Search Results (4)

Bipolar Plates (BPPs) are the most crucial component of the Polymer Electrolyte Membrane (PEM) fuel cell system. To improve fuel cell stack performance and lifetime, corrosion resistance and Interfacial Contact Resistance (ICR) enhancement are two essential factors for metallic BPPs. One of the most effective methods to achieve this purpose is adding a thin solid film of conductive coating on the surfaces of these plates. In the present study, 410 Stainless Steel (SS) was selected as a metallic bipolar plate. The coating process was performed using titanium nitride and chromium nitride by the Cathodic Arc Evaporation (CAE) method. The main focus of this study was to select the best coating among CrN and TiN on the proposed alloy as a substrate of PEM fuel cells through the comparison technique with simultaneous consideration of corrosion resistance and ICR value. After verifying the TiN and CrN coating compound, the electrochemical assessment was conducted by the potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) tests. The results of PDP show that all coated samples have an increase in the polarization resistance ($R_p$) values (ranging from 410.2 to 690.6 $\mathsf{\Omega }·{\mathrm{cm}}^2$) compared to substrate 410 SS (230.1$\mathsf{\Omega }·{\mathrm{cm}}^2$). Corrosion rate values for bare 410 SS, CrN, and TiN coatings were measured as 0.096, 0.032, and 0.060 $\mathrm{mpy}$, respectively. Facilities for X-ray Diffraction (XRD), Scanning Electron Microscope (FE-SEM, TeScan-Mira III model and made in the Czech Republic), and Energy Dispersive X-ray Spectroscopy (EDXS) were utilized to perform phase, corrosion behavior, and microstructure analysis. Furthermore, ICR tests were performed on both coated and uncoated specimens. However, the ICR of the coated samples increased slightly compared to uncoated samples. Finally, according to corrosion performance results and ICR values, it can be concluded that the CrN layer is a suitable choice for deposition on 410 SS with the aim of being used in a BPP fuel cell system. Full article

The interplay between the ion exchange capacity, water content and concentration dependences of conductivity, diffusion permeability, and counterion transport numbers (counterion permselectivity) of CJMA-3, CJMA-6 and CJMA-7 (Hefei Chemjoy Polymer Materials Co. Ltd., China) anion-exchange membranes (AEMs) is analyzed using the application of the microheterogeneous model to experimental data. The structure–properties relationship for these membranes is examined when they are bathed by NaCl and Na₂SO₄ solutions. These results are compared with the characteristics of the well-studied homogenous Neosepta AMX (ASTOM Corporation, Japan) and heterogeneous AMH-PES (Mega a.s., Czech Republic) anion-exchange membranes. It is found that the CJMA-6 membrane has the highest counterion permselectivity (chlorides, sulfates) among the CJMAED series membranes, very close to that of the AMX membrane. The CJMA-3 membrane has the transport characteristics close to the AMH-PES membrane. The CJMA-7 membrane has the lowest exchange capacity and the highest volume fraction of the intergel spaces filled with an equilibrium electroneutral solution. These properties predetermine the lowest counterion transport number in CJMA-7 among other investigated AEMs, which nevertheless does not fall below 0.87 even in 1.0 eq L⁻¹ solutions of NaCl or Na₂SO₄. One of the reasons for the decrease in the permselectivity of CJMAED membranes is the extended macropores, which are localized at the ion-exchange material/reinforcing cloth boundaries. In relatively concentrated solutions, the electric current prefers to pass through these well-conductive but nonselective macropores rather than the highly selective but low-conductive elements of the gel phase. It is shown that the counterion permselectivity of the CJMA-7 membrane can be significantly improved by coating its surface with a dense homogeneous ion-exchange film. Full article

With the popularization and development of drip irrigation under film, the problem of secondary soil salinization in Xinjiang is becoming more and more serious. To explore water and salt transport in drip irrigation under mulch and drainpipe drainage, drainage tests of drainage ditches in saline-alkali soil in the Xinjiang 112 group were used to monitor soil salinity changes by controlling field irrigation. Then, a HYDRUS (PC-Progress, Prague, Czech Republic) numerical model was used to simulate and analyze the changes in salinity during cotton growth and the autumn salt return stage in saline-alkali soil under drainage conditions. The agreement between the simulated and measured values was high, and the model parameters were reliable. During the growth period of cotton, the salinity continued to decrease, and the salt began to return after the harvest. Compared with before planting, in the 0–80 cm soil layer, the average desalinization rate reached 43.52% under the mulching films, and the average desalinization rate reached 13.83% under and between the mulching films. After the cotton was harvested, salt returned to the upper layer of soil. However, it still showed a decrease compared with the level before sowing. The average salt content of 0–80 cm soil decreased by 5.14%, and the average salt content of 0–200 cm decreased by 2.60%. This shows that the total salt content in soil will continue to decrease after long-term use of drip irrigation and underground pipe drainage. Full article

This piece will introduce Czech ostalgic films set in the normalisation period (1969–1989) and will interpret the basic divide between nostalgic representation of the period and the openly anti-communist stances of the films’ creators. The methodological frame of this research comes from Robert Rosenstone’s approach of representation of history in film. To interpret ostalgia in Czech film, I use ideas from Daphne Berdhal and Svetlana Boym. I described the nostalgic elements and their functions in the structure of the films, taking into account their story, characters, settings, film style, narration, genre, and audience response (identification, causality of emotional experience). Czech ostalgic films about the normalisation period are interpretively ambivalent. The interpretational tension appears out of a fundamental divide between a clear refusal of communism and an idyllic view of the socialist past. They cannot be simply classified into restorative or reflective nostalgia. The younger generation of spectators perceives ostalgic films in the mode of reflective nostalgia; on the other hand, the older generation perceive the films in terms of restorative nostalgia. A different way of perceiving ostalgia reveals a misunderstanding between generations of the current Czech society. Due to singular anti-communist viewpoints and emphasised liberal values, the films cannot be interpreted in a desire for an idealised home in a communist past, but as a desire for a present home and its security, which cannot be clearly conceptualised. The concept of reflective nostalgia can be linked with the theory of Berdhal. The films cannot be perceived as a desire for an idealised home in a communist past due to specific anti-communist viewpoints and highlighted liberal values, but as a need for a home and security that cannot be directly conceptualised. This appearance of reflective nostalgia can be connected with the theory stated by Berdhal. Full article