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

Abstract

The sol-gel method is used to obtain from film-forming solutions, based on solutions of tetra-ethyl-ortho-silicate and phosphoric acid with addition of calcium and sodium salts, thin structured films in the systems SiO 2 -P 2 O 5 -CaO-(Na 2 O) with the following content by weight (wt.%): 10 -85 SiO 2 , 5 -40 P 2 O 5 , 10 -50 CaO, and 10 Na 2 O. The physical-chemical processes in solutions giving rise to a transition of the true solutions into colloidal solutions via successive sol and gel states are studied. A criterion is established for the film-forming power: the viscosity of the solutions. The critical value of the viscosity for obtaining high-quality films is determined. Oxide systems form in films during kilning to temperature 600°C. The structure of the films is investigated by means of infrared spectroscopy, atomic-force microscopy, and x-ray phase analysis. The surface of the films is characterized by an extended relief and porosity, so that it should have high adhesion properties. The thickness of the films obtained does not exceed 90 nm.The problem of developing new materials with prescribed properties is one of a number of key problems of modern materials science and, in particular, medical materials science. For a number of reasons, sol-gel (SG) methods have obvious prospects for solving this problem [1]. In the sol-gel process the components interact at the molecular level and a high degree of product homogeneity obtains in multicomponent systems. 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 films were formed on silicon substrates by centrifuging (centrifuge rotation rate 3000 rpm) and drawing (draw velocity to 30 cm/min). The films were secured by heat-treatment in two stages: at 60°C (1 h) and 600 -800°C (30 min). The viscosity of the solutions was measured with a glass viscosimeter (VPZh-2, capillary diameter 0.99 mm). The infrared spectra of the films were recorded in the frequency range 400 -...

Magnesium Alloys Implants Coated with 58S Sol-Gel Bioactive Glass to Retard First Stage Corrosion

“…Finally, the insert in Figure 1 shows a wide band located between 2500~3600 cm -1 , generally associated with O-H stretching of absorbed water and Si-OH and P-OH groups. 24,28,29 The composition and presence of the different compounds in deposits or degradation process products can be analyzed by Micro-Raman spectroscopy. The analysis was focalized on the different deposits and singular points present in both systems.…”

Effectiveness of the Technologies of Titanium Implants Covering

“…Tetraethoxysilane (TEOS), H 3 PO 4 , and CaCl 2 have been used as precursors of SiO 2 , P 2 O 5, and CaO, accordingly. The content of SiO 2 in the finished films of oxide systems ranged from 20 to 85%, the Ca/P ratio was 1.67 [5]. The films have been applied on the surface of oxidized titanium by means of drawing from mature solution with speed 0.3 m/min.…”

“…This treatment removes alcohol and water (up to 400 °С), and then burning and removal of alcohol and products of thermo-oxidative degradation of etoxy groups take place (up to 600 °С). At that film system differentiates [5,6] in respect to composition with creation of the fields providing following crystallization of phases Са 2 Р 2 O 7 , СаSiO 3 , SiO 2 , and chlorapatite in quantity up to 5% in accordance with X-ray analysis. The films have specific surface 18 m 2 /g, pore size 17 nm and high adsorption properties, that was duty presence of Brensted surface-active centers (pH = 10-10.8).…”