• 대한치과교정학회지
• /
• 제51권4호
• /
• pp.270-281
• /
• 2021

Objective: The aim of this in vitro study was to evaluate the changes in friction between orthodontic brackets and archwires coated with aluminum oxide (Al₂O₃), titanium nitride (TiN), or chromium nitride (CrN). In addition, the resistance of the coatings to intraoral conditions was evaluated. Methods: Stainless steel canine brackets, 0.016-inch round nickel-titanium archwires, and 0.019 × 0.025-inch stainless steel archwires were coated with Al₂O₃, TiN, and CrN using radio frequency magnetron sputtering. The coated materials were examined using scanning electron microscopy, an X-ray diffractometer, atomic force microscopy, and surface profilometry. In addition, the samples were subjected to thermal cycling and in vitro brushing tests, and the effects of the simulated intraoral conditions on the coating structure were evaluated. Results: Coating of the metal bracket as well as nickel-titanium archwire with Al₂O₃ reduced the coefficients of friction (CoFs) for the bracket-archwire combination (p < 0.01). When the bracket and stainless steel archwire were coated with Al₂O₃ and TiN, the CoFs were significantly lower (0.207 and 0.372, respectively) than that recorded when this bracket-archwire combination was left uncoated (0.552; p < 0.01). The friction, thermal, and brushing tests did not deteriorate the overall quality of the Al₂O₃ coatings; however, some small areas of peeling were evident for the TiN coatings, whereas comparatively larger areas of peeling were observed for the CrN coatings. Conclusions: Our findings suggest that the CoFs for metal bracket-archwire combinations used in orthodontic treatment can be decreased by coating with Al₂O₃ and TiN thin films.

• 반도체디스플레이기술학회지
• /
• 제21권2호
• /
• pp.11-14
• /
• 2022

In this work, we evaluated the Al₂O₃ film, which was deposited by atomic layer deposition, degraded by exposure to harsh environments. The Al₂O₃ films deposited by atomic layer deposition have long been used as a gas diffusion barrier that satisfies barrier requirements for device reliability. To investigate the barrier and mechanical performance of the Al₂O₃ film with increasing temperature and relative humidity, the properties of the degraded Al₂O₃ film exposed to the harsh environment were evaluated using electrical calcium test and tensile test. As a result, the water vapor transmission rate of Al₂O₃ films stored in harsh environments has fallen to a level that is difficult to utilize as a barrier film. Through water vapor transmission rate measurements, it can be seen that the water vapor transmission rate changes can be significant, and the environment-induced degradation is fatal to the Al₂O₃ thin films. In addition, the surface roughness and porosity of the degraded Al₂O₃ are significantly increased as the environment becomes severer. the degradation of elongation is caused by the stress concentration at valleys of rough surface and pores generated by the harsh environment. Becaused the harsh envronment-induced degradation convert amorphous Al₂O₃ to crystalline structure, these encapsulation properties of the Al₂O₃ film was easily degraded.

• 대한치과교정학회지
• /
• 제53권1호
• /
• pp.45-53
• /
• 2023

Objective: This study aimed to evaluate the shear bond strength (SBS) of orthodontic brackets bonded to three-dimensionally (3D)-printed materials after various surface treatments and artificial aging compared with that bonded to computer-aided design/computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA)-milled materials. Methods: Eighty cylindrical specimens were 3D printed and divided into the following four subgroups (n = 20 each) according to the surface treatment and artificial aging procedure. Group A, sandblasted with 50 ㎛ aluminum oxide particles (SA) and aging; group B, sandblasted with 30 ㎛ silica-coated alumina particles (CO) and aging; group C, SA without aging; and group D, CO without aging. For the control group, 20 CAD-CAM PMMA-milled cylindrical specimens were sandblasted with SA and aged. The SBS was measured using a universal testing machine (0.25 mm/min), examined at ×2.5 magnification for failure mode classification, and statistically analyzed (p = 0.05). Results: The retention obtained with the 3D-printed materials (groups A-D) was higher than that obtained with the PMMA-milled materials (control group). However, no significant difference was found between the study and control groups, except for group C (SA without aging), which showed significantly higher retention than the control group (PMMA-SA and thermocycling) (p = 0.037). Study groups A-D predominantly exhibited a cohesive specimen mode, indicating specimen fracture. Conclusions: Orthodontic brackets bonded to 3D-printed materials exhibit acceptable bonding strengths. However, 3D-printed materials are prone to cohesive failure, which may result in crown fractures.

• Journal of Electrochemical Science and Technology
• /
• 제14권3호
• /
• pp.262-271
• /
• 2023

For electrode stability and the electrochemical performance of the Li-ion cell, it is essential that the active ingredients and unique additives in the polymer binder be well dispersed with the solvent-based slurry. The efficient procedure used to create the slurry affects the rheological characteristics of the electrode slurry. When successively adding different steps of Nmethyl-2-pyrrolidone (NMP) solvent to the cathode composition, it is evenly disseminated. The electrochemical performance of the Li-ion cells and the electrodes made with slurry formed by single step and multiple steps of addition of NMP solvent are examined. To preform rheological properties of cathode electrode slurry on Ni-rich Lithium Nickel-Cobalt-Aluminum Oxide (LiNi_0.80Co_0.15Al_0.05) (NCA). Also, we investigate different step addition of electrode formation and mechanical strength characterization like peel strength. According to the EIS study, a multi-step electrode slurry has lower internal resistance than a single-step electrode slurry, which results in better electrical characteristics and efficiency. Further, microstructure of electrodes is obtained electrochemical performance in the 18650 cylindrical cells with targeted capacity of 1.5 Ah. The slurry of electrodes prepared by single step and multiple steps of addition of NMP solvent and its effect on the fabrication of 1.5 Ah cells. A three-step solvent addition on slurry has been found to be a lower internal resistance than a single-step electrode slurry as confirmed by the EIS analysis, yielding improved electrical properties and efficiency.

• Composites Research
• /
• 제19권6호
• /
• pp.23-31
• /
• 2006

나노허니컴 구조물의 영률, 굽힘 탄성 계수. 공칭파괴강도를 구하였다. 양극산화 알루미늄은 잘 정렬된 나노허니컴 구조물의 일종으로서 공정이 간단하고, 높은 종횡비, 자가 정렬된 기공구조를 가지고 있고, 기공의 크기를 조절할 수 있다. 원자현미경으로 외팔보 굽힘 시험을 수행하였고 나노-UTM을 이용한 3점 굽힘 실험결과와 비교하였다. 또한 나노-UTM으로 인장시험을 수행하였다. 나노허니컴 구조물의 한쪽 면은 막혀 있어서, 일반적인 샌드위치 구조물의 면재에 비유될 수 있다. 하지만 이러한 막힌 면은 굽힘 강도 증가에 영향을 끼치지 못하고 균열선단으로 작용한다는 것을 알 수 있었다. 본 연구로 나노허니컴 구조물을 설계하는데 기초적인 물성을 제공하고자 한다.

• 대한융합한의학회지
• /
• 제2권1호
• /
• pp.5-12
• /
• 2021

Objectives: The purpose of this study is to fabricate an ultra-fine ginsenoside particle atomizer that can provide a new treatment method by delivering ginsenoside components that have a therapeutic effect on respiratory diseases directly to the lungs. Methods: We fabricated the AAO vibrating mesh by using the micromachining process. The starting substrate of an AAO wafer has a 350nm pore diameter with 50㎛ thickness. A photomask having several 5㎛ opening holes with a 100㎛ pitch was used to separate each nanopore nozzle. The photoresist structure was optimized to pattern the nozzle area during the lift-off process precisely. The commercial vibrating mesh was removed from OMRON's NE-U100 product, and the fabricated AAO vibrating mesh was installed. A diluted sample of 20mL with 30% red ginseng concentrate was prepared to atomize from the device. Results: As a result of liquid chromatography analysis before spraying the ginsenoside solution, ginsenoside components such as 20S-Rg3, 20R-Rg3, and Rg5 were detected. After spraying through the AAO vibrating mesh, ginsenosides of the same component could be detected. Conclusion: A nutrient solution containing ginsenosides was successfully sprayed through the AAO vibrating mesh with 350 nm selective pores. In particular, during the atomizing experiment of ginsenoside drug solution having excellent efficacy in respiratory diseases, it was confirmed that atomizing through the AAO vibrating mesh while maintaining most of the active ingredients was carried out.

• 한국포장학회지
• /
• 제29권3호
• /
• pp.223-228
• /
• 2023

Sustainable energy supplies without the recharging and replacement of the charge storage device have become increasingly important. Among various energy harvesters, the triboelectric nanogenerator (TENG) has attracted considerable attention due to its high instantaneous output power, broad selection of available materials, eco-friendly and inexpensive fabrication process, and various working modes customized for target applications. In this study, the amount of voltage and current generated was measured by applying the PSD profile random vibration test of the electronic vibration tester and ISTA 3A according to the time of Anodized Aluminum Oxide (AAO) pore widening of the manufactured TENG device Teflon and AAO. The discharge and charging tests of the integrated module during the random simulated transport environment and the recognition distance of RFID were measured while agricultural products (onion) were loaded into the returnable folding plastic box. As a result, it was found that AAO alumina etching processing time to maximize TENG performance was optimal at 31 min in terms of voltage and current generation, and the integrated module applied with the TENG module showed a charging effect even during the continuous use of RFID, so the voltage was kept constant without discharge. In addition, the RFID recognition distance of the integrated module was measured as a maximum of 1.4 m. Therefore, it was found that the surface condition of AAO, a TENG element, has a great influence on the power generation of the integrated module, and due to the characteristics of TENG, the power generation increases as the surface dries, so it is judged that the power generation can be increased if the surface drying treatment (ozone treatment, etc.) of AAO is applied in the future.

• 한국식품과학회지
• /
• 제52권6호
• /
• pp.565-572
• /
• 2020

본 연구에서는 유탕 과자 모델에서 4가지 요인(유화제 종류, 유탕 온도, 소금 함량, 유지 함량)이 결합형 3-MCPD의 생성에 미치는 영향에 대해 알아보았다. 먼저 3-MCPD 분석법 검증을 위해 검출한계, 정량한계, 직선성, 정밀성 및 정확성을 구하였고, 분석 시 흡착 컬럼으로 사용한 aluminum oxide와 Extrelut® NT-3 컬럼을 비교하였다. Aluminum oxide에 비해 Extrelut® NT-3 컬럼으로 추출하였을 때 피크 면적이 약 5배 더 높아, 흡착 컬럼으로 Extrelut® NT-3를 사용하는 방법이 3-MCPD 분석에 더 적합할 것으로 생각되었다. 직선성은 3-MCPD 표준용액 검량선의 상관계수가 0.9997 이상의 양호한 직선성을 보였다. 기기의 검출한계는 0.86 ng/mL, 정량 한계는 2.61 ng/mL이었다. 분석법의 정밀성 및 정확성은 과자 반죽을 이용하여 비교하였다. 3-MCPD 분석법의 일내 정확성은 81.3-94.0%, 일간 정확성은 82.1-89.0% 수준이었으며, 결합형 3-MCPD 분석법의 일내 정확성은 84.1-99.3%, 일간 정확성은 87.7-91.1% 수준이었다. 3-MCPD 분석법의 일내 정밀성은 1.5-7.8% RSD, 일간 정밀성은 1.1-5.6% RSD 수준이었으며, 결합형 3-MCPD 분석법의 일내 정밀성은 2.8-8.9% RSD, 일간 정밀성은 5.0-6.8% RSD 수준이었다. 유탕 과자 모델에서 유화제 종류는 결합형 3-MCPD 생성에 영향을 주어 유화제 6종 중 글리세린지방산에스테르를 첨가한 시료에서 가장 많은 결합형 3-MCPD가 검출되었다. 유탕 온도에 따른 결합형 3-MCPD 생성량을 분석한 결과 온도가 증가함에 따라 결합형 3-MCPD의 함량도 증가하였다. 190℃로 가열하였을때 145℃에 비해 결합형 3-MCPD 함량은 약 24배 높았다. 소금 함량 또한 결합형 3-MCPD 생성에 영향을 주어 소금 함량에 비례하여 결합형 3-MCPD의 생성량이 유의적으로 증가하였다. 유지 함량에 따른 결합형 3-MCPD 생성량을 분석한 결과 유지 함량이 증가하여도 결합형 3-MCPD의 생성량에는 유의적인 차이가 없었다. 본 연구를 통해 유탕 과자에서 유화제 종류, 유탕 온도와 소금 함량이 결합형 3-MCPD의 생성에 영향을 미치는 것으로 확인되었다.

• Restorative Dentistry and Endodontics
• /
• 제32권5호
• /
• pp.419-425
• /
• 2007

본 연구의 목적은 세 가지 레진계 근관충전실러 (AH 26, EZ fill, AD Seal), 산화아연 유지놀계 근관충전실러(ZOB Seal) 그리고 수산화칼슘계 근관충전실러 (Sealapex)의 방사선 불투과성 및 세포독성을 평가한 것이다. 각 실러를 제조회사의 지시대로 혼합하여 직경 10 mm, 두께 1 mm로 시편을 제작한 후 ISO 6876/2001의 규격에 따라 교합필름을 이용하여 알루미늄 스텝웨지와 함께 방사선 촬영을 시행하였다. 방사선 사진을 디지털화하여 컴퓨터에 저장한 후 Scion image 프로그램을 이용하여 각 단계의 알루미늄 스텝웨지의 두께와 비교하였다. 각 재료의 세포 독성은 불멸화된 인간 치주인대세포 (immortalized human periodontal ligament cell, IPDL)에서 MTT 분석법을 이용하여 시행하였다. EZ fill이 가장 높은 방사선 불투과성을 나타내었고 Sealapex가 가장 낮은 방사선 불투과성을 나타내었다 (p < 0.05). AH 26, AD Seal, ZOB Seal은 중등도의 방사선 불투과성을 나타내었다. Sealapex를 제외한 모든 평가된 재료는 ISO 규격에 부합하는 방사선 불투과성을 보였다. 레진계 실러의 세포독성은 모든 실험 시간대에 걸쳐 다른 계통의 실러에 비해 낮게 나타났다 (p < 0.05) 아울러, EZ fill은 24및 48시간대에서는 AD Seal에 비해, 72 시간대에서는 다른 두 레진계 실러에 비해 높은 세포독성을 보였다. 그러나 레진계 실러에서 방사선 불투과성의 정도와 세포독성과의 관련성은 없었다 (p > 0.05). 이 실험 결과로 볼 때 레진계 실러는 다른 계통의 실러에 비해 방사선 불투과성 면에서 장점을 가지며 생체적합성면에서 우수하다고 사료된다.