Functional layers of black glasses based on ladder-like silsesquioxanes


                

Project manager:

Realised by:

Grant no.:

  • 2014/15/B/ST8/02827

Start date:

  • 2015-07-06

End date:

  • 2018-07-05

Research project objectives/Hypothesis

The main objective of the proposed project is to design and obtain functional layers of black glass on metal substrates on the basis of ladder-like silsesquioxanes. Black glasses are materials with a structure of the amorphous silica (v-SiO2), in which two O2- ions were substituted by one C4- ion. As a result, local increase of bond density leads to a sharp increase in the mechanical properties of the material. Only a limited amount of carbon ions can be introduced into the v-SiO2 structure, therefore most often in the black glasses there is also present the so called free carbon, which is responsible for their black color. The main problem in the preparation of black glasses with specific functional parameters (temperature, chemical resistance, mechanical strength, etc.) is the lack of control over the amount of free carbon. Hence, the main scientific goal of this project is to obtain layers of black glasses with variable but controlled amount of free carbon. We propose to solve this problem through the use of well-defined ladder-like silsesquioxanes. Additional problem poses  the carbothermic reduction of SiO2 leading to a decrease in mechanical properties of black glass at high temperatures. We plan to solve it by introducing the aluminum ions into silicon oxycarbide structure. We believe that the appropriate selection of precursors will allow us to receive the black glasses having a predictable content of free carbon, and therefore, depending on the application, with appropriate functional parameters.

Research methodology,

The sol-gel method will be used for obtaining ladder-like silsesquioxanes. The resulting sols will be applied to appropriate metal substrates by dip-coating, spin coating and electrophoretic deposition techniques. The obtained coatings will be subjected to a ceramization process in a protective atmosphere at temperatures resulting from thermal studies (DTA, DTG, DSC). The functional parameters of silicon oxycarbides are determined by both structure of the glass network and the presence, amount and a form of free carbon. Therefore it is necessary to precisely define both the structure and microstructure of obtained materials. For this purpose, it is planned to carry out detailed spectroscopic (FTIR, Raman, MAS NMR, XPS) and microscopic (SEM, AFM, confocal microscopy) studies. It is extremely important from the point of view of future applications to conduct Raman mapping and in situ Raman studies at temperatures up to 1500oC, in different atmospheres. This will allow identifying structural changes in the studied glasses. On the basis of structural and microstructural studies models of black glass structures with different carbon content will be created. These models will then be verified by computer simulations. The functional parameters of received materials - heat resistance, chemical resistance, porosity, mechanical strength, bioactivity, conductivity, tightness, etc. will be determined on the basis of multiple studies (AFM, impedance spectroscopy Kokubo test, SAXS, nanoindentation, scratch test, and others). Obtained results of the functional parameters of glasses will be correlated with the results of structural studies and computer simulations. This will clarify and allow suggesting the most appropriate model structure for individual glasses of varying carbon content, and thus anticipating and planning properties of received materials.

Research project impact

Determination of the structure and microstructure of black glasses with a variable content of free carbon will settle the controversy about the internal structure of these materials, which will help to systematize and deepen knowledge about the structure of this group of glasses. We propose the use of black glasses obtained in the form of layers as: 1) biomaterials, 2) materials for selected elements of the fuel cells, 3) as catalyst supports. Planning and obtaining various black glasses with properties consistent with the requirements of the users gives a hope for far-reaching progress in terms of a new class of biomaterials, protective layers of metal surfaces and catalysts. This will have an indubitable impact on the quality of people's lives by gaining access to new and better biomaterials and the reduction of environmental pollution (catalysts, fuel cells).