Papers by Keyword: Precipitation Process

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Authors: Nobuyuki Kawashima, Peter G. Self, William M. Skinner, Roger St.C. Smart
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Authors: Natpasit Chaithanatkun, Korakot Onlaor, Thutiyaporn Thiwawong, Benchapol Tunhoo
Abstract: A chemical precipitation method was used to prepare zinc oxide (ZnO) nanostructure in the present of zinc nitrate and ammonium hydroxide as zinc precursor and hydroxide precursor respectively. The effect of the hydroxide concentration and the effect of adding ascorbic acid as modifier into the mixture solution on the morphology property of zinc oxide was studied. The morphology and the structural of ZnO nanostructures were investigated by field-emission scanning electron microscope (FE-SEM) and X-ray diffractometer (XRD) techniques, respectively. The results showed that the basicity solution and adding stabilizer are important parameters on the morphology and structural properties of ZnO nanostructure. At a low hydroxide concentration, ZnO exhibited flower-like structure with short petal. With a further increase to higher concentration, ZnO crystal have more crystal directional growth. When the ascorbic acid was added, the morphology changed to particle-like structure. ZnO nanostructure with different shape might be used for specific applications such as gas sensor etc.
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Authors: Ryoichi Monzen, Toshiro Sakai, Chihiro Watanabe
Abstract: The precipitation processes from G.P. zones to γ’ in a Cu−0.9wt%Be alloy single crystal containing only the G.P. zones parallel to the matrix (001)α plane are investigated by high-resolution electron microscopy. The precipitate phases follow a G.P. zone → γ” → γI + γ’ sequence. The G.P. zone to γI phase transformation occurs successively via γ” during aging, while the γ’ phase heterogeneously precipitates on the γI phase. From length-change measurements during aging, the misfit strains of γ’ precipitates in directions perpendicular and parallel to [001]α are estimated as ε11 =ε22 = −0.03 and ε33 = −0.09, respectively. The observation that the estimated absolute value of ε33 is much smaller than that of ε33 = −0.25 calculated using lattice parameters of the γ’ phase and Cu matrix is understood in terms of the relaxation of ε33 by interfacial misfit dislocations.
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