Influence of grain size distribution on the Hall–Petch relationship of welded structural steel

The strength of polycrystalline metals increases with a decrease in grain size according to the Hall-Petch relationship. However, heterogeneous microstructures deviate from this relationship dependingon the distribution of grain sizes. This paper introduces a rule of mixtures based approach fordetermining the characteristic length of the microstructure for heterogeneous weld metal. Theproposed grain size parameter, the volume-weighted average grain size, is measured experimentallyfor nine structural steel weld metals and two base materials. The weld metals are found to have alarge variety of grain size distributions that are noticeably broader than those of the base material dueto differences in phase contents. The results show that the volume-weighted average grain size is ableto capture the influence of grain size distribution on the strength of welded structural steel. Based onthe experimental results, a modified Hall-Petch relationship is formulated for the strength predictionof heterogeneous microstructures. The modified relationship is also found to be applicable to datafrom the literature.Peer reviewe

Stabilization of metal counter electrodes for dye solar cells

The purpose of this study was to identify stable metal based counter electrodes (CE) for dye solar cells (DSC). Previous studies have shown that stainless steel (StS 304) suffers from corrosion when used as a counter electrode. Therefore metals which have inherently higher corrosion resistance, such as stainless steel types 321, 316 and 316L, Inconel 600 and titanium, were investigated here. When using thermal platinization for the preparation of the catalyst layer on CE, only the titanium foil based metal based DSC remained consistently stable in the 1000 h light soaking test. The counter electrodes were also prepared with sputtering ∼20 nm thick layer of Pt which provides a highly uniform layer on the CE which acts also as a protective coating on the metal. With sputtered Pt, DSC on all studied metals expect for Inconel remained at 80–95% of the initial efficiency after light soaking test for 1000 h.Peer reviewe

Dye Solar Cells on ITO-PET Substrate with TiO[sub 2] Recombination Blocking Layers

Atomic-layer-deposited TiO2 recombination blocking layers were prepared on indium tin oxide–poly(ethylene terephthalate) (ITO–PET) photoelectrode substrates for dye solar cells and were examined using several electrochemical methods. The blocking layers increased the open-circuit voltage at low light intensities. At high light intensities, a decrease in the fill factor (FF) due to the additional resistance of the current transport through the layer was more significant than the positive effect by the reduced recombination. The decrease in the FF was reduced by a thermal treatment that made the blocking layer more conductive due to a structural change from an amorphous to a crystalline form. Therefore, thinner blocking layers of this type are required for plastic cells prepared at low temperature than for conventional glass dye solar cells made with temperature processing.Peer reviewe

Parallel Genetic Algorithm for Shortest Path Routing Problem with Collaborative Neighbors

Shortest path routing is generally known as a kind of routing widely availed in computer networks nowadays. Although advantageous algorithms exist for finding the shortest path, however alternative methods may have their own supremacy. In this paper, parallel genetic algorithm for finding the shortest path routing is resorted to. In order to improve the computation time in this routing algorithm and to distribute the load balance between the processors as well, Fine-Grained parallel GA model is opted for. The proposed algorithm was simulated on Wraparound Mesh network topologies in different sizes. To this end, several experiments were anchored to identify the most influential parameters such as Migration rate, Mutation rate, and Crossover rate. The simulation result shows that best result of mutation rate is: about 0.02 and 0.03, and migration rate for transmission to the neighbor’s node is 3 of the best chromosomes. This study has already shown that through using performance-based GA which uses fine-grained parallel algorithms, timing germane shortest path routing can be improved

Insights into corrosion in dye solar cells

The main issue in using low cost metals in dye solar cells is the corrosion caused by the liquid electrolyte. Contrary to typical applications of metals, the adverse effects of corrosion in dye solar cells are related to irreversible depletion of charge carriers from the electrolyte rather than consumption of the metal itself. It is calculated that the penetration rate due to corrosion should not exceed 10−4 mpy (a couple of nanometers per year) to ensure device lifetime longer than 1 year. This is 10 000 times slower rate than what is considered to be a general benchmark value for very low corrosion rate in the field of corrosion science and has a major effect on how corrosion should be investigated in the case of dye solar cells. Different methods, their applicability, and limitations to investigate corrosion in dye solar cells are evaluated here. The issue with most techniques is that they can detect metals that are clearly corroding, but they have significant limitations in proving a metal stable. Our investigation shows that the most reliable information on corrosion is obtained from complete dye solar cells that are exposed to working conditions. A combination of color analysis of the electrolyte to such measurement is proposed as a means to extrapolate future performance of the cells and estimate potential lifetimes of the dye solar cells in regards to corrosion.Peer reviewe

Low Cost Ferritic Stainless Steel in Dye Sensitized Solar Cells with Cobalt Complex Electrolyte

Cheap ferritic stainless steel is applied here as the counter electrode substrate in dye sensitized solar cells with cobalt complex electrolyte. A 5.0% efficiency was reached with these type of cells which is more than 2.5 times higher compared to previously reported devices with metal counter electrode and cobalt complex electrolyte. The electrochemical impedance spectra analysis showed that the best cells with the ferritic steel counter electrode had as low charge transfer resistance (3.6 Ωcm2) as the reference glass cells with the same electrolyte. While in previous studies many metals have corroded in the cobalt complex electrolyte, the stability analysis including scanning electron microscope imaging of the aged electrodes suggested that the ferritic stainless steel substrates did not corrode in the electrolyte. Hence ferritic stainless steel appears as a possible alternative counter electrode in dye solar cells with cobalt electrolyte in terms of cost, performance and stability.Peer reviewe

Stability of Dye Solar Cells with Photoelectrode on Metal Substrates

In this study, the stability of dye solar cells (DSCs) with different kinds of metals as the photoelectrode substrate is studied. Stainless steels (StSs), Inconel, and titanium substrates were tested to find stable substrate options. Photovoltaic characterization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy, and substrate polarization measurements were used in the characterization. DSCs based on different grades of StS suffered from rapid degradation of efficiency within few hours in light soaking. Good stability was demonstrated with DSCs with Inconel and Ti photoelectrode substrates. The Inconel substrates have a thick passive oxide layer, which is likely related to good stability. However, according to the EIS analysis, the oxide layer of Inconel substrates increased resistive losses, which caused a lower fill factor and photovoltaic efficiency compared to the Ti-based cells.Peer reviewe

Do Counter Electrodes on Metal Substrates Work with Cobalt Complex Based Electrolyte in Dye Sensitized Solar Cells?

Yes. Testing 7 different metals as a substrate for a counter electrode in dye sensitized solar cells (DSSC) showed that some metals can be a good option for use with cobalt electrolyte. It was found that Stainless steels 304 and 321 as well as Ni and Ti suit well to the counter electrodes in DSSCs with cobalt electrolyte. In these 4 cases both the efficiency and the lifetime were similar to the reference cells on conducting glass substrates. In contrast, the cells with Al, Cu and Zn substrates suffered from both a low efficiency and a poor stability. These three metals had clear marks of corrosion such as apparent corrosion products in the aged cells. Additionally, we also investigated how the different types of catalyst materials perform in the case of a metal counter electrode (stainless steel 304) with cobalt electrolyte in comparison to reference glass cells. Among the 5 different catalyst layers the best results for stainless steel electrode were achieved with low temperature platinization whereas polymer catalysts poly(3,4-ethylenedioxythiophene)-p-toluenesulfone and poly(3,4-ethylenedioxythiophene)-polystyrenesulfone that worked well on the glass worked very poorly on the metal.Peer reviewe

Impacting Mindset and Innovation on Sustainability via Global Thematic Hackathon

Innovations related to social, economic and environmental grand challenges are common targets not only for societies as a whole, but also for the universities and business schools in them. This paper studies an example of how an intensive intervention via a local implementation of a global 3-day design hackathon (IFTP= Invent for the Planet) on global needs has impacted participants' understanding and motivation towards sustainability issues and solving them. The paper approaches the research objective by studying via a qualitative research approach the motivation letters that the participants submitted when applying for the event, learning outcome -report immediately after the event and their self-reported orientation to the issue area one month after the event. In addition, the views of the impacts were collected from the local facilitators and coaches to reflect their considerations to the views of the learners. The theory base of the paper discusses the approaches and models of behavioural change (nudging, planned behaviour, functional triad, etc.). The analysis offers insight on whether short-term interventions can have an effect on a sample that is already exposed and interested in the topic, since a course is a non-obligatory element of studies for all participants (from both business and engineering schools).peerReviewe