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.

On 10th of February I have given a seminar on subjects regarding my previous work on maters thesis and also my plans connected to development of my PhD project.

As for my master’s thesis, significant part of my work time was devoted to building ad development of a specialized research tool for Laboratory of Analysis and Nondestructive Investigation of Heritage Objects of National Museum in Krakow. This device called “microfadometer” is capable of performing accelerated lightfastness tests of foto-degradable materials in order to identify fugitive colorants, determine objects behavior in specific lightning conditions etc. Test is performed by focusing high intensity visible wide-spectrum light on small area of specimen surface. Under conditions of intense illumination examined area of specimen is faded. Reflected spectra from illuminated spot are collected and recorded in short time intervals with included spectrometer. Based on recorded spectral data, color of sample test is calculated, and therefore color change can be associated with specific dose of light that has been applied to sample.
Thesis contains description of color measurement fundamentals, chemical and physical aspects of fading, construction and working principle of microfadometer, and collection of data from lightfastness tests performed with this device.

PhD part of my speech was associated with problems related to production of new generation of dental implants. Those new implants have complicated structural design and therefore require materials stronger than those used conventionally. One approach to this problem is to utilize pure titanium strengthened by severe plastic deformation methods. Implants constructed from such material poses all sort of advantages: biocompatibility, ability to osseointegrate, corrosion resistance, low weight, low electric conductivity and paramagnetism. Also usage of this material isn’t associated with risks that are present in case of alloyed materials such as inflammatory conditions caused by vanadium or neurologic diseases caused by aluminum.
Methods used for strengthening of titanium by severe plastic deformation that are suitable for implant production are ECAP and Hydrostatic Extrusion. KoBo method show some promising results when applied to hexagonal materials but there are no reports of titanium processed with this technique.
In my research I will be focusing on KoBo and HE methods for titanium processing. Processed materials will be investigated with modern techniques of Orientation Microscopy in SEM and TEM which will allow for precise quantitative microstructural description. Callorymetric tests also will be carried out as the material is going to be subject to heat treatment during implant production process. Other tests such as mechanical strength and corrosion tests along with wetability tests are also going to be carried out.

Luckily, this month I have managed to finish first basic features of my software toolbox. It can correctly discover geometric character of any given boundary, is able to recognize whether boundaries are near-twist, near-tilt or symmetric. It can detect, for now only for cubic system, if the boundary can be classified as CSL boundary. Now I am able to move to further, i.e. more interesting steps. Having a tool which can deal with one single boundary, one can process large date sets, and then see what happens!

My research in January:

During the first month of the year I started to conduct experiments. At first I bought 10 kg of magnesium and 50g of calcium. I also used zinc, but it was from supplies of my supervisor. I cast 25g of Mg-Zn4 wt% alloy in the presence of argon atmosphere at 750 oC. During this experiment I used steel mold and graphite crucible. Unfortunately it appeared that I got big pores in this alloy. Conclusion: steel mold has to be avoided or should be heated up before casting.