Structure and properties of nanoproducts of the system P2O5 – SiO2

Abstract

Thin films and dispersed products in the system SiO 2 -P 2 O 5 with phosphorus oxide molar content from 0 to 30% have been obtained by the sol-gel method from film-forming solutions based on tetraethoxysilane and phosphoric acid, ethyl alcohol, and water. The variations of the rheological properties in successive states of the solution -sol-gel system are established. The physical -chemical processes in solution with deposition on a substrate and with heat-treatment of the product are investigated. IR spectroscopy and atomic-force microscopy are used to study the structure and physical -chemical properties of the films and disperse products obtained.The sol-gel technology is being increasingly used to obtain oxide ceramic, glass ceramic, and glassy materials. This method for synthesizing materials in oxide systems makes it possible to extend the boundaries of the glass-formation zone and, correspondingly, the composition range for practical applications [1, 2]. Silicophosphate glasses, both binary and polycomponent, conventionally are used to obtain optical media, and in recent decades in other areas also [3 -5]. The production of silicophosphate glasses by the conventional melting of the initial materials together is a laborious process that is difficult to control, which results in uncertain composition and instability of the properties of the glass produced. At the same time, it is precisely the sol-gel methods of synthesis, specifically, of bioglass, together with the technological advantages that has a positive effect on the bioactive properties of the materials obtained [6].The purpose of the present work was to obtain materials in the system SiO 2 -P 2 O 5 with phosphorus oxide content from 0 to 30% 2 by the sol-gel method and to investigate their structure and physical -chemical properties.The materials were obtained in a finely dispersed powder state and in the form of films from film-forming solutions (FFS). They were prepared on the basis of 96% analytically pure (AP) ethyl alcohol, AP tetraethoxysilane (TEOS), and AP orthophosphoric acid with solution concentration 0.4 moles/liter. The films were obtained on different amorphous and crystalline substrates by centrifuging with rotational speeds 4000 rpm or drawn at the rate 5 mm/sec followed by heat-treatment at different temperatures. The powder materials were obtained by dryng FFS after they were completely aged.The physical -chemical processes occurring in the solutions and during treatment of the products obtained from them were studied be means of viscosimetry (VPZh-2, temperature 25°C), IR spectroscopy (Perkin Elmer "Spectrum One"), and mass-spectrometric analysis. The thermal analysis of the thin-film systems was performed on a setup using microbalances based on a piezoelectric resonator with weighing accuracy 10 -8 g. Atomic-force (Solver P47) and electron (Phillips SEM 515 scanning electron microscope) microscopy were used to study the composition and structure of the films. The index of refraction and the thickness of the films were measured w...

Production of SiO2–P2O5–CaO–(Na2O) structured films

“…Sol-gel methods make it possible to control the transition from an amorphous into a crystalline state without introducing mineralizing additives as well as to obtain monolithic articles, highly disperse powders, and thin films on different substrates [2]. Sol-gel technologies make it possible to obtain high-purity materials at low temperatures by introducing micro quantities of substances, which is of great value for obtaining biomaterials [2,3].The principles of producing nanostructured films and dispersions as well as the physical-chemical processes in a double silicophosphate system are examined in [3,4].The objective of the present work is to investigate the possibility of obtaining by the SG method structured films in the system SiO 2 -P 2 O 5 -CaO-(Na 2 O) and to study their structure.The procedure described in [3,4] was used to prepare the solutions for synthesizing the films (film-forming solutions -FFS) for oxide systems in the composition range (% 4 ) 10 -85 SiO 2 , 5 -40 P 2 O 5 , 10 -50 CaO, and 10 Na 2 O. The initial materials consisted of tetra-ethyl-ortho-silicate (TEOS), orthophosphoric acid, calcium chloride, and sodium chloride.…”

“…The principles of producing nanostructured films and dispersions as well as the physical-chemical processes in a double silicophosphate system are examined in [3,4].…”

“…The procedure described in [3,4] was used to prepare the solutions for synthesizing the films (film-forming solutions -FFS) for oxide systems in the composition range (% 4 ) 10 -85 SiO 2 , 5 -40 P 2 O 5 , 10 -50 CaO, and 10 Na 2 O. The initial materials consisted of tetra-ethyl-ortho-silicate (TEOS), orthophosphoric acid, calcium chloride, and sodium chloride.…”

“…[3,4] it was found that the viscosity h day of a solution after aging for 1 day for TEOS is 1.9´10 -3 Pa × sec, while the viscosity of solutions for obtaining two-component oxide systems is in the range (2.3 -2.7)´10 -3 Pa × sec, increasing with the content of phosphoric acid, which in terms of P 2 O 5 corresponds to a change of the latter from 10 to 30%. To obtain three-component oxide systems with increasing calcium chloride concentration in solution, corresponding to a change of the calcium chloride concentration from 10 to 50%, the value of h day of FFS varies in the range (2.6 -3.5)1 0 -3 Pa × sec in the series with 20% P 2 O 5 ( Fig.…”

“…The IR-spectroscopy data show that adsorbed water and an organic solvent, characterized by the stretching vibrations of P=O, PO 4 3-groups, siloxane chains d (Si-O-Si), and calcium bonds with oxygen, are present in the films formed at 25°C. The presence of characteristic bands at 1166 and 1259 cm -1 proves that water is present in the films right up to 800°C and that heat-treatment to 500°C completely removes organic compounds.…”