Papers by Author: Guo Qiang Tan

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Authors: Guo Qiang Tan, Cheng Zhang, Hong Yan Miao, Hui Jun Ren, Ao Xia
Abstract: BaTiO3 thin film was prepared by the self-assembled monolayers technique and liquid phase deposition. The effects of pH values and the deposition temperature on the formation of BaTiO3 film were studied. The results showed that the Si substrate was in the precursor solution with 0.025mol/L (AHFT/BN/BA=1:1:3) and pH= 1.5. At 45°C deposited for 8h and annealed at 600°C for 2h, the BaTiO3 film with higher crystalline was prepared on the functionalized Si substrate. XRD and SEM tests showed that the film deposited in the precursor solution with different pH values appeared BaTiO3 characteristic peaks on the surface of every crystal. As pH values increased to 1.5 from 0.5, the strength of the film diffraction peak increased. But the width of the peak became smaller and the crystalline increased. When pH value was 2, due to the self-polymerized deposition of [Ti(OH)6]2-, it was easy to form the larger particles on the substrate. When the deposition temperature was 45°C, the acicular BaTiO3 film formed with the regular order and homogeneous planeness on the substrate. When the deposition temperature was between 55°C and 60°C, the dewatering and polymerizing speed between [Ti(OH)6]2- ions was higher than that between [Ti(OH)6]2- and -OH. The adsorption of the film to the Si substrate was weakened. It was easy for the film to fall off.
Authors: Hai Yang Bo, Guo Qiang Tan, Hong Yan Miao, Ao Xia
Abstract: Bismuth ferrite powders were synthesized by a simple citric acid complexing co-precipitation method at much lower temperature of 600°C. The work studies the calcination temperature and molar ratio of Fe and Bi on the structure and morphology. The as-prepared BiFeO3 powder was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscope and Fourier transform infrared spectrophotometer. The result shows that the phase pure BiFeO3 powders with cubic morphology were prepared as the calcination temperature was 600°C and molar ratio of Fe and Bi was 1:1. The nanoparticles was uniform with the size of about 200nm.
Authors: Jing Yun Ma, Hong Yan Miao, Guo Qiang Tan, Zheng Qiu Sun
Abstract: Barium strontium titanate (BST) ferroelectric thin films have been successfully prepared on the single crystal silicon substrates using hydrothermal crystallization of sol-gel precursor, which combined the conventional sol-gel process and the hydrothermal method. The precursor film was deposited by the dip-coating method. The multiplayer BST gel films were hydrothermally treated in a Teflon vessel at low temperature of 160-180 °C for 1-3.5 h. The influences of the reaction conditions on the structure and crystallizing degree of BST thin films were discussed. We find that the temperature of as-dried gel films and post hydrothermal treatment are the critical parameters determining the quality of formation of BST thin films. Under optimized conditions, we can obtain well-developed perovskite BST films with smooth and pinhole-free surfaces. These results reveal that this technique is a promising low temperature process for the fabricating of thin films.
Authors: Hong Yan Miao, Min Dong, Guo Qiang Tan, Yong Ping Pu, Zheng Qiu Sun
Abstract: Bismuth titanate nanopowders were prepared by the hydrothermal method from Bi(NO3)3·5H2O, TiCl4 and KOH aqueous solution. The influences of reaction temperature and KOH concentration on the crystalline phase, morphology, and grain size of the prepared Bi4Ti3O12 powders were investigated. The results showed that well-crystallized, dispersive Bi4Ti3O12 nanopowders could be prepared by the hydrothermal treatment at 220–260°C for 6 h, in the case of [Ti]= 0.1 M, Bi:Ti = 4:3 and [KOH]=1.0–2.0 M. The prepared Bi4Ti3O12 powders of the orthorhombic structure were observed to be rectangle slice-shaped, and the grain sizes were about 30 nm in width and above100 nm in length. It was also confirmed that the desired concentration of KOH decreased with increasing of the treatment temperature.
Authors: Shi Ping Wang, Hong Yan Miao, Guo Qiang Tan
Abstract: Sodium-potassium Niobate (K0.4Na0.6NbO3, KNN) nanopowders were prepared by hydrothermal synthesis at the temperature range of 140-180°C for 12-48h using Nb2O5, NaOH and KOH as source materials. By means of XRD and SEM techniques, the effects of composition and hydrothermal treatment process, such as the rate of [R]/[Nb], the concentration of the alkali, the hydrothermal treatment temperature and the hydrothermal treatment time, on the microstructures and the crystallinity of alkali metals niobate were investigated in details. Results show that K0.4Na0.6NbO3 powders could be achieved by hydrothermal synthesis at the temperature range of 140-180°C with the alkalinity concentration of 2-8M. With the increase of hydrothermal reaction temperature and time, the crystallinity of KNN particles was improved. The obtained K0.4Na0.6NbO3 polycrystalline particles have rhombic structure.
Authors: Lei Cheng, Guo Qiang Tan, Hong Yan Miao, Yan Wang
Abstract: The experimental makes use of the liquid-phase reaction of self-assembly method, we immerse the functional glass substrates into the precursor solution to prepare SrTiO3 films, which makes (NH4)2TiF6, Sr(NO3)2, H3BO4 as raw materials, then study the growth status of SrTiO3 thin films under different pH values of precursor solution, the morphology and the phase of the films are characterized by OMS, XRD and SEM, it is shown that when the pH value of the precursor solution under 2.0, the SrTiO3 films are unable to grow, when the pH value above 3.0, a white emulsion liquid precursor solution occurred, as a result, SrTiO3 films deposition can’t be achieved. And when the pH value between 2.0 and 3.0(contain both), with the pH value increasing the deposition time of the SrTiO3 films decreases. After annealing treatment at 600°C, we can have a conclusion that under these conditions the phase of the films are pure SrTiO3 films, the surface is smooth and the grains grow uniformly.
Authors: Hong Yan Miao, Jia Li, Guo Qiang Tan
Abstract: Polycrystalline BiFeO3 multiferroic films were fabricated on Ti substrates by hydrothermal method from an aqueous Bi (NO3)3•5H2O, FeCl3•6H2O and NaOH solution. The films grow in alkaline solution at low temperatures of 120°C-240°C for 18 hours. XRD analysis showed that well-developed crystallines with single perovskite crystal phase were obtained. It was also found that the increase of reaction temperature and concentration of NaOH were favorable for crystal growth and crystallographic regularization. The microstructure, thickness and cross-section of the films were characterized by FE SEM and EDS. Results indicated that dense and homogeneous BiFeO3 thin films could be obtained in an appropriate hydrothermal condition.
Authors: Zheng Qiu Sun, Hong Yan Miao, Guo Qiang Tan, Ao Xia
Abstract: 3Y-TZP ceramics were fabricated with the addition of 10wt% MgO-Al2O3-SiO2 glass additive by cold-isostatic pressing and afterwards liquid-phase sintering at 1200-1400°C for 2 h. The densities of samples sintered at 1300°C for 2 h reaches 99.1%, but further increase of sintering temperature results in the decrease of densities. XRD analysis showed that the cordierite crystals and a small amount of amorphous phase were presented at the grain junctions, and SEM observation indicated that the mean grain size of ZrO2 with round-shape ranged from 200 to 300 nm, which was below the critical transformation size, and the increase in sintering temperature was accompanied with an increase in the mean grain size. The strength and toughness of samples were kept in the range of 396-528 MPa, 4.4-5.8 MPa·m1/2 respectively, which could meet the need of clinical applications of all-ceramic dental materials.
Authors: Hong Yan Miao, Zhi Wei Yu, Guo Qiang Tan
Abstract: Bi2Fe4O9 nanoparticles were prepared at low temperature via a facile, one-step hydrothermal synthesis process using iron(III) nitrate nonahydrate (Fe(NO3)3•9H2O) and bismuth nitrate pentahydrate (Bi(NO3)3•5H2O) as starting materials and sodium hydroxide (NaOH) as precipitant and mineralizer. XRD results indicated that the as-prepared nanoparticles are pure orthorhombic Bi2Fe4O9. SEM images revealed that the as-prepared Bi2Fe4O9 nanoparticles have a sheet-like morphology. They are paramagnetic at room temperature demonstrated by the magnetic measurements.
Authors: Hong Yan Miao, Jing Yun Ma, Guo Qiang Tan
Abstract: Barium strontium titanate, BST (BaxSr1-xTiO3), nanoparticles were prepared by a sol-gel hydrothermal technique. BST powders of different composition (x=0.1, x=0.3, x= 0.5, x=0.7, x=0.9) prepared by sol-gel technique previously were treated by hydrothermal synthesis method later. XRD results indicated that the as-prepared perovskite BST nanoparticles have the accurate proportioning composition. These results showed that the combination of sol-gel and hydrothermal technique would become a potential and promising process for fabricating BST and other nanopowders.
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