No abstract

A green synthetic strategy to design biomassderived porous carbon electrode materials with precisely tailored structure and morphology has always been a challenging goal because these materials can fulfill the demands of next-generation supercapacitors and other electrochemical devices. Potassium hydroxide (KOH) is extensively utilized as an activator since it can produce porous carbon with high specific surface area and well-developed porous channels. The exploitation of sodium hydroxide (NaOH) as an activating agent is less referenced in the literature, although it offers some advantages over KOH in terms of low cost, less corrosiveness, and simple handling procedure, all of which are appealing particularly from an industrial viewpoint. The motivation for this present study is to fabricate porous carbon spheres in a sustainable manner via a spray drying approach followed by a carbonization process, using Kraft lignin as the carbon precursor and NaOH as an alternative activation agent instead of the high-cost and high-corrosive KOH for the first time. The structure of carbon particles can be accurately transitioned from a compact to hollow structure, and the surface textural properties can be easily tuned by altering the NaOH concentration. The obtained porous carbon spheres were applied as highly packed thin film electrode materials for supercapacitor devices. The specific capacitance value of porous carbon spheres with a highly compact structure (high packing density) is 66.5 F g −1 , which is higher than that of commercial activated carbon and other biomassderived carbon. This work provides a green processing for producing low-cost and environment-friendly porous carbon spheres from abundant Kraft lignin and important insight for selecting NaOH as an activator to tailor the morphology and structure, which represents an economical and sustainable approach for energy storage devices.

Mass transfer is an essential process that can extend the performance and utilization of nanoporous materials in various applications. Therefore, improving mass transfer in nanoporous materials has always attracted much interest, and macroporous structures are currently being studied to enhance mass transfer performance. The introduction of macroporous structures into three-way catalysts (TWC), which are widely utilized to control the emission of polluted gases from vehicles, provides the potential to enhance their mass transfer property and catalytic performance. However, the formation mechanism of macroporous TWC particles has not yet been investigated. On the other hand, the influence of the framework thickness of the macroporous structure on the mass transfer enhancement is still unclear. Therefore, this report investigates the particle formation and framework thickness of the macroporous TWC particles synthesized using the template-assisted aerosol process. The formation of macroporous TWC particles was precisely controlled and investigated by altering the size and concentration of the template particles. The template concentration played a crucial role in maintaining the macroporous structure and controlling the framework thickness between the macropores. Based on these results, a theoretical calculation showing the influence of template concentration on the particle morphology and framework thickness was developed. The final results showed that increasing the template concentration can positively affect the nanoporous material’s framework thickness reduction and mass transfer coefficient improvement.

We demonstrate the synthesis of spherical submicron YAG:Ce particles with controllable particle outer diameters and crystallite sizes and their photoluminescence properties, produced by a flame-assisted spray-pyrolysis method with annealing process.

β-Quartz solid-solution has received significant attention as a consequence of its remarkable properties, including a negative thermal expansion coefficient, high mechanical strength, and excellent chemical stability. However, to date, there is no report on the successful production of crystalline spherical β-quartz solid-solution particles. Herein, the crystalline spherical β-quartz solid-solution particles derived from cordierite were successfully fabricated via a flame method followed by a calcination process, representing the first-ever demonstration of this type of synthesis. In-depth investigations of the effect of flame parameters (e.g., adiabatic flame temperature and methane gas flow rate), calcination process conditions (e.g., calcination temperature and calcination time), and the additional amount of anti-sintering agent (e.g., nano-silica) on the particle morphology and crystallinity of β-quartz solid-solution particles were assessed. As a result, the morphology of particles was confirmed to transition from non-spherical to spherical while maintaining a crystalline structure based on optimization of the nano-silica concentration. The nano-silica played an important role in the formation of particles with high crystallinity and good sphericity even at high calcination temperatures. The flame spheroidization process demonstrated herein is a rapid and effective means of fabricating spherical β-quartz solid-solution particles without the use of prefabricated spherical precursors or the addition of template materials, and this efficient method is appropriate for large-scale applications.