Papers by Author: Yi Long

Abstract: Nanostructured ZnO with versatile morphologies has great potential applications in many fields. In this work, ZnO materials with different morphologies were deposited on Zn foils by a simple aqueous solution method, and the shape of ZnO can be controlled by the concentration of Cl ions in the solution. Rods, spheres and platelets were obtained respectively with the concentration of Cl ions increase. The competition between Cl ions and growth units in the solution results the formation of ZnO materials with different morphologies. At the same time, the preferential orientation of the crystal plane is also changed by the concentration of Cl ions. The different morphologies of ZnO grown form this kind of solution method was also explained.

Abstract: Nanostructured ZnO films were fabricated by chemical vapor deposition (CVD) method with different Sn source concentrations for ethanol sensing application. It was found that the morphology of the ZnO films were obviously affected by Sn concentration, while no any Sn signals were detected in the films. The response of the nanostructured ZnO films increases with the increase of ethanol concentrations, and the S2 sample displays the highest sensitivity. Thephotoluminescence spectra show that more oxygen vacancies exist in the S2 sample than the other samples, which reveals that oxygen vacancies may play a great role to improve the gas sensing properties of the ZnO films.A possible sensing mechanism was proposed to explain these phenomena.This work provides a very simple and efficient method to prepare ZnO gas sensor, its high response and short recovery time are also a merit for the ZnO films used in gas sensor applications.

Abstract: In order to make high performance magnetic refrigeration materials, Spark Plasma Sintering (SPS) process was introduced in the preparation of LaFe_11.5Si_1.5C_0.2 materials. Results show that the size of the starting powder has a significant influence on the magnetic entropy change than the sintered temperature does. Finer starting powder induce a decomposition of 1:13 phase into α-Fe phase during sintered process. By controlling the particle size, the decomposition can be decreased. The maximum magnetic entropy change value of the sinters with the size of sutible starting powder is as same as the parent compound. Also, the hysteresis loss of the sinters decreased.

Abstract: Giant magnetocaloric effect based on first order phase transformation has been investigated extensively recently. A considerable magnetic entropy change has been found in single crystal Ni52.6Mn23.1Ga24.3, Ni53Mn22Ga25 and polycrystal Ni51.5Mn22.7Ga25.8.This change originated from a sharp magnetization jump caused by the martensitic-austenitic structure transition on heating. In this paper, magnetocaloric effect in the alloys Ni54.9Mn20.5Ga24.6 is studied. The Curie point temperature Tc of the alloy is adjusted to the vicinity of martensitic transition temperature Tm. The concurrence of martensitic structure transition and magnetic phase transition enhance the magnetocaloric effect in these alloys. The martensitic structure transition effect on the magnetic properties of the alloys is investigated. The character of magnetocaloric effect during the transition from the austenitic to martensitic state is discussed.

Abstract: This paper reported the low activation martensitic steels which are being studied to develop the structural materials in fusion reactors. The steels were based on 9Cr1.5WVTa, but the effect of alloy elements was investigated by changing the amounts of alloy elements or adding other elements. The structure and properties of the steels were studied by tensile experiment, X-ray diffraction, SEM, TEM. Also the metallurgical process and heat treatment effect were discussed.