http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/103 2026-05-19T18:04:24Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/800 Preparation and characterization of nanocomposite TiO2/SnO2 films Pham, Van Nho; Tran, Kim Cuong This work presents the preparation of nanocomposite TiO2/SnO2 films by using spray pyrolysis and followed by sol-gel technique from TiCl4 and SnCl4 solutions. Obtained films were characterized by XRD, SEM and photoconductivity measurement. It was found that in this method the nanocomposite TiO2/SnO2 films were constituted of nanosized TiO2 and SnO2 surrounded the TiO2 grains. The obtained nanocomposite TiO2/SnO2 materials were shown to have the photoconducting properties. A reason of these novel properties was discussed and practical applications of nanocomposite TiO2/SnO2 films were showed. VNU Journal of Science, Mathematics - Physics. Vol. 24 (2008), No 1, P. 42-46 2008-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/796 Determination of the annual beta dose by meaming beta activity using the liquid scintillation technique Nguyen, Quang Mien; Bui, Van Loat This paper presents a method for measuring the gross alpha/beta radioactivity of ancient pottery by using the liquid scintillation technique, Tri - carb2770TR/SL in the alpha/beta discrimination counting mode. The beta radioactivity is converted to the annual dose, which can be applied in dating of pottery by thermoluminescence technique. In comparision with the radiocarbon technique, the preliminary results shown that the liquid scintillation technique may be applied effectively for ancient ceramic dating in Vietnam. VNU Journal of Science, Mathematics - Physics. Vol. 24 (2008), No 1, P. 36-41 2008-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/793 Room-temperature large magnetocaloric effect in perovskites (La1-xNdx)0.7Sr0.3MnO3 Nguyen, Hoang Luong; Nguyen, Thi Mai Phuong; Phung, Thu Hien; Hoang, Nam Nhat; Luc, Huy Hoang; Nguyen, Chau; Nguyen, Hoang Hai Study of the effect of Nd substitution for La on magnetocaloric effect (MCE) of polycrystalline perovskites (La1-xNdx)0.7Sr0.3MnO3 (x = 0.0, 0.2 , 0.4, 0.6, 0.8, 1.0 ) is presented. Large MCE is observed in all samples. The presence of Nd affects to both maximum magnetic entropy change, | Sm|max, and Curie temperature, TC. | Sm|max slightly reduces with low content and increases with high content of Nd and gets maximum value of 4.83 J/kg.K for x = 0.8. TC of the samples determined from the thermomagnetic curves somewhat increases from 346 K for x = 0.0 to 350 K for x = 0.2, then decreases to 235 K for x = 1.0. The sample with x = 0.4 exhibiting the largest value of 74 J/kg for the relative cooling power among the studied samples has TC = 325 K, i.e. higher than room temperature. Our studied samples are promising materials for magnetic refrigerants in the room-temperature region. VNU Journal of Science, Mathematics - Physics. Vol. 24 (2008), No 1, P. 30-35 2008-01-01T00:00:00Z http://tainguyenso.vnu.edu.vn/jspui/handle/123456789/791 Photoluminescence of ZnO nano-tetrapods Nguyen, Thi Thuc Hien; Doan, Manh Ha; Ngo, Xuan Dai; Nguyen, Thi Thu Huong The ZnO nano-tetrapods have been prepared by the evaporation of metallic Zn powder at the temperature range of 700oC- 950oC in air. The influence of experimental conditions, such as the evaporation temperature and the substrate temperature, on the morphology, the size and the photoluminescence (PL) was investigated. The XRD pattern showed that the nano–tetrapods were ZnO with hexagonal structure. The branch size of the tetrapods was about two hundreds nanometers. The photoluminescence spectrum measured at room temperature consists of two bands, a narrow band at 380 nm (UV band) and a wide band around 500 nm (green band (GB)). The intensity of each band, the ratio of the peak intensity of UV band to the GB band and the GB band position depend on the experiment conditions. However, the peak position of the UV band was not changed. VNU Journal of Science, Mathematics - Physics. Vol. 24 (2008), No 1, P. 24-29 2008-01-01T00:00:00Z