Effects of Quenching Methods and Aging Processes on the Crushing Properties and Microstructure of Al–Zn–Mg Alloy Thin-Walled Square Extrusions

Hui Guo,Jin Zhang,Cheng Wang,Yun‑lai Deng 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8

In this study, the effects of different (online quenching and offline quenching) quenching methods and aging processes (T6and T73) on the crashworthiness and microstructural evolution of three Al–Zn–Mg alloys (G1–G3) were studied by conductingtensile test and axial compression tests at room temperature, combined with optical metallography, electron back scattereddiffraction, and transmission electron microscopy microstructural observations. The obtained results revealed that thecrushing properties of three different Al–Zn–Mg alloys subjected to different quenching methods and aging processes weresignificantly different. Their crushing energy absorption of are ranked as follows: G1 > G3 > G2. The highest total energyabsorption gap (between T6 and T73) is the G1 alloy, and the lowest one is the G3 alloy. The largest total energy absorptiongap between the two quenching methods is the G3 alloy, and the smallest one is the G1 alloy. The G2 alloy with the largesttotal amount of Zn + Mg has the highest number density of matrix precipitates, the largest precipitate gap (between T6 andT73) and the smallest precipitate gap between the two quenching methods. The G3 alloy with the largest Zn/Mg ratio hasthe smallest number density of matrix precipitates, the minimum precipitation gap (between T6 and T73) and the maximumprecipitation gap between the two quenching methods. The G1 alloy with the lowest Zn/Mg ratio has the smallest size ofgrain boundary precipitates and PFZ width, while their largest values are obtained for the G3 alloy with the maximum Zn/Mg ratio. As a crushing resistant structural material, the crushing properties is improved without reducing the strength. Theratio of Zn/Mg should be controlled within the range of 4.57–6.15, while the total amount of Zn + Mg should be controlledwithin the range of 6.18–7.01.

Four new compounds from the bulbs of Lycoris aurea with neuroprotective effects against CoCl2 and H2O2-induced SH-SY5Y cell injuries

An Jin,Xuelian Xiang,Yun-Yun Zhu,Heng-Yi Yu,Hui-Fang Pi,Peng Zhang,Han-Li Ruan 대한약학회 2014 Archives of Pharmacal Research Vol.37 No.3

Three new alkaloids, 2a-hydroxy-6-O-n-butyloduline,O-n-butyllycorenine, (-)-N-(chloromethyl)lycoramine(1–3), and a new phenolic compound, ((7S)-7-(4-hydroxyphenyl)-7-hydroxypropyl)-20-methylbenzene-30,60-diol (14), along with ten known alkaloids (4–13), wereisolated from the bulbs of Lycoris aurea collected fromHuaihua County of Hunan Province, China. Their structureswere elucidated by spectroscopic methods includingHRESIMS, UV, IR, and NMR. All the isolated compoundswere tested for their neuroprotective effects against CoCl2and H2O2-induced SH-SY5Y cell death. Compounds 1–7and 10 exhibited significant neuroprotective effects againstCoCl2-induced SH-SY5Y cell injury, while compounds1–5, 7, 10 and 12 showed obvious neuroprotective effectsagainst H2O2-induced SH-SY5Y cell death.

Effects of Cooling Rate on the Microstructure and Tensile Properties of Wire-Arc Additive Manufactured Ti–6Al–4V Alloy

Hui‑Jun Yi,Jin‑Woo Kim,Young‑Lak Kim,Sangyong Shin 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.8

Wire-arc additive manufacturing has emerged as a technology that could replace the conventional manufacturing processof titanium alloys. However, it produces a coarse β grain, which can accumulate via several deposited materials, resulting isstrong texture and anisotropy. To investigate potential solutions, the effects of the cooling rate on the resulting microstructureand tensile properties were studied. The cooling rate of the deposited materials was adjusted by interpass temperaturecontrol. Under rapid cooling, fine α + α′ grain with a low aspect ratio were observed and tensile and hardness propertieswere also improved.

불국사 석탑의 물성 및 지반특성 조사

최희수,서만철,오진용 공주대학교 문화재보존과학연구소 2003 문화재과학기술 Vol.2 No.1

경주 불국사의 다보탑과 석가탑은 751년에 축조된 국보급 문화재이나 오늘날은 석재의 풍화 및 지대석의 어긋남 현상들이 관찰된다. 이에 대한 정확한 이해는 두 석탑의 안정성 진단에 필수적이며 따라서 석탑의 지반환경과 석재 물성에 관한 비파괴 정밀 조사가 필요로 한다. 이 연구에서는 석재의 역학적 성질을 위해 초음파 속도 측정을 실시하였고 천부지질구조를 위해 탄성파, 전기비저항, 지하레이더 등의 비파괴 복합 지구물리탐사를 석탑 주변에서 수행하였다. 초음파 속도범위는 석가탑에서는 1217~4403 m/s이며, 다보탑에서는 584~5845 m/s이며 이로부터 추정한 일축강도 평균치는 각각 463 kg/cm^(2), 409 kg/cm^(2)이다. 대체로 두 석탑 주변의 북서쪽 구역에서 낮은 탄성파 속도와 비저항 값이 나타나, 이 부분을 비교적 연약한 지반으로 해석한다. 그리고, 탄성파 속도분포에서는 다보탑 지반이 더 큰 속도를 보여 상대적으로 석가탑 지반보다 견고함을 보여준다. 대체로 석탑지반의 전기비저항은 최대 2200 Ωm이며 200 Ωm내외의 외부지반보다 더 높은 값을 보인다. 복합 지구물리탐사 결과를 종합하면 다보탑지반의 형태는 8각형(한 변은 6 m)으로 그 깊이는 약 4 m 이나, 석가탑지반은 약 8x10 m의 직사각형 형태로 깊이는 약 3 m 이다. Two three-story stone pagodas, Seokgatap and Dabotap, built in 791 at Bulkuksa temple, are well-known national treasures. However, they have experienced weathering process and an offset of the stone alignment is observed at the base part of Dabotap. Understanding of these phenomena is essential for the structural safety diagnosis for them, and therefore the nondestructive geophysical methods was applied. Direct measurements of ultrasonic velocities was introduced for the mechanical properties of the stone. Multidisciplinary geophysical prospectings including seismic, resistivity, ground-penetrating radar(GPR) methods were carried out around two pagodas for their site characteristics. The velocity ranges of ultrasonic waves for Dabotap and Seokgatap are 1217~4403m/s and 584~5845m/s, respectively, and the estimated averages of the uniaxial compressive strength are 463 kg/cm^(2) and 409 kg/cm^(2), respectively. At the northeast of each pagodas, the lower seismic velocities and resistivities are shown, which is interpreted to be weaker subsurface section. On the basis of the higher velocity structure, the site of Seokgatap appears to have solider stability than the Seokgatap site. Near the pagodas, higher(up to 2200 Ωm) resistivity is present whereas their outskirts have as low as 200 Ωm. By the combined results of each geophyscial methods, the subsurface boundaries of each stone pagodas are revealed. The Dabotap site is in the form of an octagon having 6-m-long side with the depth of ~4 m, whereas the Seokgatap site is the 8x10 m rectangle with the depth of 3 m.

Sol-Gel법을 이용한 다공성 Silica Ceramic 합성에 있어서 물이 겔화시간 및 평형농도에 미치는 영향에 관한 연구

이진휘,김화중,이준 서울産業大學校 1992 논문집 Vol.35 No.1

본 연구에서는 sol-gel process에 의하여 silcon계 다공성 ceramic물질을 합성하고, 합성 과정에서 중요하게 작용하는 인자들을 조사하였다. 중요한 인자들로 여러가지를 들수 있는데, 본 연구에서는 gelation time과 FT-IR을 이용한 최종 생성물의 화학 구조 조사에 의하여, 반응이 평형 상태에 도달하는 데 요구되는 물의 영향에 대하여 조사하였다. 실험 결과 EtOH/TEOS molar ratio가 7.6일 때, 반응이 평형에 도달하는데 소요되는 물의 양은 약 11mole인 것으로 사료되었다. The synthesis of porous silica ceramic material using sol-gel process was performed and the influencing factors during the synthesis were evaluated. Among several influencing factors, however, in this research program, the equilibrium concentrations of H₂O during hydrolysis and poly-condensation were studied based on the investigations of gelation time and chemical structures for the final porous ceramic materials using FT-IR. The results suggested that the equilibrium concentration of H₂O was about 11 moles for 7.6 of EtOH/TEOS molar ratio.

실리콘 웨이퍼 공정용 알루미나 정전척의 제작과 특성에 관한 연구

천희곤,조동율,이영섭,박용균,최성호,정광진,Serguei Spoutai 울산대학교 기계부품 및 소재 특성평가연구센터 1999 연구보고서 Vol.1999 No.-

정전척의 유전체 물질로 열전도도와 유전특성 그리고 기계적 특성이 우수한 알루미나에 TiO₂첨가하여 유전체의 비저항을 변화시켜서 정전척(electrostatic chuck)에서 발생하는 정전력인 쿨롱힘(coulomb force)과 존슨-라벡힘(Johnsen-Fahbeck firce_의 영향을 규명하려 하였다. 그리고 비저항, 인가전압, 온도, 습도가 정전력에 어떠한 영향을 주는지 고찰하였으며, 인가전압에 따른 응답 특성에 관하여 고찰하였다. Alumina electrostatic chucks for silicon wafer process with wide range of electrical resistivity were fabricated by controlling the amount of TiO₂ addition (0 wt%, 1.3 wt%, 2 wt%, 2.8 wt%). The dependence of electrostatic force on applied voltage, temperature and humidity was investigated. In addition, response characteristics on applied voltage and relationship between electrical resistivity and electrostatic force characteristics such as Coulomb force and Johnsen-Rahbeck force were discussed

Sol-Gel법을 이용한 Silica Membrane의 제조 공정에 관한 조사 연구

이진휘 건국대학교 1991 論文集 Vol.32 No.1

The general informations of sol-gel process are reviewed. Successful applications are dependent on sufficient scientific understanding of the various stages and factors of the process. A number of factors governing the development of the structure and microstructure during gelation and subsequent drying and firing conditions are mentioned. Examples are described for applications in the areas of composites, porous solids and coatings. Opportunities for many new applications are presently available for exploitations.

Sol-Gel법을 이용한 Silica Membrane의 제조 공정에 관한 조사연구

이진휘,이준,김화중 서울産業大學校 1990 논문집 Vol.32 No.1

졸 -겔 공정에 대한 일반적인 문헌들을 검토하였다. 이와같은 문헌들을 성공적으로 적용하려면 공정에 대한 여러가지 단계와, 영향을 미치는 인자들에 관한 체계적인 이해가 먼저 요구된다. 겔화하는 동안 구조 및 미세구조의 전개에 영향을 미치는 몇가지 인자와 더불어 건조 및 열처리 조건을 조사하였다. 혼합물, 다공성 고체 및 코팅분야에 적용하기 위한 몇가지 예들을 기술하였다. 현재 이 분야의 발전에 기여할 새로운 응용기회는 많다. The general informations of the sol-gel process are reviewed. Successful applications are dependent on sufficient scientific understanding of the various stages and factors of the process. A number of factors governing the development of the structure and microstructure during gelation and subsequent drying and firing conditions are mentioned. Examples are described for applications in the areas of composites, porous solids and coatings. Opportunities for many new applications are presently available for exploitations.

감초로부터 Glycyrrhizin 추출

이진휘,장향동,최하영,서동호,이성미,김경하 서울産業大學校 1998 논문집 Vol.47 No.1

Glycyrrhiza uralensis계의 원감초 뿌리에서 추출도는 감초는 여러가지 질병의 약제로 널리 이용되어 왔다. 그 주성분인 gliycyrrhizin은 항염증 활성 및 anti-allergic activity를 갖고 있으며 이러한 생리활성은 aglycone β-gliycyrrhetinic acid 의 활성에 의한 것으로 알려져 있고, β-gliycyrrhetinic acid는 steroid 구조와 유사하며, 면역조절 특성을 갖는 것으로 인식되고 있다. 이러한 β-gliycyrrhetinic acid 의 면역조절 활성에 기여하는 인자와 그 경로에 대하여 조사된 바 있다 Glycyrrhizin은 감초뿌리의 주성분중 하나이며, 그외에도 surgars(14%), starches(30%), flavonoids, saponoids, amonoacids, gums 및 essential oil 등을 포함하고 있다. Licorice, the root extract of Glycyrrhiza uralensis, is used as a medicine for various diseases. Antiinflammatory as well as anti-allergic activities have been attributed to one of its main constituents, glycyrrhizin. These activities are mainly ascribed to the action of the aglycome β-glycyrrhetinic acid. βGlyeyrrhetinic acid has a steroid-like structure and is believed to have immunomodulatory properties, To determine whether interference with complement functions may contribute to the immunomdulatory activity of β-glycyrrbetinic acid. its effect on the classical and alternative activation pathways of human complement were investigated. The main constituent found in the root is glycyrrhizin. The plant also contains various sugars(14%), starches(30%), flavonoids, saponoids, aminoacids, gums, and essential oil etc.

Sol-Gel법을 이용한 Silica Ceramic합성에 있어서 화학 구조 변화에 관한 연구

이진휘,정은정 서울産業大學校 1995 논문집 Vol.42 No.1

Sol-gel공정에 의하여 TEOS를 이용하여 silica ceramic을 합성하는 공정중 건조 및 소성공정중의 중간생성물의 변화를 20℃, 40℃ 및 60℃로 반응시킨 시료에 대하여 TG/DTA, FT-IR 및 X-ray diffraction에 의하여 실험하였다. 실험 결과 반응온도가 높을수록 가수분해 속도가 증가되었으며 중간 생성물의 양도 증가하였다. 고립된 Si-OH중 -OH의 증발은 700∼800℃정도에서 일어나며, 60℃에서 건조한 시료의 경우 급격한 가수분해 및 축중합반응으로 인하여 역반응에 의한 약간의 불완전한 치환형태의 alkoxide가 잔류하는 것으로 사료된다. The chemical components produced by drying and sintering process during synthesizing of silica ceramic by sol-gel process were characterized by using TG/DTA, FT-IR and X-ray diffraction to evaluate the changing intermediates for the samples treated by three different drying temperatures, 20℃, 40℃ and 60℃. The results showed that the higher the reaction temperature, the faster the rate of hydrolysis and the large the concentration of intermediates. Dehydroxylation of Si-OH starts in the early stage of the thermal treatment and continues up to 700∼800℃. It is supposed that alkoxides might be formed by backward reaction derived by hydrolysis and condensation-polymerization abruptly in case of dried at 60℃.