Imparting CO₂ reduction selectivity to ZnGa₂O₄ photocatalysts by crystallization from hetero nano assembly of amorphous-like metal hydroxides

Imparting an enhanced CO₂ reduction selectivity to ZnGa₂O₄ photocatalysts has been demonstrated by controlled crystallization from interdispersed nanoparticles of zinc and gallium hydroxides. The hydroxide precursor in which Zn(II) and Ga(III) are homogeneously interdispersed was prepared through an epoxide-driven sol–gel reaction. ZnGa₂O₄ obtained by a heat-treatment exhibits a higher surface basicity and an enhanced affinity for CO₂ molecules than previously-reported standard ZnGa₂O₄. The enhanced affinity for CO₂ molecules of the resultant ZnGa₂O₄ leads to highly-selective CO evolution in CO₂ photo-reduction with H₂O reductants. The present scheme is promising to achieve desirable surface chemistry on metal oxide photocatalysts

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Mechanism of color development of the mud-mordanting dyed Oshima Tsumugi was studied by color measuring of dyed fabrics by defferent process ("Sharinbai" dyeing, Ca mordanting, Fe mordanting, mud-mordanting, separately). The result was as follows : [table

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Mechanism of flame retardation of the mud-mordanting dyed Oshima Tsumugi has been studied by several flammability tests (FF3-71,JIS L 1091 A-4,MAFT, Oxygen index) and SEM observation. The results were as follows : (1) Silk protein : High nitrogen content and low heat of combustion (2) Tannin : Char forming characteristics→suppress flaming combustion (3) Fe, (Ca) : Promoting the carbornization→increase in the char (4) Tannin-Ca-Fe complex : Covering the fiber→form an insulating char on the surface of the fiber→thermal barrier (1)+(2)+(3)+(4)→High flame retardanc

Formation Energies of Substitutional Sodium and Potassium in Hydroxyapatite

First-principles calculations are performed to investigate atomic and electronic structures of Na+ and K+ ions substituting for Ca2+ in hydroxyapatite (HAp). Formation energies of the substitutional defects are obtained from total energies of defective HAp supercells and chemical potentials determined by assuming chemical equilibrium between HAp and HAp-saturated aqueous solution containing Na+ or K+. It is found that substitutional Na+ with a charge-compensating interstitial proton is more stably formed, as compared to substitutional K+. This may be related to the fact that Na+ is generally more abundantly involved in bones and tooth enamels than K+

ハイドロキシアパタイト中の固溶原子の局所構造と電子状態

京都大学0048新制・課程博士博士(工学)甲第16038号工博第3361号新制||工||1508(附属図書館)28617京都大学大学院工学研究科材料工学専攻(主査)教授 田中 功, 教授 河合 潤, 教授 中村 裕之学位規則第4条第1項該当Doctor of Philosophy (Engineering)Kyoto UniversityDFA

Theoretical trend of ion exchange ability with divalent cations in hydroxyapatite

First-principles calculations are performed for hydroxyapatite (Hap) in order to investigate the relative ion exchange ability with divalent cations such as Mg2+, Ni2+, Cu2+, Zn2+, Sr2+, Cd2+, Ba2+, and Pb2+. Their ionic substitutional energies are calculated from total energies of supercells and chemical potentials for Ca2+ and the foreign cations determined under chemical equilibrium between HAp and its saturated solution. It is found that, in most cases, the ion exchange ability is basically dependent on the ionic sizes and the larger or smaller-sized cations than Ca2+ tend to exhibit more difficulty of substitution for Ca2+ in HAp. However, Pb2+ exhibits the extremely small substitutional energy, which originates from covalent bonds with the adjacent oxygen atoms. In particular, Pb2+ at the Ca-1 site of HAp has covalency with the second-nearest-neighboring oxygen atoms as well as the first nearest-neighboring ones. The covalent bond formation plays an important role for the distinct ion exchange ability for Pb2+ by HAp observed experimentally

First Principles Lattice Dynamics Calculations of Ag+ Doped KX (X = Cl, Br and I)

Phonon states of Ag doped potassium halides, KX:Ag+ (X=Cl, Br and I), are computed by a first principles lattice dynamic method using 64-atoms supercells. Results are compared to experimental data in literature. Phonon density of states of host KCl and KI crystals satisfactorily agree to the experimental inelastic neutron scattering data. Experimental frequencies of the impurity-induced infra-red (IR) and Raman active modes in the low frequency region are reasonably well reproduced because the vibrations are localized within the first nearest neighbour anions of the Ag+-ion. On the other hand, limitations of present calculations to reproduce the high frequency impurity-induced modes are pointed out. They are less localized to the Ag+-ion