Total Resistance Values Research Articles

In-plane gas permeability and thought-plane resistivity of the gas diffusion layer influenced by homogenization technique and its effect on the proton exchange membrane fuel cell cathode performance

In this study, in-plane gas permeability and through-plane resistivity of gas diffusion layer (GDL) made by different microporous layers (MPLs) were characterized by a new combined measurement setup under different compression ratios. Applied MPL ink-homogenizing techniques were pulse sonication, continuous sonication, bath ultrasonic and mechanical stirring. Results showed that 20% GDL compression produced optimized in-plane gas permeability and through plane resistivity, which is suitable for application in proton exchange membrane fuel cell (PEMFC). However, bath ultrasonic technique is more desirable technique for MPL ink homogenization in term of obtained gas permeability and total resistivity values; 0.45 (×10−12 m2) and 2.63 (mΩ cm2) respectively.Morphological investigation was also presented a uniformly distributed MPL microstructure without large cracks for the MPL which was prepared by bath ultrasonic technique (MPL-C).The Obtained results in H2/air PEMFC under various cathode relative humidity (RHC), 33–100%, revealed that the performance of the MEA made by MPL-C is 20% higher than others; 504 mWcm−2 versus 385 mWcm−2at 33% RHC. More analysis by electrochemical impedance spectroscopy demonstrated that MPL ink preparation by bath ultrasonic techniques resulted a lower ohmic and charge transfer resistance in PEMFC at least in small scale MEA.

Assessment of cardiovascular function from multi-Gaussian fitting of a finger photoplethysmogram

Monitoring of cardiovascular function on a beat-to-beat basis is fundamental for protecting patients in different settings including emergency medicine and interventional cardiology, but still faces technical challenges and several limitations. In the present study, we propose a new method for the extraction of cardiovascular performance surrogates from analysis of the photoplethysmographic (PPG) signal alone.We propose using a multi-Gaussian (MG) model consisting of five Gaussian functions to decompose the PPG pulses into its main physiological components. From the analysis of these components, we aim to extract estimators of the left ventricular ejection time, blood pressure and vascular tone changes. Using a multi-derivative analysis of the components related with the systolic ejection, we investigate which are the characteristic points that best define the left ventricular ejection time (LVET). Six LVET estimates were compared with the echocardiographic LVET in a database comprising 68 healthy and cardiovascular diseased volunteers. The best LVET estimate achieved a low absolute error (15.41 ± 13.66 ms), and a high correlation (ρ = 0.78) with the echocardiographic reference.To assess the potential use of the temporal and morphological characteristics of the proposed MG model components as surrogates for blood pressure and vascular tone, six parameters have been investigated: the stiffness index (SI), the T1_d and T1_2 (defined as the time span between the MG model forward and reflected waves), the reflection index (RI), the R1_d and the R1_2 (defined as their amplitude ratio). Their association to reference values of blood pressure and total peripheral resistance was investigated in 43 volunteers exhibiting hemodynamic instability. A good correlation was found between the majority of the extracted and reference parameters, with an exception to R1_2 (amplitude ratio between the main forward wave and the first reflection wave), which correlated low with all the reference parameters. The highest correlation ( = 0.45) was found between T1_2 and the total peripheral resistance index (TPRI); while in the patients that experienced syncope, the highest agreement ( = 0.57) was found between SI and systolic blood pressure (SBP) and mean blood pressure (MBP).In conclusion, the presented method for the extraction of surrogates of cardiovascular performance might improve patient monitoring and warrants further investigation.

Microchannel System Simulation for a Neutron Production Target to be Used in the Boron Neutron Capture Therapy

Microchannel system simulations have been performed in this work based on the thermal resistance model developed by Phillips (1988) and followed by Zhimin (1997). As it appears in the bibliography [Phillips (1988), Zhimin et al. (1997), Ludewigt et al. (1997), Tuckerman et al. (1981), Knight et al. (1992)], this system should be capable of removing 1 kW/cm2, for this reason it is being taken into account for the design of a neutron production target with accelerators.Based on the previously mentioned model, two codes were written in MATLAB programming platform, that solve the equations of such model in an iterative way under constant pressure between the microchannel ends and constant pumping power, respectively. The codes calculate the total thermal resistance (and its components) of the microchannel system for a given geometry, in addition to the hydrodynamic variables and the system adimentional numbers (Re and Nu).The codes report total thermal resistance values and adimentional numbers comparable to those reported in different publications [Phillips (1988), Zhimin et al. (1997), Ludewigt et al. (1997)], discrepancies lower than 10%have been found. For this reason it is being considered to design a heat sink that drains the energy depositedby the accelerator's incident beam.

THE PARAMETERS OF CENTRAL HEMODYNAMICS IN YOUNG PEOPLE DEPENDING ON THE TYPE OF BLOOD CIRCULATION DURING PHYSICAL EXERCISE

The purpose of the study : to assess the parameters of central hemodynamics in young people with different types of blood circulation during physical exercise. Materials and methods. 39 male students of Gomel State Medical University were examined by the method of tetrapolar chest reography (impedance cardiography). The following parameters of central hemodynamics were assessed: heart rate, stroke volume, cardiac output, cardiac index, total peripheral resistance and left ventricular filling pressure. The parameters of central hemodynamics were studied in quiescent state and after physical exercise. Bicycle ergometric test with stepwise increasing load was used as physical exercise. Results and discussion. The study showed that the examined students with hyperkinetic type of circulation in quiescent state were characterized by high values of stroke volume, cardiac output, cardiac index and low total peripheral resistance, which are typical for moderate hyperdinamia of cardiac activity. Students with hypokinetic type had low values of stroke volume, cardiac output, cardiac index and high total peripheral resistance, left ventricular filling pressure which characterize more economical mode of heart work. Students with normorkinetic type of circulation were characterized by average values of the studied parameters in quiescent state. The features of the central hemodynamics parameters in young people depending on the type of blood circulation during physical exertion were revealed. Conclusion. In young men with hyperkinetic type of circulation during physical exercise the heart works in the least economical mode, and the range of compensatory possibilities of this type is limited. On the contrary, hypokinetic circulation is the most economical and the cardiovascular system in this type of circulation has a large range of function mobilization.

A new approach to objective evaluation of the success of nasal septum perforation.

BackgroundPerforations in the nasal septum (NSP) give rise not only to disintegration of the septum anatomy but also impairment in normal nasal physiology. The successes of these surgical techniques are usually equated to anatomical closure of the perforation. The goal of this study is to evaluate the subjective and objective results of our surgical technique for septal perforation surgery.MethodsAll NSPs in the six patients were closed by inferior turbinate flap. The Nasal Obstruction Symptom Evaluation (NOSE) instrument was used to evaluate the preoperative and postoperative subjective sensation of nasal obstruction. Measurement of preoperative and postoperative nasal airway resistance was performed using active anterior rhinomanometry which is an objective test. Wilcoxson signed rank test and Spearman correlation test were used to analyze correlation between NOSE scores and rhinomanometric measurements.ResultsThe full closure of the septal perforations was noted in 100% of patients. The total NOSE score was 14 preoperatively and one postoperatively. The improvement in NOSE scores was statistically significant (P≤0.002). The mean preoperative total resistance (ResT150) value was 0.13 Pa/cm3s-1, which is below the normal range (0.16-0.31 Pa/cm3s-1), while the mean postoperative ResT150 value was 0.27 Pa/cm3s-1. The correlation between the improvement in NOSE scores and improvements in ResT150 values was statistically significant.ConclusionsSurgical approaches should aim to solve both the anatomical and physiological problems of NSP. The application of subjective and objective tests in the postoperative period will help surgeons assess the applied techniques.

Coupling effects of steady-state heat and water vapor transfer through fabrics

In order to measure thermal and water vapor resistance of fabrics under non-isothermal conditions, the sweating guarded hot plate was modified. A nitrogen stream was used to sweep the water vapor away. The water vapor flux across the sample was determined by detecting the relative humidity of the outgoing nitrogen stream. The water vapor resistance was then calculated first. The dry heat loss for calculating thermal resistance was obtained by subtracting the evaporative heat loss from the total heat losses. The thermal resistance was determined accordingly. The thermal and water vapor resistance values of four fabrics were determined simultaneously by this test method. The results indicated that the total and intrinsic thermal resistance values of four fabrics measured in the presence of water vapor transfer were lower than those obtained without water vapor transfer. In addition, the total and intrinsic water vapor resistance values obtained under the non-isothermal condition were higher than those under the isothermal condition.

Characterization of the Porous Transport Layer (PTL)

Water management and effective reactant transport play a vital role in enhancing performance of the proton exchange membrane (PEM) fuel cell. The porous transport layer (PTL) consists of a macro porous gas diffusion layer (GDL) coated with a micro porous layer (MPL). These layers decrease mass transport losses by removing excess water and improving reactant gas distribution. A well-known manufacturing technique to decrease mass transport losses is to increase hydrophobicity of the PTL by loading Teflon to the GDL and MPL. A polarization curve will demonstrate the influence of this increase in hydrophobicity, especially in the region of high current densities where water production is high and the cell requires more reactants. In this region, mass transport losses cause a drastic loss in power.To study the mass transport effects, three PTLs were characterized with ex-situ and in-situmethods. Two different GDLs (GDL1 and GDL2) and two different Teflon loadings in the MPL (MPLT18 and MPLT50) were compared.Two ex-situproperties that are known to influence fuel cell performance are the contact angle (CA) of water in the PTL and the pore size distribution (PSD) of the GDL and MPL. Low surface tension liquid techniques were used to find the CA of the PTL and PSD of the MPL [1]. These results are reported in Table 1. Figure 1 shows the SEM images of the three PTLs (MPL side).Two in-situ techniques that are used to characterize fuel cells are impedance measurements and, more commonly, polarization curves. As mentioned, a polarization curve shows the effect of mass transport losses in the high current density region; a more effective PTL will lead to a higher maximum power. The polarizations curves in Figure 2 demonstrate this power trend in the PTLs tested. While this is the primary technique used for fuel cell testing, it lacks information about the fuel cell performance at its true optimum level.Impedance testing is considered a valuable tool in analyzing the resistance of fuel cells in its different regions of current density [2-6]. Figure 3 shows the impedance as a function of frequency in the form of a Bode magnitude diagram for the PTLs tested. In order to evaluate the total resistance of the cell (activation, ohmic, and mass transport resistances), the low frequency impedance at 1 Hz was used. These total resistance values are plotted as a function of current density in Figure 2.Evaluating the point of minimum resistance for each PTL reveals that this point is well below the maximum power, as displayed in Figure 2. This point appears to be of high importance and warrants further research. The results also show that as the hydrophobicity of the PTL increases (higher CA/ lower PS), the performance of the cell increases. Not only did GDL1 MPLT50 produce the best performance, its total resistance only increased slightly from its minimum until 1 A/cm2, supporting the robustness of this PTL. The results from this study can be applied to the characterization of any fuel cell system for its optimum performance. References R.K. Phillips, et al., World Hydrogen Energy Conference, 763, (2012)S.M. Rezaei Niya, M. Hoorfar, J. Power Sources, 240, 281, (2013)X. Yuan, et al, J. Hydrogen Energy, 32, 4365, (2007)L. Omati, et al., J. Hydrogen Energy, 36, 8053, (2011)D. Malevich, et al., J. Electrochem. Soc., 156, B216, (2009)Y. Tang, et al., J. Electrochem. Soc., 153, A2036, (2006)

Heat Transfer Characteristics in High Power LED Packaging

This study uses the T3Ster transient thermal resistance measuring device to investigate the effects to heat transfer performances from different LED crystal grains, packaging methods and heat-sink substrates through the experimental method. The experimental parameters are six different types of LED modules that are made alternatively with the crystal grain structure, the die attach method and the carrying substrate. The crystal grain structure includes the lateral type, flip chip type and vertical type. The die attach method includes silver paste and the eutectic structure. The carrying substrates are aluminum oxide (Alumina) and aluminum nitride (AIN) ceramic substrates and metal core PCB (MCPCB). The experimental results show that, under the conditions of the same crystal grain and die attach method, the thermal resistance values for the AIN substrate and the Alumina substrate are 2.1K/W and 5.1K/W, respectively and the total thermal resistance values are 7.3K/W and 10.8K/W. Compared to the Alumina substrate, the AIN substrate can effectively lower the total thermal resistance value by 32.4%. This is because the heat transfer coefficient of the AIN substrate is higher than that of the Alumina substrate, thus effectively increasing its thermal conductivity. In addition, under the conditions of the same crystal grain and the same substrate, the packaging methods are using silver paste and the eutectic structure for die attach. Their thermal resistance values are 5.7K/W and 2.7K/W, respectively, with a variance of 3K/W. Comparisons of the crystal grain structure show that the thermal resistance for the flip chip type is lower than that of the traditional lateral type by 0.9K/W. This is because the light emitting layer of the flip chip crystal grain is closer to the heat-sink substrate, shortening the heat dissipation route, and thus lowering the thermal resistance value. For the total thermal resistance, the crystal grain structure has a lesser effect to the heat dissipation performance whereas the packaging method and the choice of the substrate have a relatively higher effect to the LED heat dissipation performance. Combining the above results, we see that selecting the flip chip crystal grain with a closer light emitting layer to the substrate, the eutectic structure that has better thermal conductivity and the AIN substrate can effectively increase the heat dissipation performance of the LED module.

Numerical Simulation of the Thermoelectric Model on Vehicle Turbocharged Diesel Engine Intercooler

A thermoelectric gas-solid heat transfer numerical model was established between an air-cooling tube-fin intercooler’s intake and cooling air passage channel on vehicle turbocharged diesel engine. The outlet temperature of intake air, the output power of the thermoelectric components and the thermal conversion efficiency are considered as the research objectives. When load value is constant, the outlet temperature of intake air decreases with the number of thermocouples increases and there exist maximum values for output power and thermal conversion efficiency; when the number of thermocouples is constant, there is little effect on the outlet temperature of intake air with the load value increases. When the load was been optimal designed, set the load value throughout equals to the value of thermoelectric component total internal resistance, the values of the maximum output power was increased by 20.3% and the thermal conversion efficiency was increased from 1.78 to 3.48%.

Heart Rate Variability in Complex Regional Pain Syndrome during Rest and Mental and Orthostatic Stress

Complex regional pain syndrome (CRPS) is a pain condition with regional sensory and autonomic abnormalities in the affected limb. The authors studied systemic autonomic and hemodynamic function in CRPS patients during rest, and during orthostatic and mental arithmetic stress. Twenty patients with CRPS and 20 age-, sex-, and body mass index-matched control subjects participated. Mean values of heart rate variability, baroreceptor sensitivity, blood pressure, stroke volume, cardiac output, and total peripheral resistance were estimated during supine rest and 60° tilt-table testing. On a separate day, heart rate variability was also measured during mental arithmetic stress testing induced by a paced auditory serial addition task. Heart rate was increased and heart rate variability reduced in patients with CRPS patients compared with control subjects during rest and mental and orthostatic stress, whereas baroreceptor sensitivity was unaffected. When tilted from supine to upright position, patients with CRPS were not able to preserve cardiac output in comparison with control subjects, and they exhibited an exaggerated increase in the total peripheral resistance. The hemodynamic changes correlated to pain duration but not to pain intensity. The increased heart rate and decreased heart rate variability in CRPS suggest a general autonomic imbalance, which is an independent predictor for increased mortality and sudden death. The inability of the patients to protect their cardiac output during orthostatic stress was aggravated with the chronicity of the disease.

Three-Dimensional Multiphysics Coupled Field Analysis of an Integrated Thermoelectric Device

Thermoelectric elements made of semiconductor plates laminated onto a highly electrical and thermally conductive inter-connector with a flow channel configuration can be treated as an integrated thermoelectric device (iTED). An element constructed with bulk crystalline n- and p-type (Bismuth-Telluride) semiconducting materials and copper as a conducting material is considered. In this study, the thermoelectric performance of such an element using fluid-thermoelectric coupled field numerical methods has been investigated. The iTED is subjected to constant cold temperature at the bottom and top surfaces, while the inter-connector channel walls are exposed to hot fluid flow; the remaining surfaces are kept adiabatic. The performance of the iTED element is studied in terms of heat input Q h , power output P 0, conversion efficiency η, produced electric current and Ohmic and Seebeck voltages for different load resistances, inlet hot fluid temperatures T in , semiconductor material heights d, and flow rates Re. For fixed T in and Re, an optimum η is shown at a load resistance which is slightly lesser than total internal resistance value. An increase in T in results in an enhancement in P 0 and η; however, it has a minimal effect on the variation of optimum load resistance. At higher T in values, the increment in load resistance showed a significant change in the heat input values. Both semiconductor material height and fluid flow rate had a prominent effect on iTED performance. The P 0 and η are increased nearly three-fold and 1.6 times, respectively, at Re = 500 in comparison to Re = 100. Further, when d = 5 mm, approximately 1.7 times in P 0 and 3.3 times in η are achieved compared to d = 1 mm values. It is recommended that for an accurate modeling, design and optimization of state-of-the-art TED with flow channels be carried out using multiphysics coupling field simulations.

A Prospective Population-based Study of Total Nasal Resistance in Korean Subjects

ObjectivesRhinomanometry is a widely accepted method for objective assessment of nasal patency. However, few studies have reported the values of otherwise healthy population for nasal resistance in East Asians. The purpose of this study was to measure normal total nasal resistance (TNR) values in a large sample of Korean adults and to reveal parameters contributing to TNR values.MethodsSubjects were enrolled from a cohort of the Korean Genome and Epidemiology Study. They were evaluated by anthropometry, questionnaire, and active anterior rhinomanometry at transnasal pressures of 100 and 150 Pascal (Pa).ResultsThe study sample consisted of 2,538 healthy subjects (1,298 women and 1,240 men) aged 20 to 80 years. Normal reference TNR values were 0.19±0.08 Pa/cm3/second at 100 Pa and 0.22±0.09 Pa/cm3/second at 150 Pa. The TNR of women was significantly higher than that of men (P<0.0001). TNR decreased with increasing age in both genders (P<0.05). In women, lower body weight was related to increasing TNR. In men, current smokers had higher TNR than ex-smokers and never smokers.ConclusionThe results of the present study provide information regarding the values of otherwise healthy population of TNR and parameters associated with TNR in Korean adults.

Assessment of Nasal Airflow Resistance in the Healthy Population of Chattisgarh by Active Anterior Rhinomanometry

The aim of present study was to define a normal range of total nasal airflow resistance in the healthy population of Chattisgarh. This study was conducted at the Department of Otorhinolaryngology, Medical College Raipur, Chattisgarh over 93 healthy adults. A proper otolaryngology examination was done prior to the study and all the subjects were free from any type upper respiratory tract infection. This was the main inclusion criteria for the present study. All the subjects were distributed according to age and sex. Active Anterior Rhinomanometry is the best recommended method for evaluating the objective assessment of nasal airflow resistance; it was preferred for the assessment of total nasal airway resistance in present study also. The present study concluded that the mean value of total nasal airway resistance was 0.21 at 150Pa pressure. However the range of total nasal airway resistance was from 0.142 to 0.34Pa/cm(3)/s at the same pressure. The present study presents the normal range and mean value of total nasal airway resistance for the healthy adult population of Chattisgarh. Total nasal airway resistance is independent of age and sex.

Electrochemical investigation on the corrosion and hydrogen evolution rate of mild steel in sulphuric acid solution

Corrosion and hydrogen evolution rate of mild steel alloy have been investigated using various electrochemical techniques. Mild steel was polarized vs. saturated calomel electrode (SCE) in naturally aerated 0.1 M H 2SO 4 solution containing three newly synthesized heterocyclic compounds in different concentrations. The data obtained from polarization technique showed that the corrosion current density, i corr, and the hydrogen evolution rate decrease with increasing concentration of heterocyclic inhibitors in 0.1 M H 2SO 4 medium, indicating a decrease in the corrosion rate of mild steel as well as an increase in the inhibition efficiency (IE) of the newly synthesized inhibitors. The impedance measurements confirmed well the polarization behaviour. Increasing the temperature leads to an increase in corrosion or hydrogen evolution rate of the mild steel and a decrease of the total resistance value ( R T ) or the relative thickness (1/ C T ) of the film. The obtained results were confirmed by surface examination using scanning electron microscope.

Direct evidence of cutaneous resistance to evaporative water loss in amphibious mudskipper (family Gobiidae) and rockskipper (family Blenniidae) fishes from Pulau Hoga, southeast Sulawesi, Indonesia

Rockskippers (family Blenniidae) and mudskippers (family Gobiidae) are amphibious fishes common to tropical intertidal zones. While their emergence patterns differ, both groups spend considerable time on land where they are subject to desiccation. Using a gravimetric wind tunnel method we determined total and cutaneous resistance to evaporative water loss of lined, Istiblennius lineatus (Valenciennes in Cuvier and Valenciennes, 1836), and Ambon, Paralticus amboinensis (Bleeker, 1857), rockskippers as well as barred, Periophthalmus argentilineatus Valenciennes in Cuvier and Valenciennes, 1837, and common, Periophthalmus kalolo Lesson, 1831, mudskippers from Hoga Island, southeast Sulawesi, Indonesia. These fishes exhibited mean total resistance values ranging between 0.82 and 0.61 s/cm; values significantly higher than their agar replicas. Mean cutaneous resistance estimates ranged from 0.38 to 0.25 s/cm. Total and cutaneous resistances were statistically similar between species ( p = 0.125 and 0.480, respectively). Water loss resistance, while marginal, likely plays an important role in extending fish emergence times. Having greater resistance values may not be compatible with cutaneous respiration or necessary for fishes that frequently return to pools to eliminate nitrogenous wastes. This is the first direct evidence of evaporative water loss resistance in fishes.

Study of Ca3-xBixCo4O9+δ(0 < x ≤ 0.5) as Novel Cathodes for IT-SOFCs

The misfit compound Ca3-xBixCo4O9+δ (CCOBix, x = 0.1-0.5) are synthesized via conventional solid state reaction and investigated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). The powders exhibit good thermal stability, as well as good chemical compatibility with Ce0.8Sm0.2O2-γ electrolyte. The SEM results indicate that the melting point decreased with increased Bi amount. The maximal conductivities are 655.9 S•cm-1 and 917.1 S•cm-1 for CCOBi0.1 and CCOBi0.3, respectively. Among the investigated compositions, Ca2.9Bi0.1Co4O9+δ shows the lowest total polarization resistance values. The preliminary results indicate that Ca2.9Bi0.1Co4O9+δ is a promising candidate as IT-SOFC cathode material.

Cytology of nasal mucosa, olfactometry and rhinomanometry in patients after CO2 laser mucotomy in inferior turbinate hypertrophy.

To evaluate the cytology of nasal mucosa and sense of smell and nasal patency in patients underwent carbon dioxide laser turbinoplasty (CO2 laser mucotomy) due to chronic nasal hypertrophy. 46 patients with inferior turbinate hypertrophy underwent complete laryngological examination, anterior rhinomanometry, olfactory measurements and cytology of nasal mucous which were performed before and 3 months after CO2 laser mucotomy. Laser mucotomy was performed under local anesthesia. Cytograms revealed significant changes in cell proportion before and after the surgery. Goblet cells predominated in nasal smears before the laser mucotomy. An average percentage of eosinophils in evaluated cytograms before the surgery was 2.1%. Three months after laser mucotomy we observed decrease in goblet cells proportion (the mean range of goblet cells was 16.4%) in nasal cytology. We have also observed improvement in olfactory function, however only in 7 patients (20.6%). The mean value of total nasal airway resistance (NAR) before treatment was 0.98+/-0.24 Pa/cm3/s at 75 Pa. Rhinomanometry after 3 months showed a reduction in mean total resistance from the pretreatment level to 0.77 Pa/cm3/s. We believe that CO2 laser mucotomy is an efficacious, minimally invasive and easy to use treatment of inferior turbinate hypertrophy which is performed under local anesthesia with little discomfort for the patient and does not require hospitalization.

Corrosion inhibition of mild steel in acidic media using newly synthesized heterocyclic organic molecules

Hydrogen evolution reaction (HER) (cathodic reaction) of mild steel immersed in H 2SO 4 acid was investigated. Electrochemical corrosion behavior and hydrogen evolution reaction of mild steel has been investigated using different electrochemical techniques. Steel was polarized vs. saturated calomel electrode (SCE) in naturally aerated 1.0 M H 2SO 4 aqueous solution containing four organic inhibitors (newly synthesized heterocyclic compounds) of different concentrations. The observed different influence of corrosion inhibitors on the hydrogen evolution reaction was associated with the different chemical composition and structure. Polarization results showed that corrosion current density, i corr, and hydrogen evolution decreases with increasing concentration of inhibitors in 1.0 M H 2SO 4, indicating a decrease in the corrosion rate. Electrochemical impedance spectroscopy (EIS) measurements confirmed this behavior. An increase of temperature leads to increase in the corrosion or hydrogen evolution rate and a decrease of the total resistance value, R T. The obtained results were confirmed by surface examination.

Electrochemical Behavior of Sn-Ag Alloys in Alkaline Solutions

Abstract The behavior of four Sn-Ag alloys and their individual metal components in sodium hydroxide (NaOH) solutions was studied using open-circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). The results reveal that each of the initial open-circuit potential at zero time, Ei, and final open-circuit potential after 60 min, Ef, (at concentrations <0.30 M) shifts toward more negative values, indicating a relatively higher rate of dissolution during the spontaneous oxide growth/oxide dissolution process under the currentless conditions. While at concentrations <0.30 M, there is no significant change in potential. The two corrosion parameters (corrosion potential [Ecorr] and corrosion current density [icorr]) show a linear relation with both the solution concentration and alloy composition. EIS results show that each of the total resistance (RT) and reciprocal capacitance (C−1) values decreases with an increase in the tin content up to 50%. After that, there is l...

Development of porous cathode powders for SOFC and influence of cathode structure on the oxygen electroreduction kinetics

Meso/macroporous La 1− x Sr x CoO 3−δ powder with the specific surface area higher than 140 m 2 g −1 has been synthesized from the corresponding nitrates, using solution thermal decomposition method. These nanopowders have been used for preparation of SOFC cathodes, demonstrating lower oxygen electroreduction activation energy than that for less porous cathodes prepared from the powders synthesized using traditional solid state reaction method. To increase macroporosity of the cathodes the special pore forming agent has been added into the raw cathode paste. The very low total polarization resistance and activation energy values have been obtained for oxygen electroreduction, depending on the cathode porosity and potential applied.