Observing and modeling the sequential pairwise reactions that drive solid-state ceramic synthesis

Solid-state synthesis from powder precursors is the primary processing route to advanced multicomponent ceramic materials. Designing ceramic synthesis routes is usually a laborious, trial-and-error process, as heterogeneous mixtures of powder precursors often evolve through a complicated series of reaction intermediates. Here, we show that phase evolution from multiple precursors can be modeled as a sequence of pairwise interfacial reactions, with thermodynamic driving forces that can be efficiently calculated using ab initio methods. Using the synthesis of the classic high-temperature superconductor YBa$_2$Cu$_3$O$_{6+x}$ (YBCO) as a representative system, we rationalize how replacing the common BaCO$_3$ precursor with BaO$_2$ redirects phase evolution through a kinetically-facile pathway. Our model is validated from in situ X-ray diffraction and in situ microscopy observations, which show rapid YBCO formation from BaO$_2$ in only 30 minutes. By combining thermodynamic modeling with in situ characterization, we introduce a new computable framework to interpret and ultimately design synthesis pathways to complex ceramic materials

Surface morphology control of thin films prepared by solution processes and its application

Surface morphology of materials brings various new properties to the surface, and thus, the control of the surface morphology is very important. In this paper, surface morphology control of sol-gel derived films using several processes has been reviewed. Hot water treatment (bottom up process), combination of UV-irradiation and chemical etching (top down process), and micropattern formation using a hydrophobic-hydrophilic patterned surface were reported. (C)2013 The Ceramic Society of Japan. All rights reserved

ジエチレングリコール及びエチレングリコールモノエチルエーテル中における化学修飾されたアルミニウムトリセカンダリーブトキシドの前駆体構造

Precursor structure of chemically modified Al(O-sec-Bu)3 with ethyl acetoacetate or diethanolamine, dissolved in diethylene glycol (DEG), ethylene glycol monoethyl ether (EGE), and sec-butyl alcohol (sec-BuOH), was investigated using 27AlNMR. 27AlNMR spectra revealed that the reaction of DEG or EGE with Al(O-sec-Bu)3 led to the formation of six-coordinated structural units. The precursor structure of Al(O-sec-Bu)3 modified with ethyl acetoacetate in EGE, which consisted of six- and five-coordinated structural units, was almost the same as that in DEG, but different from that in sec-BuOH, where four-coordinated structural units were also observed. In Al(O-sec-Bu)3 modified with diethanolamine, five- and six-coordinated structural units were present in all the solvents used in this study and the effect of solvents on the coordination state was very small