• Corrosion Science and Technology
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• 제4권6호
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• pp.217-221
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• 2005

In the present investigation, holographic interferometry was utilized for the first time to monitor in situ the thickness of the oxide film of aluminium samples during anodization processes in boric acid solutions. The anodization process (oxidation) of the aluminium samples was carried out by the technique of the electrochemical impedance spectroscopy(EIS), in different concentrations of boric acid (0.5-5.0% $H_3BO_3$) at room temperature. In the mean time, the real-time holographic interferometry was used to measure the thickness of anodized (oxide) film of the aluminium samples in solutions. Consequently, holographic interferometry is found very useful for surface finish industries especially for monitoring the early stage of anodization processes of metals, in which the thickness of the anodized film of the aluminium samples can be determined without any physical contact. In addition, measurements of electrochemical values such as the alternating current (A.C) impedance(Z), the double layer capacitance($C_{dl}$), and the polarization resistance(Rp) of anodized films of aluminium samples in boric acid solutions were made by the electrochemical impedance spectroscopy(EIS). Attempts to measure electrochemical values of Z, Cdl, and Rp were not possible by holographic interferometry in boric acid especially in low concentrations of the acid. This is because of the high rate of evolutions of interferometric fringes during the anodization process of the aluminium samples in boric acid, which made measurements of Z, Cdl, and Rp are difficult.

• The Korean Journal of Ceramics
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• 제4권4호
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• pp.387-393
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• 1998

The formation of titanium diboride ($TiB_2$ ) via the reduction of $TiO_2$ with boric oxide and carbon was studied in a partially reducing atmosphere of argon mixed with 4 vol.%H2. The effect of reaction time, temperature, partial pressure of nitrogen and $TiO_2/B_2_O3$ stoichiometric ratio on the reducibility of oxides has been studied. The phases formed were analysed by using X-ray rowder diffraction and scanning sosctron microscopic techniques. In this paper, we also investigated the presence of $CaC_2$ as a reducing agent on the reducibility of oxide mixtures and on the Ti-B-C-Ca-O phase equilibria. The morphology of $TiB_2$ formed in the presence of $CaC_2$ is compared with the microstructure of $TiB_2$ formed as a consequence of carbothermic reduction. The observed variation in $TiB_2$ crystals formed is also explained.

• 한국재료학회지
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• 제9권4호
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• pp.414-418
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• 1999

Typical metal oxide thin films having optical and electrical properties are widely used as inorganic functional materials. Liquid phase deposition(LPD) method, a new low temperature process, has been developed for the several advantages of no vacuum system, low cost, high throughput, and low processing temperature(<$50^{\circ}C$). Silica powder was added to 40wt% hydrofluoro-silicic acid($H_2$SiF\ulcorner) to obtain an immersing solution of silica-saturated hydrofluorosilicic acid solution. Boric acid solution was continuously added in the range from 0 to 0.05M to prepare supersaturated hydrofluorosilicic acid solution. LPD $SiL_2$film was formed with the variation of added amount of $H_2$O. The SiO$_2$thin film could be prepared from hydrofluorosilicic acid by LPD method. The thickness of LPD $_SiO2$film was influenced by the boric acid concentration and added amount of $H_2$O. Silicon in thin film existed as SiF\ulcorner by Raman spectrum.

• 한국세라믹학회지
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• 제41권11호
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• pp.812-818
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• 2004

무수붕산(B$_2$O$_3$)과 활성탄소를 사용하여 질소 분위기에서 육방정 질화붕소(h-BN)을 합성할 때 그 생성조건 및 반응과정을 검토하였다. 육방정 질화붕소의 생성조건은 140$0^{\circ}C$ 이상에서 질화붕소가 합성되기 시작하여 155$0^{\circ}C$에서는 대부분의 합성이 이루어졌고, 그 이상의 온도에서는 생성이 크지 않았음이 확인되었다. 합성된 질화붕소의 입자 형상은 미세한 판상 결정을 나타내었다. 반응 과정은 무수붕산이 탄소에 의하여 환원되어 붕소로 기화됨과 동시에 공존하는 질소 가스와 반응하여 육방정 질화붕소로 합성되는 반응 경로를 따를 것으로 사료된다.

• 한국재료학회지
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• 제11권4호
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• pp.329-334
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• 2001

붕산용액에서 양극산화법으로 장벽형 산화피막을 형성시킨 후 미세조직을 관찰하였다. 양극산화시 인가되는 전압에 따른 피막의 성장속도는 1.54nm/v의 직선적인 관계를 나타냈으며 300v의 인가전압에서 생성된 산화피막의 조직은 50$0^{\circ}C$에서 열처리하였을 경우 피막의 상 전이가 일어나지 않았으나 높은 인가전압에서 생성된 산화피막의 경우는 피막의 조직이 비정질에서 ${\gamma}$-alumina로 변태되는 것이 관찰되었다. 또한 피막이 전자빔 조사에 의해서도 ${\gamma}$-alumina로 전이가 일어났다.

• 한국재료학회지
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• 제16권3호
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• pp.163-167
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• 2006

The transition of europium-doped gadolinium oxide phosphor to gadolinium borate phosphor with the concentration of boron in the spray pyrolysis was investigated. The particles prepared from spray solution below 10 wt% boric acid of prepared phosphor had crystal structure of $Gd_2O_3:Eu$ phosphor, in which the crystallinity of the particles decreased with increasing the boron concentration. A single phase $GdBO_3:Eu$ phosphor particles were prepared from spray solution above 50 wt% boric acid of prepared phosphor. The phosphor particles prepared from spray solution with 20 wt% boric acid of prepared phosphor had no XRD peaks of $Gd_2O_3:Eu$ and $GdBO_3:Eu$ Therefore the phosphor particles prepared from spray solution with 20 wt% boric acid of prepared phosphor had the lowest photoluminescence intensity under ultraviolet and vacuum ultraviolet. $GdBO_3:Eu$ and $Gd_2O_3:Eu$ phosphor particles prepared from spray solutions with proper concentrations of boric acid had good photoluminescence intensity under vacuum ultraviolet. The morphology of the phosphor particles were strongly affected by the concentrations of boric acid added into spray solution.

• 공업화학
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• 제20권2호
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• pp.191-194
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• 2009

양극산화(anodization)에 의해 얻어지는 다공성 알루미나는 균일한 규칙성의 나노 구조를 지니며, 이를 제어하는 공정이 비교적 쉽고 경제적이어서 최근 연구가 광범위하게 진행되고 있다. 본 연구에서는 1차로 옥살산(oxalic acid)을 이용하여 양극 산화를 한 산화물 만들고, 이 산화물을 선택적으로 제거한 뒤 생기는 알루미늄 표면의 벌집모양의 패턴에 붕산(boric acid)을 이용하여 2차 양극산화를 하여 알루미늄 산화물 나노 돗(nanodot)을 형성하였다. 정렬된 정육면체의 모서리에 20 nm 높이의 나노 돗이 배열되어 있는 구조를 형성하기 위한 최적의 조건을 조사하였다. 알루미늄 산화물 나노 돗 층에 금을 코팅하여 육각벌집모양으로 배열된 금 나노 돗 층을 형성하였다. 이 표면은 향후 바이오센서에 적용될 것으로 기대된다.

• 한국재료학회지
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• 제29권12호
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• pp.757-763
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• 2019

A stacked high-voltage (900 V) Al electrolytic capacitor made with ZrO₂ coated anode foils, which has not been studied so far, is realized and the effects of Zr-Al-O composite layer on the electric properties are discussed. Etched Al foils coated with ZrO₂ sol are anodized in 2-methyl-1,3-propanediol (MPD)-boric acid electrolyte. The anodized Al foils are assembled with stacked structure to prepare the capacitor. The capacitance and dissipation factor of the capacitor with ZrO₂ coated anode foils increase by 41 % and decrease by 50 %, respectively, in comparison with those of Al anode foils. Zr-Al-O composite dielectric layer is formed between separate crystalline ZrO₂ with high dielectric constant and amorphous Al₂O₃ with high ionic resistivity. This work suggests that the formation of a composite layer by coating valve metal oxide on etched Al foil surface and anodizing it in MPD-boric acid electrolyte is a promising approach for high voltage and volume efficiency of capacitors.

• 한국재료학회지
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• 제17권5호
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• pp.244-249
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• 2007

The properties of anodized films on aluminum 6061 alloy in single electrolyte of sulfuric acid and mixed electrolyte of sulfuric-boric acid and sulfuric-boric-nitric acid have been studied. Polarization tests in NaC solution were used to investigate the corrosion performance. Characteristics of film formation and surface morphology were examined by optical microscopy, FE-SEM and EDS. The results obtained have indicated that oxide films growth have been promoted by nitric acid and anodized films in mixed electrolyte have superior corrosion resistance. In case of anodic films formed in mixed electrolyte, some grooves and numerous crazings were also observed at the surface.

• 대한화학회지
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• 제13권1호
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• pp.49-55
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• 1969

螢光X線을 利用하여 珪酸鹽鑛物中의 主成分인 $SiO_2$, $Al_2O_3$, $Fe_2O_3$, CaO, MgO 및 $K_2O$를 迅速히 分析할 目的으로 試料의 處理 測定 및 各條件에 對하여 檢討하였다. 試料를 Lithium Tetraborate로 용융하여 300Mesh 以上의 微粉末로 한後 40,000Lb의 壓力으로 成型하여 Tungsten과 Chromium 對陰極의 X-線管과 LiF, EDDT, ADP의 分光結晶을 使用하여 測定하였다. 各成分에 對한 檢量曲線은 Matrix Effect를 고려하여 N.B.S 및 International Rock Standard를 選定 使用하였고 Lanthanum Oxide 및 Binder로서 Borie Acid를 첨가하여 얻었다. 各成分에 對하여 本法의 再現性 및 誤差를 檢討하기를 爲하여 I.R.S T-1을 使用하여 測定한 結果 0.47($SiO_2$), 0.85($Al_2O_3$), 0.05($Fe_2O_3$), 0.07(caO), 0.02($K_2O$), 0.13(MgO)의 標準偏差를 얻었다. 또한 化學分析植에 對한 偏差를 求하고져 Clay, Kaoline, Alunite, Wallastonite 및 Zeolite 等의 珪酸鹽鑛物을 選定하여 化學分析 및 本法에 依한 分析結果를 비교하였다.