A continuous bubble-column scrubber, capturing CO 2 gas by monoethanolamine (MEA) solution in a pH-stat operation, is used to search for optimum process parameters by means of the Taguchi method. The process variables are the pH of the solution, gas flow rate, concentration of CO 2 gas, and temperature. From the measured outlet CO 2 gas concentrations, the absorption rate and overall mass transfer coefficient can be determined with the support of a steady-state material balance equation as well as a two-film model. According to the signal-to-noise ratio, the significance sequence influencing the parameters and optimum conditions can be determined. CO 2 concentration and pH value proved to be decisive parameters, while temperature and gas flow rate were minor. Five sets of optimum conditions were obtained and could be further verified by empirical equations.

Structure determines material's functionality, and strain tunes the structure. Tuning the coherent epitaxial strain by varying the thickness of the films is a precise route to manipulate the functional properties in the low-dimensional oxide materials. Here, to explore the effects of the coherent epitaxial strain on the properties of SrCoO thin films, thickness-dependent evolutions of the structural properties and electronic structures were investigated by X-ray diffraction, Raman spectra, optical absorption spectra, scanning transmission electron microscopy (STEM), and first-principles calculations. By increasing the thickness of the SrCoO films, the c-axis lattice constant decreases, indicating the relaxation of the coherent epitaxial strain. The energy band gap increases and the Raman spectra undergo a substantial softening with the relaxation of the coherent epitaxial strain. From the STEM results, it can be concluded that the strain causes the variation of the oxygen content in the BM-SCO2.5 films, which results in the variation of band gaps with varying the strain. First-principles calculations show that strain-induced changes in bond lengths and angles of the octahedral CoO and tetrahedral CoO cannot explain the variation band gap. Our findings offer an alternative strategy to manipulate structural and electronic properties by tuning the coherent epitaxial strain in transition-metal oxide thin films.

Ionic defects, such as oxygen vacancies, play a crucial role in the magnetic and electronic states of transition metal oxides. Control of oxygen vacancy is beneficial to the technological applications, such as catalysis and energy conversion. Here, we investigate the electronic structure of SrCoO 3−x as a function of oxygen content (x). We found that the hybridization extent between Co 3d and O 2p increased with the reduction of oxygen vacancies. The valence band maximum of SrCoO 2.5+δ has a typical O 2p characteristic. With further increasing oxygen content, the Co ions transform from a high spin Co 3+ to an intermediate spin Co 4+ , resulting in a transition of SrCoO 3−x from insulator to metal. Our results on the electronic structure evolution with the oxygen vacancies in SrCoO 3−x not only illustrate a spin state transition of Co ions, but also indicate a perspective application in catalysis and energy field.

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Phase transformation represents a fascinating way to tune structural and optical properties of metal halide perovskites. This work demonstrate that the macrocyclic cyclodextrin could trigger transformation of cesium copper bromide,...