Perovskite solar cells (PSCs) based on organic–inorganic lead halide are attracting a great deal of attention as next generation solar cells due to their simple manufacture, large absorption coefficient, long carrier diffusion length, high carrier mobility and high efficiency. Despite these advantages, PSCs are low in stability. Therefore, research efforts are being devoted to solving this problem and commercializing PSCs.

Stability in PSCs is that of perovskite minerals. Ionic liquids are being used to increase the stability and efficiency of perovskite solar cells (PSCs). Ionic liquids not only help to enlarge the grain size of perovskite due to their high thermal stability and low volatility, but also passivate the defects on the perovskite surface, thus increasing the stability and efficiency.

Based on this fact, Ri Chun Il, a researcher at the Faculty of Chemical Engineering, has improved the stability of PSCs by using 1-ethyl-3-methylimidazolium tetracyanoborate (EMIMTCB).

The power conversion efficiency (PCE) of the three-layer-structured PSCs fabricated using this ionic liquid was 13.8% to the maximum.

If further information is needed, please refer to his paper “Improving stability and efficiency of perovskite solar cells by 1-ethyl-3-methyl imidazolium tetracyanoborate ionic liquid” in “Journal of Saudi Chemical Society” (SCI).

During oil extraction, the permeability of reservoir changes due to the decrease in the pressure of reservoir and the increase in effective stress. Many researchers have studied the stress sensitivity of reservoir, and reservoir models taking it into account.

Previous researchers considered the influence of stress sensitivity and elastic outer boundary on the flow characteristics of fluids in reservoirs, and solved problems by considering stress sensitivity and elastic outer boundary conditions when analyzing the flow characteristics. However, they failed to analyze the stress sensitivity and elastic outer boundary conditions at the same time, so there are still errors in well test analyses.

Han Song Guk, a researcher at the Faculty of Earth Science and Technology, has developed a well test analysis model of a dual-porosity reservoir with stress sensitivity and elastic outer boundary conditions in simultaneous consideration, and obtained its solution.

Based on the consideration of stress sensitivity and elastic outer boundary conditions, he first formulated a seepage differential equation in the dual-porosity reservoir considering wellbore storage and skin factor, and defined dimensionless variables to facilitate the derivation of the solution. This mathematical model is strong in nonlinearity, so he applied the Pedrosa’s transformation and perturbation transformation to eliminate the nonlinearity of the model. Then, he performed the Laplace transformation to obtain an analytical solution of the well test model in the dual-porosity reservoir considering elastic outer boundary and stress sensitivity in the Laplace space, and applied the Laplace numerical inversion to obtain dimensionless pressure and pressure derivative model curve in the wellbore.

For more details, please refer to his paper “Analysis of Fluid Flow Characteristics for Stress-Sensitivity Dual-Porosity Reservoir considering Elastic Outer Boundary” in “Journal of Clinical Research and Reports” (SCI).

Operating characteristics and lifetime of blast furnaces depend on the cooling capacity of copper staves installed on the furnace wall. An oxygen blasting furnace is a furnace that produces iron by using anthracite and oxygen as a fuel. The structure and operating characteristics of the furnace are different from those of a coke furnace, so the structure and working conditions of the copper stave installed on the furnace wall of oxygen blasting furnaces are also different from those of coke furnaces.

Oxygen blasting furnaces have a constant height of liquid slag of 1500–1700℃ inside, so the temperature of their upper parts is also high, unlike coke furnaces. Therefore, oxygen blast furnaces should be designed to use copper with high thermal conductivity as stave material, and the structure of the copper stave should also be designed to enhance cooling capacity. In the copper pipe-mounted casting method, the cooling water is injected through the inside of copper pipe to prevent the melting of the copper pipe by hot copper solution. If the cooling capacity of cooling water is too high, fine gaps can be produced between the copper pipe surface and stave body. These micro-gaps are responsible for lowering the thermal conductivity and reducing the cooling capacity of copper stave.

To ensure normal operation of oxygen blasting furnaces and increase their lifetime, Choe Kyong Chol, a section head at the Faculty of Materials Science and Technology, has newly designed the structure of a wall copper stave, evaluated its cooling capacity and developed a casting process of the newly designed wall stave.

He determined the external dimension and wall thickness of the wall copper stave for a 20m² oxygen blasting furnace as 910mm×645mm×90mm and 25mm, respectively. The inlet diameter and length of the cooling water passing region are determined as ϕ70mm and 220mm, respectively.

For more details, please refer to his paper “COOLING CAPACITY EVALUATION AND OPTIMAL CASTING PROCESS DESIGN OF CORE-MOUNTED COPPER STAVE FOR 20m² OXYGEN BLASTING FURNACE BASED ON SIMULATION RESULTS” in “International Journal of Metalcasting” (SCI).