Dissimilar joints between steel and copper alloys are widely used in aerospace, mechanical, electrical, metallurgical and refrigeration industries because of their high strength and thermal conductivity, good mechanical properties and electrical conductivity, high corrosion resistance and low cost.

It is difficult to weld steel and copper alloys because the physical properties such as their melting points, coefficients of heat conductivity and coefficients of thermal expansion are different. It is particularly difficult to weld brass to other metal because evaporation of zinc during welding makes the weld porous.

To get a sound weld of brass, it is necessary to keep the heat input as low as possible. Then, it helps formation of a small heat affected zone (HAZ) in the weld and helps protect the welding zone against the surrounding medium. Another method used to limit the heat input into the welding pool in the welding of brass materials is to use filler materials. When these are used, the arc is concentrated on the filler material, which reduces Zn loss from the brass to be welded.

Taking it into consideration, Kim Tae Hong, a section head at the Faculty of Material Science and Technology, performed butt braze welding of brass tube to steel plate using TIG welding by selecting appropriate welding currents and arc positions, and evaluated the characteristics of the joints.

No pore was found in the joint at the welding current of 70A and different arc offset, and no crack was found in the joint after 300 times of thermal cycle. In addition, a sound joint was formed without evaporation of zinc when the arc position was inclined towards the side of steel.

You can find more information in his paper “Study on the TIG Welding of Brass to Steel” in “Proceedings of KUTIC-2025”.

The key of dimethyl ether to olefins (DTO) technology is to synthesize catalysts with high selectivity of light olefins and long lifetime. Crystalline silicoaluminophosphates (SAPO) are microporous material with many applications. SAPO-18 (with AEI framework topology) is a solid acid catalyst with microporous structure that is extensively used in the processes of methanol to olefins (MTO), DTO, CO₂/CH₄ separation and selective catalyst reduction (SCR) of NO_x, and it is structurally similar to SAPO-34 (with CHA framework). However, the drawback of these catalysts in MTO or DTO is rapid deactivation.

Many attempts have been made to enhance the catalytic performance and lifetime of SAPO-18, but the effect of post-acid treatment on DTO performance of SAPO-18 has been barely addressed.

Ho Yu Gyong, a researcher at the Institute of Nano Science and Technology, proposed post-HCl treatment as a method for improving DTO performance of SAPO-18 in DTO reactions and compared the catalytic performances such as crystalline structure, morphology, textural properties, acidity and DTO performance.

She investigated the effect of post-treatment with hydrochloric acid (1-5h with 0.01-0.2M HCl) to improve the catalytic performance of hydrothermally synthesized SAPO-18 (S-0). The microporous surface area of S-0.1-3 (S-0 treated with 0.1M HCl for 3h) was 642m²/g, and the pore channel entrance of crystal surface was extended. The single-run lifetime in DTO was prolonged by 1.5-1.7 times that of S-0 while the light olefins selectivity was increased by about 11%.

For more information, please refer to her paper “Improved DTO Performance after HCl Treatment of SAPO-18” in “Proceedings of KUTIC-2025”.

Graphene, which has been studied since 2004, has been widely used in metal-based composites as a very hard reinforcing phase due to its excellent properties. In addition to high strength and high conductivity, graphene reinforced aluminum matrix composites (AMCs) have proved to be lighter, cheaper and better than Cu matrix composites and various aluminum alloys in automotive and aerospace fields.

However, there are still some problems for practical application. Low wettability and dispersibility that have been a challenge for graphene-reinforced metal-matrix composites are also present in aluminum/graphene composites. It means poor interfacial adhesion between graphene and aluminum. Therefore, higher adhesion of the Al/graphene (Al/G) interface is essential to improve the properties of Al-based composites.

Since the surface lattice parameters of copper or nickel are less different from those of graphene than those of aluminum, pre-coating of these metals improves the bonding properties.

Taking it into consideration, Jon Sin Hyok, a researcher at the Faculty of Material Science and Technology, conducted a first-principles study of the interfacial bonding, mechanical strength and electronic properties of copper-doped graphene-Al (Al/Cu/G) composites using several superlattice models with different graphene contents.

The calculation results show that weak chemical bonding due to orbital hybridization between the coated copper and graphene layers is formed, and that the bonding is relatively strong compared to the bonding between Al and graphene layers without Cu, and the bond strength decreases gradually with increasing graphene content.

You can find the details in his paper “First Principle Study on Mechanical and Electronic Properties of Cu Doped Graphene Reinforced Al Composite” in “Proceedings of KUTIC-2025”.