Combustion Flame Method Research Articles

Influence of Diamond Seed Attachment Processing on Diamond Films Synthesized on Tungsten Carbide Substrate by Flame Combustion

The flame combustion method enables the synthesis of diamonds via acetylene-oxygen gas flame combustion in ambient air. Tungsten carbide (WC) has recently been utilized as a cutting tool in the machining industry and in dental machining applications. To obtain high-quality diamond films and achieve good adhesion on a WC substrate, diamond films are synthesized on a WC substrate by the flame combustion method. However, the surface roughness of most of the diamond films synthesized by this method increased, and it was necessary to reduce this roughness. Considering the roughness accuracy of the workpiece surface during cutting, and the performance of the cutting tool, a smaller surface roughness of the diamond films synthesized is desirable. In this study, to reduce surface roughness, the amount of diamond paste with diamond seed particles as generation nuclei was carefully varied for diamond seed attachment processing of diamond films. When diamond films were synthesized on the WC substrate surface via the flame combustion, the amount of diamond paste with diamond seed particles affected the surface morphology and surface roughness of the synthesized diamond films. Furthermore, to investigate the reason for this result, generation of nuclei on the substrate in the initial stages of synthesis and diamond seed particles on the substrate surface after the seeding treatment were observed by scanning electron microscopy. The effect of diamond seed attachment processing on the diamond films synthesized by flame combustion was studied. The relationship between the surface roughness, number of diamond generation nuclei on the substrate in the initial stages of synthesis, number of diamond particles on the substrate after the diamond seeding process, and amount of diamond paste were confirmed.

Influence of Substrate Surface Roughness on Synthesized Diamond Films by Flame Combustion on Ti Substrate for Dental Implants

The flame combustion method enables the synthesis of diamonds via acetylene-oxygen gas flame combustion in ambient air, and this method has various advantages over other methods. However, most diamond films synthesized by this method delaminate because of thermal stress during cooling. Titanium (Ti) has recently been utilized as a dental implant in the dental industry. In this study, to improve the strength, wear resistance, and biocompatibility of dental implant surfaces, diamond films were synthesized on a Ti substrate, a dental implant material, by the flame combustion method. Moreover, to obtain high-quality diamond films and achieve good adhesion on the Ti substrate, as a pretreatment of the substrate to prevent delamination, scratch processing, in which a substrate is ground with emery paper in one direction, was performed to roughen the surface. The surface roughness of the Ti substrates was varied by scratching with emery paper of #180, #400, and #1500 grain sizes. According to these results, diamond films were synthesized on the Ti substrate surface by flame combustion. The surface morphology of the synthesized films could be altered by varying the scratching process using emery paper. Delamination of the synthesized films during the scratching process with emery paper #180 (Case A) and #400 (Case B) grain size was completely prevented. However, delamination occurred during the scratching process with a grain size of emery paper #1500 (Case C). To investigate the reason for this result, the surface roughness of the pretreated Ti substrate was observed, and it affected the surface roughness of pretreated Ti substrate affected the surface morphology and delamination of the synthesized diamond films.

Construction of hierarchical functional nanomaterials for energy conversion and storage

Hierarchical functional nanomaterials have important applications in the fields of new energy and the environment because of performance advantages based on the coupling and collaboration of multi-level structures. The key to application is the design and control of the mesoscale structures, such as the crystal-facet structure, lattice orientation, defects, and dislocations. In this review, we present the controlled synthesis of novel semiconductor oxide and carbon-based nanocomposites with three-dimensional hierarchical structures by the multiphase-reaction process. We describe several typical reaction processes, such as the gas-phase flame-combustion method, the vapor-phase deposition technique, and the solid–liquid interface reaction process, to investigate the properties of fluid flow, mixing, transport, and chemical reaction. We also study the formation mechanism, structural evolution and control methods for hierarchical nanomaterials by using combined experimental and simulation methods. These well-designed and prepared hierarchical functional materials can be used in energy storage and conversion fields. Valuable information is provided for the structural design and performance control of new functional nanocomposites.

Open-air combustion synthesis of three-dimensional graphene for oil absorption and energy storage

There are promising applications for three-dimensional (3D) graphene in energy storage, catalysis, mechanical sensors, oil absorption, etc. To realize these practical applications, a scalable, cost-effective, and controllable synthesis technique for growing 3D graphene is highly desired. In this study, a combustion flame method was developed to synthesize high-quality 3D graphene within 1 min in open air, demonstrating the high efficiency, cost-effectiveness, and scalability of the method. Based on its 3D porous characteristics, the 3D graphene shows promise for applications in oil absorption and supercapacitors. It has an absorption capacity of 60 times its original weight for oil and organic solvents with a recyclability of 15 times. When the 3D graphene was electrodeposited with manganese dioxide (MnO2), the as-formed 3D MnO2/graphene hybrid electrodes demonstrated electrochemical performance comparable to other reported MnO2-based supercapacitors with an energy density of 23.8 Wh/kg at a power density of 7.5 kW/kg.

Gas bubble templated synthesis of Mn3O4-embedded hollow carbon nanospheres in ethanol flame for elastic supercapacitor

With unique templates of sulphur-based gas bubbles in ethanol flame, the hollow carbon nanospheres, embedded with Mn3O4 quantum dots in the margin regions, are quickly synthesized on co-generated nanocarbon supporter on an elastic titanium foil substrate. The fabrication is just carried out by combustion in flame and anneal in air. When used as supercapacitor electrode, the electrode reveals large activity, high cyclic and elastic stability owing to its special structure. The mass specific capacitance of this nanosphere-based electrode is 316 F g−1 at a scan rate of 2 mV s−1, which is 94.7% larger than that of the electrode without nanosphere decoration. Furthermore, the capacitance retention of nanosphere-based electrode reaches 82.4% after 2000 charge-discharge cycles, and it is 78.3% even if the electrode is continuously vibrated 36000 cycles. These indicate the flame combustion method is effective, which has potential to be applied in synthesizing extensive materials in hollow nanosphere structure for electronic devices.

One-Step Synthesis of Nanostructured Co3O4 Film on Nickel Foam As Electrode for Supercapacitor Application

In recent years, supercapacitors have drawn considerable interest from researchers as an alternative energy storage device to secondary batteries. They offer advantages such as high power density, high columbic efficiency and long cycling life [1, 2]. Among the transition metal oxides investigated for redox reaction based supercapacitors (pseudocapacitors), Co3O4 is of special interest due to its high theoretical specific capacitance (up to 3560 F g-1) and relatively low cost [3, 4]. However, low rate capability and poor cycling performance as a result of relatively low electrical conductivity limits its practical application in supercapacitors. Development of nanostructured Co3O4 materials offers a promising solution to this challenge as the transport pathways of electrons and ions are inherently short. Nanostructured Co3O4 film deposited on nickel foam has been prepared by an economical and scalable flame combustion method in one step, namely reactive spray deposition technology (RSDT). The microstructure of the electrode is investigated by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The nanostructured electrode provides high specific surface area and improves the kinetics of redox reaction [5]. The porous structure facilities the penetration of electrolyte and shortens the diffusion path of ions [6]. Electrochemical performance of the as-prepared Co3O4/Ni electrodes is evaluated by cyclic voltammetry, galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy in coin-type (CR2032) half-cells.

Smart bio-interface for spatio-confined dynamic reversible bacterial capture and release

There are promising applications for three-dimensional (3D) graphene in energy storage, catalysis, mechanical sensors, oil absorption, etc. To realize these practical applications, a scalable, cost-effective, and controllable synthesis technique for growing 3D graphene is highly desired. In this study, a combustion flame method was developed to synthesize high-quality 3D graphene within 1 min in open air, demonstrating the high efficiency, cost-effectiveness, and scalability of the method. Based on its 3D porous characteristics, the 3D graphene shows promise for applications in oil absorption and supercapacitors. It has an absorption capacity of 60 times its original weight for oil and organic solvents with a recyclability of 15 times. When the 3D graphene was electrodeposited with manganese dioxide (MnO2), the as-formed 3D MnO2/graphene hybrid electrodes demonstrated electrochemical performance comparable to other reported MnO2-based supercapacitors with an energy density of 23.8 Wh/kg at a power density of 7.5 kW/kg.

Effect of pretreatment of substrate on synthesized diamond films on Tungsten Carbide substrate by flame combustion

A flame combustion method enables the synthesis of diamond using acetylene-oxygen gas flame combustion in ambient air. Recently, tungsten carbide (WC) has been used as cutting tools in the machining industry. To obtain diamond films and to achieve good adhesion on the WC substrate, diamond films were synthesized by flame combustion method. However, synthesized diamond films delaminate as a result of thermal stress during cooling. In this study, as a pretreatment of the substrate to prevent the delamination, a chemical processing was performed. The WC substrate was pretreated by chemical etching to roughen the surface. The substrate was etched in an ultrasonic bath using Murakami’s reagent. Another processing was performed using an acid solution of hydrogen peroxide, in order to remove cobalt from the substrate surface. The pretreatment periods were varied. Moreover, the effect of the pretreatment of the substrate on synthesized diamond films by flame combustion was investigated.

Flame Synthesis of Spring-Like Nanocarbon and Its Application in Flexible Free-Standing Mattress-Like Supercapacitor Electrode

Nanocarbons in a unique spring-like helical structure were prepared by a simple and low-cost flame combustion method to act as active and conductive nano-springs in constructing a mattress-like graphene-based paper as a flexible freestanding electrode. As the electrode is applied in a supercapacitor, it simultaneously exhibits high activity, cycling and mechanical stability owing to its unique structure. At a working current density of 0.2 mA cm−2, the areal capacitance of this electrode is as high as 1.07 F cm−2, which is 228% higher than that of the electrode without the helical interlayer. In addition, the capacitive retention of the electrode reaches 93.02% after 1000 charge-discharge cycles at a current density of 2 mA cm−2, and it can remain at 81.22% even if the electrodes are bent 120° in a symmetrical supercapacitor. Such a preparation route is simple and effective, which makes it a promising method for fabricating general spring-like nanomaterials for high-performance wearable electronic devices.

Rapid Diamond Deposition on Ni and Co Coatings by Using Twin Acetylene/Oxygen Gas Welding Torches

Cermet coatings have been widely used because of their high hardness and excellent wear resistance even under high-temperature conditions. However, since cermet coatings include expensive materials such as WC, TiC, TiN and so on, low-cost hard particles as a dispersing agent need to be developed. In this study, in order to develop a low-cost diamond dispersion system for the creation of diamond/thermal sprayed metal hybrid coatings, diamond deposition on thermal sprayed Ni and Co coatings and Mo and Ni metal substrates by the combustion flame method using twin acetylene/oxygen gas welding torches was carried out. Consequently, even in cases of thermal sprayed Ni and Co coatings, diamond particles could be deposited within only 5 min. From these results, this technique is proved to have a high potential for rapid diamond deposition in order to create diamond/thermal sprayed metal hybrid coatings.

Characterization of Pt Catalysts Supported on Ta-SnO2 with Fused Aggregated Network Structure

Polymer electrolyte fuel cells (PEFCs) are attractive power generation systems for electric vehicles and residential co-generation systems. Platinum-based catalysts supported on carbon black (CB) have electronically conductive paths with gas transport paths and are suitable for catalysts for PEFCs. Cathode catalysts reach potentials of over 1.5 V during startup/shutdown, where the carbon undergoes degradation due to its intrinsic thermodynamic instability [1,2]. Such degradation problems should somehow be overcome to achieve long-term durability of PEFCs. SnO2 and TiOx are promising candidates for cathode catalyst supports with long-term durability at high potentials [3,4]. We have recently characterized Pt catalysts supported on Nb-SnO2 (Pt/Nb-SnO2), which had a CB-like fused aggregated network structure and distinctive stability with respect to high potential exposure, by half-cell and membrane electrode assembly (MEA) measurements [5-9]. The ceramic supports with these structures were able to supply both electronically conductive paths and gas diffusion paths in the catalyst layers, resulting in high cathodic activity with durability for the PEFCs. In the present study, we found that Pt supported on Ta-SnO2 (Pt/Ta-SnO2) has even higher electrical conductivity than that of Pt/Nb-SnO2, by half cell and MEA measurements. We synthesized the Pt catalysts supported on the Ta-SnO2 support by the flame combustion method and colloidal method; details of the methods and characterization were described in earlier papers [5-9].The Ta-SnO2 support powders (BET surface 45 m2 g-1; crystallite size 16.7 nm) were determined to be single-phase rutile-type SnO2 from the X-ray diffraction analysis. A transmission electron microscopic (TEM) image (Fig. 1) showed that the support was composed of fused aggregated network structures, and that the Pt nanoparticles (particle sizes 3.1 ± 0.6 nm; interparticle distances 9.4 nm; loaded amount 15.8 wt%) were uniformly dispersed on the support. The electrical conductivity of the Pt/Ta-SnO2 was ca. 4 times higher than that of Pt/Nb-SnO2. The electrochemically active surface area (ECSA) of Pt/Ta-SnO2, which was estimated from the cyclic voltammograms (CVs, Fig. 2), was 66.4 m2 g-1, similar to that of Pt/Nb-SnO2 (65.6 m2 g-1). The kinetically controlled current density and mass activity at 0.85V of Pt/Ta-SnO2 (Fig. 3) were approximately equal to those of Pt/Nb-SnO2 and were higher than that of a commercial Pt/CB catalyst (TEC10E50E, Tanaka Kikinzoku Kogyo Co.). Changes in the ECSA as a function of the logarithm of the number of potential step cycles (0.9-1.3 V, 30 s, Fig. 4) showed that the stability of Pt/Ta-SnO2 was the same as that of Pt/Nb-SnO2 and was superior to those of both a commercial Pt/CB and commercial Pt catalyst supported on graphitized carbon black (Pt/GCB, TEC10EA50E, Tanaka Kikinzoku Kogyo Co.). We also found by MEA evaluation that the ohmic resistance using the Pt/Ta-SnO2 cathode was lower than that using Pt/Nb-SnO2 (Fig. 5), and that the performance using a Pt/Ta-SnO2 cathode was superior to those using either cathodes of Pt/Nb-SnO2 or Pt/CB (Fig. 6). We consider that both the low resistivity and the high Pt utilization of Pt/Ta-SnO2 led to both the lowering of the ohmic resistance and the improvement of catalytic activity in the catalyst layer. We conclude that the Pt/Ta-SnO2catalyst is an attractive candidate for PEFC cathodes for fuel cell vehicles. Acknowledgement This research was supported by funds for the “Research on Nanotechnology for High Performance Fuel Cells” (HiPer-FC) project from the New Energy and Industrial Technology Development Organization (NEDO) of Japan, and the JSPS KAKENHI grant Number B24350093.

Effect of Nitrogen Addition on Synthesis of Nanocrystalline Diamond Films on Tungsten Carbide Substrate by Flame Combustion Method Using High-Purity Acetylene

A flame combustion method enables the synthesis of diamond using acetylene-oxygen in ambient atmosphere. It has various advantages over other methods, such as in terms of speed, safety and cost. Tungsten carbide (WC) is used as cutting tools in the machining industry. In this study, to obtain nanocrystalline diamond films and to achieve good adhesion on the WC substrate, diamond films were synthesized by flame combustion using a mixture of high-purity acetylene and oxygen gas with the addition of nitrogen gas. Nitrogen gas added as the nanocrystalline diamond promotion agent; nitrogen flow rate was varied. The results indicated that, at the mixture of high-purity acetylene and oxygen gas, the diamond nanocrystallites was not synthesized on the diamond microcrystallites at nitrogen flow rate 0.000 cm3/s. As nitrogen flow rate was increased, the diamond nanocrystallites was synthesized on the microcrystallites. The diamond nanocrystallites was synthesized with high density all over the diamond microcrystallites.

Non-metal single/dual doped carbon quantum dots: a general flame synthetic method and electro-catalytic properties.

A combustion flame method is developed for the convenient and scalable fabrication of single- and dual-doped carbon quantum dots (CQDs) (N-CQDs, B-CQDs, P-CQDs, and S-CQDs and dual-doped B,N-CQDs, P,N-CQDs, and S,N-CQDs), and the doping contents can be easily adjusted by simply changing the concentrations of precursors in ethanol. These single/dual-doped CQDs, especially B,N-CQDs, show high catalytic activities for the oxygen reduction reaction.

Annealing effects on luminescent properties of Eu3+ doped Gd2Zr2O7 nanopowders

In this report presented are structure, morphology and luminescence properties of nanopowders based on gadolinium zirconium oxide (Gd2Zr2O7) doped by europium ions (Eu3+). The nanopowders were prepared using a flame combustion method, the most frequently used process due to the simplicity and low cost of the synthesis procedures and also due to the possibility of tailoring the size and morphology of particles. The produced material is suitable for various optical devices. The luminescence properties of synthesized nanopowders were characterized by emission spectra and luminescence lifetimes obtained by using the streak camera system. Moreover, emission spectra were obtained and compared for powders as-obtained and after additional annealing at 1200o C. Luminescence emission spectra clearly show peaks characteristic for the strong emission lines at 611 nm and 630 nm corresponding to the 5D0 ? 7F2 long lived transition.

Characterization and luminescent properties of Eu3+ doped Gd2Zr2O7 nanopowders

Nanopowders based on gadolinium zirconium oxide (Gd2Zr2O7) doped by europium ions (Eu3+) were successfully prepared using a flame combustion method. This material is suitable for various optical devices. The structure of prepared materials has been confirmed and characterized using X-ray powder diffraction (XRD), scanning electron microscope (SEM) and photoluminescence (PL) techniques. The luminescence properties of synthesized nanopowders were characterized by emission spectra and luminescence lifetimes by using the streak camera system. PL spectra were obtained at three different excitation wavelengths (Optical Parametric Oscilator (OPO) at 360nm, laser diode at 365nm and Ar laser line at 514.5nm). The strong emission lines at 611nm and 630nm corresponding to the 5D0→7F2 long lived transition could be used as a new red light source in optical devices.

J1110102 燃焼炎法による合成ダイヤモンド皮膜の表面粗さに及ぼす影響因子について([J111]摩擦・摩耗制御のための材料及び表面改質)

J1110102 燃焼炎法による合成ダイヤモンド皮膜の表面粗さに及ぼす影響因子について([J111]摩擦・摩耗制御のための材料及び表面改質)

821 表面粗さを考慮した燃焼炎法によるダイヤモンド皮膜合成

821 表面粗さを考慮した燃焼炎法によるダイヤモンド皮膜合成

Electrochemical Characterization of Pt Catalysts Supported on Sn0.96Nb0.04O2-δ and Sn0.96Sb0.04O2-δ with Aggregated Structure in Rotating Disk Electrode and Membrane Electrode Assembly Measurements

not Available.

Synthesis of nitrogen-doped diamond films using vibrational excitation of ammonia molecules in laser-assisted combustion flames

Nitrogen-doped diamond was synthesized in open air using laser-assisted combustion flame method. A wavelength-tunable CO2 laser was used to resonantly excite the vibration modes of ammonia molecules, which were added into the diamond forming combustion flame. The wavelength of the CO2 laser was tuned to match frequencies of the NH wagging mode of the ammonia molecules. High efficiency energy coupling was achieved at laser wavelengths of 9.219, 10.35, and 10.719 μm, which are related to a rotational–vibrational transition (1084.63 cm−1), and splitting of the NH wagging mode (υ2+, 932.51 cm−1 and υ2−, 968.32 cm−1). Vibrational excitations of the ammonia molecules under these wavelengths actively intervenes the reaction courses, which steers the chemical reaction in the combustion flame and eventually promotes nitrogen concentration in the deposited diamond films. Concentration of the doped nitrogen atoms reaches up to 1.5 × 1020 atoms/cm3 in the diamond films deposited with a laser wavelength of 9.219 μm. Optical emission spectroscopy and mass spectrometry were used to study the evolution of chemical reactions with and without laser excitations.

SYNTHESIS OF NANOCRYSTALLINE DIAMOND FILMS ON MOLYBDENUM SUBSTRATE BY FLAME COMBUSTION METHOD

The flame combustion method enables the synthesis of diamond using acetylene-oxygen gas flame combustion in ambient atmosphere. It has various advantages over other methods. In this study, to obtain nanocrystalline diamond films and to achieve good adhesion, diamond films were synthesized by flame combustion using a mixture of commercial or high purity acetylene and oxygen gas with the addition of nitrogen gas. Nitrogen gas added as the nanocrystalline diamond promotion agent; nitrogen flow rate was varied. According to the results, at the mixture of commercial acetylene and oxygen gas, as nitrogen flow rate was increased, the diamond nanocrystallites was high density on the microcrystallites. At the mixture of high purity acetylene and oxygen gas, the optimal nitrogen flow rate was 0.500 cm3/s, and the diamond nanocrystallites was synthesized continuously on the diamond microcrystallites. They sowed very high density.