• 대한치과기공학회지
• /
• 제23권2호
• /
• pp.211-221
• /
• 2002

The purpose of this study was to analyze the commercial paste opaque products currently available in domestic of foreign as well as domestic, such as Duceram Plus(DU; Ducera Dental GmbH, Germany), VMK 95(VM; Vita Co., Germany), Noritake EX-3(EX; Noritake Co., Japan) and Ceramax(CE; Alphadent Co., Korea). They were characterized in thermal expansion coefficient, particle size distribution, viscosity and solvent using thermomechanical analyzer, particle size analyzer, rheometer and infrared spectrophotometer. Experimental results are as follows; Firstly, thermal expansion coefficients were determined $13.9{\times}10-6/^{\circ}C$ for DU, $14.3{\times}10-6/^{\circ}C$ for VM, $13.3{\times}10-6/^{\circ}C$ for EX, and $14.0{\times}10-6/^{\circ}C$ for CE. Secondly, percent of partice size below $1{\mu}m$ were 12% for DU, VM and CE, and 13% for EX, percent between $1{\mu}m$ and $5{\mu}m$ were 42% for DU, 42% for VM, 38% for EX, and 61 % for CE, percent between $5{\mu}m$ and $10{\mu}m$ were 21 % for DU, 24% for VM, 20% for EX, and 18% for CE, and over $10{\mu}m$ were 25% for DU, 22% for VM, 29% for EX, 9% for CE. Thirdly, the basic composition of the solvent in all of the commercial paste opaques were determined as ethylene glycol from FT-IR investigation. Lastly, measured viscosities were 1798 cp for DU, 536 cp for VM, 1110 cp for EX, and 721 cp for CE.

• 한국재료학회지
• /
• 제25권7호
• /
• pp.336-340
• /
• 2015

For rear metallization with Al paste, Al back contacts require good passivation, high reflectance, and a processing temperature window compatible with the front metal. In this paper, the effect of the firing ambient during the metallization process on the formation of Al rear metal was investigated. We chose three different gases as ambient gases during the firing process. Using SEM, we observed the formation of a back surface field in $N_2$, $O_2$, and Air ambients. To determine the effect of the ambient on Voc, the suns-Voc tool was used. In this study, we described the mechanism of burn-out of organic materials in Al paste during the firing process. The oxygen ambient plays an important role in the burn-out process. We calculated the efficiency with obtained the back surface recombination velocities using PC1D simulation. It was found that the presence of oxygen during the firing process influenced the uniform back surface field because the organic materials in the Al paste were efficiently burned out during heating. The optimized temperature with oxygen flow shows an absolute efficiency of 19.1% at PC1D simulation.

• International Journal of Concrete Structures and Materials
• /
• 제2권2호
• /
• pp.161-167
• /
• 2008

Optimization of concrete mixing system is very important for the production of quality mixture of concrete and requires very complicated, specialized knowledge as there are a variety of variables that influence the result. One of the methods of optimizing the concrete mixing system is to minimize the volume of cement paste which, in turn, means maximizing the volume of aggregate. The purpose of this study is to determine the minimum volume of cement paste used in the design of concrete mixture and to design the optimum concrete mixing system based on the fluidity of mortar and concrete. In determining the minimum volume of cement paste, experiments of mortar and concrete were performed based on their workability, material segregation and bleeding. Type of aggregate, granularity distribution and sand percentage were used as test parameters and measurements were taken of the distribution of granularity, usage of HRWRA, minimum volume of paste and drying shrinkage and compressive strength of concrete.

• 대한한의학회지
• /
• 제30권4호
• /
• pp.37-46
• /
• 2009

Objectives: The purpose of this study was to investigate the external application of paste preparation recorded in the Annals of the Chosun Dynasty (朝鮮王朝實錄) and to clarify the significance of modern use of plaster therapy. Methods: Of many paste preparations, records of All-applying ointment (萬應膏), One-great ointment (太一膏), Pain-relieving plaster (救苦膏), and Pus-promoting powder (促膿膏) were especially examined from the Annals of the Chosun Dynasty. Other medical records regarding how these preparations were passed onto later generations were also studied. Results: According to the records from the Annals of the Chosun Dynasty, paste preparations were mainly used to cure abscess and sore, partly to treat pain diseases. From other medical documents, it could be found that these preparations were continuously used in subsequent eras. Conclusions: From these records, the level and features of Chosun Dynasty medicine could be speculated. It is necessary to find and restore effective paste preparations in Traditional Korean Medicine to use for treating disease today. Therefore, records from the Annals of the Chosun Dynasty are important and meaningful materials.

• 한국구조물진단유지관리공학회 논문집
• /
• 제23권5호
• /
• pp.23-29
• /
• 2019

본 연구는 굵은골재의 완전 리사이클 기술개발을 위해서 시멘트계 재료를 이용한 개질 페이스트를 이용하여 원골재의 표면을 코팅하는 표면개질 기술을 적용하고 있다. 이 때에 원골재와 개질 페이스트의 계면은 개질 페이스트의 점착력과 점도에 의존되어 개질골재의 피막두께가 결정된다고 생각할 수 있다. 본 연구에서는 굳지 않은 상태에서의 개질 페이스트의 유동특성을 파악하고 표면 개질골재의 피막 두께에 대해 검토한 결과, 개질 페이스트를 빙엄유체로서 가정하여, 잉여 페이스트 이론과 유동학 정수 (항복치)를 고려하는 것으로 개질 페이스트의 정량적인 피막 두께의 설계가 가능하여, 표면개질 골재를 이용한 콘크리트의 정량적인 배합설계가 가능할 것으로 판단된다.

• 한국결정성장학회지
• /
• 제30권1호
• /
• pp.7-11
• /
• 2020

TiZrN 코팅의 도핑 공정에서 탄소 페이스트 증착 방식에 따른 탄소의 용해성 변화를 격자왜곡(lattice distortion)과 원자농도(atomic concentration)를 통해 비교 및 고찰하였다. 딥코팅, 스핀코팅과 스크린프린팅 방식을 이용하여 탄소 페이스트를 도포한 후, 레이저를 조사하여 탄소 구배층(carbon gradient layer)을 형성시켰다. 모든 구배층은 탄소가 도핑되는 구조였으며, 두께 및 탄소 도핑량은 페이스트 도포 방식에 의존하였다. 결정 구조 분석 결과, 딥코팅에 의해 코팅층을 도핑할 때 보다 스핀코팅과 스크린프린팅에 의해 코팅층을 도핑하였을 때, 더 큰 격자 팽창이 일어남을 확인할 수 있었다. 또한 XPS depth profile을 통해 딥코팅에 의한 탄소 구배층 두께는 약 30 nm, 스핀코팅과 스크린프린팅의 경우 대략 100 nm로 더 깊은 구배층이 형성됨을 확인하였다. 침탄 전 코팅의 경도는 약 30 GPa였으며, 침탄 후에는 딥코팅 시편의 평균 경도가 약 31 GPa였고 스핀코팅과 스크린프린팅의 평균 경도는 대략 37 GPa로 증가한 것으로 보아 탄소 도핑을 통한 격자팽창 및 구배층의 영향을 확인하였다.

• Carbon letters
• /
• 제23권
• /
• pp.22-29
• /
• 2017

The compressive strength and electrical resistance of pitch-based carbon fiber (CF) in cementitious materials are explored to determine the feasibility of its use as a functional material in construction. The most widely used CFs are manufactured from polyacrylonitrile (PAN-based CF). Alternatively, short CFs are obtained in an economical way using pitch as a precursor in a melt-blown process (pitch-based CF), which is cheaper and more eco-friendly method because this pitch-based CF is basically recycled from petroleum residue. In the construction field, PAN-based CFs in the form of fabric are used for rehabilitation purposes to reinforce concrete slabs and piers because of their high mechanical properties. However, studies have revealed that construction materials with pitch-based CF are not popular. This study explores the compressive strength and electrical resistances of a cement paste prism using pitch-based CF.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2021년도 가을 학술논문 발표대회
• /
• pp.172-173
• /
• 2021

With the development of nano-reinforcement technology and the increasing concern for environmental issues, TiO₂ nanomaterials have received wide attention as an additive besides carbon nanomaterials that can be used to enhance the mechanical properties of cement-based materials. Also, TiO₂-based materials can allow cement-baned materials with photocatalytic capability, providing a potentially effective approach to reduce environmental problems. In this work, compressive strength, splitting tensile strength, and degradation of methylene blue solution were used as target to assess the effect of TiO₂ nanotubes on the mechanical strength and photocatalytic effect of hardened cement paste at different curing time. According to the strength results, the optimum amount of TiO₂ was identified as 0.5% of the weight of cement. Meanwhile, the TiO₂ nanotubes-reinforced specimen exhibited better photocatalytic effect in the early stage of curing.

• 마이크로전자및패키징학회지
• /
• 제22권4호
• /
• pp.15-23
• /
• 2015

Lead-free bonding has attracted significant attention for automotive power device packaging due to the upcoming environmental regulations. Silver (Ag) is one of the prime candidates for alternative of high Pb soldering owing to its superior electrical and thermal conductivity, low temperature sinterability, and high melting temperature after bonding. In this paper, the bonding technology by Ag paste was introduced. We classified into two Ag paste bonding according to applied pressure, and each bonding described in detail including recent studies.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
• /
• pp.637-640
• /
• 2006

Corrosion from various causes of reinforcing steel in concrete structures not only shortened the life of structures but also it is necessary a great repair cost to return and protect to the health condition. Using Nitrite inhibitors is a typical protection method. But there is no materials for the study about corrosion protection using nitrite. Therefore it is important to evaluate the additional rate and influence on congealment using the nitrite inhibitors in cement paste which is originally the basic material and crucial factors consisting concrete. The purpose of this study is finding influence of the type of nitrite inhibitors and mixing ratio on congealment of cement paste, and finding best corrosion inhibitors and ratio in cement paste.