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(EDTA)^(4-) supplements as superior modifier of the in-vitro-degradation properties of the magnesium alloy coated through discharge-assisted process

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Journal of Magnesium and Alloys 2023年第3期11卷 945-957页

作者： Zeeshan Ur Rahman Maqsood Ali Ye-Tang Pan David G.Churchill bon heun koo College of Mechatronic Engineering Changwon National UniversityChangwonGyeongsangnam-doRepublic of Korea Department of Regenerative Medicines College of MedicinesSoonChunhyang UniversityCheonanRepublic of Korea National Engineering Technology Research Center of Flame Retardant Materials School of Materials Science&EngineeringBeijing Institute of TechnologyBeijingPR China Department of Chemistry Molecular Logic Gate LaboratoryKorea Advanced Institute of Science and Technology(KAIST)Republic of Korea

The(EDTA)^(4-)organic substituents were supplemented with alkaline silicates electrolyte,however in varying concentration to explore the microstructure,chemical composition and subsequent effects on the biodegradation of the PEO coated Mg AZ91 *** surface analysis-,carried out through SEM,samples with zero-(EDTA)^(4-)were found-,lacking pancake structural features;however,supplementing electrolyte with(EDTA)^(4-),bulky and layered pancakes were obtained with minimum cracks and minimum porosity for *** the phase and inner layer analysis,it was found that EDTA can significantly alter the surface layers composition and could act as a passivation agent-;however,individual polycrystalline phases were not found to *** hardness value obtained for EDT-1 was~909.69 HV,the highest value found here which occurs with the shallowest indents found in this ***-vitro degradation analysis was carried out using potentiodynamic polarization at room temperature,cyclic polarization at RT and high fever conditions(HFT~40°C).The corrosion potential for coated AZ91 was obtained as a positive value of~0.1 V,for the first time in the PEO research;however,the results were not supported by the cyclic polarization tests at room temperature and at *** post corrosion microstructural analysis confirmed the effective role of EDTA up to 1.0 g·L^(-1)and revealed the formation of thin films during the forward polarization at HFT.

关键词： EDTA Soft plasma Magnesium Biodegradation Corrosion SBF

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Chemically inducing room temperature spin-crossover in double layered magnetic refrigerants Pr1.4+xSr1.6-xMn2O7(0.0≤x≤0.5)

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Journal of Materials Science & Technology 2022年第29期124卷 232-242页

作者： Akshay Kumar Kavita Kumari Mohit K.Sharma Ankush Vij Shalendra Kumar Seok-Hwan Huh bon heun koo Department of Materials Convergence and System Engineering Changwon National UniversityChangwonGyeongnam51140South Korea School of Material Science and Engineering Changwon National UniversityChangwonGyeongnam51140South Korea Department of Physics University of Petroleum&Energy StudiesDehradun248007India Department of Physics College of ScienceKing Faisal UniversityHofufAl-Ahsa31982Saudi Arabia

The height of total entropy(S)for a magnetic refrigerant material is essentially concerned with the magnetic and structural ***,the participation of such transitions in layered materials is not well ***,the purpose of this work is to investigate the interplay between double layer lattice with their single perovskite counterpart,to achieve optimal magnetocaloric performance.A series of self-doped Pr_(1.4+x)Sr_(1.6-x)Mn_(2)O_(7)(0.0≤x≤0.5)Ruddlesden-Popper(R-P)perovskite have been prepared through the solid-state sintering *** increasing the Pr-stoichiometry,the lattice faults have increased and the double layer lattice dramatically disintegrates into single perovskite *** to the reduction of bilayer R-P phase into single perovskite the spin crossover occurs from weak bilayer(T=304 K)interactions towards the strong three-dimensional(T=308 K)interactions *** series consistently develops thermomagnetic irreversibility in zero-field cooled(ZFC)-field cooled(FC)magnetization,which is indicative of a spin-glass *** glassy nature has been ascribed collectively to the lattice strain produced because of dislocations and to an antiferromagnetic phase segregated at the *** maximum value of temperature average entropy change(TEC)and adiabatic temperature(ΔT)has enhanced nearly by 4 folds from 0.53 J kg^(-1)K^(-1),0.59 K(for x=0.0)up to 1.85 J kg^(-1)K^(-1),10 K(for x=0.5)at 2.5 T,***,the room temperature relative cooling power has improved from 26.94 J/kg up to 77.84 J/kg with an applied field of 2.5 *** findings in this work suggest that the controlled reduction of double layer lattice into single perovskite and/or existence of both phases simultaneously in bilayer R-P manganites may be very effective in obtaining the desirable characteristics of magnetocaloric effects.

关键词： Magnetic refrigerant Bilayer manganites Magnetocaloric effect Ruddlesden-popper perovskite Relative cooling power

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Effects of Ag Seed on Synthesis of FeCo Nano-Particles Prepared via the Polyol Method

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Journal of Materials Science & Technology 2010年第7期26卷 660-664页

作者： Uk-Rae Cho Geun-Woo Kim bon-heun koo School of Nano and Advanced Materials Engineering Changwon National UniversityChangwonGyeongnam641-773Korea

Nano-particles have several interesting properties which are not shown in bulk materials because of their high ratio of surface area to volume. FeCo alloy nano-particles with soft magnetic properties are demanded for various applications such as optics, eletronics and magnetics. Through the polyol method, highly purified particles with mono-dispersibility in various sizes can be produced and used as high-tech functional materials. In this study, the magnetic characteristics of FeCo alloy with Ag seed added in the production process of mono-dispersed nano-particles through the polyol method were investigated.

关键词： Polyol method FeCo Ag Seed

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Effects of Hybrid Voltages on Oxide Formation on 6061 Al-alloys During Plasma Electrolytic Oxidation

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Chinese Journal of Aeronautics 2009年第5期22卷 564-568页

作者： Kai Wang bon heun koo Chan Gyu Lee Young Joo Kim Sunghun Lee Eungsun Byon School of Nano & Advanced Materials Engineering Changwon National University Changwon 641-773 Korea Surface Technology Research Center Korea Institute of Materials Science Changwon 641-010 Korea

Plasma electrolytic oxidation （PEO） is carried out on 6061 Al-alloys in a weak alkaline electrolyte containing NaOH, Na2SiO3 and NaCl. Centered on the correlation of composition and structure, analyses by means of X-ray diffration （XRD）, scanning electron microscope （SEM） and energy dispersive spectrometry （EDS） are conducted on the specimens, which have been PEO-treated under hybrid voltages of different direct current （DC） values （140-280 V） with constant alternate current （AC） amplitude （200 V）. Attention is paid to the composition, properties and growth mechanism of oxide layers formed with hybrid voltages. Moreover, the main effects of DC value are discussed. Ceramic layers with a double-layer structure which combines hard outer and soft inner layers are found to be consist of α-Al2O3,γ-Al2O3 and mullite. With the DC values increasing, the growth of the ceramic layers tends to have increasingly obvious three-stage feature.

关键词： plasma electrolytic oxidation oxide layer aluminum alloys alkaline electrolyte hybrid voltages

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Effects of electrolytes variation on formation of oxide layers of 6061 Al alloys by plasma electrolytic oxidation

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中国有色金属学会会刊：英文版 2009年第4期19卷 866-870页

作者： Kai WANG bon-heun koo Chan-Gyu LEE Young-Joo KIM Sung-Hun LEE Eungsun BYON School ofNano ＆ Advanced Materials Engineering Changwon National University Changwon 641-773 Korea Surface Technology Research Center Korea Institute of Materials Science Changwon 641-010 Korea

Plasma electrolytic oxidation(PEO) processes were carried out to produce ceramic layers on 6061 aluminum substrates in four kinds of electrolytes such as silicate and aluminate solution with and without sodium *** PEO processes were carried out under a hybrid voltage(260 V DC combined with 200 V,60 Hz AC amplitude) at room temperature for 5 *** composition,microstructure and element distribution analyses of the PEO-treated layers were carried out by XRD and SEM & *** effect of the electrolyte contents on the growth mechanism,element distribution and properties of oxide layers were *** is obvious that the layers generated in aluminate solutions show smoother surfaces than those in silicate ***,an addition of fluorine ion can effectively control the layer porosity;therefore,it can enhance the properties of the layers.

关键词：等离子电解氧化 6061合金氧化层对格质变等离子体电解氟硅酸钠铝酸钠溶液

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Effect of Cu seed on the synthesis and characterization of FeCo alloy nano-particles by using polyol method

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Science China(Technological Sciences) 2009年第1期52卷 19-22页

作者： Uk Rae CHO Young Min LEE Shalendra KUMAR Chan Gyu LEE bon heun koo School of Nano-Advanced Materials Engineering Changwon National University Changwon

Fine metal particles with uniform shape, narrow size distribution and high purity are increasingly needed for specific uses in high tech industrial application. We report the direct chemical synthesis of FeCo alloy particles using the mixture of FeCl2·4H2O, Co (Ac)2·4H2O (Ac: acetate) and NaOH in ethylene glycol, and then obtained FeCo alloy particles better dispersed by adding the polyvinylpyrrolidone (PVP) and also the size could be controlled by adding copper. The prepared nano-particles were characterized using FESEM, XRD and VSM. The mean diameter of these particles was varied in the range of sub- mi- crometer to nanometer with metal-ion concentration. FeCo particles showed the typical soft magnetic properties.

关键词： polyol method FeCo alloy nanoparticle Cu seed soft magnetic

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电解等离子体过程中电解液对AZ31B镁合金力学性能的影响(英文)

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Transactions of Nonferrous Metals Society of China 2014年第S1期24卷 125-128页

作者： Byung Hyun AHN Jung Il SONG bon heun koo School of Nano & Advace material engineering Changwon National University Department of Mechanical Engineering Changwon National University

以NaOH+Na2SiO3为基础电解液,分别加入Na2SiF6或NaF制备镁合金涂层。将AZ31B镁合金基体在200 V交流和260 V直流的混合电压下等离子体电解处理30 min。通过XRD和SEM方法分析陶瓷涂层的结构和形态。利用销盘式磨损实验和维氏硬度实验研究... 详细信息

以NaOH+Na2SiO3为基础电解液,分别加入Na2SiF6或NaF制备镁合金涂层。将AZ31B镁合金基体在200 V交流和260 V直流的混合电压下等离子体电解处理30 min。通过XRD和SEM方法分析陶瓷涂层的结构和形态。利用销盘式磨损实验和维氏硬度实验研究涂层的耐磨性和硬度。在Na2SiF6和NaF电解液中形成的涂层主要成分是MgO和Mg2SiO4。在Na2SiF6电解液中制备的涂层的显微硬度为HV1100,而在NaF电解液中制备的涂层的显微硬度约为HV900。结果表明:AZ31B镁合金的力学性能可以通过选择适当的电解液得到增强。

关键词： AZ31B镁合金表面处理等离子体电解

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烧结温度对La_(0.6)Ca_(0.4)MnO_3结构、磁性和磁致热效应的影响(英文)

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Transactions of Nonferrous Metals Society of China 2014年第S1期24卷 141-145页

作者： Seung Rok LEE M.S.ANWAR Faheem AHMED bon heun koo School of Materials Science and Engineering Changwon National University

研究了烧结温度对La0.6Ca0.4MnO3的结构、磁转变和磁熵的影响。观察表明,该化合物属于具有Pnma空间群的斜方晶系结构,不含任何杂质。研究烧结温度对居里温度(TC)的影响,发现提高烧结温度,TC稍有增大。磁致热效应研究显示,随着烧结温度... 详细信息

研究了烧结温度对La0.6Ca0.4MnO3的结构、磁转变和磁熵的影响。观察表明,该化合物属于具有Pnma空间群的斜方晶系结构,不含任何杂质。研究烧结温度对居里温度(TC)的影响,发现提高烧结温度,TC稍有增大。磁致热效应研究显示,随着烧结温度的变化,磁熵会发生显著的变化。在外加磁场为3 T、烧结温度为1300°C时,相对冷却能(RCP)为89 J/kg。因此,该化合物可以考虑作为在室温附近或低于室温的潜在磁制冷材料。

关键词：亚锰酸盐磁热效应烧结温度巨磁阻

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单晶金红石型TiO_2纳米棒的湿法合成(英文)

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Transactions of Nonferrous Metals Society of China 2014年第S1期24卷 152-156页

作者： Rehan DANISH Faheem AHMED Nishat ARSHI M.S.ANWAR bon heun koo School of Nano and Advanced Materials Engineering Changwon National University

用TiO2粉末、NaOH和蒸馏水为原料合成金红石型TiO2纳米棒。XRD和FESEM分析表明,制备的样品为单晶且无杂质,其平均粒径约为40 nm。当样品于600°C退火2 h后,FESEM观察发现生成了TiO2纳米棒。XRD分析表明纳米棒为单晶。纳米棒表面光滑,其... 详细信息

用TiO2粉末、NaOH和蒸馏水为原料合成金红石型TiO2纳米棒。XRD和FESEM分析表明,制备的样品为单晶且无杂质,其平均粒径约为40 nm。当样品于600°C退火2 h后,FESEM观察发现生成了TiO2纳米棒。XRD分析表明纳米棒为单晶。纳米棒表面光滑,其长约为1μm,直径约为80 nm。紫外和拉曼光谱研究表明,所制备样品的能带间隙为3.40 eV。

关键词： TiO2 纳米棒湿法晶粒生长金红石

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退火时间对射频溅射p型透明SnO_2/Al/SnO_2导电薄膜结构、形貌、光学和电学性能的影响(英文)

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Transactions of Nonferrous Metals Society of China 2014年第S1期24卷 129-133页

作者： Keun Young PARK Ho Je CHO Tae Kwon SONG Hang Joo KO bon heun koo School of Materials Science & Engineering Changwon National University Photovoltaic and Optoelectronic device center Korea Photonics Technology Institute

采用SnO2和Al靶,通过射频(RF)溅射在石英基体上制备透明p型SnO2/Al/SnO2导电复合薄膜。沉积薄膜在500°C进行不同时间(1~8 h)退火处理,研究退火时间对SnO2/Al/SnO2复合薄膜结构、形貌、光学和电学性能的影响。X射线衍射结果表明:所制备... 详细信息

采用SnO2和Al靶,通过射频(RF)溅射在石英基体上制备透明p型SnO2/Al/SnO2导电复合薄膜。沉积薄膜在500°C进行不同时间(1~8 h)退火处理,研究退火时间对SnO2/Al/SnO2复合薄膜结构、形貌、光学和电学性能的影响。X射线衍射结果表明:所制备的p型导电薄膜具有四方金红石型多晶SnO2结构。霍尔效应结果显示:500°C,1 h为最佳退火条件,该条件下SnO2/Al/SnO2复合薄膜的孔隙浓度为1.14×1018 cm-3、电阻率为1.38?·cm。退火时间为1~8 h时,p型SnO2/Al/SnO2复合薄膜的光透射率可达80%以上,退火1 h时薄膜的光透射率达到最大值。

关键词：脉冲激光沉积法(PLD) 透明导电氧化物(TCO) p型多层透射率

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