Flame-assisted Spray Pyrolysis Method Research Articles

Accelerated synthesis of Li(Ni0.8Co0.1Mn0.1)O2 cathode materials using flame-assisted spray pyrolysis and additives

Nickel-rich cathode materials are promising in lithium-ion battery applications because of their high energy density and low material cost. Unfortunately, reducing the synthesis cost of nickel-rich cathode materials is challenging because of the time-consuming and energy-intensive calcination. Therefore, the current work aims to explore strategies for significantly reducing the calcination time of nickel-rich cathode material Li(Ni0.8Co0.1Mn0.1)O2 (NCM811). We used a flame-assisted spray pyrolysis method to synthesize samples with and without using low-cost urea as an additive. Both in situ thermal X-ray diffraction (XRD) and ex situ XRD revealed that urea addition weakened the sensitivity of crystallization and cation mixing to calcination conditions. As a result, with only 20 min of calcination at 875 °C and without any preheating and ramping steps, the NCM811 sample showed an ordered layered structure and comparable electrochemical performance to those with long-time calcination. Moreover, the current work demonstrated that the shortened post calcination was benefited from lithium-embedded particles that likely improved the uniformity of lithium distribution in as-synthesized powder. Therefore, carefully designing initial lithium distribution in particles prior to calcination could also be a useful strategy for other synthesis methods to shorten high-temperature calcination steps, leading to significant reductions in energy consumption and fabrication cost.

Spherical submicron YAG:Ce particles with controllable particle outer diameters and crystallite sizes and their photoluminescence properties.

The purpose of this study was to demonstrate the preparation of spherical submicron YAG:Ce particles with controllable particle outer diameters and crystallite sizes and their photoluminescence (PL) properties, which were produced using a flame-assisted spray-pyrolysis method followed by the annealing process. The correlation of particle outer diameter, crystallite size, and PL performance of the prepared particles was also investigated. Experimental results showed that the increases in the particle outer diameters have an impact on the obtainment of higher PL performance. Large particle outer diameters permitted the crystallites to grow more, whereas this is in contrast to the condition for small particle outer diameter having limitations in crystallite growth. This study also found that too large outer diameter (>557 nm) was not effective since crystallites cannot grow anymore and it permits possible scattering problems. This study provides significant information for optimizing synthesis parameters for controlling particle outer diameters and crystallite sizes, which could be relevant to other functional properties, especially for lens, solar cell, and LED applications.

Fast Production of High Performance LiNi0.815Co0.15Al0.035O2 Cathode Material via Urea-Assisted Flame Spray Pyrolysis

The high throughput and rapid flame-assisted spray pyrolysis method has been adapted to synthesize cathode materials LiNi0.apCo0.15Al0.035O2 (NCA). This method is considered low cost and simple. By varying the precursor solution concentration and sintering temperature, the optimal condition was established at temperature sintering of 800 °C and precursor solution concentration of 1 M. X-ray diffraction patterns showed the as-prepared NCA particles exhibit a pure well-ordered hexagonal layer structure with high crystallinity. Polyhedral shaped micro-sized particles are confirmed by SEM images. Galvanostic charge–discharge tests were conducted using cylindrical full-cell utilizing artificial graphite as the anode. The highest specific initial discharge capacity measured between 2.7 and 4.3 V is 155 mAh g−1 with capacity retention of 92% after cycled at 0.2 C for 50 cycles. Thus, this method is considered as a satisfying approach for NCA mass production.

Synthesis of LiNi0.8Co0.15Al0.05O2 cathode material via flame-assisted spray pyrolysis method

Long reaction and long heat treatments have become major obstacles in producing cathode materials NCA (LiNi0.8Co0.15Al0.05O2) for Li-ion batteries. Flame assisted spray pyrolysis (FASP) method followed by sintering process requires shorter reaction and sintering time and considered suitable economical alternative in NCA production. The obtained ternary oxides particles from FASP have high crystalline and homogenous properties. Furthermore, XRD pattern of NCA products obtained by lithiation of ternary oxides exhibit well-ordered layered hexagonal structure. Electrochemical performance of NCA was tested in an NCA/graphite system at 2.7–4.3 V and current density of 20 mA/g. At the optimum sintering condition (under O2 rich atmosphere for 9 h), NCA particles show the initial specific discharge capacity of 143 mAh/g, and the capacity retention of 92% after 20 cycles. This results is higher from commercial available NCA particles (specific discharge capacity of 138 mAh/g) which indicates the promise of this approach for NCA production.

Synthesis of Potassium Silicate Nanoparticles from Rice Straw Ash Using a Flame-assisted Spray-pyrolysis Method

The purpose of this study was to synthesize potassium silicate nanoparticles from rice straw ash using a flame-assisted spray-pyrolysis method. Rice straw, as one of the agricultural wastes, was used as a source of silica. In the experimental procedure, rice straw was burned at 700°C for 3 hours to produce rice straw ash. Then, the rice straw ash was extracted using an alkaline method. We used potassium hydroxide (KOH) as an alkaline chemical agent as well as a source of potassium. The solution was then put into the flame-assisted spray-pyrolysis apparatus to produce potassium silicate nanoparticles. The results showed that the spray method can assist the production of spherical potassium silicate nanoparticles with sizes of about 50 nm.

Sintering inhibition of flame-made Pd/CeO2 nanocatalyst for low-temperature methane combustion

Dispersed palladium on the high-surface-area ceria support is synthesized via one-step flame-assisted spray pyrolysis method, which applies a highly-quenched stagnation-point flame controlling catalyst sizes and structures. The X-ray photoelectron spectroscopy (XPS) spectra of Pd show a significantly high binding energy for flame-made Pd/CeO2 catalysts, possessing a value of 1.7eV larger than the reference value in literature. It suggests that the partial electron transfer occurs from metal Pd to their supports during the synthesis process, which creates Pd electron-deficient (cationic Pdδ+) and Ce electron-rich (anion Ceδ−), respectively. The catalytic activities of CH4 oxidation are performed over the temperatures ranging from 200°C to 600°C. In comparison with inert support materials, the synergistic effect is found between palladium and support ceria that leads to the enhanced catalytic activity. During the heating and cooling cycles of CH4 oxidation, Pd/CeO2 catalysts exhibit an exceptional inhibition effect against the sintering of Pd cluster and its dispersion decrement, which is related to strong electronic interaction of metal-support interfaces induced by the aforementioned partial electron transfer.

Ultra-violet C absorption and LPG sensing study of zinc sulphide nanoparticles deposited by a flame-assisted spray pyrolysis method

Solvent processed spray pyrolysis is a technique that has attracted worldwide interest for the synthesis of nanoparticles. Zinc sulphide (ZnS) belongs to a category of practical semiconductors known as metal sulphides, and it is used extensively as an optical material. In the present article, ZnS nanoparticles were successfully synthesized using flame-assisted spray pyrolysis. X-ray diffraction confirmed the formation of ZnS with an excellent crystalline structure, while scanning electron microscopy indicated that the as-synthesized materials were nanoparticles. Ultraviolet–visible spectroscopy was utilized to evaluate the optical property of the resulting product and revealed that ZnS nanoparticles have the capacity to absorb ultra-violet C. In addition, various liquefied petroleum gas (LPG) sensing properties of the ZnS nanoparticles were also evaluated.

Synthesis of composite WO3/TiO2 nanoparticles by flame-assisted spray pyrolysis and their photocatalytic activity

Abstracts Combining of tungsten trioxide (WO3) with titanium dioxide (TiO2) have been an interesting research subject because different from conventional TiO2 material, this composite can be used and activated under visible-light irradiation and has better photocatalytic efficiency. The purpose of this study was to synthesize composite WO3/TiO2 nanoparticles and to investigate the detail effect of composition of ammonium metatungstate (AMT, as a WO3 source) and titanium isopropoxide (TTIP, as a TiO2 source) in the wide range composition ratio on particle morphology (i.e.,outer size (from 20 to 90 nm), shape, and structure), crystallinity, and photocatalytic performance. To synthesize composite WO3/TiO2 nanoparticles, a flame-assisted spray-pyrolysis method was used. Experimental results showed that the amount of AMT (from 0 to 25 wt%) had shown a significant impact on the photocatalytic performance, however deviation of this amount had improve catalyst performance slightly. The change of photocatalytic activity is mainly influenced by band gap energy and surface area. To confirm the fundamental reason for this catalytic improvement, the effect of WO3 and TiO2 amounts on surface area, light absorbance, and charge separation analysis was investigated. The experimental results were also completed along with the proposal photocatalytic mechanism of particles containing WO3 and TiO2. In addition, although our present photocatalytic activity still needs to be improved, the present results open new information for creating more varied properties for application explorations.

CuO/WO 3 and Pt/WO 3 nanocatalysts for efficient pollutant degradation using visible light irradiation

CuO/WO 3 and Pt/WO 3 nanocatalysts with a nanorod morphology were used for photodegradation of organic compounds using visible light irradiation. Both nanocatalysts were prepared using flame assisted spray pyrolysis method (FASP). The prepared nanocatalysts were mechanically stable during the agitation treatment for the photodegradation test due to good interconnection between WO 3 and co-catalysts. The enhancement of photocatalytic activity was observed after the addition of CuO and Pt as co-catalysts. The addition of CuO would change the morphology of WO 3 from nanorods to cubic. The optimal concentration of the CuO addition was 0.33 wt.%. A low Pt concentration (0.12 wt.%) was required for optimal photocatalytic activity of the Pt/WO 3 nanocomposite. The addition of Pt affected neither the morphology nor the crystallite structure of WO 3.

Role of urea addition in the preparation of tetragonal BaTiO 3 nanoparticles using flame-assisted spray pyrolysis

In this study, flame-assisted spray pyrolysis (FASP) was used to produce BaTiO 3 nanoparticles with relatively high tetragonality and controlled sizes from 23 to 33 nm in a one-step process. The addition of urea into the precursor is the key factor for the formation of tetragonal BaTiO 3 nanoparticles; the lack of urea addition led to the formation of submicrometer BaTiO 3. The formation of BaTiO 3 nanoparticles was suggested from the disintegration of submicrometer particles due to the decomposition of urea presented in the interconnection of their primary particles. Also, combustion of the decomposed gases of urea produced additional heat, which improved the tetragonality of the BaTiO 3 nanoparticles. Tetragonality was enhanced from 1.0051 to 1.0071 by increasing the urea addition to as high as 4 M. The results of the present study show that addition of urea to the precursor is an effective strategy for the direct production of tetragonal BaTiO 3 nanoparticles using the FASP method.