Renata Wlodarczyk

Protection of Steel Against Corrosion in Aggressive Medium by Surface Modification with Multilayer Polyaniline-Based Composite Film

Robust, polyaniline-based, multilayer composite films containing Prussian blue and hexacyanoferrate anions are considered here for the protection of stainless steel (SS) against pitting corrosion in strongly acid media. Polyaniline serves as a stable host matrix for large inorganic anions. At the interface formed by a composite film with SS, the interaction of hexacyanoferrate(II,III) - with iron(II,III), and some chromium(III), results in the formation of a thin insoluble metal hexacyanoferrate (mostly Prussian blue) layer. This phenomenon leads to improved passivation of the steel, and it strongly inhibits metal dissolution even in the chloride acid media. Because the metal hexacyanoferrate deposits are electronically conducting, further electropolymerization of dense and adherent composite polyaniline layers with hexacyanoferrate has been readily achieved. Due to the existence of electrostatic repulsion between negatively charged hexacyanoferrate sites and pitting-causing chloride anions, their transport through the composite film and access to the surface of SS are largely blocked.

Effect of sintering atmosphere on properties of porous stainless steel for biomedical applications

This study discusses manufacturing of metallic biomaterials by means of powder metallurgy with consideration for their unquestionable advantages, i.e. opportunities of obtaining materials with controllable porosity. The paper focuses on properties of 316 L stainless steel obtained using the method of powder metallurgy with respect to compacting pressure and sintering atmosphere. All the specimens were compacted at 700, 400 and 225 MPa, and sintered at 1250 °C. In order to analyze the sintering atmosphere, three different media were used: dissociated ammonia, hydrogen and vacuum. The study covered sintering density, porosity, microstructure analysis and corrosion resistance. The proposed method of powder metallurgy allowed for obtaining materials with predictable size and distribution of pores, depending on the parameters of sinter preparation (compaction force, sinter atmosphere). High corrosion resistance of the materials (sintering in the atmosphere of hydrogen and in vacuum) and high porosity in the sinters studied offer opportunities for using them for medical purposes.

BIOCHAR TO IMPROVE THE QUALITY AND PRODUCTIVITY OF SOILS

The paper presents the results of research focused on the investigations of the possibilities to use biochar to improve the quality and productivity of soils. Biochar is a material similar to the commonly known charcoal obtained from the thermolysis process (a process similar to dry distillation of wood). The structure and technical properties of biochar depend on the type of biomass which is produced and the thermal decomposition process conditions: process time, temperature and atmosphere. It was found that a positive effect of biochar on the soil properties is manifested through the improvement of soil fertility, better water retention, improvement of the cation exchange, and the regulation of the pH. The biochar used in the present study was obtained by autothermal thermolysis of biomass at 300 °C. Three types of biochars of different origin were used. The biochar samples were subjected to ultimate and proximate analysis, as well as structural and porosimetric investigations. The experimental research were also conducted on the experimental test field and gave a positive effect of the presence of biochar on soil quality and plant yield. Biochar introduced into soil allows for longterm storage of carbon. The introduction of biochar to soil has a positive effect on plant growth, higher dose resulted in an increase in biochar and plant mass.

Properties of graphite-stainless steel composite in bipolar plates in simulated anode and cathode environments of PEM fuel cells

The use of a graphite-stainless steel composite as bipolar plates (BP) in polymer electrolyte membrane fuel cells (PEMFCs) has been evaluated. The study covers measurements of mechanical properties, microstructural examination, analysis of surface profile, wettability, porosity and corrosion resistance of the composite. The corrosion properties of the composite were examined in 0.1 mol·dm−3 H2SO4 + 2 ppm F− saturated with H2 or with O2 and in solutions with different pH: in Na2SO4+ 2 ppm F− (pH = 1.00, 3.00, 5.00) at 80 °C. The performed tests indicate that the graphite modified with stainless steel can be a good choice to be used as a bipolar plate in PEM fuel cells.

Structure and Properties of Bioceramics Layers Used for Implant Coatings

Ceramic materials included in the group of advanced materials are increasingly used in different fields of science and technology as well as in everyday life. Hydroxyapatite ceramics (HAp, HA), based on calcium phosphates, i.e. chemical compounds being a constituent of natural bone, is found to be one of the best implantation materials for bone surgeries and dentistry. Due to poor mechanical properties of hydroxyapatite ceramics, the attempts are made to modify HA materials in order to extend the scope of current applications. It is also necessary to maintain high biocompatibility and bioactivity. Reported investigations encompassed comparison of functional properties of HA and HA+ZrO2 coatings (modified with 8%wt. Y2O3) as well as coatings remelted with laser beam. Microstructural and phase analyses of the coatings before and after remelting were carried out. In order to determine biocompatibility of the coatings after plasma spraying and remelting, corrosion resistance testing was also performed in Ringer’s solution.

Structural Analysis of Sintered Materials Used for Low-Temperature Fuel Cell Plates

Bipolar plates (BPs) are key components of fuel cells. Functions of materials used for fuel cells include equal distribution of gas fuel and air, conduction of electricity between adjacent cells, heat transfer from the cell as well as prevention of gas leakage and cooldown. Moreover, the material must show particular corrosion resistance in cell’s working conditions. Meeting particular requirements or prevention of the abovementioned situations will enable efficient operation of cells. Due to multifunctional nature of fuel cell plates, choice of materials used for plates is immensely difficult. This paper presents opportunities of application of a new technology of powder sintering for creation of parts for electricity and heat generators. This work also presents analysis of structural and phase-related properties, porosity and strength tests.

Porous Composite for Bipolar Plate in Low Emission Hydrogen Fuel Cells

The paper presents the results of graphite-stainless steel composites for the bipolar plates in low-temperature fuel cells. The sinters were performed by powder metallurgy technology. The influence of technological parameters, especially molding pressure were examined. Following the requirements formulated by the DOE concerning the parameters of the materials, it indicated by the value of the parameters. The density, flowability, particle size of graphite and stainless steel powders have been evaluated. Composites have been tested by microstructure and phase analysis, properties of strength, functional properties: wettability, porosity, roughness. The special attention was paid to the analysis of corrosion resistance obtained sinters and influence of technological parameters on the corrosion. Corrosion tests were carried out under conditions simulating the environment of the fuel cell under anode and cathode conditions. The effect of pH solution during working of the cell on corrosion resistance of composites have been evaluated. Contact resistance depends on roughness of sinters. Low ICR determined high contact area GDL-BP and high electrical conductivity on the contact surface. The ICR in anode conditions after corrosion tests are not change significantly; composite materials can be used for materials for BP in terms of H2.

Sintered Stainless Steel for Interconnectors for PEM Fuel Cell

Polymer electrolyte membrane fuel cell performance strongly depends on properties of the fuel cell stack bipolar plates (BPs). Bipolar plates are a key component of fuel cells. Functions of materials used for fuel cells include even distribution of gas fuel and air, conduction of electricity between the adjacent cells, heat transfer from the cell as well as prevention of gas leakage and cooldown. Due to multifunctionality of fuel cell plates, choice of materials used for plates is immensely difficult. This paper presents opportunities of application of a new technology of powder sintering for creation of parts for electricity and heat generators. Sintered stainless steel 316LHD was investigated as a candidate material for bipolar plate materials. 316L powders were compacted with the following load: 700MPa, 550MPa, and 200MPa, and then sintered at the temperature of 1250 °C in hydrogen medium. The main criterion for selection of a particular material for components of fuel cells is their corrosion resistance in operating conditions of hydrogen fuel cells. In order to determine resistance to corrosion in the environment of operation of fuel cells, potentiokinetic curves (as a function of temperature) were registered in synthetic solution 0.1M H2SO4 + 2 ppmF- at 80°C. The investigations also covered measurements of mechanical properties and microstructural testing of sinters with austenitic structure.

Properties and Application of Sintered Stainless Steel as Interconnectors in Fuel Cell

This study presents opportunities of application of sintered materials for interconnectors in low-temperature fuel cells. The task of these cell components is to provide even distribution of both fuel and oxidant. Materials for interconnectors must possess good thermal conductivity, conduct electricity and have high strength. It is also required that the material is corrosion-resistant under cell operating conditions. Due to multifunctional nature of these elements, selection of materials for interconnectors is extremely difficult. This paper presents analysis of structural properties and effect of pH level in sulphate solutions (pH = 2, 4, 6) on corrosion resistance in austenitic and ferritic sintered materials.

The Use of Methane in Practical Solutions of Environmental Engineering

Methane is the main component of the basic conventional fuels used in modern energetics – natural gas, as well as an essential component of renewable fuel like biogas. As a result of technological processes, methane can be extracted from hydrogen fuel which is dedicated to low-temperature fuel cells, generators or electric current and heat. The article reviews the possibilities of using methane to produce electricity, practical solutions and the problems that inhibit the implementation of fuel cell technology.