Papers by Author: Jian Min Liu

Abstract: An innovative two-step route was successfully applied to the ionic liquid-assisted synthesis of C@ZrSiO₄ ceramic pigments, which is able to reduce the reflux time from many hours to a few minutes. The structure and morphology of the inclusion pigments were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). And the chromatic value of the pigments was measured by the CIE color system. The results show that the pigment in the absence of ionic liquid (IL) exhibited homogeneous single t-ZrO₂ phase, while the samples in the presence of IL showed coexistence of two crystal phases (m-ZrO₂ and ZrSiO₄). The CIE coordination L* value decreased with the increase of TEOS amounts due to the pure zircon formation. The as-prepared pigment showed high tinting ability, as L*=37.16, a*=0.71, b*=0.3, making it promising candidate for ceramic decoration.

Abstract: BaTiO₃ (BT) nano powder was prepared via non-hydrolytic sol-gel (NHSG) method by using barium acetate, titanium tetrabutoxide as precursors, glycerol and ethanol as solvents. The samples were characterized by DTA-TG, XRD, FT-IR and TEM. The influences of heat treatment temperature on the morphology and the microstructure of powder were studied, and the mechanism of low temperature synthesis was discussed. In addition, the de-esterification action between the precursors was also described in detail. The results show that the formation of Ba-O-Ti bond in the xerogel via NHSG route is duo to the de-esterification polycondensation of barium acetate and titanium tetrabutoxide, which plays the key role in the low temperature synthesis of BT powder. With the temperature rising to 700 °C, BT nano powder with good dispersion and even size distribution can be acquired and the average particle diameter is about 25 nm. Overlow and overhigh heat treatment temperatures are both not beneficial to the preparation of BT nano powder.

Abstract: Aluminium titanate (AT) ultrafine powder was prepared via hydrolytic sol-gel (HSG) method using aluminium nitrate (Al (NO₃)₃·9H₂O) and titanium tetrachloride (TiCl₄) as precursors as well as ethanol as solvent. Water required for hydrolysis reaction was supplied by the crystal water of aluminium nitrate itself. The effect of gelation processes, i.e. reflux and solvothermal treatment, on synthesis of AT powder was investigated by means of DTA-TG, XRD, SEM, and TEM, etc. The result shows that the gelation process has significant effect on the synthesis of AT powder. By reflux process, AT powder was synthesized at 1350 °C with average particle size above 1μm and serious agglomeration. Through solvothermal treatment process, however, AT powder with average particle size less than 150 nm was prepared at 1050 °C at a relatively high synthesis rate, which is due to the refinement reactants by the solvothermal treatment.

Abstract: Aluminum titanate (Al₂TiO₅) powder has been synthesized at low temperature via nonhydrolytic sol-gel method by using aluminum powder as aluminum source, titanium tetrachloride as titanium source, anhydrous ethanol as oxygen donor with different catalysts. The phase transformation of aluminum titanate xerogel powder during heat treatment and the influence of the mixing orders of raw materials, catalyst kinds on the synthesis of aluminum titanate were investigated by means of differential-thermal analysis (DTA-TG), X-ray diffraction (XRD), transmission electron microscope (TEM). The results indicated that aluminum titanate powder was easily synthesized at 750 °C by using AlCl₃ as catalyst with a mixing order of adding TiCl₄ before AlCl₃ into aluminum alcohol mixture. The catalytic order of the different catalysts in the preparation process of aluminum titanate is: FeCl₃> AlCl₃> MgCl₂. The catalyst promoted the activation of metal aluminum powder and played a major role in the synthesis of aluminum titanate powder at low temperature via nonhydrolytic sol-gel method.

Abstract: nclusion pigments of ZrSiO₄/C were prepared by nonhydrolytic sol-gel (NHSG) method combined with the process of carbon black modification. The crystalline phases, microstructure, functional groups on the surface of carbon black and chromatic value of the pigments were characterized by XRD, TEM, FTIR and Colorimeter, respectively. The surface structural changes of the carbon black modified by nitric acid and the influences of process parameters on the chromatic value of the pigments were also investigated. The results show that the process of carbon black modification enhances the affinity and binding force between carbon black and ZrCl₄ sol, which contributes to improve the effect of carbon black wrapped by ZrSiO₄. The ZrSiO₄/C inclusion pigment were obtained after calcining at 1000 °C for 8 h, and the L*, a* and b* value is 53.88, 0.74, and 1.88, respectively.

Abstract: Zircon nano–powder has been synthesized via the non-hydrolytic sol–gel route, using industral zirconium tetrachloride (ZrCl₄) and tetraethoxysilane (TEOS) as precursors, lithium fluoride (LiF) as mineralizer, PEG1000 as dispersant. The effects of solvents on the synthesis and dispersion of zircon nano-powder were investigated by means of XRD and TEM. The results indicate that the aprotic solvent N, N-dimethyl formamide (DMF) is not conducive to the nucleophilic substitution reaction, which directly affect the zircon synthesis, and the particles are easy to agglomerate due to the large surface tension; the powder with size of 30nm and good dispersion can be obtained using dichloromethane (CH₂Cl₂) as solvent; different anhydrous alcohols as solvents influence zircon synthesis, the order of the synthesis ratio is listed as EtOH›propanol (PrOH)› isopropanol (PrⁱOH). Powder particles are larger than 50nm with wide distribution and serious agglomeration when taking PrOH and PrⁱOH as solvents. Nano-zircon with good dispersion and synthesis ratio up to 94.5% can be obtained via using ethanol as solvent.

Abstract: Freestanding diamond film was prepared by hot filament chemical vapor deposition (HFCVD) method. Inter-Digital Transducer (IDT) was formed on the nucleation side of freestanding diamond film by photolithography technique. Then piezoelectric AlN film was deposited by RF reactive magnetron sputtering to obtain the AlN/diamond film structure. Surface morphologies of the nucleation side and the IDT were characterized by atomic force microscopy (AFM) and optical microscopy. The results indicated that the surface of nucleation side was very smooth and the IDT was of high quality without discontinuity and short circuit phenomenon. Room temperature frequency dependence of dielectric constant and dielectric loss for freestanding diamond film suggest a good stability of dielectric properties in high frequency region for diamond film. X-ray diffraction (XRD) pattern of the structure of AlN /diamond film structure showed a strong diffraction peak of AlN (002), which indicated that as-sputtered AlN film was highly c-axis oriented.