Effect of Sealing Treatment of Modified Aluminum Phosphate Sealing Agent on Corrosion Resistance of Fe-Based Amorphous Coating

A modified aluminum phosphate sealing agent was prepared by using aluminum dihydrogen phosphate and silica sol as raw materials, and was used for sealing treatment of iron-based amorphous coating. The phase of sealing agent was analyzed by XRD. SEM and TG-DSC were used to characterize the surface morphology of the coating before and after sealing and the heat resistance of the sealing agent. The corrosion resistance of the sealing coating was evaluated by electrochemical measurements. The results show that the modified aluminum phosphate sealing agent has good heat resistance, and fine and close sealing layer was obtained, thus the corrosion resistance is significantly improved.

Analytical models for adiabatic compressed air energy storage (A-CAES) systems in lined tunnels

Adiabatic compressed air energy storage (A-CAES) systems consist of an underground reservoir where compressed air is stored at high pressures. The ambient air is compressed by compressors located at the surface and the thermal energy is stored using thermal energy storage (TES) systems. The compressed air is stored in the subsurface reservoir (charge). Then, when the electricity is needed, the compressed air is released and expanded in gas turbines to produce electricity (discharge). In this paper, an analytical model has been developed to investigate the thermodynamic behaviour during air charge and discharge processes. Operating pressures from 4.5 to 7.5 MPa has been employed in lined tunnels in the compression and decompression stages. The model considers a 20 mm thick sealing layer, a 0.4 m thick concrete lining and a 1 m thick rock mass around the air. Air mass flow rates of 0.19 and 0.27 kg s−1 have been used in the charge processes for polymer material and steel, respectively. Finally, in the discharge processes the mass flow rate increases up to -0.38 and -0.45 kg s−1 for polymer and steel. The air temperature and pressure and the temperature and heat transfer in the sealing layer, concrete lining and rock mass have been analyzed for 100 cycles considering polymer material and steel as sealing layers. The heat transfer through the sealing layer reaches -150 and -95 W m-2 for steel and polymer, respectively. The results obtained show that the storage capacity increases when the heat transfer through the sealing layer increases.

Study of pathologies on flexible floors in the city of Teófilo Otoni, Minas Gerais State, Brazil

It is a function of the highways to provide comfort, safety, and good rolling conditions to users. Therefore, the roads must be correctly designed showing adequate quality and durability for use. However, what is observed in Brazil is that most of the existing roads are not in good condition due to the number of pathologies found in them, bringing discomfort and insecurity to users. Bearing in mind that the flexible floor is the most used in the country, it is necessary to study the defects found during its useful life, which may be of structural or functional origin, to offer adequate maintenance and possibly better-rolling conditions to those who travel through it. Thus, the present study tackles pathological problems observed on a flexible pavement in the Municipality of Teófilo Otoni, Brazil, its possible causes, and some proposals for measures to be taken in the construction and maintenance processes to reduce the appearance of these pathologies. In addition, the identification and classification of pathologies and nonconformities found in the studied places were carried out. Thus, there was a need for maintenance so that its functionality is not affected, requiring the use of recovery techniques through resurfacing or a sealing layer, improving drainage and milling, which provides longer life and avoids inconvenience to users.

Study on the Effect of the Sealers on the Steel Surface Layer Modified by Electrical Discharge Machining

The paper describes the influence of the composition of the sealer used to form a composite coating on the surface of a steel sample by electrical discharge machining along the sealing layer on the structure and properties of the coating. The object of this study is samples made of steel 45. All samples are treated by electrical discharge machining with the use of ПР-В3К (Stellite) hard alloy-based anode and modifying sealers, based on CrCNi, TiCNi, and non-stoichiometric W and Mo compounds. Besides, the paper presents the physical and mechanical properties of the obtained coatings, examined during a set of tribological tests. The conducted experiment demonstrated that the wear resistance of coated samples is higher, compared to coatless ones. The strong point of our study lies in functionality to employ sealers, based on the SHS-reagents and non-stoichiometric W and Mo compounds with ESA processing in friction units.

Thermodynamic Analysis of Compressed Air Energy Storage (CAES) Reservoirs in Abandoned Mines Using Different Sealing Layers

Million cubic meters from abandoned mines worldwide could be used as subsurface reservoirs for large scale energy storage systems, such as adiabatic compressed air energy storage (A-CAES). In this paper, analytical and three-dimensional CFD numerical models have been conducted to analyze the thermodynamic performance of the A-CAES reservoirs in abandoned mines during air charging and discharging processes. Unlike other research works, in which the heat transfer coefficient is considered constant during the operation time, in the present investigation a correlation based on both unsteady Reynolds and Rayleigh numbers is employed for the heat transfer coefficient in this type of application. A tunnel with a 35 cm thick concrete lining, 200 m3 of useful volume and typical operating pressures from 5 to 8 MPa were considered. Fiber-reinforced plastic (FRP) and steel were employed as sealing layers in the simulations around the fluid. Finally, the model also considers a 2.5 m thick sandstone rock mass around the concrete lining. The results obtained show significant heat flux between the pressurized air and the sealing layer and between the sealing layer and concrete lining. However, no temperature fluctuation was observed in the rock mass. The air temperature fluctuations are reduced when steel sealing layer is employed. The thermal energy balance through the sealing layer for 30 cycles, considering air mass flow rates of 0.22 kg s−1 (charge) and −0.45 kg s−1 (discharge), reached 1056 and 907 kWh for FRP and steel, respectively. In general, good agreements between analytical and numerical simulations were obtained.

PCL Based CIP-Loaded Double-Layer Films Deposited by Low-Electron Beam Dispersion Method and its Antibacterial Properties

In this paper, low-electron beam dispersion (EBD) method is used to prepare a kind of double-layer films on different substrates. The bottom layer is a mechanically stirred mixture of the degradable polycaprolactone (PCL) and ciprofloxacin (CIP), and the top layer is polyurethane (PU) film. The molecular structure, chemical composition and morphology of the double-layer films were investigated by FTIR, XPS and SEM. The results showed that the surfaces of the double-layer films are uniform and the thicknesses can reach micron level. In addition, the two layers are well bonded. Then the films were sliced and immersed in PBS solution, and the time-dependent variable was used to analyze the kinetic slow-release behavior of CIP in the double-layer films by agar diffusion antibacterial experiments. It can be seen that sustained release time of CIP in the double-layer films can be up to 7 days, which is due to fact that the upper PU film working as a sealing layer helps to realize the drug slow-release. Based on the above research, the comprehensive performance of the films with the composition of PCL:CIP/PU=1:1/1 is the best.

Perspectives of Using Lignin as Additive to Improve the Permeability of In-Situ Soils for Barrier Materials in Landfills

Very often, in-situ soil does not meet the requirements for landfill barriers; therefore, it is necessary to purchase the material from quarries. An increasing number of by-products have been proposed as alternative landfill barrier materials. The present study investigated the performance of two soils of Central Italy (alluvial and volcanic soils) with an organosolv lignin (sulfur-free lignin (SFL)), a widespread by-product in the world. Laboratory investigations indicated that the volcanic soil mixed with 10% in weight of lignin did not reach the permeability value required for landfill bottom liners, also showing high compressibility. On the contrary, the addition of 20% to 30% lignin to the alluvial soil reached the permeability value recommended for the top-sealing layer of landfills: scanning electron microscope analysis indicated that the improvement was due mainly to the physical binding. Large-scale investigations should be carried out to evaluate the long-term performance of the mixtures. The increasing production of organosolv lignin worldwide gives this by-product the opportunity to be used as an additive for the realization of the top-sealing layer. The approach can save the consumption of raw materials (clayey soils from quarries), giving lignin a potential new field of application and recovering in-situ soils.