Flame spray pyrolysis for finding multicomponent nanomaterials with superior electrochemical properties in the CoO(x)-FeO(x) system for use in lithium-ion batteries.

Kim, Jung Hyun,Lee, Jong-Heun,Kang, Yun Chan Wiley-VCH 2014 Chemistry - An Asian Journal Vol.9 No.10

<P>High-temperature flame spray pyrolysis is employed for finding highly efficient nanomaterials for use in lithium-ion batteries. CoO(x)-FeO(x) nanopowders with various compositions are prepared by one-pot high-temperature flame spray pyrolysis. The Co and Fe components are uniformly distributed over the CoO(x)-FeO(x) composite powders, irrespective of the Co/Fe mole ratio. The Co-rich CoO(x)-FeO(x) composite powders with Co/Fe mole ratios of 3:1 and 2:1 have mixed crystal structures with CoFe2O4 and Co3O4 phases. However, Co-substituted magnetite composite powders prepared from spray solutions with Co and Fe components in mole ratios of 1:3, 1:2, and 1:1 have a single phase. Multicomponent CoO(x)-FeO(x) powders with a Co/Fe mole ratio of 2:1 and a mixed crystal structure with Co3O4 and CoFe2O4 phases show high initial capacities and good cycling performance. The stable reversible discharge capacities of the composite powders with a Co/Fe mole ratio of 2:1 decrease from 1165 to 820?mA?h?g(-1) as the current density is increased from 500 to 5000?mA?g(-1); however, the discharge capacity again increases to 1310?mA?h?g(-1) as the current density is restored to 500?mA?g(-1).</P>

화염분무열분해법을 이용한 TiO₂:Fe,V 나노분말의 제조 및 VOCs 분해 특성

장한권,장희동,김태오,김선경,최진훈,Chang, Han Kwon,Jang, Hee Dong,Kim, Tae-Oh,Kim, Sun Kyung,Choi, Jin Hoon 한국입자에어로졸학회 2009 Particle and Aerosol Research Vol.5 No.1

Fe- and V-doped titanium dioxide nanoparticles consisting of spherical primary nanoparticles were synthesized from a mixed liquid precursor by using the flame spray pyrolysis. The effects of dopant concentration on the powder properties such as morphology, crystal structure, and light adsorption were analyzed by TEM, XRD, and UV-Vis spectrophotometer, respectively. As the V/Ti molar ratio increased, pure anatase particles were synthesized. On the contrary, rutile phase particles were synthesized as the Fe/Ti ratio increased. Photocatalytic property of as-prepared $TiO_2:Fe,V$ nanoparticles was investigated by measuring the removal efficiency for volatile organic compounds (VOCs) under the irradiation of visible light. After 2 hrs under visible light, the removal efficiencies of benzene, p-xylene, ethylbenzene, and toluene were reached to 21.9%, 21.4%, 19.8% and 17.6% respectively.

Nano-sized LiNi0.5Mn1.5O4 cathode powders with good electrochemical properties prepared by high temperature flame spray pyrolysis

김정현,강윤찬,홍영준,박병규 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.4

LiNi0.5Mn1.5O4 cathode powders with a mean particle size of 140 nm are prepared by high-temperature flame spray pyrolysis. Li/LiNi0.5Mn1.5O4 cells show two plateaus at approximately 4.1 and 4.7 V during discharge, irrespective of any excess of the lithium component in the spray solution, although the 4.1 V plateau decreases when the spray solution contained 20% excess lithium. The discharge capacity of the powder prepared from a spray solution with 20% excess lithium decreases from 133 to 126 mAh g1 by the 50th cycle at a current density of 0.1 C, which is a capacity retention of 95%.

화염법을 이용한 Pt/C 촉매 제조

최인대(Indae Choi),이동근(Donggeun Lee) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.2

Carbon black, activated carbon and carbon nanotube have been used as supporting materials for precious metal catalysts used in fuel cell electrodes. One-step flame synthesis method is used to coat 2-5nm Pt dots on flame-generated carbon particles. By adjusting flame temperature, gas flow rates and resident time of particles in flame, we can obtain Pt/C nano catalyst-support composite particles. Additional injection of hydrogen gas facilitates pyrolysis of Pt precursor in flame. The size of as-incepted Pt dots increases along the flame due to longer resident time and sintering in high temperature flame. Surface coverage and dispersion of the Pt dots is varied at different sampling heights and confirmed by Transmission electron microscopy (TEM), Energydispersive spectra (EDS) and X-ray diffraction (XRD). Crystalinity and surface bonding groups of carbon are investigated through X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.

Effect of synthesis condition and annealing on the sensitivity and stability of gas sensors made of Zn-doped γ-Fe2O3 particles

Taeyang Kim,Andrew Sharp,Bing Guo 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.3

Gas sensors made of flame-synthesized Zn-doped γ-Fe2O3 nanoparticles were found to have high sensitivity and high aging resistance. Zinc-doped γ-Fe2O3 nanoparticles and microparticles were synthesized by flame spray pyrolysis (FSP). Gas sensors were fabricated with as-synthesized particles, and with particles that had been annealed. The sensors’ response to acetone vapor and H2 was measured as fabricated, and measured again after the sensors were aged for three days. The sensors made from as-synthesized particles showed a gas sensing sensitivity 20 times higher than the literature value. However, sensors made of microparticles lost their sensing ability after three days of aging;sensors made of nanoparticles retained their gas sensing capability after aging. Sensors made of annealed particles did not have significant gas sensing capabilities. Analysis using the William and Hall method showed that the microstrains decreased significantly in both H2/O2 and H2/Air flame synthesized particles after annealing. The results showed that sensors made of flame-synthesized particles have much higher sensitivity than sensors made of particles previously reported. Especially, sensors made of flame-synthesized nanoparticles are resistant towards aging. This aging resistance may be attributed to the particles’ ability to retain their microstrains.

Doctor-bladed thick films of flame-made Pd/ZnO nanoparticles for ethanol sensing

C. Liewhiran,A.R. Camenzind,A. Teleki,S.E. Pratsinis,S. Phanichphant 한국물리학회 2008 Current Applied Physics Vol.8 No.3,4

ZnO nanoparticles doped with 0–5 mol% Pd were produced by flame spray pyrolysis (FSP) in a single step using zinc naphthenate and palladium (II) acetylacetonate as precursors dissolved in toluene/acetonitrile (80/20 vol%). The particle properties were further analyzed by XRD, BET, and HR-TEM analyses. The sensing films were produced by mixing the particles into an organic paste composed of terpineol and ethyl cellulose as a vehicle binder. The paste was doctor-bladed onto Al2O3 substrates interdigitated with Au electrodes. The gas sensing of ethanol (25–250 ppm) was studied at 400 C in dry air. In addition, 1 mol% Pd/ZnO film showed the highest sensitivity and fastest response times (within seconds). The sensitivity increased and the response time decreased with increasing ethanol concentration. ZnO nanoparticles doped with 0–5 mol% Pd were produced by flame spray pyrolysis (FSP) in a single step using zinc naphthenate and palladium (II) acetylacetonate as precursors dissolved in toluene/acetonitrile (80/20 vol%). The particle properties were further analyzed by XRD, BET, and HR-TEM analyses. The sensing films were produced by mixing the particles into an organic paste composed of terpineol and ethyl cellulose as a vehicle binder. The paste was doctor-bladed onto Al2O3 substrates interdigitated with Au electrodes. The gas sensing of ethanol (25–250 ppm) was studied at 400 C in dry air. In addition, 1 mol% Pd/ZnO film showed the highest sensitivity and fastest response times (within seconds). The sensitivity increased and the response time decreased with increasing ethanol concentration.

화염법을 이용한 Pt/C 촉매 제조

최인대(In Dae Choi),이동근(Donggeun Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

Carbon black, activated carbon and carbon nanotube have been used as supporting materials for precious metal catalysts used in fuel cell electrodes. One-step flame synthesis method is used to coat 2-5㎚ Pt dots on flame-generated carbon particles. By adjusting flame temperature, gas flow rates and resident time of particles in flame, we can obtain Pt/C nano catalyst-support composite particles. Additional injection of hydrogen gas facilitates pyrolysis of Pt precursor in flame. The size of as-incepted Pt dots increases along the flame due to longer resident time and sintering in high temperature flame. Surface coverage and dispersion of the Pt dots is varied at different sampling heights and confirmed by Transmission electron microscopy (TEM), Energy-dispersive spectra (EDS) and X-ray diffraction (XRD). Crystalinity and surface bonding groups of carbon are investigated through X-ray photoelectron spectroscoy (XPS) and Raman spectroscopy.

Zn-doped g-Fe_2O_3 sensors for flammable gas detection: Effect of annealing on sensitivity and stability

Taeyang Kim,Bing Guo 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.1

In this study,we investigated the effect of synthesis conditions and processing methods on the stability of gas sensors made of flame-synthesized Zn-doped g-Fe_2O_3 particles. Nanocrystalline Zn-dopedg-Fe_2O_3particles were synthesized by flame spray pyrolysis using either H_2/Air or H_2/O_2 coflow diffusion flames. Transmission electron microscopy (TEM),X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS),and Brunauer–Emmett–Teller surface-area-measurement (BET) were employed to characterize the particles. Gas sensors were fabricated by applying the as-synthesized and annealed particles on interdigitated electrodes. High-temperature flame (H_2/O_2) generated nanometer-sized particles; lower temperature flame (H_2/Air) generated micrometer-sized particles. The sensors made fromas-synthesized particles showed a gas sensing sensitivity that was 20 times higher than the literature value. The sensors made of microparticles lost their sensing ability after three days of aging,but sensorsmadeof nanoparticles did not showsignificant change after aging. XPS results showedsignificant Zn enrichment on the surface of as-synthesized particles.However,Znconcentration onthe surface of particles decreased significantly after annealing. The results showed that sensors made of nanoparticles have higher gas sensing signal, and higher resistance towards aging than sensors made of microparticles. In addition, the annealing process is apparently related to the solid state diffusion of the Zn dopant.

Sensing of acetone by Al-doped ZnO

Yoo, Ran,Gü,ntner, Andreas T.,Park, Yunji,Rim, Hyun Jun,Lee, Hyun-Sook,Lee, Wooyoung Elsevier 2019 Sensors and actuators. B Chemical Vol.283 No.-

<P><B>Abstract</B></P> <P>The development of chemoresistive gas sensors for environmental and industrial air monitoring as well as medical breath analysis is investigated. Flame-made ZnO nanoparticles (NPs) doped with 1 at% Aluminum exhibited higher sensing performance (<I>response</I> 245, response time ∼ 3 s, and <I>sensitivity</I> 23 ppm<SUP>−1</SUP>) than pure ZnO and those made by a hydrothermal method (HT) (56, ∼ 12 s, and 4 ppm<SUP>−1</SUP>) for detection of 10 ppm acetone. Furthermore, their sensing response of ∼10 to 0.1 ppm of acetone at 90% RH is superior to other metal oxide sensors and they feature good acetone selectivity to other compounds (including NH<SUB>3</SUB>, isoprene and CO). Characterization by N<SUB>2</SUB> adsorption, X-ray photoelectron and UV–vis spectroscopies reveals that the improved sensing performance of flame-made Al-doped ZnO NPs is associated primarily to a higher density of oxygen vacancies than pure ZnO and all HT-made NPs. This leads to a greater number of adsorbed oxygen ions on the surfaces of Al-doped ZnO NPs, which can react with acetone molecules.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ZnO nanoparticle (NP)-based sensors for detecting hazardous gas, acetone is presented. </LI> <LI> ZnO NPs are synthesized by flame spray pyrolysis and doped with Al to enhance sensing performance. </LI> <LI> The sensor based on these particles shows an outstanding sensing performance. </LI> <LI> The enhanced sensing is mainly due to the synergetic effect of oxygen vacancy, optical bandgap, specific surface area. </LI> </UL> </P>

나노크기의실버및글래스분말로부터형성된실버전극의특성

김정현 ( Jung Hyun Kim ),강윤찬 ( Yun Chan Kang ),구혜영 ( Hye Young Koo ),이장희 ( Jang Heui Yi ),고유나 ( You Na Ko ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.6

Silver conducting films were formed from nano-sized silver powders and glass frits prepared by flame spray pyrolysis. The mean sizes of the silver powders and glass frits were 73 and 63 nm, respectively. Nano-sized glass frits improved the adhesion strength of the silver conducting film to the glass substrate. The densities of the silver conducting films increased by increasing the glass contents of the films at firing temperatures of 400 and 500℃. The specific resistances of the silver conducting films with 5 wt.% glass of silver component were 7.8, 4.2 and 2.4 cm at firing temperatures of 400, 450 and 500℃.