Haiyun Yu

Solvothermal synthesis of Mg(OH)2 nanotubes using Mg10(OH)18Cl2·5H2O nanowires as precursors

Nanotubes of Mg(OH)2 have been synthesized by a simple solvothermal method using Mg10(OH)18Cl2·5H2O nanowires as precursors without any surfactant or catalyst. XRD, TEM, ED and HRTEM have been used to characterize the structure, morphology and composition of the nanotubes. The significant variation of intensity between the (001) and other lattice planes indicates preferential growth of the nanotubes. TEM results show the nanotubes are well-crystallized, and the nanotubes are 80–150 nm in outer diameter, 30–50 nm in wall thickness, and 5–10 µm in length. The ED pattern reveals that the Mg(OH)2 nanotubes are single crystals, and the nanotubes grow along the [110] direction. This conclusion was supported by HRTEM studies. The advantages of our method for the nanotubes synthesis lie in the high yield and the low temperature and mild reaction conditions, which permit large scale production at low cost.

Preparation of different morphologies of calcium sulfate in organic media

In this paper, we reported an effective method for controlling CaSO4 crystal growth in organic media. Ca2+ and SO42− ions were extracted into the organic phase using different extractants. Different morphologies and sizes of CaSO4 nanocrystals including nanoparticles and nanosheets and long fibers were prepared by changing the molar ratio of [SO42−]∶[Ca2+] in the organic solvent at room temperature. The effect of the molar ratio of [SO42−]∶[Ca2+] on the CaSO4 growth process was studied principally by TEM. In addition, it was found that the diluent polarity could also affect the growth process of CaSO4 crystals.

Control of the sizes of zinc sulfide particles by extractant

Over the past decade, considerable interest has been given to the II–VI nanostructured semiconductors because of their important nonlinear optical properties, luminescent properties, quantum size effects and other important physical and chemical properties [1–7], and much progress has been made in the synthesis and characterization of these materials [8–10]. ZnS is a II–VI semiconductor with a large direct band gap in the nearUV region, and ZnS has many uses in blue light emitting diodes, electroluminescent displays, cathodoluminescent displays and multilayer dielectric filters, light guiding in integrated optics, IR antiflection coatings and solar cell [11, 12]. It has been shown that the sizes of particles and its distribution play an important role in the properties and applications of materials. Thus, it is important to synthesize particles with the desired size and a narrow distribution in an easily-to-control condition. In order to obtain particles with desired size, a variety of methods including hydrothermal method, colloid chemistry method, solid state method and so on [13–17], have been developed for the chemical preparation of relatively monodispersed nanoparticles of various semiconductor materials. Although considerable progress has been made in the controlled synthesis of II–VI semiconductor crystallites, the control of the size and shape of particles still be the main problem in preparation of these materials. In this paper, the extractant (primary amine N1923) was used to control the size of ZnS and a new method to prepare materials, extractionsolvothermal, is proposed. The primary amine N1923 (R1R2CHNH2) was purified as described in literature [18]. The other chemicals were of analytical grade. The procedure to prepare ZnS is as follows: The negative ions of zinc, for example ZnCl2− 4 , were formed by adding NaCl into the ZnCl2 solution in which the pH value is 3; and zinc ions were extracted into organic phase by primary amine N1923 which is pretreated according to the different experimental conditions; then the organic phase was transferred into the Teflon lined stainless autoclave; after the absolute ethanol and CS2 were added into the autoclave, the autoclave was heated at 180 ◦C for 18 h.