• Qin Zhou

      Articles written in Bulletin of Materials Science

    • Preparation of Ti3AlC2 by mechanically activated sintering of 3Ti/Al/2C/0.2Sn

      Baoyan Liang Mingzhi Wang Xin Han Qin Zhou Xin Li

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      The mechanically activated sintering process was adapted to synthesize titanium aluminum carbide (Ti3AlC2) at low temperature. A mechanically induced self-propagation reaction occurred by mechanical alloying of 3Ti/Al/2C powder mixtures. In addition to powder products, a large amount of rigor granules with a size of 0.5 ∼ 10 mm were produced. Fine powders containing Ti3AlC2, Ti2AlC and TiC were obtained. The granules composed of Ti3AlC2, Ti2AlC and TiC. Adding Sn may remove Ti2AlC and enhance the synthesis of Ti3AlC2. After Sn was added, the products only contained Ti3AlC2 and TiC. The Ti3AlC2 content of the powders and granules were 75 wt% and 88 wt%, respectively. The mechanically alloyed products were pressureless sintered at 900–1300°C for 2 h. Sintering of these products at 900 ∼ 1200°C yields samples containing over 95 wt% Ti3AlC2. The sintered powder compacts with high purity Ti3AlC2 had a fine organization. The lath Ti3AlC2 of the granules had a length of 10–20 𝜇m.

    • Microstructure, dielectric and piezoelectric properties of lead-free Bi0.5Na0.5TiO3−Bi0.5K0.5TiO3−BiMnO3 ceramics

      Huabin Yang Xu Shan Changrong Zhou Qin Zhou Weizhou Li Jun Cheng

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      To improve the piezoelectric properties of Bi0.5Na0.5TiO3-based ceramics, a new perovskite-type leadfree piezoelectric (1 – 𝑥 – 𝑦)Bi0.5Na0.5TiO3−𝑥Bi0.5K0.5TiO3−𝑦BiMnO3 system has been fabricated by a conventional solid–state reaction method and their microstructure, dielectric and piezoelectric properties have been investigated. The results of X-ray diffraction (XRD) analysis reveal that the addition of small amounts of BiMnO3 did not cause a remarkable change in crystal structure, but resulted in an evident evolution inmicrostructure. An obvious secondary phase was observed in samples with high Bi0.5K0.5TiO3 content. It is found from dielectric constant curves that low-temperature hump disappeared with increasing y and it appeared again with increasing x. The piezoelectric properties significantly increase with increasing Bi0.5K0.5TiO3 and BiMnO3 content. The piezoelectric constant and electromechanical coupling factor attain maximum values of 𝑑33 = 182 pC/N at 𝑥 = 0.21(𝑦 = 0.01) and 𝑘p = 0.333 at 𝑥 = 0.18 (𝑦 = 0.01), respectively.

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