Enhancing efficiency and stability of perovskite solar cells via in-situ incorporation of lead sulfide layer

The trap states at the surface and grain boundaries of perovskite films have a great influence on the photovoltaic performance and stability of perovskite solar cells (PSCs). Herein, lead sulfide...

Hydrology-hydrochemical researches of the Caspian Sea in July-August 2019

Comprehensive research information on hydrology-hydrochemical structure of the Middle Caspian Sea in July-August 2019 on board of R/V “Issledovatel’ Kaspiya” is presented in the article. Data on dissolved oxygen, hydrogen sulfide, basic nutrients (ammonium, nitrite and nitrate nitrogen; mineral phosphorus) and dissolved organic carbon were obtained in four quasi-latitudinal sections using the probing complex SBE19 plus Sea Bird, equipped with a series of sensors and twelve Niskin bathometers. It is shown, that the distribution patterns of determined elements and vertical structure correspond to average annual values of the summer season. Despite the sea level decline, the thickness of hydrogen sulfide layer of the Caspian Sea hasn’t decreased.

Removing of sulfide corrosion layers by an arc plasma process

In this paper, the removal of the sulfide layer formed on an FV(520)B stainless steel in the simulated environment of air compressor blade service conditions in a reaction kettle by arc plasma was investigated to explore the mechanism and technology of the sulfide layer removed by arc plasma from a blade surface. The sulfide lattice energy is studied by using the Born Haber cycle. Besides, the energy balance of the removal process is calculated. The treated surface morphology of samples was analyzed by scanning electron microscopy and energy dispersive spectrometer. The results indicate that the energy of the arc spot is enough to evaporate the sulfide film. Due to the different electronic work functions, an arc spot is first formed on the sulfide film, and then the voltage signal is segmented during the removal process. The voltage signal in the removal process can remove sulfide without harming the metal matrix. Besides, the increase in current can improve the removal efficiency and the surface roughness of the sample. It can be revealed, by analyzing the surface composition of samples with different currents, that the sulfur content is very low, indicating that it is feasible to remove the sulfide layer by arc spot plasma.

Causes of the field flowline weld joint rust-through damage

The paper presents results of the flowline pipe analysis in order to determine the causes of the butt weld joint rust-through damage (wormhole). Using Baumann sulfur print technique, the presence of iron sulfides scale on the inner pipe surface was studied. Using X-ray diffraction technique, the phase composition of the corrosion products was determined. It was found that chemical composition and mechanical properties of the metal from the studied flowline fragment comply with standard requirements. The resulting hardness values including those in the weld joint zones indicate that the metal has a certain corrosion-cracking resistance. Results of metallographic studies of longitudinal polished samples with full product thickness show that the residues of the weld capping pass remained on the bottom of the corrosion pit in the area of the observed rust-through hole. They have multiple pores up to 3 mm diameter. The corrosion pit surface is covered with iron sulfide layer 1–3 mm thick. The sulfide layer thickness in the area of the corrosion pit is 10+ times higher than on the rest pipe surface; this indicate that the corrosion process progressed faster here. The authors concluded that the cause for the weld joint rust-through damage was the pit corrosion that occurred under the impact of H2S-containing fluids on the lower generating line of the pipeline in the area of the weld startstop, where the weld root side suckback was observed. Probably, there was a flaw in the first weld pass within the corrosion pit area (shrinkage cavity, incomplete fusion, pore, or other), and the accelerated corrosion was the consequence of H2S-containing liquid slug here. This suggests that there was a flaw in the first weld pass within the area of the corrosion pit that has propagated along the first weld pass start-stop line.