• Wei Zhou

Articles written in Bulletin of Materials Science

• in situ templating synthesis of conic Ba0.5Sr0.5Co0.8Fe0.2O3–𝛿 perovskite at elevated temperature

Conic Ba0.5Sr0.5Co0.8Fe0.2O3–𝛿 (BSCF) functional composite oxide was synthesized via a simple in situ templating process. The treatment of the solid precursor with concentrated nitric acid resulted in the mismatch of ionic radius at 𝐴-site and 𝐵-site of the ABO3 perovskite, due to the oxidation of cobalt/iron ions, and the formation of Ba0.5Sr0.5(NO3)2 solid solution. Therefore, instead of the direct formation of BSCF oxide, an intermediate phase of Ba0.5Sr0.5CoO3 (BSC) in hexagonal lattice structure and with conic particle shape was preferentially formed during calcination at low temperature. BSCF perovskite was then produced by the in situ templating of BSC with iron diffusing into the BSC lattice during calcination at high temperature. Wellcrystallized BSCF particles in conic shape were obtained by the calcination of the nitric acid treated precursor at 900°C.

• Synthesis of nano-particle and highly porous conducting perovskites from simple in situ sol–gel derived carbon templating process

Nano-sized La0.6Sr0.4Co0.2Fe0.8O$_{3–\delta}$ (LSCF) and La0.8Sr0.2MnO$_{3–\delta}$ (LSM) oxides were synthesized by a simple in situ sol–gel derived carbon templating process. Nano-sized LSCF–carbon and LSM–carbon composites were first obtained with a grain size of 20–30 nm. Further calcination of the obtained composites under air resulted in the nano-sized pure-phase perovskites with crystalline size of as small as 14 nm. Such a decrease in crystalline size of perovskite via the indirect calcination process was ascribed to the suppressing effect of carbon in the grain growth of perovskite. Furthermore, when the in situ created carbon was applied as a template for pore forming, a highly porous perovskite sintering body packing from the nano-sized perovskite oxide was obtained.

• Biomass carbon materials derived from macadamia nut shells for high-performance supercapacitors

The new biomass carbonaceous materials were obtained from macadamia nut shells (MNS) by immersion method and high-temperature activation (MNSCA) for high-performance supercapacitors.The morphologies and microstructuresare investigated by X-ray diffractometer, Raman spectrometer, scanning electron microscopy and transmission electron microscopy. The experimental results show that the obtained activated carbon (MNSCA) exhibits perfect porous structurefilled with more micropores and mesopores.MNSCA displays high specific surface area of 1057 m$^2$ g$^{−1}$. The porous carbon delivers an impressive specific capacitance of 325.7 F g$^{−1}$ and has no capacitance loss at the current density of 2 A g$^{−1}$ after 10,000 cycles, which demonstrates the excellent cycle stability and high specific capacitance. The biomass carbonaceousmaterials derived from MNS can be expected for the widespread application of supercapacitors.

• Controllable preparation of hollow fibrous SrCO$_3$

A simple and economic CO$_2$ bubbling crystallization reactor for preparation of strontium carbonate (SrCO$_3$) was designed. Through monitoring pH and conductivity, hollow SrCO$_3$ fibres without any morphology control agents weresuccessfully obtained. The effects of temperature and CO$_2$ flow rate on the morphology of SrCO$_3$ were analysed. This study presents a new method for carbonate crystal control and growth.

• Bulletin of Materials Science

Current Issue
Volume 42 | Issue 6
December 2019

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Posted on July 25, 2019