Zero‑dimensional model for the prediction of carbon nanotube (CNT) growth region in heterogeneous methane‑flame environment

Muhammad Thalhah Zainal,Norikhwan Hamzah,Mazlan Abdul Wahid,Natrah Kamaruzaman,Cheng Tung Chong,Mohd Hanafi Ani,Shokri Amzin,Tarit Das,Mohd Fairus Mohd Yasin 한국탄소학회 2023 Carbon Letters Vol.33 No.7

The conventional multi-scale modelling approach that predicts carbon nanotube (CNT) growth region in heterogeneous flame environment is computationally exhaustive. Thus, the present study is the first attempt to develop a zero-dimensional model based on existing multi-scale model where mixture fraction z and the stoichiometric mixture fraction zst are employed to correlate burner operating conditions and CNT growth region for diffusion flames. Baseline flame models for inverse and normal diffusion flames are first established with satisfactory validation of the flame temperature and growth region prediction at various operating conditions. Prior to developing the correlation, investigation on the effects of zst on CNT growth region is carried out for 17 flame conditions with zst of 0.05 to 0.31. The developed correlation indicates linear ( zlb=1.54zst +0.11) and quadratic ( zhb=zst(7-13zst )) models for the zlb and zhb corresponding to the low and high boundaries of mixture fraction, respectively, where both parameters dictate the range of CNT growth rate (GR) in the mixture fraction space. Based on the developed correlations, the CNT growth in mixture fraction space is optimum in the flame with medium-range zst conditions between 0.15 and 0.25. The stronger relationship between growth-region mixture-fraction (GRMF) and zst at the near field region close to the flame sheet compared to that of the far field region away from the flame sheet is due to the higher temperature gradient at the former region compared to that of the latter region. The developed models also reveal three distinct regions that are early expansion, optimum, and reduction of GRMF at varying zst.

Combustion synthesis of zero-, one-, two- and three-dimensional nanostructures: Current trends and future perspectives

Nersisyan, Hayk H.,Lee, Jong Hyeon,Ding, Jin-Rui,Kim, Kyo-Seon,Manukyan, Khachatur V.,Mukasyan, Alexander S. Elsevier 2017 Progress in energy and combustion science Vol.63 No.-

<P><B>Abstract</B></P> <P>The combustion phenomenon is characterized by rapid self-sustaining reactions, which can occur in the solid, liquid, or gas phase. Specific types of these reactions are used to produce valuable materials by different combustion synthesis (CS) routes. In this article, all three CS approaches, i.e. solid-phase, solution, and gas-phase flame, are reviewed to demonstrate their attractiveness for fabrication of zero-, one-, two-, and three-dimensional nanostructures of a large variety of inorganic compounds. The review involves five sections. First, a brief classification of combustion synthesis methods is given along with the scope of the article. Second, the state of art in the field of solid-phase combustion synthesis is described. Special attention is paid to the relationships between combustion parameters and structure/properties of the produced nanomaterials. The third and fourth sections describe details for controlling material structures through solution combustion synthesis and gas-phase flame synthesis, respectively. A variety of properties (e.g., thermal, electronic, electrochemical, and catalytic) associated with different types of CS nanoscale materials are discussed. The conclusion focuses on the most promising directions for future research in the field of advanced nanomaterial combustion synthesis.</P>

화염온도 변화에 따른 연소합성된 TiO₂나노입자의 결정구조 변화

이교우(Gyo Woo Lee),최상민(Sang Min Choi) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6

In this work, TiO₂ nanoparticles were synthesized using N₂-diluted and Oxygen-enriched coflow hydrogen diffusion flames. The effect of flame temperature on the crystalline structure of the formed TiO₂ nanoparticles was investigated. The measured maximum centerline temperature of the flame ranged from 2,103K for oxygen-enriched flame to 1339K for N₂-diluted flame. The visible flame length and the height of the main reaction zone were characterized by direct photographs. The crystalline structures of TiO₂ nanoparticles were analyzed by XRD. From the XRD analysis, it was evident that the crystalline structures of the formed nanoparticles were divided into two sorts. In the higher temperature region, over the 1,700K, the fraction of formed TiO₂ nanoparticles having anatase-phase crystalline structure increased with increasing the flame temperature. On the contrary, in the lower temperature region, below the 1,600K, the fraction of anatase-phase nanoparticles increased with decreasing the flame temperature.

Sol-Flame Synthesis: A General Strategy To Decorate Nanowires with Metal Oxide/Noble Metal Nanoparticles

Feng, Yunzhe,Cho, In Sun,Rao, Pratap M.,Cai, Lili,Zheng, Xiaolin American Chemical Society 2013 Nano letters Vol.13 No.3

<P>The hybrid structure of nanoparticle-decorated nanowires (NP@NW) combines the merits of large specific surface areas for NPs and anisotropic properties for NWs and is a desirable structure for applications including batteries, dye-sensitized solar cells, photoelectrochemical water splitting, and catalysis. Here, we report a novel <I>sol-flame</I> method to synthesize the NP@NW hybrid structure with two unique characteristics: (1) large loading of NPs per NW with the morphology of NP chains fanning radially from the NW core and (2) intimate contact between NPs and NWs. Both features are advantageous for the above applications that involve both surface reactions and charge transport processes. Moreover, the sol-flame method is simple and general, with which we have successfully decorated various NWs with binary/ternary metal oxide and even noble metal NPs. The unique aspects of the sol-flame method arise from the ultrafast heating rate and the high temperature of flame, which enables rapid solvent evaporation and combustion, and the combustion gaseous products blow out NPs as they nucleate, forming the NP chains around NWs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2013/nalefd.2013.13.issue-3/nl300060b/production/images/medium/nl-2012-00060b_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl300060b'>ACS Electronic Supporting Info</A></P>

Synthesis of terraced and spherical MgO nanoparticles using flame metal combustion

Chae, Sukbyung,Lee, Heesoo,Pikhitsa, Peter V.,Kim, Changhyuk,Shin, Seungha,Kim, Do Heui,Choi, Mansoo Elsevier 2017 Powder technology Vol.305 No.-

<P><B>Abstract</B></P> <P>Controlled synthesis of unconventional spherical/terraced MgO nanoparticles that show a unique optical property was done via the flame metal combustion method. We investigated the optimal condition for selectively producing these spherical/terraced MgO nanoparticles over conventional cubic MgO nanoparticles. Furthermore, it was possible to control the proportion of the morphology of generated MgO nanoparticles using different carrier gases. The size distribution of the MgO nanoparticles was measured to understand the surface-induced growth mechanism of the spherical/terraced MgO nanoparticles, which was different from that of cubic MgO nanoparticles grown from the normal molecule condensation. In addition, the catalytic property of the Li-doped spherical/terraced MgO particles was investigated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Spherical/terraced MgO nanoparticles were synthesized using flame metal combustion. </LI> <LI> Terrace/spherical and cube MgO were synthesized selectively by changing gas condition. </LI> <LI> Particle size distribution could be controlled by flame length. </LI> <LI> Flame-made Li/MgO catalyst nanoparticles showed high methane conversion efficiency. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Flat Premixed burner를 적용한 TiO₂, SiO₂ 이성분계 Flame Synthesis에 관한 연구

이호연(Ho Yeon Lee),차천륜(Chun Loon Cha),유창현(Chang Hyun You),황상순(Sang Soon Hwang) 한국연소학회 2019 KOSCOSYMPOSIUM논문집 Vol.2019 No.5

연소합성된 TiO₂ 나노입자의 입자특성에 대한 화염온도 변화의 영향

이교우(Gyo Woo Lee) 한국연소학회 2006 한국연소학회지 Vol.11 No.1

In this work, TiO₂ nanoparticles were synthesized using N₂-diluted and Oxygen-enriched coflow hydrogen diffusion flames. The effect of flame temperature on the characteristics of the formed TiO₂ nanoparticles was investigated. The measured maximum centerline temperature of the flame ranged from 2,103 K for oxygen-enriched flame to 1,339 K for N₂-diluted flame. The visible flame length and the height of the main reaction zone were characterized by direct photographs. The characteristics of synthesized TiO₂ nanoparticles were analyzed by SEM and TEM images. From these images, it was evident that the formed nanoparticles were divided into two sorts. In the higher temperature region, over the 1,700 K, TiO₂ nanoparticles having spherical shapes with diameters about 60 ㎚ were synthesized. In the lower temperature region, below the 1,600 K, the diameters of formed nanoparticles having unclear boundaries were ranged from 35 - 50 ㎚.

Synthesis and Application of a Polyamide-containing Phosphorous and Sulfur Flame-retardant for Nylon Fabric

Xiangdong Zhou,Yufa Sun,Yingchun Chen,Bing Sun 한국고분자학회 2018 폴리머 Vol.42 No.2

Monomer of polyamide (PA66) and flame-retardant intermediate product (FR) were firstly synthesized, and the flame-retardant (PA-FR) was further gained by polymerization of PA66 and FR. The structure of PA-FR was confirmed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), X-ray photoelectron spectroscopy (XPS), and gel permeation chromatography (GPC). The thermal properties of PA-FR and the finished fabric were evaluated by thermal gravity analysis (TGA) and differential scanning calorimetry (DSC). Moreover, X-ray diffraction analysis (XRD) showed that melting eutectic reaction occurred between PA-FR and nylon fabric. The experimental results showed that the limiting oxygen index (LOI) value of PA-FR treated fabric and PA-FR treated fabric after 10 laundries were improved to 28.8% and 26.4%, respectively. It implied that PA-FR had a good and durable function of imparting fire-resistance to nylon fabric.

화염법으로 제조된 감마-Al₂O₃ 나노입자의 화염조건에 따른 입자특성 연구

이교우(Gyo Woo Lee) 대한기계학회 2012 大韓機械學會論文集B Vol.36 No.5

본 논문은 수소를 연료로 하는 확산화염을 이용하여 알루미나 나노입자를 합성할 때, 합성되는 알루미나 나노입자의 특성에 미치는 화염온도의 영향을 조사하였다. 합성된 나노입자의 특성을 전자현미경 이미지, 결정 구조 분석, 비표면적과 기공의 크기 분석, 화염온도 측정 등의 여러 특성분석 방법으로 조사하였다. 사용된 화염의 중심축 최고온도는 산화제의 산소농도가 19, 21, 30, 47%인 각각의 실험조건에서 1507.8K, 1593.8K, 1753.1K, 1998.7K으로 측정되었다. SEM 이미지 분석 및 BET 비표면적 측정을 통해서는 47% 산소농도인 경우 에는 50 nm 수준의 독립적인 구형입자가 생성되었음을 확인할 수 있었으며, 19%와 21%의 경우에는 응집된 상태의 20-30 nm 수준의 입자를 볼 수 있었다. XRD 결과에서는 감마(γ)-알루미나가 주를 이루는 것으로 판단되었다. 이상의 결과를 바탕으로 촉매 담체로 사용하기 위한 알루미나 나노입자를 연소합성 하기 위한 가장 적절한 조건으로 실험했던 네 경우 중에서는 산화제의 산소농도가 21%인 두 번째 경우를 선택할 수 있었다. In this study, γ-Al₂O₃ nanoparticles were synthesized by using coflow hydrogen diffusion flames. The synthesis conditions were varied with using several oxygen concentrations in the oxidizing air. The particle characteristics of the flame-synthesized Al₂O₃ nanoparticles were determined by examining the crystalline structure, shape, and specific surface area of the nanoparticles. The measured maximum centerline temperature of the flames ranged from 1507.8 K to 1998.7 K. The morphology and crystal structure of the Al₂O₃ nanoparticles were determined from SEM images and XRD analyses, respectively. The particle sizes were calculated from measured BET specific surface areas and ranged from 25 nm to 52 nm. From XRD analyses, it was inferred that a large number of the synthesized nanoparticles were γ-Al₂O₃ nanoparticles including θ-Al₂O₃ nanoparticles.

대향류 확산화염내 탄소나노튜브 생성에 관한 연구

신우중,임태우,윤용섭,윤석훈,최재혁 해양환경안전학회 2011 해양환경안전학회 학술발표대회 논문집 Vol.2011 No.06

대향류 메탄/수소 확산화염을 통해 탄소나노튜브와 탄소나노섬유를 합성하였다. 탄소나노튜브 합성을 위한 촉매금속으로는 페로션을 활용하였고 샘플링을 위해 구리기판을 사용하였다. 본 실험에서 주요한 실험의 변수는 수소의 비율과 샘플링 위치이다. 그 결과, 연료중 수소의 비율이 증가하고 샘플링 위치와 버너측 노즐사이의 거리가 멀어질수록 탄소나노튜브가 다량 합성되었다. The opposed-flow methane/hydrogen diffusion flame was used to synthesize carbon nanotubes(CNTs) and carbon nanofibers(CNFs). Ferrocene was utilized as catalytic metal for CNTs synthesis. Cu substrate was used to sample of carbon nanotubes. In this work, major parameters were the mixture ratio of hydrogen and the sampling position. Results show that synthesis of carbon nanotube is increased with increasing hydrogen mixture rate and sampling position from fuel side nozzle.