We report a synthesis of non-toxic InP nanocrystals using non-pyrolytic precursors instead of pyrolytic and unstable tris(trimethylsilyl)phosphine, a popular precursor for synthesis of InP nanocrystals. In this study, InP nanocrystals are successfully synthesized using hexaethyl phosphorous triamide (HPT) and the synthesized InP nanocrystals showed a broad and weak photoluminescence (PL) spectrum. As synthesized InP nanocrystals are subjected to further surface modification process to enhance their stability and photoluminescence. Surface modification of InP nanocrystals is done at 230°C using 1-dodecanethiol, zinc acetate and fatty acid as sources of ZnS shell. After surface modification, the synthesized InP/ZnS nanocrystals show intense PL spectra centered at the emission wavelength 612 nm through 633 nm. The synthesized InP/ZnS core/shell structure is confirmed with X-ray diffraction (XRD) and Inductively Coupled Plasma - Atomic Emission Spectrometer (ICP-AES). After surface modification, InP/ZnS nanocrystals having narrow particle size distribution are observed by Field Emission Transmission Electron Microscope (FE-TEM). In contrast to uncapped InP nanocrystals, InP/ZnS nanocrystals treated with a newly developed surface modified procedure show highly enhanced PL spectra with quantum yield of 47%.

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• Synthesis and Properties of InP/ZnS core/shell Nanoparticles with One-pot process
  So Yeong Joo, Myung Hwan Hong, Leeseung Kang, Tae Hyung Kim, Chan Gi Lee
  Journal of Korean Powder Metallurgy Institute.2017; 24(1): 11.     CrossRef

We report on the successful fabrication of ZnO nanorod (NR)/polystyrene (PS) nanosphere hybrid nanostructure by combining drop coating and hydrothermal methods. Especially, by adopting an atomic layer deposition method for seed layer formation, very uniform ZnO NR structure is grown on the complicated PS surfaces. By using zinc nitrate hexahydrate [Zn(NO₃)₂ ·6H₂O] and hexamine [(CH₂)₆N₄] as sources for Zn and O in hydrothermal process, hexagonal shaped single crystal ZnO NRs are synthesized without dissolution of PS in hydrothermal solution. X-ray diffraction results show that the ZnO NRs are grown along c-axis with single crystalline structure and there is no trace of impurities or unintentionally formed intermetallic compounds. Photoluminescence spectrum measured at room temperature for the ZnO NRs on flat Si and PS show typical two emission bands, which are corresponding to the band-edge and deep level emissions in ZnO crystal. Based on these structural and optical investigations, we confirm that the ZnO NRs can be grown well even on the complicated PS surface morphology to form the chestnut-shaped hybrid nanostructures for the energy generation and storage applications.

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• Synthesis of Planar-Type ZnO Powder in Non-Nano Scale Dimension and Its Application in Ultraviolet Protection Cosmetics
  Jung-Hwan Lee, Gun-Sub Lee, Eung-Nam Park, Dong-Hyeon Jo, So-Won Kim, Hee-Chul Lee
  Materials.2023; 16(5): 2099.     CrossRef
• Rapid consolidation of nanostuctured WC-FeAl3 by pulsed current activated heating and its mechanical properties
  In-Jin Shon, Seok-Jae Lee
  International Journal of Refractory Metals and Hard Materials.2017; 65: 69.     CrossRef
• Fabrication of a Graphene/ZnO based p-n junction device and its ultraviolet photoresponse properties
  Young-Tae Kwon, Sung-Oong Kang, Ji-Ae Cheon, Yoseb Song, Jong-Jin Lee, Yong-Ho Choa
  Applied Surface Science.2017; 415: 2.     CrossRef
• Morphology Control of ZnO Nanostructures by Surfactants During Hydrothermal Growth
  Il-Kyu Park
  Journal of Korean Powder Metallurgy Institute.2016; 23(4): 270.     CrossRef

The organic binder-free paste for dye-sensitized solar cell (DSSC) has been investigated using peroxo titanium complex. The crystal structure of TiO₂ nanoparticles, morphology of TiO₂ film and electrical properties are analyzed by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Electrochemical Impedance Spectra (EIS), and solar simulator. The synthesized TiO₂ nanopowders by the peroxo titanium complex at 150, 300, 400°C, and 450°C have anatase phase and average crystal sizes are calculated to be 4.2, 13.7, 16.9, and 20.9 nm, respectively. The DSSC prepared by the peroxo titanium complex binder have higher V_oc and lower J_sc values than that of the organic binder. It can be attributed to improvement of sintering properties of TCO/TiO₂ and TiO₂/TiO₂ interface and to formation of agglomerate by the nanoparticles. As a result, we have investigated the organic binder-free paste and 3.178% conversion efficiency of the DSSC at 450°C.

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• Development of Eco-Friendly Ag Embedded Peroxo Titanium Complex Solution Based Thin Film and Electrical Behaviors of Resistive Random Access Memory
  Won Jin Kim, Jinho Lee, Ryun Na Kim, Donghee Lee, Woo-Byoung Kim
  Korean Journal of Materials Research.2024; 34(3): 152.     CrossRef
• Development of eco-friendly thin film manufacturing process using poeroxo titanium complex solution and potential for resistive random access memory
  Jinho Lee, Ryun Na Kim, Kee-Ryung Park, Woo-Byoung Kim
  Applied Surface Science.2021; 562: 150170.     CrossRef
• Preparation of ultra-thin TiO2 shell by peroxo titanium complex (PTC) solution-based green surface modification, and photocatalytic activity of homo-core/shell TiO2
  Jinho Lee, Jiyong Hwang, Hyunsu Park, Tohru Sekino, Woo-Byoung Kim
  Applied Surface Science.2021; 540: 148399.     CrossRef
• Effects of Annealing Temperature on the Crystal Structure, Morphology, and Optical Properties of Peroxo-Titanate Nanotubes Prepared by Peroxo-Titanium Complex Ion
  Hyunsu Park, Tomoyo Goto, Sunghun Cho, Soo Wohn Lee, Masato Kakihana, Tohru Sekino
  Nanomaterials.2020; 10(7): 1331.     CrossRef
• Study on thermal behavior of Ammonium Hexafluofide Titanate for Synthesis of TiO2 Powders
  Duk-Hee Lee, Jae-Ryang Park, Chan-Gi Lee, Kyung-Soo Park, Hyeon-Mo Kim
  Journal of Korean Powder Metallurgy Institute.2016; 23(5): 353.     CrossRef

Poly-methylmetacrylate (PMMA) is mainly applied in the plastic manufacturing industry, but PMMA is weak and gradually got discolor. The strength of PMMA can be improved through organic-inorganic hybrid nano composites with inorganic nano particles such as, SiO₂ or ZrO. However, inorganic nano particles are mostly agglomerated spontaneously. In this study, the zeta potential is controlled using different types of organic solvent with different concentrations, dispersibillity of SiO₂ nano particles on the PMMA particle are analyzed. When 3 M acetic acid is used, absolute value of the zeta potential is higher, SiO₂ nano particle is well attached, and dispersed on the PMMA particle surface. Results indicate that the absolute value of the zeta potential affects the stability of SiO₂ dispersion.

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• A Study of Organic Impurity Removal Efficiency for Waste LCD Touch Panel Glass by Solvents Types
  Yubin Kang, Jin-Ju Choi, Jae Layng Park, Chan Gi Lee
  Journal of the Korean Institute of Resources Recycling.2020; 29(6): 57.     CrossRef
• Hard Surface-adhesive Properties of TiO2 Nanoparticles-encapsulated Microparticles Prepared by Spray Drying and Surface Coating Method
  Su-Kyung Kim, Jong-Duk Kim, Seung-Jun Lee
  Fibers and Polymers.2018; 19(6): 1303.     CrossRef

This study attempts to manufacture a Ni-Cr-Al-Y coating layer using a kinetic spray process and investigates the microstructure and physical properties of the manufactured layer. The Ni-22Cr-10Al-1Y (wt.%) composition powder is used, and it has a spherical shape with an average diameter of 23.7 μm. Cu plate is used as the substrate. Optical microscope, X-ray diffraction, scanning electron microscope and Vickers hardness test are carried out to characterize the macroscopic properties of the coating layer. Furthermore, the coating layer underwent vacuum heat treatment at temperatures of 400°C and 600°C for 1 hour to check the effect of heat treatment temperature on the properties. The manufactured coating layer is 1.5 mm thick, and featured identical phases to those found in the powder. The porosity of the coating layer is measured at 2.99%, and the hardness is obtained at 490.57 H_v. The layer shows reduced porosity as heat treatment temperature increased, and hardness is reduced at 400°C but shows a slight increase at 600°C. Based on the findings described above, this study also discusses possible manufacturing methods for a Ni-Cr-Al-Y coating layer using the kinetic spray process.

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• Morphology Control of NiO Catalysts on NiCrAl Alloy Foam Using a Hydrothermal Method
  Dong-Yo Sin, Eun-Hwan Lee, Man-Ho Park, Hyo-Jin Ahn
  Korean Journal of Materials Research.2016; 26(7): 393.     CrossRef

Lanthanum zirconate, La₂Zr₂O₇, is one of the most promising candidates for next-generation thermal barrier coating (TBC) applications in high efficient gas turbines due to its low thermal conductivity and chemical stability at high temperature. In this study, bulk specimens and thermal barrier coatings are fabricated via a variety of sintering processes as well as suspension plasma spray in lanthanum zirconates with reduced rare-earth contents. The phase formation, microstructure, and thermo-physical properties of these oxide ceramics and coatings are examined. In particular, lanthanum zirconates with reduced rare-earth contents in a La₂Zr₂O₇-4YSZ composite system exhibit a single phase of fluorite or pyrochlore after fabricated by suspension plasma spray or spark plasma sintering. The potential of lanthanum zirconate ceramics for TBC applications is also discussed.

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• Phase Formation and Thermo-physical Properties of Lanthanum/Gadolinium Zirconate with Reduced Rare-earth Contents for Thermal Barrier Coatings
  Sujin Lee, Chang-Sup Kwon, Sung-Min Lee, Yoon-Suk Oh, Hyung-Tae Kim, Sahn Nahm, Seongwon Kim
  Journal of Korean Powder Metallurgy Institute.2015; 22(6): 420.     CrossRef

Rare-earth zirconates, such as lanthanum zirconates and gadolinium zirconates, have been intensively investigated due to their excellent properties of low thermal conductivity as well as chemical stability at high temperature, which can make these materials ones of the most promising candidates for next-generation thermal barrier coating applications. In this study, three compositions, lanthanum/gadolinium zirconates with reduced rare-earth contents from stoichiometric RE₂Zr₂O₇ compositions, are fabricated via solid state reaction as well as sintering at 1600°C for 4 hrs. The phase formation, microstructure, and thermo-physical properties of three oxide ceramics are examined. In particular, each oxide ceramics exhibits composite structures between pyrochlore and fluorite phases. The potential of lanthanum/ gadolinium zirconate ceramics for TBC applications is also discussed.

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• Rare earth zirconate nanostructures: Recent development on preparation and photocatalytic applications
  Sahar Zinatloo-Ajabshir, Masoud Salavati-Niasari, Azam Sobhani, Zahra Zinatloo-Ajabshir
  Journal of Alloys and Compounds.2018; 767: 1164.     CrossRef
• A novel Co-ions complexation method to synthesize pyrochlore La 2 Zr 2 O 7
  Chunhui Xu, Hongyun Jin, Qifeng Zhang, Can Huang, Daifeng Zou, Fujian He, Shuen Hou
  Journal of the European Ceramic Society.2017; 37(8): 2871.     CrossRef
• Fabrication and Characteristics of Thermal Barrier Coatings in the La2O3-Gd2O3-ZrO2System by Using Suspension Plasma Spray with Different Suspension Preparations
  Soyul Lee, Sung-Min Lee, Yoon-Suk Oh, Hyung-Tae Kim, Sahn Nahm, Seongwon Kim
  Journal of the Korean institute of surface engineering.2016; 49(6): 595.     CrossRef

Microstructural examination of the Nb-Si-B alloys at Nb-rich compositions is performed. The Nb-rich corner of the Nb-Si-B system is favorable in that the constituent phases are Nb (ductile and tough phase with high melting temperature) and T₂ phase (very hard intermetallic compound with favorable oxidation resistance) which are good combination for high temperature structural materials. The samples containing compositions near Nb-rich corner of the Nb- Si-B ternary system are prepared by spark plasma sintering (SPS) process using T₂ and Nb powders. T₂ bulk phase is made in arc furnace by melting the Nb slug and the Si-B powder compact. The T₂ bulk phase was subsequently ballmilled to powders. SPS is performed at 1300°C and 1400°C, depending on the composition, under 30 MPa for 600s, to produce disc-shaped specimen with 15 mm in diameter and 3 mm high. Hardness tests (Rockwell A-scale and micro Vickers) are carried out to estimate the mechanical property.

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• Fabrication of Nb-Si-B Alloys Using the Pulverized Nb-T₂ Alloy Powder
  Min-Ho Cho, Sung-Jun Kim, Hyun-Ji Kang, Sung-Tag Oh, Young Do Kim, Seong Lee, Myung Jin Suk
  Journal of Korean Powder Metallurgy Institute.2019; 26(4): 299.     CrossRef
• Mechanical properties of Mo-Nb-Si-B quaternary alloy fabricated by powder metallurgical method
  Jong Min Byun, Su-Ryong Bang, Se Hoon Kim, Won June Choi, Young Do Kim
  International Journal of Refractory Metals and Hard Materials.2017; 65: 14.     CrossRef
• Mechanical properties of Mo-Si-B alloys fabricated by using core-shell powder with dispersion of yttria nanoparticles
  Jong Min Byun, Su-Ryong Bang, Won June Choi, Min Sang Kim, Goo Won Noh, Young Do Kim
  Metals and Materials International.2017; 23(1): 170.     CrossRef
• Fabrication of Ta2O5 Dispersion-Strengthened Mo-Si-B Alloy by Powder Metallurgical Method
  Jong Min Byun, Won June Choi, Su-Ryong Bang, Chun Woong Park, Young Do Kim
  JOM.2017; 69(4): 683.     CrossRef
• Rapid consolidation of nanostuctured WC-FeAl3 by pulsed current activated heating and its mechanical properties
  In-Jin Shon, Seok-Jae Lee
  International Journal of Refractory Metals and Hard Materials.2017; 65: 69.     CrossRef

The en-riched ⁵⁸Ni powders are dissolved in acid solution and coated on a Cu target for proton irradiation at cyclotron to produce ⁵⁷Co radioisotope. The condition of the plating bath and the coating process are determined using the en-riched powders. To establish the coating conditions for ⁵⁷Co, non-radioactive Co ions are dissolved in an acid solution and electroplated on to a rhodium plate. The thermal diffusion of electroplated Co into a rhodium matrix was studied to apply a ⁵⁷Co Mssbauer source. The diffusion depth from surface to matrix of Co is depended on the annealing temperature and time. The deposited Co atoms diffuse completely into a rhodium (Rh) matrix without substantial loss at an annealing temperature of 1200 for 4 hours.

Porous thick film of alumina which is fabricated by freeze tape casting using a camphene-camphor-acrylate vehicle. Alumina slurry is mixed above the melting point of the camphene-camphor solvent. Upon cooling, the camphene-camphor crystallizes from the solution as particle-free dendrites, with the Al₂O₃ powder and acrylate liquid in the interdendritic spaces. Subsequently, the acrylate liquid is solidified by photopolymerization to offer mechanical properties for handling. The microstructure of the porous alumina film is characterized for systems with different cooling rate around the melting temperature of camphor-camphene. The structure of the dendritic porosity is compared as a function of ratio of camphene-camphor solvent and acrylate content, and Al₂O₃ powder volume fraction in acrylate in terms of the dendrite arm width.