Influence of the size of coal ash FAU zeolites used as dopants on the 2nd Coatings and Interfaces Web Conference sensing properties of Jens Martensson 15/05/2020 - 31/05/2020 Nb 2 O 5 thin films. K. Lazarova 1 , S. Boycheva 2 , M. Vasileva 1 , D. Zgureva 3 and T. Babeva 1 1 Institute of Optical Materials and Technologies ‘‘Acad. J. Malinowski’’, Bulgarian Academy of Sciences, Sofia, Bulgaria Institute of Optical Materials and Technologies 2,3 Technical University of Sofia, Bulgaria 2 Department of Thermal and Nuclear Power Engineering; 3 College of Energy and Electronics 1
Coal ash - pollutants and possibilities 1. for their utilization Na-X Faujasite (FAU) zeolites - 2. synthesis from coal ashes Jens Martensson Wet-milling of synthesized zeolites 3. Thin films from Nb 2 O 5 doped with 4. milled and not-milled zeolites Characterization of thin films - 5. optical and sensing properties Summary 6. 2
The electricity produced in Bulgaria in 2018, allocated Coal is the largest source of energy from fossil fuels according to the primary energy resource and used used for generating electricity in the world. production technology. 12% 36% 1. Releases of gaseous 7% Jens Martensson 2. Generation of solid emissions - sulfur, nitrogen and waste - ash 4% 40% carbon oxides 1% Ash macro-component composition is considered as an Thermal Power Plants (TPP) on gas alumosilicate material. TPP Black and Brown Coal TPP Lignite Different opportunities for utilization have been explored, Nuclear power plant including for the synthesis of Water Electric Power Plant zeolites. 3 Solar, wind and biomass energy
Greenhouse Released Carbon dioxide CO 2 effect gas emissions Volatile Organic Compounds (VO С s) Jens Martensson For the purposes of developing CO 2 capture Zeolites are materials with a unique porous structure, with active centers technologies in the search for new solid phase and mobile cations of alkaline and sorbents, zeolites have also been studied. alkaline-earth metals. They have valuable features such as : adsorbents catalysts separators ion exchangers FAU LTA 4
2. Na-X Faujasite (FAU) zeolites - synthesis from coal ashes highly developed specific surface LTA FAU LTA and FAU zeolites Allowing the physical Pore size Pore size have the highest carbon 7.35 Å 4.21 Å adsorption of molecules of CO 2 capture potential from size 3.2 Å Free volume Free volume 27.42 % 21.43 % Jens Martensson Zeolites High content of iron oxides ( -Fe 2 O 3 , α -Fe 2 O 3 , -Fe 3 O 4 ) synthesized from Zeolite from Determine their good pure starting coal ash - they catalytic activity materials In combination with microcomponents such as Cu, Co, Mn, V, W The process of synthesis is carried out in three stages: 1) Dissolving aluminosilicates of the ash in the alkaline solution; 2) Precipitation of an alumosilicate hydrogel; 3) Crystallization of zeolite from the alumosilicate 5 gel on undissolved solid particles.
3. Wet-milling of synthesized zeolites FAU type zeolites Part of the zeolites are subjected to subsequent wet milling in synthesized from a ball mill for 60 s to reduce their size to submicron values. coal fly ash Milled zeolites Not milled zeolites Jens Martensson ∨ Agglomerations of indistinguishable 5 000x particles are observed before milling and octahedral shape crystallites typical of the FAU phase. ∨ Inclusions of particles from other zeolite phases are also found, which often accompany the crystallization of FAU from coal fly ash. 10 000x ∨ After the mechanical processing, a clear separation of the individual particles of about 1-1.5 μm size is observed. 6
3. Wet-milling of synthesized zeolites FAU type zeolites Part of the zeolites are subjected to subsequent wet milling in synthesized from a ball mill for 60 s to reduce their size to submicron values. coal fly ash 30 Jens Martensson d 2 =716 nm Milled 60s d 1 =1472 nm Not milled 25 Size distribution changes from monomodal Intensity(a.u.) ( d 1 ) in the case of non-milled zeolites to 20 bimodal ( d 2 and d 3 ) for milled samples: 15 10 d 1 = 1470 nm d 3 =111 nm 5 d 2 = 716 nm and d 3 = 111 nm 0 10 100 1000 10000 Size(nm) 7
4. Thin films from Nb 2 O 5 doped with milled and not-milled zeolites Sol-gel Deposited on a silicon Thin films from Nb 2 O 5 doped Spin-coating substrate, method with milled and not-milled zeolites Speed - 4000 rpm, Heated for 30 min at 320 ° C Milled and not-milled Jens Martensson FAU zeolites Deposited thin films Nb 2 O 5 + Nb 2 O 5 + and milled FAU not-milled FAU in three volume concentrations 1% 2.5% 5% 8
5. Characterization of thin films - optical and sensing properties Reflectance spectra of the films are measured in order to study their optical properties and to calculate the thickness. n , k и d - calculated by Jens Martensson Concentration of zeolites 60 nonlinear algorithm for Nb 2 O 5 + Reflectance (%) 1% milled FAU minimizing the difference 2.5% 5% between measured and 40 calculated values of the reflectance R. 20 Thickness ( d ) 0 Refractive index ( n ) Extinction coefficient ( k ) 400 600 800 Wavelength (nm) Reflectance spectra of Nb 2 O 5 films with milled zeolites 9
5. Characterization of thin films - optical and sensing properties 100 Films doped with not-milled zeolites have thickness around 78 nm - 80 nm for 1% 90 concentration and there is a slight increase in d 80 d (nm) Jens Martensson to 84 nm at concentration of 2.5 %. There is no 70 further increase of d with concentration. 60 milled 50 Films doped with milled zeolites have clear not milled tendency of increasing thickness with 40 1 2 3 4 5 concentration of zeolites – from 62, 73 and 77 nm Zeolites concentration (%) for 1, 2.5 and 5 % respectively. Dependence of thickness d on zeolite concentration ( b ) of thin Nb 2 O 5 films embedded with not-milled and milled fly ash FAU zeolites. 10
5. Characterization of thin films - optical and sensing properties 2,6 2,4 Not milled Miled 60s Refractive index FAU zeolites Not milled Refractive index 2,4 2,2 1% 2.5% 2,2 2,0 5% 2,0 1,8 Milled 60s FAU zeolites 1,8 1,6 1% 2.5% 1,6 1,4 5% Jens Martensson 1,4 1,2 1,2 1,0 400 500 600 700 800 1 2 3 4 5 Wavelength(nm) Zeolites concentration(%) Dispersion curves of refractive index of thin Nb 2 O 5 films Dependence of refractive index n at wavelength of 600 embedded with not-milled and milled fly ash FAU zeolites. nm on zeolite concentration of thin Nb 2 O 5 films embedded with not-milled and milled fly ash FAU zeolites. Films of Nb 2 O 5 Using smaller zeolites + milled FAU normal dispersion curves 1. Precise control and deposition of thin films lower thickness, higher density and refractive index as with a specific thickness. compared to samples doped with not - milled zeolites. more pronounced decrease in n with increasing the zeolite 2. Control of the refractive index of the films. 11 concentration.
5. Characterization of thin films - optical and sensing properties Sensing properties Sensing properties toward liquid acetone determination method 1 Air 30 Measuring of the reflection Jens Martensson Acetone spectra of thin films before and after exposure to liquid R(%) 20 acetone. 10 2 Calculation of the acetone induced change in the 0 reflection ΔR. 400 450 500 550 600 650 700 Wavelength(nm) 2.5 % milled zeolites film 12
5. Characterization of thin films - optical and sensing properties Sensing properties toward liquid acetone 1 The addition of not-milled zeolites 25 results in a 1.6 - 2.5 % change in ΔR as Milled for 60s increase of concentration leads to decrease Not milled of reflectance change. 20 Jens Martensson Not - milled zeolites R(%) samples: 15 2.5 % max change 10 2 In the case of films with milled zeolites - as the 5 amount of zeolites increases, the change in the reflection coefficient Δ R increases from 7.6 to 19.4. 0 5% 1% 2.5% Milled zeolites samples: Zeolite concentration (%) ≈20 % max change Zeolite concentration dependence of reflectance change induced by exposure to liquid acetone of FAU not-milled (blue bars) and milled (magenta bars) embedded in thin Nb 2 O 5 films. Measurements are conducted at room temperature. 13
5. Characterization of thin films - optical and sensing properties Similar measurements made with liquid ethanol for Selectivity films with milled zeolites . for films of Nb 2 O 5 + milled FAU Ethanol selected as probing liquid due to its similar to acetone refractive index: 1.361(eth) and 1.359(ac). Acetone 20 Ethanol 1 The optical response toward ethanol is Jens Martensson almost 8 times weaker as compared to 15 R(%) acetone. Ethanol : 10 av. 2.5 % max change for all concentrations 5 2 Increase of concentration of milled zeolites leads 0 to increase of the change in the reflection 5% 1% 2.5% coefficient Δ R. Zeolite concentration (%) Acetone : Zeolite concentration dependence of reflectance change induced by exposure to ≈20 % max change for liquid acetone (yellow) and ethanol (green) of milled zeolites embedded in thin highest concentration Nb 2 O 5 films. Measurements are conducted at room temperature. 14
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