In the beginning of this month I took part in training concerning new software for 3D EBSD measurements. IT implements some new features. Additionally, it is much easier to use and (at least by now) appears to be more stable. Rest of the month was spent on further training and gaining experience in use of the new software.

During the last seminar, on January 20th, I had an opportunity to share with my colleagues the results of the research I did for my engineer’s degree. I earned the degree at the Faculty of Foundry Engineering, AGH University of Science and Technology, though I did most of the experimental work in the Foundry Research Institute in Kraków. Foundry engineering was my second course of study. My educational path was somewhat reversed – I first graduated as a MSc from the Faculty of Applied Mathematics and only after that I got my engineer’s degree.
The title of my diploma thesis was Fly ashes as a component of the reinforcement of aluminium alloy matrix composite. Fly ashes are by-products of the combustion of coal in power plants. They are removed by the dust collection systems from the exhaust gases as fine, spherical glassy particles from the combustion gases before they are discharged into atmosphere. The significance of fly ashes stems from the fact that they are widely used in concrete industry because of their fineness and pozzolanic nature.

The aim of my project was to determine the thermophysical properties. I prepared the samples for testing the temperature characteristics of fly ashes in the form of 3 mm x 3 mm cylinders, compacting the ashes in a special die for sample preparation. I put the samples into apparatus for the determination of characteristic temperatures. For the analysis of the results I used a computer software of PR-25/1750 apparatus, which assists the determination of the temperature of phase transformations.
The results I obtained allowed me to conclude that the production of vitreous materials can be an effective route for recycling of fly ash because the high temperature involved in the process leads to the complete destruction of the organic pollutants. What’s more, heavy metals can be incorporated in the glassy product.

I also carried out experiments on ceramic materials made from fly ashes. I prepared a ceramic called cordierite, which is obtained in the reaction of mullite (contained in fly ashes) with magnesium oxide and silicon dioxide. For that I used fly ashes from different different power plants situated all over the country. The protocol for preparation of codierite was as follows. First, mixture milling was applied for 2-3 h with 2500-3000 r/min, then 10% of glicerine was added, followed by another 10 minutes of milling. The samples were compacted with 20 – 40 MPa pressure and eventually moisture was removed by 3h-long treatment in 100-250°C.

What the cordierite was used for? As the more attentive readers probably have already guessed, I used them for the autoinfiltration process. The procedure was simple. Heat treatment with protective gases in 1350°C for 2.5 h, then immersion of the samples in liquid 7075 Al alloy and finally storing the samples in molten Al alloy in 1000°C for 24h. This treatment allowed me to obtain IPC, which stands for Interpenetrating Phase Composites.

When it came to autoinfiltration, I did not restrict myself to cordierite , but also investigated another fascinating material - ceramic preforms made of cenospheres (particles with a largely empty hollow core). First I immersed the preforms in molten Al alloy (700°C) and kept them there for 7 days. After 7 days I again obtained Interpenetrating Phase Composites (IPC).

That’s all for today. In the near future I will tell you more about my PhD project so stay tuned.

First try of measurement the thermodynamic properties of liquid ternary Al-Li-Zn. The measurement of electromotive force (EMF) by using lithium reference electrode. First attempt of building cell
I attended a Seminar and Workshop at SIMAP/Grenoble/France Computational Thermodynamics and Kinetics. Introduction to Thermo-calc software and DICTRA and TC-PRISMA. Thermo-calc software is indispensable tool to modelling phase diagram for binary and multi-component systems in the frame of solid solution models.

Acid textures on polycrystalline and monocrystalline silicon wafers were made. Also monocrystalline wafers were different surface orientated (100) and (111). Texture mixture of HF:HNO3:CH3COOH had various volume ratio and led to different surface morphology examined using scanning electron microscopy SEM. Chemical etched surface should have a low reflectance in order to keep solar radiation inside the material and use it in the photovoltaic effect again. Holes should have rounded shape with several nm diameter.
Selected composition: 1HF:7HNO3:2diluent and 7HF:1HNO3:2diluent where diluents is CH3COOH or H2O. The time of texturing process was determined as 1 min and in some cases, following the literature, was elongated to 2 or 3 min. The next step is to implement on silicon wafers a typical cell technology involving diffusion from a POCl3 as a source, surface passivation by oxidation, anti-reflection layer deposition, ohmic contacts screen-printing, firing and electrical characterizing.

First month of a New Year 2012 I devoted to mechanical characterization of coatings functionalized with polyelectrolytes. I made a review of the literature in the field of film stiffness control methods and evaluation of the results. Properties of the coatings could be characterized using atomic force microscopy (AFM), quartz microbalance (QCM), piezo-rheometry, methods of resonance frequencies, bulging test, hanging drops technique, osmotic pressure and qualitative/quantitative analysis of growth and cell proliferation. The stiffness obtained for polyelectrolyte layers varies in the range from a few kPa to several GPa, depending on the structural properties and the degree of cross-linking. Both the ionic cross-linking (a process dependent on the ionic strength and pH of the reaction), and covalent cross-linking of chemically induced or activated by light has an effect on the mechanical properties of the coating. I carried out a series of tests intended to verify the optimum mechanical properties of polyelectrolyte biomaterial surfaces dedicated to contact with blood using biological tests.

In January I also wrote an abstract entitled “The thermal and chemical stability of the porous scaffolds for the controlled cell deposition”, which will be presented on E-MRS 2012 Spring Meeting, Symposium G: Functional Biomaterials.