My research in February:



Table above presents all types of bioresorbable magnesium alloys, which were cast in February.
These alloys were produced in argon atmosphere in 750 C. I also focused my interest on theoretical background of TEM studying Introduction to Conventional Transmission Electron Microscopy written by Marc De Graef.

Preparation of the cell for the measurement of the electromotive force (EMF) for liquid ternary Al-Li-Zn alloys, especially in Li-rich, in which Al/Zn is 0.14. Analysis data and calculation of the partial molar thermodynamic functions, like enthalpy, entropy and Gibbs energy. Description of the temperature and concentration dependence of the electromotive force.

Last month I focused on preparing an article (“Microstructure and mechanical properties of AA7475/AlN compacts with varied reinforcing particles size”) and an abstract (“Effect of reinforcement particle size on microstructure and mechanical behavior of AlZnMgCu/AlN nano-composites produced using mechanical alloying”) for two oncoming conferences – “Composites 2012 – theory and practice” which will be held in Poraj on 18-20 April and “International Symposium on Metastable, Amorphous and Nanostructured Materials (ISMANAM)” which will be held on 18-22 June in Moscow.

Among the researches of acidic texture performed on multicrystalline silicon texture some selected wafers were subjected to the production of solar cells. Then optoelectronic parameters (reflectance in the range of 400-1100 nm and the current-voltage characteristics) were examined. I am pleased to announce that the reflectivity of the best solar cell was reduced to 10% and the effectiveness of the obtained solar cells was founded to be 13.6%.

In the last month I decided to focus my attention on polyelectrolyte layers internal structure and its influence on physico-chemical properties of the multilayer coating. Therefore I made a literature review and I prepared a series of samples for FTIR (Fourier Transform Infrared Spectroscopy) evaluation. Fourier Transform Infrared Spectroscopy is a very sensitive technique to investigate the internal structure of thin films. This is due to the fact that polypeptides, proteins and polysaccharides have specific vibration modes that can be clearly identified by infrared spectroscopy. The amide I and amide II bands of polypeptides and proteins are investigated and their decomposition allows to obtain access to the respective percentages of the different types of secondary structures (α-helix, β-sheet, random structures) [1]. For polysaccharides, the saccharide rings as well as the negatively charged carboxylic and sulfate groups present well defined chemical signatures that can be used to determine the composition of complex mixtures. It is possible to quantify ion pairing in thin films, i.e; to give a quantitative estimate of the amounts of positive and negative charges interacting between each other [2].

1. Roach P., D. Farrar, and C. C. Perry. 2005. Interpretation of protein adsorption: surface-induced conformational changes. J. Am. Chem. Soc. 127:8168-73.
2. Crouzier T., and C. Picart. 2009. Ion pairing and hydration in polyelectrolyte multilayer films containing polysaccharides. Biomacromolecules 10:433-442.

In February I also continued issue concerning polyelectrolyte coatings optimal stiffness determination. Herein I have performed observations of growth and cell morphology of commercially available HUVEC line and fibroblast line on the prepared during the previous month functionalized polyelectrolyte surfaces with varying degrees of chemical cross-linking.