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Shanjun Ke,Yanmin Wang,Zhidong Pan,He-Ping Zeng 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.3
Neodymium disilicate powders were synthesized via a sol-precipitation method with different precipitants (i.e., ammonia,ammonium bicarbonate and urea) and subsequent sintering. The samples were characterized by X-ray diffraction. In addition,a theoretical relationship between neodymium ion concentrations in different precipitation equilibrium solutions was alsoinvestigated and analyzed based on thermodynamic equilibrium calculation. The results show that the precipitant type has animpact on the phase compositions of the precursors and the sintered products. In the synthesis, neodymium ions can becompletely precipitated as amorphous neodymium hydroxide with ammonia as a precipitate at pH 8~9. For ammoniumbicarbonate as a precipitate, the precursor type is related to both carbon concentration and pH value. The excessive hydroxideforms neodymium hydroxycarbonate in a heated urea solution. The possible formation mechanism of silicon sol in the presenceof different precipitants was discussed.
Shanjun Ke,Yanmin Wang,Zhidong Pan,He-Ping Zeng 한양대학교 세라믹연구소 2019 Journal of Ceramic Processing Research Vol.20 No.3
A ceramic pigment of neodymium disilicate (i.e., Nd2Si2O7) was synthesized via solid-state reaction with pre-grinding assistanceand a mineralizer. The effects of pre-grinding and mineralizer (i.e., lithium chloride, boric acid and calcium fluoride) on thephase, microstructure and coloring properties of ceramic pigment were investigated by differential thermal analysis, X-raydiffraction, scanning electron microscopy and reflectance spectra in the visible range from 400 nm to 700 nm, respectively. Theresults show that the reaction temperature of Nd2Si2O7 can be decreased by pre-grinding, and the temperature of forming soleNd2Si2O7 phase is further decreased by 200 oC when lithium chloride is used as a mineralizer. Boric acid as a mineralizer canlead to an uneven distribution of Nd and Si components. The sample synthesized with calcium fluoride as a mineralizer cannotobtain Nd2Si2O7 phase. Nd2Si2O7 can be synthesized effectively when lithium chloride is used as a mineralizer.
Synthesis, crystal structure, and near-infrared reflective properties of ZnSxSe1-x nanopigments
Ti Zhang,Yanmin Wang,Shanjun Ke,Zhidong Pan 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.4
In this research, a series of near-infrared (NIR) reflecting nanopigments, based on ZnSxSe1-x (x = 1, 0.75, 0.55, and 0.35), havebeen synthesized via a coprecipitation reaction and subsequent calcination. Furthermore, their crystal structure, particlemorphology, chromatic properties, and NIR reflectance have been investigated in detail; the results show that ZnSxSe1-xpigments have a cubic zinc-blende structure with a space group of F-43m(216), and the pigments’ microstructure presents theagglomerates composed of the spherical particles of different nanosizes. ZnSxSe1-x pigments exhibit not only colors rangingfrom ivory white to bright yellow but also significant NIR solar reflectance, ranging from 80.96% to 86.65%.