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류병환(Beyong-Hwan Ryu),최영민(Youngmin Choi) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
It is strongly expected that inkjet printing method will be play an important role on printable electronics such as 3D integration of embedded ceramic devices (capacitor, resistor, inductor and electrode or circuit), Si-TFT and organic TFT including display C/F, RFID, FPCB, and etc. A inkjet printing method has been center of attention to strengthen the competitiveness of flat panel display on market and to open the new world of manufacturing process of printable electronics. We will survey the industrial tendency of printable electronics and flat panel display including some examples of inkjet printing and present the considerable points of inkjet printing method and some role of materials for successful inkjet printing.
Joining Method of Silicon Nitride to Carbon Steel
Choi, Young Min,Ryu, Beyong Hwan,Lee, Jae Do Trans Tech Publications, Ltd. 2005 Key Engineering Materials Vol.287 No.-
<P>We investigated the method of joining silicon nitride having on its surface a thin layer of active silicon metal to carbon steel. The active silicon layer is formed through the thermal dissociation of silicon nitride (Si3N4) into silicon (Si) and nitrogen gas (N2). The active silicon layer is directly joined to carbon steel via an induced eutectic melting reaction between the silicon and iron (Fe) found in carbon steel, or via brazing of two materials using general brazing metal such as Ag-Cu alloys. This joining process does not require the use of expensive active brazing alloys such as Ag-Cu-Ti alloys or a sputtering method designed to coat the active metals on surface of silicon nitride.</P>
Low Temperature Synthesis of Colloidal CdSe Quantum Dots
Hwang, Seongmi,Choi, Youngmin,Ryu, Beyong-Hwan American Scientific Publishers 2007 Journal of Nanoscience and Nanotechnology Vol.7 No.11
<P>In this study, the CdSe nanocrystals were prepared in phenyl ether and octyl amine to investigate the variations of their size, bandgap energy, and photoluminescence with growth time and temperature. The sizes of the CdSe nanocrystals were measured using High Resolution Transmission Electron Microscopy (HRTEM), and found to be nearly monodisperse for relatively low growth temperature, 130 °C. Their optic properties were characterized by photoluminescence measurements, which showed that the colors of the nanocrystals could be controlled. The bandgap energies of the nanocrystals were calculated theoretically and found to be in accord with quantum confinement theory. This synthetic method requires only a cheap solvent and offers good reproducibility at a lower price.</P>
류병환,이정민,고재천 ( Beyong Hwan Ryu,Jung Min Lee,Jae Cheon Koh ) 한국공업화학회 1997 공업화학 Vol.8 No.5
본 실험에서는 물유리를 사용하여 산세척액에 의하여 제조된 산화철 입자의 표면개질에 대하여 연구하였다. 사용한 물유리의 SiO₂와 Na₂O의 몰비(SiO₂/Na₂O)는 1,2,3.5이였다. 첨가되는 실리카의 양과 pH에 따라 산화철 현탁액의 분산성을 입자의 표면하전과 침강속도에 의하여 평가하였다. 그리고, 중성 영역에서 산화철 입자의 분산안정성을 유지할 수 있는 표면개질제(실리카)의 양을 도출하였으며, 물유리에 의한 산화철 입자의 표면개질을 습식 볼밀링에 의하여 슬러리 상태에서 실시하였다. 그 결과, 표면처리한 산화철 현탁액의 분산 안정성은 실리카의 양과 pH에 상호 의존하였다. 미처리한 산화철은 등전점인 pH 8에서 분산안정성을 잃고 있었으나, 산화철에 대하여 약 0.8wt%의 실리카로 표면처리한 산화철은 pH 5 이상 중성영역에서 분산안정성을 나타내었으며, 음이온성 계면활성제를 0.2wt% 이상 첨가에 의해 분산안정성이 더욱 증가되었다. The surface modification of iron oxide particle produced from steel-pickled acid by sodium silicates as silica-contained materials was studied. The molar ratio of SiO₂ to Na₂O of sodium silicate was 1, 2, 3.5, respectively. The dispersion stability of iron oxide suspension as functions of amount of silica and pH was evaluated by surface charge and sedimentation velocity of iron oxide particle. Then, the amount of sodium silicate was determined to provide a dispersion stability of iron oxide particle above pH 7. Finally, the surface modification of iron oxide particle with sodium silicate as silica-contained materials was done by wet ball milling. In the results of study, the dispersion stability of silica modified iron oxide particle was largely depended on amount of silica and pH together. The untreated iron oxide was unstable at pH 8, i.e. isoelectric point, but, the surface modified iron oxide particle with 0.8wt% silica was stable above pH 5. The dispersion stability was enhanced with 0.2wt% of anionic polyelectrolyte.
Anton Nailevich Gafurov,Thanh Huy Phung,Beyong-Hwan Ryu,Inyoung Kim,Taik-Min Lee 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.2
Screen printing has been adopted for fabricating a wide variety of electronic devices. However, the printing defects and reliability have been an obstacle for industrialization of printed electronics. In this research, the artificial intelligence (AI) model was developed and integrated with the in-house roll-to-roll screen printing system to detect smearing defect, which is one of the main defects of screen printing. The U-Net architecture was adopted, and a total of 19 models were designed with model sizes ranging from 8E + 3 to 3E + 7 number of parameters. Their performances as validation mean Intersection over Union (IoU) were analyzed, and the optimal model was chosen with a validation mean IoU of 95.1% and a number of parameters of 8E + 6. The printed line images were evaluated by the AI model for various printing conditions, such as printed line widths, printing paste premixing, printing speeds, and printed line directions, which showed that the model could effectively detect the smearing defects. Also, the AI model capabilities were investigated for repeated printing, which demonstrated that it can be used for the reliability assessment of the screen printing process.
NiCuZn Ferrite 분말제조에 있어서 Ball Mill 분쇄 공정 중에 혼입되는 불순물의 함량
고재천(Jae-Cheon Koh),류병환(Beyong-Hwan Ryu) 한국자기학회 1999 韓國磁氣學會誌 Vol.9 No.4
The pick up impurity was studied for preparing the NiCuZn ferrite powder by a ball milling method that usually uses in the industrial ceramic process. The raw materials of NiO, CuO, ZnO, and Fe₂O₃ powder were weighted according to various spinel composition and mixed for 18 hrs by a wet ball milling method after that the slurry was followed by spray dried and calcined at 700 ℃ 3 hrs. The calcined NCZF powder was finally ball milled during 65 hrs as same method. The stainless steel ball and jar are used as mixing and milling equipment and the solid concentration of the slurry was 25 vol%. The impurities, stainless steel pickup, were effected by the composition of raw materials especially iron oxide, nickel oxide in the mixing process and by the rate of calcine of NiCuZn ferrite in final milling process. The empirical equation of stainless steel pickup was driven in the wet ball milling system. Finally, the composition of NiCuZn ferrite could be controlled by the empirical equation.
Jeong, Sunho,Lee, Ji-Yoon,Lee, Sun Sook,Choi, Youngmin,Ryu, Beyong-Hwan American Chemical Society 2011 The Journal of Physical Chemistry Part C Vol.115 No.23
<P>Sol–gel-derived oxide semiconductors annealed at a low temperature have been of great interest recently in various thin-film transistor (TFT) applications. However, studies on the influence of metal salt precursor on sol–gel-derived oxide semiconductor annealed at a low temperature have not yet been reported. In this study, the impact of metal salt precursor on the chemical structure evolution of Ga-doped In<SUB>2</SUB>O<SUB>3</SUB> (IGO) semiconductor and electrical performance of thin-film transistors with a corresponding oxide semiconductor is investigated. X-ray photoelectron spectroscopy (XPS)-based chemical structure analysis is carried out in conjunction with an understanding of the electrical performance of device. It is revealed that in addition to the thermally enhanced evolution of metal oxide chemical structure, the impurities due to the incomplete thermal decomposition of metal salt precursor do not only hinder the formation of metal oxide lattice, resulting in an electrically inactive oxide semiconductor, but also significantly deteriorate the electrical performance, such as field-effect mobility, subthreshold swing, and on/off current ratio, of thin-film transistor.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-23/jp202522s/production/images/medium/jp-2011-02522s_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp202522s'>ACS Electronic Supporting Info</A></P>