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).

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).

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).