Jongee Park

Park, Jongee

Name Variants

Jongee Park
P.,Jongee
P., Jongee
J.,Park
Park J.
Park, Jongee
Park,J.
J., Park
Park,Jongee
Jongee, Park

Job Title

Profesör Doktor

Email Address

jongee.park@atilim.edu.tr

Scholarly Output

56

Articles

41

Citation Count

578

Supervised Theses

3 Scholarly Output Search Results

Now showing 1 - 10 of 54

Alumina ve Titanya eş-doplanmış zirkonya seramiklerinin mekanik ve biyolojik özellikleri
(2017) Park, Jongee; Park, Jongee; Metallurgical and Materials Engineering
Günümüzde daha doğala yakın göründüğünden dolayı zirkonya diş hekimliğinde oldukça yaygın olarak kullanılmaktadır. Ayrıca, zirkonya‟nın yüksek sertliği ve kırılma tokluğu, biyolojik uyumluluğu ve estetik görünümü sebebiyle de en çok tercih edilen seramik malzemelerin arasında yer alır. Bu çalışmada, mekanik öğütme yöntemi ile katkı maddeleri farklı oranlarda (0 ve % 2.0) % 3 mol yttria (Y2O3) içeren zirkonya içerisine sırasıyla katılmıştır. Şekillendirilen numuneler sırasıyla 1350, 1450 ve 1550 °C‟ de 2 saat süresince sinterlenmiş olup, katkı maddelerinin etkilerini gözlemlemek için yoğunluk, sertlik, kırılma tokluğu ve hücre tutunma oranı hesaplanmıştır. Sertlik ve kırılma tokluğu hesapları için Vicker‟s sertlik yöntemi kullanılmıştır. X Ray Kırınım Yöntemi (XRD) ile yalnızca titanya içeren ve hem titanya hem de alumina içeren numunelerin kristal faz analizleri yapılmıştır. Taramalı Elektron Mikroskobu (SEM) kullanılarak numunelerin tane boyutları hesaplanmıştır ve yüzey morfolojisi incelenmiştir. Deney sonuçlarına göre katkı malzemelerinin oranı arttıkça, yoğunluğun düştüğü görülmüştür. Mekanik özellikler göz önünde bulundurulduğunda en yüksek sertlik ve tokluk değerleri % 0.5 TiO2 ve % 1.0 Al2O3 numunelerinde elde edilmiştir. Titanya ve aluminanın zirkonya içerisine katılması faz değişimine sebep olmamıştır ancak tane boyutunu küçültmüştür. Ayrıca, katkı maddeleri numune yüzeyine hücrelerin tutunmasını ve büyümesini de olumlu yönde etkilemiştir.
Citation Count: 29
Boron and zirconium co-doped TiO₂ powders prepared through mechanical ball milling
(Elsevier Sci Ltd, 2013) Park, Jongee; Ozturk, Abdullah; Park, Jongee; Metallurgical and Materials Engineering
A titania photocatalyst co-doped with boron and zirconium was prepared by mechanical ball milling. The resulting powder was characterized by XRD, XPS, SEM, and EDS. The photocatalytic performance of the powder was evaluated by degradation of methylene blue (MB) solution under UV illumination. XRD patterns were refined by Rietveld analysis to obtain accurate lattice parameters and positions of the atoms in the crystal structure of the photocatalyst. XRD, XPS, and Rietveld analysis results indicated that mechanical ball milling successfully weaved the dopant elements into the crystal structure and distorted the lattice of TiO2. Also, SEM micrographs confirmed that mechanical ball milling led to a decrease in average particle size of the photocatalyst. Boron and zirconium co-doped TiO2 particles exhibited a better visible light response and photocatalytic activity than those of the mono-element doped TiO2 (i.e. B-TiO2 and Zr-TiO2) and undoped TiO2 particles. The enhanced photocatalytic activity is attributed to the synergistic effects of boron zirconium co-doping and particle size reduction. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Citation Count: 21
Facile synthesis of CsPbBr₃/PbSe composite clusters
(Taylor & Francis Ltd, 2018) Park, Jongee; Ozturk, Abdullah; Park, Jongee; Sohn, Woonbae; Tae Hyung Lee; Jang, Ho Won; Kim, Soo Young; Metallurgical and Materials Engineering
In this work, CsPbBr3 and PbSe nanocomposites were synthesized to protect perovskite material from self-enlargement during reaction. UV absorption and photoluminescence (PL) spectra indicate that the addition of Se into CsPbBr3 quantum dots modified the electronic structure of CsPbBr3, increasing the band gap from 2.38 to 2.48 eV as the Cs:Se ratio increased to 1:3. Thus, the emission color of CsPbBr3 perovskite quantum dots was modified from green to blue by increasing the Se ratio in composites. According to X-ray diffraction patterns, the structure of CsPbBr3 quantum dots changed from cubic to orthorhombic due to the introduction of PbSe at the surface. Transmission electron microscopy and X-ray photoemission spectroscopy confirmed that the atomic distribution in CsPbBr3/PbSe composite clusters is uniform and the composite materials were well formed. The PL intensity of a CsPbBr3/PbSe sample with a 1:1 Cs: Se ratio maintained 50% of its initial intensity after keeping the sample for 81 h in air, while the PL intensity of CsPbBr3 reduced to 20% of its initial intensity. Therefore, it is considered that low amounts of Se could improve the stability of CsPbBr3 quantum dots.
Citation Count: 39
MoS₂-nanosheet/graphene-oxide composite hole injection layer in organic light-emitting diodes
(Korean inst Metals Materials, 2017) Park, Jongee; Thang Phan Nguyen; Choi, Kyoung Soon; Park, Jongee; Ozturk, Abdullah; Kim, Soo Young; Metallurgical and Materials Engineering
In this work, composite layers comprising two-dimensional MoS2 and graphene oxide (GO) were employed as hole injection layers (HILs) in organic light-emitting diodes (OLEDs). MoS2 was fabricated by the butyllithium (BuLi) intercalation method, while GO was synthesized by a modified Hummers method. The X-ray diffraction patterns showed that the intensity of the MoS2 (002) peak at 14.15A degrees decreased with increase in GO content; the GO (001) peak was observed at 10.07A degrees. In the C 1s synchrotron radiation photoemission spectra, the contributions of the C-O, C=O, and O-C=O components increased with increase in GO content. These results indicated that GO was well mixed with MoS2. The lateral size of MoS2 spanned from a few hundreds of nanometers to 1 mu m, while the size of GO was between 400 nm and a few micrometers. Thus, the coverage of the MoS2-GO composite on the ITO surface improved as the GO content increased, owing to the large particle size of GO. Notably, GO with large size could fully cover the indium tin oxide film surface, thus, lowering the roughness. The highest maximum power efficiency (PEmax) was exhibited by the OLED with MoS2-GO 6:4 composite HIL, indicating that similar contents of MoS2 and GO in MoS2-GO composites provide the best results. The OLED with GO HIL showed very high PEmax (4.94 lm W-1) because of very high surface coverage and high work function of GO. These results indicate that the MoS2-GO composites can be used to fabricate HILs in OLEDs.
Citation Count: 32
Photocatalytic activity of hydroxyapatite-precipitated potassium titanate whiskers
(Elsevier Science Sa, 2010) Park, Jongee; Metallurgical and Materials Engineering
Photocatalytic properties of hydroxyapatite (HAP)-precipitated multifunctional potassium titanate (KT) whiskers were investigated in terms of the decomposition of methylene blue (MB) in aqueous solution under UV irradiation. Hydroxyapatite was formed on the surface of KT whiskers through a biomimetic process in simulated body fluid (SBF). The SBF used in this investigation had concentrations of calcium and phosphate ions 10 times greater than those of human plasma. Results revealed that hydroxyapatite precipitation enhanced the photocatalytic activity of the KT whiskers. In the case of unreacted KT whisker, complete degradation of methylene blue took 5.5 h, on the other hand degradation time decreased to 3.5 h when the whisker was precipitated with hydroxyapatite. (C) 2009 Elsevier B.V. All rights reserved.
Citation Count: 0
Effects of Graphene Transfer and Thermal Annealing on Anticorrosive Properties of Stainless Steel
(Amer Scientific Publishers, 2017) Park, Jongee; Han, Sangmok; Kim, Tae-Yoon; Park, Jongee; Ozturk, Abdullah; Kim, Soo Young; Metallurgical and Materials Engineering
Stainless steel (STS) films were annealed in a thermal quartz tube and covered with graphene to improve their anticorrosive properties. Graphene was synthesized via the chemical vapor deposition method and transferred onto the surface of the STS film by the layer-by-layer approach. The structure of the STS film changed from alpha-Fe to gamma-Fe after annealing at 700 C for 1 h, resulting in an increase of 82.72% in the inhibition efficiency. However, one-layer graphene acted as a conductive pathway and therefore deteriorated the anticorrosive properties of the STS film. To overcome this problem, graphene was transferred layer by layer onto the STS film. It was found that transfer of three layers of graphene onto the STS film resulted in a 91.57% increase in the inhibition efficiency. Therefore, thermal annealing and transfer of multilayer graphene are considered to be effective in enhancing the anticorrosive properties of STS films.
Citation Count: 28
A Newly Constructed Photoactive System, Fe(iii)-c/N-bi_{2< for Efficient Visible Light Photocatalysis}
(Elsevier Science Sa, 2018) Sudrajat, Hanggara; Park, Jongee; Hartuti, Sri; Park, Jongee; Park, Jongee; Park, Jongee; Metallurgical and Materials Engineering; Metallurgical and Materials Engineering
In this study, two strategies are simultaneously applied for photocatalytic activity enhancement of Bi2O3. The first strategy is to increase the light absorption via simultaneous carbon and nitrogen doping. The second strategy is to increase the charge carrier separation via Fe grafting. Transmission electron microscopy observation reveals the presence of Fe nanoclusters resided on the Bi2O3 surface. Near edge Xray absorption fine structure (NEXAFS) analysis confirms the valence state of the Fe species to be +3, and their coordination to be octahedral. The C K-edge and N K-edge NEXAFS spectra furthermore confirm the incorporation of C and N species in the Bi2O3 structure. This newly constructed photocatalyst, denoted as Fe(III)-C/N-Bi2O3, shows appreciably enhanced photocatalytic performance for the decomposition of 2,4-dichlorophenol under visible light as compared to bare Bi2O3. (C) 2018 Elsevier B.V. All rights reserved.
Su Arıtımı için Fotokatalitik Titanyum Dioksit Tozlarının Sol-jel Süreciyle Hazırlanması
(2018) Mohammed, Ahmed Hafedh Mohammed; Park, Jongee; Park, Jongee; Park, Jongee; Park, Jongee; Metallurgical and Materials Engineering; Metallurgical and Materials Engineering
Bu çalışma, yüksek fotokatalitik aktivite elde etmek için tetra-izopropoksit öncülü kullanılarak sol-gel yöntemiyle TiO 2 nanopartikülleri elde edilmesinin detaylarını içermektedir. Sol-gel yönteminde, farklı asitlerin (Asetik asit, Hidroklorik asit ve Nitrik asit) ve katalizör olarak hidroklorik asit kullanılarak elde edilen farklı pH değerlerinin etkileri çalışılmıştır. Sentezlenen numunelerden biri kullanılarak, kalsinasyon sıcaklığının sentezlenen TiO 2 'nin özelliklerine etkisi, 450, 550 ve 650°C olmak üzere farklı sıcaklıklar için araştırılmıştır. 550°C'de kalsine edilen tüm numuneler XRD, SEM ve UV-Vis spektrofotometre ile karakterize edilmiştir. Hidroklorik asit kullanılarak (pH: 4) hazırlanan titanyum dioksit çözeltisi, cam altlık üzerine daldırarak kaplama tekniği kullanılarak farklı döngülerle (1, 3 ve 5 defa) kaplanmıştır. Tüm TiO 2 kaplanmış camlar UV-Vis spektrometre, UV-Vis spektrofotometre ve temas açısı ölçümleri ile analiz edilmiştir. Sonuçlar farklı türdeki asitlerle sadece TiO 2 'nin anataz fazının farklı kristal boyut, kristallik ve şekillerde elde edildiğini göstermiş ve farklı asitlerle TiO 2 oluşumunun mekanizması detaylı olarak tartışılmıştır. Farklı pH değerleri için, 4, 2.8 ve 1.5 pH değerlerinde sadece anataz tipi TiO 2 gözlenmiştir. 3.3 pH değerindeki asidik koşulda, anataz ve çok az miktarda rutil elde edilmiştir. İlave olarak, kalsinasyon sıcaklığı arttıkça anataz tipi TiO 2 'nin kristalliğinin ve kristal boyutunun arttığı görülmüştür. Hidroklorik asitle (pH: 4) sentezlenen TiO 2 tozu en yüksek fotokatalitik aktiviteyi göstermiş ve bu tozun UV ışını altında metilen mavisi ile 30, 60 ve 90 dakikalarda elde edilen fotobozunum verimleri sırasıyla %76.2, %95 ve %98.1 bulunmuştur. Son olarak, 5 defa TiO2 kaplanmış cam süperhidrofobiklik göstermiş ve 7 saatlik UV ışını altında fotobozunum verimi %67 bulunmuştur.
Citation Count: 12
Tribological Behavior of Alumina-Added Apatite-Wollastonite Glass-Ceramics in Simulated Body Fluid
(Elsevier Science Sa, 2010) Park, Jongee; Park, Jongee; You, Sang-Hee; Shin, Dong-Woo; Ozturk, Abdullah; Metallurgical and Materials Engineering
Tribological properties of an alumina-added apatite-wollastonite glass-ceramic produced by controlled heat treatment of a glass in the system MgO-CaO-SiO(2)-P(2)O(5)-Al(2)O(3) have been evaluated and compared with those of selected commercial dental ceramics, Duceragold and IPS Empress. Tribological tests were performed in dry condition and in simulated body fluid (SBF) using a pin-on-disk apparatus. The friction coefficient and specific wear rate of the tested materials were measured in dry and in artificial saliva (simulated body fluid: SBF) in order to elucidate the appropriateness of the alumina-added apatite-wollastonite (A-W) glass-ceramic for dental applications. Wear rate of the materials investigated varied from 0.96 x 10(-4) mm(3) N(-1) m to 41.37 x 10(-4) mm(3) N(-1) m depending on the bioenvironmental test conditions. The results of this study revealed that the alumina-added A-W glass-ceramic becomes more wear resistant as sintering temperature is increased and exhibits tribological properties similar to those of the commercial dental materials investigated. (C) 2010 Elsevier B.V. All rights reserved.
Citation Count: 12
Antisolvent-Fumigated Grain Growth of Active Layer for Efficient Perovskite Solar Cells
(Pergamon-elsevier Science Ltd, 2021) Sajid, Sajid; Park, Jongee; Khan, Suliman; Khan, Ayub; Khan, Danish; Issakhov, Alibek; Park, Jongee; Metallurgical and Materials Engineering
High efficiency of perovskite solar cell can be obtained through various approaches, including materials and interface engineering, device modification and fabrication techniques. In all approaches, the quality of the perovskite layer has a significant impact on the efficiency of the perovskite solar cell. Antisolvent dripping is widely used in almost all fabrication methodologies to achieve a high-quality perovskite layer. However, in the conventional antisolvent dripping, there are several factors (antisolvent volume, time and point of dripping, etc.) to be strictly followed. Due to these difficult and critical tricks, researchers often get perovskite layers with pinholes, small grains, and wide grain boundaries that deteriorate the performance of the perovskite solar cells. In order to produce perovskite films with large-scale grains, narrow boundaries and smooth surface morphology, a sealed antisolvent-fumigated process is implemented. There is no need to make any substantial efforts to achieve optimal conditions for the fabrication of high-quality perovskite layers using the antisolvent-fumigated strategy. Consequently, the efficiency of perovskite solar cell improves dramatically from 18.65% to 21.45%. Our findings present a new and convenient method for fabricating highly efficient perovskite solar cells.

Park, Jongee

Name Variants

Job Title

Email Address

ORCID ID

Scopus Author ID

Turkish CoHE Profile ID

Google Scholar ID

WoS Researcher ID

Scholarly Output

56

Articles

41

Citation Count

578

Supervised Theses

3

Filters

Settings

Sort By

Results per page

Scholarly Output Search Results