• 한국기계가공학회지
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• 제20권8호
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• pp.52-59
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• 2021

In this study, we experimentally evaluated the mechanical properties and geometric form accuracy in FDM 3D printing processes based on the printing direction, building direction, and layer thickness. The specimen test results showed that the tensile strength increased by over 33% in the printing direction compared to the direction perpendicular to printing and the tensile strength becomes larger as the layer thickness decreased. Furthermore, the tensile and impact strengths in the building direction were significantly reduced due to the difference in the interlayer joining and bonding strengths of the fused material. Additionally, shrinkage of the material due to phase change induced curl distortion especially in thin and long 3D-printed products, which increased as the layer thickness increased.

• 한국분말재료학회지
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• 제4권3호
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• pp.196-204
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• 1997

Joining of AIN ceramics to W and Cu by active-metal brazing method was tried with use of (Ag-Cu)-Ti alloy as insert-metal. Joints were produced under various conditions of temperature, holding time and Ti-content in (Ag-Cu) alloy Reaction and microstructural development in bonded interface were investigated through observation and analysis by SEM/EDS, EPMA and XRD. Joint strengths were measured by shear test. Bonded interface consists of two layers: an insert-metal layer of eutectic Ag- and Cu-rich phases and a reaction layer of TiN. Thickness of reaction layer increases with bonding temperature, holding time and Ti-content of insert-metal. It was confirmed that the growth of reaction layer is a diffusion-controlled process. Activation energy for this process was 260 KJ/mol which is lower than that for N diffusion in TiN. Maximum shear strength of 108 MPa and 72 MPa were obtained for AIN/W and AIN/Cu joints, respectively. Relationship between processing variables, joint strength and thickness of reaction layer was also explained.

• 접착 및 계면
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• 제24권3호
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• pp.86-94
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• 2023

OLED 소자를 용액공정으로 제작함에 있어 음극 전극의 용액공정화가 기술적인 난제이므로 별도의 기판에 음극 전극을 형성하고 PEI 층을 접합층으로 사용하여 이를 다른 기판의 소자와 물리적, 전기적으로 연결하는 연구를 진행하였다. PEI 용액의 농도, PEI 층의 두께 및 첨가제 혼합 등을 변수로 하였으며 접착력 측정기와 EOD 소자 제작을 통하여 특성을 확인한 결과는 다음과 같다. PEI 용액의 농도가 높을수록 접착강도가 증가하였으나 막 두께의 증가로 전류 밀도가 감소하였다. 0.1 wt% PEI 용액에 첨가제로서 조비톨과 PEG를 혼합한 결과 PEG를 0.5 wt%의 농도로 혼합한 조건에서 900 mA/cm² 의 최대 전류 밀도를 얻었으며 양호한 접착 상태와 소자의 점등도 확인되었다.

• 한국세라믹학회지
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• 제20권1호
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• pp.70-78
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• 1983

This paper discusses the application of Si-Borosilicate glass sealing to a new sealing method which utilizes a large electrostatic field to pormote bound formation at relatively low temperature. Bonding mechanism and the effect of bonding time bonding temperature glass thickness and surface roughness on the bond strength were investigated. Application of a de voltage across bonded specimen gradually produced a layer of glass adjacent silicon which was depleted of mobile ions. As a consequence a n increasingly larger fraction of the applied voltage appeared across the depleted region and very large electric field resulted This field accompanyed by large electrostatic force acted as driving force the of strong bond. And stronger bond was formed with increasing bonding time and temperature. A low temperature preoxidation is advantageous for the Si surface having a rougher surface finish that 1 microinch.

• 한국음향학회지
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• 제33권2호
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• pp.102-110
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• 2014

양 전극 사이에 압전층 외에 비압전성의 접합층이 존재하는 ${\lambda}/4$ 모드 PVDF 초음파 트랜스듀서에 있어서 그 접합층이 트랜스듀서의 성능에 미치는 영향을 등가회로에 의해 해석하였다. 등가회로로서는 Kikuchi 등이 제안한 전송선로 모델[Sound of IEICE, 55-A, 331-338 (1981)]을 도입하였는데, 먼저 그 모델에 의한 해석의 타당성을 $80{\mu}m$ 두께의 PVDF 압전막이 동(Cu) 후면체에 부착되는 세 가지 경우를 가정한 KLM 모델과의 비교를 통해 검증하였다. 다음으로, 그 압전막과 더불어 $5{\mu}m{\sim}20{\mu}m$ 두께의 에폭시 접합층을 갖는 다섯 개의 트랜스듀서를 제작하여 펄스 에코 응답을 측정한 후 시뮬레이션 결과와 비교하였다. 두 결과는 서로 잘 일치하였는바, 도입한 Kikuchi 모델에 의해 접합층이 트랜스듀서의 성능에 미치는 영향을 파악할 수 있음을 알았는데, 접합층이 $20{\mu}m$일 때는 그 접합층이 없을 때에 비해 중심주파수와 대역폭은 각각 약 19.7 %, 25.0 % 감소하고, 삽입손실은 57.2 % 증가하는 것으로 나타났다.

• The Journal of Advanced Prosthodontics
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• 제11권6호
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• pp.313-323
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• 2019

PURPOSE. Shear bond strength (SBS) test is the most commonly used method for evaluating resin bond strength of zirconia, but SBS results vary among different studies even when evaluating the same bonding strategy. The purpose of this study was to promote standardization of the SBS test in evaluating zirconia ceramic bonding and to investigate factors that may affect the SBS value of a zirconia/resin cement/composite resin bonding specimen. MATERIALS AND METHODS. The zirconia/resin cement/composite resin bonding specimens were used to simulate loading with a shear force by the three-dimensional finite element (3D FE) modeling, in which stress distribution under uniform/non-uniform load, and different resin cement thickness and different elastic modulus of resin composite were analyzed. In vitro SBS test was also performed to validate the results of 3D FE analysis. RESULTS. The loading flat width was an important affecting factor. 3D FE analysis also showed that differences in resin cement layer thickness and resin composite would lead to the variations of stress accumulation area. The SBS test result showed that the load for preparing a SBS specimen is negatively correlated with the resin cement thickness and positively correlated with SBS values. CONCLUSION. When preparing a SBS specimen for evaluating bond performance, the load flat width, the load applied during cementation, and the different composite resins used affect the SBS results and therefore should be standardized.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.874-877
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• 2001

SOI(Silicon-On-Insulator) technology is proposed as an alternative to bulk silicon for MEMS(Micro Electro Mechanical System) manufacturing. In this paper, we fabricated the SOI wafer with uniform active layer thickness by silicon direct bonding and mechanical polishing processes. Specially-designed electrostatic bonding system is introduced which is available for vacuum packaging and silicon-glass wafer bonding for SOG(Silicon On Glass) wafer. We demonstrated thermopile sensor and RF resonator using the SOI wafer, which has the merits of simple process and uniform membrane fabrication.

• Macromolecular Research
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• 제17권5호
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• pp.307-312
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• 2009

Core-shell hydrogel nanocomposite was fabricated by encapsulating a silica-gold nanoshell (SGNS) with poly(N-isopropylacrylamide-co-acrylic acid) (PNIPAM-co-AAc) copolymer. The oleylamine-functionalized SONS was used as a nanotemplate for the shell-layer growth of hydrogel copolymer. APS (ammonium persulfate) was used as a polymerization initiator to produce a hydrogel-encapsulated SGNS (H-SGNS). The amounts of NIPAM (N-isopropylacrylamide) monomers were optimized to reproduce the hydrogel-encapsulated SGNS. The shell-layer thickness was increased with the increase of polymerization time and no further increase in the shell-layer thickness was clearly observed over 16 h. H-SGNS exhibited the systematic changes of particle size corresponding to the variation of pH and temperature, which was originated from hydrogen-bonding interaction between PNIPAM amide groups and water, as well as electrostatic forces attributed by the ionization of carboxylic groups in acrylic acid.

• Restorative Dentistry and Endodontics
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• 제25권2호
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• pp.180-192
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• 2000

One bottle system was recently developed in order to simplify the clinical skills and save chair time after continuous improvements on dentin bonding agents. There has been many studies to measure the bond strength of one bottle systems but no actual work has been done on micromorphologic study of resin-dentin interdiffusion zone after one bottle system application. To evaluate the bonding patterns of various commercially available one bottle systems to dentin, observation of resin-dentin interdiffusion zone under TEM was performed. Caries-free human third molars within one month of extractions were chosen for the experiments. The molars were sectioned 1mm above the cementoenamel junction and got rid of the root portions. Crown portions of the teeth were sectioned parallel to occlusal surface so that dentin discs of 1mm in thickness were remained. 7 one bottle systems and 1 two bottle system were applied according to manufacturer's instructions and followings were the results. 1. In every experimental groups, cross bandings of collagen fiber were distinguishable and tight bon dings between the bonding agents and dentin were observed. 2. Hybrid layer was clearly observed in ONE-STEP$^{(R)}$, Prime & Bond$^{(R)}$ 2.1, Syntac$^{(R)}$ SC, MAC-BOND II groups but it was not clear in Single Bond, D-Liner Dual PLUS, ONE COAT BOND groups. 3. Electron-density of hybrid layer was uniform in pattern in MAC-BOND II, Prime & Bond$^{(R)}$ 2.1 groups but not so uniform in ONE-STEP$^{(R)}$ group. 4. Electron-dense amorphous phase in most superior layer of the resin-dentin interdiffusion zone was characteristically observed in Single Bond, Syntac$^{(R)}$ SC, ONE COAT BOND groups. It can be concluded that bondings between the dentin bonding agents and dentin can be various in pattern according to their chemical compositions and the condition during applications.

• Smart Structures and Systems
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• 제5권5호
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• pp.547-564
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• 2009

Based on the theory of piezoelasticity, an analytical solution for a typical multilayer piezoelectric composite cantilever is obtained by the Airy function method. The piezoelectric cantilever may consist of any number of layers. Moreover, the material and thickness for different layers may be different. The solution obtained in the present paper is concise and can be easily applied for the bending analysis of multilayer piezoelectric actuators considering the effect of bonding layers and electrodes. At last, a comprehensive parametric study is conducted to show the influence of electromechanical coupling (EMC), the number of piezoelectric layers, the elastic modulus of elastic layer and the thickness ratio on the bending behavior of actuators. Some interesting results for the design of multilayer piezoelectric actuators are presented.