In December I performed some Vicker’s hardness test on the last series of composite samples (with submicron AlN reinforcement). It turned out that they have considerably lower hardness than the previous series (with ~1 micron AlN) – about 250 HV. The worse mechanical properties may origin from the tendency of fine AlN particles to form agglomerates.
I also calculated a matrix grain size distribution of this series of composites on the basis of TEM bright field micrographs analysis.

As December was passing by, and days until delivery of my titanium was freezing away I had the chance to read something more on plastic deformations of metals and KoBo method. Plastic deformation in low temperatures is inevitable tied to development of internal structure, decrease of ductility and increase of stress. This is related to dislocation nature of deformation. Structure formed during such deformation can be destabilized if initially set conditions of stress and temperature are altered. If such destabilization accrues with high dynamic at low temperature and high stress conditions, high dislocations energy it might lead to fracture of material. But if such process takes place with lower dynamic, for instance in higher temperatures, with low stress, destabilization of structure can be used to achieve very large plastic deformation without loosing integrity of material. This are some concepts that lead to realisation of KoBo method. Destabilisation of structure there is achieved by application of cyclically changing external stress. When internal structure is destabilised, material starts to deform by visco-plastic flow with very low internal stresses, thus allowing for very large deformation. Inventors of KoBo method argue that this type of deformation can take place at low temperatures but with specific strain conditions. The concept is that during high-rate deformation with cyclically changing deformation path high concentrations of point defects (vacancies, interstitial atoms) are created and maintained. Those defects has very low diffusion activation energies and therefore greatly improve ability of material to deform by plastic flow with almost no increase of internal stress. While this hypothesis presents completely new approach to plastic deformation it would be very interesting indeed to look closer at mechanisms involved with KoBo method. And that is one of the things I plan on doing in the foreseeable future.

In december I studied the complex formation and its stability in Zn(II)-Sn(II)-Mo(VI)-citrate systems by cyclic voltammetry method, in a series of electrolytes with different concentrations of sodium citrate, sodium molybdate, zinc sulfate(IV), and tin sulfate (IV). All electrochemical measurements were carried out in a 95 cm3 cell, in a system with a rotating disc electrode to ensure a constant and controlled hydrodynamic conditions. The measurements were performed potentiodynamically in a three-electrode cell by means of potentiostat PARSTAT 2273.
Unfortunately I had to stop suddenly, the research because of the failure of potentiostat.

This month I have focused on reading scientific literature, mainly concerning basics of focused ion beams. Additionally, I was trying to do some experiments on the sample received from IOD last month, but I didn’t manage to successfully accomplish any of the trials.

Is familiar with the methodology of sample preparation for microstructural studies (specimens), and support for Leica optical microscope. Prepared zgłady blades - very responsible of engine airplane - the test is not marked on the strengthening and anti-corrosion layers. Studies have confirmed the presence of several layers, which could not be detected using a method of acoustic microscopy. Perhaps with such a thin (several micrometers) are undetectable to the acoustic microscope, despite attempts to use different types of heads and change measurement parameters.