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Consideration of Diluents Selection and Input Amounts of the Hunter Process for Tantalum Production
Jae‑Jin Sim,Sang‑Hoon Choi,Yong‑Kwan Lee,Sung Gue Heo,Taek‑Soo Kim,Seok‑Jun Seo,Kyoung‑Tae Park 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7
Tantalum (Ta) is a heavy refractory metal with an atomic weight of 180.95 g/mol, a density of 16.6 g/cm3, and a high meltingpoint of 3017 °C. With its refractory characteristics, it shows excellent chemical and physical stability as well as corrosionand heat resistance at elevated temperatures. The demand for Ta metal and related compounds is increasing with the expansionof the electronics and chemical industries. The Hunter process was proven to be effective in producing Ta powder in1953. Hunter proposed a method in which potassium heptafluorotantalate (K2TaF7) was reduced by sodium (Na). Thus far,this process has been the primary commercial method to produce Ta powder. In this study, quantitative differences wereanalyzed for diluent selection. Additionally, consideration was given to changes in the caloric value depending on the inputamount of diluents. Finally, the optimum material input and the properties of the prepared Ta were analyzed. Stoichiometricratios of K2TaF7(1 mol), NaCl (6.2–6.7 mol), Na (5–7 mol) were weighed, to perform a metallothermic reduction reaction. After the reaction, the tantalum powder was recovered and the flush process was carried out. After that, it was dried in avacuum atmosphere. Physical properties such as oxygen concentration, PSA, ICP-OES, and XRD of powder were conductedto evaluate the characteristics of Ta powder that was finally manufactured.
Choi, Dukhyun,Choi, Min-Yeol,Choi, Won Mook,Shin, Hyeon-Jin,Park, Hyun-Kyu,Seo, Ju-Seok,Park, Jongbong,Yoon, Seon-Mi,Chae, Seung Jin,Lee, Young Hee,Kim, Sang-Woo,Choi, Jae-Young,Lee, Sang Yoon,Kim, Jo WILEY-VCH Verlag 2010 ADVANCED MATERIALS Vol.22 No.19
<B>Graphic Abstract</B> <P>The cover shows an image of fully rollable transparent nanogenerators synthesized using chemical vapor deposition grown large-scale graphene sheets as transparent electrodes and piezoelectric ZnO nanorod arrays. Sang-Woo Kim, Jae-Young Choi, and co-workers report on p. 2187 the electrical and structural stability of the nanogenerators, with excellent charge scavenging performance under external mechanical loads such as bending and rolling. This study shows that graphene-based nanogenerators are very promising for self-powered rollable transparent device applications. <img src='wiley_img_2010/09359648-2010-22-19-ADMA201090066-content.gif' alt='wiley_img_2010/09359648-2010-22-19-ADMA201090066-content'> </P>
( Seo Dong Ho ),( Jong Hyun Jung ),( Hyun Chang Choi ),( Hyun Kuk Cho ),( Hee Hang Kim ),( Suk Jin Ha ),( Sang Ho Yoo ),( Jae Ho Cha ),( Cheon Seok Park ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.9
A gene (acas) designated as α-amylase was cloned from Arthrobacter chlorophenolicus A6. The multiple amino acid sequence analysis and functional expression of acas revealed that this gene really encoded an amylosucrase (ASase) instead of α-amylase. In fact, the recombinant enzyme exhibited typical ASase activity by showing both sucrose hydrolysis and glucosyltransferase activities. The purified enzyme has a molecular mass of 72 kDa and exhibits optimal hydrolysis activity at 45oC and a pH of 8.0. The analysis of the oligomeric state of ACAS with gel permeation chromatography revealed that the ACAS existed as a monomer.
Seo, Seunggi,Yeo, Byung Chul,Han, Sang Soo,Yoon, Chang Mo,Yang, Joon Young,Yoon, Jonggeun,Yoo, Choongkeun,Kim, Ho-jin,Lee, Yong-baek,Lee, Su Jeong,Myoung, Jae-Min,Lee, Han-Bo-Ram,Kim, Woo-Hee,Oh, Il-K American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.47
<P>The reaction mechanism of area-selective atomic layer deposition (AS-ALD) of Al2O3 thin films using self-assembled monolayers (SAMs) was systematically investigated by theoretical and experimental studies. Trimethylaluminum (TMA) and H2O were used as the precursor and oxidant, respectively, with octadecylphosphonic acid (ODPA) as an SAM to block Al2O3 film formation. However, Al2O3 layers began to form on the ODPA SAMs after several cycles, despite reports that CH3-tenninated SAMs cannot react with TMA. We showed that TMA does not react chemically with the SAM but is physically adsorbed, acting as a nucleation site for Al2O3 film growth. Moreover, the amount of physisorbed TMA was affected by the partial pressure. By controlling it, we developed a new AS-ALD Al2O3 process with high selectivity, which produces films of similar to 60 nm thickness over 370 cycles. The successful deposition of Al2O3 thin film patterns using this process is a breakthrough technique in the field of nanotechnology.</P>
Sung Han Kim,In-Chang Cho,Sun Ho Kim,Jae Young Joung,Ho Kyung Seo,Kang Hyun Lee,Heong Dong Yuk,Jinsoo Chung 대한비뇨기종양학회 2014 대한비뇨기종양학회지 Vol.12 No.3
Purpose: To evaluate the renal target lesion response in metastatic renal cell carcinoma (mRCC) patients treated with targeted therapy (TT) and to determine predictive factors for maximal tumor size reduction. Materials and Methods: We reviewed the clinical and radiographic data of 43 mRCC patients with 47 primary renal target legions (RTL) treated with at least two cycles of TT between 2007 and 2011. RTL response was evaluated using Response Evaluation Criteria Solid Tumors (RECIST) v.1.1. The significant predictive factors corresponding to the best response of RTL size reduction between the size reduction group (RG, n=36) and the non-reduction group (NRG, n=11) was statistically analyzed. Results: During a median follow-up period of 7.4 months, median RTL size was 82mm and its mean change in size was -7.35mm. Multivariate analysis showed that body surface area (BSA) (p=0.016) and RTL size (p=0.024) were independently significant in shorter time to maximize size reduction. After classification of four RTL groups according to the combination of BSA of 1.62㎡ and RTL size of 82mm, significant differences in time to maximal size reduction were observed (log rank, p=0.009). Conclusions: BSA and RTL size were the best predictive factors for reduction of RTL size with time for maximal tumor response during TT.
Scaling behavior of density fluctuations in an expanding quasi-two-dimensional degenerate Bose gas
Seo, Sang Won,Choi, Jae-yoon,Shin, Yong-il American Physical Society 2014 Physical review. A. Atomic, molecular, and optical Vol.89 No.4
We measure the power spectrum of density fluctuations emerging in a freely expanding quasi-two-dimensional (2D) degenerate Bose gas, and we investigate the scaling behavior of the spectrum for the expansion time. The power spectrum shows an oscillatory shape for long expansion times, where the spectral peak positions are observed to be shifted to lower spatial frequencies than the theoretical prediction for a noninteracting expansion case. We find the spectral peak positions in good agreement with the recent numerical simulation presented by Mazets [Phys. Rev. A 86, 055603 (2012)], where the atom-atom interactions are taken into account. We present a mean-field description of the interaction effect in the expansion dynamics and quantitatively account for the observed spectral peak shifts. The spectral shift is intrinsic to the free expansion of a quasi-2D Bose gas due to finite axial confinement. Finally, we investigate the defocusing effect in the power spectrum measurement.
Three-dimensional Macropore Arrays in p-type Silicon Fabricated by Electrochemical Etching
Jae Hyun Kim,Kang-Pil Kim,Hong-Kun Lyu,Sung-Ho Woo,Hong-Seok Seo,Jung-Ho Lee 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1
Ordered macropores formed in p-type silicon substrates (10~20Ω·cm) by using electrochemical anodization in various HF-containing electrolytes was investigated under different operating conditions. The effect of electrolyte composition and etch pits on controlling the formation of macropores on periodically arranged pores is reported. The results revealed that the natures of the constituents of the solution play very important roles in determining pore formation and morphology and that stable ordered macropore growth is not possible without an inverse pyramid notch. By using a Si/SiGe/Si/SiGe/p-type silicon structure, we were able to fabricate ordered pillar structures without an etch pit formation process. A possible role of two sets of Si/SiGe layers in pillar formation is proposed. Ordered macropores formed in p-type silicon substrates (10~20Ω·cm) by using electrochemical anodization in various HF-containing electrolytes was investigated under different operating conditions. The effect of electrolyte composition and etch pits on controlling the formation of macropores on periodically arranged pores is reported. The results revealed that the natures of the constituents of the solution play very important roles in determining pore formation and morphology and that stable ordered macropore growth is not possible without an inverse pyramid notch. By using a Si/SiGe/Si/SiGe/p-type silicon structure, we were able to fabricate ordered pillar structures without an etch pit formation process. A possible role of two sets of Si/SiGe layers in pillar formation is proposed.
Acne scar successfully treated with a picosecond laser and pneumatic needless microjet injection
( Jae Min Kim ),( Ji Yeon Hong ),( Kui Young Park ),( Sang Ju Lee ),( Seong Jun Seo ),( Chang Kwun Hong ) 대한피부과학회 2018 대한피부과학회 학술발표대회집 Vol.70 No.1
Acne and subsequent scarring, as well as residual erythema and postinflammatory hyperpigmentation often cause severe effects on cosmetic aspect. If severe, it can be psychologically debilitating, leading to low self-esteem and passive mindset. There are numerous therapeutic modalities for acne scar including ablative or nonablative laser skin resurfacing, chemical peeling, microdermabrasion, subcision and filler injection. Nevertheless, effective therapy of acne scarring remains a major challenge. A 23-year-old female patient presented with multiple pitting acne scars on the cheeks. After combined treatment with the pneumatic needless microjet injection and picosecond laser, the scars were significantly improved and the patient was very satisfied with the cosmetic outcome. Our results support the use of a fractional Neodymium-doped yttrium aluminium garnet (Nd:YAG), picosecond-domain laser as an effective and safe treatment for facial acne scarring.