Jo Jul 24, 2025
Electrochemical energy storage systems have been extensively studied because they provide stable and reliable electricity for power systems. Among them, Vanadium Redox Flow Batteries (VRFBs) have attracted a great attention because of their high stability, wide application range, technological maturation, low maintenance cost and long lifetime compared to lithium batteries. In the VRFB systems, the ion exchange membrane (IEM) is a core component that transports protons while preventing both anolyte and catholyte from cross-mixing.
In general, Nafion membranes, which are widely used in fuel cells and redox flow cells, have high proton conductivity and chemical stability but their commercialization is limited by their high cost and low ion selectivity. At present, some cheaper ion exchange membrane materials are being used: sulfonated aryl-based polymers such as sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly (ether sulfone) (SPES) and sulfonated poly(phthalazinone ether ketone) (SPPEK). Of them, the SPEEK ionomer is considered as the most promising alternative to Nafion for VRFBs due to its ease of preparation, low cost, relatively good ionic conductivity, and chemical and mechanical stabilities.
Han Song Il, a post-graduate student at the Faculty of Chemical Engineering, has prepared composite membranes incorporating SPEEK as a proton conductive medium into TiO2 nanopapers to improve the mechanical and chemical stabilities of SPEEK membranes for VRFBs.
The SPEEK/TiO2 nanopaper composite membranes exhibited almost twice the tensile strength and only one-third the vanadium ion permeability compared to pristine SPEEK (DS=60%).
For more information, please refer to his paper “High durable SPEEK/TiO2 nanopapercomposite membrane for vanadium redoxflow battery” in “Journal of Saudi Chemical Society” (SCI).
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Jo Jul 23, 2025
Drying is necessary for the storage of food and agricultural products such as rice and for the extension of their shelf life. Thus, it is an important post-processing step that consumes a considerable amount of energy.
Grain dryers include fixed bed dryers, fluidized bed dryers, moving bed dryers, etc. In an attempt to get a large amount of grain with the required moisture in a given time, a packed moving bed dryer was developed. The advantages of a packed moving bed dryer are the use of a lower-temperature air source and the realization of waste heat recovery. Therefore, it is very convenient to use a packed moving bed dryer to dry large amounts of cereals to the desired moisture content in a limited time. Furthermore, it is an important task to reasonably manipulate the drying process of grain in the packed moving bed dryer of high capacity.
Jon Chol Jin, a section head at the Faculty of Heat Engineering, has proposed a numerical approach for grain drying process in a packed moving grain dryer to study the steady process of the moisture content of grains based on a newly proposed steady state equation.
He has validated the accuracy of the proposed method through a comparison with precedent experimental results for moisture content and temperature of grains dried in a fixed bed dryer.
You can find the details in his paper “Steady state analysis for heat and mass transfer of grain dried in a packed moving bed dryer” in “International Journal of Food Engineering” (SCI).
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Jo Jul 22, 2025
With excellent hardness, low density, strong corrosion resistance, high melting point, titanium is extensively applied in our daily life and industries such as aviation, aerospace, machine-building, etc.
A researcher proposed a method for the industrial production of titanium, which is energy-consuming and expensive, but titanium production has still been dependent on this process, where the titanium chloride is reduced with metallic magnesium. There were some other methods, but they only achieved successes in the laboratory. The issues of energy consumption, equipment, environment, cost reduction, raw materials supply, etc. made its industrialization difficult.
An Hyo Song, a researcher at the General Assay Office, has investigated the direct electrolysis of CaTiO3 in molten salts, with the aim of reducing the electrolysis time and of improving the electrolysis efficiency in the production of titanium by electrolysis, and compared it with the direct electrolysis of titanium dioxide.
After mixing TiO2 and CaO well in a ball mill, he prepared porous CaTiO3 by sintering the mixture at 1 100℃ for 2 hours. He used this compound as cathode, the graphite as anode and the molten CaCl2-NaCl as electrolyte for electrolysis, which was performed at 800℃ and the constant-voltage of 3.2V in dry argon atmosphere.
The CaTiO3 was electrolyzed directly to Ti2O3 initially. Oxygen ions were removed gradually with the increase of electrolysis time, and Ti3O and Ti were prepared in 50h. The time of electrolysis was reduced to 80% of the time for reduction of TiO2 alone.
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Jo Jul 21, 2025
The multi-point forming (MPF) technology is a flexible forming method for three-dimensional sheet metal parts. In multi-point forming, the conventional stamping dies are replaced by a pair of matrices of elements (punches) and the relative positions of the elements can be varied to suit the requirements.
In the multi-point forming (MPF) for sheet metal, precisely constructing the die surface according to the geometry of parts is important for improving the dimensional accuracy and shape accuracy of products.
Today, a method based on NURBS surface is one of the generating methods of die surface using multi-point elements. This method can freely describe various curves and surfaces by using a general mathematical model. However, the NURBS method tends to lose data when the surface information (boundary information and shearing information, etc.) of product is obtained.
The method of representing complex geometry and location using triangular mesh data files (STL) is being widely used in the fields of high speed forming, inverse forming, finite element analysis, etc., and it is now widely accepted as the data exchange files of CAD/CAM/CAE systems. The triangular mesh model is convenient for processing and display on a computer, and it can represent any complex surface shape. Using the file of the triangular mesh data in a multi-point forming process can overcome the shortcomings of the NURBS method and solve the problem of data loss.
Paek Kuk Song, a researcher at the Faculty of Materials Science and Technology, has introduced the finite element theory into the construction of multi-point forming die surface to calculate the height of the elements according to the product geometry given by the triangular mesh data file (STL), and optimized the multi-point forming die surface by simulation analysis.
He performed the simulation analysis using ABAQUS software, and a full-scale experiment for the product that underwent the simulation analysis. The maximum absolute error between the target surface and the formed product was 0.09mm.
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Jo Jul 20, 2025
SiC whisker reinforced aluminum composites are fabricated by vacuum hot pressing. The whisker is a kind of fine needle-like fibrous material that exists in the form of a single crystal without defects. Its internal structure is absolutely complete and defect-free. The whisker-reinforced composites have many excellent properties. SiC whiskers are widely used in metallic matrix composites as whisker reinforcements with excellent properties. Among them, SiC whisker reinforced aluminum composites have been widely used in aerospace, automotive and other industries due to their high specific strength and hardness and good dimensional stability.
The key to fabricating SiC whisker reinforced aluminum composites lies in the uniform distribution of whiskers in the matrix, and the strong bonding between whiskers and aluminum. Now, the most important techniques for preparing SiC whisker reinforced aluminum composites are die-casting and powder metallurgy. Recently, powder metallurgy has become one of the main processes for fabricating high-performance aluminum-based composites.
In the hot-pressing sintering process, the thermal conductivity values of the aluminum powder and SiC whiskers that constitute the raw mixture change with increasing sintering temperature, while the relative density of the raw mixture changes with increasing sintering pressure. When the sintering temperature is too high, the grain growth occurs, which decreases the relative density of sintered compacts. As a result, the mechanical properties decrease. It is also difficult to separate the sintered compacts from dies after sintering because of the melting of sintered compact into dies. Therefore, some process problems arise, such as the difficulty of repeated use of dies.
Kim Kuk Il, a researcher at the Faculty of Materials Science and Technology, conducted a simulation analysis of the temperature distribution in the die and the raw mixture during sintering, and experimentally confirmed it. On this basis, he has presented a new question for determining the sintering conditions such as sintering temperature, heating rate and holding time, and investigated it.
As a result, he has confirmed the optimum sintering temperature (600℃), heating rate (15℃/min) and holding time (15min).
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Jo Jul 18, 2025
Humic acid is an organic substance that is produced by a series of decomposition and transformation processes of the remains of dead animals and plants. The oxidative polymerization of polyphenols in soils is regarded as one of the main processes in the formation of humic substances.
There have been many studies to find industrial applications of humification processes. However, there are few reports on the properties of humic acids in their use as binders for coal briquette.
O Chan Sok, a researcher at the Faculty of Metal Engineering, has conducted some experiments to improve the thermal stability and aromatization of humic acid in oxidized lignite with low humic acid content, and determined the optimum conditions.
He set ferric oxide content, caustic soda content, heating temperature and heating time as experimental parameters, and varied them at three levels, respectively. The optimum conditions are as follows. The ferric oxide and caustic soda oxide were 5% and 8% of the humic acid feed, respectively, and the reaction temperature and the reaction time were 80℃ and 60min, respectively.
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