• 한국표면공학회지
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• 제27권4호
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• pp.207-214
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• 1994

In consideration of global environmental protection and fuel saving, aluminum alloy sheets for auto body panels such as hood, fender etc., are expected one of the most promising materials for weight saving of cars. The chemical conversion coating is required to prevent the filiform corrosion occurring on painted aluminum. However the conventional process for the composited material mixed with aluminum and steel is complexs; aluminum part is chromated and assembled to the body, and then the steel body undergoes Zn phosphating. In order to overcome the low productivity due to the complex process and the environmental problem with a conventional process, a simultaneous zinc phosphating process for alsuminum and steel in an assembled condition is demanded. Newly developed phosphate solution has been investigated to characterize the phosphating behavior under various conditions. The optimum conditions of the phosphating solution for the application of the paint treatment derived as follows : about 0.3 for the ratio of Zn to $PO_4$, , 200~500 ppm for the concentration of fluoride ion, and 2.5~4.0 for pH. The concentration of dissolved aluminum ion must be kept below 2--ppm and suitable accelerator is found to be a mixture of 1g/$\ell$ $NO_2\;^-$, and 6g/$\ell$ $NO_3\;^-$.

• 한국재료학회지
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• 제27권12호
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• pp.710-715
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• 2017

We synthesized YOF(yttirum oxyfluoride) powders through solid state reactions using $Y_2O_3$ and $YF_3$ as raw materials. The synthesis of crystalline YOF was started at $300^{\circ}C$ and completed at $500^{\circ}C$. The atmosphere during synthesis had a negligible effect on the synthesis of the YOF powder under the investigated temperature range. The particle size distribution of the YOF was nearly identical to that of the mixed $Y_2O_3$ and $YF_3$ powders. When the synthesized YOF powders were used as a raw material for the suspension plasma spray(SPS) coating, the crystalline phases of the coated layer consisted of YOF and $Y_2O_3$, indicating that oxidation or evaporation of YOF powders occurred during the coating process. Based on thermogravimetric analysis, the crystalline formation appeared to be affected by the evaporation of fluoride because of the high vapor pressure of the YOF material.

• Membrane and Water Treatment
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• 제12권2호
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• pp.83-93
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• 2021

In this study, defluoridation efficiency by aluminium sulphate (alum) and polyaluminium chloride (PACl) were compared for recommended Nalgonda dose (100%) and 80% of this dose in both batch and continuous modes. The residual turbidity was found to be higher in case of alum as compared to PACl with 80% dose representing lesser efficient settling of suspensions, which primarily comprise alumino-fluoro complexes that result in high residual aluminium in the treated water and this was confirmed by TEM and Zeta analysis. Moreover, the application of PACl also resulted in much lesser addition to the TDS and also required lesser lime for pH compensation due to its lower acidity. Hence this reduced dose was recommended for defluoridation. It was also observed that in case of alum, residual aluminium in treated water was 0.88 mg/L (100% dose) & 0.72 mg/L (80% dose) and in case of PACl, it was 0.52 mg/L(100% dose) & 0.41 mg/L(80% dose). After subsequent microfiltration, residual aluminium was 0.28 & 0.21 mg/L for 100% & 80% dose respectively and in case of alum and in case of PACl, it was 0.16 & 0.11 for 100% & 80% dose respectively, which conform to the Al standards(<0.2 mg/L).

• 대한구강악안면병리학회지
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• 제42권6호
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• pp.183-187
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• 2018

The supernumerary tooth which is extra tooth in comparison to normal dentition is one of the developmental problems. The most common type of supernumerary tooth is mesiodens which may cause several complications like delayed eruption, crowding, spacing et al. Moral Incisor Hypomineralization (MIH) describes the clinical appearance of enamel hypomineralization of systemic origin affecting one or more permanent first molars that associated frequently with affected incisors. We report a case of a 6 - year - old boy who visited our clinic for removal of mesiodentes. The patient was diagnosed by mesiodentes and MIH by clinical examination and radiographic examination. Under local anesthesia, Mesiodentes were removed surgically. The demarcated opacities, a feature of MIH, were observed in the removed mesiodentes. After removal of mesiodentes, the maxillary central incisors erupted normally and in order to manage the teeth affected MIH, follow-up and fluoride varnish application were done every 3 months.

• Membrane and Water Treatment
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• 제13권4호
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• pp.173-181
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• 2022

Polyvinylidene fluoride (PVDF) flat sheet hydrophobic membranes were prepared using 16 wt% PVDF in Dimethyl acetamide (DMAc) by phase inversion technique for desalination application using Membrane Distillation (MD). In this work, the effect of coagulation mediums such as ethanol and water as well their synergistic behavior on the fabricated PVDF membrane morphology was studied using SEM. Moreover, other characteristics required for the membrane distillation applications namely porosity, hydrophobicity and tensile strength were measured using the gravimetric method, sessile drop method and universal testing machine respectively. It was observed that the membrane morphology paradigm shifted from the finger-like structure to the sponge-like structure on increasing the ethanol concentration in coagulant. The porosity of the fabricated membrane was under the required MD range and found to be 57.3% at 16 weight % of PVDF in DMAc solvent under a pure ethanol coagulant bath. Moreover, the top surface contact angle ranges from 85° to 115° on increasing the bath concentration from CBC 0 to CBC 100 at 16 weight % of PVDF in DMAc solvent.

• Journal of Electrochemical Science and Technology
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• 제12권4호
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• pp.424-430
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• 2021

The element iron (Fe) is affordable and abundantly available, and thus, it finds use in a wide range of applications. As regards its application in rechargeable lithium-ion batteries (LIBs), the electrochemical reactions of Fe must be clearly understood during battery charging and discharging with the LIB electrolyte. In this study, we conducted systematic electrochemical analyses under various voltage conditions to determine the voltage at which Fe corrosion begins in general lithium salts and organic solvents used in LIBs. During cyclic voltammetry (CV) experiments, we observed a large corrosion current above 4.0 V (vs. Li/Li⁺). When a constant voltage of 3.7 V (vs. Li/Li⁺), was applied, the current did not increase significantly at the beginning, similar to the CV scenario; on the other hand, at a voltage of 3.8 V (vs. Li/Li⁺), the current increased rapidly. The impact of this difference was visually confirmed via scanning electron microscopy and optical microscopy. Our X-ray photoelectron spectroscopy measurements showed that at 3.7 V, a thick organic solid electrolyte interphase (SEI) was formed atop a thin fluoride SEI, which means that at ≥3.8 V, the SEI cannot prevent Fe corrosion. This result confirms that Fe corrosion begins at 3.7 V, beyond which Fe is easily corrodible.

• 대한소아치과학회지
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• 제43권4호
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• pp.461-466
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• 2016

치아 우식증은 어린이와 청소년에서 일생에 거쳐 지속되는 질병이며 가장 중요한 치과질환이다. 유치열기의 치아우식증은 영구치에도 영향을 미치기 때문에 유치의 치아우식증을 조기에 진단하는 것은 매우 중요하다. 또한 예방을 하는 것이 매우 중요한데 치아 우식증을 조기에 발견하여 우식 위험율이 높은 아이들에서 적극적으로 불소 도포, 치면 열구 전색 등을 미리해주는 것이 중요하다. 치아우식증을 조기에 발견하기 위한 방법들이 많이 개발되어 왔지만 더 효율적인 방법을 찾기 위해 여전히 많은 연구가 진행 중이다. 일반적으로 시진과 방사선 사진을 많이 사용해왔지만 시진의 부정확성과 방사선의 조사량 등 많은 한계점을 보이고 있다. 이번 연구에서는 치아 우식증에 있어서 새로 개발된 DIAGNOcam의 임상적 적용에 대해 알아보고 그 활용 가능성을 알아보고자 하였다. 소아치과에 내원한 환자들을 대상으로 구치부에 DIAGNOcam을 이용하여 진단한 결과 인접면 우식, 수복물의 변연 확인 및 우식의 범위 확인에 유용하게 사용될 수 있다는 점을 확인하였다.

• Restorative Dentistry and Endodontics
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• 제45권2호
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• pp.20.1-20.14
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• 2020

Objectives: To minimize the tooth sensitivity caused by in-office bleaching, many dentists use non-steroidal anti-inflammatory drugs and topical desensitizing gels containing potassium nitrate and sodium fluoride. This study aimed to evaluate the influence of these substances on inflammation and the expression of substance P and calcitonin gene-related peptide in pulp nerve fibers. Materials and Methods: Seventy-two rats were divided into 6 groups as follows: GI, control; GII, only dental bleaching; GIII, only ibuprofen; GIV, ibuprofen administered 30 minutes before and after the bleaching treatment and every 12 hours until the analysis; GV, only topical application of a desensitizing agent; and GVI, topical application of a desensitizing agent before dental bleaching. Placebo gel was applied to the upper left jaw and the bleaching agent was applied to the upper right jaw in all groups. Subsequently, the groups were divided into 3 subgroups based on the time of analysis: 0, 24, and 48 hours after bleaching (n = 8). The rats were euthanized and the maxillae were processed and evaluated by histopathological and immunohistochemical analyses. The data were analyzed using the Kruskal-Wallis test, followed by the Dunn test (p < 0.05). Results: In the bleaching groups, the inflammatory process and expression of neuropeptides decreased over time. The animals in which a desensitizing agent was applied showed better results within 24 hours. Conclusions: The use of a desensitizing agent had positive effects on inflammation and pain-related neuropeptide expression, minimizing the painful effects of dental bleaching treatment.

• Composites Research
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• 제36권3호
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• pp.224-229
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• 2023

최근 각종 전자기기의 소형화와 웨어러블 디바이스의 수요가 증가함에 따라 IT 기기들의 나노화가 진행되는 추세이며, 이에 따른 배터리의 크기 및 용량 등의 한계를 극복하기 위하여 에너지 하베스팅 기술인 마찰 대전에 대한 연구가 많은 관심을 받고 있다. 불소계 코팅을 진행한 양극산화 알루미늄은 대전 서열에서 음극 성향이 높은 대전층과 대전된 전하가 전극으로 손실없이 전달되도록 도와주는 절연층 그리고 전극을 모두 포함하고 있는 구조로서 마찰 대전 나노발전기의 적용에 있어 많은 연구가 진행되어 왔다. 본 연구에서는 마찰대전 나노발전기 적용에 유리한 양극산화 알루미늄을 활용하여 마찰대전 나노발전기에 영향을 미치는 표면 형상 및 절연층의 두께를 조절하여 발전량과의 상관관계에 대하여 분석하였다. 이러한 분석을 통하여 추후 마찰대전 나노발전기 제작에 있어 면적 대비 발전량을 증가시킬 수 있는 방향을 제시할 수 있었다.

• Restorative Dentistry and Endodontics
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• 제49권2호
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• pp.15.1-15.11
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• 2024

Objectives: This study aimed to establish a single-session associative protocol for nonrestorative management of dentin hypersensitivity (DH). Materials and Methods: Twenty-four individuals with DH and a minimum sensitivity level of 4 on the visual analog scale (VAS) were selected. The study was conducted in a split-mouth design, with each participant (n = 20) having at least 1 affected tooth in all quadrants. The management protocols consisted of control group: universal adhesive, Neural Desensitizing Protocol group: 5% potassium nitrate, Mixed Desensitizing Protocol (PAM) group: 5% sodium fluoride and 5% potassium nitrate, Remineralizing Desensitizing Protocol (PDR) group: surface-partially reacted glass technology photopolymerizable varnish. Evaluations were performed immediately after application, at 1 week, 1 month, 2 months, and 12 months using the VAS sensitivity test. Results: The scores were subjected to statistical analysis using the Friedman test (p < 0.05), Durbin-Conover test (p < 0.05), and Wilcoxon test (p < 0.05). At the 12-month evaluation, all groups showed statistically significant differences compared to the initial assessment. For the evaluation after 12 months, there was a statistically significant difference between the PAM group, the control group, and the PDR group. Conclusions: It can be concluded that all groups were effective in controlling DH, but there were significant results in the control group and PDR group. The clinical relevance of this study is to demonstrate that the application of single-session desensitizing protocols can be effective in controlling DH for up to 12 months.