Papers by Author: Jian Lin Shi

Abstract: Cr-doped Y3ScxAl(5-x)O12(Nd:YSAG) powder have been prepared with a combustion method. The powders are nanosized and a pure cubic phase when calcined at 900°C. Transparent Cr:YSAG ceramics were successfully fabricated by sintering the powder compact at 1800°C under H2 atmosphere. The optical properties were investigated in detail. It was found that after Sc substitute for Al, the The octahedral crystal-field parameter Dq and Dq/B was reduced, and that is why the absorption peak move to the longer wavelength side but the emission peak not moved.

Abstract: A series of layered-structure Bi-based oxychlorides such as BiOCl, Bi3O4Cl, Na0.5Bi1.5O2Cl, Bi4NbO8Cl and MBiO2Cl (M = Ca, Sr, Ba, Cd, Pb) used as efficient photocatalysts. Among them, Bi3O4Cl (Eg = 2.79 eV), Na0.5Bi1.5O2Cl (Eg = 3.03 eV), Bi4NbO8Cl (Eg = 2.38 eV) and PbBiO2Cl (Eg = 2.45 eV) are visible-light-responsive. The powders synthesized by solid state reactions were characterized by X-ray diffraction (XRD) and UV-Vis diffuse reflection spectrum. Their photocatalytic activities were evaluated by the degradation of methyl orange. The results generally show that the UV-induced photocatalytic performances of the novel oxychloride catalysts are better than or comparable to that of anatase TiO2. The high photocatalytic performance of Bi-based oxychlorides is mainly ascribed to the presence of strong internal static electric fields between layers.

Abstract: Nd:Gd2O3-HfO2 powder has been prepared with a co-precipitation method. The size of Nd:Gd2O3-HfO2 powder is near 50nm. Transparent Nd:Gd2O3-HfO2 ceramics were successfully fabricated by sintering the powder compact at 1800°C under H2 atmosphere. The synthesis process and optical properties were investigated in detail. By measuring the optical properties of transparent Nd:Gd2O3-HfO2 ceramics, we found that the absorption bond of Nd ions near 808nm is enlarged, and the FWHM of the emission bond near 1060nm is near 25nm. It was believed that Nd:Gd2O3-HfO2 transparent ceramic is potential laser material for the usage in solid-state heat-capacity laser(SSHCL) application.

Abstract: Eu-doped CaS phosphors were prepared from sulfurization of CaCO3 in H2S gas without flux. The doping of Eu activator was conducted in two different modes: synchronous doping during sulfurization of CaCO3 and subsequent doping by vacuumly calcinning pure CaS and Eu2O3. Comparison of the as-prepared samples indicated that subsequent doping led to larger optimum Eu concentration and lower red emission intensity than synchronous doping. The different luminescence properties are ascribed to the different activator distributions in CaS host induced by different doping modes, and the uniform distribution resulted from synchronous doping is beneficial to the luminescence of the phosphor.

Abstract: ZnS:Cu,Cl phosphors were synthesized by high temperature (1200 °C) solid state reaction, mechanical milling (rotation speed = 0, 75, 150, 250 and 350 r / min) and the final annealing at 750 °C for 1 h in different atmospheres (hydrogen sulfide, sealed evacuated silica tubes and Ar). The as-prepared phosphors were characterized by X-ray powder diffraction and photoluminescence spectra. It was found that mechanical milling led to width increases of diffraction peaks. Both the mechanical milling and atmosphere play important roles in the photoluminescence performance of the phosphors. Some phosphors prepared by the three-step method possess higher photoluminescence performances than the normal one-step method. Particularly, the luminescence intensity of the phosphor milled at the rotation speed of 75 r / min and then treated in Ar atmosphere is about one time higher than that prepared by the normal one-step process.

Abstract: La2(MoO4)3 microcrystals with rodlike morphology have been successfully grown through hydrothermal microemulsion process at 180°C, pH =9 and 12 h. Quaternary microemulsion is composed of CTAB/water/hexane/n-pentanol. The obtained sample is characterized by means of XRD, FESEM, TEM. Formation mechanism is preliminarily discussed.

Abstract: Ultrafine terbium-doped Lu2Hf2O7/Tb phosphor powders are prepared by a solution combustion process using glycine and urea as fuel. Phase evolution of the synthesized powder is determined by X-ray diffraction (XRD) techniques. Single-phase cubic Lu2Hf2O7/Tb crystalline powder is obtained by calcining the amorphous materials at 800oC and no intermediate phase is observed. Transmission electronic microscope (TEM) morphology shows that the resultant Lu2Hf2O7/Tb powders have uniform size and good homogeneity. The photoluminescence (PL) spectra of Tb3+ substituted for Lu3+ in Lu2Hf2O7 with different content has been measured on samples calcined at 1000oC.

Abstract: A family of mesoporous multilamellar silica vesicles has been successfully synthesized by using P123 as structure directing agent and hexane as co-surfactant. The structure was characterized with XRD, TEM, and N2 adsorption-desorption isotherms. This multilamellar silica vesicle materials process high specific area, large pore volume, and a bimodale pore size distribution. Furthermore, these materials are stable when the surfactant is removed at 530 oC.

Abstract: High ordered mesoporous carbon molecular sieves designated as CMK-3 and CMK-5 was synthesized using mesoporous silica SBA-15 as hard template, pre-polymerized furfuryl alcohol as a carbon souse by one-step impregnation. The effect of the furfuryl alcohol to silicas ratio have been investigated. XRD pattern, N2 sorption, FE-SEM, TEM, TG-DSC was used to characterize the property of the product. These results show that the CMK-3 and CMK-5 type mesoporous carbon can be controlled and facilely obtained.

Abstract: A novel and thermally stable hierarchically porous yttrium doped zirconia material with crystallized framework has been synthesized in a facile process. XRD, nitrogen adsorption analysis, FESEM, FETEM, were used for the structural characterizations. This novel hierarchically porous zirconia shows a well-defined ordered macroporous structure, a broad distributed mesoviods, and a very uniform mesoporous pore-distribution. Small amount of yttrium can be helpful to increase the thermal stability of the prepared hierarchically porous zirconium oxide.