixtures, and coats and adhesives are considered. It is shown that for each filler and design of the material the binder should be chosen so as to provide the specified phase composition and structure 1The previous papers of the series have been published in Nos. 1–3, 5, and 7, 1999.     

A new direction in the creation of ceramic materials with a specified composition and structure. Part 1. Preparation of binders for ceramic production by the sol-gel method. 4. Structure and properties of transformation of gels in heat treatment; Creation of carbon clathrates in gel clusters

Results of a study of the structure and transformations of gels due to slow and rapid hydrolysis in an acid aqueous medium without organic solvents are presented. The conditions of formation of clathrates in gel clusters are discussed and results of DTA, IR-, and x-ray phase analyses of gels obtained by slow and rapid hydrolysis with different catalysts are presented. Conditions of carbon clathrate formation in gel clusters are specified The preceding articles of the series have been published in Nos. 1 — 3 and 5, 1999.     

The effect of thermal annealing on Fe/TiO2 coatings deposited with the help of RF PECVD method. Part I. Chemical and phase composition

Results of the studies on chemical structure and phase composition of both non-annealed and thermally annealed iron doped TiO₂ coatings are presented. The coatings were synthesized with the help of radio frequency plasma enhanced chemical vapor deposition (RF PECVD) and characterized by iron content in the range of 0–4.76 at%. In these studies, an analysis of both elemental composition and chemical bonding was performed with the help of X-ray photoelectron spectroscopy (XPS). X-ray diffraction (XRD) was applied to determine phase composition and Fourier transform infrared spectroscopy (FTIR) was used as a supplementary source of information. The obtained elemental composition data show that, apart from titanium, oxygen and iron, traces of chlorine as well as substantial amounts of carbon are present in the coatings. While chlorine has originated from plasma decomposition of TiCl_4, used as a source of titanium, a presence of carbon is associated with a surface contamination resulting from photocatalytic reactions of TiO₂ with the adsorbed carbon dioxide. The results of XPS and FTIR indicate that thermal annealing not only modifies phase composition of these materials, but also affects chemical bonding. Finally, XRD analysis shows that iron content has an effect on the size of coherent diffraction domains present in the films.     

Characterisation of cellulose treated by the steam explosion method. Part 3: Effect of crystal forms (cellulose I,II and III) of original cellulose on changes in morphology,degree of polymerisaion,solubility and supermolecular structure by steam explosion

An attempt was made to clarify the effect of the crystal form of untreated cellulose on the morphological and structural changes of cellulose during steam explosion treatment (steam pressure P = 2.9MPa (T = 508K), treatment time t = 15-300 s). For this purpose, the crystal form of soft wood pulp (cellulose I) was converted by solid-to-solid transition, with minimal unavoidable change in other structural characteristics including morphology and average degree of polymerisation, into cellulose II or cellulose III. It was proved by both X-ray and solid-state cross-polarisation/magic-angle sample-spinning (CP/MAS) ¹³C NMR analyses that even a simple addition of water at room temperature brought about a significant structural change in the steam-untreated cellulose samples. The solubility towards 9.1 wt% aqueous sodium hydroxide, S_a, of the cellulose samples of crystal forms I and III could be improved from 31-33% up to almost 100% by selecting appropriate steam explosion conditions (for example, P = 2.9MPa, t = 30 s). Such a magnificent increase in S_a by the steam explosion treatment was not observed for the cellulose II sample, even under the rather severe conditions of the steam explosion treatment at which the cellulose III crystal was converted to a large extent to cellulose I, as confirmed by X-ray diffraction. X-ray diffraction analysis showed that crystallisation of samples with cellulose I or II crystal occurred to some extent during the steam explosion treatment. Contrary to this, the degree of breakdown of the intramolecular hydrogen bond O₃…O'₅, as estimated by CP/MAS ¹³C NMR analysis, significantly increased for cellulose I and I11 during the treatment. The decrease in the viscosity-average degree of polymerisation, P, observed for all treated samples can be roughly categorised into two or three steps of the first-order decomposition reaction with different reaction rates.