The 3D printing process provides a higher degree of freedom when designing ceramic parts than the conventional press forming process. However, the generation and growth of the microcracks induced during heat treatment is thought to be due to the occurrence of local tensile stress caused by the thermal decomposition of the binder inside the green body. In this study, an alumina columnar specimen, which is a representative ceramic material, is fabricated using the digital light process (DLP) 3D printing method. DTG analysis is performed to investigate the cause of the occurrence of microcracks by analyzing the debinding process in which microcracks are mainly generated. HDDA of epoxy acrylates, which is the main binder, rapidly debinded in the range of 200 to 500oC, and microcracks are observed because of real-time microscopic image observation. For mitigating the rapid debinding process of HDDA, other types of acrylates PETA, PUA, and MMA are added, and the effect of these additives on the debinding rate is investigated. By analyzing the DTG in the 25 to 300oC region, it is confirmed that the PETA monomer and the PUA monomer can suppress the rapid decomposition rate of HDDA in this temperature range.

2019년 3월 27일 경기도 고양시 일산동구 장항동에 위치하는 일산호수공원에서 일광욕 중이던 외래거북 한 개체가 발견되었다. 발견된 개체의 배갑 색, 배갑 중앙의 무늬, 머리 옆면의 무늬, 등껍질의 형태를 근거로 서부비단거북 (Chrysemys picta bellii)임이 확인되었다. 근처에는 서부비단거북이 아닌 외래거북들이 일광욕하고 있었다. 본 논문에서는 국내 야생에서 처음으로 확인된 서부비단거북의 관찰 사례를 보고하였다. 다양한 외래거북들이 국내 생태계에서 지속적으로 발견되고 있으나 그 실태가 잘 알려지지 않고 있다. 따라서 외래생물의 효과적인 관리를 위해서는 지속적인 조사와 보고가 있어야 할 것이라 판단된다.

In the development of advanced ceramic tools, material improvements and design freedom are critical in improving tool performance. However, in the die press molding method, many factors limit tool design and make it difficult to develop innovative advanced tools. Ceramic 3D printing facilitates the production of prototype samples for advanced tool development and the creation of complex tooling products. Furthermore, it is possible to respond to mass production requirements by reflecting the needs of the tool industry, which can be characterized by small quantities of various products. However, many problems remain in ensuring the reliability of ceramic tools for industrial use. In this study, alumina inserts, a representative ceramic tool, was manufactured using the digital light process (DLP), a 3D printing method. Alumina inserts prepared by 3D printing are pressurelessly sintered under the same conditions as coupon-type specimens prepared by press molding. After sintering, a hot isostatic pressing (HIP) treatment is performed to investigate the effects of relative density and microstructure changes on hardness and fracture toughness. Alumina inserts prepared by 3D printing show lower relative densities than coupon specimens prepared by powder molding but indicate similar hardness and higher fracture toughness values.