Jo Mar 27, 2026
Austenitic stainless steels are extensively used in a wide variety of industries including the chemical industry due to their good combination of corrosion resistance and weldability.
In high-temperature treatment of stainless steels, M23C6 and chromium carbide are formed along grain boundaries of austenite, causing preferential depletion of Cr along the grain boundary and, consequently, an increased rate of corrosion.
Therefore, many researches have been conducted on the effects of the main factors such as temperature, concentration, microstructure, welding process parameters and pH value on the corrosion characteristics of a 316 L stainless-steel welded joint in different corrosion media. To the best of our knowledge, little research has focused on the investigation of the relationship between the corrosion behaviour and microstructure of a 316 L stainless-steel welded joint in nutrient fertilizer solutions.
In our country, the recent increase in the number of greenhouses for vegetables necessitates production processes of nutrient fertilizer including Ca(NO3)2, KNO3, KH2PO4. Concentrator vessels used in these processes are made of 316 L stainless steel by welding, which requires a great wealth of information concerning the corrosion resistance of the 316 L parent material and weld metal against nutrient fertilizer solutions.
Pang Il Jin, a researcher at the Faculty of Material Science and Technology, quantitatively evaluated the corrosion resistance of 316 L weld metal and parent material, and clearly illustrated their corrosion mechanisms for the methodology of corrosion protection under the service conditions of concentrator vessels.
The test results showed that corrosion potentials of the weld were clearly lower than those of the parent material due to the heterogeneity of the microstructure in the welds.
You can find more information in his paper “A comparative study on corrosion resistance of 316 L stainless-steel welds in nutrient fertilizer solutions such as Ca(NO3)2, KNO3, KH2PO4” in “The Canadian Journal of Chemical Engineering” (SCI).
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Jo Mar 26, 2026
Water is one of the most important natural resources for all living organisms including humans, animals, plants and other organisms. High-quality water is a major factor for human health, environment protection and sustainable development.
There are many WQE methods, and the results from different methods may differ from one another. Therefore, it is necessary to decide which is better.
Yang Won Chol, a researcher at the Faculty of Material Science and Technology, has proposed a novel integrated WQE approach combined with other various WQE methods, and illustrated and compared the effectiveness by applying it to two WQE cases.
First, he developed a novel integrated WQE approach combined with multiple WQE methods based on the weighted membership degree. It consists of the following steps: determining the WQGs of evaluation objects using multiple WQE methods, determining the priority weights of the individual methods, calculating the weighted membership degrees that evaluate objects in every grade/rank, and calculating final WQG indices of objects.
He applied it to two application cases. The results showed that the proposed approach had the maximum correlation and the minimum deviation, compared to other methods, which illustrated the validity of the proposed approach.
For more information, please refer to his paper “A New Integrated Water Quality Evaluation Approach Combined with Different Evaluation Methods Based on Weighted Membership Degree” in “Water Resources Management” (SCI).
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Jo Mar 25, 2026
Since high carbon steel has high tensile strength and hardness and good wear resistance, and is cheaper than alloy steels, it has been widely used for manufacturing cutting tools, formers, springs, rails, etc. However, it is recommended to avoid welding of high carbon steel with poor weldability as much as possible because the weld zones of this steel can be easily cracked by high hardenability.
Nevertheless, there are many cases in practice that need inevitable welding. Especially, welding high carbon steel with good wear resistance and high impact strength such as 75Mn steel is one of the challenges in practice: butt-joint welding of track rails of 75Mn steel, for example.
Various welding methods were used to join high carbon steel such as rails, and in these methods, enough preheating and post-weld heat treatment were performed in order to prevent cracking. However, there may be cases where preheating or post-heating cannot be applied but should be avoided. If preheating and post-weld heat treatment of welding zones are not conducted, additional oxidation and deformation of weld zones can be prevented and welding costs can be saved.
Jon Yong Il, a researcher at the Faculty of Material Science and Technology, investigated an arc welding process for a long butt joint of high carbon 75Mn steel plates without preheating to ensure the quality of weld and high productivity.
The analysis of microstructures and mechanical properties of weld showed that the metal inert gas (MIG) welding process is a dominant one among various welding methods.
You can find the details in his paper “Application possibility of arc welding processes for long butt joint of 75Mn steel plates without preheating” in “The Journal of Engineering” (SCI).
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Jo Mar 24, 2026
Selective laser melting (SLM) technique is one of the most representative advanced manufacturing techniques.
Since SLM process parameters affect the multiple quality attributes of SLM parts, it is very important to perform optimization and effect evaluation of SLM process parameters. The SLM process optimization problem is ascribable to a multiobjective optimization one for optimizing multiple quality attributes.
Yang Won Chol, a researcher at the Faculty of Material Science and Technology, proposed a reasonable methodology for optimization of multiple quality attributes and effect evaluation of SLM process parameters using a TOPSIS-based comprehensive quality index and Taguchi method, and applied it to determine the optimal values and effects of process parameters such as laser power, scan speed and overlap rate for separately and simultaneously improving the multiple quality attributes such as tensile strength, hardness and relative density of AlSi10Mg alloy fabricated by the SLM.
He found that the optimal values of process parameters are laser power of 320 or 360 W, scan speed of 600 mm/s and overlap rate of 0.35, and the ES ranking of process parameters is scan speed, overlap rate and laser power.
For more information, please refer to his paper “Taguchi optimization and effect evaluation of process parameters using TOPSIS based comprehensive quality index of selective laser melted AlSi10Mg alloy” in “The International Journal of Advanced Manufacturing Technology” (SCI).
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Jo Mar 23, 2026
Solar hydrogen production by water splitting is one of the promising solutions to mitigate energy crisis and climate change as a green technology to convert solar energy into a form of renewable and storable fuel. Photocatalytic water splitting is considered an appealing approach and an economically feasible means of producing green H2 due to its low cost and simplicity of fabrication.
In the past several decades, many photocatalysts for water photolysis have been developed. However, the number of photocatalysts with water splitting activity under visible light is limited and simultaneous generation of H2 and O2 is almost impossible. Z-scheme water splitting system can alleviate thermodynamic requirements and choice of narrow band gaps materials.
Printable photocatalyst plates have potential usage in water splitting system for practicality of solar hydrogen production. On the printable Z-scheme photocatalyst plates, conductive nanoparticles can be inserted as a conductive mediator between hydrogen evolution photocatalyst (HEP) and oxygen evolution photocatalyst (OEP) to promote water splitting.
Kim Chol Gu, a researcher at the Faculty of Chemical Engineering, proposed a printable SrTiO3:La, Rh/ATO/BiVO4:Mo photocatalyst plate incorporating cost-effective Antimony-doped tin oxide (ATO) nanoparticles as a conductive mediator for Z-scheme water splitting.
The photocatalyst plates achieve an apparent quantum efficiency of 6.8% at a wavelength of 420 nm, with solar-to-hydrogen conversion efficiency (STH) of 0.26%.
For more information, you can refer to his paper “Z-scheme photocatalyst plates using antimony-doped tin oxide (ATO) as a conductive mediator for solar water splitting” in “Chemical papers” (SCI).
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Jo Mar 22, 2026
Methanol is a very important primary raw material for the petrochemical and energy industries. It is used to produce basic chemicals including formaldehyde, acetic acid, methyl formate, dimethyl ether, methyl and dimethylamineand dimethylamine carbonate and it is widely used in the chemical, pesticide, medical, dye and paint industries.
The ever-increasing production of chemicals creates some serious environmental problems due to the emission of greenhouse gases and wastes, and at present, environmental protection is of great importance for economic development. Therefore, production processes should be designed and operated aiming at reducing environmental pollution, and to this end, the environmental impacts of production processes should be evaluated quantitatively.
Pak Kyong Song, a researcher at the Faculty of Chemical Engineering, evaluated and compared the potential environmental impacts of two gas-to-methanol (GTM) process options according to the CO2 feed location using CO2 recycle ratios.
The results showed that, as the recycle ratio increases, both the potential environment impact (PEI) rate of the chemical process and the energy generation process decrease, and the total rate PEI output of the process and PEI generation rate decrease as a whole.
Also, process option 1 has lower PEI rates than process option 2 and it is therefore more environmentally friendly.
For more information, please refer to his paper “Potential Environmental Impact Evaluation of the Methanol Synthesis Process by Gas-to-Methanol Technology” in “ACS Omega” (SCI).
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