Solid Oxide Fuel Cells (SOFCs) are a promising technology that can provide efficient and clean energy production. The general barriers hindering their market entry are durability, i.e. resistance to aging, and costs. In parallel to the deeper insight into the different degradation sources and improved understanding of ageing factors and their interactions, work towards higher accuracy for the assessment and monitoring of real-world fuel cell ageing in necessary. The requirements for operational stability formulate the parameter “degradation rate” (DR). Most often long term durability tests are performed at constant current load and the decrease of the voltage is used for its definition. In this work a new approach based on analysis of the volt-ampere characteristics, named Differential Resistance Analysis (DRA), is presented. It operates with the differential resistance, i.e. with the derivative of the voltage in respect to the current (dU/dI = Rd) which is more sensitive to small deviations and thus increases the sensitivity of the analysis. Two performance indicators are derived (Rd, min and ∆U*) with differing selectivity: ∆U* is more sensitive to activation losses and Rd, min - to transport hindrances. The application of the DRA is demonstrated on examples from measurements in fuel cell and in reverse (fuel cell/electrolyzer) mode, as well as on modeling data. The results show that the method is at least 10 times more sensitive to DR evaluation in comparison with the classical approach.

This work investigates a diesel engine operating with different blends of diesel fuel, biodiesel and anhydrous ethanol. Anhydrous ethanol (99.8% purity) was added to diesel oil with 7% (B7) and 20% of biodiesel (B20), with the concentrations of 5% (E5), 10% (E10) and 15% (E15) and 20% (E20). The experiments were conducted on a naturally aspirated, four-stroke, four-cylinder, direct injection 44 kW diesel engine, operating at a constant speed of 1800 RPM and at the fixed load of 27.5 kW to attain the lowest specific fuel consumption (SFC). The results were compared with the standard B7 operation, and showed that ethanol addition (B7E5) reduced up to 7% carbon dioxide (CO2) emissions, associated with the decrease of the cylinder gas temperature, due to the ethanol high latent heat of evaporation, and to the ethanol lower carbon-to-hydrogen ratio and oxygen content. Total hydrocarbons (THC) emissions were reduced up to 14% with ethanol addition (B7E15), indicating higher fuel burn efficiency when ethanol is added to the fuel, as the oxygen available in ethanol molecule improves the burning during combustion. On the other hand, increasing biodiesel content in the fuel from 7% to 20% increased CO2 and THC emissions, both mitigated with the use of ethanol. Carbon monoxide (CO) and oxides of nitrogen (NOX) emissions showed different behavior, depending on ethanol and biodiesel concentration. Both biodiesel and ethanol increased SFC, due to the reduction of fuel lower heating value (LHV), although ethanol addition slightly increased fuel conversion efficiency.

A major challenge in nanofabrication is the manipulation and exact placement of nano-objects on a specific template. Artificial DNA nanostructures such as DNA origami have garnered significant interest as templates for incorporating nanomaterials at precise sites while the structures are self-assembled. This work shows the usage of the DNA origami technique in the design and fabrication of nanostructures with the shapes of a circle and a triangle using the third part of the M13 virus genome, named mini-M13, as a scaffold. These DNA origami templates were modified to have DNA binding sites with a uniquely coded sequence. This method is used to attach 5 nm gold nanoparticles functionalized with the complementary DNA sequence. Two new metallic nanostructures with different nanoparticle arrays having minimum size but recognizable morphology are provided. The formation and dimensions of the nanostructures were verified using AFM and agarose gel electrophoresis.

The microstructure of Ni-Mg-Al mixed oxides obtained by thermal decomposition of hydrotalcite-like compounds synthesized by a co-precipitation method has been studied by using X-ray diffraction (XRD) and atomic resolution transmission electron microscopy (TEM). XRD patterns revealed the formation of NixMg1-xO (x=0÷1), α-Al2O3 and traces of MgAl2O4 and NiAl2O4 phases. The peaks profile analysis indicated a small grain size, microdeformations and partial overlapping of peaks due to phases with different, but similar interplanar spacings. The microdeformations point out the presence of dislocations and the peaks shift associated with the presence of excess vacancies. The use of atomic resolution TEM made it possible to identify the phases, directly observe dislocations and demonstrate the vacancies excess. Atomic resolution TEM is achieved by applying an Exit Wave Reconstruction procedure with 40 low dose images taken at different defocus. The current results suggest that vacancies of metals are predominant in MgO (NiO) crystals and that vacancies of Oxygen are predominant in Al2O3 crystals.

Laser welding processes offer significant advantages such as high welding speed, narrow heat affected zone and quality of the welding joint. In this study, the process parameters of laser power and welding speed were modified for AISI 1018 steel plates of 8 mm thickness and compared using finite element method. The results of cross-section microstructure, heat affected zone and fusion zone were characterized. The grain refinement was affected as the parameters were modified. Tensile and microhardness tests were performed to determine the mechanical properties of the welding joints. Microhardness increased in fusion zone and decreased in heat affected zone. Tensile test showed ductile fracture in heat affected zone of the welding joints. The simulated profiles were compared with the experimental observations showing a reasonable agreement.

Two metal fillers with TiC nanoparticles (TiC NPs) of less than 100 nm for the overlay process is an alternative to hardfacing for treating surfaces subjected to severe wear. In this work, the effect of tribological behavior for TiC NPs addition on two Co-based filler materials, as well as the dilutions, was studied. Mixtures of Co-based filler metals without and with 0.5% and 2% TiC NPs were deposited onto D2 steel plates using PTA (Plasma Transferred Arc). The BET surface area was 0.17 m2 g-1 and 0.31 m2 g-1, respectively, for Stellite 6 and 12. The distribution of ca 23% macroporous for Stellite 6 was sufficient to get inside the TiC NPs, as well as in the case of Stellite 12, with a pore distribution of ca 13%. Stellite 12 has an increase in the dilutions (70%) and enthalpies showed endothermic reactions. Stellite 6 with NPs was determined to be most effective in increasing the wear resistance.

Aluminum alloys have increased their use due to the properties such as low density, resistance to corrosion under environmental conditions and mechanical properties. In this work, the alloying elements are immiscible promoting dendrites formation with different phases attributed to zinc and tin. The applied mechanical stresses promoted the modification of the dendrite sizes (interdendritic space) as well as pore sizes and shapes. The microhardness decreased in the ternary Al-Zn-Sn alloy with a subsequent increase caused by microstructural changes after cold work. By XPS, the metallic elements were detected with an aluminum oxide layer.

In the present investigation, AA7075-T6 alloys and AZ31B-H24 were joined by the FSW process using the following range of parameters: rotational speed between 200 and 800 rpm, welding speed from 30 to 60 mm/min and a tilt angle from 1° to 3°. In some cases, a tool offset of 1 mm was used into Mg-based alloy. The experimental results show that sound and good joints can be obtained by positioning the tool in the middle of the joint-line using a rotational speed of 200 rpm, a welding speed of 30 mm/min and a tool tilt angle of 1°. The hardness and ultimate tensile strength in the stir zone were 122 Hv and 61.35 MPa, respectively. Also, it is important to mention that the Al3Mg2 and Al12Mg17 intermetallics compounds were observed in the this zone besides some defects like cavities and tunnel.