Low Cost Growth Route for Single-walled Carbon Nanotubes from Decomposition of Acetylene over Magnesia Supported Fe-Mo Catalyst

Shajahan, Md.,Mo, Young Hwan,Nahm, Kee Suk 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.3

A large amount of single wall carbon nanotubes (SWTs) was successfully produced by thermal decomposition of C_2H_2 at 800℃ over magnesia supported Fe-Mo bimetallic catalysts in a tubular flow reactor under anatmosphere of hydrogen flow. The growth density of SWNTs increased with increasing the weight percent of the catalyst metals(wt% ratio of two metals : 50 : 50) supported on magnesia (MgO) from 5 to 30 wt%. The yield of SWNTs reached 144.3% over 30 wt% metal-loaded catalyst. Raman measurements showed the growth of bundle type SWNTs with diameters ranging from 0.81 to 1.96 nm. The growth of SWNTs was also identified by thermal gravimetric analysis (TGA) and Raman spectroscopy.

Praseodymium doped ceria as electrolyte material for IT-SOFC applications

Shajahan, Irfana,Ahn, Junsung,Nair, Parvathi,Medisetti, Srikar,Patil, Sunaina,Niveditha, V.,Uday Bhaskar Babu, G.,Dasari, Hari Prasad,Lee, Jong-Ho Elsevier 2018 Materials chemistry and physics Vol.216 No.-

<P><B>Abstract</B></P> <P>Praseodymium-doped ceria (PDC, Ce<SUB>0.9</SUB>Pr<SUB>0.1</SUB>O<SUB>2</SUB>) electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs) has been successfully synthesised by EDTA-citrate method. From X-Ray diffraction (XRD), fluorite structure along with a crystallite size of 5.4 nm is obtained for PDC nanopowder calcined at 350 °C/24 h. Raman spectroscopy confirmed the structure, presence of oxygen vacancies with the manifestation of the main peak at 457 cm<SUP>−1</SUP> and with a secondary peak at 550 cm<SUP>−1</SUP>. From Transmission Electron Microscopy (TEM) analysis, the average particle size is around 7–10 nm and selected area electron diffraction (SAED) patterns further confirmed the fluorite structure of PDC nanopowder. The PDC nanopowder displayed a BET surface area of 65 m<SUP>2</SUP>/g with a primary particle size of ∼13 nm (calculated from BET surface area). Dilatometer studies revealed a multi-step shrinkage behaviour with the multiple peaks at 522, 1171 and 1461 °C which may be originated due to the presence of multiple size hard agglomerates. The PDC electrolyte pellet sintered at 1500 °C displayed an ionic conductivity of 1.213E-03 S cm<SUP>−1</SUP> along with an activation energy of 1.28eV. Instead of a single fluorite structure, XRD of sintered PDC pellet showed multiple structures (Fluorite structure (CeO<SUB>2</SUB>) and cubic structure (PrO<SUB>2</SUB>).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Praseodymium doped ceria (PDC) electrolyte was synthesised by EDTA citrate method. </LI> <LI> Dilatometer study revealed multiple shrinkage behaviour of PDC. </LI> <LI> PDC showed an ionic conductivity of 1.213E-03 S cm<SUP>−1</SUP> at 700 °C. </LI> <LI> XRD at 1500 °C revealed that they crystallize as fluorite CeO<SUB>2</SUB> + cubic PrO<SUB>2</SUB> phase. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Catalytic synthesis of large scale carbon nanotubes using high performance binary (Fe-Mo/MgO or Co-Mo/MgO) systems

( Md. Shajahan ),( Y. H. Mo ),( K. S. Nahm ) 한국공업화학회 2002 한국공업화학회 연구논문 초록집 Vol.2002 No.1

Application of SWAT to estimate runoff and sediment yield of Salma Dam watershed in Afghanistan

( Sayed Shajahan Sadiqi ),남원호 ( Won-ho Nam ),홍은미 ( Eun-mi Hong ) 한국농공학회 2019 한국농공학회 학술대회초록집 Vol.2019 No.-

Sediments are a principal component in water resource projects for dam sedimentation, soil and water conservation, and design of efficient erosion control structures. High sediment rates lead to filling dam and loss of live storage of dam, which is eventually commanding to loss of production potential and evacuation of sediments from the dam is a costly process that can have large environmental impacts. A physically-based distributed hydrological model, SWAT (Soil and Water Assessment Tool), was used to estimate of runoff and sediment yield in the outlet of Salma Dam watershed in Harirud river basin measuring of 11,550㎢ catchment area. The main objectives of the study were to analyze the sediment yield in the outlet of the catchment and effect of LULC (Land Use and Land Cover) changes on sediment yield and flow values. The basin shows large heterogeneity in term of a hydrogeological parameter, LULC and soil features. The model was calibrated and validated using observed runoff and sediment yield data of 10 years (2008-2018) at the basin outlet. The average values for RSR (RMSE-observations standard deviation ratio) and NSE (Nash-Sutcliffe efficiency) for sediment are found to be 0.60 and 0.61, for runoff are found to be 0.67 and 0.64, which are within good limits for sediment and a good limit for runoff respectively. The overall average annual output for sediment at the outlet point was estimated 133.02 Met ton/month, is model monthly output. In general, the model was capable of simulating runoff and sediment in Salam dam watershed. As land development is a continuous process, for the optimum use of the land cover and water resources of the area, it is recommended that soil and watershed conservation practice should be undertaken in order to keep the sustainability of the reservoir conserving sediment reduction.

Low-Temperature RTCVD Growth and Characterization of Silicon-Carbide Nanorods Through Carbon Nanotubes

Md.Shajahan 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.41 No.5

Silicon-carbide (SiC) nanorods were synthesized at 1100 C through a two-step reaction scheme. Carbon nanotubes (CNTs) were first grown by using thermal decomposition of C2H2 over a Fe/Co metal catalyst loaded on a Si(100) wafer surface. The grown CNTs were then in - situ reacted with tetramethylsilane (TMS) to form SiC nanorods. The lengths and diameters of the grown SiC nanorods agreed with those of the CNTs used for the building blocks in the growth. The length of the SiC nanorods increased with increasing CNT growth time. The structural characterization using X-ray diffraction (XRD) and Fourier transform (FT)-Raman spectroscopy identified the growth of fi-SiC nanorods. A broad photoluminescence (PL) peak was observed at 2.32 eV from the SiC nanorods. The growth mechanism of the SiC nanorod is discussed in this work.

황강에서의 the Standardized Water Supply Demand지수를 이용한 시공간적 생태가뭄 패턴

사예드사자한사디키 ( Sayed Shajahan Sadiqi ),홍은미 ( Eun-mi Hong ),남원호 ( Won-ho Nam ) 한국농공학회 2022 한국농공학회 학술대회초록집 Vol.2022 No.-

Globally, new types of drought are arising as a result of climate change, increasing teleconnection patterns, rising water usage by people, and historical environmental influences that raise the chance of transcendent ecological effects. Understanding this altering depiction of drought and its significant ecological effects is one of today’s major challenges.The current study used a unique drought index, the standardized supply-demand water index (SSDI), and a run theory to detect ecological drought occurrences and characteristics of drought in affected in the Hwang River. Hence, to assess drought-prone areas, the bivariate probability and return period will be calculated using a two-dimensional joint copula. The core results show that the Spatio-temporal characteristics of ecological drought were successfully recognized using the spatial and temporal identification approach; in comparison to the SPEI meteorological drought index, the SSDI is more credible and can more readily and effectively capture the entire properties of ecological drought information; the Hwang river had seen the most severe drought occurrences between the late 1990s and the mid-2020s. lastly, the drought duration and severity in the Hwang area were more responsive to temperature when temperatures rise around 1.1°C, the average drought duration and severity rise around 16 % and 26 %, respectively. This suggested that the Hwang River has been exposed to more severe heat stress in the twenty-first century. This new ecological droughts index will serves as a road map for future research and management improvements that will promote forward-thinking, collaborative methods to reducing the risk of drought to our ecological systems.

지속가능한 사회-생태적 회복력을 평가하기 위한 통합적 접근: 춘천 사례를 중심으로

사예드사자한사디키 ( Sayed Shajahan Sadiqi ),홍은미 ( Eun-mi Hong ),남원호 ( Won-ho Nam ) 한국농공학회 2023 한국농공학회 학술대회초록집 Vol.2023 No.0

Given the increasing challenges posed by climate change, urbanization and resource demands, there is a growing focus on the need to promote socio-ecological resilience. This study takes an approach to assess the socio-ecological resilience of Chuncheon City in South Korea. It employs tools and methods to examine how environmental factors interact to shape the area's ability to adapt and thrive amidst changing pressures. Our goal is to gain an understanding of its current environmental situation and prospects concerning socio-ecological resilience. The analytical method includes an investigation of land use dynamics, water quality trends, and ecosystem service patterns, which is enhanced by advanced models such as Agro-IBIS, MODFLOW, SWAT, and THMP. In addition, the study employs a participatory method, involving stakeholders to improve understanding of local dynamics and what is needed. Therefore, SWAT analysis has already yielded preliminary results, suggesting fluctuating nitrogen, suspended particles, and phosphorus loadings within certain ranges from -4.5 to +2.3%, -5.8 to +29.0%, and +3.7 to +17.4%, respectively. Furthermore, forecasts predict significant shifts in evapotranspiration (+3.2% to +17.2%), streamflow (-9.1% to +8.1%), and soil moisture (0.1% to 0.7%) between 2040 and 2080. Additionally, projections of potential climate changes indicate temperatures will increase by 1.3 to 2.1°C, and precipitation will rise by 31 to 61mm by the end of the century (under SSP126 and SSP585). These findings form the cornerstone of the study's conclusions and emphasize the importance of including stakeholders in the development of effective resilience solutions. This study, which is still in progress, is expected to create a framework that not only assesses the many facets of socio-ecological resilience but also offers helpful suggestions for managing environmental pathways toward sustainable development and assisting stakeholders, policy-making to successfully address upcoming issues along with enhancing sustainability and resilience in other similar areas.

SWAT 모형을 활용한 아프가니스탄 살람 댐의 유출 및 퇴적물 추정

사디키세이드샤잔 ( Sayed Shajahan Sadiqi ),남원호 ( Won-ho Nam ),홍은미 ( Eun-mi Hong ) 한국농공학회 2019 한국농공학회 학술대회초록집 Vol.2019 No.-

Sediments are a principal component in water resource projects for dam sedimentation, soil and water conservation, and design of efficient erosion control structures. High sediment rates lead to filling dam and loss of live storage of dam, which is eventually commanding to loss of production potential and evacuation of sediments from the dam is a costly process that can have large environmental impacts. A physically-based distributed hydrological model, SWAT (Soil and Water Assessment Tool), was used to estimate of runoff and sediment yield in the outlet of Salma Dam watershed in Harirud river basin measuring of 11,550 km² catchment area. The main objectives of the study were to analyze the sediment yield in the outlet of the catchment and effect of LULC (Land Use and Land Cover) changes on sediment yield and flow values. The basin shows large heterogeneity in term of a hydrogeological parameter, LULC and soil features. The model was calibrated and validated using observed runoff and sediment yield data of 10 years (2008-2018) at the basin outlet. The average values for RSR (RMSE-observations standard deviation ratio) and NSE (Nash- Sutcliffe efficiency) for sediment are found to be 0.60 and 0.61, for runoff are found to be 0.67 and 0.64, which are within good limits for sediment and a good limit for runoff respectively. The overall average annual output for sediment at the outlet point was estimated 133.02 Met ton/month, is model monthly output. In general, the model was capable of simulating runoff and sediment in Salam dam watershed. As land development is a continuous process, for the optimum use of the land cover and water resources of the area, it is recommended that soil and watershed conservation practice should be undertaken in order to keep the sustainability of the reservoir conserving sediment reduction.

SWAT을 이용한 고지대 농업유역 내 NPS의 기후변화 영향 평가 및 저감효과 평가

사예드사자한사디키 ( Sayed Shajahan Sadiqi ),변상돈 ( Sangdon Byeon ),남원호 ( Won-ho Nam ),홍은미 ( Eun-mi Hong ) 한국농공학회 2021 한국농공학회 학술대회초록집 Vol.2021 No.-

기후 변화의 잠재적 영향과 아프가니스탄의 농업 생산성에 미치는 영향

사예드사자한사디키 ( Sayed Shajahan Sadiqi ),홍은미 ( Eun-mi Hong ),남원호 ( Wan-ho Nam ) 한국농공학회 2020 한국농공학회 학술대회초록집 Vol.2020 No.-

Climate change has a severe impact on the availability of several resources on the earth especially water resources. As a pathway agriculture is an economic sector, that is the most vulnerable sector to the climate change. Giving to the latest estimates, farmers’ adaptation of farm production to climate change is predictable. The climate characteristics that are projected have the most direct impacts on agricultural productivity are: rise in temperature, the change in the frequency and severity of precipitation and of thrilling weather phenomena, and increase the level of CO₂ accessible for photosynthesis. Based on the projection, reduction of more than 5 % annual rainfall by 2050 in the western part of Afghanistan with temperatures are expected to increase more than the global average. Under a high greenhouse gas emissions scenario (RCP8.5), maximum warming could reach about 2.3℃ until 2050, and up to 6.5℃ by 2100. Under a lower emissions scenario (RCP4.5), warming is expected to reach 1.7℃ by 2050 and then upland around 2℃ by 2100. Afghanistan will also start to experience more seasonal variation in temperature and rainfall with more warming in the winters than summers. The longevity of heat waves across Afghanistan has extended in latest years with warmer night temperatures and hotter days, and this trend is expected to continue. Observed signal suggests that climate change is already occurred and has a substantial impact on agricultural productivity. Farmers have to adapt to the expected impacts of climate change in order to sustain their standard of living. The adaptation of agriculture to climate change includes reform of crops, adapted plant varieties, cropping systems and changes in cultivation practices. Policies are essential to take into account the multidimensionality of recent agriculture and the importance of sustainable agricultural development.