Flame Deposition Research Articles

Flame synthesis of carbon nanostructures on stainless steel anodes for use in microbial fuel cells

Microbial fuel cells (MFCs) offer a promising alternative energy technology, but suffer from low power densities which hinder their practical applicability. In order to improve anodic power density, we deposited carbon nanostructures (CNSs) on an otherwise plain stainless steel mesh (SS-M) anode. Using a flame synthesis method that did not require pretreatment of SS-M substrates, we were able to produce these novel CNS-enhanced SS-M (CNS-M) anodes quickly (in a matter of minutes) and inexpensively, without the added costs of chemical pretreatments. During fed batch experiments with biomass from anaerobic digesters in single-chamber MFCs, the median power densities (based on the projected anodic surface area) were 2.9 mW m −2 and 187 mW m −2 for MFCs with SS-M and CNS-M anodes, respectively. The addition of CNSs to a plain SS-M anode via flame deposition therefore resulted in a 60-fold increase in the median power production. The combination of CNSs and metallic current collectors holds considerable promise for power production in MFCs.

Synthesis of carbon-doped photocatalytic TiO 2 nano-powders by AFD process

Carbon-doped titanium dioxide (TiO 2) nano-powders were synthesized by the aerosol flame deposition (AFD) process using 2-butanol liquid sol containing 20 wt% of titanium isopropoxide (TTIP). They were mesoporous nano-powders with particle size ranging from 20 to 40 nm, the specific surface area of 36 m 2/g, and the pore size of 19 nm. They had the anatase structure and showed high photocatalytic activity not only under UV-A light but also under fluorescent light. They reduced the concentration of methylene blue (MB) from 5.0 to 1.5 ppm within 2 h under UV-A light and from 5.0 to 2.0 ppm within 4 h under fluorescent light. And, they killed 99% of Escherichia coli ( E. coli) cells within 2 h and bacterial growth of the E. coli was not observed for 12 h under both UV-A and fluorescent lights.

FIB and TEM Studies of Diamond Films Prepared by Laser-Assisted Combustion Flame Deposition in Open Atmosphere

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

A study on characteristics of micro-porous silica films prepared by aerosol flame deposition

Abstract Porous silica thin films were prepared on silicon wafers by an aerosol flame deposition (AFD) process, and dependence of their characteristics on sintering temperature was investigated. At sintering temperatures ranging from 1270 °C to 1320 °C, films with continuous micro-pores were deposited. As the sintering temperature increased, the pores of the film were getting smaller with more uniform distribution and the thickness and surface roughness decreased. The films were found to be hydrophilic when tested by the sessile drop method and the captive bubble method. And, zeta potentials of the films in a KCl solution sharply decreased to the minimum value at pH 8 and increased again as pH increased. The minimum value for the film prepared at sintering temperature of 1320 °C was −87 mV.

Quality Improvement of Flame Sprayed, Heat Treated, and Remelted NiCrBSi Coatings

In this study, properties of NiCrBSi coatings, produced by a two-step process of flame deposition and furnace posttreatment, are analyzed. Adhesion strength, microstructure, porosity, microhardness, chemical composition, and residual stresses were analyzed after deposition and after heat treatment; that is, remelting. Numerous specimens were made to study the adhesion strength of coatings after flame deposition. The four chosen influential factors, that is, surface roughness, preheat temperature of the substrate, distance of flame torch, and type of oxyacetylene flame, were optimized to maximize the adhesion strength, using the Taguchi parametric method. The confirmation experiment showed that the developed experimental model is suitable for optimization of flame spraying deposition process. Based on the evaluation of coating properties, the best overall quality was obtained after remelting at a peak temperature 1080 °C with 5 minutes of holding time, followed by slow air cooling.

Synthesis of BaMgAl<SUB>10</SUB>O<SUB>17</SUB>:Eu<SUP>2+</SUP> Blue Phosphor by Electro-Spray Aerosol Flame Deposition

Spherical and nano-sized BaMgAl10O17:Eu2+ (BAM) phosphor particles for plasma display panel (PDP) application were synthesized by Aerosol Flame Deposition (AFD) and subsequent heat treatment at 1250 degrees C for 4 h under reducing atmosphere. The effects of various atomization methods, precursor solution and various deposition position along flame axis were investigated in order to control the morphology and size of the phosphor. Characteristics of BAM phosphor were investigated for products prepared under various condition and they were compared with those of the commercial BAM. It was found that electro-spray gas-assisted atomization produce the most fine particle, while the optimum particle size for real application in phosphor devices (200-400 nm) was produced by the gas-blast atomizer.

Fabrication of a silica ceramic membrane using the aerosol flame deposition method for pretreatment focusing on particle control during desalination

A silica membrane was fabricated using the aerosol flame deposition (AFD) method under different sintering temperatures. It was characterized, in terms of roughness, pure water permeability, contact angle, zeta potential, and effective pore size distribution. Membrane performance was evaluated with respect to removal of Suwannee River humic acids and polystyrene particles with different sizes. Both membrane thickness and pure water permeability decreased with increasing sintering temperature. The effective pore sizes of synthesized membranes ranged from 6.5 to 8.0 µm. Polystyrene particles with sizes higher than 7 μm were almost completely removed by the synthesized ceramic membranes; however, no removal for humic acids was measured with the ceramic membranes tested.

Synthesis of Carbon Containing TiO2 Nano Powders by Aerosol Flame Deposition for Photocatalyst

In-situ carbon-doped-TiO2 nano-powder was prepared by an AFD (aerosol flame deposition) technique using ethanol and isopropanol, and the photocatalytic activity of the prepared powder was examined. There were no significant effect of the solvents on the phase of the prepared TiO2, but the level of carbon in the deposits prepared with ethanol was lower than that prepared with isopropanol. Also, the average sizes of the particles prepared with ethanol were slightly smaller than that formed with isopropanol. All the samples showed excellent photocatalytic activity in the decomposing of methylene blue (MB). We even observed photocatalytic activity of the powder under visible light irradiation, although the decomposition rate of MB under this irradiation was slightly slower than under UV-A light irradiation.

Fabrication of Sn/SnO 2 composite powder for anode of lithium ion battery by aerosol flame deposition

Crystalline SnO 2 and Sn/SnO 2 composite nano-powder were synthesized by aerosol flame deposition (AFD) method employing an oxy-hydrogen flame torch and a heated deposition turn-table. The aqueous precursor solution of the tin (IV) chloride and methyl alcohol was atomized with an ultrasonic nebulizer and subsequently carried into the central tube of the torch by flowing dry Ar gas. SnO 2 were formed by oxy-hydrogen flame and deposited on a substrate placed in a heating stage. To produce Sn metal particles and control the ratio of Sn/SnO 2, as-synthesized SnO 2 were heat-treated under 5% H 2 and 95% Ar mixed gas atmosphere at a temperature of 150 °C for 3 h, and then at 600 °C for 1–4 h. The average particle size of as-synthesized SnO 2 was in the range 5–15 nm and that of Sn/SnO 2 composite powder was slightly grown to 20–90 nm depending on the heat treatment temperature. The analysis on morphology, crystalline phases, and chemical state of Sn revealed that AFD method is one of the favorable approaches to produce nano-sized Sn/SnO 2 composite powder with good morphology, size distribution, and well-controlled Sn/SnO 2 ratio.

Morphology and luminescence properties of BaMgAl10O17:Eu2+ blue phosphors by Aerosol Flame Deposition

BaMgAl10O17:Eu2+ (BAM:Eu) is widely used as a blue phosphor for fluorescent lamps and plasma display panels (PDP). The improvement of the luminescence efficiency is a significant issue for applications in plasma display panels. In this study, the Aerosol Flame Deposition (AFD) was applied to fabricate BaMgAl10O17:Eu2+ (BAM:Eu) particles with spherical shape and fine size in order to improve their luminescence. The sub-micrometer powder was synthesized in spherical shape in an oxy-hydrogen flame and deposited on a substrate in the form of porous film. The particle size of as-prepared powder increased with increasing the concentration of precursor solution and the heat treatment under reducing atmosphere increased particle size additionally with surface roughening due to the needle-like crystallized phases. Photoluminescence spectrum was observed at about 450nm due to the 5d–4f transition of Eu2+ and the intensity of phosphor was as high as 70% of that of the commercial phosphor.

Effect of heat treatment on Li 2O–B 2O 3–P 2O 5 glass soot fabricated by aerosol flame deposition

Li–B–P–O containing oxide nano-particles were synthesized from BCl 3, POCl 3 gases and an aqueous LiNO 3 by flame hydrolysis reaction. Li 2O–B 2O 3–P 2O 5 thin-film electrolyte was fabricated from as-deposited oxide particles by sintering at various temperatures between 500 and 600 °C. The effect of the sintering temperature on vitrification and electrical conductivity was investigated to find the optimum condition for the fabrication of thin-film electrolyte. Raman spectra and DTA measurement revealed that the crystalline H 3BO 3 impurity phase was included in the as-deposited film and was converted to glass former B 2O 3 during heat treatment above 550 °C. Raman spectra also indicate that the non-bridging oxygens within glass network increased with the vitrification at the elevated temperature. Accordingly, the conductivity of electrolyte was increased with increasing sintering temperature. However, in the ambient atmosphere, the diborate groups with non-bridging in glass electrolyte slowly transformed to H 3BO 3 again by reaction with moisture.

Electrochemical characteristics of LiCoO 2 nano-powder synthesized via aerosol flame deposition (AFD)

Crystalline LiCoO 2 nano-powders for lithium-ion battery were synthesized by aerosol flame deposition (AFD). The aqueous precursor solution was atomized with an ultrasonic vibrator and supplied to the oxy-hydrogen flame by flowing dry Ar gas. The as-deposited soot powders were collected on a substrate placed on a heating stage. X-ray diffraction and transmission electron microscopy (TEM) show that the soot powders were composed of nano-sized particles of Li 2CO 3, CoCo 3 and Co 3O 4 and the subsequent heat treatments at 700 °C for 5 h that converted these powders to well-layered LiCoO 2 powder. The flow rate of H 2 flame gas was discovered to have influenced the phase composition in the as-deposited soot. The electrochemical performance of synthesized nano-powders was investigated using 2032 coin-type cell. LiCoO 2 nano-powder synthesized at an H 2 flow rate of 2.5 l/min sintered at 700 °C for 5 h showed a first discharge capacity of 144 mAh/g and good rechargeability in Li//1 M LiPF 6-EC/DEC//LiCoO 2 cells between 3 and 4.3 V.

Microstructure and electrical conductivity of NiO–YSZ nano-powder synthesized by aerosol flame deposition

The aerosol flame deposition (AFD) process was capable of producing mixed metal oxide powders with 10–500 nm size from low-cost liquid precursors. The nickel oxide–yttria stabilized zirconia (NiO–YSZ) powders used as an anode of SOFC has been synthesised by using AFD process. It was demonstrated that this process is suitable for fabricating the nano-sized and spherical NiO–YSZ particles capable of enhancing three phase boundary areas. The synthesis process was studied by changing processing parameters such as the concentration and the composition ratio of the precursor solution and the flow rates of the flame gases. The sufficiently crystallized and spherically shaped NiO–YSZ particles were synthesized successfully and the size distribution was bimodal when observed by TEM. As changing contents of Ni and YSZ, the conductivities of NiO–YSZ pellet exhibited a typical mixed conductor behaviour of which the ionic conduction is in high temperature range and the electronic conduction is in lower temperature range.

Synthesis of nano-crystalline Gd 0.1Ce 0.9O 2− x for IT-SOFC by aerosol flame deposition

Nano-sized gadolinia-doped ceria (GDC) can be used as an IT-SOFC electrolyte, oxygen gas sensor or abrasives. In this study, nano-sized GDC powders with bimodal particle distribution of about 10 nm and 200 nm particle size were successfully synthesized by aerosol flame deposition (AFD). The resulting effects of sintering temperature on microstructure and electrical properties were investigated in the sintering temperature range 1100–1400 °C. The pellet had a completely dense microstructure after sintering at 1400 °C for 10 h. Raman measurement showed an increase of oxygen vacancy due to shift between reduced and oxidized states (Ce 3+ ↔ Ce 4+) with increasing sintering temperature. The formation of oxygen vacancies noticeably increased the ionic conductivity above 1300 °C.

Fabrication of LiCoO 2 cathode powder for thin film battery by aerosol flame deposition

Crystalline LiCoO 2 nano-particles for thin film battery were synthesized and deposited by aerosol flame deposition (AFD). The aqueous precursor solution of the lithium nitrate and cobalt acetate was atomized with an ultrasonic vibrator and subsequently carried into the central tube of the torch by flowing dry Ar gas. LiCoO 2 were formed by oxy-hydrogen flame and deposited on a substrate placed in a heating stage. The deposited soot film composed of nano-sized particles was subsequently consolidated into a dense film by high temperature heat treatment at 500–800 °C for 5 h and characterized by SEM, XRD, and Raman spectroscopy. The crystalline carbonates and oxide were first formed by the deposition and the subsequent heat treatment converted those to LiCoO 2. The FWHMs of the XRD peaks were reduced and their intensity increased as the heat treatment temperature increased, which is due to improved crystallinity. When judged from the low enough cation mixing and well-developed layered structure, it is believed that the LiCoO 2 film satisfied the quality standard for the real application. SEM measurements showed that LiCoO 2 were nano-crystalline structure with the average particle size <70 nm and the particle size increased with the increase of heat treatment temperature. The thickness of thin film LiCoO 2 before the consolidation process was about 15 μm and reduced to about 4 μm after sintering.

Fabrication of solid thin film electrolyte and LiCoO 2 by aerosol flame pyrolysis deposition

Aerosol flame pyrolysis deposition method was applied to deposit the oxide glass electrolyte film and LiCoO 2 cathode for thin film type Li-ion secondary battery. The thicknesses of as-deposited porous LiCoO 2 and Li 2O–B 2O 3–P 2O 5 electrolyte film were about 6 μm and 15 μm, respectively. The deposited LiCoO 2 was sintered for 2 min at 700 °C to make partially densified cathode layer, and the deposited Li 2O–P 2O 5–B 2O 3 glass film completely densified by the sintering at 700 °C for 1 h. After solid state sintering process the thicknesses were reduced to approximately 4 μm and 6 μm, respectively. The cathode and electrolyte layers were deposited by continuous deposition process and integrated into a layer by co-sintering. It was demonstrated that Aerosol flame deposition is one of the good candidates for the fabrication of thin film battery.

Fabrication of Li 2O–B 2O 3–P 2O 5 solid electrolyte by aerosol flame deposition for thin film batteries

Amorphous Li 2O–B 2O 3–P 2O 5 thin films were prepared from an aqueous precursor solution of a LiNO 3 and BCl 3, POCl 3 by Aerosol Flame Deposition. The aqueous precursor solution of the LiNO 3 was first atomized with an ultrasonic vibrator (1.7 MHz), and B 2O 3 and P 2O 5 were synthesized from BCl 3 and POCl 3 by an oxygen–hydrogen flame. Their microstructure and electrical properties were investigated by SEM, XRD, Raman spectroscopy and impedance spectroscopy. XRD analysis revealed that a crystalline phase of LiCl was formed in the glass soot as well as amorphous boron and phosphorus oxides, and the crystalline LiCl found in deposited glass soot completely disappeared by heat treatment. The correlation between the structural modification of glass network, compositional variation and the conductivity was characterized by Raman spectroscopy. The glass electrolyte fabricated in this study exhibited a maximum conductivity of about 10 − 7 S/cm at 30 sccm flow rate of BCl 3 and POCl 3.

Synthesis of nano-sized gadolinia doped ceria powder by aerosol flame deposition

In this work, aerosol flame deposition method was applied to deposit spherical and dense gadolinia-doped ceria (GDC) particles in the sub-micron range for the electrolyte application in solid oxide fuel cell. The particle size distribution was dependent on processing parameters such as the concentration of the precursor solution, the hydrogen gas flow rate, the oxygen gas flow rate, and flame conditions. GDC electrolyte thin layer was also fabricated from the liquid source materials by AFD method. Microstructure of synthesized powder was characterized using XRD and SEM.

Fabrication of NiO/YSZ anode for solid oxide fuel cells by aerosol flame deposition

Nickel oxide/yttria stabilized zirconia (NiO/YSZ) powder and thin film have been synthesized by aerosol flame deposition (AFD). The nano-sized and spherical NiO/YSZ particles were synthesized and the particle size distribution was controlled by changing processing parameters such as the concentration of the precursor solution. The synthesized powder was composed of YSZ particles of a few hundred nm size and NiO particles of a few tens nm size, which is ideal for the catalysis and reaction of hydrogen offering tremendous amount of three phase boundary. The electrical conductivity of 70% NiO/YSZ exhibited typical metallic behavior and was 10 −1 S/cm at 700 °C which is adequate for the anode of solid oxide fuel cell.

Fabrication of yttria stabilized zirconia films as the electrolyte of micro fuel cells by aerosol flame deposition

Fabrication of yttria stabilized zirconia films as the electrolyte of micro fuel cells by aerosol flame deposition