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Over the past decade, the feasibility of using ink-jet printing for the decoration of porcelain tiles has been explored, and significant advances have been made regarding the technologies underlying printing system and materials. An ink-jet printing system for porcelain tiles has many advantages compared with a conventional printing system, including the following: (1) it is a digital process; (2) it uses non-contact printing; (3) it allows random image generation; (4) it is a highly efficient process (reduced production cost); (5) it offers massive and continuous production; and (6) it uses inorganic pigment colorants. For these reasons, ink-jet printing systems for porcelain tiles have been commercialized and are at present rapidly spreading toceramics-leading countries such as Spain, Italy, China and Japan. We also developed a proprietary system involving a piezo-electric drop-on-demand method and an ink-circulation step. The resolution of this system is greater than 360 dpi after a heat treatment and the maximum printable width is 600 mm, even when setting the printing head unit with four digital colors (cyan, magenta, yellow, and black). In addition, we systematically developed ceramic colorant-containing inks and tile-printing technology applicable to our ink-jet printing system.

The antibacterial properties and durability of copper-glazed ceramic tiles were systematically investigated in detail in terms of the hydrophobicity change with glaze thickness. The water contact angle of the standard glaze without copper was 25.2° ± 0.2°, whereas the copper glaze showed hydrophobicity which was dependent on the glaze thickness. A maximum contact angle of 109.6° ± 0.4° was measured from the copper-glazed surface with thickness of 150-200 μm. As the contact angle and hydrophobicity of the copper glaze increased, the antibacterial efficiency against Staphylococcus aureus and Escherichia coli also increased. An antibacterial efficiency of 99.9% was demonstrated from the copper-glazed sample with the thickness of 150-200 μm. In addition, it was confirmed that 99.9% of the antibacterial efficiency of the copper-glazed ceramic tiles could be maintained for at least 2 years. In ion dissolution measurements of the standard and copper glazes, Ca, Na, Si, and K ions were observed, and Cu ion dissolution was only observed from the copper glaze. These results suggests that the hydrophobicity and strongly negative surface charge, which were contributed from Cu addition into the glaze composition, could block the access of bacteria to the glaze surface, and bacterial killing via Cu ion dissolution occurs.

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In this study, the effect of cold drawing and heat treatment on the microstructure of Invar36 alloy wire was investigated. Invar36 alloy wire is used as a transmission line core material, and is required to have high strength. The diameter of the Invar36 alloy wire specimens were reduced from 16 mm to 4.3 mm after three cold drawing and two heat treatment processes, thereby increasing tensile strength. Specimens were taken after each of the cold drawing and heat treatment processes, and their microstructure and tensile properties were analyzed. The Invar36 alloy wire had a γ-(Fe, Ni) phase matrix before the cold drawing and heat treatment processes. After the cold drawing processes, {220} and {200} textures were mainly achieved. After the heat treatment processes, a {220} recrystallization γ-(Fe, Ni) phase was formed with fine carbides. The recrystallization γ-(Fe, Ni) phase grains had low dislocation density, so they probably accommodated a large amount of deformation during the cold drawing processes. † (화에 따른 변형이 적으면서 고강도가 요구되지만, 기존의 송 전선용 강심 알루미늄 전선은 높은 열팽창 계수 및 고강도화 의 한계가 있으며, 이를 대체하기 위해 Invar 합금 선재를 심 선용 재료로 사용한 송전선이 개발되어 상용화 중이다 [1-6]. 상용 Invar36 합금 원소는 Fe-36Ni 조성 기준으로 Mo, Cr, Nb, V 등의 탄화물 형성 원소들이 포함된다. Invar 합금은 자 기 수축에 대한 보상 효과로 적용 온도 범위(-100~200 ℃)에 서 약 1.5 × 10 -6 cm/℃ 이하로 매우 낮은 열팽창 계수를 가지 며, 석출 강화, 고용 강화 및 마르텐사이트 강화 등의 미세조 직 제어를 통한 고강도 Invar 합금 개발에 대한 연구가 많이 진행되었다 [7,8]. 그러나 일반적으로 강도 향상을 위해 미세 조직에 포함되는 상들이 열팽창 계수를 증가시키는 효과를 나타내기 때문에 적절한 조성 및 공정 제어가 필수적이며, 최